T4 is a special alloy steel, categorized as Tungsten high-speed tool steel, one of the standard group. Because of its hardness, high toughness and high thermal resistance, it is well suited for hot work applications involving very high loads. Typical applications are hot-work forging and extrusion dies, helicopter rotor blades, etc. For longer life and higher design accuracy, properties of this type of tool steel can be improved by various types of heat treatment. Tensile test specimens manufactured from tool steel using a standard format of American Association of Materials and Testing (ASTM) standard 1985 was adopted for the study. These samples were subjected to various heat treatment sequences, consisting of Annealing, Normalising, Hardening and Tempering at different temperatures. Heat treated samples were then mechanically tested for hardness tensile properties (yield strength, ultimate tensile strength and ductility (% elongation). Stress-strain graphs are plotted for each sample to extract tensile characteristics. The strain produced for each of the specimen was in the order of annealed > normalized > tempered > hardened as observed from figures 4.1 – 4.4 which gave a clear indication of the final
state of the materials as a result of the thermal treatment received.

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Categories: Volume 3 No 2