JPH09253721A - Manufacture of stainless steel strip high in gloss - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture the stainless steel strip housing target gloss by setting a finish pass by a multiple cluster type mill or a roll speed in a final stand by a cold tandem mill or the elongation percentage of a skin pass rolling steel strip accordingly an outlet side plate speed. SOLUTION: In the skin pass rolling of the stainless steel cold rolling strip, the multiple cluster mill or a cold tandem mill is used. By setting the elongation percentage by using a prescribed regression formula found previously accordingly their finish passes or a rolling speed in the final stand. the skin pass rolling is performed. Consequently, the surface gloss of the steel strip can be made equivalent to that in low speed rolling even in high speed rolling or more satisfactory. For the preparation of the regression formula, the stainless steel strip is rolled by changing the finish pass or the rolling speed in the final stand in several stages, and also after performing bright annealing or finish annealing and pickling, the elongation percentage is changed, and the skin pass rolling is performed. Then the surface gloss of each steel strip is measured, and a relationship between the elongation percentage and the gloss is regressed by the prescribed formula.

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 high-gloss stainless steel strip, and in particular, proposes an effective method for producing a stainless cold-rolled steel strip having a high gloss by modifying temper rolling. .

[0002]

2. Description of the Related Art Conventionally, cold-rolled stainless steel strip is obtained by annealing a hot-rolled steel strip, pickling it, and then rolling it with a multistage cluster mill such as a Sendzimir mill or a cold tandem mill. It was produced by cold rolling while supplying it, further performing finish annealing pickling or finish bright annealing, and then performing finish temper rolling with an elongation of 0.5 to 1.2%.

Generally, a stainless steel plate is used in the interior of a building, a kitchen, various ornaments, etc. in the case of a ferrite type typified by SUS 430.
Especially, it is required that the product sheet after finish temper rolling has excellent surface gloss, and in the case of austenite type represented by SUS 304, it is required to have more corrosion resistance than that of ferrite type. Often used, buffing is applied after finish temper rolling to give surface gloss.

In the conventional production of cold-rolled stainless steel strip, both ferrite and austenitic steels are provided with excellent surface gloss, so that, for example, JP-A-60-227904 and JP-A-61-49705 are used. As described in (1), attempts have been made to improve the work roll diameter and roll roughness during cold rolling. However, in such a conventional method, when the roll speed or the output strip speed in cold rolling (hereinafter, these two speeds are collectively referred to as rolling speed) is increased in an attempt to increase the production efficiency, the gloss decreases and both are satisfactory. There is a problem that surface gloss cannot be obtained.

In general, as a brightening material for stainless cold-rolled steel strip, a 2B product having a white steel strip surface that has been subjected to finish annealing-pickling after cold rolling, and finish bright annealing to give a black glow like a mirror. There is a BA product having a steel strip surface. Of these, the 2B product has been adopted with a method of producing it with high efficiency by using a cold tandem mill instead of the Sendzimir mill, but it is difficult to improve the production efficiency in order to produce the BA product. We had no choice but to rely on cold rolling with a multi-stage cluster type mill using small diameter work rolls.

Regarding this point, Japanese Patent Laid-Open No. 5-7904 discloses that
It is described that in rolling a high-gloss stainless steel foil, the higher the rolling speed, the lower the surface glossiness.
This is because as the rolling speed increases, the amount of rolling oil drawn into the roll bite increases, which results in the increase of surface fine irregularity defects such as oil pits, which further increases the oil film thickness inside the roll bite, resulting in a rough surface of the roll. Is said to be difficult to transfer to the plate surface. The decrease in surface glossiness caused by this is not limited to the rolling of stainless steel foil, but applies to all stainless steel luster materials.Therefore, in order to maintain good gloss, it is necessary to roll at a significantly low rolling speed. Therefore, a significant reduction in rolling efficiency was unavoidable.

In particular, the BA product was rolled at a remarkably low speed in the finishing pass of the cluster type mill in order to obtain a gloss close to a mirror surface.

Further, in Japanese Unexamined Patent Publication No. 6-23403, when performing bright finishing in a plurality of passes by temper rolling of dry rolling, the elongation percentage distribution of each pass is made larger than that of the second and subsequent passes, and high pressure is applied. A technique for improving the surface glossiness by lowering the surface gloss is disclosed. However, in this technique, the coil when the rolling speed of cold rolling is high and the coil when the rolling speed of cold rolling are small, if the elongation rate of temper rolling is the same, the coil when the rolling speed of cold rolling is high is better. There is an unavoidable problem that the gloss decreases, and in fact, there is a problem that the rolling speed in cold rolling cannot be increased in order to maintain the product quality.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to propose a manufacturing method capable of manufacturing a high-gloss stainless cold-rolled steel strip with high efficiency regardless of the type of mill used for cold rolling.

