JP2001107149A - Method for producing ferritic stainless steel sheet excellent in ductility, workability and ridging resistance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a ferritic stainless steel sheet for working combining excellent ductility, workability and ridging resistance and also excellent in surface quality. SOLUTION: A steel stock containing, by mass, 0.01 to 0.12% C, 0.01 to 0.12% N, 11 to 18% Cr, 0.03 to 0.15% V and <=0.03% Al is subjected to hot rolling and is thereafter subjected to cold or warm rolling at a draft of 2 to 25%, by which hot rolled sheet annealing by continuous annealing at a low temperature in a short time is made possible.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an exterior material for a building,
The present invention relates to a method for producing a ferritic stainless steel sheet suitable for use in kitchen appliances, chemical plants, water tanks, heat-resistant members for automobiles, and the like, and more particularly, to improvement of ductility, workability, and ridging resistance. The steel sheet in the present invention includes a steel sheet and a steel strip.

[0002]

2. Description of the Related Art A stainless steel sheet has a beautiful surface and excellent corrosion resistance, and is therefore widely used for building exterior materials, kitchen appliances, chemical plants, water tanks and the like. In particular, austenitic stainless steel sheets have been widely used in the above-mentioned applications because of their excellent ductility and excellent press formability without ridging.

On the other hand, the formability of ferritic stainless steel sheets has been improved due to the progress of steel purification technology, and recently, austenitic stainless steel sheets such as SUS304 and SUS316 have been applied to the above-mentioned applications. Are being considered. This is a feature of ferritic stainless steel, for example, low thermal expansion coefficient, small stress corrosion cracking susceptibility, and is inexpensive because it does not contain expensive Ni,
Such advantages have become widely known.

[0004] However, in consideration of application to molded products, this ferritic stainless steel sheet has poor ductility compared to austenitic stainless steel plates, and has irregularities on the surface of the processed product called ridging. There is a problem that the appearance of the processed product is spoiled and the load of surface polishing is increased. For this reason, in order to further expand the use of ferritic stainless steel sheets, improvement in ductility and workability and improvement in ridging resistance have been required.

In response to such a demand, for example, Japanese Patent Laid-Open No.
-24913 discloses that, by weight%, C: 0.03 to 0.08%, N:
A ferritic stainless steel having excellent workability and containing 0.01% or less and Al: 2 × N% or more and 0.2% or less has been proposed. In the technology described in JP-A-52-24913,
By reducing the contents of C and N and further adding Al at least twice the N content, the amount of dissolved N is reduced, and the crystal grains can be further refined, ductility, ridging resistance, and secondary processing. It is said that the nature is improved.

Japanese Patent Application Laid-Open No. 54-112319 discloses that, by weight, (C + N): 0.02 to 0.06%, Zr: 0.2 to 0.6%, Zr: 10 (C + N) ± 0.15%, A heat-resistant ferritic stainless steel having improved ductility and r value and excellent in press formability has been proposed. JP-A-57-70223 discloses that, in terms of% by weight, sol Al: 0.08 to 0.5%, and B,
Production of ferritic stainless steel sheet with excellent workability by hot rolling a ferritic stainless steel slab containing one or more of Ti, Nb, V and Zr, then cold rolling and then final annealing A method has been proposed.

However, in the techniques described in JP-A-52-24913, JP-A-54-112319, and JP-A-57-70223, although the workability is greatly improved, Ridging properties are not yet sufficient, and when performing processing such as press molding, polishing for improving aesthetic appearance is required, and there has been a problem that the polishing load increases and the cost increases.

On the other hand, for improvement of ridging resistance, for example, JP-A-51-123720 discloses that after hot rolling,
A method for producing a ferritic stainless steel sheet with less ridging, which is subjected to rolling at a rolling reduction of 15% or more in a temperature range of -700 ° C, followed by annealing, cold rolling and final annealing, is disclosed. Also, JP-A-53-40625 discloses that, by weight,
Hot-rolled stainless steel sheet containing Al so that Al: 0.01% or more and Al / N: 2 or more is subjected to continuous annealing at a temperature of 900 ° C or more Ferritic stainless steel sheet with excellent ridging resistance Is disclosed.

