Welding Tips and Tricks

hi im new to this site, ive got a small job to do my wifes bike frame snapped on the seat pole, i believe its alloy.
im looking at getting a tig welder so that i can weld it back together, the welders ive looked at are only dc inverter mma combi tig/arc was looking at the clarke 131 tig/arc welder
most welding is steel my question is is this machine ok to weld the alloy? 2 inch diameter weld
any help and advice appreciated
thanks mike

As long as it's a steel alloy you will be ok.

Is the bike frame a Moly alloy?

I thought most bike frames were alluminum :/

Here's showing my age--

My Schwinn had a steel frame.

Any bicycle worth repairing today is either aluminum or carbon-fiber. Carbon fiber is probably the easier to repair. The Al alloys in today's bikes are generally hard for the home-shop welder to handle. There's preheat, post weld cooling, possibly normalizing to consider. These are extremely thin wall tubes, requiring back-purge and possibly cooling blocks. This repair is not for the beginner, unless you've already replaced the bike and have nothing to lose.

Steve

Aren't most bike frames fusion welded now?

I dunno. the old steel schwinns were furnace brazed, all the joints at the same time.

to the OP, just go buy a new seat post. they're not that expensive. it's really not worth the trouble.

delraydella wrote:Aren't most bike frames fusion welded now?

Since fusion is the goal of all welding processes, I'm not sure what you mean. I assume you're referring to a particular process, like sonic, laser, or friction stir?

Steve

Otto Nobedder wrote:

delraydella wrote:Aren't most bike frames fusion welded now?

Since fusion is the goal of all welding processes, I'm not sure what you mean. I assume you're referring to a particular process, like sonic, laser, or friction stir?

Steve

The process where the tube ends are flame heated to the melting point and then fused by pressing them together.

delraydella wrote:

Otto Nobedder wrote:

delraydella wrote:Aren't most bike frames fusion welded now?

Since fusion is the goal of all welding processes, I'm not sure what you mean. I assume you're referring to a particular process, like sonic, laser, or friction stir?

Steve

The process where the tube ends are flame heated to the melting point and then fused by pressing them together.

-
Ah, gotcha. The modern equivalent of forge welding.
With Al, I would guess induction heating in an O2-free environment would be required, but the process would be essentially the same.

This doesn't preclude a TIG repair, but that would depend on the alloy, as some are virtually unweldable by conventional means.

I seem to recall an episode of "How it's Made" that featured bicycles built from 6061-T6, which is weldable, but requires some sort of PWHT to achieve full strength. I've been welding a long time, and I'd have to do some research before attempting the repair the OP asked about, which is why I said it's not for the beginner, unless there's nothing to lose. (If there's nothing to lose, it would be a valuable learning experience going through the research and attempting the fix.)

Steve

If it is 6061-T6, you're gonna play hell. You'll need a helium-argon mix and then a way to preheat the aluminum prior to welding. Otherwise you'll get mega porosity.