ATBECHDEDKESFRGBGRITLILUNLSEMCPTIESILTLVFIROMKCYALTRBGCZEEHUPLSK..HRIS..MTNO....SM..................
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DIM360 Ver 2.15 (14 Jul 2008) - 1100000/0
2447384
EUROPEAN PATENT APPLICATION
published in accordance with Art. 153(4) EPC
A1
20120502
EP
10791954.0
20100603
20120105
ja
en
en
2009149579
20090624
JP
20120502
201218
20120502
201218
C22C 38/00 20060101AFI20110112BHEP
C21D 6/00 20060101ALI20110112BHEP
C22C 38/54 20060101ALI20110112BHEP
de
WÄRMEBESTÄNDIGE KOMPONENTE FÜR EINE CHEMIKALIENVEARBEITUNGSVORRICHTUNG UND HERSTELLUNGSVERFAHREN DAFÜR
en
HEAT-RESISTANT COMPONENT FOR CHEMICAL PROCESSING APPARATUS AND METHOD FOR PRODUCING SAME
fr
COMPOSANT RÉSISTANT À LA CHALEUR POUR UN APPAREIL DE TRAITEMENT CHIMIQUE ET SON PROCÉDÉ DE FABRICATION
2
National Institute for Materials Science
101039951
29.41.111319
2-1 Sengen 1-chome
Tsukuba-shi, Ibaraki 305-0047
JP
KIMURA, Kazuhiro
c/o NATIONAL INSTITUTE FOR MATERIALS SCIENCE 2-1 Sengen 1-chome
Tsukuba-shi Ibaraki 305-0047
JP
TODA, Yoshiaki
c/o NATIONAL INSTITUTE FOR MATERIALS SCIENCE 2-1 Sengen 1-chome
Tsukuba-shi Ibaraki 305-0047
JP
KUSHIMA, Hideaki
c/o NATIONAL INSTITUTE FOR MATERIALS SCIENCE 2-1 Sengen 1-chome
Tsukuba-shi Ibaraki 305-0047
JP
SAWADA, Kota
c/o NATIONAL INSTITUTE FOR MATERIALS SCIENCE 2-1 Sengen 1-chome
Tsukuba-shi Ibaraki 305-0047
JP
Hall, Matthew Benjamin
101154323
Dehns St. Bride's House 10 Salisbury Square
London EC4Y 8JD
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JP2010059450
20100603
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WO2010150636
20101229
201052
A heat-resistant component for a chemical processing apparatus is formed from a ferritic Cr-steel that contains Cr in an amount of from 13% by weight to 30% by mass. The ferritic Cr-steel has a creep rate of 1 × 10^{-5}/h or less at 700°C under stress of 100 MPa, and an oxidation weight gain of 10 mg/cm^2 or less after being maintained in a 650°C water vapor for 1,000 h. The heat-resistant component for a chemical processing apparatus is produced by hot working the ferritic Cr-steel in a temperature range of 850 to 1,200°C, forming the ferritic Cr-steel into a component shape, subjecting the steel to an annealing treatment in a temperature range of 1,000 to 1,250°C, and cooling the steel to 400°C or less at a cooling rate of 100°C/min or higher.

Technical Field
The present invention relates to heat-resistant components for use in chemical processing apparatuses used mainly for causing chemical reactions for a feedstock through high-temperature chemical treatment, such as in petroleum refineries that heat and fractionate petroleum, and in heating and synthesizing apparatuses that synthesize desired compounds through chemical reactions caused by heating a feedstock.

Background Art
From the safety standpoint, heat-resistant components used in portions in contact with a feedstock in the high-temperature chemical treatment by a chemical processing apparatus (hereinafter, referred to as "heat-resistant component for a chemical processing apparatus") require long-hour durability. Examples of such heat-resistant components for a chemical processing apparatus include valves, pipes, pressure vessels, and flanges. Generally, chemically stable ferritic high Cr-steel with sufficient strength is used as the material of the heat-resistant components.
In recent years, high heating temperatures of 650°C and higher are desired for improving heat efficiency and synthesis techniques. It is difficult, however, to meet such demands with the performance of the conventional heat-resistant components.
The devices used in high temperatures are designed according to the allowable stress formulated based on the creep strength, because the creep strength of ferritic high Cr-steel greatly drops at high temperatures above 650°C.
On the other hand, Ni-based superalloy is known as a heat-resistant material, as described in Patent Document 1. However, it is not known whether the Ni-based superalloy is applicable to heat-resistant components for a chemical processing apparatus.
- Patent Document 1: JP-A-2007-332412

Disclosure of Invention

Problems that the Invention is to Solve
Under these circumstances, it is an object of the present invention to provide a heat-resistant component for a chemical processing apparatus, and a producing process thereof with which safety can be ensured even at high temperatures of 650°C and higher.

