6xxx-series aluminum alloy plate suitable for hot stamping forming and formability integrated process, and preparation method therefor and use thereof

Abstract

Provided are a 6xxx-series aluminum alloy plate suitable for a hot stamping forming and formability integrated process and a preparation method and application thereof. The aluminum alloy plate includes the following chemical components in percentage by weight: 0.9%~1.45% of Si, 0.8%~1.35% of Mg, 0.5%~1.2% of Cu, 0~0.4% of Mn, 0~0.5% of Zn, 0~0.13% of Cr, 0~0.12% of Zr, 0~0.08% of Ti, 0~0.5% of Fe, and the balance of Al and inevitable impurity elements, herein the total content of Mn, Cr and Zr is ≤0.4%.The 6xxx aluminum alloy plate provided in the present disclosure has rapid solid solubility and low quenching sensitivity, and has good hot stamping formability and relatively good artificial age hardening properties such as baking varnish, so the 6xxx aluminum alloy plate may be well applied to the hot stamping forming and formability integrated process, and has wide application prospects in manufacturing of automobile parts.

Description

[0001] This application is based upon and claims priority to Chinese application CN202211597647.8, filed on December 14, 2022, the disclosure of which is hereby incorporated by reference again in its entirety.Technical Field

[0002] The present disclosure belongs to the technical field of non-ferrous metal aluminum alloys and relates to a 6xxx-series aluminum alloy plate suitable for a hot stamping forming and formability integrated process and a preparation method and application thereof.Background

[0003] With the rapid development of the automobile industry, brought pollution problems become increasingly severe, various countries in the world constantly strengthen the awareness of energy conservation and emission reduction, and the demand for lightweight automobiles become increasingly urgent. Aluminum alloy materials have the characteristics of low density, high specific strength, good corrosion resistance, good processability and the like, and are increasingly used in material selection for automobile lightweight designs. Herein, 5xxx-series and 6xxx-series aluminum alloy plates with relatively low strength but good formability are more commonly used in automobile body covering parts. In the traditional production of the 6xxx-series aluminum alloy automobile body covering parts, aluminum alloys are usually rolled into thin plates in factories, and after solid solution and pre-aging treatment, it is cold-stamped into parts in automobile main engine factories. The entire process is cumbersome, the cycle is long, and there are significant differences in the performance of the different alloys after hot treatment. At the same time, for the parts with relatively complex shapes and high requirements for dimensional accuracy and strength, simply using a traditional cold stamping forming method may result in defects such as cracking and problems such as difficulty in ensuring accuracy. However, if a higher temperature range (200 °C to 500 °C) is used, the increase in the temperature may increase the formability of the alloy plates, and it is beneficial for part forming.

[0004] In response to the above complex automobile body part preparation problems, a newly developed hot stamping forming and formability integrated process is available, it combines hot treatment and hot forming of the aluminum alloys, and relies on the same set of molds for aging "forming" and "controlling". By using this method, it may be guaranteed that the plasticity of materials in the forming process is improved while the material strength is not reduced. This method quickly transfers the aluminum alloy plate after the solid solution to a water-cooled mold, then quickly closes the mold to form, and then maintains the closed state of the mold to complete the quenching of the parts inside the mold. Finally, aging treatment such as baking varnish is performed to improve the strength. This process is currently a very promising new process in the hot forming of the aluminum alloy plate, and it may solve problems such as poor plasticity in material forming, large rebound, and shape distortion during the hot treatment. Complex parts may also be completed by one-time stamping, and the number of the parts is reduced.

[0005] However, although the hot stamping forming and formability integrated process is already commercialized and deep drawn parts are produced, the overall process is still in a start-up stage, and researches on high-strength aluminum alloy materials specifically developed for hot stamping processes are not publicly reported yet. Based on the process characteristics of hot stamping, the materials are required to meet the requirements of high-temperature short-term solid solution, low quenching sensitivity, good hot stamping formability, and high baking varnish hardening process adaptability. In response to this process, combined with the requirements of subsequent baking varnish processes, a specialized aluminum alloy material with high formability is developed, it may fully leverage the advantages of the hot stamping process, to obtain the aluminum alloy parts with the complex shapes, and broaden the selection range of the aluminum alloy materials on the automobile bodies.Summary

[0006] A main purpose of the present disclosure is to provide a 6xxx-series aluminum alloy plate suitable for a hot stamping forming and formability integrated process and a preparation method and application thereof, as to solve the problem of 6xxx-series aluminum alloy materials in existing technologies that are difficult to balance high-temperature short-term solid solution, low quenching sensitivity, good hot stamping formability and high baking varnish hardening process, thus it is difficult to apply to the hot stamping forming and formability integrated process.

