| Tensile properties and fracture behavior of AISI 4340 steel have been measured as a function of tempering temperature from 200℃ to 600℃ and measured direction. The tensile and yield strengths, and the hardness of specimens decreased with increasing tempering temperature and these did not vary much with test direction, whereas the ductility and toughness increased with tempering temperature. The reduction ratio in rolling direction had the higher value compared with that in transverse direction, the charpy impact value and the fracture toughness increased with increasing tempering temperature, the properties in the rolling direction were superior to those in the transverse direction, and the relation between K_(IC) and CVN values showed (K_(IC)/σ ys)² = 0.382 (CVN/σ ys+0.01) in the rolling direction and (K_(IC)/σ ys)²= 0.582 (CVN/σ ys-0.000054) in the transverse direction. |
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