JP2004524450A - Iron powder composition containing amide type lubricant and method for producing the same - Google Patents

Abstract

The invention concerns a method of preparing an iron-based powder comprising the steps of mixing and heating an iron-based powder, at least one oligomer amide type lubricant, at least one fatty acid and optionally one or more additives to a temperature above the melting point of the lubricant and subsequently cooling the obtained mixture. The invention also comprises the mixture of the iron-based powder, the oligomer amide type lubricant and the fatty acid.

Description

【Technical field】
[0001]
The present invention relates to metal powder compositions and methods for making such compositions. In particular, the present invention relates to iron-based compositions having a constant apparent density and flowability at different temperatures.
[Background Art]
[0002]
In powder metallurgy techniques, metal powders are typically compression molded using different standard temperature ranges to form metal parts. These include chill-pressing (pressing at lower than ambient temperature), cold pressing (pressing at ambient temperature), hot pressing (metal powder can maintain work hardenability) Press at a temperature higher than the temperature), and warm press (press at a temperature between the cold press and the hot press).
[0003]
Pressing at a temperature higher than ambient temperature offers distinct advantages. The tensile strength and work hardening rate of most metals decrease with increasing temperature, resulting in improved density and strength at lower molding pressures. However, extremely high temperatures of the hot press cause processing problems and accelerated wear of the mold. Therefore, efforts are currently being made to develop metal compositions suitable for warm pressing.
[0004]
U.S. Pat. No. 4,955,789 (Musella) generally describes warm compaction. According to this patent, lubricants commonly used in cold compaction, such as zinc stearate, can likewise be used in warm compaction. However, in practice, the most frequently used lubricants in cold forming today, zinc stearate or ethylene bisstearamide (commercially available as ACRAWAX®) are warm It has proved impossible to use for molding. The problems that arise are due to the difficulty in filling the mold in a satisfactory manner.
[0005]
U.S. Pat. Nos. 5,744,433 (Storstrom et al.) And 5,154,881 (Rutz) contain amide lubricants specifically developed for warm forming. A metal powder composition is described. U.S. Pat. No. 5,744,433 describes lubricants for metallurgical powder compositions containing amide type oligomers having a weight average molecular weight Mw of at most 30,000. In U.S. Pat. No. 5,154,881, amide lubricants consist of the reaction product of a monocarboxylic acid, a dicarboxylic acid, and a diamine. Particularly preferred as a lubricant is ADVAWAX® 450, an ethylene bisstearamide product.
[0006]
The lubricants described in these two patents were developed especially for warm forming compression and often work well, but these lubricants are used in metal compositions intended for large-scale production of sintered parts. It has been found that various problems occur when used in products.
DISCLOSURE OF THE INVENTION
[Problems to be solved by the invention]
[0007]
One object of the present invention is to reduce or eliminate current problems associated with large-scale production.
[0008]
Another object is to provide a new class of lubricants useful for metal compositions intended for molding compression at elevated temperatures.
[0009]
Yet another object is to provide an iron-based powder composition that is distinguished by excellent flow rates and apparent densities.
[0010]
Yet another object is to provide a powder composition that generates minimal dust and does not require the use of organic solvents in the preparation.
[0011]
Yet another object is to provide a method for warm forming such metal powder compositions.
[Means for Solving the Problems]
[0012]
These objectives include the use of iron-based powders, at least one oligomeric amide-type lubricant, at least one fatty acid, and optionally one such as a flow agent, a processing agent, and a hard phase. This is achieved by a powder composition comprising more than one type of additive.
[0013]
The method according to the invention comprises:
