Abstract: A method is provided for preventing cracking along the surface at the inner hole of a hollow shaft during water quenching, including: a step of water-quenching the inner hole of the shaft placed horizontally, while the outer circle of the shaft is in a state of air cooling, in which the cooling time of the outer circle is selected to be not lower than its Ar1 temperature so as to induce a compressive stress in the surface layer of the inner hole; and a step of water-quenching the outer circle and the inner hole of the shaft simultaneously, moreover, the quenching intensity of the inner hole is gradually reduced to cause a temperature rise in the surface layer of the inner hole to allow martensite in the surface layer to undergo self-tempering, which prevents the formation of quenching cracks along the surface of the inner hole.

Abstract: The invention provides a method for preventing cracking along the surface at the inner hole of a hollow shaft during horizontal water quenching, including: step 1: transferring the shaft from heating furnace to quenching equipment; step 2: cooling the inner hole of the shaft, while the outer circle of the shaft is in the state of air cooling, and the cooling time on the outer circle is designed based on the temperature of the shaft being not lower than its A1 temperature, therefore, the compressive stress is formed at the surface layer of the inner hole, and small tensile stress is formed at the sub-surface layer; and step 3: cooling the outer circle and the inner hole of the shaft at the same time, wherein during the cooling, the cooling intensity of the inner hole is adjusted to gradually reduce so that sub-surface layer of the inner hole still exhibits low tensile stress while martensite formed in the surface layer experiences self-tempering, which effectively prevent the formation of quenching cracks alon