CA1192229A - Erosion-resistant refractory - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
A refractory shape having improved resistance to erosion in metal melting vessels and high modulus of rupture, comprising an anhydrous refractory material, an anhydrous organic binder, from 0.3% to 30% finely divided elemental carbon having a particle size ranging from 0.01 to 1 mm, and from 0.3% to 10% particulate elemental magnesium, based on the weight of the refractory shape.
Addition of both elemental carbon and elemental magnesium results in a synergistic improvement in slag erosion resistance.

Description

/'/7:

EROSION~RESISTANT REFRACTI:)RY
BACKGROUND OF THE lNV~;N 1 lON
This inven~ion relates to a chemically bonded re:ractory shape, having particular utility in S ar~y steel-malcing plant ( except an open hearth furnace) which has an external metal jacket which pre1vent~ air from being absorbed into the cold face of the refractory, ~uch as a basic o~ygen furnace (BOF) ~ electri furnaee, argon-o~ygen degassing unit (AS:1D) ~ and vacut3m induction melting furnace (VIM). Th~o refractory shape of the present inventiorl exhibits a synergistic improvemen'c in resistance ~;n~3t slag erosion, together with ins~reased moduLlus of rupture9 crushing strength and oxidat:ion resistanee, ~ reason of additions of both particulate metallic magnesium and particul~t2 elemental carbon to the re fractory mix .
Pi~cch-bonded, hot formed refraetorJ shapes ( e. g O in the form of bricks) wh~rein the re fractory material is magnesia, dolom~, or alumina, and the pitch i~ derived from coal tar or petroleum, have found incressing use in lining vessels used for refining steel. Various proposals and additives have been suggested by the prior art for improving reslstance against erosion by slag, molcen metal ~ and hot gases.
2S The present inv~n~ion constitutes a further improvement in the desired properties, particularly erosion resistance, o refractory shapes of ~he above type for use in steel refining vesselsO
United States Patent 2,013,625 dlscloses a reractorY
article h v~ng a vitreous pro~ective surace in which the refractory aggregates are bonded by residual carbon ~which m~y be derived from tar, pitch, resin, molasses; or dextrin), and in whlch a metallic substance (such as iron, manganese, magne~ium, copper, lead, zinc, or alloys) is dispersed throughout the article~

United States Patent 2 ,741,822 discloses a shaped refractory article comprising a fused mass of a single refractory oxide ( alumina, magnesia, or silica) and granulated metal CalumirIum, magnesium, or silicon) in a ratio of about 10 parts oxide to 1 part metal, the shaped article then being oxidized at about 1000 - 1200C to oxidize and fuse the metal particles ~ubstantially completely. A vola~ile organic bonding agent is also m~xed initially with the meta:Llic oxide.
United Sta~es Patent 3,226,456 disclo~es the production of increased den~ity ceramic articles by mlxing wlth a metal oxide about O.02% to 0.1% by weight o the same metal in particulate form ranging in size betwPen about 1 and 40 microns, followed by shaping at a temperature up to about 1~25C and molding under pressure.
Metals which may be used are aluminum, beryllium, magnesium, tho~lum and zirconium. The metal is at least partially oxidlzed ;n situ during the shaping and heating step .
United States Patent 3,3223551 discloses a pitch-bonded, basic refractory to which is added from 0.5%
to 1.5% by weight of the refractory batch of finely di~ided aluminum or magnesium. When pitch having a softening point above 200F was used ~in an amount of 1%
to 10% of the total ba ch weight) as the bonding agent, an improvement in erosion resistance was obtained under conditions simulating an oxygen steel converter. The .metal particle size was less than 0.210 mm (all passing a 65 mesh ~creen), and preferably less than 0.14g mm (all passing a 100 mesh screen).
~erman OLS 3004712, published August 21, 1980; in the name of Kyusyu Refrac~orie~, discloses the produc~ion of unfired re~ractory carbon bricks by adding from 1% to 10%
al-lm~ntlm and/or magne3ium powder to a refractory material containing greater than 1%, and especially from 5% to 75%

