DE2651251A1 - SINTERABLE METAL POWDER MIXTURE - Google Patents

Description

BSA Sintered Components Ltd., Waverly Works, Coventry Road »

Birmingham Bio OHN, England

Sinterable metal powder mixture

The invention relates to a sinterable metal powder mixture based on iron with subsequent salaries in weight percent:

Nickel o.5 to 4, ο %

Manganese 0.5 to 6.0 %

Carbon (graphite) o, o5 to 1.5%

Copper, if available up to 5, ο %

Boron, if present, up to 0.4 % _t and iron and the usual impurities

the remainder up to 100 %.

In a metal powder mixture of similar composition previously known from British patent specification 975322, the manganese is contained in the form of manganese powder which, however, oxidizes. Can the manganese particles as a result, existing oxide layer is very difficult to reduce · The boron content of these known metal powder mixture is used primarily to .u reduce the oxide as oxides shindern alloying and diffusion ', vas U;? -Gleichmäßigkeiten properties , especially the degree of wear and tear

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of the sintered article. The boron turned out to be, however for this purpose as inadequate when it comes to producing sintered articles with particularly high wear resistance.

The object of the invention is to provide a metal powder mixture of the initially named type so that they become articles of higher value Wear resistance can be sintered.

The invention is characterized in that the mixed proportion of nickel and manganese is in the form of a powdered, binary alloy is contained with contents of manganese and nickel in a weight ratio in the range from 15:85 to 65:35; preferably in the area from 2o: 8o to 55:45 «

The invention makes it possible to add manganese powder and This also avoids the problems associated with it, and makes it possible to reduce the nickel content and the manganese content in the finished product Mixing by appropriate setting of the binary alloy according to the desired properties of the one to be produced Set sintered article without the need to use boron.

A preferred further development is characterized in that the contents of nickel, manganese and carbon in a metal powder mixture are in percent by weight:

Nickel 1.4 to 2.8 %

Manganese 2.1 to 3 »9 % _f and

Carbon 0.5 to 1.25 %

Particularly high wear resistance is achieved in a further development, which is characterized by salaries vie follows in weight percent:

Nickel 1.9 to 2.8 %

Manganese 3 _t o to 3 »9%, and

Carbon 0.5 to 1.25 % ; preferably

o.65 to 1.o %,

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It proves to be advantageous for the invention that the binary nickel-manganese alloy provided according to the invention is in the usual sintering temperatures in the range of 115O Celsius is in the liquid phase and therefore already diffuses completely into the mass to be sintered at the beginning of the sintering .

Preferably the salaries of nickel and manganese are in the binary Alloy, based on percentages by weight, in the range from 2o: 80 to 55: 45 · Such an alloy is already in the liquid phase at a temperature of 1100 ° Celsius. Well proven has become a binary alloy with a content of nickel and manganese in a weight ratio of about 40:60. The melting point of this Alloy is around 1025 ° Celsius. It should be expressly pointed out at this point that the sintering temperature is natural can be higher than the melting point of the alloy, for example to achieve a higher diffusion rate. The sintering can be done at temperatures up to 1350 ° Celsius will.

The grain size of the alloy powder is preferably so large that all grains can pass through a sieve with a mesh size of 200 mesh. Mesh is the unit for the mesh size according to the BSS - British Standard Specification.

The grain size of the entire powder mixture, with the exception of the iron powder, is preferably selected so that the grains in question can all pass through a 300 mesh sieve.

The grain size of the iron powder is preferably so large that all grains have a sieve with 100 mesh; 75% of the * ¹ grains can pass through a 2oo mesh sieve and 50% of the grains can pass through a 300 mesh sieve.

According to another proposal by the applicant, the binary alloy is pulverized so that 80% passes through a sieve of 325 mesh. This grain size results in a sintered product with a high proportion of austenite. It has been shown that the wear and tear

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strength of the sintered article in question is directly proportional to the austenite content, which is presumably due to it is that the austenite is converted into martensite when energy is absorbed, whereby the observed increase in hardness and wear resistance arises.

