Method for manufacturing A6xxx alloy for extrusion and extruded products having improved properties

Abstract

The present invention includes, by weight percent, Mg: 0.45 to 1.2, Si: 0.40 to 1.0, Ti: 0.05 to 0.20, V: 0.05 to 0.15, Cu: less than 0.30, Mn: less than 0.30, Cr: less than 0.15, Zr: less than 0.15, Fe: less than 0.50, Zn: less than 0.50, and the balance being aluminum and unavoidable impurities, the content of Ti+V being 0.10 to 0.30, and Si eff The present invention relates to an Al-Mg-Si aluminum alloy having an Al / Mg ratio of less than 1.0, which has improved ductility and crush properties, good energy absorption, corrosion resistance and temperature stability, and is particularly useful for structural components in areas exposed during vehicle collisions.

Description

[Technical Field] 【0001】 The present invention relates to an Al-Mg-Si aluminum alloy and its extruded products, which have excellent ductility and crushing properties, as well as good energy absorption and temperature stability, and are particularly useful for structural components of parts exposed during vehicle collisions. The extruded products according to the present invention also have high corrosion resistance. [Background technology] 【0002】 International Publication No. 2007 / 094686 discloses an Al-Mg-Si alloy to which 0 to 0.4 weight of Ti is added to improve the ductility of the alloy. The range of Mg and Si is broad, and the preferred range of Si / Mg ratio is 1.4. This patent application also teaches that the best temperature stability is found at a high Si / Mg ratio. 【0003】 European Patent No. 0936278 claims that the ductility of an Al-Mg-Si alloy is improved by the combined addition of 0.05 to 0.20 wt% of V and 0.15 to 0.4 wt% of Mn. According to this patent application, the preferred Mn / Fe ratio is 0.45 to 1.0, and more preferably 0.67 to 1.0. The role of Ti in European Patent No. 0936278 is clearly stated as a grain refiner during casting or welding. The preferred range for Ti is 0.1 wt% or less. 【0004】 In conventional techniques, profiles are water-quenched after extrusion. However, water quenching can cause distortion of the shape of the extruded portion, and the risk of distortion increases as the complexity of the profile increases. [Overview of the project] 【0005】 Extruded profiles of Al-Mg-Si(6xxx) alloys are used as structural components in parts of automobiles that are subjected to collisions. Such components are required to absorb large amounts of energy during a collision and must deform without fracturing. One means of controlling whether an extruded profile has the required properties is to test it by crushing. In this test, a specimen of a thin-walled extruded hollow profile, having one or more chambers of a predetermined length, is crushed axially at a controlled speed, reducing the length of the specimen to typically one-third of its original length. Good deformation behavior is characterized by regular folding of the specimen walls, little to no cracks in the specimen, and a smooth surface of the deformed portion. Poor deformation behavior is characterized by limited folding of the specimen walls, widespread cracking or fracture of the specimen, and a rough and uneven surface of the deformed portion. 【0006】 As an alternative to the crush test, there is a method to test how much one of the walls in the profile bends before the first crack occurs on the outside of the bend. 【0007】 Some structural components in impact-exposed parts may also be exposed to high temperatures. Such exposure can affect the mechanical properties of alloys. In such applications, it is important to select alloys that are less susceptible to the effects of thermal exposure. The term "thermal stability" refers to the ability of an alloy to retain its mechanical properties after exposure to high temperatures. This invention provides an alloy with high-temperature stability that can be manufactured using a lower cooling rate after extrusion while maintaining corrosion and crushing properties. 【0008】 The present invention is characterized by the features defined in independent claims 1, 13, and 25, and dependent claims 2-12, 14-24, and 26. 【0009】 According to the first embodiment, in weight %, Mg: 0.45~1.2 Si: 0.40~1.0 Ti: 0.05~0.20 V: 0.05 to 0.15 Cu: less than 0.30 Mn: less than 0.30 Cr: less than 0.15 Zr: less than 0.15 Fe: less than 0.50 Zn: less than 0.50 containing the remainder being aluminum and unavoidable impurities, the Ti + V content being 0.10 to 0.30% by weight, and Si eff / Mg ratio being less than 1.0, a 6xxx aluminum alloy is provided. 【0010】 Si eff = Si - (Fe + Mn + Cr) / 3 [wt%]. When Zr is contained in the alloy, Si eff = Si - (Fe + Mn + Cr + Zr) / 3 [wt%]. 【0011】 In some embodiments, the Ti content is 0.05 to 0.15% by weight or 0.07 to 0.12% by weight. 【0012】 In some embodiments, the V content is 0.07 to 0.12% by weight. 【0013】 In some embodiments, the Ti + V content is 0.14 to 0.24% by weight or 0.15 to 0.20% by weight. 【0014】 In some embodiments, Si eff / Mg ratio is 0.50 to 0.96. 【0015】 In some embodiments, Si eff / Mg ratio is 0.60 to 0.85 or 0.65 to 0.75. 【0016】 In some embodiments, Si eff / Mg ratio is 0.80 to 0.96. 【0017】 In some embodiments, the Si content is 0.45 to 0.65% by weight, and the Mg content is 0.55 to 0.75% by weight. 【0018】 In some embodiments, the Si content is 0.45 to 0.55% by weight, and the Mg content is 0.55 to 0.65% by weight. 【0019】 In some embodiments, the Mn content is 0.10 to 0.20% by weight. 【0020】 In some embodiments, the Cu content is less than 0.20 or 0.08 to 0.15% by weight. 