Aluminum, a light gray to silver-colored metal, is known for being a featherweight, non-corrosive, and low-strength metal. These features make it one of the most popular materials to weld. Nevertheless, owing to its traits such as oxidation, softness, and porousness make aluminum extremely strenuous to weld.
Additionally, although there are numerous processes of aluminum welding, GTAW/TIG welding and GMAW/MIG welding are preferable as the GTAW method is more apt for thin materials, whereas GMAW is more suitable for thick and large things. Whether it's MIG or TIG welding, one should always prioritize safety and focus on precautions, as the fumes released from welding are harmful and cause several diseases. Thus, following the necessary precautions prevent harmful diseases.
The Benefits of Using Aluminum
Aluminum has several characteristics which make a welder choose it over other metals, and it wasn't widely used until 1886, when it became available in commercial quantities on account of the discovery of an electrolytic process to separate aluminum from aluminum oxide. Given below are some of the characteristics of aluminum:
- The oxide layer covering aluminum is strong, incredibly tenacious, and self-healing. Due to these features, it provides aluminum alloys with terrific corrosion resistance and aids in avoiding additional protection, increasing the possibilities of use in exposed applications. Furthermore, anodizing can enhance corrosion resistance by forming an oxide coating with a regulated thickness.
- Aluminum is lightweight, weighing about 2.71g/cm3, making it simpler and less expensive to transport. Besides, even though the silvery-white metal’s main trait is corrosion resistance, its lightweight nature is an integral feature, as these traits assist in manufacturing vehicle planning, artwork, and kitchen fitting too.
- Electrical and thermal conductivity are principal attributes of aluminum. Additionally, it is less conductive than copper, but it weighs about a third of copper's weight, which means that aluminum wire, which is 50% lighter than copper, possesses the same amount of electrical resistance. Thus, it is used as a heatsink in prominent applications such as LED lights and motherboards.
- Its cost-efficient and recyclable features make it one of the significant factors in its popularity. Hence, cost-efficient metals, which can be recycled, are preferable during production.
- Aluminum has the potential to absorb paint; therefore, welders choose aluminum to weld for its cosmetic characteristics.
Difficulties Faced While Welding Aluminum
Aluminum's traits, such as being non-corrosive and lightweight, persuade individuals to choose aluminum as their preferred metal. However, some qualities make the metal extremely difficult to weld, and even experienced welders go wrong sometimes, but with great practice and patience, the art of welding is perfect. Let's take a look at the reasons that make aluminum difficult to weld:
There is an oxide layer on top of aluminum as it melts at a considerably higher temperature than aluminum.
In contrast, welders must be very cautious while melting past this coating due to its high heat demand and the possibility of burning the holes that are present underneath the aluminum.
When the aluminum is in the molten state, aluminum tends to absorb hydrogen at a rapid pace as it heats up. The metal solidifies when the hydrogen separates off, and this can lead to leaving bubbles behind and making metal weak and porous.
Aluminum is very sensitive, which makes it very easy to contaminate with dirt and air in the course of the welding process. Moreover, when air gets in contact with the weld, it taints the aluminum due to inadequate shielding or too lengthy arcs. Nevertheless, oxygen can lower the metal's strength. This results in an oxide formation on aluminum welds, which may impact the aluminum's appearance and increase the complexity of multi-pass welding.
Hydrogen also poses many difficulties for welding aluminum, and it can come from various sources, for instance, humid air, damp weld joints, and many more. As hydrogen ions are very small and incredibly mobile, they can diffuse outside the weld zone and combine along microstructure discontinuities. The microstructure will be stressed if the hydrogen ions reunite to generate hydrogen gas. Over time, these hydrogen pockets produce tension, which makes hydrogen break.
Welders must be well-versed in getting penetrating through slimmer materials, whereas getting through thicker aluminum materials is sufficient to generate a strong weld.
Some aluminum oxides melt at 2060 °C and a few at 1400 °C above the temperature at which aluminum melts, but it is advised to remove and spread out this oxide coating before and even in the course of welding. So that one's desired outcome will be achieved. Furthermore, when the temperature is increased, aluminum will not change its color, contrasting with steel; the welder will be bewildered, and it will be hard to judge the occurrence of the melting point. Thus, with great practice and experience, one can excel at the beautiful yet intricate craft of welding.
