Phenomena in Metal Processing

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Phenomena in Metal Processing
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• Metal Processing
• Primary Processing Semi-finished Products
• Secondary Processing Shaping Processes
• Casting
• Joining (Welding, Soldering, Brazing)
• Forging/Sheet Metal Forming (Plastic Deformation)
• Heat Treatment/Surface Treatment

Solidification Processing
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2-1 Primary Processing(Integrated Steel Mill)

• Ironmaking
• Blast Furnace (BF)
• Sintering
• Coking
• Direct Iron Ore Smelting Reduction
• Steelmaking
• Basic Oxygen Furnace (BOF)
• Secondary Refining (Ladle Refining)

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Primary Processing (Mini-Mill)

• Steel making
• Electric Arc Furnace (EAF)
• AC
• DC
• Secondary Refining (Ladle Refining)

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Continuous Casting and Rolling (both Integrated
Mill and Mini-mill)

• Continuous Casting
• Tundish Metallurgy
• Continuous Casting Mold
• Slab
• Bloom
• Billet
• Thin Slab/Strip
• Rolling
• - Hot Rolling
• - Cold Rolling

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Direct Iron Ore Smelting Reduction Process (DIOS)
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Production Steps for Stainless Steel Mini-Mill
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• A useful website
• - http//steeluniversity.org

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2-2 Secondary Processing2-2-1 Casting

• Casting is the process of production of objects
  by pouring molten material in to a cavity called
  a mould which is the negative of the object, and
  allowing it to cool and solidify.

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Types of Casting Processes

• - Sand Casting
• - Permanent Mold Casting
• - Investment Casting
• - Die Casting
• - High Pressure Die Casting
• - Low Pressure Die Casting

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2-1-1 Sand Casting

• Sand casting is a means of producing rough metal
  castings using a mould usually made from sand
  formed around a replica of the object to be cast
  that is removed once the sand has been compacted.
  As the accuracy of the casting is limited by
  imperfections in the mold making process there
  will be extra material to be removed by grinding
  or machining, more than is required by other more
  accurate casting processes.

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Casting Methods

• Sand Casting
• High Temperature Alloy, Complex Geometry, Rough
  Surface Finish

• Investment Casting
• High Temperature Alloy, Complex Geometry,
  Moderately Smooth Surface Finish

• Die Casting
• High Temperature Alloy, Moderate Geometry, Smooth
  Surface

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• For the production of gray iron, ductile iron and
  steel castings, sand casting remains the most
  widely used process. For aluminum castings, sand
  casting represents about 12 of the total tonnage
  by weight (surpassed only by die casting at 57,
  and semi-permanent and permanent mold at 19
  based on 2006 shipments). The exact process and
  pattern equipment is always determined by the
  order quantities and the casting design. Sand
  casting can produce as little as one part, or as
  many as a million copies.

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Production Steps for Sand Casting

• 1. Making the pattern which includes
• - casting object
• - running system including sprue
• - riser
• - core
• -chill
• 2. Making mold flasks
• 3. Pouring
• 4. Breaking the mold

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1. Making the pattern

• From the design, provided by an engineer or
  designer, a skilled patternmaker builds a master
  of the object to be produced using wood, metal,
  plastic, or polystyrene. The metal to be cast
  will contract during solidification. Therefore,
  the pattern must be slightly larger than the
  finished product, a difference known as
  contraction allowance. Patternmakers are able to
  produce suitable patterns using 'Contraction
  rules'. Different scaled rules are used for
  different metals because different metals /
  alloys contract at different rates. Patterns also
  have coreprints these create registers within
  the moulds, into which are placed sand cores.
  Sand cores are used to create holes which cannot
  be moulded.

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Pattern (casting)
Cope drag (top and bottom halves of a sand
mould), with cores in place on the drag. The top
and bottom halves of a sand casting mould showing
the cavity prepared by patterns. Cores to
accommodate holes can be seen in the bottom
mould, the drag.
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• In the process of casting, a pattern is a replica
  of the object to be cast, used to prepare the
  cavity into which molten material will be poured
  during the casting process. The pattern needs to
  incorporate suitable shrinkage allowances, this
  is called contraction allowance, depending on the
  alloy being cast and the exact sand casting
  method being used. Some alloys will have overall
  linear shrinkage of up to 2.5, whereas other
  alloys may actually experience no shrinkage or a
  slight "positive" shrinkage or increase in size
  in the casting process (notably certain cast
  irons)/ The shrinkage amount is also dependent on
  the sand casting process employed, for example
  clay-bonded sand, chemical bonded sands, or other
  bonding materials used within the sand.

