JP2002515542A - Iron-based composition for metallurgy containing flow agent and method of using the same - Google Patents

Abstract

The present invention concerns an improved metallurgical powder composition comprising a major amount of an iron based metal powder and a minor amount of a particulate inorganic oxide having an average particle size below 500 nm.

Description

DETAILED DESCRIPTION OF THE INVENTION

TECHNICAL FIELD The present invention relates to iron-based powder compositions for metallurgy. In particular, the invention relates to such compositions containing a flow agent which improves the flow properties of the powder composition, especially at elevated processing temperatures.

BACKGROUND OF THE INVENTION In powder metallurgy technology, metallurgical powder compositions are used to manufacture metal parts according to well-established techniques. Generally, metallurgical powders are poured into compaction dies and compacted under high pressure, in some cases at elevated temperatures, to produce compacted parts.
part), i.e., a green part. The green part is then sintered to form an agglomerated metal part. The sintering operation burns off any organic material, such as dice or internal lubricant residues, from the metallic material.

[0003] The speed and efficiency with which such components can be manufactured is affected by the flow characteristics of metallurgical powders. In most manufacturing processing techniques, metallurgical powder must flow by gravity from a storage bin into a container, or shoe, which transports the powder from a storage location to a die. The powder is then injected from the shoe into the die cavity. The speed at which the powder can flow is often the rate-limiting step in component manufacturing.

Currently, there is an increasing demand for powder metallurgical compositions, particularly iron-based powder compositions, that can be used in molding operations performed under warm pressing conditions. Improved powder compositions useful in such molding operations are described in U.S. Pat. No. 5,154,881 to Rutz and Luk, the entire contents of which are incorporated herein by reference. (Incorporated in the specification). Generally, the powder and / or die cavities are heated to a temperature of up to about 370 ° C. for molding. In some cases,
In order to increase the efficiency of such a molding process, it is desirable to preheat the powder composition to at least about 150 ° C. or higher. However, the flowability of certain iron-based powder compositions has been found to be adversely affected by these processing temperatures.

[0005] Accordingly, there is a need for powder metallurgy techniques for producing metallurgical iron-based powder compositions having improved flow properties. At the elevated temperatures associated with warm forming operations, there is a particular need to produce such iron-based powder compositions having improved flow properties.

DISCLOSURE OF THE INVENTION The present invention provides iron-based powder compositions for metallurgy characterized by having excellent flow properties, especially at elevated temperatures associated with warm forming operations. The present invention also provides a method of using the powder compositions to make molded parts. According to the present invention,
A flow agent is added to the iron-based powder composition. The presence of a flow agent determines the flowability of the powder composition,
It increases especially at elevated temperatures.

[0007] Glidant materials are nanoparticles of various metals and their oxides. Typically,
These metal and metal oxide powders have an average particle size of less than about 500 nm. In one embodiment of the present invention, the iron-based powder composition is mixed with a silicon oxide flow agent. Preferably, the silicon oxide flow agent is mixed with the iron-based powder in an amount of about 0.005 to about 2% by weight of the resulting powder composition. Preferred silicon oxides have an average particle size of less than about 40 nm.

[0008] In another aspect of the invention, an iron-based powder composition is mixed with an iron oxide flow agent. Preferred iron oxide flow agents have an average particle size of less than about 500 nm. Iron oxide fluidizers
Preferably, it is mixed with the iron-based powder in an amount of about 0.01 to about 2% by weight of the resulting powder composition. It is particularly advantageous to mix the silicon oxide flow agent and the iron oxide flow agent.

[0009] The addition of a flow agent is particularly advantageous for improving the flow characteristics of these iron-based powder compositions used in the warm forming process. As such, the composition also contains a lubricant specially designed for such warm forming applications, and if necessary, a binder specifically designed for such applications. Is preferred.

[0010] It has also been found that the addition of a flow agent unexpectedly reduces the firing force required to remove the molded part from the die. Therefore, adding the flow agent of the present invention
It is believed to reduce die wear.

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an improved metallurgical powder composition having excellent flow properties, especially at elevated temperatures. These metallurgical powder compositions generally contain an iron-based powder, and optionally a lubricant powder and / or a binder, and are improved by further adding a flow agent powder having a defined particle size distribution. Have been.

