KR20150127214A - Methods for solventless bonding of metallurgical compositions - Google Patents

Abstract

The present invention relates to a method of producing a combined metallurgical powder composition comprising melting a binder in the substantial absence of a solvent for a period of time sufficient to form a combined metallurgical powder composition and blending the molten binder with a metallurgical powder mixture . The combined metallurgical powder compositions prepared using these methods as well as compressed powder metallurgical components made using them are also described.

Description

[0001] METHODS FOR SOLVENTLESS BONDING OF METALLURGICAL COMPOSITIONS [0002]

<Mutual Application of Related Application - Reference>

This application is a continuation-in-part of U. S. Patent Application No. 61 / 781,331, the entirety of which is incorporated herein by reference.

<Technical Field>

The present invention relates to a solventless process for combining metallurgical powder compositions.

Coating or bonding of the metal powder is important not only to improve the performance of the powder during processing of the powder mixture, but also to reduce the dusting. Methods of coating or bonding powder mixtures have been described previously. For example, U.S. Pat. Patent No. 2,648,609; 3,117,027; 4,731,195; 6,280,683; And 6,602,315.

Some of these bonding methods use a combination of high shear and high applied pressure to coat the powder particles with a polymer or wax. These methods can cause agglomeration of the powder to provide a web-like structure. In another method, the powder is fluidized and then coated with a binding material that is soluble in the solvent. Generally, the binding material is in a solution comprising from 75% to 95% by weight of the solvent. After the particles of the powder have been coated, the solvent must be removed - this process is time consuming, costly, and can be dangerous because many of the solvents used are flammable liquids.

U.S.A. The coating processes described in patents 6,602,315 and 6,280,683 use a solventless "dry bond ". These processes mix the metal powder and the additive with a polymeric binder having a small particle size range at a temperature below the melting point of the polymer. On the other hand, advantageously, the range of these methods is limited due to the small particle size requirements of the binder.

There is still a need for a new method of making the combined metallurgical powder compositions.

The present invention relates to a process for producing a binder, comprising heating the binder to a temperature above the melting point of the binder for a time sufficient to cause the binder to melt in the substantial absence of solvent; And blending the melted binder with a metallurgical powder mixture for a time sufficient to allow the combined metallurgical powder composition to form in the substantial absence of a solvent. The present invention also includes bonded metallurgical powder compositions prepared using these methods as well as compressed powder metallurgical components made using them.

The present invention provides an improved method for bonding, i.e., particle-coating that provides non-agglomerated, coated particles. These processes do not use substantially any solvent to provide a combined metallurgical powder composition.

According to the invention, the combined metallurgical powder composition can be prepared by heating the binder to a temperature above the melting point of the binder for a time sufficient for the binder to melt in the substantial absence of solvent.

As used herein, "solvent" refers to any organic solvent, such as acetone, methylene chloride, toluene, benzene, ethanol, hexane, and the like.

As used herein, "substantial absence of solvent" refers to solvents from 0 wt% to less than 5 wt% of the binder. Preferred embodiments will comprise less than 5% by weight of the solvent of the binder. A more preferred embodiment will comprise less than 2% by weight of the solvent of the binder. A more preferred embodiment will comprise less than 1% by weight of the solvent of the binder. In an exemplary embodiment, the binder comprises a non-additive solvent. The amount of solvent present can be determined using any conventional method known in the art.

In the process of the present invention, what is referred to as a coating material, or "binder ", may be any solid polymer or wax with a distinct melting point. Examples of binders belonging to this substrate include, but are not limited to, stearamide, behenic acid, oleamide, polyethylene, paraffin wax, ethylene bisstearamide and cottonseed wax. In some embodiments of the present invention, the binder is melted when heated to a temperature of from about 50 캜 to about 150 캜. In another embodiment of the present invention, the binder is melted when heated to a temperature of from about 50 캜 to about 110 캜. In a preferred embodiment of the present invention, the binder is polyethylene.

