Specialized metallurgical processes – compositions for use therei – Compositions – Loose particulate mixture containing metal particles
Reexamination Certificate
1999-09-27
2001-04-10
Jenkins, Daniel J. (Department: 1742)
Specialized metallurgical processes, compositions for use therei
Compositions
Loose particulate mixture containing metal particles
C419S038000, C419S046000
Reexamination Certificate
active
06214080
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates in general to metallic powdered blends, and more particularly to a new and improved metallic powdered blend useful for making a vehicle part such as a valve seat insert.
2. Description of the Related Art
The operation cycle of an internal combustion engine is well known in this art. The physical requirements for the intake and exhaust valves, valve guides, and valve seat inserts to effectively interact in sealing the combustion have been studied extensively.
Wear resistance is a prime requirement for valve seat inserts used in internal combustion engines. In an effort to achieve a combination of good heat and corrosion resistance and machinability coupled with wear resistance, exhaust valve seat inserts have been made from cobalt, nickel, or martensite iron based alloy castings. These alloys have been generally preferred over austenitic beat-resistant steels with high chromium and nickel content because of the presence of wear resistant carbides in the cast alloys.
Powder metallurgy has been employed in the manufacture of valve seat inserts as well as other engine components, because the net end shape is fairly readily achieved. Powder metallurgy permits latitude in selecting a variety of metallic or even ceramic compositions as well as offering design flexibility.
U.S. Pat. No. 4,724,000 assigned to the Assignee of the present invention and hereby incorporated by reference describes a wear resistant article manufactured using powder metallurgy. This patent is particularly directed to a valve seat insert.
U.S. Pat. No. 5,041,158 also relates to powdered metal parts and particularly the beneficial affects of the addition of a powdered hydrated magnesium silicate. This patent is also assigned to the Assignee of the present invention and hereby incorporated by reference.
Other patents of interest include: U.S. Pat. No. 4,546,737; U.S. Pat. No. 4,671,491; U.S. Pat. No. 4,734,968; U.S. Pat. No. 5,000,910; U.S. Pat. No. 5,032,353; U.S. Pat. No. 5,051,232; U.S. Pat. No. 5,064,610; U.S. Pat. No. 5,154,881; U.S. Pat. No. 5,271,683; and U.S. Pat. No. 5,286,311.
Valve seat inserts for internal combustion engines require high wear resistance materials which can offer high wear resistance even at elevated temperatures for prolonged periods of time. Valve seat inserts further require along with the high heat resistance, high creep strength and high thermal fatigue strength even under repeated impact loading at elevated temperatures.
Typically, the valve seat insert materials that are made from high alloy powders have low compressibility. Therefore, processes such as double pressing, double sintering, high temperature sintering, copper infiltrating, and hot forging are used to achieve a desired density level. Unfortunately, this can make the material prohibitively expensive.
Thus, there still exists a need for a powdered metal blend which will result in a relatively high density, and yet only utilize a single press and/or a single sintering method. Such a material blend will be capable of being compacted to a minimum density ranging from about 6.7 g/cm
3
to about 7.1 g/cm
3
to make a component that can function in a severe engine environment. Such a powder metal blend will be fairly cost effective yet still offer significant wear resistance, high temperature resistance, machinability, high creep strength, and high thermal fatigue strength.
BRIEF SUMMARY OF THE INVENTION
The present invention is directed to solving the aforementioned problems as well as others by providing a novel powdered metal blend mixture that uses a unique combination of a valve steel powder for high temperature wear and corrosion resistance with a ferro-alloy powder such as ferro- molybdenum, ferro-vanadium and ferro-niobium powder for high temperature hot hardness (the term “hot hardness” means hardness measured at elevated temperatures) and with copper for machinability and thermal conductivity. The blend according to the present invention includes a tool steel powder for wear resistance and a solid lubricant to provide low friction and sliding wear as well as an improvement in machinability.
Accordingly, one object of the present invention is directed to a new powder metal material blend that results in a relatively high density while only requiring a single press and/or single sintering method.
Another object of the present invention is directed to a powdered metal blend which contains a mixture of valve steel powder, nickel, copper, ferro-alloy powder, a tool steel powder, a solid lubricant, graphite and a temporary or fugitive lubricant, with the balance being substantially a low alloy steel powder containing a selected amount of molybdenum.
A further object of the present invention is directed to providing a powdered metal engine component normally used in wear resistance applications that provides superior properties in hardness, hot hardness, abrasive wear, adhesive wear, scuffing, high temperature oxidation tendency, and thermal creep resistance.
Still another object of the present invention is to provide a powdered metal blend for making an engine component such as a valve seat insert.
The present invention comprises an improved powdered metal engine component having a chemical composition of between about 0.8 to about 2.0% carbon (C), from about 2.0 to about 6.0% chromium (Cr), from about 1.0 to about 20.0% copper (Cu), from about 0.5 to about 2.0% manganese (Mn), from about 5.0 to about 8.0% molybdenum (Mo), from about 4.0 to about 7.0% nickel (Ni), from about 0.05 to about 0.15% nitrogen (N), from about 0.2 to about 0.7% tungsten (W), from about 0.05 to about 0.5% vanadium (V), from about 0.2 to about 0.6% sulphur (S), and the balance being substantially iron (Fe).
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages, and specific objects attained by its uses, reference is made to the accompanying Examples and descriptive matter in which a preferred embodiment of the invention is illustrated.
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Wear, The effect of operating conditions on heavy duty engine valve seat wear, Y.S. Wang S. Narasimhan, J.M. Larson, J.E. Larson, G.C. Barber.
Sintered Valve Seat Inserts and Valve Guides: Factors Affecting Design, Performance & Machinability by H. Rodrigues.
Valve Gear Wear and Materials by S.L. Narasimhan and J.M. Larson.
Narasimhan Sundaram L.
Rodrigues Heron
Wang Yushu
Eaton Corporation
Jenkins Daniel J.
Kalka Daniel S.
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