JP3536868B2 - Manufacturing method of stainless steel pre-treated steel strip for cold rolling - Google Patents

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 cold-rolled stainless steel pretreated steel strip which can advantageously produce a cold-rolled stainless steel strip having good surface gloss.

[0002]

2. Description of the Related Art Conventionally, a cold rolled stainless steel strip is subjected to cold rolling using a steel alloy work roll in a Sendzimir mill or the like having a work roll diameter of 150 mm or less after annealing and pickling a hot rolled steel strip. After finish pickling or bright annealing, finish temper rolling at a rolling reduction of 1.2% or less is performed.

[0003] The above cold rolled stainless steel strip is, for example, SU
In the case of ferrites represented by S430, the surface after production is often used as it is, and a product after finish temper rolling is required to have excellent surface gloss. Further, in the case of an austenitic material represented by SUS304, buffing is often performed after finish temper rolling, and it is important to exhibit excellent surface gloss after buffing.

[0004] Therefore, in order to produce a stainless cold rolled steel strip with high efficiency by greatly reducing the rolling time, cold rolling is performed by a rolling mill having a large diameter work roll of 150 mmφ or more like a cold tandem mill. The method has been adopted. However, since the surface roughness of a steel strip cold-rolled with a large-diameter work roll is significantly larger than that of a steel strip rolled with a small-diameter work roll, the product cannot be used at all for applications requiring gloss.

[0005] Conventionally, Japanese Patent Publication No. 4-36762 and
As disclosed in Japanese Patent No. 169107, a technique has been proposed in which after hot-rolled stainless steel strip is subjected to annealing and pickling, pretreatment rolling is performed to smooth the steel strip surface, and then cold rolling is performed to improve the surface gloss. ing. However, in the prior art disclosed in Japanese Patent Publication No. 4-36762, since pre-treatment rolling is performed without lubrication, small seizure flaws may occur on the surface of the steel strip. In some cases, the gloss is reduced. Further, in the prior art of Japanese Patent Application Laid-Open No. 2-169107, there is a device for preventing this seizure by attaching a very thin oil film to the surface of the work roll. Therefore, a heavy investment is required, and the burden of maintenance of these facilities is large, and a better method has been desired.

[0006]

SUMMARY OF THE INVENTION The present invention relates to a method for rolling a stainless steel strip on a Sendzimir mill or the like with a small-diameter work roll, a method for rolling a stainless steel strip with a large-diameter work roll such as a cold tandem mill, or a combination thereof. In this case, it is an object of the present invention to be able to manufacture a cold-rolled stainless steel strip having excellent surface gloss.

[0007]

According to the present invention, there is provided a method for producing a stainless steel pretreated steel strip for cold rolling according to the present invention, wherein the stainless steel strip after hot rolling is annealed and pickled, and further made of a WC alloy. Non-lubricated rolling is performed at a rolling reduction of more than 5% and 30% or less using a work roll.

[0008]

Conventionally, it has been known that in order to improve the surface gloss of a cold-rolled stainless steel strip, it is better to reduce the surface roughness of the steel strip after cold rolling, which affects the surface roughness of the product. .

However, in the study of the present inventors, the surface roughness of the steel strip after the above-described cold rolling is as follows:
That is, it has been found that a part of the surface roughness of the steel strip annealed and pickled after hot rolling remains after cold rolling.

[0010] The surface roughness of the steel strip annealed and pickled after hot rolling is described below. Average roughness R in final finished product
a In the production of a cold rolled stainless steel strip with a surface roughness of 0.1 μm or less, the surface roughness of the steel strip immediately after annealing and pickling of the hot-rolled steel strip is determined by mechanical removal such as shot blasting during pickling. Average roughness R by scale treatment and pickling treatment with sulfuric acid
a It has a remarkably large roughness of 2 to 4 μm.

However, in general, a large amount of rolling oil is supplied to the roll and the steel strip from the inlet of the rolling mill during cold rolling.
This is performed in order to simultaneously perform lubrication and cooling with rolling oil, prevent the occurrence of seizure flaws such as heat streaks, and stably produce a steel strip.

