Welding Protocols and Quality Assurance in Aerospace Construction
Aerospace construction is an environment where the role of welding cannot be overstated. It requires precision, skill, and a great understanding of the industry-specific challenges and requirements to provide safety and reliability.
This article explores aerospace construction, taking a look at the welding protocols and quality assurance that are required in every project.
The Importance of Welding in Aerospace Construction
Welding is more than just joining materials in aerospace construction. It constitutes a critical discipline, integral to the engineering of aircraft and spacecraft where precision is paramount, and the stakes are high. Here, every weld must embody a blend of science and skill, contributing significantly to the final masterpiece that takes to the skies.
Criticality of Precision Welding
The margin for error is non-existent in the aerospace sector. Every weld must be executed with the utmost precision. They play a crucial role in the structural integrity and resulting performance of components. Precision welding ensures that each weld can withstand extreme conditions, from the rigorous demands of high-altitude flying to the intense pressures and temperatures of space travel. Therefore, the skill and expertise required in aerospace welding are of the highest caliber. They must guarantee that every component contributes to the safety and reliability of the final construct.
Selecting Materials and Techniques
Due to the unique demands of aerospace construction, there is a requirement for specialized materials. Titanium and aluminum alloys are common as they’re lightweight yet extraordinarily strong. Every material used can pose unique welding challenges due to the fact they have distinct properties. Welders must be aware of these properties and apply suitably advanced and precise welding techniques. They must be tailored to the specific material’s thermal and structural properties to ensure the required integrity and functionality.
Aerospace welding adopts many techniques to meet the industry’s demands. TIG (Tungsten Inert Gas) and MIG (Metal Inert Gas) welding are the most prevalent. TIG welding is favored in aerospace for its precision and superior weld quality. This makes it ideal for use with the thin and lightweight materials commonly used in aircraft and spacecraft.
MIG welding is preferred for its efficiency and the strength of the welds it produces. This is especially beneficial when working with materials that are a bit thicker. Both these methods require welders who understand the materials so that the welds can be strong, light, and flawless.
Quality Control and Safety Standards
Safety implications are immense in welding construction. There is a necessity for quality control processes, where every weld must adhere to rigorous safety and performance standards. The smallest flaw can have catastrophic consequences in aerospace; therefore, the level of scrutiny must extend beyond the weld itself. This encompasses everything from the inspection of materials and the verification of welding equipment to the certification of welders.
Quality Assurance Measures in Aerospace
Rigorous quality assurance measures are essential in providing safety and precision in aerospace welding. A comprehensive set of practices and testing must be followed to ensure the integrity of each weld. This includes advanced non-destructive testing (NDT) methods. These are an integral part of weld testing that identify potential flaws that could compromise the safety and functionality of aerospace components.
At the forefront of these NDT methods is radiographic (X-ray) inspection and ultrasonic testing. Radiographic inspection uses high-energy radiation to capture an image of the weld. This then reveals cracks, voids, and other internal flaws. Ultrasonic testing employs high-frequency sound waves through a weld to detect imperfections. They will reflect back any flaws to create a detailed internal structure picture of the weld.
There are also destructive testing methods that the aerospace industry draws upon. These methods include tensile testing, bend testing, and fracture testing. They’re used to evaluate the weld’s strength, ductility, and other physical properties. To conduct these tests, the breaking or deforming of a sample weld will occur to better understand how it performs under a variety of stress conditions.
These quality assurance protocols are also integral in enhancing future welding processes. The feedback and data from these tests can contribute to refining techniques and protocols. This reflects the industry’s relentless pursuit of perfection.
Red-D-Arc’s Expertise as a Welding Equipment Supplier
Red-D-Arc offers years of experience and deep-rooted knowledge in supplying welding equipment to manufacturers across a wide range of industries. We have established ourselves as a trusted partner in the industry for our arsenal of welding solutions.
Our range of equipment includes a number of advanced TIG and MIG welders, specifically designed to cater to the strict requirements of aerospace construction. From theMiller Syncrowave 350 LX to theMillermatic 350P Aluminum Push-Pull Gun System, our machine rentals are renowned for efficiency and capable of delivering high-quality welds at a pace that keeps your projects on schedule.
Reliability is a cornerstone of Red-D-Arc’s offerings. We ensure that every piece of equipment we offer operates at peak performance with minimal downtime. This sort of precision is critical in an industry where even the slightest error can have significant repercussions.
Collaboration is key in Red-D-Arc’s approach to the industry. We work closely with our aerospace clients to deliver the most effective solutions for your project needs. By blending our expertise into the early stages of your project, we can help navigate the complexities of aerospace welding. We will identify the best techniques and equipment for each of your aerospace endeavors.
Elevate Your Aerospace Projects: Connect with Red-D-Arc Today
If you’re facing the challenges of aerospace welding and require experience, look no further. Red-D-Arc is your go-to solution for precision equipment.
Contact us today to discuss how our welding equipment and expertise can help advance your aerospace construction projects. Our team is on hand to provide the insights and equipment you need to ensure your project’s success from the initial stages to success.
Welding aerospace parts and structural elements requires a lot of skill due to stringent industry standards and challenging specialized materials. Aircraft and spacecraft rely on materials like titanium, nickel superalloys, special aluminum types, beryllium, and specialty steels. Almost every aerospace material requires a specialized approach because the welding process can negatively alter the properties of these metals and lead to many weld discontinuities and defects.
What Makes A Good Aerospace Material?
Aerospace materials must tick several critical boxes, including but not limited to:
High strength. All materials used in aircraft must be able to withstand the forces they are subjected to. Tensile, compression, shear, and torsional forces can be extreme in aircraft, requiring the application of exceptionally strong materials.
Long-term reliability and high resistance to corrosion and fatigue cracking.
Low weight. This is essential for aircraft fuel economy. Every aerospace manufacturer prioritizes reducing weight as it’s the most critical aspect of an aircraft’s cost-effectiveness.
