核电用CF8A不锈钢大型铸件表面探伤缺陷的成因及控制  

Formation and improvement of penetrant inspection defects in CF8A stainless steel huge casting for nuclear power

作　　者：王启明 成国光 李璟宇 窦文哲 胡学文 WANG Qiming;CHENG Guoguang;LI Jingyu;DOU Wenzhe;HU Xuewen(State Key Laboratory of Advanced Metallurgy,University of Science and Technology Beijing,Beijing 100083,China;Huoshan Foundry Co.,Ltd.,Yingliu Group,Luan 237200,Anhui,China)

机构地区：[1]北京科技大学钢铁冶金新技术国家重点实验室,北京100083 [2]应流集团霍山铸造有限公司,安徽六安237200

出　　处：《钢铁研究学报》2021年第8期871-879,共9页Journal of Iron and Steel Research

摘　　要：CF8A不锈钢由于具有良好的耐蚀性和强韧性等优点,被用于铸造压水堆核电站主回路系统中循环泵的泵体,但铸件常出现表面探伤不合问题。通过对铸件表面探伤不合区域取样,并跟踪冶炼全流程取样,利用扫描电镜、能谱仪观察缺陷类型和夹杂物演变行为;结合Factsage软件计算,研究缺陷成因及控制方法。CF8A不锈钢冶炼过程中,AOD出钢前夹杂物主要为尖晶石;Ca处理后夹杂物主要为液态或双相CaO-Al_(2)O_(3)-MgO(-SiO_(2))夹杂;浇钢结束前,钢液中出现尖晶石和氧化铝夹杂;凝固过程中富氧化铝夹杂在铸件表面聚合造成铸件表面探伤不合。因此,控制钢液中Al元素的质量分数在0.01%左右,钙元素的质量分数在20×10^(-6)~30×10^(-6)左右,合理控制炉渣中SiO_(2)和Al_(2)O_(3)的含量,可以减少氧化铝类夹杂的生成,提高铸件表面探伤合格率。CF8 A stainless steel castings were used to manufacture pump casing for nuclear power due to the good corrosion resistance, excellent strength and toughness. However, the failure in penetrant inspection of castings was one of the serious problems. After sampling from the failure area of penetrant inspection and metallurgy process of CF8 A stainless steel castings, the defect type and evolution mechanism of inclusions were studied by SEM, EDS and Factsage software. During metallurgy process, the main inclusions were spinel before tapping from AOD. After Ca treatment in ladle, the main inclusions were liquid or semi-liquid CaO-Al_(2)O_(3)-MgO(-SiO_(2)). However, spinel and inclusions rich in Al_(2)O_(3) arose during casting process. With increasing of Al in molten steel, the content of spinel and CaO·2 Al_(2)O_(3) increased. Failure in penetrant inspection was caused by the floating and aggregating of inclusions rich in Al_(2)O_(3). So the content of Al and Ca should be controlled at 0.01% and 20×10^(-6)-30×10^(-6), and the content of SiO_(2) and Al_(2)O_(3) in slag should be controlled to restrict formation of inclusions rich in Al_(2)O_(3), which improved the pass rate of penetrant inspection.

关 键 词：CF8A不锈钢 铸件 表面探伤 夹杂物 

分 类 号：TF764[冶金工程—钢铁冶金]