TW201221658A - Ferritic stainless steel having excellent heat resistance and workability - Google Patents

Abstract

Provided is a ferritic stainless steel excellent in both the heat resistance (resistance to oxidation, thermal fatigue property, and fatigue property in high temperature) and the workability without adding expensive elements such as Mo and W while preventing the decrease in oxidation resistance caused by using Cu. Specifically, a ferritic stainless steel containing, in mass%, C: 0.015% or less, Si: 0.4 to 1.0%, Mn: 1.0% or less, P: 0.040% or less, S: 0.010% or less, Cr: 12% or more to less than 16%, N: 0.015% or less, Nb: 0.3 to 0.65%, Ti: 0.15% or less, Mo: 0.1% or less, W: 0.1% or less, Cu: 1.0 to 2.5%, Al: 0.2 to 1.0%, wherein Si = Al is satisfied, and the remnant is composed of Fe and unavoidable impurities.

Description

201221658 VI. Description of the Invention: [Technical Field] The present invention relates to an exhaust pipe and a catalyst outer tube material (also referred to as a "converter box") suitable for use in automobiles and motorcycles. (converter case), exhaust system components used in high-temperature environments such as exhaust air ducts of thermal electric power plants, and high heat resistance (thermal fatigue characteristics, oxidation resistance) 'High temperature fatigue characteristics' and processability of ferrite iron stainless steel. [Prior Art] Excellent exhaust fatigue is required for exhaust manifold components such as an exhaust manifold, an exhaust pipe, a converter case, and a muffler used in an exhaust system environment of an automobile. Thermal fatigue property, high-temperature fatigue property, and oxidation resistance (hereinafter collectively referred to as "heat resistance property"). The exhaust manifold and the like are subjected to heating and cooling by repeating the initiation and stop of engine operation, but are restrained due to the relationship with the peripheral components, and thus the thermal expansion and heat of the material itself. The shrinkage is limited to produce a thermal strain. The fatigue phenomenon caused by this thermal strain is thermal fatigue. On the other hand, vibration is continuously sustained in the heated state during engine start-up. The fatigue phenomenon caused by the accumulation of strain caused by the vibration is high-temperature fatigue (high-temperature 100137265 3 201221658 fatigue). The former belongs to 丨ow_cycle fatigue, and the latter belongs to high-cycle fatigue, which is a completely different fatigue phenomenon. In applications requiring such heat resistance, Cr-containing steels such as Type 429 (14Cr-0.9Si_0.4Nb) which are added with Nb and Si are often used. However, as the engine performance increases, if the exhaust gas temperature rises to a temperature exceeding 900 °C, the thermal fatigue characteristics of the Type 429 may become insufficient. In response to this problem, it has been developed: Cr-containing steels with high temperature endurance by adding Nb and Mo俾, and SUS444 (19Cr-0.5Nb-2Mo) specified by JIS G4305, reducing Cr content and adding Nb, Mo, The ferrite-grained stainless steel of W or the like (see, for example, Patent Document 1). However, since the price of rare metal raw materials such as Mo and W is abnormally high, development of materials having the same heat resistance using inexpensive raw materials is required. A material excellent in heat resistance without using the high-valent elements Mo and W is known as disclosed in Patent Documents 2 to 4. Patent Document 2 discloses that an automobile exhaust flow path member fertilizer is added by adding Nb: 0.50 mass% or less, Cu: 0.8 to 2.0 mass%, and V: 0.03 to 0.20 mass% in 1 〇 to 2 〇 mass% Cr steel. Granular iron stainless steel. Patent Document 3 discloses that in 10 to 20% by mass of Cr steel, it is added

