JPS59232232A - Manufacture of ferritic stainless steel sheet with no surface crack and high workability - Google Patents

Abstract

PURPOSE:To manufacture the titled stainless steel sheet by hot rolling a ferritic stainless steel contg. specified amounts of C, Al and Cr, carrying out reheating at a high temp., hot rolling at a high temp. and coiling at a low temp., cold rolling the hot rolled sheet without carrying out annealing, and subjecting it to recrystallization annealing. CONSTITUTION:The composition of a ferritic stainless steel billet is composed of, by weight, 0.03-0.07% C, 0.08-0.5% Al, 15-19% Cr and the balance Fe with inevitable impurities. The billet is rolled at 1,000-1,200 deg.C and >=20% total draft. The resulting plate is reheated at 1,180-1,300 deg.C and rolled at >=850 deg.C finishing temp. with a rolling mill consisting of a rough rolling mill and a continuous finish rolling mill, and rapid cooling and coiling at <=650 deg.C are carried out. The hot rolled sheet is cold rolled without carrying out annealing, and it is subjected to recrystallization annealing.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a method for manufacturing a ferritic stainless thin steel sheet, and particularly to a method for manufacturing a ferritic stainless steel sheet with excellent workability that can simplify the manufacturing process. .

(Conventional technology) Conventionally, ferritic stainless thin steel plate (SUS430)
The method is to box-anneal a hot-rolled steel strip at a temperature range of 800 to 850°C for 2 hours or more, or to perform continuous annealing for a short time in a temperature range of 900°C to 1100°C, followed by cold rolling. One of the metallurgical meanings of annealing the hot-rolled sheets produced by @ is the refinement of crystal grains through recrystallization. , low-temperature hot rolling is required, such as lowering the finish rolling temperature.

When such low-temperature hot rolling is performed, surface flaws called so-called scale flaws are likely to occur.

(Objective of the invention) The present invention provides a method for producing a ferritic stainless thin steel sheet with no surface defects and good workability using a process that does not perform such low-temperature hot rolling and omits the hot-rolled sheet annealing step. It is something.

(Structure and operation of the invention) The gist of the present invention is that C0.03 to 0.07%,
A ferritic stainless steel slab consisting of 0.08 to 0.5% At, 15 to 19% Cr, the balance iron and unavoidable impurities was rolled at a total reduction rate of at least 2 (1 or more) in a temperature range of 1000 to 1200°C. After that, 1180℃ or more 13
After being reheated to a temperature of 00°C or lower, rolled at a finishing temperature of 850°C or higher in a rolling mill consisting of a rough rolling mill and a continuous finishing rolling mill, and then rapidly cooled and rolled at a temperature of 650°C or lower, A method for producing a ferritic stainless steel thin lead plate with no surface flaws and good workability, characterized by cold rolling and recrystallization annealing without hot-rolled plate annealing.

The consistent f-day condition, which is the gist of the present invention, will be explained. Reheating the slab at high temperature after hot rolling promotes static recrystallization in this process and refines the cast structure. The reason for this is to carry out hot rolling in the region where the γ phase exists as much as possible, to finely disperse the γ phase in the hot rolled sheet, and then to roll it at a low temperature of 650°C or less. By finely dispersing a large amount of hard phase (α' phase) into the hot-rolled sheet, and by performing high-temperature slab heating and high-temperature finishing hot rolling, scale defects are prevented from occurring during hot rolling. To prevent, ■
This is to prevent the r value from decreasing by setting the finish rolling finish temperature to a high temperature.

The purpose of reheating the cast slab at a high temperature after hot rolling to refine the cast structure is to replace the microstructural refinement in hot-rolled plate annealing. The purpose of Ω, which finely disperses a large amount of hard phase (α' phase) in the hot rolled sheet, is to reduce ridging by randomizing the entangled structure after cold rolling annealing.