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• Pattern making is a skilled trade. Patternmakers
  learn their skills through apprenticeships and
  trade schools over many years of experience..
• Patterns used in sand casting may be made of
  wood, metal, plastics or other materials. Pattern
  are made to exacting standards of construction,
  so that they can last for a reasonable length of
  time, according to the quality grade of the
  pattern being built, and so that they will
  provide a repeatable dimensionally acceptable
  casting.

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• The patternmaker or foundry engineer decides
  where the sprues, gating systems, and risers are
  placed with respect to the pattern. Where a hole
  is desired in a casting, a cores may be used
  which defines a volume or location in a casting
  where metal will not flow into. Sometimes chills
  may be located on a pattern surface, which are
  then formed into the sand mold. Chills are heat
  sinks which enable localized rapid cooling. The
  rapid cooling may be desired to refine the grain
  structure or determine the freezing sequence of
  the molten metal which is poured into the mold.

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• Paths for the entrance of metal, during the
  pouring (casting) process into the mould cavity
  constitute the runner system and include the
  sprue, various feeders which maintain a good
  metal 'feed' and 'runners', and ingates which
  attatch the runner system to the casting cavity.
  Gas and steam generated during casting exit
  through the permeable sand or via the riser, are
  added either in the pattern itself, or as
  separate pieces.

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• Sprue (casting)
• Bronze casting showing sprue and risers

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• In foundry work, a Sprue is the passage through
  which metal is poured into a mold. Sprues can
  serve as filters, heat sinks and as feeders.
  Bronze in particular has a high shrinkage rate as
  it is cooling, a sprue can continue to provide
  molten metal to the casting, provided it is large
  enough to retain its heat and stay liquid, as
  metal in the main casting cools and shrinks. The
  design of the sprue and runner system can be also
  utilized to trap unwanted dross and sand from
  continuing into the main cavity, this may include
  adding porous material to the runners, or
  designing the sprue to eject the dross to the
  side of the sprue (cyclone effect).

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• Bronze casting showing sprue and risers (side
  view)

Bronze casting showing shrinkage in sprue/riser
(top view)
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• A riser or feeder is a reservoir built into a
  metal-casting mold to prevent cavities due to
  shrinkage. Because metals are less dense as
  liquids than as solids (with some exceptions),
  castings shrink as they cool. This can leave a
  void, generally at the last point to solidify.
  Risers prevent this by providing molten metal at
  the point of likely shrinkage, so that the cavity
  forms in the riser, not the casting.

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• This only works if the riser cools after the rest
  of the casting. Chvorinov's rule states that the
  solidification time t of molten metal is related
  to the constant C (which depends on the thermal
  properties of the mold and the material) and the
  local volume (V) and surface area (A) of the
  material, according to the relationship

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• Therefore, to ensure that the casting solidifies
  before the riser, the ratio of the volume to the
  surface area of the riser should be greater than
  that of the casting. The riser must satisfy two
  requirements it must be large enough so that it
  solidifies after the casting (i.e. satisfies
  Chvorinovs rule) and it must contain a sufficient
  volume of metal to supply the shrinkage
  contraction which occurs on cooling from the
  casting temperature to the completion of
  solidification. This latter requirement will be
  more important for platelike shapes the former
  will be more important for chunky shapes.

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• Because risers exist only to ensure the integrity
  of the casting, they are removed after the part
  has cooled, and their metal scrapped. As a
  result, riser size, number, and placement should
  be carefully planned to reduce waste while
  filling all the shrinkage in the casting.

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• Chills
• If it is desired to have most of theiron or
  steelcasting in a tough, ductile, state but with
  a few surfaces hard, it is possible to place
  metal plateschills in the mold, where the metal
  is to be hardened. The associated rapid local
  cooling will form a finer-grained and harder
  metal at these locations. The effect is similar
  to quenching metals in forge work. The inner
  diameter of an engine cylinder is made hard by a
  chilling core.

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• Cores
• To produce cavities within the castingsuch as
  for liquid cooling in engine blocks and cylinder
  headsnegative forms are used to produce cores.
  Usually sand-molded, cores are inserted into the
  casting box after removal of the pattern.
  Whenever possible, designs are made that avoid
  the use of cores, due to the additional set-up
  time and thus greater cost.

