Method for producing high-purity metallic chromium
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United States of America Patent
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Nov 9, 1993
Grant Date -
N/A
app pub date -
Jun 24, 1991
filing date -
Oct 23, 1990
priority date (Note) -
Expired
status (Latency Note)
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Abstract
Chromium carbide powder and/or powder of an easily sulfidable metal are added to powdered crude metallic chromium to form a mixture thereof, which is then heated in vacuum to remove S, N and O by degassing so that consequently the crude metallic chromium is free from impurities to a possible maximum extent. Alternatively, powdered crude metallic chromium is heated in an atmosphere of inert gas to temperature between 800 and 1,400.degree. C. and then an easily sulfidable metal is added thereto to form a mixture thereof. Subsequently, the mixture is, directly or after adding carbon or chromium carbide, heated again in vacuum or in an atmosphere of inert gas to eliminate S, N and O by degassing so that the crude metallic chromium is free from impurities to a possible maximum extent. Still alternatively, powdered crude metallic chromium is washed with inorganic acid such as hydrochloric acid, sulfuric acid or nitric acid or organic acid such as acetic acid to remove metal impurities such as Fe. The washed crude metallic chromium is then mixed with carbon or chromium carbide and the mixture is heated in vacuum or in an atmosphere of inert gas to eliminate S, N and O by degassing and consequently produce high-purity metallic chromium.
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