Dissimilar metal welding...

[11echo]

I have a client that wants to weld 316SS to A234 WPB cast steel pipe fitting(adding S.S. bar to a tee for pigging). I know this is possible, but is there any procures that needs to applied to the weld after assembly? ...like post heat treatment? What are the characteristics of this weld (brittle, prone to cracking?) THANKS! ...Mark

 

[Rich2001]

Here is some information to help you develop a WPS for P1-P8 GTAW Weld.

Base Metal "Austentic Stainless Steel to Carbon Steel P1-P8"
Weld Joint (mm) Thickness 6.4 12.7
Weld Position Flat

Filler Wire Specification AWS A5.9 Filler Wire Class ER 309

Single Vee Butt 4 6

Electrode Type Tungsten (EWTh-1/-2)
Cup Diameter (mm) 2.4 to 3.2 3.2 3.2 or 4.0
Number of Passes 1 to 2 2 to 3
Gas Nozzle Cup Type Water-cooled
Current (amps) - - - - - -
Current Type DC neg

Single Vee Butt 275-350 350-450

Welding Speed (mm/sec) 2.1 hard to predict


Gas Argon
Gas Flowrate (L/min) 6 7
Gas Pressure (kPa) 140
Gas Nozzle Limits (water-cooled) > 250 Amps

Out of Position Welding
Vertical and Overhead Current reduce by 10-20% reduce by 10-20%

Austentic Stainless to Carbon Steel welding is fairly common. A few words of caution -

1.Watch for hot cracking, I have had clients that have required a Liquid Pentetrant test be performed after every pass.

2. Corrosion may be an issue. The SS and CS make a fairly strong Galvanic cell.

I have also had to butter the Carbon Steel with 310 stainless before welding with 309 at another client's facility.

Check with AWS

http://www.aws.org

that may have a Quailified WPS/PQR that you may license (pay for) and use for your application.

 

[Rich2001]

Here is an article on the Nickel institute website that you might find helpful.

http://www.nidi.org/multimedia/tech...iterature_pdfs/14000_reprint_series/14018.pdf