The metal powder composition that is the subject of the present invention contains an iron-based powder of the type commonly used in powder metallurgy. Examples of the term "iron-based" powder as used herein include substantially pure iron powder; other elements that enhance the strength, curability, electromagnetic properties, or other desired properties of the final product (eg, , Steel-making elements) and pre-alloyed iron particles;
Iron particles in which such other elements are diffusion bonded; and iron particles mixed with such alloying element particles. The iron-based powder generally comprises at least about 85%, more usually at least about 90%, by weight of the metal powder composition.

[0013] Substantially pure iron powder that can be used in the present invention is an iron powder having a normal impurity content of about 1.0% by weight or less, preferably about 0.5% by weight or less. An example of such a highly compressible metallurgical grade iron powder is ANCOR Steel, available from Hoeganaes Corporation of Riverton, NJ.
STEEL) 1000 series pure iron powder, for example, 1000, 1000B and 100
0C, and similar powders available from Hegenes AB, Sweden. For example, Angkor Steel 1000 iron powder is No. About 22% by weight of particles smaller than 325 sieve (US sieve system); It has a typical sieving distribution consisting of about 10% by weight of particles larger than 100 sieves and the balance between those two particle sizes (traces larger than No. 60 sieve). Encore Steel 1000 powder is about 2.85~3.00g / cm ^3, typically has a density of apparent 2.94 g / cm ^3. Other iron powders that can be used in the present invention include Hegenes' Angkor
(ANCOR) Typical sponge iron powder, such as MH-100 powder.

[0014] The iron-based powder may comprise iron, which is preferably substantially pure iron, mixed with one or more alloying elements, pre-alloyed or diffusion bonded. Good. Examples of alloying elements that can be combined with the iron particles include, but are not limited to: molybdenum; manganese; magnesium; chromium; silicon; copper; nickel; Vanadium; Columbium (niobium); Graphite; Phosphor; Aluminum; Binary alloys of copper and tin or phosphorus; Iron alloys of manganese, chromium, boron, phosphorus or silicon; And ternary and quaternary eutectics with two or three of molybdenum and tungsten or silicon carbide; silicon nitride; aluminum oxide; and manganese or molybdenum sulfide; and combinations thereof. Typically, the alloying element is iron powder, preferably substantially pure iron powder, in an amount up to about 7% by weight, more preferably about 0.25% by weight.
Although typically combined in an amount of from about 5% to about 5%, more preferably from about 0.25% to about 4% by weight, in certain specific applications, the alloying element may comprise iron powder and It may be present in an amount from about 7% to about 15% by weight with the element.

[0015] Accordingly, the iron-based powder may include iron particles mixed with an alloying element in the form of an alloying powder. As used herein, the term "alloy powder" may be any particulate element or compound that is physically mixed with iron particles, as described above, and the element or compound is ultimately iron powder. It may or may not be alloyed. The alloying elemental particles generally have a weight average particle size of less than about 100μ, preferably less than about 75μ, more preferably less than about 30μ. It is preferable to include a binder in the mixture of the iron particles and the alloy powder so that the alloy powder does not separate from the iron powder or become dust. Examples of commonly used binders include U.S. Pat.
Nos. 483,905 and 4,676,831 [both are en-gström]
(Engstroem)] and U.S. Pat. No. 4,834,800 [Sem
el)] (herein incorporated by reference in its entirety). The binder is present in the metal powder composition at about 0.005-3% by weight, preferably about 0.05-1.5% by weight, based on the weight of the iron and alloy powder.
%, More preferably from about 0.1 to 1% by weight.

[0016] The iron-based powder may also be in the form of iron pre-alloyed with one or more alloying elements. Pre-alloyed powder is produced by making a melt of iron and the desired alloying element, then spraying the melt, whereby the sprayed droplets solidify to form a powder. Can be. The amount of alloying element (s) to be incorporated depends on the properties desired for the final metal part. A pre-alloyed iron powder blended with such alloying elements can be obtained from Hegenes as part of its Angkor steel powder.

Yet another example of an iron-based powder is a diffusion-bonded iron-based powder, an example of which is a layer or coating of one or more other metals, such as steel making elements and the alloying elements described above. Are powders that are substantially pure iron particles diffused into their outer surfaces. Such commercially available powders include DISTALOY 4600A diffusion bonded powder from Hegenes containing about 1.8% nickel, about 0.55% molybdenum, and about 1.6% copper; Distaloy 4800A diffusion bonded powder from Hegenes, containing about 4.05% nickel, about 0.55% molybdenum, and about 1.6% copper. Similar grades of powder are also available from Hegenes AB of Sweden.

