DE1533353B2 - Process for the production of a finely divided alloy powder from iron alloyed with copper - Google Patents

Description

50

The invention relates to a finely divided alloy powder made of iron alloyed with about 1 to 50% copper by reducing a mixture of a reducible iron compound and elemental copper or a reducible copper compound at elevated temperature, which is characterized in that an iron oxide is used as the reducible iron compound, the reduction in the absence of hydrogen chloride with copper contents up to 20% at the melting temperature of copper and above and with copper contents above 20% below the melting temperature of copper, preferably at 950 to 1050 ⁰ C, and the alloy powder for at least 30 minutes on one between a -; '- the transition temperature of the iron-rich phase of the alloy powder and a temperature about 150 degrees below this transition temperature.

The mixture of iron oxide and elemental copper or a reducible copper compound can, if desired, also smaller amounts of nickel, cobalt, molybdenum, tungsten or their reducible amounts Connections included.

It is known that alloying with copper improves the physical properties of iron can be. Since these two metals are practically insoluble in each other at room temperature and Even at elevated temperatures their mutual solubility is limited, one has to take various auxiliary measures seized to bring the metals mentioned in close connection with one another. So one has Copper and iron powder mixed and formed into objects using powder metallurgy. Also the so-called Infiltration techniques have been used; H. the pores of sintered iron or steel powder filled with copper.

These known processes for the production of copper-iron alloys present difficulties and disadvantages. For example, when storing and shipping mixtures of copper and Iron powder segregation will occur. Powder mixtures do not have those to guarantee optimal Properties required homogeneity. In addition, compacted powder mixtures are sintered from copper and iron to an expansion that leads to increased porosity and thus a low strength, which causes material defects and a high percentage of rejects.

Copper-iron sintered bodies of high tensile strength are obtainable according to US Pat. No. 2,754,194 by that one starts from a copper-iron powder, which is made by reducing a mixture Iron oxide and elemental copper or a copper oxide with hydrogen in the presence of hydrogen chloride was produced ". In this patent it is expressly emphasized that the desired Tensile strength of the sintered body is only achieved when the reduction in the presence of Hydrogen chloride carries out, but the tensile strength drops sharply if pure hydrogen is used for the reduction is used.

According to the US Pat. No. 2,754,193, a high tensile strength of the sintered body requires that the for the manufacture of the copper-iron powder used iron by reducing ferric chloride with hydrogen or made by reducing iron oxide with a mixture of hydrogen and hydrogen chloride became.

According to US Pat. No. 2,754,195, sintered bodies with high tensile strength are only obtained when you get the copper-iron powder by reducing a mixture of a ferric chloride and makes copper with hydrogen.

This is a prerequisite for the formation of sintered bodies with high tensile strength from copper-iron powders According to the prior art, the iron is always obtained by reducing iron oxide with a mixture from hydrogen and hydrogen chloride or by reducing ferric chloride.

Surprisingly, it has now been found that sintered bodies with high tensile strength that is even above the values of the known products, even if you get the reduction of iron oxide in the absence of hydrogen chloride, with copper contents of up to 20% the reduction at the melting temperature of copper and

above and with copper contents over 20% below the melting temperature of copper and that Alloy powder for at least 30 minutes at a temperature between the a-y transition temperature of the iron-rich Phase of the alloy powder and one about 150 degrees below this transition temperature Temperature.

The method according to the invention gives the alloy powders produced with it an extraordinary one Microstructure and ensures a close union of the copper with the iron, which is responsible for the the superior physical properties of this powder is responsible. After just pressing and sintering, the alloy powders of the present invention shrink into high density products high strength.

Copper sinters at about 825 to 850 ° C and melts To a close as possible to achieve concentration of the iron and copper in the pure state at about 1083 ⁰ C, having an iron content of 3.2% or more at about 1094 ⁰ C., the Alloy powder with a copper content of approximately 1 to 20% is produced in the process according to the invention at or above the copper melting temperature ^{, preferably at approximately 1120 to 1135 ° C.} Reduction temperatures of more than about 1150 ^° C. are undesirable since they lead to extensive agglomeration with the formation of a tough, hard mass which cannot be ground to metal powder in an economical manner. In the case of alloy powders with more than 20 percent by weight of copper, reduction temperatures of or above the melting temperature of the copper easily lead to an agglomeration of the reduced product, which is then extremely difficult to break into smaller pieces. When producing alloys with such a high copper content, the reduction temperature is therefore kept below the copper melting point, but still at least 100 ^° C. above the sintering temperature of the copper, ie preferably at a temperature of 950 to 1050 ^° C. If the reduction is below 1094 ⁰ C., but is carried out at a temperature which is at least 100 ^° C. above the sintering temperature of the copper, there is no liquefaction of the copper, but grain boundary diffusion of the reduced solids.

In the alloy powders produced according to the invention, the individual particles consist of iron with copper dispersions and thus differ from mere mixtures of copper and iron powder. This means that there is no segregation during storage or shipping.

Any iron oxides, such as hematite, magnetite, processed magnetite ores, Flue dust, synthetic oxides or reducible roll sintered from carbon steel or from low alloy steel.

