An aluminium alloy profile and a fusion casting extrusion process and a welding method thereof

Abstract

The application relates to an aluminum alloy profile and a melting-casting extrusion process and a welding method thereof, wherein the main components of the aluminum alloy profile are as follows in percentage by mass: Si: 0.60-0.70; Mg: 0.80-0.95; Fe: <=0.25; Cu: 0.12-0.27; Mn: 0.02-0.10; Cr: 0.02-0.12; Zn: <=0.03; Ti: 0.03-0.10; the balance is Al and inevitable impurities; and meanwhile, the production and welding process are overall optimized and adjusted, the problem that obvious defects are generated under high welding speed by using a tungsten electrode argon arc welding in the prior art process is solved, and the welding efficiency and quality of the aluminum alloy profile are effectively improved.

Description

Technical Field

[0001] This invention belongs to the field of aluminum alloy profile production and processing technology, specifically relating to an aluminum alloy profile and its casting and extrusion process and welding method. Background Technology

[0002] Currently, aluminum profiles are widely used in aerospace, military, automotive, transportation and other industrial fields. In order to achieve certain functions, aluminum profiles need to be welded. However, aluminum alloys have poor welding performance and are prone to defects such as welding cracks, porosity and weld pits due to their fast thermal conductivity. The occurrence of welding defects will greatly affect the performance of products.

[0003] Tungsten inert gas (TIG) welding is a preferred welding method for aluminum alloys due to its advantages such as strong adaptability, easy control of welded joints, stable quality, small deformation, resistance to corrosion and oxidation, low cost, and ease of automation.

[0004] For example, a 6-series aluminum alloy channel plate has a cross-section as shown in the figure. Figure 1 As shown, this is commonly referred to as TT plate, mainly used in container manufacturing, with a wall thickness of approximately 4mm at the welding area. The applicant company received feedback from customers stating that when using a tungsten inert gas (TIG) DC welding machine and increasing the welding speed (e.g., above 1100mm / min), welding defects became more noticeable, for example… Figure 2 As shown. With the current demand for high-efficiency production, increasing welding speed has become an inevitable trend in technological development. Therefore, this invention provides an optimized production and welding process for this type of aluminum alloy plate and similar aluminum alloy profiles, achieving high-quality welding results at high welding speeds. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide an aluminum alloy profile and its melting, casting, extrusion process and welding method, which solves the problem that the existing process will produce obvious defects at high welding speeds, and effectively improves the welding efficiency and quality of aluminum alloy profiles.

[0006] According to the technical solution of the present invention, the present invention provides an aluminum alloy profile, the main components of which, by mass percentage, are: Si: 0.60~0.70; Mg: 0.80~0.95; Fe: ≤0.25; Cu: 0.12~0.27; Mn: 0.02~0.10; Cr: 0.02~0.12; Zn: ≤0.03; Ti: 0.03~0.10; the balance being Al and unavoidable impurities.

[0007] Preferably, the mass percentage content of unavoidable impurities is ≤0.03%.

[0008] Preferably, the mass ratio of Mg to Si is less than or equal to 1.45.

[0009] The present invention also provides a melting, casting and extrusion process for aluminum alloy profiles, comprising sequentially performing steps S1 melting process, step S2 casting process, step S3 extrusion process and step S4 aging process; the composition of the final obtained aluminum alloy profile meets the requirements of any of the above-mentioned claims of the present invention.

[0010] In step S1, the material is refined three times using a refining agent, with each refining process lasting at least 10 minutes. The final temperature after refining is 700–730°C. After refining, an aluminum-titanium-boron wire refining agent is added, and the mixture is electromagnetically stirred for 4–6 minutes. The mixture is then allowed to stand for 30 minutes before casting begins. Preferably, a high-quality aluminum-titanium-boron wire refining agent (mainly AlTi5B) is used, with a Ti content of 4.7 wt%–5.5%. The TiB2 grain diameter in the aluminum-titanium-boron wire microstructure is ≤4 μm, and the AlTi3 grain diameter is <30 μm, with uniform distribution.

[0011] Further, in step S2, an automatic wire feeder is used to feed the wire, and aluminum-titanium-boron wire is added into the flow channel at a rate of 4 kg of aluminum-titanium-boron wire per ton of aluminum alloy melt; the casting temperature is 690-710℃, the casting speed is 70-75 mm / min, and the cooling water flow rate is 270-300 L / min.

