JPH08117805A - Manufacture of cold rolled stainless steel sheet - Google Patents

Abstract

PURPOSE: To manufacture a stainless steel sheet at high efficiency by executing preliminary rolling, generating a coating film on the surface of a work roll and executing rolling with the same work roll. CONSTITUTION: A ferritic stainless steel sheet, for example, is preliminarily rolled at 10% draft, large diameter rolls on the surfaces of which the coating films are preliminarily generated are prepared. These rolls are incorporated in a cold tandem mill having five stands and the steel sheet of the ferritic SUS 430 is cold-rolled. When rolling is executed in such a way, burning flaw is hard to be generated even at high rolling speed. The preliminary rolling is executed till the coating film generated on the surface of the work roll becomes >=10μm. The stainless steel sheet to be preliminarily rolled is defined as austenitic stainless steel. In this way, rolling speed is remarkably improved.

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 stainless cold-rolled steel sheet, which comprises cold-rolling a stainless steel sheet with high efficiency.

[0002]

2. Description of the Related Art Cold-rolled stainless steel sheets are generally manufactured by cold rolling using a reciprocating multi-stage rolling mill such as a Sendzimir mill that uses work rolls with a small diameter of 150 mm or less. In the cold rolling of such a stainless steel sheet, if the rolling speed is increased or a rolling with a strong reduction is carried out for the purpose of improving the production efficiency, the roll and the steel sheet will be burned and a flaw or a pattern will not be produced, so the product will not be produced.
Heretofore, a rolling method having a remarkably low efficiency under low speed and low pressure has been forced.

In recent years, in order to significantly reduce the rolling time, for example, as described in Japanese Patent Publication No. 4-36762,
Attempts have been made to manufacture stainless steel sheets by using a large-diameter work roll with a diameter of 150 mm or more and a highly efficient tandem rolling mill. In the tandem rolling mill, a large work roll diameter causes a large amount of rolling oil to be drawn into the roll bite, making it difficult for the roll and the steel sheet to contact each other and suppressing seizure flaws, resulting in high-speed rolling. Because it will be done.

However, the use of rolling oil causes a phenomenon that the surface gloss required for a stainless steel plate is significantly reduced. As a countermeasure against this, it is necessary to carry out pre-processing rolling without lubrication and low speed in advance. There are also new problems that impede sex. In addition, Japanese Patent Publication No.
As described in Japanese Patent No. 63-175097, attempts have been made to prevent seizure by using an improved rolling oil, but the preventive effect is not sufficient, and higher production efficiency can be achieved. A rolling method was desired.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a novel rolling method which can prevent seizure and achieve high production efficiency without using rolling oil.

[0006]

According to the present invention, in a method for producing a stainless cold-rolled steel sheet for cold rolling a stainless steel sheet, a film having a uniform film thickness is formed on a work roll surface by pre-rolling the stainless steel sheet. And a ferritic stainless steel plate is rolled using the work roll, which is a method for manufacturing a stainless cold-rolled steel plate, wherein the preliminary rolling of the stainless steel plate is characterized by a reduction rate of 10% or more. The method for producing a stainless cold-rolled steel sheet according to claim 1, wherein in the preliminary rolling of the stainless steel sheet, the film formed on the surface of the work roll is 10 mμ.
The method for producing a stainless cold-rolled steel sheet according to claim 1 or 2, wherein the stainless steel sheet to be pre-rolled is an austenitic steel sheet. It is a manufacturing method of the stainless cold rolled steel sheet described.

[0007]

[Operation] There is a seizure flaw called heat streak that occurs when cold rolling a plain steel sheet. Various investigations have been made on this heat streak and countermeasures have been taken, while there are almost no reports on seizure flaws on stainless steel sheets, and the mechanism and cause of occurrence are not clear.

Therefore, the present inventors first conducted a detailed investigation on seizure flaws in cold rolling of stainless steel sheets. As a result, it was confirmed that the morphology is different from that of heat streaks in ordinary steel sheets, and that the limiting conditions for the occurrence of seizure flaws are lower in both rolling speed and rolling reduction than in the case of ordinary steel sheets. In the case of heat streaks on ordinary steel sheets, there are large scratch flaws on the roll surface as the starting point, and large scale-like image sticking grows around them, but in the case of stainless steel sheets, the starting points are largely non-existent. Clear and no scaly image sticking. It is considered that such a difference is due to the difference in the composition and state of the very thin oxide film on the surface of the steel sheet between the ordinary steel sheet and the stainless steel sheet, and the difference in the composition and crystal structure of the surface layer of the steel sheet.

