JP2017133075A - Al-containing ferritic stainless steel excellent in high temperature strength - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an Al-containing ferritic stainless steel excellent in high temperature strength upon high temperature high speed deformation without relying on excess Nb, Ni, Cu, Mo, W addition and suitable for a fuel cell high temperature member.SOLUTION: The Al-containing ferritic stainless steel is provided that contains, by mass%, C:0.03% or less, Si:2.0% or less, Mn:2.0% or less, P:0.050% or less, S:0.01% or less, Cr:11 to 25%, Al:1.3 to 4.0% and N:0.03% or less, further containing one or two or more kind of Ti:0.5% or less, Nb:0.5% or less and V:0.5% or less, satisfying the following (a) and/or (b) and having the balance Fe with inevitable impurities. (a) containing Sn:0.20% or less. (b) containing one or two or more kind of B:0.005% or less, Mg:0.015% or less and Ca:0.005% or less in the range of 10×[B]+[Mg]+[Ca]≥0.004%.SELECTED DRAWING: None

Description

  The present invention is an Al-containing ferritic stainless steel suitable for a steel structure excellent in high-temperature strength during high-temperature and high-speed deformation, especially for a fuel cell high-temperature member, without relying on excessive Nb, Ni, Cu, Mo, W addition. Related to steel.

Recently, the spread of new systems replacing conventional power generation systems is accelerating due to problems such as depletion of fossil fuels such as petroleum and global warming due to CO ₂ emissions. As one of them, “fuel cell”, which has high practical value as a distributed power source and a power source for automobiles, is attracting attention. There are several types of fuel cells. Among them, polymer electrolyte fuel cells (PEFC) and solid oxide fuel cells (SOFC) have high energy efficiency, and are expected to expand in the future.

  A fuel cell is a device that generates electric power through a reaction process opposite to that of water electrolysis, and requires hydrogen. Hydrogen is produced by a reforming reaction of hydrocarbon fuels such as city gas (LNG), methane, natural gas, propane, kerosene, and gasoline in the presence of a catalyst. Above all, a fuel cell using city gas as a raw fuel has an advantage that hydrogen can be produced in an area where city gas piping is provided.

The fuel reformer is usually operated at a high temperature of 200 to 700 ° C. in order to ensure the amount of heat necessary for the hydrogen reforming reaction. Under such a high temperature operation, it is exposed to an oxidizing atmosphere containing a large amount of water vapor, carbon dioxide, carbon monoxide and the like, and the heating / cooling cycle by starting and stopping is repeated according to the demand for hydrogen. Further, in the SOFC system, when high Cr content stainless steel is applied, there is a problem of preventing poisoning of the ceramic electrode due to Cr evaporation at the SOFC operating temperature.
Until now, austenitic stainless steel represented by SUS310S (25Cr-20Ni) has been used as a practical material having sufficient durability under such a severe environment. In the future, cost reduction is indispensable for the spread of fuel cell systems, and reduction of alloy costs by optimizing the materials used is an important issue. Further, in the SOFC system, when applying high Cr content stainless steel, a steel type that can prevent poisoning of the ceramic electrode due to Cr evaporation at the SOFC operating temperature must be selected. In addition, in order to ensure the reliability of the structure in such a high temperature environment, the creep characteristics and the high temperature strength are also important.

From the background described above, application of Al-containing ferritic stainless steel having high oxidation resistance to alumina to a fuel reformer is disclosed.
In Patent Document 1, Cr: 8-35%, C: 0.03% or less, N: 0.03% or less, Mn: 1.5% or less, Si: 0.8-2.5% and / or Al: 0.6 to 6.0%, Nb: 0.05 to 0.80%, Ti: 0.03 to 0.50%, Mo: 0.1 to 4%, Cu: 0.1 A ferritic stainless steel for a petroleum fuel reformer is disclosed that contains one or two or more of -4% and has a composition in which the total amount of Si and Al is adjusted to 1.5% or more. In these stainless steels, in a thermal fatigue test in which the material is repeatedly heated and cooled in a temperature range of 200 to 900 ° C. (restraint rate 50%), the repeated repetition of damage in which the initial maximum tensile stress is reduced to 3/4 is 500 cyc or more. It is characterized by being.

