NZ211540A - Forming a tubular extrusion casting mould on a mandrel - Google Patents

Description

21 1540 Priority Date(s): .... > Complete Specification Filed Class: ?/<?.* ...& Publication Date: 3.QX rfl:imZk..

P.O. Journ.;)' Mo: . . . . J Patents Form No; 5 PATENTS ACT 1953 COMPLETE SPECIFICATION "METHOD OF MANUFACTURING OR MATERIAL TREATMENT OF CONTINUOUS MOULDS FOR EXTRUSION CASTING MACHINES" We, KABEL-UND METALLWERKE GUTEHOFFNUNGSHUTTE AKTIENGESELLSCHAFT, of Kolsterstrasse 29, 4500 Osnabruck, Federal Republic of Germany, a German Company, hereby declare the invention, for which we pray that a Patent may be granted to us and the method by which it is to be performed to be particularly described in and by the following statement (followed by page 1A) - 1A - -- *> 211540 The present invention relates to a method of manufacturing continuous moulds for extrusion casting machines, in which a piece of tube of copper or copper alloy is formed on a mandrel having the inner and final volume and/or shape of the mould to be manufactured or to be treated and is forced from outside onto the mandrel, which is subsequently removed from the piece of tube.

New Zealand Patent Specification No. 158462 already describes the manufacture of curved continuous moulds for circular curved extrusion casting machines in which a mandrel having the inner volume and the shape of the mould to be manufactured is pressed into a straight piece of tube and the piece of tube is thus initially formed to correspond to the dimensions of the mandrel. In this known method the piece of tube and mandrel are subsequently passed together through a die in order to press the inner surfaces of the piece of tube tightly onto the mandrel. Subsequently the mandrel and piece of tube are separated from one another by withdrawing the mandrel.

Likewise, a calibrating mandrel is used in another known method (British Patent Specification No. 1461744) in which the force producing the shape is applied from the outside onto at least one wall of the mould by explosive detonation.

Explosive pre-forming has already been used (British Patent Specification No. 1449868) in the manufacture of tube moulds, and also in the material treatment of used extrusion castings moulds. The walls of the mould are formed on a shaping or 2M540 calibrating mandrel which is provided within the extrusion casting mould and determines the inner contour of the mould. The shaping or calibrating mandrel guarantees high accuracy of the volume of the interior shaping space of the mould as well as high surface quality of the limiting wall surfaces, independent of which manner the shaping force is applied to the outer wall of the piece of tube on the shaping or calibrating mandrel.

Extruded cast steel manufactured with the known tube moulds has a rectangular, quadratic or round cross-sectional shape. Further working is needed with these basic cross-sections, where for example, special cross-sectional profiles are to be rolled into T- or double T- shapes. A plurality of rolling steps is necessary to produce the end product from these known cast cross-sections.

Moreover, extrusion casting moulds are already known whose shaping chambers have a cross-sectional shape deviating from the rectangular or circular form (DE-AS 12 82 8 61) (available on request) and which use a so-called divided mould with differing wall thicknesses and in which different cooling rates consequently occur during the casting process.

Tubular extrusion casting moulds with a profiled cross-section, i.e. a cross-section which deviates from the known rectangular or circular form, and with mould walls of a uniform thickness limiting the forming chamber are likewise already known (Zak-Fab "Welded Moulds, Mould Bulletin No: 410, 21 November 1968) . rv O 7 ■21154C Such welded tube mould constructions have not previously been successful, since the necessary quality requirements are not always fulfilled. Commencing from this state of the art the invention consequently has the object of manufacturing tube moulds with a moulding chamber of any cross-sectional shape having the known quality of, for example, rectangular tube moulds.

