Effect of preliminary heat treatment on the size of inclusions and the stable austenite grain size

Abstract

1. Preliminary high-temperature heat treatment can have a substantial effect on the tendency of austenite to grain growth. Rapid cooling of carbon steels with low concentrations of aluminum or titanium from 1200–1300°C leads to stable grains of smaller sizes and widening of the stable temperature range. Slow cooling has the opposite effect. Subsequent heating to 830–850°C does not affect the grain size. 2. It was shown that the tendency of austenite to grain growth and the stable grain size are connected with the size of the carbide and nitride inclusions in the steel. Treatments that reduce the size of the inclusions without changing their weight or volume in the steel lead to refinement of the grains during subsequent austenization. In carbon steel with 0.55% C and 0.03% Ti, in which the size of titanium carbide inclusions is 50–100 A, the stable austenite grain size reaches 5–6 μ.