鐵基粉末冶金材料教學(xué)文稿

1、鐵基粉末冶金材料粉末冶金簡(jiǎn)介粉末冶金是： 通過對(duì)所需基礎(chǔ)粉末，合金粉末及添加劑混合，然后將混粉填充在具有要求形狀的模腔內(nèi)進(jìn)行壓制成形，再將成型坯體在保護(hù)氣氛下進(jìn)行燒結(jié)使各種顆粒形成冶金結(jié)合， 經(jīng)過后續(xù)處理后得到最終產(chǎn)品。 由于精確的成型技術(shù)，粉末冶金產(chǎn)品具有以下特點(diǎn)： 近凈成型 形狀復(fù)雜 優(yōu)良的尺寸精度. 粉 末 冶 金 簡(jiǎn) 介粉末冶金技術(shù)發(fā)展迅速： 其原料涵蓋了近乎所有技術(shù)元素 產(chǎn)品形狀復(fù)雜程度日益提高粉末冶金產(chǎn)業(yè)主要分為兩個(gè)領(lǐng)域： 鐵基粉末冶金 非鐵基粉末冶金鐵基粉末冶金材料 自潤(rùn)滑制品 結(jié)構(gòu)件 軟磁材料自 潤(rùn) 滑 零 件 結(jié)結(jié) 構(gòu)構(gòu) 件件 零零 件件 軟 磁 零 件粉 末 冶 金 產(chǎn) 品

2、 優(yōu) 勢(shì) 近凈成型 期望的力學(xué)性能 大規(guī)模的生產(chǎn)和重復(fù)性好 表面光潔度 高尺寸精度 允許不同材料組合 多孔及孔隙度可控（自潤(rùn)滑材料） 良好的磁性能（軟磁材料）粉末冶金基本工藝過程后 續(xù) 處 理粉 末 原 料 基粉類型 合金體系 合金化方式基 粉 的 選 擇混 料 混料要求 混合方式 均勻性與偏析 松裝密度與流動(dòng)性混粉及裝粉過程中產(chǎn)生的細(xì)粉團(tuán)聚混粉及裝粉過程中產(chǎn)生的細(xì)粉團(tuán)聚壓 制 壓制方式 生坯密度與密度均勻性 生坯強(qiáng)度 生坯缺陷充模過程充模過程Care must be taken when filling thin sections as bridges may occur.The min.

3、cross section size is about 1mm.裝粉高度與模沖進(jìn)入量的計(jì)算裝粉高度與模沖進(jìn)入量的計(jì)算DieCRUPLOPLIPt1t2H2LOPLIPUPDieH1FD= 3.2g/cm3GD= 7.2g/cm3Example:t1=10mmt2=25mmH1=22.5mmH2=56 mmUPentry= 31mmH1=GD/FD*t1H2=GD/FD*t2UPentry=H2-t2粉末壓制摩擦力 Between powder particles Between punches and the die-wall Between punches and powder partic

4、les Between powder particles and the die-wall摩擦力導(dǎo)致的后果 Losses of the applied force Variation of pressure and green density Higher ejection forces (Wear of the tool-set)密度分布雙向壓制示意圖Stationary die, two moving punches.Stationary lower punch and floating die.c)Stationary lower punch, and the die being wit

5、hdrawn at half the speed of the top punch.如何減小摩擦力如何減小摩擦力 加入潤(rùn)滑劑 模壁潤(rùn)滑 優(yōu)化壓制工藝-壓制速度-壓制溫度-滑動(dòng)距離-潤(rùn)滑劑含量對(duì)生坯理論密度的影響 ASC100.29 Amount of lubricant不同潤(rùn)滑劑對(duì)生坯理論密度的影響 ASC100.29 脫模力的變化過程 Due to residual radial stresses a significant force is required to eject compacts from the die. RRSs should be kept to a minimum t

6、o avoid high ejection forces, hence avoid tooling problems.模具潤(rùn)滑狀況對(duì)脫模力的影響Good lubrication模具潤(rùn)滑狀況對(duì)脫模力的影響 Excessive die wall wear or insufficient lubrication may result in cold welding of the compact to the die wall.Good lubricationBad lubrication Results in increased ejection force and stick-slip behav

7、iour (squeaky noise)壓制缺陷壓制缺陷SEM image of a crack no sintering necks過過 壓壓 分分 層層燒 結(jié) 燒結(jié)的作用 脫除潤(rùn)滑劑 冶金粘結(jié) 元素?cái)U(kuò)散 尺寸變化 微觀結(jié)構(gòu) 防止氧化與還原氧化物 燒結(jié)溫度、燒結(jié)時(shí)間、燒結(jié)氣氛燒結(jié)過程燒結(jié)過程Metal powder compact Porous metal Sintered state (bonding between particles)Green state (cold welding)生坯與燒結(jié)件After compactionAfter sintering燒結(jié)工藝示意圖燒結(jié)工藝示意圖

