厚规格调质高强度船板心部冲击不合格原因分析

为找出厚规格调质高强度船板心部冲击不合格的原因,通过光谱仪、显微镜、SEM-EDS能谱仪等仪器,对心部试样的成分、组织进行分析,结果表明:心部冲击不合格的原因是中心偏析带上存在大尺寸MnS夹杂与Nb、Ti的夹杂物,以及较多Al2O3夹杂和Mg、Ca等外来夹杂物.分析认为,通过提高钢水洁净度,避免钢水二次氧化污染,控制钢...

Cause analysis of unqualified impact at the center of thick quenched and tempered high strength ship plate

In order to find out the reason of unqualified impact at the center of thick quenched and tempered high strength ship plate, the composition and microstructure of the core sample were analyzed by means of spectrometer, microscope and SEM EDS. The results showed that the reason for the unqualified impact at the center was the presence of large size MnS inclusions, Nb and Ti inclusions, as well as more Al2O3 inclusions and Mg, Ca and other foreign inclusions. The analysis suggested that, through the measures such as improving the cleanliness of molten steel, avoiding secondary oxidation pollution, controlling ladle furnace (LF) refining cycle and operation, reducing the degree of superheat of molten steel, optimizing the electromagnetic stirring and soft reduction process, and adopting the slow cooling for stacking, the internal quality of the slab could be improved, and meanwhile, the central segregation and inclusions could be reduced. At the same time, the core impact toughness could be effectively improved by properly optimizing the slab heating, rolling and heat treatment process.