~9~

carbon. The particle ~ize of the metal powder is preerably less than 0.125 mm, From 0O57O to 6% sillcon powder may also be added to prevent the hydration of carbides. Increased re~istance to oxidation and reduced porosity are alleged to result from ~he aluminum and/or magnesium addition.
The formation of a dense zone o magnesium oxide just behind the hot face of pitch bonded magnesia or doloma brick during service in BOF or AOD vessels is disclosed in lQ articles co-authored by the present applicant, viz.
"Microstructural and Chemical Changes of Pitch Impregnated Magnesite Br~ck under Redu~ing Conditions"~ Trans. British Ceramic Society, Vol. 71, No. 6, pp. 163-170, Sept5 1972, B. Brezny and Ro Ao Landy; and "Role of Carbon in Steel Pla~t Refractories.", The American Ceramic Society Bulletina Vol. 55, No. 7, pp. 649-654, July 1976, B. Ho Baker, B. Brezny and R. L. Shultz. A discussion of this phenomenon 81so occurs in UOS. Patent 4jl96,894 issued April 8, 1980 to the present applicant. Briefly summarized, lt appears tha~ in the carbon zone of the brick magnesium oxide is reduced to metallic magnesium by the carbon in the pitch boTld, during service~ The metalllc magnesium is vaporized and migrates tsward the hot face of the brlck. In the region just behind the hot face the m~gnesium is oxidized back to magnesium oxide and is precipitated there ~o form a dense æoneO Ary void~s originally present are filled by the magnesium oxide precipitate, preventing penetration by slag, ho~ metal and/ or gases, and therefore decreasing eros ion.
Although not intending to be bound ~y theory, it is believed that the same phenomenon as that deseribed abo~7e occurs in the refractory shape of the present lnv~n~ion during serviceO Howe~rer, ~his invention constitutes the further discovery th~t a mar~ed improvemen~ in erosion re~istance occurs when both par~icula~e elemental carbon and particulate elemental magnesium are added to a refractory mixture having an organic binder 9 this improvement being of far greater magni~ude than ~hat obtained by adding particulate elemental magnesium alone to a pitch bonded refractory~ and that obtained by adding particulate elemental carbon alone to a pitch bonded refract.ory. The addition o carbon and magnesium in combination thus produces a true synergistic ef~ect, which i3 substantiated by test data hereinaf~er set forth.
10It has been found that the markedly improved erosion resistance, which is the principal object o the pres~nt invention, is achieved by use of an anhydrous refractory material, an anhydrous organic binder, at least 0.3~
finely divided elemental carbon having a particle SiZ2 15be~ween 0.01 and about 1 mm and at least 0.3% particulate elemental magnesium, based on the ~otal weigh~ of the refractory m;x. Residual carbon derived fro~ the binder as a re~ult o coking (which occurs during service) has bean found to be ineffective in producing marked improvement in ero9ion resistance regardless of the amoun~ of magnesium added.
Where a bric~ of conven~ion~l type having about 5%
anhydrous organic binder (such as pitch) is being produced in accordance with the invention, the elemen~al carbon 25 addition ranges rrom 0.3% to 3% by weight and the elemental magnesium addition ~rom 0.3% to 3.5% by weigh~.
There is also presently available bri~k ha~ing carbon addi~ions up to 25% or even 30% for high thermal conductivity. The bric~ of the present invention can be 30 produced at carbon levels up to 30% by weigh~ if flake graphite having a par~cle size of about 1 mm is added, and in this embodiment up to about lOYo elemental magnesium is added.
According to the invention there is ~hus provided a refractory shape having improved resistance to erosion, a~3~

