Study On Microstructure And Properties Of As-cast Ferrite Nodular Iron In Solid Solution Of Silicon

In this paper,the control of ductile cast iron Si content between 2.5%～4.1%,mainly studied with the change of Si content,microstructure of as-cast ferritic nodular cast iron,the mechanical properties and strengthening and deformation behavior of ferritic matrix.The effect of Si on the microstructure and mechanical properties of as-cast ferritic ductile iron was studied by observing the microstructure,mechanical properties and low temperature impact toughness tests of as-cast ferritic ductile iron with different Si content.On this basis,EDS energy spectrum analysis,X-ray diffraction analysis,microhardness test and other experiments were used to study the distribution of Si in ferrite matrix and the mechanism of solid solution strengthening of ferrite.The main conclusions are as follows:(1)When the Si content of ductile iron changes between 2.56%～2.62%,the mechanical properties of as-cast ferrite nodular iron mainly by the relative content of ferrite and pearlite matrix and graphite morphology influence of the organization.When the graphite form is basically the same,the tensile strength and yield strength of ductile iron increase with the increase of pearlite content,but the elongation decreases.On the contrary,with the increase of ferrite content and the decrease of pearlite content,the elongation of ductile iron increases,and the tensile strength and yield strength decrease.With the increase of graphite nodularity and graphite quantity,the mechanical properties of ductile iron are improved.(2)When the Si content in 2.58%～4.06%,with the increase of Si content,as-cast ferrite ductile iron of ferritic matrix organization keeps increasing,the pearlite gradually reduce,when the Si content reaches 3.56%,the content of ferrite matrix organization of97%,when Si content is 4.06%,The matrix structure of ductile iron is all ferrite.With the increase of Si content,the morphology of graphite spheres in ductile iron was further improved,and the graphite spheres became finer and more uniform.When the Si content increased from 2.58% to 4.06%,the number of graphite spheres increased from25 to 146 mm squared,and the diameter of graphite spheres decreased from 70 um to28um.The graphite spheroidization rate increased from 87.6% to 96.1%.(3)When the Si content is in the range of 2.58%～4.06%,the tensile strength,yield strength and yield ratio of as Cast Ferritic Ductile Iron increase gradually with the increase of Si content,and the elongation first increases and then decreases.When Si content is 2.58%,the tensile strength,yield strength,yield ratio and elongation of ductile iron are 467 mpa,355mpa,0.76 and 16.8%;when Si content is 3.56%,the tensile strength,yield strength,yield ratio and elongation are 580 mpa,469mpa,0.80 and 18.7%;when Si content is 4.06%,the tensile strength,yield strength and yield ratio are 626 mpa,509mpa and 0.81 respectively The elongation can reach 17.4%.(4)When the Si content in 2.58%～4.06%,with the increase of Si content,as-cast ferrite ductile iron gradually decreases,the impact toughness of ductile to brittle transition temperature increased.When the content of Si is 2.58%,the impact energy of ductile iron at room temperature without notch is 144.6J,and the ductile brittle transition temperature is about-60℃～-40℃.When the content of Si is increased to3.56%,the impact energy of ductile iron at room temperature without notch is 39.7J,and the ductile brittle transition temperature is about-20℃～0℃.When the content of Si is further increased to 4.06%,The impact energy of ductile iron at room temperature without notch is only 16.0J,and the ductile brittle transition temperature is about 0℃～20℃.(5)The Si of ferritic matrix has a strong solid solution strengthening effect,when the Si content in 2.58% ～ 4.06%,with the increase of Si content,as-cast ferrite ductile iron ferrite group significantly higher microhardness,lattice constant of ferritic matrix is reduced,the lattice distortion increase.When the Si content increases from 2.58% to4.06%,the lattice constant of ferrite decreases by 0.067%,and the microhardness of ferrite matrix increases by 54.2HV.