EP1470261B1 - Sinterable metal powder mixture for the production of sintered components - Google Patents

Abstract

The present invention relates to sinterable powder compositions, sintered components produced therefrom, and methods for prepared such components. Sinterable powder compositions are composed of an aluminum-based powder, and a first metal powder comprising molybdenum and/or tungsten. The aluminum based powder is composed of aluminum and magnesium, silicon, copper, zinc, titanium, tin, manganese, nickel, or combinations thereof. In another embodiment, the sinterable powder composition includes a second metal powder comprising copper, tin, zinc, lithium, magnesium, or combination thereof. The sinterable powder compositions may be used for the production of sintered components, including composite components, having not only sufficient strength values but also with high hardness.

Description

The invention relates to a sinterable powder mixture for Production of sintered components, in particular for the automotive industry, based on an Al powder, and produced therefrom sintered components and a method of manufacture such components.

Aluminum is one due to its special properties preferred material, especially in the space industry and automotive industry. Made of aluminum or aluminum Materials produced components are compared with conventional, for example made of cast iron components, much easier. By reducing the weight are an increase for example in automobiles the efficiency and a reduction in fuel consumption and to achieve an improvement in exhaust emissions.

In the wake of the desirable weight reduction of automobiles There is an increasing demand for applications for aluminum in the automotive sector. For example, in engine and transmission construction become the previous steel or cast piece replaced by pieces made of aluminum or by use made of aluminum. As with a combination of steel or castings with such aluminum problems due to the different physical behavior of the Materials occur, it is desirable as many as possible "classical" components of steel or cast by such under Use of aluminum made to replace. Because of this be problems due to differences in the used Materials in terms of thermal expansion coefficients, the thermal conductivity, the elastic Properties etc. avoided. By using each other matched components, which using Aluminum are made, especially higher Achieved efficiencies.

In particular, many engine, clutch and transmission components powder metallurgically produced, there is a large Interested in making powder blends and processes to provide, by means of which aluminum components can be produced by powder metallurgy. Disadvantageous the powder metallurgical production of components under Use of aluminum is in particular that aluminum and its alloys tend to be in contact with air extremely stable metal oxide to occupy. This will in particular the specific surface increases. By relying on located the aluminum-containing material used Oxide skins becomes the diffusion necessary for sintering Particles of the powder material used hindered. Farther have components made from aluminous materials compared to those made of steel or cast iron reduced strength values, in particular a low hardness, on. In addition, they impede on the aluminum-containing Starting material oxide skins in the usual pressing the cold welding of the particles with each other.

There is therefore a need for sinterable powder mixtures, which are well processed by powder metallurgy, and from which components with good strength values and high Hardness powder metallurgy are produced. Furthermore exists a need for powder metallurgical processing methods such aluminum-containing sinterable powder mixtures.

The object of the present invention is therefore a powder mixture and components produced therefrom and corresponding To provide methods which are the aforementioned Do not have disadvantages.

This object is achieved by a sinterable Powder mixture for the production of sintered components, especially for the automotive industry, comprising 60 to 98.5 Gew%, based on the total amount of the powder mixture, preferred 75 to 92% by weight, of an Al base powder of metals and / or their alloys, including Al and optionally containing at least one of the following metals :, 0,2 to 30 wt% Mg, 0.2 to 40 wt% Si, 0.2 to 15 wt% Cu, 0.2 to 15 wt% Zn, 0.2 to 15 wt% Ti, 0.2 to 10 wt% Sn, 0.2 up to 5% by weight of Mn, 0.2 to 10% by weight of Ni and / or less than 1% by weight As, Sb, Co. Be, Pb and / or B, wherein the weight percentages each based on the total amount of Al-base powder; and 0.8 to 40% by weight, based on the total amount of Powder mixture, preferably 8 to 15% by weight, of a metal powder, selected from a first group of metals and / or their Alloys consisting of Mo and / or W, and optionally one second group of metals and / or their alloys consisting of Cu, Sn, Zn, Li and / or Mg.

By adding the first group of metals and / or their Alloys consisting of Mo and / or W, can with this Powder mixture manufactured powder metallurgical components be, which have a very high hardness. The values for the hardness is selected for components made with a powder from the first group of metals and / or their alloys, are compared to those without adding this first group of metals and / or their alloys by 5 increased to 35%, preferably 10 to 25%. By adding the first group of metals and / or their alloys to one Al base powder is in particular the by the pressing process, in particular the re-compaction, caused cold welding the particles improved with each other. hereby Eventually, the diffusion of the individual particles will also occur during the single sintering process, thereby improving Components with higher strength values and higher hardness to be obtained.

