Stud Arc Welding | Fastener Welding- Advantages and Application
Stud welding is a technique similar to flash welding where a fastener or specially formed nut is welded onto another metal part, typically a base metal or substrate. The fastener can take different forms, but typically fall under threaded, unthreaded or tapped. The bolts may be automatically fed into the spot welder. Weld nuts generally have a flange with small nubs that melt to form the weld. Weld studs are used in stud welding systems.
Stud welding is a complete one-step fastening system, using fasteners called weld studs. Weld studs come in a variety of designs, threaded, unthreaded, tapped, etc., sizes and shapes for a wide range of applications.Stud welding, also known as “drawn arc stud welding”, joins a stud and another piece of metal together by heating both parts with an arc. The stud is usually joined to a flat plate by using the stud as one of the electrodes. The polarity used in stud welding depends on the type of metal being used. Welding aluminum, for example, would usually require direct-current electrode positive (DCEP). Welding steel would require direct-current electrode negative (DCEN).
Stud welding uses a type of flux called a ferrule, a ceramic ring which concentrates the heat generated, prevents oxidation and retains the molten metal in the weld zone. The ferrule is broken off of the fastener after the weld is completed. This lack of marring on the side opposite the fastener is what differentiates stud welding from other fastening processes.
Stud Welding Equipment
The equipment required for stud welding is composed of the following:
A direct current Power Supply
A Weld Gun
Cables to tie the system components and base metal together
In most systems, the power supply and controller are combined as one component called the “Welder”.
A type of stud welding called capacitor-discharge (CD) stud welding differs from regular stud welding in that capacitor-discharge welding does not require flux. The weld time is shorter, enabling the weld to bond with little oxidation and no need for heat concentration. It also allows for small-diameter studs to be welded to thin,lightweight materials. This process uses a direct-current arc from a capacitor. The weld time in this process is between 1 and 6 milliseconds. Capacitor discharge stud welding with the latest equipment can create a weld without burn through showing on the opposite side of very thin metals. CD stud welding is often used for smaller diameter studs and pins, as well as on non-standard materials and for accuracy. On the other hand, arc stud welding is primarily for structural purposes and larger diameter weld studs.
The Stud Welding Process
Stud welding is a process by which a metal stud is joined to a metal workpiece by heating both parts with an arc. A key factor that differentiates stud welding from other fastening processes is that the fastener is attached to the workpiece without marring the other side.
The arc stud welding method provides highly reliable fastening for a wide variety of applications. This method allows almost any size or configuration of a metal stud to be welded quickly to a workpiece, while providing maximum weld penetration and reliability.
Arc stud welding permits strong, one-sided welds on base metals with thicknesses starting at 0.048″ (1.2 mm). It produces welds in as little as 0.06 seconds.
Arc stud welding utilizes a DC power supply to create the arc, a stud welding tool, metal fasteners, and in some cases, ferrules. There are three common techniques of Arc stud welding:
Drawn arc stud welding
Short arc stud welding
Gas arc stud welding
The Benefits of Stud Welding
Stud welding has many advantages over other joining processes:
It is fast. Welding a 3/4” fastener will take less than one second.
It is single sided. This means that access to the other side of the work piece is not required.
It is secure. Unlike the peripheral weld that would be used to weld a bolt in place, a stud weld is a full cross sectional weld. This means the full face of the fastener is welded in place providing a strong, worry-free weld.
It is cosmetically superior. As a single sided fastener there are no indicators that a fastener is attached.
It is welded and will not work free like a press-in fastener
Requires no special skills and little training to install.