Abstract: The longitudinal surface crack of 68 mm x 1 600 mm casting slab of Q235B steel (0. 18% C) and Q345B sleel (0. 17%C) produced by CSP process at Jiuquan Steel mainly occurred at first slab between heats with width of crack 0. 01 -0. 30 mm, depth 0. 10 mm and length ≥50 mm. The results by analyzing the influence factors on longitudinal crack show that as [ S] ≥ 008% , overheating temperature of liquid steel 340° , mold taper ≤4 mm, lower basicity and viscosity of mold powder and thickness of mold copper plat ≤12 mm, the crack index of slab obviously increases. With controlling [S] ≤0. 008% , overheating temperature of liquid steel 30 ±5 ℃ , fluctuation of liquid surface in mold + 3 mm, the occurred rate of crack for Q235B steel decreases to 0. 36% from original 2% , and for Q345B steel decreases to 0. 98% from original 5% .

Key words: Q235B and Q345B Steel, CSP, Casting Slab, Longitudinal Crack, Practice

摘要： 酒钢Q235B(0.18%C)和Q345B(0.17%C)钢CSP工艺生产的68 mm×1 600 mm铸坯的纵裂纹主要出现在炉次间的第一块铸坯,裂纹宽0.01～0.30 mm、深0.10 mm、长度≥50 mm。纵裂纹影响因素的分析结果表明,当[S]≥0.008%、钢水过热度≥40°、结晶器锥度≤4 mm时,保护渣碱度和粘度较低,以及结晶器钢板厚度≤12mm时,铸坯裂纹指数明显增加。通过控制[S]≤0.008%,钢液过热度30±5℃,结晶器液面波动±3 mm,Q235B钢裂纹发生率由2%降至0.36%,Q345B钢由5%降至0.98%。

关键词: Q235B和Q345B钢, CSP, 铸坯, 纵裂纹, 实践