In cold rolling according to the present invention, at least 60% of the reduction to be cold rolled is preferably cold rolled using large diameter work rolls of 150+ nm or more in the first stage of the 9 cold rolling steps. In this way, it is possible to improve the workability, especially the r value, to the same extent as when the total reduction is rolled with large diameter rolls of 150 mm or more, and by continuing to roll the remaining reduction with small diameter rolls, the copper plate can be rolled. Compared to the case where the surface is rolled with large-diameter rolls throughout the process, a steel plate that is more beautiful and thinner can be produced. Further, according to the present invention, the final annealing is preferably carried out at a temperature of 850° C. or higher and 900° C. or lower for a short period of time within 60 seconds. In this way, the processability, especially the r-value, and the ridging properties can be improved.

Next, the reasons for limiting the starting steel components in the present invention will be described. The reason for adding Kl was to lower the yield point, prevent the occurrence of sparkling defects, and improve the r value.The reason for creating a range for the amount of C was determined by considering the balance between the r value and ridging characteristics. This is what I did. The range for the Cr content was set in consideration of the corrosion resistance of the 5O8430 series stainless steel. The reasons for limiting each condition are explained below.The reason for setting the C content to 000.07% or less is that if the C content exceeds this value, the hot-rolled sheet will be hard in the as-hot-rolled state, and it will be difficult to cold-roll it in that state. This is because the r value of the finished product decreases and the deep drawing properties deteriorate. The reason why the content is set to be higher than CO,03 is that if the C content is less than this, the fusing characteristics deteriorate.

The reason for setting the At content to 0.08% or more is that the At content of 1 is hard in the hot state, so cold rollability deteriorates without hot-rolled sheet annealing; In some cases, the susceptibility to intergranular corrosion is large and so-called sparkling defects occur; ■ In the case of hot-rolled sheets without annealing, the yield point of the product is high and the elongation is low; ■ In the case of hot-rolled sheets without annealing, In some cases, this is due to reasons such as the low r value of the finished product. The reason why the amount of At added is set to 0.5% or less is that although the above-mentioned effects can be expected even if the amount of At added exceeds 0.5%, it is not economical to increase the amount of At added, so an upper limit was set.

The reason why the Cr content is set to 15% or more is because if the Cr content is less than this, there will be a large amount of martensite in the as-hot-rolled state, resulting in poor cold rollability and poor corrosion resistance as a 5O8430N plate. =! 1), 191Cr is set as the upper limit because adding more than this does not improve workability and is not economical.

Next, the reason for the limitation regarding the rolling process will be explained.

The hot rolling temperature of the slab before the normal hot rolling process is 1
The reason why the temperature was limited to 000°C or higher and 1200°C or lower is as follows. Although rolling at a temperature of less than 1000°C has the effect of grain refinement, rolling at a temperature of less than 1000°C is undesirable because the deformation resistance during rolling deformation is large and surface flaws are likely to occur during this rolling process. Moreover, at temperatures exceeding 1200° C., the effect of strain accumulation during hot rolling is small, and this is due to insufficient refinement of the cast structure due to static recrystallization during reheating. The reason why the rolling reduction ratio is set to 20% or more is because if the rolling reduction is less than this, static recrystallization during reheating will be insufficient and the casting structure will not be sufficiently refined. It is preferable to increase the reduction amount by 20% or more, but increasing the reduction amount is because when rolling in a normal hot rolling mill in the next step, the length of the slab is constant, so the higher the reduction amount, the more the casting Since it is necessary to reduce the piece unit weight and the productivity of hot rolling will decrease, it is necessary to determine the optimum rolling reduction amount in consideration of these factors.

