用CNC压机压制成形的事例

近年来,利用液压伺服机构的粉末成形压机日益普及,现在用CNC压机可压制成形过去用粉末冶金工艺无法压制成形的最终形零件.介绍了利用CNC压机的压制成形方法,其中包括近期才大量生产的与仍在研究大量生产的特殊产品.     

自动压制装料稳定性的研究

讨论了硬质合金生产中粉末自动压制成形时影响装料稳定性的三大因素,为评价混合料的压制性能、修正压机参数和压制工艺参数、顺利实现大批量生产提供借鉴。     

粉末热锻凸轮的数值模拟

凸轮作为装配式凸轮轴上的关键零部件之一,其制造技术很大程度上影响着凸轮轴及发动机的发展。采用验证实验的方法确认有限元法模拟粉末热锻凸轮的压制及热锻成形过程的合理性,在此基础上利用数值模拟法对凸轮的压制方式进行改进、优化热锻工艺参数。针对粉末压制成形工艺,对不同压制方式下(单向压制、双向压制、浮动压制、摩擦压制)的压坯密度进行模拟分析。而针对热锻工艺则研究分析锻压速度、摩擦因数、坯料加热温度、模具预热温度、坯料初始相对密度5组因素对锻件密度分布的影响,从而获得最佳的工艺方案。     

基于MARC的FC0205铁基粉末压制模拟技术

铁基粉末冶金零件是新能源汽车传动零件重要的批量方式生产的零件。压制工艺是制坯中不可或缺的环节，采用有限元分析方法代替实验，逐步成为零件可制造性分析的重要工具。针对FC0205牌号铁基粉末进行成形与性能实验，分析压制成形的4个阶段，选用MARC软件建立铁基粉末材质模型，提出基于连续体介质的仿真方案，考察边壁摩擦因数、压制速度、进给方向3种工艺因素以及高径比、锥角结构因素对压制品密度影响的分布规律，得出良好的结构是保证压制质量的前提，合理选择工艺因素能改善压制质量的结论，从而为粉末冶金产品提供可制造性参考。     

铁基粉末冶金液压马达阀板压制成形数值模拟

利用数值模拟软件DEFORM-3D对铁基粉末冶金液压马达阀板的压制成形过程进行数值模拟。研究了5种不同成形工艺参数方案条件下阀板压坯各区域的密度与整体密度的分布情况,分析了阀板外台阶和斜内台阶的成形密度与压坯整体密度分布不均匀的根本原因,获得了较优的阀板压制成形工艺参数并进行了生产实践验证,对提高同类铁基粉末冶金零件的成形工艺设计合理性具有重要借鉴意义。     

采用新型粘结预混粉提高零件生产稳定性

粉末冶金工艺是一种具有良好经济效益的近净成形工艺,在规模生产条件下,具有较明显的生产成本优势。然而,在压制和烧结过程中,有时会面临产品之间尺寸偏差较大等问题,从而需要额外的精整或机加工等后处理工艺来满足尺寸精度的要求。粘结预混粉(Starmix~(TM))是通过有机粘结剂将细小颗粒的添加组元牢固地粘结在基粉表面上,从而减少其在混粉中的偏析,可以提高粉末在压制过程中的填充性,进而改善零件成形过程及性能的稳定性。尝试应用添加新型润滑剂的粘结预混粉在工业生产条件下生产形状复杂并且尺寸精度要求较高的零件。结果表明,该粘结预混粉不仅提高了压制零件的尺寸精度和质量稳定性,而且改善了压制过程中的润滑性,同时可制备出更清洁的零件表面。     

成形工艺对粘结NdFeB磁体结构和磁性能的影响

在粘结NdFeB磁体模压成形过程中存在较大的压力损失，引起磁体密度分布不均匀，致使磁体密度减小。本文研究了压制压强、预压成形和压制方式等对粘结NdFeB磁体结构和磁性能的影响及机理。研究表明：随着压制压强提高，粘结NdFeB磁体的密度和磁性能显著增大；粒度配合、预压成形和双向压制等办法均可增大粘结NdFeB磁体的密度和磁性能；在适当的压制压强下，将粒度配合、预压成形及双向压制工艺结合，制备出密度达到6．5g／cm^3、磁能积达到104kJ／m^3的粘结NdFeB磁体。     

