热处理对TP347H钢组织结构及力学性能的影响

本文通过800--900℃的加速老化试验，研究热处理过程中TP347H钢的组织结构及力学性能的变化特征。结果表明：800℃，58h热处理，原奥氏体晶粒尺寸稳定，碳化物颗粒在晶界及晶内弥散析出；900℃，5．5h高温热处理后，析出碳化物聚集长大，导致晶界宽化。经900℃，5．5h高温处理后，TP347H钢仍为韧窝聚集型断裂，但断裂面相对平整，韧窝细而浅，且沿基体晶界有二次裂纹扩展。上述组织结构的变化导致热处理过程中TP347H钢的强度持续降低，而塑性先增加，后降低。

Effect of Heat Treatment on Microstructures and Mechanical Properties of TP347H Steel

An accelerated aging experiment at 800--900℃ was carried out to study changes of microstructures and mechanical properties of TP347H in the heat treatment. The results show that after annealed at 800℃ for 58h, the grain size of the previous austenite of TP347H is not varied, and there are a lot of carbides precipitated inside and along the grains. After TP347H annealed at 900℃ for 5.5h, the carbide particles aggregate and grow, resulting in broadening of its grain boundaries, and its fracture mechanism is still of dimple fracture. However, the fracture surface of the annealed TP347H steel is rather smooth, in which there set many small and shallow dimples, and the secondary cracks along the grains. The microstructural changes mentioned above lead to the strength of the steel decreases continuously, and the plasticity of the steel increases firstly, and then decreases as increasing the heat treatment temperature from 800℃ to 900℃.