JPH08141685A - Method and device for molding metal body - Google Patents

Abstract

PURPOSE: To mold a metallic body without using sealing materials, expensive devices or the like by applying high pressure with a low m.p. metal or a low m.p. alloy having high plasticity as a pressure transferring means. CONSTITUTION: A ring-shaped metallic body 1 made of high strength stainless steel is inserted into the space between a base plate 32 and a cover plate 31 under the application of pressurizing force 51 and 52. Lead 2 is penetrated into the metallic body 1 via a passage 33 in the base plate 32 by force 53 acting on a piston 4, and, desirably, the temp. of the lead 2 has been controlled to the hot molding temp. When the pressurizing force 53 is applied, a part of the lead 2 flows into an annular gap formed on the seal face between the metallic body 1 and plates 31 and 32 as a lubricating film 21, so that the metallic body 1 moves without friction and accumulates the internal pressure required for expanding. In this way, the metallic body can be molded without using sealing materials, expensive devices or the like.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a metal body by a high pressure applied through a pressure transmission medium, a method for using this method in various forming methods, and an apparatus therefor. The principle of forming a metal body is to apply a displacement member (press die, hammer) directly to the metal body to be formed, and a pressure medium (fluid such as oil or gas).
There is a method of indirectly acting via. The conventional molding methods of the first category include press molding, hammer molding, forging, and beat molding.

[0002]

BACKGROUND OF THE INVENTION The present invention relates to the above second category of molding via a pressure medium. A wide variety of aspects of this category of methods are known. As a typical example, in the method described in German Patent Publication No. 28 06 008, a tubular body is sandwiched between two annular flanges and pressed to produce a strain-hardened tubular body. This is a method of working from the inside with a fluid. Also, "Stahl und Eise
n "102 (1982) No.23, p.1183-1189 states that a steel retaining ring (retaining ring) is used to hold the coil end against the centrifugal force generated by the rotation of the rotor of a turbo generator. In this method, deformation energy is applied to the retaining ring from two frustoconical press dies via a pressure medium to expand the retaining ring. In a method of making a similar retaining ring known from 2155194, the pressure medium is surrounded by a flexible bellows.
Water can be used as a pressure medium instead of oil.
In the case of hot isostatic pressing (HIP), gas is used as the pressure medium.

[0003]

The above-mentioned conventional fluid and gaseous pressure mediums have the following drawbacks. -Since these pressure media have a very large compressibility, it is necessary to increase the moving distance of the displacement member in order to sufficiently increase the pressure. 〇 There is an unavoidable gap between the displacement member and the mold, and between the displacement member and the molding material, but the pressure medium escapes from this gap, so a pressure drop occurs and high pressure is obtained. In addition to being unable to do so, the pressure medium that escapes at high speed poses a danger to the operator.

Therefore, an object of the present invention is to improve a method of forming a metal body by applying a high pressure through a pressure transmission medium so that an extremely high pressure can be applied without causing a sealing problem. . Further, when using an extremely high pressure, it is necessary to prevent the pressure medium from escaping even if there is a leak portion in the molding device. At the same time, a high pressure can be generated even if the displacement amount of the displacement member is small.

[0005]

In order to achieve the above object, the present invention proposes to use a low melting point metal or a low melting point alloy having high plasticity as a pressure transmitting medium. This means according to the invention eliminates the problems of the prior art by pushing and sealing this metallic pressure medium into the gap created when pressure is applied. In addition, since the metallic pressure medium is much less compressible than the conventional fluid or gas pressure medium, the desired high pressure can be generated even if the displacement member has a small moving distance.

Prior to or during molding, it is desirable to heat at least a portion of the pressure transmitting medium to a temperature that enhances its plasticity. As a result, the metallic pressure medium can easily flow into the gap, cools and solidifies in the gap to increase flow resistance, and as a result of preventing further inflow, high pressure can be generated. It is desirable to heat the pressure transmission medium to a temperature of at least 40% of the liquidus temperature by absolute temperature. Here, as a usual premise, it is assumed that the range of hot forming is higher than 50% of the melting point by absolute temperature. In particular, because of the recrystallization process, strengthening such as cold forming does not occur. This is the range of hot reshaping temperatures of the metallic pressure medium where the fluidity of the metallic pressure medium is maximized.

