Mig welding square tubing and distortion

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I am welding together square tubing for a handrail and need advice. 1.5-inch square tubing. Hot rolled mild steel. 14 gauge. Mill scale removed. Lincoln 140 with 0.030 wire and 75/25 gas. I need to angle the tubing at 30 degrees. I want to cut a notch out of the bottom and two side and leave the top intact. This will mean no weld seam on the top and less welding means less distortion to ruin my angle. That distortion is what i want to ask questions about. I have two side welds and a bottom weld to make. These will be done before installation so I can make them all flat welds by flipping it around. The notch I cut will give me a chance to place a backing strip on the inside. Will this help prevent burn through and reduce contraction and distortion?  Does anybody else do this?I would appreciate advice on things such as the best weld sequence, directions of the welds and if they should be interrupted or continuous and if I need to make compensations for the expected contraction, especially on the bottom weld. Sent from my iPhone using Tapatalk
Reply:By I need to angle the tubing at 30 degrees.
Reply:Backing strap? I think you are over thinking this. I suspect (no evidence) that you will have more luck if you cut the pieces all the way through rather than trying to notch the tubing, just because notching is more difficult. I would clamp and tack everything first to make sure you have the angle you and to make sure the hand rail is flat (planar) from left to right. Weld sequence would be outside corner, then the sides inside to out and finally the inside joint. Last edited by Louie1961; 3 Weeks Ago at 03:37 PM.Miller Multimatic 255
Reply:I took it you are cutting 30* angle out of both sides and removing bottom in order to close up and have 30* angle down. I use prepunched channel on my handrails and do exactly that for where rise meets top of porch then goes horizontal. Make sure you bend straight so pieces meet, tack bottom side corners, weld bottom seam lightly, then solid weld sides. Doesn’t take a heavy weld but enough to seal. You will grind weld flat anyway. No backing plate needed. Minimize the heat input and you should be fine.Burt _____________________Miller Syncrowave 250Millermatic 211Miller 375 Plasma Cutter Hobart Handler 120www.10FtDrillBit.comwww.MyWelds.com - pictures of my work
Reply:You can get a tighter fit up by just accurately cutting the miters rather than notching out and bending. The outside corner would cause the least amount of distortion when welding anyways. A good accurate fit up from mitering will be a lot less dorking around and no backer will be needed
Reply:Thanks for the replies. It looks like a backing strip is not needed. But i have recs for cutting and mitering as well as a notch cut. Because i need practice, I will practice on both and let you know what happens.  Sent from my iPhone using Tapatalk
Reply:Sounds like you are creating a 30 degree angle by notching 15 degrees off each part?  Make sure you weld it well. Pin holes and weld lap will allow water infiltration.  Water is patient. You may notice it if you get freezing weather. Most folk never notice it.  Good luck,
Reply:My advice is to tack everything square, and then do the inside/outside welds first. Then while its still hot, do the flat faces.Murphy's Golden Rule: Whoever has the gold, makes the rules.