JP2001181798A - Hot rolled ferritic stainless steel sheet excellent in bendability, its manufacturing method, and method of manufacturing for cold rolled steel sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hot rolled ferritic stainless steel sheet excellent in bendability, a cold rolled steel sheet, and a method for stably obtaining them. SOLUTION: A rolling stock, having a composition containing, by mass, <=0.1% C, <=1.0% Si, <=1.0% Mn, <=0.1% P, <=0.01% S, 9.0-35.0% Cr, <=1.0% Ni, <=1.0% Al and <=0.1%; N, is subjected to hot rolling steps of hot roughing and hot finish rolling to manufacture the hot rolled ferritic stainless steel sheet. In this manufacturing method, the above hot finish rolling is performed while regulating finishing temperature, friction coefficient in three passes in the latter stage, and cumulative draft in three passes in the latter stage to <=800 deg.C, <=0.2, and >=50%, respectively, by which a hardness ratio between the hardness Hs in the sheet-thickness surface layer part and the hardness Hc in the sheet- thickness central part, Hs/Hc, is regulated to <=1.25. Further, hot finish rolling is carried out preferably without using water for descaling before the initiation of hot finish rolling and/or water for strip cooling at a hot finishing mill to improve surface characteristic.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a hot-rolled ferritic stainless steel sheet having excellent bending workability and surface properties, a method for producing the same, and a method for producing a cold-rolled ferritic stainless steel sheet. Hereinafter, hot rolling may simply be referred to as hot-rolled steel sheet or a hot-rolled steel sheet. Similarly, cold rolling is simply cold rolling, and a steel sheet obtained by cold rolling may be simply referred to as a cold rolled steel sheet or a cold rolled sheet. In addition, all component contents referred to in the present invention are mass%.

[0002]

2. Description of the Related Art Ferrite stainless steel sheets are generally subjected to hot rolling (hot rough rolling, hot finishing rolling),
It is manufactured by the steps of hot-rolled sheet annealing, pickling, cold rolling, finish annealing and pickling. Ferrite stainless steel is relatively inexpensive and has excellent corrosion resistance, and is therefore used in various fields such as automobile exhaust system materials, electric appliances, and building materials. Among them, when used as an automobile exhaust system material, press work of a complicated shape or work such as pipe expansion, contraction, and bending after processing a pipe is performed. Therefore, high workability is required for the material steel plate. By the way, as a conventional technique for improving workability by a hot rolling method, as disclosed in JP-A-8-311557 and JP-A-9-194937, a rolled material is strongly reduced by hot rough rolling. A technique for improving the structure by recrystallizing by making the steel stand by before finishing rolling is disclosed in JP-A-8-3115.
There is known a technique as disclosed in Japanese Patent Publication No. 42, which combines a low coefficient of friction with a high finish rolling end temperature and a high winding temperature.

[0003]

However, these techniques have a major problem that the production efficiency is lowered by waiting before hot finish rolling, and also in terms of quality, there is a problem in that high-temperature winding is required. However, there has been a problem that instability of the material properties is unavoidable due to non-uniform cooling of the coil after rolling, and a problem that the bending workability is particularly insufficient.
In particular, when a hot-rolled steel sheet is subjected to bending, wrinkles may occur on the surface at that part, and cracks may occur during bending of a cold-rolled steel sheet obtained by further cold rolling the hot-rolled steel sheet Due to the problem, as a result, the ferrite-based stainless steel sheet obtained by the above-described conventional technology cannot meet the recent demand for complicated parts processing at present. Therefore, an object of the present invention is to solve the above-mentioned problems of the prior art, without reducing the production efficiency,
An object of the present invention is to propose a hot-rolled ferritic stainless steel sheet and a cold-rolled ferritic stainless steel sheet which are excellent in bending workability, and a method for producing them.