Means for Solving the Problems
In order to solve the foregoing problems, the present invention provides a heat-resistant component for a chemical processing apparatus that performs a high-temperature chemical treatment for a feedstock at 650°C or higher,
characterized in that the heat-resistant component is formed from a ferritic Cr-steel of a chemical composition that mainly includes, in % by mass,
- Cr: 13 to 30%,
- Ni: 1 × 10^{-1} to 2.5%,
- C: 1 × 10^{-3} to 1 × 10^{-1}%, and
- N: 1 × 10^{-3} to 1 × 10^{-1}%,
wherein the ferritic Cr-steel allows for inclusion of an additional component and unavoidable impurities, includes Fe as the remaining part, and forms a ferrite phase.
It is preferable in the heat-resistant component for a chemical processing apparatus that Ni is added in an amount that satisfies the relationship Ni > 10(C + N), where Ni, C, and N each represent the amount of each component added (in % by mass), when C is added in 1 × 10^{-2}% by mass or more and/or Ni is added in 1 × 10^{-2}% by mass or more.
It is preferable in the heat-resistant component for a chemical processing apparatus that the ferrite phase is 70 volume% or more.
It is preferable in the heat-resistant component for a chemical processing apparatus that the additional component is one or more of the following in % by mass,
- Mo: 5 × 10^{-1} to 5%,
- W: 5 × 10^{-1} to 1 × 10%,
- V: 5 × 10^{-2} to 4 × 10^{-1}%,
- Nb: 1 × 10^{-2} to 1 × 10^{-1}%,
- Co: 1 × 10^{-1} to 1 × 10%, and
- B: 2 × 10^{-3} to 4 × 10^{-3}%, and
that at least one of carbide, nitride, and intermetallic compound is precipitated in crystal grains.
It is preferable in the heat-resistant component for a chemical processing apparatus that Mo and W are added in amounts that satisfy the relationship Mo + 0.5W ≥ 3.0% by mass, where Mo and W each represent the amount of each component added (in % by mass).
The present invention also provides a heat-resistant component for a chemical processing apparatus that performs a high-temperature chemical treatment for a feedstock at 650°C or higher,
characterized in that the heat-resistant component is formed from a ferritic Cr-steel that contains Cr in an amount of from 13% by mass to 30% by mass, wherein the ferritic Cr-steel has a creep rate of 1 × 10^{-5}/h or less at 700°C under stress of 100 MPa, and an oxidation weight gain of 10 mg/cm^2 or less after being maintained in a 650°C water vapor for 1,000 h.
The present invention also provides a process for producing a heat-resistant component for a chemical processing apparatus, the process including hot working the ferritic Cr-steel of the foregoing chemical composition in a temperature range of 850 to 1,200°C, forming the ferritic Cr-steel into a component shape, subjecting the steel to an annealing treatment in a temperature range of 1,000 to 1,250°C, and cooling the steel to 400°C or less at a cooling rate of 100°C/min or higher.

Advantage of the Invention
A heat-resistant component for a chemical processing apparatus and a producing process thereof according to the present invention realize a chemical processing apparatus that can perform the conventionally difficult high-temperature operation at 650°C or higher temperatures. The material of the heat-resistant component for a chemical processing apparatus is ferritic Cr-steel, a material belonging to the commonly used ferritic high Cr-steels. The heat-resistant component is thus highly practical. The invention is therefore applicable to various techniques, including the current production techniques and quality management techniques, and is very convenient because hardly any additional limitations are imposed.

Brief Description of Drawings
- FIG. 1 is a graph representing the influence of cooling rate on creep rupture time at 650°C.
- FIG. 2 is a graph representing the results of a creep test performed at 650°C.
- FIG. 3 is a graph representing the relationship between creep rate and time at 700°C under stress of 100 MPa.
- FIG. 4 is a graph representing the relationship between creep rate and time at 750°C under stress of 50 MPa.
- FIG. 5 is a graph representing creep rupture time at 750°C.
- FIG. 6 is a graph representing oxidation weight gain in a 650°C water vapor.
- FIG. 7 is a graph representing the temperature dependence of linear expansion coefficient.

