A forging method for a shaft member includes preforming at least one of a plurality of enlarged diameter portions to obtain a semi-finished member, and forming a remainder of the enlarged diameter portions in the semi-finished member using a mold. The mold includes a punch, split dies, and a workpiece receiving member. The forming of the remainder of the enlarged diameter portions includes allowing the semi-finished member having the at least one of the enlarged diameter portions to be placed on the workpiece receiving member, cramping the semi-finished member in its radial direction by closing the split dies, and filling the semi-finished member into forming surfaces of the split dies by the pressure applied by the punch under the state in which the semi-finished member is cramped.

A forging method for a shaft member includes preforming at least one of a plurality of enlarged diameter portions to obtain a semi-finished member, and forming a remainder of the enlarged diameter portions in the semi-finished member using a mold. The mold includes a punch, split dies, and a workpiece receiving member. The forming of the remainder of the enlarged diameter portions includes allowing the semi-finished member having the at least one of the enlarged diameter portions to be placed on the workpiece receiving member, cramping the semi-finished member in its radial direction by closing the split dies, and filling the semi-finished member into forming surfaces of the split dies by the pressure applied by the punch under the state in which the semi-finished member is cramped.

A cup member has a cylindrical portion, a bottom portion, and a short shaft portion having a solid shaft shape and including a joining end surface at an end portion thereof. A shaft member has a solid shaft shape and includes a joining end surface at one end thereof. The joining end surfaces of the cup and shaft members are brought into abutment against each other and welded from a radially outer side to form a welded portion. At this time, center segregation is prevented from interfering with the welded portion. The cup member is formed by forging including upsetting a billet having a columnar shape successively in a plurality of stages, extruding the cylindrical portion and the short shaft portion, and ironing the cylindrical portion. In the course of the upsetting, a region of the billet corresponding to a bottom side of the cup member is narrowed.

A cup member has a cylindrical portion, a bottom portion, and a short shaft portion having a solid shaft shape and including a joining end surface at an end portion thereof. A shaft member has a solid shaft shape and includes a joining end surface at one end thereof. The joining end surfaces of the cup and shaft members are brought into abutment against each other and welded from a radially outer side to form a welded portion. At this time, center segregation is prevented from interfering with the welded portion. The cup member is formed by forging including upsetting a billet having a columnar shape successively in a plurality of stages, extruding the cylindrical portion and the short shaft portion, and ironing the cylindrical portion. In the course of the upsetting, a region of the billet corresponding to a bottom side of the cup member is narrowed.

A method of manufacturing an outer joint member of a constant velocity universal includes forming cup and shaft members of medium carbon steel, preparing, as the cup member, a cup member having cylindrical and bottom portions integrally formed by forging, and a joining end surface formed on an outer surface of the bottom portion after the forging, preparing, as the shaft member, a shaft member having a joining end surface to be joined to the bottom portion of the cup member, and bringing the joining end surfaces of the cup and shaft members into abutment against each other. The method also includes welding the cup and shaft members from an outer side of the cup member to an abutment portion between the cup and shaft members in a radial direction of the cup member.

A method of manufacturing an outer joint member of a constant velocity universal includes forming cup and shaft members of medium carbon steel, preparing, as the cup member, a cup member having cylindrical and bottom portions integrally formed by forging, and a joining end surface formed on an outer surface of the bottom portion after the forging, preparing, as the shaft member, a shaft member having a joining end surface to be joined to the bottom portion of the cup member, and bringing the joining end surfaces of the cup and shaft members into abutment against each other. The method also includes welding the cup and shaft members from an outer side of the cup member to an abutment portion between the cup and shaft members in a radial direction of the cup member.

A fitting is disclosed that includes a body; a first flow passage extending through the body; and a second flow passage formed in the body to intersect the first flow passage. The first and second flow passages define first and second longitudinal center axes, respectively. In an exemplary embodiment, the fitting forms a portion of a manifold assembly of a frac system. In one aspect, the fitting is formed by a manufacturing process such that the body has a parting plane that is offset from, and parallel to, the first longitudinal center axis. The fitting may have a first varying wall thickness defined between the first flow passage and the external surface; and a second varying wall thickness defined between the second flow passage and the external surface. In another aspect, a curved surface is formed in the body at the intersection between the first and second flow passages.

A fitting is disclosed that includes a body; a first flow passage extending through the body; and a second flow passage formed in the body to intersect the first flow passage. The first and second flow passages define first and second longitudinal center axes, respectively. In an exemplary embodiment, the fitting forms a portion of a manifold assembly of a frac system. In one aspect, the fitting is formed by a manufacturing process such that the body has a parting plane that is offset from, and parallel to, the first longitudinal center axis. The fitting may have a first varying wall thickness defined between the first flow passage and the external surface; and a second varying wall thickness defined between the second flow passage and the external surface. In another aspect, a curved surface is formed in the body at the intersection between the first and second flow passages.