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Publication numberUS3595060 A
Publication typeGrant
Publication dateJul 27, 1971
Filing dateMar 18, 1969
Priority dateMar 21, 1968
Also published asDE1914035A1
Publication numberUS 3595060 A, US 3595060A, US-A-3595060, US3595060 A, US3595060A
InventorsBernard Brian Hundy
Original AssigneePressed Steel Fisher Ltd
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Method of forming metal alloys
US 3595060 A
Abstract  available in
Images(2)
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Claims  available in
Description  (OCR text may contain errors)

United States Patent [72] Inventor Bernard Brian Hundy [50] Field of Search 72/364, Woodstock, England 344,342; 148/115 [2|] Appl. No. 808,229 22 Filed Mar. 18, 1969 1 References Cited f' J y 1971 I UNITED STATES PATENTS I 731 33: $13? 3,340,101 9/1967 Fields, Jr. et a1 148/115 3,420,717 1 1969 F 1d ,J. t l 148 11.5 32 Priority Mu.21,196a I s r e a I 3 Britain Primary ExaminerRichard J Herbst [31 13,678/68 Attorneys-Stowe & Stowell and Thomas J. Greer, Jr.

1 ABSTRACT: A method of forming superplastic metal alloys [54] METAL ALLOYS by heating the alloy to a temperature at which it is superplastic and then forming the alloy, in which the formed alloy is heated [52] US. Cl 72/364, to a temperature above the superplastic temperature range in 72/344, 148/] 1.5 order to render it resistant to deformation before it is removed [51 1 Int. Cl ..B2ld 26/00 from the forming tool.

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SHEET 2 BF 2 FIG.2

METHOD OF FORMING METAL ALLOYS This invention relates to a method of forming metal alloys that exhibit superplasticity.

An article entitled superplasticity in an Al-Zn Alloy by W. A. Backofen, l. R. Turner and D. A. Avery, which was published in the Transactions of the A.S.M., Volume 57, 1964 pages 980-990, discloses the concept of forming superplastic metals by fonning techniques borrowed from polymer and glass processing. Moreover, one such forming technique using fluid pressure is disclosed in US. Pat. No. 3,340,101 which describes a method of forming superplastic metal blanks against a die surface by heating the blank to a temperature at which it is superplastic and then pressure or vacuum forming the blank to the shape of the die.

Compared with vacuum or pressure forming of thermoplastic synthetic plastics material and compared with press forming of conventional metal blanks, forming of superplastie metal alloys normally tends to be a relatively slow operation principally because the critical strain rate of the material, above which it does not behave in a superplastic manner, should not be exceeded.

Moreover, there may be a considerable time delay before the formed superplastic metal can be stripped from the forming tool and handled. This time delay arises from the fact that whilst the formed metal is at a temperature at which it exhibits superplasticity it is exceptionally vulnerable to deformation, and it must therefore be allowed to cool before subsequent handling; because the forming tools act as a heat sink the cooling time is excessively long for commercially viable production.

According to the present invention after the superplastic metal has been formed, it is heated to a temperature above the range at which it exhibits superplasticity before it is stripped from the forming tool and/or subsequently handled.

The heating of the formed superplastic metal renders it much more resistant to permanent deformation than when it is at the forming temperature, and the formed superplastic metal can generally be heated to a temperature at which it is sufficiently resistant to permanent deformation more quickly than it would take to cool the metal to a temperature at which it had a similar resistance to permanent deformation. Moreover, in the normal case where the formed metal has a greater coefficient of thermal expansion than the forming tool, the subsequent heating expands the formed metal more than the tool and thereby tends to free the metal from the tool whereas cooling, in many cases, tends to shrink the formed metal onto the forming tool. Furthermore the subsequent heating has the additional advantage of maintaining the forming tool at a suitable forming temperature, whereas if the formed metal and hence the forming tool is cooled to render the formed metal sufficiently resistant to deformation, further time delays occur in production whilst the forming tool is being reheated to the forming temperature before a further blank or the like can be formed.

The invention will now be described solely by way of example with reference to the following example and to the accompanying drawings in which FIG. 1 shows a schematic cross section ofa vacuum forming apparatus, and

FIG. 2 shows a schematic cross section of a pressure forming apparatus.

EXAMPLE A specimen of eutectoid zinc-aluminum alloy in the form of a standard I-Iounsfield tensometer round tensile test piece, type No. 14, was subjected to flow stress testing at various temperatures in a Hounsfield tensometer at a crosshead speed ofO. l 25 inch per inch per minute.

The results of the tests are summarized in the table:

Temperature Initial Flow Stress 270 641 pounds per square inch 290 C. 1,240 pounds per square inch 310" C. 4,770 pounds per square inch 320 C. 3.260 pounds per square inch Since resistance to deformation is relative to flow stress, it will be seen that resistance to deformation increases signifcantly up to 3 l0 C. for this alloy.