Mode for Carrying Out the Invention
The ferritic Cr-steel used for a heat-resistant component for a chemical processing apparatus of the present invention is a material that has excellent high temperature strength, heat resistance, oxidation resistance, and high toughness even at high temperatures above 650°C (here and below, the temperature is represented in units of 50°C), and that can withstand use under high temperature and high pressure for extended time periods while undergoing only a limited decrease in strength.
The ferritic Cr-steel used for the heat-resistant component for a chemical processing apparatus is produced by hot working a ferritic Cr-steel ingot in a temperature range of 850 to 1,200°C and forming the ferritic Cr-steel into a predetermined shape, and then subjecting the steel to an annealing treatment in a temperature range of 1,000 to 1,250°C, and cooling the steel to 400°C or less at a cooling rate of 100°C/min or higher.
The hot working temperature such as in hot forging is 850 to 1,200°C, preferably 950 to 1,150°C, more preferably 1,000 to 1,100°C. Above the upper limit temperature, an abrupt decrease in ductility may occur. Below the lower limit temperature, deformation resistance increases, which may lead to processing defects such as cracking.
The temperature of the annealing treatment is 1,000 to 1,250°C, preferably 1,000 to 1,200°C, more preferably 1,050 to 1,150°C. Above the upper limit temperature, serious coarsening of crystal grains may occur, which can be detrimental to various properties of the steel, including toughness, ductility, and weldability. Below the lower limit temperature, it may not be possible to completely melt the steel and to exhibit a sufficient strength.
Temperatures of 400°C and higher may cause precipitation of a second phase in the process of cooling from the annealing temperature, because of the fast precipitation rate of second-phase compounds such as carbides, nitrides, and intermetallic compounds. In order to control such precipitation of the second phase, the cooling rate of the cooling to 400°C or less following the annealing treatment is 100°C/min or higher, preferably 120°C/min or higher, more preferably 150°C/min or higher. Below the lower limit, a coarse second phase may precipitate at the crystal grain boundary during the cooling process, and it becomes difficult to disperse and precipitate a fine second phase in the crystal grains. In this case, sufficient strength may not be developed because of the failure to effectively control the precipitation state of the second phase for strength improvement.
The ferritic Cr-steel produced as above has a minimum creep rate of 1.0 × 10^{-4}/h or less at 700°C under stress of 100 MPa. A minimum creep rate exceeding the upper limit causes creep deformation during high-temperature use. This may lead to an early loss of functionality in components such as valves that require high dimension accuracy, or may encourage corrosion or oxidation.
Further, the ferritic Cr-steel has a creep rupture time of preferably 1,000 hr or more at 750°C under stress of 80 MPa, 5,000 hr or more at 750°C under stress of 50 MPa, and 10,000 hr or more at 750°C under stress of 30 MPa. A creep rupture time below the lower limit shortens the creep rupture lifetime that depends on the load generated during the operation of the chemical processing apparatus, and may thus present difficulties in ensuring a sufficient creep rupture lifetime in practical applications.
Further, the ferritic Cr-steel has a sufficiently small oxidation weight gain of 10 mg/cm^2 or less after being maintained in a 650°C water vapor for 1,000 h. The ferritic Cr-steel thus excels in high-temperature oxidation resistance, and can ensure safety at high temperatures of 650°C and higher. Oxidative degradation becomes likely and performance becomes unstable with an oxidation weight gain in excess of this upper limit.
Increasing the additive amount of Cr generally improves not only the oxidation resistance but the corrosion resistance of iron and steel materials. Thus, the ferritic Cr-steel with excellent oxidation resistance also excels in corrosion resistance.
The ferritic Cr-steel has a linear expansion coefficient of 15 × 10^{-6} or less in a temperature range of from room temperature to 850°C. Above the upper limit, the amounts of thermal expansion and contraction at the start-up and stopping of the chemical processing apparatus increase, and it becomes difficult to produce heat-resistant components with high dimension accuracy.
The ferritic Cr-steel in the form of, for example, a steel ingot to be subjected to hot working is a ferritic Cr-steel, or a ferritic high Cr-steel as it is called, whose chemical composition is adjusted to include the components below (here and below, % means % by mass).

(1) C: 1 × 10^{-3} to 1 × 10^{-1}%
C needs to be added in at least 1 × 10^{-3}% to improve creep strength. The upper limit of the C additive amount is 1 × 10^{-1}%, because the excess addition lowers toughness. When C is added in 1 × 10^{-2}% or more, it is preferable that Ni > 10 (C + N), where Ni, C, and N each represent the additive amount of each component (in % by mass).

(2) Cr: 13 to 30%
It is essential that Cr is added in 13% or more. In actual practice, Cr is added in preferably 13.5% or more to ensure a 70 volume% or more of the ferrite phase, and to improve oxidation resistance. The upper limit of Cr additive amount is 30%, because a Cr additive amount in excess of 30% notably lowers toughness.

(3) N: 1 × 10^{-3} to 1 × 10^{-1}%
N needs to be added in at least 1 × 10^{-3}% to improve creep strength. The upper limit of N additive amount is 1 × 10^{-1}%, because the excess addition lowers toughness. When N is added in 1 × 10^{-2}% or more, it is preferable that Ni > 10 (C + N), as with the case of C.

