In this study, the effects of isothermal bainite treatment (IBT) holding time on the microstructure of transformation induced plasticity (TRIP) seamless steel tube were studied via optical microscopy, TEM and XRD. Its mechanical properties and hydroformability were evaluated by tensile test and flaring test, respectively. The results revealed that the volume fraction of retained austenite (RA) increased at first then decreased with IBT holding time for a particular set of intercritical annealing (IA) temperature, IA holding time and IBT temperature. It was also demonstrated that high tensile strength of 618MPa, total elongation of 35.5%, n-value of 0.23 and better hydroformability could be successfully produced in this TRIP steel tube at IA temperature of 800°C, holding for 10 min, and IBT of 410°C for 4 min holding time.
In this study a cyclic rotating bending process for microstructure control of metal tubes was newly proposed. The AZ31 magnesium alloy tube was conducted to investigate the effect of the rotating bending process on the microstructure and mechanical properties of metal tubes. The rotating bending process was carried out with rotation speed of 20r/min for 10min at the temperature of 150, 200, 250, 300 and 350°C. The rotating bending processes carried out with various conditions show that the grains in cross-section and longitudinal section of magnesium alloy tube were refined for all samples by the rotating bending process with rotation speed of 20r/min for different rotation numbers and temperatures. The rotating bending temperature shows a various effects on the mechanical properties. When the temperature was 200°C, the highest strength as well as ductility was obtained.
The newly proposed rotating bending process of metal tubes is a novel kind of Severe Plastic Deformation (SPD) process, which is expected to refine and control the microstructure of metallic tubular materials. The stress distribution and accumulated equivalent plastic strain of deformation part have a significant influence on the microstructure refinement and control of metal tubes during the rotating bending process. The present study focused on the analysis of stress and strain of deformation part during rotating bending process of metal tubes. The model of the deforming metal tubes was proposed. The formulas for determining the stress and accumulated equivalent plastic strain were successfully achieved by analyzing the deformation of metal tubes during rotating bending process.
The metal bellows are used in a large number of industrial applications for their flexile and elastic properties. For the traditional manufacturing methods for metal bellows, the dies and (or) tools are required. It is inconvenient to change the shape of metal bellows and also leads to the high cost. To reduce the manufacturing cost and produce the metal bellows with various shapes, the semi-dieless metal bellows forming process was proposed. The deformation behavior of aluminum alloy tube in semi-dieless bellows forming process was investigated in the study. The effects of compression ratio, heating length on the convolution height, pitch of bellows during the semi-dieless bellows forming process were studied. The results showed that the deformation conditions of semi-dieless forming process have significant influences on the shape of aluminum alloy bellows and deformation behavior of aluminum alloy tube in the forming process. The increase of compression ratio, heating temperature and heating length resulted in the increase of pitch and decrease convolution height of aluminum alloy metal bellows.
Low rank coal is an important energy resource in the world, particularly in the developing countries. But its high water content causes a waste of energy and serious environmental pollution, which restricts its applications. In order to improve the efficiency of the low rank coal and reduce pollution, the drying processes for low rank coal are urgently needed. This paper presented a review of the general drying processes for low rank coal. In the review, the newly-developed vibrating fluidized bed (VFB) drying process was emphasized. This novel VFB drying process which can be used in large-scale industrial production has several advantages, such as high speed, high drying intensity and low pollution. Moreover, two VFB researches reported by the authors were also introduced. In these researches, the dynamic behavior of VFB was simulated by two commercial codes of ADAMS and ANSYS separately. According to the simulation results, the exciting force and the structure of sieve box were optimized.
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