This is one of those situations where the bike industry terms don't accurately reflect the steel industry or metallurgical terminology. The same thing happens with knives because consumers don't really know what they are reading.

"Steel" is a term that means and alloy primarily of iron - usually with at least carbon (but not always). Chrome and molybdenum are common alloying elements in tools steels which make machining, forming, welding or heat treating easier. One of the most famous bike steels was 531, which was a manganese molybdenum steel instead of chrome. You could make a bike out of basic carbon steel, but forming tubes and joining them would be far more challenging. That's why low alloy hi-ten steel is "heavy" - since it doesn't have the nicer qualities of the better alloys it is produced with thicker tube walls to have similar strength to the tool steels.

There are essentially six types of steel used in bike frames today. Hi-ten, tool steels, heat treated tool steels, air hardening steels, stainless steel and precipitation hardening stainless steels.

As steels get more expensive they get stronger and more able to be flexed without fracturing or bending - despite welding or brazing temps. So they can be made with thinner tube walls and therefore lighter.


I would avoid trying to extract too much about metallurgy from the ad copy of a bicycle company. They aren't trying to deceive, but they are avoiding presenting confusing technical details.