Japanese Patent Application Laid-Open No. 1-1111816 discloses that hot rolling is performed at a finishing temperature of 850 ° C. or more, and 10 ° C.
/ S is quenched at 550 ° C or lower, then cold rolled at a cumulative draft of 50% or more, and then annealed. It has been disclosed. However,
JP-A-51-123720, JP-A-53-40625, JP-A-1-1-1
According to the techniques described in JP-A-11816 and JP-A-10-53817, although ridging resistance is improved, both ductility and workability have not been sufficiently improved.

With respect to such a problem, there are proposals for making workability and ridging resistance compatible as follows. Japanese Patent Application Laid-Open No. Hei 10-53817 discloses that, by weight, 11 to 25% of Cr,
0.005% or less, N: 0.008 to 0.03%, Ti, Ti
Ferrite-based stainless steel slabs containing 1/48 in the range of (C / 12 + N / 14) to 5 (C / 12 + N / 14)
Rough rolling is performed in a temperature range of up to 950 ° C with a total rolling reduction of at least 1 pass or 2 passes of 50% or more, and an end temperature of 950 ° C or more. Finish rolling at a rate of 40% or more and a finishing temperature of 850 ° C. or more, with an average cooling rate of 25 for 5 seconds immediately after rolling.
A method for producing a ferritic stainless steel sheet excellent in roping resistance, ridging resistance and formability at not more than ° C./s is disclosed. According to the technique described in Japanese Patent Application Laid-Open No. Hei 10-53817, a strong reduction in hot rolling is effective in improving ridging resistance.

In Japanese Patent Application Laid-Open No. Hei 9-111354, C: 0.02 to 0.05%, N: 0.02 to 0.05%, Cr: 15 to
A slab containing 18% and Al: 0.10 to 0.30% is subjected to hot rolling at a final pass exit temperature: 950 ° C. or higher, and then a cooling rate: 20
Cooled to 500 to 650 ° C at ~ 80 ° C / s to obtain a hot rolled sheet having a composite structure of ferrite + martensite.
Anneal for 180 to 300 sec in the temperature range of 850 to 980 ° C, then quench at a cooling rate of 15 ° C / s or more, then apply cold rolling and finish annealing. Excellent in ridging resistance and press formability. A method for producing a ferritic stainless steel sheet having good surface properties is disclosed.

Further, in addition to achieving both ductility, workability, and ridging resistance, box annealing has been conventionally applied to hot rolled sheet annealing in the production of ferritic stainless steel sheets. Therefore, application of continuous annealing is aimed at. Japanese Patent Application Laid-Open No. 2-170923 discloses that a hot rolled sheet obtained by hot rolling a chromium stainless steel slab containing 13.0 to 20.0 wt% of chromium is subjected to preliminary cold rolling at a rolling reduction of 2 to 30%. A method for producing a chromium-based stainless steel cold-rolled sheet having excellent ridging resistance and press workability, which is subjected to continuous annealing, followed by continuous descaling, descaling, cold rolling, and finish annealing, is disclosed. According to the method described in Japanese Patent Application Laid-Open No. 2-170923, a strong reduction by cold rolling is applied before annealing to promote recrystallization behavior during annealing, enable continuous annealing, and improve workability and ridging resistance. I have to.

[0013]

SUMMARY OF THE INVENTION
10-53817, JP-A-9-111354, JP-A-2
There is still room for further improvement in the technique described in Japanese Patent No. 170723. For example, in the technology described in Japanese Patent Application Laid-Open No. Hei 10-53817, even the one with the highest ridging rating of 1 is included up to a maximum of 20 μm. There was a problem. Furthermore, in the technique described in Japanese Patent Application Laid-Open No. 10-53817, it is necessary to add carbon in an extremely low carbon amount and to add Ti in an amount sufficient to fix C and N, and in addition to the problem of increasing the production cost, There is a problem that generation of surface defects due to the addition of a large amount of Ti is inevitable.

In the technique described in Japanese Patent Application Laid-Open No. 9-111354, it is necessary to add a large amount of Al, the amount of inclusions in the steel increases, and the occurrence of surface defects due to this is inevitable. In addition, there remains a problem that improvement in ductility and ridging resistance is still insufficient. Further, the technique described in Japanese Patent Application Laid-Open No. 2-170923 has a problem that the improvement is not achieved until both good ridging resistance and high r value are provided. Further, there is also a problem that grain boundary erosion occurs due to sensitization during pickling of a hot-rolled sheet or a hot-rolled annealed sheet, and the surface quality of a product sheet is deteriorated without being erased by a subsequent treatment.