In one embodiment of the present invention, the pressure transmitting medium should be used with some liquid and some solid during molding. As an example of this state, when a pressure medium in a liquid state is injected into the press cavity, it is cooled and solidified by the wall surface of the press cavity, and a solidified nucleus surrounds the inside of the liquid. This liquid interior deforms better under pressure than when the metallic pressure medium exists in the solid state.

A plastically deformable wall may be provided between the pressure transmission medium and the material to be molded to prevent heat transfer.
Lead or a lead alloy has been found to be the best pressure transmitting medium. Of course, it is also possible to use a tin alloy having plastic flowability equivalent to that of lead. Lead is desirable in that it has a low melting point, and is also prominent in that it has high plastic flowability because it has low strength and high ductility. The lubricity is also outstanding. Therefore, this pressure transmission medium acts as a lubricant when it enters the gap between the parts that move relative to each other in the molding device or the gap between these parts and the molded product, and deforms the metal body under pressure. To prevent the generation of wear marks on the molding equipment. With lead or lead alloys, there is almost no residue, so there is no waste removal problem. Another advantage of lead is that it does not dissolve in iron. As a result, alloy formation with lead does not occur on the contact surface between the iron alloy molded product and the pressure medium lead. By heating lead to a temperature higher than its melting point, lead can be removed from a molding apparatus or molded product without producing a residue, and can be recovered and reused.

According to a further preferred embodiment of the present invention,
By placing the pressure-transmitting medium under pressure by the rigid displacement member under the influence of force, it is possible to mold the metal body accordingly for a predetermined portion of the volume change of the pressure-transmitting medium caused by the displacement of the displacement member. As well as
The remaining part of the volume change is to fill and seal the gap created during pressure buildup. Therefore, it is desirable to heat at least the portion of the pressure transmission medium in the immediate vicinity of the gap to a temperature that reduces the flow resistance of the pressure transmission medium. As a result, the pressure transmission medium easily enters the gap, cools and solidifies there, seals the gap, and simultaneously acts as a lubricant.

One of the preferred embodiments of the present invention is the expansion of a tubular metal hollow body having open ends such as a retaining ring. To that end, the interior of the hollow body is filled with a pressure transmission medium, both open ends are closed under pressure by rigid walls,
The pressure transmitting medium is then put under pressure by the at least one displacement member. At the same time, the metallic pressure medium can be added in solid or semi-solid / liquid state or completely in liquid state. At least one of the walls preferably constitutes a pyramidal displacement member which tapers towards the axis of symmetry of the hollow body. The pyramidal shape of the displacement member should then be selected so that the displacement member advances into the pressure transmission medium, so that the hollow body expands into the desired shape. On the other hand, the volume of the conical displacement member should be at least equal to the volume required to increase the volume when molding the material.

Another desirable application of the present invention is molding in which a long piece such as a round bar is extruded to reduce its cross section. To this end, the gap between the pressure resistant mold and the elongated product guided coaxially therewith is filled with a pressure transmission medium. The long product is extruded from the cross sectional reduction nozzle while being surrounded by the pressure transmitting medium. At that time, the pressure transmitting medium can be refilled into the mold continuously or intermittently.

In order to facilitate the forming, according to the present invention, it is also possible to heat the metal body to be formed to a high temperature, in particular to a hot forming temperature, before forming. One of the more desirable uses of the present invention is hot isostatic pressing. To this end, a press cavity for accommodating a metal body to be molded is filled with a pressure transmission medium in a liquid state, and then a high pressure is applied to this pressure transmission medium by a press die as a displacement member.

The apparatus for carrying out the forming method by hot isostatic pressing comprises a cylindrical mold having a base part which can be closed after charging the compact material. Furthermore, a press die which can be introduced into the other end of the mold, a connecting member for supplying liquid lead or a liquid lead alloy, and a central stopping means for the compact material, particularly inserted laterally into the press cavity. And a screen-like means. When liquid lead or liquid lead alloy is injected into the press cavity, the compact material floats and is held in the center of the press cavity in a non-contact manner by a screen as a stopping means. In any case, this screen allows the compact material to be fully (isotropically) through the pressure transmitting medium.
Loaded with pressure.

