This is the second in our multi-part series exploring pulsed micro tungsten inert gas (TIG) welding. Today we will cover setup tips and tricks.
Electrode diameter – The electrode diameter determines the amount of current the electrode can support. It should be sized to the process requirements. See below for the allowable current range for a variety of electrode diameters.
- For high current, a flat tip will improve electrode performance and arc stability.
Electrode material – Different materials are used for different applications. Follow the recommendations on the chart for best results.
Electrode life – Electrode life differs based on a variety of factors, including the amount of current, shielding gas used, the diameter and angle of the electrode, and cooling used. Other factors include whether the electrode is being used continuously as well as the specific workpiece being welded.
- Replace electrodes after 300 to 400 shots when more than 100 amps (A) is used and after about 8000 shots when welding micro relays at below 5A.
- Consider electrode “seasoning” after the electrode has been dressed. For example, with an electrode that has a 2.4 millimeter (mm) diameter, discharge a dummy pin 250A/200 microseconds (ms) about three times.
Cover gas nozzle – The diameter of the nozzle must be greater than the weld area.
- When welding intricately-shaped workpieces, check whether the gas flow roils because of the gas bounced back from the workpieces.
- Make sure gas is emitted straight from the nozzle. The shielding gas must protect an arc generation and weld pool, or you will not get good welds.
Weld geometry – The best geometries for micro pulse arc welding are butt and fillet. A lap weld is generally difficult because both the top and bottom piece must reach melting temperature.
Part size – Part size and heat balance is another key for success. Parts must be relatively the same size. This will allow both to heat up simultaneously and fuse together. If one is significantly larger, it will take more time to heat than the smaller, so the smaller piece may be evaporated before the large piece reaches the melting point.
Electrode stickout – The electrode stickout from a nozzle should be from 1 to 3 times the diameter of the electrode, as shown in the graphic.
If it is too short, there will not be enough access to the part. If it’s too long, there will be insufficient gas coverage, and a higher start arc voltage will be required.
- For 1.6mm diameter electrode: stickout should be 1.6mm‐4.8mm
- For 2.4mm diameter electrode: stickout should be 2.4‐7.2mm
Part positioning – Part position relative to the electrode tip determines how the energy is focused on the part. The ideal range is 1‐3mm separation. See graphic.
- For consistent welding, the tip should be consistently set to within ±0 25mm
In addition, parts need to be in close proximity to each other to allow bonding. See illustration.
Cover gas – Cover gas is required for arc formation, because the argon lowers the arc voltage required. In addition, the cover gas provides shielding of the weld to avoid oxidation.
- Provide laminar flow, typically, 20 cubic feet per minute, with good coverage on weld area.
- Start cover gas flow before weld and continue after weld.
- Use argon (most common) or argon‐helium mix.
- Add helium to improve penetration.
Electrode tip angle – The electrode and electrode tip determine the amount of current the unit can deliver and how the energy is focused on the part.
- Use 30 angle for greater than 130A and 45 degree angle for less than 130A
Many factors affect the micro TIG welding process. Welding success is achieved by selecting the correct equipment, material, and process parameters. Today’s tips focus on process settings. In our next post we will delve deeper into how to troubleshoot to improve your pulsed micro TIG results.
If you missed our first post on this topic, you can read it here: Micro TIG welding – What is it and how can I use it?