As described above, according to the above-mentioned prior art, it is impossible to manufacture a ferritic stainless steel sheet having both ductility, workability, and ridging resistance at a low cost by using hot-rolled sheet annealing as continuous annealing. there were. An object of the present invention is to solve the above-mentioned problems of the prior art and to provide a method for producing a ferritic stainless steel sheet for processing having excellent ductility, workability, and ridging resistance, and further having excellent surface quality. And

[0016]

The present inventors have conducted various studies to achieve the above-mentioned object, and as a result, have adjusted the chemical composition and obtained a relatively low temperature after hot rolling prior to hot-rolled sheet annealing. It has been found that the application of warm or cold rolling at a reduction ratio improves ductility, workability and ridging resistance. Further, by adding 0.03 to 0.15% of V and applying rolling strain to a hot-rolled sheet after hot rolling and before hot-rolled sheet annealing,
Recrystallization during hot-rolled sheet annealing is promoted, recrystallization is completed even at low temperature and short-time annealing, and hot-rolled sheet annealing can be made continuous annealing, and the continuous annealing temperature can be lowered.
It has also been found that the grain boundary erosion resistance of hot-rolled sheets and hot-rolled annealed sheets is improved, and the surface quality of products is improved. In addition, by setting the rolling finish temperature of hot rolling to 850 ° C or less,
It was also found that the minimum r value was increased and the in-plane anisotropy was improved.

First, the results of an experiment on which the present invention is based will be described. In mass%, 0.063% C-0.0330% N-0.
27% Si-0.60% Mn-16.3% Cr-0.33% Ni-0.001% Al-
Hot rolling (rolling finishing temperature: 1000 ° C) is performed on a ferritic stainless steel material having a composition containing 0.061% V to form a hot-rolled sheet, which is subjected to cold rolling at a rolling reduction of 0 to 20%, followed by continuous annealing. Hot-rolled sheet with an ultimate temperature of 830 ° C, cold-rolled so that the total draft after hot-rolling is 75%, and finish annealing at 830 ° C for 30 seconds. A cold rolled stainless steel sheet.

For these ferritic stainless steel cold-rolled steel sheets, changes in average elongation El _mean , average r value (Rankford value), and ridging grade were examined. The result is shown in FIG. From FIG. 1, the average elongation El is obtained by performing cold rolling at a rolling reduction of 2 to 15% before annealing the hot-rolled sheet.
_mean : 31% or more, r value: 1.3 or more, ridging grade:
It can be seen that A (the undulation height is 5 μm or less), the elongation El, the r value, and the ridging resistance are all improved.

Further, the present inventors investigated the effect of the finishing temperature on the r value in hot rolling in order to further improve the workability. mass%, 0.063% C-0.033% N-0.27
% Si-0.60% Mn-16.3% Cr-0.33% Ni-0.001% Al-0.
A hot-rolled sheet is formed by hot rolling a ferritic stainless steel material having a composition containing 061% V to a finishing temperature (FDT) of 1000 to 700 ° C, and then a cold-rolled sheet having a draft of 10%. After rolling, 830 ° C × 1min by continuous annealing
Hot-rolled sheet and cold-rolled so that the total reduction after hot-rolling is 75%, and then at 830 ° C for 30%.
Finish annealing was performed to maintain sec. For these ferritic stainless steel cold rolled steel sheets, the rolling direction, rolling direction and 45
Investigate the r value in each of the ゜ direction, rolling direction and 90 ° direction,
The average r value (r _mean ) and the minimum r value (r _min ) were determined. The result is shown in FIG.

From FIG. 2, it was found that by setting the FDT to 850 ° C. or lower, the r _min value was improved, the in-plane anisotropy was improved, and the press formability was further improved. In mass%, 0.06% C-0.03% N-0.3% Si-0.6%
It contains Mn-16% Cr-0.3% Ni-0.001% Al and V is 0 ~
Each ferritic stainless steel material having a composition changed to 0.15% is subjected to hot rolling (rolling finishing temperature: 1000 ° C) to form a hot-rolled sheet, and is subjected to cold rolling at a draft of 5%, and then to 750 ° C.
After continuous annealing for 1 minute, the hardness Hv was measured. The result is shown in FIG.

