1. The ironization of production tools and the development of the iron smelting industry
After the Warring States Period, due to the advancement of iron smelting technology and the changes in the social and economic system, the demand for iron tools in society increased. With the increase, the mining of iron ore, smelting and casting of iron have become important handicraft industries related to the national economy and people's livelihood. Therefore, the iron smelting industry began to develop. A lot of iron ore was developed during the Warring States Period. The book "Shan Hai Jing·Wuzang Shan Jing" of the Warring States Period recorded 37 iron-producing mountains, among which the one recorded as belonging to Nanyang was the "Imperial Mountain". There are many irons in the yin", approximately between present-day Biyang County and Nanyang County in Henan Province; the other place is "Mountain of Rabbit Bed, "Many Irons in Yang", approximately between present-day Song County and Nanyang County. During the Warring States Period, various countries had iron smelting handicraft industries. Among them, Korea and Chu had the most developed iron smelting handicraft industries and had the most famous iron smelting handicraft industries. At that time, Nanyang had become a famous iron smelting center during the Warring States Period. "Xunzi·Yi Bingpian" records: "A huge piece of iron is as miserable as a bee." By the Qin and Han Dynasties, iron tools and iron smelting technology had been widely spread and used in vast areas. Archeology has revealed that in the early Western Han Dynasty, iron farm implements and tools had replaced copper, bone, stone, and wooden tools. By the middle of the Western Han Dynasty, with the development of iron smelting technology, wrought iron tools increased, and iron weapons gradually occupied a dominant position until In the Eastern Han Dynasty, all major weapons were made of steel, thus completing the iron-based process of weapons and production tools. ?In the early years of the Western Han Dynasty, the iron smelting industry could be left to businessmen. The Kong family of Wei State was originally engaged in the iron smelting industry. After the Qin Dynasty destroyed Wei, he was forcibly moved to Nanyang and became extremely rich by smelting iron. During the reign of Emperor Wu of the Western Han Dynasty, Emperor Wu appointed Kong, an iron merchant from Daye in Nanyang, as a "big agricultural minister, responsible for salt and iron affairs" to manage the country's salt and iron industry. Nanyang became one of the handicraft industry bases in the country where iron officials were set up. In the iron smelting sites of the Han Dynasty excavated in Wafangzhuang, Nanyang, iron smelting relics from the Western Han Dynasty (furnace foundations, refractory bricks, blast pipes, casting molds and iron tools, including iron plowshares, iron columbines, and iron shovels) were discovered. , adze, ax, etc.). By the Eastern Han Dynasty, the iron smelting industry in Nanyang was based on the Western Han Dynasty. The number of iron smelting workshops increased, the scale expanded unprecedentedly, and the technology improved significantly. The iron smelting sites discovered near Nanyang after the founding of the People's Republic of China include: the Wafangzhuang Iron Casting Workshop Site in Beiguan, Nanyang City, the Dazhangpi Iron Smelting Site in Zhangpi Village, Tongbai, the Tielu Village Site in Tongbai County, and the Taishan Temple in Nanzhao County. , Caodian iron smelting site, Fangcheng County Zhaohe Village iron smelting site, Zhenping County Anguocheng iron mold and iron casting site, Xixia County Baishijian iron smelting site, etc. The iron smelting ruins of the Han Dynasty were excavated in Wafangzhuang, Beiguan, Nanyang City from 1959 to 1960. The main site area is 2800 m?2, and a large number of iron smelting remains and relics were discovered, including 9 furnaces, 8 steel-frying furnaces, and 1 forging furnace. seat. It was discovered that a hot blast furnace was used in the iron smelting process under the production conditions at that time. This was a heat-saving furnace used in our country in the early days. There are nearly 40 types of molds and models used in casting. It can be seen from the relics excavated by cultural relics and archeology that Nanyang had become the smelting center of the country at that time.