(4) Ni: 1 × 10^{-1} to 2.5%
Ni needs to be added in at least 1 × 10^{-1}% to improve toughness. When C and/or N are added in 1 × 10^{-2}% or more, it is preferable that the Ni additive amount satisfy Ni > 10 (C + N) to ensure toughness, as above. The upper limit of Ni additive amount is 2.5%, because the excess addition lowers the percentage volume of the ferrite phase.
As presented in Table 2 below, comparative steels 7 and 8 with the Ni additive amount satisfying Ni ≥ 10 (C + N) (Ni, C, and N each represent the additive amount of each component (in % by mass)) have small Charpy impact values, regardless of the cooling rate. On the other hand, the water-cooled materials of the steels 1 to 4 of the present invention satisfying the relationship Ni > 10 (C + N) have sufficiently greater Charpy impact values than those of the comparative steels 7 and 8.
The ferritic Cr-steel can be reinforced with the controlled precipitation of at least one of carbide, nitride, and intermetallic compound, specifically, by the fine dispersion and precipitation within the crystal grains. This is effective for improving creep strength. To this end, the ferritic Cr-steel allows for addition of the components below in its chemical composition, in addition to the foregoing components.

(5) Mo: 5 × 10^{-1} to 5%
Mo is a chemical component effective for precipitating an intermetallic compound, and can improve creep strength. Mo may be added in 5 × 10^{-1}% or more. The upper limit of Mo additive amount is preferably 5%, because the excess addition may lower toughness.

(6) W: 5 × 10^{-1} to 1 × 10%
As with Mo, W is a chemical component effective for precipitating an intermetallic compound, and can improve creep strength. W may be added in 5 × 10^{-1}% or more. The upper limit of W additive amount is preferably 1 × 10%, because the excess addition may lower toughness.
Note that Mo and W may be added to satisfy the relationship Mo + 0.5W ≥ 3.0% (Mo and W each represent the additive amount (in % by mass)), so as to ensure a sufficient amount of intermetallic compound precipitation.

(7) V: 5 × 10^{-2} to 4 × 10^{-1}%
V forms carbides or nitrides effective for improving creep strength. V maybe added in 5 × 10^{-2}% or more. The upper limit of V additive amount is preferably 4 ×10^{-1}%, because the excess addition is not necessarily effective for the formation of carbides and nitrides.

(8) Nb: 1 × 10^{-2} to 1 × 10^{-1}%
As with V, Nb forms carbides or nitrides effective for improving creep strength. Nb may be added in 1 × 10^{-2}% or more. The upper limit of Nb additive amount is preferably 1 × 10^{-1}%, because the excess addition is not necessarily effective for the formation of carbides and nitrides.

(9) Co: 1 × 10^{-1} to 1 × 10%
Co is a component effective for miniaturizing the precipitated carbide, nitride, and intermetallic compound, and for improving creep strength. Co may be added in 1 × 10^{-1}% or more. The upper limit of Co additive amount is preferably 1 × 10%, because the excess addition may lower the percentage volume of the ferrite phase.

(10) B: 2 × 10^{-3} to 4 × 10^{-3}%
B is a component effective for miniaturizing and stabilizing the precipitates, and for strengthening the grain boundary. B may be added in 2 × 10^{-3}% or more. The upper limit of B additive amount is preferably 4 × 10^{-3}%, because the excess addition may lead to formation of boron nitride, and may not be necessarily effective for improving creep strength.

(11) Mn: 5 × 10^{-2} to 8 × 10^{-1}%
Mn is a component effective as a deoxidant. Mn may be added in 5 × 10^{-2}% or more. The upper limit of Mn additive amount is preferably 8 × 10^{-1}%, because the excess addition is detrimental to strength and toughness.

(12) Si: 5 × 10^{-2} to 5 × 10^{-1}%
Si is a component effective as a deoxidant. Si may be added in 5 × 10^{-2}% or more. The upper limit of Si additive amount is preferably 5 × 10^{-1}%, because the excess addition accelerates the coarsening of the precipitates and lowers strength.
The remaining parts of the ferritic Cr-steel chemical composition are Fe and unavoidable impurities.
Preferably, the ferritic Cr-steel forms at least 70 volume% of the ferrite phase to improve creep strength. A tempered martensite structure with 70 volume% or more of the ferrite phase is unstable at high temperatures, whereas the ferrite phase has high structure stability at high temperatures. As presented in Table 2, furnace cooling of the steels 2 to 4 of the present invention makes the percentage volume of the ferrite phase less than 70% because of the slow cooling rate following the annealing treatment. However, the percentage volume of the ferrite phase becomes 70% or more when the cooling rate down to 400°C or less is 100°C/min or higher in water cooling. Thus, as represented in FIG. 1, the water-cooled materials of the steels 2 to 4 of the present invention have creep rupture times about 10 times longer than those of the furnace cooled materials.
Further, as presented in FIG. 2, the steels 1 to 4 of the present invention have longer creep rupture times than the comparative steels 9 to 15 in which the Cr additive amount is less than 13% and the percentage volume of the ferrite phase is less than 70%.
Examples are described below.
In the following Examples, a round bar was assumed to be a component, and various properties were measured. As noted above, the heat-resistant component for a chemical processing apparatus of the present invention is a heat-resistant component used in portions in contact with a feedstock in the high-temperature chemical treatment in a chemical processing apparatus, and may be, for example, a valve, a pipe, a pressure vessel, or a flange. It would be easily anticipated and understood that the heat-resistant component for a chemical processing apparatus produced from the ferritic Cr-steel has properties comparable to those of the ferritic Cr-steel used as the material.