粉末冶金零件需要的高性能润滑剂

目前粉末冶金零件产业要解决的主要问题是:在合理降低成本的情况下生产高密度零件。生产高密度零件的工艺方法有很多种,其中包括零件的成形工艺和烧结技术。特别是,像温压与模壁润滑之类的一次压制工艺。这种工艺依据粉末的组成,生坯密度可达到的范围为7.2~7.5 g·cm-3。尽管如此,和传统压制工艺相比,这些压制工艺一般都需要严密控制,费用也相对较高,还有可能减小生产率。为了能让冷压制或控制温度的阴模压制达到较高的生坯密度,最近开发了一些新的高性能润滑剂。本文介绍了这些新开发的高性能润滑剂在试验室与大量生产中得出的生坯与烧结件特性。特别对这些新润滑剂和其他常规润滑剂的压制与脱出特性进行了对比。     

钛及钛合金粉末近净成形技术研究进展

钛及钛合金因具有优良的综合性能,在航空航天、能源化工、医疗等领域得到了日益广泛的应用。采用粉末冶金方法生产钛制品材料利用率高,是低成本制备高质量钛合金件的实用技术。综述了热等静压成形、金属注射成形、激光快速成形、温压成形、高速压制等钛及钛合金粉末冶金近净成形技术的研究进展,通过对比各项成形工艺的优缺点,提出了未来的发展趋势;并根据攀枝花地区钛资源的特点,提出了发展粉末冶金钛及钛合金材料的优势。     

《增材制造与粉末冶金》专刊客座主编寄语

粉末冶金是一种以金属粉末为原料,通过压制和烧结形成最终零部件的金属成形工艺,可以生产形状非常复杂的工件,已有100多年的历史.粉末冶金是公认的优良生产工艺,可针对不同行业的应用需求生产高质量的烧结结构部件.与其他金属成形技术(如锻造、金属铸造及机械加工)相比,粉末冶金工艺具有成本低、灵活性高以及制备性能优秀等优势,属于...     

Analysis of the external fixator pin-bone interface

External fixator pins were inserted into tibiae of dogs under four in vivo loading conditions to examine the mechanism of pin loosening. Pins were quantitatively measured for pin torque resistance, and the pin tracts were studied radiographically and histologically. The pins holding an unstable fracture had more gross pin loosening. Pins also may become loose under static loads. Radiographic lucency of 1 mm or more in the cortical bone around a pin was evidence of gross pin loosening. Histologic examination showed that tight pin tracts were characterized by a lack of bone remodeling. Loose pin tracts were characterized by extensive bone resorption and inflammatory infiltrates. Pin loosening can be detected radiographically. Pin insertion technique is important to improve the initial pin torque resistance to minimize pin loosening. Sixty-nine percent of pins with an initial torque resistance of less than 68 Ncm became grossly loose compared with only 9% of pins with an initial torque resistance greater than 68 Ncm, regardless of the experimental group. Unstable external fracture fixation is another important factor in producing pin loosening. Pins loaded under unstable fracture fixation had the highest incidence of gross loosening. When applying an external fixator, the fracture rigidity should be critically evaluated and, if necessary, protected weight bearing must be introduced initially to minimize pin loosening.     

低松比片状银粉及其银浆的微观分析

采用电化学和高能球磨法制备了低松比片状银粉,研究不同松比的银粉对粒径分布和比表面积的对应关系,并通过SEM和EDS进行表征,结果发现：片状银粉的松比比球状银粉的小,最小松比可以达到0.4012g/cm3,片状银粉的松比跟它的比表面积有关,松比越大,比表面积越大,而与片状银粉的粒径形状关系不大;随着片状银粉松比的减小,制得浆料的微观组织变得更致密,黑色孔洞会更少,浆料表面的致密性越好。     

Effects of Pin Shape on the Tool Plunge Stage in Friction Stir Welding

Studying each stage of the friction stir welding (FSW) in detail provides a more complete understanding of the process. In this study plunge stage in FSW has been studied experimentally. Effects of pin shape on the temperature distribution around the tool during the plunge stage have been examined by placing thermocouples around the tool in the workpiece and measuring the temperature during the process. Tools which had square, triangle and cylindrical pin shape were used to investigate the effects of pin shape on the temperature of the workpiece. Temperature distribution was asymmetric around the tools and temperature was a little higher behind the tools and at advancing side. The arrangement of the points according to the temperature was similar in all samples. It was found that most of the heat is generated by friction and the effect of friction on the workpiece temperature was more than plastic deformation. Shoulder had more considerable effects on the workpiece temperature compared to the pin.     