  In Patent Document 2, Cr: 8 to 25%, C: 0.03% or less, N: 0.03% or less, Si: 0.1 to 2.5%, Mn: 1.5% or less, Al: Including 0.1 to 4%, Nb: 0.05 to 0.80%, Ti: 0.03 to 0.5%, Mo: 0.1 to 4%, Cu: 0.1 to 4% Ferritic stainless steel for alcohol-based fuel reformers containing one or more types is disclosed. In these stainless steels, in a thermal fatigue test in which the material is repeatedly heated and cooled in a temperature range of 200 to 900 ° C. (restraint rate 100%), the repetition of breakage in which the initial maximum tensile stress is reduced to 3/4 is 1000 cyc or more. It is characterized by being.

  In Patent Document 3, Cr: 12 to 20%, C: 0.03% or less, N: 0.03% or less, Si: 0.1 to 1.5%, Mn: 0.95 to 1.5% Al: 1.5% or less, including Nb: 0.1 to 0.8, Mo: 0.1 to 4%, Cu: 0.1 to 4.0 or more, A = A ferritic stainless steel for a hydrocarbon fuel reformer in which an A value defined by Cr + Mn + 5 (Si + Al) is adjusted to a range of 15 to 25 is disclosed. In these stainless steels, in a thermal fatigue test in which the material is repeatedly heated and cooled in a temperature range of 200 to 900 ° C. (restraint rate: 100%), the initial repetition of failure at which the maximum tensile stress is reduced to 3/4 is 800 cyc or more. It is characterized by being.

  In Patent Document 4, C: less than 0.02%, Si: more than 0.15 to 0.7%, Mn: 0.3% or less, P: 0.035% or less, S: 0.003% or less, Cr: 13-20%, Al: 1.5-6%, N: 0.02% or less, Ti: 0.03-0.5%, Nb: 0.001-0.1% or less, in steel When the solid solution Ti amount is [Ti] and the solid solution Nb amount in the steel is [Nb], and 13 ≦ Cr ≦ 16, 0 ≦ [Ti] ≦ [Nb] +0.05, 0 <[Nb] ≦ 0 .10 and 16 <Cr ≦ 20, 0 ≦ [Ti] ≦ 1/2 × [Nb] +0.15, [Ti] ≦ 0.12, and 0 <[Nb] ≦ 0.1 are satisfied. An Al-containing ferritic stainless steel for fuel cells is disclosed. These stainless steels are characterized by a creep rupture time of 4000 h or more at 750 ° C. and an initial stress of 10 MPa.

  In Patent Document 5, C: 0.001 to 0.03%, Si: 0.01 to 2%, Mn: 0.01 to 1.5%, P: 0.005 to 0.05%, S: 0.0001-0.01%, Cr: 16-30%, N: 0.001-0.03%, Al: 0.8-3%, Sn: 0.01-1% A high-purity ferritic stainless steel sheet excellent in oxidation resistance and high-temperature strength is disclosed, in which the 0.2% proof stress is 40 MPa or more and the tensile strength is 60 MPa or more.

As described above, components such as the fuel reformer and the heat exchanger are continuously operated in a temperature range of 200 to 700 ° C. However, when considering the safety of the SOFC system, it is preferable to select a material in consideration of the reliability of the structure against abnormal temperature rise. In the case of ferritic stainless steel, a significant decrease in strength occurs at a high temperature exceeding 700 ° C. In addition, for example, when a sudden temperature increase occurs due to an abnormality in the SOFC system, a thermal stress due to the temperature distribution of each part is suddenly applied to the steel material. That is, as a new steel material problem, it is newly required to have deformation resistance excellent in high-speed deformation in a high temperature range of about 800 ° C. exceeding 700 ° C.
However, the prior art which examined high-speed deformation in the temperature exceeding 700 degreeC by Al containing ferritic stainless steel excellent in Cr poisoning is not confirmed.

Japanese Patent No. 3886785 Japanese Patent No. 3910419 Japanese Patent No. 3942876 Japanese Patent No. 5544106 Japanese Patent No. 5709570

  The present invention has been developed to increase the reliability of steel structures, particularly SOFC structures, when an abnormal temperature rise to 800 ° C. is assumed. The present invention provides an Al-containing ferritic stainless steel excellent in high-temperature strength during high-speed deformation, and among these, application to a fuel reformer having a particularly high temperature is preferable.

