Advanced Materials Research Vols. 941-944

Abstract: Based on the characteristics of longitudinal profiled plate rolling process, longitudinal profiled plate rolling process is a non-stable rolling process. The rule of volume flow rate has not applied to the longitudinal profiled plate rolling process. So, forward slip model and metal average deformation velocity of conventional rolling do not apply to longitudinal profiled plate rolling process. Forward slip model and metal average deformation velocity of longitudinal profiled plate rolling process are deduced by according to the definition of forward slip and metal average deformation velocity.

Abstract: Current tube plate stamping die usually have some common problems, which include low standardization, low standard penetration and long mold design cycle. By analyzing stamping die used in the refrigeration industry, the cold-drawing dies blanking needs to be designed and optimized. Compared with the previous design methods, the method, that the Pro/E plug-PDX was used to design cold-drawing dies blanking with refrigeration equipment, has a lot of advantages. First, cycle was shortened to one-third of the original; second, the compound pressing method is able to reduce the pressing step and increase stripping device, in order to improve the reasonable structure and production efficiency. The new method proposed in this paper is able to increase design efficiency, shorten design cycles, reduce workload and improve the accuracy of the mold design, and reduce the cost of mold design.

Abstract: Analysis of the basic characteristic of cross wedge rolling forming process and the stress -strain research at various stages are summed up in order to obtain the basic rule of law and the metal flow regular during forming.

Abstract: Taking the geometric configuration of complex-shape forging into account, the isothermal split-die forging method, which is one multi-way die forging technology and can be operated on the general hydraulic press, is employed. The temperatures of billed and dies are 420°C and 380°C in the isothermal forging process. The coupled thermo-mechanical finite element method (FEM) is used to analyze the forging process. FEM calculation results show several folds had been formed in the final forging process due to unreasonable geometric configuration of preform. The folds mechanism is that direction of velocities become cross on the surface of billet, and the folds can be avoided if the direction would be kept convex. And then the preform is redesigned. A set of isothermal precision forming equipment is designed and manufactured. The experimental results verify the selected process and preform configuration. And all of the hardness, dimensional accuracy and surface quality of the forgings obtained by the equipments satisfy the requirements.

Abstract: The process of polymer melting plays a vital role in stable extrusion. Due to its complexity in “a black box”---extruder, it is difficult to observe directly. Therefore, the visualization technology applied in this course emerged and has been improved continuously, which is regarded as an important means of promoting the development of extrusion theory. This article describes and analyses the phenomena of bulk melting and granule melting with the aid of the submarco-and macro-scopic visual technique in single screw extrusion. Physical model of granule initial melting in extrusion was presented.

Abstract: As a consequence of post-buckling due to high residual stresses caused by the cold-rolling process, long free thin strips frequently show excessive wavy surface. In this paper, a new analytical approach by extending a classic post-buckling analysis method based on the minimum potential energy principle is used to study on the influence of strip thickness and width on the post-buckling deformation for the center and edge wave. It is concluded that the thickness of the strip has significant effect on the flatness defects, while the width does not.

Abstract: As traditional screw extrusion die tolerance analysis has characteristics like manual calculation, experience dependence so far, this paper aims at applying CAT (Computer Aided Tolerancing) into extrusion field with the assistance of tolerance modeling and self-generation algorithm of retrieval dimension chain to analyze tolerance and reassign tolerance based on the technology used for aircraft assembly referring to chemical characteristics of the manufacturing process. Practice on production line testified the rationality of improved tolerance design.

Abstract: Shrinkage porosity and segregation defects are often found in an air cooled jumbo steel ingot, which will influence the quality of the final rolled plates.The solidification behaviours for a 60t jumbo slab ingot under varied cooling conditions were simulated using the ProCast software.The influences of different cooling speed on dendrite distribution and segregation were studied.The results show the jumbo slab ingot could freeze layer by layer when the heat transfer coeffcients of mould increase to 1000W·K^-1·m^-2. The thick finer chill zone were achieved. At the same time, the columnar crystals grow preferentially parrelling to the density of heat flow, and finer equiaxied crystals are formed in the core of the ingot. They all improve the microstructure and decrease the composition segregation of jumbo slab ingot.

Abstract: The quality of extrudate is closely related to its rheological properties during extrusion. Therefore, on-line measurement of rheological properties of polymer is important in extrusion process. In the present work, comparisons between the on-line viscosities of LDPE in single screw extruder and that in lab under the same condition were made by using online rheometer. Effects of set temperature of on-line rheometer, screw configuration and different positions, as well as weight proportions of filler, size of MICA particles of LDPE/MICA multiphase system on the melt viscosity in single screw extrusion are discussed.

Abstract: The key models of flatness analysis method are the strip plastic deformation model (SPDM) and the roll stack elastic deformation model (REDM). The traditional method uses the SPDM to calculate the distribution of rolling force, and the REDM is adopted to calculate the profile of exit strip. The reverse iteration method uses the REDM to calculate the distribution of rolling force, while the SPDM is adopted to calculate the profile of exit strip. The model coupling method integrates SPDM and REDM as one set equations through their internal relation. In this paper, the basic thoughts of three methods are introduced. Through a typical example, the convergence, calculation speed and precision of three different methods are analyzed. It is found that the calculation precision of the three methods are almost the same, but the model coupling method is more outstanding than other two methods on the convergence and calculation speed, so the model coupling method is the best choice for flatness analysis.