Weld Cracking
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Freshman User
Joined: Dec 2001
Posts: 34
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From: Mesa, AZ
Weld Cracking
I know this is a mesage for the bodywork forum but nobody is there and I need a quick answer if I can get one. I'm trying to replace part of a post on my 48 F1 bed. I have a new section of post about 8" long. The section I'm replacing is in the middle of the post. When I (butt) welded it in place the bottom section keeps cracking as soon as it cools off. I tried to increase the area I was welding, but it still cracked. I am using a gas/acetylene setup. It's called a Henrob 2000. (a small diameter welder made for sheetmetal which uses 4 lbs of pressure on both oxy and ace). I'm using 1/16 copper coated rod. Obviously I am doing something wrong but I can't seem to find out what. Any ideas??
Post Fiend
Joined: Feb 2001
Posts: 6,328
Likes: 124
From: Iowa
Weld Cracking
Definitely give Brett's solution a try. I'm not a master welder by any stretch. I bought a real nice selection of brazing rods at work. The guys said thanks and continue to braze everything with coat hangers and mechanics wire. They told me the fancy stuff sometimes sticks easier but usually cracks in short order.
Elder User
Joined: Sep 2002
Posts: 948
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From: McAlester, OK
Weld Cracking
Heh heh, had the same problem with my '41 bed when I shortened it. It's been a few years. I started off with a torch and the tacks just kept on popping when it cooled. One thing I did was try to keep the whole thing hot. This worked a little, but not very well (everything would snap at once). After a few months (I had started it in shop class) I finished it up at home with a wire feed. With that I could move quicker and get the thing welded before it broke. My shop teacher had just told me to work faster with with torch while chuckling. He was useful. 
Clayton
Clayton
Senior User
Joined: Aug 2000
Posts: 288
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From: Agua Dulce, So. Calif.
Weld Cracking
I have to agree I love to gas weld sheet metal and hammer while still hot. but when I did that on my under hood seam it had problem the betal was thin and abused and mig seemed to deposit more material for holding Ed ke6bnl
Senior User
Joined: Dec 2001
Posts: 494
Likes: 1
Weld Cracking
Dennis,
I had another thought. I am not familiar with your rig. Does it put out a sufficiently large enough flame to puddle both pieces of the metal and create a thorough weld? When you examine the cracked weld, did it penetrate all the way through?
Adios,
Brett
I had another thought. I am not familiar with your rig. Does it put out a sufficiently large enough flame to puddle both pieces of the metal and create a thorough weld? When you examine the cracked weld, did it penetrate all the way through?
Adios,
Brett
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Posting Guru
Joined: Jul 2001
Posts: 2,119
Likes: 2
From: Southern New Hampshire
Weld Cracking
I use a Henrob extensively for sheet metal on old vehicles. Migs are great for cars from the 80's and newer when the alloy changed but readily available mig wire is bad on old sheetmetal.
Back to the Henrob. It sounds like you may be running too much oxygen. Back it off a bit and try again, or practice on some scrap.
Each job is different. I repaired some fender tears in a late 50's U-Haul trailer the other day with the Henrob, completely different settings from what Im used to and also went up a tip size.
Do you have the complete kit or just the torch?
Getting back to my earlier comment: Are the 2 pieces compatible or different alloys? This happens often with some repop patch panels that are made of high tensile plate or even using body shop scrap pieces to make your own.
Back to the Henrob. It sounds like you may be running too much oxygen. Back it off a bit and try again, or practice on some scrap.
Each job is different. I repaired some fender tears in a late 50's U-Haul trailer the other day with the Henrob, completely different settings from what Im used to and also went up a tip size.
Do you have the complete kit or just the torch?
Getting back to my earlier comment: Are the 2 pieces compatible or different alloys? This happens often with some repop patch panels that are made of high tensile plate or even using body shop scrap pieces to make your own.
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Joined: Apr 2003
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From: Karori
Weld Cracking
Need to give attention to pre and post weld treatments also. With chassis's it is best to heat a larger region around the weld to say 100 - 120 deg c. With chassis the large area of metal acts as a heat sink and so it is important to insulate the area as best as possible after welding. I use a heat blanket. This is particularly important on these older chassis as they do have a high carbon content.
D
D
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Freshman User
Joined: Dec 2001
Posts: 34
Likes: 0
From: Mesa, AZ
Weld Cracking
Well I tried the coat hanger theory and it worked fine. Don't understand it but as long as it works. I realize that every panel is going to be different (there are a lot of panels to weld) so I'm learning to be patient I have the complete Henrob set. I'm new to Henrob and welding in general so I know it will be a learning experience. Thanks for all your help.
Dennis
Dennis