Vacuum degassing of molten steel prior to casting is a process that has received increasing attention in recent years. Its advantages have been brought to the attention of steel users, but much less has been said about the problems that may be encountered when this process is used. One of the strong incentives for exploring the feasibility of vacuum degassing processes was the elimination of hydrogen from the steel to be used in heavy-forging stock. The presence of hydrogen in such steels may cause flakes and shatter cracks to form in heavy sections, and, under cyclic service stresses, the cracks...
Vacuum degassing of molten steel prior to casting is a process that has received increasing attention in recent years. Its advantages have been brought to the attention of steel users, but much less has been said about the problems that may be encountered when this process is used. One of the strong incentives for exploring the feasibility of vacuum degassing processes was the elimination of hydrogen from the steel to be used in heavy-forging stock. The presence of hydrogen in such steels may cause flakes and shatter cracks to form in heavy sections, and, under cyclic service stresses, the cracks may grow by a fatigue mechanism and result in the catastrophic failure of such items as generator and turbine rotors. Also, vacuum-melted steels have exhibited vast improvements in certain mechanical properties that would make them potential candidates for some critical structural applications. On the other hand, the vacuum-melting processes are quite costly and are not applicable to large-tonnage heats of steel. In the development of the vacuum-degassing process, it was hoped that some, if not all, of the advantages to be derived from the vacuum-melting process could be obtained by vacuum degassing, a process that can be applied to large-tonnage heats of steel. It would be desirable for the