RU2413025C2 - Product out of deformed aluminium alloy of aa7000 series and procedure for production of said product - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: product consists of following components, wt %: Zn 9.0-14.0, Mg 1.0-5.0, Cu 0.03-0.25, Fe <0.30, Si <0.25, Zr from 0.04 to less, than 0.3 and one or more elements chosen from group consisting of: Ti <0.30, Hf <0.30, Mn <0.80, Cr <0.40, V <0.40 and Sc <0.70, random elements and impurities, each <0.05, totally <0.15, and aluminium - the rest. The procedure for fabrication of product out of aluminium alloy consists in casting an ingot, in homogenisation and/or in preliminary heating the ingot upon casting, in hot treatment of the ingot into preliminary finished product with one or more methods, chosen from the group including rolling, extrusion and forging. Not necessarily, the preliminary treated product can be heated or hot treated and/or cold treated to a required shape of a blank; further formed blank is subjected to heat treatment to solid solution, to hardening blank heat treated to solid solution; not necessarily, hardened blank can be stretched or compressed, or cold treated by other way to stress relief, for example, by levelling sheet products or artificial ageing, till obtaining a required condition.

EFFECT: product with reduced tendency to forming hot cracks and with improved characteristics of strength, fracture toughness and hardness over 180 HB at artificially aged state.

32 cl, 6 tbl, 6 ex

Description

FIELD OF THE INVENTION

This invention relates to a welded deformable aluminum alloy of the AA7000 series in the form of a rolled, extruded or forged product, and to a method for manufacturing said product. The invention also relates to a weldment containing such a product.

BACKGROUND OF THE INVENTION

As will be understood, hereinafter, unless otherwise indicated, alloy designations and state designations refer to the designations of the Aluminum Association given in the Aluminum Standards and Data and the Registration Records, as published by the Aluminum Association.

In any description of alloy compositions or preferred alloy compositions, all references to percentages are given in mass percent, unless otherwise indicated.

According to the Aluminum Association (“AA”), the 7000 series aluminum alloys are known for their high strength, which makes them suitable for applications such as structural elements for an aircraft or for a tool plate. Alloys AA7075 and AA7055 are examples of this type of alloy and are widely used in aerospace fields due to their high strength and other desirable properties. Alloy AA7055 contains 7.6-8.4% Zn, 1.8-2.3% Mg, 2.0-2.6% Cu, 0.08-0.25% Zr, less than 0.10% Si and less than 0.15% Fe, the rest is aluminum, along with random elements and impurities. Alloy AA7075 contains 5.1-6.1% Zn, 2.1-2.9% Mg, 1.2-2.0% Cu, 0.18-0.28% Cr, less than 0.40% Si, less than 0.50% Fe and less than 0.30% Mn, the rest is aluminum, along with random elements and impurities. When it is subjected to artificial aging to its highest strength, and such artificial aging usually involves a holding period of 20 hours or more at a comparatively low aging temperature between 100 and 150 ° C, this alloy is obtained in a state that is usually called the tempering state T6. However, in this state, AA7075 alloys and similar alloys are susceptible to stress corrosion cracking (“SCC”) (“SCC”), peeling corrosion (“KSH”) (“EXCO”) and intergranular corrosion (“MKK”) (“IGS”) . This exposure can be reduced by the so-called heat treatment to T7x, but only due to a significant loss of strength. It is known that higher levels of strength can be obtained with higher levels of dopants (especially Zn, Mg and Cu), but this increase in strength leads to lower values of fracture toughness. In addition, the high copper content of the above alloys makes them susceptible to hot cracking after welding. For a tool plate, in addition to good weldability, taking into account possible repairs, it is also very important that the material provides high hardness values.

SUMMARY OF THE INVENTION

The object of the present invention is to provide an AA7000 series wrought alloy product, ideal for aerospace applications or tool plates, having a combination of improved strength and fracture toughness properties, reduced sensitivity to hot cracking during welding and being artificially aged having a hardness of more than 180 HB.

Another objective of this invention is to provide a product from a deformable alloy of the AA7000 series, having a combination of improved resistance to MCC, improved strength properties, reduced sensitivity to the formation of hot cracks during welding and, being in an artificially aged state, having a hardness of more than 180 HB.

Another objective of this invention is to provide a product from a deformable alloy of the AA7000 series, having a combination of good weldability, improved strength properties and, being in an artificially aged condition, having a hardness of more than 180 HB.

It is also an object of the present invention to provide a method for manufacturing a product from a wrought alloy of the AA7000 series, having a combination of improved strength and fracture toughness properties, reduced sensitivity to the formation of hot cracks during welding, and being in an artificially aged state having a hardness of more than 180 HB , or a product from a deformable alloy of the AA7000 series, having a combination of improved MKK resistance, improved strength properties, reduced sensitivity to the formation of hot reschin during welding and, when in an artificially aged condition having a hardness of more than 180 HB, which can be made more economical way than presently known and used in practice in industrial scale processes.

One or more of these problems and other advantages are solved or achieved by the present invention relating to a product from a deformable aluminum alloy of the AA7000 series, containing (in wt.%):

- Zn from 7.5 to 14.0

- Mg from 1.0 to 5.0

- Cu≤0.28

- Fe <0.30

- Si <0.25

and one or more elements selected from the group consisting of: Zr <0.30, Ti <0.30, Hf <0.30, Mn <0.80, Cr <0.40, V <0.40 and Sc <0.70,

residue: random elements and impurities, each <0.05, total <0.15,

and the rest is aluminum, and the product has a reduced sensitivity to the formation of hot cracks, also has improved strength and fracture toughness properties compared to AA7050 or AA7075 and, being in an artificially aged state, has a hardness of more than 180 HB.

