超声振动与激光加热耦合条件下Al基钎料在TiNi形状记忆合金表面润湿铺展行为

采用一种超声辅助激光钎焊的方法,对低熔点的Al基钎料在TiNi形状记忆合金合金表面进行了润湿性实验。研究结果表明:随超声时间增加,钎料铺展面积先增大后减少,润湿角先减小后增大。钎料润湿前沿存在Al2Si,Al3Si,AlSi等相,钎料熔滴中心靠近界面处,AlSi和AlSiTi相的晶粒尺寸及其中Si元素的含量均随超声时间增加而逐渐增大;随着激光功率的降低,钎料铺展面积逐渐降低,润湿角逐渐增大,在钎料熔滴中心靠近界面处生长出宽度小于10μm的AlSi(Ti,Ni)金属间化合物。当超声振动时间为1.0s,激光功率470W,母材表面粗糙度为0.03μm时,实验获得的最大铺展面积为106.45mm2,最小润湿角为16°。     

CeO2对Ag30CuZnSn药芯银钎料润湿性能及钎焊接头组织与性能的影响

向Ag30CuZnSn药芯银钎料中添加CeO2,研究CeO2对Ag30CuZnSn药芯银钎料的润湿铺展性能和钎焊接头性能的影响,探索CeO2对药芯银钎料润湿铺展性能和钎缝组织的作用机理.研究结果表明:药芯钎剂粉末中加入CeO2能提高Ag30CuZnSn药芯银钎料的润湿铺展性能,CeO2添加量达到0.3％(质量分数,下同)时,对药芯银钎料的改进效果最佳.理论分析认为这是因为高价态的CeO2具有氧化作用,可与T2紫铜表面的Cu2 O发生氧化反应生成CuO和Ce2 O3.同时,CuO、Cu2 O与CeO2、Ce2 O3及钎剂中的B2 O3生成CuO·Ce2 O3·B2 O3等盐类,促进了去膜反应的进行,从而提高了银钎料在紫铜板表面的润湿铺展性能.药芯钎剂粉末中添加过量CeO2时,熔点较高的CeO2反而增加了液态钎剂的粘度,未参与反应的CeO2会阻碍熔融钎剂的铺展,进而阻挡熔化的Ag30CuZnSn银钎料在T2紫铜表面的润湿铺展.CeO2作为高熔点氧化物,加入钎剂中后既能起到形核质点的作用,又能作为界面活性剂去除氧化膜.因此,火焰钎焊时,CeO2能细化Ag30CuZnSn药芯银钎料钎焊接头的钎缝组织,当CeO2添加量达到0.3％时,细化效果最佳.钎缝组织的细化使得钎焊接头抗剪强度提高了10％以上,钎焊接头断口组织的形貌和变化规律印证了上述结果.     

铝合金超声波钎焊过程中液态钎料的填缝及界面润湿行为

研究了超声波振动作用下6061Al和2024Al合金焊缝中液态钎料的填缝过程,并分析了加热温度、焊缝预留间隙值对该过程的影响。结果表明,超声波振动作用下液态钎料的填缝行为与传统毛细填缝行为有很大差别,该条件下液态钎料在不润湿母材的基础上就迅速发生填缝过程,钎料初始液-气界面为凸状;随着填缝进行,填缝速度有所下降,填缝前沿钎料/母材界面润湿程度提高,钎料液-气界面形状转变为凹状。加热温度对超声波作用下液态钎料的填缝过程无明显影响,焊缝预留间隙值增加,钎料填缝长度减小,液-气界面形态发生变化。     

轧制工艺对银钎料流铺性的影响

采用扫描电镜、XRD等分析手段对有油和无油轧制后的银基钎料进行研究.结果表明,有油轧制的钎料会在其表面残留一层含碳层,含碳层的厚度约为3~7μm;所选银钎料的主要的相组成为Cu Zn、Ag Cd、(Ag,Cu)5Zn8、Ag Cd19等,碳在钎料表面主要以游离的碳分子和Zn C8、C2Cd O4形式存在;钎料表面的含碳层在钎料熔化后将以三种不同的形式存在,部分碳分子来不及上浮到表面而被包裹在钎料内部;部分碳分子随着钎料的熔化铺展,被液态钎料推到了铺展的最前沿,在液态钎料周围形成一个包围圈;还有一部分形成含碳的复杂化合物,其存在都将明显降低钎料对钢基体的润湿性,影响后续的焊接强度等.     

