Phase transformational kinetics and hardenability of alloyed medium-carbon steels

A computational model is presented in this article for the prediction of microstructural development during heat treating of steels and resultant room-temperature hardness. This model was applied in this study to predict the hardness distribution in end-quench bars (Jominy hardness) of heat treatable steels. It consists of a thermodynamics model for the computation of equilibria in multicomponent Fe-C-M systems, a finite element model to simulate the heat transfer induced by end quenching of Jominy bars, and a reaction kinetics model for austenite decomposition. The overall methodology used in this study was similar to the one in the original work of Kirkaldy. Significant efforts were made to reconstitute the reaction kinetics model for austenite decomposition in order to better correlate the phase transformation theory with empiricism and to allow correct phase transformation predictions under continuous cooling conditions. The present model also expanded the applicable chemical composition range. The predictions given by the present model were found to be in good agreement with experimental measurements and showed considerable improvement over the original model developed by Kirkaldy et al.

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“…The predicted CCT diagram is in good agreement with those reported in the open literature. [32][33][34][35] …”

Section: B Prediction Of Phase Transformation Diagramsmentioning

confidence: 99%

A computational model for the prediction of steel hardenability

Niebuhr

Meekisho

et al. 1998

Metall Mater Trans B

201

102

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Section: Introductionmentioning

confidence: 97%

“…[11,12] Mo addition also causes the shift of bainite start temperature to lower temperature and the separation of upper and intermediate transformation ranges. [11] The synergetic effect of Mo and B was also reported. Mo has been reported to increase the effectiveness of boron by suppressing the precipitation of Fe 23 (C,B) 6 at austenite grain boundaries, which reduces the soluble boron content.…”

Section: Introductionmentioning

confidence: 97%

On the Processing of Martensitic Steels in Continuous Galvanizing Lines: Part II

Song

Kwak

Cooman

2011

Metall Mater Trans A

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The conventional continuous hot-dip galvanizing (GI) and galvannealing (GA) processes can be applied to untransformed austenite to produce Zn and Zn-alloy coated low-carbon ultra-highstrength martensitic steel provided specific alloying additions are made. The most suitable austenite decomposition behavior results from the combined addition of boron, Cr, and Mo, which results in a pronounced transformation bay during isothermal transformation. The occurrence of this transformation bay implies a considerable retardation of the austenite decomposition in the temperature range below the bay, which is close to the stages in the continuous galvanizing line (CGL) thermal cycle related to the GI and GA processes. After the GI and GA processes, a small amount of granular bainite, which consists of bainitic ferrite and discrete islands of martensite/austenite (M/A) constituents embedded in martensite matrix, is present in the microstructure. The ultimate tensile strength (UTS) of the steel after the GI and GA cycle was over 1300 MPa, and the stress-strain curve was continuous without any yielding phenomena.

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“…como "a capacidade de um aço ser transformado parcial ou totalmente da fase austenítica para alguma porcentagem de martensita em uma dada profundidade quando resfriado sob determinadas condições" [4][5]9,12,I, que descreve mais precisamente o processo físico associado ao endurecimento. Siebert, Doane e Breen [13],em seu livro sobre temperabilidade, preferem a última definição.…”

Section: -Revisão Bibliográficaunclassified

“…IGURA 13 -Influência de elementos de liga na temperabilidade e taxas de resfriamento [12) Nas equações apresentadas anteriormente não foi considerada a possível influência de fatores tais como a severidade do meio de resfriamento ou as dimensões e formato do espécime, na determinação das taxas críticas de resfriamento. Tal fato ocorre porque as velocidades, medidas nos ensaios de resfriamento, devem ser iguais às calculadas analiticamente, independente destes fatores, para uma determinada região de transição.…”

Section: Tabela 02 -Valores De M Para Diferentes Sítios De Nucleaçãol43]unclassified

Determinação de velocidades críticas de têmpera em aços por meio de curvas de resfriamento

Patrocínio¹

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Phase transformational kinetics and hardenability of alloyed medium-carbon steels

Cited by 17 publications

References 1 publication

A computational model for the prediction of steel hardenability

A computational model for the prediction of steel hardenability

On the Processing of Martensitic Steels in Continuous Galvanizing Lines: Part II

Determinação de velocidades críticas de têmpera em aços por meio de curvas de resfriamento

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