What is Plasma Welding?
‘Plasma’ is the fourth state of Matter.
Simply put, Plasma is a Gas that has been super heated to a point where it becomes highly conductive. In Welding and Cutting processes, this allows an electrical current to be transferred.
The temperature of a Plasma Arc can reach as high as 30,000 degrees Fahrenheit. (16,000 Degrees Celsius).
Plasma Welding was first introduced as a Process around the early 1960’s and was utilised in special Low current applications (Micro Plasma) from 0.5A typically or even lower, up to 500A applications for heavier industry.
In todays Market, although seen as an exotic welding process, Plasma is used across a wide range of Industries where Production volume, consistency and minimal downtime is key.
Above image : Functional graphic of how a Plasma welding torch works.
What are the benefits of the Plasma Welding Process?
One of the Major benefits of the PAW process is the focused Arc which is produced through the Tip orifice. The orifice size can be increased or decreased inline with Amperage requirements and also to suit specific applications.
The advantages of the focused Arc include:
- Deeper Penetration
- Reduced heat affected zone (HAZ)
- Increased travel speeds
- Less influence from Magnetic fields (Arc Wander)
- Precision on Automated / Robotic applications
Some applications where the focused Plasma Arc is exploited:
- Catheters (Medical Industry)
- Surgical Tools
- Edge Welded Bellows
- Flow Sensors
- Tool & Die repair
- Aerospace Components
- Tube Mills
- Pressure Vessels
Unlike the TIG process where the Tungsten Electrode is open to the atmosphere following the welding cycle, the Electrode in the Plasma process is secluded inside the chamber of the Torch and protected by a Gas shield. This allows the Electrode to remain in the same condition for longer periods of time and thus in Automation applications, dramatically reduces the need to stop the Welding process to re-sharpen the Electrode...
= Productivity Improvement
In order to prevent contamination when using the TIG process, it is necessary to use High Frequency to transfer the Arc from the Electrode to the Workpiece. In Automation applications, this can in some cases create problems where the High frequency can interfere and interrupt control equipment. This method of transfer can also wear the electrode prematurely especially in high volume, short duration welds thus increasing the requirement to re-sharpen electrodes.
The Plasma process uses a Constant Pilot Arc that allows for the transfer of the Arc without the use of High Frequency. This eliminates control system interference and also allows for reliable, accurate transfer for longer production cycles...
= Productivity Improvement.
In addition to the functions available on the Plasma Power source such as Current Control, Digital Gas control (maintaining Gas flow inline with amperage setting), Pulse and Spot timing, the Plasma Welding Torch can offer other variants to help fine tune the Arc characteristics. These include the following:
- Tip hole size
- Electrode Set Back
- Gas Flow rates.
- Multi Gas capability
Various Gases can be used to enhance the welding process.
As an example, Argon Hydrogen mix of 2% or 5% can be used as a Plasma Gas OR a Shield Gas in combination with Pure Argon.
- Argon Plasma / Argon / Hydrogen Shield – Increased heat input from the shield Gas reduces surface tension of the material and allows for faster travel speeds.
- Argon Hydrogen Plasma / Argon Shield -Concentrates heat in the Plasma stream to increase penetration. (Keyhole Mode)
Increased Travel Speed
The focused Arc and higher concentration of heat allows for faster travel speeds in some applications.
This can be seen as an immediate benefit in repetitive applications where high volume production is required.
Modes of Operation
There are two Modes of operation which are generally referred to as ‘Soft Plasma’ and ‘Keyhole’
In the Keyhole Mode, it is possible to set up Torch Parameters and configuration to allow the Plasma
Stream to punch through materials up to 10mm thick thus achieving full penetration without the need for Joint preparation.
= Productivity Improvement
Plasma welding sample photo : 8mm Stainless Steel / full penetration / butt joint (no preparation) / no filler wire / keyhole mode.
Industries & applications that benefit from the Plasma Welding Process.
- Battery Manufacture
- Pressure Vessel Manufacture
- Stainless Steel Industry
- Storage Tanks
- Thermocouple Industry
- Household and White Goods
- Industrial and Domestic Kitchen equipment
- Power Tools – Laminations
- Pipe Welding
- Tube Mills
- Tool and Die repair
- Power Plants
And many more......