Two sets of castings (bronze and aluminium) from
the above sand mold
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2. Making the casting flasks

• A multi-part molding box (known as a casting
  flask, the top and bottom halves of which are
  known respectively as the cope and drag) is
  prepared to receive the pattern. Molding boxes
  are made in segments that may be latched to each
  other and to end closures. For a simple
  objectflat on one sidethe lower portion of the
  box, will be filled with prepared casting sand or
  green sanda slightly moist mixture of sand and
  clay. The sand is packed in through a vibratory
  process called ramming and, in this case,
  periodically screeded level.

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• The pattern is placed on the sand and another
  molding box segment is added. Additional sand is
  rammed over and around the pattern. Finally a
  cover is placed on the box and it is turned and
  unlatched, so that the halves of the mold may be
  parted and the pattern with its sprue and vent
  patterns removed. Any defects introduced by the
  removal of the pattern are corrected. The box is
  closed again. This forms a "green" mold which
  must be dried to receive the hot metal. If the
  mold is not sufficiently dried a steam explosion
  can occur that can throw molten metal about. In
  some cases, the sand may be oiled instead of
  moistened, which makes possible casting without
  waiting for the sand to dry. Sand may also be
  bonded by chemical binders, such as furane resins
  or amine-hardened resins.

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3. Pouring the Casting

• With a completed mold at the appropriate moisture
  content, the box containing the sand mold is then
  positioned for filling with molten
  metaltypically iron, steel, bronze, brass,
  aluminum alloy, or various pot metal alloys,
  which often include lead, tin, and zinc. After
  filling with liquid metal the box is set aside
  until the metal is sufficiently cool to be
  strong. The sand is then removed revealing a
  rough casting that, in the case of iron or steel,
  may still be glowing red. When casting with
  metals like iron or lead, which are significantly
  heavier than the casting sand, the casting flask
  is often covered with a heavy plate to prevent a
  problem known as floating the mold. Floating the
  mold occurs when the pressure of the metal pushes
  the sand above the mold cavity out of shape,
  causing the casting to fail.

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4. Breaking the casting mold

• After casting, the cores are broken up by rods or
  shot and removed from the casting. The metal from
  the sprue and risers is cut from the rough
  casting. Various heat treatments may be applied
  to relieve stresses from the initial cooling and
  to add hardnessin the case of steel or iron, by
  quenching in water or oil. The casting may be
  further strengthened by surface compression
  treatmentlike shot peeningthat adds resistance
  to tensile cracking and smooths the rough
  surface.

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• 5. Design requirements
• The part to be made and its pattern must be
  designed to accommodate each stage of the
  process, as it must be possible to remove the
  pattern without disturbing the molding sand and
  to have proper locations to receive and position
  the cores. A slight taper, known as draft, must
  be used on surfaces perpendicular to the parting
  line, in order to be able to remove the pattern
  from the mold. This requirement also applies to
  cores, as they must be removed from the core box
  in which they are formed.

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• The sprue and risers must be arranged to allow a
  proper flow of metal and gasses within the mold
  in order to avoid an incomplete casting. Should a
  piece of core or mold become dislodged it may be
  embedded in the final casting, forming a sand
  pit, which may render the casting unusable. Gas
  pockets can cause internal voids. These may be
  immediately visible or may only be revealed after
  extensive machining has been performed. For
  critical applications, non-destructive testing
  methods may be applied before further work is
  performed.

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• 2-1-2 Die Casting
• For the casting of low melting point metals (such
  as zinc alloy pot metal, lead, aluminum, or
  magnesium), a multipart die is used in a process
  called die casting. For automotive parts such as
  the cases of automatic transmissions these dies
  may be quite complex, as they must be
  dissasembled in specific order to ensure that the
  workpiece is released freely from the casting
  die. Parts or products produced by this method
  are referred to as die cast. Compared to lost wax
  casting the marginal production can be quite
  cheap, once the substantial investment in tooling
  and materials handling equipment is made.

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• Compared to sand casting the die casting method
  can reproduce fine details on complex parts and
  yield a smooth surface, greatly reducing
  machining and polishing requirements. As some
  small portion of metal may leak between the
  mating seams of the die this can result in a
  sharp edge of metal called flash, which must be
  removed by grinding and buffing.

