A melting welding activator for aluminum alloy and its application method and workpiece

Abstract

The embodiment of the present invention provides an activator for aluminum alloy melting welding, an application method thereof, and a workpiece, wherein the activator includes 88wt% to 98wt% silicon dioxide and 2wt% to 12wt% chromium oxide. The embodiment of the present invention limits the content of SiO2 in the above activator to 88wt% to 98wt%, and limits the content of Cr2O3 to 2wt% to 12wt%. The two components work together at the above weight percentages to enhance the fluidity of the molten pool, refine the grains, and thus reduce the sensitivity of weld cracks, that is, the welding strength and workpiece airtightness will not be reduced due to the appearance of welding cracks, thereby affecting the safety and life of the battery.

Description

Technical Field

[0001] The invention relates to the technical field of laser welding, and in particular to a melting welding activator for aluminum alloy and an application method and a workpiece thereof. Background Art

[0002] Currently, the side seam welding materials of battery packs are mostly sixth-series aluminum alloys, which can ensure welding strength.

[0003] However, when performing melting welding such as laser welding, the sixth series aluminum alloy is prone to welding thermal cracks due to the high heat input, which reduces the welding strength and the air tightness of the workpiece, thereby affecting the safety and life of the battery.

[0004] Therefore, the prior art needs to be improved. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a melting welding activator for aluminum alloy and its application method and workpiece, so as to solve the technical problem that welding cracks are easy to occur in the melting welding of aluminum alloy in the prior art.

[0006] In order to solve the above problems, the present invention is achieved through the following technical solutions:

[0007] The invention provides an activator for aluminum alloy melting welding, wherein the activator comprises 88wt% to 98wt% of silicon dioxide and 2wt% to 12wt% of chromium oxide.

[0008] Furthermore, in the active agent, the active agent includes 95wt% of silicon dioxide and 5wt% of chromium oxide.

[0009] The present invention also provides a method for applying the active agent as described above, which comprises:

[0010] Coating the activating agent on the surface of the aluminum alloy workpiece to be welded;

[0011] The aluminum alloy workpieces coated with the activating agent are melt-welded.

[0012] Furthermore, in the application method, coating an activating agent on the surface of the aluminum alloy workpiece to be welded comprises:

[0013] preparing a suspension of the active agent;

[0014] Applying the suspension to the surface of the aluminum alloy workpiece to be welded;

[0015] The aluminum alloy workpiece coated with the activating agent is melt-welded, comprising:

[0016] After the activating agent is dried, the aluminum alloy workpiece coated with the activating agent is laser welded.

[0017] Furthermore, in the application method, the solvent of the suspension is alcohol.

[0018] Furthermore, in the application method, in the step of coating the activator on the surface of the aluminum alloy workpiece to be welded, the coating amount of the activator is 0.5-1.5 mg / cm 2 .

[0019] Furthermore, in the application method, the laser power of the laser welding is 2700w to 3300w, the welding speed is 250 to 350mm / s, and the defocus amount is -1.5mm to 1.5mm.

[0020] Furthermore, in the application method, before coating the activating agent on the surface of the aluminum alloy workpiece to be welded, the method further comprises:

[0021] The workpiece to be processed is preprocessed in advance.

[0022] Furthermore, in the application method, the aluminum alloy workpiece is a sixth series aluminum alloy workpiece.

[0023] The present invention also provides a workpiece, wherein the workpiece is processed by the application method as described above.

[0024] Compared with the prior art, the embodiments of the present invention have the following advantages:

