Patent Application
20230084759
This application claims priority to German Application No. DE 10 2021 210 268.9 filed on Sep. 16, 2021, the contents of which are hereby incorporated by reference in its entirety.
The present invention relates to a layer-sintered valve seat ring. The present invention additionally relates to a method for its production, combinations therewith and their use.
The use of layer-sintered valve seat rings having a support material and a function material is known. There, an expensive function material is usually combined with a costeffective support material and by way of this the material costs for a valve seat ring are lowered. The boundary surface between the support material and the function material can, based on the axis of the valve seat ring (in the axial direction of the same), be arranged either orthogonally or at a special angle, non-orthogonally.
The installation of valve seat rings in the cylinder head generally takes place as a press fit, i.e. there is an overlap between the valve seat ring outer diameter and the diameter of the receiving bore in the cylinder head which usually amounts to 40 µm to 120 µm.
While the use of layer-sintered valve seat rings combined with a cylinder head made of an aluminium alloy is unproblematic, problems with the relaxation of the valve seat rings can occur when using cylinder heads made of cast iron alloys (for example made of cast iron with lamellar graphite (GJL), cast iron with vermicular graphite (GJV) or cast iron with spheroidal graphite (GJS)). The relaxation is a plastic deformation or a thermal creep of the valve seat ring material in the hot state (i.e. during the operation). Because of this, the outer diameter of the valve seat ring becomes smaller in the cooled-down state and the valve seat ring loses a part of its overlap/press fit in the receiving bore of the cylinder head. In the process, a loosening or detaching of the valve seat ring from the cylinder head and thus an engine failure can ultimately occur.
In particular, the use of layer-sintered valve seat rings can lead to a greater relaxation of the valve seat rings since the cheaper support material generally has a lower creep resistance than the function material and thus the overlap/press fit can be lost relatively quickly.
The object of the invention is to provide a layer-sintered valve seat ring which is to be used in cylinder heads of cast iron alloys, in the case of which the relaxation, compared with conventional layer-sintered valve seat rings, is reduced. Further, a method for its production, combinations therewith and a use of the combinations are to be provided.
According to the invention, this problem is solved through the subjects of the independent Claim(s). Advantageous embodiments are subject of the dependent claims.
The present invention is based on the general idea of forming the support material in a layer-sintered valve seat ring so that its relaxation, compared with conventional layer-sintered valve seat rings, is reduced so far that a loosening or detaching of the layer-sintered valve seat ring from the cylinder head during the operation is prevented. In particular, a layer-sintered valve seat ring is designed so that it includes at least two materials, wherein one material is a function material for a tribological contact with an opposite runner and one material is a support material for the function material, wherein the support material contains: C: 0.5 to 1.8 % by weight; Cr: 3 to 16% by weight; Mo: 1 to 5% by weight; W: 0.5 to 5.5% by weight; V: 0.4 to 4.0% by weight; Cu: 12 to 25% by weight; Fe: 41.3 to 82.6% by weight; if necessary, one or more of Mn: up to 0.6% by weight; Si: up to 1.8% by weight; wherein the rest are production-related contaminations in the form of Ni, Co, Ca, P and/or S, which likewise are present in contents of <0.3% by weight each where applicable.
In an advantageous further development of the solution according to the invention, the support material contains: C: 1.0 to 1.8% by weight; Cr: 10 to 15% by weight; Mo: 2.5 to 5 % by weight; W: 0.8 to 1.5% by weight; Si: 0.2 to 1.8% by weight; V: 0.4 to 1.5% by weight; Cu: 12 to 25% by weight; Fe: 47.8 to 73.1% by weight; if necessary Mn: up to 0.6 % by weight; wherein the rest are production-related contaminations in the form of Ni, Co, Ca, P and/or S, which likewise are present in contents of <0.3% by weight each where applicable.
In an advantageous further development of the solution according to the invention, the support material contains: C: 0.7 to 1.1% by weight; Cr: 3 to 5% by weight; Mo: 3 to 5% by weight; W: 3.5 to 5.5% by weight; V: 1.0 to 2.0% by weight; Cu: 15 to 25% by weight; Fe: 54.8 to 73.8% by weight; if necessary, one or more of Mn: up to 0.6% by weight; Si: up to 1.0% by weight; wherein the rest are production-related contaminations in the form of Ni, Co, Ca, P and/or S, which likewise are present in contents of <0,3% by weight each where applicable.
In an advantageous further development of the solution according to the invention, the support material contains: C: 1.0 to 1.8% by weight; Cr: 12 to 16% by weight; Mo: 1 to 2.5 % by weight; W: 0.8 to 2.0% by weight; Si: 0.2 to 1.2% by weight; V: 0.4 to 1.5% by weight; Cu: 12 to 25% by weight; Fe: 49.4 to 72.6 % by weight; if necessary Mn: up to 0.6 % by weight; wherein the rest are production-related contaminations in the form of Ni, Co, Ca, P and/or S, which likewise are present in contents of <0.3% by weight each where applicable.
In an advantageous further development of the solution according to the invention, the support material contains: C: 0.7 to 1.5% by weight; Cr: 2 to 4% by weight; Mo: 12 to 18% by weight; W: 2 to 4% by weight; V: 1 to 2% by weight; Cu: 10 to 20% by weight; Co: 6 to 14% by weight; Fe: 34.5 to 66.3% by weight; if necessary Mn: up to 1.0% by weight; Si: up to 1% by weight; wherein the rest are production-related contaminations in the form of Ni, Co, Ca, P and/or S, which likewise are present in contents of <0,3% by weight each where applicable.