[0010]

Means for Solving the Problems The present invention provides a multi-stage cluster type for producing a high-gloss stainless steel strip through cold rolling using a multi-stage cluster type mill or cold rolling using a cold tandem mill. Roll speed or exit strip speed of either the finishing pass of the mill or the final stand of the cold tandem mill and the steel strip in temper rolling after annealing pickling or bright annealing through the finishing pass or final stand The relationship between the elongation rate and the glossiness of the product sheet obtained through each of the cold rolling is calculated, and the roll speed of either the finishing pass by the multi-stage cluster mill or the final stand by the cold tandem mill or By setting the elongation rate of the steel strip in temper rolling according to the output strip speed, it is possible to obtain a stainless steel strip with the target glossiness. Which is a process for producing a high gloss stainless steel strip, characterized.

In the above manufacturing method, the elongation percentage of the steel strip in temper rolling is set according to the following equation. Record

[Equation 1]

The elongation of the steel strip in temper rolling may be set according to the following equation. Record

[Equation 2]

For the coefficients a _V , b _V , and C _V , table data corresponding to each roll speed or exit plate speed is used, or gloss and temper rolling elongation and multi-stage cluster mill finishing pass or cold tandem mill are used. It is preferable to use the one obtained as an equation from the relationship with the roll speed of the final stand or the exit plate speed.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Factors that greatly affect the surface gloss of a stainless cold-rolled steel strip include fine irregularities on the surface of the cold-rolled stainless steel strip. This is for example
Rolling oil collected in the recesses on the surface of the mother plate before cold rolling is enclosed in the recesses at the roll bite inlet during cold rolling, and the rolling oil is difficult to compress inside the roll bite, so the material on the roll bite exit side is This is because the recesses remain, or the rolling oil sealed in the recesses at the entrance of the roll bite blows out when the high pressure is applied inside the roll bite, and the traces thereof remain around the recesses and the like. The amount of such fine irregularities generated increases as the amount of rolling oil introduced into the roll bite increases. As a result, the surface gloss of the stainless cold-rolled steel strip decreases as the rolling speed increases, as described in JP-A-5-7904.

Therefore, various investigations are made in order to improve the gloss by reducing the fine unevenness defects remaining in the case of cold rolling at a high speed to a level equal to or lower than that obtained in the case of cold rolling at a low speed. As a result of overlapping, it was found that temper rolling using a rolling roll having a roughness smaller than that of the plate under non-lubricated conditions is effective.

FIG. 1 shows the relationship between the elongation ratio in temper rolling and the area ratio of fine unevenness defects. As the elongation ratio increases, the area ratio decreases. Further, by increasing the elongation rate, the smooth roll surface pattern is more strongly transferred to the smooth surface other than the fine concavo-convex defect portion. That is, by using a roll having a finer surface roughness than the surface roughness of the plate, the effect of further improving the degree of smoothness can be obtained.

By the way, for each coil rolled when the rolling speed of cold rolling is V ₁ and V ₂ (where V ₁ <V ₂ ), micro unevenness defects on the coil surface after cold rolling are used. Comparing the above, the rolling speed V ₂ is higher than the rolling speed V ₁ . Then, this was further temper-rolled, and the area ratio of micro unevenness defects on the surface of the steel sheet was investigated.
At the same elongation, the rolling speed of cold rolling is
In the case of V ₂ , the area ratio of micro unevenness defects on the surface of the steel sheet after temper rolling becomes larger than that in the case of V ₁ . Further FIG.
As shown in, the surface gloss of the product is also affected.
Therefore, when the elongation rate of temper rolling is set to a constant value, the surface gloss of the product decreases as the rolling speed of cold rolling increases.

There is a correlation as shown in FIG. 3 between the rolling speed in cold rolling, the elongation of temper rolling and the surface gloss of the product, and the elongation of temper rolling depends on the rolling speed of cold rolling. By appropriately setting the rate, it is possible to obtain the same surface gloss or even higher gloss in the product even if the rolling speed of cold rolling is different, and the present invention is based on such findings. It is a thing. Therefore, when rolling at a high speed, it is necessary to set an optimum elongation rate according to the speed in order to obtain gloss equal to or higher than that when rolling at a low speed.

