Development of welding non-ferrous metals

Whenever a new fabrication is being developed, the designers will look over 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 new metal alloys. These application-specific alloys are why we have so many different alloys. New ferrous alloys are still being invented. However, for specialty applications such as space exploration with its need for high-strength, low-weight, and mechanical properties that can withstand large temperature swings, to high efficiency vehicles which require materials with a high strength-to-weight ratio and other applications with extreme in-service environments, non-ferrous metal alloys have and continue to be developed.

Non-ferrous alloys that are used in mass production in industry today that are weldable 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 they can produce the quality required for the weldment, such as its use with Aluminum. GTAW is used for its exceptional quality and it can weld many more non-ferrous alloys than GMAW such as the Reactive Metals that will be discussed later in this chapter such as titanium and zirconium.

Low hydrogen electrodes are a must with ferrous metals when welding thick pieces of material or other materials that are subject to hydrogen induced cracking. Likewise, the filler metals’ chemical composition is equally important for welding non-ferrous metals with difficult weldability. For example, filler metal when welding pure aluminum is required because autogenous welds, meaning welds without filler metal, will crack. These 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 welding easier. For GMAW and GTAW, the welding power supplies are more complex than they used to be. Inverter technology for power supplies enables the welding machine to digitally control the electrical signal that is going to the welders torch or gun. Manufacturers of welding machines develop waveforms that they sell which are specific to the material being welded and the filler material. These waveforms get uploaded to the welding machine, through a usb stick, and the welding machine uses that waveform along with any other welder inputs to the machine such as material thickness, shielding gas etc, and the machine 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 you can adjust the amount of penetration vs. cleaning action. This technology can also improve the arc start to make it easier for you to start welding. Chapter 5: Welding Machines covers welding machine power supplies in more detail.

Other welding processes that are beyond the scope of this book are also used to weld non-ferrous metals such as Electron Beam Welding (EBW), Laser Beam Welding (LBW), and Friction Stir Welding to name a few. These welding processes are typically performed by welding operators and not welders because they require precision that is not possible with a manual process and are automated processes. Welders perform manual and semi-automatic 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 that is the go to material. 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.

Non-ferrous materials like aluminum do not give off red light when heated to an elevated temperature like ferrous metals. This means that you can’t tell if a metal like aluminum is hot just by looking at it. This means that you need to know how the non-ferrous alloy will react to heating and if it will glow or not. The material’s rate of expansion when heated becomes 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; oxidation can flake off or remain on the metal. We 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 react very strongly with oxygen and nitrogen, both of which are found in air, making the application of adequate shielding gas a must. Sometimes these metals are welded in a glove box so the entire environment of the weldment consists of the shielding gas. The welding glove box is a box with gloves attached that provides a barrier to the outside atmosphere but allows you to place your hands in the gloves to manipulate items in the box.

These non-ferrous alloys typically have specific alloying elements that give the metals their unique properties. This makes the selection of filler metals very important. The WPS for welding non-ferrous metals needs to be followed even more carefully because non-ferrous alloys, especially reactive metals, are much less forgiving to mistakes and/or contamination.

Uses of non-ferrous metals in industry today

Non-ferrous metals such as Aluminum are used for electrical and structural applications due to its 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, and it has high corrosion resistance making it a good choice for desalination parts to obtain clean drinking water from sea water. Due to titanium’s corrosion resistance, or lack of reaction to water, titanium is used 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 is used in medical and dental implants.

Beryllium is a high strength, highly corrosive resistant metal that is used in the nuclear, aviation, and space industries. This 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 which is 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. Anytime 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.