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Applying Heat Treating Processes

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Title: Applying Heat Treating Processes


1
Applying Heat Treating Processes
2
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?

3
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.

4
Student Learning Objectives
  • Describe the heat treating processes hardening,
    tempering, and annealing.
  • Identify the safety practices to follow when
    working with hot metal.

5
Terms
  • Annealing steel
  • Cementite
  • Ferrite
  • Hardening steel
  • Martensite
  • Pearlite
  • Tempering steel

6
What are the tools and equipment used for hot
metal work?
7
There are several pieces of equipment used for
hot metal work.
8
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.

9
Hot Metal Tools
  • A forge is the most economical way to heat large
    areas of metal.

10
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.

11
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.

12
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.

13
Anvils and Bases
  • The anvil should be of good quality otherwise,
    the steel face will crack and chip.

14
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15
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.

16
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.

17
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.

18
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19
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.

20
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.

21
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.

22
Hot Metal Tools
  • Handled punches are made with round and square
    points and are used for punching holes in hot
    metal.

23
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.

24
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.

25
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.

26
How is metal measured and held?
27
In order to measure and work metal
satisfactorily, the stock must be securely and
properly held.
28
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.

29
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.

30
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.

31
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.

32
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.

33
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.

34
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.

35
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.

36
Tongs
  • Bolt tongs have a curved opening in the jaws.
  • This permits the holding of round or square
    materials.

37
How is metal heated, cut, squared, drawn out,
upset, bent, twisted, and hole punched?
38
Proper procedures must be followed to properly
heat, cut, square, draw out, upset, bend, shape,
twist, and hole punch metal.
39
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.

40
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.

41
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.

42
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.

43
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.

44
Hot metal may be cut with a hot chisel, a hardy
and a cutter, an oxyacetylene cutting torch, or
an electric arc.
45
Hot Metal Cutting
  • Hot chisels and cutters are used for cutting
    generally large and heavy metals.

46
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.

47
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48
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.

49
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.

50
When squaring hot metal follow these set
procedures
  • 5. Reheat to a cherry red color if the piece
    becomes cool before it is squared.

51
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.

52
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.

53
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.

54
  • When metal is upset, it is placed on end and
    hammered until it is enlarged and shortened to
    the correct size.

55
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.

56
  • One of the important phases of metal work is the
    bending of materials.

57
Bending Procedures
  • 1. Small pieces often may be bent cold, but some
    pieces should be heated before they are bent.

58
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.

59
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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.

61
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.

62
Twisting 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.

64
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.

65
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.

66
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.

67
Hole Punch Procedure
  • 6. Turn the piece over, and then set the punch
    directly over the hole that was started from the
    other side.

68
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.

69
How is metal hardened, tempered, and annealed?
70
Heat treating steel includes hardening,
tempering, and annealing.
71
Hardening Steel
  • Hardening steel is making it hard by heating it
    to a light cherry red and then cooling it quickly
    in warm water.

72
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.

73
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.

74
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.

75
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.

76
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.

77
Pearlite
  • The steel takes an intermediate form, austenite,
    during heating above 700F.

78
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.

79
Tempering steel
  • Tempering steel is reheating hardened steel to
    obtain the desired hardness and toughness.

80
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.

81
Tempering steel
  • The process of changing martensite back to
    pearlite is dependent on heat increase, usually
    within one of three of the following ranges

82
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.

83
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.

84
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.

85
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86
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.

87
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.

88
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.

89
What are the safety practices to be followed when
working with hot metal?
90
Observe the following general safety practices
for working hot metal.
91
Safety Practices
  • Obtain the instructors permission before using
    any tool or machine.

92
Safety Practices
  • Wear industrial quality eye protection to protect
    eyes from sparks and metal chips.

93
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.

94
Safety Practices
  • Protect hair and scalp by restraining long hair
    and wearing a cap.

95
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.

96
Safety Practices
  • Report all injuries or accidents to the
    instructor immediately, no matter how slight.

97
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.

98
Safety Practices
  • Always use the right size tool and only for its
    intended purpose.
  • Use tongs or pliers for carrying hot metal.

99
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.

100
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.

101
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.

102
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.

103
Safety Practices
  • Before leaving the laboratory or work station,
    make certain the heat source is shut off and cool.

104
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.

105
Safety Practices
  • Keep cables and hoses from coming in contact
    with hot metal and sharp objects.
  • Never point a flame at cables or hoses.

106
Safety Practices
  • Use warm water instead of quenching oil for
    quenching.
  • Quenching oil is easily confused with other oils.

107
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.

108
Review
  • Describe the heat treating processes hardening,
    tempering, and annealing.
  • Identify the safety practices to follow when
    working with hot metal.
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