过时效工艺对C-Mn-Si高强钢表面选择性氧化的影响

为了研究过时效过程露点调节技术在高强钢上的应用,采用热浸镀工艺模拟器研究了过时效工艺中气氛露点温度(-30、-10℃)和温度(250、350℃)对一种C-Mn-Si高强钢选择性氧化的影响,分别采用FE-SEM和EDS观察分析了试样表面形貌和化学成分,采用GDOES表征了试样表面的元素深度分布,采用XPS确定了氧化物种类。结果表明,高过时效温度(350℃)和高露点温度(-10℃),可显著抑制锰和硅在钢表面的选择性氧化,此时试样表面为无定型SiOx、无定型MnOx以及纯态锰。随着过时效温度和露点温度的降低,锰和硅在表面的富集明显增加,同时发现,露点温度对合金表面元素富集峰值的影响比过时效温度更显著。采用低过时效温度(250℃)和低露点温度(-30℃)时,试样表面出现大量富锰和硅的颗粒状氧化物,由晶态的Mn3O4和MnO2以及硅的非化学计量氧化物SiO1.49和SiO0.93组成。

Effects of over-aging process on selective oxidation behavior of a C-Mn-Si high strength steel

To research application of dew point technology during over-aging process on high strength steel，effects of over-aging dew point （―30 and －10 ℃） and temperature （250 and 350 ℃） on the selective oxidation behavior of a C-Mn-Si high strength steel were studied through a hot dip process simulator. FE-SEM （field emission scanning electron microscope） and EDS （energy dispersive spectrometer） were applied to analyze morphology and chemistry of the surface，respectively. Alloying elements profiles in the subsurface were detected by GDOES （glow discharge optical emission spectroscopy）. Oxides on the external surface were identified by XPS （X-ray photoelectron spectroscopy）. It was found the a combination over-aging process of high temperature （350 ℃） and high dew point （―10 ℃） could notably suppress the selective oxidation of Si and Mn on the external surface，which resulted in amorphous silicon oxides （SiOx） and amorphous manganese oxides （MnOx） and even pure Mn on the external surface. With decreasing the temperature and the dew point of the over-aging process，enrichment of Si and Mn on the external surface increased remarkably. Meanwhile，it could be found that the influence of the dew point on the enrichment of alloying elements on the external surface was much stronger than that of the temperature. Moreover，with a combination of lower temperature （250 ℃） and lower dew point （―30 ℃），much more nodule-like oxides enriched with Mn and Si are formed on the externals surface，which were identified as crystalline manganese oxides （Mn3O4 and MnO2） and non-stoichiometric silicon oxides （SiO1.49 and SiO0.93）.