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某钢厂Q345B钢供厚板轧制铸坯改直装轧制工艺后,轧制后钢板出现冷弯裂纹。通过对热装、直装轧制工艺的钢板金相组织、夹杂物、析出物进行研究,发现直装轧制工艺的钢板内的带状组织、MnS夹杂是冷弯裂纹产生的主要原因。另外直装轧制工艺钢板内析出物较少,不能充分发挥微合金元素的强化作用。带状组织产生的根本原因是连铸坯在凝固过程中碳和其他元素一起产生枝晶偏析,轧制过程中枝晶偏析逐渐转变成中间坯和成品钢板的带状偏析。硫化锰夹杂是在钢液凝固过程产生的,根据化学成分和硫化锰的形貌推断,这种均质呈带状分布的硫化锰夹杂是形成于用铝脱氧但又无其他过多合金元素的镇静钢中。通过控制硫含量、电磁搅拌、钢种成分微调等研究工作,目前直装轧制钢板内的条带状硫化锰夹杂已经减少,铸坯成分偏析也得到相应改善。
After a steel mill Q345B steel for slab rolling slab to direct rolling process, the cold rolled steel plate after cracking. By studying the microstructure, inclusions and precipitates of hot-rolled and direct-rolled steel plates, it is found that the strip structure and MnS inclusions in the steel plate of the direct rolling process are the main causes of the cold bending cracks. In addition direct rolling process less precipitation within the steel plate, can not give full play to the role of micro-alloying elements. The root cause of the ribbon structure is the dendritic segregation of carbon and other elements during the solidification of the slab. The dendritic segregation gradually changes into the ribbon segregation of the intermediate slab and the finished steel during the rolling process. Manganese sulfide inclusions are generated in the solidification of molten steel. According to the chemical composition and morphology of the manganese sulfide, the homogeneous distribution of the manganese sulfide inclusions is formed in the oxygen deoxidation but no other excessive alloying elements Calm steel. By controlling the sulfur content, electromagnetic stirring, fine tuning of steel components and other research work, the current direct rolling of the strip within the strip of manganese sulfide inclusions have been reduced, slab composition segregation has also been improved.