Therefore, the measures adopted for ordinary steel sheets cannot be applied to stainless steel sheets as they are, and it is necessary to adopt a stronger means than ordinary steel sheets. As a result of cold-rolling a stainless steel sheet under various rolling conditions, the present inventors have found that it is effective to prevent seizure by forming a certain type of film (roll coating) on the surface of the work roll before rolling. I found that.

Next, claim 1 of the present invention will be described.
That is, in cold rolling of a stainless steel plate, it is observed that a brown or black coating film is formed on the roll surface at the same time as the start of rolling. This coating is an oxide of iron and chromium, and is formed by abrasion powder generated from a stainless steel plate adhering to the roll surface. When this grows and has a uniform film thickness, contact between the roll and the steel sheet during rolling can be prevented, and seizure flaws are less likely to occur. Therefore, if the stainless steel plate is previously rolled without using rolling oil before the main rolling and the coating film is thickly and uniformly formed on the work roll surface, when the ferritic stainless steel of the main rolling is rolled, It is effective because it does not cause burn-in defects from the beginning.

Next, claim 2 of the present invention will be described.
That is, as a result of investigating a method for uniformly forming a roll coating on the surface of a work roll, it was found that the film thickness of the roll coating affects the rolling reduction during pre-rolling. FIG. 1 is a graph showing the relationship between the rolling reduction in preliminary rolling and the thickness of a film (roll coating) formed on the roll surface. As is clear from this figure, the film thickness is stably and thickly formed by setting the rolling reduction of the stand to 10% or more. According to the experiment, it is necessary to set the rolling reduction to 10% or more, since the film thickness of 10 mμ or more is required to obtain the effect of preventing the seizure. % To 25%, and the upper limit of the rolling reduction is 30%. Here, the stainless steel sheet to be pre-rolled to form a coating may be either a ferrite type or an austenitic type.

Next, claim 3 of the present invention will be described.
That is, as a result of studying a method for uniformly forming a roll coating on the surface of a work roll, the relationship between the coating thickness of the roll coating and the rolling distance was investigated. FIG. 2 is a graph showing the relationship between the rolling distance in the preliminary rolling using a work roll having a diameter of 80 mm and the film thickness formed on the roll surface. As is clear from this figure, the coating thickness increases with the rolling distance,
A thickness of 10 mμ is reached in m. According to the experiment, it is necessary to set the rolling distance to 150 m or more based on FIG. 2 because the thickness of 10 mμ or more is required to obtain the effect of preventing seizure. The coating thickness is preferably 10-
15mμ is required, and the upper limit of film thickness is 20mμ
Is. Therefore, in the case of a work roll having a diameter of 80 mm, the rolling distance required for that is 150 to 300 m.

The thickness of the coating film formed on the roll surface depends on the reduction rate, but the higher the reduction rate, the shorter the rolling distance. In short, if the thickness is 10 mμ or more, the object of the present invention is to be achieved. Can be reached Next, claim 4 of the present invention will be described. That is, as a result of studying a method for uniformly forming a roll coating on the surface of a work roll, it was found that an austenitic type is the most suitable material for the pre-rolled stainless steel plate.

On the surface of the austenitic stainless steel sheet, the crystal grains are easily removed as abrasion powder along the grain boundaries, and the abrasion powder adheres to the roll surface to form a uniform and thick film. Here, the rolling distance does not particularly depend on the rolling conditions, but if the rolling distance is 150 m or more, there is no practical problem and the object of the present invention can be achieved. It is possible to prevent seizure by using the work roll having the film thus formed in one or more stands at arbitrary positions in the tandem rolling mill and in one or more passes in the reciprocating rolling mill to roll the ferritic stainless steel sheet. It is effective as a method. During rolling of the ferritic stainless steel sheet, a strong reduction is often applied for the purpose of improving gloss, and a final stand where seizure flaws are likely to remain, or a strong reduction is often applied in the final pass, and the work of the present invention is used. It is effective to apply the roll on the final stand or the final pass.

[0015]

【Example】

Example 1 A large-diameter roll was prepared by pre-rolling a ferritic stainless steel plate at a rolling reduction of 10% to form a film on the surface in advance, and this roll was incorporated into a 5-stand cold tandem rolling mill to prepare a ferritic SUS430 steel plate. Was cold rolled.