In the present invention, when temper rolling the stainless cold rolled steel strip, a multi-stage cluster mill such as a Sendzimir mill or a cold tandem mill is used, which is obtained in advance according to the finishing pass or the rolling speed of the final stand. The elongation rate is set using the regression equation set, and temper rolling is performed.According to this, the gloss of the surface of the steel strip is performed at low speed even when high speed rolling is performed. It is possible to make it equal to or better than the case.

Creation of a specific regression equation is as follows. In cold rolling with a multi-stage cluster mill such as a Sendzimir mill or cold tandem mill, the stainless steel strip was rolled by changing the rolling speed of the finishing pass or the final stand in several stages, and the bright annealing was performed for each of the obtained strips. Alternatively, after the final annealing and pickling, the elongation is changed and temper rolling is performed. Then, the gloss of the surface of each steel strip is measured, and the relationship between the elongation and the gloss is regressed by the equation (1) or (3).

4 and 5 show the relationship between the surface gloss of the ferritic stainless steel strip that has been subjected to finish bright annealing after cold rolling using a Sendzimir mill and temper rolling, and the elongation rate in temper rolling. FIG. 3 is a diagram showing regression using the above two types of equations. The roll speed or exit strip speed of the finishing pass of cold rolling by Sendzimir mill was changed to 150 mpm, 250 mpm, and 350 mpm.

Curves 1, 2 and 3 in FIG. 4 are roll speeds or exit plate speeds of finishing passes of cold rolling using a Sendzimir mill, respectively, 150 mpm, 250 mpm and 350 mp.
This is a regression curve (using equation (1)) when m is set. (1)
A _V , b _V , c _V used as regression coefficient in equation
Is a function of the roll speed of the finishing pass of cold rolling by the Sendzimir mill or the exit plate speed V, and an appropriate expression, for example, a _V , b _V , c _V at each rolling speed is obtained, and a _V ,
The relationship may be obtained by plotting the relationship between each of b _V and c _V and V, and observing the shape to determine the optimum formula (for example, straight line or quadratic curve). If, a _V, b _V, if it is difficult to formulate c _V may be to have a _V, b _V, the c _V as table data. Further, in the temper rolling of the actual machine, the regression coefficients a _V and b _V may be determined by limiting the elongation rate setting to a certain range and directly regressing using the equation (3) within the elongation rate range.

FIG. 5 is a diagram when linear regression is performed.
Lines 1, 2 and 3 are regression lines when the roll speed or exit plate speed of the finishing pass is 150 mpm, 250 mpm and 350 mpm, respectively, and the elongation rate is 0.5% as the range of regression.
It is limited to ~ 1.5%. Here, when it is difficult to formulate a _V, a b _V may be previously with a _V, a b _V as table data.

The stainless steel sheet targeted by the present invention may be any one of ferritic, austenitic, martensitic and two-phase type. Since the delivery side plate speed can be obtained based on the roll speed and the actually measured advance rate or the predicted advance rate, it goes without saying that the delivery side plate speed may be used instead of the roll speed.

[0025]

【Example】

Example 1 A SUS 430 steel strip was used as an example of a ferritic stainless steel strip, and cold rolling and bright annealing were performed with a Sendzimir mill at three finishing roll speeds of 150 mpm, 250 mpm, and 350 mpm, respectively. . Then, as an example according to the present invention, by applying the formula (1), from the relationship of elongation-tempered rolling elongation-glossiness, it is adjusted for each roll speed of the finishing pass with the goal of obtaining a steel strip with a glossiness of 1000. The elongation of the quality rolling was set and rolled, and the gloss of the coil surface after the temper rolling was investigated. However, the maximum value of elongation that can be set is 1.5%. This is because the mechanical properties change when temper rolling is performed at an elongation rate of more than 1.5%, which causes problems in products. If the result of selecting the elongation rate to obtain the highest gloss was 1.5% or more, it was set to 1.5% and temper rolling was performed.

