Research on Hydroforming Defect Control of Large Diameter Stainless Steel Integral Elbow of Aerospace Engine
The large-diameter elbow is the key component of the fuel transfer system of space engine.The traditional method of stamping half-pipe reforming is difficult to meet the demand of high space utilization and high reliable transmission.In this paper,a hydroforming method of integral elbow is proposed,which uses axial feeding to adjust the axial strain state of pipe material,reduce the axial strain of inner and outer side walls,avoid the fracture defect,and improve the size limit and formability of the integral elbow.The theoretical calculation of the ideal feed amount of inner and outer side walls are 21 mm and 24 mm respectively.In the experiment,the axial feeding was promoted by improving the lubrication conditions,and the rupture defect caused by the excessive friction between the pipe material and the mold could not be effectively fed was avoided.There was deformation strengthening in the preforming of the prebending pipe,and the hardness was reduced by annealing heat treatment,the residual stress was eliminated,and the plastic deformation ability was improved.The formed 1Cr18Ni9Ti stainless steel integral elbow had a relative bending radius of 0.75,a diameter to thickness ratio of 67,a diameter of 200 mm,and a maximum thinning rate of about 31％.
integral elbowsmall bend radiusthin-wallhydroforming
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