Ti: 0.05 to 0.30% by mass, Nb: 0.10 to 0.60% by mass, Cii: 0.8 to 2.0% by mass, and B: 0.0005 to 0.02% by mass of the ferrite which is excellent in thermal fatigue characteristics. Patent Document 4 discloses that in the case of 15 to 25% by mass of Cr steel, Cu: 1 to 3 mass% of automobile exhaust system parts are used for ferrite-grain non-mine 100137265 4 201221658 4 kg of steel is characterized by borrowing The thermal fatigue characteristics are improved by the addition of Cu. [PRIOR ART DOCUMENT] [Patent Document 1] Japanese Patent Laid-Open Publication No. Hei 2 〇〇 〇 21 21 〇 〇 〇 〇 〇 专利 专利 专利 专利 专利 专利 〇〇 〇〇 〇〇 〇〇 〇〇 〇〇 〇〇 〇〇 〇〇 〇〇 〇〇 〇〇 〇〇 〇〇 〇〇 〇〇 〇〇 Japanese Patent Laid-Open Publication No. Hei. No. Hei. No. Hei. No. Hei. No. Hei. No. 2,297,355, the entire contents of which are hereby incorporated by In the case where Cu is added as in the technique of the above-mentioned Patent Document 2 to 4 kg, the thermal fatigue resistance is improved, but the oxidation resistance itself is lowered, and the overall heat quality is deteriorated. The weight of the vehicle body is reduced with the weight of the car body, and the space occupied by the exhaust manifold in the engine space becomes smaller. Therefore, the exhaust manifold can be processed into a complicated shape. In view of this fact, Shuming County aims to provide: to prevent the oxidation resistance caused by ^, and to add μ. High price of w, etc.: In the case of two, the heat-resistant (oxidation resistance, thermal fatigue characteristics, high-temperature fatigue characteristics) and workability are excellent. In addition, in the present invention, "excellent heat resistance, high-temperature fatigue characteristics and high-temperature fatigue characteristics, and SUS444" mean that the oxidizing property and heat are equal to or higher than the above. Specifically, 100137265 201221658 The oxidation resistance is 95 (the oxidizing property of TC is equal to or higher than SUS444). The thermal fatigue characteristic refers to the thermal fatigue when S 100-850 〇C is repeated. As described above, the high-temperature fatigue property means that the high-temperature fatigue property at 85 ° C is equal to or higher than that of SUS 444. X, the "excellent workability" of the present invention means that the three-way average elongation at room temperature is equal to or higher than that. (Means for Solving the Problem) The inventors have been able to prevent oxidation resistance caused by cu in the prior art, and have an oxidation resistance and a high-valent element such as M〇 and w. The development of the ferrite-based iron-based stainless steel with thermal fatigue characteristics was carried out intensively. The results were found to be comprehensively contained in the range of Nb: 0.3 to 0.65 mass% and Cu: 1.0 to 2.5 mass%. High temperature strength is obtained, 热 can improve thermal fatigue characteristics, and reduction in oxidation resistance due to inclusion of Cu can be prevented by containing an appropriate amount of Al (0.2 to 1.0% by mass), and therefore, for the first time Discovery By controlling Nb and A1 within the above-described appropriate range, heat resistance (thermal fatigue characteristics and oxidation resistance) equal to or higher than SUS444 can be obtained even if M〇 and w are not added. Further, it is assumed that the actual use is exhaust gas. In the case of a pipe or the like, the oxidizing resistance in a water vapor environment (hereinafter referred to as "the amount of Si" is appropriately studied (0.4 to 9% by mass). "Water vapor oxidation resistance" is also equal to or higher than SUS444. 100137265 6 201221658 Furthermore, in automotive exhaust system components such as exhaust manifolds, vibrations due to use The characteristics of the fatigue caused are also important. Therefore, the inventors and others have conducted in-depth research on the means for improving the fatigue characteristics of the local temperature. I found that by optimizing the balance between the amount of Si and the amount of A1 (Si^Al), In addition, the inventors and others have conducted in-depth research on the influence of the amount of Cr on the workability and oxidation resistance. By reducing the amount of Cr, the workability can be improved without greatly affecting the oxidation resistance at this time. Although it is known from the self-study that the workability can be improved by reducing the amount of Cr, only the amount of Cr is lowered. As a result of the reduction in oxidation resistance, it is conventionally known that, as in Patent Document 1, the addition of Mo and W in place of Cr reduces the oxidation resistance. In contrast, it has been found that the present invention adds an appropriate amount of A1. On the other hand, in the case where Mo and W belonging to the high-priced τ-α are not added, even if the amount of Cr is lowered, excellent oxidation resistance and workability can be achieved. The present invention has been completed in accordance with the findings of the present inventors as described above. That is, the present invention provides a ferrite-based iron-based stainless steel which is excellent in heat resistance and addition, and contains %:%: c: Q. 15% or less, Si:. 4~! 〇%, ' Μ11 [Ο/. Hereinafter, P. 0.040% or less, s: 〇·〇ι〇〇/〇, and Cr: 12〇/. One or more and less than 16%, N: 0.015% or less, Nb: 0.3 to 0.65%, Ti: 0·15% or less, Μό: Π 1 〇 / , , 丄 0. Ul/oM, W: 0.1% The following, CU: 1.0 ~ 2.5 〇 / 〇, A1: 0.2 ~ 1 . 〇%, and, his brother 0., the ugly foot A, the rest is composed of Fe and unavoidable impurities. 100137265 7 201221658 In addition, the present invention provides a ferrite-based iron-based stainless steel which is excellent in heat resistance and workability, and further contains, in terms of % by mass, B: 〇〇〇3% or less, rEm: 0.08% or less, Zr: 〇 5〇/〇 below, v: 〇.5〇/〇 below, c〇: 〇5% or less and Ni: 0.5% or less! Kind or more than two. (Effect of the Invention) According to the present invention, heat resistance (thermal fatigue characteristics, oxidation resistance, high temperature fatigue characteristics) equal to or higher than SUS444 (JIS G4305) can be obtained at a low cost without adding high-priced Mo and W. Processable ferrite iron is not iron. Therefore, the steel of the present invention is suitable for use in automotive exhaust system components. [Embodiment] First, a basic experiment for carrying out the present invention will be described. In addition, in the following description, the "%" indication of the 'component' means "% by mass". Laboratory Hyun C: 0.005~0.007%, N: 0.004~0.006%, P: 0.02-0.03% ' S : 0.002-0.004% ' Si : 0.85% ' Μη : 0.4% '

Cr: 14%, Nb: 0.45%, A1: 0.35%, Ti: 0.007%, Mo: 0.01-0.03%, W: 0.01 to 0.03% based on the composition of the composition, and the Cu content is in the range of 0 to 3%. The steel was changed to form a 50 kg steel block, and the steel block was forged, and heat-treated to form a steel material having a sectional area of 35 mm x 35 mm, and a thermal fatigue test specimen having a size shown in Fig. 1 was produced from the steel material. Then, heat treatment according to the restraint ratio of 0.30, heating and cooling between 100 ° C and 850 ° C was repeated, and the thermal fatigue life was measured. In addition, the above heat 100137265 8 201221658 fatigue system is set to the load detected by the loot divided by the map! The test piece is calculated by the cross-sectional area (cr〇ss section) of the heat parallel portion, and the stress is calculated as the stress and the stress of the previous cycle is the minimum number of cycles when the stress starts to decrease continuously. This is equivalent to the number of cycles in which the test piece will crack. In addition, for comparison, the same test was also carried out for the material (10): 19%-Mo: 2%-Nb: 0.5% steel. Fig. 4 is a graph showing the effect of the Cu content on the thermal fatigue life in the above thermal fatigue test. As can be seen from the figure, by setting the Cu content to 1 〇〇/〇 or more, the thermal fatigue life equivalent to or higher than the thermal fatigue life of SUS444 (about 50 cycles) can be obtained, so that the thermal fatigue property is improved. It is effective to set the CU content to 1% or more. Secondly, the laboratory melting is C: 0.006%, N: 〇, 〇〇 7%, p: 0.02~0.03%, S: 0.002~0.004%, Μη: 0.2%, Si: 〇 85%,

