CN112262223B - Method of manufacturing 7 xxx-series aluminum alloy sheet products having improved fatigue failure resistance - Google Patents
Method of manufacturing 7 xxx-series aluminum alloy sheet products having improved fatigue failure resistance Download PDFInfo
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- CN112262223B CN112262223B CN201980039243.7A CN201980039243A CN112262223B CN 112262223 B CN112262223 B CN 112262223B CN 201980039243 A CN201980039243 A CN 201980039243A CN 112262223 B CN112262223 B CN 112262223B
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
- C21D8/0226—Hot rolling
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D7/00—Casting ingots, e.g. from ferrous metals
- B22D7/005—Casting ingots, e.g. from ferrous metals from non-ferrous metals
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C21/00—Alloys based on aluminium
- C22C21/10—Alloys based on aluminium with zinc as the next major constituent
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
- C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
- C22F1/04—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon
- C22F1/053—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon of alloys with zinc as the next major constituent
Abstract
The present invention relates to a method of manufacturing a7 xxx-series aluminium alloy sheet product having improved fatigue failure resistance, said method comprising the steps of: (a) Casting an ingot made from the 7xxx series aluminum alloy, comprising (in weight%): 5 to 9 Zn, 1 to 3 Mg, 0 to 3 Cu, balance aluminum and incidental elements and impurities; (b) homogenizing and/or preheating the ingot; (c) Hot rolling the ingot into a plate product by rolling the ingot in a plurality of rolling passes, characterized in that at least one high reduction hot rolling pass is performed with a reduction in thickness of at least 25% when the intermediate thickness of the plate is between 80mm and 220mm, wherein the final thickness of the plate product is less than 75mm. The invention also relates to an aluminium alloy sheet product and an aerospace structural member produced by such a method.
Description
Technical Field
The present invention relates to a method of manufacturing a7 xxx-series aluminium alloy sheet product having improved fatigue failure resistance. The sheet products are ideal for aerospace structural applications such as wing skin panels and components, and other high strength end users.
Background
Al-Zn-Mg- (Cu) type alloys or AA7 xxx-series alloys have been used in aircraft construction for over 50 years, and particularly for e.g. wing components, the AA 7055-series alloys have been used. These aluminum alloys have the desired balance of strength, fracture toughness, and corrosion resistance, and are particularly suitable for aerospace structural applications, such as skin panels on wings. This is disclosed, for example, in U.S. Pat. No. 5,221,377. This us patent discloses that in order to obtain these high mechanical characteristics, it is necessary to subject the alloy to a three-stage artificial ageing process. However, this us patent is not concerned with the fatigue failure resistance properties of the AA7055 alloy.
It is known that high strength structural components, which are seen in terms of durability and damage tolerance as well as fatigue failure resistance, are highly desirable for aircraft manufacturers. Durability and damage tolerance may extend the inspection interval of an aircraft. Aircraft typically require two types of inspections: initial inspections and periodic inspections during the life of the aircraft. Each type of inspection is very expensive because the aircraft must be taken out of service to be inspected. Inspection may require detailed visual inspection and extensive non-destructive testing of external and internal structures.
U.S. Pat. No. 7,097,719 discloses that the fatigue failure resistance of AA7055 series alloys can be improved by using an optimized alloy composition, which is later registered as AA7255 alloy. However, in order to achieve improved fatigue failure resistance, the upper limits of the Si and Fe levels of the AA7255 alloy must be much more stringent than the AA7055 alloy. In particular, this us patent discloses that products made from AA7255 alloys having Si and Fe levels below AA7055 (i.e., si and Fe concentrations below 0.06 wt.%, preferably below 0.04 wt.%) exhibit better fatigue failure resistance. In particular, the us patent discloses in the examples that alloys with less than 0.029 wt% Si and less than 0.039 wt% Fe (while maintaining Cu, mg, zn and Zr in the range of standard AA 7055) achieve an improvement in fatigue life over standard AA7055 products with higher Si and Fe levels. Thus, the fatigue life of the AA7255 aluminum alloy product relative to a standard AA7055 product may be improved. This improvement delays the inspection interval of the aircraft structure. However, keeping the contents of impurities Si and Fe at such very low levels increases the cost of the aluminium alloy produced, since the source is a very high purity grade material.
Since fatigue performance, particularly fatigue failure resistance, is an important engineering parameter for aluminum alloy aerospace materials, as aircraft experience cyclic stresses in service, there is a need to further improve or further promote the fatigue failure resistance of AA7 xxx-series alloys (including AA 7055-series alloys).
