Effects Of Binder,Antioxidant And Amorphous Graphite On The Properties Of Low-carbon MgO-C Refractories

MgO-C refractories are widely used in the steel making industries such as BOF,EAF and steel ladles,because of their high refractoriness,excellent thermal shock,low high temperature creep and excellent corrosion resistance and antistrip performance.However,the main drawback of MgO-C refractories is its poor oxidation resistance.After the oxidation of carbon,the structure of MgO-C brick is destroyed,and then the intensity reduced.Under the effect of slag erosion and mechanical erosion,MgO particles gradually damaged by corrosion or fell off.The research mainly studied the the effects of binder types,the kinds and contents of waste Si-Si C composite powder and the contents of amorphous graphite on properties and microstructure of Low-carbon MgO-C refractory,and reduce the cost of MgO-C refractory.The main conclusions are as follows:In this paper,the research work consists three parts.In the first part,different binders(thermoplastic phenolic resin,CMC,pulp waste liquid,dextrin and EC)on the property of low-carbon MgO-C refractory(C,6wt%).The second part studies the effects of species and contents of waste Si-Si C composite powder on the property and microstructure of low-carbon MgO-C refractory then chose the optimum Si-Si C composite powder and content to compare with traditional antioxidants.In the third part,the effects of contents of amorphous graphite on the property of low-carbon MgO-C refractory are studied.(1)Binder research work finds that: contrast with the samples bonded with thermoplastic phenolic resin,using CMC,pulp waste liquid,dextrin and EC as binders of MgO-C bricks can improve the oxidation resistance of low-carbon MgO-C refractory varying degrees,but they can bring down the strength obviously.Use the thermoplastic phenolic resin diluted by PEG to 50wt% as binder can improve the oxidation resistance of MgO-C refractory without obviously decrease the strength,but the specimens heated by 1600℃ will have serious expansion and deformation,and this is harmful to the use performance of material.(2)In the research of different species and contents of Si-Si C composite powder finds:Si-Si C composite powder with higher Si and Si-Si C composite powder with higher Si C can improve the oxidation resistance of MgO-C refractory,enhance the mechanical property and influence the microstructure of MgO-C bricks.When the content of Si-Si C composite powder with higher Si is 2wt%,specimen has best mechanical properties,and its CMOR and CCS after cured at 230℃ are 9.8MPa and 61.8MPa.When the content of Si-Si C composite powder with higher Si is 3wt%,specimen has best oxidation resistance.Synthetically considering all the properties,the specimen with 2wt% Si-Si C composite powder with higher Si has better properties.(3)The oxidation resistance and mechanical properties of the specimen added with 2wt% Si-Si C composite powder with higher Si are better than the specimen added with 2wt% Si and the specimen added with 2wt% Si C.(4)Use amorphous graphite to substitute for flake graphite(1000 mesh)to prepare MgO-C refractory and study the effect of the contents of amorphous graphite on MgO-C bricks.Research finds that,with the contents of amorphous graphite increasing to 4wt%,the oxidation resistance of specimens improved.In addition,the apperent porosity of specimens cured at 230℃ reduced from 18.9% to 14.6%,and the apperent porosity of specimens coked at 1600℃ reduced from 20.2% to 16.0%.The mechanical properties of low-carbon MgO-C refractories added with different contents of amorphous graphite improved varying degrees.