Relationships between tensile and fracture mechanics properties and fatigue properties of large plastic mould steel blocks

Firrao, Donato; Matteis, Paolo; Scavino, Giorgio; Ubertalli, Graziano; Ienco, M. G.; Pinasco, M. R.; Stagno, E.; Gerosa, R.; Rivolta, B.; Silvestri, A.; Silva, Giuseppe; Ghidini, A.

doi:10.1016/j.msea.2006.07.166

Cited by 42 publications

(27 citation statements)

References 4 publications

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“…7 the present results are compared with those reported by Solter and with the previously reported thermal diffusivity of three austenitic stainless steels with different chromium and nickel content: ISO 1.4970 (or X10NiCrMoTiB15-15), containing 15 wt% Cr and 15 wt% Ni [32], AISI 310, containing 25 wt% Cr and 20 wt% Ni [33], and AISI 304, nominally containing 19 wt% Cr and 9 wt% Ni [34]. 11 With the following composition (weigth %): C 0.32, Si 0.14, Mn 0.61, Cr 0.93, Mo 0.46, Ni 2.5.…”

Section: Discussionmentioning

confidence: 53%

“…11 These measurements were performed by using the laser flash method while cooling the specimen from 1273 K to room temperature, whereas the phase transformation was detected only below 715 K, but the employed experimental and data reduction procedures were not reported, and, therefore, it is unclear how the prior thermal equilibrium condition (required by the standard method) was dealt with. Furthermore, in the examined temperature range, some stainless steels present a stable austenitic phase, due to their high alloy (and particularly Nickel) content, and their thermal diffusivity have been extensively studied by standard methods.…”

Section: Discussionmentioning

confidence: 99%

“…The alloyed, medium-carbon, ISO 1.2738 steel grade 4 [9] was chosen because it is usually employed for the production of very large pre-hardened blooms [10,11]. The heat treatment of these blooms is characterized by a large Biot number and is relevant to control mechanical properties; thus, finite-element analyses need to be performed for die design purposes.…”

Section: Methodsmentioning

confidence: 99%

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Thermal diffusivity measurements of metastable austenite during continuous cooling

Matteis¹,

Campagnoli

Firrao

et al. 2008

International Journal of Thermal Sciences

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The thermal diffusivity of the metastable undercooled austenite is relevant for the quantitative analysis of the carbon and low-alloy steel quench. The standard laser-flash method requires prior thermal equilibrium between the sample and the furnace, which may not be possible to achieve without allowing the metastable phase to transform. Nevertheless, depending upon the steel's hardenability, the thermal transient due to a laser pulse may be much shorter than a cooling transient sufficiently steep to prevent the transformation of the austenite. In one such case, flash measurements were performed during continuous sample cooling and the thermal diffusivity of the metastable austenite was determined by using an extension of the standard analytical model. The adopted analytical model and data reduction procedure are described and the limitations and uncertainties of this method are discussed, also with the aid of a non-linear numerical simulation. The measured thermal diffusivity of the undercooled low-alloy austenite decreases linearly from 5.4 · 10 −6 m 2 s −1 at 1133 K to 4.3 · 10 −6 m 2 s −1 at 755 K; this trend is in broad agreement with one previous set of measurements upon a low-alloy undercooled austenite and with a large number of previous standard measurements upon stable (high-alloy) austenitic stainless steels.

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Section: Discussionmentioning

confidence: 53%

Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Thermal diffusivity measurements of metastable austenite during continuous cooling

Matteis¹,

Campagnoli

Firrao

et al. 2008

International Journal of Thermal Sciences

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“…2-3) tratti da studi sistematici condotti nel Dipartimento degli scriventi e in Dipartimenti di altre strutture universitarie italiane su un acciaio 1.2738 -40CrMnNiMo8-6-4, ISO 4957, 3 temprato in olio e rinvenuto nell'intervallo di temperatura fra 550 e 600 °C. [6,7] 3 Può essere considerato un acciaio legato di composizione quasi eutettoidica.…”

