PURPOSE:To improve abrasion resistance so as to improve durability at the time of operation of room heating by nitrosulphurizing the crankshaft of a rotary compressor. CONSTITUTION:Into a molten salt bath of an alkali metallic salt which holds, as its fundamental salt, cyanate containing a sulfur being kept at a proper temperature such as 565 deg.C, a crankshaft 7 being comleted in a machine work is dipped, so as to be nitrosulphurized. By this nitrosulphurizing, on the extreme surface of the crankshaft 7, a porous layer 20, in which a sulphur oxide and a nitrogen compound are migled and which is excellent in oil keeping efficiency and small in coefficient of friction and further excellent in conformability, is formed. And then, by this nitrosulphurizing, moreover at the lower part of this porous layer 20, a single phase 21 of the nitrogen compound, which is high in hardness and low in coefficient of friction and besides high in its melting point and excellent in abrasion resistance property, is formed.
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