As a source of copper, elemental copper, e.g. B. reduced copper powder, copper dust, electrolytic Copper powder or copper powder obtained by wet metallurgy can be used. Less expensive is, however, a precipitated or mechanically preserved copper oxide, such as copper (I) oxide, copper (II) oxide, Rolled copper or cement copper, a by-product of mine sewage, which is common contains about 50 to 98% cupric oxide. If copper oxides are used, it can be advantageous to add nitric acid to the feed to improve dispersion. As a source of copper but can also be copper (II) nitrate or another water-soluble copper salt in aqueous solution be used.

In addition to copper and iron, the charge can be nickel, cobalt, molybdenum or tungsten or reducible Compounds of these elements, such as nickel (II) sulfate, cobalt (III) oxide, molybdenum trioxide or WoI-framtrioxid contain. You will in general

ίο in smaller amounts to increase strength used, namely up to about 6 percent by weight when using one element and up to a total about 12 percent by weight when using multiple elements. To achieve optimal dispersion they can be in the form of soluble salts, such as nitrates or acetates, or as compounds in an acid or base as a solvent such as ammonia water or nitric acid can be used.

The reactants preferably have a particle size of less than 250 μm. To be favoured Iron oxides with a particle size of less than about 50 μm and copper compounds of less than about 20 μΐη.

It is often advantageous to provide the reactants with an aqueous dispersion of an organic adhesive to add to thereby losses due to dust or increase processes during handling and suppress processing as much as possible. Suitable binders include: Glue from animal Protein, methyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose and the like will decompose these materials rapidly at the reduction temperature and should result in a small amount of ash. In general adhesive quantities of around 0.5% of the total weight of the load are completely sufficient, the water content usually making up about 18% of the total charge.

When using an adhesive, the reactants can advantageously be mixed in a pan mill The constituents become hard spheres with a diameter of up to about 25.4 mm forms, whereby a second grinding step is not necessary or only to a small extent. These globules can be added to the reduction furnace without prior drying. If no adhesive is added, then the reactants are mixed thoroughly before they are placed in the oven. The reducing conditions in the furnace can be controlled by a gaseous reducing atmosphere, e.g. B. off Hydrogen or carbon monoxide or materials that create such an atmosphere as dissociated Ammonia, water gas, generator gas and the like can be created. Reducing conditions can but can also be caused by the fact that finely divided carbon is added to the reaction mixture. Iron black, petroleum coke, anthracite abrasion, soot, bone black, among others, are suitable for this or graphite. The minimum amounts of carbon depend on the respective reactants and their proportions and can be estimated from the stoichiometry of the reaction. the however, optimal amounts are best determined experimentally. Usually you use the Carbon in amounts of about 8 to 12%. Even if a gaseous reducing agent is used it is sometimes advantageous, especially when carrying out the reaction on a large scale, "a add a small amount of carbon so that a

effective reduction is guaranteed. As is known in the art of reduction, when carbon is used as the main reducing agent, carrier gases are advantageously passed through the furnace to remove the volatile reduction products and add a. To prevent reoxidation. Suitable carrier gases include nitrogen-rich gases endothermic, exothermic gas, methane, propane, natural gas and. Like. Optionally, gases and man-made, producer gas or hydrogen comparable _ϊ0 applies to.

The reduction is carried out until the reducible compounds are practically complete, i. E. are reduced to about 93 to 98%. During the reduction, the resulting product particles form usually a weakly sintered sponge which can easily be ground or ground into the final Can convert particle size. It has been found that a residual oxygen content of 2% or more of a particularly easily friable sponge, which can be broken up better than sponges with lower oxygen content. The time to complete the reduction to that degree depends on the reduction conditions and the respective reactants. Usually that is Reduction complete within about 30 minutes to 2 hours. A reduction time of more than about 2 hours is inexpedient as it can lead to difficulties in crushing the sponge.

The following is also important for the properties of the alloy powder produced according to the invention heat treatment carried out on the reduction. The heat treatment leads to a surprising Increasing the density and strength of the sintered alloy powder. She does one "Premature shrinkage", so that the degree of shrinkage in the actual sintering stage is reduced without undesired expansion occurring at the same time.

The ay-transition temperature of the iron is about 910 ⁰ C. In the case of iron with a copper content of more than 3.5% at about 835 to 850 ° C. It has now been found that the heat treatment of the alloy powder is most effective within a temperature range between the ay transition temperature of the iron-rich phase and a temperature 150 degrees below that. The best results are achieved when the heat treatment is carried out at a temperature that is less than 50 degrees below the ay transition temperature, preferably around 825 to 845 ° C. These temperature conditions lead to the highest density with minimal shrinkage after sintering, If the temperature in the heat treatment stage exceeds 845 to 850 ^° C., the properties of the sintered bodies are abruptly deteriorated.

For best results, the alloy powder should be allowed to cool for at least about 30 minutes be heat treated. The maximum period is critical and periods of time can be up to 10 hours be applied. However, heat treatment for more than 4 hours brings no benefit. Optimal results are generally achieved with a treatment period of about one to two hours.