【0021】 In some embodiments, the Cr content is less than 0.08% by weight or less than 0.05% by weight. 【0022】 In some embodiments, the Fe content is less than 0.35% by weight. 【0023】 In some embodiments, the 6xxx aluminum alloy is an extruded alloy. 【0024】 According to the second aspect, a method for producing an extruded product from an alloy according to the first aspect or any embodiment thereof, comprising the following steps: a. By weight %, Mg: 0.45~1.2 Si: 0.40~1.0 Ti: 0.05~0.20 V: 0.05~0.15 Cu: Less than 0.30 Mn: Less than 0.30 Cr: Less than 0.15 Zr: Less than 0.15 Fe: Less than 0.50 Zn: Less than 0.50 It contains, with the remainder being aluminum and unavoidable impurities, and the Ti+V content is 0.10 to 0.30, and Si effThe step of casting a billet from a 6xxx aluminum alloy with an Al / Mg ratio less than 1.0, b. The step of homogenizing the cast billet at a temperature of 480°C to 600°C for 1 hour to 24 hours; c. The step of cooling the homogenized billet; d. The step of extruding the homogenized billet to form an extruded product; e. The step of cooling the extruded product to room temperature using a cooling rate of less than 80°C / second; f. Optionally, the step of stretching the profile; g. The step of aging the extruded product A method including these steps is provided. 【0025】 Si eff = Si - (Fe + Mn + Cr) / 3 [wt%]. When Zr is included in the alloy, Si eff = Si - (Fe + Mn + Cr + Zr) / 3 [wt%]. 【0026】 In some embodiments, the stretching in step f is 1.5% to 4% or 1.5% to 3%. 【0027】 In some embodiments, the cooling rate in step e is less than 40°C / second or less than 20°C / second. 【0028】 In some embodiments, the cooling rate in step e exceeds 5°C / second or exceeds 7°C / second. 【0029】 In some embodiments, the content of Ti + V is 0.14% to 0.24 wt% or 0.15% to 0.20 wt%. 【0030】 In some embodiments, Si eff / Mg ratio is 0.50 to 0.96. 【0031】 In some embodiments, Si eff / Mg ratio is 0.60 to 0.85 or 0.65 to 0.75. 【0032】 In some embodiments, Si eff The Mg / L ratio is between 0.80 and 0.96. 【0033】 According to a third aspect, an extruded product is provided which comprises an alloy according to the first aspect or any embodiment thereof, and is manufactured by the method of the second aspect or any embodiment thereof, wherein the material of the final extruded product has a recrystallized grain structure. 【0034】 In some embodiments, the extruded product is a structural component of a part of a vehicle that is exposed during a collision. 【0035】 Unless otherwise specified, the AA6xxx series alloys referred to herein refer to the AlMgSi alloys listed in the "International Alloy Designations and Chemical Composition Limits for Wrought Aluminum and Wrought Aluminum Alloys" published by the Aluminum Society. 【0036】 Unless otherwise specified, all alloy compositions are expressed as weight percentages based on the total weight of the alloy. [Brief explanation of the drawing] 【0037】 [Figure 1a] Figure 1a shows the yield strength values ​​Rp0.2 of seven alloys from Table 1 that were stretched by 0.5%, 2%, and 4% before aging to T6. [Figure 1b] Figure 1b shows the local elongation of the seven alloys from Table 1 that were stretched by 0.5%, 2%, and 4% before aging to T6. [Figure 2] Figure 2 shows how the bending test of the sample is performed. [Figure 3] Figure 3 shows a method for manually measuring the bending angle at which the first crack occurs in the sample. [Figure 4] Figure 4 shows the bending angles of extruded products manufactured according to this disclosure from alloys 1, 3, 5, and 7 of Table 1, and oil-quenched at a cooling rate of 50-60°C / second after SHT. [Figure 5] Figure 5 shows the bending angles of extruded parts manufactured according to the disclosures from alloys 1, 3, 5, and 7 in Table 1, and air-cooled at a cooling rate of 6–7°C / second after SHT. [Figure 6(a)] Figure 6(a) shows the yield strengths Rp0.2 of samples of alloy variants 1, 3, 5, and 7 from Table 1 that were stretched by 0.5% and subjected to water quenching (WQ), oil quenching (OQ), and air quenching (AC). [Figure 6(b)] Figure 6(b) shows the local elongation (A25mm-Ag) of samples of alloy variants 1, 3, 5, and 7 from Table 1 that were stretched by 0.5% and subjected to water quenching (WQ), oil quenching (OQ), and air quenching (AC). [Figure 7(a)] Figure 7(a) shows the average of the three deepest IGC erosions for the seven alloys in Table 1, tested after stretching by 0.5%, 2%, and 4%. [Figure 7(b)] Figure 7(b) shows optical microscope images of typical sites where the IGC values ​​shown in Figure 7(a) were measured. [Figure 8] Figure 8 shows the yield strength (Rp0.2) and ultimate tensile strength (Rm) of age-hardened extrusion profiles prepared from alloy 3 in Table 1 after thermal exposure at 150°C for 500 hours and 1000 hours. [Figure 9] Figure 9 shows a typical quenching rate along a 10 cm profile during air quenching (AQ). [Figure 10] Figure 10 shows the yield strength (a) and ultimate tensile strength (b) of the sample described in Example 5 after aging to T6. [Figure 11] Figure 11 shows crushed specimens from the three alloys of Example 5, with alloys 21-031, 21-032, and 21-033 shown in pairs from left to right (vertical columns). [Modes for carrying out the invention] 【0038】 The present invention will be further described below with reference to the drawings, using examples. The invention described herein relates to an aluminum alloy containing Mg and Si as the main alloying elements, with Ti and V added. The alloy contains an amount of Ti exceeding the amount of Ti normally added as a grain refiner. The excess Ti contributes to improved ductility and corrosion resistance of the alloy. The aluminum alloy is a 6xxx aluminum alloy. In particular, the aluminum alloy can be a 6xxx aluminum extruded alloy. 