The study of co-fusion was one of the essential topics in the history of metallurgy in China. Simulation experiments were an essential concept in the study of the co-fusion steelmaking process. This paper mainly studied the simulation experiments of co-fusion from two aspects: the replication of co-fusion swords by three different methods and the micro-analysis of the co-fusion samples. The experimental results indicated that several co-fusion swords could be made by different processes, but the carbon content and surface hardness were quite different. During repeated forge welding, the microstructure of the samples transformed from laminated to homogenized; finally, a steel with a uniform carbon content was obtained. It was challenging to determine the characteristics of co-fusion from the homogenized samples. The results prompt a rethinking of the microstructural characteristics of ancient co-fusion artifacts.

The Yungang Grottoes, a World Heritage Site, face biodeterioration risks. This study analyzed microbial communities in five microenvironments within Cave 6 using high-throughput sequencing (16S/18S rRNA). Communities showed high microenvironment specificity. Ascomycota and Proteobacteria dominated fungi and bacteria, respectively. Areas near the lighting window, with high external interaction, showed the highest diversity, while red pigment areas, likely under heavy metal stress, had the lowest diversity. Human-associated microbes (e.g., Escherichia-Shigella, Malassezia) indicated anthropogenic pollution on statue surfaces. Core microbiome and functional prediction (PICRUSt2) suggested high biodegradation risk in dust accumulation and inter-statue areas, enriched with organic-degrading and acid-producing taxa (e.g., Rubrobacter, Cladosporium). Microbial distribution and function were driven by openness, substrate, and human impact. This study identifies key risk zones and informs targeted conservation strategies for the Yungang Grottoes.

The study of co-fusion was one of the essential topics in the history of metallurgy in China. Simulation experiments had been an essential concept in the study of the co-fusion steelmaking process. This paper mainly studied the simulation experiments of co-fusion from two aspects: the replication of co-fusion swords by three different methods, and the micro-analysis of the co-fusion samples. The experimental results indicated that several co-fusion swords could be made by different processes, but the carbon content and surface hardness were quite different. During repeated forging welded, the microstructure of the samples transformed from laminated to homogenized, finally the steel with a uniform carbon content was obtained. It was challenging to find the characteristics of co-fusion from the homogenized samples. The results prompted people to rethink the microstructure characteristics of ancient co-fusion artifacts.

Observing and analyzing the microstructure of zone samples had been an essential concept in the study of co-fusion steelmaking. High-temperature confocal laser scanning microscope (HT-CLSM) provided a new method in the in-situ observation and real-time analysis of the co-fusion steelmaking process. In this research, a series of experiments had been designed based on Shen Kuo’s The Dream Pool Essays (a famous ancient Chinese literature) and carried out by HT-CLSM. The results showed that a new interface was formed with the phase transition during the heating process, which had an essential influence on promoting the carbon diffusion rate in co-fusion steelmaking. The cast iron zone occurred in mushy solidification because of decarbonization. There were collision, aggregation, and other behaviors of inclusions in the cast iron zone and they moved towards the boundary, which led to the purity of the matrix and the aggregation of a large number of inclusions at the boundary.