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For some time I have been asking myself the question about the limits of welding thick to thin. At what point does the difference in thickness start to cause problems? I assume that 2 to 1 is no problem, but what about 4 to 1? What about welding 14 ga (0.075") tubing to 1/4 inch plate, roughly 4 to 1? What about welding 20 ga to 1/4 inch plate, roughly 8 to 1? What about welding a razor blade to 1/4 inch plate? What about 20 ga to 1 inch plate? Presumably an expert could deal with a larger difference than the average Joe working in his garage. I think in a few cases in the past I have added an intermediate piece with an intermediate thickness, to prevent problems. Certainly I would do some test welds and hit them with a hammer before I start, to verify the machine settings and technique etc.For purposes of this discussion, assume that I do quite a bit of welding, but I am not a pro. I have access to stick, MIG, and TIG, all at about 200 amps, all Miller gear. I do more TIG welding than anything else, but I don't have the power to TIG weld 1/4 inch plate. I would rather MIG it, just for speed, and because I have a new MIG welder. ;-) I would probably keep flipping it to avoid out of position welding, which I rarely need to do, and am definitely not good at. If I had to do out of position I would TIG it.My practical application is building a ladder rack for a friend of mine. I built him a ladder rack to fit his old topper, somebody wrecked his truck, so now he needs a new rack for his new truck, with a new topper. I believe that I built the old rack from 1.25 sq tubing with 1/8 inch wall, 1/4 inch plate feet, so pretty stout. He liked it, I called it a brick s...house design. In hindsight I am thinking that I built it heavier than needed, but that was years ago. I am smarter now, and a better welder. The new rack has to work with a new topper that extends several inches wider than the truck bed, so the plate that slips between the two has to be fairly sturdy. I am thinking 1/4 inch thick feet, but I have not pulled out my calculator and handbook to verify what makes sense. (I am a mechanical engineer). I would design the rack for a 200 pound load, but a large safety factor, because of the dynamic loads. The new topper is a flip pac, or something similar, so the front cross bar of the ladder rack has to be removable, to allow it to flip. Like the previous design, I plan to tie the front and rear bars together with tubing. The rear rail will need to be further back than usual, so that it can stay in place when the topper flips to make a tent. It is a little more complex design than the usual, due to these factors. As you might expect, the ladder rack will only see occasional use, but could see rough roads. The topper is very heavy, so it will effectively be permanently mounted to the truck, as will the ladder rack. Unlike a commercial rack, I don't need to make it adjustable for different vehicles.I tried to address any questions that you might have, but I am sure that I left out something. ;-)Thanks in advance for your thoughts and experience.Sculptures in copper and other metalshttp://www.fergusonsculpture.comSyncrowave 200 Millermatic 211Readywelder spoolgunHypertherm 600 plasma cutterThermal Arc GMS300 Victor OA torchHomemade Blacksmith propane forge
Reply:Welding thin to thick is really about application.Simple one- you can certainly weld 20g to 1/4" i.e. Floor pan to a custom rail or similar. same for 14g to 1/4"- gonna depend on the application.Ed Conleyhttp://www.screamingbroccoli.com/MM252MM211 (Sold)Passport Plus & Spool gunLincoln SP135 Plus- (Gone to a good home)Klutch 120v Plasma cutterSO 2020 benderBeer in the fridge
Reply:14ga to 1/4 is doable, and no big deal. 20ga to 1/4 might take a bit more finesse, but still very doable.Set the heat for the thicker material, and let the puddle wash into the lighter material without focusing the heat directly into the lighter material. Keep the gun/rod/etc. focused on the heavy stuff except for a quick tie in to wet the puddle toes if necessary"Any day above ground is a good day"http://www.farmersamm.com/
Reply:Remember the welds will be no stronger than the weakest material. So welding 20 ga to 1" plate isn't going to hold any more than 20 ga to 20 ga will as far as the weld joint is concerned. In your case, the added stiffness of the base plate will resist bending of the plate itself, but would really have no real bearing on the weld itself. All this assumes a good weld to begin with. Now when we start talking about extremes, we would also have to talk about the heavy material acting as a heat sink, and ending up with poor fusion where the to meet. This would assume the settings were set for material of similar thickness or you were already maxing out the machine to begin with. The solution for this is to simply increase the power above what would be needed for the smaller piece and concentrate the heat in the larger one, washing the puddle onto the lighter material. The extra power would help deal with issues from the heavy piece soaking up too much heat and ending up with shallow fusion at the joint..No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan
Reply:tIn my experience, welding thick to thin all about the wash. Tig aluminum has no wash, and its nearly impossible, but with a spool gun and an extra long stick out, I have welded some ~.035(mesh)" to 1/4" frame. It is common to weld very thin sheet metal decking to heavy I-beams using 5/32 rods at near 200 amps, by avoiding direct arc, and just letting the puddle wash in. In my experience dual shield washes in better than solid wire. TIG is bear, you have to run enough amps to get the thick melted, then flick over to the thin just long enough to melt it, then back. Its hard, you have to be quick, and move fast or your puddle will look goofy and asymmetrical. Easiest on SS, carbon not so much.Constant Current Weldor. |
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发表于 2021-8-31 22:57:16