When performing normal hot rolling, the rolled slab is
The reason for reheating at a high temperature above ℃ and below 1300℃ is ■
This is to statically recrystallize the rolled slab by high-temperature reheating, and (2) to hot-roll it in the α+γ two-phase region up to the stage before finishing hot rolling. The reason why the reheating temperature was set at 1180°C or higher was because: 1) If the temperature is lower than this, the progress of static recrystallization in the reheating process is insufficient, and the destruction of the cast structure is insufficient; By setting the temperature to 1180° C. or higher, hot rolling is possible with as much γ phase as possible in the rough rolling process and at least before the final hot rolling process, and the hard phase increases in the as-hot rolled state. This is because the effect of reducing ridging increases, and at temperatures below this temperature, the rolling load increases and surface flaws are more likely to appear. The reason why the reheating temperature is set to 1300° C. or lower is that heating exceeding this temperature causes crystal grains to abnormally grow and become coarser during heating, which actually deteriorates the ridging properties.

The reasons for setting the hot rolling end temperature at 850°C or higher are: ■ To reduce the deformation resistance during hot rolling to reduce surface flaws; and ■ To improve the r value by performing high finish hot rolling. by. According to research conducted by the present inventors, in the hot-rolled sheet annealing process, the lower the final hot-rolling end temperature, the higher the r value, but in the hot-rolled sheet annealing process, the lower the final hot-rolling end temperature, the lower the 8r value. It has been found that the higher the hot rolling end temperature is by 850°C or more, the more desirable it is.

Next, the reason why the material is rapidly cooled and rolled up at 650° C. or lower after finish rolling will be explained.

In the case of reheating at a high temperature after the conventional hot rolling example in the method of the present invention, the dispersion state of the γ phase immediately after the end of hot rolling is different from that in the case of reheating without such hot rolling. It was found that the particles were different and finely dispersed. The reason for this is not clear, but strain is accumulated during rolling before normal hot rolling, and by reheating it, γ phase is newly precipitated in these strain accumulated areas, resulting in the as-cast state. γ of
We believe that this is because the phase distribution becomes more dispersed.

The γ phase redispersed in this way is reheated at a high temperature, part or all of which becomes solid solution again, and precipitates again during hot rolling. It was found that the precipitated γ phase was more finely dispersed than the γ phase precipitated when the slab was directly heated to high temperature and hot rolled. The γ phase finely dispersed in this way is rapidly cooled immediately after hot rolling to form a 6
When rolling at a temperature below 50°C, a considerable amount of the γ phase does not decompose into d-phase decacarides, but transforms into a hard phase (α' phase). It has been found that changing the deformation mode during the process and randomizing the texture after final annealing can significantly reduce ridging. The lower the winding temperature, the stronger the formation of a hard phase and the greater the effect of reducing ridging. However, at temperatures below 450°C, the effect of reducing ridging does not change even at lower temperatures, and production at lower temperatures It is difficult to wind up the material without reducing its properties, and if it is rolled up at a temperature lower than this,
Since defects such as edge cracks are likely to occur during cold rolling, the winding temperature is preferably 450° C. or higher.

Even in the case of ordinary hot rolling without hot rolling before hot rolling, the effect of reducing ridging can be seen by rolling at a low temperature of 650c or less, but in this case, when rolled as in the method of the present invention, Compared to this, the ridging reduction effect is less. The reason for this is that, as is clear from the above explanation, the hard phase produced by low-temperature rolling is not finely dispersed, so the deformation bands generated in the cold rolling process are not coarsely dispersed, and the texture is not uniformly randomized. As a result, the ridging reduction effect is reduced. Even with ordinary 430 steel that does not contain At, resonating can be reduced by rolling at low temperatures, but
If there is no At addition amount as in the present invention, 1) the cold rollability will be significantly deteriorated, 2) surface defects called sparkling defects will occur during the cold rolling or final annealing process, and 2) the yield point of the product will be significantly high.
There is little elongation, the r value is significantly reduced, and shallow drawing processing,
Needless to say, this is not a thin plate suitable for processing such as roll forming and close bending.

