ES2665689T3 - Lubricant for powder metallurgical compositions - Google Patents

Abstract

Particle composite lubricant for powdered metal compositions, in which the composite lubricant comprises particles consisting of a core of a solid organic lubricant, a core having fine carbon particles adhered thereon.

Description

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DESCRIPTION

Lubricant for powder metallurgical compositions

The present invention relates to a powder metallurgical composition. Specifically, the invention relates to a metal powder composition comprising a new particulate composite lubricant. The invention further relates to the new particulate composite lubricant, in addition to a method of preparing this lubricant.

In the powder metallurgy industry (MP industry), powdered metals, almost always based on iron, are used for component production. The production process involves compacting a mixture of powdered metals in a mold to form a green compact, ejecting the compact from the mold and sintering the green compact at temperatures and under conditions such that a sintered compact having sufficient strength is produced. By using the MP production path, costly losses by machining and material can be avoided compared to conventional machining of solid metal components, since components can be produced net or almost net. The MP production route is the most suitable for the production of small and quite complex parts such as gears.

In order to facilitate the production of MP parts, lubricants can be added to the iron-based powder before compaction. Using lubricants, internal frictions between individual metal particles are reduced during the compaction stage. Another reason for adding lubricant is that the ejection force and the total energy required are reduced in order to expel the green part of the mold after compaction. Insufficient lubrication will cause wear and scratches in the mold during the expulsion of the green compact.

The problem with insufficient lubrication can be solved mainly in two ways, either by increasing the amount of lubricant or by selecting more efficient lubricants. By increasing the amount of lubricant, there is an unwanted side effect in which the increase in density through better lubrication is reversed by the high amount of lubricants.

A better choice would then be to select more efficient lubricants. This is, however, a problem since compounds that have good lubricity in the context of MP tend to agglomerate during storage or contribute to the formation of agglomerates in the powder metallurgical composition, a consequence of which is that the component Subsequently compacted and synthesized, it can include comparatively large pores that have a detrimental effect on the static and dynamic mechanical properties of the component. Another problem is that lubricants that have good lubrication properties often have negative effects on so-called dust properties, such as flow rate and bulk density (DA). The flow is important due to its impact on the filling of the mold, which in turn is important for the production speed of the MP parts. A high DA is important in order to allow shorter filling depths and even the DA is important in order to avoid variations in the dimensions and weight of the finished components. Thus, it is desirable to obtain a new lubricant for powdered metal compositions that overcome or reduce the aforementioned problems.

Objects of the invention

It is, therefore, an object of the present invention to provide a lubricant that has good lubrication properties, but no reduced tendency or tendency to agglomerate.

It is another object of the present invention to provide a lubricant that has good lubrication properties and even confers improved flow or flow properties when used in an iron or iron-based powder composition.

It is another object to provide a new iron or iron-based powder composition that includes the new lubricant and that has good flow properties and a high and uniform bulk density.

It is still another object to provide a production process of a lubricant.

Summary of the invention

According to the invention, it has now unexpectedly been found that the above objectives can be met by an iron-based powder metallurgical composition comprising an iron or iron-based powder and a new particulate composite lubricant, said composite material lubricant comprising particles that have a core comprising a solid organic lubricant that has fine carbon particles adhered thereon.

The invention also relates to the particulate composite lubricant itself, in addition to the preparation thereof.

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Detailed description of the invention

The type of solid organic lubricant of the composite lubricant according to the invention is not critical, but due to the disadvantages with organometallic lubricants, the organic lubricant should preferably not include metal constituents. Thus, the organic lubricant can be selected from a wide variety of organic substances that have good lubricating properties. Examples of such substances are fatty acids, waxes, polymers, or derivatives and mixtures thereof.