Advantageously, the sinterable powder mixture further comprises the aforementioned second group of metals and / or their alloys, consisting of Cu, Sn, Zn, Li and / or Mg. The addition the aforementioned second group of metals and / or their Alloys probably causes, especially during the pressing process, in particular during the densification, with the Al base powder an alloy and / or intermetallic Phase is formed. As a result, the training of Oxide skins on the surface of the used.

Al base powder obstructed. In addition, at least partially during the actual sintering process the second group of metals and / or their alloys in one at least partially liquid state at the sintering temperature over, causing the connection in particular of the first group of metals and / or their alloys to the aluminum base powder improved becomes.

Preferably, the ratio of the amount of the first group of metals and / or their alloys to that of second group in the powder mixture in a range of 1: 8 to 15: 1 parts by weight. Preferably, the ratio in a range of 2: 1 to 6: 1 parts by weight. In such Mixing ratios will provide maximum connectivity Metals and / or alloys of the first group to the Al-base powder achieved. This can be done with the powder mixture Components are obtained with high hardness.

In a further advantageous embodiment of the invention For example, the Al base powder contains 0.2 to 15% by weight of Mg, 0.2 to 16 wt% Si, 0.2 to 10 wt% Cu and / or 0.2 to 15 wt% Zn, based in each case on the total amount of Al-based powder on. Furthermore, preferably, the second group of metals and / or their alloys Cu, Zn and / or Sn.

Preferably, the sinterable powder mixture comprises lubricant in an amount of 0.2 to 5 wt%, based on the total amount of the powder mixture. On the one hand, lubricants may be self-lubricating agents such as MoS ₂ , WS ₂ , BN, MnS, graphite and / or other carbon modifications such as coke, polarized graphite or the like. Preferably, 1 to 3% by weight of lubricant is added to the sinterable powder mixture. By using the aforementioned lubricants, self-lubricating properties can be imparted to the components made from the sinterable powder mixture.

The sinterable powder mixture can further binders and / or lubricants. These are preferably selected from a group comprising polyvinyl acetates, waxes, in particular amide waxes such as ethylenebisstearoylamide, shellac, Polyalkylene oxides and / or polyglycols. polyalkylene and / or glycols are preferably used as polymers and / or Copolymers with average molecular weights in a range from 100 to 500,000 g / mol, preferably from 1,000 to 3,500 g / mol, more preferably 3,000 to 6,500 g / mol. used. The means are preferably in an amount in a range of about 0.01 to 12% by weight, preferably in a range of 0.5 to 5 % By weight, more preferably 0.6 to 1.8% by weight, in each case on the total amount of the powder mixture used. The bandage- and / or lubricants also facilitate the removal of the components produced from the sinterable powder mixture from the mold.

The powder mixture can be made by mixing the individual ingredients with usual equipment such as tumble mixers both in the heat (warm mixing) as well as at room temperature (cold mixing) are prepared, with the warmth preferred is.

Furthermore, the present invention relates to a sintered component, produced according to the inventive method. Such sintered components according to the invention have strength values and hardnesses which are significantly higher than those which have been produced by conventional methods. The sintered components according to the invention preferably have a tensile strength of at least 140 N / mm ² , measured in accordance with DIN EN 10002-1. More preferably, the tensile strength is more than 200 N / mm ² , more preferably more than 300 N / mm ² . Advantageously, the sintered components of the invention has an elastic modulus of at least 70 kN / mm ^2, measured according to DIN EN 10002-1, on which more preferably groE ß e r 80 kN / mm ^2.

In a further preferred embodiment, the inventive sintered components have a hardness (HB 2.5 / 62.5 kg) of at least 100, measured in accordance with DIN EN 24498-1, on. The Hardness is more preferably greater than 110, more preferably greater than 125.

In a further advantageous embodiment, the sintered Component designed as a gear, impeller, in particular Ölpumpenrad, and / or connecting rod and / or rotor set.

Under sintered components in the context of the present invention are understood components that completely from a sinterable material were produced, on the other hand This also understood composite parts, wherein the main body such a composite part, for example, from a aluminum-containing powder mixture can be prepared and the body further connected to the main body of one further material, such as iron or cast steel, sintered or solid, or solid cast aluminum. Conversely, can the composite part, for example, only on the front pages or its surface a sintered layer of one aluminum-containing powder mixture, whereas the main body of, for example, steel or cast iron, sintered or massive, is. The sintered components can thereby calibrated and / or cured in the heat.

