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Another welding cast iron thread


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  #1  
Old 03-22-2016, 08:43:20 PM
G.M.Johnson G.M.Johnson is offline
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Smile Another welding cast iron thread

I've been weldoing cast iron for many years and by no means am an expert. The other day I had a piece of production equipment go down due to a broken cast iron lever. Just so happened that both my good welders where down and the only thing I had left was the good ole Miller matic MIG unit with ER70S .035 wire. So I pre heated the pieces to a nice orange color, but not hot enough to start burning the carbon out, and then welded the pieces together, and immediately buried in the sand bucket to cool. I gotta tell you, weld looked great, flowed nice, and was nice and strong! So the question is what did I manage to do right? I usually use ni55, ni99, cast arc, depending on the type of cast.

So today I did a weld strength test using the same procedure. Both test specimens where cast iron wedge pieces that there non ductile in nature. Ground edges to a v and left enough to locate pieces together. The first piece was cold welded, no peening, nothing, and let to cool. Second piece was heated at the break area to a nice orange color, welded pieces together, welder was on 4 for heat, and then let cool in sand. I then proceeded to rebreak both pieces at the welds. As you can see from the pictures the first one broke at the weld and right at the heat effected zone. Now the second piece was totally different, it broke not at the weld but at a new spot, and away from the heat effected zone. So it is possible to make a good strong weld using a MIG welder with mild steel wire. I do wonder if by pre heating to a very hot level is allowing the excess carbon from the cast iron to leach into the mild steel wire and sort of make a more comparable metallurgy? Anyway though I would share my findings.
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  #2  
Old 03-22-2016, 09:00:35 PM
G.M.Johnson G.M.Johnson is offline
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Default Re: Another welding cast iron thread

Also did a hardness test just to see if the weld was hard and the original casting was C10 and the weld was around C15 Rockwell.
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Old 03-22-2016, 09:54:13 PM
J.B. Castagnos J.B. Castagnos is offline
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Default Re: Another welding cast iron thread

Welding two loose pieces together is not as critical as welding a crack in a block. When welding two pieces together they can expand with the heat and contract when cooling. If you try to weld a crack in a block without preheating it will expand at the weld, when cooling it will probably crack somewhere on side of the weld as it cools because cast is poor in tension. Peening helps by expanding the metal a it cools but it still won't be a good structural weld, just a way to fill a crack. Arc welding brings the metal to molten temps and it cools quickly, chilling and becoming impossible to machine.
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Old 03-22-2016, 10:33:11 PM
G.M.Johnson G.M.Johnson is offline
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Default Re: Another welding cast iron thread

I did have a casting brake off a large piece of equipment once and had to weld it back on in place. I used ni55 rod and after welding applied heat by way of torch and slowly backed the heat down to help control shrinkage and cracking. That was five years ago and that machine still used every day. I agree, a block is a whole different situation all together and would crack if not done correctly. But for my own experience I am gonna try MIG we!ding some cracks on a junk block just for craps and grins.
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Old 03-23-2016, 06:04:25 PM
sunshineman sunshineman is offline
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Default Re: Another welding cast iron thread

Hi there
I welded cast iron for 35 yrs sure you can do what you have done . In my line of work automtive repairs welding cylinder heads , blocks etc where you have to machine, drill tap . You have to weld iron correctly no short cuts especially when someone is paying for perfect results . But as posted if your having fun why not experiment
Kind regards sunshineman
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Old 03-27-2016, 08:01:47 PM
larry bee larry bee is offline
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Default Re: Another welding cast iron thread

Sunshine man please share your secret
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