Aluminium alloy and associated manufacturing process

Abstract

Aluminium alloy comprising, in wt. %: Si: 6.5 to 8; Cu: 0.15 to 0.35; Mg: 0.2 to 0.45; Fe: less than 0.4; Mn: less than 0.2; Cr: less than 0.15; Ni: less than 0.3; Zn: less than 0.4; Pb: less than 0.1; Sn: less than 0.1; Ti: 0.1 to 0.2; aluminum and unavoidable impurities.

Description

[0001] TITLE: Aluminum alloy and associated manufacturing process

[0002] The present invention relates, in general, to an aluminum alloy, in particular a secondary fusion aluminum alloy.

[0003] Furthermore, the invention relates to a method for manufacturing an aluminum alloy, in particular a secondary fusion aluminum alloy.

[0004] In a motor vehicle, the cylinder heads of a thermal engine are traditionally made from a so-called "primary fusion" aluminum alloy, i.e., derived directly from an ore, Bauxite. The cylinder heads are thus manufactured by casting this alloy.

[0005] Typically, the primary aluminum alloy comprises, in % by weight:

[0006] If: between 6.5 and 7.5;

[0007] Cu: between 0.4 and 0.6;

[0008] Mg: between 0.25 and 0.45;

[0009] Fe: less than 0.2;

[0010] Mn: less than 0.1;

[0011] Cr: less than 0.15;

[0012] Ni: less than 0.3;

[0013] Zn: less than 0.1;

[0014] Pb: less than 0.05;

[0015] Sn: less than 0.05;

[0016] Ti: between 0.1 and 0.2; the remainder being aluminum and unavoidable impurities.

[0017] Primary aluminium alloy has high thermal conductivity, i.e. a high capacity of the material to allow heat to pass through, as well as a good level of elongation at break A, in %.

[0018] These performances are achieved thanks to the limited presence of residual metallic elements, such as iron, copper, magnesium and zinc, which degrade the thermal conduction properties of the aluminum alloy, as well as thanks to the application of a heat treatment.

[0019] The heat treatment applied to the primary alloy generally comprises solution treatment at a temperature of approximately 535 ± 5°C for a duration of approximately 145 ± 30 min, followed by air quenching and aging at a temperature of approximately 190 ± 5°C for a duration of approximately 105 ± 5 min. This results in a primary alloy having a thermal conductivity X of the order of 160 W / mK and an elongation at break A greater than or equal to 4%.

[0020] Such a primary aluminum alloy also has a breaking stress Rm greater than or equal to 210 MPa, a stress causing a permanent deformation of 0.2% Rp0.2 greater than or equal to 190 MPa and a hardness HB greater than or equal to 90.

[0021] However, primary aluminium alloy emits much more CO2 during its manufacture than a so-called "secondary" aluminium alloy due to the energy consumption required for its production.

[0022] Secondary alloy means a recycled aluminium alloy obtained by re-melting aluminium alloy parts and / or scrap.

[0023] Scrap refers to debris, waste or even aluminum alloy waste from all industrial sectors.

[0024] However, the use of these recycled, secondary-melting aluminium alloys cannot be considered. Indeed, their residual element content is higher than in a primary-melting aluminium alloy. This results in a negative impact on the thermal conductivity and mechanical properties.

[0025] Some applications, such as the manufacture of cylinder heads for thermal engines, require high thermal conductivity performance. Until now, it was mandatory to use a primary aluminum alloy to ensure suitable thermal conductivity.

[0026] The invention therefore aims to overcome these drawbacks and to propose an aluminum alloy with thermal conductivity performance and mechanical characteristics equivalent to a primary aluminum alloy and which can be obtained from the recovery of secondary aluminum alloy.

[0027] An aluminum alloy is therefore proposed comprising, in % by weight:

[0028] If: between 6.5 and 8;

[0029] Cu: between 0.15 and 0.35;

[0030] Mg: between 0.2 and 0.45;

[0031] Fe: less than 0.4;

[0032] Mn: less than 0.2;

[0033] Cr: less than 0.15;

[0034] Ni: less than 0.3;

[0035] Zn: less than 0.4;

[0036] Pb: less than 0.1;

[0037] Sn: less than 0.1; Ti: between 0.1 and 0.2; aluminum and unavoidable impurities.

