JPH0565686A - Production on dull roll for rolling - Google Patents

Abstract

PURPOSE:To obtain a dull roll for rolling remarkably improved in high image clarity after coating by applying Cr plating to the surface of a steel sheet. CONSTITUTION:In the working method for a roll for rolling, where high density energy irradiation is applied in a manner to scan the surface of a work roll for rolling to form fine ruggedness in numerous number in the roll surface and then the roll worked as mentioned above is immersed into a chromic acid solution to undergo chromium plating treatment, the softened part at the surface layer of the fine projecting part formed by high density energy irradiation is previously removed prior to the application of chromium plating treatment to the roll surface and then the roll is immersed into a chromic acid solution to undergo chromium plating treatment.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rolling roll having a roll surface provided with a predetermined roughness pattern, and a method for producing the rolling roll. TECHNICAL FIELD The present invention relates to a rolling roll for producing a steel sheet (cold rolled steel sheet, surface-treated steel sheet, aluminum alloy steel sheet, hot rolled steel sheet) having markedly improved pressability and press formability, and a method for producing the rolling roll.

[0002]

2. Description of the Related Art Generally, a cold-rolled steel sheet for working has a dull finish on its surface in order to facilitate press working. That is, during press working, the lubricating oil for working is stored in the unevenness formed on the surface of the steel sheet, which has the function of reducing friction between the die and the steel sheet and preventing seizure. Also, research on press formability has been conducted from both the side of the steel plate, which is the raw material, and the forming technology, but with the high precision and complexity of products, the required properties for steel plates have become more sophisticated and diversified. It's starting. For this reason, as a current situation, in temper rolling to finally adjust the steel plate roughness, a work roll dull-processed by shot blasting, electric discharge, or laser etc. is used on the steel plate surface to transfer the roughness to the steel plate surface. ing.
Moreover, the evaluation criteria in actual press forming are not sufficient only by the mechanical properties (r value, El value, etc.) of the steel sheet that have been used conventionally, and the steel plate surface roughness lubricating oil etc. also has a great influence on the press formability. Exert.

Exterior steel sheets for automobile bodies, home appliances, etc. are painted to give them an aesthetic appearance. At this time, the appearance is not impaired by the irregular reflection of the coated surface, so-called excellent image clarity. Is required. Therefore, for example, by improving the profile of the surface roughness of the steel sheet to reduce the unevenness of the coated surface after painting and to increase the proportion of the horizontal portion, the specular reflectance of light is improved and the distortion of the image is reduced. Japanese Patent Application Laid-Open No. 62-168602 discloses a steel sheet that can improve the sharpness after painting more than before. However, in this case, the laser processing roll for rolling has a large initial wear of the convex portion of the surface, and the wear resistance is unavoidably reduced. As a method for reducing the decrease in roughness at the initial stage of rolling, there is known JP-A-62-158591, which is characterized by performing chromium plating after laser processing to improve wear resistance.

[0004]

These known patents are
It is excellent in that it improves the image clarity after coating, and in Japanese Patent Laid-Open No. 62-168602, a trapezoidal shape in which the microscopic morphology constituting the surface roughness has a flat top surface. By forming a mountain portion and a groove-shaped valley portion formed so as to surround all or part of the periphery thereof,
It is intended to improve the sharpness of the coating film after coating. However, the very surface layer of the convex portion of the roll surface roughened by laser processing has a residual austenite phase that is softer than the base material, and this is the initial wear at the beginning of rolling, and the roll life is short. is there. JP-A-62-158591 for the purpose of improving the wear resistance of this roll
In the publication, by plating the surface of the residual austenite phase in the very surface layer of the convex portion of the roughened roll surface with Cr, wear resistance is imparted, and it is excellent in that it reduces wear during rolling. Even if it is present, the surface hardness of the residual austenite phase in the Cr plating base, that is, the very surface layer of the convex portion of the roll surface is low. However, there is a drawback in that the portions are depressed and the Cr plating is peeled off, so that the abrasion resistance of the laser processing roll cannot be improved.

[0005]

According to the present invention, wear resistance is imparted by Cr-plating the surface of the retained austenite phase in the very surface layer of a conventional roughened rolling roll surface convex portion. Therefore, in the technique of reducing the initial wear during rolling, since the surface hardness of the residual austenite phase of the Cr plating base, that is, the very surface layer of the convex portion of the roll surface is low, when Cr plating is performed directly on this,
At the time of rolling, the convex portion of the roughened roll surface is depressed, which in turn causes the peeling of the Cr plating, and it is intended to solve the problem that the wear resistance of the laser processing roll cannot be improved. The feature is that the surface of the work roll for rolling is scanned, and a high density energy is irradiated to form innumerable minute irregularities on the roll surface, and the roll processed in this way is treated with a chromic acid solution. In a method for processing a rolling roll that is immersed in and subjected to chrome plating, before the chrome plating on the roll surface, the softened portion of the fine convex surface layer formed by irradiation with high-density energy is previously formed. After the removal, it is immersed in a chromic acid solution and subjected to a chrome plating treatment, which is a method of manufacturing a dull roll for rolling.

