共查询到20条相似文献,搜索用时 15 毫秒
1.
TO QUENCH HARDEN STEEL MATERIAL,it isrequired to give rapid quenching in the temperaturerange required of rapid quenching.On the other hand,quenching oil comprised of mineral oil as majorcomponent can be modified of its cooling curve byusing various additives.Thereby,we havequench-hardened some steel material each havingdifferent pattern of CCT curve,using quenching oilcomprised of mineral oil modified of coolingcharacteristics by dosing additives,and surveyedrelationship between ha… 相似文献
2.
Bowang Xiao Qigui Wang Parag Jadhav Keyu Li 《Journal of Materials Processing Technology》2010,210(14):2023-2028
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. 相似文献
3.
Thomas Lübben Friedhelm Frerichs 《Journal of Materials Engineering and Performance》2013,22(8):2323-2330
Immersion quenching in evaporable fluids like oil, polymer solutions, or water is a widely used technique in heat treatment shops because this technique provides higher heat transfer coefficients than the most alternative gas quenching techniques. The disadvantages of immersion quenching in evaporating fluids are the complex heat transfer mechanisms which consist of the three phases, film boiling, nucleate boiling, and convection. Especially the transition from film to nucleate boiling—the rewetting of the sample surface—is a complex process which leads to a strong position dependence of the heat transfer coefficient of the cooled work pieces. In particular, immersion quenching of thin-walled rings can result in large changes of ovality with comparable high scattering. To understand these results, two series of experiments were performed. Rings were quenched in oil in a special quenching tank and the rewetting behavior was documented. Furthermore, bearing races were quenched in a standard tank. Before and after heat treatment, these rings were measured by a coordinate measuring system and the distortion was determined. The investigations have clearly shown that the vapor film can have an important influence on distortion generation during oil quenching. The resulting distortion can principally be explained by the observed rewetting behavior. 相似文献
4.
G. E. Totten H. M. Tensi K. Lainer 《Journal of Materials Engineering and Performance》1999,8(4):409-416
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. 相似文献
5.
对自来水作为淬火介质的两大缺点的研究 总被引:5,自引:0,他引:5
从自来水淬火时工件容易淬裂、硬度不均且畸变大等现象,列出了自来水作为淬火介质的两大缺点:一是低温冷却速度太快,二是冷却特性对水温变化太敏感。分析了自来水第二大缺点引起淬火硬度不均和畸变的原因。通过与气态介质的对比,指出了液态淬火介质共同的两类缺点:一是任何确定的液态介质,其冷却速度的可调节范围都很有限,以致同一个车间必须配备普通淬火油、中速淬火油和高速淬火油,才能满足不同工件的需要;二是工件从蒸汽膜阶段到沸腾阶段期间,冷却速度突然增大,可能引起较大的淬火畸变。提供了克服液态淬火介质第二类缺点的七类技术方法。 相似文献
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沸腾冷却区的宽度及其传达的信息 总被引:4,自引:4,他引:0
张克俭 《热处理技术与装备》2007,28(6):10-16
用摄像记录了液态介质中冷却时试样表面的冷却情况.试验发现,在液态介质中淬火时,试样表面的沸腾冷却是在呈带状的沸腾冷却区扫过的过程中完成的.这类沸腾冷却区通常多很窄,因此工件表面上任何部分经历沸腾冷却的时间都很短,靠沸腾冷却方式降低的温度都不多.淬火冷却中,从工件表面出现第一个超前扩展点开始,到蒸汽膜区完全消失为止的很长一段时间内,三种散热方式共同存在;其中,蒸汽膜冷却方式和与对流冷却方式对工件淬火冷却的贡献都比沸腾冷却的要大. 相似文献
9.
