sch-10 304 turbo manifolds keep cracking.

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I've been building turbo manifolds for a few years. They seem to keep coming back. I've tried a few things without much success. Normally the ones heated/stressed more are the ones to fail. The 4cyl's producing 400-600hp are usually a given... Just a matter of time.Currently I've been using sched-10 SS pipe. It's backpurged. I use a 3/32 tungsten (red). Normally I TIG it at about 80-100a. I have tried 1 pass and 2 passes. The joints are tightly fit with bevels - that's how the weld ells usually come. The filler rods are 308L and I've tried 1/16 as well as 3/32 - virtually no difference. I've cut apart a few test welds and the pen is usually very close to 100% with no sugar on the back.The welds usually come out a little oxydized for my taste - I'll try to get pics. I spent some time searching and my welds do look better than some posted by others. Just curious to know what I might be missing.-Michael
Reply:Michael,I think the "close to 100% is the clue, here.  When you're making a weld that is stressed, the stress tend to propogate from any discontinuity in the metal.  A less than 100% weld in a stressed tube basically is a built in notch defect, and will concentrate the stress and apply it through the weld.  Consider:  take a piece of paper, hold it with your thumb and forefinger in two corners, and tug gently.  Then put a very small tear in the paper, and tug again.  Paper rips quite easily from the existing tear.Make sure you gap the tubes when you start to weld, to ensure you completely fuse in the root.  A tight fit keeps you from getting a good burn on the root pass.  Since you've got no sugar on the inside, sounds like your purge is good.  100% penetration will help, especially with the high HP stuff.I r 2 a perfessional
Reply:80 to 100 amps is on the high side for .109 wall stainless IMO.  Remember, you should be using less heat than you would for mild steel.  If the welds are getting that greyish, oxidized appearance instead of the normal coloration, that's likely the problem.  What grade stainless are you using?Also, where are they failing?  I'm betting the crack is usually just outside the HAZ near the flanges.  If so, you may want to look into small gusset plates from the flange to the tubing.
Reply:Capnbondo shared this information:http://weldingweb.com/vbb/showthread.php?t=222709-11-2001......We Will Never ForgetRetired desk jockey. Hobby weldor with a little training. Craftsman O/A---Flat, Vert, Ovhd, Horz. Miller Syncrowave 250
Reply:As Supe said, more info (and ideally pics) on the mode of failure is needed to provide an autopsy. I'm guessing 304/304L but it'd be nice to knowOf the cracked manifolds i see/get to fix, failure typically comprises either of the modes described by KBnit and Supe- sometimes both on the same manifold!Another thread where this subject is discussed...   http://weldingweb.com/vbb/showthread.php?t=21809Personally i would steer well clear of gussetting something like this, allways seems to cause more problems than it fixs IMO, unless it's a support along the lines of the F1 example in the above link- known as 'turbo dampers' in Cosworth circlesI did dig out the manifold i referred to in that thread, a (badly) gussetted example and will DPI it and post pics tomorrow as i've got a fairly quiet day lined up - well so far at least
Reply:Hotrodder: I'm not big on manifold restraint myself.  A recurring problem I did see was oversized turbos hanging at an angle, putting a great deal of stress right at the flange.  A small, fairly non-restrictive gusset would alleviate a great deal of that stress.  Yes, it is a bit of a tradeoff, but I've seen in DRASTICALLY reduce the number of cracked manifolds by using one.  Then again, I did talk one customer into a set of inconel headers some time ago.  One of my favorite jobs, loved it when they had deep pockets
Reply:Supe, no, they've never cracked at the flanges and those are usually the best "looking" welds. I've ordered a gas lens because I suspect it wasn't getting proper coverage. I read a few complete threads on the subject before posting. Some people in Capnbondo's thread suggested butting them, others like here have suggested leaving a gap. As per the title it's 304 welded with 308L rod. The cracks are usually on the border of the weld bead, not really on the edge of the HAZ. I've got a manifold coming back that has been re-welded 5-6 times so far and it just keeps cracking in different places. I'll try to snap some photos before I excavate the cracks and reweld again.-Michael
Reply:the reason why the ones that were heated more fail on you is because 300 series stainless does not like too much heat or they will get heat embrittlement or carbide precipitation and will crack. Your amperage is way way too hot, 3/32 tungsten with 1/16 filler try from 40-70 amps.. 304 -> 308 /316 filler or  304L -> 308L / 316L filler
