MXPA05004255A

MXPA05004255A - Iron-based powder composition including a silane lubricant.

Info

Publication number: MXPA05004255A
Application number: MXPA05004255A
Authority: MX
Inventors: Per Knutsson
Original assignee: Ganaes Ab H
Priority date: 2002-10-22
Filing date: 2003-10-22
Publication date: 2005-07-05
Also published as: RU2005115465A; CN100528416C; SE0203133D0; TWI311507B; CN1705534A; BR0314361A; WO2004037467A1; PL375099A1; EP1554070B1; CA2497383C; ES2348522T3; PL207923B1; CA2497383A1; AU2003269785B2; JP4668620B2; ATE473823T1; AU2003269785A1; BR0314361B1; EP1554070A1; ZA200501301B

Abstract

The invention concerns a powder composition including an iron or iron based powder and a lubricating amount of an alkylalkoxy or polyetheralkoxy silane, wherein the alkyl or polyether group has between 8 and 30 carbon atoms and the alkoxi group includes 1-3 carbon atoms.

Description

IRON-BASED POWDER COMPOSITION THAT INCLUDES A SILANUM LUBRICANT FIELD OF THE INVENTION The present invention relates to new metallic powder compositions useful in the powder metallurgy industry. The invention also relates to a method for the preparation of high density metal components when using these compositions. There are several advantages to using powder metallurgy methods to produce structural parts compared to conventional full density steel fitting procedures. In this way, the energy consumption is much lower and the use of the material is much higher. Another important factor in favor of the powder metallurgy route is that the components with the net shape or an almost net shape can be produced directly after the sintering process without very expensive forming procedures, such as rotation, grinding, drilling or grinding. However, normally a total density steel material has superior mechanical properties compared to the components of the PM. This is mainly due to the occurrence of porosity in the PM components. Therefore, the effort has been to increase the density of the PM components in order to achieve values as close as possible to the density value of a total density steel. Among the methods used for the purpose of achieving a higher density of the PM components, the powder forging process has the advantage that the total density components can be obtained. This procedure, however, is expensive and is mainly used for mass production of heavier components, such as connecting rods. Total density materials can also be obtained by high pressures at high temperatures; such as hot isostatic pressing, HIP, but also this method is expensive. When using hot compaction, a process where the compaction is carried out at a temperature at an elevated temperature, usually 120 to 250 ° C, the density can be increased by about 0.2 g / cm3, which results in a considerable improvement in the mechanical properties. However, one disadvantage is that the hot compaction method involves additional investment and processing. Other methods, such as double pressing, double sintering, sintering at elevated temperatures, etc., can also increase the density. Also these methods will add production costs thus reducing the total cost effectiveness. In order to expand the market for the powder metallurgy components and to use the advantages of the powder metallurgy technique, there is a need, therefore, for a simple and less expensive method to achieve high density tablets with improved mechanical properties.

BRIEF DESCRIPTION OF THE INVENTION Unexpectedly it has now been found that high density components can be obtained by using high compaction pressures in combination with a new type of powder compositions. Distinctive features of these compositions are that they have less than about 5% iron particles of the iron powder or iron based with a size below 45 μ? and that the compositions include an amount of lubrication of an alkylalkoxy or polyetheralkyloxy silane. The present invention also includes method for the preparation of the untreated tablets and optionally the sintering thereof from these compositions. This method comprises the steps of providing the composition, optionally mixing said composition with graphite and other additives such as alloying elements, workability improving agents, etc., non-axially compacting the composition in a high pressure die and the ejection of the untreated body, which can be sintered later. Another aspect of the invention relates to compositions with this type of silanes in combination with iron or iron-based powders regardless of particle size, ie, in combination with conventionally used powders. Also in this case very high densities can be obtained.