[0012] Further, in step S3, the temperature of the aluminum rod on the extrusion machine is 470-500℃, the temperature of the die is 440-480℃, the extrusion speed is 3.5-4.0mm / s, the quenching temperature is 520-550℃, and the quenching end temperature is below 200℃; after extrusion, the obtained profile is straightened and pre-deformed, with a deformation ratio of 1-2%.

[0013] In step S4, the profile is kept at 195-200℃ for 4 hours, and then removed from the furnace and cooled naturally to obtain the final aluminum alloy profile.

[0014] The present invention also provides a welding method for aluminum alloy profiles, which uses aluminum alloy profiles according to any of the above claims of the present invention for welding, and includes step S6 welding step: welding is performed using a tungsten inert gas (TIG) DC welding machine, the tungsten electrode is 4.0mm x 150mm in size, the tungsten electrode extends 4mm beyond the ceramic nozzle, the tungsten electrode is 5mm away from the aluminum alloy profile, the welding current is 450A, the welding speed is 1300mm / min, and the argon gas flow rate is 15L / min; the weld is cleaned after welding.

[0015] Furthermore, the wall thickness of the aluminum alloy profile at the welding position is 4–6 mm.

[0016] Furthermore, step S5, welding preparation, is included before step S6: the two aluminum alloy profiles to be welded are joined tightly together, and the welding position is cleaned until there are no impurities.

[0017] Furthermore, the weld obtained after step S6 is a raised semi-circular arc shape.

[0018] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0019] 1. The aluminum alloy profiles, casting and extrusion processes, and welding methods of the present invention, using tungsten inert gas welding and high welding speed, ensure that the aluminum profile products are free from defects such as weld pits, porosity, and performance defects after welding, thereby improving the yield of welded products, enhancing enterprise competitiveness, and contributing to the overall technological development level of the aluminum alloy profile industry.

[0020] 2. The aluminum alloy profile of the present invention has adjusted and optimized its chemical composition. The Ti element content has been increased on the basis of the existing composition to increase the nucleation quality during welding; the Mg:Si ratio has been adjusted to produce more excess silicon in the alloy, which increases the nucleation during welding; the Mn content has been increased. The Si and Mn contents increase the melt fluidity during welding, increase the feeding ability, improve the welding quality, and have a lower cost.

[0021] 3. The melting, casting, and extrusion process of the aluminum alloy profile of the present invention optimizes and adjusts the overall process of melting, casting, extrusion, and aging, and increases the number of refining times during melting, uses high-quality aluminum-titanium-boron wire refining agent, increases the amount of TiAl3 and TiB2 nucleating particles in the aluminum alloy profile, which is more conducive to achieving grain refinement. Therefore, the produced aluminum alloy profile has better weldability and mechanical properties.

[0022] 4. The aluminum alloy profile welding method of the present invention adopts a unique parameter combination scheme, which realizes high welding speed using tungsten inert gas welding, significantly improving production efficiency, and the weld is semi-circular arc-shaped, with beautiful shape and no obvious defects. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the profile cross-section and welding position according to an embodiment of the present invention.

[0024] Figure 2 The image shows the weld seam obtained using existing aluminum alloy profiles and existing welding processes.

[0025] Figure 3 The image shows the weld obtained using the solution of this invention. Detailed Implementation

[0026] This invention provides an aluminum alloy profile and its casting and extrusion process and welding method, which solves the problem that existing processes will produce obvious defects at high welding speeds. It ensures that the aluminum profile product is free of defects such as weld pits, porosity and performance defects after welding at high welding speeds, thereby improving the yield, efficiency and welding quality of welded products.

[0027] In a first aspect, the present invention optimizes the chemical composition of aluminum alloys to provide an aluminum alloy profile, the main components of which, by mass percentage, are: Si: 0.60–0.70; Mg: 0.80–0.95; Fe: ≤0.25; Cu: 0.12–0.27; Mn: 0.02–0.10; Cr: 0.02–0.12; Zn: ≤0.03; Ti: 0.03–0.10; with the balance being Al and unavoidable impurities. More preferably, the mass percentage content of unavoidable impurities is ≤0.03%.

[0028] The component control in the specific embodiments is shown in Table 1 below (unit: mass percentage).

