JPH0959717A - Production of ferritic stainless steel strip excellent in press formability, ridging resistance, and surface characteristic - Google Patents

Abstract

PROBLEM TO BE SOLVED: To minimize the occurrence of surface defects by performing one of the passes at the time of hot rolling at respectively specified temp., coefficient of friction, and draft and also performing cold rolling by means of a work roll of specific roll diameter. SOLUTION: A steel stock, having a composition which consists of, by mass, <=0.01% C, <=1.0% Si, <=1.0% Mn, 11-30% Cr, <=0.07% Al, <=0 02% N, <=0 01% S, <=0.01% O, Ti in the amount satisfying (Ti-2×S-3×O)/(C+N)>=4 and Ti×N<=0.003, and the balance Fe and also satisfies C+N=0.006 to 0.025% and N/C>=2, is used. This steel stock is hot-rolled, annealed, pickled, and cold- rolled. At this time, one of the passes in a roughing stage is carried out under the conditions of 900-1150 deg.C rolling temp., <=0.3 coefficient of friction between the rolling stock and the roll, and 40-75% draft, and further, cold rolling is done so that at least 50% of rolling reduction is attained by means of a work roll of >=500mm roll diameter. By this method, an excellent material can be attained by a single cold rolling method, and the ferritic stainless steel strip can be inexpensively provided.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention has excellent surface properties,
Moreover, the present invention relates to a method for producing a ferritic stainless steel strip which is excellent in press formability (particularly r value, in-plane anisotropy of r value (hereinafter simply referred to as “in-plane anisotropy”) and ridging resistance. is there.

[0002]

2. Description of the Related Art Ferritic stainless steel is usually manufactured by heating a continuous cast piece and then performing hot rolling (coarse rolling and finish rolling) -hot rolled sheet annealing-cold rolling-finish annealing. It The ferritic stainless steel produced in this manner is generally widely used in various fields such as kitchen appliances and automobile parts because it is excellent in stress corrosion cracking resistance and is inexpensive. However, it had a drawback that it was inferior in press formability and ridging resistance compared to. Therefore, many efforts have been made to improve the press formability and ridging resistance of ferritic stainless steel.

For example, Japanese Patent Laid-Open Publication No. 52-31919 discloses C as a steel component for improving press formability.
A technique of lowering + N and adding an appropriate amount of Ti is disclosed. However, in such a conventional Ti-added low carbon nitrogen ferritic stainless steel, the ferrite particles of {55
4} <225> orientation is strengthened, and as a result, ridging peculiar to this steel (which occurs when tensile processing is performed in the direction of 30 to 45 ° with respect to the rolling direction, Different from the ridging that has been seen so far. Below,
There is a problem in that it is simply abbreviated as "30 ° direction ridging") (see Iron and Steel, 60 (1976), S227).

Therefore, a technique for preventing ridging in the 30 ° direction is disclosed in JP-A-53-48017. In this technology, C + N is 0.03% or less and Ti is 0.1-0.
5% ferritic stainless steel was wound up at 750 ° C or lower, warm-rolled at 450-700 at 15% or higher, and annealed in the temperature range higher than the winding temperature.
Heat at a heating rate of 0.1 ° C / sec or more to 780 ° C or more and 950 ° C.
The temperature is raised to the following, cooled after being held for 0 to 30 minutes, and then intermediate annealing is inserted to set the intermediate cold rolling rate to 50% or more and the final cold rolling rate to 30% or more and less than 50%, and the {554} orientation. Instead, it develops the {111} orientation. However, this method not only imposes extremely strict conditions in the manufacturing process but also leads to a significant increase in cost because the cold rolling is performed twice.

