A method for welding large angle end seams in aluminum alloys

Abstract

This invention discloses a welding method for large-angle end joints of aluminum alloys. The joint angle between two aluminum alloy plates is 225–270°, and MIG welding is performed. The bevel is asymmetrical, with one side having a bevel angle of 12–18° and the other side having a bevel angle of 72–78°. The bottom gap width of the bevel is 3–6 mm, and a permanent aluminum alloy backing is added to the back. The welding is a mixed multi-layer, multi-pass welding method combining flat and horizontal welding, consisting of root pass welding and cover pass welding. This invention can perform multi-layer, multi-pass MIG welding on high-strength aluminum-magnesium alloys with a thickness of 5–8 mm at an angle ≥225°, ensuring that the weld appearance meets quality requirements and has no significant surface defects. Compared with traditional welding methods, the weld has fewer pores, and the internal quality X-ray inspection rating of the weld is not lower than Grade I.

Description

Technical Field

[0001] This invention relates to the field of aluminum alloy welding technology, specifically to a welding method for end joints of large-angle aluminum alloy plates. Background Technology

[0002] Aluminum alloys are widely used in shipbuilding due to their low specific gravity, good corrosion resistance, and ease of processing. In recent years, several aluminum alloy ships in my country have experienced varying degrees of cracking, with damage manifesting as cracks or fractures at the welded joints between longitudinal ribs and the bottom plate, and cracks or fractures between the elbow plates and the side reinforcement structures. Repair work involves replacing the panels at the connection to the original hull structure, with a critical weld being the end joint at an angle of approximately 225°. Currently, there is no efficient welding method suitable for large-angle end joints in aluminum alloys. Summary of the Invention

[0003] The purpose of this invention is to provide an efficient welding method for large-angle end joints of aluminum alloy plates, so as to overcome the shortcomings of the prior art in that there is no suitable welding method for aluminum alloy large-angle splicing plates.

[0004] To achieve the above objectives, the technical solution of the present invention is as follows:

[0005] The present invention discloses a welding method for large-angle end joints of aluminum alloy plates, characterized in that the angle of the end joint of two aluminum alloy plates is 180-270°, and MIG welding is performed. The bevel is asymmetrical, with the bevel angle on one side being 12-18° and the bevel angle on the other side being 72-78°. The bottom gap width of the bevel is 3-6mm, and a permanent aluminum alloy backing is added to the back. The welding is a mixed multi-layer, multi-pass welding method of flat welding and horizontal welding, divided into root pass welding and cover pass welding. The root pass welding is flat welding and / or filler welding, and the cover pass welding is horizontal welding. The surface width of the cover pass welding is controlled at 10-15mm.

[0006] The aluminum alloy plate is a high-strength aluminum-magnesium alloy plate with a thickness of 5-8mm, including plates of equal or unequal thickness, such as 5083, 5E01, etc.

[0007] The welding wire used in the welding is a high-strength aluminum-magnesium alloy welding wire, and the composition of the welding wire meets the relevant standards or technical requirements. The diameter of the welding wire is 1.0 mm or 1.2 mm, preferably 1.2 mm. The shielding gas used in the welding is argon, and the purity of the argon gas is ≥99.995%.

[0008] Furthermore, the welding electrode manipulation method can be either linear reciprocating welding or skip arc welding.

[0009] Furthermore, the welding voltage for the root pass is 18.3–19.8V, the welding current is 100–120A, the welding speed is 30–40cm / min, and the shielding gas flow rate is 20–30L / min; the welding voltage for the cover pass is 18.8–22.5V, the welding current is 115–135A, the welding speed is 20–40cm / min, and the shielding gas flow rate is 20–30L / min.

[0010] Furthermore, the heat input of the welding is controlled at 3.9–5.8 KJ / cm; the interpass temperature is 40–55°C, preferably 50°C.

[0011] Furthermore, the liner has a width of 3-6mm and a thickness of 8-12mm, and the liner is chamfered according to the actual site conditions.

[0012] Furthermore, the present invention provides an efficient welding method for large-angle end joints of aluminum alloy plates, which can be performed under ambient temperatures not less than 0°C and relative humidity not higher than 85%, without the need for preheating during welding.

[0013] This invention enables MIG multi-layer, multi-pass welding of high-strength aluminum-magnesium alloys with a thickness of 5-8mm at an inclination angle ≥225°. It ensures that the appearance inspection of the weld joint meets the quality requirements and there are no significant surface defects. Compared with traditional welding methods, the weld has fewer pores and the X-ray flaw detection rating of the internal quality of the weld is not lower than Grade I. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the welding bevel of the aluminum alloy large-angle splicing plate of the present invention;

[0015] The labels in the attached figures are as follows: 1-aluminum alloy plate, 2-backing pad; t-aluminum plate thickness, α-bevel angle on one side, d-bottom gap. Detailed Implementation

[0016] Those skilled in the art should recognize that this embodiment is only used to illustrate the present invention and is not intended to limit the present invention. Any changes or modifications to the embodiment within the scope of the present invention are within the scope of the claims of the present invention.

