I've searched, If anyone can come up with a link, feel free to guide me to it. Anybody ever weld an old bumper and have the welds crack? I'm no expert welder here, but I like to think I can hold my own. Last night I was modifying my bumpers for my car. I think the bumper I have is a front off a 54 chevy, but not sure. Anyway, the problem I'm having is welding the center section. It welds really nice, the weld looks good, great penetration, decent heat spread. But, You smack it with a hammer and it'll bust off every time. You can see the cross cut of the weld and it looks all crystallized and brittle. I've tried to tig and mig. With the mig I threw on a couple decent tacks, same crystal look. Now, I've google'd a couple things and came up with a few answers, but nothing really saying that they've had the exact same problem. I did however see that some old bumpers were made with spring steel, and that makes sense to me. So I went to the welding store and bought some pretty damn expensive filler rod (Tig) and I'll give it a go tonight. Basically, I'm throwing out a feeler to see if anyone has had the same experience welding on bumpers, or if I just suck, or if anyone knows of what to try or how to fix it... LMK! Thanks!!
That is true with the spring steel in at least some older bumpers. Even my 65 Dodge pickup uses a medium carbon steel in its bumpers which is a real bugger to work on. Spring steel is high carbon steel. By welding it, you're locally heat treating it. You can get around your problem by annealing it after welding with the proper temperature and time soak. You would have to know what steel you have for sure to to it correctly. - EM
Don't know about Chevys. but early Ford bumpers were spring steel or something like it. I think that may give a direction of inquiry...
That sounds like it could be one of several problems: 1-The wrong welding gas or welding gas is off or to low (this will make porosity in the weld and it will be very brittle) 2-The base metal is not clean (chrome, nickle or copper plating not sanded off) 3-Oxygen from the back side is contaminating the weld. Try using a backing on the opposite side your welding (thin aluminum or copper will work) Hope this will help you out.
That's what I would try. Heat it to red along the weld and let it cool a few times to see it it helps.
Kinda what it appears like to me, but I will try all of the things mentioned so far to see what I think is best.. Thanks for the advice. Thing really pissed me off last night and I couldn't sleep thinking about it.
Actually. The anneal temperture would be below or not to a "red condition" depending on the material.
Annealing is done at high temp (1500°F), with a soak time and slow cooling. Tempering is low temp (400°-1000°) after quench hardening.
Bumper is probably high carbon low alloy steel. High carbon makes it hard to weld, and the alloying elements contribute to forming untempered martensite. Pre-heat and post-heat is the way around your problem. More is better. Heating the metal up to make it softer (more tempered or annealed) will not help your problem. It is a phase transformation problem that forms untermpered martensite (very brittle) which you are dealing with and that is why slow cooling with post-heat is the best solution. Not knowing the exact material I can't provide more detail, but my guess is that you can do it successfully with pre-heat and post-heat slow cooling. Slow cooling prevents the martensite from forming.
Well, In case anyone is wondering.. Here's what I discovered last night. (and I really need to take a couple pics) I went to my weld supply house yesterday and they sold me some tig filler rod that was super expensive, ($35 a pound) the guy told me to use that whenever you weren't sure of what you were welding on. But, contrarary to what google told me, its super high tensile strength. So I ran a bead on some scrap, looked flawless, great penetration, ect... Waited for it to cool fully, dropped it on the floor, cracked in half. JUNK. So, then I used the same rod, and beings I don't have a way to properly pre heat the metal, I took a propane heater to the joint, then grabbed my tig torch, got an arc going and ran up and down the 1" section of the joint on both sides to heat it slowly. Then I laid a thick bead, and again going back over both sides of the weld with the arc (not melting metal, just keeping it hot) and slowly backing off the throttle. Then when I was done with that I grabbed the propane torch and heated it up all around the weld. Then left it sit for about 20 mins- half hour till cool all the way. There was a little scale around the weld (junk rising to the surface) so I had no faith. But I couldn't break it to save my life. I clamped it in the vise and took a huge hammer to it, grabbed a giant cresent wrench to try to bend snap it, nothing. Its solid. I'll try to snap a few pics of the breaks and the successful welds, for future reference in case anyone else ever has this issue. Thanks for all your advice fellas!
ive been just using stainless steel filler on the bumpers ive welded and havent had it break like that crazy!
a good way to slow the cooling down is to do as you did with heating it after welding, then bury the part in a pile of speedy-dry or sand and cover it with a moving blanket. i have done this and with that combo and radiant heated floor parts stay hot for over an hour.
That's some good information!! Thanks for sharing. Can you post the spec number on the rod they sold you? I wounder how it would work to pack the welded area in vermiculite? I've used that to aneal welds and tool steel.
I have repaired quite a few bumpers but havn't had this problem, perhaps I have been lucky or it could be because I always gas weld the repairs I make. David
I had the same issue with some Packard bumpers a couple yrs ago. I'll have to dig up the wire I ended up using. I tried everything and got the same 'cast iron' effect where it broke very easy. I used this stuff and beat it to death and it wouldn't break. I don't know where the stuff is, so I may not be able to post the actual alloy until later this aft or maybe tomorrow am. It was actually mig wire, small dia, but I tigged with it. It also took chrome nice too once metal finished out. Hang in there...
Ok, the wire I found that worked: Crown RS220-1F It's .035 mig wire. I took a nice long loop of it off and folded it in 1/2, then took a cordless drill to wind it up with one end in the vise to make it heavier to tig with. I used a reasonably low heat, something like 1/2 "throttle" on 30% and filled in the V I had in the 2 parts. Once done it metal finished out real nice. Before finishing I beat it with a 2lb hammer and it didn't break. Packard bumpers are almost like castings of some sort. I'd imagine the same early bumper process was used by many OEMs back then. Good luck, it worked for me.
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