Other binders that can be used in the present invention include, for example, polyglycols such as polyethylene glycol or polypropylene glycol; glycerin; Polyvinyl alcohol; Homopolymers or copolymers of vinyl acetate; Cellulose esters or ether resins; Methacrylate polymers or copolymers; Alkyl resins; Polyurethane resin; Polyester resin; Or a combination thereof. Other examples of useful binders are U.S. Pat. Based relatively high molecular weight polyalkylene oxide-based compositions as described in US-A-5,298,055. Useful binders are also described in U. S. Pat. 5,290,336, such as azelaic acid and one or more polar components such as a polyether (liquid or solid) and an acrylic resin. U.S.A. The binders of U.S. 5,290,336 may also advantageously serve as a combination of a binder and a lubricant. Additional useful binders are U.S. Pat. Cellulose ester resins, hydroxyalkyl cellulosic resins and thermoplastic phenolic resins described in U.S. 5,368,630.

The binder may also be a solid polymer or wax such as polyester, polyethylene, epoxy, urethane, paraffin, ethylene biststearamide and cottonseed wax, and also polyolefins having an average molecular weight of less than 3,000.

In an exemplary embodiment of the present invention, the weight of the binder is about 10% by weight, based on the weight of the combined metallurgical powder composition. In another embodiment, the combined metallurgical powder composition of the present invention will comprise from about 0.1% to about 5.0% binder of the combined metallurgical powder composition. In another embodiment, the combined metallurgical powder composition of the present invention will comprise from about 0.1% to about 3.0% binder by weight of the combined metallurgical powder composition. In another embodiment, the combined metallurgical powder composition of the present invention will comprise from about 0.1% to about 2.0% binder by weight of the combined metallurgical powder composition. In another embodiment, the combined metallurgical powder composition of the present invention will comprise from about 0.1% to about 1.0% binder by weight of the combined metallurgical powder composition.

According to the invention, the molten binder in the substantial absence of solvent is added to the metallurgical powder mixture.

As used herein, "metallurgical powder mixture" refers to a metallurgical powder comprising a metal-based powder. The metallurgical powder composition of the present invention preferably comprises at least 80 wt.% Of a metal-based metallurgical powder. Preferably, the metallurgical powder composition of the present invention preferably comprises at least 90 wt.% Of a metal-based metallurgical powder.

A preferred metal-based metallurgical powder of the present invention is an iron-based powder.

The substantially pure iron powder is a powder of iron containing up to about 1.0% by weight, preferably up to about 0.5% by weight of normal impurities. Examples of such highly compressible metallurgical-grade iron powders are the ANCORSTEEL 1000 series of pure iron powders, such as 1000, 1000B, and 1000C, available from Hoeganaes Corporation, Leverton, NJ. For example, the ANCORSTEEL 1000 iron powder is No. About 22% by weight of particles less than 325 bodies (US series); About 10 wt.% Of particles larger than 100 sieves and the remainder having a typical screen profile between these two sizes (trace amounts larger than No. 60 sieves). The ANCORSTEEL 1000 powder has an apparent density of about 2.85-3.00 g / cm ³ , typically 2.94 g / cm ³ . Other substantially pure iron powders that may be used in the present invention are typical sponge iron powders, such as ANGOR MH-100 powder from Hoganas.

The metallurgical powder mixture of the present invention may be a pre-alloyed iron-based powder and a stainless steel powder. These stainless steel powders are commercially available in a variety of grades of syringe or S-ANCOR® series, such as ANCOR® 303L, 304L, 316L, 410L, 430L, 434L, and 409Cb powders. In addition, the iron-based powder includes tool steel made by a powder metallurgy process.

