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(11) | EP 4 134 186 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
| published in accordance with Art. 153(4) EPC |
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| (54) | LF REFINING LADLE MICROPOROUS CERAMIC ROD AIR-PERMEABLE UPPER NOZZLE WELL BLOCK, AND ARGON BLOWING CONTROL METHOD THEREFOR |
| (57) Provided are a ladle furnace (LF) refined ladle gas-permeable upper nozzle pocket
block with microporous ceramic rods, and an argon blowing control method thereof.
The gas-permeable upper nozzle pocket block of the present invention includes an iron
ring and microporous ceramic rods; a diameter d of each microporous ceramic rod is
35-45 mm, and a height h of each ceramic rod is 140-180 mm; 60-120 ventilation holes
are formed in the microporous ceramic rods along an axial directions of the microporous
ceramic rods; the ventilation holes are uniformly distributed on cross sections of
the microporous ceramic rods; an inner diameter of each ventilation hole is 0.075-0.1
mm; and the ventilation holes longitudinally run through upper end faces and lower
end faces of the microporous rods. The present invention further provides an argon
blowing control device and an argon blowing control method. In the present invention,
before an automatic soft blowing mode is selected, a manual bypass in an argon pipeline
system is first used to blow through the gas-permeable upper nozzle pocket block;
the argon blowing flow rate is accurately controlled; and the oxygen burning-free
blowing rate and the service life of the ladle gas-permeable upper nozzle pocket block
are improved. |
Field of the Invention
[0001] The present invention relates to a Ladle Furnace (LF) refined ladle gas-permeable upper nozzle pocket block with microporous ceramic rods, and an argon blowing control method thereof.
Background of the Invention
[0002] Bottom argon blowing for a ladle furnace (LF) refined ladle is a simple and efficient out-of-furnace refining technology. It is generally divided into two stages: blowing argon at a large flow rate for stirring and uniform mixing at the early stage, and performing small-flow-rate soft blowing for removal of inclusions at the later stage. At present, for domestic LF refined ladles of more than 100 tons, two bottom blowing ventilation bricks are generally used. The treatment time of high-quality steel is generally longer than 40 min, of which soft blowing is 8-12 min. At present, there are the following problems or deficiencies in production practice: (1 ) insufficient soft blowing time, which affects the inclusion removal effect; (2) excessive LF refining time, which causes mismatch between the furnace and the machine and becomes a restrictive procedure for increasing the productivity and improving the efficiency; (3) inaccurate soft blowing flow control: an extremely low flow affects the inclusion removal effect of soft blowing, and an extremely high flow causes the problems of an exposed molten liquid level, entrapped slag, great molten steel temperature drop, and the like.
[0003] Chinese patent document CN104028739A (patent number: 201410274221.8) discloses a ladle gas-permeable upper nozzle pocket block, and a method for controlling ladle slag entrapment. The ladle gas-permeable upper nozzle pocket block includes an upper nozzle pocket block body, a gas-permeable ceramic rod, a gas chamber box, and a gas inlet pipe, and a nozzle block. A steel flowing hole and an upper nozzle mounting hole are formed in the middle of the upper nozzle pocket block body from top to bottom; the circular-ring-shaped uniformly disposed microporous ceramic rod and the annular gas chamber box are arranged in the upper nozzle pocket block body; a bottom of the gas chamber box is connected with the gas inlet pipe; and when molten steel in a ladle is at a low liquid level, argon is blown from the gas inlet pipe to control the problem of vortex slag entrapment at the upper nozzle of the ladle. This patent is mainly aimed at suppressing the problem of slag entrapment at the upper nozzle of the ladle at the end of ladle pouring. This patent has the following shortcomings: a single gas-permeable ceramic rod has a small diameter, a small gas permeation area, and a small distribution density of pores, and the number of argon bubbles formed by argon blowing is small, which is not conducive to the metallurgical effect of inclusion removal. The single gas-permeable ceramic rod is high and is difficult to mold; argon is only blown at the later stage of the ladle pouring; there is no metallurgical function for removing inclusions by blowing argon at a small flow rate; and at the same time, the argon blowing flow rate is not correspondingly decreased according to the reduction of the molten steel level in the ladle, so that it is prone to the problems of an exposed molten steel level, entrapped slag, great molten steel temperature drop, and the like.
[0004] Chinese patent document CN109719290A (application number: 2019101296742.1) discloses a ladle circumferential weld type gas-permeable upper nozzle block and a metallurgical argon blowing method thereof. The circumferential weld type gas-permeable upper nozzle block includes a ladle upper nozzle pocket block body, a circumferential weld , a gas chamber box, and a gas inlet pipe; a steel flowing hole, a connecting hole, and an upper nozzle mounting hole which run through the ladle upper nozzle pocket block body from top to bottom are formed in the middle of the ladle upper nozzle pocket block body; in a pouring process of a continuous casting ladle, argon is blown in the whole process; the argon flow rate is automatically adjusted according to a change of the net weight of the molten steel in a ladle; the argon is formed into tiny argon bubbles through the circumferential weld; most of the argon moves up to form a ringlike gas curtain barrier around the ladle upper nozzle, and the molten steel that is going to enter the ladle upper nozzle is washed with gas; furthermore, a stable and continuous ringlike air flow is formed in the upper nozzle to suppress nodulation at the upper nozzle; and at the later stage of pouring of the ladle, the ladle slag entrapment caused by a confluence vortex and a drainage pit is effectively suppressed. This patent has the following shortcomings: A ventilation channel is a circumferential weld; a small number of large argon bubbles are formed by argon blowing, which affects the metallurgical effect of argon blowing. According to different control requirements for inclusions in steel, different argon blowing control methods are selected. Blowing argon throughout the process results in a great temperature drop in molten steel, and affects popularization and application. Furthermore, the ladle gas-permeable upper nozzle pocket block is not manually blown before automatic argon blowing, so that the ventilation channel is easily blocked by the infiltrating molten steel and steel slag, which causes that the flow rate at the early stage of argon blowing for the gas-permeable upper nozzle pocket block is small or bottom blowing is incomplete, so that the metallurgical effect of argon blowing is seriously affected.
[0005] Chinese patent document CN106041044A (patent number: 201610634268.X) discloses a continuous casting tundish gas-permeable ceramic pipe upper nozzle pocket block, including an upper nozzle pocket block body, a ceramic pipe, a gas chamber, and a gas inlet pipe; a plurality of ceramic pipes uniformly disposed in a circular ring shape and one circular-ring-shaped gas chamber; a plurality of jacks uniformly disposed in a circular ring shape; top ends of the ceramic pipes extend out of an upper surface of the upper nozzle pocket block body, and lower ends of the ceramic pipes are fixed in the jacks on the gas chamber and are communicated with the gas chamber; side portions of the ceramic pipes are connected with the gas inlet pipe and are communicated with an external argon source through metal connecting pipe fittings; after being blown, argon is upwards formed into a ringlike gas curtain barrier to wash the molten steel entering an upper nozzle; there is a certain number of argon bubbles entering the upper nozzle along with the molten steel to form a stable and continuous ringlike gas flow, so that the nodulation at the nozzle is suppressed; and furthermore, the technical problem of subsurface bubbles of a cast slab caused by the fact that protective argon bubbles enter the steel is solved. This patent has the following shortcomings: the inner diameter of ventilation holes in the ceramic pipes is large; the number of the ventilation holes in the ceramic pipes is small; a small number of relatively large argon bubbles are formed by argon blowing, which affects the metallurgical effect of argon blowing; and the ventilation holes are easily blocked by infiltrating steel and are hardly blown through.
Summary of the Invention
[0006] For the shortcomings in the prior art, the present invention provides an LF refined ladle gas-permeable upper nozzle pocket block with microporous ceramic rods, and an argon blowing control method thereof.
[0007] The technical solution of the present invention solves the following problems in the Chinese patent document CN104028739A: the ceramic rod has poor molding quality due to its large height, and the ceramic rod is hard to position and easy to block in a pouring process of the ladle nozzle pocket block body; an argon blowing flow rate is accurately controlled; the oxygen burning-free blowing rate of a gas-permeable upper nozzle pocket block for a ladle is increased; and the service life of the gas-permeable upper nozzle pocket block for a ladle is prolonged.
[0008] The burning-free oxygen blowing rate of the ladle gas-permeable upper nozzle pocket block refers to a permeation volume of the ladle gas-permeable upper nozzle pocket block that is measured off line after pouring of a ladle is completed. When the permeation volume meets a process requirement, oxygen burning-free blowing is performed, the oxygen burning-free blowing rate= the number of batches subjected to the oxygen burning-free blowing ÷ the total number of batches × 100%.
Technical solution of the present invention:
[0009] An LF refined ladle gas-permeable upper nozzle pocket block with microporous ceramic rods is provided, including a ladle nozzle pocket block body (1), microporous ceramic rods (2), a gas chamber box (3), a gas inlet pipe (4), a steel flowing hole (5), and an upper nozzle mounting hole (6).
