35CrMo钢淬火过程温度场和组织场的数值模拟

对尺寸为φ25 mm×60 mm的35CrMo钢试样的淬火过程用有限元法进行了数值模拟。模拟的淬火工艺为860℃保温1 h,然后分别在水、油和聚乙烯醇(PVAL)水溶液中淬火。结果,获得了淬火过程中试样温度、马氏体量和心部硬度随冷却时间变化的规律。     

基于FANUC系统凹槽及凹圆弧宏指令的开发

利用FANUC数控系统宏程序开发出凹槽及凹圆弧宏循环指令,该指令与复合循环指令G71结合使用,对常见的非单调性零件能简化加工程序,减少编程工作量,提高了生产效率。     

圆形零件的排样问题

根据某家电制造企业提出的圆形零件排样问题,给出了该企业提供的3种排样方式——并排、品排和品排斜排的模型。然后,对这3种排样方式进行了简单的介绍和分析,并通过对实际数据的计算说明了品排斜排的排样方式要优于并排的排样方式。针对品排斜排的排样方式,又提出多列选择,即在原始的品排斜排方案上去掉“两列一组”的限制,改为多列一组,并利用实验数据,给出品排斜排下各列对应的利用率。通过这些利用率数据发现：品排斜排方式下的利用率随列数的增加呈现一个先升后降的趋势。     

均匀化处理对6063铝合金微观组织结构的影响

采用金相显微镜、X射线衍射、扫描电镜、透射电镜和能谱分析技术,研究了均匀化温度和时间对6063合金显微组织的影响。结果表明:铸态合金由过饱和α-Al固溶体和非平衡共晶相组成;铸态合金进行均匀化处理,随温度的升高和保温时间的延长,非平衡共晶组织逐渐消失,合金枝晶偏析逐渐消除;在495℃保温6h,过饱和基体析出Mg2Si相,温度升高到555℃,Mg2Si相完全回溶,针状β-Al9Fe2Si2完全转变为颗粒状α-Al12Fe3Si,同时基体中析出亚微米级AlFeSi和AlFeCrSi相。555℃保温6h退火处理是6063合金铸锭较适宜的均匀化处理工艺。     

Mo_2C对Ti(C,N)基金属陶瓷腐蚀性能的影响

通过静态浸泡腐蚀和动电位极化两种方法,研究了Mo2C对Ti(C,N)基金属陶瓷在NaOH溶液中腐蚀性能的影响。实验结果表明:Ti(C,N)基金属陶瓷的耐蚀性明显优于WC-Co硬质合金;添加Mo2C可以大幅度提高Ti(C,N)基金属陶瓷的机械性能,硬度从91.2到94.0 HRA和抗弯强度从930到1 350 MPa,但会降低金属陶瓷的耐蚀性能;由于Mo2C的加入,会使金属陶瓷的动电位极化曲线出现两个钝化区,但是两个钝化区域的电流均未达到真正的钝化电流(10-5A/cm2),因而这些钝化现象均为伪钝化;在经动电位极化后的试样表面,粘结相Ni和白色的内环相均会被腐蚀,其中内环相为富Mo的(Mo,Ti)(C,N)固溶体,其耐腐蚀性较未溶的Ti(C,N)芯更差。随着Mo2C添加量的提高,内环形相的厚度随之会增加,从而降低了Ti(C,N)基金属陶瓷的耐蚀性能。     

Corrosion behaviors of coatings fabricated using bulk metallic glass powders with the composition of Fe68.5C7.1Si3.3B5.5P8.7Cr2.3Mo2.5Al2.0

Two different types of coatings were prepared, by a high velocity oxy-fuel spraying method and a laser spraying method, respectively, using bulk metallic glass powders with the nominal composition of Fe_68.5C_7.1Si_3.3B_5.5P_8.7Cr_2.3Mo_2.5Al_2.0. The corrosion behaviors of the two coatings in 1M HCl, H₂SO₄, NaCl and NaOH solutions were investigated based upon the microstructural differences originating from the different coating methods. The amorphous coating layer formed by the high velocity oxy-fuel spraying method exhibited higher, excellent corrosion resistance in the 1M HCl solution. The coating layer formed by the laser spraying method exhibited a high pitting tendency attributed to the dendritic microstructure with various borides and carbides. Due to a great number of pores, the HVOF coating exhibits slightly lower corrosion resistance than the LS coating in alkaline solution.     

Stability of nanopore formation in aluminum anodization in oxalic acid

The effect of applied voltage on nanopore formation stability of porous anodized alumina (PAA) in oxalic acid electrolyte was investigated. The Al anodization at a constant applied voltage is a popular electrochemical method to synthesize PAA templates. The experimental observations of Al anodization are used to compare the predictions of the THAMIDA model for interpore distance and the stability criterion of the SINGH model. It is found that, in the electrolyte of pH = 0.96, the interpore distance—applied voltage has a linear dependence coefficient of 2.24 nm/V, which agrees well with the THAMIDA model. It has also been confirmed that pore formation is instable at above 60 V which can be predicted by SINGH model. A second unstable growth regime below 30 V is also observed, which is not predicted by any of the models.     

日用瓷器的绿色包装

保护环境,合理有效地利用资源,减少废弃物对我们生存环境的压力,已成为公众瞩目的重要课题,“绿色”包装已成为设计界的一个新动向。结合实际情况,笔者分析了日用瓷器的包装现状及缺点,并从绿色设计、绿色材料的应用和开展绿色消费三方面对日用瓷器的“绿色”包装进行探讨,提出发展日用瓷器的“绿色”包装是保护环境、节约资源,其不可估量的经济、社会价值,是实施可持续发展的一项重要措施,是一项功在当代利在千秋的伟大事业。     

金属硫化物精矿的干燥特性及干燥设备

介绍金属硫化物精矿的干燥特性、常用干燥设备的结构及使用情况.重点论述蒸汽管回转干燥机的结构、工艺流程和应用效果.蒸汽管回转干燥机通过在筒体内以同心圆的方式布置换热管及通入中低压饱和蒸汽作为加热介质,对精矿进行干燥.它具有设备处理能力大、能耗低、工艺简单、需处理的尾气量小并且含尘低等优点,适合与大型硫铁矿焙烧和有色金属硫化矿熔炼配套使用.     

Electrocatalytic oxidation of d-glucose at nanoporous Au and Au-Ag alloy electrodes in alkaline aqueous solutions

Nanoporous Au-Ag alloys with different Ag content were prepared by selective dissolution of Ag from Au₄₂Ag₅₈ alloy samples in HNO₃ solutions. With gradual dissolution of Ag component, the corroded Au-Ag alloy samples display typical bicontinuous nanoporous structures after dealloying for more than 10 min. The as-prepared nanostructured Au-Ag alloys exhibit obviously enhanced catalytic activity towards the electrooxidation of d-glucose as compared with the uncorroded Au₄₂Ag₅₈ alloy. It is of interest that the existence of a tiny amount of silver in the corroded Au-Ag alloys is very advantageous to enhancing their catalytic activity for the electrooxidation of glucose. The new finding was confirmed by the significant enhancement of the catalytic activity of a nanoporous gold (NPG) electrode after modification with a monolayer of Ag atoms underpotentially deposited (UPD). The nanoporous Au-Ag alloys with appropriate amount of Ag and the NPGs modified with Ag UPD monolayers are thus expected to be promising electrocatalysts for the development of glucose sensors and glucose fuel cells.