TW202413667A - High strength aluminum alloy and manufacturing method thereof - Google Patents

Abstract

A high strength aluminum alloy and manufacturing method thereof are provided. The manufacturing method includes the following steps: providing an aluminum alloy material; applying a solid solution treatment and an artificial aging treatment to the aluminum alloy material; providing the aluminum alloy material after the solid solution treatment and the artificial aging into a heating device to heat to a first temperature of 150 ℃ to 250 ℃; transferring the aluminum alloy material heated to the first temperature to a heated mold within a transfer time, wherein the mold surface temperatures of an upper mold and a lower mold of the heated mold are controlled at a second temperature of 150 ℃ to 300 ℃; closing the upper mold and the lower mold of the heated mold, holding pressure within 10 seconds, and opening the mold and taking out the aluminum alloy material to obtain an aluminum alloy component with a high strength and a low spring back.

Description

High-strength aluminum alloy and its manufacturing method

The present invention relates to a high-strength aluminum alloy and a method for manufacturing the same, and more particularly to an aluminum alloy having high strength and low rebound by heating a mold and a method for manufacturing the same.

High-strength aluminum alloys (such as 6xxx/7xxx series) often face the following problems when cold stamping: (1) poor formability of the material at room temperature, which easily leads to cracking; and (2) large springback, which makes it difficult to control the dimensional accuracy of the parts. The traditional warm forming method uses a sheet that has been solution-treated and artificially aged (T6) to first increase the sheet temperature in a heating furnace, and then transfer it to a room temperature mold for stamping. However, parts after warm stamping are generally observed to have strength loss and obvious springback.

Therefore, it is necessary to provide a high-strength and low-rebound aluminum alloy and a manufacturing method thereof to solve the problems existing in the conventional technology.

One of the purposes of the present invention is to provide a method for forming a high-strength aluminum alloy by heating a pre-treated aluminum alloy (T4 or T6). The aluminum alloy is heated in a heating furnace and then transferred to a mold. The high-temperature mold is used for stamping and a short-time mold clamping and pressure holding, thereby improving the rebound problem of the high-strength aluminum alloy after forming.

Another object of the present invention is to provide a method for forming a high-strength aluminum alloy by heating a die, thereby improving the dimensional accuracy of parts, so that the strength of the parts after heat treatment in the forming and baking paint embodiments can be maintained at a level close to that of the T6 state.

To achieve the above-mentioned object, the present invention provides a method for manufacturing a high-strength aluminum alloy, comprising the following steps: providing an aluminum alloy material; subjecting the aluminum alloy material to a solution treatment and an artificial aging treatment; placing the aluminum alloy material subjected to the solution treatment and the artificial aging treatment in a heating device to heat the aluminum alloy to a first temperature of 150° C. to 250° C.; heating the aluminum alloy material heated to the first temperature to heat the aluminum alloy to a temperature of 150° C. to heat the aluminum alloy material to a temperature of 250° C.; The aluminum alloy material is transferred to a heated mold within a transfer time, wherein the mold surface temperature of an upper mold and a lower mold of the heated mold is controlled at a second temperature of 150° C. to 300° C. After the upper mold and the lower mold of the heated mold are closed, the aluminum alloy material is pressure-maintained for less than 10 seconds, and then the mold is opened to take out the aluminum alloy material to obtain an aluminum alloy component with high strength and low rebound.

In one embodiment of the present invention, the aluminum alloy material reaches T4 or T6 state after the solution treatment and the artificial aging treatment.

In one embodiment of the present invention, the aluminum alloy material is a 6xxx or 7xxx series aluminum alloy material.

In one embodiment of the present invention, the first temperature is 150°C to 200°C.

In one embodiment of the present invention, after the aluminum alloy material reaches the first temperature, the aluminum alloy material is transferred to the heated mold without holding the temperature.

In one embodiment of the present invention, the manufacturing method further comprises the following step: after the aluminum alloy component is taken out of the mold, a natural air cooling step is performed on the aluminum alloy component.

In one embodiment of the present invention, the heated mold is heated by a heating rod embedded in the mold.

In one embodiment of the present invention, the mold surface temperature of the upper mold is different from the mold surface temperature of the lower mold.

In one embodiment of the present invention, the mold surface temperature of the upper mold is the same as the mold surface temperature of the lower mold.

Furthermore, the present invention provides a high-strength aluminum alloy manufactured by the manufacturing method of the high-strength aluminum alloy as described above, wherein the high-strength aluminum alloy has a tensile strength between 541 MPa and 579 MPa, and a rebound amount that can be controlled between -0.5 mm and 0.5 mm.

