A high-strength, lightweight aluminum alloy profile for 6005C photovoltaic frames and its preparation method.

Abstract

This invention discloses a high-strength, lightweight aluminum alloy profile for 6005C photovoltaic frames and its preparation method, relating to the field of solar photovoltaic technology. The chemical composition, by mass percentage, includes: Si 0.7%-0.9%, Fe≤0.16%, Cu≤0.01%, Mn0.3%-0.5%, Mg0.6%-0.8%, Cr≤0.03%, Zn≤0.05%, Ti≤0.05%, with the balance being Al and other unavoidable impurities. This 6005C photovoltaic frame high-strength, lightweight aluminum alloy profile exhibits high tensile strength, sufficient toughness, high hardness, and excellent corrosion resistance and fatigue resistance.

Description

Technical Field

[0001] This invention relates to the field of solar photovoltaic technology, and in particular to a high-strength, lightweight aluminum alloy profile for 6005C photovoltaic frames and its preparation method. Background Technology

[0002] Solar photovoltaic (PV) frames are a crucial component of solar cell modules, primarily serving to protect the modules and provide structural support. Currently, most PV frames are made from 6063 aluminum alloy extruded profiles through anodizing, due to its excellent extrusion formability and easy oxidation properties. However, the strength and corrosion resistance of 6063 aluminum alloy are insufficient to meet the increasingly demanding performance requirements of PV modules. It is in this context that 6005C PV frames have emerged. 6005C aluminum alloy possesses high strength and good corrosion resistance; however, due to its composition and manufacturing process, commercially available 6005C aluminum alloys still have shortcomings in terms of strength, toughness, lightweight design, and cost. Its application in PV frames requires further optimization to meet the demands for high strength and lightweight construction.

[0003] To address the aforementioned issues, Chinese invention patent CN118028665B discloses a high-strength aluminum alloy profile for solar photovoltaic frames and its preparation method, relating to the field of aluminum alloy materials technology. Its chemical composition, by mass percentage, includes: Si 0.60–0.90%, Mg 0.40–0.70%, Fe ≤0.25%, Ti ≤0.10%, Mn ≤0.15%, Cr ≤0.15%, Zn ≤0.10%, Zr ≤0.20%, Cu 0.03–0.10%, with the balance being Al, totaling 100%. This invention, through controlling the content of Si, Fe, Mn, Mg, Cr, Zn, Ti, Zr, and Cu in the aluminum alloy profile and employing a homogenization process, produces an aluminum alloy profile with high strength, high elongation, and excellent corrosion resistance, suitable for the solar photovoltaic frame field. However, its fatigue resistance still needs further improvement.

[0004] It is evident that developing a high-strength, lightweight aluminum alloy profile for 6005C photovoltaic frames with high tensile strength, sufficient toughness, high hardness, excellent corrosion resistance and fatigue resistance, and its preparation method, meets market demand and is of great significance for promoting the development of the solar photovoltaic technology field. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a high-strength, lightweight aluminum alloy profile for photovoltaic frames with high tensile strength, sufficient toughness, high hardness, excellent corrosion resistance and fatigue resistance, as well as its preparation method.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is: a high-strength lightweight aluminum alloy profile for 6005C photovoltaic frames, the chemical composition of which, by mass percentage, includes: Si 0.7%-0.9%, Fe≤0.16%, Cu≤0.01%, Mn0.3%-0.5%, Mg0.6%-0.8%, Cr≤0.03%, Zn≤0.05%, Ti≤0.05%, with the balance being Al and other unavoidable impurities.

[0007] Preferably, the mass percentage of the other unavoidable impurities is ≤0.05%.

[0008] Preferably, the chemical composition of the 6005C photovoltaic frame high-strength lightweight aluminum alloy profile further includes the following components by mass percentage: rare earth elements 0.01%-0.03%, Nb≤0.02%, B 0.001%-0.003%, Sr≤0.01%, Ta0.005%-0.015%, and Hf≤0.01%.

[0009] Preferably, the rare earth elements are Sc, Y, and Pr mixed in a mass ratio of 1:(0.8-1.2):(1-2).

