Papers by Keyword: Cooling Rate

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Authors: Hong Liang Zheng, Lin Li, Xin Xin Yuan, Xue Lei Tian
Abstract: This paper presents the relationship between the carbon atom diffusion coefficient in the austenite and the temperature during the nodular cast iron solidification under different cooling rates or with different carbon contents. Pouring the wedge-shaped casting explores the influence of cooling rate on the diffusion coefficient. The other part explores the change of the diffusion coefficient with different carbon contents by water quenching to save the organization in the solidification. Results show that both the cooling rate and the carbon content can affect the diffusion coefficient, and it decreases as the cooling rate increases. More attempts were also done to correlate the diffusion coefficient with the temperature in different carbon content. It has been found that the diffusion coefficient decreases as the temperature increase.
Authors: R. Datta, Sanak Mishra, V. Ramaswamy, Anthony J. DeArdo
Authors: A. Shokouhi, Hossein Beladi, Peter D. Hodgson
Authors: A. Rose, O. Kessler, Fabian Hoffmann, H.W. Zoch, P. Krug
Abstract: For quenching of age hardenable aluminum alloys today predominantly aqueous quenching media are used, which can lead due to the Leidenfrost phenomenon to a non-uniform cooling of the parts and thus to distortion. In relation to the conventional quenching procedures in aqueous media, gas quenching exhibits a number of technological, ecological, and economical advantages. The quenching intensity can be adjusted by the variable parameters gas pressure, gas velocity as well as the kind of gas and thus can be adapted to the requirements of the component. By the higher uniformity and the better reproducibility, gas quenching offers a high potential to reduce distortion. Cost savings would be possible, because of reduced distortion and therefore less reworking. High-pressure gas quenching with nitrogen or helium, as well as air quenching at ambient pressure in a gas nozzle field was applied to the spray formed aluminum alloy Al-17Si-4Fe-3Cu-0.5Mg-0.4Zr (DISPAL S232). Hardness and tensile tests have been carried out to determine the mechanical properties after gas quenching and aging compared to water quenching. The distortion behavior of a forged aluminum component of the spray formed alloy was examined after gas quenching and after water quenching. Gas quenching showed remarkable advantages regarding distortion.
Authors: Anand S. Solay, B. Mohan
Abstract: In this paper the effect of particle size of aluminium powder and furnace controlled cooling after sintering on porosity level and micro hardness of an elemental 6061 aluminium alloy has been investigated experimentally and the micro hardness value is compared with the Neural network algorithm using matlab. The algorithm used here are Gradient Descent Back propagation with Adaptive Learning Rate. Aluminium particle sizes of 20µm and 150µm were used. The elemental 6061 aluminium powders are warm compacted at 175MPa. After sintering for about one hour at 600°C, the aluminium compacts were furnace cooled at the rate of 1°C/min to different temperatures of 500°C, 400°C, 300°C and 200°C. When the cooling temperature after sintering inside the furnace is effected at various temperatures from 600°C to 200°C, for a precipitate hardened aluminium compacts with aluminium particle size of 20µm, the porosity level reduced by 26% and that for aluminium particle size of 150µm, the porosity level reduced by 23%. Marked improvement in micro hardness value is also observed correspondingly. Then the Neural Network was trained using the prepared training set which was recorded by the experimental values. At the end of the training process, the test data were used to check the accuracy result. As a result the Neural Network was found successful improvement in prediction of microhardness in a slow cooled sintered powder metallurgical 6061 Aluminium alloy.
Authors: Yan Hai Yang, Xiao Xi Gao, Jin Guo Wu
Abstract: The paper uses a new energy-saving and environment-protecting road material. On the basis of comparative analysis with the road all performance of hot mix asphalt SBS modified asphalt mixture, focuses on the compaction property at the new material lower construction temperature. The results show that the energy-saving and environment-protecting road material can effectively guarantee the performance of asphalt mixture and asphalt pavement after construction temperature is lower 30°C, forming a stable compaction interval and extend the construction time. Also can reduce the emissions of harmful gases on asphalt mixing and construction process, to save energy and protect environment.
Authors: K.V. Sreenivas Rao, S. Sanman
Abstract: The cooling rate depends on the properties of the mold material which has significant influence on the formation of microstructure and in turn on the properties of the cast components. This work is aimed at preparing the Al-B4C composite using different chill materials by gravity die casting and recording the casting temperature during pouring and subsequent solidification to analyze the cooling rate of the casting. The effect of chilling on the microstructure and mechanical properties are determined. The cast specimens are cut and polished by standard metallographic procedure. Optical micrographs are taken at different magnification to reveal the microstructure and B4C particulate distribution. The micro hardness and tensile test results indicate that there is a significant increase in these properties with the increase in B4C content.
Authors: Yuan She, Wei Ming Kong, Zhao Hui Zhang
Abstract: The tests were conducted on 400MPa hot-rolled ribbed bar (HRB400). The cool bending fracture appeared frequently in the production was analyzed. The research result showed that the cool bending fracture of rebar were caused by element segregation of C, Mn, inclusions, the existence of banded structure, widmannstatten structure and bainite structure in the center and edge of rebar. The inclusions are the root cause of internal crack and one of the reasons to fracture. Reasonable cooling rate can refine grain size, while the overquick cooling speed could result in the formation of widmannstatten structure in acicular or plume, increased the brittleness of steel and reduce its cold bending properties. On this basis, some improvement opinions were put forward: using the raw material with low Mn, S and P; reducing the S content with pretreatment of hot metal; controlling the content of C and Mn respectively in C: 0.18 ~ 0.23%, Mn:1.20~1.30%; extending argon blowing time at argon flushing station, using electromagnetic stirring technology; controlling the cooling rate at 15 °C/s.
Authors: Jaideep Dutta, S. Narendranath, Aleksandr Zhilin
Abstract: This article reveals a detailed study of temperature cycle formed during Gas Tungsten Arc welding of high carbon steel (AISI 1090) butt joints. Experimental work has been carried out to estimate the temperature distribution along fusion boundary to longitudinal direction of the weldment by mounting thermocouples on the plate along with Data Acquisition System. Heat flux distribution due to moving point heat source has been demonstrated by implementing Gaussian surface heat flux and Angular Torch model. Cooling rate has predicted by application of Adams cooling rate equation. Conduction-convection phenomena plays dominant role for evaluating heat loss from the weld joint and Differential Transform Method (DTM) has been applied to judge non-dimensional temperature distribution. Analytical studies has shown well agreement with experimental temperature distribution.
Authors: Manuela Cristina Perju, Catalin Andrei Tugui, Carmen Nejneru
Abstract: For a number of methods used in the cooling heat treatment technique, are required quenching media with cooling rate lower than that of water and larger than that of oil. This can be achieved in industrial practice by using the synthetic quenching type media like gels or emulsions. The synthetic quenching coolants offer advantages such as non-flammability, safety of use and low cost price. The cooling medium to be tested is emulsifiable oil dissolved in water at various concentrations and the testing temperature is 50°C. In the paper were measured cooling curves for specified synthetic media and calculated for the same media the cooling rate variation and heat transfer coefficient on intervals. The experimental data were compared with those obtained from traditional media: water and heat treatment oil TT 50.
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