... and save labour YP-D21 20Khz Ultrasonic Metal Welding Machine By using the ultrasonic high frequeccy vibration principle, the ... various hardware and tolls, automobile and motorcycle, machine tools, hardware parts and machine parts, hardware mold, etc.4.Welding/Brazing ... and limited oxic horizon, and can gurad against any waste after annealing.8. Comprehensive Protection: It has such functions ...