US1570064A - Method of making crucibles - Google Patents

Description

Jan. 19,1926. l 1,570,064

' A. J. JACKMAN METHOD 'oF MAKING-CRUCIBLES F11ed March 18, 1925 Patented r`lan. 19, 1926i.

. 1,570,064 PATENT OFFICE.

ARTHUR JOHN JACKMAN, or Former HILLS BoaOUGH, rENNsYLvANIA, AssIGNon 'ro vEsUVIUs o nUoIBLE COMPANY, or swrssvann,y IENNSYLVANIA, A CORPORA- TION VOF IPEN'NSYLVANIA.l

' METHODOF'MAKLNGYORUOIBLES.

Application led March 18,1925.y Serial No. 16,344.

To all whom.` t mag/"conectan f i Be it known thatzI, ARTHUR JOHN. JACK- MAN, a citizen of the United States, residing at Forest Hills Borough, county of Allegheny, and State of Pennsylvania,.have invented a new and useful Improvement in Methods of Making Crucibles, of which the following is a full, clear, and exact description. Y

The present invention pertains to a method of making Crucibles and is particularly adapted to the manufacture ofgraphite crucibles such as are used in the manufacture of steel.

Metal melting crucibles, as for example, graphite c-rucibles usedk in steelv manufacture, are subjected to internal erosion of three principal sorts; namely, the oxidation of thegraphite by available oxygen in the bath, the absorption of carbon from the Crucible by the metal, and the fluxing action of the slag on the material used to bond the crucible. This last constitutes a very destructive localized attack.

I-Ieretofore it has been common practice to line such crucibles with various materials, possessing greater resistance than the body of the Crucible to the corrosive action of the slag, to obtain greater life for the crucibles Or to obtain carbon free metal. Complete linings have been found unsatisfactory, however, because of the irregularity of the amount of carbon absorbed by the metal when the lining becomes cracked, a circumstance which eventually obtains. Y

Thek repair of eroded Crucibles has also been tried. The repairs have been made by filling the crack or groove formed in the Crucible with a material similar to that of which the Crucible or Crucible lining is made. This procedure has not always proved effective because the first heat of service renders a crucible hard burned and vitreous, and material subsequentlyl filled into cracks or grooves in the surface of such a Crucible cannot become firmly bonded thereto. In addition to this, the usual practice in Crucible steel furnace operation is to charge the Crucibles while yet hot from theY previous heat and put them back into the furnace. Under suchv operating Condltions patching is impracticable.

Avoiding these obJections andy producing adcrucible of longer `life than those hitherto manufactured, my invention provides for incorporatingl a protecting ring of slag resisting material inthe interior'of the Crucible-'at the time it is manufactured.v Thus I am able to produce a crucible presenting a monolithic body of graphitic composition to the bulk 4of the metal, at the same time presenting to the slag a protective ring of a composition best vsuited to resist the fluxing action of the same. Y .Y f v In makingY these protective rings I preferably employ such materials as chromite,

sillimanite, zirconia, spinel,- Zircon, `for compositions containing one or more of. these ingredients. It will be understood, however, that I am not limited/to these materials, since it is obvious that rany highly. refractory substance that is neutral; and resistant to the iluxing action of the slags encountered will serve my purpose.. Imay also employ graphite-.in thesey rings in order that the thermal and physical rproportions of the rings will more closely approximate those of the Crucible body. These protecting rings may be bonded with any suitable bonding material, such as those now well known in the art. l,

In the accompanying-drawings, illustrating the present preferred embodiment. .of the invention- Y Figure 1 is a vertical section of a crucible having a ring Cut in the inner surface in the vicinity of the slag line; y

Figure 2 is a cross sectional view of a Crucible provided with a retaining groove having the side portions undercut.; l

Figure 3 is a sectional view to enlarged scale, illustrating a portion of the Crucible shown in Figure 2 with the protecting material in place;

Figure 4 illustrates a slag resisting ring similar to that shown in Figure 3 but provided with a protective coating to prevent abrasion of the inlay until the crucible is hard burned.

Referring first to Figure l, there is shown a Crucible 2, having an annular groove 3 whosefside walls 4 are cut substantially perpendicular to the inner surface ofthe crucible wall. The groove 3 is preferably cut while the Crucible is soft and lunburned. `I have found that the depth of this groove 3 should not be greater than two-thirds the thickness of the CrucibleJ` wall. Greater depth of cut adds no mechanical strength to the finished vslag resisting ring and may seriously weaken the crucible.

Figure 2 illustrates a crucible EZa having a retaining groove 5 cut therein. This groove Vhas sloping'sides 6 which effectively retain the material Y packed in the groove, as better shown in Figure 3. In practice it is found that the width of such a groove need not exceed eight inches, as the depth of the slags encountered does not warrant it. It Awill be understood, however, that this dimension -is not to be construed asa limit.

In constructing such a crucible as shown in fFigure -3 it is desirable that the slag resisting material 7 should have contact with the 'side walls 6 and the inner wall 8 to insure the material 7 being firmly held in place. It is obvious that if the material i' has a smaller shrinkage than the crucible wall 2 it will be crushed during drying or firing. To obviate this diculty, I prefer to form the crucible body and permit it to partially dry before-the slag ring is molded into the groove. When this is done the differential in shrinkage between the crucible body 2 and the slag resisting material 7 is reduced to practically nothing.

