JP2000328211A - Method of producing formed parts of 2024 type aluminum alloy - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for easily producing the, formed parts of an alloy whose allowable characteristics to damage is not deteriorated after deformation. SOLUTION: This method includes the following steps: (a) the casting of a plate having a compsn. composed of, by weight, 3.8 to 4.5% Cu, 1.2 to 1.5% Mg, 0.3 to 0.5% Mn, <0.25% Si, <0.20% Fe, <0.20% Zn, <0.10% Cr, <0.10% Zr and <0.10% Ti, (b) hot rolling at a starting temp. in the range from 430 to 470 deg.C, (c) the cutting of the plate, (d) solution treatment at 480 to 500 deg.C for 5 min to 1 hr, (e) quenching and (f) forming by one or plural methods among drawing, stamping forging, spinning, bending or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to aluminum associa
The present invention relates to a method for the production of highly deformable parts for machine production, in particular for aircraft production, using a plate of an aluminum alloy AlCuMg of the type 2024 according to the method of tion.

[0002]

BACKGROUND OF THE INVENTION Alloy 2024 is widely used in aircraft manufacturing and has the following composition registered by the Aluminum Association (% by weight): Si is less than 0.5, Fe is less than 0.5, Cu is 3.8-4.
9, Mn is 0.3 to 0.9, Mg is 1.2 to 1.8, Z
n is less than 0.25, Cr is less than 0.10, Ti is 0.1
Less than 5. In particular, pultrusion (the English term "stretch forming" is often used), stamping forging,
Some parts realized by spinning, bending or roll forming have good formability in addition to the properties required for normal aircraft production, such as strong mechanical strength, toughness, and resistance to crack propagation. You need a board to hold.

European Patent No. 0473122 discloses a composition (% by weight) in which Cu is 4-4.5 and Mg is 1.2-1.
5, Mn is 0.4 to 0.6, Fe is less than 0.12, Si
Describes a method for producing an alloy sheet, including an intermediate anneal at a temperature of less than 0.05 and greater than 488 ° C. These plates have been shown to have improved toughness and resistance to crack propagation over conventional 2024.

[0004] European Patent Application No. 07311185 discloses a low level of residual stress and improved toughness for strong plates, and improved elongation for thin plates.
It describes a plate of alloy 2024 that was later modified and registered with the Aluminum Association under the name 2024A. This application relates to the relationship: 0 <Mn-2Fe <0.2 (Mn and Fe contents are expressed in%) and the Mn content is 0.55.
% And that of Fe are limited to 0.25%.

[0005] Patent application WO 96/29440 discloses a process for hot rolling, annealing, cold rolling, solution treatment, quenching, and cold working which can be stretched, straightened or stamped as a process for improving formability. A method for manufacturing a 2024 type aluminum alloy product with minimal deformation at Pure base (very low iron and silicon content) and 0.5% manganese content
Having confirmed that the use of less than one improves the formability, the application proposes a suitable composition of the alloy, Cu is 4.0-4.4, Mg is 1.25-1.5. ,
It is recommended that Mn is 0.35 to 0.5, Si is less than 0.12, Fe is less than 0.08, and Ti is less than 0.06. Intermediate annealing between hot rolling and cold rolling has been shown to be advantageous for mechanical strength and toughness. This supplementary and unusual process of the method, however, has economic disadvantages. It also does not solve the problem posed by the market, that is to provide a plate with features such that its shaping is simplified.

[0006]

In order to reduce the cost of production, aircraft manufacturers have minimized the number of plate forming steps and, by means of the types of processing that are short, ie have as few discrete steps as possible, It aims to use boards that can be manufactured at low cost. With respect to the fuselage plate, the current practice of aircraft manufacturers is in the raw state (state "F" according to standard EN515), or in the annealed state (state "O"), or in the aged and quenched state (state "T3" or At “T4”), prepare a hot or cold rolled sheet according to the required thickness, put it in a solution, heat treat it, quench it, mold it, aged naturally or artificially, To obtain the required mechanical characteristics.

[0007] Generally, after solution treatment or quenching, the plate is in a state characterized by good formability, but this state is unstable (state "W"), and the forming takes place while the quench is fresh. In other words, it must be performed for a short period of time after quenching, for several tens minutes to several hours. If this is not possible for reasons of production control, the boards must be stored in a cold room at a sufficiently low temperature for a sufficiently short period of time to avoid natural ripening. Large volume,
For firmly formed parts, heat treatment in this solution requires a large size furnace, which means that
It makes the task difficult, even for the same task performed on a flat plate. The need for an optional cold room also adds to the cost and disadvantages of the state of the art. For parts that are significantly deformed, this operation may be repeated when the material does not exhibit sufficient formability in its metallurgical stage to allow it to reach the desired shape in a single operation. Must be done.

Starting from state F, the only possible forming is roll forming. The rolled plate is solution treated, quenched, and subjected to a second forming while quenching is fresh or after storage in a cold room. In all other cases, the boards are directly put into solution and quenched before shaping. When starting from the plate in state O,
After the solution processing and quenching, a second molding operation is performed. This variant is used when the desired molding is too large to be performed in a single operation starting from state W, but can be performed in two steps from state O. . In this state, the plate still has poor formability, but state O is easier to use than state W, which is unstable and requires additional heat treatment. However, the production of the plate in state O results in a final annealing of the rolled material and thus an additional production step, which is contrary to the simplification aimed at by the present invention.

[0009] Starting from a plate in state W which usually has the best formability, in some cases after solution treatment and quenching,
The use of a second molding process cannot be avoided.
This is a third variant of the method corresponding to the prior art.

This method of processing a plate of alloy 2024, which is profound and, in some cases, immediately after quenching, gradually reduces the number of assemblies as individual components become larger in size. Tend to perform well, which means that technical (assembly is the site of the onset of corrosion and fatigue cracks) and economic (assembly is a significant part of the cost of manufacturing the aircraft) It responds at the same time. It is also possible to reduce the weight of the fuselage by using large sized parts.

In all cases, in the final working, the tolerance properties for damage degrade under the influence of the cold working associated with this deformation.

It is an object of the present invention, therefore, to provide a method of forming a part to be formed which is significantly deformed by one or more methods, such as, for example, pultrusion, stamping forging, spinning or bending. Optimized chemical composition and the combination of special manufacturing methods that make it possible to avoid as much as possible
It is to simplify.

