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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.
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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?
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.
Annealing steel Cementite Ferrite Hardening steel Martensite Pearlite Tempering steel Terms
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 right-angle 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.
In order to measure and work metal satisfactorily, the stock must be securely and properly held.
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.
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.