Group 8

1
Group 8 Chapters 13 and 14

• Jason Becker
• Andrew Nawrocki
• Ryan Niehaus
• Jonathan Ogaldez
• Stephen Wakeland

2
Chapter 13

• Rolling of Metals

3
Introduction

• Movie

4
Introduction

• Rolling
• The process of reducing the thickness or changing
  the cross-section of a long workpiece by
  compressive forces applied through a set of rolls
• Not just for metal
• Used to enhance plastics, powder metals, ceramic
  slurry, and hot glass

5
Introduction
6
Introduction

• First step
• Generally an ingot or continuous cast metal is
  "hot" rolled at elevated temperatures
• Enhances material hardness and strength
• "Cold" rolling
• The material can be rolled at room temperature
• Enhances strength, hardness, and surface finish
• Requires more energy

7
Introduction

• Plates
• Thickness of gt6mm
• Structural applications
• Ship hulls, boilers, bridges, machinery, and
  nuclear vessels
• Sheets
• Thickness of lt6mm
• Typically provided as coils or flat sheets
• Large variety of applications

8
Flat-Rolling Process

• Roll gap, L
• Where reduction occurs
• Relative sliding
• To the right of the no-slip point, material moves
  faster than the roll
• To the left of the no-slip point, material moves
  slower than the roll

9
Flat-Rolling Process

• Draft
• Difference between the initial and final strip
  thicknesses (ho hf)
• Frictional Forces
• Required to move workpiece
• Must be overcome, increasing rolling forces and
  power requirements

10
Flat-Rolling Process

• Roll force
• Lateral force required to compress the workpiece
• Perpendicular to the plane of the strip

11
Flat-Rolling Process

• Reducing roll force
• Reducing friction
• Using smaller-diameter rolls
• Taking smaller reductions-per-pass
• Rolling at elevated temperatures
• Applying tensions to the strip

12
Flat-Rolling Process

• Tension (Longitudinal Force)
• Back tension
• Force applied to the strip at the entry zone
• Apply a braking action to the reel supplying the
  sheet into the roll gap (pay-off reel)
• Front tension
• Force applied to the strip at the exit zone
• Applied by increasing the rotational speed of the
  reel receiving the sheet from the roll gap
  (take-up reel)

13
Flat-Rolling Process

• Geometric considerations
• Due to roll forces, rolls may bend (deflection)
• Causes the rolled strip to be thicker at its
  center than at its edges (crown)
• Corrected for by making the rolls larger diameter
  at their center (camber)
• To counteract deflection, the rolls can also be
  externally bent at their bearings

14
Flat-Rolling Process
15
Flat-Rolling Process

• Spreading
• Strips with a more square cross-section will
  cause its width to increase significantly during
  rolling
• Increases with
• A decrease of width-to-thickness ratio
• Increase of friction
• Decrease of ratio of the roll radius to the strip
  thickness

16
Flat-Rolling Process

• Vibration and chatter
• Have significant effects on product quality and
  productivity of metalworking operations
• Chatter
• Self-excited vibration
• Can occur in rolling, extrusion, drawing,
  machining and grinding
• Leads to periodic variations in the thickness of
  the sheet and its surface finish
• Rolling speed and lubrication are the two most
  important parameters

17
Flat-Rolling Practice

• Initial Hot Rolling
• Cast structure includes coarse and non-uniform
  grains
• Hot rolling converts this to a wrought structure
  with finer grains and enhanced ductility

18
Flat-Rolling Practice
19
Flat-Rolling Practice

• First hot-rolling product
• Slab
• Large rectangular cross-section
• Bloom
• Large square cross-section
• Billet
• Square cross-section smaller than a bloom

20
Flat-Rolling Practice
21
Flat-Rolling Practice

• Conditioning
• Surface of the slab, bloom, or billet must be
  prepared for subsequent rolling
• Torch (scarfing) to remove heavy scale
• Rough grinding to smoothen surfaces
• Prior to cold rolling
• "Pickling" with acid (acid etching)
• Blasting with water
• Grinding

