SU1235573A1 - Method of preparing support rolls of quarto mills for operation - Google Patents

Description

The invention relates to rolling production and can be used in the preparation for the work of the support rolls of the quarto mill.

The aim of the invention is to increase the durability of the support rolls.

Fig. 1 shows a zhen-pattern of the distribution of residual stresses along the radius of a support roll with a peeling surface layer; in fig. 2 - the dependence of the durability of the support roll on the relative amount of metal removal along the radius.

The peeled surface layer of the support roll consists of three layers of the outer layer 1 with residual tensile stresses, the intermediate layer 2 with residual compressive stresses and the inner layer 3 in which residual tensile stresses are present.

The thickness of the outer layer 1 depends on the degree of work hardening, which is characterized by the increment of hardness of the roll, determined with the help of Shore's scleroscope on the height of the striker’s rebound. Although the hardness value in the outer layer 1 may be high (it always exceeds the hardness value in the inner layer 2), the stress state of the outer layer 1 is most unfavorable. The residual tensile stresses in the outer layer 1 contribute to the appearance and development of cracks, chips, and outgrowths. Therefore, the support rolls, prepared for work by a known method and having an outer layer 1 on the surface, are characterized by low durability. As follows from FIG. 2, at the zero value of the argument (there is no removal), the length of the support rolls is minimal.

If, after creating the surface riveted layer, the outer layer 1 is removed by regrinding the support roll on a lathe, then intermediate layer 2 with residual compressive stresses will be brought to the surface of the support roll. Although the hardness of the intermediate layer 2 is lower than that of the outer layer 1, the beneficial effect of residual compressive stresses tends to increase the durability of the support rolls.

It was established experimentally that the required removal rate of metal along the radius of the support roll (to remove the outer layer 1) is proportional to

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the increment of the hardness of its surface layer as a result of the work hardening. At a proportional ratio of 0.3-0.8, the longest durability of the support rolls is reached (Fig. 2) and the intermediate layer 2 is on their surface. When the proportionality coefficient is less than 0.3, there is a sharp decrease in the durability of the support rolls, since the outer layer 1 is not completely removed. In the case where the proportionality factor is greater than 0.8, the durability of the rolls is also reduced. This is due to the fact that the removal of the metal along the radius of the support roll is excessively large and the inner layer 3, which has residual tensile strengths, is brought onto its surface.

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Example. New 9XF steel support rolls, having barrel diameters of 1600 mm and a surface layer hardness of 40 Shore units, fill the seventh stand of the finishing group of a continuous broadband mill 2000. After this, filling of work rolls made of 760 mm cast iron is produced. and

0 hardness of the surface layer .78 Shore units. The work rolls are pressed against the support with the help of hydraulic cylinders embedded in the pillows, and they are rotated together until

 achieve 3000 loading cycles - support rolls. After the run-in is completed, workers and support rolls are thrown out of the cage. Due to such work-hardening of the surface layer of the support rolls, their hardness increases by 8 Shore units and is 48 units. The hardness of the surface layer of the support rolls is monitored with a scleroscope. Then, the support rolls are mounted on a turning machine and a partial mechanical removal (turning) of the rivet layer is carried out before the intermediate layer 2 is brought to the surface with residual compressive stresses. The outer layer 1 is completely removed. Metal removal along the turning radius is 4.40 mm. Then, the support rolls are ground and again poured into the seventh stand of the finishing group of the mill 2000, after which the metal is rolled,

As a result of this preparation for the work of the support rolls on top of them

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This will be a layer with residual helixes. The options for implementing the method and applying stresses, due to which the resistance (durability) of the rolls increases their durability. The tables are given in the table.

note

In all embodiments, the increment in hardness of the surface layer of the backup roll as a result of the work hardening is 8 units. by Shore.

As can be seen from the table, the support rolls prepared for the work on the pre-mode (options 2-D) have the greatest durability. The durability of the support rolls is 210-250 thousand tons of rolled metal. With extreme values of the proposed parameters (options 1 and 5), the durability of the support rolls decreases to 140-150 thousand tons. When rolled by a known method (option 6), the durability of the support rolls is 120 thousand tons of metal.

Thus, the proposed parameter interval is

minimum durability of the rolls.

Kneep the surface layer of the support rolls on the proposed method can be carried out simultaneously with the rolling of metal.

The technical and economic advantages of the proposed method consist in the fact that partial mechanical removal of a cold-bonded surface layer with a regulated value of removal along the radius depending on the increment of hardness as a result of work hardening allows to increase the durability of the support rolls.

Claims (1)

METHOD FOR PREPARING FOR OPERATION OF THE SUPPORT ROLLS OF THE QUARTO MILLS, including filling the backup and work rolls into the crate, pressing the work rolls to the support rolls and hardening the surface layer of the support rolls while rotating them with the work rolls, characterized in that, in order to increase the service life of the backup rolls, after hardening of the surface layer is carried out, it is partially mechanically removed, and the removal value is determined by the following ratio aR = (0.3 - 0.8) aHSh, where aR is the metal removal along the radius of the backup roll, mm; aHSR is the increment in hardness of the g surface layer of the backup roll as a result of hardening, unit Shora. SU ... 1235573 Figl