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8/13/2019 Parte da ASTM F2282 - referente aço acalmado
http://slidepdf.com/reader/full/parte-da-astm-f2282-referente-aco-acalmado 1/2
Trecho da ASTM F2282-03
Quality Assurance Requirements for Carbon and Alloy SteelWire, Rods, and Bars for Mechanical Fasteners1
X4. SILICON AND ALUMINUM
X4.1 Silicon and aluminum act as somewhat similar elements with respect to their behavior when added
during the steel making process. They both have a high affinity for oxygen and are, therefore, used to
deoxidie or !kill" the steel.
#eoxidation or !killing" is a process by which a strong deoxidiing element is added to the steel to react
with the remaining oxygen in the bath to prevent any further reaction between carbon and oxygen. $hen
carbon and oxygen react in the bath a violent boiling action occurs which removes carbon from the steel.
$hen the bath or heat reaches the desired carbon content for the grade being produced, the carbonoxygen
reaction must be stopped %uickly to prevent further elimination of carbon. This addition is accomplished by
the addition of deoxidiers such as silicon and aluminum which have a greater affinity for oxygen than does
carbon. This effectively removes oxygen, eliminating the !carbon boil" and killing the heat. &lements otherthan silicon and aluminum can be used, but these are the most common.
X4.' Silicon and aluminum can be added together or individually. This is determined by the type of steel
desired. () silicon only is added, that particular batch of steel is referred to as a silicon killed coarse grain
practice grade because silicon acts as a deoxidier without the formation of fine precipitates allowing the
formation of large or coarse austenitic grains.
X4.' sil*cio e alum*nio podem ser adicionados em con+unto ou individualmente. (sto determinado pelo
tipo de a-o dese+ado. Se s sil*cio adicionado, desse lote particular de a-o conhecido como acalmado em
sil*cio para granula-/o grosseira, por%ue o sil*cio atua como um desoxidante, sem a forma-/o de
precipitados finos, permitindo a forma-/o de gr/os austen*ticos grandes ou grosseiros.
0ustenitic grain sie is not usually a factor for consideration in cold forming, but has a significant effect in
subse%uent fastener heat treatment. 0luminum, on the other hand, not only deoxidies the steel, but also
refines the grain sie. ike silicon, aluminum removes oxygen from the bath, effectively killing the heat.
0luminum also reacts with nitrogen in the steel to form aluminum nitride particles which precipitate both at
the grain boundaries and within the austenitic grains thus restricting the sie of the grains2 even when the
steel is reheated for carburiing or neutral hardening, hence the term fine grain.
Tamanho de 3r/o 0usten*tico n/o geralmente um fator a considerar na conforma-/o a frio, mas tem um
efeito significativo no tratamento trmico subse%uente do elementos de fixa-/o. alum*nio, por outro lado,
n/o s deoxida o a-o, mas tambm refina o tamanho de gr/o. Tal como sil*cio, alum*nio remove oxig5nio a
partir do banho, acalmando eficamente o calor. alum*nio tambm reage com o nitrog5nio no a-o, para
formar part*culas de nitreto de alum*nio, %ue precipitam tanto nas fronteiras de gr/o e dentro dos gr/os
austen*ticos restringindo, assim, o tamanho dos gr/os, mesmo %uando o a-o rea%uecido para a cementa-/o
de endurecimento ou neutro, e da* o termo gr/o fino.
$hen aluminum only is added, the steel is referred to as aluminum killed, fine grain. 0 third group of steels
are referred to as silicon killed, fine grain. (n steels of this type, silicon is added as the deoxidier followed
by the addition of aluminum for grain sie control.
6uando somente o alum*nio adicionado, o a-o referido como acalmado em alum*nio, de gr/o fino. 7m
terceiro grupo de a-os s/o referidos como acalmado em sil*cio, de gr/o fino. &m a-os deste tipo, o sil*cio
adicionado como desoxidante, seguido pela adi-/o de alum*nio para controle do tamanho de gr/o.
8/13/2019 Parte da ASTM F2282 - referente aço acalmado
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X4.8 (n the two types where silicon is added, the silicon content can have several ranges with the most
common being 9.1: ; to 9.89 ;. $hen aluminum is added to these steels for grain sie control, the
aluminum content is generally in the 9.91: ; to 9.989 ; range. The aluminum content in fully aluminum
killed steels is generally 9.91: ; to 9.9:: ;, somewhat higher on average since the aluminum must both
deoxidie and control grain sie at the same time.
X4.8 <os dois tipos em %ue o sil*cio adicionado, o teor de sil*cio pode ter v=rios intervalos, sendo o mais
comum, 9,1:; a 9,89;. 6uando o alum*nio adicionado a estes a-os para controlar o tamanho de gr/os, o
teor de alum*nio geralmente na gama de 9,91:; a 9,989;. teor de alum*nio em a-os acalmados
integralmente de alum*nio geralmente de 9,91:; para 9,9::;, um pouco mais elevado, em mdia, uma
ve %ue o alum*nio tem a fun-/o tanto de desoxidar como a de controlar o tamanho do gr/o, ao mesmo
tempo.
X4.4 (n selecting the type of deoxidation practice for a particular carbon grade of steel to be used in fastener
manufacturing, a number of factors should be considered, such as, heat treated property re%uirements, heat
treat conditions, fastener sie, and steel availability, to name a few. Silicon acts as a ferrite strengthener and,
therefore, in the absence of aluminum, has somewhat greater hardenability. )or the same carbon grade and
heat treat conditions with and without aluminum, complete transformation of the fastener core during heat
treatment can take place in a larger section using a coarse grain steel. The disadvantage of silicon killed
steels can be reflected in reduced ductility and tool life during cold heading because of its ferritestrengthening characteristic. 0luminum killed steels are usually more formable and hence provide
somewhat improved tool life but reduced heat treatment response during heading, particularly in larger sie
fasteners. )or this reason, the recommended maximum diameter for oil %uenched aluminum killed carbon
grades is typically 9.1>9 in.
X4.4 <a sele-/o do tipo de desoxida-/o de uma grade espec*fica de a-o carbono para ser utiliado na
fabrica-/o de elementos de fixa-/o, um certo n?mero de fatores %ue devem ser considerados, tais como,
tratamento trmico re%uisitos de propriedades, das condi-@es de tratamento trmico, tamanho do elemento
de fixa-/o, e disponibilidade do a-o , para nomear apenas alguns. Sil*cio atua como um fortalecedor da
ferrita e, por conseguinte, na aus5ncia de alum*nio, tem um pouco maior de temperabilidade. Aara o mesmo
grau de carbono e as condi-@es de tratamento trmico com ou sem alum*nio, a transforma-/o completa do
n?cleo do item de fixa-/o durante o tratamento trmico pode ter lugar numa se-/o maior usando um a-o degr/o grosseiro. 0 desvantagem de a-os acalmados em sil*cio pode ser refletido na ductilidade reduida e
vida ?til da ferramenta durante o trabalho a frio por causa de sua caracter*stica de fortalecimento da ferrita.
0-os mortos alum*nio s/o geralmente mais mold=vel e, conse%uentemente, proporcionar um pouco melhor
a vida da ferramenta, mas reduida resposta a tratamento trmico durante dirigindo, especialmente em
grandes elementos de fixa-/o. Aor esta ra/o, o diBmetro m=ximo recomendado para a-os carbono
acalmados em alum*nio e temperados em leo tipicamente 9,1>9 polegadas.