US3495649A - Method of continuous casting an alloy having a two phase region during cooling - Google Patents

Method of continuous casting an alloy having a two phase region during cooling Download PDF

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US3495649A
US3495649A US580255A US3495649DA US3495649A US 3495649 A US3495649 A US 3495649A US 580255 A US580255 A US 580255A US 3495649D A US3495649D A US 3495649DA US 3495649 A US3495649 A US 3495649A
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lead
casting
alloy
temperature
phase
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US580255A
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Thomas Daniel Waters
Martin Edward Malam
Andrew Rutledge Robertson
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Federal Mogul Engineering Ltd
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Glacier Metal Co Ltd
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths

Definitions

  • ABSTRACT OF THE DISCLOSURE Continuously casting an alloy which exhibits, on cooling, a transition from a single homogeneous phase to a two phase liquid region to be cast, the casting is commenced in a vertical direction at a temperature high enough for the alloy to remain as a homogeneous liquid phase with a minimum casting temperature isothermal lying substantially within the upstream end of a casting die.
  • This invention relates to a method of casting, by continuous or semi continuous means, alloys of the kind that exhibit on cooling a transition from a single homogeneous phase to a two phase liquid region to be cast, with a uniform or controlled non-uniform dispersion of one phase within the other in the solid state.
  • an article of manufacture produced by the method and in particular but not exclusively to plain bearing material from which a bearing can be fabricated.
  • plain bearing is to be understood as including any member or assembly having, or designed to have in use, a surface which bears directly or through a liquid or solid lubricant against another surface relatively to which it has sliding movement, irrespective of whether the main or sole purpose is to transmit a load from one to the other of the surfaces having relative sliding movement or whether the sliding contact is solely or partly for some other purpose such, for example, as to provide a seal or to make electrical contact.
  • Alloys of the kind defined for example aluminium/ lead and aluminium/cadmium, are particularly advantageous as plain bearing materials.
  • the term lead used herein is to be understood as including not only lead in substantially pure state but also lead alloys embodying for exexample, tin, indium, antimony or other alloying elements giving to the lead corrosion resisting or other desirable characteristics.
  • the lead may contain up to 20% of its weight of tin or antimony or up to 10% of its weight of indium.
  • aluminium used herein is to be understood as including not only substantially pure aluminium but also aluminium with the impurities normally found in commercial aluminium, as well as aluminium alloys containing alloying elements such as copper, nickel, manganese, silicon, magnesium or the like for strengthening purposes.
  • minimum casting temperature when used in this specification refers to the minimum temperature at which the alloy under equilibrium cooling conditions exhibits a single homogeneous liquid phase. Further reduction in temperature below the minimum casting temperature under equilibrium cooling conditions, produces two immiscible liquid phases.
  • the minimum casting temperature isothermal indicates a boundary in the molten metal at which transition from the single homogeneous phase to a double immiscible phase condition is commencing.
  • the major difiiculty in casting alloys of the kind defined above with a uniform dispersion of one phase within the other in the solid state is in overcoming or reducing the effectsof their tendency to gross gravity segregation on cooling through the two liquid phase temperature range.
  • gravity segregation refers to a condition of non-uniform dispersion (on a microscopic scale) of one phase within the other in the solid state resulting from relative movement of said liquid phases to one another in a vertical direction under the influence of gravitational forces.
  • a method of continuously casting alloys of the kind defined includes commencing to cast the alloy in a vertical direction at a temperature high enough for the alloy to remain as a homogeneous liquid phase and casting under controlled casting conditions so that the minimum casting temperature isothermal as hereinbefore defined lies substantially within the upstream end of a die, whereby an approach to a uniform or controlled non-uniform dispersion of one phase within the other is obtained.
  • the temperature before commencing casting may be such that the alloy remains as a single homogeneous liquid phase in a feeder or tundish and in this case the minimum casting temperature isothermal will not extend into the tundish but will lie substantially wholly in the mouth of an opening from the tundish (or in the mouth of the tundish when the tundish mouth and the dies have the same internal dimensions) whereby the effects of gravity segregation are substantially reduced.
  • the tundish temperature may be maintained at not less than ll00 C.
  • the temperature in the tundish may be maintained at not less than 950 C.
  • the method of continuous casting may be vertical or horizontal and the alloy may be cast directly onto a bearing backing mate rial.
  • the temperature of the alloy in the die may be reduced by the order of 450 C. for a 20% by weight lead-aluminium alloy and by the order of 300 C. for a 10% by weight lead aluminium alloy. On emergence from the die the alloy may be partially or wholly solid.
