AISI 431不锈钢生产过程夹杂物转变机理  

Inclusion transformation mechanism of AISI 431 stainless steel during production

作　　者：王举 李阳 姜周华 孙萌 毛昀惬 马帅 WANG Ju;LI Yang;JIANG Zhouhua;SUN Meng;MAO Yunqie;MA Shuai(School of Metallurgy,Northeastern University,Shenyang 110819,Liaoning,China)

机构地区：[1]东北大学冶金学院,辽宁沈阳110819

出　　处：《钢铁》2023年第7期54-63,98,共11页Iron and Steel

基　　金：国家自然科学基金资助项目(52074075);教育服务东北振兴产学研用合作重点资助项目。

摘　　要：炼钢和模铸过程中形成的大尺寸夹杂物对钢材的冶金质量有着重要的影响,国内某钢铁企业生产的AISI 431不锈钢棒材存在严重的缺陷,经显微分析后发现缺陷处主要为大尺寸的氧化物夹杂,为了分析钢中大尺寸夹杂物的来源,基于全流程取样分析对其生产过程中夹杂物的转变机理进行了研究,利用欧波同夹杂物全自动分析系统OTSInca和商业热力学软件FactSage 8.2对不同工序的钢中夹杂物进行了检测和分析。结果表明,AOD末期钢液中夹杂物主要为SiO_(2)含量高的CaO-SiO_(2)-Al_(2)O_(3)复合夹杂物,在LF初期完成铝脱氧之后转变为尖晶石和铝酸钙。在模铸工序结束后,经分析发现钢中的酸溶铝含量明显下降,钢中新出现了大尺寸的Al_(2)O_(3)夹杂物和含Na、K的硅系复合夹杂物,其中Al_(2)O_(3)夹杂物源自模铸过程中钢液注流与空气接触后新发生的铝氧反应,而含Na、K的硅系复合夹杂物来自于保护渣的卷入。在后续的加工过程中,在轧制应力的作用下2类夹杂物的最大尺寸进一步增大,Al_(2)O_(3)沿着轧制方向呈长线状,而含Na、K的硅系复合夹杂物则有所变形、破碎。对经探伤定位得到的缺陷样品进行分析,进一步验证了这2类大尺寸夹杂物会直接导致棒材探伤不合。最后,本研究提出从减少注流暴露时间、合理控制浇注过程供气强度、铸模流场设计优化和LF末期软吹氩时间与强度的控制等几个方面考虑工艺改进。Large-sized inclusions formed in steelmaking and mold casting have a significant effect on the metallurgical quality of steel.Stainless steel AISI 431 produced by a domestic steel plant has severe defects,and these defects were found to be large-sized oxide inclusions after microscopic analysis.In order to investigate the source of large-sized inclusions in AISI 431 stainless steel bars,the inclusion evolution mechanism during production was investigated in this study based on full process sampling analysis.OTSInca inclusion analysis system and commercial thermodynamic software FactSage 8.2 were employed to investigate and analyze inclusions in every production process.It was found that the inclusions at the end of AOD were mainly CaO-SiO_(2)-Al_(2)O_(3) complex inclusions with high SiO_(2) content,which transformed to spinel and calcium aluminate after Al deoxidation at the beginning of LF.After the casting process,the decrease of dissolved Al concentration in steel is very obvious,and new large-sized Al_(2)O_(3) and Na-and K-containing SiO_(2)-based complex inclusions can be detected in steel.Al_(2)O_(3) originated from a new aluminum-oxygen reaction in the molten steel after contact with air,and Na-and K-containing SiO_(2)-based complex inclusions is from the entrapment of mold flux.During the subsequent process,the maximum size of both types of inclusions further increased.Al_(2)O_(3)was elongated as long lines along the rolling direction,while the Na-and K-containing SiO_(2)-based complex inclusions were deformed and broken.Analysis of the defects in AISI 431 stainless steel bars further verified that these two types of large size inclusions can directly lead to bar defects.Finally,this study proposes to consider process optimization in terms of reducing the exposure time of the steel flow,controlling the intensity of the gas supply during casting,the design of the casting mold flow field and the control of LF soft blowing argon.

关 键 词：不锈钢 热力学 夹杂物 二次氧化 尖晶石 

分 类 号：TF764.1[冶金工程—钢铁冶金] TF777