The metallurgical powder mixture of the present invention may also be a substantially pure iron powder pre-alloyed with an alloying element, such as molybdenum (Mo). The pre-alloyed iron powder with molybdenum is produced by atomizing a substantially pure iron melt containing about 0.5 to about 2.5 weight percent Mo. Examples of such powders are those containing about 0.85 weight percent Mo, less than about 0.4 weight percent total manganese, chromium, silicon, copper, nickel, molybdenum or other materials such as aluminum, and less than about 0.02 weight percent carbon , And ANGORASTEEL 85HP steel powder. Other examples of molybdenum-containing iron base powder include ANCORSTEEL 737 powder (about 1.4 wt.% Ni - about 1.25 wt.% Mo - about 0.4 wt.% Mn; balance Fe), ANCORSTEEL 2000 powder About 1.0 wt.% Cr to about 1.0 wt.% Of ANCORSTEEL 4300 powder), about 0.46 wt.% Ni to about 0.61 wt.% Mo to about 0.25 wt. Ni - about 0.8 wt.% Mo - about 0.6 wt.% Si - about 0.1 wt.% Mn; (Fe) and ANCORSTEEL 4600V powder (about 1.83 wt.% Ni - about 0.56 wt.% Mo - about 0.15 wt.% Mn; Other exemplary iron-based powders are disclosed in US 7,153,339, the entirety of which is incorporated herein by reference.

Additional pre-alloyed iron-based powders are available from U.S. Pat. No. 5,108,493, the entirety of which is incorporated herein by reference. These steel powder compositions are a mixture of two different pre-alloyed iron-based powders, one pre-alloy of iron with 0.5-2.5 weight percent molybdenum and one with carbon and at least about 25 weight percent Wherein the element comprises at least one element selected from chromium, manganese, vanadium and columbium. The mixture is provided at a ratio of at least about 0.05 weight percent transition element component to a steel powder composition. An example of such a powder is ANCORSTEEL 41 AB steel powder, which contains about 0.85 weight percent molybdenum, about 1 weight percent nickel, about 0.9 weight percent manganese, about 0.75 weight percent chromium, and about 0.5 weight percent carbon, It is commercially available.

The metallurgical powder mixture of the present invention may also be a diffusion-bonded iron-based material that is substantially pure iron particles that have one or more other alloying elements or metals, such as a layer or coating of steel- Powder. A conventional process for making such powders is to atomize the melt of iron and then combine the atomized and annealed powder with the alloy powder and re-anneal the powder mixture in the urine. Such commercially available powders include DISTALOY 4600A diffusion bonded powders or espoformations containing about 1.8% nickel, about 0.55% molybdenum and about 1.6% copper, and about 4.05% nickel, about 0.55% Molybdenum, and DISTALOY 4800A diffusion-bonded powder of escorporation containing about 1.6% copper.

Particles of the iron-based powder used herein, such as substantially pure iron, diffusion-bonded iron and pre-alloyed iron, have a distribution of particle sizes. Typically, these powders contain at least about 90 weight percent of the powder sample. (U. S. series), more preferably at least about 90 wt% of the powder sample is capable of passing through the No. It can pass through 60 sieve. These powders typically have a No. Passed through 70 sieve, At least about 50% by weight of powder that is greater than or equal to about 400% and retained thereon; Passed through 70 sieve, And at least about 50% by weight of the powder retained thereon or greater than 325 bodies. These powders also typically contain at least about 5 percent by weight, more usually at least about 10 percent by weight, and generally at least about 15 percent by weight. 325 sieve. We refer to MPIF Standard 05 for sieve analysis.

Thus, the metallurgical powder mixture may have a weight average particle size of less than 1 micron, or a weight average particle size of up to about 850-1000 microns, but generally the particles will have a weight average particle size in the range of about 10-500 microns . Preference is given to iron or pre-alloyed iron particles having a maximum weight average particle size of up to about 350 microns; More preferably, the particles will have a weight average particle size in the range of about 25-150. In a preferred embodiment, the metallurgical powder composition has a typical particle size of less than 150 microns (-100 mesh), such as 38 to 48% of particles having a particle size of less than 45 microns (-325 mesh) &Lt; / RTI &gt;

The iron-based powder described is preferably a water-atomized powder. The iron-base powder has a bulk density of at least 2.75, preferably 2.75 to 4.6, more preferably from 2.8 to 4.0, and more preferably from 2.8 to 3.5 g / cm ³ in some cases.

The corrosion resistant metallurgical powder mixture comprises one or more alloying additives that enhance the mechanical or other properties of the final compacted part. Alloy additives are combined with iron powders by conventional powder metallurgical techniques known to those of ordinary skill in the art, such as blending techniques, pre-alloy techniques, or diffusion bonding techniques. Preferably, the alloy additive is combined with the iron-based powder by preparing a pre-alloy technique, i.e., a melt of iron and the required alloying elements, and then atomizing the melt, whereby the atomized droplets form a powder upon solidification .