Certain of the desirable slag resisting materials, such as water ground zirconia without added bonding material, do not possess much physical strength or resistance to abrasion until they have been sintered at higher temperatures than those usually employed in the manufacture of graphite crucibles. When itis necessary to depend upon the heat of the steel furnace to give such materials a final firing, I provide for coa-ting the exposed portion of the .ring with a ceramic composition to protect it from abrasion. In Figure 4 such a composition 9 is shown extending above and below the slag resisting material 7, making contact with the crucible body `2. For such a composition.9, I preferably employ a mix sufficiently similar to that used in the Crucible body 2 that a good'bondis secured therewith above and'below the slag ring, thus insuring protection of the slag ring until the Crucible has been hard burned. rIhe protective coating 9 is soon destroyed during the early use of 'the 'crucible and the slag resisting ring performs its function as above described.

While 'I have described the preferred vein-- bodiment of the invention` it will be understood that the drawings do not define the limits of the invention, which may be otherwise embodied within the scope of the following claims.

I claim:

1. As an article of manufacture, a crucible for a melting operation wherein a is formed, having a portion adapted to contact with the slag and made froma material more resistant than the body of the Crucible to the corrosive laction of the slag, substantially as described.

2. As an article of manufacture, a crucible for a metal melting operation wherein slag is formed, having a graphitic'body portion adapted to 'Contact with the bulk of the metal and having 'a portion adapted to contact with theslag and made from a material more resistant than the said body portion to the corrosive laction of the slag, substantially as described.

3. As an article of manufacture, a 'crucible 4foran'operation wherein slag is formed, having an inlay of refractory material more resistant than `the body -of the Crucible to the corrosive actionof the slag, substantially as described.

4. As `an article lof manufacture, a crucible for an'operation wherein slag is formed, comprising a body portion of refractory material and having an interior ring of inaterial `more'resistant to the fche'mical attack of the slag than the said body yportion incorporated therein at such kportions as normally contact with the slag, substantially as described.

5. `Asan'article of manufacture, a crucible for an operation wherein slag is formed, comprising a body portion of :graphitic material and having an interior ring of material more resistant to the chemical attack of the slag than 'the said body portion incorporated therein at such portions `as vnormallycontact with the slag, substantiallyas described.

6. vAsan article `of manufacture, a crucible for an operation whereinslag is formed, comprisinga graphite body, means for Iprotecting the said body lportion .from'the corrosive action 'of the slag comprising an inlay of materialmore resistant to the chemical attack-of the sla'gthan the body portion, and means for protectingthe inlaid material from injury prior to hard burning, comprising a 'veneer of refractory material `placed thereover, substantially fas described.

7. Asan article of manufacture, a crucible `for an operation wherein slag is formed, comprising a graphite body, means -for lprotecting the said body portion lfrom the corrosive actionof the slag comprising an inlay of material 'more resistantlto the chemical attack vof the slag than thebody portion, and means forprotecting the inlaid'material from injury Vprior to hard burning, comprising a veneerof refractory material overburned at 'a lrela'tively lower temperature than required for hard burning the inlaid material, substantially as described.

v8. As 'an article of manufacture, a crucible for an operation wherein slag is formed, having a graphitic body portion, meansfor protecting the body portion fiom the corrosive action ofthe slag comprising an yannular ringv of refractory material, more resistant to the attack of the slag than the body portion, inlaid in the body portion at such portions thereof as are normally in Contact with the slag, and means for protecting the said inlaid material from injury prior to hard burning comprising a thin layer of material laced over the said inlaid material and Bonded to the said body portion, substantially as described.

9. The method of making a Crucible for an operation wherein slag is olmed Comprising forming a body portion having a groove therein at the slag Zone, and thereafter packing the groove with material more resistant than the body portion to the Corrosive action of the slag, substantially as described. f

l0. The method of making a Crucible for an operation wherein slag is formed comprising forming a body portion having an annular groove, Whose Width is greater aty the bottom thereof than at the top, at the region normally in Contact with the slag, thereafter packing said groove With material more resistant to the chemical attack of the slag than the body portion, and placing thereover a layerl of material adapted to protect the inlaid material from injury prior to hard burning, substantially as described.

l1. The method of making a graphite crucible for an operation wherein slag is 'formed comprising forming a body portion having an annular groove, Whose Width is greater' at the bottom thereof than at the top, at the region normally in contact with the slag, thereafter packing said groove With material more resistant to the chemical attack of the slag than the body portion, placing thereover a layer of material adapted to protect the inlaid material from injury prior to hard burning,and tiring the crucible so made, substantially as described.

12. The method of incorporating a slag resisting portion having a relatively lovvl d ing shrinkage into a crucible having a re atively higher drying shrinkage comprisrelatively higher drying shrinkage comprisj ing forming the Crucible to a desired shape and drying the same until a predetermined proportion of the total shrinkage has taken lace, thereafter introducing the slag resistrlng portion'into the said Crucible, and placing thereover a material adapted to protect the slag resisting portion from injury prior to hard burning, substantially as described.

lll. The method of incorporating a slag resisting ring having a relatively loW drying shrinkage into a graphite Crucible having a relatively higher drying shrinkage comprising forming the graphite crucible to a'desired shape and drying the same until a predetermined proportion of the total shrinkage has taken place, and thereafter introducing the slag resisting ring into the said graphite Crucible, substantially as described.

15. The method of incorporating a slag resisting ring having a relatively 10W drying shrinkage into a graphite crucible having a relatively higher drying shrinkage comprising forming the crucible to a desired shape and drying the same until a predetermined proportion of the total shrinkage has taken place, thereafter introducing the slag resisting ring into the said Crucible, and placing thereover a material adapted to protect the slag resisting ring from injury prior to hard burning, substantially as described.

In testimony whereof I have hereunto set my hand.

ARTHUR JOHN JACKMAN.

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