• in einem ersten Schritt die Pulvermischung in eine erste Form eingegeben wird;
• in einem zweiten Schritt die Pulvermischung zu einem Grünling gepreßt wird;
• in einem dritten Schritt der Grünling zumindest teilweise nachverdichtet wird; und
• in einem vierten Schritt der nachverdichtete Grünling gesintert wird.

Finally, the present invention relates to a method for producing sintered components, including composite parts, from a powder mixture according to the invention, wherein

• in a first step, the powder mixture is input to a first mold;
• in a second step, the powder mixture is pressed into a green compact;
• in a third step, the green compact is at least partially recompressed; and
• in a fourth step, the densified green compact is sintered.

The process according to the invention has the great advantage that by the already achieved in the third step high density Before the actual sintering components can be produced, which on the one hand excellent strength values, on the other hand also have very high densities and hardnesses. Especially can by the according to the inventive method followed by densification of the sintering step subsequent usual post-processing steps such as calibration and / or curing by aging in the Heat can be shortened considerably, or if necessary the usual afterburning or the calibration omitted become. This shortening of the whole process becomes one Productivity increase and thus an economic advantage reached.

By re-densifying in the third step of the method according to the invention is advantageously achieved that the present on the surface of the material used oxide layers are mechanically broken, whereby a better cold welding during the pressing process between the individual material particles is achieved. Furthermore, this also improves the diffusion during the actual sintering process of the individual material particles. As a result, components with increased strength values and in particular higher hardness can be obtained.
The pressing process carried out in the second and third step of the process according to the invention can be carried out both at elevated temperature, in particular with the addition of the abovementioned agents, in particular polyethylene glycols (hot pressing), but also at room temperature (cold pressing), as well as via vibration compression. Vibratory compression is understood here to mean a process in which, during the pressing process, at least at times an oscillation superimposes the pressing process, wherein the vibration can be introduced, for example, via at least one pressing ram. A combination of the aforementioned pressing method is possible. Al-based sinterable powder mixtures may also contain high melting components such as platinum or the like. The powder used and its particle size are dependent on the respective application. Furthermore, the sinterable material may be wholly or partly made of short fibers or fibers, preferably fibers with diameters between about 0.1 and 250 microns and a length of a few microns to millimeters in size, up to 50 mm such as metal fiber fleece.

If it is desired to produce composite parts which, for example, should have a sintered layer of the sinterable material on the front face of a body made of steel or cast iron, then in the first step of the process according to the invention, the sinterable material is applied to the base body by conventional methods However, it can also be provided, for example, to spray the material in powder form (Wet Powder Spraying: WPS). For this it is necessary to produce a suspension of the sinterable material. The suspension required for this purpose preferably comprises solvents, binders, stabilizers and / or dispersants. Particularly preferred solvents are selected from a group comprising water, methanol, ethanol, isopropanol, terpenes, C ₂ -C ₅ -alkenes, toluene, trichlorethylene, diethyl ether and / or C ₁ -C ₆ -aldehydes and / or ketones. Preference is given to solvents which are vaporizable at temperatures below 100 ° C. The amount of the solvents used is in a range of about 40 to 70% by weight, based on the sinterable powder mixture used, preferably in a range of about 50 to 65% by weight.

The third-stage post-compaction (which can also be called intermediate compression) can by the pressing of a greenware usual and well-known procedures be made. For example, in the second Step pressed green body again into a usual matrix form introduced and in this at least partially by appropriate Preßstempel be compacted. Preferably the Nachverdichtwerkzeuge completely or partially conical so that at certain predetermined places of the green compact particularly high densities can be achieved can.

In a preferred embodiment of the method according to the invention, the green compact is dewaxed in a further step before the third step. The dewaxing is preferably carried out under nitrogen, hydrogen, air and / or mixtures of said gases, in particular with targeted air supply. Furthermore, the dewaxing can be done with endogas and / or exogas, but also in vacuum. The dewaxing can preferably be effected by superimposed microwaves and / or ultrasound, or else only by microwaves for temperature control. Finally, the dewaxing can also be carried out via solvents such as alcohol or the like or supercritical carbon dioxide with or without the action of temperature, microwaves or ultrasound or a combination of the abovementioned methods.
Advantageously, with the method according to the invention with the densification carried out in the third step, a density is achieved which is about 2 to about 40% higher than that before the recompression, preferably 5 to 30%, more preferably 15 to 25%.

