Papers by Keyword: Cold Rolling

Abstract: In order to improve the calculation accuracy of tension distribution, a new method to calculate tension distribution for strip cold rolling is carried out. First, exit unit tension calculation model is developed by using variational calculus method. Then combined with divided element method, tension distribution and rolls deformation model are established, and the corresponding procedure is developed. Further, contact pressure between rolls and tension distribution of a single-stand reversing cold mill are calculated with the procedure. And it is proved that the results of the calculated data agreed well with the measured value. This verifies that the calculation method is reliable.

Abstract: To characterize the degradation of material at low triaxiality, the shear modified GTN damage model proposed by Nahshon and Hutchinson (2008) was introduced in this study. The details of the numericalimplementation and validation of the model was conducted. And the shear modified parameter was determined by the comparisons of experimental and simulation results of the shear test. Then, the damage model was employed to simulate the cold rolling process, and the results showed that the shear modified GTN model can reveal the damage behavior and predict edge crackingof ductile materials in cold rolling.

Abstract: In this paper, mathematic models of processing parameters and their adaptive learning principle in strip cold rolling mill are introduced. Exponential smoothing method is used during model adaptive learning. According to the contrast between actual and calculated data, adaptive learning coefficients in the process control models are modified, thus the precision of presetting model is improved. Based on three kinds of adaptive learning modes, corresponding model adaptive learning program is developed for strip cold rolling. The practical application shows that the accuracy of this method can meet the requirement of on-line process control, and it is suitable for process control in strip cold rolling mill.

Abstract: The carbon steel/stainless steel composite pipe was prepared by centrifugal compound casting-hot extrusion-cold rolling. SEM was employed in detecting the microstructure and alloy element distribution maps in stainless steel of composite pipe. The mechanical properties were measured through tensile test. The corrosion resistance of the composite pipe was detected in acid, alkali and salt solutions. The results show that the outer and inner layers are integrated with good metallurgical behavior, and the mechanical properties of the composite pipe are satisfactory, the chemical compositions are well-distributed. The grain-boundary corrosion test is qualified. This composite pipe has better corrosion resistance in 10%H₂SO₄ and 10%NaOH solution than in FeCl₃ solution at room temperature.

Abstract: The current two-dimensional (2-D) parameters for surface assessment (R_a and P_c) could not actually reflect functional properties of bearing and lubricant retention capabilities of steel sheets and rolls surface. Based on ARM9 development board, this paper has been working on secondary development of M1 mobile surface roughness meter, creating a model of calculating three-dimensional (3-D) functional characteristic parameters with 2-D profiles, and optimizing influence factors with Genetic Algorithms (GA). By comparing with measurement results by white-light interfering profile meter, the measurement error of the developed system is within10%, which was proved to be practical in the factory.

Abstract: Theoretically illustrates the principle of tension variation during flattening process. Analysis of the changing process of the tension from the perspective of energy consumption. Gives a calculation formula of tension variation on the base of plane assumption. In addition, research the the influences of technological parameters to tension variation by using finite element software . Finally, analyzing the change process of the tension during flattening process.

Abstract: Metastable austenitic stainless steel type 301LN is widely used for fabrication of structural components of Metro Coaches. The steel exhibits both high strength and enhanced plasticity due to strain hardening as well as formation of strain-induced martensite (α) during cold deformation (TRIP effect). The current market requirement, as projected by many of the ongoing Metro Rail Projects in India, calls for manufacture of this steel with ultimate tensile strength (UTS) in excess of 1000 MPa and yield (YS/UTS) ratio of less than 0.8, as this would facilitate substantial reductions in tare weight and crash-worthiness of metro coaches. The typical property requirements in high temper (HT) as per one typical Metro Coach specification are: Yield Strength (YS) ~ 751-921 MPa, Ultimate Tensile Strength (UTS) ~ 1001-1151 MPa, Elongation ~ 22% min, Hardness ~ 36 HRC max and YS/UTS ratio <0.8. previous="" plant="" experience="" has="" shown="" that="" the="" maximum="" attainable="" uts="" in="" this="" grade="" through="" cold="" rolling="" is="" only="" to="" tune="" of="" 970="" mpa="" and="" any="" excess="" deformation="" severely="" impairs="" both="" ductility="" 22="" hardness=""> 36 HRC) beyond acceptable limits. In the present work, an innovative thermomechanical processing (TMP) methodology has been evolved for the attainment of this seemingly unlikely combination of properties through experimental cold rolling and short annealing simulations in Gleeble 3500 C thermomechanical simulator. The novel process methodology entails imparting heavy cold reductions (CR) of 45-50% in Sendzimir Mill followed by brief/ short reversion annealing treatments (80-160 s) by means of single furnace operation at 750 °C at standard line operating speeds for 300 series in Annealing Pickling Line-1 (AP Line-1) of Salem Steel Plant (SSP) in India. The improvement in properties (strength-ductility combination) has been attributed to grain refinement through formation of submicron grained austenitic (γ) microstructure by controlled reversion of strain-induced martensite (α) during the short annealing treatment. The process is distinct from conventional long annealing treatments (300-360 s), which are employed to soften the steel after cold rolling by means of recovery and recrystallization processes.

