The Effects Upon The Structure Property Of The Think Section Ductile Iron Through Spheroidizing And Inoculation

Reasonable control of spheroidizing process is the key to the excellent micro structure shape and mechanical properties of heavy section ductile iron castings.However,in the actual production,it is not the same for technical characteristics and production processes according to different technical requirements of nodular iron castings production.The micro structure and mechanical properties of heavy section ductile iron castings are difficult to reach the design requirements.In this paper,production test and microstructure analysis were done,chemical composition of heavy section ductile iron castings,the production of electric furnace smelting process,the production of raw materials,such as pig iron,scrap steel,were stuied,carburizing agent technology was used,some problem as lower spheroidization rate,pearlite content,small hard particles and correspondence spheroidization and inoculation process of heavy section ductile iron by the electric furnace smelting production were studied.Light,heavy and hybrid rare earth were designed,cancel the stream inoculation and stream inoculation and spheroidizing inoculation test scheme were used,spectroscopy and ICP were used to analyze the chemical composition of casting single cast test block and a body attached test block,graphite morphology,size of graphite ball was observed by using optical comparative analysis of metallographic microscope,nodularity,ferrite and pearlite content map,microcomputer control electronic universal testing machine was used to test the tensile strength and elongation stress properties,scanning electron microscope(SEM)was used to analysis sample fracture morphology,the results was expected for the development of heavy section ductile iron casting scheme to control the organization performance and provide a theoretical basis.For the stabilization of heavy section ductile iron castings metallographic structure,mechanical properties and improving the graphite morphology,chemical composition for the theory of production of heavy section ductile iron castings was designed as the actual standard ingredients,electric furnace smelting production,raw material feeding in the furnace in order of pig iron,scrap steel,manganese,iron,carbon,ferrosilicon based on analysis microstructure characteristics and mechanical properties of specimens and the fracture surfaces,it is found to cancel the stream inoculation,the body block nodulizing grade,graphite size control is not stable,the mechanical properties significantly,control level and stable chemical composition of matrix structure,tensile strength,elongation and other mechanical properties and chemical composition and related.YFY-1A,SPI stream inoculation,the body block nodulizing is 2-3 grade,graphite size is controlled in the 6 level,compared with cancel the stream inoculation,inoculation fade effect slows,ductile iron body test of tensile strength and elongation block raise,causes the improvement of mechanical properties mainly lies in:Y,La,Ce rare earth oxide inclusions less,resulting in the transgranular fracture tendency of the sample.From graphite crystal core and graphite morphology,main factors causing graphite distortion were discussed under the spheroidization and inoculation treatment conditions,it is found to cancel the stream inoculation,sulfide content in the electric furnace smelting iron liquid with low,which did not become crystalline core graphite,mixed rare-earth nodulizer,good graphite morphology can be obtained,at the same time with strong anti graphite recession capacity,the casting body is small,round,uniform spherical graphite,and it is the main reason of graphite distortion,such as Ti,Cu elements segregation and nodularizing elements Mg or rare earth(Y,La,Ce)oxidation,destruction of the austenite shell stability.