JPS62158591A - Surface roughening of cold rolling roll - Google Patents

Abstract

PURPOSE:To form regularly rugged patterns having a fine pitch with high efficiency and to improve wear resistance by subjecting a roll surface to laser dulling then to chrome plating. CONSTITUTION:A laser beam is irradiated on the surface of the cold rolling roll by a laser device in the stage of roughening the roll surface of laser dulling. The irradiated part of the roll melts instantaneously and the molten metal splashes to the periphery to build up, by which recesses and projecting parts are formed and the roughness is provided to the surface. Since the projecting parts have the small wear resistance in metallic structure, the wear resistance is improved by plating Cr thereon. The ruggedness by the laser dulling has gentle profiles and therefore, the Cr plating having high removability can be formed. Since the exfoliation is obviated during rolling, the initial wear of rolling is considerably decreased.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for roughening a cold roll roll such as a temper roll, and more specifically, a method for roughening a cold roll roll by laser dulling, This invention relates to a surface roughening method for obtaining a cold rolling roller with wear resistance of 4.I'P by chromium plating.

[Conventional technology]

Surface quality is an important quality of rolled steel sheets.

Surface quality includes beauty, adhesion of paint and enamel, press workability, corrosion resistance, gloss, etc., and the geometric shape of the board, that is, the surface roughness, has an important influence on these properties.

The most common way to obtain a metal surface with the desired surface roughness for each application is to process the surface of a cold roll or/and temper roll roll to a predetermined roughness.
Method U: Rolls a steel plate with this roll at a predetermined pressure to transfer the roughness of the roll surface onto the plate surface.

Conventionally widely used methods for roughening the roll surface include shot blasting and electrical discharge [υ:].

Shot blasting is very simple, and this process also improves the roll's wear resistance by hardening the roll surface.
- However, the roughness is uneven, and hard rolls have long I+! There are drawbacks such as the need for loading time between . . . and difficulty in forming deep roughness.

In electrical discharge machining, roughness is controlled by rotating rolls and +lq
This is done by changing the applied voltage and frequency between the electrode moving in the l+ direction, but since the range of the spark that determines the size of the crater is determined by the shape and dimensions of the electrode, it is possible to It is difficult to obtain a small roughness, and the protrusions produced by electrical discharge machining are mechanically weak, and the initial wear of the rolls during rolling is severe, resulting in severe changes in the roughness of the transferred plate surface.

In contrast to the above two methods, a processing method using a laser beam (hereinafter referred to as laser gluing processing) has recently been proposed.

For example, JP-A-56-160892, JP-A-5G-255
57, JP-A-54-61043, JP-A-55-9479
0, etc. These describe in detail how to irradiate the laser pulse, but do not mention the characteristics of the irradiated roll.

[Problem that the invention seeks to solve]

Laser dulling can efficiently form a regular uneven pattern with a fine pitch on the roll surface. However, when temper rolling was performed using a roll whose surface had been roughened by laser dulling, it was found that the initial wear of the roll was quite large. In order to investigate the cause of this, the roll was sliced into rounds and the cross section near the surface was examined at one point and the hardness distribution. As a result, it was found that a retained austenite phase, which is softer than the IjL material, existed near the very surface of the convex part. .

The object of the present invention is to provide a method for roughening a roll that causes less wear during rolling and less decrease in roughness by imparting wear resistance to the surface of this retained austenite phase.

[Means for solving problems]

A technical means for solving the problem described in L is a cold rolling roll characterized in that when roughening the cold rolling roll, the roll surface is subjected to laser dulling and then chrome plating is applied. This is a roughening method.

[Effect]

When roughening a cold rolling roll by laser dulling, when a laser device irradiates the roll surface with a laser beam to roughen the surface, the irradiated part of the roll melts instantaneously. Roughness is imparted by the formation of four parts of the hole and a convex part as the metal scatters and bulges around the surface. This convex part has a metallographic resistance of 19
! Since the JL property is low, Cr plating is performed, which improves wear resistance.