A technique in which cold rolling is performed once is disclosed in Japanese Patent Laid-Open No. 6-279951. In this method, C and N are 0.02% or less and (C / 12) + (N / 1
4) ≤ (Ti / 48) + (Nb / 93) ferritic stainless steel is hot-rolled at a finishing temperature of 850 to 950 ° C, then rolled up at a temperature of 550 ° C or less without hot-rolled sheet annealing.
50 to 70% with rolling rolls having a roll diameter of 100 mm or more
Cold rolling is performed, and then cold-rolled sheet annealing is performed in the range of recrystallization temperature + 50 ° C to recrystallization temperature + 150 ° C. However, in this method, the r value is only about 1.1 even if hot-rolled sheet annealing is performed, although the manufacturing conditions are severely restricted.
The press moldability is not sufficiently improved. Incidentally, JP-A-59
JP-A-38334 discloses a method for improving r-value and ridging (usually caused by tension in the rolling direction) by cold rolling using a work roll having a roll diameter of 150 mm or more (preferably 300 mm or less). Is disclosed, but r
The maximum value is 1.47, which is not sufficient.

In addition to the press formability and ridging characteristics as described above, the ferritic stainless steel is used without being coated on the surface, so that the surface must be beautiful. In this regard, the Ti-added stainless steel has a problem that surface defects called titanium streaks caused by titanium nitride and oxide are more likely to occur than in ordinary ferritic stainless steel. As a technique for solving this problem, JP-A-56-3575
No. 5 discloses that in a ferritic stainless steel containing 0.1 to 0.5% Ti, [% Ti] / [% Al] = 5 to 3
0 and [% Ti] ^1.5 [% N] ≦ 4.0 × 10 ⁻⁵ , a method for suppressing the generation of surface defects is disclosed. However, this technique has a problem that sufficient press workability cannot be obtained even if surface defects are improved.

[0007]

As described above, if Ti is added to improve the press workability of ferritic stainless steel, ridging in the 30 ° direction becomes remarkable. In order to suppress this ridging, severe restrictions have been imposed on process conditions such as winding, hot-rolled sheet annealing and cold rolling. Further, there has been a limit to the attempt to increase the roll diameter in cold rolling to improve the r value. Moreover, none of these techniques improves the in-plane anisotropy, which is an important property in press molding, only focusing on the r value and the ridging property. Moreover, surface defects were generated in the Ti-added stainless steel, and it was impossible to achieve compatibility with press formability and ridging resistance.

Therefore, a main object of the present invention is to provide a method for producing a ferritic stainless steel strip which does not cause the above-mentioned problems of the above-mentioned known techniques. Another object of the present invention is press formability (particularly r
It is an object of the present invention to provide a method for producing a ferritic stainless steel strip which has excellent values, in-plane anisotropy) and ridging resistance (particularly, ridging in the 30 ° direction) and has excellent surface properties.

[0009]

Means for Solving the Problems Now, as a result of earnest research aimed at realizing the above-mentioned objects, the inventors have found that the mutual relationships among the chemical components of the ferritic stainless steel, the rough rolling condition and the cold rolling condition, in particular. The inventors have found that it can be solved by properly combining the above and completed the present invention.

That is, the present invention has the following structures. (1) C: 0.01 mass% or less, Si: 1.0 mass% or less, Mn:
1.0 mass% or less, Cr: 11 to 30 mass%, Al: 0.07 mass%
Below, N: 0.02 mass% or less, S: 0.01 mass% or less,
O: 0.01 mass% or less, and the content of these components is C + N: 0.006 to 0.025 mass%, N / C: 2.0 or more, (T
i-2 × S-3 × O) / (C + N): 4 or more, Ti × N:
A steel material containing 0.003 or less content and the balance being Fe and inevitable impurities is hot-rolled by a rough rolling process and a finish rolling process, and then annealed, pickled and cooled. In producing a ferritic stainless steel strip by performing hot rolling and finish annealing, at least one pass of the rough rolling step is performed at a rolling temperature of 90.
0 ~ 1150 ℃, the coefficient of friction between the material to be rolled and the rolling roll is 0.
3 or less, the reduction ratio is 40 to 75%, and the cold rolling, the roll diameter is 50% at least 50% of the total cold rolling reduction amount.
A method for producing a ferritic stainless steel strip having excellent press formability, ridging resistance and surface properties, which is characterized by using a work roll of 0 mm or more.

(2) In addition to the steel composition described in (1) above, Ca: 0.0003 to 0.0050 mass%, Mg: 0.0003 to 0.0050 ma
ss%, B: 0.0003 to 0.0050 mass%, one or two
A method for producing a ferritic stainless steel strip, characterized in that a steel material having a composition containing at least one kind is used.