From FIG. 3, the hardness of the hot-rolled sheet is V: 0.03 mass
%, It is found that the content is sufficiently reduced. 0.03mass
% Or more, the recrystallization is sufficiently completed and the hardness is lowered even by annealing the hot-rolled sheet at a low temperature of 750 ° C. × 1 min for a short time.
From this, it has been found that by containing V of 0.03 mass% or more and imparting rolling strain before hot-rolled sheet annealing, it is possible to lower the annealing temperature in continuous annealing. Lowering the continuous annealing temperature can suppress sensitization caused by annealing, suppress grain boundary erosion caused by subsequent pickling, and significantly improve the surface quality of the product sheet.

The present invention has been completed based on the above findings and further studies. That is, in the present invention, in mass%, C: 0.01 to 0.12%, N: 0.01 to 0.12%,
Hot-rolling a steel material containing 11 to 18% of Cr and further containing 0.03 to 0.15% of V and adjusted to not more than 0.03% of Al to form a hot-rolled sheet by hot rolling; A hot-rolled sheet annealing step of continuously annealing the sheet, a cold-rolling step of cold-rolling the hot-rolled sheet after the hot-rolled sheet annealing step to a cold-rolled sheet, and a finish annealing step of finish annealing the cold-rolled sheet. In the method for producing a ferritic stainless steel sheet having the following, after the hot-rolling step and before the hot-rolled sheet annealing step, a reduction ratio of cold or warm: 2 to 15
% Is a method for producing a ferritic stainless steel sheet excellent in ductility, workability and ridging resistance, which is characterized by performing a preliminary rolling step of performing rolling in the hot rolling step in the hot rolling step. Rolling Finish Temperature (FD
T) is preferably 850 ° C. or lower.

In the present invention, the steel material may be
And C: 0.01 to 0.12%, N: 0.01 to 0.12%, Cr: 11 to 18
%, V: 0.03 to 0.15%, Al: 0.03% or less, Si: 1.0% or less, Mn: 1.0% or less, with the balance Fe
It is preferable to use a steel material having a composition consisting of unavoidable impurities. In the present invention, the inevitable impurities are mass%, Ni: 1.0% or less, P: 0.05% or less,
S: 0.01% or less is allowable. In the present invention, in addition to the above-described composition, B: 0.0002 to 0.00
It is preferable to contain one or more selected from 50%, Ca: 0.0005 to 0.010%, and Mg: 0.0002 to 0.0050%.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the reasons for limiting the composition of the steel material used in the present invention will be described. Hereinafter, mass% in the composition is simply described as%. C: 0.01 to 0.12% In the present invention, it is preferable to reduce C as much as possible to improve ductility. However, if the C content is excessively reduced, the ridging resistance is deteriorated, and irregularities are generated in a processed portion during processing such as press molding, and the appearance of the product is impaired. For this reason, the lower limit of the C content is set to 0.01%. On the other hand, if it is contained in excess of 0.12%, ductility is reduced, and a Cr-free layer, coarse precipitates, and inclusions, which are the starting points of rust, increase.
For this reason, the upper limit of the C content is set to 0.12%.

N: 0.01 to 0.12% Like N, N is preferably reduced as much as possible to improve ductility. However, if the N content is excessively reduced, the ridging resistance is deteriorated, and irregularities are generated in a processed portion during processing such as press molding, and the appearance of the product is impaired. For this reason,
The lower limit of the N content was set to 0.01%. On the other hand, if it is contained in excess of 0.12%, ductility is reduced, and a Cr-free layer, coarse precipitates, and inclusions, which are the starting points of rust, increase. Therefore, the upper limit of the N content is set to 0.12%.

