2507超级双相不锈钢激光焊接接头组织和力学性能研究

Study of microstructure and mechanical properties of 2507 super duplex stainless steel welded joint by laser welding

使用氩气作为保护气,采用激光焊焊接2507超级双相不锈钢,获得成型良好的激光焊接接头,利用SEM和EDS研究了接头不同区域奥氏体和主要合金元素的含量,并对接头进行室温拉伸、冲击和硬度测试.结果表明:由于激光焊接过程冷却速度较快,焊缝铁素体主要以垂直于熔合线的柱状晶的形态存在,晶内析出的奥氏体更加细化,接头焊缝区,特别是热影响区中铁素体的含量明显增多.与母材相比,焊缝中主要合金元素在两相中含量的差异明显减小.接头室温力学性能测试结果显示,由于铁素体的含量升高,并且以较为粗大的柱状晶形态存在,导致接头的拉伸强度和硬度升高,冲击韧性明显下降.

Sound weld of 2507 superduplex stainless steel could be obtained from laser welding by employing the established process parameters with argon as shielding gas. The ferrite content and composition of main element in two phases of welded joint and base metal were studied by means of SEM and EDS,meanwhile the mechanical properties including tensile,impact test and micro-hardness were tested at room temperature. The results show that because of the fast cooling rate,the ferrite exists as columnar crystals perpendicular to the fusion-line and the size of intra-granular austenite becomes smaller in fusion area. Compared with the base metal,the ferrite content in fusion zone especially in heat affected zone is much lower,and the difference of the content of main element between two phases of weld joint are smaller. The mechanical tests show that because of the highercontent of ferrite in fusion area and the presence of fine intimate precipitates of austenite and coarser columnar crystals,the tensile strength and micro-hardness of welded joint are greater than those of the base mental while its toughness is obviously lower than that of the base metal.