SU1731831A1 - Method for heat treatment of rolling mill rolls - Google Patents

Abstract

Use: metallurgical engineering, surface hardening of the rolls, mainly with a ratio of length to diameter 6-10. SUMMARY OF THE INVENTION: Continuously sequential surface hardening using a source of concentrated energy begins at the center of the roll and ends at the periphery. 1 ill., 1 tab.

Description

The invention relates to the field of mechanical engineering and can be used mainly in the heat treatment of mill rolls with a ratio of length to diameter of 6-10.

The known method of heat treatment of parts consists in melting the surface and rapidly cooling to the temperature of formation of the ledeburite structure.

The disadvantage of this method is the possibility of overheating of the entire part when the surface melts and the resulting uneven quality and properties of the hardened layer.

There is a method of reflowing (quenching from a liquid state) of products, which consists in that the reflow is produced by an electric arc in an induction / preliminary method.

The disadvantage of the method is the overheating of the ends of the roll in the course of quenching and the associated uneven wear resistance over the length of the roll.

Closest to the proposed heat treatment method is the method consisting in remelting the surface with a plasma arc by a special ring-shaped device, advancing the latter from one end of the roll to the other.

The disadvantage of this method is uneven wear resistance along the length of the roll due to unequal heating conditions of the ends of the roll.

The aim of the invention is to provide uniform wear resistance over the length of the roll.

The goal is achieved by the fact that in the method of heat treatment of rolls, mainly with a ratio of length to diameter of 6-10, including surface heating using a source of concentrated energy when moving the source along the rolls, heating starts from the central part of the roll and ends at the periphery.

FIG. 1 shows a plant for hardening rolls, a general view.

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Roll 1 with the ratio of length to diameter set on a lathe. The plasma torch 2 is supplied to the central part of the length of the roll. The roll is given rotation, the plasma jet 3 of the plasma torch, moving in the direction to the peripheral part of the roll from right to left, heats up the surface of the left part of the roll. In this case, heat from the central part of the roll spreads evenly over its body at both ends. After heating the left part of the roll, the plasma torch is returned to its original position and the other (right) half of the roll is heated (from left to right). In this case, heat propagates both into the hardened and unhardened part of the roll, i.e. there is a uniform all-round distribution of heat in the roll. After quenching this part of the roll, the process is completed.

The table shows the results of tests of samples cut from rolls, strengthened by the method with the promotion of a source of concentrated energy from the center to the periphery.

Test specimens are cut out from the central and peripheral portions of the hardened rolls. Samples with a diameter of 50 mm are cut out from the rolls of a twenty-rolled mill. Wear is judged by the weight loss of the samples on the friction machine.

The quenching of the rolls is carried out on the installation for plasma surfacing of UPN-303 UHL-4. Operating mode: arc current 120A, voltage CST, plasma torch displacement speed 25 mm / s.

As can be seen from the table, heating according to the scheme from the center to the periphery contributes to a more uniform wear of the surface. The martensite score on the roll areas is approximately the same (2-3).

When heated by a known method, the martensite score at the site from which heating begins, 2, in the central part of the roll 3, at the site at which heating is completed, 6 points. This affects the reduction in wear resistance caused by the presence of a larger martensite score in the structure.

Claims (1)

Invention Formula The method of heat treatment of rolling rolls, preferably with a ratio of length to diameter of 6-10, includes continuous-sequential quenching of the roll surface with a highly concentrated energy source, characterized in that, in order to ensure uniform wear resistance along the length of the roll, quenching is carried out periphery.