Ultra-thick aluminum plate welding process

Abstract

This application relates to the technical field of sheet metal welding, and particularly to a welding process for ultra-thick aluminum plates, which includes the following steps: groove design, using an X-shaped structure as the groove type; welding, adopting the segmented backstep welding method, and using pure Ar gas or a mixed gas of Ar and He as the shielding gas, and performing welding in a swinging manner. Among them, multiple welding layers are formed in each groove. In this application, the segmented backstep welding method is further used to reduce the workload of each welding and reduce the welding deformation caused by long-term welding, thereby improving the welding quality. The selection of the shielding gas is helpful for increasing the weld penetration depth and reducing the porosity rate of the weld for aluminum plates with high welding radiation and preheating temperature, and improving the weld quality. Finally, the swinging welding method can, on the one hand, increase the welding width, reduce the number of welding passes per layer to reduce the workload of each welding, and at the same time improve the welding quality, obtaining a weld with a neat appearance, uniform structure and excellent quality.

Description

Technical Field

[0001] This application relates to the technical field of sheet metal welding, and particularly relates to a welding process for ultra-thick aluminum plates. Background Art

[0002] During the processing of the vacuum aluminum shell of a cryogenic storage spherical tank, it is necessary to form it by welding multiple arc-shaped spherical shells. Among them, due to the large thickness of the spherical shell, especially for the spherical shell of the newly built vacuum aluminum spherical shell target chamber, the material of the spherical shell is 5083-O with a thickness of 110 mm, which is relatively thick. Welding of aluminum alloys with such a thickness is the first time in the domestic same industry or related industries, which also poses great difficulties for the welding of the spherical shell.

[0003] For the above-mentioned vacuum aluminum spherical shell target chamber, due to the excessive thickness of the spherical shell, the groove depth is large. After the groove depth increases, it not only increases the difficulty of welding operation, but also the shrinkage rate of aluminum alloy welding is large, making it easier to generate pores during the welding process; in addition, the welding length required for the spherical shell is relatively large, resulting in a long welding cycle and a large workload. Therefore, it is easy to cause insufficient strength in the near-weld zone, and cracking is very likely to occur during the bending performance test. Summary of the Invention

[0004] In order to improve the strength of the near-weld zone, this application provides a welding process for ultra-thick aluminum plates.

[0005] This application provides a welding process for ultra-thick aluminum plates, adopting the following technical solutions:

[0006] A welding process for ultra-thick aluminum plates includes the following steps:

[0007] Groove design, using the X-type structure as the groove type;

[0008] Welding, using the segmented backstep welding method, and using pure Ar gas or a mixed gas of Ar and He as the shielding gas, and performing welding in a swing manner. Among them, multiple welding layers are formed in each groove.

[0009] With such settings, first of all, the structure of the X-type groove can reduce the depth and width of a single groove required for welding, thereby reducing the workload of a single welding layer; then, the segmented backstep welding method is further used to reduce the workload of each welding and reduce the welding deformation caused by long-term welding, thereby improving the welding quality. The selection of the shielding gas is helpful for increasing the weld penetration and reducing the porosity of the weld for aluminum plates with high welding radiation and preheating temperature, improving the weld quality. Finally, the swing welding method can, on the one hand, increase the welding width, reduce the number of welding passes per layer to reduce the workload of each welding, and at the same time can also improve the welding quality, obtaining a weld with a neat appearance, uniform structure and excellent quality.

[0010] Optionally: It is divided into multiple segments vertically according to the sectional backstep welding method, and the welding method for each segment is upward vertical welding.

[0011] With such a setting, on the one hand, the heat influence can be reduced to avoid deformation, and on the other hand, multiple segments can be welded simultaneously to improve the welding efficiency.

[0012] Optionally: In the X-shaped groove structure, the depths of the grooves on both sides are set differently, and the fan angle of the groove with a smaller depth is 4 - 8° larger than the fan angle of the groove with a larger depth.

[0013] With such a setting, by setting different depths of the inner and outer grooves and the sizes of the fan angles, on the one hand, the generation of prestress during the welding of the spherical tank can be better reduced to control the welding deformation; on the other hand, the welding difficulty can be reduced, that is, the welding strength of the groove with a smaller depth can be greatly reduced, and based on the characteristics of the inside and outside of the spherical shell, the overall welding strength can be reduced accordingly.