Preferred solid organic lubricants are fatty acids selected from the group consisting of palmitic acid stearic acid, behenic acid and; fatty acid monoamides selected from the group consisting of palmitamide, stearamide, behenamide, oleamide and erucamide, fatty acid bisamides such as ethylene-bis-stearamide (EBS), ethylene-bis-oleamide (EBO), polyethylene, polyethylene wax; Secondary fatty acid amides selected from the group consisting of erucilestearamide, oleylpalmitamide, stearyl rucamide, stearyloleamide, stearyltearamide, oleilestearamide.

Especially preferred solid organic lubricants are stearamide, erucamide, stearyloleamide, erucilestearamide, stearyl rucamide, EBO, EBS and EBS in combination with oleamide, erucamide, stearylleamide, stearyl rucamide or erucilyl amideramide. Currently available results indicate that metal powder compositions comprising these composite lubricants according to the invention are especially distinguished by high bulk and / or bulk densities. Additionally, these lubricants are known for their excellent lubricating properties.

The average particle size of the organic core particles may be 0.5-100 pm, preferably 150 pm and most preferably 5-40 pm. In addition, it is preferred that the particle size of the core is at least five times the particle size of the carbon particles and it is preferred that the fine carbon particles form a coating on the core surface.

In this context, the term "fine carbon particles" is intended to mean crystalline, semi-crystalline or amorphous carbon particles. Fine carbon particles may originate from natural or synthetic graphite, carbon black, active carbon, carbon and anthracite, etc., and may also be a mixture of two or more of these. The fine carbon particles adhered on the surface of the solid organic lubricant core may preferably be selected from the group consisting of carbon black and natural or synthetic graphite, which have an average particle size of less than 10 pm and greater than 5 nm.

The primary particle size of the carbon black may be less than 200 nm, preferably less than 100 nm, and most preferably less than 50 nm and greater than 5 nm. The specific surface area may be between 20 and 1000 m2 / g as measured by the BET method. Carbon black can be obtained from a supplier such as Degussa AG, Germany. The carbon black content in the composite lubricant may be 0.1-25% by weight, preferably 0.2-6% by weight and most preferably 0.5-4% by weight.

The average particle size of graphite may be less than 10 pm and greater than 500 nm. The graphite content in the composite lubricant may be 0.1-25% by weight, preferably 0.5-10% by weight and most preferably 1-7% by weight. Graphite can be obtained from a supplier such as Graphit Kropfmühl AG, Germany, or a synthetic graphite with an ultra-high surface area from Asbury Carbons, USA.

The lubricant content of composite material in the metal powder composition may be 0.05-2% by weight.

The particulate composite lubricant according to the invention can be prepared by usual particle coating technique, which involves mixing an organic particulate lubricant material and fine carbon particles. The method may further comprise a heating stage. The temperature for heat treatment may be lower than the melting point of the organic solid particulate lubricant.

The solid organic particulate lubricant can be thoroughly mixed with the fine carbon particles in a mixer. The mixer can be a high speed mixer. The mixture can be heated during mixing at a temperature and for a period of time sufficient to allow fine carbon particles to adhere to the surface of the particulate organic lubricant material during an optional cooling step that follows.

The iron-based powder may be a pre-alloyed iron-based powder or an iron-based powder having the alloy elements diffusedly bonded to the iron particles. The iron-based powder may also be a mixture of essentially pure iron powder or powder based on pre-alloyed iron and alloy elements selected from the group consisting of Ni, Cu, Cr, Mo, Mn, P, Si, V, Nb, Ti, W and graphite. Carbon in the form of graphite is an alloy element used largely in order to give sufficient mechanical properties to the finished sintered components. By adding carbon as an individual constituent to the iron-based powder composition, the dissolved carbon content of the iron-based powder can be kept low, enhancing

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The improvement of compressibility. The iron-based powder may be an atomized powder, such as a water atomized powder, or an iron powder. The particle size of the iron-based powder is selected depending on the end use of the material. The iron or iron-based powder particles may have an average particle size by weight of up to about 500 pm, more preferably the particles may have an average particle size by weight in the range of 25-150 pm, and most preferably 40-100 pm.

