高速列车制动盘用Cr-Mo-V钢的导热特性

采用激光脉冲试验法研究不同淬火和回火工艺对高速列车制动盘用Cr-Mo-V钢在50～800℃时的比热容、热扩散系数和导热系数。结果表明,当试验温度低于700℃时,随着试验温度的提高,试验料热扩散系数和导热系数逐渐降低,比热容逐渐提高;当试验温度超过700℃时,试验料热扩散系数和导热系数又随之提高,比热容随之下降。当试验温度低于700℃时,随着回火温度或淬火温度的提高,试验料在不同试验温度条件下热扩散系数和导热系数均稍有提高,比热容稍有降低;当试验温度为800℃时,几组试验料的比热容、热扩散系数和导热系数基本相当。      

高速列车转向架用钢热物理性能

针对高速列车转向架材料Q345C和S355J2W(H)钢的导热系数、热膨胀系数、比热容、热扩散率热物理性能参数进行测试,建立高速列车转向架材料热物理性能基础数据库。结果表明,Q345C的Ac1为714℃,Ac3为850℃;S355J2W(H)的Ac1为732℃,Ac3为860℃。在常温~Ac1温度区间,随着温度的升高,热膨胀系数升高;在Ac1~Ac3温度区间,材料的热膨胀系数随温度的升高而降低;当温度高于Ac3时,材料的热膨胀系数又升高;温度低于Ac1时,比热容随温度升高而升高;当温度高于Ac1时,比热容随温度升高而降低,奥氏体转变完成后,比热容趋于定值。Q345C和S355J2W(H)两种材料的热扩散系数和导热系数随温度升高而降低。     

蒸汽发生器传热管Inconel 690合金的热物理性能测定

为获得中国生产蒸汽发生器传热管Inconel 690合金的热物理性能数据,对690合金的热膨胀系数、比热容、热扩散率、热导率、弹性模量和泊松比进行了测定和分析。结果表明:690合金在100~350℃的平均热膨胀系数为11.97×10-6/℃;在350℃以下,690合金的热膨胀系数、比热容、热扩散率和热导率随温度的升高而增加,但其弹性模量和泊松比均随温度升高而减小。用最小二乘法建立了690合金在350℃内的热膨胀系数、热扩散率、热导率、弹性模量和泊松比与温度之间的函数关系。     

高炉常用耐火材料导热系数的测定

采用激光脉冲法及使用DSC实测高炉用耐火材料的热扩散率及比热容,进而获得其导热系数.重点考察了温度及温度履历对耐火材料热扩散率及比热容的影响,得出二者与温度依存关系的数学模型,进而获得各种耐火材料的导热系数对温度的依存关系.测量结果表明:（1）除铝碳质耐火材料,其他耐火材料经一次高温后,测得的热扩散率值比第一次升温时的测得值增大,且温度特性随着温度变化呈现唯一的变化关系.而铝碳质耐火材料则相反,且随着升、降温过程的延续,热扩散率值逐渐减.（2）随温度的增加,比热容先较快增大后缓慢增加,温度履历对热容的测定基本没有影响.（3）根据测定结果,建立了导热系数λ（W/m·K）与温度T（K）之间的数学模型,经检验,该模型可有效地预测高炉常用耐火材料的导热系数.     

新型镍基高温合金GH4282的热物理性能

为获得GH4282合金在1 100℃以内的热物理性能,采用不同热物理性能测试方法测定和分析了该合金的熔点、热膨胀、热扩散率、热导率、比热容、弹性模量、剪切模量、泊松比。结果表明:在1 100℃以内,GH4282合金的热膨胀系数、热扩散率和热导率均随温度的升高而增加,但其弹性模量和剪切模量均随温度升高而减小。用最小二乘法建立了GH4282合金在1 100℃以内的线性热膨胀、平均线膨胀系数、热扩散率、热导率、比热容、弹性模量、剪切模量、泊松比与温度之间的函数关系式。     

SG变质剂提高灰铸铁的热物理性能

在研究SG变质剂提高灰铸铁抗热疲劳能力的基础上,对含Na的SG变质剂处理的灰铸铁的热扩散率、导热系数、热膨胀系数和弹性模数进行了测量。用电子探针分析了Na在灰铸铁中的分布。试验结果表明,加入一定量SG变质剂可使灰铸铁的导热系数提高14%;在10~100℃,使热膨胀系数降低10%。     