(1) In mass%, C: 0.03% or less, Si: 2.0% or less, Mn: 2.0% or less, P: 0.050% or less, S: 0.01% or less, Cr: 11 to 25%, Al: 1.3 to 4.0%, N: 0.03% or less, Ti: 0.5% or less, Nb: 0.5% or less, V: 0.5% or less An Al-containing ferritic stainless steel excellent in high-temperature strength, characterized in that it contains one or more of the following, further satisfies the following (a) and / or (b), and the balance is Fe and inevitable impurities.
(A) Sn: 0.20% or less (b) B: 0.005% or less, Mg: 0.015% or less, Ca: 0.005% or less, 1 type or 2 types or more 10 × [B] + [Mg] + [Ca] ≥ 0.004% contained. Here, [B], [Mg], and [Ca] indicate the content (% by mass) of each element.
(2) One or more of Ni: 1.0% or less, Cu: 1.0% or less, Mo: 1.0% or less, W: 1.0% or less, Co: 1.0% or less The Al-containing ferritic stainless steel having excellent high-temperature strength as described in (1).
(3) Zr: 0.50% or less, Ga: 0.10% or less, Sb: 0.50% or less, La: 0.10% or less, Y: 0.10% or less, Hf: 0.10% or less , Ta: 0.1% or less, REM: 0.10% or less, Al-containing ferrite system having excellent high-temperature strength as described in (1) or (2) Stainless steel.
(4) Al having excellent high-temperature strength according to any one of (1) to (3), wherein the tensile strength when the strain rate is 0.3 min ⁻¹ at 800 ° C. is 50 MPa or more. Contains ferritic stainless steel.
(5) The Al-containing ferritic stainless steel having excellent high-temperature strength according to any one of (1) to (4), which is applied to a fuel reformer, a heat exchanger, or a fuel cell high-temperature member.
(6) The Al-containing ferritic stainless steel excellent in high-temperature strength according to any one of (1) to (4), which is applied to a high-temperature member used in at least one of a gas turbine and a power generation system .
(7) The high temperature according to any one of (1) to (4), wherein the high temperature is applied to at least one member for an automobile of an exhaust manifold, a converter, a muffler, a turbocharger, an EGR cooler, a front pipe, and a center pipe. Al-containing ferritic stainless steel with excellent strength.
(8) The Al-containing ferrite system having excellent high-temperature strength according to any one of (1) to (4), which is applied to a high-temperature member used in a combustion device of at least one of a stove and a fan heater Stainless steel.
Hereinafter, the inventions related to the steels (1) to (8) are referred to as the present invention.

  According to the present invention, it is possible to provide an Al-containing ferritic stainless steel suitable for a steel structure excellent in high-temperature strength during high-speed deformation, and particularly suitable for a fuel cell high-temperature member.

  In order to solve the above-mentioned problems, the present inventors conducted experiments on the influence of various alloy elements on the elucidation of the fracture mechanism and the increase in the high-temperature strength when an abnormal temperature rise to 800 ° C. is assumed for ferritic stainless steel. The present invention was completed through repeated studies. The knowledge obtained by the present invention will be described below.

(A) As a result of carrying out a simulation analysis assuming an abnormal temperature rise up to 800 ° C., it was newly found that the structural member is deformed at a maximum strain rate of 0.25 min ⁻¹ . Therefore, it is important for the structural member to increase the tensile strength of the Al-containing ferritic stainless steel under such conditions.
(B) Usually, solid solution strengthening is effective in increasing the high temperature strength of ferritic stainless steel. In the case of high-temperature deformation at a strain rate of 0.25 min ⁻¹ , a larger amount of strain is applied, and the applied strain progresses while forming subgrain boundaries by dynamic recovery.
(C) In order to increase the high temperature strength under such conditions, it is important to suppress the growth of subgrain boundaries and maintain a fine structure in addition to the solid solution strengthening by addition of the alloy elements described above. I found out.
(D) It has been newly found that the high-temperature strength is remarkably improved by adding a small amount of Sn, regardless of addition of excessive Al and Nb, Mo, Cu, etc. contributing to solid solution / precipitation strengthening. Sn, of course, is not only solid solution strengthened, but is also particularly segregated at the subgrain boundaries formed in the steel at the time of deformation at 800 ° C., and it has been found that the movement of the subgrain boundaries is remarkably suppressed. However, excessive addition of Sn decreases the grain boundary strength, so that early fracture occurs at the grain boundary as the starting point during high-speed deformation.
(E) B, as well as Sn, segregates at the sub-grain boundaries formed during high-temperature deformation in addition to solid solution strengthening, and remarkably suppresses the movement of the sub-crystal grain boundaries. Further, in order to segregate B to the sub-grain boundaries, by adding appropriate amounts of Ca and Mg, S and O that are easily segregated at the grain boundaries are generated as non-metallic inclusions and sulfides, It is effective to secure segregation sites.
(F) In addition, Ti, Nb, V, Ni, Cu, Mo, W, Co, Zr, Ga, Sb, La, Y, Hf, Ta, and REM are also effective for increasing high-temperature strength during high-speed deformation by solid solution strengthening. Is an additive element.