[0025] In an embodiment of the present invention, an activator for aluminum alloy fusion welding is provided, which includes 88 wt% to 98 wt% of silicon dioxide and 2 wt% to 12 wt% of chromium oxide. Among them, because the hot cracks of aluminum alloy melting welding are caused by the input of high heat, the metal components in the aluminum alloy form low-melting eutectics, resulting in weak grain boundaries during the solidification process of the weld, and cracks are generated after stress pulling; in the activator provided in the embodiment of the present application, although silicon dioxide has the function of enhancing the fluidity of the molten pool and improving the process performance, when the content is too little, it cannot effectively enhance the fluidity of the molten pool, and when the content is too much, it will enhance the oxidizability, increase the burn-off of the alloy elements in the surfacing layer, and reduce the mechanical properties and corrosion properties of the surfacing metal. At the same time, too much SiO2 will also cause the weld metal to increase silicon and increase the crack sensitivity of the surfacing metal. For this reason, the SiO2 content is controlled at 88wt% to 98wt%; although Cr2O3 can refine the grains and improve the weld formation, when the content is too low, it cannot effectively refine the grains, that is, it cannot effectively reduce the aggregation of low-melting eutectics at the arc pit, and when its content is too high, it is easy to form impurities such as insoluble substances, which will affect the welding strength.

[0026] By limiting the SiO2 content in the above-mentioned active agent to 88wt%~98wt% and limiting the Cr2O3 content to 2wt%~12wt%, the two components work together at the above-mentioned weight percentages to enhance the fluidity of the molten pool and refine the grains, thereby reducing the aggregation of low-melting eutectics in the arc pit, enhancing the grain boundary strength, and thus reducing the sensitivity of the weld crack. In other words, the welding strength and the air tightness of the workpiece will not be reduced due to the appearance of welding cracks, thereby affecting the safety and life of the battery.

[0027] It should be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a flow chart of an application method of an activator for aluminum alloy melting welding provided by an embodiment of the present invention;

[0029] Figure 2 is a photograph of the arc crater of the weld of sample A at the first magnification in Example (1) of the present invention;

[0030] Figure 3 This is a second magnification photograph of the arc crater of the weld of sample A in Example (1) of the present invention;

[0031] Figure 4 This is a second magnification photograph of the arc crater of the weld of sample B in Example (2) of the present invention;

[0032] Figure 5 This is a second magnification photograph of the arc crater of the weld of sample C in Example (3) of the present invention;

[0033] Figure 6 This is a photograph of the arc crater of the weld of sample E at the first magnification in comparative example (1) of the present invention;

[0034] Figure 7 This is a photograph of the arc crater of the weld of sample E in comparative example (1) of the present invention at the second magnification. DETAILED DESCRIPTION

[0035] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0036] An activator for aluminum alloy melting welding provided by an embodiment of the present invention comprises, by weight percentage, 88wt% to 98wt% of silicon dioxide and 2wt% to 12wt% of chromium oxide.

[0037] Among them, due to the characteristics of the material itself, aluminum alloy, especially the sixth series aluminum alloy, forms a low-melting eutectic due to the high heat input during melting welding, resulting in a weak grain boundary during the solidification of the weld, and easily generating thermal cracks after stress pulling, thereby reducing the welding strength, that is, the airtightness of the welding position cannot be guaranteed. The activator for aluminum alloy melting welding provided by the embodiment of the present invention is specifically used to be applied to the surface of the aluminum alloy workpiece to be welded before melting welding, wherein SiO2 can enhance the fluidity of the molten pool, and the addition of Cr2O3 can refine the grains. The two components work together to reduce the aggregation of low-melting eutectics at the arc pit, enhance the grain boundary strength, thereby reducing the crack sensitivity of the weld, and avoiding the problem of reducing the welding strength and the airtightness of the workpiece due to the appearance of welding cracks, thereby affecting the safety and life of the battery.

[0038] In the above-mentioned active agent, the weight percentages of silicon dioxide and chromium oxide are 88% to 98% and 2% to 12% respectively. Among them, because the main function of silicon dioxide is to enhance the fluidity of the molten pool and improve the process performance, too little content cannot effectively enhance the fluidity of the molten pool, but too much content will enhance the oxidizability, increase the burnout of the alloy elements in the cladding layer, and reduce the mechanical properties and corrosion properties of the cladding metal. At the same time, too much SiO2 will also lead to silicon increase in the weld metal and increase the crack sensitivity of the cladding metal. For this reason, the SiO2 content is controlled at 88wt% to 98wt%; the main function of Cr2O3 is to refine the grains and improve the weld formation. If its content is too low, it cannot effectively refine the grains, that is, it cannot effectively reduce the aggregation of low-melting eutectics at the arc pit. If its content is too high, it is easy to form impurities such as insoluble substances, which will affect the welding strength. Therefore, the content of Cr2O3 is controlled at 2wt% to 12wt%.