Cr: 14%, Nb: 0.49%, Cu: 1.5%, Ti: 0.007%, M〇: 〇.01 to 0.03% W: 0.01 to 0.03% of the composition of the composition, and the A1 content is 〇~2% The steel in the range changes to form a 50 kg steel block, which is formed by hot rolling, hot-rolled sheet annealing, cold rolling (c〇id r〇Uing), and finishing annealing. C〇ld rolled and annealed steel sheet having a thickness of 2 mm. A 30 mm x 20 mm test piece was cut out from the cold milk steel plate obtained above, a hole was formed in the upper part of the test piece, and the surface and the end surface were ground using #320 emery paper, and after degreased, it was supplied to the following atmosphere. Continuous oxidation test. 100137265 9 201221658 <continuous oxidation test in air> The above test piece was kept in an atmospheric environment furnace heated to 950.t for 2 hours, and the quality of the test piece before and after the heating test was measured. And to determine the oxidation increment per unit area (g / m2). Fig. 5 is a graph showing the effect of the Ai content on the oxidation addition in the above continuous atmospheric oxidation test. As is clear from the figure, the oxidizing property (oxidation increment: 19 g/m 2 or less) equivalent to or higher than SUS444 can be obtained by setting the A1 content to 〇 2% or more. Secondly, laboratory melting is C: 0.006%, N: 0.007%, p: 0.02 to 0.03%, S: 0.002 to 0.004%, Μη: 0.2%, A1: 0.45%, Cr: 14%, Nb: 0.49 %, Cu: 1.5%, Ti: 〇.〇〇7%, Mo: 〇.〇l~〇.〇3〇/0, W: 0.01~0.03% based on the composition of the composition, and various changes in Si content The steel is formed into a 50 kg steel block, and the steel block is subjected to hot rolling, hot rolled sheet annealing, cold rolling, and finish annealing to form a cold rolled annealed sheet having a thickness of 2 mm. A 30 mm&gt;&lt;20 mm test piece was cut out from the cold-rolled steel sheet obtained as described above, and a 4 mm0 hole was cut in the upper part of the test piece, and the surface and the end surface were ground by #320 sandpaper, and after degreasing, the following water vapor was supplied. Environmental continuous oxidation test. Continuation oxidation test in water vapour atmosphere &gt; Using the above test piece, make 10v〇l%CO2-20V〇l%H2O-5V〇l%〇2-bal, N2 gas 〇.5L/min circulates to form a water vapor environment, and is heated to 950 ° C in the furnace to maintain 200 small 100137265 10 201221658 day, the quality of the test piece before and after the heating test is measured, and the oxidation increase per unit area is determined Quantity (g/m2). Fig. 6 is a graph showing the effect of the content on the oxidation increase in the above steam oxidation test. As can be seen from the figure, if the Si content is less than 0.4%, the same water vapor oxidation resistance as SUS444 cannot be obtained (oxidation increment: • 37 g/m2 or less followed by 'laboratory melting to C: 0.006%) , N : 0.007%, P: 0.02 to 0.03 ° /., s : 0.002 to 0.004%, Μη: 0.2%, Cr: 14%, Nb: 0.49%, Cu: 1.5%, Ti: 0.007%, Mo: 0.01 ～0.03%, W: 〇·01~0.03% of the composition of the composition, and the Si and A1 content of the steel changed to form 5 〇 kg steel block, the steel block is hot rolled, hot rolled sheet annealing Cold-rolled and finished annealing to form a cold-rolled annealed sheet having a thickness of 2 mm. A high-temperature fatigue test piece of the shape shown in Fig. 3 was produced from the cold-rolled steel sheet obtained as described above and subjected to the following high-temperature fatigue test. Two-temperature fatigue test> Using the above test piece, the Schenck type fatigue testing machine was used to perform evaluation by biaxially vibrating at 22 ° C (1300 rpm) by using a Schenck type fatigue testing machine. During the test, the bending stress of 70 MPa is applied to the surface of the steel plate, and it is until the fracture The number of labors (cycles) was evaluated. Figure 7 shows the effect of Si_A1 on the number of fatigues (cycles) in the above high temperature fatigue test. It is known from the figure that the high fatigue life of 100137265 201221658 is obtained in the same way as SUS444 ( 24χ105 cycles), SigAl must be satisfied. Secondly, laboratory melting is C: 0.006%, N: 0.007%, P: 0.02~0.03%, S: 0.002~0.004%, Μη: 0.2%, Si: 0.85%, A1: 0.45%, Nb: 0.49%, Cu: 1.5%, Ti: 0.007%, Mo: 0.01 to 0.03%, W: 0.01 to 0.03% based on the composition of the composition, and the steel having various changes in the niobium content' A 50 kg steel block was formed, and the steel block was subjected to hot rolling, hot-rolled sheet annealing, cold rolling, and finishing annealing to form a cold-rolled annealed sheet having a thickness of 2 mm. A 30 mm x 20 mm test piece was cut out from the cold-rolled steel sheet obtained as described above. A 4 mm0 hole was drilled in the upper part of the test piece, and the surface and the end surface were ground by #320 sandpaper, and after degreasing, the steam gasification test was supplied. Fig. 8 shows that the Cr content is oxidized to increase the temperature in the above steam oxidation test. The effect is as follows: If the Cr content is 12 When it is more than %, the water vapor oxidation resistance equivalent to SUS444 is obtained (oxidation increment: the following). Further, each of the cold-rolled annealed sheets was produced in a direction perpendicular to the rolling direction (direction of one direction), a direction perpendicular to the direction of the emulsion direction (C direction), and 45 in the rolling direction. The direction (D direction) is the brain 3B tensile test piece in the stretching direction, and the tensile test was performed at room temperature twice. A tensile test in each direction was carried out at room temperature, and the elongation = length was measured, and the average elongation E1 was obtained from the following formula. , average elongation E1 (%) = (El + 2Ed + Ec) / 4 where, El: _ in the L direction, know: _ in the 〇 direction, £^ 100137265 12 201221658 El (〇 / 〇) in the direction Figure 9 The effect of the Cr content on the value of the average elongation in the three directions (L, C, and D directions) is shown. As shown in the figure, it is known that when the Cr content is less than 16%, three directions (L, C) are obtained. , D direction) The average elongation is more than 36% • Good processability. - The present invention is a result of further review based on the results of the above basic experiment. Hereinafter, the ferrite-based iron-based stainless steel of the present invention will be described in detail. First, the component composition of the present invention will be described. C : 0.015% or less The C system is an element effective for increasing the strength of the steel. However, if it is more than 0.015 / Torr, the reduction in toughness and formability tends to be remarkable. Therefore, in the present invention, the c-containing system is set to 0015% or less. Further, from the viewpoint of ensuring formability, the C-containing 1 system is preferably as low as possible, and is preferably set to 0.008% or less. On the other hand, from the viewpoint of ensuring the strength of the exhaust system component (four), the C content is preferably 1% or more, more preferably 〇 to 10 (10).

