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针对Q345钢(/%:0.14～0.18C、0.20～0.50Si、1.30～1.50Mn、≤0.025P、≤0.025S、0.015～0.060Al)250 mm×2 000 mm板坯中心偏析质量问题,建立凝固传热数学模型,并经射钉试验验证及修正,研究二冷强度(弱冷、中冷、强冷)、连铸速度(0.80～1.10 m/s)对铸坯温度场和坯壳厚度的影响,同时优化轻压下工艺和相应的连铸参数。结果表明,在典型拉速0.95 m/min及弱冷制度下,板坯凝固末端23.43 m,两相区长度7.22 m;减弱冷却强度,凝固末端后移0.56～0.67 m,两相区长度变长0.25～0.29 m;拉速增大0.15 m/min,凝固末端后移3.45～3.90 m,两相区长度变长0.94～1.22 m;优化采用弱冷冷却制度,拉速为0.95 m/min,轻压下位置对应固相率fs=0.4～0.9,总压下量达6 mm时,Q345钢板坯中心偏析Ⅰ级内平均合格率由83.1%提高到98.0%。
For Q345 steel (/%0.14~0.18C0.20~0.50Si, 1.30~1.50Mn, ≤0.025P, ≤0.025S, 0.015~0.060Al) 250 mm × 2000 mm slab center segregation quality problems, the establishment of solidification The mathematic model of heat transfer was established and verified by nailing test. The effects of secondary cooling strength (weak cold, intermediate cold and strong cold) and continuous casting speed (0.80 ~ 1.10 m / s) on the temperature field of the slab and the thickness of the shell Impact, while optimizing the soft reduction process and the corresponding casting parameters. The results show that the slab solidification tip is 23.43 m and the two-phase zone length is 7.22 m under the typical drawing speed of 0.95 m / min and the weak cooling system. The cooling strength is weakened and the solidification tip is backward shifted by 0.56-0.67 m. The length of the two- 0.25 ~ 0.29 m; the pulling speed increased 0.15 m / min, the end of the solidification moved backward 3.45 ~ 3.90 m, the length of the two-phase zone was 0.94-1.22 m long; the weak and cool cooling system was optimized and the pulling speed was 0.95 m / min. The average pass rate of Q345 steel slab center segregation grade Ⅰ was increased from 83.1% to 98.0% when the solid fraction of pressing position fs = 0.4 ~ 0.9 and the total reduction reached 6 mm.