Alloy additives are those known in the powder metallurgical industry for enhancing corrosion resistance, strength, hardenability or other desirable properties of compacted articles. The steel-providing element is the most known of these materials. Examples of alloying elements include, but are not limited to, chromium, silicon, graphite, copper, molybdenum, nickel, and the like, or combinations thereof. The amount of the alloying element or the contained element depends on the properties desired in the final metal part. A pre-alloyed iron powder comprising such an alloying element is available from Rota or Escobo &lt; (R) &gt; as part of its ANCORSTEEL line powder. When used, the metallurgical powder mixture comprises from 0.10% to about 10% of the alloy powder, based on the weight of the metallurgical powder mixture. Preferably, the metallurgical powder mixture comprises from 0.20% to about 5% of the alloy powder, based on the weight of the metallurgical powder mixture.

The molten binder may be added to the metallurgical powder mixture using any method known in the art. One exemplary method is spray application.

In some embodiments of the present invention, the metallurgical powder mixture may be heated before and / or during the application of the molten binder. For example, the metallurgical powder mixture may be heated to a temperature between about 60 [deg.] C and about 85 [deg.] C before and / or during the application of the molten binder.

Once the molten binder has been added to the metallurgical powder mixture, the molten binder and the metallurgical powder mixture are blended in the substantial absence of solvent for a time sufficient to form the combined metallurgical powder composition of the present invention. For example, blending may take from 1 to 5 minutes, depending on the amount of binder. Any blending method known in the art may be used. Preferably, the blending method can cause simultaneous heating and blending. Blending can occur at low shear in the mixer, i.e., from about 20 to about 30 rpm, or high shear, i.e., greater than 30 rpm. Blending devices that may be used in conjunction with the method of the present invention include drum mixers, such as Elrich Mixers, paddle mixers, A S. Howes mixer, a Nauta blender and a Littleford blender. Other methods of blending, such as a Wurster coater, may also be used.

One advantage of the present invention is that the U.S. Unlike the dry-bonding method described in US Pat. Nos. 6,602,315 and 6,280,683, the binder need not be of any particular size since it will be melted before adding it to the metallurgical powder. As such, the binder can start with a coarse chuck or frill that is several inches in size.

In the process of the present invention, the polymer is preferably melted in a vessel separate from the mixed blender containing the metallurgical powder. As a result, the metal powder in the blender does not need to be heated to the softening point or melting point of the polymer to be sprayed. This results in more energy savings than other dry-coupled methods known in the art. The process of the present invention has a lower energy consumption compared to the solvent-bonding process because solvent evaporation, recovery and disposal are not required. The method of the present invention is therefore more energy efficient and more environmentally friendly.

Although any method of melting can be used, direct heating of the vessel containing the polymeric material is permitted.

The metallurgical powder compositions of the present invention can be formed into a variety of product shapes known to those of ordinary skill in the art, such as billets, rods, posts, wires, strips, plates, or sheets using conventional methods.

The combined compositions are then compressed by conventional techniques known to those of ordinary skill in the art. Generally, the combined metallurgical powder composition is compressed at about 5 tonnes per square inch (tsi). Preferably, the metallurgical powder composition is compressed at about 5 to about 200 tsi, more preferably at about 30 to about 60 tsi. The resulting green compact can be sintered. Preferably, at least 2000 DEG F, preferably at least about 2200 DEG F (1200 DEG C), more preferably at least about 2250 DEG F (1230 DEG C), and more preferably at least about 2300 DEG F (1260 DEG C) Of the sintering temperature is used. Sintering operations can also be done at lower temperatures, such as at least 2100F.

The sintered parts typically have a density of at least about 6.6 g / cm ³ , preferably at least about 6.68 g / cm ³ , more preferably at least about 7.0 g / cm ³ , more preferably from about 7.15 g / cm ³ to about 7.38 g / cm &lt; ^{3 &} gt ;. More preferably, the sintered part has a density of at least about 7.4 g / cm &lt; ^{3 &} gt ;. A density of 7.50 g / cm &lt; ³ &gt; is also obtained using the metallurgical powder composition of the present invention.

