I have a bicycle repair to make. Material is Hi Ten Steel about 1/16. Can this material be mig welded like mild. If not what are the procedures. Thank you and Thank Mods for a little leeway, this is where all the expertise is!!!!! First pic is an original weld, the rest are of the damaged area. I would also like to add a gusset at the fork neck
It can be Mig welded if there is anything left after you clean off the crap. While cleaning, you also want to be sure it was not brazed! Lots of "Hi ten steel" bicycle frames were brazed so they looked pretty under the paint. The brass will have to be removed. Good luck, its really thin tubing. Gene
Looks welded, not brazed. There would be lugs if it were brazed. If the frame isn’t sentimental or valuable, I’d replace it. Sent from my iPad using The H.A.M.B. mobile app
May have been fixed before? Clean it down to the raw steel, good tip on looking for past brazing. I would gusset it as suggested.
My friends and I welded together an air frame for a Bearhawk that is 4130. We did a lot of research and study for good practices. One partner is a professional welder. There are two better ways to weld the high tensile steels. I am not a welder but was a member of an engineering group who did the NDT & managed the code weld repairs for a large pulp & papermill. The weld looks to have failed at the heat affected zone along the edge of the weld. The way to prevent that is to preheat the metal if it is to be TIG or MIG and followed immediately with heating it up to a cherry red & let it cool. That normalizes the metal adjacent to the weld. In airframes it is preferred to weld with a torch or TIG weld. MIG weld is done on air frames but in a factory situation it is done under engineering standards with QA/QC. People will jump in and say it can be MIG welded which is true but the result may not be the best. If the bike is not of high value then clean the weld area to clean metal & MIG weld. Bevel the edges of the weld so the weld is deposited in the joint. The weld should be a little proud of the surface when done. Post heat and let it cool naturally. If the bike is of value then it is best to have someone TIG weld the repair. Discuss with the welder & do all the weld prep that way the welder's time is shorter & cost. Preheat & post heat. Welders often fight the pre & post heat by the argument that the weld made it hot enough but that is not true. The whole joint needs to be heated to relieve the stresses. I fought that fight so many times.
One of the things I have learned from my time on the Hamb is to not share any of my knowledge or experience in the field of welding. Because no matter what you try to provide in the way of help, some self righteous expert asshole will try to twist things around and try to make themselves look better or smarter. Sorry.
The "cost" of replacement, is only one, of possible measures. Memory easily wins, least in my book. Worth-fixing.
As a former bike rider, I know how expensive those frames can be, so if replacement cost is the reason you are doing the repair, here is some information. I am not a certified welder, but I have done lots of welding on 4130 experimental aircraft frames, which had to be inspected, and the type of welding was similar to what would be required to make the repair you are attempting here. The three standard approved methods of welding were oxy/acetylene, TIG, and MIG. MIG is messy, but was commonly used by light aircraft manufacturers, particularly for motor mount frames, because it was faster. My two preferred methods were oxy/acetylene and TIG. I like oxy/acetylene because you can easily fill larger gaps, but after the weld, you need to allow the metal to cool slowly until the redness disappears, to remove all stress. With TIG welding, this heat issue isn't a problem, and no special cooling was required. At the time, I welded with an oxy/acetylene torch, and it was approved that you could weld with either 4130 or mild steel rod. I welded with both types of rod, and can't remember any big difference. Knowing why the weld failed would be helpful, but if it is because of weakness in the joint, then you will be wise to add gussets. Remember clean, clean, clean. In other words, the repair is easily doable. Weldingtipsandtricks.com is an excellent source of knowledge on all types of welding. Here is a link below on TIG welding a light aircraft landing gear. Bob
That 2nd pic shows the failure running down the middle of the weld. I can't say I've ever seen that before. Dunno if you can TIG it, the weld is right full of trash, looks like its inside as well. You can probably gas weld the existing seam, then I'd TIG weld a gusset plate into the 'V' letting each leg extend a couple inches out to get into new metal that hasn't been fatigued. You could wrap (sister it up) the whole joint in 16ga steel hammered to the shape of the tubes etc welding all around it. It wouldn't add much weight at all to the bike and be strong enough to last.
My .02, and probably not worth that much. If it's Hi-Ten, then it's not exactly an exotic frame. Looking at the weld, it isn't a really old frame, either. If I was guessing, I'm thinking 70's or 80s lower end Asian of some sort. If it's newer, then it's really low end. There were plenty of good riding steel frames, and Hi-Ten is mild steel. As for the advice to replace, if you like it, fix it. Clean it up, grind out the garbage, and weld it with whatever welding process you're comfortable with using. I'd use gas or quick, fast MIG. Gussets aren't a bad idea, unless you want to keep it looking original. I'm in the bicycle business, and I know how to weld. Not NASA weld, but this job isn't a heart stopper. You can fix it.
Thanks to everyone for the help. I mig welded the neck and added a gusset between the upper and lower tubes, really thin stuff. If the frame brakes again it wont be at that point on the frame. And thank you mods for the leeway
If you can get the frame in a bead blast cabinet . I would media blast the area to be welded. Then I would rind the weld down to parent material, Wash the area thoroughly with Acetone. I would use a 4130 filler tig rod and tig weld the repair looks like they may have used a mild steel filler rod and that is why it is cracked. Vic
Who out there doesn't remember pedalling like fury down the gravel road and have the frame break near the headstock? The pedals would dig into the gravel and before you knew it you'd be sailing over the handlebars and crushing your manhood on the way over. Ah, the memories.