Formation of Heterogeneous Microstructure in AA1050/AA5052/AA6061/AA1050 Layered Sheet Processed by Cold Roll-Bonding and Subsequent Annealing

A cold roll-bonding process was applied to fabricate an AA1050/AA6061/AA5052/AA1050 four-layer clad sheet and subsequently annealed. Three types of aluminum alloy sheets such as AA1050, AA6061 and AA5052 with 2 mm thickness, 40 mm width and 300 mm length were stacked up each other after such surface treatment as degreasing and wire brushing, then reduced to a thickness of 2 mm by multi-pass cold rolling. The rolling was performed at ambient temperature without lubricant using a 2-high mill with a roll diameter of 400 mm at rolling speed of 6.0 m/sec. The roll bonded AA1050/AA6061/AA5052/AA1050 clad sheet was then annealed for 0.5 h at 200~400 °C. Microstructures of the as-roll bonded and subsequently annealed aluminum sheets are investigated by electron back scatter diffraction (EBSD) measurement. After rolling, the roll-bonded AA1050/AA5052/AA6061/AA1050 sheet showed a typical deformation structure that the grains are largely elongated to the rolling direction. However, after annealing, it exhibits a very heterogeneous structure consisting of both deformation structure and recrystallization structure containing nanometer order grains. The formation of this heterogeneous structure and texture with annealing is investigated in detail through EBSD analysis.

New Manufacturing Process and Product Developments in Metal Forming Industry Using Finite Element Modelling and Optimization Techniques

The objective of this paper is to outline a practical approach using numerical modelling and optimization techniques for process and product developments in metal cold rolled forming industry. The optimum economic viability in manufacturing industry requires a minimization of the amount of material used while the structural performance of a cold roll formed product relies on maintaining the stiffness and strength of the section in applications. This leads to the development of new cold forming processes and alternative cold roll formed profiles searching for the optimal profile. In this paper, a Finite Element modelling approach was utilized to simulating complicated manufacturing process and products and optimization techniques including Design Of Experiments was used to optimize the shape design of the end products to obtain lighter products while maintaining the product strength. These developments were illustrated through two case studies of Hadley Industries plc which included (1) numerical modelling of a novel Ultra STEEL® cold roll forming process, and (2) optimization of cold roll forming sections.

Effect of Geometrical Factors on Torsion in Cold Roll Forming of the Lower Side Beam of a Car

Cold roll forming is a continuous metal forming process used to produce a large variety of profiles. A significant product of cold roll forming is asymmetric profiles, whose application is expanding in the construction of cars, houses, bridges, etc. Torsion is one of the common defects in the cold roll forming process of asymmetric section steel and sometimes seriously affects cold roll forming products. With the development of the economy and technology, many asymmetric cold roll-formed parts are being gradually applied to automobiles. Three-dimensional finite element analysis models of 12 stands with 700L sheet material were carried out using the professional COPRA RF and MSC MARC software, taking the lower beam of an automobile as the research object. Five geometric factors of the lower side beam were researched, and the influence rules of different geometric elements on the forming torsion were analyzed. We found that with the increase of web width, flange width, and vertical edge height and the decrease of the corner radius and strip thickness, the torsion defects of cold roll forming were improved to different degrees. The results also showed that the width of the flange has the most significant effect on torsion.

A Method for Rapid Prediction of Edge Defects in Cold Roll Forming Process

In order to implement rapid prediction of edge defects in the cold roll forming process, a new analytical method based on the mean longitudinal strain of the racks is presented. A cubic spline curve with the parameters of the cumulative chord length is applied to fit the corresponding points and center points of different passes, and fitting curves are obtained. As the cold roll forming is micro-tension forming, the tensions between racks are ignored. Then the mean longitudinal strains between racks are obtained. By comparing the mean longitudinal strain between racks and the yield strain of the material, we can judge whether there are defects at the edges. Finally, the reasonableness of this method is illustrated and validated by an example. With this method, the roll forming effect can be quickly predicted, and the position where a greater longitudinal strain occurred can be determined. In order to prevent the defects, the deformation angles need to be modified when the result is beyond the yield strain. To further prove the correctness of the theory, the results of the analytical method are compared with the ones of the non-linear finite element software ABAQUS. The analytical results have the same trend as the finite element results. This method can provide useful guidance to the actual design process.

Effect of Plastic Anisotropy and Process Parameters on the Final Geometry of U-shaped Product in Cold Roll Forming

Since the cold roll forming process is currently used in the production of different sections, it is necessary for manufacturers to further improve the quality of these products. Therefore, it is essential to study various factors influencing the production of these products in detail and provide effective solutions to reduce the factors causing defects in such products. This paper investigates the effect of plastic anisotropy and various factors such as strip thickness, the inter distance between stands, web width, and angle increment on the longitudinal bowing and then compares the results with the practical experiments. Accordingly, a model considering the effect of these parameters on the longitudinal bowing of the final section is considered with the accuracy of 88%. The results show that strip thickness and the increment angle at each stand, and the web width have the most influence on the longitudinal bowing, while strip anisotropy and the inter distance has the least effect on bowing.