铝合金淬火使用聚合物淬火剂的应用研究

针对铝合金淬火使用聚合物淬火剂进行了实验研究。配制了聚合物体积分数为16%和33%的淬火水溶液,选择典型材料和零件进行了一系列对比实验。结果表明:采用33%和16%两种体积分数的AQ251聚合物淬火剂得到的拉伸性能、电导率和耐蚀性与水淬比较无明显差别,处于同一水平;在聚合物冷却介质中淬火可以显著减小零件变形。     

聚合物淬火剂CH-202M的冷却特性研究

本文阐述了聚合物淬火剂 CH-202M 的基本特性和主要物理指标。作者在研究该淬火剂冷却机理之后指出,金属冷却时于金属表面形成一层聚合物隔离膜。45和40Cr 钢在不同浓度介质中淬火,可得到比水淬、油淬更大的淬透深度和更小的淬火变形,而且可以防止淬火开裂。研究结果表明,聚合物淬火剂 CH-202M 有许多优点,用于钢铁零件淬火特别有效。     

热致相分离法聚合物膜形成机理与形貌控制

介绍了近年来热致相分离(TIPS)法聚合物多孔膜研究的新进展.从热力学角度总结了TIPS的成膜机理,相图是理解TIPS机理的重要工具;液滴生长和晶粒生长是研究制膜体系TIPS动力学的两个方面.膜形貌由热力学、动力学共同控制,聚合物分子量、稀释剂种类、溶液固含量、冷却速率、成核剂是控制膜结构的五个重要方面.     

淬火工艺对HSLA钢板截面精细组织结构的影响

使用Formastor热膨胀仪、ABAQUS有限元软件、金相显微镜、TEM及EBSD等手段研究了淬火冷速对35 mm厚HSLA钢板截面组织结构的影响。结果表明:淬火冷却速度对试验钢板距表面8 mm范围内的组织和性能有显著的影响。提高淬火冷速有利于提高近表面板条马氏体/贝氏体组织含量、提高位错和小角度晶界的密度以及细化板条宽度,使近表面的硬度大幅度提高。淬火冷速对试验钢板距表面8 mm到心部的组织和性能没有显著的影响。随着淬火冷速的提高,钢板表面1/4处到心部的板条尺寸、晶界特征及MA组元没有显著的差别,其硬度在同一水平波动。此外,冷却速度对大角度晶界密度、有效晶粒尺寸的影响不显著。ABAQUS模拟结果与试验钢板的硬度分布和组织分布相吻合,钢板截面冷却速度的分布决定了最终组织的转变类型和结构特征。     

热致相分离法制备聚合物微孔膜的研究进展

分别从S-L相分离和L-L相分离两方面简述了热致相分离法制备聚合物微孔膜的成膜过程.从聚合物分子量、聚合物浓度、稀释剂与聚合物的相互作用、稀释剂的流动性及结晶、冷却速度及冷却方式、萃取剂的种类及萃取剂的抽提方式、成核剂几方面总结TIPS法制膜的研究进展,并从膜材料、膜结构以及制膜方法三方面阐述热致相分离法制膜的发展趋势.     

ANSYS有限元模拟表面冷速对超厚板截面温度场的影响

为了研究表面冷速对超厚板心部冷却能力的影响,应用ANSYS有限元软件模拟分析了超厚板淬火水冷过程的截面温度场分布.结果表明:淬火过程中,心部与表面的截面温差随着表面冷速的增大而增大,但当冷速过大时,截面温差不再增大;随着表面冷速的增大,心部冷速在高温区和中温区表现出不同的变化规律,高温区(900～600℃),心部冷速随着表面冷速的增大而显著增大,但增幅逐渐减小,当表面冷速大于80℃/s后,心部冷速达到极值;中温区(600～300℃),心部冷速几乎不受表面冷速影响;此外,增大表面冷速对心部冷速的提升作用是有限的,厚度越大这一局限越为明显.     

淬火介质对 ZL114 A 铝合金性能、变形和组织的影响

绘制了水溶性聚合物PAG、聚乙烯醇和水等3种介质的淬火冷却曲线,对介质温度和浓度对介质淬火冷却能力的影响进行了分析,研究了不同浓度和温度的PAG对ZL114A铝合金组织、性能与变形的影响.结果表明,PAG相比水和聚乙烯醇具有更好的淬火效果;介质温度和浓度越低,PAG的冷却速度越高;采用PAG作为ZL114A铝合金的淬火介质,为使淬火工件获得较好的组织与力学性能,变形量较小,应控制PAG的使用温度大约为40℃,质量分数大约为15％.     