[0017] Examples 1-2

[0018] (1) Welding materials

[0019] Examples 1 and 2 are aluminum alloy sheets: H116 temper 5083 aluminum alloy, with a thickness of 6mm. The welding wires for Examples 1 and 2 contain the following components by mass fraction: Si: ≤0.4%, Fe: ≤0.4%, Cu: ≤0.1%, Mn: 0.5%–1.0%, Mg: 4.3%–5.2%, Cr: 0.05%–0.25%, Zn: ≤0.25%, Be: ≤0.008%, Ti: ≤0.15%, with the balance being Al and unavoidable impurities. The welding wire diameter is 1.2mm.

[0020] Protective gas: Argon, purity ≥ 99.995%.

[0021] (2) Welding method

[0022] like Figure 1 The two aluminum alloy plates are subjected to MIG welding at an angle of 225°. One side has a bevel of 15° and the other side has a bevel of 75°. In Example 1, the bottom gap width of the bevel is 5mm, and in Example 2, the bottom gap width of the bevel is 6mm. Permanent aluminum alloy gaskets are added to the back of both plates.

[0023] Before welding, the oxide film on the surface within 30mm on both sides of the weld is removed by mechanical method and cleaned with anhydrous ethanol. Welding is carried out under the conditions of ambient temperature not less than 0℃ and relative humidity not higher than 85%. Welding adopts a mixed multi-layer multi-pass welding method of flat welding and horizontal welding, which is divided into root welding and cover welding. The root welding is flat welding and / or fill welding, and the cover welding is horizontal welding. The surface width of the cover welding is controlled at 12mm. The welding method is linear reciprocating method and skip arc welding method. The welding process parameters of Examples 1 and 2 are shown in Table 1.

[0024] Table 1 Welding process parameters for Examples 1-2

[0025]

[0026] When performing multi-layer, multi-pass welding, strictly control the interpass temperature to around 50℃. To ensure that the weld porosity meets the requirements of Class I weld, strictly clean the weld during the welding process. After each weld is completed, clean the weld with a milling cutter before proceeding to the next weld. When starting the arc at multiple joints, first grind the arc termination point with a milling cutter, and start the arc 50mm before the arc termination point. Note that the arc length should be reduced and the welding speed should be decreased when starting the arc. After welding is completed, grind the raised part of the weld surface.

[0027] (4) Test Results

[0028] In accordance with the relevant provisions of CB / T3747-2013 "Quality Requirements for Marine Aluminum Alloy Welded Joints", the weld surface of the weld joint shall be visually inspected. The weld surface shall be uniformly formed, dense, and smoothly transitioning to the base metal, without significant surface defects such as cracks, lack of fusion, excessive reinforcement, slag inclusions, weld beads, arc craters, and undercut. The undercut depth shall not exceed 0.5 mm, the total undercut length shall not exceed 10% of the weld length, and the continuous undercut length shall not exceed 100 mm. The surface colorimetric inspection of the weld shall comply with CB3958.

[0029] The internal quality of the weld joint is inspected by X-ray flaw detection. The X-ray flaw detection is carried out in accordance with the relevant provisions of the CB3929 standard, and the internal quality of the weld is rated as not lower than Grade I.

Claims

1. A welding method for large-angle end joints of aluminum alloys, characterized in that, The joint angle of the two aluminum alloy plates is 225-270°, and MIG welding is performed. The bevel is asymmetrical, with the bevel angle on one side being 12-18° and the bevel angle on the other side being 72-78°. The bottom gap width of the bevel is 3-6mm, and a permanent aluminum alloy backing is added to the back. The welding is a mixed multi-layer, multi-pass welding method of flat welding and horizontal welding, which is divided into root pass welding and cover pass welding.

2. The welding method according to claim 1, characterized in that, The root pass is a flat pass and / or a fill pass, the cover pass is a horizontal pass, and the width of the cover pass surface is controlled between 10 and 15 mm.

3. The welding method according to claim 1, characterized in that, The aluminum alloy plate is a high-strength aluminum-magnesium alloy plate with a thickness of 5-8mm, including plates of equal or unequal thickness.

4. The welding method according to claim 1, characterized in that, The welding wire used in the welding is a high-strength aluminum-magnesium alloy welding wire with a diameter of 1.0 mm or 1.2 mm; the shielding gas used in the welding is argon with a purity of ≥99.995%.

5. The welding method according to claim 1, characterized in that, The welding methods are linear reciprocating welding and skip arc welding.

6. The welding method according to claim 1, characterized in that, The welding voltage for the root pass is 18.3–19.8V, the welding current is 100–120A, the welding speed is 30–40cm / min, and the shielding gas flow rate is 20–30L / min; the welding voltage for the cover pass is 18.8–22.5V, the welding current is 115–135A, the welding speed is 20–40cm / min, and the shielding gas flow rate is 20–30L / min.

7. The welding method according to claim 1, characterized in that, The heat input for welding is controlled at 3.9–5.8 KJ / cm; the interpass temperature is 40–55 °C.

8. The welding method according to claim 1, characterized in that, The pad has a width of 3-6 mm and a thickness of 8-12 mm.

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