[0010] Another object of the present invention is to provide a method for preparing the high-strength lightweight aluminum alloy profile for photovoltaic frames, comprising the following steps:

[0011] Step S1: Using Al, Al-Si master alloy, Al-Fe master alloy, Al-Cu master alloy, Al-Mn master alloy, Al-Mg master alloy, Al-Cr master alloy, Al-Zn master alloy, Al-Ti master alloy, Al-rare earth element master alloy, Al-Nb master alloy, Al-B master alloy, Al-Sr master alloy, Al-Ta master alloy, and Al-Hf master alloy as raw materials, weigh each raw material according to the mass percentage, add the raw materials to the melting furnace for melting, and then perform refining, slag removal, and degassing treatment to obtain molten metal;

[0012] Step S2: Cast the refined molten metal into round ingots, homogenize them, heat them to 480-500℃, and extrude them to obtain the profiles of the desired shape.

[0013] Step S3: Perform T6 heat treatment on the profile after step S2 to obtain 6005C high-strength lightweight aluminum alloy profile for photovoltaic frames.

[0014] Preferably, the melting temperature in step S1 is 720-760°C.

[0015] Preferably, the temperature for the uniform post-treatment in step S2 is 540-560℃ and the time is 6-8h.

[0016] Preferably, the T6 heat treatment in step S3 includes solution treatment and artificial aging treatment.

[0017] Preferably, the solution treatment temperature is 530-550℃, the holding time is 1-2 hours, and the solution is water quenched.

[0018] Preferably, the temperature of the artificial aging treatment is 160-180℃, and the holding time is 5-7h.

[0019] Due to the application of the above technical solution, the present invention has the following beneficial effects:

[0020] (1) The preparation method of the 6005C photovoltaic frame high-strength lightweight aluminum alloy profile disclosed in this invention is simple in preparation process, convenient in operation and control, high in preparation efficiency and finished product qualification rate, low in dependence on equipment, suitable for continuous large-scale production, and has high promotion and application value.

[0021] (2) The high-strength lightweight aluminum alloy profile for photovoltaic frames disclosed in this invention comprises, by mass percentage: Si 0.7%-0.9%, Fe≤0.16%, Cu≤0.01%, Mn 0.3%-0.5%, Mg 0.6%-0.8%, Cr≤0.03%, Zn≤0.05%, Ti≤0.05%, with the balance being Al and other unavoidable impurities; the mass percentage of the other unavoidable impurities is ≤0.05%; by precisely controlling the content of Si, Mn, and Mg, the precipitation of the Mg2Si strengthening phase is optimized, thereby improving strength and toughness. By rationally selecting the components and their proportions, the components can better interact and influence each other, endowing the product with excellent tensile strength, toughness, hardness, corrosion resistance, and fatigue resistance. The chemical composition of the 6005C photovoltaic frame high-strength lightweight aluminum alloy profile also includes the following components by mass percentage: rare earth elements 0.01%-0.03%, Nb≤0.02%, B 0.001%-0.003%, Sr≤0.01%, Ta 0.005%-0.015%, Hf≤0.01%; the rare earth elements are Sc, Y, and Pr mixed in a mass ratio of 1:(0.8-1.2):(1-2). Through the combined addition of the above components, their interaction and synergy with other components in the composition can further improve the tensile strength, toughness, hardness, corrosion resistance, and fatigue resistance of the product; by strictly limiting the content of impurities, corrosion resistance can be effectively improved.

[0022] (3) The high-strength lightweight aluminum alloy profile for photovoltaic frames disclosed in this invention is the first to apply the optimized 6005C aluminum alloy to photovoltaic frames, filling the performance shortcomings of traditional materials; by reasonably selecting the preparation process parameters, the tensile strength, toughness, hardness, corrosion resistance and fatigue resistance of the aluminum alloy profile can be further improved. Detailed Implementation

[0023] The following description is intended to disclose the invention and enable those skilled in the art to implement it. The preferred embodiments described below are merely examples, and other obvious variations will occur to those skilled in the art.

[0024] Example 1

[0025] A high-strength, lightweight aluminum alloy profile for photovoltaic frames, comprising, by mass percentage: Si 0.7%, Fe ≤ 0.16%, Cu ≤ 0.01%, Mn 0.3%, Mg 0.6%, Cr ≤ 0.03%, Zn ≤ 0.05%, Ti ≤ 0.05%, with the balance being Al and other unavoidable impurities.

