Investigation of the morphology of internal defects in cross wedge rolling
ABSTRACT Since internal defects in the cross wedge rolling (CWR) process can weaken the integrity of the final product and may ultimately lead to catastrophic failure, it is necessary to investigate the mechanisms of their generation and growth. Using a specially designed CWR experimental apparatus, experiments were performed at more than 50 different operating conditions. The cross-sectional profiles of the workpiece specimens were examined and compared at each condition. Based on the experiments, the influence of three primary parameters in CWR process—the forming angle α, the stretching angle β, and the area reduction ΔA were determined. From the experimental results, the morphology of void generation and growth in CWR is ascertained and discussed. Through the definition of a non-dimensional deformation coefficient ε, a method for predicting the likelihood of void formation is also established and discussed with respect to optimizing CWR tooling design.
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ABSTRACT: Ni-base superalloys are a class of materials with high temperature excellent tensile, creep and corrosion properties that have widespread applications in manufacturing hot parts of gas turbines. Application of cross wedge rolling (CWR) process for manufacturing Ni-base superalloys is of least investigated areas. In this article, the effects of CWR tool parameters on formability of Nimonic® 80A and Nimonic® 115 wrought superalloys are presented. The normalized Cockcroft-Latham model is adopted through finite element analysis to predict the occurrence of internal burst. The analytical results are validated through comparing them with experimental data. Comprehensive results of the effects of various CWR tool parameters on formability of Nimonic® 80A and Nimonic® 115 are presented. The results show that in some cases for Nimonic® 115, regardless of the stretching angle value (β), the internal burst fails the process. The results also indicate that Nimonic® 80A displays a relatively good ductility in low wedge angles and low stretching angles without suffering internal bursts, leading to sound part.International Journal of Advanced Manufacturing Technology 06/2014; DOI:10.1007/s00170-014-6047-5 · 1.78 Impact Factor
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ABSTRACT: To produce preforms for complex long flat parts with an unsteady mass distribution along the longitudinal axis rolling processes, like cross wedge rolling, can be used. Tools for cross wedge rolling processes can be constructed as roller or flat, both with wedges. In the collaborative research project SFB 489 “Process chain for the production of precision forged high performance parts” the subproject “Innovative machine and tool technology for precision forging” deals with the development of a flashless forging process for a two cylinder crankshaft with pin and flange. This process is developed by IPH – Institut für Integrierte Produktion Hannover. The first preform of the developed forging sequence is produced by a cross wedge rolling process on the basis of flat with wedges. To consider the mass distribution of the two cylinder crankshaft in the preform for a rolling process four mass concentrations for the crank arms and mass concentrations for pin and flange are needed.Key Engineering Materials 02/2012; 504-506:205-210. DOI:10.4028/www.scientific.net/KEM.504-506.205 · 0.19 Impact Factor
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ABSTRACT: The rolling process of the three-roll cross wedge rolling with non-uniform temperature field was simulated with the finite element method (FEM). The distribution of the temperature and equivalent strain in radial section of rolled pieces was analyzed. The microstructures and properties of different positions in radial section were investigated. The results indicate that the temperature field and equivalent strain are ring-likely distributing in the radial section of rolled pieces. There are high temperature and small strain in the center. The temperature decreases and the strain increase gradually from the center to surface. The microstructures and properties of rolled pieces are different in different positions. The microstructure in the center consists of pearlite and proeutectoid ferrite, while the surface consists of cementite particles and fine ferrite.Applied Mechanics and Materials 06/2012; DOI:10.4028/www.scientific.net/AMM.184-185.1259