A tundish for steel casting

Abstract

 A tundish for steel casting in which overflow beams and underflow beams are disposed, characterized in that said beams base on refractory materials and have a composition consisting of 0.5-5% by weight of fibrous materials, 1-20% by weight of at least one of aluminium, magnesium and silicon carbide and 1 -10% by weight of binders, and they are shaped in such a way that water content is sucked and removed from the beams by a wet process.

Description

[0001] This invention relates to a tundish for steel casting, in which underflow beams and overflow beams are disposed to accelerate the float-up and separation of the non-metallic inclusions in the steel melt.

[0002] A tundish for steel casting plays an important role such as removing the inclusions in the steel melt, control- ing and stabilizing the flow of the molten steel when the melt is poured into a mold, and making the temperature of the molten steel uniform.

[0003] Particularly, whether the inclusions are removed or not gives a great influence upon the quality of steel so that it is necessary to pour a purified molten steel into the mold.

[0004] As a means of removing the inclusions there is generally carried out a method in which beams are disposed within a tundish for steel casting thereby to extend the flow passes of the molten steel, and by taking the advantage of the stay time of the melt within the tundish the inclusions in the molten steel are floated up for removal.

[0005] Conventionally, most of the beams are formed by a casting process, a casting process under vibration or a pressurizing process after a binder is added to a refractory material, but such known beams have many problems such that they are inferior in corrosion resistancy and compressive strength, an explosive breaking is likely to occur at pre-heating, and they are of heavy weight so that the working properties at the time of making them are bad.

[0006] The object of the invention is to improve said problematical matters and to dispose within a tundish for steel casting, as overflow beams and underflow beams, beams which base on refractory materials, which consist of 0.5 - 5% by weight of fibrous materials and 1 - 10% by weight of binders and which are formed in such a way that water content is sucked and removed by a wet process.

[0007] The beams formed by sucking and removing water content by a wet process have a more uniform structure than the known beams made by conventional casting process or pressurizing process, and they become porous so as to be light.

[0008] Accordingly, not only the workability at the time of making the beams are improved but also it is possible to reduce the temperature fall of the molten steel at the initial period of pouring, which fall is caused by said beams, thanks to the reduced thermal capacity based on the porosity.

[0009] As the refractory materials of the beam composition there are selected from at least one of the basic refractories such as magnesia, calcia, dolomite, chrome magnesia, and magnesia chrome.

[0010] On the other hand, as the fibrous materials there are selected from at least one of the inorganic fibers such as asbestos, rock wool, slag wool, glass wool, alumina fiber, magnesia fiber, silicon carbide fiber and zirconium fiber and/or organic fibers such as pulp, cotton fiber, hemp fiber, synthetic fiber, regenerated fiber and floss-silk, and they are employed in the range 0.5 - 5% by weight.

[0011] With the fibrous materials of less than 0.5% by weight in use the effect is not sufficient for the improvement of hardness and refractory property, which is the principal object of the invention, and to use them in excess of 5% by weight presents an unfavorable shaping.

[0012] Further, there are selected from at least one of aluminium, magnesium and silicon carbide and they are used in the range 1 - 20% by weight.

[0013] The object of adding these materials is to improve the compressive strength and corrosion resistancy by accelerating the shintering of the beams. Less than 1% by weight of them will not produce an effect while more than 20% by weight thereof will reduce the mixing ratio of other materials thereby to reversely deteriorate the compressive strength and corrosion resistancy.

[0014] In respect of the binders there are added at least one of the inorganic binders such as magnesium sulphate, magnesium chloride, sodium phosphate, potassium phosphate, aluminium phosphate, sodium silicate and potassium silicate, and they are used in the range 1 - 10% by weight.

[0015] If they are less than 1% by weight a sufficient effect as binders is not obtained, and even if they are used exceeding 10% by weight they will not produce any significant effect and rather due to the reduced mixing ratio of the refractory materials and fibrous materials by the binders added in excess the refractoriness or mechanical strength of the beams are lowered.

[0016] Additionally it is possible to use a small amount of an organic binder in combination with said inorganic binders.

