New solidification simulation reveals the secret of the hidden metal cores in ancient Chinese bronzes

Regardless of the tremendous number of studies on ancient Chinese bronzes and fruitful understanding of the raw materials, technologies and their cultural significance, many related issues have still not been tackled. In particular, it has been known for decades that the legs of Shang and Zhou bronzes have metal cores, but their specific function remains ambiguous. In this work, the Finite Element Method is applied to simulate the pouring and solidification process of bronze cores of different sizes. The findings illustrate that throughout the casting process, the metal core not only maintains the uniformity of the bronze and reducing its’s wall thickness but also lowers the temperature of the surrounding alloy liquid, serving as a casting chill. Specifically, the metal core allows elimination of over 60% of casting defects. In comparison with more widespread clay cores, metal cores help produce less shrinkage porosity, therefore prevent cracking of the legs that is usually caused by different shrinkage rates between the clay core and the metal wall. In summary, the use of metal cores in ancient Chinese bronzes reveals a deep knowledge about the metal properties and the solidification process since the Chinese late Shang period (ca. 1250–1045 BC).