JPH0747412A - Manufacturing method of stainless cold rolled steel sheet - Google Patents

Abstract

(57) [Summary] [Purpose] A proposal for a method for efficiently rolling a stainless steel plate with a cold tandem rolling mill without seizure flaws. [Composition] Composition of work roll C: 0.3-2.0%, C
r: 2.5 to 8.0%, Mo: 2.0 to 10.0%, V: 0.5 to 2.0
%, W: 10% or less and Co: 10% or less, and the balance is substantially Fe. In addition, the temperature of the rolling oil or its emulsion during cold rolling should be 40 ℃.
It is supplied below.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a manufacturing method capable of efficiently and advantageously producing a cold rolled stainless steel sheet.

[0002]

2. Description of the Related Art Conventionally, cold-rolled stainless steel sheets have been produced by a method of cold rolling in a Sendzimir mill having a work roll diameter of 150 mm or less. In order to manufacture steel sheets, a method of cold rolling using a large-diameter work roll having a diameter of over 150 mm is adopted.

[0003]

When these stainless steel sheets are cold-rolled, if the rolling speed is increased or the rolling is performed under high pressure for the purpose of improving the production efficiency, the roll and the steel sheet are seized to cause flaws or patterns. However, the steel plate did not become a product. Therefore, conventionally, cold rolling of stainless steel sheets has to be carried out at a low rolling speed or reduction rate.
They were forced to make extremely inefficient production.

Therefore, for example, as disclosed in JP-B-52-17516 and JP-A-57-17509, a method of improving the rolling oil component to prevent seizure flaws has been adopted. However, the prevention effect is not sufficient, and a method for further improving the rolling speed and the rolling reduction has been desired. An object of the present invention is to solve the above problems and propose a method for efficiently producing a cold rolled stainless steel sheet by using a cold tandem mill having a work roll diameter of more than 150 mm to prevent the occurrence of seizure flaws. It is to be.

[0005]

The present invention has a diameter of 150 mm.
When rolling a stainless steel sheet using a cold tandem mill with super work rolls, its composition is C:
0.3 to 2.0%, Cr: 2.5 to 8.0%, Mo: 2.0 to 10.0%,
V: 0.5 to 2.0%, W: 10% or less and Co:
Contains at least one of 10% or less, and the balance is substantially Fe.
A method for producing a stainless cold-rolled steel sheet, which comprises applying a work roll consisting of at least one stand of the cold tandem mill and rolling, and the present invention also provides:
When rolling a stainless steel sheet using a cold tandem mill having a work roll with a diameter of more than 150 mm, the cold rolling steel sheet is characterized in that the temperature of the rolling oil or its emulsion is kept at 40 ° C or lower and the feeding is performed. The present invention also provides a method of rolling a stainless steel sheet using a cold tandem mill having a work roll having a diameter of more than 150 mm, the composition of which is C: 0.3 to 2.0%,
Cr: 2.5 to 8.0%, Mo: 2.0 to 10.0%, V: 0.5 to 2.0
%, Further W: 10% or less and Co: 10% or less any one or more, a balance of substantially Fe is applied to at least one stand or more of the cold tandem mill, In addition, the method for producing a stainless cold-rolled steel sheet is characterized in that the temperature of the rolling oil or its emulsion is set to 40 ° C. or lower and the rolling is performed while feeding the rolling oil.

[0006]

The present invention will be described in detail below. Conventionally, cold rolling of ordinary steel sheets may cause seizure flaws called heat streaks, and various measures have been taken to prevent this, but this occurs when cold rolling stainless steel sheets. There have been few reports of burn-in defects that occur, and the details have not been clarified.

Therefore, the present inventors have investigated in detail the seizure flaws that occur when cold rolling a stainless steel sheet. As a result, it was found that the morphology does not always correspond to the heat streak generated in the ordinary steel sheet, and the critical conditions for the occurrence of a seizure flaw are lower than those of the ordinary steel sheet in the rolling speed and the rolling reduction. That is, in the case of heat streak that occurs in ordinary steel sheets, there is a large scratch flaw on the roll surface as the starting point, and scaly seizure grows from the large flaw, but in the case of stainless steel sheet, most of the seizure flaws occur. In many cases, the starting point is unclear and no scale-like image sticking is observed. It is presumed that these are due to the difference in the state and composition of the extremely thin oxide film on the surface of the steel sheet and the difference in the element and crystal structure of the surface of the steel sheet between the ordinary steel sheet and the stainless steel sheet.

