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分析了Q550D钢(/%:0.15C,0.25Si,1.40Mn,≤0.010P,≤0.002S,0.03Nb,0.06V,0.015Ti,0.020Alt)连铸板坯角部横裂纹,得出角部横裂纹产生于结晶器内,并进一步扩展于二冷区,另外,在弯曲段(Ⅲ脆性区)外弧铸坯受拉应力,也是造成外弧角部横裂纹产生的重要原因。通过降低结晶器宽面水流量200 L/min,窄面20 L/min,对弧精度从±0.5 mm提高至±0.3 mm,振幅和振频分别从4~5 mm和130~136 opm改进至3.6~4.5mm和140~146 opm,结晶器锥度从0.9%~1.0%增至1.0%~1.1%,二冷工艺由边部自然冷却改进为喷嘴冷却,钢中氮含量由≤60×10~(-6)降至≤40×10~(-6)等工艺措施,角部裂纹发生率大幅度降低。
The corner crack of Q550D steel (/%: 0.15C, 0.25Si, 1.40Mn, ≤0.010P, ≤0.002S, 0.03Nb, 0.06V, 0.015Ti, 0.020Alt) The transverse cracks are generated in the mold and further extend to the secondary cooling zone. In addition, the tensile stress of the arc billet in the curved section (Ⅲ brittle zone) is also an important reason for the lateral crack in the corner of the outer arc. The arc accuracy was improved from ± 0.5 mm to ± 0.3 mm and the amplitude and vibration frequency were improved from 4 ~ 5 mm and 130 ~ 136 opm, respectively, to 200 L / min for the wide face water flow and 20 L / min for the narrow face 3.6 ~ 4.5mm and 140 ~ 146opm. The taper of the mold increased from 0.9% ~ 1.0% to 1.0% ~ 1.1%. The second cooling process was improved by the natural cooling of the nozzle to cool the nozzle. The nitrogen content in the steel was reduced from ≤60 × 10 ~ (-6) down to ≤ 40 × 10 -6 (-6) and other technical measures, the incidence of corner cracks significantly reduced.