High conductivity copper alloy for semi-solid forming and manufacturing method thereof

Abstract

Disclosed is a copper alloy having high electrical conductivity of at least 70% IACS and a broad solid-liquid two-phase region, capable of being easily subjected to a semi-solid forming process even at various temperatures. The copper alloy is suitable for use in a rotor of small- and medium-sized electric motors. In addition, the prevent invention provides a method of manufacturing the copper alloy for semi-solid forming, including the step of melting a copper-calcium alloy having 0.1-1.5 wt % of calcium and the balance of copper at 1100-1150° C. to form a molten copper-calcium alloy, which is then maintained at 1100-1150° C. for a predetermined time period. Then, the molten copper-calcium alloy is poured into a mold preheated to 100-150° C. and cast to a copper alloy ingot. Thereafter, in order to remove segregation and stress generated upon casting and to convert a dendritic strucutre of a primary copper phase to a globular structure, the copper alloy ingot is subjected to thermomechanical treatment, thereby obtaining the primary copper phase comprising the globular structure suitable for semi-solid forming.

What is claimed is:  
     
         1 . A high conductivity copper alloy for semi-solid forming, comprising 0.1-1.5 wt % of calcium and the balance of copper cast together, to form cast copper-calcium alloys.  
     
     
         2 . The copper alloy as defined in  claim 1 , wherein the cast copper-calcium alloy is subjected to heat treatment to have a solid-liquid two-phase region exhibiting a temperature range of 910 to 1085° C. and an electrical conductivity of 75-95% IACS.  
     
     
         3 . The copper alloy as defined in  claim 1  or  2 , wherein the cast copper-calcium alloy is compressed by 0.1-30% before heat treatment.  
     
     
         4 . A method of manufacturing a high conductivity copper alloy for semi-solid forming, comprising the following steps of: 
 melting a copper-calcium alloy including 0.1-1.5 wt % of calcium and the balance of copper at 1100-1150° C. to form molten copper-calcium alloys, which is then maintained at the same temperature for 1-5 min;    casting the molten copper-calcium alloy to a copper alloy ingot by use of a mold preheated to 100-150° C.; and    heating the copper alloy ingot to 910-1085° C. corresponding to a solid-liquid two-phase region and maintaining the heated copper alloy ingot at 910-1085° C. for 5-10 min, followed by chilling the heated copper alloy ingot, to remove segregation and stress generated in the casting step and to convert a dendritic structure of a primary copper phase to a globular structure, thereby obtaining the primary copper phase comprising the globular structure suitable for semi-solid forming.    
     
     
         5 . The method as defined in  claim 4 , further comprising the step of compressing the copper alloy ingot by 0.1-30%, before the heating step.