Advanced Materials Research Vols. 538-541

Abstract: Multi-wedge Cross Wedge Rolling (MCWR) is an advanced technology in forming long axial parts, and it does not have the disadvantages of Single-wedge Cross Wedge Rolling (SCWR).However, it is extremely important to realize the regularity of the displacement on the end-section of the rolled parts in MCWR due to the complexity of its forming mechanism. In this paper, based on the method of the displacement on the end-section of the rolled parts in SCWR, the rules of the displacement on the end-section of a typical rolled part in MCWR were investigated theoretically, and the curve on the end -section of the rolled part in MCWR were analyzed.Based on the curve, the regularity of metal flowing and the characteristic of forming for the typical rolled part in each phase by MCWR were analyzed. It is of high value in studying the forming mechanism and designing mould and technics in MCWR.

Abstract: In this paper, Taguchi and CAE technique are combined to study the influence of process conditions on the warpage of injection molding parts through twice orthogonal design experiments, and the injection process parameters are optimized according to the warpage. For the parameters selected, melt temperature and packing pressure have effects on the warpage of injection molding parts are highly significant, injection time is significant, other parameters have little effects. Within the range of experiments, the warpage decreased with the rise of the melt temperature and packing pressure. At last, the optimum process parameters of injection are that the mold temperature is 60°C, packing time is 10s, melt temperature is240°C, packing pressure is 115MPa and injection time is 0.4s.

Abstract: By using Gleeble1500-D thermal simulation machine, Rare Earth(RE) adding Q345B steel of single-pass compression test were carried out. A study had been made of the effect of different deformed conditions in hot rolling process on Nd-modified Q345B steel recrystallization behavior and microstructure evolution.The result shows that RE steel Q345B of single compression test are consistent with the general experimental rule. Rare Earth additions significantly increased hot- deformed resistance at low temperature compression, however, it is not obvious at high temperature. The increased hot-deformed resistance and the degree of the retardation is more obvious for heavy RE Tb than light RE Nd.

Abstract: To establish the efficacy of electromagnetically assisted sheet metal stamping (EMAS), the corner-fill ability of AA5052 sheets specified in conventional deep drawing was experimentally demonstrated and evaluated within a two-step EMAS process. First, conventional axisymmetric deep drawing was conducted to make a cylindrical cup with a rough-shaped bottom corner. The second step utilized a shaped coil to force the pre-formed cup into the die cavity, and the related electromagnetically assisted corner-fill performance was investigated. Experimental results show that the ideal of hybrid stamping-EMF sequence can successfully solve the formability problem involved in conventional stamping. During electromagnetically assisted corner-fill process, the deformation dispersion effect of dynamic phenomenon works remarkably on the fully deformed sheets, which will inhibit local instability of deformation and thus enhance materials formability.

Abstract: In this paper, effects of partial remelting treatment on microstructure and properties of ZL205A alloy were studied in detail. The results show that the grain size of ZL205A alloy decreases at different degree. The grain size increases first and then decreases with increasing of returns content. The average grain size of the primary ZL205A alloy was measured to be about 60 μm, and the good result can be got of the ZL205A alloys with the average particle size of α (Al) phase being about 33 μm after adding 20wt.% returns. The ZL205A alloy with 20 wt.% returns has a considerably high tensile strength and yield strength of 525MPa and 445 MPa, respectively, which is much higher than 501 MPa and 421 MPa of primary ZL205A alloy, meanwhile the elongation level is up to14%.

Abstract: The non-metallic inclusions in FGH96 superalloy during different plastic processes were studied. The results show that SiO2 react with aluminum and titanium in FGH96 superalloy and the reaction zone is formed in the interface between SiO2 and alloy, whereas Al2O3 react with no elements in FGH96 superalloy and the transition zone between them is mechanical combination during the plastic processes. In addition the sizes of non-metallic inclusions increase in the direction perpendicular to deformation during isothermal forging process. The non-metallic inclusions are pulled into a discontinuous line in extrusion direction and areas of non-metallic inclusions in each direction are constricted during extrusion process. The non-metallic inclusions of FGH96 superalloy is conditioned by the state of the as-extrusion inclusions during extrusion+isothermal forging process. In summary, extrusion process with large extrusion ratio can break the non-metallic inclusions in FGH96 alloy effectively and improve forging quality.

Abstract: The most common issue in injection molding is warpage of work pieces. Copier parts are taken as the example. The mold flow software is used to analyze and solve defects of such parts, and the optimal mold structure can be obtained so as to save costs and improve product quality and efficiency.

Abstract: Aimed at the work conditions and the failure of the grinding ball in ball grinding, High chromium cast iron with the characteristics of long service life, high abrasion resistance and good shock resistance must be chose in the ball grinding . The best mixture ratio of chemical compositions was pointed out, and the production technological process by using die cast is introduced.

Abstract: This research explores the micro-forming process of spiral groove pattern on Fluid Dynamic Bearing(FDB), which is utilized in precision driving part of the hard disk drive(HDD), using micro desktop forming system. While EDM and ECM process has been widely used to engrave the precision pattern which generates dynamic pressure on FDBs, micro forming process is newly proposed in this study to increase the productivity and to reduce the product costs. At first, desktop forming system is designed for spiral groove pattern forming. FE simulations are followed in order to evaluate the feasibility of micro-forming. The simulation results show that forming loads of 1,500Kgf is required to fabricate micro patterns with the depth of 15 μm. Finally the formability test is carried out with various forming loads. Deformed shapes and forming loads obtained from the test are compared with those from the analysis. The results fully demonstrate that micro pattern forming techniques are available to fabricate micro spiral groove patterns in FDB.

Abstract: The effects of annealing routes (batch annealing and continuous annealing) on the development of microstructure and texture in a cold-rolled Nb-IF high strength steel sheet were studied by means of optical microscopy(OM), electron backscattered diffraction(EBSD) and ODF analysis. The results show that the finer and more homogenous recrystallization grain can be observed in the CA steel. The CA process leads to an increase in the intensity of the γ-fibers, and the very sharp and uniform γ-fibers are found in this case, which is beneficial to the deep-drawability.