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WO2003037550A1 - Moulage sous pression a faible vitesse - Google Patents

Moulage sous pression a faible vitesse Download PDF

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Publication number
WO2003037550A1
WO2003037550A1 PCT/US2002/034226 US0234226W WO03037550A1 WO 2003037550 A1 WO2003037550 A1 WO 2003037550A1 US 0234226 W US0234226 W US 0234226W WO 03037550 A1 WO03037550 A1 WO 03037550A1
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WO
WIPO (PCT)
Prior art keywords
molten metal
die
casting
temperature
metal
Prior art date
Application number
PCT/US2002/034226
Other languages
English (en)
Inventor
Samuel Michael Dan Norville
Original Assignee
Taylor's Industrial Services Llc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Taylor's Industrial Services Llc filed Critical Taylor's Industrial Services Llc
Publication of WO2003037550A1 publication Critical patent/WO2003037550A1/fr

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D17/00—Pressure die casting or injection die casting, i.e. casting in which the metal is forced into a mould under high pressure
    • B22D17/20—Accessories: Details
    • B22D17/30—Accessories for supplying molten metal, e.g. in rations
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D17/00—Pressure die casting or injection die casting, i.e. casting in which the metal is forced into a mould under high pressure
    • B22D17/20—Accessories: Details
    • B22D17/32—Controlling equipment

