Stir-fried steel
Stir-fried steel is named because it needs constant stirring during smelting, just like cooking.
The raw material for frying steel is pig iron. The key point of operation is to heat pig iron to liquid or semi-liquid, and reduce the carbon content to the composition range of steel and wrought iron by blowing or spraying concentrate powder silicon oxide, manganese and carbon. The products of fried steel are mostly low carbon steel and wrought iron, but if controlled well, medium carbon steel and high carbon steel can also be obtained.
The technology of steel explosion was invented in the Western Han Dynasty. In recent years, steel furnace sites of the Han Dynasty have been discovered in Tieshenggou, gongyi city, Henan and Wafangzhuang, Nanyang. The dating of Gongyicheng site is from the middle Western Han Dynasty to Xin Mang, and Wafangzhuang site has been used for a long time, from the middle Western Han Dynasty to the late Eastern Han Dynasty. In addition, some fried products were unearthed in Tieshenggou. After analysis, some of them have carbon content of 1.28%, while others have carbon content of 0.048%. The record of steel explosion in the literature was first seen in Volume 72 of Taiping Jing in the Eastern Han Dynasty. The book says, "Let engineers beat the stone, ask for its iron, burn it and turn it into water. Later, let the good workers forge and become Mo Xie. " This "water" should refer to pig iron water. "Wan Forging" refers to repeated forging of pig iron after decarburization into steel.
The advantages of fried steel are that the composition can be properly controlled, the productivity is higher and the quality is better. In modern times, people often refer to the process of smelting ore directly into steel as one-step smelting method or direct smelting method, while the process of smelting ore into pig iron first and then steelmaking from pig iron is called two-step method.
Melting or indirect melting. The production process of fried steel is also divided into two steps: first smelting pig iron and then steelmaking. Therefore, in a sense, the appearance of steel explosion is the beginning of two-step steelmaking and an epoch-making event. It further promoted the extensive use of ancient ironware in China and the development of social productive forces. /kloc-In the mid-8th century, Britain invented the steel frying method, which played a great role in the industrial revolution. Marx spoke highly of this innovation with great enthusiasm, saying that no amount of praise can exaggerate the significance of this innovation.
Baigang manufacturing
"Hundred Steelmaking" takes a fried product with high carbon content as raw material, and the key point of operation is repeated heating forging. The earliest 100 steel objects we see now were made in the late Eastern Han Dynasty. 196 1 year, a steel knife from the period of Zhong Ping, the mausoleum emperor of the Eastern Han Dynasty (A.D. 184 to 189) was unearthed from the tomb of Daiwa Todo Temple in Japan, and the inscription "Hard work is the right thing to do" was engraved on the knife. "Practice" means "refining" and "rigidity" means "steel". The word "hundred steelmaking" in the literature was first seen in the late Eastern Han Dynasty. Cao operates five treasure knives and is known as "a hundred refined weapons"; Chen Lin (? -2 17) "Wu" says: "A is the Duke of Donghu Que, and fine steel is refined." These objects and documents show that steelmaking technology has risen. In addition to hundred steelmaking, there were also sayings of "thirty steelmaking" and "fifty steelmaking" in ancient China. 1974 in the sixth year of Emperor Yong of the Eastern Han Dynasty (A.D. 1 12), a large steel knife was unearthed in Cangshan, Shandong Province, with the inscription "Steering a big sword" on it. 1978 in the second year of Zhang Jianli in the Eastern Han Dynasty (AD 77), a large steel sword with the word "fifty" on it was unearthed in Tongshan, Xuzhou; There are also "Mozi" golden horse calligraphers and knives in the Eastern Han Dynasty and the sixteenth year of Yongyuan (AD 104). It seems that there was a steelmaking process marked "Smelting" at the latest in the early Eastern Han Dynasty.
