Many efforts have been made to improve open-hearth and Bessemer steels, with the view to having them approach crucible steel in quality without having its high cost of production.

One of the methods used for improving open-hearth steel is known as the Whitworth process of fluid compression. This consists of applying to a mass of molten steel which has been poured from the ladle into a suitably shaped mould, a pressure varying from 2500 to 4000 lbs. per square inch.

This process is of benefit because the reliability of steel is increased if (1) the density of the mass is increased, and (2) if the mass is made homogeneous, i. e., the composition is the same throughout the mass. It is unlikely that this process increases the density of the steel itself, but it does decrease greatly the size of the gas bubbles in the steel, and compresses the particles of slag into compact masses. Piping is lessened but not prevented by this process, and possibly segregation is lessened. The steel under pressure is longer in solidifying, which gives the gas, slag, and oxides more time to rise into the discarded part of the ingot.