Papers by Keyword: Die Forging

Abstract: Isothermal forging is a common method for manufacturing titanium alloys, but it involves complex processes and equipment. The oxidation of titanium leads to the formation of an alpha-case, which in turn promotes increased crack formation. To prevent this, inert gas is typically required. However, by encapsulating the titanium billet (Ti-6Al-4V) in a steel casing made of AISI 316L, a quasi-isothermal process can be achieved without the need for inert gas. This method maintains protection against oxidation while simultaneously reducing cooling. The sealing of the capsules is crucial to ensure that the titanium is effectively enclosed and protected from the surrounding gases. In this study, various encapsulation methods are compared, including rotary friction welding, diffusion bonding, and press-fitting a lid with an interference fit. The investigation involves differing contact conditions between the titanium and steel sleeve, as well as steel wall thicknesses of 2 mm and 4 mm. These factors showed no impact on the material flow or microstructure of the formed components. Encapsulation can prevent the formation of an alpha-case. Intermetallics form between the titanium and the steel capsule, depending on the contact conditions. The use of graphite as a separating agent prevents the formation of them.

Abstract: Due to increasing product requirements regarding lightweight, functional integration and resource efficiency, research into and use of hybrid parts are steadily increasing. Tailored Forming provides an innovative process chain for manufacturing hybrid parts by using pre-joined semi-finished products. In addition to the potentials, however, challenges also result in the production of hybrid components. In particular, the material combination of steel and aluminium is demanding due to strongly differing physical properties. An inhomogeneous temperature distribution within the pre-joined semi-finished part can be used to equalize flow properties during the forming process. However, processes are sensitive to temperature deviations resulting in critical stresses and failure of the final part. This study focuses on a process design of a hybrid bearing bushing consisting of the aluminium alloy EN-AW-6082 and the steel 100Cr6 using numerical simulation. First, a closed-die forging process is analysed regarding sensitivity to process fluctuations resulting in deviations in temperature distribution. To increase process stability, a new hollow forward-impact extrusion process is numerically designed and investigated regarding its potential to reduce critical stresses and thus the risk of part failure. Furthermore, a numerical model of inductive heating is used for the consideration of inhomogeneous temperature fields. Finally, hybrid bearing bushings are produced using closed-die forging and hollow-forward extrusion to evaluate numerical results.

Abstract: In this paper, based on the finite element (FE) software Deform 3D, the simulation of the die forging process of a high pressure valve body was conducted. The deformation field and the metal flow field of billet were obtained and analyzed in detail. In addition, the effect of upsetting depth on the die forging process of high pressure valve body was also discussed. This study can provide a good guide for the following researches and practical industry.

Abstract: In view of large load, the shape of large crank forgings and forging process are designed reasonably. Large crank forging process is simulated by numerical simulation software DEFORM-3D to improve the forging process and the dies, including adding upsetting step and related dies. The result shows that improved process and dies can obtain higher quality finish forgings and the load reduces to a rational level, which provides basis for crank forging process and die design.

Abstract: In the SFB 692 HALS (High-strength aluminum based lightweight materials for safety components), subproject B-3, the production of an aluminum magnesium compound by a hydrostatic co-extrusion process was investigated. The quality of these semi-finished products, especially the stability and robustness of the interface between the aluminum (AlMgSi1) sleeve and magnesium (AZ31) core, was of particular interest. Previous papers have described the first process optimization steps as the improvement of the die design as well as the numerical methods for identification of important process parameters and the development of a quality model for the interface. This paper describes the formability of such semi-finished products with subsequent forging processes, especially die forging. Therefore, two different die forging strategies were investigated. In the first approach the strand-shaped work piece, with a circular cross-section, was formed along its longitudinal axis with die forging. In the second approach the same geometry was radially formed with die forging. Thereby, the compound was formed in longitudinal direction up to an analytical equivalent strain value of 1.61 and in radial direction up to 1.38. First results showed that the interface of the aluminum magnesium compound is very stable and ductile enough to be forged. Dye penetration tests were performed to prove the stability of the interface in a first step. Then, micro sections were made to investigate the interface metallographically. No cracks or damages were detected with both test methods in the interface of the forged aluminum magnesium compound. Furthermore, numerical simulations were performed to analyze the forging processes in detail. Therefore, a full 3D simulation model was set-up with Forge2011 and the calibration was performed with the press force as well as the geometry aspects. The correlations between experiments and simulations are very well. By means of the calibrated simulation detailed analyses of interface section are performed and the stability of the interface was investigated. This shows that the compound quality reached by the hydrostatic co-extrusion process is very suitable for subsequent forming steps as die forging. The investigations show the potential of such hybrid compounds and clarify their application, especially in the automotive sector.

Abstract: In this paper, the multi-stage die forging process of a high pressure valve bonnet was simulated by 3D coupled thermal-mechanical rigid-viscoplastic finite element (FE) method. The deformation and the metal flow field of billet were obtained. Based on the simulation, two optimized schemes were put forward for improving the yield. Both of them can save material and ensure the stability of billet during the forging process. The study can provide scientific theory foundation for practical engineering applications.

Abstract: Technological processes such as forging, die forging, pile driving, etc., are realized as a result of a collision between two bodies. The bodies’ rebound after the collision takes place due to the use of part of the energy of the hit for their elastic deformation. The paper presents results from an experimental research on the possibilities of the decrease of rebound, by the use of an additional force during the hit. A laboratory test-stand is described in which an additional force is created by the use of a cold rocket engine, working with compressed air.

Abstract: The article showed procedure of forging technological flow design modification of real component “fork”, with using of computer simulation. By using of the primary technological process at production was produced failure forgings, checking simulation showed incorrect material flow in filling of die cavity, and therefore it was needed to raw part design modifications. These modifications were suggested on base results obtained from simulation, the results were abolition of defects, resolution of problem and correctness verification of final forging technological flow.

Abstract: The finite element method has been extensively used to predict forming difficulties of die forging problems. However, the analysis for die forging problems with finite element method can lose considerable accuracy due to severely distortional meshes. Based on the equality of elements, an automatically coupling algorithm has been proposed to analyze die forging problems, which converts the FE analysis into the EFG computation to preserve the accuracy in the region where meshes have been severely distorted and still employs the FE method to ensure high computational efficiency in the region where the quality of the FE meshes is acceptable. Numerical example shows that the present algorithms exploit the respective advantages of both the FE method whose computational efficiency is high and the EFG method which can throws out mesh distortions.

Abstract: Employing the dies for aluminum alloy parts, the hot die-forging forming and numerical simulation of semi-continuous casting Mg-7.0Al-0.4Zn (AZ70) were carried out. It was indicated that AZ70 has a worse fluidity during forging and is consequently difficult to fill fully compared to aluminum alloys. The microstructure of the AZ70 forgings is in good agreement with the strain distribution generated by simulation, and strain distribution can predict the microstructure evolution. The comparison results can give a guideline on developing forging process and controlling forgings quality of the AZ70 alloy.