JP5796397B2 - Ferritic stainless steel with excellent thermal fatigue properties and oxidation resistance - Google Patents

Description

  The present invention is a ferrite having excellent thermal fatigue characteristics and oxidation resistance suitable for members used in high-temperature environments such as exhaust pipes of automobiles and motorcycles, catalyst outer cylinder materials and exhaust ducts of thermal power plants. Related to stainless steel.

  Exhaust members such as exhaust manifolds, exhaust pipes, converter cases, and mufflers used in the exhaust system environment of automobiles are required to have excellent heat resistance such as heat fatigue resistance and oxidation resistance. ing. At present, a Cr-containing steel to which Nb and Si are added, for example, Type 429 (14Cr-0.9Si-0.4Nb series) steel is often used for such applications. However, when the exhaust gas temperature rises to a temperature exceeding 900 ° C. as the engine performance improves, Type 429 steel has a problem that the thermal fatigue characteristics are insufficient.

  For this problem, Cr-containing steel with improved high-temperature proof stress by adding Nb and Mo, SUS444 (19Cr-0.5Nb-2Mo) specified in JIS G4305, ferrite added with Nb, Mo, W Stainless steel (see, for example, Patent Document 1) has been developed. However, due to the unusual rise in Mo and W raw materials in recent years, it has become necessary to develop materials that are inexpensive and have heat resistance equivalent to that of SUS444.

  Under such circumstances, for example, Patent Documents 2 to 4 disclose materials having excellent heat resistance that do not use expensive elements such as Mo and W. All of the steels disclosed therein are characterized in that the thermal fatigue properties are improved by adding Cu.

  However, according to the researches of the inventors, when Cu is added as in the techniques disclosed in Patent Documents 2 to 4, the oxidation resistance of the steel itself is lowered and the workability is also lowered. It became clear that there was a new problem.

  Steels that have improved heat resistance without using Mo, W, or Cu include those disclosed in Patent Documents 5 to 11. In these patent documents, high heat resistance is achieved by utilizing precipitation strengthening of VN.

JP 2004-018921 A International Publication 2003/004714 Pamphlet JP 2006-117985 A JP 2000-297355 A Japanese Patent No. 4369596 JP-A-7-70709 JP 2010-156008 A JP 2000-248337 A JP 2010-43327 A JP 2002-30346 A Japanese Patent Laid-Open No. 6-184637

However, in the techniques of Patent Documents 5, 7, and 8 described above, all of Nb, V, and N are not added in an appropriate amount, so that the thermal fatigue characteristics are not yet sufficient, and sensitization occurs, resulting in corrosion resistance and oxidation resistance. There is also a problem that the performance is significantly reduced. In Patent Document 6, even if V and N are added in appropriate amounts, Mn is not in an appropriate amount, so that not only oxidation resistance but also thermal fatigue characteristics are not sufficient.
Further, in Patent Documents 10 and 11, since an appropriate amount of V and N is not added, excellent thermal fatigue characteristics cannot be obtained.

  Further, in recent years, it is assumed that the engine is used at a high temperature in order to comply with the automobile exhaust gas regulations, and accordingly the exhaust gas temperature becomes high. Further, when the exhaust gas becomes high temperature, the operating temperature of the catalyst rises, and the purification effect can be increased. In this way, when the exhaust gas temperature further increases, the techniques of Patent Documents 5 to 9 do not have sufficient oxidation resistance.

  This invention is made | formed in view of this situation, Comprising: It aims at providing the ferritic stainless steel excellent in the thermal fatigue characteristic and oxidation resistance, without using Mo, W, and Cu.

  In the present invention, “excellent in thermal fatigue characteristics and oxidation resistance” means having thermal fatigue characteristics equivalent to SUS444 and 1050 ° C. oxidation resistance exceeding SUS444. Specifically, the thermal fatigue characteristics at 200/850 ° C. are equal to or higher than those of SUS444, and abnormal oxidation does not occur at 1050 ° C. in the atmosphere.