The powder metal composition may further comprise one or more additives selected from the group consisting of binders, processing aids, hard phases, machining agents if there is a need for machining of the sintered component, and solid lubricants conventionally used in the MP industry such as EBS, zinc stearate and Kenolube® available from Hoganas AB. The concentration of powdered composite lubricant according to the invention plus optional solid lubricants may be in the range of 0.05 to 2% of a metal powder composition.

The new iron or iron-based powder composition can be compacted and optionally sintered by conventional MP techniques.

The following examples serve to illustrate the invention, but the scope of the invention should not be limited thereto.

Examples

materials

The following materials were used.

(1) It was used as an atomized powder in iron-based water (ASC100.29, available from Hoganas AB, Sweden).

(2) The following substances were used as lubricant core materials; ethylene bis bis stearamide (EBS) available as Licowax ™ from Clariant (Germany), stearamide, erucamide, oleylpalmitamide, stearylolelamide, erucilestearamide, stearyylerucamide, ethylene bis oleamide (EBO) and polyethylene waxes. The average particle sizes of the lubricants can be seen in Table 2.

(3) UF-4 graphite (from Graphit Kropfmühl AG, Germany) was used as an added graphite in the iron-based powder composition.

(4) The coating particles were Graphite UF-1 (UF1) (from Graphit Kropfmühl AG, Germany) and Graphite 4827 (4827) (from Asbury Carbons, USA) which have an average particle size of 2 pm and 1.7 pm respectively, and carbon black (CB) (from Degussa AG, Germany) having a primary particle size of 30 nm.

The iron-based powder compositions consisted of ASC100.29 mixed with 0.5% by weight of graphite and 0.8% by weight of composite lubricant.

Different composite lubricants were prepared by mixing the core material according to Table 1 and 2 with fine carbon particles at different concentrations in a Hosokawa high speed mixer. Carbon black was added at concentrations of 0.75, 1.5, 3 and 4% by weight, respectively. Graphite was added at concentrations of 1.5, 3, 5 and 6% by weight, respectively, to composite lubricants. The process parameters for the mixing process, such as the temperature of the powder in the mixer and the mixing times for each composite material, can be seen in Table 2. The rotor speed in the mixer was 1000 rpm and the amount of Lube core material was 500 g.

Table 1. Lubricating substances used as core materials.

 Indicator

 Common name

 IS

 Erucilestearamide

 OP

 Oleylpalmitamide

 S

 Stearamide

 OR

 Oleamide

 AND

 Erucamida

 EBS

 Ethylene bis bis stearamide

 PW655

 Polyethylene wax

 PW1000

 Polyethylene wax

 BE

 Stearylcamide

 EBO

 Ethylene bis oleamide

 SW

 Stearyloleamide

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Table 2. Process parameters

 Indicator

 Average particle size X50 (pm) Temp. of the powder in the mixer (° C) Mixing time (min)

 S-1

 5.2 50 ° C 25

 S-2

 5.8 50 ° C 25

 S-3

 15.4 50 ° C 25

 S-4

 16.5 50 ° C 45

 S-5

 17.8 50 ° C 25

 S-6

 21.5 50 ° C 25

 S-7

 4.0 83 ° C 60

 ES-1

 24.0 25 ° C 25

 ES-2

 29.5 25 ° C 25

 AND

 20.3 25 ° C 45

 OP

 16.0 25 ° C 45

 EBS

 8.5 75 ° C 55

 EBS / O

 25.6 40 ° C 20

 PW655

 10.0 25 ° C 45

 PW1000

 10.0 40 ° C 45

 BE

 27.4 25 ° C 45

 SW

 35.4 25 ° C 45

 EBS / SE

 29.0 25 ° C 45

 EBS / SO

 29.2 25 ° C 45

 EBS / ES

 20.4 25 ° C 45

 EBS / E

 26.0 25 ° C 15

 BE

 24.3 25 ° C 45

 EBO

 16.0 50 ° C 10

Different iron-based powder compositions (mixture No. 1-63) of 25 kg each were prepared by mixing the obtained composite lubricant or a conventional particulate lubricant (used as reference) with graphite and ASC100.29 in a mixer 50 kg nauta The solid organic lubricant particles were melted in mixtures No. 36-38 and 50-61, subsequently solidified and micronized before use as core material to prepare the composite lubricants or before being added to the mixtures of reference. Bulk density (DA) and Hall flow (flow), according to ISO 4490 and ISO3923-1, respectively, were measured in iron-based powder compositions obtained 24 hours after mixing. Table 3 shows the results of the measurements.

