Thread: How do I weld Cast???

I don't know about welding cast to something else but a bloke in Cairns repaired a cracked cast iron planer table for me using Spray Facing Powder, the stuff that is used to put hard facing on mower blades & dozer blades etc.

I have welded cast iron to stainless using mig and rods both fillers were nickel not sure how it would work with steel.
The rods are dear as well as the wire but ask around you maybe able to purchase a couple and give it a try.

you can get special rods or welding cast and welding othr steels to cast. cant remember what they are called give a welding joint or similar a ring

try bronze filler rod flux and an oxy torch . cheers bob

Did in the past weld Cast using Nickel rods on an Arc welder. Doing it other ways caused cracking to the material due to expansion. TIG might work.

Studley

We need Grahame here. My understanding is that you have to clean the hell out of the pieces to be welded, then use an oxy torch to heat the metal until it turns orange, then weld it using special cast rods, then leave it alone to cool naturally.

What I have found out so far...
I called a welding place today, they said it can be done with med.- high nickel cast rods.
They will sell them to me on a per rod basis for about $5 per 3.2mm rod. or $160 per kg.

They also had what they called disimilar rods which are used for welding metals that are different eg steel to stainless etc. but they will also do spring steel and high tensile. They couldnt confirm if they would do Cast?? They are $115 per kg.

Total Tools had the high nickel cast rods but they were selling for about $114 for a packet of 12 - 15 rods.

I'll try to track down a place where i can them abit cheaper...

My understanding is similar to Ross', the parts need to be heated first so there is no thermal shock when welding begins, and a slow cooling (no quench) for the same reason.
I have done a few jobs, but not with arc rods, just Oxy-acet and a brazing technique.
Cheers

All the welding of Stainless to Cast Iron that I have done has allways been done Cold ,no preheat.
Not sure in this application how vital Pre heating maybe.
There are times that I have had to Pean the welds to relieve stress.

From memory you must preheat to fusion weld with Oxy. So the whole job gets pretty hot, then you heat the area you are welding enough to melt it. Cast runs like butter when it melts so careful. You use a rod to add material to it.

Studley

Hi Guys,
Cast iron is something you don't weld unless you really ,really need to.
Welding cast iron to itself presents enough problems but welding it to something else,well it just gets more difficult.It not a job for a novice welder.

The reason is that cast iron has 100 times the amount of carbon it it than say a piece of mild steel.Add carbon to a ferrous metal and subject it to welding temperatures and hardening will occur.
The more carbon ,the more hardening.

Is there a picture forming here yet?

So whether you are weld Ci to itself or something else there is going to be a very hard area along the bead boundary .
The other pain in the rrse charecteristic of good old CI is the shrinkage rate as it cools. In short the little inverter machine will be hard pushed to weld your cast iron and produce something you will be happy with.
Another problem that arises is that all cast irons aren't equal as there are several. I would guess your pulley bases are grey cast iron which is machinable.

If you can't be swayed from stick welding, use a pure nickel rod as first choice, a stainless steel 316L electrode as next choice and finally a low hydrogen electrode as the cheapest ,but nastiest choice .I think what will ultimately dictate your choice is the cost of the electrode,be sitting down when you get the price!

However, if you can be convinced not to stick weld ,pally up with someone who has an oxy set and braze the job - best option of the lot.

Does that help?

Grahame

Thanks Grahame,
I dont have an oxy set or any experience with oxy welding so I will have to stick to the arc option. Though I may be able to change the method of construction and use a large bolt through the center of the pulley form the under side and weld a nut to the inside of the vertical mild steel pipe.
I have heaps of old gears/pulleys sitting around so I might try it anyway just to see what happens.
Thanks for the info on the welding options
cheers

g_man,
Ok! If you have to stick weld!

• Preheat the cast to cherry red -or if its a large piece as hot as you can get,
  
• Weld it.
  
• Cool it out slowly- A tub of lime in which the recently welded item is buried in- come back 24 hrs later-slow cooling is the trick -if its going to work at all-
  if it doesn't work toss the lime into an acid soil part of the garden -Lol

As one of the other blokes said ,you might try a welding works to see if they will sell you just 1 rod.

Cheers
Grahame

For Cast iron welding this is the go.
Although the powders are expensive in the long run it works out cheaper because it works first time around.

Kev.