Iron unearthed from Tieshenggou iron smelting site in Gongxian County, Henan Province in the middle and late Western Han Dynasty? Through metallographic examination, it has radial spherical graphite, and the spheroidization rate is equivalent to the first-class level of modern standards. The modern ductile iron was not successfully developed until 1947 abroad. In ancient China, the silicon content of cast iron was low for a long time, that is to say, in the Western Han Dynasty about 2,000 years ago, spherical graphite in iron products in China was obtained by softening and annealing low-silicon pig iron castings. This is a great achievement of China's ancient cast iron technology and a miracle in the world metallurgical history.

Because of its excellent performance, nodular cast iron can sometimes replace expensive cast steel and forged steel, and is widely used in machinery manufacturing. The international metallurgical industry used to think that ductile iron was invented by the British in 1947. Some western scholars even claim that it is unthinkable to invent ductile iron without modern scientific and technological means. 198 1 year, China ductile iron experts studied 5 13 pieces of ancient Han and Wei ironware unearthed by modern scientific means, and drew a conclusion through a lot of data: spherical graphite cast iron appeared in Han Dynasty in China. Related papers were read at the 18 World Congress on the History of Science and Technology, which caused a sensation in the international foundry industry and the history of science and technology. After verifying this point in 1987, international experts in metallurgical history believe that the law of softening cast iron to make nodular cast iron was explored in ancient China, which is of great significance to the re-staging of world metallurgical history.

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In 1947, H.Morrogh of Britain found that when cerium was added to gray cast iron with * * * crystals, graphite was spherical when its content was higher than 0.02wt%. In 1948, A.P.Ganganebin and others in the United States pointed out that spherical graphite was obtained by adding magnesium to cast iron and then inoculating ferrosilicon. Since then, large-scale industrial production of ductile iron has begun. As a new engineering material, nodular cast iron has an amazing development speed. 1949, the world output of ductile iron was only 50,000 tons, 1960 was 535,000 tons, 1970 increased to 5 million tons, 1980 was 7.6 million tons, and 1990 reached 9/kloc-0. In 2000, it reached150,000 tons. The production and development of nodular cast iron in industrialized countries are particularly fast. 75% of the world's ductile iron production is produced by the United States, Japan, Germany, Italy, Britain and France. The production of nodular cast iron in China started very early, and/kloc-0 was successfully developed and put into production in 950. The annual output of nodular cast iron in China is 2.3 million tons, ranking third in the world, second only to the United States and Japan. The rare earth magnesium nodulizer suitable for China's national conditions has been successfully developed, and the production technology and research work of as-cast ductile iron and austenite-bainite ductile iron have reached a high technical level.

(1) As-cast pearlitic ductile iron crankshaft and as-cast ferritic ductile iron automobile chassis parts were put into production in China No.2 Automobile Factory, Nanjing Automobile Factory and No.1 Automobile Factory respectively. This indicates that the production of as-cast ductile iron in China has reached a higher level. The adoption of technologies such as desulfurization outside the furnace, duplex melting, instantaneous inoculation, inoculation block technology, audio detection and rapid thermal analysis indicates that the gap between the technical level of mass production of automobile castings in China and the international advanced level is narrowing.

(2) The metallurgical factors of large section ductile iron (wall thickness greater than 120mm) and the corresponding production process measures were studied experimentally. Using proper amount of yttrium-based heavy rare earth composite nodulizer, forced cooling, sequential solidification, delayed inoculation and adding trace antimony and bismuth when necessary can prevent graphite distortion and loose structure in the center of ductile iron castings. At present, it is a large-scale complex structural member with a weight of 38 tons, a diesel engine block with a weight of 17.5 tons, a nodular cast iron roller with a cross section of 805mm, etc. Has been successfully manufactured.

(3) Research and application of austenite-bainite ductile iron. At the beginning of 1970s, almost at the same time, China, the United States and Finland announced that they had successfully developed austenite-bainite ductile iron with high strength and toughness (ADI for short internationally). The tensile strength of this material reaches 65,438 000 MPa, so it is widely used in gears and various structural parts. Compared with alloy steel, ADI has remarkable economic and social benefits.

(4) Ductile iron pipes and horizontal continuous casting ductile iron profiles. China has built several ductile iron pipe factories, and several ductile iron pipe factories will be built in recent years. In 2000, the annual output of centrifugal cast ductile iron pipes in China reached 900,000 tons. In addition, the horizontal continuous casting ductile iron profile production line developed in China has passed the national appraisal and has been put into production by many enterprises. Coupled with a production line imported from China, by 2002, the annual output of ductile iron profiles in China will reach tens of thousands of tons.

(5) The mechanical properties and other properties of rare earth magnesium nodular cast iron are measured systematically, which provides relevant data for designers. The specific gravity, thermal conductivity and electromagnetic properties of rare earth magnesium ductile iron were measured, and the effects of graphite and matrix structure on the properties of ductile iron were studied in combination with metallographic standards. The properties of ferritic ductile iron under normal temperature, low temperature, static and dynamic conditions were systematically measured. In addition, the stress-strain properties, small energy multi-impact resistance and fracture toughness of rare earth magnesium ductile iron were also studied and used to guide production. Combined with the application of nodular cast iron gears, the bending fatigue strength and contact fatigue strength of nodular cast iron gears, as well as the pitting corrosion and spalling mechanism of nodular cast iron gears are systematically studied. (6) Rare earth magnesium nodular cast iron. In addition to copper and molybdenum, nickel and niobium are also being studied in high strength low alloy ductile iron. Some domestic units have done a lot of systematic work in producing vanadium-titanium alloy ductile iron with natural vanadium-titanium pig iron. Although the performance of medium manganese ductile iron is not stable enough, it has achieved remarkable economic benefits in systematic research and production application.