Resistance Welding : Working Principle, Types and Applications

In olden days, the process of metal welding can be done by heating the metals and pressed jointly which is known as forge welding method. But at present, the welding technology has been changed by the arrival of electricity. In the 19th century, resistance, gas and arc welding was invented. After this, there are different types of welding technologies have been invented like friction, ultrasonic, plasma, laser, electron beam welding. Although, the applications of welding technology mainly involves in a variety of industries. This article discusses resistance welding, working principle, different types, advantages, disadvantages, and Applications.

What is Resistance Welding?

Resistance welding can be defined as; it is a liquid state welding method where the metal-to-metal joint can be formed within a liquid state otherwise molten state. This is a thermoelectric method where heat can be generated at the It is a thermo-electric process in which heat is generated at the edge planes of welding plates because of electric resistance and a weld joint can be created by applying low-pressure to these plates. This type of welding uses electric resistance to generate heat. This process is very efficient with pollution free but the applications are limited because of the features like equipment cost is high, and material thickness is limited.

Resistance Welding Working Principle

The working principle of resistance welding is the generation of heat because of electric resistance. The resistance welding such as seam, spot, protection works on the same principle. Whenever the current flows through electric resistance, then heat will be generated. The same working principle can be used within the electric coil. The generated heat will depend on material’s resistance, applied current, conditions of a surface, applied the current time period

This heat generation takes place because of the energy conversion from electric to thermal. The resistance welding formula for heat generation is

H = I²RT

Where

• ‘H’ is a generated Heat, and the unit of heat is a joule
• ‘I’ is an electric current, and the unit of this is ampere
• ‘R’ is an electric resistance, and the unit of this is Ohm
• ‘T’ is the time of current flow, and the unit of this is second

The generated heat can be used to soften the edge metal to shape a tough weld joint with fusion. This method generates weld with no application of any flux, filler material, and shielding gases.

Types of Resistance Welding

Different types of resistance welding are discussed below.

Spot Welding

Spot welding is the simplest type of welding where the work portions are held jointly below the force of anvil face. The copper (Cu) electrodes will make contact with the work portion & the flow of current through it. The work portion material applies a few resistances within current flow which will cause limited heat production. The resistance is high at the edge surfaces because of the air gap. The current begins to supply through it, then it will reduce the edge surface.

The current supply & the time must be enough for the correct dissolving of edge faces. Now the flow of current will be stopped however the force applied with electrode continued for a second, whereas the weld quickly cooled. Later, the electrodes eliminate as well as get in touch with new spot to create a circular piece. The piece size mainly depends on electrode size (4-7 mm).

Seam Welding

This type of welding is also known as continuous spot welding where a roller form electrode can be utilized to supply current throughout work parts. Initially, the roller electrodes are getting in touch with the work part. High current can be supplied through these electrode rollers to melt the edge surfaces & shape a weld joint.

At present, the electrode rollers will begin rolling on work plates to make a permanent weld joint. The weld timing & electrode movement can be controlled to guarantee that the weld overlap & work part doesn’t acquire too warm. The speed of the welding can be about 60 in per min within seam welding, which is used to make airtight joints.

Projection Welding

Projection welding is similar to spot welding apart from a dimple can be generated on work parts at the place wherever weld is preferred. At present the work parts held among electrode as well as a huge quantity of current flow through it. A little quantity of pressure can be applied throughout the electrode on welding shields. The flow of current throughout dimple which dissolve it & the force reasons the dimple level & shape a weld.

Flash butt Welding

The flash butt welding is a form of resistance welding, used for welding tubes as well as rods within steel industries. In this method, two work parts are welded which will be held tightly during the electrode holders as well as a high pulsed flow of current within the 1,00,000 ampere range can be supplied toward the work part material.

In the two electrode holders, one is permanent & other is changeable. At first, the flow of current can be supplied & changeable clamp will be forced against the permanent clamp because of the get in touch with the two work parts at high-current, the spark will be generated. Whenever the edge surface approaches into plastic shape, the flow of current will be stopped as well as axial force can be improved to create joint. In this method, the weld can be formed because of plastic deformation.

Resistance Welding Applications

The applications of resistance welding include the following.

• This type of welding can be widely used within automotive industries, making of nut as well as a bolt.
• Seam welding can be utilized to generate leak prove joint necessary within little tanks, boilers, etc.
• Flash welding can be used for welding tubes and pipes.

Resistance Welding Advantages and Disadvantages

The advantages & disadvantages of resistance welding include the following

Advantages

• This method is simple and does not necessary high expert labor.
• The resistance welding metal thickness is 20mm, &  thinness is 0.1 mm
• Automated simply
• The rate of production is high
• Both related, &  different metals can be weld.
• Welding speed will be high
• It does not need any flux, filler metal & protecting gases.

Disadvantages

• Tools cost will be high.
• The work section thickness is limited because of the current requirement.
• It is less proficient for high-conductive equipment.
• It consumes high electric-power.
• Weld joints contain small tensile & fatigue power.

Thus, this is all about the resistance welding process, which is used for welding two metals. It includes a welding head used to hold the metal among its electrodes & applies a welding power supply & force to welding the metal. When the force is applied, the resistance produces heat, then resistance welding utilizes the heat. Likewise, whenever the flow of current attempts to move ahead throughout two metals, then heat can be generated because of the resistance of the metal. So finally this welding can be used to weld the metals using the pressure as well as heat. Here is a question for you, what are the resistance welding parameters?

Image Credits: Spot Welding and Seam Welding