Only things we’ve preheated has been hydraulic cylinders (uncles did the work) and 1” + thick material.
What kind of prep? I'm getting the "heat the metal" comment from a few guys, so there's that. What else?
Make sure you have oil and contamination free joints. Grind or flap sand the metal. Don’t use dirty rods/wire. In some instances, you actually want to start with a gap between pieces.
Clean from rust , oil , paint ,maybe some old weld if it is a repair , grind off any mill scale with a flap wheel. Make it "clean " bare metal.
Some more mastery at work… https://youtube.com/shorts/jgbdhwcOCd4?si=31GraeD3X2c4rGww all joking aside, there’s some pretty cool tricks to be learned watching these Pakistani videos.
Ok, I'll throw some scenarios out there. First, you need a machine that is/has the amperage you need to weld a specific thickness. Meaning, if your trying to weld 1/2" mild steel with a welder that only generates 100amps, well you MUST pre heat to get any type of penetration and it's gonna need to be hot! Machines have a rating up to a certain gauge or thickness. I've welded 3/4" HY80 high yield steels up around 250 amps. You are not going to do that with the garage buzz box no matter how much you pre heat. I own a Hobart Champion that will get me to about 150 amps. Your standard schedule 40 black or Galvanized pipe can be welded all day with 100 amps. When you get up in size you need to go up in power. Certain welding rods can burn right through, rust, paint, hell I've even welded through barnacles on buoy's before. There is no "One source" rod or wire for things. There are as I remember 132 welding processes and every one is a bit different. Your basics are your MIG, (metal and Inert gas, (TIG) Tungsten and Inert gas and your (SMAW) or shielded metal arc welding or better known as stick. We could get REALLY in depth but I'm no longer teaching. Know your machine and know your ranges, if you don't, look it up. You shouldn't have to "Fight" a weld for it to penetrate or stick together!!! If you are, you DON'T have enough power!
YES< YES< AND YES!!! Then post cool slow!!!!!!!!!!!!! NICI rod or 10842... slow bake at 10º back draw per hour....
At work we build various weldments out of 4140 steel fairly regularly, and after they're pinned together and prepped they go in the oven before ever seeing the welding table. Sometimes if it's a small job we can get away with not pre-heating, but if it's a complicated assembly with a lot of beads, or if it has to get annealed, then heat treated, then stress relieved afterwards, we pre-heat first. Rapid temperature changes in either direction can ruin what could've been a straight-forward job.
I can see how that would be helpful (needed) in some cases...certainly overkill (IMO/IME) for most people burning rod/wire in their garage welding up grills/mower decks, little projects, stuffs like that...
No doubt, especially if you're working out of your garage on a hot summer day. Backyard welding and industrial jobs are two different animals, as is some guy repairing the bucket of a backhoe using a stick welder compared to a guy in a lab doing a small TIG micro-weld job.
Looks like he is using 7024 rod. We used to call it drag rod. You could just stick the flux right to the metal. If you were welding flat (not a horizontal fillet) and your rod angle was correct, the arc length would remain fairly constant as the flux would melt away leaving a picture perfect weld!
So I might end up taking a class…there’s a community college nearby and I think it would be a handy skill to know how to do it well.
I've used a lot of 7028 (jet weld) over the years! doing long stretches of 1/4 and 3/8 plates. Fun rod to use and watch the slag peel off behind you! Pretty colors of the rainbow also if your heat is right!
