Undercooling and Solidification of Sn—Pb Alloy Droplets Prepared by Uniform Droplet Spray

The undercooling and solidification of 150μm and 185μm droplets of Sn-5%Pb alloy prepared by the uniform droplet spray(UDS) process have been investigated.The enthalpy of the droplet has been measured by non-adiabatic calorimetric method as a function of the flight distance.A droplet solidification simulation model has been used to compare with the experimental data.The results show that the enthalpy released by the droplets in the calorimeter 11.88J/g and 22.29J/g less than the simulated values up to a certain flight distance at 0.485m and 0.460m for 150μm and 185μm droplets respectively,but agrees with the expected values at larger distance.The nucleation of the droplets takes place at the distance where the experimental and simulated enthalpy values agree.The droplets quenched before nucleation solidify into metastable supersaturated solid solution and have large undercooling.The formation of the metastable structure in the droplets has been verified metallographically and by calculations based on a thermodynamic model.     

增塑剂PEG对聚乳酸／苎麻纤维复合材料结晶能力的影响

以聚乙二醇（PEG）为聚乳酸／苎麻纤维复合材料的增塑剂。研究不同分子量、不同组成的聚乙二醇对聚乳酸及其复合材料结晶性能的影响。结果表明,在3种不同分子量（分别为1000、2000、6000）的聚乙二醇中,PEG2000影响苎麻纤雏对聚乳酸结晶成核活性最为显著。PLA/PEG2000／15wt%RF复合材料的结晶速率是纯聚乳酸的2倍．X射线衍射（WAXD）显示,复合材料以30℃／min快速降温时仍然是结晶态,而纯聚乳酸以10℃／min速度降温时则是非晶态。     

低合金高强钢连续冷却微观组织转变研究

通过热膨胀法测定了低合金高强钢CCT曲线并分析了其微观组织的变化,结果表明,实验钢在3～50℃/s冷却范围内,均可得到贝氏体组织,当冷却速度为30℃/s以上时还会出现部分马氏体组织。随着冷却速度的提高,贝氏体开始相变温度和转变结束温度相应降低,显微组织逐渐由粒状贝氏体向板条贝氏体转变,且相变组织越加细小。     

接枝率对PP—g—MMA非等温结晶动力学的影响

用差示扫描量热仪（DSC）研究了聚丙烯（PP）和具有不同接枝率的聚丙烯接枝甲基丙烯酸甲酯（PP—g—MMA）的非等温结晶行为,用Avrami方程、莫志深（M0）方程、Dobreva方法和Kissinger方法对该过程进行分析,得到相应的非等温结晶动力学参数．通过对这些参数分析可得出,PP接枝MMA对PP结晶的成核和生长机理存在两方面影响：（1）起成核剂作用,促进PP的成核;（2）会破坏PP结晶的规整性,使PP难规则排列,影响其结晶过程和规整度．因此,对PP结晶来说有一最佳的接枝率,此时,接枝的MMA表现为促进PP的结晶．     

Secondary cooling technology for high-efficiency continuous billet-casting

The mathematical model of high-efficiency continuous billet casting was developed, incorporating the effective spraying water coefficient and the effective specific spraying water flowrate of secondary cooling. To realize uniform cooling in secondary cooling zones, the spraying cooling structure and the arrangement of nozzles were redesigned and optimized, and an additional spraying cooling zone was used. A new secondary cooling model of spraying water was built. It was found that the required spraying water flowrate of a cooling zone was related with the casting speed, the casting temperature, the compositions of liquid steel and the cooling water temperature of secondary cooling. The operation of the reformed caster proved that the spraying cooling structure and the new secondary cooling model were suitable, and the casting speed was greatly enhanced. The highest casting speed was (3.8 to 4.0) m/min for billet with a section of 150×150 mm2. The quality and the output of the billet were improved, and the economical benefit was heightened.     

