With strength steel you sacrifice ductility. Does any one know the yield of Hi-ten, Chromoly, and 531. Here is some stuff posted frome here
http://www.bikeforums.net/showthread...eeds.../page56
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Steel Alloys
Steel is a combination (an alloy) of iron and other elements designed to improve upon the material properties of pure iron. The alloying elements make up a small fraction of the material by weight (iron is 97% or more of most steel alloys) and don't significantly alter the density (weight) and stiffness of the material, but they can have a significant impact on the strength, weldablity, corrosion resistance and expense of the material.
While there are dozens of steel alloys, only a few are commonly used in bike construction and only two--high tensile and chromoly steel--are used in most mass produced bicycles today.
High-Tensile (Hi-Ten) Steel
High-tensile or carbon steel is a common and inexpensive alloy comprised of iron mixed with 0.2% to 2.0% carbon. (Of note, when iron is mixed with more than 2.1% carbon it is no longer "steel", it goes by the name "cast iron".)
High-tensile steel is an inexpensive but relatively weak alloy. Although it has essentially the same density as other steels, manufacturers working with hi-ten steel are forced to use thick walled tubes to ensure adequate strength, and rarely use butting. For this reason, high-tensile frames are much heavier than their chromoly counterparts.
Today, high-tensile steel frames are primarily used for children's bikes and are sometimes found on inexpensive adult bikes.
4130 ChroMoly (CRMO) Steel
ChroMoly is a steel alloy composed of iron combined with chromium (roughly 1% by weight), molybdenum (roughly 0.2%), carbon (roughly 0.3%), silicon (roughly 0.2%), manganese (roughly 0.04%) and sulphur (roughly 0.04%). 4130 is actually just one of a family of chromoly alloys, but it is the one used for bicycle frames. ChroMoly steel is also used in the construction of airplanes, and is sometimes known as "aircraft tubing".
Chromium is the component that makes stainless steel rust proof, but the chromium level of chromoly steel is not high enough to provide corrosion resistance. (Stainless steel is 10% to 11% chromium.)
Chromoly is frequently used to build mid-to-high-range steel framed bikes. A well made butted chromoly frame is typically only marginally heavier than an aluminum frame, and quite strong and durable.
Reynolds Steel
In 1953 the Reynolds Cycle Company began manufacturing a steel tube composed of proprietary manganese-molybdenum steel alloy they branded Reynolds 531. This alloy was strong and for its time, relatively light. It was once the preferred tubing for steel racing bikes (as well as British aircraft).
Over the years, Reynolds has introduced a number of branded steel tubes, the brand name indicating both the specific alloy and heat treatment but also the wall thickness and butting of the tubes. These include Reyolds 453 (a single-butted tube made of a manganese-titanium alloy), Reynolds 501, 520, 525 and 725 tubes (using 4130 chromoly steel), Reynolds 753 (high-end tubes made of a manganese-molybdenum alloy, essentially a better Reynolds 531), Reynolds 853 (4130 chromoly made stiffer by air hardening) and Reynolds 953 (a lightweight rust-proof maraging stainless steel introduced in 2006).
Reynolds steel is less common in bike frames today than it once was, but some of these alloys are still in use. The Reynolds 520 family is a well made class of 4130 chromoly tubes. You'll pay a bit more for the brand name, but you'll know you're getting a well manufactured tube. Reynolds 853 is a higher quality chromoly, made stiffer than usual by the way it is manufactured. Reynolds 953 is perhaps the best steel available for bikes today: Reynolds 953 frames are stronger than titanium, no heavier than high end aluminum and rust proof.