Φ430mm圆坯表面质量问题及改善措施

包钢Ф430 mm圆坯经过热轧生产的无缝钢管大批量出现外结疤,通过热酸及裂纹分析发现是因为圆坯表面存在着微裂纹,在随后的热轧生产中形成外结疤,针对Ф430 mm圆坯表面出现微裂纹的问题,通过调整炼钢连铸工艺和钢种成分,制订出相应的改进措施。圆坯表面质量得到明显改善,经过热轧生产后,钢管成材率得到提高。     

Influence of La2O3 on crystallization behavior of free-fluoride mould flux and heat transfer of slag films

In order to research the influence of La2O3 on crystallization behavior of free-fluoride mould flux and the heat transfer of slag film,free-fluoride mould flux with various La2O3 content were investigated by using self-made mould simulator,comprehensive thermal analyzer and SEM-EDS.With the increase of La2O3 content from 0% to 20%,the crystallization ratios of mould flux films were improved from 2% to 90% and the thicknesses of films were also enhanced over two times.Moreover,crystallization temperature was greatly raised and its increasing extent reached 100 oC.It could also decrease the melting temperature of casting powder about 50 oC.However,the undissolved La2O3 particles appeared in slag film if the ratio of La2O3 in free-fluoride mould flux was much too high.