The work roll diameter of the first to fourth stands is 6
00mm, the 5th stand is 300mm, and when cold-rolled material 3.0mm thickness is rolled to 1.0mm, use the coated roll for either 1st stand, 3rd stand or 5th stand. Then, the surface of the rolled steel sheet was visually inspected, and the presence or absence of seizure flaws was investigated at each rolling speed.
As a comparative example, the work roll as-polished without forming a film and the ferritic stainless steel sheet were rolled down.
A roll, which had been pre-rolled with 1% to form a film on the surface in advance, was installed in the same rolling mill, and the same SUS430 steel plate was cold-rolled under the same conditions except for the roll.

[0017]

[Table 1]

Table 1 shows the rolling speed and the presence or absence of seizure flaws.
Shown in From this table, it can be seen that, according to the present invention, seizure flaws are less likely to occur even at a high rolling speed as compared with the conventional method. Example 2 A roll prepared by pre-rolling an austenitic stainless steel sheet at a rolling reduction of 10% to form a film on the surface in advance was prepared, and this roll was incorporated into a 5-stand cold tandem rolling mill to cool a ferritic SUS430 steel sheet. Rolled.

The work roll diameter of the first to fifth stands is 4
When rolling a cold-rolled material sheet having a thickness of 4.0 mm and a thickness of 30 mm to 1.2 mm, a coated roll is used for the front two stands or the rear four stands, and the steel sheet surface after rolling is visually inspected to determine the rolling speed. The presence or absence of burn-in defects was investigated. As a comparative example, a work roll as it is not polished to form a work roll, and a roll with a stainless steel plate pre-rolled at a reduction rate of 3% to form a film on the surface in advance are installed in the same rolling mill, and the same conditions are used except for the rolls. Same SUS4
30 steel plates were cold rolled.

[0020]

[Table 2]

Table 2 shows the rolling speed and the presence or absence of seizure defects.
Shown in From this table, it is understood that the present invention makes it more difficult for seizure flaws to occur even at high rolling speeds, as compared with the conventional method. Example 3 A ferritic stainless steel sheet was pre-rolled at a rolling reduction of 25% to prepare a roll having a film formed on its surface in advance, and this roll was incorporated into a three-stand cold tandem rolling mill using a large-diameter roll. A ferritic SUS430 steel plate was cold rolled.

The work roll diameter of the first to third stands is 4
In the case of rolling a cold-rolled material with a thickness of 4.0 mm to 2.0 mm at 30 mm and using a roll with a coating in the front two stands or the rear two stands, visually inspect the surface of the steel sheet after rolling and roll it. The presence or absence of burn-in defects was investigated for each speed. As a comparative example, the as-polished work roll that does not form a film and the roll that preliminarily rolls a stainless steel plate at a rolling reduction of 1% to form a film on the surface in advance are incorporated into the same rolling mill, and the same conditions are used except for the roll. The same SUS430 steel plate was cold rolled.

[0023]

[Table 3]

Table 3 shows the rolling speed and the presence or absence of seizure flaws.
Shown in From this table, it can be seen that, according to the present invention, seizure flaws are less likely to occur even at a high rolling speed as compared with the conventional method. Example 4 A roll prepared by pre-rolling an austenitic stainless steel sheet at a rolling reduction of 25% to form a film on the surface was prepared, and this roll was incorporated into a cold tandem rolling mill using a large diameter roll to prepare a ferrite SUS430. The steel sheet was cold rolled.

The work roll diameter of the first to fifth stands is 5
30mm, the work roll diameter of the 6th stand is 450mm, and when rolling the cold-rolled material sheet thickness of 5.0mm to 1.2mm, visually inspect the surface of the steel sheet after rolling when the coated roll is used for all stands. Then, the presence or absence of seizure flaws was investigated for each rolling speed. As a comparative example, the as-polished work roll that does not form a film and the roll that preliminarily rolls a stainless steel plate at a rolling reduction of 3% to form a film on the surface in advance are installed in the same rolling machine under the same conditions except for the roll. The same SUS430 steel plate was cold rolled.

[0026]

[Table 4]

Table 4 shows the rolling speed and the presence or absence of seizure flaws.
Shown in From this table, it can be seen that, according to the present invention, seizure flaws are less likely to occur even at a high rolling speed as compared with the conventional method. Example 5 A roll prepared by pre-rolling an austenitic stainless steel sheet at a rolling distance of 200 mm to form a coating having a thickness of 15 mμ on the surface was prepared, and this roll was incorporated into a 5-stand cold tandem rolling mill to prepare a ferrite system. Cold rolled SUS430 steel sheet.

