304stainless vs 316? for headers
12-24-2003, 01:12 AM
#2
316L is an extra low carbon (ELC) grade of stainless that has only .03% carbon, making less carbon available to precipitate with the chromium. It is used extensively in marine exhausts where salt water corrosion mixed with diesel exhaust particulates and electrolysis create such a horrible environment that even other grades of stainless cower and run away!
304 is the most inexpensive and available stainless in the 300 series. It is suitable for normally-aspirated header applications, and has been successfully used by many racing teams. It does not have the high temperature fatigue resistance that 321 does, but is considerably less costly and much more available. Most 304 tubing these days has the dual designation of 304/304L.
321 and 347 are known as stabilized grades of stainless. These are alloyed with either titanium (321) or columbium (347), both of which have a much stronger affinity for carbon than does chromium at elevated temperatures. This eliminates carbide precipitation leaving the chromium where it belongs for corrosion protection. Both 321 and 347 are top choices for exhaust headers, especially turbocharger systems and rotary engines. Since 321 is much more available than 347, that leaves 321 as the first choice, with no sacrifice in needed qualities.
Of course my logs are 304 dammit.
Special thanks to Burns for this info which I hope helps you.
Material Properties
Aluminum 6061-T6
Aluminum 6061-T0
Mild Steel 1010 CREW
304 Stainless Annealed ASTM A269
321 Stainless Annealed
Titanium Cp2 Grade 2 ASTM B 338
Inconel 625
Tensile Strength
lb/in2 (70 F)
45,000
18,000
55,000
85,000
90,000
50,000
140,000
Yield Strength
lb/in2 (70 F)
40,000
8,000
40,000
35,000
35,000
40,000
77,000
Elongation
percent
12
25
20
55
55
20
47
Density
lb/in2
0.098
0.098
0.283
0.290
0.290
0.163
0.305
Modulus of Elasticity
x 106 lb/in2
10
10
29.5
28
28
15
30
Coefficient of Thermal Expansion
in/in-F x 106
( 70 F )
( 70 F )
13.1
13.1
7.228
9.9
9.6
4.8
5.5
Coefficient of Thermal Conductivity
BTU/ft-hr-F
( 70 F )
( 70 F )
96.50
104.00
26.98
9.40
9.30
12.00
5.65
Last edited by JamMasterJ; 12-24-2003 at 01:18 AM.
12-24-2003, 01:19 AM
#3
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My headers (non-turbo) are 321. I'm not familiar with 316, so can't comment on that. I know most of the stainless stuff out there is 304.
That said, you might want to check the pricing on the tubing/bends before you get your heart set on a certain alloy - especially since if you get them coated it's not as big of a difference.
That said, you might want to check the pricing on the tubing/bends before you get your heart set on a certain alloy - especially since if you get them coated it's not as big of a difference.
12-24-2003, 06:48 AM
#4
wow, nice info. the reason i ask is i have a turbo kit coming and the header was going to be 304, aparently the header guy got a smoking deal on a pile of 316 and is going to be making the headers with 316, he says it is alot better than 304, someting about less likely to crack in the cold weather.