[0007] In order to achieve the above purpose, according to one aspect of the present disclosure, a 6xxx-series aluminum alloy plate suitable for a hot stamping forming and formability integrated process is provided, and its chemical components, in percentage by weight, include: 0.9%~1.45% of Si, 0.8%~1.35% of Mg, 0.5%~1.2% of Cu, 0~0.4% of Mn, 0~0.5% of Zn, 0~0.13% of Cr, 0~0.12% of Zr, 0~0.08% of Ti, 0~0.5% of Fe, and the balance of Al and inevitable impurity elements, herein the total content of Mn, Cr and Zr is ≤0.4%.

[0008] Further, its chemical components, in percentage by weight, include: 1.0%~1.35% of Si, 0.95%~1.2% of Mg, 0.6%~0.9% of Cu, 0~0.4% of Zn, 0.15%~0.35% of Mn, 0~0.06% of Cr, 0~0.06% of Zr, 0~0.05% of Ti, 0~0.4% of Fe, the balance of Al and inevitable impurity elements, herein the total content of Mn, Cr, and Zr is ≤0.35%.

[0009] Further, its chemical components, in percentage by weight, include: 1.09%~1.33% of Si, 0.99%~1.17% of Mg, 0.59%~0.89% of Cu, 0.12%~0.32% of Mn, 0.098%~0.435% of Zn, 0.0015%~0.0451% of Cr, 0.0006%~0.0405% of Zr, 0.025%~0.027% of Ti, 0.25%~0.30% of Fe, the balance of Al and inevitable impurity elements, herein the total content of Mn, Cr, and Zr is ≥0.123% and ≤0.323%.

[0010] Further, its chemical components, in percentage by weight, include: 1.09%~1.33% of Si, 1.01%~1.17% of Mg, 0.76%~0.89% of Cu, 0.12%~0.32% of Mn, 0.112%~0.435% of Zn, 0.0015%~0.0019% of Cr, 0.0006%~0.0012% of Zr, 0.025%~0.027% of Ti, 0.25%~0.30% of Fe, the balance of Al and inevitable impurity elements, herein the total content of Mn, Cr, and Zr is ≥0.123% and ≤0.323%.

[0011] Further, the yield strength of the plate after solid solution aging treatment is ≥210 MPa, the tensile strength is ≥310 MPa, and the elongation rate is ≥15.5%, herein the solid solution aging treatment step includes: it is held at 545~565 °C for 1~15 min and solid solution is performed, it is cooled; subsequently, single-stage baking varnish is performed at 185 °C for 25 min, or multi-stage baking varnish is performed at 185 °C for 25 min and 150 °C for 30 min and 140 °C for 60 min.

[0012] Further, the plate is a cold-rolled, O-state, or T4-state plate with a thickness of 0.5~5.0 mm.

[0013] According to another aspect of the present disclosure, a preparation method for the above 6xxx-series aluminum alloy plate suitable for the hot stamping forming and formability integrated process is provided, and the preparation method includs the following steps: Step 1, an alloy is smelted and cast according to a component proportion, to form an ingot; Step 2, a two-stage homogenization treatment is performed on the ingot sequentially, to obtain a homogenized ingot; Step 3, the homogenized ingot is hot-rolled, to form a hot-rolled plate; and Step 4, the hot-rolled plate is cold-rolled, to obtain the 6xxx-series aluminum alloy plate suitable for the hot stamping forming and formability integrated process.

[0014] Further, in the Step 2, the two-stage homogenization treatment process includes: the ingot is held at 520~540 °C for 6~12 h, and first-stage homogenization is performed; subsequently, it is held at 550~570 °C for 8~16 h, and second-stage homogenization is performed, to obtain the homogenized ingot; herein, the heating rate between the first-stage homogenization and the second-stage homogenization is 10~50 °C / h.

[0015] Further, in the Step 3, the hot-rolling process includes: after the homogenized ingot is held at 520~550 °C for 1~5 h, it is hot-roughed, hot-finished, final-rolled, coiled, and air-cooled sequentially, and the hot-finishing thickness is controlled at 4~8 mm and the final rolling temperature is controlled at 250~350 °C. Further, in the Step 4, the cold-rolling amount in the cold-rolling process is controlled to 40%~70%. According to another aspect of the present disclosure, an automobile part is further provided, and it is prepared from the above 6xxx-series aluminum alloy plate suitable for the hot stamping forming and formability integrated process.

