The effect of deformation rate on the process of hot extrusion with dispensing of round hollow semi-finished products

Stamping of round hollow semi-finished products by hot reverse extrusion is one of the initial operations in the manufacture of hollow products for special purposes. The force and shape change of the metal during hot plastic forming is significantly affected by the deformation rate or the speed of movement of the deforming tool. For special-purpose products, certain mechanical properties are required in the wall height and bottom part. The wall height properties are ensured at subsequent stretching transitions with thinning of the semi-finished product obtained by hot extrusion, which involves working out the metal structure by plastic deformation to achieve the required properties. Therefore, it is an urgent task to study the effect of the deformation rate on the force and shape change of the metal during hot reverse extrusion of hollow semi-finished products.To determine the influence of the deformation rate on the parameters of hot reverse extrusion with the dispensing of hollow semi-finished products from round and square billets by means of finite element method (FEM) modeling and to compare the results of theoretical researches.Theoretical researches of extrusion power modes, specific forces, and the stress-strain state of metal were carried out by modeling using the FEM in the DEFORM software environment.The FEM was used to model the process of hot reverse extrusion with dispensing of round hollow semi-finished products from mild steel with protrusions at the end of the bottom part on the side of the cavity and on the outer surface. The deformation rate was in the range of 20 to 80 mm/sec. Round and square cross-sectional blanks were used. The dependence of the extrusion force on the punch displacement was determined. The distribution of specific forces on the deforming tool was determined. The stress-strain state and temperature distribution in the deformed metal at the end of extrusion were determined. The development of the metal structure by hot plastic deformation was evaluated and the results obtained were comparedThe effect of the deformation rate on the parameters of hot reverse extrusion with dispensing of round hollow semi-finished products was determined.