水溶性粘接剂氧化锆粉末注射成形喂料的研究

采用聚乙二醇(PEG)为水溶脱脂粘接剂,聚甲醛(POM)/聚乙烯醇缩丁醛(PVB)为保型粘接剂,混炼制备水溶性粘接剂氧化锆粉末注射成形喂料;通过傅里叶红外光谱和旋转流变测试研究硬脂酸改性氧化锆对注射成形喂料的性能影响,并通过喂料流变行为、注射生坯脱脂率、生坯弯曲强度以及生坯脱脂前后断面形貌扫描电镜分析、烧结体的X射线衍射、硬度及密度表征,研究粘接剂组分配比和喂料粉末装载量对喂料性能的影响.结果表明:硬脂酸可以成功对氧化锆粉末进行改性,并可以明显降低注射成形喂料的黏度;当粉末装载量达到52%(体积分数),粘接剂各组分配比w(PEG)∶w(POM)∶w(PVB)=6∶2∶2时,喂料具有较好的流动性且粉末分散良好,生坯中粘接剂形成网状结构赋予生坯较高的弯曲强度,4 h后水脱脂率超过80%,水脱脂后生坯形成细小且连续脱脂通道;生坯经水脱脂、1 450℃烧结2 h后,烧结体晶型主要由四方相组成,平均晶粒尺寸1μm,密度6.01 g/cm~3,平均维氏硬度达到1 147 HV,与模压成型烧结氧化锆性能相当.     

超细316L不锈钢粉末注射成形的脱脂工艺

采用溶剂脱脂和热脱脂相结合的方法,研究了超细316L不锈钢粉末注射成形坯的脱脂工艺。注重考察了升温速度和保温时间对不锈钢注射坯的热脱脂工艺的影响。研究表明注射成形坯经正己烷溶剂脱脂后,石蜡组元全部被脱除。其它组元在后续的热脱脂中被去除,确定了优化的升温速度和保温时间,试样没有出现缺陷,并缩短了脱脂周期,该周期大约为10小时。     

Al_2O_3陶瓷注射成型水基粘结剂喂料组成及脱脂工艺研究

重点研究了Al2O3陶瓷注射成型水基粘结剂喂料的配比及其脱脂工艺.结果表明,当Al2O3粉料质量分数为80%、选用聚乙二醇/聚丙烯/聚乙稀/硬脂酸(m(PEG):m(PP):m(PE):m(SA)=61 : 17 : 17 : 5)水基粘结剂时,Al2O3陶瓷试样性能较好.水脱脂过程中,PEG脱除率随着水温的升高而增大,在50℃去离子水中脱脂4h,PEG脱除率可达74%.     

FDM型3D打印316L不锈钢试样和La对析出物形貌和分布的影响

使用微米级316L不锈钢粉末和蜡基粘结剂制备热融性喂料，用FDM型金属3D打印方法和工艺3D打印成形目标模型生胚，经过脱脂和烧结成形为最终金属试样。对制备出的金属试样进行性能表征和测试，验证了此种成形方式的可行性，针对试样中析出物的形貌不规则和晶界上的夹杂物，研究了稀土La对析出物的影响。根据生胚脱脂后形成的微孔结构，提出一种液相添加稀土La的方法。结果表明:用FDM型3D打印能制备316L不锈钢试样，用液相添加法可向生胚中添加微量稀土La，质量比为0.3%的LaCl₃能显著改善烧结后试样中析出物的微观形貌和分布。     

金属粉末注射成形石蜡-油-聚乙烯粘结剂的研究

本文开发了用于Fe-2Ni粉末注射成形石蜡-油-聚乙烯粘结剂,选择了石蜡和聚乙烯组份,考察了油的加入对组份相容性、生坯强度、粉末装载量、喂料热容、溶剂脱脂速率的影响.该粘结剂用于Fe-2Ni注射成形,粉末装载量达60%(体积分数),生坯强度5.5MPa,溶剂脱脂速率2mm/h以上.     