In order to make the above and other purposes, features and advantages of the present invention more clearly understood, the preferred embodiments of the present invention are specifically cited below and described in detail with reference to the attached drawings. Furthermore, the directional terms mentioned in the present invention, such as up, down, top, bottom, front, back, left, right, inside, outside, side, periphery, center, horizontal, transverse, vertical, longitudinal, axial, radial, topmost or bottommost, etc., are only referenced to the directions of the attached drawings. Therefore, the directional terms used are used to explain and understand the present invention, but not to limit the present invention.

As used herein, reference to a numerical range for a variable is intended to mean that the variable is equal to any value within the range. Thus, for a variable that is itself discontinuous, the variable is equal to any integer value within the numerical range, including the endpoints of the range. Similarly, for a variable that is itself continuous, the variable is equal to any real value within the numerical range, including the endpoints of the range. By way of example, and not limitation, a variable described as having a value between 0-2 takes on a value of 0, 1, or 2 if the variable is itself discontinuous, and takes on a value of 0.0, 0.1, 0.01, 0.001, or any other real value ≥ 0 and ≤ 2 if the variable is itself continuous.

The term "6XXX series aluminum alloy" used in this article refers to aluminum alloys that are mainly added with magnesium and silicon. The strength of the material is obtained by forming a precipitation strengthening phase of β-Mg ₂ Si uniformly distributed in the α-Al base structure through magnesium and silicon. It has good corrosion resistance, excellent extrudability and weldability, and is mainly used in construction, vehicles, ships, and machinery.

The term "7XXX series aluminum alloy" used in this article refers to the alloys with zinc, magnesium and copper as the main additives. Zinc and magnesium will combine to form η-MgZn ₂ precipitation phase, which is the main source of strengthening. It has high strength, high toughness and good plastic processing properties, and is mainly used in aviation, automobiles, sports, and 3C technology products.

The term "T4" used in this article refers to solution heat treatment followed by natural aging. After solution heat treatment, it is not cold worked, but hardened to a stable state by natural aging.

The term "T6" used in this article refers to artificial aging after solution treatment. This is a typical heat treatment for heat-treatable alloys, which can achieve superior strength without cold working. Cold working is applied after solution treatment to improve dimensional accuracy or correction.

Referring to FIG. 1 , the present invention provides a method 100 for manufacturing a high-strength aluminum alloy, comprising the following steps: providing an aluminum alloy material (step 101); subjecting the aluminum alloy material to a solution treatment and an artificial aging treatment (step 102); placing the aluminum alloy material subjected to the solution treatment and the artificial aging treatment in a heating device to heat the aluminum alloy to a first temperature of 150° C. to 250° C. (step 103); heating the aluminum alloy material heated to the first temperature to heat the aluminum alloy to a temperature of 150° C. to 250° C. The aluminum alloy material of the present invention is transferred to a heated mold within a transfer time, wherein the mold surface temperature of an upper mold and a lower mold of the heated mold is controlled at a second temperature of 150° C. to 300° C. (step 104); after the upper mold and the lower mold of the heated mold are closed, the aluminum alloy material is pressure-maintained for less than 10 seconds, and then the mold is opened to take out the aluminum alloy material to obtain an aluminum alloy component with high strength and low rebound (step 105).

In one embodiment of the present invention, the aluminum alloy material after the solution treatment and the artificial aging treatment reaches a T4 or T6 state. Preferably, the aluminum alloy material is a 6xxx or 7xxx series aluminum alloy material. In another embodiment of the present invention, the aluminum alloy material after the solution treatment and the artificial aging treatment is placed in the heating device and then heated to a temperature of only 150°C to 200°C. Optionally, the heating device is a heating furnace.

In one embodiment of the present invention, after the aluminum alloy material reaches the first temperature, the aluminum alloy material is transferred to the heated mold within 10 seconds without holding the temperature, wherein the heated mold has been preheated to control the mold surface temperature of the upper mold and the lower mold to be between 150°C and 300°C.

Optionally, after the aluminum alloy material is pressure maintained for less than 10 seconds, the mold is opened to take out the aluminum alloy material, and then the aluminum alloy component is subjected to a natural air cooling step.

In one embodiment of the present invention, the heated mold has a male mold and a female mold (in this embodiment, the upper mold is the male mold and the lower mold is the female mold), and the mold has a heating rod embedded in a drill hole below the mold surface to heat the mold. In addition, optionally, a thermocouple can be embedded near the mold surface to measure the mold surface temperature. In addition, a heat insulation board can be set around the mold to reduce heat loss. In one embodiment of the present invention, the mold surface temperature of the upper mold is different from the mold surface temperature of the lower mold. Alternatively, the mold surface temperature of the upper mold is the same as the mold surface temperature of the lower mold.