When the oxygen content of the reduced alloy powder is more than 2%, the heat treatment is carried out most expediently carried out with reduction, so that the oxygen content

is reduced at this stage to below 2%, preferably below 1%. However, the oxygen content is already 2% or less, it can, if desired, be carried out in an inert atmosphere.

The powder is removed from the furnace as a loosely sintered mass. It cools down quickly and can close Particles are ground, a sieve with a mesh size between 0.175 and 0.246 mm happen.

The alloy powder thus obtained can be molded in a conventional manner. This is done by compacting using a pressure of about 1400 to 8400 kg / cm ² and subsequent sintering under non-oxidizing conditions at an elevated temperature, preferably at or above the melting temperature of the copper if the copper content of the alloy powder is low. If the copper content is high, sintering must be carried out below the copper melting point in order to prevent copper loss through "bubble formation" caused by agglomeration of the copper-enriched masses in the alloy powders. In the alloy according to the invention is carried powders f, in contrast to powders obtained by mixing copper and iron particles, during the sintering of the compacted particles no expansion. Expansion takes place at most in the reduction stage, while during sintering the already permeated or alloyed particles are further alloyed mainly at the boundary surfaces of the particles. The degree of shrinkage and the strength of the sintered masses depend heavily on the copper content. They are at a maximum with a copper content of around 30%. Sintered bodies with a copper content of about 1 to 6% have tensile strengths of over 31.5 kg / mm ² , while those with a copper content of 6 to 10% have tensile strengths of 42 kg / mm ² or more. Copper contents of 10 to 40% result in tensile strengths of 52.5 kg / mm ² or higher and copper contents of 40 to 50% tensile strengths above 45.5 kg / mm ² . Sintered parts made of mixtures of copper and iron powder have, however, tensile strengths of only 28 up to 31,5 kg / mm ^2, the pieces are not comparable r by a previous heat treatment of the powder mixtures. ν

They provide an insight into the microstructure of the alloy powders produced according to the invention X-ray spectra. An alloy powder with a copper content of 20% shows both after the reduction as well as after the reduction and heat treatment essentially the same diffraction spectrum, i.e. H. in both cases one enriched with α-iron Phase and a phase enriched with ε-copper. The diffraction spectrum of a 7% copper Alloy powder after reduction and heat treatment is essentially the same, has however, as expected, a smaller proportion of the copper-enriched phase. On the other hand, this shows Diffraction spectrum of an alloy powder with a copper content of 7%, which was recorded after reduction became a single phase enriched in α-iron. In the above diagrams are the iron maxima relatively flat, the copper maxima sharper.

The lack of a second phase in the latter case is surprising and makes it clear that alloy powder with a copper content below the solubility limit in iron in the reduction

7 8

temperature (about 8% at 1125 ° C) the copper after a very even dispersion of finely divided copper

the reduction contained in an extremely fine dispersion. rich particles.

This can be based on the cooling rate according to the Die F i g. 3 shows an alloy powder with a

Removal from the furnace based on the copper content of 20% after the reduction and the

Temperature in the first minute typically on 5 Fig. 4 the same powder after heat treatment,

about 490 ° C and thus the range of the maxi- both with about 3600x magnification. The on

paint changes in solubility rapidly. (The island-like areas protruding from these figures,

Solubility of copper in iron at 500 ° C is which cover most of the field of vision, being

only about 0.25%.) Apparently allows the standing of iron grains in the manner of a plateau,

closing 30minutige or longer Wärmebehand- _ϊ0 surrounded by copper-rich, removed by the acid

development within the specified temperature range »valleys«. It is noteworthy that the iron grains

the separation of a copper-enriched phase. after the reduction an irregular shape

A better insight into the microstructure of the wise, but after the heat treatment round or

Alloy particles from cuts obtained by being spherical.

microscopic examination made with a 3% 15 At higher magnification one discovers in the

Nitric acid solution in alcohol can be etched to reduce sample cracks with a length of approximately

to remove areas enriched with copper and there- 0.25 μΐη and a width of 0.085 μΐη, which after the

to make recognizable through the phases. Heat treatment are no longer available.

Alloy powder with a copper content of 1 to 10% are shown by Zeissche Gegen.According to this, they have a very uniform average dimensions and microstructure, with the copper up to an alloy content of about 8% in an alloy containing 20% copper the iron grains in the form of powder after the reduction at 1125 ⁰ C listed: ι particles with a diameter of less than

is about 0.1 μπ ^ ϊβρβ ^ ϊβΓί. Iron grains at 250x magnification

no clear grain boundaries are recognizable, so that a length of 17.50 μΐη

higher magnification with an electron micro-width 13.89 μΐη

scope is necessary. Thus, FIGS. 1 a Le distance between the grains 1.76 μΐη

alloy powder with 7% copper after reduction.

