DE928769C - Process for producing low carbon ferrochrome from high carbon ferrochrome - Google Patents

Description

Process for making low carbon ferrochrome from high carbon Ferrochrome The invention relates to a method for producing ferrochrome with low carbon from high carbon ferrochrome.

There are several methods of making ferrochrome using low carbon known to those of ferrochrome with a proportionate assume high carbon content. It has already been proposed to use a material which contains oxides of chromium and iron, to reduce silico- or aluminothermically. Low-carbon ferrochrome was obtained relatively quickly, however the consumption of silicon or ferrosilicon or aluminum was considerable, there In addition to the oxides of chromium and iron, the starting material also contains gangue, which this is also reduced.

It is also known to use a chromium oxide-containing in an electric furnace Slag with a chromium alloy with a higher carbon content than that to be produced Bring alloy into reaction. The carbonaceous chromium alloy read through chromium oxide decarburized; but since this process is carried out in a bathtub the reaction proceeded extremely sluggishly and consequently consumed a great deal of energy lots of fuel. To the Some improvement has been suggested to remove the charcoal material by roasting. But this procedure was also used in The presence of the above-mentioned slag carried out, so that the process with regard to of the end product had the same disadvantages as before. Compared to this Prior art, the present method is that one sees in Oxidation product obtained in a known manner by roasting carbonaceous ferrochromium grinds, mixed with a finely ground, non-carbonaceous reducing agent and reduced in an exothermic reaction.

It is already used for welding. Mixture of sintered, ground and sieved iron oxide and aluminum known, furthermore it is known that such a product as a result of the increased surface area of the intermediate product has a very high reaction speed. This mixture has meanwhile been only used for welding iron parts. In contrast, it is new, this one To apply the principle to the metallurgy of ferrochrome and to produce a reaction mixture, which is easy to achieve an extremely fast implementation can be comminuted by grinding. The conversion speed is due to the very fine grinding increased many times.

The method according to the invention takes place in four stages: Stage 1: The ore is reduced with carbon to form a high-carbon ferrochrome Trains-. win.

Stage 2: The high-carbon ferrochrome - is in solid, finely divided Condition is oxidized, resulting in extensive decarburization.

Stage 3: The material to be treated is now ground accordingly mixed with a finely ground, non-carbon reducing agent, like silicon, ferrosilicon, aluminum, or the grinding takes place together.

Step 4: The mixture is brought into reaction and thereby gains a profit low or carbon free ferrochrome.

Since the starting material is reduced with carbon, is this process stage is very economical because coal is cheap. The reaction is therefore less expensive than if ferrosilici.um as a reducing agent from the start or the like. Would use.

In stages 3 and 4 the reaction proceeds extremely quickly, This saves a considerable amount of fuel compared to the known processes.

According to another feature of the invention, this becomes carbon-rich Ferrochrome at a temperature below the melting point, but above 120 ° C, preferably above 1300 ° C, and then a further oxidation Subjected to 70o to 100o ° C.

This oxidation is so advantageous because it is in the first oxidation stage Chromite is formed in the presence of lime or sodium carbonate and in the second Chromium? .T, so that the end product of the roasting work is a mixture of chromite and Chromate is obtained, which is particularly well suited for the subsequent exothermic reaction is.

The decarburization is advantageously carried out so far that the decarburized metal contains less than 0.2o%, advantageously less than 0.1o percent by weight of carbon. This result can be achieved by controlling the temperature appropriately. For example, a product below about 0.3 weight percent carbon is difficult to manufacture at temperatures below 100 ° C. Even at 120 ° C., a product that contains less than 0.2% by weight of carbon is very difficult to obtain, even if roasted for many hours. Above 120 ° C, products that contain no more than 0.1% by weight of carbon can be obtained in less than 2 hours.

An essential one. The characteristic of the present proceedings is that that the material to be treated is reduced in a very finely ground state. It recommends see, the material to a particle size of about 0.15. advantageously even 0. o75 mm clearances Grind mesh size.

If the reduction is carried out with ferrosilicon, one measures its amount as well as that of the lime and the metal in the reduction material advantageous so, that a chromium-containing melt and a calcium silicate-containing melt during the exothermic reaction molten slag can be formed.

Claims (5)

PATENT CLAIMS: 1. A process for the production of low-carbon ferrochromium from carbon-rich ferrochrome, wherein the carbon-rich ferrochrome is ground and oxidized in the solid state and the oxidation product consisting of oxides of chromium and iron is reduced to a chromium-iron alloy, characterized in that the oxidized ferrochrome is ground, mixed with a finely ground, non-carbonaceous reducing agent and reduced in an exothermic reaction. 2. The method according to claim i, characterized in that the carbon-rich Ferrochrome at temperatures below the melting point, but above 120 ° C, advantageously above 1300 ° C, and then a further oxidation treatment at 70o to 1000 ° C -is subjected. 3. The method according to claims i and 2, characterized in that a mixture is subjected to oxidation, which is ground to a particle size of 0.15 to 0.075 mm mesh size. 4. Process according to Claims 1 to 3, characterized in that the decarburization is driven so far that the decarburized metal is less than 0.2o%, advantageous contains less than 0.1% by weight carbon. 5. The method according to claims r to 4, characterized in that at. Carrying out the reduction with ferrochrome silicon or ferro silicon the amount of the latter, a calcium surcharge, and the metal to be reduced is such that a chromium-containing melt and a molten slag consisting of calcium silicate are formed during the exothermic reaction. Cited publications: German patent specifications No. 401 I72, 465489, 621 794, 628428.