I found this on the net and I'll be searching around for more...
Properties of 321 stainless steel v 304/304L stainless steel..

It definately comfirms what race engineers and race teams already know, 321 is more suitable then 304/304L for high temp situations such as in turbo headers.

Notable excerpts-

"304L strength rapidly decreases above 425F."

"304 has excellent LOW temp. properties"

"321...is suitable in applications where 304 becomes sensitized or where 304L has insufficient hot strenght"

It appears that 304L shouldn't even be used period in high temp applications...

I'll dig up more Factual information too...there has got to be a glut of it out there...

Heres the link for addtional in depth info-


http://www.askzn.co.za/tech/tech_grade_321.htm


SX 321 Technical Data

SX 321 is a titanium-stabilised version of SX 304, used in particular applications within the sensitizing temperature range. Its resistance to sensitization, coupled with its higher strength at high temperature makes it suitable in application where SX 304 will become sensitized, or where SX 304L has insufficient hot strength.

C Mn P S Si Cr Ni Ti
SX Analysis 0.08 max 2.0 max 0.045 max 0.030 max 1.0 max 17.0 - 19.0 9.0 - 12.0 5X%C min
0.5 max
Typical 0.06 1.2 0.020 0.020 0.5 17.5 9.4 0.48

. Mechanical Properties at Room Temperature


Typical Minimum
Tensile Strength, MPa 580 515
Proof Stress (0.2 % offset), MPa 280 205
Elongation (Percent in Lo = 5.65 So) 60 40
Hardness (Brinell) 163 -
Endurance (fatigue) limit, MPa 260 -

2. Properties at Elevated Temperatures
Short Time Elevated Temperature Tensile Strength

Temperature, oC 600 650 700 750 800 850
Tensile Strength, MPa 390 329 280 230 190 140


Recommended Maximum Service Temperature
(Oxidising Conditions)

Continuous Service 950oC
Intermittent Service 870oC

SX 304 / 304L Technical Data

Summary

SX 304 is the most versatile and the most widely used of all stainless steels. Its chemical composition, mechanical properties, weldability and corrosion/oxidation resistance provide the best all-round performance stainless steel at relatively low cost. It also has excellent low temperature properties and responds well to hardening by cold working. If intergranular corrosion in the heat affected zone may occur, it is suggested that SX 304L be used


Chemical Composition (ASTM A240)

SX oC Mn P S Si Cr Ni
304
304L 0.08 max
0.03 max 2.0
max 0.045
max 0.030
max 1.0
max 18.0 to
20.0 8.0 to 10.50
8.0 - 12.0

. Mechanical Properties at Room Temperature

304 304L
Typical Minimum Typical Minimum
Tensile Strength, MPa 600 515 590 485
Proof Strength, (Offset 0.2 %), MPa 310 205 310 170
Elongation (Percent in 50mm) 60 40 60 40
Hardness (Brinell) 170 - 170 -
Endurance (fatigue) limit, MPa 240 - 240

2. Properties at elevated temperatures
All these values refer to 304 only.
304L values are not given because its strength decreases markedly above 425oC.

Time Elevated Temperature Tensile Strength
Temperature, oC 600 700 800 900 1000
Tensile Strength, MPa 380 270 170 90 50

Maximum Recommended Service Temperature (FOR 304 ONLY NOT 304L)
(Oxidising Conditions)
Continuous Service 925oC
Intermittent Service 850oC


[Modified by SuperT, 9:38 PM 3/20/2003]

 

i dont have time to sit here and discuss this now, but read this nice disclaimer:

 

Jeezus, guys...let up, ok?

We just had a thread that praised a comparison of different manifolds and this post is one of the first. It goes into detail about the differences in materials commonly used in manifolds.

I see the relevance.

Sonny

 

yep...If I had the money, i would use 321 in all of my personal manifolds...

 

Cmon Mase, you can do better than that...Every site has a disclaimer...

This has and always has been common knowledge that 321 is better in HIGH heat applications then 304 or 304L...

Just to appease you...I will find you several more studies just to eliminate any possible bias...

So far people have told me the People at Burns stainless know nothing now i find another site that confirms it and even goes further with property studies and it still isn't good enough...

Heres my challenge...Why dont those who think 304/304L is better, find me FACTUAL published studies that show it is better then 321...Im looking but have found none...

I ran across some more on 321 so I'll get the links up ASAP...

Lets keep this civil and not a flame war as the other ones have turned into...I dont want peoples personal opinions on which is better, I want Facts...

I think this is a very informative thread for those out there considering purchasing a manifold...

Regards,
Dave

 

you gotta be kidding me

interesting stuff Super T

 

Thanks falconGSR...

Heres more promised links-


http://www.nks.com/nks/material_data...ess_steel.html

Quote from this site-

"The corrosion resistance of Type 321 in fully annealed condition is about the same as Type 302. Type 321 has superior resistance to Type 302 and Type 304 when service covers 800-1600°F"

Oxidation

Oxidation or scaling resistance of this grade depends on atmospheric and operating conditions. For continuous service, the maximum recommended temperature is 1650°F; and for intermittent service, 1500°F.

I'll keep them coming...I found more too...