[0014] Optionally: Before welding and after each welding layer is completed, the groove needs to be polished until there are no obvious concave and convex grooves and wrinkled tool marks on the groove.

[0015] With such a setting, the fusion degree of welding is improved, and it is avoided that the concave and convex grooves and tool marks on the groove surface cannot be melted by the molten pool, resulting in multiple strip unfused phenomena.

[0016] Optionally: When welding the first welding layer of the two grooves, the wire diameter used is larger than that used in other layers of welding, and the root face height between the two grooves is greater than the wire diameter during the first layer of welding and not greater than twice the wire diameter during the first layer of welding;

[0017] When welding the first welding layer of the two grooves, the welding points on both sides are arranged relatively and move synchronously in a straight line.

[0018] With such a setting, the root face setting plays a role in preventing the root of the groove from being burned through. By using two relatively arranged welding torches for welding and setting the dimensions of the root face height and wire diameter, the welding efficiency at the root face position is high, and the welding of the first welding layer of the two grooves can be completed in one pass without using oscillatory welding, and the difficulty is low. In addition, due to the use of the relative welding method, the generation of pores can be better reduced and the penetration depth can be ensured, improving the welding quality.

[0019] Optionally: The root face height between the two grooves is greater than the wire diameter during the first layer of welding and less than twice the wire diameter during the first layer of welding, and the welding current and voltage of the groove with a smaller depth are both greater than those of the groove with a larger depth.

[0020] With such settings, the penetration depth and width of the side with a smaller groove depth are increased. On the one hand, it can ensure penetration, reduce or even prevent the generation of pores, and at the same time prevent defects such as oxidation, welding beads, and incomplete penetration in the weld.

[0021] Optionally: When welding the first welding layer, pure Ar gas is used as the shielding gas, and for the remaining welding layers, a mixed gas of Ar and He is used as the shielding gas.

[0022] With such settings, the penetration depth of the first welding layer during welding is sufficient to meet the usage requirements. Therefore, pure Ar gas can be used. However, during the welding of subsequent welding layers, pore formation is likely to occur. Therefore, a mixed gas of Ar and He is used to increase the penetration depth and reduce the porosity rate.

[0023] Optionally: When using a mixed gas of Ar and He, the proportion of He gas is at least 40%.

[0024] With such settings, increasing the proportion of He gas can increase the penetration depth and reduce the influence of the shrinkage rate during aluminum alloy welding, thereby reducing the generation of pores during welding. However, correspondingly, the cost will also increase. Therefore, a shielding gas with a mixing ratio of 40% He + 60% Ar is a better choice.

[0025] Optionally: When welding the first welding layer, the electrode polarity is direct current straight polarity, and for the remaining welding layers, the electrode polarity is direct current reverse polarity.

[0026] With such settings, using direct current straight polarity for the first layer makes the penetration depth deeper; for the remaining layers, since oscillatory welding is required, the direct current reverse polarity method is more stable, less likely to generate pores, reduces the welding difficulty, and better controls the deformation. In addition, direct current reverse polarity can also break the oxide film during aluminum plate welding and improve the welding quality.

[0027] Optionally: Before welding, the aluminum plate is preheated to a temperature of 150 - 160°C, and during welding, the preheating temperature at the root of the groove is increased to 178 - 185°C. Among them, after the root of the groove reaches the preheating temperature, it is insulated for 15 minutes before starting welding;

[0028] After welding, stress relief treatment is carried out by insulating at 300 - 370°C for 2 - 4 h, where the heating width is 5*(R*S)*0.5 mm, R is the diameter of the spherical tank, and S is the wall thickness.

[0029] With such settings, adopting the above preheating method can improve the welding effect of the aluminum plate, reduce the appearance of pores, and perform stress relief treatment after welding, thereby further improving the welding quality. Description of the Drawings

[0030] Figure 1 is a schematic structural diagram of the X-shaped groove in this embodiment;

[0031] Figure 2It is a schematic structural diagram of the weld bead and weld layer after welding in this embodiment;

[0032] Figure 3 It is a sectional view of the sampling position for trace element monitoring in this embodiment;

[0033] Figure 4 It is a microstructure diagram of the base metal of the test plate weld;

[0034] Figure 5 It is a microstructure diagram of the test plate weld after welding. Specific implementation mode

[0035] The following further details this application in conjunction with the accompanying drawings.