[0039] Different from traditional welding activators, the activator for aluminum alloy melting welding provided by the embodiment of the present invention, i.e., the activator for aluminum alloy melting welding, can be composed only of silicon dioxide (SiO2) and chromium oxide (Cr2O3). It has simple composition and good stability, and can meet the needs of large-scale mass production.

[0040] In practical applications, the weight percentage of silicon dioxide in the above active agent can be specifically 95%, and the weight percentage of chromium oxide can be specifically 5%.

[0041] Preferably, the above-mentioned activator is applied to the melting welding of the six-series aluminum alloy, because the Mg, Al, Si and other components in the six-series aluminum alloy are more likely to form low-melting eutectics during the melting welding process, resulting in weak grain boundaries during the solidification of the weld and cracks after stress pulling; the SiO2 added to the above-mentioned activator can enhance the fluidity of the molten pool, and the addition of Cr2O3 can refine the grains. The two components work together to effectively reduce the aggregation of low-melting eutectics at the arc pit of the six-series aluminum alloy, thereby significantly enhancing the grain boundary strength. Among them, the above-mentioned melting welding can be selected as laser welding. Due to the higher heat input parameters of laser welding, it is easier to form welding cracks, and the addition of the above-mentioned activator can effectively reduce the side seam weld crack rate formed by laser welding at the welding point of the six-series aluminum alloy.

[0042] In practical applications, the above-mentioned activator is applied to the laser welding of six-series aluminum alloy workpieces. The activator is coated on the surface of the six-series aluminum alloy workpiece to be welded, and then laser welding is carried out under the conditions of laser power of 2700w~3300w, welding speed of 250~350mm / s, and defocus of -1.5mm~1.5mm to obtain welds with low crack rate and high welding strength.

[0043] The embodiment of the present invention also provides a method for applying the active agent as described above.

[0044] See also Figure 1 , shows a flow chart of the application method of the above-mentioned micro-arc oxidation electrolyte provided by a preferred embodiment of the present invention, such as Figure 1 As shown, the method may include steps S100 to S200:

[0045] Step S100, coating the activating agent on the surface of the aluminum alloy workpiece to be welded;

[0046] Step S200: performing melt welding on the aluminum alloy workpiece coated with the activating agent.

[0047] In the embodiment of the present invention, the above-mentioned aluminum alloy melting welding activator composed of silicon dioxide and chromium oxide is first coated on the surface of the aluminum alloy workpiece that needs to be melt-welded, and then the aluminum alloy workpiece is melt-welded, that is, a dense and smooth blue ceramic film layer can be formed on the surface of the weld of the above-mentioned aluminum alloy workpiece. When melting welding is performed, the metal components in the aluminum alloy form low-melting eutectics due to the input of high heat, resulting in weak grain boundaries during the solidification process of the weld, and thermal cracks are easily generated after stress pulling, thereby reducing the welding strength, that is, the airtightness of the welding position cannot be guaranteed. Before melting welding, it is coated on the surface of the aluminum alloy workpiece to be welded, and the SiO2 therein can enhance the fluidity of the molten pool, while the addition of Cr2O3 can refine the grains. The two components work together to reduce the aggregation of low-melting eutectics at the arc pit, enhance the grain boundary strength, thereby reducing the crack sensitivity of the weld, and avoiding the reduction of welding strength and workpiece airtightness due to the appearance of welding cracks.

[0048] In practical applications, the above-mentioned aluminum alloy workpiece can be a six-series aluminum alloy workpiece, such as a 6061 aluminum alloy workpiece, specifically a six-series aluminum alloy battery pack. Because Mg, Al, Si and other components in the six-series aluminum alloy are more likely to form low-melting eutectics during the melting welding process, resulting in weak grain boundaries during the solidification of the weld and cracks after stress pulling, the above-mentioned activator is more suitable for the melting welding of six-series aluminum alloy workpieces, and can significantly reduce the side seam weld crack rate formed by laser welding at the six-series aluminum alloy weld.