22
Flat-Rolling Practice

• Cold rolling
• Carried out at room temperature
• Produces sheets and strips with
• Better surface finishes (lack of scale)
• Better dimensional tolerances
• Better mechanical properties
• Pack rolling
• Two or more layers of metal are rolled together
  to improve productivity
• Aluminum Foil

23
Flat-Rolling Practice

• Defects
• Adversely affect strength, formability, and other
  manufacturing characteristics
• Wavy edges (a)
• Result from roll bending and is thinner along its
  edges than at its center
• Cracks (b c)
• Usually result from poor material ductility
• Alligatoring (d)
• Typically caused by defects in the original cast
  material

24
Flat-Rolling Practice
25
Flat-Rolling Practice

• Other characteristics
• Residual stresses
• Small-diameter rolls tend to deform the metal
  more at its surface than in its bulk
• Large-diameter rolls tend to deform the metal
  more in its bulk than at its surface

26
Flat-Rolling Practice

• Other characteristics (cont'd)
• Dimensional tolerances
• Thickness tolerances for cold-rolled sheets are
  more stringent than for hot-rolled sheets
• Due to thermal effects, the final thickness of
  hot-rolled sheets is more difficult to predict
• Surface roughness
• Hot-rolled sheets are likely to require finishing
  operations, while cold-rolled sheets likely are
  not
• Gage numbers
• Smaller number thicker sheet

27
Section 13.4 Rolling Mills

• Hot Rolling
• Cold Rolling
• Types of Mills
• Materials
• Lubricants

28
Types of Mills

• Two-High Rolling Mills
• Three-High Rolling Mills
• Four High Rolling Mills
• Cluster Mills
• Tandem Rolling

29
Two-High Mills
Three-High Mills

• Aka reversing mills
• Plate or material being rolled will be raised and
  lowered throughout the machine from upper to
  lower roll gaps.

• Used for hot rolling in the initial passes
• Used on cast ingots
• Used in continuous casting
• Roll diameters .06m-1.4m

30
Four-High Mills

• Same principles as cluster mills, Sendzimir mills
  or Z mills
• Utilize smaller rolls for lower roll forces
• Also lower power requirements and reduce
  spreading
• Rolls are cheaper to replace
• Small rolls deflect more so they must be
  supported by smaller rolls
• Very adept for cold rolling thin sheets
  high-strength materials

31
Four-High Rolling Mill
32
Cluster, Sendzimir or Z mill
33
Tandem Rolling

• Strip of Material continuously rolled through
  several stands
• Gauges of stands get smaller progressively
• Each stand (train) has its own rolls
• Requires highly automated systems to control
  thickness and speed

34
Tandem Rolling Mill
35
Rolls

• Rolls must be made of materials with high
  strength and resistance to wear
• Common materials include cast iron, cast steel
  and forged steel
• Forged steel has higher strength, stiffness and
  toughness but costs more
• Tungsten carbides can be used for smaller
  diameter rolls
• Rolls are polished for cold-working and special
  applications
• Rolls are heat specific-misuse results in heat
  checking and spalling

36
Lubricants

• Hot Rolling Ferrous alloys-None or Graphite
• Hot Rolling Non-Ferrous Alloys-Oils, emulsions
  and fatty acids
• Cold Rolling-Oils, emulsions, paraffin and fatty
  oils

37
13.5 Various Rolling Processes and Mills

• Shape Rolling
• Roll Forging
• Skew Rolling
• Ring Rolling
• Thread rolling
• Rotary Tube Piercing
• Tube Rolling

38
Shape Rolling

• Used for straight and long structural shapes
• I-beams, rails, channels
• Structures usually formed at higher temperatures
• Requires a series of rolls (material deformed
  non-uniformly)

