US3808671A - Method of making hollow cast articles from metal alloys having long freezing ranges - Google Patents

Method of making hollow cast articles from metal alloys having long freezing ranges Download PDF

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US3808671A
US3808671A US00217014A US21701472A US3808671A US 3808671 A US3808671 A US 3808671A US 00217014 A US00217014 A US 00217014A US 21701472 A US21701472 A US 21701472A US 3808671 A US3808671 A US 3808671A
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mold
casting
molten metal
molten
metal
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US00217014A
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R Krock
W Richmond
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Duracell Inc USA
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PR Mallory and Co Inc
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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
    • B22D21/00—Casting non-ferrous metals or metallic compounds so far as their metallurgical properties are of importance for the casting procedure; Selection of compositions therefor
    • B22D21/002—Castings of light metals
    • B22D21/007—Castings of light metals with low melting point, e.g. Al 659 degrees C, Mg 650 degrees C
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22C—FOUNDRY MOULDING
    • B22C9/00—Moulds or cores; Moulding processes
    • B22C9/06—Permanent moulds for shaped castings
    • B22C9/061—Materials which make up the mould
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T29/00—Metal working
    • Y10T29/49—Method of mechanical manufacture
    • Y10T29/49972—Method of mechanical manufacture with separating, localizing, or eliminating of as-cast defects from a metal casting [e.g., anti-pipe]
    • Y10T29/49975—Removing defects
    • Y10T29/49977—From center of ingot to leave hollow blank
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T29/00—Metal working
    • Y10T29/49—Method of mechanical manufacture
    • Y10T29/4998—Combined manufacture including applying or shaping of fluent material
    • Y10T29/49988—Metal casting
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T29/00—Metal working
    • Y10T29/49—Method of mechanical manufacture
    • Y10T29/4998—Combined manufacture including applying or shaping of fluent material
    • Y10T29/49988—Metal casting
    • Y10T29/49989—Followed by cutting or removing material

