Method for preventing local blackening of welding seam after anodizing of aluminum alloy part

Abstract

The invention belongs to the field of aluminum alloy welding, discloses a method for preventing local blackening of a welding seam after anodizing of an aluminum alloy part, and is used for the situation that anodizing is needed after the aluminum alloy part is welded. The method comprises the following steps: carrying out chemical cleaning treatment on a to-be-welded part of the aluminum alloy part before welding, and removing an oxide film and oil stain at the to-be-welded part; the aluminum alloy parts are combined on an assembly clamp, the relative position relation of the aluminum alloy parts is guaranteed, and positioned welding is conducted through an argon tungsten-arc welding method; correcting positioned welding deformation; welding of welding seams of the aluminum alloy parts is completed through an argon tungsten-arc welding method, and an arc suppression method is controlled; the part is taken down from the assembly clamp; and anodizing the part. The problem of local blackening of the welding seam after anodizing of the aluminum alloy part can be effectively solved.

Description

Technical Field

[0001] The invention belongs to the field of aluminum alloy welding, and particularly relates to a method for preventing a weld of an aluminum alloy part from being partially blackened after anodizing. Background Art

[0002] Aluminum alloy welding structures are mostly used in aircraft products. A typical product is obtained by welding thin plate (thickness 1 to 3 mm) parts of 5 series aluminum alloy (5A06, 5A03, 5A02, etc.) and then anodizing them.

[0003] The common method is to assemble the medium and thin plates on the assembly fixture, ensure the relative position relationship between the parts, and then use tungsten inert gas welding for welding, and then anodize. Since there are inevitably a small amount of impurities (mainly non-metallic oxides such as Si) in the liquid metal of the molten pool during welding, the impurity content of the weld metal that solidifies first is small, and the color is normal after anodizing, while the impurity content of the molten pool metal that solidifies last is high, concentrated in the arc closing part, resulting in partial blackening of the weld arc closing part after anodizing, and unqualified appearance. Summary of the invention

[0004] The purpose of the present invention is to provide a method for preventing local blackening of welds of aluminum alloy parts after anodizing, which is used for preventing local blackening of arc closing points of medium and thin plate (thickness 1 to 3 mm) parts of 5 series aluminum alloys (5A06, 5A03, 5A02, etc.) during anodizing after welding, so as to avoid failure of parts due to local blackening of welds after anodizing, thereby affecting delivery.

[0005] The present invention provides a method for preventing a weld of an aluminum alloy part from being partially blackened after anodizing. The method comprises the following steps:

[0006] Step 1: Chemically clean the parts to be welded of the aluminum alloy parts to remove the oxide film and oil stains on the parts to be welded;

[0007] Step 2: Assemble aluminum alloy parts on the assembly fixture;

[0008] Step 3: Use tungsten inert gas arc welding method to perform positioning welding;

[0009] Step 4: Correct the positioning welding deformation;

[0010] Step 5: Set the welding parameters and use tungsten inert gas welding to complete the welding of the aluminum alloy parts. At the end of the weld, the arc is closed and the welding current is attenuated. At the same time, the welding gun is gradually lifted up and the speed is increased to pass through the arc closing area;

[0011] Step 6: Remove the part from the fixture;

[0012] Step 7: Anodizing the aluminum alloy parts;

[0013] Step 8: Check the surface quality of parts.

[0014] Optionally, in step 1, the chemical cleaning process is as follows:

[0015] First degreasing in sodium phosphate and first caustic soda solution,

[0016] Then, it is alkaline-etched in a second caustic soda solution.

[0017] Finally, the light was emitted in a nitric acid solution;

[0018] Among them, the chemical formula of sodium phosphate is Na2PO4˙12H2O, and the concentration is 40-60g / L;

[0019] The first caustic soda uses sodium hydroxide NaOH with a concentration of 8 to 12 g / L;

[0020] The second caustic soda uses sodium hydroxide NaOH with a concentration of 40-60 g / L;

[0021] The concentration of nitric acid solution is 300-500g / L.

[0022] Optionally, in step 2, assembly welding needs to be completed within 48 hours after chemical cleaning.

[0023] Optionally, in step 5, the welding wire used during welding is an aluminum alloy welding wire of the same series as the aluminum alloy to be welded, such as using 5A06 welding wire for welding 5A06, and using 5A03 welding wire for welding 5A03 and 5A02.

[0024] Optionally, in step five, argon gas is used to protect the weld area during welding, and the purity of the argon gas is not less than 99.99%, and the quality of the argon gas should comply with the requirements of GB / T4842.

