Machining a weld on high carbon steel casting

[kddave]

Hi, and welcome, my name is Dave and I recently opened a job shop. We mostly machine parts, but do some welding to.

Some good news is, I have a job that that came in, it is a High Carbon steel casting for a large forklift pivot. It is 20" OD and 12" ID, non-concentric. It needed to be welded up on the ID where a large snap ring hogged it out, it then needs to be turned on a lathe, grove cut with a boring bar.

Bad news is a destroyed the first piece. I MIG'd it with mild-steel and I broke 3 carbides on the lathe trying to break through the weld. So I heated it up red hot to try to draw the carbon to the surface, but that warped the part badly because the meat on one side is much more than the other side (you should see the counterweight rigging I had to do on the lathe just to spin it up!).

So I have one more shot to do this right. I was thinking TIG it with nearly pure Nickel rod, maybe preheat to 400? I cannot preheat too much or it may warp.

Any advice is appreciated? I am new at this, new here, and I just want to learn, learn, learn! Thanks, the folks here seem the most knowledgeable and brotherly.. Dave

 

[TechnicAl]

The dilution from the High Carbon Casting will cause the weld to be hard. Using Nickel prevents the carbon migration so the weld would remain relatively soft.
If you are going to use TIG you dont need 400oC preheat. The max would be 250oC depending on the carbon content and thickness of the casting....it could be less.

If you had run very slowly with very small cuts using ceramic tips you may have done it in the first place

 

[Flathead_Dave]

+1 for ceramic tips.
You were in effect doing an intermitant cut,and carbide won't stand it.
I had some 3mm thick steel discs with slots in I had to reduce from 380mm to 350mm diameter.Slow speed and ceramic tips got it done.