(3) At least one pass of the finish rolling step is performed at a rolling temperature of 600 to 950 ° C. and a reduction rate of
The method for producing a ferritic stainless steel strip according to (1) or (2) above, which is performed under the condition of 20 to 45%. (4) The method for producing a ferritic stainless steel strip according to the above (3), which is carried out under the condition that the friction coefficient between the material to be rolled and the rolling roll is 0.3 or less.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION First, the results of the experimental research that led to the present invention will be described. C: 0.0015 to 0.
0050mass%, N: 0.0045-0.0200mass%, Ti: 0.0050-
Stainless steel with 0.25 mass% and Cr: 16 to 17 mass% was melted, heated to 1220 ° C, and then hot rolled with a 4-stand rough rolling mill and a 7-stand finishing mill.
Hot rolled sheet. This hot-rolled sheet was annealed according to the usual method by hot-rolled sheet annealing (850 to 1050 ° C for 60 seconds) -pickling-cold rolling-finish annealing (850 to 1050 ° C for 60 seconds) to a thickness of 0.7 m.
It was a cold rolled annealed sheet of m 2. Here, in the hot rolling, the rolling reduction of the fourth stand in the rough rolling process was changed to two levels of 33% and 50%, the rolling temperature was 1050 ° C, and the friction coefficient was 0.2.
And constant. Furthermore, the roll diameter in cold rolling was changed under each rough rolling condition. The adjustment of the friction coefficient in these rough rolling is performed by changing the mixing ratio of the low-melting-point glass-based lubricant and water, and the value of the friction coefficient is based on the mixed friction rolling theory by Orowan of a known method. I asked. Specimens were taken from the cold-rolled and annealed sheets, and the r value and 30 ° direction ridging characteristics were investigated. FIG.
Shows the effects of the rolling reduction (hereinafter abbreviated as “R ₄ ”) and N / C at the 4th stand of rough rolling on the r value and ridging (30 ° direction ridging) characteristics. From Figure 4, R ₄ is 50%
It can be seen that, when N / C is 2.0 or more, good values can be obtained for both the r value and the ridging characteristic. FIG.
Shows the effect of the cold rolling work roll diameter on the r value, and it can be seen that when R ₄ is 50%, the r value is improved when the cold rolling roll diameter is 500 mm or more.

Next, the reason why the chemical composition and the manufacturing conditions of the ferritic stainless steel in the present invention are limited to the above-mentioned gist constitution will be explained. -C: 0.01 mass% or less C is an element that reduces the r value and corrosion resistance, and 0.01
If the mass% is exceeded, the effect will be significant, so 0.01 mass%
The following is assumed. Note that C is preferably 0.0005 to 0.0080 mass% in consideration of the current manufacturing and analysis limits.

Si: 1.0 mass% or less Si is an element effective for deoxidation, but excessive addition causes hardening of the steel sheet and deterioration of ductility, so the range of addition is
The amount is 1.0 mass% or less, preferably 0.05 to 0.4 wt%.

Mn: 1.0 mass% or less Mn is an element effective for improving hot workability and toughness of welded portions. For this purpose, addition of 1.0 mass% or less is sufficient, and preferably 0.05 to 0.70 wt%
It is.

Cr: 11 to 30 mass% Cr is an essential element for ensuring the corrosion resistance as stainless steel. When the amount is less than 11 mass%, the corrosion resistance is insufficient, while when it exceeds 30 mass%, the r value is extremely lowered, so that the addition range is 11 to 30 mass%, preferably 14
~ 19 mass%.

Al: 0.07 mass% or less Al is an element which, if added excessively, produces Al ₂ O ₃ to generate surface defects. In particular, if it is added in excess of 0.07 mass%, the effect becomes remarkable, so the content should be 0.07 mass% or less.

N: 0.02 mass% or less N forms TiN during slab casting, and reduces the volume of columnar crystals (that is, the length and width of columnar crystals) which are considered to be harmful to ridging resistance. That is, the effect of improving ridging in the present invention is not due to the increase in the equiaxed crystal ratio as conventionally considered, but the volume of columnar crystals is reduced by optimizing the balance of the addition amounts of C, N and Ti. It is thought that this is one of the factors. To obtain such an effect, it is necessary to add a certain amount of N, but 0.02
Since the addition of more than mass% leads to the deterioration of the surface properties due to the precipitation of a large amount of TiN, the upper limit of the N addition amount is set to 0.02 mass%. The lower limit of the N amount is determined by the limits of N / C and C + N.

