Process of DH Vacuum Refining Process in Japan

Beginning in early 1960, the Dortmund Horder (DH) and Rheinstahl und Heraeus (RH) techniques were introduced in Japan as a vacuum refining method for steels. A schematic shows fundamental constitution of DH in which argon gas is injected through suction nozzle, up to splash formation chamber and finally to vacuum area. Many companies like: Sumitomo, Nippon Steel Corporation, Kobe Steel, etc. are using these methods and a bar chart provides number of reported papers on DH equipments by these firms between 1955-1990, followed by full page of DH related technological advancements. At Yawata Steel Works, first 70 t DH equipment was developed in 1961, and the degassing degree (of hydrogen) has reached to 5 mm Hg at 1 ppm. Specification of their 1964 DH is provided followed by graphs showing behavior of carbon and oxygen during degassing operation. Finally DH and RH capacities are compared for minimum C and nitrogen levels.