Shen Kuo's Meng Qian Bi Tan (Volume III) in Song Dynasty recorded in detail the technological operation of 100 steelmaking, saying that "refined iron" is "pure steel" if it is tempered by 100 or more fires until its weight is not reduced. "Where iron has steel, if there are tendons on the surface and the soft surface is exhausted, then meet the tendons." Shen Kuo's "refined iron" should not be pig iron or wrought iron in the modern sense. According to the scientific investigation of "50-inch sword" at the beginning of Jian and "30-inch broadsword" at the beginning of Yong, and related literature, it should be a fried product with a slightly higher carbon content. This fried product contains a lot of nonmetallic inclusions. When forging, it is said to be light because these inclusions are gradually eliminated, and iron scales are constantly produced and shed. Finally, it is relative to say "not losing weight". In fact, if you keep heating and forging, mill scale will come into being and fall off, and the weight will always decrease. Carburization and decarbonization are not the main links in the tempering process. The main operations of copper smelting process are repeated heating and forging. Forging can remove inclusions, reduce the size of residual inclusions, make the composition uniform and compact, and sometimes refine the grains, thus greatly improving the strength of materials. Cao Zhi (192—232) praised Bai Steelmaking Knife in his Bao Dao Fu, which can "cut the rhinoceros skin to the ground and break the dragon boat in the water". In the third volume of Meng Qian's Notes, Shen Kuo said that Bai Steelmaking Knife "is bright and polished, but it has dark, blue and black colors, which is very different from ordinary iron." This shows its excellent steelmaking performance.
On the basis of repeated forging of massive iron carburized steel, with the development of steel explosion technology and sword technology, hundred steelmaking appeared. The expression of "ten smelting" and "thirty smelting" appeared in the late Western Han Dynasty in the first century BC and was originally used for copper smelting. During the Wei and Jin Dynasties, Hundred Steelmaking reached its peak. After that, it was weakened due to some technical and social reasons, but it was still used in Ming and Qing Dynasties. It is difficult to build a hundred steel mills, and the cost is relatively high. It is mainly used to make precious items such as treasure knives and swords. It embodies the industriousness and wisdom of the working people in ancient China, and to some extent reflects the advanced level of metal smelting and processing technology at that time.
Decarburized cast iron
Decarburization of cast iron is achieved by heat treatment. The key point of its operation is to produce white cast iron, and then decarburize and anneal in oxidizing atmosphere, so that the carbon content is reduced below the composition range of steel, and graphite does not precipitate or rarely precipitates. Its metallographic structure is similar to that of modern steel and wrought iron.
Decarburization technology of cast iron can be traced back to the early Warring States period. Two shovels were unearthed from the ash pit site of Luoyang cement products factory in the early Warring States period. Metallographic analysis of a shovel shows that its surface layer has been decarburized, slightly pearlite, and its center is white iron structure. This shows that thulium has undergone incomplete decarburization annealing and should belong to the predecessor or early stage of decarburization of cast iron. From the Qin, Han, Wei and Jin Dynasties to the Southern and Northern Dynasties, this technology developed to a quite mature stage, mainly in the following aspects: First, there are many instruments for this treatment. In recent years, it has been found in Dabaotai in Beijing, Wu 'an in Hebei, Mianchi, Wafangzhuang in Nanyang, Guxing Town, Zhengzhou, Wang Chenggang and Lushan. There are special-shaped parts such as iron axe, iron scissors, shovel, iron knife, iron chisel, shovel, iron plow and shovel, as well as semi-finished products such as trapezoidal and rectangular small iron plates. Secondly, the entire cross section of most devices has been decarburized into steel or wrought iron, with no residual white iron structure in the center and no or only a small amount of graphite precipitated at the grain boundary. Thirdly, after decarburization into steel or wrought iron as a whole, some devices have achieved better service performance through local forging, edge carburizing or other treatments. Fourthly, decarburized cast iron is mainly used as the blade of axe, scissors and sickle of handicraft tools, while common malleable cast iron is mainly used as hoe, shovel and spade of agricultural tools. As for household appliances, white iron and gray iron were mostly used in production tools and vehicles such as iron pot, iron fans and bearings, which showed that people had a good understanding of the properties of these materials at that time, and also showed the decarbonization technology and ductility of cast iron. After the Northern and Southern Dynasties, due to the development of smelting technology and frying technology, the decarburization technology of cast iron and malleable cast iron gradually lost their important position in production, and they were rarely seen after the Tang Dynasty.
