RU2351434C2 - Sintered metallic composition of matter, containing secondary amides in capcity of lubricant and/or binding agent - Google Patents

Abstract

FIELD: metallurgy. ^ SUBSTANCE: invention relates to powder metallurgy. Particularly it relates to sintered metallic composition of matter on the basis of iron. Composition of matter contains powder on the basis of iron and lubricant and/or binding agent, containing at least one secondary amide with common formula R1-NH-CO-R2, where R1 and R2 - are equal or different, linear or branch, saturated or unsaturated aliphatic hydrocarbon groups. Admixture containing at east one secondary amide can be used in the capacity of lubricating and/or binding component for powders on the basis of iron, and also in the capacity of lubricant for die wall. ^ EFFECT: composition of matters usage provides effort decreasing for pressed details ejection and to decrease surface defect after sintering. ^ 20 cl, 1 dwg, 10 tbl, 5 ex

Description

FIELD OF THE INVENTION

The present invention relates to a powder metal composition. In particular, the invention relates to a powder metal composition comprising a lubricant and / or a binder comprising at least one secondary amide. The invention also relates to a method for preparing a preform, to a method for preparing a bound iron-based powder composition and to the use of a lubricant and / or binder.

BACKGROUND OF THE INVENTION

Metal powders are used in industry for the manufacture of metal products by pressing a metal powder in a matrix at high pressure, extracting the compact, and then optionally sintering the product. In most powder metallurgy (PM) applications, a lubricant is included in the powder in order to ensure proper sliding between the powder particles during the compaction process and between the die and the compact during its removal from the matrix. A lubricant obtained by incorporating a lubricant into a metal powder refers to internal lubrication, unlike external lubrication, which is achieved by applying a lubricant to the walls of the matrix in which the powder is pressed. Inadequate lubrication during the extraction process leads to excessive friction between the compact and the die, which in turn leads to high ejection forces and damage to the surfaces of the die and the article.

Internal lubrication is carried out using special lubricants. Typically, these lubricants in powder form are mixed with iron powder or iron-based powder. Some lubricants can be used to induce additives, such as, for example, alloying elements, with iron particles or iron-based particles. In these cases, the lubricants thus function as binding agents and reduce or completely eliminate the segregation of additives during transport and handling.

Lubricants traditionally used for PM applications are metal soaps, such as lithium and zinc stearate. A disadvantage of this type of lubricant is that the metal oxides in the lubricant contaminate the internal parts of the sintering furnace as a result of the release of metals from the lubricant during sintering; another problem is that after sintering, defects (spots) can form on the surface of the product. Another commonly used lubricant is ethylene bis stearamide (EBS). Defects on the surface of the product can form after sintering, when this lubricant is also used, but to a lesser extent compared to the use of, for example, zinc stearate. Since the lubricant strongly affects the properties / quality of pressing and sintering of metal powder, the optimization of the quantity, composition and structure of the lubricant used is relevant for obtaining high, uniform densities and good surface quality of the manufactured parts.

OBJECTS OF THE INVENTION

The aim of the present invention is to provide a new powder metal composition containing a lubricant and / or a binder that reduce or eliminate the problems associated with high ejection forces and defective surfaces of sintered parts.

The invention also aims to develop a method for preparing pressed articles and sintered or heat-treated parts, a method for preparing a combined powder metal composition, and the use of a lubricant and / or binder.

SUMMARY OF THE INVENTION

These goals are achieved by a powder metal composition containing iron-based powder and a lubricant and / or binder containing at least one secondary amide. The invention also relates to a method for manufacturing a workpiece by pressing the above composition.

A method for producing a bonded powder metal composition comprises mixing an iron-based powder with at least one secondary amide and heating the mixture to a temperature above the melting point of the at least one secondary amide.

In addition, the invention relates to the use of at least one secondary amide as a lubricant and / or binding agent for iron-based powders and to its use for lubricating a matrix wall.

