关键词: 奥氏体气阀钢, 固溶时效, 组织, 析出相, 性能

Abstract: Effect of solution and aging treatment on microstructure and properties of 34Cr24Ni11Mn4Nb2 austenitic valve steel was investigated by using metallographic microscope, scanning electron microscope, and electronic universal testing machine. The results show that after solution treatment at 1040-1190 ℃ for 30 min, the austenite grains grow significantly with the increase of solution temperature. After solution treatment at 1160 ℃ for 30 min, most of the primary undissolved phases in the original forged state are basically dissolved into the matrix, and the hardness of the alloy decreases gradually. After solution and aging treatment, a large number of secondary phases precipitate in the grain and at the grain boundaries. With the increase of aging temperature(700-850 ℃) and time (1-6 h), granular M₂₃C₆ phases gradually precipitate at the grain boundaries, which plays a good pinning role on the grain boundaries and inhibits the re-growth of grains. When aged at a relatively high temperature above 800 ℃, lamellar precipitates appear in the alloy matrix, leading to a significant decrease in the plasticity of the alloy. During the aging process, the hardness of the alloy shows an overall trend of first increasing and then decreasing. After aging at 750 ℃ for 4 h, the hardness of the alloy reaches a maximum of 324.5 HV, the tensile strength reaches 1159.4 MPa, the yield ratio is 19.1% lower than that of the as-forged, and the total extension after fracture reaches 29.52%.

Key words: austenitic valve steel, solution and aging treatment, microstructure, precipitated phase, properties