Fusion welding of non-ferrous materials: Techniques and best practices

Fusion welding is an essential primary technique in the manufacture of products in various industrial sectors, especially when working with non-ferrous materials. These materials, such as aluminum, copper, and their alloys, require a specialized approach to avoid problems and maximize efficiency.

In the context of non-ferrous metals, controlling the heat-affected zone is essential to maintaining the structural integrity of the component. The selection of operating parameters in processes such as TIG welding or MIG welding determines the quality of penetration and the reliability of the asset in critical industrial applications.

What is fusion welding?

In the energy industry, welding and inspection are not only complex techniques that require a great deal of technical preparation. Knowing the types of welding is vital. In this context, fusion welding consists of joining two or more pieces of material by applying heat, which causes them to change to a liquid state (fusion) and form a solid bond after cooling. When referring to non-ferrous materials, the focus is on metals and alloys that lack significant amounts of iron.

These materials, which include aluminum, copper, magnesium, and titanium, are characterized by their corrosion resistance, lightness, and high thermal and electrical conductivity. These properties make them essential in industrial applications where iron is not suitable, although they present unique technical challenges due to their high reactivity.

Importance of welding non-ferrous materials

The use of non-ferrous metals has grown exponentially thanks to their strength-to-weight ratio and chemical durability. In sectors such as aeronautics, automotive, and energy, the correct execution of fusion welding guarantees the integrity of the final products.

However, these metals present particular challenges, such as their propensity for rapid oxidation, which requires specific atmospheric controls. Mastering these techniques is key to ensuring the quality and strength of joints; an incorrect process causes defects that compromise structural safety. Precision in the choice of equipment maximizes the service life of components in critical applications.

Primary methods: GTAW, GMAW, and SMAW

The selection of the welding process depends on the chemical composition of the material, the thickness of the joint, and the productivity requirements.

TIG welding (Gas Tungsten Arc Welding – GTAW)

This process uses a non-consumable tungsten electrode and an inert gas, usually argon, to protect the molten pool. It is the preferred technique for highly reactive materials.

• Advantages: Precise control of heat input, aesthetically clean weld beads, and no spatter.
• Limitations: Reduced deposition speed; requires a high level of technical expertise on the part of the operator.

MIG welding (Gas Metal Arc Welding – GMAW)

It uses a consumable wire that acts as both an electrode and filler material. It is the standard for large-scale industrial production.

• Advantages: High production efficiency and versatility in welding positions.
• Limitations: Increased risk of porosity if gas flow is not controlled; more complex equipment to configure.

Manual arc welding (SMAW)

Although less common in thin non-ferrous alloys, the use of specific coated electrodes remains essential for field repairs and maintenance of heavy structures where portability is a priority.

Technical comparison of welding processes

The following table summarizes the operating parameters of the main industrial techniques:

Process	Main application	Key advantage	Limitation
GTAW (TIG)	Aerospace / Precision tubing	High-purity solders	Low deposition rate
GMAW (MIG)	Automotive / Structures	High speed and efficiency	Sensitive to pollutants
SMAW	Heavy maintenance	Portable and versatile	Frequent electrode replacement
Laser Welding	Electronics / Medical	Minimum ZAC; high precision	High initial equipment cost

Anatomy of defects in non-ferrous materials

The main defects in these materials are systematically divided into geometric and metallurgical defects. Identifying these flaws is vital to meeting engineering standards.

Geometric defects

They are caused by problems in equipment handling or technical deficiencies:

• Incorrect torch angle: Causes asymmetrical heat distribution.
• Inappropriate speed: Inconsistent progression affects weld bead uniformity.
• Incorrect electrical parameters: Incorrect voltages or amperages result in weak joints or excessive penetration.

Metallurgical defects

Linked to the chemical properties and thermal cycle of the metal:

• Impurities in the base material: External elements that weaken the metal matrix.
• Inadequate temperature cycling: Alters the internal structure, forming brittle phases.
• Incompatible filler metal: Using the wrong filler metal causes mechanical failures.
• Porosity: Caused by trapped gases (hydrogen) during solidification, common in aluminum.
• Hot cracking: Cracks that appear when the material cools too quickly.

Critical technical factors: ZAC and Fusion Zone

To ensure joint integrity, the Heat Affected Zone (HAZ) must be monitored. This area adjacent to the fusion zone does not melt, but undergoes microstructural changes that can impact the mechanical properties of the metal. Controlling the heat source and penetration depth is essential to avoid defects such as porosity or hot cracking.

Best practices: Preparation and temperature control

The best practices used by companies today in these welding processes are the basic principles or procedures for achieving satisfactory results and management and performance indicators that are acceptable to the customer. We will focus on this topic in the three most important steps of this welding process:

Preparation of the material

Preparation is vital to achieving a strong and flawless bond. The most important steps are outlined below:

• Surface cleaning: Non-ferrous metals often have a layer of surface oxide that must be removed before welding. In the case of aluminum, for example, aluminum oxide is usually removed by mechanical brushing or with a specific cleaning solution.
• Preheating the material: Materials such as copper and its alloys may require preheating to reduce thermal deformation and improve the fluidity of the filler material.
• Filler material selection: It is essential to choose a filler material that is compatible with the base metal to avoid welding defects. For aluminum, aluminum-silicon or aluminum-magnesium filler alloys are commonly used, while for copper, copper-zinc alloys are commonly used.
• HAZ management: Monitor the Heat Affected Zone to avoid thermal deformation.
• Adjustment of welding parameters: Proper adjustment of the current, voltage, and electrode feed speed is essential to avoid welding defects and achieve uniform fusion.