DETAILED DESCRIPTION OF THE INVENTION

The lubricant and / or binder in the powder metal composition in accordance with the invention is at least one secondary amide, which can be determined in accordance with the General formula:

R ₁ -NH-CO-R ₂

where R ₁ and R ₂ are groups that may be the same or different, linear or branched, saturated or unsaturated aliphatic hydrocarbon groups.

Preferably, R ₁ and R ₂ independently include from 10 to 24 carbon atoms.

Preferably, R ₁ and R ₂ are selected from the group consisting of alkyls and alkenyls.

The selected alkyl groups can be decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl, eicosyl, geneycosyl, docosyl, tricosyl, tetracosyl.

The selected alkenyl groups can be decenyl, undecenyl, dodecenyl, tridecenyl, tetradecenyl, pentadecenyl, hexadecenyl, heptadecenyl, octadecenyl, nonadecenyl, eicosenyl, geneukosenyl, docosenyl, tricosenyl, tetracosenyl.

Examples of preferred secondary amides are shown in table 1.

The amounts of secondary amides may be 0.05-2.0 wt.% Of the powder metal composition, preferably 0.05-1.0 wt.%.

One embodiment of the invention relates to a powder metal composition comprising a lubricant and / or a binder, comprising at least one primary amide in conjunction with at least one secondary amide. At least one primary amide is preferably a saturated or unsaturated fatty acid amide having 12-24, preferably 14-22 carbon atoms and most preferably 16-22 carbon atoms.

Of the primary amides, amides of stearic acid (stearamide), behenic acid (behenamide), erucic acid (erucamide), palmitic acid (palmitamid) and arachidic acid amide (arachidamid) are particularly preferred.

Primary and secondary amides according to the invention are either commercially available or can be synthesized from commercially available materials using methods well known in the art.

The amount of primary and secondary amides may be in the aggregate 0.05-2.0 wt.% Powder metal composition, preferably 0.05-1.0 wt.%.

For an embodiment of the invention comprising two types of amides, the amount of at least one primary amide may be 0.05-1.0 wt.%, And the amount of at least one secondary amide may be 0.05-1, 0 wt.%.

Such a lubricant and / or binder may be added to the metal powder composition in the form of solid particles of each amide. The average particle size may vary, but it is desirable that it be less than 150 microns.

Alternatively, a lubricant and / or binder may be added to the metal powder composition in the form of a molten and then solidified mixture of amide particles. This can be achieved by mixing amides in a fixed amount, then the mixture is melted, cooled and then ground into a lubricating powder.

At least one secondary amide according to the invention can be used as a binder to form a bound mixture in which possible alloying elements and at least one secondary amide are connected to an iron-based powder. This can be achieved by mixing the iron-based powder with at least one secondary amide according to the invention and heating the mixture to a temperature above the melting point of the at least one secondary amide. At least one primary amide may be further intervened in the above mixture, the heating temperature of the mixture being lower than the melting point of this primary amide.

In addition to the lubricant and / or binder described above, the powder metal composition of the invention may optionally contain other lubricants, such as zinc stearate, lithium stearate, EBS, etc.

In order to achieve the bonding of the powder metal composition according to the invention, alkides, cellulose ester resins, hydroxyalkyl cellulose resins having 1-4 carbon atoms in the alkyl group, or thermoplastic phenolic resins can be used as other types of connecting systems.

Used in the description and the accompanying claims, the expression "iron-based powder" means that the powder consists mainly of pure iron, iron powder doped with other elements that improve strength, hardening properties, electromagnetic properties or other desired properties of the final products, and iron particles mixed with particles of such alloying elements (diffusion annealed mixture or purely mechanical mixture). Examples of alloying elements: copper, molybdenum, chromium, manganese, phosphorus, carbon in the form of graphite, nickel, silicon, boron, vanadium, titanium, aluminum, cobalt and tungsten; alloying elements are used either separately or in combination, for example, in the form of compounds (Fe ₃ P and FeMo).

For the preparation of soft magnetic parts, iron-based powders can be used, which for this application can be electrically isolated. The electrical insulation of the powder particles can be made from inorganic material. The most suitable type of insulation for the above purpose is described in United States Patent 6348265, which refers to particles of a basic powder consisting of highly pure iron having an oxygen and phosphorus-containing insulating barrier. Isolated powder particles are available as Somaloy ^™ 500 and 550, Hoganas AB, Sweden.