No flaming though guys, lets keep it civil...

Those who think 304 or 304L is better, need to show some studies, not opinions and not your personal critique of the engineers who performed these tests and no "what ifs" etc.. etc...

Lets keep is factual...

Dave





[Modified by SuperT, 10:52 PM 3/20/2003]

 

as for factual, the Hendrix Group sent me this information today about a company who came to them w/ this problem:

"For a borax solution vessel (alkaline, temp. of about 80 deg. C), our steel supplier sent us SS 321 instead of SS 304. SS304 works fine. SS 321 was found to be corroded after a few days."

More to come, but right now i have school work to do.

 

Here's more

 

hmm.. good stuff .
ive got a few books on this stuff.
dont feel like pulling anything from them

 

This only proves the 304 does have applications its suitable...this was an akaline solution at 80F!!!

This was not a high heat fatique and strenght test...

No one is claiming that 304 doesnt have applications where it isn't better then 321, but high heat is not one of them...

Lets stick to the topic...

321 v 304 in high heat applications such as in turbo headers...


dave





[Modified by SuperT, 12:35 AM 3/21/2003]

 

so you're saying you will always have your car running 24/7 ?????

P.S. what i meant by that, i consider corrosion a big part of picking a manifold. i dont know about you, but my car is not running more than it is.....and its outside all of the time when im at school


[Modified by Mase, 4:40 PM 3/20/2003]

 

And this test here is just its corrosion resistance to the atmosphere at normal temperatures...

We are not talking about corrosion...304 is great for that, thats why its used so heavily in the cooking and medical industry...

Lets focus in on whats important to turbo headers...high heat...

I provided charts and data that show 321 is better at high temps...


I found a chart on 321 and heat..I'll post it up asap..supper time...

Dave

 

so answer this.

What happens when your metal corrodes when you are not using it in High Heat?, what do you think is going to happen to the strength of the material then???

 

Will corrosion even be an issue if the manifold is properly coated?

I know the stuff that DC Sports uses wears off and I've seen their headers rust, but stuff like HPC and Jet Coat seems indestructable.

Just curious...

Sonny

 

Great point sonny, corrosion will probably not come into play. However, i like my steel to bling, haha


to a great thread

 

Cmon Mase, lets keep this clean and factual...

No ones manifold is going to rust away from an alkaline solution or getting rained on in our lifetime...Many people have 321 and 304/L manifolds that have never rusted away due to alkaline baths being soaked on them by evil people sneaking in the middle of the night and placing there manifolds in acid baths or mother natures fury raging on them over and over for what would probably need to be years on end...

Lets stick to relevant data about the heat properties of the materials...


Can we agree to not let this go to a hater thread...PLEASE?


Dave


[Modified by SuperT, 1:12 AM 3/21/2003]


[Modified by SuperT, 1:14 AM 3/21/2003]


[Modified by SuperT, 1:16 AM 3/21/2003]

 

Great thread!

 

thats totally wrong.

Failure analysis is the science of determining how and why a component has failed, due to either mechanical or corrosion means, with the goal of preventing additional, similar failures. Simply verifying the failure mode is sometimes of little practical use. It is also important to determine what factors influenced the failure or "why" it failed. The "why" of failure analysis is the driving force behind "root cause" failure analysis.

Representative mechanical failures that we have studied include those occurring due to:

fatigue
stress rupture
fretting
brittle fracture
tensile overload
fretting fatigue

intergranular fracture
transgranular fracture
temper embrittlement
885 embrittlement
Wear
brinneling




Typical corrosion related failure projects have included those due to:

intergranular corrosion
stress corrosion cracking
corrosion pitting
crevice corrosion
hydrogen embrittlement
erosion-corrosion
oxidation
carburization
sulfidation
carburization
hot corrosion
coating degradation






[Modified by Mase, 5:21 PM 3/20/2003]

 

Did you copy that right out of a book?

 

Here is another link to temp ratings for 304, 304L and 321-

http://www.ces.clemson.edu/chemeng/uolab/metal4.htm

In summary- Maximum working heat range-

304 1000F

304L 1400F

321 1600F

 

This is very interesting, because before this topic of materials was started that never crossed my mind when buying a manifold. I value both sides info, please keep it coming. My exhaust manifold on my Twin Turbo Buick is 321, and its been on the car now for 8 years with no rust or corosion and I have never had to weld her up once (1200whp). But after reading up on what FFgeoff & SuperT says I also realize that good prep and design play a major roll in that aswell. This site has been a eye opener for me in many repects. Full race & SuperT you guys really make this site worth visiting.

 

I think my cast Revhard manifold had about 2 square inches of rust on it when I pulled it off after 1 year. I always assumed the high temps helped deter rust.

 

Heres a really good one about 321 heat resistance properties...

Even talks about how they use it in Jet engines(for whatever thats worth..lol)

http://www.clandestinehardware.com/p...datasheet.html

 

Your right, ...I didn't mean 99% of ALL failures...as obviously bad welding, striking something as the motor rocks forward, etc etc can make it fail..

but to the other garbage....will you PLEASE read the Links and quit turning this into a pissing match...

Provide data about these materials and how they relate to the high temp environments they live in...

Thanks...

Dave