Tube closure welds, commonly called pinch welds, are made by solid state upset welding, where quality assurance consists of process control and geometric feature verification. Ultrasonic nondestructive evaluation demonstrated the feasibility for sorting oxide contaminated pinch welds from clean welds. Until now contaminated pinch welds could only be detected by destructive testing. Two approaches are presented in this paper. First, a study was conducted to detect the variation in the ultrasonic signal caused by interaction with the pinch weld. Correlations between the good and bad welds were accomplished with feature extraction and pattern recognition techniques. The second approach involved high resolution scanning of the pinch weld with an acoustic microscope. The acoustic microscope produced excellent color images of the weld which clearly distinguished the pre-weld cleanliness.