Continuous cooling transformation kinetics and microstructure of mild and low-alloy steel weld metals
Continuous cooling transformation kinetics and microstructure of mild and low-alloy steel weld metals
Twelve continuous cooling transformation (CCT) diagrams, applicable to reheated (coarse grained region) mild and low-alloy steel weld metals were produced using techniques of high speed dilatometry, thermal analysis, and quantitative metallography. A detailed study of these CCT diagrams revealed the practical significance of variations in weld cooling rate, alloy content, prior austenite grain size, and oxygen-rich inclusion content, on weld metal y a phase transformation behaviour. Carbon, manganese and nickel were all shown to have a similar influence on CCT kinetics. This generally involved depression of the CCT curves to lower temperatures and longer times and encouraged the development of fine grained intragranular acicular ferrite at the expense of grain boundary nucleated morphologies. The role of niobium was shown to be complex and highly dependent on overall hardenability. Molybdenum was shown to have a very strong influence on separation of the bainite and ferrite noses of the CCT diagram. Oxygen-rich inclusion content and austenite grain size were found to be inter-related in reheated weld metals due to grain boundary pinning. The CCT kinetics of the phase transformation were also seen to be influenced by an inclusion related nucleation effect. All these factors have been discussed in detail and a new theoretical model has been presented which explains weld metal microstructural development in terms of competitive nucleation and supercooling from Ae3. A practical model based on CCT data has also been presented to predict optimum toughness transformation regimes in C-Mn and C-Mn-Ni weld metals.
University of Southampton
Harrison, Peter Lindley
4a4dcd3e-fa29-48a7-92d8-7c912a8d8abf
1982
Harrison, Peter Lindley
4a4dcd3e-fa29-48a7-92d8-7c912a8d8abf
Harrison, Peter Lindley
(1982)
Continuous cooling transformation kinetics and microstructure of mild and low-alloy steel weld metals.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
Twelve continuous cooling transformation (CCT) diagrams, applicable to reheated (coarse grained region) mild and low-alloy steel weld metals were produced using techniques of high speed dilatometry, thermal analysis, and quantitative metallography. A detailed study of these CCT diagrams revealed the practical significance of variations in weld cooling rate, alloy content, prior austenite grain size, and oxygen-rich inclusion content, on weld metal y a phase transformation behaviour. Carbon, manganese and nickel were all shown to have a similar influence on CCT kinetics. This generally involved depression of the CCT curves to lower temperatures and longer times and encouraged the development of fine grained intragranular acicular ferrite at the expense of grain boundary nucleated morphologies. The role of niobium was shown to be complex and highly dependent on overall hardenability. Molybdenum was shown to have a very strong influence on separation of the bainite and ferrite noses of the CCT diagram. Oxygen-rich inclusion content and austenite grain size were found to be inter-related in reheated weld metals due to grain boundary pinning. The CCT kinetics of the phase transformation were also seen to be influenced by an inclusion related nucleation effect. All these factors have been discussed in detail and a new theoretical model has been presented which explains weld metal microstructural development in terms of competitive nucleation and supercooling from Ae3. A practical model based on CCT data has also been presented to predict optimum toughness transformation regimes in C-Mn and C-Mn-Ni weld metals.
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Published date: 1982
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Local EPrints ID: 460239
URI: http://eprints.soton.ac.uk/id/eprint/460239
PURE UUID: 814e479d-7e84-44ce-931e-1a59efc22639
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Date deposited: 04 Jul 2022 18:15
Last modified: 16 Mar 2024 18:37
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Author:
Peter Lindley Harrison
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