Regarding a _V , b _V and c _V in the equation (1), rolling is carried out in advance by changing the roll speed of the finishing pass of cold rolling by a Sendzimir mill, then bright annealing is performed, and the steel after bright annealing is subjected. From the relationship between the surface gloss data measured after temper rolling with varying elongation, the elongation of temper rolling, and the roll speed of the finishing pass of cold rolling with a Sendzimir mill, the formulas (5) and (6) were used. , (7) and determined each coefficient. a _V = a ₁ × V ² + a ₃ --- (5) b _V = (b ₁ / V) −b ₂ --- (6) c _V = −c ₁ × V + c ₂ --- (7)

For comparison, in cold rolling with a Sendzimir mill, the roll speed of the finishing pass was 150, respectively.
Although the mpm, 250 mpm, and 350 mpm were changed, the gloss of the coil surface was also investigated when the elongation was constant at 0.9% in the temper rolling after bright annealing. The surface gloss of stainless cold-rolled steel strip is JIS Z8742 Gloss Measurement Method 5 (G _S
20 °), and the glossiness of 950 or higher was evaluated in 5 grades, with the gloss of 950 or more as special A, 800 to 950 as A, 600 to 800 as B, 400 to 600 as C, and 400 or less as D. Table 1 shows the results.

[0028]

[Table 1]

The stainless cold-rolled steel strip having the elongation set and temper-rolled according to the present invention is temper-rolled with the elongation kept constant despite the roll speed of the finishing pass in the cold rolling being high at 350 mpm. It was confirmed that the steel strip had better luster than the steel strip.

Example 2 Using SUS 304 steel strip as an example of austenitic stainless steel strip, cold rolling was carried out by a cold tandem mill with the roll speed of the final stand divided into three stages of 100 mpm, 500 mpm and 1000 mpm. Finish annealing It was pickled. Then, as an example of the present invention, by applying the formula (1), from the elongation-tempered rolling relationship of the temper rolling, with the goal of obtaining a steel strip with a gloss of 800, for each roll speed of the finishing pass. Rolling was performed by setting the elongation of temper rolling, and after temper rolling, # 400 buffing was performed for 5 passes to examine the gloss of the surface of the steel strip. However, the maximum value of elongation that can be set was 1.0%. This is a growth rate of 1.0%
This is because, if the temper rolling is carried out over the range, the mechanical properties will change, causing problems in the product. When the result of selecting the elongation rate to obtain the highest gloss is 1.0% or more, it was set to 1.0% and temper rolled.

In the formula (1), a _V , b _V , and C _V are previously rolled by changing the roll speed of the final stand of cold rolling by a cold tandem mill, then finish annealing, pickling, and finish annealing. The steel strip after pickling was temper-rolled with varying elongation and then subjected to 5 passes of # 400 buffing, surface gloss data measured, elongation of temper rolling, and cold tandem mill cooling. From the relationship of the roll speed of the final stand of hot rolling, it was determined as in equations (8), (9) and (10), and the respective coefficients were obtained. _{a V = a 1 (V-} a 2) 2 + a 3 --- (8) b V = b 1 / (V-b 2) + b 3 --- (9) c V = -c 1 V + c 2 - -(Ten)

For comparison, the roll speed of the final stand of the cold rolling in the cold tandem mill was divided into the same three stages as above, but the elongation rate was constant at 0.7% in the temper rolling after the final annealing and pickling. The gloss of the steel strip surface in each case was also examined under the same conditions as above.

The surface luster of the cold rolled stainless steel strip is JIS Z8
741 Gloss measurement method (G _S 20 °) is used, and in order of goodness, gloss of 950 or higher is special A, 800 to 900 is A, 600 to 800.
Was evaluated as B, 400 to 600 as C, and 400 or less as D. Table 2 shows the results.

[0034]

[Table 2]

As is clear from Table 2, the cold-rolled stainless steel strip manufactured according to the present invention had better gloss than the conventional steel strip that was temper-rolled with a constant elongation.

Example 3 Using a SUS 430 steel strip as an example of a ferritic stainless steel strip, cold rolling was performed by a cold tandem mill with the roll speed of the final stand divided into three stages of 100 mpm, 500 mpm and 1000 mpm. A final annealing pickling was performed. Then, as an example according to the present invention, by applying the formula (3), from the elongation-tempered rolling relationship of the temper rolling, with the goal of obtaining a steel strip with a gloss of 800, for each roll speed of the finishing pass. The elongation of the temper rolling was set and rolled, and the gloss of the surface of the steel strip after the temper rolling was investigated. However, the maximum value of elongation that can be set is 1.5%. This is because the mechanical properties change when temper rolling is performed at an elongation rate of more than 1.5%, which causes problems in products. When the result of selecting the elongation rate to obtain the highest gloss is 1.5% or more, it was set to 1.5% and temper rolled.