It is evident that any new method of manufacturing parts that are significantly deformed must reach parts with mechanical and use characteristics at least as good as existing products.

Another object of the present invention is to obtain a component whose tolerance to damage does not deteriorate after deformation.

[0015]

Means for solving the problems of the present invention are as follows. First, a method of manufacturing a significantly deformed part made of an AlCuMg alloy, including the following steps. a) The composition (% by weight) is 3.8 to 4.5 for Cu, 1.2 to 1.5 for Mg, 0.3 to 0.5 for Mn, and 0.2 for Si.
Less than 5, Fe less than 0.20, Zn less than 0.20, C
r is less than 0.10, Zr is less than 0.10, Ti is 0.1
Casting of a plate that is less than zero. b) optionally at a temperature comprised between 460 and 510 ° C. for 2 to 12 hours, preferably 470 to 5 hours.
Homogenization between 00 ° C. for a length of 3 to 6 hours. c) Hot rolling at a starting temperature comprised between 430 and 470 ° C, preferably between 440 and 460 ° C. d) In some cases, cold rolling of the strip. e) optionally annealing the strip at a temperature comprised between 350 and 450 ° C. f) Cutting the board. g) solution treatment between 480 and 500 ° C. for a length comprised between 5 minutes and 1 hour. h) Quenching. i) Forming by one or more methods such as pultrusion, stamping forging, spinning or bending. This shaping can also be entered after step f).

Second, the first forming is performed before the solution processing, and the part to be formed undergoes the following steps after the solution processing and quenching. . a) optionally, 10 ° C. of the part just after quenching
Rapid transfer to a cold room at a temperature below, preferably below 0 ° C. b) Novel shaping of the plate by one or more methods such as pultrusion, stamping, spinning or bending less than one hour after quenching or less than one hour after the part is removed from the cold room.

Third, a method of manufacturing a significantly deformed part made of an AlCuMg alloy according to the first aspect, including manufacturing a plate by the following steps. a) The composition (% by weight) is 3.8 to 4.5 for Cu, 1.2 to 1.5 for Mg, 0.3 to 0.5 for Mn, and 0.2 for Si.
Less than 5, Fe less than 0.20, Zn less than 0.20, C
r is less than 0.10, Zr is less than 0.10, Ti is 0.1
Casting of a plate that is less than zero. b) optionally at a temperature comprised between 460 and 510 ° C. for 2 to 12 hours, preferably 470 to 5 hours.
Homogenization between 00 ° C. for a length of 3 to 6 hours. c) Hot rolling at a starting temperature comprised between 430 and 470 ° C, preferably between 440 and 460 ° C. d) Cutting the plate. These plates exhibit an ultimate elongation A in the directions L and LT of more than 13.5%, preferably more than 15%, and are used for the production of parts which are significantly deformed by the following processes. e) Forming the plate by one or more methods such as pultrusion, stamping forging, spinning or bending. f) Solution treatment of the molded part at a temperature comprised between 480 and 500 ° C. and for a length comprised between 5 minutes and 1 hour. g) Quenching.

Fourthly, the method according to any one of the first to third features, characterized in that the plate is plated on one or both sides with another aluminum alloy plate.

Fifth, the exit temperature from hot rolling is 300
A method according to claim 3 or 4, characterized in that the temperature is higher than 0 ° C, preferably higher than 310 ° C.

Sixth, the method according to any one of the first to fifth aspects, wherein cold rolling is performed between hot rolling and cutting of the sheet.

Seventh, the Cu content is 3.9 and 4.3.
%, Preferably between 3.9 and 4.2%.

Eighth, if the Mg content is 1.2 or 1.4,
%, Preferably between 1.25 and 1.35%, characterized in that it is comprised between 1.25 and 1.35%.

Ninth, the content of Mn is 0.30 and 0.1.
The method according to any one of claims 1 to 8, characterized in that it is comprised between 45%.

Tenthly, the method according to any one of the first to ninth aspects, wherein the content of Si is less than 0.10%, preferably less than 0.08%.

Eleventh, the method according to any one of the first to tenth aspects, wherein the Fe content is less than 0.10%.

Twelfth, Zn is less than 0.20%, Cr is less than 0.07%, preferably less than 0.05%, Zr is less than 0.07%, preferably less than 0.05%, Ti0.
Method according to any of the first to eleventh, characterized in that it is less than 07%, preferably less than 0.05%.

Thirteenth, a method for producing a significantly deformed part made of an AlCuMg alloy according to the first aspect, comprising the following steps. a) The composition (% by weight) is 3.8 to 4.5 for Cu, 1.2 to 1.5 for Mg, 0.3 to 0.5 for Mn, and 0.2 for Si.
Less than 5, Fe less than 0.20, Zn less than 0.20, C
r is less than 0.10, Zr is less than 0.10, Ti is 0.1
Casting of a plate that is less than zero. b) optionally at a temperature comprised between 460 and 510 ° C. for 2 to 12 hours, preferably 470 to 5 hours.
Homogenization between 00 ° C. for a length of 3 to 6 hours. c) Hot rolling at a starting temperature comprised between 430 and 470 ° C, preferably between 440 and 460 ° C. d) In some cases, cold rolling. e) Cutting the plate. f) Solution treatment of the plate between 480 and 500 ° C. for a length comprised between 5 minutes and 1 hour. g) Quenching. h) Forming the plate by one or more methods such as pultrusion, stamping forging, spinning or bending.

Fourteenth, the Cu content is 3.9 and 4.
A method according to claim 13, characterized in that it is comprised between 3%, preferably between 3.9 and 4.2%.

Fifteenth, the content of Mg is 1.2 and 1.
A method according to claim 13 or 14, characterized in that it is comprised between 4%, preferably between 1.25 and 1.35%.

(16) The method according to any one of (13) to (15), wherein the Mn content is between 0.30 and 0.45%.

