Resistance Projection Welding
This is a resistance welding procedure in which elevated sections or projections on preset locations on one of the workpieces are used to make two or more spot welds at the same time.
The heat of the welding circuit is localised via these projections. The components to be welded are held in place by electrodes who keep pressure on them.
The planned contact spot for welding should be roughly equal to the thickness of the weld metal.
Projection welding is demonstrated via the welding of a nut on an automobile chassis.
Welding with Resistance Upset Butt and Flash Butt
This welding is also used to join metal parts end to end, however it has mostly supplanted butt-welding for tiny crosssection weld items. It can also be used to make thick sections.
The current is turned on first, and then one end of the moving component to be welded is gently pushed closer to the fixed end of the other component to localise heat at the ends, quickly raising the temperature of the ends to welding temperatures.
After the fixed end and moveable end have made contact with one other, the moveable end is forced against the fixed end using mechanical pressure.
As a result, the molten metal and slag are forced out as sparks, allowing the pure metal to form the joint and preventing the heat from spreading back.
- It is significantly faster than butt welding.
- When compared to butt welding, this approach uses less current because just a tiny piece of the metal is heated for a successful weld.
- The joint created by this welding is substantially stronger than the junction created by butt welding.
- In addition, the weld created has a great strength, even higher than the underlying metal.
- Unlike butt-welding, the ends of the metal components to be welded in this welding do not need to be squared.
- In terms of weld length alignment, a high degree of precision can be easily obtained.
- Machine maintenance and insulation replacement are required on a regular basis because flashing particles of molten metal are thrown out during welding and may enter the sliding ways and insulation of the setup.
- The welder must exercise sufficient caution to avoid a potential fire hazard caused by flashing during welding.
- Extra stock must be available to compensate for metal loss during flashing and upsetting. Welding costs rise as a result of this.
- The cost of removing flash weld metal by cutting, chipping, grinding, and other methods will raise the welded product’s cost.
- The surfaces of the tasks that come into contact with the gripping surfaces should be clean; otherwise, the flow of electric current will be restricted.
- The size and cross sectional area of the works to be welded are limited by the available power, opening between the jaws of the grasping clamps, and upsetting pressure of the welding set.
- Flash welding is a simple process that may be used on any conductive forged metal.
- By carefully adjusting the welding conditions, a variety of dissimilar metals can be fused.
- Lead, tin, antimony, zinc, bismuth, and their alloys are often welded metals, as are low carbon steels, stainless steels, alloy steels, tool steels, copper alloys, aluminium alloys, magnesium alloys, nickel alloys, molybdenum alloys, and titanium alloys.
- This procedure is employed in the automobile industry, in the aerospace industry, in the welding of band saw blades, in the welding of tool steel drills, reamers, and taps to mild steel or alloy steel shanks, and in the welding of pipes and tubes.
Resistance welding has a number of advantages.
- It is ideally suited for mass production. (Extremely high output rates are feasible.)
- It is cost-effective to operate because just electricity is consumed.
- Welders with advanced skills are not required.
- Welds are made swiftly.
- Welding incompatible metals is conceivable.
- There is no need for filler metal or flux.
- Operator skill level is lower than that necessary for arc welding.
- A high level of reproducibility and dependability
The following are some of the disadvantages of resistance welding:
- The resistance welding equipment has a high starting cost.
- Some resistance welding techniques are only applicable to lap joints.
- In applications where fatigue is evident, a lap joint has an inherent service between the two metal components, causing stress concentrations. When corrosion is prevalent, this service may cause problems.