Therefore, on the entry side of the cold rolling mill, rolling oil having a thickness of several μm or more adheres to the roll and the steel strip surface,
Rolling oil accumulates in extremely large dents on the surface of the steel strip annealed and pickled after hot rolling, and is bitten by the roll bite. The oil that has accumulated in the dent has no escape during the contact between the roll and the steel strip in the roll bite, and is rolled while being sealed.

In general, liquids including rolling oil are much less likely to be compressed than gases such as air, so the dents that contain oil during rolling are somewhat smaller than before rolling.
Most remains after rolling.

As described above, the surface roughness of the steel strip before cold rolling remains even after cold rolling and significantly impairs the surface gloss of the product.

Therefore, it is understood that in order to obtain a steel strip having a good surface gloss, it is preferable to previously reduce irregularities on the surface of the steel strip before cold rolling. From the above-mentioned knowledge, this can be realized by performing non-lubricated rolling without using a liquid such as rolling oil. However, when non-lubricated rolling is applied, the roll and the steel strip are seized to generate fine seizure flaws, and these flaws remain even after cold rolling, resulting in a case where the surface gloss of the steel strip is reduced.

Therefore, the present inventors have studied a pretreatment method for a stainless steel strip which can simultaneously satisfy the following two points. (1) The roll and the steel strip shall not seize during pre-treatment rolling. (2) Pretreatment can be performed to such an extent that unevenness on the surface of the steel strip after annealing and pickling of the hot-rolled steel strip does not remain after cold rolling.

As a result, the following method was found to be suitable. (a) Use stainless steel strip and non-seizing roll material. (b) A very thin film of rolling oil is formed on the roll surface.

Here, the thin film lubrication method (b) requires equipment for forming a thin oil film on the roll surface, and is disadvantageous in that the cost is high.

In contrast, the method of (a) in which the material of the roll is changed is such that the roll and the steel strip are prevented from seizing, so that the lubrication-free rolling can be easily achieved.

Therefore, the present inventors applied rolls of various roll materials to the pretreatment rolling of the present invention. as a result,
It has been found that it is preferable to use a work roll made of a WC alloy.

That is, when the phenomenon of seizure between the roll and the steel strip is observed in detail, the metal part on the roll surface adheres to the steel strip, and the adhesion is repeated as the roll rotates, and the roll surface temperature decreases. It became extremely high, and it was understood that the adhesion increased and seizure occurred. Also, if the carbide is on the roll surface,
It was found that the adhesion stopped at the carbides, and even if the adhesion was repeated with the rotation of the roll, the adhesion did not progress any further. This means that the roll and steel strip do not seize if most of the roll surface can be covered with carbide. For that purpose, the present inventors examined various roll materials, and found that the roll of the present invention containing WC (tungsten carbide) as a main component has finely dispersed carbide on the roll surface, and the roll and the steel strip do not seize. I found that. The WC alloy has, for example, a WC of 50% to 99% and a Co0 of 30%.
% And / or Ni0-30% and / or other combinations.

In the present invention, an integral roll of a WC alloy may be used. However, because of the high cost, the roll barrel portion is made of a WC alloy and the roll neck portion is made of a conventional steel-based alloy. Preferably, only the surface layer of the portion is made of a WC alloy. Further, as a method of forming only the surface layer of the roll barrel portion into a WC alloy, the WC alloy may be fitted to a conventional steel-based alloy or may be thermally sprayed.
It is desirable to set it to mm or more.

Also, in the method according to the present invention, as a preliminary treatment before cold rolling, from the above-mentioned knowledge, it can be seen that the non-lubricated rolling without supplying a liquid such as rolling oil has a rolling reduction of more than 5% to 30% or less. And is applied.

