40Cr钢喷雾淬火换热系数的计算及数值模拟

为计算ф25 mm×100 mm 40Cr圆柱试件喷雾淬火冷却过程的换热系数,采用四通道采样系统测定了喷雾淬火过程的冷却曲线,并用反传热法中的非线性估算法计算出换热系数。计算结果表明,喷雾淬火过程分3个阶段:膜沸腾阶段、核沸腾阶段和对流换热阶段,并在冷却到120℃时,换热系数达到峰值9800 W·m-2·℃-1。采用此换热系数作边界条件,对40Cr钢的喷雾淬火过程进行了数值模拟,得到淬火过程中不同时刻的温度场、组织场、硬度场和应力场。     

An experimental study of heat transfer in aluminum castings during water quenching

The influence of quenching orientation and agitation conditions on heat transfer of aluminum alloys during water quenching was experimentally investigated with a test casting. The results indicate that heat transfer in water quenching of casting aluminum alloy consists of film boiling, nucleate boiling and convection stages. The highest heat transfer coefficients (HTC) are observed in the nucleate boiling, while the lowest is in the convective cooling stage. The heat transfer coefficients on the horizontal surfaces facing down during quenching are lower than those of other surfaces regardless whether the water is agitated or not. Agitation enhances heat transfer process especially when castings are at high temperatures and heat transfer process is in the film boiling stage.     

Performance of vegetable oils as a cooling medium in comparison to a standard mineral oil

Immersion quenching is the most widely used quenching technique today and is usually one of the last steps in heat treat processing. Improper hardening to incorrect cooling is generally a great loss and causes a great percentage of manufacturing costs. To avoid a failure in cooling, researchers are committed to describing the cooling effect as precisely as possible. The cooling of immersion cooled workpieces or probes is generally characterized by the process of wetting. Evaporable fluids exhibit the three well known stages of cooling: vapor blanket stage, boiling stage, and convective heat transfer. Therefore cooling behavior is influenced by a wide variety and depends on a number of parameters, that is, type of quenchant used, bath temperature, rate of agitation, and the physical and chemical properties of the quenched parts. Environmental pollution has caused the search for new products in har dening and shock cooling of steels. The use of soybean oils as quenching fluids is new, and compared with standard mineral oils, there are many advantages mainly concerning the environment and the health of workers.     

Identification of Heat Transfer Coefficients by Use Conditions of Quenching Oil

Heat transfer coefficients of the quench medium are necessary for heat-treatment simulation. Cooling characteristics of quenching oil vary with kinds and usage greatly. Users are selecting oil solutions that come up to their desired hardness and quenching distortion requirements. In particular cooling performance rises by agitation and decompression. Therefore we identified a heat transfer coefficient by usage and kinds of quenching oil. Cooling characteristics are different greatly by a kind of quenching oil. A difference of a cooling characteristic by a kind of oil depends on a temperature range of a boiling stage and the maximum heat transfer coefficient mainly. On the other hand, in a convection stage, there are few changes in a boiling stage. Even if quenching oil temperature is changed, heat transfer coefficients do not change greatly. When quenching oil stirred, heat transfer coefficients of vapor blanket stage and a convection stage rise, but there are a few changes in a boiling stage. When quenching oil is decompressed a temperature range of a high heat transfer coefficient moves to the low temperature side. In addition, a heat transfer coefficient in a vapor blanket stage comes down. For precision improvement of heat-treatment simulation, it is important that the heat transfer coefficient is calculated in conformity to the on-site use reality.     

42CrMo钢量化水淬应用研究

研究了量化水淬对42CrMo钢淬硬层深度及淬火畸变的影响,将其与普通水淬和油淬进行了比较.结果表明,量化水可以获得介于普通水和油之间的冷却特性,但300 ℃时的冷速仍明显高于油的冷速.42CrMo钢量化水淬时,可以获得介于普通水淬和油淬之间的硬化层深度和淬火硬度,量化水淬的淬火畸变也介于二者之间. 从不同试样的畸变开裂情况来看,形状复杂的42CrMo钢零件不宜采用水或量化水淬,而简单形状的42CrMo钢零件,可以根据工件的淬火要求,通过调节量化水的参数,获得所需的冷却速度,达到淬火目的.     

