Study On The Hardness Uniformity Of Casting Surface Of Large Diesel Engine Cylinders

When high-strength large-scale diesel engine gray cast iron cylinders were produced using medium-frequency induction furnaces,it was found that there was a problem of large hardness difference in the surface of the castings.In the past,this problem was solved by adopting a low-alloying method.This article is based on the case of adding only manganese alloys.Through the use of new inoculants,changing gestation methods,rationalizing the ratio of ingredients,adding non-alloying elements and other technological methods to improve the microstructure of the castings,in order to find a best way to solve the problem of large surface hardness differences of large diesel engine cylinder castings.Through a series of experimental studies,it can be concluded that adding a certain amount of recarburizer and silicon carbide together without changing the carbon equivalent can not only change the morphology of the graphite,but also improve the content of pearlite in the matrix.Can improve the mechanical properties of the cylinder castings,while greatly reducing the pearlite spacing,thereby reducing the casting surface hardness.This experiment focuses on the adjustment of the ratio of the two to choose the best ratio.In this paper,the content of Mn was adjusted to change the graphite morphology and pearlite content in the matrix.The result revealed that the properties and the surface hardness uniformity of the cylinder were optimal when the content of Mn.Due to the large tonnage and thicker wall thickness of the large-scale diesel engine blocks,the amount of hot metal needed is large,and the traditional FeSi-75 inoculation will easily lead to recession.The graphite shape of the castings is poor and the overall performance is low.Therefore,to strengthen the gestation effect can change the graphite morphology,pearlite spacing,the number of eutectic groups,casting surface hardness difference.This article through the addition of different types of inoculants,the experimental comparison of the best inoculants.There has also been a major improvement in the method of gestation,using a combined gestation method that involves inoculation and inoculation.Traditional methods of gestation use the flushing method.This gestation method has the obvious disadvantage that the inoculant burns very badly in molten iron and is very unstable.The use of inoculation method has strict control over the treatment temperature,less burning,less inoculants used,stable gestation effect.At the same time,in view of the characteristics of large wall thickness and slow cooling of large-size cylinder castings,a compound inoculation method was adopted that combines inflow and inoculation with inoculation and inoculation.By comparing these three inoculation methods,graphite morphology,pearlite spacing,and total.Finally determine the best way of gestation.