Therefore, there is a need for an Al-Zn-Mg- (Cu) type alloy having desirable strength, toughness and corrosion resistance properties as well as high fatigue failure resistance. There is also a need for aircraft structural parts that exhibit high fatigue failure resistance.
Objects of the invention
It is an object of the present invention to provide a method of manufacturing a7 xxx-series aluminium alloy sheet product having a high fatigue failure resistance compared to a7 xxx-series and in particular AA7055 aluminium alloy sheet product of similar size and temper produced by conventional methods.
It is another object of the present invention to provide an aluminium alloy sheet product with improved fatigue failure resistance compared to AA7055 sheet products.
It is another object to provide aerospace structural components, such as upper wing skins, from improved fatigue resistant aluminum alloy sheet products.
Disclosure of Invention
These and other objects and further advantages are met or exceeded by the present invention which provides a method for manufacturing an aluminium alloy rolled sheet product with improved fatigue failure resistance, said aluminium alloy rolled sheet product having a final thickness or final gauge of less than 75mm, preferably less than 50mm, which is ideally suited for use as a space sheet product, said method comprising the steps in the following order:
(a) Casting an aluminum alloy ingot of the 7xxx series, the aluminum alloy comprising (in weight%):
zn is contained in an amount of 5 to 9,
(ii) from 1 to 3 of Mg,
the content of Cu is 0 to 3,
the content of Fe is at most 0.20,
the content of Si is at most 0.15,
zr up to 0.5, preferably from 0.03 to 0.20,
the balance aluminum and impurities;
(b) Homogenizing and/or preheating the ingot;
(c) Hot rolling the ingot into a plate product by rolling the ingot in a plurality of rolling passes, wherein at least one high reduction hot rolling pass is performed with a reduction in thickness of at least 25% when the intermediate thickness of the plate is between 80mm and 220mm, preferably between 100mm and 200 mm;
(d) Optionally solution heat treating the plate product and cooling to ambient temperature, preferably by quenching means;
(e) Optionally stretching the solution heat treated sheet product;
(f) Optionally artificially ageing said plate product.
In the context of an aluminum alloy, the term "comprising" is understood that the alloy may contain other alloying elements, as exemplified below.
The method according to the invention is applicable to a wide range of 7 xxx-series aluminium alloys, consisting of (in wt.%):
zn 5% to 9%, preferably 5.5% to 8.5%, more preferably 7% to 8.5%,
1 to 3 percent of Mg,
cu 0% to 3%, preferably 0.3% to 3%,
si up to 0.15%, preferably up to 0.10%,
fe up to 0.20%, preferably up to 0.15%,
one or more elements selected from the group consisting of:
zr up to 0.5%, preferably from 0.03% to 0.20%,
ti is at most 0.3%
Cr is at most 0.4%
Sc is at most 0.5%
Hf is at most 0.3%
Mn is at most 0.4%
V is at most 0.4%
Ag up to 0.5%, and
the balance being aluminum and impurities. Typically, such impurities are present in an amount of <0.05% each, and <0.15% total.
In another embodiment, the aluminum alloy has a chemical composition within the following range: AA7010, AA7040, AA7140, AA7449, AA7050, AA7150, AA7055, AA7255, AA7081, AA7181, AA7085, AA7185, AA7090, AA7099, AA7199, and modifications thereof.
In a specific embodiment, the aluminum alloy has a chemical composition in the range of AA 7055.
As will be understood hereinafter, aluminum alloy designations and temper designations refer to aluminum association designations in the aluminum Standards and Data and Registration Records (aluminum Standards and Data and the Registration Records) published by the aluminum association in 2016 and are well known to those skilled in the art, unless otherwise indicated.
For any description of an alloy composition or preferred alloy composition, all references to percentages are by weight unless otherwise indicated.
The terms "≦" and "up to about" as used herein expressly include, but are not limited to, the possibility that the weight percent of the particular alloying component for which it is referred to is zero. For example, up to 0.4%Cr may include alloys without Cr.
In the method of the invention, it is preferred not to perform the cold rolling step when rolling the sheet product to final gauge (thickness) in order to avoid at least partial recrystallization during the subsequent solution heat treatment step, resulting in a negative impact on the balance of engineering properties of the final sheet product.