[0036] A welding process for ultra-thick aluminum plates includes the following steps:

[0037] S1. Groove design: V-shaped grooves are provided on both the inner and outer sides of the aluminum plate, a root face is formed between the two V-shaped grooves, and an X-shaped groove is formed through the two V-shaped grooves. Among them, the depths of the grooves on both sides are set differently, and the fan angle of the groove with a smaller depth is 4-8° larger than the fan angle of the groove with a larger depth.

[0038] S2. Assembly: Fix two aluminum plates through a fixture, and adjust the arc and spacing between the two aluminum plates.

[0039] S3. Surface treatment: Grind the surfaces of the two grooves until there are no obvious uneven grooves and wrinkled knife marks. Among them, when there are many uneven grooves before grinding, tools such as planing saws can be used for surface treatment first, and then grinding. After finishing grinding, stand the aluminum plate upright.

[0040] S4. Preheating: Preheat the aluminum plate through an electric heating plate. Among them, the electric heating plate can be fixed on the surface of the aluminum plate, and the preheating temperature is 150-160°C. When preparing for welding, the preheating temperature at the root of the groove is increased to 178-185°C, and it is kept warm for 15 minutes after reaching the preheating temperature.

[0041] S5. First layer welding: Welding torches are arranged in both grooves. The two welding torches are arranged oppositely and move synchronously. The two welding torches are located on the symmetry plane of the two aluminum plates and move in a straight line on the symmetry plane. Among them, it is preferred to use a fully automatic welding machine or a semi-automatic welding machine in this step, that is, the moving speed of the two welding torches is realized by an electric method.

[0042] In this step, the height of the root face between the two grooves is greater than the diameter of the welding wire during the first layer welding and not greater than twice the diameter of the welding wire during the first layer welding. Among them, it is preferably less than twice the diameter of the welding wire during the first layer welding, and the distance between the two root faces is set the same as the height of the root face.

[0043] After 15 minutes of heat preservation, welding can begin. Upward vertical welding is used, that is, the welding direction is from bottom to top. During welding, pure Ar gas is used as the shielding gas. Among them, the welding current and voltage for the groove with a smaller depth are both greater than those for the groove with a larger depth, and the straight polarity is used during welding, and heating is maintained at 130 - 150 °C throughout the welding process.

[0044] S6. Grinding: Grind the surface of the first layer of weld. After completion, repeat the preheating step of S4.

[0045] S7. Welding: Divide it into multiple segments along the vertical direction according to the block sequence backstep welding method, and use the upward vertical welding method to weld multiple segments of the two grooves in sequence or synchronously. The welding polarity is reverse polarity direct current. Among them, the wire diameter used for welding is smaller than the wire diameter used for welding in step S5. The welding uses a mixed gas of Ar and He as the shielding gas, and the proportion of He gas is at least 40%.

[0046] During welding, a swing welding method is used, and there are at least two weld beads in this layer of weld. Heating is maintained at 130 - 150 °C throughout the welding process.

[0047] S8. Repeat welding: After completing the welding of the two grooves, repeat the above steps S6 and S7 until the welding of all weld layers of the two grooves is completed.

[0048] S9. Stress relief: After welding, perform stress relief treatment by heat preservation at 300 - 370 °C for 2 - 4 h. Among them, the heating width is 5*(R*S)*0.5 mm, where R is the diameter of the spherical tank and S is the wall thickness.

[0049] Example:

[0050] As Figure 1 and Figure 2 shown, in this example, an aluminum plate with a thickness of 110 mm is taken as an example. The depth of the outer groove is 60 mm and the sector angle is 55°. The depth of the inner groove is 42 mm and the sector angle is 60°. The root face height between the two grooves is 8 mm, and the distance between the two grooves is also 8 mm.

[0051] The pre-welding process specification is shown in Table 1 below:

[0052]

[0053]

[0054] Table 1

[0055] Among them, after completion of welding, the standard is 17 layers and 54 weld beads on the outside and 13 layers and 34 weld beads on the inside. In actual operation, the maximum number of weld beads allowed is 105.