8、Temp.TimeRT Delubrication (300 - 700C) C - dissolution (800 - 950C)4321 Sintering (1100 - 1300C) Cooling (Cooling Rate)1234影響燒結(jié)的因素影響燒結(jié)的因素 Temperature Time Atmosphere Material composition Alloying method Lubricant content Sintering cycle燒結(jié)過程的實(shí)質(zhì)燒結(jié)過程的實(shí)質(zhì) Particle bonding Microstructure Dimensional chang

9、eSintering necksPoresPhases/structuresSizeShapeAlloyingHomogenization燒結(jié)驅(qū)動(dòng)力燒結(jié)驅(qū)動(dòng)力V1 + V2 = V3E1 + E2 E3123E1 + E2E3EHigh energy stateLow energy stateDriving Force: Surface energy固態(tài)燒結(jié)固態(tài)燒結(jié) By the Diffusion of the metal atomsCu spheres孔隙變化孔隙變化From sharp corners to flatter parts of the pore surfaceFrom sm

10、all pores to near-by larger pores and grain boundaries均勻化過程均勻化過程 Ni in Fe-base影響均勻化的因素影響均勻化的因素Ni particle size:5 um, 10 umTemperature:1000 - 1300CWeighing factor: Temperature Ni particle size TimeTime: 0.5 -500 h燒結(jié)的分類燒結(jié)的分類 Temperature (1150C) Furnace (batch, pusher, belt, walking beam) Atmosphere (“

11、vacuum”, Endo, N2/H2) State (liquid, solid) Pressure (atmospheric, pressure-assisted)高溫?zé)Y(jié)高溫?zé)Y(jié) Accelerates the atomic motion (better sintering necks) Improves the surface reduction of particles (activates sintering) Increases the sintered density Improves the homogenization Improves pore rounding Imp

12、roves mechanical properties 瞬時(shí)液相燒結(jié)瞬時(shí)液相燒結(jié)Secondary poreFe Cu系膨脹機(jī)理系膨脹機(jī)理90%Fe10%Cu1150 CFe-Cu 系與系與Fe-Cu-C 系的尺寸變化系的尺寸變化 CuCu + 1%C燒結(jié)常見的問題燒結(jié)常見的問題 Achieve sufficiently tight tolerances Oxidation (alloying elements, sintering atmosphere) Carburisation (temperature, sintering atmosphere) Decarburisation (te

13、mperature, sintering atmosphere) Poor surface finish (delubrification)影響尺寸變化的因素影響尺寸變化的因素 Particle size Alloying element Uneven filling and compaction Uneven distribution of alloying elements in the component Liquid phase formation Sintering temperature and time Uneven temperature distribution of the

14、 sintering furnace Poor control of gas flow in the sintering furnace脫蠟缺陷脫蠟缺陷 (Blistering)Fe + 2.5% Ni + 0.4% C燒結(jié)缺陷燒結(jié)缺陷 Poor sintering necks (sponge) Poor sintering necks (atomised) Oxidation during sintering弱燒結(jié)頸和游離石墨弱燒結(jié)頸和游離石墨燒結(jié)脫碳燒結(jié)脫碳 NC100.24 + Cu + Ni + 1% C D. AB + 0.6% C Astaloy CrM + 0.3% C燒結(jié)滲碳燒

15、結(jié)滲碳 PASC 30 + 0% C D. HP-1 + 0.5 % C 過低的燒結(jié)溫度過低的燒結(jié)溫度 Free Cu in Distaloy material后 續(xù) 處 理TreatmentDefinitionExamplesCoatings- a deposition of a layer of a separate material onto the surface of the substrate without any chemical reactionElectroplatingPaintingmetallizingChemical conversion treatmentsA c

16、hemical reaction between the surface layers of the original substrate and an external reactantSteam treatmentPhosphatising,etcThermochemical treatmentsDiffusion of other species, such as C, N, into the surface layers of the original substrateCarburisingCarbonitridingNitrocarburisingNitridingPlasma t

17、reatments, etc后 續(xù) 處 理TreatmentDefinitionExamplesThermal treatmentsChange in microstructure of the surface layers of the original substrate by thermally cycling through a phase transformationInduction hardeningLaser hardeningMechanical deformationMechanical deformation in the surface layers of the or

18、iginal substrate, mainly to induce compressive stresses, but also to provide densification of the surface layerSurface cold rolling, etc發(fā) 展 趨 勢(shì) 高密度 高性能 高尺寸精度 低單位成本 新工藝 新材料發(fā) 展 趨 勢(shì)HighMediumLow Very lowVery poor Poor Medium Good Very goodPlasticsCasting +ForgingPMTolerancesStrength粉 末 冶 金 關(guān) 注 領(lǐng) 域高高 中中