[0049] Optionally, in the above step S100, the coating amount of the active agent is 0.5-1.5 mg / cm 2 If the coating amount is too small, it cannot effectively reduce the aggregation of low-melting eutectics at the arc pit and enhance the grain boundary strength, that is, it cannot effectively reduce the crack sensitivity of the weld; while if the coating amount is too large, it is easy to form impurities in the weld due to insoluble substances, affecting the welding strength and other side effects. Preferably, the coating amount of the active agent is controlled to be 0.8-1 mg / cm 2 .

[0050] Optionally, in the above step S100, the active agent can be first configured into a suspension, for example, the active agent is dispersed in alcohol to form an active agent suspension; then the suspension is coated on the surface of the aluminum alloy workpiece to be welded, and after the solvent evaporates and the active agent dries, the active agent can be evenly coated on the surface of the aluminum alloy workpiece to be welded.

[0051] Optionally, before applying the activator to the aluminum alloy to be welded, the aluminum alloy workpiece to be welded is pre-treated in advance to remove surface oil stains, oxide film, etc., to facilitate subsequent melting welding. Wherein, the pre-treatment includes degreasing and acid etching or laser cleaning the workpiece to be treated. Wherein, the degreasing treatment can remove the oil stains on the surface of the workpiece, while the acid etching and laser treatment can remove the original oxide film layer on the surface of the workpiece, which is convenient for the subsequent melting welding process to form a dense, firm and crack-free weld on the surface of the aluminum alloy workpiece. Wherein, the degreasing treatment can be carried out using existing degreasing technology. Preferably, alcohol is used for degreasing. More preferably, water washing is carried out after the degreasing and acid etching treatments to avoid contamination between the reagents and affect the melting welding treatment effect.

[0052] Specifically, in the above step S200, after the activator is dried, the aluminum alloy workpiece coated with the above activator is laser welded by laser welding. Among them, because laser welding has a high heat input, the welding process can be completed quickly; but because of the high heat output, welding cracks are more likely to form, and the addition of the above activator can effectively reduce the weld crack rate formed by laser welding at the aluminum alloy welding point.

[0053] Specifically, in step S200, laser welding is carried out under the conditions of laser power of 2700W to 3300W, welding speed of 250 to 350mm / s, and defocus of -1.5mm to 1.5mm, that is, a dense, firm weld with few cracks can be formed on the surface of the workpiece, and the laser welding swing width and track spacing can be adjusted according to welding needs, for example, the laser power is controlled to 3000W, the welding speed is 300mm / s, the defocus is 0mm, the swing width is 2mm, and the track spacing is 0.5mm.

[0054] In addition, the present invention also provides a workpiece, which is obtained by processing the application method as described above.

[0055] The present invention is described in detail below by way of examples.

[0056] Example 1

[0057] (1) An activator for aluminum alloy melting welding composed of Cr2O3 and SiO2 is prepared, wherein the weight percentage of Cr2O3 is 12% and the weight percentage of SiO2 is 88%.

[0058] (2) Add alcohol to the active agent in step (1) to form a suspension.

[0059] (3) Before the solid components are precipitated, the suspension of step (2) is applied to the surface of the workpiece to be welded, with a coating amount of 1 mg / cm 2,The workpiece material is double-layer 2mm thick 6061 aluminum alloy.

[0060] (4) After the activating agent is dried, laser welding is performed with the following welding parameters: laser power P = 3000 W, welding speed 300 mm / s, defocus 0 mm, swing width 2 mm, track spacing 0.5 mm, and sample A is obtained.

[0061] (5) Observe sample A under a 20x microscope. Figure 2 As shown, the measured crack length is 1.65 mm.

[0062] Example 2

[0063] (1) An activator for aluminum alloy melting welding composed of Cr2O3 and SiO2 is prepared, wherein the weight percentage of Cr2O3 is 8.5% and the weight percentage of SiO2 is 91.5%.

[0064] (2) Add alcohol to the active agent in step (1) to form a suspension.