Quenching- oil cooling curves obtained using a silver specimen (Japanese Industrial Standard K 2242) in-dicate three stages
of cooling: vapor blanket, boiling, and convection. The temperatures at which the va-por blanket stage transfers to the boiling
stage and the boiling stage transfers to the convection stage are referred to as the characteristic temperature (CT) and the
convection- stage starting temperature (CSST), respectively. As the amounts of CT- improving additives are increased in increments
of 1,2,3,6, 8, 10, and 12%, the CTs become higher, as clearly shown in the cooling curves obtained using a silver specimen.
Likewise, as the amounts of CSST- improving additives are increased from 1 to 2 to 3%, the CSSTs become lower. These tendencies
are similarly observed when using an Alloy 600 specimen, and both additives effectively improve cooling performance. However,
in the case of 6,8,10, and 12% CT- im-proving additions, the differences among the additive concentrations are more pronounced
in cooling curves obtained using the silver specimen than in those obtained using the Alloy 600 specimen. This can be attributed
to the greater temperature sensitivity of the silver specimen thermocouple. In field quench-ing operations, such phenomena
as insufficient hardness, inverse quench hardening, and unstable distor-tion can be remedied by additive treating. However,
one must know what type of additive and how much to use. To this end, cooling curve measurement using silver specimens is
useful. 相似文献
10.
用标准探棒检测出的油或者水的冷却速度曲线既不能反映探棒表面的冷却情况,也不能用来推测工件表面的冷却过程。因此,应直接观测工件的冷却过程。淬火冷却过程的直接观测和研究发现,除了淬火介质的冷却能力和工件某部位的有效厚度之外,不同工件表面蒸气膜内气体的流动状况和工件表面从蒸气膜向沸腾冷却方式转型的次序,对工件表面的冷却速度和整个工件的冷却均匀性都有很大影响。业已揭示了后两种新因素影响工件冷却速度和冷却均匀性的基本规律,从而可以在淬火冷却过程中对同一工件表面的不同部位的冷却速度分别加以控制,这种控制技术被称为精细淬火冷却技术。 相似文献
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《International Heat Treatment & Surface Engineering》2013,7(2):61-64
AbstractIn 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. 相似文献
13.
KiyoshiFunatani 《材料热处理学报》2004,25(5):434-436
The control of cooling power is very important to introduce desired properties. Usually, higher the cooling rate higher the quench hardness and distortion and the optimization of cooling power is the base for good heat treatment. The change of cooling speed during quenching is one of the effective methods to balance hardness and distortion. Different form the general knowledge of the demerit of vapor blanket stage, oil with long vapor blanket stage is also one of effective methods to reduce distortion. The reduction of distortion with enough quench hardness seems to be possible by optimization of cooling condition by the help of computer simulation. The exhibition of higher core hardness than surface in through hardening steels experienced in the “Inverse quench hardening” was introduced by Prof. Tamura and Shimizu. This mechanism is well explained by Arimoto et al, by analysis of computer simulation. In this paper, plural steps cooling methods are compared, in relation with cooling curve and heat transfer coefficient that is necessary to simulate quench results and the possibility of advanced cooling technology is discussed. 相似文献
14.
According to inverse heat transfer theory, the evolutions of synthetic surface heat transfer coefficient (SSHTC) of the quenching surface of 7B50 alloy during water-spray quenching were simulated by the ProCAST software based on accurate cooling curves measured by the modified Jominy specimen and temperature-dependent thermo-physical properties of 7B50 alloy calculated using the JMatPro software. Results show that the average cooling rate at 6 mm from the quenching surface and 420–230 °C (quench sensitive temperature range) is 45.78 °C/s. The peak-value of the SSHTC is 69 kW/(m2·K) obtained at spray quenching for 0.4 s and the corresponding temperature of the quenching surface is 160 °C. In the initial stage of spray quenching, the phenomenon called “temperature plateau” appears on the cooling curve of the quenching surface. The temperature range of this plateau is 160–170 °C with the duration about 3 s. During the temperature plateau, heat transfer mechanism of the quenching surface transforms from nucleate boiling regime to single-phase convective regime. 相似文献
15.
