RU2153008C1 - Method for electric-contact heat treatment of part surfaces - Google Patents

Abstract

FIELD: machine engineering industry branches, namely, heat treatment, possibly case hardening of working faces of parts. SUBSTANCE: method for electric-contact heat treatment of surfaces of parts from ferrum-carbon alloys comprises steps of passing electric current through contact members forced by pressure to treated surface; at treating curvilinear portions of wheels of cars of rolling stock successively placing contact members in such a way that they are shifted one from to another by angle 70-110 degrees relative to line being tangent to generatrix of hardened surface for heat treating portions in the form of stripes; providing ratio of radius values of curvilinear surface and profile of contact member in range 1: (0.8-0.98) when curvilinear surface is concave and in range 1:(1.08-1.17) when curvilinear surface is convex. Mutually shifted contact members may be placed with overlapping for providing annealing zone of hardened strip provided by first contact member. Stripes may be intermittent and they may be arranged in staggered fashion. EFFECT: reduced inner stresses of part, increased wear resistance of heat treated surface. 4 cl, 1 dwg, 3 ex

Description

 The invention relates to the field of heat treatment of parts and can be used in the engineering industry for hardening the working surfaces of parts, in particular, the invention relates to a method for surface contact heat treatment of parts.

A known method of surface hardening, according to which a high-temperature jet is supplied to the forming surface at an angle of 30-60 ^o / 1 /.

 A known method of surface contact hardening of parts, according to which the surface is heated by passing electric current through moving contact rollers, pressed to the workpiece with the required pressure and moved at the required speed, followed by cooling of the heating zone. In this case, pressure is created between the contact rollers on the surface of the part / 2 /.

 A disadvantage of the known methods is the impossibility of heat treatment of curved sections of parts, including the fillet transition and the "fillet" / crest / wheels of the rolling stock to increase wear resistance and reduce internal stresses.

 The purpose of the invention is to reduce internal stresses and increase the wear resistance of the heat-treated surface.

This goal is achieved by the fact that in the method of surface electrical contact heat treatment of parts, including heating the part by passing electric current through the contact elements pressed to the surface to be treated under pressure, and cooling the heating zone, when the contact surface heat treatment of parts on curved sections of the wheels of the rolling stock, the contact elements are arranged offset relative to each other and one after the other at an angle of 70-110 ^o to the tangent line to the forming prochnyaemoy surface portions forming a heat-treated in the form of bands, wherein the ratio of the radii of the curved surface and the profile of the contact element is 1: 0,8-0,98 at a concave curved surface, and 1: 1,08-1,17 with a convex surface.

 The contact elements displaced relative to each other are installed overlapping to obtain a tempering zone of the hardened strip formed by the contact element leading in front.

 Stripes can be intermittent and staggered.

 As contact elements, rollers, sliders can be used.

The location of the contact elements at an angle less than 70 or greater than 110 ^o does not provide processing of the flattening straight sections, and this in turn reduces the wear resistance of the treated surface.

 The location of the contact elements with an offset relative to each other and sequentially one after another allows to obtain heat-treated and non-heat-treated areas in the form of strips on the treated surface, which makes it possible to adjust the ratio of the areas of heat-treated and non-heat-treated areas, and this provides adjustable wear resistance of the hardened surface.

 When processing a concave curved surface, the radius of the profile of the contact element should not be less than 0.8 from the radius of the curved hardened surface, otherwise very narrow heat-treated strips will form, which will lead to a decrease in the overall wear resistance of the hardened surface, if the radius of the profile is greater than 0.98, then the contact elements and the hardened surface will fit snugly against each other and during the processing, mutual wear of the contact surfaces occurs.

 When machining convex curved surfaces, the radius of the profile of the contact element must be at least 1.08 so that mutual wear of the contact surfaces does not occur, and with a radius of more than 1.17 narrow heat-treated strips will be formed.

 When the contact element is displaced relative to each other with partial overlap, a tempering strip is formed in the overlap zone, which reduces internal stresses at the edges of the hardened strip.

 The method is illustrated by the drawing, which shows the profile of the machined curved surface of the wheel of the rolling stock.

 The method of surface contact heat treatment is as follows.

 Contact elements 1 on a curved workpiece surface 2 are installed sequentially one after another with offset relative to each other and pressed against it with the required pressure.

 The current source is turned on and voltage is applied to the contact elements. The hardened zone of the workpiece quickly heats up to the temperature of the heat treatment and the formation of heat-treated strips is carried out with the required depth of heat treatment / hardening and / or tempering /.

 Example 1

 A surface hardening is applied to the fillet portion 3 of the rolling stock wheel. For this, contact elements with a profile radius of 0.9 from a curved surface are used. The result is hardened strips with the wear resistance of the hardened curved surface, increased by 2-2.5 times compared with the starting material.

 Example 2

 Convex section / fillet 4 / wheels of rolling stock is subjected to surface hardening. For this, contact elements with a profile radius of 1.10 from the radius of the curved surface are used. In this case, also the wear resistance of the hardened curved surface increases by 2-2.5 times in comparison with the starting material.

 Example 3

 The curved surface of the rolling stock wheel is subjected to surface heat treatment: fillet portion / concave curved surface / or fillet / convex curved surface /. The contact elements are mounted offset relative to each other and sequentially one after another so that the contact element coming from the rear partially overlaps the strip obtained in front of the contact element. As a result, a tempering strip is formed in the overlapping zone, which reduces internal stresses along the edges of the hardened strip. Overlap can be 0.15-0.5 of the width of the hardened strip.

 According to the invention, the method of surface electrical contact heat treatment allows you to restore worn parts in curved sections with adjustable wear resistance. This method can be widely used in the repair of tram and railway wheels, giving them high operational reliability.

Sources of information taken into account when preparing the application
1. RF patent N 2107739, cl. C 21 D 1/09, 03/27/98
2. Copyright certificate of the USSR N 1713943, cl. C 21 D 1/06, 02/23/92.

Claims (4)

1. The method of surface electric contact heat treatment of parts made of iron-carbon alloys, comprising heating the part by passing electric current through moving contact elements pressed to the surface to be treated under pressure, and cooling the heating zone, characterized in that during electric contact surface heat treatment of curved sections of the wheels of the rolling stock, the contact elements have with offset relative to each other and sequentially one after another at an angle of 70 - 110 ^o to the tangent line to the forming hardened surface, forming heat-treated areas in the form of strips, with the ratio of the radii of the curved surface and the profile of the contact element is 1: 0.8 - 0.98 for a concave curved surface and 1: 1.08 - 1.17 for a convex surface.  2. The method according to claim 1, characterized in that the contact elements displaced relative to each other are installed overlapping to obtain a tempering zone of the tempered strip formed by the front contact element.  3. The method according to claim 1, characterized in that the stripes are formed intermittently.  4. The method according to claim 3, characterized in that the intermittent stripes are staggered.