[0004]

Means for Solving the Problems Now, the present inventors have investigated in detail the factors for improving the bending workability in order to realize the above-mentioned object. As a result, by appropriately performing the hot finish rolling of the ferritic stainless steel, it is possible to control the hardness ratio of the hot-rolled steel sheet in the thickness direction to a predetermined range, thereby bending the hot-rolled steel sheet and the cold-rolled steel sheet. The inventors have found that the processability can be significantly improved, and have completed the present invention. That is, the gist configuration of the present invention is as follows.

(1) In mass%, C: 0.1% or less, Si: 1.0%
% Or less, Mn: 1.0% or less, P: 0.1% or less, S: 0.01% or less, Cr: 9.0 to 35.0%, Ni: 1.0% or less, Al: 1.0% or less, N: 0.1% or less, the balance Has a composition of Fe and unavoidable impurities, and has a hardness ratio Hs / Hc between the hardness Hs of the surface layer portion of the sheet thickness and the hardness Hc of the center portion of the sheet thickness of 1.25 or less. Excellent hot-rolled ferritic stainless steel sheet.

(2) The steel sheet according to the above (1), further comprising at least one component selected from one or more of the following groups A to E in addition to the above components. Ferritic stainless steel hot-rolled steel sheet with excellent bendability characterized by the following characteristics. Group A: Ti: 1.0% or less, Nb: 1.0% or less Group B: Mo: 2.0% or less, Cu: 2.0% or less, Co: 2.0% or less Group C: V: 0.5% or less, Zr: 0.5% or less Group D: B: 0.005% or less Group E: Ca: 0.005% or less

(3) In mass%, C: 0.1% or less, Si: 1.0
% Or less, Mn: 1.0% or less, P: 0.1% or less, S: 0.01% or less, Cr: 9.0 to 35.0%, Ni: 1.0% or less, Al: 1.0% or less, N: 0.1% or less, the balance Rolled material consisting of the composition of Fe and inevitable impurities, in the method of manufacturing a hot-rolled ferritic stainless steel sheet in the hot-rolling process,
Hot finishing rolling, the finishing temperature is 800 ° C or less, the friction coefficient of the latter three passes is 0.2 or less, and the cumulative rolling reduction of the latter three passes is 50%.
A method for producing a hot-rolled ferritic stainless steel sheet as described above.

(4) By mass%, C: 0.1% or less, Si: 1.0
%, Mn: 1.04 or less, P: 0.1% or less, S: 0.01% or less, Cr: 9.0 to 35.0%, Ni: 1.0% or less, Al: 1.0% or less, N: 0.1% or less, and the balance is In the method of producing a hot-rolled ferritic stainless steel sheet, a rolled material comprising a composition of Fe and unavoidable impurities is produced in a hot-rolling process.
Hot finishing rolling, the finishing temperature is 800 ° C or less, the friction coefficient of the latter three passes is 0.2 or less, and the cumulative rolling reduction of the latter three passes is 50%.
A method for producing a hot rolled ferritic stainless steel sheet, which is performed without using water for descaling before starting hot finishing rolling and / or water for cooling a strip of a hot finishing rolling mill. Production method.

(5) The rolled material according to (3) or (4) further comprises at least one member selected from one or more of the following groups A to E in addition to the above components: A method for producing a hot-rolled ferritic stainless steel sheet, comprising: Group A: Ti: 1.0% or less, Nb: 1.0% or less Group B: Mo: 2.0% or less, Cu: 2.0% or less, Co: 2.0% or less Group C: V: 0.5% or less, Zr: 0.5% or less D Group: B: 0.005% or less Group E: Ca: 0.005% or less

