Singlespeed & Fixed Gear - what exactly is cro-moly?

What I mean is, is all steel tubing considered cro moly? I know there are different variations in steel tubing and all that, I'm just wondering if a bike frame says, "Dedacciai cro-moly" what exactly is that saying? it's saying it's a dedacciai steel tube set right? is there a difference between the description "columbus steel tubes" or "columbus cro-moly tubes"?

good question. what is the alchemy we (many of us) hold to such standard as if it were crafted from the anvil and hammar of Thor?

yeah....like, is the term "steel tube set" the same as "cro-moly tube set"? are the two terms interchangable, or is a "steel tube set" different than "cro-moly"?

certain types of steel feature chromium and molybdinum [sp?!] [cro-mo] for their metalurgical properties. but not all steels are cro-mo.

fssb
sparky

Well cro-mo is tubing that the primary alloying componets are chromium and molybendium. Variations in "steel tubing" are percentages of whatever alloying componets make up the tube itself, and whatever treating properties if any are used, wall thickness, butting, etc. All these things, and variations are what makes the finished frame feel the way it does.

Steel alloys range all over the map. You have carbon steels, Chromium steels, Ni-Cr steels, Manganese steels, Cr-Moly steels, Ni-Moly steels. Of course these only descibe the primary alloying agents. Many alloys include lesser agents. The blending of these determine the eventual properties of the material. A popular bicycle cro-moly steel 4130. It is a low-carbon steel with 0.30% carbon. This makes it weldable. Anymore carbon and the steel becomes a pain to weld. It has a normalised tensile strength somewhere in the lower 90Ksi range which can be doubled when heat-treated. In the normalised condition, it's relatively tough and has good elongation properties which makes it great for bicycle applications because the tensile strength is adequate and the elongation allows the material to soak bending forces without cracking.

cool...thanks for all the replies. so when I see "tubing options" on a custom frame builder's web site and he's offering Columbus Thron tubing, is the "Thron" just a certain type of cromoly steel, or is it something all together different than cromoly?

cool...thanks for all the replies. so when I see "tubing options" on a custom frame builder's web site and he's offering Columbus Thron tubing, is the "Thron" just a certain type of cromoly steel, or is it something all together different than cromoly?

Tubing brands do something other than just draw a tube of steel. They'll shape the tubing or play other manufacturing tricks such as butting to tweak the properties and thus the ride qualities.

Thanks people. This has been informative.

Chro-moly is the actual metal a tube is made from. Thron is bascially the shape of the tubes. ie A set of Thron tubes might have certain diameters, lengths and butt lengths (a butt is where the wall gets thinner or thicker, butt length is how long the thick part is before it gets thinner), and maybe even different tube shapes (aero shapes etc).

Where to heck is Thylacine (sorry if I got it wrong, Bro) when you need his knowledge. Speak up, make us smart!

Sorry, I was just eating lunch AKA daydreaming about Karstens recently placed order for a fixie...but anyway, i digress.

Yeah, Cro-Mo is just a type of steel alloyed with some Chromium and Molybdenum. I have no idea how to spell that stupid word, so please forgive me. Also, I ain't no metalurgist, so if I'm wrong....too bad. :P

All tubing companies have their own alloys in which they draw into tubes. The lower end stuff is some form of 4130 or 25CrMo4 alloy, the mid range stuff is usually some form of micro-alloy where they throw in other alloying elements like Vanadium and Niobium into the mix to improve the grain structure or the metals reaction to heating, and the high end stuff is usually some crap that actually gets stronger in the heat affected zones. How they do that is anyones guess....maybe ask an metalurgist.

The true secret of Chro-Moly is that it captures the essence of certain minor deities in the process of forming tubing, and as such steel frames can sometimes border on divine. This is more pronounced with certain steel frames (*cough*Colnago*cough*), but generally exists to some extent in most decent steel frames. I sh*t you not...