Studies on the Refractories Used in Non—Ferrous Metals Smelting Furnace and Their Application in China

The paper describes the reaction between car-bon-containing refractories,magnesia-chrome re-fractories and matte,converter slag.The results show that carbon-containing refractories have good resistance to matte and converter slag in nitrogen at-mosphere,The practical results are unsuitable for converter,high performace magnesia chrome re-fractories are promising materials.Newly devel-oped high quality direct bonding magnesia chrome,rebonded co-clinker magnesia chrome,semi-rebonded magnesia chrome,fused cast magnesia chrome used in smelting furances are introduced briefly.     

The State—of—art of Magnesia—chrome Refractories for P—S Converter in China‘s Non—ferrous Industry

The state-of-art of magnesia-chrome refractories from direct-bonded magnesia chroma brick to fused-grain rebounded magnesia chrome brick for P-S converter is discribed.The Cr2O3 conternt of the brick is continually increased with the reduction of the impurity content of brick ,the pre-synthetic raw material is applied and the operating condition of conerter is optimized so that the service life of converter is largely enhanced.     

Development of High Chrome Refractories for Coal Slurry Gasifiers in China

This paper briefly describes the theoretical basis,developing trend and technical properties of high chrome refrctory for coal slurry gasifier in our country ,In the environment of high temperature and high pressure,the coal gas composition and coal ash slag make it inevitable to use only high chrome refractories in coal slurry gasifiers.     

Chemical Corrosion Mechanisms of Magnesite-chrome Bricks by Converter Slag

The corrosion resistance of four kinds magnesitechrome bricks against converter salg was investigated by static crucible slag tests. The microstructures of the asdelivered and tested refractories were analyzed by means of SEM and EDS. The results showed that： Different magnesite-chrome bricks have different slag resistances. Generally, the slag resiantance sequence is as follows： rebounded fused magnesite-chrome brick 〉 semi-reboun- ded magnesite-chrome brick 〉 direct-bonded magnesitechrome brick 〉 silicate bonded magnesite-chrome brick. Slag reacts with the periclase of magnesite-chrome refractories, which results in the dissoving of periclase in fayalite slag. However, the complex spinels have superior slag resistance.     

Progress of Environment-friendly Basic Refractories for Cement Industry

The chrome pollution from cement industry was introduced briefly,the research on chrome free basic refractories for cement kilns was reviewed,the production technologies of magnesia calcia,magnesium aluminate spinel,magnesia hercynite refractories,etc. were specified,the principles to improve thermal shock resistance and coating adhesiveness of refractories were analyzed,the measures to extend service life by improving production equipment and service conditions of refractories were put forward,the future of chrome free refractories was expected and some developing suggestions were given.     

Wear of MgO-C Refractories in EBT Type Furnaces Experienced at lranian Mobarakeh Steel Plant

Mobarakeh steel Company produces 3 million tons of steel annually with eight 180 tons EBT furnaces.Different types of magnesia-carbon refractories have been employed at slagline during last 5 years.In the present study the wear and corrosion of MgO-C refractories of these furnaces have been studied via post-mortem analysis of used bricks and the observation of operational effects.Laboratory corrosion tests were also arranged to investigate the effect of slag chemistry and the mechanism of chemical corrosion.Characterization of different magnesia-carbon bricks clarified that the crystal size,type and chemistry of magnesia as well as graphite structure have the main influence on corrosion resistance.The CaO:SiO2 ratio in slag also plays a vital role in the wear of slagline refractories.The iron oxide content of slag also has a major role in graphite oxidation.Of metallurgical parameters,the electric power input and the contact time have great influence on refractories life.The results will be discussed with emphasis on particular operational factors in Mobarakeh steel plant.     

High Temperature Interactions of Chrome Oxide Free Refractories with Coal Slag Under Simulated Gasification Conditions

Chrome oxide free refractories have significant economic benefits for the development of gasification technology. Spinel based and SiC based refractories are corroded by coal slag at 1 500 ℃ under reducing atmosphere. Moreover, interactions between refractory materials and molten slag are also predicted by thermodynamic calculations under the same conditions. The results indicate that spinel based refractories are corroded by dissolution of molten slag, while SiC based refractories are corroded by oxidation of CO and FeO. Both of the spinel and SiC based refractories show good corrosion resistance against coal slag by the present experimental tests. Finally, preliminary developed spinel-SiC composite materials are prepared and corroded by coal slag as well, the research of which shows great potential to be used in slagging gasifiers.     

esearch and Application of Burned Microporous High Alumian—Graphite（Al／C） Brick in Blast Furnace

This paper inroduces the research background,technology,product property and application of burned microporous high alumina-graphite brick (Al2O3-C brick) used in blast furnace,The difference of property between Al2O3-C brick and other blast furnace refractories is discussed .The results of simulative tests show that ,Al2O3-C brick has good alkali resistance,slag resistance,thermal shock resistance,oxidation resistance,high thermal conductivity,low permeability and low solubility in molten iron,The brick with micropores of average radius less than 1μm has been successively applied to fourteen blast furnaces, the lining life of the brick is almost as long as that of Si3N4 bonded SiC brick Al2O3-C brick will be widely used in lower stack ,belly,bosh and hearth in the future.     