A preferred iron-based powder consists of iron pre-alloyed with molybdenum (Mo). The powder is made by spraying a substantially pure iron melt containing about 0.5% to about 2.5% Mo by weight. One example of such a powder is Hegenes' Angkor Steel 85HP steel powder, which contains about 0.85% Mo by weight.
And contains less than about 0.4% by weight total other materials such as manganese, chromium, silicon, copper, nickel, molybdenum, or aluminum, and less than about 0.02% by weight carbon. Another example of such a powder is Hegenes' Angkor Steel 4600V steel powder, which contains about 0.5-0.6% by weight molybdenum and about 1.5% nickel.
-2.0% by weight, about 0.1-0.25% by weight manganese, and about 0.02% carbon.
Contains less than 10% by weight.

Another pre-alloyed iron-based powder that can be used in the present invention is Causton.
ston), “Steel powder mixture containing distinctly pre-alloyed powders of iron alloys” (Steel
No. 5,108,93, entitled Powder Admixture Having Distinct Pre-alloyed Powder of Iron Alloys, which is incorporated herein by reference in its entirety. This steel powder composition is a mixture of two different pre-alloyed iron-based powders, one containing 0.5 of molybdenum.
~ 2.5% by weight of iron, the other being a prealloy of iron with carbon and at least about 25% by weight of a transition element, the latter being from the group consisting of chromium, manganese, vanadium and niobium. Contains at least one selected element. The mixture is such that it provides at least about 0.05% by weight of the transition element component to the steel powder composition. One example of such a powder is commercially available as Hegenes' Angkor Steel 41AB steel powder, which contains about 0.85 molybdenum.
%, About 1% nickel, about 0.9% manganese, about 0.7% chromium.
5% by weight, and about 0.5% by weight of carbon.

Another iron-based powder useful in the practice of the present invention is a ferromagnetic powder. One example is a composition consisting of substantially pure iron powder mixed with a small amount of phosphorus and pre-alloyed iron powder.

[0021] Yet another iron-based powder useful in the practice of the present invention is disclosed in US Pat.
198,137, the entire content of which is incorporated herein by reference, so as to provide a substantially uniform coating of the thermoplastic material. Are iron particles coated with. Each particle preferably has a substantially uniform coating surrounding the core iron particles. Sufficient thermoplastic material has been used to provide a coating of about 0.001 to 15% by weight of the coated iron particles. Generally, the thermoplastic material is present in an amount of at least 0.2% by weight of the coated particles, preferably about 0.4-2%, more preferably about 0.6-0.9%. Thermoplastics, such as polyethersulfone, polyetherimide, polycarbonate, or polyphenylene ether, having a weight average molecular weight in the range of about 10,000 to 50,000 are preferred. Iron-based powders coated with other polymers include:
Includes those having an inner coating of iron phosphate, as described in U.S. Pat. No. 5,063,011 to Rats et al., The entire contents of which are incorporated herein by reference. It is.

The particles of pure iron, pre-alloyed iron, diffusion bonded iron, or thermoplastic coated iron have a weight average particle size of less than 1μ, or as small as about 850-1000μ In general, the particles have a weight average particle size in the range of about 10 to 500 microns. Those having a maximum number average particle size of about 350μ or less, preferably 50-150μ are preferred.

The flow behavior of the iron-based powder composition is an important physical property. Because it directly affects the speed at which parts are manufactured using conventional powder metallurgy techniques. The present invention is to improve the flowability of a commonly used known iron-based powder by adding a granular flow agent. It has been found that the presence of a flow agent having a defined particle size distribution improves the flow characteristics of the metal powder composition, especially at elevated temperatures. The flow agent must not adversely affect the moldability of the powder composition,
Powder) or the sinterability of the resulting parts.

The flow agents of the present invention can be referred to as “nanoparticles” in that they are particulate materials and most of the powder has a particle size of less than 1μ. The particle size distribution of the flow agent can be determined by various methods. The term “average particle size” as used in connection with the present invention is determined on a weight basis according to formula (I): APS = 6 / (ρ × SA) (I) where APS = average particle size ρ = powder Density SA = powder surface area

The density of the powder is determined using standard methods such as those described in standard test method ASTM D70. Surface area is the BET (Brunauer, Emmet, Teller) surface area determined using standard methods such as those described in ASTM D4820. Particle size distribution can be demonstrated by electron microscopy, which can be used to visually check the particle size of the powder.

