Papers by Keyword: Continuous Casting Slab

Abstract: Mechanical properties and creep behavior of continuous casting slab subjected to uniaxial tensile tests at 1100 and 1150 °C were considered in this paper. All of specimens was given a typical in-situ melting thermal history and interrupted cooling cycle before testing. An increase in load and temperature accelerates the creep rate thereby decreasing the steady state range. A new creep equation whose parameters are calculated by inverse-estimation using the regression analysis was proposed based on Norton-Bailey creep law. Primary and secondary creep stages could be described accurately by the new equation. Positive creep effects on straightening technology in continuous casting slab were presented in this paper. Involute continuous straightening technology could give full play to the role of steel creep deformation at high temperature. This research is helpful for the design of the new casting machine and improvement of old casting machine in using depended on high temperature creep behavior.

Abstract: The temperature field and stress field were simulated using the finite element software (ABAQUS) for Q345c continuous casting slab during cooling process. The hot ductility curve, high temperature tensile strength curve, and the surface stress value were obtained according to thermal simulation experiments. The results show that the temperature of brittleness zone is at 600-850°C, and the value of surface stress is larger than the high temperature tensile strength in the slab cooling process. The heat insulation device should be installed between the flame cutting machine and the heating furnace to avoid hot crack defects caused by excessive thermal stress on the surface in the process of hot slab delivery.

Abstract: The internal quality of continuous casting billet mainly refers to the low power structure, center segregation, inner crack and the levels of inclusions. It seriously affects the comprehensive performance of steel and rolling slab of the casting billet center segregation and crack existing. The influence rules of the slab internal quality about the process and the factors of equipment combining with field production data have been discussed in this paper. Then using the improved BP algorithm with added momentum item and the prediction model of central segregation of continuous casting billet base on BP artificial neural network have been built.

Abstract: The hot ductility behavior of 800MPa ultra high strength niobium containing steels has been investigated with Gleeble3500 hot simulator. Tensile test was carried out at 650°C1300°C at a constant true strain rate of 0.001 s¹. Experimental results showed that steel A has quite well ductility, and the brittle zone is narrow. Due to pro-eutectoid ferrite film formation along the prior austenite grain boundary at 650°C-750°C, samples showed a loss of hot ductility, and the fracture morphology of the specimens was brittle intercrystalline fracture, indicating the third brittle zone of the steel. However, the third brittle zone can be avoided during continuous casting, if the temperature of straightening could be kept over 800°C.

Abstract: The behaviour of the surface defects on the continuous casting slab during hot rolling is investigated using the commercial FE-code LS-DYNA. The thermo-elastic-plastic material model is chosen in the simulation models, and the material implemented in the simulation is the austenitic stainless steel 304. The numerical results show the significant morphological changes of the surface defects during hot rolling and afford valuable indications for a deeper understanding of the underlying process. An accelerated crack growth and propagation are observed for the edge cracks, and the closure behaviour is found in the transverse and longitudinal cracks. The effect of temperature is significant on both the roll and the strip in hot rolling process. The developed models consider different types of mesh and element, thermal conditions, and rolling schedules. The predicted relationship between rolling conditions, the temperature distribution of crack, and the full history of temperature variation are discussed in this study.

Abstract: Through studying the inclusions of low carbon steel slabs produced in different casting stages, the results are dawn as follow. The reoxidation of liquid steel is very serious in casting starting,but the casting ending is not. Most of large-inclusions containe K or Na are found in the first and final slabs, which may relate to serious slag entrapment in the mould in the casting starting and ending. Many MgO-Al2O3 and Al2O3-CaO-SiO2-MgO inclusions suggest the serious entrapment of the tundish in the casting ending.

Abstract: The straightening of curved slab results in a greater straightening strain. During the process of multi-point straightening, the peak value of the straightening strain rate will appear at each straightening point. If the strain rate is too large, the straightening cracks will appear. Solidification and heat transfer of a slab is analyzed and the generation of the solidified shell and the three-dimension temperature field of the slab are calculated by using three-dimensional finite element method (FEM). Based on the finite element analysis of five-point straightening of the curved slab, the strain and strain rate of each straightening point were obtained, which is a base of the analysis of straightening cracks.

Abstract: In hot slab continuous casting (CC) process, the Machine Vision (MV) inspection method for slab surface defects has been becoming a research focus with the development of charge-coupled device (CCD) camera imaging technologies. To acquire a informative and reliable defects image is a prerequisite that means a maximum defects detection rate and minimum false recognition in the next image processing stage. In this paper, based on the CCD imaging principle and definition evaluation algorithm, the slab surface radiation feature at high temperature and CCD optical imaging properties had been analyzed under the focal plane, meanwhile, the CCD image definition of optical integral time controlling method had also been studied, which the defect image variance (IV) function, image average gradient (IAG) and information entropy (IIE) were calculated and analyzed. In the end, the image definition controlling algorithm for hot slab surface ROI imaging that adopted IIE evaluation algorithm, based on CCD integral time imaging controlling principle, had been proposed. This method also can support practical value for other machine vision engineering.

Abstract: In order to research the forming mechanism lateral bending during side pressing for continuous casting slab, the simulation model was established using finite element method. It is mainly studying object for the effect of the different position of double dies on the lateral bending, to make nodes displacement fluctuation in corresponding position of slab head and tail as the degree of lateral bending of continuous casting slab along its width direction. It can obtain the rules of metal flow along the rolling direction, when dies position deviation respectively is 0 mm, 10mm, 20 mm, 30 mm, 40 mm and 50 mm, under the other conditions remain unchanged, the bigger the dies position deviation, the bigger the corresponding pitch nodes displacement, and the bigger the lateral bending for slab. The results provide the theoretically support for the controlling position accuracy of the dies in live and enhancement the useful rate of the slab for production field.

Abstract: The modeling of solidification in Continuous Casting demands the mechanical properties of steels at high temperature. These mechanical properties parameters provide the design data for the target surface temperature curve and dynamic control modeling of secondary cooling system, and are used to research hot delivery and crack mechanisms of cast slab. The properties parameters of steels can be obtained by physics simulation experiment. Following processing parameters in Continuous Casting, the stress-strain curves and mechanical properties of steel Q345 were tested and analyzed. Then the curves of relationships between the yield strength, tensile strength, reduction of area, Young’s modulus, plastic modulus of steel Q345 and temperature were obtained. We found the strength of steel Q345 cast slab felled down basically; the ductility was decreased below 700°C, in the range of 725°C-900°C and 1275°C-melting point. The plastic modulus was analyzed with the different temperatures and the different strains in detail. The parameters of mechanical properties for steel Q345 were obtained for using in elastic-plasticity stress model.