Microstructural evolution and mechanical properties of 55NiCrMoV7 hot-work die steel during quenching and tempering treatments

Yu, Xingsheng; Wu, Chaohua; Shi, Ruxing; Yuan, Yasha

doi:10.1007/s40436-021-00352-3

Cited by 10 publications

(4 citation statements)

References 30 publications

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“…The kinetic model used to describe the effect of thermal softening assumes that one carbide species exists that dominantly determines the mechanical properties [30]. Works on the microstructure of martensitic hot work steels have shown that various carbides precipitate in different sizes during the heat treatment [52,53]. Furthermore, the sizes of secondary carbides, namely MC and M 2 C, are observed at approximately one nanometer, respective to the size of M 23 C 6 at approximately seven nanometers after austenitization and tempering [52].…”

Section: Thermal-softening and Cyclic-softening Modelmentioning

confidence: 99%

A Temperature-Dependent Viscoplasticity Model for the Hot Work Steel X38CrMoV5-3, Including Thermal and Cyclic Softening under Thermomechanical Fatigue Loading

2023

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In this paper, a temperature-dependent viscoplasticity model is presented that describes thermal and cyclic softening of the hot work steel X38CrMoV5-3 under thermomechanical fatigue loading. The model describes the softening state of the material by evolution equations, the material properties of which can be determined on the basis of a defined experimental program. A kinetic model is employed to capture the effect of coarsening carbides and a new isotropic cyclic softening model is developed that takes history effects during thermomechanical loadings into account. The temperature-dependent material properties of the viscoplasticity model are determined on the basis of experimental data measured in isothermal and thermomechanical fatigue tests for the material X38CrMoV5-3 in the temperature range between 20 and 650 ∘C. The comparison of the model and an existing model for isotropic softening shows an improved description of the softening behavior under thermomechanical fatigue loading. A good overall description of the experimental data is possible with the presented viscoplasticity model, so that it is suited for the assessment of operating loads of hot forging tools.

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Section: Thermal-softening and Cyclic-softening Modelmentioning

confidence: 99%

A Temperature-Dependent Viscoplasticity Model for the Hot Work Steel X38CrMoV5-3, Including Thermal and Cyclic Softening under Thermomechanical Fatigue Loading

2023

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“…The production of this material includes processes such as steel ingot smelting, forming, and heat treatment. In recent years, numerous studies have been conducted on this material, concentrating on optimising heat treatment process parameters, [2][3][4] thermal deformation behaviour, 5 macrosegregation control, 6 microstructure evolution, 1,[7][8][9] the relationship between microstructure and properties, 10,11 and cavity defect closure behaviour. 12 Most of these studies have focused on laboratory-scale or small to medium-sized steel ingot forging and heat treatment process optimisation in industrial practices.…”

Section: Introductionmentioning

confidence: 99%

Formation mechanism of inspection defects in hundred-ton class 55NiCrMoV7 die steel forging

Zhang,

Cheng

et al. 2024

Ironmaking & Steelmaking: Processes, Products and Applicati

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Using an ultrasonic flaw detector, this study precisely located the dimensions and distribution characteristics of defects during the manufacturing process of 55NiCrMoV7 die steel forgings weighing hundreds of tons. The probing defects of the forging are predominantly concentrated in the central region, spanning approximately 4200 mm in length, 400 mm height and 1500 mm width. Detailed research on the characteristics of these probing defects was conducted through dissection sampling and scanning electron microscope analysis. The research results reveal that the maximum diameter of an individual defect can reach Φ10 mm, and localised cracking phenomena exist in specific areas within the forging. The flaws exhibit characteristics such as millimetre-sized, large, elongated MnS inclusions, with spacing between inclusions ranging from 200μm to 500μm. Furthermore, based on elemental analysis, the sulphur content from the surface to the core of the forging increased from 0.001% to 0.002% to a maximum of 0.0085%. Through analysis using thermodynamic and growth kinetics models, it was determined that in regions with higher sulphur content (S = 0.0085) at a certain distance from the steel ingot surface, the radius of MnS inclusions can reach up to 380μm under low cooling rates (1 K/min). After forging deformation, these can evolve into millimetre-sized MnS inclusions, leading to internal inspection defects. Therefore, we propose that reducing the sulphur content in the molten steel and increasing the degree of undercooling can effectively inhibit the precipitation and growth of MnS inclusions. Practical results indicate that this improvement strategy effectively enhances the inspection quality of the 55NiCrMoV7 die steel forgings weighing hundreds of tons.

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“…A kind of hot-working die steel with high strength and wear resistance, 55NiCrMoV7 has good impact resistance and tempering stability and is widely used in dies for forgings, such as in aviation, the military, and automobiles [8][9][10][11]. As the die industry develops in the direction of large-scale, complex, precise, high-efficiency, and fast-paced applications, its service environment is becoming more and more harsh, which requires higher requirements for die materials [12][13][14][15]. In a service environment of 600 • C, due to insufficient thermal strength, steel undergoes high-temperature wear, collapse, sag, and other failure phenomena, which seriously affect its service life [16].…”

Section: Introductionmentioning

confidence: 99%

Microstructure Evolution and Fracture Mechanism of 55NiCrMoV7 Hot-Working Die Steel during High-Temperature Tensile

Yuan

Wang

Shi

et al. 2023

Metals

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In this paper, through high-temperature tensile tests of 55NiCrMoV7 steel, high-temperature fracture behavior, microstructure evolution, and carbide distribution characteristics of both the thermal–mechanical coupling zone (fracture zone) and thermal stress zone (clamping zone) at different temperatures were studied. Intrinsic relationships between high-temperature fractures and carbide types, distribution and size were revealed, and evolution mechanisms of microstructure near cracks in 55NiCrMoV7 hot-working die steel during high-temperature deformation was clarified. Samples were stretched at different temperatures from 25 °C to 700 °C, and microscopic examinations were carried out using SEM and TEM. The results showed the following. With the increase in temperature, tensile strength and yield strength decreased, elongation and reduction of area increased, and fracture mode changed from brittle fracture to ductile fracture by transition temperature at about 400 °C. During high-temperature deformation, the grain dislocation density decreased and the tempered martensite decomposed, recovered, recrystallized, and then grain grew. M7C3 and M23C6 carbides precipitated and grew along the grain boundary, and a small amount of fine granular MC carbides was dispersed in the grain. The work done by the external force on the deformation zone would cause the temperature of it to be higher than the tensile temperature, which provides thermodynamic conditions for the redissolution of small carbides near the fracture zone and the grain growth of large carbides, resulting in a decrease in small carbides and increase in large carbides in thermal–mechanical coupling zones.

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Microstructural evolution and mechanical properties of 55NiCrMoV7 hot-work die steel during quenching and tempering treatments

Cited by 10 publications

References 30 publications

A Temperature-Dependent Viscoplasticity Model for the Hot Work Steel X38CrMoV5-3, Including Thermal and Cyclic Softening under Thermomechanical Fatigue Loading

A Temperature-Dependent Viscoplasticity Model for the Hot Work Steel X38CrMoV5-3, Including Thermal and Cyclic Softening under Thermomechanical Fatigue Loading

Formation mechanism of inspection defects in hundred-ton class 55NiCrMoV7 die steel forging

Microstructure Evolution and Fracture Mechanism of 55NiCrMoV7 Hot-Working Die Steel during High-Temperature Tensile

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