The glidant can be selected from metals and metal oxides having an average particle size of less than about 500 nm, preferably less than about 250 nm, and more preferably less than about 100 nm, so that these Called particulate material. Representative metals that can be used as nanoparticle materials in the form of metals or metal oxides include silicon, aluminum, copper, iron, nickel, titanium, gold, silver, platinum, palladium, bismuth, cobalt, manganese, magnesium, Includes lead, tin, vanadium, yttrium, niobium, tungsten, and zirconium. Such materials are
It is commercially available from ULTRAM International. These nanoparticulate materials may comprise from about 0.005 to about 2%, preferably from about 0.01 to about 1%, more preferably from about 0.025 to about 0.2% by weight, based on the total weight of the metallurgical composition. 5% by weight
In the metallurgical composition. The preferred flow agent is an oxide of silicon, and other nanoparticulate materials can advantageously be mixed with the silicon oxide to further improve the flowability of the metallurgical powder composition.

Silicon oxides that are particularly useful in the practice of the present invention have a specific surface area of about 75 to about 600 m ² /
g, preferably from about 100 to about 500 m ² / g, more preferably from about 150 to about 50
0 m ² / g. The density of the silicon oxide is preferably from about 0.02 to about 0.15 g / cm ^3, preferably from about 0.035～ about 0.1 g / cm ^3, more preferably from about 0.04 to about 0.08 g / cm ³ . The silicon oxide has an average particle size of less than about 40 nm, advantageously about 1 to about 35 nm, preferably about 1 to about 25 nm, more preferably about 5 to about 20 nm, as determined according to formula (I) above. (Generally number average particle size determined by visual inspection with an electron microscope). The particle size distribution of the silicon oxide is, based on the number of particles, about 90% less than about 100 nm, preferably 75 n
Preferably, the distribution is less than m, more preferably less than about 50 nm.

The silicon oxide comprises from about 0.05 to about 2%, preferably from about 0.01 to about 1%, more preferably from about 0.025 to about 0% by weight, based on the total weight of the metallurgical composition. It is present in the metallurgical composition in an amount of 0.5% by weight. Preferred silicon oxides are both hydrophilic and hydrophobic types of silicon dioxide materials, which are commercially available from Degussa Corporation as Aerosil-based silicon dioxides such as Aerosil 200 and R812 products.

Another preferred type of glidant is an oxide of iron. Useful iron oxides in the practice of the present invention is from about 2 to about 150 meters ² / g, preferably from about 5 to about 50 m ² / g, more preferably those having a specific surface area of from about 5 to about 20 m ² / g is there. The density of silicon oxide is
Generally from about 3 to about 5 g / cm ^3, preferably about 4 to about 5 g / cm ^3, more preferably from about 4.4 to about 4.7 g / cm ^3. The iron oxide, as determined according to formula (I) above, is preferably less than about 500 nm, advantageously about 10 to about 400 nm, preferably about 25 to about 300 nm, more preferably about 40 to about 200 nm. Particle size (generally number average particle size determined by visual inspection with an electron microscope). Preferably, the particle size distribution of the iron oxide is such that, based on the number of particles, about 90% is less than about 1 μ, preferably less than 750 nm, and more preferably less than 500 nm.

[0030] The iron oxide is present in an amount of about 0.01 to about 2%, preferably about 0.05 to about 1%, more preferably about 0.05 to about 0.5% by weight based on the total metallurgical composition. % In the metallurgical composition. Preferred iron oxides are Fe ₃ O ₄ materials. For example, a useful iron oxide is Bayferrox 31 from Miles Inc.
Commercially available as biferrox-based iron oxides such as 8M and 330 pigment products. It is preferable to use an iron oxide material together with a silicon oxide material in order to give a synergistic flow improving property to the metal powder composition.

[0031] The metal powder composition of the present invention may further include a lubricant to reduce the firing force required to remove the molded part from the die cavity. Examples of typical powder metallurgy lubricants include ethylene bisstearamide, together with a lubricant such as a stearate, generally zinc stearate and lithium stearate; molybdenum sulfide, boron nitride, and boric acid. Such as synthetic waxes. Lubricants generally comprise up to about 15%, preferably about 0.1 to about 10%, more preferably about 0.1 to 2%, and most preferably about 0.2 to 1% by weight of the metal powder composition. % In the metal powder composition.

