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REFRACTORIES FOR EVERY USE By C. L. NORTON, JR. Executive Assistant Refractories Division The Babcock & Wilcox Company Bulletin RR-36 Reprinted from Chemical Engineering June 1953 Babcock & Wilcox Refractories Division Augusta, Georgia Just recently he has been appointed the industry makes light-weight in executive assistant in charge of all devel opment and engineering for this same division. A 1925. graduate of Mass achusetts Institute of Technology, and a native of Massachusetts, his first post graduate activity was as a research asso ciate and later as an instructor in met allurgy at MIT. During that period he worked on development of light-weight refractories for B & W, later being put sulating refractories; refractory cast ables, which are refractory-base gran ules mixed with hydraulic cement; ramming mixtures for monolithic re fractory linings; and special materials such as high-temperature ceramic coatings for metals, and the metalceramic combinations called cermets. Refractories produced in the form in charge of the company's Refractories Division laboratory at Augusta, Ga. He has authored a number of scientific of brick and tiles are summarized in Table I. Jmm Rmtbmn C L. NORTON Jr., author of this arti cle, was for over 20 years technical director of the Refractories Division of the Babcock & Wilcox Co., New York, papers, holds several patents on ceramic processes and products, is a fellow of the American Ceramic Society, and past chairman of the Refractories Division of that society. He also holds committee appointments in the Refractories Section of the ASTM. ALUMINA-SILICA REFRACTORIES Fireclay Refractories--Fireclay re fractories constitute the largest group of refractories produced. They are made largely from fireclays obtained from New Jersey, Kentucky, Pennsyl vania, Ohio, and Missouri and are divided into four main groups, based Refractories for Every Use partly on maximum service temperatores which drey can withstand. These groupings are: (1) Low-duty Temperature limits for refractories are moving upward fireclay brick; (2) intermediate fire- but maximum output per unit of cost still rules choice. day brick; ( J) high-duty fireclay brick; and (4) superduty fireclay brick. Fireclay brick as a group are rela Although the refractories industry their compressive strength under heat, tively cheap. They are used to some s a comparatively small one, it is to their tendency to disintegrate in extent in almost every furnace struc critical because nearly all other in furnace atmospheres of CO or H* to ture built, where operating temper dustries depend on it. Refractories their resistance to erosion from slags, atures are within their temperature contain our heating processes, and corrosive vapors or mechanical abra service range and where no special their characteristics to a large degree sion, and to splitting or spalling owing conditions of reducing furnace atmos determine the types of heating opera to rapid heating and cooling cycles. pheres or special problems are en tions we can perform satisfactorily and By far the greatest proportion of countered. Their low cost makes them economically. Without proper refrac refractories is produced in the stand an economical material. tories we would be without steel pro ard weight types formed as brick, as Alumina-Diaspore Fireclay Brick-- duction, steam generation, glass manu special shapes or as tile. In addition. These brick have a higher melting facture, portland cement, many chem icals--to mention only a few. There Is no ideal refractory for all applications. Choice of the most eco nomical one in any case depends on a number of factors. In some cases very expensive refractories costing several dollars per brick may give the lowest refractory cost per unit of output. At the other extreme, sometimes the low est cost fireclay brick obtainable may be the most economical. Installed cost per unit of production over the life of the refractory is the proper criterion for choice in most cases, rather than f.o.b. price. However, the cost of shut downs and unplanned outages must be considered as well. Refractories need not only with stand their necessary operating tem perature without melting or shrinking, but they must be satisfactory from several other standpoints. For exam ple, consideration must be given to Fig. 1--REFRACTORIES by destination and types. The chart an the left shows how refractories use breaks down by industry groups. Chemical process Industries include a part of the power group, a part of the non-ferrous metals group, the ceramic, chemical and petroleum groups. The chart on the right shows that fireclay refractories, including all day brick as well as insulating refractories, mortars, plastics and castables, encompasses nearly half the total Industry product. The special refrac tories include fused alumina, SiC, mullite, sillimanite, foroterite, zircon, carbon and other special refractories, and their non-brick forms. Table I--Classification and Use Properties of Refractory Brick Com poai lion. Name Percent AUmina-Sflka Finclij bM Fint quality.................. 35-40 AUOi 54-60 SiOt Semi lira..................... 70-80 SiOi Superduty..................... 41-45 AbOa 51--55 SiOi High bgrwd euperduty. 41-45 AbOa 51-55 SiO* 50% alumina................ 50 AliOi 60% alumina................ 60 Al*Oi 70 % alumina................ 70 AUOi 80% alumina................ 80 AliOs 90% alumina................ 90 AIjOi Kyanite bane.................... AbOrStOi 58-68 AUOa Kaolin base....................... AUO2SiOi (High-fired) 44-45 AliOi Fueed mullite baoe..,.... 3AbO*2SiOi 72-75 AUOa Silica Standard........................... Superduty........ ................. SiOi MepwHi Burned.............................. Chemically bonded.......... CWhh- Boned.............................. Chemically bonded.......... feiKrti.............................. 801cm carbide..................... MfO phis SiOi, FeiOa, CnOa MfO phis FeO, CraOs FeO-CnO. pure; plus some AUOa MiO, FeiOn SiO* FeO-CnOa plus MfO 2Mf0 8i0i SiC Faeed alumina...................... Zircon.................................... Xlreenla (Stabilised)............ Office (Graphite)............... AliOi ZrOStO, ZtO> C Msltinf Point, F. 3.090-3.175 2.940-3.060 3,175-3,200 3.175-3.200 3,200-3.245 3,245-3.310 3.290-3.335 3,335-3,390 3.390-3,425 3,250-3,300 3,190 3,325-3,350 3,142 (pure) 3.142 (pure) 5,070 (purs) 3,540-3,990 3,540-3,990 3.461 (pun) Dissociates st 4,082 3.722 (purs) 4,532 (pue) 4,870 (pure) 6.330 Normal Use limit, F. Approx. 