Cr: 11 to 18% Cr is an element effective in improving corrosion resistance. In order to have corrosion resistance in various corrosive environments, Cr is at least 11%.
% Is required. On the other hand, if the content exceeds 18%, the workability decreases. For this reason, Cr was limited to the range of 11 to 18%. Al: 0.03% or less Al acts as a deoxidizing agent, but excessive content frequently causes surface defects due to inclusions such as oxides. Therefore, in the present invention, the content of Al is limited to 0.03% or less. Preferably,
It is 0.01% or less.

V: 0.03-0.15% V combines with C and N to form carbides, nitrides or carbonitrides, reduces the amount of solute C and solute N, and suppresses coarsening of crystal grains. Is an element that has the effect of Furthermore, V
The carbides, nitrides, and carbonitrides are the places where dislocations accumulate when a hot-rolled sheet is cold-worked, and have the effect of lowering the annealing temperature in continuous annealing to promote recrystallization during annealing. Have. Further, V suppresses sensitization of grain boundaries by fixing C and N, suppresses sensitization caused by hot rolling, hot-rolled sheet annealing or cold-rolled sheet annealing, and grain boundary erosion during pickling. The occurrence of is suppressed. Such an effect is recognized when the content of V is 0.03% or more. On the other hand, if the content exceeds 0.15%, the cold workability is reduced, and if the content is large, the production cost increases and it is economically disadvantageous. From this, V is 0.03-0.15%
Limited to the range.

Si: 1.0% or less Si is an element acting as a deoxidizing agent, but if contained in a large amount, ductility and cold workability are reduced. For this reason, Si
It is preferably set to 1.0% or less. In addition, more preferably, it is 0.03 to 0.50%. Mn: 1.0% or less Mn is an effective element that combines with S and reduces solid-solution S to suppress grain boundary segregation of S and prevent cracking during hot rolling. This causes a reduction in cold workability and corrosion resistance. Therefore, Mn is preferably limited to 1.0% or less. Incidentally, the content is more preferably 0.05 to 0.8%.

Ni: 1.0% or less Ni is an element that improves corrosion resistance, but a large amount of Ni lowers the cold workability. In the present invention, Ni is an element inevitably contained, but it is preferable to limit the content to 1.0% or less even when added as necessary. From the viewpoint of workability, Ni is more preferably set to 0.7% or less.

P: 0.05% or less P is an element that deteriorates hot workability and generates pits, and is preferably reduced as much as possible. Up to 0.05%, its adverse effect is not significant, so up to 0.05% is acceptable. S: 0.01% or less S is an element that forms sulfides, lowers the cleanliness of steel, becomes a starting point of rust as MnS, and further segregates at crystal grain boundaries to promote grain boundary embrittlement. Is preferred. Up to 0.01%, the adverse effect is not significant and is acceptable.

B: 0.0002-0.0050%, Ca: 0.0005-0.01
0%, Mg: one or two or more selected from 0.0002 to 0.0050% B, Ca, and Mg each have an effect of improving workability, and are selected as necessary, and may be used alone or in combination. Can be contained. B improves workability through improvement of secondary work brittleness resistance, but no effect is observed at less than 0.0002%. On the other hand, if the content exceeds 0.0050%, workability is rather lowered. For this reason, B is preferably limited to the range of 0.0002 to 0.0050%. Ca improves workability through control of inclusion morphology, but no effect is observed at less than 0.0005%. On the other hand, if the content exceeds 0.010%, surface defects due to oxides occur frequently and the surface quality deteriorates. For this reason, Ca
Preferably, it is limited to the range of 0.0005 to 0.010%. Further, Mg has an effect of improving hot workability,
The effect is recognized at a content of 0002% or more. On the other hand, 0.00
If the content exceeds 50%, the surface quality deteriorates. For this reason, Mg is preferably limited to the range of 0.0002 to 0.0050%.

The remainder of the steel material used in the present invention other than the above components is Fe and inevitable impurities. Next, a method for producing a ferritic stainless steel sheet using the steel material having the above-described composition will be described. First, the molten steel having the above-described composition is smelted in a commonly known smelting furnace such as a converter or an electric furnace, and then further subjected to vacuum degassing (RH method).
It is preferable that the steel material is refined by a known refining method such as a VOD method or an AOD method and then cast into a slab or the like by a continuous casting method or an ingot making method.