  The inventors have intensively studied to solve the above problems. As a result, in order to effectively utilize the precipitation strengthening of VN and improve the thermal fatigue characteristics, it is necessary to optimize the Nb, V, and N contents, and excellent oxidation resistance at high temperatures. In order to obtain it, it was found that it is effective to optimize the amount of Cr after optimizing the amount of Mn.

  Specifically, with mass%, Si is 1.0% or less, Mn is 0.5% or less, Nb is 10 × (C + N) to 0.6%, and N is 0.015 to 0.040. The strength at high temperature is maintained for a long time by containing V so that V is in the range of 0.15 to 0.6% and V × N is 0.003 to 0.015. It has been found that even if Mo, W and Cu are not contained, heat fatigue characteristics equivalent to SUS444 can be obtained. Further, when Mn is 0.5 mass% or less, the oxidation resistance at 1000 ° C. is equal to or higher than that of SUS444, and when Cr is more than 20 mass% and 23 mass% or less, 1050 ° C. oxidation resistance exceeding SUS444 is obtained. I found out that

  The present invention has been completed based on the above findings of the present inventors.

That is, the present invention is mass%, C: 0.015% or less, Si: 1.0% or less, Mn: 0.5% or less, Al: 0.30% or less, P: 0.040% or less, S: 0.010% or less, Cr: more than 20% and 23% or less, Ni: 0.5% or less, N: 0.015 to 0.040%, Nb: 10 (C + N) to 0.60%, V: 0.15 to 0.60%, Ti: 0.01% or less (including 0) , Zr: 0.01% or less (including 0 ), Ta: 0.01% or less (including 0) , Mo: 0.1% or less (including 0) , W: 0.1% or less (including 0) , and satisfies 0.003 ≦ V × N ≦ 0.015, with the balance being Fe and inevitable impurities A ferritic stainless steel having excellent thermal fatigue characteristics and oxidation resistance is provided.

  Moreover, in addition to said component composition, this invention contains 1 type or 2 types of B: 0.0004-0.0020% and Co: 0.05-0.1% by mass% further. Ferritic stainless steel with excellent thermal fatigue characteristics and oxidation resistance characterized by

  Furthermore, the present invention provides a ferritic stainless steel excellent in thermal fatigue characteristics, oxidation resistance and steam oxidation resistance, characterized by containing Si in a range of 0.4 to 1.0%.

  According to the present invention, thermal fatigue characteristics equivalent to or better than SUS444 and 1050 ° C. oxidation resistance exceeding SUS444 can be achieved without containing expensive Mo, W, and Cu, and it is suitable for automobile exhaust members and the like. Ferritic stainless steel can be obtained.

It is a graph which shows the influence of N content which acts on a thermal fatigue characteristic. It is a graph which shows the influence of V content which acts on a thermal fatigue characteristic. It is a graph which shows the influence of VxN which acts on a thermal fatigue characteristic. It is a graph which shows the influence of Zr, Ti, Ta content which acts on a thermal fatigue characteristic. It is a graph which shows the influence of Mn content which affects oxidation resistance (oxidation increase). It is a graph which shows the influence of Cr content which gives to 1050 degreeC oxidation resistance (oxidation increase).

First, the basic experiment that led to the completion of the present invention will be described. In the following description, all percentages in the components are mass%.
First, the influence of N content on thermal fatigue characteristics was examined.
0.005-0.010% C-0.45-0.55% Si-0.15-0.25% Mn-0.040-0.050% Al-20.5-21.5% Cr- Based on a component system of 0.40 to 0.50% Nb-0.30 to 0.40% V, steel with various changes in N content in the range of 0.007 to 0.048% was obtained in the laboratory. The steel ingot was made into a steel ingot, this steel ingot was forged and heat-treated into a steel material, and a thermal fatigue test piece was produced from this steel material. Then, heating / cooling at 200/850 ° C. was repeated at a restraint rate of 0.8 to evaluate the thermal fatigue life. The thermal fatigue life was defined as the number of cycles in which the load detected at 200 ° C. was less than 80% of the initial load. For comparison, SUS444 (18% Cr-2% Mo-0.5% Nb steel) was also evaluated in the same manner.