[0029] Table 1 Chemical Composition Control Table for Aluminum Alloy Profiles of the Invention

[0030]

[0031] In this optimized solution, the Ti content must be greater than or equal to 0.03% and less than or equal to 0.10%, which increases the Ti content compared to the currently used aluminum profile, thus improving the nucleation quality during welding. Specifically, due to the high power and melting temperature of TIG welding, the aluminum alloy profile melts into a liquid state at high temperature during welding, and then cools and crystallizes to form the weld, which is equivalent to a recasting process. During cooling and crystallization, the cooling rate is slow, and the supercooling at the crystallization front is small. At the same time, the Ti content in the existing aluminum alloy composition (the mass percentage of the main components in the currently used aluminum profile is shown in Table 2 for two examples) is low, resulting in fewer effective TiB2 and other nucleating particles in the melt. This leads to the formation of elongated columnar crystals in the weld area. In the last solidified part, there are fewer nucleating particles, and the melt feeding is insufficient, thus forming weld pits on the weld surface, forming a similar Figure 2 The weld shown is poorly welded and affects its use.

[0032] Table 2 Chemical Composition of Aluminum Profiles from Original Process

[0033] Si Mg Fe Mn Cu Zn Ni Cr Ti B Ga Na Al 0.595 0.937 0.171 0.01 0.191 0.004 0.0023 0.058 0.015 0.002 0.016 0.002 97.96 0.596 0.942 0.168 0.01 0.191 0.006 0.0023 0.057 0.015 0.002 0.016 0.002 97.96

[0034] The welding quality of aluminum alloy profiles is closely related to the nucleation mechanism at the microscopic level, specifically including factors such as nucleating ions and grain growth rate. This invention increases the Ti content and the amount of TiAl3 and TiB2 particles. During the crystallization nucleation process in welding, the dispersed TiAl3 particles can increase nucleation and grain size, while TiB2 particles can inhibit grain growth. Therefore, this solution results in more nuclei and a slower grain growth rate, achieving a good grain refinement effect.

[0035] Furthermore, this scheme adjusts the Mg:Si element mass ratio to less than or equal to 1.45, while the existing conventional scheme generally has a Mg:Si element mass ratio of 1.71, thus matching the Mg2Si generated by Mg and Si during alloy casting. After adjustment, this scheme is equivalent to increasing the Si content and / or decreasing the Mg content, thereby forming an appropriate amount of excess Si, which helps grain nucleation and achieves grain refinement.

[0036] Furthermore, the Mn content in the currently used aluminum profiles is generally around 0.003 to 0.01 wt%, and is even usually considered an impurity element. This solution increases the Mn content. Both Mn and excess Si play a role in increasing the fluidity of the melt during welding, increasing the feeding capacity, and improving the welding quality.

[0037] Furthermore, while existing aluminum alloys use rare earth elements to refine grains and enhance material properties, this solution can achieve the desired grain refinement effect without adding rare earth elements, thus meeting material performance requirements at a relatively low cost.

[0038] A second aspect of this invention optimizes the profile production process by providing a melting, casting, and extrusion process for aluminum alloy profiles. This process mainly includes sequentially performed steps S1 (melting), S2 (casting), S3 (extrusion), and S4 (aging). The resulting aluminum alloy profile conforms to the composition requirements of any of the above-described embodiments of this invention.

[0039] More specifically, in step S1, the specific steps required for the smelting process, such as batching, charging, and slag removal, can follow existing conventional methods and will not be elaborated upon. The main improvement of this method to the smelting process is that, during the refining process, a refining agent is used for refining three times, with each refining time lasting more than 10 minutes, resulting in a final temperature of 700–730°C after refining. Existing conventional products can be used as the refining agent, and there are no restrictions in this invention. The amount of refining agent added to the aluminum melting furnace during each refining is selected according to needs, for example, approximately 4 kg of refining agent is added per ton of raw material. After refining (including slag removal), an aluminum-titanium-boron wire refining agent is added to the aluminum melting furnace and electromagnetically stirred for 4–6 minutes (e.g., 5 minutes), then allowed to stand for 30 minutes before casting begins. The preferred high-quality aluminum-titanium-boron (ATiB) wire refining agent is an existing one. This high-quality ATiB wire refining agent (mainly composed of AlTi5B) has a Ti content of 4.7 wt%-5.5%, and the TiB2 grain diameter in the metallographic structure of the ATiB wire is ≤4 μm, while the AlTi3 grain diameter is <30 μm, and they are uniformly distributed. For example, approximately 4 kg of high-quality ATiB wire refining agent is added per ton of raw material. The main function of the ATiB wire refining agent is to increase the Ti content. Alternatively, the amount of ATiB wire refining agent can be reduced, while increasing the Ti element content in the raw material can achieve a similar effect. That is, by increasing the Ti content, the amount of TiAl3 and TiB2 nucleation particles in the aluminum alloy mold is increased in subsequent processes, which helps to achieve grain refinement. During the smelting process in step S1, the conventional process is followed, and the composition is adjusted simultaneously as needed, so that the composition detected at the end of smelting meets the requirements of this invention.