(6) A method for producing a cold-rolled steel sheet, wherein the hot-rolled steel sheet is produced by the method described in the above (3) to (5), and then cold-rolled.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The results of experiments performed by the inventors will be described. Experiment 1 In producing a hot-rolled steel sheet having a thickness of 3.5 mm from a ferritic stainless steel slab having the composition shown in Table 1,
The hot rolling was performed by changing the friction coefficient in the three subsequent passes of the hot finish rolling. Here, the friction coefficient can be changed to three values of 0.13 to 0.16, 0.17 to 0.20, and 0.28 to 0.32 by changing the lubricating oil.
It was a stage. However, the conditions of hot finish rolling are as follows: the end temperature is 750-850 ° C, and the cumulative rolling reduction of the latter three passes is 35-65%.
Rolled as For the hot-rolled steel sheet thus hot-rolled (before hot-rolled sheet annealing), the hardness of the surface layer portion of the sheet thickness (average hardness within 1/5 of the sheet thickness from the sheet surface, the same applies hereinafter) Hs and sheet The hardness ratio Hs / Hc to the hardness at the center of the thickness (average hardness in the range of 1/5 of the plate thickness sandwiching the center of the thickness, the same applies hereinafter) Hc was measured, and the bending workability was investigated. Here, the bending workability is 20 mm x 100 mm from the hot rolled steel sheet.
A test piece of mm × sheet thickness was sampled, bent at 90 ° with a radius of curvature of 2 mm inside the test piece, and evaluated by the depth of wrinkles generated on the outer surface of the bent portion. FIG. 1 shows the relationship between the wrinkle depth and the hardness ratio Hs / Hc. According to FIG. 1, Hs /
It can be seen that the hot rolled steel sheet satisfying Hc ≦ 1.25 has a small wrinkle depth and good bending workability.

[0012]

[Table 1]

[0013] The hot-rolled steel sheet obtained by the above method is further subjected to 1.
The bending workability of a cold-rolled steel sheet that had been cold-rolled to 2 mm and then annealed at 900 ° C. was examined. The test piece size of the bending workability is 20 mm x 100 mm x the plate thickness.
The contact bending was performed, and the occurrence rate was determined from the ratio of the number of test pieces where cracks occurred among the number of repetitions of 2. FIG. 2 shows the hardness ratio Hs /
The effect of Hc is shown. From FIG. 2, it can be seen that the bending workability of the cold-rolled steel sheet also has a favorable relationship with Hs / Hc, similar to that of the hot-rolled steel sheet, and that the cold-rolled steel sheet whose base material is Hs / Hc ≦ 1.25 It turns out that it has good bending workability.

Experiment 2 Using a ferritic stainless steel slab having the composition shown in Table 2, the friction coefficient in the three subsequent stages of hot finish rolling was changed, and the end temperature of hot finish rolling (finish rolling mill output) Side temperature, also referred to as FDT). Here, the rolling was carried out with the cumulative draft of the latter three passes being constant at 60%. FIG. 3 shows the relationship between the hardness ratio Hs / Hc of the obtained hot-rolled steel sheet, the rolling end temperature and the friction coefficient. FIG.
Therefore, Hs / Hc has a clear relationship with the coefficient of friction when the end temperature is 800 ° C or lower, but the relationship between the two becomes unclear when the end temperature is higher than 800 ° C. When the coefficient is 0.2 or less, Hs / Hc becomes a stable low value. On the other hand, when the coefficient of friction is as high as 0.28 to 0.32, Hs / Hc becomes high.
Although / Hc shows a tendency to decrease as the end temperature rises, it can be seen that its value is higher than that obtained when the friction coefficient is 0.2 or less.

