The problem of ironmaking in ancient times

China mastered ironmaking technology in ancient times, and gradually matured in the Warring States Period after the end of the Spring and Autumn Period.

The basic principle of ironmaking is basically the same as now. First, iron smelting, using carbon reduction process. At the earliest time, iron ore and charcoal particles were spread out layer by layer and burned at the bottom of the furnace. Because the temperature is not high enough, the impurity content of the produced soft green iron block is high. Then these soft iron blocks are forged into the desired shape, which is rough. Later, the blowing tool was invented, so that a large blast furnace was built, the furnace temperature was raised, and liquid pig iron could be extracted. So there was cast iron technology, which used clay or iron as a model and poured molten iron into it to create fine products, so iron farm tools and cutting-edge weapons were popularized. In addition, steel with less carbon content and better flexibility will be manufactured. However, in ancient China, the furnace temperature was not high enough, and only by heating and forging for a long time, the "unqualified" steel was made, but this has made great progress compared with ordinary pig iron. At the same time, related technologies have also made great progress. For example, it is found that alloys with special properties can be prepared by adding other metal ores in the ironmaking process, and bone powder (containing phosphorus) can play a catalytic role in the carburizing process.