According to the invention this object is solved by a method of manufacturing continuous moulds for extrusion casting machines, in which a tube of copper or copper alloy is cold drawn or rolled and cut into a pre-form having a cross-section approximating the final cross-section of the mould and subsequently pressed onto a mandrel and deformed from outside by force, to fit tightly onto the mandrel, said mandrel having outer dimensions equivalent to the final inner volume of the mould, said mandrel having a cross-section of T-, double T-, U- or L-shaped profile, and being subsequently removed from the mould to produce said cross-sectional shape of T-, double T-, U- or L-shaped profile respectively of the mould. The high volume accuracy and the quality of the cast extrusion that can be produced enables the subsequent worker to commence with cross-sectional profiles •which already have the correct initial rolling shape and which only need the smallest possible re-shaping of the material to achieve the desired quality requirements. Thus, to produce, a railway line profile, for example, the operative starts with a steel extrusion cast in a tube mould having a double T-cross-sectional chamber to enable him to roll it out subsequently into the final shape and with the desired quality. One can ^ *7 thus avoid the need for a plurality of rolling mills for its conversion into the final profile. However, it is only here that the invention has essential advantages. In performing the invention it is also possible by starting from the desired final profile to choose with predetermined dimensions and qualities the profile of the roller required to produce this final profile.

The invention relates to "profiled" cross-sectional shapes that deviate from the rectangular shape, from the quadratic shape and from the circular shape, the "profiled" cross-sections being T-, double T-, U- or L- shaped cross-sectional profiles.

Moreover, the mandrel which can be inserted or pressed into the piece of tube, i.e. into the mould, is essential to the invention. This mandrel can also be formed conical, either single or double, in order to ensure conicity of the forming chamber of the mould, where required. The mould can also be bent to guarantee the application according to the invention of the manufactured tubular moulds to circular curved extrusion casting machines.

The different profiling of the moulding chamber can require undercuttings in the forming of the calibrating mandrel. After forming the tube or mould walls on the mandrel surface during calibration of the interior of the forming chamber and the subsequent withdrawal of the mandrel from the mould chamber it has been shown preferable in the further execution of the invention to then recalibrate the tube or the mould from the outside. The profiling pressed outwardly on withdrawing the calibrating mandrel can thus again be drawn back into the position taken up after forming on the mandrel.

/A further advantageous possibility of solving the problem of the harmless withdrawal of the calibrating mandrel forming the 1 211540 inner chamber of the mould with undercuttings is to cut the mandrel twice or more. Thus the cutting of the mandrel can be effected longitudinally and/or transversely of the axial direction of the mould.

Relevant to the invention is the use of a calibrating mandrel on which the tube or the mould is formed by outer application of * > force. The forming force can be produced in various ways.

As is already known for tubular moulds which are rectangular in cross-section, the mandrel and the piece of tube.or the mould can be passed together through a forming die for this purpose. However the other known possibility in which the force producing the shape can also be applied by explosive detonation can be advantageous for the purposes of the invention.

As well as this method already known for other purposes it is also sometimes advantageous to produce the shaping force for calibrating the tube or the mould by a forging process, by rolling or even by hydrostatic pressure.

A previously completely unknown way of producing shaping forces for mould manufacture and/or material treatment is so-called electro-hydraulic forming. In this method the energy is introduced by means of an electrical spark gap in the acting medium e.g. water, and transferred to the workpiece to be deformed. The electrical energy necessary is made available with a surge current apparatus"; ■:;;i - " >" 1540 One method for deforming work pieces by means of work energy is the so-called electro-magnetic deforming. In this method the electrical energy stored in condensors is discharged via a coil, which for example, is arranged around the mould to be deformed. This current produces a magnetic field which induces a counter-current around the walls of the mould. The magnetic field thus exerts a force on the wall of the tube which causes its application to the mandrel surface. With the help of so-called field formers the desired pressure distributions adapt themselves to the tube wall.

The two last-mentioned methods are also suitable in pursuing the invention, using a calibrating mandrel to manufacture moulds of any cross-sectional form, rectangular or round, but also of the desired profile, high quality and volume accuracy.