Further, the present invention provides a combination of a valve seat ring according to the invention and a valve, wherein the valve is hard-faced or nitrided.
Further, the present invention provides a combination of a valve seat ring according to the invention and a valve, wherein the valve is formed from a nickel-based alloy or an iron-based alloy with an Ni content of 10 to 40% by weight.
Further, the present invention provides a combination of a valve seat ring according to the invention and a cylinder head of a cast iron alloy, wherein the cast iron alloy contains lamellar graphite, vermicular graphite or spheroidal graphite, and wherein the valve seat ring is inserted into the cylinder head with a press fit.
Further, the present invention provides a method for producing a layer-sintered valve seat ring according to the invention, including the steps: producing starting material powders for a support material and a function material with compositions as stated above; uniaxial pressing of the starting material powder; sintering the uniaxially pressed starting material powders under an endogas atmosphere or a nitrogen-hydrogen atmosphere at a temperature in the range from 1055° C. to 1152° C.; and heat-treating of the sintered material by tempering or annealing.
In an advantageous further development of the method according to the invention, the uniaxial pressing is carried out at a pressure in the range from 40 MPa to 140 MPa at a temperature in the range from 12° C. to 60° C. and for a time in the range from 0.5 s to 1.8 s.
In an advantageous further development of the method according to the invention, the sintering is carried out for a time in the range from 10 min to 30 min at sintering temperature.
In an advantageous further development of the method according to the invention, the heat-treating is carried out by tempering, wherein the tempering is preferentially carried out by hardening at 850° C. to 950° C., oil-quenching and annealing at 510° C. to 610° C. in this order.
In an advantageous further development of the method according to the invention, the heat-treating is carried out by annealing, wherein the annealing is preferentially carried out by heating at 550° C. to 620° C.
In an advantageous further development of the method according to the invention, one of the combinations mentioned above is used in an internal combustion engine, which is partly or completely operated with hydrogen as fuel gas.
Further important features and advantages of the invention are obtained from the subclaims, from the drawings and from the associated figure description by way of the drawings.
It is to be understood that the features mentioned above and still to be explained in the following cannot only be used in the respective combination stated, but also in other combinations or by themselves without leaving the scope of the present invention.
Preferred exemplary embodiments of the invention are shown in the drawings and are explained in more detail in the following description, wherein same reference numbers relate to same or similar or functionally same components.
There it shows, in each case schematically
According to
The valve seat ring according to the invention can be produced in particular with the following method.
In a first step, starting material powders for the support material 2 and the function material 1 are produced with compositions as stated above. This is followed by a uniaxial pressing of these starting material powders, preferentially at a pressure in the range from 40 MPa to 140 MPa, at a temperature in the range from 12° C. to 60° C. and for a time in the range from 0.5 s to 1.8 s. Here, one of the starting material powders, prior to the joint final compaction by uniaxial pressing can be subjected to a pre-compaction. By way of this, the boundary surface between the support material and the function material can be pre-adjusted to a desired angle with respect to the valve seat ring axis in the manner shown in
Following this, the uniaxially pressed starting material powder is sintered under an endogas atmosphere or a nitrogen-hydrogen atmosphere at a temperature in the range from 1055° C. to 1152° C., wherein the sintering is carried out preferentially for a time in the range from 10 min to 30 min.
Finally, the sintered material is heat-treated by tempering or annealing. The tempering is preferably carried out by hardening at 850° C. to 950° C., oil-quenching and annealing at 510° C. to 610° C. in this order. The annealing is preferably carried out by heating at 550° C. to 620° C.
The valve seat ring according to the invention is preferably used in a combination with a hard-faced or nitrided valve as opposite runner. Alternatively, the application as valve seat ring can take place combined with a valve of a nickel-based alloy or an iron-based material with an Ni content of 10-40 % by weight as opposite runner.
In the following, examples of the present invention in the form of two fired engine tests are described. Here, the outer diameter each of the valve seat rings after the engine test was measured in three planes and the receiving bore in the cylinder head was likewise measured in three planes. From this the overlap of the respective valve seat ring in the planes was then calculated.
The engine test 1 was a high performance load cycle with a runtime of 1063 hours at a rated output of 260 kW (engine with 7.7 1 cubic capacity). This customer-specific cyclical continuous operation takes place with a high full-load proportion. The support material was a material according to the present Claim 2 and the function material was a material according to the present Claim 5. The angle (6) between the function material and the support material amounted to approximately 90°. The cylinder head material was cast iron with lamellar graphite (GJL). The initial overlap between valve seat ring and cylinder head amounted to 40 to 60 µm and the outer diameter of the valve seat ring amounted to 40.068 ± 0.008 mm. The comparison material was the cast material PL 500. For comparing the material according to the invention with the comparison cast material, the mean value of 4 VSR exhaust valve seat rings each was formed.
The engine test 2 was a customer-specific “cold-warm-continuous operation” with a runtime of 264 hours (engine with 12.81 cubic capacity). The support material was a material according to the present Claim 2 and the function material was a material according to the present Claim 5. The angle (6) between the function material and support material amounted to 60 to 68°. The cylinder head material was cast iron with lamellar graphite (GJL). The initial overlap between valve seat ring and cylinder head amounted to 50 to 70 µm and the outer diameter of the valve seat ring amounted to 43.078 ± 0.008 mm. The comparison material was the sinter material PLS 259. For comparing the material according to the invention with the comparison cast material, the mean value of 3 VSR exhaust valve seat rings each was formed.
In
| Number | Date | Country | Kind |
|---|---|---|---|
| 102021210268.9 | Sep 2021 | DE | national |