[0016] The 6xxx aluminum alloy plate provided in the present disclosure has rapid solid solubility and low quenching sensitivity, and has good hot stamping formability and relatively good artificial age hardening properties such as baking varnish, so it may be well applied to the hot stamping forming and formability integrated process, and has wide application prospects in manufacturing of automobile parts.Brief Description of the Drawings

[0017] Drawings of the description for constituting a part of the present disclosure are used to provide further understanding of the present disclosure. Schematic embodiments of the present disclosure and descriptions thereof are used to explain the present disclosure and do not constitute improper limitations on the present disclosure. In the drawings: Fig. 1 shows a metallographic photograph of a grain structure of an aluminum alloy plate after hot treatment in Embodiment 1; Fig. 2 shows a metallographic photograph of a grain structure of an aluminum alloy plate after hot treatment in Embodiment 3; Fig. 3 shows a metallographic photograph of a grain structure of an aluminum alloy plate after hot treatment in Embodiment 4; Fig. 4 shows a metallographic photograph of a grain structure of an aluminum alloy plate after hot treatment in Embodiment 5; Fig. 5 shows a metallographic photograph of a grain structure of an aluminum alloy plate after hot treatment in Embodiment 6; Fig. 6 shows a metallographic photograph of a grain structure of an aluminum alloy plate after hot treatment in Contrast example 1; Fig. 7 shows a metallographic photograph of a grain structure of an aluminum alloy plate after hot treatment in Contrast example 2; and Fig. 8 shows a metallographic photograph of a grain structure of an aluminum alloy plate after hot treatment in Contrast example 4. Detailed Description of the Embodiments

[0018] It should be noted that embodiments in the present disclosure and features in the embodiments may be combined with each other without conflicting. The present disclosure is described in detail below with reference to the drawings and in combination with the embodiments.

[0019] As described in the background section, the 6xxx-series aluminum alloy materials in the existing technologies are difficult to balance high-temperature short-term solid solution, low quenching sensitivity, good hot stamping formability and high baking varnish hardening process, thus it is difficult to apply to the hot stamping forming and formability integrated process. In order to solve the above problem, the present disclosure provides a 6xxx-series aluminum alloy plate suitable for a hot stamping forming and formability integrated process, and its chemical components, in percentage by weight, include: 0.9%~1.45% of Si, 0.8%~1.35% of Mg, 0.5%~1.2% of Cu, 0~0.4% of Mn, 0~0.5% of Zn, 0~0.13% of Cr, 0~0.12% of Zr, 0~0.08% of Ti, 0~0.5% of Fe, and the balance of Al and inevitable impurity elements, herein the total content of Mn, Cr and Zr is ≤0.4%.

[0020] The above 6xxx aluminum alloy plate has rapid solid solubility and low quenching sensitivity, and has good hot stamping formability and relatively good artificial age hardening properties such as baking varnish, so it may be well applied to the hot stamping forming and formability integrated process, and has wide application prospects in manufacturing of automobile parts.

[0021] Herein, Mn, Cr, and Zr are trace elements that control the grain size and may exist individually or simultaneously, but its total amount needs to be controlled to be ≤0.4%.

[0022] In order to further improve the comprehensive performance of 6xxx aluminum alloy plate and make it more suitable for applications in the hot stamping forming and formability integrated process, in a preferred implementation mode, its chemical components, in percentage by weight, include: 1.0%~1.35% of Si, 0.95%~1.2% of Mg, 0.6%~0.9% of Cu, 0~0.4% of Zn, 0.15%~0.35% of Mn, 0~0.06% of Cr, 0~0.06% of Zr, 0~0.05% of Ti, 0~0.4% of Fe, the balance of Al and inevitable impurity elements, herein the total content of Mn, Cr, and Zr is ≤0.35%.

[0023] Based on the requirements for the properties of the aluminum alloy material using the hot stamping forming and formability integrated process, the present disclosure controls the content of main elements, to ensure that the second phase full solid solution is achieved within a short solid solution holding time. At the same time, based on the continuous baking varnish hardening effect, the content of Mg, Si, and Cu elements is controlled, and an aging precipitation strengthening mechanism is fully utilized to ensure sufficient aging hardening. An appropriate amount of the Zn element is added simultaneously, to assist in promoting the baking varnish hardening effect.

[0024] The present disclosure strictly controls the content of trace elements Mn, Cr, and Zr, to ensure low quenching sensitivity of the alloy. At the same time, the grain size is controlled, so that the plate has a better grain structure and the final performance of the alloy may not be decreased due to the quenching sensitivity.

[0025] The alloy components provided in the present disclosure has certain control on the content of the impurity Fe element. On the one hand, it aims to reduce the overall raw material cost and subsequent usage cost of the alloy, while the content is controlled not to be too high so that a coarse crystalline phase is formed in the structure, which is not beneficial for the performance and formability of the plate.

[0026] Preferably, its chemical components, in percentage by weight, include: 1.09%~1.33% of Si, 0.99%~1.17% of Mg, 0.59%~0.89% of Cu, 0.12%~0.32% of Mn, 0.098%~0.435% of Zn, 0.0015%~0.0451% of Cr, 0.0006%~0.0405% of Zr, 0.025%~0.027% of Ti, 0.25%~0.30% of Fe, the balance of Al and inevitable impurity elements, herein the total content of Mn, Cr, and Zr is ≥0.123% and ≤0.323%.

