New, Cold Formable Fe/Al/C Dual Phase Steels

摘要

Alloy design programs in dual phase low carbon steels have been carried out at Berkeley during the past ten years. In the present work attention has been paid to adapting their physical metallurgy to batch plant processing conditions. The alloys are based on ferritic-martensitic low carbon steels containing aluminum, but without manganese or microalloying elements. The two-phase mixture rule provides a fairly good approximation of the mechanical behavior of these duplex systems, but it has been recognized that the properties of both the ferrite and martensite depend on the volume fraction of martensite produced in the final morphology. Thus ferrite strengthening can be effected by precipitation hardening, and the strength of martensite may increase due to carbon enrichment as its volume fraction is decreased. Utilization of both of these factors results in a composite whose properties do not depend very much upon the martensite volume fraction (up to about 0.4). This allows greater flexibility in heat treatment, and thus suggests that dual phase steel can be produced by batch processing without requiring strict temperature control to achieve consistent properties. In each case a desirable tensile to yield strength ratio is maintained for cold forming characteristics, e.g., for applications in sheet, wire rod, etc. 12 figs. (ERA citation 11:003174)