US2343842A - Method of coating ingots - Google Patents

Description

March 7, 1944.

G. R. HATCHER 2,343,842

3nnentor Patented Mar. 7,1944

UNITED *STATES? PATENT OFFICE 2,343,842 ME'rnonoF coarmo moors George R. Hatchet, Youngstown, Ohio, asslg nor to The Mahoning Paint and Oil Company, Youngstown, Ohio, a corporation Application September 5, 1942, Serial No. 457,383

' 6 Claims. (Cl. 22-192) This invention relates methods for casting ingots, and the like, and is concerned with methods for materially extending the life of ingot molds, and with methodsfor noticeably improving the character of the ingots cast in the ingot molds. 1

It has been proposed heretofore to coat the inside of an ingot mold prior to casting an ingot therein. In the commercial practice these methods have been limited .to substantially the dry '10 pitch or sugar dusting method and to the liquid tar blowing method. In the dry pitch or sugar dusting method one man inserts a regular ai-r hose into the mold and swings the hose around and around to agitate Ithe air, and at thesame l5 timeganotherman dusts dry pitch or sugar into the molds with a dipper; The molds must be hot enough to melt the pitch or sugar onto the mold surface. However, if the mold is too hot the pitch or sugar burns away leaving only a car-' 2 bonaceous residue which is injurious to an ingot, surface, and with the steel of'the ingot very possibly absorbing the carbonaceous residue to alter the chemical characteristics'of the steel ingot. If the mold is too cold the pitch or sugar 25 will not be deposited on the mold but will collect A in a large puddle at the bottom of the mold (as it sometimes does even though the mold is of the proper coating temperature) and this puddle of mold coating material at the bottom of the mold will splash and-even explode when the molten steel is first poured into the ingot mold, and thereby provides a very dangerousand unsatisfactory condition. In any event, the very haphazard coating achieved by the procedure just described invariably resultsv in a non-uni-. form coating on the ingot mold surface even though the ingot mold is of exactly the proper temperature to melt the dry pitch or sugar without burning. Uneven coating on the ingot mold surface results in a non-uniform action on the ingot cast with too much-coating material in some parts of the ingot ,mold and too little coating material in other parts of the mold.

The liquid tar blowing method of coating ingot molds also requires the services of two men,

one to insert the end of a hose into a bucket-of heated tar and to control the supply of hot tar, and the other to handle a blow pipe adjacent the mold and through which compressed air is 69 passed. The hose from the tar bucket'is con nected to the blowpipe so that the passage of air through the pipe causes a suction in the hose from the tar bucket to pull tar into the blow pipe.

The blow pipe is inserted into the ingot mold and 66 moved around therein to efiect a coati'ngoperation, and the tar hose is inserted into the pail of heated tar intermittently causing a bubbling and intermittent type of 'flowof tar in the tar hose. The result is a. non-uniform and uncontrolled type of coating action with the emission of vary 1 considerable smoke and oiIensive fumes. In this method of liquid tar blowing an atomizing or spraying action is not achieved, but the air blown through the blow pipe merely serves to scatter the tar around. One very definite fault of this liquid tar blowing method is that thecoating applied is much too heavy, and in this connection I have found that a very thin coating is decidedly superior to a thick coating which may have an adverse gaseous bubbling action and which may alter the chemical analysis of the ingot cast in -the coated mold. This is; particularly true in dead-killed steels and in the higher alloy steels.

Problems of too hot or too ,cold ingot molds adversely affect the liquid tar blowing method of coating ingot molds, and with the molds too hot the liquid tar may be burnt ofl to form a carbonaceous residue which is'undeslrable for reasons discussed above. If the molds are too cold the liquid tar may not properly adhere to the inner surface of the mold. hi any event, and in the practice of the described-methods of'ingot mold coating several steel companies have gone so far as to build ingot molds preheating plants for bringing the ingot nrolds to exactly the dean insufficient number of ingot molds available the usual result is that the lngotmolds must be used to cast additional ingots so soon after previous casting operations that the ingot molds never return to atmospheric temperature. It is possible to coat ingot molds with the known methods if the ingot molds do not exceed temperatures of approximately 350 degreesFahren- =heit. However, in large steel production operations many of the ingot molds are being returned to be used for casting with the ingot molds at temperatures of over 350 degrees Fahrenheit. It

is substantially impossible to coat ingot molds with known methods when the ingot mold has a temperature of more than about 350 degrees Fahrenheit. It is therefore necessary to allow the mold temperature todrop by natural cooling or lay-artificial means to a temperature below 350 degrees Fahrenheit if the ingot mold. is to be coated, or, as is often done, the coating operation is dispensed with and the steel. is cast directly in the uncoated ingot mold. It is now well understood that ingot mold life is materially reduced if the mold is not coated.

