Title: Applying Heat Treating Processes
1 Applying Heat Treating Processes
2Interest 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?
3Student 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.
4Student Learning Objectives
- Describe the heat treating processes hardening,
tempering, and annealing. - Identify the safety practices to follow when
working with hot metal.
5Terms
- Annealing steel
- Cementite
- Ferrite
- Hardening steel
- Martensite
- Pearlite
- Tempering steel
6What are the tools and equipment used for hot
metal work?
7There are several pieces of equipment used for
hot metal work.
8Hot 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.
9Hot Metal Tools
- A forge is the most economical way to heat large
areas of metal.
10Hot 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.
11Torch
- 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.
12Hot 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.
13Anvils and Bases
- The anvil should be of good quality otherwise,
the steel face will crack and chip.
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15Anvils 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.
16Hot 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.
17Hot 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.
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19Hot Metal Tools
- Blacksmiths 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.
20Hot Metal Tools
- Blacksmiths 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.
21Hot 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.
22Hot Metal Tools
- Handled punches are made with round and square
points and are used for punching holes in hot
metal.
23Hot 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.
24Hot 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 right-angle bends.
25Hot 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 machinists vise with six
inch jaws is necessary for the heavy bending and
shaping of hot metal.
26How is metal measured and held?
27In order to measure and work metal
satisfactorily, the stock must be securely and
properly held.
28Measuring stock
- Measuring stock is very important.
- In construction work it is best to secure a plan
or a blueprint, if possible, which will indicate
exact dimensions.
29Measuring 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.
30Measuring 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.
31Measuring 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.
32After 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.
33After 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.
34After 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.
35Tongs
- 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.
36Tongs
- Bolt tongs have a curved opening in the jaws.
- This permits the holding of round or square
materials.
37How is metal heated, cut, squared, drawn out,
upset, bent, twisted, and hole punched?
38Proper procedures must be followed to properly
heat, cut, square, draw out, upset, bend, shape,
twist, and hole punch metal.
39Heating 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.
40Heating 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.
41Heating 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.
42Heating 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.
43Heating Metal
- Malleable cast iron cannot be heated above
1,375F, because it will revert to some of the
characteristics of white cast iron when cooled.
44Hot metal may be cut with a hot chisel, a hardy
and a cutter, an oxyacetylene cutting torch, or
an electric arc.
45Hot Metal Cutting
- Hot chisels and cutters are used for cutting
generally large and heavy metals.
46Hot 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.
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48When 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.
49When 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.
50When squaring hot metal follow these set
procedures
- 5. Reheat to a cherry red color if the piece
becomes cool before it is squared.
51Drawn 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.
52Drawn 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.
53Drawn 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.
54- When metal is upset, it is placed on end and
hammered until it is enlarged and shortened to
the correct size.
55Metal 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, well-directed
blow so the entire heated section will be upset
uniformly.
56- One of the important phases of metal work is the
bending of materials.
57Bending Procedures
- 1. Small pieces often may be bent cold, but some
pieces should be heated before they are bent.
58Bending 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.
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60- Hot metal may be twisted by clamping one end in a
vice and turning the other end with a wrench.
61Twisting 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.
62Twisting Procedure
- 2. The length of the twist will be determined by
the distance between the vise jaws and the
wrench.
63- Holes are punched in hot metal with the handled
punch.
64Hole 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.
65Hole 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.
66Hole Punch Procedure
- 5. Strike the head of the punch with a sledge,
driving the point about two-thirds of the way
through the piece. - The punch should be cooled frequently in water to
prevent drawing its temper and upsetting its end.
67Hole Punch Procedure
- 6. Turn the piece over, and then set the punch
directly over the hole that was started from the
other side.
68Hole 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.
69How is metal hardened, tempered, and annealed?
70Heat treating steel includes hardening,
tempering, and annealing.
71Hardening Steel
- Hardening steel is making it hard by heating it
to a light cherry red and then cooling it quickly
in warm water.
72Steel 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.
73Steel 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.
74Steel 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.
75Basic 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.
76Pearlite
- Steel that has not been heat treated is pearlite.
- Steel can be hardened by heat treatment because
pearlite, when heated to 1,3201340F, then
quickly cooled by warm water becomes martensite.
77Pearlite
- The steel takes an intermediate form, austenite,
during heating above 700F.
78Martensite
- 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.
79Tempering steel
- Tempering steel is reheating hardened steel to
obtain the desired hardness and toughness.
80Tempering 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.
81Tempering steel
- The process of changing martensite back to
pearlite is dependent on heat increase, usually
within one of three of the following ranges
82Tempering steel
- The first range is obtained by reheating the
steel to a temperature between 200 and 400F. - Steel that is heat treated to this temperature
retains most of its original hardness but does
gain some strength and toughness.
83Tempering steel
- The second range is obtained by reheating the
steel to a temperature between 400 and 700F. - In this range steel is moderately hard and
moderately tough.
84Tempering steel
- The third range is between 700 and 1,000F.
- Steel reheated to this temperature range retains
only a little of its original hardness however,
it becomes very strong and tough.
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86Annealing 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.
87Annealing steel
- To anneal a piece of steel, heat it until all the
steel is in the austenite form, light cherry red
or above 1,320F, depending on the carbon
content.
88Annealing 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.
89What are the safety practices to be followed when
working with hot metal?
90Observe the following general safety practices
for working hot metal.
91Safety Practices
- Obtain the instructors permission before using
any tool or machine.
92Safety Practices
- Wear industrial quality eye protection to protect
eyes from sparks and metal chips.
93Safety 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.
94Safety Practices
- Protect hair and scalp by restraining long hair
and wearing a cap.
95Safety 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.
96Safety Practices
- Report all injuries or accidents to the
instructor immediately, no matter how slight.
97Safety 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.
98Safety Practices
- Always use the right size tool and only for its
intended purpose. - Use tongs or pliers for carrying hot metal.
99Safety 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.
100Safety 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.
101Safety Practices
- When lifting heavy objects, obtain help.
- Lift with the legs and not the back.
- Straining to lift heavy objects can cause serious
injury.
102Safety 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.
103Safety Practices
- Before leaving the laboratory or work station,
make certain the heat source is shut off and cool.
104Safety 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.
105Safety Practices
- Keep cables and hoses from coming in contact
with hot metal and sharp objects. - Never point a flame at cables or hoses.
106Safety Practices
- Use warm water instead of quenching oil for
quenching. - Quenching oil is easily confused with other oils.
107Review
- 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.
108Review
- Describe the heat treating processes hardening,
tempering, and annealing. - Identify the safety practices to follow when
working with hot metal.