洁净钢用耐火材料现状与发展

1、Li HongxiaLuoyang Institute of Refractories Research Introduction Basic principle of refractories Selection for the clean steel production Refractories for the clean steel SummaryThe optimization of steel product structure and improvement of steel quality The demands for clean steels The low cost an

2、d high efficient clean steels metallurgy.Why? The restrict of resource, energy and environment factors The clean steelsl Factors: O, N, S, P, H (sometimes including C), the non-metallic inclusions Reasonable low level The structure and distribution of non-metallic inclusionsslaginclusionsSteel moveS

3、teel move Influence of refractories Influencing the composition of the steelComponent dissolution(C,O,S.) Non-metallic inclusionsCleaning and or changing inclusion structureDecrease the quality of billet steel Increasethe quality of the billet steelHarmful factorHarmful factorBeneficial factorsBenef

4、icial factorsMetallurgical processes on which refractories take influence Secondary Secondary metallurgicalmetallurgicalContinuous castingContinuous castingLadleTundishSlide gateTypical characteristics of refractories for the clean steelsl Little contaminations to molten steell Good corrosion resist

5、ancel Taking cleaning function roles l Excellent thermal shock resistancel High reliability and qualily consistency lElements such as P, S, O, N, H (sometimes include C) is the main harmful elements for the clean steel, the followings are non-metallic inclusionslThe elements pick-up tendency in the

6、molten steel caused by refractories can be calculated theoretically according to thermodynamics Oxygen pick-upMgO, ZrO2 ,CaO and MgOAl2O3 materials should be selected for the metallurgical process of the clean steel with low content of oxygenSulfur in molten steellThe degree of sulfer pick-up in mol

7、ten steel is closely related to the equilibrium oxygen potential of oxides or their compounds in molten steellThe higher the equilibrium oxygen potential of refractory oxides, the higher sulfur pick-up in molten steellBasic refractories are beneficial to desulfurization of molten steelPhosphor in mo

8、lten steell The phosphor content in refractories is very lowl When phosphates are used as binder or additives in refractories, P pick-up in molten steel from refractories may occurl In this case, keeping reasonable CaO content in MgO-based refractories could inhibit P pick-up in molten steel.Hydrgen

9、 in molten steellThe residual water or binder in refractories may result in hydrogen pick-up in molten steel, which can increase the risk of hydrogen embrittlement of steel products Carbon pick-up in molten steellSolubility of carbon in iron is 5.41% at 1600lFocus on the contamination of high carbon

10、-containing refractories to the molten steel, especially low to carbon or ultra-low carbon molten steellDeveloping low carbon-containing refractories for low / ultralow carbon steelInclusions in the molten steel lRefractories materials also can influence the types and morphologies of inclusions in t

11、he molten steel RefractoriesRefractoriesAlAl2 2O O3 3-MgO -C-MgO -CMgOMgOMgO-CaO -CMgO-CaO -CInclusionssilicate inclusionsforsterite compositeCaO-Al2O3-SiO2-FeOInfluence of Al2O3-MgO castables with different compositions as the working linings for 82B steel on inclusions RefractoriesRefractoriesAlAl

12、2 2O O3 3-rich Al-rich Al2 2O O3 3- -MgO castableMgO castableMgO-rich AlMgO-rich Al2 2O O3 3- -MgO castableMgO castableInclusionsSiO2 inclusionsMgO or CaO aluminosilicate inclusionsCharacteristics of inclusionslarge dimensions high hardnesssmall dimensions good plasticity low hardnessRefractories Re

13、fractories for secondary refining for secondary refining processprocessProcessRefractoriesAODMgO-Cr2O3, MgO-CaOVODMgO-C, Alumina-Spinel, Dolomite brickLFMgO-CaO, Al2O3-MgO refractories, high Alumina brickRHMgO-Cr2O3, MgO-C, Al2O3-MgO -spinelRefractories for secondary refining processMgO-CaO Refracto

14、riesExcellent high temperature mechanical propertiesHigh corrosion resistance to slagAbsorbing S and P in the molten steeldecrease of the amount and the size of non-metallic inclusionshardness of the inclusions is loweredPoor Poor hydration resistancehydration resistancethe manufacture and the appli

15、cation of MgO-CaO refractories are restricted(2) MgO-CaO RefractorieslFuture development for MgO-CaO RefractoriesnHigh grade MgO-CaO raw materialsnHigh CaO contentnMgO-CaO castable /BricknQuality consistency(2) MgO-CaO Refractoriesl Environmental friendly performancel Low contamination to molten ste

