Welding is a permanent joining technique that uses local fusion and mechanical pressure to join two parts together. It is a crucial process in many areas of industry, including construction, civil engineering, automotive manufacturing, aerospace, boiler making, sheet metal work and many others. There are many different welding processes for metal parts, including resistance welding, electric arc welding (TIG, MIG, MAG, electrode, etc.), friction fusion welding and explosion welding.

In this article, we explore the equipment and techniques used in stud welding, as well as the advantages and disadvantages of each method.

The different types of stud welding

There are three processes for stud welding: long arc, short arc (SC) and capacitor discharge (CD). The process to be used is determined by the materials used and the dimensions of the parts (mainly sheet thickness and stud diameter).

Arc welding

How is arc welding carried out ?

Arc welding is a welding process that uses an electric arc to melt the metals to be welded and create a strong bond between them. An electrical voltage is first applied between the parts to be joined, one of which is the stud and the other the part to which it is to be attached. Once the current has been established, the arc is created by raising the stud above the workpiece, hence the name “drawn arc”. The intense heat created by the arc melts the parts to be joined locally, creating a molten pool. It is at this point that the parts are brought into contact with mechanical pressure. As the molten pool cools, the metals solidify, creating a strong, permanent bond.

When is arc welding used?

Arc welding is often used to weld ferrous metals such as steel and stainless steel, as well as non-ferrous metals such as aluminium.

What are the different types of arc welding ?

Arc welding can be carried out using short-time welding (<100ms) or long-time welding (>100msec).

Short-time arc welding is recommended for thin sheet metal and is particularly suitable for small diameter studs (typically up to diameter 8). It can be carried out in air or under neutral gas.

Long-time arc welding is used to weld very large diameter studs (25mm). It can be done under neutral gas or with a ceramic ring.

One point to note: the geometry of the part of the studs that is welded must be adapted to the welding process chosen.

Capacitor discharge welding

How does capacitor discharge welding work ?

Capacitor discharge welding is a welding method that uses the energy stored in power capacitors to create a very intense electrical pulse (which can 5000A) of short duration (<10msec). This electrical impulse is used to melt the metals to be welded. First of all, this process requires studs fitted with a firing pin. During the electrical impulse, a very strong current is created which vaporises the pin. Once the pin has disappeared, a short arc is created that melts the top of the part and the underside of the stud. Contact with mechanical pressure then creates a solid, permanent bond after cooling.

When is capacitor discharge welding used ?

Capacitor discharge welding is often used to weld steel, stainless steel, aluminium, titanium and brass parts. It is also often preferred for welding very thin sheet metal, as it can produce high-quality welds without damaging the parts.

Advantages and disadvantages of arc welding and cartridge discharge welding

Stud welding is a fast and economical process, for example when compared to trial and error bolting a screw or TIG welding a screw to a workpiece. A stud welding machine, also known as a stud welder, consists of a generator (to send the electrical energy), a welding gun or welding head into which the stud is placed and which is used to position it on the workpiece to be welded, and a ground cable which rests on the workpiece at the generator to close the electrical circuit.
This equipment has evolved considerably in recent years. Inverter technology is tending to replace transformer/rectifier technology, with savings in power consumption and weight of up to 50%.

Advantages of arc welding

• Size : can weld studs from 3mm to 25mm in diameter
• Power and weld quality : modern machines allow fine-tuning of welding parameters (time and intensity) and can include a library of recommended settings for different types of studs, to optimise weld quality. Arc welding is therefore ideal for applications such as sheet metal work and structural components.
• Versatility : arc welding can be used to weld a wide variety of parts of different shapes and sizes. In the same way, there are three different ways of welding: with a ceramic ring, under neutral gas and without protection (short time).
• Flexibility : arc welding is more tolerant than capacitor discharge welding than capacitor discharge welding.

Disadvantages of arc welding

• Power supply : Most machines are supplied with a 400 V three-phase power supply.
• Heat-affected zone : arc welding generates a large amount of heat, which can affect the area surrounding the weld, leading to deformation or distortion of the parts.
• Energy use : arc welding can require a large amount of electrical energy.
• Noise and fumes : arc welding can produce fumes, in some cases requiring an extraction system at the workstation.

Advantages of cartridge discharge welding

• Cost: the equipment is more economical than that used for arc welding.
• Heat-affected zone: capacitor discharge welding produces little or no distortion or deformation of the parts, which can reduce the need for additional finishing work.
  distortion or deformation of parts, which can reduce the need for additional finishing work.
• Suitable for heat-conducting materials: the method is particularly suitable for welding metals with high thermal conductivity, such as aluminium and brass, and thin sheet metal.
• Power supply : the power supply is 230V single-phase and some equipment, such as the
  Pégasar and Accu-Twin even operate on battery power.

Disadvantages of capacitor discharge welding

• Noise : tank discharge welding causes detonation.
• Lack of flexibility : this process requires clean, flat surfaces free of rust, grease and other contaminants.
• Size : stud diameters are limited to 10mm for stainless steel and 8mm for aluminium.

In conclusion, there is no single best type of welding. Your choice will depend on the materials to be welded, the thickness of the parts, the time available to weld and the cost.

For guidance or any technical questions, don’t hesitate to contact our Titanox product expert.