利用非线性超声检测技术，测量了不同晶粒尺寸铁素体不锈钢的非线性参数，并与传统线性超声技术的评估结果进行了比较。结果表明，随着铁素体不锈钢晶粒尺寸的增大，声速变化并不明显，相对变化量为1.89%，衰减系数的相对变化量也只有5.65%，而非线性参数随晶粒尺寸的增加而持续减小，这是由于声波在材料内的传播过程中，其非线性效应很大一部分产生在晶界等不连续处，随着晶粒尺寸的增大，晶界面积减小，非线性效应减弱。

The nonlinear parameters of ferritic stainless steels with different grain sizes were measured by nonlinear ultrasonic testing technique, and the results were compared with that of the traditional ultrasonic technology. The results show that with the increase of the grain size of ferrite stainless steel, the variation of sound velocity is not obvious, its relative change is only 1.89% and the relative change of attenuation coefficient is 5.65%. The nonlinear parameters whereas decrease continuously with the increase of the grain size, which is due to a large part of the nonlinear effect being generated in the grain boundary when the acoustic waves propagate in the material. With the increase of grain size, the grain boundary area is reduced, so the nonlinear effect is weakened.