DETAILED DESCRIPTION OF THE INVENTION The term "high density" refers to tablets having a density of at least 7.3 g / cm3. "High density" is not an absolute value. A density that can be achieved typical according to the state of the art for single pressed, individual sintered components is about 7.1 g / cm3. When using a hot compaction, an increase of 0.2 g / cm3 can be achieved. In this context, the term "high density" is intended to include tablets having a density of about 7.35-7.65 g / cm3 and more, depending on the type and amount of additives used, and the type of iron-based powder used. Components that have lower densities may, of course, also occur but are thought to be of less interest. The iron-based powder according to the present invention includes pure iron powder, such as iron powder atomized with water or gas, sponge iron powder, reduced iron powder; steel powder in partial alloy with diffusion; and steel powder completely in alloy. Diffused partial alloy steel powder is preferably a partial alloy steel powder with one or more of Cu, Ni, Mo. The total alloy steel powder is preferably a powder of alloy steel with Mn, Cu, Ni , Cr, Mo, V, Co, W, Nb, Ti, Al, P, S and B. Also the stainless steel powders are of interest. With respect to the shape of the particle it is preferred that the particles have an irregular shape as obtained by the atomization of water. Sponge iron powders also have irregular shaped particles and may also be of interest. A feature of the invention is that the used powder has coarse particles, ie the powder essentially does not have fine particles. The term "essentially without fine particles" refers to that less than about 5% of the iron or iron-based powder particles have a size less than 45 μ? as measured by the method described in SS-EN 24 497. Until now most of the results of interest have been achieved with powders consisting essentially of particles with a size above 106 μ? t? and particularly above 212 μ ??. The term "consisting essentially" means that at least 40%, preferably at least 60% of the particles have a particle size above 106 and 212 μ? T ?, respectively. So far the best results have been obtained with powders that have an average particle size above 212 μp? and only less than 5% below 212 μp ?. The maximum particle size can be about 2 mm. The particle size distribution for the iron-based powders used in the manufacture of PM is normally distributed with a Gaussian distribution with an average particle diameter in the region of 30 to 100, um and about 10-30%, lower at 45 μ ?? Iron-based powders essentially free of fine particles can be obtained by removing the finer fractions from the powder or by manufacturing a powder having the desired particle size distribution. The influence of the particle size distribution and the influence of the particle shape on the compaction properties and properties of the compact body have undergone intensive studies. In this way, the patent of E.U.A. No. 5,594,186 discloses a method for producing PM components with a density greater than 95% theoretical density by using substantially linear, non-circular metal particles having a triangular cross-section. Powders having coarse particles are also used for the manufacture of soft magnetic components such as those described, for example, in U.S. Patents. Nos. 6,309,748 and 4,190,441. A critical feature according to the invention and for the purpose of obtaining high density products is the type and amount of lubricant. Therefore, it has been found that a specific type of lubricants that previously have not been used together with the metal powders provide very promising results. These lubricants belong to the group of alkylalkoxy or polyether silanes and more specifically alkylalkoxy or polyether silanes wherein at least one substituent on the Si atom is an alkyl group having at least 3 carbon atoms, wherein the alkyl group may be interrupted by one or more O atoms. Compounds wherein the alkyl group includes one or more oxygen atoms used according to the present invention are called polyether-syntans. The chain length of the alkyl or polyether group is an important characteristic of the silanes used according to the present invention and has an influence on the lubricating properties of the silane. Hitherto it has been found that the results of greatest interest are obtained with alkyl or polyether chains having between 8 and 30, preferably between 10 and 24 carbon atoms. Preferably the syllabus is selected from the group consisting of octyl tri-methoxy silane, hexadecyl tri-methoxy silane and polyethylene ether-trimethoxy silane with 10 ethylene ether groups. In this context it can be mentioned that the patents of E.U.A. 5766304, 5989304, 6139600, 6235076 and 6451082 describe that very small amounts, ie 0.05% by weight or less of the total composition can be compacted, of organoalkoxysilanes that can be used as surface treatment agents for iron powder or based on in iron in combination with lubricating agents. In the first four patents of E.U.A. the following silane compounds are analyzed: α-methacryloxypropyl trimethoxy silane, y-glycidoxypropyl trimethoxy silane, N-beta (aminoethyl) -y-trimethoxy silane, methyl trimethoxy silane, phenyl trimethoxy silane, and diphenylethymethoxy silane . In the patent of E.U.A. 6451082 the compounds triphenylmethoxysilane, diphenyldimethoxysilane, phenyltrimethoxysilane, isobutyltrimethoxysilane, and methyltriethoxysilane have been used. The type of lubricating organosilanes used according to the present invention in this manner is neither mentioned nor analyzed. The organosilane with lubricating effect according to the present invention is preferably used in such a way that it is dissolved or dispersed in a suitable solvent, for example, an organic solvent, such as acetone or ethanol. The solution or dispersion obtained subsequently is added to the iron-based powder during mixing and optionally heating. The solvent is finally optionally evaporated in vacuo. According to a preferred embodiment of the invention and contrary to the common practice in powder metallurgy, when conventional PM lubricants are used in the iron powder mixture, or when a lubricant is used in combination with a binder and / or surface treatments, such as those described in the E: UA patents referred to above, iron or iron-based or iron-based powder should not be mixed with a separate (conventional) lubricant before it is transferred to the die. Nor is it necessary to use an external lubrication (lubrication of the die stop) when the walls of the same are provided with a lubricant before the compaction is carried out. However, the invention does not exclude the possibility of, when it is of interest, using conventional internal lubrication (in an amount of up to 0.5% by weight), external lubrication or a combination of both.