Reply:Some guys at a speed shop in my area run alot of 4 cyl turbos pushing over 400hp to the wheels. They use Sch 40 mild steel weld els for thier custom manifolds. He mentioned he had a similar problem to yours when he was using the Sch 10 stainless. He said the quality of  the stainless steel in those chinese elbows is sub par, and they come apart too easy, and thats why he switched to the Sch 40 mild. Is it true, who knows?Now as far as the gusset is concerned, I do know that a buddy of mine ran a modified mild steel manifold on his 4 cyl turbo. It was originally set up for a right hand drive car in japan, but here in the states the steering components get in the way. He had the wastegate moved to clear the linkages, and a gusset was added for strentgh. After one day the tube had cracked at the weld along the exhaust manifold. After that he brougnt it to me and I rewelded the tube. The next day he was back, it had done the same thing. After some hard thinking, we surmized that the extreme heat on the tube required some room for expansion and movement of the tube. I cut out the old tube that held the wastegate as well as the gusset, and fabbed a new wastegate down tube out of thicker tubing. I left the gusset out of this design, and thankfully the thing didnt fail again. It took a major beating at the track, every other weekend for about a year, and was still solid when he sold the car. Who knows if its still going today.Miller Syncrowave 200Hobart Handler 140Thermal Dynamics Cutmaster 38E-Z Tube BenderPlasma Cam DHC2
Reply:I don't know if this pic will post but here is a case of one needing to be supported if there ever was one. This happened after 50 hours run time on this airboat.f171_12.JPG (37.0 KB) Attached Images
Reply:That one is holding quite a bit of weight. I think cast iron manifolds are best for turbo applications since they can support more weight. They might not perform like the tubular type, but reliability is better.Miller Syncrowave 200Hobart Handler 140Thermal Dynamics Cutmaster 38E-Z Tube BenderPlasma Cam DHC2
Reply:Originally Posted by hackishSupe, no, they've never cracked at the flanges and those are usually the best "looking" welds. I've ordered a gas lens because I suspect it wasn't getting proper coverage. I read a few complete threads on the subject before posting. Some people in Capnbondo's thread suggested butting them, others like here have suggested leaving a gap. As per the title it's 304 welded with 308L rod. The cracks are usually on the border of the weld bead, not really on the edge of the HAZ. I've got a manifold coming back that has been re-welded 5-6 times so far and it just keeps cracking in different places. I'll try to snap some photos before I excavate the cracks and reweld again.-Michael
Reply:Manifold is off an S13 Nissan, apparently less than 9 months use with a standard size turbo...This is the reason it was brought to me...Pretty clear from this pic that after welding another pulsed autogenous pass was made to get 'the look' . Looks to have been 'well cooked' in placesThe gussets were a pain with regards to DPI but this is what we have after around 10 mins contact time
Reply:Close up time...
Reply:Maybe I am just to new to this stuff, but wouldn't 308, or 316 be better suited for this?
Reply:1-So much for making things look 'so pretty', with autogenous/fusion welds. Those NDT pics say volumes as to 'why' one needs to use filler, nice fairing, no undercut.....especially in stainless.Those really are great pics!2-I just had a Mazda, aftermarket, ss turbo collector in a week ago, for some supposedly 'minor' touchup welding. Well, this thing was cracking, upon cool down--outside fresh bead. Then got to looking some more (didn't bother with penetrant inspection) and it had all manner of tight cracking in various places. This part had seen a good amount of service, in use. The stainless was totally degraded. It was 304 SS. The collector was junk.Reason I'm mentioning the above, is yes--in high output, high heat applications---304 definitely has a limited life cycle, even with competent fabrication. Aircraft exhaust manifolds, which are like 18-20 gauge, ss--use 347--for better heat resistance--and significantly higher cost factor.Maybe the lowbuck approach is to use heavier guage 304--not the S. 10 304, for increased service lifeBlackbird
Reply:Originally Posted by dave powelson1-So much for making things look 'so pretty', with autogenous/fusion welds. Those NDT pics say volumes as to 'why' one needs to use filler, nice fairing, no undercut.....especially in stainless.Those really are great pics!2-I just had a Mazda, aftermarket, ss turbo collector in a week ago, for some supposedly 'minor' touchup welding. Well, this thing was cracking, upon cool down--outside fresh bead. Then got to looking some more (didn't bother with penetrant inspection) and it had all manner of tight cracking in various places. This part had seen a good amount of service, in use. The stainless was totally degraded. It was 304 SS. The collector was junk.Reason I'm mentioning the above, is yes--in high output, high heat applications---304 definitely has a limited life cycle, even with competent fabrication. Aircraft exhaust manifolds, which are like 18-20 gauge, ss--use 347--for better heat resistance--and significantly higher cost factor.Maybe the lowbuck approach is to use heavier guage 304--not the S. 10 304, for increased service life