[0056] The chemical composition of the welding wire is shown in Table 2 below:

[0057]

[0058] Table 2 Test plate weld structure and trace elements and impurities change monitoring is shown in Table 3 below:

[0059]

[0060]

[0061] Table 3

[0062] The trace element monitoring process is to take the element content of the weld area, heat-affected zone, and base material area in each welding layer on the outer groove side or inner groove side as the welding layer increases, and observe whether the content of several specific elements exceeds the standard during the welding process.

[0063] Sampling location diagram Figure 3 .

[0064] The chemical composition comparison of multiple sampling locations is shown in Table 4 below:

[0065]

[0066] Table 4

[0067] The monitoring results show that Mg is burned to a certain extent during the welding process, especially in the weld, but the loss is trace. The monitoring results of several other specific elements meet the requirements. Among them, those <0.01 in the table indicate that they have reached the detection limit of the energy spectrometer and cannot be measured. The changes in elements during the welding process meet the requirements.

[0068] The embodiments of this specific implementation method are all preferred embodiments of the present application and are not intended to limit the scope of protection of the present application. Therefore, any equivalent changes made based on the structure, shape, and principle of the present application should be included in the scope of protection of the present application.

Claims

1. A welding process for ultra-thick aluminum plates, comprising the following steps: S1. Groove design: V-shaped grooves are provided on both the inner and outer sides of the aluminum plate. A root face is formed between the two V-shaped grooves, and an X-shaped groove structure is formed by the two V-shaped grooves. Among them, the depths of the grooves on both sides are set differently, and the sector angle of the groove with a smaller depth is 4-8° larger than that of the groove with a larger depth; S2. Alignment: Fix two aluminum plates with a fixture and adjust the curvature and spacing between the two aluminum plates; S3. Surface treatment: Grind the surfaces of the two grooves until there are no obvious concave-convex grooves and wrinkled knife marks. Among them, when there are many concave-convex grooves before grinding, first perform surface treatment with a planer saw and then grind. After grinding, stand the aluminum plate upright; S4. Preheating: Preheat the aluminum plate with an electric heating plate. Among them, the electric heating plate can be fixed on the surface of the aluminum plate. The preheating temperature is 150-160°C; when preparing for welding, the preheating temperature at the root of the groove is increased to 178-185°C and kept warm for 15 minutes after reaching the preheating temperature; S5. First-layer welding: Welding torches are arranged in both grooves. The two welding torches are arranged oppositely and move synchronously. The two welding torches are located on the symmetry plane of the two aluminum plates and move in a straight line on the symmetry plane; the wire diameter used for welding the first welding layer of the two grooves is larger than that used for welding other layers, and the root face height between the two grooves is larger than the wire diameter during the first-layer welding and not more than twice the wire diameter during the first-layer welding; The welding is carried out by upward vertical welding, that is, the direction is from bottom to top. During welding, pure Ar gas is used as the shielding gas. Among them, the welding current and voltage of the groove with a smaller depth are both greater than those of the groove with a larger depth, and the polarity during welding is DC straight polarity. During welding, heating is always maintained at 130-150°C; S6. Grinding: Grind the surface of the first-layer weld. After completion, repeat the preheating step of S4; S7. Welding: Divide into multiple segments along the vertical direction according to the segmented backstep welding method, and use the upward vertical welding method to weld multiple segments of the two grooves in sequence or synchronously. The welding polarity is DC reverse polarity; among them, the wire diameter used is smaller than the wire diameter used for welding in step S5. The welding uses a mixed gas of Ar and He as the shielding gas, and the proportion of He gas is at least 40%; S8. Repeat welding: After completing the welding of the two grooves, repeat the above steps S6 and S7 until all welding layers of the two grooves are welded.

2. The super-thick aluminum plate welding process according to claim 1, wherein: Before welding and after each welding layer is completed, the groove needs to be ground until there are no obvious concave-convex grooves and wrinkled knife marks.

3. The welding process of ultra-thick aluminum plates according to claim 1, characterized in that: The root face height between the two grooves is larger than the wire diameter during the first-layer welding, smaller than twice the wire diameter during the first-layer welding, and the distance between the two root faces is set the same as the root face height.

4. The welding process for ultra-thick aluminum plates according to claim 1, characterized in that it further comprises the step of: S9. Stress relief: After welding, perform stress relief treatment by keeping warm at 300-370°C for 2-4h.

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