Definitions

  • the following method is used to improve the physical properties of relatively thin walled hollow castings and prevent hot tearing caused by cores in alloys having long freezing ranges.
  • the casting is inverted from the normal casting position and preferably no core is used,
  • the exterior of the casting is contoured to the shape of a metal mold which causes rapid soldification with resultant improved soundness and high physical properties.
  • the center section acts as a riser to feed the outer shell and minimize interdentritic shrinkage and hot tearing.
  • the interior is then machined out to form the desired wall thickness.
  • FIG. 1 is a view of a mold set up for the casting of-hollow sections according to the prior art.
  • FIG. 2 is a sectional view of the coreless casting method according to the present invention.
  • FIG. 3 is a view of a casting produced in accordance with the present invention.
  • FIG. 4 is a view of the beryllium-aluminum phase diagram illustrating the long freezing of this system.
  • alloys having long freezing ranges have been difficult to cast in thin section sizes in hollow configurations.
  • the problems involved include hot tearing of the metal during casting.
  • the resulting castings often contain shrinkage resulting from the difference in dimensions between the material when first cast as compared to the room temperature dimensions.
  • a metal mold 10 made for example, of copper, steel or graphite includes a base portion 11, a cylindrical portion' 12, and a core 15 is utilized to form the casting. If desired an insulating sleeve 17 for example, made of alumina or zirconia also can be used to define a hot top portion 18. Alternatively the hot top portion may be defined by the interior surface 13 of material 12. Water cooling systems (not shown) are sometimes utilized in connection with the prior art construction of FIG. 1.
  • a mold 100 may be used having a base portion 101 and a cylindrical portion 102.
  • Base portion 101 defines the external surface of the casting at 103.
  • the preferred mold material or the mold is metal and most preferably it is made of steel, copper, or cast iron. Graphite may also be used if desired.
  • a hot top section is provided in conjunction with portion 102.
  • an insulating sleeve 121 may be provided which may be made of for example alumina or zirconia.
  • the improvements observed according to the casting technique of the present invention are achieved because the massive mold section 101 removes heat very rapdily as a result of which rapid solidification occurs at and near the surface 103.
  • the center section 134 of casting acts as a riser to feed the outer shell 131. As a result interdentritic shrinkage and hot tearing are minimized, and good physical properties are obtained at and near the surface of the casting, particularly for wall thickness less than about onehalf inch.
  • the casting 130 is removed from the mold and is machined to desired dimensions. If desired the casting may be simply cropped off along the line 132 of FIG. 3, and then the leg portion 131 machined as illustrated, removing center section 134. Alternatively it may be desirable for the leg portion 131 to be longer including portion 135 in which case the casting will not be cropped at 132 and the machining will include the portion 137, as illustrated.
  • the present invention is applicable to a wide variety of alloys having a long freezing range, generally having a freezing range of at least about 500 C and preferably above 550 C.
  • alloys having a long freezing range, generally having a freezing range of at least about 500 C and preferably above 550 C.
  • Examples include the beryliumaluminum system shown in FlG. 4, incluing alloying additives such as copper, magnesium, silicon, precious metals, either singly or in combination, preferably not totaling above about 10 percent, which may be used for various purposes such as strengthening the aluminum matrix and facilitating nucleation during casting.
  • the preferred alloys contain about 80 to about 95 atomic percent beryllium.
  • Additional alloying systems include aluminumgermanium perferably about 90-to 99'atomic percent germanium, gold-germanium preferably 85 to 99 atomic percent germanium, lead-germanium preferably 75 to 99 atomic percent germanium, galliumgermanium preferably 20 to 99 atomic percent germanium, silver-silicon preferably 65 to 99 atomic percent silicon and silicon-tin preferably 10 to 99 atomic percent silicon.
  • a berylliumaluminum alloy containing 75 weight percent beryllium about 24.7 weight percent aluminum alloy and about 0.3 percent platinum was heated to a melting temperature of about l,400 C and was then poured into the mold shown in FIG. 2 at about 1,200 C.
  • a similar com-' position was poured into the mold shown in FIG. I having been heated to the same melting and pouring temperatures, and otherwise similarly processed.
  • the resulting mechanical properties for the alloy cast in the mold shown in FIG. I was 19,000 psi ultimate tensile strength; 0.2 percent yield strength, 18,000 psi from a tensile bar taken near the surface of core 15. Radiography revealed extreme shrinkage and porosity adjacent the core in the resulting casting.
  • the castings produced according to the design in FIG. 2 had a tensile strength of 32,000 psi and 25,000 psi 0.2 percent yeild strength from a tensile bar taken from section 131. Radiography revealed very little shrinkage and porosity in the channel portion formed adjacent surface 103 in the lower portion of the mold 101.
  • a method of making a relatively thin walled hollow tapered cast article from molten metal having an extremely long freezing range comprising the steps of feeding molten metal having a freezing range of about 500 C or longer into a mold having an inverted tapered mold cavity and having a massive tapered bottom portion capable of withdrawing heat more rapidly from molten metal than an adjacent insulated upper portion of the mold, solidifying ,molten metal in the massive bottom portion of the mold where heat is more rapidly withdrawn from the molten metal than withdrawn in the adjacent insultated portion of the mold and wherein molten metal at about the center of the mold acts as riser means and then solidifying the remainder of the molten metal in the mold to form a solidified casting of solid taper cross-section containing a minimum of hot tearing, removing the solidified casting from the mold, and removing solidified metal from the interior of the solidified casting to form the hollow cast article.
  • the molten material having a freezing range of about 500 C or longer is a molten alloy selected from the group consisting of Be base alloys, Si base alloys or Ge base alloys.

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

Abstract

A technique for improving the physical properties of thin walled castings and reduction or avoidance of hot tearing in such castings involves casting in the inverted position, preferably using no core. The exterior of the casting is contoured to the shape of a metal mold which causes rapid solidification with resultant improved soundness and improved physical properties. Metal is then removed from the interior of the casting for example by machining to form the desired wall thickness.

