Leidenfrost effect and wettability on High Pressure Die Casting Lubricant Spraying

AUTHORS

 B. Zabalaa,c, A. Igartuaa, V. Scarpisa,b, G. Timellib, F.Girotc

 a) IK4-TEKNIKER, Parque Tecnológico de Eibar, Calle Iñaki Goenaga 5, 20600 Eibar, Spain

b) Department of Management and Engineering, University of Padova, Stradella S. Nicola 3, I-36100 Vicenza, Italy

c) ETSIB – UPV/EHU & IKERBASQUE, Alameda de Urquijo s/n, 48013 Bilbao, Spain

 

ABSTRACT

This study tries to find out a better cooling and temperature homogenization on High Pressure Die Casting (HPDC) spray lubrication. A test procedure has been set up to study the Leidenfrost Point (LFP) and Contact Angle (CA) of lubricants typically used to protect the die surfaces during the High Pressure Die Casting process, studying their influence in different controllable process parameters (type of material, oxidation of the surface, temperature, roughness, droplet diameter, water hardness, lubricant concentration,..). The increase of the LFP, avoiding film boiling regime, and a reduced CA, improves the cooling and film ability of HPDC moulds during spraying. The study of the different variables that affect LFP and CA result in a better insight of the involved phenomena and allows selecting the most favourable operating window for high pressure die casting lubrication.

 KEYWORDS

 High Pressure Die Casting, Spraying, Leidenfrost Point, Contact Angle

AKNOWLEDGMENTS

 The authors would like to thanks the collaboration of industrial partners from Motultech-Baraldi and SAEN s.r.l for supplying the lubricants, mould materials and their kind suggestions, as well as to other laboratory colleagues that have helped to make this work. The research leading to these results has received funding from the European Union’s Seventh Framework Programme [FP7-2012-NMP-ICT-FoF] under Grant Agreement Number 314145.

For further information about this paper and the MUSIC Project, plase contact: borja.zabala@tekniker.es

 

Experimental study about Thermal Fatigue and Erosion on HPDC moulds

 T. Cundari, Thesis at University of Padova, October 2015

 ABSTRACT

 There are different wear mechanisms that contribute to damage the High Pressure Die Casting moulds, and erosion and thermal fatigue are both the topic of this thesis. Erosion and thermal fatigue are both long term failures, that are very difficult to predict and expensive to repair. Erosion is a mechanical action of the flux against the mould surface, and thermal fatigue is the cracking that results from the repeated compression and tension due to the rapid heating and cooling of the mould surface. Laboratory tests have been used to simulate both phenomena and understand them better, in order to predict their appearance in the HPDC moulds.

 

High Pressure Die Casting: Contradictions and Challenges

AUTHORS

 Franco Bonollo1, Nicola Gramegna2, Giulio Timelli1*

1. University of Padova, Department of Management and Engineering, Stradella S. Nicola, 3 I-36100 Vicenza, Italy. (Franco Bonollo: bonollo@gest.unipd.it, Giulio Timelli: timelli@gest.unipd.it)

2. Enginsoft Spa, Via Giambellino, 7 I-35129 Padova, Italy. (Nicola Gramegna: n.gramegna@enginsoft.it)

 (*Corresponding author. Tel.: 00 39 0444 998769; fax. 00 39 0444 998889. E-mail address: timelli@gest.unipd.it (G. Timelli)).

 ABSTRACT

The high-pressure die-casting (HPDC) is particularly suitable for high production rates and it is applied in several industrial fields; actually, about half of the world production of light metal castings is obtained by this technology. An overview of the actual status of HPDC technology is described in the present work, where both critical aspects and potential advantages are evidenced. Specific attention is paid to the quality requirements from the end-users, as well as to the achievable production rate, the process monitoring and control, the European and worldwide scenario. This overview leads to individuate the most relevant challenges for HPDC industry: “zero-defect” production, real time process control, understanding the role of the process variables, process optimization, introduction of R&D activities, disseminating the knowledge about HPDC technology. Performing these actions, HPDC foundries could be able to achieve a more mature and efficient approach to large end-users, and to exploit their really relevant potential.

KEYWORDS

High-pressure die-casting; Light alloys; Process control; Optimization; Quality

The publication is available on-line at the following link: http://link.springer.com/article/10.1007/s11837-015-1333-8

Experimental study about the aluminum-iron interaction in presence and absence of lubricant, with a tribologicla pin-on-disc test and DSC/GTA Chemical analysis

 M. Peggiato, thesis at University of Padova, April 2015

ABSTRACT

The present work is inserted into an European Project that is denominated ‘’MUSIC’’ project. The part of the project connected to the topic of this work  is the ‘’die damage’’ in HPDC technological process. The die damage is one of the most important element into the general costs of the HPDC, in fact it leads to a very long down-time and very high services costs, for example to repair the mould in the part where is damaged.