Preferably, in the second step of the process according to the invention, green compacts having an initial density in a range of 2.1 to 2.5 g / cm ³ , preferably 2.2 to 2.4 g / cm ³ , more preferably 2.25 to 2.38 g / cm ³ , measured according to DIN ISO 2738, pressed.

In a further embodiment of the method according to the invention is advantageously a form in which the optionally dewaxed green compact is introduced before introduction of the green compact sprayed with a lubricant. It The dewaxed green compact can also be soaked in lubricant become. Furthermore, it is particularly advantageous that the sintering process in the fourth step under nitrogen with a dew point less than -40 ° C, preferably less than -50 ° C, is performed. In this case, the sintering is preferably carried out under pure nitrogen. Furthermore, the sintering at a corresponding density and / or composition of the green body also under air, hydrogen, Mixtures of nitrogen and hydrogen with or without targeted air supply, endogas, exogas or in a vacuum be performed, wherein the sintering by superimposed microwaves or via microwaves for temperature control can be done.

The sintering step may preferably be followed by an optional one necessary heat treatment, in particular a homogenization annealing, be connected. In this case, the heat treatment depending on the chemical composition of the obtained component. Alternatively or In addition to the heat treatment, the sintered component also starting from the sintering or homogenizing annealing temperature preferably in water or via a gas-fired cooling be deterred.

Before or after sintering, an additional surface compaction, more generally: an introduction of residual compressive stresses in surface areas, by sand or shot peening, rolling or the like is possible. Likewise, a calibration can be carried out before or after the homogenization annealing. Here, the calibration is carried out at room temperature or elevated temperature up to the forging temperature, even using pressures up to 900 N / mm ² . Optionally, the calibration can be made even above the solidus line, in which case the component can also be removed directly from the sintering heat.

The calibration and / or forging tools used for calibration can be completely or partially conical be, whereby on certain areas of the components particularly high densities can be achieved. The temperature of the Calibration and / or forging tools can depend on of the component to be processed differ and, where appropriate be kept in the isothermal range. A surface compaction or introduction of compressive residual stresses in the surface is also before or after a heat treatment or calibration possible.

Finally, coatings on the sintered component are applied. Preference is given here Method by which the components hardcoat and / or anodizing, such as thermal spraying like plasma spraying, flame spraying or physical and / or chemical processes such as PVD, CVD or the like. However Coatings also purely chemical way such as by means of anti-friction varnishes, which may contain Teflon, or Nanocomposite materials are applied. Through a coating can the surface of the components in terms of Hardness, roughness and coefficient of friction exactly on the Purpose to be modified modified.

These and other advantages of the present invention will be illustrated by the following examples.

Example 1:

An Al base powder of composition Al4Cu1Mg0.5Si (corresponds the designation AC2014 of a conventional aluminum alloy, wherein the base powder 4 wt% Cu, 1 wt% Mg, 0.5 Wt% Si and 94.5 wt% Al, based on the total amount of powder, ) of the company ECKA granules GmbH & Co. KG, Velden, Germany, with the company name ECKA Alumix 123 (92.5% by weight Al), with 1.5% by weight of an amide wax as binder the company Hoechst with the name micro wax C was with molybdenum or tungsten powder according to the table below 1 mixed. The mixture was carried out in a tumble mixer by adding the molybdenum or tungsten powder to the submitted Al-base powder at room temperature for 5 min.

The Al base powder had a particle size distribution between 45 and 200 μm, the average particle diameter D _{50 being} 75 to 95 μm. The admixed molybdenum or tungsten powder was obtained from HC Starck GmbH & Co. KG, Goslar, Germany, and had an average particle diameter D ₅₀ of 25 μm with a particle size distribution in a range of about 5 to 50 μm.

Subsequently, the powder mixture was placed in a mold and pressed under a pressure of about 175 N / mm ² (calculated for a wheel face of 20 cm ² ) for about 0.2-0.5 sec at room temperature to a green compact in the form of a pump wheel. The density of the green compacts was about 2.35 to 2.38 g / cm ³ . Subsequently, the green compact thus produced was dewaxed for about 30 minutes at about 430 ° C and then at a sintering temperature of 610 ° C under a pure nitrogen atmosphere with a dew point of -50 ° C in a belt furnace, which at a speed of 3.4 m / h, sintered for 30 min. In this case, the green bodies were on Al ₂ O ₃ plates. Subsequently, homogenizing annealing was carried out for 1.5 hours at a temperature of 515 ° C. Subsequently, the sintered impeller was shock-cooled by quenching with water at a temperature of about 40 ° C for 10 sec.

