I do not have my books at hand to see what grade of Duplex you particular material is, but generally duplexes are relatively weldable. I will therefore give you "general" pointers.

The fillers used are usually of a semi-matching composition. They are usually not exactly the same, because most duplex steels have quite a high Nitrogen content. This is not practical to place in a consumable, so they generally have a higher Nickel content to make up for this.

The major issue with welding duplex S/Steels, is to balance your heat input. This ensures that you end up with the required ferrite content. Usually pre-heats are not required, although on massive sections such as castings, a 50°C pre-heat may be usefull when using a process such as SMAW. Also keep the maximum interpass temperature to below 200°C or so. Do not weld on the low heat input end of your process's range. Also do not overdo the heat input, especially with FCAW.

Generally, PWHT is not required.

Hope this is of help.

Niekie Jooste

Glenn,
In my literature, the J93380 seems to correspond with ASTM A351 CD3MWCuN (your's didn't have the M in the middle). I believe that this corresponds with the trade name "Zeron 100" and is also found in ASTM A890 as grade 6. We are preparing to qualify a weld procedure in the near future, and the filler metal that we found was "Zeron 100 XKS" which is imported from Metrode (England) by Euroweld. As far as PWHT, for duplex sst we ususally do one of two things. Either we solution heat treat it, or we do no PWHT at all. The advice by Nieke is true for welds with no PWHT, you need to achieve the correct cooling rate to obtain the right proportion of austenite and ferrite. I think that no PWHT would be the way to go as far as you are concerned since you are welding on a machined part because solution heat treating ruins you tolerences and finish on machined parts. However, some customers have a hard time approving a WPS without PWHT. Your best resource on this problem though, should be the foundry the part came from. Any decent foundry will usually have several tried and true welding procedures for each material they pour, and could reccomend filler metals, heat inputs, PWHT time and temps, etc. They also should have qualified WPSes already, and might be able to make the repair for you so that you don't have to go to the time and expense of qualifying a weld procedure you may never use again. Hope this helps you.

Greg
Atlas Foundry