Abstract: According to a casting method, a molten metal is sustained at a sustain position between a casting and the next casting, and the molten metal flow is divided from one pouring gate (44) to a plurality of sprue runners (46 and 47) in the casting. The sprue runners (46 and 47) are branched by a V-shaped portion (45) in a V-shape, and the sustain position of the molten metal is set above (any one of P1, P2 and P4) the V-shaped portion (45). The V-shaped portion (45) is filled with the molten metal while a repeated casting is carried out.

Abstract: A breathable salt core is provided that is placed in a cavity of a casting mold in order to mold a hollow part of a cast product and that is dissolved and removed after casting, the breathable salt core being formed by powder molding innumerable salt particles into a predetermined shape corresponding to the hollow part, wherein a gap that can retain a gas remaining in the cavity in a casting process is formed between the innumerable salt particles that have been powder molded. The breathable salt core thus manufactured assures that residual gas within the cavity pushed by the molten metal to enter the gap formed between salt particles of the salt core, thereby avoiding any incomplete filling of the molten metal, and which can be formed with a simple production process at a low cost.

Abstract: A casting device includes a mold provided with an insert die, a molten metal supply device for supplying molten metal into the mold, and a gas supply mechanism for supplying a gas, which is used for forced cooling, to the insert die. The insert die is made of tungsten having a thermal conductivity significantly higher than that of die steel. The insert die has a spiral or meandering gas passage therein. The spiral or meandering gas passage has a passage length much longer than a straight passage.

Abstract: A piston includes a piston body and a piston ring fitted into a ring groove. The piston ring has a top surface that includes: a convex portion formed between an inner edge position and a central position at which a radial direction thickness is ½, with the piston ring in a free state, and a planar portion or an inclined peripheral portion continuous with the convex portion on a radially outer side of the convex portion. In a predetermined status of the piston body and the piston ring, an angle between the top surface of the ring groove and the planar portion or the inclined peripheral portion is at least 18 arcminutes in a cross-section that is parallel to a central axis of the piston body and includes the central axis.

Abstract: A piston includes a piston body and a piston ring fitted into a ring groove. The piston ring has a top surface that includes: a convex portion formed between an inner edge position and a central position at which a radial direction thickness is ½, with the piston ring in a free state, and a planar portion or an inclined peripheral portion continuous with the convex portion on a radially outer side of the convex portion. In a predetermined status of the piston body and the piston ring, an angle between the top surface of the ring groove and the planar portion or the inclined peripheral portion is at least 18 arcminutes in a cross-section that is parallel to a central axis of the piston body and includes the central axis.

Abstract: A pair of main molds forming an outer peripheral face of a piston and a pair of side cores forming the pair of cutout recess parts of the piston are prepared, the main mold and the side core are set so as to form a cavity corresponding to the piston, the cavity is charged with molten metal, and when the side core is moved downward and in a direction away from the central axis of the piston so as to carry out mold release from the cutout recess part after the piston within the cavity has solidified, the side core is tilted in a direction in which an upper end thereof approaches the central axis of the piston. Thus, it is possible to release a core smoothly from a cutout recess part without it biting into an inside face of the cutout recess part.

Abstract: A metal continuously melting and retaining furnace including a retaining chamber which retains therein a molten metal fed from a melting chamber, a ladling chamber from which the molten metal is ladled out, and a treating chamber between the retaining and ladling chambers and having means of producing bubbles of a molten metal-refining gas and means of stirring the molten metal. A molten metal inlet port between the retaining chamber and the treating chamber and a molten metal outlet port between the treating chamber and the ladling chamber are disposed so as not to face directly to each other. In addition, a bubble baffle plate stands on the bottom surface of the treating chamber near the molten metal outlet port so as to oppose thereto. This makes it possible to provide a molten metal with a good yield, which is refined to a higher degree and is most suitable for producing a high quality thin cast product by casting.