RU2000339C1 - Method for heat treatment of steel - Google Patents

Abstract

The invention relates to ferrous metallurgy and can be used in mechanical engineering for machining structural, ball-bearing, high-speed and tool steels. The goal is to increase the operational reliability of parts made of hardened steels, including those with coatings. SUMMARY OF THE INVENTION that hardened steel is irradiated with an electron beam, while the temperature of the article is maintained at not higher than 300 ° C. The positive effect is to reduce the level of residual microstresses, decomposition of residual austenite, substructural hardening of the steel while maintaining its original hardness.

Description

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The invention relates to ferrous metallurgy and can be used in mechanical engineering and other technical fields for the treatment of structural, ball-bearing, high-speed and tool steels. At present, hardened steels are widely used in various fields. Steel quenching can significantly increase its hardness. However, this is associated with the appearance of a high level of microstresses in them. Generally, coatings applied to them do not have sufficient adhesion strength. To solve these problems, tempering is usually used, which reduces residual microstresses, causes decomposition of residual austenite and precipitation of carbides. At the same time. the use of tempering is not quite effective in a number of cases 1. So, for example, the amount of residual austenite after standard tempering of high-carbon alloy steels can vary from 5 to 30%, and residual austenite is a phase, the presence of which does not provide adequate adhesion to the steel coated. In addition, after tempering, a high level of residual microstresses can be maintained, which reduces the resistance of steels to fracture and increases their tendency to delayed fracture.

Closest to the claimed is the method described in 2. In accordance with it, the hardened steel is subjected to tempering with additional electron beam heating to temperatures of 720-770 ° C. The method improves fatigue strength and corrosion resistance for

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counting surface stresses. The application of the known method involves heating the material to high temperatures, and this leads to a decrease in hardness, which in some cases, for example. when machining tool steels is unacceptable. Such relaxation treatment does not lead to hardening of the material,

There is a known method of substructural hardening of a material by the thermoplastic method 3, based on the creation of stabilized interface subsurfaces in the metal, which prevent the free movement of dislocations within the grain by the combined mechanical (plastic deformation) and thermal (heating) effects on the workpiece. In most practically important cases, the implementation of this processing method is difficult due to technological difficulties.

Thus, the author was faced with the task of creating a method for processing steels that would simultaneously intensify tempering processes of hardened steels and ensure their hardening, and in the case of processing hardened steels with a coating, increase their adhesion to the substrate.

To solve this problem, it is proposed to treat hardened steel with an electron beam at temperatures below 300 ° C. Steel with various types of coatings can be processed: galvanic, sprayed, diffusion, implanted. In addition, coatings can be either metallic or non-metallic, as well as multi-layer.

The invention is based on the effect of the interaction of radiation defects (vacancies and interstitial atoms) arising from irradiation with high energy electrons (more than 500 keV) with dislocations and their clusters. As a result of the creeping of dislocations, a substructure is formed in martensite, which is close to polygonal, which in turn causes a decrease in the level of microstresses. Irradiation also contributes to the formation of carbides and the decomposition of residual austenite. The indicated processes proceed most efficiently in the temperature range up to 300 ° C, above which intense annealing of radiation defects occurs. The processing depth can reach 1.5-2 mm.

To prove the feasibility of the proposed method, the following information

Example. Irradiation of steel SHKh-15 (after standard heat treatment) with an electron beam with an energy of 5 MeV and a fluence of 2 x 1016 el / cm2 reduces the microstress level by 30%, and the amount of residual austenite from b to 1%. The microhardness after this treatment increases by 2 units. IIRC.

EXAMPLE 2. Irradiation of steel P6M5FZ 0 (after standard heat treatment) with an electron beam with an energy of 5 MeV and a fluence of 2 x 1016 el / cm2 leads to a decrease in the level of microstresses by 28%, and the amount of residual austenite from 23 up to 4%. 5 EXAMPLE 3. The operational stability of the work roll (SHX-15 steel) of the 160 machine with a TIN sprayed coating increases by 3 times if it is irradiated with an electron beam with an energy of 5 Mvs and a fluence of 0 5 x 1016 el / cm2.

Using the proposed method for processing hardened steels of various classes will allow:

- maintain the original hardness of the steel;

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-decrease the level of residual microstresses (by 20% or more);

-Reduce the amount of residual austenite (by 30% or more);

-to promote the occurrence of finely dispersed carbide phase;

-to ensure the formation of a substructure close to polygonal;

-provide the necessary adhesion strength of the coated steel.

Claims (3)

5 claims 1. The method of heat treatment of steel, including surface treatment of hardened steel by an electron beam, is distinguished by the fact that the electron beam treatment is carried out at a temperature of no higher than 300 ° C. 2. The method of pop, 1 characterized in that the electron beam treatment is carried out at an electron energy of more than 500 keV in the stationary mode. 3. The method according to claim 1, characterized in that the electron beam processing is carried out in a batch mode. 04. The method according to claim 1, characterized by treating volumetric hardened steels with an electron beam 5. The method of pop. 1. Characterized in that they are treated with an electron beam 5 surface hardened steels 6. The method according to claim 1, characterized in that the hardened coated steels are treated with an electron beam 7. The method according to claim 6. characterized in that it is treated with an electron beam 520003396 hardened steel with plating-10. The method of claim b, wherein thiem. that is treated with an electron beam hardened steels with implanted steel 8. Method according to claim 6, characterized in. covered. by that. which is treated with an electron beam5 11. The method according to claim b, characterized in hardened steels with a spray coating - treated with an electron beam m.hardened multilayer steels. 9. The method according to item b. characterized 12. The method according to p. characterized in that it is treated with an electron beam, wherein the electron beam is treated with hardened steels with diffuser coating-hardened steels with non-metallic weld coating.