PL198679B1 - Iron powder composition including an amide type lubricant and a method to prepare it - Google Patents

Abstract

A powder composition for warm compaction comprising an iron-based powder and a lubricant powder consisting essentially of an amide described by the following formula D-Cm-B-A-B-Cm-D wherein D is -H, COR, CNHR, wherein R is a straight or branched aliphatic or aromatic group including 2-21 C atoms; C is the group -NH(CH)nCO-; B is amino or carbonyl; A is alkylene having 4-16 C atoms optionally including up to 4 O atoms m is an integer 1-10 and n is an integer 5-11.

Description

Description of the invention

Field of the Invention

The present invention relates to metal powder based compositions, and more particularly to iron based compositions which are compressible at higher temperatures.

Background of the invention

In the field of powder metallurgy, generally different standard temperature regimes are used to compress a metal powder to form a metal component. These regimes include cold pressing (pressing below ambient temperatures), cold pressing (pressing at ambient temperatures), hot pressing (pressing at temperatures above temperatures at which the metal powder is able to maintain solidification), and semi-hot pressing (pressing at ambient temperatures). temperatures between cold pressing and hot pressing).

Ironing at temperatures above the ambient temperature has various advantages. The tensile strength and rate of hardening of most metals decrease with increasing temperatures, and higher density and strength can be obtained with lower pressing pressures. However, the extremely high hot-pressing temperatures create processing problems and accelerate the wear of the dies. Hence, current efforts are directed to the development of metallic compositions suitable for semi-hot pressing processes.

From US Patent No. 4,955,789 (Musella), semi-hot pressing is generally known. According to this patent, lubricants generally used in cold pressing, for example zinc stearate, can also be used for semi-hot pressing. In practice, however, it has proved impossible to use zinc stearate or ethylene bisstearamide (commercially available as ACRAWAX®), which are currently the most common cold-pressing, semi-hot-pressing lubricants. The problems that arise are caused by difficulties in filling the dies in a satisfactory manner.

US Pat. Nos. 5,744,433 (Storstrom et al.) And 5,154,881 (Rutz) disclose metal powder compositions containing amide lubricants which are specially developed for semi-hot pressing.

A lubricant according to US Patent No. 5,744,433 contains an amide-type oligomer that has an average molecular weight of M _of at most 30,000. Very high wet densities and strengths can be obtained by semi-hot pressing of powder compositions when the lubricant has a molecular weight above 4,000. the preferred lubricant molecule has a molecular weight of about 6,500. However, it has been found that this lubricant tends to stick to the die walls, requiring frequent cleaning. Another disadvantage is that the obtained wet moldings are colored.

US 5,154,881 discloses an amide lubricant which consists of the reaction product of a monocarboxylic acid, a dicarboxylic acid and a diamine. The only lubricant tested according to this patent specification is ADVAWAX® 450, the composition of which is not described in detail, but the resulting reaction product according to Chemis-CIVS contains, inter alia, ethylene bisstearamide. Experience with this product has shown that it is difficult to obtain consistent composition and quality, which in turn can result in variable quality components, which in turn can cause problems when the lubricant is used in large-scale industrial production.

Objectives of the invention

It is an object of the present invention to reduce or eliminate the current problems associated with large-scale production.

A second object of the invention is to develop a new type of lubricant useful in high temperature pressable metallic compositions.

The third aim is to develop a metal powder for producing stain free component parts.

The fourth object is to develop a metal composition containing a lubricant that does not deposit on the die wall during the pressing of the metal powder.

Summary of the invention

These aims are achieved by using a powder composition comprising an iron-based powder and a new oligomeric amide type lubricant. The composition may also include one

Or more additives such as binders, flow improvers, processing aids and hard phases.

Semi-hot pressing may be carried out by mixing an iron-based powder with an oligomeric amide type lubricant and optionally a binder, preheating the powder composition, and pressing the metal powder composition in a preheating device.