[0010] The steel flowing hole (5) and the upper nozzle mounting hole (6) run through, and are mounted in the middle of the ladle nozzle pocket block body (1);
the gas chamber box (3) is buried in a surface layer of an upper portion of the ladle nozzle pocket block body (1); a plurality of jacks (8) are formed in the gas chamber box (3); the jacks (8) are used for fixing the microporous ceramic rods (2);
a plurality of microporous ceramic rods (2) are annularly uniformly distributed in the ladle nozzle pocket block body (1); a top end of each microporous ceramic rod (2) extends out of an upper surface of the ladle nozzle pocket block body (1); a bottom end of each microporous ceramic rod (2) extends into the gas chamber box (3);; the shapes, number, and positions of the jacks (8) correspond to the shapes, number and positions of the microporous ceramic rods (2);
one end of the gas inlet pipe (4) is communicated to a side portion of the gas chamber box (3), and the other end of the gas inlet pipe extends out from a side portion of the ladle nozzle pocket block body (1).
[0011] Preferably, the microporous ceramic rods (2) are cylindrical, a diameter d of which is 35-45 mm; and a height h of each ceramic rod is 140-180 mm.
[0012] Preferably, in the present invention, 60-120 ventilation holes are formed in the microporous ceramic rods (2) along an axial directions of the microporous ceramic rods; the ventilation holes are uniformly distributed on cross sections of the microporous ceramic rods; an inner diameter of each ventilation hole is 0.075-0.1 mm; and the ventilation holes longitudinally run through upper end faces and lower end faces of the microporous rods.
[0013] Preferably, in the present invention, the microporous ceramic rods (2) are fired at a high temperature in an extrusion-forming manner, and adopt zirconium oxide toughened corundum or zirconium oxide toughened corundum mullite.
[0014] Preferably, in the present invention, six to ten microporous ceramic rods (2) are uniformly disposed in a circular ring shape, and a diameter ⊄ of the circular ring formed by the microporous ceramic rods (2) is 300-320 mm on the basis of the centers of the microporous ceramic rods (2).
[0015] Preferably, in the present invention, a height m of the upper end of each microporous ceramic rod (2) extending out from the upper surface of the ladle nozzle pocket block body (1) is 5-10 mm, and a height n of the bottom end of each microporous ceramic rod (2) extending into the gas chamber box is 5-10 mm.
[0016] Preferably, in the present invention, the gas-permeable upper nozzle pocket block with the microporous ceramic rods includes an iron ring (7); and the iron ring (7) is buried in a surface layer of a lower portion of the ladle upper nozzle pocket block body (1).
[0017] The iron ring (7) is buried in the surface layer of the lower portion of the ladle nozzle pocket block body (1), which effectively suppresses the problem of cracks caused by a thermal stress of the ladle upper nozzle pocket block body.
[0018] Preferably, in the present invention, the entire iron ring (7) is circular-ring-shaped, a height L of which is 40-50 mm; a distance a between a lower end of the iron ring and a lower end of the ladle upper nozzle pocket block body (1) is 50-60 mm; and a depth z of the iron ring (7) buried in the surface layer of the ladle nozzle pocket block body (1) is 10-20 mm.
[0019] Preferably, in the present invention, the iron ring (7) is formed by welding an iron sheet with a thickness of 1 mm; and an overlap length of a joint is 40-50 mm, and full welding is adopted.
[0020] Preferably, in the present invention, the entire gas chamber box (3) is of a circular ring shape; the gas chamber box adopts a metal box manufactured by a steel plate with a thickness of 1.5-2.0 mm; a longitudinal section of the metal box is a rectangle with a width × of 50-60 mm and a height y of 30-40 mm; a cross section of the metal box is a circular ring; and the plurality of jacks (8) are uniformly distributed on the circular ring.
[0021] Preferably, in the present invention, the ladle nozzle pocket block body (1) is cast and formed from a chrome corundum castable, with a bulk density ≥3.0 g/cm3, a high-temperature flexural strength ≥12Mpa, a high-temperature compressive strength ≥80 Mpa, and an AL2O3 content ≥92%, and a Cr2O3 content ≥3%.
[0022] Preferably, in the present invention, longitudinal center lines of the steel flowing hole (5) and the upper nozzle mounting hole (6) and a longitudinal center line of the ladle nozzle pocket block body (1) are on one straight line; an upper portion of the steel flowing hole (5) is truncated cone shaped; a diameter d1 of an upper port of the truncated cone is 190-210 mm, and a diameter d2 of a lower port is 140-160 mm; the truncated cone has a height c of 55-80 mm; a lower portion of the steel flowing hole (5) is a cylindrical channel; a diameter of the lower cylindrical channel is consistent with the diameter of the lower port of the upper truncated cone; and the cylinder has a height b of 250-270 mm.
[0023] Preferably, in the present invention, an upper portion of the upper nozzle mounting hole (6) is truncated cone shaped, and a fitting size of the upper nozzle mounting hole is designed according to an outline size of an upper nozzle.
[0024] Preferably, in the present invention, the ladle nozzle pocket block body (1) is cylindrical; and the cylindrical shape has an outer diameter D of 380-400 mm and a height H of 470-490 mm.
[0025] The gas inlet pipe (4) of the present invention is made of a heat-resistant stainless steel round pipe, an end portion of which is provided with a connecting thread, and the dimension is M16×1.5.
[0026] In the LF refined ladle gas-permeable upper nozzle pocket block with the microporous ceramic rods in the present invention, 60-120 ventilation holes are formed in the microporous ceramic rods (2) along the axial directions of the microporous ceramic rods; the ventilation holes are uniformly distributed on cross sections of the microporous ceramic rods; the inner diameter of each ventilation hole is 0.075-0.1 mm; the height h of each ceramic rod is 140-180 mm; the iron ring is buried in the surface layer of the lower portion of the ladle nozzle pocket block body; and the ladle nozzle pocket block body is cylindrical. These designs are essentially technological innovations for the problems in the existing technology and are obtained via lots of researches and production tests: First, based on lots of researches on laboratory mathematical and physical simulation, by means of reducing the inner diameter of the ventilation hole in the ceramic rod and increasing the number of the ventilation holes in the ceramic rods, argon bubbles that are more and smaller than those formed in the ceramic pipe in the Chinese patent document CN106041044B (patent number: 201610634268.X) are formed by argon blowing, so that the capabilities of capturing the argon bubbles and removing inclusions are improved, and the function of suppressing the ladle slag entrapment caused by a confluence vortex and a drainage pit at the end of pouring is enhanced; and furthermore, the ventilation holes are not prone to steel infiltration and are easy to blow through after the inner diameter of the ventilation hole is reduced. Second, the height of the microporous ceramic rod is reduced as much as possible according to an erosion residual height, so that the problems that the ceramic rod in the Chinese patent document CN104028739B has poor molding quality due to its large height, and the ceramic rod is hard to position in a pouring process of the ladle nozzle pocket block body. Third, lots of production and application tests show that the iron ring is buried in the surface layer of the lower portion of the ladle nozzle pocket block body, so that the problem of cracks caused by a thermal stress on the ladle nozzle pocket block body, and the service life of the ladle gas-permeable nozzle pocket block with the microporous ceramic rods.
[0027] The present invention further provides an argon blowing control device for an LF refined ladle gas-permeable upper nozzle pocket block, which is characterized in that an argon pipeline system and an electrical control system are provided, having a function of selecting a manual blowing mode for a gas-permeable upper nozzle pocket block and an automatic soft blowing mode. Furthermore, by means of introducing a weighing signal for molten steel in a ladle, an argon flow rate is synchronously adjusted according to a change in a net weight of the molten steel in the ladle, and the argon blowing flow rate for the gas-permeable upper nozzle pocket block is accurately controlled.
[0028] Preferably, in the present invention, the argon pipeline system is divided into a gas source main path, an automatic branch, a manual bypass, and a release branch; the gas source main path, the automatic branch, and the manual bypass are communicated through a gas confluence bar 18; the gas source main path includes a gas source main path first ball valve 9a, a first pressure gauge 10a, a first gas filter 11 a1, a second gas filter 11 a2, a pressure adjuster 12, and a first pressure sensor 15a in sequence; the automatic branch includes an automatic branch second ball valve 9b1, a first electromagnetic valve 13b, a special metallurgical mass flow rate controller 14, a second pressure sensor 15b, a second pressure gauge 10b, and an automatic branch third ball valve 9b2 in sequence; the manual bypass includes a manual bypass fourth ball valve 9c and a manual adjustment valve 16 in sequence; and the manual bypass is connected in parallel with the second ball valve 9b1, the second electromagnetic valve 13b, and the special metallurgical mass flow rate controller 14 to perform manual operation and application after the automatic branch fails. The argon pipeline system in the present invention is further used for high-pressure blowing through before automatic argon blowing of the LF refined ladle gas-permeable upper nozzle pocket block. In the present invention, the release branch is also arranged at a rear end of the manual adjustment valve 16, and includes a second electromagnetic valve 13c and an exhaust throttle valve 17 in sequence to discharge gas and release pressure when a gas inlet metal hose connected to the gas-permeable upper nozzle pocket block needs to be plugged.
