JP3908167B2 - Iron powder composition containing amide type lubricant and method for preparing the same - 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

  The present invention relates to a metal powder composition. The present invention relates to an iron-based composition particularly suitable for molding at high temperatures.

  Powder metallurgy techniques generally use various standard temperature methods for forming metal powders to form metal parts. These are chill-pressing (press below ambient temperature), cold-pressing (cold-pressing, ambient temperature press), hot-pressing (metal powder can retain work hardening) Presses at temperatures above temperature) and warm presses (warm-pressing, presses at temperatures between cold presses and hot presses).

  A significant advantage arises from pressing at temperatures above ambient temperature. The tensile strength and work hardening rate of most metals decreases with increasing temperature, and improvements in density and strength can be achieved with lower forming pressures. However, when the temperature of the hot press rises extremely, it causes a problem in processing and promotes die wear. Therefore, current efforts are directed towards the development of metal compositions suitable for the warm pressing method.

  US Pat. No. 4,955,789 (Musella) generally describes warm forming. According to this patent, generally, lubricants used for normal temperature molding such as zinc stearate can also be used for warm molding. However, in practice, it has been found that the zinc stearate or ethylene stearamide (commercially available as ACRAWAX (registered trademark)), which is currently most commonly used for cold forming and warm forming, cannot be used. ing. The problem that arises is due to the difficulty of filling the die perfectly.

  US Pat. Nos. 5,744,433 (Storstrom et al.) And 5,154,881 (Rutz) disclose metal powder compositions containing amide lubricants specially developed for warm forming.

  The lubricant described in US Pat. No. 5,744,433 contains an amide type oligomer having a weight average molecular weight Mw of at most 30,000. If the lubricant has a molecular weight of 4000 or higher, very high density and green strength can be obtained, with the preferred lubricant having a molecular weight of about 6500. However, it has been found that this lubricant tends to adhere to the die wall and requires frequent cleaning of the die. Another disadvantage is that the resulting green body is soiled.

  In US Pat. No. 5,154,881, amide lubricants consist of reaction products of monocarboxylic acids, dicarboxylic acids and diamines. The only lubricant considered in accordance with this patent is not described in detail, but the resulting reaction product is ADVAWAX® in a composition comprising ia ethylene bisstearamide according to Chemis-CIVS. 450. Our experience with this product is that it is difficult to obtain a consistent composition and quality, which can result in molded articles with varying quality. This can cause problems when the lubricant is used in large scale industrial production.

(Object of invention)
The object of the present invention is to reduce or eliminate the current problems associated with large scale production.

  A second objective is to provide a new type of lubricant useful for metal compositions intended for forming at high temperatures.

  A third object is to provide a metal powder for producing a molded article free from dirt.

  A fourth object is to provide a metal composition including a lubricant that does not adhere to the die wall during molding of the metal powder.

(Summary of the Invention)
These objectives are achieved by using a powder composition comprising iron-based powder and a novel oligomeric amide type lubricant. The composition can include one or more additives such as binders, flow agents, processing aids and hard phases.

  Warm forming can be performed by mixing iron-based powders with an oligomeric amide type lubricant, and optionally a binder, preheating the powder composition, and forming the metal powder composition in a preheated tool.

(Detailed description of the invention)
The novel amide type lubricant used in accordance with the present invention can be represented by the following chemical formula:
DC _ma -BABC _mb -D
in this case,
D is -H, COR, CNHR, where R is a linear or branched aliphatic or aromatic group containing 2 to 21 carbon atoms,
C is a —NH (CH ₂ ) _n CO— group,
B is amino or carbonyl,
A is alkylene having 4 to 16 carbon atoms, optionally containing up to 4 oxygen atoms,
ma is an integer from 1 to 10,
mb is an integer from 1 to 10,
n is an integer of 5 to 11.

D is COR, where R is an aliphatic group of 16-20 carbon atoms, C is —NH (CH ₂ ) _n CO—, where n is 5 or 11; B is amino; A is an alkylene having 6 to 14 carbon atoms, optionally containing up to 3 oxygen atoms, and ma and mb are preferably integers of 2 to 5, which may be the same or different.

である。 Examples of preferred lubricants for use in the iron-based composition described in the present invention are:

It is.

