Do you know the yield strength, factor of safety, and tensile strength for 4130 (chromoly) steel?

Answer 1

The basic components of 4130 cromoly steel are Chromium, Molybdenum, Manganese and Carbon. If made properly, and as long as a frame is not pushed beyond it's maximum yield, a 4130 cromoly frame can last a lifetime. Of special note; the Yield strength of "standard" cromoly is @760N\mm2 compared to a quality cold worked 3-2.5 Titanium's number of 792N\mm2. Steel is durable. Steel can also be comfortable and efficient. The reason that companies make springs out of steel is because the material can retain energy and expend it back. A steel frame doesn't absorb the force of a pedal stroke or the impact of a water bar, it stores it. The gathering of force is what makes a frame comfortable and it is the return of that energy that gives a steel frame its' lively feel.

OX Platinum air-hardened tubing was developed by True Temper along with the US Steel Alliance. It actually gains strength through a metallurgical transformation in the heat affected zone, the result of welding. It is composed of Chromium, Molybdenum and Vandium with 217 ksi ultimate tensile strength. It is highly temper-resistant, resulting in 11% increase in fatigue life and 20% increase in impact strength compared to other superlight chromoly tubes.

Answer 2

Factor of safety depends entirely upon the nature of the loading. Generally, the factor of safety would be the strength of the steel divided by the in-service stress. It is up to the engineer to decide if ultimate tensile strength, yield strength, or fatigue limits are appropriate for the numerator, and it is often difficult to accurately determine the stress for the denominator, especially in cyclic or variable loading conditions. A material does not have a "factor of safety" by itself. It is a function of the material properties, the design of the component, and the loading on the component.