42CrMo surface quenching treatment

Study on Heat Treatment Process of 42CrMo Steel

Abstract

42CrMo steel is a kind of high-alloyed steel which has good hardenability, hardness and wear resistance performance, and is widely used in many fields. The research on the heat treatment process of 42CrMo steel has important guiding significance for the use of the steel. In this study, the heat treatment process of 42CrMo steel was explored, and its effect on the hardness, wear resistance and microstructure of the steel were analyzed and discussed.

1 Introduction

Alloy steels play an important role in various engineering applications because of their superior mechanical, physical and chemical properties. 42CrMo steel is a high-alloy steel which is widely used in many fields. It has good plasticity, toughness, strength and hardenability, and is mainly used in the production of automobiles, mining machinery, agricultural machinery and other fields. Due to the good mechanical properties and hardness of 42CrMo steel, its application is increasing, and its heat treatment technology is also gradually improved. The heat treatment process can adjust and improve the performance and structure of the steel, and an appropriate heat treatment process can maximize the performance of the steel. Therefore, it is of great significance to study the heat treatment process of 42CrMo steel, so as to better meet the needs of engineering application.

2 Heat Treatment Process of 42CrMo Steel

Heat treatment is an important way to adjust and improve the performance of the steel. The heat treatment process of 42CrMo steel mainly includes normalizing, quenching and tempering, and low temperature tempering.

? Normalizing: Normalizing is the process of heating a steel to a temperature above its critical temperature Ac3 and cooling it in the air without holding for a certain period of time. This process can refine the crystal grains,improve the plasticity and toughness,and eliminate the internal stress.Therefore, it is necessary to carry out normalizing heat treatment before quenching and tempering heat treatment.

? Quenching and tempering: quenching and tempering is the process of heating 42CrMo steel to austenitized, quench to form martensite or pseudo-martensite, and then temper it. It can improve the hardness and strength of steel, and also reduce brittleness to complete combination of strength and toughness.

? Low-temperature tempering: low-temperature tempering is the process of heating 42CrMo steel to Ac1-ACm, holding for a certain period of time and cooling in air or oil. The purpose of this process is to further improve the toughness,eliminate internal stress and reduce brittleness of steel.

3 Analysis of the Effects of Heat Treatment on the Performance and Microstructure of 42CrMo Steel

The heat treatment of 42CrMo steel has a great influence on its properties, performance and microstructure.

? Influence on hardness: after quenching and tempering heat treatment,the hardness of 42CrMo steel can be increased. When the tempering temperature is about 360-400℃, the hardness for once quenching + tempering can reach more than 250HBW.

? Influence on wear resistance: after quenching and tempering heat treatment, the wear resistance of 42CrMo steel can be improved. Low temperature tempering can further improve the wear resistance of the steel.

? Influence on microstructure: the microstructure of the 42CrMo steel can be changed by the heat treatment process of quenching and tempering.The main components of the microstructure are martensite, bainite and ferrite.

4 Conclusion

In this study, the process and effects of heat treatment on 42CrMo steel have been investigated. 42CrMo steel is a kind of high-alloyed steel with good hardenability, hardness and wear resistance performance, and its heat treatment process mainly includes normalizing, quenching and tempering, and low temperature tempering. The heat treatment process can significantly improve the hardness and wear resistance of 42CrMo steel and change its microstructure. In general, an appropriate heat treatment process can guarantee the performance and application effect of 42CrMo steel.

Quenching treatment of 42CrMo

42CrMo is a kind of medium-carbon alloy structural steel with good comprehensive mechanical properties, which has high strength, toughness and good hardenability.

Quenching of 42CrMo steel:

1. Preheat. Preheat the 42CrMo steel to a temperature of 800~900℃ before quenching.

2. Heating. The temperature of the 42CrMo steel should be heated to the quenching temperature of the medium, usually 850~870 ℃.

3. Quenching method. The 42CrMo steel can be quenched with quenching medium such as water, oil or sodium chloride solution, or by natural cooling or convection cooling.

4. Tempering. Tempering should be carried out after quenching to eliminate the internal stress caused by quenching and obtain the desired mechanical properties. Generally, the tempering temperature should be carried out at low temperature (180 ~ 250 ℃).

Surface treatment of 42CrMo steel:

When 42CrMo steel is hot working, due to the phenomenon of high hardness, the surface of the hot working parts should be subjected to normal tempering or high tempering treatment after hot working. Hardness can be obtained by a certain number of high tempering treatments. The surface of the hot-worked parts can be carburized, nitrified and atimony treated. The carburization layer should be treated by normalizing or high tempering after carburizing.

In order to improve the corrosion resistance of 42CrMo steel and enhance its wear resistance, the surface of the hot working parts should also be subjected to surface quenching treatment after hot working, generally using nitriding or non-oxidation black treatment.