  FIG. 1 shows the influence of the N content on the thermal fatigue life in the thermal fatigue test. From this figure, it can be seen that a thermal fatigue life superior to that of SUS444 is obtained when the N content is in the range of 0.015 to 0.040%. Therefore, in order to obtain excellent thermal fatigue characteristics, it is necessary that the N content is 0.015 to 0.040%.

Next, the influence of the V content on the thermal fatigue characteristics was examined.
0.005-0.010% C-0.45-0.55% Si-0.15-0.25% Mn-0.040-0.050% Al-20.5-21.5% Cr- Based on a component system of 0.40 to 0.50% Nb-0.015 to 0.025% N, steel with various changes in the V content in the range of 0.08 to 0.73% was obtained in the laboratory. The steel ingot was made into a steel ingot, this steel ingot was forged and heat-treated into a steel material, and a thermal fatigue test piece was produced from this steel material. Similarly, heating / cooling at 200/850 ° C. was repeated at a restraint ratio of 0.8 to evaluate the thermal fatigue life.

  FIG. 2 shows the influence of the V content on the thermal fatigue life in the thermal fatigue test. From this figure, it can be seen that a thermal fatigue life superior to that of SUS444 is obtained when the V content is in the range of 0.15 to 0.60%. Therefore, in order to obtain excellent thermal fatigue characteristics, the V content needs to be 0.15 to 0.60%.

Next, the optimum value of V × N was examined.
In addition to the experimental results shown in FIGS. 1 and 2, V and N contents are changed based on the same composition, and a steel ingot is produced in the same manner, then forged and heat-treated to obtain a steel material. A test piece was prepared, and similarly, heating / cooling at 200/850 ° C. was repeated at a constraint ratio of 0.8 to evaluate the thermal fatigue life.

  FIG. 3 shows the influence of the value of V × N on the thermal fatigue life in the thermal fatigue test. As shown in this figure, it can be seen that the thermal fatigue life is lower than SUS444 when the value of V × N is less than 0.003 or more than 0.015, even if V and N are within the above ranges, respectively. It was. Therefore, in order to obtain excellent thermal fatigue characteristics, it is necessary that the contents of V and N satisfy the above range, and the value of V × N is in the range of 0.003 to 0.015.

Next, the influence of Zr, Ti, and Ta contents on thermal fatigue characteristics was examined.
0.005-0.010% C-0.45-0.55% Si-0.15-0.25% Mn-0.040-0.050% Al-20.5-21.5% Cr- Based on a component system of 0.40 to 0.50% Nb-0.30 to 0.40% V-0.015 to 0.025% N, the contents of Zr, Ti, and Ta are each 0.003%. Steels changed in the range of ˜0.018%, 0.005 to 0.018%, 0.004 to 0.015% are melted in the laboratory to form steel ingots, and the steel ingots are forged. Then, heat treatment was performed to obtain a steel material, and a thermal fatigue test piece was produced from this steel material. Similarly, heating / cooling at 200/850 ° C. was repeated at a restraint ratio of 0.8 to evaluate the thermal fatigue life.

  FIG. 4 shows the influence of the Zr, Ti, and Ta contents on the thermal fatigue life in the thermal fatigue test. As shown in this figure, even if V, N, and V × N are within the above range, if the content of any of Zr, Ti, and Ta exceeds 0.01%, the thermal fatigue life is lower than SUS444. I found out that Therefore, in order to obtain excellent thermal fatigue characteristics, it is necessary that the contents of Zr, Ti, and Ta are all 0.01% or less.

