Abstract: A heating apparatus (2) includes a high frequency power supply (3), a left conductive plate (4), a right conductive plate (5), a left heating coil (11), and a right heating coil (12). The left heating coil (11) includes a left conductor portion (21). The left conductor portion (21) faces a gear tooth (7a) of a helical gear (7) and extends in a direction orthogonal to the direction in which the gear tooth (7a) extends. The left heating coil (11) includes a focusing magnetic body (31) which focuses magnetic flux in the left conductor portion (21) and concentrates the magnetic flux on a surface of the gear tooth (7a). The left heating coil (11) includes an upper inducing magnetic body (32) which induces a part of the magnetic flux flowing in a tooth root of the gear tooth (7a) into a tooth tip of the gear tooth (7a).

Abstract: A heating apparatus (2) includes a high frequency power supply (3), a left conductive plate (4), a right conductive plate (5), a left heating coil (11), and a right heating coil (12). The left heating coil (11) includes a left conductor portion (21). The left conductor portion (21) faces a gear tooth (7a) of a helical gear (7) and extends in a direction orthogonal to the direction in which the gear tooth (7a) extends. The left heating coil (11) includes a focusing magnetic body (31) which focuses magnetic flux in the left conductor portion (21) and concentrates the magnetic flux on a surface of the gear tooth (7a). The left heating coil (11) includes an upper inducing magnetic body (32) which induces a part of the magnetic flux flowing in a tooth root of the gear tooth (7a) into a tooth tip of the gear tooth (7a).

Abstract: A nitriding process for a maraging steel is provided in order to increase the compressive residual stress of the maraging steel. A workpiece is made of maraging steel in which titanium is solid solved, and a partial amount of the titanium is oxidized at the surface of the workpiece so that titanium oxide is positively generated and concentrated at the surface. Then a reducing treatment is sufficiently performed as a pretreatment of a nitriding step, thereby removing oxygen. As a result, surface concentration of the titanium in an activated state is increased. Next, by performing the nitriding treatment, the reduced titanium and the solid solved titanium combine with nitrogen as titanium nitride. The titanium is in the activated state and is thereby easily nitrided. Moreover, the surface concentration of the titanium in the activated state is high, whereby a large amount of nitrogen infiltrates into the workpiece.

Abstract: In a disclosed composite plating method for a hollow member, an insertion electrode is loosely inserted with a space into a cylinder of a hollow member, a composite plating solution supplied from a solution supply pipe is circulated into the space of the cylinder, a base metal electrode is connected to the hollow member and composite plating is applied onto the inner peripheral surface of the hollow member. The current density between the insertion electrode and the inner peripheral surface of the hollow member is set at a low value at the beginning and is increased after a lapse of a predetermined time. More preferably, bubbles are produced by supplying gas into the composite plating solution almost simultaneously with the above-mentioned increase of the current density.

Abstract: A hollow member whose internal surface is to be applied with composite plating is held in a condition in which a generatrix of the internal surface extends vertically. An electrode is inserted into the hollow member with a predetermined clearance to the internal surface of the hollow member. A composite plating liquid supply passage has a discharge opening which is in communication with an opening at a lower end of the hollow member. A gas is entrained in a form of bubbles into a composite plating liquid which is supplied into the clearance through the supply passage.