and FIG. 2 the same powder after the heat- copper particles in the iron grains

treatment, each in approximately 1,000,000 times the magnification- 30 length 0.0423 μΐη

tion. At the places that appear as depressions, width 0.0371 μm

the copper was removed by the corrosive acid, distance between the particles 0.0352 μm

so that the fineness of the dispersion easily. ,,., ...,

is recognizable. Upon further investigation of the fields, iron particles in the copper-rich areas

one can see that the sample after the Re 35 length 0.0268 μπι

Production of dispersed, copper-rich ribbon-shaped width 0.0216 μm

heaped particles with a diameter of approximately the distance between the particles 0.0894 μm
0.035 μm, the average distance between the copper particles being about 0.015 μm. On closer inspection, the iron grains show the amount. The distance between the clusters 40 F i g. 4 has a much coarser structure than that of FIG. 3. is 0.05 to about 0.75 μm. Between the to The F i g. 5 shows part of the field of view of FIG. 4 'clusters of copper-rich particles are discovered, their magnification is around 17,700 times. The prominent diameter also about 0.035 μm is a striking feature of this figure, but it can be assumed that there are also particles under the drawn "valley" or a copper-rich area between the resolution limit of 0.005 μm. ₄₅ see parts of two adjacent iron grains. Furthermore, cracks in the microstructure with a reproduced area of the iron grains have a length of about 0.1 to 0.3 μm and a width from the bottom of the removal of the copper-rich particles with 0.04 to 0.09 μm and angular cavities with an acid Cavities on. It can be seen that the diameters from 0.1 to 0.9 μΐη determine. After the copper particles inside the iron grain two heat treatment, the cracks are no longer visible, 50 different size ranges. belong: the primary and the clusters now appear as bands or mary particles have a diameter of about rings with a length of 10 μΐη ± 5 and a 0.1 to 0.5 μΐη, the secondary particles a diameter of 3 μηι ± 1. The copper particles in this knife below about 0.05 μπα.

Rings have a mean diameter of about This structure only occurs after heat treatment 0.04 μπι with a particle distance of about 0.015 μΐη. 55 on. Probably the bigger, primary ones The recognizable copper particles between the particles agglomerates of the original copper clusters have a mean diameter of particles in the reduced samples that represent due to about 0.0176 μΐη with a particle distance of about the different solubility of copper in 0.055 µπα. Iron at reduction temperature (about 8% at 1125 ° C) The microscopic examination of the invention and at the heat treatment temperature (approx according to the alloy powders produced with a 3.5% at 835 ° C). One can assume Copper content greater than 10 and up to 50 weight- that the primary copper particles are in excess Percent reveals that these alloy powders are unusually soluble at the heat treatment temperature borrowed fine, densely packed iron-rich granules to represent copper, which during these treatments whose larger or largest diameter 65 agglomerated treatment stage. You can continue to about 35 μπι take at a mean distance between that the smaller, secondary particles represent adjacent iron granules of less than about the copper that is used in the heat treatment-5 μπι is. These iron-rich granules contain a temperature of up to saturation dissolved in the iron

and then said goodbye while cooling to room temperature. The fact that this secondary particles correspond in size to the copper particles which after reduction in the iron grains exist, corroborates this hypothesis. Below are the average dimensions of an alloy powder containing 20% copper after heat treatment at 835 ° C:

Iron grains

Length 20.09 μΐη

Width 16.39 μm

Distance between the grains 1.66 μΐη

Primary copper particles in the iron grains

Length 0.2713 μΐη

Width 0.2404 μΐη

Distance between the particles 0.2865 μΐη Secondary copper particles in the iron grains

Length. ' 0.0331 µΐη

Width 0.0254 μm

Distance between the particles 0.0287 μm

Iron particles in the copper-rich areas

Length 0.1238 μm

Width. ■ 0.1122 μΐη

Distance between the particles 0.4720 μm

From the dispersion of a larger amount of copper in the iron grains of those produced according to the invention Alloy powder explains the high strength after sintering.

Even if the reduction below the melting point of the copper-rich phase, but at least 100 ⁰ C above the copper-sintering temperature is performed (e.g., as in a 40% copper-containing alloy powder at 950 ° C) yields the mikrokospische investigation that the iron- and copper-rich particles form a close bond with fusing at the grain boundaries. This applies to both the reduction and heat treatment processes.

There was also a microscopic examination after compaction and sintering of the invention made alloy powder. As a result, the sintered alloy particles were found to be similar to the unsintered particles. The sintering closes the particles by grain boundary diffusion only to a mass, what from a Comparison of the average iron grain sizes as well as the distances between the grains of a heat-treated powder and a sintered part made therefrom with a copper content of 20% shows:

Heat treated
Alloy powder ...

Sintered part

Length of the iron grains

20.09 22.09

Width of the iron grains

around

16.39 17.39

Distance between the iron grains

μΓΠ

1.66 1.68 The resistance to further grain growth during sintering appears to be structural stability the new alloy powder to reflect.

The excellent strength properties that can be achieved with the copper-iron alloy powders produced according to the invention can be increased by various procedures up to values of 105 kg / mm ² . So z. B. the addition of smaller amounts of graphite before molding and sintering increases the tensile strength. Usually, amounts of graphite of about 0.5 to 2% will suffice. Pressing and sintering again is also useful for increasing density and strength, as are various post-treatments such as quenching, drawing and normalizing.

