1. Bulk Deformation Processes
Shape changes on the workpiece by plastic deformation under forces applied by various tools and dies
Primary working operations (break ingot down into shapes such as slabs, plates, and billits) forging, rolling, and extrusion
Secondary working operations involve further processing of the product from primary working into final or semifinal products (bolts, sheet metal parts, wire)

3. Hot forming hot rolling or forging to break down the ingot structure
diffusion processes are accelerated by the high temperature and by the reformation of grains
the chemical nonhomogeneity of the casting is reduced
blowholes and porosity are eliminated

4. In order to refine the original dendritic structure of the ingot, it is necessary to reach deformation degrees of about 5 to 6
a fibrous structure that leads to anisotropy
favorable directions of fibers is of the importance, special design requirement in performing the individual steps in closed die forging
impurities will segregate along grain boundaries (grains will recrystallize but not segregates)
design the forging process so as to result in fibers following the overall shape of the forging

6. a) cooling of an ingot
b) heating up the ingot for forging
c,d,e) forging finished at subsequently lower temperatures
f) forging continued below A1. This is cold working, there is no more grain refinement; the material strain-hardens

8. a crystallographic fibrous structure
due to lattice rotations, the grains elongate in the directions of rolling or drawing (this kind of structure is called texture)
cold work is mostly combined with annealing and/or stress-relieving heat treatment
recovery or stress-relieving at 0.3 to 0.5 Tm, grain size does not change, mechanical properties change only slightly
residual stresses produced by cold work are eliminated

9. recrystallization can only occur in a metal that has been plastically deformed, and it depends strongly on the degree of that deformation

10. the grain coarsening process becomes much more intensive if the temperature is increased above the recrystallization temperature

11. through recrystallization, the ductility of the metal is fully restored, and all increase of strength and hardness obtained by cold work is eliminated

12. Cold work and anneal cycle
cold rolling
cold drawing
primary cold forming operations are followed by annealing
grain boundaries have high surface energy and therefore serve as preferential sites for solid state reaction such as
diffusion
phase transformation
precipitation
higher concentrations of solute atoms than the interior of the grains
lattice rotations lead to the formation of deformation bands
material strain hardness

14. Forging
5000 BC
typical parts made by forging are crankshafts and connecting rods for engines, turbine disks, hand tools, and many types of structural components for machinery and transportation equipment
can be carried out at room temperature and at elevated temperature
the three basic categories of forging are
open die
impression die
closed die

15. Open die forging

17. Forces and work of deformation under ideal conditions
friction is zero
material is perfectly plastic
workpiece is a cylinder
volume stays constant
the ideal work of deformation is the product of the volume of the specimen and the specific energy. This is the minimum energy or the ideal energy required for uniform deformation
for the strain hardening materials
the force at any stage during deformation is
Yf - the flow stress of the material

18. the work of deformation is
Y - the average flow stress
u represents the work dissipated in uniaxial deformation
for triaxial states of stresses the work of deformation per unit volume is
The work is W = uV and represents the minimum energy required for homogenous deformation

19. The efficiency of a process is
the energy for actual deformation is
Utotal=Uideal+Ufriction+Uredundant
The efficiency of a process is
depends on
the particular process
frictional conditions
die geometry
other process parameters
30-60% for extrusion
75-95% for rolling

20. Open die forging
all types of hammers or presses may be used in open die forging
the forging is too large
the required quantity is too small

24. Roll forging it could be used as the final forging operation
most often is used as a preliminary operation eliminating the need for too many impressions in the forging dies

26. Closed die forging
a wide variety of sizes and from different materials
big volume production of parts with complex shapes
high requirements on structural integrity, strength, and toughness
the forgings may be made in various degrees of tolerance
blocker
conventional
precision forgings
the largest user of forgings is the aerospace industry. 32% of the total value of forgings in the USA
the second largest user of forgings is the automotive industry. 20%

27. Closed die forging
the workpiece acquires the shape of the die cavities (impressions)
because of high length to thickness ratio, the flash is subjected to high pressure causing high frictional resistance to material flow in the radial direction in the flash gap
the flash is cooling faster than the bulk of the workpiece causing the resistance to deformation

29. Closed die forging flashless forging, precision forging
proper control of the volume of material is essential to obtain a forging of desired dimensions
it requires higher capacity forging equipment than do other forging processes
particularly suitable for Al and Mg alloys
it requires special dies
much less machining is involved
the forging is done in several steps
in the performing stages, the material in the form of rod is redistributed along its length so as to roughly correspond to the needs of the final shape
the distribution of the material leads to better die life and improved quality of the forging
drawing out - reduction of one end
fullering - reduction of the center
edging or rollering - increasing the cross section

31. the design of forgings, preforms, and dies is a difficult task
CAD - that incorporates rules based on experience and on methods of computation of pressure and temperature loads in the dies
shapes with tall and slender vertical projections are most difficult to forge

32. Hot and cold upsetting
hot upset forging enlarges and reshapes the cross sectional area of the end of a bar or tube of uniform cross section
developed for heading bolts, flanges shafts, etc.

35. the isothermal forging or hot die forging the dies are heated to the same temperature as the hot blank
cooling of the workpiece is eliminated
the low flow stress of material
material flow in the die cavities is improved
the dies are made of nickle alloys
expensive

44. Rolling
accounts for about 90% of all metals produced by metalworking processes
developed in the late 1500s
basic products:
plates
sheet

46. Primary hot rolling to produce slabs, blooms, and billets
defects, such as cracks, folds, scabs, seams, etc. should be removed before the next hot rolling process

47. After conditioning, the semifinished steel is heated again for further rolling into plates, bars, rods, various profiles such as I, U, H, and railroad rail.
The amount of reduction of thickness is called draft.

48. larger draft requires larger radius of rollers, and therefore a larger length of contact.

49. Rolling mill configurations

59. Hot forming of tubes and pipes
gas, oil, and water transportation
construction of railing, scaffolds, columns, and bridges
drilling for oil and natural gas
for boilers and heat exchangers
two processes
butt welding
d = mm hot compression
up to 500mm electric resistance welding
seamless pipes
d up to 650mm
high tensile stress is generated, causing a crack
produced by
hot rolling
hot extrusion
cold drawing

64. Roll deflection and flattening
the flattening of the rolls elastically
the higher the elastic modulus of the roll material, he less the roll distorts

66. Defects
surface defects caused by inclusions and impurities, scale, rust, dirt, roll marks
structural defects - affect the integrity of the rolled product

67. Residual stresses
caused by inhomogeneous plastic deformation in the roll gap