US2669511A - Method for refining ferrous metals - Google Patents

Description

Feb. 16, 1954 1 l.. WHITNEY, JR 2,669,511

METHOD FOR REFINING FERROUS METALS Filed April 6, 1950 2 Sheets-Sheet l r/llll J Q www, om; mi W @m wm 25C@ |10 www @NNI www JHM- @w @l #.LLIFLI. l\ W y www f W Feb. 16, 1954 L. L. WHITNEY, JR

METHOD FOR REFINING FERRoUs METALS 2 Sheets-Sheet 2 Filed April 6, 1950 l1. Y A

Nhoh n www @u 3M Patented Feb. 1.6, 1954 `UNITED STATES PATENT OFFICE METHOD FOR REFINING FERRGUS METALS Loren L. Whitney, Jr., Alliance, lOhio Application April 6, 1950, Serial No. 154,330

(Cl. 'i5- 43) 3 Claims.

This invention relates to the melting and relining of ferrous metals and alloys charged into metallurgical furnaces, such as open hearth and electrical furnaces, and more particularly to a novel method and means for accelerating the melting of the charge.

It will be understood that the production of any foundry is limited by the output of its furnaces, and accordingly by decreasingthe time necessary to melt the charge the output of the furnaces may be increased thereby decreasing the cost of melting.

The present invention comprehends a novel method and means for reducing the time for melting such a charge to about ten percent of the time required according to prior art practices.

A primary object of the present invention is to accelerate the melting of a ferrous metal charge in a furnace by introducing a powder which accelerates oxidation of part of the charge necessary to provide heat to melt the remainder thereof.

A further object of the invention is to devise a novel method and burner means for introducing the powder in such a manner as to afford maximum effectiveness thereof.

The foregoing and further objects of the invention will become apparent from the following specification and the accompanying drawings, wherein:

Figure l is a diagrammatic view of an open hearth furnace, partly in section to illustrate the novel burner means applied thereto;

Figure 2 is a fragmentary enlarged View showing the burner means;

Figure 3 is an enlarged fragmentary, axial sectional view of the burner means shown in Figure 2; and

Figure 4 is a view similar to Figure 3 showing a modified burner means.

Describing the invention in detail and referring first to Figure l, a conventional open hearth furnace is somewhat diagrammatically illustrated at 2, although it will be understood that the invention is equally applicable to other types, such as electrical furnaces.

One of the novel burner devices generally designated 4 is inserted through an opening in each end wall 6 of the furnace above the adjacent end of the hearth 8 which is adapted to receive a charge (not shown) as hereinafter described. The burner 4 is supported by an adjusting bracket IIl hereinafter described in detail.

It may be noted that the furnace 2, which is of conventional design is provided at each end thereof with a downtake flue I2 adapted to discharge outiiowing gases into a chamber I4 communicating with a flue I5 which discharges into a stack (not shown). The ue I5 is provided with the usual checkerwork at I6 by which heat of outflowing gases is absorbed to be later irnparted to air entering the furnace 2 as will be understood by those skilled in the art.

Referring now to Figure 2 which is an enlarged fragmentary view of the structure shown in Figure l, it will be seen that the burner d comprises a. pair of tubes I8 and Z0 mounted in the bracket I8, which is provided with a shaft 24 connected thereto and threaded into a handwheel 26 rotatably mounted in a bearing 28 supported by the end wall 6 of the furnace 2. Thus as the shaft 2d is moved up and down by rotation of the handwheel 2S the tubes I8 and 20 are adjustably rotated in unison about their fulcrum points 3l) and 32 respectively where they are supported within diagonal openings Sd and 36 of a hollow frame 3l having a water inlet 38 and a water outlet 40. It will be understood that the tubes I8 and 20 are loosely mounted in the bracket to accommodate the limited rotation necessary for adjustment in service.

As shown in Figure 3, the tube I8 comprises a front section 42 and a rear section 44 removably attached as by bolt and nut assemblies 4B. The rear section comprises a mixing chamber 48 connected to fuel oil line 50 and a superheated steam line 52, whereby the oil and steam are mixed under any desired pressure in the chamber 48 and are discharged through a pipe 511 into the furnace. The rear section 44 of the tube I8 `also comprises a passage or conduit accommodating a pipe 56 having a container 58 (Figure 2) of powdered catalyst, such as iron, connected thereto by a port 68 in a fitting 82. A compressed air line is connected to the fitting t2 and to the container 58 as at 5l beneath a plate 59, to blow the powdered catalyst from the container 5B and discharge the powder into the furnace through the pipe 56. Pipe 56 extends loosely within pipe 55. Pipe 68 constitutes a compressed air line which discharges compressed air into pipe of the tube I8 to pick up the catalyst powder as it leaves tube 56 and diffuse it as it enters the furnace.

