A Study On Processes And Properties Of Using Yunnan Local Pig Iron To Produce Compacted Graphite Iron

Compacted graphite cast iron provides high strengh and a certain toughness,better thermal conductivity,thermal fatigue resistance and good casting properties,thus easier to lightweight the thin-walled casting;At the same time,because of its lower cost of production,and little impact on the environment pollution during production process.therefore,CGI become the ideal material for high-performance diesel engine cylinder head.The process condition of CGI is very strict,the quality of pig iron has an important effect on casting quality,the foundary plant usually use benxi high-quality pig iron.In recent years,owing to the shortage and price rise of benxi pig iron,the provision of high-quality benxi pig iron cannot guaranteed.In order to solve the source of raw materials,experimental use the yunnan local pig iron to manufacture compacted graphite iron.So a study on processes and properties of using yunnan local pig iron to produce compacted graphite iron becomes the main work in this paper.This paper investigated effects of the process parameters on the microstructure and property of compacted graphite cast iron.on this basis,influence of raw material on the microstructure and property of compacted graphite cast iron has been investigated in details.At last,the study on casting properties and friction and wear properties during medium temperature scope of compacted graphite cast iron (CGI) were mainly described.Thourgh the experiment,we can draw conclusion as follows:Results indicated that residual rare earth content increased and graphite morphology gradually transition from flake to spherical with increasing the amount of vermicular agents, and tensile strength and hardness is increased. Results of experiments indicated that using yunnan local pig iron base iron can get compacted graphite cast iron which possess more ideal microstructure and property by appropriate vermicularizing process.Under the same vermicularizing process conditions, the nodular amount decreased and the percentage of vermicular graphite increased with increasing the amount of yunnan local pig iron, whereas the tensile strength and elongation decreased. Charging ratio showed dramatic influence on properties of compacted graphite cast iron,the addition of scrap improved the graphite morphology and property of compacted graphite cast iron.The friction and wear properties during medium temperature scope of CGI indicated that compared with HT250,CGI have the lower wear value and better wear resistance. The wear value of CGI decreased with increasing percentage of vermicular graphite.Therefore,for the higher vermicularity in CGI, the friction and wear value also improved.Under the certain ambient temperature,with the increase in load,the wear value of CGI increased,and each curve has a turning point,while external load below the critical point, the wear value is low.With the increasing of sliding velocity,friction coefficient of CGI first decreased and then increased.The critical sliding velocity exsited between 150～550rpm,while sliding velocity below 350rpm, the wear value decreased with the increasing of sliding velocity;Above this critical sliding velocity, the wear value increased rapidly.This subject comes form the Kunming Yunnei Power Co.Ltd research project "application of compacted graphite cast iron cylinder head on pressure charging diesel engines." What we have done made the preparation for produce compacted graphite cast iron cylinder head in large scale.