Those of ordinary skill in the art will recognize that many variations and modifications can be made to the preferred embodiments of the invention and such variations and modifications can be made without departing from the scope of the invention. The following examples further illustrate metallurgical powder compositions.

<Examples>

Example 1

Blending of iron-based and alloy powders and polyethylene (Polywax 655) binder was performed using two methods. Method A is U.S. 6,602,315. Method B is a method according to the present invention. The test composition contained 0.80% graphite, 98.45% ANCORSTEEL A1000 iron-based powder and 0.75% polyethylene as alloy powder.

For Method 1A, the polyethylene was ground to an average particle size of 20 microns and added to a blender containing the test composition. The contents of the blender were heated to approximately 180 ° F (82 ° C).

For Method 1B, the polyethylene was heated to a temperature above its melting point and sprayed onto a blender containing the test composition. The contents of the blender were heated to approximately 180 ° F (82 ° C).

Table 1 shows the dust resistance or coupling efficiency for graphite in utilizing both bonding techniques. The composition prepared according to Method 1B has improved binding efficiency.

Joining method Combined  Graphite ( % ) Method 1A 84 Method 1B 95

Example 2

The test compositions were prepared by mixing 2.9% ferrophospherus (Fe ₃ P) (average particle size = 10 microns), 98.45% ANCORSTEEL A1000B iron-based powder, 0.20% polyethylene, 0.50% ethylene bisstearamide 20 microns).

The test composition for Method 2A comprises 2.9% ferrofosperm (Fe ₃ P) (average particle size = 10 microns) as alloy powder, 98.45% ANCORSTEEL A1000B iron-based powder and 0.20% polyethylene. For Method 2A, the polyethylene was dissolved in acetone and combined with other components according to solvent-based bonding methods known in the art. One of the disadvantages of dissolving the binder in the solvent is that the solubility of the binder is limited. Moreover, a limited amount of dissolved binder is not sufficient to provide adequate lubrication for compression, so that additional lubricant should be added to the solvent-bonded formulation to allow compression to occur. For Method 2A, the additional lubricant is 0.50% ethylene bisstearamide ("EBS") (average particle size - 20 microns).

For Method 2B, the polyethylene was melted and spray-applied to the other components using the method of the present invention. Since the amount of binder was not limited in solubility, EBS was not required for the test composition used in Method 2B.

Table 2 shows the coupling efficiency for Fe ₃ P in utilizing the two coupling techniques. The composition prepared according to Method 2B has improved binding efficiency.

Joining method Combined  Graphite ( % ) Method 2A 80 Method 2B 97

Example 3

In the prior art solvent-bonding process, an additional lubricant is added to the powder form, which can be susceptible to dusting. If additional lubricants are added during the bonding process, some of the binders act to bond to additional lubricants and are unable to bond to alloy powders, such as Fe ₃ P. As the polymer acts as both a binder and a lubricant, this is in contrast to the process of the present invention.

For the preformulation, the test composition comprised 0.8% graphite (mean particle size = 6 microns), 98.45% ANCORSTEEL A1000 iron-based powder and 0.75% EBS (average particle size = 20 microns) as alloy powder. The test compositions were mixed using conventional mixing techniques.

For Method 3B, the test composition contained 0.8% graphite (mean particle size = 6 microns), 98.45% ANCORSTEEL A1000 iron-based powder and 0.75% polyethylene as alloy powder. The polyethylene was melted and spray-applied to the other components using the method of the present invention.

An advantage of the bonding method of the present invention is that the binder forms a thin coating on the outside of the iron powder, which is then added to any additive particles; In this embodiment, to "adhere" to graphite. Since the binder acts as a lubricant, the amount of lubricant added to the powder form can be eliminated or greatly reduced. Due to the limited surface area on the iron-based powder for the particles to be bonded, the smaller the number of particles to be attached to the base powder, the better the bonding efficiency. It can be seen from Table 3 that the coupling efficiency (as measured by total carbon) using Method 3B is 95%, compared to Method 3A, where the coupling efficiency is only 55%.

