Quote:
Originally Posted by toddoky
All of the issues discussed here is why I don't use 304 for building exhaust systems; it is an un-stabilized austenitic grade of stainless that is not recommended for use in high temperature applications (850 degree F. use temp threshold). If you need increased high-temperature strength beyond what mild steel provides, 321 and 347 are the stabilized grades that can provide it by design. 304 became the poor-mans stainless exhaust material due to its availability and affordable price (relative to 321 and 347) and the fact that its the only lower-cost option most people think they have besides using 409ss. If you want to use an affordable stainless material that is designed for use in a high-temp environment with better corrosion resistance than 304 in cyclic high-temp applications (i.e. exhaust systems) look at the stabilized 2nd-generation ferritic grade 439. It has the same 18 percent chromium content that 304 has (409 has 11.5 percent)without the nickel content, which is the real price driver of the austenitic grades. I've used it to build headers and exhaust systems for 15 years without any issues and highly recommend it. Its coefficient of thermal expansion is closer to mild steel than it is to 304. The trouble with using it is in finding it in U/J-bend form but you can find them in many different tube diameters from Bassani Manufacturing in Anaheim, Ca.
|
and because average people don't know about alternatives...its become an industry standard.
What is the cost difference and what filler is used with it?