陶瓷注射成型工艺及进展

综述了陶瓷注射成型目前的发展状况，重点介绍了陶瓷注射成型技术的基本工艺过程，讨论了陶瓷注射成型技术的发展趋势。     

钛合金粉末注射成形工艺参数的优化

采用正交试验法系统研究了注射压力、注射温度、注射速度、模具温度及其交互作用对注射成形坯质量的影响.经过直观分析和方差分析,评价了各参数对生坯质量影响的显著程度,优化了注射成形参数.试验结果表明:注射压力、注射温度、模具温度及注射压力与注射温度的交互作用对生坯抗弯强度影响显著,注射压力、注射温度、注射速度及注射压力与模具温度的交互作用对生坯密度影响显著.注射压力增加,生坯密度和抗弯强度都增大;注射温度提高,生坯密度降低,注射温度在155～160℃之间时,生坯抗弯强度变化不大,超过160℃时抗弯强度明显降低.模具温度和注射速度分别为30℃和40%时,生坯密度和抗弯强度达到最大值.尺寸为6.38mm×6.38mm×48mm长方体生坯的最佳注射参数为:注射压力100MPa,注射温度160℃,注射速度60%,模具温度30℃.     

Influence of the Compacts Homogeneity on the Incidence of Cracks during Thermal Debinding in Ceramic Injection Molding

During thermal debinding in ceramic injection molding, the inhomogeneity of green body is a key origin of cracks. In this study, the impact of low molecular weight binders on the homogeneity of the green body was investigated. Incidence of cracks during thermal debinding indicated that the volume ratio of wax to stearic acid should be out of high viscosity and incompletely wetting region. In these two formulation regions,typical inhomogeneous microstructures were observed. By mercury intrusion method, it was shown that pore size distribution of the debinded compacts was determined by thermal degradation of low molecular weight binders. A particle-rich region model was established to predict the nucleation of cracks caused by solid loading fluctuation. The criterion of cracks nucleation was that local capillary force from solid loading fluctuation was larger than the suction force from the surroundings.     

钛合金粉末注射成形工艺中粉末特性的研究

采用统计分析的方法系统研究了原料粉末特性如粒度和粒度分布、颗粒形状、粉末比表面积对PIM工艺过程的影响规律,从原料粉末的特性参数中筛选出显著影响喂料性能和PIM工艺过程的参数,并建立相应的经验模型.振实密度与粉末特性的关系式为:ft=235.0 0.20Dv 32.18σ-29.17Sw-26.81Ar,粉末流动性与粉末特性的关系式为Mi=240.38-33.54Sw-32.08Ar,注射温度、注射压力和保压时间与粉末特性表达式分别为Ti=12.35 1.86σ-16.0Sw 145.5Ar,Pp=-289.63-18.35Sw 256.28Ar,th=-2.36 5.63Ar 0.10Dv-0.95Sw.     

粉末注射成型工艺参数对产品性能的影响

粉末注射成型是一项新型近净成型技术,被用于生产较小尺寸及形状复杂的制品。相比较传统的加工技术,虽然粉末注射成型工艺经济技术优势明显,但是该技术面临的技术问题也十分突出。结合该工艺的特点,本文论述了包括混料、注射成型、脱脂、烧结4道工序中涉及的工艺参数对制品质量的影响。粉末注射成型工艺在陶瓷、金属材料方面得到了很好的应用。     

Plastic Injection Molding of High-Aspect Ratio Micro-Rods

Technological advancements have led to an increase in demand for fabrication of small and cheap miniature components or parts, especially in the medical and electronic fields. In this research work, micro-rods of varying lengths and diameters were molded using a specially designed tabletop injection molding machine. The main purpose was to investigate whether complete filling of the microcavities was possible and whether small cavity openings will restrict melt flow into the cavities.

Process parameters, such as injection pressure, mold temperature and melt temperature were varied. The micro-rods obtained were analyzed with Scanning Electron Micrographs (SEM). The results showed that injection pressure was the most important parameter for microinjection molding. The use of a vacuum system also yielded better results.     