Detailed Description of Preferred Embodiments

This invention provides a product from a deformable aluminum alloy AA7000 series, consisting essentially of, in wt.%:

- Zn from 7.5 to 14.0

- Mg from 1.0 to 5.0, preferably from 2.0 to 4.5

- Cu≤0.28

- Fe <0.30, preferably <0.14, more preferably <0.08

- Si <0.25, preferably <0.12, more preferably <0.07,

- and one or more of:

- Zr <0.30, preferably 0.04-0.15, more preferably 0.04-0.13

- Ti <0.30, preferably <0.20, more preferably <0.10

- Hf <0.30

- Mn <0.80, preferably <0.40

- Cr <0.40

- V <0.40, preferably <0.30

- Sc <0.70, preferably ≤ 0.50,

residue: random elements and impurities, each <0.05, total <0.15, and the rest is aluminum, and the product has a reduced sensitivity to the formation of hot cracks, also has improved strength and fracture toughness properties and, being in an artificially aged state, has hardness over 180 HB. Preferably, the hardness is more than 185 HB, and more preferably more than 190 HB. And in the best examples, a hardness of more than 210 HB was obtained in the state of precipitation hardening during aging. In the case of this description, when hardness measurements are given or mentioned, one skilled in the art will understand that they were measured at a thickness average over the cross section, since it is precisely this that represents the most quench-sensitive place of the wrought product.

With a decrease in sensitivity to the formation of hot cracks, the weldability of the material is significantly improved. The iron and silicon contents should preferably be kept low, for example, not exceeding about 0.08% Fe and / or about 0.07% Si or less. In any case, it is likely that slightly higher levels of both impurities, up to about 0.14% Fe and / or up to about 0.12% Si, may be acceptable, although on a less preferred basis. In particular, for embodiments with plates for molds or molds or tool plates, even higher levels of up to 0.3% Fe and up to 0.25% Si or less are permissible.

By increasing the Zn content in the alloy along with the Mg content and at the same time keeping the Cu content low, very high strengths can be achieved, while maintaining fracture toughness levels equal to or higher than that of comparative material AA7055, and with good weldability, which is considered to be a large extent the result of low copper content in the alloy. The alloy also provides high hardness when it is in an artificially aged state, such as a state of type T6 or T7, but with improved weldability compared to comparative material AA7075 in state T6, which is considered due to the low copper content in the alloy. Artificially aged material may be, for example, state T6, T74, T76, T751, T7451, T7651, T77 or T79.

Each of the disperseoid-forming elements Zr, Sc, Hf, V, Cr, and Mg can be added to control the grain structure and quench sensitivity. The optimal levels of dispersing agents depend on the treatment, but in the case when one single chemical composition for the main elements (Zn, Cu and Mg) is selected within the preferred range, and this chemical composition will be used for all forms of the corresponding products, then the Zr levels are preferably less than 0.13%.

The preferred maximum for the Zr level is 0.15%. A suitable range for the Zr level is from 0.04 to 0.15%. More preferably, the upper limit of the Zr additive is 0.13%. Zr is the preferred alloying element in the alloy product of the invention.

The Sc additive is preferably not more than 0.50%, or more preferably not more than 0.3%, and even more preferably not more than 0.18%. When combined with Sc, the sum of Sc + Zr should be less than 0.3%, preferably less than 0.2%, and more preferably a maximum of 0.17%, especially when the ratio of Zr and Sc is between 0.7 and 1 ,four%.

Another dispersing agent that can be added separately or together with other dispersing agents is Cr. Cr levels should preferably be less than 0.3%, and more preferably a maximum of 0.20%, and even more preferably 0.15%. A preferred lower limit for Cr will be 0.04%. Although Cr alone may not be as effective as separately Zr, at least when using a wrought alloy product in a tool plate, similar hardness results can be obtained. When combined with Zr, the sum of Zr + Cr should not be higher than 0.20%, and preferably not more than 0.17%.

The preferred amount of Sc + Zr + Cr should not be higher than 0.4%, and more preferably not more than 0.27%.

Mn may be added as a single dispersing agent or in combination with one of the other dispersing agents. The maximum for Mn supplement is 0.80%. A suitable range for the Mn additive is from 0.05 to 0.40%, and preferably from 0.05 to 0.30%, and even more preferably from 0.12 to 0.30%. The preferred lower limit for the Mn additive is 0.12%, and more preferably 0.15%. When combined with Zr, the sum of Mn + Zr should be less than 0.4%, preferably less than 0.32%, and a suitable minimum is 0.12%.

In another embodiment of a deformable aluminum alloy product according to the invention, the alloy does not contain (free from) Mn, and from a practical point of view this will mean that the Mn content is <0.02%, and preferably <0.01%, and more preferably the alloy is substantially free or substantially free of Mn. Saying “practically does not contain” or “essentially does not contain”, we mean that no special additives of this alloying element to the alloy were made, but that due to impurities and / or leaching due to contact with production equipment, trace amounts of this element may nevertheless end up in the final product of this alloy.

In a preferred embodiment of the wrought aluminum alloy product according to the invention, the alloy does not contain intentional additive V, so that it is present, if at all, at a typical impurity level of less than 0.05%.

The copper content has a significant effect on the sensitivity of the alloy to the formation of hot cracks and, therefore, also on the weldability of the alloy. It was found that weldability was further improved with copper contents of 0.28% or below 0.25%. Very good weldability was obtained with copper contents below 0.25% or even below 0.20%. The preferred minimum Cu addition is 0.03%, and more preferably 0.08%. When an alloy product according to this invention is used in a tool plate, weldability properties play an important role, especially during tool board repair operations.

