Papers by Author: Xiao Ming Zhang

Abstract: To obtain a low cost, environmentally friendly and effective lubricant, a novel nanoTiO₂ additive oil-in-water (O/W) lubricant for hot steel rolling has been developed. Based on the contact angle, tribological and hot rolling tests, the performance of the nanoTiO₂ additive O/W lubricants was evaluated and discussed. The results show that the strongest adhesion force between the nanoTiO₂ additive O/W lubricant and the work roll is obtained after addition of 4% nanoTiO₂ additive in the 1% O/W lubricant. The nanoTiO₂ nanoparticles can reduce coefficient of friction (COF) and rolling force, and enhance the surface quality of the hot-rolled product. The lubrication mechanism of nanoTiO₂ additive O/W-based lubricant has been proposed.

Abstract: In the paper, a crystal plasticity finite element method (CPFEM) model was developed based on ABAQUS to analyse the surface roughness transfer during metal manufacturing. The simulation result shows a good agreement with the experimental result in the flattening of surface asperity, and the surface roughness decreases significantly with an increase of reduction with considering friction effect. Lubrication can delay surface asperity flattening. The effect of surface roughness on produced metal defect (crack) was also studied, and the surface roughness affects the crack initiation significantly in cold strip rolling. In addition, the surface roughness variation along the metal plate width contributes to stress distribution and then inhibition of crack nucleation.

Abstract: The simulation studies were carried out on the oriented silicon steel produced by thin slab casting and rolling (TSCR) and twin-roll strip casting in the laboratory. The precipitation of inhibiter, formation of microstructure and texture were investigated before cold rolling. The inhomogeneous microstructure and texture gradient were observed in the 7-pass hot-rolled strip（2mm）for TSCR process, and texture gradient was not changed after normalizing, and the twin-roll strip casting directly supplied a strip with approx 2mm of thickness being same as that of hot-rolled strip by TSCR. The microstructure of twin-rolling casting strip was almost composed of all equiaxed grains which similar to the normalizing microstructure in TSCR process, but the random texture was obtained by twin-rolling strip casting. The dispersed and clustered precipitates were presented in hot-rolled strip when the ingots were soaked at 1200°C and 1150°C respectively for the TSCR process. And disperse and acicular precipitates were observed by TEM for air-cooling cast strips for process twin-rolling casting.

Abstract: In twin-roll thin strip casting, the temperature distribution of casting roll affects the roll thermal stress, and influences the thermal deformation, the generation of roll surface cracks, the strip shape, and the service life of casting roll. In this paper, the temperature distributions of casting roll have been analysed, the effects of the roll sleeve thickness on the temperature field and thermal stress of casting roll have been simulated and discussed. The developed temperature model of casting roll is helpful in optimising the processing parameters and the design of casting roll during twin-roll thin strip casting.

Abstract: In twin-roll thin strip casting, the temperature of casting roll affects the roll thermal stress, and influences the thermal deformation, the generation of roll surface cracks, the strip shape and the service life of casting roll. In this paper, the features of the casting roll materials have been analysed, the effects of the clad materials and thickness on temperature field of the casting roll have been simulated and discussed. The developed temperature model of casting roll is helpful in optimising processing parameters and the design of casting roll during twin-roll thin strip casting.

Abstract: In twin-roll strip casting process, the temperature variation of casting roll can result in roll thermal stress and fatigue. It not only affects the thermal deformation of casting roll and the generation of the roll surface cracks significantly, but also influences the surface quality, shape and profile of the produced strip, and the service life of the casting roll. In this paper, a 3D coupling thermal-flow finite element modelling has been conducted. For twin-roll casting of stainless steel, the influences of the casting speed and liquid level in molten pool on the temperature field of casting roll have been simulated and discussed. The developed model is very helpful in optimising the processing parameters and the design of casting roll during twin-roll thin strip casting.

Abstract: In twin-roll strip casting process, metal flow and temperature distribution in the molten pool directly affect the stability of the process and the quality of products. In this paper, a 3D coupling temperature-flow finite element simulation during twin-roll strip casting has been carried out, and the influences of the outlet angle and the submerged depth on the temperature and flow fields in the molten pool were investigated for the twin-roll casting of stainless steel. An inverse method was used to determine the boundary conditions between the roll and molten pool. Simulation results are consistent with the experimental values. Numerical simulation is helpful to optimise the twin-roll strip casting process and to improve the quality of products in practice.

Abstract: In twin-roll strip casting process, the casting speed has a significant influence on the metal flow and temperature distribution in the molten pool, which will affect the stability of this process and the quality of the produced products. Based on a 3D coupled thermal-flow analysis, a combination of the experimental results for twin-roll strip casting of stainless steel, heat equilibrium calculation and simulation results was conducted, and the boundary conditions of the heat exchange between the rolls and molten pool has been treated effectively. The effect of the casting speed on the flow and temperature in the molten pool was given. Simulation result is in agreement with the measured value.