Referring now to FIG. 1 of the accompanying drawings, the apparatus includes a die box 11 in which is mounted a forming tool comprising a die or mold I2 having relief passages 13. A sealing ring I4 clamps a blank 15 of Zn-Al eutectoid alloy which has been treated to exhibit superplasticity, to the die box 11. The die box 11 is connected by a pipe 16 to a vacuum source and also to a source of compressed air through suitable control valves (not shown).

A heater indicated generally at 17 comprises arrays of ceramic electrical heaters, such as 18, mounted below an aluminum reflector plate 19 and asbestos insulation 20. The heater 17 is suspended on cables 21 passing around pulley wheels 22 and connected to a counterweight 23 such that the heater is easily retractable.

In practicing the invention the blank 15 is mounted as shown, the heater ,17 is lowered and energized to raise the temperature of the blank 15 to 275 C. and then maintain that temperature by a suitable thermostat. The control valves are then operated in known manner to connect the die box 11 to the vacuum source and thereby vacuum form the blank 15 to the shape of the surface of the die 12.

During the vacuum forming operation the control valves are regulated to ensure that the critical strain rate of the material of the blank 15 is not exceeded and the operation normally takes a minimum of about 3 to 4 minutes. When forming is completed the control valves are operated to disconnect the die box 11 from the vacuum source, and the thermostat controlling the heater 17 is overridden to allow the heater to raise the temperature of the formed blank. The clamps around the sealing ring 14 are released and the sealing ring is removed, and when the temperature of the formed blank has reached about 310 C., the control valves are operated to admit a blast of compressed air into the die box 11 to strip the formed blank from the die 12. The heater 17 is then switched off and raised, the formed blank is removed and placed aside in a position where it can cool without further handling, and a fresh blank, which may be preheated, is loaded into the apparatus.

FIG. 2 illustrates a pressure forming apparatus that includes a porous refractory forming tool or die 24 having thermostatically controlled electrical heaters 25 embedded therein ad j'acent the forming surface. The upper surface of the die 24, is provided with a sealing ring 26 and the die 24 is contained within a vented die box 27. A pressure box 28, which has a sealing ring 29 and a flexible pipe 30 connecting the interior of the box 28 to a source of compressed air through suitable control valves (not shown), is mounted on a hydraulically controlled cylinder device 31. Banks of radiant electrical heaters, such as 32 are mounted in the pressure box 28 and are thermostatically controlled.

In operation, a blank 33 of eutectoid zinc-aluminum alloy which had been heat-treated to exhibit superplasticity and which may be partially preformed as shown and also may be preheated is placed on the sealing ring 26. The hydraulic cylinder 31 is then operated to clamp the blank 33 between the sealing rings 26 and 29, and the heaters 25 and 32 are actuated to heat the blank 33.

When the blank 33 reached a temperature of about 250 C, the control valves are operated to supply compressed air at about pounds per square inch to the pressure box 28 thereby slowly forming the blank 33 over a period of about 3 minutes to the shape of the forming surface of the die 24.

When forming is completed the thermostats controlling the heaters 25 and 38 are overridden thereby allowing the temperature of the blank to rise. When the temperature has reached about 310 C. the heaters are switched off, the pressure box 28 is raised by the hydraulic cylinder 31 and the formed blank is stripped from the die 26 by a plurality of pinejectors (not shown) mounted in the upper surface of the die 26.

The formed blank can then be placed aside to cool and a further blank placed in the forming apparatus.

Whatl claim is:

l. A method of deforming a metal alloy workpiece formed of an alloy which exhibits superplastic behavior including the steps of, heating the alloy to within its superplastic tempera-