Definitions

  • This invention relates generally to systems and methods for die-casting and, more particularly, to a system and method for low- velocity die-casting.
  • the two processes which have already met some target production needs and, as their technologies develop, will continue to expand their applications are squeeze casting and semi-solid metal casting (SSM).
  • FILL the actual filling of the cavity is accomplished at a wide range of speeds; however, tight control to avoid turbulence is essential.
  • TURBULENCE Both processes are designed to achieve minimum porosity and oxides; therefore, turbulence is to be avoided at all costs.
  • PRESSURE Through the use of hydraulic mechanisms, pressures in excess of 20 MPA and as high as 175 MPA (equipment dependent) are applied to the material in the die cavity.
  • SOLUTION TREATMENT The majority of parts produced by these two processes are heat treated to maximize their mechanical properties and fatigue life. This secondary processing requires the highest internal integrity in the high pressure casting.
  • Squeeze casting is a term commonly used today to refer to any process in which liquid alloy is cast without turbulence and gas entrapment and subsequently held at high pressure throughout the freezing cycle to yield high quality heat treatable components.
  • Squeeze casting originally was developed as a liquid forging process in which liquid metal was poured into the lower half of a vertically oriented die set and subsequently closed die forged (now termed "direct squeeze casting').
  • direct squeeze casting' now several "indirect” approaches involving injection of metal into a cavity via massive gates, which allow adequate feeding of solidification shrinkage while the casting freezes.
  • squeeze casting almost universally relates to a process utilizing a runner and gating system.
  • Squeeze castings are made on machines and in steel tooling that are, in many respects, like those employed in conventional die casting. Machines and dies are very robust and capable of containing very high molten metal pressures without deflecting or losing dimensional control. Squeeze casting machines and tools are designed to introduce clean molten metal into the tool in a precise, repeatable, controlled flow pattern, filling the cavity quickly but without turbulence.
  • SSM casting differs from squeeze casting in that it uses a unique "semi-solid" material.
  • SSM casting begins with a semi-solid mass of metal processed in such a way that the solid portion is in the form of "globules" allowing a free flowing but viscous fluid behavior.
  • the principal difference is that the higher viscosity semi-solid metal allows higher metal velocities to be implemented before the onset of turbulence and, of course, the metal is already partially solidified at the time of casting.
  • the SSM microstructure has far superior flow characteristics when compared to a particularly solidified dendritic structure.
  • Specially cast billets produced on continuous casting systems, equipped with one of several types of electromagnetic stirrers, are currently the most common solid feedstock processing a very uniform fine grained but essentially equiaxed dendritic microstructure. After cutting to length for a prescribed shot weight (slug), these slugs are then heated to the semi-solid temperature range and cast. During heating, the fine grained billet microstructure becomes globular.
  • SSM manufacturing process apply either a self-supporting slug that is 50-75% solid (globular structure) in the injection chamber of the die cast machine or a slurry that is 40-60% solid having the approximate consistency of peanut butter.
  • liquid metal can be poured into the injection chamber (shot sleeve) and electrical energy used to transform the dendritic structure into a semi-solid globular structure.
  • a mechanical robot can be used to transfer the slug to a slot in the shot sleeve.
  • a plunger advances to inject the semi-solid alloy into the die cavity and the material flows uniformly as a semi-solid mixture.
  • Billets continuously cast, using electromagnetic stirrers, are the popular feedstock for the SSM casting process. They are produced using all the standard techniques to control and monitor metal chemistry, cleanliness, grain size, gas content and microstructure, such that they represent a high quality incoming raw material. Other methods for continuously casting feed stock utilize artificial grain refinement instead of electromagnetic stirring to create very fine grains and are suitable for certain alloys, especially those having low silicon contents.
  • slugs For SSM casting, slugs must be heated to the semi-solid condition.
  • AISi7Mg A356
  • a temperature around 580°C (1080°F) corresponds to approximately 55 percent solid and 45 percent liquid. At this point, essentially all of the eutectic portion of the alloy is liquid.
  • SSM casters are utilizing both horizontal and vertical injection systems, although horizontal injection is the more common. SSM casters often, in fact, use horizontal die casting machines fitted with precisely controlled injection units, which provide the control necessary to avoid turbulence during injection of the semi- solid metal into the cavity. As with squeeze casting, the metal is fed to the cavity through relatively massive runners and gates, which provide paths for the liquid fraction to be fed into the cavity to feed solidification shrinkage.
  • the present invention in one embodiment involves a system and a method for low-velocity die-casting.
  • the casting process of this invention focuses on the existing die-casting applications while offering benefits heretofore not , available in die-casting.
  • the benefits that the users receive from this process include longer tool life (up to 5 times).
  • the tool cost for an aluminum component is very substantial from a cost break down analysis; therefore, extending the tool life is a significant advantage.
  • the other major benefit is better part quality (i.e., less internal porosity and better dimensional capability).
  • the process utilizes molten metal at the die cast machine.
  • This invention is distinguishable from semi-solid molding or forming due in large part to the use of molten metal.
  • SSM is universally understood as being a casting process which begins with a semi-solid mass of material, typically 50% - 60% solid and 40% - 50% liquid slugs which are self- supporting and stiff enough to retain their shape.
  • the die casting technology according to this invention utilizes molten (100% liquid) metal as input to the die casting machine.
  • the molten metal is not self-supporting nor is it a semi-solid material.
  • the ladle operation that delivers the molten metal to the injection chamber is another primary feature of this invention.
  • Known furnaces that hold the molten metal at the die cast machine typically have an operating range of +/- 10 degrees F.
  • a controller is utilized that communicates with the furnace thermocouple and the ladle (delivery system).
  • the temperature of the molten metal is controlled within +/- 1 degree F. This is very important for the next step in the operation. Introducing the molten metal to the injection chamber of the die cast machine at a controlled temperature allows the next step of the operation to be fixed.
  • the ladle cup pour speed is also important. When the molten metal is poured from the ladle cup to the injection chamber, there is a temperature loss. By controlling the temperature curve of the metal during pouring, the alpha grains form very small crystals, which will grow over time.
