Lecture 3: Shaping Flashcards
(35 cards)
What happens during hot deformation?
Hot deformation involves deforming materials at temperatures close to their melting points (70-80%), which reduces the force required but uses a lot of energy and lead to recrystallization for improved structure.
What is warm deformation and its benefits?
Warm deformation occurs at 30-40% of the melting temperature of the material. It reduces the force needed for deformation without causing recrystallization, striking a balance between energy use and material strength.
Describe cold deformation and its effects.
In cold deformation, materials are deformed at or near room temperature, leading to work hardening as the existing crystal structures are compressed and twisted without heat softening.
Compare continuous and discrete shaping processes.
Continuous processes (e.g., rolling, extrusion) are ongoing as long as material is supplied. Discrete processes (e.g., forging, sheet-metal forming) create individual pieces one at a time.
Explain the 5 characteristics of Forging
1.Shaping by applying compressive forces.
2.High equipment and labor costs.
3.Achieves high strength/toughness materials.
4.Allows for complex shapes and production of small to large products.
5.Usually done in batches.
Cold forging :(3)
-Good surface finish and
accuracy
- Crystal deformation
- A lot of force needed
Hot forging (3):
- Lower forces required
- Worse surface finish
and accuracy. - Strengthening
Differentiate between Open-Die Forging (2) and Closed-Die Forging (3):
Open-Die Forging:
1.Limited shapes, small quantities, mostly hot forging.
2.Leaves parting line and flash.
Closed-Die Forging:
1.Used for complex shapes and larger quantities.
2.Mold more expensive due to die shape information.
3.Leaves parting line and flash but molds hardly ever completely close.
Heading =
= changing the shape in a number of steps, each step gets
closer to the shape we want.
Coining =
= a process with high accuracy and surface finish. We do not have any
flash in coining.
What are the key 4 characteristics of the Extrusion process (hot and cold):
1.Uses machines.
2.Moderate-to-high die and equipment cost, low-to-moderate labor cost.
3.Involves enormous forces to push material through die.
4.Hot extrusion has low ductility and heat requirements, used for batches; cold extrusion has high ductility and is often combined with forging, individual production
What are the 3 primary features of products produced through Extrusion?
1.Product geometry: long lengths, constant cross-section, discrete products.
2.Made in batches or semi-continuous processes.
What challenges arise in extrusion when attempting to create sharp corners and work with very strong materials?
1.Very sharp corners and unbalanced voids are difficult to achieve.
2.Extrusion with extremely strong materials, like steel, is not feasible due to the inability of dies to withstand the high forces involved.
What are the 2similarities and 3 differences between Drawing and Extrusion processes?
Similarities:
1.Both have low-to-moderate equipment and labor costs.
2.Low-to-moderate operator skills required.
Differences:
1.Drawing: Material pulled out of the die.
2.Extrusion: Material pushed through the die.
3.Drawing works only with cold material and results in increased strength.
Describe the product geometry and process nature of Drawing.
Product geometry: Long rods and wires with different cross-sections.
Process is continuous.
What are 2 key requirement for the material in the Drawing process, and how does it affect the material’s properties?
Drawing only works when the material is cold.
Cold drawing strengthens the material.
What are the characteristics of sheet metal components in terms of surface-to-volume ratio and thickness?
Extremely large surface-to-volume ratios.
Thickness typically ranges from 1mm to 1.5mm.
What is involved in metal rolling for sheet metal?
Metal rolling involves passing metal sheets through one or more pairs of rolls to reduce thickness, improve surface finish, and adjust material properties like grain structure.
What are 5 characteristics of metall rolling?
Requires significant forces.
Expensive equipment.
Low-to-moderate labor cost.
Can be semi-continuous.
Produces flat plates and foil, or profiles and rails.
Differentiate between hot rolling and cold rolling in metal rolling processes.
Hot Rolling:
Results in a coarse-grained structure.
Improves strength, hardness, and surface finish.
Cold water may be sprayed to prevent excessive hardening.
Cold Rolling:
Results in higher strength, hardness, and better surface finish.
Produces anisotropic materials due to cold deformation.
What are 4 specific applications of metal rolling techniques?
Skew rolling for metal balls.
Thread rolling for screw threads.
Hollow tube rolling.
Flat rolling for sheet metal production.
What 3 factors influence the maximum thickness of material that can be put through metal rolling in flat rolling?
Friction between the rolls and material.
Compromise between friction and slip due to high forces.
Role diameter does not determine maximum thickness; friction does.
How can roll forces be reduced in metal rolling processes?(4)
1.Using smaller diameter rolls.
2.Reducing thickness reductions.
3.Applying back or front tension to the strip.
4.Using crowned rolls to prevent material bending.
What is sheet metal forming?
Sheet metal forming involves shaping operations where sheets of metal are deformed into complex three-dimensional shapes without removing any material, primarily through bending, stretching, and drawing processes.