[0025] Optionally, in step five, the welding technical parameters are: welding current 60-180A, argon gas flow rate 8-12L / min, and welding wire diameter φ2-3.5mm.

[0026] Optionally, in step seven, the welded parts are anodized using the following method: solution composition: sulfuric acid 180-200 g / L, chloride ≤0.2 g / L, aluminum ion ≤20 g / L; temperature 13-26° C.; time 20-60 min.

[0027] Optionally, in step eight, after the aluminum alloy parts are anodized, the surface color of the weld is normal, the appearance is qualified, and there is no local blackening at the arc closing point.

[0028] The present invention provides a method for preventing local blackening of welds of aluminum alloy parts after anodizing. The process method for preventing local blackening of welds of aluminum alloy medium-thin plate parts after anodizing according to the present invention has the significant advantages of preventing local blackening of the arc closing position of the weld when the parts are anodized after welding, thereby avoiding failure of the parts due to local blackening of the welds after anodizing, which affects delivery. DETAILED DESCRIPTION

[0029] In order to make the purpose and advantages of the present invention more clearly understood, the present invention is specifically described below in conjunction with the embodiments. The following text is only used to describe one or several specific implementations of the present invention, and does not strictly limit the protection scope of the specific claims of the present invention.

[0030] The present invention provides a method for preventing a weld of an aluminum alloy part from being partially blackened after anodizing, comprising the following steps:

[0031] Step 1: Chemically clean the parts to be welded of the aluminum alloy parts to remove the oxide film and oil stains on the parts to be welded;

[0032] Step 2: Assemble aluminum alloy medium and thin plate parts on an assembly fixture;

[0033] Step 3: Use tungsten inert gas arc welding method to perform positioning welding;

[0034] Step 4: Correct the positioning welding deformation;

[0035] Step 5: Set the welding parameters and use tungsten inert gas welding to complete the welding of the aluminum alloy parts. At the end of the weld, the arc is closed and the welding current is attenuated. At the same time, the welding gun is gradually lifted up and the speed is increased to pass through the arc closing area;

[0036] Step 6: Remove the part from the fixture;

[0037] Step 7: Anodizing the aluminum alloy parts;

[0038] Step 8: Check the surface quality of parts.

[0039] Further, in step 1, the chemical cleaning process is as follows:

[0040] First degreasing in sodium phosphate and first caustic soda solution,

[0041] Then, it is alkaline-etched in a second caustic soda solution.

[0042] Finally, the light was emitted in a nitric acid solution;

[0043] Among them, the chemical formula of sodium phosphate is Na2PO4˙12H2O, and the concentration is 40-60g / L;

[0044] The first caustic soda uses sodium hydroxide NaOH with a concentration of 8 to 12 g / L;

[0045] The second caustic soda uses sodium hydroxide NaOH with a concentration of 40-60 g / L;

[0046] The concentration of nitric acid solution is 300-500g / L.

[0047] The oxide film of aluminum alloy material is composed of aluminum oxide (Al2O3), which is non-conductive and hinders the welding process. In addition, the melting point of aluminum oxide is about 2050℃, which is much higher than the melting point of aluminum alloy (about 660℃). It cannot melt in the molten pool and forms non-metallic slag inclusion defects in the weld after cooling. If the oil stains on the surface of the parts are not removed, weld pores will be formed during welding, greatly reducing the strength and load-bearing capacity of the weld. Therefore, chemical cleaning is required.

[0048] Furthermore, in step five, welding must be completed within 48 hours after chemical cleaning to avoid the formation of new oxide films and contaminants on the pretreated surface of the parts.

[0049] Furthermore, in step 5, the welding wire used during welding is an aluminum alloy welding wire of the same series as the aluminum alloy medium and thick plate to be welded. For example, 5A06 welding wire is used for welding 5A06, and 5A03 welding wire is used for welding 5A03 and 5A02.

[0050] Furthermore, in step 5, argon is used to protect the weld area during welding, and the purity of argon is not less than 99.99%, and the quality of argon should meet the requirements of GB / T4842. Argon arc welding is sensitive to the purity of argon. When the purity of argon is reduced or the moisture content in argon exceeds the standard, the tendency of pores to form in the weld increases significantly, thereby reducing the quality of the weld.

[0051] Furthermore, in step five, the welding technical parameters are: welding current 60-180A, argon gas flow rate 8-12L / min, and welding wire diameter φ2-3mm.