  Hereinafter, each requirement of the present invention will be described in detail. In addition, "%" display of the content of each element means "mass%".

  The reasons for limiting the chemical components will be described below.

<C: 0.030% or less>
C inhibits oxidation resistance by forming a solid solution or forming Cr ₂₃ C ₆ in the ferrite phase. Further, it promotes the precipitation of Cr ₂₃ C ₆ at the grain boundaries during welding. For this reason, the smaller the amount of C, the better. The upper limit is made 0.03%. However, excessive reduction leads to an increase in refining costs, so the lower limit is preferably 0.001%. A more preferable range is 0.002 to 0.020%.

<Si: 2.0% or less>
Si is an important element in securing oxidation resistance. Moreover, it is an element which raises high temperature strength by solid solution strengthening. In order to obtain these effects, the lower limit is preferably 0.2%. On the other hand, excessive addition may impair the toughness and workability of steel and inhibit the formation of an Al-based oxide film, so the upper limit is made 2.0%. A preferable upper limit is 1.2%.

<Mn: 2.0% or less>
Mn is dissolved in the oxide film together with Si in the reformed gas environment to enhance the protection. In order to obtain these effects, the lower limit is preferably 0.1%. On the other hand, excessive addition inhibits the corrosion resistance of steel and the formation of an Al-based oxide film, so the upper limit is made 2.0% or less. From the viewpoint of oxidation resistance and basic characteristics, 1.2% or less is preferable.

<P: 0.050% or less>
P hinders manufacturability and weldability. Further, since it is an element that easily segregates at grain boundaries, it is an element that inhibits grain boundary segregation of Sn and B. The lower the content, the better, so the upper limit is made 0.050%. However, excessive reduction leads to an increase in refining costs, so the lower limit is preferably 0.003%. From the viewpoint of manufacturability and weldability, the preferred range is 0.004 to 0.035%.

<S: 0.010% or less>
S is an inevitable impurity element contained in the steel, and lowers the protective properties of the Al-based film. In particular, the presence of Mn-based inclusions and solute S also acts as a fracture starting point for Al-based oxide films when used at high temperatures for long periods of time. Further, since it is an element that easily segregates at grain boundaries, it is an element that inhibits grain boundary segregation of Sn and B. Therefore, the lower the amount of S, the better. Therefore, the upper limit is made 0.010%. However, excessive reduction leads to an increase in raw materials and refining costs, so the lower limit is made 0.0001%. From the viewpoint of manufacturability, oxidation resistance, and 475 ° C. brittleness, the preferred range is 0.0001 to 0.0050%.

<Cr: 11.0 to 25.0%>
In addition to corrosion resistance, Cr is a basic constituent element for ensuring the protection of the surface oxide film, and in order to obtain these effects, an amount of Cr of 11.0% or more is required. On the other hand, excessive addition of Cr promotes the precipitation of Cr ₂₃ C ₆ . Moreover, it promotes the generation of the σ phase which is an embrittlement phase. The upper limit is set to 25.0% because it may promote an increase in alloy costs and Cr evaporation. A preferable range is 13.0 to 20.0%.

