[chrisharon]

Hi all, I'm trying to TIG braze steel to a cast/nodular iron housing using aluminum bronze like Jody did here:
https://www.youtube.com/watch?v=xQN_yz-4Hhg&t=186s

I V ground both my test piece of 3/8" steel strap (about 1-1.5" wide) and the cast, and preheated.

After about 50 medium strength hits on the unsupported edge of the steel with a 5lb hammer/sledge the steel came off with the aluminum bronze and a thin layer of the cast attached.

What I'm wondering is, is that normal/expected failure or am I overheating and crystalizing the cast? How much of a beating should it take to get failure?

This is my first time dealing with cast, and though it's not critical, I'd like to get it as right as I can.

Thanks in advance!

Chris

[Poland308]

That would be a normal failure. It's possible that you could increase the strength a little more by slow cooling the cast in a sand bed or some similar method. But even then it's most likely that the cast will fail first in an impact test like you did.

[Coldman]

+1 you don't want go beating up on cast. It will break.


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[Mike]

Chris, welcome to the forum.

[chrisharon]

Thanks for the welcome, Mike.

And thanks to Josh and Coldman for your replies. Nice to know I'm at least on the right track, just need to practice a bit more.

Chris

[Arno]

+1 you don't want go beating up on cast. It will break.

^^^ this...

Cast iron of any type is very strong in compression and stable, but it does not tolerate bending stresses or impacts well. The material is too brittle for that purpose. I would expect a braze to hold and 'cushion' the mating surface, but (as you experienced) that the base cast iron material will fracture and break right behind it under impacts.

When that sort of use is expected you usually see objects made from cast steel which is more ductile and can tolerate impacts and bending stresses, but is less temperature stable and wear resistant.

Good example of the difference in use/application is the difference between a car brake disc which is usually a high carbon cast iron and the machined to tolerance and the uprights/hub-carriers which may look similar but are usually a cast (and sometimes forged) steel and then machined part.

Bye, Arno.