JPH0976003A - Method for cold-rolling high-gloss metallic sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a metallic sheet excellent in glossiness and without sheet twist and minute flaws by using rolls the direction of grinding mark of which is taken as the axial direction for rolling at one before stand. SOLUTION: In a cold rolling mill, the final stand in a tandem rolling method and rolling of the final pass in a reverse rolling method are taken as a roll cross system. The rolls 1 the direction of grinding mark of which is taken as the axial direction are used at least for the one before stand or preceding rolling of the pass. It is better to make the surface roughness of roll in the stand of the pre-stage or the earlier pass at the first half rougher. And, it is better to use the emulsion of the rolling oil whose viscosity at 50 deg.C is 7-30CSt. In this way, a stainless steel sheet attaching importance to glossness is manufactured at high efficiency.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cold rolling method for producing a metal sheet such as a stainless steel sheet having excellent surface glossiness and having no surface flaw or shape defect with high efficiency.

[0002]

2. Description of the Related Art In recent years, consumers have become more and more demanding for the quality of rolled sheets of various metals including thin stainless steel sheets (hereinafter simply referred to as metal sheets).
Above all, stainless steel sheets are required to have particularly high gloss.

The glossiness of a metal sheet is mainly influenced by the amount of lubricating oil during cold rolling. When the amount of lubricating oil is large, the surface of the metal plate is freely deformed to form minute recesses called oil pits, and the glossiness is lowered.

[0004] In the prior art, in order to obtain a metal plate having a high glossiness, cold rolling with a Sendzimir mill is generally performed. Sendzimir mill has a small work roll diameter,
Since the rolling speed is slow, the amount of lubricating oil introduced into the roll bite is reduced and the gloss of the metal plate is improved. However, on the other hand, cold rolling with a Sendzimir mill has a problem that the rolling pass is repeated by the lever type and that the rolling speed is slow because the roll diameter is small, resulting in low productivity.

Recently, as the demand for inexpensive and high-gloss metal sheets has increased, attempts have been made to efficiently produce them using a tandem rolling mill capable of high-speed rolling. However, when high-speed rolling is performed with a tandem mill having a large roll diameter, the amount of lubricating oil introduced increases and the glossiness decreases rather. Therefore, it is necessary to develop new technology.

For example, Japanese Patent Laid-Open No. 61-49701 discloses cold rolling using a tandem rolling mill equipped with a work roll having a diameter of 150 mm or more and a small diameter roll having a diameter of 100 mm or less. A cold rolling method is disclosed in which a stainless steel sheet with few surface defects is obtained by performing finish rolling using a Sendzimir mill as a work roll. However, although this method certainly improves the glossiness, it requires two types of equipment, a tandem rolling mill and a Sendzimir mill,
Furthermore, since the Sendzimir mill is finally used, there is a problem that the rolling speed is still limited and the productivity is not improved.

Further, Japanese Unexamined Patent Publication No. 62-137106 discloses a method in which the roll roughness is roughened by a front stand of a tandem mill and gradually reduced as the rear stand is rolled. However, even with this method, when the roll diameter exceeds 120 mm, oil pits occur in high-speed rolling at a rolling speed of 400 m / min or more, and it is not possible to obtain a sufficiently glossy surface.

Further, in Japanese Patent Laid-Open No. 4-200908, at least the initial pass and / or the final pass in the levers mill, and the first stand and / or in the tandem mill.
Alternatively, there is disclosed a method in which a final stand is rolled by using a roll having an abrasive grain in an axial direction. In this method, a high gloss level comparable to that of a conventional Sendzimir mill can be achieved.
Although it can be obtained at a rolling speed of 400 m / min or more, there is a problem in that minute scratches in the widthwise direction that the roll surface is transferred to the metal surface remain, resulting in a glossy feeling different from that of the Sendzimir mill rolled material.
This is because the human visual perception of gloss makes a comprehensive judgment including subtle unevenness, color tone, texture, etc., in addition to the scale indicated by glossiness. This is because the higher the value, the more likely it is to catch the eye of the person, which gives a sense of discomfort. In particular, when the Sendzimir mill rolled material and the tandem mill rolled material are used as the materials for the same product, the tandem mill rolled material having an unprecedented gloss feels a sense of discomfort and causes a problem of discrimination. The same can be said when a user purchases materials from a plurality of manufacturers and manufactures a product.