<Al: 1.3-4.0%>
In addition to the deoxidizing element, Al is an additional element essential for forming an Al-based oxide film and suppressing Cr evaporation. Moreover, it is an element which raises high temperature strength by solid solution strengthening. In order to obtain these effects, the lower limit is made 1.3%. However, excessive addition of Al promotes the toughness of steel and brittle fracture in welds, so the upper limit is made 4.0%. A preferable range is 1.5 to 3.5%.

<N: 0.030% or less>
N, like C, inhibits the target oxidation resistance of the present invention. For this reason, the smaller the amount of N, the better. The upper limit is made 0.030%. However, excessive reduction leads to an increase in refining costs, so the lower limit is made 0.001%. A preferred range is 0.002 to 0.020%.

<Sn: 0.20% or less>
Sn is an element that increases the high temperature strength by solid solution strengthening. Further, it is an element that increases the high temperature strength by segregating at the sub-crystal grain boundary during high-speed deformation at 700 ° C. to 800 ° C. and suppressing the movement of the sub-crystal grain boundary. In order to obtain these effects, the lower limit is made 0.005%. On the other hand, excessive addition of Sn conversely weakens the grain boundary strength and promotes grain boundary fracture during high-speed deformation. In addition, since the manufacturability is also reduced, the upper limit needs to be 0.20%. The preferred Sn content is 0.01 to 0.15%.

<Ti, Nb, V: 0.50% or less each>
Ti, Nb, and V are elements that contribute to the suppression of Cr ₂₃ C ₆ production during welding by the action of a stabilizing element that fixes C and N. Furthermore, it is an element that contributes to an increase in high-temperature strength. In order to obtain these effects, the lower limit is preferably 0.01%. On the other hand, excessive addition leads to a decrease in manufacturability and a decrease in oxidation resistance due to an increase in alloy cost and a recrystallization temperature, so the upper limit is 0.50%. A preferable range is 0.10 to 0.40%.

<B: 0.005% or less, Mg: 0.015% or less, Ca: 0.005% or less>
<10 × [B] + [Mg] + [Ca] ≧ 0.005%>
B, Mg, and Ca are additive elements essential for increasing the tensile strength at 800 ° C., which is a target of the present invention. In order to obtain this effect, B: 0.0005% or more, Mg: 0.001% or more, Ca: 0.0005% or more is contained, and these elements are included in one or more kinds, and 10 × [B] + [Mg] + [Ca] ≧ 0.0040% shall be satisfied. On the other hand, excessive addition of these elements lowers manufacturability and corrosion resistance of steel, so B is preferably 0.005% or less, Mg: 0.015% or less, and Ca: 0.005% or less. .

<Ni, Cu, Mo, W, Co>
These elements increase the high temperature strength by solid solution strengthening. To obtain this effect, Ni: 0.020% or more, Cu: 0.010% or more, Mo: 0.010% or more, W: 0.001% or more, Co: 0.005% or more, these elements It is preferable to contain 1 type or 2 types or more. On the other hand, excessive addition of these elements leads to a decrease in manufacturability and an increase in alloy cost, so Ni: 1.0% or less, Cu: 1.0% or less, Mo: 1.0% or less, W: It is preferable that 1.0% or less, Co: 1.0% or less, and the total content of these elements be 2.0% or less.

<Zr, Ga, Zn, Sb, La, Y, Hf, Ta, REM>
These elements increase the high temperature strength by solid solution strengthening. Zr, La, Y, Hf, Ta, and REM are elements that are conventionally effective for improving hot workability, steel cleanliness, and improving oxidation resistance. Ga, Zn, and Sb are concentrated near the surface to suppress the oxidation of Cr. In order to obtain these effects, Zr: 0.0001% or more, Ga: 0.001% or more, Zn: 0.01% or more, Sb: 0.003% or more, La: 0.0001% or more, Y: 0 It is preferable to contain one or more of these elements at 0.0001% or more, Hf: 0.0001% or more, Ta: 0.002% or more, and REM: 0.001% or more. On the other hand, excessive addition of these elements leads to a decrease in manufacturability and an increase in alloy cost, so Zr: 0.50% or less, Ga: 0.10% or less, Zn: 0.1% or less, Sb: These elements are 0.50% or less, La: 0.10% or less, Y: 0.10% or less, Hf: 0.10% or less, Ta: 0.50% or less, REM: 0.10% or less. It is necessary to contain 1 type or 2 types or more. The total content of these elements is preferably 0.20% or less.

