In this article, we will discuss what is forging? How does it work? Types of forging, Operations, Advantages, Disadvantages, and more.
What is Forging Operations ?
Forging operations are the operations which is used for giving the desired shape to any job of metal by heating or cooling it and then striking it either with an hammer.
What is Forging ?
Forging is a manufacturing process that involves shaping metal with localized compressive forces. The blows are delivered with a hammer or a die. Forging is frequently classified according to the temperature at which it is performed: cold forging, warm forging, or hot forging.
Small forging jobs can be done by striking it with a hammer, but heavy forging jobs can only be done by machines. There are three methods for forging.
- Hand forging
- Drop forging
- Power forging or machines forging
1. Hand forging
Hand forging or smithing is the process of shaping a job by striking it with a hammer. Hand forging is employed only to shape a small number of light forgings chiefly in repair shops. Hand forging has recent years, been superseded by power forging.
2. Drop forging
Drop forging is the process of shaping metal and increasing its strength. In most forging, an upper die is forced against a heated workpiece positioned on a stationary lower die. If the upper die or hammer is dropped, the process is known as drop forging.
3. Power forging
Power Forging is a manufacturing process that results in the shaping of metal by using calculated force. Forging is executed with a power hammer or a die during the shaping process to produce the intended design of the forged metal object.
Smith Forging Operations
A number of operations are used to change the shape of the raw material to the finished form. The typical forging operations are :
- Upsetting Operation
- Drawing down Operation
- Settings down Operation
- Bending Operation
- Welding Operation
- Cutting Operation
- Punching Operation
- Fullering Operation
All these operations are carried out with the metal in a heated condition, which must be maintained by taking a ‘fresh’ heat when the work shows signs of getting cold.
1. Upsetting Operation
Upsetting or heading is the process of increasing the thickness of a bar at the expense of its length and is brought about by end pressure. The pressure may be obtained by driving the end of the bar against the anvil, by supporting on the anvil and hitting with the hammer, by placing in swage block hole and hitting with the hammer or by clamping in vice and then hammering a
Fig. 8.6 (a) shows the effect of heavy hammer blows on a uniformly heated bar ; (b) shows the effect of comparatively light hammer blows. Local upsets may be obtained as shown at (C) and at (d) by heating only the end or the middle of the bar.
2. Drawing Down or Swaging Operation
It is the process of increasing the length of a bar at the expense of its width or thickness or both. In Fig. 8.7, A, B, and C illustrate this operation. A represents the original stock, B shows the stock after hammering with a straight peen hammer or with a top fuller and sledge, and C shows the finished forging after the flatter has been used.
3. Setting Down Operation
It is a localized drawing-down or swaging operation as illustrated at D in 8.7. In other words, it may be said as the process of local thinning effected by the set-hammer or set. Usually, the work is fullered at the place where the setting down commences. In Fig. 8.7, E shows the process of setting down both edges of a bar using the top and bottom fuller and F illustrates how the flatter may be used close to a shoulder.
4. Punching Operation
It is the process of producing holes, generally cylindrical, by using a hot punch over the pritchel hole of the anvil, over a cylindrical die, or over a hole of the correct size in the swage block. Fig. 8.8 shows the stages in punching a hole.
5. Bending Operation
Bending is an important forging operations and is very frequently used. This may be classified as angular or curvilinear. Bending may be done over the edge of the anvil face, over the anvil horn, in special forms such as the swage block edges, or for bar stock, by inserting the end in the pritchel hole and bending the bar with a wrench or tong.
6. Welding or Shutting Operation
It is perhaps the principal forging operations performed by the smith. The metal which remains pasty over a wide range of temperature is most easily welded, and in this respect wrought iron and mild steel have some advantage over other metals. The first essential to the production of a sound weld is that the surfaces in contact must be perfectly clean, both mechanically and chemically so that cohesion will take place when the metal is in a plastic state.
A protection to the metal is a coating of flux which covers the surfaces of the metal and, by excluding the air prevents oxidation. Fluxes which are commonly used in forge welding consist of clean quartz sand, calcined borax, or a mixture of four parts of borax with one part of sal-ammoniac.
7. Cutting Operation
Cutting-off is a form of chiseling whereby a long piece of stock is cut into several specified lengths, or a forging is separated (cut-off) from its stock. For hot chiseling, steel must be heated in a blacksmith’s hearth or furnace to a light cherry red heat, i.e., from 850 to 950°C. When cutting with chisels, the hammer blows are directed on to the chisel head, which must be slightly rounded.
8. Fullering Operation
In metalworking, a fuller is a tool used to form metal when hot. The fuller has a rounded, either cylindrical or parabolic shape nose. Fullering or spreading the metal is done along the length of the job by working at separate sections. In this case, the axis of the job is positioned perpendicular to the width of the flat die.
In these forging operations the fuller is placed against the metal stock, and then either the fuller (for an upper fuller) or the stock (for a lower fuller) is struck with a hammer. The rounded nose of the fuller spreads the metal more efficiently than the flat face of the hammer. The process leaves ridges in the stock, which may then be flattened out later with the hammer or other tools.
