JPH048121B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of rolling a metal sheet using a multi-stage cluster rolling mill.

Improvement in rolling efficiency is achieved by high pressure and high rolling deceleration. A multi-stage cluster rolling mill such as a Sendzimer rolling mill is one type of rolling mill that can roll a plate material at a high rolling reduction ratio. The rolling torque is transmitted from the driven intermediate roll to the work roll by the friction between the two rolls.

However, when high-speed rolling is performed using a multi-stage cluster rolling mill, there is a problem in that slips occur between the work roll and the driving intermediate roll. This is because the friction coefficient between the rolls decreases as the rolling speed increases. Slip induces chatter in work rolls, etc., and causes so-called chatter marks on the rolled plate material, impairing the surface quality.
In addition, the slip causes the rolls, housing, etc. to chatter, making it impossible to perform stable rolling.

This invention was made to solve the above-mentioned problems in rolling plate materials using a multi-stage cluster rolling mill, and aims to provide a rolling method that does not cause slips between the rolls at high speed and under high pressure. It is something.

This invention attempts to prevent roll slip by focusing on the roll surface roughness, which has hitherto had no particular restrictions in relation to roll-to-roll slip. That is, in this invention, the equivalent roll surface _roughness a of the work roll and the driving intermediate roll is 0.1μ.
The plate material is cold rolled using work rolls of m or more and drive intermediate rolls. The equivalent roll surface roughness _a is given by the square root of the mean square value of the average roughness of the slope portion (or its equivalent portion) of the work roll and the driving intermediate roll.

By limiting the surface roughness of the work roll and the driving intermediate roll as described above, the coefficient of friction between the rolls can be maintained above a required value, and slip between the rolls can be prevented. Therefore, roll chatter does not occur, high-speed rolling is possible, and a rolled plate material with excellent surface properties without chatter marks can be obtained. Furthermore, since the rolling torque is efficiently transmitted to the work rolls from the driving intermediate rolls, high reduction rolling is possible.

Furthermore, since the method of the present invention merely adjusts the surface roughness of the work roll and intermediate roll, it can be easily applied even to existing equipment. This invention is particularly effective for rolling plate materials that do not require high gloss.

The surface roughness of the work roll is transferred to the product.
Therefore, the upper limit of the equivalent roll surface finish _a is determined by the required surface quality of the product. Generally, it is desirable that the equivalent raw surface roughness _a is 8 μm or less.

Further, the surface hardness of the work roll and the driving intermediate roll must be 70° or more in terms of Shore hardness. If the angle is less than 70°, the surface texture of the back-up roll will be transferred to the driving intermediate roll.

This invention will be explained in detail below.

FIG. 1 is a diagram showing the relationship between the roll circumferential speed V _R and the inter-roll friction coefficient μ _R using the roll surface roughness as a parameter. As is clear from this diagram, as the roll circumferential speed V _R increases, the friction coefficient μ _R decreases, and when the roll circumferential speed V _R increases to a certain extent (for example, 100 to 200 m/min or more), the friction coefficient becomes almost constant. Become.

On the other hand, FIG. 2 is a diagram showing the relationship between the equivalent roll surface roughness _a and the inter-roll friction coefficient μ _R using the roll circumferential speed V _R as a parameter. As is clear from this diagram, as the surface _roughness a increases, the friction coefficient μ _R gradually increases. In addition, the diagram shows that when the roll peripheral speed V _R becomes high speed of 300 m/min or more, _a
The relationship between and μ _R is represented by curve A shown by a dotted line in the figure.

By the way, when the intermediate rolls are driven in a multi-stage cluster rolling mill, the friction coefficient μ _R is required for torque to be transmitted from the intermediate rolls to the work rolls.
must be as follows.

μ _R T/PRsinθ Where, R: Radius of the work roll P: Rolling load T: Rolling torque converted to the work roll θ: Angle between the center lines of the work roll and the intermediate roll and the horizontal (see Figure 3) Above formula The necessary friction coefficient μ _R given by was determined by actual rolling, and was found to be 0.04 to 0.055 at a rolling reduction of 50 to 50%. According to the actual measurement results, in order to perform high-speed rolling without causing slip between the rolls, the friction coefficient μ _R must be 0.06 or more with some margin. According to FIG. 2, in the case of high-speed rolling (curve A), the equivalent roll surface roughness _a must be 0.1 μm in order for the friction coefficient μ _R to be 0.06 or more.

The rolling conditions in the actual rolling described above are as follows.

The configuration of the roll cluster is as shown in Figure 3, and the roll diameters are Work roll 1: 200 mm, Intermediate roll 2: 290 mm, Side back up roll 3: 630 mm, Center back up roll 4: 290 mm, and the plate material is 3.2 mm thick x 1000 mm wide. It was made of 40K high tensile strength steel and the rolling speed was 300 m/min.

A multi-stage cluster rolling mill to which this invention is applied does not necessarily have to have roll clusters symmetrically arranged vertically. For example, it may be a rolling mill in which a six-stage roll cluster is arranged on the upper side and two stages of rolls (work rolls and back-up rolls) are arranged on the lower side.

Example work roll diameter: φ200mm Intermediate roll diameter: φ290mm Side back-up roll diameter: φ630mm Center back-up roll diameter: φ290mm Work roll surface roughness R _aW : 0.32 μmR _a Intermediate roll surface roughness R _aI : 0.45 μm R _a Equivalent roll surface roughness _a : 0.39μmR _A plate material: thickness 3.2mm, width 1000mm 40K high tensile steel rolling reduction rate 20~35% When rolled at a rolling speed of 200~350m/min or higher, slip between the rolls occurred. The invention of chattering was not recognized.

[Brief explanation of drawings]

Figure 1 is a diagram showing the relationship between roll peripheral speed and friction coefficient between rolls, Figure 2 is a diagram showing the relationship between equivalent roll surface roughness and friction coefficient between rolls, and Figure 3 is an example of a roll cluster. , and is an explanatory diagram of a calculation formula for a friction coefficient. 1...Work roll, 2...Intermediate roll, 3,
4... Backlash Prowl.

Claims (1)

[Scope of Claims] 1. A method of rolling a plate material using a rolling mill equipped with at least one roll cluster consisting of a work roll, a driving intermediate roll, and a back-up roll, wherein the equivalent roll surface roughness of the work roll and the driving intermediate roll is A method for rolling a plate material using a multistage cluster rolling mill, characterized in that the width _a is 0.1 μm or more and 8 μm or less. however, R _aW : Slope average roughness of the work roll surface R _aI : Average roughness of the slope equivalent part of the driving intermediate roll surface