JP2000144344A - Ferritic stainless hot rolled steel sheet excellent in surface roughening resistance after forming and high temperature fatigue characteristic - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a ferritic stainless hot rolled steel sheet good in surface roughening resistance after forming and high temp. fatigue characteristics and moreover free from deterioration in forming workability. SOLUTION: This steel sheet has a componential compsn. contg., by weight, <=0.03% C, <=2.0% Si, <=0.8% MA, <=0.03% S, 6 to 25% Cr, <=0.03% N, <=0.3% Al, <=0.4% Ti, 0.02 to 0.4% V, 0.0002 to 0.0050% B and <=0.5% Nb so as to satisfy Ti/48>N/14, Ti/48+Nb/92>N/14+C/12 and V/B>10, and the balance Fe with inevitable impurities.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hot-rolled ferritic stainless steel sheet which is suitable for forming work and is particularly excellent in surface roughening resistance and fatigue properties after forming.

[0002]

2. Description of the Related Art Ferritic stainless steel is slightly inferior in workability and corrosion resistance compared with austenitic stainless steel, but is excellent in stress corrosion cracking resistance and inexpensive, so it can be used in various kitchen appliances and automobile exhausts. Widely used in fields such as system parts (exhaust manifolds, exhaust pipes, converter shells, mufflers, etc.). When used in such processing applications, in order to improve the workability of ferritic stainless steel, for example, JP-A-51-14811, JP-A-51-14811
As disclosed in JP-14812-A, JP-A-52-31919, etc., techniques for adding elements such as Ti and Nb to fix impurity elements such as C and N which form a solid solution in steel are widely used. Is being done.

[0003] Now, this ferritic stainless steel sheet is usually manufactured by heating a continuous cast slab, followed by steps of hot rolling, hot rolling sheet annealing, pickling, cold rolling, finish annealing, and pickling. Is done. Therefore, some of these steps,
In particular, hot-rolled stainless steel sheets manufactured by omitting the steps after cold rolling can significantly reduce equipment and operating costs after cold rolling, so ferritic stainless steel sheets are cheaper than austenitic steel sheets. Can be manufactured at lower cost and in a shorter time, and the industrial advantage is extremely large.

[0004]

However, in general, hot-rolled steel sheets have a problem that crystal grains after annealing are large compared with cold-rolled steel sheets, and the surface roughness after forming is large. The coarse crystal grains and the rough surface after the forming process not only impair the appearance of the surface but also degrade the high-temperature fatigue characteristics of components that are subject to vibration at a high temperature, such as an engine, such as automobile exhaust system parts (exhaust pipes, etc.). There was also the problem of lowering. This phenomenon is that, in a high-temperature fatigue environment, in a structure with coarse crystal grains, fatigue fracture easily occurs at grain boundaries with lower strength than the base material, or stress concentrates on the rough surface surface and becomes the starting point of fracture Described by By the way, the crystal grain size of the steel sheet, which greatly affects the surface roughness and fatigue fracture characteristics after processing, can be adjusted to some extent by conditions such as annealing temperature and time. When annealing is performed at a low temperature and for a short time, a complete recrystallized structure cannot be obtained, and a portion near the center in the thickness direction of the steel sheet retains the expanded structure during hot rolling. As a result, the Rankford value (r value), which is an index of elongation (El.) And deep drawability, becomes small, and sufficient moldability cannot be obtained. These facts make it difficult to achieve both good formability and excellent surface roughening resistance and high-temperature fatigue characteristics in a hot-rolled ferritic stainless steel sheet. This was a major factor hindering the application of hot rolled stainless steel sheets.

Accordingly, an object of the present invention is to provide a hot-rolled ferritic stainless steel sheet having good surface roughness resistance and high-temperature fatigue characteristics after forming and without impairing formability.

[0006]

Means for Solving the Problems As a result of diligent research for realizing the above-mentioned object, the inventors have found that, in ferritic stainless steel, C and N are fixed by Ti, V and B are fixed.
It was found that by adjusting the chemical composition, such as the addition of a composite, to an appropriate range, it is possible to manufacture a hot-rolled stainless steel sheet with excellent surface roughness after forming, high-temperature fatigue properties, and formability. The invention has been completed.

