Material for sliding parts having self lubricity and wire material for piston ring

Abstract

A material for use as self-lubricating sliding parts, which consists of a steel containing, by mass, from not less than 0.4% to less than 1.5% of C (carbon), 0.1 to 3.0% of Si, 0.1 to 3.0% of Mn, from inclusive zero to 0.5% of Cr, 0.05 to 3.0% of Ni, 0.3 to 2.0% of Al, 0.3 to 20% in total (Mo+W+V) of at least one element selected from the group consisting of Mo, W (tungsten) and V (vanadium), and 0.05 to 3.0% of Cu, wherein there can be observed graphite particles having an average particle size of not more than 3 μm in a section of the metal structure of the steel. The steel is also used as piston rings. In the steel, the graphite particles observed in the structural section occupy an area rate of not less than 1% in the overall area of the structural section, and have an average particle size of not more than 3 μm. The steel may further contain not more than 0.3% of S and / or not more than 0.01% of Ca. The steel is subjected to nitriding treatment for use.

Description

TECHNICAL FIELD [0001] The present invention relates to material for use as sliding parts, e.g. piston rings, cylinder liners and vanes, which are incorporated in automotive engines or other internal combustion engines, as well as usual plain bearings, roller bearings, ball bearings, gears and dies. BACKGROUND ART [0002] Materials having excellent wear resistance property have been applied so far to sliding parts such as cylinder liners and vanes. Materials for piston rings used in internal combustion engines, especially automotive engines, have been changed from cast steel to steel wire, which is processed to ring forms. In usual, the piston rings are produced in such a manner that an ingot with a predetermined composition is hot-worked to wire by forging, hot-rolling or the like, the thus obtained wire is further formed to have a given cross-sectional form corresponding to a small sectional form of a piston ring by drawing or the like, the formed wire is conditioned to have a give...

AI Technical Summary

Benefits of technology

The present invention provides a material for sliding parts that has excellent wear resistance and low friction coefficient properties. The material is made of a steel that contains specific amounts of carbon, silicon, and other elements such as molybdenum, tungsten, vanadium, and copper. The steel also contains graphite particles that have a specific size and distribution. The invention also provides a wire material for piston rings that has a specific metal structure with graphite precipitates, which improves seizure resistance and lowers friction coefficient. The invention addresses the problem of poor seizure resistance and high friction coefficient of sliding parts, which are exposed to severe conditions in their environments. The invention provides a solution to improve durability and workability of sliding parts.

Problems solved by technology

Steel piston rings are outstandingly excellent in mechanical properties and wear resistance property than those of cast iron rings, but have poor seizure resistance property, which is one of reasons that second rings of steel have not been made good progress.

But, such unsolved problems still remain as a cost for surface-treatment and aluminum adhesion which occurs at the interface between a piston and a piston ring.

As countermeasures against such disadvantages, the patent literature No. 2 proposes surface-treatments such as PVD, whereas an increase of a manufacturing cost cannot be avoided according to such surface-treatment.

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