RU2673252C1 - Method of manufacturing composite material with aluminum matrix - steel deoxidizer - Google Patents

Abstract

FIELD: metallurgy.SUBSTANCE: invention relates to the field of metallurgy and can be used in the manufacture of composite materials with aluminum matrix for use as a deoxidizer in steel production. In the method, the molded freestanding preform is heated to a temperature which is higher than the melting point of aluminum and lower than the melting point of the iron-rich component, for a time that ensures the transition of aluminum to a liquid state, applying pressure to the free-standing preform to obtain a densely compacted iron-rich component of the free-standing preform and solidification of molten aluminum in it. Free-standing preform may also consist of aluminum particles and particles of components selected from the group consisting of steel, ferromanganese, silicocalcium, calcium carbide, rare earth metals, ferroalloy, with the exception of ferromanganese, and combinations thereof.EFFECT: invention allows to obtain an effective and economical composite material with an aluminum matrix – steel deoxidizer, which is almost completely dense, free of brittle intermetallic compounds and allows aluminum to penetrate deep into molten steel, eliminating the unnecessary loss of this valuable metal to its unnecessary oxidation reactions in slag and atmosphere.20 cl

Description

LINK TO THE ASSOCIATED APPLICATION

This application declares priority and uses the United States Interim Application Serial No. 62 / 079,558 of November 14, 2014, the contents of which are incorporated by reference.

Field of Invention

The invention generally relates to a method for the production of composite materials and in particular to a method for manufacturing a composite material with an aluminum matrix for use as a deoxidizer in the manufacture of steel.

Description of the Prior Art

Deoxidation of steel (i.e. removal of oxygen from molten steel before casting) is a necessary technological operation in a modern steelmaking process. During the casting operation, while the steel cools and hardens, the dissolved oxygen reacts with carbon to form gas bubbles of carbon monoxide (CO), which get stuck in steel slabs and ingots, resulting in porosity. Porosity is a serious defect in the production process, causing a decrease in the mechanical properties of steel and flat steel in particular, and therefore oxygen must be removed.

To deoxidize molten steel, metallurgists typically introduce strong oxide-forming elements such as Mn, Si, and Al into the steel melt. These elements react with dissolved oxygen and form solid particles of oxides, which are lighter than molten steel and float to the surface of the melt joining the slag that protects the surface of the molten steel.

Aluminum is one of the most powerful deoxidizing agents used for almost all flat steel products, accounting for about 60% of all steel produced. Aluminum is typically fed into molten steel in two stages of a steelmaking process. The first supply, where most of the aluminum is used, is made when steel is released into a ladle from an electric arc or oxygen-converter furnace in the form of ingots or cones placed on the bottom of an empty ladle and / or a stream of steel being thrown into the funnel. In addition to its primary task of deoxidation, the supply of aluminum during production also increases productivity, since aluminum deoxidation proceeds quickly and reaches its end while the ladle is transferred to the next operation. The second feed, where less aluminum is usually used, is made directly into the ladle at the out-of-furnace steel processing (OVOS) installation - a special intermediate unit between the melting furnace and the crystallizer, whose main task is to improve the quality of the molten steel and refine its composition to the corresponding specification. The industry average uses 2 kilograms of aluminum per tonne of steel.

The main problem of using aluminum for steel deoxidation is that this valuable metal is irretrievably lost. After aluminum reacts with oxygen to form aluminum oxide or aluminum-containing oxides that float to the surface of the molten steel and mix with the coating slag, there is no practical way to restore aluminum to a metallic state. As a result, up to 4% of the primary (recovered from bauxite ore) aluminum produced in the world irrevocably is lost in the process of steel deoxidation. However, only about 30% of these losses are technologically necessary and the result of the reaction of oxygen dissolved in steel with aluminum, the remaining 70% are useless losses. To understand why, imagine that during deoxidation, aluminum in the form of ingots or small cones is loaded into a ladle containing molten steel. The surface of the molten steel in the ladle is covered with protective slag containing a large amount of iron oxide. Since aluminum has a much lower density than molten steel (2.2 versus 7 g / cc at this temperature), it floats to the surface of the melt, where it gets stuck in the slag covering the surface of the molten steel, and most of the aluminum (70%) is in contact and reacts with oxygen in iron oxide in slag or in atmospheric air instead of oxygen dissolved in steel, and therefore is lost uselessly.