The carbon, which is preferably added in the form of fine graphite powder ("micronized graphite"), is preferably, based on percent by weight, with a content in the range of 0.45 to 1.5 % _f, even better in the narrower range of o, 65 to 1.0 %, added ■

The iron is preferably added as a soft iron powder. A small proportion of the iron content can be replaced by the same amount by weight of one or more other elements which do not impair the tensile strength and ductility of the articles sintered from the powder. The proportion of iron replaced in this way should not, however, exceed 5% of the total weight of the mixture.

The following is a list of elements that can be used to replace part of the iron, with the maximum weight percentages in brackets, based on the entire mixture :

Al (1%), B (0.3 %), Cr (5%), Mg (1%), Nb and / or Ta (4%), P (0.3%), Si (1% ), Ti (15Q, W (4%), V (o, 3%), Zr (o, 6? 0, Se (o, 6 #), and Pb (0.5%).

Copper can be added to the mixture, up to 5 percent by weight. An additional copper content promotes the strength of the sintered article and has little or no effect on the wear resistance. The copper component is preferably added to the mixture in the form of a copper powder, the grain size of the copper powder preferably being selected so that it can pass through a sieve with 100 mesh.

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It is a particular advantage of the invention that it is not necessary to use boron as a flux, although boron can also be used within the scope of the invention. If boron is used, then it is used up to a weight content of up to 0.47ί. It can be used in the form of amorphous boron or in the form of one or more alloys, for example an iron- boron alloy, or in the form of one or more chemical compounds with boron, such as, for example, metallic borates, for example copper borate.

A metal powder according to the invention can be sintered into a solid article using known sintering techniques. After the individual components of the powder mixture have been weighed out, they are mixed with one another so that a homogeneous powder mixture is produced. Liquids such as hard paraffin, stearate or the like are mixed into this mixture. The resulting mixture is then compressed into the desired shape using pressing pressures of at least approx. 2.5 tons per square centimeter and then in a protective atmosphere, preferably made of cracked ammonia and propane, at temperatures in the range of 11oo ° Celsius to 135o ° Celsius, that are used for at least 5 minutes, sintered.

The invention is explained in more detail with the aid of the following examples. All percentages in these examples are percentages by weight and all temperatures are given in ° Celsius.

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EXAMPLE 1

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4, ο % powdery, binary nickel-manganese alloy with a nickel and manganese content in the ratio 4o: 6o, 1 % copper powder, 0.8% very fine (micronized) graphite powder and the rest up to 100 % soft iron powder - become one Metal powder mixture mixed. The granule size of the iron powder used is such that it can completely pass through a 100 mesh sieve, 75% of which can pass a 2oo mesh sieve and 50 % of which can pass a 300 mesh sieve.

All other components of the mixture can pass through a 300 mesh sieve. 0.7 % zinc stearate is mixed into the metal powder mixture.

Blanks with a diameter of about 7 cm and a density of 6.8 grams per cubic centimeter are pressed from this mixture exhibit. These blanks are in a temperature of 114o ° Celsius, which is applied for 30 minutes Sintered atmosphere of cracked ammonia and propane. The sintered articles have a surface hardness of the order of magnitude of 21ο (HV5Kg) and an austenite content of approximately 9 a standard deviation in content of about 2.75 · This result is much better than that achievable according to the prior art. The improvement is also attributed to the fact that no boron is used.

EXAMPLE 2

Four batches of metal powder are prepared with the same salaries, namely 1.6 % nickel, 2.4 % manganese, 1.25 % carbon, 1.0% copper and the remainder except for 100 % iron. The nickel and the manganese are each added in the form of a powdered, binary alloy, the nickel-manganese ratio of which is 4o: 6o. The particle size of the pulverized, binary alloy is different in the individual batches, as will be indicated below. In each batch, the carbon content is added in the form of micronized graphite powder and that is copper

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added as elemental copper and the iron in the form of soft iron. The particle size of graphite, copper and Iron is the same as given in Example 1.

