Papers by Author: Hai Bo Xie

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: In this paper, a new technique to set up non-sinusoidal oscillations of the mold in continuous casting is presented. The waveform functions of this non-sinusoidal oscillation technique and operational parameters are analyzed and the design to realize the non-sinusoidal oscillation of mold is presented. It is anticipated that this technique will be widely applied as it has many advantages such as lower investment and maintenance cost, simple equipment which is easy to manufacture and maintain.

Abstract: Cracks in metal product significantly decrease quality and productivity of the rolled thin strip. In this paper the stress intensity factor (SIF) solution of edge crack defect of thin strip during cold rolling was investigated, and a globe analysis was applied to the problem of free edge of thin strip. The effective stress intensity factor range is important because it represents the major physical cause of crack growth. The present study provides insights of the mechanics of edge crack growth that has been frequently observed during thin strip rolling. The efficiency and reliability of the SIF analytical modelling has been demonstrated. The proposed method for predicting edge crack is useful for producing defect-free products in rolling, and provides insights of the mechanism of edge crack growth.

Abstract: Surface roughness plays an important role in determining the tribological behaviour of mechanical components (e.g. gears and roller bearings etc.) under full-film and mixed (or partial) elastohydrodynamic lubrication conditions. This paper describes a detailed mechanics analysis of the surface roughness transformation of thin strip which has been cold rolled on an experimental mill. Low carbon steel strips were rolled at various speeds and reductions, and the effects of rolling parameters on surface roughness are studied. The results of surface roughness can provide important information to optimise the rolling schedule and to improve the rolled strip quality.

Abstract: Rolling temperature is an important factor affecting mechanical properties of hot rolled strip significantly. Traditional techniques cannot meet higher precision control imperatives. In the present work, a novel knowledge-based system has been developed for the temperature prediction in hot strip mills. Neural network has been used for this purpose, which is an intelligent technique that can solve nonlinear problem of temperature control by learning from the samples. Furthermore, an annealing robust learning algorithm was presented to adjust the hidden node parameters as well as the weights of the adaptive neural networks. Simulations in a multi-object mode have been carried out to verify the effectivity of new neural optimization system. Calculation results confirm the feasibility of this approach and show a good agreement with experimental values obtained from a steel plant.

Abstract: Asymmetric rolling of thin strip has become important due to a significant decrease of rolling force, which contributes to obtain the extremely thin strip, to reduce the rolling passes, and to save the energy by a decrease of anneal treatment. In asymmetric rolling of thin strip, edges of work rolls may contact and deform when no or small work roll bending force is applied. Work roll edge contact forms a new deformation feature. In this paper, the effects of initial thickness of strip and friction coefficient on the rolling pressure, roll edge contact length and strip crown during asymmetric rolling of thin strip with work roll edge contact effect has been discussed, and the calculated rolling force with work roll edge contact is compared with the measured value.

Abstract: Effects of the extrusion ratio, on-line solution temperature and cooling speed on the microstructures, mechanical properties and conductivity of AA-6201 feedstock have been investigated. Experimental results show that the size of the grain of the feedstock grows slowly with an increase of on-line solution temperature, the size of strengthening phase becomes smaller and the density becomes bigger with an increase of extrusion ratio. The tensile strength of AA-6201 feedstock after T-6 treated increases with an increase of extrusion ratio, on-line cooling speed, and with a decrease of solution temperature, and the conductivity is a little penalty. Under the conditions of the extrusion ratio 16.5, on-line solution temperature 793.15K and ageing temperature 423.15K, the tensile strength, elongation and conductivity are 324 MPa, 10.1 % and 53.0% IACS respectively. A feedstock with high quality can be produced by a method of continuous casting and extrusion.

Abstract: Based on optimization setup technology, an online adaptive calculation method for improving accuracy of strip coiling temperature control on the run-out table (ROT) has been developed and implemented in hot strip mill (HSM). Multi-objective control strategies, which include coiling temperature, middle target temperature and appropriate cooling rates have been finalised. Cooling strategies, elements tracking, and dynamic correction are employed in the control system. In addition, the model optimization and soft-measure method are also introduced in the study. Rolling tests with various grades of steel covering a wide range of thickness show that the developed model can improve the accuracy of coiling temperature control to obtain an uniform mechanical properties. Good correlation has been found between the predicted temperatures and the actual coiling ones.