On the other hand, JP-A-6-91306 and JP-A-6-142702 disclose methods by cross roll rolling. In the cross roll rolling, a high glossiness similar to that of Sendzimir mill rolling can be obtained, but plate distortion occurs due to shear deformation in different directions in the width direction of the rolled material in different directions. Since the twist hinders the sheet passing property in the subsequent cleaning step and annealing step, as shown in JP-A-6-91306, do not perform the cross roll rolling in the final pass of the rolling or the final stand, or check the cross angle. Had to be as small as possible. However, in that case, oil pits are generated in high-speed rolling at a rolling speed of 400 m / min or more, and it is not possible to obtain a surface having a sufficiently high glossiness.

[0010]

DISCLOSURE OF THE INVENTION The present invention has been made with the object of developing a technique capable of rolling a metal plate having an excellent gloss comparable to that of a product rolled at a low speed with a Sendzimir mill, particularly a stainless steel sheet, with high efficiency. It is a thing.

Specifically, the present invention has an object of developing a rolling technique for a metal plate, especially a stainless steel sheet, which has a gloss equivalent to that of a product rolled at a low speed by a Sendzimir mill even at a high speed rolling of 400 m / min or more. And

[0012]

MEANS FOR SOLVING THE PROBLEMS The present inventors first focused on cold rolling using a highly productive tandem rolling mill for ordinary steel and a reversing rolling mill capable of high-speed rolling. In the process of research on increasing the glossiness of a plate, the tandem rolling method uses a final stand, and the levers rolling method uses a roll with the polishing grain direction as the axial direction to roll the stand or the path immediately before the final pass. We obtained the finding that if the rolling of the stand or the final pass is performed by the cross-roll method, it is possible to obtain a metal plate that does not suffer from plate twisting and micro flaws, which are the drawbacks of each rolling, and that synergistically achieves high gloss. Thus, the present invention has been completed.

The present invention relates to a cold rolling mill,
The tandem rolling method uses the final stand, and the levers rolling method uses the roll cross method for rolling the final pass, and at least the preceding stand or pass uses a roll with the direction of the polishing grain as the axial direction. It is a method of cold rolling a high-gloss metal sheet.

Further, when the present inventors continued their research and development, it was found that the roll roughness in the roll roll with the direction of the polishing grain before the roll roll as the axial direction was determined from the roll roughness in the cross roll rolling of the final stand or the final pass. It was found that the rougher the roll roughness, the higher the gloss and the more difficult the plate twist was.

Therefore, in the present invention, the roll surface roughness may be made rougher in the former stand or the first half pass. Further, it was found that these effects are greater when the viscosity of the stock solution of the rolling oil emulsion used is somewhat lower at 50 ° C. Therefore, an emulsion of rolling oil having a viscosity at 50 ° C. of 7 to 30 cSt may be used.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention uses a tandem rolling mill, which is a high-speed rolling mill with a large work roll diameter and high productivity, and a reversing type rolling mill, that is, a reversing rolling mill, which is used for low-speed rolling with a Sendzimir mill. It is a technology that enables highly efficient rolling of metal sheets with excellent gloss comparable to that of stainless steel sheets, in particular, stainless steel sheets. (Referred to as rolling) and roll cross rolling can be combined to obtain a metal plate that is free from the twists of the metal plate and microscopic flaws in the plate width direction, which are the drawbacks of both methods. You can get it.

The advantages and disadvantages of the axial polishing roll rolling and the cross roll rolling will be described first, and then the effects of combining them according to the present invention will be described. Figure 1 (a), (b)
Is a schematic explanatory view showing the direction of the polishing eyes of the roll,
Fig. 1 (a) shows a normal roll with grinding marks in the circumferential direction.
(b) shows axial polishing rolls each having a polishing grain in the axial direction.

