Study On Microstructure And Properties Of As Cast High Strength And High Toughness Ductile Iron

Ductile iron is widely used due to its low cost and good mechanical properties, making it an good choice in the field of engineering machinery, automotive etc. With the development of lightweight、low cost and high performance of automotive, so the requirement for the performance of the structure (the chassis frame, the balance beam suspension) is becoming more and more strict. At present, the preparation of high strength and high toughness ductile iron is mainly realized by heat treatment, but it is very strict to the control of the production process, at the same time, the product rejection rate and the production cost are too high, therefore, it is very practical significance to prepare high strength and high toughness ductile iron in the casting state.This paper mainly through adjusting Si/C ratio, controling the content of Cu and Mo, adding modification agent GF300, Te alloy elements, compound modifier and heat remained normalizing process to changes the primary austenite transformation process of growth, adjust the content of pearlite and ferrite content, solution-strengthening ferrite, fine grain size strengthening and refining lamellar spacing of pearlite, and develop a process for the production of as cast high strength and high toughness ductile iron.Firstly, the difference of microstructure and properties of ductile iron was compared under the condition of inoculation and inoculation, the results show that the inoculation treatment can highly improve the morphology of graphite and the matrix structure, and improve the mechanical properties; Secondly, the effects of different contents of GF300 and micro alloying element Te on the microstructure and properties of nodular graphite cast iron were studied, GF300 modifier and Te have greatly improved the content of pearlite and refine lamellar spacing of pearlite, promote primary austenite in space network development, and improve the comprehensive mechanical properties of ductile iron, it is concluded that when the 0.6wt.%GF300 and X2Wt.%Te were added, the tensile strength is more than 800MPa, and the elongation is greater than or equal to 5%; Thirdly, cancel the addition of antimony, improve the content of Si, reduce the content of Cu, Mo, adding B compound modifier, which greatly promoted the increase of the content of ferrite in the matrix, the elongation rate reached 12%, but the tensile strength was only about 600MPa; finally, through the modification, alloying and heat remained normalizing processing, increase the cooling rate during solidification, adjust the content of pearlite and ferrite in the matrix, refine of pearlite lamellar spacing and develope a process for the production of as cast ductile iron with a stable tensile strength greater than 800MPa and a toughness greater than or equal to 5%.