It should be noted that aluminum is a very highly energy-intensive metal in production, requiring 174 GJ of electrical energy to produce one ton of primary aluminum from bauxite ore. Fortunately, aluminum is very resistant to atmospheric corrosion and can be easily reused by remelting scrap - an operation that uses 10 times less energy than the primary production of aluminum from ore. Therefore, in the light of global climate change caused by the emission of carbon dioxide, produced largely in the process of generating electric energy, irretrievable losses of aluminum in general, and useless irretrievable losses in particular, are a very serious environmental problem.

An obvious engineering solution to the problem of aluminum floating onto the surface of the steel during deoxidation would be to combine aluminum with a heavier component so that the aluminum is deeper immersed at the time of loading in molten steel. The logical choice of the weighting component would be iron or steel, since it can weight the joined material without contaminating the steel melt. Indeed, if we consider the previous well-known practice of solving this problem, such a material called ferroaluminium alloy obtained by alloying at high temperature of iron (or steel) with aluminum has been offered on the market since about the 1970s - see [Deely P.D. "Ferroaluminum -Properties and Uses" in Ferroalloys and Other Additives to Liquid Iron and Steel, ASTM STP 739, J.R. Lampman and A.T. Peters, Eds, American Society for Testing of Materials, 1981, pp. 157-169]. Its practical application in the steel industry has shown that aluminum consumption for deoxidation can be halved. However, being technologically successful, ferroaluminium suffers from several drawbacks that prevented its widespread use in industry. Since the alloy is produced by melting at high temperature, it turned out to be expensive to manufacture due to the high cost of electricity and repair of furnaces, as well as large losses of aluminum due to oxidation. Another problem associated with the high temperature of the process is the susceptibility of ferroaluminium to cracking during its loading into molten steel due to the presence of thermal stresses and large brittle intermetallic phases in the microstructure. Some of these intermetallic phases also react with water vapor in the atmosphere, so that the ferro-aluminum alloy often breaks down into dust even during storage. Cracked deoxidizing agent is much less effective because light crumbs easily get stuck in the slag on the surface of the molten steel when the deoxidizer is loaded into the steel melt.

It is claimed that the above disadvantages of ferroaluminium can be overcome by mechanical briquetting a mixture of aluminum-steel particles in accordance with US patent No. 6350295. Another approach to combining aluminum with a heavier component described in previous practice is to melt aluminum and pour it around prefabricated steel molds - see, for example, US Patent No. 4,801,328 or Chinese Patent CN 2,1102974 Y. The technique for introducing aluminum wire for deoxidation is described, for example , in US patent No. 333160. Innovative technology for the manufacture of aluminum deoxidizing material is disclosed in RF patent No. 2269586.

However, although several attempts have been made to create an efficient aluminum deoxidizing material, a practical solution acceptable to the steel industry is still lacking, as evidenced by the current deoxidation practice of loading aluminum cones and ingots into molten steel, an inefficient process leading to huge irreversible losses aluminum and energy spent on its production. Thus, there is a real need for a new aluminum deoxidizing material, which would ensure a more efficient use of aluminum in the deoxidation of steel compared to current practice, as well as in a technologically and economically feasible process for its production.

SUMMARY OF THE INVENTION

The presented composite material and the method of its manufacture, as is very clearly shown here, are not derived from, are not represented as obvious, or even mentioned in any previously known techniques and mechanisms, either by themselves, or in any combination thereof. Therefore, several examples of embodiments of the present production method are presented below.

The purpose of this production method is to obtain an effective and economical deoxidizing composite material with an aluminum matrix, almost completely dense, free of brittle intermetallic inclusions, providing deep immersion in molten steel, thereby reducing unnecessary losses of this valuable metal due to parasitic oxidative reactions with slag and the atmosphere.

Another objective of this production method is to provide an innovative and cost-effective production technology of a deoxidizing composite material with an aluminum matrix based on in-situ pressure impregnation technology, which means impregnating a porous preform for impregnating (preform) steel-aluminum or other black metal filler -aluminium is an aluminum component that is present in situ (in situ) inside the porous preform for impregnation, that is, the preform.