[0038] In this alloy, the percentages are defined in relation to the total weight of the alloy.

[0039] Surprisingly, it was found that a copper content of between 0.15 and 0.35% by weight ensures sufficient mechanical strength of the aluminum alloy material up to 275°C, while ensuring a low negative impact of copper on the thermal conductivity of the material.

[0040] The temperature resistance provided by the copper content of between 0.15 and 0.35% by weight is particularly advantageous for applications of the aluminum alloy in a motor vehicle thermal engine.

[0041] Another subject of the invention relates to a method for manufacturing an aluminum alloy comprising the following steps: a) providing an aluminum alloy as described above; b) carrying out a heat treatment on the alloy provided in step a) comprising the following steps: i) solution-treating the aluminum alloy at a temperature of 535 ± 5°C for a period of time between 145 and 175 min; ii) carrying out air quenching; and iii) carrying out aging at a temperature of between 200 and 220°C, preferably between 200 and 215°C, for a period of time between 90 and 275 min, preferably between 195 and 275 min, more preferably between 180 and 260 min.

[0042] Other characteristics, aspects, objects and advantages will emerge from the description which follows and from the following examples, given for purely illustrative purposes.

[0043] In what follows, the expression "at least one" used is equivalent to the expression "one or more".

[0044] Moreover, the limits of a domain of values ​​are included in this domain, notably in the expression "between".

[0045] Furthermore, for the purposes of the invention, the expression “less than” is equivalent to the expression “strictly less than”.

[0046] In the example developed, the aluminum alloy is a secondary aluminum alloy intended for the manufacture of a cylinder head for a thermal engine for a motor vehicle.

[0047] The aluminum alloy according to the invention comprises, in % by weight:

[0048] If: between 6.5 and 8;

[0049] Cu: between 0.15 and 0.35; Mg: between 0.2 and 0.45;

[0050] Fe: less than 0.4;

[0051] Mn: less than 0.2;

[0052] Cr: less than 0.15;

[0053] Ni: less than 0.3;

[0054] Zn: less than 0.4;

[0055] Pb: less than 0.1;

[0056] Sn: less than 0.1;

[0057] Ti: between 0.1 and 0.2; aluminum and unavoidable impurities.

[0058] Preferably, the total unavoidable impurities represent less than 0.15% by weight.

[0059] Preferably, each unavoidable impurity is present at less than 0.05% by weight.

[0060] The aluminium alloy therefore comprises aluminium in the majority quantity, as well as residual elements and unavoidable impurities.

[0061] In one embodiment, the aluminum alloy may consist of, in % by weight:

[0062] If: between 6.5 and 8;

[0063] Cu: between 0.15 and 0.35;

[0064] Mg: between 0.2 and 0.45;

[0065] Fe: less than 0.4;

[0066] Mn: less than 0.2;

[0067] Cr: less than 0.15;

[0068] Ni: less than 0.3;

[0069] Zn: less than 0.4;

[0070] Pb: less than 0.1;

[0071] Sn: less than 0.1;

[0072] Ti: between 0.1 and 0.2; the remainder being aluminum and unavoidable impurities.

[0073] For the purposes of the invention, silicon, iron, copper, manganese, magnesium, chromium, nickel, zinc, lead, tin and titanium are residual elements.

[0074] The copper content of 0.15 to 0.35 wt.% ensures sufficient mechanical resistance to temperature of the aluminum alloy material, while ensuring, however, a low negative impact of copper on its thermal conductivity. The iron and manganese contents in wt.% are, respectively, strictly less than 0.4 and strictly less than 0.2. Such ranges of iron and manganese values ​​ensure a limited impact on the thermal conductivity and elongation at break properties of the aluminum alloy.

[0075] In particular, an iron content of less than 0.4% by weight leads to the formation of a low quantity of intermetallic compounds so that the elongation at break capacities of the aluminum alloy are not impacted.

[0076] In one embodiment, the aluminum alloy may comprise an iron content, in wt%, of: 0.2 < Fe < 0.4.

[0077] In another embodiment, the aluminum alloy may comprise an iron content, in wt%, of: 0.2 < Fe < 0.4.

[0078] In another embodiment, the aluminum alloy may comprise an iron content, in wt%, of: 0.25 < Fe < 0.4.

