| 摘要 |
PURPOSE:To obtain a screw having abrasion resistance and capable of being easily processed so as to have a smooth surface by coating the surface composed of a hard material of the screw with a metal component having hardness lower than that of the hard material. CONSTITUTION:A screw is used in a general extruder and constituted, for example, so as to have a spiral groove surface structure and at least the surface thereof is constituted of a hard material such as WC-Co. The surface constituted of this hard material of the screw is coated with a metal component having hardness lower than that of the hard material, for example, Ni. The surface coated with the metal component of the screw is ground if necessary by a usual grinding method to be smoothed so as to have a uniform gloss surface before the screw is practically used. Even if the coated metal component is partially abraded by long-time operation and a part of the hard material is exposed to the surface of the screw, the surface of the screw is kept smooth by the remaining metal component and the hard material and, therefore, no trouble is generated even if the kneading/molding of a resin is executed. |