There are different wear mechanisms that contribute to damage the die, but the most important is called ‘’die soldering’’. This phenomena is due to an interaction between the aluminium, which is forming, and the iron of the die; this interaction is mainly based on a diffusion interaction and a consequent formation of some intermetallic layers. The reason why this phenomena leads to a damage of the die is caused by a sticking, or better soldering, between aluminium and die; this leads to a local damage of the die and an imcrease of the effort that is required to extract the part from the mould.

This interaction mechanism isn’t typical only on the HPDC, but it is possible to find a very strong interaction between aluminium and iron also in others massive technological processes, such as the extrusion of aluminium or others forming processes, but in all these technologies, this kind of  interaction is connected with the diffusion process.

This work is based on this interaction mechanism between aluminium and iron. This interaction is divided in two different parts: the liquid interaction (that is typically in the HPDC technology during the filling process) and the  solid state interaction (that is present in almost all the massive technological processes, where the melting condition isn’t reached, and during the solidification process in HPDC  where a thin skin of solidify aluminium is formed  on the die surface).

The liquid state interaction is abundantly  discussed in the literature, because there’re a lot of publications where the liquid interaction, with theoretical or experimental observations and approaches, is studied; on the contrary, concerning  the solid state interaction, the literature isn’t complete maybe because a lot of authors think that it is a negligible effect as compared with liquid state interaction.

The focus of the first part of this work, is  only the solid state interaction between aluminium and iron. This interaction will be studied with a typical tribological test, that is called pin on disc test. This test will be done  at high temperature conditions , but always below the melting point. This test simulates which is the solid-solid interaction between aluminium and iron at high temperature conditions and it will be performed in  absence and presence of lubricant; in the first case we’ll analyze which is the pure interaction between these two materials, while in the second case ,we’ll study how physical parameters (as speed, pressure and temperature) affect the lubricant degradation and which is the effect of the lubricant in the solid interaction. The reason why we’ve added a part where the properties and the effects of the lubricant are studied is because the main aim of the lubricant is to create a diffusion and interaction barrier, so a study of the aluminium-iron interaction has not been considered complete without a study of the lubricant effect. The lubricant study is completed with an execution of  a chemical TGA test.

In the second part of this work has gone far beyond respect the previous studies and it is focused on the intermetallic reactions, trying to study them with a Calorimetric test that is called DSC (differential scanning calorimetric). This kind of test gives the possibility to improve the knowledge about the intermetallic reactions that occur near the melting point of the aluminium (in both cases of the liquid and solid interaction), obtaining a quantitative information  about the intermetallic reactions.

 

New classification of defects and imperfections for aluminum alloy castings

E. Fiorese, F. Bonollo, G. Timelli, L. Arnberg, E. Gariboldi,

(2015), International Journal of Metalcastings , 9 (1), pp. 55-66

Fluidity of aluminum foundry alloys: Development of a testing procedure

D. Caliari, G. Timelli, F. Bonollo, P. Arnalberto, P. Giordano,

(2015), Metallurgia Italiana, 107 (6), pp. 11-18

Influence of injection parameters on the porosity and tensile properties of high-pressure die cast Al-Si alloys: A review

A.R. Adamane, L. Arnberg, E. Fiorese, G. Timelli, F. Bonollo,

(2015), International Journal of Metalcastin, 9, (1), pp. 43-52

Process parameters affecting quality of high-pressure die-cast Al-Si alloy

E. Fiorese, F. Bonollo, 8th European Metallurgical Conference 2015, 14-17 June 2015, Dusseldorf

 ABSTRACT

In the last years, aluminium alloys have become more and more relevant because of their low density, coupled with good mechanical and corrosion properties. Different processes are available for the production of aluminium alloy components, but a very significant role is played by foundry processes. However, defects and imperfections are physiologically generated by foundry techniques, as a result of the process itself, of the alloy properties and of the die design. Particularly, high-pressure die-casting (HPDC) is considered a “defect generating process”, since an average of 5-10 % scrap is typically generated by this process. Several process parameters need to be controlled in order to obtain sound and reliable castings. Among the different process variables, the determination and control of the injection parameters remain a key requirement throughout the HPDC process.

