Piston for swash-plate type compressor and manufacturing method of the same

Abstract

The present invention intends to provide a manufacturing method of a piston for a swash-plate type compressor being excellent in the wear-proof character, no blister being generated, and capable of manufacturing the piston by low cost. A manufacturing method of a piston for a swash-plate type compressor, comprising a molten metal treating step including at least adding treatment for adding Na and/or Sr by 20 to 1000 ppm to a Al—Si alloy molten metal including Si of 7 to 18 wt %; and a die casting step for die casting the Al—Si alloy molten metal.

What is claimed is:  
     
         1 . A manufacturing method of a piston for a swash-plate type compressor, comprising: 
 a molten metal treating step including at least adding treatment for adding Na and/or Sr by 20 to 1000 ppm to a Al—Si alloy molten metal including Si of 7 to 18 wt %; and    a die casting step for die casting the Al—Si alloy molten metal.    
     
     
         2 . A manufacturing method of a piston according to    claim 1   , wherein added amount of Na and/or Sr is 30 to 150 ppm.  
     
     
         3 . A manufacturing method of a piston according to    claim 2   , wherein only Na is added.  
     
     
         4 . A manufacturing method of a piston according to    claim 3   , wherein added amount of Na is 100 ppm.  
     
     
         5 . A manufacturing method of a piston according to    claim 1   , wherein the Al—Si alloy molten metal includes Si of 12 wt %.  
     
     
         6 . A manufacturing method of a piston according to    claim 1   , wherein said molten metal treating step further includes a degassing treatment and a dreg-removing treatment performed before the adding treatment.  
     
     
         7 . A manufacturing method of a piston according to    claim 1   , wherein an eutectic Si phase in the Al—Si alloy is sphered in said molten metal treating step to have an average particle diameter of 1.5 to 3.0 μm.  
     
     
         8 . A manufacturing method of a piston according to    claim 1   , further comprising an artificial-age treating step to increase strength of the casted article, after said die casting step.  
     
     
         9 . A manufacturing method of a piston according to    claim 1   , wherein no solution treatment is performed after said die casting step.  
     
     
         10 . A piston for a swash-plate type compressor obtainable by said manufacturing method according to one of    claims 1    to    9   , and has a cyilindrical main body and a shoe receiving portion formed at one axial end thereof.