INTRODUCTION Forging process may be defined as a metal working process by which metals or alloys are plastically deformed to the desired shape by a compressive force applied with the help of a pair of dies. One die is stationary and the other has a linear motion .Forging process can be carried out both in cold and hot state of the metal. But, unless otherwise mentioned, forging process is considered to be “hot forging process”. Forging improves the quality of steel, which becomes stronger after forging. ue to this, the parts which are sub!ected to heavy duty are generally made of forging. "ime ofproduction is very often reduced. #uch less steel is consumed in forging operation. $ence the cost of any given part is reduced. %n forge shops, steel is received as ingots or as rolled sections. %ngots are used for manufacturing heavy forgings while rolled billets are used forlighter forgings. Forgings, which have to undergo subsequent machining, are called &blanks'. "hose which do not need a ny further machining are c alled &finished' forgings. Forgings may be produced in either open or close dies. %n open die forging is also known as “flat die forg ing”, the hot metal is struck or pressed between two flat surfaces orsimple contoured dies. "he compressive force is progressively applied locally on different parts of the metal shock. "he flow of metal, that is, the changing of its dimensions and shape is controlled with the aid of various blacksmiths tools. %n closed die forging process, cavities or impressions are cut in the die Block, the compressive force is applied to the entire surface and the metal is forced to take its final shape and dimensions as it flows in to and fills the die cavities. "he flow of metal is limited by the surfaces of the recesses or cavities in the dies. (hen the pair of dies approaches each other for completing the forging, the e)cess, metal squirts out of the cavity as a thin ribbon ofmetal called “flash”. Because of flash, the term “closed *die forging” is a bit of misnomer. +losed *die forging means no flash .so, a better description of the process with recesses or cavities in the die blocks would be “%mpression *die forging”. 1
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8/10/2019 Manufacturing Process of an Automobile Component
Forging process may be defined as a metal working process by which metals or
alloys are plastically deformed to the desired shape by a compressive force applied with thehelp of a pair of dies. One die is stationary and the other has a linear motion .Forging process
can be carried out both in cold and hot state of the metal. But, unless otherwise mentioned,
forging process is considered to be “hot forging process”.
Forging improves the quality of steel, which becomes stronger after forging. ue to
this, the parts which are sub!ected to heavy duty are generally made of forging. "ime of
production is very often reduced. #uch less steel is consumed in forging operation. $ence
the cost of any given part is reduced. %n forge shops, steel is received as ingots or as rolled
sections. %ngots are used for manufacturing heavy forgings while rolled billets are used for
lighter forgings. Forgings, which have to undergo subsequent machining, are called &blanks'.
"hose which do not need any further machining are called &finished' forgings.
Forgings may be produced in either open or close dies. %n open die forging is also
known as “flat die forging”, the hot metal is struck or pressed between two flat surfaces or
simple contoured dies. "he compressive force is progressively applied locally on different
parts of the metal shock. "he flow of metal, that is, the changing of its dimensions and shape
is controlled with the aid of various blacksmiths tools.
%n closed die forging process, cavities or impressions are cut in the die Block, the
compressive force is applied to the entire surface and the metal is forced to take its final
shape and dimensions as it flows into and fills the die cavities. "he flow of metal is limited
by the surfaces of the recesses or cavities in the dies. (hen the pair of dies approaches each
other for completing the forging, the e)cess, metal squirts out of the cavity as a thin ribbon of metal called “flash”. Because of flash, the term “closed *die forging” is a bit of misnomer.
+losed *die forging means no flash .so, a better description of the process with
recesses or cavities in the die blocks would be “%mpression *die forging”.
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8/10/2019 Manufacturing Process of an Automobile Component
@ fillet means the rounding of the ape) of an internal angle and corner radius means
the rounding of the ape) of the e)ternal angle. 3harp edges on the body of the forging
and hence the die cavity increases the tendency towards forging defects and
accelerates die wear. @lso sharp edges will hinder the complete filling of the die
cavities. "herefore, generous fillet and corner radii are the most desirable features of a
closed : de forging because it assists the flow of hot metal and eliminates the
possibility of forging laps or shuts. @lso, the premature die failures due to stress
cracks and abrasions are prevented. $ence, larger the fillet and corner radii, longer
will be the die life and better will be the forging quality. "he usual values of fillet and
corner radii are given in table-
3. PARTING LINE:
"he parting line is the line along the forging where the two halves of a pair of forging
dies meet. %t divides the die impression into two parts from which one is made in the
top die and the other in the lower die. "he shape and location of the parting line is
very %mportant as these have considerable influence on the flow of metal, die cost anddraft requirements, etc. regarding the location of the parting line, the die designer
should always remember the fundamental factor that in forging, the metals flows
much more easily in the lateral direction /path of least resistance1 than in the direction
of applied force. "hus in forging process, it is easier to spread metal than to force it
into deep die impression. 3o in most forgings the parting line is at the largest cross *
section of the part. @nother fundamental factor is that the metal fills the top die first,
so the deep and intricate of the impression should be cut in the top die. (hen owing
to the shape of the forging, a complete impression is arrived at in on part of the dieE
this should be the top die. %n such a case the lower die remains without the impression
and will have only locating elements to secure the proper location of the forging.