[0015]

[Table 2]

Experiment 3 Using a ferritic stainless steel slab having the composition shown in Table 3, the friction coefficient in the three subsequent passes of the hot finish rolling was changed, and the cumulative rolling reduction in the three subsequent passes was varied. In this case, the finish temperature of the hot finish rolling is 76
Rolling was performed at 0 ° C. constant. Hardness ratio Hs of the obtained hot rolled steel sheet
FIG. 4 shows the relationship between / Hc and the cumulative rolling reduction and friction coefficient of the latter three passes. From FIG. 4, Hs / Hc shows a tendency to decrease with an increase in the cumulative rolling reduction in the latter three passes irrespective of the friction coefficient. Particularly, in order to keep Hs / Hc low, the friction coefficient is set to 0.2 or less. It can be seen that it is effective to set the cumulative rolling reduction of the latter three passes to 50% or more. On the other hand, when the friction coefficient is 0.28 to 0.32, Hs / Hc cannot be suppressed to 1.2 or less even if the cumulative rolling reduction is increased.

[0017]

[Table 3]

As a result of further study based on the above experiments, in order to improve the bending workability of the hot-rolled steel sheet and the cold-rolled steel sheet, the hardness ratio of the hot-rolled steel sheet is set to Hs / Hc ≧ 1.25. In order to achieve Hs / Hc ≧ 1.25, the rolling friction coefficient should be 0.2 in the three subsequent stages of hot finish rolling.
In the following, it has been found that it is necessary to set the cumulative rolling reduction to 50% or more and to set the hot rolling end temperature to 800 ° C.

The reason why the hardness ratio Hs / Hc of the hot-rolled steel sheet affects the bending workability is considered as follows. When the hardness ratio is low, the limit workability up to uneven deformation over the entire thickness is relatively constant, whereas when the hardness ratio is high, Since the surface layer portion is more work-hardened, the surface layer portion has a lower limit of workability than the central portion. On the other hand, in the bending process, the largest strain is applied to the surface layer portion, so that the surface layer portion is partially unevenly deformed and wrinkled. It is considered that such work hardening in the surface layer portion of the hot-rolled steel sheet is due to an additional shear strain caused by friction with the roll in the surface layer portion of the material to be rolled.

The end temperature of hot finish rolling and Hs
The relationship of / Hc is as shown in FIG. 3. The result of FIG. 3 will be described below together with its estimation mechanism. In the region where the rolling end temperature is 800 ° C. or lower, if the coefficient of friction in the latter stage of the hot finish rolling is low, the shear distortion due to the friction with the roll on the surface layer of the material to be rolled is suppressed, so that the hardness ratio Hs / Hc. Is low and constant,
On the other hand, when the coefficient of friction is high, the amount of strain accumulation in the surface layer portion is larger than that in the central portion of the sheet thickness, and the hardness ratio is large. Further, the reason why the hardness ratio Hs / Hc varies in the region where the rolling end temperature exceeds 800 ° C. is that partial recrystallization is performed. Cannot be obtained. Further, the relationship between the hardness ratio Hs / Hc of the hot-rolled steel sheet and the bending workability of the cold-rolled steel sheet is as shown in FIG. 2. When the hardness ratio is low, the shear deformation of the hot-rolled steel sheet thickness surface layer is suppressed, and the effect remains after cold rolling. It is considered that the bending workability was improved.

In order to further improve the bending workability, the inventors have proposed water for descaling before the start of hot finishing rolling and / or water for cooling the strip between stands of the hot finishing rolling mill. It has been found that it is effective to perform hot rolling without using any of them. That is, in general, in hot rolling, descaling is performed using water with a scale breaker before hot finishing rolling is completed after hot rough rolling, and coating is performed between rolling mill stands in hot finishing rolling. Water for cooling the strip is used to adjust the temperature of the rolled material. On the other hand, in the present invention, rolling is performed without using any one or both of the cooling waters. The reason why at least one of the water is not used in the present invention is to advantageously use the lubrication effect of the scale. In other words, when these waters are used, the material to be rolled is quenched and the scale growth rate is reduced, so that there is a so-called metal contact portion where the scale does not intervene between the material to be rolled and the rolling rolls. Is decreased, the surface layer portion is increased in strain, and the hardness ratio is increased. In addition, in the case of metal contact, burn-in flaws are generated to deteriorate the surface properties, which may indirectly lower the bending workability. Even if the above-mentioned water is not used, since the water leaking from the roll cooling water falls on the material to be rolled, the present invention also prevents only this water from leaking completely onto the material to be rolled. Although it is difficult to do so, it is very effective to prevent water other than such inevitable water from being applied.