The gist of the present invention is as follows, embodying the above concept. (1) C: 0.03 wt% or less, Si: 2.0 wt% or less Mn: 0.8 wt% or less, S: 0.03 wt% or less, Cr: 6 to 25 wt%, N: 0.03 wt% or less, Al: 0.3 wt% or less , Ti: 0.4 wt% or less, V: 0.02-0.4 wt%, B: 0.0002-0.0050 wt%, Nb: 0.5 wt% or less, and the following formula: Ti / 48> N / 14 Ti / 48 + Nb / 92 > N / 14 + C / 12 V / B> 10, with the balance being Fe and unavoidable impurities, the ferrite-based stainless steel heat having excellent surface roughening resistance and high temperature fatigue properties after forming. Rolled steel sheet.

(2) C: 0.03 wt% or less, Si: 2.0 wt% or less Mn: 0.8 wt% or less, S: 0.03 wt% or less, Cr: 6 to 25 wt%, N: 0.03 wt% or less, Al: 0.3 wt% or less, Ti: 0.4 wt% or less, V: 0.02-0.4 wt%, B: 0.0002-0.0050 wt%, Nb: 0.5 wt% or less, and the following formula: Ti / 48> N / 14 Ti / 48 + Nb / 92> N / 14 + C / 12 V / B> 10 is contained, and any one or two selected from Ca: 0.01 wt% or less, Mo: 2.0 wt% or less Cu: 2.0 wt% or less A hot-rolled ferritic stainless steel sheet having excellent wear resistance and high-temperature fatigue properties after forming, characterized by containing at least one seed and the balance consisting of Fe and unavoidable impurities.

[0009]

The reasons for limiting the respective chemical component values of the steel according to the present invention in the manner described above will now be described. C: 0.03 wt% or less C is an element that lowers the formability (r value) and the corrosion resistance, so that it is desirable to reduce it as much as possible. In order to exert the effect of V as described later, it is desirable to reduce the amount of solid solution as much as possible. Therefore, in the present invention, C is fixed by adding Ti or further Nb, the adverse effect on the formability and ferrite stability is reduced, and the effect of V is sufficiently exhibited. However, if the C content exceeds 0.03 wt%, the amount of precipitates in the steel sheet increases, leading to a decrease in workability and deterioration of surface properties, so that the content range is 0.03 wt% or less, preferably 0.3 wt%.
015 wt% or less.

Si: 2.0 wt% or less Si is an element that is effective for deoxidizing steel and also improves oxidation resistance at high temperatures and high-temperature salt damage characteristics. But 2.
If the content exceeds 0 wt%, the elongation characteristics will be deteriorated.
Limited to 2.0 wt% or less. When used for applications such as automobile exhaust system members, it is desirable that the content be 0.6 wt% or more.

Mn: 0.8 wt% or less Mn is an element effective for precipitating and fixing S in steel and improving hot rollability, but is an element harmful to formability. Therefore, the addition range is 0.8 wt% or less, preferably
0.5 wt% or less.

S: 0.03 wt% or less S is a harmful element that degrades hot workability. However, since it is usually combined with Mn to form MnS, the effect is small if the content is 0.03 wt% or less. However, when the content exceeds 0.03 wt%, the precipitated MnS becomes a starting point of initial rust and deteriorates corrosion resistance, and segregates at crystal grain boundaries to promote grain boundary embrittlement. Therefore, the content is 0.03 wt% or less, preferably 0.
Limit to 005 wt% or less.

Cr: 6 to 25 wt% Cr is an indispensable element for improving corrosion resistance and oxidation resistance at high temperatures. If the added amount of Cr is less than 6% by weight, a sufficient effect cannot be obtained. On the other hand, if the added amount exceeds 25% by weight, the workability is deteriorated and the material cost is increased. Therefore, the added amount is 6% by weight to 25% by weight. . 15% by weight for use in applications that prioritize moldability
When used for applications requiring corrosion resistance at room temperature, the content is preferably 10 wt% or more.

N: 0.03 wt% or less N, like C, is an element that lowers the formability (r value) of a steel sheet, and therefore it is desirable to reduce it as much as possible. Also, in order to exert the effect of B as described later, it is desirable to reduce the amount of solid solution as much as possible. Therefore, in the present invention, N is fixed by adding Ti or further Nb to render it harmless. However, if its content exceeds 0.03 wt%, the amount of precipitates in the steel sheet increases, and the formability decreases and the surface becomes harder. This leads to deterioration of properties. Therefore, the content of N is 0.03 wt% or less, preferably 0.1 wt%.
Limit to 01 wt% or less.

