Mig welding cast iron.

[Gritineye]

Hi folks, just registered after lurking and learning for a few months.

I have successfully (it seems) MIG welded a couple of cast turbo outlet bends for Diesel engine transplants I have done, I vee'd both edges, tacked together, then preheated in my Rayburn range fire, welded whilst almost cherry and returned to the fire for a bit and then cooled in the oven 250 deg F.

These where done a while ago now but it still worries me somewhat, have any of you guys done a similar thing and has it lasted?

 

[TechnicAl]

What filler wire did you use?

 

[Gritineye]

Hi TechnicAl, not sure now as I have used that roll but it was just 0.8 gp type for mild steel.

Not too worried about the one shown as it is my vehicle and I can re-do it if needed, but the other one was for someone else!

 

[awemawson]

Well if it fails its not presumably a life threatening event, just be a bit noisy until fixed!

 

[TechnicAl]

I assume it was mild steel then

As you got it so hot it will probably be OK. The weld will be a bit hard and brittle. It may fail through vibration.............eventually.

Should be fine for quite a while

You often find that after heating it to that sort of temperature it distorts and doesnt fit anymore. The controlled cooling will have helped to reduce / eliminate this.

 

[Gritineye]

Well if it fails its not presumably a life threatening event, just be a bit noisy until fixed!

Strangely it was very quiet with just the stub on, nice whistle too, it got noisier as I added more to the system, so much so that I had to fit a silencer

Should be fine for quite a while

You often find that after heating it to that sort of temperature it distorts and doesnt fit anymore. The controlled cooling will have helped to reduce / eliminate this.

That was my thinking too, I just don't know enough about the metallurgy, thanks for your thoughts..

 

[Seano]

If you don't already know, pein'ing your welds as you go will also help relieve some of the stress in your welds....

 

[TechnicAl]

If you don't already know, pein'ing your welds as you go will also help relieve some of the stress in your welds....

I doubt it if hes using MS

If it was Ni or Ni Fe peening would definitely help

but on ms that has been diluted by the cast iron, peening may break it....it would be like hitting the cast iron

 

[Gritineye]

Yes did know about that but keeping it hot, turning it, welding it, getting it back in fire before it cooled and stopping my gloves from burning was enough to be doing, hammering it as well would have been all a bit frantic!

Would cast have stood up to bashing it though?

 

[Gritineye]

I doubt it if hes using MS

If it was Ni or Ni Fe peening would definitely help

but on ms that has been diluted by the cast iron, peening may break it....it would be like hitting the cast iron

My thoughts exactly..

 

[Seano]

I doubt it if hes using MS

If it was Ni or Ni Fe peening would definitely help

but on ms that has been diluted by the cast iron, peening may break it....it would be like hitting the cast iron

I though he was using M/S wire 0.8.....

 

[TechnicAl]

he is

which is why it could pick up carbon from the cast iron.........this would make it hard and brittle......and hitting it with a hammer might break it

 

[JRSolutions_82]

Ok I am contemplating a repair on a stove that I have which is cracked, now I know that heating it etc is nesacerry to preventing a new crack forming straight away, but seeing as its only a stove top surely being brittle because of using an ordinary mig wire wont matter as it is not under stress like vibrations, but just geetting hot and cold through use...

 

[dannyp]

i quite on find manifolds espectaly off turbo engines as bout the easyest cast there is to weld

aparently this is because they often have quit a lot of nickel in the mix anyway

 

[anto]

I welded a cast turbo housing with just MS wire in a mig. No preheat/ postheat etc and so far it has remained intact.
I realise it isnt ideal but i didnt have the option to heat it.
It has been on the car for 5months now with no cracks that i can see.

 

[JRSolutions_82]

I have a plan hatched, I have ordered 99% Ni rods from flea bay for £8 for 5 delivered and am getting some thermal blanket that is used for lining kilns and such like things. I think a roll of blanket is 1 m x 10 m, this means I will be able to preheat the cast stove top whilst it rests on the blanket then weld it and then reheat and then wrap and allow to cool slowly, will probably take all day to cool down as the blanket is very good. I even have a couple of pyro metric cones that I can use to tell how hot I am getting the metal before welding. Just got to wait for the rods to arrive now....

 

[Paul.]

I have a plan hatched, I have ordered 99% Ni rods from flea bay for £8 for 5 delivered and am getting some thermal blanket that is used for lining kilns and such like things. I think a roll of blanket is 1 m x 10 m, this means I will be able to preheat the cast stove top whilst it rests on the blanket then weld it and then reheat and then wrap and allow to cool slowly, will probably take all day to cool down as the blanket is very good. I even have a couple of pyro metric cones that I can use to tell how hot I am getting the metal before welding. Just got to wait for the rods to arrive now....

Unless you have the means to evenly preheat to around 500deg c and hold it there while welding followed by very slow cooling I wouldn't bother, it is better to keep the job cool (below around 50deg c) to reduce local expansion, weld it using short runs and then if possible peen between runs,

 

[JRSolutions_82]

I tried a little test the other day on it and using my tig torch I tried to (i am NOT a tig welder) fuse the metal back together, using the foot pedal to apply current it started to work but I only done a very small area and straight after I could hear the metal making a horrible noise that sounded like cracking?? I was planning on using a propane torch to heat the metal up and using the pyro metric cones to tell that I have heated the piece evenly up to the right temperature 600 deg c, weld it using short runs of about 25mm and peening between runs. Using the propane torch and blanket in a formation I should be able to reduce the heat slowly enough to allow the stresses to be relived, I could build an oven but tbh that is something for a later date, I have built a couple of kilns for a local company and have access to all the materials needed, making a very large one at the moment. I appreciate your comments and will happily do the job cold but am nervous that it wont work. Also if I can pull of a hot repair and it works then I will be completely chuffed ;-)

 

[drjim]

I stuck a steel piece in to the top of a cast fire fender today, used mild steel mig wire and turned the power up a bit higher than I would for steel alone. Gave the cast a good grinding back and melted away. I need to do some more grinding, and as it's a painted fender piece I can get away with some filler in there but the weld itself seemed to stick together pretty well. I have stuck it in the fireplace in front of the new gas fire with test paint on (was originally for a solid fire so I have filled in the gap where the fire basket was, gas fire has flat face) for a couple of hours, it got hot the weld didn't crack and the paint didn't blister. Your stove may be a different matter!

 

[Sean]

Is it possible the " well i welded a turbo and its fine" were perhaps a case of the housing being cast steel, rather than the cast iron used for decorative parts and stoves etc?