It is the general object of my invention to avoid. and overcome the foregoing and other difliculties of and objections to known ingot mold coating methods by the provision of an improved ingot mold coating method for quickly and umformly coating an ingotmold whether hot or cold.

Another object of my invention is the provision of an ingot mold-coating method whereby the ingot mold can be properly and uniformly ness on the ingot molds. Another object of my invention is the provision of a method of coating an ingot mold in less'than about 30- seconds and so that each square foot of mold surface has deposited thereon. less than about .01" pound of coating material. i v

Another object of my invention is the provision of'a methodof coating ingot molds and the like andwhereby the coating material is atomized and directed to coating position byv aninert gas,,such as carbon dioxide, so as to materially reduce the-burning oif of the coating at elevated mold temperatures.

Another object of my invention is the provision of a method of coating an ingot mold wherein the air normallywithin the ingot mold' is displaced by an inert gas and then the entire mold Su "m'ateriaLfl is sprayed with atomized j coating "Another" object of my invention is the pro- 'vision of a ,mold coating method including the steps of spraying atomized coating material in the form of substantially a circular cone and efiecting relative movement between the axis of the cone and the axis of the mold to uniformly coat the entire mold surface.

I Another object of my invention is the provision of. a mold coating method which can be .quickly' and uniformly practiced by a single operator, and which substantially eliminatessupplemental mold heating or cooling equipment. The foregoing objectsof my invention, and other objects which, will become apparent as the description proceeds,- are achieved by the provision of a coating method which includes the steps of standing the ingot mold upright, atomizing a liquid coating material with a gas, directing the atomized liquid coating material with the with an inert gas heavier than air, such as cartypical apparatus adapted to practice the method of my invention; and Fig. 2 is a side elevation rather diagrammatically indicating the manner of practicing the method of ,my invention.

Having particular reference to the drawing, the numeral I6 indicates generally a storage tank for storing the liquid coatingmaterial. I

should say here that the principles of my'invention are broadly applicable to the handling and depositing of an ingot mold surface of any of a wide variety of coating materials. However,

- the method of my invention is best practiced in conjunction with the improved coating material including pigment, resin, drying oil, and thinner, all fully disclosed and claimed in Harold A. Kelly Patent No. 2,289,709. Associated with the storage'tank l0 may be any suitable agitating mechanism l2. The storage tank I0 is adapted to be connected by a suitable conduit l4, usually of flexible character, with any atomizing and spraying apparatus indicated as a whole by the numeral l6. 5

The apparatus l6 includes a long handle portion formed of a pair of pipes I8 and 20 connected together by clips 22 and a casting 24 so that the pipes l8 and 20 are held in parallel relation. The conduit I4 is connected to the pipe 20 and the pipe 20 in turn extends to a spray gun 26 of the atomizing type and controlled by a trigger". The spray gun 26 has a long nozzle portion 30 terminating in a discharge head 32. The nozzle 30 is approximately as long as the depth of the ingot mold to be coated, for example, usually about 6 feet. The pipes l8 and 20 connected to the gun 26 are generally about 4, feet long, and are positioned, as shown, at right angles to the nozzle 30 so that the apparatus is adapted to themold coating operation, as hereinafter particularly described.

The pipe I8 is connected to the spray gun 26 in the manner shown, 'and at its other end is connected to a conduit 34 of flexible character which in turn extends to a suitable source of gas under pressure. If the gas employed is air the conduit 34' will be connected to the usual air supply line (not shown) in the plant where the equipment is used. If the gas employed is carbon dioxide or other inert gas the conduit 34 extends, as illustrated in the drawing, to a gas transformer36 adapted to control the pressure of gas flowing to the conduit 34. The gas transformer 36 is connected to a suitable gas storage atomizing gas so as to form a fully circular subtank 38 which may or may not have a conduit 40 extending to a source of additional gas.