Next, the influence of the Mn content on the oxidation resistance was examined.
0.005 to 0.010% C-0.45 to 0.55% Si-0.040 to 0.050% Al-20.5 to 21.5% Cr-0.40 to 0.50% Nb- Based on a component system of 0.30 to 0.40% V-0.015 to 0.025% N, a test piece was made from a steel plate having a composition in which the amount of Mn was changed in the range of 0.08 to 0.84%. The surface of this test piece was polished with # 320 emery paper, and then subjected to a continuous oxidation test at 1000 ° C. for 200 hours in the atmosphere. The oxidation resistance was evaluated by the amount of increase in oxidation. For comparison, SUS444 (18% Cr-2% Mo-0.5% Nb steel) was also evaluated in the same manner.

  FIG. 5 shows the influence of the Mn content on the increase in oxidation in the 1000 ° C. continuous oxidation test. From this figure, it can be seen that continuous oxidation resistance equal to or better than that of SUS444 can be obtained when the Mn content is 0.5% or less. Therefore, from the viewpoint of oxidation resistance, the Mn content needs to be 0.5% or less.

Next, the influence of the Cr content on the higher temperature 1050 ° C. oxidation resistance was examined.
0.005 to 0.010% C-0.45 to 0.55% Si-0.15 to 0.25% Mn-0.040 to 0.050% Al-0.40 to 0.50% Nb- Based on a component system of 0.30 to 0.40% V-0.015 to 0.025% N, it was produced from a steel plate having a composition in which the Cr content was changed in the range of 17.2 to 22.9%. Using the test piece, a continuous oxidation test was conducted at 1050 ° C. for 200 hours in the same manner as the above-described continuous oxidation test.

FIG. 6 shows the influence of the Cr content on the increase in oxidation in the 1050 ° C. continuous oxidation test. From this figure, it is understood that if the Cr content exceeds 20%, abnormal oxidation (= oxidation increase ≧ 100 g / m ² ) does not occur, and oxidation resistance exceeding SUS444 is obtained.

  The present invention has been completed as a result of further studies based on the results of the basic experiment as described above.

Hereinafter, the ferritic stainless steel according to the present invention will be described in detail.
First, the component composition of the present invention will be described.

C: 0.015% or less C is an element that increases the strength of steel, but if it exceeds 0.015%, the toughness and formability are significantly reduced. Therefore, in the present invention, the C content is set to 0.015% or less. From the viewpoint of moldability, the C content is preferably as low as possible, and is preferably 0.010% or less.

Si: 1.0% or less Si is an element that improves oxidation resistance and is also used as a deoxidizer. On the other hand, if the content exceeds 1.0%, the workability decreases. For this reason, Si content shall be 1.0% or less.
On the other hand, since an automobile exhaust system member is actually used in a gas containing water vapor, steam oxidation resistance is also important. Si is an element effective for improving the steam oxidation resistance, and its effect can be obtained by adding 0.4% or more. The reason why the steam oxidation resistance is improved by Si is not fully understood, but by making the Si content 0.4% or more, a dense Si oxide layer is continuously formed on the steel sheet surface. This is considered to be due to the generation and suppression of gas components from the outside. Therefore, when steam oxidation resistance is required, the Si content is preferably 0.4 to 1.0%. When oxidation resistance under a more severe steam-containing atmosphere is required, the Si content is preferably 0.5% or more.

Mn: 0.5% or less Mn acts as a deoxidizer, but if contained excessively, a γ phase is likely to be generated at a high temperature, not only reducing heat resistance but also reducing oxidation resistance. For this reason, Mn content shall be 0.5% or less. Preferably, it is 0.35% or less, more preferably 0.3% or less.

P: 0.040% or less P is an element that lowers toughness, and is desirably reduced as much as possible. For this reason, the P content is set to 0.040% or less. Preferably, it is 0.030% or less.