[0065] (3) Before the solid components are precipitated, the suspension of step (2) is applied to the surface of the workpiece to be welded, with a coating amount of 1 mg / cm 2 ,The workpiece material is double-layer 2mm thick 6061 aluminum alloy.

[0066] (4) After the activating agent is dried, laser welding is performed with the following welding parameters: laser power P = 3000 W, welding speed 300 mm / s, defocus 0 mm, swing width 2 mm, track spacing 0.5 mm, and sample B is obtained.

[0067] (5) Observe sample B under a 20x microscope. Figure 4 As shown, the measured crack length is 1.12 mm.

[0068] Example 3

[0069] (1) An activator for aluminum alloy melting welding composed of Cr2O3 and SiO2 is prepared, wherein the weight percentage of Cr2O3 is 5% and the weight percentage of SiO2 is 95%.

[0070] (2) Add alcohol to the active agent in step (1) to form a suspension.

[0071] (3) Before the solid components are precipitated, the suspension of step (2) is applied to the surface of the workpiece to be welded, with a coating amount of 1 mg / cm 2 ,The workpiece material is double-layer 2mm thick 6061 aluminum alloy.

[0072] (4) After the activator is dried, laser welding is performed with the following welding parameters: laser power P = 3000 W, welding speed 300 mm / s, defocus 0 mm, swing width 2 mm, track spacing 0.5 mm, and sample C is obtained.

[0073] (5) Observe sample C under a 20x microscope. The results are as follows: Figure 5 As shown, the measured crack length is 0.89 mm.

[0074] Example 4

[0075] (1) An activator composed of Cr2O3 and SiO2 for aluminum alloy melting welding is prepared, wherein the weight percentage of Cr2O3 is 3.5% and the weight percentage of SiO2 is 96.5%.

[0076] (2) Add alcohol to the active agent in step (1) to form a suspension.

[0077] (3) Before the solid components are precipitated, the suspension of step (2) is applied to the surface of the workpiece to be welded, with a coating amount of 1 mg / cm 2 ,The workpiece material is double-layer 2mm thick 6061 aluminum alloy.

[0078] (4) After the activating agent is dried, laser welding is performed with the following welding parameters: laser power P = 3000 W, welding speed 300 mm / s, defocus 0 mm, swing width 2 mm, track spacing 0.5 mm, and sample D is obtained.

[0079] (5) Sample D was observed under a 20x microscope and the crack length was measured to be 0.98 mm.

[0080] Comparative Example 1

[0081] (1) The workpiece to be welded is directly laser welded with the following welding parameters: laser power P = 3000 W, welding speed 300 mm / s, defocus 0 mm, swing width 2 mm, track spacing 0.5 mm, and sample E is obtained.

[0082] (2) Observe sample E under a 20x microscope. The results are as follows: Figure 6 and Figure 7 As shown, the measured crack length is 4.88 mm.

[0083] Comparative Example 2

[0084] (1) An activator for aluminum alloy melting welding is prepared, which is composed of V2O5, NaF and Cr2O3, wherein the weight percentage of V2O5 is 12%, the weight percentage of NaF is 81.4%, and the weight percentage of Cr2O3 is 6.6%.

[0085] (2) Add alcohol to the active agent in step (1) to form a suspension.

[0086] (3) Before the solid components are precipitated, the suspension of step (2) is applied to the surface of the workpiece to be welded, with a coating amount of 1 mg / cm 2 ,The workpiece material is double-layer 2mm thick 6061 aluminum alloy.

[0087] (4) After the activating agent is dried, laser welding is performed with the following welding parameters: laser power P = 3000 W, welding speed 300 mm / s, defocus 0 mm, swing width 2 mm, track spacing 0.5 mm, and sample F is obtained.

[0088] (5) Sample F was observed under a 20x microscope and the crack length was measured to be 2.48 mm.

[0089] By comparing Example 1 with Comparative Example 1, Example 2 with Comparative Example 1, Example 3 with Comparative Example 1, and Example 4 with Comparative Example 1, it can be seen that when the activator provided in the embodiments of the present invention is coated on the surface of a six-series aluminum alloy workpiece to be welded and then the aluminum alloy is laser welded, the weld crack length can be significantly reduced, thereby improving the welding strength and the density of the workpiece.

