Materials Science Forum Vols. 704-705

Abstract: In order to predict the microstructure evolution and grain size of GH4169 alloy blade in finish forging process and optimize the parameters, a coupled simulation between thermal mechanical and microstructure evolution was realized through embedding the developed user subroutines into the DEFORM-3D software. The temperature, equivalent strain, dynamic recrystallization fraction, average grain size and grain size distribution were predicted and discussed. The experimental results of microstructure under the same forging condition were investigated. The average grain degree in the blade rabbet and body are 8 and 10 respectively. The calculated results of microstructure have a good agreement with the measured value from experimental data and the prediction error of average grain size is less than 6.7%. The developed program is reliable and the accuracy is satisfying. The distribution of grain size along the blade body is decreased from the middle to the leading and back edge. The shape and microstructure after finish forging under the condition of technology parameters meet the user’s requirement. Keywords: Blade, GH4169 alloy, Numerical simulation, Microstructure, Forging

Abstract: The hot hole flanging process of a connection tube in a thick-wall head was researched by finite element analysis and experiment in this paper. The deforming mechanism, main influencing factor and defects in hole flanging were analyzed. According to the stress state and the flow mode of deforming metal, the hole flanging process can be divided into two stages, that is, blending and hole flanging. Processing parameters, such as diameter of pre-holes, space ratio of die cavity, punch shape and size and their effect on forming were researched. The 1:3 scaled experiment was done in 30MN hydraulic press using A508-Ⅲ steel. The formed connection tube had a good quality and its end face was smooth without any crack. The measuring result showed that the error between simulation data and test data was less than 5%, which verified the feasibility of hot hole flanging process and provided an important reference for virtual production. Keywords: Connection Tube Thermal Hole Flanging Thick-wall Head Pro-hole Diameter Space Ratio Scaled Experiment

Abstract: Using thermal simulator (Gleeble 1500D), the thermal deformation behavior of Cu-P weathering steel containing Cr, Ni, Mo under the conditions of various deformation temperatures and strain rates was studied. The true stress-true strain curves at various thermal deformation conditions were got, and the thermal deformation equation was established. Then the microstructure features of the steel under various deformation temperatures and strain rates were analyzed when the true strains were same. The results show that with the same strains and strain rates, the higher the deformation temperature, the easier the recrystallization occurs, and the greater the size of the recrystal grains. And with the same strains and deformation temperatures, the lower the strain rate, the easier the recrystallization occurs, and the greater the proportion and size of the recrystal grains. Keywords:Weathering steel, Deformation temperature, Strain rate, Thermal deformation equation, Recrystallization

Abstract: In micro-manufacture field, micro-forming is paid much attention due to its efficiency for mass production. However, owing to the particularity of deformation, mass researches for specialized micro-forming processes to direct the industrial production are of great urgency. As a similar process with the micro-forming, the forming property of micro-feature forming in coining process was investigated by the experimental research and numerical analysis. Firstly, utilizing the workpieces with different thicknesses and micro-feature sizes, the coining processes were numerically simulated to study the forming property of micro-feature. The height of micro-feature was selected as the evaluation criteria for the deformation behavior. Then, the pure copper specimens with different thicknesses were coined experimentally, using a die with a micro-hole by the universal testing machine to verify the simulation results. Finally, a modified scheme was successful to be proposed which could improve the manufacturability of the processes. The research results could provide technical references for manufacturing micro-parts and those with micro-features.

Abstract: The hot deformation behavior of Cu-Ni-Si-P alloy have been investigated by means of isothermal compression tests on a Gleeble-1500D thermal mechanical simulator in the temperature ranges of 873-1073 K and strain rate ranges of 0.01-5s^-1. The results show that the dynamic recryatallization occurs in Cu-Ni-Si-P alloy during hot deformation. The peak stress during hot deformation can be described by the hyperbolic sine function. The influence of deformation temperature and strain rate on the peak stress can be represented using the Zener-Hollomon parameter. Moreover, the activation energy for hot deformation of Cu-Ni-Si-P alloy is determined to be 485.6 kJ / mol within the investigated ranges of deformation temperature and strain rate. The constitutive equation of the Cu-Ni-Si-P alloy is also established. Keywords: Cu-Ni-Si-P alloy; Hot deformation; Dynamic recrystallization; Zener-Hollomon parameter.

Abstract: In the paper, the high-temperature compression test of BTi-62421S alloy was carried out in the temperature range from 850°C to 1050°C, strain rate range from 0.01 s ^-1 to 30 s ^-1, and the deformation of 70%. The results show that the flow stress of BTi-62421S alloy significantly increased with the decreasing of the temperature and the increasing of the strain rate. By calculating the activation energy of deformation and analyzing the stress-strain curve, it can be seen that the softening mechanism of hot deformation of BTi-62421S alloy is different near the （α+β）/β phase transforming temperature. The softening mechanism of hot deformation is mainly dynamic recrystallization in （α+β） area and it is mainly dynamic recovery above β phase transforming temperature. According to hyperbolic sine model, the alloy’s constitutive equation is established. Key word: BTi-62421S alloy; high temperature figuration; constitutive equation

Abstract: The warm deformation behavior of as-quenched and as-annealed ASTM 1045 steel was studied by isothermal compression testing on a Gleeble3500 machine. The temperature range was 550-700°C and the strain rate range 0.001-0.1s^-1. Transmission electron microscopy (TEM) was used to study the microstructures associated with the observed deformation phenomenons. The results show that the flow stress of quenched specimens is higher than that of annealed ones at 550°C when strain rates are greater than 0.001s^-1. However, at 600-700°C and strain rate of 0.001s^-1, the whole flow curves of quenched specimens are below that of annealed ones. Under the rest conditions, the flow stress of quenched specimens is higher at the beginning of compression and then the opposite is true after the strain is greater than a critical value. The microstructure examination proves that the dynamic recrystallization easily occurs in quenched specimens during warm compression, which results in the above phenomenons. Keywords: warm deformation, flow stress, steel, quenching, annealing

Abstract: According to the equation of pass surface in skew rolling, the characteristic curves are obtained by VC++ programming, a three-dimensional model of the roller is constructed by using of modeling function of Pro/E software, it is done for numerical simulation of Φ21.6mm Al ball forming process in skew rolling by means of ANSYS6.0 software, the stress and strain distributions are obtained in this simulation. It provides the important foundation for the design of dies and making clear the cause of the rolled piece inner defect. Key words: Skew rolling; Numerical simulation; Pro/E modeling; Al ball

Abstract: The stretch reducing process is the last hot deformation process of the hot-rolled seamless steel tube’s production. Its role is to decrease the tube’s diameter under the large tension and expand the range of product specifications. But the stretch reducing process often results in wall thickness tolerance at the head and end of the tube. In order to solve the problem, a 3D elastic-plastic finite element analysis model was established to simulate the stretch reducing process of φ159 unit. Based on this, the tube’s wall thickness distribution was studied and the parameters of sharpen rolling process was put forward. Numerical simulation results indicate that with the parameters of sharpen rolling process, the length of wall thickness tolerance was shorten and the rate of finished products was proved.

Abstract: The soft cobbing, used in steel’s continuous casting, is widely applying in technologies of rolled metal manufacturing. It is important to know ingot’s stress-strain state and dynamics of ingot’s changes while cobbing, when there is a liquid metal in the centre of section. The complex questions of numerical modeling of soft cobbing process and experimental investigation on physics plasticine models are considered in presented work. The analysis of findings is presented in the article.