US3151975A - Process for treating molten ferrous metal - Google Patents

Description

United States Patent 3,151,975 PROCESS FOR TREATING MOLTEN FERROUS METAL Julius D. Madaras, Rockwall Place, Longview, Tex. No Drawing. Filed May 4, 1960, Ser. No. 26,696 3 Claims. (Cl. 7548) My invention is a new method for refining iron and steel, for carburizing iron, and for adding additives to iron to form nodular iron.

For refining molten iron and steel a mixture of lime and alumina is prepared and, if so desired, preheated to a temperature below the slag formation. This mixture may be in any desired form, pellets, briquettes, rods, porous or densely compressed. When these are poured or placed over the top of molten metal contained in a ladle or vessel, hot lumpy carbon such as charcoal, loose or in briquette form, is placed over the whole charge and the carbon layer is then pressed down into the metal by a suitable plunger. The pressure on the plunger is then released, the carbon lifts and is again pressed into the molten bath. This operation is repeated for any desired number of times until the desired reaction is completed.

These lumps of lime and alumina may also be placed into the empty ladle, preferably on a layer of carbon, then covered by hot carbon. This carbon pile is held down by a plunger or by any other suitable means and molten iron is poured into the ladle. The molten iron heats the lumps, forming molten slag which rises to the top through the molten iron and at the same time refines the molten iron. The pressure on the carbon pile is released several times and the carbon pressed down into the molten metal bath in order to make the mixing of the slag and iron and thereby the refining more complete.

High carburization may also be accomplished by repeated plunging of the carbon pile into the iron bath.

The lumps of lime and alumina may contain other slag forming elements as desired. It may also contain carbon which will facilitate the further carburization of the molten iron.

My method will also be useful for putting into the metal bath alloys lighter than the metals themselves. For instance, by my method magnesium metal can be added easily and economically to the iron for alloying the two metals. Lumps or bars or sheets of magnesium are placed on the bottom of the furnace and hot carbon lumps are placed over the solid magnesium and the carbon pile is held down as previously described. The molten iron melts the magnesium, absorbs it and becomes alloyed with it. In this way the oxidation of most of the magnesium is prevented, practically all the magnesium is absorbed and the amount is controlled, except for the amount which combines with the oxygen contained in the molten iron. The hot carbon maintains a reducing atmosphere so that there will not be much tendency for oxidizing the magnesium.

If absorption of carbon is not desired, some very dense carbon such as broken electrodes or possibly dense refractories may be utilized.

The solid magnesium can also be held down at the bottom of the furnace by the plunger, a solid carbon rod, column or electrode which preferably has a hollow space at the bottom, while the molten metal is poured into the furnace. The magnesium will be prevented from floating to the top and therefore from becoming oxidized. The molten metal then will dissolve and absorb the magnesium, part of which will also act to deoxidize the molten metal. The additive can be attached to a suitable rod of steel and be thrust into the bath to be absorbed.

It should be kept in mind that, while for the sake of simplicity and brevity only magnesium as light metal has been mentioned, nevertheless all other nodulizing metals or their mixtures, such as calcium, barium, titanium, cesium, etc., may be used, or even heavy metals or any combination thereof may be used without departing from my invention.

Another but similar method of carburizing the metal and at the same time putting in the deoxidizing light metal or other alloys is as follows:

Finely divided or granular carbon and finely divided or granular metal or metals are mixed and made into briquettes, rods or any other suitable form. If desirable, a suitable hinder or other materials such as lime, alumina, etc., may be also mixed in. This mixture may also be coated with suitable coating like tar or clay, or may be enclosed into metallic casing to prevent slow oxidization or even possible ignition. The briquettes may have any desired looseness and porosity, or the mixture may even be kept in a loose state when surrounded by a casing or coating. These briquettes will then be submerged into the furnace as described above. Since the molten iron has a great afiinity for the magnesium and other similar elements mentioned above, it will absorb the magnesium, leaving the carbon very porous and thereby facilitating the absorption of carbon also.

A combination of slag forming refractories such as alumina, silica and lime may also be so mixed with carbon that they react with each other in the molten iron and form slag. The carbon mixed with them is absorbed by the metal to provide the proper carburization or to add the balance of carbon desired. Preferably, mainly alumina and lime should be used as slag forming materials. At the same time the slag forming materials are reacting to form slag, they develop a large amount of heat helping not only the carburization but also, if desired, the temperature rise of the molten metal as well as the refining of the metal.

This, for instance, will be very important when making iron or steel with nodular structure, the so-called nodular iron. In the nodular iron the very low sulphur content is very important. The hot slag formation which will cause boiling and agitation of the molten metal will have great afiinity for the sulphur, especially if so proportioned that it is strongly on the basic side. It is also partly due to the high temperature developed.

If it is desired to raise the temperature of the molten iron, after releasing the pressure on the carbon, air at any temperature or oxygen or enriched air may be blown into it in order to raise the temperature of the carbon by the resulting combustion. After that the hot carbon is pulverized into the metal to raise its temperature.

This application is a continuation-in-part of my application Serial No. 454,102, filed September 3, 1954, and now abandoned, which in turn is a continuation-in-part of my application Serial No. 125,934, filed November 7, 1949, now Patent No. 2,688,535, dated September 7, 1954.

What I claim as my invention is:

1. Metallurgical process which comprises placing solid metal having nodulizing properties in a container, covering the metal layer with carbon, and pouring molten ferrous metal into the container while maintaining the metal submerged until it melts and nodulizes the iron.

2. Metallurgical process which comprises placing solid magnesium metal in a container, covering the metal layer with carbon, and pouring molten ferrous metal into the container while maintaining the magnesium metal submerged until it melts and nodulizes the iron.

3. Metallurgical process which comprises placing a solid metal of the class consisting of magnesium, calcium, barium, titanium and cesium in a container, covering the metal layer with carbon, and pouring molten ferrous metal into the container while maintaining the metal submerged until it melts and nodulizes the iron.

(References on following page) 0 References Cited in the file of this patent UNITED STATES PATENTS Koneman Sept. 29, 1903 Pacz Aug. 24, 1926 Moore Nov. 28, 1933 Priestly May 9, 1939 Perrin June 4, 1940 H012 Mar. 18, 1947 FOREIGN PATENTS Great Britain 1876

Claims (1)

1. METALLURGICAL PROCESS WHICH COMPRISES PLACING SOLID METAL HAVING NODULIZING PROPERTIES IN A CONTAINER, COVERING THE METAL LAYER WITH CARBON, AND POURING MOLTEN FERROUS METAL INTO THE CONTAINER WHILE MAINTAINING THE METAL SUBMERGED UNTIL IT MELTS AND NODULIZES THE IRON.