Non fusion welding

We have already studied, that welding is a precise, reliable, cost-effective and a highly technical method for joining materials in manufacturing industries.  Welding requires to generate heat using electricity, gases, base materials (that may be pre -heated), welding rods / filler materials, etc.   All types of welding can be divided basically in to 2 varieties:

1. Non- Fusion Welding
2. Fusion Welding

In this article, we will study about various types of Non-Fusion welding.

Non-Fusion Welding – The metal to be welded is heated up to semi molten state and pressure is applied to complete the weld. No heat is applied but only adequate pressure is applied to complete the joint.  Metal parts are heated to forging temperature. Heating is carried out by Oven, Oxy fuel flame or Electric Resistance. Pressure is applied on heated parts – by Hammer, Hydraulic Press or Mechanical lever.

Types of Non Fusion Welding –

1. Forge Welding
2. Resistance Butt
3. Flash Welding
4. Stud Welding
5. Spot Welding
6. Resistance Seam welding

1. Forge Welding – Forge welding (FOW) is a solid-state welding process, that joins two pieces of metal by heating them to a high temperature and then hammering them together. It may also consist of heating and forcing the metals together with presses or other means, creating enough pressure to cause plastic deformation at the weld surfaces. The process is one of the simplest methods of joining metals and has been used since ancient times. Forge welding is versatile, being able to join a host of similar and dissimilar metals. With the invention of electrical and gas welding methods during the Industrial Revolution, manual forge-welding has been largely replaced, although automated forge-welding is a common manufacturing process.
2. Resistance Welding – Resistance welding, sometimes called electrical resistance welding (ERW), is a process by which pressure can be created by joining metals together and through a combination of metals to heat the welding joint. Electric current is used in this process.
3. Flash Welding – Is a type of resistance welding that does not use any filler metals. The pieces of metal to be welded are set apart at a predetermined distance based on material thickness, material composition, and desired properties of the finished weld. Current is applied to the metal, and the gap between the two pieces creates resistance and produces the arc required to melt the metal. Once the pieces of metal reach the proper temperature, they are pressed together, effectively forge welding them together.
4. Stud Welding – 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 falls under threaded, unthreaded or tapped. The bolts may be automatically fed into the stud welder. Weld nuts generally have a flange with small nubs that melt to form the weld. Weld studs are used in stud welding systems. Manufacturers create weld studs for the two main forms of stud welding: capacitor discharge stud welding and drawn arc stud welding.
5. Spot Welding – Spot welding (also known as resistance spot welding) is a resistance welding process. This welding process is used primarily for welding two or more metal sheets together by applying pressure and heat from an electric current to the weld area. The process involves applying pressure and heat to the weld area using shaped alloy copper electrodes which convey an electrical current through the weld pieces. The material melts, fusing the parts together at which point the current is turned off, pressure from the electrodes is maintained and the molten “nugget” solidifies to form the joint.
6. Seam welding – Seam welding is the joining of work pieces made of similar or dissimilar materials along a continuous seam. Seam welding can be broken down into two main techniques : resistance seam welding and friction seam welding.
   • Resistance Seam Welding – Resistance seam welding is a variation of resistance spot welding with the main difference being that the welding electrodes are motor driven wheels rather than stationary rods. Ideal for sheet metal fabrication, this welding method passes an electric current through the sheets of metals to be joined while they are held together by a mechanical force in a lap configuration between shaped copper electrodes. As with other types of resistance welding, fusion is produced where the sheet surfaces come into contact due to this being the point of highest electrical resistance and thereby the place where heat generation is at its greatest. The heat from the disc-shaped electrode wheels creates a continuous weld as the work pieces are fed between them, resulting in a rolling resistance weld or a non-hermetic seam weld.
   • Friction Seam Welding – This joining method uses friction to generate heat for the weld joint rather than using electrodes. As with other friction welding processes, the work pieces are joined in the solid phase without melting the materials, meaning that there is no fusion and thereby virtually no inter diffusion between the consumable and the substrate. This is an ideal process for joining materials that are difficult to weld using conventional arc welding techniques. Friction seam welding creates heat via a rotating consumable bar which is axially pressed into a V or U shaped groove. The work pieces are moved under the rotating consumable as a deposit is laid down in the groove.