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1

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.

2

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.

3

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.

4

Evaluation of the Temperature Distribution of a Die Casting Mold of X38CrMoV5_1 Steel

Majernik J., Podařil M.

Archives of Foundry Engineering

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2019

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iss. 2

107--112

EN

Relatively cold die material comes into contact with the substantially higher temperature melt during the casting cycle, causing high thermal fluctuations resulting into the cyclic change of thermal field. The presented contribution is devoted to the assessment of the impact of temperature distribution on individual zones in the die volume. The evaluated parameter is the die temperature. It was monitored at two selected locations with the 1 mm, 2 mm, 5 mm, 10 mm and 20 mm spacing from the die cavity surface to the volume of cover die and ejector die. As a comparative parameter, the melt temperature in the middle of the runner above the measuring point and the melt temperature close to the die face were monitored. Overall, the temperature was monitored in 26 evaluation points. The measurement was performed using the Magmasoft simulation software. The input settings of the casting cycle in the simulation were identical to those in real operation. It was found, that the most heavily stressed die zones by temperature were within the 20 mm from the die face. Above this distance, the heat supplied by the melt passes gradually into the entire die mass without significant temperature fluctuations. To verify the impact of the die cooling on the thermal field, a tempering system was designed to ensure different heat dissipation conditions in individual locations. At the end of the contribution, the measures proposals to reduce the high change of thermal field of dies resulting from the design of the tempering channel are presented. These proposals will be experimentally verified in the following research work.

5

Analysis of Interaction between Position of Gate and Selected Properties of Low-Weight Casts on the Silumin Basis

Majernik J., Gaspar S.

Archives of Foundry Engineering

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2019

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iss. 3

106--110

EN

Final quality of casts produced in a die casting process represents a correlation of setting of technological parameters of die casting cycle, properties of alloy, construction of a die and structure of gating and of bleeding systems. Suitable structure of a gating system with an appertaining bleeding system of the die can significantly influence mechanical and structural properties of a cast. The submitted paper focuses on influence of position of outfall of an gate into the cast on its selected quality properties. Layout of the test casts in the die was designed to provide filling of a shaping cavity by the melt with diverse character of flowing. Setting of input technological parameters during experiment remained on a constant level. The only variable was the position of the gate. Homogeneity represented by porosity f and ultimate strength Rm were selected to be the assessed representative quality properties of the cast. The tests of the influence upon monitored parameters were realized in two stages. The test gating system was primarily subjected to numerical tests with the utilization of a simulation program NovaFlow&Solid. Consequently, the results were verified by the experimental tests carried out with the physical casts produced during operation. It was proved that diverse placement of the gate in relation to the cast influences the mode of the melt flowing through the shaping cavity which is reflected in the porosity of the casts. The experimental test proved correlation of porosity f of the cast with its ultimate strength Rm. At the end of the paper, the interaction dependencies between the gate position, the mode of filling the die cavity, porosity f and ultimate strength Rm.