Research of power parameters of the low-waste draftless hot die forging process on the basis of the combined strain pattern of "expansion-extrusion"

This paper presents a continuation of the topic on the development of technology for low-waste draftless hot die forging of axisymmetric parts, particularly weld neck flanges, based on the “expansion-extrusion” strain pattern. The present article derives the general function of the process` power parameters based on previous works, dedicated to determining the boundary conditions and the kinematic characteristics of the operation. Based on the conditions and strain pattern, a torus coordinate system is accepted. The derivation of general function is carried out according to the method of A.L. Vorontsov. Since the process is axisymmetric, the plane stress state of the strain zone is considered. Presented mathematical model is designed to provide an upper estimate of the strain force, which is linked with the necessity of performing technological calculations at production site. This paper also presents a modeling according to a new strain pattern in order to qualitatively evaluate the plastic flow of the material. Based on the modeling results, the practical applicability of the method in practice is proved, which confirms the previous assumptions as well. The graphic of forging force dependence on the motion is also considered. In this particular case, the graphic has a dome shape due to a change in the contact area of the working tool with the work piece. In order to obtain a more accurate picture of the strain process, a laboratory experiment has been carried out on the basis of the laboratory of the Machines and Processes of Pressure Metal Working Department using the hydraulic unit VZHM-2M (ВЖМ-2М), lead material grade S2C GOST 3778-98. The hydraulic unit VZHM-2M is characterized by the convenient implementation and reasonable force. This experiment gave positive results, thereby confirming the modeling with the use of the finite element method. In order to completely verify the correctness of the mathematical model, a non-full factorial experiment is planned. A package of design and technological documentation is developed, at the current project stage the equipment is being manufactured at the “REC Mashinostroyeniye”. Development of an experimental batch of flanges at the LLC “Chelyabinsk Tractor Plant (ChTZ) - UralTruck” on a dimension type with a nominal diameter D50 is also planned.