Sol-Gel法制备KTN薄膜的结构和形貌研究(英文)

本文用XRD和SEM等分析测试手段,详细研究了Sol－Gel法不同工艺过程制得KTN薄膜样品的结构和形貌。发现KTN薄膜的结构和形貌主要受热处理工艺的烧结温度、升降温速率、烧结气氛等影响,详细分析讨论了产生这些影响的原因。在SrTiO3（100,111）基片上制备出了高取向、纯钙钛矿结构、表面形貌良好的KTN薄膜。     

空压机冷却系统的改造与应用

潘-矿空压机原冷却系统采用水冷方式，由于冷却水流量不足，空压机只能单机运行，有必要对冷却系统进行改造，以满足生产需要；对空压机冷却系统的组成、工作原理进行了系统论述，在原冷却管路上进行改造，减小管道阻力，增大水泵流量，增强空压机的冷却效果，提高设备的利用率；采用这种方法改造投入的费用较少，改造部分可自行完成，达到良好的效果。     

Experimental study on spray cooling performance of pressure atomizing nozzle

Aiming at the problem of air-cooled condenser output limit,a spray humidification system was presented to reduce the inlet air temperature.The pressure atomizing nozzle TF8 was chosen for inlet air spr...     

等离子割炬喷嘴热－流耦合分析及优化设计

等离子割炬工作原理复杂,喷嘴在冷却水温度场和流场耦合作用下工作,实物实验难度较大,文章采用CFD软件针对两种割炬喷嘴进行数值模拟,分析在不同冷却水流速度下的温度云图和温度曲线图,确定喷嘴结构,给出建议冷却水流速度。     

冷却速度对多元微合金钢组织及性能的影响

利用热模拟实验,通过金相和透射电镜观察及硬度测量,分析了低碳多元微合金钢完全奥氏体化后以不同速度连续冷却到室温所得到的组织类型。结果表明:冷速在1℃/s时,得到粒状贝氏体和极少量针状铁素体组成的混合组织;当冷却速度在10~50℃/s,合金组织主要以板条贝氏体和粒状贝氏体为主,并且随着冷却速度的增加,板条逐渐细化,试样硬度缓慢上升。在较低的连续冷却过程中有细小的碳氮化物析出。     

Effect of aluminium and silicon on high temperature oxidation resistance of Fe-Cr-Ni heat resistant steel

Fe-Cr-Ni heat resistant steels with different contents of Al and Si were cast in intermediate frequency induction furnace with non-oxidation method. With oxidation weight gain method, the oxidation resistance of test alloys was examined at 1 200℃ for 500 h. The effects of Al and Si on oxidation resistance were studied through analyses of X-ray diffraction (XRD) and scanning electron microscope (SEM). It is shown that the composition of oxide scales is a decisive factor for the oxidation resistance of heat resistant steels. The compounded scale composed of Cr2O3, ar-Al2O3, SiO2 and Fe(Ni)Cr2O4, with flat and compact structure, fine and even grains, exhibits complete oxidation resistance at 1 200℃ Its oxidation weight gain rate is only 0.081 g/(m2·h). By the criterion of standard Gibbs formation free energy, a model of nucleation and growth of the compounded scale was established. The formation of the compounded scale was the result of the competition of being oxidated and reduction among Al, Si, and the matrix metal elements of Fe, Cr and Ni. The protection of the compounded scale was analyzed from the perspectives of electrical conductivity and strength properties.     

多种不可逆性对铁电埃里克森制冷循环性能的影响

建立不可逆铁电埃里克森制冷循环模型,探索有限热源、热阻、固有的回热损失、附加的回热损失和工质内不可逆性等对制冷循环性能的影响,应用有限时间热力学方法,导出制冷率与制冷系数和输入功率间的优化关系解析表式,进而获得最大制冷率及其它优化性能参数．所得结论对实际铁电制冷机的优化设计和性能改善具有一定的参考价值．     

Thermal Response Test by Improved Test Rig with Heating or Cooling Soil简

An improved test rig providing both the heat and cold source was used to perform thermal response test(TRT), and the line source model was used for data analysis. The principle of determining the temperature difference between the inlet and outlet of test well can keep the heating or cooling rate constant, along with a reduced size of test rig. Among the influencial factors of the line source model, the temperature difference was determined as the most important, which agreed with the test results. When the gravel was taken as the backfill material, the soil thermal conductivities of heating and cooling at the test place were 1.883 W/(m·K) and 1.754 W/(m·K), respectively, and the deviation of TRT between heating and cooling soil was 6.8%. In the case of fine sand, the thermal conductivities of heating and cooling were 1.541 W/(m·K) and 1.486 W/(m·K), respectively, and the corresponding deviation was 6%. It was also concluded that different velocities of water had less influence on TRT than the temperature difference.     

