I have searched and I don't find what I'm looking for, so here goes. Would it be possible to sand bend stainless exhaust tube? I want to do some exhaust work, in stainless and I would rather not piece it together from mandrel bends (not that many pieces anyway). So I am wondering if the normal sand bending procedure (cap, pack with sand, screw / weld in adjustable end, leave "vent hole" and heat as required) would work on stainless. My major concern is the heat required, would this need to be so hot that the sand might embed into the stainless (due to the higher strength of stainless at elevated temperatures am I going to have to get it that much hotter)? I would expect that for 304 or 409 that I wouldn't get it hot enough to make glass (but maybe I'm wrong). Ideas? Oppinions? People that know better (I hope)?
IMHO - WELD IT!! Bending tubing - is a bit of an art to begin with - the "allowances" involved vary some based on the material. It seems to me unless you had a very experienced person to "hold your hand" you might start scrapping big pieces of stainless tube quick. TIG it! - nicely done it'll look totally sweet!!
using heat to affect the bending? every SS weld I've seen has chrome migration...meaning: the heat affected zone allows the alloying atoms to find new places to take up residence. the result is the area that loses the chrome or nickel atoms begins to corrode, as the scientists would call it, "Differential nobility" or corrosion potential, or? I was struck by the rust lines forming near a weld....on a SS pipe.
If you are a good tig welder I would recommend welding it also. Much more forgiving if you do need to adjust at all. As for the rust that Pitman mentioned, If you are working on any carbon steel in the same shop as the stainless you are going to get rust sooner or later unless you passivate the stainless after you are done.
I would atleast try it!!!!.........but Rambler is right, a good looking tig weld always looks good....Littleman
I wish to thank you all. All of your responses were in obvious good faith. I figured there was a reason I couldn't find a thread on it (I forgot all about the alloy migration, and the resultant Galvanic incompatibility, duh). I could mock up what I want in mild (or something flexible and fiberglass over it) and send it out, but it would likely cost more than the next project I have in the works (our '50 GMC). If I can't bend it hot, how can I bend it without crushing it?
Could you borrow one??? (A TIG that is) Well they bend stainless brake lines - If it were me, with what you said, I would go ahead and try it with a regular hossfeld type bender - experimentation may lead you to success. I dunno. I'm guessing it's gonna work harden fairly quick - might mean you have to bend - anneal - bend again. Them damn Hossfeld type benders have always amazed me. I've bent "unbendable" aluminum in mine on an occassion or two. Can't ever say I've tried stainless - but what the heck - no welder - you gotta try something. I wonder....can you gas weld stainless???? What about brazing it? You could get prebent sections - put the straight sections in the exhaust epander and slip fit them together. Who knows - it might actually look cool.
You can sand bend stainless, 304 is about the same strength as mild steel and little better at elevated temps but it can be done. If you don't have a TIG though how do you plan to weld it to the header flange and the collector. Don't say mig! You go to all of the effort, and it is a real effort, I helped Doane Spencer build some sand bend headers for a Lola T600 he was crew chief on and you really need to have a "feel" for it! Anyway you get the tubes bent and then weld them with a "MUD GUN"!!! Buy, steal, rent a TIG better yet find a friend that has one and have him do it. When you weld the stainless to the header flanges and also to the collector there is a special flux that you can use, can't remember the name starts with "sun something"! that will prevent the weld from being really ugly on the inside and also makes it stronger. Other way is to purge in argon. Most race headers that are made from stainless are made from 321 as it has a higher strength at temperature. F-1 headers are from 625 inconel which is ver strong, very expensive and a real bitch to work with. Rex
Too bad your not closer to me, you could bring it over and we would bend it right up!!! I have a hosfeld bender that i have bent alot of stainless pipe with and it does a great job. I also think if you use the right wire and prep your pipes properly a stainless mig weld looks fine. I weld alot of stainless pipes every day at work and the only thing i use the tig for is small high preasure lines and fittings (2"and under) so in my opinion the mig will be just fine if thats all you have. As for putting heat to the pipe to bend it even 304 is going to be hard to get enough heat in evenly to let the pipe relax. I would try a peice and just see what happens if that doesnt work go back to the drawing board, good luck!!!!
Do you have drawings or sketches of the bends you need? I might be able to help. Custom mandrel bending can get time-consuming and pricey but if you can send drawings we can at least see what I can do for you. Hank
Thank you to all that have posted. I was planning to tack it together, and if I can't beg or borrow a tig, I was going to try gas welding (on some scrap first). If I can't get it to look right, I would have one of the local welding shops weld it for me (there are a couple here that I know weld stainless on a semi regular bassis) but the hourly rates are pretty steep, and they haven't been interested in a 'side job' of this type in the past (with stainless, I expect them to be even less enthusiastic). I have considered using braze, it could look cool if done right. I hadn't thought of MIG welding it, I expect that would be REAL ugly (even with a back purge). At least in my hands. Would a greenlee bender work? The kind that hooks to a port a power, or has a jack in the middle. Yes Inconel in any of it's various specie would be the ultimate, but I can't afford the shipping crate for it, let alone the metal, pure unatanium for me.
REX, do you have any pearls of wisdom on sand bending it, I would be willing to scrap a piece to learn (likely the only way I could) but I'd rather start off with a better idea than I have currently. I would also prefer to use 409, I know it doesn't polish up worth a damn, but I only want to build this once.
Would a greenlee bender work? The kind that hooks to a port a power, or has a jack in the middle. that type of bender is for pipe, pipe is measured on the inside, tube is measured on the outside so the dies will not fit your tube correctly, you could go to an exhaust shop and have your tube bent, it dosent look as nice as a mandrel bender, as for welding it with a mig of course it can be done to look nice, you just have to take your time and maybe touch up your welds with a grinder a little, not grind them off just make them look neat. i built myself a hydraulic mandrel bender but you live to far away and so far i only have 1-1/2" dies for it.
If you are concerned with "heat affected area";why not use a muffler shop type bender and sand pack the tube as if you were to use the flame.This would probably make the tube behave a lot more like round bar giving you better,smoother bends.Good compromise no?
Did the same thing for a homebuilt airplane. Bought the s/s tubing from the dairy supply people, (Surge, was the business name at that time.) and took it to the local muffler shop. I bent a coat hanger wire to the shape of each pipe, and the guys used them as the pattern. Turned out great.
The flux that was mentioned for stainless steel welding is called Solar Flux Type B Golden Empire corp. Morehead city N.C. distr. by Harris. prevents oxide inclusions protects the backside from oxidation prevents burn thru eliminates porosity Ago
Wow, thanks guys. I want to use 409 because (acording to the literature) it's 'titenated' (sp?, I don't have said literature handy) that means it has a small amount of titanium and that supposedly eliminates the carbide precipitation problem. I hadn't thought of using sand as a mandrel (in a crimp bender), it should work (or at least help). So far I am having dificulty locating the sizes and thickness I wanted to build this out of. I have been behind the curve on the car so the thrash currently is to get the car back on the road (had a guy promise to do some work in exchange for some stuff, didn't happen, so pops and I are behind the curve, again). I saw a thread that mentioned Imco as a source for stainless exhaust tube, I have yet to check into that (I'll have to). I'll check into the dairy suply thing, we just had a cremery open (well, one closed the new one opened up in the same place, I think, so???) so I'll have to check. Thanks for the tip on the flux.
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