2. Development of iron smelting technology and processes
Iron smelting technology further developed during the Qin and Han Dynasties. Blast furnace ironmaking has become an economical and effective method of ironmaking. The blast furnace is charged with iron from the top and air is blown from the bottom, resulting in a relative movement of the charge falling and the gas rising. The high-temperature gas generated by the fuel rises through the material layer and transfers heat to the furnace material. The carbon monoxide contained in it also reduces the iron oxide. In this way, the thermal energy and chemical energy of the fuel are fully utilized at the same time. The lower charge is gradually reduced and even melted. The upper charge slowly descends from the top of the furnace. The fuel is preheated and can reach a higher combustion temperature. This is indeed a relatively reasonable smelting method, so it has strong vitality and has been spread for a long time. The development of its smelting level is reflected in the following aspects: First, the furnace building technology in blast furnace ironmaking has reached a relatively high level. Some are built with rectangular or curved refractory bricks fired from yellow or red refractory clay containing high silica content. The refractory bricks unearthed from the Wafangzhuang site in Nanyang have different materials, thicknesses and shapes in different parts. Some use white quartz sand with a diameter of 0.3 to 0.5cm mixed with a small amount of fine sand. Some are made of grass mixed with mud, yellow clay and a large amount of quartz sand. The quartz sand used is not only natural, but also processed and crushed.
The fire resistance strength of these refractory bricks reaches between 1463°C and 1469°C, which is obviously the result of the sand and gravel containing quite high silica content being mixed into the refractory clay. This kind of acidic refractory material with a high silica content is suitable considering that most of the blast furnaces in ancient my country are acidic slag. Second, most of the raw materials used in blast furnace ironmaking have been processed. Smelting workers have discovered from long-term practical experience that uniform particle size of the charge can reduce resistance to gas. Therefore, raw materials must be processed before smelting. Thousands of tons of ore powder were unearthed from the Zhangfan Village site in Tongbai County, indicating that great attention was paid to the processing of ore at that time. In addition to blast furnace ironmaking, crucible ironmaking technology was also discovered during the Western Han Dynasty. In the Wafangzhuang site in Beiguan, Nanyang City, 17 crucible furnaces were found, 3 of which were relatively complete and all approximately rectangular. One of them is 3.6 meters long, 1.82 meters wide, and 0.82 meters deep. The construction method of the furnace is to dig a rectangular pit in the ground and leave the furnace door. The surrounding wall is tamped and then coated with a thin layer of mud. The top of the furnace is made of arc-shaped refractory bricks. The sizes of the bricks are different. The inner surface of the bricks is coated with a layer of refractory mud about 1 cm thick. There is still a thin layer of gray-white magma on the surface of the mud. The back of the bricks is coated with a thicker ( About 5 cm) of grass mixed with mud. Some are made of adobe and grass mixed with mud. The furnace consists of four parts: door, pool, kiln chamber and chimney. The door is at the front of the furnace and is used for loading and ventilation. The left and right walls have been burned by fire and have turned into brick gray. The pool is inside the door, and the surrounding walls are also burned into brick gray. There is fine sand about 1 cm thick on the bottom of the pool, which is used as a "wind nest" during burning. The furnace is rectangular, with grass and mud on the surrounding walls. The fire is light. It is used to hold rows of crucibles and fuels such as firewood and charcoal. There are three chimneys at the rear of the furnace, which are used to discharge furnace smoke. Some furnaces are filled with firewood ash, while others have a lot of burned earth and brick fragments piled at the bottom. Three crucibles were found, all of which were oval-shaped earthenware pots with round bottoms. The outside of the pots was covered with grass-mixed mud about 3 to 4 centimeters thick. The inside of the mud was burned to a red brick color, and the surface was a bright dark black with a layer of off-white light. magma. There are also fragments of iron slag stuck to the inner wall of a crucible. From the structure of the furnace and the crucible iron-making method passed