[0026] The mass percentage of the other unavoidable impurities is ≤0.05%.

[0027] The chemical composition of the 6005C photovoltaic frame high-strength lightweight aluminum alloy profile also includes the following components by mass percentage: rare earth elements 0.01%, Nb≤0.02%, B 0.001%, Sr≤0.01%, Ta 0.005%, Hf≤0.01%; the rare earth elements are Sc, Y, and Pr mixed in a mass ratio of 1:0.8:1.

[0028] A method for preparing the high-strength, lightweight aluminum alloy profile for photovoltaic frames of the aforementioned 6005C includes the following steps:

[0029] Step S1: Using Al, Al-Si master alloy, Al-Fe master alloy, Al-Cu master alloy, Al-Mn master alloy, Al-Mg master alloy, Al-Cr master alloy, Al-Zn master alloy, Al-Ti master alloy, Al-rare earth element master alloy, Al-Nb master alloy, Al-B master alloy, Al-Sr master alloy, Al-Ta master alloy, and Al-Hf master alloy as raw materials, weigh each raw material according to the mass percentage, add the raw materials to the melting furnace for melting, and then perform refining, slag removal, and degassing treatment to obtain molten metal;

[0030] Step S2: The refined molten metal is cast into round ingots, homogenized, heated to 480°C, and extruded to obtain the profile of the desired shape.

[0031] Step S3: Perform T6 heat treatment on the profile after step S2 to obtain 6005C high-strength lightweight aluminum alloy profile for photovoltaic frames.

[0032] The melting temperature in step S1 is 720℃; the temperature of the homogenization post-treatment in step S2 is 540℃ and the time is 6h; the T6 heat treatment in step S3 includes solution treatment and artificial aging treatment; the solution treatment temperature is 530℃, the holding time is 1h, and water quenching is performed; the artificial aging treatment temperature is 160℃ and the holding time is 5h.

[0033] Example 2

[0034] A high-strength, lightweight aluminum alloy profile for photovoltaic frames (6005C) comprises, by mass percentage: Si 0.75%, Fe ≤ 0.16%, Cu ≤ 0.01%, Mn 0.35%, Mg 0.65%, Cr ≤ 0.03%, Zn ≤ 0.05%, Ti ≤ 0.05%, with the balance being Al and other unavoidable impurities.

[0035] The mass percentage of other unavoidable impurities is ≤0.05%; the chemical composition of the 6005C photovoltaic frame high-strength lightweight aluminum alloy profile also includes the following components by mass percentage: rare earth elements 0.015%, Nb≤0.02%, B0.0015%, Sr≤0.01%, Ta0.007%, Hf≤0.01%; the rare earth elements are Sc, Y, and Pr mixed in a mass ratio of 1:0.9:1.2.

[0036] A method for preparing the high-strength, lightweight aluminum alloy profile for photovoltaic frames of the aforementioned 6005C includes the following steps:

[0037] Step S1: Using Al, Al-Si master alloy, Al-Fe master alloy, Al-Cu master alloy, Al-Mn master alloy, Al-Mg master alloy, Al-Cr master alloy, Al-Zn master alloy, Al-Ti master alloy, Al-rare earth element master alloy, Al-Nb master alloy, Al-B master alloy, Al-Sr master alloy, Al-Ta master alloy, and Al-Hf master alloy as raw materials, weigh each raw material according to the mass percentage, add the raw materials to the melting furnace for melting, and then perform refining, slag removal, and degassing treatment to obtain molten metal;

[0038] Step S2: The refined molten metal is cast into round ingots, homogenized, heated to 485°C, and extruded to obtain the profile of the desired shape.

[0039] Step S3: Perform T6 heat treatment on the profile after step S2 to obtain 6005C high-strength lightweight aluminum alloy profile for photovoltaic frames.

[0040] The melting temperature in step S1 is 730℃; the temperature of the homogenization post-treatment in step S2 is 545℃ and the time is 6.5h; the T6 heat treatment in step S3 includes solution treatment and artificial aging treatment; the solution treatment temperature is 535℃, the holding time is 1.2h, and water quenching is performed; the artificial aging treatment temperature is 165℃ and the holding time is 5.5h.

