The earliest artificial iron smelting discovered by archaeology belongs to the Spring and Autumn Period. At present, there are about 20 pieces, including concave hoe (hoe) blade, trapezoidal chisel blade, scraper, sword, tripod and so on. By metallographic examination, most of them belong to solid reduction block ironmaking (referring to carbon-free iron).
In the late Spring and Autumn Period, people mastered the mass melting carburized steel and its quenching process, which greatly improved the practical performance of iron, and created technical conditions for the extensive application of iron in military and agricultural production after the mid-Warring States period.
Extended data:
Ironmaking in ancient China was invented in the Spring and Autumn Period. From the Warring States to the Western Han Dynasty, steel weapons gradually appeared. After the mid-Western Han Dynasty, most of the main weapons except bows and arrows were made of steel. In order to improve the hardness and strength of steel, quenching technology came into being.
In the Han Dynasty, steel quenching technology was widely used. Hardened steel knives and swords have been found in Mancheng, Hebei Province, Liu Sheng's tomb in the middle of the Western Han Dynasty, Sandaohao site in Liaoyang, Liaoning Province, and Cangshan County, Shandong Province, and there are also written records about hardening in history books.
With the in-depth development of quenching technology, the ancients found that quenching agent had a great influence on quenching quality. Puyuan in the Three Kingdoms period (AD 222-265) and his mother Huai Wen in the Southern and Northern Dynasties made great contributions in this respect.
References:
Baidu Encyclopedia-casting iron technique in ancient china