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Conformal thermostating of high-pressure die castings with the increased tightness

Figurski Krzysztof, Pasierb Łukasz, Piekło Jarosław, Burbelko Andriy

Polish Technical Review

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2024

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No. 1

2--7

EN

In the paper, the exemplary concept, together with the analysis of the obtained results from the experimental trials of thermostating using the conformal system in the cold-chamber high-pressure die casting process of aluminium alloy, was described. Construction of the experimental system of thermostating channels, mapping the surface of the cavity, as being placed in the core, shaping the internal geometry of casting with a required increased tightness was performed. The results of the numerical simulations for a given case and the results of the experiments and RTG examinations of the castings made on a real system, utilizing the designed cores, performed in increment technology from steel 1.2709 were submitted.

PL

W pracy przedstawiono przykładową koncepcję wraz z analizą otrzymanych wyników z prób eksperymentalnych dla konformalnego układu termostatowania odlewniczej formy wysokociśnieniowej do odlewania zimnokomorowego stopów aluminium. Dokonano konstrukcji doświadczalnego układu kanałów termostatujących odwzorowujących powierzchnię wnęki formy, umieszczonych w rdzeniu kształtującym wewnętrzną geometrię odlewu o wymaganej podwyższonej szczelności, przedstawiono wyniki symulacji numerycznych dla zadanego przypadku oraz wyniki doświadczeń oraz badań RTG odlewów wykonanych na rzeczywistym układzie wykorzystującym zaprojektowane rdzenie wykonane w technologii przyrostowej z stali 1.2709.

2

SEM/TEM Investigation of Degradation of Bi-Layer (Cr,Al)N/Cr2N3 Duplex Coatings Exposed to AlSi Alloy High Pressure Die Casting Cycles

Wilczek A., Morgiel Jerzy, Sypień Anna, Pomorska Małgorzata, Rogal Łukasz

Archives of Metallurgy and Materials

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2022

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Vol. 67, iss. 4

1341--1348

EN

High pressure die casting (HDPC) allows to produce aluminum parts for car industry of complicated shapes in long series. Dies used in this process must be robust enough to withstand long term injection cycling with liquid aluminum alloys, as otherwise their defects are imprinted on the product making them unacceptable. It is expected that nitriding followed by coating deposition (duplex treatment) should protect them in best way and increase intervals between the cleaning/repairing operations. The present experiment covered investigations of the microstructure of the as nitride and deposited with CrAlN coating as well as its shape after foundry tests. The observations were performed with the scanning and transmission electron microscopy (SEM/TEM) method. They showed that the bottom part of this bi-layer is formed by roughly equi-axed Cr2N crystallites, while the upper one with the fine columnar (CrAl)N crystallites. This bi-layers were matched with a set of 7x nano-layers of CrN/(CrAl)N, while at the coating bottom a CrN buffer layer was placed. The foundry run for up to 19 500 cycles denuded most of coated area exposed to fast liquid flow (40 m/s) but left most of bottom part of the coating in the areas exposed to slower flow (7 m/s). The acquired data indicated that the main weakness of this coating was in its porosity present both at the columnar grain boundaries (upper layer) as well as at the bottom of droplets imbedded in it (both layers). They nucleate cracks propagating perpendicularly and the latter at an angle or even parallel to the substrate. The most crack resistant part of the coating turned-out the bottom layer built of roughly equiaxed fine Cr2N crystallites. Even application of this relatively simple duplex protection in the form of CrAlN coating deposited on the nitride substrate helped to extend the die run in the foundry by more than three times.

3

The Effect of the Return Material Implementation into the Production of Silumin Casts on Technological and Economic Indicators of Production Process

Gaspar S., Majernik J., Trytek A., Podaril M., Benova Z.

Archives of Foundry Engineering

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2022

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Vol. 22, iss. 1

69--76

EN

The production of high pressure die casts also brings difficulties regarding the processing of the waste material. It is mainly formed by runners, overflows and other foundry supplements used and, in the case of machines using the cold chamber, also the remainder from this chamber. As this material is often returned to the production process, we refer to it as return material. In the production process, it is therefore essential to deal with the proportion issue of return material against primary material that can be added to the melt to maintain the required cast properties. The submitted article monitors the quality properties of the alloy, selected mechanical properties of casts and porosity depending on the proportion of the return material in the melt. At the same time, the material savings are evaluated with regards to the amount of waste and the economic burden of the foundries. To monitor the above-mentioned factors, series of casts were produced from the seven melting process variants with a variable ratio of return to the primary material. The proportion ratio of return material in the primary alloy was adjusted from 100% of the primary alloy to 100% of the return material in the melting process. It has been proven that with the increasing proportion of the return material, the chemical composition of the melt changes, the mechanical properties of the alloy decrease and the porosity of the casts increases. Based on the results of the tests and analyzes, the optimal ratio of return and primary material in the melting process has been determined. Considering the prescribed quality of the alloy and mechanical properties, concerning the economic indicator of the savings, the ratio is set at 70:30 [%] in favor of the primary material.

