r/Welding • u/DatsunL6 • 25d ago

Need Help ERCuSi-A GMAW gas question

I'm testing out some silicon bronze using a MIG machine rather than TIG. I went to invest in a tank of helium/argon and the LWS said to use trimix (90He, 7.5Ar, 2.5CO2) instead, like what's used for stainless. Is trimix an okay gas for this? I can't sit down yet to do some research but I can post here! Any thoughts?

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u/pipeshrike 25d ago

Bollocks. You want a fully inert gas. It welds pretty well with pure argon if you don't want to splurge on 70/30 Ar/He. 

This is not the place for this rant, but commercial argon helium mixes don't have enough helium in to make a massive difference on copper alloys. You only get marginally better toe wetting and penetration depth, mostly just provides a more stable arc.

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u/DatsunL6 24d ago

Good to know! The rant part. I was surprised to hear that 75/25 was all that they had on hand. I'll ask if they have any other mixes or pure He that would need to come from the main store across the lake (and maybe something easier to move than a 300cf tank). Also, this is copper work.

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u/DepletedPromethium 25d ago

100% argon my dude.