JPH09271813A - Roll for cold rolling - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rolling roll compatible for a long life and stabilized passing by forming many oval holes in the work roll for cold rolling and specifying the angle formed between the major axis of hole and roll axis. SOLUTION: By irradiating the surface 2 of the work roll 1 for cold rolling with pulse laser beam, many oblong holes are formed. At this time, the angle θformed between the major axis of hole and roll axis is gradually enlarged symmetrically to the center line more toward a roll end part from a roll center part. By this method, distribution of a friction coefficient is formed so as to maximize the coefficient of friction at the roll center part and to prevent meandering of plate, the work roll 1 for cold rolling capable of executing stabilized and low cost operation is obtained.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a work roll used for cold rolling of metal.

[0002]

2. Description of the Related Art Conventionally, since the surface roughness of a rolling roll is inversely proportional to the rolling tonnage and the frictional force with the steel sheet is reduced to cause slip, the roll is replaced at a constant tonnage. . The surface of the roll drawn from the rolling mill is roughened for the purpose of recovering the frictional force with the steel sheet. As a method of surface roughening, there are grinding stone, shot blast, electric discharge machining and the like. These methods have a problem that the controllability of the unevenness of the roll surface is poor, and sometimes the plate meanders during rolling. As a method for solving such a problem, a method using a pulse laser is known (see, for example, Japanese Patent Publication No. 58-25557). The conventional laser drilling of rolls has been to drill circular holes at regular intervals.

In the method of roughening the roll surface using a pulse laser, it is possible to form holes at a constant interval with good reproducibility, but the mechanism of generating the frictional force between the roll and the steel sheet is not fully understood. Didn't. Therefore, it has not been possible to establish the strip running stability over the entire time during use in the rolling mill.

[0004]

SUMMARY OF THE INVENTION The present invention has been proposed in view of the problems of the prior art as described above, and an object of the present invention is to provide a long life in a metal cold rolling process.
An object of the present invention is to provide a rolling work roll capable of always achieving stable strip passing.

[0005]

The present invention advantageously solves the problems of the prior art in a work roll for cold rolling in which a large number of holes are formed on the roll surface by irradiation with pulsed laser light. , The shape of the hole is an ellipse, and the angle formed by the long axis of the hole with respect to the roll axis is formed so as to increase as the position of the hole goes from the center to the end of the roll. Is characterized by. Further, the shape of the holes is a circle, and the distance between the holes in the cylinder length direction is formed so as to increase as the position of the holes increases from the center to the end of the roll.

The present invention is based on the following facts newly found as a result of detailed investigation and research on the effect of imparting unevenness to the roll surface. That is, as a result of detailed research on the influence of the hole shape on the roll surface on the generation of frictional force, the inventors made the hole shape an ellipse, and the angle formed by the long axis of the hole with respect to the roll axis is the hole. It has been found that as a result of forming so that the position of becomes larger from the central part to the end part of the roll, remarkable threading stability not obtained by the conventional method can be obtained.

The inventors of the present invention firstly found that the determining factor of the frictional force of a roll having a hole machined on its surface is the edge length of the hole projected in the roll axial direction. This is the knowledge obtained from the following experiment. That is, diameter 70mm, trunk length 100mm
Laser drilling with various ellipticities is performed on the surface of the small work rolls with a constant area ratio of holes, and it is installed in a cold rolling experimental machine and a rolling experiment is performed at a plate speed of 500 m / min. Was measured.

FIG. 3 is a diagram showing the dependence of the friction coefficient of the roll on the rolling amount using the ellipticity of the hole as a parameter.
Here, the ellipticity is defined by the ratio of the hole width in the roll cylinder length direction to the hole width in the roll circumferential direction. The rolling load is converted to the actual machine. The axis of the ellipse of the hole drilled on the roll is aligned with the roll axis. Hole width in the roll circumferential direction is 100μ
It was fixed at m, and the hole width in the lengthwise direction of the roll was changed. FIG.
It can be seen that the friction coefficient increases as the ellipticity increases. Further, it can be seen that after the period of decreasing the friction coefficient at the initial stage of rolling, the amount of attenuation of the friction coefficient decreases, and the friction coefficient is maintained at a substantially constant level. In FIG. 3, the dotted line shows the result of the grinding wheel grinding roll for comparison.

Assuming that the rolling amount that causes slipping is the limiting rolling amount, the limiting rolling amount of the laser hole drilling roll can be at least twice as much as that obtained by the ordinary grinding wheel grinding (slip at about 1000 tons). I understand. That is, the laser hole drilling roll can be expected to have a rolling life that is at least twice as long as that of the grindstone grinding roll used for normal operation. However, in terms of operation, it is not so good that the ellipticity of the hole is increased, and there are restrictions due to the balance of frictional force with the rolls in the front-back process and the plate quality. Taking this into consideration, the ellipticity of 1 at which the friction coefficient is 0.01 to 0.15
-12 are desirable.

