EFFECTS OF AIR-COOLING-HOLE GEOMETRIES ON A LOW-PRESSURE DIE-CASTING PROCESS

A significant precondition for the production of high-quality castings is keeping an optimum temperature of the respective parts of the die cavity surface. This temperature depends on the temperature of the material, the quantity of metal, the method of cooling the casting die, the thermal conductivity of the die material, and the time during which the casting remains in the die. In addition, the cooling characteristics of alloy steel dies, used in the production of aluminum-alloy wheels with the low pressure die casting (LPDC) method, have critical effects on the mechanical and metallurgical properties of the product. Ducted air coolers are widely used for the cooling of these alloy steel dies. However, the geometrical designs of the air-cooling holes are limited. In this study, we define the effects of the geometry of the cooling holes on the cooling power of the die, the efficiency of the air consumption with the Full Factorial Experimental Design method and to determine the optimum values for LPDC. Pilot production has been carried out on an industrial scale to verify the data obtained by experimental design. The experimental and real data were compared based on the values of the yield strength and the secondary dendrite arm spacing in the microstructure.

Simulation and Experimental Validation of Secondary Dendrite Arm Spacing for AlSi7Mg0.3 Chassis Parts in Low Pressure Die Casting

The structural properties of cast aluminum parts are strongly affected by the solidification in the production process. The solidification dynamics determines the Secondary Dendrite Arm Spacing (SDAS), directly affecting the structural strength of the alloy. Simulation techniques enable the integrated design of chassis parts and their production equipment. However, in order to effectively predict the SDAS formation, the simulation models need to be investigated and calibrated. The present research investigates the SDAS formation models and identifies a robust relation to be used in Design by Simulation phases for AlSi7Mg0.3 parts.

ANALISIS GAGAL LEAK TEST PADA PRODUK CYLINDER HEAD TYPE-A HASIL PROSES LOW PRESSURE DIE CASTING DENGAN MATERIAL AC4B DI PT. X

Abstrak--Keadaan yang sedang terjadi pada seksi LPDC di PT. X adalah banyaknya cacat pada produk hasil casting sesuai data cacat pada bulan Januari-Juni 2018 yaitu persentase total cacat tertinggi sebesar 20.64% pada seksi LPDC In Plant dan Next Process di bulan April 2018. Jenis cacat tertinggi pada seksi LPDC In Plant adalah Misrun dinding chain sebesar 3.48% dan pada LPDC Next Process adalah gagal leak test sebesar 4.93%. Hal ini sangat merugikan perusahaan baik dalam biaya produksi yang meningkat dan waktu produksi yang lama. Karakterisasi yang dilakukan pada penelitian ini adalah pengujian leak lest, radiografi (x-ray), optical emission spectroscopy, penetrant, metalografi, SEM, dan uji EDS. Berdasarkan hasil dari karakterisasi yang diperoleh, menunjukkan bahwa produk gagal leak test mengalami cacat internal yaitu shrinkage porosity. Berdasarkan hasil analisis fenomena cacat shrinkage porosity tersebut disebabkan oleh adanya inklusi oksida aluminium yang terbawa ke dalam produk Cylinder Head Type-A yang menjadi inisiasi terbentuknya shrinkage porosity. Terdapatnya oksida aluminium pada produk Cylinder Head Type-A disebabkan oleh waktu transfer molten dari melting furnace yang relatif lama dan jarak auto carrier yang relatif tinggi sehingga turut mempengaruhi waktu pouring ke holding furnace. Kata Kunci: Cylinder Head, Low pressure die casting, leak test, shrinkage porosity, oksida.

Ca and Ce Effect on the Corrosion Resistance of Hot-Rolled AZ31 Mg Alloys

In this study, AZ31 Mg alloys with added Ca and Ce were produced by low pressure die casting and were rolled at 400°C. The corrosion properties of the materials were determined by immersion test for 72 hours at a 3.5% NaCl solution. The microstructure of the samples was investigated by light optical microscopy (LOM) and scanning electron microscopy (SEM) before the corrosion test. Twins, dynamic recrystallization (DRX), and the alloying elements have an important role in imparting the final corrosion resistance of the investigated materials.

Determination of Acceptable Quality Limit for Casting of A356 Aluminium Alloy: Supplier’s Quality Index (SQI)

Aluminium and its alloys have been widely used in the automotive industry for some time and A356 is one of the most popular aluminium alloys today in the sector. It contains approximately 7 wt.% Si and 0.3 wt.% Mg. Due to the defects that may be present in the cast parts, expected mechanical properties may not be reached and this alloy may perform in service under its potential. In a low pressure die casting, several precautions have to be taken in order to produce high quality and defect-free castings. Temperature of casting and the schemical composition of the melt is recorded continuously. Die temperature, pressure levels and their durations are optimized; degassing and fluxing operations are performed. Yet, regardless of the precautions, there could still be rejected parts. It is becoming clear that a good quality raw material is one of the most underrated points of the industry and that the starting material has a great effect on the final product and it should be taken in to account more seriously. Therefore, regarding the first rule of Campbell’s 10 Rules of Casting, in this study, the quality of the starting material of supply chains for a wheel manufacturer was investigated. Chemical compositions were compared, fluidity tests, mechanical tests and bifilm indexes of these various sources and ingots were measured and a final quality index was proposed to create a reference for the quantification of quality of supplier’s ingots. This new index was compared with the rejection rates.