Notes on Roll Failures with Reference to Chilled Iron Cast Rolls Containing Chromium and Molybdenum

Abstract

The details of some remarkable fractures of chromium-molybdenum rolls are given in this paper, and they are compared with the fractures usually associated with ordinary chilled iron rolls. Some interesting and informative foundry experiments with chromium-molybdenum rolls are described and illustrated by photographs.

The probable causes of fracture of the chromium-molybdenum rolls are discussed in the light of the quality and structure of the iron, the design of the rolls, and the effect of thermal stress. It is suggested that the causes of failure were (1) low strength of the iron, resulting from excess of chromium, (2) the defective design of the roll wobbler, and (3) the thermal stresses set up in the rolls during service. Detailed consideration is given to the effect of the wobbler design in preventing the free contraction of the roll after casting. It is suggested that the interference set up had produced definite planes of weakness in the rolls.

Particulars of an unusually long life of an ordinary chilled iron roll are given together with a comprehensive analysis of the iron in this roll.