PRODUCTION OF JOINING TYPE VALVE SEAT MADE OF SINTERED ALLOY, AND SINTERED ALLOY MATERIAL FOR JOINING TYPE VALVE SEAT

摘要

PROBLEM TO BE SOLVED: To produce a sintered alloy material for a joining type valve seat free from the generation of cracks by subjecting raw material powder having a specified componental compsn. to compacting, executing sintering under heating, cooling this sintered body at a specified cooling rate and thereafter executing air cooling. ;SOLUTION: Raw material powder is mixed so as to compose a compsn. contg., by weight, 0.5 to 2.0% C, 3.0 to 20.0% Cr, 4.0 to 20.0% Cu, and the balance Fe with inevitable impurities, which is compacted and sintered under heating. At the time of cooling this sintered body from the heating temp. or at the time of furthermore heating the same to the Ac₃ or Acm transformation point to 1200°C and executing cooling, it is cooled to ≤650°C at a cooling rate of ≤4.5°C/min, and after that, air cooling is executed. In this way, the sintered alloy material for a joining type valve seat having a granular pearlitic structure in which fine carbides are precipitated and further, in which sintering pores are sealed with Cu or infiltrated with Cu or a Cu alloy, excellent in elongation characteristics and furthermore excellent in durability can be obtd.;COPYRIGHT: (C)1998,JPO