High-strength welding method for marine 1561 aluminum alloy thick plate

Abstract

The invention discloses a high-strength welding method for a marine 1561 aluminum alloy thick plate, relates to a high-strength welding method for an aluminum alloy thick plate, and aims to solve the problems that the welding coefficient of the aluminum alloy thick plate welded by the existing method is not high (generally lower than 0.8), more pores exist in a welding seam, and the grain structure is coarse. The method comprises the steps that a 1561 aluminum alloy thick plate is adopted as a to-be-welded piece and a 1561 welding wire, and then groove machining is conducted; surface cleaning and fixing; preheating is conducted; according to the welding process, high-quality welding of the 1561 aluminum alloy plate with the thickness of 20 mm can be stably achieved, the quality of a weld joint reaches the I level, and the defects of obvious air holes, slag inclusion and the like do not exist; the welding strength reaches 350 to 355MPa, and the welding coefficient is 0.88 to 0.9; fine isometric crystals are formed in a weld zone, the grain size is far smaller than that of base metal, and the toughness and fatigue resistance of a weld are improved; the method is applied to the technical field of aluminum alloy material welding.

Description

Technical Field

[0001] This invention relates to a high-strength welding method for marine 1561 aluminum alloy thick plates. Background Technology

[0002] 1561 aluminum alloy is an Al-Mg alloy with moderate strength, excellent corrosion resistance, and weldability, and is widely used in shipbuilding, vehicles, and armor protection. Welding 1561 aluminum alloy plates with a thickness of 15mm or more presents several challenges: First, thick plate welding requires a large heat input, which can easily lead to coarse grains in the weld joint and a decrease in mechanical properties; second, aluminum alloys have high thermal conductivity and a fast solidification rate in the molten pool, making it easy to generate hydrogen porosity during welding, severely affecting the density and strength of the weld; third, the internal stress and deformation generated during thick plate welding are significant and difficult to control.

[0003] In existing technologies, conventional MIG welding is commonly used for welding thick aluminum alloy plates. However, this method often suffers from problems such as a low welding coefficient (typically below 0.8), numerous weld pores, and coarse grain structure, making it difficult to meet the requirements of high-strength and high-reliability applications in shipbuilding. Therefore, developing a novel welding process that can significantly improve the welding strength and quality of 1561 aluminum alloy thick plates has significant industrial application value. Summary of the Invention

[0004] This invention aims to address the problems of low welding coefficient (usually below 0.8), numerous weld pores, and coarse grain structure in existing methods for welding thick aluminum alloy plates, and provides a high-strength welding method for marine-grade 1561 aluminum alloy thick plates.

[0005] The high-strength welding method for marine 1561 aluminum alloy thick plates of the present invention includes the following steps:

[0006] 1. Process the side of the 1561 aluminum alloy thick plate to be welded into a double V bevel with symmetrical upper and lower edges. The bevel angle on one side is 28-32°, and a 0.5-1mm blunt edge is left in the middle. Then clean the surface of the side to be welded. Fix the two plates to be welded on the workbench. The gap between the two plates at the beginning of the weld is 1mm, and the gap between the two plates at the end of the weld is 2mm.

[0007] 2. After fixing in step one, the entire thick plate is uniformly preheated to 80℃-100℃. 1561 welding wire is used for welding. Under a protective gas, single-sided two-layer two-pass welding is adopted. The first pass is a straight pass welding and the second pass is an 8-shaped swaying pass welding, thus completing the welding.

[0008] Beneficial effects of this invention:

[0009] 1. Excellent weld quality: After welding, X-ray non-destructive testing shows that the weld quality reaches Grade I, with no obvious defects such as porosity or slag inclusions, meeting the requirements for high reliability applications;

[0010] 2. High welding strength: Welding sample tests show that the welding strength reaches 350-355MPa, and the welding coefficient is 0.88-0.9, which is far higher than the weld strength level of existing processes and close to the strength of the base material;

[0011] 3. Refined grain structure: Fine equiaxed grains are formed in the weld zone, with grain size much smaller than that of the base material, which improves the toughness and fatigue resistance of the weld. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of the double V-shaped bevel structure used in this invention; where A is the bevel angle and B is the blunt side;

[0013] Figure 2 This is a schematic diagram of the welding sequence for a single-sided two-layer, two-pass structure according to the present invention;

[0014] Figure 3 This is an X-ray non-destructive testing image of the weld after welding using the method of the present invention;

[0015] Figure 4 The grain structure of the welded joint obtained by the method of the present invention;

[0016] Figure 5 The local grain structure of the welded joint obtained by the method of the present invention is shown in (a) as the weld zone and (b) as the base material zone. Detailed Implementation

[0017] The technical solution of the present invention is not limited to the specific embodiments listed below, but also includes any combination of the specific embodiments.