Therefore, it is not possible to directly adopt the method adopted for the ordinary steel sheet, and it is necessary to adopt a more effective method for preventing seizure as compared with the case of the ordinary steel sheet. Therefore, as a result of cold rolling the stainless steel sheet under various conditions, the present inventors examined the material of the work roll in order to prevent the occurrence of seizure flaws. That is, when the roll material is changed, the degree of seizure flaws differs.As a result, by selecting the roll material, it is possible to roll efficiently without causing seizure flaws even if the rolling speed and the rolling reduction are increased. I found out.

This is for the following reason. That is, in the case of a stainless steel plate, unlike a normal steel plate, at the same time when rolling is started, a brown or black roll coating is formed on the surface of the roll. This roll coating is an oxide of iron and chromium, and wear particles generated from a stainless steel plate are adhered to the roll surface. When the roll coating is generated, the roll and the steel sheet are prevented from directly contacting each other during rolling, and as a result, seizure flaws are prevented. Therefore, it is preferable that the roll coating is uniformly thick on the roll surface.

Therefore, the present inventors have examined the roll material, that is, the roll composition, for producing a uniform and thick roll coating. As a result, C: 0.3 to 2.0
%, Cr: 2.5 to 8.0%, Mo: 2.0 to 10.0%, V: 0.5 to
Contains 2.0% and 1 or more of each of W and Co
We have found that a roll containing less than 0.0% is desirable.

When C, Cr, Mo, and V have a low proportion of any of these components, the roll coating is non-uniformly formed, so that a seizure flaw easily occurs from a thin roll surface portion of the roll coating. Also, C, Cr, Mo,
If the proportion of any of V, W or Co is too large, the roll coating becomes too thin and seizure flaws occur.

Further, it is desirable to apply the work rolls containing these components to all stands, but a large amount of cost is required due to the high cost of introduction and high basic unit. Therefore, if the applicable stand is limited to a stand having a high reduction rate and a high rolling speed that easily cause seizure flaws, for example, a first stage stand or a final stand, a stainless steel plate can be manufactured efficiently at low cost.

The present inventors have also examined from another viewpoint the problem of defects due to seizure that occurs when rolling a stainless steel sheet using a cold tandem mill having a work roll with a diameter of more than 150 mm. As a result of cold rolling a stainless steel sheet under various conditions, the present inventors supply rolling oil or an emulsion thereof in order to prevent contact between the roll and the steel sheet, but if this temperature is reduced, seizure flaws will occur. It has been found to be effective in preventing. That is, in the past, in order to stabilize the emulsification of the emulsion and prevent the rotting of the rolling oil, the temperature of the rolling oil or its emulsion was empirically heated to a range of 50 to 70 ° C., but the rolling oil or The temperature to supply the emulsion is 40
It was understood that seizure flaws are significantly less likely to occur when the temperature is lower than or equal to ℃, compared to the conventional rolling conditions.

In recent years, rolling oils have used a large amount of synthetic esters, and emulsification, safety and spoilage can be prevented without heating, and the problems are relatively small. Further, if additives for improving these performances are added, the problems of emulsion stability and spoilage are eliminated even at low temperatures. It is considered that if the rolling oil or its emulsion is used at a temperature of 40 ° C. or lower, seizure can be prevented as a result of keeping the temperature at which the contact between the roll and the steel strip increases significantly due to normal friction and deformation of the steel sheet.

[0015]

【Example】

Example 1 Hereinafter, using a SUS 430 steel plate as an example of a stainless steel plate, a roll having a component according to the method of the present invention, one example of which is shown in Table 1, is applied, and a 5-stand cold tandem mill using a large diameter roll is applied. The normal supply flow rate to each stand is 20
While supplying a coolant of m ³ / min and a temperature of 60 ± 5 ° C. to a roll bite, it was rolled to a predetermined thickness at various rolling speeds. The roll diameter was 530 to 550 mmφ from the first stand to the fourth stand, and 300 mmφ from the fifth stand. Further, a roll having a component according to the method of the present invention,
It was applied to the 5th stand, which has the highest rolling speed and is apt to cause seizure flaws, and the 1st stand, which has the largest reduction amount.

As a conventional example, Table 1 shows an example thereof. C: 0.5-1.0%, Cr: 2.5-5.5%, Mo: 0.5%
Rolls containing V, W, and Co, each of which is included below, were applied and rolled at various rolling speeds. The surface of the steel strip after these rollings was visually inspected, and the presence or absence of seizure flaws was examined at each rolling speed.

With respect to these results, Table 1 shows the relationship between the steel plate speed on the tandem mill outlet side and the presence or absence of seizure flaws. From this table, it can be seen that the method of the present invention is significantly less likely to cause seizure flaws even at a higher rolling speed than the conventional method.