S: 0.01 mass% or less Since S forms titanium sulfide and reduces the effective amount of Ti, it is desirable to reduce it as much as possible. Therefore, the upper limit is set to 0.01 mass%, preferably 0.005 mass%.

O: 0.01 mass% or less O forms titanium oxide and reduces the effective amount of Ti, so it is desirable to reduce it as much as possible. Therefore, the upper limit is set to 0.01 mass%, preferably 0.005 mass%.

N / C: 2.0 or more N / C is one of the particularly important constituent features in the present invention. Since TiN precipitates at a temperature far higher than that of TiC, it has the effect of reducing the volume of columnar crystals if the amount of TiN precipitation is appropriate. The volume reduction effect of this columnar crystal is
It is small when N / C is less than 2.0. Further, since TiN has a larger grain size of precipitates than TiC and is thermally stable during finish annealing, it is effective in suppressing the amount of solute C and N before recrystallization to be low. When N / C is set to less than 2 as in the case of conventional Ti-added ferritic stainless steel and a large amount of TiC is finely precipitated, {554} orientation is significantly developed during finish annealing and 30 ° direction ridging occurs. On the other hand, when N / C is set to 2.0 or more, the {111} recrystallized texture mainly develops and the occurrence of ridging at 30 ° can be suppressed. For the above reasons, set the lower limit of N / C to 2.
Limited to 0. On the other hand, the upper limit of N / C is ideally C = 0p
In the case of pm, it is infinite, so no limit is set.

C + N: 0.006 to 0.025 mass% C and N were considered to be desirably reduced as much as possible in the conventional ferritic stainless steel, but in the present invention, a certain amount is contained for the following reason. There is a need. That is, even if C is 0.01 mass% or less, N is 0.02 mass% or less, and N / C is 2.0 or more, C + N is 0.006 mass% or less.
If the amount is less than r, the r-value is high, but the amount of precipitation of TiN is insufficient, resulting in poor ridging resistance. On the other hand, C + N is 0.025
If it exceeds mass%, the r value and the corrosion resistance deteriorate. Therefore, the content of C + N is set in the range of 0.006 to 0.025 mass%. In addition, the preferable range of C + N is 0.01 to 0.02 mass.
%.

(Ti-2 × S-3 × O) / (C + N):
4 or more and Ti × N: 0.003 or less (each component amount unit in the formula is mass%) In order to obtain a high r value and good surface properties, Ti, C,
The balance of N, O, and S components is important. (Ti-2 x S
If -3 × O) / (C + N) is less than 4, it is difficult to obtain r value ≧ 1.5. Further, when Ti × N exceeds 0.003, the surface properties are remarkably deteriorated. For the above reasons (Ti-2 × S
The value of −3 × O) / (C + N) was 4 or more, and the value of Ti × N was 0.003 or less.

-Ca: 0.0003 to 0.0050 mass%, Mg: 0.0003
˜0.0050 mass%, B: 0.0003 to 0.0050 mass% Ca, Mg and B are all elements that prevent nozzle clogging during casting. To get the effect, both are 0.
It is necessary to add 0003 mass%, but if it is added excessively, corrosion resistance will be deteriorated, so the upper limit is made 0.0050 mass%. The preferable addition amount of these elements is 0.0005 to
It is 0.0020 mass%.

Next, the processing conditions for producing a ferritic stainless steel strip from the materials adjusted to the above composition will be described below.・ Rough rolling process: Rolling temperature: 900-1150 ℃ If the rolling temperature of rough rolling is less than 900 ℃, recrystallization of ferritic stainless steel is difficult to proceed and ridging resistance is not improved. The nature becomes large. In addition, the roll life at the time of large reduction rolling is significantly shortened. On the other hand, when the rolling temperature exceeds 1150 ° C, the ferrite grains extend in the rolling direction due to the large reduction rolling, and the ridging resistance is deteriorated. The preferred rolling temperature is 950 to 1100 ° C.
It is.

