φ300 mm连铸坯的表面缺陷及其预防

Surface Defects of 300-mm-diam Continuously Cast Slab and Its Precautions

45、40Cr和60Mn钢φ300 mm连铸坯表面出现渣沟、气孔等缺陷。采用扫描电镜、能谱仪以及贺利氏定氢、定氧仪分析了缺陷的特征和产生机制。研究发现:连铸坯气孔的产生主要是钢水中的氢含量过高所致。采取了增加真空循环脱气工序、改变入炉料结构、烘烤合金及原材料等措施,有效遏制了渣沟、气孔缺陷,改善了连铸坯的表面质量。

Surface defects such as slag trough and blowhole appeared on 300-mm-diam continuously cast slabs of 45,40Cr,or 60Mn steel.Characteristics and engendering mechanism of the defects were investigated by means of scanning electron microscope,spectrometer,and Heraeus hydrogen and oxygen analyzers.It was revealed that the blowhole on the continuously cast slab was primarily traced to the excessively high hydrogen content in the molten steel.Formations of the slag trough and blowhole on the continuously cast slabs has been effectively suppressed by the adoption of a vacuum circulation degassing process,change in structure of the charge materials,baking of the alloy and raw materials,thus improving surface quality of the continuously cast slabs.