US2241818A - Cinder pot - Google Patents

Description

Patented May 13, 1941 UNITED STATES PATENT OFFICE Y claman Por William4 Johnston, Jr., Wilkinsburg, Pa. Application December 4, 1940, serial No. 368,417

(ol. aes-ss) 2 Claims.

'Ihis invention relates to vessels adapted to vreceive molten slag from the making of iron and steel, and which I herein generically term cinder pots.

These cinder pots. which are themselves iron or steel castings, receive the slag either directly from a furnace or from a ladle, and usually retain it until the slag solidies. In that service, and this is particularly true of cinder pots which receive the slag formed in open-hearth steelmaking furnaces, some molten ferrous metal is frequently carried into the cinder pot with the molten slag. As the slag stands in the cinder pot for solidiflcation, this ferrous metal gradually drains to the bottom of the pot, where it forms a button of iron or steel. If, as often happens, this button of ferrous metal welds to the ferrous metal of the cinder pot wall to form a sticker," its removal is dilcult and sometimes causes injury to the cinder pot.

It is the object of my invention to provide in the bottom region of the cinder pots parting surfaces which are enduringly capable of preventing the ferrous metal which drains out of the slag from sticking in the bottom of the cinder pot, as the slag and the ferrous metal solidify.

This object I attain by equipping the bottom region of the cinder pot with a thin liner of a non-ferrous metal of relatively high melting point, which is capable of forming in the presence of the hot slag a protective coating of unctuous oxide, which provides a good parting surface and which adheres to the body of the liner to inhibit its destruction by abrasion or by alloying with the ferrous metal which drains from the slag. I have discovered that the non-ferrous metal copper, either in relatively pure state, or as alloyed in substantial proportion with other high-melting non-ferrous metals such as aluminum, tin, nickel and the like, has the ability under the conditions existing in a slag-filled cinder pot to form an unctuous oxide of that sort.

Accordingly I apply interiorly of cast iron and cast steel cinder pots, in their bottom regions, liners of copper. or the various copper alloys which in their variant constitution are known generally as bronze or brass, or other alloys of 4copper containing a substantial content of copper. Whereas the base walls of the cinder pots are relatively thick, commonly having a thickness of 2 to 4 inches, the liners may be quite thin. In fact I have employed liners from '/a inch down to i inch in thickness. In the cinder pot, and under the conditions of use of the cinder pot, I have found that these liners endure to provide eiective parting surfaces for bodies of iron and steel congealed against them for a great many fillings of the cinder pot. Apparently they will endure for approximately the en tire useful life of the cinder pot.

I am aware that molds, and mold parts made of iron and steel have been provided with liners of copper, nickel, aluminum, or chromium, to give castings having smooth and cleanly defined surfaces, and that such lined molds incidentally provide parting surfaces to facilitate stripping .the molds from ferrous castings made in them.

Experience has shown, however, that in molds for ferrous castings the liners must be renewed after but relatively few uses of each mold, or mold-part, carrying the liner. Whereas the expense of relinng molds and mold parts at frequent intervals may be permissible in making ferrous castings of the finer sorts, it is inadmissible in cinder pots. These latter are relatively rough cast vessels of great capacity, which are intended to receive material of low value, namely slag from the making of iron and steel. It would not be economical to protect these vessels, by applying to them relatively expensive liners which require frequent renewal.

It is a matter of surprise that a liner of suitable metal will endure for a long period of service in a cinder pot, although a liner of the same metal is rapidly destroyed in a mold for ferrous castings. 'Ihis I have found to rise from the fact that in the cinder pot there is an initial formation of unctuous oxide, which protects the metal of the liner from alloying with molten ferrous m'etal in the cinder pot. I have discovered that the reason for this effect lies in the copper oxide which is formed on the hner, this copper oxide being unctuous and adherent to the metal which it covers, rather than granular and readily detachable from it. In a mold made of ferrous metal, and used for the casting of ferrous metal, a. liner of copper, or copper-containing non-ferrous metal, does nol-I have an opportunity to acqulre a useful coating of copper oxide. This I have discovered largely to be because of the different properties of molten slag from iron and steel making and molten iron and steel hemselves. Thus, when it is teemed into a mold,

molten iron and steel are each at much higher temperature than the corresponding slag of that metal as itis poured into a cinder pot, and has each a heat content several times that of its slag. In molds for making ferrous castings heat dissipation is slow. Heat abstraction from the slag in a cinder pot is relatively rapid for the rst few hundred degrees drop in temperature, and the molten iron or steel draining from the slag is much lower in temperature than the same metal teemed into a mold.

Thus, in the normal use of cinder pots the liner forms an oxide coating which protects it against alloying with the molten ferrous metal, but in the normal use of a mold in making ferrous castings the liner is rapidly destroyed by such alloylng action, so that liners of copper, bronze and the like are no more enduring than vliners which are not inherently capable of forming a coating of copper oxide. Otherwise stated, I have discovered that in a cinder pot the conditions are such that a protective coating of black' cupric oxide (CuO) forms on the liner, while in a mold the liner is rapidly destroyed by alloying with the ferrous metal of the casting. I believe that in the cinder pots the gases carried by the slag, as well as the temperature conditions, favor the formation of a cupric oxide coating on the metal of the liner.