[0079] In another embodiment, the aluminum alloy may comprise a manganese content, in wt%, of: 0.1 < Mn < 0.2.

[0080] Preferably, the aluminum alloy comprises a silicon content of between 7 and 8% by weight. Maintaining silicon within such a range of values ​​makes it possible to reduce its negative impact on the thermal conductivity of the aluminum alloy.

[0081] Advantageously, the magnesium content is between 0.2 and 0.45% by weight, ensuring a limited impact of magnesium on the thermal conduction properties of the aluminum alloy.

[0082] Preferably, the magnesium content is between 0.3 and 0.4% by weight. Magnesium helps ensure mechanical characteristics after heat treatment.

[0083] The zinc content in % by weight is strictly less than 0.4. Such a range of zinc values ​​guarantees a limited impact on the thermal conductivity of the aluminum alloy.

[0084] In one embodiment, the aluminum alloy may comprise a zinc content, in wt%, of: 0.1 < Zn < 0.4.

[0085] In one embodiment, the aluminum alloy may comprise a zinc content, in wt%, of: 0.1 < Zn < 0.4.

[0086] In one embodiment, the aluminum alloy may comprise a zinc content, in wt%, of: 0.15 < Zn < 0.4.

[0087] The lead and tin contents in % by weight are strictly less than 0.1. Such ranges of values ​​for lead and tin ensure a limited impact on thermal conductivity. In one embodiment, the aluminum alloy may comprise a lead content, in % by weight, of: 0.05 < Pb < 0.1.

[0088] In another embodiment, the aluminum alloy may comprise a lead content, in wt%, of: 0.05 < Pb < 0.1.

[0089] In another embodiment, the aluminum alloy may comprise a lead content, in wt%, of: 0.075 < Pb < 0.1.

[0090] In another embodiment, the aluminum alloy may comprise a tin content, in wt%, of: 0.05 < Sn < 0.1.

[0091] In one embodiment, the aluminum alloy may comprise a tin content, in wt%, of: 0.05 < Sn < 0.1.

[0092] In another embodiment, the aluminum alloy may comprise a tin content, in wt%, of: 0.075 < Sn < 0.1.

[0093] According to one example, the aluminum alloy may comprise 7.46 wt% silicon, 0.25 wt% copper, 0.35 wt% magnesium, 0.34 wt% iron, 0.15 wt% manganese and 0.15 wt% titanium.

[0094] The manufacturing method according to the invention of an aluminum alloy comprises the following steps: a) providing an aluminum alloy as described previously; b) carrying out a heat treatment on the alloy provided in step a) comprising the following steps: i) dissolving the aluminum alloy at a temperature of 535 ± 5°C for a duration of between 145 and 175 min; ii) carrying out air quenching; and iii) carrying out aging at a temperature of between 200 and 220°C for a duration of between 90 and 275 min.

[0095] In a first step i), the aluminium alloy is heated to a temperature suitable for the aluminium alloy in order to obtain a solid solution and lead to a homogeneous distribution of the different soluble components, formed by the residual elements and the unavoidable impurities, within the aluminium.

[0096] Quenching is then carried out in a second step ii). Quenching means cooling the aluminium alloy in air until its temperature reaches room temperature so as to freeze the solid solution obtained in step i).

[0097] In the example developed, the ambient temperature is 23°C.

[0098] The aluminum alloy is then heated in a third step iii) so as to form a homogeneously distributed precipitate and induce hardening of the alloy leading to its final thermal conductivity and elongation at break properties. According to an exemplary implementation, the aluminum alloy provided in step a) may be a secondary aluminum alloy.

[0099] The heat treatment of an aluminum alloy as described above makes it possible to achieve mechanical properties and thermal conductivity equivalent to a primary aluminum alloy.

[0100] It is thus possible to obtain, from a secondary aluminium alloy, a material with a thermal conductivity of around 160 W / mK.

[0101] It is also possible to achieve an elongation at break of up to 4%, a breaking stress Rm greater than or equal to 210 MPa, a stress causing a permanent deformation of 0.2% Rp0.2 greater than or equal to 190 MPa and a hardness HB greater than or equal to 90.

[0102] These performances of the aluminum alloy are particularly advantageous for the manufacture of a cylinder head for a thermal engine for a motor vehicle.

