DE1151665B - Process for increasing the grain size of carbonyl nickel powder, carbonyl iron powder or copper powder - Google Patents

Description

GERMAN

PATENT OFFICE

INTERNAT. KL. C 22 b

M43620VIa / 40a

REGISTRATION DATE: DECEMBER 7, 1959

NOTICE
THE REGISTRATION
AND ISSUE OF THE
EDITORIAL: JULY 18, 1963

Carbonyl nickel powder, carbonyl iron powder and copper powders also consistently fall with a small mean grain size in the range of approximately 2 to 8 microns. The invention is based on the object of determining the particle size of these powders to increase.

The invention achieves this in that the powder, which has an average particle size of about 2.0 to 8.0 microns, is ground for several hours in a high-speed ball mill which generates a centrifugal force corresponding to ^{at least twice the acceleration due to gravity g = 981 cm / sec 2} and which is only about half filled with steel or tungsten carbide balls and dry powder with the proviso that the weight of the balls is several times the weight of the powder.

The grinding of metal powder in ball mills is known per se. However, there is a reduction the grain size of the input material is sought and achieved, even if it is lamellar flaky powders, e.g. B. made of crushed aluminum foil can be used. The processing of carbonyl nickel powder, carbonyl iron powder or copper powder according to the process In contrast, the invention surprisingly causes exactly the opposite result, namely a Growth of the powder particles subject to the grinding process. Here, from a distant powder with im essentially spheroidal shape produces a coarse powder with a grain diameter of over 500 microns will.

Grinding the fine starting powder with the addition of a liquid in the mill, e.g. B. of alcohol or water, generally has a reduced effect compared to dry grinding Increase in the particle size of the material and is therefore not recommended.

A well-known high-speed ball mill is equipped with a cylindrical container with rotates around its vertical axis at high speed and rotates in the opposite direction and high angular velocity moves on a circular path. A mill like this is for that The method of the invention is expedient and in the exemplary embodiments to be described later used.

The particle size of the finished powder can be influenced by changing the grinding conditions will. The greater the ratio of the weight of the balls to the weight of the powder, the greater they are finished powder particles and the lower the output of coarse powder in the unit of time. That Process for increasing the grain size

of carbonyl nickel powder,
Carbonyl iron powder or copper powder

Applicant:

The International Nickel Company (Moon) Limited, London

Representative: Dr.-Ing. G. Eichenberg

and Dipl.-Ing. H. Sauerland, patent attorneys,

Düsseldorf, Cecilienallee 76

Claimed priority:
Great Britain 9 December 1958 (No. 39 686)

DeWitt Henry West,
Port Eynon, Swansea, Glamorganshire, Wales,

and David Myers Llewelyn,

Samhelen, Cwmdwr, Clydach, Swansea,

Glamorganshire, Wales (UK),

have been named as inventors

is evidently related to the fact that a hardening effect occurs, which increases the tendency of the particles to grow together, attenuates, so that if the meal is too large, the mean one finally decreases Grain size of the powder occurs. With a smaller ratio of ball to powder weight, there is the hardening effect less. For the maximum output of coarse particles per unit of time, there is accordingly a optimal ratio of ball to powder weight. This is why it can be beneficial after a certain amount of time Meal, remove the material from the mill, divide it into two fractions by sieving and the fine fraction, expediently after an intermediate annealing, is subjected to another grinding. By the annealing eliminates the hardening effect that develops and the output per unit of time is coarse Well raised. For example, powder made of nickel is included for 1 hour for this purpose 800 ° C to glow in hydrogen.

A coarse-grained powder produced according to the invention has better flow properties than one made from very fine particles of powder and can therefore be used with particular advantage in powder metallurgy, e.g. B. in the production of alloys and for

309 647/198

pulls on welding electrodes are used. If the coarse powder is nickel, then it is a particularly valuable product for use in a carbonyl decomposer, whereby Nickel is deposited on the individual grains and nickel pellets are formed.

The invention is explained using the following exemplary embodiment:

The starting material is a nickel powder made of spherical particles with an average grain size of around 4.1 microns used. The container of a ball mill holding the material has a diameter of 17.8 cm and an axial length of 8 inches. It moves at 190 rev / min. on a circular path of 15.3 cm Radius, rotates at 100 rev / min. around its own axis and is fitted with steel balls from 9.5 to 12.7 mm Diameter occupied.

A load (steel balls + powder) of 5 kg shows after 3 hours of milling at a 10: 1 weight ratio from steel balls to powder the following grinding fractions:

Finally, in Table 3, the influence of the weight of the charge (steel balls + powder) is shown:

Table 3

weight
in kg Frequency (in o / o)
the grain diameter (in microns) «Obis500 j 250 to 150 i 21.7 I- under 150 2.5 over 500 j: 8.3 j 28.6 70.0 5 43.7 I 24.6 ! 8.8 7.5 18.9 ■ 39.4 ! 28.3 j 20.4 10 16.4 i 21.6 '48.4 1.8 I.

Percentage ownership %

Grain size in microns over 500 250 to 500 250 to 1501 under 150

18.9

43.7

28.6

8.8

The influence of changed grinding conditions is set out below, with one influencing variable in each case is changed and the other conditions are retained.

Table 1 shows the dependence of the coarse grain content of the material on the grinding time:

35

40

45

Tabel 1 Grinding time Percentage good
at least 150 microns
Grain diameter
(Sieve residue) 1 hour 59.1
80.1
91.2 2 hours 3 hours

Table 2 illustrates the influence of the weight ratio of steel balls to powder.

Table 2

Ge

Percentage of good Ratio of steel ball at least 150 microns to powder weight Grain diameter (Sieve residue) 2: 1 40.5 3: 1 60.2 4.5: 1 71.1 6: 1 87.2 8: 1 89.3 10: 1 91.2

55 In the production of powder particles with a grain diameter of more than 500 microns by sieving the coarse fraction and re-grinding of the fine is a grinding time of 3 hours each, a ratio of ball to powder weight of 3: 1 and a charge (balls + powder) totaling kg is advantageous for a high output per unit of time.

Claims (3)

PATENT CLAIMS: 1. Process for increasing the grain size of nickel obtained by carbonyl decomposition or Iron powder and copper powder, characterized in that powder with a mean Particle size of about 2.0 to 8.0 microns for several hours in a high speed, one Generating centrifugal force corresponding to at least twice the acceleration due to gravity Ball mill is ground, which is only about half with steel or tungsten carbide balls and dry powder is filled with the proviso that the weight of the grinding balls is several times the weight of the powder. 2. The method according to claim I _5, characterized in that the grinding of the powder takes place in a ball mill equipped with a cylindrical container which rotates at high speed about a vertical axis and thereby moves in the opposite direction at high speed on a circular path. 3. The method according to claims 1 and 2, characterized in that the ball mill leaving powder divided into two fractions by sieving, the fraction with the smaller Particle size is annealed and ground again. Documents considered: German Patent No. 939 537. © 309 647/198 7.63