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对探伤不合格的厚度不小于25 mm钢板进行取样,分别做了低倍酸洗、刨削、金相、SEM及能谱分析,分析认为探伤不合格的主要原因是中心偏析分层、内部裂纹、中心部位的氢致裂纹、大颗粒外来夹杂(夹渣)。在生产压缩比小于6.0的宽厚规格钢板时,应围绕钢水质量、板坯低倍质量、缓冷时效(≥48 h)、轧后时效(≥24 h)有针对性地选择工艺路线,其中钢水质量主要为钢中氢的质量分数应控制在2.0×10-6以下,硫的质量分数控制在0.010%以下,氧的质量分数控制在25×10-6以下;板坯低倍质量主要由过热度(15~25℃)、拉速(恒拉速)、动态配水、动态软压下、液面控制(±4 mm)及设备工况等综合工艺条件决定。
The unqualified thickness of not less than 25 mm steel samples were taken low pickling, planing, metallography, SEM and energy spectrum analysis, the main reason that the testing failed unqualified center segregation stratification, internal cracks , The central part of the hydrogen-induced cracks, large particles of foreign inclusions (slag). In the production of wide and thick gauge steel with a compression ratio of less than 6.0, the process should be targeted around the quality of the molten steel, slab low magnification, slow cooling (≥ 48 h) and post-rolling aging (≥ 24 h) The quality is mainly that the mass fraction of hydrogen in steel should be controlled below 2.0 × 10-6, the mass fraction of sulfur is controlled below 0.010% and the mass fraction of oxygen below 25 × 10-6; Heat (15 ~ 25 ℃), speed (pull rate), dynamic water distribution, dynamic soft pressure, liquid level control (± 4 mm) and equipment conditions and other comprehensive process conditions decision.