Reduction ratio: 40 to 75% If the reduction ratio of rough rolling is less than 40%, a large amount of unrecrystallized structure remains in the center of the plate thickness, resulting in poor ridging resistance and in-plane anisotropy. Not improved. On the other hand, if the rolling exceeds 75%, there is a risk of defective biting, seizure between the roll and the steel plate, and further variation in the plate thickness due to the impact at the time of biting. Therefore, the rolling reduction of rough rolling must be 40 to 75%. The preferable range of the rolling reduction is 45 to 64%.

Coefficient of friction: 0.30 or less When the coefficient of friction of rough rolling exceeds 0.30, recrystallization occurs in the strong shear strain region of the surface layer of the steel sheet, but most of the unrecrystallized structure (giant ferrite band) in the center of the sheet thickness Since it remains as a structure), the ridging resistance is inferior and the r value and the in-plane anisotropy are not improved. Moreover, seizure between the steel sheet and the roll deteriorates the surface properties of the steel sheet. Therefore, if the coefficient of friction of rough rolling is set to 0.30 or less, static recrystallization in the central portion of the plate thickness is significantly promoted, and ridging resistance, r value and in-plane anisotropy can be improved. Therefore, the coefficient of friction of rough rolling needs to be 0.30 or less, preferably 0.2 or less. The lower limit value of this friction coefficient may be set to any value within a range in which the roll can bite and roll the material. The lubrication method for reducing the friction coefficient may be any method known to those skilled in the art.

By performing "at least one pass rolling" which simultaneously satisfies the three conditions in the rough rolling step, the crystal grains after hot rolling annealing (before cold rolling) are made finer, and in the next step, a large amount is obtained. The effect of improving ridging resistance, r-value and in-plane anisotropy by cold rolling with a radial roll is further enhanced. The above-mentioned "rolling of at least one pass" may be performed at any stage of the rough rolling process, but in practice, in the pass of the stand satisfying the above in the rough rolling process, if rolling under the conditions of and is performed, Good.

Finishing rolling Following the rough rolling process under the above conditions, further performing at least one pass of the rolling that satisfies the following conditions in the finishing rolling process, further improving the ridging resistance, r value and in-plane anisotropy. It becomes possible to do. Rolling temperature: 600-950 ° C If the rolling temperature is less than 600 ° C, it becomes difficult to secure a reduction rate of 20% or more, and the friction of the roll becomes severe. On the other hand, when the rolling temperature exceeds 950 ° C., the accumulation of rolling strain is small, and the effect of improving the r value and in-plane anisotropy cannot be expected. Therefore, the rolling temperature must be in the range of 600 to 950 ° C, preferably 750 to 900 ° C. Reduction ratio: 20 to 45% If the reduction ratio is less than 20%, the r value and in-plane anisotropy are not improved, while if it exceeds 45%, the surface properties deteriorate.
Therefore, the rolling reduction is 20 to 45%, preferably 25 to
35%. If the above-mentioned finish rolling conditions are satisfied, the r-value and the in-plane anisotropy can be improved by rolling under these conditions in any pass of the finish rolling process. Furthermore, in the pass satisfying the above-mentioned finish rolling conditions, the coefficient of friction between the roll and the material to be rolled is 0.
When it is 3 or less, it becomes possible to manufacture a steel sheet having a more excellent r value and in-plane anisotropy without causing shape defects.

· Cold rolling When rolling with a work roll having a roll diameter of less than 500 mm, shear strain is concentrated on the surface layer of the steel sheet, so {111}
Azimuth development is hindered. In contrast, the roll diameter is 50
The use of a work roll of 0 mm or more uniformly introduces strain in the plate thickness direction, which is advantageous for the development of the {111} orientation. However, this effect is obtained by performing rolling at a rolling temperature of 900 to 1150 ° C., a rolling reduction of 40 to 75%, a friction coefficient of 0.3 or less in the rough rolling process, and a cold rolling total rolling reduction of 50.
%, Preferably 65% or more for work roll diameter 500 mm
It cannot be obtained without rolling.

