COMPUTER SIMULATION OF THE SHS CASTING FEED IN INVESTMENT CASTING
Problem Statement (Relevance): This article describes the results of a study into the solidification of metal in a 42kg body casting designed to be used on backbone oil and gas lines. The study was based on the use of the LVM Flow Computer Simulation System and one of the resource saving techniques applied in casting to get a higher yield - i.e. exothermic-insulating sleeves. This is a critical part, so it should satisfy a number of operational requirements. A part body of that weight can be produced by investment casting or by green sand casting, with the cost of the running and gating system being approximately 200% and 100% of the weight of the casting correspondingly. The metal consumtion efficiency is determined by the yield, which is 40 to 70% for steel castings. This means that up to 55% of liquid metal is wasted on feeder heads and the gating system, which does not appear to be cost-effective. Due to the application of the SHS technique (i.e. exothermic heat (0.5 to 3.5 mm thick layer) and exothermic heads) the yield can be increased up to 90% and the consumption of liquid metal reduced. After 3D-models were built of the casting with the running and gating system used by the foundries, a study was conducted by means of LVM Flow that looked at the solidification processes. Various thermophysical parameters were used for solidification modelling purposes depending on the casting process applied. Objectives: The aim of this work was to prove the feasibility of using the SHS technique in investment casting, the latter being the least cost-effective casting technology in terms of yield, by studying the efficiency of the exothermic heads by BIMAX from Finland in the casting manufacture in the context of using the Voronezh Mechanical Plant’s process for the production of large investment castings, and by means of computer modelling. Method Applied: The LVM Flow computer modeling method was applied. For LVM Flow calculations, 3D models were built of various design castings with the running and gating system, which were then converted into the required format. The 3D models were built with the help of the SolidWorks 2010 programme. Originality: The above study shows that the proposed running and gating system and the investment casting process are capable of producing castings with no shrinkage cavities. As the exothermic feeding process involves complicated physics and would require an additional mathematical model to be built, the computer simulation for the SHS technique was only carried out for exothermic feeder heads. LVM Flow has this capability, which was tested in green sand casting. Before that the geometry of the exothermic caps was calculated, which depends on the geometry of the casting. The caps have an identical design; in the case of investment casting the thickness of the wall is 3.5 mm. A special feature of the investment casting caps was a 10 mm high and 30 mm wide V-edge located on the inside of the cap cover. The V-edge goes along the cap and functions as an exothermic core creating additional pressure in the feeder head and heating its top. This proposition was verified as true by computer testing. The computer simulation carried out helped establish the possibility of obtaining flower-shaped body castings by means of investment casting involving SHS. In that case the yield was 70%, provided a sound casting was produced. It was confirmed that exothermic cores produce a significant positive effect on the casting feed and improve the quality of the casting in the riser zone. This paper describes the first LVM FLоw study that proves the possibility of obtaining high-quality castings in investment casting with exothermic heat. This is an undoubtfully important development for the casting industry and it distinguishes this work. Practical Relevance: With the help of the obtained data further experiments can be carried out and sound castings with exothermic heat can be obtained with the help of the given casting technique.