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US3340101 *Apr 2, 1965Sep 5, 1967IbmThermoforming of metals
US3420717 *Mar 28, 1966Jan 7, 1969IbmMetal softening process and product thereof
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US3864176 *Jun 14, 1973Feb 4, 1975Isc Alloys LtdMoulding of superplastic alloy sheet
US3898827 *Aug 15, 1973Aug 12, 1975Isc Alloys LtdForming of superplastic alloy sheet
US3920175 *Oct 3, 1974Nov 18, 1975Rockwell International CorpMethod for superplastic forming of metals with concurrent diffusion bonding
US3927817 *Mar 20, 1975Dec 23, 1975Rockwell International CorpMethod for making metallic sandwich structures
US3934441 *Jul 8, 1974Jan 27, 1976Rockwell International CorporationControlled environment superplastic forming of metals
US3974673 *Apr 7, 1975Aug 17, 1976Rockwell International CorporationTitanium parts manufacturing
US3997369 *May 12, 1975Dec 14, 1976The British Aluminium Company LimitedProduction of metallic articles
US4065302 *Dec 29, 1975Dec 27, 1977The International Nickel Company, Inc.Powdered metal consolidation method
US4137105 *Jun 20, 1977Jan 30, 1979Gulf & Western Industries, Inc.Method of forming tooling for superplastic metal sheet
US4145903 *Apr 3, 1978Mar 27, 1979Textron Inc.Sheet forming method and apparatus
US4493737 *May 21, 1980Jan 15, 1985The United States Of America As Represented By The United States Department Of EnergyMethod for fabricating uranium alloy articles without shape memory effects
US5410132 *Oct 15, 1991Apr 25, 1995The Boeing CompanySuperplastic forming using induction heating
US5571436 *Apr 17, 1995Nov 5, 1996The Boeing CompanyInduction heating of composite materials
US5587098 *Jun 7, 1995Dec 24, 1996The Boeing CompanyJoining large structures using localized induction heating
US5591369 *Jun 5, 1995Jan 7, 1997The Boeing CompanyMethod and apparatus for consolidating organic matrix composites using induction heating
US5591370 *Jun 5, 1995Jan 7, 1997The Boeing CompanySystem for consolidating organic matrix composites using induction heating
US5599472 *Nov 18, 1994Feb 4, 1997The Boeing CompanyResealable retort for induction processing of organic matrix composites or metals
US5624594 *Jun 6, 1995Apr 29, 1997The Boeing CompanyFixed coil induction heater for thermoplastic welding
US5641422 *Jun 16, 1995Jun 24, 1997The Boeing CompanyThermoplastic welding of organic resin composites using a fixed coil induction heater
US5645744 *Jun 6, 1995Jul 8, 1997The Boeing CompanyRetort for achieving thermal uniformity in induction processing of organic matrix composites or metals
US5683607 *Aug 14, 1996Nov 4, 1997The Boeing Companyβ-annealing of titanium alloys
US5683608 *Jun 5, 1995Nov 4, 1997The Boeing CompanyCeramic die for induction heating work cells
US5700995 *Mar 17, 1995Dec 23, 1997The Boeing CompanySuperplastically formed part
US5705794 *May 26, 1995Jan 6, 1998The Boeing CompanyCombined heating cycles to improve efficiency in inductive heating operations
US5710414 *Jun 6, 1995Jan 20, 1998The Boeing CompanyInternal tooling for induction heating
US5723849 *Jun 6, 1995Mar 3, 1998The Boeing CompanyReinforced susceptor for induction or resistance welding of thermoplastic composites
US5728309 *Jun 6, 1995Mar 17, 1998The Boeing CompanyMethod for achieving thermal uniformity in induction processing of organic matrix composites or metals
US5747179 *Jun 5, 1995May 5, 1998The Boeing CompanyPack for inductively consolidating an organic matrix composite
US5793024 *Jun 6, 1995Aug 11, 1998The Boeing CompanyBonding using induction heating
US5808281 *Jun 6, 1995Sep 15, 1998The Boeing CompanyMultilayer susceptors for achieving thermal uniformity in induction processing of organic matrix composites or metals
US5821506 *May 22, 1997Oct 13, 1998The Boeing CompanySuperplastically formed part
US5847375 *Jul 19, 1996Dec 8, 1998The Boeing CompanyFastenerless bonder wingbox
US5914064 *Jul 9, 1997Jun 22, 1999The Boeing CompanyCombined cycle for forming and annealing
US6040563 *Dec 22, 1997Mar 21, 2000The Boeing CompanyBonded assemblies
US6087640 *May 26, 1995Jul 11, 2000The Boeing CompanyForming parts with complex curvature
US6211497Jun 5, 1995Apr 3, 2001The Boeing CompanyInduction consolidation system
US6914225Jun 18, 2003Jul 5, 2005The Boeing CompanyApparatus and methods for single sheet forming using induction heating
US7126096Jun 6, 1995Oct 24, 2006Th Boeing CompanyResistance welding of thermoplastics in aerospace structure
US7431196Mar 21, 2005Oct 7, 2008The Boeing CompanyMethod and apparatus for forming complex contour structural assemblies
US7866535Jul 21, 2008Jan 11, 2011The Boeing CompanyPreform for forming complex contour structural assemblies
DE4200047A1 *Jan 3, 1992Jul 8, 1993Chuang Tung HanProdn. of workpiece by super-plastic forming - is carried out simultaneously with bonding on of second workpiece
DE4341281C1 *Dec 3, 1993Dec 15, 1994Chuang Tung HanMethod for the production of parts by superplastic forming
EP0165869A1 *Jun 14, 1985Dec 27, 1985AEROSPATIALE Société Nationale IndustrielleApparatus for forming and welding blanks of superplastic material
Classifications
U.S. Classification72/364, 148/564, 72/344
International ClassificationB21D26/055, C21D7/13, C21D8/00, B21J5/00, C22F1/00
Cooperative ClassificationC22F1/00, C21D8/00, B21D26/055, C21D7/13, B21J5/00
European ClassificationC21D7/13, B21J5/00, C22F1/00, C21D8/00, B21D26/055