Welding cast iron

[loose nut]

Got to argue that back.
If you do proper preheat and very slow cool,
you can MIG weld freaking cast iron.
Seriously.

-Doozer

But how many home shop guys have a mig welder with enough juice to weld a thick cast iron piece?

It is best, frequently necessary, to preheat cast (depending on the work piece and rod) but as I posted earlier there are rods that under some situations get by with out it. Joe average may have a buzz box and maybe an OX-ACET set up so telling them to tig or mig it is not helping.

[Doozer]

But how many home shop guys have a mig welder with enough juice to weld a thick cast iron piece?

It is best, frequently necessary, to preheat cast (depending on the work piece and rod) but as I posted earlier there are rods that under some situations get by with out it. Joe average may have a buzz box and maybe an OX-ACET set up so telling them to tig or mig it is not helping.

"But how many home shop guys have a mig welder with enough juice to weld a thick cast iron piece?"

Mig welder with enough juice ? I can not answer how many, nor can you.
Enough juice (watts?)... If you pre-heat it, you need enough juice to make the weld deposit stick and fill the gap prep.

"Joe average may have a buzz box and maybe an OX-ACET set up so telling them to tig or mig it is not helping."

How do you know what they have? And why do you think they have a stick welder and a torch, and you don't think
they have a Mig or Tig? I would make the guess (and only a guess) that many shops have Mig welders, as popular
as I see them in many home shops. People seem to be afraid of torches and stick machines, (thank you dumbing
down of America, and the socialized de-industrialization of this country, believing the brainwashing that makes the
people fear everything that involves work and risk, and you maintain control of an ignorant population).

How am I not helping? Because my recommendations based on the science of metallurgy, and quantified by my
own welding and cast iron repair experiences, do not match up with your experience ? What qualifies in your mind
as Helping? Do I have to know what equipment is in everyone's shop, who I have never even met ? Sounds like it
by the way you make a case. Look, I am telling you what works me be, based on my experience in my own shop,
experience on the job, experience from materials science textbooks, and 2 degrees in related subjects.
You can take it or leave it. I don't care. But to question me trying to help, and trying to discredit my contribution
using the argument that someone might not have a mig welder ? Maybe you have been arguing politics too long
with weak minded individuals, who don't call you out on your verbal garbage. Not going to fly here.

-Doozer

[nc5a]

In post #20 I said Muggy weld rod is very expensive and mentioned $1 per rod, my mistake. Doc was right it's more like $10 per rod and that was a couple years ago. I need to order some more so I'll know shortly how much it's gone up.

[nickel-city-fab]

Got to argue that back.
If you do proper preheat and very slow cool,
you can MIG weld freaking cast iron.
Seriously.

-Doozer

I've seen it done and it does work. It wouldn't be my first choice on a highly-stressed part for a customer at work, but there is no denying it can get you out of a jam. I think the process works because if you use a *lot** of preheat with a MIG, then you get insane penetration. Due to the energy concentration at the end of the wire. This means, a lot of mixing of the metals. And since there's a lot of admixture, the effects of the chemistry and physics are spread out over a greater area -- there is no deadly sharp temperature gradient, nor is there a deadly sharp boundary of different chemistries. Lots of preheat and lots of postheat and peening can make this work.

*- (Where "lots of preheat" means "just starting to glow in a dark corner")

[J Tiers]

All I know about this is that I have some cast iron machine parts that were brazed (not by me). They are as good as the cast iron, there has been no sign of them moving or failing. One of them holds a dovetail on a mill knee. Works fine.

The whole temperature thing is talked up a lot....but maybe not everyone know why. The parts were cast, and even casting runs the risk of cracking in the mold due to temperature differentials.

So, if you "weld" you are melting just "part of" the material, in other words you are introducing a temperature differential that is much worse than the one when the part was molded. Even with pre-heating, you are not going to get the conditions when it was cast, because you will be hundreds of degrees colder with the preheat.

So why screw around with that huge differential when brazing has much less, and preheat can be done more easily if needed? Braze is also almost surely more ductile than the iron, so it will likely absorb the contraction as everything cools.

A lot of people seem to forget that heated metal expands, and it contracts when it cools. So welding of steel even, causes issues of warps and moving on account of that. A small area has to cool down from just below the melting temp to room temp. Folks forget the amount of shrinking that small welded are is going to do.

If the muggyweld will hold up, it melts way below even braze, and the stuff is ductile. It's just surely going to do better as far as cracking and distortion. Strength might be another issue.

[JRouche]

"But how many home shop guys have a mig welder with enough juice to weld a thick cast iron piece?"

Mig welder with enough juice ? I can not answer how many, nor can you.
Enough juice (watts?)... If you pre-heat it, you need enough juice to make the weld deposit stick and fill the gap prep.
-Doozer

Slow down youngster.

Nobody here is looking to bust some balls. If so let me know . JR

[Doozer]

I am thinking a small heat treat oven or small pottery kiln might be a good investment.
Thinking back, most of the cast iron parts that I have brazed and repaired were
smaller than a bread box. So a small oven for uniform preheat would be a worthwhile
accessory to have in the shop. Both for part preheat and for heat treating / hardening
steels. A bonus would be that electricity is cheaper than my acetylene. And furnace
brazing with silver solder works so nice. I do some parts like that at work.