Before molding, the metal body to be molded is preferably coated with a heat insulating film such as an enamel layer or a ceramic layer whose deformation resistance does not hinder the molding process. Hereinafter, the present invention will be described in more detail by way of examples with reference to the accompanying drawings.

[0015]

EXAMPLE As shown in FIG. 1, a ring-shaped metal body 1 made of high-strength stainless steel was placed between a base plate 32 and a cover plate 31, and the metal body 1 was loaded by applying pressure forces 51 and 52. Insert it between both plates. The lead 2 is pushed into the metal body 1 through the passage 33 in the base plate 32 by the force acting on the piston 4 as the displacement member. In this case, the temperature of the lead is between room temperature and its melting point, preferably the hot forming temperature. When a pressure is applied, a part of lead is introduced into the lubricating film 21 in the annular gap formed in each sealing surface between the metal body 1 and each of the plates 31 and 32.
Flows in as. As a result, the two plates 31, 32
The movement of the metal body 1 with respect to is performed virtually without friction, and the metal body 1 is expanded. Since lead, which is a pressure medium, seals each annular gap, pressure accumulation can be performed up to the internal pressure required for expanding the metal body 1.

FIG. 2 shows another embodiment, in which the inclination of the outer pyramidal surface 41 of the upper die 41 changes.
The volume displacement occurs when the conical portion enters the metal body 1. This displacement must match at least the amount of volume increase of the expanded annular metal body 1, and the difference that does not match can flow out as the lubricating film 21. An experiment was conducted using the pressurizing device schematically shown in FIG. 18% chromium, 18% manganese, 0.
A ring material made of nitrogen-containing high-strength austenitic stainless steel containing 6% nitrogen as an essential alloy component was subjected to expansion processing for the purpose of strain hardening. The initial size of the ring material is 20
It was 0 mm, the outer diameter was 280 mm, and the length was 370 mm. Parts made of this steel were used as so-called retaining rings when making a generator. The part must not exhibit ferromagnetism and must exhibit high strength along with high toughness. Required yield points 1100-150
0 MPa can only be obtained by strain hardening. This can be done without difficulty by expanding using a cone-shaped member and a series of wedge members in the case of a ring with a large diameter, but with a ring with a small inner diameter, the surface friction increases. This method cannot be used because good processing cannot be performed even if expensive lubrication technology is used.

After the annular metal body 1 is placed on the base plate 32, liquid lead at about 400 ° C. is injected into the hollow space of the metal body 1. At the contact surface between the metal body 1 and the base plate 32, and at the contact surface between the downward-moving cone-shaped upper die 41, lead rapidly solidifies, and as a result, the metal body 1 and the base plate are formed. A lubricating film 21 of solidified lead is formed in the gap between the metal body 1 and the conical upper die 41. Immediately after the conical outer surface of the upper die 41 touches the upper annular opening of the hollow metal body 1, the hydraulic pressure rapidly increases. At the same time, the lubricating film 21 is maintained at a thickness of a few hundredths of a millimeter, which promotes relative movement of the metal body 1 with respect to the base plate 32 and the upper die 41 during the expansion process of the metal body 1. The obtained expansion degree was 40%. The maximum value of the pressing force during the expansion processing was 2300t. Considering the opening of the expanded metal body 1, this corresponds to a pressure in the lead of about 2400 bar. By this processing, the variation of the ring diameter is 2mm with respect to the total ring length.
It was nothing more than That is, under the conditions as described above, lead is a practically ideal hydraulic medium having a hydrostatic pressure distribution. Next, the conical pressure die 41 was raised to melt and discharge lead. In the tensile test, a yield point of 1475 MPa was obtained for the expanded hollow body.

The embodiment of FIG. 3 is similar to that of FIG. 2, but in this case, the metal body 1 is a metal sheet wound in a coil shape and welded, and the metal body 1 is placed in an airtight casing and heated to a high temperature. The molding temperature was heated to 1200 ° C. This metal sheet coil is separated from the pressure transmission medium 2 by an insulating and easily deformable layer 6. The layer 6 reduces the heat transfer between the hot metal sheet and the pressure transfer medium 2, thus preventing unacceptable overheating of the medium 2 and excessive quenching of the metal sheet coil.

