Research Of Large Castings And Forgings Ultrasonic Nondestructive Testing Technology

With the rapid development of economy, large castings and forgings are applied to ironand steel industry, metallurgy, wind power, nuclear power, petroleum, chemical industry,engineering equipment, aerospace and so on. So, there is a high request for productioncapacity and product quality of large castings and forgings. Ultrasonic nondestructivetesting technology is a very important and widely applied to nondestructive testing(NDT) technology, it is closly combined with modern computer technology, automationtechnology and information technology, and thus the detection accuracy and reliability areimproved greatly.Based on the ultrasonic testing theory, the defect theory of the large castings andforgings was researched, the signal characteristics of ultrasonic echo of the defects in thelarge castings and forgings were discussed, the large castings and forgings ultrasonictesting methods and equipments were analyzed systematically. In order to determine theaccuracy of the digital ultrasonic detector, the ultrasonic standard sample was tested withthe digital ultrasonic detector. The samples of the large castings and forgings wereanalysised with the method of immersion ultrasonic pulse reflection. The samples ofcontinuous casting slab, cast iron, roller riser were tested respectively with the ultrasonicautomatic testing to get the characteristics of ultrasonic echo signal and experiment results.Combined with the microstructure of the samples of continuous casting slab, cast iron,roller riser, the influence of the ultrasonic echo signal in different grain size wereanalysised.The experimental results show that digital ultrasonic detector can realize automaticultrasonic detection of large castings and forgings, and ensure the veracity and reliabilityof the results. Ultrasonic detection of different materials by digital ultrasonic detector mustadjust parameters reasonably to get the accurate characteristics of ultrasonic echo signal.Different characteristics of ultrasonic defect echo signal are different. The changes ofgrain size have great influence on characteristics of ultrasonic echo signal. Therefore, theresearch of ultrasonic testing technology in large castings and forgings is great importantfor large castings and forgings products inspection.