The final thickness of the rolled sheet product is less than 75mm, preferably less than 50mm, preferably less than 45mm, more preferably less than 40mm and most preferably less than 35mm. In a useful embodiment, the final thickness of the board product is greater than 10mm, preferably greater than 12.5mm, more preferably greater than 15mm and most preferably greater than 19mm.
The aluminium alloy may be provided in the form of a rolled ingot or slab by casting techniques routinely used in the art of casting products (e.g. DC casting, EMC casting, EMS casting) and preferably has a thickness in the range of 300mm or more, for example 400mm, 500mm or 600mm. On a less preferred basis, it is also possible to use slabs made by continuous casting, such as a belt casting machine or a roll casting machine, which may be particularly advantageous when producing thinner gauge end products. Grain refiners, such as those containing titanium and boron, or titanium and carbon, may also be used, as is well known in the art. After casting the rolling alloy feedstock, the ingot is typically trimmed (scalped) to remove segregation zones near the casting surface of the ingot.
Next, the rolling ingot is homogenized and/or preheated.
As known in the art, the purpose of the homogenization heat treatment has the following purpose: (i) Possibly dissolving much of the coarse soluble phase formed during solidification, and (ii) a low concentration gradient to facilitate the dissolution step. The pre-heat treatment also achieves some of these goals.
Generally, preheating refers to heating an ingot to a set temperature and soaking at this temperature for a set time, and then starting hot rolling around this temperature. Homogenization refers to a heating and cooling cycle applied to the rolling ingot, in which the final temperature after homogenization is ambient temperature.
Typical preheating temperatures for AA7 xxx-series alloys used in the process according to the invention should be temperatures in the range of from 400 ℃ to 460 ℃ and soaking times in the range of from 2 to 50 hours, more typically from 2 to 20 hours.
First, the soluble eutectic phases (e.g., S-phase, T-phase, and M-phase) in the alloy feedstock are dissolved using routine industrial practice. This is typically done by heating the feedstock to below 500 ℃ (typically in the range 450 ℃ to 490 ℃) because of the S-phase eutectic phase (Al) in AA7 xxx-series alloys 2 MgCu phase) has a melting temperature of about 489 c and an M phase (MgZn) 2 Phase) has a melting point of about 478 deg.c. This can be achieved by performing a homogenization treatment in the temperature range and allowing cooling to the hot rolling temperature, or after homogenization, the material is subsequently cooled and reheated and then hot rolled, as is known in the art. The routine homogenization process may also be carried out in two or more steps (if desired), and for AA7 xxx-series alloys this is typically at a temperature in the range of 430 ℃ to 490 ℃The method is carried out in the inner process. For example, in a two-step process, there is a first step between 455 ℃ and 465 ℃ and a second step between 470 ℃ and 485 ℃ to optimize the dissolution process of the various phases, depending on the exact alloy composition.
According to industrial practice, soaking times at homogenization temperatures are alloy dependent, as is well known to the skilled person, and typically range from 1 to 50 hours. The heating rate that can be applied is a heating rate that is routine in the art.
Hot rolling of an ingot is performed in a plurality of hot rolling passes, and is generally performed in a hot rolling mill. The number of hot rolling passes is generally between 15 and 35, preferably between 20 and 29. When the hot rolled sheet product has an intermediate thickness between 80mm and 220mm, preferably between 100mm and 200mm, the method applies at least one high reduction hot rolling pass with a reduction in thickness of at least about 25%, preferably at least about 30% and most preferably at least about 35%. In useful embodiments, the reduction in thickness in this high reduction pass is less than 70%, preferably less than 60% and more preferably less than 50%. The "reduction in thickness" of a rolling pass, also referred to as reduction, is preferably the percentage of plate thickness reduction in an individual rolling pass.
This at least one high reduction hot rolling pass was not performed in conventional commercial hot rolling practice when producing 7xxx series plate products. Thus, according to a non-limiting example of the invention, the hot rolling pass between 80mm and 220mm can be described as follows (see the middle thickness of the plate): 203mm-190mm-177mm-167mm-117mm-102mm-92mm. The high reduction hot rolling pass of 167mm to 117mm corresponds to a thickness reduction of about 30%. For aluminium alloy sheet produced by conventional hot rolling processes, the reduction in thickness per hot rolling pass is typically between 9% and 18% when the intermediate thickness is between 80mm and 220 mm. Thus, according to an example of a conventional method, hot rolling passes between 80mm and 220mm can be described as follows (see the intermediate thickness of the plate): 203mm-188mm-166mm-144mm-124mm-104mm-92mm. The method according to the invention thus defines a hot rolling step in which at least one high reduction hot rolling pass is carried out. Such high pressure rate passes are defined by a thickness reduction of at least about 25%, preferably at least about 30% and more preferably at least about 35%.
