Capacitor Discharge Welding Percussion Welding Magnetic Force (AC) Stud Welding The stud welding process is a process used to weld studs onto a workpiece in order to attach that workpiece to some other structure using the stud. It is commonly used for attaching fascia to buildings or for attaching automotive or appliance body panels or trim, etc..

Stud Welding Learning Activities View Slides; Lesson Objectives Read Notes, Listen to lecture Do on-line workbook Lesson Objectives When you finish this lesson you will understand: The three methods of stud welding Typical Applications of this process Keywords Stud Welding, Capacitor Discharge, Initial Contact Method, Initial Gap Method, Drawn Arc Method

Variations of Capacitor Discharge Stud Welding Initial Contact Method Initial Gap Method There are a couple of variations in the stud welding process. They all have some sort of a stud, either threaded or not, but vary in the application of the stud to the workpiece. These variations include the “initial contact method” the “initial gap method” and the “drawn arc method” as illustrated here. In the initial contact method, there is usually a nib on the end of the stud which is brought into contact with the workpiece before the weld contactors are closed and before and current flows. When the contactors are closed, all the current from the capactors discharge through the nib, melting it and providing heat while the stud is rammed into the part, the liquid fluxing the interface and the weld made. In the initial gap method, the stud is separated from the workpiece by a short distance, the contactor is closed but no current flows because of the gap. Then the stud is rammed into the workpiece. At the moment of contact of the nib, current flows, melting occurs and the weld is made. The drawn arc process is a little different. Usually the drawn arc studs do not have a nib on the end, but rather have a somewhat rounded or conical shape, and they tend to be of the larger diameter. The studs are initially in contact with the workpiece, the contactor is closed and the stud is drawn back from the workpiece to start an arc. The the motion is revered and the stud is rammed into the workpiece making the weld. The drawn arc process takes a little more control but the current is larger so large studs, up to 1 inch diameter, can be welded. Drawn Arc Method AWS Welding Handbook

Initial Contact Method is used only with portable quipment, principally for welding mild steel studs. Equipment simplicity makes it ideal for welding mild steel insulation pins to galvanized duct work. Initial Gap Method is used with portable and fixed equipment for welding mild steel, stainless steel, and aluminum. Generally, it is superior to both the drawn arc and initial contact methods for welding dissimilar metals and aluminum. Inert gas is not needed for welding aluminum. Above is a description of the most often used applications and materials with each of the methods. Drawn Arc Method is ideally suited for high speed production applications involving automatic feed systems with either portable equipment or fixed position. Inert gas is required for aluminum. AWS Welding Handbook

Typical Parameters For the Three Variations Peak Welding Currents Vary from 600 - 20,000 amps Here is the weld current vs. time (in milliseconds) curves for each of the processes. The initial contact and initial gap methods generally have higher current peaks but shorter time of current flow than does the drawn arc method. The peak weld currents can reach 600 to 0ver 20,000 amps. Drawn Arc has lower peak current - longer time AWS Welding Handbook

This is a table from the Welding Handbook with typical materials that can be stud welded. Notice the wide variety of materials listed. AWS Welding Handbook

A good stud weld looks like that presented in A A good stud weld looks like that presented in A. There is some liquid metal squeezed out to effect the fluxing action. A poor weld with power too high shows excessive splashing, while a poor low power weld show no melting at all. Any tangential load on this stud would probably cause a weld centerline failure. AWS Welding Handbook

This is as an example of the stud before welding with the nib clearly showing. After welding the nib and part of the base melt and the weld metal squeezes out at the bond line. Metals Handbook, ASM, 1983

to facilitate arc start Most often used, easily machined Flange Used for Drawn Arc. Slightly pointed to facilitate arc start Most often used, easily machined Used for critical applications and nonflanged Aluminum Here are a few examples of stud shapes and the applications in which they are used. Metals Handbook, ASM, 1983

Here is an example of a initial gap stud welding gun Here is an example of a initial gap stud welding gun. The stud is places into the brass collate at the end. The three feet help position and stabilize the gun for application of the stud. AWS Welding Handbook

This is the hook-up arrangement with the gun, power supply and workpiece. Metals Handbook, ASM, 1983

Here is an example of a drawn arc stud welding arrangement attached to an automated device. AWS Welding Handbook

The are a number of ways to apply the accelerated force to the stud The are a number of ways to apply the accelerated force to the stud. In this case the gun is spring loaded which activates upon trigger application. Spring Loaded Hand Gun Metals Handbook, ASM, 1983

Gravity Drop In this case, gravity drop mechanism applies the force. Metals Handbook, ASM, 1983

Automated Initial Gap Machines often have a detergent spray With Detergent Spray Weld spatter is often a concern with stud welding and it has been found that the application of some detergent to the weldment before welding helps reduce the spatter. Without Detergent Spray Automated Initial Gap Machines often have a detergent spray between gap before welding to reduce weld spatter. Metals Handbook, ASM, 1983