Title of Invention	"MIXTURE FOR THE PRODUCTION OF SINTERED PARTS AND METHOD THEREOF"
Abstract	Mixture for the production of sintered molded parts, which comprises a metallic and/or plastic material as herein described and a pressing aid, wherein the pressing aid comprises 25-60 wt.% of a polyglycol, based on the total weight of the pressing aid, and 40-75% of a montan wax, based on the total weight of the pressing aid.

Full Text

The present invention concerned a mixture for the production of sintered molded parts and method thereof. Sintered molded parts find a wide variety of applications, especially in automobile manufacturing, and there especially as molded engine and transmission parts. One of the difficulties involved in the production of sintered molded parts is their production with the highest possible density. A molded part is pressed in one or more layers from a sinterable powder by a standard powder metallurgy (P/M) method. In a second step, this molded part, which is generally referred to as a green compact, is then sintered under a protective atmosphere to obtain a strong and dimensionally accurate molded metal part. The density of sintered molded parts produced in this way depends essentially on the density of the green compact produced in the first compaction step, i.e., the so-called green density (compact density). Therefore, it is desirable to produce green compacts in [the first compaction step that have a density that is as high as possible. However, the high compaction pressures usually used in the state of the art cause, on the one hand, high wear of the die itself and, on the other hand, increased ejection sliding friction of the finished green compact. As a result, higher ejection forces must be applied, which are accompanied by correspondingly increased wear of the die. Furthermore, high ejection forces involve the danger of undesired localized after-compaction and cracking of the green compact. Therefore, the objective of the present invention is to make available a mixture with which the aforementioned disadvantages can be avoided. In accordance with the invention, this objective is achieved with a mixture for the production of sintered molded parts, which comprises a metallic and/or plastic material and a pressing aid, which consists of 25-60 wt.% of a polyglycol, based on the total weight of the pressing aid, and 40-75% of a montan wax, based on the total weight of the pressing aid. In the context of the present invention, sinterable molded parts are understood to mean molded parts that have been produced entirely from a sinterable material. On the other hand, this is also understood to include composite parts. The main component of such a composite part can be produced, for example, from an aluminum-containing or iron-containing mixture, and the other component joined with the main component can be produced from a different material, for example, cast steel, sintered or massive, or massive cast aluminum. On the other hand, the composite part can also have a sintered layer that consists, for example, of an aluminum-containing or ceramic-containing mixture, for example, only on its end faces or on its surface, whereas the main component is, for example, steel or cast iron, sintered or massive. In this connection, the sintered molded parts can be sized and/or age-hardened. Metallic and/or plastic materials in accordance with this invention are especially powders or mixtures of metallic, ceramic, and/or plastic components, for example, mixtures of steels, such as chromium-nickel steels, bronzes, nickel-base alloys such as Hastelloy, Inconel, metal oxides, nitrides, silicides, or the like, as well as aluminum-containing powders and mixtures. The mixtures can also contain high-melting components, such as platinum or the like. The powder that is used and its particle size depend on the specific purpose intended. Preferred iron-containing powders are the alloys 316L, 304L, Inconel 600, Inconel 625, Monel, and Hastelloy B, X, and C. Furthermore, the metallic and/or plastic material can consist wholly or partly of milled fibers or fibers, preferably fibers with diameters of about 0.1 to 2µmand lengths of a few µm to as high as 50 mm. Montan waxes in accordance with this invention are bitumens of lignite that were formed from resins, waxes, and fats of Tertiary plants. They are composed of esters of so-called montan acids (fatty acids) with long-chain wax alcohols, especially C20-C36 fatty acid esters, and preferably C24-C34 fatty acid esters. In