Abstract：Specimens of 304 stainless steel exposed to solution treatment at 1080℃ for 1, 2h have been evaluated employing ultrasonic testing in order to discuss the feasibility and ultrasonic nondestructive characterization parameters for average grain size in 304 stainless steel solution treatment product. The results showed that the ultrasonic velocities decreased gradually and the attenuation coefficient increased apparently after solid solution treatment. The velocities continued decreasing slowly and the attenuation coefficient increased further with increasing solution treatment time at the same temperature. The spectral analysis exhibited an obvious decrease of the peak frequency and a gradual increase of the peak amplitude after solution treatments. The above studies are mainly attributed to the effects of the solution treatment to the grain size and the effects of the grain size to the propagation of ultrasonic wave through materials. Based on the least square method, the linear relationships between transverse wave velocity vt,longitudinal wave velocity vl and the average grain size were obtained vt=-0.49254d+3188.40138,vl=-0.07632d+5772.88964; meanwhile, the relevance of the attenuation coefficient to the average grain size was also described in the studied specimens as followed as α=1.2605×10-15d6.5012+0.0995.
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