TY - THES

T1 - Thermal physical and mechanical properties of raw sands and sand cores for aluminum casting

AU - Wang, Xin

N1 - embargoed until 22-09-2017

PY - 2014

Y1 - 2014

N2 - A better understanding of the thermal physical and mechanical properties of raw sands and sand cores is of great importance to optimize and improve the quality of the casting productions in casting industry. By adjusting the properties of sand cores, higher efficiency and lower cost of casting productions can be achieved. However, there is still a lack of the detailed investigation on the thermo-physical and mechanical properties of raw sands and sand cores. This thesis is aimed to investigate the thermo-physical and mechanical properties of different raw sands (natural and synthetic sands) bonded in cores with different binders. Furthermore, the tested and optimized sand cores were used for experimental Al alloys casting. Simulation was also employed to obtain thermal conductivity λ value of the sand cores, with an aim to use accurate parameters for the real Al alloy castings and also to improve the experimental accuracy of the simulation. Five different raw sands, (MIN sand / Cerabreads 650 sand / Zircon sand / H32 silica sand / Kerphalite sand) were investigated. Their grain size distributions, microscopic surface, roughnes and morphology were obtained using sieve Analysis, granulometry, Scanning Electron Microscopy (SEM) and optical microscopy. The mechanical properties of sand cores were investigated with a special focus on the de-coring ability of sand cores. Five different sand cores composed of the same silica sand but with different binders and process parameters were tested. Silica sand cores were found to be consistent with the observation using SEM. However, binder systems were found to have different effects on decoring and the binder bridges between sand grains. Thermal physical properties were determined indirectly using a ‘Dipping trial’ and a ‘Ring mould’ with defined process parameters. Such types of instrumented experimental casting can be indirectly related to the thermal behaviour in the inner core moulds, which are surrounded by the molten Al alloy. Simulations were also performed to obtain a technological thermal conductivity of the sand cores relative to SiO2 sand. A good agreement was obtained between simulations and experiments is the ‘dipping trials’. The temperature transfer was compared for different sand cores of various raw sands, which were bonded by organic binders or inorganic binders. Especially, sand cores dried by microwave were also investigated to elucidate the origin of the water peak during the experimental casting process. In summary, this thesis provides a comprehensive experimental investigation on thermal physical and mechanical properties of sand cores with different binders and raw sands. The obtained results can be used to optimize the production of sand cores and the selection of raw sands.

AB - A better understanding of the thermal physical and mechanical properties of raw sands and sand cores is of great importance to optimize and improve the quality of the casting productions in casting industry. By adjusting the properties of sand cores, higher efficiency and lower cost of casting productions can be achieved. However, there is still a lack of the detailed investigation on the thermo-physical and mechanical properties of raw sands and sand cores. This thesis is aimed to investigate the thermo-physical and mechanical properties of different raw sands (natural and synthetic sands) bonded in cores with different binders. Furthermore, the tested and optimized sand cores were used for experimental Al alloys casting. Simulation was also employed to obtain thermal conductivity λ value of the sand cores, with an aim to use accurate parameters for the real Al alloy castings and also to improve the experimental accuracy of the simulation. Five different raw sands, (MIN sand / Cerabreads 650 sand / Zircon sand / H32 silica sand / Kerphalite sand) were investigated. Their grain size distributions, microscopic surface, roughnes and morphology were obtained using sieve Analysis, granulometry, Scanning Electron Microscopy (SEM) and optical microscopy. The mechanical properties of sand cores were investigated with a special focus on the de-coring ability of sand cores. Five different sand cores composed of the same silica sand but with different binders and process parameters were tested. Silica sand cores were found to be consistent with the observation using SEM. However, binder systems were found to have different effects on decoring and the binder bridges between sand grains. Thermal physical properties were determined indirectly using a ‘Dipping trial’ and a ‘Ring mould’ with defined process parameters. Such types of instrumented experimental casting can be indirectly related to the thermal behaviour in the inner core moulds, which are surrounded by the molten Al alloy. Simulations were also performed to obtain a technological thermal conductivity of the sand cores relative to SiO2 sand. A good agreement was obtained between simulations and experiments is the ‘dipping trials’. The temperature transfer was compared for different sand cores of various raw sands, which were bonded by organic binders or inorganic binders. Especially, sand cores dried by microwave were also investigated to elucidate the origin of the water peak during the experimental casting process. In summary, this thesis provides a comprehensive experimental investigation on thermal physical and mechanical properties of sand cores with different binders and raw sands. The obtained results can be used to optimize the production of sand cores and the selection of raw sands.

KW - Thermophysikalische Eigenschaften von Sanden

KW - mechanische Eigenschaften von Sanden

KW - Rohsande

KW - thermal physical properties of sands

KW - mechanical properties of sands

KW - raw sands

M3 - Master's Thesis

ER -