Examples
The round bars of steels 1 to 8 with the chemical compositions presented in Table 1 (steels 1 to 6 of the present invention, and comparative steels 7 and 8) were each prepared from a 10-kg steel ingot subjected to 850 to 1,150°C hot forging to have a diameter of 15 mm. After 1,200°C annealing treatment, each specimen was cooled by furnace cooling or water cooling.
Note that Table 1 also presents the chemical compositions of the existing ferritic heat-resistant steels (steels 9 to 15; comparative steels).
Table 1 also presents steel 16 (comparative steel). The chemical composition of comparative steel 16 is such that Ni and Cr are added in amounts below the lower limits for the steels of the present invention.

Table 1
Specimen No. | Component (Mass%)
C | Si | Mn | Ni | Cr | Mo | V | Nb | W | Co | N | B | Fe
The present | 1 | 0.051 | 0.20 | 0.50 | 1.99 | 14.94 | 0.99 | 0.20 | 0.051 | 6.05 | 0.01 | 0.041 | 0.0029 | Remaining
steel | 2 | 0.049 | 0.20 | 0.51 | 1.21 | 15.02 | 1.00 | 0.20 | 0.051 | 6.04 | 2.96 | 0.042 | 0.0028 | Remaining
| 3 | 0.048 | 0.21 | 0.51 | 1.60 | 15.00 | 1.00 | 0.20 | 0.050 | 6.03 | 2.95 | 0.044 | 0.0026 | Remaining
| 4 | 0.048 | 0.23 | 0.51 | 2.00 | 14.96 | 0.99 | 0.20 | 0.050 | 6.07 | 2.98 | 0.036 | 0.0029 | Remaining
| 5 | 0.047 | 0.21 | 0.51 | 0.42 | 14.93 | 1.00 | 0.20 | 0.050 | 6.05 | 2.96 | 0.041 | 0.0029 | Remaining
| 6 | 0.048 | 0.20 | 0.51 | 0.78 | 15.00 | 1.00 | 0.20 | 0.050 | 6.05 | 2.96 | 0.042 | 0.0029 | Remaining
Comparative | 7 | 0.110 | 0.24 | 0.49 | 0.02 | 15.21 | 0.98 | 0.20 | 0.051 | 2.95 | - | 0.072 | 0.0028 | Remaining
steel | 8 | 0.100 | 0.20 | 0.48 | - | 14.88 | 1.01 | 0.19 | 0.045 | 6.01 | 2.96 | 0.002 | 0.0028 | Remaining
| 9 | 0.110 | 0.10 | 0.41 | 0.17 | 9.26 | 0.42 | 0.16 | 0.057 | 1.67 | - | 0.046 | 0.0020 | Remaining
| 10 | 0.098 | 0.29 | 0.42 | 0.13 | 9.50 | 0.36 | 0.19 | 0.062 | 1.74 | - | 0.046 | 0.0020 | Remaining
| 11 | 0.120 | 0.28 | 0.61 | 0.34 | 10.50 | 0.36 | 0.21 | 0.060 | 2.05 | - | 0.069 | 0.0029 | Remaining
| 12 | 0.140 | 0.26 | 0.65 | 0.40 | 11.03 | 0.29 | 0.20 | 0.070 | 1.95 | - | 0.064 | 0.0030 | Remaining
| 13 | 0.120 | 0.30 | 0.60 | 0.32 | 10.65 | 0.34 | 0.19 | 0.050 | 1.89 | - | 0.054 | 0.0029 | Remaining
| 14 | 0.130 | 0.31 | 0.60 | 0.36 | 10.65 | 0.33 | 0.19 | 0.050 | 1.87 | - | 0.057 | 0.0024 | Remaining
| 15 | 0.110 | 0.27 | 0.59 | 0.33 | 12.10 | 0.34 | 0.19 | 0.060 | 1.82 | - | 0.066 | 0.0030 | Remaining
| 16 | 0.100 | 0.24 | 0.44 | 0.04 | 8.74 | 0.94 | 0.21 | 0.076 | - | - | 0.058 | - | Remaining
These test pieces were subjected to a Charpy impact test at 100°C. The results are presented in Table 2.
Impact value smaller comparative steels 7 and 8 in which Ni was added in small amounts outside the rate for the steels of the present invention, regardless of the cooling rate after the annealing treatment. In contrast, the steels 1 to 4 of the present invention had greater impact values of 300J/cm^2 or more than the furnact cooled materials and comparative steels 7 and 8 in water cooling with a high cooling fate, though the values were small in furnace cooling that involves a lower cooling rate.