Reply:D'oh forgot my camera again today. Hotrodder what is that red stuff you're using to find the cracks? That looks like a chinese manifold - I see and replace a lot of them around my shop. I'm not sure what they put in their stainless but it's really shiny and polishes well but they always crack. It's advertised as 304 when you buy it from the chinese supplier but it sure doesn't weld like 304 and it's a brittle as hell. I've cracked it before by just heating and tapping on a section to shrink it.I've never had trouble with short logs like the one posted on the VW. It's usually the more complex ones. On another point does anyone know where to get 321 or 347 weld ells in 1.5 and 1.25 sc-10 size?-Michael
Reply:Hackish,It's 'dye penetrant inspection' (DPI), one of many different forms of NDT for surface flaws- wikipedia probably has an article on it. Any welding store should carry it, it's cheap (under £20 for the three aerosols needed- dye penetrent, cleaner and devolper), easy to use and a bitch to remove from clothingBasically you clean the area to be tested, spray a generous coating of penetrant (the red) and have a tea/beer etc while it does it's thing- getting drawn into flaws via capillary action. Contact time is 10 mins minimum, longer contact time = detection of finer flaws. Excess dye is then removed with a clean lint free cloth before more thorough solvent cleaning- saturate a cloth in the cleaner and go over the area to remove any remaining dye on the surface. Don't spray the area directly with cleaner as that can result in the removal of dye from flaws. When it's clean and dry the devolper is applied- in this case a dryish white powder which helps 'draw out' the dye and is a contrasting colourIt'll work on any metal (almost any non porous surface really) but the 'etched zone' on aluminium will hold dye so needs removing first reallyYes, this manifold is from the far east i believe but i can't really comment on the quality of the tubing of this one- i've repaired/modified identical/similar manifolds that worked/welded fine. I just cut and shut some intake piping made from the 'really shiney' far eastern stainless, welded like crap, very dirty so i do know where you're coming from. 321/347, never found it as preformed mandrel bends in the UK, the only stockists typically specialise in aerospace (my local supplier hadn't even heard of 321 ) and only carry straight lengths
Reply:Smokeshow,A gross simplification but 304, 316 even 321 all have the same upper temperature limits and they're all 'modifications' of the basic chromium nickel alloy- adding a little molybdenum to 304 improves corrosion resistance, particuarly in chloride environments. This is 316, sometimes refered to as 'marine grade'. 321/347 are 'stabilised' (contain titanium/niobium respectively). While the maximum service temp is not increased they don't 'degrade' at intermediate temperatures/fluctuating temperatures the way 304/316 can, hence Dave and Fat Bastard mentioning themFat Bastard,I don't specialise in this sort of work (far easier ways to make a living) but to say 304 WILL fail is an over simplification IMO. Typically i use sanitary bends (so 16g) and have never had a failure- not had any customers running the same set up for 9 years though, they usually change things around in the search for more power/better torque spread before that much time has passed. The manifold i posted a few months ago was bought second hand and had a year or so use before i was asked to modify it- entire thing was made from 16g 304, as were my mods. I expect the 'turbo damper' is probably the key. Titanium would however be an expensive mistake for a turbo manifold
Reply:Thanks!I was just checking.  I was trying to find out why everyone tends to use 304 and not others.
Reply:These are closeups of the manifold on my car. It didn't turn out quite nice enough to give to a customer so I used it on my own. Overall photo. Pretty dirty and has been used now for 4 days. Not too much heat yet.The flange looks OK. Never really had a problem with welding flanges.As you can see some of the round stuff is a bit sloppy and of course with a big macro lense it looks even worse.Here is the collector - more of the ugly colour. I assume too much heat? A little undercutting too but haven't figured out how to fix that. Torch is too big for those areas.Here are some more of a collector I was working on:Feel free to make any suggestions.
Reply:A little hot in spots.  My advice is to get a gas lens setup.  It's a LOT easier to get into those tight spots when you've got 3/4" - 1" of tungsten stickout.
Reply:Originally Posted by smokeshowThanks!I was just checking.  I was trying to find out why everyone tends to use 304 and not others.
