EvilRufusKay Posted April 13, 2004 Share Posted April 13, 2004 I have been doing some patch work using mig welding, flux core wire. My problem is with burn thru or blow thru. If I am using a slightly higher gage sheet, patching to the original on the car, unless the mating surface is exactly right the original, lighter sheet wants to burn thru. I know set up is key. Everthing must be clean etc, no gaps if possible. Unfortunately these patches are on the unibody at the point wher ethe lower fender bolts go. These patches have several bends and to make a patch with no gaps is extremely difficult. I got one side done but was wondering if anyone had any techniques they use when doing similar welding. Thanks!! Quote Link to comment Share on other sites More sharing options...
240Z2NV Posted April 13, 2004 Share Posted April 13, 2004 Using gas and non-flux wire is the preferred method, I'm told. I'm new to welding, as well, and was told that the gas cleans the welds as you go, and reduces temps. Quote Link to comment Share on other sites More sharing options...
Brad-ManQ45 Posted April 13, 2004 Share Posted April 13, 2004 AFAIC, flux core and auto sheet metal don't mix - too hot. You really need C25 and .23 or .24 solid core wire. Quote Link to comment Share on other sites More sharing options...
EvilRufusKay Posted April 13, 2004 Author Share Posted April 13, 2004 Unfortunately the welder I am borrowing is not set up for gas. I don't think the Argon reduces temp though. I am pretty sure it's only intention is to blow away impurities. I have used both types of welders and definately prefer the gas type. My buddy ( a welder) told me that flux core welding is actually stronger. Quote Link to comment Share on other sites More sharing options...
Tim240z Posted April 13, 2004 Share Posted April 13, 2004 Ok...although I'm no expert (maybe John Coffey will pipe in), I self taught myself over the years, so take this advice as such: 1. Concentrate the weld pool on the thicker material and 'dip' onto the weaker material. 2. Weld in shorter bursts to decrease the heat in the metal. 3. If there are gaps where it is diffucult to shape the new metal to the old, weld up to the point where the gap begins, then, while the metal is still hot from welding, hammer it into shape so that there is a good meeting of the two metals. 4. Take your time. You may need to do it as little as a small 'tack' at a time to prevent burn through. You'll find that once it has some weld material, it will be easier to run a second pass to get good penetration....but this only works where cosmetics are not too important... Tim [edit] Flux core is not stronger. The gas is used to shield the weld from atmospheric impurities (oxygen). Gas shielding is usually better, neater and stronger. That said....all my welding was done with flux core wire[/edit] Quote Link to comment Share on other sites More sharing options...
gramercyjam Posted April 13, 2004 Share Posted April 13, 2004 What size wire are you using? If you are using the .035 size, maybe you will have better luck with the thinner wire. If you can stabilize your power source (wire it straight to the breaker box, big fat extension, don't run other tools or appliances, etc), that can help too. But honestly, I was never able to overcome the problems you describe with my old flux core welder. I finally ditched it got a small name brand MIG welder with the gas shielding and that kind of welding turned out to be so much better. Quote Link to comment Share on other sites More sharing options...
johnc Posted April 13, 2004 Share Posted April 13, 2004 I am pretty sure it's only intention is to blow away impurities. The shielding gas is there to do just that, shield the weld pool from active gasses (oxygen, nitrogen, hydrogen) that cause embrittlement. The flux in your flux core wire is supposed to do the same, but its a less effective method. Impurities have to be cleaned from the parts before welding. A shielding gas gives better control over heat input into the weld, makes the weld pool more visible, and allows you to run less voltage for the same penetration. There are also better filler wires for welding sheet metal. ER70S-6, "EasyGrind", etc. work better then flux core wire. Try what Tim mentions above if you stay with the flux core welder. Quote Link to comment Share on other sites More sharing options...