Low thermal expansion. Cooling and heating cause materials to shrink and expand, leading to cyclical thermal stresses in critical aircraft and spacecraft parts.
Good weldability. Metals used in the aerospace industry often require welding with specialized processes. The easier the material is for welding, the better. But, this is hardly ever the case with aerospace materials.
Aerospace materials directly influence the initial and ongoing costs of an aircraft, fuel economy, design options, speed and range of an aircraft, safety, recycling, and even the passenger’s comfort.
Just to name one example of how material selection can alter the characteristics of an airplane, we can look at how aluminum use influences passengers’ experience. Humidity must be intentionally lowered during flight to prevent aluminum oxidation if the airplane uses aluminum for structural materials. As a result, passengers may get dehydrated on long flights and have a less convenient flight. So, seemingly unrelated phenomena like using aluminum in the airplane can have unexpected outcomes. The importance of alloy selection for any aircraft cannot be overstated, as all metals have pros and cons that must be carefully weighed.
When engineers design aircraft, they must consider a vast array of problems and choose materials to meet the most critical demands of the aircraft. However, welding technologies and the weldability of the materials play a crucial role in alloy selection.
Welding Aerospace Materials – Challenges And Solutions
Welding codes and aerospace industry standards require exceptional weld quality in almost all welding applications, especially critical parts. Landing gear, structural elements, fuel tank, exhaust system, and fuel and hydraulic lines must be welded with utmost quality. There is no room for error. Meticulous non-destructive testing (NDT) can spot all weld flaws, usually prompting rework.
Such stringent requirements paired with highly exotic alloys that do not respond well to high heat make welding in the aerospace industry very challenging. However, every problem has a solution. There is always at least one welding process that can be configured to meet the demands of almost any alloy in the aerospace industry.
Aluminum
Aluminum has been the top choice for most aerospace applications ever since it superseded wood in the 1920s/1930s. The first aluminum alloy used for aircraft was Duralumin. Today, modern aircraft rely on far more advanced and highly specialized aluminum alloys for excellent structural integrity, recyclability, and low cost and weight.
While aluminum does pose challenges like oxidation, as we mentioned earlier, it’s still a highly relevant material for commercial, military, and private aircraft. Aluminum has excellent machineability, long fatigue life, high damage tolerance and facture toughness, and a good corrosion resistance.
There are many aluminum alloys in the aerospace industry. Some alloys can be fusion welded, while others require friction welding and other specialized welding processes. For example, the most commonly used aluminum alloys for aerospace structural components are the 2000 and 7000 series aluminum, which usually require friction stir welding.
Aluminum alloys like 1000, 3000, and 5000 are also frequently used in aerospace construction for wing ribs, stiffeners, tanks, framework, ducting, flaring, wheel pants, nose bowls, cowlings, fillets, oil tanks, and other important aircraft parts. These alloys can be fusion welded using the MIG and TIG welding processes.
TIG welding aluminum produces the best fusion welding results. The TIG welding process allows precise heat input control, filler metal addition, and weld accuracy. This welding process is also exceptionally clean, with a minimal chance of inclusions.
Aluminum has a surface oxide layer that melts at a significantly higher temperature than the base metal underneath. This is one of the biggest challenges when welding aluminum. However, this problem is eliminated when using advanced AC TIG power sources. The positive side of the alternating current breaks the oxide layer, while the negative side melts the base material. High-end power sources give you precise control over the AC balance and individual amperage values for cleaning and penetration sides of AC TIG. The best example is theMiller Dynasty 400 AC/DC TIG welder with its extensive array of highly customizable functions.
Welding aluminum for aerospace applications also benefits from pulsed AC TIG and multiple waveform selection. Aluminum can easily warp due to excessive heat input, but applying a correct pulsed waveform can make distortion less likely to occur. This is critical for the aerospace industry, where distortion tolerances are minimal.
Magnesium
Magnesium is 33% lighter than aluminum, making it one of the lightest structural metals in use today. However, magnesium isn’t used in significant quantities in aircraft due to its high cost and lower stiffness and strength compared to aluminum. It used to be one of the most commonly used materials for aircraft in 1940s and 1950s, but aluminum has superseded it in many applications.
Today, magnesium is still used for gearboxes and gearbox housings of aircraft, covers of components, electronic housings, flight control systems, aircraft wheels, and the transmission housing of helicopters. While aluminum is less costly and can have higher strength, magnesium’s low weight and excellent machineability make it an irreplaceable material for certain commercial and military aircraft parts.
Welding magnesium for aerospace applications often requires the friction welding process. However, less critical aerospace parts can be fusion welded with TIG and MIG. This is especially the case when repairing aircraft parts and engine castings.
Welding castings from magnesium requires high expertise. Magnesium is flammable, castings can soak in oil (which can significantly impact the weld quality), and magnesium alloys can contain zinc (which evaporates and can cause porosity).
Like aluminum, magnesium has oxides on its surface that must be removed before welding. But, AC TIG can significantly reduce the chances of oxide inclusion when set correctly.
The MIG welding process can often be a better choice for magnesium, depending on the welded part. When repairing a thick magnesium piece, MIG’s high heat and deposition rate is beneficial. Since magnesium conducts heat rapidly like aluminum, you need more heat to keep the puddle going, and this is especially the case with thick casting walls.
However, like aluminum, magnesium filler metal wire is much softer than steel wire, which requires using a specialized wire feeding system. This is where advanced aluminum and magnesium MIG welding systems come in.
TheMiller AlumaFeed Synergic aluminum MIG welder coupled with the Miller XR-Aluma-Pro Push-Pull gun, offer a seamless MIG welding experience with soft filler materials with advanced arc output control. With up to 900 inches per minute wire feeding speed and up to 425A output, you can weld most aluminum and magnesium thicknesses with high efficiency. In addition, Miller’s Profile Pulse allows you to achieve a TIG-like weld appearance using a pulsed MIG welding process.
Titanium
Titanium is the holy grail of metals. It’s the most critical material in the aerospace industry thanks to its incredible strength, low weight, excellent corrosion resistance, and ability to retain its mechanical properties under high temperatures. Titanium ticks all boxes except price, so its applications are limited to critical aircraft parts like airframe structures and jet engine components.