【0039】 This disclosure is expressed in weight percent. Mg: 0.45~1.2 Si: 0.40~1.0 Ti: 0.05~0.20 V: 0.05~0.15 Cu: Less than 0.30 Mn: Less than 0.30 Cr: Less than 0.15 Zr: Less than 0.15 Fe: Less than 0.50 Zn: Less than 0.50 It contains , with the remainder being aluminum and unavoidable impurities, and the Ti+V content is 0.10-0.30, Si eff The Mg ratio is less than 1.0 for 6xxx aluminum alloys. 【0040】 Si eff =Si-(Fe+Mn+Cr) / 3 [weight%]. If Zr is present in the alloy, Si eff =Si-(Fe+Mn+Cr+Zr) / 3 [weight%] 【0041】 This alloy may contain copper (Cu) for further strength and temperature stability. The Cu content should be less than 0.30% by weight. In some embodiments, the Cu content can be less than 0.20% by weight. Cu content of 0.08–0.15% by weight exhibits good strength and temperature stability in some embodiments. 【0042】 This alloy may contain up to 0.50 wt% Fe. Iron is typically an impurity element arising from sources such as aluminum oxide, manufacturing processes, and metal scrap. Excessively high Fe content can degrade the alloy's corrosion properties and reduce its strength by binding Si to the AlFeSi-containing primary particles. However, increasing the maximum Fe content or having a relatively high Fe content allows for greater use of post-consumer scrap, which is important for reducing the carbon footprint of aluminum. 【0043】 The number density of dispersed particles formed per weight percentage of added element is significantly higher for Cr than for Mn (O. Lohne and AL Dons: Scand. J. Metall. vol. 12(1983) pp. 34-36), meaning that lower Cr additions are required than Mn additions to achieve a particular number density of dispersed particles. Dispersed particles have three adverse effects on the extrusion process. The first adverse effect is that the material's resistance to hot deformation increases, leading to decreased productivity. The second adverse effect is that the increased number density of dispersed particles increases the demand for a cooling rate after extrusion to avoid loss of hardening ability of the alloy. This is because the dispersed particles act as nucleation sites for unhardened Mg-Si precipitates. The third adverse effect relates to the grain size of the extrusion profile. With slightly fewer dispersed particles than needed to prevent recrystallization, only a few particles can grow, resulting in a very coarse grain structure in the extrusion profile. Subsequently, orange peeling may occur over a wide area as the extrusion profile is formed. In the final product, coarse grains negatively affect crushing and bending behavior. Therefore, we try to avoid adding more Mn and Cr than necessary to gain the benefits of improved ductility. The optimal content of Mn and Cr depends strongly on the processing conditions and profile shape. 【0044】 The final extruded product manufactured according to the methods disclosed herein is preferably recrystallized and therefore has a recrystallized grain structure. Materials with a large number of dispersed particles sufficient to prevent recrystallization after extrusion have higher deformation resistance and are therefore more difficult to extrude compared to materials with fewer dispersed particles. Furthermore, a large number of dispersed particles increases the quenching sensitivity of the material, which may necessitate quenching to meet the strength requirements of the product. In such cases, it may be difficult to meet dimensional tolerance requirements due to distortion of the extruded profile during quenching. 【0045】 Therefore, the alloys according to this disclosure may contain up to 0.30 wt% of Mn. In some embodiments, the amount of Mn may be 0.10 to 0.20 wt%. Cr may be added up to 0.15 wt%. In some embodiments, the amount of Cr may be less than 0.08 wt% or even less than 0.05 wt%. The alloys according to this disclosure may contain 0.10 to 0.20 wt% of Mn and up to 0.15 wt% of Cr. When combining two elements, Mn and Cr, it may be necessary to reduce the amount of each element in order to maintain the total number of dispersed particles at an acceptable level. Too much Mn and / or Cr can result in mixed grain structures (recrystallized and non-recrystallized) that lead to undesirable mechanical properties. 【0046】 The addition of Zr is not very common in 6xxx alloys, but it forms dispersed particles, similar to the addition of Mn or Cr. Zr may be added up to 0.15 wt%, but the same considerations as with the addition of Mn and Cr are necessary to maintain the total number of dispersed particles at an acceptable level. 【0047】 This alloy may contain up to 0.50% by weight of Zn to allow for the addition of more post-consumer scrap to the molten material. In one embodiment, this alloy contains up to 0.20% by weight of Zn. Some Zn does not significantly affect the extrudeability, mechanical properties, or corrosion properties of the aluminum alloy. Since higher Zn concentrations slightly reduce extrudeability and corrosion properties, the upper limit for Zn is 0.50% by weight. 【0048】 This alloy was developed for extruded products requiring good crushing behavior. It is optimized for productivity and high ductility without the need for rapid quenching of the extruded profile in the extrusion press. Therefore, the alloy according to this disclosure is particularly suitable for extruded materials with complex profiles. However, it can also be used for other products, such as forgings, where improved ductility or corrosion resistance is required. 