The present invention is characterized in that after hot rolling, hot rolled sheet annealing,
The present invention is applied to the steps of pickling, cold rolling, finish annealing, and pickling. Although the manufacturing conditions other than those described above are not particularly defined, it is desirable to select the following condition ranges. That is, the heating temperature in hot rolling is
If too low, deformation resistance becomes high and rolling becomes difficult.On the contrary, if it is too high, irregularities due to deformation during heating cause scratches during transport by the table roller, which are transferred to the subsequent rolling mill and reduce the surface quality, It is desirable to be in the range of 1000 to 1300 ° C. Also, the winding temperature is desirably 500 ° C. or more and the finish-rolling machine exit side temperature or less because excessive quenching causes shape defects. In addition, the hot-rolled sheet annealing is performed to recrystallize the hot-rolled sheet as necessary, but if it is too low, it does not recrystallize, and if it is too high, the crystal grains become coarse and workability is reduced. It is desirable that the temperature be set to not lower than 1100 ° C. Further, the cold rolling is performed to achieve a target product sheet thickness by one or two cold rolling steps including intermediate annealing. However, if the rolling reduction is low, recrystallization does not occur in finish annealing and workability is reduced. The rolling reduction is desirably 50% or more. Furthermore, the finish annealing of the cold rolled sheet is recommended to be performed at a temperature of 800 ° C. or more and 1100 ° C. or less in order to complete the recrystallization and not to coarsen the crystal grains.

Next, the component composition of the ferritic stainless steel used in the present invention will be described. C: 0.1% or less C forms a compound with Cr and deteriorates corrosion resistance, and also has a bad effect on workability. Therefore, C is preferably as small as possible. If it exceeds 0.1%, its adverse effect appears greatly, so C is set to 0.1% or less. .

Si: 1.0% or less Si is an element that is advantageous for improving corrosion resistance. On the other hand, Si is also an element that increases hardness and deteriorates workability, so its upper limit is made 1.0%.

Mn: 1.0% or less Mn is an element that suppresses hot brittleness. However, if contained excessively, Mn forms an austenite phase in the hot rolling temperature range and deteriorates the sheetability during hot rolling due to a change in deformation resistance. Since dimensional defects are likely to occur, the upper limit is set to 1.0%.

P: 0.1% or less Since P forms precipitates with Fe and Ti and delays recrystallization during annealing, its upper limit is made 0.1%.

S: 0.01% or less S is limited to 0.01% or less because a large amount of S deteriorates hot workability and workability of a product after cold rolling.

Cr: 9.0-35.0% Cr is an important element that contributes to the corrosion resistance of the material. If its content is too small, its effect is not sufficient. On the other hand, even if it is added excessively, its effect is saturated and the cost increases. 9.0-35 to invite.
It is contained in the range of 0%.

Ni: 1.0% or less Ni is an element that improves the corrosion resistance. However, if Ni is contained excessively, an austenite phase is formed in the hot rolling temperature range, and deterioration of the sheetability during hot rolling due to a change in deformation resistance and size. Since defects easily occur, the upper limit is set to 1.0%.

Al: 1.0% or less Al contributes to deoxidation. When Ti is added in a complex manner, Ti contributes to preferentially form carbides and nitrides instead of oxides. However, excessive addition increases the amount of inclusions and degrades the surface quality.
And

N: 0.1% or less N forms a compound with Cr, deteriorates corrosion resistance, and lowers workability. Therefore, N is preferably as small as possible. 0.1% content
Exceeding the limit has an adverse effect, so the upper limit is 0.1%.