Seventeenth, the AlC according to any one of the thirteenth to sixteenth aspects, including the production of a plate by the following process:
A method of manufacturing a largely deformable part made of a uMg alloy. a) The composition (% by weight) is 4 to 4.5 for Cu and 1 for Mg.
25-1.45, Mn 0.30-0.45, Si less than 0.10, Fe less than 0.20, Zn less than 0.20, Cr less than 0.05, Zr less than 0.03 , Ti casting less than 0.05. b) optionally at a temperature comprised between 460 and 510 ° C. for 2 to 12 hours, preferably 470 to 5 hours.
Homogenization between 00 ° C. for a length of 3 to 6 hours. c) Hot rolling at a starting temperature comprised between 430 and 470 ° C, preferably between 440 and 460 ° C. d) In some cases, cold rolling. e) Cutting the plate. f) Solution treatment of these plates between 480 and 500 ° C. for a length comprised between 5 minutes and 1 hour. g) Quenching. These plates are pultruded, stamped forged,
Used in the manufacture of parts that are significantly deformed by one or more methods such as spinning or bending.

Eighteenth, in any one of the thirteenth to seventeenth aspects, the molding is performed within one hour after quenching.
The method described in one.

Nineteenthly, between the quenching and the forming, the plate immediately after quenching is stored in a low-temperature room at a temperature lower than 0 ° C. A method according to any one of the preceding claims.

Twentieth, the hot rolled sheet has a thickness of 5 mm, ε ₁ > 0.1 for L = 300 mm.
8, or exhibiting a forming limit curve characterized by ε ₁ > 0.22 for L = 500 mm,
The method according to the eighteenth or nineteenth.

Twenty-first, between quenching and forming, cold working by rolling or wrinkling elongation, followed by controlled tension with permanent deformation comprised between 0.5 and 5%. The method according to any one of the thirteenth to seventeenth aspects.

Twenty-second, solution treatment, quenching,
Characterized in that the plate cold-worked by rolling or wrinkling and possibly tensioned with a permanent deformation comprised between 0.5 and 5% exhibits at least one of the following properties: 21. The method according to the twenty-first aspect. a)-TL, L and elongation A measured at 45 ° direction
Average of more than 20%, preferably 22
% And three values R measured in the direction of TL, L and 45 °
Mean value of _p0.2 exceeds 305 mPa, and the value of LDH exceeds 72mm The thickness of -1.6Mm, or the thickness of 3.2mm values of LDH 7
LDH values of greater than 80 mm for thicknesses greater than 6 mm or comprised between 4 and 7 mm. b) the average of the three values R _p0.2 measured in the directions TL, L and 45 ° exceeds 305 MPa, and the three values A measured in the directions TL, L and 45 °
The average value of _g exceeds 18%. c) -TL, L and elongation A measured in the direction of 45 °
The average of the three values is greater than 22%, and the three values R measured in the direction of TL, L and 45 °
Mean value of _p0.2 exceeds 305 mPa, and, -TL, L and 45 ° 3 one value A which is measured in the direction of
The average value of _g % exceeds 18%. d) the average of the three values R _p0.2 measured in the directions TL, L and 45 ° is greater than 305 MPa, and three plane tensile forces measured in the directions TL, L and 45 ° The average value of A _tp is more than 18%, and the value of LDH is more than 72 mm for the thickness of -1.6 mm, or the value of LDH is more than 76 mm for the thickness of 3.2 mm, or between 4 and 7 mm. The value of LDH exceeds 80 mm for the thickness contained in.

Twenty-third, solution treatment, quenching,
A plate cold-worked by rolling or wrinkling and possibly tensioned with a permanent deformation comprised between 0.5 and 5% exhibits at least one of the following three properties: 21. The method according to item 21 or 22, wherein (A) Value LDH is 40 m for thickness less than 4 mm
m, or 74 for thicknesses greater than 4 mm.
mm. (B) The forming limit curve shows a coefficient ε ₁ > 0.18 at L = 500 mm for a thickness between 1.4 mm and 2 mm. (C) The forming limit curve shows a coefficient ε ₁ > 0.35 at L = 500 mm for a thickness between 5.5 mm and 8 mm.

Twenty-fourth, solution treatment, quenching,
A plate cold-worked by rolling or wrinkling and possibly tensioned with a permanent deformation comprised between 0.5 and 5% is characterized by exhibiting at least one of the following properties: , 21st to 23rd. (A) K _c (LT)> 120 MPa√m (b) K _c0 (LT)> 90 MPa√m (c) K _c (TL)> 125 MPa√m (d) K _c0 (T- L)> 80 MPa @ m

Twenty-fifth, AlCu includes the following steps:
Manufacturing method for parts of Mg alloy that are significantly deformed. a) The composition (% by weight) is 3.8 to 4.5 for Cu, 1.2 to 1.5 for Mg, 0.3 to 0.5 for Mn, and 0.2 for Si.
Less than 5, Fe less than 0.20, Zn less than 0.20, C
r is less than 0.10, Zr is less than 0.10, Ti is 0.1
Casting of a plate that is less than zero. b) Hot rolling at a starting temperature comprised between 430 and 470 ° C, preferably between 440 and 460 ° C. c) Cutting the plate. d) solution treatment between 480 and 500 ° C. for a length comprised between 5 minutes and 1 hour. e) Quenching. f) Forming by one or more methods such as pultrusion, stamping forging, spinning or bending.

Twenty-sixth, a method of manufacturing a significantly deformed part made of an AlCuMg alloy, including manufacturing a plate by the following process. a) The composition (% by weight) is 3.8 to 4.5 for Cu, 1.2 to 1.5 for Mg, 0.3 to 0.5 for Mn, and 0.2 for Si.
Less than 5, Fe less than 0.20, Zn less than 0.20, C
r is less than 0.10, Zr is less than 0.10, Ti is 0.1
Casting of a plate that is less than zero. b) Hot rolling at a starting temperature comprised between 430 and 470 ° C, preferably between 440 and 460 ° C. c) Cutting the plate. d) Forming the plate by one or more methods such as pultrusion, stamping forging, spinning or bending. e) solution treatment of the molded part at a temperature comprised between 480 and 500 ° C. and for a length comprised between 5 minutes and 1 hour. f) Quenching.

[0041]

DETAILED DESCRIPTION OF THE INVENTION The subject of the present invention is a method of manufacturing a 2024 type AlCuMg alloy which is significantly deformed, comprising the following steps. a) The composition is as follows: Cu is 3.8 to 4.5, Mg is 1.2 to
1.5, Mn is 0.3-0.5, Si is less than 0.10,
Fe is less than 0.20, Zn is less than 0.20, and Cr is less than 0.20.
Casting plates with less than 05, Zr less than 0.03 and Ti less than 0.05. b) optionally at a temperature comprised between 460 and 510 ° C., preferably between 470 and 500 ° C.
Homogenization of this plate for a length of up to 6 hours. c) between 430 and 470 ° C., preferably 440 to 4
Hot rolling to obtain a strip, with a starting temperature comprised between 60 ° C. d) In some cases, cold rolling of the strip. e) In some cases, annealing of the band. f) Cutting the band into plates. g) solution treatment between 480 and 500 ° C. for a length comprised between 5 minutes and 1 hour. h) Quenching. i) Forming by drawing, stamping forging, spinning or bending. This shaping can also be entered after step f).

