TIG welding cast iron to steel

[mad dog]

I've read the posts about welding cast, how you need to preheat and V it out.
I'm just welding some thin cast iron brackets to steel, not a manifold or anything. So I don't think it'll crack.

What kind of filler rod is used? Something more special than ER 70S-3?

Thanks- md

[chipmaster]

mad dog
i think you would be better off to braze your parts than try to weld them.
some cast iron does not weld but i have never found one i could not braze.
my .02 worth good luck
chipmaster

[mad dog]

Thanks chipmaster. I did some reading after posting and saw others suggest this.

With TIG, I read you can use a nickle based rod (Ni55 or Ni99) or 309 stainless! Why stainless? I have some on hand, but no nickle of course. Anyone TIG'd cast to steel with stainless?

[Sandy]

Stainless, naturally, has nickle in it also. So it is closer to nickle rod than mild steel.

[elderthewelder]

the 309 is more for joining stainless to mild steel, when I weld cast or other types of disimilar ferrous metals I use a high nickel rod, either a Inconel or a Hastelloy. See if your local welding supply has either of them and would sell a small quantity.

[MetalSculptor]

Airgas Sells NI 55 or NI 99 Stick rod, or break off the flux you you know have tig rod.

I Love it !!!

[dandimand]

I have routinely used 309 tig rod for welding cast its tricky but ive seemed to have found a method that sort of works well on cracks anyways .

[KEENAVV]

OA brasing cast to steel works very well. I used to make split manifolds for dual exhaust systems for friends in the mid 50's. Oop's showing my age!

[pulser]

I tend to side with Chipmaster and the suggestion to braze cast iron to steel. Depending on the joint type and fit-up, you could silver braze a lap joint, or brass braze weld a fillet joint. In both these cases you are not melting the base metals, thus you can avoid a brittle weld or heat affected zone. Also, a weld has very high tensile stresses that promote cracking. The stress in a braze or braze weld will be minimal.

Proper welding of cast iron, and prevention of cracking, can be much more involved. The high nickel rods you mentioned can provide a ductile weld deposit but then preheat and slow cooling is needed to help minimize a hard brittle heat affected zone. As mentioned by Elderthewelder, 309 is suitable for stainless to steel, and is highly alloyed enough to avoid a hardenable weld metal chemistry.

Not to pick on Metalsculptor, but I would caution against knocking the coating off of any stick rod to use it for TIG. It is my understanding that the stick coating may contain alloying elements necessary for the proper stick weld chemistry, and/or, the rod itself may be more highly alloyed than a TIG filler, in order to compensate for element losses in the harsh stick welding arc environment. Stick rod is made for stick welding, and TIG filler is made for TIG welding.

Let us know how it goes!

[JohnnyWeld]

DAng I thought tig welding cast with stainless was my little secret. EVERYONE I ever heard talking about it always says in a robotic tone "you need Ni rod stupid!" I always used 308 simply because I have alot if it around and only once did I not have success- that was with an old Gray engine water manifold. I guess the older folks in the place I used to work in couldnt be taught anything.