A displacement threshold was used to control DC upset butt welding process, and constantpressure and varied pressure tests were carried out on Q235 a steel strips.
采用位移门槛电压控制焊接过程，对Q 235 - A钢进行了变压式和等压式扁钢带直流电阻对焊试验。
2
Consequently it is difficult to optimize the weldingpressure in pressure constant mode used in conventional ultrasonic plastic welder.