Preferably, the alloy has a copper content between 3.9 and 4.3% (more preferably between 3.9 and 4.2%).
% And a magnesium content of between 1.2 and 1.4% (more preferably between 1.25 and 1.3).
5%), manganese content between 0.3 and 0.45%, iron content less than 0.10%, silicon content of 0.1
It is less than 0% (preferably less than 0.08%) and the titanium, chromium and zirconium content is less than 0.07% (preferably less than 0.05%). The method according to the invention comprises:
As is usually the case for fuselage fuselage plates, it may be possible to use plates that are optionally plated, for example plates coated with alloys that are more resistant to corrosion.

A first feature of the present invention consists in using an improved alloy over the conventional 2024. The first improvement is that the contents of Si and Fe are 0.25 and 0.2%, respectively.
To be less than 20%, preferably less than 0.10%. Also, the content of Mn is also
It is lower than 0.5%, preferably lower than 0.45%. Finally, the Cu content is also slightly reduced and kept below 4.5%, preferably 4.3%, and even below 4.2%. The Mg content is also slightly reduced and kept below 1.5%, preferably between 1.2 and 1.4%, and even between 1.25 and 1.35%.

The inventor has observed that this composition proposed by the prior art by itself cannot reach the required formability.

The alloys are cast into plates, which are
In some cases, a temperature comprised between 460 and 510 ° C. (preferably between 470 and 500 ° C.) and between 2 and 1
Homogenize for 2 hours (preferably 3 to 6 hours). In some cases, peel the plate. Hot rolling is performed at a starting temperature comprised between 430 and 470 ° C (preferably between 440 and 460 ° C). The outlet temperature of the strip is preferably higher than the normal temperature, especially if a part of the shaping is performed before the solution treatment.
Temperatures above 00 °, preferably above 310 °.

When the hot rolling is completed, the strip is wound up.
It shows at this stage more than 13.5%, often more than 15% elongation in the L and TL directions. It can optionally be cold rolled if the required thickness cannot be achieved by hot rolling.
The strip is then cut into plates.

A first variant of the invention consists in carrying out the forming by pultrusion, stamping forging, spinning or bending directly into this state F without annealing or any other preceding treatment. The partially formed plate is then solution treated at a temperature comprised between 480 and 500 ° C. for a time comprised between 5 minutes and 1 hour,
Generally, it is quenched with cold water.

The molding is performed in two or more steps. The part that has just been quenched (less than 1 hour) can immediately undergo a new molding, or it is transferred to a cold room at a temperature below 10 ° C., preferably below 0 ° C. It is molded where it is delivered. Plates plated on one or both sides can be used, but this is most often the case for gas body plates,
1000 series alloys, for example alloys 1050, 11
00, 1200, 1135, 1145, 1170, 11
75, 1180, 1185, 1188, 1199, 12
30, 1235, 1250, 1285, 1350 or 1435.

A second variant consists in carrying out the shaping on a plate which has been subjected to solution treatment and quenching. Molding is in state T
3 or T4 (hardened and aged with or without subsequent cold working) or, for more deformed parts, in state W, ie less than 1 hour after quenching,
Alternatively, it can be performed on a plate stored in a cold room immediately after quenching.

When using a plate in state T3 or T4,
These plates exhibit an intermediate state between mechanical strength and formability corresponding to at least one of the following overall properties: a)-TL, L and elongation A measured at 45 ° direction
Average of more than 20%, preferably 22
% And three values R measured in the direction of TL, L and 45 °
Mean value of _p0.2 exceeds 305 mPa, and the thickness of -1.6Mm, while the value of LDH exceeds 72 mm, or the value of the LDH for the thickness of 3.2mm is more than 76 mm, or from 4 to 7mm The value of LDH exceeds 80 mm for the thickness contained in. b) the average of the three values R _p0.2 measured in the directions TL, L and 45 ° exceeds 305 MPa, and the three values A measured in the directions TL, L and 45 °
The average value of _g exceeds 18%. c) -TL, L and elongation A measured in the direction of 45 °
The average of the three values is greater than 22%, and the three values R measured in the direction of TL, L and 45 °
Mean value of _p0.2 exceeds 305 mPa, and, -TL, L and 45 ° 3 one value A which is measured in the direction of
The average value of _g % exceeds 18%. d) the average of the three values R _p0.2 measured in the directions TL, L and 45 ° is greater than 305 MPa, and three plane tensile forces measured in the directions TL, L and 45 ° The average value of A _tp is more than 18%, and the value of LDH is more than 72 mm for the thickness of -1.6 mm, or the value of LDH is more than 76 mm for the thickness of 3.2 mm, or between 4 and 7 mm. The value of LDH exceeds 80 mm for the thickness contained in.

These plates in the T3 or T4 state exhibit formability characterized by at least one of the following three properties. (A) For a thickness where the value LDH is less than 4 mm, 40
mm, or for thicknesses greater than 4 mm,
Exceeds 74 mm. (B) The forming limit curve shows a coefficient ε ₁ > 0.18 at L = 500 mm for a thickness between 1.4 mm and 2 mm. (C) The forming limit curve shows a coefficient ε ₁ > 0.35 at L = 500 mm for a thickness between 5.5 mm and 8 mm.

It also shows an improved, damage-tolerant property, characterized by at least one of the following properties: (a) K _c (LT)> 120 MPa√m (b) K _c0 ( _{L-T)> 90MPa√m (c} ) K c (T-L)> 125MPa√m (d) K c0 (T-L)> 80MPa√m

In state T3 or T4, as well as in state W, the parts realized on the plate are, after the last molding operation,
If the difference is less than 6%, there is very little degradation in tolerance for damage.

In the above and in the following examples, the various parameters used to characterize generic terms indicating formability and the relative ease of deformable metals are defined as follows: Have been.