分子量1240.10を有する

分子量8738.04を有する

分子量1580.53を有する

分子量1980.86を有する

分子量2429.69を有する

および分子量2283.73を有する

である。 Another example is
Having a molecular weight of 370.49

Having a molecular weight of 1240.10

Having a molecular weight of 8738.04

Having a molecular weight of 1585.53

Having a molecular weight of 1980.86

Having a molecular weight of 2429.69

And has a molecular weight of 2283.73

It is.

The chemical difference between the new lubricant and the lubricant described in US Pat. No. 5,744,433 is that the new molecule has the same end groups at both ends as the central diamine or diacid component. The chemical difference between the new lubricant and the lubricant described in US Pat. No. 5,154,881 is that the new lubricant molecule contains —NH (CH) _n CO— units. In contrast to the lubricants known from US Pat. No. 5,154,881, no EBS is formed when preparing the lubricants described in this invention. EBS is a molecule having the chemical formula CH ₃ (CH ₂ ) ₁₆ CO—HN (CH ₂ ) ₂ NH—OC (CH ₂ ) ₁₆ CH ₃ ) and having no lactam units in contrast to the lubricants described in the present invention. It is.

  With regard to the molecular weight of the new lubricant, preferred lubricants have been found to have a molecular weight of 1000 to 5000, most preferably 1500 to 3000.

  Lubricant molecules can be prepared, for example, according to amide oligomer standard methods as described in Principles of Polymerization Volume 3 by George Odian (John Wiley & Sons, Inc.). According to the present invention, the lubricant preferably comprises at least 80% of an amide having the above chemical formula. Therefore, other types of lubricants can be added up to 20% by weight, as long as the advantageous properties of the new lubricant are not adversely affected.

  This lubricant added to the iron-based powder is preferably in the form of a solid powder, based on the total amount of the metal powder composition, up to 0.1 to 1% by weight, preferably 0.2 to 0.8% by weight of the metal powder composition. Can consist of%. The fact that the lubricants described in the present invention can be used in small amounts is a particularly advantageous feature of the present invention because high density can be achieved.

As used in the detailed description of the invention and the appended claims, the expression “iron-based powder” refers to a powder consisting essentially of pure iron; strength, curability, electromagnetic properties of the final product. Or iron powders prealloyed with other materials that improve other desirable properties; and iron particles (diffusion annealed mixture or fully mechanical mixture) mixed with the alloying elemental component particles described above. Examples of alloying elements are copper, molybdenum, chromium, manganese, phosphorus, graphitic carbon, tungsten, which are used individually or in the form of compounds (Fe ₃ P and FeMo). When the lubricant described in the present invention is used in combination with an iron-based powder having high formability, an unexpectedly good result is obtained. In general, the powder has 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.

  Apart from iron-based powders and lubricants, the new powder composition can contain one or more additives such as binders, flow agents, process aids, hard phases.

  The binder can be added according to the method described in US Pat. No. 5,368,630 (inserted here for reference) and can be a cellulose ester resin, a hydroxyalkyl cellulose resin having 1 to 4 carbon atoms in the alkyl group, or It can be an organic compound such as a thermoplastic phenolic resin.

  One type of flow agent that can be used in accordance with the present invention is disclosed in US Pat. No. 5,782,954, which is hereby incorporated by reference. The flow agent is preferably silicon dioxide and is about 0.005 to about 2% by weight, preferably about 0.01 to about 1% by weight, more preferably about 0.025 to about 0.5% by weight, based on the total amount of the metallurgical composition. Use in quantity. Further, the flow agent should have an average particle size of less than about 40 nm. Preferred silicon oxides are both hydrophilic and hydrophobic silicon dioxide materials and are commercially available from Degussa Corporation as Aerosil-based silicon dioxides such as Aerosil 200 and R812 products.

  The processing aids used in the metal powder composition can consist of talc, forsterite, manganese sulfide, sulfur, molybdenum disulfide, boron nitride, tellurium, selenium, barium difluoride and calcium difluoride, which are Use individually or in combination.

Hard phases used in metal powder compositions are tungsten, vanadium, titanium, niobium, chromium, molybdenum, tantalum and zirconium carbides, aluminum, titanium, vanadium, molybdenum and chromium nitrides, Al ₂ O ₃ and various Can be made of ceramic material.

  The invention is explained in more detail in the following examples, which are merely interpreted as examples and do not limit the scope of protection.

