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Hi al, You have way to much root opening in any case. You didn't say sch40 pipe or? Your probably in too much of hurry and too many amps. Try .045 filler rod for the root pass and use .045 filler rod as the gap and land measurement measurement. Yes you will have suckback but slow down and add filler rod to fill the outside and the undercut will go away. Once the root pass is in, then crank up some amps and haul butt with 1/16 or 3/32" filler rod. When you start your root pass, hold the arc in one spot until you see the weld puddle swrilling, this should take about 2 minutes at proper amps for a given land thickness and given joint gap, at that point you starting to penetrate the land, then all of a sudden the weld puddle will sink to the inside, thats when 100% weld penetration occurs to the inside, add filler rod and move the torch at the same time. Your base metal fills the inside and the filler rod fills the joint. I rock the root pass if the test pipe is sch40 or more, if not then I drag the torch ligthy on the base metal using a ceramic cup. Do not use a lava cup without rocking or not touching the base metal as the lava cups stick to the base metal amd makes the weld puddle to hard to control. Use a clear welding lenns on the end of the pipe so you can see your root pass on the inside. Masking tape works great for holding the lens and for making a end plate cover. Use a 1/16" diamter bleed hole at the "top" of the endcap as argon is heavier than air with 5cft/hr purge flow. Clean 1" on either side of the weld joint. Clean until white metal is seen. That is the oxidation. Yes all metals will oxidize including SS. When the SS wire brush starts grabbing the base metal is when the white metal should show up. Let me know if I can help. T_Bone
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