Titanium aircraft can withstand supersonic speeds higher than Mach 2. Aluminum becomes soft when exceeding Mach 1.5 due to friction between the airplane skin and the air. Titanium was the material USAF used to develop and construct the SR-71 Blackbird in the 1960s, allowing this engineering marvel to reach speeds above Mach 3. No other material could provide the necessary strength and heat resistance for the most sophisticated and fastest aircraft of all time. On its last flight in 1990, the SR-71 Blackbirdset a speed record by flying from Los Angeles to Washington, D.C. in 64 minutes and 20 seconds. Titanium’s contribution to the speed of modern aircraft cannot be overstated.
Today, military aircraft, like the famous F-22 Raptor, still utilize titanium alloys in far greater quantities than commercial aircraft. That’s because titanium structural members can withstand extreme loads generated by air maneuvers that jets must be able to handle. But, titanium is an irreplaceable material for all aircraft and spacecraft. Commercial airliners, helicopters, military jets, drones, and other aircraft rely on titanium’s strength for structural members and low weight to improve their range and fuel economy.
Welding titanium is challenging because this material quickly oxidizes at high temperatures and requires exceptional weld cleanliness and purity. High weld accuracy and impeccable arc stability are non-negotiable when working with titanium in the aerospace industry.
Pure commercial titanium, alpha and near alpha, and some alpha-beta alloys are weldable, while some alpha-beta titanium alloys are very challenging to weld. However, the extremely strong alpha-beta titanium alloy Ti-6Al-4V is weldable, which is one of the reasons it is commonly used for aerospace structural components.
Welding titanium requires meticulous care in ensuring the shielding gas coverage. Not only does the weld pool need to be protected with argon gas, but you also need a trailing shielding gas coverage to protect the weld as you move along the joint. Since titanium is highly reactive with oxygen at elevated temperatures, it’s critical to ensure that the welded joint is covered with a shielding gas as it cools. One of the best indications of an overly oxidized titanium weld is discoloration, which is why AWS D17.1 requires discolored titanium welds in a range from violet to white to be rejected. Overly oxidated titanium welds become brittle and cannot withstand the forces exerted on the aircraft’s structural members or engine components.
Pulsed TIG can help prevent oxidation by reducing the heat input. The lower the heat, the lesser the chance of titanium to react with the oxygen in the atmosphere. This is again where advanced TIG welding machines, like theMiller Dynasty 400 AC/DC, can save the day. The Dynasty can output up to 5000 pulses per second in DC TIG, giving you better control over the heat input and reducing the chances of titanium oxidation. Likewise, using such extreme pulse speeds concentrates the arc, allowing higher travel speed, which again reduces excessive heat input.
One particular benefit of high pulses per second when welding sluggish materials like titanium is breaking surface tension through arc pulses. This can sometimes help eliminate porosity and improve puddle wetting.
Superalloys
Titanium can operate at high temperatures and retain its properties, but its limit is at about 1100°F (600°C). On the other hand, the temperatures in jet and rocket engines reach far higher temperatures of up to 3100°F (1700°C). The need for materials that can withstand these extreme temperatures led to the development of nickel, iron-nickel, and cobalt superalloys.
Superalloys are some of the greatest human inventions yet. Nothing like them exists in nature. These materials retain all of their mechanical properties in brutal conditions at extreme temperatures where jet fuel meets air, pressure, and fire, resulting in combustion that would melt or negatively influence pretty much any material known to us. The development of these alloys has allowed engineers to dramatically raise the thrust power of jet-powered engines, resulting in far greater speed and significantly lower fuel consumption.
Superalloys are usually named by the company that developed them. The most critical nickel superalloy used in jet engines is the Inconel 718. Other examples include Hastelloy X, Inconel 625, Inconel 901, Rene 95, and Discaloy.
All superalloys contain a very carefully selected mix of alloying elements that can include niobium, yttrium, cerium, ruthenium, platinum, iridium, zirconium, titanium, tantalum, tungsten, and many other rare-earth materials.
Welding superalloys is challenging because it’s extremely important not to negatively alter the material in the weld zone and heat affected zone (HAZ). Some of the biggest welding challenges are:
Alloying elements with a low melting point can cause embrittlement. Lead and sulfur are a good example.
Cracking due to stress concentration in the HAZ.
Incomplete fusion.
Carbide precipitation and subsequent crack development.
Successfully manipulating the weld metal. The challenge is the sluggishness of nickel alloys, which makes welding accuracy difficult.
Excessive heat input can cause harmful metallurgical changes, resulting in weld cracking and loss of corrosion resistance.
The TIG welding process can produce excellent results when welding many aerospace superalloys, particularly with the Inconel 718 and similar superalloys with excellent weldability. Of course, like with all aerospace alloys, the welding process selection depends on many variables, not limited to the application.
AdvancedTIG welding power sources can make welding superalloys less challenging thanks to high-end features that allow maximum arc control. For example, pulsed DC TIG can help reduce excessive heat input and improve the solidification structure and tensile properties of the weld. Nickel and cobalt superalloys are very sensitive to the welding approach, which is why it’s critical to use a TIG power source that has an extensive array of settings.
Sometimes, the difference between an inspection-passing weld and a flawed weld is just about micro adjustments on the power source. This is particularly true when using pulsed TIG, as high pulses per second can make it far easier to weld highly sluggish nickel alloys. Nickel alloys aren’t as fluid as steel when in the molten state. So, high arc pulses can help break their surface tension and settle the weld better by agitating the puddle. But, to maximize this effect, the pulse settings must be set according to your travel speed, the alloy type, thickness, and desired weld profile.
Specialty Steels
The aerospace industry wouldn’t be complete without steel. But, not all steels can meet the criteria for aircraft and spacecraft. The steels used are usually about two times the strength of titanium and three times stronger than aluminum. However, as strong as specialty steels can be, there is no getting around their excessive weight. So, high-strength steels are only used for about 5-10% of aircraft’s structural elements. Steel application is usually limited to critical elements like landing gear and wing box components.
