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Questions and Answers
What is the primary function of rotating rolls in the manufacturing process?
What is the primary function of rotating rolls in the manufacturing process?
What is the primary purpose of the hot rolling process?
What is the primary purpose of the hot rolling process?
Which of the following best describes flat rolling?
Which of the following best describes flat rolling?
What is the typical shape and size of a bloom after the first hot rolling operation?
What is the typical shape and size of a bloom after the first hot rolling operation?
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What type of rolling process is commonly used for producing finished sheet and plate stock?
What type of rolling process is commonly used for producing finished sheet and plate stock?
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What is a key advantage of thread rolling over thread cutting?
What is a key advantage of thread rolling over thread cutting?
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Which of the following statements correctly describes a billet?
Which of the following statements correctly describes a billet?
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In shape rolling, how is the desired shape achieved?
In shape rolling, how is the desired shape achieved?
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What transformation occurs to internal defects during the hot rolling process?
What transformation occurs to internal defects during the hot rolling process?
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Which of the following is NOT a product of the rolling process?
Which of the following is NOT a product of the rolling process?
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Which type of rolling mill configuration supports smaller work rolls with backing rolls?
Which type of rolling mill configuration supports smaller work rolls with backing rolls?
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What form of rolling is specifically a bulk deformation process to create threads?
What form of rolling is specifically a bulk deformation process to create threads?
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How is a slab typically defined in terms of its cross-section?
How is a slab typically defined in terms of its cross-section?
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Which rolling process is typically used to form shapes like I‑beams and U‑channels?
Which rolling process is typically used to form shapes like I‑beams and U‑channels?
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What initial form is processed by the rolling mills to create blooms or billets?
What initial form is processed by the rolling mills to create blooms or billets?
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What characteristic of the wrought structure is improved by the hot rolling process?
What characteristic of the wrought structure is improved by the hot rolling process?
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What is the purpose of the accumulating drums in wire drawing machines?
What is the purpose of the accumulating drums in wire drawing machines?
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What does the area reduction formula in wire drawing measure?
What does the area reduction formula in wire drawing measure?
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Which of the following materials is used for die production to provide improved wear resistance?
Which of the following materials is used for die production to provide improved wear resistance?
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In bar or rod drawing, what characterizes the stock used?
In bar or rod drawing, what characterizes the stock used?
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How is tube drawing accomplished?
How is tube drawing accomplished?
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What is a characteristic feature of the hydraulic press?
What is a characteristic feature of the hydraulic press?
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Which defect in forging is specifically attributed to exhausted ductility?
Which defect in forging is specifically attributed to exhausted ductility?
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What process is comparable to squeezing toothpaste out of a tube?
What process is comparable to squeezing toothpaste out of a tube?
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Which of the following types of extrusion involves lower force due to the billet moving relative to the container wall?
Which of the following types of extrusion involves lower force due to the billet moving relative to the container wall?
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What is the purpose of process annealing between steps in forging?
What is the purpose of process annealing between steps in forging?
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What is the primary factor that influences the extrusion force?
What is the primary factor that influences the extrusion force?
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How is the extrusion ratio (ER) defined?
How is the extrusion ratio (ER) defined?
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What role does friction play in direct extrusion?
What role does friction play in direct extrusion?
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What is the primary characteristic of shallow drawing?
What is the primary characteristic of shallow drawing?
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In the process of ironing, what is the result of reducing the thickness of the sheet?
In the process of ironing, what is the result of reducing the thickness of the sheet?
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What is a characteristic of reverse redrawing when compared to direct redrawing?
What is a characteristic of reverse redrawing when compared to direct redrawing?
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Which of the following describes the primary function of the stripper ring in the deep drawing process?
Which of the following describes the primary function of the stripper ring in the deep drawing process?
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What type of can is produced by using the ironing process followed by deep drawing?
What type of can is produced by using the ironing process followed by deep drawing?
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How does the clearance between the punch and die affect the ironing process?
How does the clearance between the punch and die affect the ironing process?
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What challenges are typically addressed by redrawing operations?
What challenges are typically addressed by redrawing operations?
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What is a common issue that can occur during drawing operations?
What is a common issue that can occur during drawing operations?