In addition to the above components, if necessary, at least one of the components described below can be further contained. Ti: 1.0% or less, Nb: 1.0% or less Ti and Nb form carbides and nitrides to reduce solid solution C and solid solution N, thereby improving workability and weldability. The inclusion excessively increases the amount of precipitates, but rather degrades the workability. Therefore, the upper limits of these components are all set to 1.0%.

Mo: 2.0% or less, Cu: 2.0% or less, Co: 2.0
Mo, Cu and Co are elements useful for improving corrosion resistance, but excessive addition causes embrittlement, so the upper limit of each of these components is 2.0%.

V: 0.5% or less, Zr: 0.5% or less V and Zr suppress the formation of Cr carbonitride particularly at the welded portion,
Although it has the effect of improving corrosion resistance, excessive addition lowers toughness and ductility, so 0.5% is added as an upper limit.

B: 0.005% or less B contributes to the improvement of corrosion resistance and workability particularly by fixing N, but its effect is saturated even if it is added excessively.
% As the upper limit.

Ca: 0.005% or less Ca is an effective element for suppressing nozzle clogging during continuous casting and improving the productivity, but excessive addition causes deterioration of the surface quality due to inclusions. Add up to 0.005%.

[0037]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below based on embodiments. After heating a ferritic stainless steel slab having the components shown in Table 4 to 1100 ° C, the finishing temperature in hot finish rolling, the friction coefficient and the cumulative rolling reduction in the latter three passes, and the descaling before starting the hot finish rolling Table 5 shows the use of water and water for cooling the strip between stands of the hot finishing mill.
The hot rolling was performed under various conditions as shown in FIG. Then, it was wound at 580 ° C. to produce a hot-rolled steel sheet having a thickness of 3.5 mm. After that, a part of the hot-rolled steel sheet was further subjected to hot-rolled sheet annealing (920 ° C), pickling, cold rolling (rolling reduction 65%),
Finish annealing (900 ° C) and pickling were performed to obtain cold-rolled steel sheets. With respect to the obtained hot-rolled steel sheet, a hardness ratio Hs / Hc between the hardness Hs of the surface layer portion and the hardness Hc of the central portion in the thickness direction is obtained. The test piece was bent at 90 ° with a radius of curvature of 2 mm inside, and the depth of wrinkles generated on the outer surface of the bent portion was measured.
Also, for cold-rolled steel sheets, in the same manner as described above,
180 ° close contact bending was performed to determine the crack occurrence rate. Table 5 also shows the obtained results. As for hardness, Vickers hardness was measured.

[0038]

[Table 4]

[0039]

[Table 5]

As shown in Table 5, the hardness ratio of each of the hot-rolled steel sheets manufactured according to the method of the present invention is in an appropriate range of 1.25 or less, and the bending workability is good. Further, it can be seen that the bending workability of the cold-rolled steel sheet manufactured using the hot-rolled steel sheet as a base material is also good.

[0041]

As described above, according to the present invention, by controlling the finish rolling conditions in hot rolling to obtain a hot rolled ferritic stainless steel sheet having an appropriate hardness ratio, In addition, it is possible to improve the bending workability of a cold-rolled steel sheet manufactured using the hot-rolled steel sheet as a base material. Further, the surface properties can be improved.

[Brief description of the drawings]

FIG. 1 is a graph showing a relationship between bending workability and a hardness ratio of a hot-rolled steel sheet.

FIG. 2 is a graph showing the relationship between the bending workability of a cold-rolled steel sheet and the hardness ratio of a hot-rolled steel sheet.

FIG. 3 is a graph showing the relationship between the finish temperature of hot finish rolling and the coefficient of friction, which affect the hardness ratio of a hot-rolled steel sheet.

