双相区热处理对A508-3钢的冲击性能及断口形貌的影响

Effect of double-phase area heat treatment on impact property and impact section of A508-3 steel

采用Charpy(V型缺口)试样对A508-3钢调质处理试样和双相区热处理试样在-196～20℃温度范围内进行示波冲击试验,用扫描电镜对冲击断口形貌进行观察,研究了冲击温度对两种热处理制度下该钢的冲击性能和断口形貌的影响。调质处理试样随着温度的降低,其冲击功和侧膨胀量急剧降低,断裂方式从韧脆混合断裂变为脆性断裂,断口形貌中纤维区和剪切唇面积不断减少,放射区面积相应增大;双相区热处理试样在-20～-100℃冲击时,其冲击功和侧膨胀量改变甚小,断裂方式为全韧性断裂,断口形貌全部为剪切唇和纤维区组成,随着温度的继续降低,冲击功和侧膨胀量开始急剧下降,断裂方式变为韧脆混合断裂,断口形貌出现放射区,放射区微观特征为准解理。与调质处理相比,该钢经双相区热处理后冲击性能大大提高,韧脆转变温度急剧降低。

The impact test of A508-3 steel after QT and double-phase area heat treatment was carried out using the Charpy V notch samples at the temperature of-196 ℃ to 20 ℃.The fracture pattern of the samples was observed under the SEM.The effects of impact temperature on impact toughness and fractograph of the steel after QT and double-phase area heat treatment were investigated.The results show that with the decrease of temperature,the impact energy and lateral expansion of the steel after QT have a sharp reduction,the fracture type is changed from a mix of ductile and brittle rupture to cleavage fracture,the fiber area and the shear lip area are decreased,and the radiation area is increased.When the double-phase area treated samples tested at the temperature of-100 ℃ to-20 ℃,the impact energy and the lateral expansion are changed slightly,the fracture type is full ductile fracture,the impact section is composed of the fiber area and the shear lip area.As the temperature continued to decline,the impact energy and the lateral expansion begin to sharp decline,the fracture type is changed to a mix of ductile and brittle rupture,the radiation area emerges on the fracture surface,the characteristic of the radiation area is quasi-cleavage.Compared with QT,the impact toughness is greatly increased and the ductile-brittle transition temperature（DBTT） dramatically reduces when the A508-3 steel is conducted double-phase area heat treatment.