Welding Tips and Tricks

My work has a way of randomly changing things and throwing it at me hoping I can weld it. Usually it works out but I am struggling this time.

I am trying to weld a 12" circular .5" thick A48 Class 40 Cast iron plate into a A48 Class 30 cast iron part. The part has a recess machined into it for the circular plate and both the part and insert are chamfered for the weld to penetrate.

I have done this a few times where both parts are Ductile Iron and my method results in an 80-90% chance of success. But this cast iron is kicking my butt.

I preheat both parts with a rosebud to as close as I can get to 450F. I wish I had an oven or something because past 350 is difficult with the size of the part. Anyways once its hot, I weld using a United Alloys Supercast 1/8" rod at 120A DCEP. I run one rod and spin the part 180 and run another rod on the other side, and then back, the 2nd pass is from a fresh area into the start of the previous weld, not starting where the last pass ended. I continue like this until its welded fully around. At this point the whole assembly is still 350F or so. I post heat back up to 450F and cover with thermal blankets folded over, so maybe 16-32 layers. It stays warm so long I leave it till the next morning. Then I check it with Radnor crack check kit and both times now it cracked around the full circumference of the weld. On the outside between the weld and the main part.

What am I doing wrong? Is the solution something I don't have like an oven? Too much amps?

In this first photo the center plate is slightly taller than the face of the outer part, and the entire surface is getting faced on a machine after my weld so the look of my weld doesn't matter so much in that regard.

That's a toughy the steel is cooling faster than the large cast peice I believe an oven may be needed or at least you could try packing it in sand or vermiculite and blankets to fill the air space

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Just to be clear both parts are Cast Iron, but it would make sense if the small plate being welded in is being cooled faster. I just don't have an oven to control the cooling process so this might have to be an outside process for us. We do these so infrequently that an oven doesn't make financial sense.

If it would fit in a domestic oven you could get a cheap used one off CL or used trader and use it to properly soak a preheat and slow cool it over a couple of days. I recon the company would bone up $100 for this.

Coldman wrote:If it would fit in a domestic oven you could get a cheap used one off CL or used trader and use it to properly soak a preheat and slow cool it over a couple of days. I recon the company would bone up $100 for this.

That would work? I wasn't sure those had enough power or temperature.

It should work I have one in the shop it's great for bearings and pizza

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Get 400F out of it no worries, then it's just a matter of time to soak that big part to temp, use temp sticks or IR thermometer or just leave it in there a few hours and have at it. As long as it fits. Then reverse for cool down. Turn it down a little every few hours - stretch it out a couple days.

If you are doing more than one pass, run a stainless bead in there or just run it pure stainless.

Stainless has enough flex to prevent it from cracking, I've welded a fair amount of cast iron and steel and by using stainless, I don't have to preheat, no burying it, none of that, the S.S will flex with the cast material and it shouldn't crack.

Depending on the situation, you may still have to preheat but my experience, I don't.

Give it a shot.

Olivero wrote:If you are doing more than one pass, run a stainless bead in there or just run it pure stainless.

Stainless has enough flex to prevent it from cracking, I've welded a fair amount of cast iron and steel and by using stainless, I don't have to preheat, no burying it, none of that, the S.S will flex with the cast material and it shouldn't crack.

Depending on the situation, you may still have to preheat but my experience, I don't.

Give it a shot.

Thats very interesting, what variety of stainless would you use? Stick? I have 316L for Stick, TIG, or Mig dual shield or solid. I have 410NiMo dual shield for Mig, and 308L, 309L, 316L, or 2954 for TIG.

Delasangre wrote:

Olivero wrote:If you are doing more than one pass, run a stainless bead in there or just run it pure stainless.

Stainless has enough flex to prevent it from cracking, I've welded a fair amount of cast iron and steel and by using stainless, I don't have to preheat, no burying it, none of that, the S.S will flex with the cast material and it shouldn't crack.

Depending on the situation, you may still have to preheat but my experience, I don't.

Give it a shot.

Thats very interesting, what variety of stainless would you use? Stick? I have 316L for Stick, TIG, or Mig dual shield or solid. I have 410NiMo dual shield for Mig, and 308L, 309L, 316L, or 2954 for TIG.

I would do 308L, personally that's what I use and TIG it.

Olivero wrote:

Delasangre wrote:

Olivero wrote:If you are doing more than one pass, run a stainless bead in there or just run it pure stainless.

Stainless has enough flex to prevent it from cracking, I've welded a fair amount of cast iron and steel and by using stainless, I don't have to preheat, no burying it, none of that, the S.S will flex with the cast material and it shouldn't crack.

Depending on the situation, you may still have to preheat but my experience, I don't.

Give it a shot.

Thats very interesting, what variety of stainless would you use? Stick? I have 316L for Stick, TIG, or Mig dual shield or solid. I have 410NiMo dual shield for Mig, and 308L, 309L, 316L, or 2954 for TIG.

I would do 308L, personally that's what I use and TIG it.

Ok, I have never TIG'ed cast iron, so how would you do it? DCEN?

Yeah, same way you would regular steel, just be aware of popping and if there's any oil or anything stuck in the metal it can "bleed" it out, so just be ready to clean it a lot, steel brush helps a lot.

It's called buttering. For obvious reasons. Like buttering bread. Do a run of each of the parts before hand with a high nickel filler and then join the pieces as per requirement. It's just that the nickel layer provides a crack resistant area. Good luck

You can even use a high % silver braze rod like 45% or above. Keeps the heat input low like a preheat.

Delasangre wrote:

I'm struggling to understand what is going on as well. Can you please fix the pictures and I will forward this to someone that may have an answer. I have no idea if any of this will help with your particular job.

It seems that your practice of post-heating aligns from what I've learned in cast iron repairs. The pre-heat rises inside the oven and under cover as much as possible. This may be where you're going left. No violent heat in ramp-up or ramp-down. Only expose enough area to do the work just outside of your heat insulation and oven. As is an inch or so in all directions. I'm generally observing some form of O/A brazing when this process happens on large repairs and large parts. Then shove it all back into the oven and do a very slow ramp down overnight. I have a long ways to to go in understanding cast iron and mixing alloys on the fly. I would love to offer more, but this all I have for now.

This person was using an O/A rig, AC stick iron repair rods, and a variety of fillers on hand. I've seen an oven build with refractory cement, fire brick, ceramic insulation, propane burner, and thin sheet metal. It doesn't need to be expensive and the cement filled table can be covered and used for other jobs. Race winning iron blocks and heads have been repaired on this very table. Today, there is a better table and a DC machine.

As suggested, a nickel/chromium rod (stainless) should help your situation. Always pre heat and slow cool as cast iron is a high carbon steel.

Im using a United Alloys supercast rod designed for cast iron, should I be using a Ni-55 or Ni-99 instead? I have 99X maintenance rod.

Delasangre wrote:Im using a United Alloys supercast rod designed for cast iron, should I be using a Ni-55 or Ni-99 instead? I have 99X maintenance rod.

Try stainless, it should help.

I like the over alloyed 309.
I always make sure I have 309 rod around. Usually have some 316l around also.

Delasangre wrote:Im using a United Alloys supercast rod designed for cast iron, should I be using a Ni-55 or Ni-99 instead? I have 99X maintenance rod.

I don't believe you are on the wrong track with the filler metal selection. Just a matter of process. With 99 percent nickel, you can actually do what's called touch welding. Where you do a small weld less than 2 inch and let it cool until you can touch without a glove. No preheat obviously. Also peen every bead with a hammer or needle gun if possible. Got to help the metal stretch