HIGHLY THERMALLY CONDUCTIVE VALVE SEAT RING

Abstract

The invention relates to a powdermetallurgically produced valve seat ring having a carrier layer and a function layer. It is the objective of the invention to provide a valve seat ring of the kind mentioned above that offers significantly higher thermal conductivity properties. To achieve this objective and based on a valve seat ring of the kind first mentioned above the invention proposes that the carrier material of the carrier layer has a thermal conductivity higher than 55 W/m*K at a total copper content ranging between >25 and 40% w/w.

Claims

1. Powdermetallurgically produced valve seat ring comprising a carrier layer (2) and a function layer (3), characterized in that the carrier material of the carrier layer (2) has a thermal conductivity in excess of 55 W/m*K at a total copper content ranging between >25 and 40% w/w.

Description

[0041] Exemplary embodiments of the invention are illustrated by way of the following drawings where

[0042] FIG. 1 is a sectional representation of the valve seat ring;

[0043] FIG. 2 is a micrograph of the old carrier layer;

[0044] FIG. 3 is a micrograph of the new carrier layer;

[0045] FIG. 4 is a diagram of the thermal conductivity of the entire valve seat ring according to prior art and according to the teaching of the invention;

[0046] FIG. 5 is a diagram of the thermal conductivity of the carrier layer according to prior art and according to the teaching of the invention;

[0047] FIG. 1 is a sectional view of a valve seat ring 1. The carrier layer 2 volumetrically forms the biggest part of the valve seat ring 1, with function layer 3 being situated in the upper portion of valve seat ring 1 and essentially serving as supporting face for valves. Clearly visible is the inclination between carrier layer 2 and function layer 3 extending along the valve seat ring as parallelly as possible to the supporting face of the valves. At the point where carrier layer 2 and function layer 3 meet, a diffusion layer 4 forms. Said diffusion layer 4 forms in particular during sintering of the previously densified green compact.

[0048] In FIGS. 2 and 3 micrographs of the carrier layer 2 of valve seat ring 1 are shown. FIG. 2 depicts the microstructure of a conventional carrier layer 2 according to prior art while FIG. 3 illustrates within the scope of the present invention a micrograph taken of the carrier layer 2 of a valve seat ring 1. As can be clearly seen, the micrograph of carrier layer 2 in FIG. 3 shows a significantly higher copper content. In FIGS. 2 and 3 the bright spots/spaces represent the copper constituents whereas the dark spots show the share of the iron respectively iron-copper constituents.

[0049] Diagrams illustrating the thermal conductivity of the valve seat rings 1, respectively the carrier layer 2 are shown in FIGS. 4 and 5. In the diagrams, the old method of manufacturing valve seat rings 1 (acc. to prior-art; SdT) are compared with the new manufacturing method (teaching of the invention; LdE). The thermal conductivity was measured at RWTH Aachen making use of the laser flash method.

[0050] FIG. 4 shows a diagram of the thermal conductivity of finished valve seat rings 1. The composition of the function layer 3 in variant 1 differs from the composition of variant 2. Function layer 3 according to prior art is assumed to be known. Regarding the composition of the carrier layer a distinction is made according to prior art and according to the teaching of the invention; It is clearly evident that the thermal conductivity of variants 1 and 2 according to the teaching of the invention considerably exceeds the thermal conductivity of variants 1 and 2 reflecting prior art.

[0051] FIG. 5 shows a diagram of the thermal conductivity of carrier layers 2 for two different variants of function layers 3 of valve seat rings 1. It can be seen that beginning with 48 W/m*K the thermal conductivity of the customary prior-art carrier layer 2 decreases as the temperature rises. In contrast, the thermal conductivity of carrier layer 2 for both variants according to the teaching of the into is on average slightly above 70 W/m*K. At a temperature of 500 C. the thermal conductivity of variants 1 & 2 according to the teaching of the invention (appr. 70 W/m*K) is 46% w/w higher than the thermal conductivity of variants 1 & 2 according to prior art (appr. 38 W/m*K).

[0052] The invention is explained in more detail by way of the following example:

EXAMPLE

[0053] The carrier layer consisting of a carrier material is press formed at 550 MPa to obtain a semi-finished product. The carrier material in this case consists of a combination of copper powder and an iron-copper alloy powder. The carrier layer has the form of a ring, with said ring having a great inwardly sloping inclination. Said semi-finished product is subsequently covered with a function material of powdery consistency and then press formed into a green compact thus producing the function layer. This green compact is sintered at 1100 C., with copper in wire form being added. Said added copper melts and penetrates by capillary action into the green compact during the sintering process. The alloy composition of the carrier layer of the finished valve seat ring is 1.2% w/w C, 0.3% w/w Mn, 0.2% w/w S, and 35% w/w Cu, with the alloy composition of the function layer amounting to 1.1% w/w C, 9.7% w/w Co, 1.4% w/w Mo, 2.5% w/w Ni, 3.0% w/w Cr, 0.5% w/w Mn, 0.5% w/w S, and 19.0% w/w Cu, in which the copper contents of the iron-copper alloy, the copper powder, and copper infiltration have been summarized.

[0054] The manufactured valve seat ring features high strength, good thermal conductivity, and lubricity.