For a plate having a thickness of 3 mm or more, a proportional test piece having an initial length between indices Lo determined according to the area So of the initial cross section is performed according to the relational expression Lo = 5.65√So. And for plates having a thickness of less than 3 mm, the following parameters are obtained from the uniaxial tensile test according to the standard EN10002-1, performed on non-proportional type 1 specimens according to EN10002-1, Table 4. -R _p0.2: Permanent elongation of elastic limit stipulated in 0.2% (MPa) -R _m: ultimate tensile strength (MPa) -A: elongation after rupture (%). It may be represented by the symbol “A%”. -A _g: elongation not proportionality at full load. Also called split elongation (%).

For each plate, generally three different samplings are performed. In the rolling direction (direction L), in the width direction (TL), and in the directions L and TL
Between 45 °.

All values from the uniaxial tensile test are averages from two specimens sampled at the same location.

The division and extension are performed in the area of the plastic deformation, that is,
The difference in elongation between the beginning and the end of the region of permanent deformation of the deformation curve before section shrinkage.

The planar tensile extension A _tp corresponds to the ultimate elongation in a tensile test called the planar tensile test and, contrary to the uniaxial tensile test, is in two dimensions, and therefore in a plane rather than three dimensions, ie ε ₂ = Prepare to have deformation at ε ₂ = 0 instead of −ε _1/2 .

Parameter LDH (limit dome height)
Is widely used for evaluating the stamping forgeability of a plate having a thickness of 0.5 to 2 mm. It has been the subject of numerous publications. Above all, R. Thompson, "The LDH test to evaluate sheet metal
formabiblity "-Final report of the LDH committee of
the North American Deep Drawing Research Group ",
SAE conference, Detroit, 1993, SAE paper no.93081
5.RAAyres, WGBrazier and VFSajewski, "Evaluati
ng the GMR limiting dome height test as a new meas
ure of press formability near plane strain ", J. Appl. Metalworking, 1979, vol.1, pp.41-49, JMStory," Comparison of Correlations between Pre
ss performance and Dome tests results using two do
me test procedures ", J. Appl. Metalworking, 1984, v
ol.3, pp.292-300.

The LDH test is a stamping forging test of a metal disk whose periphery is blocked by a rod. The wrinkle-pressing pressure that guarantees this blocking is 240 MPa. This metal disc with a size of 500 × 500 mm is subjected to two equiaxial extensions. Lubrication between the punch and the plate is ensured by the plastic film and the grease. L
The DH value is the critical depth of punch movement at break, ie, stamping forging. Establish an average of three tests.

The same method can be used to increase the thickness (3 to 9 m).
m) used to characterize the formability of the plate, but then a larger size (punch diameter = 250 mm)
Tools must be used.

The elastic return R _e is defined by a bending test under tension which makes it possible to compare the elastic return of different component changes (for plates of equal thickness) for a given deformation.

A flat specimen having a length L = 250 mm, a width λ = 12 mm and a thickness 0.1 mm <e <5 mm is inserted between two automatically blocking claws,
It is held together with the test device under tension by a hydraulic jack. The pre-defined pulling force is kept constant during bending by adjusting the hydraulic pressure with the servo valve of the pulling jack. The hysteresis loop of regulation has a tensile stress as measured by a piezoelectric sensor (Kistler washer). The tensile stress is
It depends on the alloy and the thickness of the test piece.

A movement sensor connected to the data acquisition computer allows for continuous control of the parameters of the test,
Calculate the bending angle of the test piece. The punch, integral with the upper frame of the tensioning machine, provides support for the specimen. The bending angle used in the test is radius r = 7
For a 0 mm punch, it was 140 °. Each bent sample is inspected after analysis by a probe shape measuring instrument. This measuring device makes it possible to evaluate the final angle and the radius of the obtained curve.

The tension applied to the specimen, which corresponds to the desired dimensional deformation, is defined by a theoretical tension curve by graphically showing the stress corresponding to the desired deformation rate. The initial deformation defining the bending stress was kept constant at 0.2% during the test.

The elastic return is given by the following equation.

(Equation 1) Here, α _f = angle measured by the shape measuring instrument (°) α _o = angle measured by PC when bending (°) _Re = elastic return (0 when no return, complete return 1).

The calculation based on the measurement of the radius of the curve gives a value with less variation, but is performed as follows.

(Equation 2) Where R _o = radius of the punch R _f = radius measured by the shape measuring instrument R _e = elastic return (equivalent to 0 for no return and 1 for complete return).

[0069] In practice, in order to make easy the progressive and reliability of molding operation, as low as possible, ideally demanded equal elastic return R _e to zero.

The molding limit curve is based on the standard ISO 12004
(1987). 500 × L (L is 3
A rectangular format with dimensions of 00 mm or 500 mm) is pre-printed with a grid (2 × 2 mm ² mesh) and then stamped and forged by the LDH test. L
= 500mm is the test after stamping forging, ε ₁ ≒ ε
₂ (deformation in two axes), and the test at L = 300 mm leads to ε ₂ ≒ 0 (deformation in a plane) after stamping forging.

After the break, the automatic system CamSy
s is analyzed near the crack zone.
Software Asame-CamSys is JHVogel
And D. Lee, "The automated measurement of strains
from three dimensional deformed surfaces ", JO
M., vol. 42, 1990, pp. 8-13, making it possible to establish a map of the deformation of the zone to be measured. The critical deformation before local cross-section shrinkage is thus evaluated and shown in the shaping diagram with the coordinates ε ₁ and ε ₂ .

The tolerance to damage is based on the standard ASTM E56.
1 (test of curve R). The test was performed with a crack length 2a ₀ = 133 mm and a width W = 400 mm
In a specimen with a central crack. The critical factor of the stress intensity K _c at the plane stress and the factor of the apparent stress intensity K _c0 (sometimes indicated by the abbreviation K _app ) are measured simultaneously.

[0073]

Example 1 Various alloys having the compositions shown in Table 1 were smelted. The rolled plate was cast, peeled and then homogenized at a temperature comprised between 460 ° C and 510 ° C for 2 to 12 hours. After plating with alloy 1050, the plate was hot rolled to a final thickness of 4 mm or more. For smaller thicknesses, the strip was cold rolled. The board was characterized by the final thickness. The results are summarized in Table 2.

Examples 1a, 1b, 1k, 1L, 1m, 1n,
1p and 1q correspond to the invention. Examples 1c, 1d,
1e, 1f, 1g, 1h, 1i and 1j correspond to the prior art.

