Effects Of Material And Technological Factors On Microstructure And Processing Properties Of Compacted Graphite Cast Iron

Vermicular cast iron is a kind of cast iron materials with excellent comprehensive properties.The mechanical property of vermicular cast iron is similar to that of nodular cast iron,and the castability,earthquake resistant performance,thermal conductivity also approach those of gray cast iron.In recent years,with the deepening research,vermicular cast iron plays an irreplaceable role in the automobiles and other heavy industries.But when vermicular cast iront is machined by the existing processing production line of gray cast iron,a series of machining problems emerge,such as tool tipping,tool breakage,the machining accuracy insufficient.However,at present,there is no comprehensive research both in the domestic and overseas.In this paper,the aspects such as the charge,alternative vermiculizer category,and alloying elements that are used in the research of vermicular cast iron materials in cylinder block of YTO GROUP CORPATION is studied.The purpose is to explore the impact of the charge,vermiculizer,alloying elements and melted iron filtration on the processing properties of vermicular cast iron.In this paper,the microstructure and processing properties of vermicular cast iron under different conditions were mainly studied.The conditions included whether adding filter screen or not,vermiculizer category,standing time,adding alloying elements,different charges,.the machinability of cast irons with different tensile strength and that different cast iron categories of the same tensile strength.The tensile strength,yield strength and elongation were measured by tensile test on universal tensile testing machine repectively.Brinell hardness was measured by Brinell hardness tester.The graphite morphology and pearlite content were evaluated by optical microscope under national standard(GB).The spacing of pearlite was measured by scanning electron microscopy(SEM).Calibration and determination of cutting force were tested by dynamic and static strain gauges.Then,the influence of the charges and technological factors on the microstructure and cutting performance of vermicular graphite cast iron was analyzed.The experimental results showed that the vermicularity of vermicular cast iron are significantly improved and the organization is optimized by the addition of the filter screen.For vermicular cast iron with Z14 iron as the main charge,the hardness and tensile strength is effectively improved,the section sensitivity is reduced,the cutting force is increased slightly.While there is rarely effect on the performance of vermicular cast iron with high pure iron as the main charge.Compared to the use of the FeSi RE15Mg3 vermiculizer,the vermicular cast iron which is treated by the Fe SiRE6Mg6 vermiculizer obtains higher vermicularity and smaller section sensitivity.By using the FeSiRE15Mg3 vermiculizer,the tensile strength of the vermicular cast iron reaches 400 MPa,that with high pure iron as the main charge and treated the vermiculizer of 3-15,but the vermicularity is low.Being treated by the FeSiRE6Mg6 vermiculizer,the vermicular cast iron that with high pure iron as the main charge not only obtains higher vermicularity,but also smaller section sensitivity,and the tensile strength of it reaches 350 MPa.With the compound addition of Cu and Sn alloy elements,the section sensitivity of cast iron is significantly reduced,and the vermicular cast iron with high pure iron as the main charge obtains higher vermicularity,pearlite content,tensile strength and brinell hardness,but the cutting force also is significantly increased.While for the vermicular cast iron with Z14 iron as the main charge,it is easy to iron.Therefore,it is unsuitable to add Cu and Sn alloy elements to improve the mechanical property.With the extension of the standing time,the section sensitivity of cast iron is increased significantly,and the cutting force is decreased slightly.Vermicular cast iron,with high pure iron as the main charge,still maintains a high vermicularity over 80%,and the tensile strength reaches 330 MPa.But for the vermicular cast iron with Z14 as the main charge,it is also easy to iron.There is no strict correspondence between tensile strength and cutting force of cast iron.The tensile strength and cutting force are both influenced by the graphite morphology and content of pearlite cast iron at a certain degree.But the effect of graphite morphology on the tensile strength is more significant,and the effect of pearlite content in matrix of cast iron on cutting force is higher.The pearlite content and the pearlite spacing determine the amount of brinell hardness and are the main factor which influence the cutting force of the cast iron.There is the the same changing trend of the brinell hardness and the cutting force.