Al: 0.3 wt% or less Al is an effective element for deoxidation. However, excessive addition of Al deteriorates the workability of the hot-rolled annealed sheet.
Preferably, it is 0.1 wt% or less.

Ti: 0.4 wt% or less Ti is a powerful element for stabilizing C and N, and has an effect of improving moldability. Further, it also has an effect of suppressing grain boundary precipitation of Cr carbonitride and improving corrosion resistance. In order to exhibit these effects, the amount of Ti added needs to satisfy the relationship with C and N as described later. On the other hand, if the amount of Ti exceeds 0.4 wt%, the formability is rather deteriorated, and the workability of the weld is significantly reduced. Also,
It causes deterioration of toughness and lowers manufacturability. Therefore,
The amount of Ti added is set to 0.4 wt% or less.

V: 0.02 to 0.4 wt%, B: 0.0002 to 0.0050 wt%, and V / B> 10 V and B are extremely important elements in the present invention. V and B are respectively 0.02 to 0.4 wt%, 0.0002 to 0.
The addition of the composite material in an amount of 0.5 wt% and V / B> 10 has an effect of refining the crystal grains of the hot-rolled annealed sheet and suppressing the grain growth after recrystallization. Although the reason why such an effect can be obtained is not clear, V forms a solid solution in the ferrite grains to suppress refining of the recrystallized grains and suppress grain growth during annealing, and B indicates the ferrite after the annealing recrystallization. It is considered that concentration at the grain boundaries and delay of grain boundary movement assists grain growth suppression. Further, it is considered that the effect differs depending on the content ratio of V and B, because the balance between the volume of ferrite crystal grains and the area of the ferrite grain boundary is related. As a result of the refinement of the crystal grains as described above, the surface roughness after the forming process is remarkably improved, and furthermore, high-temperature mechanical vibration such as automobile exhaust system members (exhaust pipes) at high temperatures. The fatigue properties of the material subjected to the heat are also improved. It is considered that the reason why the fatigue characteristics are improved by the refinement of the crystal grains is as follows. 1) The roughened surface after the forming process, which is likely to be a starting point of destruction due to stress concentration, can be reduced. 2) The grain boundary has a large stress concentration and becomes a crack propagation path.
If the grain size is reduced, stress concentration per unit grain boundary is reduced due to an increase in grain boundary area. 3) Grain boundary strength is enhanced by the grain boundary concentration of B. Here, when precipitation and fixation of C by Ti and Nb is not sufficient, V reacts with C and precipitates as V ₂ C or VC, and the effect of suppressing grain growth is reduced. On the other hand, B is Ti
If the precipitation fixation of N is not sufficient, it reacts with N and precipitates as BN, which in turn promotes grain growth. Thus, C is a stronger carbide-forming element than V, Ti,
With sufficient addition of Nb, N must be precipitated and fixed by sufficient addition of Ti, a stronger nitride forming element than V and B. In addition to the above, the effect of the addition of B promotes the accumulation of processing strain during hot rolling, increases the accumulation of {111} planes in the recrystallization texture after annealing, and also has the effect of improving the formability. Therefore, the significance of addition is significant for hot-rolled steel sheets that are inferior in formability as compared with cold-rolled steel sheets. The effect of adding V and B described above is that the V content is 0.02 wt% or more and the B content is
It is exhibited only when 0.0002 wt% or more and the ratio V / B> 10 of each addition amount is satisfied. On the other hand, if V and B are added in excess of 0.4 wt% and 0.0050 wt%, respectively, the effects of grain refinement and growth suppression during annealing and the effect of improving formability are saturated, and conversely, the material hardens. The elongation characteristic deteriorates and the moldability decreases. Therefore, the amount of V is 0.02
~ 0.4 wt%, B content is 0.0002 ~ 0.0050wt%, and V / B>
Assume 10

Nb: 0.5 wt% or less Nb is a C and N stabilizing element, complements Ti to improve formability and suppresses grain boundary precipitation of Cr carbonitride to improve corrosion resistance. It has the effect of doing. In order to exhibit these effects, the amount of Nb added needs to satisfy the relationship with C and N as described later. On the other hand, if the amount of Nb exceeds 0.5 wt%, the formability is rather deteriorated, and the workability of the weld is significantly reduced. Also,
It causes deterioration of toughness and causes trouble in the manufacturing process. Therefore, the Nb addition amount is set to 0.4 wt% or less. In addition,
When combined with Ti, it is preferable to limit Ti + Nb to 0.6 wt% or less.

