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| AdeV:
--- Quote from: mattinker on November 06, 2013, 06:08:20 AM --- --- Quote from: BenH on November 06, 2013, 04:44:00 AM --- --- Quote from: mattinker on November 06, 2013, 03:57:54 AM --- --- Quote from: DavidA on November 05, 2013, 07:03:40 PM ---AdeV, ... the more oxygen needs to be in the shield gas.,, I never knew that. I always assumed that the idea of shield gas was to keep out oxygen. And I've been welding for fifty or more years. Just shows how one can bumble along. Dave :doh: --- End quote --- Well spotted, somebody got it the wrong way round! Free oxygen (not attached like the O in CO2) it to be kept out by the shield. Regards, Matthew --- End quote --- No that's correct it's really only MIG (metal inert gas) welding with pure Argon (as used for Aluminium) CO2 or Argo shield is MAG (metal active gas) welding, with Co2 some of it breaks downs and the free oxygen burns the steel to create more heat, you get less of that with Argo shield light but then Argo shield heavy has added oxygen to burn off more steel and add more heat to the weld. It is the nitrogen your trying to keep out of the weld more than other things as it makes the weld brittle. --- End quote --- This interesting and new to me, I was always told that one had to avoid oxidisation, I started stick welding forty years ago, I got into MIG and TIG within the last ten years. I am so used to stick that I use it whenever I can. I did a TIG Al welding course a few years ago, the oxidisation problem with Al was ever present. I haven't done any TIG on steel so I can see that I am probably off course about the shield gases! Regards, Matthew --- End quote --- TIG welding uses pure argon generally as the shield gas. You don't want O2 when TIG welding because it will oxidise the electrode... To get extra deep penetration with TIG welding, you crank up the amps, use a fatter electrode, and just weld a bit slower. In fact, if anything, the problem with TIG welding is it tends to really load the part up with heat - much more so than MIG in my experience. MIG, because it's laying down new metal, if you want to go deep (oo-er) you need to get more heat into the weld quickly. Best way to do that is to add some O2 to the argon, the O2 reacts with the steel to make extra heat which melts more metal & allows you to make strong welds even in thick metal with minimal warpage. I'd imagine that if you were mig welding aluminium you'd want pure argon rather than argoshield. |
| mattinker:
--- Quote from: AdeV on November 06, 2013, 07:31:32 AM --- TIG welding uses pure argon generally as the shield gas. You don't want O2 when TIG welding because it will oxidise the electrode... To get extra deep penetration with TIG welding, you crank up the amps, use a fatter electrode, and just weld a bit slower. In fact, if anything, the problem with TIG welding is it tends to really load the part up with heat - much more so than MIG in my experience. MIG, because it's laying down new metal, if you want to go deep (oo-er) you need to get more heat into the weld quickly. Best way to do that is to add some O2 to the argon, the O2 reacts with the steel to make extra heat which melts more metal & allows you to make strong welds even in thick metal with minimal warpage. I'd imagine that if you were mig welding aluminium you'd want pure argon rather than argoshield. --- End quote --- Thanks, I thought I had it all clear in my mind! New parametres to ingurgitate! Regards, Matthew |
| DavidA:
You may find this usefull. http://www.mig-welding.co.uk/gas-composition.htm I use Air Products Cougar 5 for my MIG and TIG 93% Argon, 5% Co2, 2% Oxygen. Dave. |
| DavidA:
...and going through the zinc coating by stitching with a mig and getting the zinc to flow back evenly was fun... You could have made your life a lot easier if you had removed the zinc first. Must be a sure way of getting inclusions in your welds ? Dave. |
| Fergus OMore:
--- Quote from: DavidA on November 06, 2013, 02:53:19 PM ---...and going through the zinc coating by stitching with a mig and getting the zinc to flow back evenly was fun... You could have made your life a lot easier if you had removed the zinc first. Must be a sure way of getting inclusions in your welds ? Dave. --- End quote --- Err Umm? One word- Thatcham covers it. Norman |
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