Abstract
Fracture process of band-type spalling which often occurs on the barrel surface of cold rolling work rolls, is known to be controlled by the fracture toughness KIC of the roll steel in many cases. In order to study the factors improving the KIC value, fracture toughness tests were carried out on the test pieces which were taken from the actual roll of 0.85%C-3%Cr steel, and were quenched and tempered in several conditions.
The main results obtained are as follows:
(1) KIC values were highly dependent on the hardness. In the same hardness level, the higher the austenitizing temperature was, the higher the KIC value became, and as for the subzero treatment, non-subzero steel gave higher KIC values.
(2) In comparison between fully quenched steel and slack quenched steel containing some lower bainite in its structure, the latter gave higher KIC values.