In addition to iron-based powder and a lubricant and / or a binder, the powder metal composition of the invention may contain one or more additives selected from the group consisting of excipients and solid phases.

The excipients used in the powder metal composition may consist of talc, forsterite, manganese sulfide, sulfur, molybdenum disulphide, boron nitride, tellurium, selenium, barium difluoride and calcium difluoride, which are used either individually or in combination.

The solid phases used in the metal composition of the powder may consist of carbides of tungsten, vanadium, molybdenum, chromium, Al ₂ O ₃ , B ₄ C and various ceramic materials.

The invention also relates to a method for manufacturing a workpiece, comprising: pressing a powder metal composition into a compressed part according to the invention, where the composition comprises iron-based powder and a lubricant and / or a binder containing at least one secondary amide with the general formula R ₁ —NH — CO — R ₂ , where R ₁ and R ₂ are the same or different, linear or branched, saturated or unsaturated aliphatic hydrocarbon groups. The pressed part may be sintered or heat treated.

Using standard techniques, iron-based powder, a lubricant and / or a binder and optional additives can be mixed into a substantially homogeneous powder composition prior to the pressing step.

Prior to the pressing step, the powder metal composition and / or matrix may be preheated.

The invention also relates to the use of at least one secondary amide, which is defined as described above, as a lubricant and / or binding agent for iron powder or iron-based powder.

An embodiment of the invention also relates to the use of at least one secondary amide, which is defined, as described above, as a lubricant for the matrix wall.

Detailed description of the drawing

The drawing illustrates the formation of defects on the surface of the part after sintering, depending on the use of various lubricants.

1a) Ethylene bissteramide (EBS).

1b) Oleyl palmitamide (secondary amide according to the invention).

The invention will now be further described with the following numerous examples.

Examples

In the following examples, lubricants having the formulas shown in Table 2 (below) were used.

table 2 Chemical name Structural formula* Amide type Sample Comparison: Ethylene Bis Stearamide (EBS) CH ₃ (CH ₂ ) ₁₆ CONH (CH ₂ ) ₂ NHCO (CH ₂ ) ₁₆ CH ₃ bis amide Stearamide (S) CH ₃ (CH ₂ ) ₁₆ CONH ₂ primary Arachidamide (A) CH ₃ (CH ₂ ) ₁₈ CONH ₂ primary Erukamide (E) CH ₃ (CH ₂ ) ₇ CH = CH (CH ₂ ) ₁₁ CONH ₂ primary Begenamide (B) CH ₃ (CH ₂ ) ₂₀ CONH ₂ primary Stearyl stearamide (SS) R1 = C18: 0 R2 = C17: 0 secondary Erucil Stearamide (ES) R1 = C22: 1 R2 = C17: 0 secondary Oleyl Palmitamide (OP) R1 = C18: 1 R2 = C15: 0 secondary Stearyl erucamide (SE) R1 = C18: 0 R2 = C21: 1 secondary Oleyl Stearamide (OS) R1 = C18: 1 R2 = C17: 0 secondary Stearyl Oleamide (SO) R = C18: 0 R2 = C17: 1 secondary * The structural formulas of the secondary amides, as previously indicated, correspond to R ₁ —NH — CO — R ₂ .

Example 1

This example shows the lubricating properties of various secondary amides and various combinations of secondary and primary amides, which are added in powder form to a mixture of iron-based powders.

ASC 100.29 base powder (available from Hogans AB, Sweden) was mixed with 0.5 wt.% Graphite (uf-4 from Kropfmuhl) and 0.8 wt.% Lubricants (from tables 3 and 4) in a Lödige mixer in for 2 minutes. Ethylene bissteramide (EBS, available as Lincowax ™, Clariant, Germany) was used as a reference sample. Lubricants had particle sizes of less than 150 microns. Compositions containing both a secondary amide and a primary amide included 50% of each amide (0.8% by weight of the total composition).

