Transactions of Materials and Heat Treatment

Title：Analysis on disqualification reason and improvement measures of steel 70Cr3Mo back-up roll by ultrasonic inspection

Authors： Lu Baoshan Wang Leigang Ji Yeyi

Unit： Suzhou Institute of Industrial Technology Jiangsu University

KeyWords： back-up roll heavy forging ultronic inspection dye penetrant inspection metallographic experiment non-metallic inclusions

ClassificationCode：TG316.1

year,vol(issue):pagenumber：2017,42(7):6-13

Abstract：

Two back-up roll forgings of steel 70Cr3Mo with the weight of 44800 kg and 19500 kg were respectively made. The ingot was melted and poured by the EAF+LF+VD+VC method, and one ingot was forged into two pieces. After spheroidizing annealing and cooling, the blanks were checked through ultrasonic inspection. The result shows that the light roll is up to standard, but there are excessive defects in the roll neck of the heavy one. In order to explore the technological rationality of forging, two ends of the heavy roll neck part were cut to forge a new light back-up roll based on the qualified body. Nevertheless, there are still overproof defects in the roll neck of the new one except the roll barrel. Thus, the hole defects and inclusions were analyzed by a series of experiments, and the reasons for the disqualification of the back-up roll were determined after ultrasonic inspection. Furthermore, the non-metallic inclusions in the ingot widely distributing on the defect split the continuity of the steel matrix and deteriorate the steel performance, which result in the disqualification of ultrasonic inspection. In addition, the source and harmfulness of non-metallic inclusions were analyzed and the corresponding improvement measures were put forward to prevent such defects.

Funds：

国家自然科学基金资助项目（51275216）；2017年度苏州工业职业技术学院院级课题资助项目（SGYKJ201708）；江苏高校品牌专业建设工程资助项目（PPZY2015B186）

作者简介：陆宝山(1981-)，男，博士研究生，E-mail：lubs@siit.edu.cn；通讯作者：王雷刚(1963-)，男，教授，博士生导师，E-mail：lgwang@mail.ujs.edu.cn

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