FIGS. 2 (a) to 2 (e) are similar schematic explanatory views showing the rolling between the normal rolls and the relationship between the rolls and the rolled material during the rolling. 2 (a) is an overall view of FIG.
(b) shows the roughness (cross section) in the axial direction of the roll. Since the direction of the grind is the circumferential direction, which coincides with the direction of relative slip between the roll and the rolled material during rolling, the grind is emphasized and transferred to the surface of the rolled material as shown in Fig. 2 (c). . Fig. 2 (d)
As shown in, an oil film exists at the valley of the roll roughness, and a new recess (small defect) is generated on the surface of the corresponding metal plate. FIG. 2 (e) shows the surface roughness of the rolled material in the plate width direction at that time.

FIGS. 3 (a) to 3 (e) are schematic explanatory views of rolling with a roll having an abrasive grain in the axial direction and the relationship between the roll and the rolled material at the time of rolling. Fig. 3 (a) is the overall view, and as shown in Fig. 3 (b), when the grinding marks perpendicular to the rolling direction slide on the surface of the rolled material, the grinding marks transferred and left are those near the exit side. The polishing grain transferred on the entry side and the newly generated microdefects are almost crushed by the ridges of the adjacent polishing grain sliding on the surface of the rolled material and disappeared. Therefore, the unevenness in the plate width direction becomes gentle as shown in FIG. 3 (c), and the gloss in the plate width direction is significantly improved. However, as shown in Fig. 3 (d), there is a slight transfer of roll-polished eyes (projections formed in front of the crests of the polished eyes) in the rolling direction, and the roughness of the rolled metal plate surface in the rolling direction remains. As shown in Fig. 3 (e).

The protrusions formed at this time are crushed and smoothed during temper rolling, which is a process after cold rolling, but traces thereof remain as a pattern, resulting in impaired appearance quality.

4 (a) to 4 (d) are plan views for explaining the cross roll rolling. The roll used is usually ground. Work roll 1 as shown in Fig. 4 (a)
The lower work roll 2 and the lower work roll 2 are crossed in a plane parallel to the rolling plane so that each cross angle is θ, and the metal plate is rolled in the X direction. In this rolling, the direction of the peripheral speed Vr of the upper work roll 1 becomes the direction of the rolling speed Vs of the metal plate,
Since there is a deviation of the angle θ, a slip F occurs on the upper surface of the metal plate 3 in the plate width direction (Y direction) between the metal material and the roll. At the same time, since the direction of the rotational peripheral speed of the lower work roll 2 also deviates from the direction of the rolling speed of the metal plate by the angle θ,
Even on the lower surface of the metal plate 3, a slip F occurs between the metal plate and the roll in the plate width direction. The shear stress generated at this time works in the plate width direction at the surface layer portion of the metal plate 3 to smooth the surface of the metal plate 3.

Therefore, as shown in FIG. 4 (b), when cross roll rolling is performed using a roll having a normal polishing grain, for example, the convex portion of the polishing grain of the upper work roll 1 has a metal plate 3
With respect to the plate width direction Y, it moves while sliding relatively. At this time, the convex portion of the upper work roll 1 crushes and smoothes the surface of the metal plate 3. This action is similar to that at the time of rolling the axial polishing roll described above.

However, as shown in FIG. 4 (c), the slip stress generated on the surface of the metal plate 3 has opposite directions on the front and back surfaces of the metal plate, and the metal plate is sheared and deformed, so that the slip stress shown in FIG. Plate twist occurs as shown in (). This plate twist increases when the frictional force between the metal material and the roll during cold rolling is large.

However, when rolling is performed using a rolling stand before cross roll rolling or an axial polishing roll in a rolling pass, as shown in FIG. 5 (a), the metal surface before rolling has a widthwise direction. There are few irregularities, and there are irregularities in the rolling direction. When the convex portion of the polishing grain of the roll slides in the plate width direction, the friction force becomes large because it is necessary to overcome the irregularities transferred by the polishing grain on the surface rolled by the normal polishing roll as shown in FIG. 5 (b). On the surface rolled by the axial polishing roll as shown in FIG. 5 (a), such unevenness is small and the frictional force is also small. Therefore, the plate twist of the metal plate is reduced. In addition, as shown in FIG. 3, microscopic flaws generated in the axial polishing roll are smoothed by cross roll rolling,
Synergistically, the glossiness and the glossiness by the visual sense are improved.