The work roll diameter of the first to fourth stands is 6
00mm, the 5th stand is 300mm, and when cold-rolled material 3.0mm thickness is rolled to 1.0mm, use the coated roll for either 1st stand, 3rd stand or 5th stand. Then, the surface of the rolled steel sheet was visually inspected, and the presence or absence of seizure flaws was investigated at each rolling speed.
As a comparative example, the as-polished work roll was installed in the same rolling mill, and the same SUS430 was used under the same conditions except for the roll.
The steel sheet was cold rolled.

[0029]

[Table 5]

Table 5 shows the rolling speed and the presence or absence of seizure flaws.
Shown in From this table, it can be seen that, according to the present invention, seizure flaws are less likely to occur even at a high rolling speed as compared with the conventional method. Example 6 A ferritic stainless steel plate was pre-rolled at a rolling distance of 300 m to prepare a roll having a coating film having a thickness of 15 mμ formed on the surface in advance. This roll was incorporated into a 5-stand cold tandem rolling mill to prepare a ferritic stainless steel plate. Cold rolled SUS430 steel sheet.

The work roll diameter of the first to fifth stands is 4
When rolling a cold-rolled material with a thickness of 4.0 mm and a thickness of 30 mm to 1.2 mm, use a roll with a coating in the first or second stage, visually inspect the surface of the steel sheet after rolling, and check for seizure flaws at each rolling speed. Was investigated for the occurrence of. As a comparative example, the as-polished work roll was incorporated into the same rolling mill, and the same SUS430 steel plate was cold-rolled under the same conditions except for the roll.

[0032]

[Table 6]

Table 6 shows the rolling speed and the presence or absence of seizure flaws.
Shown in From this table, it is understood that the present invention makes it more difficult for seizure flaws to occur even at high rolling speeds, as compared with the conventional method. Example 7 A roll prepared by pre-rolling an austenitic stainless steel sheet at a rolling distance of 100 m to form a film having a thickness of 10 mμ on the surface was prepared. The steel sheet was cold rolled.

The work roll diameter of the first to fourth stands is 5
30mm, the 5th stand is 450mm, and when rolling cold rolled material 5.0mm thick to 2.0mm, all the stands are coated with rolls and the steel sheet surface after rolling is visually inspected. The presence or absence of burn-in defects was investigated.
As a comparative example, the as-polished work roll was installed in the same rolling mill, and the same SUS430 was used under the same conditions except for the roll.
The steel sheet was cold rolled.

[0035]

[Table 7]

Table 7 shows the rolling speed and the presence or absence of seizure flaws.
Shown in From this table, it can be seen that, according to the present invention, seizure flaws are less likely to occur even at a high rolling speed as compared with the conventional method. Example 8 A ferritic stainless steel plate was pre-rolled at a rolling distance of 150 m to prepare a roll having a film having a thickness of 10 mμ formed on the surface in advance, and this roll was cold tandem-rolled by four stands using a large-diameter roll. Ferrite-based SU installed in the machine
The S430 steel plate was cold rolled.

The work roll diameter of the first to third stands is 6
00mm, the work roll diameter of the 4th stand is 300mm, and when rolling a cold-rolled material with a thickness of 3.0mm to 1.0mm, roll the coated roll on one of the 1st, 2nd or 4th stand. The surface of the steel sheet after rolling was visually inspected, and the presence or absence of seizure flaws was investigated at each rolling speed.
As a comparative example, the as-polished work roll was installed in the same rolling mill, and the same SUS430 was used under the same conditions except for the roll.
The steel sheet was cold rolled.

[0038]

[Table 8]

Table 8 shows the rolling speed and the presence or absence of seizure flaws.
Shown in From this table, it can be seen that, according to the present invention, seizure flaws are less likely to occur even at a high rolling speed as compared with the conventional method. Example 9 SUS304 which is an austenitic stainless steel sheet was pre-rolled at a rolling reduction of 7% and a rolling distance of 150 m to prepare a roll having a film formed on its surface in advance. This roll was put into a 5-stand cold tandem rolling mill. Built-in ferrite type SUS430
The steel sheet was cold rolled.

The work roll diameter of the first to fourth stands is 6
00mm, the 5th stand is 300mm, and when cold-rolled material 3.0mm thickness is rolled to 1.0mm, use the coated roll for either 1st stand, 3rd stand or 5th stand. Then, the surface of the rolled steel sheet was visually inspected, and the presence or absence of seizure flaws was investigated at each rolling speed.
As a comparative example, a work roll that does not form an as-polished coating was incorporated into the same rolling mill, and the same SUS430 steel plate was cold-rolled under the same conditions except for the roll.

