Hollow casting and manufacturing method therefor, and method and apparatus for smoothing internal surface of hollow casting

Abstract

There is provided a hollow casting in which a surface roughness Ra of a casting wall portion surface forming a hollow portion formed by a wall portion is 10 μm or less. Such a hollow casting can be obtained by a manufacturing method for the hollow casting in which after molten metal is poured into a mold to be molded by casting, processing of removing residual matters on the casting wall portion surface forming the hollow portion and processing of smoothing the casting wall portion surface forming the hollow portion are performed at the same time under predetermined conditions. According to the present invention, a casting which has the hollow portion formed by the wall portion and whose wall portion surface forming the hollow portion is very smooth and which has a low passage resistance can be manufactured at a lower cost without increasing an environmental load in the manufacturing process.

What is claimed is:  
     
         1 . A hollow casting having a hollow portion formed by a wall portion, 
 wherein a surface roughness Ra of a wall portion surface forming said hollow portion is 10 μm or less.    
     
     
         2 . A hollow casting according to  claim 1 , wherein the hollow casting is any one part selected from a vehicular air intake system parts group consisting of an intake manifold; turbine housing; compressor cover; cylinder head; and air duct.  
     
     
         3 . A manufacturing method for a hollow casting, in which a casting having a hollow portion formed by a wall portion is manufactured, 
 wherein after molten metal is poured into a mold to be molded by casting, processing of removing residual matters on a casting wall portion surface forming said hollow portion and processing of smoothing the casting wall portion surface forming said hollow portion are performed at the same time.    
     
     
         4 . The manufacturing method for a hollow casting according to  claim 3 , 
 further comprising a process in which after said molding by casting, a smoothing material is put in the hollow portion formed by the wall portion and the casting is oscillated.    
     
     
         5 . A method of smoothing an internal surface of a hollow casting, in which a casting wall portion surface forming a hollow portion of a casting having said hollow portion formed by a wall portion is smoothed, 
 wherein a smoothing material is put in said hollow portion and the casting is oscillated.    
     
     
         6 . The method of smoothing the internal surface of a hollow casting according to  claim 5 , 
 wherein a frequency of the oscillation is about 0.5 to 20 Hz.    
     
     
         7 . The method of smoothing the internal surface of a hollow casting according to  claim 5 , 
 wherein a stroke of the oscillation is about 30 to 200 mm.    
     
     
         8 . The method of smoothing the internal surface of a hollow casting according to  claim 5 , 
 wherein the total number of oscillation time of the oscillation is about 3 to 120 minutes.    
     
     
         9 . The method of smoothing the internal surface of a hollow casting according to  claim 5 , 
 wherein a percentage by volume of said smoothing material put in said hollow portion to said hollow portion is about 5 to 50%.    
     
     
         10 . The method of smoothing the internal surface of a hollow casting according to  claim 5 , 
 wherein said smoothing material is one or two or more mixtures containing at least metal balls or cut wires.    
     
     
         11 . The method of smoothing the internal surface of a hollow casting according to  claim 5 , 
 wherein a principal material constituting said casting is cast iron or an aluminum alloy for casting.    
     
     
         12 . An apparatus for smoothing an internal surface of a hollow casting, in which a casting wall portion surface forming a hollow portion of a casting having said hollow portion formed by a wall portion is smoothed, 
 wherein said apparatus comprises: 
 a bed capable of fixing a casting in which a smoothing material is put in said hollow portion in an arbitrary direction; and  
 oscillating means for oscillating said bed.  
   
     
     
         13 . The apparatus for smoothing an internal surface of a hollow casting according to  claim 12 , 
 wherein said oscillating means has a prime mover and a crank connected to said prime mover.