Sintered valve guide and method for producing same

Patent metadata

Field	Value
Publication number	US-12060628-B2
Application number	US-201916971821-A
Country	US
Kind code	B2
Filing date	Feb 22, 2019
Priority date	Feb 23, 2018
Publication date	Aug 13, 2024
Grant date	Aug 13, 2024

Abstract

A sintered valve guide having a metallic structure that has a matrix composed of a martensite phase dispersed in a pearlite single phase structure or a mixed structure of ferrite and pearlite, and a pore dispersed within the matrix, wherein the martensite phase exists in a proportion such that an area ratio of the martensite phase in a structure cross-section is within a range from 1 to 10% of the matrix is provided. A method for producing a sintered valve guide is provided, the method includes preparing a mixed powder by adding a copper-phosphorous alloy powder, a nickel powder and a graphite powder to an iron powder, molding the mixed powder into a molded body having a density of 6.8 to 7.2 Mg/m 3 , and sintering the obtained molded body at a temperature of 950 to 1,200° C.

First claim

The invention claimed is:

1. A sintered valve guide having a metallic structure that has a matrix composed of a martensite phase dispersed in a mixed structure of ferrite and pearlite, and pores dispersed within the matrix,
wherein the martensite phase exists in a proportion such that an area ratio of the martensite phase in a structure cross-section is within a range from 1 to 10% of the matrix, and wherein a composition of the sintered valve guide comprises, by mass, 0.8 to 5.7% of Cu, 0.2 to 3.0% of Ni, 0.24 to 1.2% of P, and 0.5 to 1.5% of C, with a remainder comprising Fe and unavoidable impurities, and
wherein the martensite phase is of a size having an average area-equivalent circle diameter of 1 to 200 μm in a structure cross-section.

2. The sintered valve guide according to claim 1 , wherein the composition of the sintered valve guide comprises, by mass, 1.5 to 3.0% of Ni.

3. The sintered valve guide according to claim 1 , wherein the composition of the sintered valve guide comprises, by mass, 0.8 to 5.7% of Cu, 0.2 to 2.0% of Ni, 0.24 to 1.2% of P, 0.5 to 1.5% of C, and 0.01 to 1.5% of a machinability improver, with a remainder comprising Fe and unavoidable impurities.

4. The sintered valve guide according to claim 1 , wherein the matrix composed of a martensite phase dispersed in a mixed structure of ferrite and pearlite, and pores dispersed within the matrix, contains an Fe—P—C compound in the pearlite, and wherein the pearlite is partially micronized.

5. The sintered valve guide according to claim 3 , wherein the machinability improver comprises, by mass relative to the composition, at least one of 0.01 to 0.5% of boron nitride, 0.05 to 1.0% of a magnesium silicate mineral, and 0.1 to 1.5% of manganese sulfide.

Assignees

• Hitachi Chemical Co Ltd
• Resonac Corp

Inventors

• Fukae Daisuke
• Kawata Hideaki

Classifications

• F01L3/08

  Valves guides; Sealing of valve stem, e.g. sealing by lubricant · CPC title

• B22F2301/35

  Iron · CPC title

• B22F5/00

  Manufacture of workpieces or articles from metallic powder characterised by the special shape of the product · CPC title

• B22F3/1003

  Use of special medium during sintering, e.g. sintering aid · CPC title

• B22F5/008

  of engine cylinder parts or of piston parts other than piston rings (of piston rings B22F5/02) · CPC title