-Mixing the iron-based powder, the lubricant, the fatty acid, and the additives, if any, and heating to a temperature above the melting point of said lubricant;
Cooling the resulting mixture,
Process.
[0014]
DETAILED DESCRIPTION OF THE INVENTION As used herein and in the claims, the expression "iron-based powder" refers to pure iron; strength, curability, electromagnetic, or Iron powder prealloyed with another substance which improves other desired properties of the final product; and iron particles (diffusion-annealed mixture or purely mechanical mixture) mixed with particles of such alloying elements; From powders consisting essentially of Examples of alloying elements are nickel, copper, molybdenum, chromium, manganese, phosphorus, carbon in the form of graphite, and tungsten, which can be used separately or in combination, for example in the form of compounds (Fe ₃ P and FeMo). Used as Unexpectedly good results are obtained when the lubricant according to the invention is used in combination with an iron-based powder having a high compressibility. Generally, such powders 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 Hoeganaes AB, Sweden.
[0015]
The lubricant used according to the invention is new and can be represented by the following formula:
DC _ma -BABC _mb -D
Wherein D is -H, COR, CNHR, where R is a linear or branched aliphatic or aromatic group having 2 to 21 C atoms;
C is -NH _(CH) n CO- group,
B is amino or carbyl;
A is alkylene having 4 to 16 C atoms and optionally containing up to 4 O atoms;
ma is an integer of 1 to 10,
mb is an integer of 1 to 10,
n is an integer of 5 to 11.
[0016]
Lubricants, D is COR (wherein, R represents an aliphatic group which has 16 to 20 C atoms) and, C is -NH _(CH) n CO- (where, n is 5 Or 11), B is amino, A is alkylene having 6 to 14 C atoms and optionally up to 3 O atoms, and ma and mb are the same or different , 2 to 5 are preferred.
[0017]
Examples of such lubricants can be selected from the group consisting of:
_{CH 3 (CH 2) 16 CO-} [HN (CH 2) 11 CO] 2 -HN (CH 2) 12 NH- [OC (CH 2) 11 NH] 2 -OC (CH 2) 16 CH 3
_{CH 3 (CH 2) 16 CO-} [HN (CH 2) 11 CO] 2 -HN (CH 2) 12 NH- [OC (CH 2) 11 NH] 3 -OC (CH 2) 16 CH 3
_{CH 3 (CH 2) 16 CO-} [HN (CH 2) 11 CO] 3 -HN (CH 2) 12 NH- [OC (CH 2) 11 NH] 3 -OC (CH 2) 16 CH 3
_{CH 3 (CH 2) 16 CO-} [HN (CH 2) 11 CO] 3 -HN (CH 2) 12 NH- [OC (CH 2) 11 NH] 4 -OC (CH 2) 16 CH 3
_{CH 3 (CH 2) 16 CO-} [HN (CH 2) 11 CO] 4 -HN (CH 2) 12 NH- [OC (CH 2) 11 NH] 4 -OC (CH 2) 16 CH 3
_{CH 3 (CH 2) 16 CO-} [HN (CH 2) 11 CO] 4 -HN (CH 2) 12 NH- [OC (CH 2) 11 NH] 5 -OC (CH 2) 16 CH 3
_{CH 3 (CH 2) 16 CO-} [HN (CH 2) 11 CO] 5 -HN (CH 2) 12 NH- [OC (CH 2) 11 NH] 5 -OC (CH 2) 16 CH 3
[0018]
Other examples are as follows:
Having a MW of _{370.49, CH 3) CO-HN} (CH 2) 5 CO-HN (CH 2) 2 NH-OC (CH 2) 5 NH-OC (CH 3),
Having a MW of _{1240.10, CH 3 (CH 2)} 20 CO-HN (CH 2) 11 CO-HN (CH 2) 12 NH-OC (CH 2) 11 NH-OC (CH 2) 20 CH 3,
Having a MW of _{8738.04, 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 ,
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 with a MW of 1580.53 ₂ ) ₄ CH ₃ ,
CH ₃ (CH ₂ ) ₄ CO- [HN (CH ₂ ) ₅ CO] ₇ -HN (CH ₂ ) ₆ NH- [OC (CH ₂ ) ₅ NH] ₇ -OC (CH with a MW of 198.86 ₂ ) ₄ CH ₃ ,
Having a MW of _{2429.69, CH 3 (CH 2)} 20 CO- [HN (CH 2) 5 CO] 7 -HN (CH 2) 6 NH- [OC (CH 2) 5 NH] 7 -OC (CH ₂ ) CH ₃ (CH ₂ ) ₁₆ NH— [OC (CH ₂ ) ₁₁ NH] ₄ —CO (CH ₂ ) ₁₀ CO— [HN (CH ₂ ) _{11 with 20} CH ₃ and a MW of 2283.73. _{CO] 4 -HN (CH 2)} 16 CH 3
[0019]
The oligomer amide-type lubricant added to the iron-based powder is preferably in the form of a solid powder, 0.1 to 1% of the metal powder composition, preferably 0.1 to 1% based on the total weight of the metal powder composition. 0.2 to 0.8%. The fact that the lubricant according to the invention can be used in small amounts is a particularly advantageous feature of the invention. Because it allows to achieve large densities.
[0020]
The fatty acids used according to the invention are preferably fatty acids having 10 to 22 C atoms. Examples of such acids are oleic, stearic, and palmitic acids. Although the amount of fatty acids is small, the effect on flow rate and apparent density is significant. The amount of fatty acid, calculated on the total weight of the powder composition, is usually 0.005 to 0.15, preferably 0.010 to 0.08, most preferably 0.015 to 0.07%. A fatty acid content of less than 0.005 makes it difficult to achieve a uniform distribution of the fatty acids. If its content is greater than 0.15, there is a considerable risk of poor flow.
