CAJ | 학술논문

系统分析了国内某钢厂复合脱氧工艺下 CrMo 石油钻杆钢夹杂物在 EAF- LF- VD- CC 流程中的析晶和衍变规律。由于铝酸盐的上浮,LF 冶炼前钢中 T[O]含量较低,冶炼过程中氮含量逐渐升高。电镜下钢中大尺寸夹杂物(50μm 左右)只出现在 LF- VD 阶段,主要为低熔点的硅锰酸盐、包含 Na2 O 的混合物和含有少量 CaO 的镁铝尖晶石,中间包阶段大尺寸夹杂物完全消失。小尺寸夹杂物(<10μm)出现在精炼全过程中,主要成分是 Mg、Al、Si 和 Ca 的复合氧化物、CaS 以及二者的复合物,LF 冶炼前到中间包阶段小尺寸夹杂物粒径相似,铸坯中其粒径稍微增加。随着精炼过程的进行,钢中小尺寸夹杂物的成分逐渐向复合氧化物的低熔点区域转移,夹杂物中 CaO 和 MgO 含量存在竞争关系。铸坯中大型夹杂物(>100μm)包括卷渣引起的复合夹杂,耐材剥落产生的 MgO- CaO 夹杂和钢液内生的铝酸盐夹杂。内生铝酸盐与精炼过程中小尺寸夹杂物成分相似,外层包覆 CaS,轧制过程中容易破碎成链状引发钻杆钢裂纹。建议适当延长 VD 处理后钢液的镇静时间,以去除钢中大型铝酸盐夹杂,提高钻杆钢质量。
계통분석료국내모강엄복합탈양공예하 CrMo 석유찬간강협잡물재 EAF- LF- VD- CC 류정중적석정화연변규률。유우려산염적상부,LF 야련전강중 T[O]함량교저,야련과정중담함량축점승고。전경하강중대척촌협잡물(50μm 좌우)지출현재 LF- VD 계단,주요위저용점적규맹산염、포함 Na2 O 적혼합물화함유소량 CaO 적미려첨정석,중간포계단대척촌협잡물완전소실。소척촌협잡물(<10μm)출현재정련전과정중,주요성분시 Mg、Al、Si 화 Ca 적복합양화물、CaS 이급이자적복합물,LF 야련전도중간포계단소척촌협잡물립경상사,주배중기립경초미증가。수착정련과정적진행,강중소척촌협잡물적성분축점향복합양화물적저용점구역전이,협잡물중 CaO 화 MgO 함량존재경쟁관계。주배중대형협잡물(>100μm)포괄권사인기적복합협잡,내재박락산생적 MgO- CaO 협잡화강액내생적려산염협잡。내생려산염여정련과정중소척촌협잡물성분상사,외층포복 CaS,알제과정중용역파쇄성련상인발찬간강렬문。건의괄당연장 VD 처리후강액적진정시간,이거제강중대형려산염협잡,제고찬간강질량。
The crystallization and evolution of non-metallic inclusions in CrMo drill pipe steel refined with a complex deoxidizer were investigated for the EAF- LF- VD- CC process flow of a domestic steel plant. As a result of aluminates floating, lower T[O] con-tent in the steel before the LF refining was shown, while nitrogen content in the steel gradually increased during the whole flow. Large size inclusions (about 50 μm), namely, silicic manganates with low melting point, complexes with Na2 O and magnesium aluminate spinels with a little CaO, appeared at the LF- VD stage and disappeared completely after the tundish process. Small size inclusions ( < 10 μm) could be found during the whole refining flow. Their size at different refining stages was similar to each other, while smal-ler than that of the casting blank. The small size inclusions were complex oxides which consist of Mg, Al, Si, Ca and CaS respectively. The composition of the small size inclusions gradually moved to the liquid phase region during the smelting flow, and competition exis-ted between CaO and MgO contents in these inclusions. Macro inclusions ( > 100 μm) in the casting blank included complex inclusions caused by entrapped slag, MgO- CaO inclusions from refractories and endogenous aluminate inclusions coated by a CaS layer, whose composition was similar to small size inclusions in the smelting processes. The macro aluminate inclusions were easily broken into chain and further resulted in cracks in the steel during the rolling process. Hence, it is suggested to prolong the steel standing time after the VD operation to remove detrimental aluminate inclusions.