玻璃-陶瓷基粘接层热障涂层体系的热学性能（英文）

研究了8YSZ/BaO-MgO-SiO2玻璃-陶瓷/Ni基合金热障涂层体系的热学性能。在相同条件下,热障涂层体系的热扩散系数和导热系数均比基底和只有玻璃-陶瓷涂层时的小。热障涂层体系的比热容、热扩散系数和导热系数随着温度的增加而增大,而导热系数随表层涂层厚度的增加而减小。     

7A85铝合金表面换热系数研究

为了测量7A85铝合金表面换热系数以及优化反传热法计算表面换热系数的偏差,利用精密测温仪(GL900)对7A85铝合金片状试样进行了淬火冷却曲线测量,测量点A和B距端面间距为20 mm和40 mm。使用激光导热仪测量了在30～500℃之间试样的比热容,并进行了线性拟合。随后通过有限差分法外推得到端面冷却曲线,进而计算出表面换热系数。结果表明,使用室温比热容数据计算得到的端面淬火冷却曲线比实际曲线高,使用线性拟合后的比热容计算得到的端面淬火温度更准确。7A85铝合金端面换热系数随着温度降低,先增大后出现波动段,最终降低,在270℃时的最大表面换热系数为2250 W·m-2·℃-1。     

蠕墨铸铁的热物理性能和力学性能

对蠕墨铸铁的热扩散率、导热系数和比热容等热物理参数进行了测定,并对比分析了它的抗拉强度、屈服强度、延伸率及硬度.     

4 GPa高压热处理对TC4钛合金组织及热物理性能的影响

利用热常数测试仪和膨胀仪测试了4 GPa压力热处理前后TC4钛合金在27~600℃温度范围的热扩散系数和热膨胀系数,并借助光学显微镜、扫描电镜和透射电镜分析了合金的显微组织,探讨了高压热处理对TC4钛合金组织及热物理性能的影响。结果表明,高压热处理能细化合金组织,增大合金的热膨胀系数;当温度低于约235℃时,高压热处理使钛合金的热扩散系数变小,而在高温下高压热处理使钛合金的热扩散系数变大。     

Thermal conductivity of a zirconia thermal barrier coating

The conductivity of a thermal-barrier coating composed of atmospheric plasma sprayed 8 mass percent yttria partially stabilized zirconia has been measured. This coating was sprayed on a substrate of 410 stainless steel. An absolute, steady-state measurement method was used to measure thermal conductivity from 400 to 800 K. The thermal conductivity of the coating is 0.62 W/(m×K). This measurement has shown to be temperature independent.     

机械形体热变形的非相似性研究

机械零件在工作温度和环境温度偏离标准设计温度后,其形状会发生改变,但由于温度场分布的不均匀性、构件材料的原子间距、内部缺陷形态等因素的影响,使得构件的热膨胀不能自由发生,导致构件热变形前后在形状上具有非相似性,理论和实验都证明这种非相似性是普遍存在的。     

等离子喷涂Sm_2Zr_2O_7热障涂层的热冲击性能数值模拟

利用ANSYS软件对2Cr13、1Cr13Ni9Ti基体等离子喷涂的Sm2Zr2O7热障涂层在热冲击过程中的热应力分布进行了数值模拟,并比较了不同基体对涂层热冲击性能的影响.结果表明,热冲击过程中在涂层表面均存在较大的径向冲击热应力,同时在表面陶瓷层/金属粘结层界面处存在较大的应力梯度,2Cr13基体涂层的热冲击性能优于1Cr13Ni9Ti基体涂层,有限元计算结果与试验结果吻合良好.     

电力电缆拉线机的变极电机的保护控制

文章针对某电缆厂的拉线机的电动机故障问题,给出一些切实可行的保护措施.对其他电动机的保护也有一定的参考价值.     