Combined  Graphite ( % ) Premix 55 Method 3B 95

Example 4

The influence on the apparent density and flow of the binder or lubricant is important. Apparent density is a measure of how much powder can fill a fixed volume, and a high value relates to a better charge of the die to produce the part. The flow of powder is the time required to fill the die cavity (fixed volume). As the generation of the PM component involves repeatedly charging the die, the better the flow in a fixed time (lower time), the more parts can be created, thus increasing the productivity of the parts production process. The shape of the powder particles or bonded particles can affect the flow and apparent density of the powder mixture. The more rounded shape improves both the apparent density by improving particle packing and the flow by reducing particle friction.

In the combined blend of powders, the shape of the powder may be considered as a combination of base powder, alloy powder, lubricant and binder. In the process of the present invention, because the binder can be uniformly applied around the base powder, the bound particles tend to be spherical in shape compared to the bonded powder produced using the "dry bond" method of the prior art .

The composition of the formulations used in this example is as follows:

(Average particle size = 8 microns) as alloy powder, 96.45% ANCORSTEEL A1000B iron-based powder, 0.75% EBS (ethylenebisstearamide ) (Average particle size = 20 microns).

Formulation for Method 4A: 2.0% 8081 copper powder (average particle size = 20 microns), 0.80% graphite as alloy powder (average particle size = 8 microns), 96.45% ANCORSTEEL A1000B iron-based powder, 0.75% polyethylene injected.

Formulation for Method 4B: 0.20% EBS, 2.0% 8081 copper powder (average particle size = 20 microns), 0.80% graphite (average particle size = 8 microns) as alloy powder, 96.45% ANCORSTEEL A1000B iron- 0.55% of polyethylene melted and sprayed according to EBS, plus an additional 0.20% EBS (average particle size = 20 microns).

(Average particle size = 8 microns) as alloy powder, 96.45% ANCORSTEEL A1000B iron-based powder, 0.20% dissolved in acetone, Polyethylene. There is also 0.50% EBS with an average particle size of 20 microns. The polyethylene is applied using a prior art solvent-based process.

Table 4 shows the flow and apparent density of the combined powders according to the present invention (methods 4A and 4B) vs. standard preformulation and solvent-bonding combination (method 4C).

Sample Apparent density flow Premix 2.99 40.0 Method 4A 3.68 28.7 Method 4B 3.57 30.8 Method 4C 3.29 31.4

Method 4A with 0.75% injected polyethylene exhibits improvement in bulk density (increased) and flow (lowered) over preformulations of similar composition. Both Methods 4A and 4B showed better results than the pre-combination or standard solvent-coupled combination (Method 4C).

Usually, it is difficult to obtain an apparent density greater than 3.40 g / cc in the pre-blend or solvent-blended blend. Together with the preformulation, the electrostatic force of the unbonded polymer and the frictional effects of the additives tend to have a negative impact on apparent density and flow. Because the solubility limits the amount of binder with the solvent-bonded combination, the bound particles tend to have a more irregular shape than the bound particles made according to the present invention. The improved apparent density and flow observed using the method of the present invention can lead to improved dimensional control and weight consistency for the compressed part.

Example 5

The binder must also be able to function as a lubricant. Lubricants are needed to assist in compressing and ejecting parts from the die and reducing friction during initial and ejection. If the binder can serve as a lubricant, the force required to compress the part can be reduced and higher densities can be achieved.

The materials bonded in accordance with the present invention exhibit similar improvements in apparent density and flow similar to the results shown in Table 4. &lt; tb &gt; &lt; TABLE &gt;

Strips and slides which are a measure of the jetting properties of the powder blend are shown in Table 5. The strip pressure is the pressure required for the compressed part to start moving from the die during the ejection cycle. The lower the strip pressure, the easier the part is to be removed from the die and less force is required by the compression press. Slide pressure is the force required to keep the part out of the die until it is out of the die's constraint. In most cases, the lower the slide pressure, the easier it is removed from the die and the better the surface finish.

