轴承钢水口结瘤与棒材中大型夹杂物关系研究

Investigation on relationship between nozzle clogging and large inclusions in bearing steel bars

针对南钢轴承钢棒材样上无规律性出现的大型夹杂物问题,采用扫描电镜、X射线荧光光谱(XRF)和X射线衍射(XRD)分析仪在对棒材样上大型夹杂物和水口结瘤物成分、形态对比分析基础上,利用热力学计算,研究了钢水及精炼渣成分、包衬耐材与钢水中夹杂物存在形态的热力学关系。研究得出,水口中堆积的尺寸小于10μm颗粒状MgO·Al_2O_3和CaO-Al_2O_3(-MgO)高熔点结瘤物的脱落,是棒材上大尺寸长条状夹杂物的来源;现工艺条件的钢水及钢包渣成分,使MgO·Al_2O_3夹杂物在钢水中能稳定存在,为水口结瘤提供了夹杂物来源;控制浇铸过程钢包水口下渣及减少中间包耐材的侵蚀是控制轴承钢随机性大型夹杂物的关键。

In this paper,in order to control irregular large inclusions in bearing steel bars in Nanjing Steel,thermodynamic relationship among compositions of molten steel and refining slag,lining refractory and existing forms of inclusions in molten steel were studied by thermodynamic calculation base on the comparison of compositions and existing forms between large inclusions in bars and nozzle clogs. Scanning electron microscope（ SEM）,X-ray Fluorescence（ XRF） and X-Ray Diffraction（ XRD） were applied to analyze the compositions and existing forms of inclusions and clogs. It is showed that the large long strip type inclusions in bars come from the granular heaped MgO·Al2O3and CaO-Al2O3（-MgO） clogs with high melting point fell off from nozzle,whose dimension are less than 10 μm. Compositions of molten steel and ladle slag in present process make the MgO·Al2O3inclusion exists stably,and provides inclusion resource for nozzle clogging. In all,preventing ladle slag down from the nozzle during casting process and reducing the erosion of tundish lining refractory are the keys to control irregular large inclusions in bearing steel bars.