firstly without touch, then driving the welding electrode slowly together with a preheat current to flash clean the oxidation and uneven surface to make welding area as hot plasticizing.
The temperature of welding area turn to more and more heat and the welding current density increasing together, flash and splash make two touch surface has melted together.
Finally perform a fast upsetting force on welding joint to finish welding and breaking current. This type welding joint has high strength without false welding and pores.
