Advanced Materials Research Vols. 1004-1005

Abstract: Maglev uses MTS815.02 rock mechanics experimental electro-hydraulic systems and NM-4A nonmetallic ultrasonic testing analyzer for coal fire area overlying rock outcrop samples were heated fracture mechanics properties of experimental studies of rock samples reveal the strength and deformation characteristics with temperature the variation. The results showed that: rock microstructure changes at high temperatures on the mechanical properties have a significant effect, the higher the temperature, the greater the sandstone porosity, fissures, the more velocity is smaller; fire zone in the role of coal outcrops, rocks and mineral composition and structure has changed, the internal expansion of initial damage evolution, a large amount of leakage fissures, heat pressure increases, resulting in the upper part of the coal temperature of natural convection of air through the crack, thereby maintaining the vicinity of the coal to maintain a certain concentration of oxygen. Dynamic evolution of coal seam outcrop fire mechanism provides a theoretical basis.

Abstract: Equal channel angular pressing (ECAP) is widely studied for its potential to produce ultra-fine grained (UFG) structure in TiNi shape memory alloys (SMA). In the present work, the effect of multipass ECAP parameters on the deformation behavior and strain distribution was investigated, at various deformation temperatures through different planes in the ECAPed billet. Three-dimensional (3D) geometric model with corner angle 120^◦ was designed by finite element method (FEM) software for ECAPing Ti-50.8%Ni by route B_c in DEFORM-3D software. Two methods were used to quantify deformation homogeneity through various planes in the processed billet, including strain standard deviation (SSD) and inhomogenity index (C_i). The simulation results demonstrate that by increasing ECAP passes, the cumulative average strain can increase and obtain UFG structure, but heterogeneity still exist across planes. In addition, temperature has a remarkable effect on homogeneity distribution .As well as C_i exhibits good results for multipass ECAP at various deformation temperature compared to SSD value.

Abstract: An automatic control method to prevent thin strip steel from breaking in cold rolling is presented in this paper. The strip width detector is equipped at the entry and exit sections of the cold rolling mill respectively, thus the width reduction of the strip steel before and after the mill can be real-time detected . The signal of the width reduction rate exceeding a certain value means that the strip edge is too tight. Then, via the strip shape adjusting mechanism, the edge of the strip steel becomes loose and the strip breakage can be avoided. By applying this method, the incidence of strip breakage can be reduced and the productivity capacity can be increased, and more, the width control accuracy of the rolled steel strip can be improved. The validity of the proposed method is verified by the example simulation.

Abstract: This paper firstly analyzes the problems that exist in the cold rolling of steel industry. Secondly, a new approach is proposed to temper and straighten the strip steel based on the temper leveling mill, shortly, TLM. The required high quality of the wave, surface and mechanical properties can be achieved only with TLM. TLM holds the functions of both temper machine and straightening mill and can produce good quality strip steel, no only the waviness, mechanical properties, but also the surface quality. The usage of TLM can lower the cost of the production of tempering, straightening and equipment investment.Finally, the experiments are done and verify the validity of the approach.

Abstract: This paper proposes an automatic control strategy of the strip width in cold rolling process. The prediction model for the exit strip width of each stand is established. In addition to the strip width variation of the incoming hot-rolled material between the measured and the pre-set values, the variations of the rolling force, tension, bending force and the roll shift amount of each stand are utilized to model and forecast the stand exit width deformation. Then, the model can be used to determine the compensation values of the different profile adjustment mechanism and the exit strip width can be controlled in high accuracy. In this way, the effect of the strip width variation of the incoming hot-rolled material and the fluctuation of the stand rolling process parameters on the exit strip width can be eliminated. Moreover, the feed-forward control of the strip width can reduce the incidence of abnormal situation, such as the strip breakage and off-tracking ,and improve the stability of the cold rolling process.

