Thread: Cast iron welding questions

I have welded cast before, and had all knockers tell me it won't work..

One was the knotter arm on a Bamford hay baler.. I ground it and kept it warm, not hot, and then welded it up with WIA 140G stainless rods.. That baler did another 100,000 bales before it was retired totally worn out, but arm still holding..

Next biggy was my truck engine block, it cracked a chunk off the rear where the gearbox adapter plate bolts on..
(no not a little 5 tonne) The truck was a Mack 237hp R 600.. I ground it up and used the new adaptor to hold it in place, then I heated till blue in colour, and started stitching it in place..
1st one end, then other then middle.. Then check it all, always keeping the heat on..
Once welded I kept putting heat onto work and surrounding area, allowing it to cool slowly..(about an hour before cool enough to touch)..

Now I used a torch in one hand and a mig in the other, using .9 mm gasless wire.. That truck was still going 10 years later with no sign of weakness, but as I had sold it about 5 yrs after, I don't know if its still going now, last seen it 5 years ago.. The bloke that bought it off me is now fertilising daisies..

The main thing with Cast is the cracking from shrinkage, so gentle and keep the heat on, it should work.. Using cast rods, hmm, can't say, never used them and always too far from any sort of civilisation to get more than a beer..(and I'm a scotch drinker..)..

Best of luck..

PS, Baler was cast steel, hence stainless rods..

I've done a few cast iron repairs at work.

Get the nickel rods and turn your amps down 70-80 for 3.2 rods.

Do short runs just to build up the weld. In between runs peen the weld area with your chipping hammer.

Don't try to rush it, don't overheat it, make sure its warm to start with. Doesn't have to be hot just warm to touch.

Usually the weld direction should be along the crack. If you find that the crack keeps opening up then go across the crack to give some support then go back to following the crack.

Once you are finished, wrap it in a leather welding jacket or similar so it can cool down slowly.

Cast iron welding is never pretty so don't be dissappointed if it isn't

Originally Posted by BenM78

Cast iron welding is never pretty so don't be dissappointed if it isn't

That was the old days. Now there is cast iron mig wire that does a great job and looks nice. Polish it off for a perfect color match....Bob

preheat welding temp for cast is 900 to 1100 F degrees. since it is not structural anything should work. stop drill the crack. Grind a minimum trough. weld from the stop drill hole to the open end. If you don't preheat take your time and do small tacks the whole way letting each completely cool before applying the next don't jump from one end of the crack to the other. keep the heat low and the deposit to a minimum. Either the mig (wire feed) or the arc with your rod will be fine. If and when you grind to clean it up take your time as well the heat distribution while grinding can wreck the HAZ as well.

Don't underestimate the value of peening the weld also, this removes much of the potential stress in the weld therefore lessening the potential to crack.
One comment relating to cast iron in general, cast iron varies greatly in quality and therefore weldability. Some cast iron, typically older cast iron is a joy to weld, (well, almost), whereas some of the newer cast irons, typically those found in cheap tools and the like are really not worth the effort.
I notice that the method of welding cast iron with low hydrogen electrodes has not been mentioned. This is one of my favourite methods. Preheat the job to a dull red, having already vee'd out the crack and drilled the normal hole at each end of the crack, weld up the crack with either E4816 or E4818 electrodes at lower than normal amperage because you are working on parent metal that is already well heated, if necessary heat during welding to maintain the heat in the job, allow to cool slowly away from breezes - even covered over in a bed of lime. Job done. This works really well on manifolds and the like, just remember to face off the manifold should it warp at all, (I weld the manifold clamped to a strong back during welding and check when cool).
One of the best peening tools is a cheap air chisel with the chisel edge ground off so it does not cut, turn the air down to lessen blow force if need be and work the tool over the weld to peen it. This is of particular benefit when using nickel electrodes and the "cold" method of welding cast.
It pays to not over reinforce the weld as this can cause cracking if the component is exposed to heating and cooling cycles.

Originally Posted by Karl Robbers

This works really well on manifolds and the like, just remember to face off the manifold should it warp at all,

Not to hijack your post and i have used 7018 for many years on storm grating but i do like cast rods better. Prob the reason why lo hi works so well is the amount of steel in the cast iron mix when its made. Anyway here is an exhaust manifold i did a few months back with cast iron mig wire and argon gas. No preheat just clean up the area and weld a bead. The face was burned away from a gasket leak. Welded it and the guy filed it off and the fit is perfect. No more leak. 1st pic is the weld next pic is the cleanup before the weld...Bob

That manifold came up quite nicely.
I would imagine that the cast iron mig wire, (nickel/iron mix?), is not cheap though.
I guess that there are many tools in our collective toolboxes.

Originally Posted by Karl Robbers

That manifold came up quite nicely.
I would imagine that the cast iron mig wire, (nickel/iron mix?), is not cheap though.
I guess that there are many tools in our collective toolboxes.

Yes lots of tools. I paid 75 dollars US for a 2# spool of .035 Crown Alloys 44-30 and it is worth every penny. I do lots of custom cast iron repairs that most guys won't touch. I just had a guy drive 8 hours for a 10 minute fix because 30 other guys wouldn't touch it...Bob

I was chatting to a guy who teaches welding at TAFE about cast iron the other day
He said the main aims were to have the metal "sizzling hot" but not red hot before welding, and then to cool down really slowly
He recommended wrapping the welded piece in a fibreglass fire blanket (which all welders should have handy anyway) and letting the cool down period extend over a few hours
He said the main problem with brittle cast iron was cracking due to heat stress

Originally Posted by SimonP

I was chatting to a guy who teaches welding at TAFE about cast iron the other day
He said the main aims were to have the metal "sizzling hot" but not red hot before welding, and then to cool down really slowly
He recommended wrapping the welded piece in a fibreglass fire blanket (which all welders should have handy anyway) and letting the cool down period extend over a few hours
He said the main problem with brittle cast iron was cracking due to heat stress

Alot of cast iron welding depends on the type of rod or wire used. Some rods require preheat and some don't. Thats why i buy new rods and read the booklet and see for sure. Some guys just grab any cast iron rod and go for it. Just my thoughts. But i will agree to cool slow as possible after welding...Bob

Originally Posted by aametalmaster

Yes lots of tools. I paid 75 dollars US for a 2# spool of .035 Crown Alloys 44-30 and it is worth every penny. I do lots of custom cast iron repairs that most guys won't touch. I just had a guy drive 8 hours for a 10 minute fix because 30 other guys wouldn't touch it...Bob

That's actually not too bad price wise - couldn't buy the equivalent in cast iron sticks for that. I might look in to that myself. Like you I don't mind doing cast iron repairs, which many shy away from.

Originally Posted by aametalmaster

Anyway here is an exhaust manifold i did a few months back with cast iron mig wire and argon gas....Bob

Nice weld job, manifolds are always a place of drama, especially the older stuff..

Why is it, you come across good solutions, years after the job was done..

The amount of times I have sat out in a paddock trying to fix things, but have found out it pays to keep tin fruit and eggs handy in the tool box. (Tin fruit tastes good and the tin, with a bit of wire helps seal pipes(even exhaust) and the eggs allow you to keep radiator full to get home..)

These alloys these days have made it a lot harder, need to know aluminium

here is a few of some cast welding I done last week.

THe most important thing I found was the downslope. Being controlled by a pedal and not pre-programmed, I am guessing my downslope was around 1.5-2 seconds all the way from 90 amps to my base current of 5 amps.

It was a root pass and 2 filler passes. All done with er70s2, I know its not the best, but all I had on me.

Why not just braze it?