Cast iron to steel?

[rcfp]

I'm trying to weld steel square tubing to a cast iron well casing. Any clues? It needs to be strong enough to support teenagers pretending they're NBA stars (it's for a basketball goal backboard and post).:blob3:

[John C]

You might want to find something other than cast iron for the job.
There are many different ways to stick cast iron to steel, but none that I know of for any type of structural strength.
Cast iron is usually only welded to make a repair.

[pjt]

If no one suggests how to achive structural strength with this combination, build your goal support to CLAMP to the cast iron, with maybe a weld or welded gusset to keep it from sliding down. Take comfort in knowing after they get to the NBA they will be rich enough to buy you all the best toys...(oops,TOOLS)

[Shade Tree Welder]

The only chance you may have is to get nickel rod but I do not think it will hold. Also if you have never welded cast iron it is not easy or straight forward. You will have to per heat it to a very dull red (550-650F) then weld it immediate befor the het is lost. Then since the casting is large you need to cool it ssslllooowwwlllyyy or the cast will crack. You need to insulate it with dry (no moisture) kitty little, oil dry or sand. Oh yeah and a pound of nickel rod is ~$25 bucks.

Better yet, find an old 55 gallon drum cut it off at an appropriate height and fill it with cement, and stick the tubing in that. Oh yeah, you should supervise it from a lawn chair and have the kids do all the work.

[david_r]

rcfp,
Depending on the size of your pipe, you may be able to find riser clamps at a decent plumbing supply. They are steel and you could weld to those after clamping them to your cast iron.

[OlPilot]

I think I'd forget welding it. All cast irons have one thing in common - too much carbon, which causes a brittle high carbon martensitic grain structure to form adjacent to the weld, which promotes cracking. Fusion welding produces local thermal stresses and the base metal must be capable of some plastic deformation to relieve them, if the weld is to be a success. For this reason, you'd have better success with ductile and mallable cast iron rather than grey cast iron. Preheat (500-1100 F) and postheat would also help.

Suggestion - why not grab an O/A torch and braze the joint with flux and a brass filler. It'll be plenty strong and you'll avoid all the metallurgical mess.

[bikeitswift]

Originally posted by OlPilot
I think I'd forget welding it. All cast irons have one thing in common - too much carbon, which causes a brittle high carbon martensitic grain structure to form adjacent to the weld, which promotes cracking. Fusion welding produces local thermal stresses and the base metal must be capable of some plastic deformation to relieve them, if the weld is to be a success. For this reason, you'd have better success with ductile and mallable cast iron rather than grey cast iron. Preheat (500-1100 F) and postheat would also help.

Suggestion - why not grab an O/A torch and braze the joint with flux and a brass filler. It'll be plenty strong and you'll avoid all the metallurgical mess.
My first thought went with Olpilot. Why not braze it? I agree that steel clamp brackets are the real ticket. You can weld away on them , the hoop, supports, etc, but clamp it to that post.
My very limited understanding of cast iron is that, just as you have been advised, it has to heat up to dark cherry very slowly and evenly, then very slowly down, but the weld itself has to be able to endure the contraction of the cooling, which is why brass brazing seems to be the only"welded" solution. I'd stick with the clamp approach.
I have also wondered about fusing the two, though, I am a novice sculptor (see my flaming drag bike in my signature!), and want to try some creations using old cast iron gears, and such, and figured brazing was the way to go. Not much of a safety factor involved, other tha a piece falling apart. Will thgis work? or do I weld up steel connectors for everything and incorporate it in my design?

[david_r]

bikeitswift,
I can't resist. You ever get beat up for riding a "flaming drag bike" in Texas? I can see that being acceptable in Kalifornia and Massachusetts but not Texas :D

Why not braze it? There's plenty of high end bike frames that are fillet brazed and they take more stress than a scuplture. Besides, it seems more artsy to picture a guy welding with a torch than an arc welder.