FIG. 4 is a graph showing the influence of the cumulative rolling reduction and the friction coefficient of the latter three passes in hot finishing rolling on the hardness ratio of a hot-rolled steel sheet.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Atsushi Miyazaki, 1st Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Prefecture Inside the Technical Research Institute of Kawasaki Steel Co., Ltd. (72) Susumu Sato 1st Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Kawasaki (72) Inventor: Toshiki Hiruda, 1st Kawasaki-cho, Chuo-ku, Chiba City, Chiba Prefecture F-term (reference) 4K037 EA01 EA02 EA04 EA05 EA09 EA10 EA12 EA13 EA15 EA17 EA18 EA19 EA20 EA23 EA25 EA27 EA31 EA32 EA35 EB06 EB09 EB14 FB08 FB10 FC01 FC02 FC03

Claims (6)

[Claims] C .: 0.1% or less, Si: 1.0% by mass%
Hereinafter, Mn: 1.0% or less, P: 0.1% or less, S: 0.01% or less, Cr: 9.0 to 35.0%, Ni: 1.0% or less, Al: 1.0% or less, N: 0.1% or less, and the balance is Bending workability characterized by a composition of Fe and unavoidable impurities, and a hardness ratio Hs / Hc of hardness Hs of the surface layer portion of the sheet thickness to hardness Hc of the sheet thickness center portion is 1.25 or less. Excellent hot rolled ferritic stainless steel sheet. 2. The steel sheet according to claim 1, further comprising at least one component selected from one or more of the following groups A to E in addition to the above components. Ferritic stainless steel hot rolled steel sheet with excellent bending workability. Group A: Ti: 1.0% or less, Nb: 1.0% or less Group B: Mo: 2.0% or less, Cu: 2.0% or less, Co: 2.0% or less Group C: V: 0.5% or less, Zr: 0.5% or less Group D: B: 0.005% or less Group E: Ca: 0.005% or less 3. In mass%, C: 0.1% or less, Si: 1.0%
Hereinafter, Mn: 1.0% or less, P: 0.1% or less, S: 0.01% or less, Cr: 9.0 to 35.0%, Ni: 1.0% or less, Al: 1.0% or less, N: 0.1% or less, and the balance is In a method of manufacturing a hot-rolled ferritic stainless steel sheet in which a rolled material composed of Fe and unavoidable impurities is manufactured in a hot-rolling process, hot finish rolling is performed, the finishing temperature is 800 ° C or less, and the friction coefficient in the third three passes is reduced. 0.2 or less, 50% reduction in cumulative rolling reduction for the latter three passes
A method for producing a hot-rolled ferritic stainless steel sheet as described above. 4. In mass%, C: 0.1% or less, Si: 1.0%
Hereinafter, Mn: 1.0% or less, P: 0.1% or less, S: 0.01% or less, Cr: 9.0 to 35.0%, Ni: 1.0% or less, Al: 1.0% or less, N: 0.1% or less, the balance being In a method of manufacturing a hot-rolled ferritic stainless steel sheet in which a rolled material composed of Fe and unavoidable impurities is manufactured in a hot-rolling process, hot finish rolling is performed, the finishing temperature is 800 ° C or less, and the friction coefficient in the third three passes is reduced. 0.2 or less, 50% reduction in cumulative rolling reduction for the latter three passes
A method for producing a hot rolled ferritic stainless steel sheet, which is performed without using water for descaling before starting hot finishing rolling and / or water for cooling a strip of a hot finishing rolling mill. Production method. 5. The rolled material according to claim 3 or 4,
A method for producing a hot-rolled ferritic stainless steel sheet, further comprising at least one component selected from one or more of the following groups A to E in addition to the above components. Group A: Ti: 1.0% or less, Nb: 1.0% or less Group B: Mo: 2.0% or less, Cu: 2.0% or less, Co: 2.0% or less Group C: V: 0.5% or less, Zr: 0.5% or less Group D: B: 0.005% or less Group E: Ca: 0.005% or less 6. A method for producing a cold-rolled steel sheet, comprising: producing a hot-rolled steel sheet by the method according to claim 3;