Table 5 shows the ejection forces (strips and slides) for three different compression pressures (30, 40 and 50 tsi). The materials bonded according to the present invention exhibit lower strips and slides compared to conventional preformulation and solvent-bonded formulations. The green density of the material prepared according to the present invention is similar to the preformulation and is improved over the solvent-bonded formulation.

Table 5 shows the results of the compressive properties of the various formulations. The blend used in this experiment is A1000 + 0.80% graphite + 0.75% organic material. "Preformulation" refers to a non-bound material. MB # 1 and MB # 2 are bonded materials prepared according to the present invention, i.e., the binder is melted in the substantial absence of solvent and blended with other materials. The binders used for MB # 1 and MB # 2 are behenic acid and ethylene non-stearamide. MB # 1 has a total lubricant of 0.40% from the binder. MB # 2 also has a binder used as a lubricant. AB1 (Ancorbond 1) was coupled using solvent-bonding, which is used as a comparative example. AB1 includes an organic binder including polyethylene, polyglycol, and ethylene non-stearamide. In the tested mixture, the combination of the binder and the ethylene non-stearamide is 0.75% by weight of the mixture.

Example 6

An exemplary method of the present invention involves heating a mixture of metal powder and alloy powder into a blending device to a preselected temperature. The binder is melted in a separate vessel, and the mixture is injected into the blending device while being blended. The resulting combined powder is cooled to ambient temperature. Additional additives may be added at this time.

Claims (19)

Melting the binder in the substantial absence of a solvent; And
Blending the molten binder with the metallurgical powder mixture in the substantial absence of solvent for a time sufficient to form the combined metallurgical powder composition
&Lt; / RTI &gt; The method of claim 1, wherein the binder comprises less than 5% by weight of solvent based on the weight of the binder. The method of any one of claims 1 to 3, wherein the binder comprises less than 2% by weight of solvent based on the weight of the binder. 4. The process of any one of claims 1 to 3, wherein the binder is free of added solvent. 5. A combined metallurgical powder composition according to any one of the preceding claims wherein the binder is selected from the group consisting of stearamide, behenic acid, oleamide, polyethylene, paraffin wax, ethylene bisstearamide, cottonseed wax, Gt; 6. The method of any one of claims 1 to 5, wherein the melting step comprises heating the binder to a temperature above the melting point of the binder for a time sufficient to cause the binder to melt. 7. The method of claim 6, wherein the binder is heated to a temperature from about 50 [deg.] C to about 110 [deg.] C. 8. The method of any one of claims 1 to 7, wherein the binder is polyethylene. 9. A process according to any one of claims 1 to 8, characterized in that the metallurgical powder mixture
At least about 80 weight percent metal-based powder based on the weight of the mixture; And
One or more alloy powders
&Lt; / RTI &gt; 10. The method of claim 9, wherein the metallurgical powder mixture comprises at least about 90 weight percent metal-based powder. 10. The method of claim 9, wherein the metal-based powder is an iron-based powder. 10. The method of claim 9, wherein the metallurgical powder mixture further comprises from 0.20% to about 5.0% by weight of the alloy powder. 13. The method of any one of claims 1 to 12, wherein the combined metallurgical powder composition comprises from about 0.15% to about 2.0% binder of the composition. 7. The method of claim 6, wherein the metallurgical powder mixture is heated to about 60 &lt; 0 &gt; C to about 85 &lt; 0 &gt; C. 15. The method according to any one of claims 1 to 14, wherein the molten binder is applied to the metallurgical powder substantially in the absence of solvent by spraying the molten binder in the metallurgical powder prior to the blending step, &Lt; / RTI &gt; The method of any one of claims 1 to 6, wherein the molten binder is applied to the metallurgical powder substantially in the absence of solvent by spraying the molten binder to the metallurgical powder before the blending step . 17. The method of claim 16, wherein the binder contains less than 2 weight percent solvent based on the weight of the binder. 18. A combined metallurgical powder composition prepared according to any one of claims 1 to 17. Compressed powder metallurgical component produced using the combined metallurgical powder composition of claim 6.