Ractice of EF3 Ultra-low Phosphorus Smelting Process for High-grade Pipeline Welding Wire
In order to realize the stable batch production of ultra-low P welding wire EF3 for high-grade pipelines,the con-ditions of dephosphorization were determined by studying the thermodynamic and dynamic conditions of dephosphoriza-tion.Through the process of molten iron dephosphorization,100 t converter dephosphorization,ladle dephosphorization,slagging,secondary LF refining and anti-return P process,combined with low P alloy,stable production of ultra-low P welding wire EF3 is realized.By controlling molten iron w[Si]≤0.15% and making high basicity slag with R=6,it can remove P and S at the same time,achieve molten iron w[P]≤0.020%,iron w[S]≤0.005%;The end temperature of converter is from 1 595℃to 1 610℃,the basicity of the final slag is about 4.0,the content of FeO in the final slag is 23.0%-26.0%,the tapping w[P]of the converter is less than 0.008%;The molten steel w[P]is less than 0.004% by ladle dephosphorization;After dephosphorization with slag removal process,slag removal before and after the basic does not return P,Secondary LF is used to prevent P increase.P increase is very little with low P alloy.The slag removal process is adopted,the P content of molten steel w[P]≤0.005% in tundish can be achieved
Ultra-low P Welding Wire EF3ConverterDephosphorizationSlagP Content
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