硬质合金挤压成形喂料热脱脂特性

开发出了适用于硬质合金挤压成形的成形剂及相应的热脱脂技术，通过优化配方设计与制备方式及工艺条件，制得了性能优良，分布均匀的成表剂。研究了成形剂及喂料的热脱脂工艺与机遇，发现热脱脂可分为低温区与高温区2个阶段，其脱脂机理均为热扩散，但2阶段热脱脂反应活化能不同；无论是成形剂还是喂料，其它组元的加入起了催化剂的作用，能有产地降低热脱脂反应活化能。     

硬质合金增塑粉末螺杆挤压成形

探讨了用于硬质合金粉末螺杆挤压成形技术的新粘结剂制备及挤压棒的组织形貌。新粘结剂由几种低分子量组元与1种热塑性弹性体高分子组元构成。采用溶剂溶解与加热熔融相结合的办法制备粘结剂。室温下，用合适的剪切力搅拌，能很快将粘结剂与YG8粉末混合均匀，制得组成均一的料浆式挤压用喂料。用扫描电子显微镜观察了挤压毛坯的微观组织及脱脂试样的组织结构与缺陷。用热重(TG)与微分热重(DTG)方法研究了热脱脂机理与动力学，发现了三维扩散控制热脱脂的速率。在脱脂的第1阶段，低分子量组元被脱除掉，挤压毛坯内形成了连通毛细孔。在脱脂的第2阶段，剩下的高分子量组元被完全脱除；第2阶段的热脱脂能以较快的升温速率进行。制备出了φ20mm的硬质合金挤压棒。     

LOW TEMPERATURE THERMAL DEBINDING BEHAVIOR OF WAX-BASED MULTI-COMPONENT BINDER FOR TUNGSTEN HEAVY ALLOY

１ＩＮＴＲＯＤＵＣＴＩＯＮＰｏｗｄｅｒｉｎｊｅｃｔｉｏｎｍｏｕｌｄｉｎｇ（ＰＩＭ）ｉｓａｎｅｗｐｒｏｃｅｓｓｆｏｒｍａｎｕｆａｃｔｕｒｉｎｇｎｅａｒｎｅｔｓｈａｐｅｐａｒｔｓｗｉｔｈａｄｖａｎｔａｇｅｓｏｆｌｏｗｃｏｓｔ,ｈｉｇｈｐｅｒｆｏｒｍａｎｃ...     

The effects of nanoparticle addition on binder removal from injection molded aluminum nitride

The effects of nanoparticle addition on the multi-step debinding of injection molded aluminum nitride (AlN) samples were studied. Experiments varying the solvent debinding conditions (time, temperature and aspect ratio) were performed on monomodal, microscale (μ) and bimodal, micro-nanoscale (μ-n) AlN samples. Variations in the solvent debinding kinetics as a result of the reduced particle size and increased powder content were examined. The bimodal μ-n AlN samples showed a slower solvent extraction of binder components compared to monomodal μ-AlN samples. The activation energy for solvent extraction estimated from diffusion coefficients (Arrhenius equation) was in close agreement with the value estimated by the master debinding curve (MDC) method. An activation value around 50 kJ/mol was estimated by both the methods for μ and μ-n AlN samples. The thermal debinding behavior of dewaxed samples was also studied and the trends correlated with the solvent debinding behavior.     

Novel PEG-based binder system and its debinding properties for MIM

1　ＩＮＴＲＯＤＵＣＴＩＯＮＭｅｔａｌｐｏｗｄｅｒｉｎｊｅｃｔｉｏｎｍｏｌｄｉｎｇ (ＭＩＭ )ｉｓａｎｅ ｍｅｒｇｉｎｇａｄｖａｎｃｅｄｎｅｔ ｓｈａｐｉｎｇｔｅｃｈｎｏｌｏｇｙ ,ｗｈｉｃｈｏｆ ｆｅｒｓｉｍｐｏｒｔａｎｔａｄｖａｎｔａｇｅｓｏｖｅｒｔｈｅｃｏｎｖｅｎｔｉｏｎａｌｐｏｗ ｄｅｒｍｅｔａｌｌｕｒｇｙ .Ｔｈｉｓｔｅｃｈｎｏｌｏｇｙｈａｓａｔｔｒａｃｔｅｄｍｏｒｅａｎｄｍｏｒｅａｔｔｅｎｔｉｏｎａｎｄｕｎｄｅｒｇｏｎｅｒａｐｉｄｄｅｖｅｌｏｐｍｅｎｔｉｎｔｈｅｒｅｃｅｎｔｙｅａｒｓ[1～ 4 ] .…     