In a preferred embodiment of the present invention, large-diameter rolls are employed in the preceding stage of cold rolling.
(222) increases the polar density, and degrades the r value (200) since the polar density decreases, processability, especially the r value, improves. The effect of improving the r value by changing the texture in this way is more effective as the roll diameter increases, but in the present invention, the lower limit of the preferred work roll diameter is set to 150.
The reason why it is set as - is that even if the roll diameter is less than 150 mm, the r value is improved as the roll diameter becomes larger, but the effect is smaller than when rolling at 150 mm or more, and that the productivity improvement is difficult with roll diameters less than ζ150 mm. It's unfavorable, so it's 150 or more in agony. Also, the reason why the amount of rolling that should be rolled with large diameter rolls should be 60% or more of the total rolling amount is because the r value increases as the rolling ratio with large diameter rolls increases, but if the rolling ratio is increased to 60% or more, This is because it is possible to obtain a high r value that is almost the same level as when rolling with a 100 eIb large diameter roll.

However, if rolling is performed 100% with large-diameter rolls, a good surface quality of the steel sheet cannot be obtained. Therefore, in order to obtain surface gloss, the present invention requires a combination with small-diameter rolls, and the reduction amount Good results can be obtained with just one attack.

Next, a preferred range of final annealing conditions will be described.

For ordinary 430 steel with an At content of 0.08% or less, the hot rolled sheet is box annealed at a temperature of about 800 to 850°C for 2 hours or more, then cold rolled and final annealed. It is commonly manufactured. The hard phase that existed in the hot rolled sheet changes to a ferrite phase + carbide, and therefore becomes a ferrite phase and a carbide phase in the hot rolled sheet annealed state.

If such a material is heated after cold rolling, recovery and recrystallization will occur, and the microstructure after recrystallization will be equiaxed grains, and the grain size will be almost unaffected by soaking temperature and time. It becomes constant.

The temperature at which recrystallization is completed varies slightly depending on the ingredients, hot rolling conditions, and cold rolling reduction ratio, but if the material temperature reaches 800°C or higher, it will recrystallize regardless of the soaking time, and if it recrystallizes, it will reach the soaking temperature. , an almost constant r value and ridging characteristics can be obtained regardless of time.

However, when the starting steel of the present invention containing a large amount of At is cold-rolled and recrystallized without hot-rolled sheet annealing, the recrystallization temperature is higher than that when the hot-rolled sheet is annealed and then cold-rolled. The grains are also mixed grains. When completely recrystallized, the grain size is almost unaffected by the soaking temperature and time and remains constant; however, the r value and ridging characteristics vary depending on the soaking temperature and time. Change. In other words, in the soaking temperature range up to 875°C, the r value increases as the temperature increases for a longer period of time;
At temperatures up to 0°C, the deterioration is at about the same level or at a slower rate, but at a higher level than at temperatures below 850°C. The longer the soaking time is, the more remarkable the r-value improvement effect is, but this is only when the soaking temperature is about 875°C or lower; if the soaking temperature exceeds about 875°C, the soaking time is longer than 10 seconds. For example, even if the soaking time is increased further, the r value will only improve slightly.

The influence of the final annealing cycle on the properties of the solder and song is complex, but when annealing is performed at various temperatures with a constant soaking time, the minimum glue song is obtained at a certain soaking temperature, and the Ridging increases both when the temperature is low and when it is high, and the optimum temperature shifts to a higher temperature side as the soaking time is shorter.The optimum temperature range is narrower, and there is a tendency for the tendency for the reduction of ridging to be large. For example, when the soaking time is as long as 60 seconds, the relative value of ridging is relatively large and is 825-875℃.
It shows a constant value over a wide range of 1 mm, and at higher or lower temperatures, the ridging properties tend to deteriorate, and when the soaking time is as short as 10 seconds, the soaking temperature In a relatively high temperature and narrow temperature range of 875-900°C, the ridging shows a low value, and this absolute value is lower than the soaking time of 60°C.
This is better than the ridging value obtained by annealing at the optimum temperature for a long time of seconds.