The three most commonly used steel types in the aerospace industry are:
Maraging Steel – This is a unique steel type with exceptionally low carbon content but incredibly high strength, ductility, and fracture toughness. Maraging steel is one of the strongest metals ever discovered, and it’s often used for heavily loaded aerospace components.
Precipitation Hardening Stainless Steel – PH stainless steel is corrosion resistant and very strong, making it an excellent choice for applications where these properties are critical.
Medium Carbon Low-Alloy Steels – These steel types contain between 0.25% and 0.5% and various alloying elements to increase hardness and high-temperature strength. They are typically used for undercarriage parts.
These specialty steels are best welded with minimal heat input and high travel speed. For example, Maraging steel should not be held at elevated temperatures for a long time. While these materials can be MIG welded, TIG welding again produces a better result due to its clean nature. Still, pulsed MIG can be more favorable in some applications for productivity gain.
Specialty steels may require post-welding heat treatment (PWHT) and specific interpass temperatures to be maintained, depending on the alloy and application. Whenever the work requires precise temperature control, we recommend theMiller ProHeat 35 induction heating system. Induction heating heats the material from within, resulting in high efficiency, ease of setup, maximum temperature control, and uniform heat treatment.
Red-D-Arc – Your Source For Specialized Welding Equipment
The number of materials in the aerospace industry is enormous, and each requires a different welding approach. Even composite materials rely on welding for mold fabrication and repair. Our team of experts can help you choose and optimize the most suitable arc welding process for fusion welding of aerospace parts, whether you are a small repair shop or a large contractor in the aerospace industry.
We have a massive fleet of specialized welding equipment for all industries, and aerospace is no exception.Contact us today to learn more about our advanced MIG and TIG power sources and how we can help you meet your client’s expectations.
You have a welding project you’re working on. It’s already tricky because the pieces you’re welding are aluminum. You love using flux-core wire for the convenience of not needing extra shielding gas, but you’re pretty sure the stuff you use on steel won’t work. So, you go hunting for flux-core aluminum welding wire. What do you find?
Nothing.
Well, that’s not quite true. You’re going to find a lot of options, but the deeper you look, the worse the situation will become.
First up, you find flux-cored aluminum wire, but it’s not for welding. It’s for brazing and soldering. Brazing and soldering are similar to welding, but they operate via thermal rather than electrical energy, and they’re a lot lower temperature than welding. If you tried to feed one of these wires through your welder, not only would the welder get all gummed up with crumpled wire, but you would incinerate the wire before you even got a glimpse of what a weld would look like.
Second, you find aluminum welding wires, some of which even advertise themselves as being flux-cored. Sounds ideal, right? Well, not quite. Unfortunately, all of these listings are either soldering or brazing wires as above, or they’re solid, not flux-cored. Solid aluminum welding wire exists, and is quite common, as are mislabeled eBay listings and storefront product pages.
is not the only process capable of producing high-quality welds on aluminum alloys. The high degree of control that the process provides makes it well-suited to tackling very thin materials, but as material thickness increases, the relatively slow speed of the process becomes more apparent. When ease-of-use and cost-effectiveness are prime considerations in an aluminum welding application, many fabricators choose to implement MIG (GMAW). While the process fundamentals are unchanged from MIG welding steel, MIG welding aluminum requires some specialized equipment and additional care to achieve high-quality results with minimal frustration.
Delivering the Aluminum Wire
Much of the additional care required is focused within the wire delivery system, since the lower columnar strength of aluminum wire makes it susceptible to burn-back and bird’s nesting. MIG welding aluminum typically requires fabricators to choose between “push-pull” or “spool gun” welding torches.
The Push Pull Gun:
Ideal when the workpiece can be brought within 15-25 feet of the power source
Advantages: Lighter and more maneuverable; can utilize wire packaging of any size (meaning reduced changeover cost)
Disadvantages: Reduced forgiveness to compounding issues in the feeding system
Regardless of the MIG welding gun being used, it is critical to ensure that the MIG consumables used are properly sized and in good condition. For example, both gun types require contact tips. Ensure that the wire diameter stamped on the contact tip matches the wire diameter being used and that the contact tip is inspected periodically for the formation of a keyhole shape at either end that is an indicator of wear. As the contact tip wears, micro-arcing between the contact tip and wire can lead to costly burn-backs that are prevented by a quick change of consumables.
A typical carbon steel MIG welding setup will typically use steel liners, brass inlet and intermediate wire guides, and either V-groove or V-knurled drive rolls. Users of a push-pull gun will need to go beyond simply changing contact tips. When MIG welding aluminum, it is important to use ALL the following: U-groove drive rolls, Teflon inlet and intermediate wire guides, and Teflon liners. Ensuring that these components are properly installed (and dedicated for aluminum use only) will help to minimize the potential for wire shaving that can cause the liner to become clogged and complicate wire feeding. Likewise, users of bulk wire packaging such as drums should carefully read the drum’s set up instructions and carefully consider the drum placement and conduit routing to help keep the overall “drag” in the system as low as possible.
Selecting Aluminum Welding Parameters
As with welding steel, it is possible to weld aluminum using one of several “transfers” depending on the specific wire feed speed and voltage combinations used.
Thin materials typically require a short circuit transfer that is the result of low wire feed speed and low voltage. These “low” settings help to minimize penetration to prevent burn-through from occurring. Attempting to use short-circuit on thick material without proper base metal preparation may lead to lack-of-fusion defects.
Thicker aluminum is best welded using a spray transfer. The higher wire feed speeds and voltages required to achieve the stable spray transfer provides additional penetration. Attempting to use spray transfer on thin aluminum will require significantly higher travel speeds than when welding using short-circuit.
