We are TIG welding SS316 tube of 8.0mm dia in He atmosphere at 1.3kgf/cm2. It is a autogenous welding with out filler wire & arc starting using HF unit to avoid 'Tn' inclusion. Welding is carried out in a chamber with He atmosphere at 1.3kgf and 'He' gas flow during welding. My question is as follows:
1. Will a standard HF unit create such high voltage for arc initiatiation in He atmosphere ?. Arc starting in He atm is difficult, as it has high ionization potential.
2. As He is under slightly high pressure, will it be more difficult to weld under pressure ?
Please give me some tips on this.
prabs.
Hi Prabs,
A normal hf unit may not serve the purpose of initiating the arc. A special purpose unit should be designed for reliable starting at low currents. At high currents it may not be much of a hassle. I have worked on a similar job and have got good results . The higher pressure is not much of a problem and i assume there is a continuous flow of gas ?
Could you consider a gas mixer for the shielding gas line to your torch head? A minimal argon mixture would likely solve your arc starting problems without minimizing the heat generation potential of the Helium.
It might also be a less expensive solution than the additional high frequency unit (beware your circuit boards) or an inverter.
If your arc length is determined by adaptive feedback controls tied to arc voltage you may need to tweek them down as the addition of even small amounts of argon will likely lower the arc voltage a significantly.
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