[0103] Advantageously, the manufacturing method according to the invention may comprise, prior to step a), a step of adjusting the quantity of chemical elements of the secondary melting aluminum alloy to obtain an aluminum alloy as described above. The producer of the secondary melting alloy may adjust the quantities and types of scrap at his disposal to meet the chemical composition requirements at his melting and holding furnaces before casting the secondary melting ingots.

[0104] Preferably, aging is carried out at a temperature between 200 and 215°C.

[0105] Preferably, aging step iii) is carried out at a temperature between 195 and 275 min.

[0106] More preferably, the aging step iii) is carried out at a temperature of between 180 and 260 min., thanks to which the thermal conduction capacity obtained is optimal.

[0107] Another object of the invention relates to a part for a motor vehicle comprising at least one aluminum alloy as previously described.

[0108] In particular, it may be provided that a cylinder head, a chassis part, a rim or any other part of a motor vehicle incorporates at least one aluminum alloy as described above.

[0109] Advantageously, the aluminum alloy provided in step a) is cast in a mold so as to obtain a part, for example a cylinder head.

[0110] The heat treatment of step b) is thus carried out directly on the part. Another object of the invention relates to a motor vehicle comprising at least one aluminum alloy as defined in any one of claims 1 to 6 and / or at least one cylinder head as defined in claim 10.

[0111] It may also be provided that a part in the aeronautics, railway or freight transport sector incorporates at least one aluminum alloy as described above.

[0112] The aluminum alloy and the heat treatment of the aluminum alloy according to the invention make it possible to manufacture parts requiring high thermal conductivity from secondary aluminum alloy.

[0113] This makes it possible, in particular, to consider increasing the rate of recycled material in motor vehicles.

[0114] Using secondary aluminum alloy is a much more economical solution than using primary aluminum alloy.

[0115] Furthermore, the production of parts from recycled aluminium alloy is particularly environmentally friendly given the drastic reduction in CO2 emissions that such a manufacturing process generates. In fact, the CO2 level emitted during the production of a part made from secondary aluminium alloy is more than three times lower than that emitted for a part made from primary aluminium alloy.

Claims

CLAIMS 1. Aluminum alloy comprising, in % by weight: If: between 6, 5 and 8; Cu: between 0.15 and 0.35; Mg: between 0.2 and 0.45; Fe: less than 0.4; Mn: less than 0.2; Cr: less than 0.15; Ni: less than 0.3; Zn: less than 0.4; Pb: less than 0.1; Sn: less than 0.1; Ti: between 0.1 and 0.2; Aluminum and unavoidable impurities.

2. Alloy according to claim 1, comprising Si between 7 and 8% by weight.

3. Alloy according to claim 1 or 2, comprising, in % by weight: 0.1 < Mn <0.

2.

4. Alloy according to any one of the preceding claims, comprising: Mg between 0.3 and 0.4% by weight.

5. Alloy according to any one of the preceding claims, comprising, in % by weight: 0.2 < Fe < 0.

4.

6. Alloy according to any one of the preceding claims, comprising, in % by weight: 0.1 < Zn < 0.

4.

7. A method of manufacturing an aluminum alloy comprising the following steps: a) providing an aluminum alloy as defined in any one of the preceding claims; b) carrying out a heat treatment on the alloy provided in step a) comprising the following steps: i) dissolving the aluminum alloy at a temperature of 535 ± 5°C for a period of between 145 and 175 min; ii) carrying out air quenching; and iii) carrying out aging at a temperature of between 200 and 220°C, preferably between 200 and 215°C, for a period of between 145 and 175 min; between 90 and 275 min, preferably between 195 and 275 min, more preferably between 180 and 260 min.

8. Manufacturing method according to claim 7, wherein the aluminum alloy provided in step a) is a secondary melting alloy.

9. Manufacturing method according to claim 8, comprising, prior to step a), a step of adjusting the quantity of chemical elements of the secondary melting aluminum alloy to obtain an aluminum alloy as defined in any one of the preceding claims.

10. Part for a motor vehicle comprising at least one aluminum alloy as defined in any one of claims 1 to 6.

11. Motor vehicle comprising at least one aluminum alloy as defined in any one of claims 1 to 6 and / or at least one part as defined in claim 10.