[0041] Example 3

[0042] A high-strength, lightweight aluminum alloy profile for photovoltaic frames, comprising, by mass percentage: Si 0.8%, Fe ≤ 0.16%, Cu ≤ 0.01%, Mn 0.4%, Mg 0.7%, Cr ≤ 0.03%, Zn ≤ 0.05%, Ti ≤ 0.05%, with the balance being Al and other unavoidable impurities.

[0043] The mass percentage of other unavoidable impurities is ≤0.05%; the chemical composition of the 6005C photovoltaic frame high-strength lightweight aluminum alloy profile also includes the following components by mass percentage: rare earth elements 0.02%, Nb≤0.02%, B0.002%, Sr≤0.01%, Ta0.01%, Hf≤0.01%; the rare earth elements are Sc, Y, and Pr mixed in a mass ratio of 1:1:1.5.

[0044] A method for preparing the high-strength, lightweight aluminum alloy profile for photovoltaic frames of the aforementioned 6005C includes the following steps:

[0045] Step S1: Using Al, Al-Si master alloy, Al-Fe master alloy, Al-Cu master alloy, Al-Mn master alloy, Al-Mg master alloy, Al-Cr master alloy, Al-Zn master alloy, Al-Ti master alloy, Al-rare earth element master alloy, Al-Nb master alloy, Al-B master alloy, Al-Sr master alloy, Al-Ta master alloy, and Al-Hf master alloy as raw materials, weigh each raw material according to the mass percentage, add the raw materials to the melting furnace for melting, and then perform refining, slag removal, and degassing treatment to obtain molten metal;

[0046] Step S2: The refined molten metal is cast into round ingots, homogenized, heated to 490°C, and extruded to obtain the profile of the desired shape.

[0047] Step S3: Perform T6 heat treatment on the profile after step S2 to obtain 6005C high-strength lightweight aluminum alloy profile for photovoltaic frames.

[0048] The melting temperature in step S1 is 740℃; the temperature of the homogenization post-treatment in step S2 is 550℃ and the time is 7h; the T6 heat treatment in step S3 includes solution treatment and artificial aging treatment; the solution treatment temperature is 540℃, the holding time is 1.5h, and water quenching is performed; the artificial aging treatment temperature is 170℃ and the holding time is 6h.

[0049] Example 4

[0050] A high-strength, lightweight aluminum alloy profile for photovoltaic frames (6005C) comprises, by mass percentage: Si 0.85%, Fe ≤ 0.16%, Cu ≤ 0.01%, Mn 0.45%, Mg 0.75%, Cr ≤ 0.03%, Zn ≤ 0.05%, Ti ≤ 0.05%, with the balance being Al and other unavoidable impurities.

[0051] The mass percentage of other unavoidable impurities is ≤0.05%; the chemical composition of the 6005C photovoltaic frame high-strength lightweight aluminum alloy profile also includes the following components by mass percentage: rare earth elements 0.025%, Nb≤0.02%, B0.0025%, Sr≤0.01%, Ta0.013%, Hf≤0.01%; the rare earth elements are Sc, Y, and Pr mixed in a mass ratio of 1:1.1:1.8.

[0052] A method for preparing the high-strength, lightweight aluminum alloy profile for photovoltaic frames of the aforementioned 6005C includes the following steps:

[0053] Step S1: Using Al, Al-Si master alloy, Al-Fe master alloy, Al-Cu master alloy, Al-Mn master alloy, Al-Mg master alloy, Al-Cr master alloy, Al-Zn master alloy, Al-Ti master alloy, Al-rare earth element master alloy, Al-Nb master alloy, Al-B master alloy, Al-Sr master alloy, Al-Ta master alloy, and Al-Hf master alloy as raw materials, weigh each raw material according to the mass percentage, add the raw materials to the melting furnace for melting, and then perform refining, slag removal, and degassing treatment to obtain molten metal;

[0054] Step S2: Cast the refined molten metal into round ingots, homogenize them, heat them to 495°C, and extrude them to obtain the desired profile shape.

[0055] Step S3: Perform T6 heat treatment on the profile after step S2 to obtain 6005C high-strength lightweight aluminum alloy profile for photovoltaic frames.