down to later generations, it can be inferred that the iron-making method at that time was: first mix the crushed ore with charcoal and co-solvent, then put it into the crucible. Before loading, put the iron at the bottom of the furnace. Lay a layer of appropriate number of brick fragments to ventilate the bottom of the furnace; leave many "fire openings" to put in flammable materials for ignition, then lay a layer of charcoal, and install rows of crucibles on the charcoal; and then place them on the charcoal. A layer of charcoal is laid on top of the first layer of crucible, and a row of crucibles is installed on the charcoal. When the furnace is full, the fire can be ignited from the "fire port" and blasted to reduce the ore in the crucible and melt it into pig iron. ?Third, the development of blast technology. The development of blast furnace ironmaking and iron smelting technology is inseparable from the improvement of blast technology. In ancient my country, iron-making blast furnaces used leather "gouges" as blowers. With the passage of time and the accumulation of experience, people gradually changed the method of blowing. In a large smelting furnace, there is more than one blower, but a blower and a blower pipe are added to fully burn the fuel in the furnace, increase the temperature of the furnace, and accelerate the smelting process. In the iron smelting site of Wafangzhuang, a large number of blast pipes were unearthed, including some ceramic blast pipes with elbows. The inner diameter of the thick end is about 100mm, the inner diameter of the thin end is 50mm, and the length is about 400mm. Since the mud layer under the ceramic blast tube was burned, the burning temperature was measured to be between 1250℃ and 1280℃. From the temperature and the excavated objects, it can be judged that the iron smelting furnace in Nanyang in the Han Dynasty was equipped with a hot blast device ("Iron Smelting in Nanyang in the Han Dynasty", Zhongzhou Ancient Books Publishing House, December 1995, page 23.). This device uses the waste heat from the furnace mouth to turn the cold air in the air duct into hot air and blows it into the furnace, which not only increases the temperature of the furnace, but also shortens the smelting time and improves the quality of the molten iron. As far as the blowing power is concerned, there are "human platoon" blowing power and animal-powered blowing power, such as "horse platoon", "steak", etc. In the seventh year of Jianwu of the Eastern Han Dynasty (31 AD), Du Shi served as the prefect of Nanyang, created the "water row" of water-powered air blowing, and promoted it. Using water rows to blow air to cast agricultural tools requires "less effort and more results" than using human power to blow air, and achieves good results.
The iron smelting ruins excavated today in Zhangfan Village, Tongbai County are far away from the mines and were built next to the river. It is likely that "water drainage" was used to blow the wind. The invention and application of water drainage not only improved the blasting capacity, but also greatly reduced the cost, so it has been used by the iron smelting industry for a long time. Water-powered blowing machinery like this did not appear in Europe until more than 1,100 years ago. ?
The improvement of blast technology has promoted the development of iron smelting technology. In addition to the rapid development of pig iron smelting technology, a cast iron softening process was also created, and gray cast iron and ductile iron appeared. Among the iron tools unearthed from the Han Dynasty iron smelting site in Wafangzhuang, Beiguan City, Nanyang City, after analysis and examination, it can be seen that the agricultural tools of the Han Dynasty mainly used malleable cast iron. Among the 12 farm tools inspected, 9 were malleable cast iron, 2 were cast iron decarburized steel, and 1 was white iron. This shows that softening technology has been used in cast iron. In terms of quality, the cast iron softening technology at that time was quite stable. The graphite structure of the No. 135 iron nugget unearthed from the Eastern Han Dynasty strata at the Wafangzhuang iron smelting site was not from the cast state, but was formed during high-temperature annealing. However, the shape is regular and close to spherical, and the edges are also very smooth, thus improving the improve the mechanical properties of the workpiece.
3. Fried steel, cast iron, decarburized steel and casting technology
In order to meet social needs for steel products, the "fried steel" technology was created in the late Western Han Dynasty. This technology heats pig iron to a molten or basically molten state and stirs it to decarburize the iron into steel or wrought iron. ?