Reply:Originally Posted by SupeA little hot in spots.  My advice is to get a gas lens setup.  It's a LOT easier to get into those tight spots when you've got 3/4" - 1" of tungsten stickout.I wanted to get one of those little mini  water cooled torches for inside the collectors but I haven't been able to find many custom torches - was getting to the point of wanting to just make one. I ordered a gas lens today but like everything it's out of stock.-Michael
Reply:I always love these threads. I am continuously trying to figure out how to prevent cracks. First thing: That thread where I was "desprionging" headers- I did some testing and it is unnecessary. The metal "normalizes" after a few heat cycles. Second thing:As hotrodder showed, those "gussets" people put on the runners where they meet the flange are rediculous. Ultimate tensile strength is not the issue here. Third thing:DO NOT USE ANY MORE HEAT THAN YOU HAVE TO! 100A IS WAY TOO HOT. People cooking the crap out of the stainless appears to be the #1 cause of failure form what I have seen. If you dig for pics of cracked manifolds on the 'net, they will almost always be in the HAZ right beside a weld that was obviously performed with 50% more amperage than was necessary. Again, as little HAZ as possible, only as much filler as is needed (not much at 60 amps, I also use 0.035" 309L mig wire for tig rod). The first sched 10 header I made several months ago now is still going great, not a single issue so far. It was welded at 60 amps, one pass. Maybe 70% penetration. Seriously, it seems to be the HAZ that almost always fails, not the weld. 4th thing: The idea that the material becomes "brittle from heat" is in error. People overstate heat cycle issues and understate vibration issues. Temps up at 1400-1500 degrees CAN start to cause carbide precipitation in 304, but the turbo is rarely heated to that kind of tmep for a long time. 304 is not "heat treatable" it does lose some strength at those higher temps, but it returns to normal. With mild bracing even at high temps, four or more runners made from 0.109" thick, 1.5" pipe are more than strong enough to hold up 40lbs worth of turbo. 304 work hardens like crazy. People seem to bypass this fact and blame it on heat. But when your engine vibrates and you flex the joints back and forth THOUSANDS of times, there is just a WEE bit of potential for work hardening there. This is why bracing can be a good thing,.Bracing to help support weight is ok, and more importantly damp vibration is a good thing. But, there is some discretion required, as overbracing certainly makes life hard for the header as well. The brace I am using is a simple piece of 1/8" x 3/4" flatbar that just tires the turbo flange back to the cylinder head flange. It isn't very rigid, but it keeps the header from trying to shake itself apart as the engine vibrates. So, in summary, less heat, and some bracing that mildly supports the weight, but is primarily geared towards vibration damping.
Reply:Smokeshow,Fat Bastard nailed the main reason. 321 is significantly more expensive, as for inconel, well if you have to ask...Hackish, It's as much a lack of shielding as too much heat IMO- improve the gas shield and the undercut will improve some too. As the others have said a gas lens set up will help when you have to extend the tungsten a bunch to reach the joint. A very steady hand is necessary to completely eliminate undercut in very tight spots thoughThe shielding could be better on the easy to reach 'tube to tube' butts as well, torch angles may be partly responsible may be just a combination of a little too much heat and less than perfect shieldingIf you're using an aircooled No17 torch your at a disadvantage trying to reach tight spots- a No20 water cooled is a lot smaller. An aircooled No9 is the same size as a 20 but limited on the amperage it can handle- more than adequate for this sort of work though, rated at 125A DCENI build collecters a different way but for tight spaces that require a bunch of stickout i usually get away with upping the preflow to purge the area (starting the postflow by tapping the pedal can accomplish the same thing), sometimes i'll 'dam up' the area first and i have, rarely, supplimented the torch gas with an extra argon line
Reply:So far I've spent about 3 hours at Linde (formerly BOC Gaz) trying to get the parts I need. They got me a gas lens that sticks out from the torch body by about an inch. I returned it and will wait for the cups to come in before deciding for sure it's the wrong part. I do have a WP-17. The TIG machine is right next to a sink so I'm considering going to a water cooled torch and just hooking it up to the tap.I'm working on a new manifold today for someone else so I'll try some of the suggestions. I like the idea of bending the tungsten, but I'm wondering how you accomplish that? Heat it with the TIG and bend that way or just use acetylene?-Michael