【0049】 To find the optimal Si / Mg ratio for an alloy, it must be considered that some of the Si is confined within the Fe-containing primary particles and other unhardened particles formed during the casting and homogenization of the alloy. This Si can be considered "lost" or ineffective with respect to age hardening. Si eff =Si-(Fe+Mn+Cr) / 3 [weight%], in the case of an alloy containing Zr, Si eff The "effective Si content" is defined as =Si-(Fe+Mn+Cr+Zr) / 3 [weight%]. eff This term can be introduced. 【0050】 The alloy according to this disclosure has 0.45 to 0.2 wt% Mg and 0.40 to 1.0 wt% Si. To optimize the crush resistance of extruded products manufactured from the alloy according to this disclosure, Si eff The / Mg ratio should be less than 1.0. eff The Mg / Mg ratio is preferably maintained within the range of 0.50 to 0.96. The optimal Si ratio is within the range of 0.60 to 0.85 or 0.65 to 0.75. eff The / Mg ratio has been found to be advantageous, as demonstrated by the examples. However, in some embodiments, Si eff The Mg / / Mg ratio may be between 0.80 and 0.96. 【0051】 According to some embodiments, the optimal composition of Mg and Si for ductility and temperature stability is 0.45–0.65 wt% Si and 0.55–0.75 wt% Mg, or, in a more narrowly defined composition, 0.45–0.55 wt% Si and 0.55–0.65 wt% Mg. 【0052】 Titanium (Ti) is typically added to Al alloys during casting, along with boron (B) or carbon (C), to refine the grain size of the alloy. Excess Ti in the molten metal enhances the grain refinement effect of TiB2 particles. The Ti content required for grain refinement in Al-Mg-Si alloys is typically in the range of 0.005 to 0.03 wt%. The amount of Ti in the alloy according to this disclosure is in the range of 0.05 to 0.20 wt%, for example, 0.05 to 0.15 wt% or 0.07 to 0.12 wt%. Furthermore, the amount of V in the alloy according to this disclosure is in the range of 0.05 to 0.15 wt% or 0.07 to 0.12 wt%. Both Ti and V are peritectic elements that typically segregate toward the center of the grain during solidification. During extrusion, Ti and V-rich regions in the grains are stretched into fine bands. While we do not wish to be bound by theory, it is believed that these Ti- / V- bands reduce the diffusion rate of Mg and Si toward grain boundaries at high temperatures, and therefore can reduce the cooling rate after extrusion without impairing material properties such as bending angle, strength, and crushability. Adding 0.10% by weight or more of both Ti and V in total, for example, 0.14% by weight or more, improves the crushability and corrosion resistance of the Al-Mg-Si alloy according to this disclosure. This requires a Ti content higher than that typically used for grain refinement. Therefore, according to this disclosure, the total amount of Ti and V (Ti+V) should be 0.10 to 0.30% by weight. In some embodiments, the Ti+V content may be 0.14 to 0.24% by weight, for example, 0.15 to 0.20% by weight. The total amount of Ti+V should not be too high, as this will result in the precipitation of undesirable primary particles. Since Ti and V in the solid solution increase deformation resistance and decrease extrudeability, the total amount of Ti and V should also be kept within the specified limits. The improvement in crushing performance obtained by adding Ti and V to the Al-Mg-Si alloy is demonstrated by the embodiments of the present invention. 【0053】 This disclosure further relates to a method for manufacturing extruded products. This method includes the following steps: Step a. By weight %, Mg: 0.45~1.2 Si: 0.40~1.0 Ti: 0.05~0.20 V: 0.05~0.15 Cu: Less than 0.30 Mn: Less than 0.30 Cr: Less than 0.15 Zr: Less than 0.15 Fe: Less than 0.50 Zn: Less than 0.50 It contains, with the remainder being aluminum and unavoidable impurities, and the Ti+V content is 0.10 to 0.30, and Si eff A billet is cast from a 6xxx aluminum alloy with a Mg ratio of less than 1.0. This alloy may have either the composition according to the above disclosure or one of the above disclosed embodiments of the alloy that further specifies other amounts of alloying elements. Si eff =Si-(Fe+Mn+Cr) / 3 [weight%]. In the case of an alloy containing Zr, Si eff =Si-(Fe+Mn+Cr+Zr) / 3 [weight%] 【0054】 Step b. Homogenize the cast billet at a temperature of 480-600°C for 1-24 hours. The homogenization step homogenizes the microstructure of the cast billet. A typical homogenization temperature is above the sorbus temperature of the relevant alloy in order to dissolve the Mg and Si contained in the alloy. 【0055】 Step c. Cool the homogenized billet from the homogenization temperature to room temperature. The cooling rate from the homogenization temperature may exceed 100°C per hour. Typically, the cooling rate from the homogenization temperature may exceed 200°C per hour or even exceed 300°C per hour. 【0056】 Step d. The billet is extruded to form an extruded product. Before extrusion, the extruded billet should be reheated to an appropriate extrusion temperature, typically 450-510°C. According to this disclosure, the billet may be overheated before being cooled to the desired extrusion temperature. 