共查询到18条相似文献,搜索用时 781 毫秒
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高压气淬过程中,由于冷却速率较大,工件易产生热应力,甚至发生塑性变形或开裂,因此能准确预测高压气淬过程中工件热应力分布对于工业生产尤为重要.本研究运用计算流体力学法建立了交流流动型立式高压气淬炉气淬过程的数值传热和湍流模型,模拟了Ti2AlNb超塑成形/扩散连接空心结构件的气淬过程,并通过间接耦合法得到Ti2AlNb结... 相似文献
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张克俭 《热处理技术与装备》2010,31(5)
与高压气淬或者低温盐浴淬火相比,油淬工件的淬火畸变特点是:畸变数据零乱而没有规律;最大畸变程度通常也更大。出于对淬火油冷却特性曲线的错误认识而演变出来的工件表面温度与表面热流密度之间的一一对应关系,不能解释这种特点的成因。试验观测证明,表面温度与表面热流密度之间存在的是所处条件下的非一一对应关系。这种非一一对应关系是由蒸汽膜内气体的流动规律和冷却的中间阶段特性所引起的。应用这种非一一对应关系,既能解释淬火畸变程度更大的原因,也能解释畸变数据无规律的成因。 相似文献
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《International Heat Treatment & Surface Engineering》2013,7(1-2):52-59
AbstractHigh pressure gas quenching has the advantages of pure convective heat transfer, high levels of control, avoidance of cleaning the quenched parts and low environmental impact. However, typical gas quenching facilities exhibit inhomogeneous flow conditions through the quench load and the parts, resulting in scatter in final properties. The upstream flow profile of the load has been identified as a key factor determining local flow conditions and heat transfer. The intensity of the quenching process is determined by the pressure drop that results from the flow resistance of the quench load, although a significant part of the flow passes between the load and the chamber walls and does not contribute to the quenching process. A simulation of the flow inside a commercial high pressure gas quenching chamber was carried out, using a multiscale model to give faster convergence. An experimental analysis of the flow inside a model quenching chamber through velocity measurements and flow visualisation was also performed. Finally, a quenching run with cylindrical parts in a double-chamber vacuum furnace was used to validate the model results. Various upstream velocity profiles were applied to demonstrate their influence on the quenching result. The multiscale simulation approach and the results of the flow process investigation are reported. Guidelines for gas quenching process optimisation are outlined. 相似文献
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Numerical simulation of high pressure gas quenching of H13 steel 总被引:1,自引:0,他引:1
Jing Wang Jianfeng Gu Xuexiong Shan Xiaowei Hao Nailu Chen Weimin Zhang 《Journal of Materials Processing Technology》2008,202(1-3):188-194
Aided by the computational fluid dynamics software package FLUENT flow and heat-transfer model has been established to simulate the high pressure gas quenching process of a large H13 die. The complicate geometry mesh of finite volume method (FVM) simulation was exactly built according to the practical chamber set-up of vacuum furnace. The velocity and temperature distribution of gas, as well as the temperature field in H13 die, were obtained by simulation. The validation of simulation results has been carried out by comparing the simulated cooling curves of certain points inside the die with the measured ones. It can be found that the temperature depended thermal physical properties of gas and H13 die, such as thermal conductivity, specific heat and viscosity, have dramatic effects on the accuracy of simulation results. The possible improvement of the numerical simulation based on the detailed discussion is also elucidated. 相似文献
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Florent Chaffotte Linda Lefevre Didier Domergue Aymeric Goldsteinas Xavier Doussot 《材料热处理学报》2004,25(5)
AMONG the carburising and quenching technologieslow-pressure carburising in line with high pressure gasquenching knows a strong development[1],[2],[3].Thisprocess offers indeed an environmentally-friendlyalternative to standard atmosphere carburisingassociated to oil quenching.Gas quenching allows toeliminate parts washing and oil residues processingsteps.Besides low pressure carburising and quenchingprocesses allow more automation of the processFinally gas quenching offers process controopp… 相似文献
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A mixture of pure gases that produce maximum heat transfer characteristics for quenching 总被引:1,自引:0,他引:1
Gas quenching provides a desirable alternative to conventional liquid quenching in heat treating from the standpoint of quality,
