Why is Titanium so special for exhaust?
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Joined: Jun 2001
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From: Ottawa
About the welding point: Titanium is as hard if not harder to weld than aluminium. Plus stainless steel is also a "B*tch" to weld.
Strength to weight:
Aluminium and Steel have an equivalent strength to weight (density) ratio (strength - elasticity / Young's Modulus), Aluminium has the advantage that it can achieve the same structural strength in a pipe for example by using a larger diameter, where as steel meets the limit of its weldable wall thickness trying to achieve the same size pipe at the same weight.
Titanium comes in multiple grades, for 'high performance' applications only the correct grade should be used. One of the most common high grade titanium's is an alloy with aluminium and vanadium. So on and So forth.
If you have made it this far through this awfully arranged reply try this link and it may give you a quick answer:
http://titanium.net/GIsec2b.htm
NS2000X
Strength to weight:
Aluminium and Steel have an equivalent strength to weight (density) ratio (strength - elasticity / Young's Modulus), Aluminium has the advantage that it can achieve the same structural strength in a pipe for example by using a larger diameter, where as steel meets the limit of its weldable wall thickness trying to achieve the same size pipe at the same weight.
Titanium comes in multiple grades, for 'high performance' applications only the correct grade should be used. One of the most common high grade titanium's is an alloy with aluminium and vanadium. So on and So forth.
If you have made it this far through this awfully arranged reply try this link and it may give you a quick answer:
http://titanium.net/GIsec2b.htm
NS2000X
Joined: Dec 2000
Posts: 4,307
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From: Ogden
Titanium is preferred as it is lighter in weight and resistant to corrosion. Aluminum is not preferred due to it's high coefficient of expansion (Delta "L"=L x Alpha x Delta T). Coefficient of linear expansion for aluminum is 26 X 10-6. So if the exhaust (~12 ft)temperature were raised by 200 degrees the pipe would grow 3/4 of an inch". The corossion noted here is known as galvanic corrosion. It occurs between dissimilar metals. Metals are grouped into 4 types based on this affinity. You cannot put them in intimate contact without some form of protection. For instance zinc chromate is used to install steel inserts into aluminum heads. It has to due with the affinity of certain metals to borrow electrons. The previous poster is on the right track as the copper with two positive charges (i.e. Cu++) will "loan" an electron to the aluminum (AL-). As for welding, if you know what your doing they all weld quite well but have different problem statements and thus different welding methods and pre-weld treatments. Titanium grains expand when welded which allows for easier fill when you are "hanging a bead" on a tube. Aluminum is easy to weld as long as you remove the aluminum oxide layer from the aluminum. Aluminum oxide melts at a much hogher tempertaure the "virgin" aluminum. Stainless can be difficult unless you use the proper technique and weld rod matched to the application. And lastly....Ti just looks plain cool when the colors come on with age.
Utah
Utah
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Joined: Feb 2001
Posts: 202
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From: Dallas
Originally posted by Utah S2K
Titanium is preferred as it is lighter in weight and resistant to corrosion. Aluminum is not preferred due to it's high coefficient of expansion (Delta "L"=L x Alpha x Delta T). Coefficient of linear expansion for aluminum is 26 X 10-6. So if the exhaust (~12 ft)temperature were raised by 200 degrees the pipe would grow 3/4 of an inch". The corossion noted here is known as galvanic corrosion. It occurs between dissimilar metals. Metals are grouped into 4 types based on this affinity. You cannot put them in intimate contact without some form of protection. For instance zinc chromate is used to install steel inserts into aluminum heads. It has to due with the affinity of certain metals to borrow electrons. The previous poster is on the right track as the copper with two positive charges (i.e. Cu++) will "loan" an electron to the aluminum (AL-). As for welding, if you know what your doing they all weld quite well but have different problem statements and thus different welding methods and pre-weld treatments. Titanium grains expand when welded which allows for easier fill when you are "hanging a bead" on a tube. Aluminum is easy to weld as long as you remove the aluminum oxide layer from the aluminum. Aluminum oxide melts at a much hogher tempertaure the "virgin" aluminum. Stainless can be difficult unless you use the proper technique and weld rod matched to the application. And lastly....Ti just looks plain cool when the colors come on with age.
Utah
Titanium is preferred as it is lighter in weight and resistant to corrosion. Aluminum is not preferred due to it's high coefficient of expansion (Delta "L"=L x Alpha x Delta T). Coefficient of linear expansion for aluminum is 26 X 10-6. So if the exhaust (~12 ft)temperature were raised by 200 degrees the pipe would grow 3/4 of an inch". The corossion noted here is known as galvanic corrosion. It occurs between dissimilar metals. Metals are grouped into 4 types based on this affinity. You cannot put them in intimate contact without some form of protection. For instance zinc chromate is used to install steel inserts into aluminum heads. It has to due with the affinity of certain metals to borrow electrons. The previous poster is on the right track as the copper with two positive charges (i.e. Cu++) will "loan" an electron to the aluminum (AL-). As for welding, if you know what your doing they all weld quite well but have different problem statements and thus different welding methods and pre-weld treatments. Titanium grains expand when welded which allows for easier fill when you are "hanging a bead" on a tube. Aluminum is easy to weld as long as you remove the aluminum oxide layer from the aluminum. Aluminum oxide melts at a much hogher tempertaure the "virgin" aluminum. Stainless can be difficult unless you use the proper technique and weld rod matched to the application. And lastly....Ti just looks plain cool when the colors come on with age.
Utah
MAN!!!! I was just about to say EXACTLY that!
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Joined: Jan 2001
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From: Laurel
Ti is lighter and stronger but its main benefit is that it is now available. Virtually the entire production of Ti was used in defense applications until just a few years ago. Now the rest of us get to play with it. Oh, and it has a very high "cool factor".
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