【0057】 Step e. Cool the extruded product to room temperature. The cooling rate of the extruded product should be less than 80°C / second. The cooling rate may be less than 40°C / second, or even less than 20°C / second. However, the cooling rate should be greater than 5°C / second, and in some embodiments, greater than 7°C / second. If the cooling rate is too low, the Mg and Si contained in the alloy may precipitate as large Mg2Si, which does not contribute to strengthening during aging, thus reducing the potential strength of the final product. This results in less Mg and Si available for the precipitation of the strengthening nano-sized precipitate phase that forms during artificial aging. By using a lower cooling rate for extrusion, it is possible to manufacture complex extruded sharps with the desired strength and crushing properties without introducing geometric distortion into the profile. The advantages of using a lower cooling rate to cool the extruded product are demonstrated by the examples. 【0058】 Step f. Optionally, stretch the profile. Any stretching step f may include stretching the cooled profile to 4%. Stretching between 1.5 and 4%, for example, 1.5 to 3%, has been shown to be beneficial to the ductility of the material, as demonstrated by the examples. Stretching is typically performed a short time after extrusion, for example, within 10 to 30 minutes after extrusion, but the indicated time is not critical, and stretching may be performed later. 【0059】 Step g. Aging the extruded product. Aging step g includes artificially aging the product to a desired strength level. It should be understood that the aging step may also include natural aging, as natural aging is practically unavoidable in industrial production. To achieve the desired crushing performance, the extruded product may be aged to T6 temper. Profiles drawn according to step f may be designated as T8 temper (aged after cold working), but in this disclosure, the T6 designation is used for all aged profiles. The aging temperature is typically in the range of 160–210°C for 1–24 hours, with a typical aging temperature in the range of 175–205°C. Artificial aging may be carried out in one step or in stages. 【0060】 The extruded product manufactured according to the method disclosed above has the following composition (weight %): Mg: 0.45~1.2 Si: 0.40~1.0 Ti: 0.05~0.15 V: 0.05~0.15 Cu: Less than 0.30 Mn: Less than 0.30 Cr: Less than 0.15 Zr: Less than 0.15 Fe: Less than 0.50 Zn: Less than 0.50 The remainder consists of aluminum and unavoidable impurities, with Ti+V content ranging from 0.10 to 0.30, and Si eff The Mg ratio is less than 1.0. Includes alloys having the following properties. 【0061】 The alloy composition of the extruded product may have any composition as described in the above disclosure. 【0062】 Si eff =Si-(Fe+Mn+Cr) / 3 [weight%]. In the case of an alloy containing Zr, Si eff =Si-(Fe+Mn+Cr+Zr) / 3 [weight%] 【0063】 Extruded products manufactured by the methods of this disclosure should have a recrystallized grain structure. In some embodiments, the extruded products have a recrystallized grain structure and a yield strength Rp0.2 of at least 240 MPa (C24 alloy requirement). Furthermore, extruded products of the alloys of this disclosure manufactured by the methods of the present invention exhibit excellent bending angle characteristics and have a combination of excellent crushability and corrosion resistance. As will be apparent from the following examples, the extruded products also have good temperature stability. [Examples] 【0064】 <Example 1> Seven alloys having the compositions shown in Table 1 were cast into 95 mm diameter billets by DC casting. 【0065】 [Table 1] 【0066】 Homogenization was performed at a temperature of 575°C for 2 hours and 15 minutes, followed by cooling at a rate of approximately 350°C / hour. 【0067】 The billets were heated to approximately 550°C for 8-10 minutes, then cooled to approximately 490-500°C immediately before extrusion. Hollow rectangular profiles with external dimensions of 29 × 37 mm and wall thickness of 2.8 mm were extruded from different alloys. The profiles were quenched in water at a quenching rate estimated to be over 300°C / second at a distance of approximately 50 cm behind the die exit. After extrusion, the profiles were stretched to either 0.5%, 2%, or 4%. Approximately 24 hours after extrusion, the profiles were aged to T6 by heating to 150°C at a rate of 200°C / hour, holding at 150°C for 1.5 hours, heating to 195°C at a rate of 15°C / hour, and holding at 195°C for 2 hours for the 0.5% stretched profiles, holding at 195°C for 1 hour and 40 minutes for the 2% stretched profiles, and holding at 195°C for 1 hour and 20 minutes for the 4% stretched profiles. Figure 1(a) shows the yield strength values ​​Rp0.2 of the seven alloys from Table 1 that were stretched by 0.5%, 2%, and 4% before aging to T6. The strength levels of the different variants are very similar. This is expected, as vanadium and titanium both have little effect on their strength under T6 conditions. The strength of the profiles stretched by 2% and 4% is slightly lower compared to the profile stretched by 0.5% before T6 aging. Tensile tests were performed according to ISO 6892-1 - Metallic materials - Tensile tests - Part 1: Test methods at room temperature. 【0068】 Uniform elongation or total elongation is not a good measure of the ductility of a material subjected to deformation by crushing. Total elongation (A 25mm ) and uniform elongation (A gThe difference between this and the ductility of the material is known as local elongation and is a better measure of the material's ductility. Figure 1(b) shows the local elongation of the seven alloys tested. In the water quenching profile, the addition of either vanadium or titanium has only a slight positive effect. Increasing the elongation from 0.5% to 2% or 4% before T6 aging appears to have a better effect on local elongation. 