1. Fundamentals of Metal Forming Chapter 18
Manufacturing Processes, MET 1311
Dr Simin Nasseri
Southern Polytechnic State University
(© Fundamentals of Modern Manufacturing; Materials, Processes and Systems,
by M. P. Groover)

2. FUNDAMENTALS OF METAL FORMING
Overview of Metal Forming
Material Behavior in Metal Forming
Temperature in Metal Forming

3. Metal Forming
Large group of manufacturing processes in which plastic deformation is used to change the shape of metal workpieces
The tool, usually called a die, applies stresses that exceed the yield strength of the metal
The metal takes a shape determined by the geometry of the die

4. Stresses in Metal Forming
Stresses to plastically deform the metal are usually compressive
Examples: rolling, forging, extrusion
However, some forming processes
Stretch the metal (tensile stresses)
Others bend the metal (tensile and compressive)
Still others apply shear stresses

5. Material Properties in Metal Forming
Desirable material properties:
Low yield strength
High ductility
T Ductility Yield Strength
These properties are affected by temperature:
Ductility increases and yield strength decreases when work temperature is raised

6. Basic Types of Deformation Processes
Bulk deformation
Rolling
Forging
Extrusion
Wire and bar drawing
Sheet metalworking
Bending
Deep drawing
Cutting
Miscellaneous processes

7. Bulk Deformation

8. Bulk Deformation Processes
Characterized by significant deformations and massive shape changes
"Bulk" refers to workparts with relatively low surface area‑to‑volume ratios
Starting work shapes include cylindrical billets and rectangular bars

9. Rolling
The slab is heated in a furnace and rolled between powered rollers until the plate is made with desirable thickness.
Figure Basic bulk deformation processes: (a) rolling

10. Forging
Forging is the process of forming the metal by impacting and/or squeezing a preheated part between two halves of a die. A succession of dies may be needed to achieve the final shape.
Figure Basic bulk deformation processes: (b) forging

11. Extrusion
Billets are preheated and forced by a ram through one or more dies to achieve the desired cross-section. The product is long in relation to its cross-sectional dimensions and has a cross section other than that of rod and bar and pipe and tube.
Aluminum part
Figure Basic bulk deformation processes: (c) extrusion

12. Wire and Bar Drawing
Drawing is an operation in which the cross-section of solid rod, wire or tubing is reduced or changed in shape by pulling it through a die.
Figure Basic bulk deformation processes: (d) drawing

13. Sheet Metal Working

14. Sheet Metalworking
Forming and related operations performed on metal sheets, strips, and coils
High surface area‑to‑volume ratio of starting metal, which distinguishes these from bulk deformation
Often called pressworking because presses perform these operations
Parts are called stampings
Usual tooling: punch and die

15. Sheet Metal Bending
Straining of a metal sheet or plate to take an angle.
Figure Basic sheet metalworking operations: (a) bending

16. Deep Drawing
Forming of a flat metal sheet into a hollow or concave shape, by stretching the metal.
Figure Basic sheet metalworking operations: (b) drawing

17. Shearing of Sheet Metal
Shearing operation which cuts the work by using a punch and die.
Figure Basic sheet metalworking operations: (c) shearing

18. Test yourself!
Name the metal forming process used for each object (bulk deformation or sheet metalworking).
sheet metalworking

19. Test yourself! Name the metal forming process used for each object.
sheet metalworking
sheet metalworking

20. Test yourself! Bulk deformation
Name the metal forming process used for each object.
Bulk deformation

21. Test yourself! sheet metalworking
Name the metal forming process used for each object.
sheet metalworking

22. Test yourself! Forging (Bulk deformation)
Name the metal forming process used for each object.
Forging (Bulk deformation)

23. Test yourself!
Extrusion (bulk deformation)

24. Test yourself!
Gutter
sheet metalworking
Bending
Deep drawing

25. Temperature in Metal Forming

26. Temperature in Metal Forming
Any deformation operation can be accomplished with lower forces and power at elevated temperature
Three temperature ranges in metal forming:
Cold working
Warm working
Hot working

27. Temperature in Metal Forming
Cold working refers to plastic deformation that occurs usually, but not necessarily, at room temperature.
Warm working: as the name implies, is carried out at intermediate temperatures. It is a compromise between cold and hot working.
Hot working refers to plastic deformation carried out above the recrystallization temperature.

28. Temperature in Metal Forming
Increasing temperature
Melting temperature
Room temperature Tm 0.5 Tm Tm Above Tm
Casting
Hot working
Cold working
Warm Working
Recrystallization

29. Cold Working Performed at room temperature or slightly above
Cold Forming is the primary manufacturing operation of the fastener industry.
Many cold forming processes are important mass production operations
These operations are near net shape or net shape processes (Minimum or no machining usually required)

30. Advantages of Cold Forming
Better accuracy, closer tolerances
Better surface finish
No heating of work required
Cold forming can make tiny, complex precision parts in one machining step. Tolerances of in. are possible.

31. Disadvantages of Cold Forming
Higher forces and power required in the deformation operation
Ductility and strain hardening limit the amount of forming that can be done
In some cases, metal is simply not ductile enough to be cold worked

32. Warm Working
Performed at temperatures above room temperature but below recrystallization temperature
Dividing line between cold working and warm working often expressed in terms of melting point:
0.3Tm,
where Tm = melting point (absolute temperature) for metal

33. Advantages of Warm Working
Lower forces and power than in cold working
More complex work geometries possible

34. Hot Working
Deformation at temperatures above the recrystallization temperature
Capability for substantial plastic deformation of the metal ‑ far more than possible with cold working or warm working
Recrystallization temperature = about one‑half of melting point
In practice, hot working usually performed somewhat above 0.5Tm (Metal continues to soften as temperature increases above 0.5Tm, enhancing advantage of hot working above this level)

35. Advantages of Hot Working
Workpart shape can be significantly altered
Lower forces and power required
Metals that usually fracture in cold working can be hot formed

36. Disadvantages of Hot Working
Lower dimensional accuracy
Higher total energy required (due to the thermal energy to heat the workpiece)
Shorter tool life