Detailed Description of the Invention

The new amide type lubricant used in the present invention can be represented by the following formula:

^DC has ^-BABC mb ^-D where:

D is -H, COR, CNHR, where R is a straight or branched aliphatic or aromatic group containing from 2 to 21 carbon atoms,

C is the group -NH (CH ₂ ) _n CO-,

B is an amino or carbonyl group,

A is alkylene of 4 to 16 carbon atoms and optionally up to 4 oxygen atoms, ma is an integer of 1-10, mb is an integer of 1-10, n is an integer of 5-11, with D being preferred when COR , where R is an aliphatic group containing 16-20 carbon atoms, C is -NH (CH ₂ ) _n CO-, where n is 5 or 11, B is amino, A is alkylene containing from 6 to 14 carbon atoms and optionally to 3 oxygen atoms a ma and mb, which can be the same or different, represent an integer of 2-5.

Examples of preferred lubricants used in the iron-based compositions of the present invention include:

CH3 (CH ₂ ) 16CO- [HN (CH ₂ ) 11CO] ₂ -HN (CH ₂ ) 1 ₂ NH- [OC (CH ₂ ) 11HN] ₂ -OC (CH ₂ ) 16CH3,

CH ₃ (CH ₂ ) ₁₆ CO- [HN (CH ₂ ) ₁₁ CO] ₂ -HN (CH ₂ ) ₁₂ NH- [OC (CH ₂ ) ₁₁ HN] ₃ -OC (CH ₂ ) ₁₆ CH ₃ ,

CH3 (CH2) 16CO4HN (CH2) 11CO] 3rHN (CH2) 12NH- [OC (CH2) 11HN] 3rOC (CH2) 16CH3,

CH ₃ (CH ₂ ) ₁₆ CO- [HN (CH ₂ ) ₁₁ CO] ₃ -HN (CH ₂ ) ₁₂ NH- [OC (CH ₂ ) ₁₁ HN] ₄ -OC (CH ₂ ) ₁₆ CH ₃ ,

CH3 (CH2) 16CO- [HN (CH2) 11CO] 4-HN (CH2) 12NH- [OC (CH2) 11HN] 4-OC (CH2) 16CH3,

CH ₃ (CH ₂ ) ₁₆ CO- [HN (CH ₂ ) ₁₁ CO] ₄ -HN (CH ₂ ) ₁₂ NH- [OC (CH ₂ ) ₁₁ HN] ₅ -OC (CH ₂ ) ₁₆ CH ₃ ,

CH3 (CH2) 16CO- [HN (CH2) 11CO] ₅ -HN (CH2) 12NH- [OC (CH2) 11HN] ₅ -OC (CH2) 16CH3,

Other examples include:

(CH ₃ ) CO-HN (CH ₂ ) ₅ CO-HN (CH ₂ ) ₂ NH-OC (CH ₂ ) ₅ NH-OC (CH ₃ ) with a molecular weight of 370.49,

CH3 (CH2) 160CO-HN (CH2) 11CO-HN (CH2) 12NH-OC (CH2) 11NH-OC (CH2) 20CH3 with a molecular weight of 1240.10,

CH ₃ (CH ₂ ) ₂₀ CO- [HN (CH ₂ ) ₁₁ CO] ₁₀ -HN (CH ₂ ) ₁₂ NH- [OC (CH ₂ ) ₁₁ NH] ₁₀ -OC (CH ₂ ) ₂₀ CH ₃ molecular weight 8738.04,

CH ₃ (CH ₂ ) ₄ CO- [HN (CH ₂ ) ₁₁ CO] ₃ -HN (CH ₂ ) ₁₂ NH- [OC (CH ₂ ) ₁₁ NH] ₃ -OC (CH ₂ ) ₄ CH ₃ molecular weight 1580.53,

CH3 (CH2) 4CO- [HN (CH2) 5CO] 7-HN (CH2) 6NH- [OC (CH2) 5NH] 7-OC (CH2) 4CH3 with a molecular weight of 1980.86,

CH3 (CH2) 20CO- [HN (CH2) 5CO] 7-HN (CH2) 6NH- [OC (CH2) 5NH] 7-OC (CH2) 20CH3 with a molecular weight of 2429.69 and CH ₃ (CH ₂ ) ₁₆ NH - [OC (CH ₂ ) ₁₁ NH] ₄ -CO (CH ₂ ) ₁₀ CO- [HN (CH ₂ ) ₁₁ CO] ₄ -HN (CH ₂ ) ₁₆ CH ₃ with a molecular weight of 2283.73.

