电站锅炉用HR3C新型奥氏体耐热钢的激光焊接

超(超)临界电站锅炉用新型铁素体、奥氏体耐热钢对传统焊接技术提出了挑战.激光焊接技术作为一种可靠高效的先进焊接方法,为此类钢的焊接提供了经济可行的解决办法.采用窄间隙激光填丝焊接技术,研究了10 mm厚HR3C新型奥氏体耐热钢管的激光焊接性,并对接头显微组织及高温持久强度进行了分析.试验采用3 500 W Slab CO2激光器,填充焊丝为T-HR3C.结果表明,通过优化激光焊接工艺参数,可以获得X射线探伤和渗透检验合格的焊接接头;焊缝具有明显的沿中心对称形态,以细小的柱状晶为主,混夹着少量细小的等轴晶;热影响区晶粒没有明显长大,焊缝与母材的显微硬度相当,没有明显的软化区;焊态下的激光焊接接头高温持久强度较固溶处理的热丝TIG焊接头有明显提高.

Laser welding of new type austenite heat-resistant steel HR3C for ultra supercritical boilers

New types of ferrite and austenite heat-resistant steels used in supercritical or ultra supercritical boilers have issued challenges to conventional welding techniques.As a reliable and advanced joining technique, laser welding may be one of the promising solutions for the welding of these steels due to the low heat input.A slab CO₂ laser with an output power of 3500 W was applied and the narrow gap laser welding process was adopted with T-HR3C filler wire to weld HR3C tubes of the new type austenite steel with a thickness of 10 mm.The joint microstructure and high temperature lasting strength were investigated.It is found that a sound joint can be obtained by optimizing the process parameters.The microstructures in the weld bead are fine column austenite grains with a few fine equiaxed austenite grains, appear more or less symmetrically along the bead center.The grain size in the HAZ is not obviously coarsening.The micro-hardness in the weld is correspondence with that of the base metal, and no obvious softened zone is observed.The high temperature lasting strength of the laser welded joint in the as-welded condition is distinctly improved compared to that of TIG welding joint with post-weld heat treatment.