Comparison of the microstructures in continuous-cooled and quench-tempered pre-hardened mould steels

Hoseiny, Hamed; Klement, Uta; Sotskovszki, Peter; Andersson, Joel

doi:10.1016/j.matdes.2010.06.045

Cited by 27 publications

(12 citation statements)

References 4 publications

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“…The micrographs of samples processed in forging both at 850°C and 800°C and direct air-cooling are composed of lath-boundary carbides separating the martensite laths, which seem coarser than those produced on cooling from above 1,000°C. Besides martensite/ bainite fractions ferrite islands, in which apparent sub grain structure ranging 2-6 mm can be observed, with uniformly scattered particles of M 3 C carbides of globular shape which can be the effect of tempering or autotempering (Hoseiny et al, 2011), strengthening the softer phase.…”

Section: Microstructure and Mechanical Propertiesmentioning

confidence: 99%

Properties of direct-quenched aircraft forged component made of ultrahigh-strength steel 300M

Skubisz¹,

Sińczak²

2018

AEAT

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Purpose This paper aims to investigate the possibilities and determination of hot and warm forging of ultrahigh-strength steel 300M and subsequent quenching with accelerated air. Analysis of microstructure and mechanical properties of forged steel 300M focused on investigation of the effect of processing conditions on final properties, such as strength, impact strength and hardness, taking into consideration temperature gradients and within-part strain nonuniformity occurring in forging and direct cooling of aircraft landing gear. Design/methodology/approach The research involved semi-industrial physical modeling of hot deformation and direct cooling, aided with numerical analysis of both deformation and kinetics of phase transformations on cooling, with process conditions determined on the basis of numerical simulation of industrial process. Examination of forged and quench-tempered samples involved testing mechanical properties (tensile properties, hardness and impact strength) and microstructure. Findings Three major findings were arrived at: first, assessment of the effects of energy-saving method of cooling conducted directly after forging. Second, tensile properties, hardness and impact strength, were analyzed on the background of microstructure evolution during hot-forging and direct cooling; hence, applied temperature and cooling rates refer to actual condition of the material including varied deformation history. Third, the accelerated air cooling tests were carried out directly after forging with accurately measured and described cooling efficiency, which enabled the acquisition of data for heat treatment simulation with use of untypical cooling media. Research limitations/implications The conclusions formulated on the strenght of studies carried out in semi-industrial conditions with the use of model samples, despite strain and strain rate similarity, wait for full-scale verification in industrial conditions. The direct cooling tests carried out in semi-industrial conveyor Quenchtube are of cognitive value. Industrial realization of the process for the analyzed part calls for special construction of the cooling line and provision of higher cooling rate for heavy sections. Practical implications The results present microstructure properties’ relations for good-hardenability grade of steel, which is representative of several similar grades used in aircraft industry, which can support design of heat treatment (HT) cycles for similar parts, regardless of whether direct or conventional quenching is used. As they illustrate as-forged and direct-cooled microstructure and resultant mechanical properties, the studies concerning processing the steel of areas of lower temperature are transferable to warm forging processes of medium-carbon alloy steels. The geometry of the part analyzed in the case study is typical of landing gear of many aircrafts; hence, there is the high utility of the results and conclusions. Social implications The direct heat treatment technologies based on utilization of the heat attained in the part after forging allow significant energy savings, which besides cost-effectiveness go along with ecological considerations, especially in the light of CO2 emission reduction, improving economical balance and competitiveness. The presented results may encourage forgers to use direct cooling, making use of the heat attained in metal after hot forging, for applications to promote environmentally friendly heat treatment-related technologies. Originality/value Direct heat treatment typically seems to be reserved for micro alloyed steel grades and sections small enough for sufficient cooling rates. In this light, taking advantage of the heat attained in forged part for energy-saving method of cooling based on direct quenching as an alternative to traditional Q&T treatment used with application to relatively heavy sections is not common. Moreover, in case the warm-work range is reached in any portion of the forged part, effect of direct cooling on warm-forged material is addressed, which is a unique issue to be found in the related studies, whereas in addition to warm forging processes, the results can be transferable to coining, sizing or shot peening operations, where gradient of properties is expected.

