IF钢轿车外板表面短线缺陷形成机理及改进措施

为了减少IF钢轿车外板表面短线缺陷,采用热重分析仪、扫描电镜和电子探针从无限冷硬轧辊的组织及其氧化特性的角度对IF钢轿车外板表面短线缺陷形成机理进行研究。结果表明,IF钢轿车外板表面短线缺陷呈现疤体形貌特征,疤体周围开裂区域存在氧化铁皮残留,疤体内微量元素呈现出高镍、低铬和低硅的特点,与无限冷硬轧辊表层组织的成分存在明显的对应关系;无限冷硬轧辊表层组织存在耐磨颗粒尺寸不均和石墨相球化不完全等问题。由此提出IF钢轿车外板表面短线缺陷主要源自轧制过程中无限冷硬轧辊在使用时表层氧化铁皮剥落和热疲劳开裂的交互作用。采取优化热轧排产制度和精轧机组负荷、加强对轧辊质量轧辊冷却水和润滑剂的管控以及提高轧辊表面质量等改进措施,效果良好。

Forming mechanism and improvement measures of short line defects on IF steel car outer plate

In order to reduce short line defects on IF steel car outer plate, the formation mechanism of short line defects were studied in detail based on indefinite chill double pour (ICDP) roll microstructure and its oxidation characteristics by means of thermogravimetric analyzer, scanning electron microscope and electron microprobe analyses. The results show that the short line defects on car outer plate surface of IF steel show scar morphology, and there are oxide film residue in the cracking area around the scar. Trace elements in the scar show the characteristics of high nickel, low chromium and low silicon, which is corresponding to the surface composition of ICDP roll obviously. There are some problems in ICDP roll, such as incomplete spheroidization of graphite phase and poor size uniformity of wear resistant particles. Therefore, short line defects are considered to be mainly caused by oxide film spalling and thermal fatigue cracking of ICDP roll during rolling. The defects can be effectively controlled through the improvement measures such as optimizing hot rolling scheduling system and finishing mill load, strengthening control of roll quality, roll cooling water and lubricant, and improving roll surface quality.