Description

United States Patent [19] v Krock et al.
Appl. No: 217,014
[73] As'signee:
U.S Cl...; 29/526.5, 29/527.5 29/527.6,
Int. Cl. 322d 2.7/04
Field of Search 164/69, 126; 29/526.4,
References Cited UNITED STATES PATENTS 12/1970 Richmond et a1. 164/68 I A technique for improving the physical properties of 1451 May 7,1974
11/1926 Otto... ..29/526.4 ux 1/1971 $1. 01111; l64/69X Primary Examiner-Charles W. Lanham Assistant Examiner-'D. C. Reiley, lll Attorney, Agent,- or Firm-Richard H. Childress; Charles W. Hoffmann; Robert F. Meyer ABSTRACT thin walled castings and reduction or avoidance of hot tearing in such castings involves casting in the inverted position, preferably using no core. The exterior of the casting is contoured'to the shape of a metal mold which causes rapid solidification with resultant improved soundness and improved physical properties. Metal is then removed from the interior of the casting for example by machining to form the desired wall thickness.
6 Claims, 4 Drawing Figures PA TENTEII 7 I974 PRIOR ART FINE. 2
ALU M I NUM BERYLLIUM PHASE DIAGRAM WEIGHT PER CENT BERYLLIUM O m 9 o l m4 O OIQ 9 7 O- 6 0 O 8 5 O- .m 4 I O 6. 3 v m 0 M 5 O- 2 O 4 RIJI O 2 5- w mm III] IIIIO 2 6 I. i o O. I k O O O O 0 O O OO O 0 O O O O O O O O B m m w 9 a w s w w 1 METHOD OF MAKING HOLLOW CAST ARTICLES FROM METAL ALLOYS HAVING LONG FREEZING RANGES The invention described herein was made in the course of, or under, a subcontract issued under Prime Contract W-7405-ENG-48 with the United States Energy Commission.
SUMMARY OF THE INVENTION The following method is used to improve the physical properties of relatively thin walled hollow castings and prevent hot tearing caused by cores in alloys having long freezing ranges. The casting is inverted from the normal casting position and preferably no core is used, The exterior of the casting is contoured to the shape of a metal mold which causes rapid soldification with resultant improved soundness and high physical properties. The center section acts as a riser to feed the outer shell and minimize interdentritic shrinkage and hot tearing. The interior is then machined out to form the desired wall thickness.
DRAWINGS FIG. 1 is a view of a mold set up for the casting of-hollow sections according to the prior art.
FIG. 2 is a sectional view of the coreless casting method according to the present invention.
FIG. 3 is a view of a casting produced in accordance with the present invention.
FIG. 4 is a view of the beryllium-aluminum phase diagram illustrating the long freezing of this system.
BACKGROUND OF THE INVENTION In accordance with techniques of the prior art, alloys having long freezing ranges have been difficult to cast in thin section sizes in hollow configurations. The problems involved include hot tearing of the metal during casting. Also the resulting castings often contain shrinkage resulting from the difference in dimensions between the material when first cast as compared to the room temperature dimensions.
The common method of casting hollow members with alloys having long freezing ranges is shown in FIG.
-1. A metal mold 10 made for example, of copper, steel or graphite includes a base portion 11, a cylindrical portion' 12, and a core 15 is utilized to form the casting. If desired an insulating sleeve 17 for example, made of alumina or zirconia also can be used to define a hot top portion 18. Alternatively the hot top portion may be defined by the interior surface 13 of material 12. Water cooling systems (not shown) are sometimes utilized in connection with the prior art construction of FIG. 1.
However, with or without water cooling, hot tearing has always been a problem in casting according to the prior art construction with alloys having a long freezing range. Additionally, interdentritie shrinkage and shrinkage resulting from the dimensional differences between the as cast material and the material at lower room temperature are serious problems.
In accordance with the present invention it has been found that if the casting is inverted from the position shown in FIG. 1 and the core is not used the problems of shrinkage and hot tearing are eliminated or are substantially reduced.
As shown in FIG. 2, a mold 100 may be used having a base portion 101 and a cylindrical portion 102. Base portion 101 defines the external surface of the casting at 103. The preferred mold material or the mold is metal and most preferably it is made of steel, copper, or cast iron. Graphite may also be used if desired.
A hot top section is provided in conjunction with portion 102. If desired an insulating sleeve 121 may be provided which may be made of for example alumina or zirconia.
While not being wished to be bound by any particular theory, it is believed that the improvements observed according to the casting technique of the present invention are achieved because the massive mold section 101 removes heat very rapdily as a result of which rapid solidification occurs at and near the surface 103. The center section 134 of casting acts as a riser to feed the outer shell 131. As a result interdentritic shrinkage and hot tearing are minimized, and good physical properties are obtained at and near the surface of the casting, particularly for wall thickness less than about onehalf inch.
