Mild vs Stainless Question
08-22-2009, 09:32 AM
#21
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I build my own headers. First set I built were mild steel that I wrapped. Within 2 weeks they were all cracked/melted, where they had been wrapped.I only use stainless 304 now. Too much work to have to build them over again. Stainless is never out of style. Just my opinion. If they get ugly just sand blast and paint flat black.
I don't now of any header company who will warranty a mild steel header that has been wrapped. It's easy to tell also. They get yellow hot under the wrap.
Last edited by ssvolvo; 08-22-2009 at 09:37 AM.
08-22-2009, 09:41 AM
#22
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most cracking issues come from the weight of the turbo not being supported, using the tubing itself to support the weight of the turbo, will crack the manifold, ive built plenty of manifolds using 16ga ss and support the weight with a bracket and it will not crack. heres a pic of a kit that has been in service for 2+ years now and never cracked and its 16ga ss
08-22-2009, 01:23 PM
#23
most cracking issues come from the weight of the turbo not being supported, using the tubing itself to support the weight of the turbo, will crack the manifold, ive built plenty of manifolds using 16ga ss and support the weight with a bracket and it will not crack. heres a pic of a kit that has been in service for 2+ years now and never cracked and its 16ga ss
...we dont want to see that crap, make the bad man stop!
LOL
I think that if the welds are done correctly and everything is installed correctly (proper clamps, enough space, the right braces where needed like mentioned above) and you are running a tune that matches ur setup, then there should be no problem with SS, but if you trying to save a few bucks, then coated MS would be cheapest and most sufficient next in line.
08-22-2009, 02:10 PM
#24
You have to have some kind of structural knowledge before just welding a bunch of stuff together and expecting it to not crack. Its not the material that makes it crack, its the way someone built it. Designed and welded correctly you wont have any problems. You have to keep in mind stress, weight, heat cycles....all play a part. Even a poorly designed mild steel setup will crack and break.
08-22-2009, 02:47 PM
#25
Let also be known that you probably don't have a clue what you are talking about. We have built SEVERAL THOUSAND STAINLESS turbo manifolds and I can count all of the cracking issues we've had with my fingers. Mild steel can be made to work but it will never last as long if Stainless was used.
I am glad you have had goodluck with your fabrication. I don't care how you cut the cookie stainless move's around alot under heat. I'm not saying that the issue's people have with stainless could not be avoided with better bracing and such. Mild steel will hold up under all circumstances reguardless of the build/weld/back purging/bracing.
You have to have some kind of structural knowledge before just welding a bunch of stuff together and expecting it to not crack. Its not the material that makes it crack, its the way someone built it. Designed and welded correctly you wont have any problems. You have to keep in mind stress, weight, heat cycles....all play a part. Even a poorly designed mild steel setup will crack and break.
I have built probably 50 kit's at this point with 45 of them being mild steel. I have hung a 60 lb un-supported turbo on a 6.0l style y/merge pipe and have never ever have one mild steel problem.
08-22-2009, 07:18 PM
#27
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also how long will the mild steel last before it needs replaced. I know this is vague but is it 1-2 years or is it like 5-6 years.
For a street car that hardly sees rain, I don't see the point of going SS, you can spend money in other areas. If you have the money though SS would be nice to know that you only have to buy/make it once.
For a street car that hardly sees rain, I don't see the point of going SS, you can spend money in other areas. If you have the money though SS would be nice to know that you only have to buy/make it once.
08-23-2009, 01:10 PM
#30
Alot of people dont know how to weld either, they think that fusing is welding. Welding non-ferrous metals (stainless, aluminum) is totally different than welding ferrous metals (mild steel).
Ive seen LOTS of turbo builds that people TIG weld (or attempted) and you can clearly see there is not enough filler rod added, there is like a scribe line down the center of the weld where it sucked in. That is a line that when it has a few heat cycles, and some stress......even a bump in a road....will crack.
This is a Honda turbo manifold a friend has, he said he paid a grand for it. I was dumbfounded when he asked me to fix it and I had to re-weld like 6 complete welds. One tube was literally completely separated. Decent header design?? Flow wise maybe....structurally - FAIL!!!
Each tube was independent of each other, Why? When all 4 together could have the strength to support 3 times the weight of the turbo??
It was really flexible without the braces in it. I welded some 1/8" plates of stainless in to brace it and it is now rock solid.
Some of the welds on this were sufficient, but design killed it. The one marked "bad weld" there is not enough weld on it. I wonder why they put like this huge 1/4" weld on the tubes meeting the head flange, those are nice, but all the other ones are **** and some of them are tiny??
I dont know who made this but I think they were completely clueless. This was also his second one from this place, the first one broke as well.
Little braces make a world of difference.
Yes this is a stainless header/manifold. Made of schedule 10 weld elbows, .109 wall thickness.
08-23-2009, 06:49 PM
#31
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Stainless Steel seems likes its the way to go, anybody want to correct me if im wrong on that, because it seems that there is many pro's and less con's for Stainless
08-24-2009, 12:58 PM
#32
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Let it be known that I have been building these cars for year's while you were still working on ricer's.
