Applying Heat Treating
Processes
Interest Approach
I
am going to heat this piece of metal
with my gas torch.
 Once the metal is hot, what can I
now do with this piece of metal and
why?
 Is there a connection here for
treating metals with heat?
Student Learning Objectives
 Identify
the tools and equipment used for
hot metal work.
 Explain the processes of measuring and
holding metal.
 Describe the methods of heating, cutting,
squaring, drawing out, upsetting,
bending, twisting, and punching holes in
hot metal.
Student Learning Objectives
 Describe
the heat treating
processes: hardening, tempering,
and annealing.
 Identify
the safety practices to follow
when working with hot metal.
Terms
 Annealing
steel
 Cementite
 Ferrite
 Hardening
steel
 Martensite
 Pearlite
 Tempering
steel
What are the tools and
equipment used for hot
metal work?
There are several pieces of
equipment used for hot
metal work.
Hot Metal Tools
 Equipment
used in the heating of
stock may be a gas welding/cutting
torch, a carbon arc torch, a forge, a
furnace or a stove.
Hot Metal Tools
 A forge
is the most economical way
to heat large areas of metal.
Hot Metal Tools
 When
the metal to be heated cannot
be removed from a machine, or
when the area to be heated is small,
a gas welding/cutting torch or a
carbon arc torch can be used.
Torch
 When
heating with the gas
welding/cutting torch or carbon arc
torch, care must be exercised
because of the intense heat.
 If too much heat is used, the metal
may oxidize and checking of the
metal may occur.
Hot Metal Tools
 Anvils
and bases are a necessity in
hot metal work and are also used in
other repair jobs, such as bending,
straightening, cutting, and riveting
cold metal.
Anvils and Bases
 The
anvil should be of good quality;
otherwise, the steel face will crack
and chip.
Anvils and Bases
 Various
types of anvil bases are
used; chunks of wood, masonry, or
metal frames with the top of the anvil
at a convenient working height.
 If concrete or metal frames are used,
a two inch block of wood should
separate the anvil from the base to
serve as a cushion.
Hot Metal Tools
 The
cutting edge of the anvil hardy is
similar to a cold chisel.
 It
has a square shank that fits into
the hardy hole of an anvil and is
used to cut both hot and cold metal.
Hot Metal Tools
 The
anvil fullers are used for making
grooves and rounding inside corners
and angles, and fits into the hardy
hole of the anvil.
 The anvil swages are used to shape
round or oval objects.
Hot Metal Tools
 Blacksmith’s
hammers, used only
with one hand, range in weight from
1 to 14 lbs., with a 1.5 to 2 lb. used
for most jobs.
Hot Metal Tools
 Blacksmith’s
sledges require the use
of both hands and are used for
heavy bending and shaping.
 Weights range from 5 to 20 lbs.,
however an 8 lb. sledge is big
enough for most jobs.
Hot Metal Tools
 Hot
cutters have handles, can be
purchased with cutting edges of
different widths, and are used to cut
metal that has been heated.
 A hot cutter is generally used when a
helper is available to do the striking.
Hot Metal Tools
 Handled
punches are made with
round and square points and are
used for punching holes in hot metal.
Hot Metal Tools
 Flatters
are used to remove hammer
marks and to make the surface of
the metal smooth and flat.
 A magnet
is necessary to determine
when the metal is hot enough to lose
its magnetic properties.
Hot Metal Tools
 Set
hammers are used for making
square, sharp corners and
shoulders.
–They are placed on the metal and
struck with a hammer or sledge.
 Small
metal squares are used to
measure stock and to check rightangle bends.
Hot Metal Tools
 Tongs
come in many shapes and
sizes for hot metal work, the most
common are straight-lip for flat metal
and bolt for round stock.
 A strong heavy-duty machinist’s vise
with six inch jaws is necessary for
the heavy bending and shaping of
hot metal.
How is metal measured and
held?
In order to measure and work
metal satisfactorily, the stock
must be securely and properly
held.
Measuring stock
 Measuring
 In
stock is very important.
construction work it is best to
secure a plan or a blueprint, if
possible, which will indicate exact
dimensions.