The hard phase, which exists in the as-hot rolled state by several tens of percent, is stretched in the rolling direction in the subsequent cold rolling process, decomposed in the final annealing process, and becomes a ferrite phase and carbide. At a temperature of , this ferrite phase also recrystallizes. By high-temperature annealing, the carbides separated from the hard phase and the fine carbides that were already present become aggregated and coarsened, cleaning the matrix and inhibiting the activity of dislocations that become active during processing deformation. In addition, due to the precipitation of AtN during annealing,
This improves the r value. When hot-rolled sheets are annealed, the size and dispersion of carbides are determined during the hot-rolled sheet annealing process, and solid solution N is also fixed by chromium nitride and a small amount of At, etc. In the process, the dispersion state of these precipitates does not change depending on the annealing method, so once recrystallization is completed, the r value does not change regardless of the annealing conditions. The reason why the r value gradually deteriorates when the hot-rolled sheet annealing temperature exceeds 875°C in the steel of the present invention is because
AAN starts to re-dissolve, carbide re-dissolves,
This is because the particles become fine again and the solid solution C and Hp in the matrix becomes high.

Next, regarding the ridging property, the reason why it deteriorates when the annealing temperature is low is that in the starting steel of the present invention, AtN precipitates during annealing, so the recrystallization completion temperature becomes high and as a result, complete recrystallization is not achieved. This is because the randomization of the texture becomes insufficient. Furthermore, as the annealing temperature increases, the song properties tend to deteriorate because fine carbides re-dissolve into solid solution, causing the fine grains that existed at the grain boundaries of the old ferrite phase to disappear, causing adjacent elongation. This is because the ferrite phase is often composed of low-angle grain boundaries, so it essentially acts in the same way as coarse crystals become coarser, and as a result, the ridging properties deteriorate.

The present invention has been described above with respect to the case where At is added to 430 steel, but the present invention also applies to copper in which up to 1% Cu − + up to 0.1% Ti or Nb, and up to 100 ppm of B are added singly or in combination. Needless to say, it is included in the steel subject to the invention.

The present invention will be specifically described below according to examples.

(Example) Example 1 A ii>J7 piece with a thickness of 250 m1 having the component composition shown in Table 1 was heated at a temperature of 1100°C for 1 hour, and then rolled at 3 nogs and 175 rymi (total reduction rate of 30 after) 1240
Heat it for 120 minutes at a temperature of ℃ and immediately roll it.
It was made into a hot rolled sheet of mm. The hot rolling end temperature was 870°C. This hot-rolled sheet was then rolled at 580°C and 750°C. The hot-rolled sheet thus produced was cold-rolled to a thickness of 0.4 mm by cold-rolling between work rolls with a diameter of 60 mm without annealing the hot-rolled sheet. Then 840℃ x 2
Annealing between min was #-j.

Table 2 shows the mechanical properties, r value, and ridging properties of the annealed materials. As shown in Table 2, when the inventive steel containing AA is treated according to the method of the present invention, the yield point is lower, the yield point elongation is less, and the r value is higher than the comparative steel with low At content. , showed good processability. Further, in the comparative steel, some occurrence of material phase defects due to intergranular corrosion was observed during the cold rolling process, but in the case of the steel of the present invention, no such defects were observed. When the steel of the present invention containing M was also rolled at 750°C, the r value was good, but the ridging was thick. In addition, since both were rolled at high temperatures, no surface flaws were observed during hot rolling.

Table 1 Ingredients (%) of test material Table 2 Product characteristics Example 2 A slab of 250 mm thick was made into 1150
After heating to a temperature of 180 mm, it was made into a slab of 180 mm in three passes.

Then 1000℃, 1100℃, 1200℃.

After heating at 1250° C. at four different humidity levels, a hot-rolled sheet with a thickness of 3.0 mm was obtained. The hot rolling end temperature was 770°C for the 1000°C slab heated material, 820°C for the 1100°C material, 870°C for the 1200°C material, and 910°C for the 1250°C material.

The rolling temperature was 550°C for each slag heating temperature, and in the case of slab heating temperatures of 1200°C and 1250°C, hot rolled sheets were also created by rolling at 750°C.

