HSLA steels need extremely low levels of tramp elements like P,S,H and O t.During tapping the steel is deoxidized with aluminum and in the secondary metallurgy sulphur (【 10 ppm) and hydrogen (【 1 ppm) are extracted...HSLA steels need extremely low levels of tramp elements like P,S,H and O t.During tapping the steel is deoxidized with aluminum and in the secondary metallurgy sulphur (【 10 ppm) and hydrogen (【 1 ppm) are extracted.After tank degassing the steel is strongly Ca-treated by wire feeding to form CaS instead of MnS.Non-metallic inclusions in the steel and centre segregation with MnS are sinks for hydrogen which result in HIC (Hydrogen Induced Cracking).Therefore these steels ask for excellent oxide cleanness and S-contents of 【 10 ppm.Macro inclusions of 】 50 μm are harmful for the product.These large inclusions are seldom and difficult to be detected.Small inclusions of 【 15 μm do no harm to the product.The origin of non-metallic inclusions is,roughly spoken,one third each of de-oxidation-/reoxidation products,refractory and casting powder.Slag carry-over is mainly avoided by sensitive electronic devices.Slag covers and shrouding systems of the steel stream during the transfer of metal between ladle,tundish and mold are effective to avoid reoxidation.Systems to control the flow of steel in tundish and mold favor the floatation of inclusions and their even distribution in the strand.展开更多
The experimental results of niobium enrichment in laboratory and in blast furnace in Baotou Iron and Steel Corporation were reported.The effects of temperature,constituents of slag and silicon content in hot metal on ...The experimental results of niobium enrichment in laboratory and in blast furnace in Baotou Iron and Steel Corporation were reported.The effects of temperature,constituents of slag and silicon content in hot metal on niobium recovery were studied and the results have been verified by blast furnace operation.Optical and electronic microscopy and EPMA was observed that at the metal-slag interface there is NbC deposit layer obstructed Nb entering into the metal,By raising the temperature of hearth and agitating the bath,the reduc- tion of niobium oxide in slag could be speeded up,the solubility of Nb in hot metal could increase and the deposited NbC layer became thinner and even disappeared,in result,Nb recovery was increased.A compre- hensive extraction process combining ore dressing with pyro-hydro-metallurgy was suggested for Baotou niobium resource which was difficult to be concentrated formerly.The methods of increasing niobium recovery were also suggested.展开更多
文摘HSLA steels need extremely low levels of tramp elements like P,S,H and O t.During tapping the steel is deoxidized with aluminum and in the secondary metallurgy sulphur (【 10 ppm) and hydrogen (【 1 ppm) are extracted.After tank degassing the steel is strongly Ca-treated by wire feeding to form CaS instead of MnS.Non-metallic inclusions in the steel and centre segregation with MnS are sinks for hydrogen which result in HIC (Hydrogen Induced Cracking).Therefore these steels ask for excellent oxide cleanness and S-contents of 【 10 ppm.Macro inclusions of 】 50 μm are harmful for the product.These large inclusions are seldom and difficult to be detected.Small inclusions of 【 15 μm do no harm to the product.The origin of non-metallic inclusions is,roughly spoken,one third each of de-oxidation-/reoxidation products,refractory and casting powder.Slag carry-over is mainly avoided by sensitive electronic devices.Slag covers and shrouding systems of the steel stream during the transfer of metal between ladle,tundish and mold are effective to avoid reoxidation.Systems to control the flow of steel in tundish and mold favor the floatation of inclusions and their even distribution in the strand.
文摘The experimental results of niobium enrichment in laboratory and in blast furnace in Baotou Iron and Steel Corporation were reported.The effects of temperature,constituents of slag and silicon content in hot metal on niobium recovery were studied and the results have been verified by blast furnace operation.Optical and electronic microscopy and EPMA was observed that at the metal-slag interface there is NbC deposit layer obstructed Nb entering into the metal,By raising the temperature of hearth and agitating the bath,the reduc- tion of niobium oxide in slag could be speeded up,the solubility of Nb in hot metal could increase and the deposited NbC layer became thinner and even disappeared,in result,Nb recovery was increased.A compre- hensive extraction process combining ore dressing with pyro-hydro-metallurgy was suggested for Baotou niobium resource which was difficult to be concentrated formerly.The methods of increasing niobium recovery were also suggested.