I am glad you have had goodluck with your fabrication. I don't care how you cut the cookie stainless move's around alot under heat. I'm not saying that the issue's people have with stainless could not be avoided with better bracing and such. Mild steel will hold up under all circumstances reguardless of the build/weld/back purging/bracing.
I am glad you have had goodluck with your fabrication. I don't care how you cut the cookie stainless move's around alot under heat. I'm not saying that the issue's people have with stainless could not be avoided with better bracing and such. Mild steel will hold up under all circumstances reguardless of the build/weld/back purging/bracing.
The application of who works on what kind of vehicle is null and void for this topic. I wouldn't call it good luck with our fabrication, we know what we're doing and have put plenty of thought into doing what we do. You are correct in saying the thermal coefficient of expansion of Austenitic Stainless Steels is a good bit more than Carbon Steels. I do believe that Martensitic & Ferritic Stainless have a lower expansion rate than carbon steel, although it's not really used in our applications. What you're failing to look at is the high temp stability of the materials. Look into the material properties, they should be fairly easily found on the web. Compare the creep strength, stability, oxidation resistance, tensile strength, etc...
Stainless is a Ferrous material BTW. Nice pics!
08-24-2009, 01:51 PM
#33
I'm sorry your focus has been to limited to one platform. Expand your horizons you might learn a thing or two. The application of who works on what kind of vehicle is null and void for this topic.
I wouldn't call it good luck with our fabrication, we know what we're doing and have put plenty of thought into doing what we do. You are correct in saying the thermal coefficient of expansion of Austenitic Stainless Steels is a good bit more than Carbon Steels. I do believe that Martensitic & Ferritic Stainless have a lower expansion rate than carbon steel, although it's not really used in our applications. What you're failing to look at is the high temp stability of the materials. Look into the material properties, they should be fairly easily found on the web. Compare the creep strength, stability, oxidation resistance, tensile strength, etc...
Stainless is a Ferrous material BTW. Nice pics!
The application of who works on what kind of vehicle is null and void for this topic. I wouldn't call it good luck with our fabrication, we know what we're doing and have put plenty of thought into doing what we do. You are correct in saying the thermal coefficient of expansion of Austenitic Stainless Steels is a good bit more than Carbon Steels. I do believe that Martensitic & Ferritic Stainless have a lower expansion rate than carbon steel, although it's not really used in our applications. What you're failing to look at is the high temp stability of the materials. Look into the material properties, they should be fairly easily found on the web. Compare the creep strength, stability, oxidation resistance, tensile strength, etc...
Stainless is a Ferrous material BTW. Nice pics!
I did not mean to make it sound like your work holding up was luck.
When I reccomended mild to the OP it was just a generalized reccomendation based on the part's that are out there. Do you think that everyone in the business know's as much as you about making stainless hold up? Do you think there are any kit's/manifold's currently out there that crack? Can we agree that a stainless manifold/kit takes more engineering, bracing, and wall thickness to hold up? Does everyone that uses stainless keep that in mind? Prime example would be the ebay manifold's, at this point there are alot of them out there, they are stainless, and they CRACK.
If this guy goes out and buy's a random vendor's turbo kit it has a better chance of never cracking if it is a mild steel kit.
I know this to be a fact based upon the amount of repair done to other people's work and the fact that 95% of the time it's stainless repair.
Last edited by black98ws6ta; 08-24-2009 at 01:58 PM.
08-25-2009, 12:07 PM
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Can we agree that a stainless manifold/kit takes more engineering, bracing, and wall thickness to hold up? Does everyone that uses stainless keep that in mind? Prime example would be the ebay manifold's, at this point there are alot of them out there, they are stainless, and they CRACK.
If this guy goes out and buy's a random vendor's turbo kit it has a better chance of never cracking if it is a mild steel kit.
I know this to be a fact based upon the amount of repair done to other people's work and the fact that 95% of the time it's stainless repair.
If this guy goes out and buy's a random vendor's turbo kit it has a better chance of never cracking if it is a mild steel kit.
I know this to be a fact based upon the amount of repair done to other people's work and the fact that 95% of the time it's stainless repair.
Comparing EBAY/China manifolds needs to be taken with a grain of salt. The craftsmanship is very poor, they often use sub par materials(some are even made of 409ss), and the welding process is terrible. They are often welded once and then gone back over with a pulse welder to make them look purty
I've fixed a good bit of stainless manifolds from other places. The way I've always looked at it is that most everyone uses SS to build there turbo stuff. The chance of failure is a lot higher if the ratio of SS to MS manifold is 5 to 1 or whatever it works out to be.
08-25-2009, 12:32 PM
#37
Stainless's thermal expansion rate is greater than mild. So expanding and contracting and heat are the main contributors that cause it to become more brittle. Then of course anything putting stress on it. While you can leave individual runners loose with mild, it has enough flex in it to absorb a lot of thermal expansion, but brittle like cast iron, stainless needs to be all tied together (my opinion) for structural applications (holding turbos up). But when I did hard tubing on compressors and such, if you couldnt anchor is securely, a loop was made to absorb vibrations expansions. But that cant have ANY weight on it. So depending on your application, a long loose runner may be good for vibrations and such, but then devistating if theres any stress on it (weight), and even stress created by bumps in the road.
08-25-2009, 01:42 PM
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