Kinetics of Shape Control of Alumina Inclusions with Calcium Treatment in Line Pipe Steel for Sour Service

The rate of shape control of alumina inclusions with calcium in line pipe steel for sour service is determined by a 30 kg high frequency induction furnace. The shape control of alumina inclusions proceeds with the increase in time after calcium addition. The degree of shape control is increased with the increase of stirring energy supplied and the decrease of the time from aluminum addition to calcium addition. Applying the unreacted core model to experimental results, the rate determining step in the shape control of alumina inclusions is believed to be calcium diffusion in the calcium-aluminate product layer.