The reduction in the hot rolling pass of the process of the invention before and after the high reduction pass is comparable to that of the hot rolling pass of the conventional hot rolling process. Thus, the reduction in thickness of each hot rolling pass before and after the high-reduction hot rolling pass is between 8% and 18%. Since the thickness reduction differs depending on the thickness of the plate, e.g. a thick plate with more than 300mm or a thin plate with less than 30mm, the claimed method is characterized in that the high pressure reduction step is performed when the intermediate thickness of the plate product is reduced by between 220mm and 80mm, preferably between 200mm and 100mm, most preferably between 200mm and 120 mm. This thickness is selected to ensure that the high deformation/shear is consistent throughout the thickness of the sheet product. For sheet products thicker than 220mm, it is difficult to ensure consistent deformation throughout the sheet. Typically, in thicker sheet products, the deformation in the center (half thickness) of the sheet product is less than at a quarter thickness or in the subsurface region.
Preferably, one hot rolling pass at high pressure is performed. In an alternative embodiment, two high reduction hot rolling passes are performed. If a high reduction hot rolling pass is applied, the high reduction hot rolling pass is preferably one of the last seven or eight hot rolling passes.
Prior to starting the hot rolling process, the rolled ingot is preheated to a temperature routine in the art and known to the skilled person, such as 390 ℃ to 480 ℃, preferably 400 ℃ to 460 ℃, more preferably 400 ℃ to 430 ℃, such as 410 ℃. It is therefore possible to maintain the inlet temperature of the hot rolling mill above 380 c, preferably above 390 c. The maximum temperature of the hot rolling pass is not higher than 450 ℃, since it has been observed that coarsening of the S-phase may occur above this temperature and there is a risk of incipient melting.
It has been found that in case of manufacturing of a sheet product with a final thickness of less than 50mm, the deformation rate during the hot rolling process also has an influence on the final sheet product properties. Thus, in a useful embodiment of the process, the deformation rate during at least one high reduction pass is preferably less than <1s-1, preferably ≦ 0.8s-1. It is believed that this intense shear results in the fragmentation of the component particles (e.g., fe-rich intermetallics).
The rate of deformation during hot rolling for each rolling pass can be described by the following equation:
wherein
h 0 Entrance thickness of the plate (in mm)
h 1 Outlet thickness of the plate (in mm)
v 1 Rolling speed of work rolls (in mm/s)
R radius of the work roll (in mm).
The rate of deformation is the change in strain (deformation) of a material with respect to time. Sometimes also referred to as "strain rate". The formula shows that not only the inlet thickness and outlet thickness of the aluminum alloy sheet, but also the rolling speed of the work rolls all have an influence on the deformation rate.
For conventional industrial scale hot rolling practice, the rate of deformation per rolling pass is typically equal to or greater than 2s -1 . As already outlined above, according to an embodiment of the method according to the invention, the deformation rate is reduced to during the high pressure rate pass<1s -1 Preferably ≤ 0.8s -1 . By using a low deformation rate, it is possible to achieve more intense shear within the sheet material.
Further, if desired, the aluminum alloy sheet product produced by the present invention may be subjected to Solution Heat Treatment (SHT), cooled (preferably by means of quenching), stretched and artificially aged after the hot rolling to final gauge step. If Solution Heat Treatment (SHT) is performed, the sheet product should be heated (similar to the homogenization heat treatment prior to hot rolling) to a temperature typically in the range of 430 ℃ to 490 ℃ to bring all or substantially all of the soluble zinc, magnesium and copper into solution. After a set soaking time at high temperature, the sheet product should be rapidly cooled or quenched to complete the solution heat treatment procedure. This quenching is preferably carried out by water quenching, for example via water immersion or water jets.
After cooling to ambient temperature, the sheet product may be further cold worked by means of stretching in the range of 0.5% to 8% of its original length to relieve its residual stresses and improve the flatness of the product. Preferably, the stretch ranges from 0.5% to 5%, more preferably from 1% to 3%.