Examples of the present invention will be described below.
The ferritic stainless steels represented by symbols A1 to A14 and symbols B1 to B11 whose components are shown in Table 1 are melted, and after hot rolling, annealing pickling, cold rolling, a thickness of 1.0 mm is obtained by finish annealing and pickling. A cold-rolled annealed steel sheet was produced.

A tensile test piece having a thickness of 1.0 mm shown in FIG. 1 was taken from each ferritic stainless steel sheet. The test piece was sampled so that the direction of the pressed piece of the cold-rolled annealed steel plate coincided with the longitudinal direction of the tensile test piece.
The tensile strength at 800 ° C. was measured by a high temperature tensile test. The test piece was heated from room temperature to 800 ° C. at 100 ° C./min and held at 800 ° C. for 10 minutes, and then a tensile test was started. The strain rate was constant at 0.3 / min, and the test was performed by stroke displacement control. The tensile strength was calculated from the maximum load during the test.

Table 2 shows the tensile strength at 800 ° C. The target of the present invention was to exceed the tensile strength (50 MPa) of SUH21 under the same test conditions.
Symbols A1 to A14 satisfy the component ranges defined in the present invention. As a result, it exceeded the target tensile strength of SUH21 at 800 ° C.

  Symbol B1 has Sn content exceeding the upper limit prescribed | regulated by this invention. As a result, excessive Sn segregation to the grain boundary occurred, causing the grain boundary fracture due to a decrease in grain boundary strength, which was below the target tensile strength.

  The symbol B2 indicates that the Mg content and 10 × [B] + [Mg] + [Ca] exceed the upper limit defined in the present invention. As a result, the ductility decreased due to the fracture starting from inclusions, which was lower than the target tensile strength.

  The symbol B3 indicates that both the Sn content and 10 × [B] + [Mg] + [Ca] are below the lower limit defined in the present invention. As a result, it was not possible to obtain a sufficient effect of increasing the high-temperature strength by these elements, which was lower than the target tensile strength.

  The symbol B4 indicates that the Al content exceeds the upper limit defined in the present invention. As a result, an early fracture occurred due to a decrease in the ductility of the steel material, which was below the target tensile strength.

  The symbol B5 indicates that the C content exceeds the upper limit defined in the present invention. As a result, early fracture due to ductility reduction due to the formation of carbide occurred, which was below the target tensile strength.

  Symbol B6 exceeds the upper limit which Ti content prescribes | regulates by this invention. As a result, an early fracture occurred due to a decrease in the ductility of the steel material, which was below the target tensile strength.

  Symbol B7 has Cu content exceeding the upper limit prescribed | regulated by this invention. As a result, the internal defect of the test piece at the time of manufacture of the test piece was the starting point, the ductility of the steel material was reduced, and the early tensile fracture occurred, which was below the target tensile strength.

  In symbol B8, both the Mo content and the Co content exceed the upper limit defined in the present invention. As a result, the internal defect of the test piece at the time of manufacture of the test piece was the starting point, the ductility of the steel material was reduced, and the early tensile fracture occurred, which was below the target tensile strength.

  Symbol B9 indicates that the Cr content exceeds the upper limit defined in the present invention. As a result, premature rupture due to the generation of σ phase occurred, which was below the target tensile strength.

  In the symbol B10, the B content exceeds the upper limit defined in the present invention. As a result, the formation of B-based precipitates was promoted, and the amount of B segregated to the subcrystal grain size was reduced, so that it was estimated that the target tensile strength was exceeded.

  In the symbol B11, the Sb content exceeds the upper limit defined in the present invention. As a result, excessive Sb segregation to the grain boundary occurred, resulting in grain boundary breakage due to a decrease in grain boundary strength and lowering the target tensile strength.

  According to the present invention, Al-containing ferritic stainless steel having excellent high-temperature strength during high-temperature high-speed deformation can be applied to a high-temperature member without relying on excessive addition of Nb, Ni, Cu, Mo, and W. In particular, for fuel cells, it is suitable for application to high-temperature members of fuel cells such as fuel reformers. In addition, heat exchangers or gas turbines and power generation systems, exhaust manifolds, converters, mufflers, turbochargers, EGR The present invention can also be suitably applied to combustion equipment such as a cooler, a front pipe and a center pipe, a stove, and a fan heater.