Si · 0.4 to 1.0% * Sl is an important element for improving oxidation resistance in a water vapor environment. As shown in Fig. 6, in order to obtain the same water vapor oxidation resistance as SUS444, it is necessary to contain 0.4% or more. On the other hand, if the Si content exceeds 1.0%, the workability is remarkably lowered. Therefore, the Si content is set to a range of 0.4 to 1_0 ° / 〇. The better system is set to 0.5 to 0.9% of the range of 100137265 13 201221658. The detailed mechanism for improving the oxidation resistance of water vapor by setting S#f to G. 4% or more is not sufficiently clear, but it can be considered that the surface of the steel sheet can be formed by setting Si to 0.4% or more. The formation of the Si oxide layer is continuously formed, and the intrusion of gas components from the outside is suppressed, thereby enhancing the resistance to water vapor oxidation. When the oxidation resistance in a more severe environment is required, it is preferred to set the Si content to 0.5% or more. Μη : 1.0% or less Μ 系 is an element that increases the strength of steel and also acts as a deoxidizer. However, if it is excessively contained, the γ phase is likely to be formed at a high temperature, resulting in a decrease in heat recovery. Therefore, the Μη content is set to be below the coffee. Preferably, the system is less than 7%. Further, in order to obtain an effect of improving strength and a deoxidizing effect, it is preferably 0.05% or more. Ρ : 0.040% or less The lanthanum is a harmful element that reduces the secret, and should be reduced as much as possible. Therefore, the niobium content is set to 0.040% or less. Preferably, the system is less than 3%. S: 0.010% or less S is a harmful element that lowers the elongation and the r value, adversely affects the properties, and lowers the resistance of the basic characteristics of the stainless steel, and thus is preferably reduced as much as possible. Therefore, the S content is set to be 0.% or less. Preferably, it is 0.005% or less.

Cr : 12% or more and less than 16%

The Cr system is an important element for improving the resistance of the stainless steel to the characteristics of the metal, and the oxidation resistance is 100137265 14 201221658. However, if the content is less than 12%, sufficient oxidation resistance cannot be obtained. On the other hand, Ci: is an element which hardens and hardens steel by solid solution strengthening at room temperature. In particular, if the content is 16% or more, the above disadvantages tend to be conspicuous. Therefore, the 'Cr content system is set to be in the range of 12% or more and less than μ%. Better range of 12 to 15%. N: 0.015% or less N is an element which lowers the boring property and formability of steel. If it contains more than 0.015% Å, the above-mentioned decrease tends to be conspicuous. Therefore, the n content is set to 0.015% or less. Further, N is preferably as small as possible from the viewpoint of ensuring toughness and formability, and is preferably set to less than 0.01 〇〇/. .

Nb : 0.3~0.65%

The Nb system is formed by forming a carbide, a nitride or a carbonitride with C and N, and has improved corrosion resistance, formability, and a grain boundary rot of the fused portion ( The action of jntergranuiar corrosion resistance' has an effect of increasing the high-temperature strength and improving the thermal fatigue characteristics. This effect is manifested by containing 0.3% or more. On the other hand, when the content exceeds 〇.65%, Laves 'phase (Fe2Nb)' which is a mesogen compound of Fe and Nb is easily precipitated to promote embrittlement. Therefore, the Nb content is set in the range of 0.3 to 0.65%. It is preferably in the range of 0.4 to 0.55%.

Mo : 0.1% or less

Mo is a high-priced element and is not actively added from the gist of the present invention. 100137265 15 201221658 Added. However, there are cases in which scraps or the like belonging to raw materials are mixed in a range of 0.1 〇 / 〇 or less. Therefore, the Mo content is set to 0.1 〇/〇 or less W: 0.1% or less. The W system is a high-priced element similarly to Mo, and is not actively added from the gist of the present invention. However, it is sometimes mixed with waste materials such as raw materials in a range of 0.1% or less. Therefore, the W content is set to be 0.1% or less.

Cu: l.〇~2.5%

The Cu system is an element that is very effective for improving the thermal fatigue characteristics. As shown in Fig. 3, in order to obtain the same thermal fatigue characteristics as SUS444, the Cu content must be 1.0% or more. However, if the content exceeds 25%, ε-Cu precipitates upon cooling after the heat treatment, resulting in remarkably hardening of the steel and easy embrittlement during hot working. More importantly, although the thermal fatigue resistance is improved by the inclusion of Cu, the oxidation resistance of the steel itself is lowered, and as a whole, the heat resistance is lowered. Although the reason for this is not sufficiently clear, it is considered that the redispersion of the Cu-based layer in the de-Cr layer directly under the generated scale causes the re-diffusion of the element Cr which is an original oxidation resistance of the stainless steel to be suppressed. Therefore, the 'Cu content is set to 丨〇~2 5%. Better 丨 丨 丨 8% range.