addition to the these components, montan wax can also contain additional free fatty acids and free wax alcohols as well as montan resins, ketones, and asphalt-like material. Montan waxes are generally mixtures of various fatty acid esters. Preferred montan waxes have an acid value (mg KOH/g) in the range of 5-30, and preferably 10-25, and/or a saponification number (mg KOH/s) [surely a misprint for "mg KOH/g" — Tr. Ed.] in the range of 100-200, and preferably 120-160. The viscosity (m- Pas) at 10O°C is preferably in the range of 10-40, and especially 15-35. Surprisingly, it was found that the addition of the pressing aid defined above to a sinterable material in the metallurgical compaction process makes it possible to produce green compacts, which, on the one hand, have significantly increased values of green strength and green density, especially at a die temperature of room temperature, but which, on the other hand, also require considerably lower ejection forces for the removal of the green compacts from the die. This not only significantly reduces the wear of the die that is used, but also reduces the danger of cracking or localized after-compaction of the green compact that is produced. Furthermore, the green densities that can be produced with the mixture of the invention are increased, especially at a die temperature of room temperature, and are close to the green densities of the finished and sintered molded part. The mixture of the invention can contain additional components, particularly lubricants, especially in an amount of 0.2 to 5 wt.%, based on the total amount of the mixture. Lubricants that can be used include, on the one hand, self-lubricating agents, for example, M0S2, WS2, BN, N [surely a misprint, but for what we have no idea - Tr. Ed.] and nS [again, surely a misprint, but for what we have no idea — Tr. Ed.], as well as graphite and/or other carbon modifications, such as coke, polarized graphite, or the like. Preferably, 1 -3 wt.% of the lubricant are added to the sinterable mixture. Self-lubricating properties can be imparted to the molded parts produced from the sinterable mixture through the use of the aforementioned lubricants. The mixture of the invention can also contain other lubricants or Aerosils [We can't believe they are adding an Aerosil, which is a silica product, to the mixture for lubrication purposes. We noticed that tungsten disulfide is used as a lubricant and aerosol, so we suppose "aerosols" is what they meant. — Tr. Ed.]. It can be produced by mixing the individual components with standard equipment, such as asymmetric moved mixers. The mixing can be carried out either at elevated temperatures (hot mixing) or at room temperature (cold mixing), but hot mixing is preferred. Preferred mixtures contain polyglycols in amounts of 30-55 wt.%, and especially 32-53 wt.%, and montan waxes in amounts of 45-70 wt.%, based in each case on the total amount of the pressing aid. It is advantageous to use polyethylene glycols as the polyglycols contained in the pressing aid of the mixture of the invention. In the context of this invention, polyethylene glycols also include mixtures of polyethylene glycols of various molecular weights. It is especially advantageous to use nolvethylene glycols with a molecular weight in the range of about 100 to 20,000 g/mole, preferably 100 to 7,000 g/mole, more preferably 100 to 6,500 g/mole, and most preferably 3,000 to 6,000 g/mole. The great advantage of the specified polyethylene glycols lies in the fact that they have a relatively low softening point, generally in the range of 40-100°C, which makes it possible to fill the dies used in the metallurgical process with cold material, so that lumping or the like is avoided. When the die is heated in the pressing operation, the selected polyethylene glycols, together with the montan waxes that are used, allow lubrication, so that higher green densities and green strengths of the green compacts are achieved. It is advantageous for the montan waxes of the pressing aid used in the mixture of the invention to contain fatty acid esters based on C24-C34 fatty acids. The present invention also concerns a method for the production of the mixture of the invention, in which — in a first step, the polyglycols and montan waxes that compose the pressing aid are melted together; and — in a second step, the pressing aid produced in the first step is added to the metallic and/or plastic material. In a preferred embodiment of the method of the invention, after the first step, the