In the present invention, manufacturing conditions other than the above-mentioned processing conditions may be in accordance with ordinary methods. For example, the slab heating temperature range is 1050 to 1300 ℃, and the rough rolling process is 900 to 1300
℃, finish rolling process 550-1050 ℃, hot rolled sheet annealing 700
It is preferable that the temperature is ˜1100 ° C., and the cold rolled sheet annealing is 750 to 1100 ° C. Further, the type of lubricating oil and the lubricating method may be determined in accordance with a conventional method.

[0033]

EXAMPLES Example 1 Steels A to W (21 types) having the chemical compositions shown in Table 1 were melted,
After forming into a slab, it was heated to 1220 ° C., and then a hot-rolled sheet having a thickness of 4.0 mm was formed by a hot rolling mill including a 4-stand rough rolling mill and a 7-stand finish rolling mill. This hot-rolled sheet is annealed (850-1050 ° C x 60 sec) -pickling-cold rolling-finish annealing (850-1050 ° C x 60 sec) according to the usual method.
A 0.7 mm cold rolled annealed sheet was used. Here, in the hot rolling, the rolling reduction and the friction coefficient of the third or fourth stand in the rough rolling process were changed. The coefficient of friction was adjusted by changing the mixing ratio of the low melting glass lubricant and water. The value of the friction coefficient was obtained based on the known method of mixed friction rolling by Orowan. Furthermore, the roll diameter in the cold rolling was changed to change the ratio of the reduction amount using the work roll of 500 mmφ or more to the total reduction amount of the cold rolling.

[0034]

[Table 1]

Using the steel sheet obtained by the above method as a test material, the r value, the in-plane anisotropy Δr and the characteristic values of ridging were measured by the following methods. -R value After applying a 15% tensile strain using a JIS No. 13 B test piece, the r value in each direction was determined by the three-point method and expressed as an average value by the following formula. r = (r _L + 2r _D + r _C ) / 4 where r _L , r _D , and r _C are r values in the rolling direction, 45 ° to the rolling direction, and 90 ° to the rolling direction, respectively. Represent -Δr From the r value in each direction obtained by the above method, Δr = (r _L -2
It was calculated by r _D + r _C ) / 2.・ Ridging After applying a tensile strain of 20% to a JIS No. 5 test piece taken from a direction of 30 ° to the rolling direction in addition to the rolling direction, the ridging height (μm) was determined by a surface roughness meter.・ Surface defects Visually inspect the entire length of the coil (excluding both ends 10m),
The number of linear defects generated was calculated and converted per unit area. Table 2 shows the maximum rolling reduction in one pass in the rough rolling step, each condition of the friction coefficient and rolling temperature at that time, each condition of cold rolling and the obtained characteristic values. In addition, all the steel sheets manufactured by the method of the present invention were good without any biting failure or shape failure. From Table 2, all of the steel sheets to which the method of the present invention is applied show excellent r-value and ridging resistance, the absolute value of Δr is very small at 0.3 or less, and the occurrence rate of surface defects is 0.001 to 0.005. / M ²
It turns out that it is extremely small.

[0036]

[Table 2]

Example 2 Steels A to W (21 steel types) having the chemical compositions shown in Table 1 were melted,
After forming into a slab, it was heated to 1220 ° C., and then a hot-rolled sheet having a thickness of 4.0 mm was formed by a hot rolling mill including a 4-stand rough rolling mill and a 7-stand finish rolling mill. This hot-rolled sheet is annealed (850-1050 ° C x 60 sec) -pickling-cold rolling-finish annealing (850-1050 ° C x 60 sec) according to the usual method.
A 0.7 mm cold rolled annealed sheet was used. Here, in the hot rolling, the rolling reduction and the friction coefficient of the third stand in the rough rolling step, and the rolling reduction and the rolling temperature of the sixth or seventh stand in the finish rolling were changed. The friction coefficient of rough rolling was adjusted in the same manner as in Example 1. Furthermore, the roll diameter and the amount of reduction in cold rolling were changed. Using the steel sheet obtained by the above method as a test material, the r value, Δr and each characteristic value of ridging were measured by the same method as in Example 1. One pass maximum rolling reduction in the rough rolling process, each condition of friction coefficient and rolling temperature at that time, rolling reduction in finish rolling, each manufacturing condition of rolling temperature, each condition of cold rolling and obtained characteristic value Is shown in Table 3. In addition, all the steel sheets manufactured by the method of the present invention were good without any defective biting or defective shape. From Table 3, all of the steel sheets to which the method of the present invention is applied show r-value and ridging resistance superior to those in Example 1, and the absolute value of Δr is 0.15.
Very small as below, and the occurrence rate of surface defects is 0.00
It can be seen that it is extremely small at 1 to 0.005 pieces / m ² .

