Abstract:  In order to realize the stable batch production of ultra-low P welding wire EF3 for high-grade pipelines， the conditions of dephosphorization were determined by studying the thermodynamic and dynamic conditions of dephosphorization. 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

Key words: Ultra-low P Welding Wire EF3, Converter, Dephosphorization, Slag, P Content

摘要： 为实现高级别管线用超低P焊丝EF3的批量稳定生产，对脱P的热力学条件和动力学条件研究，明确脱P的条件。通过铁水脱P、100 t转炉脱P、钢包脱P配合扒渣、二次LF精炼防回P工艺，配合低P合金，实现了超低P焊丝EF3的稳定生产。控制铁水w［Si］≤0.15%，造高碱度（R=6）的炉渣，可同时脱P、脱S，实现铁水w［P］≤0.020%、铁水w［S］≤0.005%；转炉终点温度在1 595～1 610 ℃，终渣碱度4.0左右，终渣中w［FeO］在23.0%～26.0%，可实现转炉出钢w［P］≤0.008%；采用钢包脱P，可实现钢水w［P］≤0.004%；钢包脱磷后配合扒渣工艺，扒渣前后基本不回P，采用二次LF精炼防增P，配合低P合金，增P量极少；从而可实现中间包钢水w［P］≤0.005%。

关键词: 超低P焊丝EF3, 转炉, 脱P, 扒渣, P含量