Welding Cast Iron

[Dennis H.]

It seems like I can't find the post somewhere on here that someone explains how to weld Cast iron. So maybe someone can help me out.

I am looking to weld a few bolts to the inside of the cast iron door on my evap to hold a sheet of steel about 1 1/2" away from the door to sort of protect the door from the intense heat of the fire.

I remember something about I will need to get the door really hot in a fire right before welding but I need to know if there is a special type of wire that I will need for my mig welder and if it will take a special gas. Right now I use CO2 on my mig.

Thanks for any info.

[Haynes Forest Products]

The part about heating is to keep the area from cracking after welding You dont have to get it that hot. They use high nickel alloy wire from what I was told. I weld cast all the time black pipe fittings are cast and when I made my tanks for my vacuum system I used 9 differant size fittings and not one broke or leaked. Old cast can be a problem if its been heated and cooled alot it gets brittle. Your not trying to weld 2 cast items together so small welds and dont over weld with big gobs they shrink alot and seperate. Mild steel will streach as it cools and cast doesnt. I would tack in place and let the heat spread out and then small welds so it doesnt over expand. Practice on a fitting till your happy.

[Bucket Head]

Dennis,

I do not know of a mig wire that does cast iron. There is Nickel rod for cast iron, but thats for arc welding. Brazing it would be a better idea. And probably cheaper too.

In my opinion, and I will be doing this to mine shortly, is to just drill some holes in the doors and with fender type washers bolt some fiberglass insulation to them. I have the 1" thick matting that Leader sells. I lined my whole rig with it. But don't buy it from them! I forget the website now, but its the same stuff they use to insulate pottery kilns. Find a supplier for pottery kilns and purchase it from them. Leaders prices on everything is outrageous.

The cast iron will drill easily with a good bit, and the bolts and washers will be cheaper than the welding/brazing material.

Steve

[Bucket Head]

Haynes Forrest Products,

What did you use on your black pipe fittings? The high nickel alloy stuff, or mild steel wire?

Steve

[Specklefield Farm]

if you are just making a heat shield for the door, drill 1/4" holes and get some electric fence insulators to space your shield back off of the cast iron. I did this in a different application, but it worked great.

[RileySugarbush]

Welding cast iron is tricky and I wouldn't want to risk my door while learning.

A better choice might be to not weld at all. I used a cheap cast iron door for my arch front and when I insulated it with ceramic blanket, I tapped the door through in several places and threaded in some stainless threaded rod. Works grate with stainless nuts and washers. They don't loosen up and no welding required.

[Fred Henderson]

Don't weld anything. What I did was drill 5/16" holes in the door then I used 1/2" pipe spacer cut to the lenght that I needed. I then put creamic wool on then a piece of 1/4" SS plate ( I got from juckyard). The spacers keep the wool from being compressed and the SS plate protects the wool. You can use this method and just use the steel plate but it will only last a couple of years.

[Dennis H.]

Thats a bummer that I can't use the mig, I am not much of a stick welder. Well I can make the stick stick, Nice glow rod!

So a normal good sharp drill bit will go thru cast iron?

I like the idea of using fence insulators or pipe as stand offs.

I was kind of worried about trying to weld the bolts to the door without asking around. That would be a total bummer if I ruined the door 1 month from go-time.

Thanks all for the tips.

[RileySugarbush]

I drilled and tapped mine for #10-24 very easily. Also, i didn't worry about the plate, I just held the blanket on with stainless fender washers. Wood doesn't really hit the inside of the door like it would the walls of the fire box. Plus it's easy to replace if needed.

[Fred Henderson]

If you go the drilled hole route make the holes a few sizes bigger than the bolt size that you will use. It will give the cast doors a little more area to expand to. Beleive me I am an retired maintenance welder. Have seen it all and welded it all. You can make a nice weld on cast but it takes a lot of prep time and proper cooling after welding.

[WF MASON]

I'm not sure what it is about cast , Ive repaired cracked fronts that were early 1900's and every decede after, some weld(tig) like a dream, others like a night mare, crumbling like a sand castle, I always assumed it was the quality of the cast material itself.
Drilling and bolting for the doors is the way to go.

[brookledge]

I've always had good luck with Ni-rod. But like others have said drilling and bolting is a good way also.
Keith

[Fred Henderson]

I'm not sure what it is about cast , Ive repaired cracked fronts that were early 1900's and every decede after, some weld(tig) like a dream, others like a night mare, crumbling like a sand castle, I always assumed it was the quality of the cast material itself.
Drilling and bolting for the doors is the way to go.

Bill, After the doors have been heated a few hundred time the cast tends to lose its carbon content. The carbon is what makes the cast so very hard. After its gone about all that is left is a grainy metal something like sand. Grates are a nightmare to try and weld.

[Haynes Forest Products]

You never know what they used to make old cast iron with as they reused it they didnt realloy it they just threw in what they had, Its like rebar and tree stakes there the dregs of the scrap heap.