Reply:I would suggest trying a WP20 for the tig torch, it's smaller and much nice for the fine work that you would like to do. Try a #7 cup with a gas lens, it's a nice set up and we use this for 90% of our aerospace applications.   Running the water from the tap works fine and I do this as well, just be careful if your machine doesn't have a solenoid to stop the water from flowing when the torch is not being used. In the hot humid weather condensation can build up on torch and inside the cup etc from the cool circulating water. This moisture can cause defects (porosity) and when severe can make it easy to get HF shocks when initiating the arc. Where are you located?RegardsER70S-2
Reply:I get shocks all the time from my torch. Makes me wear gloves  When I was taking the torch apart to test fit the gas lens that Linde provided I found that the collet body had separated from its threads - not sure how that happened. I pulled it out of the torch and found the copper had disintegrated to powder. So I cleaned the threads out with a tap and replaced it. I haven't done any welding since but hopefully that will fix the problem.My welder isn't set up for water so no worries about a solenoid. BTW I'm in Ottawa.-Michael
Reply:Originally Posted by hackishSo far I've spent about 3 hours at Linde (formerly BOC Gaz) trying to get the parts I need. They got me a gas lens that sticks out from the torch body by about an inch. I returned it and will wait for the cups to come in before deciding for sure it's the wrong part. I do have a WP-17. The TIG machine is right next to a sink so I'm considering going to a water cooled torch and just hooking it up to the tap.I'm working on a new manifold today for someone else so I'll try some of the suggestions. I like the idea of bending the tungsten, but I'm wondering how you accomplish that? Heat it with the TIG and bend that way or just use acetylene?-Michael
Reply:Originally Posted by hackishThese are closeups of the manifold on my car. It didn't turn out quite nice enough to give to a customer so I used it on my own. Overall photo. Pretty dirty and has been used now for 4 days. Not too much heat yet.The flange looks OK. Never really had a problem with welding flanges.As you can see some of the round stuff is a bit sloppy and of course with a big macro lense it looks even worse.Here is the collector - more of the ugly colour. I assume too much heat? A little undercutting too but haven't figured out how to fix that. Torch is too big for those areas.Here are some more of a collector I was working on:Feel free to make any suggestions.
Reply:Hackish,Weldcraft part #s for a No17 torch http://www.weldcraft.com/pdf/WP17ENG_1.pdfGas lens for a No 17/18 torch is BIG. They're more compact on the No 9/20 but all the ceramics have a larger OD as Dave said
Reply:You tried one pass and two?  How about three?  If you fit it PROPERLY, with a bevel and gap, you wouldn't be able to weld it in one pass, and two would be tough.When you say ALMOST full penetration, that's the problem.  The outer part of the pipe is fused together...   The inside heats up first, since that's where the heat is.  As the part inside that isn't fused heats up, it expands.  Each piece of pipe begins to push against the other, and the outer part that's welded is trying to hold together.  The result can be a crack.  If you're not going to get full penetration, put a gap in it large enough that the root inner surfaces won't touch and have room to expand. Originally Posted by hotrodderClose up time...Attachment 22129
Reply:Originally Posted by EngloidYou tried one pass and two?  How about three?  If you fit it PROPERLY, with a bevel and gap, you wouldn't be able to weld it in one pass, and two would be tough.
Reply:Originally Posted by EngloidThey like to call this "fish scale."  I call it a series of craters that will have millions of microscopic cracks.  .
Reply:Lol, you want to see too much heat, check this out: This was my first stainless project a year or so ago... I had no idea what I was doing(Still don't!). I did get FULL penetration, I backpurged the hell out of it and the inside of the welds look far better than the outside. Tubing is 0.065" wall 321, with 304 flanges. I have had it glowing bright orange on a 530whp rotary many times with no cracks yet. The 321 is damn expensive as stated before (~$80 per U-bend from Burns) but it seems well worth the price, because it sure as hell isn't holding together on account of my welding! I can't wait to make another one knowing what I know now...I do have it braced to support the 45lb turbo (made same time as the manifold):Last edited by LimitedSlip7; 08-02-2008 at 12:17 AM.
Reply:Found this thread a long time ago while looking into techniques for welding manifolds. All the talk about 321 got me interested. Interested enough to spend some money. Found a source for 321 butt weld fittings in 1 1/2 and 1 1/4 sch5 and sch10. If any one is interested feel free to send me a PM.
Reply:Originally Posted by HerbieFound this thread a long time ago while looking into techniques for welding manifolds. All the talk about 321 got me interested. Interested enough to spend some money. Found a source for 321 butt weld fittings in 1 1/2 and 1 1/4 sch5 and sch10. If any one is interested feel free to send me a PM.
Reply:409 is better 304 doesn't take to heat very well Sent from my VS980 4G using TapatalkLincoln Power Arc 4000 Thermal Arc Fabricator 252 iThermal arc 186Thermal Arc 26 tigTweeko 200 amp spool gunHobart AirForce 400WP-17V-12R