The weldability of aluminum alloy refers to the difficulty of forming a high-quality welded joint during welding and the reliability of the welded joint under the conditions of use. The difference in weldability of different types of aluminum alloys is mainly determined by their alloy composition, microstructure and heat treatment status.
Starting from the typical alloy series, the following detailed analysis of weldability characteristics, main problems and applicable processes:
- Pure aluminum (1xxx series)
Typical grades: 1060, 1100, 1A97
Weldability characteristics
– Advantages: high purity (Al ≥ 99%), narrow crystallization temperature range (about 660℃), extremely low tendency to thermal cracking, and less alloy element burnout during welding.
– Joint performance: The weld strength is about 80%~90% of the parent material, and the corrosion resistance is close to the parent material, but the plasticity is slightly lower.
Applicable welding methods
– First choice: TIG welding (AC power supply, using the cathode crushing effect to break the oxide film), MIG welding (suitable for thick plates).
– Second choice: gas welding (need to be combined with aluminum welding powder), resistance welding (thin plate overlap).
- Al-Mn series (3xxx series, rust-proof aluminum)
Typical grades: 3003, 3105, 5A02 (some 5xxx series also contain Mn)
Weldability characteristics
– Advantages: Mn element (content 1.0%~1.7%) improves corrosion resistance, has no aging strengthening effect, no softening phenomenon in the heat-affected zone, and excellent weldability.
– Joint performance: The weld strength can reach more than 90% of the parent material, and the corrosion resistance is equivalent to that of the parent material, which is suitable for marine and chemical environments.
Applicable welding methods
– General: TIG, MIG, resistance welding (spot welding, seam welding), stir friction welding (FSW).
– Process points: No preheating is required, and welding wire with a composition similar to that of the parent material (such as ER5356) can be used.
- Al-Mg series (5xxx series, rust-proof aluminum)
Typical grades: 5052, 5083, 5A06
Weldability characteristics
– Advantages: Mg content (2%~8%) improves strength and corrosion resistance, no tendency to thermal cracking, and excellent weldability.
– Joint performance: The weld strength is 85%~90% of the parent material, and the seawater corrosion resistance is outstanding.
Applicable welding methods
– Recommended: TIG welding (low current, ER5356 welding wire), MIG welding (pulse mode reduces Mg burning).
– Note: Strict degreasing is required before welding (Mg reacts with grease to generate hydrogen), and natural aging can be used after welding to increase strength.
- Al-Si series (4xxx series, cast aluminum)
Typical grades: 4043 (welding wire), A356 (casting alloy), 4A11
Weldability characteristics
– Advantages: Si content (4.5%~12%) reduces melting point (eutectic temperature 577℃), excellent fluidity, suitable for casting and repair welding.
– Joint performance: weld strength is about 70%~80% of the parent material, corrosion resistance is medium, suitable for castings under static load.
Applicable welding methods
– First choice: TIG welding (add Si welding wire, control heat input to reduce shrinkage), gas welding (casting repair welding).
– Key points of the process: preheating before welding (150~200℃) to reduce temperature difference stress, slow cooling after welding to prevent cracks.
- Al-Cu series (2xxx series, hard aluminum)
Typical grades: 2A12 (LY12), 2024, 2A14
Weldability characteristics
– Disadvantages: Cu content (3.8%~5.0%) forms Al₂Cu strengthening phase, but the crystallization temperature range is wide (about 160℃), and the tendency of thermal cracking is extremely high.
– Joint performance: low weld strength, poor corrosion resistance (Cu accelerates electrochemical corrosion), only suitable for non-load-bearing or post-weld heat-treated components.
Applicable welding methods
– Special processes:
– Friction stir welding (FSW): solid-state welding, avoiding the melting process, the joint strength can reach 90% of the parent material.
– Electron beam welding: concentrated energy, narrow heat-affected zone, and requires ER2319 (Al-Cu-Mn) welding wire.
– Taboos: gas welding, MIG welding and other methods with large heat input are prone to cracks.
- Al-Zn-Mg-Cu series (7xxx series, super-hard aluminum)
Typical grades: 7075, 7A04, 7475
Weldability characteristics
– Disadvantages: high degree of alloying (Zn=5.6%~7.0%, Mg=2.1%~3.1%), the worst weldability, and extremely strong sensitivity to thermal cracks.
– Joint performance: It is difficult to obtain reliable joints with conventional welding methods, and special process control is required.
Applicable welding methods
– High-end processes:
– Laser welding: high energy density (10⁶~10⁷W/cm²), extremely narrow heat-affected zone (≤0.5mm), and cracks can be reduced with ER5356 welding wire.
– Friction stir welding (FSW): the only method that can achieve high-strength connection, the joint strength can reach more than 85% of the parent material, and is widely used in aerospace structures.
– Taboos: Traditional methods such as manual arc welding and gas welding are not available.
- Al-Mg-Si series (6xxx series, forged aluminum)
Typical grades: 6061, 6063, 6A02
Weldability characteristics
– Medium difficulty: Mg₂Si strengthening phase makes the aluminum alloy have aging strengthening characteristics, and the weldability is between 5xxx series and 2xxx series.
– Joint performance: The weld strength is 70%~80% of the parent material, and artificial aging after welding (175℃×8h) can be restored to 90%.
Applicable welding methods
– Commonly used: TIG welding (ER5356 or ER6061 welding wire), MIG welding (pulse mode, suitable for automotive parts).
– Key points of the process: Timely aging treatment after welding to avoid natural aging leading to reduced strengthening effect.
Common welding methods and adaptability
- Tungsten inert gas arc welding (TIG welding)
Features: stable arc, controllable heat input, suitable for welding thin plates (≤3mm) and high-precision components.
Application: High-quality welding of pure aluminum, Al-Mg, and Al-Si alloys, such as thin-walled parts in aerospace.
- MIG welding
Features: High deposition efficiency, suitable for welding of medium and thick plates (≥3mm), pulse MIG welding can be used to reduce heat input.
Application: Industrial aluminum structure, automobile body frame welding.
- Friction stir welding (FSW)
Features: Solid-state welding, no melting process, completely solve the problems of thermal cracks and pores, and high joint strength.
Application: Long weld welding of high-speed rail body and aerospace aluminum alloy plates.
- Laser welding
Features: High energy density, extremely narrow heat-affected zone, fast welding speed, suitable for automated production.
Application: Aluminum alloy automobile parts (such as battery housing, door frame).