[0027] Most preferably, its chemical components, in percentage by weight, include: 1.09%~1.33% of Si, 1.01%~1.17% of Mg, 0.76%~0.89% of Cu, 0.12%~0.32% of Mn, 0.112%~0.435% of Zn, 0.0015%~0.0019% of Cr, 0.0006%~0.0012% of Zr, 0.025%~0.027% of Ti, 0.25%~0.30% of Fe, the balance of Al and inevitable impurity elements, herein the total content of Mn, Cr, and Zr is ≥0.123% and ≤0.323%.

[0028] The yield strength of the above 6xxx aluminum alloy plate after solid solution aging treatment is ≥210 MPa, the tensile strength is ≥310 MPa, and the elongation rate is ≥15.5%, herein the solid solution aging treatment step includes: it is held at 545~565 °C for 1~15 min and solid solution is performed, it is cooled; subsequently, single-stage baking varnish is performed at 185 °C for 25 min, or multi-stage baking varnish is performed at 185 °C for 25 min and 150 °C for 30 min and 140 °C for 60 min. The above cooling process may be air-cooling, mold-cooling, or water-cooling.

[0029] Preferably, the plate is a cold-rolled, O-state, or T4-state plate with a thickness of 0.5~5.0 mm. In conclusion, the present disclosure provides a 6xxx-series aluminum alloy plate specifically used for the manufacturing of high-strength automobile body aluminum parts suitable for a hot stamping intra-mold forming-quenching process combined with a continuous baking varnish process, and the plate is the cold-rolled, O-state, or T4-state plate with the thickness of 0.5~5.0 mm.

[0030] According to another aspect of the present disclosure, a preparation method for the above 6xxx-series aluminum alloy plate suitable for the hot stamping forming and formability integrated process is provided, and the preparation method includs the following steps: Step 1, an alloy is smelted and cast according to a component proportion, to form an ingot; Step 2, two-stage homogenization treatment is performed on the ingot sequentially, to obtain a homogenized ingot; Step 3, the homogenized ingot is hot-rolled, to form a hot-rolled plate; and Step 4, the hot-rolled plate is cold-rolled, to obtain the 6xxx-series aluminum alloy plate suitable for the hot stamping forming and formability integrated process.

[0031] The above 6xxx aluminum alloy plate provided in the present disclosure has rapid solid solubility and low quenching sensitivity, and has good hot stamping formability and relatively good artificial age hardening properties such as baking varnish, so it may be well applied to the hot stamping forming and formability integrated process, and has wide application prospects in manufacturing of automobile parts.

[0032] In order to further improve the homogenization effect and enhance the performance of the plate, in a preferred implementation mode, in the Step 2, the two-stage homogenization treatment process includes: the ingot is held at 520~540 °C for 6~12 h, and first-stage homogenization is performed; subsequently, it is held at 550~570 °C for 8~16 h, and second-stage homogenization is performed, to obtain the homogenized ingot; herein, the heating rate between the first-stage homogenization and the second-stage homogenization is 10~50 °C / h. In the specific implementation process, after the two-stage homogenization is completed, it may be directly rolled, or air-cooled or wind-cooled to a room temperature.

[0033] In a preferred implementation mode, in the Step 3, the hot-rolling process includes: after the homogenized ingot is held at 520~550 °C for 1~5 h, it is hot-roughed, hot-finished, final-rolled, coiled, and air-cooled sequentially, and the hot-finishing thickness is controlled at 4~8 mm and the final rolling temperature is controlled at 250~350 °C.

[0034] More preferably, in the Step 4, the cold-rolling amount in the cold-rolling process is controlled to 40%~70%.

[0035] According to another aspect of the present disclosure, an automobile part is further provided, and it is prepared from the above 6xxx-series aluminum alloy plate suitable for the hot stamping forming and formability integrated process. Preferably the above hot stamping forming and formability integrated process is the hot stamping intra-mold forming-quenching process combined with the continuous baking varnish process.

[0036] The present disclosure is further described in detail below in combination with specific embodiments, and these embodiments should not be construed as limiting the scope of protection claimed by the present disclosure.Embodiment 1

[0037] This embodiment provided a preparation process for a 6xxx-series aluminum alloy plate, and it was specifically as follows.

