Study of Quench Cracking of a High Carbon and Chromium Steel Bar : 1st Report, Effects of Austenitizing Temperature and Properties of Polymer Quenchant on Quench Cracking

Abstract

Ouench cracking is generally considered to occur under thermal and transformational stresses. In this paper, some of the quench effects on cracks (fin and/or vertical), hardness and residual stresses of a SUJ 2 bar were examined by using polyalkylene glycol (PAG) solutions. The fin crack by water quenching occurred in all specimens at the austenitizing temperatures higher than 800°C. Similarly, the vertical crack occurred in all specimens at higher than 900°C. The increase in PAG polymer concentration results in the decrease of a fin crack and increase of a vertical crack. The PAG quenchant temperature is closely related to the fin crack, because of the clouding points of PAG solutions. The residual stresses caused by quenching were mearured by the X-ray diffraction method. A considerable tensile stress existed on the surface area of all specimens.