DE1962410A1 - Process for deforming superplastic metals - Google Patents

Description

IBM Germany Internationale Büro-Maechinen Gesellschaft mbH

Boeblingen, December 11, 1969 ru-rz

Applicant: International Business Machines

Corporation, Armonk, N.Y. 10

Official file number: New registration File number of the applicant: Docket LE 967 060

Process for the deformation of superplastic metals

The invention relates to a method for deforming superplastic metals in heatable molding devices or pressing devices.

Both in mechanical engineering and in electrical engineering, it is very often necessary that small components with a carrier made of metal must be connected. This can be done once by the fact that the correspondingly shaped for the individual components Holes are made in this plate by drilling or etching and that then the pins by pressing, Soldering, welding or riveting device with the common plate get connected. Apart from the fact that the making of holes for components to be picked up in the base plate is very time-consuming and, moreover, inaccurate, the base plate must be processed in several previous work steps if it is also intended to accommodate depressions or elevations or reinforced approaches.

So-called stretching or stress deformation processes have become known for thermoplastics and for glass. A shape is used that is practically "complementary to the product to be manufactured". The zn ver

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Shaping material is placed in this mold and the deformation force is applied, which causes stretching or deformation of the material and presses the material into the sometimes complexly shaped surface of the mold. A summary These processes are reported in the "Thermoforming Today" article by Lowell L. Scheiner, Plastics Technology, Vol 10, No. 8, August 1964, pages 45 to 56.

In addition, in Article ¹¹ A Review of Superplasticity and Related Phenomena "by Ervin E. Underwood, Journal of Metals, December 1962, pages 914 to 919, an effect is dealt with which has recently been called the superplasticity effect of metals. This phenomenon was observed over 40 years ago and has indeed been studied extensively during the past 10 years. Strains on the order of 600% have been observed in experiments, which is a sign of a high degree of plasticity. It has therefore been suggested to use these superplastic metals Manufacture complex machine housings by making a negative mold of the shell and pressing superplastic material into it * Be-jor the superplastic material is pressed into the mold * wild ee heated evenly either outside or inside the mold in order to get into the superplastic state Attempts have now found that the evenly When the superplastic starting metal plate heats up at the corners and edges, the material is stretched more than on smooth surfaces. This results in the major disadvantage that the finished workpiece does not have a uniform wall thickness in the final state, but that wall thicknesses of different thicknesses are present, which on the one hand cause stresses in the workpiece and on the other hand significantly influence the strength of the workpiece. In addition, it has been found e3 that the superplastic !! Alloys are not constant in all phases of the transformation. In addition?: Poor due to the properties of a eutectoean, caused by the relatively rassher teein © e-seßs grain size of the Matesricils.

Docket LE! DC? GuOj η η 3 P 0 1 I 1 <3 η 7

1962 A 1 Ο

_w ο _β

The invention is therefore based on the object of creating a method for deforming superplastic metals in heatable pressing or molding devices, which enables a larger grain size to be achieved on the one hand and thus greater strength and, on the other hand, the utilization of the individual phases of the eutectoid in Bx warming exploits in order to obtain a certain strength and a certain structure of the molded objects.

The inventive solution to the problem consists in a method which is characterized in that the blank of superplastic metal to a temperature immediately below the critical temperature for the respective superplastic metal is brought that after inserting the blank in the mold the mold is brought to a temperature which is the desired critical temperature of the superplastic metal allows and that then the blank is pressed against the mold by vacuum or pressure to the desired part to shape.

The advantage of this procedure is _? As a result of the exact heating to just below the critical temperature for the respective superplastic material, the molding process is much more precise, that it runs much faster and that the structure and strength of the molded workpiece compared to workpieces formed from superplastic metals according to the previously known methods have been improved.

The invention will now be illustrated with reference to in the drawings Embodiments described in more detail.

In the drawings:

1 shows a partially sectioned mold;

2 shows a sectional front view of the compression mold with a Docket LE 967 060 0 0 9 8 2 7/1307

1 96241Q

- 4 in the shape molded part and

3 shows a phase diagram to illustrate a eutectic phase phenomenon which occurs in a zinc-aluminum eutectoid occurs.

In FIGS. 1 and 2 a mold can be seen which consists of a lower part IO which has a cavity 11, which is complementary to the shape that the desired part P is to have after the molding operation. To eject the done molded part P, an eject pin 12 is arranged in this shape. In addition, there are heating devices in the base plate 10, e.g. in the form of electrical resistance heaters, available. These heating elements 13 are arranged at a distance 14 within the base plate 10 from the mold cavity 11, For example, if the base plate 10 is made of steel and the material to be formed is a zinc-aluminum eutectoid, then the wall thickness or the distance 14 is determined by the speed with which the heat from the radiators

13 can be transferred to the part P to be molded. If, for example, the conductivity in the zinc-aluminum alloy four times faster than in steel, then the distance can

14 as a control body for the speed of the temperature, which takes on the outer surface of the part P to be molded, serve. The radiators are used to supply the required electricity 13 connected by a cable 15.