On the other hand, the actual rolling roll has a body length of 2000
The width is about mm, and the degree of contact with the board varies depending on the location. The rolling roll is crowned for the purpose of promoting outward plastic flow from the center of the plate (the center of the roll is thickest and narrowed toward both ends). Deformation of the plate in the roll axis direction enables rolling with a uniform thickness. Further, it is desirable that the central portion is strongly contacted to prevent meandering.

From the above, it is desirable to increase the friction coefficient of the roll in the central portion. According to the above knowledge, it can be inferred that this can be realized by lowering the ellipticity of the hole from the center to the end of the roll, but in order to actually change the hole shape, a complicated mechanism is required. Is necessary and is not necessarily suitable for industrial application.

The inventors have focused on changing the angle of the ellipse and reducing the hole area ratio as a method of changing the friction coefficient while keeping the shape of the hole the same. According to experiments by the inventors,
The frictional force of the roll whose surface is machined is determined by the edge length of the hole projected in the roll axial direction. Therefore, if the principal axis angle of the ellipse with respect to the roll axis is changed or the hole area ratio is reduced, the edge length of the hole projected in the roll axis direction can be expected to be changed. FIG. 4 is a diagram showing the dependency of the friction coefficient of the roll on the rolling amount, with the elliptical hole having a major axis of 300 μm and a minor axis of 100 μm, and the angle of the major axis with respect to the roll axis as a parameter. From FIG. 4, by changing the major axis angle of the ellipse with respect to the roll axis, it is possible to change the friction coefficient while keeping the hole shape the same.

As another method, when the shape of the holes is a circle, the distance between the holes in the cylinder length direction is formed so as to increase as the position of the holes increases from the center to the end of the roll. As a result, the hole area ratio can be reduced. Also by this method, the friction coefficient can be changed while keeping the hole shape the same.

The working method of the cold rolling roll of the present invention is as follows:
A pulse laser beam having a pulse time width of 30 μs or less is condensed into a circle or an ellipse to form a hole. Pulse width is 30 μs
If it exceeds, the hole formability (depth) deteriorates due to heat transfer loss. Furthermore, assuming high-speed machining in the production process, with a pulse with a long time width, with the roll rotation,
The irradiated site moves in the roll circumferential direction. Therefore, the equivalent irradiation area is increased and the heat input density is decreased. As a result, the workability is deteriorated and desired hole drilling cannot be performed. Therefore, the processing laser is required to have both short pulse and high-speed repetition. As a pulse laser having such performance, a carbon dioxide gas laser having a Q switch mechanism inside the resonator can be used.

A cylindrical lens or a cylindrical mirror is used to collect the pulsed laser light output from the laser device into an elliptical diameter. The elliptical beam can be rotated by rotating the cylindrical lens or mirror in a plane perpendicular to the beam. This allows the axial direction of the holes on the roll to be freely controlled. Also, by controlling the moving speed of the laser beam in the roll axis direction,
The area ratio of holes can be changed. In this way, the stability of strip running over the entire time of use in the rolling mill is established,
It is possible to realize a long-life cold-rolling work roll that can be applied to actual operations.

[0016]

FIG. 1 shows a work roll 1 for cold rolling.
It is a figure which shows typically a part of elliptical hole 3 formed in the surface 2 of (only a trunk | drum is displayed). FIG. 2 shows the elliptical hole 3 in an enlarged manner. The long axis of the hole formed on the surface of the work roll 1 has an angle θ with respect to the roll axis. Since the friction coefficient depends on the projection length of the wet edge length of the hole in the roll axial direction 4, the friction coefficient can be reduced by increasing the angle θ. Therefore, by gradually increasing the angle θ of the hole from the center of the roll toward the end of the roll, the distribution of the friction coefficient can be formed so as to maximize the friction coefficient of the center of the roll. The roll axial pitch Pa and the roll circumferential pitch Pc of the holes are appropriately determined according to the hole dimensions, the area ratio of the hole processing area to the total surface area of the roll, and the like, and the roll axial pitch Pa is 300 to 1000 μm.
Degree, roll pitch Pc is 300 to 2000 μm
The degree is appropriate.

FIG. 5 is a schematic diagram of an apparatus showing an example of a processing apparatus for forming the elliptical hole 3 on the roll surface 2. The laser beam L output from the laser oscillator 5 is guided to a focusing head 7 installed on a stage 6 that is capable of translational movement in the roll axis direction 4. The condensing head 7 is a plane mirror 8,
It is composed of a cylindrical lens 9, a spherical lens 10, and a processing head 11. The assist gas 12 is supplied into the processing head 11 from the gas introduction port 13. The work roll 1 is supported by a stand 14 and is rotated at a constant speed by a rotation drive device 15.

The laser oscillator 5 is a Q-switch carbon dioxide laser in which a Q-switch device consisting of a telescope lens and a rotating chopper is arranged inside the resonator. FIG. 6 shows the time waveform of the output light pulse of the Q-switch carbon dioxide laser. This laser has an initial spike component with a time width of 100 ns to 1 μs and a peak power of 5 kW to 300 kW, a time width of 0.9 μs to 29 μs, and a peak power of 2 kW to 5 k.
A laser pulse composed of a tail component of W is generated.

