外场处理对低合金钢焊接接头组织和性能的影响

Effects of External Field on the Structure and Properties of the Low Alloy Steel Welding Joint

研究了电磁搅拌、氩弧表层处理、超声喷丸处理对低合金钢焊接接头组织和性能的影响。结果表明 :电磁搅拌促进奥氏体晶粒内针状铁素体生成和细化 ,使针状铁素体的含量由 85%提高到 92 % ,从而提高了焊缝金属的韧度。氩弧加热处理使焊缝表层发生熔化和重结晶 ,可消除焊缝表层的柱状晶 ,处理后的组织主要由针状和细晶铁素体组成。对接头焊趾部位进行氩弧快速重熔处理可消除焊趾部位的几何截面突变 ,使焊缝与母材圆滑过渡 ,有利于消除焊趾部位的应力集中 ,对抗应力腐蚀性能十分有益 ;焊趾部位热影响区中粗大的晶粒细化。表面高能喷丸处理使焊接接头表面层形成尺寸均匀的等轴状纳米晶 ,不仅提高了表层的硬度 ,而且可使焊接接头的疲劳强度提高 50 %。

The effects of electromagnetic stirring treatment, TIG surface treatment and high energy shot peening (HESP) treatment process on the microstructures and properties of deposited metals and joint were investigated. Experimental results showed that electromagnetic stirring promoted the formation and refining of acicular ferrite (AF) within austenite gains. The contents of AF within austenite grains were increased from 85% to 92% and the low temperature toughness of deposited metal was improved. TIG surface treatment process eliminated columnar grain structures of surface layer of welds. The acicular ferrite was greatly refined. This process can also make the welding toe more smooth, which can eliminate stress concentration there and refine the columnar grain of the coarse HAZ grain. Surface high energy shot peening treatment process increased not only the hardness of welding joint surface,but also improved the fatigue strength by 50%,which attributed to the formation of the uniform size and equiaxial nanometer microstructure in the welding joint surface.