[0041]

[Table 9]

Table 9 shows the rolling speed and the presence or absence of seizure flaws.
Shown in From this table, it can be seen that, according to the present invention, seizure flaws are less likely to occur even at a high rolling speed as compared with the conventional method. Example 10 Austenitic stainless steel sheet SUS304 was pre-rolled at a rolling reduction of 7% at a rolling distance of 150 m to prepare a roll having a film formed on its surface in advance, and this roll was subjected to a 5-stand cold tandem rolling mill. Built-in ferrite type SUS430
The steel sheet was cold rolled.

The work roll diameter of the first to fifth stands is 4
When rolling a cold-rolled material with a thickness of 4.0 mm and a thickness of 30 mm to 1.2 mm, use a roll with a coating in the first or second stage, visually inspect the surface of the steel sheet after rolling, and check for seizure flaws at each rolling speed. Was investigated for the occurrence of. As a comparative example, the as-polished work roll was incorporated into the same rolling mill, and the same SUS430 steel plate was cold-rolled under the same conditions except for the roll.

[0044]

[Table 10]

Table 10 shows the rolling speed and the presence or absence of seizure defects.
Shown in From this table, it is understood that the present invention makes it more difficult for seizure flaws to occur even at high rolling speeds, as compared with the conventional method. Example 11 Austenitic stainless steel sheet SUS304 was pre-rolled at a rolling reduction of 7% and a rolling distance of 150 m to prepare a work roll having a film formed on its surface in advance. This work roll was reciprocating cold with a small diameter roll. A ferritic SUS430 steel plate was cold-rolled by incorporating it into a rolling mill.

The work roll diameter is 100 mm and the entrance side plate thickness is 1.2.
With respect to a pass for rolling a steel sheet having a diameter of 1.0 mm to 1.0 mm, the surface of the steel sheet after the rolling was visually inspected, and the occurrence of seizure flaws was investigated at each rolling speed. As a comparative example, the as-polished work roll was incorporated into the same rolling mill, and the same SUS430 steel plate was cold-rolled under the same conditions except for the roll.

[0047]

[Table 11]

Table 11 shows the rolling speed and the presence or absence of seizure flaws.
Shown in From this table, it can be seen that, according to the present invention, seizure flaws are less likely to occur even at a high rolling speed as compared with the conventional method.

[0049]

EFFECTS OF THE INVENTION According to the present invention, when cold rolling a stainless steel sheet, no rolling oil is used and seizure does not occur, so that the rolling speed can be greatly improved and highly efficient production can be realized. It has the excellent effect of

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the reduction ratio of pre-rolling and the film thickness formed on the roll surface.

FIG. 2 is a graph showing a relationship between a rolling distance of preliminary rolling and a film thickness formed on a roll surface.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kunio Isobe, 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Kawasaki Iron & Steel Manufacturing Co., Ltd. Kawasaki-Cho, Kawasaki Steel Co., Ltd. Chiba Steel Works, Steel Development & Production Headquarters (72) Inventor Kazuhito Okada 1 Kawasaki-cho, Chuo-ku, Chiba City, Chiba Prefecture Kawasaki Steel Co., Ltd. Chiba Steel Works (72) Inventor Yoshikazu Kiyono 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Kawasaki Steel Corporation Steel Development & Production Division Chiba Steel Works Inside (72) Inventor Hajime Nagai 1 Kawasaki-cho, Chuo-ku, Chiba-shi Kawasaki Steel Co., Ltd. Steel Development & Production Division Chiba Steel Works

Claims (4)

[Claims] 1. A method for producing a stainless cold-rolled steel sheet, comprising cold rolling a stainless steel sheet, wherein a stainless steel sheet is pre-rolled to form a film having a uniform film thickness on the surface of a work roll, and the work roll is used. A method for producing a cold-rolled stainless steel sheet, which comprises rolling a ferritic stainless steel sheet. 2. The method for producing a stainless cold-rolled steel sheet according to claim 1, wherein the preliminary rolling of the stainless steel sheet has a reduction rate of 10% or more. 3. The method for producing a stainless cold-rolled steel sheet according to claim 1, wherein the preliminary rolling of the stainless steel sheet is performed until the coating film formed on the surface of the work roll reaches 10 mμ or more. 4. The method for producing a cold rolled stainless steel sheet according to claim 1, 2 or 3, wherein the stainless steel sheet to be pre-rolled is an austenitic type.