The chemical differences between the novel lubricant and the lubricant disclosed in US Pat. No. 5,744,433 are that the novel molecule has a central diamine or di-acid moiety and identical end groups at both ends. The chemical difference between the new lubricant and the lubricant known from US 5,154,881 is that the molecule of the new lubricant contains the unit -HN (CH2) nCO-. Unlike the lubricant known from US Patent No. 5,154,881, no EBS is formed in the preparation of the lubricant according to the invention. EBS has the chemical formula CH3 (CH2) 16CO-HN (CH2) 2NH-OC (CH2) 16CH3) and is

In contrast to the lubricants of the present invention, this is a molecule without lactam units.

Regarding the molecular weight of the new lubricant molecule, it has been found that the preferred lubricants have a molecular weight of from 1,000 to 5,000, especially from 1,500 to 3,000.

The lubricant molecule can be obtained by standard amide oligomer procedures, as described, for example, in George Odiana's "Principles of Polymerization", 3rd edition (John Wiley & Sons, Inc.). According to the present invention, the lubricant preferably consists of at least 80% of the amide of the formula described above, and thus up to 20% by weight of other types of lubricants may be added as long as this does not adversely affect the beneficial properties of the new lubricant.

This lubricant which is added to the iron-based powder is preferably in the form of a solid powder and may constitute up to 0.1-1% by weight of the metal powder-based composition, in particular 0.2-0.8% by weight, based on the total amount of the metal powder-based composition. The possibility of using the lubricant according to the present invention in low amounts is a particularly advantageous feature of the invention as it allows high densities to be obtained.

The expression "iron-based powder" as used in the description and the appended claims includes powder obtained essentially from pure iron, iron powder which has been alloyed with other substances to improve strength, hardening properties, electromagnetic properties or other desired properties of the finished products, and iron particles. mixed with particles of such alloying elements (annealed mixture or a purely mechanical mixture). Examples of the alloying elements include copper, molybdenum, chromium, manganese, phosphorus, carbon as graphite and tungsten, which are used either alone or in combination, for example as compounds (Fe ₃ P and FeMo). Unexpectedly good results are obtained when the lubricants according to the invention are used in combination with iron-based powders which have a high compressibility. Such powders generally have a low carbon content, preferably less than 0.04% by weight. Such powders include, for example, Distaloy AE, Astaloy Mo and ASC 100.29, all of which are commercially available from Hoganas AB, Sweden.

In addition to the iron-based powder and the lubricant, the new powder composition may contain one or more additives such as binders, flow agents, processing aids and hard phases.

The binder may be added to the powder composition according to the method of US 5,368,630 (which is incorporated herein by reference) and may be an organic compound such as cellulose ester resins, hydroxyalkyl cellulose resins containing 1-4 carbon atoms. in the alkyl group, or thermoplastic phenolic resins.

A type of flow improver that can be used in the present invention is known from US Pat. No. 5,782,954 (which is hereby incorporated by reference). The flow improver, which is preferably silicon dioxide, is used in an amount of from about 0.005 to about 2% by weight, preferably from about 0.01 to about 1% by weight, and more preferably from about 0.025 to about 0.5% by weight based on the total weight of the metallurgical composition. Moreover, the flow improver should have an average particle size less than about 40 nanometers. Preferred silicon oxides include silicon dioxide materials, in both hydrophilic and hydrophobic forms, commercially available as an aerosilic series of silicon oxides, such as the Aerosil 200 and R812 products from Degussa Corporation.

Processing aids used in the metal powder composition may include talc, forsterite, manganese sulfide, sulfur, molybdenum disulfide, boron nitride, tellurium, selenium, barium difluoride, and calcium difluoride, which are used alone or in combination.

