Korean Journal of Metals and Materials (대한금속재료학회지)

The Korean Institute of Metals and Materials (대한금속재료학회)
권호 표지

Effect of Non-Metallic Inclusions and Hot Rolling Process Parameters on Hydrogen Induced Cracking of Linepipe Steels

라인파이프 강재의 수소유기균열에 미치는 열간압연 공정변수의 영향

  • Koh, Seong Ung (Plate Research Group, Technical Research Lab., POSCO) ;
  • Jung, Hwan Gyo (Plate Research Group, Technical Research Lab., POSCO) ;
  • Kang, Ki Bong (Plate Research Group, Technical Research Lab., POSCO)
  • 고성웅 (포스코 기술연구소 후판연구그룹) ;
  • 정환교 (포스코 기술연구소 후판연구그룹) ;
  • 강기봉 (포스코 기술연구소 후판연구그룹)
  • Received : 2007.12.06
  • Published : 2008.04.22
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Abstract

AHydrogen induced cracking (HIC) was phenomenologically studied in terms of the effect of nonmetallic inclusions and hot rolling process parameters. By comparing the level of non-metallic inclusions in two different kinds of commercial grade steels having different HIC resistance, the role of non-metallic inclusions in HIC occurrence was investigated. Change in inclusion morphology and distribution during hot rolling was also studied throughout slab, rolling at austenite recrystallization region (roughing mill; RM) and rolling at austenite non-recrystallization region (finish mill; FM). In addition, the contribution of RM and FM parameters to HIC was investigated from the standpoint of change in inclusion morphology during hot rolling processes. As a result, HIC was closely related to the separation of large complex inclusion during hot rolling process. Large complex inclusions originated from the improper Ca treatment, after which equilibrium composition of slag should have resulted in eutectoid composition. By controlling the equilibrium slag composition equivalent to eutectoid one, HIC resistance could be improved due to the reduced size of inclusions. In addition, change in reduction/pass in RM had an effect on HIC resistance of steels while that in FM did not. Increase in the reduction/pass in the latter stage of RM improved HIC resistance of steels by enhancing the void enclosure around inclusions.

Keywords

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