In one embodiment of the invention, the Zn content is in the range of 7.5 to 14.0%, preferably the amount of Zn is in the range having a lower limit of 8.5%, 9.0% or 9.5%, and the upper limit is 12.0%, 11.0% or 10.0%, for example, the Zn content is preferably in the range of 8.5 to 11.0%, and more preferably Zn is in the range of 8.5 to 10.0%, features for use in aerospace applications. At the same time, for use in a tool plate, the upper limit of the Zn content is 14.0%, preferably 12.0%, and more preferably 11.0%.

By limiting the Zn content to a maximum of 12.0%, 11.0%, or 10.0%, corrosion resistance and especially KS are kept at a high level, which is especially important for aerospace applications of the products according to this invention.

In one embodiment of the invention, the Mg content is in the range from 1.0 to 5.0% or from 2.5 to 5.0%. A preferred upper limit is 4.5%. When the alloy product of this invention is used as a tool plate, a more preferable upper limit for the Mg content is 4.0%.

Adding Mg significantly increases the strength of the alloy. The maximum content of 5.0% is used in order to avoid the formation of adverse magnesium excretions, such as Mg ₅ Al ₃ or Mg ₅ Al ₈ , which can cause undesirable sensitivity to MCC and SCC.

In one embodiment of the invention, the amount of Mg in the alloy is at least the value provided by the ratio Mg≥6.6- (0.45 × Zn), and preferably Mg≥10- (0.79 × Zn).

Mg and Zn form precipitates of MgZn ₂ , which are precipitates of the secondary phase, which have a strong effect on the final properties of hardness and strength after hardening and aging. If the Mg content lies above the values specified by the above ratios, an excess of magnesium will contribute to the hardening of the alloy.

The present invention is directed to an alloy composition which, when processed into a variety of products, such as, but not limited to, sheet, plate, thick plate, etc., will satisfy and exceed the desired material properties. The balance of properties of such a product will exceed the balance of properties of a product made of currently commercially available alloys.

Preferably, the alloy product according to the invention is processed to thicker "calibers" from more than 1 inch (25.4 mm) and up to about 11 inches (279.4 mm) or more and will provide improved properties in the case of structural elements of the aircraft, such as solid parts obtained by machining from a plate, or to form a solid spar for use in the construction of the wing of the aircraft, or in the form of a stiffener for use in the construction of the wing of the aircraft or in the form f plate covering the upper surface of the wing. Products of a thicker "caliber" can also be used as a tool plate or plate for foundry molds or molds, for example, molds for the production of molded plastic products by injection molding, injection molding, injection molding or comparable methods. When the thickness ranges are set in the aforementioned manner, it will immediately be apparent to those skilled in the art that this thickness is at the thickest cross section in an alloy product made of such a thin or thick plate. The alloy products according to the invention can also be provided in the form of an extruded, stepwise variable section or extruded (extruded) spar for use in the construction of an aircraft or, for example, in the form of a forged spar for use in the construction of an aircraft wing.

In the embodiment where the alloy product has been extruded, preferably these products have been extruded into profiles having a thickness at the thickest cross section in the range of up to 10 mm, and preferably in the range of 1-7 mm. However, in the extruded form, the alloy product can also replace the plate material, which is traditionally processed on the machine using methods of high-speed cutting or milling into a shaped structural element. In this embodiment, the extruded alloy product preferably has a thickness at the thickest cross section in the range of 2 inches (50.8 mm) to 6 inches (152.4 mm).

In one embodiment of the invention, the product is an aerospace plate with high strength and fracture toughness, such as a wing skin panel, and the Mg content in this product preferably depends on the Zn content in accordance with the ratio Mg≥6.6- (0 , 45 × Zn).

It was found that a particularly favorable combination of mechanical properties, fracture toughness properties and corrosion resistance was obtained if the Mg content was at least equal to or greater than the value specified by the aforementioned ratio between Mg and Zn, i.e. a combination of properties that is especially attractive for plates or extruded aerospace profiles with high strength and fracture toughness.

In one embodiment of the invention, the product is a high-strength tool plate, preferably having a hardness after artificial aging of more than 185 HB, preferably more than 190 HB, and the Mg content in this product preferably depends on the Zn content in accordance with a ratio of Mg≥6.6- (0 , 45 × Zn), and more preferably in accordance with the ratio Mg≥10- (0.79 × Zn). It should be noted that all hardness values in this description and the claims are Brinell hardness values measured in accordance with ASTM E10, version 2002, and the hardness is measured on the average cross-sectional thickness.

It was found that a particularly favorable combination of mechanical properties, hardness, weldability and corrosion resistance was obtained if the Mg content is at least equal to or greater than the value specified by the above ratios between Mg and Zn, i.e. a combination of properties that is especially attractive for a high-strength tool board.

In one preferred embodiment, the wrought alloy product is a tool plate in a T6 or T7 state and has a composition consisting essentially of:

In another embodiment, said tool plate further comprises 0.05-0.40% Mn.

In a preferred embodiment, the wrought alloy product is a tool plate in a T6 or T7 state and has a composition consisting essentially of:

In another preferred embodiment, the deformable alloy product of the invention is an aerospace product selected from the group consisting of a sheet, plate, extruded product, or an aircraft structural member made of such a sheet, plate or extruded product, and located in state T6 or T7 and having a composition consisting essentially of:

In a more preferred embodiment of the aerospace product, it has a Mg content of 2.0 to 4.5%, and the Mg content depends on the Zn content in accordance with the ratio Mg≥10- (0.79 × Zn). In a further embodiment of the aerospace product, it has a Zn content in the range from 7.5 to 11.0%, and preferably from 8.5 to 10.0%.

