DE1018441B - Process for the production of iron powder with a low level of impurities - Google Patents

Description

Iron powder used for powder metallurgical purposes should have as low a content as possible Have impurities, as these affect partly the compressibility of the powder and partly to wear of the pressing tools contribute. Quartz and silica compounds are special because of their hardness harmful. So if iron powder is made by reducing iron ores, then you have to these are freed of silicate minerals as far as possible, which is easiest with magnetite ores Magnet separation takes place after fine grinding has taken place.

Of course, pure iron powder can be produced from a pure starting material if the Reduction no impurities are introduced. This can be achieved in three different ways :

1. By reduction with a gaseous reducing agent, e.g. B. hydrogen, carbon dioxide or one Mix of both;

2. by heating a mixture of iron oxide and solid, low-ash reducing agent, e.g. B. Charcoal or petroleum coke;

3. by heating a mass of layered iron oxide and reducing agent that then does not need to be low in ash.

However, all three reduction methods have their disadvantages. The first two need proportionately expensive reducing agents, the loading of the latter is cumbersome, and the Reduction temperature are high so that adequate reduction times are obtained.

The cheapest and also known method for the production of iron powder consists in heating a mixture of iron oxide in fine-grained form and solid, ash-containing, cheap reducing agent at the reduction temperature and grinding the cooled iron sponge obtained into powder, from which the ash constituents of the reducing agent are separated out by means of magnetic separation. With this method, depending on the quality of the ores and the magnetic separator, it is possible _{to achieve SiO 2} contents below 0.5% and in special cases below 0.2%. However, the presence of particularly good ores and the best possible magnetic separator is a prerequisite for this.

In contrast, the invention has set itself the task, regardless of the quality of the ores and to achieve purer end products than before for a given magnetic separation apparatus, which are for powder metallurgical purposes are suitable. According to the invention this is achieved in that the Reducing agents, e.g. B. coke, of the finest particles, which have a grain size of less than 0.19 mm, is released. This will make the touch method of manufacture

of low content iron powder

of impurities

Applicant:

Höganäs-Billesholms Aktiebolag,
Höganäs (Sweden)

Representative: Dipl.-Ing. E. Jourdan, patent attorney,
Frankfurt / M., Kronberger Str. 46

Dr. Nils Hermann Brundin, Höganäs (Sweden),
has been named as the inventor

area between the reduced iron and the ash particles remaining after the reduction and thus reducing the possibility of the ash particles sticking to the iron that has been reduced. The result is favorably influenced if the reducing temperature is as low as possible, preferably below 1000 ° C.

The following experiments show the increase in the quality of the iron powder achieved by the invention can be:

Magnetic particles of about 0.55 mm grain size, freed as far as possible from impurities, are mixed with 19.2% coke bushes with an ash content of about 15%. _{About 50% SiO 2 was} found in the ashes of the coke bush.

The coke swab used was obtained in three different tests in the following grain sizes used:

1. <0.83 mm

2. 0.83 to 0.19 mm

3. <0.15 mm

All three mixtures were reduced in a capsule by heating to a maximum of 1000 ° C. the Temperature was maintained until the completion of the reduction

709758/138

maintained. Thereafter, the obtained sponge iron was taken out, ground to 0.16 mm and magnetically separated. The SiO ₂ contents before and after the magnetic separation were:

Grain size
of the coke

0.83 mm
0.83 to
0.19 mm
<0.15 mm

Before the
Magnetic separation

2.62% SiO ₂

2.14% SiOo
2.64% Si Upper Austria

After
Magnetic separation

A comparison of experiments 1 and 2 shows that the removal of the finest coke grains brings about a considerable reduction in the SiO ₂ content after the magnetic separation.

The significance of the reduction temperature can be seen in the table below, which _{indicates the Si O 2} content of a powder of <C 0.15 mm before and after the magnetic separation. The powder was obtained by heating to different temperatures from a mixture of Schlich and coke bushes of 0.83 mm and subsequent grinding of the sponge iron formed.

temperature Before the
Magnetic separation After
Magnetic separation 900 ° C
100 ° C
115O ⁰ C 2.86% SiO ₀
2.62% SiO ₂
2.93% Si O ₂ 0.32% SiO ₂
0.42% SiO ₂
0.65% SiOo

0.42% Si O ₂ ίο

0.21% SiOo 0.78% SiO ₂

Claims (1)

PATENT CLAIM: Process for the production of iron powder, in which iron oxide in fine-grained form, e.g. B. Schlich, mixed with a solid, ash-containing reducing agent, the mixture to reducing temperature heated and held until the end of the reduction, the obtained sponge iron cooled, for the desired grain size is ground and subjected to magnetic separation, characterized in that that the reducing agent consists of the finest particles, which have a grain size of less than 0.19 mm exhibit, is exempt. Considered publications:
R. Kieffer and W. Hotop: "Sintereisen und Sinterstahl", 1948, p. 43; "Powder metallurgy and sintered materials", 1943, p. 188, line 9 from below, to p. 189, paragraph 1. © 709 758/138 10.57