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2-2 Plastic Deformation 2-2-1 Forging

• Forging is the working of metal by plastic
  deformation. It is distinguished from machining,
  the shaping of metal by removing material, such
  as by drilling, sawing, milling, turning or
  grinding, and from casting, wherein metal in its
  molten state is poured into a mold, whose form it
  retains on solidifying. The processes of rolling,
  drawing and upsetting are essentially forging
  operations although they are not commonly so
  called because of the special techniques and
  tooling they require.

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• Forging results in metal that is stronger than
  cast or machined metal parts. This is because
  during forging the metal's grain flow changes in
  to the shape of the part, making it stronger.
  Some modern parts require a specific grain flow
  to ensure the strength and reliability of the
  part.

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• Scan of sectioned, forged connecting rod that has
  been etched to show grain flow.

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• Many metals are forged cold, but iron and its
  alloys are almost always forged hot. This is for
  two reasons first, if work hardening were
  allowed to progress, hard materials such as iron
  and steel would become extremely difficult to
  work with secondly, most steel alloys can be
  hardened by heat treatments, such as by the
  formation of martensite, rather than cold
  forging. Alloys that are amenable to
  precipitation hardening, such as most structural
  alloys of aluminium and titanium, can also be
  forged hot, then made strong once they achieve
  their final shape. Other materials must be
  strengthened by the forging process itself.

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• Forging was done historically by a smith using
  hammer and anvil. In industry a distinction is
  made between open- and closed-die forging. In
  open-die work the metal is free to move except
  where contacted by the hammer, anvil, or other
  (often hand-held) tooling. In closed-die work the
  material is placed in a die resembling a mold,
  which it is forced to fill by the application of
  pressure. Many common objects, like wrenches and
  crankshafts, are produced by closed-die forging,
  which is well suited to mass production. Open-die
  forging lends itself to short runs and is
  appropriate for art smithing and custom work.

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• Closed-die forging is more expensive for mass
  production than is casting, but produces a much
  stronger part, and is used for tools, high
  strength machine parts and the like. Forgings are
  commonly used in automotive applications, where
  high strength is demanded, with a constraint on
  the mass of the part (high strength-to-mass
  ratio). Forged parts are more suitable for mass
  production. The process of forging a part becomes
  cheaper with higher volumes. For these reasons
  forgings are used in the automotive industry,
  usually after some machining. One particular
  variant, drop forging, is often used to mass
  produce flat wrenches and other household tools.

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Drop Forge
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• Drop forging
• The workpiece, say a wrench, is created by
  hammering a piece of hot metal into an
  appropriately shaped die. The metal (in an easily
  produced shape like a rod or brick) is heated and
  placed on the bottom part of a die. The top part
  of the die then drops onto the piece, which gives
  the forge its name. The die may drop under
  gravity or be powered, but in all cases drop
  forging involves impact. The force of the impact
  causes the heated metal to flow into the shape of
  the die, with some metal squirting out of the
  thin seams between the dies. This thin metal is
  called "flash" and is cut away in the next stage
  of processing. The drop-forged pieces usually
  need further processing, like machining and
  polishing of working surfaces, to provide tighter
  tolerances than forging alone can provide, and to
  produce a good finish.

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• Hydraulic press forge
• In hydraulic press forging the work piece is
  pressed between the two die halves with gradually
  increasing force, over a period of a few seconds.
  The quality of the pieces is better than drop
  forging as there is more control over metal flow,
  but takes longer and requires more energy. It
  also makes the same shape continuously.

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2-2-2 Stamping Stamping Die
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• Progressive die with strip and punchings
• A progressive stamping die ("die") is a
  metalworking device that is designed and built to
  convert a strip of metal raw material into parts
  that conform to blueprint specifications.
•  

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• The "dies" are placed into a stamping press. As
  the stamping press moves up, the die opens. As
  the stamping press moves down, the die closes.
  The raw material (metal) moves through the die
  while the die is open, being fed into the die a
  precise amount with each stroke of the press.
  When the die closes, the die performs its work on
  the metal and one or more finished parts are
  ejected (usually by gravity) from the die. The
  stamping die can modify the raw material in
  several ways, such as bending, coining, and
  punching. Holes that are cut into the raw
  material can be almost any shape.
•  

