Wu Huaiwen, the secretariat of Xinzhou in Northern Qi Dynasty, is an expert in steelmaking. He is a man who values Taoism. He once forged an "iron knife", which was later called "pouring steel".
"Cast steel", also known as "Tuangang", is a kind of high-quality steel with high carbon content and uniform structure, which is made by smelting pig iron and wrought iron (iron with carbon content of 0.05%-2.0% is called steel). This primitive steel casting smelting method was invented at least in the Southern and Northern Dynasties.
According to the biography of northern history and art, Su Tiedao was made by Shu Huaiwen. His method is to select high-grade iron ore, smelt high-quality pig iron, and then pour liquid pig iron into wrought iron, which is smelted many times to become steel. After the steel was tempered, he used wrought iron as the back of the knife and steel as the blade, and quenched it with animal urine and grease. The iron knife made by this method can cut off more than 30 pieces of overlapping nail pieces at a time. To quote Tao Hongjing: "Steel is a sword and a sickle." Both historical materials record the pouring method of steel. By melting molten pig iron and wrought iron, the carbon content spreads and tends to be uniform, and it becomes high-quality steel with high carbon content. Carbon in liquid pig iron reacts with oxides in wrought iron, which is beneficial to remove impurities, purify tissues and improve steel quality.
Double liquid quenching method
Tao Hongjing's historical materials tell us that casting steel has been widely used, which can not only make swords, but also make sickles. The germination of steel casting technology can be traced back to the Eastern Han Dynasty. RoyceWong's Ming Dow has a phrase "pour, pour", in which "pour" refers to folding and "pour" refers to pouring, indicating that there has been an attempt to pour steel at this time. The steel casting method is another great contribution of China to the world after steel explosion and steelmaking.
"The drowning bath of five animals, the fat quenching of five animals", is to use animal urine and animal fat to quench into steel. Livestock urine contains salt, which is used as quenching cooling medium, not only has a fast cooling speed, but also the quenched steel is harder than the steel quenched with water. Quenching with animal fat is slower than water, and hardened steel is harder than water. It can be seen that great progress has been made in steelmaking and quenching technology during the Southern and Northern Dynasties. Bei Tang Shuchao (volume 123) quoted the Biography of Puyuan, which recorded that Puyuan made knives for Zhuge Liang in Gu Jie (now Meixian County, Shaanxi Province). Because "the Hanshui River is light and cannot be quenched", he sent someone to Chengdu to fetch the river water, which was mixed with eight liters of Fucheng water and was discovered by Puyuan. Although this legend is somewhat exaggerated, it shows that people have paid full attention to the influence of water quality on quenched steel at that time. "Jin Taikang Geography" also said: "There is a long spring in Xiping, Runan, which can quench the blade and is very strong." This is another example of people's concern about the influence of water quality on quenching at that time. It is in these accumulated experiences that the two-liquid quenching method was developed.
blasting technique
In order to raise the furnace temperature and shorten the smelting time, the working people in ancient China adopted the technology of blowing air into the smelting furnace very early. The earliest blowing tool is called "wood", which is the skin made of leather. Blowing with a fan is to open and close them one by one through repeated actions of pulling and pressing, and blow the wind into the furnace. During the Warring States period, it developed into multiple rows of bricks blowing into the furnace, which is called "brick row" or "brick row" for short. Using exhaust air blast can increase air intake and strengthen combustion firepower, which is much more advanced than single blast, but it requires a lot of manpower. It is called "human platoon" by manpower. Then there is the "horse raft" with animal power as the blowing force, and the required animal power is also considerable. The heavy consumption of manpower and animal power is a serious obstacle to the further development of iron smelting industry.
After the mid-Western Han Dynasty, a number of large smelting furnaces appeared in the iron smelting industry, which needed to provide considerable air volume and air pressure, which required people to improve the existing blast device. Du Shi, the magistrate of Nanyang (now Nanyang, Henan) in the Eastern Han Dynasty, designed and manufactured a set of iron smelting blowers powered by water power-water exhaust.
On the basis of Du Fu's poems in the Eastern Han Dynasty, the Han Dynasty in the Three Kingdoms period further extended the water platoon to the official smelting workshop of Wei State, replacing the past horse platoon and human platoon with water platoon, which lasted for four seasons. Drainage not only saves manpower and animal power, but also improves work efficiency and promotes the development of iron smelting industry. At this time, it has been clearly recorded that Han Ji's flurry platoon saves manpower and animal power, and its efficiency is three times higher than that of horse platoon. Drainage was used in China for a long time, and it was still used in some places until 1970s.