melt that has been produced is cooled and then ground or atomized. Surprisingly, it was found that the method of the invention results in green strengths of the green compacts that are significantly greater than those that can usually be achieved with state-of-the-art pressing aids. In an alternative method of the invention, — in a first step, the polyglycols and montan waxes that compose the pressing aid are mivxed together and — in a second step, the pressing aid produced in the first step is added to the metallic and/or plastic material. The green compacts obtained after the metallurgical pressing operation with this alternative method also have green strengths that are greater than those obtained with customary prior-art pressing aids. Furthermore, the present invention concerns the use of the mixture of the invention for the production of sintered molded parts. In addition, the present invention concerns a pressing aid in accordance with Claims 1 to 4. Finally, the present invention concerns green compacts produced from the mixture of the invention, which have a green strength, as determined in accordance with ISO 3995-1985, of greater than 7.55 N/mm at a die temperature of room temperature and a pressure of 600 MPa. In addition, it is advantageous for the green compacts of the invention to have a green density, as determined in accordance with ISO 3927/1985, of at least 7.14 g/cm3 at 800 MPa and a die temperature of room temperature. These and other advantages of the present invention are described on the basis of the following examples. Mixtures were produced from the sinterable metal powder Ancorsteel 85 HP produced by Hoeganaes Corporation, USA, with 0.65 wt.% carbon and 0.6 wt.% of the following pressing aids, based in each case on the total amount of the mixture: (a) Licowax C, Clariant GmbH, Frankfurt am Main, which is a bisstearoylethylenedi-amine (amide wax); (b) Acrawax C, Lonza AG, Basel, Switzerland, which is an N,N'-ethylenebisstearamide (amide wax); (c) Kenolube PI 1, Hoganas AB, Hoganas, Sweden., which is a mixture of 22.5 wt.% zinc stearate and 77.5 wt.% of an amide wax; (d) Polyglycol 6000 PF, Clariant GmbH, Frankfurt am Main, which is a polyethylene glycol with a molecular weight of about 6,000 g/mole; (e) Licowax E, Clariant GmbH, Frankfurt am Main, which is a montan wax composed of esters of C24-C34 fatty acids with an acid value (mg KOH/g) in the range of 15-20 and a saponification number in the range of 130-160; (0 a mixture of 67 wt.% Licowax E and 33 wt.% Polyglycol 6000 PF, based in each case on the total amount of the pressing aid; this mixture was produced by melting the montan wax and the polyethylene glycol together, solidifying the melt, possibly followed by cooling (e.g., with liquid nitrogen), and then grinding the solidified melt to a powder; (g) a mixture of 50 wt.% Licowax E and 50 wt.% Polyglycol 6000 PF, which was produced by melting the montan wax and the polyethylene glycol together, solidifying the melt, possibly followed by cooling (e.g., with liquid nitrogen), and then grinding the solidifed melt to a powder; (h) a mixture of 67 wt.% Licowax E and 33 wt.% Polyglycol 6000 PF, which was mixed in a standard asymmetric moved mixer without first melting the components together; (i) a mixture of 50 wt.% Licowax G and 50 wt.% Polyglycol 6000 PF, which was mixed in a standard asymmetric moved mixer without first melting the components together; based in each case on the total amount of the pressing aid. As an alternative to grinding the mixtures in accordance with (f) and (g), the melt can also be atomized. The amount of pressing aid added can generally be in the range of about 0.1 to 5 wt.%, preferably 0.3 to 3 wt.%, and especially 0.5 to 1.5 wt.%, based on the total amount of the mixture of the invention. The specified mixtures were introduced into a standard die and pressed into cylinders with a diameter of 14.3 mm and a length of 12 cm at various pressures (400, 600, and 800 MPa). The physical properties of the green compacts obtained in this way are given in Tables 1 and 2. The values in Table 1 are based on a die temperature of 20°C (room temperature), and the values in Table 2 are based on a die temperature of 70°C. TABLE 1 (Table Removed) TABLE 2 (Table Removed) The values reproduced in Tables 1 and 2 are the mean values of three measurements. The physical properties specified in Tables 1 and 2 were determined in accordance with ISO 3923-1979 for the bulk density, ISO 4490-1978 for the flow time, ISO 3927-1985 for the