浸入式水口结构对连铸大圆坯质量的影响

为研究不同结构的浸入式水口对大规格连铸圆坯质量的影响,以某钢厂生产断面直径为500 mm的 42CrMo连铸圆坯为背景,对使用侧孔浸入式水口和传统直通浸入式水口的使用效果开展研究。结果表明,采用侧孔浸入式水口浇铸时,结晶器进出水温差由传统直通水口的3.30 ℃提高至3.54 ℃;连铸圆坯中心疏松由1.5级改善至1.0级,中心偏析指数由0.93~1.21降低到0.98~1.02,近表层至近中心碳极差由0.050%~0.075%降至0.035%~0.053%,使用侧孔浸入式水口的连铸圆坯碳偏析得到改善;铸坯内弧侧表层至3/4R处氧化物夹杂物总量减少0.5个/mm2;铸坯从1/4R处向内长度不小于13 μm的硫化物数量减少0.35个/mm2;轧材全氧质量分数平均降低0.000 12%,夹杂物中B类氧化物夹杂均在1.5级以内,钢中大尺寸夹杂物明显减少,钢的洁净度得到改善。

Influence of submerged nozzle structure on large-size continuous casting round billet quality

In order to study the influence of submerged nozzle with different structures on the quality of large-size continuous casting round billet, the effect of side hole submerged nozzle and traditional straight submerged nozzle on the production of 42CrMo continuous casting round billet with the section diameter of 500 mm was studied. The results show that water temperature difference between the inlet and the outlet of mould increases from 3.30 ℃ to 3.54 ℃ when side hole submerged nozzle is used. The central porosity of continuous casting round billet is improved from grade 1.5 to 1.0, the central segregation index decreases from 0.93~1.21 to 0.98~1.02, and the carbon range from near surface to near center decreases from 0.050%~0.075% to 0.035%~0.053%. The carbon segregation of continuous casting round billet is improved by side hole submerged nozzle. The total amount of oxide inclusions decreases by 0.5/mm2 from the surface layer of inner arc side to 3/4R. The quantity of sulfide bigger than 13 μm from 1/4R inward decreases by 0.35/mm2; The total oxygen mass fraction of rolled steel is reduced by 0.000 12% on average, the B-type oxide inclusion in inclusions is all within grade 1.5, large size inclusions are reduced obviously, and the cleanliness of the steel is improved.