Another objective of this production method is to ensure the production of an almost completely dense, free of brittle intermetallic compounds and, therefore, not crumbling deoxidizing composite material with an aluminum matrix, which can be easily and safely used in the steelmaking process without any replacement of equipment or modification of existing manual or automatic deoxidation processes used in industry.

Another objective of the present production method is the manufacture of a deoxidant-modifier composite material with an aluminum matrix containing one or more deoxidizing and modifying additives in addition to aluminum, thereby making the new material even more effective for deoxidizing and improving the properties of steel.

In one embodiment of the present manufacturing method, a method for manufacturing an aluminum matrix composite material is provided. This method includes the steps of forming a porous free-standing preform including aluminum and an iron-rich component, heating the free-standing preform to a temperature above the melting point of aluminum and below the melting point of the iron-rich component, and applying pressure to compact the free-standing preform and solidify it.

In yet another embodiment of the present manufacturing method, the iron rich component is steel. Aluminum is present in an amount of 10-50% by weight of the composite material. Also, in one embodiment of the present manufacturing method, aluminum is 30% by weight of the composite material.

Another embodiment of the presented production method involves the use of a free-standing preform molded using mechanical pressing, briquetting, container use, inorganic binder, or a combination of any of the above processes.

One of the embodiments of the presented production method involves the use of a certain amount of heat, which is transferred to a free-standing preform in order to raise its temperature to more than 661 degrees Celsius. In one embodiment, heat is transferred to the free-standing preform using a process selected from the group consisting of induction heating, heating in a resistance furnace, and an organic fuel burner furnace. Further, another embodiment of the present production method assumes that a certain amount of external pressure is applied to the free-standing preform, sufficient for the molten aluminum component to fill almost all the pores and gaps between the iron-rich component. And yet another embodiment of the presented production method involves the application of an amount of external pressure to a free-standing preform to seal it. This pressure is applied to seal by pressing in a closed die.

One embodiment of the present manufacturing method assumes that the iron-rich component is selected from the group consisting of ferromanganese and a mixture of steel and ferromanganese.

In yet another embodiment, a free-standing preform is bonded and supported by a process selected from the group consisting of mechanical pressing, use of an inorganic binder, use of a steel container, and any combination thereof. Further, the amount of heat transferred to the free-standing preform is transferred using processes that may include induction heating, heating in an electrical resistance furnace, and heating in an organic fuel burner furnace.

One embodiment of the present manufacturing method provides a method of manufacturing an aluminum matrix composite material. The steps of the method include the molding of a porous free-standing preform having a plurality of small-sized aluminum particles and a plurality of small-sized particles of a material selected from the group consisting of steel, ferromanganese, silicocalcium, calcium carbide, rare-earth metals, any ferroalloy except ferromanganese. Then, transferring the amount of heat to the free-standing preform sufficient to raise its temperature above the melting point of aluminum and below the melting point of other components of the preform and applying an amount of pressure to compact the free-standing preform to an almost fully dense state, allowing the aluminum in the free-standing preform to solidify.

Thus, rather broadly, the most important features of the method of manufacturing a composite with an aluminum matrix were highlighted, so that its subsequent detailed description could be more understandable, and that the present contribution to the state of the art could be better appreciated. There are additional characteristics of the composite material and the production method that will be described hereinafter and which will constitute the subject of the attached claims.

In order to achieve the foregoing and related ends, some illustrative aspects are described herein in connection with the following description. These aspects show various ways of applying the principles disclosed herein, and all aspects and their equivalents are intended to be within the scope of the subject of the claims. Other advantages and new features will become apparent from the following detailed description.

In this regard, before a detailed explanation of at least one implementation of a method for producing a composite material will be given, it should be understood that this methodology is not limited to its application with respect to only a detailed description of the composite material and steps of the production process as presented in the following description. The present production method may have other implementations and may be practiced and embodied in various ways. It should also be understood that the phraseology and terminology used here are used for descriptive purposes and should not be considered limiting.

All this, together with other goals of the composite material and the production method, along with various novelty features that characterize the system, are clearly identified and indicated in the claims attached to, and forming part of the information disclosed. For a better understanding of the methodology, its operational advantages and the specific results achieved as a result of its use, reference should be made to descriptive material containing an illustrative description of preferred embodiments of the present production process.

