View Full Version : Weldable?

04-02-2008, 06:29 PM
I have a frame I'd like to hack & use, but I'm not sure if I can. It's "4130". Not weldable, is it?

Wood Butcher
04-02-2008, 07:59 PM
I'm not a professional welder, but here's what I have learned...

4130 (CrMo) can be welded (it welds similar to mild steel). However, due to the grain structure of 4130 the resulting weld may be prone to cracking after it cools. It is really better suited to either o/a or TIG welding, but it can be welded using stick or MIG.

If stick or MIG is your only option, two items are a must:

1) The base metal cannot be too clean--no grease, oil, rust or paint. After you have removed all the contaminants, clean it again. Wipe down the area to be welded with a solvent like acetone or lacquer thinner.

2) Preheat the area to be welded--200-300F will do the job. Don't let it cool down--get to welding once it is up to temperature.

All that being said, we're not talking about aircraft quality work here. A lot of cycling purists tear their hair out at the mention of using EMT on a bicycle frame, in addition to welding the joints instead of brazing them.

To illustrate the point, one of my co-workers built a TE Clone five years ago using two junked CrMo frames and enough 3/4" EMT to make the chainstays. He MIG welded all the joints with the only preparation being removal of paint and rust with a wire wheel on his angle grinder. He now has over 1500 miles on the bike and has not had any sort of weld failure. Call it what you will, it's either dumb luck, excellent craftsmanship (uh...not quite) or the 4130 weld issue is somewhat overblown on bicycle frames.

That's my $0.02 worth. YMMV.

04-02-2008, 08:13 PM
Okay, thanx. That's about what I thought. I was pretty sure it was Cro-Mo, but wasn't certain.

I'm not gonna fool with it... more hassle (& risk, considering my lack of welding skills) than it's worth.

BTW, it's about time you re-joined the team, Woody! Good to hear from you again! :)

04-03-2008, 02:13 AM
My Meridian, and I suspect most others, had 4130 cromo seat and chainstays, as well as the pilot steering tube, from donor bikes. It's pretty hard to find donor bikes that aren't made of cromo these days. I didn't do any prep other than to wire brush the paint off the donor parts, and the coating off the square tubes. I had no problems with the welds. In fact, the only problem I had with the frame was that the 1 1/2" square tube main boom bowed slightly under the seat. I wouldn't be surprised if the donors you used for your projects were cromo. Not all cromo frames are stamped.



04-03-2008, 11:17 AM
Well, that takes a load off my mind! I have several frames in the pile that are either partially or completely CrMo... I was going to scrap or Freecycle them! Now I know better!