Q345D钢精炼过程夹杂物生成及演变行为  

Formation and evolution of inclusions in Q345D steel during secondary refining process

作　　者：王章印 姜敏[1] 王新华[1] WANG Zhang-yin;JIANG Min;WANG Xin-hua(School of Metallurgical and Ecological Engineering,University of Science and Technology Beijing,Beijing 100083,China)

机构地区：[1]北京科技大学冶金与生态工程学院,北京100083

出　　处：《钢铁》2022年第2期63-72,共10页Iron and Steel

基　　金：中央高校基本科研业务费资助项目(FRF-DF-20-08)。

摘　　要：冶炼Q345D钢时由于夹杂物导致的探伤不合格情况时有发生,为了进一步去除和控制钢中非金属夹杂物,通过工业试验研究了"LF精炼→RH真空精炼→钙处理→软吹→连铸"工艺中的夹杂物生成及演变规律,并通过热力学计算优化钙处理工艺。结果表明,转炉炉后及LF进站时采用铝强脱氧,夹杂物主要为Al_(2)O_(3),LF精炼过程采用高碱度、强还原性炉渣精炼,LF精炼结束时,夹杂物为CaO-MgO-Al_(2)O_(3)、MgO-Al_(2)O_(3),其数量所占比例分别为67%、33%;RH真空精炼搅拌强烈,RH破空时,夹杂物为CaO-MgO-Al_(2)O_(3)、MgO-Al_(2)O_(3)、CaO-Al_(2)O_(3),其数量所占比例分别为49%、12%、39%。RH破空后向钢液中喂入钙线,钙处理后,钢液中CaO-MgO-Al_(2)O_(3)系夹杂物更多地向着低熔点液相区域靠近,夹杂物中CaS质量分数达到了27%,CaS更多地在钙铝酸盐表面析出,形成了CaS-CaO-Al_(2)O_(3)系夹杂物;软吹及浇注过程夹杂物中CaS的质量分数增加到42%。此外,精炼过程夹杂物数量密度和平均尺寸呈现共轭关系,夹杂物数量密度从LF进站时的2.32个/mm;增加至连铸中间包内的32.23个/mm;,夹杂物平均尺寸从LF进站时的2.88μm降低至连铸中间包内的1.74μm。热力学分析表明,温度为1 873 K时,钢液中铝质量分数为0.04%,钙质量分数控制在0.001 2%~0.002 8%时,更有利于夹杂物的液态化改性。The unqualified flaw detection caused by inclusions occurs from time to time when smelting Q345 D. In order to further remove and control non-metallic inclusions in steel. The formation and evolution of inclusions in Q345 D refined by " LF refining→RH vacuum refining→calcium treatment→soft blowing→continuous casting" was studied through industrial experiments. The process of calcium treatment modified effectively by thermodynamic analysis. The results showed that the inclusions in liquid steel were consisted of Al_(2)O_(3)when aluminum was used in liquid steel after the converter and at the beginning of LF refining. Slags which have high alkalinity and strong reducibility are used in liquid steel during the LF refining. Liquid steel was strongly stirred during RH vacuum refining. Calcium was wired into the liquid steel after RH vacuum refining. The inclusions in liquid steel were consisted of CaO-MgO-Al_(2)O_(3)ternary system and MgO-Al_(2)O_(3)binary system at the end of ladle furnace refining. The percentages of CaO-MgO-Al_(2)O_(3)ternary system and MgO-Al_(2)O_(3)binary system were 67% and 33%, respectively. At the end of RH vacuum degassing, inclusions in liquid steel were consisted of CaO-MgO-Al_(2)O_(3)ternary system, MgO-Al_(2)O_(3)binary system and CaO-Al_(2)O_(3)binary system, and their percentages were 49%, 12% and 39%, respectively. After RH vacuum refined, the calcium wire was fed into liquid steel for calcium treatment. Average mass percent of CaS in inclusion was about 27% after calcium treatment. More CaS precipitated on the surface of calcium aluminate to generate an outer layer of CaS-CaO-Al_(2)O_(3)ternary system. And the cores of CaO-MgO-Al_(2)O_(3)ternary system were closer to the low-melting zone in the liquid steel. In the afterwards soft blowing and casting, mass percent of CaS in inclusions increased to 42%. In addition, the relationship between the quantitative density and the average size of inclusions during refining is conjugated. Quantitative density of inclusions increased fr

关 键 词：Q345D 夹杂物 炉外精炼 钙处理 CAS 

分 类 号：TF769[冶金工程—钢铁冶金]