Sintered valve guide and manufacturing method thereof

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.

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.

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.

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.