电磁搅拌法制备复合材料过程的工艺优化

分析比较了电磁搅拌法制备复合材料工艺中 3种颗粒加入方式对铸锭宏观组织的影响 ,提出了在旋转熔体中加入挡板来改进工艺的方法。3种颗粒加入方式中 ,底部加入法使得颗粒和合金液之间的剪切力最大 ,强的剪切力有利于混合过程的进行。利用工程计算软件ANSYS模拟了旋转磁场作用下的流场 ,分析了不同挡板形状、倾斜角度对流场的影响 ,设计了一种复合挡板 ,获得了最佳工艺参数。加入挡板能限制旋涡的产生 ,并在轴向上产生强烈的流动。倾斜角度呈 6 0°时 ,效果最佳。利用复合挡板和底部加入法 ,制得了组织致密、颗粒分布均匀的铝 /电气石复合材料。     

电厂模拟焊接架的研制

电厂600 MW以上机组出现了大量的特殊焊接位置,焊接空间狭小,视线受阻.为适应大机组焊接的需要,总结大机组特殊焊接位置的种类并进行原尺寸复制,研制出多位置模拟焊接架和多角度模拟焊接架.焊接架的研制有利于开展车间规模化培训,为培养特殊焊接位置焊工提供了可能,同时缩短了培训时间.     

On the infiltration mode during fabrication of aluminium composite

Porous Al 6061–2Mg–1Sn–3nylon preforms were nitrided and subsequently infiltrated with Al–Si and Al–Si–Mg alloys at different temperatures. Different infiltration modes were identified and confirmed by numerical simulation. When infiltration happens under conditions close to the eutectic points, it proceeds in the conventional slug flow mode with a well-defined infiltration front. However, as the infiltration conditions depart from the eutectic points, the infiltration mode changes gradually to extreme non-slug flow, where the infiltrant preferentially fills small pores irrespective of their distance from the infiltrant entrance, leading to homogeneous infiltrated structures without any infiltration front. The occurrence of different infiltration modes can be attributed to the competition between thermodynamic and kinetic factors. Extreme non-slug flow occurs under thermodynamically favourable conditions where the preform is well wetted by an infiltrant with sufficient fluidity. In contrast, slug flow occurs under kinetically favourable conditions when the low infiltration temperature at the eutectic points makes mass transport difficult.     

One-step fabrication of short electrospun fibers using an electric spark

The one-step fabrication process that was developed in this study used an electric spark to produce short electrospun fibers. For this process, a polymer solution of cellulose acetate and organic solvent was ejected from a syringe needle then the electrospun polymer fiber was adhered to a collector plate after it passed through the gap between the tips of two electrodes that generated an electric spark. Short fibers were recognized on the collector plate, although continuous fibers were also observed. The dimensions for the mean lengths and diameters of the prepared short fibers were 230 μm and 1 μm, respectively. The electrospun fiber was stretched by the electric field, and then the thermal energy of the electric spark burned and truncated the short fibers.     

浅论德国高压隔膜泵进出料阀的国产化改进

德国Ｅｍｍｒｉｃｈ泵厂生产的高压隔膜泵是中国长城铝业公司管道化溶出一水硬铝石攻关项目的心脏设备。在试生产过程中,因进出工损坏频繁,严重影响了试生产和攻关的进行。本文经过现场观察、理论分析及生产实践,初步确定了高压隔膜泵进出料阀的国产化改进方案,为提高设备的运转率、保证正常生产创造了条件。     

镍-金刚石复合镀层的制备工艺及耐磨性比较

沉降共沉积技术是提高复合镀层颗粒含量的有效途径.为了进一步提升复合镀层中的颗粒含量,采用由该技术衍生出的悬浮法和埋砂法制备Ni-金刚石复合镀层.随后对复合镀层的耐磨性进行了试验评价.研究结果表明,温度对悬浮法制备的镀层颗粒含量影响显著,而镀液中的金刚石颗粒浓度对两种工艺结果的影响趋势基本相当.两种方法综合比较表明,当镀...     

