Welding Tips and Tricks

Hello all. I'm looking for some help. I've been welding for a few years full time and off and on hobby level for 12, primarily dual shield on standard steel, nothing certified or structural. I just got a new job where I'm going to be doing alot of stainless and cast welding and mostly TIG and Stick.

My first job is to weld a ductile iron thrust ring into the face of a cast iron plate. The machinist cut a pocket so the ductile ring sits flush and there is a nice V groove to weld in. The first one was iffy because the welder was broken and running cold. Plus I didn't really know what I was doing. The 2nd one went much better when I setup a different machine that wasn't broken. Both parts passed the crack check spray.

The third part looks and felt the best, I welded it with United Alloys Ultracast 1/8" rod at 120 amps and it was preheated to about 400F. After the weld it cooled slowly down to 100F under a thermal blanket. But when I crack checked it it was cracked all the way around right on the outer edge of the weld where it meets the Cast part.

Wondering what went wrong. My coworker who's a very experienced welder suggested I switch to a Ni-rod 99 maintenance alloy and maybe it wasn't preheated hot enough?

This reading material from the Ductile Iron Society may be of help to you?

http://www.ductile.org/didata/Section8/ ... tm#WELDING

It's all about the composition of the cast iron plate versus the composition of the filler metal. These have to be nearly the same or exactly the same. Without knowing what the composition is of the plate then you would be guessing what the proper heat treatment should be and from what it looks like, it was not done right for its composition.

Next, I'm sure you know but the length of weld that you can actually do in one pass is very short depending on the thickness of the plate. Maybe try reducing how long of a weld you do in one shot and spread that evenly around until the whole thing is welded.

But if it's cracked it means one of two things more or less: either the cast iron itself got too hot and cooled too fast for its composition by itself or the filler rod's composition cooled out of sync with the plate and from the sound of it that's what it seems to be since the crack is at the toe of the weld.

Well I talked to the salesman for United Alloys who makes the rod I was using and he said that the Ultracast I was using is meant for Ductile to Ductile, so he is sending me a sample of their Supercast which is designed for welding all types of cast together and may solve my problem.

I also made a rookie mistake and since I am using a TIG/Stick machine I still had it on DCEN. I ground the weld out and switched to DCEP and still using the Ultracast while waiting on the other rod I laid another bead in there and this one did not crack. It may be that the EP vs EN helped but it didn't seem to weld much different.

Once I get the other rod they recommend I will try that and see if it welds these materials better.

I forgot about DCEP as well. I'm sure it will help and I suspect with a more uniform fusion from the new rod it will make for an easier time to fit the tolerances and it won't be so hit or miss and nerve wracking. At least I hope.