The trigger 28 of the spray gun 26 is conveniently controlled by a rocking lever 42 pivoted to the pipe 26 andconnected by a pull rod 44 to a handle 46 pivotally secured, as at 48 to a bracket 50 extending up from the casting 24.

Turning now to Fig. 2 of the drawing, the nu- 1 coating. operation.

7 material in the dried on state, and usually about meraliO-indicates an ingot mold, partly brokenaway in section, adapted to be treated by the coating" method of my invention. The ingot mold 50 is carried in an upright position upon any suitable type ofilat car, drag, or dolly 52, and usuallyadapted to mount a plurality of molds along in side by side relation. Ordinarily,-a plurality of the fiat cars 52 are connected in end to end v relation for movement along a track 54 which runs parallel to an elevated platform 56 so that once a row of ingot molds 50 have been moved into position along side of the platform 56 an operator can walk along the platform and perform a mold coating operation upon eachingot mold in turn. Fig. 2 illustrates gen- 1 erally the manner in which an operator will employ the apparatus of Fig. l to achieve amold Specifically, the operator grasps the handle portion of the apparatus provided by the pipes l8 and 20 and holds the handle portion substantiatlly horizontal to the ground with the nozzle portion 30 of theapparatus extending in a substantially vertical position. Now I the operator will position the nozzle 30 axially of the ingot mold cavity and will move the head liquid coating material and to spray the atomized coating material against the ingot mold cavity surfaces that a very definite'flash resistant resuit is obtained. I believe that this result is due to the fact that the atomized liquid coating mate'riai is substantially surrounded by and directed by the inert gas which excludes .the presence of air or oxygen from contactwiththe liquid coating material so that it can be deposited upon ingot mold cavity walls even though thesecavity walls are at temperatureswhich would be suillcient to flash or ignite the coating material if air or oxygen .were preesnt adjacent the material.

Further,, l2 believe that the inert gas used to.

atomize and direct the coating material against the ingot mold walls is absorbed to a considerable extent in the liquid coating material and "is, in fact, deposited therewith so that the inert gas acts as a deoxidizer and makes the burn ofi perature of a coating materialhigher. In other 3.2 of the nozzle down to the bottom of the mold. Thereafter the operator will depress the handle-46 to o gun 26 and the apparatus will throw a fully circular substantially conical or u'mbrellalike spray of finely atomized liquid coating material out against the sides of the ingot mold: Theo rator will then raise the apparatus to eifect'relative movement of the nozzle with respect to the axis of the mold, and preferably the apparatus is raised by the operator at a speed so that theentireinner surface of the ingot mold is coated in less than about 30 seconds. The apparatus is adapted to very finely atomize the liquid coating material with the gas from the storage chamber 38, and with the same gas being used to direct the ,firlely atomized liquid coating material against the inner walls of the ingot mold being coated. The speed of movement of the atomizing and spraying apparatus with respect to the inside of, the. mold is such that no square foot of ate the trigger 28 of the' spray words, the relatively thin layer of uniformly applied coating material of my invention does not burn ofi of the ingot mold surface in advance of the molten steel vin the same way that results with other moldcoating materials and applied by different methods.

When operating upon ingot molds having relatively high'residual temperatures prior to coating. for example, temperatures of over 350 degrees Fahrenheit, and up to or over 800 degrees Fahrenheit, it is naetimes advisable to displace the air ingot mold surface receives morethan about .01

pound and never more than .015 pound of coating .005 pound of coating material per-square foot of ingot mold surface.' I have found that one gal-' I Ion of the improved liquid coating material 'disclosed and claimed in Mr. Kelly's-above identitreated with a gallon of'coatmg materiaivto b 60' castingioperation sothat substantially no inert from the inside of the .ingot mold by an'inert gas prior to coating the'ingot molds. This may be ac larlycontemplate directing the inert gas into the ingot mold by means of the apparatu IS with the apparatus being 'adlusted sothat no liquid coating material is atomized andinjected into the ingot mold until a considerable proportion of the air in the ingot mold has been] displaced by the inert gas, usually, an inert gas having a greater specific gravity than air; for example carbon dioxide. Again, I may-introduce into the ingot mold antadditional conduit which will displace the air from the inside of the ingot mold prior to'the atomizing and spraying of the ingot mold with the liquid coating material. Finally, I may throw several, pieces of dry ice, solidified carbon, dioxide, into the bottom of-each ingot mold a minute-or so prior-to atomizingv and, spraying a liquid coating on the ingot mold surfaces.