Table 2
Specimen | Impact value at 100°C (J/cm^2) | Percentage volume of ferrite phase (%) | Remarks
No. | Furnace cooling | Water cooling | Furnace cooling | Water cooling
1 | 6 | 300 | 94 | 100 |
2 | 6 | 333 | 56 | 83 |
3 | 5 | 367 | 48 | 77 |
4 | 6 | 366 | 40 | 72 |
7 | 12 | 32 | 100 | 100 | Out of Ni range, Out of Co range
8 | 5 | 12 | - | 91 | Out of Ni range
FIG. 1 is a graph representing the influence of cooling rate on creep rupture time at 650°C in the steels 2 to 4 of the present invention. It can be seen that the water-cooled materials with a high cooling rate have creep rupture times about 10 times longer than those of the furnace cooled materials involving a low cooling rate.
Table 3 represents the measured data used to create FIG. 1.

Table 3
Stress (MPa) | Creep rupture time at 650°C (hr)
The present steel 2 | The present steel 3 | The present steel 4
Water cooling | Furnace cooling | Water cooling | Furnace cooling | Water cooling | Furnace cooling
240 | 2405 | - | 2222 | - | 2008 | -
200 | 5789 | - | 4620 | - | 3911 | -
140 | 25776 | 1507 | 20074 | 1478 | 13211 | 1810
120 | 49380 | 2883 | 43299 | 3063 | 25076 | 3508
It was confirmed that required cooling rate conditions include an annealing treatment within a temperature range of 1,000 to 1,250°C, and the subsequent cooling to 400°C--a temperature that essentially does not allow for precipitation of carbides, rides, and intermetallic compounds--at a high cooling rate that can suppress the precipitation of these components, specifically at 100°C/min or higher.
FIG. 2 is a graph representing the results of a creep test at 650°C.
It can be seen that the steels 1 to 4 of the present invention have higher creep strengths than comparative steels 9 to 15 in which Cr is added in less than 13% by mass, and in which the percentage volume of the ferrite phase is less than 70%.
Table 4 represents the measured data used to create FIG. 2.

Table 4
Stress (MPa) | Creep rupture time at 650°C (hr)
The present steel | Comparative steel
1 | 2 | 3 | 4 | 9 | 10 | 11 | 12 | 13 | 14 | 15
240 | - | 2405 | 2222 | 2008 | - | - | - | - | - | - | -
200 | 3834 | 5789 | 4620 | 3911 | - | - | - | - | - | - | -
180 | - | - | - | - | - | 6 | - | - | - | - | -
160 | - | - | - | - | 11 | 20 | - | - | - | - | -
140 | 36418 | 25776 | 20074 | 13211 | 66 | 171 | 122 | 127 | 157 | 289 | 241
130 | - | - | - | - | 194 | 564 | - | - | - | - | -
120 | - | 49380 | 43299 | 25076 | - | - | 804 | 670 | 985 | 1004 | 1008
110 | - | - | - | - | 1689 | 2589 | 1670 | 1478 | 2171 | 1934 | 1615
100 | - | - | - | - | 3739 | 4831 | - | - | - | - | -
90 | - | - | - | - | 10002 | 11219 | 6473 | 4853 | 7249 | 5721 | 3412
80 | - | - | - | - | 21717 | 21505 | 11283 | 6966 | 14462 | 10713 | 4783
70 | - | - | - | - | 50871 | 46437 | 16377 | 12802 | 25632 | 18158 | 6909
60 | - | - | - | - | - | 65959 | 27733 | 25438 | 40713 | 34223 | 9734
FIG. 3 is a graph representing the relationship between creep rate and time at 700°C under stress of 100 MPa.
It can be seen that the creep rates of the stells 2 and 4 of the present invention are only about 1/1,000 of the creep rates of comparative stells 9 to 11, and that the creep rupture times are least about 100 times longer.
Table 5 represents the minimum creep rates obtained from FIG. 3. The steels 2 and 4 of the present invention have a minimum creep rate of 1.0 × 10^{-4}/h or less, or 1.0 × 10^{-5}/h or less. 1.0 × 10^{-5}/h or less.

Table 5
700°C, Stress 100 MPa
Tested material | Minimum creep rate (h^{-1})
The present steel 2 | 2.0 x 10^{-6}
The present steel 4 | 1.9 x 10^{-6}
Comparative steel 9 | 2.1 x 10^{-3}
Comparative steel 10 | 1.1 x 10^{-3}
Comparative steel 11 | 2.5 x 10^{-3}
FIG. 4 is a graph representing the relationship between creep rate and time at 750°C under stress of 50 MPa.
The steel 4 of the present invention did not rupture during the course of testing. The creep rates of the stells 2 and 4 of the present invention were only 1/100 or less of the creep rates of comparative steels 9 and 13, and the creep rupture times were at least about 100 times longer.
Table 6 represents the measured data used to create FIG. 4.