Ti / 48> N / 14 and Ti / 48 + Nb / 92> N / 1
4 + C / 12 Ti and Nb are effective for the above-mentioned effects of V and B, that is, N is TiN and C is T
It is added to precipitate and fix as iC or NbC.
Therefore, from the stoichiometric ratio, in the case of a composite addition of Ti and Nb, Ti / 48> N / 14 and Ti / 48 + Nb / 92> N / 14 +
It is necessary to add an amount satisfying C / 12.

In the present invention, the following elements can be further contained as needed. Ca: 0.01 wt% or less Ca is an element useful for generating CaS in molten steel and suppressing nozzle clogging due to TiS-based inclusions generated when casting molten steel containing Ti. However, if added excessively, the corrosion resistance deteriorates, so the amount of addition is limited to 0.01 wt% or less, preferably in the range of S ≦ (32/40) Ca ≦ 1.5 S in relation to the S content.

Mo: 2.0 wt% or less Mo has the effect of further improving the corrosion resistance, and can be added as necessary. However, the amount added was 2.
If the content exceeds 0 wt%, the workability during hot rolling is reduced.
2.0 wt% or less. In addition, in the case of adding a composite with Cu, the total content of both is desirably 2.0 wt% or less.

Cu: 2.0 wt% or less Cu has the effect of further improving the corrosion resistance, and can be added as needed. However, the amount added was 2.
If the content exceeds 0 wt%, the workability during hot rolling is reduced.
2.0 wt% or less. When Mo and Mo are added in combination, the total content of both is desirably 2.0 wt% or less.

Although P was not mentioned, P
Is generally 0.03% by weight or less, because it increases the hot cracking property and decreases the hot rolling property and the hot rolled sheet toughness similarly to Pb and Sn. In the production of the steel sheet of the present invention, the heating temperature: 1,250 to 1,050 ° C and the finishing temperature: 900 to 900 ° C.
600 ℃, winding temperature: 800 ℃ after hot rolling below 700 ℃
Annealing at ~ 1100 ° C is desirable.

[0024]

The present invention will be described below in detail with reference to examples. Steels 1 to 22 having the chemical compositions shown in Table 1 were melted in a vacuum melting furnace having a capacity of 30 kg. After heating the obtained small ingot to 1250 ° C, a hot-rolled sheet having a thickness of 2 mm was manufactured by hot rolling comprising a finishing temperature of 700 ° C and a number of rolling passes of eight. This hot-rolled sheet was annealed at a temperature shown in Table 2 for 60 seconds and pickled.

[0025]

[Table 1]

[0026]

[Table 2]

The surface of the obtained hot-rolled annealed sheet was # 10
Polishing was carried out with emery paper No. 00 to remove the influence of the hot roll surface. From this test material, JIS No. B
Tensile test specimens were sampled, and the r value (measured by a three-point method after 15% tensile strain) was measured. Further, the surface roughness (Ra) in the tensile direction of the test piece after 15% tension was examined as an index of the surface roughness. Finally, the test piece was pulled to break and the elongation at break (El.) Was measured. The high-temperature fatigue characteristics were evaluated using a plate-shaped test piece shown in FIG. 1 by a Schenk-type high-temperature plane bending fatigue tester at a test temperature of 700 ° C. and a bending speed of 1700 times / minute. The outline of the test method is to perform a fatigue test by fixing one end of a test piece and repeatedly applying a bending moment to the opposite side, as shown in FIG. FIG. 3 shows the results of No. 8 (inventive example) and No. 6b (comparative example) as an example of the test results. Stress such test results from damage life is 10 ⁷ cycles (10 ⁷ fatigue limit stress,
Hereinafter, it is simply abbreviated as “fatigue limit stress”. ). Formability (r value, elongation at break), surface roughness resistance (Ra), and high temperature fatigue properties (fatigue limit stress) were evaluated by the above method. The test results are shown in Table 2.