[0075]

[Table 1]

[0076]

[Table 2]

It has been found that the proper selection of the chemical composition proposed by WO 96/29440 is not sufficient by itself to improve the formability in a manner consistent with the objects of the present invention. Conversely, the inventor has determined that by selecting a high exit temperature from the hot rolling mill, the ultimate elongation A
Was observed to result in an improvement in formability, represented by Chemical composition (especially Cu less than 4.3, preferably less than 4.2, Si less than 0.10, Fe less than 0.
The effect of <10) is only ancillary.

It can be seen that the process according to the invention guarantees a better suitability for the molding of state F, expressed as A%, LDH or FLD (molding limit curve), than the process according to the prior art. More specifically, the cold-rolled strip according to the invention has an LDH value of more than 42 mm, preferably more than 44 mm, while the hot-rolled strip has a value of 7 mm.
It has an LDH value of more than 3 mm, preferably more than 75 mm. It can also be seen that for a given thickness, the preferred composition gives better formability than conventional compositions.

The mechanical characteristics of the intermediate product (R _m , R _p0.2, etc.) are such that the finished product from the overall process is at least as sophisticated as the product from the prior art process in this context. It has no significance as long as it has features. Proposed standard prEN4211 in July 1995
6m in state T42, as defined by
For a thickness of m and the same product type, the two products have equal mechanical properties.

For the process according to the invention, high exit temperatures from the hot rolling mill (1 compared to Examples 1k and 1n)
Also note is the cumulative effect of e and 1j) and the chemical composition (1p and 1q compared to Examples 1k and 1n).

The value of LDH and the level of curve FLD are:
For cold worked sheets, it is lower than for sheets that have only been hot rolled. This effect is known. In contrast, surprisingly, in some methods (hot rolling or hot rolling followed by cold rolling) and comparable thicknesses, one of the appropriate parameters for measuring formability is LDH. The value is in the region where the chemical composition is suitable, that is, C
u 3.9-4.3, preferably 3.9-4.2, Mg
1.2 to 1.4, preferably 1.25 to 1.35, Mn
The inventor has confirmed that when it is located at 0.30 to 0.45, Si is less than 0.10, preferably less than 0.08, and Fe is less than 0.10, it is significantly increased. Also, the inventor:
It has been found that formability is further improved when some additions and impurity elements are tightly controlled as follows. Zn is less than 0.20%, Cr is less than 0.07%,
Preferably less than 0.05%, less than 0.07% Zr, preferably less than 0.05%, 0.07% Ti, preferably less than 0.05%.

[0082]

Example 2 Various alloys having the compositions shown in Table 3 were smelted. The rolling plate was cast, peeled, and then homogenized at a temperature comprised between 470 ° C and 510 ° C for 2 to 12 hours. After plating with alloy 1050, the plate was hot-rolled (method abbreviated as "LaC") to a final thickness of 4 mm or more. For smaller thicknesses, the strip was cold rolled. After cutting the strip into plates, it is subjected to a solution treatment typical of this type of alloy (9
(See Jul. 5, prEN4211), quenched and characterized 30 minutes after quenching. The results are summarized in Table 4. Solution processing and quenching are performed on ready-to-use processed specimens so that specimens can be compared rigorously, and for each characterization of mechanical properties, deformation is To 3
Started after 0 minutes. Examples 2a, 2b, 2e, 2j, 2
k and 2n correspond to the present invention. Example 2h, 2L, 2m,
2p corresponds to the prior art.

The method according to the invention can be used with comparable thicknesses
Is found to provide better formability in state W.
It has the following properties: total elongation A%, split
Extension A _g, Plane tensile elongation A_tp, LDH, FLD
I will. Regarding the forming limit curve, in the case of the present invention, 5 mm
For a plate of thickness (example 2n)
Unlike a plate of almost the same thickness (eg 2p), L = 500
The coefficient ε for mm₁> 0.22 and L = 500
ε for mm_Two> 0.18
You.

The advantage of the method according to the invention over the prior art is therefore that in state W deeper shaping can be carried out and furthermore the elimination of intermediate solution processing for very deep shaping.

As described above, in the prior art, two steps were required to realize a component, but it was possible to manufacture it in only one step.

[0086]

[Table 3]

[0087]

[Table 4]

[0088]

Example 3 Various alloys having the compositions shown in Table 5 were smelted. The rolling plate was cast, peeled and then homogenized at a temperature comprised between 460 ° C and 510 ° C for 3 to 6 hours. After plating with alloy 1050, the plate was hot rolled to a final thickness of 4 mm or more. For smaller thicknesses, the strip was cold rolled. Plates cut from these strips were subjected to a solution treatment typical of this type of alloy shown in Table 6 (pr.
EN4211), quenched and aged (at least 48 hours at ambient temperature). Next, cold-working by wrinkling was performed, followed by tension controlled by permanent deformation, aimed at 1.5%. The results are summarized in Table 6.

Examples 3s, 3t, 3u, 3v, 3w correspond to the prior art. Examples 3e, 3f, 3g, 3h, 3i, 3
j, 3k, 3L, 3m, 3n, 3p, 3q, 3r, 3x
Corresponds to the present invention. Examples 3a, 3c, 3d correspond to Examples 2h, 2L and 2m of Example 2. They are shown here as a comparison to represent the prior art state W 2024.

The plate used in the method according to the invention (optimized composition in state T3) is replaced by the plate used in the method according to the prior art, namely state T3 (Example 3).
s, 3t, 3u, 3v, 3w) or state W (Example 3a,
3b, 3c, 3d), it is confirmed that for a certain thickness, the method according to the invention leads to an ultimate elongation and, in particular, better formability, as can be seen from the values LDH and FLD. You. The elastic return is lower than in the prior art.

More specifically, if the chemical composition is in the preferred range, the method results in improved formability, as characterized by the parameters listed above. It is possible to achieve much more demanding molding than in state of the art T3, or alternatively, the method according to the invention provides at least as good a formability property as the product in state W from the method according to the prior art. It is even possible to omit the solution treatment, since it leads the product to the state T3 having.

The two boards were also drawn so that a total elongation of 3% or 5% was obtained and before and after drawing, the damage tolerance properties, ie TL and L-
The toughness K _C0 and K _C in the T direction were measured. TL
In the direction, the mechanical features were also measured. The results are summarized in Table 7.