The values a _V , b _V , and C _{V in the} equation (3) are previously rolled by changing the roll speed of the final stand of the cold rolling by the cold tandem mill, and then subjected to finish annealing pickling and finish annealing acid. Data of surface gloss measured after temper rolling the steel strip after washing with varying elongation and 0.8-1.5 of temper rolling.
%, The a _v and b _V at each output side strip speed are calculated from the relationship between the elongation rate limited to the range of% and the output side strip speed of the final stand of cold rolling by the cold tandem mill, and the values are shown in Table 3 as shown in Table 3. I decided to bring it.

[0038]

[Table 3]

As a comparative example, in cold rolling with a cold tandem mill, the exit side plate speed of the final stand was 100 mp.
Although the m, 500 mpm and 1000 mpm were changed, the gloss of the surface of the steel strip was also investigated when the elongation was set to 0.9% for temper rolling. The surface gloss of stainless cold-rolled steel strip is JIS Z8741.
Glossiness measurement method 5 (G _S 20 °) is measured in order of goodness, with glossiness of 950 or more as special A, 800 to 900 as A, 600 to 800 as B, 400 to 600 as C, and 400 or less as D. The grade was evaluated. The results are shown in Table 4.

[0040]

[Table 4]

As is clear from Table 4, the stainless steel strip produced according to the present invention had a better gloss than the conventional stainless steel strip temper-rolled at a constant elongation.

[0042]

EFFECTS OF THE INVENTION According to the present invention, even if a multi-stage cluster mill such as a Sendzimir mill is used for rolling at a high speed, the gloss is not significantly reduced, so that the rolling efficiency can be remarkably improved.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the elongation rate of a steel strip in temper rolling and the area rate of micro unevenness defects.

FIG. 2 is a graph showing the relationship between the elongation rate of a steel strip in temper rolling and the area rate of micro unevenness defects.

FIG. 3 is a graph showing the relationship between the elongation percentage and the glossiness of a steel strip in temper rolling.

FIG. 4 is a graph showing the relationship between the elongation rate and the glossiness of a steel strip in temper rolling.

FIG. 5 is a graph showing the relationship between the elongation rate and the glossiness of a steel strip in temper rolling.

Front page continuation (72) Inventor Kazuhito Kenmochi 1 Kawasaki-cho, Chuo-ku, Chiba, Chiba Prefecture, Kawasaki Steel Corporation Technical Research Institute (72) Shigeru Sato 1 Kawasaki-cho, Chuo-ku, Chiba, Chiba Prefecture Kawasaki Steel Inside the Chiba Works (72) Inventor Junichi Yamamoto 1 Kawasaki-cho, Chuo-ku, Chiba, Chiba Kawasaki Works Inside the Chiba Works

Claims (4)

[Claims] 1. When producing a high-gloss stainless steel strip through cold rolling using a multi-stage cluster mill or cold rolling using a cold tandem mill, a finishing pass of the multi-stage cluster mill or a cold tandem is used. The roll speed or exit plate speed of either of the mill's final stands,
Relationship between elongation rate of steel strip in temper rolling after annealing pickling or bright annealing through the finishing pass or final stand and glossiness of any product sheet obtained through each cold rolling By setting the elongation rate of the steel strip in temper rolling according to the finishing pass with a multi-stage cluster mill or the roll speed or the exit strip speed of the final stand with a cold tandem mill, the target glossiness can be obtained. A method for producing a high-gloss stainless steel strip, which comprises: 2. The method according to claim 1, wherein the elongation percentage of the steel strip in temper rolling is set according to the following formula. Note {Glossiness (G _S 20 °)} = a _V ln [b _V × {Elongation (%)
_{} +1] + c V a V} , b V, c V: wherein regression _{coefficients, a V = f a (V} ) b V = f b (V) c V = f c (V) V: in multi cluster mill rolling Rolling speed or exit strip speed at finishing stand in finishing pass or cold tandem mill rolling 3. The method according to claim 1, wherein the elongation percentage of the steel strip in temper rolling is set according to the following equation. Serial {glossiness _{(G S 20 °)} =} a V × { elongation _{(%)} + b V a} V, b V, c V: wherein regression _{coefficients, a V = f a (V} ) b V = f _b (V) V: Finishing pass in multi-stage cluster mill rolling or roll speed or exit strip speed at the final stand in cold tandem mill rolling 4. For the coefficients a _V , b _V , and c _V , table data corresponding to each roll speed or delivery side plate speed is used, or
The method according to claim 2 or 3, wherein a value obtained from the relationship between gloss, elongation of temper rolling and multi-stage cluster mill finishing pass or roll speed or exit side plate speed of a cold tandem mill final stand is used.