Foreign R & D
Some foundry companies such as GF, Fiat and FCD have established enterprise standards and started to produce high strength and high toughness ductile iron.
1.1 FCD of Japan
The properties of high strength and high plasticity pearlitic ductile iron developed by FCD company of Japan are compared with those of original ductile iron. Fcd450a is a ductile iron with ferrite matrix, and its tensile strength is only 450 MPa; Fcd800 is a nodular cast iron with pearlite matrix, and its elongation is only 2%; Although fcad900 has excellent comprehensive performance, it is obtained by means of isothermal quenching heat treatment, which is difficult to process, high cost and difficult to popularize. D80as is a pearlitic ductile iron with high strength and high plasticity. High strength (700 ~ 820 MPa) and high plasticity (elongation 7% ~ 12%) can be obtained without heat treatment (or low cost heat treatment).
1.2 GF Switzerland
According to the enterprise standard of GF company, sibodur 700-10 and sibodur 800-5 belong to high strength and high plasticity pearlitic ductile iron. The properties of sibodur500 are: yield strength 330 ~ 360 MPa (average 345mpa), tensile strength 500 ~ 560 MPa (average 533 MPa), elongation 11% ~ 15% (average 12.8%), hardness 170 ~ 200 HB (average 186 HB); The volume fraction of pearlite is 50% ~ 59%. It is a kind of high strength and high plasticity ductile iron strengthened by weak solution and a little alloy.
1.3 Fiat, Italy
According to Fiat ductile iron standard, gh75-45-05 and gh90-52-05 belong to high strength and high plasticity pearlitic ductile iron. According to Fiat’s ductile iron standard, the performance indexes of both ferrite based and pearlite based ductile iron are higher than European standards and international standards. Fiat’s high-performance ductile iron obtains high spheroidization rate, high graphite number and stronger matrix structure through strict process control.
Domestic R & D
Some domestic foundry enterprises also began to develop or produce high strength and high plasticity pearlitic ductile iron
(1) High purity pig iron and Cu Mn alloying were used in Beijing Feimeite Xieli Foundry Co., Ltd. the as cast tensile strength, yield strength and elongation of ductile iron were 801 ~ 853 MPa, 494 ~ 542 MPa and 5% ~ 9.5%, respectively, which met the requirements of qt800-5.
(2) Shanghai shengdman Foundry Co., Ltd. used low S liquid iron, Cu alloying and low Mg nodularizing agent to produce car crankshaft in shell mold and shot back mold. The as cast tensile strength of nodular iron reached 810 ~ 840 MPa and the elongation was 5% ~ 7%.
(3) Guangxi Yuchai Machinery Co., Ltd. trial produced nodular cast iron crankshaft by adopting sand coated iron mold process, Cu alloying and multiple inoculation. Its as cast tensile strength is 862 ~ 879 MPa and elongation is 6.1% ~ 7.3%.
In addition, Nantong Tangchen, Shandong Tianrun, Henan Changge Fuxing, Dongfeng Group and other enterprises use them to produce auto parts, and Henan Luoyang, Jiangxi Pingxiang, Jiangsu Suzhou and other enterprises use them to produce or trial produce high-speed rail parts.
There is no standard of high strength and high plasticity ductile iron in China, and the brands of various enterprises are not the same. Experts from China Foundry Association are actively collecting data and working with relevant enterprises to formulate the group standard of high strength and high plasticity ductile iron.