Controlling the wall thickness during the manufacture of seamless steel tubes and cast-iron pipe is critical in meeting specifications and minimizing scrap. Ultrasonic measurements typically are performed on tube or pipe at room temperature, many hours after forming is complete. At this point in the forming process, if dimensional specifications are not met, the feedback to the production system is too late to provide any benefit. The ability to perform measurements at high forming temperatures (up to 1,200 degrees C) and at high speeds (up to 5 meters per second) allows inspection during the production process, thereby providing much more immediate and effective feedback to the machine operator. To avoid scrapping a tube or pipe because its wall is too thin, designers typically overdesign the wall to ensure the minimum thickness specification is met. This safety margin results in a significant waste of raw materials. Additionally, if the wall thickness is not constant over the tube length or around the circumference, product performance and customer satisfaction are less than optimal. An in-process measurement of thickness as a function of length, as well as tube eccentricity, allows the mill operator to make immediate corrections that reduce the amount of raw material required to meet specifications and to improve product quality.
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