DETAILED DESCRIPTION OF SEVERAL EMBODIMENTS

A new material, a steel deoxidizer, which is a product of the present production method, is best described as an aluminum matrix composite. Composite materials are usually defined as consisting of discrete particles or fibers of a hardener or filler contained in, or surrounded by a continuous matrix material. Unlike ordinary metal alloys, consisting of various metal phases, whose interactions obey the laws of thermodynamic equilibrium, composites with a metal matrix are often called materials with predetermined properties. The hardener and matrix of the composites are combined using engineering-developed production processes and, generally speaking, are not in thermodynamic equilibrium, in many cases being chemically inert to each other - such as refractory ceramic particles in a composite with an aluminum matrix.

From an engineering point of view, there is a compelling reason to add composite materials to a wide arsenal of existing metals and alloys. It lies in the fact that composites allow the development of materials with a microstructure and properties inaccessible in the case of using conventional methods of melting, casting heat treatment, cold and hot pressure treatment, which rely on physicochemical processes and reactions in metal systems. For example, to make the deoxidizing material heavier than aluminum, fusion of aluminum and iron at high temperature can be used, resulting in the metallurgical ferroaluminium described previously in the text. Ferroaluminium is heavier than aluminum, but contains a large number of brittle and corrosive intermetallic phases, which cause it to break when stored or when it is loaded into molten steel. However, if steel particles can be combined with an aluminum matrix into a fully dense composite material with predetermined properties using a manufacturing method different from alloying at high temperature, the resulting material will have a significantly higher density than aluminum, but at the same time be free from brittle intermetallic phases, which reduce the effectiveness of ferroaluminum deoxidizer due to crushing.

There are many technological methods for the production of composite materials with a metal matrix, which are well known to specialists in this field. For example, casting, where hardener particles are first mixed with molten metal, and then the mixture is poured into the mold. Another example is powder metallurgy methods, when the solid particles of the hardener and matrix are mixed, pressed into a mold, and then sintered in the solid state at high temperature. Another well-known widely used method can be generally described as pressure impregnation technology. In its usual design, a dry preform is first made from hardener particles, which is heated, placed in a mold, and then molten matrix metal is poured into the mold from above and impregnated with a dry preform under the influence of external pressure applied to the matrix metal, usually through a hydraulic press punch. The disadvantages of conventional pressure impregnation technology are the need for sophisticated rigging and precise control of production parameters for each individual briquette. Another most critical drawback is the need to melt and maintain large batches of matrix metal in this form, which in the case of aluminum leads to large losses of aluminum in the form of slag.

The new aluminum matrix-based composite deoxidizing material described herein is manufactured using pressure impregnation technology that is radically improved over conventional impregnation in order to make it economical to use and minimize the loss of valuable aluminum. Unlike conventional technology, in the new technology, matrix aluminum impregnating material does not have to pass from one border of a dry preform consisting of steel particles through the thickness of the preform to the end to the opposite border to completely impregnate the preform. Such a long path of molten aluminum makes it necessary to produce complex and precisely machined molds to eliminate aluminum emissions under pressure, and also carries the risk of premature cooling of aluminum, and as a result, incomplete impregnation of the preform. Instead, in the new technology, aluminum has to travel only a short distance to fill the space between the steel particles of the preform. This is because aluminum is mixed with steel in advance at the preform manufacturing stage - an operation that also automatically guarantees the exact weight ratio of aluminum to steel in the new composite deoxidizer. Pre-mixed aluminum becomes liquid during heating of the preform and only a distance comparable to the average particle size of the steel must pass to fill the space around them when the preform is compressed in the mold of a hydraulic press. This technology can be called in-situ pressure impregnation, since the aluminum impregnation material is present in-situ inside the preform that is impregnated.

In a preferred embodiment, first, the free-standing porous preform is formed of crushed chips, planed waste, waste boring, or other sufficiently small aluminum particles mixed with crushed chips, planed waste, boring waste, or other sufficiently small particles of steel, and it is preferred that the weight the proportion of aluminum was close to 30%. Molding is a manufacturing operation well known to those skilled in the art, for which it is preferable to use mechanical pressing or briquetting. Alternatives to molding the preform may be to use a container, an inorganic binder (e.g. sodium silicate), or both to make it self-supporting. Preform geometry may vary. In a preferred embodiment, the geometry may be cylindrical with a diameter between 20 and 200 millimeters and a height between 20 and 200 millimeters, with a ratio of diameter to height of 1 to 1 or close to that.