For some applications it may be necessary to add smaller amounts of graphite to the powder mixture that will be compacted. In this way, the graphite in amounts of between 0.1-1.0, preferably 0.2-1.0 and more preferably 0.3-0.8% by weight of the total mixture to be compacted should be added before compaction. Other additives may also be added to the iron-based powder prior to compaction such as the alloying elements comprising Mn, Cu, Ni, Cr, Mo, V, Co, W, Nb, Ti, Ai, P, S and B which are compounds that increase workability, hard phase material and flow agents. The term "high compaction pressure" refers to pressures of about 800 MPa. More interesting results are obtained with higher pressures, such as above 900, preferably above 1000, more preferably above 100 MPa. Conventional compaction at high pressures, ie pressures above 800 MPa with conventionally used powders include finer particles, are generally considered unsuitable due to the high forces required to eject the tablets from the die, the high inherent wear of the die and the fact of that the surfaces of the components tend to be less bright or deteriorate. By using the powders according to the present invention unexpectedly it has been found that the ejection force is reduced at high pressures, around 1000 MPa, and that components having acceptable or even perfect surfaces can be obtained. The compaction can be carried out with standard equipment, which means that the new method can be carried out without expensive investments. The compaction is carried out in a non-axial manner and preferably in a single stage at ambient or elevated temperature. Alternatively, the compaction can be carried out with the aid of a percussion machine (Hydropulsor model HIP 35-4) as described in patent publication WO 02/38315. The sintering can be carried out at temperatures normally used within the PM field, for example, at low temperatures such as 1 100-1 140 ° C or at higher temperatures such as 1200-1300 ° C and in conventionally used or vacuum atmospheres . Other treatments of the untreated or sintered component can also be applied, such as machining, cover hardening, surface densification, steam treatment. In short, the advantages obtained by using the method according to the present invention are that the high density untreated tablets can be produced in an effective manner in relation to the cost. The new method also allows the production of more superior components that are difficult to produce when using the conventional technique. In addition to standard compaction equipment, it can be used to produce high-density tablets that have an acceptable or even perfect surface finish.

Examples of products, which can be manufactured adequately by the new method, high performance structural parts such as connecting rods, cam projections, gears and other structural components subjected to high loads. When using stainless steel powders the eyelashes are of special interest. As a main objective of the present invention is to achieve high density products where the silanes having lubrication effect have been particularly described together with coarse powders. However, it has been found that these silanes can be used in combination with powder that includes higher amounts of fine particles, i.e., the type of powders that are conventionally used in the P industry today. Example 4 below illustrates the effect of the silanes according to the present invention on both conventional and coarse powders. As noted, very high densities are also obtained with a conventional powder that includes higher amounts of fine particles. Compositions that include iron or iron-based powders with the normal particle size distributions and the silanes according to the present invention may be of special interest for certain applications and are also within the scope of the invention. The invention is also illustrated by the following examples.

EXAMPLE 1 The alloy is made of the iron-based powder composition prepared from AstaloyMo, which is pre-alloyed iron-based powder, with 1.5% by weight of molybdenum available from Hóganás, Sweden, and where the particles below 212 μ? they have been eliminated and mixed with 0.1 and 0.15% respectively, of trimethoxy silane of hexadecyl. The mixing procedure is carried out as follows: The hexadecyl trimethoxy silane is diluted in ethanol to a 20% solution, by weight, and the solution is stirred for 60 minutes. An amount of this solution corresponding to 0.1 and 0.15% by weight, respectively, is added during mixing to the iron-based powder mixtures, which have previously been heated to 75 ° C in the mixer. Intense mixing is carried out in the same mixer for three minutes after mixing at a lower speed for 30 minutes and during vacuum for the purpose of evaporating the solvent. The obtained mixture is sieved with a sieve of 500μ? T ?. Rings with an internal diameter of 35 mm have an external diameter of 14 mm and a height of 10 mm are compacted non-axially in a single stage at different compaction pressures. As can be seen from Figure 1A, the density of the untreated tablet of 7.67 g / cm 3 is obtained at a pressure of 1 00 Mpa for both compositions. The total energy needed for the ejection is somewhat lower for the tablets prepared from the composition with 0.15% silane than for the ejection of the tablets prepared from the powder which has been treated with 0.1% by weight of silane , see figure B.