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Section: Microstructure and Mechanical Propertiesmentioning

confidence: 99%

Properties of direct-quenched aircraft forged component made of ultrahigh-strength steel 300M

Skubisz¹,

Sińczak²

2018

AEAT

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“…The influence of microstructure on fracture toughness properties [ 8 ], and tensile as well as fatigue properties of large 718H heat-treated mold steels were studied by Firrao [ 9 ]. In addition, Hoseiny investigated the microstructures in continuous-cooled and quench-tempered pre-hardened mold steel [ 10 ], as well as the effect of heat treatment on the microstructure and machinability of pre-hardened mold steel [ 6 ]. At the same time, the optimal tempering temperature of 718H pre-hardened mold steel had been determined in the range of 530 to 560 °C by our previous research [ 11 ].…”

Section: Introductionmentioning

confidence: 99%

Improvement of Strength-Toughness-Hardness Balance in Large Cross-Section 718H Pre-Hardened Mold Steel

Liu

et al. 2018

Materials

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The strength-toughness combination and hardness uniformity in large cross-section 718H pre-hardened mold steel from a 20 ton ingot were investigated with three different heat treatments for industrial applications. The different microstructures, including tempered martensite, lower bainite, and retained austenite, were obtained at equivalent hardness. The microstructures were characterized by using metallographic observations, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and electron back-scattered diffraction (EBSD). The mechanical properties were compared by tensile, Charpy U-notch impact and hardness uniformity tests at room temperature. The results showed that the test steels after normalizing-quenching-tempering (N-QT) possessed the best strength-toughness combination and hardness uniformity compared with the conventional quenched-tempered (QT) steel. In addition, the test steel after austempering-tempering (A-T) demonstrated the worse hardness uniformity and lower yield strength while possessing relatively higher elongation (17%) compared with the samples after N-QT (14.5%) treatments. The better ductility of A-T steel mainly depended on the amount and morphology of retained austenite and thermal/deformation-induced twined martensite. This work elucidates the mechanisms of microstructure evolution during heat treatments and will highly improve the strength-toughness-hardness trade-off in large cross-section steels.

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“…Therefore, their ductility, impact toughness, fatigue and machining behavior can significantly be improved with spheroidizing heat treatment which is conducted with long-time annealing about at A c1 (eutectoid transformation) temperatures [1]. On the other hand, cementite phases can also be spheroidized by over-tempering martensite phase at a high temperature which is produced from austenite by quenching at high temperature [2,3]. The reason for this is that many potential nucleations are ensured in the martensite lath boundaries as the tempering heat rises and with the fast diffusion of carbon as the rapid formation of stable cementite type carbide is ensured, *Corresponding author: tel.…”

Section: Introductionmentioning

confidence: 99%

Analysis of spheroidized AISI 1050 steel in terms of cutting forces and surface quality

Baday¹,

Başak²,

Güral³

2016

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In this study, the effects of microstructure differences obtained with the application of different spheroidizing heat treatment cycles on medium carbon steel on cutting forces and surface roughness values were investigated. For this purpose, a group of AISI 1050 materials was annealed at 700• C below Ac1 temperature for 720 min and cementite phases were spheroidized by the traditional method. Another group of materials was quenched after austenitization at 850• C for 15 min and then cementites were spheroidized in the ferrite matrix by over-tempering separately at 600• C for 15 and 60 min and at 700• C for 60 min. Machining of the samples was tested under dry cutting conditions in CNC turning center with SNMG 120408 cementite carbide cutting tool and proper PSBNR 2525M12 tool holder with 75-degree edge angle. Cutting forces of traditionally spheroidized samples were lower than the samples spheroidized after quenching. In addition, their cutting forces decreased due to the increase in the average sizes of spheroidal cementite. Minimum surface roughness value was obtained from the samples which were spheroidized at 600• C for 15 min after quenching. However, surface roughness rate of the sample increased as spheroidizing time increased. K e y w o r d s : spheroidizing, cutting forces, surface roughness, medium carbon steel

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Comparison of the microstructures in continuous-cooled and quench-tempered pre-hardened mould steels

Cited by 27 publications

References 4 publications

Properties of direct-quenched aircraft forged component made of ultrahigh-strength steel 300M

Properties of direct-quenched aircraft forged component made of ultrahigh-strength steel 300M

Improvement of Strength-Toughness-Hardness Balance in Large Cross-Section 718H Pre-Hardened Mold Steel

Analysis of spheroidized AISI 1050 steel in terms of cutting forces and surface quality

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