39
Shape Rolling
40
Roll Forging Skew Rolling

• Aka cross rolling
• Cross section of a round bar is shaped by passing
  it through rolls with varied groves
• Used to produce leaf springs, knives and hand
  tools

• Similar to roll forging
• Used for making ball bearings
• Wire/rod is fed into the roll gap to form
  spherical blanks

41
Ring Rolling

• Used to create large rings for rockets and
  turbines, jet engine cases, flanges and
  reinforcing rings for pipes
• Involves using two rollers to expand a thick
  small ring into a thin large ring
• Utilizes a series of rollers, driven and
  stationary
• The rings thickness is reduce while its diameter
  is increased (volume of material stays the same.
• Pieces can be as big as 3m in diameter
• Advantages short production time, close
  tolerances, material savings, increased strength
  (favorable grain flow)

42
Thread Rolling

• Thread s are formed on round rods or wire by
  passing between dies
• Cold forming process
• Two reciprocating dies or rotary dies
• Used to create threads on screws, bolts etc.
• Production rates of up to 80 pieces per second
• Generates treads with good strength (cold
  working)
• Compressive residual stresses improve fatigue
  life
• Gears can also be produce in a similar manner
• Lubrication is especially important in thread
  rolling for finish surface and integrity

43
Rotary Tube Piercing

• Aka Mannesmann Process
• Used to make long, thick-walled seamless pipe and
  tubing
• Hot working process
• Developed in the 1880s
• Rolled bar under cyclical compression develops a
  cavity that grows down the tube
• Cavity is then expanded/pierced by a floating
  mandrel

44
Tube Rolling

• Process used to reduce the diameter and thickness
  of pipes/tubes
• With or without mandrels
• Process can be stepped

45
13.5.1

• Integration Mills
• Large facilities that integrate the entire
  production of a part
• Includes production of metals, casting rolling
  and the finished product

• MiniMills
• Recycles scrap metals, usually from local sources
  to reduce cost, and casts and rolls the metals
• Usually only produce one kind of product (rod,
  bar, angle iron)

46
Forging of metals

• Forging is the basic process which the material
  is shaped by compressive forces that is applied
  through various tools and dies.
• Forging operations create discrete parts
• Forged parts have good strength and toughness
  because the grain of the metal can be controlled,
  thus making ideal for highly stressed
  applications, such as large rotors for turbines,
  gears, bolts and rivets, railroads, aircraft, and
  a variety of other transportation equipment.

47
Open-Die forging

• Simplest type of forging
• Dies are inexpensive
• Wide range of part sizes, ranging from 30-1000lbs
• Good strength qualities
• Generally good for small quantities

• Limited to simple shapes
• Difficult to hold close tolerances
• Needs to be machined to final shape
• Low production rate
• Poor utilization of materials
• Highly skilled operation

1100 Ton Hydraulic Forging Press and 20 Ton
Capacity Manipulator
48
Open-Die forging
49
Impression Die Forging

• Better properties of Open Die Forgings
• Dies can be made of several pieces and inserts to
  create more advanced parts
• Presses can go up to 50,000 ton capacities
• Good dimensional accuracy
• High production rates
• Good reproducibility

• High die cost
• Machining is often necessary
• Economical for large quantities, but not for
  small quantities

Completed part before removal of the flash
50
Impression Die Forging operation

• This form of forging is used to make more
  complicated parts from Blank bar stock. The
  Blanks are compressed between two or more dies to
  shape the part. Once the part is shaped, the
  flash is removed by either grinding it, trimming,
  or machining.

