High mechinability iron base sintered alloy for valve seat inserts

Abstract

A ferrous sintered valve seat material is made of mixed powders comprising a sinter-hardenable phase and a finely dispersed carbide phase. The powder mixture comprises a sinter-hardening prealloyed powder forming 75 to 90 wt.% of the mixture and a tool steel powder with finely dispersed carbides forming 5 to 25% of the mixture. Machinability additives of MnS, CaF2 or MoS2 types are added in an amount of 1 to 5 wt.%. Improved thermal conductivity is obtained by infiltrating the compact with Cu up to 25 wt.%.

Description

technical field [0001] The present invention relates generally to iron-based sintered alloy compositions for use in the manufacture of valve seat plates for internal combustion engines. Valve seat inserts (VSI) work in very harsh environments. Seat backing alloys need to resist wear and / or sticking caused by mating seating surfaces, resist softening and degradation caused by high operating temperatures, and resist corrosion caused by combustion products. Background technique [0002] The valve seat backing plate is machined after being inserted into the cylinder head. The cost of machining the valve seat backing plate accounts for a large portion of the total cost of machining the cylinder head. During machining operations, this becomes a major problem in the design of seat backing plate alloys since the hard material phase that makes the alloy wear resistant also causes severe wear to cutting tools. [0003] Sintered alloys have replaced cast alloys for valve seat back p...

AI Technical Summary

Problems solved by technology

Although Co alloys exhibit a good balance of various properties, the price of Co is that these alloys are too expensive for automotive applications