Comparing cleanliness of 23CrNi3Mo hollow drill steel at home and abroad
HUANG Yu1,XIE You2,CHENG Guoguang1
（1. State Key Laboratory of Advanced Metallurgy, University of Science and Technology Beijing, Beijing 100083, China 2. Technology Center, Zenith Steel Co., Ltd., Changzhou 213011, Jiangsu, China）
Abstract：By comparing the cleanliness of 23CrNi3Mo drill steels at home and abroad, it was found that there are some gaps in metallurgy quality of the domestic and overseas drill steels. And the theoretical thermodynamics calculations of the formation mechanism of inclusions in abroad drill steels were carried out. The experiment results indicated that the abroad drill steel has better cleanliness and the lower content of the easy segregation elements such as As and P, and the simple MgAlO inclusion and complex inclusion, for which the MgAlO inclusion acted as the nucleation core of pure MnS, were the main types of inclusion with the main size of 03 μm. And on the longitudinal section, there were many elongated MnS inclusions with obvious fusing phenomenon and the aspect ratio was in the range of 36. The main inclusions in domestic drill steel were simple MgAlO inclusions and complex MgAlO＋(Ca,Mn)S inclusions, whose main size was in the range of 36 μm, and the (Ca,Mn)S almost did not deform in the direction of rolling. Thermodynamic calculations showed that the two precipitations of MnS inclusions were the main reasons for the encapsulation rate of MgAlO inclusions of 70% and the smaller size of complex inclusions.
2018, Vol. 28 
