Last Updated on April 30, 2021 by Antonio H. Johnson
In welding, plasma is used in the Plasma Arc Welding (PAW) process. This arc welding process is very similar to the GTAW/Gas Tungsten Arc Welding Process.
Plasma is super hot. Since plasma is used in this process, excessive temperatures are obtained, which makes welding efficient. This process yields excellent results. Quality and control both are well-ensured in Plasma Arc Welding. However, this process has a high maintenance cost.
This article will discuss how plasma is used in the PAW process, how to weld using the PAW process, how hot is plasma in the PAW arc, what are its advantages and disadvantages, and so on. Let’s get started!
- 1 What is plasma, and how is it produced?
- 2 What is Plasma Arc Welding (PAW)?
- 3 How many modes of Plasma Arc Welding (PAW) are there?
- 4 How hot is plasma in Plasma Arc Welding (PAW) Process?
- 5 Equipment of Plasma Arc Welding
- 6 Advantages of Plasma Arc Welding
- 7 Limitations of Plasma Arc Welding
- 8 Frequently Asked Questions
- 9 Conclusion
What is plasma, and how is it produced?
The fourth state of matter is known as plasma. It’s a state of matter which consists of partially ionized gas.
Apparently, you might wonder how hot is plasma? Extreme or Ultra extreme? The core temperature of plasma ranges from 11,000° – 14,500° Fahrenheit. To put that into perspective, the temperature of boiling water is north of 212 degrees Fahrenheit.
Super nerdy stuff, yeah!
Upon heating any gas to extreme temperatures, ionization occurs, and it causes the electrons and protons of the gas molecules to be separated from each other. Thus, now we have a mixture of free-roaming positive (protons) and negative (electrons) ions. This state is known as plasma.
What is Plasma Arc Welding (PAW)?
Plasma Arc Welding (PAW) process is an arc welding process in which an arc is formed between the tungsten electrode and the surface you want to work on.
Here, the plasma arc is separated from the shielding gas envelope by placing the electrode within the torch body. Afterward, through the copper nozzle, the plasma is expelled, which generates the arc.
How many modes of Plasma Arc Welding (PAW) are there?
In this process, there are three modes of operation. They vary based on the diameter of the nozzle and the rate of flow of plasma gas. The methods of operation are as follows:
- Microplasma: The current ranges from 0.1 to 15 A in this mode. At shallow currents, the microplasma arc is the best mode of welding. This mode is generally used to weld metals of the thickness of up to 0.1mm.
- Medium Current: The current ranges from 15 to 200 A in this mode. It works like the TIG arc at this current range, but here the arc is stiffer due to the constriction of the plasma. The gas flow of plasma can be increased or decreased to improve the weld pool’s penetration, but safety measures should be taken first.
- Keyhole Plasma: The current has to be over 100 A in this mode. In this mode, with an increment of plasma gas flow and current, a potent plasma beam similar to the laser beam welding can be obtained. This mode is ideal for welding metals of high thickness as it can penetrate them easily in a single pass.
How hot is plasma in Plasma Arc Welding (PAW) Process?
As we already know, plasma itself exists in very high temperatures. That is why this state of matter is considered an influential component in welding. But when plasma is used in welding, we have to increase its temperature even higher.
To do this, we use the current to excite the plasma. After exciting it, we pass it through the copper nozzle, which restricts the flow of plasma and exits through the orifice. This results in the plasma being expelled at unbelievably high velocities and too high temperatures.
The higher the electric power that has been supplied for creating the arc plasma, the higher is the temperature obtained in the plasma torch. The plasma’s typical temperatures in the plasma torch reach up to 28,000 °C (50,000 °F) or even higher!
To put that into perspective, the typical temperature that is obtained in a standard electric welding arc is about only 5500 °C (10000 °F). As we can see, the difference in the temperatures is immensely, and that occurs due to the plasma.
Equipment of Plasma Arc Welding
Some of the important equipment used in Plasma Arc Welding are discussed below:
- Fixture: To be safe from atmospheric contamination of molten metal under the bead, this is necessary.
- Plasma Torch: The plasma torch can be either transferred or non-transferred arc type. Presently, automated systems are well used. Water cooling is used to sustain the lifespan of the torch. The nozzle and the flow of plasma can be regulated by the need.
- Power Supply: A DC power source of drooping properties and having an open-circuit voltage of 70 volts or above is required for PAW. Typically, rectifiers over generators are preferred.
- Plasma and Shielding Gases: Typically, Argon for the plasma gas, Argon, and 2-5% hydrogen gas as shielding gases are used.
Advantages of Plasma Arc Welding
Plasma Arc Welding has some remarkable advantages that are discussed below:
- Can weld through all types of metals.
- Due to the concentrated heat of plasma, the keyhole effect occurs, which provides absolute penetration with a single pass.
- Can cut metals faster than most other welding processes.
- Easy automation.
- Narrower kerf.
Limitations of Plasma Arc Welding
Some of the limitations of Plasma Arc Welding is mentioned below:
- The equipment of Plasma Arc Welding is quite expensive.
- Specialized training and supervision are required for this process.
- It produces more noise than other types of welding.
Frequently Asked Questions
1. Why is the keyhole method not used in manual PAW?
Answer: While welding metals of thickness above 0.25 inch, it’s preferable not to use the keyhole effect in a single pass because the keyhole pool might break down and cause disfiguration, unwanted penetration of the workpiece.
2. How many Plasma Arc Welding modes are there?
Answer: There are three modes of operations in Plasma Arc Welding based on the flow of current and demand for the application.
Plasma Arc Welding is an expensive and instrumental branch of welding. Due to the use of scorching plasma, exceptional results are obtained.
The core to it is the acceleration of the plasma gas and restricting its path and then expelling it at very high speeds, which results in too high temperatures. That’s the real reply of how hot is plasma!
Presently, Plasma Arc Welding is a very well-known and prevalent form of welding. Although the equipment is not budget-friendly, Plasma Arc Welding is worth it if you’re looking to weld through tough and thick metals and obtain the best results.