The following examples explain the process according to the invention:

B e i s ρ ie I 1 alloy powder with a copper content of 7%

A. Reduction

Rolled iron 1247.1 g

Dried cement copper 77.0 g -

Hydroxyethyl cellulose 5.3 g

Water 285.0 g

The iron roll sinter is a by-product from a steel pre-rolling or post-rolling mill and is so fine that it passes a sieve with a mesh size of 0.044 mm, with about 50% ± 5% being coarser than 20 μm. This roll sinter has a bulk density of 1.8 to 2.2 g / cm ³ and the following analytical composition:

Fe 74.58%

(70.50% FeO)

O 24.58%

Mo <0.05%

Mn 0.308%

Ni 0.038%

C 0.006%

S 0.027%

P 0.100%

SiO ₂ 0.301%

Al ₂ O ₃ 0.010%

The cement copper of the above approach is a by-product of mine sewage. Its degree of fineness is below 20 μm, about 85% even below 10 μm. The cement copper has a bulk density of 0.8 to 1.5 g / cm ³ and the following analytical composition:

Cu 90.80%

(2.91% Cu, 96.72% Cu ₂ O, 2.61% CuO)

O 8.03%

Zn 0.22%

Fe 0.47%

SiO ₂ 0.03%

Other metals 0.26%

Soluble nitrates 0.01%

Soluble chlorides 0.08%

Soluble sulfates 0.10%

After their union, the ingredients are in a pan mill, which ensures close mixing allowing minimal crushing, ground into pellets and placed in a reduction furnace of about 1120

registered up to 1135 ° C. They are kept at this temperature for 45 minutes under hydrogen or dissociated ammonia. After the reduction, the beads are removed from the oven and first crushed in a hammer mill to a size of 3.175 mm and below and then in a microminder so that all the particles pass through a sieve with a mesh size of 0.175 mm. The product has a bulk weight of 2.3 to 2.5 g / cm ³ and an oxygen content of about 1.6% (determined by 30minutige hydrogen reduction at 1050 ⁰ C) or 2.37% (by the Leco method - Melting in vacuo at 1926 ° C). The weight loss in hydrogen only provides information about the content of reducible oxygen.

Instead of the iron roll sintering, hematite (Fe ₂ O ₃ ) or magnetite (Fe ₂ O ₃ · FeO) can also be used in such an amount that the same iron content is achieved. You can also replace the cement copper with pure copper (I) oxide.

For the reduction, instead of hydrogen, carbon monoxide or with carbon monoxide or Hydrogen enriched gas such as generator gas can be used.

B. Heat treatment

150 g of the reduced powder are placed in the reduction oven Maintained at 825 to 845 ° C for 1 hour and then cooled. The powder comes in the form of a loose the sintered mass is taken out of the furnace and ground so finely in the same way as after the reduction, that the particles pass through a sieve with a mesh size of 0.175 mm. The calcined powder has an oxygen content of 0.3% (determined by the weight loss in hydrogen) or 1.14% (according to the Leco method).

Alloy powders, which were produced in the same way using the copper sources specified below, ^{compacted at a pressure of about 700 kg / cm 2} and then sintered for 45 minutes at! 120 ^° C. under hydrogen, had the following properties:

of the iron roll sintering, hematite (Fe ₂ O ₃ ) or magnetite (Fe ₂ O ₃ · FeO) can also be used in an appropriate amount.

The copper (II) nitrate can be replaced by equivalent amounts of copper (II) oxide and nitric acid or copper (II) acetate be replaced.

B e is ρ i el 3
Alloy powder with 14% copper and 1% nickel

Iron roll sinter 1153.3 g

Dried cement copper 154.0 g

Animal protein glue ..... 6.0 g

Water 270.0 g

Nickel nitrate (20.3% Ni) 49.5 g

As in Example 1, this batch is shaped into spheres, ^{reduced at 1110 °} C. and then heat-treated. Instead of the iron roll sinter and the nickel nitrate, equivalent amounts of hematite (Fe ₂ O ₃ ) and nickel (II) acetate tetrahydrate can be used. The cement copper can be replaced by the equivalent amount of pure copper (I) oxide.

Example4

Alloy powder with 20% copper

Rolled iron 1072 g

Dried cement copper 205.2 g

30. Copper (II) nitrate trihydrate 37.1 g

Iron black 105.1 g

Methyl cellulose 7.9 g

Water 153 g

density
after Tensile strength Copper source Sintering speed g / cm ³ kg / mm ² Copper (II) oxide (83.02% Cu) .... 6.81. 35.07 Rolled copper sinter (88.64% Cu) .. 6.80 35.84 Cement copper No. 1 (90.80% Cu) 6.85 44.31 Cement copper no; 2 (93.04% Cu) 6.88 47.60 Reduced copper powder (99.52% Cu) 6.75 48.44

Example 2

Alloy powder with a copper content
from 1 and 2%

Rolled iron 1314.2 g

Copper (II) nitrate trihydrate ... 37.5 or 76 g

Carboxymethyl cellulose 6.2 g

Water 300.0 g

These batches are ^{reduced at 1150 °} C. and then heat-treated, the procedure described in Example 1 being followed. ^{Instead, these constituents are formed into spheres, placed in a reduction oven and kept at 1095 °} C. for 75 minutes while a weakly endothermic carrier gas (about 84% nitrogen, 10% carbon monoxide and 6% hydrogen) is passed through.

