Papers by Keyword: Die Casting

Abstract: In the pressure die casting process, a great attention is paid to a die castings quality improvement. This quality has to be ensured with a great reliability and, at the same time, it is necessary to apply control methods to a technological process which provide a complete picture of a die casting process as well as internal quality of the produced die castings. It requires control of the present technological factors of a pressure die casting process. The contribution deals with the effect of die casting plunger velocity inside a filling chamber on mechanical properties of a die casting product from EN AC 47100 alloy.

Abstract: In this study, semi-solid Al-Mg-Si alloy (AC4C) was produced by using the Gas Induced Semi-Solid (GISS) die casting process. The tensile strength and ductility of the semi-solid die cast Al alloy (GISS-DC) after T6 heat treatment were investigated and compared with those of the conventional liquid die casting (CLDC). The microstructures of GISS-DC and CLDC observed by an optical microscopy were presented. The ultimate tensile strength (UTS) and yield strength (0.2% YS) of GISS-DC are compatible with those of the CLDC. However, the GISS-DC has better ductility than the CLDC, this may be due to the smaller and more globular primary α-Al phase and rounder shaped-Si particle microstructures presented in the GISS-DC. Common shrinkage pores and defects were also observed by SEM from the fracture surfaces of both alloys.

Abstract:

Magnesium alloys have been finding increasingly more types of application in the automotive and aerospace industries for over twenty years. Despite the fact conventional magnesium alloys have limited high-temperature strength and creep resistance, especially when they contain aluminium as an alloying element. Aluminium is necessary to improve the castability when high-pressure die casting is the favoured process. Applications with higher operating temperatures require additional alloy elements, which form precipitates with the aluminium during solidification and therefore prevent the formation of Mg₁₇Al₁₂, which is responsible for the low creep resistance of magnesium alloys that contain aluminium. The precipitates formed may also strengthen grain boundaries and so improve the creep strength. Barium and calcium were investigated as elements in a magnesium alloy containing aluminium (DieMag422: 4 wt.-% Al, 2 wt.-% Ba, 2 wt.-% Ca). The compression creep strength was compared at 240°C for stresses between 60 and 120 MPa with two commercial creep-resistant magnesium alloys, AE42 and MRI230D. The stress exponents were calculated from the stress dependence of the minimum creep rate. The concept of a threshold stress was applied and true stress exponents n_t close to 5 were found. The new alloy DieMag422 exhibits improved creep strength compared to both commercial alloys and also has proven it is die castable.

Abstract: The present study focuses on the inhouse melting process in front of a die casting process. The complexity and time-dependent dynamic of melting, distribution and casting process lead to the use of a dynamic process simulation approach. The goal of the simulation is to calculate the time-dependent discharge of the aluminum mass flux. Important parameters are identified and characterized by the use of a realistic process model. Thereby the influence on the analysis of parameters influence on storage, output and process stability is analyzed. It is shown that storage factor and melting capacity distribution have a significant impact. Moreover the control scheme for liquid aluminum distribution shows a strong influence. In preparation for future investigations on energy efficiency the load factor of the melting furnaces, its effects on process stability and potential for further process optimization is observed.

Abstract: The belonging amplitude and the phase characteristic and the transient characteristic are for K=1 and P=1 identical as for the action quantity. The core puller at pulling cores it is possible to consider as the regulation system with the force of cores pulling F₁ as the inlet quantity and the course of core movement x respectively the speed of core movement v as the outlet quantity. The equation of the regulation system is identical with the equation of regulation system obtained by a gradual integration from the measured course at pulling cores at the die cast. At application of the proportional regulator the amplitude, the phase and the transient characteristic of the action quantity and the control of the regulation circuit constructed on the basis of the transmission state that the circuit is stable a periodic. The amplitude, the phase and the transient characteristic of the regulation circuit defect constructed on the basis of the transmission state that the defect in the regulation circuit lowers relatively quickly.

Abstract: Die casting is a cost-efficient method of forming geometrically complex near net-shaped products with close tolerances and excellent surface finishes.Due to the thermal shock characteristics, a number of test methods have been proposed to understand thermal fatigue behaviours of the die material as real die casting dies experience.This study reveals the differences of these methods by numerical modelling the thermal behaviour of the test specimen. Simplified die casting process is firstlyproposed to facilitate numerical computation. Test specimens are then optimized to be more representative of a real die. From the comparison results, we can conclude that least divergence can be obtained between immersion tests and induction heating based tests while furnace heating based tests would result in low thermal shock effects on the test sample.

Abstract: Solidification and microstructural characteristics of Al-5wt.%Mg-1.5wt.%Si-0.6wt.%Mn-0.2wt.%Ti alloy have been investigated in high pressure die casting. The average size of dendrites and fragmented dendrites of the primary α-Al phase formed in the shot sleeve is 43 m, and the globular α-Al grains formed inside the die cavity is 7.5 m. Solidification inside the die cavity also forms the lamellar Al-Mg2Si eutectic phase and the Fe-rich intermetallics. The size of the eutectic cells is about 10 m, in which the lamellar α-Al phase is 0.41 m thick. The Fe-rich intermetallic compound exhibits a compact morphology and is less than 2 m. Calculations using the Mullins and Sekerka stability criterion reveal that the solidification of the primary α-Al phase inside the die cavity has completed before the spherical α-Al globules begin to lose their stability, but the α-Al grains formed in the shot sleeve exceed the limit of spherical growth and therefore exhibit a dendritic morphology.

Abstract: The flow and filling characteristics during injection of liquid aluminum in high pressure die casting is of significant importance for the product quality. As shown in [ the planar jet of liquid aluminum can be triggered by the design of the gating geometry. Depending on the inlet velocity and the gating design the liquid jet will disintegrate at the jet surface by drop formation and the free jet is dominated by atomization at the gating or by wavy disintegration at low flow velocities. Metallography of samples cast utilizing different nozzle designs are discussed with respect to casting inhomogeneities and microstructural changes respectively. These results are compared to numerical studies on the die filling flow characteristics as well as experimentally water modeling approaches.

Abstract: The paper deals with analysis of influence of pressing speed, of melt temperature and of casting position in a mold upon ultimate tensile strength R_m of die casting from aluminium. The monitored parameters of die casting are very important in terms of production efficiency and quality of casting, which is positively reflected in economic indicators of the production.

Abstract: The production of die castings cast into a metal mold has in recent years achieved an expansive growth in the volume as well as the range of production and that is particularly in aviation and automobile industry. A primary criterion for achieving reliability, efficiency and quality of production is to ensure minimization of the castings defects occurrence. For this reason it is necessary to describe the type, scope and frequency of die castings defects and to define the cause of their occurrence.