The hard phases used in the metal powder composition may include tungsten, vanadium, titanium, niobium, chromium, molybdenum, tantalum and zirconium carbides, aluminum, titanium, vanadium, molybdenum and chromium nitrides, Al2O3 and various ceramics.

The invention will be further illustrated by the following examples, which should only be interpreted as examples, but should not limit the scope of protection.

P r z k ł a d 1

The following tables compare the properties of components obtained from powder mixtures containing the lubricant of the present invention and the amide-type lubricant known from US Pat. No. 5,744,433.

PL 198 679 B1

T a b e l a 1

Lubricant Pressing pressure (MPa) GD (g / cm ³ ) Ejection force (N / mm ² ) Ejection energy (J / cm ² ) Springing (%) Invention 500 7.14 11.5 19.3 0.147 600 7.29 11.4 23.3 0.162 700 7.38 11.8 24.6 0.192 Orgasol 3501 * 500 7.09 11.9 29.9 0.191 600 7.22 13.8 40.0 0.187 700 7.30 16.0 48.5 0.229

T a b e l a 2

Lubricant Pressing pressure (MPa) Look wet part die wall Invention 500 no stains no sediment 600 few stains no sediment 700 few stains no sediment Orgasol 3501 * 500 many stains some sediment 600 many stains more sludge 700 many stains more sludge

powder / matrix temperature: 120 ° C / 120 ° C * preferred lubricant according to US Patent No. 5,744,433

The iron-based powder was Distaloy AE available from Hoganas AB, Sweden. This powder was mixed with 0.3% by weight of ultrafine graphite and 0.6% by weight of the lubricant of the present invention. The flow aid, Aerosil® 200, was added in an amount of 0.06% by weight. As can be seen, the novel oligomeric amide type lubricant of the present invention has advantages not only in ejection force, ejection energy, springback, but also in the appearance of the compressed component, and furthermore, the lubricant does not deposit on the die walls.

P r z k ł a d 2

The following table shows a comparison of the properties of components obtained from powder mixtures containing the lubricant of the present invention and the amide-type lubricant known from US 5,154,881.

As can be seen, the lubricant according to the present invention has advantages in terms of push-out force, push-out energy and springback.

T a b e l a 3

GD (g / cm ³ ) Ejection force (N / mm ² ) Ejection energy (J / cm ² ) Springing (%) The lubricant according to the present invention 7.46 9.7 20.9 0.121 A lubricant according to US 5154881 7.40 15.4 21.9 0.201

Pressing pressure 700 MPa.

Powder / matrix temperature 130 ° C / 150 ° C

The iron-based powder was Distaloy AE available from Hoganas AB, Sweden.

This powder was mixed with 0.3% by weight of ultrafine graphite and 0.6% by weight of the lubricant of the present invention. The flow aid Aerosil was added in an amount of 0.06% by weight.

PL 198 679 B1

P r z k ł a d 3

The following example compares the density of wet articles obtained with oligomeric amide based lubricants which are used in the present invention and which have different molecular weights. The iron-based powder was Distaloy AE available from Hoganas AB, Sweden.

This powder was mixed with 0.3% by weight of ultrafine graphite and 0.6% by weight of the lubricant of the present invention. The flow aid Aerosil was added in an amount of 0.06% by weight.

The powder was heated to 130 ° C and the die temperature was 150 ° C. The pressing pressure was 700 MPa.

Molecular Weight:

GD lubricant (g / cm ³ )

2000 7.44

3000 7.41

4000 7.32

If the molecular weight of the oligomeric amide lubricant is less than (about) 2000, the properties of the powder composition deteriorate in flowability, and the lubricant itself tends to adhere to the die walls and ejected surface of the compact. The adhesive nature of such surfaces increases the risk of rough surfaces forming on the end component due to powder that may accumulate on the ejected part.

