Pre-heating with O/A before Arcing?

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I friend of mine does car repos.  He stopped by yesterday and wants some work done to his lift.  One of the things he wants is some loops welded on for the tie down straps.  He brought over 4 links of chain that are 5/8" thick.  I thought I would just cut the links in half, but to weld them on to the lift, I noticed something....  He had another welder do the same thing a year ago, but it looks like the weld came loose.  The part I will be welding the links to is 1 1/2" thick sold bars (the ones that slip under the tires and lift it up).So, I was wondering if it would do any good to heat up the base prior to arcing the chain links on?  If so, just heat it, or make it glow?  I just figured that heating it up may soften the base a bit and allow better/deeper penetration. Also, I was thinking 7018?  Thoughts?
Reply:Ya, preheat would be a good idea.  I dont have the bible around but dont make it glow, get it up to 4-600F and you should be fine.  Also put a little bevel in the chain links.Have we all gone mad?
Reply:Since they've already broken once, I wouldn't cut the links in half, I'd use full links. There's much more welded surface area.9-11-2001......We Will Never ForgetRetired desk jockey. Hobby weldor with a little training. Craftsman O/A---Flat, Vert, Ovhd, Horz. Miller Syncrowave 250
Reply:500 degrees is pretty hot, even for thick or heavy steel. 150 is good, mainly dry up all the moisture in the pores of the metal all around the weld area. You'll see the water evaporate out as you go. Red hot is way, way too hot!!Edit: Someone is likely to mention that chain welding is not a good thing also...there, I said it. I normally run an old u-bolt through the first link and weld the bolt.Last edited by tanglediver; 04-26-2009 at 02:25 AM.City of L.A. Structural; Manual & Semi-Automatic;"Surely there is a mine for silver, and a place where gold is refined. Iron is taken from the earth, and copper is smelted from ore."Job 28:1,2Lincoln, Miller, Victor & ISV BibleDanny
Reply:Whenever you heat metal beyond a dull cherry you alter the coarse grain structure to a fine grain that is weakenes it to mild steel.
Reply:Could you post pictures of what this lift looks like and how it works? There was a good thread a while back about welding forks of a f.lift in which some suggested that modifying/welding wasn't safe, and I wonder if this might be a similar situation.Might be better to make some tube sections to go around the lift part, and weld-shrink them on, after welding chain to them?
Reply:Yes preheat.  Keep in mind that preheat has nothing to do with the welding itself.  It might aid in penetration a bit but it key function is to reduce the cooling rate of your weld.  A weld that cools rapidly from red heat can be hard and brittle. Take a look at the old weld.  You say the weld "came loose"  Was it a brittle fracture or did it bend quite a bit before breaking?
Reply:Thanks everyone.  I don't have a picture of HIS truck, but I just found this one on the net.  It's very similar.  On the U shaped gripper thingy's that go under the tires, he wants a chain link welded on to make a loop for tie down straps. Attached Images
Reply:7018 is a low hydrogen rod. at 5/8 thick with a low hydrogen electrode you are not required to preheat unless base metal is below 32* F. the other weld prolly failed because the other guy couldnt weld! maybe thats why he didnt go back to him this time. slow cooling rates do promote ductility in steel like the guy a few posts ago said. but to me it sounds pretty small, your tacks alone would prolly give you enough preheat to weld that.only thing worse than an ugly woman is an ugly weld
Reply:I think cutting some hooks out of 3/8" flat bar and welding those on would be better than using cut pieces of chain link.  Just my opinion.   You can even buy weld-on chain hook plates from towing parts suppliers like www.awdirect.comMM350P/Python/Q300MM175/Q300DialarcHFHTP MIG200PowCon300SMHypertherm380ThermalArc185Purox oaF350CrewCab4x4LoadNGo utilitybedBobcat250XMT304/Optima/SpoolmaticSuitcase12RC/Q300Suitcase8RC/Q400Passport/Q300Smith op
Reply:Here is a good example-http://www.awdirect.com/weld-on-grab...6wgh/hardware/MM350P/Python/Q300MM175/Q300DialarcHFHTP MIG200PowCon300SMHypertherm380ThermalArc185Purox oaF350CrewCab4x4LoadNGo utilitybedBobcat250XMT304/Optima/SpoolmaticSuitcase12RC/Q300Suitcase8RC/Q400Passport/Q300Smith op
Reply:Here is another style, weld-on D-rings-http://www.awdirect.com/buyers-produ...-b40/hardware/MM350P/Python/Q300MM175/Q300DialarcHFHTP MIG200PowCon300SMHypertherm380ThermalArc185Purox oaF350CrewCab4x4LoadNGo utilitybedBobcat250XMT304/Optima/SpoolmaticSuitcase12RC/Q300Suitcase8RC/Q400Passport/Q300Smith op
Reply:Those are nice.  I'll have to check with him to see if the straps will work with that hook.  Not doubting you at all, just curious, why would those be better than a chain link?