As can be seen from Table 3, the flow rate of iron-based powder compositions improves and higher bulk densities can be obtained if the different composite lubricants according to the invention are used as lubricants compared to the use of a conventional lubricant. Actually, when an MP composition containing a conventional lubricant has no flow, the MP composition containing the inventive composite lubricant provides the flow. Especially high and / or high bulk densities were obtained for the powdered metal compositions containing composite lubricants according to the invention containing stearamide, erucamide, erucilestearamide, stearyl rucamide, EBO, EBS and EBS in combination with oleamide or stearyl rucamide.

In order to measure the tendency of composite lubricants and conventional lubricants to form agglomerates, the lubricants were screened in a standard 315 pm sieve after storing at least one week. The amount of retained material was measured.

Table 4 shows that the tendency to form agglomerates decreases when the organic lubricating core material is covered by fine carbon particles, producing a composite lubricant according to the invention.

The same type of measurements as shown in Table 4 were repeated with certain iron-based powder compositions in order to assess the tendency to form agglomerates in an iron-based powder composition containing conventional lubricants and composite lubricants according to the invention, respectively.

Table 5 shows that the tendency to form agglomerates is less pronounced in iron-based powder compositions containing the composite lubricant according to the invention compared to compositions comprising a conventional lubricant.

Table 3. Flow rate and bulk density (DA) ^ of compositions 1-63

 Mix No.

 Conventional lubricant used as a reference Core of lubricating composite material Type of carbon particles adhered on the lubricating core Percentage of carbon particles in relation to the total amount of lubricating composite material (%) Flow (seconds / 50 g) DA (g / cm3 )