The front section 42 of the tube I3 comprises radially inner and outer annular chambers 68 and 'I0 respectively, interconnected by ports 112 at the forward end of the tube, said chambers being connected to water inlet and outlet ports 'I3 and 14, respectively, by means of which coolant water may be circulated through said chambers.

The `lower tube 20 of the burner 4 comprises inner and outer annular chambers 16 and 'I8 interconnected at the forward end of the tube 20 and connected, respectively, to inlet and outlet conduits 80 and 82 for coolant water; and an oxygen pipe 84 extends centrally through the inner chamber 'I6 for delivering substantially pure oxygen to the furnace under any desired Referring now to Figure 4, a modified burner is shown wherein parts corresponding to those of Figure 3 are identified by corresponding numerals. In Figure 4 it will be seen that the top tube i8 contains two mixing chambers 48 each connected to a discharge pipe 54, an oil inlet line 50 and a superheated steam inlet line 52; and the bottom tube 20 contains the catalyst discharge pipe 56 extending through the oxygen pipe 84, to discharge the powder into the furnace at the forward end of the tube 20 where the catalyst and the pure oxygen from the pipe 84 are mixed as they enter the furnace.

It may be noted that the novel process hereinafter described may be used in connection with the melting of iron and any alloys thereof, such as for example stainless steel alloys; and the process although described in connection with an open hearth Jfurnace may be also used in other types of melting devices such as electric furnaces, wherein the electrode would preferably not be lowered until the novel process hereinafter described had leveled the charge.

In general, it has been discovered that by forcing oxygen of high purity and a powdered oxidizable material such as powdered iron, together with a flame fed by any of the conventional fuels such as fuel oil, pitch, natural gas, or blast furnace gas (or a flame of an electric arc, in which case the fuel would be electricity), the charge may be leveled in about ten percent of the time normally required, whereupon the oxygen and powder may be discontinued and the heat continued by the fuel flame alone until ready for pouring.

Any one of the following metallic exothermic materials has proved effective, because they iinmediately lundergo an exothermic reaction in the presence of oxygen at the melting temperature of the charge, as distinguished from materials which must undergo a roasting period before they are resolved into components capable of undergoing an exothermic reaction under these conditions. Preferably these exothermic materials are in the form of fine powder, passing wire screen having 200 mesh per square inch, although coarser powder may be used with diminished effectiveness, the maximum size of grain being that capable of passing a screen having 100 mesh per square inch. For the purpose of this disclosure the term #metallic materials shall include silicon.

1. Iron of high purity 2. Cast iron 3. Iron and silicon mixture in any ratio 4. Iron, calcium, manganese, and silicon in any ratio 5. Iron, calcium, manganese, silicon and aluminum in any ratio The theory of the phenomenon is that the powder acts as an accelerating medium by burning to an oxide. This reaction is, of course, exothermic, producing a few thousand B. t. u. However, this small amount of added heat could I not be responsible for the unusual acceleration of melting, because the additional heat, if proe duced by an increase of fuel and oxygen, will not produce this result.

Theoretically one cubic foot of oxygen will oxidize 0.3 pound of iron producing about 600 B. t. u. from 200 pounds of powder, yet it has been found that about 4,500,000 B. t. u. are required to process one ton of steel. It has also been discovered that after a temperature of 2700o F. is reached, about 5% of the charge must be oxidized to provide heat to melt the remainder, much of this oxide being later reduced to metallic iron by the ore boil.

Thus according to the present invention, I have discovered that the initial oxidization of the powder accelerates the reaction:

2 Fe (5% of charge) plus O2 2 FeO which produces suflicient heat to transform the remainder of the charge from thesolid to the molten state.

After the charge is under cover, that is when the charge is melted level and a slag begins to form, the oxygen and powder are discontinued. This is the beginning of the refining period which is not affected by the novel process. As is known, during the refining period the slag is intermittently fluXed with calcium fluoride and calcined lime to remove undesirable elements such as phosphorus and sulphur. Either iron ore or lanced oxygen is employed in the usual manner to remove carbon to the desired tapping range. On completion of the refining period which ordin narily is completed within about two hours, molten metal may, if desired, be deoxidized by any of the usual agents, such as l5 ferro silicon, ferro manganese, or Silico-manganese.

