JPH08311543A - Production of ferritic stainless steel having good glossiness and excellent in ridging resistance and formability - Google Patents

Abstract

PURPOSE: To produce a steel sheet small in the anisotropy of r value and excellent in glosiness by subjecting a ferritic stainless steel in which the relationships among the contents of C and N and the amounts of Ti and Nb to be added are specified to rough rolling, thereafter executing bending and heat holding treatment under specified conditions and subjecting the same to finish rolling. CONSTITUTION: The compsn. of a ferritic stainless steel is constituted of the one contg. by weight, <=0.01% C and <=0.015% N and contg. either or both of Ti and Nb so as to satisfy the conditions of C/12+N/14<Ti/48+Nb/93. This steel is subjected to rough rolling, is thereafter subjected to bending so as to regulate the radius of curvature to <=1.5m, is coiled into a coil shape at <=1100 to >=850 deg.C and is held for 10sec to 30min. Next, it is recoiled, is subjected to finish rolling and is subjected to cold rolling and annealing. Thus, the ferritic stainless steel sheet having good glossiness and excellent in ridging resistance and formability can be obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a deep-drawing phyllite stainless steel sheet which suppresses the occurrence of ridging, which is a problem of ferritic stainless steel sheets, and has little anisotropy.

[0002]

2. Description of the Related Art In some cases, a ferritic stainless steel sheet may have a peculiar surface irregularity along the rolling direction called ridging during press working, which may cause remarkable deterioration of the surface quality of the product.

As a measure for preventing ridging, low-temperature finish rolling is carried out, followed by hot-rolled sheet annealing, followed by cold-rolling and annealing (Japanese Patent Publication No. 45-34016), which combines low-temperature hot-rolling and high-temperature winding. A method (Japanese Patent Laid-Open No. 1-136930) and the like are disclosed. However, it is difficult to achieve the low temperature of hot rolling and the high temperature of winding, assuming that the existing hot rolling equipment is used. Further, adding the hot-rolled sheet annealing proposed by the former causes an increase in manufacturing cost.

On the other hand, ferritic stainless steel sheets are often used for deep drawing, and in this case, it is desired that not only the r value is high but also the anisotropy is small. r
As a measure to improve the value, steel is used as an IF (Interstitial atom fre
e), hot rolling by lubrication, etc. have been proposed (Japanese Patent Laid-Open Nos. 59-226149 and 1-136).
No. 930) does not disclose any technique for reducing the r-value anisotropy.

Further, there is almost no technical disclosure regarding the influence of the manufacturing process of the hot rolling process on the gloss.

[0006]

DISCLOSURE OF THE INVENTION The present invention has excellent gloss, suppresses the occurrence of ridging, exhibits low anisotropy, and has high r.
A method for producing a ferritic stainless cold-rolled steel sheet of high value is provided.

[0007]

The present inventors have found that the gloss,
Experiments to optimize the components and hot rolling conditions in order to improve ridging resistance and deep drawability including anisotropy, and after rough rolling, perform bending with a certain curvature or more and hold for a short time It has been found that, as a result, glossiness and ridging resistance are significantly improved. It has been clarified that not only the improvement of the r value can be achieved but also the anisotropy is reduced by optimizing the components.

Based on the above experimental results, a manufacturing technique for a ferritic stainless steel sheet for deep drawing having excellent gloss and ridging resistance and having small anisotropy was established. That is, the gist of the present invention is, in weight%, C: 0.01% or less, N:
Including 0.015% or less, one or both of Ti and Nb is C / 12 + N / 14 <Ti / 48 + Nb /
After roughly rolling the ferritic stainless steel contained so as to satisfy the condition of No. 93, bending is performed with a radius of curvature of 1.5 m or less, and the steel sheet is wound into a coil at a temperature of 1100 ° C. or less and 850 ° C. or more. After holding for at least 2 seconds and not more than 30 minutes, rewind and finish rolling at 800 ° C or higher,
It is a method for producing a ferritic stainless steel sheet having good gloss, which is characterized by performing ordinary cold rolling and annealing, and having excellent ridging resistance and formability.

[0009]

The present invention will be described in detail below. First, the limiting conditions of the components will be described. C is 0.01% or less and N is 0.015% or less. Beyond these amounts, C, N
When added, the workability deteriorates and it becomes difficult to obtain a high r value.

In the present invention, one or both of Ti and Nb is C / 12 + N / 14 + S / 32 <T.
It is added so as to satisfy the relationship of i / 48 + Nb / 93. By fixing C and N in the steel mostly in the form of precipitates with Ti or / and Nb, the orientation is advantageous for improving the deep drawability of the product (111) <11.
2>, (554) <225>, and the like because a highly integrated texture can be obtained.

From the viewpoint of corrosion resistance, Mo <3%, Ni
Addition of <2% and Cu <3% does not impair the gist of the present invention. The ferritic stainless steel sheet of the present invention is a stainless steel sheet having a product sheet ferrite rate of 90% or more.

Next, the limitation of process conditions will be described. After roughly rolling the ferritic stainless steel with the above specified components, the bending process with a radius of curvature of 1 m or less is performed.
The most important point of the present invention is to wind the steel sheet into a coil at a temperature of 0 ° C. or lower and 850 ° C. or higher and hold it for at least 10 seconds or longer and 30 minutes or shorter. The reason why the radius of curvature of bending after rough rolling is limited to 1.5 m or less is that the gloss and r-value anisotropy of the final product are not improved even if bending is performed with a radius of curvature larger than this.