The metal powder composition of the present invention is formed in a die according to standard metallurgy.
Typical molding pressures are about 5-200 t / in ² (tsi) (69-2760 MP
a), preferably in the range of about 20-100 tsi (276-1379 MPa), more preferably in the range of about 25-60 tsi (345-828 MPa). Following molding, the part can be sintered at a temperature and other conditions appropriate for the iron-based powder composition according to standard metallurgical techniques. Metal powder compositions having a thermoplastic coating are generally not sintered following molding, but rather, Oliver and Crisby.
sby) is subjected to a post-molding heat treatment as described in US Pat. No. 5,225,459, the entire contents of which are incorporated herein by reference.

The oxide flow agents of the present invention have been found to advantageously improve the flow characteristics of metal powder compositions designed for molding under “warm” temperature conditions. Molding according to the warm temperature method generally requires that the metal powder composition be compressed at a molding temperature of up to about 370 ° C. (700 ° F.), measured as the temperature at which the composition is being formed. And had Molding is generally above 100 ° C (212 ° F), usually about 1 ° C.
Performed at a temperature greater than 25 ° C. (260 ° F.), preferably at about 150 ° C. (300 ° F.)
) To about 370 ° C (700 ° F), more preferably from about 175 ° C (350 ° F) to about 260 ° C (500 ° F). Metal powder compositions designed for use in warm forming conditions preferably include a lubricant compatible with high temperature forming. If the iron-based powder to be warm-formed is of a type that includes alloying elemental particles, the composition typically includes a binder to prevent segregation and dusting. Useful high temperature lubricants and various binders that perform well in such compositions contemplated for warm forming are described in US Pat. No. 5,368,630 to Luke, to which reference is made. The entire contents of which are incorporated herein.

The high temperature lubricants described in US Pat. No. 5,368,630 are polyamide lubricants, which are essentially high melting waxes. The lubricant formed by the condensation reaction is a polyamide characterized by having a melting point range instead of a single melting point. One skilled in the art will recognize that the reaction product is generally a mixture of moieties that vary in molecular weight, and thus the properties dependent on it. Overall, the polyamide lubricant begins to melt at a temperature of between about 150 ° C. (300 ° F.) and 260 ° C. (500 ° F.), preferably between about 200 ° C. (400 ° F.) and about 260 ° C. (500 ° F.). The polyamide generally melts completely at about 250 ° C. above this initial melting temperature, but it is preferred that the polyamide reaction product melt over a range of about 100 ° C. or less. A preferred lubricant is ADVAWAX 45 sold by Morton International of Cincinnati, Ohio.
Commercially available as No. 0 or PROMOLD 450 polyamide, it is ethylene bisstearamide having an initial melting point of about 200 ° C to 300 ° C.
The high temperature lubricant is generally added to the composition in the form of solid particles. The particle size of the lubricant may vary, but is preferably less than about 100μ. Most preferably, the lubricant particles have a weight average particle size of about 10 to 50μ.

The binder described in US Pat. No. 5,368,630 is a polymeric resin material that is soluble or insoluble in water, but it is preferred that the resin be insoluble in water. The resin preferably has the ability to form a film around the iron-based powder and alloying powder in its natural liquid state or dissolved in a solvent. The binder resin is
It is important that it be selected such that it does not adversely affect the molding process at elevated temperatures. Preferred binders include cellulose acetate having a number average molecular weight (MW) of about 30,000 to 70,000, cellulose acetate butyrate having a MW of about 10,000 to 100,000, about 10,000 to 100,000. Cellulose ester resins such as cellulose acetate propionate having a MW of 0.1 and mixtures thereof. A high molecular weight thermoplastic phenolic resin having a MW of about 10,000 to 80,000, and about 50,000 having an alkyl moiety having 1 to 4 carbon atoms.
Also useful are hydroxyalkyl cellulose resins having a MW of ~ 1,200,000 and mixtures thereof. Another preferred binder is polyvinylpyrrolidone, which is PEG, as described in US Pat. No. 5,432,223.
It is preferably used in combination with plasticizers such as glycerol and its esters, esters of organic diacids, sorbitol, phosphate esters, cellulose esters, arylsulfonamide-formaldehyde resins and long-chain alcohols.

