Research On The Co-fusion Process Of Steelmaking

The highly developed iron and steel in ancient China was built on the cast iron smelting technology.Relying on cast iron,the important raw material,a series of steelmaking technologies emerged.Co-fusion steelmaking technology was an important part of the ancient steelmaking technology system in China.Therefore,it was of great significance to understand the history of iron and steel metallurgy based on the co-fusion process(Guan gang)of steelmaking in ancient China and even in the whole ancient world.Based on ancient literature research,combined with the archaeological data and the results of previous simulation experiments,the simulation experiments of co-fusion were carried out respectively in a sword workshop and the laboratory.Compared with the ancient co-fusion artifacts,a comprehensive discussion of the co-fusion process was carried out,and the following main understandings were obtained:This study carried out the ancient literature related to the co-fusion,thinking of the early co-fusion process often to make high-quality steel swords.At present,the earliest direct recorded of guan gang was Su You’s San Pin Yi Shen Bao Ming Shen Dan Fang Xu.Detailed records of the Song dynasty and the Ming Dynasty showed that the co-fusion steelmaking went through a series of technological improvements.By using cast iron and wrought iron,combining the two raw materials in a certain proportion,forging then welding,to form the mainframe of defining the co-fusion process.Only the one that meets the above three points could be called co-fusion steelmaking.It could be defined as a similar co-fusion process if the process conditions were relaxed to use cast iron and wrought iron.The above processes formed the generalized co-fusion technology system.Based on the co-fusion process recorded in ancient literature,the restoration simulation experiments were carried out according to "co-fusion directly""inserting cast iron into wrought iron" and "cast iron covered on wrought iron".The results showed that all three processes could be used to produce co-fusion artifacts with certain properties.Under similar conditions,the quality of the first product was far worse than the latter two processes.According to the analysis results of the simulated samples,it was concluded that there were different degrees of delamination in the microstructures of the co-fusion products.And the inclusions were also different in several regions and had an obvious corresponding relationship with the microstructures.With the increase of forging times,the delamination phenomenon gradually decreases and disappears.The in-situ characterization method was introduced first into the research of the co-fusion process.The microstructure changes and inclusion migrations in co-fusion could be observed directly by using high-temperature confocal laser scanning microscopy(HT-CLSM),which was of great significance to understand the process connotation.On this basis,the regional statistical methods of the area fraction,density,and average size of inclusions were applied to the discussion of the ancient samples.The results showed that the statistical results of the ancient samples could form a good correspondence with the simulation results.Based on the results,the inclusion characteristics if co-fusion samples were summarized and different from other steelmaking process samples.The co-fusion process was closely related to the ancient Chinese philosophy of "harmony" and "combination of hardness and softness".Under the influence of the ideology of "harmony”,the co-fusion process solved the difficulty of preparing medium and high carbon steel in ancient China and had an important position in the ancient steelmaking technology system.The co-fusion process mixed the high carbon steel with low carbon steel to develop a balance in the middle of the carbon content,and it required multiple factors such as temperature,atmosphere,and environment.It had an important status in the thought of metallurgical industry history.