8/M. 9-in- Equit. True Specific Gravity 2,400-2,700 2.400-2.700 2.500-2.800 2,500-2.800 2.500-2.800 2.700-2,900 2.700-2.900 2.800-3.000 2,800-3.200 2.800-3,000 2,800-2,900 2,900-3,200 95 100 115 155 160 200 235 260 1,175 500-680 2.60-2.70 2.40-2.45 2.65-2.75 2.65-2.75 2.75-2.85 2.90-3.05 3.15-3.25 3.35-3.45 3.55-3.65 3,00-3.06 170-335 2.65-2.75 685-1,370 3.08-3.25 3,000 3,000 plus 3,000-4,000 2,900-3,100 2.800-3,200 95-100 110 520 465 430 2.30-2.38 2.30-2.38 3.40-3.60 3.60-3.80 3.60-4.10 2.900-3,100 3.000 2,800-3,300 3,400 3,400 4,800 4,000 (reduc atm.) 450-485 S30 1,520 2,000 1,210 9,430 1,600 3.90-4.10 3.30-3.40 3.19 3.70-3.90 4.70 5.75 2.25 Bulk Daaly. Lb./Ft.1 125-140 125-140 130-145 130-145 130-145 130-145 135-150 140-155 172 140-150 135-145 150-160 100-105 100-105 160-165 170-175 185-190 170-180 150-155 155 175-195 206 275 137 Source Fireclay FireeUy Flint fireclay Flint fireclay Fireclay, diaspore. bauxite Fireclay, diaspora, bauxite Diaspora, bauxite Diaspora, bauxite Calcined alumina Kyanite Kaolin Bauxite and synthetic Quarts sand, canister Quarts sand, canister Macaesite. sea water, brinee, brucite Macneeite, sea water, brines, brucite Chromite ores Chromite ores Olivias or synthetics Synthetic Bauxite Zircon sands Zircon sands Carbon Netei "fTnrmsI itw limit** temperatures in approximate only because nrriw conditions sometimes win chann allowable temperature* by several hundred decree*. Such conditions may include heavily reducinc atmospheres and unusual loading. point and an alumina content which varies from 50 to 70 percent. As a class, they are used much less than the ordinary fireclay brick because of their higher price. They are used only where their higher use limit and melt ing point, and in some cases resistance to slag, make them a more economical selection. One important use of the 70 percent alumina type is in the lin ings of rotary cement kilns. Special Alumina-Silica Refractories --In this classification we have the sillimanite and mullite- types usually made from kyanite with an over-all alumina percentage between 58 and 65 percent. These bricks are consider ably more expensive than the aluminadiaspore class and are used where the service temperature of this latter group is exceeded. In this classification are also the kaolin base refractories which are made from relatively pure china clay which has been heated to very high temperatures to render it volume stable at high application temperatures. Also in this group are mullite refrac tories which have a true mullite com position with an alumina content of approximately 75 percent. These brick are usually made from electrically fused mullite grain, with a bond which also develops theoretical mullite com positions on firing. These brick have extremely good compressive strength1 under load at high temperatures. They resist rapid heating and cooling cycles, and are resistant to certain types of slag attack. They are volume stable at higher temperatures than the refractories previously Jlisted. SILICA REFRACTORIES Silica refractories are the second largest group of refractories produced and large quantities of them are used by the steel and glass industries. They are made from crushed sandstone or quartzite, bonded with a small amount of lime water. Silica brick have the advantages of being relatively low priced and have good load bearing ca pacity at high temperatures close to their melting point. Because of their thermal expansion characteristics they have poor resistance to rapid heating and cooling and for that reason are used primarily in furnaces where the temperature is held constant for long periods of time. Recently a new development in silica refractories has been made, known as the superduty silica brands. This superduty silica brick is one in which the total alumina content is lower than in the normal brands and as a result it has a somewhat higher use limit than the standard silica re fractories. MACNESITK REFRACTORIES Magnesite refractories are produced from calcined magnesite rock or from calcined magnesium carbonate re covered from sea water. In the heiting process the CO, contained in the magnesium carbonate of the starting materia] is driven off to form MgO. The MgO granules are then bonded, sometimes with the addition of chrome ore, to form bricks and shapes. Some of these are fired to high tem peratures as in the case of other re fractories and some are chemically bonded by a process which requires no firing. Magnesite brick are used mainly where they are in contact with basic slags. These brick are consider ably more expensive than fireclay brick and for that reason are used where the cheaper fireclay brick will not give an economical life. There is also a type of electrically fused MgO refractory produced from nearly pure magnesia which has a higher use limit than normal mag nesite brick, suitable for use at very high temperatures. CHROME REFRACTORIES Chrome refractories are produced from natural chrome ore and, like magnesite, can be made either as fired or as chemically bonded brick. The chemically bonded structures always contain some MgO additions. Chrome brick is relatively neutral chemically and does not react at moderately high temperatures with silica, magnesite, or alumina refractories. For that rea son it is often used as a separator in furnace constructions between two refractories which would react with each other if allowed to come into contact FORSTERITE REFRACTORIES Forsterite refractories are usually made from olivine rock to which some MgO has been added to adjust the composition ratio to 2MgO SiO.. Forsterite refractories can also be made by synthetic mixtures of MgO and SiO,. These refractories are made only as a fired refractory and are re ported to be particularly, good against the attack of alkali vapors at high tem peratures. SILICON CARBIDE REFRACTORIES Silicon carbide is an electric furnace product used primarily as an abrasive and is known under trade names such as Carborundum and Crystolon. When this material is produced in re fractory shapes it provides a very high rate of heat conduction, approximately 10 times that of fireclay brick. (See Fig. 2. Due to its hardness it is some times used where mechanical abrasion ^| | | 400 800 | | jrwwWRg fw+vrr*v | [ 1,200 1.600 2000 2,400 2000 feitoon ttmptrfetur*. detj. f. Fig. 2 --REFRACTORY BRICK show widely varying thermal conductivities. (Data from various sources; values vary considerably depending on test method.) is severe and also where it is exposed to certain types of slag. Its property of high