高压锅炉管钢P12铸锭中夹杂物分布解剖研究

分别采用解剖、总氧分析(TO])、原位统计分析、金相显微镜统计分析和小样电解实验研究了16.8 t高压锅炉管钢P12铸锭中夹杂物的分布.发现在铸锭的上中部存在夹杂物数量较低的负偏聚区域,而在中心及尾部中心部位存在夹杂物数量较高的正偏聚区域.为了表征夹杂物的偏聚程度,提出了夹杂物偏聚指数的新概念.总氧分析和原位统计分析结果表明铸锭中下部氧化物夹杂物偏聚指数达到1.4～1.6,而在上中部氧化物夹杂物的偏聚指数为0.5～0.7.金相统计分析和小样电解实验可同时分析钢中氧化物和硫化物等夹杂,其分析结果表明铸锭上中部夹杂物的偏聚指数为0.7～0.8,铸锭中下部夹杂物的偏聚指数为1.15～1.35.铸锭中心及锭尾中心区域氧化物夹杂平均尺寸明显大于其他区域,表明大夹杂物在上浮过程中被结晶雨捕获并沉降到底部是铸坯中下部夹杂物偏聚的主要机制.

Investigation of inclusion distribution in ingots of high pressure boiler tube steel P12 by dissection

Inclusion distribution in 16.8t ingots of high pressure boiler tube steel P12 was studied by dissection,total oxygen analysis,original position statistic distribution analysis(OPA),metallographic microscope static analysis and small sample electrolysis.It was found that a negative inclusion segregation area existed in the central part of the ingot head where the inclusion quantity is lower;while a positive inclusion segregation area existed in the center and lower part of the ingot where the inclusion quantity is higher.A new concept of inclusion segregation index was put forward to describe the segregation degree of inclusions.Total oxygen analysis and OPA results demonstrated that the segregation indexes of oxide inclusions were 1.4 to 1.6 in the central and lower part of the ingot and 0.5 to 0.7 in the central part of the ingot head.As both oxide and sulphide inclusions were tested by metallographic microscope static analysis and slime small sample electrolysis,the inclusion segregation indexes were about 0.7 to 0.8 in the central part of the ingot head and 1.15 to 1.35 in the center and lower part of the ingot.The average size of oxide inclusions in the central and lower part of the ingot was bigger than that in other places,showing that the main mechanism for inclusion segregation in the central and lower part of the ingot is the picking of large inclusions by showering crystallites during floatation.