  • MMC metal matrix composite
  • Fig. 1 is a front elevational view, partly in cross section, of the shot mechanism for an exemplary side gate version of a die casting machine according to one embodiment of the present invention
  • Fig. 2 is an enlarged elevational, sectional view showing the shot injector of an exemplary die casting machine according to one embodiment of this invention with the shot sleeve partially filled with molten metal and the shot plunger moving forward on its injection stroke;
  • Figs. 3-4 are elevational and plan views, respectively, of an example of a part, such as an automobile wheel, which is produced in the die-casting machine of Fig. 1 according to this invention.
  • Die casting machines generally include stationary front and back plates and a movable or traveling plate which is reciprocally mounted between the two stationary plates. The relative positions of the stationary plates are maintained by a number of tie bars which extend between the two stationary plates. Die halves are fastened to the front plate and the traveling plate, respectively, and the traveling plate is extended and retracted to respectively close and open the die. After the die is closed, molten metal is injected into the die to form a die cast part. After a part is thus formed, the die is opened by retracting the traveling die and, after the traveling plate has moved a predetermined distance, bumper pins are commonly used which are slidably mounted in apertures located both in the die and the traveling plate engage a bumper plate which is located behind the traveling plate.
  • Fig. 1 there is shown a perspective view of the die casting system 8 according to the present invention. Examples of die-casting machines which could be utilized with this invention are shown in U.S. Patent Nos. 4,362,205 and 4,886,106, each of which are hereby incorporated by reference.
  • Machine 10 includes a frame 12 on which are mounted stationary plates 14 and 18 with a movable plate 16 therebetween. Plates 14 and 18 are secured together by tie rods 24 and plate 16 is movable between plates 14, 18 on the tie rods
  • a metal melter or furnace 30 is provided for melting the die cast metal 20.
  • the die casting metal 20 may be any suitable metal such as high purity aluminum but may also be other suitable alloys.
  • the molten metal 20 is transferred by a ladle 22 or other appropriate mechanism/system from the melter 30 over a travel path shown by arrow
  • the ladle 22 has the capability of regulating, maintaining and/or adjusting the temperature of the metal 20 contained therein.
  • Ladle systems compatible with this invention are commercially available from E-Jay Thermo Products of South Haven, Michigan.
  • the ladle 22 may include a thermocouple for temperature control and/or to wick heat away at a pre-determined rate.
  • a shot cylinder 36 is provided to move the charge of molten metal 20 from the cold chamber 34 into the die cavity.
  • a hydraulic power unit 38 provides the movement for the shot cylinder 36 as is understood in this art.
  • a runner cavity or sprue cavity (not shown) is provided into which the hot molten metal 20 is transferred by the shot cylinder 36 from the cold chamber 34. The hot molten metal 20 then is forced into the die cavity as is common for die-casting operations.
  • Figs. 1 and 2 it can further be seen that the cold chamber sleeve 34 which extends through aperture 38 in stationery plate 18 has been supplied with hot molten metal 20 from the ladle 22 so that the stationary shot cylinder 36 is now in position to move shot rod 40 toward the left whereby the hot molten metal 20 is forced through the runner system in die plate 42 and into the die cavity (not shown).
  • the ladle 22 pours the molten metal 20 downwardly through fill passage 32 into shot sleeve 34 wherein it forms a pool 44.
  • Fill passage 32 is formed adjacent stationary plate 18 and shot sleeve 34.
  • the shot is injected by plunger 36 received within shot sleeve 34 and actuated by a cylinder rod 40.
  • Plunger 36 moves forward at slow speed to gradually fill the shot sleeve 34 with the molten aluminum 20, which will occur sometime after plunger 36 clears the opening 46 in fill passage 32.
  • the plunger 36 moves at a rate of about 10 inches/second until it passes the opening 46 according to this invention.
  • plunger 36 will continue to be advanced at a relatively low speed to inject the molten aluminum through the passage into the die chambers.
  • the plunger 36 moves at a rate of about 15 to about 30 inches/second after it passes the opening 46. This rate is significantly slower than the 80 to 130 inches/second typical of the prior art.
  • a controller 28 is utilized that communicates with the furnace
  • thermocouple and the ladle delivery system 22 thermocouple and the ladle delivery system 22.
  • the temperature of the molten metal 20 is controlled within +/- 1 degree F at the furnace 30, through the delivery by the ladle 22 to the shot sleeve 34. This is very important for the next step in the operation. Introducing the molten metal 20 to the shot sleeve 34 of the die cast machine 10 at a controlled temperature allows the next step of the operation to be fixed.
  • the ladle 22 pour speed of th metal 20 is also important.
  • the temperature curve of the metal 20 during pouring the alpha grains form very small crystals, which will grow over time. This keeps the dendritic formation of the microstructure from being created and allows the metal 20 to easily flow into the die chamber.
  • the small grains have been formed from the pouring operation to solidification of the molten metal, a very homogenous microstructure is produced and higher mechanical properties than dendritic microstructure are provided.
  • This formation of the grains allows for the use of many different alloys as well as a metal matrix composite (MMC) to be introduced into the ladle 22 during the temperature control wait time. Therefore, the pour rate of metal 20 into the shot sleeve 34 is a function of the temperature of the metal 20 in the ladle 22. In this way, very small alpha grain crystals are formed.
  • the pour rate of the metal 20 is adjusted by the controller 28 as a function of the metal temperature.
  • FIG. 3-4 an example of a finished part which can be die-cast in accordance with this invention is a wheel generally identified by the numeral 110 is shown in Figs. 3 and 4.
  • the wheel 110 contains a number of roughly rectangular contours 111 around the periphery, each of the contours containing a punched or machined hole
  • a hub area 113 contains four cored and tapped holes 114 and four larger punched or machined holes 115.
  • a wheel configuration of this complexity is normally readily produced by die casting techniques and is accordingly appropriate for manufacture according to this invention.
  • the wheels 110 made according to this invention have the very important capability of being lighter in weight than comparable wheels of the prior art.
  • Representative alloys useful in this die-casting process are, in addition to aluminum alloys, ferrous alloys such as the stainless steels, tool steels, low alloy steels and irons and copper alloys of the type normally used in castings and forgings.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Molds, Cores, And Manufacturing Methods Thereof (AREA)