The thickness of the Cr plating layer is 10JLm to 15#Lm. The plating layer thickness was 1104m-15B for 15J.
This is because if the thickness exceeds Lm, peeling will occur easily, and l
This is because sufficient #yl abrasion resistance cannot be ensured if less than ogm. In laser dull processing, unlike the sharp unevenness in shot dull processing, etc., the unevenness of the rough surface has a gentle profile, so when Cr plating, the potential density is uniform and the II! The two pressures become equal. Therefore, there is an advantage that peeling of the Cr film during rolling is less likely to occur.

〔Example〕

Using a small laboratory-type rolling mill with a roll diameter of 1 yen 70 mm, the hoop-shaped material was continuously rolled using the unrolled 1 roll to check the wear of the rolls and changes in the roughness of the material surface.

-The chemical composition of the roll subjected to the e test is: C: 0.85’T(,,::% Si: 0.8 tonzuke% Mn: 0.4 revision! −% Ni: 0.15 nails 1% Cr: 2.9% by weight Mo: 0.29% by weight V: 0.01 Ball amount% This is the component □ system that is usually widely used.

The manufacturing process of the roll is as follows.

That is, after casting the molten steel with the above components, the temperature is 110
Forged at 0°C to a forging ratio of 3.5. Then 950°C
The so-called norm treatment was performed by heating and air cooling. This is 8
After performing carbide spheroidization treatment at 00°C for 10 hours and at 700°C for 10 hours, it was machined to predetermined dimensions. After machining, heating at 900℃ and quenching in oil, 65
It was tempered at 0°C (If and machined to final dimensions).The surface layer was further heated to 900°C by induction heating.
After heating to °C, it was quenched in water, tempered at a low temperature of 150 °C, and then subjected to final surface polishing.

The roll subjected to such treatment exhibits a solid structure in which spherical particles are uniformly distributed in the Marsantate matrix.

The surface of this roll was roughened to a predetermined roughness by irradiating a pulsed CO2 gas laser beam using a mechanical chopper.

The laser irradiation conditions are as follows.

Laser output 2KW Pulse frequency: 56KHz Laser beam diameter: 200m Energy placement: 6.4X l 06W/ctn'
Irradiation time per pulse: 13 ILsec Pitch of crater formed on the roll surface 2. 70 uLm in both the roll circumferential direction and the axial direction Next, the roll surface was defilmed and cleaned and coated with Cr.

I went to Ki. The thickness and plating conditions of Cr plating are as follows.

The plating bath is Sargent bath (Cr03: 200g/vertical,
A Cr plating thickness of 10 #Lm was obtained using static IJ using H2S04 (2 g/d) at a bath temperature of 50'O1 and a density of 30 A/d.

Using this roll, a cold-rolled and annealed plate of low carbon An-killed steel having a plate thickness of 0.8 mm was subjected to skin pass rolling at a reduction ratio of 0.8%, and a decrease in plate surface roughness was examined. Root surface roughness reduction ΔRa after rolling 50 km in length calculated from the number of roll transfers
The results of the evaluation are shown in Table 1. Table 1 also lists comparative examples in which only laser dull processing was performed.

A comparative example in which Cr plating was performed after shot blasting is also shown.

In the examples of the present invention, by combining the advantages of laser dull processing with Cr plating, the decrease in root surface roughness was small and the wear resistance was improved.

C Effects of the invention] By using the undeveloped IJJ method, it is possible to form a well-ordered concavo-convex pattern with fine pinches on the roll surface by laser processing with high efficiency, and since this is Cr-plated, III#
WiIc properties are improved, and the unevenness formed by laser dulling has a gentle profile, so
Cr plating with high peeling resistance can be formed and peeling does not occur during rolling.

Initial rolling wear can be significantly reduced.

Claims (1)

[Scope of Claims] 1. A method for roughening a cold roll roll, which comprises performing laser dulling on the roll surface and then applying chrome plating upon roughening the cold roll roll.