Protecting the arc and the weld pool requires that welders make use of the shielding gas to prevent any contaminants. And there are more of these advantages. The shielding gas will affect –
- Deposition rate
- Depth of weld penetration
- Corrosion resistance
- Strength of the weld
The right combination of shielding gas with the given metal is an essential determinant of the quality of the weld. An inaccurate combination will increase the chance of the gas reacting with the weld pool and creating defects. This is the reason most arc welding processes make use of inert gasses.
Although argon is the most used shielding gas, the use of helium is prioritized when working with very thick metals. With higher heat input, consistent arc, and deeper penetration, helium GTAW can be a process of choice for specialized welding applications.
Quality of Helium as a Shielding Gas
Helium is a commonly used shielding gas alongside argon for gas tungsten arc welding (GTAW). In its pure form, or as a mixture, helium has the following properties –
- Inert nature
- Higher thermal conductivity
- Greater ionization potential
- Lightweight
When welding, the higher thermal conductivity supports the formation of a hotter arc which can generate a higher heat input. The increment in heat input is beneficial when welding significantly thicker materials. An example includes a drive shaft of a turbine whose thickness can range up to meters. The higher heat input, as supported by helium, improves the consistency of the weld bead and facilitates weld penetration through the entire thickness of the workpiece. The lightweight nature of the gas facilitates higher travel speed, improving welding productivity.
However, using 100% helium can be a disadvantage in many cases as the higher ionization potential (24.5 volts) makes the initiation of arc difficult. Therefore, the argon-helium mixture is ideal to balance the heat input and ionization potential between two gasses. Adding argon also allows helium to maintain the high purity level that may be required for some welding processes.
Hot Wire GTAW With Helium
When conducting helium GTAW, there are a few things to take note of –
- Pure helium will require DCEN (Direct current Electrode Negative) when GTAW welding.
- When working with AC-GTAW, it is preferred to have 25% helium in the gas mixture.
- More than 25% helium in the mixture can create an unstable arc during AC-GTAW.
Apart from this helium content, it is important to understand the heat requirement for certain thicknesses of metal. While thinner metal can be easily fused with traditional GTAW, thicker metal will require the use of filler metal. It is possible to use helium for hot-wire GTAW so thicker metals can be welded with precision.
Hot wire GTAW provides a much higher deposition rate which is further enhanced by the thermally conductive properties of helium. The desired gas mixture is usually 75% helium with 25% argon but pure helium may also be used. Controlled supply of the gas for hot-wire helium GTAW means wider profile and deeper penetration with excellent results along the root pass. For much thicker walled pipes, hot-wire narrow groove welding with helium GTAW can weld with precision for up to several hundred millimeters.
Helium GTAW for Efficiency
In many areas of manufacturing that requires purity and precision, the use of helium has been useful. From austenitic stainless steel to aluminum to carbon steel, the application of helium GTAW for welding means excellence in strength due to its consistent and precise approach to arc control. In addition, helium can also be associated with productivity and cost-efficiency due to its high heat input and faster travel speed, even for thicker workpieces.
Depending on your arc initiation, heat input requirement, and compatibility with your welding machines, you can use helium GTAW with orbital welding to enhance the overall process at your facility.
Arc Machines, Inc. is a leading provider of high-quality automated GTAW welding equipment and solutions. To learn more about the implementation of helium GTAW using these solutions, contact us today and learn about its benefits. For inquiries regarding products, contact sales@arcmachines.com. For service inquiries, contact service@arcmachines.com. Arc Machines welcomes the opportunity to discuss your specific needs.