THERMAL DEBINDING MECHANISM OF METAL INJECTION MOLDING COMPACTS IN VACUUM

１ＩＮＴＲＯＤＵＣＴＩＯＮＤｕｒｉｎｇｔｈｅｐａｓｔｆｅｗｙｅａｒｓ,ｐｏｗｄｅｒｉｎｊｅｃｔｉｏｎｍｏｌｄｉｎｇ（ＰＩＭ）ｈａｄｅｍｅｒｇｅｄａｓａｎａｄｖａｎｃｅｄｍａｎｕｆａｃｔｕｒｉｎｇｔｅｃｈｎｏｌｏｇｙ［１］．Ｔｈｅｃｏｍｂｉｎａｔｉｏｎ...     

硬质合金注射成形脱脂过程中的碳含量控制

研究了不同脱脂气氛 (不同比例N2 与H2 的混合气体 )和脱脂方法 (热脱脂、溶剂脱脂 热脱脂、冷凝蒸汽脱脂 热脱脂 )对PIM硬质合金脱脂坯及合金碳含量的影响。结果表明 :N2 热脱脂粘结剂容易以炭黑的形式残留在脱脂坯中 ,造成合金增碳 ;H2 热脱脂导致合金脱碳 ;75 %N2 2 5 %H2 (体积分数 )混合气体热脱脂既能有效地脱除粘结剂 ,又能保证合金碳含量相对稳定 ;溶剂脱脂和冷凝溶剂脱脂能显著缩短脱脂时间 ,而且由于高温保持时间短 ,在后续热脱脂过程中采用H2 作保护气也可获得满意的碳含量 ,说明该方法对工艺条件的适应性强。通过调整热脱脂高温保持时间 ,可在一定范围内对脱脂坯的碳含量进行调整 ,说明过程的可调控性好。与溶剂脱脂相比 ,冷凝蒸气脱脂粘结剂脱除率更高 ,脱脂坯有较高的强度 ,有效地防止了脱脂坯软化变形的现象。     

金属注射成形的脱脂临界厚度

通过对脱脂动力学的分析，发现在脱脂过程中，存在动力学控制步骤转化的过程，提出了临界厚度的概念。临界厚度越大，意味着脱脂初始阶段升温速率可以较快，脱脂所需时间可以相对缩短。临界厚度越小，那么脱脂初始阶段必须缓慢升温，以免产生鼓泡、裂纹、变形等缺陷。生产实践中临界厚度越大，脱脂处理越容易进行。对脱脂过程中控制步骤的理论计算，得到脱脂临界厚度与粉末大小、脱脂温度和装载量的关系：临界厚度与粉末颗粒大小成正比，粉末颗粒越大，临界厚度也大；临界厚度与保温温度成反比关系，温度越高，临界厚度越小；临界厚度与装载量成反比，装载量越高，临界厚度越小。     

“一步热脱脂+烧结”工艺对注射成形硬质合金显微结构与性能的影响

采用注射成形．溶剂脱脂．“一步热脱脂＋烧结”工艺制备了硬质合金。系统研究了一步热脱脂气氛和烧结工艺对合金性能的影响。结果表明：溶剂脱脂率控制在55％～58％时,通过“一步氢气热脱脂＋气压烧结”可以有效解决合金的控碳难和致密度低的问题。制备出的YG10X硬质合金制品抗弯强度达2690MPa,比常规模压．烧结法制备的合金性能大大提高。其硬度、钴磁、矫顽力控制在正常范围之内,它们分别是：维氏硬度为1320MPa,钴磁为8．6％。矫顽力为12．5kA·m^-1。     

粉末注射成形硬质合金异形件热脱脂工艺的研究

对硬质合金异形件表带注射成形的热脱脂工艺进行了研究 ,根据喂料的热失重曲线确定了热脱脂的四个阶段 ,并确定了理论预脱脂曲线 ,然后采用实验对该预脱脂曲线进行校正和条件优化 ,得出较理想的实际热脱脂曲线 ;研究了不同热脱脂工艺对硬质合金碳含量控制的影响 ,研究结果表明 ,使用露点低、氧含量低的氢气热脱脂气氛、选择合适的保温温度以及保温时间都能较有效地控碳。     

