RU2356666C1 - Method of surface preparation of cold rolling mill rollers - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: method includes making incisions by fraction up to defined roughness on shotblast unit. Regulated roughness is provided ensured by roll die of the first and last stand of wide-strip rolling mill of cold rolling after preliminary grinding of its barrels is notched by iron shot of fraction 0.7…1.5 mm at linear velocity of device wheel V-60 m/s up to receiving of roughness ≥4 mcm, and rollers of the first stand of two-cage reversing mill also after the preliminary grinding of its barrel is notched iron shot of the same fraction at V=60 m/s up to receiving of roughness 3.5…4.0 mcm, herewith operation of notching is implemented for one passage for one passage at amount of cycles, equal to two.

EFFECT: improvement of surface finish of iron cold-rolled sheet.

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Description

The invention relates to a tool for metal forming and can be used in preparation for operation of the rolls of a cold strip steel mill.

Rolls are the main working tool of rolling mills, and in quarto stands they are divided into work and backup rolls. The features of operation and preparation for work of rolls of cold rolling mills are described in sufficient detail, for example, in the book of LI Borovik “Operation of rolls of cold rolling mills”, M., “Metallurgy”, 1968. Preparation of rolls includes processing of their barrels in order to obtain the desired roughness (microgeometry) of the working surface.

There is a method of finishing the rolling rolls of cold rolling mills by electrospark surface treatment of their barrels during rotation of the roll with the installation of a certain gap between the roller and the electrode (see US Pat. No. 3878353, CL B23K 9/16, publ. 15.04.75). However, the implementation of this method is impossible to obtain the required surface roughness of the roll barrels due to the uncertainty of the method parameters.

The closest analogue to the claimed method is the technology of preparing the surface of the rolls of a cold rolling mill, described in the book of V. K. Belosevich and N. P. Netesov "Improving the cold rolling process", M., "Metallurgy", 1971, S. 219-224 .

This technology consists in notching the surface of the roll barrels with steel or cast iron to a predetermined roughness in a shot blasting machine and is characterized by the fact that the hardness of the cast iron chipped fraction is within 700 ... 850 units. HV, and the hardness of steel shot is 580 ... 800 units. Hv. A disadvantage of the known technology is the uncertainty of the basic parameters of the notch (linear rotation speed of the shot blasting wheel, as well as the number of passes and notching cycles) to obtain a specific surface roughness of the rolls.

The technical task of the present invention is the provision of regulated roughness and surface finish of cold rolled steel sheet.

To solve this problem, in the proposed method of preparing the surface of the rolls by notching it with a shot to a predetermined roughness in a shot blasting machine, the work rolls of the first and last stands of a broadband cold rolling mill after preliminary grinding of their barrels are incised with a cast-iron fraction of 0.7 ... 1.5 mm fractions at linear speed V = 60 m / s until a roughness of ≥4 μm is obtained, and the rolls of the first stand of a two-stand mill, also after preliminary grinding of their barrels, are incised with a pig-iron shot of the same fraction at V = 60 m / s until a rough sti 3.5 ... 4.0 microns, while the notching operation is carried out in one pass with the number of cycles equal to two.

The above process parameters are obtained empirically and are empirical.

The essence of the claimed technical solution is to optimize the process of preparing the surface of the roll barrel by notching it with a shot, which ensures the required microgeometry of this surface, and when rolling (training) strip steel, the required clean surface of the sheets.

When implementing this method, pre-selected cast iron fraction based on its size (fraction). Then, the polished rolls are placed in a shot blasting machine, where the barrels are notched in one pass, performing this operation twice. The notch occurs at a given rotation speed of the impeller (shot blasting wheel) of the installation wheel.

An experimental verification of the proposed technology was carried out at OJSC Magnitogorsk Iron and Steel Works. To this end, when notching the work rolls I and IY of the stands of a broadband mill 2500 cold rolling, as well as similar rolls of the 1st stand of a two-stand reversing mill 1700, the notching parameters were varied, evaluating the results on the yield of sheet metal of the required surface microgeometry obtained by rolling on these mills .

The best results (yield quality sheets up to 99.7%) were obtained when implementing the proposed method. Deviations from its recommended parameters worsened the achieved indicators.

So, for example, the use of cast iron fractions of other fractions (other than those offered) reduced the yield of good quality sheet metal to 63 ... 97% when working with the claimed linear speed of the shot blasting wheel of the installation, and the use of steel fraction did not yield high-quality rolled products more than 47% (under high-quality rolled metal refers to sheet steel with the required microgeometry) Reducing the V wheel also reduced the yield of good quality rolled metal. To solve the problem, it was enough to carry out one pass of the notch, twice performing this operation.

It was also found that the goal is achieved by notching the work rolls of only I and IV (last) stands of a broadband continuous mill and only the 1st stand of a reversing mill.

The roll preparation technology selected as the closest analogue (see above) was not tested in the experiments due to the uncertainty of the parameters of the notch operation. Thus, the experiments confirmed the acceptability of the technical solution found to achieve the goal and its advantage over the known object.

Feasibility studies conducted at the Central Laboratory of OJSC MMK showed that the implementation of the present invention in the preparation of rolls of cold rolling mills will increase the yield of quality sheets by at least 5%, with a corresponding increase in profit from sales.

Case Studies

1. Work rolls of the first and last stands of a broadband cold rolling mill 2500 are cut in a shot blasting machine with V = 60 m / s. Rolls are pre-sanded; cast iron fraction of 1.1 mm fraction is used. Roughness (average microroughness height) of the barrel surface 5 microns.

2. The polished work rolls of the 1st stand of the two-stand reversing mill 1700 are subjected to notching at V = 60 m / s with a cast-iron shot of the same fraction. The roughness of the obtained surface is 3.8 μm.

In both cases, the notch is carried out in one pass in two cycles.

Claims (1)

A method of preparing the surface of the rolls of cold rolling mills, including notching it with a shot to a predetermined roughness in a shot blasting machine, characterized in that the work rolls of the first and last stands of the broadband mill after preliminary grinding of their barrels are cut with a cast iron fraction of 0.7 ... 1.5 mm with linear the rotational speed of the wheel of the shot blasting machine V = 60 m / s until a roughness of ≥4 μm is obtained, and the rolls of the first stand of a two-stand reversing mill after preliminary grinding of their barrels are incised with a cast-iron shot of the same fraction at V = 60 m / s to obtain a roughness of 3.5 ... 4.0 mm in this operation when the sipe is performed in a single pass with the number of cycles equal to two.