Aluminum & Modern Pulsed Waveforms
“Pulse” is a feature found on many modern power sources where the output of the power source is “pulsed” between a low “background” and high “peak” current. By offering the “best of both worlds”, pulsed waveforms are beneficial when welding a wide range of common aluminum thicknesses. Using thinner material as an example: the “peak” current maintains a stable arc when welding at the “low” settings needed for thin material while the “background” current helps to keep overall heat input low to further minimize the risk of both distortion and burn-through.
Looking through a welder rental supplier’s catalog will reveal that there are many choices to be made when selecting aluminum MIG welding equipment. Consult with these experts to learn which combinations are best for your application; they may even have MIG welding packages which can help to alleviate some guesswork by bundling popular options together.
Before pulling the trigger, make sure to purchase some 100% Argon (or 75% Helium/25% Argon shielding gas for a little extra “punch”), set the flow rate to 35-50 cubic feet per hour, and always remove the oxide layer from the weld zone! With some modern technology and a little knowledge, achieving great results when MIG welding aluminum doesn’t necessarily have to be difficult.
When they’re learning to weld, most people use scrap pieces of mild steel. Mild steel is easy to work with, relatively consistent, and very forgiving of a beginner’s mistakes. It’s also fairly common in the wild and will be a frequent target for welding, so it’s good to learn the practicalities right away.
Aluminum is a different story entirely. It shows up in construction, automotive uses, and many more. Aluminum is used all over the place because it’s corrosion-resistant, relatively durable for its weight, and exceptionally lightweight. It also forms alloys with other metals quite well, generally introducing a variety of properties that can be beneficial in specific uses.
The trouble is that many of aluminum’s benefits are also why it can be tricky to weld. Welding aluminum presents several unique challenges, including:
Despite its qualities, aluminum requires more heat than mild steel to weld properly.
The weld puddle for aluminum looks very different than steel, so your visual cues will be different.
It’s surprisingly easy to burn through aluminum and drop your weld pool right through the material, especially with thinner material.
Different alloys require different kinds of filler to weld properly, and picking the appropriate filler can be difficult.
Welding aluminum is often considered difficult, but it’s not necessarily as tricky as it is different. If you’re used to working with mild steel, you’ll need to break yourself out of your habits and turn off your mental auto-pilot to weld aluminum properly.
Can You MIG Weld Aluminum?
MIG welding is entirely possible to use on aluminum, yes. Most professionals recommend TIG welding if possible, but MIG is perfectly acceptable (if a little more challenging) to get right.
Depending on who you ask, MIG might be better for thinner metal gauges, or TIG may be the preferred method.
This decision is largely down to preference and the comfort level of the welder; if you’re a beginner, TIG may be a better alternative if you have the equipment.
The key is the type of aluminum you are welding and the type of welder you have. Aluminum is a generic term and refers to many kinds of alloys, which we’ll get to here in a bit. If it’s an alloy compatible with MIG welding, you can weld it with a MIG gun.
What Equipment is Necessary to MIG Weld Aluminum?
If you’re planning on MIG welding aluminum, you must get your equipment and tool settings configured before you begin. Otherwise, you risk the metal not reacting as you expect, and the whole project can fail in various ways.
What do you need?
1. Cleaning Tools
One of the essential parts of welding aluminum is ensuring that the surface you’re working with is clean. This step is only sometimes necessary for particular welding projects and metals, but it’s a requirement for aluminum.
Why?
Aluminum oxides are much more heat-resistant than plain old aluminum or aluminum alloys. If there are any oxides on your work surface, the heat from your welder will melt the aluminum, but not the oxides. The aluminum melts at around 1200 degrees, while the oxides don’t melt until a whopping 3700 degrees! Those oxides will sink into your weld puddle and create inclusions, pockets, and weak spots in the weld.
Cleaning is also essential when welding aluminum because the oxide coating on aluminum can make it more challenging to adhere to. You may need to use a wire brush or sandpaper with your wire wheel for the best results.
After removing dirt, corrosion, and coatings, you must clean both of the parts you want to join with solvent or soapy water.
Not only is it critical to clean your surface before welding, but it’s also just as important to clean it the right way. For example, a steel brush can contaminate the surface just as quickly as if you left it dirty. An aluminum brush is recommended, and you’ll want to be careful with softer aluminum to ensure that you don’t muddle over inclusions rather than brush them away.
2. Filler Rods of the Proper Alloy
Selecting the right filler rod can be a significant chore. The wrong alloy can leave your weld susceptible to cracking or breaking, weaker than the joint should be, or otherwise not suitable for the job.
Choosing the appropriate alloy filler depends on the answers to several questions:
What is the base designation of the materials?
Does your weld need to withstand prolonged high temperatures?
Will the weldment be anodized when completed?
Does your weld have specific flexibility, strength, or toughness considerations?
Will it need to be heat treated?
These questions and a chart like this can help you decide what filler is best for your job.
That said, this is a beginner’s guide. That means you’re likely welding practice materials or learning directly from a mentor with more specific, practical advice. Everyone who teaches welding has their concept of what is most important, so be sure to ask them for specifics if necessary.
To further narrow things down, filler rods 4043 and 5356 generally apply to a vast majority of aluminum welding applications. It’s not perfect – there are certain situations where other rods will be necessary – but keeping those two on hand will cover many of your bases.
If you’re curious about the designations for filler rods, here’s a rundown. In short:
1XXX is close to pure aluminum.
2XXX is a copper alloy primarily used in heat treatment welds.
4XXX is a silicon alloy and is extremely common in various forms.
5XXX is a magnesium filler typically used in high-strength welds.
Each has numerous pros and cons, so choosing the appropriate filler is critical in many applications.
3. The Right Gas
Picking the correct gas is also vital for welding aluminum. Your choice of shielding gas will be a primary factor in the quality of the resulting joint.
For the vast majority of projects, the go-to choice is Argon gas. 100% pure Argon is a good shielding gas because of its ionization potential and ability to keep a weld clean.