safety, and environmental issues. There is convincing evidence that gasquenched parts heat treated in vacuum furnaces are
clean and bright and do not require a postcleaning process that may result in additional production costs. The cooling rates
for thicker section parts that are heat treated may be increased by increasing the magnitude of the heat transfer coefficient
of the gaseous medium. This heat transfer coefficient, which is dependent on the thermal conductivity, viscosity, specific
heat, and density of gases can be maximized by utilizing gas mixtures instead of pure gases. Substantial increases in heat
transfer rates for the gas quenching process can be achieved by appropriately mixing gases such as helium and argon. 相似文献
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D.D Hall I Mudawar R.E Morgan S.L Ehlers 《Journal of Materials Engineering and Performance》1997,6(1):77-92
Optimal cooling of aluminum alloys following the high- temperature extrusion process suppresses precipitation of intermetallic
compounds and results in a part capable of possessing maximum strength and hardness after the subsequent age- hardening process.
Rapid quenching suppresses precipitation but can lead to large spatial temperature gradients in complex- shaped parts, causing
distortion, cracking, high residual stress, and/or nonuniform mechanical properties. Conversely, slow cooling significantly
reduces or eliminates these undesirable conditions but allows considerable precipitation, resulting in low strength, soft
spots, and/or low corrosion resistance. This study presents a systematic method of locating and operating multiple spray nozzles
for any shaped extrusion such that uniform, rapid cooling and superior mechanical and metallurgical properties are achieved.
A spray nozzle data base was compiled by measuring the distribution of spray hydrodynamic parameters (volumetric spray flux,
mean drop diameter, and mean drop velocity) throughout the spray field of various industrial nozzles. Spray heat transfer
correlations, which link the local spray hydrodynamic parameters to the heat transfer rate in each of the boiling regimes
experienced by the surface, defined the spatially nonuniform boundary conditions in a numerical model of the quenching process
that also accounted for interference between adjacent spray fields. New correlations, offering increased accuracy and less
computational time, were formulated for the high- temperature boiling regimes which have a critical influence on final mechanical
properties. The quench factor technique related predicted thermal history to metallurgical transformations occurring within
the extrusion to predict hardness distribution. The validity of this unique approach was demonstrated by comparing model predictions
to the temperature response (and hardness after artificial aging) of an L- shaped Al 2024- T6 extrusion to quenches with multiple,
overlapping water sprays. The validation study reported herein concludes by exploring the possibility of applying quenching
technology to improving the properties of extruded metal- matrix composites such as SiCp/Al 6061 and cast alloys. 相似文献
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The cooling curves of 6061 aluminum alloy were acquired through water quenching experiment. The heat transfer coefficient was accurately calculated based on the cooling curves and the law of cooling. The online quenching process of complex cross-section profile was dynamically simulated by the ABAQUS software. The results suggest that the heat transfer coefficient changes during online quenching process. Different parts of the profile have different cooling velocity, and it was verified by water quenching experiment. The maximum residual stress of the profile was predicted using FEM simulation based on ABAQUS software. The relations between the temperature and stress were presented by analyzing the data of key points. 相似文献
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针对淬火过程的畸变问题,介绍了一种有效控制畸变的模压淬火技术与装备。通过控制作用力大小、周期与方式,调整淬火模具的结构与尺寸,控制冷却液的流量、流态及流向等,控制畸变过程,减小工件的畸变,在满足淬火要求的前提下,把模具与机床组合为一体,提供实现淬火过程的模压淬火工艺装备,在保证硬度和金相要求的同时,保持淬火工件的一致性,把淬火质量控制在最佳水平,并付诸工业应用,综合降低了淬火畸变。 相似文献