INFLUENCE OF TEMPERING, PRESTRAINING, AND RETEMPERING ON THE STRENGTH AND TOUGHNESS OF HIGH-STRENGTH 4340 STEEL
ARMY MATERIALS AND MECHANICS RESEARCH CENTER WATERTOWN MA
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The influence of tempering, prestraining, and retempering on the strength and toughness of martensitic and bainitic 4340 steel rods was investigated. The initial heat treatment consisted of a quench and temper to obtain martensite in one group and formation of bainite at 575 F followed by tempering in the second group. Reductions of area of 4 to 5 percent were effected by cold drawing through a die with and without backpull, followed by a retempering treatment. Ultimate tensile strengths approaching 385,000 psi for the martensitic structure and 283,000 psi for the bainitic structure resulted with yield-tensile strength ratios approaching unity. Notch tensile strength of the bainite was superior to that of martensite at comparable strength levels. The prestraining also caused a yield point drop andor serrations in the flow curves. This was influenced by specimen test temperature and strain rate, tempering temperature, and retermpering temperature.
- Metallurgy and Metallography
- Fabrication Metallurgy