RU2231406C1 - Roll operation method in skin pass four-high rolling stand - Google Patents

Abstract

FIELD: rolled stock production, possibly in one -stand skin-pass four-high rolling mills.

SUBSTANCE: method comprises steps of multiple alternation of stand operation when rolling rolls are in contact with backup rolls and knurling their barrels; realizing knurling of mean portion of roll barrels along length equal to that of skin pass rolled strips according to surface roughness Ra less than respective value on end portions of roll barrels by 1.4 - 2 times; sustaining linear load at contact of rolling rolls with backup rolls in range 0.06 -0.18 t/mm. Invention provides compensation of backup roll wear caused by influence of rolling roll roughness and of linear effort of mutual forcing of rolls.

EFFECT: enhanced strength of backup rolls, improved quality of rolled strips.

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Description

The invention relates to rolling production and can be used on single-cage quarto training mills.

There is a known method of operating rolls during multi-pass rolling of strip metal, according to which the surface roughness is created on the work rolls, the roughness of the rolls being uneven along the length of the barrels, and in even passages, the roughness of the work rolls decreases, and in odd passages it increases from 1.2 to 2.5 from the middle of the barrel to the edges times [1].

The disadvantage of this method is the formation of a non-uniform roughness across the width of the strips, as well as uneven wear of the backup rolls. This method is not applicable for training mills.

There is also a known method of operating rolls of a continuous cold strip rolling mill, according to which various roughnesses are applied to the work rolls along the barrel length and along the stands of the 5-stand mill. At the same time, work rolls are used in stands with heavy loads (the first stands of the mill), in which the surface of the middle part along the roll length has a small roughness (less than 0.3 μm Ra), and rough at the end sections of the roll (0.7-1, 0 μm Ra). In stands with lower loads, work rolls with a rougher surface in the center of the roll than at the edges are used [2].

The specified method of operation of the rolls leads to increased wear of the backup rolls, the formation of uneven roughness along the width of the strips and is not applicable for single-train temper mills.

The closest in its technical essence and the achieved results to the proposed invention is a method of operating rolls of a training stand of a quarto, including the multiple alternation of work in a stand of work rolls in contact with support with resurfacing and notches of their barrels with a shot [3] - prototype.

The disadvantages of this method are as follows. In the process of training the strips, the work rolls with the notched barrel wear out the surface of the backup rolls, and this wear is maximum in the middle part of the backup roll barrel in a section whose length is equal to the width of the strip, and the force of mutual pressing of the rolls is maximum. The end sections of the back roll barrel wear less intensively. Uneven wear of the back roll barrel leads to a violation of its profiling, deterioration in the accuracy and flatness of the strips, and also necessitates additional transshipments and regrindings that reduce its durability.

The technical problem solved by the invention is to increase the resistance of the backup rolls and the quality of the trained strips.

To solve the technical problem in the known method of operating the rolls of a training stand of the quarto, including the repeated alternation of work in the stands of work rolls in contact with the support with resurfacing and notches of their barrels, according to the proposal, a notch of the middle part of the barrel of work rolls for a length equal to the width of the trained strips is carried out to a surface roughness Ra, smaller than the end sections of the barrel, 1.4-2.0 times, and when working in the stand, the linear load in the contact of the work rolls with the supporting rolls is kept equal to 0, 06-0.18 t / mm.

The invention consists in the following. The notch of the middle part of the barrel of the work roll with a length equal to the width of the strip to a given surface roughness allows you to get a strip with high quality surface finish. Since the end sections of the barrel of the work roll are cut to a surface roughness of 1.4-2.0 times more than its middle part, during the rotation of the mutually pressed work and back-up rolls during training in areas with a higher surface roughness, the wear of the back-up roll increases and, Thus, alignment of the wear of the backup roll along the length of its barrel is achieved. The uniform wear of the back roll barrel improves the quality of the trained strips and increases its durability. At the same time, wear leveling, the most complete transfer of the microrelief of the rolls to the annealed steel strip and the elimination of the yield area in the tensile diagram of the strip samples are achieved with a linear load in the contact of the work and backup rolls in the range of 0.06-0.18 t / mm.