S: 0.010% or less S is an element that lowers elongation and r value, degrades formability, and lowers corrosion resistance, which is a basic characteristic of stainless steel, and is desirably reduced as much as possible. For this reason, S content shall be 0.010% or less.

Cr: more than 20% and 23% or less Cr is an element that improves oxidation resistance. As shown in FIG. 6, when Cr is contained exceeding 20%, abnormal oxidation does not occur even at 1050 ° C. On the other hand, Cr hardens and lowers ductility by solid solution strengthening at room temperature, and if it exceeds 23%, workability deteriorates. For this reason, Cr content is made into the range of more than 20% and 23% or less.

N: 0.015 to 0.040%, V: 0.15 to 0.60%, and V × N: 0.003 to 0.015
V and N are important elements in the present invention. By containing V and N, these precipitate finely as VN at 600-800 degreeC, and improve a thermal fatigue characteristic by making steel materials high intensity | strength. The effect is recognized when the N content is 0.015% or more and the V content is 0.15% or more. However, excessive inclusion not only deteriorates the toughness and formability of the steel, but also causes the VN to become coarse and reduce the thermal fatigue life. Therefore, the N content is in the range of 0.015 to 0.040%, and the V content is in the range of V: 0.15 to 0.60%. Even if V and N are within the above ranges, the desired thermal fatigue life cannot be obtained unless V × N satisfies 0.003 to 0.015. For this reason, V × N was set to 0.003 to 0.015.

Nb: 10 (C + N) to 0.60%
Nb is a beneficial element that fixes C and N, has an effect of enhancing sensitization characteristics, formability, and intergranular corrosion resistance of welds, and increases thermal fatigue characteristics by increasing high-temperature strength. . However, if the content is less than 10 (C + N), the fixation of C and N becomes insufficient, and sensitization of the steel material is recognized. When sensitization occurs, corrosion resistance and oxidation resistance in the welded portion are remarkably lowered, so that it is necessary to add 10 (C + N) or more of Nb. Depending on the amount of Nb, the same phenomenon may occur in the base material portion. On the other hand, if its content exceeds 0.60%, the Laves phase is likely to precipitate and not only becomes brittle, but also the precipitation of VN, which is important in the present invention, is suppressed, and the thermal fatigue characteristics deteriorate. For this reason, Nb content shall be 10 (C + N)-0.60% of range. Preferably, it is 0.55% or less, more preferably 0.50% or less.

Mo: 0.1% or less (including 0)
Mo is an expensive element and is not actively added for the purpose of the present invention. Since the mixing amount from scrap or the like as the melting raw material is at most 0.1%, the Mo content is set to 0.1% or less (including 0) .

W: 0.1% or less (including 0)
W is an expensive element like Mo and is not actively added for the purpose of the present invention. Since the amount of mixing from scrap, which is a melting raw material, is at most 0.1%, the W content is set to 0.1% or less (including 0) .

Ti, Zr, Ta: 0.01% or less (including 0)
Ti, Zr, and Ta have the effect of fixing C and N to improve the corrosion resistance, formability, and intergranular corrosion of the weld, but suppress the precipitation of VN, which is important in the present invention. Even if the amounts of V and N specified in the above are satisfied, if they are contained in an amount exceeding 0.01%, the thermal fatigue characteristics are deteriorated. Therefore, the contents of Ti, Zr, and Ta are all 0.01% or less (including 0) .

Al: 0.30% or less Al is an element effective in improving oxidation resistance and high-temperature salt damage corrosion resistance. However, if the content exceeds 0.30%, the steel becomes hard and the workability is significantly reduced. For this reason, Al content shall be 0.30% or less. More preferably, it is 0.03 to 0.20%.

Ni: 0.5% or less Ni is an element that improves toughness, but is not only expensive, but also a strong γ-phase-forming element, and a γ-phase is formed at a high temperature to reduce oxidation resistance. Therefore, the Ni content is 0.5% or less.

