Study On Gas Protected Magnesium Alloys Flotsam Refining Control System

As the lightest commercialized metallic structural material at present, magnesium alloys have many advantages, such as, low density, high specific strength, high specific rigidity, good damping, good electromagnetic shielding and good casting capability. They are finding more and more applications in automobile, motorbike, communication, aviation and electric tooling industries.However, during the course of Mg processing, a big portion of Mg alloys becomes scrap. The Mg die-casting scrap can be divided into two categories in accordance with their nature of formation. One is called processing scrap consisting of runners, overflows and disqualified castings, the other consists of disqualified casting identified in the following processes post casting and the Mg parts out of service. The processing scrap can mount up to 70%～50% of the poured melt used for casting, and the value of which can be down-graded by 7000 RMB Yuan currently if it is sold back to ingot supplier. Therefore, it is economically important for die-casting enterprises to build their own capability to recycle the Mg processing scrap themselves.As part of R&D task named"Slug-free Mg Scrap Recycling System"from Chongqing SinoST Co. Ltd, The present study is focused on the central control unit based on the Mg melting, refinement and metered pouring techniques. Taking the programmable logic controller (PLC) as main control unit and a touch-sensitive panel as man-machine interface, this study is devoted to the development of integrated control system for"Slug-free Mg Die-casting Scrap Recycling System". With the program developed, the control system is able to integrally control all the functions, such as, Mg alloys melting and holding, refining, shielding gas flux and concentration, accurate melt pouring, safety monitoring, etc. At the same time, with the abundant monitoring menu which made the parameters and working process visualized, Touch Panel provides operating platform that greatly reduces the malfunction of equipment and control operation, ensures the efficiency and accuracy of melting and pouring action while provides the flexibility and the versatility of system.At the time of completing the system hardware collocation, software design and man-machine interface design, the fuzzy controller had been studied with emphasis. The involved analogs parameters are temperature, flux and pressure. As an important parameter, temperature is monitored by a PID controller in PLC software. Experimentation is introduced to set parameters because of the big thermal inertia and heavy interference of the system. After a great deal of experiments, the optimal PID parameter is found.