The alternative, used by many pro welders, is a mixture of Argon and Helium. Helium offers a more significant ionization potential and thermal conductivity, making for broader, deeper welds. As a beginner, a wider, deeper aluminum weld is much more likely to burn through, so stick with Argon until you’re comfortable with it. Helium is best added to the mix for more extensive, thicker pieces of aluminum where weld depth and penetration are required.
The critical piece of information here is that using CO2 in your gas mixture won’t work, which is why many attempts to MIG weld aluminum fail.
4. What Settings are Best for MIG Welding Aluminum?
Properly configuring your MIG welding equipment is also important.
First, set your gas flow rate properly. You need enough gas flow to shield your weld correctly. Since you’ll be moving reasonably fast, a flow rate of around 20-30 cubic feet per hour is the general range to work in.
Second, the voltage of your welding gun should be appropriately configured. Usually, a voltage of around 21-24 is ideal. You’ll also want to ensure your MIG gun is set to DCEP (Direct Current Electrode Positive) polarity for the proper process.
Finally, welding aluminum is best done with the spray welding procedure. With this procedure, your arc is constant, and tiny molten filler droplets are sprayed from your gun along the arc and onto your weld surface.
Another common issue beginners run into is a cheap welding gun that jams rather than smoothly feeding the filler wire. Your gun needs a fast feed speed for its filler for this process to work correctly. Wire feed settings can also vary depending on the thickness of the wire you’re using.
5. What’s the Right Technique for MIG Welding Aluminum?
Welding aluminum is a high-heat process. Aluminum melts quickly, but it’s very thermally conductive, so the heat dissipates just as readily. This characteristic means it’s susceptible to variations in movement, and if you move the wrong way, your weld won’t work.
Proper aluminum welding requires three things.
First, you need a fast travel speed. This requirement is due to the heat involved; if you linger too slowly as you move, you’ll put too much heat into your materials, and risk burn-through. This scenario is prevalent with newbies attempting to weld aluminum. The travel speed required is much faster than with steel, and it will feel uncomfortably fast until you get used to it.
The second requirement is using the forehand technique. Where a backhand technique angles the gun away from the direction of travel, this does not facilitate good shielding gas coverage when you’re moving as fast as you need to. That means regular air will get into the weld pool and contaminate it. The forehand technique, where you tilt the gun 15 degrees toward travel, ensures proper shielding.
Third, you want to use simple weave patterns as you weld and avoid complex patterns. Using zigzag, looping, or other welding patterns is a technique used on steel to widen a weld and let heat linger a bit longer to increase depth.
Both are bad when welding aluminum and dramatically increase the risk of burn-through.
In cases where you’re welding thicker pieces of aluminum or need a larger fillet weld, multiple straight passes are better than an attempt at a wider weave.
My Weld is Bad: What Went Wrong?
If you’ve tried out a few aluminum welds using the MIG process and had mixed results, there are a lot of possible points of failure to diagnose. You can start by narrowing it down based on what went wrong.
1. Your weld burned through.
Burn-through or melt-through is caused by excess heat in one spot. There are numerous possible causes, but the most common for beginners is moving too slowly across the joint. Even if you think you’re moving fast enough, it’s likely that you aren’t.
It’s also possible that your joint type isn’t appropriate for the project. Instead of using an edge joint, you may benefit from a corner joint instead, or vice versa. This decision is very situational, however. Similarly, using thicker materials as a base might be appropriate, though you don’t always have a choice.
For more significant welds, you may need to work in shorter bursts to allow the material to dissipate some heat along the way.
2. Your welds are dirty.
Reactions or inclusions in the weld pool usually cause dirty welds.
First, check to make sure you’re using the proper technique. Forehand or push welding is necessary to properly shield your weld as you move, and if you don’t have the angle correct, you’re likely to end up with very dirty welds.
If you’re using the correct technique, it’s possible that your voltage needs to be higher, particularly considering your amperage. You won’t get a spray transfer without sufficient voltage, and your weld won’t work.
Also, make sure you’ve correctly cleaned the surface using aluminum-only tools. The wrong kind of tools will leave particulate matter behind that will cause inclusions in your weld.
Finally, double-check to ensure you’re using the correct shielding gas and filler rod. If either is incorrect, your welds will end up pretty bad.
3. Your welding gun gums up.
Two common problems can crop up, particularly with low-quality MIG welders.
First, the filler material burns back into the gun and causes problems. This scenario usually occurs if you haven’t maintained the proper tip-to-work distance along your weld, or right at the end of the weld.
There are a few “cheats” you can use to get this right, so talk to your mentor about it.
The second is when the feeding process for your filler wire is unsteady or prone to coiling up behind the gun, known as birdnesting. There are several common causes of this, which you can read more about here.
Putting It All Together
Many people claim that MIG welding aluminum is impossible. Some have never attempted to weld aluminum because they believe it is, and they are intimidated by it; others have had a bad experience trying. Others say so to warn off beginners from doing something much more challenging than welding steel. The truth is that MIG welding aluminum is possible; it’s tricky and requires proper settings and technique, but it’s easier than the rumors make it out to be.
However, since there are so many ways that aluminum welding projects can go wrong, it also requires practice and training to get them right consistently.
Steel and aluminum (and its alloys) are among the most widely used structural materials in the world. Steel has been used by human beings for several millennia in construction, transportation, warfare and many other industries. Aluminum doesn’t have nearly the same tenure being only discovered by Hans Christian Ørsted in 1825 and the ore refining process being more complex than iron ore.
Ever since its discovery aluminum has gained extensive use due to its low weight compared to most metals. Due to the desire for more lightweight designs, aluminum is becoming increasingly employed. However, steel and other alloys have significantly higher strength and higher operating temperature than aluminum. The requirements for high strength from steel and lower weight in aluminum generate the need for steel-aluminum dissimilar joining.
Issues
Steel and aluminum are rarely, if ever, directly welded together via fusion welding like TIG and MIG welding due to the brittle intermetallic compounds that form in the fusion zone. The brittle intermetallic compounds may affect the ductility of the weld and high temperature properties of both metals. The specific intermetallic compounds formed largely depends on the specific steel and aluminum alloy being formed. Additionally, steel and aluminum have different coefficients of thermal expansion, so in elevated or cryogenic temperatures, the steel and aluminum will be subject to thermally-induced stresses since the metals will not expand at the same rate.