The steel material is then heated and hot-rolled to form a hot-rolled sheet, a pre-rolling step of performing rolling to impart a rolling strain to the hot-rolled sheet cold or warm, and a pre-rolling step. A hot-rolled sheet annealing step of continuously annealing the hot-rolled sheet after the step, a cold-rolling step of cold-rolling the hot-rolled sheet after the hot-rolled sheet annealing step into a cold-rolled sheet, and finishing the finish of the cold-rolled sheet. An annealing step is sequentially performed.

In the hot rolling step of the present invention, the hot rolling conditions for obtaining a hot rolled sheet need not be particularly limited, and there is no problem with hot rolling having a normal rolling finish temperature. When it is necessary to increase the r value and improve the in-plane anisotropy, it is preferable to set the finishing temperature of hot rolling to 850 ° C. or lower. The obtained hot rolled sheet is subjected to a descaling treatment, and is then subjected to a preliminary rolling step before being subjected to hot rolled sheet annealing.

In the preliminary rolling step, rolling is performed at a rolling reduction of 2 to 15% in a cold or warm state. By this rolling, rolling distortion is introduced, and the elongation, r value, and ridging resistance are all improved by a combination of the subsequent hot rolled sheet annealing, cold rolling, and cold rolled sheet annealing. When the rolling reduction is less than 2%, the improvement in elongation, r value and ridging resistance is small, while when it exceeds 15%, the elongation, r
Value and ridging resistance both deteriorate. For this reason, the rolling reduction in the preliminary rolling step is limited to the range of 2 to 15%. The rolling in the pre-rolling step is performed in a cold region or a warm region of less than 450 ° C. When the rolling temperature is 450 ° C. or higher, the rolling distortion introduced by the rolling is recovered, and the effect of the preliminary rolling is reduced.

The pre-rolling may be performed after the hot rolling step and before the hot-rolled sheet annealing step. For example, while the coil is cooled to below 450 ° C. to room temperature after hot rolling,
The coil may be rolled while still above room temperature.
The pre-rolled hot rolled sheet is then annealed in a hot rolled sheet annealing step. Annealing in the hot-rolled sheet annealing step is continuous annealing. In the continuous annealing, it is preferable that the ultimate temperature is 700 ° C. or more and the holding time is 30 seconds or more. The ultimate temperature is more preferably 750 to 880 ° C. In the present invention, since V is contained, the recrystallization initiation temperature is low, and the recrystallization can be sufficiently completed even by continuous annealing at a relatively low temperature for a short time.

The hot-rolled sheet that has undergone the hot-rolled sheet annealing step is subjected to descaling treatment as necessary, and is then cold-rolled into a cold-rolled sheet in the cold-rolling step. In cold rolling in the cold rolling process, the rolling reduction
It is preferably at least 30%. Incidentally, more preferably 50
~ 95%. If the rolling reduction is less than 30%, the r value and ridging resistance may be insufficient.

After the cold rolling step, in the finish annealing step, the cold rolled sheet is subjected to finish annealing. Finish annealing is preferably performed at a temperature of 600 ° C. or more at which recrystallization occurs in order to improve workability. The more preferable temperature range of the finish annealing is 70.
0-900 ° C. The finish annealing is preferably a continuous annealing in consideration of productivity. In the present invention, the cold rolling step and the finish annealing step may be repeated two or more times. By repeating the cold rolling step and the finish annealing step, the r value, elongation, and ridging resistance are further improved.

The finish of the cold-rolled sheet may be 2
Needless to say, various finishes such as D finish, 2B finish, and BA finish can be made.

[0040]

EXAMPLES (Example 1) Molten steel having the composition shown in Table 1 was smelted in a converter-secondary refining process and made into a slab by a continuous casting method.
After reheating these slabs, a hot-rolled sheet having a thickness of 3.2 to 4.0 mm was formed by a hot-rolling step of performing hot rolling at a finishing temperature shown in Table 2. Then, after pickling these hot-rolled sheets, a pre-rolling step, a hot-rolled sheet annealing step by continuous annealing, a pickling step, a cold-rolling step, and a finish annealing step are sequentially performed to perform cold-rolling annealing with a sheet thickness of 0.8 mm. Board. Table 2 shows the rolling conditions of the preliminary rolling and the annealing conditions of the hot-rolled sheet. In the cold rolling process after pickling the hot rolled sheet, the cold rolling reduction was adjusted to obtain a cold rolled sheet having a sheet thickness of 0.8 mm. The total reduction after hot rolling was 75 to 80%. Annealing in the final annealing step was continuous annealing, and was maintained at 830 ° C. for 30 seconds.