Steels 1 to 3 are based on 11 wt% Cr. No. 1a, annealed at 850 ° C., of Steel 1 with insufficient amounts of V and B, had a low annealing temperature, lacked recrystallization, and had a low elongation and low r-value. No. 1 with an annealing temperature raised to 900 ° C
1b is elongation, r value is improved and workability is satisfied,
The surface roughness was as high as Ra = 7.3, and severe skin roughness was confirmed visually. Further, No. 1c in which the annealing temperature was increased to 950 ° C. not only further deteriorated the rough surface resistance,
Manufactured at an annealing temperature that satisfies moldability and fatigue limit stress
It can be seen that the temperature is reduced by 7.7% with respect to No. 1b, and the high temperature fatigue property is also deteriorated. Further, No. 2 obtained by annealing steel having an insufficient amount of B at 900 ° C. slightly improves the surface roughening resistance and the high-temperature fatigue property with respect to No. 1b, but the effect is not sufficient. The same applies to No. 3 where the amount of V added is insufficient.

Steels 6 to 12 are 15Cr-based and Ti-Nb composite added. Steel 6 with insufficient amounts of V and B added
In 950 ° C. annealing (No. 6a), recrystallization was not sufficient, elongation and r value were low, and the annealing temperature was 1000 ° C.
When it is increased to (No. 6b), the workability is improved, but the recrystallized grains are coarsened, and the surface roughening resistance and the high temperature fatigue property are deteriorated. No. 7 where V / B is too low even if V and B are contained
In the case of No. 6b, although the surface roughening resistance and the fatigue properties are slightly improved as compared with No. 6b, the effect is slight. On the other hand, Invention Example No. No.
Nos. 8 to 10 all have good moldability, show good surface roughness resistance (Ra: 3.0 or less), and further have good high-temperature fatigue properties (fatigue limit stress: 90 MPa or more; 11% or more). In each of Comparative Example No. 11 containing excessive B and Comparative Example No. 12 containing excessive V, workability (elongation, r value) is inferior.

The steels 13 to 22 are of 18Cr type. In No. 13 in which the amounts of V and B are insufficient, the recrystallized grains are coarse, and the surface roughening resistance and the high temperature fatigue properties are inferior. No. 14 having an excessive C content not only has poor moldability at room temperature, but also has poor surface roughness resistance and high temperature fatigue strength. No. 15 in which Ti is insufficient with respect to the N content is inferior in rough surface resistance. In contrast, Invention Examples Nos. 16, 17, 18a, and 19 all have excellent surface roughness resistance and high-temperature fatigue characteristics. Also, the grain growth of 18b annealed at a higher temperature of 1100 ° C. was suppressed, and Comparative Example No. 13 annealed at 1050 ° C.
It shows better moldability, surface roughening resistance, and high temperature fatigue properties. This tendency can be seen in No. 20 and Cu with further addition of Mo.
The same applies to No. 21 to which Mo is added and No. 22 to which Mo and Cu are added.

[0031]

As described above, according to the present invention, it is possible to improve the surface roughness after forming and the high-temperature fatigue characteristics in a high-temperature vibration environment without deteriorating the formability. Therefore, it is possible to provide a hot rolled ferritic stainless steel sheet which can also be used for automobile exhaust system members and the like, which has conventionally had to use expensive cold rolled steel sheets. Furthermore, according to the present invention, an annealing temperature range during annealing of a hot-rolled steel sheet can be allowed in a wide range, so that it can be industrially easily manufactured.

[Brief description of the drawings]

FIG. 1 is a view showing a plate-shaped test piece for a Schenk type high temperature plane bending fatigue test.

FIG. 2 is a view schematically showing a Schenk type high-temperature plane bending fatigue test method.

FIG. 3 is a graph showing a relationship between a fracture life and a fatigue limit stress by a high-temperature fatigue test.

[Procedure amendment]

[Submission date] January 7, 2000 (2000.1.7)

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[Claims]

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[0003] Now, the ferritic stainless steel sheet is generally after heating the continuously cast slab, hot rolling - hot-rolled sheet annealing, pickling - cold rolling - through each step of finish annealing, pickling production Is done. Therefore, some of these steps,
In particular, hot-rolled stainless steel sheets manufactured by omitting the steps after cold rolling can significantly reduce equipment and operating costs after cold rolling, so ferritic stainless steel sheets are cheaper than austenitic steel sheets. Can be manufactured at lower cost and in a shorter time, and the industrial advantage is extremely large.

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[0006]

Means for Solving the Problems As a result of diligent research for realizing the above-mentioned object, the inventors have found that, in ferritic stainless steel, C and N are fixed by Ti, V and B are fixed.
Of By adjusting the appropriate range of chemical composition, such as a combined addition, found that molding after surface roughening resistance, can be manufactured of stainless hot-rolled steel sheet excellent in any of the high temperature fatigue characteristics and moldability, the The invention has been completed.

