Nb Micro Research SAE9310 Steel Alloy Microstructure And Properties

Because of surface properties with high hardness, high wear resistance and good toughness heart performance, SAE9310steel was widely used in aerospace, nuclear power, ships and other military manufacturing fields. The grain coarsening occurs easily as carburizing at high temperature in the high purity SAE9310carburized steel, used in aviation engine, helicopter and other shaft, and which may lead to some performance degradation. In this paper, aiming at the grain coarsening phenomenon put forward the idea of using niobium microalloying technology to improve and optimize the comprehensive mechanical properties of SAE9310steel. The addition of trace Nb based on SAE9310steel,4different components of the experiment steels were designed. By means of heat treatment and hot compression simulation test and mechanical test, the effects on hardenability and grain growth in the high temperature carburizing process of Nb-Microalloyed SAE9310steel were studied; Effect of heat treatment temperature in different process on microstructure and properties of Nb microalloyed SAE9310steel was studied; Hot deformation behaviors of Nb microalloyed SAE9310steel was also studied.The results are as follows:Nb microalloying can effectively prevent SAE9310steel grain coarsening at high temperature, improved the grain coarsening temperature of SAE9310steel; Nb-microalloyed SAE9310steel, austenite grain slowly at high temperature. With the content of Nb increasing, the ability to stop the coarsening become stronger.when Nb content is0.046%, the average grain size of austenite was less than50μm at1200℃; Effect of Nb on the hardenability of steel is less than other elements, resulting in hardenability decreased; The transformation point of Al, A3, Ms temperature were almost not affected by Nb microalloying.Effect of Nb microalloying on S AE9310steel is mainly that the toughness of the steel is improved and effect on the tensile strength, yield strength is not obvious; In the same heat treatment process, SAE9310steel with0.017%Nb has good comprehensive mechanical properties; This topic experiment, the heat treatment process of Nb-microalloyed SAE9310steel, the optimal annealing temperature is650℃, the best of normalizing temperature is between930℃～950℃, the optimum tempering temperature is between150℃～250℃, at these temperature range, the yield strength, tensile strength, impact toughness and hardness of SAE9310steel are the best proportion; With the tempering temperature rise, strength and hardness of steel decreased and plasticity and toughness increased.Nb-microalloyed SAE9310steel, in the condition that true strain is0.92, temperature is900℃～1200℃, strain rate is0.01s-1～10s-1, with the increase of strain rate, the critical temperature of full dynamic recrystallization was gradually increased; With the increase of Nb content, the dynamic recrystallization critical deformation and peak stress increased, thermal activation energy increased, RRT curve move to the right, this is because the Nb microalloying delayed or prevented SAE9310steel dynamic recrystallization; Hot deformation equation of Nb-microalloyed SAE9310steel is established, and the relationship between peak stress and the Z parameters is obtioned.