The invention of decarburization of cast iron is of great significance. In ancient times, there was generally no cast steel, but the productivity of forged steel was very low, it was difficult to process and shape, and it contained many impurities. In ancient China, it was an important invention of China's ancient metallurgical technology to obtain castings with similar structure and properties to modern cast steel by decarburization annealing, taking advantage of the advantages of high productivity, easy molding and few inclusions.
Cast steel
The so-called "casting steel", in the words of Su Song in the Song Dynasty, is "a person who confuses softness with life and regards it as the blade of a sword". "Raw" is pig iron, "soft" should be malleable cast iron, and only from the perspective of carbon content, it should include modern steel and wrought iron. Therefore, according to Su Song, cast steel is a kind of steel with high carbon content and good quality, which is smelted from pig iron and malleable cast iron and used to make sword blades.
It seems that the invention of steel casting can be traced back to the Han, Wei and Jin Dynasties. At the end of the Eastern Han Dynasty, RoyceWong (177-2 17) wrote in Dao Ming: "The irrigation has been calculated, and the quality has been achieved." Zhang Xie of the Western Jin Dynasty said in "Seven Lives": "It's fine and bright, and it's a thousand irrigation." "Bi" and "Bi" are homonyms, meaning "stacking", which refers to the multi-layer stacking and multiple folding of steel. "Pouring" should mean "pouring", that is, "pouring steel".
During the Southern and Northern Dynasties, steel casting technology developed to a certain extent. Tao Hongjing in the Southern Dynasties said that casting steel was "a man who mixed swords and sickles". Since pouring steel has been used as a common production tool and household appliances such as knives and sickles, it can be seen that its production has become more common. During the Northern Dynasties, the Eastern Wei Dynasty and the Northern Qi Dynasty, Wu Huaiwen used cast steel to make a big steel knife, which was called "Su Tiedao" and "cut more than 30 nails". It is very sharp.
Historically, there have been several different operations of pouring steel. One is to tie pig iron and soft iron sheets together, seal them with mud and put them into a furnace for smelting. For example, Shen Kuo said in Volume III of Meng Qian's Bi Tan, "When bending a plate with soft iron, pig iron is trapped in it, sealed with mud and forged, which is called' group steel' or' pouring steel'." One is to put pig iron on a piece of wrought iron (malleable cast iron), and the pig iron melts first and penetrates into the wrought iron. As Song said in Tiangong Volume 14, "Make a thin piece of iron with a finger width and a half inch length, wrap it tightly with a bundle of iron sheets, put iron on it, cover it with broken straw sandals, and wrap it with mud, and the fire will rise." Take it out and hammer it, then refine it and hammer it, and so on. It is commonly known as Tuangang, and it is also said that it is poured. "One is" Suzhou Steel ",which is the advanced stage of the development of cast steel, and the advantages of cast steel have been fully demonstrated here.
The key points of operation of Suzhou Iron and Steel Co., Ltd. are as follows: firstly, put the wrought iron into the furnace for blast heating, and then put one end of pig iron into the furnace mouth for heating. When the furnace temperature reaches about 1300 degrees Celsius, the pig iron in the furnace keeps dropping and the wrought iron has softened, so the pig iron is clamped with pliers to make the molten iron evenly poured on the wrought iron. After pouring, stop blowing, clip out the steel ball and hammer it on the anvil to remove the inclusions. Generally, it should be infiltrated twice. There are two bright spots in the smelting of Suzhou Iron and Steel Co., Ltd.: First, the microstructure of wrought iron is relatively loose, with more oxide inclusions and higher contents of silicon, manganese and carbon, and the oxidation reaction is fierce during casting, which is beneficial to the separation of slag and iron. Secondly, after iron oxide in wrought iron reacts with carbon in pig iron, part of iron can be reduced, which improves the metal yield.
Pig iron and malleable cast iron are used as raw materials for pouring steel, and the pouring operation is carried out above the melting point of pig iron, which has higher productivity and better separation of slag and iron. People can control the composition of products by controlling the proportion of raw materials and blowing, so the quality of products is better. Before the invention of crucible liquid steelmaking in A.D. 1740, the steelmaking processes in the world were basically solid melting and semi-liquid melting, and it was difficult to separate slag from iron. Like pouring steel, the composition is easier to control and the slag and iron are easier to separate, which is very rare in ancient steelmaking technology.