Need Help to setup my mig for Chomoly 4340 and Mild steel jobs

admin

Alright so trying to help my father get the small Lincoln Mig we have setup to do some light work on some atv frames we have.the aftermarket frames we have are 4340 chromoly, and we need to replace motor mount tabs and a-arm mounts. so what Wire should we be looking for. the frames are not thick they are 3/4"(DOM i think) and 1" tubes flanges 1/8" thick max generallyand what gas should be used for this. and what is the best route for bottle to do meaning what size, should we buy the bottle seperate and fill it or just get it full from a welding supply?not gonna be a heavy use application here.my next question is we are also going to be doing some Mild steel work on one of the other frames it is OEM honda frame thats cracked.can we use the same suggested wire as above for the chromoly? if not do i need to have a seperate liner for this new wire?and also same gas as above or is it better to move to a flux core for mild steel and use the gas for only the chomoly.I'm waiting on the model of the welder and some pics of it soon as i get it ill post it up.I know its a Small Lincoln Mig thats probably near 10years old now im guessing its a 140 amp.Unfortunately i am overseas working so i cant just walk into the store with the welder and say set me up.  So i must prepare my mother with the right instructions to go to the Local welding supply or order things online.Thanks for the help in advance
Reply:no replies? noone welds 4340 around here?
Reply:c25 gasER70S-6 wireEd Conleyhttp://www.screamingbroccoli.com/MM252MM211 (Sold)Passport Plus & Spool gunLincoln SP135 Plus- (Gone to a good home)Klutch 120v Plasma cutterSO 2020 benderBeer in the fridge
Reply:http://www.lincolnelectric.com/en-us...el-detail.aspxhttp://www.lincolnelectric.com/en-us...ly-detail.aspx4340 is usually going to be heat-treated.  Welding such an alloy would not be as simple as welding some plain mild steel.  Some 'agressive' preheat (650-700F) is usually called for, and welding parameters and filler selection depend a bit on whether you can rely on just running single-pass welds and have enough alloy pick-up from the base/parent material to give you OK welds and metallurgy, or whether you need to go to the low-alloy fillers and such.Shielding gas depends on the weld parameters and the filler material used.  Also, a 'little' 120V MIG machine is going to be kind of iffy for welding some 1/8 inch thick pieces with GMAW.  The 120V MIG machines usually seem to top-out at about 14-16 gauge for GMAW, which is not quite up to the power/heat need to weld 1/8 inch thick steel.In the 'just weld it together' category for non-critical use?  C25 gas and ER70S-6 wire.Last edited by MoonRise; 05-02-2012 at 12:10 PM.  The best laid schemes ... Gang oft agley ...
Reply:OffshoreNDT, could you post the source for those frames? I'd be very suprised if they were really 4340 and not 4140 (aircraft tubing). Anyway if they are 4140 mig is not a good choice without preparation and a good PWHT.4340 hardens much deeper so something like thin wall tube will through harden from welding and need a furnace anneal.MattPS. I can't remember ever seeing 4340 tubing... 8620/30/40 yes but not 4340.Last edited by Matt_Maguire; 05-03-2012 at 08:52 AM.
Reply:Originally Posted by Matt_MaguireOffshoreNDT, could you post the source for those frames? I'd be very suprised if they were really 4340 and not 4140 (aircraft tubing). Anyway if they are 4140 mig is not a good choice without preparation and a good PWHT.4340 hardens much deeper so something like thin wall tube will through harden from welding and need a furnace anneal.MattPS. I can't remember ever seeing 4340 tubing... 8620/30/40 yes but not 4340.
Reply:Yea that ^  Nice catch Paul!Matt
Reply:Good catch guys its 4130 chromoly tubing here is a link to the frame http://www.lsracing.com/honda-250r-r...atv-utv-racingi have one newer i just dropped off to a pro fabricator ill post a link to some similar work he did for another guy.hes going to rework the mounts on this frame to handle the 80 horsepower single cylinder motor i have.but still want to play with the older frame rather then junk it. Attached Images
Reply:and here is my quad on the frame i broke all the mounts off of its possible we can upgrade the welder to a stronger unit we have 220v available to use.i thought our welder was a lincoln but here is the unit we have i know its nothing spectacular but give me your honest opinions.tig welder at the moment is a bit out of reach maybe next year i can look into one.im familar with preheat/ and PWHT but some guidance on what procedure for 4130 would me very well appreciated. Attached Images
Reply:I wouldn't even "think" about mig welding that.Syncro 250 DX Dynasty 200 DXMM 251 w/30A SG XMT 304 w/714 Feeder & Optima PulserHH187Dialarc 250 AC/DCHypertherm PM 1250Smith, Harris, Victor O/ASmith and Thermco Gas MixersAccess to a full fab shop with CNC Plasma, Water Jet, etc.
Reply:I had one of those little Power migs. The list of failings on them is about the same as most other import migs. They are tough if not impossible to find parts for, feed can be erratic at best, they'll top out at under 1/8" under real world conditions ( I wouldn't trust mine over 14 ga at best) just to name a few.. Looking for a small cheap mig to do sheet metal repairs on a vehicle, they'd probably work fine, but I wouldn't trust one to do welds on what you have..No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan
Reply:okay, so for mild steel what am i looking for to get setup with a bottle and gas with this thing?next question what would be an acceptable setup to use for this application.i have welded on the red frame with this welder( for the footpegs) but fluxcore cheap *** wire was we'll say less than ideal, more like a nightmare one pass 10min grinding the massive defects away before the next pass.
Reply:I would Tig the frame honestly, but that's just me.
Reply:Originally Posted by DSWI had one of those little Power migs. The list of failings on them is about the same as most other import migs. They are tough if not impossible to find parts for, feed can be erratic at best, they'll top out at under 1/8" under real world conditions ( I wouldn't trust mine over 14 ga at best) just to name a few.. Looking for a small cheap mig to do sheet metal repairs on a vehicle, they'd probably work fine, but I wouldn't trust one to do welds on what you have.
Reply:Originally Posted by justinTI would Tig the frame honestly, but that's just me.
Reply:Engine mount tabs are subject to severe vibration loads, and that means fatigue is going to be a problem. Especially if you used mild steel filler. You can use the little spatterbox MIG for fit-up. But I strongly recommend taking it to a professional and having them TIG it with 4130 filler.With TIG you apply heat and lay down filler metal in a slower, much more controlled fashion. With MIG, weld speeds are very fast and heat input is quite low. This can be beneficial for some kinds of steels, but not for 4130. With MIG you'd end up with a small heat-affected zone right under the weld, and due to the rapid cooling it would be very brittle. With TIG the heat affected zone would be quite a bit larger, but due to the slower rate of cooling, the brittleness would be a lot less.
Reply:I think your wrong, Joefromsaltlake.If i remember correctly, you only use 4130 filler if you are going to heat treat after.ER70S-6 or ER80S-6 are the most common for chassis work.
Reply:Originally Posted by LarryOI think your wrong, Joefromsaltlake.If i remember correctly, you only use 4130 filler if you are going to heat treat after.ER70S-6 or ER80S-6 are the most common for chassis work.
Reply:thanks for the help guys, anyone reccomend a tig that would do go for this purpose?not in need of a professional 4000$ unit something used or cheaper for occasional use.
Reply:i'm a complete rookie but imho 4130 tubing on a chassis like that should only be tigged and i believe the most recommended filler is er70s-2. as for a tig machine i would think there are just too many variables to really recommend any particular one not the least of which is the price.