- Thread starter BIG JAY VTR
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BIG JAY VTR
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just got back on and read the thread, thanks for the positive comments on my welds im quite happy with them 
ill be doing some thin tests soon, i have mainly been adding the strenthening gussets to my trike frame, the bulk of the welding has been done with argosheild so im thinking it should be fine, if i see any signs of fracture during the first few months ill buy some argosheild from somewhere and vee the welds and re do them, i didnt know that co2 makes the weld brittle so ill take the chance this time, well it will probably be the only time as ill not need to build another trike after this one lol, ill post photos of the thin tests when i do some
ill be doing some thin tests soon, i have mainly been adding the strenthening gussets to my trike frame, the bulk of the welding has been done with argosheild so im thinking it should be fine, if i see any signs of fracture during the first few months ill buy some argosheild from somewhere and vee the welds and re do them, i didnt know that co2 makes the weld brittle so ill take the chance this time, well it will probably be the only time as ill not need to build another trike after this one lol, ill post photos of the thin tests when i do some
shenion
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CO2 can make some metals brittle like stainless steel. The Japanese have welded their cars and bikes with CO2 with no problems. Until recently, they did not have any argon supply.
CO2 can add a bit of carbon to the metal. On mild steel there is so little, a bit more wont make a difference.
High-strength steels are a different issue. Adding bit more carbon and the heat of welding can have negative effects that require heat treatment. CO2 does run hotter than argon mixes, so the chance of HAZ effects gets worse.
If I get a chance I'll redo tests with CO2. I had done mix tests before.
CO2 can add a bit of carbon to the metal. On mild steel there is so little, a bit more wont make a difference.
High-strength steels are a different issue. Adding bit more carbon and the heat of welding can have negative effects that require heat treatment. CO2 does run hotter than argon mixes, so the chance of HAZ effects gets worse.
If I get a chance I'll redo tests with CO2. I had done mix tests before.
Quite what that has to do with weld chill caused by the excellent cooling properties of CO2, is a mystery to me....
shenion
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Especially since every welding site, gas supplier says CO2 adds heat to the weld via disassociation and the released O2 burning the surface of the weld.
Ahh.
You read it somewhere. So much more reliable than observation...
Easy really,weld something with Argon mix, put a file to the weld.
Weld something identical with CO2, put a file to the weld.
This of course ought to be something in the region of 2-3mm thick as we're talking motorcycle frames and that's typical of those.
That easy.
shenion
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Would more likely be due to added carbon.
If you have used pure argon (I have) you will see it cools the weld much more than CO2 and lays caterpillar shapd welds with a narrow penetration as the argon cools the outer edge considerably.
If you have used pure argon (I have) you will see it cools the weld much more than CO2 and lays caterpillar shapd welds with a narrow penetration as the argon cools the outer edge considerably.
So, now you're saying it does harden the weld, but not for the reason I said, but for a reason you said it didn't in an earlier post.
What's your point here?
shenion
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I doubt your tube frames are mild steel. I have not seen it harden mild steel as it takes a considerable amount of carbon added to make it hard. The little bit added by CO2 does not make much of a difference.
Has been said here many times before, it is near impossible to heat harden mild steel without an ice quench.
Has been said here many times before, it is near impossible to heat harden mild steel without an ice quench.
martinez
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have to say I've never noticed a problem with the weld hardening (unlike stick welding), I'm always very frugal with the gas and only ever use enough to create a decent weld, maybe too much CO2 could cause cooling and brittleness, but I've not seen anything myself.
As I said before, I would consider using a better gas if it was an important weld; and in making up expensive parts, reducing the chance of having to bodge it makes it more cost effective, I would also consider having the parts heat treated afterwards.
Have to say that if the Japanese used CO2 without bad effect, maybe it'd be fine anyway? but I do remember some pretty poor welding on 1970s Jap-bike frame though.
Must also say that I think a motorcycle frame made from 2-3mm steel may be a bit on the heavy side, I would have thought 1-1.2mm would be more like it, although Trikes are a different kettle of fish
As I said before, I would consider using a better gas if it was an important weld; and in making up expensive parts, reducing the chance of having to bodge it makes it more cost effective, I would also consider having the parts heat treated afterwards.
Have to say that if the Japanese used CO2 without bad effect, maybe it'd be fine anyway? but I do remember some pretty poor welding on 1970s Jap-bike frame though.
Must also say that I think a motorcycle frame made from 2-3mm steel may be a bit on the heavy side, I would have thought 1-1.2mm would be more like it, although Trikes are a different kettle of fish
Nope, only borderline road race frames are that thin (1-1.2mm) in the wall. Thinnest I've seen on a reasonably sized road bike is 1.8mm, 2mm is more usual. Even then look at a japanese steel mid sized motorcycle frame and ask your self why they did that on the swing arm gusset. The bits that aren't welded aren't welded so they don't create stress raisers.
Take piece of ERW and hacksaw with 32 tpi blade. Cut tube.
Did you noice what happened when you cut across the seam? It's harder, which is why ERW usually starts cracking by splitting along the seam.
Take your MIG, prepare a couple of tube joints in something like 2-3mm wall tube. Weld one, then preheat the other until it's just starting to discolour and weld that. Use Argon mix gas.
Allow both welds to cool in air.
Get a round file and have at the welds. The preheated one is easier to file than the other one.
So, how is that not harder then?
Incidentally, I'd prefer it if you didn't infer that I was incompetent in my professional capacity by implying that I don't know what I'm making frames out of.
martinez
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so after welding my suspension wishbones, would you suggest heat treatment ? I had only considered the stress relief issue when I made some engine mounts (mild steel) last year and hadn't got proper facilities, so built a fire and threw them in. Bit low tech I know, but that C & G I got 30 years ago finaly came in useful
shenion
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You can buy a gas mixer (I have one.)
Not something a DIY user can afford. My mixer lists for $1500.00
(not what i paid though )I have seen people use two regulators and two flowmeters and wye the outputs together. These need to be the ball/tube type to work right. Should have check valves in case the regs have different pressures. For 10LPM 25% CO2, set argon flowmeter to 7.5LPM and CO2 at 2.5LPM. Probbaly works when going, but bet the mix is off when starting.