Ti : 0.15% or less

Similarly to Nb, the Ti system fixes c and N, and has a function of improving the resistance of the decorative f·forming form I and the grain boundary of the welded portion. However, such an effect is saturated in the system of the present invention having 3 Nb, and if it exceeds the content, 100137265 16 201221658 is saturated, and the steel is hardened by solid solution hardening. Therefore, the Ti content is set to be 0.15 〇 / 〇 or less. Compared with Nb, the Ti phase is more likely to bond with N and easily form coarse TiN. Since coarse TiN tends to be a starting point of cracking, resulting in a decrease in toughness, it is preferably 0.01% or less when the toughness of the hot rolled sheet is required. Further, in the present invention, the diterpene does not need to be actively contained, so the lower limit contains ruthenium/iridium. A1 · 〇.2~1.〇% A1 is shown in Figure 5. 'It is an indispensable element for improving the oxidation resistance of Cu-added steel. Further, A1 also functions as a solid solution strengthening element by solid solution in steel, and particularly has an effect of increasing the high temperature strength in a temperature exceeding 8 〇〇〇c, and thus is used in the present invention to improve high temperature fatigue. An important element of the feature. In order to obtain the oxidation resistance equivalent to or higher than SUS444 for the purpose of the present invention, it is necessary to make A1 0.2. /. the above. On the other hand, if it is more than 1.0%, the steel will be hardened and the workability will be lowered. Therefore, the A1 content is set in the range of 0.2 to 1.0%. Better range 0 3~1〇%. Better system 〇 3 ~ 〇 5% range.

Si^Al As described above, A1 is also a solid solution strengthening element which is also dissolved in steel, and particularly has an effect of increasing the high temperature strength in a temperature exceeding 800 ° C. In the present invention, it is an important element for improving high-temperature fatigue characteristics; and Si is an important element for effectively utilizing such A1 solid solution strengthening. When the amount of Si is less than 100137265 201221658 A1, A1 preferentially forms an oxide (.) or a nitride (n-n 6) at a high temperature to reduce the amount of solid solution, thereby causing A1 to contribute no reinforcement. On the other hand, if the amount of Sl is more than the amount of A1, Sl is preferentially oxidized, and a dense oxide layer is continuously formed on the surface of the steel sheet. The oxide layer acts as a barrier to oxygen and nitrogen diffusion (▲), and suppresses the diffusion of oxygen and nitrogen from the outside. Therefore, A1 does not oxidize and nitrite to maintain a solid solution state, and solid solution strengthens the steel. Strengthening can improve high temperature fatigue characteristics. Therefore, in order to obtain high-temperature fatigue characteristics equivalent to or higher than SUS444, it is necessary to satisfy ^^. The ferrite-based stainless steel of the present invention may contain, in addition to the above-mentioned essential components, two or more kinds depending on the following range. B : 0.003% or less B is an element effective for improving workability (especially secondary workability). However, if the content exceeds 0.0030%, BN is formed, resulting in a decrease in workability. Therefore, when B is contained, the content is set to 〇3〇〇% or less. Since the above effect is effectively exerted at 0.0004 〇/〇 or more, it is more preferably in the range of 0.0004 to 0.0030%. REM: 0.08% or less, Zr: 0.5% or less REM (rare earth element) and Zr are elements which improve oxidation resistance, and may be contained as needed in the present invention. However, if the REM content exceeds 0.080%, the steel will be embrittled, and if the Zr content exceeds 0.50%, the precipitation of the Zr-based metal compound will still cause the steel to become brittle. Therefore, when REM is contained, the content of 100137265 18 201221658 is set to be less than or equal to the side of the crucible, and when zr is contained, the content is set to be less than 0.5% by weight. Since the above effect is effectively exhibited by REM of 0.01% or more and Zr of 0.0050% or more, the rem content is preferably 0.01 to 0% by weight, and the Zr content is preferably in the range of Q_% to Q. • REM: 0.08% or less, Zr: 〇5% or less, V: 0.5% or less V is an effective part for improving the workability and oxidation resistance. If the content exceeds 〇., it will lead to coarse v. The precipitation of (c, N) causes deterioration of surface properties. Therefore, when v is contained, the content is set to 〇 or less. Since the effect of increasing the X-addition and the oxidation resistance is effectively performed at G15% or more, it is preferable to use "Λ^Λ〇/ ^ 乂 乂 0.1 0.15 to 0.50%. Better system 〇 15 ~ 〇 4% range.

Co : 0.5% or less

The Co system is an effective element for the promotion of the secret. However, &amp; is a high-priced genus and even if its content exceeds 5%, the above effect is saturated. Therefore, when 〇&gt; is contained, the content is set to 〇 50/0 or less. Since the above effect is effectively exerted at 0.02% or more, it is preferable to follow the range of ~. More preferably in the range of 0.02 to 0.2%.

