Hot working method of high-performance small-distortion carburized outer ring

Abstract

The invention discloses a hot working method of a high-performance small-distortion carburized outer ring, relates to the technical field of hot working methods, and solves the technical problems of complex manufacturing process, non-uniform carburized layer depth and poor quality consistency of the existing outer ring, and is suitable for forging and heat treatment of the outer ring made of 17Cr2Ni2MoVNb steel, the diameter of the outer ring is 150-200 mm, and the wall thickness of the outer ring is 8-10 mm. The hot working method comprises the following steps of constructing a true stress-strain curve and a hot working diagram, forging, normalizing and tempering at a high temperature, roughly machining, thermal refining, roughly machining a tooth shape and the like, performing gas/liquid composite carburizing and tempering at a high temperature, quenching and tempering at a low temperature. According to the hot working method, the ovality of the carburized and quenched outer ring is controlled to be less than or equal to 0.15 mm, the grain size is greater than or equal to 8.5 grades, and the rotating bending fatigue strength of a furnace sample is greater than or equal to 1000 MPa; and the part has high performance, meanwhile, only small heat treatment deformation exists, and good industrial application value is achieved.

Description

Technical field [0001] The present invention relates to the technical field of thermal processing methods, and more particularly to the technical field of thermal processing methods for high performance minor-alveatic carbon outer rings. Background technique [0002] The outer ring is a core part of a liquid torque converter, while taking into account the performance and weight loss requirements, and the tooth requires carbon quenching; 20Cr2NI4A steel has good comprehensive mechanical properties after carburizing and high temperature tempering, It is widely used in manufacturing various outer rings; but due to its high hardening resistance and large grains, the outer rings produced often occurs seriously, and has a large fatigue life fluctuation range; 20Cr2NI4A steel with a φ186mm, 78mm The outer ring is an example, the part needs to reach the 1.4 mm permeable layer deep, and it is necessary to heat insulation at a high temperature of about 930 ° C; due to the long heating time...

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Problems solved by technology

[0002] The outer ring is the core part of a hydraulic torque converter, taking into account the requirements of performance and weight reduction, and the teeth require carburizing and quenching; 20Cr2Ni4A steel has good comprehensive mechanical properties after carburizing and high temperature tempering, so it is It is widely used in the manufacture of various outer rings; however, due to its high hardenability and large grain size, the manufactured outer rings often have problems such as severe heat treatment deformation and large fluctuation range of fatigue life; a 20Cr2Ni4A steel with a diameter of 186mm and a height of 78mm Take the outer ring as an example. To reach a carburized layer depth of 1.4mm, the part needs to be kept at a high temperature of about 930°C for 492 minutes. Due to the long heating time at high temperature, the grain size and fatigue strength of the part are not ideal. Level 6, the rotational bending fatigue strength of the sample is about 750MPa; in addition, if free state carburizing and quenching is used, the ellipticity of this type of parts is about 0.3mm; in order to ensure the accuracy of the parts, the depth of the carburized layer must be increased and more The grinding allowance of the outer ring will bring problems such as complex manufacturing process of the outer ring, uneven depth of the carburized layer, and poor quality consistency, which will lead to a decrease in the fatigue performance of the outer ring parts

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