Formation of martensite austenite constituent in continuously cooled Nb-bearing low carbon steels

N. Takayama, G. Miyamoto, N. Kamikawa, H. Nako, T. Maki, T. Furuhara

Research output: Chapter in Book/Report/Conference proceedingConference contribution

4 Citations (Scopus)

Abstract

Fe-0.15%C-1.5%Mn-0.2%Si (Nb-free alloy) and Fe-0.15%C-1.5%Mn-0.2%Si-0.03%Nb (Nb-added alloy) were continuously cooled to room temperature at constant cooling rates in the range from 0.1 to 20K/s. At lower cooling rates, such as 0.1K/s, the Nb addition retards the ferrite transformation, resulting in a decrease in the transformation temperature and an increase in the volume fraction of bainite. The fraction of martensite-austenite constituent (MA) increases by the Nb addition and the largest fraction of MA, about 0.5 %, is observed in the Nb-added specimen cooled at 5K/s. In the specimens cooled at 5K/s, relatively coarse bainite without cementite precipitation is formed near the austenite (γ) grain boundary in both alloys. Most of MA is localized between such relatively coarse bainitic ferrite (BF). On the other hand, MA is hardly observed in the bainite formed with cementite precipitation in γ grain. Based on microstructure observation of the continuously cooled specimens down to intermediate temperatures followed by quenching, it is concluded that small-sized untransformed γ near γ grain boundary partly remains as MA whereas relatively larger untransformed γ in the γ grain decompose into bainite with cementite precipitation.

Original languageEnglish
Title of host publicationTHERMEC 2009
EditorsTara Chandra, Tara Chandra, Tara Chandra, N. Wanderka, N. Wanderka, N. Wanderka, Walter Reimers, Walter Reimers, Walter Reimers, M. Ionescu, M. Ionescu, M. Ionescu
PublisherTrans Tech Publications Ltd
Pages3080-3085
Number of pages6
ISBN (Print)0878492941, 9780878492947
DOIs
Publication statusPublished - 2010
Event6th International Conference on Processing and Manufacturing of Advanced Materials - THERMEC'2009 - Berlin, Germany
Duration: 2009 Aug 252009 Aug 29

Publication series

NameMaterials Science Forum
Volume638-642
ISSN (Print)0255-5476
ISSN (Electronic)1662-9752

Other

Other6th International Conference on Processing and Manufacturing of Advanced Materials - THERMEC'2009
CountryGermany
CityBerlin
Period09/8/2509/8/29

Keywords

  • Bainite
  • Continuous cooling
  • Low carbon steel
  • Martensite-austenite constituent (MA)
  • Niobium

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering

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