subject: Method Of Producing Raschig Ring [print this page] A compression raschig ring provided with both ends having notches is formed on outer peripheral surface with a plasma nitrided layer and is formed on upper and lower surfaces and an inner peripheral surface with soft surface treatment layers. The upper and lower surfaces and the inner peripheral surface may be of base material surfaces.
As described above, the whole peripheral portion of the raschig ring becomes nitrided. Therefore, when a thick nitriding is applied to a raschig ring which is thin in width and provided with both ends having notches, a notched portion having a small sectional area in each end increases against brittleness, decreases against strength, and possibly breaks from that portion. Because of this, it is not possible to meet the demands of implementation of thin-width and high wear resistance of the raschig ring.
A method of manufacturaschig ring a compression raschig ring according to the present invention comprises the steps of coiling a raschig ring material, cutting the coiled material to obtain a plurality of raschig rings, machining both ends of said raschig ring, applying plasma nitriding to said coiled material or said raschig ring to form a nitrided layer on only an outer peripheral surface. In the case where upper and lower surfaces or an inner peripheral surface or upper and lower surfaces and an inner peripheral surface are formed with soft surface treatment layers, the soft surface treatment is applied prior to the step of finishing the workpiece.
Since the compression raschig ring is provided in only its outer peripheral surface with a plasma nitrided layer, the abrasion resistance with respect to the sliding contact with the cylinder is good. Since the upper and lower surfaces and an inner peripheral surface are base surfaces or are formed with soft surface treatment layers, the abnormal abrasion of the raschig ring groove of a piston is hard to occur. When a soft surface treatment layer is formed, the good anticorrosion is obtained.