Since the roughness in the circumferential direction of the axial polishing roll is rougher, the unevenness in the plate width direction is smaller. Therefore, the roll roughness in the plate width direction is larger than that in the cross roll rolling. Shearing force is small, plate twist is small, and gloss is high.

Therefore, as a specific roll roughness for that purpose, if the roll roughness of the cross roll rolling in the final stand or the final pass is too large, plate twisting occurs, and if it is small, an oil pit occurs and gloss is produced. Therefore, Ra: 0.1 to 0.4 μm is desirable. Further, if the roll roughness of the axial polishing roll rolling before that is also small, the gloss is not sufficiently improved, and there is no effect of reducing the plate twist during the cross roll rolling. If the roughness is too large, microscopic flaws in the rolling direction remain even after cross-roll rolling. Therefore, Ra: 0.
2 to 0.6 μm is desirable. More preferably, the roughness of the cross roll is Ra: 0.2 to 0.3 μm, and the roughness of the axial polishing roll is Ra: 0.35 to 0.5 μm.

As shown in FIGS. 3 and 4, the gloss improving action of the axial polishing roll rolling or the cross roll rolling is caused by the relative slip between the roll and the rolled material.
The larger the roll diameter, the larger the relative slip and the more remarkable the effect. Therefore, the effect is small in the case of the small-diameter roll rolling which can obtain high gloss even in the normal rolling, and the effect of the rolling method of the present invention becomes more remarkable when the roll diameter is 120 mm or more. More preferable roll diameter of the present invention is 18
It is 0 mm or more.

By the way, the gloss after rolling is influenced by the surface roughness of the base material before rolling. However, the base material that is generally used for cold rolling has a surface roughness R after pickling after hot rolling.
a: 2-3 μm, which is extremely large. Therefore, it is necessary to crush this unevenness by using the front stand or the initial pass. For that purpose, it is preferable that the roll roughness is large because the action of crushing the irregularities of the base material is large. Specifically, the roll roughness at the front stand or pass is preferably Ra: 0.4 to 1.0 μm, and it is preferable that the roll roughness is gradually reduced toward the latter stage. The rolling at this time may be normal rolling, but higher gloss can be obtained by cross roll rolling or axial polishing roll rolling.

Further, the lower the undiluted solution viscosity of the rolling oil emulsion used, the thinner the oil film thickness and the higher gloss.
Specifically, if the viscosity at 50 ° C is higher than 30 cSt, the oil film thickness during rolling becomes large and oil pits are generated, resulting in a decrease in gloss. On the other hand, if the viscosity at 50 ° C is less than 7 cSt, seizure due to oil film breakage occurs. A more preferable viscosity range is 50 ° C
Has a viscosity of 10 to 25 cSt.

Although the rolling oil composition is not particularly limited, synthetic esters having stable properties are preferable to natural fats and oils that easily cause emulsion deterioration due to hydrolysis and the like. Further, since mineral oil is inferior in lubricity, synthetic mineral oil such as α-olefin is preferable. Further, in order to improve the boundary lubricity, a P-based, P-S-based, or S-based extreme pressure additive may be used in the rolling oil.

[0031]

EXAMPLES Next, the present invention will be described more specifically by way of examples. Table 1 shows roll conditions when cold rolling is performed to confirm the effect of the present invention.

First, using a 5-stand 4Hi tandem rolling mill having a work roll diameter of 400 mm, work rolls having various surface roughness shown in Table 1 were combined as shown in Table 2 and subjected to annealing-acid treatment. Cold-rolled JIS SUS430 stainless steel strip having a thickness of 3.2 mm that had been washed was used as a test material. During rolling, the rolling oil having the composition and properties shown in Table 3 was supplied to rolls and rolled materials. Table 4 shows the rolling conditions for each stand.
As shown in.