The flow agents of the present invention can be mixed with iron-based powders by conventional mixing techniques to form metallurgical compositions. Generally, the iron-based powder contains the optional alloying powder, but is mixed in any order with any of the flow agents, lubricants, and binders of the present invention. In the embodiment where the metal powder contains an iron-based powder, which is an iron powder mixed with an alloying powder together with a binder and a lubricant, the method described in US Pat. No. 5,368,630 is used. A metal powder mixture can be prepared. Generally, it is preferred that the binder be in liquid form and mixed with the powders for a time sufficient to achieve good powder wetting. Preferably, the binder is dissolved or dispersed in the organic solvent to better disperse the binder in the powder mixture and thereby substantially uniformly distribute the binder throughout the mixture. Lubricants can be added in their dry particle form, generally before or after the binder is added. Preferably, the lubricant is first dry mixed with the iron-based powder, and then the binder is applied to the metal powder composition,
The solvent is removed and then the flow agent is added by dry mixing.

[0037] The order of addition of the binder and the lubricant can be varied to change the final properties of the powder composition. In addition to the described mixing method of adding the binder after mixing the lubricant with the iron-based powder, two other mixing methods can be used. In a preferred method, about 50% to about 99%, preferably about 75% to about 95%, by weight of a portion of the lubricant is added to the iron-based powder, then the binder is added, and then the solvent is removed. Subsequently, the remaining lubricant is added to the metal powder composition. Another method is to first add a binder to the iron-based powder, remove the solvent, and then add the entire amount of lubricant. The flow agent is then mixed with the metal powder composition thus formed.

It has been found that the flow agents of the present invention provide an additional advantage during the molding process in that they reduce both the maximum firing power and the maximum injection pressure required to remove the molded part from the die cavity. ing. As such, the flow agent may serve as an internal lubricant during the molding process.

Although the flow properties at elevated temperatures have been described in particular for the purpose of warm forming, when the flow agent according to the invention is used in a binder powder mixture, the flow agent-free binder mixture can also be used at ambient temperature. By comparison, it should also be emphasized that the filling of the die cavity has unexpected advantages. An example of such an advantage is that a more uniform packing density is obtained in different sized cavities, and increased performance is obtained by increasing the shoe feed rate during pressing. Thus, by adding a flow agent to the combined powder mixture, more uniform densities can be obtained in molded parts of complex shape and powder metallurgy parts can be manufactured at greater rates.

[0040]

【Example】

Example 1 The improvement of the flow properties of a metal powder composition by incorporating silicon dioxide powder as a flow agent was studied. Flowability was determined according to standard test method ASTM B213-77, where the flow device was maintained in a temperature controlled room.

A metal powder composition having a composition as described in Table 1.1 was prepared. This powder was prepared by mixing Angkor Steel 1000B powder, graphite powder, and about 90% by weight lubricant powder in a standard laboratory bottle mixer for about 15-30 minutes. The binder dissolved in acetone (about 10% by weight binder) was then poured into the mixture and mixed with a spatula in a suitably sized steel ball with a spatula until the powder was well wetted. The solvent was then removed by air drying and the mixture was passed through a 60 mesh sieve to break any large aggregates that might have formed during drying, but no significant agglomeration was observed. . Finally, the remaining lubricant was mixed with the powder composition. Mixing is
This was performed until the powder composition reached a substantially uniform state.

[0042]

¹ —Pure iron powder: Hegenes. ^2- Asbury 3203: Asbury Graphite Mills (Asbur)
y Graphite Mills, Inc.). ^3- Promold 450; Molton International. ⁴ -Cellulose acetate butyrate CAB-381; Eastman Chemical Products, Inc.

The metal powder compositions described in Table 1.1 served as control powders. The control powder was then mixed in small amounts with two different silicon dioxide powders in the amounts shown in Table 1.2 as weight percent of the control powder composition. Mixture A is a flow agent Aerosil 200 (
Mixture B used the flow agent Aerosil R812 (mean particle size = 7 nm), both of which were obtained from Degassa. The flow properties results are described in Non-dissolved 1.2 and show that the flow properties of the metal powder are extended beyond 95 ° C (200 ° F) by the addition of both flow agents. Such expansion allows the powder compositions to be used in warm forming processes where it is desirable to heat the powder to a higher temperature near the die temperature before forming. The symbol NF means that the powder did not flow under the conditions described.