comprising a refractory material ~ an organic binder in an amount sufficient to bond said refractory material, and elemental carbon, characteri~ed in that said refractory material and said organic blnder are anhydrous, that said elemental carbon is present in an amount of rom 0.3% to 30% and has a particle slæe ranging from 0.01 to 1 mm, and that from 0.3% to 1070 by weight particulate elemental magnesium is dispersed in said refractory material, based on the total weight of ~he refractory shape~
According to the invention there is further provided a method of increasing res1 stance to erosion of reractory linings which comprises mixing a refractory ma~erial, an organic binder therefor, and ~nely divided elemental carbon, characterized i~ that s~id reractory material and 15 said organic binder are anhydrous, that said elemental carbon has a particle size ranging from 0.01 ~o 1 mm and is present in an amount of at leas~ 0.3% by weight, that at least 0.370 particulate elemental magnesium is added, based on the ~otal welght of the refra~tory mix, that the 20 mixture is formed into briclcs~ and that said brick are positioned in a melting vessel at least in reglons thereof sub~ect to severe eros ion .
Reference is made to the accompanying drawing wherein:
Fig. 1 ~s a diagrammatic vertical sectional view of a 25 slag erosion cest apparacus used to evaluate refract:ory Rhape s .
Fig. 2 is a :Eragmerltary top view of ~he apparatus o Fig. 1.
Fig. 3 is a fragmentary diagrammatic vertical section 30 of a refractory brick of the irl~ention showing the conditions occurring during servlce at the hot ace cont minated with slag.
The reractory material may be of conventional type ordinarily used for production of refraccory brick derived 35 from magnesia, doloma, or ~lumi{la. For a magnes-La ref~accory exemplary particle size distribution may be as follows:
coarse grains 42%
f ine coarse 18%
int ermed i ate ( - 2 8 M ) 1 5%
ball mill fines 25%
The refractory material must be an~ydrous since metallic magnesium reacts with water even at room temperature to form magnesium oxid~
The organic binder ms~ be coal tar or petroleum pitch or an anhydrous res:Ln, preferably a thermosetting resin.
Resin composi'cions containing water or producing water during polym~rization cannot be used for the reason se~
forth above. Anhydrous epoxy resins are presently 15 avail ab le .
In the conventional forming of chemically bond~d brick the brick is ordinarily dried after being pre~sed into shape at A t emperature of about 260C. The purpose of the drying step, when anh~drous refractory material and 20 anhydrous organic binder are ~lsed, is to drive of volatile components from the binder, thereby minimizing smoke probl~ms when in service, and ~o increase the green strength of the brick. In the practice of ~he present i~vention, when coal 'car or petroleum pitch is used as the 25 organic binder, the softening point of the pltch does not constitute a limitation.
The finel~ divided elemental carbon may be thermal b lack, graphite, syn~chetic graphite, ground coke, ground used electrodes, coal dust,, or coke breeze7 and good 30 results have been obtained with carbon having a particle size of about 0.075 mm. A preferred particle size range is thus from about 0.05 to about 0.08 mm, although carbon having a particle size dist;r~bution throughout the commercially avallable ranges of 0.01 to 1 mm can be used.
35 The very fine sizes less than about 0.05 mm are more 9~

difficult ~o use because of dusting, compressibillty and wettability problems.
The par~icle si~.e of the metallic magnesium is no~
critical and can range up ~o about 0.50 mm. Good results have been obtained with powdered magnesium passing a 40 mesh screen (U.S. Standard~ having openings of 0.42 mm.
At least 0.3% finely divided elemental carbon is necessary in order to ob~ain ~he marked improvemPnt in ero3ivn resistance of the pre~ent inven~ion~ An upper limi~ of about 3% carbon for the l~wer carbon embodiment described above is preferred, since amcun~cs in exs~ess of about 3% adversely affect ~he compressibili~y of the refractory ~hape unless the carbon is added in the form of graphite having a particle size of about 1 mm. More preferably from about 0.5% to about 2.7% carbon is used, in the form of graphlte or carbon blac~ having a par~icle size ranging from about 0.05 to about 0.08 mm. A minimum of 0.3% particulate metallic magnesium must be present in order to achieve the marked improvement in erosion resistance of the present invention~ A maximum o about 3.5% magnesium is preerred in the low carbon embodiment described above, while up to about 10% magnesium is preerred when carbon is added in amo~nts up to 30% by weight. More preferably from about 0.5% to about 3.0~
magnesium is present. Best results are obtained when the sum total of elemental carbon plus magnesium is at least abou~ 2.0% by weight, based on ~he total weight of the refractory ~hape.
The present invention does no~ extend to the production of high fired brick. Such ~rick is fired at temperatureq up to or exceeding abo~t 1500C~ Sincé elemental magnesium boils at 1107C, the firing would vaporize the magnesium and cause it to difuse from the bric~c, even if reducing conditions were maintained within the brick.
A~ indicated above, the presen~ inven~ion constitutes a ~3~J~o.