The hot-rolled sheet produced in this way was rolled to a thickness of 0.2 mm by rolling in a cold rolling mill with a work roll diameter of 450 without annealing the hot-rolled sheet.
It was made into a thin plate of 7 mm. Then, annealing was performed at 875° C. for 10 seconds, and the annealing bond song was measured. The measurement results are shown in Table 4, and the ones that were reheated at a high temperature and wound at a low temperature as in the present invention showed good song characteristics. In addition, when the reheating temperature was set to a low temperature of 1000°C and 1100°C, scratches were observed during hot rolling, but when hot rolling was carried out at a high temperature as in the present invention, no scratches were generated during hot rolling. , a good surface was obtained.

Table 3 Main chemical components of the test material (%) Table 4 Finished product gluing height μm) Example 3 A slab with a thickness of 200 mm was prepared with the composition shown in Table 5.
After rolling at a temperature of 0℃ for 150 minutes to make a 0-thickness slab, 1
After reheating to a temperature of 250℃, the rolling end temperature was 900℃ and 7
A hot-rolled sheet with a thickness of 3.7 mm was obtained under two conditions of 00°C and rolled at a temperature of 600°C.

For comparison, a slab with a thickness of 200 mm was directly heated to a temperature of 1250°C without being rolled during the process, and then the rolling end temperature was 900°C.
A hot-rolled sheet with a thickness of 3.7mm was obtained under conditions of 750°C and a winding temperature of 750°C. The hot-rolled sheet produced in this way was rolled in a cold rolling mill with a work roll diameter of 60 mm without hot-rolled sheet annealing to form a thin sheet with a thickness of 0.7 mm, and then annealed at 850°C for 2 min. It was. Table 6 shows the r value and resong height after annealing, and the thin plates produced by the method of the present invention had good r values and resong properties. The material, which was rolled before hot rolling in the same way as the present invention, but whose rolling finish temperature was as low as 700°C, showed good song characteristics similar to the present invention material.
The value was low, and surface defects were observed during hot rolling. Materials that were not rolled before hot rolling and were not cold-rolled had significantly poor ridging properties.

Table 5 Main chemical components (cracks) of the test material Table 6 R value of finished product, Risong Example 4 Hot rolled sheet according to the method of the present invention in Example 3 (rolled before hot rolling and finished at 900°C) After finishing the rolling, the rolled product was rolled at 600° C.) by the method shown in Table 7 using a cold rolling mill with a 150 mm diameter work roll and a cold rolling mill with a 60 mm diameter work roll. Cold rolling was performed to obtain a cold rolled sheet with a thickness of 0.7 mm.

Then, annealing was performed at 840° C. for 2 min, and the r value was measured.

Table 8 shows the relationship between the r value and the cold rolling conditions.
It can be seen that by doing the above, it is possible to obtain an r value that is almost the same as when the entire rolling amount is rolled with large diameter rolls. When hot-rolled sheets are cold-rolled without annealing, when approximately 60% of the total rolling percentage is rolled with large-diameter rolls, the r value is slightly lower than when the entire rolling amount is rolled with large-diameter rolls. , total rolling f
It can be seen that the r value is greatly improved when compared with the case of rolling = ni' with small diameter rolls. In addition, compared to rolling with only large-diameter rolls, when rolling with small-diameter rolls was added, a beautiful surface texture similar to that obtained when the entire rolling amount was rolled with only small-diameter rolls was obtained.

Example 5 A slab with a thickness of 250 mm was made into a 1100 mm thick slab with the composition shown in Table 9.
After heating at a temperature of 1250° C. for 1 hour and rolling with a total reduction ratio of 30%, the sheet was heated to a temperature of 1250° C. for 1 hour and immediately rolled to obtain a hot rolled sheet of 2.5 mIn. The rolling end temperature is 90
The winding temperature was 590°C.