Then, the molded preform is heated to a temperature above the melting point of aluminum, but below the melting temperature of steel, and for a time sufficient for aluminum to transition to a liquid state. The exact value of the heating temperature may vary. In a preferred embodiment, the temperature range may be between 661 and 800 degrees Celsius. Possible heating methods are well known to those skilled in the art. In a preferred embodiment, this method can be induction heating, since it is extremely effective in heating materials containing ferromagnetic components, in particular carbon steel.

It should be noted that although some oxidation of the aluminum preform will occur, it will be greatly reduced compared to the melting and aging of large batches of aluminum in open-air furnaces, due to the shortness of the process and the difficult access of air to the preform.

Further, the heated molded preform is compressed in a sufficiently sealed space at a pressure level sufficient for the in situ aluminum component of the preform to fill almost all porosity and the gaps between the steel particles so that the steel composite is almost completely dense, with a density of at least higher 90 percent is theoretically possible, and preferably in excess of 95 percent is theoretically possible. Pressure must be applied to the preform until the molten aluminum solidifies. The compression operation can be performed in a variety of ways well known to those skilled in the art. In a preferred embodiment, this method may be extrusion in a closed mold mounted on a hydraulic press. A mold suitable for a compression operation can be much less complex than that used in conventional pressure impregnation technology. This is due to the fact that in a conventional pressure impregnation technology, the punch of a hydraulic press must push a relatively large volume of molten metal under high pressure for a considerable distance until it completely impregnates the dry preform. Hot molten metal can escape from the mold if it finds at least a tiny gap between the walls of the punch and the mold. Precise machining of the punch and die is necessary to avoid emissions and minimize clearance, which in turn leads to difficulties in removing the punch from the mold after the impregnation is completed.

Difficulties with the extraction of the punch often lead to further complication of the design of the mold. For example, to extract, instead of a unitary cylindrical mold, it may be necessary to use a composite mold. In the case of in-situ pressure impregnation, the punch must only go a short distance to seal the preform, and the material pressed by the punch is semi-liquid, and not completely liquid like aluminum in the case of conventional pressure impregnation technology. This allows the use of much less tight gaps between the walls of the punch and the mold and facilitates the extraction problem, so that a simple unitary cylindrical mold can be used.

In alternative embodiments of this manufacturing method, the weight fractions of aluminum in a free-standing porous molded preform may range between 10% and 50%.

In another alternative embodiment of this production method, the molded porous free-standing preform is formed from crushed chips, planed waste, boring waste, or other sufficiently small aluminum particles mixed with sufficiently small particles of ferromanganese, so that the weight fraction of aluminum is close to 25%. The remaining steps of the process, including heating the molded preform and compressing it, are almost the same. The rationale for replacing steel with ferromanganese is that, on the one hand, specialists in this field know that the combined effect of aluminum and manganese as deoxidants is stronger than from each element separately. On the other hand, ferromanganese can perform the same functions as steel in terms of weighting the aluminum deoxidizer and ensuring effective induction interaction during induction heating of the molded porous free-standing preform.

In other alternative embodiments of this manufacturing method, some of the steel and aluminum in the molded free-standing porous preform may be replaced by additives useful in the steelmaking process, such as silicocalcium, calcium carbide, rare earth metals and other useful additives. Such additives can help deoxidize steel even better than aluminum alone, or modify the shape and size of oxides and other non-metallic particles suspended in molten steel, making them smaller and more compact, thereby improving the appearance and mechanical properties of the final product - flat products.

In a preferred embodiment, a new aluminum matrix steel deoxidizing composite material manufactured in accordance with the preferred embodiment described above is used to deoxidize steel at the stage of its release from an electric arc furnace or converter into a ladle, as a direct substitute for aluminum ingots or cones. Without reference to a specific theory, the ratio of the weight of the deoxidizing composite material to the weight of the aluminum ingot or cones that it replaces can be estimated at 1.66 to 1 based on the following considerations. From previous manufacturing practice, it is known that non-crushed ferroaluminium, containing about 30% aluminum by weight, saves about 50% aluminum compared to using ingots or deoxidation cones. Thus, each kilogram of aluminum ingot or cones can be replaced by 0.5 kilograms of aluminum contained in ferroaluminium, or in the case of this production method, in a deoxidizing composite with an aluminum matrix. For the preferred weight ratio of aluminum to steel 30 to 70, you can calculate the total weight of the new deoxidizer, replacing one kilogram of aluminum ingots or cones, as 0.5 kilograms multiplied by 100 and divided by 30, which equals 1.66 kilograms.

