The Oheyama plant of Nippon Yakin Kogyo Co., Ltd. was built here at Miyazu city in 1942, for treatment of low grade nickel oxide are (0.4-0.7% Ni) from nearby Oheyama mine by Krupp-Renn process. but at the end of war in 1945, the nickel smelting operation was stopped.
In 1950, the Kawasaki plant of Nippon Yakin Kogyo Co., Ltd. succeeded in producing stainless steel for the first time in Japan by oxygen top blowing in an arc-furnace, paving the way to mass production of stainless steel. This achievement quickly increased the demand for nickel, an important raw material of stainless steel, making the Oheyama plant resume its operation in 1952 by switching to higher grade nickel oxide ores imported from New Caledonia. Thus Nippon Yakin Kogyo Co., Ltd. established a vertically-integrated production process from Ni smelting to finished stainless steel products for the first time in Japan.
Since then the process of the Oheyama plant has been greatly modified and developed to establish “Nippon Yakin Oheyama Process”, the only method in the world that uses a rotary kiln for smelting nickel oxide ores.
The nickel ores are first ground by both dry and wet methods and blended well with anthracite and limestone, to be formed into briquets. They are first dried and preheated efficiently in a grate directly connected with a rotary kiln and then charged into the kiln, where all the metallurgical reactions such as dehydration, reduction, slag-formation and refining by excess air near discharge end, occur to form ferro-nickel nodules (0.3-20mm).
The Oheyama Process is considered a very useful method to obtain nickel material for stainless steel production, because its low energy cost as well as individuality of its product, easy to handle and almost free of impurities, help significantly reduce the cost of stainless steel production.
The Oheyama plant is now producing 1, 150t of Ni as ferro-nickel a month, and besides, 35, 000t of byproduct, “NAS Sand” a month from slag, which is mainly used as public works materials such as asphalt aggregate, concrete aggregate and so on.
Situated near Amano-hashidate, one of Japan's Three Famous Views, the Oheyama plant pays full attention to protecting the surrounding environment and to existing in harmony with nature.