Pollution of Chrome Bearing Materials and the Solutions

This paper summarizes the pollution, situation and solutions of chrome bearing materials used in high temperature industry. Hexavalent chromium compounds are readily soluble in water and associated with carcinogen. Therefore, serious environmental problems appeal for the study and application of chrome free materials. Chrome free products include: magnesia based materials, dolomite based materials, magnesia spinel materials, magnesia hercynite or magnesia galaxite materials and zirconia containing materials,and other substitutes. Although any product has its advantages and disadvantages, the trend to development of chrome free products is inevitable.     

China‘s Refractories Industry on the Advance

The advancement made in China‘s refracto-ries industry in product qualities and varieties for the past 15 years since the eighties have been briefly reviewed.The policy of technical devel-opment of refractories in China and the main trends of developments in high performance re-fractories are discussed.     

A Retrospective Review of Alumina-magnesia-carbon Refractories

The residual expansion of in-situ spinel formation in using of alumina-magnesia-carbon(AMC)bricks monolizes the lining of steel-making ladles with the closure of their joints,which has been an effective solution avoiding washing out of the joints in ladle lining by the reduction of the penetration of liquid slag and molten steel.Alumina-magnesiacarbon refractories are overall reviewed,in terms of major raw materials,thermal evolution,corrosion and oxidation,and thermomechanical behavior,as well as type,addition and fraction of magnesia used.General commercial products contain 5%-10%MgO and 5%-10%C with a certain amount of metallic aluminum powder,which is believed to facilitate spinel formation at early stage of heating-up,although high magnesia containing AMC bricks are studied and used sometimes.With low ratio of Al₂O₃/C=12.9 and the carbon content of 6.4%C,AMC brick exhibits the highest corrosion resistance.It is important to determine the type,addition and fraction of magnesia used in AMC refractories for demonstrating high corrosion resistance and superior thermomechanical behavior.     

Slag Corrosion Resistance of MgO-ZrO2 Refractories

Slag corrosion resistance of MgO ZrO2 refractories was investigated in this work. The results indicate that in a non-oriented electric steel slag system with a high ratio of calcia to silica,the slag resistance of MgO ZrO2 refractories can be described as follows: ZrO2 reacts with CaO forming calcium zirconate compound which strengthens the material and blocks the channel of the slag infiltration; however,in an oriented electric steel slag system with a high concentration of silica and the low ratio of calcia to silica,the slag corrosion resistance of MgO ZrO2 refractories is different; ZrO2 reacts with CaO forming the calcium zirconate and simultaneously one more product C2S as well; C2S can improve corrosion resistance by blinding pore and enhancing slag viscosity; therefore,it is expected to be the major reason for the enhanced corrosion resistance observed for MgO ZrO2 refractories.     

The Effect of Sintering T emperature on Microsturcture of High Chrome Bricks

The microstructure of high chrome bricks made at different sintering temperature are analyzed by SEM.The results indicate that the sintering temperature of high chrome bricks has an optimum range,it is not the higher,the better,The high chrome bricks made at this sintering temperature have th moderate crystal size in the matrix and of dense structure,The Closed bonding structure could be obtained between grains nd matrix and no crckle occurred.The high chrome bricks with this microstructure have the best dynamic properties.     

Eco-Friendly Smokeless Al2O3-SiC-C Brick for Hot Metal Ladle

Hot metal transfer ladles were historically lined with high alumina refractories because of compatibility of high alumina refractories with the highly acidic slag, which is transferred .from the iron making plant along with hot metal. With the introduction of higher capacity ladles, technological advancement in the process and increased productivity, calls for a higher campaign life of hot metal ladles, which could not be performed by ordinary high alumina refractories. Resin bonded Al2O3- SiC-C （hereinafter ASC ） bricks gradually developed which at present taking place replacing the conventional refractories. Considerable work has been carried out in developing the ASC refractory to reach the present state. However, for higher capacity ladles still there is a lot of scope for improvement. The present paper deals with the newly developed ASC bricks, which was used in 165 ton capacity hot metal ladles in one European plant and has given a substantial increase in performance. But, the customer was not fuUy satisfied since the brick was reported to produce smokes during preheating of the ladle. In the subsequent supply the smoke generation problem was taken care by adjusting the binders and additives and eco-friendly bricks were re-engineered and supplied to the same plant, which also performed splendidly and created all time record in their plant history.     

