Stud Welding

Date 01-04-2005 05:34

The two basic methods of stud welding are known as stud arc welding and capacitor discharge welding.
There are three different methods of capacitor discharge stud welding include: initial contact, initial gap, and drawn arc. In our experience, the initial contact method required a better surface preparation than the stud arc method, but produced less strength than the arc type, and the capacitor discharge welding that we used is impossible to pass the test requirements of ASME Section IX. The only reason that our customer specified to use capacitor discharge method is based on the reason of this method would result in less heat input and less deformation of the component, and the studs are to be used as anchors on the water wall panel of a boiler for the refractory which actually required very little strength to hold the refractory in place. The stud arc method can penetrated the base metal to provide a strength weld but this method generally need a ferrule, and would result in heavy deformation of the component, which required a futher torch heating at the opposite side for straighten up of the work piece.
Kind regards
H.Chang

By H. Chang (*)

Date 01-04-2005 05:52

Auto feed system can be used for both methos, but for capacitor discharge method, because no ceramic ferrule is required, is suited for high speed autou feed application. But again, if we are dealing with boiler stud, we always use manual, there is no meaning to use auto feed gun, you can't save much time for welding, when you handling a heavier gun in different welding positions.
Kind regards
H.Chang

By chinnaphat Date 01-08-2005 10:43

Any body know what is drawn-arc capacitor discharge stud welding?
How is it different from common drawn-arc or capacitor discharge?
and how can I find more data about it

By swnorris (****)

Date 01-08-2005 12:58

Hi chinnaphat,

As H. Chang mentioned, there are three types of capacitator discharge stud welding. The initial contact method, the initial gap method, and the drawn arc method. The three differ primarily in the manner of arc initiation. Initial contact and initial gap capacitator discharge studs have a small, specially designed projection tip on the weld end of the stud. Drawn arc stud welding creates a pilot arc as the stud is lifted off the work piece by a gun, which is similar to arc stud welding. In the drawn arc method, arc initiation is accomplished in a manner similar to that of arc stud welding. The stud does not require a tip on the weld face. An electronic control is used to sequence the operation. Weld time is controlled by an electrical circuit in the unit. The welding gun is similar to that used for arc stud welding. The stud is positioned against the work;the trigger switch on the stud welding gun is actuated, energizing the welding circuit and a solenoid coil in the gun body. The coil motion lifts the stud from the work, drawing a low amperage pilot between them. When the lifted coil is de-energized, the stud starts to return to the work. The welding capacitators are then discharged across the arc. The high amperage from the capacitators melts the end of the stud and adjacent work surface. The spring action of the welding gun plunges the stud into the molten metal to complete the weld.