Bolting and Fastening
There are a few solutions if you find yourself in need of steel-aluminum welding. Starting with the simplest option, bolting and fastening is one way to join steel to aluminum while avoiding several of the drawbacks. As long as the steel-aluminum joint is primarily structural, bolting is one of the more cost-effective ways of joining. Bolting and fastening, however, is not recommended to for joints that must be seamless such as for a pipe joint because the joint is not airtight or watertight. Furthermore, bolting aluminum to steel requires electrical insulation in the presence of salt water or other conductors. A plastic washer will accomplish the electrical insulation goal. Keep in mind that using a plastic washer may limit your operating temperature.
Interlayers
Another well-known option is inserting an interlayer prior to welding. The purpose of the interlayer is to provide a “barrier” to direct interaction between steel and aluminum, preventing the formation of the intermetallic compounds. Additionally, an interlayer can help ease the thermal stresses induced by the difference in coefficient of thermal expansion (CTE) Thus, the interlayer must be thick enough to prevent interaction between iron and aluminum and, in the case of thermal and cryogenic, have a CTE between steel and aluminum.
Most interlayers for steel-aluminum joining are bimetallic transition inserts that can be purchased from many companies. Bimetallic inserts for steel-aluminum welding are typically aluminum in one section and steel in the other. When welding with bimetallic inserts, always consult the manufacturer documentation for proper utilization and details about the metallic insert composition, but most are compatible with MIG, TIG, and GMA welding.
Not that not all aluminum alloys and steels are the same or have the same weldability. For instance, some 7000 series of aluminum tend to be difficult to weld. Be mindful that commercially-provided bimetallic inserts are meant to fit specific structures and not necessarily suitable for more customized or irregular structures. Therefore, do proper research before purchasing a bimetallic insert.
Some academic articles report using a copper interlayer for joining steel to aluminum. Keep in mind that copper can form intermetallic phases with aluminum, some of which are beneficial to aluminum, and does not tend to do so with steel. Another interesting development was using a Al0.5FeCoCrNi interlayer to weld 6061-T6 aluminum to St-12 low carbon steel in an academic article published in the Intermetallics journal in 2020. Using a material other than marketed bimetallic inserts may have more flexibility in terms of accommodating customized or irregular structure and may come as a foil, welding wire, or powder.
Coatings
The last common steel-aluminum joining remedy is to coat one or both sides of the joint with a different metal prior to welding. The most common one for steel-aluminum welding is hot dip aluminizing which coats the steel side of the joint with aluminum. When using this technique, only melt the aluminum and be sure that the arc does not touch the steel! Touching the steel with the arc will cause the aluminum coating and the steel to melt and react to form intermetallic phases. While the aluminum coating does adhere to the steel, it is not actually bonded and the strength of the joint is not as strong as steel-steel or aluminum-aluminum joints.
Other coatings can be used such as copper when welding aluminum to steel. For hot dip coating, it is generally a safer bet to coat the steel since aluminum would also melt in a pool of liquid copper. In general, dip coating is more flexible than using bimetallic inserts since dip coating can conform to most geometries.
Electroplating is a “cold” coating option that does not involve any molten metal and is not used as frequently for welding compared to the above options. Electroplating uses controlled electrolysis to transfer the desired metal coating from the anode (made of the same metal as the desired coating) to the cathode (the part being plated). Aluminum can be electroplated with copper, but steel cannot. If you choose aluminum as the piece to be electroplated, your joining options are typically limited to spot welding, high-precision laser welding, brazing, and emerging solid state welding processes.
Keep in mind that electroplating can be a rather slow process that can take several minutes and the surface area of the workpiece that can be plated depends on the size of the container holding the plating solution and the amount of current you can generate. When electroplating, having a current or voltage that is too high will cause the plating process to proceed out of control as seen by dendrites growing on the workpiece surface.
If the cathode and anode are not parallel to each other, then the electric field that governs the electroplating process will be uneven and so will the coating thickness. The plating may have poor adhesion of the process is not well controlled or the surface is not well cleaned. If the current or voltage is too low then the electroplating will either be slowed or not work at all. As such, electroplating is recommended only for relatively small, flat work pieces and not large structural pieces.
Geometry considerations
One other consideration to note is the geometric requirements of your welding operation. If welding something with a very specific geometry like a hollow part made by additive manufacturing, you may consider using a brazing over welding to avoid damaging the structure via torch brazing or induction heating. Keep in mind this may require a filler metal that is guaranteed to melt before the geometry-sensitive part will melt and is compatible with both materials.
Closing remarks
When considering your steel-aluminum welding needs ask the following questions:
What is the purpose of the steel-aluminum joint?
What type of steel and aluminum are you welding?
What are your load-bearing requirements?
What are your thermal requirements?
Are there any environmental factors to consider (i.e. thermal, corrosive, gas, etc.)?
Tungsten Inert Gas (TIG) welding—more formally known as Gas Tungsten Arc Welding (GTAW)—is well-suited for welding aluminum. Although the process is significantly slower than GMAW (MIG), TIG welding offers unmatched control of weld penetration and profile. This level of control is enhanced by the features available on modern TIG welders.
Aluminum alloys continue to gain popularity in metal fabrication worldwide due in part to the ease with which these alloys can be fabricated—bent, welded, and most importantly, cut. The ease at which aluminum can be cut to shape and size can have a big influence on the cost and quality of subsequent operations and the final component itself. As with steel, the use of plasma arc cutting (PAC) on aluminum alloys is a popular choice for quickly producing high-quality cuts.
Speed is one of the greatest justifications for plasma arc cutting aluminum over mechanical cutting methods. Laser cutting can certainly exceed the speed of plasma but is not without its own process disadvantages. Waterjet cutting certainly has advantages over plasma from a metallurgical and edge quality perspective. Instead, cutting aluminum with plasma provides an excellent balance of speed, quality, and cost. Compared to these other processes, it has a notably lower capital investment and is also simpler to implement as a handheld process for in-service repairs in both the field and shop.
