Papers by Keyword: Rolling

Abstract: This study examines the forging process of an aluminum upper control arm for automotive applications. To address the geometric complexity and forming challenges, a multi-step forging route, comprising of roll forging, two-stage bending, pre-forging, and final forging, is developed. Finite element analysis (FEA) using DEFORM-3D software is employed to optimize key forming process parameters in the pre‑forging stage. The response surface methodology (RSM), combined with the Box–Behnken design, is utilized to construct predictive models and identify optimal parameter combinations. A successful forged upper control arm is subsequently produced using these optimized forming parameters. The findings demonstrate that integrating FEA with statistical process optimization strengthens the predictive accuracy of the process design and supports defect‑free forging of AA6082 upper control arms.

Abstract: Multi-material components that consist of copper and aluminum enable the combination of advantageous mechanical, thermal, and electrical properties at competitive cost. While roll bonding is an efficient-solid state joining technique, its implementation requires fully processed, cold-rolled strip material from two process routes. Continuous compound casting in contrast offers a more efficient approach by combining aluminum and copper during casting, followed by flat rolling in a single process route. However, the differences in flow stress between the metals can cause non-uniform elongation and therefore significant shear stresses at the interface during rolling. These stresses may lead to a delamination of the compound if process conditions are not well controlled. This study investigates whether a geometrically structured interface, introduced during compound casting, can contribute to withstanding interfacial shear stresses through mechanical interlocking. In finite element simulations varying process parameters including height reduction, initial temperature, rolling speed ratio, and pass schedule were examined. Results show that a structured interface can effectively resist shear stresses at the copper-aluminum boundary, thereby improving joint stability during deformation. Furthermore, the strain distribution as well as the fluctuation of the shear stresses can be controlled by the process parameters. The findings indicate that the mechanical interlocking by a geometric interface combined with optimized process parameters can enhance the rolling of compound-cast copper-aluminum composites.

Abstract: Recently, high strength at high temperature can be achieved by inducing kink bands in alloys having aligned lamellar microstructure. However, the kink-bands formation has been confirmed only in alloys with lamellar microstructures, where slip plane is limited to the plane parallel to the lamellar interface, and not confirmed in alloys with rod-like or Chinese script microstructures. In this study, we clarified the contribution of rod-like Si phases in Al-Si alloy on the mechanical properties and focused on the feasibility of introduction of kink bands in the alloys without lamellar structure. The results showed that in Al-Si eutectic alloys, the non-lamellar second phase, i.e., the Si phase, is aligned by directional solidification, and refined by rolling. The directionally-solidified sample showed high yield strength with long and aligned Si phase, while the rolled samples showed high ductility with refined microstructure. The rolled samples were uniformly deformed in all the samples with variety of reduction ratios, and wedge-shaped deformation bands were observed after the compression test, especially in the 5-10% rolled specimens. Crystallographic orientation analysis indicated that these deformation bands were not kink bands but were localized slip bands.

Abstract: Next generation rolls such as super-cermet rolls and all-ceramic rolls can be manufactured using only sleeve assembly type rolls, which have the advantage of being able to reuse the shaft by replacing the damaged sleeves. However, in some cases, failures with unknown causes may occur such as circumferential slippage, shaft pull-out or residual bending deformation at the shrink-fit interface. Such slipping failures cannot be prevented by conventional design concept. This is because even if the resistant torque is greater than the motor torque, the circumferential slippage will occur. Through numerical simulation and miniature roll experiment, the following results are obtained. 1) Even under free rolling condition without motor torque, the circumferential slippage occurs. 2) The slippage is caused by the accumulation of irreversible slip during the roll rotation. 3) The motor torque accelerates the sip amount significantly. 4) The geometry of slippage defect can be identified experimentally. 5) The fatigue strength of sleeve assembly rolling rolls can be evaluated by using √area parameter characterizing the identified slip defects. 6) By preventing the slip damage, the fatigue strength of sleeve rolls can be nearly equal to that of conventional solid rolls without shrink-fit.

Abstract: In order to increase strength while maintaining the ductility of material, pure titanium was improved through the thermomechanical treatment that combines rolling and heat treatment. The tensile properties of pure titanium treated by rolling and heating were investigated. Test material was JIS Grade 2. This material has a higher corrosion resistance. However, the strength of JIS Grade 2 is lower than that of JIS Grade 3. JIS Grade 2 with high strength while maintaining corrosion resistance is being developed. Techniques for improving the properties of materials with simple compositions are important. Thermomechanical treatment is used as a method for improving material properties. In the present study, the effect of thermomechanical treatment on the material properties of JIS Grade 2 was investigated. Rolling was performed at room temperature and the reduction ratio ranged from 70 to 90 %. The heating temperature was in the range of 300 to 700 °C. Heat treatment from 400 to 500 °C showed an increase in tensile strength while maintaining ductility. When the heat treatment temperature was 450 °C, the strength and elongation were approximately 600 MPa and 25 %. Tensile stress of JIS Grade 4 and the tensile strain of JIS Grade 1 were exhibited.