After the casting operation the casting 130 is removed from the mold and is machined to desired dimensions. If desired the casting may be simply cropped off along the line 132 of FIG. 3, and then the leg portion 131 machined as illustrated, removing center section 134. Alternatively it may be desirable for the leg portion 131 to be longer including portion 135 in which case the casting will not be cropped at 132 and the machining will include the portion 137, as illustrated.
Obviously the particular casting configurations shown are by way of example, only, and a wide variety of configurations may be cast and machined to desired shape according to the present invention.
The present invention is applicable to a wide variety of alloys having a long freezing range, generally having a freezing range of at least about 500 C and preferably above 550 C. Examples include the beryliumaluminum system shown in FlG. 4, incluing alloying additives such as copper, magnesium, silicon, precious metals, either singly or in combination, preferably not totaling above about 10 percent, which may be used for various purposes such as strengthening the aluminum matrix and facilitating nucleation during casting. The preferred alloys contain about 80 to about 95 atomic percent beryllium.
Additional alloying systems include aluminumgermanium perferably about 90-to 99'atomic percent germanium, gold-germanium preferably 85 to 99 atomic percent germanium, lead-germanium preferably 75 to 99 atomic percent germanium, galliumgermanium preferably 20 to 99 atomic percent germanium, silver-silicon preferably 65 to 99 atomic percent silicon and silicon-tin preferably 10 to 99 atomic percent silicon.
Insofar as preparing the molten metal for casting is concerned, a wide variety of techniques are available As an example of the present invention, a berylliumaluminum alloy containing 75 weight percent beryllium about 24.7 weight percent aluminum alloy and about 0.3 percent platinum was heated to a melting temperature of about l,400 C and was then poured into the mold shown in FIG. 2 at about 1,200 C. A similar com-' position was poured into the mold shown in FIG. I having been heated to the same melting and pouring temperatures, and otherwise similarly processed.
The resulting mechanical properties for the alloy cast in the mold shown in FIG. I was 19,000 psi ultimate tensile strength; 0.2 percent yield strength, 18,000 psi from a tensile bar taken near the surface of core 15. Radiography revealed extreme shrinkage and porosity adjacent the core in the resulting casting.
The castings produced according to the design in FIG. 2 had a tensile strength of 32,000 psi and 25,000 psi 0.2 percent yeild strength from a tensile bar taken from section 131. Radiography revealed very little shrinkage and porosity in the channel portion formed adjacent surface 103 in the lower portion of the mold 101.
What is claimed is:
l. A method of making a relatively thin walled hollow tapered cast article from molten metal having an extremely long freezing range, the method comprising the steps of feeding molten metal having a freezing range of about 500 C or longer into a mold having an inverted tapered mold cavity and having a massive tapered bottom portion capable of withdrawing heat more rapidly from molten metal than an adjacent insulated upper portion of the mold, solidifying ,molten metal in the massive bottom portion of the mold where heat is more rapidly withdrawn from the molten metal than withdrawn in the adjacent insultated portion of the mold and wherein molten metal at about the center of the mold acts as riser means and then solidifying the remainder of the molten metal in the mold to form a solidified casting of solid taper cross-section containing a minimum of hot tearing, removing the solidified casting from the mold, and removing solidified metal from the interior of the solidified casting to form the hollow cast article.
2. The method of claim 1, wherein the molten material having a freezing range of about 500 C or longer is a molten alloy selected from the group consisting of Be base alloys, Si base alloys or Ge base alloys.
3. The method of claim 2, wherein the molten alloy is a Be base alloy containing Al.
4. The method of claim 1, wherein the molten material is poured into the mold. I
5. The method of claim I, wherein the mold is a coreless mold.
6. The method of claim 5, wherein the solidfied castshrinkage.
UNITED STATES PATENT OFFICE I CERTIFICATE OF CORRECTION Patent No. 3808671 Dated Ma 7 1974 Inventofl Richard H. Krock & William J. Richmond It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:
Col. 1, line 7, after "States" insert ---Atomic-.
Col. 1, line32, after "freezing" insert -range-.
Col. 2, line 13, change "rapdily" to --rapid1y-.
Col. 4, line 4, after "than" insert -is--.
Signed and sealed this 10th day of September 1974.
(SEAL) Attest:
McCOY GIBSON, JR. I C. MARSHALL DANN Attesting Officer Commissioner of Patents FORM PO-1050 (10-69) USCOMWDC 6037mm U. 5. GOVERNMENT PRINTING OFFICE: I969 0-366-334,