discovery that residual carbon derived from the organic binder as a resulc of coking does not produce a synergistic effect with metallic magnesium in improVLng erosion resistance. The reason for this is not known at S the present tim~, although it is noted that residual carbon derived ~rom pitch is ex~remely fine in particle size. The particle size of the elemental carbon ( in the form of grap~ite or thermal black~ added in accord~nce with the present in~rerstion is on ~he order of about 100 10 times larger than ~he particle size o residual carbon rom pitch. It is possible that the diference in particle si2e or perhaps distribution of residual carbon accounts for its inability to function in th~ same manner as t-he elemental carbon hav~ng a particle size ranging ~5 from 0.01 to about 1 mm, which is added in accordance with the present invention.
Reference is made to Fig. 3, which is a diagrammatic illustration oE the manner in which a dense magnesia zone is formed during service behind the hot face of a brick.
20 In Fig. 3 the hot face is indicated a~ 10, the hot face slag zons at 12, the dense zone at 14, and the carbon zone of the brick at 16. It should be recognized ~hat the dimension~ of the zones are not accurately por~rayed in Flg. 3, and that the dense zone 14 starts a~ a dis~ance 25 slightly leqs than 1.25 mm rom the hot face 10 and extends inwardly therefrom a relatively shor~ distance of several millimeters. The carbon æone 16 extends throughout the remainder of the brick. In the carbon zone 16 of Fig. 3 the partial pressure of oxygen is no greater 30 than about 10~6 atmospheres. Accordingly~ magnesia, residual carbon, elemental magnesium and added elemental carbon are all present. As the ~empera~ure in the carbon zone increases during service the reactions which occur are shown in Fig. 3. Altho~gh very lit~le oxygen is 35 present, th~t which does exist co~bines w~ th carboll to ~3.

