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为了解大型铸锭在轧制过程中产生边裂的原因,通过对比铸坯中部和边部的成分、不同温度下相比例、两相硬度差等的变化规律,利用光学显微镜,扫描电子显微镜和电子背散射衍射观察分析试验钢的微观组织和断口形貌,分析了边部容易开裂的原因.结果表明,和中部相比,边部晶粒细小,且铁素体含量较多,但边部开裂更严重.这说明晶粒尺寸和相比例并不是影响使边部开裂严重的主要原因.而和中部比,铸锭边部试样两相硬度差较大,使两相在热变形过程中应变分配不均匀,容易在相界处产生应力集中,导致开裂.同时边部析出物较中部多,相界析出物的产生破坏了基体的连续性,容易在相界处产生显微裂纹,导致开裂.
In order to understand the reason of the large ingot ingot cracking during the rolling process, by comparing the composition of the middle and the edge of the slab, the phase contrast at different temperatures and the difference of the two phase hardness, the microstructure of the ingot was analyzed by optical microscope, scanning electron microscope and Electron backscatter diffraction was used to analyze the microstructure and fracture morphology of the test steel and the reasons for the easy cracking of the edge were analyzed.The results show that the edge grains are small and the ferrite content is higher than the middle part, Cracking more serious.This shows that the grain size and phase ratio is not the main reason to affect the serious edge cracking.And the middle than the ingot edge of the sample two phase difference between the larger hardness so that the two phases in the thermal deformation process Strain distribution is not uniform, easy to produce stress concentration in the phase boundary, leading to cracking.At the same time the edge of the precipitate is more than the middle, the occurrence of phase boundary precipitates undermine the continuity of the matrix, easy to produce micro-cracks in the phase boundary, resulting in Cracking.