US2611693A - Method for refining molten metal - Google Patents

Description

Sept. 23, 1952 w. T. GEYER METHOD FOR REFINING MOLTEN METAL I Filed. March 51, 1948 I0 75 I I 39 III I 30 ll j I, I

I I 7 BY Patented Sept. 23, 1952 UNITED STATES PATENT OFFICE 'METHOD FOR'BEFINI NG MOLTEN METAL Wallace Thomas Geyer, Mount Rainier, Md.

' Application'March'31, 1948, Serial No. 18.183 p '1 Qlaim. (CI. 75-58) My invention has for its primary-object'to pro-' 4 or which can be cast directly'into ingots preparatory to rolling. drawing, .or forging.

My invention also .comprehends the method of operating a .suitable apparatus by means of which the foregoing may be accomplished expeditiously in an economical manner in batches received directly from a blast furnace and according to the output desired.

To. these and other ends my invention comprises .further' improvements and advantages as will be'further described in the accompanying specification, the novel features thereof beingset forth in the appended claim.

Int-he drawing: v v

Figure I is. a sideelevation of a retort or'crucible shown partly in ,section illustrating one meansjby'which my invention may be carried out.

Figure 2 is an enlarged vertical section the discharge end of the retort.

Similar-referencenumerals", int-he several figures, indicate "similar parts.

In carryingout my invention I employ a rotary vessel of heavy construction, such as shown in Fig. 1, comprising anouter circular metallic shell having-sidewalls l-li sloping upwardly and outwardlyfrom a comparatively restricted bottom H provided with-a controlled recess I21 "The inner surface of the side walls and the bottom are protected by a refractory lining [3, the area of the bottom surrounding the opening l2 being dish" shaped, or depressed somewhat, as indicated at 1'4, below the upper or inner end of said opening to form asurroundi-ng' shallow well. Exten-ding over the upper end-of the vessel is a hood-havinga depending-rim t5 and a conical top IBfrom the'center of which is an upwardly extending stack- H containing an exhaust fan l8;. At one side of-the hood is a charging funnel IS having a spout Zfldischarging close to one side of the vessel.

Extending downwardly from the'hood are arms 21 forming a frame work carrying a guide 22 in which is a vertically movable rod 23 which may be raised and lowered by means of a cable 24 trained over a pulley 25 also carried within the hood. The rod carri s at its lower en a showing pointed plug or-stopper 26 designed to control the outflow of materials through the'opening I2.

I support the retort for'high speed rotary movement on a frame work 30, its weight being carried on-a bottom ring 3| and an intermediate ring 32 with relation to each'of which are cor-- responding rings 33 and 34 on said'frame. The latter each comprise channels inwhich the rings 3| and 32 are centered in 'Babbitted bearings whereby not only is the weight of the retort carried on suitable bearings which also serve to prevent its lateral displacement. The upper supporting ring 32 also comprises a laterallyprojecting horizontal portion which isrprovided with bevel gear teeth 38 to which power is imparted by a bevel pinion 39 on a shaft 40 driven by a motor 4|.

The retort operates as a centrifuge. It is preferably charged while at rest .by pouring therein through the funnel l9 a quantity of molten pig iron, received in the state in which it flows from the blast furnace, suflicient to partially fillyit to approximately the level indicated by the line A. As the rotary speed of the retort increases the liquid metalmoves upwardly along the sloping inner sides of the vessel: generating a paraboloid of revolution B. This action, due to the centrifugal power generated in the molten metal, may be derivedfrom Newtons equation.

F=Ma

where F is the force, M the mass, and a-the acceleration.

In practice I increase the rotary speed oithe 1 vessel until such time as the .shape of the inner surface B of the metal at. the bottom coincides with theopening of the central-orifice 12. Thereafter the speed is maintained constant during the time required for treatment.- of thebatch, or charge, in the manner now to be explained.

It will be realized that this high speed of the retort imparts a force to the: molten metal which causes the pure iron particles in the molten mass to move outwardly thus displacingv the lighter impurities which may be classified generally as compounds andparticularly as those impurities which may remain in pig iron after the slag; has

been tappedoii These impuritiesttogether with occluded gases, I cause. to be displaced inwardly to the inner facesof the paraboloid. When these impurities arrive at this pointthey will flow downwardly while the eruptinggasesthus re- 3 leased to the air are exhausted upwardly through the stack IT.

The foregoing action may be represented by the following formula in which An represents the normal acceleration of the pure iron particles which exerts a reaction outward force serving to drive the lighter impurities inwardly. Assuming the vessel to be rotating at a constant speed.

V the velocity=rw, the latter character repre-' senting the angular velocity created; r being the radius of the vessel. Wherefore An=rw Substituting this in the previous formula where F:Ma the resultant becomes FzMrw showing that the force applied to the mass introduced into the retort is directly dependent upon the character of such mass, and the distance separate particles thereof are removed fromthe axis of rotation. Hence, the lighter a particle the less is the resultant force tending to move it outwardly.

