George@R.A.I
10-28-2009, 11:31 AM
Materials Overview
Below is an overview of the two most common materials used in the fabricating industry. I would like this to help educate those who are not hardcore fabricators or materials scientists. In the near future I will also be posting up some information regarding common polymers and compomsites used in the industry. Most of this information is courtesy of Burns Stainless.
Stainless Steel
Widely used throughout the racing community, stainless steel is an iron based alloy that contains a minimum of 12% chromium. It is superior to mild steel in all engineering facets. Stainless Steel has a much lower carbon content than mild steel. A certain amount of carbon is needed to maintain harness levels at elevated temperatures. However, as a general rule of thumb, the lower the carbon content, the more resistant the material is to various types of corrosion. Stainless steel comes in a multitude of varieties. Within the racing community, the 300 series is what is most commonly used. Below is breakdown of the different types of 300 series SS:
-321 and 347 are known as stabilized grades of stainless. These are alloyed with either titanium (321) or columbium (347). 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 a horrible environment.
-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.
Stainless steels come in both tubing and pipe sizes. Since certain pipe sizes are almost identical in dimension to tubing sizes, pipe may sometimes be substituted for tubing, and vice versa.
There are as many uses for stainless steel as there are projects in the shop. Whether it is 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.
Aluminum
Aluminum is widely used throughout the race industry to make everything from intake manifolds to gauge panels to engine blocks. The properties of aluminum that make it so attractive to racers include light weight, strength, ease of fabricating and corrosion resistance. Aluminum is approximately 1/3 the weight of steel, yet some aluminum alloys exhibit tensile and yeild strengths greater than some low carbon steels.
Many alloys can be heat treated to improve strength properties. Aluminum is available in many wrought forms such as tubing, extruded shapes, sheet and bar. Aluminum can also be cast using a variety of foundry methods using moderate strength heat treatable alloys. Forging can also be used to form aluminum. This material can be fastened with rivets, bolts, or welding. Welded fabrications can also be heat treated.
Wrought aluminum alloys are designated using a four-digit system, with the first digit specifying the alloying element. The following table lists the major series including the alloying elements and general uses for each series.
Some of the most common aluminum alloys used by racing fabricators include 3003, 2024, 6061 and 7075.
-3003 is a non-heat-treatable wrought-alloy, which has excellent workability and weldability and is used for low-strength applications including tanks, boxes and brackets.
-2024 is a heat-treatable, high-strength alloy with limited formability and is not weldable. It is an excellent choice for chassis skins and spars and for flywheels. 7075 is heat-treatable and the strongest and stiffest of the commonly available aluminum alloys. Due to its strength, it is not readily formable and lends itself to be used for machined components and straight suspension pieces. 7075 also has poor welding characteristics.
-6061 is the least expensive and most versatile of the heat-treatable alloys. It is a favorite alloy of many fabricators as it is a weldable alloy with moderate to high strength in tempered condition. It also has good formability in the annealed condition. It is the best choice for intake manifold and inter-cooler plumbing due to the weldability and formability of the alloy.
Below is an overview of the two most common materials used in the fabricating industry. I would like this to help educate those who are not hardcore fabricators or materials scientists. In the near future I will also be posting up some information regarding common polymers and compomsites used in the industry. Most of this information is courtesy of Burns Stainless.
Stainless Steel
Widely used throughout the racing community, stainless steel is an iron based alloy that contains a minimum of 12% chromium. It is superior to mild steel in all engineering facets. Stainless Steel has a much lower carbon content than mild steel. A certain amount of carbon is needed to maintain harness levels at elevated temperatures. However, as a general rule of thumb, the lower the carbon content, the more resistant the material is to various types of corrosion. Stainless steel comes in a multitude of varieties. Within the racing community, the 300 series is what is most commonly used. Below is breakdown of the different types of 300 series SS:
-321 and 347 are known as stabilized grades of stainless. These are alloyed with either titanium (321) or columbium (347). 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 a horrible environment.
-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.
Stainless steels come in both tubing and pipe sizes. Since certain pipe sizes are almost identical in dimension to tubing sizes, pipe may sometimes be substituted for tubing, and vice versa.
There are as many uses for stainless steel as there are projects in the shop. Whether it is 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.
Aluminum
Aluminum is widely used throughout the race industry to make everything from intake manifolds to gauge panels to engine blocks. The properties of aluminum that make it so attractive to racers include light weight, strength, ease of fabricating and corrosion resistance. Aluminum is approximately 1/3 the weight of steel, yet some aluminum alloys exhibit tensile and yeild strengths greater than some low carbon steels.
Many alloys can be heat treated to improve strength properties. Aluminum is available in many wrought forms such as tubing, extruded shapes, sheet and bar. Aluminum can also be cast using a variety of foundry methods using moderate strength heat treatable alloys. Forging can also be used to form aluminum. This material can be fastened with rivets, bolts, or welding. Welded fabrications can also be heat treated.
Wrought aluminum alloys are designated using a four-digit system, with the first digit specifying the alloying element. The following table lists the major series including the alloying elements and general uses for each series.
Some of the most common aluminum alloys used by racing fabricators include 3003, 2024, 6061 and 7075.
-3003 is a non-heat-treatable wrought-alloy, which has excellent workability and weldability and is used for low-strength applications including tanks, boxes and brackets.
-2024 is a heat-treatable, high-strength alloy with limited formability and is not weldable. It is an excellent choice for chassis skins and spars and for flywheels. 7075 is heat-treatable and the strongest and stiffest of the commonly available aluminum alloys. Due to its strength, it is not readily formable and lends itself to be used for machined components and straight suspension pieces. 7075 also has poor welding characteristics.
-6061 is the least expensive and most versatile of the heat-treatable alloys. It is a favorite alloy of many fabricators as it is a weldable alloy with moderate to high strength in tempered condition. It also has good formability in the annealed condition. It is the best choice for intake manifold and inter-cooler plumbing due to the weldability and formability of the alloy.