Study On Rolling Wear Property Of Vermicular Cast Iron With Different Vermicularity

Heavy vehicles play an increasingly important role in national economy, and the demand is increasing.Modern diesel engine requires high power,light weight,and small volume.Vermicular cast iron with excellent casting performance and high mechanical performance, can fully satisfy the using requirements of complex and the uneven thickness of engine cylinder block.In the working process of engine,the surface of kinematic pair occur friction phenomenon,among them the wear form of cylinder block and cylinder head is complex,which belongs to the composite roll sliding wear form.So it is especially meaningful to explore roll wear performance of vermicular cast iron.The shape of diesel engine cylinder block and cylinder head is complex,which is not the same as the wall thickness. In the process of casting,cooling speed of cylinder block and cylinder head is different,which get different vermicularity. At present it is not much for the research reported for rolling wear property of vermicular cast iron,especially vermicularity as an influencing factors.So it is of a certain practical significance to research rolling wear property of vermicular cast iron.In this paper,it had been studied for micro-structure and mechanical property of vermicular cast iron with different vermicularity,and rolling wear property under the condition of dry friction and oil lubrication.The main results are as follows:1.when the vermicularity increased,vermicular graphite distributed more homogeneous.With the increase of vermicularity,the tensile strength,elongation and hardness of vermicular cast iron declined linearly.Compacted graphite iron with vermicularity 60% had tensile strength of 513 MPa, the elongation of 4% and the hardness of 272 HB.Compacted graphite iron with vermicularity 90% had tensile strength of 452 MPa, the elongation of 1% and the hardness of 239 HB.Nodular cast iron had tensile strength of 547 MPa, the elongation of 4% and the hardness of 280 HB.2.With the increase of vermicularity,the mass lose of compacted graphite iron grew rapidly.Under 400 N load,the mass lose of compacted graphite iron withvermicularity 60% and 90% had a difference of 6.6%.Under high load of 1000 N,the mass lose of compacted graphite iron with vermicularity 60% and 90% had a difference of 17.3%.Under a bad working conditions,vermicularity had a greater effect on rolling wear property of compacted graphite iron.3.Under the condition of dry friction, with the increase of vermicularity,the mass lose of compacted graphite iron grew rapidly within a certain range.Under 400 N load,the mass lose of compacted graphite iron with vermicularity 60% and 90% had a difference of 7.2%.Under high load of 1000 N,the mass lose of compacted graphite iron with vermicularity 60% and 90% had a difference of 3.9%.Under a bad working conditions of dry friction,vermicularity had a lower effect on rolling wear property of compacted graphite iron.4.With the increase of vermicularity, the hardness and wear resistance of compacted graphite iron declined linearly.Compacted graphite iron with low vermicularity was close to nodular cast iron.On the contrary,compacted graphite iron with high vermicularity was close to gray cast iron.The mass lose of nodular cast iron was the smallest,which was about 77.8% of compacted graphite iron.The mass lose of gray cast iron was the biggest,which was 2.7 times as much as compacted graphite iron. The flake graphite of gray cast iron appears micro cracks.5.Although vermicular graphite had self-lubricating function, which was broken under cyclic contact stress due to the low hardness, surface fatigue crack source was formed.The surface fatigue wear and delamination damage were the main rolling wear mechanism of vermicular cast iron. Hollows appeared on the wear surface, since layer structure had split away from the surface.A large amount of heat generated in the friction process had an effect on the function of lubrication.