Effect Of Si,Cu,and V On Thermal Conductivity And Thermal Conductivity Mechanism Of Vermicular Cast Iron Matrix Alloy

Vermicular graphite cast iron has the strength and toughness of ductile iron and thermal conductivity of gray iron,so it is widely used in the manufacture of internal combustion engine,cylinder block,cylinder head,cylinder liner,ingot mold and other products.These components are subjected to high thermal and mechanical loads due to their high temperature service conditions.The high thermal conductivity can effectively improve the cooling efficiency of the cooling system,reduce the thermal stress,and improve the working performance and service life of components.Therefore,it is necessary to study in depth how to improve the thermal conductivity of vermicular graphite cast iron.At present,the study found that the morphology of graphite,the orientation of graphite and the connectivity of graphite affect the mechanism of thermal conductivity on vermicular graphite cast iron,and there are fewer research papers about the effect of microstructure on thermal conductivity of vermicular graphite cast iron.The purpose of this paper is to study the influence of elements Si,Cu and V on the thermal conductivity of vermicular graphite cast iron matrix.The metal matrix composition of vermicular graphite cast iron was obtained by EDS energy spectrum analysis and Pandat software phase diagram calculation of serving cylinder heads,and vacuum arc melting was used to produce Fe-x Si-0.9Cu-0.6C-0.1Mn-0.05V(x=1.2wt%,1.5wt%,1.8wt%,2.1wt%),Fe-1.8Si-y Cu-0.6C-0.1 Mn-0.05V(y=0.6wt%,0.9wt%,1.2wt%,1.5wt%)and Fe-1.8Si-0.9Cu-0.6C-0.1Mn-z V(z=0.02wt%,0.05wt%,0.08wt%,0.1wt%)alloys.The alloy ingot prepared by vacuum arc smelting was annealed,and the annealing process was 930?+2h.The matrix microstructures were analyzed and characterized using X-ray diffractometer(XRD),optical microscope(OM),scanning electron microscope(SEM),transmission electron microscope(TEM),and energy spectrum analysis(EDS),and the thermal diffusion coefficients at different temperatures were measured by laser thermal conductivity(TA DLF-1200).The effect of Si,Cu and V on thermal conductivity of vermicular graphite cast iron matrix was studied.The main results of the study are as follows:(1)The pearlite gradually decreases as with the increment of Si.When the Si content was1.2% to 1.5%,the pearlite content was reduced from 60.1% to 51%,and as the Si content was further increased,the pearlite change was not obvious,and 2.1% Si changed to 48.7%.The Si content increased from 1.5% to 2.1%,and lamellar spacing of pearlite firstly increases and then decrease.The lamellar spacing of pearlite with Si content of 1.8% is the smallest.When Si content increases from 1.8% to 2.1%,the lamellar spacing of pearlite increases by 0.1?m.The thermal conductivity decreases first and then increases with the increase of Si content.The addition of Si is 1.8% and the thermal conductivity is the lowest.At 100 ° C,the Si content increased from 1.2%to 1.8%,and the thermal conductivity was reduced from 23.58 W/(m·k)to 20.48 W/(m·k),a decrease of 15.36%.(2)The pearlite increases firstly and then decreases with the increment of Cu.Cu content is0.6%,pearlite content is 56%.When the Cu content increases to 0.9%,the content of pearlite decreases to 58%,and when Cu content is increased from 1.2% to 1.5%,the pearlite content is57.6% and 57%,respectively.The Cu content increases,and the heating coefficients are reduced first and then increased.The Cu content is 0.9%,and the thermal conductivity is the lowest.At100?,Cu content increases from 0.9% to 1.5%,and thermal conductivity increases from 22.13W/(m·k)to 26.92 W/(m·k),an increase of 21.6%.(3)The pearlite decreases firstly and then increases with the increment of V.When V content is 0.05%,pearlite content is 50.8%.When V content increased to 0.08% and 0.1%,pearlite content increased to 55% and 56.4%,respectively.When V content is 0.05%,the thermal conductivity coefficient is the highest.At 100?,when the V content increases from 0.02% to0.05%,the thermal conductivity increases from 18.96 W/(m·k)to 21.41W/(m·k),an increase of12.9%.(4)Compare the effects of different Si,Cu,V on thermal conductivity,Fe-1.8si-1.5Cu-0.05V-C-Mn has the best thermal conductivity,and the thermal diffusion coefficient and the thermal conductivity are the largest.When the content of V is 0.05% by the content of Cu by1.5%,the thermal conductivity of 100? increases from 21.41W/(m·k)to 25.84W/(m·k),an increase of 20.69%.