Effect Of Oxygen Content On Fatigue Properties Of Carburized Gear Steel

The oxygen content of the gear steel has an important influence on its inclusions,which in turn affects its fatigue properties.Vacuum treatment is generally used in production to control the oxygen content is below 20ppm,important gears require the oxygen content is below 15ppm,and key gears require the oxygen content is below10ppm or even lower.Therefore,it is of great significance to systematically study the effect of oxygen content on the fatigue properties of gear steels.In this thesis,the quantitative analysis of inclusions in steel with different oxygen content is studied.and the relationship between the oxygen content and the size of the largest oxide inclusions in the test steel was studied by the maximum extremum method.The fatigue properties and fatigue failure behavior of test steels with different oxygen contents were studied by the method of rotational bending fatigue test.The results showed that as the oxygen content decreases,the number of oxide inclusions per unit area is greatly reduced,mainly due to the reduction in the number of small-sized oxide inclusions?5¹0?m?,and the amount of oxide inclusions is mainly concentrated in the small-sized oxide inclusions?5¹0?m?.The maximum extremum method estimated that x_max?[O]=13ppm?,x_max?[O]=10ppm?and x_max?[O]=5ppm?were75.4?m,62.1?m,and 64.9?m respectively.The size of the largest oxide inclusions in[O]>10ppm steel is significantly increased,and the size of the largest oxide inclusions between[O]?10ppm steels is similar.Teststeelsfatiguelimitarethat:?_-1?[O]=13ppm?=993MPa??_-1?[O]=10ppm?=1029MPa??_-1?[O]=5ppm?=1020MPa,It is mainly related to the influence of oxygen content on the size of the largest oxide inclusions in steel,through the fatigue fracture,it is actually observed that,when the oxygen content is higher than10ppm,the maximum oxide inclusion size in the test steel is significantly bigger than the maximum oxide inclusion in the test steel with oxygen content lower than 10ppm,it leads to a decrease in fatigue performance,and the difference in the size of the largest oxide inclusions in the test steel with an oxygen content of less than 10 ppm is similar,and the difference in fatigue performance is similar too.Considering the production cost and performance,it is best to control the oxygen content of gear steel below 10ppm.