[0052] Furthermore, the aluminum alloy parts welding operation adopts "fast belt arc closure" (while the welding current is attenuated during arc closure, the welding gun is gradually lifted up and the speed is increased to "bring" it through the arc closure area) to reduce the concentration of impurities in the molten pool metal at the arc closure position.

[0053] Furthermore, the aluminum alloy parts are made of 5 series aluminum alloy, and the material thickness is 1 mm to 3 mm.

[0054] Furthermore, the aluminum alloy sheet to be welded is a 5 series aluminum alloy, and the welding wire is a 5 series aluminum alloy welding wire. The aluminum alloy sheet to be welded is a 5A06 aluminum alloy, and a 5A06 welding wire is used. The aluminum alloy sheet to be welded is a 5A03 or 5A02 aluminum alloy, and a 5A03 welding wire is used.

[0055] Furthermore, the aluminum alloy parts are anodized after welding using the following method: solution composition: sulfuric acid (H2SO4) 180-200 g / L, chloride (as NaCl) ≤ 0.2 g / L, aluminum ion ≤ 20 g / L; temperature 13-26°C; time 20-60 min.

[0056] This embodiment provides a method for preventing the local blackening of the anodized weld of aluminum alloy parts after welding. The thickness of the aluminum alloy medium and thin plate is 1 to 3 mm; the method includes: chemically cleaning the surface of the aluminum alloy medium and thin plate parts before welding to remove the oxide film and oil stains on the parts to be welded; fixing the aluminum alloy medium and thin plate parts on a fixture for positioning welding; welding the aluminum alloy medium and thin plate parts with tungsten inert gas arc welding equipment; and using the "fast belt arc closure" method when closing the arc of the aluminum alloy parts.

[0057] In this embodiment, the surface of the aluminum alloy parts is chemically cleaned before welding to remove the oxide film and oil stains, and reduce the tendency of defects such as weld porosity to form during welding. The oxide film of the aluminum alloy material is composed of aluminum oxide (Al2O3), which is non-conductive and hinders the welding process. In addition, the melting point of aluminum oxide is about 2050℃, which is much higher than the melting point of aluminum alloy (about 660℃). It cannot melt in the molten pool and forms non-metallic slag inclusion defects in the weld after cooling. If the oil stains on the surface of the parts are not removed, weld porosity will be formed during welding, greatly reducing the strength and bearing capacity of the weld.

[0058] In this embodiment, the chemical cleaning method before welding of parts is as follows: first, degreasing in a sodium phosphate (Na2PO4˙12H2O, 40-60g / L) + caustic soda (NaOH, 8-12g / L), 60-70°C solution for 3-5min, then alkaline corrosion in a caustic soda (NaOH, 40-60g / L), 50-60°C solution for 2min, and finally polishing in a nitric acid (HNO3, 300-500g / L) solution.

[0059] In this embodiment, welding must be completed within 48 hours after chemical cleaning to avoid the formation of new oxide films and contaminants on the pre-treated parts surface.

[0060] In this embodiment, the welding wire used during welding is an aluminum alloy welding wire of the same series as the aluminum alloy medium and thick plates to be welded. For example, 5A06 welding wire is used for welding 5A06, and 5A03 welding wire is used for welding 5A03 and 5A02.

[0061] The parent material of this embodiment is an aluminum alloy, such as 5A06, 5A03, 5A02, etc. The welding wire uses an aluminum alloy welding wire of the same series as the parent material, such as 5A06 welding wire is used for welding 5A06, and 5A03 welding wire is used for welding 5A03 and 5A02. The use of aluminum alloy welding wire of the same series as the parent material can obtain excellent weld microstructure and properties to ensure that the weld quality that meets the requirements is obtained.

[0062] In this embodiment, the purity of argon is required to be no less than 99.99%, and the quality of argon should meet the requirements of GB / T4842. Argon arc welding is sensitive to the purity of argon. When the purity of argon is reduced or the moisture content in argon exceeds the standard, the tendency of pores to form in the weld increases significantly, thereby reducing the quality of the weld.

[0063] In this embodiment, tungsten inert gas arc welding equipment is used for welding, and the welding technical parameters are: welding current 60-180A, argon gas flow rate 8-12L / min, and welding wire diameter φ2-3mm.

[0064] In this embodiment, the "fast belt arc closure" is adopted when the aluminum alloy parts are welded. When the arc is closure, the welding current is attenuated while the welding gun is gradually lifted up and the speed is increased to "bring" it through the arc closure area, so as to reduce the concentration of impurities in the molten pool metal at the arc closure part.

