Effect Of Te And B On Microstructure And Properties Of High Strength Ductile Cast Iron

Ductile iron is widely used due to its high strength,high toughness and low cost,making it a good choice in the field of engineering machinery,shipping,automotive etc.With the development of lightweight,high performance and low cost of automotive.The current nodular cast iron has been gradually dissatisfied the needs of industry.At present,the preparation of high strength and high toughness ductile iron is mainly realized by heat treatment,but 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 studies the micro alloying elements Te,B and its composite on microstructure and mechanical properties of ductile iron.The initial realization of the performance requirements of QT700-10 ductile iron which the component is optimized by adding appropriate amount of micro alloying elements Te and B.;On this basis,the effect of alloying elements Mo and nano TiC is studied on microstructure and properties of the ductile cast iron,so that it is the realization of stable production of ductile iron QT700-10.The main results of this paper are as follows:1.The effects of alloying elements Te and B on the microstructure and properties of ductile cast iron:When the Te content increased,the spheroidization of graphite increases first and then decreases,and the pearlite content is gradually decreased.T The change trend of tensile strength of ductile iron increases first and then decreases,while elongation increases continuously.The best mechanical properties of nodular cast iron which tensile strength is 764MPa,elongation rate is 7.20%when the optimized Te content is 0.001 lwt.%;Adding Te fixed the content,the spheroidization of graphite increases first and then decreases and the pearlite content is gradually decreased with the increase of B content.The tensile strength of ductile cast iron decreases continuously,while the elongation increases.When the content of B is 0.001 wt.%,the tensile strength of nodular cast iron is 711MPa,and the elongation is 12.28%.2.The influence of nano TiC on the structure and properties of nodular cast iron was investigated.The inclusion of 0.02wt.%TiC-Al master alloy has little effect on graphite,but the content of pearlite decreases.As the result,tensile strength decreases and elongation increases.The addition of 0.02wt.%TiC-Cu master alloy has little effect on graphite,but the pearlite content increases,and the interlamellar spacing is small.As the result,the tensile strength and elongation increase.When the 0.02wt.%TiC-Cu master alloy is added,the tensile strength of ductile cast iron is 715MPa,and the elongation is 10.6%,which meets the requirement of performance index of dutile cast iron QT700-10.3.The relationship between tensile properties and microstructure of nodular cast iron was investigated,and the microstructure which achieves the goal of nodular cast iron QT700-10 must meet the following conditions:When the spheroidization rate is at the level of 1,the pearlite content is 35%?45%,the ferrite content is 55%?65%,and the pearlite lamellar spacing is about 240nm at this time;when the spheroidization rate is at the level of 2?3,the pearlite content is 45%?55%,and the ferrite content is 45%?55%.At this time,the interlamellar spacing is less than 220nm;When the spheroidization rate is at the level of 4-5,the pearlite content is 50%-65%,and the ferrite content is 35%-50%.At this time,not only the lamellar spacing of pearlite is less than 220nm,but also the form of pearlite is combined so that the toughness is improved.