Sintered valve guide and manufacturing method thereof

Abstract

Disclosed is a sintered valve guide guide formed of a sintered alloy consisting essentially of 3.5 to 5% copper, 0.3 to 0.6% tin, 0.04 to 0.15% phosphorus, 1.5 to 2.5% carbon and the balance iron, by mass, and as occasion needs, further containing 0.46 to 1.41% metal oxide, and MnS and/or magnesium silicate. The metallographic structure has: a matrix containing a pearlite phase, a Fe—P—C compound phase and a Cu—Sn alloy phase; pores; and a graphite of 1.2 to 1.7% by mass of the sintered alloy. In the cross section, the ratio of the pearlite phase to the matrix is 90 area % or more, the ratio of the Fe—P—C compound phase is 0.1 to 3 area % of the cross section, the ratio of the Cu—Sn alloy phase to the cross section is 1 to 3% by area, and the ratio of a portion of the Fe—P—C compound phase having a thickness of 15 microns or more is 10 area % or less of the whole Fe—P—C compound phase.

1 . A sintered valve guide formed of a sintered alloy consisting essentially of 3.5 to 5% copper, 0.3 to 0.6% tin, 0.04 to 0.15% phosphorus, 1.5 to 2.5% carbon and the balance iron, by mass, 
 wherein the sintered alloy has a metallographic structure comprising: a matrix having a pearlite phase, a Fe—P—C compound phase and a Cu—Sn alloy phase; pores; and a graphite phase being dispersed at a ratio of 1.2 to 1.7% by mass of the sintered alloy, and    wherein, in a cross section of the metallographic structure of the sintered alloy, the ratio of the pearlite phase to the matrix is 90% by area or more, the ratio of the Fe—P—C compound phase to the cross section of the metallographic structure is 0.1 to 3% by area, the ratio of the Cu—Sn alloy phase to the cross section of the metallographic structure is 1 to 3% by area, and the ratio of a portion of the Fe—P—C compound phase having a thickness of 15 microns or more to whole of the Fe—P—C compound phase is 10% by area or less.    
   
   
       2 . A sintered valve guide formed of a sintered alloy consisting essentially of 3.5 to 5% copper, 0.3 to 0.6% tin, 0.04 to 0.15% phosphorus, 1.5 to 2.5% carbon, 0.46 to 1.41% metal oxide and the balance iron, by mass, 
 wherein the sintered alloy has a metallographic structure comprising: a matrix having a pearlite phase, a Fe—P—C compound phase, a Cu—Sn alloy phase and a metal oxide phase; pores; and a graphite phase being dispersed at a ratio of 1.2 to 1.7% by mass of the sintered alloy, and    wherein, in a cross section of the metallographic structure of the sintered alloy, the ratio of the pearlite phase to the matrix is 90% by area or more, the ratio of the Fe—P—C compound phase to the cross section of the metallographic structure is 0.1 to 3% by area, the ratio of the Cu—Sn alloy phase to the cross section of the metallographic structure is 1 to 3% by area, and a portion of the Fe—P—C compound phase having a thickness of 15 microns or more to whole of the Fe—P—C compound phase is 10% by area or less.    
   
   
       3 . A sintered valve guide formed of a sintered alloy consisting essentially of 3.5 to 5% copper, 0.3 to 0.6% tin, 0.04 to 0.15% phosphorus, 1.5 to 2.5% carbon, 1% or less of at least one solid lubricant selected from the group consisting of manganese sulfide and magnesium silicate minerals, and the balance iron, by mass, 
 wherein the sintered alloy has a metallographic structure comprising: a matrix having a pearlite phase, a Fe—P—C compound phase and a Cu—Sn alloy phase; pores; a graphite phase; and said at least one solid lubricant being dispersed in the pores or intergranularly dispersed in the metallographic structure, and    wherein, in a cross section of the metallographic structure of the sintered alloy, the ratio of the pearlite phase to the cross sectioin of the metallographic structure is 80% by area or more, the ratio of the Fe—P—C compound phase to cross section of the metallographic structure is 0.1 to 3% by area, the ratio of the Cu—Sn alloy phase to the cross section of the metallographic structure is 1 to 3% by area, the graphite phase is dispersed in the pores at a ratio of 0.8 to 3.2% by area of the cross section of the metallographic structure, and the ratio of a portion of the Fe—P—C compound phase having a thickness of 15 microns or more to whole of the Fe—P—C compound phase is 10% by area or less.    
   
