Effect of repeated austenitisation and cooling on the microstructure, hardness and tensile behaviour of 0.16 WT % carbon steel

Abstract

Repeated austenitisation and furnace cooling of homogenised 0.16 wt. % carbon steels result in ferrite grain sizes between 27 μm and 24 μm. Similarly, repeated austenitisation and normal-air cooling produces ferrite grain sizes between 17 μm and 12 μm; while repeated austenitisation and forced-air cooling produces a minimum grain size of 9.5 μm. Furnace cooling decomposes the austenite eutectoidally to lamellar pearlite; while normal-air cooling and forced-air cooling after austenitisation cause degeneration of pearlite regions producing grain boundary network as well as cluster of cementite and other carbides. Forced-air cooled samples provide the highest YS (364 MPa) and UTS (520 MPa); while furnace cooling provides the lowest (290 MPa and 464 MPa) leaving the normal-air cool performance in between. Hardness values depict the role of individual ferrite and pearlite content and the extent of pearlite degeneration occurring after each cyclic treatment.