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What is Scandium Sc7000?(4 posts)

What is Scandium Sc7000?Wannabe
Nov 2, 2001 8:09 AM
Okay, I know it's a lightweight material used in high end racing bikes and won Paris-Roubaix this year. What I really mean is what does it bring ride-quality-wise to a road bike? Is this an aluminum alloy?

Andy - Wannabe
re: What is Scandium Sc7000?DMoore
Nov 2, 2001 9:08 AM
Scandium is an element. A tubeset made by Easton with a tiny amount of Scandium in an aluminum alloy is marketed as Scandium 7000 tubing. Dedacciai markets a tubeset marked "SC61.10A" or something like that, and controversy rages as to whether or not that alloy actually contains Sc. Their marketing doesn't claim it, but in any event it too is a superlight Al alloy.

The Easton SC 7000 tubeset is marked by its externally butted tubes. The top tube and downtube are larger diameter for about 6" or so back from the headtube, and then are "necked down" (like a bottleneck rifle cartridge, if that means anything to the reader) for the rest of its length. The alleged benefit is that the SC alloy allows the tube to be stronger, and permits a smaller diameter tube to have the same strength as a larger diameter tube of a "lesser" alloy. AFAIK, the SC tubes are only available for the main triangle - seat stays and chain stays aren't available in SC 7000 and so are made of other Al alloys.

The claimed result is that the frame is a little lighter, and a little more compliant, than a frame made from large diameter Aluminum. Advertised weights for SC 7000 frames certainly are very low.

Some people swear by their SC frames; others swear at them. One racing friend has an Sc frame - it's superlight and he likes the ride. It has broken before, but at the chainstay joint with the b/b, so you can't blame that on the Sc tubing since neither the b/b shell nor the stay are made of that material.

I have to think that a bike that wins Paris-Roubaix has taken more pounding in that one day than most road bikes would endure in a lifetime. Merckx, Fuji, and several other framebuilders are making bikes with SC 7000.
It is an aluminum alloyvanzutas
Nov 2, 2001 9:17 AM
Scandium is alloyed with Aluminum at about .4%. It increases the yield strength of aluminum. The main alloying element in aluminum is magnesium . magnesium and zinc have high solubility in Aluminum so they can be present up to about 10%. 6061 Al has about 1% magnesium and 7005 has 1-1.8%. these elements increase the yield strength by forming interstitials that impede the deformation of the material. scandium is slightly different. it can only be present up to .5% in aluminum. Scandium is used as a grain refineing element. it causes the grains to be very small which increases the yield strength of the material. one source says that it can increase the yield strength by 40 to 50% in 6061 and 7005 alloys. I think that number is a little high. It is also reported to increase the weldability.

http://www.scandium.org/Sc-Al.html

http://www.wmlewisimports.com/QA/Scandium-RoadTest.htm

http://www.matweb.com/SpecificMaterial.asp?bassnum=MA6016&group=General
the road test link is from the distributor.vanzutas
Nov 2, 2001 11:08 AM
just a note that the link to wmlewisimports is the distributor of the frame that they "review" so the 40-50% strength number is from there. they have some more info on ride on that site. if that is more what you are interested in.

Keep in mind that the stiffness of a metal does not change signigicantly with the different alloys. ie 6061 and 7005 are about the same stiffness but the yield strength is different. this is the same with Iron alloys (steel)