In an experiment using the above apparatus, a laminate of stainless steel sheets was made to produce a high strength thick ring. Chrome with a thickness of 0.6 mm and a width of 350 mm
After nitriding the nickel steel sheet at 1200 ° C in a nitrogen atmosphere to make the nitrogen content 0.4%, the diameter is 420 mm.
Was tightly wound around a core having both side walls and a shaft having an outer diameter of 260 mm. The final wrap layer is at 415 mm,
The total weight of the stainless steel sheet was 196 kg. A steel sheet was tightly wound around the final winding layer and wound, and then a space between both side walls was welded to form a seal portion to obtain an airtight package. This was heated in a gas heating furnace for 6 hours. A stainless steel tube having a wall thickness of 2 mm and a length of 350 mm was filled with lead and wound with a composite sheet of a stainless steel sheet and hard cardboard. It was wound 11 times to give an outer diameter of 235 mm. Next, the uppermost layer of the stainless steel sheet was spot-welded to the layer immediately below it several times by a welding facility to form an integral tubular body which was fitted exactly to the inner diameter of 250 mm of the stainless steel sheet coil. In parallel, a thick outer ring 7 having an inner diameter of 449 mm was prepared. A high temperature stainless steel sheet coil was loaded in the ring 7 and the space between them was filled with quartz sand to reduce the filling volume. The assembly was brought to a press where the wrapped and lead-filled tube was already standing on the pressure table. The stainless steel sheet coil was then lowered onto the lead-filled tube with the ring 7 around it. The clearance volume between the stainless steel sheet coil and the cooled outer surface of the lead-filled tube was filled with quartz sand. Next, a conical die was placed on the lead surface and a force of 51 was applied. Since the total setup time was less than 9 minutes, the temperature drop of the hot stainless steel sheet coil was negligible.

After the power of the press was turned on, as a first step, the lead-filled tube was expanded and brought into contact with the hot stainless steel sheet coil. As a second step, the internal pressure of lead was raised to about 500 bar to bring the stainless steel sheet coil into contact with the support ring 7. This was found by increasing the press pressure to 2100 bar. After holding at this pressure for 0.5 minutes, the pressure was released. As a result, it was found that lead was still solid and that the composite sheet of cardboard and steel sheet worked effectively. The intermediate ring transferred the lead pressure to the stainless steel sheet coil while preventing heat exchange between the stainless steel sheet coil and the lead. In just 2 hours, the temperature in the lead increased to the point where melting started. Since the intermediate ring was previously placed on the collection container, lead could be removed without difficulty in this way. Subsequent examination of the metallic structure of the stainless steel sheet coil revealed that the individual sheets within the coil were well welded together.

As another example, FIG. 4 shows a cold expanding process for the tubular body 1. With the expansion of the tubular body 1, the tubular body 1
A displacement member 41 having a truncated truncated cone-shaped pressure surface is pressed by a force 51 through a die serving as the displacement member 4 passing through.
The hollow space of the tubular body 1 is filled with lead 2. As the displacement member 4 advances, the lead 2 is displaced through a gap between the displacement member 4 and the tubular body 1, and a lubricating film 21 is formed between both members and the tubular body 1.

FIG. 5 shows extrusion molding of a long product (a round bar in this example). The metal body 1 to be processed is inserted into the hollow space 33 of the extrusion mold 34, and lead 2 is filled in the space between the metal body 1 and the wall surface of the hollow space. Press die 4
The metal body 1 to be processed is extruded through the extruding nozzle 35 while the cross-section is reduced by the pressing force 51 applied to the. The lead film 21 extruded while reducing the cross section between the inner surface of the extrusion nozzle 35 and the outer surface of the metal body 1 accelerates the extrusion process.

FIG. 6 shows the automatic lead refilling mechanism of the extruder. Holes 39 are regularly distributed in the drum 37.
The tubular body 24, for example lead, is inserted into the hole 39 at one point. When the drum 37 is properly rotated, the lead tubular body 24 is positioned at the entrance of the hollow space of the extrusion mold 34. FIG. 7 shows an extrusion device similar to that of FIG. However,
In the embodiment of FIG. 7, in a method similar to the die casting method,
Liquid lead is injected or pressed into the hollow space 33. The direct contact portion of the extrusion nozzle 35 and / or the extrusion mold 34 is water-cooled. As a result, the lead solidifies in this region 23 and the increased flow friction forms the seal and lubrication film 21, which allows the hydraulic pressure in the hollow space 33 in the extrusion mold 34 to accumulate.

