Internal void closure during the forging of large cast ingots using a simulation approach

A new method of plate forging with V-shaped dies is proposed. The deformation state of a metal workpiece during forging has been investigated. The proposed method of forging increases the uniformity of the strain distribution with a high level of strain in the workpiece. The values of angles for V-shaped dies range from 120° to 140°. This range of die angles is the most rational from the standpoint of strain distribution uniformity and maximum widening. V-shaped die usage for plate forging leads to an increase in widening coefficient of 35 % in comparison with forging with flat dies. This forging technique provides the possibility of eliminating the operation of billet upsetting during plate forging. V-shaped die usage for plate forging also results in a decrease in deformation load in comparison with flat die forging. The scheme of plate forging by V-shaped dies results in the formation of an irregular compression state in the axial zone. It leads to the closing of defects during forging. The new technology of plate forging with V-shaped dies was tested under industrial conditions. The forged piece has satisfied the requirements of the customer’s technical criteria. The ultrasonic check results have shown that the application of the proposed technology provides an increase in metal continuity within the central zone of the forged piece. The experimentally derived forging results have confirmed that upsetting operations can be eliminated, and as a result, energy expenditures and the overall cycle time of the forging operation have been reduced by 15 %.

Development of a new process for forging plates using intensive plastic deformation

An integrated open-die forging centre can realize programmed incremental forging processes to improve safety and efficiency; the centre consists of a forging press and one or two heavy-duty manipulators. This paper focuses on the coordinated kinematic modelling of the integrated system. First a newly designed serial—parallel forging manipulator is presented and the closed-form inverse kinematic solution is derived based on homogeneous co-ordinate transformation. Then the deformation of the forged workpiece is investigated by the spread coefficient method of plastic deformation theory, and the relation between the motion of the holding end of the workpiece and the movement of the upper die is formulated. Finally, the coordinated kinematic modelling of the integrated system is established, where the press and the manipulator are coordinated in movement. Simulation of a typical open-die forging process shows that the gripper of the manipulator should have good compliance abilities in horizontal and v...

Coordinated kinematic modelling for motion planning of heavy-duty manipulators in an integrated open-die forging centre

A new manufacturing approach has been developed, which applies energy-saving processes for forging parts from ingots with convex dies without the need for upsetting the ingots. A new forging process provides a complete closing of an ingot’s axial defects. It has been established that an increase in convex die wedge angle and an increase in the degree of reduction result in the linear growth of (a) the level of compressive stress and (b) the intensity of the axial defect closure. The rounding of a “four-beam” workpiece with concave cross-section using flat dies leads to a decrease in deformation force by a factor of 1.5–3.0 times in comparison with rounding using cut dies. The effective geometric shapes of die tooling and efficient process parameters have been determined. The convex die angle has to be in the range of 160–170°. The depth of the concavity faces has to be on the order of 25 %. The tool for rounding has to be in the shape of flat dies. The method of workpiece positioning in the dies has to be “edgeways.” A new process for forging large shafts with a 2000-mm diameter using convex dies without an upsetting operation has been proposed, reported, verified, and industrially implemented. Industrial implementation of this new technology resulted in an increase in forging process productivity of 15–20 % and a decrease in heating number from 8 to 6 during the forging of large parts. Research results in the form of process and design recommendations have been successfully validated and implemented at a metal forming industrial workplace.

A new process for forging shafts with convex dies. Research into the stressed state

Hot compression tests on a newly designed hot extrusion Nickel-based powder metallurgy superalloy are conducted at various deformation conditions. The contact friction coefficient (f) between the die and forged part is determined as 0.30–0.40 by analyzing the results of simulation and the real experiment. A new coefficient B is introduced to evaluate the bulging levels and relate the value of f. The critical strains to prevent peripheral cracks are found to relate closely to the processing parameters. Thermally induced porosity and MC type carbides of grain boundaries are the primary mechanism for inducing cracks. Examinations on microstructure of cracking demonstrate that the cracks propagate along grain boundaries. A model is proposed to illustrate the formation of fractures during hot forging.

S.K. Choi

Papers

Optimization of open die forging of round shapes using FEM analysis