[0018] Specific Implementation Method 1: The high-strength welding method for marine 1561 aluminum alloy thick plates in this implementation method includes the following steps:

[0019] 1. Process the side of the 1561 aluminum alloy thick plate to be welded into a double V bevel with symmetrical upper and lower edges. The bevel angle on one side is 28-32°, and a 0.5-1mm blunt edge is left in the middle. Then clean the surface of the side to be welded. Fix the two plates to be welded on the workbench. The gap between the two plates at the beginning of the weld is 1mm, and the gap between the two plates at the end of the weld is 2mm.

[0020] 2. After fixing in step one, the entire thick plate is uniformly preheated to 80℃-100℃. 1561 welding wire is used for welding. Under a protective gas, single-sided two-layer two-pass welding is adopted. The first pass is a straight pass welding and the second pass is an 8-shaped swaying pass welding, thus completing the welding.

[0021] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that the thickness of the 1561 aluminum alloy plate is 20mm. Everything else is the same as in Specific Implementation Method One.

[0022] Specific Implementation Method Three: This implementation method differs from Specific Implementation Method One or Two in that the composition of the 1561 aluminum alloy thick plate, by mass fraction, is: Si≤0.4%, Fe≤0.4%, Cu≤0.14%, Mn:0.7-1.1%, Mg:5.5-6.5%, Zn≤0.2%, Ti:0.01-0.06%, Zr:0.02-0.12%, with the balance being Al. Everything else is the same as in Specific Implementation Method One or Two.

[0023] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that: 1561 welding wire with a diameter of 1.2mm is used for welding, and its composition by mass fraction is: Si: 0.01-0.06%, Fe: ≤0.12%, Cu: ≤0.01%, Mn: 0.7-0.9%, Mg: 5.9-6.5%, Cr: <0.01%, Zn: ≤0.02%, Ti: 0.02%-0.09%, Zr: 0.08-0.12%, and the balance being Al. Everything else is the same as in Specific Implementation Methods One to Three.

[0024] Specific Implementation Method Five: This implementation method differs from Specific Implementation Methods One to Four in that the single-sided bevel angle is 30°. Everything else is the same as in Specific Implementation Methods One to Four.

[0025] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One to Five in that the protective gas is 99.9% Ar with a flow rate of 20-25 L / min. Everything else is the same as in Specific Implementation Methods One to Five.

[0026] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods One to Six in that the welding current is 250A-270A and the welding speed is 55cm / min-70cm / min. Everything else is the same as in Specific Implementation Methods One to Five.

[0027] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Methods One to Seven in that it uses a figure-eight oscillation welding method with a oscillation welding frequency of 3-5Hz and an oscillation amplitude of 2.5-3.5mm. Everything else is the same as in Specific Implementation Methods One to Seven.

[0028] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Methods One to Eight in that it uses a figure-eight oscillation welding method with a welding frequency of 3Hz and an amplitude of 3mm. Everything else is the same as in Specific Implementation Methods One to Eight.

[0029] Specific Implementation Method Ten: This implementation method differs from Specific Implementation Methods One to Nine in that the weld strength after welding is 350-355 MPa, and the welding coefficient is 0.88-0.9. Everything else is the same as in Specific Implementation Methods One to Nine.

[0030] The beneficial effects of the present invention are verified using the following embodiments:

[0031] Example 1: The high-strength welding method for marine 1561 aluminum alloy thick plates is as follows:

[0032] 1. Preparation of workpieces to be welded and welding wire

[0033] (a) 1561 aluminum alloy thick plate: thickness 20mm, size 300mm×150mm, composition (mass fraction %) is Si: 0.067, Fe: 0.15, Cu: 0.012, Mn: 0.85, Mg: 6.13, Zn: 0.04, Ti: 0.02, Zr: 0.02, mechanical properties are tensile strength 392MPa, yield strength 203MPa, elongation 18%;

[0034] (b) 1561 welding wire: diameter φ1.2mm, composition (mass fraction %) is Si: 0.02, Fe: 0.074, Mn: 0.81, Mg: 6, Zn: 0.007, Zr: 0.1, Ti: 0.02, mechanical properties are tensile strength 304MPa, yield strength 162MPa, elongation 17%.

[0035] 2. Beveling

[0036] Use a milling machine to process double V-grooves (such as...) Figure 1 As shown), the single-sided bevel angle is 30°, the blunt edge thickness is 0.8mm, and the bevel depth is adapted to a 20mm thick plate to ensure that the two-layer welding can achieve full penetration.

[0037] 3. Surface cleaning and fixing

[0038] (a) Use a stainless steel wire brush and acetone to thoroughly clean the bevel and both sides until the surface has a metallic luster and no oxidation spots;

[0039] (b) Place the two thick plates on the welding workbench, fix them with pressure plates, and adjust the gap between the two plates: 1 mm at the starting end (welding start position) and 2 mm at the tail end (welding end position).

[0040] 4. Preheating

[0041] The plate is heated to 80°C using a flame gun and held at that temperature for 20 minutes to ensure uniform temperature throughout the thick plate. During the preheating process, an infrared thermometer is used to monitor the surface temperature to prevent localized overheating.

