The fracture of a camshaft made of chilled cast iron,installed in a home-made Fukang car,happened only after running over a distance of 6,200 km.The fractured camshaft was received to conduct a series of failure analy...The fracture of a camshaft made of chilled cast iron,installed in a home-made Fukang car,happened only after running over a distance of 6,200 km.The fractured camshaft was received to conduct a series of failure analyses using visual inspection,SEM observation of fracture section,microstructure analysis,chemical composition analysis and hardness examination and so on,while those of CKD camshaft made by Citroēn Company in France was also simultaneously analyzed to compare the difference between them.The results showed that the fracture of the camshaft mainly results from white section in macrostructure and Ledeburite in microstructure;the crack in the fractured camshaft should be recognized to initiate at the boundary of coarser needle-like carbide and matrix,and then propagate through the transverse section.At the same time,the casting defects such as dendritic shrinkage,accumulated inclusion and initiated crack and abnormal external force might stimulate the fracture of camshaft as well.Based on failure analysis,some measures have been employed,and as a result,the fracture of home-made camshafts has been effectively prevented.展开更多
Inoculation can reduce the chill depth of a chilled iron,and therefore influence the microstructure and properties of the iron.In this paper,the effect of rare earth Lanthanun (La) on the microstructure and properties...Inoculation can reduce the chill depth of a chilled iron,and therefore influence the microstructure and properties of the iron.In this paper,the effect of rare earth Lanthanun (La) on the microstructure and properties of a chilled iron camshaft was studied.The results show that the La addition efficiently enhances the mechanical properties,yet with the unfavorable effect of decreasing the chilled depth and hardness.Moreover,La promotes graphite concentration and results in large graphite size,as well as A-type graphite.It is also found that excessive La destroys the interconnection and directivity of ledeburite.According to the experimental results,the optimum adding content of La should be no more than 0.02wt.%.展开更多
Rebuilt engine 'break-in' is the most critical period for long-term durability for a flat-tappet valvetrain.Zinc dialkyl dithio phosphate(ZDDP) has proven to be a cost-effective engine oil additive for anti-we...Rebuilt engine 'break-in' is the most critical period for long-term durability for a flat-tappet valvetrain.Zinc dialkyl dithio phosphate(ZDDP) has proven to be a cost-effective engine oil additive for anti-wear protection and oxidation resistance.But,tightening exhaust emission standards are requiring modern lubricants to have reduced levels of ZDDP additives.If the valvetrain break-in is successfully completed,then modern low-phosphorus lubricants can be used with confidence at subsequent oil change service intervals.展开更多
基金supported financially by the postdoctoral foundation from Yituo Group Co.,Ltd.,Chinathe doctoral foundation from Henan Polytechnic University,Henan,China.
文摘The fracture of a camshaft made of chilled cast iron,installed in a home-made Fukang car,happened only after running over a distance of 6,200 km.The fractured camshaft was received to conduct a series of failure analyses using visual inspection,SEM observation of fracture section,microstructure analysis,chemical composition analysis and hardness examination and so on,while those of CKD camshaft made by Citroēn Company in France was also simultaneously analyzed to compare the difference between them.The results showed that the fracture of the camshaft mainly results from white section in macrostructure and Ledeburite in microstructure;the crack in the fractured camshaft should be recognized to initiate at the boundary of coarser needle-like carbide and matrix,and then propagate through the transverse section.At the same time,the casting defects such as dendritic shrinkage,accumulated inclusion and initiated crack and abnormal external force might stimulate the fracture of camshaft as well.Based on failure analysis,some measures have been employed,and as a result,the fracture of home-made camshafts has been effectively prevented.
基金supported by the Science and Technology Project of Xi’an,China (grant No.CXY1134WL18)
文摘Inoculation can reduce the chill depth of a chilled iron,and therefore influence the microstructure and properties of the iron.In this paper,the effect of rare earth Lanthanun (La) on the microstructure and properties of a chilled iron camshaft was studied.The results show that the La addition efficiently enhances the mechanical properties,yet with the unfavorable effect of decreasing the chilled depth and hardness.Moreover,La promotes graphite concentration and results in large graphite size,as well as A-type graphite.It is also found that excessive La destroys the interconnection and directivity of ledeburite.According to the experimental results,the optimum adding content of La should be no more than 0.02wt.%.
文摘Rebuilt engine 'break-in' is the most critical period for long-term durability for a flat-tappet valvetrain.Zinc dialkyl dithio phosphate(ZDDP) has proven to be a cost-effective engine oil additive for anti-wear protection and oxidation resistance.But,tightening exhaust emission standards are requiring modern lubricants to have reduced levels of ZDDP additives.If the valvetrain break-in is successfully completed,then modern low-phosphorus lubricants can be used with confidence at subsequent oil change service intervals.
