Cast Iron and Stainless Steel

By TimGary (****)

Date 01-22-2004 17:05

A friend of mine asked me yesterday if he could weld a cast iron pipe flange to stainless steel pipe.
He didn't have all of the information required, except the following:

Size = 6" sch 40
Cast type = ?
SS type = ?
Service = Low pressure waste water
Rods available = Nickel SMAW x 1/8" (ENI-Ci) and ER309 SS GTAW rod x 1/8"

With that information, I suggested that he try a mock up piece first by welding a buttering layer of the nickel rod on the bevel of the cast flange, and then weld the SS pipe to the buttering layer using the 309 rod. Additionally, I said he should preheat the cast flange to a dull red in color, and wrap the assembly in K-wool after welding completion to aid in slow cooling.

If the cast turns out to be ordinary gray or ductile type, and the SS is 300 series, do you folks think there is a chance this procedure might work? Perhaps he should use the nickel rod for both welds?
I realize the procedure would have to be qualified prior to production welding. This is just research prior to qualification.

Thanks for your input,
Tim

By jfolk

Date 01-22-2004 22:02

Tim,

If welding a stainless flange to the stainless pipe is out of the question and then bolting the two together, then I would suggest the following.

1. For direction, you might consider AWS D11.2-89, "Guide for Welding Iron Castings".

2. Special Metals Welding Products (formally Inco Alloys) provides a wealth of technical assistance for this type of joint and others..

3. Consider Nirod 44 or Nirod 55 for the joining of cast irons to themselves and wrought carbon steels and austenitic stainless steel.

4. You might consider performing a spark test, (crude I know), to determine carbon content of casting, or scrapings for metallurgical analysis.

5. Pre- heat, anyone's guess to the time at temp, etc, etc.

John Folk