Chasing down an inclusion.

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I failed a welding test on monday. 3G 3/8" groove with backing. Dual shield with my millermatic250x and hobart excelarc 71 .045 wire, 75/25 gas.Should have been a piece of cake.Inclusions in the root.I've been chasing it down every evening this week. I tried more heat. Less heat. Pre-heat. Pushing. Pulling. Angle flat. Angle up. Angle down. More gas. Less gas.I finally found it. Prep. I thought I was doing a fine job, but I was wrong. I ground the mill scale, and wire wheeled it on all the others. No good. This time I used a brand new sanding disc. Et viola. No inclusions. Attached ImagesIan TannerKawasaki KX450 and many other fine tools
Reply:Nice job!  Great prep on your coupon as well.  Based on your photo, your first coupon passes, per D1.1.  But I too insist my students keep going until they can consistently produce a near discontinuity free set bends.Sent from my Nexus 7 using Tapatalk 2Jay DavisAWS-CWIC-60 Specialty Welding ContractorLoving husband, and father of two boys (
Reply:Oh and, that's a good lesson to learn in regards to mill scale, a wire wheel just shines it up, does not remove it.Sent from my Nexus 7 using Tapatalk 2Jay DavisAWS-CWIC-60 Specialty Welding ContractorLoving husband, and father of two boys (
Reply:Yup, the cleaner the metal the better the weld ALL THE TIME.
Reply:Glad you found the solution. I like flap discs best for removing mill scale. Regular sanding discs get dull fast, mill scale is some nasty s#!t!JohnA few weldersA lot of hammersA whole lot of C-clamps
Reply:For all those that poo poo'ed the Plasma welder I use, mill scale does not cause a problem with plasma welding and you also don't get inclusions.Ian.