In yet another embodiment of an aerospace product, it additionally consists of Mn in the range from 0.05 to 0.40%, and preferably from 0.05 to 0.30%.

The invention is also implemented in a welded part containing at least one first part of the part, which is a product according to the invention, and at least one second part of the part, and these parts of the part are welded together to form a welded part, while preferably a welded part It is a welded structural element of the aircraft. More preferably, the first and second parts of the part comprise a product according to the invention. Even more preferably, substantially all or even all parts of the part forming the welded part or welded structural member of the aircraft comprise the product of the invention. Good weldability and other favorable properties are used to “provide” a welded part or a welded structural element of an aircraft with excellent strength, corrosion properties and weld quality.

In another aspect of the invention, there is provided a method for manufacturing a product from a deformable aluminum alloy of the AA7000 series, as described above and set forth in the examples, comprising the following process steps:

casting an ingot having the composition set forth in the present description;

homogenization and / or preheating of the ingot after casting;

hot processing of the ingot into a pre-processed product by one or more methods selected from the group consisting of: rolling, extrusion and forging;

optionally heating the pre-processed product and either

hot processing and / or cold processing of the pre-processed product to the desired shape of the workpiece;

solid solution heat treatment (TTR) of the molded preform at a temperature and time sufficient to transfer substantially all of the soluble components in the alloy to a solid solution;

quenching of a heat-treated solid solution preform, preferably one of quenching by spray cooling or quenching by immersion in water or oil, or other quenching media;

optionally stretching or compressing the hardened billet or otherwise cold working to relieve stresses, for example, leveling sheet products;

artificial aging of a hardened and optionally stretched or compressed preform to achieve the desired state, in particular, a state of type T6 or T7, such as conditions selected from the group including: T6, T74, T76, T751, T7451, T7651, T77 or T79, and

wherein the homogenization treatment includes a first stage of homogenization and optionally a second stage of homogenization, the duration and temperature of the first stage of homogenization for the ingot or slab being chosen so that the unheated place, and the said unheated place is defined as the coldest place in the ingot or slab , in an ingot or slab, is at a dissolution temperature for at least the dissolution time necessary to dissolve essentially all of the m-phase precipitates .

Optionally, the homogenization treatment also includes at least a second homogenization step following the first homogenization step. It should be noted that the dissolution temperature is reached at an earlier time on the perimeter of the ingot or casting, and that the temperature in an unheated place slowly increases to the dissolution temperature. In practice, the temperature of dissolution is usually called the temperature of homogenization.

The alloy products of the present invention are conventionally obtained by melting and can be cast into ingots by direct cooling (“direct chill casting” or D.C.) or other suitable casting techniques. Hot processing of an alloy product can be carried out by one or more methods selected from the group consisting of rolling, extrusion, and forging. Hot rolling is preferred for the present product. The solid solution heat treatment is usually carried out in the same temperature range that is used for homogenization, although the holding times can be chosen slightly shorter.

In one embodiment, a method is provided in which the duration of the first homogenization step for the ingot or slab is selected so that the unheated place is at the dissolution temperature for at least the dissolution time necessary to dissolve the m-phase precipitation, wherein preferably, the dissolution time is at most 2 hours, more preferably 1 hour, more preferably as short as possible, for example 30 minutes or 20 minutes, or even shorter. Preferably, the homogenization temperature is about 470 ° C.

In one embodiment, a method is provided in which the duration of the first homogenization step for an ingot or slab is at most 24 hours, more preferably at most 12 hours, while preferably the homogenization temperature is 470 ° C.

In one embodiment, a method is provided in which, for an ingot or slab with Cu 0 0.28%, even more preferably with Cu 0 0.20%, the first homogenization step is at most 12 hours at 470 ° C., and there is no second stage of homogenization.

In one embodiment, a method is provided in which for an ingot or slab with Cu> 0.20%, preferably with Cu> 0.25%, more preferably with Cu max. 0.28%, the homogenization step includes a first homogenization step and a second homogenization step, wherein the first homogenization step is at most 24 hours, preferably at most 12 hours, at 470 ° C., and the second homogenization step is at most 24 hours, preferably at most 12 hours, at 475 ° C.

By the method according to the invention, a product is obtained having a reduced sensitivity to hot cracking, also having improved strength and fracture toughness properties and, being in an artificially aged condition, having a hardness of more than 180 HB. With a content of Cu≤0.25% or even Cu≤0.20%, homogenization treatment for at most 24 hours, preferably at most 12 hours, at 470 ° C is sufficient to dissolve all m-phase precipitates and give a product having the desired properties after TTR, hardening, optional stretching and aging. By choosing the shortest possible stage of homogenization and the lowest possible temperature of homogenization, depending on the copper content, the method can be carried out in a very economical way, while maintaining excellent properties and achieving excellent weldability. The method can be carried out even more economically if the artificial aging is a single-stage artificial aging. In this way, a product is obtained having a reduced sensitivity to hot cracking, also having improved strength and, being in the T6 state, having a hardness of more than 180 HB, is excellently suited for applications in high-strength tool boards. In two-stage artificial aging, a product is obtained that has an advantageous combination of improved mechanical properties, artificially aged hardness, fracture toughness and corrosion resistance properties, excellent for welded aerospace plates with high strength and high fracture toughness. After one-stage and two-stage aging treatment, an improvement in corrosion resistance was observed, especially resistance to MKK and KSh.

