Q345B中厚钢板表面裂纹原因分析

通过板坯表面酸洗、钢板表面抛丸、氮氧分析、扫描电镜能谱仪和金相显微镜等手段,对唐钢所生产Q345B中厚钢板的表面裂纹处进行观察、检测,研究了热装板坯在轧制过程中产生表面裂纹的原因和机理.同时还进行了板坯热装、温装、冷装对比试验.结果表明,含铝低合金钢板由于板坯热装温度处于第三低温脆性区域,冷却过程中奥氏体向铁素体的转变不完全,AIN在奥氏体晶界析出,削弱晶界能,体积膨胀加剧了晶界强度的减弱,在轧制时扩展形成表面裂纹.

Cause Analysis of Surface Crack on Q345B Medium and Heavy Plate

By means of slab surface acid corrosion, plate surface shot blasting, nitrogen and oxygen determina- tion, scanning electron microscopy spectrometer and metallographic microscope, observation and testing are carried out to the surface cracks on Q345B steel plate produced by Tang, gang, causes and mechanism of surface cracks formed dur- ing wiling of hot charged slab are studied, while comparisons are made on the slabs hot charged, warm charged and cold charged. The results show that the surface cracks formed on low alloyed plate with A1 content are caused by in- complete transformation from austenite to ferrite during cooling due to various factors such as slab hot charging tempera- ture in third temperature region of brittleness , A1N precipitates at austenite grain boundary impairing the grain bounda- ry energy and volume expansion further impairing the grain boundary strength, which develop into surface cracks during rolling.