heat conduction, however, is probably its outstanding physical char acteristic and for this reason it is used widely for muffles and various air cooled furnace and recuperator con structions. FUSED ALUMINA REFRACTORIES Fused alumina is another electric furnace product whose primary use is in abrasives. When compounded into refractory shapes it also has a high heat conduction, but considerably lower than silicon carbide. Its heat flow is approximately 2.5 times that of ordinary fireclay brick. It is also used for muffles and air cooled sec tions and replaces silicon carbide where the latter is unsatisfactory for other reasons. It has a very Iflgh use limit in both oxidizing and reducing atmospheres and it is used where ex treme temperature levels rule out other materials. ZIRCON REFRACTORIES Zircon refractories are made mainly from the natural mineral zircon which is often found concentrated in certain beach sands. It has a high melting point and use limit and is resistant to some types of siliceous slags. ZIRCONIA REFRACTORIES These refractories are made from purified zirconium oxide with small additions of lime, magnesia, or other ingredients to render it stable in volume. Pure unstabilized zirconium oxide inverts on cooling from the high temperature form to a low tempera ture form with a considerable volume change which is sufficient to cause cracking and disintegration. The stabi lized. structure retains the high tem perature form on cooling without un dergoing a change in volume. These refractories have a very high melting point and use limit and are employed where extreme temperatures are en countered. An interesting physical property is that even at extremely high temperatures the thermal con ductivity is low so that the heat flow through a furnace section is relatively low. These refractories are relatively high priced and can be justified eco nomically only for extreme use. CARBON REFRACTORIES Carbon (graphite) refractories are produced by heating a mixture of tar and coke. The refractories in brick or block form have been used in blast furnaces and in some other industries. They are limited to applications where the furnace operates reducing. INSULATINC FIREBRICK Insulating firebrick are produced mainly from clays which are mixed with some type of combustible mate rial such as sawdust. When fired, the combustible material burns out, leav ing a highly porous refractory struc ture. These light-weight products can be used as the exposed lining in the furnace chamber in the same way as other refractories. They are made in several grades, the lowest grade being suitable for temperatures of 1,600 deg. F., and the highest temperature grade being satisfactory at 3.000 deg. F. The weight per brick ranges be tween 1.25 and 4 lb. as contrasted to 8 lb. for a standard firebrick. It is the low weight of these re fractories which makes them of im portance. The time necessary to raise a cold furnace to operating temper ature is proportional to the weight of the furnace lining, assuming equal fuel inputs to the structure. Likewise, Table II--Classification of Insulating Firebrick Type Group 16............................... .... Group 20........................... ........ Group 23............................. ........ Group 26 ........................... ........ Group 28 ............................ ........ Others................................... Compostlion. Percent 15-37 AliOi 30-60 SiOi plus TiO*. FetO* Aik. 26-38 AltO* 45-61 SiOt plus TiO* FeiOi, Aik. 25-42 AliOi 45-67 SiOt plus TiO*. FetO*. Aik. 40-46 AliOi 47-55 SiO* plus TiOt, Fe*0*. Aik. 45-53 AliOi 42-52 SiO* plus TiOt. FeiO* Aik. 65 AbO* 90 AbOi Normal Use Limit, F.t 1.600 2,000 2,300 2.600 2,800 2,200 3,000 3.250 Approx. S/M. 2-in. Equir. 115 126 150 105 260 286 480 750 * Group number is std. A.S.T.M. classification, indicating normal use limit (X100). t See note under Table L Bulk Density, Lb./FU 21-37 26-45 77-47 43-64 45-65 52 69 81 Table III--Classification of Refractory Castables (Refractory aggregates plus hydraulic cement) Name, Standard Types Composition Normal Use limit, F.* Atemlna-Sillea Fireclay type.............................. AbO*. SiO* plus CaO. FeiOk TiOa Aik. Superduty type.......................... AbO*, SiOi plus CaO, FetO*, TiOa, Aik. Chrome........................................... FeO*CrsOa plus AltOt, litenlatiog Types CaO. StOi Expanded mica................................................... Distomaceous base.................... SiOi plus AbO* impurities Bloated clay base...................... AlsO*. SiOi plus CaO. FeiO. TiO* Aik. Porous refractory base.............. AbO* SiOi plus CaO. FeaO* TiO*, Aik. 2,400-2,700 2,700-3,000 2,700-3,100 1,600-1.800 1,800-2,000 3,000 2,000-2,500 See note under Table L Approx. Coot, S/T., CL 60-75 Bulk Density, Installed 6 Fired. Lb./FM 100-140 100-170 100-140 96-150 160-190 40-60 65-70 70-100 20-130 50-20 the time necessary to cool the furnace structure down is proportional to the weight. In actual practice it is not uncommon to effect fuel reductions of 30-65 percent in a cyclic heating proc ess when insulating firebrick arc sub stituted for standard refractories. The high porosity of insulating fire brick also gives them a low heat flow, the thermal conductivity being roughly proportional to their weight as shown in Fig. 3. This means that for con tinuous heating operations, thin wall sections can be used having the same heat flow as more massive firebrick sections backed up by insulation. Insulating firebrick have application limitations, however, and are confined to heating operations where there are conditions of clean heat, freedom from mechanical abrasion, and free dom from slag. It is largely because porous structures are unsatisfactory when subjected to slag that insulating firebrick are made from alumina-silica compositions, since the better slag re sisting properties of magnesite, chrome or similar materials would have little advantage in a sponge-like texture. ^ REFRACTORY CASTABLES Refractory castables are concretes, similar to structural concrete except that the sand and gravel of structural concrete is replaced by a carefully pre pared and sized aggregate of crushed refractory material. The cement used is usually the same as in structural concrete, being portland or highalumina cement. More recently, a more refractory cement composed of nearly pure lime and alumina in the /- Table IV--Classification of Refractory Plastics and Ramming Mizes Name Compostioa Melting Point, F. * Nomal Use limit, F.