结晶器数学模型的广义矩变换解法

结晶器数学模型由粒数衡算方程、溶质质量衡算方程、晶体生长和成核动力学方程及相应的初值与边界条件组成，为一组偏微分一常微分方程。把矩变换的定义从整数域扩展到实数域并扩展定义晶体尺寸后。矩变换能将与粒度有关的生长的结晶器模型化为一组常微分方程。对Bransom模型、ASL模型、Strong模型描述的三种结晶器模型进行变换后导出了相应的常徽分方程组，为最一般的结晶器数学模型的求解提供一种通用的方法。以分批式结晶器为例。给出了一个算例。     

线材冷却过程模拟计算的数学模型

建立了线材斯太尔摩冷却过程有内热源的一维非稳态数学模型;以CCT曲线为依据计算线材冷却过程的相变潜热,利用能量平衡法对数学模型进行离散求解,得出线材在冷却过程中搭接点与非搭接点处的温降规律,并通过现场测试验证了模拟计算结果的准确性.     

Field evaluation of a ground-coupled heat pump in hot-summer and cold-winter regions

The experimental performance of small-sized ground-coupled heat pump (GCHP) is researched intensively. However, there are little data documenting the operation performance of existing large-sized GCHP system. We presented the actual performance measurement of a GCHP installed for apartment buildings in Wuhan, Hubei province, P. R. China. The system was constructed with a closed vertical typed ground heat exchanger with a total pipe length of 32 000 m. During one year, various operating parameters were monitored, including the outdoor temperature, the flow rate, the electrical consumption, and the water temperature. The seasonal coefficients of performances of the heat pumps and the system based on the measured data were found to be 4.01 and 2.96 in the cooling season, and 3.54 and 2.86 in the heating season, respectively. The GCHP system was more economical than the air-source room air conditioner in the energy efficiency which was increased by 29 in cooling mode and 50 in heating mode. There was an obvious heat imbalance of soil between the injection rate and the extraction rate in the residential GCHP system operation.     

Numerical Modelling of Performance of R22 and R290 in Adiabatic Capillary Tubes Considering Metastable Two-Phase Region--Theoretical Model Description and Validation

A homogeneous theoretical model is developed to predict the performance of R22 and R290 in adiabatic capillary tubes. The model is based on conservation equations of mass, momentum and energy. Metastable both liquid and two-phase flow regions are considered in the model. In metastable two-phase region, superheated liquid is introduced into the metastable mixture viscosity and two methods are presented to evaluate it. The model is validated by comparing the predicted pressure and temperature profile and mass flow rate with several investigators′ experimental data of R22 and one of its alternatives R290 reported in literature. All of the predicted mass flow rates are within ±8% of measured values. Comparisons are also made between the present model and other investigators′ models or sizing correlation. The model can be used for design or simulation calculation of adiabatic capillary tubes.     

本钢FTSC生产热轧板卷边裂的原因分析及控制

本钢采用FTSC短流程工艺生产热轧卷板时,因钢中[Al]、[N]、[B]控制不当,生成[AlN]及[BN]析出造成晶界脆性,二冷水量冷却不均、钢板在弯曲和矫直时产生边裂。文章通过控制钢中[Al]、[B]的含量,减少中碳钢生产过程中增氮、降低薄板坯二冷水量等措施,减少了边裂缺陷的发生。     

低碳高强船板钢连续冷却转变规律研究

以低碳高强船板钢为研究对象,用热膨胀法、金相法测得了试验钢的连续冷却转变曲线,并对试验钢连续转变曲线CCT测定过程的各个冷却速度下的显微组织分别予以讨论。结果表明,尽管试验钢连续转变曲线CCT测定过程出现组织多元化、形成机制复杂化的现象,但仍然可以按照相变组织简单归类为多边形铁素体(PF)和珠光体(P)、退化珠光体(PD)、贝氏体(B)、马氏体(M)。其中PF和P为近似平衡态相变,因PD的形成需要局部或一定的过冷度,故它是非平衡转变产物。     

衬底温度对金刚石膜选择性沉积的影响

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