In order to measure the lubricating properties of the studied amides, rings with an inner diameter of 45 mm, an outer diameter of 55 mm and a height of 10 mm were pressed at ambient temperature and three different pressing pressures (400, 600 and 800 MPa). During the extraction of the pressed parts, the ejection force was recorded. After extraction, the density of the green parts was measured, and the total ejection energy necessary for extracting the samples from the matrix was calculated, relative to the area of the surrounding surface.

The obtained ejection energies and densities are shown in Tables 3 and 4. When the powder metal composition of the invention was used, lower ejection energies were achieved compared to the ejection energies when using the reference sample — a composition containing EBS.

Table 3 Densities and expulsion energies (secondary amides and reference sample) Lubricant Pre mixed The density of green material (g / cm ³ ) Ejection Energy (J / cm ² ) 400 MPa 600 MPa 800 MPa 400 MPa 600 MPa 800 MPa Ebs
(Sr. Avg.) 6.70 7.04 7.17 19.2 26.1 28,2 SS 6.72 7.06 7.19 17.6 24.7 27.9 ES 6.78 7.12 7.23 16.3 20.3 20.8 OP 6.78 7.14 7.25 16.7 21.3 20.3 SE 6.78 7.13 7.24 16.8 21.9 21.8 OS 6.78 7.13 7.24 17.7 21.3 20.5 SO 6.79 7.13 7.23 15.9 21,4 20,4

Table 4 Densities and buoyancy energies (secondary + primary amides 1: 1 and reference sample). Lubricant Pre mixed The density of green material (g / cm ³ ) Ejection Energy (J / cm ² ) 400 MPa 600 MPa 800 MPa 400 MPa 600 MPa 800 MPa Ebs
(Sr. Avg.) 6.70 7.04 7.17 19.2 26.1 28,2 SS + E 6.69 7.06 7.21 19.1 24.2 23.6 OP + S 6.70 7.06 7.19 18.2 22.1 22.3 ES + S 6.71 7.06 7.19 17.9 21.5 21.8 ES + E 6.72 7.11 7.23 17.8 20.7 19.0

Example 2

ASC 100.29 main powder was mixed with 2 wt.% Copper (-100 μm), 0.8 wt.% Graphite and 0.8 wt.% Lubricant (a) EBS or b) oleyl palmitamide) in a Lödige mixer in for 2 minutes. The lubricant had a particle size of less than 150 microns. In order to measure the formation of defects on products after sintering, cylindrical products were pressed at ambient temperature with a diameter of 64 mm and a height of 32 mm to a density of green material of 7.1 g / cm ³ . The weight of one such cylinder was 700 g. Products were sintered in an atmosphere containing 90/10 N ₂ / H ₂ at 1120 ° C for 15 minutes.

Photographs of the products obtained are shown in Figure a) ethylene bissteramide (EBS) and b) oleyl palmitamide. As shown in the drawing, the obtained part a) has surface defects in contrast to part b) obtained from the powder composition of the present invention, which does not have such defects.

Example 3

This example shows the lubricating properties of various combinations of secondary and primary amides, which were melted together, cooled and ground before mixing with iron-based powder mixtures.

Combinations of lubricants were prepared in accordance with the following method: mixed lubricants, 50% primary and 50% secondary amide were melted together at 80-110 ° C, after which the materials were ground to an average particle size of less than 150 microns.

ASC 100.29 basic powder was mixed with 0.5 wt.% Graphite and 0.8 wt.% A combination of lubricants (see table 5) in a Lödige mixer for 2 minutes. In order to measure the lubricating properties, rings with an inner diameter of 45 mm, an outer diameter of 55 mm and a height of 10 mm were pressed at three different pressing pressures of 400, 600 and 800 MPa, at ambient temperature. The obtained ejection energies and densities are shown in table 5.