In this work, a statistically significant sample of castings in AlSi9Cu3(Fe) alloy has been manufactured through different injection parameters in order to identify the most relevant process parameters and estimate their correlations with the quality of the casting. In particular, the plunger I and II phase velocities (v1 and v2), the switch point between two phases (SW) and the intensification pressure (IP) have been varied randomly in accordance to the Design of Experiment methodology. The static mechanical properties of the castings have been measured using the bending test. Furthermore, the castings have been analysed by X-rays and their percentage of porosity has been estimated by means of image analysis software. Some novel aggregate parameters, representing a measure of the mechanical energy related to the plunger motion and the thermal energy exchanged with the die have been extracted from the plunger displacement curves and from thermocouple signals. The application of statistical concepts, methods and models demonstrates that these novel parameters allow explaining and forecasting both the mechanical properties and the porosity, and therefore the overall quality of the castings.

KEYWORDS: Al-Si alloy, high-pressure die-casting, process parameters, quality

 

Auffinden von Korrelationen Im Aluminum Druckgiessprozess mittels Computertomographie und Thermographie

R. Cornelsen, University of Aalen, September 2015

ABSTRACT

Das Druckgießverfahren ist eine hochproduktive Fertigungstechnologie mit der auch komplexe Gussteile in kurzen Zykluszeiten hergestellt werden können. Jedoch wird der Druckgießprozess von vielen Faktoren, wie zum Beispiel Gießkolbengeschwindigkeit in der ersten und zweiten Phase, Umschaltpunkt, Höhe des Nachdrucks, Trennmittelmenge, Vakuumdrücke usw. bestimmt, welche die Gussteilqualität beeinflussen. Durch das Zusammenspiel dieser Faktoren kann es zu Ausschussraten von 15 - 25% kommen. Das Ziel des europäischen Forschungsvorhabens MUSIC ist die Entwicklung eines kognitiven Systems, dass die Gussteilqualität prognostizieren kann und somit die Ausschussraten reduziert werden können. Für diese Bachelorarbeit bestand die Aufgabe darin, anhand der Auswerteverfahren:

- die Porosität in Teilbereichen des Gussteils zu bestimmen und zu quantifizieren mit Hilfe digitaler Bildverarbeitung,

- Biegeuntersuchungen durchzuführen und auszuwerten,

- thermographische Falschfarbenbilder auszuwerten,

- sowie den Datenbestand zu erhöhen und Korrelationen zwischen Ergebnissen und der Gussteilqualität bzw. Sensormesswerten zu ermitteln. 

Optimierung des Druckgiessverfahrens durch den Einsatz innovatiever Sensorik

T. Feyertag, University of Aalen, September 2015

ABSTRACT

Das Druckgießverfahren ist im Moment eines der wichtigsten Verfahren um Bauteile aus Nichteisenmetallen in großen Stückzahlen herzustellen. Die Ausschussquoten liegen dabei zwischen 5 % und 15 %. Im Vergleich zu anderen Produktionsverfahren, bei denen die Ausschussquote in parts per million angegeben wird, erscheint die oben genannte Ausschussquote im Druckgießverfahren sehr hoch. Der Grund liegt in der Komplexität des Druckgießprozesses. Viele Prozessparameter beeinflussen die Gussteilqualität. Die Auswirkung einzelner Parameter oder deren Wechselwirkungen untereinander sind
nicht eindeutig bekannt. Ein weiteres Problem liegt in der Erfassung von Prozessdaten. Oftmals beschränkt sich die Erhebung von Daten aus dem Prozess auf die Signale des Kolbenwegs, der Kolbengeschwindigkeit und des Maschinendrucks. Eine weitere Verarbeitung und Auswertung der Daten erfolgt jedoch nicht. Das Ziel dieses Forschungsvorhabens ist die Implementierung eines ganzheitlichen
Sensornetzwerks im Druckgießprozess, um Aussagen über einzelne Prozess-parameter und
deren Auswirkung auf die Gussteilqualität treffen zu können. Durch das Abgießen eines speziellen Demonstratorbauteils, an dem Fehler bewusst erzeugt werden, werden die Prozessdaten erhoben und mit der Auswertung der Qualitätsmerkmale verknüpft. Um vorab Erfahrungen mit den Sensoren, der  esstechnik und dem gießspezifischen Ablauf zu sammeln, wurde ein Vorversuch mit einem vorhandenen Werkzeug durchgeführt. Die Gussteile wurden ausschließlich auf das Qualitäts-merkmal Porosität untersucht. Die gesammelten Datensätze wurden durch statistische Programme (Data Mining und
Design of Experiment) ausgewertet. Eine getrennte Auswertung wurde mit den Kurven der Sensorsignale durchgeführt.  Die statistische Auswertung gibt Informationen über die Parameter, die auf den Prozess einen signifikanten Einfluss haben. Durch die Auswertung einzelner Sensorsignale können  prozessbedingte Abweichungen, wie einen Kolbenklemmer oder einen nicht aufgebauten Nachdruck, erkannt werden.