【0069】 <Example 2> The bending test was performed according to standard VDA 238-100, with the exception of using a 1% load drop instead of 60 N as the stopping criterion. The bending angle measured based on this criterion typically corresponds to the angle at which the first crack is observed in the specimen. The test specimen was taken from the widest sidewall of the profile of Example 1. The specimen was 30 mm wide, 60 mm long, and 2.8 mm thick. The specimen was bent along an axis 90° to the extrusion direction (i.e., perpendicular to the extrusion direction) (see Figure 2). Figure 3 shows how the bending angle at which the first crack occurred in the specimen was measured manually. 【0070】 To investigate the effect of different cooling rates after extrusion on bending properties, extruded samples stretched by 0.5% after extrusion were subjected to separation solution treatment (SHT) at 530°C for 20 minutes (measured from the time the temperature reached 525°C), and then cooled in air, oil, or water. 【0071】 One set of samples (the first set) was quenched in water at a temperature of approximately 25°C. The cooling rate in the temperature range between 450°C and 250°C is estimated to be 300°C / second or more. After quenching, the samples were stretched by 0.5% and 2%, and then aged to T6 using the same method as in Example 1. 【0072】 Another set of samples (the second set) was quenched in oil maintaining a temperature in the range of 26–28°C. The cooling rate in the temperature range between 450°C and 250°C was measured to be in the range of 50–60°C / second. After quenching, the samples were stretched by 0.5% and 2%, and then aged to T6 in the same manner as described in Example 1. 【0073】 The third set of samples was cooled in forced air. To obtain a higher cooling rate than that obtained for all hollow profile samples, a blank for a bent sample with a width of 30 mm, a length of 150 mm, and a thickness of 2.8 mm was prepared before SHT. The cooling rate in the temperature range between 450°C and 250°C was measured to be in the range of 6-7°C / second. After cooling to room temperature, the samples were stretched by 0.5% and 2%, and then aged to T6 in the same manner as described in Example 1. 【0074】 The bending angles of the water-quenched samples all exceeded the limits of the apparatus, so the results here are not representative. 【0075】 Figure 4 shows the bending angles measured as described in Example 2 for extruders manufactured according to the present invention from alloys 1, 3, 5, and 7, and oil-quenched after SHT at a cooling rate of 50-60°C / sec. In this case, a clear effect of adding Ti or V is observed, but according to the present invention, the best effect is obtained by adding Ti and V together. This is also a very clear effect of a 2% stretch compared to 0.5% before aging to T6. 【0076】 Figure 5 shows the bending angles of extruded products manufactured according to the present invention from alloys 1, 3, 5, and 7 of Table 1, and air-cooled at a cooling rate of 6-7°C / second after SHT. Air cooling reduces the bending angle of all alloys, and in this case, the effect of adding Ti or V is clearly observed, but according to the present invention, the best effect is obtained by adding Ti and V together. Furthermore, there is a very clear effect of a 2% draw compared to 0.5% before aging to T6. 【0077】 While water-quenched and oil-quenched specimens exhibit superior bendability compared to air-cooled specimens, very high cooling rates impose limitations on the available profile shapes and geometric tolerances. By using the composition according to the present invention, it is possible to obtain a bending angle close to that of conventionally faster quenched specimens using extruded and air-cooled specimens. 【0078】 Figure 6(a) shows the yield stress Rp of alloy variants cooled at different cooling rates after SHT. 0.2 The values ​​are shown. Compared to the water-cooled sample, the air-cooled sample showed Rp 0.2 The Rp did not decrease significantly, and all variants had a minimum Rp of 240 MPa. 0.2 It meets the typical requirements. 【0079】 In Figure 6(b), the total extension A 25mm and uniform growth A g The difference between these two values ​​(called local elongation) is plotted for the same alloy variants as in Figure 6(a). Local elongation is best at the highest cooling rate. The addition of Ti or V (variants 3 and 5) increases local elongation compared to the low-Ti and V alloy variant (variant 1). However, the greatest increase in local elongation is found according to the present invention when both elements are added together (variant 7). 【0080】 <Example 3> Intergranular corrosion (IGC) testing was performed according to ISO 11846 Method B. Three parallel samples from each specimen were immersed in the same beaker. The IGC results for the seven alloys are shown in Figure 7. For each sample, four regions were investigated, and the three deepest IGC erosion points were measured. 【0081】 Figure 7(a) shows the average of the three deepest IGC erosions for seven alloys tested after 0.5%, 2%, and 4% drawing. The alloys were water-quenched after extrusion and drawn before aging to T6. The alloy containing neither Ti nor V (Alloy 1) underwent the deepest corrosion erosion, with the maximum average depth measured ranging from 350 to 410 μm. 