In the Han Dynasty iron smelting site in Zhaohe Village, Fangcheng County, Nanyang City, six furnaces of the same type as those in the Han Dynasty iron smelting site in Tieshenggou, Gong County were also found. This kind of iron-frying furnace has a small volume and is in the shape of a gou, so the temperature can be concentrated; it is dug into the ground to become an underground furnace, which dissipates less heat and is conducive to temperature rise; the lower part of the furnace is shaped like a "goo bottom" to facilitate loading and stirring. In addition, several steel-frying furnaces were also found in the iron smelting site of Wafangzhuang, Beiguan, Nanyang City. The shapes and construction methods are similar, and there are iron blocks at the bottom of the furnace. Judging from the excavation of this site, the iron smelting workshop in Wafangzhuang, Nanyang, not only cast iron objects, but also used pig iron to stir-fry steel or wrought iron to forge tools and other components. Chisels, cymbals, etc. were also unearthed at this site, which were probably made by the workshop. Archaeological data proves that by the Eastern Han Dynasty, steel frying technology had become very popular. An Eastern Han Dynasty iron knife was unearthed in the eastern suburbs of Nanyang. It has a special shape, similar to a cooking knife. The blade has a forging mark parallel to the blade. The knife is 11.2 cm wide, about 17 cm long, and the back is about 0.5 cm thick. centimeter, relatively well preserved, and forged from fried steel (Henan Provincial Museum, etc.: "A Preliminary Study on the Iron Smelting Technology of the Han Dynasty in Henan", "Acta Archaeologicala" Issue 1, 1978.). ?
In the late Western Han Dynasty, simple steel-frying furnaces were created to fry pig iron into mature iron or steel. This marked the development of steel-making technology
to a new stage. This greatly increased the output of steel, which was of great significance to the improvement of production tools and the promotion of steel products at that time.
Ancient steelmaking used lump iron or wrought iron with low carbon content as raw materials, and was made into steel by carburizing method (this method is still used today)
, This method uses pig iron with high carbon content as raw material and decarburizes it in the solid state to make steel. During the Warring States Period, the softening process was used to decarburize and anneal pig iron, and decarburized cast iron steel parts with incomplete decarburization were obtained (Li Zhong: "Discussion on the Development of Steel Smelting Technology in the Early Feudal Society of China", "Acta Archeology" , Issue 2, 1975), this process was still used in the Han Dynasty. For example, the iron ax unearthed from the Wafangzhuang Iron Smelting Site in Nanyang has white tissue in the center and steel on the surface. Iron tools like this have also been found in other sites. They are all made of white iron blanks, which are annealed in an oxidizing atmosphere to decarburize the outer layer. From the surface to the inside, they become pure ferrite, subferrous analyte, and chromium analyte structures. Due to incomplete decarburization, , the interior is still iron, actually a composite material composed of steel and iron. Another situation is that the decarburization is relatively complete, and the white tissue has been completely removed, but some graphite has precipitated in the inner layer. For example, an iron chisel unearthed from Wafangzhuang in Nanyang looks like a casting from the appearance, but the surface metallographic analysis shows the structure of steel, so it is easy to mistake it for a steel casting.
Under the technical conditions of the Han Dynasty, liquid cast steel would not have been possible without high temperatures above 1500°C and corresponding refractory materials. Another iron chisel unearthed from Wafangzhuang, Nanyang, was inspected and found that the base was made of chromium-ionized steel with residual graphite in the inner layer, proving that it was a decarburized steel tool. In addition, formed thin iron plates were unearthed from the Wafangzhuang iron smelting site in Nanyang. These iron plates were actually decarburized and heat-treated and became steel plates with lower carbon content. They could be forged into tools and actually created the invention of steel plates. A new steelmaking process. This expands the scope of use of pig iron and increases the source of high-quality steel, which plays a significant role in steel production. ?
The heat treatment technology of cast iron developed greatly during the Han Dynasty and reached maturity. Of the 9 farm tools excavated at the Wafangzhuang Iron Smelting Site in Nanyang
8 were tested to be black-core ductile cast iron, with good quality, and some were no longer significantly different from modern black-core ductile cast iron. There are also some white-core tough cast irons. White-heart tough cast irons can be used to make hand tools that are impact-resistant and have good performance. Black-heart tough cast irons can be used to make wear-resistant farm tools. Among the cast ironware, some of the iron ingots, iron columbines, and iron columbines are white-core ductile cast iron. ?
Judging from the discovered iron smelting sites of the Han Dynasty, some of the workshops at that time were mainly engaged in iron smelting and casting ironware, and some were specialized in casting ironware.