Aluminum welding is one of the most critical processes in manufacturing. By understanding the challenges of aluminum welding, manufacturers can produce stronger and more reliable products. Aluminum is a unique material that requires special techniques to weld properly. It is valued for it’s lightness and is often used in aircraft construction. This guide will discuss the different steps involved in the aluminum welding process and why you must follow a specific protocol when welding with this material. (more…)
05 October, 21 1:55 pm ·Leave a comment·
Red-D-Arc Welderentals
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If you’re looking for a portable, hassle free, full-featured spool gun solution for your steel or aluminum welding projects, look no further than Lincoln’s Magnum PRO 250LX GT K3569-2 spool gun for you next in-field welding job. The Magnum PRO 250LX GT connects directly to Red-D-Arc’s new GX330XL (and Lincoln’s Ranger 330MPX) without the need for additional adapters or control boxes. It’s simply a matter of attaching the gas hose, attaching the 7-pin control cable, and attaching the power cable to the output studs for .025”, .035” steel wire welding or .030”-.035” and 3/64” aluminum wire welding. (more…)
Welding aluminum just got easier with the help of the Magnum SG spool gun from Lincoln Electric. The Magnum SG is a lightweight, semiautomatic spool gun designed to provide easy and reliable aluminum wire feeding. It works with a variety of CV power sources and engine-driven welders. Rated 250 amps @ 60%, the Magnum® SG features a 25 ft (7.5 m) gun cable and integrated wire feed speed control in the handle to reduce the need for walking back to the power source. (more…)
How To Weld Aluminum To Steel: Is It Possible? What Are My Options?
If you’re new to welding, you may be wondering if it’s possible for you to weld aluminum to steel. Welding “like-to-like” metals like steel-to-steel and aluminum-to-aluminum is usually very straightforward. However, when you try to weld together two very different metals like aluminum and steel – such as two components manufactured by tube laser cutting – things can get a little bit more complicated. So, is it possible to weld aluminum to steel? What are your options for doing so? Let’s discuss everything you need to know. (more…)
30 August, 19 3:58 pm ·Leave a comment·
Red-D-Arc Welderentals
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There may only be one thing better than eating delicious barbecue cooked slow and low on a smoker, and that is eating some delicious barbecue that you cooked slow and low on the barbecue smoker that you made. Making barbecue smokers has long been a favorite hobby of backyard cooks and professional pitmasters alike. (more…)
When MIG welding was first invented, it used a constant voltage source of electricity for the arc. While this method is still used today, the invention of pulsed MIG (or MIG pulse) welders has allowed welders to realize several advantages over conventional MIG welders, several are listed below:
Pulsed MIG can be used to weld thin materials. Conventional MIG welders run at a constant amperage whereas pulsed GMAW welding runs a peak and background amperage. The constant switching between these two amperages enables the welder to put out a lower overall heat input into the material. This helps prevent blowouts on thin materials.
There is less spatter than conventional MIG welders. Pulsed MIG welders use peak electrical currents to cleanly burn the wire off at a high amperage. It also employs a lower background welding amperage immediately after the peak electrical current to prevent the interaction of the electrical arc and the wire from becoming unstable. This ultimately results in a reduced amount of spatter.
MIG pulse welding is excellent for out of position welding. At the same voltage and wire feed settings, conventional MIG tends to have a weld puddle that is larger and more fluid than that of pulsed. MIG pulse welding has a more controllable puddle that prevents it from falling out when gravity is a concern during out-of-position welding. Furthermore, the reduced amount of spatter that can be achieved with this method makes it safer for the welder to perform the out-of-position operation.
Red-D-Arc Carries a Number of Pulsed MIG Welder Machines
Whether you’re looking for an EXtreme 360 MAP, a Lincoln Power Wave S350, a D325K 3+12 Diesel, or Millermatic 350P – we have it all!
When electrically conductive materials need to be cut, gouged, or marked, plasma cutting is a cost-effective and practical alternative to the oxy-fuel, laser, and water jet cutting processes. Plasma cutting is used in a vast array of industries for an even wider range of applications. Below are some examples:
CNC plasma cutting can be used to cut complex shapes, make holes, and mark surfaces at high speeds in manufacturing industries.
Mechanized plasma cutting (using what is known as a welding tractor or carriage) is used to bevel edges of steel beams and plates, gouging the backsides of welds to achieve complete joint penetration.
Plasma is especially popular in the petrochemical and energy sectors since stainless steel and non-ferrous alloys cannot be cut using oxy-fuel cutting.
Because plasma can be used to cut all electrically conductive materials, such as aluminum, brass, bronze, and copper, it is also an excellent addition to the home workshop or art studio.
Plasma can be used to help complete jobs faster and more cost-effectively. However, this only works if the operator has an understanding of safe operation using high-quality equipment that is appropriately sized for the application.
27 February, 19 4:53 am ·Leave a comment·
Red-D-Arc Welderentals
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Most people who have been in a technical profession know the constant need for a variety of tools. One minute you may need a pliers, then a knife, then a file, then a screwdriver, and once the day is all done, a bottle opener. This is the reason why multi-tools have become so popular; they combine all of these tools into one. In the world of welding, there is something similar to a multi-tool. It is known as a multi-process welder. Red-D-Arc carries multi-process welders because we know that one minute you might be self-shielded flux core welding some dirty, ½” thick steel and then the next minute be fitting up 18 gauge aluminum that you need to gas tungsten arc weld.
Having worked in shipyards for seven years, I’m familiar with how dirty this type of job site can be. Ship repair worksites and welding surfaces are often filthy with rust, dust and other contaminants. Even in shops and yards where fabrication is ongoing, cleanliness is often lacking. If fabricated or refurbished pieces are being installed onboard, the surface to which the piece will be welded could be rusty, coated with scale, or have other types of corrosion. (more…)
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