One of the most common metals used in Metal Fabrication is Aluminum. To be converted into a product of value, aluminum has to be cleaned, welded using a technique most suited, cut, and shaped using a drill press, lathe machines, or other desired metal shaping machines and made into a final product. Its non-corrosive and light-weighted nature makes it a very desirable choice of material for different kinds of welding.

Difficulties in Welding Aluminum

Aluminum is a soft, highly sensitive metal insulated by a tough oxidized layer, which makes welding the metal rather tricky. In its molten state, aluminum is also prone to impurities causing porous and weak welds.

The melting point of aluminum is 1,200°F (650°C), and that of oxide is 3,700°F (2,037°C). Since oxide melts at a temperature higher than aluminum, the tough oxidized layer insulating aluminum should be cleaned before welding the metal.

Cleaning and Storing

The first step in welding aluminum is cleaning the metal, which can be done by using a stainless-steel wire brush and solvents like acetone or a mild alkaline solution to remove oil, grease, water vapor from the aluminum's surface. To avoid contamination, it has to be kept covered, dry, and at room temperature.

Choosing the Right Welding Technique

Considering the application requirements and the proficiency level of the welder are essential to choosing the right aluminum welding technique.

Methods of Aluminum Welding

Stick Welding (SMAW)

Stick welding, also known as manual welding, arc welding, or shielded metal arc welding (SMAW), is an easy, effective, and widely used process. An electrode is a metal rod used to convert electric current to heat, melt, and weld aluminum. Any slag that rises after the weld is laid is chipped off and cleaned with a wire brush.

Oxyacetylene Welding / Oxy-Fuel Welding (OFW)

Fuel and oxygen contained in two different tanks are mixed inside the torch's handle and used to generate a flame to create a metal pool to produce the weld. Metal can be bent and shaped using this technique of welding. However, it is expensive and not very economical.

Flux Welding / Flux-Cored Arc Welding (FCAW)

An electrode containing a wire with shielding elements is heated to generate shielding gas used to weld aluminum. This method can be done even in remote job sites prone to dirt and dust as it does not require intense cleaning. It reduces the downtime of changing tanks and is cost-effective. Moreover, the machines can be easily converted into MIG welders.

MIG Welding (GMAW)

Gas metal arc welding (GMAW), referred to as metal inert gas (MIG), consists of a welding machine, gas tank, a gun to feed the wire, and a grounding clamp. This technique requires prior cleaning, as dust, oil, or rust can contaminate the weld.

• Different MIG wire electrodes with different filler metals such as ER4043, ER4047, ER5183, ER5356 have been designed for welding aluminum pieces to avoid porosity and other defects in welding aluminum.
• Selecting a shielding gas such as pure argon (Ar) or a mixture of argon and helium (Ar-He) over Carbon Dioxide (CO2) or Oxygen (O2), which is more potent to oxidize, can considerably affect the quality of the weld and prevent porosity. A system to measure and maintain the shielding gas flow is to be set up.
• Preheating the aluminum before welding to a temperature not exceeding 230 degrees Fahrenheit can prevent deformities. It is preferable to use methods that do not use an open flame, such as the induction method.
• Depending on the type of welding, a suitable wire feeder, i.e., a Push-Pull gun or a Spool Gun, should be chosen.
• Welding time can be extended by using a heat sink to absorb excess heat.
• The only suitable type of current used for MIG welding is Direct current, reverse polarity.
• Wire type and size, contact tip, Wire feed speed are other essential variables that affect aluminum welding.

TIG Welding (GTAW)

In the GTAW (gas tungsten arc welding) method, aluminum is welded by forming an electrical circuit between a non-consumable tungsten electrode and an aluminum workpiece. The heat generated through the torch is manually regulated with a pedal, thus giving the welder more control over the temperature and process of welding. TIG, also known as tungsten inert gas (TIG), welding is very costly and difficult to master but one of the most excellent choices of welding techniques.

• Prior cleaning is required as dust, oil, or rust can contaminate the weld.
• Preheating the aluminum before welding to a temperature not exceeding 230 degrees Fahrenheit can prevent deformities. It is preferable to use methods that do not use an open flame, such as the induction method.
• Welding time can be extended by using a heat sink to absorb excess heat.
• Argon (Ar) and Helium (He) is preferred as Shielding gases to shield the welds from porosity.
• The current utilized for TIG welding is AC (alternating current), and there is no wire feeder used in this welding method, making the process a clean one.

Choice of Welding Machinery and Supplies

Depending upon the kind and thickness of materials, location of welding, i.e., fixed in one location or moving between one or more locations, the experience of the welder and weld appearance, a welding machine such as a TIG – tungsten inert gas – welding machine, MIG machine that most suits the requirements should be picked.

Various welding supplies that are required include:

• Safety Gear – Hood, jacket, gloves.
• Tools for cutting aluminum – Drill press, milling machine, lathe machines, grinding machine, drilling machine, shaper machine, planer machine, shearing machine, hobby machine, broaching, and saw machines.
• Power Tools – Grinder, wire snips, chipping hammer.
• Advanced Tools – Band saw, welding cart, belt sander, welding table, heavy-duty magnets.

Conclusion

Welding aluminum poses a great challenge even to professional welders. Knowledge of the properties of aluminum and the different welding techniques and processes is required to produce the best welds and prevent deformities. With practice and patience, welding Aluminum can be mastered successfully.

About the Author:

Vincent HuaVincent Hua is the Marketing Manager at TSINFA. He is passionate about helping people understand high-end and complex manufacturing processes. Besides writing and contributing his insights, Vincent is very keen on technological innovation that helps build highly precise and stable CNC Machinery.