高强双相钢表面选择性氧化行为对磷化性能的影响

目的确定高强双相钢表面Si、Mn元素选择性氧化行为对磷化性能的影响,以改善高强双相钢的磷化性能。方法在具备不同表面选择性氧化行为的试样表面制备磷化膜。采用X射线光电子能谱仪(XPS)、辉光光谱仪(GDS)、透射电镜(TEM)等手段,分析高强双相钢表面Si、Mn元素的选择性氧化行为,通过扫描电镜观察磷化膜的结晶状态,并采用电化学技术分析钢板在磷化液中的反应过程。结果当高强钢表面Si含量较少时,表面氧化物主要以弥散分布的小颗粒状Mn Al_2O_4形态存在,能够加快在磷化液中酸蚀反应速度,磷化晶粒均匀、致密,尺寸小于4mm,覆盖率为100%。当高强钢表面Si含量较高时,形成的Mn_2SiO_4容易在晶界聚集,颗粒尺寸较大,减慢了酸蚀反应速度,磷化晶粒尺寸大于8mm,均匀致密性差。而提高材料表面Mn元素的富集程度,可以减轻Mn_2SiO_4聚集的现象,提高酸蚀反应速度,磷化晶粒均匀、致密,尺寸小于4mm,覆盖率100%。结论减轻双相高强钢表面Si元素的富集程度,而提升Mn元素的富集程度,可以加快钢板在磷化液中的酸蚀反应,进而改善磷化性能。

Effect of Selective Oxidation Behavior of High Strength Dual-phase Steel Surface on Phosphating Properties

The work aims to determine the effect of selective oxidation behavior of Si and Mn on the phosphating properties of high strength dual-phase steel surface, so as to improve the phosphating properties of dual-phase steel. The phosphating films were prepared on the surface of samples with different selective oxidation behavior. X-rayphotoelectron spectroscopy (XPS), glow spectrometer(GDS), transmission electron microscopy (TEM) and other means were used to analyze the selective oxidation behavior of Si and Mn elements on the surface of high strength dual-phase steel. The crystalline state of phosphating film was observed by SEM, and the reaction process of steel plate in phosphating solution was analyzed by electrochemical technology. When the content of Si on the surface of high strength steel was low, the oxide mainly existed in the form of dispersed small granular MnAl2O4, which could speed up the acid etching reaction in phosphating solution, and the phosphating grains were uniform, dense and less than 4 mm in size, and the coverage rate was 100%. When the Si content on the surface of high strength steel was high, the formed Mn2SiO4 was easy to aggregate at the grain boundary, and the particle size was large, which slowed down the acid etching reaction speed, and the phosphating grain size was larger than 8 mm, and the uniformity and compactness were poor. However, increasing the concentration of Mn on the surface of the steel could reduce the accumulation of Mn2SiO4 and increase the rate of acid etching reaction, and then the phosphating grains were uniform and dense, with the size less than 4 mm and the coverage rate of 100%. Reducing the enrichment of Si and increasing the enrichment of Mn on the surface of dual-phase high strength steel can accelerate the acid etching reaction of steel plate in phosphating solution and improve the phosphating properties.