Scientific analysis of hammerscales excavated from the Chengba and Guantian sites (‌50 BC to AD 400‌) in Southwest China

Abstract

The study of hammerscale is a key for identifying ancient forging sites and restoring iron and steel forging processes, while the systematic research on hammerscale from Han-Jin periods sites in southwest China is still insufficient, and a unified identification standard for archaeological hammerscale has not been formed in China. In this paper, 21 ancient hammerscale samples excavated from Chengba site (Sichuan) and Guantian site (Hunan) were taken as the research objects, with 4 modern traditional forging hammerscale samples as the control group. Metallographic microscopy and SEM-EDS analysis were used to carry out systematic scientific analysis on the microstructure and chemical composition of the samples. The results show that the core identification indicators of archaeological hammerscale are the microstructure has a layered iron oxide structure formed by high-temperature forging oxidation, or chain silicate inclusions distributed along the forging direction; the main component is iron oxide (often > 90%), and the trace element characteristics are related to raw materials, fuel and flux in the forging process. There are significant differences in the content of CaO, SO₃ and P₂O₅ between ancient and modern samples, which are mainly caused by the differences in smelting and forging processes, fuel types and raw material background. This study clarifies the formation mechanism of hammerscale and its indicative significance for forging technology, provides a standardized identification basis for forging relics in field archaeological work, and supplements basic comparative data for the study of iron and steel forging technology in the Han-Jin periods in southwest China.