Determination of thermophysical properties and boundary conditions of direct chill-cast aluminum alloys using inverse methods

Drezet, Jean‐Marie; Rappaz, M.; Grün, Gerd-Ulrich; Gremaud, M.

doi:10.1007/s11661-000-0172-5

Cited by 89 publications

(35 citation statements)

References 12 publications

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“…along the casting direction, at a rate of 90 mm/min. These boundary conditions account for primary cooling through the mould, air gap formation and secondary cooling at the point where the water hits the ingot and flows along its surface [24]. To simulate the presence of a wiper, an adiabatic condition was used below the location of the wiper.…”

Section: Thermomechanical Model Of Castingmentioning

confidence: 99%

Neutron Diffraction Measurement of As-Cast Residual Stresses in Aa7050 Rolling Plate Ingots: Influence of A Wiper

et al. 2014

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During casting, thermally induced deformations give birth to ingot distortions and residual stresses. For some high strength alloys, ingot cracking can happen during casting per se or during cooling down. Ingot distortions such as rolling face pull-in, but curl and but swell are rather easy to quantify as opposed to internal stresses. As aluminium is rather transparent to neutrons, residual stress measurements using neutron diffraction appeared to be a good way to validate the thermomechanical models aimed at simulating the stress build-up during casting. This technique has been applied to DC cast AA7050 rolling plate ingots with special attention to the stress generation in the transient start-up phase, i.e. in the foot of the ingot. Additional results using the hole drilling method complement the measurements. The measured stress distributions are compared with the results of a numerical model of DC casting for ingots cast with and without a wiper. I IntroductionIn the fabrication of aluminum rolling plates, the first step is the semi-continuous casting of a rectangular ingot. The most commonly used process is known as direct chill (DC) casting [1]. This process gives rise to large thermally induced strains that lead to several types of casting defects (distortions, cold cracks, porosity, solidification cracking, etc.). During casting, thermally induced stresses are partially relieved by permanent deformation. When these residual stresses overcome the deformation limit of the alloy, cracks are generated either during solidification (hot tears) or during cooling (cold cracks). The formation of these cracks results in rejection of the cast part. Furthermore, thermally induced stresses can cause downstream processing issues during the sawing stage prior to rolling. For large ingot formats and high strength alloys, sawing becomes a delicate task owing to the risk of saw pinching or crack initiation ahead of the saw. The use of wipers during casting largely reduces the level of as-cast stresses.The computation of stresses during DC casting of aluminum alloys has been the scope of several studies since the late 90's [2-10] and is a well established technique nowadays. Many numerical models have allowed researchers to compute the ingot distortions and the associated residual stresses. The validation of these models was often done by comparing the computed and measured ingot distortions, e.g. the butt-curl [8] and the rolling face pull-in for rolling sheet ingots produced by DC [9] or electromagnetic casting [11].Validation against the computed room-temperature residual stresses is limited simply owing to the difficulty of measuring the internal strains and the high variability in the measurements. While some measurements are available for quenching [12] or welding [13], they remain rare, uncertain and usually are limited to one or two components of the stress tensor, and to the skin of round billets for as-cast materials [14][15]. In contrast to destructive methods for measuring residual stresses (hole-drilli...

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Section: Thermomechanical Model Of Castingmentioning

confidence: 99%

Neutron Diffraction Measurement of As-Cast Residual Stresses in Aa7050 Rolling Plate Ingots: Influence of A Wiper

et al. 2014

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“…The bottom of the billet was cooled using a constant heat flux of 1000 W/m 2 to simulate heat transfer between the billet and the bottom block. Further details on these boundary conditions can be found in [21].…”

Section: Model Formulationmentioning

confidence: 99%

“…Although this law also includes the effects of fs and fp, this variation in these parameters in different regions of the casting is not taken into account in this initial study (i.e. (a) fp is assumed to be 0 and hence Kp=1 [21], and (b) the cooling-rate effects on the evolution of fraction solid with temperature are ignored). At temperatures above Tcoh, the mechanical behavior was considered elasto-plastic with a small yield stress and independent of strain rate.…”

Section: Mechanical Behaviormentioning

confidence: 99%

“…In the current work, the constitutive law presented in Eqs. (2)- (5) has been implemented into a previously-developed DC casting model for Al alloy round billets [21].Stress-strain predictions from a series of simulations were then analyzed with respect to the casting speed, grain size and different coherency temperatures. These results were used to investigate the effects between casting parameters, microstructure and hot tearing in DC castings.…”

Section: Introductionmentioning

confidence: 99%

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Hot Tearing Susceptibility in DC‐Cast Aluminum Alloys

Jamaly

Phillion

Cockcroft

et al. 2012

Supplemental Proceedings

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“…A wide number of papers focused on the application of inverse modelling to metal casting simulation exists but most of them are focused on the determination of the heat transfer coefficient between the mold and the alloy, as occurs in bibliographic references [6][7][8][9].…”

Section: Introductionmentioning

confidence: 99%

Finite Element Model Correlation of an Investment Casting Process

Anglada

Meléndez

Maestro³

et al. 2014

MSF

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Abstract. The achievement of reliable simulations, in the case of complex processes as is the investment casting, is not a trivial task. Their accuracy is significantly related with the knowledge of the material properties and boundary conditions involved, but the estimation of these values usually is highly complex. One helpful option to try to avoid these difficulties is the use of inverse modelling techniques, where experimental temperature measurements are used as base to correlate the simulation models. The research presented hereafter corresponds to the correlation of a finite element model of the investment casting process of two nickel base superalloys, Hastelloy X and Inconel 718. The simulation model has been developed in a commercial software focused specifically on metal casting simulation. The experimental measurements used as base for the adjustment, have been performed at industrial facilities. The methodology employed combines the use of an automatic tool for model correlation with the manual adjustment guided by the researchers. Results obtained present a good agreement between simulation and experimental measurements, according to the industrial necessities. The model obtained is valid for the two studied cases with the only difference of the alloy material properties. The values obtained for the adjusted parameters in both cases are reasonable compared with bibliographic values. These two circumstances suggest that the obtained correlation is appropriate and no overfitting problems exist on it.

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Determination of thermophysical properties and boundary conditions of direct chill-cast aluminum alloys using inverse methods

Cited by 89 publications

References 12 publications

Neutron Diffraction Measurement of As-Cast Residual Stresses in Aa7050 Rolling Plate Ingots: Influence of A Wiper

Neutron Diffraction Measurement of As-Cast Residual Stresses in Aa7050 Rolling Plate Ingots: Influence of A Wiper

Hot Tearing Susceptibility in DC‐Cast Aluminum Alloys

Finite Element Model Correlation of an Investment Casting Process

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