  The following table shows a comparison of properties between molded articles prepared from powder mixtures containing the lubricants described in this invention and the amide type lubricants disclosed in US Pat. No. 5,744,433.

Table 1

温度 粉末／ダイ：120℃／120℃
*米国特許5,744,433に記載の好ましい潤滑剤 Table 2

Temperature Powder / Die: 120 ℃ / 120 ℃
* Preferred lubricant as described in US Patent 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 described in the present invention. The flow enhancer Aerosil® 200 was added in an amount of 0.06% by weight.

  As described above, the amide type lubricant, which is a novel oligomer described in the present invention, is excellent not only in terms of jetting power, jetting energy, and return, but also in the appearance of a molded product. Furthermore, the lubricant does not adhere to the die wall.

  The following table shows a comparison of the properties of molded articles prepared from powder mixtures containing the lubricants described in the present invention and the amide type lubricants disclosed in US Pat. No. 5,154,881.

  As described above, the lubricant according to the present invention is excellent in terms of injection force, injection energy, and return.

成形圧 700 MPa
温度 粉末／ダイ 130℃／150℃ Table 3

Molding pressure 700 MPa
Temperature Powder / Die 130 ℃ / 150 ℃

  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 described in the present invention. The flow enhancer Aerosil was added in an amount of 0.06% by weight.

  The following examples show a comparison of the density of green bodies used in accordance with the present invention and obtained with oligomeric amide lubricants having 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 described in the present invention. The flow enhancer Aerosil was added in an amount of 0.06% by weight.

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

Lubricant molecular weight GD (g / cm ³ )
2000 7.44
3000 7.41
4000 7.31

  If the molecular weight of the oligomeric amide lubricant is less than (about) 2000, the properties of the powder composition will deteriorate the flow and the lubricant will tend to adhere to the die wall and the surface of the injection molded article. The adhesion of the surface increases the risk of forming a rough surface on the final molded product because the powder may collect in the injection molded product.

Claims (10)

A powder composition for warm molding comprising iron-based powder and lubricant powder, wherein the lubricant consists essentially of an amide represented by the following chemical formula:
DC _ma -BABC _mb -D
in this case,
D is -H, COR, CNHR, where R is a linear or branched aliphatic or aromatic group containing 2 to 21 carbon atoms,
C is, -NH (CH _{2) n} CO- group,
B is amino or carbonyl,
A is alkylene having 4 to 16 carbon atoms, optionally containing up to 4 oxygen atoms,
ma is an integer from 1 to 10,
mb is an integer from 1 to 10,
n is a powder composition which is an integer of 5 to 11. D is COR, where R is an aliphatic group of 16-20 carbon atoms, C is —NH (CH ₂ ) _n CO—, where n is 5 or 11; B is amino; A is an alkylene having 6 to 14 carbon atoms, optionally containing up to 3 oxygen atoms; ma and mb are each an integer of 2 to 5, where ma and mb are the same The powder composition according to claim 1, which can be different or different. The powder composition according to claim 1 or 2, wherein the lubricant comprises a compound selected from the group consisting of the following substances.

  The powder composition according to any one of claims 1 to 3, wherein the amide has a molecular weight of 1500 to 3000 and is present in the composition in an amount of less than 1% by weight.   The powder composition according to any one of claims 1 to 4, wherein the lubricant powder is provided at a concentration of 0.2 to 0.8% by weight of the composition.   The powder composition according to any one of claims 1 to 5, further comprising one or more additives selected from the group consisting of a binder, a process aid and a hard phase.   The powder composition according to any one of claims 1 to 6, wherein the iron-based powder is moldable, and at least 80% by weight of the lubricant powder comprises the amide oligomer.   The powder composition according to any one of claims 1 to 6, wherein the composition is essentially free of ethylene bisstearamide.   The powder composition according to any one of claims 1 to 8, wherein the iron-based powder has a carbon content of at most 0.04% by weight. In the production method of sintered products:
(a) mixing an iron-based powder with a lubricant powder as defined in any of the preceding claims;
(b) pre-heating the metal-powder composition;
(c) shaping the metal-powder composition in a preheated tool; and, optionally,
(d) sintering the molded metal-powder molding at a temperature higher than 1050 ° C. to form a sintered product;
Manufacturing method.