"Cast steel", also known as "Tuangang". It is a kind of high-quality steel with high carbon content and uniform structure, which is made of 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. Apart from those unsung heroes, according to the literature, the first practitioner of this advanced technology we know is the famous metallurgist Qi Wuhuaiwen in the Eastern Wei and Northern Qi Dynasties (around 550 AD).
Qi Wu Huai-wen is a person who attaches importance to Taoism, and has done the work of secretariat in Xinzhou, Beiqi. He once refined an "iron knife". This "iron tree" is what later generations call "pouring steel". "Northern history? His invention is recorded in an art biography .. The book records:
"Huaiwen cold iron knife, the method of burning pig iron essence, with a soft collar, several nights and just (steel). Take soft iron as the blade ridge, bathe in the drowning of five beasts, and quench with the fat of five beasts, and cut more than 30 pieces of armor. "
I don't want to be an iron knife. His method is to select high-grade iron ore, smelt high-quality pig iron, and then pour liquid pig iron into wrought iron to melt it for many times and turn it into 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.
It can be seen from this record that Qi Wu Huaiwen not only practiced the smelting method of "pouring steel" at the earliest time, but also created two quenching media, animal urine and oil, which is a great innovation of Qi Wu Huaiwen in steel heat treatment technology. Before Wu Huaiwen, people generally used water as quenching medium, while Wu Huaiwen used animal urine and animal fat as coolant, which on the one hand expanded the use range of quenching medium; On the other hand, it is more important to obtain different cooling rates, so as to obtain high-quality steel with different properties.
The steel casting method is an outstanding achievement of China's ancient steelmaking technology. Its invention and popularization are of great significance for increasing the output of steel and improving the quality of weapons, farm tools and hand tools. Therefore, in the Sui and Tang Dynasties, this method was favored by smelters. In the Song Dynasty, it was popular all over the country and was innovated and improved, which became the main steelmaking method at that time. In Shen Kuo's Meng Qianbi Tan, the word "pouring steel" was first mentioned in addition to recording the smelting method at that time. He said:
"The so-called steelworkers in the world are bending plates with soft iron, trapping pig iron in them, sealing and refining them, and forging them into a group of steel. This is called group steel, also called pouring steel."
Steel-making in society means winding wrought iron into coils in a steel-making furnace, embedding raw iron sheets among the coiled wrought iron bars, and then sealing the steel-making furnace with mud for smelting. After refining, take it out for forging. The steel made in this way is called group steel, also called pouring steel.
By the Ming dynasty, the smelting technology of this kind of pouring steel had developed greatly. Song, a famous scientist, described the cast steel technology at that time in detail in his book "Heavenly Creations". He said:
"Where the steelmaking method is used, the wrought iron is cut into thin slices as wide as fingers and one and a half inches long, and the iron bundle is sharp, pig iron is placed on it, covered with broken straw sandals, and coated with soil below. When the fire came, the raw steel was melted first, and the wrought iron was infiltrated. They fell in love. Take it out and hammer it, then refine it and hammer it, and so on. Commonly known as Tuangang, it is also said that the steel caster is also. "
Song's words mean: the method of steelmaking is to first beat the wrought iron into thin sheets about one and a half inches wide, then wrap them tightly with bundles of wrought iron, and then put pig iron on the tightly tied wrought iron. Then, cover the straw sandals (the ones stained with mud to avoid being burned immediately), and in addition, apply mud under the iron sheet. When all this is done, put it in the furnace and blow it hard to reach the required temperature. At the temperature, pig iron will first melt into molten iron and penetrate into the wrought iron below, and the two will merge with each other. Then you can take out the hammer. After refining and tempering, it will be repeated many times. Such tempered steel, commonly known as group steel, is also called cast steel.
It is not difficult to find that the smelting method of pouring steel in Ming Dynasty is very different from that in Song Dynasty: people no longer use mud to seal the furnace, but use mud-coated straw sandals to cover the furnace; Raw iron sheets are not embedded in rolled wrought iron bars, but covered on tightly bound wrought iron sheets. The improvement of these two methods is very progressive. As Mr. Yang Kuan analyzed in the book "The Development History of Ancient Iron Smelting Technology in China": "They covered it with mud-coated sandals, not sealed it with mud. On the one hand, the steelmaking furnace can still get oxygen from the air to melt pig iron in the reducing atmosphere; On the one hand, most of the flame is reflected into the furnace, which increases the melting temperature. They beat the wrought iron into thin slices and then clamped them, so that the molten iron of pig iron was accurately sandwiched between several thin slices of wrought iron, and the contact surface between pig iron and wrought iron was increased, so that the wrought iron could easily absorb the molten iron of pig iron and the carbon could penetrate evenly. "
In the Ming Dynasty, besides the improved casting steel technology described by Song Dynasty, a new casting steel smelting method was also produced, which is the "Suzhou Steel" smelting method. "Suzhou Steel" is an advanced stage of the development of cast steel, and the advantages of cast steel have been fully demonstrated here. [-(@_@)-]
According to legend, "Su Gang" was invented by Jiangsu people, so it is called "Su Gang". Its smelting method, Tang Shunzhi of the Ming Dynasty, in his book Wu Bian? Pre-editing? There are brief records in iron. He said, "Cast pig iron and wrought iron together. When the pig iron is ripe and ready to flow, put it on the wrought iron and knead it in. " That is to say, pig iron and wrought iron are smelted together. When pig iron melts and iron juice wants to flow, pig iron water rubs into wrought iron and steel is poured in.
After the invention of "Cycas" smelting method, it prevailed in the late Ming and early Qing dynasties. Until modern times, there were still smelters using this method to make steel, but this method went a step further. The specific operation points are as follows:
When making steel, first put the wrought iron (pig iron) into the furnace for blast heating. Two minutes later, hold one end of pig iron with pliers and place it obliquely at the mouth of the furnace, and continue to blow, so that the temperature in the furnace will continue to rise. When the furnace temperature rises to about 1300℃, one end of pig iron inclined at the furnace mouth begins to melt, and molten iron begins to drip continuously. At this time, the steel-making workers clamped one end of pig iron outside the furnace with tongs and moved it left and right, so that the molten iron was sprayed evenly on the wrought iron. At the same time, the wrought iron is constantly turned, so that all parts of the wrought iron can absorb molten iron evenly. After the wrought iron is drenched twice, it is clamped on the anvil for forging. Impurities are removed to obtain the required blank, commonly known as "steel ball".
Above, we have introduced the different operation techniques of "casting steel". These advanced scientific and technological achievements are the crystallization of the wisdom of the ancient working people in China. It is because of their invention and creation that China's ancient steelmaking technology stood on its own feet in the world and won honor for our Chinese nation.