51
Precision Forging

• High forging forces
• Thus higher capacity equipment is required
• Intricate dies leading to increased die cost
• Precise control over the Blanks volume and shape
• Accurate positioning of the Blank in the die
  cavity

• Close dimensional tolerances
• Very thin webs and flanges are possible
• Very little or no machining is required
• Little or no scrap after part is produced
• Cheaper to produce from less finishing operations
  and faster production
• Typical applications are gears, connecting rods,
  and turbine blades
• Common materials used in precision forging are
  aluminum, magnesium alloys, steel, and titanium

Some examples of precision forged products
Piston heads, connecting rods, and turbocharger
fans
52
Forging Operations

• Coining
• Heading
• Piercing
• Isothermal forging
• Rotary and tube swaging

53
Coining

• Closed die system
• Can produce fine detail
• Lubrication cannot be used

54
Heading

• Also called upset forging
• Care must be taken so that work piece does not
  buckle
• Can be highly automated

55
Piercing

• Used to make indentations on the surface of the
  work piece
• Force depends on the cross-sectional area of the
  punch

56
Isothermal Forging

• Also known as hot die forging
• Complex parts with good dimensional accuracy can
  be made
• It is expensive and has low production rates
• Can be economical for intricate forge designs.
• Aluminum, titanium, and other super alloys are
  typically used

57
Rotary Swaging

• Rotary swaging
• Work piece remains stationary while the dies
  rotate
• Dies strike the piece up to 20 times a second
• Dimensional tolerances are around .05 to .5m
• Suitable for medium to high production rates

58
Tube swaging

• Used to decrease the diameter of a tube with or
  without a mandrel

59
Forgeability of Metals

• - Upsetting test
• Uses 2 flat dies

60
Hot twist test

• The specimen is twisted until failure
• Done at different temperatures
• The temperature related to the maximum twists
  becomes the forging temperature.

61
Forging Defects

• Insufficient material causes laps (voids in the
  work piece)
• Excessive material causes internal cracks

62
Grain-flow pattern

• If the pattern is perpendicular to the surface,
  which is called end grains, the environment can
  attack the surface making it rough.

63
Die Design, Materials, and Lubrication

• Die design relies on the properties of the work
  piece, distortion, most importantly the knowledge
  of the material flowing to the least resistance.
• Software has helped model the forging process
• Design features
• The parting line is at the largest
  cross-sectional area
• Designed in such a way that the dies lock
  together
• Flash is limited to 3 of the greatest thickness
  of the part
• Draft angles are necessary in almost all forging
• Internal angles range from 7 to 10 degrees
• External angles range from 3 to 5 degrees
• Careful selection of radii for corners and
  fillets
• Small radii tend to wear the die and shorten its
  life

64
Die Materials and Lubrication

• General requirements
• Strength and toughness at high temperatures
• Hardenability
• Resistance to thermal and mechanical shock
• Wear resistance
• Lubrication
• Reduce friction and wear
• Act as a thermal barrier
• Act as a parting agent

65
14.7, 14.8, 14.9

• DIE FAILURES,
• FORGING MACHINES,
• AND ECONOMICS OF FORGING.

66
14.7 DIE MANUFACTURING METHODS- DIE FAILURES

• DIES, MANUFACTURING METHODS.
• DIE COSTS
• DIE FAILURES

67
MANUFACTURING METHODS

• CASTING- object formed by a mold
• FORGING- forming a hot or cold metal into a fixed
  shape by hammering, pressing or rolling
• MACHINING- To remove excess or unwanted stock by
  use of machine tools for rough or finish turning,
  boring, drilling or milling
• GRINDING- to reduce the amount of material by
  pressure or impact
• ELECTRICAL AND ELECTRO-CHEMICAL METHODS (EDM)-
  uses an electrode to create a hole or cut.
• LASERS- An intense light beam used to create a
  cut and shape material

68
DIE COSTS

• GREATLY DEPENDS ON THE SIZE
• SHAPE AND COMPLEXITY
• APPLICATION
• SURFACE FINISH
• DIE MATERIAL AND MANUFACTURING

69
DIE FAILURES

• Improper design
• Defective heat-treatment finishing operations
• Overheating and heat checking (causes cracking)
• Excessive wear
• Overloading
• Improper alignment
• Misuse of die
• Improper handling