A test piece was collected from the obtained cold-rolled annealed sheet,
A tensile test was performed to measure elongation El, r value, and ridging grade. The methods for measuring elongation, r value, and ridging grade are as follows. (1) Elongation Each direction of each cold-rolled annealed sheet (rolling direction, 45 ° to the rolling direction)
Direction, a direction perpendicular to the rolling direction), take a JIS No. 13 B test piece, conduct a tensile test, and elongate El (E
_{l 0, El 45, El 90} ) were measured. The average elongation El _mean was determined from the elongation El in each direction by the following equation: El _mean = (El ₀ +2 El ₄₅ + El ₉₀ ) / 4. Here, El ₀ is the elongation in the rolling direction, El ₄₅ is the elongation in the 45 ° direction with respect to the rolling direction, El
₉₀ is the elongation in the 90 ° direction (perpendicular) to the rolling direction. (2) r value Each direction of each cold-rolled annealed sheet (rolling direction, 45 ° to the rolling direction)
Direction, a direction perpendicular to the rolling direction). When a 15% uniaxial tensile prestrain was applied to these test pieces, the width strain and the thickness strain of each test piece were determined, and the ratio of the width strain to the thickness strain r = ln (w / w ₀ ) / ln (T / t ₀ ) (where w ₀ and t ₀ are the width and thickness of the test piece before the test, and w and t are the width and thickness of the test piece before the test) in each direction. _Was obtained, and the average r value r _mean was obtained by the following equation: r _mean = (r ₀ + 2r ₄₅ + r ₉₀ ) / 4. Here, r ₀ is the r value in the rolling direction, r ₄₅ is the r value in the 45 ° direction with respect to the rolling direction, r ₉₀
Is the r value in the 90 ° direction (perpendicular) to the rolling direction. (3) Ridging grade Samples of JIS No. 5 were taken from the rolling direction of each cold rolled annealed sheet,
One side of this test piece was finish-polished with # 600 abrasive paper. Next, after applying a uniaxial tensile prestrain of 20% to these test pieces, the height of undulation (ridging irregularities) generated on the test pieces was measured at the center of the test pieces by a roughness meter. The degree of ridging was evaluated from the height of the undulation.

The degree of ridging was evaluated on a four-point scale. A was used when the undulation height was 5 μm or less.
C was determined to be greater than 20 μm, and D was determined to be greater than 20 μm. In the case of A and B in this evaluation standard, the ridging resistance at the time of press molding is good. In addition, the surface of the cold-rolled annealed sheet was observed using a scanning electron microscope, the presence or absence of grain boundary erosion was investigated, and the surface quality was evaluated. When no erosion occurred, it was evaluated as O, and when erosion occurred, it was evaluated as X.

Table 2 shows the obtained results.

[0044]

[Table 1]

[0045]

[Table 2]

[0046]

[Table 3]

All of the examples of the present invention have an El _{mean of} 31% or more, a r _mean value of 1.25 or more, a ridging grade of A, and have good properties in elongation, r value and ridging resistance. Also, no occurrence of grain boundary erosion was observed in pickling,
Surface quality is good. On the other hand, in Comparative Examples outside the range of the present invention, any of elongation, r value, and ridging resistance are reduced. In the comparative example, grain boundary erosion occurs during pickling,
The surface quality of the product sheet after cold rolling annealing is degraded. (Example 2) Molten steel having a partial composition shown in Table 1 was converted to converter-2.
It was melted in the next refining process and made into a slab by a continuous casting method. After reheating these slabs, as shown in Table 3, a hot-rolled sheet having a thickness of 3.2 to 4.0 mm was formed by a hot-rolling step of performing hot rolling at various finishing temperatures. Next, after pickling these hot-rolled sheets, a pre-rolling step, a hot-rolled sheet annealing step by continuous annealing, a pickling step, a cold rolling step, and a finish annealing step are sequentially performed to obtain a sheet thickness of 0.8 mm.
Cold-rolled annealed sheet. Table 3 shows the rolling conditions of the preliminary rolling and the annealing conditions of the hot-rolled sheet. In the cold rolling process after pickling the hot rolled sheet, the cold rolling reduction was adjusted to obtain a cold rolled sheet having a sheet thickness of 0.8 mm. The total reduction after hot rolling was 75 to 80%. Annealing in the final annealing step is continuous annealing and is performed at 830 ° C for 30 minutes.
sec held.