Compared with the manufacturing method of heating the aluminum alloy or magnesium alloy sheet to a forming temperature greater than the ambient temperature, then transferring the heated sheet to a room temperature mold, then closing the upper and lower molds to form the sheet, and cooling the sheet in the mold, the sheet is first heated and then sent to the room temperature mold for forming. For high-strength sheets (such as 6061-T6 or 7075-T6) that have been artificially aged, the formed parts will have obvious rebound phenomenon, and the parts will have strength loss after forming. The poor dimensional accuracy of the parts will cause difficulties in the subsequent assembly of the sub-assembly.

In addition, the temperature of the die is first heated to 160 to 250°C, while the temperature of the punch is kept at room temperature. The 6XXX-T4 sheet with a thickness of 0.8 to 1.5 mm is placed on the die without heating for forming. After the forming is completed, the die needs to be pressurized for less than 5 minutes, and then the formed sheet is taken out and air-cooled to room temperature. This process requires about 5 minutes of pressurization after the die is formed to obtain the main strengthening phase β, but too long a pressurization time will reduce the production rate.

In addition, the solution treated and tempered T4 sheet (2XXX/ 6XXX/ 7XXX/ 8XXX/ 9XXX) is heated to 150 to 350°C for 2 to 6 minutes. The heated sheet is transferred to the mold for forming within 15 seconds. The sheet after the above process is in a state of about T6. However, the sheet in the T4 state needs to be heated before stamping and kept in the heating furnace for 2 to 6 minutes to allow more strengthening phases to precipitate to increase the strength of the sheet to the T6 state. The holding time in the heating furnace will cause the production rate to decrease. However, the sheet is stamped at a strength close to T6. Due to the high strength, the parts will have a more obvious rebound phenomenon after stamping.

The present invention proposes a mold heating forming method for high-strength aluminum alloys (such as 6xxx/7xxx), which puts the aluminum plate that has been solid solution and artificially aged (T4 or T6 state) into a heating furnace for heating. After the plate temperature rises to 150 to 250°C, it can be taken out without additional temperature holding, and the plate is transferred to a high-temperature mold for stamping. The punch and die of the mold are heated by heating rods to reach a specific mold surface temperature (150 to 300°C). After the mold is closed, the mold is maintained in a closed mold pressure holding state for 5 to 10 seconds, and then the mold is opened to take out the formed parts for natural air cooling. Compared with stamping with a normal temperature mold, stamping with a high temperature mold can reduce the stress difference between the upper and lower surfaces of the part, improve the rebound of the part, and have better dimensional accuracy. The strength of the part after heat treatment in the baking paint embodiment can also reach a level equivalent to that of the T6 state.

The test method of this application uses 7075-T6 plates with a thickness of 2 mm, and conducts stamping experiments at different plate temperatures (150 and 200°C) and different mold temperatures (25/150/200/250/300°C). The formed parts are heat treated (185°C/20min) to simulate the paint baking example used by general car manufacturers. The tensile strength test data of the parts are shown in Table 1. [Table 1] Embodiment Sheet temperature (℃) Upper die (punch) temperature (℃) Lower die (die) temperature (℃) Paint Heat Treatment Example Parts tensile strength (MPa) 1 150 25 25 185℃ 20min 537 2 150 150 548 3 200 546 4 250 541 5 300 579 6 200 25 25 574 7 200 200 573 8 250 572 9 300 571

It can be observed from the data in Table 1 that the overall strength of the parts when the plate temperature is heated to 200°C and then stamped (571 to 574 MPa) is higher than the data when the plate temperature is heated to 150°C (537 to 579 MPa). The data of Examples 1 to 4 show that when the plate temperature and the mold temperature are not high enough, the strength of the formed parts decreases (537 to 541 MPa).

In contrast, Examples 5 to 9 are formed at relatively high plate and mold temperatures, and the strength of the parts obtained is close to the strength level of the original material T6 (572 MPa), which means that the material may experience re-dissolution and re-precipitation of the strengthening phase during the heating/pressing and paint-baking heat treatment processes. Compared with traditional warm forming that causes strength loss, this process has the advantage of maintaining part strength.

Next, the manufacturing method of the present application also has the advantage of improved rebound compared to traditional warm forming (Example 1). The scanning results of the part dimensional accuracy of Examples 1 to 9 are shown in Figures 2 to 10. The numbers marked on the parts represent the measured deviation between the actual part and the standard drawing size. It can be observed that the scanning results at plate temperatures of 150°C and 200°C both show that the part dimensional accuracy of Example 1 (Figure 2) and Example 6 (Figure 7) using traditional warm forming room temperature molds for stamping is the worst, and a maximum deviation of +1.77mm is observed at the bottom of the side wall and the flange. As the temperature of the die increases (Figures 3 to 6 and Figures 8 to 10), the dimensional accuracy of the parts is improved. The parts stamped by Example 9 (Figure 10, plate temperature 200°C, punch temperature 200°C, die temperature 300°C) have the best dimensional accuracy, and the maximum deviation observed at the bottom end of the side wall and the flange is reduced to +0.28mm.