The Batch 1 binary alloy is a finely ground nickel-manganese powder that does not pass through a 100 mesh sieve. In Batch 2, the binary alloy is ground to a powder that is fractionated, sieved in succession with 14o mesh, 2oo mesh, 325 mesh and 4oo mesh. A sieve fraction comprising 0.2% is retained in the sieve with 14o mesh. A sieve fraction comprising 5.2 % is retained in the 200 mesh sieve. In the 325 mesh sieve, a sieve fraction comprising 38.0 % is retained and in the sieve with 400 mesh a sieve fraction comprising 31 % is retained while the remainder, comprising 25.6%, passes through the 400 mesh sieve. In Batch 3, the binary alloy is a finely atomized powder that is fractionally sieved, 14o mesh, 2oo mesh, 325 mesh, and 4oo mesh in sequence. A sieve fraction comprising 0.1% is retained in the sieve with 14o mesh. A sieve fraction comprising 0.2 % is retained in the 200 mesh sieve. In the sieve with 325 mesh a sieve fraction comprising 10.3 % is retained and in the sieve with 400 mesh a sieve fraction comprising 26.0% is retained while the remainder, comprising 63.4 %, passes through the sieve with 400 mesh. In Batch 4, the binary alloy is finely atomized so that the powder completely passes through a 400 mesh sieve.

0.7% zinc stearate is mixed into each of the four batches. Then blanks with a diameter of about 7 centimeters and a density of 6.8 grams per cubic centimeter are pressed from the powder batches and the blanks are sintered at 110 ° C for 30 minutes in an atmosphere of cracked ammonia and propane.

The sintered test pieces were then measured. The measurement results are given in Table 1 below.

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TABLE 1

Batch No. 1 2 3 4

Average _{iqi 8} oiq ο poo -3 ο ** λ

Surface hardness (HV5Kg) ¹⁹¹ ' ^{b 213} ' ^{3 229} ' ^{3 236} ' ⁶

Average austenite content 6.57 8.96 15.5 17.15

Standard deviation _οΛ . _o " _o7 . ^ _fl

the austenite content ^{2 '63 2} ' ^{71 2 '73} ^ ⁶⁸

It can be seen from the table that all four batches lead to better sintered products than those produced with metal powders according to the prior art, which is attributed, among other things, to the fact that no boron is used. It is also shown that the particle size of the powder of the binary alloy has an influence on the hardness and the austenite content and thus also on the wear resistance. Batch No. 3, in which 89.4 % of the alloy powder passes through a sieve with 325 mesh, results in a considerably better product than Batches 1 and 2, while with Batch 4, where 100 % of the alloy powder has a sieve of 4oo mesh happens, even better results are achieved.

Not only the austenite content is sintered from batch 4 Item higher than the one from batch 3, but also the standard deviation and thus the variations in the austenite content are lower.

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Claims (1)

P 38 6o6 EXPECTATIONS * Sinterable metal powder mixture based on bisse with the following Salaries in percent by weight: nickel O , 5 until 4.0 % manganese O , 5 until 6.0 % Carbon (graphite) O , 05 until 1.5 % Copper, if any until to 5, o % Boron, if present until to 0.4 %, and Iron and the usual impurities the remainder up to 100%, characterized in that the mixture proportion of nickel and Manganese is contained in the form of a powdered, binary alloy with contents of manganese and nickel in weight ratio in the range of 15:85 to 65:35. 2 metal powder mixture according to claim 1, whose contents of nickel, Manganese and carbon in percent by weight are: Nickel 1.4 to 2.8 % Manganese 2.1 to 3 »9 % _t and Carbon 0.5 to 1.25 % 709821/0667 - 2 ρ 38 6ο6 3 · metal powder mixing according to claim 2, characterized by Salaries in percent by weight as follows: Nickel 1.9 to 2.8 % Manganese 3, ο to 3.9 %, and Carbon 0.5 to 1.25 % » 4 · metal powder mixture according to claim 3, characterized in that the carbon content is from 0.65 to 1.0% - in percent by weight ■. 5. Metal powder mixture according to one of the preceding claims, characterized by contents of nickel and manganese in the pulverized, binary alloy in a weight ratio in the range from 2o: 8o to 55:45. 6. metal powder mixture according to claim 5, characterized in that that the binary alloy is continuously soluble and contains nickel and manganese in a weight ratio of about 4o: 6o 709821/0667