高强焊丝熔敷金属力学性能及组织分析

Property and microstructure of deposited metal with high strength wire

利用金相显微镜、扫描电子显微镜(SEM)及附带能谱仪(EDS)并通过常温拉伸和低温冲击等试验研究了不同保护气体下高强焊丝熔敷金属组织和强韧性变化.结果表明,针对此高强度气体保护焊焊丝,采用Ar+5%CO2保护气体,熔敷金属强韧性最佳;焊缝金相组织为粒状贝氏体+板条贝氏体,细小板条束可有效提高焊缝韧性;M-A组元存在明显C元素富集的现象,大量块状M-A组元的出现造成M-A组元基体间位错塞积,引起应力集中,在裂纹形核阶段易萌生微裂纹,对韧性不利;采用Ar+2%O2和Ar+20%CO2保护气体,焊缝中较大尺寸夹杂物数量增多,是诱发准解理断裂引起冲击吸收功降低的主要原因.

The microstructure and mechanical properties of deposited metal under different shielded gases were investigated by means of optical microscopy,scanning electron microscopy with EDS,tensile and impact tests. The results indicate that the best mechanical properties of deposited metal with the medium alloy solid wire were acquired when welded with Ar + 5% CO2 mixed gas. The granular bainite dominated the microstructure of the deposited metal,and the existence of fine lath bainite improved the toughness effectively. In addition,carbon obviously enriched in M / A constituents,and massive M / A constituents could cause stress concentration by dislocation pile-up between M / A and base metal. Meanwhile,the micro crack appeared fre-quently at the stage of crack nucleation. The increase of inclusions with large size was the main reason of the appearance of quasi-cleavage fracture and the decrease of impact absorbed energy.