[0029] Preferably, in the present invention, the electrical control system adopts the existing technology, including a network switch, an argon blowing control system PLC, a touch screen, and a continuous casting basic automation system; the argon blowing control system PLC and the touch screen are arranged in a control box; the argon blowing control system PLC, the touch screen, and the continuous casting basic automation system are all connected to the network switch through Ethernet communication; a weighing system for molten steel in a ladle collects and sends a weight of the molten steel in the ladle to the continuous casting basic automation system, and uploads the weight to the argon blowing control system PLC through the Ethernet communication and the network switch, as shown in FIG. 5. The continuous casting basic automation system receives weight data of the molten steel in the ladle of the molten steel weighing system, and uploads the data to the argon blowing control system PLC through Ethernet communication and the network switch. The argon blowing control system PLC receives the weight data of the molten steel in the ladle, and controls gas feeding and gas discharging of the ladle.
[0030] Preferably, in the present invention, the gas-permeable upper nozzle pocket block in the above-mentioned argon blowing control device is the gas-permeable upper nozzle pocket block in the present invention.
[0031] The present invention further provides an argon blowing control method, which is characterized by including the following steps:
in a first step, applying the argon blowing control device of the present invention for the first time to measure an initial flow rate value of soft blowing of a full-ladle gas-permeable upper nozzle pocket block;
in a second step, communicating, after the ladle is at a pouring position on a continuous casting ladle turntable, the gas inlet pipe (4) of the above-mentioned gas-permeable upper nozzle pocket block to a gas source outlet of an argon control device using a metal hose; transferring the ladle to the pouring position for pouring and flowing, and then blowing through the above-mentioned gas-permeable upper nozzle pocket block immediately using the manual bypass in the argon pipeline system: gradually increasing the pressure by 1-10 mbar at each time by adjusting the pressure adjuster 12 of the gas source main path in the argon pipeline system until the above-mentioned gas-permeable upper nozzle pocket block is blown through;
in a third step, enabling, according to different control requirements for inclusions in steel, different automatic soft blowing modes immediately after the gas-permeable upper nozzle pocket block is blown through; blowing argon using the automatic main path in the argon pipeline system, and linearly adjusting an argon flow rate according to the change of the net weight of the molten steel in the ladle, a set value of an argon flow rate in a molten steel pouring process = the net weight of the remaining molten steel in the ladle ÷ the net weight of the molten steel in the full ladle × the initial flow rate value during soft blowing of the full ladle in the step I + (2-5) NL/min; blowing argon at the flow rate of 2-5 NL/min after the pouring volume of the molten steel reaches 30-100% of the total volume of the molten steel in the ladle; and stopping the argon blowing after the pouring of the ladle is completed and the ladle is transferred back to the pouring position of the continuous casting turntable.
[0032] Preferably, according to the present invention, the step III of selecting different automatic soft blowing modes according to different control requirements for the inclusions in the steel includes:
- (1) selecting automatic soft blowing mode A for a low-end steel grade without an inclusion control requirement: enabling the automatic soft blowing mode immediately after the gas-permeable upper nozzle pocket block is blown through; blowing argon using the automatic main path in the argon pipeline system, and linearly adjusting an argon flow rate according to the change of the net weight of the molten steel in the ladle, a set value of an argon flow rate in a molten steel pouring process = the net weight of the remaining molten steel in the ladle ÷ the net weight of the molten steel in the full ladle × the initial flow rate value during soft blowing of the full ladle in the step I + (2-5) NL/min; blowing argon at the flow rate of 2-5 NL/min after the pouring volume of the molten steel reaches 30-40% of the total volume of the molten steel in the ladle; and stopping the argon blowing after the pouring of the ladle is completed and the ladle is transferred back to the pouring position of the continuous casting turntable;
- (2) selecting automatic soft blowing mode B for a medium-end steel grade with an inclusion control requirement: enabling the automatic soft blowing mode immediately after the gas-permeable upper nozzle pocket block is blown through; blowing argon using the automatic main path in the argon pipeline system, and linearly adjusting an argon flow rate according to the change of the net weight of the molten steel in the ladle, a set value of an argon flow rate in a molten steel pouring process = the net weight of the remaining molten steel in the ladle ÷ the net weight of the molten steel in the full ladle × the initial flow rate value during soft blowing of the full ladle in the step II + (2-5) NL/min; blowing argon at the flow rate of 2-5 NL/min after the pouring volume of the molten steel reaches 50-60% of the total volume of the molten steel in the ladle; and stopping the argon blowing after the pouring of the ladle is completed and the ladle is transferred back to the pouring position of the continuous casting turntable;
- (3) selecting automatic soft blowing mode C for a high-end steel grade with strict
inclusion control: enabling the automatic soft blowing mode immediately after the
gas-permeable upper nozzle pocket block is blown through; blowing argon using the
automatic main path in the argon pipeline system, and linearly adjusting an argon
flow rate according to the change of the net weight of the molten steel in the ladle
and the following formula:
blowing argon at the flow rate of 2-5 NL/min after it is found that the ladle has slag entrapment or a slag entrapment detection system sounds an alarm; and stopping the argon blowing after the ladle is transferred back to the pouring position of the continuous casting turntable.
[0033] Preferably, in the present invention, the step I of measuring an initial flow rate value of soft blowing of a full-ladle gas-permeable upper nozzle pocket block includes: during soft blowing of the full ladle at the later stage of LF refining in the existing technology, shutting off argon of an original ladle bottom-blowing gas-permeable block, connecting argon to the gas-permeable upper nozzle pocket block, gradually increasing the argon flow rate, and observing that the molten steel level in the ladle slightly fluctuates, wherein an argon blowing flow rate value when the molten liquid level is not exposed is the initial flow rate value of the soft blowing of the full ladle.
[0034] Preferably, in the present invention, the above gas-permeable upper nozzle pocket block in the above-mentioned argon blowing control method is the gas-permeable upper nozzle pocket block in the present invention.
[0035] The net weight of the molten steel when the ladle is full comes from the weighing system for molten steel in a ladle which is arranged on the continuous casting turntable. When the full ladle is disposed on the continuous casting turntable, the system automatically subtracts a calibrated tare weight of the ladle by the total weight of a weighed tare weight of the ladle and the net weight of the molten steel in the ladle to obtain the net weight of the molten steel in the full ladle. The tare weight of the ladle refers to a weight of an empty ladle.
[0036] The net weight of the remaining molten steel in the ladle comes from the weighing system for molten steel in a ladle which is arranged on the continuous casting turntable. In the ladle pouring process, the system automatically subtracts a calibrated tare weight of the ladle by the total weight of a weighed tare weight of the ladle and the net weight of the remaining molten steel in the ladle to obtain the net weight of the remaining molten steel in the full ladle. The tare weight of the ladle refers to a weight of an empty ladle.
The present disclosure has the beneficial effects:
[0037]
- 1. The diameter d of the ceramic rod in the ladle gas-permeable upper nozzle pocket block with the microporous ceramic rods in the present invention is 35-45 mm; 60-120 ventilation holes are formed in the microporous ceramic rods along the axial directions of the microporous ceramic rods; the ventilation holes are uniformly distributed on cross sections of the microporous ceramic rods; and the inner diameter of each ventilation hole is 0.075-0.1 mm. Based on lots of researches on laboratory mathematical and physical simulation, by means of reducing the inner diameter of the ventilation hole in the ceramic rod and increasing the number of the ventilation holes in the ceramic rods, argon bubbles that are more and smaller than those formed in the ceramic pipe in the Chinese patent document CN106041044B (patent number: 201610634268.X) are formed by argon blowing, so that the capabilities of capturing the argon bubbles and removing inclusions are improved, and the function of suppressing the ladle slag entrapment caused by a confluence vortex and a drainage pit at the end of pouring is enhanced; and furthermore, the ventilation holes are not prone to steel infiltration and are easy to blow through after the inner diameter of the ventilation hole is reduced. The present invention is applied to a dual-flow slab continuous casting machine to produce ultralow-carbon aluminum killed steel DC04. Automatic soft blowing mode C is selected; the weight of electrolytic inclusions of a continuous casting slab test sample is reduced by 20% or above on year-on-year basis, and the pouring remain of the molten steel in the ladle is reduced by 20% or above on year-on-year basis. Meanwhile, the height of the microporous ceramic rod is reduced according to an erosion residual height of the LF refined ladle gas-permeable upper nozzle pocket block of the present invention; the height h of the microporous ceramic rod is designed to be 140-180 mm, so that the problems that the ceramic rod in the Chinese patent document CN104028739B in the existing technology has poor molding quality due to its large height, and the ceramic rod is hard to position in the pouring process of the ladle nozzle pocket block body.
- 2. According to the LF refined ladle gas-permeable upper nozzle pocket block and the argon blowing control method thereof of the present invention, by means of the actual initial flow rate value of the soft blowing of the full ladle, the set value of the argon flow rate in the ladle pouring process = the net weight of the remaining molten steel in the ladle ÷ the net weight of the molten steel in the full ladle × the initial flow rate value during soft blowing of the full ladle + (2-5) NL/min; and furthermore, different soft blowing modes are selected according to different control requirements for the inclusions in the steel, so that the problems of an exposed molten liquid level, entrapped slag, great molten steel temperature drop, and the like are effectively solved, which are caused by the fact that the argon blowing flow rate in the comparative example CN104028739B (patent number: 201410274221.8) is not correspondingly reduced according to the lowering of the molten steel level in the ladle; and the average temperature drop of the molten steel in the ladle is reduced by 0.1 °C/min or above on year-on-year basis.