Table 5 Densities and expulsion energies (secondary + primary amides and reference sample) Lubricant Molten and hardened The density of green material (g / cm ³ ) Ejection Energy (J / cm ² ) 400 MPa 600 MPa 800 MPa 400 MPa 600 MPa 800 MPa Ebs
(Sr. Avg.) 6.70 7.04 7.17 19.2 26.1 28,2 SS + E 6.70 7.06 7.20 18.8 22.4 22.6 OP + S 6.71 7.07 7.20 18.5 23,2 24.4 ES + S 6.71 7.07 7.20 18.9 22.7 23.5 ES + E 6.70 7.07 7.20 17,2 19.8 18.0

Comparing the test results (table 5), it can be seen that samples prepared from the powder metal composition of the invention exhibit lower ejection energies compared to samples prepared from the known EBS lubricant.

Example 4

This example demonstrates the lubricating and binding properties of various combinations of amides in a powder metal composition.

The lubricant particles had a size of less than 150 microns. ASC 100.29 main powder was mixed with 2 wt.% Cu-100, 0.8 wt.% Graphite and 0.8 wt.% Lubricant / binder combination (from table 6) in a Lödige mixer for 2 minutes. The mixture with EBS was saved as a reference sample, while the mixtures containing amides were heated to a temperature above the melting point of the secondary amide, but below the melting point of the primary amide while stirring in another mixer, then cooled to achieve the compound additives with iron powder. In this mixture, the secondary amide will thus act as a binder, and the primary amide will act as a lubricant. The melting points of amides are shown in table 7.

Next, the buoyancy energies were measured for rings having an outer diameter of 55 mm, an inner diameter of 45 mm and a height of 10 mm, pressed at three different pressing pressures of 400, 600 and 800 MPa at ambient temperature. The obtained ejection energies and densities of the green material are shown in Table 8.

Table 6 Combination lubricant / binder for example 4 Secondary amide (0.2 wt.%) Primary amide (0.6 wt.%) ES B OP S OP B EBS (Sample avg.) (0.8 wt.%)

Table 7 Amide melting points Amide Melting point (° C) ES 72.9 OP 66.9 B 101.9 S 106.6

Table 8 Densities and buoyancy energies (primary + secondary
amides and sample) Binder / Lubricant Fused The density of green material (g / cm ³ ) Ejection Energy (J / cm ² ) 400 MPa 600 MPa 800 MPa 400 MPa 600 MPa 800 MPa ES + B 6.75 7.06 7.19 18.5 24.6 28.1 OP + S 6.73 7.09 7.18 19.3 26.6 28.3 OP + B 6.77 7.08 7.19 19.9 25.3 27.1 Ebs
(Sr. Avg.) 6.74 7.06 7.17 21,4 30.8 32.8

Samples obtained using the lubricant / binder of the invention exhibit lower ejection forces than samples obtained using a reference sample as a lubricant, i.e. EBS. The use of a powder composition containing the lubricant / binder of the present invention made it possible to obtain compacted sintered parts (sintered in 90/10 N ₂ / H ₂ at 1120 ° C. for 30 min) with excellent surface quality, i.e. virtually no scratches and no staining of defect areas.

Example 5

Large coarse magnetically soft iron-based powder was mixed in which the particles are surrounded by an inorganic insulating layer and secondary amide as a lubricant (table 9). As lubricants - comparison samples, known compounds — zinc stearate and EBS — were used. The particle size distribution of the iron-based powder used is shown in Table 10.

The resulting mixtures were transferred to a matrix and pressed into cylindrical test specimens (50 g) having a diameter of 25 mm, with the press moving along one axis and a pressing pressure of 1100 MPa. The matrix material used was ordinary tool steel. The pushing force during the extraction of the compressed samples was recorded. The total ejection energy needed to extract the samples from the matrix was calculated, relative to the area of the surrounding surface.

The measurement results, such as the ejection energies, the density of the green material and the surface quality of the green parts, are shown in Table 9. The use of the powder metal composition according to the invention resulted in the production of compressed samples with excellent surface quality and lower ejection energies compared to known compositions taken as reference samples.