减少小方坯连铸漏钢的实践

针对抚顺新钢铁有限责任公司炼钢厂小方坯连铸漏钢事故频发的情况,从钢水浇铸条件、工艺操作和环境因素等方面,分析了造成钢水溢漏率高的原因,通过完善结晶器水冷制度,降低中间包钢水过热度,严格规范保护渣操作,进行射钉试验测定坯壳厚度等,使方坯溢漏率明显下降,平均溢漏率降至0.03%。     

干法球磨从废铝边角料中制取片状铝粉工艺研究

对在氮气惰性气氛下,利用废弃铝边角料生产片状铝粉的可行性进行了研究。研究发现在球磨过程中,废铝片通过钢球的微锻作用相互挤压分层、延展、细碎、最后形成片状铝粉,球罐中的钢球球径大小与片状铝粉的产出性能有着重要的关系,球径大的钢球研磨对铝粉的形成更有利;在球磨的前25h过程中,适当次数的间歇停机冷却球罐可以提高铝粉的细度;硬脂酸的加入可以减少铝粉与铝粉,铝粉与钢球或罐壁的摩擦,降低球磨效率。加入3％的硬脂酸作为助磨剂球磨效果最佳。所得片状铝粉可用于指纹鉴定,加气节能混凝土等。     

扰流柱参数对半固态AlSi9Mg组织的影响

提出将扰流冷却技术应用于半固态合金制备中,在自制的倾斜冷却装置内安放扰流柱,制备半固态AlSi9Mg合金水淬试样,用定量分析技术分析试样组织,研究扰流柱形状、排列方式和排列间距对半固态AlSi9Mg合金组织的影响.结果表明:扰流柱为水滴形时,制备的半固态AlSi9Mg合金中初生α-Al相较多,组织均匀,边缘轮廓清晰,初生α-Al相为球形或近球形,水淬组织特征为初生固相率53.54%,晶粒尺寸5.59μm,形状因子0.61.扰流柱的排列方式和排列间距对半固态Al-Si9Mg合金组织有较大的影响,叉排优于顺排,理想的排列间距为行间距S=15 mm,列间距L=40 mm.     

Breaking strength retention and histologic effects around 1.3-mm. ORTHOSORB polydioxanone absorbable pins at various sites in the rabbit

Absorbable 1.3-mm polydioxanone (ORTHOSORB) pins were implanted in 75 New Zealand White rabbits in three sites: within the lateral subcutaneous tissue parallel to the femur, down the femoral intramedullary canal, and mediolaterally across the femoral condyles (transcondylar). Pins were harvested at periodic intervals up to 56 and 365 days for mechanical and histologic analyses, respectively. Mechanical analyses were performed by loading the pin in double shear. Histologic analyses were performed on the pin and surrounding tissue. Histologic observations revealed a typical nonspecific foreign-body reaction at all implant sites that resolved at 1 year after resorption of the pin. On histologic examination, there was complete resorption of the pin material in the subcutaneous site by day 182, and there was complete resolution of all response to the pin in six of nine rabbits by day 365. In the intramedullary site, pin material was completely resorbed, based on histologic examination, in five of six rabbits by day 182, and there was complete resolution of the response to the pin in eight of nine rabbits by day 365. The pin material was completely resorbed based on histologic examination of the transcondylar site by day 210, and there was complete resolution of the response to the pin in four of six rabbits by day 270 and in four of nine rabbits by day 365. No enlarged pin tracks or sinus formations were observed in or near the implants sites. The average initial shear strength as 171.4+/ 5.1 MPa, and the breaking strength retention decreased with increasing implantation time. Pins from the subcutaneous regions maintained above 97% of their initial strengths at 28 days, and those from the intramedullary canals maintained above 92%. At later times the strength of the pins implanted in the intramedullary canal decreased more rapidly than those from the subcutaneous region. Overall, the average breaking strength of the subcutaneous pins was significantly greater than that of the intramedullary pins at all time points beyond 14 days. These data indicate that the pins exhibited a strength retention profile sufficient to allow normal healing of bone without enlarged pin tracts, allergic reactions, or sinus formations.     

冶金四连杆锯平衡重计算

在分析四连杆锯运转轻便的原因的同时,提出用调整平衡重的方法,均衡电机负荷,使之合理分配的新观点.     

金属粉末轧制

金属粉末轧制机理与传统的致密金属轧制机理不同 ,在这里适用的是粉末轧制前后粉末重量相等原理。粉末轧制变形区可简单地化分为粉末供料区和压实区。影响带材性能的主要因素有原始金属粉末的工艺性能和轧制工艺条件。     

汽车活塞销用钢质量检验与改善试验

采用一种定性的塔形检测方法对活塞销用20CrH圆钢进行了检验分析,并与其他钢厂进行了对比。研究发现,该圆钢中心部分存在簇状黑线为中心的偏析线且较严重,不能满足用户要求。为改善中心偏析,对轧制加热工艺进行优化,效果不明显,需要进一步优化炼钢工艺,缓解铸坯中心偏析。通过这种定性的塔形检测方法,能够较为全面地反映活塞销的外工作面、内部质量和内孔质量,为活塞销用钢检验以及标准的制定提供了指导和参考。