 one

 S-1 Does not flow 2.97

 2

   S-1 UF1 3.0 Does not flow 2.99

 3

   S-1 CB 1.5 34.5 2.85

 4

   S-1 CB 3.0 30.4 2.92

 5

 S-2 Does not flow 2.98

 6

   S-2 UF1 3.0 Does not flow 2.99

 7

   S-2 CB 3.0 32.9 2.91

 8

 S-3 Does not flow 3.05

 9

   S-3 UF1 3.0 29.5 3.17

 10

 S-4 Does not flow 3.12

 eleven

   S-4 UF1 3.0 28.3 3.18

 12

   S-4 CB 0.75 27.1 3.21

 13

   S-4 CB 1.5 27.2 3.17

 14

 S-5 30.6 3.05

 fifteen

   S-5 CB 0.75 28.5 3.13

 16

   S-5 CB 1.5 27.3 3.13

 17

   S-5 4827 5.0 29.3 3.17

 18

 S-6 31.5 3.06

 19

   S-6 UF1 3.0 27.7 3.20

 twenty

   S-6 CB 0.75 26.9 3.21

 twenty-one

 S-7 28.2 3.17

 22

   S-7 UF1 3.0 26.1 3.19

 2. 3

   S-7 CB 3.0 26.0 3.11

 24

 ES-1 Does not flow 3.10

 25

   ES-1 CB 1.5 33.1 3.19

 26

 ES-2 Does not flow 3.13

 27

   ES-2 CB 1.5 31.3 3.15

 28

   ES-2 4827 1.5 29.7 3.18

 29

 E Does not flow 3.03

 30

   E CB 1.5 30.3 2.97

 31

   E CB 3.0 28.8 3.01

 32

 OP Does not flow 2.92

 33

   OP CB 1.5 34.3 2.94

 3. 4

 EBS 33.5 3.01

 35

   EBS CB 1.5 30.8 3.00

 36

 EBS / O 31.0 3.03

 37

   EBS / O UF1 3.0 30.4 3.10

 38

   EBS / O CB 3.0 28.4 3.09

 39

 PW655 Does not flow 2.76

 40

   PW655 CB 1.5 32.1 2.82

 41

 PW1000 Does not flow 2.78

 42

   PW1000 CB 1.5 32.5 2.85

 43

 Zn Stearate 35.4 3.18

 44

 SE Does not flow 2.96

 Four. Five

   SE CB 3.0 29.9 3.11

 46

   SE UF1 6.0 31.2 3.08

 47

   SE 4827 5.0 30.4 3.10

 48

 SO Does not flow 2.95

 49

   SO CB 1.5 30.9 2.98

 fifty

 EBS / SE Does not flow 2.98

 51

   EBS / SE CB 1.5 29.6 3.17

 52

 EBS / SO Does not flow 2.95

 53

   EBS / SO CB 1.5 30.9 3.03

 54

 EBS / ES Does not flow 3.00

 55

   EBS / ES CB 1.5 33.4 2.99

 56

 EBS / E Does not flow 2.96

 Mix No.

 Conventional lubricant used as a reference Core of lubricating composite material Type of carbon particles adhered on the lubricating core Percentage of carbon particles in relation to the total amount of lubricating composite material (%) Flow (seconds / 50 g) DA (g / cm3 )

 57

   EBS / E CB 1.5 30.0 3.03

 58

 S / E Does not flow 3.00

 59

   S / E CB 4.0 29.1 3.16

 60

   S / E UF1 6.0 28.4 3.17

 61

   S / E 4827 5.0 28.2 3.18

 62

 EBO Does not flow 2.95

 63

   EBO CB 3.0 34.0 3.04

Table 4 Tendency to form agglomerates for conventional lubricants and lubricating composite materials ____________________________________ according to the invention ____________________________________

 Conventional lubricant

 Core material of the lubricating composite material Type of carbon particles adhered to the lubricating core material Percentage of carbon particles in relation to the total amount of lubricating composite material (%) Tendency to form agglomerates

 S-1

       Aggl

 S-1 CB 1.5 Less agl

 S-1 CB 3.0 Less agl

 S-2

       Aggl

 S-2 CB 3.0 Less agl

 S-4

       Aggl

 S-4 UF1 3.0 No agl

 S-4 CB 0.75 No agl

 S-4 CB 1.5 No agl

 S-5

       Aggl

 S-5 CB 0.75 No agl

 S-5 CB 1.5 No agl

 S-5 4827 5.0 No agl

 S-7

       Aggl

 S-7 UF1 3.0 No agl

 S-7 CB 0.75 No agl

 ES-2

       Aggl

 ES-2 CB 1.5 No agl

 ES-2 4827 1.5 No agl

 AND

       Aggl

 E CB 1.5 Less agl

 OP

       Aggl

 OP CB 1.5 No agl

 EBS

       Not agl

 EBS CB 1.5 No agl

 EBS / O

       Not agl

 EBS / O UF1 3.0 No agl

 BE

       Aggl

 SE CB 1.5 No agl

 SE UF1 6.0 No agl

 SE 4827 5.0 No agl

 SW

       Aggl

 SO CB 1.5 No agl

 EBS / SE

       Aggl

 EBS / SE CB 1.5 No agl

 EBS / SO

       Aggl

 EBS / SO CB 1.5 No agl

 EBS / ES

       Aggl

 EBS / ES CB 1.5 No agl

 EBS / E

       Aggl

 EBS / E CB 1.5 No agl

 BE

       Aggl

 S / E CB 4.0 No agl

 Conventional lubricant

 Core material of the lubricating composite material Type of carbon particles adhered to the lubricating core material Percentage of carbon particles in relation to the total amount of lubricating composite material (%) Tendency to form agglomerates

 S / E UF1 6.0 No agl

 S / E 4827 5.0 No agl

 EBO

       Aggl

 EBO CB 3.0 No agl

Table 5 Tendency to form agglomerates in iron-based powder compositions containing conventional _______________ lubricants and the composite material lubricant according to the invention ______________

 Mix No.