Subsequently, a calibration was performed to a theoretical density of 97 to 98% using a pressure of about 810 N / mm ² at 200 ° C.

After calibration, a curing of the sintered pump wheels was then carried out in the heat at 160 ° C for 16 h. Subsequently, the tensile strength R _m , the modulus of elasticity and the elongation according to DIN EN 10002-1 were determined on standardized samples. Furthermore, the hardness was determined according to DIN EN 24498-1 (Brinell hardness) with a hardened steel ball as indentor with a diameter of 2.5 and with a load of 62.5 kg. The values determined are shown in Table 1 below. material R _m * Modulus A ** hardness N / mm ² kN / mm ² % HB ⊘ 2.5 / 62.5 kg Al4Cu1Mg0.5Si + 8 wt% Mo 205 87 0.01 122 Al4Cu1Mg0.5Si + 14 wt% Mo 152 104 0.01 148 Al4Cu1Mg0.5Si + 8 wt% W 144 74 0.01 105 Al4Cu1Mg0.5Si + 14 wt% W 135 74 0.01 102 R _m * = tensile strength A ** = stretch

Example 2

The experiments mentioned in point 1 above were repeated except that a copper powder marketed by Eckart Granules under the trademark Ecka Kupfer CH-S was additionally mixed in. The admixture was carried out such that first the molybdenum or tungsten powder was mixed with the copper powder in a tumble mixer at room temperature for 5 min and this was then admixed in a tumble mixer to the Al-base powder for 5 min. The copper powder had a mean particle diameter D ₅₀ of 25 microns and a particle size distribution in a range of about 5 to about 50 microns. The copper powder was produced electrolytically, the individual particles were present in dendritic form.

Different mixtures were produced, whereby these were sintered to pump wheels with and without recompression as described under section 1. For the densification after pressing the green compact was dewaxed under a nitrogen atmosphere for 30 min at about 430 ° C and then sprayed in a form identical to the first mold form, which is sprayed with the lubricant GLEITMO 300, Fuchs Lubritech GmbH, Weilerbach, Germany was densified at a pressure of 760 N / mm ² for about 0.2 - 0.5 sec at room temperature such that the density of the densified green compact at about 2.8 - 2.9 g / cm ³ and thus by about 19 - Was 23% higher than that of the non-densified impeller green body and thus at about 95% of the theoretical density.

Subsequently, the produced green compacts were sintered as described above, calibrated to a theoretical density of 97-98% at a pressure of 810 N / mm ² , but at room temperature, and cured. The mixing ratio of molybdenum or tungsten powder to the copper powder was 5: 1 parts by weight. Table 2 shows the mixing ratios as well as the determined physical values. No. material recompression R _m * Modulus of elasticity A ** hardness Yes No N / mm ² kN / mm ² % HB ⊘ 2.5 / 62.5kg 2a Al4Cu1Mg0.5Si + 8 wt% (80 wt% Mo + 20 wt% Cu) x 226 88 0.03 138 2a ' Al4Cu1Mg0.5Si + 8 wt% (80 wt% Mo + 20 wt% Cu) x 253 89 0.01 146 2 B Al4Cu1Mg0.5Si + 10 wt% (80 wt% Mo + 20 wt% Cu) x 206 93 0.01 142 2 B' Al4Cu1Mg0.5Si + 10 wt% (80 wt% Mo + 20 wt% Cu) x 227 96 0.03 150 2c Al4Cu1Mg0.5Si + 12 wt% (80 wt% Mo + 20 wt% Cu) x 187 96 0.01 159 2c ' Al4Cu1Mg0.5Si + 12 wt% (80 wt% Mo + 20 wt% Cu) x 193 100 0.01 164 2d Al4Cu1Mg0.5Si + 14% by weight (80% by weight Mo + 20% by weight Cu) x 178 101 0.01 159 2d ' Al4Cu1Mg0.5Si + 14% by weight (80% by weight Mo + 20% by weight Cu) x 191 107 0.01 179 2e Al4Cu1Mg0.5Si + 8 wt% (80 wt% W + 20 wt% Cu) x 155 75 0.03 110 2e ' Al4Cu1Mg0.5Si + 8 wt% (80 wt% W + 20 wt% Cu) x 237 79 0.04 122 2f Al4Cu1Mg0.5Si + 10 wt% (80 wt% W + 20 wt% Cu) x 173 74 0.05 107 2f ' Al4Cu1Mg0.5Si + 10 wt% (80 wt% W + 20 wt% Cu) x 243 81 0.03 121 2g Al4Cu1Mg0.5Si + 12 wt% (80 wt% W + 20 wt% Cu) x 147 73 0.05 107 2g ' Al4Cu1Mg0.5Si + 12 wt% (80 wt% W + 20 wt% Cu) x 233 86 0.04 121 2h Al4Cu1Mg0.5Si + 14 wt% (80 wt% W + 20 wt% Cu) x 146 76 0.05 107 2h ' Al4Cu1Mg0.5Si + 14 wt% (80 wt% W + 20 wt% Cu) x 213 84 0.03 130 R _m * = tensile strength A ** = stretch

