Heat forming / shaping metal......

[YELLAHEEP]

I'm gonna build a brace to tie the front unibody rails together using steel tube. I don't have a bender readily available and was thinking I could just heat it and bend it since the angles I need won't be very big. My question is:

Is it better to let the metal cool on its own or dunk it in water after bending? I seem to remember someone talking about preserving some tensile strength by doing one or the other.

Thanks!

 

[Loose_Nuts_Enterprises]

Not sure about heat forming, but when welding critical strength components like spindles, knuckles, etc, you want it to cool as slow as possible, or else it will be brittle. We usually use a synthetic wool/fiberglass stuff to pack the part in, and it takes a real long time to cool down. Maybe if some like beezil will chim in...

Not sure if this helps, something to think about though.

Dan

 

[robs]

On plain DOM tubing, you're ok to water quench it.

For Chrome Moly tube, let it cool slow.

For welds, let them cool slow.

When you heat steel to over approximately 1330°F, it changes phases... it goes from a ferrite / carbide mixture to austenite.

When it cools back down, it has to transform again. If allowed to cool slowly it will go back to ferrite / carbide (as long as it's not a tool steel)... cool it quickly and it "could" go to martensite... which is very strong and brittle (unless tempered).

DOM tubing has little carbon and little hardenability. Very little worries about martensite... and if it does form, it's not gonna be that hard nor brittle. Chrome Moly tube (4130) can harden out...

Welds in general are under a lot of stress during their solidification.. it's best to let them cool on their own... and if it's a critical design... take some Mapp gass and heat it back up until it's just about red (roughly 1100°F) as that will help reduce the stresses... I did this with my exhaust and it's held for a loooooong time....

On something like a frame truss (post pictures!!)... it wouldn't hurt to weld gussets at the bends for mechanical help anyway..

For what it's worth.