In order to manufacture the profiled cross-sectional shape it has been found necessary to use pieces of tube of approximately T-, double T-, U- or L- shaped initial cross-section, when it is desired to give corresponding profiles to the form-producing mould chamber. Thus, for' example, these initial cross-sections can be manufactured by extrusion pressing, and the subsequent formation of the cross-section over an inserted mandrel then requires only 15-25% of cross-sectional shaping, relative to the initial cross-section. This relatively small ratio of deformation then serves to ■v <211540 — 7 - improve the quality, for example, to increase the Brinell hardness.

An initial shape (pre-form) with already "profiled" cross-section is manufactured by extrusion pressing a rouml or oval tube with subsequent drawing or rolling.

As already mentioned in the state of the art, tubular moulds consisting of welded sheets are known. These are of further advantage in applying the invention. Correspondingly formed initial shapes (pre-forms) are used for the manufacture of a T-,double T-, U- or L- shaped mould, for example, which shapes are then deformed by outer force onto a calibrating mandrel. With the method according to the invention the known welded tubular moulds can also be calibrated after their manufacture and thus provide an essential improvement and increase in quality.

The invention will be described below with the aid of the embodiment shown in Figures 1 to 5 showing the manufacture of double T- profiles by way of example only.

Figure 1 shows a blank, drawn, straight copper tube 1 with a Brinell hardness of, for example, HB50-60 manufactured from an extrusion-pressed round tube by tube drawing. . This tube 1 is cut to the desired length of mould according to the working requirements.

■ In the next step this initial tube is'brought to the shape shown in Figure 2, e.g. by drawing, with the use "^TiifiwM■ a .n rMir'_ . .'.Vj n n njniimT 21154 of a profiled die and a corresponding mandrel or by rolling (pre-form) with correspondingly profiled rollers. This preliminary shape/ 2 with a cross-section approximating to the desired cross-sectional shape of the mould must now be brought to the desired dimensions and an increase in quality ensured. To this end, the hard, chromium plated mandrel 3 with double T-shaped cross-section shown in Figure 3 is used. This mandrel 3 is, as can be seen from Figure 4, pressed into the pre-form 2 and subsequently the pre-form 2 is deformed onto the mandrel 3 by outer force. This deformation can be effected by passage of the preliminary form 2 and mandrel 3 together through a pressure ring, whereby the pre-form 2 is brought tightly onto the surface of the mandrel 3. Such cold forming of the copper pre-form 2 produces an absolute dimensional stability of the mould 4 thus manufactured as is shown in enlarged detail in Figure 5. The Brinell hardness is hereby increased from the original value to approximately HB80-100.

The deforming of the pre-form 2 on the mandrel 3 can be effected in a different way from this , for example, with the help of the originally described method of detonation of explosive or by a forging or rolling process, in which the mandrel and preliminary form together proceed through one or several working stages in sequence.

Other possible ways of bringing the pre-form 2 tightly onto the mandrel 3 is calibration by means of electrical discharge or by producing a magnetic field or with the help of 7 hydrostatic pressure.

The mould 4 shown in Figure 5 can also, for example, be a mould produced by the welding together of sheet parts, which subsequently or after lengthwise extension are subjected to a calibrating step by means of an inserted mandrel.

The mandrel 3 according to Figure 3 can also be bent to adapt the mould to be finished or treated to the curved arched shape of the extrusion casting unit, and if necessary, can be formed conical or partly conical. By pressing such a mandrel into the straight pre-form mould 2 corresponding shaping of the tubular mould then occurs.

Obviously by using an additional step the pre-form - mould 2 can already be given the curved form before even a curved mandrel is insertedi into it.

The example according to the invention shows the manufacture of moulds or their treatment in relation to profiled cross-sections of a double T- profile. Any other profiles can be appropriately manufactured' whereby, for example, with T-, U-, or L-profiles and correspondingly shaped mandrels, the preliminary shape (pre-form is adapted to hold the degree of deformation within predetermined limits.

