Vpliv aluminijevega nitrida na vročo duktilnost malolegiranih jekel. Opazovanja v elektronskem mikroskopu (Režime)
T. Goyard,* P. Heritie,* A. Fourdeaux,* A. KobiIansky*
Influence du nitrure d'alluminium sur la ductilite a chaud des aciers faiblement allies. Observations au microscope electronique (Resume)
Raziskovali smo pogoje za zmanjšanje duktil-nosti med 800 in 1100°C, ki se v splošnem pripisuje prisotnosti aluminijevega nitrida v malolegiranih jeklih, v zlitinah železo-aluminij-dušik, žele-zo-aluminij in železo-dušik z vročimi raztržnimi preizkusi. Prisotnost aluminijevega nitrida A1N, ki je bila potrjena z opazovanji v elektronskem mikroskopu, je izgleda potreben pogoj za degradacijo duktilnosti; nekateri rezultati pa kažejo, da to ni zadosten pogoj.
PRIPOMBA.
G. D. Funnell, TI Research Laboratories
V Tube Investments Research Laboratories smo raziskovali mehanizem vpliva A1N na vročo predelovalnost jekla s kombinacijo opazovanj na avstenitnih in na ogljikovih jeklih. To delo dovoljuje sklep, da se vpliv A1N lahko raztolmači z blokiranjem avstenitnih mej. Majhni izločki A1N (< 0.1 p,m) blokirajo avstenitne meje in so vzrok za majhno duktilnost, ob prisotnosti večjih izločkov (> 0.2 jim), ali manjših volumskih delov A1N, se vrši migracija kristalnih mej relativno lahko in je vzrok za večjo duktilnost.
Podobno, kjer se uporablja obdelava s titanom, da bi se preprečili problemi zaradi A1N, se doseže uspeh le, če so precipitati titanovega nitrida zadosti veliki, da ne morejo učinkovito blokirati avstenitnih kristalnih mej.
* ENSM Saint Etienne, Francija
Les conditions de la baisse de ductilite entre 800 et 1100°C, generalement attribuee a la pre-sence de nitrure d'alumiinium, ont ete recher-chees dans des aciers faiblement allies, ainsi que dans des alliages fer-aluminium-azote, fer-alumi-nium et fer-azote, par des essais de tracion a shaud. La presence de nitrure d'aluminium A1N, confirmee par microscopie electronique, apparait bien comme une condition necessaire de degra-dation de la ductilite; certains resultats permet-tent cependant de penser qu'elle n'en constitue pas une condition suffisante.
COMMENT.
Concerning the mechanism by vhich A1N influ-ences the hot workability of steel, this has been studied at Tube Investment Research Laboratories by combining observations on fully austenitic alloys with those made on plain carbon steels. This work suggests that the influence of A1N can be explained in terms of austenitic grain boundary pinning. Small A1N particles (<0.1 ixm) which pin the austenitic grain boundaries cause poor ducti-lity, whilst in the presence of coarse particles (> 0.2 y,m) or low volume fraction of A1N, grain boundary migration occurs relatively easily result-ing in superior ductility.
Similarly, where titanium treatment is used to avoid problems due to A1N, success will be only achieved if the titanium nitride particles are sufficiently coarse so than ithey do not effectively pin austenitic grain boundaries.
VAD (Vacuum Are Degassing) Process
Satisfies ali requirements for greater productivity and higher quality. Heating, degassing, refining and alloy addition take plače under vacuum
Ladle degassing with inert gas flushing
Simple, reliable affording a large reaction area.
VODC (Vacuum Oxygen Decarburization Converter) process
This process combines the proven VOD method vvith BOF converter practice.This results in little chromium slag vvith correspondingly low consumption of reducing agents, inert gas (argon) and phosphorizing substances.
VOD (Vacuum Oxygen Decarburization) process
VOD is used in making stainless steels, decarburization of high chromium alloyed qualities to ELC grades with highest chromium yield
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Vacuum Ingot casting
Used for casting large ingots for forging. Castings weighing more than 5001 are now feasible.The low hydrogen content shortens annealing times. Vacuum ingot casting is a reliable casting process in which deleterious effccts of the atmosphere are completely excluded.