Claims (6)

1. A method of making a relatively thin walled hollow tapered cast article from molten metal having an extrely long freezing range, the method comprising the steps of feeding molten metal having a freezing range of about 500* C or longer into a mold having an inverted tapered mold cavity and having a massive tapered bottom portion capable of withdrawing heat more rapidly from molten metal than an adjacent insulated upper portion of the mold, solidifying molten metal in the massive bottom portion of the mold where heat is more rapidly withdrawn from the molten metal than withdrawn in the adjacent insultated portion of the mold and wherein molten metal at about the center of the mold acts as riser means and then solidifying the remainder of the molten metal in the mold to form a solidified casting of solid taper cross-section containing a minimum of hot tearing, removing the solidified casting from the mold, and removing solidified metal from the interior of the solidified casting to form the hollow cast article.
2. The method of claim 1, wherein the molten material having a freezing range of about 500* C or longer is a molten alloy selected from the group consisting of Be base alloys, Si base alloys or Ge base alloys.
3. The method of claim 2, wherein the molten alloy is a Be base alloy containing A1.
4. The method of claim 1, wherein the molten material is poured into the mold.
5. The method of claim 1, wherein the mold is a coreless mold.
6. The method of claim 5, wherein the solidfied casting of the alloy experiences a minimum of interdentritic shrinkage.
US00217014A 1972-01-11 1972-01-11 Method of making hollow cast articles from metal alloys having long freezing ranges Expired - Lifetime US3808671A (en)

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1607475A (en) * 1924-07-08 1926-11-16 Youngstown Sheet And Tube Co Manufacture of seamless tubing
US3548915A (en) * 1969-06-11 1970-12-22 Mallory & Co Inc P R New procedure for chill casting beryllium composite
US3557437A (en) * 1969-01-14 1971-01-26 John C St Clair Method of fabricating large vessels capable of withstanding high internal pressures

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1607475A (en) * 1924-07-08 1926-11-16 Youngstown Sheet And Tube Co Manufacture of seamless tubing
US3557437A (en) * 1969-01-14 1971-01-26 John C St Clair Method of fabricating large vessels capable of withstanding high internal pressures
US3548915A (en) * 1969-06-11 1970-12-22 Mallory & Co Inc P R New procedure for chill casting beryllium composite

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