 

Correlations between process parameters and quality characteristics in Aluminum High Pressure Die Castings

 M. Winkler, L. Kallien, University of Aalen, October 2015

This paper has been presented during the "Process Control & Engineering" session at the Die Casting Congress & Exhibition, held on October 5-7, 2015 in Indianapolis, organized by NADCA, North American Die Casting Association.

ABSTRACT

Aluminum high pressure die casting is one of the most productive manufacturing processes. The complexity of the parts rise and the quality requirements are increasing. The challenge in high pressure die casting is to reach the high quality standards in spite of the huge number of quality influencing process parameters. The interaction of all quality influencing parameters leads to extremely high scrap rates of up to 10 - 25%. The parameters are not centrally monitored by one single unit but by the various systems of the process such as the die casting machine, the furnace, the thermal regulation system etc. The typical parameters being measured in the process to date are piston speed in the first and second phase, intensification pressure and others, but there are many parameters such as the humidity of the evacuated air which also control part quality. The European research project MUSIC (MUlti-layers control and cognitive System to drive metal and plastic production line for Injected Components) has the aim to decrease the scrap rates in high pressure die casting by developing an intelligent cognitive system taking all quality controlling parameters into account. In the frame of the project a special casting geometry has been developed, that allows the production of parts with several defects such as shrinkage porosity, cold shuts and distortion. The die is instrumented with many new and innovative sensors to monitor new process parameters, such as the sound of the shot, which have not been applied to date. The sensor data, the process parameters of the machine and the peripheral devices are stored together with the quality index of the castings in one common database. The cognitive network will then be able to calculate the quality index for future parts based upon the measured sensor data.

Application and analysis of MDTS (multi-depth temperature sensor) for High Pressure Die Casting

 N. De Marchi, Thesis at University of Padova, June 2015

Analytical computation of the plunger kinematic parameters affecting quality in HPDC

E. Fiorese, D. Richierei, F. Bonollo, University of Padova - International CAE Conference 2015, Pacengo di Lazise, 19-20 October 2015

ABSTRACT

High Pressure Die Casting (HPDC) is the most used process for manufacturing Al alloy components, thanks to its high production rate. Nevertheless, HPDC is considered a “defect generating process”, due to high scrap percentage usually detected. Thus, identification and determination of the parameters affecting quality of castings is the challenge towards an efficient and effective production.

In their previous work, the Authors have found and statistically demonstrated that some novel parameters, representing a measure of the mechanical energy related to the plunger motion and transmitted to the melt, allow explaining and forecasting both mechanical properties and porosity of the castings. In this work, an analytical approach for computing these novel parameters, starting from the plunger displacement curve or its notable points, has been proposed and extensively explained. Hence, the optimization of process can be achieved by choosing in advance the best plunger kinematic parameters affecting quality of castings.

Corraltion between process, microstructure and properties in high Pressure Die Casting Aluminum-Silicon alloys


E. Battaglia1,a, F. Bonollo1,b, G. Timelli1,c, E. Fiorese1,d, G. Kral1,e

1DTG - Stradella S. Nicola 3, 36100, Vicenza, Italy

a battaglia@gest.unipd.it, b bonollo@gest.unipd.it, c timelli@gest.unipd.it, d fiorese@gest.unipd.it,   egkral@tiscali.it

AMPT 2015 - Advances in Materials and Processing Technologies Conference - Madrid, 14-17 December 2015

ABSTRACT

Nowadays automotive industry and, in general, transportation one increasingly needs light components in order to reduce total weights and therefore limit harmful emissions and fuel consumption.

The die casting process, on one hand, is a versatile and highly productive process but, on the other, the elevated amount of defects found in the castings sometimes compromises the characteristics of the final product. For this reason it is important to know how the process works and investigate all the variables that may have effects on the product quality and may damage its mechanical characteristics, or worse may cause rejection.

The paper presents the results of the analyses carried out using a Reference Die, referred to as horse-shoe shaped die, specifically designed to generate as many kinds of defects as possible, at different levels of severity. Correlations between process parameters and casting quality have been deduced analyzing the data collected through the equipments installed on the die casting machine: in-cavity sensor network, plunger speed and displacement sensors. Visual inspection, x-ray investigations and micrograph analyses have been carried out in order to assess the casting quality.

KEYWORDS: high pressure die casting, visual inspection, radiographic testing, defects, process parameters, horse-shoe shaped casting