70
14.8 FORGING MACHINES

• HYDRAULIC PRESSES
• MECHANICAL PRESSES
• SCREW PRESSES
• HAMMERS
• DROP HAMMERS
• COUNTERBLOW HAMMERS
• HIGH-ENERGY-RATE FORGING (HERF) MACHINES

71
Hydraulic and Mechanical press

• Hydraulic Press- are slower and involve higher
  initial costs, and require less maintenance. They
  consist of a frame with two or four columns,
  pistons, cylinders, rams, and hydraulic pumps
  driven by electric motors.
• Mechanical Press- are crank or centric type,
• they are stroke limited the energy is
  generated by
• a large flywheel power by an electric motor.

Left a mechanical press Right a hydraulic press
72
Principles of Various Forging Machines (cont.)
73
Screw Presses

• Screw presses- derive their energy from a
  flywheel and are energy limited. The forging load
  is transmitted by a large vertical screw, and ram
  comes to a stop when energy is used up. They are
  used for open-die and closed-die forging
  operations. Used for small production quantities
  and for thin parts.

74
Hammers, drop hammers and counterblow hammers.

• Hammers- derive their energy from the potential
  energy, which is then converted into kinetic
  energy, which makes them energy limited. To
  complete forging several successive blows are
  usually made onto the same die. They are the most
  versatile and least expensive type of forging
  equipment.
• Drop hammers- the ram is accelerated by a steam
  air or hydraulic pressure usually 750kPa.
• Couterblow hammers- This type has two rams that
  simultaneously approach each other horizontally
  or vertically to forge a part. They operate in
  high speeds and transmit less vibrations to their
  base.

75
High-energy-rate forging (HERF) machines.

• HERF machines- in this type of machine the ram is
  accelerated rapidly, by high pressures and
  gases, and parts are forged usually with one blow
  at very high speeds.
• Problems with HERFS machines- there are problem
  with maintaining such machines and operating them
  are also a hassle. Safety and die breakage are
  considerations that cause problems with HERFS and
  make them undesirable to the industry.

76
14.9 Economics of Forging

• Complexity of the forging
• Tool and die costs
• Die material
• Size of forgings

77
Works Cited

• http//www.me.gatech.edu/jonathan.colton/me4210/de
  form.html
• http//images.google.com/imgres?imgurlhttp//www-
  materials.eng.cam.ac.uk/mpsite/process_encyc/pictu
  res_for_details/forging4.jpgimgrefurlhttp//www-
  materials.eng.cam.ac.uk/mpsite/process_encyc/non-I
  E/forging.htmlh264w330sz22tbnidRzDAS5ziYax
  5NMtbnh91tbnw114hlenstart13prev/images
  3Fq3Dforging2Bflash26svnum3D1026hl3Den26lr
  3D26safe3Doff
• http//www.qcforge.com/rapidIR/
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  oducts?VID138521deframe1
• http//images.google.com/imgres?imgurlhttp//www.
  fusheng.com/precision/images/casting.jpgimgrefurl
  http//www.fusheng.com/precision/h252w320sz
  30tbnidrEG6iitNYwFdhMtbnh88tbnw113hlenst
  art69prev/images3Fq3Dprecision2Bforging26st
  art3D6026dnum3D2026svnum3D1026hl3Den26lr3
  D26safe3Doff26sa3DN

78
Works Cited

• step.polymtl.ca/coyote/ dragonlance_misc.html
  FORGING OLD MAN AND MIGET
• www.airhydraulics.com/. ../Animation.htm
  Hydraulic press.
• Kalpakjian Schmid Manufacturing Engineering and
  Technology copy 2001 Prentice-Hall page 347-395
• www.qform3d.com/ en/62.html animation for
  mechanical press
• www.farthingales.on.ca/ bone_tip_machines.html
  press and dies steel real
• www.emeraldsurgical.com/ production_tour.htm
  forging pic with red glow

79
Works Cited

• http//www.msm.cam.ac.uk/phase-trans/2002/FR.html