In a preferred embodiment, the plate product obtained by the present invention is artificially aged. All ageing practices known in the art and which may be subsequently developed may be applied to the AA 7000-series alloy products obtained according to the process of the present invention to develop the required strength and other engineering properties.
In a particularly preferred embodiment, the plate product is artificially aged to a T7 temper, preferably a T79 or T77 temper. The artificial aging step may be performed in one step or in multiple aging steps. Preferably, a two-step aging procedure is performed.
The desired structural shape is then machined from these heat treated plate sections, more typically after artificial aging, such as a complete wing spar.
An advantage of the present invention is that the aluminum alloy product exhibits improved fatigue failure resistance without the need to maintain its iron and silicon content at extremely low levels. According to the prior art, both Fe and Si are generally considered to be detrimental to fatigue failure resistance. However, the aluminum alloy sheet products produced by the process of the present invention have greater resistance to the presence of Fe and Si while still providing the desired balance of properties, including high fatigue failure resistance. In embodiments, the alloy may contain more than 0.05%, preferably more than 0.06% fe. In embodiments, it may contain more than 0.05%, preferably more than 0.06% si. In another preferred embodiment, the Fe and Si contents are each equal to or higher than 0.07 wt%. In another embodiment, the Si content is between 0.06% and 0.10%, and the Fe content is within 0.06% to 0.15%. Thus, for example, commercially available AA7055 aluminum alloy may be used in the claimed process.
In other embodiments, fe and Si levels are kept at very low levels to achieve further improvements in properties. For example, the Fe content may be maintained at less than 0.05%, preferably less than 0.03%, and the Si content may be less than 0.05%, preferably less than 0.03%.
The AA 7000-series alloy plate product when manufactured according to the invention may be used as an aerospace structural component, such as a fuselage frame member, an upper wing plate, a lower wing plate, a thick plate of machined parts, a thin sheet of stringers, a spar member, a rib member, a floor beam member and a bulkhead member, among others.
In particular embodiments, the aluminum alloy sheet product is used as a wing panel or component, more particularly as an upper wing panel or component.
Thus, the plate product manufactured according to the invention provides improved properties compared to a plate product manufactured according to conventional standard methods for this type of aluminium alloy having otherwise the same dimensions and processed to the same temper.
Drawings
Embodiments of the present invention will be described by way of non-limiting examples, and comparative examples representing the prior art are also given.
FIG. 1 is a graph of maximum net stress versus failure cycle for a panel made according to the method of the present invention and a panel made by a conventional method.
Fig. 2 is a graph showing the average logarithmic fatigue life of the plates prepared according to the method of the present invention and the plates prepared by the conventional method, wherein the lines connect the data points corresponding to the average values.
Detailed Description
The rolling ingot was a DC casting of aluminum alloy AA7055, with the composition given in table 1.
TABLE 1
| Si | Fe | Cu | Mg | Zn | Zr | |
| Batch | ||||||
| A、B、C、D、E | 0.07 | 0.07 | 2.35 | 1.94 | 8.05 | 0.12 |
The thickness of the rolled ingot is about 400mm. The homogenization of the ingot is carried out in the form of a two-step homogenization process at 465 deg.C (first step) and 475 deg.C (second step)Line, then cool to ambient temperature. After trimming, the ingot was preheated to 410 ℃ for hot rolling. Hot rolling was performed on a hot rolling mill having a work roll radius of about 575 mm. Batches a and B were processed according to the invention, i.e. both batches received high reduction passes during the hot rolling process. During the high pressure rolling pass, batch a received a thickness reduction of about 30% (167 mm to 117 mm) and batch B received a thickness reduction of about 28% (165 mm to 118 mm). The rolling speed during this high reduction pass was about 25m/min, giving about 0.53s -1 The rate of deformation of (a). Lots C, D and E were processed according to conventional hot rolling methods (thickness reduction between 9% and 18% for each hot rolling pass of thickness between 220mm and 80 mm). The rolling speed during the standard hot rolling pass was about 105m/min, which gave a rolling speed of 1.61s -1 (inlet thickness 188 mm) and 2.27s -1 (inlet thickness 123 mm) of the sample. Plate a received 27 hot rolling passes, with the high reduction pass being 19 passes. Plate B received 25 hot rolling passes with the high reduction pass being pass number 17.
The final thicknesses of the sheets A, C and E after the hot rolling process were 19mm, and the final thicknesses of the sheets B and D after the hot rolling process were 25.4mm. After hot rolling, all final thickness plates were solution heat treated at a temperature of about 470 ℃, quenched and stretched by about 2%. An artificial aging step is applied to make the product in the T7951 condition.