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• Progressive die with strip and punchings
• A progressive stamping die ("die") is a
  metalworking device that is designed and built to
  convert a strip of metal raw material into parts
  that conform to blueprint specifications.
• The "dies" are placed into a stamping press. As
  the stamping press moves up, the die opens. As
  the stamping press moves down, the die closes.
  The raw material (metal) moves through the die
  while the die is open, being fed into the die a
  precise amount with each stroke of the press.
  When the die closes, the die performs its work on
  the metal and one or more finished parts are
  ejected (usually by gravity) from the die. The
  stamping die can modify the raw material in
  several ways, such as bending, coining, and
  punching. Holes that are cut into the raw
  material can be almost any shape.
• Since additional work is done in each "station"
  of the die, it is important that the strip be
  advanced very precisely so that it aligns within
  a few thousandths of an inch as it moves from
  station to station. Bullet shaped or conical
  "pilots" enter previously pierced round holes in
  the strip to assure this alignment since the
  feeding mechanism usually cannot provide the
  necessary precision in feed length.
• The key components of dies are made of tool steel
  to withstand the high shock loading involved,
  retain the necessary sharp cutting edge, and
  resist the abrasive forces involved.
• An excellent example of the product of a
  progressive die is the lid of a beer or soft
  drink can. The pull tab is made in one
  progressive die and then automatically mated to
  the lid which is made in another progressive die.
•  

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• Since additional work is done in each "station"
  of the die, it is important that the strip be
  advanced very precisely so that it aligns within
  a few thousandths of an inch as it moves from
  station to station. Bullet shaped or conical
  "pilots" enter previously pierced round holes in
  the strip to assure this alignment since the
  feeding mechanism usually cannot provide the
  necessary precision in feed length.
•  

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• The key components of dies are made of tool steel
  to withstand the high shock loading involved,
  retain the necessary sharp cutting edge, and
  resist the abrasive forces involved.
• An excellent example of the product of a
  progressive die is the lid of a beer or soft
  drink can. The pull tab is made in one
  progressive die and then automatically mated to
  the lid which is made in another progressive die.
•  

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• 2-2-3 Hydroforming

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• Hydroforming (or hydramolding) is a
  cost-effective way of shaping malleable metals
  such as aluminum into lightweight, structurally
  stiff and strong pieces. One of the largest
  applications of hydroforming is the automotive
  industry, which makes use of the complex shapes
  possible by hydroforming to produce stronger,
  lighter, and more rigid unibody structures for
  vehicles. This technique is particularly popular
  with the high-end sports car industry and is also
  frequently employed in the shaping of aluminium
  tubes for bicycle frames.

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• Hydroforming is a specialized type of die forming
  that uses a high pressure hydraulic fluid to
  press room temperature working material into a
  die. To hydroform aluminum into a vehicle's frame
  rail, a hollow tube of aluminum is placed inside
  a negative mold that has the shape of the desired
  end result. High pressure hydraulic pistons then
  inject a fluid at very high pressure inside the
  aluminum which causes it to expand until it
  matches the mold. The hydroformed aluminum is
  then removed from the mold.

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• Hydroforming allows complex shapes with
  concavities to be formed, which would be
  difficult or impossible with standard solid die
  stamping. Hydroformed parts can often be made
  with a higher stiffness to weight ratio and at a
  lower per unit cost than traditional stamped or
  stamped and welded parts.
• This process is based on the 1950s patent for
  hydromolding by Milton Garvin of the Schaible
  Company of Cincinnati, OH.

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Tubular Hydroforming Technology
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?Characteristics of Tubular Hydrofomring
Manufacturing Technology
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?Tubular Hydroforming Applications in Various
Vehicle Systems
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Exhaust systems 2 Hydroformed components
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Tube Hydroforming
Sheet Hydroforming
Process Simulation (Pamstamp)
Hydroforming Technology
130Ton Hydraulic Press
2000Ton Hydroforming Press
?Closing Force 130 Ton?Stroke 350mm
? Closing Force 2,000Ton?Internal Pressure
4000bar(Max.)?Axial Force150Ton
International Cooperation ?Japan Yamamoto
Suiatu Kogyosho Co.
Promotion Strategy?RD Alliance of Tubular
Hydroforming for Automobile Parts?Application
Industries Automobile, Motorcycle, Bicycle,
Pipe Tube, Petro-Chemical
Industrial Benefit?To assist equipment locally
manufactured?To assist Innovative application of
tubular hydroforming technology in the bicycle
industry ?Technology transfer Giant,King Lai...
Technology Establishment?Tubular Formability
Analysis -Bulging Test Forming Limit
Diagram?Tubular Hydroforming Simulation ?Tubular
Hydroforming Manufacturing Process and Mold
Design Technology