Abstract
Taps are subjected to high cutting torque in the tapping process.Therefore, higher toughness and shear strength are strongly required as materials for taps.However, the shear strength of high-speed steel (SKH51) after secondary hardened was about 40% of bending strength and the tensile strength was 64% of bending strength. As for the fracture aspects, ductile fracture occurred under torsion.On the other hand, the tensile and bending specimens were damaged by carbide cracks and debondings in the interface of matrix and carbide. In this investigation, the fracture mechanisms were examined from the SEM microstructures.
