RU2100451C1 - Method of thermally treating molded parts of low-carbon and low- alloyed steel - Google Patents

Abstract

FIELD: mechanical engineering. SUBSTANCE: invention concerns parts of steel with 0.15-0.30% carbon applicable to automatic coupling devices in railway equipment and consists in that parts are hardened by cooled water flow from cooling chamber operated under gage pressure 0.1-0.2 MPa, which moves relative to bearing cross-sections of parts with velocity satisfying the following equation: v = (0.7- 3.0)$$$, m/s, where S is thickness of part in its bearing cross- sections. EFFECT: increased lifetime and operation reliability of parts.

Description

 The invention relates to the field of engineering, in particular, to cast parts of low carbon and low alloy steels containing 0.15 - 0.30% carbon, and used, in particular, in automatic couplers of rolling stock of railways.

 A known method of heat treatment of cast steel parts, including heating to a quenching temperature with cooling in water and high tempering.

 In conditions of intense high-speed movement, the service life of these parts is insufficient due to their wear and fatigue damage in operation.

 The present invention solves the problem of increasing the durability and operational reliability of cast parts of an automatic coupler.

The problem is solved in that in order to increase the wear resistance and fatigue strength of the parts, cooling is carried out by introducing the part into the moving part
V (0.7.3.0) S ^0.34
the flow of water under an overpressure of 0.1-0.2 MPa, where V is the velocity of water, m / s; S thickness of the part in bearing sections, mm.

These cooling conditions make it possible to realize the capabilities of steel to the greatest extent, providing surface hardening to a hardness of 40 47 HRC. The wear resistance of parts increases by more than 1.5 times, the endurance limit increases by at least 15%
An overpressure of 0.1 0.2 MPa in the cooling chamber ensures the density of the water flow and the uniformity of cooling of parts of a complex asymmetric shape, which are parts of an automatic coupler. The movement of pressurized water at a speed of (0.7.3.0) S ^0.34 provides a critical hardening rate, a cooling rate sufficient to obtain a predominantly martensitic structure in the surface layers and is not accompanied by an unjustified overspending of electricity to power the pumps that supply water to cooling device.

 The novelty of the solution, characterized by its distinguishing features, is that the combination of pressure of the water flow rate creates uniformity and cooling rate, which provides effective hardening of cast parts from standard structural steels of ordinary quality and increases the durability and reliability of the parts in operation.

 The proposed solution is as follows.

A molded case of an automatic coupler with a wall thickness of 21 m made of 20GL steel was heated in a gas feed furnace to 950 ^o C, transferred to a cooling device, the design of which provided, when using centrifugal pumps with a total capacity of up to 900 m ³ / h, overpressure in the cooling chamber 2.8 m / with, which satisfies the above ratio.

 No tempered parts were dispensed.

The hardness of the surface parts after quenching HRC was 46 _Oe wear resistance test results increased by 1.7 times compared with serial items and endurance limit increased by 19%
Using the proposed solution provides, in comparison with the prototype, the following advantages: increased durability and reliability of parts in operation.

Claims (1)

The method of heat treatment of cast parts from mild and low alloy steel, including through heating the part to quenching temperature and cooling, characterized in that the cooling is carried out by introducing the part into the moving at a speed of (0.7 3.0) S ^{0 , 3 4} m / s water flow under pressure 0.1 0.1 MPa, where S is the thickness of the part in bearing sections, mm