RU2368441C1 - Operation method of rollers for cold rolling - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: method includes alternation of cyclic loadings of roll and at its operation in stand with regrinding. Excluding of shaft flake at rational usage of effective layer of its surface is provided ensured by acceptable number of cycles loading is defined by increasing of barrel hardness for 3-5 units by Shore from initial value, and removal at refacing is implemented up to reduction of barrel hardness up to initial value.

EFFECT: increasing of rollers resistance of stands for cold rolling of sheet metal.

6 ex, 1 tbl

Description

The invention relates to rolling production, and more particularly to the operation of rolls, and can be used on cold rolling mills of sheet steel.

A known method of operating a roll of a continuous mill quarto cold rolling strips. The method includes alternating the work of the roll in the stand with regrinding. The condition of the roll is controlled by the hardness of the barrel. As the diameter and hardness of the barrel decreases (due to wear and resurfacing), the roll is rearranged in stands, starting with the latter, against the rolling course [1].

The disadvantage of this method is that the roll has a low resistance due to fatigue phenomena developing in the surface layer of the barrel, leading to crumbs and the need for increased removal during refinishing.

There is also a known method of operating the roll, including its operation in the stand, determination of the amount of wear and regrinding of the barrel after each dumping from the stand, and removal during refinishing is 1.7 ... 2.2 of the maximum amount of wear. As the diameter and hardness of the barrel decreases, the roll is rearranged against the direction of rolling from the finishing stands to the draft [2].

The specified method also does not provide high roll resistance, because does not take into account the degree of hardening of the surface layer, determined by the increment of hardness of the barrel.

The closest in their technical essence and the achieved results to the proposed invention is a method of operating a sheet-roll, including the alternation of their work in the mill with an allowable number of loading cycles, with resurfacing with removal of the surface layer of the barrel [3] - prototype. The disadvantage of this method is that the removal during regrinding does not take into account the hardening of the surface layer of the barrel: with insufficient removal of the riveted layer, the roll is crumbled, and with increased - the irrational use of the active layer of the barrel. This leads to a decrease in roll resistance.

The technical problem is to increase the resistance of the roll.

This is achieved by the fact that in the known method, comprising alternating the work of the rolls in the stand with an allowable number of loading cycles, with resurfacing with removal of the surface layer of the barrel, according to the proposal, the permissible number of loading cycles is determined by increasing the hardness of the barrel by 3-5 Shore units from the initial value , and eat during resurfacing lead to a decrease in the hardness of the barrel to its original value.

The essence of the invention is as follows. During the operation of a sheet-rolling roll in a stand, hardening (hardening) of its working layer of a barrel occurs due to the action of cyclic loading. The degree of hardening is expressed in an increase in its shore hardness.

Studies have established that if an increase in hardness of more than 3-5 units is allowed, then the working layer of the roll may collapse, which will lead to an emergency on the mill. When resurfacing without taking into account the increase in hardness due to hardening, the riveted layer and part of the non-riveted layer are removed. Therefore, according to the invention, in the process of grinding the rolls, the hardness of the barrel is measured, and when the hardness decreases to the initial level, grinding is stopped.

As a result, during resurfacing, a complete removal of the riveted layer containing germ microcracks is ensured, and a healthy non-riveted hardened layer is not ground.

Thus, the working layer of the barrel is used most rationally and the roll resistance is increased.

It was experimentally established that with an increase in the degree of hardening of more than 5 units according to Shore, the roll may be destroyed due to the development of fatigue cracks in it. When decommissioning rolls with a lower degree of hardening than by 3 Shore units, the operating time for one filling is shortened, and in addition, a healthy layer of the barrel is removed during refining.

Studies have revealed that if during grinding, leave part of the riveted layer (when removing, which does not provide a decrease in hardness to the original value) and put the roll into operation, then it is possible to spall the surface layer of the barrel and reduce the roll resistance. When grinding the surface layer with the complete removal of the riveted and part of the non-riveted layer with damage, the roll resistance also decreases.

Method implementation examples

Back-up roll made of 75KhMF steel with a diameter of 1490 mm and a hardness of 60 units. HSD (Shore) overwhelmed with the bottom in the 4th stand of the five-stand mill 1700 cold rolling. During the rolling process, the rolls are subjected to cyclic loading. Periodically during rolling, a measurement of the surface hardness is carried out and when the hardness is 64 units. HSDs reload and regrind the roll. During grinding of the roll, the hardness of the surface layer of the roll is measured and after the hardness is reduced to its initial value of 60 units. HSD grinding is stopped and the roll is put into operation.

After the active layer of the roll barrel is completely used up, the roll is rejected. The resistance of the roll during such operation increases, which is characterized by a decrease in the coefficient of specific consumption of rolls: K = 0.8 kg per ton of rolled metal.

Implementation options for the proposed method of operation of the backup rolls are shown in the table.

Table Operating modes and specific consumption of backup rolls from the original
hardness of 60 units Hsd No. p / p The increase in hardness during operation, units Hsd Hardness after grinding, units Hsd K, kg / t one 2 58 0.95 2 3 60 0.85 3 four 60 0.80 four 5 60 0.85 5 6 62 0.93 6 not regl. not regl. 0.94 prototype

From the table it follows that when implementing the proposed method (options 2-4), the roll resistance increases. In cases of transcendental value of the claimed parameter (options 1 and 5) and the implementation of the prototype method (option 6), the roll resistance decreases, as evidenced by the increase in the specific consumption of the rolls.

The technical and economic advantages of the proposed method are that if the permissible number of loading cycles is determined by increasing the hardness of the barrel by 3-5 Shore units from the original value, and removal during resurfacing is carried out to reduce the hardness of the barrel to its original value, this allows you to restore service properties of the roll, to avoid fatigue failure of its barrel and to exclude the removal of a healthy layer. This ensures an increase in the resistance of the roll.

The prototype method is taken as the base object. Using the proposed method will increase the level of profitability of the production of cold rolled sheet steel by 5-7%.

Information sources

1. Polukhin P.I. and others. Sheet rolling and roll service. - M.: Metallurgy, 1967, p. 284 and 285.

2. USSR copyright certificate No. 1342549, class. B21B 28/02, 1987.

3. Borovik L.I. Operation of rolls of hot rolling mills. - M.: Metallurgy, 1968, p.186 and 187.

Claims (1)

A method of operating rolls of cold rolling mills, including the alternation of their work in the mill with an allowable number of loading cycles with regrinding with removal of the surface layer of the barrel, characterized in that the allowable number of loading cycles is determined by increasing the hardness of the barrel by 3-5 Shore units from the original value, and the removal of the surface layer of the barrel during resurfacing is carried out to obtain a surface layer with an initial value of hardness.