Brad-ManQ45 Posted April 13, 2004 Share Posted April 13, 2004 C25 will make for less penetration than straight CO2 - which to me means cooler. Don't take my word for ir - go to Hobart's BBB: http://www.hobartwelders.com/techtips.html#mig Quote Link to comment Share on other sites More sharing options...
ThomaZ Posted April 13, 2004 Share Posted April 13, 2004 You could also try pressing a heat sink for example a copper bar against the joint from the other side; it helps burn through a little. Personally I gave up trying to wells butt joints; even if I hade the slightest gap I burnet through. Instead I bought a pliers at an auto repair shop that could joggle the edge of the repair piece. I find it much easier to weld lap joints and if you joggle the edge I think it looks god enough. Quote Link to comment Share on other sites More sharing options...
EvilRufusKay Posted April 13, 2004 Author Share Posted April 13, 2004 Thanks for the help guys...alot of useful info. I will try a coupleof the suggestions like thinnerwire. The hobbart page answered a question I had about stick out length. Unfortunately all my $$$ is tied up in parts so I wont be getting the miller welder I want. I will have to "stick" with the $150 jobber I borrowed. John you brought up a very interesting point. I noticed I have been having trouble seeing what I am doing as in the actual weld pool. I have been trying but have bee basically going by feel. I wondered why when I used my buddies gas welder I could see so much better. It makes sense now. The flux burning off makes it difficult to see. The only voltage control is max and min. Originally I had it set on min but found that I get a much better weld and less splatter on the max setting. It didn't seem to effect the burn through much either. I was thinking about trying some sort of heat sink but these patches are sealed from the back side so no luck. Thanks again guys!! Quote Link to comment Share on other sites More sharing options...
johnc Posted April 13, 2004 Share Posted April 13, 2004 I noticed I have been having trouble seeing what I am doing as in the actual weld pool. What shade lens are you using in the helmet? It sounds counter intuitive, but to see better, use a darker shade lens. I suggest you start with an 11 and see how that works. Quote Link to comment Share on other sites More sharing options...
EvilRufusKay Posted April 13, 2004 Author Share Posted April 13, 2004 I have a cheap auto darkening hemut from Harbor Freight. I currentl have it set at 11. Maybe I should step it up? I definately notice a big difference once again between my buddies nice auto and this chep one. Even in slight cold it acts funny. Does not darken quick enough. I had to remove the protective outer plastic (sheilds the lens from splatter my buddies is sealed glass) because moisture would collect between the lens and the protector. Now the lens has all kinds of burns from splatter. Life lesson...cheap tools = poor function and greater risk of injury. I actually knew this but now it has been re-enforced!! Quote Link to comment Share on other sites More sharing options...
TOMAHAWKZ Posted April 21, 2004 Share Posted April 21, 2004 Dude trash that harbor freight helmet if your still using it. you will regret it a few years down the line. even if you can't afford a really good welder make sure you protect your eyes with a quality helmet with the proper lenses for the welding your doing. I have too many friends that regret going the cheap way.. First thing to go will be the night vision... Quote Link to comment Share on other sites More sharing options...
Pop N Wood Posted April 22, 2004 Share Posted April 22, 2004 They sell replacement splatter sheilds. Buy a few glass ones and keep them handy. Even the most expensive helmet will be ruined if you run it without the shield. Can't blame the tool for that one. I hear you on being able to see. In my case it is the trifocals rather than the helmet. Try a halogen work light to help illuminate the weld area. And the smoke from the flux core does complicate seeing the weld. Quote Link to comment Share on other sites More sharing options...
EvilRufusKay Posted April 22, 2004 Author Share Posted April 22, 2004 Unfortunately if I get too close to even a incadesent work light the shield darkens. I have to weld "sans" light in order for the helmet to function properly. In reply to blaming the tool... if the sheild sealed better against the lens, I wouldn't have removed it. Unfortunately it is made in such a cheap fashion that it collects moisture and fogs up very badly. Quote Link to comment Share on other sites More sharing options...
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