Validation of Energy Saving Novel Single Shot Melting Process for Foundry Industry

Abstract

Casting is a metal forming process: Pouring the melt metal into a desired shaped mould wait it solidifies. It is often used to manufacture complex parts, which are too expensive or time consuming to produce by other methods. However, casting probably is one of the most challenging manufacturing process. It is a highly technical engineering process requiring deep scientific understanding. A typical modern casting process contains six different stages, which named as melting, alloying, moulding, pouring, solidification and finishing respectively. At each stage, high level and precision of process control is required. Casting process also is one of the most energy intensive manufacturing processes. The metal melting consumes over half of the energy in a casting process. Therefore, the expenses on the casting process has been a significant concern due to the rising of the energy prices. A new casting process, CRIMSON (Constrained Rapid Induction Melting Single Shot Up-casting), has been developed by teams from Cranfield University and the N-TEC Ltd. It can improve the energy efficiency of a casting process without reducing the quality. The process, firstly, uses the rapid induction furnace to melt just enough metal for one single casting; then transfer the molten charge to a computer controlled counter gravity casting platform. Finally, the highly controlled metal flow is pushed into the mould to finish the pouring and solidification. Such process reduces the defect generation and energy consumption by rapid melting, minimum holding and smooth filling of the mould. Since the CRIMSON process is a relatively new casting production process. The main objective of this dissertation is to validate the CRIMSON process by different approaches. Firstly, the concept of the sound casting running system design and the principle of the novel CRIMSON process has been introduced. Secondly, Flow3D (A comprehensive, general-purpose computational fluid dynamics software) has been used to investigate the filling patterns of the novel CRIMSON process and the gravity sand casting process. Thirdly, life cycle assessment (LCA) method has been used in this project to review the energy consumption of the conventional casting sector and the novel CRIMSON process. The inventory data was used to assess the environmental impacts of the both casting processes. Moreover, this project investigated the productivity of the CRIMSON process. The productivity of the CRIMSON process for certain range of the casting product has been investigated and compared with the conventional casting process. Finally, the cost of the CRIMSON process has been estimated. The total variable cost of the CRIMSON process was investigated and compared with the conventional casting process as well. Key conclusions can be addressed as below:  Because of the geometry requirement, the gravity poured running system cannot avoid generating double oxide film defect during the filling.  For the CRIMSON process, all the important parameters (such as temperature, time, and velocity) are under control. The piston only needs to move at low speed to guarantee the liquid metal is delivered smoothly and the double oxide films are not formed or entrapped.  The material flow and the embedded energy of the casting making can be evaluated by the lift cycle inventory data collection method. The embedded energy of the sand casting is about 55 MJ/kg. However, to consider the recycling and reusing the internal material, the energy burden of the CRIMSON and the conventional sand casting are 16 MJ/kg and 18 MJ/kg respectively. Considering the energy burden for saleable casting, the CRIMSON process consumes 230 MJ/kg to make saleable casting; the conventional process consumes 449 MJ/kg to make saleable casting.  By using the collected inventory data, the environmental impact assessment can be carried out for both the casting process. The results indicate that the CRIMSON process is environmental friendly compared with the conventional sand casting process.  A complete foundry model was developed in order to investigate the productivity of the CRIMSON process. The WITNESS simulation tool was used to assess the productivity investigation. For casting size less than 2 kg, the conventional sand casting process is productive. However, as the casting size increases, the CRIMSON process becomes more productive.  Cost estimation also carried out for the CRIMSON process. The total variable cost of the casting process was investigated. It was found that the most expensive variable cost is the raw material cost, which can be 80% of the total variable cost. Furthermore, it is concluded that the CRIMSON process has less variable cost compared with the conventional sand casting process under most of the circumstances.