金属注射成形多功能脱脂炉的设计

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技术。脱脂是金属注射成形的重要工艺，包括热脱脂、溶剂脱脂、虹吸脱脂和催化脱脂。本文设计了一种可用于多种脱脂工艺的多功能脱脂炉，包括催化、溶剂、冷凝蒸汽和虹吸脱脂。介绍了该炉的设计原则、结构特点和经济性能。多功能脱脂炉对金属注射成形技术的工业化有重要意义。     

催化脱脂型粘结剂组分的相容性

对催化脱脂型粘结剂组分的相容性进行研究,对催化脱脂型粘结剂组元的溶解度参数进行热力学计算,采用DSC和扫描电镜分别对粘结剂进行热分析和端口形貌观察来表征粘结剂组元的相容性。结果表明:粘结剂主要组元聚醋酸乙烯(EVA)分别与聚甲醛(POM)和高密度聚乙烯(HDPE)均具有较好的相容性;m(POM)/m(HDPE)/m(EVA)为75/5/1时表现出良好的工艺相容性;设计了以75POM-5HDPE-1EVA(质量分数)为主要组元,同时添加一定量改性剂(石蜡(PW)、邻苯二甲酸二辛醋(DOP)和硬酯酸锌(ZS))的催化脱脂型粘结剂,该粘结剂与93W-Ni-Fe复合粉经混炼制得了均一、稳定的喂料。     

A novel binder and binder extraction method for powder injection molding of tungsten cemented carbide

1　INTRODUCTIONPowderinjectionmolding (PIM ) ,whichisde rivedfromplasticinjectionmolding ,isakindofnet shapepowdermetallurgyformingprocess[13] .Com bininghigh partcomplexitywithhigh productionquantities ,itsupplementstheestablishedprocesseslikediecompaction ,machiningandinvestmentcasting[4 6 ] .Comparingtoconventionalpressing/sinteringprocess,thePIMhasgreattechniqueandcostadvantagesforthepro ductionofcementedcarbidecomponentswithcomplexshapes[7,8] .Sincehydraulicpressureisappliedduringi…     

Solvent de-binding of water-soluble binder in powder injection moulding

１　ＩＮＴＲＯＤＵＣＴＩＯＮＲｅｃｅｎｔｌｙｍａｎｙｄｅｂｉｎｄｉｎｇｔｅｃｈｎｉｑｕｅｓｈａｖｅｂｅｅｎｓｔｕｄｉｅｄｉｎｍｅｔａｌｐｏｗｄｅｒｉｎｊｅｃｔｉｏｎｍｏｌｄｉｎｇ（ＭＩＭ）,ｉｎｃｌｕｄｉｎｇｔｈｅｒｍａｌｄｅｂｉｎｄｉｎｇ,ｃａｐｉｌｌａｒｙｄｅｂｉｎｄｉｎｇ,ｃａｔａｌｙｚｅｄｄｅｂｉｎｄｉｎｇｅｔｃ［１～５］．Ｃｏｍｐａｒｅｄｗｉｔｈｏｔｈｅｒｄｅｂｉｎｄｉｎｇｔｅｃｈｎｉｑｕｅｓ,ｔｈｅｓｏｌｖｅｎｔｄｅｂｉｎｄｉｎｇｈａｓｔｈｅａｄｖａｎｔａｇｅｓｏｆｌｉｔｔｌｅｄ…     

Pore opening and binder flow during initial stage of thermal debinding in MIM

1　INTRODUCTIONMetalinjectionmolding(MIM )isanet shapingtechnology ,whichhasthecharacteristicsoftheplas ticinjectionmoldingandconventionalpowdermetal lurgy(PM ) .MIMenablestheproductionofproductswithgreatershapecomplexity ,andwithbetterper formances.This processconsistsofthefollowingsteps :certainamountofbinderisblendedwithprop erpowders ,inorderforpreparingsuitablefeed stockstoinjection ;afterinjectionmolding ,partsarede boundandthensinteredandinthiswayfinalproductsareformed[1,2 ] .Th…     

