What is Stud Welding?

Stud Welding is a one-step metal fastening process in which a metal fastener is applied by a welding arc to another piece of metal for a high-quality, high-strength permanent bond. The strength of the weld is often stronger than the stud and parent material combined. There are many fasteners that can be stud welded included threaded studs, unthreaded studs, tapped studs, weld pins and more. Stud welding works for all types of metals including mild steel, stainless steel, aluminum, titanium, zinc, copper, brass and many alloys. The equipment required for stud welding is made up of a power supply, a stud gun, ground and weld cables.

TYPES OF STUD WELDING

Capacitor Discharge Stud Welding – The CD stud welding process utilizes a powerful bank of capacitors to store energy at a specific voltage determined by stud size and material. When a weld is initiated, this energy is “discharged” through a special “ignition tip” at the base of the stud, creating an instantaneous arc which melts both the base of the stud and the adjoining surface on the work piece. At the same time, the welding gun forces the stud into the work piece, resulting in a permanent bond as the molten material solidifies. This process is suitable for studs ranging in size from #4-40 (M3) thru 3/8-16 (M10).

Drawn Arc Stud Welding - Drawn arc stud welding joins a stud to another piece of metal together by heating both parts with an arc.It is suitable for larger diameter welds on materials of 3/8” and above thickness, including metals with curvature or imperfections such as rust and grease.

WHAT IS THE STUD WELDING PROCESS?

1. The weld stud or weld pin is placed in the stud gun.
2. The stud gun trigger is pressed and a weld arc is drawn that melts the welding stud base and the a proportionate area of the base metal.
3. The weld stud is then forced into the melted area and held in place until the metals harden. The weld process is completed in less than one second.

WHAT ARE THE BENEFITS OF STUD WELDING?

FAST - Welds take milliseconds per stud.
COST EFFECTIVE - Stud welding is more efficient than other fastening systems saving you time and money.
STRONG - Stud welding gives you a complete cross-sectional weld with a bond that is stronger than the surrounding metal unlike a hand weld that only has a fillet on the outside.
ACCURATE - Stud welding allows you to locate your welded stud precisely. You can also automate the process.
DECORATIVE - CD studs are welded to one side of the work piece, allowing an attractive appearance on the back side.
SIMPLE - Stud welding is simple and easy to learn. We can get up an running in 20 minutes.
MATERIALS - Stud welding is compatible with a variety of metals as well as able to Join different materials together.
DIAMETER - Welds studs with diameters between 0.079” to 1.25”.

STUD WELDING TERMINOLOGY

Common Terminology for Both CD and Drawn Arc Stud Welding:

• Stud: The fastener being welded. It can be threaded, unthreaded, headed, collared, etc., and made from various metals like steel, stainless steel, aluminum, etc.
• Base Metal (or Parent Material or Workpiece): The material onto which the stud is being welded.
• Weld Gun (or Hand Tool): The tool the operator uses to hold and position the stud during the welding process. It contains the mechanism for applying force (plunge) and sometimes lift.
• Power Source (or Controller): The electrical unit that provides the necessary voltage and current for the welding process. The type of power source differs significantly between CD and Drawn Arc.
• Ground Cable (or Work Cable): The cable that connects the power source to the base metal, completing the electrical circuit.
• Chuck (or Collet): The part of the weld gun that securely holds the stud. Different stud types and sizes require different chucks.
• Weld Cycle: The entire sequence of events that occurs during the stud welding process, from initiation to the completion of the weld.
• Plunge: The amount of the stud sticking out past the foot or ferrule.
• Weld Fillet: The bead of weld material that forms around the base of the stud where it joins the base metal. A good fillet indicates a sound weld.
• Weld Time (or Arc Time): The duration for which the welding current flows and the arc is maintained. This varies greatly between CD and Drawn Arc.
• Tensile Strength: The maximum stress that the weld can withstand while being pulled apart.
• Shear Strength: The maximum stress that the weld can withstand when forces are applied parallel to the weld.
• Weld Penetration: The depth to which the weld metal fuses into the base metal.
• Spatter: Molten metal expelled during the welding process. Excessive spatter can indicate incorrect settings or technique.
• Bend Test – A test to ensure a good weld by bending the stud or pin with a piece of tubing, or by striking it with a hammer. The stud can be bent 30 degrees away from its weld axis or until failure occurs. Satisfactorily welded studs should exhibit a complete 90 degree bend without failure. The stud or pin should fail in the shank portion of the stud or pin, not at the weld base. In the case of thin base metal, a plug may be pulled out of the base metal.
• Burn Off – The amount of stud that is consumed during the weld. This burn off material forms the weld fillet. 
• Burn Through – A situation where the weld excessively distorts or actually melts through the base material. This is caused by an excessively hot weld or by using base material that is too thin.
• Cold Weld – A cold weld can be identified if the fillet is not formed completely around thee stud being pushed into the weld pool. There is little or no splatter at the weld site and there may be a void between the stud and the workpiece. Adjust the voltage upwards.
• Hot Weld – A hot weld can be identified by excessive splatter and a thin weld fillet. To get a better weld, adjust the voltage downward.
• Control Cable – The thin cable that connects the stud gun to the controller. This cable carries the trigger signal from the gun to the controller and the lifting voltage back from the controller to the gun.
• Controller -The controller initiates the pilot arc, sends the lift signal to the stud gun, starts the weld current at the right time and controls the duration of the weld.
• Current – Current is the flow of electrons. Stud welding uses DC (Direct Current). 
• Fillet – The ring of weld metal that surrounds the stud after welding.
• Flux Ball – A metal tip or nib pressed into the end of most weld studs. During the weld process the flux ball vaporizes and consumes the oxygen at the weld site. This helps to eliminate contaminates in the weld itself.
• Stud - The fastener an operator can affix to a metal sheet using stud welding. Welding studs come in a range of materials, including stainless steel, mild steel, pure aluminum, aluminum alloy, lead-free brass, and copper. The studs can take different forms, but typically fall under threaded, unthreaded, or tapped.
• Torque Test – A test to ensure a good weld for threaded and non threaded studs. Twist the stud to the point of failure by applying a twisting tensile load using a collar, washer and nut.
• Welding Time – Time is the duration of the weld. It starts at initial ignition and ends at the extension of the main arc.
• Weld Zone - The area under the welded cross-section.

