Influence of the microstructure on fatigue and fracture toughness properties of large heat-treated mold steels

Firrao, Donato; Matteis, Paolo; Spena, Pasquale Russo; Gerosa, R.

doi:10.1016/j.msea.2012.08.113

Cited by 37 publications

(16 citation statements)

References 6 publications

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“…The results indicated that tempering effects vary significantly from bainitic to martensitic microstructures helping to draw a clearer picture of the phase transformations in different microstructures. The following conclusions can be drawn from the present study: (1) In the bainitic microstructure, retained austenite decomposed to lower bainite associated with volume expansion during tempering in contrast to martensite tempering where great length decrease occurred due to decomposition of medium-carbon martensite to low carbon martensite plus carbides. (2) Phase transformations during tempering of martensite occurred at slightly higher temperatures than bainite tempering, owing to the auto-tempering effect through bainite formation.…”

Section: Discussionmentioning

confidence: 56%

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In Situ Study of Phase Transformations during Non-Isothermal Tempering of Bainitic and Martensitic Microstructures

Talebi

Ghasemi-Nanesa

Jahazi

et al. 2017

Metals

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Abstract:Phase transformations during non-isothermal tempering of bainitic or martensitic microstructures obtained after quenching of a medium-carbon low-alloy steel was studied. The microstructures correspond to different locations of an as-quenched large-sized forged ingot used as a die material in the automotive industry. High-resolution dilatometry experiments were conducted to simulate the heat treatment process, as well as to investigate different phenomena occurring during non-isothermal tempering. The microstructures were characterized using optical and scanning electron microscopy. Dilatometry analyses demonstrated that tempering behavior varied significantly from bainitic to martensitic microstructures. Retained austenite, which exists between bainitic ferrite sheaves, decomposes to lower bainite causing a remarkable volume increase. It was found that this decomposition finishes below 386 • C. By contrast, martensite tempering was accompanied with a volume decrease due to the decomposition of medium-carbon martensite to low carbon martensite and carbides.

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Section: Discussionmentioning

confidence: 56%

“…Consistent and uniform mechanical properties throughout the volume of the die material are required by industry [1]. The die materials are generally made of medium-carbon low-alloy steels and their manufacturing process consists of ingot casting, open die forging, quenching, tempering, and final machining [1,2].…”

Section: Introductionmentioning

confidence: 99%

In Situ Study of Phase Transformations during Non-Isothermal Tempering of Bainitic and Martensitic Microstructures

Talebi

Ghasemi-Nanesa

Jahazi

et al. 2017

Metals

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“…Tool steels with a microstructure of tempered a 0 -martensite are used in a variety of applications, for instance hot extrusion, polymer processing, press hardening, and die casting [1][2][3][4]. In addition to wear resistance and mechanical properties such as strength, ductility, and toughness, several thermophysical properties are relevant for tool design.…”

Section: Introductionmentioning

confidence: 99%

The influence of heat treatment and resulting microstructures on the thermophysical properties of martensitic steels

et al. 2013

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This research study investigates the influence of heat treatment on the thermal conductivities of three different tool steels at room temperature. The results reveal not only that tempering plays a decisive role in their thermophysical properties, but also that the changes in thermal conductivity due to heat treatment are dependent on the degree of alloying. Isobaric heat capacities c p are found to be less dependent on heat treatment than thermal diffusivities a. The results are discussed with respect to the resulting microstructures and, for high-tempered conditions, under consideration of Calphad calculations. The results are relevant for the thermal design of tools, in particular, for tailored tempering of tools used for press hardening.

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“…When the cooling rate increases to 3–5 °C s −1 , the volume fraction of ferrite was reduced to near‐absence and the transformed microstructure was dominated by pearlite (Figure b). When the cooling rate was increased to greater than 10 °C s −1 , the transformation microstructure primarily composed of martensite (Figure c and d), which was harmful to the high speed railway wheel in terms of resistance of fracture …”

Section: Resultsmentioning

confidence: 99%

Microstructural Refinement and Mechanical Properties of High‐Speed Niobium‐Microalloyed Railway Wheel Steel

Zhang

et al. 2014

steel research int.

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The relationship between microstructure and mechanical properties was studied in a Nb‐bearing high‐speed railway wheel steel and compared with a traditional low‐alloyed medium carbon steel. The microstructure of medium carbon steel comprised of ferrite and pearlite and the percentage of ferrite was increased from 4 to 24% on the addition of 0.06 wt% Nb and the grain size was refined. The addition of Nb inhibited mixed microstructure and delayed the coarsening temperature of austenite grains from 880 to 960 °C. The yield strength of Nb‐bearing steel was increased from 385 to 455 MPa and the Charpy v‐notch energy at −20 °C was increased from 7.0 to 19.0 J with no apparent reduction in tensile strength. Niobium formulates grain refinement and transformation of austenite to ferrite and pearlite over a wide region of cooling rate (<10 °C s−1) and temperature range (530–690 °C) in the medium carbon steel. With the calculation of Thermal‐Calc software and solid solubility formula, Nb exists in the form of precipitates. The grain refining and precipitation strengthening are roles of niobium in promoting ferrite–pearlite transformation and improve toughness in the medium carbon steel.

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Influence of the microstructure on fatigue and fracture toughness properties of large heat-treated mold steels

Cited by 37 publications

References 6 publications

In Situ Study of Phase Transformations during Non-Isothermal Tempering of Bainitic and Martensitic Microstructures

In Situ Study of Phase Transformations during Non-Isothermal Tempering of Bainitic and Martensitic Microstructures

The influence of heat treatment and resulting microstructures on the thermophysical properties of martensitic steels

Microstructural Refinement and Mechanical Properties of High‐Speed Niobium‐Microalloyed Railway Wheel Steel

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