【0082】 Figure 7(b) shows optical microscope images of typical sites measured for the average IGC values ​​shown in Figure 7(a). 【0083】 Images in Figures 7(a) and 7(b) clearly show that increasing the Ti and V content in these alloys significantly reduces the IGC depth. Alloy 7, with high Ti and V content, clearly showed the least IGC erosion, followed by alloys 6 and 3. Pre-aging stretching of 2% and 4% appears to reduce the maximum IGC depth compared to stretching of 0.5%. 【0084】 <Example 4> Figure 8 shows the decrease in yield strength (YS) and ultimate tensile strength (UTS) after thermal exposure at 150°C for 500 and 1000 hours for age-hardened extrusion profiles produced from alloy 3 in Table 1. This result indicates that the Mg and Si content selected according to the present invention results in high thermal stability. Since thermal stability is considered independent of Ti and V content, the obtained results should be valid for all alloys in this study. 【0085】 <Example 5> Three alloys with varying Mg / Si ratios were cast. The nominal chemical compositions of the three alloys are shown in Table 2. The material was GC cast with a diameter of 95 mm. 【0086】 [Table 2] 【0087】 Homogenization was performed at a temperature of 575°C for 2 hours, followed by cooling to room temperature at a rate of approximately 350°C / hour. 【0088】 A single chamber crush box profile measuring 28mm x 37mm x 2.8mm with a seam weld in the center of the profile wall was extruded. The billet was preheated to 560°C and held at the same temperature in an air-circulating furnace, and then water-quenched to 500°C before extrusion. The extrusion tool / container was held at 430°C. The profile was quenched in water at a distance of approximately 50cm behind the die exit. 【0089】 Individual solution heat treatment (SHT) was performed before each cooling test. Each sample was solution heat treated (SHT) at 530°C for 20 minutes (starting when the temperature reached 525°C). Next, different quenching rates of water quenching (WQ), oil quenching (OQ), and air quenching (AQ) were applied. The following sections describe the three different quenching lines. All profiles were stretched by 0.5% or 2% immediately after quenching, naturally aged for approximately 24 hours, and then artificially aged to T6. The aging to T6 was performed using the temperature profiles shown in Table 3. The results shown here are those after the final AA process to T6, unless otherwise specified. 【0090】 [Table 3] 【0091】 Water quenching after SHT A 35 cm long profile sample was subjected to SHT as described above. The profile was immediately quenched in water maintained at approximately 25°C. The water was not stirred. The average quenching rate was over 300°C / second. After being stretched immediately after quenching, the profile was naturally aged (NA) at room temperature for approximately 24 hours from AA to T6. 【0092】 Oil quenching after SHT A 35 cm long profile was subjected to SHT as described above. The profile was quenched in oil maintained at 26-28°C. The oil was stirred during quenching. The average quenching rate was approximately 55°C / second. The profile was stretched immediately after quenching. Subsequently, the profile was naturally aged (NA) at room temperature for approximately 24 hours from AA to T6. 【0093】 Air cooling after SHT The sample was subjected to SHT at 530°C for 20 minutes (after the temperature reached 525°C). Next, the profile was air-cooled by holding it on a fan for 1 minute, and then quenched in water. The average quenching rate was approximately 7°C / second. The profile was stretched immediately after quenching and then held at room temperature for approximately 24 hours from AA to T6. The experimental setup and sample shape used during AQ are shown in Figure 9, along with the corresponding temperature records. Here, T1 is the lower curve in the figure, and T2 is the upper curve. 【0094】 The mechanical properties of the profiles were tested. For tensile tests, standard flat tensile test specimens of 12 cm in length were machined from the narrowest profile walls of each alloy variant. Two parallel materials were tested under each condition. The tensile tests were carried out according to ISO 6892-1 - Metallic materials - Tensile tests - Part 1: Test methods at room temperature. 【0095】 The results of the tensile test are shown in Figures 10a) and 10b). The quenching rate is as described above. The yield strength and ultimate tensile strength in Figures 10a) and 10b) are both for Si eff It increases slightly with increasing Mg ratio. From Figure 10b), Rm increases with increasing elongation from 0.5% to 2% for all quenching rates. Regarding the yield strength in Figure 10a), the effect of elongation after SHT does not appear to be very significant. However, at the slowest quenching rate (AQ), Rp0.2 increases by 4-8 MPa with elongation from 0.5% to 2%. 【0096】 In the crush test, two parallel samples were cut for crush testing of each alloy, WQ and after 0.5% stretching. All crush boxes were crushed to 1 / 3 of their original height. The crushed specimens are shown in Figure 11. Lowest Si eff The 21-031 alloy with a suitable Mg ratio showed the best performance, obtaining a perfect crush score of 10, as shown in Figure 11(a). This means that the specimen showed no signs of cracking. Refer to Figure 11(b), higher Si effThe 21-032 alloy with a high Mg ratio also showed good performance, but its crushing rating was slightly lower. eff The 21-033 alloy with a high Mg ratio exhibited the worst performance, with at least one deep corner crack developing.