[0038] An alloy ingot was prepared according to a component proportion, and after the alloy ingot preparation was completed, the following two-stage homogenization treatment was performed: the alloy ingot was held at 525 °C for 10 h, then held at 560 °C for 12 h, a heating rate of the homogenization treatment was 30 °C / h, and a homogenized ingot was directly rolled; before hot-rolling, the homogenized ingot was held at 525 °C for 3 h, and then hot-roughed and hot-finished to a thickness of 4 mm, the final-rolling temperature was 260 °C, and then the hot-rolled plate was coiled and air-cooled to a room temperature; subsequently, the hot-rolled plate with the thickness of 4 mm was cold-rolled to a required thickness, and the cold-rolling amount was controlled at 70%. The alloy components and thickness state were shown in Table 1.Embodiments 2 to 7

[0039] The difference from Embodiment 1 was that: the alloy components were different, see Table 1 for details.Embodiment 8

[0040] The difference from Embodiment 1 was that: the alloy components were different, see Table 1 for details, the preparation process parameters were different, and it was specifically as follows.

[0041] An alloy ingot was prepared according to a component proportion, and after the alloy ingot preparation was completed, the following two-stage homogenization treatment was performed: the alloy ingot was held at 520 °C for 12 h, then held at 550°C for 16 h, a heating rate of the homogenization treatment was 50 °C / h, and the alloy ingot was air-cooled; before hot-rolling, a homogenized ingot was held at 520 °C for 5 h, and then hot-roughed and hot-finished to a thickness of 4 mm, the final-rolling temperature was 250 °C, and then the hot-rolled plate was coiled and air-cooled to a room temperature; subsequently, the hot-rolled plate with the thickness of 8 mm was cold-rolled to a required thickness, and the cold-rolling amount was controlled at 62.5%. The alloy components and thickness state were shown in Table 1.Embodiment 9

[0042] The difference from Embodiment 1 was that: the alloy components were different, see Table 1 for details, the preparation process parameters were different, and it was specifically as follows.

[0043] An alloy ingot was prepared according to a component proportion, and after the alloy ingot preparation was completed, the following two-stage homogenization treatment was performed: the alloy ingot was held at 540 °C for 6 h, then held at 570 °C for 8 h, a heating rate of the homogenization treatment was 10 °C / h, and a homogenized ingot was directly hot-rolled; before hot-rolling, the homogenized ingot was held at 550°C for 1 h, and then hot-roughed and hot-finished to a thickness of 4 mm, the final-rolling temperature was 350 °C, and then the hot-rolled plate was coiled and air-cooled to a room temperature; subsequently, the hot-rolled plate with the thickness of 4 mm was cold-rolled to a required thickness, and the cold-rolling amount was controlled at 70%. The alloy components and thickness state were shown in Table 1.Embodiment 10

[0044] The difference from Embodiment 1 was that: the alloy components were different, see Table 1 for details, the preparation process parameters were different, and it was specifically as follows.

[0045] An alloy ingot was prepared according to a component proportion, and after the alloy ingot preparation was completed, the following two-stage homogenization treatment was performed: the alloy ingot was held at 530 °C for 9 h, then held at 560 °C for 10 h, a heating rate of the homogenization treatment was 30 °C / h, and a homogenized ingot was directly hot-rolled; before hot-rolling, the homogenized ingot was held at 550 °C for 2 h, and then hot-roughed and hot-finished to a thickness of 4 mm, the final-rolling temperature was 280 °C, and then the hot-rolled plate was coiled and air-cooled to a room temperature; subsequently, the hot-rolled plate with the thickness of 4 mm was cold-rolled to a required thickness, and the cold-rolling amount was controlled at 70%. The alloy components and thickness state were shown in Table 1.Contrast examples 1 to 4

[0046] The difference from Embodiment 1 was that: the alloy components were different, see Table 1 for details. Table 1: Plate component (wt%)SiMgCuZnMnCrZrTiFeAlStateEmbodiment 11.091.040.820.1120.120.00190.00090.0250.30Balance1.2 mm cold-rolling stateEmbodiment 21.331.170.890.1140.160.00150.00080.0260.25Balance1.2 mm cold-rolling stateEmbodiment 31.271.060.760.1230.320.00190.00120.0270.30Balance1.2 mm cold-rolling stateEmbodiment 41.111.010.840.4350.170.00170.00060.0250.25Balance1.2 mm cold-rolling stateEmbodiment 51.321.110.860.1350.160.00230.04050.0260.28Balance1.2 mm cold-rolling stateEmbodiment 61.311.090.800.1460.180.04510.00100.0270.25Balance1.2 mm cold-rolling stateEmbodiment 71.190.990.590.2320.130.00240.00080.0270.27Balance1.2 mm cold-rolling stateEmbodiment 81.171.090.830.1010.180.00170.00110.0260.26Balance3.0 mm cold-rolling stateEmbodiment 91.231.060.780.1020.210.00160.00100.0260.25Balance1.2 mm T4-stateEmbodiment 101.281.120.810.0990.170.00190.00090.0270.25Balance1.2 mm O-stateContrast example 11.050.940.710.2700.430.15000.00050.0270.29Balance1.2 mm cold-rolling stateContrast example 21.191.040.150.0220.130.02700.00020.0260.27Balance1.2 mm cold-rolling stateContrast example 31.250.990.110.0190.460.00040.00060.0280.28Balance1.2 mm cold-rolling stateContrast example 41.240.990.100.0190.130.00110.12800.0270.25Balance1.2 mm cold-rolling state