Section: Resistenza All'intaglio E Tenacità a Frattura DI Acciai Con unclassified

Fracture toughness and fatigue resistance of quenched and tempered steels with microstructures deriving from a slant quench. Consequences on technical standards

Firrao¹,

Matteis²

2011

Frattura Ed Integrità Strutturale

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RIASSUNTO.Componenti meccanici di acciai allo stato bonificato, caratterizzati da microstrutture miste derivanti da condizioni di tempra incompleta, si incontrano frequentemente nella pratica costruttiva, a causa della tendenza verso acciai progressivamente meno legati o a causa di componenti con sezioni piuttosto elevate. La bassa resistenza all'intaglio di microstrutture miste è stata messa in evidenza già negli anni '50, ma da allora non è stata più oggetto di indagine e si è trascurato, anche nella normativa, di metterne in evidenza la pericolosità. Quando alla martensite rinvenuta ed alla bainite si accompagnano anche perlite e ferrite, la tenacità alla frattura scende a livelli estremamente pericolosi. I risultati di una campagna di ricerche condotte sulla tenacità a frattura di acciai per stampi di materie plastiche caratterizzati da microstrutture miste vengono presentati, individuando le combinazioni di microstrutture con tenacità a frattura troppo basse. Anche la propagazione delle cricche di fatica risulta negativamente influenzata dalla presenza di più costituenti. Le norme di uso dei manufatti dovrebbero tenere presenti le considerazioni sviluppate.ABSTRACT. Mechanical components fabbricated with quenched and tempered steels, exhibiting mixed microstructures as derived from slant quench conditions, are frequently encountered in the industrial practice, owing to a tendency to employ quite low alloy steels or due to quite large sections. The low notch strength of mixed microstructure steel samples was already emphasized in the 1950s; yet, it has never been investigated again. Also, technical standards have not addressed the risk deriving from the use of steel components with mixed microstructures. When pearlite and ferrite are present alongside tempered martensite and bainite, the fracture toughness of steel pieces diminishes to very dangerous levels. Results of an experimental program on the fracture toughness of plastic mould steels are reported, singling out microstructure mixtures with too a low toughness. In addition, the fatigue crack propagation rate is adversely affected by inhomogeneous metallographic structures. It is inferred that experimental results and ensuing considerations should be taken into account when formulating technical norms.

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“…Such large mold blooms, which are usually used for bumpers and dashboards, have mainly been manufactured with quench-tempered (QT) steel grade DIN 40CrMnNiMo [1]. Recently, direct-cooled and tempered (DT) bainitic mold steel with medium carbon content has been developed.…”

Section: Introductionmentioning

confidence: 99%

Effect of microstructure on the impact toughness of a bainitic steel bloom for large plastic molds

Zhang

Zhou

et al. 2015

Int J Miner Metall Mater

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The correlation between the impact toughness and microstructural characteristics of a large bainitic steel bloom has been investigated. The study focuses on microcrack nucleation and propagation in the basic cleavage plane. To analyze the phase transformation during the wind-cooling process, the temperature field of the bloom was acquired by computer simulation, and a continuous cooling transformation experiment was conducted. The results show that compared with the surface of the bloom, the toughness of the bloom's core is decreased by the increase in proeutectoid ferrite and the coarsening of tempered martensite-austenite constituents. The proeutectoid ferrite decreases the toughness via its effects on carbide precipitation, the formation of martensite-austenite constituents, and the bainite transformation. The relatively large tempered martensite-austenite constituents are conducive to microcrack nucleation and propagation.

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Relationships between tensile and fracture mechanics properties and fatigue properties of large plastic mould steel blocks

Cited by 42 publications

References 4 publications

Thermal diffusivity measurements of metastable austenite during continuous cooling

Thermal diffusivity measurements of metastable austenite during continuous cooling

Fracture toughness and fatigue resistance of quenched and tempered steels with microstructures deriving from a slant quench. Consequences on technical standards

Effect of microstructure on the impact toughness of a bainitic steel bloom for large plastic molds

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