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Metal Casting Technologies : June 2007
16 www.metals.rala.com.au BACKGROUND n recent years manufacturing industry in Thailand has experienced spectacular growth but most of this has resulted from ready made technology brought in via joint venture companies from overseas. For example, in the automotive and electronics sectors, virtually all of the R&D and technical work such as materials and process selection, tooling and methods is completed in the mother country outside Thailand. Apart from the joint venture operations, most Thai manufacturing companies, including foundries and Al diecasters, are small to medium sized enterprises. Many SME metal casters have responded to competition from China and elsewhere by continuing to look for improvements in their technical and business performance, and by developing workforce skills through training. However, although they recognize the need for technical progress, most of these SME companies remain unwilling to fund or even take part in science or technology based research projects . As elsewhere nearly all the problem solving and process development research is left to the multinational raw materials and equipment suppliers. Consequently almost all technology based research in Thailand including casting is carried out in government backed research institutions or in the universities. MTEC -- the National Metals & Materials Technology Center is continuing to encourage the Thai cast metals industry to interact with the academics in Thai universities and in research centers, notably through the specialized casting technology units at Chulalongkorn University and at King Mongut's University of Technology Thonburi (KMUTT). For several years MTEC operated a special initiative called the Manufacturing Design and Technology Center (MDTC) which was set up to encourage Thai industry in general to become involved in product design and to make more use of computer based engineering tools. Having established training programmes and product development consultancy in rapid prototyping, rapid tooling, computer-aided engineering, and in engineering design and analysis methods the original MDTC project has been transformed into a Manufacturing & Design Research Group. The aim of this group is to integrate research on materials, processing and performance with computer based design and engineering aspects, including work on cast metals. The group contains a Foundry Engineering R&D Unit (FERDU) which performs co-operative work with universities and companies in seeking to improve technical capability in the Thai castings industry. This short overview describes some of the recent R&D into light metals castings carried out by this group and by researchers in Thai universities. At present almost all the work relates to commercial Al Alloys and there is very little work on Mg or Ti Alloys. QUALITY OF LIQUID ALUMINIUM Over the past two years the FERDU group at MTEC has placed emphasis on helping Al die-casters to improve die filling and reduce defects, and on helping many small Al foundries to improve the quality of their liquid metal [2-5]. Small companies cannot always afford to import process control equipment so FERDU has developed low cost equipment for gas content determination using a quantitative reduced pressure test and for thermal analysis together with easy to use Windows base software . A portable automated permanent mould system for pouring standard tensile test specimens has also been developed for use in shop floor research projects. This equipment has proved to be invaluable in avoiding the variations associated with manually poured test bars. Manually poured test bars have a Weibull Modulus of around 15 compared to bars poured by the automated system which have a modulus of 29 [4,5]. Current work includes the development of alternative systems to measure fluidity and melt cleanliness, and a study of efficiency in rotary-injection degassing. SOLIDIFICATION AND GRAIN REFINEMENT With MTEC support a research group at KMUTT has carried out a number of studies on grain and eutectic refinement of Al Alloys including ultrasonic treatment, fading effects, effect of re-melting cycles and treatment with Scandium [6-10]. The aim of much of this work is to help foundries improve the consistency of grain refining and other treatments particularly when they are using significant proportions of secondary ingot and foundry returns in charges. The initial effectiveness and fading of a number of refining agents has been studied together with the influence of residual TiAl3 and TiB2 in recycled material. Scandium was seen to grain refine A356 and A380 alloys , it increased the fluidity of A356 (low Cu content) but decreased that of A380 (3%Cu) possibly due to the formation of the W-phase (intermetallic of Al-Cu-Sc). Further work is studying this effect. Another project  has examined the use of Sr, Mg and Cr to reduce the harmful effects of β-Al5FeSi phase on mechanical properties. It was found that Sr and Mg can partly refine this phase and Cr levels of above 0.3% can prevent its formation. A study of By Dr. John Pearce Light Metals Castings Research in Thailand