MECHANICAL PROPERTIES OF COLD-DRAWN MARTENSITIC SAE 4340 STEEL ROD.

In the cold drawing of steel rods, the processing conditions can have an appreciable effect on the mechanical properties. Processing variables were prior heat treatment, consisting of a quench and temper at 1150 F, 1000 F, 800 F, 500 F, or room temperature reduction 10 to 40 percent back pull 0 to 16,650 lb drawing speed 10 to 40 feet per minute and aging temperature room or 400 F. Final rod diameter was 0.409 inch. Engineering tensile, notch tensile, hardness, and true stress-true strain properties are presented. The maximum increase in engineering tensile and yield strengths was realized in the material pretempered at room temperature, drawn 10 percent and aged at 400 F. Yield and tensile strengths were increased from 222,000 psi to 368,000 psi and from 316,000 psi to 371,000 psi, respectively, with improved ductility. The primary effect of cold drawing, to strengthen by strain hardening, is dependent upon the pretempering temperature. An additional strengthening increment is due to aging at 400 F and appears to be essentially independent of the pretempering temperatures. Incomplete strain hardening based on the tensile stress-strain curve, appearances of a sharp yield point andor yield point drop for some processing conditions, and effects of the Bridgman correction on the flow curves were observed and are discussed. Author