| Dear mustaffi, Mostly Duplex and super duplex are TIG welded using pure argon, (Some recommend adding of 10% nitrogen to the shielding gas and backing gas for the balance between ferrite and austenite phases and the material superior corrosion resistance, however this make welding difficult as it can cause porosity and contamination of the tungsten electrode unless the correct welding technique is used,to much nitrogen will form a layer of Austenite on the weld surface). Backing / Purging gas should contain less than 25ppm oxygen recommended for optimum corrosion resistance. With regards. P.B.R -------Original Message------- Hi All Can anybody can tell me, what it's the best gases to proceed welds for TIG process on Duplex Steel Material Regards Mus |
Hi, You are correct, Minimum refers to the one cycle for which this part will expose until final work shop PWHT. hence mill test certificate shall include this. Max. SPWHT, refers to additional cycles of heat treatment that are reserved for future repairs during equipment lifetime. Again, these simulated no. Of cycles shall be specified in MTC. The idea is we need to make sure that steel mechanical properties are not compromised upon exposure to multiple repairs (i e 4 cycles in your case). One could say, if steel is subjected to 4 cycles and is ok, then it should by defacto be good for one cycle, yet, this is wrong assumption cause mechanical problems and microstructure of materials varies accordingly based on no. Of cycles for which material will expose. This is apparent in alloy steel and especially for impact test values as an example. In your case, this forged CS with properties before PWHT can be understood to be " as forged" condition (i.e. Wit...
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