Flashcards
L#13 Forging
Cards in this deck (44)
- 1What is the principle of forging? (1)A workpiece is shaped by compressive forces applied through various dies and tooling (1)
- 2Give some traditional and modern example of forged components (2)Traditional: Jewelry, coins
Modern: Large rotors for turbines, gears, bolts, rivets, cutlery hand tools, numerous structural components for machinery, aircraft and railroads. - 3What are the physical properties of forged components? Why? What use are they therefore useful for? (3)Forged parts have good strength and toughness (1) because metal flow in a die and the material's grain structure can be controlled (1) therefore they can be used reliably for highly stressed and critical applications (1)
- 4Draw diagrams of grain structure for: a) Casting b) Machining from a blank c) Forging (3)See notes
- 5What are the two fundamental pieces of equipment required for forging? (2)1. A set of dies
2. A press or powered forging hammer - 6What are the advantages and disadvantages of cold forging? (3)1. It requires higher forces (because of the higher strength of the workpiece material
2. The metal most possess sufficient ductility at room temperature to undergo the necessary deformation without cracking.
3. Cold-forged parts have a good surface finish and dimensional accuracy - 7What is the advantage and disadvantage of hot forging? (2)1. Hot forging requires lower forces than cold forging
2. The dimensional accuracy and surface finish of the parts are not as good as in cold forging - 8Why might additional finishing operations be used on forgings? Which is often used?1. Heat treatment to modify properties
2. Machining to obtain accurate final dimensions with a good surface - 9How can the required finishing operations for forgings be reduced? (1)Through precision forming, an example of a net -shape or near-net-shape forming process (1)
- 10Give the 5 types of forging processes.1. Open die
2. Closed die
3. Blocker
4. Conventional
5. Precision - 11Give the advantages and limitations of open die forging (10)Advantages: Simple and inexpensive dies (1); Wide range of part sizes (1); Good strength characteristics (1); Generally for small quantities (1)
Limitations: Limited to simple shapes (1); Difficult to hold close tolerances (1); Machining to final shape necessary (1); Low production rate (1); Relatively poor utilization of material (1); High degree of skill required (1). - 12Give the advantages and limitations of closed die forging (8)Advantages:
Relatively good utilization of material (1)
Generally better properties than open-die forgings (1)
Good dimensional accuracy (1)
High production rates (1)
Good reproducibility (1)
Limitations:
High die cost (1)
Not economical for small quantity (1)
Machining often necessary (1) - 13Give the advantages and limitations of Blocker forging (4)Advantages:
Low die costs (1)
High production rates (1)
Limitations:
Machining to final shape necessary (1)
Parts with thick webs and large fillets (1) - 14Give the advantages and limitations of conventional forging (4)Advantages:
Requires much less machining than blocker type (1)
High production rates (1)
Good utilization of material (1)
Limitations:
Higher die cost than blocker type (1) - 15Give the advantages and limitations of conventional forging (4)Advantages:
Requires much less machining than blocker type (1)
High production rates (1)
Good utilization of material (1)
Limitations:
Higher die cost than blocker type (1) - 16Give the advantages and limitations of precision type forging (7)Advantages:
Close dimensional tolerances (1)
Very thin webs and flanges possible (1)
Machining generally not necessary (1)
Very good material utilization (1)
Limitations:
High forging forces (1)
Intricate dies (1)
Provision for removing forging from dies required (1) - 17Which is the simplest type of forging operation? (1)Open-die forging (1)
- 18What is the size weight range for open-die forgings? (2)Generally 15 to 500 kg, sometimes as heavy as 275 metric tons (1)
Size from very small to very large (1) - 19Draw a diagram of open-die forging, annotatedSee notes
- 20What is the formula for forging force for an open-die forging operaion on a solid cylindrical workpiece? (1)F = (Yf)(pi)(r^2)(1+(2ur/3h))
where:
Yf is the flow stress of the material
u is the coefficient of friction between the workpiece and the die
r an h are respectively the instantaneous radius and height of the workpiece - 21What is an alternative method for estimating forging force? (1)Using true stress strain curves
- 22What is the other name for closed die forging? (1)Impression-die forging (1)
- 23How does impression die forging work (1)The workpiece takes the shape of the die cavity while being forged between two shaped dies (1)
