Effect Of Inoculation On Microstructure And Properties Of High Carbon Gray Cast Iron

As an important part of the braking system of an automobile,brake discs are crucial in the safety of automobile driving.Gray cast iron has been the main material for brake discs because of its strength,good wear resistance and thermal conductivity.The graphite in the microstructure of gray cast iron is harmful to strength and beneficial to thermal conductivity.It is of great scientific significance and practical value to solve the problem of mutual constraint between strength and thermal conductivity of gray cast iron.In this thesis,the effect of carbon content on the microstructure and properties of high-carbon gray cast iron,the effect of different inoculants on the microstructure and properties of high-carbon gray cast iron,and the effect of graphite morphological characteristics on thermal conductivity are systematically studied.The results show that: with the increase of carbon content from 3.67 wt.% to3.83 wt.%,the graphite length increases significantly,the pearlite lamellae spacing remains the same,and the number of eutectic clusters decreases;the tensile strength decreases with the increase of carbon content;the thermal conductivity has an overall tendency to increase with the increase of carbon content.Among the seven inoculants in the experimental comparison,Mn N inoculant,Cr N inoculant and silicon-strontium inoculant can significantly shorten the graphite length and increase the graphite quantity,among which Cr N inoculant has the best refinement effect,and Mn N inoculant and Cr N inoculant can also passivate the graphite tip;Mncontaining inoculant can slightly reduce the graphite length and increase the graphite bending degree;Sn-containing inoculant can increase the graphite length and improve the Sn inoculants can increase graphite length and improve graphite uniformity;siliconcalcium inoculants can reduce the number of graphite,increase graphite length and make graphite flatter;silicon-barium inoculants can increase graphite length and quantity and reduce graphite thickness.Seven kinds of inoculants have a certain refining effect on the pearlite matrix of gray cast iron,and the refining effect of pearlite lamellae spacing is better than that of ferrosilicon inoculants.Except for Sn inoculant and Mn N inoculant,the refinement effect of the other five inoculants on eutectic groups is better than that of ordinary Si Fe inoculants,and the best eutectic group refinement effect is achieved by silicon-calcium inoculants.The relationship between thermal conductivity and graphite morphological characteristics was obtained by multiple linear regression analysis: the average graphite length,graphite quantity,and graphite area were positively correlated with thermal conductivity,and the average graphite thickness and average graphite curvature were negatively correlated with thermal conductivity.The number of graphite has the greatest effect on the thermal conductivity.