Re: [MW:11137] Re : Gas use for Backing and Purging

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-------   From: mustaffi Date: 05/24/11 08:47:12 To: materials-welding@googlegroups.com Subject: [MW:11130] Re : Gas use for Backing and Purging   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