A multi-angle spatial compound imaging method was developed to suppress the speckles and artifacts in ultrasonic immersion testing using a single transducer. The multi-angle echo signals were acquired by an ultrasonic immersion testing system with different incident angles. With consideration of the acoustic difference between water and the specimen, the deviation of the time of flight (TOF) and refraction were corrected. Then the corrected signals were superimposed to reconstruct a multi-angle spatial compound image. The performance of the proposed method is assessed with quantitative accuracy, signal to noise ratio (SNR) and contrast to noise ratio (CNR). Compared with the conventional B-scan imaging, the quantitative accuracy of the longitudinal and lateral sizes of the defect holes in proposed method are respectively improved by an average of 12.3% and 15.8%, and the SNR and CNR are increased by an average of 6.13 dB and 2.65 dB, respectively. The results show the advantage of the proposed multi-angle spatial compound imaging for ultrasonic immersion testing in terms of the less quantitative error and artifacts.

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Under the condition of oil cooling, the effect of quenching temperatures on the structure and abrasive wear resistance of medium carbon steel containing 2% B has been studied. The results show that the metallic matrix of Boron-containing Medium Carbon Steel (BMCS) transforms into the martensite from the mixture of martensite, pearlite and ferrite while quenching at 900 8C -1050 8C. The change of boron carbide existing in BMCS is few in different quenching temperature. After quenching the hardness of BMCS excels 56 HRC, and the change of quenching temperature has no obvious effect on the hardness of BMCS. The increase of quenching temperature leads to the increase of impact toughness, and impact toughness has no obvious change when quenching temperature exceeds 1000 8C. Moreover, the increase of quenching temperature leads to a slight decrease of weight loss and the abrasive wear resistance of BMCS has a slight increase while increasing quenching temperature. Quenching at 1000 8C -1050 8C BMCS has excellent comprehensive property.