Time and temperature dependent softening of H11 hot-work tool steel and definition of an anisothermal tempering kinetic model

Markežič, Rok; Mole, Nikolaj; Naglič, Iztok; Šturm, Roman

doi:10.1016/j.mtcomm.2019.100744

Cited by 8 publications

(12 citation statements)

References 13 publications

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“…There are also JMA model based on Johnson–Mehl–Avrami equation and LSW model based on Ostwald ripening mechanism. [ 35,36 ] Some studies have pointed out that, [ 37 ] compared with the JMA model, the LSW model is more suitable for analyzing and predicting the hardness change of steel at low test temperatures ( T ≤ 600 °C). Therefore, considering the heating and holding temperature of this study, the tempering parameter model and LSW model will be used to calculate the softening rate and tempering transition activation energy of the two steels, respectively.…”

Section: Discussionmentioning

confidence: 99%

“…In addition, the coarsening constant k increases with the extension of holding temperature, which is consistent with the results in and the general law of tempering. [ 37 ] According to the k value and Equation (9), the tempering activation energy of 1# and 2# can be obtained as Q 1# = 320.0 and Q 2# = 300.0 kJ mol −1 , respectively. For 1#, it indicates that the diffusion of carbon and other alloy atoms need to cross a higher energy barrier, the precipitation and growth of carbides are delayed, and the softening of the martensitic matrix occurs more slowly.…”

Section: Discussionmentioning

confidence: 99%

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Effect of Nitrogen‐Substituted Carbon on Thermal Stability of Cr‐Mo‐V Hot‐Working Die Steel

Zhang

et al. 2020

steel research int.

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To extend service life of Cr‐Mo‐V hot‐working die steel, a method of alloying with nitrogen‐substituted carbon is proposed. The mechanical properties of the test steels in the long‐time heating and holding process are measured. The effect of nitrogen‐substituted carbon on thermal stability is characterized and analyzed by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Thermo‐Calc. The results show that the ratio of N in V(C,N) can be increased by nitrogen‐substituted carbon at high temperature, which significantly improves its stability. As a result, it can not only refine the grain but also broaden the austenitizing temperature range and promote the complete solution of alloy elements such as Cr, Mo. In the process of long‐term heating and insulation, nitrogen‐substituted carbon can effectively reduce the precipitation of harmful carbides and the coarsening rate by raising the activation energy of tempering transformation with 20.0 kJ mol−1, and increase the precipitation of the main strengthening phase V(C,N). Nitrogen‐substituted carbon, as an effective alloying method, innovatively improves thermal stability and service life of Cr‐Mo‐V hot‐working die steel.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Effect of Nitrogen‐Substituted Carbon on Thermal Stability of Cr‐Mo‐V Hot‐Working Die Steel

Zhang

et al. 2020

steel research int.

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“…The fitted D value can be used in Equation ( 8) to calculate the activation energy (Q ). The tempering ratio τ is defined by Equation ( 12): [9] τ ¼…”

Section: Jma Modelmentioning

confidence: 99%

“…The JMA model was constructed according to the theory of solid-state phasetransition diffusion proposed by Johnson and Avrami, [7] which was based on the diffusion-driven mechanism of precipitation and growth of secondary carbides. The LSW model based on the Ostwald ripening mechanism [8,9] described the dissolution, precipitation, and coarsening of secondary carbides at a constant volume fraction, and related the softening behavior to the evolution of the average size of secondary carbides. However, the aforementioned three models describing the softening behavior have not been compared in detail, especially the applicability of the models.…”

Section: Introductionmentioning

confidence: 99%

Softening Behavior and Hardness Prediction of H13 Hot‐Work Die Steel during Isothermal Tempering

Feng,

Wang,

et al. 2023

steel research int.

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In this study, the microstructural evolution of H13 hot‐work die steel during isothermal tempering at 500∽650 °C was evaluated, and kinetic equations and a neural network were constructed to describe the softening behavior. The results showed that the softening behavior appeared as a loss of hardness with increasing isothermal tempering temperature and time. The softening mechanism was ascribed to the decomposition of martensitic laths, annihilation and rearrangement of dislocations, formation of sub‐grains and precipitation and coarsening of secondary carbides. The evolution of secondary carbides included the coarsening of V‐rich MC nanoprecipitates, and the precipitation and coarsening of secondary phases (Cr‐rich M23C6 and Mo‐rich M6C carbides) during long‐term isothermal tempering. Regarding the applicability of the model in precipitation evolution and hardness prediction, the Johnson‐Mehl‐Avrami (JMA) model was considered to be more suitable than the Hollomon‐Jaffe (H‐J), Lifshitz‐Slyozov‐Wagner (LSW) and back‐propagation neural network (BPNN) models.This article is protected by copyright. All rights reserved.

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“…Since hot-work tool steels usually operate at elevated temperatures, the high-temperature oxidation behaviour of H11 hot-work tool steel is of great importance. Several authors [3][4][5][6][7][8][9] have studied the effect of elevated temperatures on the mechanical and physical properties of hot-work tool steels. With this consideration, we investigate the oxidation kinetics of AISI H11 in the temperature range between 400 • C and 700 • C.…”

Section: Introductionmentioning

confidence: 99%

High-Temperature Oxidation Behaviour of AISI H11 Tool Steel

Balaško

Vončina

Burja

et al. 2021

Metals

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The high-temperature oxidation of hot-work tool steel AISI H11 was studied. The high-temperature oxidation was investigated in two conditions, the soft annealed condition, and the hardened and tempered condition. First, calculations of the compositions of the oxide layers formed were carried out using the CALPHAD method. The samples were oxidised in a chamber furnace and in a simultaneous thermal analysis instrument, for 100 h in the temperature range between 400 °C and 700 °C. The first samples were used for metallographic (optical microscopy and scanning electron microscopy) and X-ray diffraction analysis of the formed oxide layers, and the second ones for the analysis of the oxidation kinetics by thermogravimetric analysis. Equations describing the high-temperature oxidation kinetics were derived. The kinetics can be described by three mathematical functions, namely: exponential, parabolic, and cubic. However, which function best describes the kinetics depends on the oxidation temperature and the thermal condition of the steel. Hardened and tempered samples have been shown to oxidise less, resulting in a slower oxidation rate. The oxide layers consist of three sublayers, the inner one being spinel-like oxide (Fe, Cr)3O4, the middle one a mixture of magnetite and hematite and the outer one of hematite. At 700 °C there is also some wüstite in the inner oxide sublayer of the soft annealed sample.

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Time and temperature dependent softening of H11 hot-work tool steel and definition of an anisothermal tempering kinetic model

Cited by 8 publications

References 13 publications

Effect of Nitrogen‐Substituted Carbon on Thermal Stability of Cr‐Mo‐V Hot‐Working Die Steel

Effect of Nitrogen‐Substituted Carbon on Thermal Stability of Cr‐Mo‐V Hot‐Working Die Steel

Softening Behavior and Hardness Prediction of H13 Hot‐Work Die Steel during Isothermal Tempering

High-Temperature Oxidation Behaviour of AISI H11 Tool Steel

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