CA1273775A - Coated refractory shapes useful in bottom pouring of ingot molds - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
An assembly of refractory tubular tiles and runners for bottom pouring molten metal in an ingot mold, the tubular tiles and runners having smooth inner surfaces for guiding said molten metal and having a penetrating heat insulating graphite coating on said inner surfaces for controlling heat transfer from said molten metal to said refractory tubular tiles and runners to control thermal shock and thereby avoid cracking and spalling of the refractory tiles and runners.

Description

~273775 COATED REFRACTORY SIIAPES USEFUL IN BOTTOM
POURING OF INGOTS IN INGOT ~OLDS
Background of the Invention _ Technical Field:
This inven-tion relates to coated refractory shapes such as those used in bottom pouring of ingo-ts in ingot molds.
Description of the Prior ~rt:
Prior devices and assemblies used in bot-tom pouring of ingots and cast shapes from molten metal have included various structures such as those seen in U.S. Patents 3,604,598, 3,810,506, 3,929,184, 3,865,177, 4,111,254, 4,356,994, 4,452,296 and 4,506,813.
Typical arrangements of multiple mold bottom pouring are illustrated in the above Patents 3,810,506 and 3,865,117 wherein a vertically standing fountain or trumpet is positioned adjacent one or more ingot molds or the like.
Patent 3,604,598 adds electrical heating to a bottom pour-teeming vessel. Patent 3,92g,184 discloses the metal receiving and transferring fountain or -trumpet formed of a plurality of refractory sections. Patent 4,111,254 discloses -the formation of a casting mold made of sheet metal embedded in a supporting mass of refractory particles. Patent 4,356,994 -4' li ~

~27 ~7P75 discloses the units of a pouring system for a so-called uphill teeming as comprising an outer casing having an inner refractory liner and a refractory insulating material therebetween.
Patent 4,452,296 discloses an aluminum-diffusion coated steel pipe gating system which represents the fountain or trumpet of a bottom pour assembly including a mold. Patent 4,506,813 discloses a fountain or a trumpet of a bottom pour arrangement formed of a refractory tube in a sheath with a body of par-ticu-late material between the refractory tube and the sheath.
The present invention eliminates -the problems found in the prior art devices by forming the tiles or inserts which are sometimes -termed a refractory lining in a fountain or a trumpet as refractory shapes having an inner coating of a graphite composition capable of pene-trating the refractory surface to form a coating that resists flaking or parting of the refractory when subjected to molten metal by controlling the degree of heat transfer for a period of time sufficient to permit the refractory to adjust to the elevated temperature at a rate of expansion less than that resulting in flaking or parting of the refractory.

s Summary of -the Invention Coated refractory shapes usefu] in bottom pouring of ingots in ingot molds are disclosed, the refractory shapes being coated on their hot metal engaging surfaces with a graphite containing composition that penetrates the refractory and with it forms a ~ining that controls -the rate of heat exchange between the lining and -the balance of the refractory-shape which eliminates normal thermal shocking and the resulting flaking or parting of the refractory as well as substan-tially reducing the erosion rate of the penetrated refractory to render the same totally predic-table by precalculating the desired depth of the graphite coating.
Description of the Drawings Figure 1 is a schematic arrangement in vertical section of a mold assembly for bottom pouring incorporating the coated refractory shapes;
Figure 2 is a perspective view of a quarter section of a tile used in the mold assembly shown in Figure l; and Figure 3 is a perspective view of a quarter section of a runner used in the mold assembly shown in Figure 1.
Descr _t_on of -the Preferred Embodiment By referring to the drawings and Figure 1 in par-ticular it ~L2~737~

will be seen -that a vertical section of a schematic arrangement of parts o~ a mold assembly ior bo-ttom pouring is illus-trated wherein a mo].d stool 10 supports an ingot mold 11 and a -trumpet 12. The ingot mold 11 is illustrated with a ho-t top 13 -thereon and wi-th its open bottom resting upon refractory units 14 includ-ing runners 15 having outlets 16 in their upper surEace. The runners 16 are hollow and positioned in end -to end rela-tion with interlocking end configurations 17 and 18 respectively as best seen in Figure 3 of the drawings. The -trumpet 12 rests on a plate 19 posi-tioned on the mold stool 10 over the runners 15 and/or an open topped shape incorporating a bottom section including a king brick 20. The trumpe-t 12 is -formed o:L a -tubu:Lar meta] shape 21 which may be water cooled if clesired and :Eo:rms a vertical passageway 22 in which a plurality O:e coated re:Eractory shapes in the form o-f tiles 23 are arranged in superimposed rela-tion. The ends oE the tiles 23 have interlockirlg configurations 24 and 25 respectively, formed thereon as best seen in Figure 2 of the drawings. Each o:E the runners 15 and each o-f the tiles 23 have an inner coating 15C and 23C respectively, which in the quarter sec-tions o~