Abstract: The influence of moderate thermomechanical rolling and heat treatment time on the microstructure and mechanical properties of normalised Ni-containing Nb-Ti-V microalloyed plate steels was investigated. Conventional rolling (CR) and low austenitic temperature rolling (TM) schedules were applied to 25 and 55mm thick plates. Predicted plate thermal profiles were used to simulate normalising of 25 and 55mm thick plates at the mid-thickness. As expected, the microstructure after TM rolling was finer due to austenite sub-structure development below the no-recrystallisation temperature which increases the amount of ferrite nucleation sites. The tensile strength of the CR plates was generally higher due to a larger pearlite volume fraction resulting from slow cooling from a relatively coarse austenite. In 25mm plate, the presence of acicular ferrite after CR resulted in a higher yield strength than that obtained after TM rolling. Furnace residence times of 0.75min/mm and longer allowed for plates to be completely normalised – characterised by continuous, well-defined polygonal ferrite grain boundaries. Short furnace residence times restricted the plate temperature to below the end of the ferrite-to-austenite transformation (Ac₃), where untransformed ferrite is retained from the as-rolled microstructure and is characterized by poorly defined grain boundaries. Rolling practice and normalising residence time had little to no effect on impact toughness, but significantly influenced the normalised yield strength of thicker plate.

Abstract: This study utilized friction stir welding for butt joining of A1050 and C1020 plates, investigating the effects of cold rolling and annealing on the structure of the bonding interface and the hardness of the materials. The experiments revealed successful joint formation with minimized copper dispersion in aluminum and the formation of intermetallic compounds. Cold rolling resulted in increased hardness without significant crack propagation along the bonding interface. Annealing effectively reduced the difference in hardness, indicating that copper recrystallizes earlier than aluminum.

Abstract: Recent past witnessed the widespread use of High Strength Low Alloy steels in several structural applications, including pressure vessels, line-pipe transportation of crude oil in the oil industry and many more. API X-65 grade is widely used as a promising material for line-pipe applications in the oil industry. HSLA X-65 plate steels are produced by normalising, Controlled Rolling (CR), Direct Quenching & Tempering (DQT) or Quenching & Tempering (Q&T) techniques. These steels are characterised by their low carbon concentration while maintaining low alloy additions. Micro alloy additions such as V, Ti, and Nb provide substantial precipitation strengthening effect. Strengthening, hardness and microstructural examinations are conducted in all the stages to ascertain X-65 HSLA steel's ageing behaviour.

Abstract: Rolling operations with flat dies allow the highly efficient production of cylindrical parts in large quantities. [1] Latest trends towards shorter lifecycle times and increasing product complexity [2] strengthen the need for an efficient design process of flat die rolling operations. Finite element modelling plays a major role in establishing an efficient design process. Precise modelling of the friction conditions during rolling operations with flat dies is still posing a challenge today. [3] The present work aims to experimentally identifying the limits of rolling of an axisymmetric part, using flat dies. By gradually increasing the stroke rate, the process limits caused by excessive slippage are determined for six different tribological systems. The workpiece rotation and tool movement is measured optically by using a digital camera system. Large differences in slippage are observed, depending on the tribological system. While systems with polymer based lubricants show excessive slippage at low stroke rates, systems using oil or no lubricant bear higher stroke rates before process limits are reached. Furthermore the optical measurements reveal that slip may also occur without complete process failure leading to the assumption that the process limit of excessive slippage in rolling operations is rather fluent than binary. Based on this experimental data, future investigations will focus on methods to predict these process limits through FEM using advanced friction modelling and tribometer tests.

Abstract: The effect of pre-aging on properties of Cu0.24Cr0.20Sn alloy before rolling and aging was studied in details. The results displayed the pre-aging was useful to improve the microhardness and conductivity of Cu0.24Cr0.20Sn alloy before cold rolling and aging, and the effect increased with the extension of pre-aging time. The microhardness and electrical conductivity of Cu0.24Cr0.20Sn alloy by first pre-aging at 400 °C for 2 h, second 85% rolling and then aging at 300 °C for 1 h can reach 189 HV and 85.4 %IACS, respectively. The TEM results indicated the density of precipitates increased with the increase of pre-aging time, and the interaction between precipitates and dislocations was gradually strengthened in the subsequent room-temperature rolling. The increase caused by pre-aging treatment before rolling and aging was mainly due to dislocation density strengthening.