Plastic Injection Molding of High-Aspect Ratio Micro-Rods

Technological advancements have led to an increase in demand for fabrication of small and cheap miniature components or parts, especially in the medical and electronic fields. In this research work, micro-rods of varying lengths and diameters were molded using a specially designed tabletop injection molding machine. The main purpose was to investigate whether complete filling of the microcavities was possible and whether small cavity openings will restrict melt flow into the cavities.

Process parameters, such as injection pressure, mold temperature and melt temperature were varied. The micro-rods obtained were analyzed with Scanning Electron Micrographs (SEM). The results showed that injection pressure was the most important parameter for microinjection molding. The use of a vacuum system also yielded better results.     

大尺寸ZrO2注射成型坯体热脱脂缺陷成因探究

采用蜡基ZrO2粉末喂料注射成型获得大尺寸ZrO2陶瓷粉末注射产品（坯体）,并根据喂料热分析曲线的变化特点,系统研究了大尺寸ZrO2坯体的热脱脂过程及规律。通过对热脱脂前后坯体的重量损失、尺寸收缩、外观缺陷和微观组织形貌的分析评估,着重探讨了大尺寸ZrO2坯体热脱脂过程中存在的主要缺陷和成因。研究表明,流蜡、鼓泡和开裂等热脱脂缺陷主要发生在低温脱脂阶段,其主要原因是液态石蜡扩散及分解过程的失衡。为此,结合“失重率控制”的思路和喂料的热失重规律,对热脱脂工艺进行了优化,在不延长总脱脂时间的前提下,显著提高了大尺寸ZrO2坯体的脱脂合格率。     

Effects of thermal debinding on surface roughness in micro powder injection molding

Micro metal injection molding (μMIM) is a promising process for the replication of metallic microstructures. In the micrometer regime, surface roughness is important in view of the dimensional tolerance and the applications of microstructured parts. In this paper, the effects of debinding on the surface roughness of 316 L stainless steel microstructured parts were investigated. Experimental results showed that using higher heating rates during debinding increased the weight loss of debound parts. The debound parts of higher weight loss gave better surface finish after sintering. Comparing the increase of sintering time and temperature, the surface finish improvement was more significant for increasing temperature.     

钛合金粉末注射成形热脱脂工艺的研究

采用粉末注射成形方法制备了钛合金坯体,然后利用溶剂脱脂方法脱除坯体中可溶性粘结剂.在热脱脂速率为2.0℃/min、最高脱脂温度600℃、保温时间为1h和真空脱脂气氛条件下脱除坯体中剩余粘结剂,坯体中残余碳氧含量分别0.092%(质量分数)和0.28%,低于国外报道的PIM钛合金脱脂坯中残余碳氧含量.XRD结果表明,脱脂坯中只存在α相,没有TiC,Ti3Al,TiO和TiN等杂质相存在.N2气氛下脱脂,脱脂坯中残余碳含量较低,但氧含量较高.     

各向异性钕铁硼粘结磁体的注射成形技术

论述了注射成形各向异性Nd-Fe-B粘结磁体的特点及工艺过程,并对其生产工艺过程中的5个关键要素:磁粉及耦联剂、粘结剂、混炼过程、注射过程、磁场取向工艺的研究状况进行了综合评述.同时还论述了各向异性Nd-Fe-B磁粉的生产原理及生产现状.指出了注射成形Nd-Fe-B粘结磁体的现在和潜在的应用市场.在此基础上,指出了今后开展研究工作的方向.     