- 3. The ladle nozzle pocket block body of the present invention is designed to be cylindrical, not the traditional square; the iron is buried in the surface layer of the lower portion of the ladle nozzle pocket block body, which effectively suppresses the problem of cracks caused by a thermal stress of the ladle upper nozzle pocket block body, and the service life of the ladle gas-permeable upper nozzle pocket block with the microporous ceramic rods is prolonged. Compared with the average service life of the comparative example CN104028739A (patent number: 201410274221.8), the average service life is prolonged by four batches on year-on-year basis.
- 4. Compared with the ladle circumferential weld type gas-permeable upper nozzle block and the metallurgical argon blowing method thereof described in Chinese patent document CN109719290A (application number: 2019101296742.1), the LF refined ladle gas-permeable upper nozzle pocket block with the microporous ceramic rods and the argon blowing control method thereof described in the present invention have essential differences. First, the ventilation channels are different; the sizes and quantities of bubbles formed by argon blowing are different; and the metallurgical effects of argon blowing are different. The gas channels of the present invention are the ventilation holes in the ceramic rods; 60-120 ventilation holes are formed in the microporous ceramic rods along the axial directions of the microporous ceramic rods; the ventilation holes are uniformly distributed on cross sections of the microporous ceramic rods; and the inner diameter of each ventilation hole is 0.075-0.1 mm. The diameter, measured in a water phantom experiment, of the bubbles near the ceramic rods is less than 1.8 mm, and the inclusion removal rate obtained by a digital model is 54-67%; the gas channel of CN109719290A (application number: 2019101296742.1) is a circumferential weld with a width a of 1.3-1.7 mm; the diameter, measured in the water phantom experiment, of bubbles of the circumferential weld is less than 2 mm, and the inclusion removal rate obtained by the digital model is 37-48%. The metallurgical effect of argon blowing of the ladle gas-permeable upper nozzle pocket block with the microporous ceramic rods of the present invention is outstanding. Second, the argon blowing control methods are different. In the present invention, before the automatic soft blowing mode is selected, the manual bypass in the argon pipeline system is first used to blow through the gas-permeable upper nozzle pocket block; the one-time blow-through rate of the gas=permeable upper nozzle pocket block is 99% or above; the flow rate is maintained at 2-5 NL/min at the later stage of ladle pouring, so that the molten steel and steel slag are prevented from infiltrating into the ventilation channels of the gas-permeable upper nozzle pocket block, and the oxygen burning-free blowing rate of the ladle gas-permeable upper nozzle pocket block is increased. Furthermore, different automatic soft blowing modes are selected according to different control requirements for the inclusions in the steel. In automatic soft blowing modes A and B, the argon is not blown in the whole process. When the molten steel pouring volume reaches 30-40% and 50-60% of the total volume of the molten steel in the ladle, the argon is blown at the flow rate of 2-5 NL/min. Results of a comparison test on the dual-flow slab continuous casting machine to produce ultralow-carbon aluminum killed steel SPHC in a certain steel works show that compared with the argon blowing control method for the ladle gas-permeable upper nozzle pocket block in the comparative example CN109719290A (application number: 2019101296742.1), the argon blowing control method applied to the ladle gas-permeable upper nozzle pocket block of the present invention has the advantages that the average temperature drop of the molten steel in the ladle is reduced by 0.06 °C/min on year-on-year basis; the one-time blow-through rate of the ladle gas-permeable upper nozzle pocket block is increased by 11% on year-on-year basis; and the oxygen burning-free blowing rate of the ladle gas-permeable upper nozzle pocket block is increased by 13% on year-on-year basis. The advantages of the argon blowing control method of the ladle gas-permeable upper nozzle pocket block with the microporous ceramic rods of the present invention are outstanding.
Brief Description of the Drawings
[0038]
FIG. 1 is a structural front view of an LF refined ladle gas-permeable upper nozzle
pocket block in an embodiment of the present invention;
in the drawing: 1: ladle nozzle pocket block body; 2: microporous ceramic rod; 3:
gas chamber box; 4: gas inlet pipe; 5: steel flowing hole; 6: upper nozzle mounting
hole; and 7: iron ring.
FIG. 2 is a top view of an LF refined ladle gas-permeable upper nozzle pocket block
in an embodiment of the present invention;
in the drawing: 1: ladle nozzle pocket block body; 2: microporous ceramic rod; 3:
gas chamber box; 4: gas inlet pipe; and 7: iron ring.
FIG. 3 is a schematic structural diagram of a gas chamber box in an embodiment of
the present invention;
in the drawing: 8: jack.
FIG. 4 is a schematic diagram of an argon pipeline system in an embodiment of the
present invention;
in the drawing: 1: ladle nozzle pocket block body; 4: gas inlet pipe; 9: ball valve
(including a gas source main path first ball valve 9a, an automatic branch second
ball valve 9b1, an automatic branch third ball valve 9b2, and a manual bypass fourth
ball valve 9c); 10: pressure gauge (including a first pressure gauge 10a and a second
pressure gauge 10b); 11: gas filter (including a first gas filter 11a1 and a second
gas filter 11a2); 12: pressure adjuster; 13: electromagnetic valve (including an automatic
main path first electromagnetic valve 13b and a manual bypass second electromagnetic
valve 13c); 14: special metallurgical mass flow rate controller; 15: pressure sensor
(including a gas source main path first pressure sensor 15a and an automatic branch
second pressure sensor 15b); 16: manual adjustment valve; 17: exhaust throttle valve;
and 18: gas confluence bar.
FIG. 5 is a schematic diagram of an electrical control system in an embodiment of the present invention.
Detailed Description of the Embodiments
[0039] The present invention is further described below in combination with the accompanying drawings and embodiments, but the protection scope is not limited to this.
Embodiment 1
[0040] An LF refined ladle gas-permeable upper nozzle pocket block with microporous ceramic rods is provided, as shown in FIG. 1 to FIG. 3, including a ladle nozzle pocket block body 1, microporous ceramic rods 2, a gas chamber box 3, a gas inlet pipe 4, and an iron ring 7; a steel flowing hole 5 and an upper nozzle mounting hole 6 which run through the ladle upper nozzle pocket block body from top to bottom are formed in the middle of the ladle nozzle pocket block body; ten microporous ceramic rods 2 are annularly uniformly distributed in the ladle nozzle pocket block body 1; a top end of each microporous ceramic rod 2 extends out of an upper surface of the ladle nozzle pocket block body 1; a bottom end of each microporous ceramic rod 2 extends into the gas chamber box; ten jacks 8 for fixing the microporous ceramic rods are formed in the gas chamber box; the shapes, number, and positions of the jacks correspond to the shapes, number and positions of the microporous ceramic rods; a side portion of the gas chamber box 3 is connected with the gas inlet pipe 4; one end of the gas inlet pipe is communicated with the gas chamber box, and the other end of the gas inlet pipe extends out from a side portion of the ladle nozzle pocket block body 1; the microporous ceramic rods 2 are cylindrical, a diameter d of which is 35 mm; and a height h of each ceramic rod is 140 mm.
[0041] 60 ventilation holes are formed in the microporous ceramic rods (2) along axial directions of the microporous ceramic rods; the ventilation holes are uniformly distributed on cross sections of the microporous ceramic rods; and an inner diameter of each ventilation hole is 0.1 mm.
[0042] Ten microporous ceramic rods 2 are uniformly disposed in a circular ring shape, and a diameter ⊄ of the circular ring is 300 mm.
[0043] The entire gas chamber box 3 is of a circular ring shape; the gas chamber box adopts a metal box manufactured by a steel plate with a thickness of 2.0 mm; and a cross section of the metal box is a rectangle with a width × of 50 mm and a height y of 30 mm.
[0044] A height m of the upper end of each microporous ceramic rod 2 extending out from the upper surface of the ladle nozzle pocket block body 1 is 5 mm, and a height n of the bottom end of each microporous ceramic rod 2 extending into the gas chamber box is 10 mm.
[0045] The gas-permeable upper nozzle pocket block with the microporous ceramic rods includes the iron ring 7; the iron ring 7 is buried in a surface layer of a lower portion of the ladle nozzle pocket block body 1, which effectively suppresses the problem of cracks caused by a thermal stress of the ladle upper nozzle pocket block body.
[0046] The entire iron ring (7) is circular-ring-shaped, a height L of which is 40 mm; a distance a between a lower end of the iron ring and a lower end of the ladle upper nozzle pocket block body 1 is 50 mm; and a depth z of the iron ring 7 buried in the surface layer of the ladle upper nozzle pocket block body 1 is 10 mm.
[0047] The iron ring 7 is formed by welding an iron sheet with a thickness of 1 mm; and an overlap length of a joint is 40 mm, and full welding is adopted.
[0048] The ladle nozzle pocket block body 1 is cast and formed from a chrome corundum castable, with a bulk density ≥3.0 g/cm3, a high-temperature flexural strength ≥12 Mpa, a high-temperature compressive strength ≥80 Mpa, and an AL2O3 content ≥92%, and a Cr2O3 content ≥3%.
[0049] The microporous ceramic rods 2 are fired at a high temperature in an extrusion-forming manner, and adopt zirconium oxide toughened corundum.
