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  Iron-based powder combinationUSPTO Application #: 20080089801Title: Iron-based powder combination Abstract: The invention relates to a powder metallurgical combination comprising an iron-based powder A essentially consisting of core particles of iron pre-alloyed with molybdenum and having 6-15%, preferably 8-12% by weight of copper diffusion alloyed to the core particles, an iron-based powder B essentially consisting of particles of iron pre-alloyed with molybdenum and having 4.5-8%, preferably 5-7% by weight of nickel diffusion alloyed to the core particles, and an iron-based powder C essentially consisting of particles of iron pre-alloyed with molybdenum. The invention also relates to the powders A and B per se. Further the invention relates to a method for preparing an iron-based sintered component comprising 0.3-2% by weight of molybdenum, 0.2-2%. Preferably 0.4-0.08% by weight of copper and 0.1-4% by weight of nickel and to a method to obtain a sintered component having a predetermined strength and a predetermined dimensional change during sintering. (end of abstract) Agent: Buchanan, Ingersoll & Rooney PC - Alexandria, VA, US Inventor: Mats Larsson USPTO Applicaton #: 20080089801 - Class: 419011000 (USPTO) Related Patent Categories: Powder Metallurgy Processes, Powder Metallurgy Processes With Heating Or Sintering, Metal And Nonmetal In Final Product, Nonmetal Is Elemental Carbon The Patent Description & Claims data below is from USPTO Patent Application 20080089801. Brief Patent Description - Full Patent Description - Patent Application Claims
FIELD OF THE INVENTION [0001] The present invention refers to iron-based powder metallurgical combinations and to methods for preparing sintered powder metallurgical components therefrom. More specifically the invention refers to the production of sintered components including copper, nickel and molybdenum by using these combinations. BACKGROUND OF THE INVENTION [0002] Within the powder metallurgical field, copper, nickel and molybdenum has since long been used as alloying elements in the production of high strength sintered components. [0003] Sintered iron-based components can be produced by mixing alloying elements with the pure iron powders. However, this may cause problems with dust and segregation which may lead to variations in size and mechanical properties of the sintered component. In order to avoid segregation the alloying elements may be pre-alloyed or diffusion alloyed with the iron powder. In one method molybdenum is pre-alloyed with iron powder and this pre-alloyed iron powder is subsequently diffusion alloyed with copper and nickel for production of sintered components from iron-based powder compositions containing molybdenum, nickel and copper. [0004] It is however obvious that, when producing a sintered iron-based component, from a powder wherein molybdenum is pre-alloyed and wherein copper and nickel are diffusion alloyed, the content of the alloying elements in the sintered iron-based component will be substantially identical with the content of alloying elements in the used diffusion alloyed powder. In order to reach different contents of the alloying elements in the sintered component, yielding different properties, iron-based powders having different contents of the alloying elements have to be used. [0005] The present invention provides a method of eliminating the need of producing a specific powder for each desired chemical composition of the sintered iron-based component having alloying elements from molybdenum, copper and nickel. The invention also offers the advantage of providing a method for controlling the dimensional change and the tensile strength to predetermined values. In a specific embodiment the dimensional change is independent of the carbon content and the density. SUMMARY OF THE INVENTION [0006] In brief the invention concerns a powder metallurgical combination of three different iron-based powders. The first of these iron-based powders consisting of core particles of iron, pre-alloyed with molybdenum, which is additionally diffusion alloyed with copper and the second iron-based powder consisting of core particles of iron, pre-alloyed with molybdenum, which is diffusion alloyed with nickel. The third iron-based powder essentially consists of particles of iron pre-alloyed with molybdenum. [0007] The invention also concerns the two diffusion alloyed iron-based powders. [0008] A method according to the invention comprises the steps of combining these three iron-based powders in predetermined amounts, mixing the combination with graphite, compacting the obtained mixture and sintering the obtained green body. [0009] Another aspect of the invention concerns a method of providing a sintered component having a predetermined strength and a predetermined dimensional change during sintering. DESCRIPTION OF THE DRAWINGS [0010] FIG. 1-4 illustrate diagrams for determining the copper and nickel content in the powder metallurgical combination for a predetermined strength and dimensional change. DETAILED DESCRIPTION OF THE INVENTION [0011] Specifically the iron-based powder metallurgical combination according to the invention comprises: [0012] an iron-based powder A essentially consisting of core particles of iron pre-alloyed with molybdenum, whereby 6-15%, preferably 8-12% by weight of copper, is diffusion alloyed to the core particles. [0013] an iron-based powder B essentially consisting of core particles of iron pre-alloyed with molybdenum, whereby 4.5-8%, preferably 5-7% by weight of nickel, is diffusion alloyed to the core particles, and [0014] an iron-based powder C, essentially consisting of particles of iron pre-alloyed with molybdenum. [0015] The amount of pre-alloyed molybdenum in the particles in the iron-based powders A, B and C, respectively, may vary between 0.3-2% by weight, preferably 0.5 and 1.5% by weight. In one embodiment the particles in all three powders are pre-alloyed with the same amount of molybdenum. Amounts above 2% of Mo does not give an increase of the strength justifying the increase of the costs. Amounts of Mo below 0.3% does not give a significant effect of the strength. [0016] The amount of copper and nickel which is diffusion alloyed to the core particles is limited in the upper range to 15% copper and 12% nickel. The lower limit of copper and nickel which is diffusion alloyed to the core particles should be substantially higher than the amount required in the sintered component to achieve the advantages of the invention. Thus, for practical reasons an iron-based powder essentially consisting of core particles pre-alloyed with molybdenum and comprising at least 6% copper diffusion alloyed to the core particles and an iron-based powder having core particles pre-alloyed with molybdenum and comprising at least 4.5% nickel diffusion alloyed to the core particles are of special interest. [0017] The powders A, B and C, respectively, essentially consist of particles of iron pre-alloyed with molybdenum, but other elements, except unavoidable impurities, may be pre-alloyed to the particles. Such elements may be nickel, copper, chromium and manganese. [0018] In order to produce a sintered component from the powder combination according to the present invention, the respective amounts of powder A, B and C are determined and mixed with graphite in the amount required for the predetermined strength. The obtained mixture may be mixed with other additives before compaction and sintering. The amount of graphite which is mixed in the powder combination is up to 1%, preferably 0.3-0.7%. [0019] Other additives are selected from the group consisting of lubricants, binders, other alloying elements, hard phase materials, machinability enhancing agents. [0020] In accordance with one embodiment of the powder metallurgical combination, powder C is essentially free from Cu and Ni. [0021] The relation between powder A, B and C is preferably chosen so that the copper content will be 0.2-2% by weight, the nickel content will be 0.1-4% by weight and the molybdenum content will be 0.3-2% by weight, preferably 0.5-1.5% by weight of the sintered component. [0022] In one embodiment the copper content is 0.2-2%, preferably 0.4-0.8% and the nickel content is 0.1-4%. It has unexpectedly been found that in this particular embodiment the dimensional change during sintering is independent of the carbon content and sintered density. Continue reading... Full patent description for Iron-based powder combination Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Iron-based powder combination patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. 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