EXAMPLE 2 The same powder and the same procedure as in Example 1 is used except that the powder is mixed with 0.2% by weight of hexadecyl trimethoxysilane. Two compositions are prepared one with 0.2% by weight of graphite and the other with 0.6% by weight of graphite. The density of the untreated tablet and the strength of the untreated tablet are measured. As can be seen from Figure 2B, a density of the untreated tablet above 7.65 g / cm 3 is obtained for an untreated component containing 0.2% graphite compacted at 1200 MPa. For an untreated component containing 0.6% graphite, an untreated tablet density of 7.58 g / cm 3 is obtained. Figure 2A shows that the strength of the untreated component increases with increasing compaction pressure and that the strength of the untreated component is high enough to allow handling of the untreated components.

EXAMPLE 3 This example shows the effect of removing different fractions of the iron-based powder. Four different iron-based powder compositions are analyzed. Three of the iron-based powder compositions contain Astaloy Mo which include 0.2% hexadecyl trimethoxysilane and the mixing procedure described in Example 1 is used. The first composition contains Astaloy Mo with particles thicker than 45 μ ??, the second composition contains Astaloy Mo with particles thicker than 106 μ? and the third composition contains Astaloy Mo with particles thicker than 212 μ. The fourth composition contains Astaloy Mo which has particles thicker than 212 m. The particles of this composition are mixed with 0.1% by weight of trimetoxysilane of hexadecyl. In addition, all compositions contain 0.2% graphite. All the compositions are compacted non-axially in a simple step in a die forming rings with an external diameter of 35 mm, internal diameter of 14 mm and a height of 10 mm. Figure 3A shows that the densities of the untreated tablet increase and the ejection forces decrease as the particle sizes increase. Figure 3B shows that the ejection forces decrease when the amount of silane is increased from 0.1 to 0.2% by weight.

EXAMPLE 4 This example demonstrates the effect of the chain length of the alkyl or polyether group, the particle size distribution and the added amount of silanes in the lubrication properties in the ejection after compaction with high pressures. Two types of powders are used, that is to say a powder based on 100 standard mesh iron, Astaloy 85 Mo with about 20% of the particles below 45 μ? (powder S) and a powder having the same chemical composition without fine particles and a weight average particle size of about 212 μ? t? (powder C). Five different types of silanes are used according to table A A Methyl tri-methoxy silane B Propyl tri-methoxy silane C Octyl tri-methoxy silane D Hexadecyl tri-methoxy silane E Polyethylene ether trimethoxy silane with 10 ethylene ether groups. Different contents of silane are added to the iron-based powder and the obtained mixtures are compacted at 1 100 MPa in a non-axial pressure movement in cylindrical pieces with a diameter of 25 mm and a height of 12 mm. During the ejection the dynamic ejection force is measured and after the ejection, the surface finish is evaluated and the density is measured as shown in table A.

