SK18372001A3 - Zinc-based metal foamed bodies - Google Patents

Abstract

The foam is made using metal powder. An Independent claim is included for use of the powder to make the foam, i.e. the corresponding process.

Description

Technical field f

The present invention relates to zinc-based metal foam bodies.

BACKGROUND OF THE INVENTION

Metal foams are produced in a variety of ways and are used for a variety of purposes. A common feature of all foams is the low weight to volume ratio and generally high mechanical stability to weight. Other properties of metal foams are low electrical conductivity, low thermal conductivity and sound insulation. Depending on the production method, closed-cell or open-cell foams are obtained, which are occasionally referred to as porous structures only. Depending on the method of manufacture and further processing, the pores may be more or less spherical or may be lenticular or elongated in shape. Depending on the method of manufacture, regions with different pore sizes and different wall thicknesses may also be formed inside the insert body. In addition, metal foams are specifically processed into sandwich structures or inserted into hollow bodies or hollow profiles.

In the melt metallurgical foaming process, it has proven to be useful to mix viscosity-increasing alloying elements or solid bodies insoluble in the metal bath several times in a metal bath. Foaming methods have also been found to be useful in which foaming agents (blowing agents) which decompose above a certain temperature to form a foam are added to the metal and optionally to the viscosity-increasing additives. As foaming agents, for example, metal hydrides, carbonates, hydrates, powdered organic substances, nitrogen compounds such as nitrides, hydroxides, bicarbonates or mixtures of oxides with carbon can be used which indirectly form gases; see also DE-A-198 13 176, in which so-called die casting is also described in more detail. Special methods using special alloys and special foaming agents are described in US-A3,087,807 and US-A-3,758,291.

Metal foams with anisotropic thermal and electrical conductivity are specifically described, for example, in DE-C-44 24 157. Further methods are described in DE-C-41 01 630, DE-C-41 24 591 and DE-C-40 18 360. Special metal foams and their use for sound insulation and electromagnetic shielding are described in EP 0 210 803 B1. Reference is also made to the publication in the Symposium Metallschäume (Metal Foam Symposium) 6-7.3, 1997, Bremen, published by MIT Verlag, with contributions from J. Bauméister, pages 3 to 13, by M. Hartmann and RF Šinger, pages 39 to 39 57 and P. Weigand and J. Banhart on pages 91 to 102. In this last paper, there is also a paragraph on pages 94 to 96 on the expansionary behavior of zinc foams, in which zirconium hydroxide was chosen as a foaming agent. These tests were mainly about foaming behavior of the metals and mechanical properties of the foams thus obtained. The use of lightweight aluminum foam structures in vehicle construction is found in an article by Banhart, Bauméistra, Melzer, Seeliger and Weber in Werkstoffe 98.

In this state of the art in the manufacture and use of metal foam, the choice of alloys has continued to be of importance only for foaming behavior and finished foam properties, with pore structure, achievable density, foams and isotropic or anisotropic properties predominant. Practically no attention has been paid to the corrosion properties of the metal foams, and in particular in the case of open-cell foams, i.e., parts with a porous structure, more or less severe corrosion due to the ingress of liquids may occur. It has also been found in the manufacture of sandwich structures that the choice of foamable alloy material as well as cover plates has a great influence on the corrosion behavior.

It is therefore an object of the present invention to provide zinc-based metal foams which can be easily processed into foams having good mechanical properties and in addition having good corrosion resistance. The aim is to minimize the density with good mechanical properties.

SUMMARY OF THE INVENTION i

This problem is now solved by the fact that the metal foam bodies contain, in addition to zinc and the usual admixtures, 2 to 20 wt. aluminum. Preferably, they comprise from 2 to 16 wt. aluminum. ' Optimal properties are obtained at a content of 4 to 16 wt. aluminum.

In addition, the properties can be optimized in foaming as well as in finished foams and in particular with respect to corrosion resistance by admixing or adding up to 4 wt. % copper, up to 4 wt. % magnesium, up to 2 wt. % manganese, up to 2 wt. % titanium and up to 0.1 wt. india.

Aluminum, zinc, steel and / or galvanized steel covering sheets are particularly suitable for forming the sandwich structure. Furthermore, the metal foams according to the invention can be inserted very well into the interior of hollow bodies or hollow profiles consisting of aluminum, zinc, steel and / or galvanized steel.