Abstract: The microstructure evolution and control for Alloy 690 during cold rolling and annealing treatment was investigated. Cold rolling specimens were deformed in the strain range from 15% to 70% with strain rates from 0.01 to 10s^-1. Subsequent annealing treatment was carried out in the range of 1060~1100°C for dwell time 3~15mins. Rolling reduction, annealing temperature and annealing time except strain rate had obviously influence on grain size and hardness. Little coarsening of grains were observed below 1060°C during annealing treatment, whereas grains coarsened obviously over 1080°C. Besides, the behavior of grain growth for alloy 690 was investigated systematically.

Abstract: The paper deals with solutions to particular process problems in production of thin sheets of special nickel and iron-based alloys. Experiments were focused on trial operation of a new melting furnace, on hot rolling of feedstock from experimental heats and on fine-tuning hot and cold rolling processes with the aid of numerical modelling in DEFORM 3D software. The paper also gives description of results of FEM simulation of cold rolling of strips. A FEM model of the cold rolling process with front and back tension was developed. In order to describe the behaviour of nickel alloys in the FEM simulation, a specific material model was proposed. This material model combines the material data obtained from Rastegaev compression test and the results of thermodynamical calculation from JMatPro software.

Abstract: The general framework of this paper is in the field of numerical simulation of asperity crushing. Different material forming processes, such as strip-rolling and deep drawing, imply mixed lubrication. In this lubrication regime, two types of contact are present at the same time: a direct contact between the two solids at the asperity level and also valleys filled with pressurized oil. Theses contact conditions have a large influence on friction and wear taking place during the upsetting process. As this mixed type of contact is not yet fully understood from the physics point of view, numerical models are essential to achieve a better understanding. For example, semi-analytical asperity crushing models have been developed by Wilson&Sheu [1] and Sutcliffe [2] to take into account the influence of bulk plastic deformations on asperity crushing. The finite element method has also been used to model asperity crushing. Ike&Makinouchi [3] studied the behavior of 2D triangular-shaped asperities under different boundary conditions. Krozekwa et al. [4] modeled 3D triangular asperities behavior, for various bulk strain directions. More recently, Lu et al. [5] compared experimental results of pyramid-shaped asperity and ridge-shaped asperity crushing with finite element simulation results. As in the three former references mentioned above, it has been decided, to study the interaction between a rigid plane and a simplified geometry asperity without lubricant. In this article, numerical asperity crushing results obtained with Metafor[6], a home made large strains software, will be presented. Those results will illustrate the influence of boundary conditions, contact pressure, large bulk strain and geometry of asperities on the evolution of the contact area. As the asperity crushing behaviour is known to be very sensitive to the boundary conditions, in this article, we will also present results using boundary conditions from a cold rolling model named MetaLub. MetaLub [7-8] is a software developed at the University of Liege in partnership with ArcelorMittal R&D center. It iteratively solves the equations resulting from the discretisation using the slab method of the strip coupled to a mixed lubrication model at the interface. This lubrication model takes into account the evolution of the oil film thickness as well as the asperity crushing along the roll bite. We will compare the evolution of the relative contact area obtained with MetaLub to the results obtained with finite elements simulations using the same boundary conditions. [1] Wilson, W.R.D and Sheu, S. Real area of contact and boundary friction in metal forming. Int. J. Mech. Sci. 1988, 30(7), 475-489. [2] Sutcliffe, M.P.F Surface asperity deformation in metal forming processes. Int. J. Mech. Sci., 1988, 30(11), 847-868. [3] Ike, H. and Makinouchi, A. Effect of lateral tension and compression on plane strain flattening processes of surface asperities lying over a plastically deformable bulk. Wear, 1990, 140, 17-38. [4] Korzekwa, D.A., Dawson, P.R. and Wilson W.R.D., Surface asperity deformation during sheet forming. Int. J. Mech. Sci., 1992, 34(7), 521-539. [5] Lu, C., Wei, D., Jiang, Z., and Tieu, K., Experimental and theoretical investigation of the asperity flattening process under large bulk strain, Proc. Inst. Mech. Eng. J. 222 (2008), 271–278. [6] LTAS-MN2L. ULg. http://metafor.ltas.ulg.ac.be/. [7] Stéphany, A., Contribution à l’étude numérique de la lubrification en régime mixte en laminage à froid. PhD dissertation (in French), Université de Liège (2008) [8] Carretta, Y., Stephany, A., Legrand, N., Laugier, M., and Ponthot, J.-P., MetaLub – A slab method software for the numerical simulation of mixed lubrication regime. Application to cold rolling. In Proceedings of the 4th International Conference on Tribology In Manufacturing Processes (ICTMP), 2010,799-808.