* Approx. Bulk Density, Cost. */T,,CL Fired, Lb./Fts Fireclay base........... Superduty base. . .. Kyanite baae........... Fused muDite base.. Maciwff Grain... Mixtures Deleshe. . Chrome... SUIeeo carbide.......... Fused efemias.......... Zlreen........................ i (Stabilised). AbO* SiOi, pine FeOi, TiO* Aik. AbO* 8tO* ptae FeaO* TiO* Aik. AbOr&Oa, ptue FsriO* TIO* Aik. sAbOisaOi plus FttOi, TiO* Aik. 8iOi 2,860-4,100 2,600-2,700 2,700-3,000 3.000-3,100 3.000-3,200 3,142 (pure) 2,800-3.000 McO 6,070 (pure) 2,200-3,100 CaO Mg0 2CO* 4,650-6,070 (pure) 2.900-3,100 FeO-CnOs 3,765 (pure) 2,200-3,100 plus AbO* MgO SiC Dissociates at 4,062 2,8004.150 AbO* 3.722 (pure) 2.2004,400 ZrOStOi 4,532 (pure) 3,200 ZrO 4.870 (pure) 3.800 * See note under Table L 50-70 60-80 160-176 -W*.n 70-100 126-140 130-140 140-160 160-160 150-100 146-165 180-200 160-170 176-126 205 275 Fij. 3--INSULATING FIREBRICK have thermal conductivities much below most standard weight refractories. (Data on one maker's products.) ratio of >CaO 5A1.0, has been used. With alumina-silica base aggregates, castables are available for service tem'peratures from 2,400 deg. F. to tem peratures somewhat above 3,000 deg. F. The alumina-silica base castables constitute the bulk of the market, al though special castables are made with chrome, fused alumina and other bases. Just as in the case of preformed re fractories, there is a class of light weight castables made by using a por. ous aggregate. The advantages of light weight in a castable are the same as in the case of insulating firebrick. At the present time, the general use of castables is being extended consid erably due to their low cost of in stallation. Refractory concrete is mixed and placed in a manner similar to structural concrete, and is a de sirable material to use in areas where skilled brickmasons are hard to ob tain. When the proper grade is se lected for a given application, a castable will provide a volume stable monolithic lining in manv instances giving equal or better service life than a lining of regular brickwork. PLASTIC AND RAMMINC REFRACTORIES There is another gToup of refractory products known as plastic refractories or ramming mixes. These composi tions are generally composed of clays or other binders mixed with crushed refractor)' aggregate and tempered with water to bring the mixture to proper working consistency. The plas tic or ramming mix is installed by pounding or ramming into place, and for this reason the installation costs are usually somewhat higher than for a similar castable installation. Plastic or ramming mixtures are made in alumina-silica compositions with temperature use limits ranging from 2,500 to over 3,000 deg. F. There are also compositions using fused alumina, chrome ore, magnesite, pcriclasc; silicon carbide, and other refractory base aggregates. REFRACTORY MORTARS Many types of mortars are produced for laying up or jointing preformed refractory brick. There are two main types, those which develop their bond strength only when heated to temper ature in the furnace-- known as "heat setting" mortars--and those which de velop a high bond on drying, called "air setting" mortars. Both types have their applications, and the best guide is to follow the recommenda tion of the manufacturer supplying the brick used with the mortar. METAL-CERAMIC COMBINATIONS Various combinations of ceramic materials have been Qsed as coatings on metals, including parts for nuclear reactors and heat-resistant compon ents for both jet-propulsion and re ciprocating aircraft engines. These coatings can be used to impart chem ical inertness at high and low temper atures to the metal, and have good thermal shock resistance and low porosity. Ceramic-coated low-alloy steels can replace the higher alloyed strategic materials. These coatings re duce oxidation and inter-granular cor rosion of the base metal up to a tem perature of 1,900 deg. F. Although the better coatings contain a consider able portion of strategic material in their composition, the thinness of the coating together with the substitution of lower alloy content steels represent a considerable over-all saving in strate gic materials. The U. S. Bureau of Standards and several industrial con cerns have done considerable work in developing this type of material. Many of these mixtures consist essen tially of an enameling frit of alumina and silica with additions of metallic oxides such as chromium and cobalt. Another approach to metal-ceramic combinations which has spurred con siderable research in recent years is the class of cermets. This work has been prompted by the scarcity of hightemperature metals requiring strategic materials. Cermets are mechanical and chemical combinations of metals and ceramics whose properties in the com bined state differ from those of either component. Ceramic materials them selves are limited by low tensile strength and thermal shock resistance, whereas metals have good tensile and shock-resistant properties, but lose rapidly with increase in temperature. Cermets attempt to blend thedesir able properties of both, securing the advantages of improved thermal shock resistance, wear resistance and me chanical strength at elevated temper atures, compared with ceramics. Also they have a higher strength-to-weight ratio than ordinary refractories. They can be formed by methods similar to those used in powder metallurgy. Usually, the ceramic components are 1 M O Table V--Refractory C--pounds with Re ported Melting Points A>-vive 4,000 Deg. F. Material Formula M.P., Beryllium oxide (BromeQite) Calfhim oxide (lime)........... Cerium oxide......................... f*!hmniinin avu4 Hafnium oxide....................... Tanthiam oxide...................... Magneehim oxide (Periclaee) Strontium oxide..................... Thorium onde........................ Yttrium oxide........................ Zirconium oxide..................... `TIHraria Zirconium eilieate (Zircon). . Nitrite Boron nitride......................... Hafnium nitride..................... Scandium nitride................... Tantalum nitrid* Titanium nitride.................... Zirconium nitride................... Beriden Hafnium boride..................... Tuneaten boride..................... Zirconium boride................... CarMte Boron carbide......................... Calcium carbide..................... Columbium carbide............... Hafnium carbide.................... Molybdenum carbide Silicon carbide........................ Tantalum carbide.................. Thorium earbide.................... Titanium carbide................... Tungsten carbide................... Uranium carbide.................... Vanadium earbide................. Zirconium earbide ................ Tlrceaatee Barium rireonate................... Calcium sireooate ................ Strontium sireooate.............. Thorium rirconate................. BeO CaO CM, CnOi HfOi LaaOa McO SvO TbOt YUO* ZrOi 4.580 4.050 4.710 4.410 5,090 4.208 5.070 4.410 5.520 4.370 4.870 ZrOt SiOs 4.532 BN HfN SeN TaN TiN ZrN 5.432 5.970 4.800 6.080 5.250 5.340 HfB WB ZrBr 5,549 5.288 5,414 BC CaCt CbC HfC MC SiC TaC ThCi TiC wc uc VC ZrC 4,230 4,170 6,330 7.530 4.320 4.890 7,020 5.020 5,670 5,036 4,350 5,130 6,380 BaO-ZrOi 4.748 CfcO-ZrOi 4,262 SrO*ZrOi >5.072 ThOrZiO* 5,072 refractory oxides, carbides and nitrides, while such metal components as chromium, nickel, molybdenum and titanium are used. Hence such mate rials are costly, and many of the avail able types require strategic materials. SPECIAL REFRACTORIES The refractory products which have been described above constitute the bulk of refractories which are in com mercial production and are readily available. In addition to these prod ucts, there are many other refractory materials which have been used only on limited or small-scale applications. To give a picture of the possibilities of these materials a list has been made in Table V of materials having melt ing points reported to be in excess of 4,000 deg. F. These might well be termed the refractories of the future, since if processes are carried out at higher and higher temperature levels, refractories for furnace constructions may be drawn from this list or from other untested materials of similar characteristics. Babcock & Wilcox Refractories Division Augusta, Georgia For your reference, the B&W sales office serving your area is: SALES OFFICES Atlanta, Georgia 30328................................ 5775-A Glenridge Drive, N.E..................... (404) 256-4950 Augusta, Georgia 30903 .............................. 1288 Merry Street.................................... (404) 7384573 Baton Rouge, Louisiana 70806 _............... 7400 Exchange Place................................ (504) 927-7753 Boston (Lynn), Massachusetts 01905......... 400 Bostdn Street ................................... (603) 424-7851 Buffalo (Orchard Park), New York 14127.. 3623 Eggert Road ................................... (716) 662-9751 Chicago (Oak Brook), Illinois 60521 ......... 900 Jorie Boulevard.................................(312)887-1090 Clarksville, Indiana 47130 .......................... 813 Eastern Boulevard ........................... (812) 282-6691 Cleveland (Beachwood), Ohio 44122........ 23215 Commerce Park Drive................. (216) 464-8717 Denver (Lakewood), Colorado 80215 ...... 11011 West 6th Ave., Suite 303-A......... (303) 232-8760 Detroit (Southfield), Michigan 48075 ...... 510 Northland Towers East................... (313) 353-6440 Houston, Texas 77055 .......................... . 4050 West 11th Street .......................... (713)861-9161 La Mirada, California 90638 .................... 15701 Heron Avenue............................. (213)921-8657 New York, New York 10017.................... 161 East 42nd Street ............................ (212)687-6700 Philadelphia (Wayne), Pa. 19087.............. 150 Strafford Ave., Rm. 202 Bid. 1...... (215) 293-0750 Pittsburgh, Pennsylvania 15237 .............. 7805 McKnight Road............................ (412) 9314490 Portland, Oregon.97204 ........................... 900 South West 5th Ave., Suite 1801.... (503) 228-0410 Seattle, Washington 98104........................ 305 Norton Building............................... (206) 622-1496 St. Louis (Clayton), Missouri fftl05......... 7777 Bonhomme Avenue .................... (314) 721-3214 Tulsa, Oklahoma 74135............................. 5200 South Yale Ave., Suite 501.......... (918) 663-2425 Burlington, Ont., Canada ........................ 1185 Walkers Line .................................. (416) 637-2333 . Montreal, Quebec, Canada........................ 3285 Cavendish Blvd............................... (514) 482-2673 Reprinted Irom nn Xaowool Ceramic Fiber: A Star Is Born Babcock & Wilcox Kaowool: a star is born Already installed in 5.000 different furnaces across the globe, B & W's "miracle" fiber is currently in white hot demand. The ceramic blanket's energy conservation talents, low thermal conductivity, resistance to thermal shock and ease of installation have sparked interest and sales in metal making plants throughout the country. "Greater than the tread of mighty armies is an idea whose time has come. "--Victor Hugo. "I'd rather have a market than a mil! "--Early U.S. Steel sales executive. There, quotation tans, is a double-nutshell descrip tion of the current status of Kaowool, Babcock & Wil cox's ceramic fiber. The coming of Kaowool's time clocked-in with the advent of the energy crisis, when demand for the now familiar insulating refractory material created a market bigger than existing plant capacity could comfortably meet. "There's no question that we were caught with ex cess of demand over capacity in the fall of '73," says Thomas R. Tate, B&W Refractories Division market group manager. "We had been shipping at 95 percent of our rated capacity when demand suddenly ex ploded as fuel supplies started tightening up. We immediately began expanding on a world-wide basis, adding 100 percent to the capacity of our main manu facturing plant in Puerto Rico and enlarging our oth er plants in Augusta. Georgia, Burlington, Ontario, England, Belgium and Japan. We even made plans to add a plant in Brazil." What caused this sudden spurt of capacity ex pansion within the company that pioneered a way to convert kaolin clay into fibers that could be matted and made into flexible blankets to replace conven tional refractory bricks in a myriad of high-heat areas? Simply stated, it was the equally-sudden shortage of fossil fuels, whose scarcity made them hideously expensive in certain forms--even if they were available. B&W's five-year plan "Our expansion plans carry through 1979," Tate explains. "By then, we ll have just about quadrupled our 1970 capacity. The way we see it, whatever else happens to the economy--low auto sales, consumer resistance and so on--the outlook for fuel makes it almost certain that there will be no reduction in the demand for insulating refractory materials. "Actually, going to Kaowool or a similar product is an investment people can't afford not to make," Tate contends, "because there's no question about fuel prices rising. Just in the