A method for vacuum smelting and variable pressure solidification forming aluminum alloy piece with ultra-thin wall and high gas tightness is provided, in which an induction heating furnace is set in a vacuum tank, a quartz crucible with thickness of 58 mm is used; a preheated aluminum alloy ingot is placed in the crucible, side doors of the tank is closed, and a vacuuming processing is performed for the tank; the melt is filled from the bottom layer of the casting; when the melt reaches to the top, the main valve and the air-release valve are turned on until the inside and outside pressures are consistent, and then the casting is taken out. The requirement of high air tightness for vacuum tank is reduced, and aluminum alloy casting with high quality can be obtained at lower cost.

A low-pressure casting unit capable of alternately using crucible type heat preservation furnaces, consisting of a low-pressure casting machine, a crucible type heat preservation furnace I, a crucible type heat preservation furnace II, a trolley transfer system, a heat preservation furnace lifting system, a control system, and a transversely moving guide rail, the heat preservation furnace lifting system being arranged at a bottom of the low-pressure casting machine, the heat preservation furnace lifting system lifting the crucible type heat preservation furnace I or the crucible type heat preservation furnace II up and down in the low-pressure casting machine, one side of the low-pressure casting machine being provided with a trolley transfer system in front and the trolley transfer system moving on the transversely moving guide rail. According to the invention, the concept is ingenious, the alternative use of the two crucible type heat preservation furnaces can be realized only by adding a transversely moving guide rail on the outer side of the low-pressure casting machine and adding a transfer trolley. The problem of aluminum slags deposited at the bottom of the crucible type heat preservation furnace is well solved.

With the simple cylindrical body shape of gate valves that are currently on the market, the welded portions have three-dimensionally curved shapes and welding is difficult for general purpose welding machines. Moreover, in manufacture by casting, there are many defects in the material such as cavities and sand trapping, and man-hours and cost are necessary to repair same. In the gate valve according to the present invention, a body has openings to accommodate two connecting pipes and a gate. The two connecting pipes respectively pass through the two openings and are disposed so as to face the gate from two sides. The two connecting pipes are each joined to the body by welding at an opening and the shape of said welded sections is a circular ring. Moreover, when producing the body in the present invention, the body portion is manufactured by forging instead of casting and after machining, is unified by welding.

A method for producing a casting using a gas-permeable casting mold comprising a cavity composed of a production cavity and a flow path, the flow path comprising a sprue through which a gravity-poured melt flows downward, and a runner connecting the production cavity to the sprue, comprising gravity-pouring a metal melt in a volume smaller than that of the entire cavity and larger than that of the production cavity into the gas-permeable casting mold; supplying a gas through the sprue to push the metal melt in the flow path, thereby pushing the metal melt upward in the production cavity, so that the production cavity is filled with the metal melt; in a hypothetical equilibrium state in which a hypothetical liquid fills the production cavity by the supplied gas, setting the volume of the metal melt to be poured to be equal to the volume of the hypothetical liquid, such that the surface height hs of the hypothetical liquid remaining in the flow path after filling the production cavity, the height h1 of the lowest ceiling portion of the runner, and the height h2 of a point at which a ceiling of the runner is connected to the sprue, meet the relation of h2>hs>h1.

A method for producing a casting using a gas-permeable casting mold comprising a cavity composed of a production cavity and a flow path, the flow path comprising a sprue through which a gravity-poured melt flows downward, and a runner connecting the production cavity to the sprue, comprising gravity-pouring a metal melt in a volume smaller than that of the entire cavity and larger than that of the production cavity into the gas-permeable casting mold; supplying a gas through the sprue to push the metal melt in the flow path, thereby pushing the metal melt upward in the production cavity, so that the production cavity is filled with the metal melt; in a hypothetical equilibrium state in which a hypothetical liquid fills the production cavity by the supplied gas, setting the volume of the metal melt to be poured to be equal to the volume of the hypothetical liquid, such that the surface height hs of the hypothetical liquid remaining in the flow path after filling the production cavity, the height h1 of the lowest ceiling portion of the runner, and the height h2 of a point at which a ceiling of the runner is connected to the sprue, meet the relation of h2>hs>h1.

A method for casting comprising: providing a seed, the seed characterized by: an arcuate form and a crystalline orientation progressively varying along an arc of the form; providing molten material; and cooling and solidifying the molten material so that a crystalline structure of the seed propagates into the solidifying material.

A method for casting comprising: providing a seed, the seed characterized by: an arcuate form and a crystalline orientation progressively varying along an arc of the form; providing molten material; and cooling and solidifying the molten material so that a crystalline structure of the seed propagates into the solidifying material.

A method for producing a casting using a gas-permeable casting mold comprising a cavity composed of a production cavity and a flow path, the flow path comprising a sprue through which a gravity-poured melt flows downward, and a runner connecting the production cavity to the sprue, comprising gravity-pouring a metal melt in a volume smaller than that of the entire cavity and larger than that of the production cavity into the gas-permeable casting mold; supplying a gas through the sprue to push the metal melt in the flow path, thereby pushing the metal melt upward in the production cavity, so that the production cavity is filled with the metal melt; in a hypothetical equilibrium state in which a hypothetical liquid fills the production cavity by the supplied gas, setting the volume of the metal melt to be poured to be equal to the volume of the hypothetical liquid, such that the surface height hs of the hypothetical liquid remaining in the flow path after filling the production cavity, the height h1 of the lowest ceiling portion of the runner, and the height h2 of a point at which a ceiling of the runner is connected to the sprue, meet the relation of h2>hs>h1.

A method for producing a casting using a gas-permeable casting mold comprising a cavity composed of a production cavity and a flow path, the flow path comprising a sprue through which a gravity-poured melt flows downward, and a runner connecting the production cavity to the sprue, comprising gravity-pouring a metal melt in a volume smaller than that of the entire cavity and larger than that of the production cavity into the gas-permeable casting mold; supplying a gas through the sprue to push the metal melt in the flow path, thereby pushing the metal melt upward in the production cavity, so that the production cavity is filled with the metal melt; in a hypothetical equilibrium state in which a hypothetical liquid fills the production cavity by the supplied gas, setting the volume of the metal melt to be poured to be equal to the volume of the hypothetical liquid, such that the surface height hs of the hypothetical liquid remaining in the flow path after filling the production cavity, the height h1 of the lowest ceiling portion of the runner, and the height h2 of a point at which a ceiling of the runner is connected to the sprue, meet the relation of h2>hs>h1.

A casting apparatus for producing castings using molds each having a sprue, comprising a mold-conveying means for conveying molds each containing a melt poured through the sprue; nozzles each having a gas-introducing opening attachable to and detachable from the sprue; nozzle-attaching/detaching means each moving each nozzle to attach and detach the gas-introducing opening to and from the sprue; moving means for moving the nozzle-attaching/detaching means, such that the nozzle-attaching/detaching means moves following a mold conveyed by the mold-conveying means, while keeping the connection of the gas-introducing opening to the sprue by the nozzle-attaching/detaching means; and a gas supply means connected to each nozzle for supplying a gas to the gas-introducing opening.