[0018]

[Table 1]

Example 2 Hereinafter, using a SUS 430 steel plate as an example of a stainless steel plate, applying a roll having the components shown in the conventional example to Example 1, and using a 5-stand cold tandem mill using a large diameter roll, According to the present invention, while supplying a coolant of 35 ± 5 ° C. to the roll bite, it was rolled at various rolling speeds to a predetermined thickness. The roll diameter was 430 to 450 mmφ from the first stand to the fifth stand.

Further, as a conventional example, Table 2 shows an example thereof, and while supplying a normal coolant of 60 ± 5 ° C. to a roll bite, it was rolled at various rolling speeds. The surface of the steel strip after these rollings was visually inspected, and the presence or absence of seizure flaws was examined at each rolling speed. Regarding these results, Table 2 shows the relationship between the steel plate speed on the tandem mill exit side and the presence or absence of seizure flaws.

From this table, it can be seen that the method of the present invention is significantly better than the conventional method in that seizure flaws are less likely to occur even at high rolling speeds.

[0022]

[Table 2]

Example 3 In the following, a SUS 430 steel plate was used as an example of a stainless steel plate, and a roll having a component according to the method of the present invention, whose example is shown in Table 3 is applied, and a four-stand cold roll using a large diameter roll is applied. In the inter-tandem mill, according to the present invention, a coolant of 30 ± 5 ° C. was supplied to the surface of the roll bite and the surface of the steel plate on the entrance side, and rolled to various thicknesses at various rolling speeds. The roll diameter is 350 to 380 mm from the 1st stand to the 3rd stand.
And the fourth stand was 200 mmφ. Further, the rolls having the components according to the method of the present invention were applied to the fourth stand having the highest rolling speed and being apt to cause seizure flaws and the third stand having the greatest rolling reduction.

As a conventional example, Table 3 shows an example thereof. C: 0.5-1.0%, Cr: 2.5-5.5%, Mo: 0.5%
Rolls containing V, W, and Co, each of which is included below, are applied and rolled at various rolling speeds while supplying the conventional coolant of 60 ± 5 ° C. to the roll bite and the surface of the incoming steel plate. . The surface of the steel sheet after these rollings was visually inspected, and the presence or absence of seizure flaws was examined at each rolling speed.

Regarding these results, Table 3 shows the relationship between the steel plate speed on the tandem mill exit side and the presence or absence of seizure flaws. From this table, it can be seen that the method of the present invention is significantly less likely to cause seizure flaws even at a higher rolling speed than the conventional method.

[0026]

[Table 3]

In the above-mentioned Examples 1 and 3, the roll of the composition of the present invention was used for each specific stand. However, if it is applied to other stands, even better results can be expected.

[0028]

INDUSTRIAL APPLICABILITY As described above, the method of the present invention has a remarkably excellent anti-seizure effect as compared with the conventional methods, and can improve the rolling speed of cold rolling or increase the rolling reduction. , Greatly contributes to a significant improvement in rolling efficiency.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Kazuhito Okada 1 Kawasaki-cho, Chuo-ku, Chiba, Chiba Kawasaki Steel Co., Ltd. Chiba Steel Works (72) Inventor Eisuke Kawasumi 1 Kawasaki-cho, Chuo-ku, Chiba Kawasaki Steel Co., Ltd. Chiba Steel Works (72) Inventor Makoto Suzuki 1 Kawasaki-cho, Chuo-ku, Chiba City Chiba Prefecture Kawasaki Steel Co., Ltd. Chiba Steel Works

Claims (3)

[Claims] 1. When rolling a stainless steel sheet using a cold tandem mill having a work roll having a diameter of more than 150 mm, its components are C: 0.3 to 2.0% and Cr: 2.5 to 8.
Work roll containing 0%, Mo: 2.0 to 10.0%, V: 0.5 to 2.0%, W: 10% or less and Co: 10% or less, and the balance substantially Fe. Is applied to at least one stand of the cold tandem mill and rolled, and a method for producing a cold rolled stainless steel sheet. 2. When rolling a stainless steel sheet using a cold tandem mill having a work roll with a diameter of more than 150 mm, the temperature of the rolling oil or its emulsion is kept at 40 ° C. or lower and the feeding is performed. Method for producing a cold rolled stainless steel sheet. 3. When rolling a stainless steel sheet using a cold tandem mill having a work roll with a diameter of more than 150 mm, its components are C: 0.3-2.0%, Cr: 2.5-8.
Work roll containing 0%, Mo: 2.0 to 10.0%, V: 0.5 to 2.0%, W: 10% or less and Co: 10% or less, and the balance substantially Fe. Is applied to at least one stand or more of the cold tandem mill,
A method for producing a stainless cold-rolled steel sheet, which comprises rolling while supplying the rolling oil or its emulsion at a temperature of 40 ° C. or lower.