[0090] By comparing Example 1 with Comparative Example 2, Example 2 with Comparative Example 2, Example 3 with Comparative Example 2, and Example 4 with Comparative Example 2, it can be seen that when the activator is coated on the surface of a six-series aluminum alloy workpiece to be welded and then the aluminum alloy is laser welded, the aluminum alloy product coated with the activator provided by the embodiment of the present invention has a shorter weld crack length and better workpiece density.

[0091] By comparing Example 1, Example 2 and Example 3, it can be seen that when the activator provided by the embodiment of the present invention is coated on the surface of the six-series aluminum alloy to be welded and then subjected to laser welding, the length of the weld crack can be reduced by increasing the content of silicon dioxide and reducing the content of chromium oxide. By comparing Example 3 and Example 4, it can be seen that the continued increase in the content of silicon dioxide will lead to insufficient content of chromium oxide, which cannot effectively refine the grains, but is not conducive to reducing the length of the weld crack.

[0092] In summary, in this embodiment, the activator provided for aluminum alloy melting welding includes silicon dioxide and chromium oxide, wherein, because the thermal cracks in aluminum alloy melting welding are caused by the high heat input causing the metal components in the aluminum alloy to form a low-melting eutectic, resulting in weak grain boundaries during the solidification process of the weld, and are generated after stress pulling; and by limiting the SiO2 content in the above-mentioned activator to 88wt%~98wt%, and limiting the Cr2O3 content to 2wt%~12wt% to 2wt%~12wt%, the two components work together at the above-mentioned weight percentages to enhance the fluidity of the molten pool and refine the grains, thereby reducing the aggregation of low-melting eutectics at the arc pit, enhancing the grain boundary strength, and thus reducing the crack sensitivity of the weld, that is, the welding strength and the airtightness of the workpiece will not be reduced due to the appearance of welding cracks, thereby affecting the safety and life of the battery.

[0093] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they are aware of the basic creative concept. Therefore, the claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the embodiments of the present invention.

[0094] The above is a detailed introduction to an activator for aluminum alloy melting welding and its application method and workpiece provided by the present invention. Specific examples are used in this article to illustrate the principle and implementation method of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea; at the same time, for a general technician in this field, according to the idea of ​​the present invention, there will be changes in the specific implementation method and application scope. In summary, the content of this specification should not be understood as a limitation on the present invention.

Claims

1. An activator for aluminum alloy melting welding, characterized in that: The active agent is composed of silicon dioxide and chromium oxide, and the active agent includes 88wt% to 98wt% of silicon dioxide and 2wt% to 12wt% of chromium oxide; The activator is applied to laser welding of six series aluminum alloy workpieces.

2. A method for using the active agent as claimed in claim 1, characterized in that: include: coating the activating agent on the surface of the aluminum alloy workpiece to be welded; The aluminum alloy workpieces coated with the activating agent are melt-welded.

3. The application method according to claim 2, characterized in that: The active agent is applied to the surface of the aluminum alloy workpiece to be welded, including: preparing a suspension of the active agent; Applying the suspension to the surface of the aluminum alloy workpiece to be welded; The aluminum alloy workpiece coated with the activating agent is melt-welded, comprising: After the activating agent is dried, the aluminum alloy workpiece coated with the activating agent is laser welded.

4. The application method according to claim 3, characterized in that: The laser power of the laser welding is 2700w-3300w, the welding speed is 250-350mm / s, and the defocusing amount is -1.5mm-1.5mm.

5. The application method according to claim 2, characterized in that: The solvent of the suspension is alcohol.

6. The application method according to claim 2, characterized in that: In the step of coating the activator on the surface of the aluminum alloy workpiece to be welded, the coating amount of the activator is 0.5-1.5 mg / cm 2 .

7. The application method according to claim 2, characterized in that: Before coating the activating agent on the surface of the aluminum alloy workpiece to be welded, the method further comprises: The aluminum alloy workpiece to be welded is pre-treated in advance.

8. A workpiece, characterized in that: Obtained by the application method described in any one of claims 2 to 7.

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