Fatigue tests were carried out in accordance with DIN EN 6072 by using single-open-hole specimens (single open hole test coupon) with a net stress concentration coefficient Kt of 2.3. The test specimens were 150mm long by 30mm wide by 3mm thick and had a single hole diameter of 10mm. Each side of the hole was drilled to a depth of 0.3mm. The test specimen receives axial stress at a stress ratio (minimum load/maximum load) of R = 0.1. The test frequency was 25Hz and the test was carried out in high humidity air (RH. Gtoreq.90%). The individual results of these tests are shown in table 2 and in fig. 1 and 2. The lines in fig. 2 are the interpolation between the calculated log mean data points.
TABLE 2
Figure 1 illustrates that by using the method of the invention it is possible to significantly improve the fatigue life and thus the fatigue failure resistance relative to AA7055 alloy sheets prepared by conventional methods. For example, at an applied net section stress of 175MPa, the life of plate a was 470421 cycles, representing a 3.2 fold improvement in life compared to AA7055 alloys (i.e., alloys C and E having a life of 142655 cycles). Thus, in an alloy prepared by the method of the invention and having a final thickness of 19mm, 200000 cycles of life (see log mean curve in fig. 2) correspond to a maximum net stress of about 210MPa for the invention compared to 175MPa in a7055 alloy according to the conventional standard. This represents an improvement of more than 20% and the aircraft manufacturer can be used to increase the design stresses of the aircraft, thereby saving weight while maintaining the same inspection interval for the aircraft.
FIG. 2 shows the log average of lots A and B made according to the method of the present invention and the log average of lots C, D and E made according to the conventional method for the same alloy as given in FIG. 1, with the lines showing the interpolation between the calculated log average data points. It is apparent from this figure that by using the same alloy composition, the inventive method results in an improvement in fatigue life compared to the conventional method.
The invention is not limited to the embodiments described before, which may be varied widely within the scope of the invention as defined by the appended claims.
Claims (30)
1. A method of manufacturing a7 xxx-series aluminum alloy sheet product having improved fatigue failure resistance, said method comprising the steps of:
(a) Casting an aluminum alloy ingot of the 7xxx series, the aluminum alloy comprising, in weight percent:
zn is contained in an amount of 5 to 9,
(ii) from 1 to 3 of Mg,
the content of Cu is 0 to 3,
the content of Fe is at most 0.20,
the content of Si is at most 0.15,
zr is at most 0.5 of the total weight of the alloy,
the balance aluminum and impurities;
(b) Homogenizing and/or preheating the ingot;
(c) Hot rolling the ingot into a sheet product by rolling the ingot in a plurality of rolling passes, characterized in that when the intermediate thickness of the sheet is between 80mm and 220mm, at least one high reduction hot rolling pass is performed with a reduction in thickness of at least 25%;
wherein the final thickness of the board product is less than 75mm.
2. The method of claim 1, wherein the aluminum alloy includes 0.03 to 0.20 wt.% Zr.
3. The method of claim 1, wherein the final thickness of the sheet product is less than 50mm.
4. The method of claim 1, wherein the method further comprises the steps of:
(d) Subjecting the sheet product to solution heat treatment;
(e) Cooling the solution heat treated sheet product;
(f) Optionally stretching the solution heat treated and cooled sheet product, and
(g) Artificially aging the solution heat treated and cooled sheet product.
5. A process according to claim 4, wherein in step (e) cooling is carried out by means of quenching.
6. The method of any one of claims 1 to 5, wherein the method does not include the step of cold rolling to final gauge.
7. The method of any one of claims 1 to 5, wherein the high reduction hot rolling pass is performed with a reduction in thickness of at least 30%.
8. The method of claim 7, wherein the thickness is reduced by at least 35%.
9. The method of any of claims 1 to 5, wherein the rate of deformation during the high-reduction hot rolling pass is<1s -1 。
10. The method of claim 9, wherein the rate of deformation is ≦ 0.8s -1 。
11. The method of any one of claims 1 to 5, wherein the intermediate thickness of the plate prior to the high reduction hot rolling pass is between 100mm and 200 mm.
12. The method of claim 11, wherein the intermediate thickness of the plate is between 120mm and 200 mm.
13. The method of any of claims 1-5, wherein the aluminum alloy has a Si content and/or Fe content equal to or greater than 0.05 wt.%.
