Multipass Tutorial

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I've taken the step of making a step by step photo tutorial of some welding processes. This is a 1/4" thick mild steel sample Attached ImagesStangnetShop Full Of Stuff. Joey
Reply:For 1/4" material being welded with a 125volt mig machine, More than one pass is required to fuse the metal correctly, This is called "Multipass" In this step we need to bevel our metal's edge to be welded. Attached ImagesStangnetShop Full Of Stuff. Joey
Reply:Further photo example and position of weldment (piece to be welded)Note: Shop towel used as visual aid in photo to show position, Do not weld near these towels!! Attached ImagesStangnetShop Full Of Stuff. Joey
Reply:In this step we apply the "Root Pass", This is the first of three welds we are using to get the penetration we need on this material thickness. The Root pass needs to go directly down the middle of the joint. Attached ImagesStangnetShop Full Of Stuff. Joey
Reply:The root pass has been completed, i recommend you clean the weld area with a wire wheel or wire brush, This is Pass #2, It is positioned to the left or right of the root pass, In this scenario, I used the left side, When welding this pass, Overlap your bead into the Root Pass. Attached ImagesStangnetShop Full Of Stuff. Joey
Reply:Pass #3, Overlap this bead into the root pass as well. Attached ImagesStangnetShop Full Of Stuff. Joey
Reply:While it it not necessary, I went ahead and made a 4th pass on this piece, If you choose this as i did, Make your pass over the root pass, Overlapping your bead into the 2nd and 3rd pass. Attached ImagesStangnetShop Full Of Stuff. Joey
Reply:This is our last step, merely for appearences only, I used an angle grinder to make our surfaces flush. I hope this helps out anybody who is just starting out!! Attached ImagesStangnetShop Full Of Stuff. Joey
Reply:Not a bad sequence, but a few comments:I would use a narrower included angle for the bevel. You are at about 120 degrees, and you really want to be less than 90, preferably 60 or so. The smaller the angle, the less weld metal needed and the less distortion.You also want a slight gap at the root on the fitup, about the same gap as the size of the land (unbeveled portion at the bottom of the groove). You have about a 1/16" flat, so a gap of around 1/16" will help insure full penetration. The gap can be narrower if you can insure that you have burn in to the full depth of the root face, but if you have spots where you don't fuse the full depth, you have a built in crack to run under stress. When needed, try to set up so that the weld shrinkage, which tends to pull the groove closed (causing the finished piece to be slightly vee shaped) is compensated for prior to welding. One way to do this (on the bench) is to lay a piece of wire under each piece near the weld line prior to rooting. This lifts the seam off the bench, and the root goes in with a slight vee opposite the shrinkage tendancy. The second, third, etc passes pull the piece to flat. How much is an experience thing.
Reply:Just A quiky,for apperence sake, cold yo add more weld, to help fill in the beveled are, so when you grind it, it appears to be one piece. or will this weaken the weld.  as ive herd multiple welds do.thanks Viper, i like seeing examples and tutorials laid out like that, since i am new to welding. its very helpfull.Matt
Reply:I don't know who told you that multipass welds are weaker. My experience says that properly performed multipass welds are far superior to one big high heat pass and it has to do with the heat effected zone. The more amps your pushing the larger the heat effected zone. All the nuclear pipe welds we did in the Navy were multipass welds with 60 amps. These welds were RT on the root  and final pass with PT on the rest of the passes.
Reply:I agree w/ddsmith
Reply:The pictures are too blurry, does your camera have a macro setting? You may want to take a look and see so everyone can make out the details in the pictures,
Reply:yes it has a macro setting. It's just something done to help beginners out.StangnetShop Full Of Stuff. Joey
Reply:Thanks for the tutorial Vipermanz. You used a 125volt machine,what about the wire diameter? Cored wire? Shielding gas mix?You mentioned using a wire wheel or wire brush between runs.Is that to chip out the flux?Thanks,Don
Reply:a hobart 125v machine, .030 weld-it brand flux core wire, i used a wirewheel to clean the flux off before the next passStangnetShop Full Of Stuff. Joey