16、ell Good high temperature stability l Poor wettability to molten slag or molten steel High cost and the difficulties in preparation.MgAlON Refractoriesl The refractories used at lower vessel, upper vessel, the snorkels of RH are commonly MgO-Cr2O3 refractories. l Cr+6 causing environmental pollution

17、, the alternative materials should be developed: environment-friendly, long service life, little contaminationl The promising Cr2O3 free materials such as MgO-spinel-ZrO2, MgO-CaO-ZrO2 refractories have been in field trials, good results have been given.Refractories for RHRefractories Refractories f

18、or tundishfor tundishl refractory coating of MgO-CaO materials with CaO content higher than 40% has been developed to absorb harmful elements and eliminate inclusionsl Environment-friendly new type MgO-CaO materials, binderl CaO, ZrO2 ceramic filtersl Optimizing inner structure of tundish to push th

19、e up movement of inclusion Refractories for tundishl Slag dam, weirs, gas curtain and turbulence inhibitor are placed in the tundish to control the flow of the molten steel for obtaining stable flow and eliminating inclusions to a great degree, which is helpful for the producing the clean steelRefra

20、ctories for flow controlling systeml Slide gate, long nozzle, submerged nozzle and monolithic stopper: carbon-containing refractories C pick-up l Long nozzle or submerged nozzle with carbon free liner was developed and has been successfully applied in practicel Low or free carbon refractories for fl

21、ow controlling refractoriesRefractories Refractories for flow controlling in continuous castingfor flow controlling in continuous castingAnti-clogging of Al2O3 n Influence the production efficiencyn Decrease the quality of the steel Anti-clogging by structure Anti-clogging by materials: ZrO2-CaO-C i

22、nner SEN Free carbon and silicon Al2O3-SiO2 inner SENn No or little cloggingn C pick-up decrease form 3.8ppm to 1.1ppm3.3 Refractories for flow controlling in continuous castingRefractories for flow controlling in continuous castingProperties ProductsInner AInner BSlag lineAl2O3 % 71.5869.38ZrO2 %6.

23、7676-80MgO %23.6621.92C %15-20A.P. %14-17B.D. g/cm32.562.653.5-3.6CCS MPa242120-25CMOR MPa5.5-7.5l Carbon content of MgO-C refractories is the key factor for C pick-up in molten steelsl MgO-C refractories with higher carbon content at ladle slag line cause the more carbon pick-up in the molten steel

24、RefractoriesRefractoriesC%C%1MG8.32MG15.53MG17.9Pyrohyllite-SiC3.7MgO-Al2O3-SiC4.1Relationship between carbon pick up o f IF steel caused by carbon containing refractories and soaking time in liquid steel3.43.4 Low carbon MgO-C refractories Low carbon MgO-C refractoriesl The development of low carbo

25、n containing of MgO-C refractories has become much more importantl Problems for low-carbon MgO-Cnpoor thermal shock resistancenbad spalling resistance ncorrosion resistance decrease l How to balance and compensate these properties is a main bottleneck for the developing low carbon MgO-C refractories

26、l Many investigationnMetal (Al, Al/Mg, Si, etc.)nCarbide (SiC, B4C, TiC, etc.)nNitride (TiN, TiCN, etc.)nBoride (ZrB2, CaB6, etc.)nNano carbon black, etc. The properties of low carbon MgO-C refractories can be improved. l with improved microstructure and propertiesl A new concept using a catalytic-g

27、rowth technique to generate in-situ formed carbide/oxide nanofibres or carbon nanotube in carbon containing refractory bricks was introduced.Novel concept for low-carbon containing refractoriesl Composite binder was heat treated under a reducing atmosphere, carbon nanofiber of approximately 200 nm i

28、n diameter was obtained by KIDOl The novel preparation conception can also be applied to develop other low carbon containing materials, such as Al2O3-C、ZrO2-C refractories for continuous casting l carbon-free and basic refractories have the very promising application future as ladle lining refractor

29、iesl The main non-carbon ladle refractories includedlIntegral castable refractories (Al2O3 Spinel, Al2O3 MgO refractories)lCarbon free precast block Non-carbon ladle refractoriesl New carbon free materials used as working lining for LF-VD with capacity of 150mt has been developed by Luoyang Institute of Refractories Researchl The field trials showed that service span was 120 heats (average) with the residual thickness of 110mm after use. Physical and chemical properties of ref