铁基粉末冶金材料.ppt

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1、铁基粉末冶金材料内 容 提 要概述工艺过程产品种类混料、成型、烧结及后处理发展趋势粉末冶金简介粉末冶金是：通过对所需基础粉末，合金粉末及添加剂混合，然后将混粉填充在具有要求形状的模腔内进行压制成形，再将成型坯体在保护气氛下进行烧结使各种颗粒形成冶金结合，经过后续处理后得到最终产品。由于精确的成型技术，粉末冶金产品具有以下特点：近净成型 形状复杂 优良的尺寸精度.粉 末 冶 金 简 介粉末冶金技术发展迅速：其原料涵盖了近乎所有技术元素 产品形状复杂程度日益提高粉末冶金产业主要分为两个领域：铁基粉末冶金 非铁基粉末冶金铁基粉末冶金材料自润滑制品结构件软磁材料自 润 滑 零 件 结结 构构 件件 零

2、零 件件 软 磁 零 件粉 末 冶 金 产 品 优 势近净成型期望的力学性能大规模的生产和重复性好表面光洁度 高尺寸精度 允许不同材料组合多孔及孔隙度可控（自润滑材料）良好的磁性能（软磁材料）粉末冶金基本工艺过程后 续 处 理粉 末 原 料基粉类型合金体系合金化方式基 粉 的 选 择混 料混料要求混合方式均匀性与偏析松装密度与流动性混粉及装粉过程中产生的细粉团聚混粉及装粉过程中产生的细粉团聚压 制压制方式生坯密度与密度均匀性生坯强度 生坯缺陷充模过程充模过程Care must be taken when filling thin sections as bridges may occur.Th

3、e min.cross section size is about 1mm.装粉高度与模冲进入量的计算装粉高度与模冲进入量的计算DieCRUPLOPLIPt1t2H2LOPLIPUPDieH1FD=3.2g/cm3GD=7.2g/cm3Example:t1=10mmt2=25mmH1=22.5mmH2=56 mmUPentry=31mmH1=GD/FD*t1H2=GD/FD*t2UPentry=H2-t2粉末压制摩擦力Between powder particlesBetween punches and the die-wallBetween punches and powder partic

4、lesBetween powder particles and the die-wall摩擦力导致的后果Losses of the applied forceVariation of pressure and green densityHigher ejection forces(Wear of the tool-set)密度分布双向压制示意图a)Stationary die,two moving punches.b)Stationary lower punch and floating die.c)Stationary lower punch,and the die being withdr

5、awn at half the speed of the top punch.如何减小摩擦力如何减小摩擦力加入润滑剂模壁润滑优化压制工艺-压制速度-压制温度-滑动距离-润滑剂含量对生坯理论密度的影响 ASC100.29 Amount of lubricant不同润滑剂对生坯理论密度的影响 ASC100.29 脱模力的变化过程Due to residual radial stresses a significant force is required to eject compacts from the die.RRSs should be kept to a minimum to avoid

6、high ejection forces,hence avoid tooling problems.模具润滑状况对脱模力的影响Good lubrication模具润滑状况对脱模力的影响Excessive die wall wear or insufficient lubrication may result in cold welding of the compact to the die wall.Good lubricationBad lubricationResults in increased ejection force and stick-slip behaviour(squeak

7、y noise)压制缺陷压制缺陷SEM image of a crack no sintering necks过过 压压 分分 层层烧 结烧结的作用 脱除润滑剂 冶金粘结 元素扩散 尺寸变化 微观结构 防止氧化与还原氧化物烧结温度、烧结时间、烧结气氛烧结过程烧结过程Metal powder compact Porous metal Sintered state(bonding between particles)Green state(cold welding)生坯与烧结件After compactionAfter sintering烧结工艺示意图烧结工艺示意图Temp.TimeRT Delu

8、brication(300-700C)C-dissolution(800-950C)4321 Sintering(1100-1300C)Cooling (Cooling Rate)1234影响烧结的因素影响烧结的因素TemperatureTimeAtmosphereMaterial composition Alloying methodLubricant contentSintering cycle烧结过程的实质烧结过程的实质 Particle bonding Microstructure Dimensional changeSintering necksPoresPhases/structu