Following the reduction, the feed is processed using the procedure of Example 1 ground and heat treated.

Following the procedure of Example 1, the following ingredients are made into an alloy powder made with 20% copper and 1% molybdenum:

Rolled iron 1072.8 g

Dried cement copper 220.5 g

Molybdenum trioxide 15.0 g

Ammonia water (26 Be °) 34.0 g

Carboxymethyl cellulose 6.0 g

Water 275 g

In the same way, but using 12.6 g of tungsten trioxide (WO ₃ ) instead of the molybdenum trioxide, a similar alloy powder with a tungsten content of 1% is produced. An equivalent cobalt content is achieved with 14.1 g of cobalt (III) oxide instead of molybdenum trioxide. Furthermore, the iron roll sintering can be replaced by hematite (Fe ₂ O ₃ ) by adjusting the amount added.

Example 5
Effect of heat treatment

150 g samples of the alloy powder from Example 1A with a copper content of 7% are subjected to the heat treatment of Example 1B, each

however, the following temperatures and treatment times are used. Each sample is after the Heat treatment at a pressure of about 7000 kg /.

cm ² compacted and sintered under hydrogen ^{at 1120 ° C. for 45 minutes.} The physical data obtained are summarized below.

1 hour 2 hours 3 hours 2.39 2.41 2.39 6.33 6.34 6.29 29.61 29.12 27.37 1.1 1.1 1.0 0.83 0.80 0.71 B 42.4 B 43.1 B 40.7 2.44 2.45 2.46 6.52 6.59 6.50 33.46 34.30 28.63 2.0 2.0 IS 0.80 0.62 0.54 B 52.7 B 53.1 B 49.2 2.58 2.56 2.50 6.83 6.89 · 6.70 44.31 45.57 40.95 3.1 3.0 2.8 0.79 0.62 0.53 B 63.3 B 64.9 B 59.2 2.52 2.51 2.47 6.80 6.80 6.78 40.81 42.00 36.33 2.9 3.0 2? 0.77 0.70 0.55 B 61.0 B 61.9 B 58.8 2.36 2.48 2.47 6.68 6.60 6.51 35.00 35.84 31.85 2.0 2.1 1.8 0.77 0.69 0.51 B 60.1 B 61.2 B 58.1 2.25 2.23 2.21 6.30 6.30 6.21 32.34 31.01 27.16 1.1 0.8 0.8 0.91 0.87 0.70 B 54.2 B 56.2 B 49.1 2.15 2.11 6.09 6.10 5.82 24.15 22.82 21.00 '1.0 0.8 0.8 1.42 1.39 1.12 B 38.0 B 38.2 B 34.5

Heat treatment at 900 ^° C
Bulk weight of the alloy powder, g / cm ³ .

Density after sintering, g / cm ³

Tensile strength, kg / mm ²

Strain, % -

Linear shrinkage,%

hardness

Heat treatment at 850 ° C

Bulk weight of the alloy powder, g / cm ³ .

Density after sintering, g / cm ³

Tensile strength, kg / mm ²

Strain, %

Linear shrinkage,%

hardness

Heat treatment at 835 ⁰ C

Bulk weight of the alloy powder, g / cm ³ .

Density after sintering, g / cm ³

Tensile strength, kg / mm ²

Strain, %

Linear shrinkage,%

hardness

Heat treatment at 800 ° C

Bulk weight of the alloy powder, g / cm ³ .

Density after sintering, g / cm ³

Tensile strength, kg / mm ³

Strain, %

Linear shrinkage,%

hardness

Heat treatment at 700 ^° C

Bulk density of alloy powder, g / cm ³ ,

Density after sintering, g / cm ³

Tensile strength, kg / mm ²

Strain, %

Linear shrinkage,%

hardness

Heat treatment at 600 ° C

Bulk density of alloy powder, g / cm ³ ,

Density after sintering, g / cm ³

Tensile strength, kg / mm ³ ,

Strain, %

Linear shrinkage,%

hardness

Heat treatment at 500 ^° C

Bulk density of alloy powder, g / cm ³ ,

Density after sintering, g / cm ³

Tensile strength, kg / mm ²

Strain, %

Linear shrinkage,%

hardness

Tempe
rature tensile strenght strain Linear
shrinkage hardness ⁰ C kg / mm ² % % 810 40.95 2.0 0.73 B 60.2 820 41.16 2.0 ' 0.75 B 59.4 830 42.49 2.9 0.69 B 62.0 835 44.31 3.1 0.79 B 63.3 840 44.66 3.0 0.82 B 64.1 845 41.02 2.1 0.84 B 60.0

The above values show that the best results are obtained at a heat treatment temperature of 835 ° C. The procedure was therefore repeated, and the temperature range between 810 and 85O ⁰ C for a temperature control of ± 2 ° C and a treatment time of 60 minutes, examined in more detail. The following average values were obtained:

Tempe
rature
C. Tensile wedge
kg / mm ² strain
% Linear
shrinkage
O/
/O hardness 850 34.37 2.0 0.80 B 52.7

The bulk density of the alloy powder was between 2.44 and 2.58 g / cm ³ and the density after sintering between 6.52 and 6.84 g / cm ³ .