Table 9 Density, ejection energy and surface quality Mixture number Lubricant (0.2 wt.%) Ejection Energy (J / cm ² ) The density of green material (g / cm ³ ) Surface quality one ES 76 7.65 Perfect 2 SE 71 7.66 Perfect 3 SS 78 7.63 Perfect four OP 76 7.66 Perfect Arr. Wed one Zinc stearate 117 7.66 Unacceptable Arr. Wed 2 Ebs 113 7.64 Perfect

Table 10 Particle size (μm) Coarse powder (wt.%) > 425 0.1 425-212 64,2 212-150 34.1 150-106 1,1 106-75 0.3 45-75 0.2 <45 0

Claims (23)

1. A powder metal composition containing iron-based powder and a lubricant and / or binder containing at least one secondary amide of the formula R ₁ —NH — CO — R ₂ , characterized in that in the secondary amide R ₁ and R ₂ - identical or different, linear or branched, saturated or unsaturated aliphatic hydrocarbon groups. 2. The composition according to claim 1, in which R ₁ and R ₂ independently contain from 10 to 24 carbon atoms. 3. The composition according to claim 1 or 2, in which R ₁ and R ₂ selected from the group consisting of alkyls and alkenyls. 4. The composition according to claim 3, in which the alkyl groups are selected from decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl, eicosyl, geneukosyl, docosyl, tricosyl, tetracosyl. 5. The composition according to claim 3, in which the alkenyl groups are selected from decenyl, undecenyl, dodecenyl, tridecenyl, tetradecenyl, pentadecenyl, hexadecenyl, heptadecenyl, octadecenyl, nonadecenyl, eicosenyl, geneukozenyl, docosenyl, tricosenyl, tetracosenyl. 6. The composition according to claim 1, in which the secondary amide is selected from oleyl palmitamide, stearyl stearamide, oleyl stearamide, stearyl stearamide, oleyl oleamide, stearyl erucamide, erucil stearamide, erucil oleamide, erucyl ericulamide laricamide, 7. The composition according to claim 1, further comprising at least one primary amide. 8. The composition according to claim 7, in which the primary amide is an amide of a saturated or unsaturated fatty acid containing 12-24 carbon atoms. 9. The composition according to claim 7, in which the primary amide is selected from the group consisting of palmitamide, stearamide, arachidamide, behenamide and erucamide. 10. The composition according to any one of claims 1 to 9, in which the lubricant is a free-flowing powder. 11. The composition according to any one of claims 7 to 9, in which the lubricant contains a molten and then hardened bulk mixture of at least one secondary amide and at least one primary amide. 12. The composition according to any one of claims 1 to 9, in which the composition is a combined mixture. 13. The composition according to item 12, in which at least one secondary amide is used as a binding agent. 14. The composition according to any one of claims 1 to 9, in which the particles based on iron are surrounded by an inorganic insulating layer. 15. A method of obtaining a workpiece, comprising pressing a powder metal composition according to any one of claims 1 to 9. 16. The method according to clause 15, also comprising a heat treatment or sintering step. 17. A method of preparing a bound iron-based powder composition, comprising mixing the iron-based powder with at least one secondary amide to obtain a composition according to any one of claims 1 to 9 and heating the resulting mixture to a temperature above the melting point of at least one secondary amide . 18. The method according to 17, in which the composition also contains at least one primary amide, and in which the heating temperature is less than the melting point of the primary amide. 19. The use of additives containing at least one secondary amide with the formula R ₁ -NH-CO-R ₂ , where R ₁ and R ₂ are the same or different, linear or branched, saturated or unsaturated aliphatic hydrocarbon groups, as a lubricant and / or a binder for iron-based powder. 20. The use of additives containing at least one secondary amide of the formula R ₁ -NH-CO-R ₂ , where R ₁ and R ₂ are the same or different, linear or branched, saturated or unsaturated aliphatic hydrocarbon groups, as a lubricant and / or a binder for the matrix wall.
Priority on points: 09/17/2004 according to claims 1-6, 10, 14 and 15; 01/12/2005 according to claims 7-9, 11-13, 15, 19-20; September 16, 2005 according to claims 17, 18.

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