Preparation And Damage Mechanism Of Low Carbon Magnesium Carbon Brick For VOD Refining Furnace

With the development of science and technology and production,the conditions of steel smelting have become more and more severe.With the increase of smelting temperature and the change of slag composition,the refractory in slag line of ladle is seriously damaged.Magnesia carbon brick is often used as the lining material of VOD furnace,so it is of great significance to study the preparation and damage mechanism of magnesia carbon brick,and reduce the damage rate of magnesia carbon brick through proper selection of raw materials and particle size distribution,so as to improve its service life and steel quality.In this paper,the damage mechanism of low carbon magnesia carbon brick was revealed through the used brick detection,slag resistance experiment and preparation research of magnesia carbon brick for VOD furnace.The effect of Cr₇C₃and its composite as a new antioxidant on the performance of magnesia carbon brick was explored.The conclusions are as follows:(1)The slag in slag line Mg O-C brick infiltrates into the material along the matrix part,which has weak erosion ability to large particle magnesia,and the cracks in the brick are filled by molten steel.The slag will obviously erode the large particles of magnesia in the molten pool magnesia carbon brick,and the cracks in the brick will be filled by the slag.(2)When the alkalinity is in the range of 1?2.5,the higher the alkalinity is,the weaker the slag erosion ability is.When the basicity is high,the penetration of Si O₂into the slag decreases,and the dissolution of Mg O into the slag decreases.When the basicity of slag is 2.5and there is more calcium fluoride(>2wt%),the addition of calcium fluoride will reduce the viscosity of slag and promote the penetration of calcium,aluminum and silicon into the material.When the basicity of slag is 2.5,the content of titanium oxide in slag increases,and the[Ti O₆]^8-octahedron will reduce the viscosity of slag and increase the penetration of slag.The slag is mainly composed of calcium and silicon penetrating into Mg O-C brick.The permeability of iron oxide in slag is affected by the content of silicon in slag.Therefore,by controlling the basicity of slag at about 2.5,Ca F₂content within 4%and reducing the content of Ti O₂,the corrosion of slag on magnesia carbon refractories can be reduced.(3)The results show that the addition of Cr₇C₃powder can effectively improve the oxidation resistance of low carbon magnesia carbon bricks,and the addition of 3wt%is the best.Cr₇C₃can react with oxygen prior to carbon to form chromium oxide and magnesia chromium spinel,which can fill the pores.In addition,Cr₇C₃can reduce the iron oxide in the slag and improve the slag resistance of the material.The appropriate addition amount is 2wt%.At the same time,the addition of Cr₇C₃can improve the strength retention of the material after thermal shock.In conclusion,the best addition amount of Cr₇C₃powder is 2wt%.(4)The results show that the composite of Cr₇C₃powder and iron powder has better oxidation resistance at 1600?and 1650?(the optimum ratio is 3:1).The results show that the composite powders can form solid solution in the oxidation region,and form ferro chrome spinel(Mg(Fe,Cr)₂O₄)at high temperature to plug the pores;in the non-oxidation region,the composite powders can react with graphite to form ferrochrome carbide,which can inhibit the consumption of graphite.