[0047] Based on the characteristics of the hot stamping forming and formability integrated process, the alloy cold-rolled plates in the embodiments and contrast examples were subjected to rapid solid solution treatment at 545~565 °C, the holding time was 1~15 min, and three different quenching modes, namely water-cooling quenching (WQ), mold-cooling quenching (MQ), or air-cooling quenching (AQ), were respectively performed, herein the water-cooling and the air-cooling were extremely fast and extremely slow cooling rates respectively, and the mold-cooling was a commonly used cooling mode in the hot stamping forming and formability integrated process. Subsequently, the plates were subjected to single-stage baking varnish treatment (BH) at 185 °C for 25 min or multi-stage baking varnish treatment (Multi-BH) at 185 °C for 25 min and 150 °C for 30 min and 140 °C for 60 min. A mechanical test was conducted on the plates treated with the different processes, and test results were shown in Table 2. Table 2: Mechanical properties of platesAlloyTreatment processYield strength MPaTensile strength MPaElongation rate%Embodiment 1WQ-BH22734025.7MQ-BH22134526.7WQ+Multi-BH26836425.3MQ-Multi-BH26536625.8AQ+Multi-BH29935917.3Embodiment 2WQ-BH23434627.2MQ-BH22934025.8WQ+Multi-BH27036925.8MQ-Multi-BH26837025.7AQ+Multi-BH28735116.8Embodiment 3WQ-BH24235119.5MQ-BH22332425.0WQ+Multi-BH27637525.0MQ-Multi-BH25936425.5AQ+Multi-BH25532915.3Embodiment 4WQ-BH24535827.0MQ-BH23334822.2WQ+Multi-BH27437625.0MQ-Multi-BH27136821.3AQ+Multi-BH26934315.8Embodiment 5WQ-BH22633625.0MQ-BH21332224.5WQ+Multi-BH26236424.0MQ-Multi-BH24835523.5AQ+Multi-BH24933016.5Embodiment 6WQ-BH22833423.0MQ-BH21233023.8WQ+Multi-BH26035822.2MQ-Multi-BH24735423.5AQ+Multi-BH24633117.2Embodiment 7WQ-BH21832423.8MQ-BH21631726.0WQ+Multi-BH24234925.0MQ-Multi-BH24334425.2AQ+Multi-BH24833916.5Embodiment 8WQ-BH23931420.5MQ-BH21831924.6WQ+Multi-BH27237025.4MQ-Multi-BH25536226.1AQ+Multi-BH25332415.6Embodiment 9WQ-BH24331819.6MQ-BH22532325.0WQ+Multi-BH27037426.0MQ-Multi-BH26036625.3AQ+Multi-BH25432916.3Embodiment 10WQ-BH24232120.3MQ-BH22432525.5WQ+Multi-BH27337125.8MQ-Multi-BH26136424.8AQ+Multi-BH25432115.8Contrast example 1WQ-BH25236619.0MQ-BH22832922.2WQ+Multi-BH28137921.0MQ-Multi-BH24936520.5AQ+Multi-BH19329015.5Contrast example 2WQ-BH19630029.0MQ-BH19129122.0WQ+Multi-BH23732424.0MQ-Multi-BH23431720.2AQ+Multi-BH23130916.7Contrast example 3WQ-BH22632017.0MQ-BH17526025.0WQ+Multi-BH25334819.0MQ-Multi-BH21131224.8AQ+Multi-BH19926917.0Contrast example 4WQ-BH20129525.3MQ-BH17928726.3WQ+Multi-BH24732821.0MQ-Multi-BH22131023.5AQ+Multi-BH17324415.2

[0048] From Table 2, it may be seen that the alloys in the embodiments of the present disclosure all have good mechanical properties and have good single-stage and multi-stage baking varnish hardening effects. Compared with the water-cooled, mold-cooled, and air-cooled samples of the alloys in the contrast examples, it may be seen that the quenching sensitivity of the plates in the embodiments is relatively low, and the properties of the mold-cooled and water-cooled plates are comparable, even the air-cooled samples do not show significant strength degradation. The plates in the embodiments all achieve the yield strength >210 MPa, the tensile strength >310 MPa, and the elongation rate >15.5%.

