GD钢组织及低温冲击韧性研究

Study on microstructure and low temperature impact toughness of GD steel

分析了900℃淬火及200℃回火后GD钢的显微组织、硬度及低温冲击的断口形貌,研究结果表明:900℃淬火后GD钢组织由粗针状马氏体、残余奥氏体、碳化物组成,200℃回火时,马氏体中析出部分碳化物,回火组织由回火马氏体和碳化物组成。900℃淬火+200℃回火后的GD钢冲击时,随着温度的降低,其冲击功随之减小,随着GD钢所处的环境温度不断升高,断口宏观形貌中反映起裂区和裂纹纤维扩展区所占比例越来越大,微观形貌中存在解理面、撕裂棱和韧窝,其断裂机理为准解理断裂。

The microsturcture,hardness of GD steel after 900℃ quenching and 200℃ tempering,and the impact toughness and fractography of GD steel after impact test at low temperature were observed and analyzed.The results showed that the microstructure of 900℃ quenched GD steel was composed of coarse needle martensite,retained austenite,and carbide.Some carbide was precipitated from martensite after 200℃ tempering.When GD steel was quenched at 900℃ and tempered at 200℃,the impact energy decreased with the decrease of temperature.With the increase of the ambient temperature of the GD steel sample,the ratio of the crack initiation zone and the crack fiber propagation zone in the macro-morphology of the fracture surface became larger and larger.There were cleavage planes,tearing edges and dimples in the micro morphology,and the fracture mechanism was quasi-cleavage fracture.