Ni : 0.5% or less The price is an element that enhances the edge. However, since the Ni system is expensive and is a strong γ phase forming element, a 丫 phase is formed at a high temperature, and if the content exceeds 0.5%, the oxidation resistance is lowered. _, when the content of ^ 100137265 19 201221658 is contained, the content is set to 0.5% or less. Since the above effect is effective at 0.05% or more, it is effective as a range of 5 to 5%. More preferably in the range of 0.05 to 0.4%. The rest are Fe and inevitable impurities. Among the unavoidable impurities, it is preferable that 0 is 〇.〇1()〇/0 or less, Sn is 〇5% or less, Mg is 〇5% or less, and Ca is 0.005% or less. More preferably, the system is 〇〇 5% or less, Sn is 0.003% or less, Mg is 〇 〇〇 3% or less, and ca is 〇.〇〇3〇/0 or less. Next, the method for producing the ferrite-based iron-based stainless steel of the present invention will be described. The stainless steel of the present invention can be produced by a usual production method of ferrite-based iron-based stainless steel. The production conditions are not particularly limited. Preferred manufacturing methods include melting a steel by a known melting furnace such as a steel converter or an electric furnace, or further refining by ladle refining and vacuum refining ( Vacuum refining), such as secondary refining, to form a steel having the above-described composition of the present invention, followed by continuous casting or ingot casting-blooming rolling Steel sheet (slab), then, by hot rolling, hot rolled sheet annealing, pickling, cold rolling, finishing annealing And a method of forming a cold rolled and annealed sheet by various steps such as pickling. Further, the above-mentioned cold rolling may be carried out in a single pass or in two or more stages of insert annealing, and various steps such as cold rolling, finish annealing, and pickling may be repeated. Further, according to the situation, the hot-rolled sheet annealing may be omitted. When the surface glossiness of the steel sheet is required, the skin rolling may be performed after cold rolling or after completion annealing. The manufacturing conditions are as follows. Preferably, some of the conditions of the hot rolling step and the cold milk step are set to specific conditions. Further, in the case of steelmaking, it is preferable to carry out the marting of the steel containing the above-mentioned essential components and the components which are required to be used, and to perform the VOD method (Vacuum Oxygen Decarburization method, vacuum blowing decarburization). Secondary refining. The molten steel to be melted can be formed into a steel material according to a known production method, and is preferably carried out by a continuous scale method from the viewpoint of productivity and quality. The steel material obtained by continuous casting is heated to, for example, 1000 to 1250 ° C, and hot rolled to form a hot rolled sheet having a desired sheet thickness. Of course, it is also processed in a form other than sheet metal. The hot-rolled sheet is subjected to batch annealing of 600 to 800 C or ccmtimums annealing of 900 to 1100 X as needed, and then subjected to descaling by pickling or the like to form a hot rolled sheet. product. Further, if necessary, shot blasting may be performed before pickling to perform scale descaling. Further, in order to obtain a cold rolled annealed sheet, the cold rolled sheet is formed by the cold rolling step in accordance with the hot rolling annealing obtained as described above. In the cold rolling step, depending on the production, two or more cold rollings including intermediate annealing may be performed as needed. The total rolling ratio of the cold rolling step consisting of single or secondary cold rolling is 60% or more, and preferably 7 G% or more. The cold-rolled sheet is subjected to continuous annealing (finished annealing) of 135 to 1120 ° C, preferably followed by pickling, to form a cold-rolled annealed sheet by performing 100137265 21 201221658 900 1150 C. Further, depending on the application, after the cold retreat, a slight rolling (skin reduction) may be added, and the shape and quality of the steel sheet may be adjusted. By using a hot-rolled sheet product obtained by such a manufacturing method, or a cold-rolled annealed sheet product, a bending process (bending w〇rk), etc., which is used for the respective use, is formed into an exhaust pipe or a catalyst outside the automobile or the locomotive. The cylinder material and the exhaust gas of the thermal power plant ¥ or the fuel cell related components (for example, a separator (separat〇r), an internal interconnector, a reformer, etc.). The welding method for welding the members is not particularly limited, and MIG (Metal Inert Gas), MAG (Metal Active Gas 'metal electrode active gas), TIG (Tungsten Inert Gas), tungsten electrode can be applied. Ordinary arc welding, or resistance welding such as spot welding, seam welding, and electric resistance welding High-frequency resistance welding, high frequency induction welding 0 [Examples] [Example 1] No. 1 having the composition shown in Table 1 was melted by a vacuum melting furnace. Steel of ~23 is cast to form 50kg steel block, forged and divided into two parts. Then, one of the two-section steel blocks is heated to 炱117〇£5 (: after '100130265 22 201221658 hot rolling to form a hot-rolled plate with a thickness of 5 mm, and then heat is applied at a temperature of 1 〇 2 〇 &lt; t The rolled sheet is annealed, pickled, and then subjected to cold rolling at a rolling rate of 60%, subjected to finish annealing at a temperature of 1〇4°°c, and then subjected to a cold