Papers by Author: Qing Dong Zhang

Abstract: A cylindrical indenter was designed to simulate the roller and 304 stainless steel / Q235A carbon steel plate with different roughness were bonded together. The interfacial bonding behavior was investigated by SEM, ultrasonic “C” scanning detection and nanoindentation test. The result reveal that with the increase of contact pressure between interfaces, the atoms of dissimilar metals begin to diffuse across interfaces in some regions, then form island-like bonding regions, and eventually extend to the whole interface. There are no obvious cracks on the surface of stainless steel and carbon steel after deformation. The cold roll-bonding mechanism of stainless steel and carbon steel is that elements on both sides of the interface diffuse and form a shallow diffusion layer under pressure to ensure the joint strength, and the joint bonding strength is greater than the strength of carbon steel matrix. In addition, the surface morphology of base metal has a great influence on the interfacial bonding quality. The higher surface roughness values increases the hardening degree of rough peak, which makes real contact area difficult to increase and reduce the interfacial bonding quality.

Abstract: To characterize the mechanical behavior of TRIP780 steel in quenching process, Uniaxial tensile tests are performed on Gleeble-3500 thermo-simulation machine at temperature 323K~1073K and corresponding stress-strain curves are obtained. The results show that flow stress is affected by deformation temperature significantly and declines with increasing temperature. Based on simplified and modified Zerrilli-Armstrong model, the impact factor of temperature with quadratic polynomial fitting is introduced and the constitutive relationships with temperature dependent are established. The accuracy of the constitutive equations is verified and the flow stress predicted by the proposed model is consistent with experimental results. Therefore, the constitutive model can be applied for numerical simulation of quenching process.

Abstract: Three-dimensional finite element model of rolling mill with six rolls in a factory is modeled by nonlinear FEM software called ABAQUS. It is a three-dimensional elastic-plastic rolling model. It includes not only elastic-plastic deformation of strip but also the bending of roll system and flattening of rolls. It can describe the changes in friction force between rolls better. Conclusions are as follows. When the driving roll is the backup roll, friction force between the backup roll and the intermediate roll is easy to reach the maximum value, slipping phenomenon is easy to appear. When the driving roll is the intermediate roll, friction force between the intermediate roll and the work roll is easy to reach the maximum value, slipping phenomenon is easy to appear. When the driving roll is the work roll, the changes in frictional force between the rolls is smooth. Slipping phenomenon is not easy to appear.

Abstract: This paper study the key technique of very thin specifications DI tinplate based on 1420 tandem cold mill in Baosteel, to improve the strip edge shape quality. In our paper we put forward the idea to improve the DI tinplate edge drop control performance using the work roll contour technology, enhance the flatness control ability using the intermediate roll contour technology. The mill type of this CVC tandem cold mill is improved by these technologies, and its edge shape control capability is significantly increased. Production trial show that the improved mill type can effectively improve the edge shape quality of the very thin specifications DI tinplate, improve production efficiency and have a good application.

Abstract: The edge drop of steel strip is an important factor in determining the quality of rolled products. Edge drop control system used on 1420 mm cold tandem mill is introduced, which was developed by BAOSTEEL. Edge drop control system went into operation in December 2011. Now system works normally at all times and gives better control performance for the edge drop.

Abstract: The warps (curvatures) of strip in the continuous annealing can be classed as longitudinal and transverse warps. The analysis of warp is simplified from a three-dimensional elasticity problem to a plane problem, and it is proposed in this paper that the residual strain caused by metal rolling is the main reason for the transverse warps. The relationship between the different warps is also discussed on the basis of elastic analyses. Analytical estimates are derived and compared against field measurement. The warp mechanism on the strip steel production process is revealed which can provide the theory basis for decreasing warp.

Abstract: This article suggests that divide the strip surface quality into the damage class, the adhesion class as well as the surface vision class. In order to improve the surface vision quality of the tin plate, the chromaticity of gloss and lightness are used to measure the tin plate surface vision quality. Predictive models of gloss and lightness are established to determine the influencing factors by stepwise regression in the article. The research indicats: the gloss and lightness of tin plate are closely related with tin coating weight and the roughness of tin mill black plate, including profile arithmetic average error and superficial peak density. By enhancing the roughness control accuracy of tin mill black plate, the surface visual quality of tin plate has been greatly improved and the chromatic aberration after printing is solved.

Abstract: Extrusion die is a key factor in tube extrusion deformation. This paper, studying Inconel 690 alloy steel tube hot extrusion process by adopting Deform-2D software, analyses the influence of flat dies, cone die and flat-cone die on extrusion force, temperature rise, and metal flow rule during superalloy extrusion process and find that cone die is more helpful for superalloy tube extrusion. Based on it, the influence rule of cone die angle on extrusion force and temperature rise is studied, and the best die angle for superalloy tube extrusion is provided, which offer the evidence for the design of superalloy tube extrusion die

Abstract: A two-dimensional axi-symmetric finite element model for the tube hot extrusion process was developed based on Deform-2D software by consideration of the billet transfer, glass lubrication and the constitutive characteristics of IN 690 superalloy. An enhanced technique for adaptive mesh refinement (AR) is used to solve the large deformation problem. This model was then used to study the effect of boundary conditions and process parameters in tube hot extrusion. The Non-uniform deformation index as the representative parameter, which denotes the non-uniform deformation during the steady state of tube hot extrusion, is presented accordance to the feature of metal flow at deformation zone. The bigger of Non-uniform deformation index, the worse of non-uniform strain distribution. When the non-uniform deformation index getting smaller, the equivalent strain distribution along the length and cross section become more uniform and better product quality could be obtained. An increase in the billet and die preheating temperature could reduce the non-uniform deformation index individually. But the billet and die preheating temperature should not be too high. The increase of friction coefficient, the non-uniform deformation index also increased, which indicate appreciable results of metal flow. With the ram speed increase, the non-uniform deformation index decreases, but too fast speed is inadmissibility.

Abstract: We describe an integrated tension controller design for a tandem cold rolling mill in steel plants. To achieve stable rolling and ensure strip quality, it is very important to control the tension of the cold rolling mill. Previous researches examined only the operation of a single stand. But it is not sufficient to examine the operation and effect of whole stands because the operation is wholly interdependent. To solve the problem, this paper proposes an integrated control strategy for tension control of tandem cold mill, the full stand model for the tension system of a tandem cold mill is built, and the interaction of all the stands is analyzed. Then applying the method of μ-synthesis design a integrated robust tension controller. Simulation with the practical data proves the integrated robust tension controller can achieve more robust performance than that of typical industrial approach.