P对Sn-9Zn-0.1S无铅钎料性能的影响

为研究P含量对Sn-9Zn-0.1S钎料显微组织、抗氧化性、润湿性及耐腐蚀性能的影响,通过光学显微镜观察钎料的显微组织,采用静态刮渣法测定钎料在不同温度下的抗氧化性能,用润湿铺展面积评价不同温度下钎料在Cu基板上的润湿性,采用腐蚀失重法衡量钎料在pH值为3.7的HCl溶液中的耐腐蚀性,并通过扫描电镜(SEM)和X射线衍射仪(XRD)对钎料在不同温度下的氧化产物和酸性腐蚀条件下形成的腐蚀产物进行形貌观察和物相分析。结果表明：适量P的添加可以细化Sn-9Zn-0.1S钎料层片状共晶组织,但短棒状富Zn相随P的添加而变长、变粗且数量减少;钎料的抗氧化性及润湿性能随P的添加先提高后降低,P含量在0.06%时钎料的抗氧化性及润湿性最好;同时,P通过改善钎料显微组织及腐蚀产物的致密性,提高了钎料的耐腐蚀性能,P含量在0.1%时钎料的耐腐蚀性能较好。     

不锈钢表面电镀锡银钎料的润湿特性

为揭示不锈钢表面电镀锡银钎料的润湿特性,借助润湿试验炉、影像式烧结点试验仪、扫描电镜、X射线衍射仪、能谱分析仪对电镀锡银钎料的润湿行为、动态铺展过程、界面组织、物相组成及润湿界面化学元素分布进行了分析。研究表明,优先铺展的前驱膜是改善电镀锡银钎料润湿性的本质原因。润湿过程中出现的前驱膜效应,主要是试验中FB102钎剂中的硼酐引起的。电镀锡银钎料与不锈钢界面出现的Cu41Sn11相过渡层,垂直于润湿界面呈柱状向钎料内生长。随着Sn含量升高,电镀锡银钎料在不锈钢表面的润湿面积呈增大趋势;与同Sn含量(2.4%~7.2%,质量分数)的传统AgCuZnSn钎料相比,电镀锡银钎料在不锈钢表面的润湿面积提高了8.1%~12.5%。当Sn含量为7.2%时,电镀锡银钎料的润湿面积高达481mm2。电镀锡银钎料与不锈钢母材的接合界面是扩散-化合物混合型形式。     

SiO2f/SiO2复合材料与TC4,Ti3Al和TiAl的钎焊

在880℃/10min规范下,采用AgCuTi活性箔带钎料完成了SiO2f/SiO2/TC4,SiO2f/SiO2/Ti3Al和SiO2f/SiO2/TiAl三种接头的连接,每种接头界面均结合良好。接头显微组织结果表明,三种接头组织形貌较为相似,均在靠近SiO2f/SiO2母材的界面处形成了一层薄薄的扩散反应层组织,在该组织中出现了Ti和O的富集。分析认为,钎焊过程中钎料中的Ti会优先向SiO2f/SiO2母材边缘扩散,同时,金属母材中的元素在液态钎料的作用下不断向钎缝中溶解,其中一部分母材中的Ti也会向复合材料母材边缘扩散,两种不同来源的Ti共同与SiO2发生反应生成Ti-O相,根据三种接头扩散层中Ti和O的原子比例推断Ti-O相为Ti2O。三种接头的钎缝基体区主要由白色组织和灰色组织共同组成,其中白色组织中富含Ag,主要以Ag基固溶体形式存在,而灰色组织中富含Ti和Cu,二者结合生成Ti-Cu组织。     

液态Sn-Ag-Cu钎料润湿性能的优化

采用钎料改性工艺制备了Sn-3.5Ag0.6Cu合金,用润湿平衡法测试了液态Sn-3.5Ag0.6Cu钎料在铜基体表面的润湿性,研究了钎料制备工艺、钎剂卤素含量、浸渍温度和时间等因素对润湿性能的影响.结果表明:采用改性工艺可增强钎料的润湿性能,当钎剂卤素含量为0.4wt%、在270℃下浸渍2～3s时,液态Sn-3.5Ag0.6Cu钎料对铜表面的润湿性可以达到最佳状态.指出降低钎料的熔点和液态表面张力是提高润湿性的关键.     

