US1572475A - Ipany of america - Google Patents

Description

Feb. 9, me. 1,57%475 F. C. FRARY REFRACTORY LINING FOR CRUCIBLES AND THE LIKE Filed Jan. l5, 1924 ATTORNFV Patented eb. 9, 19126.

UNIT-En STATES 1,572,475 PATENT ounce.

FRANCIS C. FRARY, 0F OAKMONT, PENNSYLVANIA, ASSIGNOR TO ALUMINUM COM- IIPANYOF AMERICA., 0F PITTSBURGH, PENNSYLVANIA, A CORPORATION OF PENN- SYLVANIA.

REFEACTORY LINING FOR ACIBUCIBLES lAiNI'l THE LIKE.

Application led. January 15, 1924. Serial No. 686,270.

high as 2000 C. or higher, and in conseuence the alloy is so het when tapped from t e furnace into the crucible, ladle, or other y receptacle provided to receive it, that recep acles of ordinary construction or material have been found practically useless for the purpose. A ,furnace operating on power around 1500 kw. will produce as high as two tons of alloy per tapping, and hence the crucible must be mechanically strong enough to sustain and transport such a load. Further the surface in contact with the molten allo must vnot be melted or attacked by the alloy at the high temperatures encountered, since such meltin or attack, would not only destroy the crucible or-the lining thereof but might also contaminate the alloy itself and thereby impair its quality, A steel shell lined with carbon answers the purpose for only a few tappings, since the violent temerature changes produced by the rapid inow of such quantities of intensely hot metal cause the lining to crack, even though it be preheated. This cracking mayy` be due in part to compressive strains produced in the'lining by the stresses incident to lifting Vand transporting the loaded crucible. But in any case the cost of frequent relining is prohibitive. Fire brick and other refractories such as used for lining cruciblcs em ployed in the iron and steel industry are fused by and react with the aluminum-copper-silicon alloy at the temperatures referred to, so that the lining itself is rapidly destroyed and the alloy seriously contaminated.

0f the various materials tried l have found that a linin made of a mixture oit alumina and a utc solution of sodium silicate answers the requirementsv in a highly satisfactory manner. Such a mixture is cheap, and durable cnousrh to stand long use. It is also refractory, non-combustible, andv is substantially inert to the alloy even at the high temperature at which the/latter is tapped. 'An formyof alumina may be used, but I pre er alumina which has been produced. by electrothermal reduction of iron,\silicon, titanium and other oxidspresent as impurities in the original bauxite or other material, .leaving the major'v portion of the alumina. unreduced. A.. method of producing alumina in this manner is described in the copending application of William Hoopes, Junius D. Edwards and myself, Serial No. 608,283, filed December 21 1922. This product appears tobe denser than the alumina obtained by calcination of aluminum hydrate precipitated'irom sodium aluminate solutions, and when finely divided its sharper and more angular particles pack together better and are more securely bound by the sodium silicate.

Referring to the accompanying drawing, Fig. 1 is a side view, partly in section, illustrating a crucible lined with alumina andsodium silicate mixture.

Fig. 2 is a cross section, on line 2 2 of Fig. l, illustrating the process of lining the crucible shell according to the preferred method.

The Crucible shown comprises a steel shell 10, which may be about 36 to 42 inches in diameter and about 30 inches high., 'lhe ln the preferred method of carrying out my invention the alumina is ground to the inenoss of ordinary-sand and is mixed with dilute "sodium silicate solution, say of about 20` Baume, in amount suicient to give the mixture a consistency about like that' of ordinary molding sand. The steel shell having been prepared I tam rmly on the bottom a layer ,14, Fig. 2, o the alumina and sodium silicate mixture, of suitabl thickness. 'lhen placing in the shell a steel form 1li-of the proper' size and shape, preferably with a slight downward taper to facilitate removal, the annular space between the form and the shell is filled with the lining mixtu1'e,which is rammed tightl in place. The form is now removed, lifting it out by means of the ears 15, after which the Crucible is set aside to dry slowly. It is baked at a low temperature, say about 200 C., to drive off vthe last of the Water. The lining thus produced, composed of line particles of aluminum oxid bound together by sodium silicate, is hard and strong, enabling it vto withstand the mechanical stresses incident to even rough usage in the rapid handling and ltransportation of large uantities of molten metal. lt is very reractory, being inusible at temperatures encountered in the use described, and can sta-nd sudden and extreme temperature changes Without cracking. At the same time neither it nor the highly heated alloy is injured by Contact with each other., even though the alloy contains a metal (in the present instance aluminum) which has a very high aiiinity for oxygena l have also found the mixture highly Leraars advantageous in other places Where a refractory lining is desired which will stand high temperatures and sudden temperature changes without cracking, especially where resistance to chemical or other attack hyV superheated aluminum-copper-silicon alloy is a requisite; as for example the tapping spout or trough of a furnace .in which such alloy is produced or melted. For such purposes the mixture described is markedly superior to the customary magnesite comsignature.

FRANCIS C. FRARY.

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