Claims (10)

A semi-hot pressing powder composition, characterized in that it comprises an iron-based powder and a lubricant powder, said lubricant consisting essentially of an amide represented by the following formula: ^DC has ^-BABC mb ^-D where D is -H, COR, CNHR, where R is a straight-chain or branched aliphatic or aromatic group containing from 2 to 21 carbon atoms, C is the group -NH (CH ₂ ) _n CO-, B is an amino or carbonyl group, A is alkylene having from 4 to 16 carbon atoms and optionally up to 4 oxygen atoms, ma is an integer of 1-10, mb is an integer of 1-10, n is an integer of 5-11. 2. A composition according to claim 1 A compound according to claim 1, characterized in that D is COR, where R is an aliphatic group containing 16 to 20 carbon atoms, C is -NH (CH2) nCO-, where n is 5 or 11, B is amino, A is alkylene containing from 6 to 14 carbon atoms and optionally up to 3 oxygen atoms, a ma and mb are respectively an integer of 2-5, where ma and mb may be the same or different. 3. A composition according to p. The lubricant according to claim 1 or 2, characterized in that the lubricant consists of a compound selected from the group consisting of: CH3 (CH2) 16CO- [HN (CH2) 11CO] 2-HN (CH2) 12NH- [OC (CH2) 11HN] 2-OC (CH2) 16CH3, CH ₃ (CH ₂ ) ₁₆ CO- [HN (CH ₂ ) ₁₁ CO] ₂ -HN (CH ₂ ) ₁₂ NH- [OC (CH ₂ ) ₁₁ HN] ₃ -OC (CH ₂ ) ₁₆ CH ₃ , CH3 (CH2) 16CO- [HN (CH2) nCO] 3-HN (CH2) 12NH- [OC (CH2) nHN] 3-OC (CH2) 16CH3, CH ₃ (CH ₂ ) ₁₆ CO- [HN (CH ₂ ) ₁₁ CO] ₃ -HN (CH ₂ ) ₁₂ NH- [OC (CH ₂ ) ₁₁ HN] ₄ -OC (CH ₂ ) ₁₆ CH ₃ , CH3 (CH2) 16CO- [HN (CH2) 11CO] 4-HN (CH2) 12NH- [OC (CH2) 11HN] 4-OC (CH2) 16CH3, CH ₃ (CH ₂ ) ₁₆ CO- [HN (CH ₂ ) ₁₁ CO] ₄ -HN (CH ₂ ) ₁₂ NH- [OC (CH ₂ ) ₁₁ HN] ₅ -OC (CH ₂ ) ₁₆ CH ₃ , CH3 (CH ₂ ) 16CO- [HN (CH ₂ ) 11CO] 5-HN (CH ₂ ) 1 ₂ NH- [OC (CH ₂ ) 11HN] 5-OC (CH ₂ ) 16CH3, PL 198 679 B1 4. A composition according to p. 3. The method of claim 1, 2 or 3, characterized in that said amide has a molecular weight of from 1500 to 3000 and its content in said composition is less than 1% by weight. Composition according to any one of claims 1 to 5 3. The lubricant powder content of any of the preceding claims, wherein the lubricant powder is 0.2 to 0.8% by weight of the composition. 6. A composition according to p. A method as claimed in any one of the preceding claims, characterized in that it additionally comprises one or more additives selected from the group consisting of binders, processing aids and hard phases. 7. The composition according to p. 1., characterized in that said iron-based powder is compressible and at least 80% by weight of said lubricant powder is said oligomeric amide. 8. A composition as claimed in p. 1, or 2, or 3, or 4, or 5, or 6, characterized in that said composition is substantially free of ethylene bisstearamide. 9. A composition according to p. 1, or 2, or 3, or 4, or 5, or 6, or 7 or 8, characterized in that said iron-based powder has a carbon content of at most 0.04% by weight. 10. The method of producing sintered products, characterized in that it comprises: (a) mixing an iron-based powder with a lubricant powder as defined in the preceding claims, (b) preheating the metal powder composition, (c) pressing the metal powder composition in a preheated tool, and optionally (d) sintering the compacted metal powder composition in above 1050 ° C to form a sintered product.