Although the reason why the r-value anisotropy is improved is not clear, it is easy to recrystallize and grow grains in a particular orientation by bending, and the precipitation behavior changes within the plate thickness. By doing so, the texture formed by annealing after cold rolling may be affected, and the anisotropy of the final product sheet may have decreased. Further, even if the holding temperature is 1100 ° C. or higher, improvement in gloss cannot be obtained.

Similarly, even if the holding time exceeds 30 minutes, improvement in gloss cannot be achieved. The mechanism for understanding the effect of thermo-mechanical treatment conditions after rough rolling on the gloss of the final product is not clear yet, but it is considered to have some relation with the formation state of oxide scale. That is, it is considered that the surface layer is deformed by bending and is appropriately heat-treated in a specific temperature range to form a surface state advantageous for gloss of the final product.
The holding temperature is set to 850 ° C. or higher because the gloss, ridging resistance and moldability cannot be sufficiently improved at a temperature lower than this temperature. For the same reason, the lower limit of the holding time was set to 10 seconds.

If the thermo-mechanical treatment after rough rolling as shown in the present invention is performed, the glossiness, ridging resistance and moldability can be improved without particularly limiting the finishing temperature and the winding temperature.

[0016]

EXAMPLES The present invention will be specifically described with reference to Examples. Table 1
A steel having the composition shown in Table 1 was used. 2 of these steels
A slab having a thickness of 50 mm was formed, and after heating at 1200 ° C., rough rolling was performed to a rough bar thickness of 30 mm, and bending was performed. Bending is
It was done by running a coarse bar and hitting it against a sloping wall. At this time, the radius of curvature was changed by changing the inclination angle. After bending, it was wound into a coil and held. The conditions are shown in Table 2. After that, rewinding, finishing temperature FT: 910 ° C, winding temperature CT: 75
Hot rolled at 0 ° C. After that, after cold rolling at a cold rolling rate of 75%, recrystallization was performed at an annealing temperature ST: 820 ° C. However, Experiment 2,
The material having a low coiling temperature after rough rolling such as No. 3 deviates from the standard conditions, and FT: 820, 750 ° C. and CT: 70, respectively.
It reached 0,660 ° C. r value is 15 for JIS No. 5 test piece
% Calculated from the dimensional change after pulling. The values of Δr in the table are shown as absolute values.

The ridging resistance is J cut out from the rolling direction.
After pulling the IS5 tensile test piece by 15%, the surface was measured with a roughness meter and evaluated from the undulation height of the steel sheet. Rank 1 has a swell height of 20 μm or less, Rank 2: 20 to 3
0 μm, Rank 3: 30-40 μm, Rank 4: 40-
70 μm, Rank 5: 70 μm or more. It is said that there is no practical problem up to rank 2.

The glossiness was measured according to JIS Z8741. As for the rating, 1000 or more was 1, 1000 to 950 was 2, 950 to 900 was 3, and 900 or less was 4. In practice, a rating of up to 2 is acceptable.

[0019]

[Table 1]

[0020]

[Table 2]

Experiment numbers 1, 2 satisfying the scope of the present invention
The materials 4, 6, 8, 12, and 14 have a high r value, a small anisotropy, and a good glossiness and ridging. The material of Experiment No. 3 having a winding temperature after bending of the rough bar lower than the range of the present invention and the material of Experiment No. 5 having a short winding time are inferior in deep drawability, glossiness and ridging. On the contrary, the material of Experiment No. 7 in which the winding time was longer than the range of the present invention showed good results with respect to the r value and ridging, but the glossiness was poor. The glossiness of the material of Experiment No. 10 in which the winding temperature after bending the rough bar was higher than the range of the present invention is also low. The material of Experiment No. 9 which had a large bending radius of bendability was
The r value anisotropy was large. The materials of Experiment Nos. 11, 13, and 15, which were subjected to finish rolling without undergoing bending after rough rolling, exhibited poor results in all properties of deep drawability, glossiness, and ridging, as compared with the materials of the present invention. . With the materials of Experiment Nos. 16 and 17 using comparative steel, excellent deep drawability cannot be obtained.

[0022]

EFFECTS OF THE INVENTION According to the present invention, a ferrite system having excellent deep drawability, which is excellent in glossiness and ridging resistance and has small anisotropy, is obtained by performing a bending process after a rough rolling and a heat treatment. A stainless steel plate can be manufactured. This eliminates the need for high-temperature hot-rolled sheet annealing, has an additional property that the r-value anisotropy is small, and has excellent gloss, and is thus more versatile than ever.

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[Procedure amendment]

[Submission date] December 27, 1995

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0010

[Correction method] Change

[Correction content]

In the present invention, one or both of Ti and Nb is C / 12 + N / 14 <Ti / 48 +
It is added so as to satisfy the relationship of Nb / 93 . By fixing C and N in the steel in the form of precipitates by Ti or / and / or Nb, the orientation is advantageous for improving the deep drawability of the product (111) <112>, (55
4) It is possible to obtain a highly integrated texture such as <225>.

Claims (1)

[Claims] 1. By weight%, C: 0.01% or less, N:
Including 0.015% or less, one or both of Ti and Nb is C / 12 + N / 14 <Ti / 48 + Nb /
After roughly rolling the ferritic stainless steel contained so as to satisfy the condition of No. 93, bending is performed with a radius of curvature of 1.5 m or less, and the steel sheet is wound into a coil at a temperature of 1100 ° C. or less and 850 ° C. or more. Ferrite stainless steel sheet with good luster, excellent in ridging resistance and formability, which is characterized by performing rewinding, finish rolling, cold rolling, and annealing after holding for not less than 2 seconds and not more than 30 minutes. Manufacturing method.