last three or four years. No. 6 fuel oil in some areas has jumped from $0.5.3/ million BTU's to about $1.75, and there are govern ment projections that show the price will hit $2.18 next year." "And you have high prices coupled with allocations, so saving fuel becomes a matter not only of saving money, but of just plain staying in business. If a company has an allocation of X number of mil lion BTL"s. it becomes a matter of shutting down or making its equipment operate in a manner that will allow it to keep going.'' One steel mill Tate knows about has already linked its natural-gas usage to a computer because if the facility even exceeds its allocation in any 15 day period, it's hit with a heavy financial penalty. "That company has begun using Kaowool in its re heat furnaces for economic reasons, if nothing else," he says. What makes a ceramic fiber refractory material such a boon to the hard-pressed energy consumer engaged in preparing metals for reworking since this happens to be Kaowool's principal application? Low thermal conductivity is key The answer, according to Tate, is low thermal con ductivity coupled with ease of installation and maintenance, light weight and almost complete resistance to one of the bugaboos of nearly all other refractories--thermal shock. "When we first started marketing Kaowool seri ously," Tate recalls, "we were stressing the installa tion and maintenance features over everything else because fuels were cheap and plentiful. But when the turnaround came in late 1973, we realized that the product was much more important to our customers as a"rrteans of encapsulating heat than for any other reason." Almost everyone who bought Kaowool prior to 1974 to line such installations as heat-treating, normaliz ing. car-bottom, forging, stress-relieving, continuous tunnel-type and other furnaces did so because the material was easy to handle and install, Tate reports. "Since the cost of using Kaowool was about the same as refractory bricks or castables," he continues, "the savings in fuel it provided were interesting, but not that important. Now, however, it's a different 1975 by McGraw-Hill Inc All ng~:s 'eserved A 4'4-in. thick lining of Kaowool in this single stack an nealing cover reportedly reduced heat storage in the cover to less than 20 percent of that with a brick lining, increased available inner volume and cut the lining weight in half A popular use of Kaowool ceramic Fiber insulation is in heat treating furnaces. Kaowool insulation is attached to furnace walls by means of threaded studs, speed clips, and nuts and washers picture. Heat users almost have to go for it just to save on heating costs. There isn't much anybody can do about melting operations, because it's going to take a fixed number of BTU's per ton to do that in almost any system. But where savings can be made-- in reheating, for example--the companies involved in metals production are going to have to find them. And reheating is one area where savings can be made. Fuel-use research, a case study from Big Steel Tate cites the case of one major integrated steel producer which established a special section in its research laboratory just to find wavs of cutting fuel costs in its secondary operations. The firm was afraid that if it continued to spend money in ever-increasing amounts for energy it would soon lose out in the worldwide competition for its market share. Searching for someone to head the section, the company went outside the industry for an engineer who "wouldn't know about all the things that couldn't be done." gave him a strong mandate to produce results, and'turned him loose on the firm's steel plants. One of the first items on this engineer's agenda was a five-zone reheat furnace at a midwestern mill. "He invited B&VV and other refractory manufac turers to help analyze the situation," Tate says. "Then he told us that he was going to take B&W's word on what we could do to help save energy in that furnace. Within four weeks, he had set up a moni toring system for the furnace, decided what mate rials--including Kaowool--he wanted to use, placed an order with us for SoO.OOO worth of materials, and had them installed. "This was an extraordinary performance--getting operators to go along with a research engineer to install thermocouples in a furnace needed to keep production moving and getting the purchasing de partment to process a major order in almost record time. To me, it demonstrates that the company in volved is not just paying lip service to the idea of saving fuel, but is seriously committed to making it work. "We see this as the forerunner of similar depart ments in every major steel company in the country," Tate says. "Our own Tubular Products Division now has a combustion engineering department to supple ment existing activities in this area. Using Kaowool in our own furnaces provides a convenient yardstick for predicting the results other customers can expect to get." 5,000 furnaces using Kaowool Based on B&W's own experience and that of other companies that have applied it in some 5,000 dif ferent furnaces around the world, a newcomer to Kaowool can, according to Tate, look forward to some rather spectacular results. "The first benefit he's going to receive," Tate reportsT^is complete flexibility of furnace operations. The only limiting factor on how fast a user can heat up a Kaowool-lined furnace is the product being heated. Kaowool has such a low heat stroage charac teristic that he won't have to pump BTU's into the furnace walls before the `ware' starts to heat up. So once the furnace is turned on, he can put BTU No. 1 into the slab, coil or whatever else is being treated. "Secondly, the user doesn't have to worry about keeping a furnace hot between cycles to avoid damag ing the lining. A typical example would be a shop nrnan.'iiETMr or spray it on. No matter how you install it, all of the 32 Kaowool ceramic fiber products help cut costs. In bulk form, Kaowool cuts joint packing costs 25% because its long fibers have greater resiliency. Gives greater recovery from compression. Babcock & Wilcox has a full line of Kaowool products to cut the high cost of heat in temperatures up to 2300F. Even higher in some applications. Kaowool is lightweight. It resists shock, flame erosion, or wetting by molten aluminum and zinc. And it saves time and labor, too. B&W Kaowool is Kaolin clay in wool form. Its fiber length averages 4 in. Some go as high as 10 in. These fibers, thor- j oughly interlaced in the production process, give Kaow^fc products unsurpassed strength without the addition of^r binder system. And because it has no organic binder, Kaowool can't contaminate furnace atmospheres or emit offensive odors. Check the picture and find the Kaowool form closest to your application. Then call or write your representative listed on the back. He'll help you figure the size, density and thickness requirements for your particular application. 