[0040] In step S2 of the casting process, for example, a casting machine is used to manufacture round bars with a diameter of 292mm. The specific operation method is not detailed here. The main improvement of this scheme in the casting process is that an automatic wire feeder is used to feed the wire during casting, adding aluminum-titanium-boron wire into the runner (sprue). The addition rate is, for example, 4kg of aluminum-titanium-boron wire is added uniformly per ton of molten aluminum alloy. The casting temperature is 690–710℃, the casting speed is 70–75mm / min, and the cooling water flow rate is 270–300L / min. After casting, a raw material aluminum bar for extrusion is obtained.

[0041] In step S3, the extrusion process, for example, uses an extrusion press. The specific operation method is not detailed here. The main improvement in this scheme is that the aluminum rod is heated using a combination of a multi-rod furnace and a gradient induction heating furnace for isothermal extrusion. The aluminum rod temperature is 470–500℃, the die temperature is 440–480℃, the radial temperature difference of the die is less than 10℃, the extrusion speed is 3.5–4.0 mm / s, the quenching temperature is 520–550℃, and the quenching end temperature is below 200℃. After extrusion, the obtained aluminum alloy profile is straightened and pre-deformed, with a deformation ratio of approximately 1%–2%.

[0042] In step S4, the aging process, for example using an aging furnace, involves holding the aluminum alloy profile at 195–200°C for 4 hours, then removing it from the furnace and allowing it to cool naturally. This yields the final aluminum alloy profile product.

[0043] Using the casting process in step S2 of this invention, the obtained aluminum rod has fine equiaxed grains, a uniform microstructure, and a surface segregation layer of less than 1.2 mm, enabling extrusion without the need for a car body. In step S3, by combining a multi-bar furnace with a gradient induction heating furnace, an axial temperature difference of 10-15°C is achieved between the head and tail of the aluminum rod, enabling isothermal extrusion. Under high-intensity cooling conditions, an excellent extruded microstructure is obtained. In step S4, under this aging process, the obtained profile microstructure exhibits rounded and uniformly distributed precipitates, without agglomeration at grain boundaries or within the grains. This fine and uniform microstructure also contributes to improved weldability of the profile.

[0044] A third aspect of the present invention optimizes the welding process parameters, providing a welding method for aluminum alloy profiles. The operation steps begin with step S5, welding preparation: placing two aluminum alloy profiles to be welded (e.g., ...) Figure 1 The TT plates shown are spliced ​​together tightly with no obvious gaps after splicing. The welding area is cleaned with a dry cotton cloth until it is free of oil, moisture, dust, and other impurities. In a specific embodiment, the wall thickness of the aluminum alloy profile at the welding location is 4-6 mm.

[0045] Then proceed to step S6, welding: Use a tungsten inert gas (TIG) DC welding machine with a maximum current of, for example, 500A. The tungsten electrode should be 4.0mm x 150mm, extending 4mm beyond the ceramic nozzle during welding. The distance between the tungsten electrode and the aluminum alloy profile should be 5mm. The welding current should be 450A, the welding carriage speed 1300mm / min, and the argon gas flow rate 15L / min. After welding, clean the weld seam with a brush or scouring pad.

