Pre-heating with O/A before Arcing?

[JC'sWelding]

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?

[sn0border88]

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.

[Craig in Denver]

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.

[tanglediver]

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.

[pistolnoon]

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.

[Oldiron2]

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?

[lotechman]

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?

[JC'sWelding]

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.

[El_Lloydeo]

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.

[DesertRider33]

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.com

[DesertRider33]

Here is a good example-

http://www.awdirect.com/weld-on-grab...6wgh/hardware/

[DesertRider33]

Here is another style, weld-on D-rings-

http://www.awdirect.com/buyers-produ...-b40/hardware/

[JC'sWelding]

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?

[sn0border88]

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.

[JC'sWelding]

Ahh.... Makes sense.

[farmersamm]

This is a question, not advice

Isn'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

[Dualie]

everything that desertrider said X2

The 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.

[the Q]

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.

[boatbuoy]

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.

[tanglediver]

Originally Posted by boatbuoy

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.

I don't buy it. Take the flame away, and the wetted edge is still there. We dry up the steel surface which is porous, or rough enough to hold water on the surface of the metal. It may appear smooth, it may hold water as a vessel, but pour out the water and dry it off with a flame. As you take the heat away, it cools a bit and condensation begins again. The water needs to evaporate. Moisture on steel when welding creates bad ingredients for a good weld fusion. Keep it off the steel and keep it off those 7018 rods.



Some metallurgy for kicks. I am not gonna get into that debate.

http://steel.keytometals.com/Articles/Art3.htm

[Burnit]

Originally Posted by JC'sWelding

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?

Call 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.

[lotechman]

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.

[Pookie]

Originally Posted by Burnit

Call 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.

Relax...

He is talking about welding a ring to secure the tie-down straps. The L-arms of a wheel lift autoloader minimal 1/4" thick steel. The area these straps attach to is minimal. My advice: crank the heat up and pull the trigger. This is a common problem and these L-arms are welded on all the time without problems.

**If you have any question about it, call Holmes/Century Mfg in the Chattanooga Tn area. They are always helpful.

[Burnit]

Originally Posted by Pookie

............. This is a common problem and these L-arms are welded on all the time without problems.

Except the last time somebody welded on the one he is working on.

I'm not worried about the base metal of the lift arm being changed so much as an alloy chain being welded, it properties changing, and breaking again.

[JC'sWelding]

I decided against the chain link, since the last welder did it twice, and it kept coming loose. I went with the hook.