[0056] The melting temperature in step S1 is 750℃; the temperature of the homogenization post-treatment in step S2 is 555℃ and the time is 7.5h; the T6 heat treatment in step S3 includes solution treatment and artificial aging treatment; the solution treatment temperature is 545℃, the holding time is 1.8h, and water quenching is performed; the artificial aging treatment temperature is 175℃ and the holding time is 6.5h.

[0057] Example 5

[0058] A high-strength, lightweight aluminum alloy profile for photovoltaic frames, comprising, by mass percentage: Si 0.9%, Fe ≤ 0.16%, Cu ≤ 0.01%, Mn 0.5%, Mg 0.8%, Cr ≤ 0.03%, Zn ≤ 0.05%, Ti ≤ 0.05%, with the balance being Al and other unavoidable impurities.

[0059] The mass percentage of other unavoidable impurities is ≤0.05%; the chemical composition of the 6005C photovoltaic frame high-strength lightweight aluminum alloy profile also includes the following components by mass percentage: rare earth elements 0.01%-0.03%, Nb≤0.02%, B 0.001%-0.003%, Sr≤0.01%, Ta 0.005%-0.015%, Hf≤0.01%; the rare earth elements are Sc, Y, and Pr mixed in a mass ratio of 1:1.2:2.

[0060] A method for preparing the high-strength, lightweight aluminum alloy profile for photovoltaic frames of the aforementioned 6005C includes the following steps:

[0061] Step S1: Using Al, Al-Si master alloy, Al-Fe master alloy, Al-Cu master alloy, Al-Mn master alloy, Al-Mg master alloy, Al-Cr master alloy, Al-Zn master alloy, Al-Ti master alloy, Al-rare earth element master alloy, Al-Nb master alloy, Al-B master alloy, Al-Sr master alloy, Al-Ta master alloy, and Al-Hf master alloy as raw materials, weigh each raw material according to the mass percentage, add the raw materials to the melting furnace for melting, and then perform refining, slag removal, and degassing treatment to obtain molten metal;

[0062] Step S2: Cast the refined molten metal into round ingots, homogenize them, heat them to 500°C, and extrude them to obtain the desired profile shape.

[0063] Step S3: Perform T6 heat treatment on the profile after step S2 to obtain 6005C high-strength lightweight aluminum alloy profile for photovoltaic frames.

[0064] The melting temperature in step S1 is 760℃; the temperature of the homogenization post-treatment in step S2 is 560℃ and the time is 8h; the T6 heat treatment in step S3 includes solution treatment and artificial aging treatment; the solution treatment temperature is 550℃, the holding time is 2h, and water quenching is performed; the artificial aging treatment temperature is 180℃ and the holding time is 7h.

[0065] Comparative Example 1

[0066] A high-strength, lightweight aluminum alloy profile for photovoltaic frames (6005C) and its preparation method are basically the same as in Example 1, except that no rare earth elements and Ta are added.

[0067] Comparative Example 2

[0068] A high-strength, lightweight aluminum alloy profile for photovoltaic frames and its preparation method are basically the same as in Example 1, except that no homogenization treatment and solution treatment steps are added.

[0069] To further illustrate the beneficial technical effects of the high-strength lightweight aluminum alloy profiles for 6005C photovoltaic frames involved in the various embodiments of the present invention, relevant performance tests were conducted on the high-strength lightweight aluminum alloy profiles for 6005C photovoltaic frames involved in Examples 1-5 and Comparative Examples 1-2. The test results are shown in Table 1. The test methods are as follows: Tensile strength, yield strength, and elongation were tested according to GB / T 16865-2013 "Tension Test Specimens and Methods for Processed Products of Wrought Aluminum, Magnesium and Their Alloys"; Webster hardness was tested according to the standard YS / T 420 "Webster Hardness Test Method for Aluminum Alloys"; and Amsler... The specimens were subjected to constant amplitude fatigue tests (maximum load 100MPa, minimum load 20MPa) on the HFP-422 high-frequency fatigue testing machine, and the fatigue life was recorded and statistically analyzed. The aluminum alloy profiles were subjected to salt spray corrosion resistance tests at a temperature of 35℃. A 5% sodium chloride aqueous solution was sprayed in the test chamber to simulate accelerated corrosion in the environment. The tolerance time of the aluminum alloy profiles (i.e., the time it takes to remain rust-free) determines their corrosion resistance performance.

