摘要
The most important characteristics of the ultra clean ferritic stainless steel is that the carbon,nitrogen and other interstitial elements are very low.The ultra clean ferritic stainless steel has been widely used for household appliances,auto exhaust system,elevator,water treatment system,building roof and other various fields,because of its low cost,pro-environment,excellent properties.They can replace some traditional austenitic stainless steel.such 304 and 316L.The addition of titanium to liquid steel has become common for stabilizing nitrogen and carbon in steel.Titanium reacts with nitrogen,carbon,and oxygen to form titanium nitride,carbide, carbonitride and oxide.These inclusions may have a deleterious effect on the properties such as toughness, ductility,weldability and corrosion.In addition,the inclusions can also agglomerate and cause surface quality problem of the slab and clogging of the submerged entry nozzle during continuous casting process. The formation rules of inclusions in ultra clean ferritic stainless steel were investigated by the thermodynamic calculation,and methods of controlling inclusions were put forward to improve the quality of product.The composition,type,amount,size and distribution of the inclusions in the slab are investigated by optical microscope and scanning electron microscope.The results can be concluded as follows.(1) In the slab,the main original inclusions,with size of larger than 2μm,are Al_2O_3,TiN or Ti(CN) and complex TiN or Ti(CN) inclusion with core of MgO,MgO-Al_2O_3 and Ti_2o_3,which will not affect the performance of the steel if they are in diffusing distribution.The size of these inclusions are less than 10μm except some Al_2O_3 inclusions in size of 10-40μm.(2) Foreign inclusions are Ti_2O_3-Al_2O_3-MgO-SiO_2 in size above 50μm covered by TiN or Ti (CN).Although these inclusions are few,they do harm to the surface quality of stainless steel.It is able to reduce the risk of forming this kind of inclusion by aluminium deoxidation with increasing Al content to restrain the formation of Ti_2O_3.(3 ) TiN or Ti(CN) is easy to precipitate on inclusions such as MgO,MgO-Al_2O_3 and Ti_2O_3,except Al_2O_3.Controlling the content of[Ti]and[N]and the formation of the oxides can be used to control the precipitation of TiN or Ti(CN).
The most important characteristics of the ultra clean ferritic stainless steel is that the carbon,nitrogen and other interstitial elements are very low.The ultra clean ferritic stainless steel has been widely used for household appliances,auto exhaust system,elevator,water treatment system,building roof and other various fields,because of its low cost,pro-environment,excellent properties.They can replace some traditional austenitic stainless steel.such 304 and 316L.The addition of titanium to liquid steel has become common for stabilizing nitrogen and carbon in steel.Titanium reacts with nitrogen,carbon,and oxygen to form titanium nitride,carbide, carbonitride and oxide.These inclusions may have a deleterious effect on the properties such as toughness, ductility,weldability and corrosion.In addition,the inclusions can also agglomerate and cause surface quality problem of the slab and clogging of the submerged entry nozzle during continuous casting process. The formation rules of inclusions in ultra clean ferritic stainless steel were investigated by the thermodynamic calculation,and methods of controlling inclusions were put forward to improve the quality of product.The composition,type,amount,size and distribution of the inclusions in the slab are investigated by optical microscope and scanning electron microscope.The results can be concluded as follows.(1) In the slab,the main original inclusions,with size of larger than 2μm,are Al_2O_3,TiN or Ti(CN) and complex TiN or Ti(CN) inclusion with core of MgO,MgO-Al_2O_3 and Ti_2o_3,which will not affect the performance of the steel if they are in diffusing distribution.The size of these inclusions are less than 10μm except some Al_2O_3 inclusions in size of 10-40μm.(2) Foreign inclusions are Ti_2O_3-Al_2O_3-MgO-SiO_2 in size above 50μm covered by TiN or Ti (CN).Although these inclusions are few,they do harm to the surface quality of stainless steel.It is able to reduce the risk of forming this kind of inclusion by aluminium deoxidation with increasing Al content to restrain the formation of Ti_2O_3.(3 ) TiN or Ti(CN) is easy to precipitate on inclusions such as MgO,MgO-Al_2O_3 and Ti_2O_3,except Al_2O_3.Controlling the content of[Ti]and[N]and the formation of the oxides can be used to control the precipitation of TiN or Ti(CN).
作者
CHEN Zhaoping~(1)),XU Yingtie~(1)),GU Leiming~(1,2)),LI Shi~(3)),GU Xuehong~(3)) 1) Research Institute,Baoshan Iron & Steel Co.,Ltd.,Shanghai 201900,China 2) Cold Rolling Plant,Baoshan Iron & Steel Co.,Ltd.,Shanghai 200240,China 3) Stainless Steel Business Unit,Baoshan Iron & Steel Co.,Ltd.,Shanghai 201900,China
