氩气泡致管线钢内部缺陷的控制理论与实践

Control theory and practice of argon bubble-induced internal defects in pipeline steel

随着石油和天然气工业的快速发展,对管线钢的强度、韧性和焊接性能的要求不断提高。优化连铸过程中的氩气密封工艺对于减少或避免因氩气泡引起的内部缺陷至关重要,对提高管线钢产品质量具有重要意义。以L485M管线钢为研究对象,通过控制连铸结晶器浸入式水口密封氩气的流量和铸机拉速等参数研究了密封氩气流量对管线钢L485M内部缺陷的影响规律,并提出优化的浸入式水口密封氩气流量和拉速以解决氩气泡导致的连铸坯内部缺陷问题。研究表明,浸入式水口密封氩气流量过大时会在浸入式水口内产生氩气泡,易被铸坯凝固前沿捕获导致铸坯内部缺陷的发生,在轧制后形成椭圆扁平状缺陷,分布于距钢板上表面位置;密封氩气流量升高或拉速提高均会导致钢板缺陷发生率的上升,合理的氩气流量和铸机拉速是保证气泡能及时上浮而不进入铸坯的重要参数。规格为260 mm×2070 mm的L485M管线钢板坯的合理拉速为0.75 m/min,分体式水口的氩气流量不宜大于2.5 L/min;采用整体式水口可有效避免氩气泡造成的铸坯内部缺陷。研究结果对完善管线钢连铸过程的氩气密封工艺理论和提高管线钢产品质量具有重要意义,对其他钢种的浸入式水口密封工艺优化、连铸拉速对氩气泡致钢坯内部缺陷的影响、氩气泡在连铸保护浇铸工艺中的作用行为也具有借鉴意义。

With the rapid development of oil and gas industry,the requirements for the strength,toughness and weldability of pipeline steel are constantly increasing.Optimizing the argon sealing process during continuous casting is crucial for reducing or avoiding internal defects caused by argon bubbles,which is of great significance for improving the quality of pipeline steel products.L485M pipeline steel was taken as the research object,the effect of the sealed argon flow rate of the submerged entry nozzle on the internal defects of the pipeline steel L485M was studied by controlling the sealed argon flow rate and the casting speed.Then optimized the argon flow rate and casting speed to solve the internal defects of the slab caused by the argon bubble.The results show that,the argon bubble is generated when the flow rate is too high,which is easily captured by the solidification front of the slab and leads to the internal defects of the slab,formed elliptical flattened defects after rolling,distributed near the surface of the steel plate;An increase in argon sealing gas flow rate or casting speed will both lead to a higher occurrence rate of steel plate defects.Reasonable argon flow rate and casting speed of continuous casting machine are important parameters to ensure that bubbles can float up in time and not enter the slab.The reasonable casting speed of L485M pipeline steel slab with a specification of 260 mm×2070 mm is 0.75m/min,and the argon flow rate of split nozzle should not be greater than 2.5 L/min.The integral nozzle can effectively avoid the internal defects caused by argon bubble.The research results are of great significance for improving the theoretical process of argon sealing in the continuous casting of pipeline steel and enhancing the quality of pipeline steel products.They also provide reference value for the optimization of the submerged entry nozzle sealing process for other steel grades,the effect of continuous casting speed on internal defects caused by argon bubbles in slab,and the behavior of argon bubbles in the protective continuous casting process.