Abstract: A core molding method for molding a core having a twisted shape by use of a core mold includes a curing step and a mold extracting step. In the curing step, after the core mold is disposed along a vertical direction within a frame whose top is open, a self-hardening sand formed of a kneaded mixture of a sand, a resin and a curing agent is charged into the frame from the top of the frame, and then cured. In the mold extracting step, the core mold is extracted in the vertical direction from the core formed of the cured self-hardening sand while rotating the core mold and the frame relatively to each other around an axis of the core mold.

Abstract: A mold molding method includes a binder reaction amount calculation step of calculating a reaction amount ?C(?, ti) [wt %] (i=1, 2) of a binder, a specimen room temperature compressive strength calculation step of calculating room temperature compressive strength ?c(?, t) [MPa] of a specimen, a mold room temperature compressive strength prediction step of predicting room temperature compressive strength ?ca(?, t) of the mold in advance, and a mold room temperature compressive strength extraction step of extracting room temperature compressive strength ?ce(?, t) of the mold. When the mold is actually molded, the model is removed just after elapse of the time t1, as one of the molding condition parameters which satisfies the room temperature compressive strength ?ce(?, t).

Abstract: A mold molding method includes a binder reaction amount calculation step of calculating a reaction amount ?C(?, ti) [wt %] (i=1, 2) of a binder, a specimen room temperature compressive strength calculation step of calculating room temperature compressive strength ?c(?, t) [MPa] of a specimen, a mold room temperature compressive strength prediction step of predicting room temperature compressive strength ?ca(?, t) of the mold in advance, and a mold room temperature compressive strength extraction step of extracting room temperature compressive strength ?ce(?, t) of the mold. When the mold is actually molded, the model is removed just after elapse of the time t1, as one of the molding condition parameters which satisfies the room temperature compressive strength ?ce(?, t).

Abstract: A core molding method for molding a core having a twisted shape by use of a core mold includes a curing step and a mold extracting step. In the curing step, after the core mold is disposed along a vertical direction within a frame whose top is open, a self-hardening sand formed of a kneaded mixture of a sand, a resin and a curing agent is charged into the frame from the top of the frame, and then cured. In the mold extracting step, the core mold is extracted in the vertical direction from the core formed of the cured self-hardening sand while rotating the core mold and the frame relatively to each other around an axis of the core mold.

Abstract: When a core die is being removed from a core while being rotated around its axis, the hardening time of self-hardening sand, the frictional forces generated between the core and the core die during die removal, and the strength of the core during die removal are optimized.

Abstract: Provided is a casting method using lost foam capable of forming a small highly-finished hole with a diameter of 18 mm or less and a length of 50 mm or more by casting. A casting method using lost foam of the present embodiment includes the steps of embedding, in foundry sand, a casting pattern formed by applying a mold wash with a thickness of 1 mm or more to a surface of the foam pattern, the foam pattern having a hole with a diameter of D (mm); replacing the foam pattern with molten metal by pouring the molten metal into the casting pattern and losing the foam pattern; and forming a casting having a small hole with a diameter of 18 mm or less and a length of 50 mm or more by cooling the molten metal, and the method satisfies the following formulas (0) and (1): 2<D?19.7??Formula (0) ?c??0.36+140/D2??Formula (1) where ?c (MPa) is transverse rupture strength (bending strength) of the mold wash that is heated to decompose resin constituting the mold wash and then returned to room temperature.

Abstract: Provided is a casting method using lost foam capable of forming a small highly-finished hole with a diameter of 18 mm or less and a length of 50 mm or more by casting. A casting method using lost foam of the present embodiment includes the steps of embedding, in foundry sand, a casting pattern formed by applying a mold wash with a thickness of 1 mm or more to a surface of the foam pattern, the foam pattern having a hole with a diameter of D (mm); replacing the foam pattern with molten metal by pouring the molten metal into the casting pattern and losing the foam pattern; and forming a casting having a small hole with a diameter of 18 mm or less and a length of 50 mm or more by cooling the molten metal, and the method satisfies the following formulas (0) and (1): 2<D?19.7 ??Formula (0) ?c??0.36+140/D2 ??Formula (1) where ?c (MPa) is transverse rupture strength (bending strength) of the mold wash that is heated to decompose resin constituting the mold wash and then returned to room temperature.

Abstract: When a core die is being removed from a core while being rotated around its axis, the hardening time of self-hardening sand, the frictional forces generated between the core and the core die during die removal, and the strength of the core during die removal are optimized.