Abstract: Disclosed is a leadless free-cutting copper alloy that exhibits superior machinability, cold workability and dezincification resistance and a method for producing the same. The leadless free-cutting copper alloy comprises 56 to 77% by weight of copper (Cu), 0.1 to 3.0% by weight of manganese (Mn), 1.5 to 3.5% by weight of silicon (Si), and the balance of zinc (Zn) and other inevitable impurities, thus exhibiting superior eco-friendliness, machinability, cold workability and dezincification resistance.

Abstract: Disclosed is a leadless free-cutting copper alloy that exhibits superior machinability, cold workability and dezincification resistance and a method for producing the same. The leadless free-cutting copper alloy comprises 56 to 77% by weight of copper (Cu), 0.1 to 3.0% by weight of manganese (Mn), 1.5 to 3.5% by weight of silicon (Si), and the balance of zinc (Zn) and other inevitable impurities, thus exhibiting superior eco-friendliness, machinability, cold workability and dezincification resistance.

Abstract: A coin assembly and a medal assembly which have triple-structures, respectively, and a method for fabricating the same are disclosed. The coin assembly includes an internal ring; an external ring coupled to an outside of the internal ring; an insert coupled to an inside the internal ring; a first recess formed in an outer surface of the internal ring, to have a predetermined portion of an outer surface of the external ring inserted therein, when the internal ring and the external ring are assembled with each other; and a second recess formed in an outer surface of the insert, to have a predetermined portion of an outer surface of the internal ring therein, when the insert and the internal ring are assembled with each other.

Abstract: A coin assembly and a medal assembly which have triple-structures, respectively, and a method for fabricating the same are disclosed. The coin assembly includes an internal ring; an external ring coupled to an outside of the internal ring; an insert coupled to an inside the internal ring; a first recess formed in an outer surface of the internal ring, to have a predetermined portion of an outer surface of the external ring inserted therein, when the internal ring and the external ring are assembled with each other; and a second recess formed in an outer surface of the insert, to have a predetermined portion of an outer surface of the internal ring therein, when the insert and the internal ring are assembled with each other.

Abstract: Bimetallic coin or a medal and a method for producing the same, which is easy to form a ring and an insert composing the coin or the medal, yet costs low, and can assure a higher joining force between the ring and the insert. The method includes processes for forming a ring by subjecting a first metal to blanking, annealing, and pickling, forming an insert thicker than the ring by subjecting a second metal to blanking and annealing, forming a thickened rim on each side, and an annular ridge around the circumferential surface of the insert, and pickling the insert, and joining the ring and the insert by causing plastic metal flow of the ridge of the insert into the inner circumferential surface of the ring through pressing the insert inserted in the center of the ring; and a bimetallic coin formed with the method.

Abstract: Bimetallic coin or a medal and a method for producing the same, which is easy to form a ring and an insert composing the coin or the medal, yet costs low, and can assure a higher joining force between the ring and the insert.The method includes processes for forming a ring by subjecting a first metal to blanking, annealing, and pickling, forming an insert thicker than the ring by subjecting a second metal to blanking and annealing, forming a thickened rim on each side, and an annular ridge around the circumferential surface of the insert, and pickling the insert, and joining the ring and the insert by causing plastic metal flow of the ridge of the insert into the inner circumferential surface of the ring through pressing the insert inserted in the center of the ring; and a bimetallic coin formed with the method.