A contractor is going to make a repair, in a hydro power plant, on the weld between a 15 feet diameter runner outer cover made of stainless steel to a carbon steel draft tube, because there are cracks and corrosion at the joint.
-The contractor proposes to do the welding with E309L-16 with a 200 deg F preheat, because there are indications that that's probably what was done 20 years ago
- An expert we've consulted believes welding with ENiCrFe3 with a 500 deg F preheat would be better. This expert says that this material and level of preheat temperature is needed to avoid future cracking, which may happen with the E309 because we are not sure of what kind the stainless steel is, so he's proposing a 'silver bullet". In this case there is concern about distortion with such a large diameter piece.
I'd appreciate your comments and advise on kind of electrode to use and level of preheat.
Thanks
jemayen
You would be well advised to do a chemical analysis on both the carbon steel and the stainless steel. It is relatively easy to establish the chemistry and, if possible, the material specification they meet before making the repair on "unknown" base metals. The cost of the tests are insignificant compared to the cost of the repair you are making.
Good luck - Al
I 100% agree with the reccomendation of Al. Call a local company that has portable PMI equipment, and that will let you know what the material is (with the exception of lighter elements such as carbon). Another way to get a chemistry is to get some drilling chips and send them off to a reputable lab. Either way you will be able to tell whether the preheat is needed, or detremental. If the stainless is austenitic, but not low carbon, the 500f preheat could cause severe senstitization, but if it is martensitic stainless, 500F could be needed.
Thanks 803056 and GRoberts for your advises. We'll do that
Forum