[0049] Specifically, in Embodiments 1 and 2, the content of Cu element is relatively high, the content of Mn is relatively low, and there are almost no trace elements. The alloy baking varnish hardening is significant, the mechanical properties are relatively high after the baking varnish, and the quenching sensitivity of the alloys is very low. The strength of the alloy after air-cooling is similar to that of the water-cooled and mold-cooled plates. In Embodiment 7, the content of Cu element is relatively low, and the overall alloy strength is slightly decreased. After the multi-stage baking varnish, the precipitation of a precipitated phase of the alloy plates in Embodiments 1 and 2 is more complete, the strength of the plates is significantly improved compared to the single-stage baking varnish, and the high Cu alloy is more beneficial for the multi-stage baking varnish. The strength of the low Cu alloy in Contrast example 2 is significantly lower than that of the embodiments, and the baking varnish hardening effect is not ideal. The increase of the content of Cu element mainly enhances the precipitation strengthening of the alloy, and has no significant effect on the grain size of the alloy, it is about 40 µm (metallographic photographs of the plates in Embodiment 1 and Contrast example 2 are shown in Fig. 1 and Fig. 7).

[0050] The addition of the Mn element in the alloy may assist in regulating the grain structure, while a dispersed phase precipitated is beneficial for improving the material properties. The alloy with relatively high Mn content exhibits certain advantages in strength after short-term single-stage baking varnish, but does not have significant additional baking varnish hardening effect for the longer multi-stage baking varnish. Moreover, the addition of excessive Mn may significantly increase the quenching sensitivity of the alloy, and it is not beneficial to the alloy integrated mold quenching process. As shown in the results, compared with Embodiments 1 and 2, Embodiment 3 shows a slight decrease in grain size after the Mn content is increased (Fig. 2), but the quenching sensitivity of the plate is improved. Excessive Mn in Contrast examples 1 and 3 results in very high quenching sensitivity of the alloy, and the strength of the alloy is decreased significantly after air-cooling.

[0051] The addition of an appropriate amount of the Zn element in Embodiment 4 helps to assist precipitation strengthening. After the baking varnish treatment, the strength of the plate in Embodiment 4 is improved compared to Embodiments 1 and 2, the quenching sensitivity is slightly increased, and the alloy grain size remains basically unchanged (Fig. 3). The appropriate amount of the Zn element is beneficial for improving the performance of the plate without affecting its quenching sensitivity.

[0052] A trace amount of the Zr element in the alloy of Embodiment 5 assists in regulating the grain size. Compared with the embodiments without the Zr element, the grain size is reduced (as shown in Fig. 4), but at the same time, it also increases the quenching sensitivity of the alloy and reduces the mechanical properties of the mold-cooled and water-cooled plates. When excessive Zr is added in Contrast example 4, the grain size of the alloy is significantly decreased, but the quenching sensitivity is also increased significantly, and the final plate performance is reduced (as shown in Fig. 8).

[0053] The alloy in Embodiment 6 contains a trace amount of the Cr element. Compared with the alloys in the embodiments that almost do not contain Cr, the grain size of the plate is regulated to a certain extent (as shown in Fig. 5), but at the same time, it also increases the quenching sensitivity of the alloy. Excessive Cr and Mn elements in Contrast example 1 led to significant reduction in the grain size of the alloy plate (Fig. 6), but it has the very high quenching sensitivity, and finally the performance of the mold-cooled and air-cooled alloys is seriously reduced.

[0054] In conclusion, the addition of the trace elements such as Mn, Zr, and Cr may all have the regulating effect on the grain structure of the alloy, and the grain size is effectively reduced, herein the addition of Mn in the alloy may also improve the alloy performance to a certain extent. But as the content of these elements is increased, the quenching sensitivity of the plate may also be significantly increased, and it is not beneficial for the alloy performance. It is necessary to add an appropriate amount of elements for regulation according to the actual performance situations and the grain structure requirements of the plate. Compared with Embodiment 3, Embodiments 8 to 10 have basically similar alloy components, but the final thickness and state of the prepared plates are different. Embodiment 3 is a 1.2 mm cold-rolled plate, Embodiment 8 is a 3 mm cold-rolled plate, and Embodiments 9 and 10 are T4-state and O-state plates respectively. Although the final plate states are different, the mechanical differences after solid solution baking varnish are not significant, and the quenching sensitivity of the plates is similar.

[0055] In conclusion, the aluminum alloy plates in Embodiments 1 to 4 perform better in terms of the comprehensive performance compared to other embodiments.

[0056] The above descriptions are only preferred embodiments of the present disclosure and are not intended to limit the present disclosure. For those skilled in the art, the present disclosure may have various modifications and variations. Any modifications, equivalent replacements, improvements and the like made within the spirit and principles of the present disclosure shall be contained within the scope of protection of the present disclosure.