form gaseous C0~ Magnesium in solid form is vapori2 ed, and at least part of this magnesium vapor diffuses into t'ne dense zone 14 where the oxygen partial pressure is on the order of 10-8 atmospheres. Zone 14 is substantially carbon free and hence no carbon is availabla to react with oxygen present in zone 14. The v~po:rized magnesium di~fusing into chis zone thus reacts wi~h oxygen to produce magnesium oxide which is deposited in the volds ~mong the partlcles of the magnesia refraetory material 10 already pres~nt. This depo~ition of magnesium oxide results in formation of the dense zon~ which is rela~ively imper~ious to penetration by slag, molten metal and/or ho~
gase~ which do penetrate the ho~ ace slag zone 12. In ~one 12 the o2ygen pareial pressurc is s~ill higher, being 15 on the order of 1 o-6 to 1 o-8 atmospheres, due to the pre~ence of vari~us oxides -Ln the slag which come in~o contact with the hot faee 10. It will of course be understood that as the hot face 10 is gradually eroded in service, the zones 12 and 14 gradually move toward the 20 carboll zone, i.e. toward the right in Fig. 3.
The formation of metallic magnesium as a result o~
reduction of magnesia by carbon occurs in conventional re~ractory bric~s in the car~on zone, but the addition of metallic magneslum and elemental carbon in accordance with 25 this invention increases the amount of vaporized ma~nesium which migrates or diffuses into the dense zone 14 and thus increases the amount of magne~ium oxide deposited in the dense zone~ I~c will be understood that the hot face 10 is sub~ected to temperatures of at least about 1600C durîng 30 service and that the temperature gradient gradually decreases from this value through the hot Eace slag zone and the dense zone to a much lcwer temperature within the interior of the brick in the carbon zonP.
An initial serle3 of compositions wa~ prPpared ha~ing 35 varyirlg combinations of powdered me~allic magneslum and elemental carbon along with comparative compositions in which one or the o~her of magnesium or carbon was omitted.
These were subjected ~o ~ests and the proper~ies were determined. The compositions and test results are set forth in Table I.
All samples were prepared from the same batch of magnesite refrac~ory material having 42% coarse grains, 18% fine coarse, 15% intermediates (W28M) and 25% ball mill fines.
For comp~racive purposes samples A and B contained no elemental carbon additions but con ained additlor.s of particulate elemental ~agnesium. Samples E and H were regarded as standards for comparison since they contained additions of elemental carbon (thermal black) and no 15 magnesium9 which is now conventional. Samples L, M and 0 also contained no magnesi~m, and the elemental carbon additlons therein were somewhat higher than ~he current standard.
The synthetic resin used as an organic binder in samples H through 0 was a phenol-formaldehyd~ ~pe containing about 25% water when added as a binder.
It is evident that the addition of metallic magnesium increased ~he modulu~ of rup~ure of the bricks very significantly, particularly af~er coking, for samples A
through D~ F and G9 as compared to sample E containing no magnegium. In ~he case of samples H through 0~ ~he pre~ence o water in the resln binder is believed to have resulted in oxidation of ~he magnesium powder added in sample~ I, J, K and N. As a result, modulus of rupture values sho~ed no consistent increase.
Density of the pressed bricks and porosity after coking were not ~ubstantially affected.
Turning next to the proper~y of principal interest, namely erosion by slag, it is evident that samples C, and G exhibited very substantial increases in erosion resistance as compared to sample A containing no added elemental carbon and 2.5% magnesium, and sample E
containing 2.6% thermal black carbon and no magnesium.
Samples H through O, in which ~:he or~anic binder was a resin containing water, exhibited erratic erosion resistance values, regardless of additives. The best value was sample M con~aining 2.4% thermal black carbon~
1.0% flake graphite and no magnesium powder~ Examples H
through O are believed to demonstrate the criticali~y o using an anhydrouq organic binder.
The ~ample bricks o Table I were dried at 260C before tests and were coked at about 980~C in a nitrogen a~mosphere.
The values reported in Table I or percent erosion were determined by the stand rd Rotary Slag Test, wherein a rP~ractory specimen in the form of a ~ube is mounted with one end dipped into molten slag while gases are injected inta the oppo~ite end. The tube is rotated ~or a ~pecified time~ and erosion is then measured as a

2~ percentage.
A second series of test bricks was prepared from a magnesite of the same type as that used in the first ~eries with varying combinations of powdered metallic magnesium and elemental carbong together with comparative ~amples ln which either magnesium or carbon was omitted.
These sample~ were dried ak abou~ 260C and coked at about 980C in a nitrogen atmosphere. The samples were then tested for re~stance against erosion în a test apparatus illustrated in Figs. 1 and 2, and the tes~ resul~s were reported as depth of erosion in millime~ers9 rather than as a percentage. The amount of additive and depth of eroqion for each o~ the second series of samples is repor~ed in Table II. All samples contained 4O0% pitch binder.
Erosion values as repcr~ed in Table II were determined by ~he Thermal Gradien~ Slag Teæt~ illustrat~d ln Figs. 1 and 2. A brick size sample indicated at 3, o 225 mm length, has 2 cups 4 and 5 drilled therein each of 5~ mm diameter with the edge of cup ~L positioned 25 mm behind the hot face 3 ' of the bri::k. Each cup is filled with a 200 gm sample of test slag, and the sample is then placed in the door 6 of a gas fired labora~ory furnace 7 în the manner shown in Fi8. 1. The t:hermal gradient is measured by a set oE P~-Rh thernocouples (not shown) placed at 25 mm intervals behi.nd the hot :Eace o the test sample. (The thermal gradien~ can be va~ied by changing the position of a test sample relative to the front wall of the furnace. ) Sample~ were tested at a urnace ~emperature of 1650C
for three hours. The depth o erosion in mm in the ~ups 4 and 5 was then determined.
For slag testing under reducing conditions a ceramic t~ibe 8 i~ provided, which ~ s posltioned in a pre-cut groove in the test brick 3, and a mixt~e of C5 and Cû2, or natural gas, i9 injected into the cups d~ing ~he slag 2 0 test .
In Table II, sample 1 contAining no elemental carbon or elemental magnesium addition, exhibited very poor erosion resistance. Samples 2 and 3 containing ~lemental c~rbon additions o 0.6% a~d 2.6% respectively, but with no elemental magn~sium addition, exhi~ited sligh~ improvement oYer sample 1. Samples 4 and 5, containing elemental magnesium additlons of 1.5% and 2.5% respectively, but with no elemental carbon addition, ~lso exhibited slight improvement over sample 1. Samples 6 ~hrough 15 ~ which were representative of the present invention, showed increases in erosion reslstance in compar;son to samples 1 through 5, with the preferred and more preferred compositlons of samples 7 through 11, 14 arld 15 showing very marked impruv,~ ~nt, thus demonstrating the synergistic effect resulting rom addition of both "