[0042] 5. Welding equipment and parameter settings

[0043] (a) Welding equipment: Gas metal arc welding machine (MIG welding);

[0044] (b) Shielding gas: 99.9%Ar, flow meter set to 20L / min, gas nozzle distance from weld surface 15mm;

[0045] (c) Using a single-sided, two-layer, two-pass welding method (e.g.) Figure 2 As shown, where 1 is the first pass weld on the front side, 2 is the second pass weld on the front side, 3 is the first pass weld on the back side, and 4 is the second pass weld on the back side), welding parameters: First pass weld on the front side: current 260A, speed 60cm / min, straight pass weld; Second pass weld on the front side: current 260A, speed 60cm / min, figure-eight oscillation weld (frequency 3Hz, amplitude 3mm); First pass weld on the back side: current 260A, speed 60cm / min, straight pass weld; Second pass weld on the back side: current 260A, speed 60cm / min, figure-eight oscillation weld (frequency 3Hz, amplitude 3mm).

[0046] 6. Root cleaning treatment

[0047] (a) After the first pass of welding on the front side, wait for the weld temperature to drop below 150°C, then use a reamer head to clean the root to a depth of 2-3 mm to ensure that fresh metal surface is exposed.

[0048] (b) Before the first weld on the back side, repeat the above root cleaning steps to clean the root area on the back side.

[0049] 7. Detection and Results

[0050] (a) Non-destructive testing: X-ray inspection of the welded joint (e.g., Figure 3 As shown in the figure, the weld has no defects such as porosity, slag inclusion, or lack of fusion, and is rated as a Class I weld.

[0051] (b) Mechanical property test: The weld strength was 355 MPa and the weld coefficient was 0.90.

[0052] (c) Microstructural observation: The weld zone and the base metal zone were observed using a metallographic microscope (e.g., Figure 4 , 5 As shown in the figure, the weld zone consists of fine equiaxed grains, and the grain refinement effect of the weld is significant compared with that of the base material.

[0053] This embodiment demonstrates that the welding process of the present invention can stably achieve high-quality welding of 20mm thick 1561 aluminum alloy plates, meeting the mechanical and quality requirements of ship plates.

Claims

1. A high-strength welding method for marine 1561 aluminum alloy thick plates, characterized in that, The welding method includes the following steps:

1. Process the side of the 1561 aluminum alloy thick plate to be welded into a double V bevel with symmetrical upper and lower edges. The bevel angle on one side is 28-32°, and a 0.5-1mm blunt edge is left in the middle. Then clean the surface of the side to be welded. Fix the two plates to be welded on the workbench. The gap between the two plates at the beginning of the weld is 1mm, and the gap between the two plates at the end of the weld is 2mm.

2. After fixing in step one, the entire thick plate is uniformly preheated to 80℃-100℃. 1561 welding wire is used for welding. Under a protective gas, single-sided two-layer two-pass welding is adopted. The first pass is a straight pass welding and the second pass is an 8-shaped swaying pass welding, thus completing the welding.

2. The high-strength welding method for marine 1561 aluminum alloy thick plates according to claim 1, characterized in that, The thickness of the 1561 aluminum alloy plate is 20mm.

3. The high-strength welding method for marine 1561 aluminum alloy thick plates according to claim 1, characterized in that, The composition of the 1561 aluminum alloy thick plate by mass fraction is: Si≤0.4%, Fe≤0.4%, Cu≤0.14%, Mn:0.7-1.1%, Mg:5.5-6.5%, Zn≤0.2%, Ti:0.01-0.06%, Zr:0.02-0.12%, and the balance Al.

4. The high-strength welding method for marine 1561 aluminum alloy thick plates according to claim 1, characterized in that, Welding uses 1561 welding wire with a diameter of 1.2mm. Its composition by mass fraction is Si: 0.01-0.06%, Fe: ≤0.12%, Cu: ≤0.01%, Mn: 0.7-0.9%, Mg: 5.9-6.5%, Cr: <0.01%, Zn: ≤0.02%, Ti: 0.02%-0.09%, Zr: 0.08-0.12%, and the balance Al.

5. The high-strength welding method for marine 1561 aluminum alloy thick plates according to claim 1, characterized in that, The bevel angle on one side is 30°.

6. The high-strength welding method for marine 1561 aluminum alloy thick plates according to claim 1, characterized in that, The protective gas is 99.9% Ar, with a flow rate of 20-25 L / min.

7. The high-strength welding method for marine 1561 aluminum alloy thick plates according to claim 1, characterized in that, Welding current 250A-270A, welding speed 55cm / min-70cm / min.

8. The high-strength welding method for marine 1561 aluminum alloy thick plates according to claim 1, characterized in that, Figure-eight oscillation welding, oscillation welding frequency 3-5Hz, oscillation amplitude 2.5-3.5mm.

9. The high-strength welding method for marine 1561 aluminum alloy thick plates according to claim 1, characterized in that, Figure-eight oscillation welding, oscillation welding frequency 3Hz, oscillation amplitude 3mm.

10. The high-strength welding method for marine 1561 aluminum alloy thick plates according to claim 1, characterized in that, The weld strength after welding is 350-355 MPa, and the welding coefficient is 0.88-0.9.

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