Here, the reason why a rolling reduction exceeding 5% is required during non-lubricated rolling is as follows. In the study of the present inventors, through variously reducing the rolling reduction during non-lubricating rolling before cold rolling, and then passing through cold rolling, supply of rolling oil, finish annealing pickling or finish bright annealing, and finish The surface gloss of the finished product after temper rolling was investigated. The surface glossiness is measured in accordance with JIS Z 8741 glossiness measurement method 5 (GS20 °).
It was measured according to. As a result, both in the case of a cold tandem mill using a large-diameter work roll and in the case of a Sendzimir mill using a small-diameter work roll, when the rolling reduction during non-lubricating rolling was increased, the surface gloss almost changed to a rolling reduction of 5%. However, if it exceeds 5%, the surface gloss becomes remarkably good.

As described above, non-lubricating rolling at a rolling reduction of more than 5% significantly improves the surface gloss, but on the other hand, requires a high rolling reduction which is not available in the prior art. On the other hand, in the conventional roll, the roll and the steel strip are in direct contact with each other in a non-lubricated state, so that seizure flaws are easily generated. Therefore, it is necessary to roll at low speed to prevent seizure flaws. In the study of the present inventors, as a result of examining the presence or absence of seizure by variously changing the reduction ratio during non-lubrication pretreatment rolling using a WC alloy work roll, the seizure progressed to a reduction ratio of 30%. Therefore, it was decided that the rolling reduction had to be 30% or less.

The lubrication-free rolling in the method of the present invention may be performed at any timing and at any position as long as it is performed after annealing and pickling of the hot-rolled steel strip and before cold rolling.

[0027]

【Example】

(Example 1) (Table 1) Material thickness as an example of a ferritic stainless steel strip 4.
After annealing and pickling a hot-rolled steel strip using a SUS430 steel strip of 0 mm, as an example of the method of the present invention, a WC alloy containing 10% Co is fitted to the roll outer circumference with a high-speed steel core. 13% reduction of the steel strip by applying a work roll
Pre-rolled without lubrication.

As a comparative example, a work roll using a normal 5% Cr forged steel was applied and pre-processed and rolled at the same rolling reduction.

Further, as a conventional example, no pretreatment rolling was performed at all, and only annealing pickling was performed. These steel strips were cold-rolled to a finished thickness of 1.0 mm using a five-stand cold tandem mill, then finish-annealed, pickled, temper-rolled at an elongation of 1.0%, and the gloss of the steel strip surface was examined.

The surface gloss of these stainless steel cold-rolled steel strips was measured by JIS Z 8741 gloss measurement method 5 (GS20 °), and in order of goodness, gloss 950 or more was rated A, 800-950 was rated A, and 600-800 was rated A. B, 400 to 600 were evaluated as C, and 400 or less as D, and evaluated on a 5-point scale.

From the results shown in Table 1, the cold rolled stainless steel strip manufactured by the method of the present invention had significantly better gloss than the steel strip manufactured by the method of the comparative example and the conventional example.

[Table 1]

(Example 2) (Table 2) Material thickness as an example of a ferritic stainless steel strip 5.
After annealing and pickling a hot-rolled steel strip using a SUS430 steel strip of 0 mm, as an example of the method of the present invention, an integrated work roll of a WC alloy containing 30% of Co is applied to reduce the steel strip. Pretreatment rolling was performed at a rate of 20% without lubrication.

As a comparative example, a work roll using ordinary 3% Cr forged steel was applied and pre-processed at the same rolling reduction.

Further, as a conventional example, no pretreatment rolling was performed at all, and only annealing pickling was performed. These steel strips were cold-rolled to a finished thickness of 2.0 mm by a five-stand cold tandem mill, then finish-annealed, pickled, and temper-rolled at an elongation of 1.2%, and the gloss of the steel strip surface was examined.

The evaluation method for gloss was the same as that in Example 1.
From the results shown in Table 2, the stainless steel cold-rolled steel strip manufactured by the method of the present invention had significantly better gloss than the steel strips manufactured by the comparative example and the conventional example.

[Table 2]

(Example 3) (Table 3) Material thickness as an example of a ferritic stainless steel strip 3.
After annealing and pickling a hot-rolled steel strip using a SUS430 steel strip of 0 mm, as an example of the method of the present invention, a WC containing 5% Ni on the outer periphery of the roll is made of cold die steel as a roll core.
Apply a work roll fitted with an alloy to reduce the steel strip.
Pretreatment rolling was performed at 9% without lubrication.

