淬火温度对高Ti低合金耐磨钢组织及力学性能的影响

研究了淬火温度对高Ti低合金耐磨钢组织转变、析出相和力学性能的影响,并分析了组织演变和力学性能变化的原因。结果表明:试验钢经不同温度淬火和200 ℃回火后的组织均为高位错密度板条马氏体;析出相尺寸主要为微米-亚微米-纳米三种尺度,微米级析出相呈杆棒状,亚微米以及纳米析出相呈球状,马氏体板条上分布着细小的(Ti, Mo)C析出相。随着淬火温度的升高,试验钢的屈服强度、抗拉强度和维氏硬度均先升高后降低,均在920 ℃时有最大值,分别为1248 MPa、1535 MPa和434 HV,此时伸长率为10.0%。随淬火温度升高,纳米级析出相逐渐回溶,数量减少且尺寸逐渐长大,沿轧制方向被压扁拉长的原奥氏体晶粒尺寸以及马氏体板条块尺寸略有增大,但马氏体板条宽度却无明显长大。大量的弥散分布的5～10 nm的(Ti, Mo)C粒子是促进耐磨钢硬度升高的主要因素。细小的(Ti, Mo)C析出相逐渐长大以及原奥氏体晶粒的增大都不利于耐磨钢硬度的提高。

Effect of quenching temperature on microstructure and mechanical properties of high Ti low alloy wear-resistant steel

Effect of quenching temperature on microstructure, precipitated phase and hardness of a high Ti low alloy wear-resistant steel was investigated, and the reasons of the change of microstructure and mechanical properties were analyzed. The results show that the microstructure after quenching and tempering is lath martensite with high dislocation density; the size of precipitated phase is mainly divided into micron-, submicron-, and nano-scales, in which the micron-sized precipitates are rod-shaped, and the sub-micron and nano-sized precipitates are spherical; fine (Ti, Mo)C precipitates are distributed on the martensite laths. As the quenching temperature increases, the yield strength, tensile strength and hardness of the steel first increases and then decreases, and reaching the maximum values of 1248 MPa, 1535 MPa and 434 HV respectively when the quenching temperature is 920 ℃, meanwhile, the elongation reaches 10%. With the increase of the quenching temperature, the nano-scale precipitates gradually dissolves and decreases in content but the size gradually increases; and the sizes of the prior austenite grain and the martensitic lath are slightly increased by flattening along the rolling direction, while the width of martensite laths does not increase significantly. The dispersed (Ti, Mo)C precipitates of 5-10 nm in large quantity are the main factor for promoting the hardness increase of the wear-resistant steel. As the quenching temperature increases, the coarsening of both the fine (Ti, Mo)C phase and the prior austenite grain are not conducive to the improvement of the hardness of the wear-resistant steel.