Table 6
750°C, Stress 50 MPa
Tested material | Minimum creep rate (h-^1)
The present steel 2 | 1.1 x 10^{-6}
The present steel 4 | 7.4 x 10^{-7}
Comparative steel 9 | 5.3 x 10^{-4}
Comparative steel 13 | 5.2 x 10^{-4}
FIG. 5 is a graph representing creep rupture time at 750°C.
The steels 2 and 4 of the present invention did not rupture during the course of testing under stresses of 50 MPa and 30 MPa. Further, the steels 2 and 4 of the present invention tested under stresses of 80 to 50 MPa had creep rupture times at least about 100 times longer than the rupture times of comparative steels 9 to 15. It can also be seen that the creep rupture times are longer thatn those of the austenite heat-resistant steel (steel No. X: SUS316) presented in Table 7. Further, it can be seen that, even under stress of 30 MPa, the steels 2 and 4 of the present invention have creep rupture times comparable to that of SUS316.
Tables 7 and 8 represent the measured data used to create FIG. 5. Table 7 represents the creep rupture time (h) of the austenite steel SUS316 (steel No. X) at 750°C. Table 8 represents the mean values for the steel No. X presented in Table 7, along with the creep rupture times (h) of the steels 2 and 4 of the present invention, comparative steels 9 to 15, and X measured at 750°C.

Table 7
Creep rupture time of austenite steel SUS316 (steel No.X) at 750°C (h)
Stress (MPa) | 88 | 69 | 61 | 53 | 47 | 41 | 37 | 33 | 26
Run 1 | 127 | 555 | 1371 | 1725 | 5547 | 5384 | 9613 | 11188 | 33279
Run 2 | 135 | 577 | | 2095 | | 6564 | 23693 | 18173 | 37610
Run 3 | 145 | 615 | | 2137 | | 8302 | | 23024 | 44459
Run 4 | 162 | 641 | | 2651 | | 8873 | | 33224 | 46417
Run 5 | 163 | 656 | | 2691 | | 9266 | | | 53844
Run 6 | 170 | 680 | | 2726 | | 11767 | | | 130478
Run 7 | 173 | 802 | | 2735 | | | | |
Run 8 | 194 | | | 2979 | | | | |
Mean value | 159 | 647 | 1371 | 2467 | 5547 | 8359 | 16653 | 21402 | 57681

Table 8
Creep rupture time at 750°C (hr)
Stress (MPa) | The present steel | Comparative steel
2 | 4 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | Steel No.X
88 | | | | | | | | | | 159
80 | 2173 | 3550 | | | | | | | |
69 | | | | | | | | | | 647
61 | | | | | | | | | | 1371
60 | | | | | 24 | | | | |
53 | | | | | | | | | | 2467
50 | 9033 | >16154 | 97 | 97 | | 108 | 92 | | |
47 | | | | | | | | | | 5547
41 | | | | | | | | | | 8359
40 | | | 430 | 362 | 326 | 516 | 392 | 239 | 204 |
37 | | | | | | | | | | 16653
35 | | | | | 579 | 970 | | | 384 |
33 | | | | | | | | | | 11188
30 | >21023 | >20973 | 1994 | 1488 | 1043 | | 1730 | 1018 | 667 |
26 | | | | | | | | | | 57681
25 | | | 3621 | 3079 | 2333 | 3882 | | | 1307 |
20 | | | 5713 | 5050 | | 7884 | 7115 | 4209 | 2819 |
FIG. 6 is a graph representing the oxidation weight gain in a 650°C water vapor. The oxidation weight gain was measured for the steels 2 and 4 of the present invention, and for comparative steel 16. In the comparative steel 16 with the small Cr additive amount, the oxidation weight gain increased to 15 mg/cm^2 or more after 1,000 h. In contrast, in the steels 2 and 4 of the present invention, the oxidation weight gain remained sufficiently small at 10 mg/cm^2 or less even after 1,000 h. It can be seen from these results that the steels 2 and 4 of the present invention have excellent oxidation resistance at high temperatures.
Table 9 represents the measured date used to create FIG. 6. in the table, 2 and 4 correspond to the steels 2 and 4, respectively, of the present invention, and 16 corresponds to comparative steel 16.

Table 9
Time held (h) | Oxidation weight gain in 650°C, water vapor (mg/cm^2)
2 | 4 | 16
100 | 5.968 | 5.862 | 8.031
500 | 8.533 | 8.484 | 11.010
1000 | 9.905 | 9.307 | 15.310
FIG. 7 is a graph representing the temperature dependence of expansion coefficient. The graph represents the results of the comparison of the linear expansion coefficients of the steels of the present invention and practical heat-resistant materials.
The steels 2 and 4 of the present invention were heated from room temperature to 1,000°C at a rate of 1,000°C/h, and the thermal expansion was measured to determine a linear expansion coefficient at each temperature. The linear expansion coefficients of the practical heat-resistant materials are values specified in the boiler and pressure vessel specifications of the American Society of Mechanical Engineers (ASME).
Table 10 represents the measured data used to create FIG. 7.