SiCp/Al复合材料近净成形制备及性能

采用SiCp预制坯成形及铝液无压浸渗法相结合的工艺,实现了SiCp /Al复合材料的近净成形制备.研究了造孔剂含量对SiCp预制坯的孔隙率、尺寸变化及其复合材料相对密度的影响.测试了SiCp /Al复合材料的热物理性能.结果表明,当造孔剂含量大于12%时,随造孔剂含量增加,SiCp预制坯的孔隙率增加,SiCp /Al复合材料的热导率和热膨胀系数增大明显.造孔剂的挥发气体的膨胀力导致SiCp预制坯尺寸变化.当造孔剂含量为18%时,SiCp /Al复合材料相对密度最大.     

Studies of corrosion in power plant boiler tubes by measurement of oxygen isotopes and trace elements using secondary-ion mass spectrometry

Recent advances in secondary ionization mass spectrometry (SIMS) techniques allow the resolution of differences in the natural abundances of the isotopes of ¹⁸O and ¹⁶O, and their ratio in both conducting and insulating materials. These techniques have been used in this study to measure the oxygen isotope signatures and their spatial distribution in corrosion products formed during high-temperature oxidation of steel boiler tubes from fossil-fuel power plants. The data obtained in this study are interpreted in terms of oxygen isotope fractionation between the available oxygen reservoirs and oxides formed on or within the metal. Results are presented for three different corrosion scenarios: steamside/fireside corrosion, aqueous phosphate corrosion and corrosion due to H₂ damage. Constant, but isotopically depleted values observed in magnetites formed during steamside corrosion and H₂ damage are indicative of interaction with locally derived meteoric water (which constitutes the boiler feed water). In contrast, isotope distributions in maricite (NaFePO₄) suggest equilibrium fractionation between this phase and precursor magnetite. Oxygen isotope patterns in fireside magnetites exhibit a complex zoning that requires at least two isotopically distinct species with significantly different transport rates.     

Analysis of parameters and microcomputer control for the electric upsetting process for forging engine valves

Using both theoretical analysis and practical experiment, it is clearly indicated that the electric upsetting process should be divided into two stages: preform upsetting and finish upsetting. The main process parameters influencing the forming quality of engine valves, balancing and matching of these parameters, and the microcomputer system used to control them are described. By using the microcomputer system to control the whole process automatically, the rate of efficient production could be considerably increased.     

Rapid fabrication of C/C/SiC composite by PIP of HMDS

The C/C/SiC composite was fabricated within several days by the method of precursor impregnation and pyrolysis (PIP) using hexamethyldisilazane (HMDS) as the precursor. The carbon fiber plates, woven and punctured with two-dimensional orthogonal continuous carbon bundle and short carbon fiber, were used as the reinforced preforms. The characters of the C/C/SiC composite were analyzed using XRD, EDS and SEM, and three-point-bending test. The results indicated that pyrolyzed substance of the precursor contained excessive carbon, followed by silicon, and a small amount of nitrogen. There were micro-cracks on the massive matrix. The phase composition was difficult to distinguish, primarily considered as the Si–C–N composite. The structure of C/C/SiC was dense and homogeneous with some pores whose sizes were less than 5 μm between fibers and less than 100 μm between the carbon fiber bundles, respectively.

Fiber pull-out was observed on the bending fracture surface. The stress–strain curve of both at room temperature and 1300 °C appeared ascending zigzag. Flexural strength was 150 MPa at 1300 °C, higher than 121 MPa at room temperature.     

Technology for heat treatment of engine valves of VAZ passenger cars

The valve gas-distributing mechanism is an important part of an internal combustion engine. Its main components are inlet and discharge valves, which have to meet specific requirements due to the conditions of their operation. The general requirement on all valves is their close fitting to the seats under a high pressure in the cylinder, which is realized due to the conical camfer that serves as the seat surface. For this reason, the camfers are ground thoroughly. The rod of the valve, which moves inside a guide bush, is also fabricated with high precision. The valves operate at an elevated temperature and therefore are produced from high-temperature alloys. The present paper is devoted to the manufacturing technology for valves of the gas-distributing mechanism.Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 10, pp. 6–9, October, 1996.     