Measuring stock
 Measure
the required length and
mark with chalk.
 If
the piece is to be heated, the mark
must be made with a center punch
or a file because a chalk mark will
burn off.
Measuring stock
 If
a bent piece of metal is to be
duplicated, take a lightweight piece
of wire and follow the bends with the
wire.
 Then remove the wire, straighten it,
and measure its total length.
 The wire should be placed near the
center of the piece being measured.
Measuring stock
 The
amount of material required for
making a ring is 3.5 times the
diameter of the ring plus ½ the
diameter of the stock.
 In measuring a piece to be welded,
add the length needed for upsetting
to the total length needed.
After the stock to be worked has been
marked it must be properly held.
 Select
tongs which fit the work.
–The jaws should be parallel when
clamped on the stock.
–If necessary, heat the jaws to a
cherry red and bend them to fit and
hold the stock firmly.
After the stock to be worked has been
marked it must be properly held.
 Keep
the tongs cool by dipping them
frequently in water.
 Be
careful not to bend the jaws or
handles of the tongs.
After the stock to be worked has been
marked it must be properly held.
 There
are several different kinds of
tongs, but only a few are frequently
used in agricultural mechanics.
–The type of tongs to use depends
upon the kind of work that is to be
done.
Tongs
 Flat-jawed
tongs with a lengthwise
groove in the middle of each jaw
help hold materials securely.
 Link
tongs with a crosswise groove
in the jaws help in holding links,
rings, and similar materials.
Tongs
 Bolt
tongs have a curved opening in
the jaws.
–This permits the holding of round
or square materials.
How is metal heated, cut,
squared, drawn out, upset,
bent, twisted, and hole
punched?
Proper procedures must be
followed to properly heat, cut,
square, draw out, upset, bend,
shape, twist, and hole punch
metal.
Heating Metal
 When
heating metal, heat should be
applied to all parts of the metal being
fabricated.
 Heating
in one spot may cause
damage to the metal due to uneven
expansion.
Heating Metal
 Do
not use excessive air or oxygen
in heating.
–This will cause the metal to scale, and
increase the time required for heating.
 Working
any metal heated to less
than a cherry red may cause it to
crack.
Heating Metal
 Wrought
iron and low carbon steel
can be heated to a white heat for
shaping.
–If the heated part sparkles, cut off
that part because its value has
been destroyed.
Heating Metal
 Tool
steel or high carbon steel
should be heated only to a cherry
red to prevent cracking the metal,
damaging the grain structure, and
destroying the carbon content.
Heating Metal
 Malleable
cast iron cannot be heated
above 1,375°F, because it will revert
to some of the characteristics of
white cast iron when cooled.
Hot metal may be cut with a hot
chisel, a hardy and a cutter, an
oxyacetylene cutting torch, or an
electric arc.
Hot Metal Cutting
 Hot
chisels and cutters are used for
cutting generally large and heavy
metals.
Hot Metal Cutting
 When
cutting a light piece of
material, often it is not necessary to
use the cutter.
–Merely place the stock over the hardy
and deliver hammer blows directly to
the stock.
When squaring hot metal follow
these set procedures:
 1.
Mark the piece to be squared with
a file, using a steel square.
 2. Heat the piece to a cherry red
color.
–Only a small portion should be heated;
other-wise, the piece may enlarge
when it is struck on its end.
When squaring hot metal follow
these set procedures:
 3.
Place the piece over an anvil, and
hammer it.
–Be sure that the face of the hammer
falls parallel with the face of the anvil.
 4.
Continue to hammer, turning the
piece until it is square.
When squaring hot metal follow
these set procedures:
 5.
Reheat to a cherry red color if the
piece becomes cool before it is
squared.
Drawn Out Procedure
 When
a piece of iron or steel is
pounded so that it is longer and
smaller in diameter, it is said to be
drawn out.
Drawn Out Procedure
 This
procedure is as follows:
 1. Heat the portion of the stock to be
enlarged to a white heat.