As a comparative example, a work roll using a normal 5% Cr forged steel was applied and pre-processed and rolled at the same rolling reduction.

Further, as a conventional example, no pretreatment rolling was performed at all, and only annealing pickling was performed. These steel strips were cold-rolled to a finished thickness of 0.7 mm by a five-stand cold tandem mill, then finish-annealed, pickled, and temper-rolled at an elongation of 0.8%, and the gloss of the steel strip surface was examined.

The method for evaluating the gloss was the same as in Example 1.
From the results shown in Table 3, the cold rolled stainless steel strip manufactured by the method of the present invention had significantly better gloss than the steel strip manufactured by the method of the comparative example and the conventional example.

[Table 3]

Example 4 (Table 4) Material thickness as an example of a ferritic stainless steel strip 4.
After annealing and pickling a hot-rolled steel strip using a SUS430 steel strip of 0 mm, as an example of the method of the present invention, a work in which a roll neck is semi-high-speed steel and a roll barrel is provided with a WC alloy containing 15% Ni. The steel strip was subjected to pretreatment rolling at a rolling reduction of 15% without lubrication by applying a roll.

Further, as a comparative example, a work roll using a normal 3% Cr forged steel was applied and pre-processed and rolled at the same rolling reduction.

Further, as a conventional example, no pretreatment rolling was performed, and only annealing pickling was performed. These steel strips are cold-rolled to a finished thickness of 1.3 mm using a five-stand cold tandem mill, and then a small-diameter work roll of cold-die steel is used.
Finished thickness from intermediate thickness 1.3mm with 20-high Sendzimir rolling mill
It was rolled to 1.0 mm in 5 passes, finish-annealed, pickled, and temper-rolled at an elongation of 1.0%.

The method for evaluating the gloss was the same as in Example 1.
From the results shown in Table 4, the cold rolled stainless steel strip manufactured by the method of the present invention had significantly better gloss than the steel strip manufactured by the method of the comparative example and the conventional example.

[Table 4]

(Example 5) (Table 5) An example of the method of the present invention after annealing and pickling a hot-rolled steel strip using a SUS304 steel strip having a material thickness of 4.0 mm as an example of an austenitic stainless steel strip. WC containing high-speed steel as the roll shaft core and containing 10% Co on the outer periphery of the roll
Apply a work roll fitted with an alloy to reduce the steel strip.
Pretreatment rolling was performed at 13% without lubrication.

As a comparative example, a work roll using a normal 5% Cr forged steel was applied and pre-processed and rolled at the same rolling reduction.

Further, as a conventional example, no pretreatment rolling was performed, and only annealing pickling was performed. These steel strips were cold-rolled to a finished thickness of 1.3 mm using a five-stand cold tandem mill, followed by finish annealing, pickling, temper rolling at an elongation of 0.6%, and three passes of # 600 buffing. The gloss of the steel strip surface was investigated.

The evaluation method for gloss was the same as in Example 1.
From the results shown in Table 5, the cold rolled stainless steel strip manufactured by the method of the present invention had significantly better gloss than the steel strips manufactured by the comparative example and the conventional example.

[Table 5]

Example 6 (Table 6) An example of the method of the present invention after annealing and pickling a hot-rolled steel strip using a SUS304 steel strip having a material thickness of 5.0 mm as an example of an austenitic stainless steel strip. 30% of Co
The steel strip was subjected to a pretreatment rolling without lubrication at a rolling reduction of 30% by applying a work roll of a WC alloy to be contained.

As a comparative example, a work roll using a normal 3% Cr forged steel was applied and pre-processed and rolled at the same reduction ratio.

Further, as a conventional example, no pretreatment rolling was performed at all, and only annealing pickling was performed. These steel strips are cold-rolled to a finished thickness of 2.3 mm using a five-stand cold tandem mill, then finish-annealed, pickled, temper-rolled at an elongation of 0.8%, and subjected to # 400 buffing for 5 passes. The gloss of the steel strip surface was investigated.