[0046] The selection of parameters is the key to this scheme. Experimental studies show that using other similar combinations of process parameters cannot achieve the optimal technical effect described in this invention. Specifically, a higher welding speed requires a higher welding current, and the welding current is directly related to the heat generated. Excessive current can lead to burn-through. In practice, the current affects the amount of heat absorbed by the weld, the grain size of the heat-affected zone, and the shape of the weld. Too fast a welding speed results in rapid solidification and is prone to porosity. The diameter of the tungsten electrode is usually positively correlated with the welding current, but if this scheme uses a tungsten electrode with a diameter of 5mm or more, or changes the distance of the tungsten electrode extending from the ceramic nozzle, the optimal effect cannot be obtained. The length of the tungsten electrode extending from the ceramic nozzle affects the arc discharge and heat accumulation; a longer extension results in a larger arc discharge area and a larger heat-affected zone. The distance between the tungsten electrode and the welding material is directly related to the quality of the arc formation. The argon gas flow rate plays a protective and heat dissipation role; if it is too low, the weld will not form properly or will collapse, failing to achieve the desired effect. Figure 3 The weld shown is a raised, semi-circular arc shape, aesthetically pleasing, and without obvious defects.

[0047] In summary, the aluminum alloy profiles, casting and extrusion processes, and welding methods of the present invention, using tungsten inert gas welding and high welding speeds, ensure that the aluminum profile products are free from defects such as weld pits, porosity, and performance issues after welding. This improves the efficiency and quality of welded products, has extremely high practical value, and helps to enhance enterprise competitiveness and improve the overall technological development level of the aluminum alloy profile industry.

Claims

1. A welding method for aluminum alloy profiles, characterized in that, Aluminum alloy profiles are produced through a melting-casting-extrusion process, which includes sequential steps S1 (melting), S2 (casting), S3 (extrusion), and S4 (aging). The main components of the final aluminum alloy profiles, by mass percentage, are: Si: 0.60–0.70; Mg: 0.80–0.95; Fe: ≤0.25; Cu: 0.12–0.27; Mn: 0.02–0.10; Cr: 0.02–0.12; Zn: ≤0.03; Ti: 0.03–0.10; the balance being Al and unavoidable impurities. The aluminum alloy profile welding method includes step S6: welding is performed using a tungsten inert gas (TIG) DC welding machine with a tungsten electrode specification of 4.0mm x 150mm, the tungsten electrode extending 4mm beyond the ceramic nozzle, the tungsten electrode being 5mm away from the aluminum alloy profile, a welding current of 450A, a welding speed of 1300mm / min, and an argon flow rate of 15L / min; the weld is cleaned after welding.

2. The aluminum alloy profile welding method as described in claim 1, characterized in that, The wall thickness of the aluminum alloy profile at the welding location is 4-6 mm.

3. The aluminum alloy profile welding method as described in claim 1 or 2, characterized in that, Before step S6, step S5 is included for welding preparation: the two aluminum alloy profiles to be welded are joined tightly together, and the welding area is cleaned until there are no impurities.

4. The aluminum alloy profile welding method as described in claim 1 or 2, characterized in that, The weld obtained after step S6 is a raised semi-circular arc shape.

5. The aluminum alloy profile welding method as described in claim 1, characterized in that, The mass percentage of unavoidable impurities is ≤0.03%.

6. The aluminum alloy profile welding method as described in claim 1, characterized in that, The mass ratio of Mg to Si is less than or equal to 1.

45.

7. The aluminum alloy profile welding method as described in claim 1, characterized in that, In step S1, the material is refined three times with a refining agent, each refining time being more than 10 minutes. The final temperature after refining is 700-730℃. After refining, an aluminum-titanium-boron wire refining agent is added and the material is electromagnetically stirred for 4-6 minutes. Then, the material is allowed to stand for 30 minutes before casting begins.

8. The aluminum alloy profile welding method as described in claim 1, characterized in that, In step S2, an automatic wire feeder is used to feed the wire, and aluminum-titanium-boron wire is added to the flow channel at a rate of 4 kg of aluminum-titanium-boron wire per ton of aluminum alloy melt. The casting temperature is 690-710℃, the casting speed is 70-75 mm / min, and the cooling water flow rate is 270-300 L / min.

9. The aluminum alloy profile welding method as described in claim 1, characterized in that, In step S3, the aluminum rod temperature is 470–500℃, the die temperature is 440–480℃, the extrusion speed is 3.5–4.0 mm / s, the quenching temperature is 520–550℃, and the quenching end temperature is below 200℃. After extrusion, the obtained profile is straightened and pre-deformed, with a deformation ratio of 1–2%. In step S4, the profile is kept at 195-200℃ for 4 hours, and then removed from the furnace and cooled naturally to obtain the final aluminum alloy profile.

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