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
2、件,结 构 件 零 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,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,Care must be taken when filling thin sections as bridge
3、s may occur.The min. cross section size is about 1mm.,装粉高度与模冲进入量的计算,t1,t2,FD= 3.2g/cm3 GD= 7.2g/cm3,粉末压制,摩擦力,Between powder particles Between punches and the die-wall Between punches and powder particles Between powder particles and the die-wall,摩擦力导致的后果,Losses of the applied force Variation of pres
4、sure and green density Higher ejection forces (Wear of the tool-set),密度分布,双向压制示意图,Stationary die, two moving punches.Stationary lower punch and floating die.c) Stationary lower punch, and the die being withdrawn at half the speed of the top punch.,如何减小摩擦力,加入润滑剂 模壁润滑 优化压制工艺-压制速度-压制温度-滑动距离-,润滑剂含量对生坯理论
5、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 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
6、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 lubrication,Bad lubrication,Results in increased ejection force and stick-slip behaviour (squeaky noise),压制缺陷,SEM image of a crack no sintering necks,过 压 分 层,烧 结,烧结的作用脱除润滑剂 冶金粘结元
7、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,Metal powder compact Porous metal,Sintered state (bonding between particles),Green state (cold welding),生坯与烧结件,After compaction,After sintering,烧结工艺示意图,Temp.,Time,RT,Delubrication (300 - 700C)C - dissolution (800 - 950C),4,3,2,1,Sintering (1100 - 1300C)Coo
8、ling (Cooling Rate),1,2,3,4,影响烧结的因素,Temperature Time Atmosphere Material composition Alloying method Lubricant content Sintering cycle,烧结过程的实质,Particle bonding Microstructure Dimensional change,Sintering necks,Pores,Phases/structures,Size,Shape,Alloying,Homogenization,烧结驱动力,V1 + V2 = V3 E1 + E2 E3,1
9、,2,3,E1 + E2,E3,E,High energy stateLow energy state,Driving Force: Surface energy,固态烧结,By the Diffusion of the metal atoms,Cu spheres,孔隙变化,From sharp corners to flatter parts of the pore surface,From small pores to near-by larger pores and grain boundaries,均匀化过程 Ni in Fe-base,影响均匀化的因素,Ni particle si
10、ze: 5 um, 10 um,Temperature: 1000 - 1300C,Weighing factor:TemperatureNi particle sizeTime,Time: 0.5 -500 h,烧结的分类,Temperature (1150C) Furnace (batch, pusher, belt, walking beam) Atmosphere (“vacuum”, Endo, N2/H2) State (liquid, solid) Pressure (atmospheric, pressure-assisted),高温烧结,Accelerates the ato
11、mic motion (better sintering necks) Improves the surface reduction of particles (activates sintering) Increases the sintered density Improves the homogenization Improves pore rounding Improves mechanical properties,瞬时液相烧结,Secondary pore,Fe Cu系膨胀机理,90%Fe 10%Cu1150 C,Fe-Cu 系与Fe-Cu-C 系的尺寸变化,Cu,Cu + 1%C
12、,烧结常见的问题,Achieve sufficiently tight tolerances Oxidation (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,Particle size Alloying element Uneven filling and c
13、ompaction Uneven distribution of alloying elements in the component Liquid phase formation Sintering temperature and time Uneven temperature distribution of the sintering furnace Poor control of gas flow in the sintering furnace,脱蜡缺陷 (Blistering) Fe + 2.5% Ni + 0.4% C,烧结缺陷,Poor sintering necks (spon
14、ge) Poor sintering necks (atomised),Oxidation during sintering,弱烧结颈和游离石墨,烧结脱碳,NC100.24 + Cu + Ni + 1% C D. AB + 0.6% C,Astaloy CrM + 0.3% C,烧结渗碳,PASC 30 + 0% C D. HP-1 + 0.5 % C,过低的烧结温度,Free Cu in Distaloy material,后 续 处 理,后 续 处 理,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,粉 末 冶 金 关 注 领 域,高,中,低,中,高,低,Fe-Cr-Mo-Ni-C Liquid phase,Fe-Cr-Mo-Ni-C Mix,Astaloy CrM D. HP-1,Fe-Cu-Mo-Ni-C,Fe-Cu-Mo-Ni-C Starmix,Distaloy AE Astaloy CrL,Fe-Cu-CCu met.,Fe-Cu-CDistaloy ACu,Fe-Cu-C Dist.ACu, Starmix,尺寸公差,强 度,
