Study On Migration Of Alkali Metals And Erosion Mechanism Of Refractories In Synthesis Process Of Vanadium-nitrogen Alloys

Vanadium-nitrogen alloy is widely used in the production of microalloyed steel and alloy steel.Due to nitrogen can promote vanadium precipitation efficiently.Strengthening grain refinement and precipitation strengthening.The production of vanadium-nitrogen alloys is mostly used V₂O₅ or V₂O₃ as the raw materials.There is no doubt that the current process of vanadium extraction with salt roasting lead to the vanadium oxide products with a small amount of sodium compounds and potassium compounds.Alkali metals of sodium and potassium have some negative impact on the synthesis process of vanadium-nitrogen alloy.An enterprise uses V₂O₃ as raw material to product vanadium-nitrogen alloy by the pusher kiln method.The alkali metal volatilization forms deposit and that erodes the top refractory material of the furnace.In severe case,the deposit lead to block the furnace and stuck graphite crucible,which seriously affect the production.Based on this,this paper studies the material flow characteristics of sodium and potassium alkali metals in the synthesis process of vanadium-nitrogen alloy.What's more,this paper studies the erosion mechanism of sodium and potassium alkali metals on different types of refractories.Which can provide some reference for optimize process operation and select refractory of pusher kiln.The evolution of vanadium-containing phase in the synthesis of vanadium-nitrogen alloy was calculated by FactSage software.Combine with the experimental results,it was found that the carbonization reaction and nitridation reaction of V₂O₃ proceed simultaneously.There without vanadium carbide product was produced in carbonization reaction and nitridation reaction.Nitrogen atmosphere can reduce the start reaction temperature of carbonization reaction.When the temperature exceeds 1180^oC,some VN will be carbonized to V₁₀C₈.If the C content is insufficient,the intermediate product VC_x O_y will be formed.The main temperatures range of sodium and potassium alkali metals participate chemical reactions are 650¹240^oC.At high temperature,sodium and potassium alkali metals will form Na and K vapors and escape the ball.But Na and K vapors will be oxidized by other gases.In the flue mouth,the main forms of sodium and potassium alkali metals are Na₂CO₃,Na₂S,Na₂SO₄,K₂CO₃,K₂S and K₂SO₄.The main temperatures range of sodium and potassium alkali metals volatilization escape are670¹220^oC.Tthe volatilization rate of sodium and potassium alkali metals increase with increasing temperature.At 670^oC,the volatilization rates of sodium and potassium are less than 7%.The volatilization rates of sodium and potassium are 37%and 39%at970^oC,respectively.And at 1170^oC,the sodium and potassium volatilization rates are79%and 78%,respectively.When the temperature is 1510^oC,the sodium and potassium alkali metal volatilization rates are all about 80%.The alkali metal corrosion resistance of magnesia brick is better than that of SiC-Si₃N₄ composite brick.When sodium and potassium alkali metals etched SiC-Si₃N₄composite brick,Na₂CO₃ performed more actively.While K₂CO₃ performed more actively in sodium and potassium alkali metals etched magnesia brick.The magnesia brick was eroded for 16h by alkali metal sodium or potassium.The surface of magnesia brick was slightly pulverized,but the overall structure was intact.The magnesia brick SiC-Si₃N₄ composite brick was eroded for 1h by alkali metal sodium or potassium.SiC-Si₃N₄ composite brick showed obvious shedding phenomenon,and alkali metal had migrated to the inside of SiC-Si₃N₄ composite brick.When the erosion time of SiC-Si₃N₄ composite brick is 3h,SiC-Si₃N₄ composite brick showed obvious deformation.Firstly,the alkali metal is immersed in the interior of the refractory by capillarity.Then alkali metal reacted with the matrix materials of refractory.The order of alkali metal sodium or potassium reaction with SiC-Si₃N₄ composite brick matrix materials is Si₃N₄>SiC>SiO₂.The alkali metal sodium or potassium etched magnesia brick only react with the matrix material SiO₂ of magnesia brick.