【作者】 苏兴武；

【导师】 顾敏；

【作者基本信息】 机械科学研究总院 ， 机械设计及理论， 2008， 硕士

【摘要】 淬火在金属学中的定义是加热工件“受控的放热”,是金属工件获得所需组织和性能的重要工艺手段。生产中因淬火引起的畸变和内在质量问题是导致工件返修和报废的重要原因。淬火畸变产生的因素很多,但淬火冷却的不均匀性是淬火畸变和开裂的主要原因。所以研究淬火槽内介质流速场不仅能对淬火槽槽体、搅拌和均流系统的优化设计具有指导意义,而且结合工件的形状和装炉方式还能有助于分析、预测畸变易发生的部位,指导工件的合理装夹,提高工件淬火冷却的均匀性和减少畸变,这对于热处理实际生产具有重要的应用价值。本文依据车间使用的淬火油槽DZC40(有效淬火区φ2500mm×3000mm)建立计算模型,应用大型计算流体力学软件Fluent6.2对淬火油槽空载和加载与实际尺寸一致的盘状齿轮、齿轮轴和齿圈三种典型工件进行了三维建模和数值计算,通过模拟计算和实验验证得到:1)淬火槽空载时,在槽体的中上部形成了大范围的流速均匀的“有效淬火区”,当加载工件后,流速场变化显著,介质根据工件形状和装夹方式介质形成了全新的流速场分布。2)当加载盘状齿轮叠放的工件串时,工件串的正上部和下部形成了明显的低速区,而位于工件串外层的齿面周边边沿处介质的流速却明显高于其余部位;3)加载多件齿轮轴立装于盘状夹具之上时,齿轮轴外侧流速较高且均匀,而内侧的底部流速却很低;4)加载齿圈叠放于盘状实心和空心夹具上时,中上层齿圈内外侧流速均较均匀,而下层齿圈内外侧的流速差别较大;5)本文对盘状齿轮的冷却模拟过程进行了试验验证。通过在流速场模拟的几个特征区放置40Cr棒状试棒,根据其心部硬度和端淬曲线找出其处的淬火烈度和介质流动状态,试验结果与模拟吻合较好。6)通过对淬火槽流速场的模拟,得到空载和加载后介质流场的分布及其特点,为淬火槽的设计及不同形状齿轮的装夹提供了理论上的参考依据,从而为提高齿轮淬火质量和减小热处理畸变起到有益的作用。更多还原

【Abstract】 In metallography, the definition of quenching is "the controlled extraction of heat",it is the most important process for components to get required microstructures and proper mechanical. In production, the main cause of reject and reversion of the products is workpiece distortion or inner quality question in quenching. In the factors inducting distortion and cracking the main cause is the non-uniformity in cooling. While the hot workpieces are quenched in the quenching tank, and the distribution of quenchant flow field in it has an crucial influence on the quenching uniformity of the workpiece.Therefore research on the quenchant flow field in the tank not only can optimize the desigen of tank corporeity, agitator system and flow-equalizing equipment, and but also can analyse and predict where the distortion easliy occured by workpiece shap and racking, and then improve the quenching uniformity of workpiece to avoid from large distortion and quenching cracking.In order to study the quenchant flow field in the quencing oil tank used in the workshop, a 3-D model of the tank(effective quenching zoneφ2500mm×3000mm) with real workpiece dimensionescaped dimension error was first established. Aided by the Fluent 6.2——a good-size commercialsoftware the quenchant velocity in the quenching tank without and with workpieces was obtained. The results of simulation and experiments are as following:(1) When the tank is without loading, a "effective quenching zone" will be formed in the middle and top of the tank . After loading of workpieces the distribution of quenchant flow field will produce great chang and the new distribution of it will be formed by the racking mode of the partes and the part shap.(2) When the tank is with loading of geares piled up on the rack, the quenchant velocity on the top and bottom of the rack appears very slow,but the velocity on the edge of the gears is faster than other position.(3) The simulation result of quenchant flow field in the tank with gear shafts standing on a disk showes that: The quenchant velocity is fast and symmetrical around the gear shafts except the inner region of bottom of the gear shafts.(4) A quenching tank with gear rings standing on the disk or rack was selected to simulate the flow field. The simulation result showes that the velocity around the gear rings on the top and middle of the rack is symmetrical , but it is different around gear rings on the bottom of rack.(5) In order to validate the simulation result,a test was conducted,several test bars of 40Cr steel were placed separably on the special spots of rack,according to the correction of core hardness and the hardenability of sample, the quench severity of each spot was found.(6) Through the simulation of the quenchant flow field in the tank with or without workpieces,there distribution and characteristic were obtained. The present work is helpful for design of the tank and the racking of different gears,and could improve the quenching quality of gear and decrease the quenching distortion.更多还原