Although the above description contains many specific details, they should not be construed as limitations on the scope of the present production method, but rather, as examples of its preferred implementation. Many other variations are possible. Accordingly, the scope of this production method should not be determined by the implementations shown as illustrations, but by the appended claims and their legal equivalents.

Claims (20)

1. A method of manufacturing a deoxidizing composite material with an aluminum matrix for the steelmaking process, comprising forming a porous free-standing preform consisting of aluminum and an iron-rich component, and applying pressure to the free-standing preform, characterized in that the molded free-standing preform is heated to a temperature that is higher than the temperature melting of aluminum and below the melting temperature of the iron-rich component, over a period of time, ensuring the transition of aluminum to liquid th state, while pressure is applied to the preform to obtain a free-tightly compacted iron-rich component freestanding preforms and solidification therein molten aluminum. 2. The method according to p. 1, characterized in that the iron-rich component is steel. 3. The method according to p. 1, characterized in that aluminum is present in the range from ten to fifty percent by weight of the composite material. 4. The method according to p. 3, characterized in that aluminum makes up thirty percent of the composite material by weight. 5. The method according to p. 1, characterized in that the free-standing preform is formed using a process selected from the group consisting of: mechanical pressing, briquetting, using a container, using an inorganic binder and any combination of them. 6. The method according to p. 1, characterized in that the heating of the free-standing preform is carried out above six hundred sixty one degrees Celsius. 7. The method according to p. 1, characterized in that the heating of the free-standing preform is carried out using a process selected from the group including induction heating, heating in an electric resistance furnace, heating in an oven with a fossil fuel burner, and any combination of them. 8. The method according to p. 1, characterized in that they apply pressure to the free-standing preform, sufficient to fill the pores and gaps between the iron-rich components of the molten aluminum component. 9. The method according to p. 1, characterized in that they apply external pressure to seal the preform by pressing in a closed matrix. 10. The method according to p. 1, characterized in that the iron-rich component is selected from the group consisting of: ferromanganese, a mixture of steel and ferromanganese. 11. The method according to p. 10, characterized in that the free-standing preform is formed using a process selected from the group including mechanical pressing, the use of an inorganic binder, the use of a steel container and any combination of them. 12. The method according to p. 11, characterized in that the heating of the free-standing preform is carried out using a process selected from the group consisting of: induction heating, heating in an electric resistance furnace, heating in an oven with a fossil fuel burner and any combination of them. 13. A method of manufacturing a deoxidizing composite material with an aluminum matrix for a steelmaking process, comprising forming a porous self-supporting preform and applying pressure to a self-supporting preform, characterized in that the self-supporting preform consists of aluminum particles and particles of components selected from the group consisting of steel, ferromanganese, silicocalcium, calcium carbide, rare-earth metals, ferroalloy, with the exception of ferromanganese, and combinations thereof, heat molded freely toyaschey preform to a temperature and for a time to ensure a transition alumina in a liquid state, the pressure is applied to the preform to obtain a freestanding densely compacted preform free-mentioned components and the solidification of molten aluminum therein. 14. The method according to p. 13, wherein the aluminum is present in the range from ten to fifty percent by weight of the composite material. 15. The method according to p. 13, characterized in that the aluminum is thirty percent of the composite material by weight. 16. The method according to p. 13, characterized in that the free-standing preform is formed using a process selected from the group consisting of: mechanical pressing, briquetting, using a container, using an inorganic binder, and any combination of them. 17. The method according to p. 13, characterized in that the heating of the free-standing preform is carried out above six hundred sixty one degrees Celsius. 18. The method according to p. 13, characterized in that the heating of the free-standing preform is carried out using a process selected from the group consisting of: induction heating, heating in an electric resistance furnace, heating in an oven with a fossil fuel burner and any combination of them. 19. The method according to p. 13, characterized in that they apply pressure to the free-standing preform, sufficient to fill the pores and gaps between the iron-rich components of the molten aluminum component. 20. The method according to p. 13, characterized in that the pressure to seal the preform is carried out by pressing in a closed matrix.