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[0007] The present invention provides the following that embodies the above concept.
The gist of the configuration is as follows. (1) C: 0.03 wt% or less, Si: 2.0 wt% or less Mn: 0.8 wt% or less, S:0.002 or more0.03wt%,  Cr: 6 to 25 wt%, N: 0.03 wt% or less, Al: 0.3 wt% or less, Ti: 0.4 wt% or less, V: 0.02 to 0.4 wt%, B: 0.0002 to 0.0050 wt%, Nb: 0.5 wt% or less And the following formula: Ti / 48> N / 14 Ti / 48 + Nb / 92> N / 14 + C / 12 V / B> 10, the balance being Fe and unavoidable impurities.
Characterized by high skin roughness after molding
Ferritic stainless steel hot rolled steel sheet with excellent thermal fatigue properties.

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(2) C: 0.03 wt% or less, Si: 2.0 wt% or less
Lower Mn: 0.8 wt% or less, S:0.002 or more0.03wt%,  Cr: 6 to 25 wt%, N: 0.03 wt% or less, Al: 0.3 wt% or less, Ti: 0.4 wt% or less, V: 0.02 to 0.4 wt%, B: 0.0002 to 0.0050 wt%, Nb: 0.5 wt% or less And satisfying the following formula: Ti / 48> N / 14 Ti / 48 + Nb / 92> N / 14 + C / 12 V / B> 10, Ca: 0.01 wt% or less, Mo: 2.0 wt % Or less Cu: 2.0 wt% or less
Characterized in that the part consists of Fe and inevitable impurities
Excellent in surface roughening resistance and high temperature fatigue properties after molding
Hot-rolled stainless steel sheet.

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N: 0.03 wt% or less N, like C, is an element that lowers the formability (r value) of a steel sheet, and therefore it is desirable to reduce it as much as possible. Also, in order to exert the effect of B as described later, it is desirable to reduce the amount of solid solution as much as possible. Therefore, in the present invention, N is fixed and rendered harmless by the addition of Ti or Nb . However, if the content exceeds 0.03 wt%, the amount of precipitates in the steel sheet increases, leading to deterioration in formability and deterioration in surface properties. Therefore, the content of N is 0.03 wt% or less, preferably 0.1 wt%.
Limit to 01 wt% or less.

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[0025]

[Table 1]

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[0026]

[Table 2]

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Susumu Sato 1 Kawasaki-cho, Chuo-ku, Chiba City, Chiba Prefecture Inside the Technical Research Institute of Kawasaki Steel Co., Ltd. (72) Koji Yamato 1 Kawasaki-cho, Chuo-ku, Chiba City, Chiba Prefecture Kawasaki Steel Research Institute

Claims (2)

[Claims] C: 0.03 wt% or less, Si: 2.0 wt% or less Mn: 0.8 wt% or less, S: 0.03 wt% or less, Cr: 6 to 25 wt%, N: 0.03 wt% or less, Al: 0.3 wt% %, Ti: 0.4 wt% or less, V: 0.02 to 0.4 wt%, B: 0.0002 to 0.0050 wt%, Nb: 0.5 wt% or less, and the following formula: Ti / 48> N / 14 Ti / 48 + Nb / 92> N / 14 + C / 12 V / B> 10, with the balance being Fe and unavoidable impurities, characterized by having excellent surface roughening resistance and high temperature fatigue properties after forming. Stainless hot rolled steel sheet. 2. C: 0.03 wt% or less, Si: 2.0 wt% or less Mn: 0.8 wt% or less, S: 0.03 wt% or less, Cr: 6 to 25 wt%, N: 0.03 wt% or less, Al: 0.3 wt% %, Ti: 0.4 wt% or less, V: 0.02 to 0.4 wt%, B: 0.0002 to 0.0050 wt%, Nb: 0.5 wt% or less, and the following formula: Ti / 48> N / 14 Ti / 48 + Nb / 92> N / 14 + C / 12 V / B> 10, and any one or two selected from Ca: 0.01 wt% or less, Mo: 2.0 wt% or less Cu: 2.0 wt% or less A hot-rolled ferritic stainless steel sheet having the above characteristics, the balance being Fe and unavoidable impurities, and having excellent surface roughening resistance and high-temperature fatigue properties after forming.