 2. Place the stock on the anvil in a
perpendicular position, forming right
angles to the face of the anvil to
prevent the stock from bending.
Drawn Out Procedure
 3.
Strike the cold end of the stock with
hard blows.
–If the stock bends, place it over the anvil
and straighten it.
When metal is upset, it is
placed on end and hammered
until it is enlarged and
shortened to the correct size.
Metal Upset Procedure
 1.
The metal must be heated
uniformly over the entire section to
prevent it from increasing in size at
one point.
 2. Strike the metal with a sharp, welldirected blow so the entire heated
section will be upset uniformly.
One
of the important phases
of metal work is the bending of
materials.
Bending Procedures
 1.
Small pieces often may be bent
cold, but some pieces should be
heated before they are bent.
Bending Procedures
 2.
Square and angle bends can be
made by placing the heated metal
over the edge of the anvil and
hammering the end down along the
side.
–Clamp one end of the metal in a heavy
vise and bend it against the jaws.
Hot
metal may be twisted by
clamping one end in a vice
and turning the other end with
a wrench.
Twisting Procedure
 1.
To make a long twist without
bending the metal, slip a piece of
pipe over the metal between the vise
and the wrench.
Twisting Procedure
 2.
The length of the twist will be
determined by the distance between
the vise jaws and the wrench.
Holes
are punched in hot
metal with the handled punch.
Hole Punch Procedure
 1.
The end of the punch must be
kept flat and the sides shaped so the
corners or edges will be sharp.
–In most cases a helper is needed to
strike the punch with a larger hammer
or sledge.
Hole Punch Procedure
 2.
To punch a square hole lay out
and center punch the location of the
hole.
 3. Heat the metal to nearly white.
 4. Quickly place the metal flat on the
face of the anvil.
–Center the end of the punch over the
mark.
Hole Punch Procedure
 5.
Strike the head of the punch with
a sledge, driving the point about twothirds of the way through the piece.
–The punch should be cooled frequently
in water to prevent drawing its temper
and upsetting its end.
Hole Punch Procedure
 6.
Turn the piece over, and then set
the punch directly over the hole that
was started from the other side.
Hole Punch Procedure
 7.
Drive the punch in from this side
until almost through.
–Then, slide the metal over the round
hole of the anvil to allow the metal to
be punched completely to the same
size from the top side.
How is metal hardened,
tempered, and annealed?
Heat treating steel includes
hardening, tempering, and
annealing.
Hardening Steel
 Hardening
steel is making it hard by
heating it to a light cherry red and
then cooling it quickly in warm water.
Steel Hardening
 The
hardness of steel is determined
by two factors: the amount and type
of carbon present in the steel and
the heat-treating process used in
hardening the steel.
Steel Hardening
 The
presence of carbon affects the
physical properties most; however,
carbon content and heat treatment go
together.
–Carbon content will change the physical
properties only slightly without heat
treatment.

Heat treatment would have little effect if not
for the carbon content of the steel.
Steel Hardening
 Carbon
is important to the treating
process.
 During heat treatment, carbon atoms
can bond or link up with iron atoms
to form new compounds with
different physical properties.
Basic elemental iron is called
ferrite.
 When
ferrite has carbon dissolved in
it, a new form, cementite or iron
carbide will form.
 Cementite is usually found in a
mixture with ferrite.
 The resulting mixture is called
pearlite, because it is pearly white
crystals.
Pearlite
 Steel
that has not been heat treated
is pearlite.
 Steel can be hardened by heat
treatment because pearlite, when
heated to 1,320–1340°F, then
quickly cooled by warm water
becomes martensite.
Pearlite
 The
steel takes an intermediate
form, austenite, during heating
above 700°F.
Martensite
 Austenite
forms martensite upon
quick cooling.
 Martensite is a new substance with a
crystal structure that gives steel its
hardness.
 The more martensite present, the
harder and more brittle the steel.
Tempering steel
 Tempering
steel is reheating
hardened steel to obtain the desired
hardness and toughness.
Tempering steel
 The
second heating is to a lower
temperature which must be very
carefully controlled.
–This is to allow some of the hard
martensite to revert to its original
pearlite form.