When the paraboloid of revolution is created the slag or lighter particles are erupted, or displaced by the heavier pure iron and as they exude become subject to the action of gravity according to the formula:

where y represents the exuded light particles above the vortex; w the angular velocity; 1' the radius of the vessel, and g the acceleration due to gravity.

The undesired impurities are allowed to escape via the central passage l2 which is opened by elevating the stopper 26.

The second step in carrying out my invention comprises reducing the metallic free iron which I have purified, up toa certain point, as above described by still further removing from it the combined impurities to render it capable of conversion into an alloy. Generally this second step is accomplished by the addition of a more active element or compound to the free iron while the mass is still at the high velocity which maintains its inner surface as a paraboloid.

In carrying out this step of the process I melt a proportional quantity of aluminum and slowly pass it into the funnel l9 the off center spout 20 of which discharges it against the surface B of the molten iron. It will be seen that the aluminum due to its light weight will gravitate slowly along the surface of the molten iron during which time various chemical reactions with the aluminum occur viz.

(a) It, the aluminum, reduces the remaining or ferric oxide oxygen in the mass of iron leaving free iron and A1304.

(1)) It combines with sulphur converting it into aluminum sulphide.

(c) It combines with the phosphorus forming aluminum phosphide.

(d) Residual gases which are being continued to be expelled from the iron will be absorbed by the molten aluminum.

(e) It combines with the excess carbon creating A14C3.

(f) After the above reductions have taken place other complex compounds of aluminum and iron will occur and these are likewise removed.

The above chemical reactions are known to produce heat and this is a desirable factor as they tend to maintain, rather than reduce, the temperature of the body of metal undergoing treatment.

When, either empirically, or by observation, it is determined that the reactions have been completed the unwanted expelled compounds are allowed to escape through the bottom exit [2 in the same manner as before described with reference to the slag. Thereafter the stopper 25 is replaced and the vessel is allowed to come to rest.

Since the molten mass has now been freed of substantially all impurities the batch is ready to receive such additional constituents as may be required to convert it into steel of the desired quality, or any desired alloy, following which it may be discharged from the retort and cast into ingots preparatory to forging, rolling or drawing processes.

It will be noted that a particular advantage results from practicing my invention in that since I am able to remove the impurities existing in the pig iron asit is received from the blast furnace'to such a, substantial extent that at the time when the alloying materials are added it is unnecessary to use any of the counter acting effect substances currently employed in the production of metal alloys.

A still further advantage I am able to obtain results from the fact that the treatment of the molten iron is accomplished without the necessity of maintaining a constant heat under the retort. This is primarily due to the speed with which the impurities are removed and secondarily because of the reaction occurring when the melted aluminum is added which serves to raise the temperature of the mass.

More or less frequently in the treatment of batches of pig iron they will contain a small percentage of other elements or compounds which molecularly are heavier than the iron particles. These are deemed inconsequential for all practical purposes and commercially no attention is paid to them, however, in order to eliminate any possible effect they might have on occasion in the practicing of my invention I provide means in the retort for segregating them. Observing Fig. 2 it will be seen that the inner end of the outlet 12 is elevated slightly above the surrounding bottom of the retort. This arrangement forms a shallow circular depression, or well, in which such heavier substances may be trapped during the rotation of the vessel and as the surface of the well is curved it will be seen that when the batch as a whole is permitted to escape such heavier elements will be held in the retort, from which they may be subsequently removed separately.

Iclaim:

The method of producing substantially pure iron consisting in centrifuging a mass of molten iron to create an inner paraboloid face thereon, then reducing all compounds of iron in said mass by continuously applying molten aluminum to the upper edge of said paraboloid face allowing said molten aluminum to gravitate slowly along the surface of the revolving mass whereupon said molten aluminum reacts with all compounds of iron in the mass to form the free iron metal, and removing the aluminum compounds from the bottom of the paraboloid face.

WALLACE THOMAS GEYER.

(Refer nc s on following page) Number Name Date REFERENCES CITED 1,332,585 White Mar. 2, 1920 The following references are of record in the 1,347,741 Hadfield July 1920 file Of this patent: 1,635,513; Maxmofi e1; a1. Aug. 21, 1922 5 2,0 Ben er e a Nov. 6, 93 UNITED STATES PATENTS 2,128,444 Vroonen Aug. 30, 1938 Number Name Date 2,134,905 Bampfylde Nov. 1, 1938 196,204 Eaton Oct. 16, 1877 2,355,362 Campbell Aug. 8, 1944 399,117 Adams, Jr., et a1. Mar. 5, 1889 2,355,885 Merle Aug. 15, 1944 433,142 Peck July 29, 1890 10 2,395,286 Merle Feb. 19, 1946 811,522 Seaman Jan. 30, 1906 2,507,490 Cohen May 16,1950

1,196,829 Wescott Sept. 5, 1916

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