[0050] Longitudinal center lines of the steel flowing hole 5 and the upper nozzle mounting hole 6 and a longitudinal center line of the ladle nozzle pocket block body 1 are on one straight line; an upper portion of the steel flowing hole 5 is truncated cone shaped; a diameter d1 of an upper port of the truncated cone is 203 mm, and a diameter d2 of a lower port is 152 mm; the truncated cone has a height c of 65 mm; a lower portion of the steel flowing hole 5 is a cylindrical channel; a diameter of the lower cylindrical channel is consistent with the diameter of the lower port of the upper truncated cone; and the cylinder has a height b of 263 mm.
[0051] An upper portion of the upper nozzle mounting hole 6 is truncated cone shaped, and a fitting size of the upper nozzle mounting hole is designed according to an outline size of an upper nozzle.
[0052] The ladle nozzle pocket block body 1 is cylindrical; and the cylindrical shape has an outer diameter D of 380 mm and a height H of 470 mm.
[0053] The gas inlet pipe 4 of the present invention is made of a heat-resistant stainless steel round pipe, an end portion of which is provided with a connecting thread, and the dimension is M16×1.5.
[0054] The present invention further provides an argon blowing control device for an LF refined ladle gas-permeable upper nozzle pocket block with microporous ceramic rods. An argon pipeline system and an electrical control system are provided, having a function of selecting a manual blowing mode for a gas-permeable upper nozzle pocket block and an automatic soft blowing mode. Furthermore, by means of introducing a weighing signal for molten steel in a ladle, an argon flow rate is synchronously adjusted according to a change in a net weight of the molten steel in the ladle, and the argon blowing flow rate for the gas-permeable upper nozzle pocket block is accurately controlled.
[0055] The argon pipeline system, as shown in FIG. 4, is divided into a gas source main path, an automatic branch, a manual bypass, and a release branch; the gas source main path, the automatic branch, and the manual bypass are communicated through a gas confluence bar 18; the gas source main path includes a gas source main path first ball valve 9a, a first pressure gauge 10a, a first gas filter 11a1, a second gas filter 11a2, a pressure adjuster 12, and a first pressure sensor 15a in sequence; the automatic branch includes an automatic branch second ball valve 9b1, a first electromagnetic valve 13b, a special metallurgical mass flow rate controller 14, a second pressure sensor 15b, a second pressure gauge 10b, and an automatic branch third ball valve 9b2 in sequence; the manual bypass includes a manual bypass fourth ball valve 9c and a manual adjustment valve 16 in sequence; and the manual bypass is connected in parallel with the second ball valve 9b1, the second electromagnetic valve 13b, and the special metallurgical mass flow rate controller 14 to perform manual operation and application after the automatic branch fails. The argon pipeline system in the present invention is further used for high-pressure blowing through before automatic argon blowing of the LF refined ladle gas-permeable upper nozzle pocket block with the microporous ceramic rods. In the present invention, the release branch is also arranged at a rear end of the manual adjustment valve 16, and includes a second electromagnetic valve 13c and an exhaust throttle valve 17 in sequence to discharge gas and release pressure when a gas inlet metal hose connected to the gas-permeable upper nozzle pocket block needs to be plugged.
[0056] The electrical control system adopts the existing technology, including a network switch, an argon blowing control system PLC, a touch screen, and a continuous casting basic automation system; the argon blowing control system PLC and the touch screen are arranged in a control box; the argon blowing control system PLC, the touch screen, and the continuous casting basic automation system are all connected to the network switch through Ethernet communication; a weighing system for molten steel in a ladle collects and sends a weight of the molten steel in the ladle to the continuous casting basic automation system, and uploads the weight to the argon blowing control system PLC through the Ethernet communication and the network switch, as shown in FIG. 5.
[0057] The elements in the argon pipeline system are all purchased from the market. The type specification of the ball valve 9 (including the gas source main path first ball valve 9a, the automatic branch second ball valve 9b1, the automatic branch third ball valve 9b2, and the manual bypass fourth ball valve 9c) is DN20 63bar 304SS G1; the type specification of the pressure gauge 10 (including the first pressure gauge 10a and the second pressure gauge 10b) is YT60; the type specification of the gas filter 11 (including the first gas filter 11a1 and the second gas filter 11a2) is AF60-F10, G1, with a filtering level of 5 um and pressure bearing capability of 3.0 MPa, having a manual water drainage function; the type specification of the pressure adjuster 12 is BK201-25, with a withstand pressure of 40 bar and a pressure adjustment range of 0.5-25bar; the type specification of the electromagnetic valve 13 (including the automatic main path first electromagnetic valve 13b and the manual bypass second electromagnetic valve 13c) is DC24V, G1/2 MS; the type specification of the special metallurgical mass flow rate controller 14 is FLOX[on]62, IP65, with a flow rate of 200 NL/min; the type specification of the pressure sensor 15 (including the gas source main path first pressure sensor 15a and the automatic branch second pressure sensor 15b) is PT5403, 0-25bar G1/4, 4-20mA 316L; the type specification of the manual adjustment valve 16 is PN50; the type specification of the exhaust throttle valve 17 is G1/2 MS, 25bar; and the type specification of the gas confluence bar 18 is 3.0MPa G1/2.
[0058] The elements in the electrical control system are all purchased from the market. The type specification of the PLC control system is Siemens S7, PLC S7200-Smart, containing accessories such as AI, AO, DI, and DO; and the type specification of the touch screen is a Siemens 7-inch touch screen.
[0059] An argon blowing control method using the above-mentioned LF refined ladle gas-permeable upper nozzle pocket with the microporous ceramic rods, and the argon blowing control device includes the following steps:
This embodiment is used for pouring a 130t LF refined ladle to produce ultralow-carbon aluminum killed steel DC04.
[0060] In the first step: an initial flow rate value of soft blowing of a full ladle before initial application is measured: during soft blowing of the full ladle at the later stage of LF refining in the existing technology, argon of an original ladle bottom-blowing gas-permeable block is shut off; argon to the above gas-permeable upper nozzle pocket block is connected; the argon flow rate is gradually increased, and it is observed that the molten steel level in the ladle slightly fluctuates, wherein an argon blowing flow rate value when the molten liquid level is not exposed is the initial flow rate value of the soft blowing of the full ladle, and the initial flow rate value is 45 NL/min.
[0061] In a second step, after the ladle is at a pouring position on a continuous casting ladle turntable, the gas inlet pipe 4 of the above-mentioned gas-permeable upper nozzle pocket block is communicated to a gas source outlet of an argon control device using a metal hose; the ladle is transferred to the pouring position for pouring and flowing; the above-mentioned gas-permeable upper nozzle pocket block is blown through immediately using the manual bypass in the argon pipeline system: the pressure is gradually increased by 3 mbar at each time by adjusting the pressure adjuster 12 of the gas source main path in the argon pipeline system until the above-mentioned gas-permeable upper nozzle pocket block is blown through.
[0062] When the gas-permeable upper nozzle pocket block is blocked, a pressure displayed on the second pressure gauge 10b is greater than or equal to 1200 mbar; the pressure adjuster 12 of the gas source main path in the argon pipeline system is adjusted to gradually increase the pressure, and the pressure value displayed on the second pressure gauge 10b continuously increases until the gas-permeable nozzle pocket block is blown through, the pressure value displayed on the second pressure gauge 10b starts to gradually decrease.
[0063] In a third step, different automatic soft blowing modes are selected according to different control requirements for inclusions in steel:
if the ultralow-carbon aluminum killed steel DC04 is a high-end steel grade with strict inclusion control, automatic soft blowing mode C is selected: the automatic soft blowing mode is enabled immediately after the gas-permeable upper nozzle pocket block is blown through; argon is blown using the automatic main path in the argon pipeline system, and an argon flow rate is linearly adjusted according to the change of the net weight of the molten steel in the ladle, a set value of an argon flow rate in a molten steel pouring process = the net weight of the remaining molten steel in the ladle ÷ the net weight of the molten steel in the full ladle × the initial flow rate value 45 NL/min during soft blowing of the full ladle in the step I + 5 NL/min; argon is blown at the flow rate of 5 NL/min after it is found that the ladle has slag entrapment or a slag entrapment detection system sounds an alarm; and the argon blowing is stopped after the ladle is transferred back to the pouring position of the continuous casting turntable.
Embodiment 2
[0064] A difference from the LF refined ladle gas-permeable upper nozzle pocket block with the microporous ceramic rods of Embodiment 1 is as follows:
The microporous ceramic rods 2 are cylindrical, a diameter d of which is 45 mm, and a height h of each ceramic rod is 180 mm. 120 ventilation holes are formed in the microporous ceramic rods 2, and an inner diameter of each ventilation hole is 0.075 mm. Six microporous ceramic rods 2 are uniformly disposed in a circular ring shape, and a diameter ⊄ of the circular ring is 320 mm.
[0065] The entire gas chamber box 3 is of a circular ring shape; the gas chamber box adopts a metal box manufactured by a steel plate with a thickness of 1.5 mm; and a cross section of the metal box is a rectangle with a width x of 60 mm and a height y of 40 mm.
[0066] A height m of the upper end of each microporous ceramic rod 2 extending out from the upper surface of the ladle nozzle pocket block body 1 is 10mm, and a height n of the bottom end of each microporous ceramic rod 2 extending into the gas chamber box is 5mm.
[0067] The entire iron ring (7) is circular-ring-shaped, a height L of which is 50mm; a distance a between a lower end of the iron ring and a lower end of the ladle upper nozzle pocket block body 1 is 60mm; and a depth z of the iron ring 7 buried in the surface layer of the ladle upper nozzle pocket block body 1 is 20mm.