注水压力对圆管件水辅注塑填充过程的影响

以开源代码Open FOAM为基础,采用有限体积法和流体体积法构建了粘弹多相流的新求解器,数值模拟了圆管件的溢流法水辅注塑填充过程。基于熔体所固有的粘弹特性,解释了注水压力对熔体残余壁厚的影响,注水压力的变化导致熔体内变形速率的增加或减小,引起熔体抵抗变形能力的增强或减弱,直接影响到水相注入时受到阻力的大小,表现为熔体残余壁厚的多少。最后采用实验的方法进行验证,得出的结论与数值模拟所得的结论一致,并对数值大小的差异进行了解释。     

Replication of metal microstructures by micro powder injection molding

In this paper, a study on the production of 316L stainless steel microstructures by μPIM (powder injection molding) is presented. Two types of mold inserts were used and the molding was conducted on a conventional injection molding machine. Based on the characteristics of the mold inserts and the feedstock, suitable processing parameters were selected. Some requirements for the production of the microstructures are discussed. For example, a relatively high mold temperature, high injection pressure and holding pressure were required. The study showed that 316L stainless steel microstructures of φ100 × 200 μm can be injection molded, but there were incomplete filling and demolding problem in the case of smaller microstructures of φ60 × 191 μm. The molded parts were successfully debound and sintered.     

粉末注射成型喂料中添加剂的作用机理

在概述粉末注射成型工艺基本过程的基础上,首次系统分析了添加剂在粉末注射成型过程喂料制备中的作用机理,为制备组织结构均匀、流动性优良的粉末注射成型喂料探寻添加剂选择方面的科学基础.     

粉末注射成形的研究进展

概述了粉末注射成形的主要技术特点及优势,简要介绍了粉末注射成形工艺的主要应用领域和市场发展状况,总结了目前的研究热点,并在此基础上提出了今后的发展趋势和研究方向。     

水辅助注塑制件壁厚分析

根据水辅助注塑技术应用短射法成型中空圆管制品的聚合物熔体流动的基本特征,把水辅助注塑充模阶段聚合物熔体流动行为简化为等温条件下幂率流体的稳态流动,应用流体力学理论,对圆管水辅助注塑中影响制件壁厚的因素进行分析。结果表明,制件的壁厚主要由水与熔体界面处的压力梯度和熔体前端压力梯度的比值确定,同时制件壁厚也受熔体的流变性能影响。     

AlN粉末注射成形喂料的流变性能研究

以自蔓延法合成的AlN粉末为原料,加入5% Y2O3(质量分数,下同)为烧结助剂,选用石蜡(PW)、聚丙烯(PP)和硬脂酸(SA)粘结剂体系制成注射成形喂料,使用毛细管流变仪测定喂料的流变参数,通过线性回归分析,计算出非牛顿指数和粘流活化能.结果表明:喂料的粘度随着温度的升高以及剪切速率的增大而减小,具有较好的充模性,呈假塑性流体.在三种组分的喂料中,聚丙烯(35%)、石蜡(60%)和硬脂酸(5%)粘结剂体系与AlN粉末形成的喂料的综合流变性能最好,在160℃和526.02s-1剪切速率条件下,其粘度η,非牛顿指数n和粘流活化能E分别为277.93 Pa·s,0.5074和24.94kJ·mol-1.     

粉末注射成形的成形原理与发展趋势

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。本文综述了粉末注射成形技术的发展历程;概述了粉末注射成形原理,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;分析了粉末注射成形技术的局限性;展望了粉末注射成形技术的发展趋势,认为其材料体系将朝多方向发展,且应开发新的粘结剂和新的脱脂工艺以减少脱脂后在材料中的残留,开发少粘结剂、无粘结剂注射成形工艺;微粉末注射成形将朝成形数微米甚至纳米级的零部件的方向发展,防止粉末的氧化和保形是关键。     

粉末注射成形技术在烧结NdFeB永磁体制备中的应用

全面介绍了采用注射成形技术制备烧结NdFeB永磁体的工艺过程；总结了粘结剂、磁场取向及成形、脱脂和烧结工艺对最终产品的影响；比较了注射成形和传统粉末冶金压制成形制备的NdFeB磁体的性能；在分析现状的基础上，指出了现阶段存在的问题。