It was found that in the case of alloys according to the invention with Cu ≤0.28%, the m-phase precipitates dissolve quickly, and even faster at lower copper contents ≤0.25% and ≤0.20%, respectively, so that the method can be done a more economical way of choosing the duration of the first stage of homogenization, which is chosen so that the unheated place, the aforementioned unheated place being defined as the coldest place in the ingot or slab, usually the center of the ingot or slab, is in the ingot or slab at a homogenization temperature, for example 470 ° C, over At least a dissolving time necessary to dissolve the m-phase, wherein preferably the dissolving time is at most 2 hours is preferred - 1 hour, more preferably - as short as possible. Ideally, homogenization treatment ends when all m-phase precipitates are dissolved, after which the slab or ingot can be transferred to the hot rolling mill so that it can be hot rolled immediately after the slab reaches the rolling temperature, optionally after it has been subjected heat-treated by heating to bring the slab or ingot to or down to the rolling temperature.

In one embodiment, controls are used to control the homogenization treatment, such as a computer model on a mathematical or physical basis for calculating the development of the temperature of the ingot or casting during the homogenization treatment, in order to determine the optimal length of time the ingot or slab remains at the homogenization temperature from the condition that the unheated place of the ingot or slab is maintained at a homogenization temperature, for example, about 470 ° C, for at least Oren required to dissolve m-phase precipitates. It will be clear to a person skilled in the art that the annealing times and temperatures are interchangeable to a certain extent according to the concept of equivalent time, which is described in EP 0876514 B1 (paragraph [0028]) and is hereby incorporated by reference, although, of course, the minimum annealing temperature must be high enough to to make possible the dissolution of secretions. It may also be important to avoid the dissolution of certain other precipitates, so that the freedom to choose the annealing temperature is limited by the maximum and minimum homogenization temperature.

In one embodiment of the method of the invention, artificial aging step (i) includes a first aging step at a temperature in the range of 105 ° C to 135 ° C, preferably 2 to 20 hours, and a second aging step at a temperature in the range of 135 ° C to 210 ° C, preferably for 4 to 20 hours. In yet another embodiment, a third aging step can be applied at a temperature in the range of 105 ° C to 135 ° C, and preferably for 20 to 30 hours.

The invention will be further clarified by the following non-limiting examples.

Examples

Example 1

Laboratory ingots of chemical compositions A.1 to A.7, shown in Table 1, were cast and processed in accordance with the following technological route (v = heating rate, @ = at):

Homogenization: v = 30 ° C / h + 12 h @ 470 ° C,

Heating: v = 35 ° C / h + 6 h @ 420 ° C,

Hot rolling: from a thickness of 80 mm to 30 mm,

TTR: v = as soon as possible, 2 h @ 470 ° C followed by quenching with water,

Elongation: 1.5%

Aging: T76, v = 30 ° C / h + 5 h @ 120 ° C / h,

plus v = 15 ° C / h + 12 h @ 145 ° C / h.

As can be seen from table 1, by increasing the contents of Zn and Mg, but keeping the Cu content at a low level, it is possible to obtain very high strengths, while at the same time maintaining fracture toughness levels equal to or higher than that of comparative materials. From table 1 it is also seen that in order to achieve the desired strength level of at least 580 MPa, the Mg level depends on the Zn level in accordance with the ratio Mg≥6.6- (0.45 × Zn).

Example 2

The laboratory bullion of the chemical compositions B.1 to B.4, shown in Table 2, were cast and processed in accordance with the above process route, except that the final thickness of the hot rolling was 3 mm, and that the alloy B.2 was homogenized for a longer time (12 h @ 470 ° C, followed by 24 h @ 475 ° C), and the step of homogenization included the first and second stage.

table 2 The composition of the alloys in wt.% (0.06 Fe, 0.04 Si, 0.04 Ti, 0.10 Zr, the rest is aluminum). Alloy Zn Mg Cu R _p (MPa) KSh B.1 9.3 2,3 0.16 565 EA / B B.2 9,4 2,3 0.80 564 The EU B.3 9.3 2,8 0.16 598 EA B.4 10.7 2,8 0.15 626 EA

The mechanical (direction L) and corrosive (KS measured in accordance with ASTM G34-97) properties of the alloys are also shown in Table 2. The Cu level of 0.8% (see alloy B.2) does not improve the mechanical properties, but it has an adverse effect. effect on the corrosion properties of the alloy. On the other hand, additional amounts of Mg and Zn (see alloys B.3 and B.4) lead to better corrosion properties and a significant increase in strength.

Example 3

Seven alloys were investigated with the compositions shown in Table 3. Most alloys (C.1-C.5) have low Cu levels, but some contain more Cu (alloy C.6, C.7). All of them were processed into 3.5 mm thick slabs in accordance with the following technological route:

Casting of ingots, machining of blocks for rolling with dimensions of 80 × 80 × 100 mm ³ of these ingots.

Homogenization: v = 30 ° C / h + 470 ° C @ 12 h for Cu≤0.20%, v = 30 ° C / h + 470 ° C @ 12 h, v = 15 ° C / h + 475 ° C @ 24 h for Cu> 0.20%, Hot rolling: heating @ 430 ° C, rolling from a thickness of 80 mm to 3.5 mm, TTR: 1 h @ 470 ° C followed by quenching in water or oil, Stretching: 1.5%

After TTR, all alloys in this example were aged to the T6 state.

