Method of manufacture of a fixing member 1 shows an axial half cross section of smaller diameter by cold forging a steel wire drawn a strong hardening by work-hardening

摘要

Threaded fastener is produced from a highly work hardenable steel wire rod by rough drawing, regeneration heat treatment, finish drawing and cold forging. Production of a threaded fastener, by cold forging drawn wire of less than 4.5 mm diameter (Df) formed from highly work hardenable steel wire rod, comprises: (a) drawing the wire rod to obtain a wire blank of diameter (De) equal to 1.12 to 1.29 * Df; (b) austenitizing and then cooling to below 100 deg C; (c) drawing to diameter Df; and (d) cold forging and optionally surface coating. Preferred Features: The steel is a two-phase steel of composition (by wt.) (i) 0.02-0.15% C, 1.4-2% Mn, 0.7-1.3% Si, balance Fe and impurities (ferritic matrix containing 7-25 vol.% martensite + residual austenite islands); or (ii) 0.15-0.25% C, 0.8-1.3% Mn, = 0.005% B, balance Fe and impurities (ferritic-pearlitic structure).