The table below shows that even with a shorter treatment time at 835 ° C., good results be achieved:

15th Density after compression Heat treatment during 45 min. 60 min. 20 mation, g / cm ³ (first density) 30 min. Sintered material 6.40 6.65 Linear shrinkage,% .. 5.91 Tensile strength, kg / mm ² 0.97 0.79 1.21 40.67 44.31 39.69

Example 6 Effect of the reduction temperature and the heat treatment

The procedure of Example 1A is repeated, except that a .Teil the feed at 1000 ⁰ C and a portion is reduced at 1120 to 1135 ° C. Each batch is then compacted at a pressure of about 7000 kg / cm ² , sintered for 45 minutes at 1120 ° C under hydrogen, and then the physical properties of the samples are examined:

Desc. 1 1000 ⁰ C Reduction temperature Desc. 1 1125 ° C Desc. 3 Desc. 2 Desc. 2 Desc. 3 Reduced alloy 2.15 2.35 2.44 powder 1.83 2.39 Bulk density, g / cm ³ 35.4 1.73 30.7 29.9 Flow velocity, 40.0 29.3 Sec / 50 g no Powder, the sieve with clearer meshes 42.2 32.8 42.8 width of 0.044 mm 59.8 36.7 happened, % 1.70 67.9 1.21 1.29 Weight loss 1.93 1.22 H ₂ ,% **) 2.07 Density after the com 6.40 5.76 . 5.73 priming (first 6.29 5.67 density), g / cm ³ 6.33 Sintered material 6.31 5.96 6.04 Density according to the 28.63 6.20 27.72 6.02 27.65 Sintering, g / cm ³ 1.3 22.54 6.09 1.0 28.07 1.3 Tensile strength in kg / mm ² 1.4 28.00 1.1 Strain, % (0.90) *) 10 1.81 1.82 Linear B 55.3 (0.13) *) B 32.3 1.75 B 34.0 Shrinkage,% .... B 50.7 (0.14) *) B 30.7 hardness B 48.0

*) Expansion.
**) 30 minutes at HOO ¹³ C.

209 547/340

17th

Samples of the reduced in the above manner alloy powders are heat-treated for 1 hour at 835 ⁰ C. The powders are then compacted and sintered in the manner indicated. Their physical properties are listed below:

Reduction temperature

Complaint I

! 000 ⁰ C coating 2

Desc. 3

Desc. 1

! 125 ⁰ C coating 2

Complaint

Powder after heat treatment

Bulk density, g / cm ³

Flow rate, sec / 50 g

Powder that passes through a sieve with a mesh size of 0.044 mm,%

Weight loss of H _2> % *)

Density according to the
Compression
(Initial density), g / cm ³

Sintered material

Density according to the

Sintering, g / cm ³ .... tensile strength, kg / mm ²

Strain, %

Linear

Shrinkage,% .... hardness

2.44 33.3

40.5 0.51

6.68

37.45

1.9

1.49 B 60.9

2.12 38.6

53.9 0.52

6.37

6.55

34.30

2.0

1.31 B 59.4

2.10
no

60.0
0.67

6.30

6.52

33.25

1.8

1.53
B 63.0

2.69

25.3

34.1
0.30

6.65

6.83

44.31

3.1

.0.79
B 63.3

2.58 25.7

40.2 0.22

6.73

6.80

42.77 3.2

0.77 B 58.9

*) HOO ⁰ C for 30 minutes.

2.57 25.0

45.0 0.20

6.66

6.76

43.82

2.9

0.64 B 60.4

The above values show that when producing an alloy powder with a copper content of 7% better results are obtained if the reduction is above the melting temperature of the copper performs.

Example 7 Influence of other metals

. Following the procedure of Examples 3 and 4 will contain molybdenum. They are produced as in the above alloy powder with 7% copper, with examples compacted and sintered and each of these powders with 1% cobalt, nickel or ₅ % as well as a heat-treated state being examined:

tensile strenght
kg / mm ² strain
% Density according to
Sintering
g / cm ³ Linear
shrinkage
% hardness 1% cobalt
reduced 22.26
38.64
22.68
45.57
24.71
45.85 1.9
4.0
1.9
2.3
1.8
1.9 5.97
6.79
5.94 ■
6.77
5.99
6.90 1.43
0.72
1.54
0.90
1.73
0.69 B 29.1
B 59.7
B 33.0
B 70.9
B 28.1
B 74.5 and heat treated
1% nickel
reduced and heat treated
1% molybdenum
reduced and heat treated

Example 8 "

Following the procedure of Example 1A, a series of copper-iron alloy powders of different sizes are prepared Made of copper. The reduced powders are made with 0.75% stearic acid as a lubricant

