About Cracks in DI Pipes

What did Google say about "DI welding" or "ductile iron welding"?

Use threaded connections.

i think the welding procedure was the main cause. heat induced stress fracturing of DI is a common problem with less experienced welders.

It may be of no importance, but what kind of stress is on the flanges ?

Whilst I'm here, can anybody explain (in plain terms) the difference between DCI (ductile cast iron) and SGI (spheroidal graphite iron) ? As far as I know, it's how the matrix is arranged. Long time since I tried (badly) to figure this out, but I'd appreciate any not-too-tech explanation. A lot of people seem to use the terms interchangably, but there is a difference in material properties. Anybody got a few seconds to explain this for me ?

(sorry to hijack your thread a little, parvatheni, but the info may be of use to you as well)

Only difference is the name.

Are you sure ?

The link you provided certainly seems to support the same conclusion....

'....Ductile iron is characterized by having all of its graphite occur in microscopic spheroids.....' (the first sentence)

Check out post #3. What think ye ?

I think durtieduck is correct.

What am I missing here?

I don't think you're missing anything. Ta for bearing with me.

durtieduck's explanation sounds good to me, I was just veering a bit OT on the dci/sgi difference. I've no idea if it makes any difference to the welding, though it may be relevent to the original question (which was a bit short on info).

'...a bit short on info...'

Exactly. I orginally thought the OP was referrring to pipes for Deionized Water.

I don't think he slightling you. I think you are reading an insult, that isn't really there, into the conversation.

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How did anyone's sexual preference become the subject? How is that relevant to this post, or particularly relevant to an engineering blog? The sexual preference of other posters is not something that comes up frequently if ever in my mind, and it is never of consequence. But perhaps I am alone in this.....do other people spend alot of time thinking about the sexual habits of other posters?

yes. let cooler heads prevail. thanks.

There is no straight answer to your question.

There are several welding procedures for ductile iron. Some have specific pre/post heat treatments, others have none, and the filler materials for them are all different.

Did you do preheat? Preheat is essential variable in all welding processes.

Some, but not all.

Then the only thing if not the rod would be that the joint cooled to quickly thus causing the flange to crack. Maybe some heat blankets could be used as soon as the welding is done?

a late addum, we use an acetyline-oxygen torch with a "rosebud" tip to pre-heat and annel the iron as the joint is welded.