elemental carbon and elemen~al magnesium within the percentage ranges defined above.
The data of Table II indicate that no particular ratio of carbon to magnesium needs to be observed, as will be apparent from a comparison of samples 6, 7, 12 and 13.
Subs~antial~y equivalent resul~s were obtained with carbon a~ 0.3% and 0.6%, respectively (plus 1,5% magnesium), and magnesium at O .3% and O .6% respectlvely ( plus 2 .0% carbon) provided that a suf~icient addition of the other element was present, It is ~herefore believed that a sum total of carbon pl~ magnesium o~ at least about 2.0%, with 2 minimum of at least 0.3% of either elemental carbon or magnesium9 provides optimum resultsO
For a low carbon brick of the type described above 3 about 3% to 5~O pitch ordinarily is added as a binder. For the high ~arbon brick ( c:ontaining up to about 3û% carbon~
up to about 8% pitch may be needed as a binder.
From the above description it is apparent that the present in~ention also provides a method of inc~easing re~is~ance to erosion of refractory linings, which comprises ~; n~ an anhydrous refractory material, an anhydrous organic binder therefor, at least 0.3% flnely divided elemental carbon having a particle size ranging from 0.01 to about l mm, and at least 0.3% particulate elemental magnesium, based on the total weight of the reractory mlx, forming the mixture into bric~s, drying the bricks, and positioning the brlcks in a melting vessel at least in the regions ~hereof subject to severe erosion.
In the preerred and more preferred practice of the method, the preferr2d and more preferred percentage ranges of elemental carbon and elemental magnesium are mixed with the refractory material and the binder.
While the invention has been described in terms o exemplary compositions, modifica~ions may be made witho~t departing ~rom the spirit and scope of the invention, and it will be unders~ood that ~he invention is not to be limi~ed except insofar as set forth in the accompanying claims.

~ ~9 ~

o~r o ~ r ~ u- r o l ~, -- or~ ~, zr~O
I o~r o o ~ t~ oco Z ~ 7 ~ O
o ~ o _ O ~ ~r7 Or7 r 1~t~o I o ~ o ~ atD a ,-71~r tr7 oOr7 U~)Z a7 r O NO OtD ul(~
~: ~r O tr~ 7ZtD 7 O t9 0 0 ~~tD ~I
! .
~-7 ~r O ~ ~'7 ~tDr-tr r O tDO OtQ
. . ~~D
r ~ ~ ~ o ~7~'7~7 u~ ' 4 tO ~-- tS~ tD
1er ~ o o,) t~ ~1` ~
a O tOO ~0U7 U7 u O C
Z: . . . . . . . . "7 ~r ~ O r7 ~ - ~r O t~) Z Io tD a)~ a ~~'7 '-I
rN Ot`l '7 0 Za~
E~
O\D a7 o or~ O 7 ~r ~
J I OO n O CO ; ~ ~ =' x a l~r ~ o ~'7 ~ r~
~ In OtD U~O r ~ m r ~r O O r~ i ~ r 7 a~