添加Ge元素对CsF-AlF_3钎剂熔化特性、物相结构及铺展性能的影响

在CsF-AlF_3二元共晶钎剂基础上利用湿法合成工艺制备不同锗(Ge)元素添加量的含锗铯盐钎剂,对新制备钎剂的熔化特性、物相结构以及微观组织进行观察与分析,并在含Ge 4%(质量分数,下同)的钎剂作用下480℃成功钎焊2024铝合金。结果表明:当含Ge超过4%时,钎剂液相线温度从477℃下降到440℃左右,并以CsAlF_4,Cs_2GeF_6为主相成分;同时新相Cs_2GeF_6的存在使得钎剂微观形貌中的絮状物减少,而块体变得更为规则有序。含Ge 4%的钎剂在480℃范围内显著促进了Zn-15Al钎料在2024铝合金上的铺展,同时该温度下的2024铝合金钎焊接头抗剪强度达到110MPa,接头组织均匀,未发现明显宏观缺陷。     

半导体激光钎焊无铅钎料润湿铺展性能的研究

采用半导体激光软钎焊系统对Sn-Ag-Cu无铅钎料在Cu基体上进行了润湿铺展性能实验,研究了半导体激光工艺参数对Sn-Ag-Cu无铅钎料润湿铺展性能的影响规律.结果表明:随着激光输出功率的增加,无铅钎料的铺展面积逐渐增加,润湿角逐渐减小;当激光输出功率增加到某一特定范围时,无铅钎料的润湿铺展性能达到最佳.在一定的激光输出功率范围内,随着激光钎焊时间的增加,无铅钎料在Cu基体上的润湿铺展性能逐渐优化,并在激光钎焊时间达到一定值时达到最佳.当激光输出功率过低或过高时,无论怎样改变激光钎焊时问,液态钎料在Cu基体上的润湿铺展效果均很差.     

Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures

In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

The Research of Anti-Wear Properties of Organomolybdenum Compounds in the Engine Oils

A four-ball tester was used to evaluate the anti-wear performance of three kinds of organomolybdemun compounds in the engine oils, i. e., molybdenum dialkyldithiophosphate (MoDDP), molybdenum dialkyldithiocarbamate ( MoDTC), and sulphur and phosphorus freeorganomolybdeum (Molybdate). The results indicate that a low concentration of MoDDP doesn' t improve the anti-wear properties of the commercial engine oils, but a high concentration of MoDDP can obviously improve the anti-wear properties and the load-carrying capacity of the engine oils. MoDTC doesn' t improve the antiwear properties of the engine oils, but worsens the anti-wear properties of the oils. Signifi can timprove ment of frictional and wear characteristics is obtained with Molybdate added in the commercial engine oils and the formulated oils.     

Flow calorimeter for enthalpy increment measurements on condensed gases

A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa.     

Refrigerators Enter a New Era of Health Preservation Frestech initiates the establishment of China's first standard for household sterilization refrigerators

On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.……     

Optimum-Simulation von Ernteprozessen

Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß.     

A study of centrifugal cast high boron high speed steel

In the present study a high‐boron high speed steel (HSS) roll material was designed. Many expensive alloy elements have been substituted by cheap boron alloy, and high‐boron high speed steel roll has been manufactured by centrifugal casting method. The microstructures, mechanical properties and wear resistance of centrifugal casting high‐boron high speed steel roll have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD) analysis, hardness test, impact test and wear test. The results indicated that the solidification microstructures of high‐boron high speed steel roll consisted of M₂(B,C), (W,Mo)₂(B,C), M₃(B,C), M₂₃(B,C)₆ type borocarbides and martensite, a small amount of retained austenite. Borocarbides were continuously distributed over the grain boundary. After quenching from 1050 °C, local broken network appeared in partial borocarbides, and fine secondary borocarbide precipitated from the matrix. After tempering from 525 °C, the amount of precipitated borocarbide increased significantly. After heat treatment, the hardness of high‐boron high speed steel roll excelled 60 HRC, and its impact toughness excelled 8.0 J/cm². The single groove steel rolling amount of high‐boron high speed steel rolls increases by 500% than that of bainite cast iron roll, when the rolls are used in K₁ mill housing of bar mill.     

Certification Becomes Important for the I Quality; and Safety Supervision of the Chinese Liquor Sector

The end of 2007, over 200 unit products of more than 80 Chinese firms have passed the quality grade certification for liquor products. These products involve distilled spirits, beer, wine, yellow wine, fruit syrup wine and others, and cover over 80% of the national top-branded liquor products.……     

Deposition and Coating Properties on CVD Tungsten

Surface characterization and microstructure studies are performed on chemical vapor deposited (CVD) tungsten coating. There is about 2 μm thickness diffusion layer of tungsten in the molybdenum substrate. The thermal shock test shows tungsten coating has good adhesion with molybdenum substrate, but the elements of oxygen and carbon in the tungsten coating have the bad affection to the adhesion. The result of high-temperature diffusion experiment is the diffusion rate from molybdenum substrate to tungsten coating is faster.