Various Welding Processes
Welding processes are vital to producing different products, for example, frames and pressure vessels. However, these processes are generally high-cost and time-consuming. Besides there are several welding processes, but here below are given the most pre-eminent processes:
Gas Tungsten Arc Welding(GTAW)
Gas tungsten arc welding is also called inert tungsten gas(TIG). This type of welding process utilizes an electric arc and a non-consumable electrode to melt metal by heat. Besides, GTAW uses an inert or active shielding gas, which works as a safeguard for the electrode and the weld metal, whereas arc metal works as a heat source so that it can work even without filler materials. Furthermore, the advantage of this process is that it produces high-quality welds, although the drawback is that deposition happens slowly and has limitations in thickness.
GTAW is generally performed using alternating current (AC) as the layer of oxide elimination happens on the positive electrode half of the cycle, while weld bead penetration occurs on the AC sine wave's electrode negative half cycle.
In the case of aluminum alloys, this process is suitable as aluminum's thickness is no more than 6mm, and greater thickness aims to make the welding process more costly. Also, this process protects the aluminum from contamination, making it one of the most popular processes for welding aluminum.
Gas Metal Arc Welding
Gas metal arc welding is commonly known as an inert metal gas (MIG). A gas metal arc is generally known as an inert metal gas(MIG). GMAW is a type of process that melts and connects metals by heating and creating an electric arc between the metals being welded and an electrode. Besides, a gas that may be inert or active is used to shield the arc and the molten metal.
In the GMAW process, there are three basic metal transfers:
- Globular Transfer: Metal drops are typically larger than the electrode's diameter. They move through the plasma gas and are incredibly impacted by the force of gravity. One feature of this transfer is that it aims to spatter an erratic arc.
- Spray Transfer: Spray transfer happens at higher current levels, and metal droplets travel through because of high electromagnetic forces; the frequency level is higher than the frequency of globular transfer.
- Short-circuiting Transfer: the transfer has small electrode diameters and is linked with low current levels.
In contrast, the advantages of this process are: One can weld in any position. 2) Weld's quality is good. Slag is not being produced.
The welding process is executed using a laser beam as the main source of energy for melting the materials being joined.
Laser welding is employed widely in the aerospace and automotive industries to weld different materials. The laser welding of aluminum causes many problems due to its high thermal conductivity and high reflectivity, resulting in poor-quality welds.
Welding causes several health issues for welders and others in proximity. Therefore, one must be aware of these hazards that are caused by welding. Some of these hazards are listed below. Let's take a look:
- While welding, one is exposed to various types of fumes that are invincible, such as chromium and nickel oxides, and these fumes go through your lungs; frequent exposure to fumes will lead to lung infection and further development of pneumonia. Besides, some more health diseases are caused by weldings, such as cancer, occupational asthma, and many more.
- Electric shock is one of the most common injuries caused by welding. Additionally, utilizing live electrical circuits, a pool of molten metal is produced during the arc welding procedure. For this reason, you may experience an electric shock. An individual mainly experiences shock when they are working in damp conditions or wearing wet clothes. Hence, one must be cautious and take the necessary precautions while welding.
- When high-temperature welding arcs, UV rays, and molten metal combine, the chance of experiencing severe burns during welding increases, as burns can harm the eyes or skin.
Safety must be the top priority, and before welding, one must check whether he has taken precautions or not. Here are some of the precautions below:
One must have the proper personal protective equipment (PPE), which includes
1) respiratory protective equipment to keep you safe from gasses.
2) welding helmets, whose purpose is to safeguard against UV rays, debris, and chemical burns.
3) Fire-resistant clothing safeguards one from heat and fire
4) hearing protection, which helps to get rid of noise harm.
5) Gloves and boots protect the wearer from electric shock and heat.
One must cross-check all the welding equipment and go through all the provided information. Besides, using damaged products is a strict no-no as it may lead to shock injuries and electrocution.
Welding is a pleasing craft with certain complications, and this applies to welding aluminum too. Aluminum has traits that make welding easy and a few qualities that make the craft difficult, but with practice, one can go through all the obstacles and excel at the skill. Furthermore, every skill has some precautions, and welding is no different. It is necessary to go through the precautions and protect your health from harmful fumes and gasses.