Welding cast iron...

[Jaguar1]

Hiya gents.

Just a quick question, I have a cracked cast iron exhaust manifold am I right in thinking that you can weld cast iron with the right rods?

I was told you can use a Mig but i'm sceptical, so I came to those who know

 

[BrokenBiker]

Yea you can and it's a whole thing about how...

Some say you need nickel rods, some say use stainless rods, some say mild steel filler, some say tig it, stick it, mig it, braze it...

It's a lot about understanding the properties of cast iron and how it shrinks when cooling. Preheat and a very slow cool down helps more than most things.

I've mig welded and stick welded cast iron with standard er70 mig wire and 6013 stick rods...sometimes it's fine, others it cracks.

You will want to groove that crack all the way out though. Mig brazing could be an easy option, a small reel of wire isn't massively expensive although I've never done it myself

 

[harveyp6]

Years back I had a Jensen cast iron manifold broken in half, and I took it to a professional welder. I told him I wanted it welded back together. He asked me if I wanted it welded back together, or put back together so it wouldn't break again. I picked the latter, so he heated it in an oven and brazed it back together while it was hot, and he was right, it didn't break again, which he said it would if it was stick or mig welded. Over the years he did fair bit of work for me.
Just my two cents worth.

 

[doubleboost]

Brazing is the best method .
Silicone Bronze and TIG is how I do them .

 

[doubleboost]

If it irreplaceable or stupid expensive I would repair it for You.

 

[nickk]

I always arc it with nickel ferrite rods,pre heat,short runs,peen for a couple of minutes then weld again,slow cool in the forge coke by submerging with coke to cover it. When ever I’ve seen migged repairs,they’re always hardened.

 

[Puglet1]

Ok, here we go….back in the 80’s I worked for a Swedish blacksmith installing industrial bakery ovens. He taught me so much about welding including what to do if I needed to weld cast iron.
So, to cut a long story short, I was driving a mk3 escort van when it started to misfire. I was an ex motor mechanic and quickly found that it was due to a rocker breaking in half. We were somewhere in the depths of Wales with no garages around.
I had no choice but to knock on the door of a house in a country lane and ask the lady of the house if she would sell me 10 minutes of electricity for £10 so that I could try to weld the tappet back together.
I used a 1.6mm stainless rod and stitch welded the 2 halves whilst turning the tappet between welds to displace the heat.
We then refitted the tappet, and drove the car from Wales up to the NEC to complete our exhibition, the drove back to Bristol at 70mph down the motorway.
I’ll always be grateful to Bo for sharing his knowledge with me.

 

[tom2207]

Ok, here we go….back in the 80’s I worked for a Swedish blacksmith installing industrial bakery ovens. He taught me so much about welding including what to do if I needed to weld cast iron.
So, to cut a long story short, I was driving a mk3 escort van when it started to misfire. I was an ex motor mechanic and quickly found that it was due to a rocker breaking in half. We were somewhere in the depths of Wales with no garages around.
I had no choice but to knock on the door of a house in a country lane and ask the lady of the house if she would sell me 10 minutes of electricity for £10 so that I could try to weld the tappet back together.
I used a 1.6mm stainless rod and stitch welded the 2 halves whilst turning the tappet between welds to displace the heat.
We then refitted the tappet, and drove the car from Wales up to the NEC to complete our exhibition, the drove back to Bristol at 70mph down the motorway.
I’ll always be grateful to Bo for sharing his knowledge with me.

knowledge is easily carried.

my grandad used to tell me that fifty years ago ,,, and as usual , he was right.

 

[Dozzer]

I have miged cast a long time ago, but was using an old oven to get it above 200c.
using a sand bath to slow the cooling is what i was told helped.
Think that if you can get it bronze TIG'ed that seems to be the most favoured.
Some manifolds on modern cars look like cast iron, but they are a form of stainless.

 

[BrokenBiker]

I have miged cast a long time ago, but was using an old oven to get it above 200c.
using a sand bath to slow the cooling is what i was told helped.
Think that if you can get it bronze TIG'ed that seems to be the most favoured.
Some manifold on modern cars look like cast iron, but they are a form of stainless.

I got caught out with that, can't remember what car but just assumed it was cast iron from the look of it...tried to mig weld it after a preheat with a torch and was going to use the torch to allow the cooling...but it cracked as I was welding it, worse than the original crack, then I found out it was some weird stand alone stainless blend that wasn't weldable