2. Vacuum processes

2.1 General

Vacuum processes are often used because they allow ..:

• isolate the liquid metal from the oxygen in the air, thus preventing reoxidation of the steel;

• high yields, even with the addition of highly oxidizable metallic elements;

• reduce dissolved gas content, particularly nitrogen, hydrogen and oxygen. Dissolved gas contents obey Sieverts' law, and depend on the pressure and stirring conditions inside the vacuum chamber;

• reduce the metal oxide content through the formation of CO, a reaction that is all the more effective the lower the pressure:

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