@nother factor in the selection of parting line is that should avoid deeper die
impressions to minimie die wear. eeper die impressions would require high forging
pressure for complete filing and might lead to die breakage. @ proper parting line may
eliminate the chances of grain flow reversal and improve the mechanical properties. @
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more e)act cshaping the finishing operation. Blocking impression aids in prevention of the
forging defects such as cold shuts.
3econd reasons for the use of blocking impression are to reduce the wear of the finishing
impression. 6)cessive wear of the finishing impression reduces the useful die life. %n case of
certain forgings, which are symmetrical in shape, the blocking impression is only a
preparatory impression. %n blocking impression, the length and width smaller, the height or
thickness is more, but the center distance is the same as in the final impression. "he
difference may be 2to 4 mm on each side, but higher clearance of 5 to 8mm can be
recommended where partial displacement of metal occurs. For flange yoke the difference is
taken as 8mm.
One blow is generally required for blocking operations.
3. Fii'7i4 I6+*''i0:
"his impression represents the e)act shape of the finished forging. "he shape and sie
of the finishing impression is checked in the process of manufacture of die by plaster of Haris
or lead cast. "he finishing impression is located in the middle of the die block but it is notnecessarily in its central a)is. $owever, it is vital to locate the final impression in such a
manner that there will be no horiontal forces that give a side thrust and make as die shaft. %t
is this advisable to have the loud center of forging directly below the a)is of ram.
F'7 ,*+
"he flow of plastic metal under the blows of the drop banner or the pressure of
forging press, proceeds first to fill up the finishing impression and then a small quantity of
the e)tra metal moves into shallow cavity provided a round the finishing impression of the
die. "hese small cavities which are directly outside the die impression are known as flash
gutter. "he flash gutter is separated from the die impression by narrow passage, which is the
flash land. "he volume of the flash land and the flash gutter should be about 4CM to 48M of
the volume forging.
"he amount of e)cess metal from the finishing impression may be too large to permit
the complete closing of the dies. "he gutter is provided to ensure complete closing of the die.%t acts as storage for the e)cess material after it is passed through the flash land. "oo large a
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Hure iron, wrought iron, and e)tremely low:carbon steels have very little hardening
properties and are difficult to harden by heat treatment. +ast iron has limited capabilities for
hardening. (hen you cool cast iron rapidly, it forms white iron, which is hard and brittle.
@nd when you cool it slowly, it forms gray iron, which %s soft but brittle under impact.
TEMPERING:
@fter the hardening treatment is applied, steel is often harder than needed and is too
brittle for most practical uses. @lso, severe internal stresses are set up during the rapid
cooling from the hardening temperature. "o relieve the internal stresses and reduce
brittleness, you should temper the steel after it is hardened. "empering consists of heating the
steel to a specific temperature /below its hardening temperature1, holding it at that
temperature for the required length of time, and then cooling it, usually instill air. "he
resultant strength, hardness, and ductility depend on the temperature to which the steel is
heated during the tempering process. "he purpose of tempering is to reduce the brittleness
imparted by hardening and to produce definite physical Hroperties within the steel. "empering
always follows, never precedes, the hardening operation. Besides reducing brittleness,
tempering softens the steel. "hat is unavoidable, and the amount of hardness that is lostdepends on the temperature that the steel is heated to during the tempering process. "hat is
true of all steels e)cept high:speed steel.
UENCHING MEDIA:
"he cooling rate of an ob!ect depends on many things. "he sie, composition, and
initial temperature of the part and final properties are the deciding factors in selecting the
quenching medium. @ quenching medium must cool the metal at a rate rapid enough to
produce the desired results. #ass affects quenching in that as the mass increases, the time
required for complete cooling also increases. 6ven though parts are the same sie, those
containing holes or recesses cool more rapidly than solid ob!ects. "he composition of the
metal determines the ma)imum cooling rate possible without the danger of cracking or
warping. "his critical cooling rate, in turn, influences the choice of the quenching medium.
"he cooling rate of any quenching medium varies with its temperatureE therefore, to getuniform results, you must keep the temperature within prescribed limits.
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8/10/2019 Manufacturing Process of an Automobile Component