9. Edging Operation
This forging process involves striking or forcing the metal plate into the desired shape. The workpiece is pressed against two die edges.
Advantages of Forging Operations
- The metal’s tensile strength is reduced, and it gains the property of plasticity, allowing us to shape the metal to our specifications.
- Drawing out, jumping, and bending operations are made simple by the properties of plasticity and malleability.
- A forged job is simple to finish because its shape is nearly complete and it takes less time.
- Other machine activities can be easily carried out on the job after forging on hand metal.
- There is little metal waste.
- Hot forging improves the structure of metal.
- On the metal, there is little room for stresses and cracks.
Disadvantages of Forging Operations
- When metal is heated, oxidation occurs, which harms the metal.
- Brittle metals are incapable of being forged.T
- he forging process does not allow for finishing.
- The size of jobs has changed.
MCQs on Forging Operations
1. In which of the following forging operation no special die is used?
a) Drop forging
b) Smith forging
d) Press forging
Explanation: Smith forging is also called flat die and open die forging. It includes the broad field of forging work produced between flat faced dies and possibly supplemented by stock tooling. The final shape of the forging depends on the skill of the smith for size and shape. Smith forging operations produces work pieces of lesser accuracy as compared to impression or closed die forging. Tooling is simple, inexpensive and allows the production on large variety of shapes.
2. In which of the following forging operations repeated hammering and closed die is used?
a) Drop forging
b) Smith forging
d) Press forging
Explanation: Hammer forging is also called as drop forging where a hammer hits the work piece repeatedly to deform it. There are different types of hammers like gravity drop, counter blow and powder hammers.
3. In which of the following forging operation instead of repeated hammering gradual force is applied?
a) Drop forging
b) Smith forging
d) Press forging
Explanation: Press forging is variation of drop-hammer forging. Unlike drop-hammer forging, press forges work slowly by applying continuous pressure or force. The amount of time the dies are in contact with the workpiece is measured in seconds (As compared to milliseconds of drop-hammer forges). The press forging operation can be done either cold or hot. The main advantage of press forging, as compared to drop-hammer forging, is its ability to deform the complete workpiece.
4. Coining and forming are two special kinds of which forging operation?
Explanation: Coining is a severe metal squeezing operation in which the flow of metal occurs at the top layers of the material and not throughout the values The operation is carried out in closed dies mainly for the purpose of producing fine details such as needed in minting coins, and metal or jewellery making. The blank is kept in the die cavity and pressure as high as five to six times the strength of material is applied. Depending upon the details required to be coined on the part, ore than one coining operation may be used.
5. Which of the following forging operation is used for parts having uniform cross section?
Explanation: In upset forging, a bar of uniform cross section usually round, is held between grooved dies, pressure is applied on the end in the direction of the axis of the bar by using a heading tool which spreads the end by metal displacement.
6. In which of the following technique shaping of a cross section of tubes or rods is done by means of repeated impacts or blows?
Explanation: Swaging is a mechanical deformation technique of reducing or shaping the cross section of rods or tubes by means of repeated impacts or blows.
7. Heading is a kind of which forging operation?
Explanation: A heading tool or ram is positioned perpendicular to the cross sectioned end face of a rod or bar gripped in a die. On application of pressure, the length of the rod is reduced, and the diameter is increased (upset). This manufacturing process used extensively in the production of fasteners, to form bolt heads, screw heads etc.
8. In heading to avoid buckling the length to diameter ratio should be?
Explanation: Buckling is characterized by a sudden sideways failure of a structural member subjected to high compressive stress, where the compressive stress at the point of failure is less than the ultimate compressive stress that the material is capable of withstanding. In upset forging, the aspect ratio (length to diameter ratio) should be 3:1.
9. Which operation is used in making raised figures on sheets with its corresponding relief on the other side?
a) Roll forging
Explanation: Embossing is an operation in which sheet metal is drawn to shallow depths with male and female matching dies. The operation is carried out mostly for the purpose of stiffening flat panels. The operation is also sometimes used for making decoration items like number plates or name plates, jewellery, etc. Embossing operation with two dies, letters, numbers and designs on sheet-metal parts can be produced by the is operation.
10. Which of the following operation is used to make ball bearing?
a) Skew rolling
b) Roll forging
c) Press forging
Explanation: A special type, skew rolling is used to manufacture milling steel ball, bearing ball blanks.
11. In the forging operation, fullering is done to:
a) Draw out the material
b) Bend the material
c) Upset the material
d) Extrude the material.
Explanation: The fullering is done to draw out the material. In the fullering, the material is distributed away from the forging area. Fullering is the process of reducing the cross-section of the workpiece or lengthening a preparation of the stock in preparation for the subsequent operation. In other words fullering is done to reduce cross-section and increase length.
These were the various types of forging operations which are performed in the industry. Hope you liked the article. Please give your feedback in the comment section below.
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