Papers by Keyword: Cold Rolling

Abstract: This paper proposes an automatic control strategy of the strip width in cold rolling process. The prediction model for the exit strip width of each stand is established. In addition to the strip width variation of the incoming hot-rolled material between the measured and the pre-set values, the variations of the rolling force, tension, bending force and the roll shift amount of each stand are utilized to model and forecast the stand exit width deformation. Then, the model can be used to determine the compensation values of the different profile adjustment mechanism and the exit strip width can be controlled in high accuracy. In this way, the effect of the strip width variation of the incoming hot-rolled material and the fluctuation of the stand rolling process parameters on the exit strip width can be eliminated. Moreover, the feed-forward control of the strip width can reduce the incidence of abnormal situation, such as the strip breakage and off-tracking ,and improve the stability of the cold rolling process.

Abstract: This paper firstly analyzes the problems that exist in the cold rolling of steel industry. Secondly, a new approach is proposed to temper and straighten the strip steel based on the temper leveling mill, shortly, TLM. The required high quality of the wave, surface and mechanical properties can be achieved only with TLM. TLM holds the functions of both temper machine and straightening mill and can produce good quality strip steel, no only the waviness, mechanical properties, but also the surface quality. The usage of TLM can lower the cost of the production of tempering, straightening and equipment investment.Finally, the experiments are done and verify the validity of the approach.

Abstract: A 3D elastic-plastic finite element method (FEM) model of cold strip rolling for 6-high continuous variable crown (CVC) rolling mill was developed. The rolling force distributions were obtained by the internal iteration processes. The calculated error has been significantly reduced by the developed model. the absolute error between the simulated results and the actual values is obtained to be less than 10μm, and relative error is less than 1%. The developed model is significant in investigating the profile control capability of the CVC cold rolling mill in terms of work roll bending, intermediate roll bending and intermediate roll shifting.

Abstract: To help optimize cold rolling operations, mixed lubrication models have been developed and embedded in roll bite models. The resulting models combine micro-fluidics in a porous medium (the lubricant flow between the contacting rough surfaces), microplasticity (roughness flattening / scratching), macro-plasticity (strip reduction) and roll thermo-elasticity. They are therefore really complex and need a lot of physical data. Based on previous developments, a new, simpler version of our lubrication model has been coupled with a new roll bite model recently presented: slab method for the strip elastic-plastic deformation (Prandtl-Reuss equations), a complete influence functions set for the roll deformation with circumferential displacements, and an efficient, adaptive relaxation technique when iterating between roll and strip models. The lubrication model is elaborated on Wilson and Sheu’s mixed lubrication model. The paper describes the implementation and compares its results with our previous, more complex version; a reasonable agreement is found. Several test cases of increasing difficulty show the robustness of the model and of its implementation. As a conclusion, a brief perspective is provided on how this new type of roll bite model could be used in industry.

Abstract: Abstract. Metallic nuclear fuel plates are nowadays an alternative to the ceramic ones in the sense that the uranium density can be increased at lower enrichment. Higher thermal conductivity is also a key factor favouring such fuels for power reactors. Uranium reacts promptly with oxygen and nitrogen at high temperatures to catastrophic corrosion due to non-protective oxide layers, which imparts hot forming processes. The gamma phase body centred cubic structure can be retained at room temperature by annealing the U-7.5Nb-2.5Zr (wt.%) alloy followed by quenching, where the deformation can be extensive. The resulted highly deformed gamma supersaturated structure is subjected further to competitive recovery/recrystallization and phase precipitation phenomena whose are studied in the work. The U-7.5Nb-2.5Zr alloy was melted into plasma and induction furnaces and afterwards annealed to gamma phase. The normalized alloy was cold rolled and underwent isochronal and isothermal treatments. The microstructure evolution was monitored by optical microscopy, X-ray diffraction analysis and hardness measurements. The results show the precipitation events of α” and α+γ₃ phases are dominant over recovery in the range 200oC < T < 500oC. Above 500oC the recrystallization is the main process leading to softening and initial Vickers hardness recovery. One refined gamma phase grain structure was obtained (~8.0 μm) after annealing at 700oC for 2.5 hours.

Abstract: Although 6.5wt% high silicon electrical steel has pretty excellent soft magnetic properties, it is hard to be obtained by cold rolling at room temperature, by virtue of appearance of ordered phases in this alloy. In this research we report that very thin 6.5wt%Si composite sheet with 0.05-0.08mm thickness was fabricated by proper heat treatment and cold rolling after hot deformation. The 6.5wt%Si composite plate exhibits some extent of ductility at room temperature when the stage of hot deformation was finished. The effect of heat treatment on mechanical properties of this composite plate was investigated by optical microscope. After heat treatment, ductility of this composite plate is increased due to the ordered DO₃ phase transformation inhibited by cooling fast. It is provided a referable method to produce 6.5wt% high silicon steel with conventional forming process.

Abstract: In order to obtain the best position of mid-roll shift, this paper studies the effect of different mid-roll shift position on the strip flatness of CVC 6-H mill. Strip element variation method and influence function method are put forward to analyze the effect of mid-roll shift on strip flatness. The results show the CVC 6-H mill is able to get good strip shape. The best shift position is obtained from the calculation results. The conclusion has a good significance for the practical application.

Abstract: The automatic control system is one of the most important parts of improve cold rolling strip precision and increase the automate level. The improved cold strip mill process control system has been developed and successfully applied to several new cold strip production lines. This paper introduces the Key Technical Features and New Technology of the system include the system architecture, hardware configuration and new control algorithms, etc. System operation and actual production proves that the system has the features of shorter commissioning time, convenient maintenance, high reliability, high automatic level and control precision.

Abstract: Mechanical properties of 3-ply Cu-Ni-Zn/Cu-Cr/Cu-Ni-Zn clad composite plates prepared by explosive bonding and cold-rolling. No intermetallic compounds were observed at the Cu-Ni-Zn/Cu-Cr interface after explosive bonding and cold-rolling and heat-treatment at 723K. The strength of as-rolled clad plate reached up to 575MPa with the ductility of 30% after heat treatment at 723K for 1 hour. The strength dropped to 510MPa and the ductility increased to 48% after heat treatment at 723K for 1.5 hour. There are no stepwise drops of the flow stress before final fracture, meaning three plates were bonded together until the last moment of the stress-strain curve. The observation of the fractured specimens revealed no interface separation even after fracture. The excellent mechanical reliability and the good interfacial bonding strength can be attributed to the absence of detrimental interfacial reaction compounds between Cu-Ni-Zn and Cu-Cr after annealing.

Abstract: In this paper the characterization of the edge crack in the strip steel are studied by using numerical simulation method. The developments of the stress and strain near the crack tip are obtained and the value of the J-integral of edge crack under the rolling process is then examined. FE simulation result shows that the J-integral is not always path independent in the whole rolling process. When the crack is far away from the roller, the J-integral is path independent. When the crack enters the cold rolling region, the unload phenomena will occur near the crack tip which cause the incremental theory of plasticity failed and the conservation of the J-integral is not valid any more. The J-integral failure region is then determined by a series of FE simulations.