The present invention will be described below with reference to the drawings.
FIG. 1 schematically shows the cross-sectional shape of the roll surface according to the present invention, and FIG. 1A shows the cross-sectional shape of the roll according to the conventional method. By irradiating the surface of the roll 1 with a laser, Cr plating 3 is applied on the softened portion 2 of the fine convex surface layer formed on the surface of the roll 1, with the aim of reducing the reduction in wear of the convex portion at the initial rolling stage. It is characterized by the point. However, since the soft layer 2 sandwiched between the Cr plating 3 on the convex portion of the roll surface and the roll base 1 has a residual austenite phase softened as compared with the roll base 1 and has a low hardness, when rolled as it is, There is a problem that the raised convex portion of the surface of the roll is depressed, and the Cr plating is peeled off, so that the abrasion resistance of the laser processing roll cannot be improved.

FIG. 1 (b) schematically shows a roll cross-sectional shape according to the present invention which solves the conventional problem. Innumerable minute irregularities are formed on the surface of the roll 1, and the surface layer of the convex portion is formed. After the softening part 2 of 1 is removed in advance, the Cr plating 3 is processed to form the residual austenite phase softened as compared with the roll base 1 on the convex surface layer. It should be noted that the softened portion 2 of the surface layer of this roll convex
In addition to the electrolytic etching method used this time, mechanical removal by surface polishing after laser dull processing and forced removal of the softened portion on the surface of the convex portion of the roll surface by roll idling before rolling , Etc., and in any of the methods, the softened portion of the roll convex portion surface layer can be removed in substantially the same manner.

FIG. 2 shows conditions for removing the softened portion 2 on the surface layer of the convex portion of the roll according to the present invention. Innumerable minute irregularities are formed on the surface of the roll 1, and Cr is formed on the surface layer of the convex portion.
It shows the electrolytic etching conditions in a Cr acid solution for removing the softened portion 2 of the roll convex portion in advance before applying the plating 3. This electrolytic etching is carried out in a Cr acid solution using the roll as an anode, but (current density) ×
It is important to manage by (processing time). in this case,
The higher the current density (DA), the shorter the processing time (T),
In the opposite case, it is desirable to take a long processing time, but the relationship between the required current density and the processing time is: 1000 ≦ DA × T ≦ 17000, (1) 10 ≦ DA ≦ 50, (2) .. DA × T is less than 1000 and DA is 10
If it is less than A / dm ² , etching is insufficient and Cr
The adhesion of the plating is deteriorated, and the removal of the soft portion of the surface layer of the convex portion is insufficient, and when Cr plating is performed from above, the depression of the convex portion on the roughened roll surface, and eventually C
The r plating is peeled off, and the abrasion resistance of the laser processing roll cannot be improved. On the other hand, DA × T is 17,000
When the DA exceeds 10 A / dm ² , the etching proceeds excessively and the cleanliness of the surface layer of the roll is improved, but the shape of the convex portion is deteriorated and the required profile cannot be obtained.

Further, in the present invention, the above (1) and (2)
It is desirable to satisfy the following relationship within the range of. DA × T ≧ −0.1 DA + 6 (× 10 ³ A / dm ² sec) (3) DA × T ≦ −0.1 DA + 18 (× 10 ³ A / dm ² sec) (4) DA × T is the expression (3). If it is less than the lower limit of 3, the etching may be insufficient and the removal of the soft portion of the surface of the convex portion may be insufficient.
Occurs with a frequency of 0-40%. The reason for this is that if the electrodes are gradually deteriorated, the addition efficiency of the plating will be deteriorated unless more than necessary is applied with a small current density.
If DA × T is equal to or higher than the upper limit of the equation (4), the energized state may become supersaturated especially when the electrode is new at a large current density, so that etching proceeds excessively and the shape of the convex portion deteriorates. Not desirable. As described above, FIG. 2 shows the range in which the relationship between DA and DA × T of the present invention satisfies the above expressions (1) to (4).

[0010]

Example The surface of a work roll for a 5% Cr forged steel temper rolling roll having a diameter of 610 mm was irradiated with a laser beam by a YAG laser processing machine, and laser dull processing was applied to a predetermined roughness pattern. The laser irradiation conditions are as follows. Laser average output: 60 W Laser processing frequency: 8 KHz Roll processing pattern: Hole diameter 170 μm, hole pitch 34
0 μm (both in the roll circumferential direction and the axial direction) Next, the roll is heated to an alkali solution temperature of 50 ° C. and a degreasing time of 120
After electrolytic degreasing and cleaning for sec, electrolytic etching was performed in a Cr acid solution at a liquid temperature of 50 ° C.

