Thermal Analysis And Prediction Of Mechanical Properties Of Vermicular Graphite Cast Iron

Vermicular graphite cast iron is widely used in cylinder block and cylinder head of diesel engine because of its high strength,heat-resistant fatigue performance and good processing performance.However,with the increasing demand for engine power,the performance indicators of vermicular graphite cast iron must be further improved.However,the traditional mechanical property testing is time-consuming and laborious,which can not meet the needs of rapid test results.Therefore,the accurate and rapid detection of mechanical properties of vermicular iron parts is particularly important.At present,thermal analysis technology is the key technology for mass production of vermicular iron parts,so the rapid development of thermal analysis technology provides a new method for the rapid detection of mechanical properties.This thesis combines the production of vermicular graphite cast iron parts in Weichai Heavy Machinery Foundry to carry out experiments,and uses thermal analysis methods to combine the raw iron,vermicularizing agent,inoculant and other raw materials of the plant to conduct a large number of research tests,through linear or nonlinear.The regression method is used to predict the mechanical properties of vermicular graphite cast iron and achieve the purpose of quickly and accurately evaluating the mechanical properties of vermicular graphite iron.In addition,the effects of carbon,copper and residual magnesium content on the characteristic values of thermal analysis curves and mechanical properties were explored through experiments.Research indicates:(1)For the same brand of vermicular graphite cast iron,when the carbon content increases from 3.50%to 3.80%and the silicon content remains at 2.2%,the liquidus temperature T_L first decreases and then increases with the increase of carbon content,the eutectic minimum temperature T_EU and eutectic maximum temperature T_ER show an upward trend,and the eutectic re glow temperature?Tr gradually decreases and with the increase of carbon content,the hardness slightly increases,while the tensile strength and elastic modulus have no change.The creep rate increased slightly.(2)With the increase of copper content from 0.18% to 0.39%,liquidus temperature T_L decreases,eutectic minimum temperature T_EU and eutectic maximum temperature T_ER show an upward trend,and the mechanical properties such as tensile strength,hardness and elastic modulus are strengthened with the increase of pearlite content;with the increase of residual magnesium content from 0.012%to 0.018%,liquidus temperature T_L increases re glow temperature?Tr shows a downward trend,eutectic maximum temperature?Tr shows a downward trend.However,the tensile strength and hardness increase slightly,the elastic modulus does not change significantly,and the creep rate decreases.(3)Based on the characteristic value of thermal analysis curve,the mathematical models for predicting elastic modulus,tensile strength and hardness are established by nonlinear regression analysis method,and they all have high accuracy.Through the actual test,the prediction mathematical model meets the requirements of prediction accuracy,and can achieve the purpose of rapid prediction of mechanical properties of vermicular graphite cast iron parts.