blue_leaf Posted July 20, 2006 Share Posted July 20, 2006 Will both the stainless steel and mild steel be suitable? What are the other chatracteristics that I should consider when purcahsing tubing for fabrication of custom exhaust manifold? Are the same materials used for turbo exhaust manifolds manufacture as the manifolds for NA cars? Quote Link to comment Share on other sites More sharing options...
veritech-z Posted July 20, 2006 Share Posted July 20, 2006 Generally, turbo manifold fabrication involves thicker material due to the higher heat it's going to experience. As for what materials, what do you have the capability to weld? The procedure varies from type to type. Quote Link to comment Share on other sites More sharing options...
johnc Posted July 20, 2006 Share Posted July 20, 2006 Your budget, more then anything else, will determine your choice of materials. For example: A 1.75" OD u-bend in 304 stainless is typically 110% more expensive then a similar wall thickness mild steel u-bend. In 321 stainless its 185% more expensive then mild steel. If you go with Inconel, expect the same u-bend to be 310% more expensive then mild steel and if you're thinking about Titanium, well, you wouldn't be asking this question on this board. Material selection depends a great deal on intended use. A header for a NA street car can be made out of mild steel because street engines are only run at full throttle for very short periods of time. The same can be said for a turbo header on a street car. Adding a high temp coating (Jet Hot 2000, Swain) extends the service life of a mild steel part. For an engine that's run at full throttle a large part of its service life stainless steel and Inconel have better heat cycling properties then mild steel. They also have built in corrosion resistance but will expand and contract more then a mild steel header. Quote Link to comment Share on other sites More sharing options...
blue_leaf Posted July 21, 2006 Author Share Posted July 21, 2006 Thanks for your replies people - its is already becoming more clear... But what does 304 and 321 stand for in materials? What is standard wall thickness for street NA and turbo manifolds? Would 16 ton pipe bender be enough to bend mild/stainless steel and inconel? PS and no I am not planning on using titanium Quote Link to comment Share on other sites More sharing options...
johnc Posted July 21, 2006 Share Posted July 21, 2006 Here in the US we can typically get header and exhaust tubing in wall thicknesses of .035", .049", and .063" in mild steel, stainless, nickel steel (Inconel), and titanium. A racing turbo exhuast manifold will typically be built using .063" stainless and .049" Inconel or titanium. A racing NA exhaust will typiclaly be built using .063" mild steel, .049" stainless, or .035" Inconel or titanium. The same thicknesses are typically used for a street exhaust and a tubing bender won't work bending thin wall exhaust tubing. The tubing will just kink or collapsed. Search for tubing bend suppliers in your part of the world. Here in the US typical sources are: http://www.burnsstainless.com/ http://www.spdexhaust.com/ http://www.summitracing.com/ And many, many others. 304 and 321 refer to the types of stainless steel. 304 is more common and 321 is stabilized with Columbium to reduce carbide precipitation. Quote Link to comment Share on other sites More sharing options...
veritech-z Posted July 22, 2006 Share Posted July 22, 2006 Also www.mcmaster.com offers a bunch of different tube sections. Quote Link to comment Share on other sites More sharing options...
MatMan Posted July 24, 2006 Share Posted July 24, 2006 ...snip...But what does 304 and 321 stand for in materials? ...snip... In the AISI grading sytem, the 300 (austenitic) series steels are set apart by their minimum carbon content. The 304 steel has a carbon content of 0.04%, while the 321 steel has 0.21% C. It's the same grading as the 400 (stainless) series. When you see an L or H just after the grade, it means that there is less or more than this target percentage (it's impossible to be exact, anything close counts in molten metal). For example, 304 has a range of 0.03 to 0.08% C. IIRC, these percentages are based on weight. Quote Link to comment Share on other sites More sharing options...
johnc Posted July 24, 2006 Share Posted July 24, 2006 In the AISI grading sytem, the 300 (austenitic) series steels are set apart by their minimum carbon content. The 304 steel has a carbon content of 0.04%, while the 321 steel has 0.21% C. It's the same grading as the 400 (stainless) series. No. You are confusing the 4 digit steel SAE grading system with the 3 digit AISI grading system used for stainless. 304 stainless has the following composition: Carbon .08 Mn 2.00 Si 1.00 Cr 18.0 - 20.0 Ni 8.0 - 15.0 P .05 S .03 321 stainless has the following composition: Carbon .08 Mn 2.00 Si 1.00 Cr 17.0 - 19.0 Ni 8.0 - 12.0 P .05 S .03 Ti .40 - 1.00 There are low carbon (L), free machining (F), Normalized (N), and additional suffixes added to the AISI 3 digit number (i.e. 303Se is AISI 303 stainless steel with Selenium added). BTW... I was mistaken when I said 321 had Columbium, it has Titanium added as a stabilizer. 347 has Columbium and Tantalum added. Quote Link to comment Share on other sites More sharing options...
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