Before artificial aging, the alloys were quenched in both water and oil in order to study the sensitivity of the alloys to quenching. Oil quenching is comparable to the cooling rate in the core of a plate with a thickness of about 70 mm, and the core of the plate cannot be cooled as quickly as the surface. After aging, Brinell hardness was measured in accordance with ASTM E10, version 2002. The achieved hardness values are shown in Table 3. Table 3 shows that the values for quenching in water are usually higher or similar to those for quenching in oil. Alloys with a higher total content of alloying components are more sensitive to quenching. Alloys C.2, C.3, C.5, C.7, which all contain ≥9.3% Zn, achieve hardness values of at least 190 HB. In alloy C.6, the addition of Cu significantly increases hardness compared to the exclusion of this addition (alloy C.1), however, in alloy C.7 with a higher Zn content, the addition of Cu hardly leads to any additional increase in hardness in the state of oil quenching . In contrast to the metallurgical expectation that combinations of Mg and Cu will result in higher strength than the equivalent amount of Mg alone, unexpectedly, at higher Zn contents, Cu becomes already ineffective in increasing hardness compared to additional Mg.

Moreover, alloys with a low Cu content, even when quenched in oil, show excellent intercrystalline corrosion resistance (MKC, tested in accordance with ASTM G110-92), while alloys with a high Cu content show an insignificant degree of MKC. Thus, such an alloy is less sensitive to quenching, which has various advantages in processing the alloy, since it has greater resistance to deviations during the process.

Example 4

Five alloys were investigated with the compositions shown in Table 4. The alloys have low Cu levels. They were processed into 3 mm thick slabs in accordance with the following process route:

Casting of ingots, machining of blocks for rolling with dimensions of 80 × 80 × 100 mm ³ of these ingots.

Homogenization: v = 30 ° C / h + 470 ° C @ 12 h Hot rolling: heating @ 430 ° C, rolling from a thickness of 80 mm to 3 mm, TTR: 1 h @ 470 ° C followed by water quenching, Stretching: 1.5% Aging 1-stage or 2-stage artificial aging to the state of T6.

Table 4 gives the resulting average hardness values after 1- or 2-stage aging. The results in table 4 indicate that for a hardness of 190 HB or higher, for a given Zn content of 9.47%, there is a minimum level of Mg, which lies between 1.92% and 2.85%. Table 3 provides a value of 2.8. Moreover, comparable hardness levels were obtained for 1-stage and 2-stage artificial aging. This extends the applicability of this alloy to a variety of product ranges, depending on whether 2-stage aging is required (requirements for aerospace materials) or preferably 1-stage aging (cost reduction).

Table 4 shows that the aging time for the 145 ° C stage of artificial aging provides the ability to be in a wide range to achieve hardness levels of 190 HB or higher.

The composition ratio between the Mg and Zn contents, above which high strength can be expected with proper alloy processing, can be derived from Tables 3 and 4. The ratio between the Mg and Zn contents can be approximately expressed by the ratio Mg = 10-0.79 · Zn in wt.%. For a higher Mg content than what is given by this ratio, depending on the Zn content, a hardness of at least 185 HB, even at least 190 HB, is provided, especially for alloys where the Zn content is over 7.4 %

Example 5

Three alloys according to the invention (E.1-E.3), which are particularly suitable for use in a tool plate, were processed in accordance with the method according to the invention and subsequently aged to a maximum at 130 ° C. for 24 hours. The mechanical tensile properties (yield strength and tensile strength) were determined in the L direction, and hardness was measured on the average thickness over the cross section. The alloys were compared with conventional alloys AA7050 and AA7075 in the T-651 state.

The compositions and properties of the alloys are listed in Table 5. From these results it can be seen that the alloy according to the invention is able to achieve very high hardness values, which makes it very suitable for use as a tool plate.

Table 5 The composition of the alloys according to the invention in wt.% (0.12% Zr, 0.05% Fe, 0.03% Si, 0.15% Cu, the rest is aluminum) and mechanical tensile properties and hardness Alloy Zn (wt.%) Mg (wt.%) condition R _p (MPa) R _m (MPa) Hardness (HB) AA7050 6.2 2,3 T651 532 575 180 AA7075 5,6 2.5 T651 533 462 150 E.1 9,4 3,5 Aged to the maximum 695 708 236 E.2 11.5 3,1 Aged to the maximum 734 736 246 E.3 11,4 3.0 Aged to the maximum 680 689 245

Example 6

The weldability of the three alloys processed according to the invention (F.1-F.3) was evaluated using an established methodology that was used to assess the hot crack susceptibility of an aluminum alloy and which is also known as the Houldcroft test described in the Simple Test for cracking for use with argon-arc welding "(" A simple Cracking Test for use With Argon-Arc Welding "), PT Houldcroft, British Welding Journal, October 1955, pp. 471-475, incorporated herein by reference. This technique uses either a sample with a fish-bone geometry or a sample with a cone-shaped geometry, and a laser with a cone-shaped sample, which was used for this example and had a thickness of 2 mm, is preferred for laser welding. The laser was used to create a full penetration weld bead welded onto the plate. The weld begins at the narrow end of the sample and extends along the entire length of the sample. A hot crack forms during the hardening of the weld pool, and at a certain point this crack stops. Crack length is a measure of sensitivity to hot cracking, so the longer the crack, the higher the sensitivity to hot cracking. Samples were not limited during the test, and all welds were obtained without the addition of filler wire. In the tests, a yttrium aluminum garnet laser with neodymium (Nd: YAG) with a weld point diameter of 0.45 mm (lenses with a focal length of 150 mm) and a focus position on the upper side of the plate was used. The laser processing parameters remained constant at a laser power level of 4,500 W and at a welding speed of 4 m / min.

