Effect of rapid condensation on nitrogen content control of high nitrogen and high manganese steel
As people put forward higher strength,toughness,wear resistance and corrosion resistance requirements for high manganese steel materials,high nitrogen and high manganese steel came into being.At present,it is mainly produced by high pressure solidification,and the cost is high.Therefore,the method of adding supersaturated nitro-gen to molten steel at the end of smelting and reducing the escape of nitrogen in molten steel by rapid condensation during solidification of molten steel was proposed to control its nitrogen content.The high nitrogen and high manga-nese steel with nitrogen mass fraction of 0.218％was melted in a high temperature vertical melting furnace and then air-cooled and water-cooled respectively.The nitrogen content,microstructure,and primary dendrite spacing of high nitrogen high manganese steel under different cooling conditions were detected,and a calculation model for pri-mary dendrite spacing was established.The results show that the nitrogen mass fraction of air-cooled sample is 0.181％,and the nitrogen escape rate in the steel is 17％,while the nitrogen mass fraction of water-cooled sample is 0.206％,and the nitrogen escape rate in the steel is only 6％.The average primary dendrite spacing of air-cooled sample is 63.34 μm,and that of the water-cooled sample is 41.67 μm.The solidification micro-region of water-cooled sample is smaller.The local nitrogen-containing micro-bubble of air-cooled sample are larger,and the distri-bution is more concentrated,showing a loose state.The size of the nitrogen-containing micro-bubble in water-cooled sample is small,below 20 μm,and the number of micro-pores is small.The kinetic model of micro-bubble nuclea-tion and growth during solidification of molten steel shows that the higher the ambient pressure,the greater the ex-ternal direct inhibition force,the more difficult it is to form micro-bubbles,and the smaller the solidification micro-zone.The calculation model of primary dendrite spacing shows that with the increase of interface growth rate and temperature gradient,the dendrite spacing decreases gradually and can reach below 50 μm,and the solidification mi-crozone in steel also decreases,which is beneficial to inhibit the escape of nitrogen.Therefore,rapid condensation of high nitrogen and high manganese steel and reducing the escape of nitrogen from the molten steel during solidifica-tion are effective methods to increase the nitrogen content in high manganese steel.
high nitrogen and high manganese steelrapid condensationnitrogen contentdendrite spacingnitro-gen bubble
NETL
NSTL
万方数据
