The quality of spot welding joint in 1mm SUS304 austenitic stainless steel sheet was evalua-ted by using ultrasonic water immersion focusing method.The features of the ultrasonic C-scan image and nugget diameters were analyzed under different welding process parameters.Furthermore,the tensile-shear tests were carried out to examine the mechanical behavior of sport welding joint.The re-sults show that the C-scan image can effectively get nugget diameter from the inner pattern of the spot welding joint based on ultrasonic water immersion focusing C-scan method.The measured nugget diameter is range from 4.76mm to 5.25mm,and it is 2.6%-5.3% larger than inspection diameter. When the welding current is changed from 4kA to 8kA,the failure load average increases from 7116.8N to 9707.1N and energy absorption value increases from 66.3J to 196J.And the nugget diam-eter of the ultrasonic C-scan image increases from 4.76mm to 5.11mm,too.When the welding cur-rent is added to 9kA,the failure strength decreases to 6799.5N and energy absorption value decreases to 41.3J rapidly,it can get the information which includes splash,solder to wear and other weld defects from the ultrasonic C-scan image.%利用超声波水浸聚焦入射法,对1mm厚的SUS304奥氏体不锈钢板点焊接头进行超声C扫描成像检测,研究不同焊接工艺参数下接头的C扫描图像特征,检测分析点焊的熔核直径,并对点焊接头进行拉伸-剪切实验.结果表明:超声波水浸聚焦C扫描成像法能够有效检测点焊熔核直径,为4.76~5.25mm,比金相实测值大2.6%~5.3%;随着焊接电流的增加(4~8kA),接头的失效载荷均值从7116.8N增加到9707.1N,能量吸收均值从66.3J增加到196J,同时反映在C扫描图像上的熔核直径也从4.76mm增加到5.11mm;当焊接电流增加至9kA时,接头的失效载荷均值下降至6799.5N,能量吸收均值下降至41.3J,此时在C扫描图像上反映出飞溅、焊穿等典型的焊接缺陷.
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