SM490A-B铸坯角部裂纹的分析

Analysis of Corner Cracks in SM490A-B Slab

用金相显微镜、扫描电镜及能谱仪分析低碳含硼钢SM490A-B铸坯角部裂纹的特征和成因。结果表明:铸坯角部裂纹主要为横裂纹,裂纹沿发达的柱状晶和粗大的奥氏体开裂,铁素体膜和裂纹内的氧化铝夹杂促进了裂纹的萌生和扩展。冷却不均匀和高的过热度造成奥氏体晶粒粗大,且不同区域的铸坯角部组织不一致;铸坯内外大的温度梯度使柱状晶发达。

The characteristics and causes of corner cracks of SM490 A-B slab used for low-carbon and boron-bearing steel were analyzed by the metallographic microscope, scanning electron microscope and energy spectrometer. The results showed that the cracks in the corner of the slab were mainly transverse cracks; the crack was cracked along the developed columnar crystals and coarse austenite. The ferrite film and the alumina inclusions in the crack promoted the initiation and expansion of the cracks. The coarse austenite grain was caused by uneven cooling and high superheating, and the angular structure of the slab in different regions was not consistent; the large temperature gradient inside and outside the slab developed the columnar crystal.