Surprisingly, there are particularly advantageous foaming properties as well as foam end properties when zinc powder and / or aluminum powder and / or zinc alloy powder and aluminum, which are produced as thermal spraying waste and / or waste, are admixed to the above zinc alloys. in sputtering and / or metal and / or alloy recovery processes. Zinc, aluminum and / or zinc-aluminum alloys, which are produced as thermal spray waste, are mostly referred to as overspray powders ("overspray powders") and have so far been sent back to thermal spray wire suppliers. Until now, they could not be used directly for processing into metallic materials because these powders are coated with a relatively thick oxide coating. The same applies to powders which are produced as a waste by spraying or other treatments such as zinc dust, aluminum dust or zinc-aluminum alloy dust, for example as filter dust in filtering equipment. These powders generally have a particle size of 5 to 1000 µm. According to the prior art, the thin oxide coating of aluminum powder was already considered to be disturbing and harmful; Baumeister, cit. lit. page 8.

Surprisingly, it has been found that these oxide-coated wastes can be used together in an excellent manner in large quantities for the manufacture of metal foam bodies according to the invention. An undesirable oxide coating is likely to lead to mechanical stabilization during the foaming process. Depending on the composition of these powders, the corrosion resistance of the foam bodies can also be improved. At least, the corrosion resistance due to these particles does not deteriorate.

Improvement of the property can be observed in some cases already from 0.5 wt. addition of overspray powder. Up to the use of more than 80 wt. overspray powder from the thermal spraying process allows mechanical cohesion of the foam body during compression. 2 to 40 wt. % and in particular 5 to 30 wt. overspray powder.

The corrosion resistance of the metal foam bodies and the sandwich structure with the metal foam bodies according to the invention is tested, for example, in the salt chamber test according to DIN 500 21-ss and in the condensate / SO 2 test according to DIN 500 18. It has been shown reduced. In contrast, impurities of more than 0.1 wt. iron, which in particular causes intercrystalline corrosion and impairs mechanical properties.

In contrast, the additions of copper, magnesium, manganese, titanium and indium are capable of improving corrosion resistance and mechanical properties.

In particular, zirconium hydride, titanium hydride and magnesium hydride have proven to be suitable as foaming agents, while titanium and / or magnesium forming can also have a positive effect with respect to foaming behavior and corrosion resistance.

In particular, aluminum, zinc, steel and / or galvanized steel have proven successful in the production of sandwich structures or filled hollow bodies or hollow profiles, since these are capable of forming solder joints at metal foam contact points. Zinc-aluminum alloys have excellent soldering properties for the above materials. When using steel cover plates, the metal foam body according to the invention simultaneously acts as a cathodic corrosion protection of the steel. Thus, sandwich structures, hollow bodies or hollow profiles are protected from the inside against corrosion.

Particularly preferably, zinc, aluminum or galvanized steel sheets or hollow bodies are used, since they can be alloyed with the zinc alloys used according to the invention during foaming and the melting point is increased and this can lead to additional stabilization of the foam and transition regions between the foam and the cover. a sheet or hollow profile that encloses it.

However, it is also possible to use glass for forming, which practically does not deform and does not stick to the zinc alloys when foaming the alloys, so that it is suitable for several applications or for longer production times, while allowing good dimensional stability. The foaming process can be monitored even optically. ; '· ·. .

If zinc, aluminum or a zinc-aluminum alloy powder is used in the manufacture, the particle sizes should preferably be in the range of 50-4000 μιη. However, prior to foaming, these alloys can also be processed by rolling, cladding and preforming or drawn into wires, which are then further processed into metal foam bodies. It has proven to be very advantageous here that the foamable semi-finished product is processed into a granulate in the range of 2 to 20 mm and the granulate is put into a foam mold and then foaming.

The following examples describe typical embodiments, but are not intended to limit the scope of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Example 1

A powder blend consisting of 14 wt. % aluminum, 0.8 wt. zirconium hydride (ZrH) and zinc-forming residue. Then the semi-finished product was foamed. A density of 0.7 g / cm ³ was achieved. In the salt chamber test according to DIN 500 21-ss, the foam structures according to the invention showed a markedly improved corrosion resistance compared to fine zinc alloys. The removal rate could be reduced by approximately five times. In the condensate / SO ₂ test according to DIN 500 18, a significantly improved corrosion resistance was achieved. Metal removal could improve more than tenfold.

Example 2

A powder mixture consisting of 4 wt. % aluminum, 0.8 wt. zirconium hydride (ZrH) and zinc forming the rest. Then, the foamable semi-finished product was clad with aluminum cover sheets. These sandwich structures were then foamed. A foam density of 0.6 g / cm ³ was achieved. The cover plates have undergone the foaming process without visible changes. In the region between the foam and the aluminum cover sheet, a solid fusible metallurgical joint was formed.

