YungBurke

Can someone sum up or post a link to the characterics of the different types of steel tubing? For instance what is the difference between 331 and 531 cro moly? is it just strength --> less metal --> less weight?

Scooper

I'll take a stab at it; perhaps others will offer corrections or more details.

Steel alloys have properties (strength, hardness, mallebility, weldability) that vary considerably depending on the composition of the alloy, heat treating, whether it's air hardening, etc.

There are SAE-AISI standard designations for alloys like 1020 carbon steel and 4130 Chromium Molybdenum (see https://www.materialsengineer.com/E-Alloying-Steels.htm), and there are manufacturer's designations like Reynolds' 531, 631, 753, 853, 953, and Columbus SL, SP, SLX, Life, Genius, MAX, Spirit, Zona, Brain, and XCr. Some alloys, like Reynolds 531, are Manganese Molybdenum rather than Chromium Molybdenum.

Some of the heat treated steels lose strength at the joints if the joints are heated too much during the joining process, while newer air hardening steels actually become stronger at the joints with higher heat. For this reason, frames built using heat treated steels like Reynolds 753 are usually built using lugs and silver brazing rather than welding, and air hardening steels like Reynolds 853 can be TIG welded without too much concern that the heat used in joining the tubes will weaken the steel.

All steels have roughly the same density and elasticity, but the strength of different alloys varies significantly. So, stronger alloys can have tubing with thinner walls which makes frames that weigh less. But because the thinner walls are more flexible (remember, all steels have the same modulus of elasticity), oversized tubes with larger diameters make up for the loss of stiffness inherent in the thinner walled tubes.

Most bicycle tubing today is "butted", which means the walls are thicker at the ends - where most of the stress is concentrated - than in the middle. Double-butted means both ends are thicker than the middle section, while single-butted means only one end is thicker. Typically, seat tubes are single-butted with the butted (thicker) end at the bottom bracket and the thinner end at the seatpost end.

Some lower end frames are built with plain, straight gauge carbon steel. Because carbon steels like 1020 don't have the strength of more sophisticated alloys, the tubes are not usually butted, and therefore the frames are heavier.

The tubing manufacuturers have websites that usually describe their tube sets, including the alloy used, lengths and outside diameters of the various tubes, and the butting profiles of the tubes, along with characteristics of the alloy like ultimate tensile strength.

Hope this helps.

YungBurke

To be more specific. My frame reads that it is composed of 331 Chrome-molybdenum tubing. Is there a place which lists all the characteristics of this tubing like how it was treated, alloy composition, etc.?

Scooper

Is there a tubing manufacturer's name anywhere? Who made the frame?

I think I recall someone mentioning they had a Fuji with 331 tubing, and the concensus was that it was probably Fuji's proprietary designation for their butted 4130 chromoly, but that was a while ago.

EDIT -

It appears "331" is a proprietary Fuji chromium molybdenum tubing.

1983 Fuji America catalog page. Note the frame material is "FUJI 331, double butted chrome molybdenum steel tubing with back stay, chain stay 7" C.P."

Based on the frame pricing in the 1983 catalog, it looks like 331 was second or third in terms of quality among the proprietary Fuji tube sets:

Top of the line

FUJI 9658 quadruple butted chrome molybdenum steel tubing
FUJI 331 double butted chrome molybdenum steel tubing
FUJI VALite 1769 quadruple butted steel tubing
FUJI 441 chrome molybdenum steel tubing
FUJI VALite 212 double butted steel tubing
FUJI VALite 414 butted steel tubing
FUJI 661 high tension steel tubing

Bottom of the line

YungBurke

mine is a similar vintage (82) fuji Team so probably the same tubing

NoReg

Fine sumary.


"Some of the heat treated steels lose strength at the joints if the joints are heated too much during the joining process"

Though this should be dealt with by the fact the tubing is thicker at the butts.

", while newer air hardening steels actually become stronger at the joints with higher heat."

Though the degrees to which this is true is not praticularly controlable and just a characteristic of the kind of steel used. The main advantage is that any hardness in this kind of steel isn't drawn by heating, not that it gains some degree of strength from random heat exposure

"For this reason, frames built using heat treated steels like Reynolds 753 are usually built using lugs and silver brazing rather than welding,"

I'm not familiar with these steels but if they are heat treated the hardness will be drawn by heating them to the degree required by either process mentioned, and heat treating the whole frame would be done at elevated temps that could even flow the brass. We are talking unifrom cherry heat here. Though brass is harder to flow on the reheat. Hey if they are doing this stuff, more power to them.

"and air hardening steels like Reynolds 853 can be TIG welded without too much concern that the heat used in joining the tubes will weaken the steel."

Again, not really a concern. People are just reading the tech and saying because something happens, that in some context is positive it has to be key here also. There isn't any problem with TIG on any chromo.

Scooper

It looks like they went to the quad butted FUJI 9658 for the '83 Fuji Team.

1983 FUJI Team catalog page

Scooper

Thanks, Peterpan..

YungBurke

interesting, my bike looks almost exactly like that but it seems they used different tubing for that next year, and I have got what must be an aftermarket bontrager/ rocket crankset with 48t

DannoXYZ 

https://www.matweb.com