  The ferritic stainless steel of the present invention may further contain the following components in addition to the above components.

One or two of B: 0.0004 to 0.0020% and Co: 0.05 to 0.1% B is an effective element that improves workability, particularly secondary workability. Such an effect is effectively exhibited at 0.0004% or more. However, when the content exceeds 0.0020%, BN is generated and workability is deteriorated. For this reason, when it contains B, the content shall be 0.0004 to 0.0020% of range.
Co is an element effective for improving toughness. Such an effect is exhibited at 0.05% or more. However, Co is an expensive element, and the above effect is saturated even if its content exceeds 0.1%. For this reason, when Co is contained, the content is set to 0.05 to 0.1%.

Next, the manufacturing method of the ferritic stainless steel of this invention is demonstrated.
The ferritic stainless steel of the present invention can be manufactured by a general ferritic stainless steel manufacturing method, and the manufacturing conditions are not particularly limited. For example, molten steel having a composition within the scope of the present invention is smelted by a smelting method using a smelting furnace such as a converter or an electric furnace, or using a smelting method such as ladle smelting or vacuum smelting, and continuous casting. It is preferable to make a steel slab by the method and the ingot-making method, and to form a cold-rolled annealed plate through the respective steps of hot rolling, hot-rolled sheet annealing, pickling, cold rolling, finish annealing, and pickling. Further, the cold rolling may be one or two or more cold rolling including intermediate annealing. The steps of cold rolling, finish annealing, and pickling may be repeated. In some cases, the hot-rolled sheet annealing may be omitted. Furthermore, when glossiness of the steel sheet surface is required, it can be produced as a steel sheet with good workability even if a skin pass or the like is applied.

  No. shown in Table 1. The test shown below was done using the steel which has a component composition of 1-40. No. Among the component compositions of 1 to 40, No. 1 1 to 17 are examples of the present invention, No. 1 within the scope of the present invention. 18 to 40 are comparative examples that are out of the scope of the present invention. Of the comparative examples, No. 31, 32, 33, 34, and 35 are Japanese Patent No. 4369596 (Patent Document 5), Japanese Patent Laid-Open No. 7-70709 (Patent Document 6), Japanese Patent Laid-Open No. 6-158162, and Japanese Patent Laid-Open No. 2000-144344, respectively. This corresponds to the component composition disclosed as an example in Japanese Laid-Open Patent Publication No. 2010-43324, and 36 corresponds to SUS444. No. 37, 38, 39, and 40 are disclosed in JP 2010-156008 A (Patent Document 7), JP 2010-43327 A (Patent Document 9), and JP 2002-30346 A (Patent Document 10), respectively. This corresponds to the component composition disclosed as an example in Japanese Laid-Open Patent Publication No. 6-184637 (Patent Document 11).

  No. above. 50 kg steel ingots having a component composition of 1 to 40 were prepared, and these steel ingots were heated to 1170 ° C., and then hot rolled into hot rolled sheets having a thickness of 5 mm. Next, hot-rolled sheet annealing (annealing temperature: 1040 ° C.)-Pickling-cold rolling (cold rolling reduction: 60%)-finish annealing (annealing temperature: 1040 ° C., average cooling rate) for these hot-rolled sheets: 30 ° C./s)—Pickling was performed sequentially to obtain a cold-rolled annealed plate having a thickness of 2 mm.

  Test pieces were prepared from these cold-rolled annealed plates and subjected to an oxidation test. In the oxidation test, the surface of the test piece was polished with # 320 emery paper and then subjected to continuous oxidation in the atmosphere at 1000 ° C. and 1050 ° C. for 200 hours. The oxidation resistance was evaluated by the increase in oxidation at that time.