Example 3

A powder mixture consisting of 4 wt. % aluminum, 0.8 wt. zirconium hydride (ZrH) and zinc-forming residue. Then, the foamable semi-finished product was clad with galvanized steel and non-galvanized steel cover sheets. These sandwich structures were then foamed. A foam density of 0.6 g / cm ³ was achieved. The cover plates have undergone the foaming process without visible changes. The adhesion of the cover plates was very high in both cases.

Example 4

A powder mixture consisting of 5 wt. % Zinc overspray, 5 wt. % Aluminum overspray, 5 wt. % Overspray ZnA115, 0.8 wt. % zirconium hydride (ZrH), 10 wt. aluminum and zinc forming the remainder. A foam density of 0.5 g / cm ³ was achieved. The pore structure of the foam body was very homogeneous and finely porous. Foam stability in the foaming process was clearly increased. The corrosion resistance is comparable to the alloys according to the invention of Example 1.

Example 5

A powder mixture consisting of 75 wt.% Was placed in the inlet channel of the pressurized zinc die casting machine. % zinc and 25 wt% zirconium hydride (ZrH). As a die casting alloy, a zinc die casting alloy comprised of 10 wt. % aluminum, 1.0 wt. copper and zinc forming the residue. The melt to powder ratio was adjusted so that the fraction of the foaming agent in the die casting part was about 1% by weight. The total die casting was foamable and the foam density was approximately 0.8 g / cm ³ . The pore structure of the foam body was very homogeneous and finely porous.

Example 6

A powder blend consisting of 14 wt. % aluminum, 1.0 wt. the zirconium hydride (ZrH) and the zinc forming residue were cold preformed and then compacted in an extruder. Then a semi-finished product was produced by foaming. A density of approximately 0.5 g / cm ³ was achieved. In the salt chamber test according to DIN 21-ss, the foam structures according to the invention showed a markedly improved corrosion resistance compared to the foamed fine zinc alloys. The removal rate could be reduced by approximately five times. In the condensate / SO ₂ test according to DIN 500 18, a significantly improved corrosion resistance was achieved. Metal removal could improve more than tenfold. The same experiment was carried out with 1.0 wt. titanium hydride instead of zirconium hydride and led to comparable results. Only the density of the foam was slightly higher than that of zirconium hydride.

Example 7

A powder blend consisting of 15 wt. % aluminum, 1.0 wt. the zirconium hydride (ZrH) and the zinc forming residue were cold preformed and then compacted in an extruder. Then, the foamable semi-finished product was clad with aluminum cover sheets. These sandwich structures were then foamed at 500 ° C. A very high stability of the foam has been observed which can be inferred from the fact that the foam alloy increased its melting point due to the aluminum alloy in the foaming process. A foam density of approximately 0.5 g / cm ³ was achieved.

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In the region between the foam and the aluminum cover sheet, a solid fusible metallurgical joint was formed.

Example 8

% Powder blend consisting of 4 wt. % aluminum, 1.0% copper, 1.0% wt. the zirconium hydride (ZrH) and the zinc-forming residue were cold preformed and then compacted in an extruder. Then, the foamable blank was clad with aluminum cover sheets. These sandwich structures were then foamed at 420 ° C. A very high stability of the foam has been observed which can be inferred from the fact that the foam alloy increased its melting point due to the aluminum alloy in the foaming process. A foam density of approximately 0.5 g / cm ³ was achieved. In the region between the foam and the aluminum cover sheet, a solid fusible metallurgical joint was formed. The same experiment was performed without copper as an alloying additive element and resulted in a comparable result.

Example 9

% Powder blend consisting of 4 wt. % aluminum, 1.0% copper, 1.0% wt. the zirconium hydride (ZrH) and the zinc-forming residue were cold preformed and then compacted in an extruder. Then, the foamable semi-finished product was clad. Galvanized steel cover plates. These sandwich structures were then foamed at 420 ° C. A very high stability of the foam has been observed which can be inferred from the fact that the foam alloy increased its melting point due to zinc alloying in the foaming process. A foam density of approximately 0.5 g / cm ³ was achieved. A solid fusible metallurgical joint was formed in the region between the foam and the cover sheet. The same experiment was performed without copper as an alloying additive element and resulted in a comparable result.

