Development of Welding Non-Ferrous Metals

Whenever a new fabrication is being developed, the designers  consider existing materials to find ones that meet the mechanical properties required and the desired cost. In some cases the material that is needed for the application does not exist yet. This results in research being conducted to create a new metal alloy for the project. The existence of such  application-specific alloys are why we have so many different alloys today.

New ferrous alloys are still being invented. However, specialty applications with extreme in-service environments such as space exploration—with its need for high-strength, low-weight, and mechanical properties that can withstand large temperature swings—and high-efficiency vehicles which require materials with a high strength-to-weight ratio and other applications, require new non-ferrous metal alloys, which is why they have and continue to be developed.

Non-ferrous alloys that are weldable and used in mass production in industry today are usually welded using the main welding processes that you are learning in your welding labs: gas metal arc welding (GMAW) and gas tungsten arc welding (GTAW). GMAW is typically used for higher production fabrication needs if it can produce the quality required for the weldment, such as with aluminum. GTAW is used when exceptional quality is required; it can also weld many more non-ferrous alloys than GMAW, such as the reactive metals titanium and zirconium.

When welding ferrous metals with thick pieces of material, or other materials that are subject to hydrogen-induced cracking, the use of low-hydrogen electrodes is a must. Likewise, the filler metal’s chemical composition is equally important for welding non-ferrous metals with difficult weldability. For example, when welding pure aluminum the use of filler metal is required because autogenous welds (welds without filler metal) would crack. Filler metals were developed through careful research and trial and error before a workable filler metal alloy was found.

Luckily for us welders, companies are constantly developing better welding machines and better filler metals that make the task of welding easier. For GMAW and GTAW, the welding power supplies available today are more complex than they used to be. Inverter power supply technology for power supplies enables the welding machine to digitally control the electrical signal that is going to the welder’s torch or gun. Also, manufacturers of welding machines sell waveforms  that are specific to the material being welded and the filler material. Uploaded through a USB stick the welding machine uses that waveform along with any other inputs the welder makes to the machine (such as material thickness, shielding gas used, etc.) and produces an electrical output that enables better welding. This is important for welding non-ferrous metals such as aluminum because it can provide more cleaning action to remove oxidation for those tougher welds. Or the welder could adjust the amount of penetration versus cleaning action. This technology can also improve the arc start to make it easier to start welding. (Chapter 5 covers welding machine power supplies in detail.)

Other welding processes that are also used to weld non-ferrous metals are beyond the scope of this book, but some include electron beam welding, laser beam welding, and friction stir welding. These welding processes are typically performed by welding operators and not welders because they require precision that is more likely from automated processes (welders perform manual and semiautomatic welding while welding operators operate machines that perform automated welding, such as welding processes that use robots).

Basics of Welding Non-Ferrous Metals

There are always exceptions to the rule but, generally speaking, non-ferrous metals have a lower weldability than low-carbon steels. Because steel has easy weldability and is less expensive than most alloys, usually it is the go-to material. But when an application needs to have higher strength, higher corrosion resistance, better ability to survive in-service conditions, or a higher strength-to-weight ratio, other metal alloys are used.

Unlike ferrous metals, non-ferrous materials like aluminum do not glow red when heated to an elevated temperature This means that you can’t tell if  aluminum is hot just by looking at it ,so you’ll need to know how the non-ferrous alloy will react to heating. Knowing the material’s rate of expansion when heated is important because the alloy may shrink more than initially expected, leading to higher stresses in the weldment and possibly cracking.

In addition, metals like aluminum oxidize very quickly. The rust on iron is oxidation, which can flake off or remain on the metal. Welders prefer metals that form an oxide layer that remains to protect the underlying base material. The oxide layer on aluminum starts to form immediately after cleaning; if you take a break after cleaning your aluminum you should clean it again to remove any new oxide layer that formed.

Stainless steel wire brushes are typically used for cleaning and working with aluminum and titanium alloys. It is important to mark the handle of these tools with “Aluminum Only” or “Titanium Only” so you do not contaminate your metal by using the brush on another material.

Reactive metals are very strongly affected by oxygen and nitrogen, both of which are found in air, so the application of adequate shielding gas when welding non-ferrous metals is a must. Sometimes these metals are welded in what’s called a glove box—a box that provides a barrier to the outside atmosphere but with gloves attached to be able to manipulate items in the box—so the entire environment of the weldment consists of the shielding gas.

Non-ferrous alloys typically have specific alloying elements that give the metals their unique properties. This makes the selection of filler metals very important, as non-ferrous alloys, especially reactive metals, are much less forgiving to mistakes and contamination. When welding non-ferrous metals, follow the Welding Procedure Specifications (WPSs) carefully.

Uses of Non-Ferrous Metals in Industry Today

Non-ferrous metals are used for electrical and structural applications due to their high strength-to-weight ratio. Reactive metals, such as titanium, zirconium, and beryllium, are used in harsh environments with corrosive or radioactive substances.

Titanium has an excellent strength-to-weight ratio, making it an alloy used in the aerospace industry. It also has high corrosion resistance (lack of reaction to water), making it a good choice for desalination parts to obtain clean drinking water from sea water and use in medical and dental implants.

Zirconium is used by the nuclear industry in nuclear power plants, especially for the tubes that hold the ceramic fuel pellets because it performs well in high-temperature, high-radiation environments. Zirconium, like titanium, is also highly corrosion resistant and used in medical and dental implants.

Beryllium is a highly corrosive resistant and strong metal that is used in the nuclear, aviation, and space industries. However, it is a highly poisonous metal that should only be fabricated by trained personnel. Undisturbed, the metal is OK to handle: it’s the dust from machining that causes berylliosis of the lungs, a life-threatening disease. Your body will have an immune response to inhaled beryllium that could be immediate or take months or years to develop. Any time you work with a new metal or material, it is important that you understand what you are working with so you can safely produce fabrications and not cause unnecessary damage to your health.