1 Kaowool paper: Produced from Kaowool ceramic fibers and processed on a papermaking machine. Thicknesses: 20 mil, 40 mil, and 80 mil. Density uncompressed 12-13 lb per cu ft. Recommended for use up to 2300F. O Kaowool mesh enclosed: Produced by covering ceramic fiber " shapes with alloy wire mesh. Tufted with alloy buttons and tufting. The alloy wire mesh covering can provide resistance to corrosion at temperatures up to 2100F. Available in blanket, cable, wrap and strip. Special shapes and sizes are available. 3 Kaowool blanket: Contains no organic binder. Blanket will not contaminate furnace atmospheres or emit offensive odors. Maintains structural integrity up to 2300F. Available in nominal densities of: 3,4,6 and 8 lb per cu ft. Width: 2' and 4'. Length: 25'. Available Thickness Density Vs in. lA in. Vz in. 12 Ib/cu ft 6, 8 Ib/cu ft 3, 4, 6, 8 Ib/cu ft 1 in. 3,4, 6, 8 Ib/cu ft lVz in. 2 in. 3, 4, 6, 8 Ib/cu ft 3, 4 Ib/cu ft 4 Kaowool bulk fiber: Longer fibers offer greater resiliency, greater recovery from compression. Lightweight, low thermal conductivity. Easily packed to firm densities. Also available chopped or completely inorganic. 5 Kaowool surface coatings: Cement: Air-setting, and easy-to-use. Cement has excellent thermal shock resistance, and continuous exposure ability to 2300F. Rigidizer: A liquid binder used to increase hardness and erosion resistance of B&W Kaowool ceramic fiber. ma,1m1: : d Kaowool strip: The interlacing effect of longer fibers provides Kaowool die-cut shapes: Made to design specifications from greater stability, high tensile strength and resiliency needed to blanket, paper or wire mesh enclosed. Simplifies job of withstand vibration and physical abuse. Available widths: 1 '' installing insulation around odd-size openings and shapes. to 11 ".Thicknesses: Vi" to 2". Densities: 3, 4, 6, 8 lb per cu ft. Kaowool die-cut shapes are available in the same thicknesses jM "J Kaowool spray mix: A lightweight high temperature ceramic and densities as Kaowool blanket or paper. * ' fiber insulation designed for pneumatic gun placement. 1 1 Kaowool block and expansion joint board: Formed from Kaowool k I It is composed of Kaowool ceramic fiber and inorganic binders, A ceramic fibers under controlled conditions. A strong durable which after being mixed with water at the spray gun nozzle, refractory block extremely resistant to thermal shock. It can be will adhere to the surface to be insulated. quickly cut to fit and studded for easy installation. Kaowool. O Kaowool vacuum formed shapes: Produced from Kaowool ceramic fibers and a suitable binder system. Density expansion joint board allows quicker and more uniform firebrick constructions using expansion joints. j averages 12 lb per cu ft. Practically any shape is available, Kaowool wet felt: Made from Kaowool ceramic fiber blanket. I including irregular hot tops, combustion chambers, tundishes, Pliable, moist. Packed in plastic bags. Easily formed in place. 1 sprue liners and cones. Air dries. No pins or straps required. Available in Z x 3' * Q Kaowool M board: A vacuum formed board produced from Kaowool ceramic fibers having very good handling and sheets in thicknesses of Vs" to 1". Special sizes available upon request. j;. structural strength. Surface can be rigidized for molten metal Block insulation (mineral fiber): A resilient mineral fiber contact applications. It can be easily cut for easy field block, formed and cut to precise tolerances. The block has installation. high breaking strength and low thermal conductivity, which results in an economical and efficient backup material. that works five days and is shut down for two. Normally, the operator would have to idle his fur naces at about 800 F for the weekend to eliminate possible thermal shock at start up. With Kaowool linings, these same furnaces can be shut off com pletely Friday night and fired again on Monday with no damage or wasted energy." Because its thermal conductivity is so low, a cus tomer can take advantage of Kaowool in two ways-- reducing fuel usage while maintaining existing pro duction levels or increasing output with no corres ponding hike in energy consumption. Reducing fuel usage To illustrate the first contention, Tate cited the case of a Pittsburgh area steel mill that decided to give Kaowool a try in its nine car-bottom annealing furnaces in an effort to offset a 45 percent increase in fuel costs mated to a 15 percent- reduction in allotments. Originally designed to be lined with A'/i in. of insu lating fire brick and 9 in. of dense firebrick, each car was given a 4'/a in. course of dense fire brick on the hearth and around the car-pier bases, plus a 3 in. blanket of 4 lb. density Kaowool topped by a 1 in. blanket of 8 lb. density. The change produced the following before-and- after heat-flow factors at 1,500 F operations: Heat loss--440 BTU/sq ft/hr before, 250 after. Heat storage--11,820 BTU/sq ft before, 2,080 after. Cold-face temperature--253 F before, 195 F after. In addition, the mill reduced its cycle time approx imately 15 min., allowing it to cycle one additional load every eight hrs. This was accompanied bv a "significant" reduction in the fuel cost on a per-ton basis, and delivery of a more uniformly annealed product. In addition, it used to take two bricklayers and a helper two or three days to reline a car deck; the job can now be completed by laborers in less than four hrs. In a non-metals application, Tate relates the case of a construction-brick producer in the Birmingham, Alabama area, who decided to veneer the inner faces of the 25 in. thick refractory walls of his beehive kilns with 2 in. blankets of Kaowool and found himself pro ducing "twice as many bricks per hour with the same amount of fuel because the material keeps the heat in the kiln and out of the walls." A bottom-edge seal of Kaowool ceramic fiber for annealing furnace covers can eliminate problems associated with the use of sand for such seals, according to Babcock & Wilcox, manufacturer of the material. The resilient kaolin-clay-base fiber seal eliminates the adherence of sand to the metal coil being annealed and reduces maintenance expense. Furnace design could change