[0021]
The melting point of the fatty acid should be lower than the melting point of the amide oligomer lubricant.
[0022]
Apart from the iron-based powder and the lubricant, the novel powder composition may contain one or more additives selected from the group consisting of processing aids and hard phases.
[0023]
Processing aids used in the metal powder composition may consist of talc, forsterite, manganese sulfide, sulfur, molybdenum disulfide, boron nitride, tellurium, selenium, barium difluoride, and calcium difluoride, They are used alone or in combination.
[0024]
Hard phases used in the metal powder composition include tungsten, vanadium, titanium, niobium, chromium, molybdenum, tantalum, and zirconium carbides, aluminum, titanium, vanadium, molybdenum and chromium nitrides, Al ₂ O ₃ , and It may be made of various ceramic materials.
[0025]
Examples of flow agents that can be used in accordance with the present invention are described in U.S. Patent No. 5,782,954, which is incorporated herein by reference. The glidant is preferably silicon dioxide, but from about 0.005 to about 2% by weight, preferably from about 0.01 to about 1% by weight, more preferably about 0. 1% by weight, based on the total weight of the metallurgical composition. 025 to about 0.5% by weight. Further, the flow agent should have an average particle size of less than about 40 nm. Preferred silicon oxides are both hydrophilic and hydrophobic types of silicon dioxide materials, commercially available from Degussa Corporation as Aerosil lines of silicon dioxide, such as Aerosil 200 and R812 products. I have.
[0026]
According to an embodiment of the present invention, the iron-based powder, at least one oligomeric amide-type lubricant, at least one fatty acid, and optionally one or more additives, such as processing aids and hard phases, are added to the melting point of the lubricant. Heating to a higher temperature, cooling the resulting mixture below the melting point of the lubricant and above the fatty acid, adding a powder flow agent to the resulting mixture, which is then mixed; Cooling.
[0027]
The powder mixture tested consisted of Distaloy AE (an iron-based powder available from Feganes AB, Sweden), 0.6% by weight of an organic material consisting of an oligomer amide type lubricant as defined above and 0.03 or 0.05 stearic acid. % By weight and dry blended. 0.3% by weight of graphite was also added and the resulting mixture was heated to 165 ° C. The mixture was cooled to 110 ° C. and 0.06% by weight of aerosil was added at this temperature. Essentially the same results were obtained when aerosil was added at ambient temperature.
[0028]
The results shown respectively in FIGS. 1 and 2 demonstrate that a clear and unexpected effect on both the apparent density and the flowability can be obtained with the powder composition according to the invention.
[0029]
The above mixture containing 0.03% by weight of stearic acid was also tested for dust reduction compared to the mixture made according to US Pat. No. 5,368,630. The known mixture also contained 0.6% by weight of organic material, where the organic material consisted of 0.55% by weight of a lubricant and 0.15% by weight of an organic binder (cellulose butyrate). Had become. In both mixtures, the iron-based powder was Distaloy AE. Preparation of the known mixture involves dry blending the iron-based powder, the lubricant according to the aforementioned U.S. patent, and 0.3% by weight of graphite. The organic binder was dissolved in acetone and added to the dry mixture, after thorough mixing, the acetone was removed and 0.06% by weight aerosil was added to the dry mixture.
[0030]
The following table summarizes the results from the study.
[0031]
Sample dust formation (mg / m ³ min.g [mixture])
Mixtures 41 according to the invention
Mixture 70 according to U.S. Patent No. 5,368,630
[Brief description of the drawings]
[0032]
FIG. 1 is a graph showing the effect of the combination of an oligomer amide type lubricant as defined above and a fatty acid (stearic acid) on the apparent density.
FIG. 2 is a graph showing the effect of a combination of a lubricant as defined above and a fatty acid (stearic acid) on flow rate.