[0065] In this embodiment, the aluminum alloy parts are anodized by the following method after welding: solution composition sulfuric acid (H2SO4) 180-200 g / L, chloride (as NaCl) ≤ 0.2 g / L, aluminum ion ≤ 20 g / L; temperature 13-26°C; time 20-60 min.

[0066] In this embodiment, the color of the weld of the aluminum alloy part after anodizing is normal, and the weld will not be unqualified due to obvious blackening of the color at the end of the arc.

[0067] Taking a certain aluminum alloy medium and thin plate welded part as an example, the main process of preventing the local color of the weld arc end point from turning black after the part is anodized is as follows:

[0068] (1) Chemically clean the surface of the welding part of the aluminum alloy thin plate parts to remove the oxide film and oil stains;

[0069] (2) Assemble aluminum alloy medium and thin plate parts on the assembly fixture to ensure their assembly position relationship;

[0070] (3) Position welding using tungsten inert gas welding method;

[0071] (4) Correction of positioning welding deformation;

[0072] (5) When completing the welding of the weld seams of thin plate parts of aluminum alloy, pay attention to the use of "fast belt arc closing" when closing the arc;

[0073] (6) Anodizing the aluminum alloy parts;

[0074] (7) Check the appearance quality of aluminum alloy parts and whether the color of the weld after anodizing is normal;

[0075] (8) Complete the warehousing procedures for qualified parts.

[0076] The above is only a preferred embodiment of the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made without departing from the principles of the present invention, and these improvements and modifications should also be considered as the protection scope of the present invention. The structures, devices and operating methods not specifically described and explained in the present invention shall be implemented according to the conventional means in the art unless otherwise specified and limited.

Claims

1. A method for preventing local blackening of welds of aluminum alloy parts after anodizing, characterized in that: The method comprises the following steps: Step 1: Chemically clean the parts to be welded of the aluminum alloy parts to remove the oxide film and oil stains on the parts to be welded; Step 2: Assemble aluminum alloy parts on the assembly fixture; Step 3: Use tungsten inert gas arc welding method to perform positioning welding; Step 4: Correct the positioning welding deformation; Step 5: Set the welding parameters and use tungsten inert gas welding to complete the welding of the aluminum alloy parts. At the end of the weld, the arc is closed and the welding current is attenuated. At the same time, the welding gun is gradually lifted up and the speed is increased to pass through the arc closing area; Step 6: Remove the parts from the fixture; Step 7: Anodize the aluminum alloy parts; Step 8: Check the surface quality of parts.

2. The method according to claim 1, characterized in that In the step 1, the chemical cleaning process is as follows: First degreasing in sodium phosphate and first caustic soda solution, Then, it is alkaline-etched in a second caustic soda solution. Finally, the light was emitted in a nitric acid solution; Among them, the chemical formula of sodium phosphate is Na2PO4˙12H2O, and the concentration is 40-60g / L; The first caustic soda uses sodium hydroxide NaOH with a concentration of 8 to 12 g / L; The second caustic soda uses sodium hydroxide NaOH with a concentration of 40-60 g / L; The concentration of nitric acid solution is 300-500g / L.

3. The method according to claim 1, characterized in that In the step 2, the assembly welding must be completed within 48 hours after the chemical cleaning treatment.

4. The method according to claim 1, characterized in that: In the step 5, the welding wire used during welding is an aluminum alloy welding wire of the same series as the aluminum alloy to be welded. For example, when welding 5A06, use 5A06 welding wire; when welding 5A03 and 5A02, use 5A03 welding wire.

5. The method according to claim 1, characterized in that In the step 5, argon gas is used to protect the weld area during welding, and the purity of the argon gas is not less than 99.99%, and the quality of the argon gas should meet the requirements of GB / T4842.

6. The method according to claim 1, characterized in that In the step 5, the welding technical parameters are: welding current 60-180A, argon gas flow rate 8-12L / min, and welding wire diameter φ2-3.5mm.

7. The method according to claim 1, characterized in that In the step 7, the welded parts are anodized by the following method: solution composition: sulfuric acid 180-200 g / L, chloride ≤0.2 g / L, aluminum ion ≤20 g / L; temperature 13-26° C.; time 20-60 min.

8. The method according to claim 1, characterized in that In the step eight, after the aluminum alloy parts are anodized, the surface color of the weld is normal, the appearance is qualified, and there is no local blackening at the arc closing point.