硅对铁素体耐热不锈钢组织与性能的影响

 18Cr-Al-Si铁素体耐热不锈钢作为一种结构连接件的新型材料,主要应用于超(超)临界火力发电领域。为了明确硅含量对该钢组织和性能的影响,以18Cr-Al-Si铁素体耐热不锈钢为成分基础,施以添加2组不同成分的硅含量,通过室温拉伸和高温氧化等试验方法,同时借助金相显微镜(OM)、扫描电子显微镜(SEM)和X射线衍射仪(XRD)等表征手段,对不同硅含量试验钢组织和性能进行了系统分析。结果表明,硅含量的增加会细化铁素体的晶粒尺寸并增加M₂₃C₆碳化物的数量,试验钢的抗拉强度和屈服强度升高,伸长率下降,断裂方式由韧性断裂向韧-脆混合型断裂方式转变;1.35Si试验钢氧化增重较大,因其钢中析出的M₂₃C₆碳化物较多,减少了固溶于基体及形成氧化膜的Cr含量,降低了其抗高温氧化性。

Effect of silicon on microstructure and properties of ferritic heat-resistant steel

The 18Cr-Al-Si ferritic heat-resistant stainless steel as a new type of structural connection material is mainly used in the field of supercritical or ultra-supercritical thermal power generation.In order to clarify the influence of Si content on the structure and properties of this steel,based on 18Cr-Al-Si ferritic heat-resistant stainless steel,the Si content of two groups of different components is added.Through the test methods such as room temperature tensile test and high temperature oxidation test,meanwhile,with the help of metallurgical microscope(OM),scanning electron microscope(SEM)and X-ray diffractometer(XRD)and other characterization methods,the structure and properties of different Si content test steels were systematically analyzed.The results show that the increase of Si content will refine the grain size of ferrite and increase the amount of M23C6,the tensile strength and yield strength of the test steel will increase,and the elongation will decrease.The fracture mode will change from ductile to tough-brittle mixed mode.1.35 Si steel has greater mass gain,this is because more M23C6 carbides are precipitated in the steel,thereby reducing the content of Cr dissolved in the matrix and forming the oxide film,and decreasing its high-temperature oxidation resistance.