Analysis and control of flaw detection unqualified reasons for die steel 718H of thick specifications
QI Min-xiang1, ZHONG Yang-yang1, LI Zhen-xing1, ZHENG Wei1, XU Qing-tai2
1. Liaoning Medium Plate Professional Technology Innovation Center, Minmetals Yingkou Medium Plate Co., Ltd., Yingkou 115000, Liaoning, China; 2. Quality Center, Angang Steel Co., Ltd., Anshan 114021, Liaoning, China
Abstract：During ultrasonic flaw detection of die steel 718H with thick specifications, the disqualification at 1/2 of the thickness of the die steel was found. Inspected by macroscopic examination, optical microscope, SEM and energy spectrum, the results show that the main reasons for the defects are loose center and segregation defects of continuous casting billet, which are left in the central area of steel plate thickness without rolling, eliminating or improving. According to the above reasons, a series of control measures of smelting and rolling were adopted, and the pass rate of steel plate flaw detection was significantly increased, from 96.18% to 99.16% for steel plate with thickness of 100 mm and above. Key words: flaw detection; segregation; loose center; rolling; free surface of metal
2020, Vol. 39 
