25SiMn2钢部分170mm连铸板坯吊运断裂原因分析和改进措施

An Analysis on Crane-Conveying Fracture of Partial 170 mm Casting Slab of Steel 25SiMn2 and Improving Measures

分析了在吊运过程部分25SiMn2钢重22t170mm×1650mm×10000mm连铸板坯断裂的原因。结果表明，浇铸时中间包钢水过热度高（30—36℃），引起铸坯厚度1／4位置柱状晶发达，钢液凝固时流动性不好，补缩不足，出现大量显微缩孔，并在反复吊运后在自身重力作用下，显微缩孔处应力集中开裂而造成铸坯断裂。通过降低中间包钢水过热度（10—30℃）、减少吊运次数可有效避免铸坯断裂。

The cause for fracture of partial 22 t 170 mm × 1 650 mm× 10 000 mm casting slab of steel 25SiMn2 dur- ing crane-conveying process has been examined and analyzed. Results show that during casting the superheating extent of liquid steel in tundish is higher （30 ～ 36 ℃ ） led to significant columnar crystal growth at 1/4 thickness of slab, poor fluid- ity of molten steel and lack back feeding during solidification, as result a lot of micro-shrinkage cavity occur causing crack at micro-shrinkage cavity by stress concentration effect and finally causing fracture of slab by repeating crane-conveying and acting with self-gravity. The fracture of casting slab is availably avoided by decreasing superheating extent of liquid in tundish to 10 - 30 % and reducing times of crane-conveying of slab.