Powder Powder 1 Powder Powder Powder Powder Powder Powder | Powder DC powder 'CCCSCSS Silane 0.03% 0.05% 0.1% 0.2% 0.2% 0.3% 0.3% 0.4% 0.4% 0.5% E Retention 62kN 39kN 39kN 65kN 33kN 68kN OK OK OK OK OK OK 7 67 7.66 7.67 7.61 7.66 7.63 g / cm3 g / cm3 ^ / cm3 g / cm3 g / cm3 g / cm3 j D 48kN 46kN 47kN 36kN 64kN 29klM OK OK OK OK OK OK 1 7.65 7.66 7.63 7.64 7.62 7.56 ¡! g / cm3 g / cm3 g / cm3 g / cm3 g / cm3 g / cm3 C i Retention 37kN 66kN 97kN OK OK OK 1 1 7.60, 7.60 7.53! g / cm3 g / cm3 q / cm3 B Retention n (Ok = fine / satisfactory surface finish Retention - dimensioned component surface with scratch marks As can be seen from Table A, a chain length of at least 8 atoms in the chain of aikiene is needed to successfully eject the component for an aggregate amount of silanes of 0.05-0.5%. The amounts added above 0.5% are thought to be of less interest because the density of the untreated component is negatively influenced. Table A also shows that when the silane content is less than 0.05% the ejection without damage of the component and the surface of the die is not possible for the silanes, with a chain length of 30 atoms. From Table A above it can be concluded that also the powder with a standard particle size distribution can be compacted at high densities of 7.60 g / cm3 and more, and the ejection can be carried out successfully, as long as the quantity of added silane is less than 0.5% and the length of the aikenylene or polyethylene ether chain is greater than 8 atoms.

Claims

NOVELTY OF THE INVENTION CLAIMS 1. - A powder composition that includes an iron or iron-based powder where less than about 5% of the powder particles have a size smaller than 45 μ? T? and an amount of lubrication of an alkylalkoxy or polyether-alkoxy silane, wherein the alkyl group of the alkylalkoxy silane and the polyether chain of the polyether-alkoxy silane include between 8 and 30 carbon atoms, and the alkoxy group includes 1 to 3 carbon atoms. 2 - The composition according to claim 1, further characterized in that the alkyl group and the polyether chain of the alkylalkoxy or polyether-alkoxy silane have between 10 and 24 carbon atoms. 3. The composition according to claim 1 or 2, further characterized in that the silane is selected from the group consisting of octyl tri-methoxy silane, hexadecyl tri-methoxy silane, polyethylene ether trimethoxy silane with ethylene ether groups. 4. The composition according to any of claims 1 -3, further characterized in that alkoxy silane is present in an amount of 0.05-0.5%, preferably between 0.1 -0.4% and more preferably between 0.15-0.3% by weight. 5. The composition according to any of claims 1-4, further characterized in that 40%, preferably at least 60% of the iron or iron-based powder consists of particles having a particle size above about 106 μ. ?? 6. - The composition according to any of claims 1-5, further characterized in that at least 40%, preferably at least 60% of the iron-based powder consists of particles having a particle size higher than about 212 μ? t). 7. The composition according to any of claims 1-6, further characterized in that it includes up to 1% by weight of graphite. 8. The composition according to any of the preceding claims, further characterized in that it includes alloying elements in an amount of up to 10% by weight. 9. - The composition according to claim 8, further characterized in that the alloying elements are selected from the group consisting of Mn, Cu, Ni, Cr, Mo, V, Co, W, Nb, Ti, Al, P, S and B. 10. A process for the preparation of high density untreated tablets comprising the following steps: providing an iron-based powder composition according to any of claims 1 to 9; optionally mix the composition with graphite and other additives; compacting the powder non-axially in a die at a compaction pressure of at least about 800 MPa; and carry out the ejection of the body without treating. 1. - A powder composition that includes an iron powder or an iron-based powder and an amount of lubrication of an alkylalkoxy or polyether-alkoxy silane, wherein the alkyl group of the alkylalkoxy silane and the polyether chain of the polyether-alkoxy silane include between 8 and 30 atoms of carbon and the alkyl group includes 1-3 carbon atoms. 12. The composition according to claim 1, further characterized in that the alkyl group or the polyether chain of the alkylalkoxy or polyether-alkoxy silane has between 10 and 24 carbon atoms. 13. The composition according to claim 1 or 12, further characterized in that the silane is selected from the group consisting of octyl-tri-methoxy silane, hexadecyl-tri-methoxy silane, polyethylene ether trimethoxy silane with ethylene ether groups. 14. The composition according to any of claims 1-13, further characterized in that alkoxy silane is present in an amount of 0.05-0.5%, preferably between 0.1 -0.4% and more preferably between 0.15-0.3% by weight. 15. - The composition according to any of claims 1 1-14, further characterized in that it includes up to 1% by weight of graphite. 16. The composition according to any of claims 1 1-15, further characterized in that it includes up to 10% by weight of alloying elements. 17. - The composition according to claim 16, further characterized in that the alloying elements are selected from the group consisting of Mn, Cu, Ni, Cr, Mo, V, Co, W, Nb, Ti, Al, P, S and B.