Claims

1. A 6xxx-series aluminum alloy plate suitable for a hot stamping forming and formability integrated process, wherein its chemical components, in percentage by weight, comprise: 0.9%~1.45% of Si, 0.8%~1.35% of Mg, 0.5%~1.2% of Cu, 0~0.4% of Mn, 0~0.5% of Zn, 0~0.13% of Cr, 0~0.12% of Zr, 0~0.08% of Ti, 0~0.5% of Fe, and the balance of Al and inevitable impurity elements, wherein the total content of Mn, Cr and Zr is ≤0.4%.

2. The 6xxx-series aluminum alloy plate suitable for the hot stamping forming and formability integrated process according to claim 1, wherein its chemical components, in percentage by weight, comprise: 1.0%~1.35% of Si, 0.95%~1.2% of Mg, 0.6%~0.9% of Cu, 0~0.4% of Zn, 0.15%~0.35% of Mn, 0~0.06% of Cr, 0~0.06% of Zr, 0~0.05% of Ti, 0~0.4% of Fe, the balance of Al and inevitable impurity elements, wherein the total content of Mn, Cr, and Zr is ≤0.35%.

3. The 6xxx-series aluminum alloy plate suitable for the hot stamping forming and formability integrated process according to claim 1, wherein its chemical components, in percentage by weight, comprise: 1.09%~1.33% of Si, 0.99%~1.17% of Mg, 0.59%~0.89% of Cu, 0.12%~0.32% of Mn, 0.098%~0.435% of Zn, 0.0015%~0.0451% of Cr, 0.0006%~0.0405% of Zr, 0.025%~0.027% of Ti, 0.25%~0.30% of Fe, the balance of Al and inevitable impurity elements, wherein the total content of Mn, Cr, and Zr is ≥0.123% and ≤0.323%.

4. The 6xxx-series aluminum alloy plate suitable for the hot stamping forming and formability integrated process according to claim 1, wherein its chemical components, in percentage by weight, comprise: 1.09%~1.33% of Si, 1.01%~1.17% of Mg, 0.76%~0.89% of Cu, 0.12%~0.32% of Mn, 0.112%~0.435% of Zn, 0.0015%~0.0019% of Cr, 0.0006%~0.0012% of Zr, 0.025%~0.027% of Ti, 0.25%~0.30% of Fe, the balance of Al and inevitable impurity elements, wherein the total content of Mn, Cr, and Zr is ≥0.123% and ≤0.323%.

5. The 6xxx-series aluminum alloy plate suitable for the hot stamping forming and formability integrated process according to claim 1, wherein the yield strength of the plate after solid solution aging treatment is ≥210 MPa, the tensile strength of the plate after solid solution aging treatment is ≥310 MPa, and the elongation rate of the plate after solid solution aging treatment is ≥15.5%, wherein the solid solution aging treatment step comprises: holding at 545~565 °C for 1~15 min and performing solid solution, cooling; subsequently, performing single-stage baking varnish at 185 °C for 25 min, or multi-stage baking varnish at 185 °C for 25 min and 150 °C for 30 min and 140 °C for 60 min; and / or, the plate is a cold-rolled, O-state, or T4-state plate with a thickness of 0.5~5.0 mm.

6. A preparation method for the 6xxx-series aluminum alloy plate suitable for the hot stamping forming and formability integrated process according to any one of claims 1 to 5, comprising the following steps: Step 1, smelting and casting an alloy according to a component proportion, to form an ingot; Step 2, performing two-stage homogenization treatment on the ingot sequentially, to obtain a homogenized ingot; Step 3, hot-rolling the homogenized ingot, to form a hot-rolled plate; and Step 4, cold-rolling the hot-rolled plate, to obtain the 6xxx-series aluminum alloy plate suitable for the hot stamping forming and formability integrated process.

7. The preparation method according to claim 6, wherein in the Step 2, the two-stage homogenization treatment comprises: holding the ingot at 520~540 °C for 6~12 h, and performing first-stage homogenization; subsequently, holding at 550~570 °C for 8~16 h, and performing second-stage homogenization, to obtain the homogenized ingot; wherein, the heating rate between the first-stage homogenization and the second-stage homogenization is 10~50 °C / h.

8. The preparation method according to claim 6, wherein in the Step 3, the hot-rolling process comprises: after holding the homogenized ingot at 520~550 °C for 1~5 h, hot-roughing, hot-finishing, coiling, and air-cooling sequentially, wherein the hot-finishing thickness is controlled at 4~8 mm and the final rolling temperature is controlled at 250~350 °C.

9. The preparation method according to any one of claims 6 to 8, wherein in the Step 4, the cold-rolling amount in the cold-rolling process is controlled to 40%~70%.

10. An automobile part, wherein it is prepared from the 6xxx-series aluminum alloy plate suitable for the hot stamping forming and formability integrated process according to any one of claims 1 to 5.

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