Example 10 I. . I

% Powder blend consisting of 4 wt. % aluminum, 1.0% copper, 1.0% wt. the zirconium hydride (ZrH) and the zinc forming residue were cold preformed and then compacted in an extruder. Then, the foamable semi-finished product was clad with zinc cover sheets. These sandwich structures were then foamed at 400 ° C. A very high stability of the foam has been observed which can be inferred from the fact that the foam alloy increased its melting point due to zinc alloying in the foaming process. A foam density of approximately 0.5 g / cm ³ was achieved. A solid fusible metallurgical joint was formed in the region between the foam and the zinc sheet. The same experiment was performed without copper as an alloying additive element and resulted in a comparable result.

Example 11

Four powder mixtures consisting of 2, 4, 16 and 20 wt. % aluminum, 1.0 wt. The zirconium hydride (ZrH) and the zinc forming residue were cold pre-pressed and then compacted in an extruder to form a 6 mm wire diameter. The wires produced in this way were processed into granules. The length of the sections was 6 to 10 mm. Then, the granulate produced in this way was foamed in foaming form of aluminum, steel, galvanized steel and glass. Foam densities of approximately 0.5 g / cm ³ were achieved. The pore structure of the foam body was very homogeneous and finely porous. The foam stability in the foaming process was very high. The corrosion resistance is comparable to the alloys according to the invention of Example 1.

The same experiment was carried out with 1.0 wt. titanium hydride instead of zirconium hydride and led to comparable results. Only the density of the foam was slightly higher than that of zirconium hydride.

Example 12

A powder blend consisting of 80 wt. % Overspray of ZnA115 thermal spray powder, 1.0 wt. the zirconium hydride (ZrH) and the zinc forming residue were cold preformed and then compacted in an extruder. A foam density of approximately 0.5 g / cm ³ was achieved. The pore structure of the foam body was very homogeneous and finely porous. The stability of the foam in the foaming process was very high. The corrosion resistance is comparable to the alloys according to the invention of Example 1.

Example 13

A powder mixture consisting of 75 wt.% Was placed in the inlet channel of the pressurized zinc die casting machine. % Overspray of ZnA115 powder from thermal spraying and 25 wt. zirconium hydride (ZrH). As a die casting alloy, a zinc die casting alloy comprised of 4 wt. % aluminum, 1.0 wt. copper and zinc forming the residue. The melt to powder ratio was adjusted so that the fraction of the foaming agent in the die cast part was about 1.0 wt. The total die casting was foamable and the foam density was approximately 0.6 g / cm ³ . The pore structure of the foam body was very homogeneous and finely porous. The same experiment was carried out with 1.0 wt. titanium hydride instead of zirconium hydride and led to comparable results.

Claims (9)

PATENT CLAIMS A process for the manufacture of zinc-based metal foam bodies comprising, in addition to zinc and customary additives, 2 to 20 wt. % aluminum and up to 4 wt. % copper, up to 4 wt. % magnesium, up to 2 wt. % manganese, up to 2 wt. % titanium and up to 0.1 wt. indium, characterized in that the metal foam bodies are made using powdered metals. Method according to claim 1, characterized in that the metal foam bodies are produced using powdered metals which are produced as waste in thermal spraying, sputtering or metal and / or alloy recovery processes. Method according to claim 2, characterized in that the powder metals are used in amounts of 2 to 80% by weight. Method according to one of Claims 1 to 3, characterized in that the metal foam bodies comprise 4 to 16 wt. aluminum. Method according to one of Claims 1 to 4, characterized in that the metal foam bodies are inserted into a sandwich structure with covering sheets of aluminum, zinc, steel and / or galvanized steel. Method according to one of claims 1 to 4, characterized in that the metal foam bodies are inserted inside the hollow bodies or hollow profiles of aluminum, zinc, steel and / or galvanized steel. Modified letter Use of alloys containing, in addition to zinc and the usual admixtures, 2 to 20% by weight, preferably 4 to 16% by weight. % aluminum and up to 4 wt. % copper, up to 4 wt. % magnesium, up to 2 wt. % manganese, up to 2 wt. % titanium and up to 0.1 wt. Indium for the manufacture of metal foam bodies, at least a portion of which is fed to the inlet channel of the pressurized zinc die casting machine, in powder form. Use according to claim 7, characterized in that zinc powder and / or aluminum powder and / or zinc-aluminum alloy powder which is produced as overspray powder and / or is used. overspray powder and / or metal and / or alloy recovery processes. Use according to claim 7 or 8, characterized in that up to 80 wt. zinc and / or aluminum powder and / or zinc-aluminum alloy powder which is produced as waste by thermal spraying and / or overspraying and / or metal and / or alloy recovery processes.