Abstract

L'invention concerne un procédé de moulage fondé sur des applications de moulage sous pression existantes et apportant des améliorations à celles-ci. On peut citer parmi les améliorations dont les utilisateurs du procédé bénéficient : une plus longue durée de vie des outils (jusqu'à 5 fois plus longue), l'amélioration principale permettant d'obtenir une meilleure qualité de partie (par exemple, moins de porosité interne et une capacité dimensionnelle améliorée). Le procédé consiste à utiliser un métal (20) fondu au niveau d'une machine de moulage sous pression. L'utilisation de métal (20) fondu ou de métal complètement liquide permet notamment de distinguer le procédé selon l'invention de moulage ou formation à l'état semi-solide. Le procédé selon l'invention est caractérisé en ce qu'il comprend une opération de poche (22) amenant le métal fondu (20) dans la chambre d'injection (34) et en ce qu'une unité de commande (28) est utilisée pour communiquer avec le four (30) et le système d'amenée sous forme de poche (22), aux fins de régulation de la température du métal (20) fondu et de la vitesse d'écoulement.
PCT/US2002/034226 2001-10-26 2002-10-25 Moulage sous pression a faible vitesse WO2003037550A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US33065101P 2001-10-26 2001-10-26
US60/330,651 2001-10-26

Publications (1)

Publication Number Publication Date
WO2003037550A1 true WO2003037550A1 (fr) 2003-05-08

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Application Number Title Priority Date Filing Date
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US (1) US20030226651A1 (fr)
WO (1) WO2003037550A1 (fr)

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4834166A (en) * 1986-01-10 1989-05-30 Akio Nakano Die casting machine

Family Cites Families (15)

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Publication number Priority date Publication date Assignee Title
US4771818A (en) * 1979-12-14 1988-09-20 Alumax Inc. Process of shaping a metal alloy product
US4362205A (en) * 1981-02-02 1982-12-07 Hpm Corporation Rotor die casting method
US4607682A (en) * 1981-08-03 1986-08-26 Alumax, Inc. Mold for use in metal or metal alloy casting systems
US4709746A (en) * 1982-06-01 1987-12-01 Alumax, Inc. Process and apparatus for continuous slurry casting
US4569218A (en) * 1983-07-12 1986-02-11 Alumax, Inc. Apparatus and process for producing shaped metal parts
US4687042A (en) * 1986-07-23 1987-08-18 Alumax, Inc. Method of producing shaped metal parts
US4712413A (en) * 1986-09-22 1987-12-15 Alumax, Inc. Billet heating process
US4886106A (en) * 1986-12-09 1989-12-12 Hpm Corporation Die cast machine with a turret
US5388633A (en) * 1992-02-13 1995-02-14 The Dow Chemical Company Method and apparatus for charging metal to a die cast
JP2994511B2 (ja) * 1992-03-12 1999-12-27 東芝機械株式会社 ダイカストマシンの射出速度制御方法
JP2001049376A (ja) * 1999-05-12 2001-02-20 Daiki Aluminium Industry Co Ltd 高強度加圧鋳造用アルミニウム合金及び同アルミニウム合金鋳物
JP3808264B2 (ja) * 2000-01-19 2006-08-09 日本軽金属株式会社 塑性加工されたアルミニウム合金鋳物，アルミニウム合金鋳物の製造方法及び塑性変形を利用した締結方法
US6432160B1 (en) * 2000-06-01 2002-08-13 Aemp Corporation Method and apparatus for making a thixotropic metal slurry
US6399017B1 (en) * 2000-06-01 2002-06-04 Aemp Corporation Method and apparatus for containing and ejecting a thixotropic metal slurry
US6402367B1 (en) * 2000-06-01 2002-06-11 Aemp Corporation Method and apparatus for magnetically stirring a thixotropic metal slurry

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4834166A (en) * 1986-01-10 1989-05-30 Akio Nakano Die casting machine

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