Acta Metallurgica Sinica (English Letters) ›› 2018, Vol. 31 ›› Issue (10): 1059-1072.DOI: 10.1007/s40195-018-0759-8

Special Issue: 2018年钢铁材料专辑

• Orginal Article • Previous Articles     Next Articles

Control of Secondary Phases by Solution Treatment in a N-Alloyed High-Mn Cryogenic Steel

Xiao-Jiang Wang1,2(), Xin-Jun Sun2(), Cheng Song1, Shuai Tong2, Luo-Jin Liu2, Huan Chen2, Wei Han2, Feng Pan1   

  1. 1 Department of Materials Science and Engineering, Tsinghua University, Beijing 100084, China
    2 Department of Structural Steels, Central Iron and Steel Research Institute, Beijing 100081, China
  • Received:2018-05-29 Revised:2018-05-29 Online:2018-10-10 Published:2018-10-30

Abstract:

The secondary phases of the steels have significant effects on the microstructure and mechanical properties, making controlling these secondary phases important. The control of MnS inclusions and AlN precipitates in a N-alloyed high-Mn twin-induced plastic cryogenic steel via solution treatment was investigated with several different techniques including microstructural characterization, 298 K tensile testing, and 77 K impact testing. The solutionizing temperature (ST) increased from 1323 to 1573 K, where the elongated MnS inclusions and large-sized AlN precipitates became spheroidized and dissolved. The aspect ratio of the MnS inclusions decreased as the ST increased and the number density increased. The impact toughness of the steels showed anisotropy and low impact energy values, due to the elongated MnS inclusions and large-sized AIN precipitates. The anisotropy was eliminated by spheroidizing the MnS inclusions. The impact energy was improved by dissolving the large-sized AlN precipitates during the solution treatment. The austenite grain size increased when the dissolution of the AlN precipitate increased, but the effect of the grain size on the yield strength, toughness, and the strength-ductility balance was weak.

Key words: Cryogenic, Solutionizing temperature, Low-temperature toughness, Spheroidize, Dissolution