The Ultrasound-assisted Hot-dip Aluminizing Technology For Remanufacturing

Remanufacturing has important significance for the recycling of resources. By the recycling of worn-out parts, it can save resources and reduce environmental pollution. With the use of hot dipping technology, the surface of worn-out parts can be repaired. Then the surface can be enhanced by using micro-arc oxidation process. To obtain accurate repair of the dimension, the process of hot-dipped aluminum is researched below:The microscopic structure and composition of the hot dip aluminum samples were analyzed by Optical Microscopy, Scanning Electronic Surface Microscopy, X-ray Diffraction and Energy Dispersive Spectroscopy. The results showed the coating consisted of the surface layer and intermetallic layer. The component of the surface layer was Al mainly with a little FeAl3 which was the same to the aluminum bathes. The main component of the intermetallic layer was Fe2Al5. There was a thin layer of FeAl3 phase between the two main layers.The factors were analyzed with orthogonal experiment which affected both layers such as the dipping temperature, dipping time and extractive velocity. The results indicated:The factors’effects to the thickness of surface and intermetallic layers were different. Since the process of hot-dipped aluminizing was a complex nonlinear system and there were many factors affecting the process, it was difficult to use a mathematical model to describe the process quantitatively. Then the neural networks prediction model was established. The model was trained using orthogonal experimental data. With the help of neural networks prediction model, the effect of different factors to the thickness and quality of coating was obtained. The results showed:both the dipping temperature and dipping time had main effect to the thickness of intermetallic layer, the thickness of surface layer was determined by the extractive velocity, the quality of coating was mainly affected by the dipping temperature and extractive velocity. The most optimal process parameters were concluded from the neural networks prediction model as below:dipping temperature was 750℃, dipping time was 6 min and extractive velocity was 8 m/min.The flow field simulation was carried though Fluent fluid simulation software. The results showed that:the effect of ultrasonic vibration to the aluminum bath was obvious. The area below the vibration head had the largest bath pressure and fastest flow rate. The transient pressure and flow rate were IMpa and 30m/s respectively. The average pressure was 0.4-0.6Mpa under the stable state. With the help of ultrasonic vibration, the fluidity and wetting property were improved, especially the area below the vibration head.Since many parts had complex surface such as holes, gaps inner walls and so on, in order to dip them successfully, an ultrasonic amplitude transformer with a central cooling waterway was designed based on longitudinal vibration of variable cross-section rod wave equation. The ultrasound-assisted hot dip aluminized experiment platform was built up with the use of ultrasonic amplitude transformer designed before. The platform can be used in the experiment appropriately below. Compared with the experiment without ultrasound-assisted, the results showed that:the thickness of both layers was reduced, the thickness of intermetallic layer reduced about 20um and the thickness of surface layer reduced about 10um compared with the results without ultrasound-assisted, the coating density improved and the grain was refined which resulted in long lifetime of the plating pieces.