What is Resistance Welding?
Resistance welding is a type of electric welding that uses electrical resistance to generate heat for welding. In resistance welding, a high-current, low-voltage electrical current is passed through the joint area of two metal pieces to be welded. The electrical resistance of the metal causes the temperature at the joint to increase, melting the metal and allowing it to be joined together.
To perform resistance welding, two electrodes of low resistance are used to apply the electrical current to the metal pieces. The current used in resistance welding is typically more than 100 amps, and the voltage ranges from 4 to 12 volts, depending on the composition, area, and thickness of the metal being welded. The heat generated in the joint area is expressed as I2R t, where 't' is the time the current flows.
Pressure is also applied to the joint area through the electrodes to complete the weld. Resistance welding is typically performed using an alternating current (AC) power supply, as it is easier to obtain the desired combinations of voltage and current using a transformer. AC power is also preferred because it allows for more precise control of the weld process.
Advantages of resistance Welding:
- Speed: One of the main advantages of resistance welding is its speed. This process is much faster than other welding methods, which makes it suitable for mass production.
- No filler material: Another advantage is that no filler material is required in resistance welding. This can reduce costs and make the process more efficient.
- Welding of similar and dissimilar metals: Resistance welding can be used to weld both similar and dissimilar metals, which makes it a versatile process.
- Localized heating: The heat generated in resistance welding is localized to the area being welded, which can be an advantage in certain situations.
- Automation: The resistance welding process can be automated, which can increase productivity and reduce the need for labor.
- Environmental friendliness: Resistance welding does not produce any harmful emissions or pollutants, making it an environmentally friendly process.
- Ease of use: Operating a resistance welding machine does not require any special skills, which makes it easy to use.
- Suitability for mass production: Due to its high rate of production, resistance welding is well suited for mass production.
What is Arc Welding?
Arc welding is a type of electric welding that uses an electric arc to generate heat to melt and join metal pieces together. In arc welding, an electric current is passed between an electrode and the metal workpiece, creating an arc of electricity that generates intense heat. This heat is used to melt the metal at the joint area, which is then filled with a filler material to complete the weld.
There are several types of arc welding, including carbon arc welding, metal arc welding, and hydrogen arc welding. In carbon arc welding, the electrode is made of carbon and is used to create the arc and provide filler material for the weld. In metal arc welding, the electrode is made of metal and is used to create the arc and provide filler material for the weld. Hydrogen arc welding is a variation of metal arc welding that uses hydrogen gas to shield the arc and reduce the risk of defects in the weld.
Arc welding can be performed using either alternating current (AC) or direct current (DC) power. AC power is often used for welding thin materials, while DC power is typically used for welding thicker materials. The type of power supply used can also affect the properties of the weld, such as its strength and appearance.
Advantages of Arc Welding:
- Versatility: Arc welding can be used on a wide variety of materials, including steel, aluminum, and stainless steel. This makes it a versatile process that can be used in a variety of applications.
- High strength: Arc welds can be very strong, depending on the type of process and the materials being used. This makes them suitable for applications that require high strength and durability.
- Portability: Many arc welding processes are portable, which makes them convenient for on-site or fieldwork. This allows welders to bring the welding equipment to the work location, rather than having to transport the workpieces to a fixed welding station.
- Deep weld penetration: Arc welding can produce deep weld penetration, which is useful for certain applications. This allows the weld to reach deeper into the workpiece and provide better support and strength.
- High deposition rates: Arc welding can have high deposition rates, which means that it can be a fast process. This makes it suitable for high-volume production or for projects with tight deadlines.
- Good for outdoor use: Some arc welding processes, such as shielded metal arc welding (SMAW), are less sensitive to wind and drafts, making them suitable for outdoor use.
- Good for out-of-position welding: Arc welding can be used for welding in positions that are difficult to access, such as overhead or vertical positions. This makes it a versatile process that can be used in a variety of welding positions.
- No special equipment required: Arc welding does not require any special equipment, making it an accessible and convenient process. This can be an advantage for those who do not have access to specialized welding equipment.
Comparison Between Resistance Welding and Arc Welding:
| Resistance Welding | Arc Welding | |
|---|---|---|
| Power supply | AC | AC or DC |
| Filler material needed | No | Yes |
| Voltage required | Low | High |
| External pressure required | Yes | No |
| Heat production source | Contact resistance | Arc |
| Temperature | Low | High |
| Power factor | Lagging (0.25-0.3) | Poor |
| Suitable for mass production | Yes | No |
| Suitable for repair work | No | Yes |
| Types of electrodes | Roller, flat, bar | Flux-coated metal |
Key Comparision Between the Resistance and Arc Welding:
- Power supply: AC supply is mostly used for resistance welding, while both AC and DC supplies can be used for arc welding.
- Filler material: No additional material is required for resistance welding, while a filler material is used in arc welding to add strength to the weld.
- Voltage and current: Resistance welding requires low voltage with high currents, while arc welding requires higher voltage to strike the arc and maintain it.
- External pressure: External pressure is applied in resistance welding, while no external pressure is required in arc welding.
- Heat generation: The heat produced in resistance welding is mainly due to the contact resistance, while the heat produced in arc welding is due to the arc formed between the electrode and the metal workpiece.
- Temperature: The temperature in resistance welding is lower compared to the temperature in arc welding.
- Power factor: The power factor of resistance welding is 0.25 or 0.3 lagging, while the power factor of arc welding is very poor.
- Suitability: Resistance welding is suitable for mass production, while arc welding is suitable for repair work.
- Electrodes: Resistance welding uses roller, flat, or bar-type electrodes, while arc welding uses flux-coated metal electrodes.