The Home Machinist!

Hi Everyone hope you're all safe in this time of Covid

I have a steering part off of an old tractor brought to me (cant buy a new one ). It was welded by someone 15 years ago and now has broken again.
I believe it to be cast steel

The weld is not full penetration which may have been part of the problem, but it did break when it was new as well.

Correct me if i am wrong, but my plan was to:
#1 V out the weld area & preheat to 300 degrees in the oven
#2 TIG weld using( ER70 s 2 ) or (ER 70 s 6) Not sure of which one would be better?
#3 Then maybe post heat? No idea of temperature or duration and limited in what I can do.

If I am way off base here, please let me know.

Thanks
Sandman

Peen the weld and the heat affected area.

Is this a solid piece?

Cast iron, preheat is a must. Cast steel, not so much. I would just warm it up a bit with a torch after I had it all set up to weld.
For cast steel, just flip a coin for -2 vs -6. It's not going to make much difference. Personally, I wouldn't TIG it. I'd use a wire feed, or just good old fashioned 7018.
I would stress relieve it, both as you weld, and when you are done, a few times more, as it cools. Needles scalers do a great job at that, but a slag pick is fine too, just more work.
A far as post heat, I wouldn't bother. Again, important on cast iron, but not with cast steel.

Bill

If it is hollow, as the photo suggests, insert a backing strip, makes getting a full pen weld much easier. As noted, 7018 would be an option if cast steel. If cast iron, consider a nickel rod.

If it's cast iron braze, don't weld. I think it is probably steel, though. I can't see making that part iron.

Check with a sharp drill bit; spirals and it's steel, little graphite looking flakes it's iron.
Just to be sure.

Thanks everyone an update
I do not have Mig so that's out the part is u shaped hollow in the middle

You might think about adding a stiffner. Cut it to fit, and lay it inside the ‘U’ and weld it on the sides.

That would be good for a backing strip for the repair but the most effective stiffener would be a plate spanning the open side of the U.

I just learned it is possible to TIG weld cast iron using cast iron rod. Alternatively torch weld it with cast iron rod using flux. I have been torch welding it for years. In many cases Tig would have been easier. If it is cast iron preheat and postheat with slow cool are essential. On critical parts I send them to a heat treat shop for normalizing.

I also think it must be iron; steel would have bent instead of breaking.
It's clearly a steering part, the original break could have been the result of an accident.
Cast iron seems a poor choice of material for a part like that but you have to work with what you have.