8 to 10 are schematic sectional views showing a press machine for hot isostatic pressing (HIP). The pressure-resistant container 34 shown in FIG. 8 can be closed at the bottom by the base cover 32. The diameter of the inner hole is, for example, 40 mm, and the lower part is thermally insulated by the ceramic lining 61. The heat insulating portion 61 is formed by inserting, for example, ceramic paper, and a ceramic filter plate 62 made in the same form as a strainer core in a known casting sprue system is arranged at the uppermost portion thereof. Above the filter plate 62, the hollow space 33 of the pressure vessel 34 is tapered in the section 33a, and is matched with the inner diameter of the cylindrical portion 33b in which the pressure die 4 can move by a predetermined stroke. The pressure vessel has another hole in the lateral direction, through which the liquid lead 2 can be introduced through the ceramic tube inserted therein.

The base cover 32 is opened, and the metal body 1 to be processed is introduced into the interior 33 which has been heated to the processing temperature in the heating device in advance. Next, the cover 32 is closed and the container 3
Tighten to 4 airtight. The container 34 includes a water cooling system (not shown). As shown in FIG. 9, liquid lead 2 is injected from the side pipe 8 in the direction of arrow 81. At this time, a known die-casting technique can be used. At the same time, the atmosphere in the container space 33 is released to the outside from the air gap between the die 4 and the inner surface 33b. The filling state of lead 2 is as shown in the liquid level 82, for example. Due to the buoyancy of heavy molten lead, the metal body 1 floats, but the filter plate 62 prevents further rise.

Immediately after the filling process is completed, the solidified shell 23 (FIG. 10) is spontaneously formed at the position where the liquid lead comes into contact with the cold metal wall, and the seal gap of the base cover 32 and the seal gap of the die 4 are formed. Both are sealed enough to withstand high pressure. Solid lead flows in the air gap in accordance with the basic principles of the invention, thereby providing a lubricating action. If a force of 60 t is applied to the die 4 having a diameter of 40 mm, for example, the hydrostatic pressure will be 500 in a few seconds.
It rises to 0 bar, and as a result, the metal body 1 solidifies in an instant. Since the metal body 1 is in the "insulated ceramic cage", the temperature drop will be correspondingly slow. However, if the wall thickness is appropriately adjusted, it can be changed in a wide range.

When the pressurizing cycle is completed, the pressure is released and the base cover 32 is opened, at which time the contents are discharged. Then, for example, it falls onto a screen, where residual heat is discharged together with lead and flows to a collecting tank. From there it can be used for the next molding.

[0028]

The above device has the following advantages over ordinary HIP. * Do not use expensive furnaces. 〇 Do not use expensive pressurizing equipment. 〇 No sealant is used.

O Expensive pressurized gas is not consumed. As a particularly advantageous point, lead has a low melting point of 327 ° C, but a boiling point of more than 1600 ° C. Therefore, at the solidification temperature of ordinary metal, for example, 1150 ° C, the vapor pressure is only 10 mb.
It is about ar. However, since a thick solidification nucleus is formed immediately after the injection, lead heated to a high temperature does not come into contact with the atmosphere.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view schematically showing an embodiment in which a method of the present invention is applied to expand a tubular hollow body such as a retaining ring.

FIG. 2 is a vertical sectional view showing another embodiment using a cone-shaped upper die.

FIG. 3 is a vertical cross-sectional view schematically showing a pressing device for expanding a multilayer tubular hollow body.

FIG. 4 is a vertical cross-sectional view schematically showing a state in which a conical forming die is coaxially guided in a cylindrical hollow body to expand the hollow body.

FIG. 5 is a vertical sectional view schematically showing an extrusion process.

6 is a vertical sectional view showing a process of intermittently placing a pressure medium on the apparatus of FIG.

FIG. 7 is a vertical cross-sectional view showing the extrusion process of another embodiment.

FIG. 8 shows a hot isostatic press (HI) according to the present invention.
It is sectional drawing which shows the 1st procedure in the process of P).

FIG. 9 shows a hot isostatic press (HI) according to the present invention.
It is sectional drawing which shows the 2nd procedure in the process of P).

