汽车大梁钢粉状氧化铁皮剥落定量评价分析

大梁钢板热轧生产后直接用于汽车零件的冲压成型,其表面氧化铁皮的控制直接关系到冲压过程的稳定性及车间环境,因此开展汽车大梁钢粉状氧化铁皮剥落定量评价分析具有重要的理论与实践意义。针对大梁钢氧化铁粉剥落严重的问题,通过工业试验,开展了不同热轧终轧温度及卷取温度下氧化铁粉剥落量检测与成分分析,采用扫描电镜分析了氧化铁皮的层状结构与致密度,并定量研究了610L大梁钢热轧卷氧化铁皮中Fe₃O₄、FeO含量与氧化铁皮剥落的关系,得到氧化铁皮中Fe₃O₄质量分数为80%且FeO质量分数为3%左右时,610L钢的氧化铁皮最不容易脱落,形成不掉粉、高塑性的“黑皮钢”特性。针对后续冷加工过程中氧化铁皮剥落问题,通过三点弯曲试验进行了FeO含量与氧化铁粉剥落特性关系研究,发现FeO含量高的氧化铁粉在塑性弯曲的小变形阶段,其剥落多于FeO含量少的样品,但在大变形情况下,氧化铁粉剥落少于FeO含量较少的样品,其剥落质量差呈现出“先负后正”的特点。随着弯曲位移的增大,氧化铁皮剥落逐渐增多,且受压面氧化铁皮剥落多于受拉面。受拉面...

Quantitative evaluation and analysis on spalling of powdered iron oxide scale for automobile beam steel

After hot rolling,the automobile beam steel plate is directly used for stamping and forming of automobile parts. The control of its surface iron oxide scale is responsible to the stability of the stamping process and the workshop environment. Therefore,it is of great theoretical and practical significance to carry out quantitative evaluation and analysis on the spalling of powdered iron oxide scale for automobile beam steel. In order to improve the serious powdered iron oxide flaking of beam steel,the spalling amount and composition analysis of iron oxide powder have been carried out under different hot rolling finishing temperatures and coiling temperatures through industrial tests. The layered structure and density of iron oxide scale have been investigated by scanning electron microscope. The relationship between iron oxide in Fe₃O₄ and FeO contents and iron oxide flaking problem has been studied on the hot rolled 610L steel through industrial tests. When the mass percent of Fe₃O₄ is 80% and the mass percent of FeO is of about 3%,iron oxide of 610L steel is the least likely to fall off. The oxide scale is able to form the "black steel" characteristics with high plasticity and non-falling powder. The relationship between FeO content and flaking characteristics of iron oxide scale has been investigated through a three-point bending experiment for simulating the subsequent cold forming processing with oxide scale spalling. The iron oxide scale with high FeO content flakes more than those with low FeO content under small deformation condition in plastic bending process. In the case of large deformation,the iron oxide scale peels less than the sample with less FeO content. The characteristics of flaking weight shows a "first negative and then positive" trend. With the increase of bending displacement,the oxide scale spalling increases gradually. The scale spalling on the compression surface is more than that on the tension surface. Under the action of tensile stress,the iron oxide scale on the tensile surface produces a strip crack perpendicular to the length of the specimen,while the iron oxide scale on the compressive surface peels off in the form of a large fragment. The low strength and excellent plasticity of FeO is responsible to the flaking rule of iron oxide scale with different FeO contents.