Then, cold rolling was performed without annealing the hot rolled sheet, and Table 10
The entire annealing process was carried out under the conditions shown in Figure 2, and the rf [reinforcement] was measured. As is clear from Table 10, those annealed at high temperature and for a short time according to this study have r values.

Both songs were good. For comparison, the results are also shown when a conventional hot-rolled sheet of 430 Suzu 1, which does not contain At, was box-annealed and then cold-rolled. It can be seen that the law makes little difference.

Table 9 Main surface chemical components of sample (%) (Effects of the invention) As explained in the examples above, if the method of the present invention is followed, the surface can be easily processed without hot-rolled plate annealing, which was considered indispensable in the past. It becomes possible to manufacture a thin ferritic stainless steel pan plate that is free from defects and has excellent workability, and the economic effects brought about by the present invention are extremely large.

Patent Applicant Nippon Steel Corporation Procedural Amendment (Voluntary) July 11, 1980 Director-General of the Patent Office Kazuo Wakasugi 1 Indication of the Case Patent Application No. 107199 of 1988 2 Title of the invention Manufacturing method for thin ferritic stainless steel plate with no defects and good workability 3. Relationship with the case of the person making the amendment Patent applicant representative Takeshi 1) Yutaka 4, agent 〒io.

6. Subject of correction (1) Amend the claims as shown in the attached sheet.

(2) Specification page 3 lines 11-12 r C0,03-0,
07chi.

A70.08~0.5 Section" rco, 02~009ch,
AA! Correct to 0.03-0.5%J.

(3) rco, o9%J
Correct to.

(4) Same page 6 line 8 1'-CQ, 03'' rco, 02J
Correct to.

(5) Same page 6 line 11 “All 0.08%j rAIo
, 03chi''.

(6) Table 1 on page 19 will be amended as follows.

Table 1 Components of sample material (%') (7) Table 9 on page 27 is as below! ll Correct.

Table 9 Main chemical components of sample (H) Claim range Cr 15~19H, balance iron and unavoidable impurities Ferritic stainless steel slab 1000~1200
After rolling with a total reduction rate of at least 20φ in the temperature range of 1,180 °C to 1,300 °C, the rolling mill consisting of a rough rolling mill and a continuous finishing mill Rolled at finishing temperature, then rapidly cooled to 6
A method for producing a ferritic stainless thin steel sheet having no surface flaws and good workability, characterized by rolling the sheet at a temperature of 50° C. or less, then cold rolling without hot-rolling the sheet, and recrystallizing the sheet.

(2) The method according to claim 1, wherein a reduction amount of 60φ or more to be rolled in the cold rolling step is cold rolled in the preceding stage of the cold rolling step using a work roll having a diameter of 150 mm or more. .

(3) Recrystallization annealing after cold rolling at 850-900°C
The method according to claim 1, wherein the method is carried out within 60 seconds at a temperature range of .

(4) The method according to claim 1, wherein the ferritic stainless steel slab blade is continuously cast slab.

Claims (4)

[Claims] (1) CO, 03-0.07%, At0.08-0
．． 5%. A ferritic stainless steel slab consisting of 15 to 19 Cr, the balance iron and unavoidable impurities was heated at 10oO to 1200℃.
After rolling with a total reduction rate of at least 20% in the temperature range of
Rolled at a finishing temperature of 850°C or higher, then rapidly cooled to 65°C.
A method for producing a ferritic stainless thin steel sheet free from surface defects and having good workability, characterized by rolling the sheet at a temperature of 0° C. or lower, then cold rolling without hot-rolling the sheet and recrystallization annealing. (2) The method according to claim 1, wherein a reduction amount of 60 inches or more to be rolled in the cold rolling step is cold-rolled in the preceding stage of the cold rolling using work rolls having a diameter of 150 mm or more. (3) The method according to the scope of patent RtW, item 1, in which recrystallization annealing after cold rolling is performed within 60 seconds at a temperature range of 850 to 900°C. (4) The method according to claim 1, wherein the ferritic stainless steel slab is a continuously cast slab.