9、resSizeShapeAlloyingHomogenization烧结驱动力烧结驱动力V1+V2=V3E1 +E2 E3123E1 +E2E3EHigh energy stateLow energy stateDriving Force:Surface energy固态烧结固态烧结 By the Diffusion of the metal atomsCu spheres孔隙变化孔隙变化From sharp corners to flatter parts of the pore surfaceFrom small pores to near-by larger pores and grai

10、n boundaries均匀化过程均匀化过程 Ni in Fe-base影响均匀化的因素影响均匀化的因素Ni particle size:5 um,10 umTemperature:1000-1300CWeighing factor:Temperature Ni particle size TimeTime:0.5-500 h烧结的分类烧结的分类Temperature(1150C)Furnace(batch,pusher,belt,walking beam)Atmosphere(“vacuum”,Endo,N2/H2)State(liquid,solid)Pressure(atmospheri

11、c,pressure-assisted)高温烧结高温烧结Accelerates the atomic motion(better sintering necks)Improves the surface reduction of particles(activates sintering)Increases the sintered densityImproves the homogenizationImproves pore roundingImproves mechanical properties 瞬时液相烧结瞬时液相烧结Secondary poreFe Cu系膨胀机理系膨胀机理90%F

12、e10%Cu1150 CFe-Cu 系与系与Fe-Cu-C 系的尺寸变化系的尺寸变化 CuCu+1%C烧结常见的问题烧结常见的问题Achieve sufficiently tight tolerancesOxidation(alloying elements,sintering atmosphere)Carburisation(temperature,sintering atmosphere)Decarburisation(temperature,sintering atmosphere)Poor surface finish(delubrification)影响尺寸变化的因素影响尺寸变化的因

13、素Particle sizeAlloying elementUneven filling and compaction Uneven distribution of alloying elements in the componentLiquid phase formationSintering temperature and timeUneven temperature distribution of the sintering furnacePoor control of gas flow in the sintering furnace脱蜡缺陷脱蜡缺陷(Blistering)Fe+2.5

14、%Ni+0.4%C烧结缺陷烧结缺陷 Poor sintering necks(sponge)Poor sintering necks(atomised)Oxidation during sintering弱烧结颈和游离石墨弱烧结颈和游离石墨烧结脱碳烧结脱碳 NC100.24+Cu+Ni+1%C D.AB+0.6%C Astaloy CrM+0.3%C烧结渗碳烧结渗碳 PASC 30+0%C D.HP-1+0.5%C 过低的烧结温度过低的烧结温度 Free Cu in Distaloy material后 续 处 理TreatmentDefinitionExamplesCoatings-a de

15、position of a layer of a separate material onto the surface of the substrate without any chemical reactionElectroplatingPaintingmetallizingChemical conversion treatmentsA chemical reaction between the surface layers of the original substrate and an external reactantSteam treatmentPhosphatising,etcTh

16、ermochemical treatmentsDiffusion of other species,such as C,N,into the surface layers of the original substrateCarburisingCarbonitridingNitrocarburisingNitridingPlasma treatments,etc后 续 处 理TreatmentDefinitionExamplesThermal treatmentsChange in microstructure of the surface layers of the original sub

17、strate by thermally cycling through a phase transformationInduction hardeningLaser hardeningMechanical deformationMechanical deformation in the surface layers of the original substrate,mainly to induce compressive stresses,but also to provide densification of the surface layerSurface cold rolling,et

18、c发 展 趋 势高密度高性能高尺寸精度低单位成本新工艺新材料发 展 趋 势HighMediumLow Very lowVery poor Poor Medium Good Very goodPlasticsCasting+ForgingPMTolerancesStrength粉 末 冶 金 关 注 领 域高高 中中低低 中中 高高低低Fe-Cr-Mo-Ni-CLiquid phaseFe-Cr-Mo-Ni-CMixAstaloy CrMD.HP-1Fe-Cu-Mo-Ni-CFe-Cu-Mo-Ni-CStarmixDistaloy AEAstaloy CrLFe-Cu-CCu met.Fe-Cu-CDistaloy ACuFe-Cu-CDist.ACu,Starmix 尺寸公差尺寸公差强强 度度 粉末冶金发展趋势粉末冶金发展趋势