US2069469A - Process for the production of metals and alloys with very small contents of carbon - Google Patents

Description

Feb. 2, 1937. G. ANDERSEN 2,069,469

PROCESS FOR THE PRODUCTION OF METALS AND ALLOYS WITH VERY SMALL CONTENTS OF CARBON Filed Dec. 22, 1933 (Hinder-so Patented Feb. 2, 193 7 2 UNITED STATES PATENT OFFICE Gustav Andersen, Copenhagen, Denmark Application December 22, 1933, Serial No. 703,641

3 Claims.

This invention relates to a process for the production of metals and alloys with very small contents of carbon.

It is known that very important dimculties are met in the production of metals and alloys with very small contents of carbon, for instance chromium and manganese with very small contents of carbon as well as their alloys, especially chromeor manganese-iron and steel alloys, due to the fact that the said metals possess a great aflinity for carbon.

As a rule, the production of stainless steel, for instance, is realized by using an alloy of chromium and iron, having a high chromium content but a low content of carbon, which alloy is added to the finished, melted steel.

Obviously, the indirect producing processes are very expensive, on the one hand due to difficulty of making such a chrome-iron alloy and on the other hand due to the losses arising from the melting together, and accordingly it is better to use a direct process in which a direct reduction of the alloy metals in the main metal is effected. In one of said processes, bricks of chromite thoroughly ground are added, with ferro-silicon or with a silicon containing reducing means, to melted and overheated iron. The additional metal in the alloy is reduced in the bath of metal which is thoroughly stirred, a direct production of the alloy being thus effected, having the desired analysis, for instance a stainless steel.

Very often a process is used in which no carbon-containing reducing means are used, and in which electrodes are used that are not allowed to come into direct contact with the metal for reduction purposes, but it is clear that an alloy will be obtained having a variable and too high a content of carbon. This process is especially suitable for high carbon contents. Apparently, in the above process, the carbon which is absorbed comes from the raw materials, ore, ferrosilicon or slag. I

Analyses made with the ore used show that it has a carbon content of 0.04 to 0.10% or even more. In a further process ferrosilicon and limestone are used. Carbon is likely to be found in the foreign matters, plant fibers, leaves, earth, etc. getting mixed with the ore in the course of transportation or in ore bunkers.

An output of more than 60 to 70% of the Norway December 31, 1932 Before a charge of correctly determined quan- 10 titles of ore, ferro-silicon or other silicon containing reduction means and limestone is put into an overheated main-metal bath, which only contains a very small quantity of carbon, it is submitted to a pre-treatment by heating it to a temperature of 1000 to 1100 C. i. e. without melting it in a strongly oxidizing flame, in order to burn out the carbon which is in the charge, and to have the limestone transformed into caustic lime.

process is practiced. Fig. 1 is a vertical section taken on the line I-I of Fig. 2 of a furnace adapted to the purpose. Fig. 2 is a horizontal view of the same furnace.

The drawing shows diagrammatically how the The charge is ground to a suitable size of grain (like grits or even smaller) thoroughly stirred up and loaded through a feeder i in a thin layer (about 4" thick) over a continuously rotating heating platform 2 where it will meet the combustion gases from a hot strongly oxidizing flame 3 in countercurrent, the furnace being for instance of the type described in the U. S. A. patent application Ser. No. 703,640 of 1933.

After the treatment, the hot charge is discharged at 4 into closed iron boxes 5 for cooling and storing purposes.

If the combustion gases are to be used again in the process for heating purposes, the carbon dioxide is previously separated, for instance by directing the gases which are conducted up through the feeder i through a caustic potash filter 6 or similar product before the gases are conducted back by a fan I to the furnace at the point where the oxidizing flame 3 is produced.

This purification by which sulphur is also eliminated, is very important if good results are to be obtained. Similarly it is necessary to use a strong oxidizing flame.

The charge which has been freed from carbon,

may be added directly to melted metal for a final high-temperature treatment. for instance to an iron bath having a very low carbon content. The determined quantity of charge is poured into the iron bath directly from the closed box I in which it is stored in order to prevent its oxidizatlon. Thus a metal having the precise, desired analysis is obtained.

Having thus described my invention what I claim is:

1. A process for the production of metals and alloys with a very small content of carbon, by direct reduction of ore with silicon-containing reduction means on an over-heated metal bath with a very small content of carbon, the said method including the use 01 a charge consisting of ore, limestone and silicon-containing reduction means, submitted, before being charged into the main metal bath, to a pre-treatment by heatmaterial in a closed chamber and protecting the 1 said material against contamination.

GUSTAV ANDERSEN.

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