Applying Heat Treating Processes

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Applying Heat Treating Processes
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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?

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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.

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Student Learning Objectives

• Describe the heat treating processes hardening,
  tempering, and annealing.
• Identify the safety practices to follow when
  working with hot metal.

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Terms

• Annealing steel
• Cementite
• Ferrite
• Hardening steel
• Martensite
• Pearlite
• Tempering steel

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What are the tools and equipment used for hot
metal work?
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There are several pieces of equipment used for
hot metal work.
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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.

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Hot Metal Tools

• A forge is the most economical way to heat large
  areas of metal.

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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.

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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.

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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.

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Anvils and Bases

• The anvil should be of good quality otherwise,
  the steel face will crack and chip.

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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.

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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.

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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.

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Hot 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.

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Hot 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.

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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.

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Hot Metal Tools

• Handled punches are made with round and square
  points and are used for punching holes in hot
  metal.

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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.

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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 right-angle bends.

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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 machinists vise with six
  inch jaws is necessary for the heavy bending and
  shaping of hot metal.

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How is metal measured and held?
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In order to measure and work metal
satisfactorily, the stock must be securely and
properly held.
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Measuring 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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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Tongs

• Bolt tongs have a curved opening in the jaws.
• This permits the holding of round or square
  materials.

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How is metal heated, cut, squared, drawn out,
upset, bent, twisted, and hole punched?
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Proper procedures must be followed to properly
heat, cut, square, draw out, upset, bend, shape,
twist, and hole punch metal.
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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.

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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.

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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.

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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.

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Heating 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.

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Hot metal may be cut with a hot chisel, a hardy
and a cutter, an oxyacetylene cutting torch, or
an electric arc.
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Hot Metal Cutting

• Hot chisels and cutters are used for cutting
  generally large and heavy metals.

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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.

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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.

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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.

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When squaring hot metal follow these set
procedures

• 5. Reheat to a cherry red color if the piece
  becomes cool before it is squared.

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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.

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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.

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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.

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• When metal is upset, it is placed on end and
  hammered until it is enlarged and shortened to
  the correct size.

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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, well-directed
  blow so the entire heated section will be upset
  uniformly.

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• One of the important phases of metal work is the
  bending of materials.

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Bending Procedures

• 1. Small pieces often may be bent cold, but some
  pieces should be heated before they are bent.

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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.

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• Hot metal may be twisted by clamping one end in a
  vice and turning the other end with a wrench.

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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.

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Twisting Procedure

• 2. The length of the twist will be determined by
  the distance between the vise jaws and the
  wrench.

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• Holes are punched in hot metal with the handled
  punch.

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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.

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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.

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Hole 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.

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Hole Punch Procedure

• 6. Turn the piece over, and then set the punch
  directly over the hole that was started from the
  other side.

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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.

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How is metal hardened, tempered, and annealed?
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Heat treating steel includes hardening,
tempering, and annealing.
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Hardening Steel

• Hardening steel is making it hard by heating it
  to a light cherry red and then cooling it quickly
  in warm water.

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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.

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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.

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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.

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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.

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Pearlite

• 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.

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Pearlite

• The steel takes an intermediate form, austenite,
  during heating above 700F.

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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.

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Tempering steel

• Tempering steel is reheating hardened steel to
  obtain the desired hardness and toughness.

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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.

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Tempering steel

• The process of changing martensite back to
  pearlite is dependent on heat increase, usually
  within one of three of the following ranges

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Tempering 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.

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Tempering 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.

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Tempering 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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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.

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Annealing steel

• To anneal a piece of steel, heat it until all the
  steel is in the austenite form, light cherry red
  or above 1,320F, depending on the carbon
  content.

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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.

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What are the safety practices to be followed when
working with hot metal?
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Observe the following general safety practices
for working hot metal.
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Safety Practices

• Obtain the instructors permission before using
  any tool or machine.

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Safety Practices

• Wear industrial quality eye protection to protect
  eyes from sparks and metal chips.

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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.

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Safety Practices

• Protect hair and scalp by restraining long hair
  and wearing a cap.

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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.

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Safety Practices

• Report all injuries or accidents to the
  instructor immediately, no matter how slight.

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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.

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Safety Practices

• Always use the right size tool and only for its
  intended purpose.
• Use tongs or pliers for carrying hot metal.

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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.

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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.

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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.

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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.

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Safety Practices

• Before leaving the laboratory or work station,
  make certain the heat source is shut off and cool.

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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.

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Safety Practices

• Keep cables and hoses from coming in contact
  with hot metal and sharp objects.
• Never point a flame at cables or hoses.

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Safety Practices

• Use warm water instead of quenching oil for
  quenching.
• Quenching oil is easily confused with other oils.

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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.

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Review

• Describe the heat treating processes hardening,
  tempering, and annealing.
• Identify the safety practices to follow when
  working with hot metal.