[0038]

[Table 3]

[0039]

As described above, according to the method of the present invention, a ferritic stainless steel strip which is excellent in r value and ridging resistance (30 ° direction ridging resistance) and has a small in-plane anisotropy can be obtained. It is possible to suppress the generation to an extremely low value and manufacture. Moreover, according to the method of the present invention, since such an excellent material can be achieved by the cold rolling once method, the ferritic stainless steel strip can be provided at low cost.

[Brief description of drawings]

FIG. 1 shows the influence of r value and N on ridging resistance in the direction of 30 °.
It is a graph which showed the influence of / C and rough rolling conditions.

FIG. 2 is a graph showing the effects of hot rough rolling and cold rolling on the r value.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasushi Kato 1 Kawasaki-cho, Chuo-ku, Chiba, Chiba Prefecture, Kawasaki Steel Corporation Technical Research Laboratory (72) Inventor Susumu Sato 1 Kawasaki-cho, Chuo-ku, Chiba, Chiba Prefecture Kawasaki Steel Engineering Co., Ltd.

Claims (4)

[Claims] 1. C: 0.01 mass% or less, Si: 1.0 mass% or less, Mn: 1.0 mass% or less, Cr: 11 to 30 mass%, Al: 0.07 mass% or less, N: 0.02 mass% or less, S: 0.01 mass% or less, O: 0.01 mass% or less, and the content of these components is C + N: 0.006 to 0.025 mass%, N / C: 2.0 or more, (Ti-2 * S-3 * O) / (C + N) : 4 or more and Ti × N: 0.003 or less are contained, and the rest of the steel material having a composition of Fe and inevitable impurities is subjected to hot rolling including a rough rolling step and a finish rolling step, and then,
In producing a ferritic stainless steel strip by performing hot-rolled sheet annealing, pickling, cold rolling, and finish annealing, at least one pass rolling in the rough rolling step is performed at a rolling temperature of 900 to 1150 ° C. The coefficient of friction between the material to be rolled and the rolling roll is 0.3 or less, the reduction ratio is 40 to 75%, and the cold rolling is performed at a roll diameter of 500 mm or more for at least 50% of the total cold rolling reduction amount. A method for producing a ferritic stainless steel strip excellent in press formability, ridging resistance and surface properties, which is characterized in that it is performed using a work roll. 2. As a steel material, C: 0.01 mass% or less, Si: 1.0 mass% or less, Mn: 1.0 mass% or less, Cr: 11 to 30 mass%, Al: 0.07 mass% or less, N: 0.02 mass% or less. , S: 0.01 mass% or less, O: 0.01 mass% or less, and the content of these components is C + N: 0.006 to 0.025 mass%, N / C: 2.0 or more, (Ti-2xS-3xO). / (C + N): 4 or more, Ti × N: 0.003 or less is contained, and further Ca: 0.00
03-0.0050mass%, Mg: 0.0003-0.0050mass%, B: 0.
[0003] Manufacture of a ferritic stainless steel strip according to claim 1, characterized in that one containing one or more of 0.003 to 0.0050 mass% and the balance consisting of Fe and unavoidable impurities is used. Method. 3. At least one of the finish rolling steps
Pass rolling is performed at a rolling temperature of 600-950 ° C and a rolling reduction of 20-
The method for producing a ferritic stainless steel strip according to claim 1 or 2, which is carried out under the condition of 45%. 4. The coefficient of friction between the material to be rolled and the rolling roll is 0.
3. The method for producing a ferritic stainless steel strip according to claim 3, wherein the rolling is performed under the following conditions.