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Figures 2 and 3 of the drawings are shown penetrating the refractory material of tbe runners 15 and tiles 23 respectively to a desi.rable dep-th so as -to form with the refrac-tory material of the runners 15 and tiles 23 a lining which controls heat transfer from mol-ten meta.l to the remainder O-r the runners 15 or tiles 23.
The refrac-tory material o-f which the runners 15 and tiles 23 are ~ormed is preferably clay or a mix-ture of clay including dolomi-te, sand, granulated slag and ground fired clay toge-ther wi.th a suitable bonding material which may be anyone o -the following: resin urea -formaldehyde, sodium silicate, and pheno]i.c :resin. The graphite coating ma-terial is preferably synthetic graphite of colloidal size ineluding micron colloi.dal and micro micron colloidal par-ticle size or larger. The liqu:icl carrier i.s preferably an aqueous.solution inc:l.uclillg hyclrochloric acid, sodium silica-te and water s.oluable carboxy vinyl poly~er resin. A typi.eal liquid coa-ting material would include substantially 10% by weight m:ic-ron colloidal partieles of graphi-te, 7% by weigh-t coneen-trated hydroehloric acid of subs-tantially 90% purity, substantially 1~% by weight .: ~ .::. , :
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wa-ter, substarltially 32% by weight aqueous sodium silicate solution wherein the soclium sili.cate is present at about ~0%
by weigh-t of -the solution and substantially 33% by weight water soluable carboxy vi.nyl polymer resin as a powder wherein the resin is presen-t a-t substan-tially 8% by weight of the solution.
An alternate liquid carrier has been -Eouncl-to produce a suitable suspension of -the micron particles of graphite by subs-tituting xanthan gum for the carboxy vinyl. polymer resin, the gum is a natural high moleculr weigh-t linear polysaccharide Eunctioning as a hydrophilic coll.oid to maintain -the micron par-ticles of graphi-te itl suspension and contribute -to the penetrating of the coating as described hereinbefore.
~ ,:E:eective coa-tings :Eor -the reE:rac-tory -tiles and runners may be :Eormed with colloidal gr~lphi-te in amounts between 5,6 to 25% by weight, be-tween 3~ to 75% by weigh-t oE a solution o:E water and sodium silicate whereill -the water is presen-t at about 60% o:E the solution, between about 2% to 10% concentrated hydrochloric acid of a 90% purity wei.ght, between abou-t 33~ to 75C,~ oE a solution of water, acid carboxy vinyl polymer resin wherein -the resin is present in amounts between 1% to 10%
of the solu-tion by weigh-t and between about 15% to 20% water by weight.
Those skilled in -the ar-t will observe that the liquid carriers described herein comprise an efeective wetting agent which con-tributes to the ability of the particles of colloidal graphi-te to penetrate the reeractory material Oe the tiles and runners and iorm a smooth dry coating on the penetrated sur eace .
It is believed that the penetrating ability of the liquid carrier and graphite suspension is improved by the addition o-f from 1 to 10 parts by weight O:e micron silicon particles.
It wil.l occur to -those slcilled in the ar-t that the thickness o:E the coating material Eorming the lining O:e the runner 15 and tile 23 as seen in Figures 2 and 3 o:E the drawings has been somewhat exagge:rated and i-t wil.l occur to -those skilled in the art that -the -thickness o:E the coating -Eormed a:Eter the penetration o:E the graphite material into the re-Eractory may be varied by applying successive coatings o e the graphite suspension material as hereinbeEore described.
It will eurther occur to those skilled in the ar-t -tha-t by :~ .
.
. .
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forming s]eeve-like liners of -the graphite ma-terial herein-beLore described and hardening the same, the sleeve-like liners may be installed in -the runners and tiles before or after the same have been heat dried and/or fired as necessary in the formation o-~ such refractory articles and that the resul-ting sleeve-like linings Oe the graphi-te ma-terial will also resist heat transfer from molten metal to the refrac-tory sufficiently -to eliminate the usual thermal shock and the resultirlg flaking or parting of -the refractory.
A fur-ther modi-fica-tion of the invention applies -the graphite ma-terial -to all Oe the surfaces of the tiles 23 or runrlers 18 or o-ther simi]ar refractory shapes by submerging the tiles, rurlllers, and other re:eractory shapes in the liquid carrier sus~ension Oe the graphi-te :Eor a time su-fficient for the penetration O:e -the several sur:Eaces o:E the refractory shapes -to occur and -the -formation O:e a smooth coating on the several sur:Eaces of -the re:Erac-tory shapes.
Such trea-tmen-t of the refrac-tory shapes can be easily formed by dipping the shapes in -the liquid carrier of -the graphite suspension and the subsequen-t drying -thereof.

Claims (5)

The embodiments of the present invention in which an exclusive property or privilege is claimed are defined as follows:

1. A plurality of refractory tubular tiles and runners forming an assembly for bottom pouring molten metal in an ingot mold wherein said tubular tiles and runners have smooth inner surfaces for guiding said molten metal and a penetrating heat insulating coating on said inner surface controlling heat transfer from said molten metal to said refractory tubular tiles and runners.

2. In an ingot mold assembly for the bottom pouring of molten metal into said ingot mold having a plurality of connecting horizontally disposed hollow tiles communicating with said ingot mold and a plurality of connecting vertically disposed hollow tiles communicating with said horizontally disposed hollow tiles; the improvement comprising said hollow tiles being formed of refractory material and a penetrating heat insulating lining in the interior of said hollow tiles for controlling heat transfer from molten metal therein to said refractory material whereby thermal shock and resultant cracking and spalling of said refractory material is controlled.

3. The improvement in the ingot mold assembly of claim 1 and wherein said hollow tiles are formed of a mixture of materials from a group comprising clay, dolomite, sand, granulated slag, and ground fire clay and bonding material from a group comprising resin urea formaldehyde, sodium silicate, and phenolic resin, said hollow tiles being capable of penetra-tion by said heat insulating lining.

4. The improvement in the ingot mold assembly of claim 1 and wherein said heat insulating lining is formed from a liquid suspension of colloidal graphite particles, said liquid consisting of an aqueous solution of hydrochloric acid, sodium silicate, and water soluble carboxy vinyl polymer resin so as to form a smooth dry lining penetrating the refractory material of said hollow tiles.

5. The improvement in the ingot mold assembly of claim 1 and wherein said heat insulating lining is formed of a liquid suspension of colloidal graphite particles, the liquid consist-ing of an aqueous solution of hydrochloric acid, sodium silicate, and water soluble xanthan gum so as to form a smooth dry lining penetrating the refractory material of said hollow tiles.