portion 'acid pickled' at an average cooling rate of 5t/sec. Cold-warved annealed sheet having a thickness of 2 Å. No. 1 to 11 are examples of the present invention within the scope of the present invention, and Nos. 12 to 23 are comparative examples exceeding the scope of the present invention. Further, in the comparative example, N 〇19 corresponds to τ_29, and "No.2 〇 is equivalent to the composition of SUS444" No. 21, 22, and 23 are respectively equivalent to the hairpin j 3 of the document 2, and the invention example 3 of the exclusive 3 Composition of Inventive Example 5 of Patent Document 4. For the cold-rolled annealed sheets of N (U~23) obtained as described above, two kinds of continuous oxidation test, high-temperature fatigue test, and room temperature tensile test are shown below. Continuation oxidation test in air &gt; Samples were taken from various cold rolled annealed sheets obtained above, in the upper part of the sample Set 4mm0 holes, and use #32〇 sandpaper to grind the surface and end surface. After degreasing, suspend it in an atmospheric ring furnace heated to 950 , and keep it for 200 hours. After the test, determine the quality of the sample. Take the difference between the pre-test pre-test mass and calculate the oxidation increment (g/m). In addition, the test system is implemented twice, and the average value is used to evaluate the oxidation resistance in the atmosphere. 〇 H H 兄 兄 兄 兄 兄 兄 兄 兄 兄 兄 兄 兄 兄 & & & & & & & & & & & & & & & & & & & & & & & & 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 Hole of 4mm 0, and grinding the surface and end surface with #320 sandpaper for degreasing. Then, 10 vol% C02-20 vol ° / 〇 H20-5 vol% 02-bal. N2 gas is circulated to form water vapor at 0.5 L/min. The environment was maintained in a furnace heated to 950 ° C for 200 hours. After the test, the mass of the sample was measured, and the difference between the mass before the test and the mass measured beforehand was determined, and the oxidation increment (g/m 2 ) was calculated. <South-temperature fatigue test (high-temperature fatigue) Test)> A test piece having the shape shown in Fig. 3 was cut out from the various cold-rolled annealed sheets obtained as described above. The steel sheet was vibrated in two directions at 1300 rpm (22 Hz) by a Schenck type fatigue tester at 85 〇t:. Further, at the time of the test, a bending stress of 70 MPa was applied to the surface of the steel sheet, and the number of fatigues up to the fracture was evaluated. &lt;Room-Temperature Tensile Test&gt; Each of the cold-rolled annealed sheets was produced in a direction perpendicular to the rolling direction (L direction), a direction perpendicular to the direction of the emulsion (C direction), and a direction of 45° in the rolling direction (D direction). The tensile test piece was stretched in the direction of HS13B, and subjected to tensile test in each direction at room temperature to measure the elongation at break, and the average elongation Ei was obtained from the following formula. Average elongation E1 (%) = (El + 2Ed + Ec) / 4 where ' El : El (〇 / 〇) in the L direction, Ed : El (〇 / 0) in the D direction, &amp; El in the c direction (%) [Example 2] The remaining steel piece of the 50 kg steel block which was divided into two in Example 1 was heated to 100137265 24 201221658 1170 ° C, and then hot rolled to form a strip having a thickness of 3 mm mm x width: 150 mm. . Then, the strip was forged and formed into a 35 mm □ strip, which was annealed at 40 ° C, and then machined into a thermal fatigue test piece of the size shown in Fig. 1 for thermal fatigue as shown below. test. <Thermal fatigue test> The thermal fatigue test measures the thermal fatigue life by repeating the temperature rise and temperature drop between 100 ° C and 85 (TC temperature) at a restraint rate of 0.30. At this time, the heating rate (heating rate) The cooling rate is set to l〇°C/sec, the holding time at 100 °C is set to 2 min, and the holding time at 850 ° C is set to 5 min. (thermalfatiguelife) is calculated by dividing the load detected at 100 ° C by the cross-sectional area of the parallel parallel portion of the test piece to calculate the stress, and the stress begins to decrease with respect to the stress of the previous cycle. The number of cycles. The results of the continuous oxidation test in the atmosphere of the above Example 1, the continuous oxidation test in the water vapor environment, the temperature fatigue test and the room temperature tensile test, and the results of the thermal fatigue test of Example 2 are summarized. It is shown in Table 2. It is clear from Table 2 that the steel of the present invention in the range of the present invention has heat resistance (oxidation resistance, thermal fatigue property, high temperature fatigue property) equal to or higher than that of SUS444, and is at room temperature. Three directions (L In the C, D direction, the excellent workability of the average elongation of 36% or more satisfies the object of the present invention. On the other hand, it is confirmed that the steel of the comparative example which exceeds the range of the present invention has oxidation resistance, thermal fatigue characteristics, and high temperature fatigue characteristics. And the workability is poor, and the object of the present invention is not achieved. 