Claims

[Claim 1] In weight percentage, Mg: 0.55-0.75 Si: 0.45 to 0.65 Ti:0.07~0.15 V:0.07~0.15 Cu: Less than 0.30 Mn: Less than 0.30 Cr: Less than 0.08 Zr: Less than 0.15 Fe: Less than 0.50 Zn: Less than 0.50 It contains, with the remainder being aluminum and unavoidable impurities, and the Ti+V content is 0.14 to 0.24% by weight, Si ｅｆｆ The Mg / / ratio is 0.60 to 0.85, and Si eff = Si - (Fe + Mn + Cr + Zr) / 3 [weight %], a 6xxx aluminum alloy. [Claim 2] The 6xxx aluminum alloy according to claim 1, wherein the Ti content is 0.07 to 0.12% by weight. [Claim 3] The 6xxx aluminum alloy according to claim 1 or 2, wherein the V content is 0.07 to 0.12% by weight. [Claim 4] The 6xxx alloy according to claim 1 or 2, wherein the Ti+V content is 0.15 to 0.20% by weight. [Claim 5] Si ｅｆｆ The 6xxx aluminum alloy according to claim 1 or 2, wherein the Mg ratio is 0.65 to 0.

75. [Claim 6] The 6xxx aluminum alloy according to claim 1 or 2, wherein the Si content is 0.45 to 0.55% by weight and the Mg content is 0.55 to 0.65% by weight. [Claim 7] The 6xxx aluminum alloy according to claim 1 or 2, wherein the Mn content is 0.10 to 0.20% by weight. [Claim 8] The 6xxx aluminum alloy according to claim 1 or 2, wherein the Cu content is less than 0.20% by weight. [Claim 9] The 6xxx aluminum alloy according to claim 1 or 2, wherein the Cu content is 0.08 to 0.15% by weight. [Claim 10] The 6xxx aluminum alloy according to claim 1 or 2, wherein the Cr content is less than 0.05% by weight. [Claim 11] A method for producing an extruded product from the alloy described in claim 1, the following: a. In weight percent, Mg: 0.55-0.75 Si: 0.45 to 0.65 Ti:0.07~0.15 V:0.07~0.15 Cu: Less than 0.30 Mn: Less than 0.30 Cr: Less than 0.08 Zr: Less than 0.15 Fe: Less than 0.50 Zn: Less than 0.50 It contains, with the remainder being aluminum and unavoidable impurities, and the Ti+V content is 0.14 to 0.24% by weight, and Si ｅｆｆ The Mg ratio is 0.60 to 0.85, and Si eff = Si - (Fe + Mn + Cr + Zr) / 3 [weight %], and the process involves casting a billet from a 6xxx aluminum alloy. b. A process of homogenizing the cast billet at a temperature of 480°C to 600°C for 1 to 24 hours, c. A process of cooling the homogenized billet, d. A step of forming an extruded product by extruding the billet, e. A step of cooling the extruded product to room temperature using a cooling rate of less than 80°C / second, f. A process of stretching the profile by 1.5 to 4%, g. The process of aging the extruded product and A method for manufacturing extruded products, including [a specific component]. [Claim 12] A method for manufacturing an extruded product according to claim 11, wherein the stretching in step f is 1.5 to 3%. [Claim 13] A method for manufacturing an extruded product according to claim 11 or 12, wherein the cooling rate of step e is less than 40°C / second. [Claim 14] The method for manufacturing an extruded product according to claim 11 or 12, wherein the cooling rate of step e is less than 20°C / second. [Claim 15] A method for manufacturing an extruded product according to claim 11 or 12, wherein the cooling rate of step e is greater than 5°C / second. [Claim 16] The method for manufacturing an extruded product according to claim 11 or 12, wherein the cooling rate of step e is greater than 7°C / second. [Claim 17] A method for producing an extruded product according to claim 11 or 12, wherein the Ti+V content is 0.15 to 0.20% by weight. [Claim 18] Si ｅｆｆ A method for producing an extruded product according to claim 11 or 12, wherein the Mg / mg ratio is 0.65 to 0.

75. [Claim 19] A method for producing an extruded product according to claim 11 or 12, wherein the Si content is 0.45 to 0.55% by weight and the Mg content is 0.55 to 0.65% by weight. [Claim 20] A method for producing an extruded product according to claim 11 or 12, wherein the Cu content is less than 0.20% by weight. [Claim 21] The method for producing an extruded product according to claim 11 or 12, wherein the Cu content is 0.08 to 0.15% by weight. [Claim 22] A method for producing an extruded product according to claim 11 or 12, wherein the Cr content is less than 0.05% by weight. [Claim 23] An extruded product having good crushability, corrosion resistance and temperature stability, wherein by weight %, Mg: 0.55-0.75 Si: 0.45 to 0.65 Ti:0.07~0.15 V:0.07~0.15 Cu: Less than 0.30 Mn: Less than 0.30 Cr: Less than 0.08 Zr: Less than 0.15 Fe: Less than 0.50 Zn: Less than 0.50 It consists of aluminum and unavoidable impurities, with a Ti+V content of 0.14 to 0.24% by weight, and Si ｅｆｆ The Mg / / ratio is 0.60 to 0.85, and Si eff = Si - (Fe + Mn + Cr + Zr) / 3 [weight %], containing 6xxx aluminum alloy. The final product material has a recrystallized grain structure and a yield strength Rp0.2 of at least 240 MPa in T6 tempering, and is an extruded product. [Claim 24] The extruded product according to claim 23, wherein the extruded product is a structural component of a part that is exposed during a vehicle collision.

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