连铸板坯表层网状裂纹的成因研究

Research of Causes of Surface Network Cracks on Continuous Casting Slabs

统计分析了攀钢所产管线钢、梁板钢等200mm×1300mm连铸坯表层网状裂纹的影响因素;发现钢中碳、锰硫比、合金元素(Al,Ti,V)、连铸机设备和浇注状况对其形成和扩展都有重要影响。通过金相显微镜、SEM、TEM和EDS等手段,研究了铸坯表层网状裂纹的形貌特点,认为此裂纹是连铸坯表面冷却不均匀而产生γ→α→γ反复相变,并伴有各种碳氮化物在晶界析出,连铸坯在外力(热应力、弯曲矫直应力等)作用下沿晶界开裂所致。

For the surface network cracks in 200 mm thickness slabs for pipeline and vehicle frame, it is found that the carbon content, Mn/S ratio and Al, Ti, V, Nb alloy additions and continuous caster conditions are attributable to the formation and propagation of surface and subsurface network cracks. The microscope, SEM, TEM and EDS results revealed that the particles precipitated in pre-austenite grain boundaries will result in surface network cracks under sufficient stress such as thermal stress, bending and straightening stress due to uneven cooling of slab surface.