100137265 25 201221658 (Industrial Applicability) The steel of the present invention is not only suitable for use as an exhaust system component of an automobile or the like, but also suitable for requiring the same characteristics. An exhaust system component of a thermal power generation system, and a member for a fuel cell of a solid oxide type. 100137265 26 201221658 .. /0¥铋 [5 Remarks of the present invention Example of the invention | Example of the invention 丨 Example of the invention The invention of the invention EXAMPLES OF THE INVENTION Example of the invention Example 1 of the invention Example 1 of the invention Example of comparative example Comparative example of vehicle comparison example Comparative example 1 Comparative example Comparative example than vehicle intersection example Comparative example *1 Comparative example *2 Comparative example * 3 1 -Ο Comparative Example*5 Si-Al 0.33 0.36 0.24 0.31 0.23 0.46 1 0.39 0.35 0.33 I 0.36 I 0.42 1 0.97 ?l 0.79 -0.21 0.27 0.13 0.33 0.84 0.291 0.310 0.458 0.168 Others V : 0.21 B : 0.0015 Co : 0.09 Ni : 0.34 V : 0.06 Ni : 0.10, V : 0.10 Ni : 0.10 ' V : 0.03 &gt; B : 0.0030 Ni : 0.15 2: 0.008 0.009 0.007 0.008 1 0.008 | 0.007 j 0.006 1 0.007 | 0.007 1 0.008 1 0.007 | 0.006 j 0.007 1 0.008 1 10.006 1 0.008 0.008 0.007 0.007 0.008 0.010 0.007 0.006 窆0.02 0.01 0.02 0.03 0.02 0.03 0.02 0.01 0.01 0.02 0.02 0.03 0.02 0.02 0.02 0.01 0.02 0.03 0.01 0.02 0.02 0.02 0.02 ο s 0.02 0.03 0.02 0.02 0.01 0.01 0.03 0.02 0.02 0.01 0.01 0.01 0.02 0.02 0.03 0.02 0.02 0.01 0.01 1.87 0.01 0.01 0.02 0.008 0.007 β.009 0.007 0.006 | 0.008 1 0.009 | 0.007 | 0.008 1 0.008 1 | 0.007 | 0.006 j 0.009 1 1 0.007 j 1 0.008 1 0.007 1 0.003 0.008 0.030 0.003 0.002 0.080 0.090 0.48 0.46 0.49 0.47 0.44 0.49 0.461 0.45 0.45 0.431 0.45 0.46 LMtJ 0.48 0.46 0.44 0.48 0.43 0.44 0.52 0.33 0.35 0.42 1 a 1.32 1.45 1.48 ro CN 1.37 \U9 1.55 1.46 ll29| 0.53 1.46 1.64 0.02 0.02 1.93 1.36 ό 12.8 14.5 ι-Ή 13.4 U52J 15.5 Limj 13.5 12.7 15.6 14 .4 13.9 m 14.8 18.7 17.0 18.9 18.8 κη 0.002 0.003 0.003 0.003 - 1 1 0.004 0.003 [0.003 ] 1 0.003] | 0.004 | 1 0.002 1 1 0.002 | 0.003 0.002 0.003 0.002 1 0.003 0.004 0.003 0.002 0.003 0.002 0.003 0.005 C1h 0.031 0.029 0.030 | 0.028 1 0.027 1 0.028 j 1 0.029 j 1 0.025 | 0.026 j 1 0.026 1 I 0.028 | 0.024 0.025 0.027 1 0.029 0.026 0.030 0.027 0.029 0.031 0.028 0.029 0.005 0.51 0.40 0.67 0.38 1 0.31 0.43 0.37 1 0.45 | 0.40 1 0.32 j I 0.52 | 0.37 j 1.49 ML· 0.68 0.54 0.39 0.43 0.03 0.02 0.01 0.00 0.05 Μη 0.25 0.28 0.31 0.29 0.54 0.48 0.24 0.73 0.81 0.69 0.39 0.50 0.44 0.78 0.63 0.35 0.21 0.84 0.33 0.42] 0.05 0.54 0.05 m 0.84 0.76 0.91 I 0.69 0.54 0.89 0.76 0.80 Γθ.73 0.68 0.94 134 0.69 0.92 0.47 0.81 0.52 0.76 0.87 0.31 0.32 0.46 0.22 1 u 0.008 0.007 0.008 | 0.009 1 0.006 0.007 1 0.009 1 1 0.007 1 0.007] | 0.008 | | 0.007 | 0.006 0.007 0.0070.00 0.0070.000.000.00 0.006 Sample No. CS cn 寸卜00 Os 〇tH (N m 2 Bu 00 ON 3 3 Ll s(nz.£100 Isf size: s* ei set ebao 5: inch* Γ isDs : CN* 6&lt;Nt^KL :r ^ w H ^ 201221658 [Table 2] Sample No. 埤 埤 (g/nv) Thermal fatigue life ( Cycle) Vapor oxidation increment two-way average elongation (%) at 850C high temperature fatigue life CxlO5 pass period) Remarks 1 18 1330 34 Ίβ~~~ 30 _ invention 2 Π 1340 34 16~~'~~ 33 Inventive Example 3 16 1350 33 • -------- 36 26 Inventive Example 4 17 1370 34 37 29 Inventive Example 5 16 1340 35 &quot;37~~~ 27 Inventive Example 6 16 1310 33 --- ----- 36 32 Inventive Example 7 16 1370 34 H 31 Inventive Example 8 17 1360 34 16'~~ 36 The present invention 9 16 1340 34 &quot;36~~~~ 27 The present invention ~ϋΓ 10 18 1300 34 _ ------- 37 29 The present invention 丨 11 11 1410 33 33 The present invention i 12 17 1280 39 A 'Tr---- 32 30 Compare 彳^~~ 13 18 1380 7i ^Ti 9 Example 14 55 1300 49 37~~~~ 15 Comparison~~ 15 17 1290 77 11 彳 彳 16 15 910 32 T8~~ ~~ 26 Comparative habits~~ 17 13 1440 29 34 31 Comparison 1818 15 1300 &gt; 100 3F~~~~ 14 19 45. 630 &gt; 100 34~~~ 8 Comparison life fsy 20 19 1250 37 ----- 31 24 Comparative Example *2 21 &gt;100 1650 &gt; 100 ~ΤΓ~~~~ 15 Comparative Example* 3 22 &gt; 100 1380 &gt; 100 35 ' 10 Comparative Example *4 23 &gt;100 1540 &gt; 100 γζ--- 12 Comparative Example * The factory bottom line is beyond the scope of the present invention ----- *2: SUS444 *3: Inventive Example 3 of Patent Document 2 *4. Inventive Example 3 of Patent Document 3 *5: Invention of Patent Document 4 EXAMPLES [Simple Description of the Drawings] Fig. 1 is a view showing a thermal fatigue test piece. Fig. 2 is a view showing the temperature and restraint conditions of the thermal fatigue test. Fig. 3 is a view showing the high temperature fatigue test piece. Fig. 4 is a graph showing the effect of CU content on fatigue characteristics. Fig. 5 shows the effect of the A1 content on the oxidation resistance (increase in oxidation). Fig. 6 is a graph showing the effect of the Sl content on the vapor oxidation characteristics (increase in oxidation) of 100137265 28 201221658. Fig. 7 is a graph showing the effect of Si content - A1 content (Si-Al) on high temperature fatigue characteristics. Fig. 8 is a graph showing the effect of the Cr content on the water vapor oxidation resistance (increase in oxidation). Fig. 9 is a graph showing the effect of the Cr content on the three-direction average elongation at room temperature. 100137265 29

Claims (1)

201221658 VII. Patent application scope: 1. A ferrite-based iron-based stainless steel, according to the mass%, containing: C: 0.015% or less, Si: 0.4 to 1.0%, Μη: 1_0% or less, P: 0.040% or less, S : 0.010% or less, Cr: 12% or more and less than 16%, Ν: 0.015% or less, ]^): 0.3 to 0.65%, 1^: 0.15% or less, ]\4〇: 0.1% or less, \¥: 0.1% or less, Cu: 1.0 to 2.5%, A1: 0.2 to 1.0%, and the remainder of Si$ A is composed of Fe and unavoidable impurities. 2. A type of ferrite-based iron-based stainless steel, further comprising, by mass%, B: 0.003% or less, REM: 0.08% or less, Zr: 0.5% or less, V: 0.5% or less, Co: 0.5% or less, and Ni: One or two or more selected from 0.5% or less. 100137265 30