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Study Notes
Forging Presses
- Apply gradual pressure to accomplish compression operation
- Mechanical press - Converts rotation of drive motor into linear motion of ram
- Hydraulic press - Hydraulic piston actuates ram
- Screw press - Screw mechanism drives ram
Forging Defects
- Fracture - Exhausted ductility or intergranular fracture
- Barreling - Friction
Extrusion Process
- A plastic deformation process in which metal is forced under pressure through a die to produce the desired shape
- Similar to squeezing toothpaste out of a tube
- Used to produce long parts with uniform cross sections
- Typical products include railings, tubing, structural and architectural shapes, doors, and window frames
- Extrusion Ratio - Ratio of the cross-sectional area of the billet to the cross-sectional area of the extruded product (A o / A f)
- Extrusion Force - Force required to extrude the metal, calculated using the formula F = A o K Ln (A o/A f)
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Types of Extrusion:
- Direct Extrusion (Forward Extrusion) - Billet is placed in a chamber and forced through a die opening by a hydraulically-driven ram
- Indirect Extrusion (Backward Extrusion) - Metal is forced to flow through the die in the opposite direction of the ram's motion
- Hydrostatic Extrusion - Extrusion is performed under high pressure using a fluid
- Impact Extrusion - Extrusion is performed using a high-velocity impact
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Extrusion Force Factors:
- Friction
- Material Properties
- Reduction in Area
- Speed
- Temperature
- Geometry of the Die
Rolling Process
- Metal deformation process used to reduce work thickness by compressive forces exerted by two opposing rolls
- Initial breaking down of an ingot or continuously cast slab is done by hot rolling
- Cast structure includes coarse and non-uniform grains, which are usually brittle and may contain porosities
- Hot rolling converts the cast structure to a wrought structure, which has finer grains and enhanced ductility, both resulting from breaking up the brittle grain boundaries and closing up of internal defects.
- Products of hot rolling operations are called bloom, slab, or billet.
- Bloom - square or rectangular cross-section with a thickness greater than 6" and a width no greater than 2x the thickness, further processed into structural shapes
- Slab - rectangular cross-section with a width greater than 2x the thickness, rolled into plates, sheets, and strips
- Billets - square or circular cross-section smaller than a bloom, rolled into various shapes like round rods and bars
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Types of Rolling:
- Flat Rolling - used to reduce the thickness of a rectangular cross-section
- Shape Rolling - square cross-section is formed into a shape such as I‑beam
- Hot Rolling - most common due to the large amount of deformation required
- Cold Rolling - Produces finished sheet and plate stock
Thread Rolling
- A bulk deformation process used to form threads on cylindrical parts
- Important industrial process for mass producing bolts and screws
- Performed by cold working in thread rolling machines
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Advantages over thread cutting:
- Higher production rates
- Better material utilization
- Stronger threads and better fatigue resistance due to work hardening
Rolling Mills
- Heavy and expensive equipment
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Configurations:
- Two-high - Two opposing rolls
- Three-high - Work passes through rolls in both directions
- Four-high - Backing rolls support smaller work rolls
- Cluster mill - Multiple backing rolls on smaller rolls
- Tandem rolling mill - Sequence of two-high mills
Wire Drawing
- A metal forming process used to reduce the diameter of wire
- Consists of multiple draw dies (typically 4 to 12) separated by accumulating drums
- Each drum provides proper force to draw wire stock through upstream die
- Each die provides a small reduction, so the desired total reduction is achieved by the series
- Annealing is sometimes required between dies to relieve work hardening
- Area Reduction in wire Drawing - Change in size of work is usually given by area reduction, calculated by: (Ao - A f) / Ao where 'r' is the area reduction in drawing, 'Ao' is the original area of work, and 'Af' is the final work.
Die Materials
- Tool steels and carbides are commonly used materials
- Diamond dies are used for fine wire
- To improve wear resistance, steel dies may be chromium plated, and carbide dies may be coated with titanium nitride
- Cast-steel dies are used for hot drawing
Bar or Rod Drawing
- A metal forming process where stock is pulled through one die opening
- Accomplished as a single draft operation
- Beginning stock has a large diameter and is a straight cylinder
- Requires a batch type operation
Tube Drawing
- Metal is pulled through the sides of the mandrel, which is placed between dies
Deep Drawing
- A sheet metal forming process to produce cups or shells from flat sheet metal
- Shallow drawing - depth of formed cup D/2
- Deep or moderate drawing - depth of formed cup > D/2
Ironing Process
- Process to reduce the thickness of the sheet metal as it enters the die cavity, resulting in a cup with a constant wall thickness
- A cup is forced through the die with a punch having a smaller diameter than the die opening.
- Smaller clearance between the punch and the die, results in a greater amount of ironing.
Redrawing Operations
- Containers or shells that are too difficult to draw in one operation are generally redrawn.
- Reverse redrawing is a process in which the metal is subjected to bending in the direction opposite to its original bending configuration. It results in lower forces and a more ductile material.
Aluminum Two-Piece Beverage Can
- Aluminum beverage cans are made using a metal-forming process involving a number of steps:
- Blanking - Sheet metal is cut into the desired shape.
- Deep drawing - The blank is formed into a cup.
- Ironing - The walls of the cup are thinned to the desired thickness.
- Beading - A bead is formed around the top edge of the cup to ensure a good seal.
- Bottoming - The bottom of the can is formed.
- Necking - The top of the can is necked down to fit the lid.
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Description
Test your knowledge of forging presses, defects, and the extrusion process. This quiz covers mechanical, hydraulic, and screw presses, as well as common forging issues like fractures and barreling. Additionally, explore the principles and applications of metal extrusion.