[0068] The iron ring 7 is formed by welding an iron sheet with a thickness of 1 mm; and an overlap length of a joint is 50mm, and full welding is adopted.
[0070] Longitudinal center lines of the steel flowing hole 5 and the upper nozzle mounting hole 6 and a longitudinal center line of the ladle nozzle pocket block body 1 are on one straight line; an upper portion of the steel flowing hole 5 is truncated cone shaped; a diameter d1 of an upper port of the truncated cone is 210mm, and a diameter d2 of a lower port is 160mm; the truncated cone has a height c of 80mm; a lower portion of the steel flowing hole 5 is a cylindrical channel; a diameter of the lower cylindrical channel is consistent with the diameter of the lower port of the upper truncated cone; and the cylinder has a height b of 270mm.
[0071] The ladle nozzle pocket block body 1 is cylindrical; and the cylindrical shape has an outer diameter D of 400mm and a height H of 490mm.
[0072] An argon blowing control method using the above-mentioned LF refined ladle gas-permeable upper nozzle pocket with the microporous ceramic rods, and the argon blowing control device includes the following steps:
This embodiment is used for pouring a 130t LF refined ladle to produce ultralow-carbon aluminum killed steel SPHC.
[0073] In the first step: an initial flow rate value of soft blowing of a full ladle before initial application is measured: during soft blowing of the full ladle at the later stage of LF refining in the existing technology, argon of an original ladle bottom-blowing gas-permeable block is shut off; argon to the above gas-permeable upper nozzle pocket block is connected; the argon flow rate is gradually increased, and it is observed that the molten steel level in the ladle slightly fluctuates, wherein an argon blowing flow rate value when the molten liquid level is not exposed is the initial flow rate value of the soft blowing of the full ladle, and the initial flow rate value is 42 NL/min.
[0074] In a second step, after the ladle is at a pouring position on a continuous casting ladle turntable, the gas inlet pipe 4 of the above-mentioned gas-permeable upper nozzle pocket block is communicated to a gas source outlet of an argon control device using a metal hose; the ladle is transferred to the pouring position for pouring and flowing; the above-mentioned gas-permeable upper nozzle pocket block is blown through immediately using the manual bypass in the argon pipeline system: the pressure is gradually increased by 5 mbar at each time by adjusting the pressure adjuster 12 of the gas source main path in the argon pipeline system until the above-mentioned gas-permeable upper nozzle pocket block is blown through.
[0075] In a third step, different automatic soft blowing modes are selected according to different control requirements for inclusions in steel:
If the low-carbon aluminum killed steel SPHC is a medium-end steel grade with an inclusion control requirement, automatic soft blowing mode B is selected: the automatic soft blowing mode is enabled immediately after the gas-permeable upper nozzle pocket block is blown through; argon is blown using the automatic main path in the argon pipeline system, and an argon flow rate is linearly adjusted according to the change of the net weight of the molten steel in the ladle, a set value of an argon flow rate in a molten steel pouring process = the net weight of the remaining molten steel in the ladle ÷ the net weight of the molten steel in the full ladle × the initial flow rate value 42 NL/min during soft blowing of the full ladle in the step I + 3 NL/min; argon is blown at the flow rate of 3 NL/min after the pouring volume of the molten steel reaches 60% of the total volume of the molten steel in the ladle; and the argon blowing is stopped after the ladle is transferred back to the pouring position of the continuous casting turntable.
Embodiment 3
[0076] A difference from the LF refined ladle gas-permeable upper nozzle pocket block with the microporous ceramic rods of Embodiment 1 is as follows:
The microporous ceramic rods 2 are cylindrical, a diameter d of which is 40 mm, and a height h of each ceramic rod is 160 mm. 105 ventilation holes are formed in the microporous ceramic rods 2, and an inner diameter of each ventilation hole is 0.085 mm. Eight microporous ceramic rods 2 are uniformly disposed in a circular ring shape, and a diameter ⊄ of the circular ring is 310 mm.
[0077] The entire gas chamber box 3 is of a circular ring shape; the gas chamber box adopts a metal box manufactured by a steel plate with a thickness of 1.8 mm; and a cross section of the metal box is a rectangle with a width x of 55mm and a height y of 35 mm.
[0078] A height m of the upper end of each microporous ceramic rod 2 extending out from the upper surface of the ladle nozzle pocket block body 1 is 7 mm, and a height n of the bottom end of each microporous ceramic rod 2 extending into the gas chamber box is 7 mm.
[0079] The entire iron ring (7) is circular-ring-shaped, a height L of which is 45 mm; a distance a between a lower end of the iron ring and a lower end of the ladle upper nozzle pocket block body 1 is 55 mm; and a depth z of the iron ring 7 buried in the surface layer of the ladle upper nozzle pocket block body 1 is 15 mm.
[0080] Longitudinal center lines of the steel flowing hole 5 and the upper nozzle mounting hole 6 and a longitudinal center line of the ladle nozzle pocket block body 1 are on one straight line; an upper portion of the steel flowing hole 5 is truncated cone shaped; a diameter d1 of an upper port of the truncated cone is 190mm, and a diameter d2 of a lower port is 140mm; the truncated cone has a height c of 55mm; a lower portion of the steel flowing hole 5 is a cylindrical channel; a diameter of the lower cylindrical channel is consistent with the diameter of the lower port of the upper truncated cone; and the cylinder has a height b of 250mm.
[0081] The ladle nozzle pocket block body 1 is cylindrical; and the cylindrical shape has an outer diameter D of 390mm and a height H of 480mm.
[0082] An argon blowing control method using the above-mentioned LF refined ladle gas-permeable upper nozzle pocket with the microporous ceramic rods, and the argon blowing control device includes the following steps:
This embodiment is used for pouring a 130t LF refined ladle to produce Q345B.
[0083] In a first step: an initial flow rate value of soft blowing of a full ladle before initial application is measured: during soft blowing of the full ladle at the later stage of LF refining in the existing technology, argon of an original ladle bottom-blowing gas-permeable block is shut off; argon to the above gas-permeable upper nozzle pocket block is connected; the argon flow rate is gradually increased, and it is observed that the molten steel level in the ladle slightly fluctuates, wherein an argon blowing flow rate value when the molten liquid level is not exposed is the initial flow rate value of the soft blowing of the full ladle, and the initial flow rate value is 40 NL/min.
[0084] In a second step, after the ladle is at a pouring position on a continuous casting ladle turntable, the gas inlet pipe 4 of the above-mentioned gas-permeable upper nozzle pocket block is communicated to a gas source outlet of an argon control device using a metal hose; the ladle is transferred to the pouring position for pouring and flowing; the above-mentioned gas-permeable upper nozzle pocket block is blown through immediately using the manual bypass in the argon pipeline system: the pressure is gradually increased by 7 mbar at each time by adjusting the pressure adjuster 12 of the gas source main path in the argon pipeline system until the above-mentioned gas-permeable upper nozzle pocket block is blown through.
[0085] In a third step, different automatic soft blowing modes are selected according to different control requirements for inclusions in steel:
If the Q345B is a low-end steel grade without an inclusion control requirement, automatic soft blowing mode A is selected: the automatic soft blowing mode is enabled immediately after the gas-permeable upper nozzle pocket block is blown through; argon is blown using the automatic main path in the argon pipeline system, and an argon flow rate is linearly adjusted according to the change of the net weight of the molten steel in the ladle, a set value of an argon flow rate in a molten steel pouring process = the net weight of the remaining molten steel in the ladle ÷ the net weight of the molten steel in the full ladle × the initial flow rate value 40 NL/min during soft blowing of the full ladle in the step I + 2 NL/min; argon is blown at the flow rate of 2 NL/min after the pouring volume of the molten steel reaches 30% of the total volume of the molten steel in the ladle; and the argon blowing is stopped after the ladle is transferred back to the pouring position of the continuous casting turntable.
Comparative example 1
[0086] A difference from Embodiment 1 is that the ladle gas-permeable upper nozzle pocket block disclosed in Embodiment 1 in Chinese patent document CN104028739B (patent number: 201410274221.8) is used to replace the gas-permeable upper nozzle pocket block with microporous ceramic rods in Embodiment 1, and other contents are all the same.
Comparative example 2
[0087] A difference from Embodiment 2 is that the ladle gas-permeable upper nozzle pocket block disclosed in Embodiment 2 in Chinese patent document CN104028739B (patent number: 201410274221.8) is used to replace the gas-permeable upper nozzle pocket block with microporous ceramic rods in Embodiment 2, and other contents are all the same.
Comparative example 3
[0088] A difference from Embodiment 3 is that the ladle gas-permeable upper nozzle pocket block disclosed in Embodiment 3 in Chinese patent document CN104028739B (patent number: 201410274221.8) is used to replace the gas-permeable upper nozzle pocket block with microporous ceramic rods in Embodiment 3, and other contents are all the same.
Comparative example 4
[0089] A difference from Embodiment 2 is that the argon blowing control method for the nozzle pocket block is different. The argon blowing control method using the circumferential weld type gas-permeable upper nozzle block disclosed in Embodiment 2 in Chinese patent document CN109719290 (patent number: 2019101296742.1) is used to replace the argon blowing control method using the ladle gas-permeable upper nozzle pocket block with the microporous ceramic rods in Embodiment 2, and other contents are all the same.