Reply:For starters, more weld area and they are designed to take that kind of loading, chain links welded to a frame will just want to bend.Have we all gone mad?
Reply:Ahh....  Makes sense.
Reply:This is a question, not adviceIsn't most graded chain case hardened or something.  I wonder if welding it alters the hardening, or in some way ruins the properties?I've seen it done a lot, but I sorta wondered"Any day above ground is a good day"http://www.farmersamm.com/
Reply:everything that desertrider said X2The reason the chain failed is that it was never meant to be welded in such a fashion.   And who knows what grade of chain was used originally.  It might have been grade 43 and the working load limit on grade 43 isn't even worth the effort to bother with it ever.If he's using straps I think that a welded D ring would be a better option.  I build parts for a company that assembles a lot of wreckers I will see how they recommend securing cars to that wheel lift.    I be live that to be an eagle claw wheel lift.Vantage 500's LN-25's, VI-400's, cobramatics, Miller migs, synch 350 LX, Powcon inverters, XMT's, 250 Ton Acurrpress 12' brake, 1/4" 10' Atlantic shear,Koikie plasma table W/ esab plasmas. marvel & hyd-mech saws, pirrana & metal muncher punches.
Reply:i am a crane/equipment operator and we are taught that if you weld on a lifting structure; hook, bridle,etc.then you become liable. that car grabber is under enormous stress while towing and i wouldn't recommend heating/welding it. imho.plenty tough and union made.
Reply:saw a couple of common mis-information items above. i dont believe any steel is porous enough to hold moisture. the moisture you see is condensation from the flame when it hits the cold steel.water is a natural byproduct of combustion. the other item is grain size. high heat causes coarse or large grain size not fine grain. rapid cooling of high carbon steel will cause fine grain size--which you want if you are trying to harden the steel.
Reply:Originally Posted by boatbuoysaw a couple of common mis-information items above. i dont believe any steel is porous enough to hold moisture. the moisture you see is condensation from the flame when it hits the cold steel.water is a natural byproduct of combustion. the other item is grain size. high heat causes coarse or large grain size not fine grain. rapid cooling of high carbon steel will cause fine grain size--which you want if you are trying to harden the steel.
Reply:Originally Posted by JC'sWeldingSo, I was wondering if it would do any good to heat up the base prior to arcing the chain links on?  If so, just heat it, or make it glow?  I just figured that heating it up may soften the base a bit and allow better/deeper penetration. Also, I was thinking 7018?  Thoughts?
Reply:The "Moisture" is at an atomic level .. actually hydrogen which you definitely cannot see.  If plate had water in it then how come if you put the flame under a plate you don't get wetting on the top surface?  Generally preheating is a good thing to do and allows trapped hydrogen to migrate out of the metal.  Hydrogen cracking may or may not occur but preheating and postheats are good insurance.  We are not talking red here,,,, just hot.
Reply:Originally Posted by BurnitCall me crazy but if you are here asking whether or not pre-heat does anything, maybe you have no business welding on something that lifts and hauls cars on public highways.
Reply:Originally Posted by Pookie............. This is a common problem and these L-arms are welded on all the time without problems.
Reply:I decided against the chain link, since the last welder did it twice, and it kept coming loose.  I went with the hook.