Independent of the profile shape the invention guarantees high quality tubular moulds with constant walls and thus uniform cooling ratios as compared to known arrangements. Thus it is important that the mandrel is formed corresponding to the desired mould casting cross-section, i.e. itself has for example, 2 U 5.40 a T-, double T-, U-, or L- shaped cross-section according to the invention. If the above mentioned pre-forxns are formed on such a mandrel, the force must consequently act on all sides, for example, also in the edge region. When forming with pressure rings, matrices, rolling arrangements and the like, the tools used must therefore be appropriately constructed.

The representations of Figures 1-5 show the pre-form mandrel and finished moulds of straight construction. This straight construction was chosen as the simplest representation, however, the invention should not be limited to this.

Deviating from this,generally a curved calibrating mandrel is used,since the majority of steel extrusion casting units used today are curved units with correspondingly curved shaped moulds.

The curved mandrel of cross-section, for example, T-, double T-, U—, L-shape can then either be pressed into the curved pre-form or to be pressed into a straight pre-form somewhat corresponding to Figure 2. ' ' O 2ii540

Claims (18)

WHAT WE CLAIM IS:

1. A method of manufacturing continuous moulds for extrusion casting machines, in which a tube of copper or copper alloy is cold drawn or rolled and cut into a pre-form having a cross-section approximating the final cross-section of the mould and subsequently pressed onto a mandrel and deformed from outside by force, to fit tightly onto the mandrel, said mandrel having outer dimensions equivalent to the final inner volume of the mould, said mandrel having a cross-section of T-, double T-, U- or L- shaped profile, and being subsequently removed from the mould to produce said cross-sectional shape of T-, double T-, U- or L- shaped profile respectively of the mould.

2. A method according to claim 1, characterised in that the application of force from the outside is produced through the common passage of the mandrel and the pre-form mould through a die.

3. A method according to claim 1 characterised in that the application of force is applied from outside by detonation of explosive.

4. A method according to claim 1, characterised in that the application of force is effected by application of electrical discharge. 211540

5. A method according to claim 1, characterised in that the application of force is effected from outside under the influence of a magnetic field.

6. A method according to claim 1, characterised in that the application of force is effected from the outside by a forging process.

7. A method according to claim 1, characterised in that the application of force is effected from outside by a rolling process.

8. A method according to claim 1, characterised in that the application of force is effected from outside by means of hydrostatic pressure.

9. A method according to any one of the preceding claims, characterised in that the T-, or double T-, U-, or L-shaped cross-sectional pre-form is produced by extrusion pressing with cross-sectional deformation from 15-25% relative to the pre-form cross-section on subsequent calibration with a mandrel.

10. A method according to any one of the preceding claims, characterised in that the T-, or double T-, U-, or L-shaped cross-sectional pre-form is attained by extrusion pressing of a round or oval tube followed by drawing or rolling.

11. A method according to any one of the preceding claims, characterised in that the tube is also bent intp'a curved pre-form. /v > I; t 7 MAR i987 V » 13 a 211540

12. A method according to any one of the preceding claims characterised in that a tube welded from sheet metal is used as to form the pre-form.

13. A method as claimed in any one of the preceding claims using an undivided calibrating mandrel characterised in that the mould formed on the mandrel is calibrated from outside after removal of the mandrel from the mould inner chamber.

14. A method according to any one of the preceding claims, characterised in that the mandrel is shaped conical or partly conical.

15. A method according to any one of the preceding claims characterised in that the mandrel is curved.

16. A method according to any one of the preceding claims characterised in that the mandrel is divided twice or more.

17. A method according to claim 16, characterised in that the division of the mandrel is longitudinal and/or transverse to the axial direction.

18. A method for the manufacture of continuous moulds for extrusion casting machines as hereinbefore described with reference to the accompanying drawings. 6f " * r>, <*orv ■ iriii i O SON & CAREY _