Introduction
Because of its corrosion resistance, lightness, and versatility, aluminum has become a favored material in many industry sectors. Nonetheless, welding it is no easy task. This is due, in large part, to the factors that make aluminum attractive in the first place—its lightweight properties and its toughness. Aluminum is a relatively soft metal and is therefore susceptible to various forms of deformation. When heated at the relatively low temperatures used in welding operations, aluminum will tend to distort. To deal with these matters properly, we need to understand what goes on when aluminum is heat treated and to learn a bit about the many aluminum alloys available today.
Aluminum’s Unique Properties
- Aluminum’s thermal conductivity is high, and this means that it can dissipate heat rapidly. If heat can’t be managed during a welding operation, then things like warping, distortion, and incomplete fusion can happen. Aluminum welding can have issues, and when it does, it can result in welds that fail in important applications. However, these should be seen as opportunities for learning and improving the overall quality of the welding process. The key to getting good aluminum welds is understanding the issues, offering verifiable solutions, and then implementing those solutions in the day-to-day operations on the shop floor.
- Aluminum forms a hard and high-melting-point oxide layer on its surface when it comes into contact with air. This can cause problems when it comes to welding aluminum. The oxide can interfere with the action of the weld, making it difficult to achieve an acceptable weld that can handle the sort of loads you might put on a beam or an automobile part, for example. The image I used to imagine what’s going on during the welding process is that of trying to melt chocolate chips and combine them into one mass. And you know you can achieve that result much more easily if you’ve cleaned off your work surface.
- Aluminum’s low melting point—relative to that of steel—makes it susceptible to warping or burn-through effects if too much heat is applied for too long. Given aluminum’s poor heat conductivity, however, heat control in its welding is a much less straightforward matter than with steel. Moreover, while aluminum welded together can achieve a strength about 90% that of the unwelded base metal, the same is not true of steel welds.
Welding Aluminum: Considerations and Techniques
- The very selection of a welding process is determined by the particular application and desired appearance. Tungsten inert gas (TIG) welding is often preferred when precise control is needed and for its ability to make superior quality welds on aluminum. Another very popular process is metal inert gas (MIG) welding, which is favored for its high deposition rates and fast welding speeds.
- The proper selection of welding wire is vital for achieving success with aluminum welding. Wires made especially for aluminum are available in many alloys. Each alloy, and hence, each of the wire types made from them, has slightly different metallurgical properties that influence the welding. However, by selecting from the two most common wire types, much of the guesswork regarding suitability between an alloy and a wire can be eliminated. The 5356 wire is better for 5xxx series (i.e., “marine grade”) aluminum. The better of the two for 6xxx series (“aircraft grade”) and other aluminum alloys is 4043.
- Protective gasses play an influential role in TIG welding. They help to shield the arc and molten pool from the atmosphere, which would otherwise cause an oxidized and weakened weld. Argon is the most commonly used gas for TIG welding, but helium is sometimes used as well. For MIG welding, a mixture of argon and a small amount of helium is used to protect the weld from the atmosphere. The proper choice of shielding gas results in a reliably stable arc and a penetration depth that is achievable with reasonable skill.
- Before you can weld, it is vital to clean the surfaces that will be joined. This ensures that any oxides on the metal will be eliminated and that the welded joint will be of good quality. You must also consider the intended area of the weld and the conditions it will be exposed to. If the metal is particularly dirty, you may need to wash the area in order to see it clearly.
- Before welding, it’s a good idea to preheat the aluminum. This accomplishes three goals: It reduces “shock” to the high-thermal conductivity aluminum; it’s been done long enough to know that it “works.” Second, preheating may minimize some distortion that the intense heat of welding can cause. Finally, it may improve penetration and, thus, mechanical and other properties.
- Welding with aluminum requires an especially skillful touch. The technique is everything when it comes to achieving top-quality welds. You must finish up with a steady arc, control the heat as you travel along the joint, and—you guessed it—get the right amount of filler wire moving through the puddle. (Filler wire is not used in autogenous (fusion) welds, but it is a staple of aluminum welding. We’ll cover what makes a good filler wire in an upcoming section.)
Tips for Successful Aluminum Welding
Try out your technique on scrap aluminum before you attempt important welds. This helps you gain an understanding of both the material and the welding process. Make certain you use the right tools for the job—ones that are actually designed for welding aluminum. In addition to a suitable welder, you also need the proper filler metal and the correct shielding gas. You might find suggestions in welding guides and manuals, or you could consult online resources. If you’re not confident in what you’re doing, reach out to those with more experience. Talk to professional welders or seek out advice from your school’s welding instructor, if necessary.
Conclusion
Welding aluminum can be highly gratifying, as long as you know what you are doing. The particular qualities of this metal—its great thermal conductivity and high energy radiation (e.g., X-ray and gamma-ray) reflective power—make aluminum a bit difficult to weld. Owing to its high thermal conductivity, the risk of melting aluminum can be a constant concern unless you understand and practice a few basic techniques. However, if you arm yourself with the right knowledge and skills and practice some patience, you can yield successful results in working with aluminum. Plus, you’ll then be able to use all the resultant fabulous and bountiful pots and arrays for whatever project for which you were fabricating when you started.
Find more information about welding wire and welding techniques at UDO website – https://www.udo.co.th/
