摘要
氧化铁皮结构控制是评价铁皮黏附力的重要指标,直接影响产品冲压过程铁皮掉粉量以及表面质量。目前高强系列钢种中普遍添加Mn元素提高产品强度级别,为了研究Mn元素添加对氧化铁皮结构以及共析转变的影响机理,以Mn质量分数为1.8%~1.9%的大梁钢和Mn质量分数为0.15%~0.25%的低碳钢为分析对象,首先利用热重分析仪和电镜分析手段观察了含Mn钢不同温度下FeO转变特点,分析发现高温下随着保温时间增加,在靠近Fe_(3)O_(4)交界的FeO层中氧含量容易达到过饱和状态而发生分解,形成以先共析Fe_(3)O_(4)层状转变为主的特点;低温条件下Fe离子迁移扩散速率降低表现为短距离扩散特点,FeO分解特点转变为中部析出花瓣状Fe_(3)O_(4);同时明确了含Mn钢FeO共析转变的鼻尖温度在450℃附近,共析反应始于FeO和Fe_(3)O_(4)交界位置处,源自两相区的交界面处存在的相起伏与能量起伏为新相的形核和长大创造有利驱动力。对比含Mn钢(1.8%)和低Mn钢(0.18%)在450℃保温60 min下FeO的共析转变存在差异,含Mn钢FeO共析转变比例为18%而低Mn钢高达60%;含Mn钢的共析片层间距平均为350 nm而低Mn钢片层间距为250 nm。针对生产热卷样品铁皮结构分析发现,相同工艺条件下含Mn钢热卷铁皮中FeO比例存在升高趋势。结合扫描电镜和电子探针分析明确了含Mn钢FeO共析转变过程中共析组织(Fe_(3)O_(4)和α-Fe)存在明显的排Mn特点,引起临近区域未分解的FeO内Mn元素出现升高趋势;根据二元相图分析发现MnO在FeO中的溶解可以稳定FeO相,使相变驱动力减小,造成总体上含Mn的FeO共析转变得到抑制的现象。由此可见,针对含Mn高强钢(热系-冷系)需要考虑MnO-FeO对氧化铁皮结构转变的影响,冷轧高强钢从易破鳞酸洗角度,热轧黑皮钢从共析铁皮比例控制角度,结合热轧连续冷却特点,有差异性匹配卷取温度和冷却模式是下一步继续研究的
Structure control of iron oxide scale is an important index to evaluate the adhesion of scale,which directly affects the amount of powder loss and surface quality during product stamping.Currently,Mn element is commonly added to high-strength series steel to improve product strength level.In order to study the influence mechanism of Mn addition on the structure and eutectoid transformation of iron oxide scale,Girder steel with Mn mass percent of 1.8%-1.9%and low carbon steel with Mn mass percent of 0.15%-0.25%were used as the analysis objects.Firstly,the FeO transformation characteristics of Mn-containing steel at different temperatures were observed by thermograys and electron microscopy.It was found that with the increase of holding time at high temperature,the oxygen content in the FeO layer near the interface of Fe_(3)O_(4)easily reached susaturated state and decomposed,forming the characteristics of pre-eutectoid Fe_(3)O_(4)layer transformation.At low temperature,Fe ion migration and diffusion rate decrease in short distance and FeO decomposition change to petal-like Fe_(3)O_(4)in the middle.At the same time,it is confirmed that the nose tip temperature of FeO eutectoid transformation of Mn-containing steel is around 450℃.It is found that the eutectoid reaction always starts at the interface of FeO and Fe_(3)O_(4),because there are phase fluctuations and energy fluctuations at the interface of the two phase regions,which creates favorable conditions for the nucleation and growth of the new phase.The eutectoid decomposition of FeO is different between Mn containing steel(1.8%)and low Mn steel(0.18%)at 450℃for 60 min.The eutectoid decomposition ratio of Mn containing steel is only 18%,while that of Mn containing steel can reach 60%.The average interval between the eutectoid sheets of Mn-containing steel was 350 nm by SEM.The layer spacing of low Mn steel is 250 nm.It is found that FeO proportion of Mn steel in hot coil sheet increases under the same process conditions.At last,SEM and electron probe analysi
作者
王畅
韩赟
于洋
惠亚军
王林
张亮亮
WANG Chang;HAN Yun;YU Yang;HUI Yajun;WANG Lin;ZHANG Liangliang(Research Institute of Technology,Shougang Group Co.,Ltd.,Beijing 100043,China;Beijing Key Laboratory of Green Recyclable Process for Iron and steel Production Technology,Beijing 100043,China)
出处
《钢铁》
CAS
CSCD
北大核心
2024年第8期125-137,共13页
Iron and Steel
基金
河北省重大科技成果转化专项资助项目(22281001Z)
河北省重点研发计划资助项目(20311004D)。
