FeMnAlC TWIP钢加热过程中的氧化行为GD-OES研究

GD-OES study on oxidation behavior of FeMnAlC TWIP steel sheets during heating

以成分(质量分数)为Fe-16%Mn-1.5%Al-0.6%C-0.11%Cr的TWIP钢为研究对象,采用模拟试验研究了加热过程中的氧化行为,使用GD-OES分析了加热温度和加热气氛中O_(2)含量对表面元素深度分布的影响。结果表明,当TWIP钢在N_(2)-0.05%(体积分数)O_(2)的气氛中加热至550~700℃时,表面会形成Fe-Mn氧化层,次表层会形成贫锰层、脱碳层及内氧化层,各层厚度随加热温度升高而增大。在氧化性气氛中加热时,Al元素优先在次表层形成内氧化,少量的Cr元素在氧化层/基体界面上形成外氧化,表面氧化层中基本不含Al和Cr。当加热温度为650℃时,气氛中O_(2)体积分数在0.025%~0.2%之间变化对氧化层厚度影响较小,均可获得厚度介于400~500 nm的氧化层。由此可见,为获得TWIP钢合适的预氧化层厚度,同时减少预氧化层/基板界面位置的氧化物,直火加热出口温度控制比空燃比控制更重要。

The oxidation behavior of Fe-16%Mn-1.5%Al-0.6%C-0.11%Cr TWIP steel sheet during heating process was studied by simulation experiments.The effects of heating temperature and O_(2)content in heating atmosphere on the depth distribution of surface elements were analyzed by GD-OES.When TWIP steel sheet is heated to 550-700℃in the atmosphere of N_(2)-0.05 vol%O_(2),an oxide layer composed of Fe,Mn and O covers the surface,a Mn depleted zone,a decarburized zone and an internal oxidation zone will be formed in the subsurface layer.The thicknesses of the oxide layer and the subsurface zones increase with heating temperature increasing.When being heated in an oxidizing atmosphere,Al preferentially forms internal oxidation in the subsurface layer,and a small amount of Cr forms external oxidation at the oxide layer/matrix interface.The surface oxide layer basically contains no Al and Cr.When the heating temperature is 650℃,the change of O_(2)volume fraction in the atmosphere between 0.025%-0.20%has little effect on the thickness of the oxide layer,and the oxide layer with a thickness of 400-500 nm can be obtained.In order to obtain the appropriate thickness of the pre oxide layer of TWIP steel and reduce the oxide at the interface between the pre oxide layer and matrix interface,the temperature control of the direct fire heating outlet is more important than the air-fuel ratio control.