A357铝合金大型复杂薄壁构件的淬火温度场、残余应力及变形的有限元分析(英文)

基于ABAQUS软件,采用有限元模拟计算的方法对A357铝合金大型复杂薄壁构件的淬火过程进行研究。通过采用传统的反传热方法,对不同淬火介质在不同温度下的换热系数进行精确求解。精确的换热系数确保对A357铝合金大型复杂薄壁构件淬火过程中温度场预测的准确性。采用3种淬火介质(水、机油,5%-UCON淬火试剂A)。通过综合考虑淬火介质及温度因素,对薄壁构件的残余应力及变形的分布和大小进行有限元预测,得到构件淬火结束后的最大残余应力及变形。     

不锈塑料模具钢模块喷淬系统研究

模具钢模块在淬火过程中易出现水、油浸淬开裂、变形且淬火油会污染环境,空淬组织硬度不均匀等缺陷,为克服上述缺陷,设计并研制一套喷水淬火系统,选4Cr13模块对喷水淬火系统进行了初步试验,试验结果表明,用此系统喷淬的模块硬度均匀,无变形,可以避免开裂现象。     

网带炉油槽机构对深沟球轴承淬火锥度畸变的影响

深沟球轴承常使用网带炉进行热处理,网带炉油槽机构和淬火油的粘度及冷速对轴承的淬火畸变影响较大。基于6206/01轴承套圈,探讨了其锥度畸变的产生机理。结果表明:轴承套圈热处理锥度畸变与淬火冷却均匀性相关较大,将小网带运行翻转速度调整为15 s时,可改善该轴承套圈的淬火冷却均匀性,较好控制6206/01轴承套圈的锥度畸变。对其他规格的轴承套圈也具有借鉴意义。     

曲轴调质悬链炉的研制及应用

研制了用于曲轴调质的悬链炉，从而更新了主要的热处理设备。该悬链炉炉温可以自动控制，曲轴在悬挂状态下加热、淬火和回火，解决了曲轴的热处理变形问题，并避免了曲轴在热处理过程中相互碰撞。此外，改进了淬火槽，解决了合金钢曲轴的热处理问题，提高了曲轴的热处理质量。     

矿物淬火油及其应用

目前,矿物淬火油仍在广泛应用.矿物淬火油通过加氢精炼去除S、N、O及某些金属元素是提高其淬火冷却性能和使用寿命的主要手段.矿物淬火油的冷却特性与冷却过程中膜沸腾阶段、核沸腾阶段和对流阶段的温度范围及添加剂等因素有关.指出了矿物淬火油的选用依据,如合乎要求的闪点,较低的油污形成倾向,不锈蚀工件,合适的传热性能等.简述了矿...     

Estimation of heat flux in array of jets quenching using experimental and inverse finite element method

This work presents the combined experimental and numerical technique to estimate the heat flux in the metal quenching process by array of jets. Experimental techniques are explained for the measurement of temperature. A two-dimensional inverse heat conduction problem (IHCP) is solved through the Ling et al. [Ling, X., Keanini, R.G., Cherukuri, H.P., 2003. A non-iterative finite element method for inverse heat conduction problems. International Journal for Numerical Methods in Engineering 56 (9), 1315–1334] non-iterative finite element method (FEM) using the experimental temperature data. Wetting front which separates the film boiling and nucleate boiling zone, changes the order of the heat flux. Maximum heat flux position and its propagation velocity are plotted as a function of time. It is demonstrated that increase in water velocity decreases the maximum heat flux and delays the wetting front movement.     

Numerical Simulation and Experimental Validation of Residual Stresses in Water-Quenched Aluminum Alloy Castings

Aluminum alloy castings are normally water quenched after solution treatment to improve mechanical properties. Rapid water quenching can result in high-residual stress and severe distortion which significantly affect functionality and performance of the products. To optimize product design and durability, one needs to model and predict residual stress and distortion produced in the water-quenched components. In this article, a finite element-based approach was developed to simulate the transient heat transfer and residual stress development during water quenching. In this approach, an iterative zone-based heat transfer algorithm was coupled with material constitutive model called mechanical threshold stress (MTS). With the integrated models, a good agreement was achieved between the numerically predicted and the experimentally measured residual stresses in the aluminum alloy frame-shape casting. The integrated FEA-based heat transfer and residual stress models were also applied to a water-quenched cast aluminum cylinder head with a great success.     