I O u~
a~ ~ ~ ~ Z ~ Q
~ U~
O U'l O O ~1 tD
1 ~ O C ~3 ~ U'l tD o ~1 .L;
C ~i D ., X .~ d ,~ ~ U C
dd~~1 . 3 ~ 5 ,,,~
~D 3 3 Q I 1 tL~
o U~
C~ ~ :~ U ~ (~) U I ~ r O
r ~ ~ I ec u~
E'i (D la~ U ~ - ~ ~ - O 1:4 U J~
iZ

~.~s~

T A B L E II
SLAG EROSION TEST

Sample C Mg Depth of Wt . % Wt . % Erosion (mm) 2 0.6 a 9

3 2.6 0 8

4 0 1.5 9 0 2.5 9 6* 0.3 1.5 7 7* 0.6 1.5 4 ~* 2.6 2.5 2 9* 2.~ 3.0 10* 2.6 1.5 2 1~* 2.0 2.5 2 12* 2.0 0.3 5 13* ~0O 0.6 6 14* û.6 2.5 4 15* 2,~ 1.0 4 * Present lnvention

Claims (16)

Claims:

1. A refractory shape having improved resistance to erosion, comprising a refractory material, an organic binder in an amount sufficient to bond said refractory material, and elemental carbon, characterized in that said refractory material and said organic binder are anhydrous, that said elemental carbon is present in an amount of from 0.3% to 30% and has a particle size ranging from 0.01 to 1 mm, and that from 0.3% to 10% by weight particulate elemental magnesium is dispersed in said refractory material, based on the total weight of the refractory shape.

2 . The refractory shape according to claim 1, containing from 0.3% to 3% elemental carbon and from 0.3% to 3.5% elemental magnesium.

3. The refractory shape according to claim 1, containing from 0.5% to 2.7% elemental carbon in the form of graphite or carbon black having a particle size ranging from 0.05 to 0.08 mm, and from 0.5% to 3.0% elemental magnesium.

4. The refractory shape according to claim 1, wherein the sum total of elemental carbon plus elemental magnesium is at least 2.0%.

5. The refractory shape according to claim 1, wherein said refractory material is derived from at least one of magnesia, doloma, and alumina, and said binder is coal tar or petroleum pitch.

6. The refractory shape according to claim 5, containing 3% to 5% of said pitch, based on the total weight of the refractory shape.

7. The refractory shape according to claim 1, wherein said elemental magnesium has a particle size up to 0.50 mm.

8. The refractory shape according to claim 1, wherein said organic binder comprises 3% to 5%

anhydrous resin, based on the total weight of the refractory shape.

9. The refractory shape according to claim 2, characterized in that said shape is a brick used in a metal melting vessel which, during service, develops a dense zone of magnesium oxide within said brick adjacent the hot face thereof.

10. The refractory shape according to claim 9, characterized in that said metal melting vessel is a steel making plant.

11. A method of increasing resistance to erosion of refractory linings which comprises mixing refractory material, an organic binder therefor, and finely divided elemental carbon, characterized in that said refractory material and said organic binder are anhydrous, that said elemental carbon has a part-icle size ranging from 0.01 to 1 mm and is present in an amount of at least 0.3%
by weight, that at least 0.3% particulate elemental magnesium is added, based on the total weight of the refractory mix, that the mixture is formed into bricks, and that said bricks are positioned in a melting vessel at least in regions thereof subject to severe erosion.

12. The method according to claim 11, characterized in that from 0.3% to 3% elemental carbon and from 0.3% to 3.5% elemental magnesium are mixed with said refractory material and said binder.

13. The method according to claim 11, characterized in that from 0.5% to 2.7% elemental carbon having a particle size ranging from 0.05 to 0.08 mm, and from 0.5% to 3.0% elemental magnesium are mixed with said refractory material and said binder.

14. The method according to claim 11, characterized in that said organic binder comprises 3% to 5% coal tar or petroleum pitch, based on the total weight of the refractory mix.

15. The method according to claim 11, characterized in that said organic binder comprises 3% to 5% anhydrous resin, based on the total weight of the refactory mix .

16. The method according to claim 11, characterized in that said melting vessel ls a steel making plant.