Experimental case
[0090] The applications of Embodiments 1-3 to a slab continuous casting machine of a certain steel works to produce the ultralow-carbon aluminum killed steel DC04, the ultralow-carbon aluminum killed steel SPHC, and plain carbon steel Q345B are compared with the applications of the technical solutions of comparative examples 1-4. A large electrolytic test sample is taken from the 1/4 position of a cast slab and is machined into a round rod with a diameter of 60 mm and a height of 100 mm; large electrolytic inclusion detection and comparison are performed; the same slag entrapment detection system is set when the pouring remains of the molten steel for producing the ultralow-carbon aluminum killed steel DC04 are compared and measured. Comparison results are shown in the following table 1.
Table 1 t
| Item | Steel grade | Content (mg/10kg) of large electrolytic inclusion of the cast slab | Pouring remain (ton/pack age) of the molten steel in the ladle | Average temperature drop (°C/min ) of the molten steel in the ladle in the soft blowin 9 process | Average life(batch) of the ladle gas-permeable upper nozzle pocket block | One-time blow-through rate (%) of the ladle gas-permeable upper nozzle pocket block | Oxygen burning -free blowing rate (%) of the ladle gas-permeable upper nozzle pocket block |
| Embodiment 1 | DC04 | 0.84 | 0.44 | 0.17 | 51 | 99.1 | 30 |
| Embodiment 2 | SPHC | 1.37 | / | 0.14 | 99.2 | 32 | |
| Embodiment 3 | Q345B | 2.43 | / | 0.11 | 99.6 | 35 | |
| Comparative example 1 | DC04 | 1.07 | 0.56 | 0.28 | 47 | 92.1 | 26 |
| Comparative example 2 | SPHC | 1.72 | / | 0.26 | 93.7 | 28 | |
| Comparative example 3 | Q345B | 3.57 | / | 0.24 | 91.3 | 27 | |
| Comparative example 4 | SPHC | 1.68 | / | 0.20 | 49 | 88.1 | 19 |
[0091] By means of comparing the data in the above table 1, compared with the ladle gas-permeable upper nozzle pocket block provided in the comparative example CN104028739A (patent number: 201410274221.8), the ladle gas-permeable upper nozzle pocket block with the microporous ceramic rods in the present invention is hard to block and easy to blow through; the weight of electrolytic inclusions of a continuous casting slab test sample is reduced by 20% or above on year-on-year basis; the average temperature drop of the molten steel in the ladle is reduced by 0.1 °C/min or above on year-on-year basis; the oxygen burning-free blowing rate of the ladle gas-permeable upper nozzle pocket block is increased by 4% on year-on-year basis; the pouring remain of the molten steel is reduced by 20% or above on year-on-year basis; and the average life of the ladle nozzle pocket block is prolonged by 4 batches on year-on-year basis. Compared with the argon blowing method for the ladle gas-permeable upper nozzle pocket block provided in the comparative example CN109719290A (patent number: 2019101296742.1), the argon blowing control method for the ladle gas-permeable upper nozzle pocket block in the present invention has the advantages that the average temperature drop of the molten steel in the ladle is reduced by 0.06 °C/min on year-on-year basis; the one-time blow-through rate of the ladle gas-permeable upper nozzle pocket block is increased by 11% on year-on-year basis; and the oxygen burning-free blowing rate of the ladle gas-permeable upper nozzle pocket block is increased by 13% on year-on-year basis.
[0092] A continuous casting tundish of a slab of a certain steel works is used as an experimental research object. According to the same research method, a water phantom experiment and a mathematical model research are carried out on the ladle gas-permeable upper nozzle pocket block with the microporous ceramic rods in the present invention and the ladle circumferential weld type gas-permeable upper nozzle block in Chinese patent document CN109719290A (application number: 2019101296742.1). Research results of the water phantom experiment show that when a simulated argon blowing volume under a normal process condition is 3 NL/min, the diameter, measured in the water phantom experiment, of the bubbles near the ceramic rods in the present invention is less than 1.8 mm, and the diameter of the bubbles near the circumferential weld in Chinese patent document CN109719290A is less than 2 mm. Results of the mathematical model research show that the inclusion removal rate of the ladle gas-permeable upper nozzle pocket block with the microporous ceramic rods in the present invention is 54-67%, and the inclusion removal rate of the ladle circumferential weld type gas-permeable upper nozzle block in Chinese patent document CN109719290A is 37-48%.
1. An LF refined ladle gas-permeable upper nozzle pocket block with microporous ceramic
rods, comprising a ladle nozzle pocket block body (1), microporous ceramic rods (2),
a gas chamber box (3), a gas inlet pipe (4), a steel flowing hole (5), and an upper
nozzle mounting hole (6), wherein
the steel flowing hole (5) and the upper nozzle mounting hole (6) run through, and are mounted in the middle of the ladle nozzle pocket block body (1);
the gas chamber box (3) is buried in a surface layer of an upper portion of the ladle nozzle pocket block body (1); a plurality of jacks (8) are formed in the gas chamber box (3); the jacks (8) are used for fixing the microporous ceramic rods (2);
a plurality of microporous ceramic rods (2) are annularly uniformly distributed in the ladle nozzle pocket block body (1); a top end of each microporous ceramic rod (2) extends out of an upper surface of the ladle nozzle pocket block body (1); a bottom end of each microporous ceramic rod (2) extends into the gas chamber box (3); the shapes, number, and positions of the jacks (8) correspond to the shapes, number and positions of the microporous ceramic rods (2);
one end of the gas inlet pipe (4) is communicated to a side portion of the gas chamber box (3), and the other end of the gas inlet pipe extends out from a side portion of the ladle nozzle pocket block body (1).
2. The nozzle pocket block according to claim 1, wherein the microporous ceramic rods
(2) are cylindrical, a diameter d of which is 35-45 mm; and a height h of each ceramic
rod is 140-180 mm.
3. The nozzle pocket block according to claim 1, wherein the gas-permeable upper nozzle
pocket block with the microporous ceramic rods comprises an iron ring (7); and the
iron ring (7) is buried in a surface layer of a lower portion of the ladle upper nozzle
pocket block body (1).
4. The nozzle pocket block according to claim 3, wherein the entire iron ring (7) is
circular-ring-shaped, a height L of which is 40-50 mm; a distance a between a lower
end of the iron ring and a lower end of the ladle upper nozzle pocket block body (1)
is 50-60 mm; and a depth z of the iron ring (7) buried in the surface layer of the
ladle upper nozzle pocket block body (1) is 10-20 mm.
5. The nozzle pocket block according to claim 3, wherein the iron ring (7) is formed
by welding an iron sheet with a thickness of 1 mm; and an overlap length of a joint
is 40-50 mm, and full welding is adopted.
6. The nozzle pocket block according to claim 1, wherein 60-120 ventilation holes are
formed in the microporous ceramic rods (2) along an axial directions of the microporous
ceramic rods; the ventilation holes are uniformly distributed on cross sections of
the microporous ceramic rods; an inner diameter of each ventilation hole is 0.075-0.1
mm; and the ventilation holes longitudinally run through upper end faces and lower
end faces of the microporous rods;
six to ten microporous ceramic rods (2) are uniformly disposed in a circular ring shape, and a diameter ⊄ of the circular ring is 300-320 mm.
six to ten microporous ceramic rods (2) are uniformly disposed in a circular ring shape, and a diameter ⊄ of the circular ring is 300-320 mm.
7. The nozzle pocket block according to claim 1, wherein a height m of the upper end
of each microporous ceramic rod (2) extending out from the upper surface of the ladle
nozzle pocket block body (1) is 5-10 mm, and a height n of the bottom end of each
microporous ceramic rod (2) extending into the gas chamber box is 5-10 mm.
8. The nozzle pocket block according to claim 1, wherein the microporous ceramic rods
(2) are fired at a high temperature in an extrusion-forming manner, and adopt zirconium
oxide toughened corundum or zirconium oxide toughened corundum mullite.
9. The nozzle pocket block according to claim 1, wherein the entire gas chamber box (3)
is of a circular ring shape; the gas chamber box adopts a metal box manufactured by
a steel plate with a thickness of 1.5-2.0 mm; a longitudinal section of the metal
box is a rectangle with a width x of 50-60 mm and a height y of 30-40 mm; a cross
section of the metal box is a circular ring; and the plurality of jacks (8) are uniformly
distributed on the circular ring.
10. The nozzle pocket block according to claim 1, wherein the ladle nozzle pocket block
body (1) is cast and formed from a chrome corundum castable, with a bulk density ≥3.0
g/cm3, a high-temperature flexural strength ≥12Mpa, a high-temperature compressive
strength ≥80 Mpa, and an AL2O3 content ≥92%, and a Cr2O3 content ≥3%.
11. The nozzle pocket block according to claim 1, wherein longitudinal center lines of
the steel flowing hole (5) and the upper nozzle mounting hole (6) and a longitudinal
center line of the ladle nozzle pocket block body (1) are on one straight line; an
upper portion of the steel flowing hole (5) is truncated cone shaped; a diameter d1
of an upper port of the truncated cone is 190-210 mm, and a diameter d2 of a lower
port is 140-160 mm; the truncated cone has a height c of 55-80 mm; a lower portion
of the steel flowing hole (5) is a cylindrical channel; a diameter of the lower cylindrical
channel is consistent with the diameter of the lower port of the upper truncated cone;
the cylinder has a height b of 250-270 mm.