In this regard, Tate believes Kaowool may revolu tionize furnace design. "For years," he says, "people have been building furnaces out of refractory brick, making them as big as houses to provide sufficient heat resistance and structural strength. Now, they can make them smaller without sacrificing a thing in the way of capacity or insulating qualities." Partly, this claim is based on Kaowool's light weight in relation to its thermal conductivity, which Tate says is the "lowest of any product on the market for handling temperatures in the 2,000 F range." Kaowool can also, according to Tate, provide the user with advantages that aren't as readily identified on the bottom line as lower fuel consumption and re duced installation and maintenance costs, since these benefits fall into the realm of employee comfort and safety. Reduction of temperatures at the cold face of a furnace makes it less of a hazard to people who must work in close proximity to it, to say nothing of reduc ing ambient temperatures in the shop. Kaowool can also be put to use as a sound insula ting material as well as a heat encapsulator. One Midwestern steel mill is meeting Occupational Safety and Health Act requirements for soundproof pulpits in areas where ear protection is indicated by constructing two such units with a 2 in. layer of Kaowool sandwiched between a steel-plate outside wall and an expanded metal inner surface. Tate re ports that the ceramic fiber blankets are cheaper than polyurethane foam and are fireproof, to boot. Fiber earns a safe bill of health Further, working with Kaowool poses no known health hazards--either to the people who make it or those who use it. "Ceramic fibers are quite different from other re fractory fibers such as asbestos,". Tate explains. "We've'been monitoring the possible effects of work ing with Kaowool for the past 10 years and we're happy to report there is no toxicity. "In fact, many of the applications Kaowool has been put to in the last year or so have been strictly replacements for asbestos because of the restrictions on the use of that material." Despite the good qualities he lists for Kaowool, Tate acknowledges that it can't solve every problem that might arise in a metals plant. For example, B&W thought it had found the per fect way, in Kaowool. to reduce the weight of bricklined soaking pit covers. Based on early limited successes, it had proved an estimable product for sealing such covers because of its compressability. But when B&W had devised a Kaowool system for lining the entire cover and convinced several steel companies to test it, the embarrassing discovery was made that when exposed to iron oxide at tempera tures above 2,400 F, the soaking pit atmosphere fluxed the ceramic fibers and left them blackened and hanging in tatters in about eight days. The company hasn't given up entirely on the idea, however. "We are producing a new grade with 60 to 63 percent alumina compared to the original half alumina, half silica formula that may be able to handle temperatures up to 2,600 F in the presence of iron oxide," Tate reports. "The cost will be about 60 percent higher than the old product, but if it works, it could be the most exciting new thing soaking pit operators have seen for a long time; they'd really love to have it." As noted earlier, the softness of Kaowool, the very property that lets it shrug off the damaging effects of sudden temperature changes, obviates its use in areas where it would be subjected to physical wear and tear. Gas velocities over 50 ft/sec are also Kaowool bugaboos, although B&W has developed a special Kaowool board or block that can withstand veloci ties nearly' twice that level. Future once in doubt Seemingly destiny's child in the 1970's, Kaowool nearly wound up an infant-mortality statistic 30 years earlier. Here's the way Tate describes the product's birth and early tribulations: "Kaowool was originally developed during World War II when our people discovered that if they melted kaolin clay and then hit it with steam or a high-speed air it would attenuate into fibers 4 to 10 in. long that could be collected and formed into blankets. It was an interesting, wooly material that our researcher knew had good insulating properties, but because B&W was not familiar with marketing insulating fiber, it was put aside. "The product stayed on the shelf until 1950, when two of our competitors, in effect, jointly rediscovered it by combining silica and alumina, melting the blended material and blowing it into fibers. When their combined sales reached $1 million/yr by 1960, B&W realized that there was a strong demand for ceranoic-fiber insulation and started an intensive development program that began paying off by 1965. In less than five years, Kaowool had taken over the top spot in the market, a position it still holds log ging the major portion of total sales, mostly because we have concentrated on proving its value to heavy industry, especially steel." With non-ferrous industries such as aluminum, copper and brass, chemical process and petroleum refining coming on strong as Kaowool converts, Tate is convinced that B&W's main concern will be keep ing production abreast of demand. CTI For more information contact your nearest B&W sales office orThe Babcock & Wilcox Company, Refractories Division, Augusta, Georgia 30903 Atlanta. Ga 30328 5775-A Glenridge Drive. N E (404) 256-4950 Denver (Lakewood). Colo 80215 . . . 11011 W 6th Ave (303)232-8760 Portland, Oregon 97204 . . 900SW 5thAve, Suite 1801 . (503)2' Augusta, Ga 30903 . 1288 Merry St. (404)738 4573 Detroit (Sthfld), Mich 48075 . 510 Northland Twrs E (313)353-6440 Seattle. Wash 98104 .......................... 305 Norton Bldg . (206)62. Baton Rouge, La 70806 Buffalo (Orchard Park), N Y 14127 . Chicago (Oak Brook), III 60521 Clarksville, Ind 47130 7400 Exchange Place 3623 Eggert Road 900 tone Blvd 813 Eastern Blvd (504)927 7753 (716)662-9751 (312)887-1090 (812) 282 6691 Houston, Texas 77055 La Mirada. Calif 90638 NewYork, N Y 10017 . Philadelphia (Wayne), Pa 19087. . , 4050W 11th Street (713)861-9161 . 15701 Heron Ave (213)921 8657 161 East 42nd Si. (212) 687 6700 150 Strafford Ave .(215)293-0750 St Louis (Clayton), Mo 63105 7777 Bonhomme Ave .(314) 721 3214 Tulsa, Oklahoma 74135 . . 5200 S Yale Ave. Suite 501 (918) 663-2425 Canada Babcock & Wilcox Refractories Limited A subsidiary of The Babcock & Wilcox Company Cleveland (Beachwood). Ohio 44122 . 23215 Comm Park Dr (216)464-8717 Pittsburgh. Pa 15237.... . . .7805 McKmght Road .(412)931-4490 Burlington, Ontario and Montreal, Quebec