Furthermore, the present invention provides a high-strength aluminum alloy manufactured by the manufacturing method of the high-strength aluminum alloy as described above, wherein the high-strength aluminum alloy has a tensile strength between 541 MPa and 579 MPa, and a rebound amount that can be controlled between -0.5 mm and 0.5 mm.

Although the present invention has been disclosed with preferred embodiments, they are not intended to limit the present invention. Any person skilled in the art may make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the scope defined in the attached patent application.

101～105: Steps

[Figure 1]: Schematic flow chart of the manufacturing method of the high-strength aluminum alloy of the embodiment of the present invention. [Figure 2]: Dimensional accuracy scan of the high-strength aluminum alloy part of the embodiment 1 of the present invention (plate temperature 150°C, punch 25°C, die 25°C). [Figure 3]: Dimensional accuracy scan of the high-strength aluminum alloy part of the embodiment 2 of the present invention (plate temperature 150°C, punch 150°C, die 150°C). [Figure 4]: Dimensional accuracy scan of the high-strength aluminum alloy part of the embodiment 3 of the present invention (plate temperature 150°C, punch 150°C, die 200°C). [Figure 5]: Dimensional accuracy scan of the high-strength aluminum alloy part of the embodiment 4 of the present invention (plate temperature 150°C, punch 150°C, die 250°C). [Figure 6]: Dimensional accuracy scan of high-strength aluminum alloy parts of Example 5 of the present invention (plate temperature 150°C, punch 150°C, die 300°C). [Figure 7]: Dimensional accuracy scan of high-strength aluminum alloy parts of Example 6 of the present invention (plate temperature 200°C, punch 25°C, die 25°C). [Figure 8]: Dimensional accuracy scan of high-strength aluminum alloy parts of Example 7 of the present invention (plate temperature 200°C, punch 200°C, die 200°C). [Figure 9]: Dimensional accuracy scan of high-strength aluminum alloy parts of Example 8 of the present invention (plate temperature 200°C, punch 200°C, die 250°C). [Figure 10]: Dimensional accuracy scan of the high-strength aluminum alloy parts of Example 9 of the present invention (plate temperature 200°C, punch 200°C, die 300°C).

101~105: Steps

Claims (10)

A method for manufacturing a high-strength aluminum alloy comprises the following steps: (a) providing an aluminum alloy material; (b) subjecting the aluminum alloy material to a solution treatment and an artificial aging treatment; (c) placing the aluminum alloy material subjected to the solution treatment and the artificial aging treatment in a heating device to heat the aluminum alloy to a first temperature of 150°C to 250°C; (d) transferring the aluminum alloy material heated to the first temperature to a heated mold within a transfer time, wherein the mold surface temperature of an upper mold and a lower mold of the heated mold is controlled at a second temperature of 150°C to 300°C; (e) After the upper mold and the lower mold of the heated mold are closed, the aluminum alloy material is pressurized for less than 10 seconds, and then the mold is opened to take out the aluminum alloy material to obtain an aluminum alloy part with high strength and low rebound. A method for manufacturing a high-strength aluminum alloy as described in claim 1, wherein the aluminum alloy material reaches a T4 or T6 state after the solution treatment and the artificial aging treatment. A method for manufacturing a high-strength aluminum alloy as described in claim 1, wherein the aluminum alloy material is a 6xxx or 7xxx series aluminum alloy material. A method for manufacturing a high-strength aluminum alloy as described in claim 1, wherein the first temperature is 150°C to 250°C. A method for manufacturing a high-strength aluminum alloy as described in claim 1, wherein when the aluminum alloy material reaches the first temperature, the aluminum alloy material is transferred to the heated mold without maintaining the temperature. The method for manufacturing a high-strength aluminum alloy as described in claim 1 comprises the following steps: after the aluminum alloy component is opened and taken out of the mold, the aluminum alloy component is subjected to a natural air cooling step. A method for manufacturing a high-strength aluminum alloy as described in claim 1, wherein the heated mold is heated by a heating rod embedded in the mold. A method for manufacturing a high-strength aluminum alloy as described in claim 1, wherein the die surface temperature of the upper die is different from the die surface temperature of the lower die. A method for manufacturing a high-strength aluminum alloy as described in claim 1, wherein the die surface temperature of the upper die is the same as the die surface temperature of the lower die. A high-strength aluminum alloy manufactured by the method for manufacturing a high-strength aluminum alloy as described in claims 1 to 9, wherein the high-strength aluminum alloy has a tensile strength between 541 MPa and 579 MPa, and a rebound amount controlled between -0.5 mm and 0.5 mm.