Application Study on β-Sialon-AI_2O_3 Brick in Iron Ladle

The microstructure and slag erosion fractal dimension of reaction interface of β-Sialon-Al2O3 brick used in 300 Mt iron ladle of Baosteel have been studied by SEM and XRD. The results indicated that β-Sialon-Al2O3 brick exhibited excellent slag resistance. The main wear mechanism of β-Sialon-Al2O3 brick is mainly from the spalling caused by thermal mechanical stress and attacked by slag secondly.     

Replacement of Flake Graphite in Aluminacarbon Refractories by Hexagonal Boron Nitride

Three kinds of composite alumina refractories were prepared with tabular alumina （3-1 and 1-0 mm） as aggregates,tabular alumina powder,α-Al2 O3 micropowder,and Si powder as matrix,adding 3 mass％ hexagonal boron nitride （h-BN）,3 mass％ flake graphite and 10 mass％ flake graphite,respectively.Cold physical properties,hot modulus of rupture,oxidation resistance,thermal shock resistance and slag corrosion resistance of the specimens were compared.The results show that：（1） physical properties and hot modulus of rupture of Al2 O3-h-BN refractories are slightly different from those of low carbon Al2 O3-C refractories,but better than those of traditional Al2 O3-C refractories with 10 mass％ graphite ; （2） Al2 O3-h-BN refractories have better thermal shock resistance and oxidation resistance than the carbon containing refractories,while similar slag resistance with low carbon Al2 O3-C refractories ; （3） h-BN can replace flake graphite as a starting material for the preparation of composite alumina refractories,considering the overall properties of the material.     

Discussion on Wear Mechanism of High Chrome Brick Used in Coal Slurry Gasifier

The microstructure and phase composition of high chrome brick used in coal slurry gasifier has been analyzed by means of SEM and Energy Spectrum. The results indicate that the used brick can be divided into different zones as slag-adhered zone, reaction zone, penetration zone and unaltered zone. The phase composition and microstructure are different and cracks occurred in different degree at these zones. A dense ring belt was formed with complex spinel ( Mg, Fe)( Cr,Al, Fe2O4) in the reaction zone near the hot face. The wear mechanism of the brick during its employment has been discussed. It is considered that the reaction and penetration of coal slag and strong reduetant bring about the composition change of the brick and destroys its original network inlayed structure and consequently result in its structure spalling and weakening strength, which is the main wear mechanism of the brick and followed by temperature fluctuation and high mechanical im-pact of flowing fluid with high-speed.     

Dear readers

正Since the modern steel-making technology arose in the 1950s,magnesia based refractories have been playing an increasingly important role to resist basic slag in prolonged service life of BOF,EAF and LF.China is well known as the primary source of various magnesia,     

Service Results and Analysis of Fully Co—clinkered Magnesite—Chrome Brick in Slagline Area of VOD Vessel

Operating condition and service results of several tested bricks in slagline area of the VOD vessel are described,It has been shown that the fully co-clinkered magnesite chrome brikc is superior,followed by two-stage calcined magnesite-dolominte brick,preracted magnesite-chrome brick and one-stage calcined moagnesite-dolomite brick. Chemical and petrologial examination were carried out by conventional analysis and optical microscope respectively,The reason of damage of the tested bricks are discussed and described as follows:(1) MgO in brick is erosed and dissolved by slag to destroy structure of the direct bond;(2)slag penctrating into the brick and then reacting with it to from various belts leading to spalling;(3)reducing action of reucing agents;(4) vaporiztion of some composition in the brick at high temperature under vacuum causes reducing weight and increasing porosity and (5) serious machanic abrasion.Therefore,Some opinions on increasing lining life of VOD vessels are suggested.     

Effects of Refractories on the Total Oxygen Content and Inclusions in the IF Steel

The effects of refractories of quarz-corundum consisting of 45 mass% quartz and 55 mass% corundum,fused corundum and fused magnesia on the total axygen content(TOC) and the composition of inclusions in intersitital free(IF) steel were studied,3 mass% microsilica was added into the three refractories as binder.The refractories were shaped as lining of the graphite crucible by castable method IF steel was placed in the crucibles,then they were heated at 1600℃ for 90min and 45min respectively.Oxygen contents of the steel samples were obtained by axygen determinator.Inclusions were analyzed by SEM and EDS.The results show that the TOC of steel increase with ncrease of Index of Oxygen Potetial (IOP) of the refractories.The steel sample coped with MgO refractories having the lowest IOP has the lowest TOC.