–Then the steel is cooled slowly or
quenched in warm water.
Tempering steel
 The
process of changing martensite
back to pearlite is dependent on
heat increase, usually within one of
three of the following ranges:
Tempering steel
 The
first range is obtained by
reheating the steel to a temperature
between 200 and 400°F.
 Steel that is heat treated to this
temperature retains most of its
original hardness but does gain
some strength and toughness.
Tempering steel
 The
second range is obtained by
reheating the steel to a temperature
between 400 and 700°F.
 In
this range steel is moderately
hard and moderately tough.
Tempering steel
 The
third range is between 700 and
1,000°F.
 Steel reheated to this temperature
range retains only a little of its
original hardness; however, it
becomes very strong and tough.
Annealing steel
 Annealing
steel is softening the
metal and removing the brittleness.
 The
annealing process allows
hardened or tempered steel to be
made soft so it can be filed, cut, or
shaped.
Annealing steel
 To
anneal a piece of steel, heat it
until all the steel is in the austenite
form, light cherry red or above
1,320°F, depending on the carbon
content.
Annealing steel
 Then
allow it to cool slowly in an
insulating material such as
vermiculite.
 This
allows the austenite to be-come
soft pearlite instead of martensite.
What are the safety practices
to be followed when working
with hot metal?
Observe the following general
safety practices for working
hot metal.
Safety Practices
 Obtain
the instructor’s permission
before using any tool or machine.
Safety Practices
 Wear
industrial quality eye
protection to protect eyes from
sparks and metal chips.
Safety Practices
 To
protect against burns, wear
clothing such as coveralls, high-top
shoes, leather aprons, and leather
gloves.
 Remove all paper from pockets, and
wear cuff-less pants.
Safety Practices
 Protect
hair and scalp by restraining
long hair and wearing a cap.
Safety Practices
 In
the event of an emergency, all
students involved in or observing the
emergency should call for help
immediately.
 You should know the location of fire
extinguishers and fire blankets and how
to use them.
 You should also know the approved
procedure for exiting the laboratory.
Safety Practices
 Report
all injuries or accidents to the
instructor immediately, no matter
how slight.
Safety Practices
 Keep
the work area and tools clean.
 Dirty, greasy, and oily tools and
floors can cause accidents.
 Clean and put away all unneeded
tools and materials.
 Clean up oil spills and scrap metal
from the floor and equipment.
Safety Practices
 Always
use the right size tool and
only for its intended purpose.
 Use
tongs or pliers for carrying hot
metal.
Safety Practices
 Loud
talking, as well as, pushing,
running, and scuffling while working
with hot metal can cause serious
accidents.
 Keep
your mind on your work.
Safety Practices
 Work
in a well-ventilated area.
 Fumes
and intense heat are a part
of hot metalwork and require that
work be done outdoors or in a
forced-ventilated area.
Safety Practices
 When
lifting heavy objects, obtain
help.
 Lift
with the legs and not the back.
 Straining
to lift heavy objects can
cause serious injury.
Safety Practices
 To
avoid the possibility of accidental
burns, keep hot metal in a safe place
until it cools.
 Use
tongs or pliers for handling hot
metal.
Safety Practices
 Before
leaving the laboratory or work
station, make certain the heat
source is shut off and cool.
Safety Practices
 Do
not perform hot metalwork on
wood floors or near flammable
materials.
 Never
work on containers that have
been used for storage of
combustible material.
Safety Practices

Keep cables and hoses from
coming in contact with hot metal and
sharp objects.
 Never
hoses.
point a flame at cables or
Safety Practices
 Use
warm water instead of
quenching oil for quenching.
 Quenching
other oils.
oil is easily confused with
Review
 Identify
the tools and equipment used for
hot metal work.
 Explain the processes of measuring and
holding metal.
 Describe the methods of heating, cutting,
squaring, drawing out, upsetting,
bending, twisting, and punching holes in
hot metal.
Review
 Describe
the heat treating
processes: hardening, tempering,
and annealing.
 Identify
the safety practices to follow
when working with hot metal.