93W-Ni-Fe粉末挤压成形坯溶剂脱脂工艺

以93W-Ni-Fe粉末挤压成形坯为研究对象,在研究溶剂脱脂动力学的基础上,考察溶剂种类、溶剂加入方式以及脱脂温度对溶剂脱脂过程的影响,并对脱脂前后的坯体断口进行SEM观察。结果表明:以正庚烷作为脱脂溶剂,具有较高的脱脂率,脱脂坯无鼓泡、开裂等缺陷;通过分段优化的脱脂工艺,在45℃的正庚烷中脱脂8 h,脱脂过程中周期性更换溶剂,最终可脱除65%以上的石蜡,且整个脱脂过程均为扩散控制,相应的动力学参数为1.6751×10-5 cm2/s。     

埋粉对热脱脂速率和传质过程的影响

对比了活性碳、γ-Al_2O_3、ZrO_2粉、α-Al_2O_3和刚玉等5种埋粉对热脱脂中低分子量粘结剂脱除速率及传质过程的影响.结果表明比表面积高的活性碳和γ-Al_2O_3对脱脂的促进作用可以保持低分子量粘结剂脱除的整个过程,而低比表面积的刚玉粉、α-Al_2O_3粉、ZrO_2粉则只在起始阶段起作用.空气气氛和低比表面积埋粉的热脱脂过程可以用扩散传质方程描述,而高比表面积埋粉对传质的促进作用体现在液相抽吸和气体吸附两个方面,气体吸附作用不能在扩散方程中得到体现.     

Effect of thermo-mechanical properties of PIM feedstock on compacts shape retention during debinding process

1　ＩＮＴＲＯＤＵＣＴＩＯＮＡｍｏｎｇｃｒｉｔｉｃａｌｉｓｓｕｅｓｉｎｔｈｅｐｏｗｄｅｒｉｎｊｅｃｔｉｏｎ ｍｏｌｄｉｎｇｐｒｏｃｅｓｓｔｈｅｒｅａｒｅｔｈｅｃｏｎｔｒｏｌａｎｄａｖｏｉｄａｎｃｅｏｆｄｉｓｔｏｒｔｉｏｎｄｕｒｉｎｇｔｈｅｒｍａｌｄｅｂｉｎｄｉｎｇａｎｄｔｈｅｍｉｎｉ ｍｉｚａｔｉｏｎｏｆｓｔｒｅｓｓｅｓｉｎｔｈｅｃｏｍｐａｃｔａｆｔｅｒｄｉｅｆｉｌｌｉｎｇ[1] .Ａｆｔｅｒｍｏｌｄｉｎｇｔｈｅｓｔｒｅｎｇｔｈｏｆｔｈｅｃｏｍｐａｃｔｓｉｓｄｅｐｅｎ ｄｅｎｔｏｎｔｈｅｐａｒｔｉｃｌｅ…     

Fabrication of 93W–Ni–Fe alloy large-diameter rods by powder extrusion molding

A powder extrusion molding (PEM) process has been used for the manufacturing of tungsten heavy alloy rods with large length to diameter ratio. An improved wax-based multi-component binder was developed for PEM of 93W–Ni–Fe alloy. The miscibility of its components and the characteristics of the binder were evaluated and good thermal–physical properties were obtained. Also, the feedstock rheological properties, extrusion molding and debinding process were studied. The feedstock exhibited a pseudo-plastic flow behavior. The large length to diameter ratio rods, with diameters up to 36 mm were extruded at 65 °C by optimizing the extrusion process. A two-step debinding process was employed to remove the binder in the extruded rods. Solvent debinding was carried out in n-heptane at 45 °C to extract the soluble components. A process of repeated short time immersion and drying of the extruded rods (called short-period solvent debinding) was developed and using this novel technique the binder removed was raised from 45% to 60%. SEM analyses indicated that a large volume of pores was formed in debound rods, but had not created interpenetrating pore channels yet. The rest of the binder could be thermally extracted at a high heating rate without defects.     

Debinding of stainless steel foam precursor with 3-D open-cell network structure

The thermal debinding behavior of stainless steel foam precursor in vacuum was studied and compared with that in hydrogen.The formation cause of pore channel was analyzed.The experiment results show that the binder removal rate in vacuum is higher than that in hydrogen.In vacuum,the organic compounds can be removed effectively without change of pore size and the pore morphology for the sample.After pre-sintering,some sintering necks form and the sample has certain intensity.The initial surface pore forms with the temperature increasing at first,and then the internal melting binder is aspirated to form initial pore because of the capillary force and the metal powders re-arrange with the migration of binder at the same time.