[0045]

Example 2 The flow properties of a powder composition containing a ferrophosporus alloy powder were investigated by adding a flow agent according to the invention. A reference powder composition as described in Table 2.1 was used as a control powder, where the lubricant and binder were the same as in Example 1. This powder is Angkor Steel 1000
B powder and ferrophosphor powder (15-16 wt% P; Hegenes, Sweden) are dry-mixed and then a binder (about 10 wt% binder) dissolved in acetone is mixed with an appropriate size steel. In a bowl, the powder was mixed with a spatula until it was sufficiently wet. The solvent was then removed by air drying and the mixture was passed through a 60 mesh sieve to break any large aggregates that might have formed during drying, but no significant agglomeration was observed. . Finally, the lubricant was mixed in its entirety with the powder composition. Mixing was performed until the powder composition reached a substantially uniform state.

[0047]

The flow agent Aerosil 200 silicon dioxide powder as used in Example 1 was mixed into the reference mixture in various amounts as% by weight (of the control powder composition) described in Table 2.2, and mixtures C to C E was formed. The results of the flow properties are set forth in Table 2.2, which shows that the flow properties of the reference powder were significantly improved by the addition of the silicon dioxide powder.

[0049]

Example 3 The rheological properties of a metal powder composition containing a silicon dioxide flow agent were further evaluated using iron oxide, Fe _Three O_FourImproved by the addition of a flow agent. Bayferrox 3 obtained from Miles
Two different types of Fe, 18M and 330 pigments_ThreeO_FourPowder was used. 318M powder
(Average particle size = 100 nm) was used for mixture FG, and 330 powder (average particle size = 2
00 nm) was used for mixture H. Mixtures C and F from Example 2 using the bottle mixing method
e_ThreeO_FourA powder composition was prepared by mixing with the powder. Mixtures F and H are:
Based on the weight of Mixture C, it contains 0.08% by weight of iron oxide and Mixture G contains 0.12%
It contained oxide by weight. The flow properties of these mixtures are described in Table 3.1.

[0051]

[0052] By the addition of a flow agent, the metal powder composition can be processed at increasingly higher temperatures.

Example 4 The effect on firing force required to remove a molded part from a die cavity was studied,
It was unexpectedly discovered that the addition of a flow agent significantly reduced both the maximum firing power and the maximum injection pressure. Maximum firing power is defined as the maximum force per unit cross-sectional area of the die cavity recorded during injection of the molded part from the die. This is a measure of the maximum force applied to the punch to extrude the molded part from the die cavity. The maximum injection pressure is calculated as the quotient of the maximum load during injection divided by the total cross-sectional area of the part in contact with the die surface. This is also a measure of the maximum frictional force between the molded part and the surface of the die that must be overcome to complete the injection process.

A reference composition mixture as described in Table 4.1 was prepared using the same FeP powder, lubricant, and binder used in Example 2. Experimental mixtures C1, D1, E1, and F1 containing the same amount of flow agent (s) as mixtures C to F of Examples 2-3.
Was prepared. That is, 0.04% by weight of Aerosil 200 silicon dioxide powder was added.
8% by weight and 0.12% by weight were added to the reference mixture to give mixtures C1, D1 respectively.
, And E1, and 0.04% by weight of Aerosil 200 powder and 0.08% by weight of Biferox 318M Fe ₃ O ₄ powder are added to the reference mixture to give mixture F.
1 was formed.

[0055]

The mixture is then brought to a temperature of about 150 ° C. (300 ° F.) at 50 t / in ² (t
Molded at a pressure of si). The maximum firing power and the maximum injection pressure are shown in Table 4.2. The presence of the flow agents significantly reduced firing force and pressure, thereby gaining additional benefits from their incorporation into the metal powder composition.

[0057]

Example 5 The benefits of adding a flow agent on the flow properties of metal powders were studied. In this case, the iron-based powder was a previously alloyed iron material. The iron-based powder used in this experiment was Hegenes 85HP powder, and the composition of the control powder is described in Table 5.1. graphite,
The lubricant and binder were the same materials as in Example 1. 0.04 to this control powder
Test mixture I was prepared by adding weight percent Aerosil 200 silicon dioxide powder.

[0059]

^1- INCO nickel powder 123; INCO (INCO Ltd.)

The flow properties of these two powders at different temperatures are listed in Table 5.2. The introduction of the flow agent significantly extended the temperature range over which the powder flows.

