According to the hardness,the tooth surface can be divided into soft tooth surface and hard tooth surface.The bearing capacity of gear with soft tooth surface is low,but it is easy to manufacture,and it runs well.It is mostly used in general machinery with no strict limit on transmission size and weight,as well as in small quantity production.Because the paired gear,the small wheel burden is heavier,so in order to make the working life of the large and small gears roughly equal,the tooth surface hardness is generally higher than that of the large wheel.Hard tooth surface gear bearing capacity is high,it is in the gear after cutting,then quenching,surface quenching or carburizing quenching treatment,in order to improve the hardness.But in the heat treatment,the gear will inevitably produce deformation,so after the heat treatment must be grinding,grinding or fine cutting,in order to eliminate the error caused by deformation,improve the accuracy of the gear.The steel commonly used for making gears is quenched steel,quenched steel,carburized quenched steel and nitriding steel.Cast steel has a slightly lower strength than forged steel and is often used in larger gears.The mechanical properties of gray cast iron are poor,which can be used in open gear transmission under light load.Ductile iron can partly replace steel to make gear;Plastic gear is used for light load and low noise requirements,and its matching gear is generally good thermal conductivity of steel gear.

The temperature field and flow field of gear chamber die casting were simulated numerically

The temperature field and flow field of the gear chamber die casting were numerically simulated.The variability of the process was evaluated by statistical analysis,and the law of casting defects was obtained quickly.On this basis,process optimization and quality control measures are put forward,and the results show that the voids in castings are greatly reduced and the expected results are achieved.

The size and structure of the gearbox are large and complex.For the processing surface,some parts are not allowed to have holes,and some parts are allowed to disperse holes,but there is a certain size limit;In some key parts of casting,the size and distribution of holes are required to meet the corresponding inspection standard.Therefore,for this kind of casting,the difficulty of design and production is increased,casting process design is often difficult to take into account the requirements of different parts of this kind of casting,production process adjustable range is often very narrow.In actual production,the existence,size and distribution of hole defects in key parts of castings are the main reasons for casting abandonment.The defect parts were intercepted and observed by scanning electron microscopy(SEM).It was found that some of the pore walls were rough and dendritic.At high magnification,the bottom of the pore could be seen to be connected with each other.Some of the pore wall is smooth,and the hole is deep,with the characteristics of stomatal defects;Other holes are porosity and porosity(porosity)connected together.