When inertg'as'is employed to atomize and spray the coating materlai'or when inert gas is used to "displace the airlnside of the mold prior to coating or when a combination of these methmore or leSsthan-the last indicated number.

- or' explosion.

ods is employed I usuallyposition a sheet of metal over the top of the ingot mold until the ingot gas will escape from the moldbefore ingot casting. This further eliminates any possible flash From the foregoing it'will be recognized that so that t e act al sp a i e per each in o t5 the various objects of my invention. have been mold is often closer to 15 seconds than to 30.

The method and apparatus just described is adapted to'be employed with'airzas the atomiz ing gas when performing coating operationson grees Fahrenheit. In operations upon ingot moldsv havingtemperatures of greater than 350 degrees Fahrenheit, and up to about 800 degrees Fahrenheit'or more, the atomizing gas employed is an achieved by the provision of an improved, relatively whereby a single operator can uniformly and efliciently' coat a large plurality of ingot molds. ingot molds below temperatures oflabout 350 de- (0 The ingot mold canv b uniforml d properly coated substantially irregardless of the ingot inert gas, such as carbon dioxide. I have found 16. atures of 800 degrees Fahrenheit or even more,

that when employing an inert gas to atomize theemv hieved in a plurality of ways, but I particu-- inexpensive, easilypracticed; method I A very finely-divided and atomized coating is provided of relatively thin but uniform character over the entire mold surface which not only eifects an economy of coating material but which '1 has been found to be definitely superior to relatively thick non-uniform coatings and t'o'avoid in uncoated molds or produced inmolds coated by the dry pitch or sugar dusting method or by the liquid tar blowing method. In fact, the savings resulting from the improvement in cast ingot quality have been found to pay many times over for the mold coating, costs.

Whil in accordance with the patent statutes I have specifically illustrated and described at least one embodiment of my invention, nevertheless it is to be particularly understood that I am not to be-limited thereto or thereby, but that the scope of my invention is defined in the appended claims.

I claim:

1. That method of coating ingot molds which includes the steps of standing the ingot mold upright, atomizing a liquid coating materialwith an inert gas, directing the atomized liquid coating material with the atomizing gas so as to form a fully circular substantially conical fine spray, efi'ecting relative movement between the spray and the ingot mold axially oftthe mold and at a speed so that substantially the entire inner surface of the ingot mold i coated in less than about 30 seconds and each square foot of mold surface has deposited thereon less than about .01 pounds of coating material.

2. That method of coating ingot molds which includes the steps of standing the ingot mold upright, atomizing a liquid coating material with an inert gas, directing the atomized liquid coating material with theatomizing gas so as to form a fully circular substantially conical'flne spray, and effecting relative movement between the spray and the ingot 'moldaxially of the mold.

3. That method of coatingingot molds which includes the steps of standing the ingot'mold upright, atomizing a liquid coating material with carbon dioxide gas, directing the atomized liquid'coating material with the carbon dioxide gas so as to form a fully circular spray, moving the spray upwardly through the ingot mold at a speed so that each square-foot of mold surface has deposited thereon less than about .01 pound of coating material.

4. That method of coating molds which includes the steps of atomizing a liquid coating material with an inert gas, directing the'atomized li'quid coating material with the inert gas so as to form aspray, and effecting relative movement between the spray and the mold to coat the surface ofthe mold.

5. That method of casting an ingot which includes the steps of standing an ingot mold upright, displacing the air fromv the mold cavity by an inert gas, atomizing a liquid coating material with an inert gas, directing the atomized liquid coating material with the atomizing inert gas through the inert gas in the mold cavity and against the mold cavity surface to form a coating thereon, covering the ingot mold to prevent the escape of inert gas from the cavity thereof until the ingot is cast, removing the cover, and casting molten metal in the mold.

6. That method of coating an ingot mold which includes the steps of standing an ingot mold upright, displacing the air from the mold cavity by an inert gas, atomizing a liquid coating material with an inert gas, directing the atomized liquid coating material with the atomizing inert gas through the inert gas in the mold cavity and against the mold cavity surface to form a coating thereon.

GEORGE R. HATCHER.

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