In the accompanying drawing Fig. I is an elevational view of a vessel illustrative of vessels of the sort I herein term cinder pot, with the wall of the vessel regionally broken away to indicate the highest level to which I nd it useful to line it. Fig. II is a fragmentary vertical sectional view, on a scale larger than that of Fig. I, showing the liner applied to the interior of the cinder pot wall, and in the condition in which it exists before the cinder pot is used to receive moltenslag. Fig. III is a view similar to Fig. II, but showing the condition of the liner with an adherent coating of copper oxide thereon, after the cinder pot has been used to receive molten slag.

In the drawing the cinder pot, designated gen'- erally by the reference numeral i, is shown as one of the specialized corrugated type, having a side wall downwardly tapered to a. rounded bottom; but it is to be understood that my invention may with equal advantage find embodiment in cinder pots of any otherwise suitable contour and wall arrangement. All the vessels which are used to receive slag from the making of iron and steel, and which I herein generically call cinder g pots, are hollow iron or steel castings in the form of hollow bodies, consisting of a bounding wall extending upwardly from a closed bottom, and are open at their upper ends. The heat of the molten slag standing in the cinder pots is dissipated from the upper surface of the slag, through the bounding wall, and at the bottom of the vessel.

' In Figure I the liner 2 is shown as terminated upwardly of the cinder pot at a line A, below which any normally encountered segregation of molten metallic iron or steel will lie. In Fig. II the liner 2 consists simply of the copper, or copper alloy, of which it is composed, the cinder pot being in unused condition. I have found that this fundamental liner structure may be applied to the inner surface of the cinder pot wall in a variety of ways. Thus it may be built up by deposition from a metallizing spray, may be formed by electro-deposition, or may be a pre` formed, bowl-like structure which is integrated with the cinder pot wall when the cinder pot is cast. If a preformed liner is made and applied in such manner, it is necessary that the mold for, casting the cinder pot be so arranged as to provide rapid heat dissipation from the preformed liner structure. Otherwise, the heat of the ferrous metal of which the cinder pot body is composed raises the temperature of the preformed liner to a stage at which it alloys with the ferrous metal of the cinder pot body. In following any of the ways in which the liner may be applied, it is very desirable to clean the relatively rough surface to which the liner is to be applied, as by grit-blasting and brushing.

Fig. III shows the metallic liner 2 on the inner surface of the cinder -pot wall, and a coating 3 of copper oxide formedfrom the metal of the liner and adherent tp its remaining metallic fil structure. I have found that this coating of black amorphous cupric oxide begins to form with the first use of the cinder pot, and increases in thickness with repeated use of the cinder pot up to a point at which no more oxide forms. As a precaution against loss of metallic copper by alloying with iron or steel which drains from the slag, I prefer that, in the first few uses of the lined cinder pot, the slag does not have a high content of molten metal, in order that the protective coating of cupric oxide be given ample opportunity to form Vbefore the metal of the liner is exposed to conditions which tend to promote loss of liner substance by alloying with the molten ferrous metal. This is a precautionary procedurepurposed to insure against reduction in the thickness of the liner substance rather than a matter of necessity.

It is to be noted that the cuprie oxide is dense, and is so firmly adherent to the underlying metal that it is removed only with difficulty. This density and adherence of the copper oxide coating is a property of primary importance, since it prevents dissipation of the metal of the liner by repeated formation and removal of oxide. The cpric oxide being an amorphous substance has a texture which feels and may be called "unctuous, and it forms a parting surface which is more effective than the initial metallic surface of the copper, or copper alloy, itself.

The effectiveness and endurance of a copper oxide coating in a cinder pot is astonishing. In several cinder pots having a capacity greater than 200 cubic feet, and which have been `filled with slag more than 1500 times in serving both blast furnaces and open-hearth furnaces,both the oxide coatingvand the layer of metal underlying it were found to be in a condition of perfect continuing utility. None of those lined cinder pots had suffered from a sticker" in the form of a button of iron or steel bonded in the bottom of the cinder pot.

The endurance of the copper liners in cinder pots is not only unexpected in view of other experience with such liners, but is a consideration of the utmost importance in cinder pot practice. It gives in cinder pots a permanent parting surface better than parting surfaces of lime or carbon, which must be renewed after each use of the cinder pot.

'I'he application hereof constitutes a continuation in part of my copending application, Serial No. 331,993, filed April 27, 194i).

.I claim as my invention:

l. A vessel for receiving and holding molten slag from the making of iron and steel formed as a hollow ferrous structure with open top and closed bottom, and a liner of oxidizable coppercontaining metal in the bottom region of the said vessel presenting to the cavity thereof a coating of copper oxide formed from the substance of the said liner.

2. A vessel for receiving and holding molten slag from the making of iron and steel formed as a hollow ferrous structure with open top and closed bottom, and a liner of copper-containing metal in the cavity of the said vessel in the bottom region thereof oxidizable under the conditions of use of the said vessel to present to the cavity thereof a parting surface composed of copper oxide from the oxidation of the said coppercontaining liner.

WILLIAM JOHNSTON, JR.

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