Table 10
Temperature °C | Linear expansion coefficient (×10^{-6})
The present steel | Comparative steel
2 | 4 | Ferrite steel | Austenite steel | Ni-based superalloy
9Cr-1Mo | 12Cr, 13Cr | 18Cr-8Ni | 25Cr-20Ni | NCF600 | NCF800
50 | 8.8 | 10.9 | 10.8 | 11.1 | 15.9 | 15.2 | 12.8 | 14.9
150 | 9.3 | 11.1 | 11.7 | 11.9 | 17.7 | 16.8 | 13.9 | 16.4
250 | 9.9 | 11.4 | 12.4 | 12.2 | 18.8 | 17.2 | 14.9 | 17.0
350 | 10.4 | 11.6 | 13.0 | 12.5 | 19.3 | 17.9 | 15.5 | 17.5
450 | 11.0 | 11.8 | 13.5 | 12.9 | 19.8 | 18.5 | | 18.0
550 | 11.6 | 12.0 | 14.1 | 13.2 | 20.7 | 19.2 | | 18.6
650 | 12.1 | 12.2 | 15.1 | 13.3 | 21.6 | 20.0 | | 19.4
750 | 12.7 | 12.4 | | 13.4 | 21.1 | 20.9 | | 20.7
850 | 13.2 | 12.6 | | | | | | 23.7

Industrial Applicability
The present invention realizes a heat-resistant component for a chemical processing apparatus with which safety can be ensured even at high temperatures of 650°C and higher. The invention enables a high-temperature operation of a chemical processing apparatus at high temperatures of 650°C and higher. The material of the heat-resistant component for a chemical processing apparatus is ferritic Cr-steel, and thus the heat-resistant component is highly practical. The invention is applicable to various techniques, including the current production techniques and quality management techniques, and is very convenient because hardly any additional limitations are imposed.
1. A heat-resistant component for a chemical processing apparatus that performs a high-temperature chemical treatment for a feedstock at 650°C or higher,
characterized in that the heat-resistant component is formed from a ferritic Cr-steel of a chemical composition that mainly includes, in % by mass,
Cr: 13 to 30%,
Ni: 1 × 10^{-1} to 2.5%,
C: 1 × 10^{-3} to 1 × 10^{-1}%, and
N: 1 × 10^{-3} to 1 × 10^{-1}%,
wherein the ferritic Cr-steel allows for inclusion of an additional component and unavoidable impurities, includes Fe as the remaining part, and forms a ferrite phase.
2. The heat-resistant component for a chemical processing apparatus according to claim 1, wherein Ni is added in an amount that satisfies the relationship Ni > 10(C + N), where Ni, C, and N each represent the amount of each component added (in % by mass), when C is added in 1 × 10^{-2}% by mass or more and/or Ni is added in 1 × 10^{-2}% by mass or more.
3. The heat-resistant component for a chemical processing apparatus according to claim 1 or 2, wherein the ferrite phase is 70 volume% or more.
4. The heat-resistant component for a chemical processing apparatus according to claim 1 or 2,
wherein the additional component is one or more of the following in % by mass, Mo: 5 × 10^{-1} to 5%,
W: 5 × 10^{-1} to 1 × 10%,
V: 5 × 10^{-2} to 4 × 10^{-1} %,
Nb: 1 × 10^{-2} to 1 × 10^{-1}%,
Co: 1 × 10^{-1} to 1 × 10%, and
B: 2 × 10^{-3} to 4 × 10^{-3}%, and
wherein at least one of carbide, nitride, and intermetallic compound is precipitated in crystal grains.
5. The heat-resistant component for a chemical processing apparatus according to claim 4, wherein Mo and W are added in amounts that satisfy the relationship Mo + 0.5W ≥ 3.0% by mass, where Mo and W each represent the amount of each component added (in % by mass).
6. A heat-resistant component for a chemical processing apparatus that performs a high-temperature chemical treatment for a feedstock at 650°C or higher,
characterized in that the heat-resistant component is formed from a ferritic Cr-steel that contains Cr in an amount of from 13% by mass to 30% by mass, wherein the ferritic Cr-steel has a creep rate of 1 × 10^{-5}/h or less at 700°C under stress of 100 MPa, and an oxidation weight gain of 10 mg/cm^2 or less after being maintained in a 650°C water vapor for 1,000 h.
7. A process for producing a heat-resistant component for a chemical processing apparatus,
the process comprising hot working the ferritic Cr-steel of the chemical composition of claim 1 in a temperature range of 850 to 1,200°C, forming the ferritic Cr-steel into a component shape, subjecting the steel to an annealing treatment in a temperature range of 1,000 to 1,250°C, and cooling the steel to 400°C or less at a cooling rate of 100°C/min or higher.

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
- JP
2007332412
A
[0005]