Originally Posted by
Bonzo Banana
I didn't think that was true because the older weaker cheap high tensile steel frames with low carbon were exceptionally easy to weld and could be welded by anyone with basic equipment but these newer high carbon steel frames are harder to weld and need better equipment. The way I read it is many of the smaller bicycle factories which weld themselves are still welding low carbon (easy welding) high tensile tubes for their frames but new improved processes allow for welding high carbon steel frames with heat treatment to enable a cheap not too brittle frame of decent tensile strength. I didn't think 1010 to 1018 were considered high carbon steels which are the steels used for more basic high tensile bike frames of the past I thought they were low carbon steels. 1045 is classed a medium carbon steel and beyond that perhaps somewhere around 1065 we have high carbon steels. So I wouldn't of thought they were the same. I think there has been some movement in manufacturing towards using high carbon steel in bicycle frames thanks to new welding equipment and processes. Weight of steel frames has been dropping for these cheap steel frames and they are much more competitive in weight now.
Carbon content in steel runs from .1% to 3%. There is no set "medium carbon steel".
Hi-ten is easy to work with because it is thick and isn't heat treated. The steels that are difficult to work with have very thin walls and special heat treatments to make that okay. They need to be welded/brazed with more care because they are thin and can only take so much heating.
Difficulty goes along with thinness. If you had really thin low carbon tubing you'd still need to be careful - its just that you can't make cheap alloys too thin.
I'd get the carbon content thing out of your head. The air hardening steels have a lot of carbon, and are less susceptible to overheating than some lower carbon steels.