Moreover, the test piece produced from the said cold-rolled annealing board was used for the oxidation test in water vapor | steam atmosphere. In the steam atmosphere oxidation test, a 30 mm × 20 mm test piece was cut out from each cold-rolled annealed plate, a hole of 4 mmφ was made in the upper part of the test piece, and the surface and end face were polished with # 320 emery paper and degreased. This test piece was heated to 950 ° C. with 10% CO ₂ -20% H ₂ O-5% O ₂ -bal. N ₂ gas was flowed at 0.5 L / min and held in a furnace in a steam atmosphere for 200 hours. After the test, the mass of the test piece was measured, the difference from the pre-test mass measured in advance was determined, and the increase in oxidation (g / m ² ) was calculated. The evaluation was performed twice, and finally the average value was evaluated.

Further, 15 mm × 10 mm was cut out from the cold-rolled annealed plate, and oxalic acid etching (JIS G 571) was performed on the L cross section. A 10% oxalic acid solution was used for etching, and a current of 1 A / cm ² was passed for 90 minutes at room temperature. Subsequent structures were observed, and those where significant grain boundary corrosion (grooved structures) was observed were judged as sensitizers.

  On the other hand, the above-mentioned No. A steel ingot having a component composition of 1 to 40 was heated to 1170 ° C. and then hot rolled to form a hot rolled sheet bar having a width of 150 mm and a thickness of 35 mm. A bar of 30 mm □ was formed by forging, annealed at 1040 ° C., then processed into a thermal fatigue test piece by machining, and used for evaluation of the thermal fatigue life.

  In the thermal fatigue test, the temperature was repeatedly raised and lowered between 200 ° C. and 850 ° C. with a restraint ratio of 0.8. The temperature rise / fall was 5 ° C./s, and the 850 ° C. holding time was 1 minute. The definition of thermal fatigue life is the same as in the evaluation of FIG.

  The obtained results are shown in Table 2. As is apparent from Table 2, all of the examples of the present invention showed a thermal fatigue life equal to or higher than that of SUS444 and oxidation resistance at 1050 ° C. exceeding that of SUS444, and it was confirmed that the objective of the present invention was achieved. It was. On the other hand, in the comparative example outside the scope of the present invention, both characteristics were not satisfied at the same time, and it was confirmed that the target of the present invention was not achieved. Moreover, sensitization occurred in the comparative examples having a Nb content of less than 10 (C + N).

  Moreover, it was confirmed that among the examples of the present invention, those having Si of 0.4% or more can obtain excellent steam oxidation resistance.

  The steel of the present invention is not only suitable for exhaust system members such as automobiles, but also suitably used as exhaust system members for thermal power generation systems and solid oxide fuel cell members that require similar characteristics. be able to.

Claims (3)

In mass%, C: 0.015% or less, Si: 1.0% or less, Mn: 0.5% or less, Al: 0.30% or less, P: 0.040% or less, S: 0.010% Hereinafter, Cr: more than 20% and 23% or less, Ni: 0.5% or less, N: 0.015 to 0.040%, Nb: 10 (C + N) to 0.60%, V: 0.15 to 0. 60%, Ti: 0.01% or less (including 0) , Zr: 0.01% or less (including 0 ), Ta: 0.01% or less (including 0) , Mo: 0.1% or less ( 0) , W: 0.1% or less (including 0) , 0.003 ≦ V × N ≦ 0.015 is satisfied, and the balance consists of Fe and inevitable impurities Ferritic stainless steel with excellent thermal fatigue characteristics and oxidation resistance.   In addition to the above component composition, the composition further comprises one or two of mass%, B: 0.0004 to 0.0020%, Co: 0.05 to 0.1%. 1. Ferritic stainless steel excellent in thermal fatigue characteristics and oxidation resistance as described in 1.   The ferritic stainless steel having excellent thermal fatigue characteristics, oxidation resistance, and steam oxidation resistance according to claim 1 or 2, wherein Si is contained in a range of 0.4 to 1.0%.

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