一种容器用钢的连续冷却转变研究

针对一种容器用钢,采用膨胀法在L78R1TA型淬火相变仪上测定了其连续冷却转变的膨胀曲线,结合显微组织和硬度,获得了每个冷速下对应的相变点温度。结果表明,在1-10℃／min的冷速范围内,为高温转变的铁索体和珠光体区,夹杂少量贝氏体;冷速继续增加至20—120℃/min,为巾温转变的贝氏体Ⅸ;当冷速大于3000℃／min时,组织中完全为马氏体。随着冷却速度的增大,硬度值也逐渐增大,这为制定合理的热处理工艺提供了依据。     

304奥氏体不锈钢凝固相转变规律曲线(SPT曲线)建立

利用自行设计的高温凝固相转变测定实验装置,研究了304奥氏体不锈钢在不同冷却速度下的高温凝固相转变过程,得到了凝固过程中液相(L)到高温铁素体(δ)到奥氏体(γ)的相变温度.在此基础上分析了304奥氏体不锈钢在不同冷却速度下的高温凝固相转变规律,从而建立了304奥氏体不锈钢的低冷速凝固相转变规律曲线—SPT(Solidification phase transformation)曲线.结果表明:对试样进行液氮酒精淬火有效地保留了试样高温时各相的状态.可以清楚的显示在不同冷速下的不同温度淬火时液相和固相的各相成份比例及在不同淬火温度下各成份体积比例的变化.通过研究体积比例变化,可以得到304奥氏体不锈钢在不同冷速下的液相线、固相线及各种反应开始和结束的转变温度(即SPT曲线).由SPT曲线也可以看出,随着冷却速度的增大,相转变模式会发生变化,相图会向左移动,各相变反应的温度区间减小.     

奥氏体不锈钢凝固相转变规律曲线(SPT曲线)建立

利用自行设计的高温凝固相转变测定实验装置,研究了304奥氏体不锈钢在不同冷却速度下的高温凝固相转变过程,得到了凝固过程中液相（ L）到高温铁素体（δ）到奥氏体（γ）的相变温度。在此基础上分析了304奥氏体不锈钢在不同冷却速度下的高温凝固相转变规律,从而建立了304奥氏体不锈钢的低冷速凝固相转变规律曲线—SPT（Solidification phase transforma?tion）曲线。结果表明：对试样进行液氮酒精淬火有效地保留了试样高温时各相的状态。可以清楚的显示在不同冷速下的不同温度淬火时液相和固相的各相成份比例及在不同淬火温度下各成份体积比例的变化。通过研究体积比例变化,可以得到304奥氏体不锈钢在不同冷速下的液相线、固相线及各种反应开始和结束的转变温度（即SPT曲线）。由SPT曲线也可以看出,随着冷却速度的增大,相转变模式会发生变化,相图会向左移动,各相变反应的温度区间减小。     

Application of polymeric quenchant in heat treatment of crack-sensitive steel mechanical parts: Modeling and experiments

Success or failure of a quenching process is determined by selecting an appropriate quenchant. In this work, the quenching process of the automobile tie rods in different media including water, oil, and a polymeric solution was investigated. The microstructures and mechanical properties of the rods were predicted by a finite element simulation model. Several specimens were cut from the tie rods and heat treated by quenching in five different quenching media including water, oil, and PAG aqueous solutions with polymer concentrations of 10, 20, and 30%. The hardness tests and metallographic analyses were performed on the specimens. Considering the results of the simulations and the experiments, the optimum quenchant was selected and the tie rods were heat treated using this quenchant. The results showed that the use of Poly Alkylene Glycol (PAG) solution quenchants, with respect to its unique cooling mechanism, outperformed water and oil quenchants. The distortion and cracking was reduced compared to water quenching and, on the other hand, the mechanical properties which were not achievable by oil quenching were resulted using polymer-based quenching medium.     

A comparative analysis of outcome of carbide-tool holder quenching in various liquids upon induction brazing

The paper provides some results of prediction of hardness and hardened layer thickness of a 35KhGSA steel holder of carbide tool upon quenching in aqueous solution of salts and bases, in water, and in oils at various quenchant temperatures. Thermokinetic cooling paths of the holder surface points are shown to differ quantitatively and qualitatively between the first two quenchants and oils at room temperature. Numerical investigation of quenching in water at 100°C has revealed an abrupt increase, by a factor of 2–3, in the holder surface cooling rate as soon as the cooling curve enters the austenite-to-bainite phase transformation region. For the case of quenching in an aqueous solution of salts and bases a functional relation has been found between the thickness of the holder surface layer quenched to maximum hardness and the quenchant temperature.     

Nanoconfinement‐Induced Giant Electrocaloric Effect in Ferroelectric Polymer Nanowire Array Integrated with Aluminum Oxide Membrane to Exhibit Record Cooling Power Density

The electrocaloric effect (ECE) offers a unique mechanism to realize environmentally friendly and highly efficient solid‐state cooling that completely differs from the conventional vapor‐compression refrigeration. Here a new class of hybrid films composed of ferroelectric polymer nanowire array and anodic aluminum oxide (AAO) membrane is reported, which displays pronounced ECE driven by relatively low electric fields. Under confinement and orientation of AAO channels on the crystallization of the polymer, the polymer nanowire array shows substantially enhanced ECE that is about three times that of the corresponding thin films. Simultaneously, the integrated AAO membrane forms thermally conducting channels for the polymer nanowires, enabling the efficient transfer of cooling energy and operation of the EC materials under high frequencies, which are unattainable based on the currently available EC structures. Consequently, the integrated polymer nanowire–AAO hybrid film exhibits the state‐of‐the‐art cooling power density, outperforming the current ferroelectric polymers, ceramics, and composites. This work opens a new route for the development of scalable, high‐performance EC materials for next‐generation refrigeration.     