(1) In mass%, C: 0.03% or less, Si: 2.0% or less, Mn: 2.0% or less, P: 0.050% or less, S: 0.01% or less, Cr: 11 to 25%, Al: 1.3 to 4.0%, N: 0.03% or less, Ti: 0.5% or less, Nb: 0.5% or less, V: 0.5% or less one or comprise two or more, further the following (a) and (b) meet, Al-containing ferritic stainless steel balance excellent in high temperature strength, which is a Fe and unavoidable impurities.
(A) Sn: 0.005 to 0.20% or less (b) B: 0.005% or less, Mg: 0.015% or less, or B: 0.005% or less, Mg: 0.015% or less, Ca: over 2 or more kinds selected from 0.005% or less, containing at 0.062%> 10 × [B] + [Mg] + [Ca] ≧ 0.004% range . Here, [B], [Mg], and [Ca] indicate the content (% by mass) of each element.
(2) In mass%, C: 0.03% or less, Si: 2.0% or less, Mn: 2.0% or less, P: 0.050% or less, S: 0.01% or less, Cr: 11 to 25%, Al: 1.3 to 4.0%, N: 0.03% or less, Ti: 0.5% or less, Nb: 0.5% or less, V: 0.5% or less An Al-containing ferritic stainless steel excellent in high-temperature strength, characterized in that it contains one or more of the following, further satisfies the following (a) and (b), and the balance is Fe and inevitable impurities.
(A) Sn: 0.005 to 0.180% or less
(B) B: 0.005% or less, Mg: 0.015% or less, or B: 0.005% or less, Mg: 0.015% or less, Ca: 0.005% or less 2 types or more are contained in the range of 0.062%> 10 × [B] + [Mg] + [Ca] ≧ 0.004%. Here, [B], [Mg], and [Ca] indicate the content (% by mass) of each element.
(3) In mass%, C: 0.03% or less, Si: 2.0% or less, Mn: 2.0% or less, P: 0.050% or less, S: 0.01% or less, Cr: 11 to 25%, Al: 1.3 to 4.0%, N: 0.03% or less, Ti: 0.5% or less, Nb: 0.5% or less, V: 0.5% or less An Al-containing ferritic stainless steel excellent in high-temperature strength, characterized in that it contains one or more of the following, further satisfies the following (a) and (b), and the balance is Fe and inevitable impurities.
(A) Sn: 0.005 to 0.056% or less
(B) B: 0.005% or less, Mg: 0.015% or less, or B: 0.005% or less, Mg: 0.015% or less, Ca: 0.005% or less 2 types or more are contained in the range of 0.062%> 10 × [B] + [Mg] + [Ca] ≧ 0.004%. Here, [B], [Mg], and [Ca] indicate the content (% by mass) of each element.
( 4 ) One or more of Ni: 1.0% or less, Cu: 1.0% or less, Mo: 1.0% or less, W: 1.0% or less, Co: 1.0% or less The Al-containing ferritic stainless steel excellent in high-temperature strength according to any one of (1) to (3) .
( 5 ) Zr: 0.50% or less, Ga: 0.10% or less, Sb: 0.50% or less, La: 0.10% or less, Y: 0.10% or less, Hf: 0.10% or less , Ta: 0.1% or less, REM: 0.10% or less, or one or more of (1) to ( 4 ) , which is excellent in high temperature strength Contains ferritic stainless steel.
( 6 ) The tensile strength at a strain rate of 0.3 min ⁻¹ at 800 ° C. is 50 MPa or more, and Al having excellent high-temperature strength according to any one of (1) to ( 5 ) Contains ferritic stainless steel.
( 7 ) The Al-containing ferritic stainless steel having excellent high-temperature strength according to any one of (1) to ( 6 ), which is applied to a fuel reformer, a heat exchanger, or a fuel cell high-temperature member.
( 8 ) The Al-containing ferritic stainless steel excellent in high-temperature strength according to any one of (1) to ( 6 ), which is applied to a high-temperature member used in at least one of a gas turbine and a power generation system. .
( 9 ) The high temperature according to any one of (1) to ( 6 ), characterized in that the high temperature is applied to at least one member for an automobile of an exhaust manifold, a converter, a muffler, a turbocharger, an EGR cooler, a front pipe, and a center pipe. Al-containing ferritic stainless steel with excellent strength.
( 10 ) The Al-containing ferrite system having excellent high-temperature strength according to any one of (1) to ( 6 ), which is applied to a high-temperature member used in a combustion device of at least one of a stove and a fan heater Stainless steel.
Hereinafter, the inventions related to the steels (1) to ( 10 ) are referred to as the present invention.

