MORE 304 vs 321
As far as the SSAutochrome headers.I e-mailed them on e-bay "ask seller a question" about the fact that in their ad at one place it says 304 and at two other places it says 321! My ? to them was what are the tubes made of and what are the flanges made of? And why the contradictory 304/321 in the ad?
Haven't gotten a reply yet , but it's only been a day or two.I'll post their reply when I receive it.
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For those wanting more reading Info to help form your own opinion :
Burns Stainless
In short ,
Within the 300 series of stainless steels, there are four types that are suitable, available and cost effective for the racer. These are 304, 316L, 321, and 347.
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...remember our discussion of intergranular corrosion? 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.
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.
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304 stainless steel tubing combines excellent physical properties with a remarkable resistance to corrosive agents found in automotive exhaust emissions.
304 tube is the most cost-effective grade of nonmagnetic stainless steel for general applications, but some professional racing teams use the higher heat-resistant properties of aircraft grade 321 stainless steel.
We have considerable experience with stainless header fabrication and will gladly advise our valued customers.
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321 stainless steel tubing is one of the most desirable materials for exhaust systems because of its excellent resistance to fatigue and cracking at elevated temperatures.
It is usually the material of choice for high temperature turbo applications, unless extreme requirements indicate the use of Inconel.
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Use 347 filler rod to weld 321 to 321
Use 308 filler rod to weld 321 to 304
Use 309 filler rod to weld 321 to mild steel
Enjoy your reading.
. Phil