SnAgCu／Cu界面热循环及时效条件下化合物的生长行为

通过对等温时效与温度循环两种条件下钎料与基板间金属间化合物（IMC）生长的对比．研究了界面IMC生长的规律。采用了两条低温极限不同保温时间和循环周期相同的循环曲线,等温时效温度采用循环高温峰值温度。结果表明,随着循环周期的增加,界面IMC层的厚度增加,且低温极限温度越低时IMC生长越快。与时效条件下界面IMC生长的对比表明,在高温阶段保温时间相同时,时效条件下界面IMC的生长速率快于循环条件。     

INFLUENCE OF TOP TEMPERATURE OF THERMAL CYCLE ON THERMAL STRESS/STRAIN AND THERMAL FATIGUE BEHAVIOR OF PURE IRON

１．ＩｎｔｒｏｄｕｃｔｉｏｎＦｉｇ．１　ＴｈｅｒｍａｌｆａｔｉｇｕｅｔｅｓｔｍａｃｈｉｎｅｗｉｔｈＯｕｔｅｒｃｉｎｓｔｒａｉｎｔＴｈｅｄａｍａｇｅｃａｕｓｅｄｂｙｔｈｅｒｍａｌｆａｔｉｇｕｅｉｓｏｎｅｏｆｔｈｅｍａｉｎｆａｉｌｕｒｅｆｏｒｍｓｏｆｍｅｔａｌｗｏｒｋｉｎｇｐｉｅｃｅｓｕｎｄｅｒｔｈｅｔｅｍｐｅｒａｔｕｒｅｖａｒｉａｔｉｏｎｃｏｎｄｉｔｉｏｎｓ．Ａｌｏｔｏｆｔｈｅｒｍａｌｆａｔｉｇｕｅｔｅｓｔｓｃｏｎｃｅｒｎｉｎｇｔｈｅｆａｉｌｕｒｅｗｅｒｅｃｏｎｄｕｃｔｅｄｏｎｔｈｅｖａｒｉｏｕ…     

Anisotropic thermal conductivities of plasma-sprayed thermal barrier coatings in relation to the microstructure

Anisotropic thermal conductivities of the plasma-sprayed ceramic coating are explicitly expressed in terms of the microstructural parameters. The dominant features of the porous space are identified as strongly oblate (cracklike) pores that tend to be either parallel or normal to the substrate. The scatter in pore orientations is shown to have a pronounced effect on the effective conductivities. The established quantitative microstructure-property relations, if combined with the knowledge of the processing parameters-resulting microstructure connections, can be utilized for controlling the conductivities in the desired way.     

316不锈钢的裂纹扩展性能

从实用出发对3168不锈钢管材进行了热循环下的裂纹扩展试验,试验表明该材料在交变热应力下的裂纹扩展速率缓慢,带裂纹的管道在监督下可以继续运行。     

The effect of a high thermal gradient on sintering and stiffening in the top coat of a thermal barrier coating system

Superalloy substrates coated with plasma-sprayed CoNiCrAlY bond coats and yttria-stabilized zirconia top coats (TCs) have been subjected to a high heat flux under a controlled atmosphere. The sintering exhibited by the TC under these conditions has been studied and compared with the behavior observed during isothermal heating. Sintering has been characterized by (a) microstructural examinations, (b) dilatometry, in both the in-plane and through-thickness directions, and (c) stiffness measurements, using both cantilever bending and nanoindentation. A numerical model has been used to explore the stress state under isothermal and thermal gradient conditions. Dilatometry data indicate significant linear contractions during holding at elevated temperatures, particularly in the through-thickness direction. This is largely attributed to microstructural changes associated with sintering, with any volume changes due to phase transformations making relatively small contributions. Sintering proceeds faster at higher temperatures but is retarded by the presence of tensile stresses (from differential thermal expansion between the coating and substrate) within the TC. Thus, it occurs preferentially near the free surface of the TC under gradient conditions, not only due to the higher temperature, but also because the in-plane stress is more compressive in that region.     

Study of the performance of TBC under thermal cycling conditions using an acoustic emission rig

An experimental rig based on the use of infrared quartz lamps has been developed to monitor the degradation mechanisms causing failure of thermal barrier coatings (TBC) under thermal-cycling conditions. An acoustic emission (AE) technique monitored these degradation mechanisms, and advanced signals processing identified the key parameters that classify the AE signals according to the long-term behavior of the TBC. The AE technique enabled the localization of degradation sources inside the TBC with a linear resolution of ∼5 mm by the use of two transducers fixed at both ends of the sample. Furthermore, sample zones of high AE activity showed typical vertical cracks at the surface and delaminations at the interface between the ceramic and the bond-coat layer. Vertical cracks were induced preferentially during the heating period of the thermal cycles when the ceramic coating was in a tensile-stress state, while delaminations were induced during the cooling period when the TBC was in a compressive-stress state.