金属粉末注射成形的原理与发展趋势

金属粉末注射成形技术是一种高效的近净成形技术,适用于生产小型的、具有复杂形状的零部件。本文综述了金属粉末注射成形技术的发展历程;概述了金属粉末注射成形原理,包括粉末和粘结剂的选择、混炼,注射成形及后续的脱脂、烧结;并介绍了金属粉末微注射成形技术的技术特点、注射工艺和微注射成形的应用;分析了金属粉末注射成形技术的局限性;展望了金属粉末注射成形技术的发展趋势,认为预制复合粉末有助于解决混炼和注射造成的成分不均匀,减小烧结过程由于收缩不均匀导致的制件变形,且应开发新的粘结剂和脱脂工艺以减少脱脂后其在材料中的残留和碳化,开发少粘结剂注射成形工艺。     

钛及钛合金粉末的注射成形

介绍了钛及钛合金粉末注射成形技术的发展、应用现状及制备工艺.指出了钛及钛合金粉末注射成形技术研究方向和扩大应用的途径是:①使用价格低廉的氢化脱氢粉和气体雾化粉混合得到的钛及钛合金粉作为注射成形的原料粉末;②开发新型高效的钛及钛合金粉末注射成形用的粘结剂体系;③优化混炼工艺;④优化注射条件参数以消除注射缺陷;⑤开发先进的脱脂工艺,使脱脂时间进一步缩短并减少脱脂缺陷,以降低成本;⑥研究钛及钛合金烧结工艺以及超小型零件的注射成形工艺,控制产品尺寸精度,提高产品性能,扩大产品的尺寸.     

粉末注射成形粘结剂及脱脂技术研究进展

综述了粉末注射成形中粘结剂配方及其脱脂技术研究进展,并比较了现行工业上常用的三大脱脂方法,讨论了粉末注射成形脱脂工艺的发展趋势。     

粉末注射成形技术

1 项目简介 粉末注射成形是传统粉末冶金与现代塑料注射成形工艺相结合而形成的一门零部件新型成形技术,其基本工艺过程是:首先将固体粉末与有机粘结剂均匀混合,经制粒后在加热状态下用注射成形机将粒状料注入模腔内冷凝成形,然后用化学或热分解的方法将成形坯中的粘结剂脱除,最后经烧结致密化得到最终产品。该技术的最大特点是可以直接制造出具有最终形状的零部件,最大限度地减少机加工量和节省原材料,而且材料适应性广,凡是可以制成粉末的金属、合金、陶瓷等均可用此技术直接     

粉末注射成形新型快速脱脂工艺——催化脱脂

粉末注射成形工艺包括四个阶段：混炼、成形、脱脂和烧结,其中脱脂是粉末注射成形工艺中最复杂、最重要的环节。本文论述了一种粉末注射成形新型快速脱脂工艺——催化脱脂,详细介绍了催化脱脂原理、脱脂特性及脱脂设备,评述了催化脱脂技术发展现状,并对催化脱脂技术发展作出展望。     

金属注射成形技术的研究

金属注射成形技术是近年来发展最为迅速的粉末冶金近净成形枝术.从粘结剂、脱脂、烧结、精度及成分控制和计算机模拟等方面阐述了金属注射成形技术(MIM)的研究现状,指出MIM技术的应用领域和材料体系向多方面拓展、粘结剂体系的多样化与脱脂方法的多样化和计算机技术的应用将使MIM技术更加完善.     

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.     

金属粉末注射成形粘结剂

金属粉末注射成形是一种从塑料注射成形引伸出来的新型粉末冶金近净成形技术,该技术的核心和关键是粘结剂。讨论了粘结剂的作用和特征以及各类粘结剂体系的优缺点,综述了粘结剂及脱脂的研究进展,指出了粘结剂研究和开发的若干问题。     

Ti(C,N)基金属陶瓷注射成形脱脂技术研究

使用传统蜡基粘结剂和改进型蜡基粘结剂分别研究了Ti(C,N)基金属陶瓷粉末注射成形,热脱脂和溶剂脱脂 热脱脂工艺过程,其中包括根据粘结剂TGA制定并优化热脱脂的工艺曲线、不同的溶剂和温度对溶剂脱脂的影响、后续热脱脂工艺路线的确定.结果表明:使用改进型蜡基粘结剂的2#试样热脱脂工艺简单、周期短并易于控制;2#溶剂脱脂率明显高于使用传统蜡基粘结剂的1#试样;经过溶剂脱脂 热脱脂,1#试样脱脂率达到93%,2#试样脱脂率达到96%以上;1#烧结试样的抗弯强度为700 MPa左右,2#则达到1300 MPa,从烧结样品抗弯断口和显微组织的SEM图片得到了验证.Ti(C,N)基金属陶瓷注射成形采用改进型蜡基粘结剂比传统蜡基粘结剂脱脂效果好、力学性能高,改进型蜡基粘结剂更适合Ti(C,N)基金属陶瓷注射成形.     

超细WC-Co硬质合金注射成形的研究进展

总结了近年来超细WC-Co硬质合金注射成形在原料粉末、粘结剂体系、混炼、注射成形、粘结剂脱除和烧结等方面的研究现状.讨论了不同脱脂方式的发展及其对碳含量的影响,重点阐述了控制晶粒长大、尺寸精度等关键技术存在的困难及解决途径.展望了超细WC-Co硬质合金注射成形技术的发展前景.     

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.……     

From Industry 4.0 to Research 4.0. Development of High Performance Fibers in the Light of Digitization

We associate a variety of innovations with the term ＂Industry 4.0＂. The pioneer of many 4.0 modifications forms the basisfor the trend towards the integrated di...     

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.……     

Roman iron and steel: A review

ABSTRACT

The production of ferrous metal increased during the Roman Late Republican period, Principate and Empire. The direct bloomery process was used to extract the metal from its ores using slag-tapping and slag-pit furnaces. The fuel was charcoal and an air blast was introduced by bellows-operated tuyères. Iron formed as a bloom, often as a spongy mass of metal, which contained impurities from the smelting process, including unreacted ore, fuel, slag and fragments from the furnace walls, while the metal was often inhomogeneous with varied carbon contents. Blooms were either smithed directly into bars or ingots or they were broken up, which also allowed the removal of gross impurities and a selection of pieces with similar properties to be made. These could then be forge-welded together and formed into characteristically shaped ingots. Making steel in the furnace seems to have been achieved: it depended on the ore and the furnace and conditions within it. Surface carburization was also carried out. Iron and steel were used extensively in construction and for tools and weapons. Fire welding was often used to add pieces of steel to make the edges of tools and weapons, which could be heat-treated by quenching to harden them.     

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 ...