Abstract: Discrete element modeling (DEM) is the most suitable modeling technique to simulate the mass flow of particles in chamber recently, which is an important part of VSI to break rock. DEM is presented in this message to predict sand production within a US7 vertical shaft impact crusher. Sand production is one of important parameters to judge the productiveness of VSI. Despite complicated particle movements in vertical shaft impact crusher, it is a necessary work to study the sand production of VSI. Vertical shaft impact crusher is simulated under different conditions in EDEM software.In order to investigate effects of different parameters on sand production, four parameters which include rotor rotation, inputs, radius of particle and interval between the rock bed and throwing material hammer were separately set into simulation tests.

Abstract: A common mechanical model of ball-end milling cutter is analyzed in this paper, and take advantage of the orthogonal experiment method to make experiment of milling to identify the milling force coefficients with the titanium alloy material as the test object.Then put the coefficients in the mechanical model of ball to use MATLAB software to predict the milling force. The results of experiment and results of simulation are basically identical, it shows that the mechanics model of ball milling is proved to be correct.

Abstract: A new type of high strength and low cost bainitic steel with ultra-low carbon content and high Si content has been developed on the basis of Mn-series air-cooling bainitic steels. The tensile properties of YS>690MPa and the impact toughness of A_KV>60J at-40°C were obtained by controlling the processing parameters. This was attributed to the formation of the grain boundary allotriomorphic ferrite (F_GBA) and the granular bainite (GB) with different shape of M/A islands. The high strength due to the inter-lath lamellar M/A islands or retained austenite companying with high dislocated bainitic ferrite laths of average 300nm width. The effect of microstructure on the impact crack initiation and propagation was studied. The results showed that crack initiation occurred in two different types of sites: at interphase boundaries of bainite ferrite (BF) and M/A islands, at grain boundaries. The F_GBA and bainite ferrite (BF) both had blunting effect on microcrack tip to reduce the crack propagation path. Because of the presence of F_GBA, the unit crack path was short, at less than 5μm. The blunting effect of BF could be enhanced by the M/A islands, which force the cracks change the propagation path and reduce the unit crack path to less than the size of bainite packets. The mechanism of low temperature microcrack origin of the ultra-low carbon bainitic (ULCB) steel with the microstructure of the F_GBA and GB was also discussed.

Abstract: AP1000 nuclear power main pipe, a type of complicated thick-walled tube structure with both high and thick-walled nozzles, is one of the key parts in nuclear island. It is required to be manufactured by integral plastic forming technique. Up to now, no economical and efficient plastic forming process for AP1000 main pipe has been reported. To aim for forming the tube structure with a nozzle such as AP1000 main pipe, a radial upset-extruding (RUE) process was developed, in which the initial billet is an extruded tube with a hole. RUE process is an extrusion method which realizes radial outflow of the metal around the hole of tube billet through an axial upsetting force and restriction of dies. Thick-walled tube structure with a nozzle derived from AP1000 main pipe was simplified to be a thick-walled three-way pipe, on which RUE process was analyzed based. Combined with reduced scale model experiments, thermomechanical coupled finite element analysis integrated with recrystallization models of 316LN was performed to investigate RUE process. Metal flow, deformation distribution, recrystallization distribution, and extrusion load and clamping load in RUE process was analyzed. The experimental workpiece of pure lead based on reduced scale model validate metal flow behavior predicted by using numerical simulation. The results indicate that the essence of RUE process is to deflect the flow of the material around the orifice of the tube billet. The loads of dies are significantly sensitive to the initial forming temperature and the friction coefficient, while the impact of the extrusion velocity is negligible. RUE process could be used to form thick-walled tube structure with a nozzle, and it has a potential for solving the manufacture of AP1000 main pipe.

Abstract: The austenite steel after rolling was radiated by the alternating magnetism, and the effects that alternating magnetic on the austenite transition was studied. The result shows that the alternating magnetism promotes the austenitic grain growth of low carbon steel. If the magnetic field intensity is increased, it could provide better performance of raw materials to cold rolling processing.