I've been reading and watching videos most all day but it'd sure be nice to just ask an experienced welder some basic questions.
Ask away. When I actually worked for a living I did some welding so I understand the basics. I have several certified welders on my crew that can probably answer your questions.
I'm getting ready to fabricate a custom exhaust for a turbocharged engine with an external waste gate, at the moment I plan on using Inconel 625 inside the engine compartment and 321 SS for everything else. I had hoped to find a reasonably priced fabricator but then started thinking I'll need some 4130 steel welding and probably some thick gauge 6061 aluminum as well later on. So maybe I should consider learning to weld and purchasing some low end basic equipment. I believe TIG is the preferred method for Inconel and aluminum but I'm told it's also more difficult to master. Based on my limited research I came under the impression that I might be able to weld Inconel 625, 4130 and 6061 with an Oxy Fuel torch. And it would be a relatively quick method to master given I have no experience. In short I'm trying to decide on stick, MIG, TIG or GAS welding in hopes I could get all my needs covered with a single method, even if it's not optimum for all the metals, and hopefully a method not to time consuming to learn. Comments and suggestions?
I don't know what engine you are talking about, assuming it is an US made 8 cyl, small or a big block. Do not complicate thinghs with supercustom exhaust as cost of such fabrication will cost you about $1,800 plus headers. Buy pair of suitable headers from any catalog online shop then have a local mufler shop do the rest with basic steel exhaust and superflow muflers. same performance, less than half of the cost .
MIG is absolutely the easier of the 3 to learn, but TIG is the application you're looking for. Yes you can use a Oxy tourch, but your puddle will run like hell until you master the technique. TIG is not something you'll master over a weekend, where as MIG you could probably get somewhat proficient in a few hours. Bottom line with welding, it's all about burning rod over and over again ubtil you get a feel for it. Here's a link that you may find helpful, but there is no substitute for time under the hood. If you're going to buy a MIG don't cheap it out. You'll have constant wire feed problems. http://www.metalworking.com/tutorials/ARMY-TC-9-237/chap11.pdf
An even more important consideration: Do you really want to be at 5000 ft when one of your noob welding jobs goes south and the engine dies? Leave the home welding shit to projects that your life doesn't depend on. Get your stuff fabbed by a pro...
It's a Mazda 20B three rotor rotary engine, which were never sold here in the states. And it's going in an aircraft so weight is an issue. So far as I know I can either use the very heavy cast iron stock manifold or fabricate. If you know of someone who sells an off the shelf exhaust that fits I'd be all too happy to hear about it.
That was my original plan. Do you know of someone here in Atlanta? Someone who does more than simply weld off the self pipes and mufflers together? Not that I totally disagree with you but I wouldn't be the first guy to learn welding solely for the purpose of fabricating an exhaust/aircraft.
A great PDF, thanks. So an appropriate MIG unit will satisfactorily handle Inconel 625, 321 SS, 4130 and 6061 Aluminum? Even though it's not optimum for all. (I understand ally is tougher regardless of the method) If so I'm leaning toward a decent MIG unit then.
A MIG will handle it, but as a rookie it'll be a bitch. Inconel is considered a "dirty" type of weld and it's tough to manuever the puddle and get a clean weld. I suggest to visit your local Airgas dealer and tell them what you're trying to do. They can make suggestions and can probably steer you towards a weld shop that can do the job if that's what you decide to do. Here's a link for Atlanta Airgas dealers. Ask them about used or rebuilt welders. A new rig won't be cheap. http://www.millerwelds.com/wheretobuy/?search