The alloys selected for the study, as well as the results of weldability tests are shown in table 6. Sensitivity to cracking is presented as% cracking, which is the length of the crack divided by the length of the sample; thus, a lower% cracking rate indicates a lower susceptibility to cracking. It can be clearly seen that as the total content of dissolved Zn and Mg increases, the sensitivity to cracking decreases, which leads to better weldability. For comparison, the aluminum alloy AA7017 was also tested, since it is generally considered in the aluminum industry as a weldable (i.e. weldable) alloy. It can be clearly seen that all the alloys according to the invention were better weldable than AA7017.

Table 6 The composition of the alloys according to the invention in wt.% (0.12% Zr, 0.05% Fe, 0.03% Si, 0.15% Cu, the rest is aluminum) and the results of the Welcroft weldability test. Alloy Zn Mg Zn + Mg % cracking AA7017 (comparative) 4.0-5.2 2.0-3.0 6.0-8.2 53 F.1 9.3 2,8 12.1 31 F.2 9.5 3.3 12.8 28 F.3 10.7 2,8 13.5 31

Of course, it should be understood that the present invention is not limited to the described embodiments and the above examples, but covers any and all embodiments within the scope of the description and the following claims.

Claims (32)

1. The product is from a welded deformable aluminum alloy series AA7000, consisting essentially of, wt.%:
Zn 9.0-14.0; Mg 1.0-5.0; Cu 0.03-0.25; Fe <0.30; Si <0.25; Zr from 0.04 to less than 0.3;
and one or more of:
Ti <0.30; Hf <0.30; Mn <0.80; Cr <0.40; V <0.40; Sc <0.70;
residue: random elements and impurities, each <0.05, total <0.15, and the rest is aluminum, and the product has a reduced sensitivity to the formation of hot cracks, also has improved strength and fracture toughness properties and, being in an artificially aged condition, has a hardness of more than 180 HB. 2. The product according to claim 1, in which Cu is ≤0.20%. 3. The product according to claim 1, in which the Cu content has a lower limit of 0.08%. 4. The product according to claim 1, in which the Zr content is in the range of 0.04-0.15%, preferably in the range of 0.04-0.13%. 5. The product according to claim 1, in which the Zn content has a lower limit of 9.5%. 6. The product according to claim 1, in which the content of Zn has an upper limit of 12.0%. 7. The product according to claim 1, in which the Zn content has an upper limit of 11.0%. 8. The product according to claim 1, in which the content of Zn has an upper limit of 10.0%. 9. The product according to claim 1, in which the Mg content has a lower limit of 2.5%. 10. The product according to claim 1, in which the Mg content has an upper limit of 4.5%, preferably an upper limit of 4.0%. 11. The product according to claim 1, in which the content of Fe is up to 0.14%, preferably up to 0.08%. 12. The product according to claim 1, in which the Si content is up to 0.12%, preferably up to 0.07%. 13. The product according to claim 1, in which the Mn content is in the range of 0.05-0.40%. 14. The product according to claim 1, in which the content of Mn is <0.02%. 15. The product according to claim 1, in which Mg≥6.6- (0.45 · Zn), preferably Mg≥10- (0.79 · Zn). 16. The product according to claim 1, wherein this product is in the form of a sheet, plate or extruded product. 17. The product according to claim 1, wherein this product is in a state of type T6 or type T7. 18. The product according to claim 1, wherein this product is a welded aerospace product in the form of a sheet or plate in a state of type T6 or type T7, and wherein said product consists essentially of, wt.%:
Zn 9.0-11.0; Mg 1.0 - 5.0, while the Mg content depends on the Zn content in accordance with the ratio Mg≥6.6- (0.45 · Zn); Cu 0.03-0.25; Zr 0.04 - 0.15; Ti <0.10; Fe <0.08; Si <0.07;
residue: random elements and impurities, each <0.05, total <0.15, the rest is aluminum. 19. The product according to claim 1, wherein this product is a welded aerospace product in the form of a sheet or plate in a state of type T6 or type T7, wherein said product consists essentially of, wt.%:
Zn 9.0-11.0; Mg 2.0 - 4.5, while the Mg content depends on the Zn content in accordance with the ratio Mg≥10- (0.79 · Zn); Cu 0.03-0.25; Zr 0.04 - 0.15; Ti <0.10; Fe <0.08; Si <0.07;
residue: random elements and impurities, each <0.05, total <0.15, the rest is aluminum. 20. The product according to claim 1, and this product is a welded product for aerospace purposes in the form of a sheet or plate in the state of type T6 or type T7, while the said product consists essentially of, wt.%:
Zn 9.0-10.0; Mg 2.0 - 4.5, while the Mg content depends on the Zn content in accordance with the ratio Mg≥10- (0.79 · Zn); Cu 0.03-0.25; Zr 0.04 - 0.15; Ti <0.10; Fe <0.08; Si <0.07;
residue: random elements and impurities, each <0.05, total <0.15, the rest is aluminum. 21. The product according to claim 1, wherein this product is a welded aerospace product in the form of a sheet or plate in a state of type T6 or type T7, wherein said product consists essentially of, wt.%:
Zn 9.0-10.0; Mg 2.5 - 4.5, while the Mg content depends on the Zn content in accordance with the ratio Mg≥10- (0.79 · Zn); Cu 0.03-0.25; Zr 0.04 - 0.15; Ti <0.10; Fe <0.08; Si <0.07;
residue: random elements and impurities, each <0.05, total <0.15, the rest is aluminum. 22. The product according to claim 1, wherein this product is a welded extruded aerospace product in a state of type T6 or type T7, and wherein said product consists essentially of, wt.%:
Zn 9.0-11.0; Mg 1.0 - 5.0, while the Mg content depends on the Zn content in accordance with the ratio Mg≥6.6- (0.45 · Zn); Cu 0.03-0.25; Zr 0.04 - 0.15; Ti <0.10; Fe <0.14; Si <0.12;
