The tempering parameter for evaluating softening of hot and warm forging die steels

Virtanen, E.; Tyne, C. J. Van; Lévy, Bernard; Brada, G. A.

doi:10.1016/j.jmatprotec.2013.03.003

Cited by 45 publications

(25 citation statements)

References 8 publications

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“…There is some difference between the response of cold worked and martensitic microstructure at elevated temperatures [ 28 ], and a martensitic microstructure found to be more stable. The similarity between the microstructure of HT3 and HT5 shows that the lath microstructure is fairly stable at 500 °C, which is consistent with the work of others [ 28 , 29 ].…”

Section: Resultssupporting

confidence: 91%

The Influence of Lath, Block and Prior Austenite Grain (PAG) Size on the Tensile, Creep and Fatigue Properties of Novel Maraging Steel

et al. 2017

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The influence of martensitic microstructure and prior austenite grain (PAG) size on the mechanical properties of novel maraging steel was studied. This was achieved by looking at two different martensitic structures with PAG sizes of approximately 40 µm and 80 µm, produced by hot rolling to different reductions. Two ageing heat-treatments were considered: both heat-treatments consisted of austenisation at 960 °C, then aging at 560 °C for 5 h, but while one was rapidly cooled the other was slow cooled and then extended aged at 480 °C for 64 h. It is shown that for the shorter ageing treatment the smaller PAG size resulted in significant improvements in strength (increase of more than 150 MPa), ductility (four times increase), creep life (almost four times increase in creep life) and fatigue life (almost doubled). Whereas, the extended aged sample showed similar changes in the fatigue life, elongation and hardness it displayed yet showed no difference in tensile strength and creep. These results display the complexity of microstructural contributions to mechanical properties in maraging steels.

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Section: Resultssupporting

confidence: 91%

The Influence of Lath, Block and Prior Austenite Grain (PAG) Size on the Tensile, Creep and Fatigue Properties of Novel Maraging Steel

et al. 2017

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“…There is a negative linear relationship between the yield strengths and the logarithm of time, as shown in Figure a. The research showed that the mechanical properties of the tested steels, such as hardness and strength, were linearly related to the tempering parameter in the tempering process . The tempering parameter ( T P ) is given as:

T_{normalp} = T \times true(normalC + \log t true)

where T is the tempering temperature (K), C is the constant, and t is the tempering time (h).…”

Section: Resultsmentioning

confidence: 99%

Effects of Nb and Tempering Time on Carbide Precipitation Behavior and Mechanical Properties of Cr–Mo–V Steel for Brake Discs

Wang

Cheng

et al. 2018

steel research int.

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To improve the performance of the steel for brake discs, like mechanical properties and thermal fatigue resistance, Nb is added to the steel. In this paper, the effects of Nb and tempering time on the microstructure and mechanical properties of the steel have been studied. The investigation of precipitation behaviors is based on Thermo‐Calc software and transmission electron microscopy. The results show there is a negative linear relationship between the yield strength and the logarithm of time, and tempering time should not exceed 2 h. V‐rich M8C7 and NbC occur during austenitizing, while (Mo,V)C, M23C6, and M7C3 precipitate during tempering. (Mo,V)C has a strong strengthening effect at the early stage of tempering, but it grows faster than M8C7. With 0.025% Nb addition, the yield strength and impact energy increase simultaneously due to the refinement of martensite; the addition of 0.045% Nb promotes the tempering stability due to the suppression of precipitation and coarsening of Cr carbides and the precipitation strengthening of M8C7 and NbC, therefore, the addition of 0.025–0.045% Nb is conducive to improving the performance of the steel. Moreover, the suppression of Cr carbides with 0.045% Nb addition makes up for the damage of large NbC to toughness.

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“…Although empirical, the parameter is acknowledged widely to rationalise the combined effects of time and temperature during tempering [e.g. [29][30][31] Two conclusions can be drawn from Figure 3. First, that cementite seems to be the most stable phase over a wide temperature range when the strength of the heat treatment is greatest within the scope of the dataset.…”

Section: First Principles Calculation Datamentioning

confidence: 99%

Critical Assessment 34: Are χ (Hägg), η and ϵ carbides transition-phases relative to cementite in steels?

Bhadeshia

Chintha

Lenka

2019

Materials Science and Technology

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Hägg carbide (χ) is, during the tempering of carbon-rich martensite, referred to as a transition carbide which eventually gives way to cementite. However, there are Fe-C binary phase diagrams estimated using thermodynamic data, that define a low-temperature phase field where a mixture of Hägg carbide and ferrite is more stable than that of cementite and ferrite. In this scenario, it may be cementite which is the transition carbide. Evidence is presented here that the predominance of Hägg carbide over cementite in the circumstances described is unlikely to be correct based on historical and new observations. Literature data are also interpreted to show that η and ε-carbides are best regarded as transition-phases relative to mixtures of cementite and ferrite.

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The tempering parameter for evaluating softening of hot and warm forging die steels

Cited by 45 publications

References 8 publications

The Influence of Lath, Block and Prior Austenite Grain (PAG) Size on the Tensile, Creep and Fatigue Properties of Novel Maraging Steel

The Influence of Lath, Block and Prior Austenite Grain (PAG) Size on the Tensile, Creep and Fatigue Properties of Novel Maraging Steel

Effects of Nb and Tempering Time on Carbide Precipitation Behavior and Mechanical Properties of Cr–Mo–V Steel for Brake Discs

Critical Assessment 34: Are χ (Hägg), η and ϵ carbides transition-phases relative to cementite in steels?

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