Terminology Specific to Capacitor Discharge (CD) Stud Welding:

• Capacitor Bank: The component in the power source that stores the electrical energy to be discharged rapidly for the weld.
• Discharge: The rapid release of stored electrical energy from the capacitor bank through the stud.
• Collet – A collet is always required for CD stud welding. It is important that the proper sized collet be used and that it is in good condition. Loose fitting collets will result in arcing on the stud and poor welds. A different collet is required for each pin and stud diameter.
• Collet Protector – A collet protector is used when welding insulation pins. Using a protector allows you to weld various lengths of studs or pins without a set up change. It also keeps weld platter away from the collet.
• Pip (or Weld Tip): A small projection on the end of a CD stud that initiates the arc upon contact with the base metal in contact CD welding. This vaporizes during the weld.
• Contact CD Welding: A type of CD welding where the stud is initially in contact with the base metal, and the discharge creates the arc at the point of contact.
• Gap CD Welding: A type of CD welding where the stud is initially held slightly away from the base metal, and a pilot arc is established before the stud is plunged. This allows for very fast welding, often used for aluminum.
• Minimal Backside Marking: Due to the very short weld cycle, CD welding often results in minimal heat transfer and distortion on the reverse side of the base metal.
• Flanged – Flanged Capacitor Discharge weld studs have a projecting flat rim or collar on the weld end of the stud. The stud gun fires the stored electricity through the stud and melts the projection onto the base material. By using flanged CD weld studs, a strong bond between the base material and stud is created.
• Spark Shield – The spark shield protects the collet from stabilizing the pin or stud during the weld cycle. The spark shield will require occasional cleaning and periodic replacement.
• Stop – A stop is required when welding CD studs. It is put in the collet and used to ensure the right amount of the weld stud is in the collet. Hanlon recommends using a Universal stop that can be cut down to your desired length. Some collets have a built in stop.

Terminology Specific to Drawn Arc Stud Welding:

• Drawn Arc: The welding process where the stud is lifted from the base metal to create an arc, which melts the end of the stud and the base metal before the stud is plunged into the molten pool.
• Chuck Adapter – This holds the drawn arc chuck in the stud gun and connects to the internal lifting mechanism. The weld current flows from the weld cable to the lifting mechanism to the chuck adapter to the chuck and finally into the stud.
• Ferrule (or Ceramic Ferrule) – Disposable ceramic protective rings are used to shield the stud during welding. They are used to concentrate the heat generated, prevent oxidation, and contain the molten metal created during the welding process while keeping the gasses and impurities out. It is broken off after the weld is complete.  There are several types of ferrules based on your application: Flat, Thru Deck, Vertical, Inside Angle, Outside Angle and Heavy Duty.
• Ferrule Grip – Ferrule Grips are used on the drawn arc stud gun to hold the ferrules during the stud welding process. Ferrule Grips, sometimes called Ferrule Holders, are available in closed grip or a split grip. Generally, studs 2" or shorter can use a closed ferrule grip but for longer studs use a split arc foot and split ferrule grip to make it easier to load studs in the gun.
• Lift – Lift is the distance the gun pulls the drawn arc stud away from the base material. Before the weld is started, the stud and base metal are in contact. Lift creates an air gap that the electric current must bridge. The current flow across the resistance of this gap creates the arc heat to melt the stud and base material.
• Flux: A material, often aluminum, applied to the weld end of some drawn arc studs. It helps to initiate the arc and deoxidize the weld pool.
• Shielding Gas: In some drawn arc applications, a shielding gas (like argon) may be used to protect the weld pool from atmospheric contamination, especially for certain materials or when a ferrule is not sufficient.
• Burn-off (or Melt-off): The small amount of the stud that is consumed during the drawn arc welding process.
• Alignment – Alignment is the proper centering of the stud in the ceramic ferrule so that the stud does not contact the ceramic ferrule during lift and plunge.
• Arc Blow – The effect where the weld fillet ‘runs away’ from the ground connection. The electric fields generated during the weld repel the fillet material away from the location of the ground. If this is a concern, it can frequently be fixed through the use of double grounds.
• Bellows – The rubber boot that slides over the chuck adapter. It helps to keep dirt, weld splatter and other foreign contaminants from entering the internal gun mechanism.
• Plunge Dampner – A device that slows the rate at which the stud plunges into the weld pool. This reduced the amount of splash from the molten metal and helps to form a uniform weld fillet.