How to smelt iron in ancient times

Ancient Chinese iron smelting technology pig iron and softening treatment technology pig iron we usually say "iron" is divided into "pig iron" and "cooked iron" two kinds, including the "steel", are based on iron (Fe) and carbon (C) two elements of an alloy. Steel", including "steel", are iron (Fe) and carbon (C) two elements of an alloy. People usually call the carbon content of less than ○○5 percent cooked iron, ○○5 percent to 20 percent called steel, 20 percent to 667 percent called pig iron. Cooked iron made by early mankind is usually called lump iron, which is obtained by direct reduction of iron ore with charcoal at about 800 to 1,000 degrees Celsius. The product is a spongy solid mass with a large number of non-metallic inclusions. Block iron and pig iron compared, there are several shortcomings: First, it can not flow from the furnace, remove the iron, the hearth to be damaged to varying degrees, can not be continuous production, productivity is relatively low, the output is relatively small. Secondly, it is labor-intensive and time-consuming to form. Third, it contains more non-metallic inclusions, to be excluded through repeated forging. Fourth, the carbon content is often low, and thus very soft. Pig iron smelting temperature is one thousand one hundred and fifty to one thousand three hundred degrees Celsius, out of the product is liquid, can be continuous production, can be casting molding, non-metallic inclusions are relatively small, the texture is relatively hard, smelting and molding rate is relatively high, so that the yield and quality are greatly improved. From block ironmaking to pig iron is a leap in the history of ironmaking technology. China's iron and steel smelting technology development path and the world is not exactly the same. Foreign countries are generally the first block ironmaking, after a long period of slow development before pig iron. In many parts of Europe, block ironmaking was invented around 1000 BC, but there was no pig iron until the fourteenth century AD. This was not the case in our country. China's iron smelting was invented around the Western Zhou Dynasty, later than Europe, but once it was invented, soon appeared pig iron, later on, so that China became the world's first invention and use of pig iron in the country. 1964, jiangsu liuhe chengqiao town unearthed a piece of late spring and autumn period of the iron, was identified as a white mouth pig iron. This is until now China's earliest unearthed and scientifically analyzed pig iron objects. In the middle and late Warring States period, iron in China's agricultural and handicraft production occupied a dominant position. According to incomplete statistics, the current unearthed iron production tools of the Warring States about sixteen or so, most of which are pig iron and its softening treatment parts, block iron in a supporting position. This shows that at this time our country pig iron production has had a relatively large development. China's pig iron technology invented earlier for a variety of reasons, we think that the technology should include at least the following points: First, China's copper smelting technology is very early in the use of a relatively strong wind device. Secondly, the raw materials for smelting were selected and processed very early. Thirdly, the taller smelting shaft furnace was invented very early. It is generally believed that the invention and development of China's pig iron technology and bronze technology has a close relationship. Malleable cast iron malleable cast iron is originally white iron by high temperature annealing of a high-strength cast iron, with a certain degree of plasticity and impact toughness. According to the difference of heat treatment conditions, and can be divided into white malleable iron and black malleable iron two kinds: white malleable iron to decarburization, also called decarburized malleable iron; black malleable iron to graphitization, also known as graphitized malleable iron. Foreign white-centered malleable cast iron was first invented by the French in 1722 AD. In 1826 A.D., the Americans invented the black core malleable cast iron. Since then a fairly long period of time, people are white malleable cast iron is called "European malleable cast iron", black malleable cast iron is called "American malleable cast iron". In fact, these two kinds of malleable cast iron, our country as early as two thousand years ago have been invented. "Luoyang cement products factory early Warring States ash pit site unearthed a shovel, shovel body basic corrosion, only in the axe (qióng) part (mounted handle of the hole) have part of the metal residue, in the metallurgical microscope shows the black heart malleable cast iron organization, the matrix is ferrite, above the distribution of flocculent annealed graphite. This is to date the world's earliest scientifically analyzed cast iron malleable annealed parts. After the middle and late Warring States period, malleable treatment process has a relatively large development, mainly in: first, the distribution of a wider geographical area. In the north, currently analyzed by the Hebei yixian yanxiadu site of the iron iron, iron hoe, iron butt end, etc., in the south there are the empty head axe excavated in hubei baoshan, hunan changsha excavated shovels, etc.. Secondly, some of the devices have been handled better, the device section is basically malleable cast iron organization, there is no white mouth iron residue in the center, such as the iron butt end of Yan Xia Du. Han Dynasty to the North and South Dynasties period, the cast iron malleable technology development to a more mature stage: First, the scope of use has been further expanded. In recent years, such devices have been found in Xuecheng in Shandong, Nanyang, Mianchi and Gongyi in Henan, Qinghe and Dazaotai in Beijing, and Tonglushan in Hubei. There are twelve pieces of agricultural tools unearthed in Wafangzhuang, Nanyang, which have been analyzed, nine of which are ordinary malleable cast iron, two of which are cast iron decarburized steel, and only one of which is white-ported iron. Second, the technical level has been further improved. Where handled ware companion, the center of very few white iron organization residue, graphite development is relatively good, the form of more and modern malleable cast iron is comparable. These malleable iron, there are white-centered, black-centered, most of the agricultural tools. Cast iron malleable treatment has very important significance. At room temperature, carbon in cast iron has two main forms of existence: one is the chemosynthesis state, mainly carburized body; the second is the free graphite state, there are strip, group flocculent, spherical graphite and so on. Carbon exists in different forms, the same composition of cast iron, performance is not the same. White iron, carbon all in the form of carburized form, because the carburized body is very high hardness, plasticity is very low, so the white iron is hard and brittle. Through the malleable treatment, white iron in the carbon or free graphite form precipitation, or due to oxidation and removal, so that the material strength, hardness and brittleness to reduce the comprehensive mechanical properties have been improved. After the middle of the Warring States period, our country in agriculture, handicrafts so widely used iron, malleable cast iron invention and development is played an important role. Ductile malleable cast iron ductile malleable cast iron is named for the graphite contained is spherical. It has relatively high strength, plasticity and toughness, and its casting and machining properties are relatively good. 1974, Henan Mianchi excavated a Northern Wei iron cellar, which housed more than 4,000 pieces of iron from the Han Dynasty to the Northern Wei Dynasty, with types of tools of production, weapons, daily-use utensils, and casting models, iron