W18Cr4V钢真空气淬和普通油淬的组织与性能比较

采用真空气淬法和普通空气加热油淬法分别对W18Cr4V钢进行热处理。利用金相显微镜和洛氏硬度计对热处理后W18Cr4V高速钢的组织和硬度进行了比较观察和测试分析。结果表明,两种淬火工艺处理的试样组织基本一致,均为隐晶形的淬火马氏体基体组织、大颗粒状的共晶碳化物和细小点粒状的二次碳化物及残留奥氏体,气淬后的组织更均匀;回火后的组织也很相似,为回火马氏体及未溶解的共晶碳化物和二次碳化物。经真空气淬的试样硬度（65HRC）仅比普通空气加热油淬的（66HRC）略有降低,但能满足工模具的硬度要求,而且试样表面光洁,呈银灰色,变形微小,对于要求精度不太高的零件,无需进行后续加工,对环境也无污染。     

余热淬火循环泵数量对锻造转向节内部组织的影响

针对汽车转向节余热淬火容易出现淬火裂纹等质量问题,以江淮瑞风汽车转向节的余热淬火试验为例,通过启动一台和启动两台淬火介质循环搅拌泵,检测转向节在不同工况下的硬度剖面梯度、金相组织、晶粒度等级参数,并分别对其进行现场试验研究。通过分析热淬火油槽内循环搅拌泵的开启数量对转向节内部组织的影响,可知在温度和介质冷却特性不变时,循环搅拌泵开启台数对淬透层深度有明显的影响。并证明了开启两台循环搅拌泵是最佳选择,同时使用两台循环搅拌泵,既能保证冷却均匀性,又能提高锻件整体淬火硬度,还能提高金相组织级别。     

Optimising Gas Quenching Technology through Modelling of Heat Transfer

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…     

45钢量化水淬应用研究

研究了45钢量化水淬的淬硬深度和淬火畸变，并与普通水淬和油淬进行了比较分析。结果表明，调整量化水淬参数，可在水与油之间渊整水的冷却特件，使45钢得到相应的淬硬深度和较小的淬火畸变量。     

Thermal flow simulation and visualisation of PAG quenchants in cooling evaluation equipment with twin stir

Abstract

In this research, the formation and movement of bubbles in boiling film during quenching process was investigated with high speed video camera and particle image velocimetry (PIV) technology as the visualisation method. Cooling curves of surface temperature during quenching of a silver cylinder were measured and the heat transfer coefficients between quenchant and quenching parts were identified. The cooling ability of the coolant used for the quenching technology was evaluated relative to the quality the machine part. As for this paper, the cooling capacity of the PAG quenchants (polyalkylene glycol solutions) was evaluated. In addition, the heat transfer behaviour in the quenching process is clarified with regard to the generation and the destruction of the thermal flow and collapse of the steam film by using the PIV method of visualisation. The effect of mechanical stirring of the quenchant on the steam film and heat transfer is also studied.     

铝件浸液式非标淬火设备的研制

通过介绍铝件淬火工艺基本原则、铝件在水介质中浸液式淬火可能出现的问题以及换热系数与淬火介质温度和流速的关系,为铝件浸液式淬火设备的非标设计提供科学依据。根据本团队研制的非标铝件浸液式淬火设备工程应用中遴选典型案例,分析其在设计和产业化过程中遇到的一些关键问题,阐明了淬火时保证铝件预期性能的前提下减少畸变的解决方法。     

A comparative study on determination method of heat transfer coefficient using inverse heat transfer and iterative modification

The distortion control of heat-treated steel parts is a main consideration when dealing with hardening by quenching process. Before implementing this heat treating process, prediction of distortion is necessary to be done by experiment and computer simulation for determining a quenching technique which gives the smaller distortion. Temperature-dependent heat transfer coefficient (HTC) estimated from SUS304 cylinder can be determined by both iterative modification of lumped heat capacity method (LumpHC) and inverse heat transfer method (InvHT). Predicted HTC from silver probe is needed for the LumpHC, whereas initial set of assumption is needed for the InvHT. The zone-based HTC estimated from SUS304 cylinder then is employed on S45C cylinder. The prediction accuracy results from both methods are evaluated. As expected, stir quenching gives less distortion than that of still quenching. More accurate prediction of cooling curves, cooling rate curves, and distortion is achieved by employing the LumpHC than that by the InvHT. All analyses were performed by DEFORM-HT 2D.     

Acoustic technique to discriminate boiling state during quenching

Abstract

In quench hardening, it is important to determine the boiling state (film, nucleate or convection), in order to control the cooling process. However, the boiling state changes with time and with position on the specimen. A new method developed to discriminate the boiling states is described. High frequency induction heating was applied to stabilise the boiling state and the sound of boiling was monitored with an underwater microphone. The results were evaluated by using fast Fourier transform spectroscopy. For the results obtained using high frequency induction heating and various quenching methods, the boiling states could be discriminated by matching the sound frequency of the sample. Consequently, it was possible to discriminate the boiling states from the frequency observed in nucleate boiling, which has a characteristic frequency band and high intensity compared with film and convection states.