Example 1 As the electrolytic etching conditions, current density DA = 20 to 3
It was carried out at 0 A / dm ² and time 400 to 500 sec. After that, chrome plating was performed with a chromic acid solution to a thickness of 5 μm. Using this roll, an annealed coil of low carbon Al-killed steel having a plate thickness of 0.8 mm was temper-rolled at a rolling reduction of 1.0%, and the abrasion resistance of the convex portion of the roll surface was investigated. FIG. 3 shows the wear behavior of the protrusions on the roll surface after rolling 50 Km under pressure regulation. In the conventional method, about 10 before rolling.
The height of the convex portion of the roll surface is 7 μm due to the initial rolling wear.
Therefore, the roll life limit is reached at a rolling length of 10 km. On the other hand, in the present invention, the rolling initial wear of the roll surface projection is not observed in the rolling initial wear in the conventional method, and the roll life is also increased. In the example of the present invention, the initial wear of the rolling was prevented by the Cr plating treatment after removing the soft part of the roll surface layer, and the wear resistance was dramatically improved.

Example 2 As electrolytic etching conditions, current density DA = 20-4
It was carried out at 0 A / dm ² and time 50 to 200 sec.
After that, chrome plating was performed with a chromic acid solution to a thickness of 5 μm. (A) In the case of DA = 20 A / dm ² and DA × T = 3 × 10 ³ (T = 150 sec), as the frequency of use of the electrode increases, the etching becomes insufficient and the removal of the soft portion of the convex surface layer becomes insufficient. The phenomenon will occur. (Area less than the lower limit of expression (3)) (B) In the case of DA = 40 A / dm ² and DA × T = 3 × 10 ³ (T = 75 sec), the abrasion resistance of the convex portion on the roll surface is the same as that in Example 1. It was almost the same.

Example 3 As electrolytic etching conditions, current density DA = 20 to 4
It was carried out at 0 A / dm ² and time 350 to 800 sec. Then, chromium plating was performed with a chromic acid solution to a thickness of 5 μm. (C) In the case of DA = 20 A / dm ² and DA × T = 15 × 10 ³ (T = 750 sec), the abrasion resistance of the convex portion on the roll surface was almost the same as in Example 1. (D) In the case of DA = 40 A / dm ² and DA × T = 15 × 10 ³ (T = 375 sec), when the electrode is new, the energized state becomes a supersaturated state, etching proceeds excessively, and the convex shape is formed. Undesirably deteriorates.

[0014]

INDUSTRIAL APPLICABILITY According to the method of the present invention, it is possible to form innumerable minute irregularities on the surface of the roll by laser dull processing, and by treating this with Cr plating, the abrasion resistance of the roll is improved. Before processing this Cr plating,
It is possible to remove the softened portion of the convex surface layer and form Cr plating with high wear resistance from the state where there is no retained austenite phase softened compared to the roll base, and peeling of the convex portion during rolling occurs In addition, the initial wear during rolling can be greatly reduced, and the roll life can be dramatically improved.

[Brief description of drawings]

FIG. 1 is a diagram showing a cross-sectional shape of a roll surface according to the present invention,

FIG. 2 is a diagram showing electrolytic etching conditions for removing a soft portion of a roll surface convex portion according to the present invention;

FIG. 3 is a diagram showing roll life of the roll of the present invention.

[Explanation of symbols]

 1 roll 2 softening part 3 Cr plating

Claims (2)

[Claims] 1. A surface of a work roll for rolling is scanned so as to irradiate it with high density energy to form innumerable minute irregularities on the roll surface, and the roll thus processed is immersed in a chromic acid solution. In the rolling roll processing method of immersing and chrome-plating, before the chrome-plating treatment of the roll surface, the softened portion of the fine convex surface layer formed by irradiation with high-density energy was removed in advance. Then, a method for producing a dull roll for rolling, which comprises immersing it in a chromic acid solution and subjecting it to chrome plating. 2. A rolling roll which is subjected to chrome plating after the softening portion of the fine convex surface layer on the surface of the rolling roll is removed in advance, and the chrome plating on the roll surface includes degreasing, washing, and electrolysis. Electrolytic chromium plating of 2 to 15 μm is applied to the surface of the roll through etching or the like. At this time, the electrolytic etching is performed in a chromic acid solution with the roll serving as an anode within the range of the following formula to obtain the surface of the rolling roll. A method for producing a dull roll for rolling, characterized in that the softened portion of the surface layer of minute convex portions is removed in advance, and then immersed in a chromic acid solution for chrome plating. 1000 ≦ DA × T ≦ 17,000 DA; current density (A / dm ² ) 10 ≦ DA ≦ 50 T; processing time (se
c)