It has been found that the method according to the invention, unlike the method according to the prior art, does not result in a significant reduction in the damage tolerance after shaping by drawing. It has even been found that the method according to the invention improves the tolerance for damage in the withdrawn state, ie in the final state of the part.

[0094]

[Table 5]

[0095]

[Table 6]

[0096]

[Table 7]

[0097]

According to the present invention, a method of manufacturing a part which is significantly deformed by a method such as pultrusion of the formed part is optimally capable of avoiding the solution treatment of the formed plate as much as possible. The simplification can be achieved by combining a simplified chemical composition and a special manufacturing method. Further, according to the present invention, it is possible to obtain a component whose tolerance to damage does not deteriorate after deformation.

──────────────────────────────────────────────────の Continuation of the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C22F 1/00 631 C22F 1/00 631A 681 681 683 683 683 685 685Z 690 690 691 691B 691C 694 694A 694B (72) Inventor Gui-Michel Reino United States of America, Dave Vevey, Ravenswood, 26164, Hillcrest Drive, 800 (72) Inventor Ronan Diff France, 38590 Saint-Etienne-de-Saint-Jouire (72 ) Inventor Martin-Peter Schmidt France, 38140 La Miuret, Schmand-du-Clapier, 245

Claims (26)

[Claims] 1. A method of manufacturing a significantly deformed part made of an AlCuMg alloy, comprising the following steps. a) The composition (% by weight) is 3.8 to 4.5 for Cu, 1.2 to 1.5 for Mg, 0.3 to 0.5 for Mn, and 0.2 for Si.
Less than 5, Fe less than 0.20, Zn less than 0.20, C
r is less than 0.10, Zr is less than 0.10, Ti is 0.1
Casting of a plate that is less than zero. b) optionally at a temperature comprised between 460 and 510 ° C. for 2 to 12 hours, preferably 470 to 5 hours.
Homogenization between 00 ° C. for a length of 3 to 6 hours. c) Hot rolling at a starting temperature comprised between 430 and 470 ° C, preferably between 440 and 460 ° C. d) In some cases, cold rolling of the strip. e) optionally annealing the strip at a temperature comprised between 350 and 450 ° C. f) Cutting the board. g) solution treatment between 480 and 500 ° C. for a length comprised between 5 minutes and 1 hour. h) Quenching. i) Forming by one or more methods such as pultrusion, stamping forging, spinning or bending. This shaping can also be entered after step f). 2. The method according to claim 1, wherein the first shaping is performed before the solution processing, and the part to be formed undergoes the following steps after the solution processing and quenching. a) optionally, 10 ° C. of the part just after quenching
Rapid transfer to a cold room at a temperature below, preferably below 0 ° C. b) Novel shaping of the plate by one or more methods such as pultrusion, stamping forging, spinning or bending, in less than one hour after quenching or less than one hour after the part is removed from the cold room. 3. The method of claim 1, wherein the method comprises the steps of: manufacturing a plate made of an AlCuMg alloy; a) The composition (% by weight) is 3.8 to 4.5 for Cu, 1.2 to 1.5 for Mg, 0.3 to 0.5 for Mn, and 0.2 for Si.
Less than 5, Fe less than 0.20, Zn less than 0.20, C
r is less than 0.10, Zr is less than 0.10, Ti is 0.1
Casting of a plate that is less than zero. b) optionally at a temperature comprised between 460 and 510 ° C. for 2 to 12 hours, preferably 470 to 5 hours.
Homogenization between 00 ° C. for a length of 3 to 6 hours. c) Hot rolling at a starting temperature comprised between 430 and 470 ° C, preferably between 440 and 460 ° C. d) Cutting the plate. These plates exhibit an ultimate elongation A in the directions L and LT of more than 13.5%, preferably more than 15%, and are used for the production of parts which are significantly deformed by the following processes. e) Forming the plate by one or more methods such as pultrusion, stamping forging, spinning or bending. f) Solution treatment of the molded part at a temperature comprised between 480 and 500 ° C. and for a length comprised between 5 minutes and 1 hour. g) Quenching. 4. The method as claimed in claim 1, wherein the plate is plated on one or both sides with another aluminum alloy plate. 5. The method according to claim 1, wherein the outlet temperature from the hot rolling is higher than 300 ° C., preferably higher than 310 ° C.
The method according to claim 3. 6. The method according to claim 1, wherein cold rolling is performed between hot rolling and cutting of the sheet.
The method described in one. 7. The method according to claim 1, wherein the Cu content is comprised between 3.9 and 4.3%, preferably between 3.9 and 4.2%. A method according to any one of the preceding claims. 8. The method according to claim 1, wherein the Mg content is comprised between 1.2 and 1.4%, preferably between 1.25 and 1.35%. A method according to any one of the preceding claims. 9. The Mn content is 0.30 and 0.45%.
The method according to any one of claims 1 to 8, characterized in that it is comprised between: 10. The method as claimed in claim 1, wherein the content of Si is less than 0.10%, preferably less than 0.08%. 11. The method as claimed in claim 1, wherein the content of Fe is less than 0.10%. 12. Zn is less than 0.20% and Cr is less than 0.00%.
Less than 7%, preferably less than 0.05%, Zr is 0.07
%, Preferably less than 0.05%, Ti 0.07%,
The method according to any one of claims 1 to 11, characterized in that it is preferably less than 0.05%. 13. The method according to claim 1, further comprising the steps of: a) The composition (% by weight) is 3.8 to 4.5 for Cu, 1.2 to 1.5 for Mg, 0.3 to 0.5 for Mn, and 0.2 for Si.
Less than 5, Fe less than 0.20, Zn less than 0.20, C
r is less than 0.10, Zr is less than 0.10, Ti is 0.1
Casting of a plate that is less than zero. b) optionally at a temperature comprised between 460 and 510 ° C. for 2 to 12 hours, preferably 470 to 5 hours.
