The Research Of The Heat Treatment Of The Low-alloy High Strength Steel

At present, the property of the wear-resistant steel that was produced in some country was better than the steel produced in china. It is very important to improve the properties of the wear-resistant steel for many factories and companies. Improving the property of the steel and decreasing the amount of the steel could increase the profits. In this paper, the microstructure and the properties of the SB wear-resistant steel and the B24S wear-resistant steel were studied. With the results of the study, the new heat treatment craft was made to improve the properties of the B24S steel.The microstructures of the B24S steel were observed by using the light microscope and the scanning electronic microscope (SEM). The properties of the steel were tested by using the universal tester. Some heat treatment crafts were designedThe microstructures of the SB steel are bainite and lath martensite. The steel has high tensile strength and high yield strength. The tensile strength is 1360 Mpa, and the yield strength is 1240 Mpa.The microstructures of the B24S steel are bainite and sorbite. There are many carbides and inclusions in the microstructure.After the samples were cooled in the water or the oil, the microstructures were bainite and martensite ,so the samples had high tensile strength and high yield strength. When the sample was cooling , the overcooling austenite transformed to the bainite . the bainite cut up the austensite. When the sample started martensite transformation, the small lath martensite was made, which increased the tensile strength and the yield strength of the steel. When the temper temperature increased, the tensile strength and the yield strength of the sample were decreased.The amount of the bainite of the microstructure influences the property of the steel. With the increasing of the amount of the bainite, the amount of the martensite decreased. And the baintie will be together like the underbrush, the bainite could not cut up the austensite effectively. When the scale of the bainite was 1%, the B24S steel has maximal tensile strength and good yield strength. The tensile strength was1645.43 Mpa, and the yield strength was 1258.69 Mpa.From the research results, the best heat treatment of the B24S steel was that the steel was heated at 900℃for 30 min and cooled to 500℃, isothermal treated for 5 seconds, and cooled in the water. After being treated, the tensile strength was1645.43 Mpa, and the yield strength was 1258.69 Mpa.