Claims (12)

A powder composition comprising an iron-based powder, at least one oligomeric amide type lubricant, a fatty acid, and optionally one or more additives. The composition of claim 1, wherein the melting point of the fatty acid is lower than the melting point of the amide lubricant. 3. The composition according to claim 1, wherein the fatty acid has 10 to 22 C atoms. 4. The composition of claim 3, wherein the fatty acid is selected from the group consisting of oleic acid, stearic acid, palmitic acid, or a combination thereof. The oligomer amide type lubricant has the following formula:
_{D-C ma -B-A-} B-C mb -D
Wherein D is -H, COR, CNHR (where R is a linear or branched aliphatic or aromatic group having 2 to 21 C atoms),
C is a —NH (CH) _n CO— group,
B is amino or carbyl;
A is alkylene having 4 to 16 C atoms and optionally containing up to 4 O atoms;
m is an integer of 1 to 10,
n is an integer of 5 to 11. ]
The composition according to claim 1, represented by: The lubricant may be such that D is COR (where R is an aliphatic group having 16 to 20 C atoms) and C is -NH (CH) _n CO- (where n is 5 Or 11), B is amino, A is alkylene having 6 to 14 C atoms and optionally up to 3 O atoms, and ma and mb are the same or different The composition according to claim 5, wherein the composition has a chemical structure when it is an integer from 2 to 5. Claims wherein the amount of fatty acid is 0.015 to 0.15, preferably 0.02 to 0.08, most preferably 0.03 to 0.07%, calculated based on the total weight of the powder composition. Item 5. The composition according to any one of Items 3 to 4. The composition according to any one of claims 1 to 7, comprising one or more additives selected from the group consisting of a binder, a flow agent, a processing aid, and a hard phase. Based on the total weight of the metallurgical composition, the flow agent comprises from about 0.005 to about 2%, preferably from about 0.01 to about 1%, more preferably from about 0.025 to about 0.5% by weight. 9. A composition according to any one of the preceding claims, wherein the composition is used in an amount of less than about 40 [mu] m. The composition of claim 9, wherein the glidant is silicon dioxide. a) mixing an iron-based powder, at least one oligomer amide type lubricant, at least one fatty acid, and optionally one or more additives and heating to a temperature above the melting point of said lubricant;
b) cooling the resulting mixture;
A method for producing an iron-based powder in which a step is performed. 11. The method according to claim 10, wherein the mixture obtained in step a) is cooled to a temperature below the melting point of the lubricant, but above the melting point of the fatty acid, and adding a powder flow agent to the mixture.

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