 Conventional lubricant Core material of the lubricating composite material Type of carbon particles adhered to the lubricating core material Percentage of carbon particles in relation to the total amount of lubricating composite material (%) Tendency to form agglomerates

 one

 S-1 Agl

 3

   S-1 CB 1.5 No agl

 4

   S-1 CB 3.0 No agl

 5

 S-2 Agl

 7

   S-2 CB 3.0 No agl

 24

 ES-1 Agl

 25

   ES-1 CB 1.5 No agl

 29

 E Agl

 30

   E CB 1.5 Less agl

 31

   E CB 3 No agl

 32

 OP Agl

 33

   OP CB 1.5 No agl

 3. 4

 EBS No agl

 35

   EBS CB 1.5 No agl

 39

 PW655 Agl

 40

   PW655 CB 1.5 No agl

 41

 PW1000 Agl

 42

   PW1000 CB 1.5 No agl

 43

 Zn Stearate No agl

 44

 SE Agl

 Four. Five

   SE CB 1.5 No agl

 46

   SE UF1 6.0 No agl

 47

   SE 4827 5.0 No agl

 48

 SO Agl

 49

   SO CB 1.5 No agl

 fifty

 EBS / SE Agl

 51

   EBS / SE CB 1.5 No agl

 52

 EBS / SO Agl

 53

   EBS / SO CB 1.5 No agl

 54

 EBS / ES Agl

 55

   EBS / ES CB 1.5 No agl

 56

 EBS / E Agl

 57

   EBS / E CB 1.5 No agl

 58

 S / E Agl

 59

   S / E CB 4.0 No agl

 60

   S / E UF1 6.0 No agl

 61

   S / E 4827 5.0 No agl

 62

 EBO Agl

 63

   EBO CB 3.0 No Agl

Claims (14)

5 10 fifteen twenty 25 30 35 40 Four. Five 1. Particle composite lubricant for powdered metal compositions, in which the composite lubricant comprises particles constituted of a solid organic lubricant core, a core having fine carbon particles adhered thereon. 2. A metal powder composition comprising an iron-based powder metallurgical composition comprising an iron or iron-based powder, mixed with a particulate composite lubricant according to claim 1. 3. A metal powder composition according to claim 2, wherein the carbon particles are selected from natural or synthetic graphite, carbon black, active carbon, carbon and anthracite. 4. A metal powder composition according to claim 2, wherein the carbon particles are selected from natural or synthetic graphite and carbon black. 5. A metal powder composition according to claim 2, wherein the carbon particles form a coating on the core. 6. A metal powder composition according to claim 2, wherein the organic core particles are selected from the group consisting of fatty acids, waxes, polymers, or derivatives and mixtures thereof. 7. A metal powder composition according to claim 2, wherein the average particle size of the organic core particles is 0.5-100 pm. 8. A metal powder composition according to claim 2, wherein the lubricant content of composite material in the metal powder composition is 0.05-2% by weight. 9. A powder metal composition according to claim 2, wherein the core particle size is at least five times the particle size of the carbon particles. 10. A metal powder composition according to claim 3, wherein the carbon black particle size is less than 200 nm. 11. A metal powder composition according to claim 3, wherein the carbon black content in the composite lubricant is 0.1-25% by weight. 12. A metal powder composition according to claim 3, wherein the average particle size of graphite is less than 10 pm. 13. A metal powder composition according to claim 3, wherein the graphite content in the composite lubricant is 0.1-25% by weight. 14. A process for producing a particulate composite lubricant according to claim 1, comprising: mixing an organic particulate lubricant material with fine carbon particles in a mixer, for example a high speed mixer, at a temperature and for a period of time sufficient to allow fine carbon particles to adhere to the surface of the lubricant material Organic particulate, the mixture can be optionally heated during mixing.