The method for evaluating gloss was the same as in Example 1.
From the results shown in Table 6, the cold rolled stainless steel strip manufactured by the method of the present invention had significantly better gloss than the steel strips manufactured by the method of the comparative example and the conventional example.

[Table 6]

(Example 7) (Table 7) An example of the method of the present invention after annealing and pickling a hot-rolled steel strip using a SUS304 steel strip having a material thickness of 3.0 mm as an example of an austenitic stainless steel strip. The rolled core was made of cold die steel, a work roll fitted with a WC alloy containing 5% of Ni was applied to the outer periphery of the roll, and the steel strip was pretreated and rolled at a rolling reduction of 9% without lubrication. .

Further, as a comparative example, a work roll using ordinary 3% Cr forged steel was applied and pre-processed and rolled at the same rolling reduction.

Further, as a conventional example, no pretreatment rolling was performed at all, and only annealing pickling was performed. These steel strips were cold-rolled to a finish thickness of 0.98 mm using a five-stand cold tandem mill, then finish-annealed, pickled, temper-rolled at an elongation of 1.0%, and subjected to # 400 buffing for one pass. The gloss of the steel strip surface was investigated.

The evaluation method for gloss was the same as in Example 1.
From the results shown in Table 7, the cold rolled stainless steel strip manufactured by the method of the present invention had significantly better gloss than the steel strips manufactured by the comparative example and the conventional example.

[Table 7]

Example 8 (Table 8) An example of the method of the present invention after annealing and pickling a hot-rolled steel strip using a SUS304 steel strip having a material thickness of 3.0 mm as an example of an austenitic stainless steel strip. A work roll having a roll neck made of semi-high-speed steel and a roll barrel provided with a WC alloy containing 15% of Ni was applied, and the steel strip was subjected to a non-lubrication pretreatment rolling at a reduction of 13%.

As a comparative example, a work roll using a normal 5% Cr forged steel was applied to perform pre-treatment rolling at the same reduction ratio.

Further, as a conventional example, no pretreatment rolling was performed at all, and only annealing pickling was performed. These steel strips are cold-rolled to a finished thickness of 1.3 mm using a 5-stand cold tandem mill, and then cold-rolled from an intermediate thickness of 1.3 mm to a finished thickness of 0.8 mm in a 12-stage cluster mill using small-diameter work rolls of high speed steel. Finish annealing, pickling, temper rolling at an elongation of 0.6%, and buffing at # 600 for two passes were performed to examine the gloss of the steel strip surface.

The method of evaluating gloss was the same as in Example 1.
From the results shown in Table 8, the cold rolled stainless steel strip manufactured by the method of the present invention had significantly better gloss than the steel strip manufactured by the method of the comparative example and the conventional example.

[Table 8]

[0060]

As described above, the cold-rolled stainless steel strip manufactured by the method of the present invention has a significantly superior surface gloss as compared with the steel strip manufactured by the method of the comparative example and the conventional example. In particular, in the case of rolling using a large-diameter work roll such as a cold tandem mill, the surface gloss is equal to or better than that of rolling using a small-diameter work roll such as a Sendzimir mill, which has heretofore been impossible at all. Further, according to the method of the present invention, it is possible to achieve a reduction in equipment investment of the rolling oil coolant and a reduction in maintenance management of the equipment. Further, since the seizure does not progress, the speed of the pretreatment rolling can be increased, and the effect of improving the rolling efficiency can be obtained.

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yoshikazu Kiyo 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Kawasaki Steel Works Co., Ltd. Chiba Works (72) Inventor Takashi Akazawa 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Kawasaki (56) References JP-A-63-290602 (JP, A) JP-A-64-83307 (JP, A) JP-A-3-204102 (JP, A) JP-A-3-128103 (JP, A) JP-A-61-63310 (JP, A) JP-A-8-39103 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B21B 1/00-3 / 02 B21B 27/00-27/02

Claims (1)

(57) [Claims] The stainless steel strip after the completion of hot rolling is annealed and pickled, and further lubricated at a reduction ratio of more than 5% to 30% or less using a work roll made of a WC alloy. A method for producing a stainless steel pretreated steel strip for cold rolling, characterized by rolling.