  • the die may be of graphite and of sufficient length in the direction of casting as to enable heat extraction to cause solidification of the alloy.
  • An apparatus for the continuous casting of aluminium lead including a tundish provided with heating means for maintaining aluminium lead above the minimum temperature at which it exists as a homogeneous liquid, a die opening from the tundish and cooling means surrounding the die.
  • the temperature of the alloy is reduced while it is in the die by a temperature of the order of l5%50% of the minimum casting temperature while the minimum casting temperature isothermal lies wholly within the upstream opening into the die from the tundish.
  • a further aspect of the invention provides an aluminium lead bearing material having up to 50% by weight of lead produced by a continuous or semi-continuous casting process as defined, or in apparatus as defined.
  • the apparatus may be a horizontal casting apparatus or a vertical casting apparatus and in either case the casting of aluminium lead may be carried out directly onto a metal backing so as to provide a strip of material from which bimetallic bearings can be fabricated.
  • a non-uniform distribution of a secondary phase within a primary phase may in some instances be desirable and control over the distribution of this secondary phase in a lateral plane is possible by varying the shape of the die and/ or tundish and their position relative to the minimum casting temperature isothermal.
  • the projected area of the plane at which the minimum casting temperature isothermal exists in relation to the projected area of the die at the primary solidification front, it is possible to control closely the distribution of the secondary phase within the primary phase in a non-uniform manner.
  • FIGURE 1 shows a graph correlating the minimum casting temperature and the weight percentage of lead in the aluminium
  • FIGURE 2 shows a diagram of an apparatus for carrying out the method according to the invention in connection with vertical casting
  • FIGURE 3 shows a diagram for an apparatus for carrying out the invention in connection with horizontal casting direct onto a meal backing strip
  • FIG. 4A, FIG. 4B, FIG. 4C, FIG. 4D, and FIG. 4B show various shapes or die which produce difference forms of phase distribution in the cast product.
  • FIGURE 5 shows a casting apparatus for an alloy in which the constituent of higher specific gravity predominates over the constituent of lower specific gravity.
  • the temperature at which the molten alloy is maintained is above a curve A, aluminium and lead will exist as a homogeneous single liquid phase.
  • the curve A is the minimum casting temperature curve plotted for various percentages of lead in the alloy.
  • the actual casting temperatures or the temperature at which the alloy is maintained in the tundish should be approximately 40 C. above the minimum casting temperature in order to ensure that fluctuations in operating conditions do not move the minimum casting temperature isothermal beyond the position limits.
  • the primary solidification temperature at which solidification commences is shown at B and the secondary solidification temperature at which solidification is complete is shown at C.
  • the lines shown in FIGURE 1 represent alloy with more aluminium than lead.
  • the rate of heat extraction, speed of casting, and length of die 3 are regulated such that the minimum casting temperature isothermal A is maintained wholly within the confines of the die and the primary solidification from B is so disposed relative to the lower end of the die that the cast product can be satisfactorily withdrawn.
  • Subsidiary water sprays may be employed to facilitate the requisite heat extraction from the cast product.
  • the progressive precipitation of the lead-rich phase previously described occurs with three major factors influencing the relative distribution of the two phases. Firstly, equilibrium cooling conditions may not be attained when continuously casting: secondly, the lead-rich phase once precipitated will fall through the less dense aluminium-rich liquid phase under the influence of gravitational forces; and finally the geometry of the die and friction between the molten metal and the die wall will interfere with the flow pattern.
  • the maximum rate of fall of the lead-rich phase through the aluminium-rich phase depends on the size and shape of the lead particles and also the total time interval between the initial precipitation of those particles and their subsequent incorporation in the solidifying aluminiumrich phase at the primary solidification front.
  • the relative velocity between the phases increases up to a maximum with increase in time after initial precipitation, and with increase in size of the precipitate. (The maximum relative velocity between phases may not be achieved in practice, as this depends on the secondary phase reaching its terminal velocity.)
  • the extent of the lead-rich phase formation in the region D, FIGURE 2, and its attendant segregation under gravity is time/temperature dependant.
  • the greater the temperature gradient (i.e. the smaller the distance D) existing between the primary solidification front B and the minimum casting temperature isothermal A the less will be the extent of the lead-rich phase formation and hence gravity segregation.
  • the precipitated particles will become smaller with (i) increasing extent of supercooling, (ii) lower lead content of the alloy and (iii) with increasing rates of casting. Therefore, the solution to these conflicting requirements is somewhat of a compromise between obtaining a casting rate such as to promote a suitably flat solidification front and, at the same time, promote small sized precipitated particles.