- 24Under what conditions is impression-die forging carried out? Why (2)At elevated temperatures (1)
To lower the required forces and attain enhanced ductility in the workpiece (1) - 25Draw an annotated diagram to explain closed-die forgingSee notes
- 26Give the parting line considerations for impression-die forgings (3)For most forgings, the parting line is located at the largest cross section of the part (1)
For simple symmetrical shapes, the parting line is normally a straight line at the centre of the forging (1)
For more complex shapes the line may not lie in a single plane (1) - 27What is an important design consideration for impression-die forging dies? Why is this important? (2)Dies designed in such a way that they lock during engagement (1)
Avoids side thrust, balance forces, and maintain die alignment during forging (1) - 28Why is lateral flow constrained in closed-die forging? (1)To ensure proper die filling (1)
- 29Why is the flash material allowed to flow into a gutter in impression-die forging? (1)So that the extra flash does not increase the forging load excessively (1)
- 30Give the general guidelines for flash thickness and land length for closed die forgings (2)Flash thicknedd is 3% maximum thickness of forging
Length of land is usually two to five times the flash thickness - 31Why are draft angles important in forging dies? (1) What values are used for internal and external draft angles? (2) why is this (1)Important to facilitate the removal of the part from the die. (1)
internal draft angles: 7 to 10 degrees (1)
external draft angles: 3 to 5 degrees (1)
This is because upon cooling the forging shrinks both radially and longitudinally (1) - 32Why is selection of the proper radii for corners and fillets important in closed die forging? (2)1. To ensure smooth flow of metal into the die cavity.
2. To To improve die life - 33Why are small radii generallly undesirable in closed die forging? (3)1. They have an adverse effect on metal flow
2. Tendency to wear rapidly (as a result of stress concentration and thermal cycling)
3) They can cause fatigue cracking of the dies - 34What is a general rule for the radii used in closed die forging? (1)As large as is permitted by the design of the forging
- 35What is the formula for forging force to carry out impression die forging? (1)F = k(Yf)A
where:
Yf is the flow stress of the material at the forging temperature
A is the projected area of the forging including the flash
k is a multiplying factor as follows (1)
Simple shapes without flash 3-5
Simple shapes with flash 5-8
Complex shapes with flash 8-12
(2) - 36What are the advantages of precision forging? (2)Reduced number of additional finishing operations required
In order can reduce the cost - 37Which components are typically precision forged? (3)Gears, connecting rods, turbine blades
- 38What are the four requirements of precision forging?1. Special and more complex dies
2. Precise control of the blanks volume and shape
3. Accurate positioning of the blank in the die cavity
4. Higher capacity equipment equipment due to the higher forces required to obtain fine details on the part - 39Which materials are particularly suited to precision forging? (2) Why? (1) Which other materials can also be used? (2)1. Aluminium and magnesium alloys
2. Relatively low forging loads and temperatures they require
3. Steels and titanium - 40What are the four additional forging operations?1. Coining
2. Heading
3. Piercing
4. Hubbing - 41Describe coining with some examplesA closed die forging process which is typically used in the minting of coins, medallions and jewelry
- 42Describe heading with some examplesAlso called upset forging, heading is essentially an upsetting operation, usually performed on the end of a round rod or wire in order to increase the cross section. Typical products are nails, bolt heads, screws, rivets and various other fasteners
- 43Describe piercing operation with some examplesProcess of indenting (but not breaking through) the surface of a workpiece with a punch in order to produce a cavity or an impression. The workpiece may be confined in a container (such as a die cavity) or may be unconstrained
- 44Describe the hubbing operation with some examplesProcess consists of pressing a hardened punch with a particular tip geometry into the surface of a block of metal. The cavity produced is subsequently used as a die for forming operations, such as those employed in the making of tableware
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- Manufacturing Operations and Technology Flashcards on L#13 Forging, created by Block on 16/03/2014.
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