Sulfide ore is crushed and the sulfides are separated by flotation. Nickel and copper sulfides are further separted by another float. Nickel sulfides are roasted, which removes some sulfur, and then undergo a Bessemer type process. Impurities are removed by oxidation. A mixture of molten copper, nickel, and iron sulfide is obtained after further chemical treatment.
Segregation occurs during cooling.
Unwanted products are removed mechanically. The nickel sulfide is then sintered, forming an oxide, and pure nickel is formed by means of a reduction process using hydrogen and electrolysis. Except for high strength and high high temperate alloys, they are therefore reasonably easy to form to the required shape, even though a high rate of work hardening may require inter-stage annealing. The properties of nickel alloys which make them of industrial importance are varied, and include good corrosion resistance to many gaseous and liquid environments at normal temperatures, resistance to oxidation at elevated temperatures, good mechanical strength at high temperatures and special physical properties- electric, magnetic and dimensional. Many may also be produced as castings.