高氮奥氏体不锈钢金属注射成形喂料的流变行为研究

采用金属注射成形制备高氮奥氏体不锈钢,研究了石蜡(PW)、高密度聚乙烯(HDPE)、聚丙烯(PP)以及硬脂酸等几种聚合物组成的注射成形喂料的黏度、剪切速率以及温度对黏度的影响,比较了聚合物组元对喂料流变行为的影响。研究结果表明,黏结剂配方为65%PW/30%HDPE/5%SA(质量分数,下同)所组成喂料具有较好的综合流变性能,更适合作为高氮奥氏体不锈钢粉末注射成形的有机载体。     

新型陶瓷注射成形喂料催化脱脂过程的研究

陶瓷注射成形是一种受到日益广泛关注的技术 ,但其中脱脂一步传统采用的热脱脂技术脱脂速度慢 ,效率较低。本研究采用以聚甲醛为主要粘结剂制备了可快速脱脂的新型陶瓷注射成形喂料体系 ,并进行催化脱脂工艺的研究 ,记录了该过程中样品失重的情况 ,分析了脱脂阶段不同特征及其原因 ,指出催化脱脂过程速度的控制因素是气态催化剂和气体产物扩散过程。通过脱脂前后样品表面及截断面的扫描电镜分析 ,直观反映了脱脂前后样品微观形貌上的差异及特点。观察了脱脂过程不同时刻样品外围与中心区域的微观形貌 ,证明了脱脂过程是由外围逐渐向内部扩散的 ;记录了经注射成形的试样烧结前后的密度变化     

新型陶瓷注射成形喂料催化脱脂过程的研究

陶瓷注射成形是一种受到日益广泛关注的技术，但其中脱脂一步传统采用的热脱脂技术脱脂速度慢，效率较低，本研究采用以聚甲醛为主要粘结剂制备了可快速脱脂的新型陶瓷注射成形喂料体系，并进行催化脱脂工艺的研究，记录了该过程中样品失重的情况，分析了脱脂阶段不同特征及其原因，指出催化脱脂过程速度的控制因素是气态催化剂和气体产物扩散过程，通过脱脂前后样品表面及截断面的扫描电镜分析，直观反映了脱脂前后样品微观形貌上的差异及特点，观察了脱脂过程不同时刻样品外围与中心区域的微观形貌，证明了脱脂过程是由外围逐渐向内部扩散的；记录了经注射成形的试样烧结前后的密度变化。     

注射成形高密度钨合金脱脂工艺的研究

采用石蜡基多组元粘结剂体系,研究了注射成形高密度钨合金喂料的热脱脂工艺参数,包括样品厚度,温度,低温预脱脂和升温速率的。实验表明,当温度小于２５０℃时,脱脂量的对数与厚度的倒数呈比例,在长时间情况下,ＰＷ可以在２５０℃以衣全部脱除。温度,脱脂量和升温速率的撑峭当将导致脱脂缺陷的产生。     

热处理对增材制造核用不锈钢微观结构的影响

目的 以选区激光熔化（SLM）制备的核用316L奥氏体不锈钢为研究对象,探究不同热处理工艺对其微观结构的调控机制,为设计新型的核用不锈钢材料提供实验依据。方法 使用X射线衍射仪、扫描电镜、透射电镜和电子背散射衍射等设备和技术手段,对600℃和1 050℃热处理后的SLM样品的合金成分、物相、晶粒形貌等开展表征和分析。结果 SLM技术成形的核用316L不锈钢内部无明显的裂纹和空洞,柱状及胞状亚晶粒清晰可见,各合金元素分布均匀;热处理温度的升高促进了亚晶粒中的应变能释放,导致部分亚晶界消失;当热处理温度为1 050℃时,小角度晶界比例急剧下降,亚晶粒发生重结晶。相比于传统的加工技术,SLM技术通过急速升温与降温的方法引入了高密度亚晶粒,利用位错强化和析出相强化机制提高了材料的硬度。结论 升高热处理温度可以提高激光增材制造核用316L不锈钢中大角度晶界的比例和铁素体相的含量。位错密度大幅度减小是不锈钢硬度降低的主要原因。     

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.……     

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.     

Thixotropy of Systems with Shear Thinning and Plastic Flow Behavior

The definition of the thixotropy is a decrease in viscosity with time in shear and a subsequent recovery of viscosity after the shear deformation is removed.We ...     

Brainstorming for ISO Strategy 2016-2020

正Responding to ISO’s appeal for survey for the to-be-developed ISO Strategy Plan for 2016-2020,SAC hosted a special workshop over the needs and comments of various fi elds on June 8 in Beijing.The workshop was attended by ISO President-elect and Ansteel General Manager Zhang Xiaogang,SAC Vice-Administrator Yu Xinli,and 30 experts from     

CNAS Passes APLAC's PTP Review

正The review group of Asia Pacific Laboratory Accreditation Cooperation(APLAC)carried out a 4-day peer review of the proficiency testing provider(PTP)for China National Accreditation Service for Conformity Assessment(CNAS)from July 28 to 31,2014.CNAS passed the PTP review with excellent performance.Two senior peer reviewers of APLAC made a comprehensive,rigorous and detailed review of CNAS’s PTP accreditation activities,and made the on-spot inspection of the review groups in Shanghai and Shenzhen respectively.