[0070] Table 1

[0071] project tensile strength Yield strength Elongation at break Webster hardness Fatigue life Corrosion resistance unit MPa MPa ％ HW 10,000 times h Example 1 343 320 13.1 17.0 16.5 1020 Example 2 348 323 13.3 17.5 16.8 1060 Example 3 350 327 13.7 17.5 17.0 1092 Example 4 354 333 14.0 18.0 17.5 1115 Example 5 360 338 14.2 18.0 17.6 1132 Comparative Example 1 312 300 12.4 15.5 14.9 978 Comparative Example 2 324 310 11.8 16.0 15.5 992

[0072] As can be seen from Table 1, the 6005C photovoltaic frame high-strength lightweight aluminum alloy profile involved in the embodiments of the present invention has higher tensile strength, toughness, hardness, corrosion resistance and fatigue resistance than the comparative product; the combined use of rare earth elements, Ta, homogenization treatment and solution treatment steps is beneficial to improving the above properties.

[0073] The above embodiments are only for illustrating the technical concept and features of the present invention. Their purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be used to limit the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A high-strength, lightweight aluminum alloy profile for 6005C photovoltaic frames, characterized in that, The chemical composition, by mass percentage, includes: Si 0.7%-0.9%, Fe≤0.16%, Cu≤0.01%, Mn 0.3%-0.5%, Mg 0.6%-0.8%, Cr≤0.03%, Zn≤0.05%, Ti≤0.05%, rare earth elements 0.01%-0.03%, Nb≤0.02%, B 0.001%-0.003%, Sr≤0.01%, Ta0.005%-0.015%, Hf≤0.01%, with the balance being Al and other unavoidable impurities; the rare earth elements are Sc, Y, and Pr mixed in a mass ratio of 1:(0.8-1.2):(1-2).

2. The high-strength, lightweight aluminum alloy profile for photovoltaic frames according to claim 1, characterized in that, The mass percentage of the other unavoidable impurities is ≤0.05%.

3. A method for preparing a high-strength, lightweight aluminum alloy profile for a 6005C photovoltaic frame according to any one of claims 1-2, characterized in that, Includes the following steps: Step S1: Using Al, Al-Si master alloy, Al-Fe master alloy, Al-Cu master alloy, Al-Mn master alloy, Al-Mg master alloy, Al-Cr master alloy, Al-Zn master alloy, Al-Ti master alloy, Al-rare earth element master alloy, Al-Nb master alloy, Al-B master alloy, Al-Sr master alloy, Al-Ta master alloy, and Al-Hf master alloy as raw materials, weigh each raw material according to the mass percentage, add the raw materials to the melting furnace for melting, and then perform refining, slag removal, and degassing treatment to obtain molten metal; Step S2: Cast the refined molten metal into round ingots, homogenize them, heat them to 480-500℃, and extrude them to obtain the profiles of the desired shape. Step S3: Perform T6 heat treatment on the profile after step S2 to obtain 6005C high-strength lightweight aluminum alloy profile for photovoltaic frames.

4. The method for preparing the high-strength, lightweight aluminum alloy profile for 6005C photovoltaic frames according to claim 3, characterized in that, The melting temperature in step S1 is 720-760℃.

5. The method for preparing the high-strength, lightweight aluminum alloy profile for 6005C photovoltaic frames according to claim 3, characterized in that, The homogenization process in step S2 is carried out at a temperature of 540-560℃ for 6-8 hours.

6. The method for preparing the high-strength, lightweight aluminum alloy profile for 6005C photovoltaic frames according to claim 3, characterized in that, The T6 heat treatment in step S3 includes solution treatment and artificial aging treatment.

7. The method for preparing the high-strength, lightweight aluminum alloy profile for 6005C photovoltaic frames according to claim 6, characterized in that, The solution treatment temperature is 530-550℃, the holding time is 1-2 hours, and then water quenching is performed.

8. The method for preparing the high-strength, lightweight aluminum alloy profile for 6005C photovoltaic frames according to claim 6, characterized in that, The temperature for the artificial aging treatment is 160-180℃, and the holding time is 5-7 hours.