Effect of the copper content

medium, compressed at a pressure of about 7000 kg / cm ² and sintered for 45 minutes at 1120 ° C under hydrogen. The following physical properties were determined:

copper 0,% C) Density according to
Sintering tensile strenght strain Linear
shrinkage hardness % g / cm ³ kg / mm ² % % 2 1.22 5.90 26.46 1.9 1.82 B 27.2 4th 1.20 5.90 26.60 1.9 1.84 B 29.7 6th 1.26 5.92 26.95 1.1 1.81 B 35.2 7th 1.21 ' 5.96 27.72 1.0 1.81 B 34.0 8th 1.20 5.98 27.79 1.0 1.80 B 35.5 10 1.26 6.08 28.28 1.9 2.20 B 42.2 12th 1.23 6.29 32.13 1.8 2.35 B 49.3 14th 1.28 .6.37 34.23 2.0 2.64 B 51.6 16 1.26 6.54 36.12 2.1 3.17 B 55.6 18th 1.20 6.75 39.62 2.0 3.61 B 68.2 - 20th 1.97 6.87 42.35 3.0 3.68 B 69.6 30 ^b ) 1.20 6.81 55.79 3.9 8.13 B 90.9 40 ^c ) 1.84 6.88 40.74 3.8 8.48 B 86.4 50 ^d ) 1.99 7.27 29.40 4.0 8.44 B 53.8

") Determined from the weight loss of hydrogen during a 30 minute treatment at 1100 ° C.") 30 minutes at 1050 ° C reduced sintered for 10 minutes at 1120 ⁰ C. Reduced ') 30 minutes at 950 ⁰ C, sintered for 10 minutes at 1120 ° C. ^d ) reduced at 950 ^° C. for ^{30 minutes, sintered at 1095 °} C. for 10 minutes.

The reduced powders prepared above were heat treated under hydrogen at 835 ° C for 60 minutes before being ^{compacted at a pressure of about 7000 kg / cm 2} and at 1120 ° C for 45 minutes

sintered under hydrogen. The following. Table shows that the heat treatment improves the physical properties of the alloy powders will.

copper 0,% C) Density according to
Sintering porosity tensile strenght strain Linear
shrinkage hardness % g / cm ³ % kg / mm ² % 2 0.29 6.80 13.8 34.30 4.9 0.77 B 42.2 4th 0.30 6.82 13.8 36.12 4.8 0.80 B 50.0 6th 0.27 6.83 14.0 40.81 3.9 0.75 B 53.9 7th 0.30 6.83 14.1 44.31 3.1 0.79 B 63.3 8th 0.23 6.89 13.4 48.23 4.0 0.93 B 66.1 10 0.28 6.89 13.6 57.96 3.9 1.14 B 77.2 12th 0.31 7.02 12.3 58.59 4.1 1.32 B 80.0 14th 0.30 7.12 11.2 59.36 4.0 1.55 B 80.9 16 0.28 7.23 10.1 60.13 ■ 4.0 1.97 B 83.1 18th 0.23 7.38 8.4 60.69 3.9 2.32 B 84.8 20th 0.23 7.46 7.8 61.18 4.1 2.58 B 88.1 30 ") 0.32 7.48 8.8 61.11 3.0 1.39 B 89.3 40 ^c ) 0.31 7.55 9.3 55.23 3.1 2.03 B 79.7 50 ¹¹ ) 0.33 7.75 8.1 46.48 3.9 2.18 B 76.5

") Determined from the weight loss in hydrogen during a 30-minute treatment at HOO ⁰ C. *) Reduced for 30 minutes at 1050 ° C, sintered at 1120 ° C for 10 minutes.

reduced ^c) 30 minutes at 950 ⁰ C, sintered for 10 minutes at 112o C ^0.

reduced ^d) 30 minutes at 950 ° C, sintered for 10 minutes at 1095 ⁰ C.

1 sheet of drawings

Claims (6)

Patent claims: 1. A process for the production of a finely divided alloy powder from iron alloyed with about 1 to 50% copper by reducing a mixture of a reducible iron compound and elemental copper or a reducible copper compound at elevated temperature, characterized in that an iron oxide is used as the reducible iron compound Reduction in the absence of hydrogen chloride with copper contents up to 20% at the melting temperature of copper and above and with copper contents above 20% below the melting temperature of copper, preferably at 950 to 1050 ⁰ C, carried out and the alloy powder for at least 30 minutes on one between the ay -Transition temperature of the iron-rich phase of the alloy powder and a temperature about 150 degrees below this transition temperature is maintained. 2. The method according to claim 1, characterized in that that the heat treatment is carried out at a temperature which is less than 50 degrees below the a-y transition temperature. 3. The method according to claim. 2, characterized in that the alloy powder on a Temperature is maintained between 825 and 845 ° C. 4. Application of the method according to any one of claims 1 to 3 to a mixture of iron oxide with a particle size below 50 μΐη and made of copper or a copper compound with a Particle size below 20 μm. 5. Application of the method according to one of claims 1 to 4 to a mixture of iron oxide and elemental copper or a copper compound and smaller amounts of tungsten, Nickel, cobalt, molybdenum or their reducible compounds. 6. Finely divided iron powder alloyed with 1 to 10% copper, characterized in that it is a Has a uniform microstructure in which up to 8% of the copper is as particles with a diameter of less than 0.1 μΐη are dispersed in the iron particles.