Effect of tempering on hardness of Q&T steel plate

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Effect of tempering on hardness of Q&T steel plate. / Goodall, Aimee; Ju, Yulin; Davis, Claire; Strangwood, Martin.

In: Materials Science Forum, Vol. 941, 01.12.2018, p. 311-316.

Research output: Contribution to journalConference articlepeer-review

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@article{cfa488019b8d4084be6b2c1425245308,
title = "Effect of tempering on hardness of Q&T steel plate",
abstract = "Commercial production of high strength steel plates by the quenching and tempering (Q&T) route requires control of alloy design and heat treatment parameters to achieve the desired strength and toughness through thickness. Plates with different thicknesses (up to approximately 100 mm) are produced for applications in the energy and power or lifting and excavation sectors. For thick plate the difference in cooling rate through thickness affects the as-quenched microstructure with martensite, auto-tempered martensite and lower and/or upper bainite being present. The different as-quenched microstructures can show a different response to tempering which affects the final strength and toughness.In this study the starting microstructure of a low alloy 0.17 wt% C Q&T steel has been varied using isothermal heat treatment at 430 °C to create mixed martensite and lower bainite microstructures (nominally 25:75; 50:50 and 75:25 percentages). The effects of tempering at 600 °C for times between 0.5 and 16 hours on the carbide precipitates and hardness of the mixed microstructures have been investigated and compared to the tempering response of single phase (martensite and lower bainite) microstructures. It has been found that the hardness decrease due to tempering is larger in the martensitic structure than the bainitic structure due to more rapid carbide coarsening. The as-quenched hardness of the mixed microstructures can be predicted by a rule of mixtures using the single phase properties. The tempering response of the mixed microstructures is discussed.",
keywords = "Q&T steel, tempering, martensite, bainite",
author = "Aimee Goodall and Yulin Ju and Claire Davis and Martin Strangwood",
year = "2018",
month = dec,
day = "1",
doi = "10.4028/www.scientific.net/MSF.941.311",
language = "English",
volume = "941",
pages = "311--316",
journal = "Materials Science Forum",
issn = "0255-5476",
publisher = "Trans Tech Publications Inc",
note = "THERMEC'2018 International Conference on PROCESSING & MANUFACTURING OF ADVANCED MATERIALS Processing, Fabrication, Properties, Applications , THERMEC'2018 ; Conference date: 08-07-2018 Through 13-07-2018",

}

RIS

TY - JOUR

T1 - Effect of tempering on hardness of Q&T steel plate

AU - Goodall, Aimee

AU - Ju, Yulin

AU - Davis, Claire

AU - Strangwood, Martin

PY - 2018/12/1

Y1 - 2018/12/1

N2 - Commercial production of high strength steel plates by the quenching and tempering (Q&T) route requires control of alloy design and heat treatment parameters to achieve the desired strength and toughness through thickness. Plates with different thicknesses (up to approximately 100 mm) are produced for applications in the energy and power or lifting and excavation sectors. For thick plate the difference in cooling rate through thickness affects the as-quenched microstructure with martensite, auto-tempered martensite and lower and/or upper bainite being present. The different as-quenched microstructures can show a different response to tempering which affects the final strength and toughness.In this study the starting microstructure of a low alloy 0.17 wt% C Q&T steel has been varied using isothermal heat treatment at 430 °C to create mixed martensite and lower bainite microstructures (nominally 25:75; 50:50 and 75:25 percentages). The effects of tempering at 600 °C for times between 0.5 and 16 hours on the carbide precipitates and hardness of the mixed microstructures have been investigated and compared to the tempering response of single phase (martensite and lower bainite) microstructures. It has been found that the hardness decrease due to tempering is larger in the martensitic structure than the bainitic structure due to more rapid carbide coarsening. The as-quenched hardness of the mixed microstructures can be predicted by a rule of mixtures using the single phase properties. The tempering response of the mixed microstructures is discussed.

AB - Commercial production of high strength steel plates by the quenching and tempering (Q&T) route requires control of alloy design and heat treatment parameters to achieve the desired strength and toughness through thickness. Plates with different thicknesses (up to approximately 100 mm) are produced for applications in the energy and power or lifting and excavation sectors. For thick plate the difference in cooling rate through thickness affects the as-quenched microstructure with martensite, auto-tempered martensite and lower and/or upper bainite being present. The different as-quenched microstructures can show a different response to tempering which affects the final strength and toughness.In this study the starting microstructure of a low alloy 0.17 wt% C Q&T steel has been varied using isothermal heat treatment at 430 °C to create mixed martensite and lower bainite microstructures (nominally 25:75; 50:50 and 75:25 percentages). The effects of tempering at 600 °C for times between 0.5 and 16 hours on the carbide precipitates and hardness of the mixed microstructures have been investigated and compared to the tempering response of single phase (martensite and lower bainite) microstructures. It has been found that the hardness decrease due to tempering is larger in the martensitic structure than the bainitic structure due to more rapid carbide coarsening. The as-quenched hardness of the mixed microstructures can be predicted by a rule of mixtures using the single phase properties. The tempering response of the mixed microstructures is discussed.

KW - Q&T steel

KW - tempering

KW - martensite

KW - bainite

U2 - 10.4028/www.scientific.net/MSF.941.311

DO - 10.4028/www.scientific.net/MSF.941.311

M3 - Conference article

VL - 941

SP - 311

EP - 316

JO - Materials Science Forum

JF - Materials Science Forum

SN - 0255-5476

T2 - THERMEC'2018 International Conference on PROCESSING & MANUFACTURING OF ADVANCED MATERIALS Processing, Fabrication, Properties, Applications

Y2 - 8 July 2018 through 13 July 2018

ER -