<B: 0.005% or less, Mg: 0.015% or less of any one, or B: 0.005% or less, Mg: 0.015% or less, Ca: is selected from 0.005% or less More than 2 types >
<0.062%> 10 × [B] + [Mg] + [Ca] ≧ 0.005%>
B, Mg, and Ca are additive elements essential for increasing the tensile strength at 800 ° C., which is a target of the present invention. To obtain this effect, B: 0.0005% or more, Mg: 0.001% or more, or B: 0.0005% or more, Mg: 0.001% or more, Ca: 0.0005% to contain two or more selected from the above, the content of these elements is, shall meet the 10 × [B] + [Mg ] + [Ca] ≧ 0.0040%. On the other hand, excessive addition of these elements decreases manufacturability and corrosion resistance of steel, so 0.062> 10 × [B] + [Mg] + [Ca], and the upper limit of each content is B : 0.005% or less, Mg: 0.015% or less, Ca: 0.005% or less .

Table 2 shows the tensile strength at 800 ° C. The target of the present invention was to exceed the tensile strength (50 MPa) of SUH21 under the same test conditions.
Symbols A1 , A3 to A8, A10 to A11, and A14 satisfy the component ranges defined in the present invention. As a result, it exceeded the target tensile strength of SUH21 at 800 ° C.

Claims (8)

In mass%, C: 0.03% or less, Si: 2.0% or less, Mn: 2.0% or less, P: 0.050% or less, S: 0.01% or less, Cr: 11-25 %, Al: 1.3-4.0%, N: 0.03% or less, Ti: 0.5% or less, Nb: 0.5% or less, V: 0.5% or less Alternatively, an Al-containing ferritic stainless steel excellent in high-temperature strength, including two or more, and further satisfying the following (1) and / or (2), the balance being Fe and inevitable impurities.
(1) Sn: 0.20% or less (2) B: 0.005% or less, Mg: 0.015% or less, Ca: 0.005% or less, one or two or more 10 × [B] + [Mg] + [Ca] ≧ 0.004%. Here, [B], [Mg], and [Ca] indicate the content (% by mass) of each element.   Ni: 1.0% or less, Cu: 1.0% or less, Mo: 1.0% or less, W: 1.0% or less, Co: 1.0% or less The Al-containing ferritic stainless steel having excellent high-temperature strength according to claim 1.   Zr: 0.50% or less, Ga: 0.10% or less, Sb: 0.50% or less, La: 0.10% or less, Y: 0.10% or less, Hf: 0.10% or less, Ta: The Al-containing ferritic stainless steel excellent in high-temperature strength according to any one of claims 1 and 2, characterized by containing one or more of 0.1% or less and REM: 0.10% or less. .   The Al-containing ferrite system having excellent high-temperature strength according to any one of claims 1 to 3, wherein the tensile strength at a strain rate of 0.3 / min at 800 ° C is 50 MPa or more. Stainless steel.   The Al-containing ferritic stainless steel excellent in high-temperature strength according to any one of claims 1 to 4, which is applied to a fuel reformer, a heat exchanger, or a fuel cell high-temperature member.   The Al-containing ferritic stainless steel excellent in high-temperature strength according to any one of claims 1 to 4, which is applied to a high-temperature member used in at least one of a gas turbine and a power generation system.   The high-temperature strength according to any one of claims 1 to 4, wherein the high-temperature strength is applied to at least one of an automobile member of an exhaust manifold, a converter, a muffler, a turbocharger, an EGR cooler, a front pipe, and a center pipe. Al-containing ferritic stainless steel.   5. The Al-containing ferritic stainless steel excellent in high-temperature strength according to claim 1, wherein the Al-containing ferritic stainless steel is excellent in high-temperature strength, which is applied to a high-temperature member used in at least one of a stove and a fan heater.