It has been experimentally established that if the ratio of the surface roughness at the end portion of the barrel of the work roll Ra _to the surface roughness in its middle part Ra _s is less than 1.4, then increased wear of the middle part of the barrel of the backup roll is maintained. The same type of wear will occur when the linear load in the contact of the work and backup rolls is less than 0.06 t / mm. An increase in the ratio of Ra _to Ra _from more than 2.0 or linear load q more than 0.18 t / mm will lead to overcompensation: in this case, the wear of the end sections of the back roll barrel will exceed the wear of the middle part. Uneven wear reduces the stability of the backup roll and the quality of the trained strips.

Method implementation examples

For the training of cold-rolled annealed strips with a cross section of 0.5x1000 mm, the working and backup rolls are prepared. Work rolls of a temper mill with a barrel length S = 1400 mm, having a barrel diameter of 250 mm and a shore hardness of 94 HSD, are ground and profiled with zero convexity. The polished work rolls are placed in the chamber of the shot blasting machine and subjected to notching by cast-iron shot in two stages. The middle sections of the barrels of both rolls with a length of B = 1000 mm are incised to a surface roughness Ra _c = 2.5 μm, and the end sections of 200 mm each are each incised to a roughness Ra _k = 4.25 μm. In this case:

.

.

In the cage of the single-chamber training mill 1400, first, the polished back-up rolls with a barrel diameter of 840 mm and Shore hardness 62 HSD, profiled with zero convexity, are filled up, then the incised work rolls are covered up.

Rolls of cold-rolled strips are sequentially installed on the unwinder, the strips are set in rolls. Using hydraulic pressure devices create a training force P = 168 t and train the bands. The linear load q in the contact of the work and backup roll in this case is:

Periodically, after training 200-250 tons of strips, the work rolls are transshipped with a worn surface roughness.

In the process of training, the middle part of the back roll barrel is loaded more intensively. But due to the fact that the surface roughness of the barrel of the work roll in its middle part with a length of B = 1000 mm is less than at the end sections, the wear is aligned along the length of the roll of the backup roll. Due to more uniform wear of the back-up roll, its resistance is increased to 10 thousand tons of trained metal in one campaign, the quality (accuracy and flatness) of the strips is improved, the need to adjust machine profiling of work rolls as the back-up is worn out is eliminated.

Variants of the implementation of the method of operating the rolls of the training stand of the quarto and indicators of their effectiveness are presented in the table. From the table. it follows that when implementing the proposed method (options 2-4), an increase in the stability of the backup rolls and the quality of the trained strips is achieved. In cases of transcendental values of the declared parameters (options 1 and 5), the stability of the backup rolls and the quality of the strips are reduced. Also lower indicators of the stability of the backup rolls and the quality of the trained strips occur during the implementation of the prototype method (option 6).

Technical appraisal and economic advantages of the proposed method are as follows. The wear rate of the backup rolls directly depends on the surface roughness of the work rolls and the linear force of their mutual pressing. The influence of these two factors is mutually compensated.

Therefore, the notch of the middle part of the barrel of work rolls for a length equal to the width of the trained strips, to a surface roughness Ra, less than the end sections of the barrel, 1.4-2.0 times, and when working in a stand with a linear load in contact of the work rolls with supporting equal 0,06-0,18 t / mm, provide alignment of wear along the length of the barrel of the backup roll, increasing its durability and quality of the strips.

As a basic object in determining the economic efficiency of the proposed method adopted the prototype method. Using the proposed method will increase the profitability of the production of cold rolled sheet steel by 3-4%.

Sources of information

1. Autosvid. USSR No. 1215772, IPC B 21 V 1/38, 1986.

2. Application No. 59-10403, Japan. IPC 21 V 1/28, 21 V 27/02, 1984.

3. L.I. Borovik, A.I. Dobronravov. Technology for the preparation and operation of rolls of sheet mills. - M.: Metallurgy, 1984, p. 6-8, 54-55.

Claims (1)

A method of operating rolls of a quarto training stand, including multiple alternating work in the stand of work rolls in contact with support grindings and notches of their barrels, characterized in that the notch of the middle part of the barrel of work rolls for a length equal to the width of the trained strips is carried out until the surface roughness Ra, less than the end sections of the barrel, 1.4-2.0 times, and when working in a stand, the linear load in the contact of the work rolls with the support rolls is kept equal to 0.06-0.18 t / mm.