In this study, the microstructure and mechanical properties of AZ31 magnesium alloy were investigated through asynchronous rolling. The results demonstrate that the rolled sample exhibits a refined grain structure with a significant presence of continuous dynamic recrystallization. Notably, as the roll speed ratio increases, the grain refinement becomes more apparent. For the sample with a roll speed ratio of 1.3, the tensile strength in the rolling direction (RD) reaches 273 MPa, while the elongation measures 20.2%. Similarly, in the transverse direction (TD), the tensile strength reaches 282 MPa, accompanied by an elongation of 18.9%. These values indicate a substantial improvement in elongation compared to conventional rolling processes. The enhanced elongation can be attributed to two primary factors. Firstly, recrystallization contributes to a grain refinement recrystallization ratio of 86%, promoting improved mechanical properties. Secondly, the recrystallized grains induce a favorable Schmidt factor, further supporting elongation. Overall, the findings of this research highlight the benefits of asynchronous rolling in refining the microstructure and enhancing the mechanical properties of AZ31 magnesium alloy.

A pure Ni interlayer with a thickness of 0.1 mm was introduced between high-strength interstitial free steel and Al–Mg–Si alloy, which were friction stir lap welded, producing an excellent welded joint. The interface layer consisted of a γ-Ni solid solution, and the mixed stirring zone contained alternate lamellae of γ-Ni and α-Fe solid solutions. The addition of a Ni interlayer strongly suppressed the reaction between Al and Fe because of the atomic arrangement of Ni. Furthermore, the insertion depth of the stirring pin has a significant influence on the Al/steel interfacial reaction. Under shallow insertion depth, the intermetallic compounds of both FeAl and Fe₂Al₅ were observed at the interface layer. A maximum tensile-shear fracture load of 4.3 kN was achieved, with fractures being present in the steel substrate far away from the Al/steel weld.

Tension control in cold-rolling pilot mills (CRPMs) with hydraulic tension is subject to extraneous forces resulting from positional disturbances, strong coupling, and time-varying characteristics, making it challenging to achieve ideal control results using the existing control methods. Therefore, in this study, a mathematical model of tension is first derived and then used to analyze the properties and difficulties associated with tension control. Second, a hydraulic servo-control system based on servovalves and proportional pressure relief valves is developed. In this system, redundant feedforward flow is generated by a servovalve according to the rolling schedule. The surplus flow is absorbed by a proportional pressure relief valve in the closed-loop control of tension. Third, simulation analysis is performed. Under severe friction disturbance (maximum 0.2 kN), and with the wide range of forward and backward slip, an accuracy of ±0.27 kN in tension control can still be achieved using the proposed control strategy, thereby demonstrating its effectiveness. Moreover, it has obvious advantages over existing control methods. Finally, an experimental study of tension is carried out in the cold-rolling mill with a maximum tension capacity of 50 kN, achieving ±0.2 kN tension control precision in the multipass rolling process.

Three-way servovalve controlled cylinder (TSCC) is the main method used in hydraulic automatic gauge control (HAGC) system of rolling mill, which generally only foucus on the screw-down speed of HAGC cylinder under load resistance. However, with the development of plan view pattern control and variable gauge rolling, the lifting-up speed of HAGC cylinder is required to be as high as the screw-down speed. At present, high frequency response and large flow servovalves or even double servovalves in parallel are usually used to achieve high lifting-up speed, resulting in a substantial increase in equipment cost. In this paper, the nonlinear mathematical models of the TSCC and four-way servovalve controlled cylinder (FSCC) are firstly established, and the steady-state speed equations of the two methods are derived. Then, the steady-state speed of the two methods with different HAGC cylinder sizes under different load conditions is compared and analyzed, and it is proved that FSCC has obvious advantages in lifting-up speed. Finally, simulation experiments of variable gauge rolling on a 1050mm cold-rolling mill are carried out. In the rolling process of transition zone where the roll gap increases, the FSCC has higher control precision and wider dynamic adjustment ability, which is more conducive to improving rolling speed, production efficiency and shape quality.