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Stainless Steel and exhaust systems. Such a system will produce more horsepower and last "'til the cows come home". It is an excellent solution. Now that you are sold on the merits of stainless steel, there are a number of things you need to know about the different types available before you launch into a header and exhaust system project. A three-digit numerical classification system is used throughout the industry. The racer needs to be familiar with only one of these three-digit series within the system - the 300 series. They offer the fabricator a wide array of choices, from ornamental quality up through the highest-temperature and closest-tolerance aircraft quality. 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 hostile environment that even other grades of stainless have difficulty coping with it. sizes, pipe may sometimes be substituted for tubing, and vice versa. Numerous wall thicknesses are available, but for headers, normally .049" ( 18 gage ) to .065" ( 16 gage ) is used. Different specifications are used to meet particular requirements for the military (MIL), the American Society of Testing Materials (ASTM), and the Society of Automotive Engineers (SAE). Examples of what to look for when you order stainless tubing are as follows: ASTM A-554 304 stainless is a welded mechanical tubing used primarily for ornamental purposes. It is not fully annealed and is work-hardened slightly in manufacturing. It has good column strength and good bendability. ASTM A-269 304 stainless is a general service commercial specification that is higher quality and is fully annealed for better ductility. It is available in both welded seam and seamless, and is a good spec for the racer to use. We have not seen any difference in longevity between welded seam and seamless stainless tubing in header use, but there is a substantial cost difference. The column strength is not as good as A-554, but it has excellent bendability with a higher cost due to the full annealing. MIL-T-8808/8606\MIL-T-6737 321 stainless are military specifications for aircraft tubing. Suffice it to say that some MIL-specs are not necessarily better or even as good as some ASTM standards. There is no particular magic here. There are as many uses for stainless steel as there are projects in the shop. I can think of nothing else that transmits an image of quality and skill to the majority of fabricators than a cleanly constructed stainless steel project. Whether it be a set of headers, intake stacks, or even a stand for one's dyno engine cooling fan, stainless steel has such great mechanical properties that its use should be considered for many projects beyond exhaust systems. 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. Practically speaking, there are overlapping applications of 304 and 321 stainless in header construction, but knowing you've got the insurance of the aircraft-grade 321 for the job is definitely worth consideration despite the extra cost..if your application requires it. Stainless steels come in both tubing and pipe sizes. Since certain pipe sizes are almost identical in dimension to tubing 26 Burns Stainless LLC 949.631.5120 Monday - Friday 7:30 am to 4:30 pm fax 949.631.3184 burnsstainless.com
Inconel® Inconel refers to a family of trademarked high strength austenitic nickel-chromium-iron alloys that have exceptional anti-corrosion and heat-resistance properties. These alloys contain high levels of nickel and can be thought of as super-stainless steels. Inconel alloys are used for a variety of extreme applications including navy boat exhaust ducts, submarine propulsion motors, undersea cable sheathing, heat exchanger tubing and gas turbine shroud rings. For many years, Inconel has been used for Formula One and Champ Car exhaust systems. More recently, several Winston Cup racing teams have utilized Inconel for producing ultra-light, highdurability exhaust headers. Burns Stainless recommends Inconel 625 alloy for exhaust systems due to its excellent strength, corrosion resistance and fabricability. This alloy also exhibits high creep and rupture strength; outstanding fatigue and thermalfatigue strength; as well as excellent weldability (though the guy welding it might have a different opinion!). Inconel 625 contains molybdenum and columbium, which stiffens and strengthens the nickelchromium matrix without precipitation hardening treatments. Some hardening however does occur when heated to intermediate temperatures (1200 F to 1600 F) increasing room temperature strength. Also, this alloy retains over 75% of its room temperature strength at 1200 F. This alloy is available in a wide variety of forms including tubing, sheet, bar, plates and castings. Burns Stainless typically stocks welded and drawn Inconel 625 tubing. The tubing specification is SAE AMS 5581, Nickel Alloy, Corrosion and Heat Resistant, Seamless or Welded Tubing. Inconel 625 can be welded using conventional stainless steel TIG welding techniques. Inconel Filler Metal 625 rod is used to weld Inconel to Inconel as well as to dissimilar metals including stainless steel. Inconel weldments are high strength and are highly resistant to corrosion and Typical Formula 1 Inconel Headers oxidation. Many welders describe welding Inconel as "dirty". In other words, the weld pool appears to be under a "skin" and is not well defined. In addition, the weld pool is somewhat "sluggish" as compared with steel or stainless steel. These characteristics tend to result in a "coarse" appearing weldment as compared to stainless steel. Welding Inconel is not necessarily more difficult to weld than stainless, just different. By following the welding procedures outlined in the header construction tips article on burnsstainless.com, successful welds with Inconel 625 are possible. A BMW F1 engine lights up its Inconel pipes Formula 1 Ferrari Inconel periscope Burns Stainless LLC 949.631.5120 Monday - Friday 7:30 am to 4:30 pm fax 949.631.3184 burnsstainless.com 27
Page 3 and 4: Due to increasing materials costs,
Page 5 and 6: Surcharge may apply 304 Stainless S
Page 11 and 12: Surcharge may apply 6061 Aluminum U
Page 13 and 14: Surcharge may apply Inconel Tubing
Page 15 and 16: Surcharge may apply Base Merge Coll
Page 17 and 18: Surcharge may apply Transitions and
Page 19 and 20: Surcharge may apply DynoSYS TM and
Page 21 and 22: Surcharge may apply Flat-band Clamp
Page 23 and 24: Turbo Inlet, Downpipe and Wastegate
Page 25 and 26: Surcharge may apply UltraLight Stai
Page 27: Stainless Steel Stainless steel is
Page 31 and 32: variety of applications including p
Page 33 and 34: Reference Tables Fraction to Decima
Page 35 and 36: Burns Stainless Caps, T-shirts, and

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