12. The nozzle pocket block according to claim 1, wherein an upper portion of the upper
nozzle mounting hole (6) is truncated cone shaped, and a fitting size of the upper
nozzle mounting hole is designed according to an outline size of an upper nozzle;
the ladle nozzle pocket block body (1) is cylindrical; and the cylindrical shape has an outer diameter D of 380-400 mm and a height H of 470-490 mm.
the ladle nozzle pocket block body (1) is cylindrical; and the cylindrical shape has an outer diameter D of 380-400 mm and a height H of 470-490 mm.
13. An argon blowing control device for a gas-permeable upper nozzle pocket block, wherein
an argon pipeline system and an electrical control system are provided, having a functional
module of selecting a manual blowing mode for a gas-permeable upper nozzle pocket
block and an automatic soft blowing mode, receiving a weighing signal for molten steel
in a ladle, calculating a change in a net weight of the molten steel in the ladle,
and synchronously adjusting an argon flow rate;
the gas-permeable upper nozzle pocket block is the gas-permeable upper nozzle pocket block with the microporous ceramic rods according to claim 1.
the gas-permeable upper nozzle pocket block is the gas-permeable upper nozzle pocket block with the microporous ceramic rods according to claim 1.
14. The argon blowing control device according to claim 13, wherein the argon pipeline
system is divided into a gas source main path, an automatic branch, a manual bypass,
and a release branch; the gas source main path, the automatic branch, and the manual
bypass are communicated through a gas confluence bar (18); wherein
the gas source main path comprises a gas source main path first ball valve (9a), a first pressure gauge (10a), a first gas filter (11a1), a second gas filter (11a2), a pressure adjuster (12), and a first pressure sensor (15a) in sequence;
the automatic branch comprises an automatic branch second ball valve (9b1), a first electromagnetic valve (13b), a special metallurgical mass flow rate controller (14), a second pressure sensor (15b), a second pressure gauge (10b), and an automatic branch third ball valve (9b2) in sequence;
the manual bypass comprises a manual bypass fourth ball valve (9c) and a manual adjustment valve (16) in sequence;
the manual bypass is connected in parallel with the automatic branch second ball valve(9b1), the second electromagnetic valve (13b), and the special metallurgical mass flow rate controller (14) to perform manual operation and application after the automatic branch fails;
the release branch is further arranged at a rear end of the manual adjustment valve (16), and comprises a second electromagnetic valve (13c) and an exhaust throttle valve (17) in sequence to discharge gas and release pressure when a gas inlet metal hose connected to the gas-permeable upper nozzle pocket block needs to be plugged.
15. The argon blowing control device according to claim 13, wherein the electrical control
system comprises a network switch, an argon blowing control system PLC, a touch screen,
and a continuous casting basic automation system; the argon blowing control system
PLC and the touch screen are arranged in a control box; the argon blowing control
system PLC, the touch screen, and the continuous casting basic automation system are
all connected to the network switch through Ethernet communication; a weighing system
for molten steel in a ladle collects and sends a weight of the molten steel in the
ladle to the continuous casting basic automation system, and uploads the weight to
the argon blowing control system PLC through the Ethernet communication and the network
switch.
16. An argon blowing control method, comprising the following steps:
in a first step, applying the argon blowing control device of claim 13 for the first time to measure an initial flow rate value of soft blowing of a full-ladle gas-permeable upper nozzle pocket block, wherein the gas-permeable upper nozzle pocket block is the gas-permeable upper nozzle pocket block with the microporous ceramic rods according to claim 1;
in a second step, communicating, after the ladle is at a pouring position on a continuous casting ladle turntable, the gas inlet pipe (4) of the above-mentioned gas-permeable upper nozzle pocket block to a gas source outlet of an argon control device using a metal hose; transferring the ladle to the pouring position for pouring and flowing, and then blowing through the above-mentioned gas-permeable upper nozzle pocket block immediately using the manual bypass in the argon pipeline system: gradually increasing the pressure by 1-10 mbar at each time by adjusting the pressure adjuster 12 of the gas source main path in the argon pipeline system until the above-mentioned gas-permeable upper nozzle pocket block is blown through; and
in a third step, enabling, according to different control requirements for inclusions in steel, different automatic soft blowing modes immediately after the gas-permeable upper nozzle pocket block is blown through in the second step; blowing argon using the automatic main path in the argon pipeline system, and linearly adjusting an argon flow rate according to the change of the net weight of the molten steel in the ladle,
a set value of an argon flow rate in a molten steel pouring process = the net weight of the remaining molten steel in the ladle ÷ the net weight of the molten steel in the full ladle × the initial flow rate value during soft blowing of the full ladle in the first step + (2-5) NL/min;
blowing argon at the flow rate of 2-5 NL/min after the pouring volume of the molten steel reaches 30-100% of the total volume of the molten steel in the ladle; and stopping the argon blowing after the pouring of the ladle is completed and the ladle is transferred back to the pouring position of the continuous casting turntable.
17. The argon blowing control method according to claim 16, wherein the first step of
measuring an initial flow rate value of soft blowing of a full-ladle gas-permeable
upper nozzle pocket block comprises: during soft blowing of the full ladle at the
later stage of LF refining in the existing technology, shutting off argon of an original
ladle bottom-blowing gas-permeable block, connecting argon to the gas-permeable upper
nozzle pocket block, gradually increasing the argon flow rate, and observing that
the molten steel level in the ladle slightly fluctuates, wherein an argon blowing
flow rate value when the molten liquid level is not exposed is the initial flow rate
value of the soft blowing of the full ladle;
the third step of selecting different automatic soft blowing modes according to different control requirements for the inclusions in the steel comprises:
the third step of selecting different automatic soft blowing modes according to different control requirements for the inclusions in the steel comprises:
(1) selecting automatic soft blowing mode A for a low-end steel grade without an inclusion control requirement: enabling the automatic soft blowing mode immediately after the gas-permeable upper nozzle pocket block is blown through; blowing argon using the automatic main path in the argon pipeline system, and linearly adjusting an argon flow rate according to the change of the net weight of the molten steel in the ladle, a set value of an argon flow rate in a molten steel pouring process = the net weight of the remaining molten steel in the ladle ÷ the net weight of the molten steel in the full ladle × the initial flow rate value during soft blowing of the full ladle in the first step + (2-5) NL/min; blowing argon at the flow rate of 2-5 NL/min after the pouring volume of the molten steel reaches 30-40% of the total volume of the molten steel in the ladle; and stopping the argon blowing after the pouring of the ladle is completed and the ladle is transferred back to the pouring position of the continuous casting turntable;
(2) selecting automatic soft blowing mode B for a medium-end steel grade with an inclusion control requirement: enabling the automatic soft blowing mode immediately after the gas-permeable upper nozzle pocket block is blown through; blowing argon using the automatic main path in the argon pipeline system, and linearly adjusting an argon flow rate according to the change of the net weight of the molten steel in the ladle, a set value of an argon flow rate in a molten steel pouring process = the net weight of the remaining molten steel in the ladle ÷ the net weight of the molten steel in the full ladle × the initial flow rate value during soft blowing of the full ladle in the second step + (2-5) NL/min; blowing argon at the flow rate of 2-5 NL/min after the pouring volume of the molten steel reaches 50-60% of the total volume of the molten steel in the ladle; and stopping the argon blowing after the pouring of the ladle is completed and the ladle is transferred back to the pouring position of the continuous casting turntable; and
(3) selecting automatic soft blowing mode C for a high-end steel grade with strict inclusion control: enabling the automatic soft blowing mode immediately after the gas-permeable upper nozzle pocket block is blown through; blowing argon using the automatic main path in the argon pipeline system, and linearly adjusting an argon flow rate according to the change of the net weight of the molten steel in the ladle, a set value of an argon flow rate in a molten steel pouring process = the net weight of the remaining molten steel in the ladle ÷ the net weight of the molten steel in the full ladle × the initial flow rate value during soft blowing of the full ladle in the second step + (2-5) NL/min; blowing argon at the flow rate of 2-5 NL/min after it is found that the ladle has slag entrapment or a slag entrapment detection system sounds an alarm; and stopping the argon blowing after the ladle is transferred back to the pouring position of the continuous casting turntable.
REFERENCES CITED IN THE DESCRIPTION
This list of references cited by the applicant is for the reader's convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.
Patent documents cited in the description
- CN104028739A [0003] [0007] [0037] [0091]
- CN201410274221 [0003] [0037]
- CN109719290A [0004] [0037] [0037] [0037] [0091] [0092] [0092] [0092]
- CN2019101296742 [0004] [0089]
- CN106041044A [0005]
- CN201610634268X [0005] [0026] [0037]
- CN106041044B [0026] [0037]
- CN104028739B [0026] [0037] [0037] [0086] [0087] [0088]
- CN201410274221A [0037] [0091]
- CN2019101296742A [0037] [0037] [0037] [0091] [0092]
- CN201410274221B [0086] [0087] [0088]
- CN109719290 [0089]