FIG. 7 shows the cross-sectional distribution of the laser light intensity, and the circular laser beam S ₀ output from the laser device S is incident on the cylindrical lens 9. Circular laser beam S
Reference numeral ₀ denotes a cylindrical lens 9 which is an oval (elliptical) laser beam S
Converted to ₁ . The elliptical laser beam S ₁ is focused on the roll surface 2 by the spherical lens 10. The distance X between the cylindrical lens 9 and the spherical lens 10 is approximately the focal length of the cylindrical lens 9.

FIG. 8 is a copy of a photomicrograph of the hole 3 formed on the roll surface 2 observed from above, and a sectional shape view of the hole measured by a stylus type surface shape measuring instrument. The depth of the hole is about 25 μm, the short side diameter is about 100 μm, and the long side diameter is about 20.
0 μm.

FIG. 9 is a diagram showing the relationship between the hole forming method and the meandering frequency in the strip. It can be seen from FIG. 9 that the work roll of the present invention has a smaller meandering frequency than the conventional method in which circular holes are formed on the surface at equal intervals.

[0022]

EXAMPLE A steel plate was cold-rolled at a rolling reduction of 30% using a work roll drilled by the method of the present invention and a conventional method.
The material of the roll is Cr-containing forged steel, the dimensions are 570 mm in diameter,
The body length is 1420 mm. Raw steel, thickness 2 mm, width 100
It is 0 mm. The number of rolling tests is 10 in each example. The results of the rolling test are as follows.

[Invention Example 1] Laser conditions: Q-switch carbon dioxide laser Pulse energy: 50 mJ Pulse repetition frequency: 12 kHz Average output: 600 W Focused beam shape: 90 × 320 μm Hole shape: FIG. 7 long axis 300 μm short axis 100 μm Depth 30 μm Major axis angle: Roll center 0 ° to roll end 45 ° (increase in cubic function) Hole machining area ratio: 6% Meander frequency: 1 time / 1000 tons

[Invention Example 2] Laser condition: Q-switch carbon dioxide laser Pulse energy: 50 mJ Pulse repetition frequency: 12 kHz Average output: 600 W Focused beam shape: 90 × 320 μm Hole shape: Circle diameter 170 μm Depth 30 μm Hole interval: Roll Central 340 μm to roll end 640 μm (increase in cubic function) Meandering frequency: once / 1000 tons

[Comparative Example 1] Cold rolling was performed with a roll having circular holes formed at equal intervals on the roll surface. In this example, the roll of the present invention has a higher meandering frequency, requires constant monitoring by a skilled operator, and has a high production cost.

[0026]

As is clear from the above description, according to the work roll of the present invention, in the cold rolling of steel, the friction coefficient at the center of the roll can be maximized and the meandering of the plate can be prevented. It is possible to provide a cold-rolled work roll capable of stable and inexpensive operation.

[Brief description of drawings]

FIG. 1 is a view schematically showing the appearance of holes formed on the surface of a work roll for cold rolling.

FIG. 2 is a diagram schematically showing an enlarged appearance of holes formed on the surface of a work roll for cold rolling.

FIG. 3 is a diagram showing a relationship between a roll friction coefficient and a rolling amount with a hole ellipticity as a parameter.

FIG. 4 is a diagram showing a relationship between a friction coefficient and a rolling amount with an angle formed by a long axis of a hole with respect to a roll axis as a parameter.

FIG. 5 is a schematic view showing an example of a processing device for forming an elliptical hole with a variable angle on the roll surface.

FIG. 6 is a diagram showing an example of a time waveform of a pulse laser used for processing an elliptical hole.

FIG. 7 is a diagram schematically showing a cross-sectional shape of pulsed laser light on an incident side and an emitting side of a cylindrical lens and a spherical lens.

FIG. 8 is a copy of an enlarged photograph of the elliptical hole of the present invention taken from above and a sectional shape view of the hole measured by a stylus type surface shape measuring instrument.

FIG. 9 is a diagram showing the relationship between the meandering frequency of the present invention and the conventional method.

[Explanation of symbols]

 1 Work Roll 2 Roll Surface 3 Elliptical Hole 4 Roll Axial Direction 5 Laser Device 6 Translation Stage 7 Focusing Head 8 Planar Mirror 9 Cylindrical Lens 10 Spherical Lens 11 Processing Head 12 Assist Gas 13 Gas Inlet 14 Stand 15 Rotation Drive

Claims (2)

[Claims] 1. A work roll for cold rolling in which a large number of holes are formed on a roll surface by irradiation with pulsed laser light, the shape of the holes is an ellipse, and the long axis of the holes is formed with respect to the roll axis. A work roll for cold rolling, characterized in that corners are formed so as to be symmetrically increased from the center of the roll to the end of the roll. 2. A work roll for cold rolling in which a large number of holes are formed on the roll surface by irradiation with pulsed laser light, the shape of the holes is circular, and the distance between the holes in the cylinder length direction of the work roll is A work roll for cold rolling, characterized in that the hole is formed so that the position of the hole increases from the central portion of the roll toward the end portion.