[0062]

Example 6 The following example demonstrates the improved flow and filling properties of a bonded iron powder mixture when tested in a die filling simulator while increasing the shoe filling rate. Powders containing the reference compositions listed in Table 6.1 were studied using a dice filling simulator using polished rectangular cavities of various sizes and rectangular filling shoes. The results from two sizes of cavities (L = 30 mm, H = 30 mm, W = 13 mm) with measured volumes of 11.7 cm ³ and 1.8 cm ^{3 respectively} were used in this study. Filling was performed using a cavity oriented parallel to the shoe filling direction. The data for the packing density of the two cavities was processed according to the following formula: filling index = (FD _max −FD _min ) / FD _max (II) where FD _max = packing density of the larger cavity (g / cm ³ ) FD _min = Filling density of the smaller cavity (g / cm ³ ) Thus, a smaller filling index results in a more uniform filling, ie the powder is less affected by the cavity size .

[0064]

¹ -Pure iron powder: Hegenes AB, Sweden. ² -Graphite; C-uf4; Graffitwerk Klopmühl AG, Germany
afitwerk Kropfmuehl AG). ³ -Ethylenebis-stearamide; Hoechst Wax C Micropowder PM, Germany; Clariant Gm
bH. ⁴ -Polyvinyl acetate; Vinac B15; Air Products and Chemicals Inc., USA. ⁵ -copper; Cu-200; Makin, UK.

The results in Table 6.2 demonstrate the effect of adding 0.04% Aerosil 200 to the binding mixture. At higher shoe filling rates, two effects are observed: a smaller filling index, ie, more uniform filling, and better, more uniform performance.

[0067]

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Claims (10)

[Claims] 1. A large amount of iron-based metal powder and (b) a small average particle diameter of 500
An improved metallurgical powder composition comprising: 2. The metallurgical powder composition according to claim 1, wherein the iron-based powder comprises at least about 85% of the composition and the amount of oxide is 0.005 to 2% by weight. 3. The metallurgical powder composition according to claim 2, wherein the particulate inorganic oxide is silicon dioxide having an average particle size of less than about 40 nm. 4. An inorganic oxide comprising aluminum, copper, iron, nickel, titanium,
The metallurgical powder composition according to claim 2, wherein the composition is selected from the group consisting of gold, silver, platinum, palladium, bismuth, cobalt, manganese, magnesium, lead, tin, vanadium, yttrium, niobium, tungsten and zirconium. 5. The metallurgical powder composition according to claim 1, further comprising an additive selected from the group consisting of a lubricant, graphite, a binder, a thermoplastic material and a plasticizer. 6. In addition to the particulate inorganic oxide, 0.1 to 2% by weight of a lubricant, 0.005 to 3% by weight of a binder, 0 to 0.5% by weight of a plasticizer, and 0.1% of graphite. 0 to 1% by weight, 0 to 2% by weight of a thermoplastic material, and 0 to 7% by weight of alloying elements; the balance is essentially pure iron powder, partially pre-alloyed iron powder 6. The metallurgical powder composition according to claim 5, wherein the powder is an iron powder selected from the group consisting of: and a pre-alloyed iron powder. 7. The lubricant is selected from the group consisting of an amide containing wax or a metal stearate; wherein the binder is tall oil, polyethylene glycol, polypropylene glycol, glycerol, polyvinyl alcohol, polyvinyl acetate, cellulose ester, or Selected from the group consisting of other resins, methacrylate polymers or copolymers, alkyd resins, polyurethane resins, polyester resins other than alkyd resins, or polyvinylpyrrolidone; the plasticizer is polyethylene glycol, glycerol and its esters, organic The thermoplastic material is selected from the group consisting of acid esters, sorbitol, phosphate esters, cellulose esters, arylsulfonamide-formaldehyde resins, or long-chain alcohols; 7. The inorganic oxide is a silicon oxide having an average particle size of about 1 to 25 nm in an amount of about 0.005 to about 2% by weight selected from the group consisting of amide, polycarbonate, or polyphenylene ether; A metallurgical powder composition as described. 8. A method of manufacturing a molded powder metallurgy part comprising: (a) adding at least about 90% by weight of an iron-based metal powder and a metal powder or a metal oxide powder having an average particle size of less than about 500 nm to about 0.005 to about Providing a metallurgical powder composition containing 2% by weight; (b) molding the metallurgical powder composition in a die at a pressure of about 5-200 t / in ² to form the part; The above manufacturing method. 9. The method according to claim 7, wherein the shaping is carried out at a temperature above 70 ° C., preferably above 125 ° C. 10. The method according to claim 9, wherein the shaping is performed at 125 to 370 ° C.