焊接热输入对低碳贝氏体金属粉芯焊丝(CHT120CK4)熔敷金属组织和力学性能的影响

Effect of welding heat input on microstructure and mechanical properties of deposited metal for a low carbon bainite metal powder cored wire(CHT120CK4)

采用一种低碳贝氏体金属粉芯焊丝进行对接焊接,研究不同热输入(13.4~20.6 kJ/cm)对低碳贝氏体金属粉芯焊丝熔敷金属组织、拉伸性能和冲击韧性的影响。结果发现,低碳贝氏体熔敷金属的原始焊缝、焊缝内再热区组织都由粒状贝氏体和准多边形铁素体(QPF)组成。随着热输入的增加,原始焊缝、焊缝内再热区中的粒状贝氏体含量呈现先增大后降低的变化规律,随着热输入的增加,熔敷金属的屈服强度、抗拉强度先增大后降低,与微观组织的变化趋势一致;17.9 kJ/cm热输入下熔敷金属的屈服强度、抗拉强度均达到峰值;随着热输入的增大,冲击韧性逐渐降低。在室温和-50℃下13.4 kJ/cm热输入的熔敷金属具有较好的拉伸塑性和冲击韧性,这主要与低热输入下的细小晶粒相关。

In this study,a kind of low carbon bainite metal powder cored wire was used for butt welding,and the effects of different welding heat inputs on the microstructure,tensile properties and impact toughness of deposited weld metals were investigated.The results showed that the microstructure of original weld(cover weld)and reheated zone in low carbon bainite deposited weld metals consists of granular bainite and quasi polygonal ferrite.The granular bainite content in the original weld metal and the reheated zone in the deposited weld metals first increases and then decreases with the increase of welding heat input.The yield strength and ultimate tensile strength of the deposited weld metals also increase first and then decrease with the increase of welding heat input,which is directly related to the change of the microstructure.The maximum yield strength and ultimate tensile strength of the deposited weld metals can be reached at the welding heat input of 17.9 kJ/cm,while the impact toughness decreases with the increase of welding heat input.The deposited weld metal at the heat input of 13.4 kJ/cm shows the best impact toughness at room temperature and-50℃,which is directly related to the fine grains with smaller heat input.