  • the alloy after leaving the die 3, the alloy is in the condition in which it is part solid and part liquid and eventually after the secondary soldification front C the alloy is wholly solid and can be extracted by normal continuous casting extraction means.
  • the invention can be executed using a horizontal continuous casting technique.
  • the minimum casting temperature isothermal A is confined wholly within the vertical section of the die 3, whereas the primary solidification front B is contained partially in the vertical and partially in the horizontal section of the die 3.
  • the latter feature is most important to facilitate withdrawal of the cast product.
  • the aluminium-lead alloy is shown being cast directly onto a backing strip of steel 6, moved horizontally under the die.
  • the close control of the following parameters may 'be used to minimize the extent of such deleterious compound formation.
  • the lead distribution in the final product may be controlled by varying the temperature gradient occurring during the casting, for example, the temperature gradient between the primary solidification front B and the minimum casting temperature isothermal A
  • a billet of aluminium-lead produced by a process according to the invention may require further heat treatment to precipitate any lead remains as a non-equilibrium solid solution.
  • a vacuum, or inert atmosphere may be required during melting the alloy and subsequent casting operations.
  • FIGURE 4 shows some examples of how the secondary phase of the alloy can be controlled as a non-uniform distribution in a primary phase by varying the geometry of the die.
  • FIGURE 4A shows, for the example of an aluminium lead alloy, the dispersion of the secondary phase from a parallel die 7. The primary solidification front and minimum casting temperature isothermal are indicated.
  • FIGURE 4A The section underneath FIGURE 4A has the lead evenly dispersed and the reference N indicates the lead concentration obtained from using a parallel sided die.
  • FIGURE 4B shows a stepped die 8 which gives the result shown in the underlying section of a lead concentration indicated by the region H which is higher than N and two outer regions where the lead concentration L is less than N.
  • FIGURE 4C shows a die 9,. of a convergent shape and this produces as shown in the section a region of concentration N and outer regions H of higher lead concentration.
  • FIGURE 4D shows a combination of the effects of FIGURES 4B and C by using a stepped and tapered die 12.
  • FIGURE 4E shows a die 113 having an entry portion 14 leading to two passages 15 and 16 and then opening into a parallel die portion.
  • the controlled bands of concentrations are carried out with a view to providing a range of bearing materials suitable for various applications and also with a View to the bonding of the cast material onto steel backing strip.
  • An outside layer of reduced concentration of lead say L may assist the bonding of the cast material across the face to a metal backing; an increased content of lead say H, may be advantageous at parts of a journal bearing surface spaced from the edge.
  • FIG. 5 illustrates this concept and shows a substantial head of liquid alloy composition above the level at which secondary solidification phenomenon occurs in the die (here shown as having a cooling jacket about it). The height of said liquid alloy is indicated by the double-arrowed vertical line extending above the said level.
  • the invention while concerned with controlling or preventing segregation between two liquid phases is equally applicable to alloys in which a solid phase segregates through a continuous liquid phase.
  • a method of continuously casting alloys of the kind which on cooling exhibit a transition from a single homogeneous phase to a two-phase liquid region to be cast comprising the steps of causing the alloy to flow from a feeder to a casting die, the commencement of movement being in a vertical direction, maintaining the temperature of the alloy in the feeder high enough for the alloy to remain as a homogeneous liquid phase in the feeder with a minimum casting temperature isothermal lying substantially within the upstream end of the casting die, cooling the metal at a rate such that the primary solidification temperature is within the die, and withdrawing the cast metal from the die when the temperature of the metal has reached the secondary solidification temperature.
  • a method of continuously casting alloys of the kind which on cooling exhibits a transition from a single homogeneous phase to a two-phase liquid region in which region one phase precipitates relative to the other comprising the steps of causing the alloy to flow to a casting die, the commencement of movement being in a vertical direction; maintaining the temperature of the alloy high enough for the alloy to remain as a single homogeneous liquid phase with a minimum casting temperature isothermal lying substantially within the upstream end of a casting die; extracting heat from the alloy such that the minimum casting temperature isothermal and a primary solidification front are substantially normal to the direction of precipitate movement, maintaining the isothermal and the primary solidification front so disposed relative to one another that the rate of precipitation generation of one phase relative to the other is substantially matched by the rate at which the precipitate is arrested at the primary solidification front and withdrawing the cast metal from the die when the temperature of the metal has reached a secondary solidification temperature at which both said phases are solid.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
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US580255A 1965-09-20 1966-09-19 Method of continuous casting an alloy having a two phase region during cooling Expired - Lifetime US3495649A (en)