FIG. 10 shows a hot isostatic press (H
It is sectional drawing which shows the 3rd procedure in the process of (IP).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Metal body to be formed 2 ... Lead (pressure transmission medium) 4 ... Displacement member 6 ... Insulating and easily deformable layer 21 ... Lubrication film 31 ... Cover plate 32 ... Base plate 34 ... Extrusion mold (pressure resistant container) 35 … Extrusion nozzle 41… Conical upper die 51, 52… Pressing force

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Heinrich Fiftinger Zeher-8128 Hinterech, Imbat 1 Switzerland (72) Inventor Geralt Stein, Federal Republic of Germany, De-45133 Essen, Campelfeld 12 ( 72) Inventor Joachim Menzel, Federal Republic of Germany, De-45133 Essen, Bidenburg 58 (72) Inventor Joachim Ruek, Federal Republic of Germany, De-44789 Bochum, Steinring 45 Ar

Claims (19)

[Claims] 1. A method for forming a metal body by applying a high pressure through a pressure transmission medium, which comprises using a highly plastic low melting point metal or low melting point alloy as the pressure transmission medium. 2. The method of claim 1, wherein at least a portion of the pressure transmitting medium is heated to a temperature that increases plasticity before or during molding. 3. The method according to claim 2, wherein the pressure transmission medium is heated to a temperature of at least 40% of the liquidus temperature. 4. The method of claim 3, wherein the pressure transmitting medium is used in a partially liquid and partially solid state during the molding. 5. A plastically deformable wall between the pressure transmission medium and the metal body to be formed blocks heat transfer, as claimed in any one of the preceding claims. Method. 6. The method according to claim 1, wherein lead or a lead alloy is used as the pressure transmission medium. 7. An alloy having fluidity equivalent to that of lead is used as the pressure transmission medium.
The method according to any one of the above. 8. The force applied to the pressure transmission medium by the displacement of the displacement member is set to a metal body for a predetermined portion by placing the pressure transmission medium under pressure by the displacement member having rigidity affected by the force. 8. The molding according to claim 1, wherein the remaining part of the force fills the gap formed during the pressure accumulation with a part of the pressure transmission medium. The method described in. 9. The method according to claim 8, wherein at least a portion of the pressure transmission medium located in the immediate vicinity of the gap is cooled to a temperature that increases its flow resistance. 10. A method for expanding a tubular hollow metal body having open ends, such as a retaining ring, by using the method according to claim 1, wherein the hollow metal body Filling the interior with the pressure transmitting medium, closing both open ends under pressure by rigid walls, and placing the pressure transmitting medium under pressure by at least one displacement member. 11. The method of claim 10, wherein at least one of the walls comprises a conical displacement member that tapers toward the axis of symmetry of the hollow metal body. 12. The method of claim 11, wherein the conical displacement member causes the hollow metal body to expand into a desired shape by its movement into the pressure transmission medium. . 13. A method for reducing the cross-section of a long product such as a round bar by extrusion using the method according to any one of claims 1 to 9, wherein a pressure-resistant mold and coaxial therewith. The pressure transmission medium is filled in the space between the long product guided in a shape of, and the long product is extruded from the cross-section reducing nozzle by using the pressure transmission medium surrounding the long product as a lubricating film. How to characterize. 14. The method of claim 13, wherein the pressure transmission medium is refilled into the mold continuously or intermittently. 15. The method according to claim 1, wherein the metal body is heated to a high temperature, especially to a hot forming temperature before forming.
The method according to any one of the above. 16. A method of performing hot isostatic pressing using the method according to claim 1 and the method according to claim 15, wherein a metal object to be molded is housed. The method is characterized in that the pressurizing cavity is filled with the pressure transmitting medium and then pressed by a press die as the displacement member. 17. An apparatus for carrying out the method according to claim 16, wherein a base body (32) which can be closed at one end after charging a metal body to be pressed and which can be introduced into the end. A cylindrical press mold (34) with a die (4), a connecting member (8) for supplying liquid lead (2) or a liquid lead alloy, and a central stop for the metal body (1). An apparatus comprising means. 18. A device according to claim 17, characterized in that the stopping means are filtration plates (62) laterally inserted into the pressure cavity (33). 19. The method according to claim 16, wherein the metal body to be molded is covered with a heat insulating layer such as an enamel layer or a ceramic layer having a deformation resistance that does not hinder the molding process before molding.