针对超声检测火力发电厂锅炉小径管奥氏体钢与低合金钢对接异种钢焊缝的技术难题，文章通过理论分析、试验研究及现场检测验证，研究了常规小径管探头异种钢焊缝超声波检测方法。结果表明，对于如熔合线裂纹类缺陷选用小角度探头(K1~1.5)效果较佳；对于焊缝内缺陷宜选用大角度探头(K2~2.5)。利用该方法能有效检测出焊缝内各种缺陷，保证了机组安全运行也取得了较好的经济效益，对异种钢焊缝小径管超声波检测具有较强的借鉴意义。

In order to solve the ultrasonic testing technical problem of dissimilar steel small diameter tube nickel butt welding of austenitic steel and low alloy steel in thermal power plant, one new ultrasonic inspection method with small diameter tube adapted ultrasonic probe was researched by theory verification, experimental data and field experience. The results showed that the degrees of the influences of different defects on ultrasonic testing parameters were different. Better sensitivity for the fusion zone cracking in dissimilar steel smalldiameter tube welding joint testing was obtained when K value of transverse wave probe was small, such as K1~1.5. And it is good that K value of transverse wave probe was big (K2~2.5) for internal defects in dissimilar steel smalldiameter tube welding joint testing. This detective means had good detection effect for various excessive weld defects, which could ensure the safe operation of power units, improve economic benefits. The detection method mentioned in this paper could give assistance to the ultrasonic testing of dissimilar steel smalldiameter tube welds.