This study investigated the mechanical properties of steel in flanges, with the goal of obtaining high strength and high toughness. Quenching was applied alone or in combination with tempering at one of nine combinations of three temperatures TTEM and durations tTEM. Cooling rates at various flange locations during quenching were first estimated using finite element method simulation, and the three locations were selected for mechanical testing in terms of cooling rate. Microstructures of specimens were observed at each condition. Tensile test and hardness test were performed at room temperature, and a Charpy impact test was performed at −46 °C. All specimens had a multiphase microstructure composed of matrix and secondary phases, which decomposed under the various tempering conditions. Decrease in cooling rate (CR) during quenching caused reduction in hardness and strength but did not affect low-temperature toughness significantly. After tempering, hardness and strength were reduced and low-temperature toughness was increased. Microstructures and mechanical properties under the various tempering conditions and CRs during quenching were discussed. This work was based on the properties directly obtained from flanges under industrial processes and is thus expected to be useful for practical applications.
16 October 2014 in Acta Metallurgica Sinica (English Letters)
The porosity, permeability, and capillary force of porous sintered copper were examined in relation to the effects of copper powder size, pore-forming agent, and sintering conditions. Cu powder with particle sizes of 100 and 200 μm was mixed with pore-forming agents ranging from 15 to 45 weight percent, and the mixture was sintered in a vacuum tube furnace. Copper powder necks were formed at sintering temperatures higher than 900 °C. The porosity, as determined by the Archimedes measurement method, and the permeability performance of the sintered body displayed higher values when the Cu powder size was uniform or small. To investigate the capillary force of the sintered foam, a test was conducted using a raised meniscus test device. As more forming agent was added, the capillary force increased. It was also higher when the Cu powder size was larger and the size of the powders was not uniform. The result was discussed in relation to porosity and pore size distribution.