SU1752828A1 - Method of hardening steel pieces - Google Patents

Abstract

Usage: the invention relates to the chemical heat treatment of steel components, in particular to cementation and the subsequent local surface plastic deformation. Summary of the Invention: A lacquer pattern is applied to a steel product, electrolytic etching of uncoated places is applied, a copper mask is applied to prominent areas, and then cementation, heat treatment and surface plastic ejection of exposed non-cemented areas are performed at room temperature. 2 ill., 1 tab.

Description

The invention relates to chemical heat treatment, in particular to cementation, and subsequent local surface plastic deformation in order to increase the durability of steel parts by creating a heterogeneous macrostructure of the surface.

It is known that there is a relationship between the endurance characteristics of a material and its strength and hardness. If you take measures only to increase strength, it can. prove inadequate to increase endurance, including durability. Reinforcement leads to difficult nucleation of fatigue cracks. If plasticity is significantly reduced, the spread of an already formed crack will be facilitated. Therefore, it is most appropriate to focus on correlation with any combination of strength and plastic properties:

rt - n 9ftrr Fi l ";," (1 + VM1-W Sc - 0.260TS1 - 0, In IT --- y-T -. J,

where o is the endurance limit, Iffla, CTg is the ultimate strength, MPa%, (J / is the final relative narrowing;

(|) „- the greatest uniform narrowing.

Thus, in order to increase durability, it is necessary to strengthen the part in such a way that its plasticity does not decrease. Since the majority of hardening metal treatments lead to an increase in hardness and strength, but a decrease in ductility, the possibilities of homogeneous materials are close to exhaustion. The combination of these opposite properties is possible with the creation of a material with an irresistible (heterogeneous) regularly changing macrostructure of the surface. Known methods for the preparation of structurally inhomogeneous materials on o / -

H

sla

00

Yu

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new steels of austenitic and t tervochod classes, where local plastic deformation is first carried out with a degree of deformation of 5 greater than 40%, and then the total plastic deformation is about 30%. In the deformation zone, martensite is formed, and the matrix remains austenitic. Thus, it is possible to create a martensite grid with any given configuration consisting of sections with different hardness and ductility of structural components.

The disadvantage of this method is its inapplicability to carbon i became m.

There is a method of creating a heterogeneous macrostructure, where, after conducting thermal or thermoplastic

j

0

obtain a heterogeneous structure and mechanical properties. The pattern is fixed by electrolytic etching in 10% aqueous NaCl solution for 10–15 min. The etching depth of 0.15-0.20 mm. It is determined from the formula

Mr. KG6h2

Synt

where C is the depth of etching, mm {

K - coefficient taking into account the depth of work hardening Ј h - depth of the cemented layer,

MMJ

P is the modulus of elasticity of the matrix,

MPa "N - thickness of the part, mm

z | Figure 2).

Steel is hardened or tempered or tempered.

i The disadvantage of this method is the complexity and high cost of the necessary equipment,

There is a known method of hardening steel elastic elements, where a heterogeneous surface is obtained by cementation through a protective copper mask. Additional strength can be achieved if uncemented sections are subjected to surface plastic deformation at room temperature, as a result of which cemented areas will be extremely compressed and, in the process of operation, the parts will be less subjected to tensile stresses.

The aim of the invention is to increase the durability of steel parts by increasing strength while maintaining ductility by creating a heterogeneous macrostructure.

This goal is achieved by the fact that after conducting chemical-thermal treatment through a protective mask, the part undergoes additional surface-plastic deformation.

On Aig.1 and 2 shows the scheme that implements the method.

The method is carried out as follows.

A steel plate of steel 20 is applied through a lacquer stencil on a steel sheet. pattern of a given geometry (figure 1). The proposed pattern sizes are optimal in terms of technology.

0

five

five

Then, protrusion of the protruding portions is carried out for 20-25 minutes in a standard electrolyte. After cementation at 920–930 ° S of a solid carburetor and subsequent normalization, quenching from 770–780 ° C to water and low tempering on the surface, high-speed, soft sections with HRC 25–30 are obtained.

and solid areas with HRC 62 - 63.

i

With the help of surface plastic

deformations (treatment with a hammer, roller or shot) soft areas vDav- (close between hard ones without destroying them. Thus, large compressive stresses are created on the surface after cementation and as a result of plastic deformation. At the same time; hardness of soft plots increase by 1.3-1.5 times with a degree of deformation of 10-15%. Residual compressive stresses increase the endurance limit, and the presence of soft and hard structures ensures a high

with strength and ductility, which is impossible with most treatments.

Mechanical characteristics of the material After processing by this method are shown in table

The tensile strength of SGB, the limit of elasticity Gu and plasticity In determined in conditions of bending. The durability of N characterizes the number of kinks at a given angle before destruction. An increase in the endurance of parts also contributes to an increase in internal friction Q due to the formation of a heterogeneous structure, the measurements of which are carried out according to standard methods. Ra-,

0

17

The Berenov D capacity is calculated by the formula

And fci CVЈ.

where di. - fill factor di

stretch agrams, C tensile strength, IfflaJ B - plasticity,%.

From the table it can be seen that the working capacity increases by 1.4-1.5, and the durability - 1.2-1.3 times as compared to the known ... method. FORUMAWLAH AND ISLANDS

The method of hardening steel parts, including the application of lacquer

Processing method 0);

at

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Known Pattern:

rhombic

- - i

zigzag

,

:

ten

pattern, deposition of a copper mask with a zigzag or rhombic pattern, cementation and heat treatment, so that, in order to increase the durability of parts by creating a heterogeneous macrostructure on the surface, before applying the copper mask Electrolytic etching of places not covered with lacquer, applying a copper mask is carried out on protruding areas, and after cementation and heat treatment, surface plastic deformation of protruding non-cemented areas is performed at room temperature.

tfa, MP

b,% L 1.0GJ / m IN, cycles

4133.4

3450

246: 0.15

: Ј & I

1

2

Claims (1)

Claim The method of hardening steel parts, including applying varnish 1752828 ⁶ patterns, application of a copper mask with a zigzag cli rhombic pattern, cementation and heat treatment, which can be done in order to increase the durability of parts by creating a heterogeneous macrostructure on the surface, before applying a copper mask electrolytic etching of places not covered. with varnish, the copper mask is applied on the protruding sections, and after cementation and heat treatment, surface plastic deformation of the protruding non-cement sections is carried out at room temperature. I '’' '' Processing method C) c, MPa G ^, MPa. e,% D> 10 ^G J / m ³ N, cyc-1 fishing I ----- Famous Pattern: rhombic 1670 '413 . 3.4; 3450 246 7 0.15 zigzag 1680 354 S ³ 4030 208 0.14 Proposed Pattern: rhombic 2510 '511 W, ¹ 5185 324 ’ 0.37 zigzag 1530 509 4.1 6035 ²⁶³ 0.31 μμμμμμμ "mmmmmmmm — m - mm ^ -mmmm—- »M 'm i * m m m m m m m m ""AND,. mm ** I .1 752828 f VAT 62 S3 a I;