The original iron castings were cast directly from molten iron in the iron-making furnace. In the Han Dynasty, special iron furnaces appeared, which were of great benefit in improving the quality of molten iron and obtaining high-quality castings. Looking at the Wafangzhuang site in Nanyang, the structure and construction materials of the iron-making furnace are obviously different from the iron-making furnace, indicating that the division of labor between iron-making and iron-making at that time was very clear. ?
Seven iron furnaces were unearthed from the Wafangzhuang iron smelting site in Nanyang. The construction method is as follows: on the flat ground, lay grass-mixed mud with a diameter of about 2.6m and a thickness of 50mm, and then bake it. Orange yellow, as the furnace base. The furnace bottom is hollow and consists of an integral base, waist-shaped pillars, peripheral walls and the bottom of the hearth. The base is about 45mm thick and is paved with refractory clay mixed with a large amount of large-grained sand. The particle size of the sand is about 10mm. The surrounding walls and pillars are made of slightly different materials than the base. There are a lot of small grains of sand. The peripheral wall thickness is 40~50mm, the diameter of the pillars is 70~120mm, and the height is 70cm. Based on the size of the rectangular refractory bricks unearthed from the site, it is estimated that there may be about 15 pillars, and the bottom of the hearth is built on the foundation. ?
The furnace body is entirely made of curved refractory bricks. Judging from the different melting degrees of the inner surfaces of the bricks, the furnace body can be divided into three areas: the furnace mouth and the lower three and four layers of bricks (bricks). (36cm long, 17cm wide, 6-9cm thick), the furnace lining is slightly molten, has many cracks, and has the lowest temperature, which is the preheating zone. The third and fourth layers of bricks in the middle part of the furnace body all have burnt glaze on the furnace lining, indicating that the temperature is relatively high and should be the reduction zone. In the next three or four layers of bricks, the furnace lining is generally burned, or even completely shed, exposing the brick body. The temperature is highest here, and it is the oxidation zone close to the tuyere. According to the height of the refractory bricks and the above-mentioned furnace wall burning conditions, the height of the furnace body of the iron furnace is about 3 to 4 meters. The furnace wall of the iron furnace is divided into three layers. The arc-shaped refractory bricks are specially shaped bricks, which are coated with grass mixed with mud on the outside and are about 15-50mm thick. The inner lining is about 40mm thick. According to the curvature of the 14 relatively complete refractory bricks when unearthed, the minimum outer diameter of the iron furnace is 1.16m, the inner diameter is 0.92m, the maximum outer diameter is 2.3m, the inner diameter is 2.14m, and its average inner diameter is about 1.5m. After identification, the refractory bricks are all made of sand and clay. Judging from the particle composition of quartz sand, there are round and angular white quartz and a small amount of feldspar, indicating that in addition to natural sand, artificially crushed sand has been used. There are cracks in the quartz particles, acicular mullite crystals precipitated in the glass phase, and a flow structure, all of which indicate that the iron furnace was able to reach quite high temperatures at that time. ?From the large number of blast pipes unearthed from the site, it is speculated that a heat exchange hot air device may have been used when iron was melted. There is a ceramic blast pipe, which is covered with grass-mixed mud about 45mm thick, and the surface of the lower mud material is melted. When it drips, the mud near the corner melts and flows down the corner. According to the measured temperature, the burning temperature should be between 1250℃~1280℃.
One explanation for the burnt state of the air duct is that it may have been installed on the top of the furnace and used as a preheating duct. ?