4

Influence of Overflow Connecting Channel Cross-Section Design on Selected Parameters of High Pressure Die Casting

Majernik J., Podařil M., Gojdan D.

Archives of Foundry Engineering

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2021

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Vol. 21, iss. 2

75--80

EN

High pressure die casting technology (HPDC) is a method enabling the production of shape-complex casts with good mechanical properties, with high repeatability of production within narrow tolerance limits. However, the casts show, to some extent, basic porosity, which may reduce their mechanical and qualitative properties. One of the main areas to focus on in order to reduce the porosity of casts is the correct design and structure of the gating and overflow system. Submitted article is devoted to the assessment of the connecting channel cross-section design for connecting the overflows to the cast on selected parameters of the casting process. Five different cross-section designs of connecting channels are considered, enabling the removal of gases and vapors from the volume during the molding. The connecting channels are designed with a constant width g = 10mm and variable height h1 =1.50 mm, h2 = 1.25 mm, h3 = 1.00 mm, h4 = 0.75 mm and h5 = 0.6 mm. The primary monitored parameter is the gas entrapment in selected points of the cast. The following is an evaluation of the pressure conditions change in the mold cavity at the end of the filling mode and local overheating of the mold material just below the surface of the mold face. With regard to the monitored parameters, based on the performed analyzes, the most suitable design solution of the connecting channel is assessed and recommendations for the design and structure of the overflows and their connection to the cast are derived.

5

An Evaluation of the Effect of Ultrasonic Degassing on Components Produced by High Pressure Die Casting

Silva da Manel, Bajusz Attila, Pabel Thomas, Petkov Tose, Plantà Xavier

Journal of Casting & Materials Engineering

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2020

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Vol. 4, no. 4

58--64

EN

Ultrasonic treatment is known to be efficient for aluminium melt degassing with the additional benefits of being both economical and environment friendly. This paper describes the effect of ultrasonic degassing on the preparation of an AlSi9Cu3(Fe) alloy for High Pressure Die Casting (HPDC). The degassing efficiency was assessed in terms of the indirect evaluation of the melt, by means of the reduced pressure test and the porosity evaluation of the cast parts. Additionally, the corresponding hydrogen content was estimated with an experimental equation reported in the literature. Ultrasonic degassing shows greater efficiency in terms of hydrogen removal from the melt than conventional N2 + Ar lance bubbling. Components produced by HPDC without degassing, with ultrasonic degassing and with lance degassing, were analysed by computed tomography and by metallography. The results show that the components produced by HPDC after ultrasonic degassing have a similar porosity level to components degassed with conventional lance bubbling, both showing an important improvement over components produced without degassing treatment. Hardness values were similar for all different treatment conditions and well over the minimum value established for the alloy by the corresponding standard.

6

Influence of Runner Geometry on the Gas Entrapment in Volume of Pressure Die Cast

Majernik J., Podařil M.

Archives of Foundry Engineering

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2019

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iss. 4

33--38

EN

The high pressure die casting technology allows the production of complex casts with good mechanical properties, with high production repeatability within narrow tolerance limits. However, the casts are somewhat porous, which may reduce their mechanical properties. There are several recommendations for reducing the porosity of casts, which are aimed at setting the technological parameters of the casting cycle. One of the primary and important ways to reduce the porosity and air entrapment in the melt is a suitable gating system design. Submitted contribution is devoted to assessing the influence of the runner branching geometry on the air entrapment within the cast volume during the filling phase of the casting cycle. Four variants of the gating system for a particular cast are compared with different design of main runner branching. The initial design is based on a real gating system where the secondary runner is connected to the main runner at an angle of 90 °. The modified designs are provided with a continuous transition of the main runner into the secondary ones, with the change in the branching runner radius r1 = 15 mm, r2 = 25 mm and r3 = 35 mm. The air entrapment in the melt is assessed within the cast volume behind the cores, which have been evaluated as a critical points with respect to further mechanical treatment. When designing the structural modification of geometry it was assumed that by branch changing using the radius value r3 = 35 mm, the melt flows fluently, and thus the value of the entrapped air in the volume of the cast will be the lowest. This assumption was disproved. The lowest values of entrapped air in the melt were found in the casts with runner transition designed with radius r1 = 15 mm. The conclusion of the contribution explains the causes of this phenomenon and from a designing point of view it presents proposal for measures to reduce the entrapment of the air in casts.