Research Of Heat Treatment Process On High Performance Steel

The steel materials is the basic material to human society and a sign of social civilization. With the rapid development of the world economy, ordinary steel materials can not meet development of the community, those high-performance steel materials play a more and more important role in life. In order to obtain the required properties, they often need to be heat-treated to change the microstructure of the steel materials, than improving the performance of the steel to meet the practical need. In this paper, taking SA516Gr60N-HIC acid vessel steel, X80 M pipeline steel, 60Si2 CrVAT spring steel as the research object, the main results are as follows:(1) The Grain growth behavior of austenite under different austenitizing temperature and solid solution regularity of microalloyed elements(Nb,Ti and V) in SA516Gr60 N acid vessel steel were studied via metallographic microscopy. The research results shown that, with the increase of austenitizing temperature, The austenite grain size were increased. When austenitizing temperature was 990~1070 ℃, with the increase of austenitizing temperature, the austenite grain size increased slowly, and the austenite grain were small and homogeneous; When austenitizing temperature was 1070~1150 ℃, the austenite grain size grew up rapidly with greatly obvious heterogeneity. When austenitizing temperature was 1170~1210 ℃, the austenitic grain size became more uniform with increasing austenitizing temperature.With the increase of austenitizing temperature, the amount of solid solution of microalloyed elements(Nb,Ti and V)were gradually increased. When austenitizing temperature was under 1070 ℃, there were lagre amounts of undissolved microalloyed carbonitride particles; When austenitizing temperature was 1070~1150 ℃, most of microalloyed carbonitride particles were dissolution; In 1150~1210 ℃, when the size of microalloyed carbonitride tend to stable, or far more than the dissolution temperature of microalloyed carbonitride, austenitizing grain occured normal grow and their size gradually became uniform. So it was recommended that the heating temperature was controlled at about 1200 ℃.(2) The Grain growth behavior of austenite under different austenitizing temperature and solid solution regularity of microalloyed elements(Nb,Ti) in X80 M pipeline steel were studied via metallographic microscopy. The research results shown that, with the increase of austenitizing temperature, The austenite grain size were increased. When austenitizing temperature was 1120~1150 ℃, austenitizing grain were uniform and increased slowly; When austenitizing temperature was 1165 ℃, partial austenitizing grain occured coarsening phenomenon; When austenitizing temperature was 1180 ℃, austenitizing grain was significantly increase, and obvious nonuniform phenomenon emerge. When austenitizing temperature was 1195 ℃, the heterogeneity phenomenon austenitic grain were more obvious; When austenitizing temperature is 1210 ℃, the austenitizing grain were more thick.With the increase of austenitizing temperature, the amount of solid solution of microalloyed elements(Nb,Ti)were gradually increased. When austenitizing temperature was under 1165 ℃, there were lagre amounts of undissolved microalloyed carbonitride particles; When austenitizing temperature was over 1165 ℃, due to the dissolution of microalloyed carbonitride particles, the effect of pinning was reduced, so the austenitizing grain began to grow. So it was recommended that the heating temperature was controlled at about 1700~1200 ℃.(3) Using scanning electron microscope, metallurgical microscope and so on, through three different induction heating heat-treatment technology to study the change on tempered microstructure and properties of 60Si2 CrVAT spring steel. The research results shown that, With the tempering temperature increased, the hardness and tensile strength of 60Si2 CrVAT spring steel gradually decreased. The surface hardness of sample varied greatly, the hardness of 1/2 the radius to the center was relatively uniform; the samples surface occured decarburization under three heat-treatment. For decarburization, either pre-rod existed decarbonization layer or heat treatment temperature was unreasonable, or paint apply uneven, it remained to be further studied.