compressibility, and ISO 3995-1985 for the green strength. As Tables 1 and 2 show, the green compacts produced from the mixtures (f) to (i) have not only high green strength values but also high green density values. These mixtures are clearly superior to the mixtures that contain the prior-art pressing aids (mixtures (a), (b), and (c)), but they are also superior to the mixtures that contain either only a polyethylene glycol as the pressing aid (mixture (d)) or only a montan wax as the pressing aid (mixture (e)). In addition, the die ejection force was determined for the green compacts produced from mixtures (a) to (i). These values are reproduced in Tables 3 and 4. Table 3 shows the values of the die ejection force at a die temperature of room temperature (20°C), while Table 4 shows the die ejection force values determined at a die temperature of 70°C. TABLE 3 (Table Removed) TABLE 4 (Table Removed) Tables 3 and 4 clearly show that the die ejection forces of green compacts produced from mixtures (f) to (i) are significantly reduced compared to those of green compacts produced from mixtures (a) to (e). The die ejection force is about 25% lower here. This places much less stress on the dies that are used, so that their wear is reduced and their service life is increased. Furthermore, the green compacts produced in this way show virtually no localized after-compaction or cracks. The present invention makes available a mixture, which reduces two prevalent disadvantages of previously known mixtures in a single mixture. Specifically, on the one hand, the mixture of the invention makes it possible to achieve high green strengths and high green densities of the green compacts produced from this mixture, and, on the other hand, the die ejection force can be considerably reduced, which results in a longer service life of the die. The quality of the green compacts produced from the mixtures of the invention is excellent. The reduced cracking and the reduced development of sites of localized after-compaction ensure qualitatively consistent and high-grade production. WE CLAIM: 1. Mixture for the production of sintered molded parts,, which comprises a metallic and/or plastic material as herein described and a pressing aid, wherein the pressing aid comprises 25-60 wt.% of a polyglycol, based on the total weight of the pressing aid, and 40-75% of a montan wax, based on the total weight of the pressing aid. 2. Mixture as claimed in claim 1, wherein the polyglycol comprises polyethylene glycols. 3. Mixture as claimed in with either of the preceding claims, wherein the pressing aid contains polyethylene glycols with a molecular weight of 100 to 20,000 g/mole, and preferably 100 to 7,000 g/mole. 4. Mixture as claimed in any of the preceding claims, wherein that the montan waxes comprise C24-C34 fatty acid esters. 5. Method for the production of a mixture as claimed in. any of claims 1 to 4, in which: in a first step, the polyglycols and montan waxes' that compose the pressing aid are melted together; and in a second step, the pressing aid produced in the first step is added to the metallic and/or plastic material. 6. Method as claimed in claim 5, wherein after the first step, the melt that has been produced from polyglycol and montan wax is cooled and then ground or atomized. 7. Method for producing a mixture as claimed in claims 1 to 4, wherein in a first step the polyglycols and montan waxes included in the compaction aid are mixed together; and in a second step the compaction aid produced according to the first step is added to the metallic and/or plastics material. 8. Green compact produced from a mixture as application claim in any of claims 1 to 4.

Documents:

455-delnp-2005-abstract.pdf

455-delnp-2005-claims.pdf

455-delnp-2005-complete specificatin granted.pdf

455-delnp-2005-Correspondence Others-(08-04-2011).pdf

455-delnp-2005-Correspondence-Others-(31-03-2011).pdf

455-delnp-2005-correspondence-others.pdf

455-delnp-2005-correspondence-po.pdf

455-delnp-2005-description (complete).pdf

455-delnp-2005-drawings.pdf

455-delnp-2005-form-1.pdf

455-delnp-2005-form-18.pdf

455-delnp-2005-form-2.pdf

455-delnp-2005-Form-27-(08-04-2011).pdf

455-delnp-2005-form-3.pdf

455-delnp-2005-form-5.pdf

455-delnp-2005-gpa.pdf

455-delnp-2005-pct-210.pdf

455-delnp-2005-pct-301.pdf

455-delnp-2005-pct-304.pdf

455-delnp-2005-pct-308.pdf

455-delnp-2005-pct-332.pdf

455-delnp-2005-pct-338.pdf

455-delnp-2005-pct-409.pdf

455-delnp-2005-Petition 138-(31-03-2011).pdf

455-delnp-2005-petition-137.pdf