You raise a good point in a way, but there is more to it. Heat treating is one way to change the mechanical properties of a tube. Heat treating can increase properties like yield strength or, in the case of annealing, decrease them. There are other properties, like fracture toughness that run generally counter to yield strength. Another method of changing the mechanical properties is cold working. Cold working occurs during all the drawing and shaping processes. Some of these processes may require annealling or the material will be over wrought. The degree to which a given amount of cold working changes the properties is very alloy specific although, in the case of steel, it is probably mostly driven by the carbon content. Work hardening increases strength by pinning distortions in the crystal lattice structure called dislocations.
Heat treated tubes, like 753, refers to tubes that are treated after all the drawing processes, not during. In that case the tube mechanical properties are not primarily derived from the drawing process. This type of heat treating creates a different phase of alloy with higher strength.
So to get back to bikes, the properties of 531 and 971 tubes, which are not heat treated after drawing, could vary considerably based on differences in the alloys and drawing processes.
I should also say that my original comment about the ease of straightening Motobecane forks also should have reflected the effect of the soft and non too robust crowns on these forks.
By the way- I never was a metallurgist and I am even a little hesitant to call myself an engineer these days.
At 09:05 AM 11/11/00 -0500, Jerry & Liz Moos wrote:
>Joe, perhaps you remember your engineering materials courses better than I, but
>I think yield strength is a term properly applied to the material, not the the
>tubes made from it. Doubt that two high quality non-heat treated alloy steels
>like 531 and Vitus 971 would vary much in yield strength. It may be though,
>that Vitus had thinner walls than 531 forks, resulting in the easier bending.
>Maybe that is why Rivendell uses Vitus frame tubes but as for as I know, uses
>only Reynolds forks. I'd think the curreent Vitus tubes are different fom 971,
>but maybe they still make forks too light.
>Joseph Bender-Zanoni wrote:
>> Vitus would even seem to be less favored by the French manufacturers.
>> Reynolds was favored which says a lot given the French preference for
>> things French. When I sold a lot of Motobecanes, about a third of the high
>> end bikes would have misaligned forks (bent back) (they had the flimsiest
>> boxes in the business). Straightening these Vitus forks would be all too
>> easy. I liked the ride of these bikes but I tended to sell them to lighter
>> built riders.
>> To put it in my usual engineering terms, I do not think Vitus tubes
>> achieved the yield strength of competitive tubes.
>> At 11:03 PM 11/10/00 -0500, Russ Fitzgerald wrote:
>> >If memory serves me, Rivendell still uses some Vitus tubes in some frames.
>> >They are apparently still around, still using steel.
>> >I know it was available at least as early as 1973, as it was used on the
>> >repair of a frameset that was rebuilt that year with Vitus for top and seat
>> >My perception is that the better Vitus stuff was as good as anything
>> >Reynolds made - but like all things French, it was vastly under-rated.
>> >Russ Fitzgerald
>> >Greenwood SC