One example of the novel process as applied to a 61,000 pound charge in an open hearth furnace follows:

1. The furnace was charged in about 35 minutes. This step included placing a protective layer of flat scrap on the bottom of the hearth, then placing a layer of lime on the flat scrap, and then charging the balance consisting of scrap and pig iron. An oil ame atomized with superheated steam was applied by the burner tube i8 to the scrap and pig iron for the purpose of preheating as it was charged on top of the lime. Oxygen at a pressure of 100 p. s. i. was discharged by pipe 84 during the last 14 minutes of the charging period, to obtain a higher degree of preheat.

2. Immediately upon completion of the charge, oxygen was forced into the furnace through pipe 84, and powdered iron of high purity was forced through pipe 56 by compressed air in line S4 at a pressure of the order of ninety pounds per square inch. At the end of thirteen minutes the charge was melted level and a molten slag had formed over the top of the metal.

3. The balance of the heat constituting the reiining period was completed using an oil flame only, and the oxygen and iron powder was discontinued.

Total oxygen time 27 minutes Total oxygen consumpticn 5,530 cubic feet Oxygen rate 13,000 cubic feet per hour Total iron powder tirne r 13 minutes Total iron powder consumptionpounds Iren powder rate 7.3 pounds per minute It will be understood by those skilled in the art that ordinarily about two and one half hours A are required to melt the charge level and thus' a it will be seen that the above described process reduces this period of the heat to about ten percent of the time formerly required.

Similar results have been obtained using the other agents heretofore described, and I have found that any powder which will immediately oxidize at l000 F. will greatly reduce the melt ing time.

I claim:

1. In a method of refining a charge of ferrous metal or alloy thereof, in a metallurgical furnace, the steps of first inserting said charge into the furnace, then melting sai-d charge by heating it to the melting temperature thereof While simultaneously directing against said charge a stream of substantially pure oxygen and a stream of powdered iron and then after the charge has melted substantially level terminating the flow of oxygen and powdered iron while refining the charge by continuing to heat the same.

2. A method of refining ferrous or alloy thereofcomprising inserting a charge of said metal or alloy into a furnace, then melting the charge by directing a llame, a stream of substantially pure oxygen, and a stream of powdered iron against the charge and then after the charge is melted level terminating the streams of oxygen and powdered iron while continuing to heat the charge With said flame until the charge has been refined.

3. In a method of refining a charge of ferrous metal or alloy thereof in a metallurgical furnace, the steps of first inserting said charge into the furnace, then melting said charge by directing a name against said charge While simultaneously directing against said charge a stream of substantially pure oxygen and While simultaneously directing against said charge a stream of exothermic metallic powder which immediately undergoes an exothermic reaction at the melting temperature of said charge in an amount which is sufficient to reduce 'the melting time of said charge, and then, after the charge has melted substantially level, terminating the flow of oxygen and powder while refining the charge by continuing to heat the same With said flame.

LOREN L. WHITNEY, JR.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 103,940 Menne July 1, 1902 968,350 Harrison Aug. 23, 1910 1,030,152 Barbansen et al. June 18, 1912 1,825,841 Zifferer Oct. 6, 1931 2,182,498 Longenecker Dec. 5, 1939 2,286,191 Aitchison et al, June 16, 1942 2,362,085 Morgan Nov. '7, 1944 2,446,511 Kerry et al. Aug. 3, 1948 2,451,422 Wagner Oct. 12, 1948 2,466,258 Morgan Apr. 5, 1949 2,470,999 Meincke May 24, 1949 2,491,440 Bodecker Dec. 13, 1949 2,515,670 Slottman et al July 18, 1950 OTHER REFERENCES Open Hearth Proceedings, vol. 31, pages 91 to 94, inclusive. Published in 1948 by the A. I. M. E., New York, New York.

Claims (1)

1. IN A METHOD OF REFINING A CHARGE OF FERROUS METAL OR ALLOY THEREOF, IN A METALLURGICAL FURNACE, THE STEPS OF FIRST INSERTING SAID CHARGE INTO THE FURNACE, THEN MELTING SAID CHARGE BY HEATING IT TO THE MELTING TEMPERATURE THEREOF WHILE SIMULTANEOUSLY DIRECTING AGAINST SAID CHARGE A STREAM OF SUBSTANTIALLY PURE OXYGEN AND A STREAM OF POWDERED IRON AND THEN AFTER THE CHARGE HAS NITROGEN, MELTED SUBSTANTIALLY LEVEL TERMINATING THE FLOW

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