Next, the gloss of the metal plate after cold rolling was measured by JI
It was measured by a gloss meter with an incident angle of 45 ° specified in S.
Table 5 shows the measurement results. A glossiness of 500 or more is ◎, 400 to less than 500 is ○, 200 to less than 400 is △, 20
Those with less than 0 are shown in the gloss column as x, and those with a difference in gloss between the upper and lower surfaces of less than 10% are ◎, 10% or more and less than 20% are good, 20% or more and less than 40% are △, 40%. The above was marked with x and described in each of four ranks. In addition, ◯ indicates that there is no visual gloss defect due to the presence or absence of plate twisting or micro scratches, and there is no seizure, etc., but there is a slight mark, □ indicates that it is visually noticeable and the quality is impaired, and x indicates a markedly defective mark. It is also shown in Table 5.

[0034]

[Table 1]

[0035]

[Table 2]

[0036]

[Table 3]

[0037]

[Table 4]

[0038]

[Table 5]

As shown in Table 5, according to the cold rolling method of the present invention, the gloss of the metal plate after rolling becomes 400 or more, and a beautiful surface on the front and back surfaces without twisting, fine flaws, and seizure is obtained. To be In particular, Examples 5 and 9 in which the roll surface roughness was made rougher toward the front stand, and Examples 3, 4, 5, and 6 in which an emulsion of rolling oil having a viscosity at 50 ° C of 7 to 30 cSt was used.
In Nos. 9 and 10, the glossiness after rolling was 450 or more, which shows that the rolling method is much more excellent.

Next, the same rolling as the rolling method of Example 3 of the present invention and Comparative Example 1 which is a conventional method was carried out by the 6Hi method, 250, 400, when the work roll diameters were 50, 85 and 120 mm.
In the case of 600 mm, it was carried out using a Levers rolling mill capable of adopting the 4Hi system. The surface glossiness after rolling is shown in a graph in FIG.

As can be seen from FIG. 6, according to the rolling method of the present invention, the surface gloss after rolling is remarkably improved when the work roll diameter is 120 mm or more, and the gloss is equal to or more than that when the work roll diameter is 85 mm or less. I see.

[0042]

EFFECT OF THE INVENTION By carrying out the cold rolling according to the present invention, it is possible to obtain a metal plate which is extremely excellent in glossiness, and is free from plate twist and fine flaws. Moreover, since a tandem rolling machine having a large roll diameter is used, high-speed rolling is possible, and it is possible to highly efficiently manufacture a stainless steel sheet having a high degree of gloss.

[Brief description of drawings]

FIG. 1 (a) and FIG. 1 (b) are schematic explanatory views each showing a direction of a polishing eye of a roll.

2 (a) to 2 (e) are schematic diagrams for explaining an outline of rolling with a normal roll and a relationship between a roll and a rolled material at the time of rolling.

3 (a) to 3 (e) are schematic diagrams for explaining an outline of rolling with an axial polishing roll and a relationship between the roll and a rolled material at the time of rolling.

4 (a) to 4 (d) are schematic views illustrating a cross roll rolling method.

FIG. 5 (a) and FIG. 5 (b) are explanatory views showing the distribution of frictional force in the plate width direction when the axial polishing roll rolling and the roll cross rolling of the present invention are combined.

FIG. 6 is a graph showing the relationship between the work roll diameter and the surface gloss of the rolled metal plate.

Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location B21B 45/02 310 B21B 45/02 310 (72) Inventor Yasushi Tomobe 4-533 Kitahama, Chuo-ku, Osaka City Sumitomo Metal Industries Co., Ltd.

Claims (3)

[Claims] 1. In a cold rolling mill, a tandem rolling system uses a final stand, and a levers rolling system uses a roll cross system for rolling the final pass, and at least one preceding stand or pass is rolled in the direction of the polishing grain. A method for cold rolling a high-gloss metal sheet, characterized by using oriented rolls. 2. The method for cold rolling a high-gloss metal sheet according to claim 1, wherein the roll surface roughness is made rougher in the former stand or the first half pass. 3. The method for cold rolling a high-gloss metal sheet according to claim 1, wherein an emulsion of rolling oil having a viscosity at 50 ° C. of 7 to 30 cSt is used.