Method for manufacturing plastic worked article

Abstract

The method for manufacturing a plastic worked article includes the steps of shaping an article for plastic working by a semisolid molding in which molten metal including both a solid phase and a liquid phase is introduced into a die; performing a pre-plastic working heat treatment on the article for plastic working for causing blisters by expanding gas cavities included in the article for plastic working; and forming a plastic worked article by plastic working the article for plastic working after the pre-plastic working heat treatment. The plastic working of the article for plastic working is performed in such a manner that a tensile stress applied direction at a tensile stress applied portion to which tensile stress is principally applied in actual use of the plastic worked article substantially accords with a plastic flow direction at a portion of the article for plastic working corresponding to the tensile stress applied portion.

What is claimed is:  
     
         1 . A method for manufacturing a plastic worked article by plastic working an article for plastic working, comprising the steps of: 
 shaping an article for plastic working by a semisolid molding in which molten metal including both a solid phase and a liquid phase is introduced into a die;    performing a pre-plastic working heat treatment on the article for plastic working for causing blisters by expanding gas cavities included in the article for plastic working; and    forming a plastic worked article by plastic working the article for plastic working after the pre-plastic working heat treatment,    wherein the plastic working of the article for plastic working is performed in such a manner that a tensile stress applied direction at a tensile stress applied portion to which tensile stress is principally applied in actual use of the plastic worked article substantially accords with a plastic flow direction at a portion of the article for plastic working corresponding to the tensile stress applied portion.    
     
     
         2 . The method for manufacturing a plastic worked article of  claim 1 , 
 wherein the pre-plastic working heat treatment is performed with a processing temperature in a range of 300° C. to 550° C.    
     
     
         3 . The method for manufacturing a plastic worked article of  claim 2 , 
 wherein the pre-plastic working heat treatment is performed with a processing time of 1 hour or more.    
     
     
         4 . The method for manufacturing a plastic worked article of  claim 3 , 
 wherein the pre-plastic working heat treatment is performed with a processing temperature in a range of 350° C. to 450° C. and a processing time of 20 hours or less.    
     
     
         5 . The method for manufacturing a plastic worked article of  claim 4 , 
 wherein the pre-plastic working heat treatment is performed with a processing time in a range of 10 hours to 20 hours.    
     
     
         6 . The method for manufacturing a plastic worked article of  claim 1 , further comprising a step of performing a post-plastic working heat treatment on the plastic worked article obtained by the plastic working with a processing temperature in a range of 250° C. to 400° C. and a processing time in a range of 20 minutes to 10 hours.  
     
     
         7 . The method for manufacturing a plastic worked article of  claim 1 , 
 wherein the article for plastic working is shaped by the semisolid molding using an injection molding apparatus equipped with a cylinder and a screw.    
     
     
         8 . The method for manufacturing a plastic worked article of  claim 1 , 
 wherein a thick part is provided on the portion of the article for plastic working corresponding to the tensile stress applied portion, and the article for plastic working is shaped into a desired shape by the plastic working by allowing the thick part to flow in a direction substantially according with the tensile stress applied direction.    
     
     
         9 . The method for manufacturing a plastic worked article of  claim 1 , 
 wherein the plastic worked article is a road wheel, and    the plastic working of the article for plastic working is performed in such a manner that a direction substantially along an extending direction of a spoke of a wheel disk of the road wheel substantially accords with a plastic flow direction at a portion of the article for plastic working corresponding to the wheel disk.    
     
     
         10 . The method for manufacturing a plastic worked article of  claim 1 , 
 wherein the plastic worked article is a road wheel, and    the plastic working of the article for plastic working is performed in such a manner that a direction substantially along a width of a wheel rim of the road wheel substantially accords with a plastic flow direction at a portion of the article for plastic working corresponding to the wheel rim.