Homogenization between 00 ° C. for a length of 3 to 6 hours. c) Hot rolling at a starting temperature comprised between 430 and 470 ° C, preferably between 440 and 460 ° C. d) In some cases, cold rolling. e) Cutting the plate. f) Solution treatment of the plate between 480 and 500 ° C. for a length comprised between 5 minutes and 1 hour. g) Quenching. h) Forming the plate by one or more methods such as pultrusion, stamping forging, spinning or bending. 14. The method according to claim 13, wherein the content of Cu is comprised between 3.9 and 4.3%, preferably between 3.9 and 4.2%. . 15. The method according to claim 13, wherein the Mg content is comprised between 1.2 and 1.4%, preferably between 1.25 and 1.35%. the method of. 16. The Mn content is 0.30 or 0.45.
%.
A method according to any one of the preceding claims. 17. AlCuM according to any one of claims 13 to 16, comprising the production of a plate by the following process:
A method of manufacturing a g-alloy that is significantly deformed. a) The composition (% by weight) is 4 to 4.5 for Cu and 1 for Mg.
25-1.45, Mn 0.30-0.45, Si less than 0.10, Fe less than 0.20, Zn less than 0.20, Cr less than 0.05, Zr less than 0.03 , Ti casting less than 0.05. b) optionally at a temperature comprised between 460 and 510 ° C. for 2 to 12 hours, preferably 470 to 5 hours.
Homogenization between 00 ° C. for a length of 3 to 6 hours. c) Hot rolling at a starting temperature comprised between 430 and 470 ° C, preferably between 440 and 460 ° C. d) In some cases, cold rolling. e) Cutting the plate. f) Solution treatment of these plates between 480 and 500 ° C. for a length comprised between 5 minutes and 1 hour. g) Quenching. These plates are used to make parts that are significantly deformed by one or more methods such as pultrusion, stamping forging, spinning or bending. 18. The method according to claim 13, wherein the shaping takes place in less than one hour after quenching. 19. The method according to claim 13, wherein, between the quenching and the forming, the as-quenched plate is stored in a cold room at a temperature below 0 ° C. the method of. 20. The hot rolled sheet shows a forming limit curve characterized by ε ₁ > 0.18 for L = 300 mm for a thickness of 5 mm or ε ₁ > 0.22 for L = 500 mm. 2. The method of claim 1, wherein
20. The method according to 8 or 19. 21. A method according to claim 1, characterized in that between quenching and forming, cold working by rolling or wrinkling and then controlled tensioning with a permanent deformation comprised between 0.5 and 5%. Item 18. The method according to any one of Items 13 to 17. 22. Solution treated, quenched, cold worked by rolling or wrinkling, optionally
22. The method according to claim 21, wherein the tensioned plate with a permanent deformation comprised between 0.5 and 5% exhibits at least one of the following properties: a)-TL, L and elongation A measured at 45 ° direction
Average of more than 20%, preferably 22
% _And the average of the three values R _p0.2 measured in the −TL, L and 45 ° directions exceeds 305 MPa and the LDH value is 7 for a thickness of −1.6 mm.
LD over 2mm or 3.2mm thickness
LDH values greater than 80 mm for thicknesses where the value of H is greater than 76 mm or comprised between 4 and 7 mm. b) the average of the three values R _p0.2 measured in the −TL, L and 45 ° directions exceeds 305 MPa, and −T
The average of the three values _Ag measured in the L, L and 45 ° directions exceeds 18%. c) -TL, L and elongation A measured in the direction of 45 °
The average of the three values is greater than 22%, and -TL,
The average of the three values R _p0.2 measured in the L and 45 ° directions exceeds 305 MPa, and the average of the −TL, L and three values A _g % measured in the 45 ° direction is 1
Over 8%. d) the average of the three values R _p0.2 measured in the -TL, L and 45 ° directions exceeds 305 MPa and -T
The average of the three plane pulling forces A _tp measured in the L, L and 45 ° directions is greater than 18% and -1.6
mm thickness, the LDH value exceeds 72 mm,
Or LDH value of 76 mm for 3.2 mm thickness
Or for thicknesses comprised between 4 and 7 mm, the LDH value exceeds 80 mm. 23. A solution treated, quenched, cold worked by rolling or wrinkling, optionally
23. The method according to claim 21 or 22, characterized in that the tensioned plate with a permanent deformation comprised between 0.5 and 5% exhibits at least one of the following three properties. (A) Value LDH is 40 m for thickness less than 4 mm
m, or 74 for thicknesses greater than 4 mm.
mm. (B) The forming limit curve shows a coefficient ε ₁ > 0.18 at L = 500 mm for a thickness between 1.4 mm and 2 mm. (C) The forming limit curve shows a coefficient ε ₁ > 0.35 at L = 500 mm for a thickness between 5.5 mm and 8 mm. 24. Solution treated, quenched, cold worked by rolling or wrinkling, optionally
24. The method according to any one of claims 21 to 23, wherein the tensioned plate with a permanent deformation comprised between 0.5 and 5% exhibits at least one of the following properties: Method. (A) K _c (LT)> 120 MPa√m (b) K _c0 (LT)> 90 MPa√m (c) K _c (TL)> 125 MPa√m (d) K _c0 (T- L)> 80 MPa @ m 25. A method of manufacturing a significantly deformed part made of an AlCuMg alloy, comprising the following steps. a) The composition (% by weight) is 3.8 to 4.5 for Cu, 1.2 to 1.5 for Mg, 0.3 to 0.5 for Mn, and 0.2 for Si.
Less than 5, Fe less than 0.20, Zn less than 0.20, C
r is less than 0.10, Zr is less than 0.10, Ti is 0.1
Casting of a plate that is less than zero. b) Hot rolling at a starting temperature comprised between 430 and 470 ° C, preferably between 440 and 460 ° C. c) Cutting the plate. d) solution treatment between 480 and 500 ° C. for a length comprised between 5 minutes and 1 hour. e) Quenching. f) Forming by one or more methods such as pultrusion, stamping forging, spinning or bending. 26. A method comprising the production of a plate by the following process:
A method of manufacturing a significantly deformed part made of lCuMg alloy. a) The composition (% by weight) is 3.8 to 4.5 for Cu, 1.2 to 1.5 for Mg, 0.3 to 0.5 for Mn, and 0.2 for Si.
Less than 5, Fe less than 0.20, Zn less than 0.20, C
r is less than 0.10, Zr is less than 0.10, Ti is 0.1
Casting of a plate that is less than zero. b) Hot rolling at a starting temperature comprised between 430 and 470 ° C, preferably between 440 and 460 ° C. c) Cutting the plate. d) Forming the plate by one or more methods such as pultrusion, stamping forging, spinning or bending. e) solution treatment of the molded part at a temperature comprised between 480 and 500 ° C. and for a length comprised between 5 minutes and 1 hour. f) Quenching.