Sliding and sticking vapour bubbles under inclined plane and curved surfaces

In flow boiling heat is transferred by the combined effects of nucleate boiling, with local generation of bubbles, and evaporative and convective cooling by the passage of bubbles generated elsewhere. In this study, nucleate boiling was eliminated by measuring the heat transfer near injected steam bubbles sliding under an inclined plate heated to low superheats, using liquid crystal thermography combined with high speed video recording and computerised image analysis. Heat was transferred by evaporation of the thin liquid film between the bubble and the wall and by enhanced convection in a wake region wider than the bubble and many bubble diameters long. Evaporation was the dominant mechanism for large, easily deformed, slow-moving bubbles. For small, faster-moving bubbles the reduction in evaporation was offset by an improvement in convection.     

Two-way shape memory effect in polymer laminates

Novel polymer laminate exhibiting two-way shape memory effect has been prepared by layer technique with the shape memory polymer and elastic polymer. In this paper, we demonstrate the two-way shape memory behavior, i.e., bending on heating and reverse bending on cooling; describe the preparation procedure; and investigate its two-way shape memory mechanism. Finally, it suggests that the mechanism can be ascribed to the release of elastic strain of shape memory polymer layer upon heating, and the elastic strain recovery induced by the bending force of substrate layer upon cooling.     

Evaluation of apparatus for assessing effect of forced convection on quenching characteristics

Abstract

Two systems for the generation of controlled convection conditions in quenching baths for laboratory tests are presented that differ significantly in complexity of design. The cooling of cylindrical samples heated to temperatures considerably above the boiling point of the quenchant is determined from the effect of convection on the kinematics of wetting. It was found from experiments carried out using aqueous polymer solutions that in general surface active substances have a stabilising effect on film boiling. Using pure water and two concentrations of an aqueous polymer solution as sample fluids, it was also found that data obtained in a simplified convection system may satisfactorily reflect the influence of the intensity of convection on the cooling process. The cooling results to be expected in commercial quenching applications employing forced convection can be predicted from the experimentally ascertained influence of convection on the cooling performance of quenching baths.

MST/801     

Mathematical modeling of falling liquid film evaporation process

A mathematical model of evaporation process from a laminar falling liquid film on a vertical plate of constant temperature is presented. The model is developed with and without interfacial shear stress due to the vapor flow at the liquid film surface. The vapor pressure drop, vapor exit velocity and cooling rate are calculated for different liquid mass flow values. It is shown that lower liquid mass flow produces higher cooling rate. The results also show that the interfacial shear stress has a considerable negative effect on the cooling rate. It is proved that there exists an optimum distance between the plates, which gives the maximum volumetric cooling rate.     

热致相分离法EVOH微孔膜的制备和形态

选择乙烯的摩尔分数为38％的乙烯-乙烯醇的共聚物(EVOH)为原料，聚乙二醇(PEG)为稀释剂，采用热致相分离方法(TIPS)制备了亲水性高分子微孔膜．用扫描电子显微镜观测了微孔膜的形态．结果表明，分相的方式及微孔的大小由聚合物的含量及冷却速度决定．EVOH含量越少，则越易发生液-液相分离；冷却速度越慢，则微孔的尺寸也越大、EVOH摩尔分数为60％时，如果冷却速度很慢，则发生液-固相分离；如果冷却速度较快，则可同时观察到液-固相分离和液-液相分离的形态．     

聚乙烯醇/纳米氧化锌复合材料的非等温结晶动力学

为了研究聚乙烯醇/纳米氧化锌复合材料的结晶性能,通过熔融共混挤出的方法制备了复合材料,并在差示扫描量热分析(DSC)的基础上通过Jeziomy法和Liu法研究了聚乙烯醇薄膜和聚乙烯醇/纳米氧化锌复合材料的非等温结晶动力学行为.结果表明,聚乙烯醇薄膜和聚乙烯醇/纳米氧化锌复合材料的非等温结晶行为强烈地依赖于冷却速率,随着冷却速率的提高,结晶速率常数增大,结晶的不完善程度也增大.在相同的冷却速率下,复合体系的Avrami指数n值和结晶速率常数Z。较大,晶体的完善程度较高.要达到相同的结晶度,复合材料所需的冷却速率要小于聚乙烯醇薄膜,即纳米氧化锌的加入使材料中聚乙烯醇的结晶速率增加,对聚乙烯醇具有异相成核作用.     

Polymer-film cooling on a drum,taking into account temperature dependence of heat conduction

The cooling of a polymer film is solved by the Biot method, taking into account the temperature dependence of the heat conduction. The solution obtained is numerically verified.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 38, No. 1, pp. 129–133, January, 1980.