The mold also consists of an upper plate 16 which closes the mold cavity 11 and contains an opening 17 through which the zn- forming superplastic material P 'can be introduced into the mold. It should also be mentioned that the upper plate 16 can also be provided with heating elements as shown and described in connection with the lower plate 10 of the mold, in particular this can be done when very large parts are to be molded. In the case of particularly long molding processes, the upper plate 16 can also be provided with an insulating material for better thermal insulation. Docket LE 967 060 0 0 9 8 2 7/1307

1962A10

During the operation of the pressing device, the upper plate 16 is firmly connected to the lower plate 10 of the press mold and the superplastic material P ¹ is introduced into the mold via the opening 17. Before this, the superplastic material from which the article is molded is preheated to a temperature which is a little below the molding temperature of the material. If, for example, a zinc-aluminum alloy is used as the superplastic material, which has a critical mold temperature of approx. 250 ° C., then the superplastic material P ¹ to be molded is heated to approx 245 °. Thereafter, a piston 18 is lowered onto the superplastic material P 'to be shaped, which piston deforms the superplastic material as a result of the pressure and presses it into the cavity 11 of the press mold. The molding time is chosen so that all parts of the workpiece to be molded are completely molded. The workpiece or the part P is then left in the cavity 11 of the press mold for a short period of time in order to achieve complete shaping of the superplastic material. Thereafter, the upper part 16 of the mold is removed and the workpiece P can be ejected from the mold by the eject pin 12. If a zinc-aluminum alloy is used, as in the present example, then the ejected workpiece can be cooled slowly by air directly or under controlled conditions in a heating furnace in order to increase the grain size and to change the phase of the alloy, which brings about the equilibrium of the eutectic causes to enable.

The properties of the material that is suitable for use as the starting blank P * are shown in FIG. 3 with the aid of a zinc-aluminum phase diagram. This diagram also shows the typical equilibrium phase relationships that are characteristic of a eutectoid. This specific eutectoid used here has a critical phase reversal with a eutectic invariant of approx. 25O ° C and a very solid phase tC ' up to a temperature of 385 °, Pi® JL phase has a «firmness» characteristic, oils in about cten conventional docket LE 967 060 0 0 9 S 2 7/1 3 0 7

Metals, while the strength of the material is abnormally low just below the eutectic invariant is when it is in a predetermined state.

Based on the Pign. 4 and 5 the phase transition for this material is shown with the aid of an experiment. As from Fig. 4 As can be seen, cylinders S are made of cooled 78% zinc and 22% aluminum alloy between heating plates 21 and 28 brought. In addition, spacer bolts 23 made of steel are arranged between the plates 21 and 22 to prevent deformation of the between to avoid the two plates lying cylinder S. In the middle of the cylinder S, a thermocouple 24 was attached and thus the temperature change for a time, during which the cylinder S of the lower critical superplastic temperature was heated to the upper, recorded.

The plate temperature was varied between 260 and 310 ° in order to carry out various tests and to record characteristic curves such as, for example, öi © curve S. in FIG. It is noted that tlai <Vms Tesstatumwandliingspunkt S _{2 is} an essential part of this temperature & nsti @ gg & urve. The following data show the height of the SQS lateral transition point relative to the plate temperature for a body S to be inserted, which has a cylindrical shape with a diameter of approx. 50 mm and a height of approx. 50 mm.

Plate temperature Duration of the thermal break point

310-315 ° C 30

285-288 ° C 45-50

265-266 ° C, 270

In the following, an example will be described in which a part shown in Fig. Β was molded by the present invention. The cog wheel shown in Fifo € has a diameter of 31, a thickness of 32 a »?. eiae greets length 33 of the hub »Bs wircl angeiioMnan _f that fii-SFSs Sabroad © to Ssssss 1,7? 9 nafe, Der Rohlinsi fiss AaGeiasfsm & tQrAals 1st one

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Disc with a diameter of approx. 65mm, a thickness of approx. 12mm and a bore with a diameter of approx. 8mm. This blank is now prepared by homogenization at approx. 280 ° for approx. One hour and then cooled with water. This achieves the lower temperature curve. The blank was preheated up to 235 ° during the molding process, which lasted approx. 2 minutes. In addition, the actual mold made of steel was heated to a temperature of 290 ° to 300 ° C. The preheated cylinder or blank is then placed in the mold and shaped by applying pressure. The molded part is ejected after the molding process and cooled by air cooling, as already described.

Another embodiment is shown in FIG. A die 40 is critical to the above Temperature of the starting material B brought by heating rods 41. By applying a vacuum through an antechamber 42, a Negative pressure is generated in the mold, which is opposite to the opposing surfaces B and B of the inserted blank B acts, which deforms it and sicfe the shape adapts. After molding, the molded TiI can also again removed from the mold by an ejector pin or by other known means.

Docket LE 967 060 0 0 9 8 2 7/1307

Claims (4)

PATENT CLAIMS Process for the deformation of superplastic metals in heatable molding devices, characterized in that that the blank of superplastic metal to a temperature immediately below the critical temperature for the respective superplastic metal is brought that after inserting the blank into the mold, the mold is brought to a temperature that enables the desired critical temperature of the superplastic metal and that thereafter the blank is pressed against the die by vacuum or pressure to form the desired part to shape. 2. The method according to claim 1, characterized in that the blank ^, in particular made of a eutectic alloy, consisting of 78 percent by weight zinc and 22 percent by weight aluminum, before the actual molding process and Vorerwänaungsprozess is shaped cylindrically. 3. The method according to claims 1 and 2, characterized in that the metal blank before the actual Forming process to just below the critical temperature for the superplastic metal used, in particular is brought up to 2% below the critical temperature. 4. The method according to claim 3, characterized in that the formed workpiece after the direct molding is left in the form for a certain time, about total transformation and shaping of the blank accordingly to ensure the shape. Docket LE 967 060 009 827/1307