US1481747A - Refining of ferrochrome - Google Patents

Description

Patent Jan. 22, 1924.

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- EEIEINING OF FEEBOCHROHE.

Ho Drawing.

"iRIcK, a subject of the King of Great Britain, residing at The Acacias, Higher Drive, Purley, Surrey, England, have in-.

vented new and useful Improvements in and Relating to the Refining of Ferrochrome, of

which the following is a specification. I The invention relates to the refining of ferro-chrome, whereby the carbon content ofi the alloy may be reduced or eliminated.

According to the present inventionthe molten alloy is subjected to a refining blast or blowing operation by means of a gaseous medium containing both oxidizing and reducing ga'ses'in the form of steam and hydrogen.

In addition to the use of hydro n and; steam, this gaseous admixture may e used in conjunction with other oxidizin gases, as for example, carbon dioxide an air as oxidizing gases, and carbon monoxide as an additional reducing gas.

This gaseous admlxture may be directed on to the surface of the molten alloy, or injected or blown through the molten metal, or the gases may be used for the refining operation in both of these ways.

In carrying out the refining operation according to the present invention, the molten alloy is preferably maintained within a temperature range of 1500 C. to 1600 C., and as near a temperature of 1500 0., as possible. As the refining operation proceeds, a higher temperature may be necessary. But the temperature should not be permitted to rise undulyhigh, as a lower temperature is more favourable to the productionof a refined alloy with a minimum loss of the chromium content. The upper limit of temperature of the molten alloy should not exceed 1650 C., or 1700 (3., at the most.

All or part of the steam and hydrogen mixture may bedirected so as to impinge on the surface of the molten alloy, in which case extreme fluidity of the alloy may not be so necessary. I find a convenient way of employing the I refining gases so as to work Within the desired temperature limits is to impinge a steam and hydrogen mixture on to the surface of the molten alloy and to employ a more vigorous oxidizing gaseous refining admixture for blowing throughv the molten alloy. This blast through the alloy may be or cause Application filed January 17, 1923. semi m. 613,292.

- A convenient form of refining blast withv in the scope of the invention is producer gas, or f water gas, which a roportion of steam has been added to be included therewith. Y As will be understood, the gaseous mixture employed according to my invention may .be preheated, in order to avoid too strong a local cooling action at the pointcarbon dioxide either In this way, the rise medium which imor blast furnace gases, to

where it is projected either through or on to the surface of the molten alloy.

By the use of a blast containi both oxidizlng and reducing gases, as in ti described, the carbon is subjected to an oxidizing action in the well-known manner, while the reducing gas or gases exert a restraining action on the. oxidation of the metals of the molten alloy.

I am aware that inthe treatment of molten metals such as iron' or steel it known to use a blast of air or steam or both and to dissociate the steam into its constituents but the treatment of ferro-chrome involves considerations peculiar to this allo It is well known that this alloy is a-difiicu t e manner alloy to refine economically by reason of its strong afiinity for carbon, its high melting pomt, and its high chromium content.

Vhen the high-carbon molten fined by treatment with an air hitherto been proposed, the oxidatiou'of the carbon and silicon present as impurities rapalloy is reblast, as has idly raises the temperature of the molten alloy to a point where severe oxidation of the chromium occurs simultaneously with an elimination of the oxidizable impurities. There is also a loss of chromium by evaporation at the high temperature of the molten bath. According to the process for the preparation of refined ferro-chrome constitutin the present invention, both hydrogen and steam are employed as a refining gaseous mixture and these ases ma be um either with or without other suita le gas or ases as has hereinbefore been described. ile the steam is both an oxidizing agent and a temperature regulator, and particularly 9 as chrome to produce an alloy when used in the manner described, the presenoe of hydro en in the refining blast pro- Vides for a iminished oxidation of the molten alloy constituents thus permiting the blowing operation to be continued for such a period as will enable the molten alloy to be refined sufi'iciently without severe losses of the chromium content, which is an important consideration.

What it claim is 1. A process for refining molten ferrochrome to produce an alloy of low carbon content, comprising, subjecting molten ferro-ohrome to the action of a gaseous mixture containing both hydrogen and steam.

2. A process according to claim 1, the molten ferro-chrome being maintained at a temperature of from 1500 C. to 1650 C.

3. A process for refining molten ferroof low carbon content, comprising, directing a blast 0th} drogen' and steam to impinge on the surface of a bath of molten term-chrome.

4. A process for refining molten ferrochrome to produce an alloy of low carbon content, comprising, directing blasts of hydrogen and steam bot-l1 upon the surface of a bath of molten 'ferro-chrome, and also through the molten mass.

5. process for refining molten ferrochrome to produce an alloy of low carbon content, comprising, directingia blast of an oxidizing and reducing gas admixture onto the surface of a bath of molten term-chrome, and simultaneously directing a more highly oxidizing gas admixture of oxidizing and reducing gases through the molten ferrochrome.

W. R. SALTRICK.