HiroyukiHoshino HiromitsuMurakami HideoYokota SatoshiSuda HidekiTsuge KoichiTerasaka ToshiakiWakabayashi 《材料热处理学报》2004,25(5):475-479
In quenching, the cooling uniformity is most important to diminish distortion occurring on work pieces. As a trial to accomplish uniform cooling, therefore, there exist various mixing methods of a quenchant and the quenchant circulation with an external pump has so far been the well accepted mixing method. However, this study proposes an advanced oscillation mixing method that can improve more the cooling uniformity in quenching. The proposed method includes a stirrer in oscillating motion, so that the simultaneous oscillating and mixing movements of the stirrer are considered to provide efecfively the uniform cooling characteristics for the quenchant. In comparison with the case of the circulation pump mixing, the investigation using the oscillation mixing method has demonstrated the following two experimental facts:(1) the short vapor blanket stage caused by the quick breakage of the oil vapor blanket and (2) the reduced variation of the quenching distortion. 相似文献
16.
钢的淬火介质的冷却机制 总被引:1,自引:0,他引:1
从传导、对流和辐射等3种热传递方式的角度,分析了钢在水淬、高压气淬和流态床淬火时的冷却机制.介绍了近期国外文献的某些技术数据,如水、油、高压气体、熔盐等淬火剂的热传递系数,不同温度水的冷却特性,水淬和油淬时淬火烈度(H值)随碳钢圆柱体温度和尺寸的变化等. 相似文献
17.
Bowang Xiao Gang Wang Qigui Wang Mohammed Maniruzzaman Richard D. Sisson Yiming Rong 《Journal of Materials Engineering and Performance》2011,20(7):1264-1270
Cast aluminum alloys are usually subject to solution treatment, quenching, and aging hardening for improved mechanical properties.
Cooling rate during quenching plays an important role in residual stress, distortion, and mechanical property distributions
in the resultant cast aluminum components. As the cooling rates of work pieces heavily depend on the interfacial heat transfer
coefficient (HTC) between work pieces and quenchants, it is important to understand how HTC varies with different quenching
conditions so that optimal quenching process can be achieved. In this study, a quenching system and an experimental procedure
of obtaining HTC are presented. A series of experiments have been conducted to study the variations of HTC with respect to
air temperature, air humidity, air velocity, and part orientation. 相似文献
18.
空心圆柱体GCr15钢淬火过程的计算机模拟 总被引:6,自引:1,他引:6
用有限元法研究了GCr1 5钢圆柱体在油淬过程中的温度、组织及应力变化。在实测了淬火油换热系数的基础上 ,对轴对称空心圆柱体淬火时的温度场和组织场进行了模拟。同时运用热弹塑性理论 ,对圆柱体内外表面点及中心点应力的演化过程进行了模拟。模拟结果表明 :圆柱体内表面的冷速小于外表面。在淬火初期 ,由于热应力的作用使工件表面受拉而心部受压 ,在发生应力反向前 ,发生了组织转变 ,并使表面应力迅速转向 ,在应力达到最低点后又逐渐回升 ,最后表面形成了拉应力。心部的应力变化正好相反 ,最终形成了组织应力型的内应力分布。 相似文献
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基于DEFORM反传热模型表面换热系数的确定 总被引:1,自引:0,他引:1
以7075铝合金厚板淬火过程为对象,研究DEFORM反传热模型中控制参数对表面换热系数计算和温度预测精度的影响规律。结果表明,当选择实测温度曲线上的拐点温度作为温度控制点,且表面换热系数初始值接近平均换热系数时,采用反传热模型确定的表面换热系数所预测的冷却曲线与实测曲线吻合较好。在此基础上选取合理的控制参数,并确定了7075铝合金厚板淬火过程的表面换热系数,经冷却曲线预测结果与实测值对比表明,采用DEFORM反传热模型确定的表面换热系数所预测的温度场有较高精度,可以满足工程应用需要。 相似文献