●Eliminates or minimizes machining by producing parts at, or close to final dimensions.
●Eliminates of minimizes scrap losses by typically using more than 97% of the starting raw material in the finished part.
●Permits a wide variety of alloy systems.
●Produces good surface finishes.
●Provides materials which may be heat treated for increased strength or increased wear resistance.
●Provides controlled porosity for self lubrication or filtration.(自潤滑或過濾)
●Facilitates manufacture of complex or unique shapes which would be impractical or impossible with other metal working processes.
●Is suited to moderate-to high-volume component production requirements.
●Offers long-term performance reliability in critical applocations.
●Is cost effective.
Powder metallurgy, or PM, is a process for forming metal parts by heating compacted metal powders to just below their melting pints.
● forging and metal casting
● advantages in material utilization
● shape complexity
● near-net-shape(近淨形，接近成品的形狀)
● lower costs(便宜)
● greater versatility(多樣性)
press-and-sinter壓完燒結→conventional PM
metal injection molding (MIM)金屬射出成型
hot isostatic pressing (HIP)熱(均)壓
powder forging (PF)
●cold room temperature compaction
●warm 100~ 200°C compaction
●hot 600°C compaction
Hot pressing 指熱壓和燒結同時進行，而compction只有壓的意思。
1.粉末混合
2.成型
3.燒結
●原料廠商
●提供設備(tooling)
●製程廠商(powder, lubricants, industrial gases)
Auto motive 70% 汽車零件
Chapter 1
1.粉末冶金的基本製程：粉末混合→加壓成型→燒結→後加工
2.粉末冶金製品的優點、特性
(1)多孔性(CPU熱導管、軸承、過濾器，利用可控制的孔隙大小)
(2)可製作高熔點金屬的元件：W(鎢)、Mo(鉬)絲燈，高爾夫球桿的配重器。
(3)可製作互不相溶的複合材料(或合金)
(4)經濟性cost effective
比較：
燒結法(PM法)：產品尺寸接近最終尺寸、省略(簡化)加工步驟、無廢料。
一般機械加工：加工速率慢、廢料多、成本高(人工、時間)。
鍛造：速率慢、尺寸需再加工。
(5)組織均勻
比較：
粉末冶金法：晶粒(grain)不具方向性、異相間混合均勻。
傳統製成：晶粒會有方向性、晶粒較粗大、使韌性及磨耗性變差。
3.粉末冶金的缺點
(1)多孔性
機械性質(強度、延展性、抗疲勞度變差)
缺陷、應力(stress)集中、形成破壞
在電鍍時，殘留的電鍍液在孔隙中長出結晶
(2)設備費用昂貴、原料費用昂貴(表面積很大，能量很大)
(3)截面積受到限制，截面積大的工件，不易生產(和壓胚有關)→不能太厚，會不夠緻密。
(4)原料以重量計算時，昂貴→適合小型，複雜的零件。
(5)模具貴、需大量生產，才會符合經濟效益。
留言列表
