Advanced Materials Research Vols. 652-654

Abstract: Linear defect is a common defect of galvanized sheet. Formation mechanism of linear defect was analyzed by scanning electron microscopy (SEM) and energy disperses spectroscopy (EDS). The results indicate that Al2O3 particles which have a size less than 7μm are enriched in the shallow surface of the substrate. Al2O3 particles are exposed during rolling, resulting in scratches and rough spots on cold-rolled sheet. The places where Al2O3 inclusions enrich are easy to form surface micro-cracks. Linear defects are formed at the places of scratches or cracks during hot dip galvanizing. Optimum measures are putted forward based on Al2O3 inclusions and cracks.

Abstract: The UFC (ultra fast cooling) system has great powerful cooling ability (cooling rate higher than 300°C/s for 4mm sheet). In order to make up for the deficiency of the laminar cooling system in production development, the CSP of LY steel adopted the front located solution of UFC (located between the finishing mills and the laminar cooling system). By good match between UFC and the laminar cooling system, fine adjusting the chemical composition and changing the rolling technology of Q235B, the CSP of LY steel had carried out the industrial production of Q345XJ steel (upgraded by Q235B , only need to add extremely small amounts of alloys ), the production cost of Q345XJ steel is greatly decreased.

Abstract: A test study of deformation resistance of S50C medium carbon steel in hot rolling process was conducted by using Gleeble 3500 Thermal-mechanical testing machine. The relationship of deformation resistance with different deformation temperature and deformation rate and deformation degree was analyzed through the stress-strain curve of S50C medium carbon steel which measured in the test. The results show that the deformation resistance increase with decrease of deformation temperature and increase of deformation rate and deformation degree. The math model of plastic deformation for metal of tested steel is established by using 1stopt software with multi-component non-regression. The model is proved has good curve fitting characteristics though a regression analysis of the model, it can be used provide theory basis for the formulation of rolling process and calculation of the mechanical parameters.

Abstract: In the hot stamping process, die gap may affect cooling efficiency of the die and the condition of stress-strain. When other conditions are same, die gap were taken for 0.9t, t, 1.1 t, 1.2 t, t is sheetthickness. Temperature field and thickness distribution of the parts are simulated by ANSYS/LS-DYNA module, it is discovered that the distribution of temperature and thickness is uniform when the die gap is 1t and 1.1t. Finally, an experimental is designed to verify the simulation accuracy.

Abstract: In this paper, the multi-stage die forging process of a high pressure valve bonnet was simulated by 3D coupled thermal-mechanical rigid-viscoplastic finite element (FE) method. The deformation and the metal flow field of billet were obtained. Based on the simulation, two optimized schemes were put forward for improving the yield. Both of them can save material and ensure the stability of billet during the forging process. The study can provide scientific theory foundation for practical engineering applications.

Abstract: Work roll temperature prediction model is an important part of shape control system in hot strip mill. This article performs work roll mesh generation, and establishes difference equations of each lattice point using two-dimensional alternating difference method. Then, the work roll temperature distribution at any time is acquired after solving equations with chasing method. The model established in this article has high stability, fast solving speed and high operation precision. The results, compared with the measured data, indicate that the model has high reliability and meets the demand of strip quality in hot rolling.

Abstract: Take a automobile bumper for example, analysis of effect of process parameters on warpage of a automobile bumper, including melt temperature, injection time, cooling time and packing pressure, on the warpage of the automobile bumper were analyzed by means of Moldflow software. The results show the warpage decrease of the increase of the injection time, the cooling time and the packing pressure, but when the packing pressure reached 45MPa, the warpage slightly increased; the melt temperature should be picked out by the characteristics of the plastics material.

Abstract: Axial force is an important affecting factor on the service life of rolls’ bearings. Based on Timoshenko’s deep beam theory and finite difference method, the efficient and accurate roll stack deformation model is built to provide the deformed rolls’ shape and contact stress distribution. And then, the formation mechanism and calculation method of axial force for 4-high mill is presented. By contrasting with the result given by commercial FEA package, the error between ANSYS and home-made program is less than 10%, the accuracy of axial force model is validated.

Abstract: TC4 alloy is widely used in engine. The method of forming is forging and mechanical process in the old days. With the complex profile of Titanium alloy, the process is quite difficult and lead to low ratio of qualified products. Therefore the method of hot rolling is chosen. According to the basic theory of hot rolling and applying the FEM simulation technology, the one symmetrical pass with different gauge between the two rollers is designed to obtain expected section with the complex profile. In order to restrict the rise of temperature basing on the characteristic of TC4 and make the flowing uniformly to meet the performance requirements, the optimum matching scheme of the pass with the roller is designed first, then the reasonable shape and dimension of the blank is determined, finally the three rolling passes of one blank rolled in one pass with different gauge is decided.

Abstract: Solid freeform fabrication (SFF) technology has been widely used to fabricate three-dimensional (3D) cell constructs. As multi-cell construct is a heterogeneous object (He-Object), it is a trend of biomanufacturing to use SFF technology to fabricate multi-cell constructs. In this paper, a novel multi-nozzle deposition system, called as 3D direct controlled cell assembling (CA) system, was developed to fabricate 3D multi-cell constructs. The developed system design was demand-oriented and applied functional modular design method. As the key part of this system, the multi-nozzle system was designed and described in details. Experimental study was conducted and results showed that the system could meet the requirements of the process and be used to fabricate complex 3D cell constructs. By comparison, the developed system could precisely deposite biomaterials with high viscocity and form constructs with big size in continuous deposition mode.