A test piece was collected from the obtained cold-rolled annealed plate,
A tensile test was performed to measure elongation El, r value, and ridging grade. The methods for measuring elongation, r value, and ridging grade were the same as in Example 1. Note that the r value, r ₀ , r ₄₅ ,
the minimum value of r ₉₀ was r _min. In the same manner as in Example 1, the surface of the cold-rolled annealed plate was observed using a scanning electron microscope, the presence or absence of grain boundary erosion was investigated, and the surface quality was evaluated. When no erosion occurred, it was evaluated as O, and when erosion occurred, it was evaluated as X.

Table 3 shows the obtained results.

[0050]

[Table 4]

All of the examples of the present invention have an El _{mean of} 32% or more, a r _mean value of 1.30 or more, a ridging grade of A, and have good properties in elongation, r value and ridging resistance. By setting the rolling finishing temperature in the hot rolling step to 850 ° C. or lower, r _min is increased and the in-plane anisotropy of the r value is improved. Further, no occurrence of grain boundary erosion due to pickling was observed, and the surface quality was good.

On the other hand, in Comparative Examples outside the range of the present invention, any of elongation, r-value and ridging resistance are lowered. In Comparative Examples in which V, C, and N are out of the range of the present invention, grain boundary erosion occurs during pickling, and the surface quality of the product sheet after cold rolling annealing is deteriorated.

[0053]

According to the present invention, a ferritic stainless steel sheet having excellent ductility, workability, and ridging resistance and excellent surface quality can be manufactured efficiently and at low cost, and has a remarkable industrial effect. .

[Brief description of the drawings]

FIG. 1 shows the preliminary rolling reduction, the average elongation El _mean (a),
It is a graph which shows the relationship between an average r value r _mean (b) and a ridging grade (c).

FIG. 2: Rolling finish temperature FD of hot rolling on r value
6 is a graph showing the effect of T.

FIG. 3 is a graph showing the effect of V content on hardness after hot-rolled sheet annealing.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kouki Uki 1 Kawasaki-cho, Chuo-ku, Chiba City, Chiba Prefecture Inside the Technical Research Institute of Kawasaki Steel Co., Ltd. (72) Susumu Sato Susumu 1 Kawasaki-cho, Chuo-ku, Chiba City, Chiba Prefecture Kawasaki F-term (Reference) 4K032 AA00 AA01 AA02 AA04 AA05 AA08 AA13 AA16 AA21 AA23 AA27 AA29 AA31 AA36 BA01 CC03 CC04 CF02 CF03 CG02 CH04 4K037 EA01 EA02 EA05 EA13 EA03 EA09 EA09 FC04 FC05 FF03 FG03 FH01 FJ04 FJ05 FJ06 HA05 JA06

Claims (2)

[Claims] [Claim 1] In mass%, C: 0.01 to 0.12%, N: 0.01
0.12%, Cr: 11-18%, V: 0.03-0.15
% And Al: 0.03% or less.
A hot rolling step of forming a hot rolled sheet by hot rolling, a hot rolled sheet annealing step of continuously annealing the hot rolled sheet, and cold rolling the hot rolled sheet after the hot rolled sheet annealing step to form a cold rolled sheet. In a method for producing a ferritic stainless steel sheet having a cold rolling step and a finish annealing step of finish annealing the cold rolled sheet, after the hot rolling step and before the hot rolled sheet annealing step, reduction in cold or warm is performed. A method for producing a ferritic stainless steel sheet having excellent ductility, workability and ridging resistance, wherein a preliminary rolling step of rolling at a rate of 2 to 15% is performed. 2. A rolling finishing temperature of hot rolling in the hot rolling step is 850 ° C. or less.
3. The method for producing a ferritic stainless steel sheet according to item 1.