Development of High-Efficient NDI System for Conveyance Rolls Using Vibrothermography

抄録

Large numbers of conveyance rolls are installed in the rolling processes in steelworks. Although these rolls are inspected by magnetic particle testing (MT) after disassembling the roll components, inspection efficiency is extremely poor due to the disassembly and reassembly operations. Recently, a high-efficiency crack inspection technique for conveyance rolls using vibrothermography, which does not require disassembly, has been reported. Vibrothermography detects cracks as a local temperature rise when excited by ultrasonic vibration. In this method, it is important to propagate enough ultrasonic vibration. In this paper, a suitable horn shape for a structure which has a curved surface, such as a conveyance roll, is newly suggested. Laboratory tests and off-line tests of the suggested ultrasonic horn were conducted, and improvement of crack detectability was confirmed. A high-efficiency inspection system for actual production lines that consists of an infrared reflector, an ultrasonic vibrator, the new type of ultrasonic horn and an infrared thermography device is also proposed. Inspection efficiency can be improved significantly in the actual production line with this inspection system.