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GB40002/65A GB1164116A (en) 1965-09-20 1965-09-20 Improvements in or relating to Continuous Casting

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US (1) US3495649A (de)
DE (1) DE1508856B2 (de)
FR (1) FR1572131A (de)
GB (1) GB1164116A (de)
NL (1) NL6613209A (de)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4964453A (en) * 1989-09-07 1990-10-23 The United States As Represented By The Administrator Of The National Aeronautics And Space Administration Directional solidification of superalloys
US4996025A (en) * 1986-01-23 1991-02-26 Federal-Mogul Corporation Engine bearing alloy composition and method of making same
US5053286A (en) * 1986-01-23 1991-10-01 Federal-Mogul Corporation Aluminum-lead engine bearing alloy metallurgical structure and method of making same

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2182876A (en) * 1985-11-14 1987-05-28 Atomic Energy Authority Uk Alloy strip production
DE3938234A1 (de) * 1988-11-19 1990-05-31 Glyco Metall Werke Verfahren und vorrichtung zur herstellung eines schichtwerkstoffes fuer gleitelemente
JPH04504229A (ja) * 1989-11-17 1992-07-30 グリコ・アクチェンゲゼルシャフト 滑り要素の層材料の製造方法及びその装置
DE4026907A1 (de) * 1990-08-25 1992-02-27 Glyco Metall Werke Lagerwerkstoff und verfahren zu dessen herstellung
EP0947260A1 (de) * 1998-02-04 1999-10-06 Deutsches Zentrum für Luft- und Raumfahrt e.V. Gleitlager aus monotektischen Legierungen

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US635054A (en) * 1899-09-11 1899-10-17 William A Mcadams Method of casting aluminium alloys.
US2672665A (en) * 1950-03-13 1954-03-23 Kaiser Aluminium Chem Corp Casting metal
US2715252A (en) * 1951-06-21 1955-08-16 Clevite Corp Continuous casting apparatus for aluminum onto metallic strip material
CA598409A (en) * 1960-05-24 A. Fromson Howard Two-stage method for the casting of fusible materials
US3354935A (en) * 1963-04-13 1967-11-28 Fuchs Kg Otto Manufacture of light-metal castings
US3410331A (en) * 1966-03-16 1968-11-12 Gen Motors Corp Method of casting an aluminumbased bearing alloy

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CA598409A (en) * 1960-05-24 A. Fromson Howard Two-stage method for the casting of fusible materials
US635054A (en) * 1899-09-11 1899-10-17 William A Mcadams Method of casting aluminium alloys.
US2672665A (en) * 1950-03-13 1954-03-23 Kaiser Aluminium Chem Corp Casting metal
US2715252A (en) * 1951-06-21 1955-08-16 Clevite Corp Continuous casting apparatus for aluminum onto metallic strip material
US3354935A (en) * 1963-04-13 1967-11-28 Fuchs Kg Otto Manufacture of light-metal castings
US3410331A (en) * 1966-03-16 1968-11-12 Gen Motors Corp Method of casting an aluminumbased bearing alloy

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4996025A (en) * 1986-01-23 1991-02-26 Federal-Mogul Corporation Engine bearing alloy composition and method of making same
US5053286A (en) * 1986-01-23 1991-10-01 Federal-Mogul Corporation Aluminum-lead engine bearing alloy metallurgical structure and method of making same
US4964453A (en) * 1989-09-07 1990-10-23 The United States As Represented By The Administrator Of The National Aeronautics And Space Administration Directional solidification of superalloys

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Publication number Publication date
GB1164116A (en) 1969-09-17
NL6613209A (de) 1967-03-21
FR1572131A (de) 1969-06-27
DE1508856B2 (de) 1973-06-14
DE1508856A1 (de) 1969-11-13

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