Effects of Si and Cr on bainite microstructure of medium carbon steels

Takeshi Suzuki, Yoshiki Ono, Goro Miyamoto, Tadashi Furuhara

Research output: Contribution to journalArticlepeer-review

26 Citations (Scopus)

Abstract

Effects of Si and Cr contents on bainite microstructure of medium carbon steels have been examined in order to obtain important information for good strength-ductility balanced spring steel. Four practical medium carbon steels, JIS-S55C, SUP9, SUP7 and SUP12 were isothermally transformed at temperatures between 300°C and 500°C after austenitized at 1 000°C. The microstructure was observed by means of scanning electron microscopy and transmission electron microscopy. While carbide was formed from the early stage of bainite transformation in S55C without Si and Cr, carbide precipitation was suppressed by the increase of Si particularly in SUP7 and SUP12. The fraction of retained austenite was increased with increasing of Si and Cr at the intermediate stage of bainite transformation because of the increase of C concentration in retained austenite. Particularly, Si addition promoted carbide-free bainitic ferrite and leading to larger amounts of retained austenite by carbon enrichment.

Original languageEnglish
Pages (from-to)1476-1482
Number of pages7
JournalIsij International
Volume50
Issue number10
DOIs
Publication statusPublished - 2010

Keywords

  • Austempering
  • Bainite
  • Medium carbon steel
  • Pearlite
  • Retained austenite
  • Spring steel

ASJC Scopus subject areas

  • Mechanics of Materials
  • Mechanical Engineering
  • Metals and Alloys
  • Materials Chemistry

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