1、研究生課程高等粉末冶金學 Advanced Powder Metallurgy程繼貴材料科學與工程學院 本講內容提要 緒論部分粉末冶金基本概念 粉末冶金的特點粉末冶金的應用和前景一、粉末冶金的基本概念 定義 工藝過程 What isWhat is Powder Metallurgy (PM ?Powder Metallurgy (PM ? Powder metallurgy, or PM, is a Powder metallurgy, or PM, is a process for manufacturing metal or alloyed powders, and/orforming m

2、etal parts by heating compacted metal powders to just below their melting points.MPIF :Powder Metallurgy isa namegiven to process whichblended fine powder materials, pressed into desired shape, heated (sintered in controlled atmospheres to desired properties Textbook : 1 Powder ManufactureAtomizatio

3、n Produces a liquid-metal stream by injecting molten metal through small orifice. The stream is broken up by jets of inert gas, air, or water.Reduction Uses gases (hydrogen and CO to remove oxygen from metal oxides.Electrolytic deposition Utilizes aqueous solutions or fused salts. Produces purest fo

4、rm of metal powder.Atomization:stream gas, water, oil injection to molten metal Carbonyls Are formed by letting iron or nickel react with CO. The reaction products are then decomposed to iron and nickel.Comminution Mechanical Mechanical comminutioncomminution comminution involves crushing, involves

5、crushing, milling in a ball mill.Mechanical alloying Powders of two or more pure metals are mixed in a ball mill. This process forms alloy powdersMechanical comminuting methods Electrolytic process Powder manufactureOver 80% of all commercial powder are fromfrom “ “ AtomizationAtomization” ”Almost a

6、ny metal or nonmetal can be converted into powder form by one or more production methodsAtomization with rapid cooling rate, if exceeds 106O C/sec., metals can be solidify without becoming crystalline Amorphous metalsAmorphous metals, given unusualproperties, expanded possibility, good formability ,

7、 high strength, improved corrosion resistancePowder manufacture2 Powder Blending or Mixing Blending or Mixing Mixture of various grades or sizes of powder, or different compositions with lubricants or binders Some powders, such as, graphite, can be lubricant and composition in iron-carbon Most lubri

8、cants are not wanted in final product3 Compacting 4 Sintering Three stages of operations:1. Burn-off: create permeability by remove lubricants or binders2. High temperature stage: solid-state diffusion and bonding the particles with sufficient time to produce desired density3. Cooling period: lower

9、temperature while retain controlled atmosphere, prevent oxidation occur or thermal shock 傳統粉末冶金工藝以 鋼(剛模壓制成 形 (壓制、壓型, forming, compacting, brequtting 為基礎;包括三個基本的工序(單元操作 粉末準備(制粉、粉末混合、 壓制 成形、燒結在基本工序后可增加一些輔助工序,賦予 材料、制品特殊的性能、形狀尺寸等Secondary OperationsObjectives To provide enhanced precision To improve pro

10、perties To special characteristicsSecondary Operations Secondary Operations Secondary Operations Secondary OperationsOthers Heat treatment Machining Surface treatment Hot Hot IsostaticIsostatic Isostatic Pressing (HIP Pressing (HIPPressing and sintering in the same stepIncrease density (99%Attractiv

11、e for brittle materialsExpensive and unattractive for high volume production Metal Injection Molding(MIM or Powder InjectionMolding (PIMPowder materials areinjected into the moldcavityRelatively high final density (75%-90% to 95%-99%Possible to produce thinner shapeAttractive method for impossible t

12、o compact in a conventional pressOther Technique to produce High-Density P/M Products Uniform fine grain size, and alloy composition PM 三要素:粉末、模具、爐子(一 普通材料加工方法無法生產 的具有特殊性能的材料(ability to produce materials which can not be produced by other methods粉末冶金的不可替代作用! 二、粉末冶金的特點 Powder Metallurgy:Porous Metals

13、 Powdered Metal Transmission Gear Warm compaction method with 1650-ton press Teeth are molded net shape: No machining UTS = 155,000UTS = 155,000 psipsi 30% cost savings over the original forged part Powder Metallurgy: Connecting Rods Forged on left; P/M on right(三粉末冶金優缺點Advantages , disadvantages an

14、d limitations Advantages Possible wide variations in compositions Available variations in properties- High production rate Complex shapes can be produced in short time Rather lower mechanical properties, for their pores in partsSize and morphological limitation, for press machine.Rather lower wrough

15、t properties, for the products may contain oxide that induce materials brittle.Disadvantages and limitationsLimitations High cost of powder metals compared to other raw materials High cost of tooling and equipment for small production runs Rather small industry background compared with casting and conv