residue: random elements and impurities, each <0.05, total <0.15, the rest is aluminum. 23. The product according to claim 1, wherein this product is a welded aerospace product in the form of a sheet or plate in a state of type T6 or type T7, wherein said product consists essentially of, wt.%:
Zn 9.0-10.0; Mg 2.5 - 4.5, while the Mg content depends on the Zn content in accordance with the ratio Mg≥10- (0.79 · Zn); Cu 0.03-0.25; Cr 0.04-0.20; Zr 0.04 - 0.15; Ti <0.10; Fe <0.08; Si <0.07;
residue: random elements and impurities, each <0.05, total <0.15, the rest is aluminum. 24. The product according to claim 1, wherein this product is a welded product in the form of a tool plate in a state of type T6 or type T7, while the said product in the form of a plate consists essentially of, wt.%:
Zn 9.0-14.0; Mg 1.0 - 5.0, while the Mg content depends on the Zn content in accordance with the ratio Mg≥6.6- (0.45 · Zn); Cu 0.03-0.25; Zr 0.04-0.15; Ti <0.10; Fe <0.30; Si <0.25;
residue: random elements and impurities, each <0.05, total <0.15, the rest is aluminum. 25. The product according to claim 1, wherein this product is a weldable product in the form of a tool plate in a state of type T6 or type T7, wherein said product in the form of a plate consists essentially of, wt.%:
Zn 9.0-14.0; Mg 2.0 - 4.0, while the Mg content depends on the Zn content in accordance with the ratio Mg≥10- (0.79 · Zn); Cu 0.03-0.25; Zr 0.04-0.15; Ti <0.10; Fe <0.30; Si <0.25;
residue: random elements and impurities, each <0.05, total <0.15, the rest is aluminum. 26. The product according to claim 1, wherein this product is a welded product in the form of a tool plate in a state of type T6 or type T7, and wherein said product in the form of a plate consists essentially of, wt.%:
Zn 9.0-12.0; Mg 2.0 - 4.0, while the Mg content depends on the Zn content in accordance with the ratio Mg≥10- (0.79 · Zn); Cu 0.03-0.25; Zr 0.04-0.15; Ti <0.10; Fe <0.30; Si <0.25;
residue: random elements and impurities, each <0.05, total <0.15, and the rest is aluminum. 27. The product according to claim 1, wherein this product is a weldable product in the form of a tool plate in a state of type T6 or type T7, and wherein said product in the form of a plate consists essentially of, wt.%:
Zn 9.5-12.0; Mg 2.5 - 4.5, while the Mg content depends on the Zn content in accordance with the ratio Mg≥10- (0.79 · Zn); Cu 0.03-0.25; Zr 0.04-0.15; Ti <0.10; Fe <0.30; Si <0.25;
residue: random elements and impurities, each <0.05, total <0.15, and the rest is aluminum. 28. The product according to claim 1, wherein this product is a welded product in the form of a tool plate in a state of type T6 or type T7, while the said product in the form of a plate consists essentially of, wt.%:
Zn 9.0-11.0; Mg 2.5 - 4.5, while the Mg content depends on the Zn content in accordance with the ratio Mg≥10- (0.79 · Zn); Cu 0.03-0.25; Zr 0.04-0.15; Ti <0.10; Fe <0.30; Si <0.25;
residue: random elements and impurities, each <0.05, total <0.15, and the rest is aluminum. 29. The product according to claim 1, wherein this product is a welded product in the form of a tool plate in a state of type T6 or type T7, and wherein said product in the form of a plate consists essentially of, wt.%:
Zn 9.5-12.0; Mg 2.5-3.5; Cu 0.03-0.25; Zr 0.04-0.15;
Ti <0.10; Fe <0.30; Si <0.25;
residue: random elements and impurities, each <0.05, total <0.15, and the rest is aluminum, and has a hardness of more than 190 HB. 30. A welded part of a welded deformable aluminum alloy, which is a welded structural element of an aircraft, containing at least one first part of the part, which is a product according to claim 1, and at least one second part of the part, these parts of the part being welded together to form a welded part, wherein said at least one first and at least one second part of the part are products according to claim 1. 31. A method of manufacturing a product from a welded deformable aluminum alloy of the AA7000 series according to any one of claims 1 to 22, comprising the following steps:
a) casting an ingot having the composition according to claim 1,
b) homogenization and / or preheating of the ingot after casting,
c) hot processing of the ingot into a pre-processed product by one or more methods selected from the group consisting of rolling, extrusion and forging,
d) optionally, heating the pre-processed product and either,
e) hot processing and / or cold processing of the pre-processed product to the desired shape of the workpiece,
f) heat treatment for solid solution (TTR) of the molded preform at a temperature and time sufficient to transfer to a solid solution essentially all of the soluble components in the alloy,
g) quenching of a heat-treated solid solution preform, preferably one of quenching by cooling by spraying or quenching by immersion in water or other quenching media,
h) optionally, stretching or compressing the hardened billet or otherwise cold working to relieve stresses, for example, leveling sheet products,
i) artificial aging of the hardened and optionally stretched or compressed preform to achieve the desired state, and
wherein the homogenization treatment includes a first stage of homogenization and, optionally, a second stage of homogenization, the duration and temperature during the first stage of homogenization for the ingot or slab being chosen so that the unheated place, and the said unheated place is defined as the coldest place in the ingot or slab, the ingot or slab is at a dissolution temperature for at least the dissolution time necessary to dissolve the T phase precipitation. 32. The method according to p, in which during step i) of the method, the product is subjected to artificial aging to a state of type T6 or type T7.