[0017] Then by providing upward through holes in the overflow beams and/or underflow beams the molten steel flow is guided upward to promote the floating-up of the inclusions and the weight of the beams is reduced by the portions of said holes, so that the workability is improved and since the thermal capacity is reduced the temperature of the molten steel is less lowered, said temperature being lowered by the heat absorbed by said beams. Further, the dispersion effect of the molten steel pressure received by said beams leads to an improved hardness of the beams, and the same effect may be obtained with the provision of groove in the overflow beams and/or underflow beams.

[0018] Furthermore, by arranging reinforcing materials such as ferro-bar, wiring and ceramic within the beams it is possible to improve the strength further.

[0019] The invention will now be described more in detail, by way of Examples, with reference to the accompanying drawings in which

Figs. 1 and 2 are cross sectional views showing the concrete examples of the tundish according to the invention;

Fig. 3 is a front view of the overflow beams of the invention; and

Figs. 3 and 4 is a front view of the overflow beams or the underflow beams of the invention.

[0020] In the drawings, reference 1 designates a ladle nozzle and reference 2 a tundish. Fig. 1 is an example in which overflow beams 3 are disposed in the central portion while underflow beams 4 are arranged outside the overflow beams. Each of said overflow beams 3 is provided with a number of through holes 6 directed outward and upward. Reference 7 shows a reinforcing material provided within each of the overflow and underflow beams.

[0021] Further in the drawings, reference 5 designates tundish nozzle.

[0022] Fig. 2 is an example in which the underflow beams are disposed in the central portion of the tundish while the overflow beams are arranged outside the underflow beams.

[0023] Fig. 3 shows a front view of the overflow beams or underflow beams provided with a number of through holes 6 for the melt, and Fig. 4 shows a front view of the overflow or underflow beams provided with groove 8.

[0024] The following is an Example of making the beams of the invention.

[0025] 35% by weight of water was added to and mixed with a refractory composition having a mixing ratio of 85% by weight of magnesia, 3% by weight of silicon carbide, 4% by weight of aluminium, 4% by weight of asbestos and 4% by weight of magnesium chloride, beams were made of such admixture, water content was removed by sucking from the beams for shaping, the shaped beams were dried and hardened, and thereafter they were disposed as overflow beams and underflow beams in a 10 ton capacity tundish for continuous casting whereby slabs for thick plate were cast.

[0026] As a result, the beams of the present invention did not generate explosive breaking even if quickly heated at the time of pre-heating, showed superior mechanical strength and corrosion resistancy to conventional beams, and could promote the floating-up of the inclusions whereby purified slabs for thick plate could be obtained.

Claims

1. A tundish for steel casting in which overflow beams and underflow beams are disposed, characterized in that said beams base on refractory materials and have a composition consisting of 0.5 - 5% by weight of fibrous materials, 1 - 20% by weight of at least one of aluminium, magnesium and silicon carbide and 1 - 10% by weight of binders, and they are shaped in such a way that water content is sucked and removed from the beams by a wet process.

2. A tundish for steel casting as described in Claim 1 wherein the refractory materials are at least one of the basic refractories such as magnesia, calcia, dolomite, chrome magnesia and magnesia chrome.

3. A tundish for steel casting as described in Claim 2 wherein the fibrous materials are at least one of the inorganic fibers such as asbestos, rock wool, slag wool, glass wool, alumina fiber, magnesia fiber, silicon carbide fiber and zirconium fiber and/or organic fibers such as pulp, cotton fiber, hemp fiber, synthetic fiber, regenerated fiber and floss-silk.

4. A tundish for steel casting as described in any of Claims 1 to 3 wherein the binders are at least one of the inorganic binders such as magnesium sulphate, magnesium chloride, sodium phosphate, potassium phosphate, aluminium phosphate, sodium silicate and potassium silicate.

5. A tundish for steel casting as described in any of Claims 1 to 4 wherein the overflow beams and/or the underflow beams are provided with upward through holes.

6. A tundish for steel casting as described in any of Claims 1 to 4 wherein the overflow beams and/or the underflow beams are provided with groove.

7. A tundish for steel casting as described in any of Claims 1 to 6 wherein each of the overflow beams and/or the underflow beams is provided internally with a reinforcing material.

Drawing