-Doozer

[nickel-city-fab]

I am thinking a small heat treat oven or small pottery kiln might be a good investment.
Thinking back, most of the cast iron parts that I have brazed and repaired were
smaller than a bread box. So a small oven for uniform preheat would be a worthwhile
accessory to have in the shop. Both for part preheat and for heat treating / hardening
steels. A bonus would be that electricity is cheaper than my acetylene. And furnace
brazing with silver solder works so nice. I do some parts like that at work.

-Doozer

I like this line of thinking. Of course, I'd like an oven too. Stan at Bar-Z Industrial Fab is manufacturing some nice small ovens, with an optional hose connection for controlled inert atmospheres. Mostly designed for small tool heat-treating. http://www.barzindustrial.com/Hotshot-Ovens.aspx

[loose nut]

All I know about this is that I have some cast iron machine parts that were brazed (not by me). They are as good as the cast iron, there has been no sign of them moving or failing.

A proper braze job is just as strong as the parent cast iron metal itself. A poor braze job not so much.

[loose nut]

Look, I am telling you what works me be, based on my experience in my own shop,
experience on the job, experience from materials science textbooks, and 2 degrees in related subjects.
You can take it or leave it. I don't care. But to question me trying to help, and trying to discredit my contribution
using the argument that someone might not have a mig welder ? Maybe you have been arguing politics too long
with weak minded individuals, who don't call you out on your verbal garbage. Not going to fly here.

-Doozer

I wasn't try to discredit you, your attitude does that for you.

You may have texts and degrees while I only have 30 years as a P & P welder in mild, stainless, chrome, monel. inconel ,nickel alloys etc. using stick, mig, tig , sub arc, automatic and yes even brazing, so I do have a little bit of knowledge on the subject. God knows practical experience doesn't match up to a paper hanging on the wall.

All the time on this site I see people saying to others asking for advice on something "oh you need to EDM that or use a 4 axis CNC" ETC., equipment very few have that are not in a commercial shop. That includes industrial grade Mig or TIG equipment. And what is it with everything having to be TIG welded now. Tig has it's purpose but not everything needs it. It is slow for one thing. People at work (when I still worked) would bring small delicate jobs to us mere welders and I would break out the 3/64" (that's not a typo) stick and have it done befog others could have the TIG gear ready to go.

Answers should be aimed at the "average" guys equipment level, unless the poster says he has something more.That was the only point I was trying to make. Now you will have to excuse me I have to go and glue my head back on since you bit it off.

[Doozer]

My loose nutted friend. All I said is, if you use proper preheat and post cool with cast iron,
you can even Mig weld it. (a process not normally associated with welding cast).
I did not suggest using Mig. Only that it worked with proper heat and cool.
I did not suggest using Mig. Only that it worked with proper heat and cool.
I did not suggest using Mig. Only that it worked with proper heat and cool.
I did not suggest using Mig. Only that it worked with proper heat and cool.

"Answers should be aimed at the "average" guys equipment level, unless the poster says he has something more."

Again, I was not suggesting anything, other than if proper heat and slow cool was adhered to, even an un-common
welding process for iron would be successful.
Who are you to moderate what the "Answers" should or should not look like ?
And if you had such authority (which you don't) then how do I know what is an average guy and what this so called
average guy has for average equipment ? All which is irrelevant because all I suggested was a process of proper
heating and slow cooling.
Then you whip out the ol' I've got 30 years experience line. So basically you are saying "trust me".
I could whip out my experience as a certified DOT bridge welder and related welding jobs,
but I won't because I don't care, and I am sure you don't care. I'm not trying to impress anybody.
I was trying to offer the importance of preheat and post slow cool when welding cast iron.
You are trying to make up some rules for posting replies here. Go find a small island to dictate. Have fun.

-D

[mickeyf]

Ah, the Internet!
It never fails us no matter what the forum or what the topic! In these challenging times, I'm grateful to have something I can rely on!

[loose nut]

. Go find a small island to dictate. Have fun.

-D

I imagine I will find it right next to the one you lord over. Don't accuse others of doing something wrong when you are doing the same thing. Nuff said!

[The Metal Butcher]

Darryl,

You've done it now.

I'll add my two cents to the ring. I'm no good with a torch, so Tig and Silicon Bronze is my go to. It is difficult to apply no doubt. When done right, it's strong and permanent.

I've seen too much failed nickle rod to be a fan. I'm sure it works right under the right conditions. I like brazing because it isn't too sensitive to pre and especially post heat. The only one I've ever had fail on me were might fault when I didn't get really any adhesion to the base metal at all and it popped right off. Caveat is that it takes ~210ish amps to get the stuff to puddle. No problem for me, but for a tig with a 20% duty cycle well... forget about it.

IMO for your average repair, the classic brass and O/A is the way to go. If your fluxing is good, it wicks in, holds well, and almost never cracks.

I've stayed away from muggy rod due to the price. Clearly Doc has had very good results, but I have to call BS on his price comparison. I can buy 3 lbs of bronze and 3 bottles of gas for the price of one lb of muggy. Pre and post heat cost nothing if you have a woodstove. Stick it down in the ashes and let it die overnight if one is concerned about cracking. I've never went to that level of effort.

Best of luck.

[The Metal Butcher]

So do these methods actually make a puddle or do they all simply make a joint? Is the filler and the casting integrated on a molecular level?

For brazing, you do not want the materials to mix. The iron will bubble up to the surface and be hard as glass. Not really an issue for O/A.