As can be seen from Table 2, are by a Post-compaction positively influences the physical properties. In particular, a further increase in hardness the produced pump wheels are achieved.

With the present invention, it is possible to sinter Produce components based on an Al powder, which not only excellent strength values, but in particular have a high hardness. This allows Such components advantageously on heavily used Jobs, especially in the engine or transmission used become. In addition, due to the possible omission of the calibration and curing by aging in the heat sintered components are produced cheaper and faster.

Claims (14)

1. Sinterable powder mixture for producing sintered components, in particular for automobile manufacture, comprising 60 to 98.5 wt.%, related to the total amount of the powder mixture, of an Al-based powder of metals and/or the alloys thereof, comprising Al and optionally with contents of at least one of the following metals: 0.2 to 30 wt.% Mg, 0.2 to 40 wt.% Si, 0.2 to 15 wt.% Cu, 0.2 to 15 wt.% Zn, 0.2 to 15 wt.% Ti, 0.2 to 10 wt.% Sn, 0.5 to 5 wt.% Mn, 0.2 to 10 wt.% Ni and/or less than 1 wt.% of As, Sb, Co, Be, Pb and/or B, wherein the weight percents are in each case related to the total amount of Al-based powder; and 0.8 to 40 wt.%, related to the total amount of the powder mixture, of a metal powder selected from a first group of metals and/or the alloys thereof, consisting of Mo and/or W, as well as optionally a second group of metals and/or the alloys thereof, consisting of Cu, Sn, Zn, Li and/or Mg.
2. Sinterable powder mixture according to Claim 1, characterised in that the ratio of the amount of the first group of metals and/or the alloys thereof to that of the second group in the powder mixture is in a range from 1:8 to 15:1 parts by weight.
3. Sinterable powder mixture according to any one of the preceding Claims, characterised in that, in addition to Al, the Al-based powder comprises 0.2 to 15 wt.% Mg, 0.2 to 16 wt.% Si, 0.2 to 10 wt.% Cu and/or 0.2 to 15 wt.% Zn, in each case related to the total amount of the Al-based powder.
4. Sinterable powder mixture according to any one of the preceding Claims, characterised in that the second group of metals and/or the alloys therefore comprises Cu, Zn and/or Sn.
5. Sinterable powder mixture according to any one of the preceding Claims, characterised in that this comprises lubricant in an amount of 0.2 to 5 wt.%, related to the total amount of the powder mixture.
6. Sintered component, produced from a sinterable powder according to any one of Claims 1 to 5.
7. Sintered component according to Claim 6, characterised in that it has a tensile strength of at least 140 N/mm², measured according to DIN EN 10002-1.
8. Sintered component according to Claim 6 or 7, characterised in that it has a modulus of elasticity of at least 70 kN/mm², measured according to DIN EN 10002-1.
9. Sintered component according to any one of Claims 6 to 8, characterised in that it has a hardness (HB 2.5/62.5 kg) of at least 100, measured according to DIN EN 24498-1.
10. Method for producing sintered components, also composite parts, from a powder mixture according to any one of Claims 1 to 5, wherein

    in a first step the powder mixture is fed into a first die;

    in a second step the powder mixture is pressed into a green compact;

    in a third step the green compact is at least partly repressed; and

    in a fourth step the repressed green compact is sintered.
11. Method according to Claim 10, characterised in that the green compact is dewaxed prior to the third step.
12. Method according to either of Claims 10 and 11, characterised in that the density which is obtained with the repressing carried out in the third step is approximately 2 to 40% above that prior to repressing.
13. Method according to any one of Claims 10 to 12, characterised in that in the third step, prior to introducing the green compact into a second die, this is sprayed with a lubricant.
14. Method according to any one of Claims 10 to 13, characterised in that the sintering process in the fifth step is carried out under nitrogen with a dew point below - 40° C.