14. The method of any of claims 1-5, wherein the aluminum alloy has a composition consisting of:
5 to 9 percent of Zn,
1 to 3 percent of Mg,
0% to 3% of Cu,
at most 0.15% of Si,
fe is 0.20% at most,
one or more elements selected from the group consisting of:
at most 0.5% of Zr,
ti is at most 0.3%
Cr is at most 0.4%
Sc is at most 0.5%
Hf is at most 0.3%
Mn is at most 0.4%
V is at most 0.4%
At most 0.5% of Ag,
the balance being aluminum and impurities.
15. The method of claim 14, wherein the aluminum alloy has a composition consisting of:
5.5 to 8.5 percent of Zn,
1 to 3 percent of Mg,
0.3 to 3 percent of Cu,
at most 0.10% of Si,
fe is 0.15% at most,
one or more elements selected from the group consisting of:
zr 0.03-0.20%
Ti is at most 0.3%
Cr is at most 0.4%
Sc is at most 0.5%
Hf up to 0.3%
Mn is at most 0.4%
V is at most 0.4%
0.5 percent of Ag at most,
the balance being aluminum and impurities.
16. The method of any of claims 1-5, wherein the aluminum alloy has a composition according to AA 7055.
17. The method according to any one of claims 1 to 5, wherein the final thickness of the board product is less than 45mm.
18. The method of claim 17, wherein the final thickness of the sheet product is less than 40mm.
19. The method of claim 17, wherein the final thickness of the sheet product is less than 35mm.
20. The method according to any one of claims 1 to 5, wherein the final thickness of the board product is greater than 10mm.
21. The method of claim 20, wherein the final thickness of the board product is greater than 12.5mm.
22. The method of claim 20, wherein the final thickness of the board product is greater than 15mm.
23. The method of claim 20, wherein the final thickness of the board product is greater than 19mm.
24. The process of any one of claims 1 to 5, wherein in process step (c), the hot rolling mill inlet temperature is greater than 380 ℃.
25. The method of claim 24, wherein the hot rolling mill inlet temperature is greater than 390 ℃.
26. The method according to any one of claims 1 to 5, wherein the plate product is artificially aged to a T7 temper.
27. The method of claim 26, wherein the plate product is artificially aged to a T79 or T77 temper.
28. An aluminum alloy sheet product which is manufactured according to any one of claims 1 to 27 and which has improved fatigue failure resistance.
29. An aerospace structural member, made from an aluminum alloy sheet product obtained by the process of any one of claims 1-27.
30. Use of an aluminium alloy sheet product manufactured according to any one of claims 1 to 27 for manufacturing structural members of an aircraft.
Applications Claiming Priority (3)
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| EP18177389.6 | 2018-06-12 | ||
| EP18177389 | 2018-06-12 | ||
| PCT/EP2019/064719 WO2019238509A1 (en) | 2018-06-12 | 2019-06-05 | Method of manufacturing a 7xxx-series aluminium alloy plate product having improved fatigue failure resistance |
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| Publication Number | Publication Date |
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| CN112262223A CN112262223A (en) | 2021-01-22 |
| CN112262223B true CN112262223B (en) | 2023-02-14 |
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| CN201980039243.7A Active CN112262223B (en) | 2018-06-12 | 2019-06-05 | Method of manufacturing 7 xxx-series aluminum alloy sheet products having improved fatigue failure resistance |
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| US (1) | US20210246523A1 (en) |
| EP (1) | EP3807434B1 (en) |
| JP (1) | JP7282106B2 (en) |
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| CN (1) | CN112262223B (en) |
| BR (1) | BR112020023249A2 (en) |
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| ES (1) | ES2929839T3 (en) |
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| WO (1) | WO2019238509A1 (en) |
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| EP3842561B1 (en) * | 2019-12-23 | 2022-08-17 | Novelis Koblenz GmbH | Method of manufacturing an aluminium alloy rolled product |