DCS在火电厂的应用

介绍了DCS在火电厂应用的设计方案、系统配置、系统功能以及技术特点等。     

电站锅炉SA335-P91高温高压蒸汽钢管焊接工艺

SA335P91钢属改良型9Cr-1Mo高强度马氏体耐热钢,与传统的Cr-Mo耐热钢相比,具有高温强度高、抗蠕变性能和抗氧化性能好等优点。SA335P91钢焊接性的主要问题是冷裂纹敏感性较强以及冲击韧性下降。针对上述问题进行焊接工艺评定试验,选择GTAW+SMAW焊接方法,制定了合理的焊接工艺:氩弧焊封底时其预热温度为100℃～150℃,焊条电弧焊的焊前预热温度为200℃～300℃;焊条电弧焊层间温度应为200℃～300℃;焊接线能量在25～30 kJ/cm以下,GTAW在12～15 kJ/cm;焊后热处理温度750℃～770℃,保温4～6 h,升降温速度小于150℃/h。根据现场环境条件,采取有效的工艺控制措施,获得了较好的焊接质量,综合性能良好。     

电力系统信息监测控制系统

通过对具有高精端加工设备企业的电力系统的分析，开发了针对10kV总配的电力系统信息监测控制系统。     

电力机柜中的铜排铆接工艺

电力机柜制造中,铜排连接一般采用螺钉连接,但其占用空间大而影响足够的电气间隙,在紧凑型机柜结构的限制下,结构设计困难,还会产生潜在的尖端放电,破坏空气绝缘水平。为解决此问题,研究出以铜排连接新工艺代替螺钉连接,包括无钉铆接和有钉铆接。分析了铆接的原理和成形工艺过程,同时,用ANSYS Workbench软件施以力学仿真以核对一致性。随后检测了连接后的振动、温升和电阻效果,并与传统螺钉连接工艺对比以验证其可行性。此外,建立了2种铜排搭接处电场的有限元分析模型,获得了电场分布特征及电场集中区域,这进一步显示了铆钉连接的价值。最后,总结了铆接工艺的优势及适用范围,为产品设计和工艺改进提供更多的技术方案。     

High-temperature superconductors for electric power and high-energy physics

The various devices currently being constructed for electric power and high-energy physics applications demand different performance, cost, and geometry requirements of high-temperature superconductors. At Intermagnetics General Corporation, four types of high-temperature superconductors (powder-in-tube Bi-2223, surface-coated Bi-2212, powder-in-tube Bi-2212, and γBa₂Cu₃O_x) are at various stages of development to meet this demand. V. Selvamanickam earned his Ph.D. in materials engineering at the University of Houston in 1992. He is currently a senior materials scientist with Intermagnetics General Corporation. Dr. Selvamanickam is a member of TMS. D.W. Hazelton earned his M.Sc. in mechanical engineering at Union College in 1984. He is currently a senior engineer with Intermagnetics General Corporation. L. Motowidlo earned his Ph.D. in solid state physics at the University of Connecticut in 1981. He is currently a senior staff scientist with Intermagnetics General Corporation. Dr. Motowidlo is a member of TMS. F. Krahula earned his B.S. in mechanical engineering at Hudson Valley College. He is currently a manager with TDO. J. Hoehn, Jr., earned his B.S. in physics at Sienna College in 1990. He is currently a development engineer with Intermagnetics General Corporation. M.S. Walker earned his Ph.D. in physics at Carnegie Mellon University in 1970. He is currently a senior staff scientist with Intermagnetics General Corporation. P. Haldar earned his Ph.D. in materials science at Northeastern University in 1988. He is currently a manager in the Advanced Devices and Systems Division with Intermagnetics General Corporation. Dr. Haldar is a member of TMS.     

逆变式电焊机对电网污染的治理

分析了逆变式弧焊电源中输入侧三相整流滤流电路对谐波和功率因数的影响，介绍了改善谐波的方法以及滤波参数的设计计算。