In addition, among the large amounts of broken iron and slag unearthed, there are many trapezoidal iron plates and fragments of iron tools such as plows, adzes, adzes, hoes, axes (thickness is about 40~70mm) . These relics may be the raw materials used in the iron furnace. The square anvil and hammer are both forging tools and tools for crushing raw materials. A large amount of charcoal slag indicates that the fuel used was charcoal, and charcoal clumps remained in the furnace, some of which were condensed with slightly molten iron on the surface. Some of the shapes of the vessels can still be identified. It is speculated that this phenomenon may be the result of layered charging. Judging from the unearthed furnace lining, the section is clearly divided into three layers. The furnace has been shut down and repaired at least twice. The materials used for repairing the furnace are the same as those used for refractory bricks. According to the unearthed relics, it is speculated that such a large furnace must be operated semi-continuously. Every certain period of time, molten iron will be discharged and a batch of casting molds will be poured. When the melting time is too long or the casting mold has been completed, the furnace must be shut down in a timely manner. This shows that craftsmen in the Han Dynasty had a good grasp of the operating procedures of the furnace. The casting technology of the Han Dynasty also developed in the technology of casting iron and bronze wares during the Warring States Period. At this time, the molds used for casting included clay molds, pottery molds and iron molds. Especially the use of iron molds improved the quality and efficiency of iron castings to varying degrees. Judging from the various molds and models excavated in Nanyang Wafangzhuang, the process is roughly as follows: the mold-making workers select yellow clay on the spot, mix it with about 35% fine sand, add water to mix the mud, make the template, and then finely The mold surface is carved out of the ground, and the shapes of various parts on different mold surfaces are shaped according to strict dimensional requirements. After the mold surface is prepared, paint is applied and allowed to dry. This is the first necessary mold making process. Before casting, first close the mold, paste and reinforce the mud, and then send the mold to the kiln for baking. After reaching a certain temperature, stop baking and exit the kiln. Use the heat to pour the cast iron juice. During pouring, fill the gate and riser with the iron juice. , to adapt to the needs of mold cavity shrinkage. After the iron juice solidifies to a certain extent in the mold cavity, open the reinforcing mud, take off the mud mold, and then knock off the sprue iron to obtain an iron casting mold. Then, the cast iron upper and lower iron molds are combined into the mold, and then the iron mold core is inserted into the mold cavity, and some iron tools are used to tie and clamp the iron mold to prevent it from cracking due to the thermal expansion of the iron liquid during pouring. After the mold is combined, it can also be baked in the kiln, and the iron juice is poured into it while the iron is hot. After the iron juice solidifies to a certain extent, the iron mold is opened and the gate and riser iron are knocked off to obtain the product. ?The development of casting technology methods is also reflected in stack casting technology. Stack casting technology is to stack many mold pieces or mold blocks layer by layer, and use a unified sprue to cast multiple castings at one time. This method has been invented during the Warring States Period (Zi Xi: "Talk about the Model of Several Ancient Artifacts", "Cultural Relics Reference Materials", Issue 8, 1957.), and it is mainly suitable for the mass production of small castings. In the Han Dynasty, stack casting technology has further developed. For example, a Han Dynasty mold kiln was excavated in Wenxian County, Henan Province. More than 500 sets of stack casting molds were unearthed, with 16 types of castings and 36 specifications. One set of molds has 4 to 14 layers. Each layer has 1 to 6 castings, and a maximum of 84 pieces can be cast at one time, which greatly improves production efficiency. Several stacked micro-melting relics and three to five "V" shaped iron plowshare stacked relics were unearthed from the Wafangzhuang iron smelting site in Nanyang, which fully proves that Nanyang was the first major iron smelting county to adopt double stack casting technology. ?The design of the casting mold is also quite scientific. The mud layer between the mold cavities is very thin. In order to make the mold surface compact and reduce the amount of mud as much as possible, the sprue of some molds is made into an oblate shape, which fits the mortise and tenon positioning of the mold. The structure is also arranged according to this principle. The shape of the fan matches the mold cavity. Many casting molds cut off the corners to make the edge thickness as consistent as possible. This not only reduces the volume of the fan and the amount of mud used, but also makes the heat dissipation more uniform and improves the quality of the casting. ?For the manufacture of the model core, in addition to the clay core itself, the simple shape is pressed into the core base with a mud strip. Complex ones, such as car (vehicle) mud cores, are made of mud split core boxes. The multi-stack stacked casting (car mouth) mold found in Nanyang Wafangzhuang during the Eastern Han Dynasty has a split vertical parting surface for the mold block, and a single sprue is used for the two stacks of casting molds, resulting in a higher metal yield. , the pouring time is shorter, indicating that the stack casting technology has further developed.