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Title:The influence of the morphology of iron powder particles on their compaction in an automatic die
Authors:ID Šuštaršič, Borivoj (Author)
ID Godec, Matjaž (Author)
ID Donik, Črtomir (Author)
ID Paulin, Irena (Author)
ID Glodež, Srečko (Author)
ID Šori, Marko (Author)
ID Ratej, Milan (Author)
ID Javornik, Nada (Author)
ID Inštitut za kovinske materiale in tehnologije (Copyright holder)
Files:.pdf Materiali_in_Tehnologije_2015_Sustarsic_et_al._the_Influence_of_the_Morphology_of_Iron_Powder_Particles_on_Their_Compaction_in_an_Automa.pdf (1,18 MB)
MD5: 0A4F2506C3C17B18D491DD939DE49C71
 
URL http://mit.imt.si/Revija/izvodi/mit152/sustarsic.pdf
 
Language:English
Work type:Article
Typology:1.04 - Professional Article
Organization:FNM - Faculty of Natural Sciences and Mathematics
Abstract:Fe- and steel-based powder metallurgy (P/M) products, such as steel gears, spurs, locking mechanisms, porous filters, sliding bearings and bushes, as well as other machine parts and structural elements, are mainly produced with the so-called conventional sintering technology. It is the most efficient technology for the mass production of small, complex, functional and structural parts. Therefore, it is the most convenient and popular among all of the P/M technologies. The most important end-user of sintered parts is the automotive industry. However, small, complex, sintered parts can also be frequently used in the furniture and household industries, precise mechanics, articles for recreation and sports. A fine, iron-based powder mixture or prealloyed powder is first automatically uniaxial-die compacted (ADC) into the final shape of the product with a mechanical or hydraulic press and then sintered in a protective atmosphere at approximately 1100 °C. The metal powder mixture must have the appropriate engineering properties given by the chemistry and particle morphology, enabling a fast and reliable die-compaction process. The most important are a high tap density, a good powder flowability and a low compressibility. All this gives the green compacts an appropriate final shape with a smooth surface, a relatively high and uniform green density, as well as a green strength without internal flaws and cracks. In the case of very small two-or-more-heights products, for example, spur gears with a low module, it is very difficult to obtain a uniform green density at acceptable compaction pressures. Often small cracks are formed at height crossings and big differences in the green density appear in smaller or thinner regions. In the frame of our investigation we analysed the influence of the selected prealloyed commercial iron powder’s morphology and its technological properties on automatic die compaction, as well as the sintering process in the case of small two-level sintered gear dimensions of 5/40–7/10×7mm with module m = 0.5. The original iron powder was sieved and the finest powder particle fraction (< 45 µm) was compared with the original powder mixture considering ADC and sintering process. It was found that the selection of the finer powder mixture could not contribute to the improvement in the overall ADC process, as well as a better green compact. In the present paper the results of our investigations are presented and the reasons why a finer powder mixture cannot contribute much to an improvement of the conventional sintering process.
Keywords:Fe-based alloy powders, particles, morphology, microstructure, automatic die compaction, sintering
Publication status:Published
Publication version:Version of Record
Article acceptance date:24.10.2014
Publication date:16.12.2014
Year of publishing:2015
Number of pages:str. 303-309
Numbering:Letn. 49, št. 2
PID:20.500.12556/DKUM-65254 New window
ISSN:1580-2949
UDC:621.762:621.77
ISSN on article:1580-2949
COBISS.SI-ID:1130666 New window
NUK URN:URN:SI:UM:DK:HTYGDRBF
Publication date in DKUM:27.03.2017
Views:1568
Downloads:403
Metadata:XML DC-XML DC-RDF
Categories:Misc.
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Record is a part of a journal

Title:Materiali in tehnologije
Shortened title:Mater. tehnol.
Publisher:Inštitut za kovinske materiale in tehnologije
ISSN:1580-2949
COBISS.SI-ID:106193664 New window

Secondary language

Language:Slovenian
Title:Vpliv morfologije delcev železovega prahu na njegovo sposobnost za avtomatsko enoosno stiskanje
Abstract:Jekleni izdelki, izdelani po P/M-postopkih, kot so npr. zobniki, mehanizmi za zaklepanje, porozni filtri, drsni ležaji in puše, kakor tudi drugi strojni elementi ali strukturni deli, se v glavnem izdelujejo po konvencionalni tehnologiji sintranja. To je najbolj učinkovita in zato najpopularnejša tehnologija za masovno proizvodnjo majhnih kompliciranih funkcionalnih in strukturnih izdelkov. Avtomobilska industrija je najbolj pomemben končni uporabnik sintranih delov, vendar se le-ti pogosto uporabljajo tudi v pohištveni industriji, beli tehniki, precizni mehaniki, v izdelkih za šport in rekreacijo itd. Fina prašna mešanica na osnovi Fe ali predlegiranih jeklenih delcev se najprej avtomatsko enoosno stiska v končno obliko na mehanskih ali hidravličnih stiskalnicah in nato sintra v zaščitni atmosferi pri pribl. 1100 °C. Kovinska prašna mešanica mora imeti primerne tehnološke lastnosti, ki omogočajo hiter in zanesljiv proces zgoščevanja v surovce želene oblike in velikosti. Te so definirane s fizikalno-kemijskimi lastnostmi in predvsem morfologijo (obliko in velikostjo) delcev. Najbolj pomembne so visoka nasipna gostota, dobra tekočnost in nizka stisljivost prašne mešanice. Vse to daje surovemu izdelku želeno končno obliko z gladko površino, relativno visoko in enakomerno zeleno gostoto in trdnostjo brez lokalnih napak in razpok. Pri zelo majhnih dvo- ali večvišinskih izdelkih, kot so npr. dvojni zobniki z majhnim zobniškim modulom, je zelo težko dobiti surovce (zelence) brez napak in z enakomerno gostoto pri sprejemljivih tlakih stiskanja. Pogosto na surovcih nastajajo razpoke na prehodu iz tanjšega v debelejši del zobnika zaradi velikih razlik v zeleni gostoti. V okviru naših raziskav smo analizirali vpliv morfologije izbranega predlegiranega komercialnega Fe-prahu in njegovih tehnoloških lastnosti na razmere pri avtomatskem enoosnem stiskanju in sintranju majhnega dvovišinskega sintranega zobnika dimenzij 5/40–7/10×7mmz modulom m = 0,5. Originalni Fe-prah smo presejali in najfinejšo frakcijo prahu (< 45 µm) uporabili za stiskanje in sintranje ter jo primerjali z originalno prašno mešanico. Ugotovili smo, da finejši prah ne prispeva k izboljšanju postopka avtomatskega enoosnega stiskanja oz. k boljšim surovcem iz več razlogov. V tem prispevku predstavljamo rezultate naših raziskav in razloge, zakaj izbira finejše prašne mešanice ne prispeva celovito k izboljšanju konvencionalnega sintrnega postopka.
Keywords:legirani prahovi, avtomatsko enoosno stiskanje, morfologija, mikrostruktura, vpliv, sintranje


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