   
       4 . A sintered valve guide formed of a sintered alloy consisting essentially of 3.5 to 5% copper, 0.3 to 0.6% tin, 0.04 to 0.15% phosphorus, 1.5 to 2.5% carbon, 0.46 to 1.41% metal oxide, 1.6% or less of at least one solid lubricant selected from the group consisting of manganese sulfide and magnesium silicate minerals, and the balance iron, by mass, 
 wherein the sintered alloy has a metallographic structure comprising: a matrix having a pearlite phase, a Fe—P—C compound phase, a Cu—Sn alloy phase and a metal oxide phase; pores; a graphite phase; and said at least one solid lubricant being dispersed in the pores or intergranularly dispersed in the metallographic structure, and    wherein, in a cross section of the metallographic structure of the sintered alloy, the ratio of the pearlite phase to the cross sectioin of the metallographic structure is 90% by area or more, the ratio of the Fe—P—C compound phase to cross section of the metallographic structure is 0.1 to 3% by area, the ratio of the Cu—Sn alloy phase to the cross section of the metallographic structure is 1 to 3% by area, the graphite phase is dispersed in the pores at a ratio of 0.8 to 3.2% by area of the cross section of the metallographic structure, and the ratio of a portion of the Fe—P—C compound phase having a thickness of 15 microns or more to whole of the Fe—P—C compound phase is 10% by area or less.    
   
   
       5 . The sintered valve guide as set forth in  claim 2 , wherein the metal oxide includes at least one oxide of a metal selected from the group consisting of aluminum, silicon, magnesium, iron, calcium and tin.  
   
   
       6 . The sintered valve guide as set forth in  claim 1 , wherein, in the cross section of the metallographic structure, the ratio of another portion of the Fe—P—C compound phase having a thickness of 5 microns or more and less than 15 microns to whole of the Fe—P—C compound phase is 10 to 40% by area, and the balance Fe—P—C compound phase has a thickness of less than 5 microns.  
   
   
       7 . A method of manufacturing a sintered valve guide, comprising: 
 preparing a powder mixture comprising, by mass: 0.27 to 0.7% of a Fe—P alloy powder; 3.93 to 5.44% of a Cu—Sn alloy powder; 1.7 to 2.7% of a graphite powder and the balance iron powder, wherein the Fe—P alloy powder consists essentially of 15 to 21% phosphorus, an inevitable amount of impurities and the balance iron, the Cu—Sn alloy powder consists essentially of 8 to 11% tin, an inevitable amount of impurities and the balance copper;    forming the powder mixture into a tubular compact by pressing the powder mixture in a tubular cavity; and    sintering the tubular compact in a non-oxidizing atmosphere at a sintering temperature of 950 to 1,050 degrees C.    
   
   
       8 . The manufacturing method as set forth in  claim 7 , wherein the iron powder includes an ore reduced iron powder containing 0.5 to 1.5% by mass of metal oxide.  
   
   
       9 . The manufacturing method as set forth in  claim 7 , wherein the iron powder is a mixture of an ore reduced iron powder and an atomized iron powder, wherein the content of the atomized iron powder in the mixture is 10 to 30% by mass.  
   
   
       10 . The manufacturing method as set forth in  claim 7 , wherein the iron powder has a maximum particle size of 104 to 200 microns.  
   
   
       11 . The manufacturing method as set forth in  claim 7 , wherein the Fe—P alloy powder has a maximum particle size of 61 to 104 microns, and the Cu—Sn alloy powder has a maximum particle size of 35 to 61 microns.  
   
   
       12 . The manufacturing method as set forth in  claim 7 , wherein the sintering time is 15 to 90 minutes.  
   
   
       13 . The manufacturing method as set forth in  claim 7 , wherein the preparing of the powder mixture further comprises: 
 mixing at least one powder of a manganese sulfide and magnesium silicate minerals into the powder mixture to adjust the ratio of said at least one powder in the powder mixture to 1.6% by mass or less.    
   
   
       14 . The manufacturing method as set forth in  claim 7 , wherein the tubular cavity is tapered at a ratio of 1/5000 to 1/1000 by inclining at least one of an inner bore surface of a die and a circumferential surface of a punch which define the tubular cavity.  
   
   
       15 . The manufacturing method as set forth in  claim 7 , further comprising: 
 dipping in an oil the sintered compact obtained by the sintering.    
   
   
       16 . The manufacturing method as set forth in  claim 7 , further comprising: 
 cooling the sintered compact obtained by the sintering at a cooling rate of 8 degrees C./min.