| CN111118418B (en) * | 2019-12-27 | 2020-12-29 | 燕山大学 | Aging treatment method for improving toughness of Al-Zn-Mg-Cu aluminum alloy, high-toughness aluminum alloy and preparation method thereof |
| CN113528866B (en) * | 2021-06-16 | 2022-05-20 | 天津忠旺铝业有限公司 | Preparation method of high-strength corrosion-resistant 7xxx aluminum alloy plate for aviation |
| CN113430431B (en) * | 2021-06-16 | 2022-08-05 | 山东南山铝业股份有限公司 | High-damage-tolerance 7-series aluminum alloy thick plate for aviation and preparation method thereof |
| CN113667867A (en) * | 2021-07-30 | 2021-11-19 | 宁波吉胜铸业有限公司 | High-strength connecting piece |
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| US5221377A (en) | 1987-09-21 | 1993-06-22 | Aluminum Company Of America | Aluminum alloy product having improved combinations of properties |
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| EP0686705A1 (en) | 1994-06-09 | 1995-12-13 | Hoogovens Aluminium Walzprodukte GmbH | Aluminium alloy plate and method for its manufacture |
| JPH11140610A (en) | 1997-11-13 | 1999-05-25 | Furukawa Electric Co Ltd:The | Production of aluminum alloy structural material excellent in toughness and weldability |
| JP3926934B2 (en) * | 1998-10-15 | 2007-06-06 | 株式会社神戸製鋼所 | Aluminum alloy plate |
| NL1018817C2 (en) | 2001-08-24 | 2003-02-25 | Corus Technology B V | Method for processing a continuously cast metal slab or belt, and plate or belt thus produced. |
| CA2506393C (en) | 2002-11-15 | 2009-10-27 | Alcoa Inc. | Aluminum alloy product having improved combinations of properties |
| CN100547098C (en) * | 2003-04-10 | 2009-10-07 | 克里斯铝轧制品有限公司 | A kind of Al-zn-mg-cu alloy |
| BRPI0606957B1 (en) * | 2005-02-10 | 2016-09-13 | Alcan Rhenalu | Rolled or forged aluminum alloy worked product and process for its production |
| FR2907467B1 (en) * | 2006-07-07 | 2011-06-10 | Aleris Aluminum Koblenz Gmbh | PROCESS FOR MANUFACTURING ALUMINUM ALLOY PRODUCTS OF THE AA2000 SERIES AND PRODUCTS MANUFACTURED THEREBY |
| JP2007182628A (en) | 2006-12-25 | 2007-07-19 | Kobe Steel Ltd | Aluminum alloy sheet and method of producing the same |
| JP2009167464A (en) * | 2008-01-16 | 2009-07-30 | Furukawa-Sky Aluminum Corp | Method for producing aluminum alloy material having excellent toughness |
| US9469892B2 (en) | 2010-10-11 | 2016-10-18 | Engineered Performance Materials Company, Llc | Hot thermo-mechanical processing of heat-treatable aluminum alloys |
| JP5758676B2 (en) * | 2011-03-31 | 2015-08-05 | 株式会社神戸製鋼所 | Aluminum alloy plate for forming and method for producing the same |
| CN103540880B (en) * | 2013-09-30 | 2015-08-26 | 中国航空工业集团公司北京航空材料研究院 | A kind of Al-Zn-Mg-Cu aluminum alloy strengthens tough aging process |
| CN103469035B (en) * | 2013-10-08 | 2015-08-19 | 湖南大学 | A kind of high-strength, lightweight, anti-corrosion, the Al-Zn-Mg alloy that can weld and preparation method |
| WO2015132932A1 (en) * | 2014-03-06 | 2015-09-11 | 株式会社Uacj | Structural aluminum alloy and process for producing same |
| RU2569275C1 (en) * | 2014-11-10 | 2015-11-20 | Федеральное государственное унитарное предприятие "Всероссийский научно-исследовательский институт авиационных материалов" (ФГУП "ВИАМ") | Plate from high-strength aluminium alloy and method of its production |
| US20160348224A1 (en) * | 2015-06-01 | 2016-12-01 | Kaiser Aluminum Fabricated Products, Llc | High Strength 7xxx Series Aluminum Alloy Products and Methods of Making Such Products |
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| PT3807434T (en) | 2022-10-06 |
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| BR112020023249A2 (en) | 2021-02-23 |
| JP7282106B2 (en) | 2023-05-26 |
| US20210246523A1 (en) | 2021-08-12 |
| EP3807434A1 (en) | 2021-04-21 |
| CN112262223A (en) | 2021-01-22 |
| KR102547038B1 (en) | 2023-06-26 |
| CA3100242C (en) | 2023-08-08 |
| KR20210020992A (en) | 2021-02-24 |
| WO2019238509A1 (en) | 2019-12-19 |
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