Failure to apply this best practice in accordance with procedures, regulations, and good management indicators will result in the most common defects. Below, we list the main defects and how to avoid them:

Main welding defects and how to avoid them

During the fusion welding of non-ferrous metals, certain defects are common if the appropriate parameters and techniques are not applied. Below are some of the most common defects and strategies for avoiding them.

• Porosity: Porosity is a common defect in non-ferrous metal welding, especially in aluminium. This defect occurs when gas becomes trapped in the molten material and forms small bubbles that weaken the weld structure.
  • Solution: Use high-purity inert gas and ensure that the surface is completely clean. It may also be helpful to increase the gas flow to improve protective coverage.
• Hot cracking: Hot cracking occurs when the material cools too quickly after melting, causing cracks in the solidified metal.
  • Solution: Preheat the material before welding to reduce the cooling rate and prevent cracks from forming.
• Thermal deformation: The high thermal conductivity of some non-ferrous metals, such as copper, can cause deformation during the welding process.
  • Solution: Control the temperature by preheating and apply controlled cooling after welding.
• Oxide inclusions: In TIG and MIG welding, oxides can become trapped in the weld, weakening it and causing joint failure.
  • Solution: Clean and brush the material properly before starting, and maintain a constant inert gas atmosphere during the process.

Welding quality control

Performing quality controls at different stages is highly recommended in order to comply with product quality and codes, norms, and standards such as API, ASME, ANSI, among others, thus complying with the engineering design.

• Visual inspection: Visual inspection is one of the most common and effective methods for assessing the quality of fusion welds. This process involves examining welds with the naked eye or using basic welding measurement tools (calipers, verniers, squares) and magnifying glasses, looking for visible defects and characteristics that guarantee the structural integrity of the joint.

• Positive Material Identification (PMI): Positive Material Identification (PMI) is a key technique for ensuring that non-ferrous metals selected for fusion welding meet the specifications and properties required for the application. In welding, especially in industries where structural integrity and corrosion resistance are crucial, such as petrochemical, energy, and aerospace, using the right material is crucial to prevent failure and maximize the service life of the joint.
• Application of non-destructive testing (NDT): Non-destructive testing (NDT) is essential for verifying the integrity of welds. Methods such as ultrasound and radiography can identify internal defects in non-ferrous metals, while penetrant testing is useful for detecting surface cracks in aluminum and copper. The choice of test depends on the properties of the material and the type of welding performed.

Other recommendations

To achieve the best results in this type of welding, it is important to keep in mind some practical tips:

• Maintenance of high-quality welding equipment: Precision in TIG and MIG welding depends largely on the quality of the equipment and its components.
• Properly train personnel: The skill and experience of the welder: These are essential to minimize welding defects and ensure proper fusion.
• Adjust the working environment: Non-ferrous metals are sensitive to oxidation and other contaminants. Working in a controlled environment helps reduce the risk of defects.

Industrial applications

Fusion welding is used in various industries in the energy and industrial sectors, including:

• Aerospace: Extensive use of GTAW in aluminum fuselages due to precise heat control. It is used to assemble aircraft structures, engines, and spacecraft components. All welding activity in this area is governed by the AWS D17.1 standard. This document is the main guideline for qualifying personnel and inspecting fusion welds, ensuring safety in every component in the sector.
• Automotive: Implementation of GMAW and laser welding for rapid assembly of aluminum chassis. It is used in the manufacture of vehicle frames, exhaust systems, and structural reinforcements.
• Shipbuilding: Essential for welding large steel structures in marine construction.
• Medical device manufacturing: Used for precision welding of surgical instruments and implants.
• Construction and infrastructure: Applied in the welding of structural beams, pipes, and bridges.
• Oil & Gas: Specialized techniques for coating corrosion-resistant alloys (CRA) in subsea equipment.

Emerging innovations and technologies in fusion welding

Among the most important advances in technology are: automatic and robotic welding for non-ferrous materials:

• Automated and robotic welding offers precision and repeatability in industrial processes, especially in the fusion welding of non-ferrous metals. Welding robots, integrated with vision systems, enable precise heat application and improve weld quality in high-volume production runs.

And in new materials, alloys, and their impact on fusion processes:

• The development of new alloys, such as aluminum-lithium and nickel alloys, with improved melting properties, has facilitated the use of non-ferrous metals in extreme conditions. These innovations allow for better weldability and durability, expanding the industrial applications of these materials.

Conclusions

Fusion welding on non-ferrous materials can be successfully performed when precise and appropriate techniques, equipment, and trained personnel are applied. The choice between TIG and MIG welding methods should be based on material properties and project requirements, ensuring optimal adaptation to the context of each application. This approach reduces defects and improves weld integrity, thereby contributing to process efficiency and final product quality.

Non-ferrous metal fusion welding is a complex process that requires precision, knowledge, and proper technique. The choice between TIG and MIG welding will depend on the characteristics of the material and the specific requirements of the project. With proper preparation, the use of quality equipment, and ongoing staff training, it is possible to achieve strong, defect-free welds, thereby maximizing efficiency and product quality.

References

1. Air Liquide: ¿Cuáles son los defectos de soldadura más comunes?https://es.airliquide.com/soluciones/soldadura-industrial/cuales-son-los-defectos-de-soldadura-mas-comunes
2. Arccaptain: ¿Qué es la soldadura por fusión? Su proceso y aplicaciones (17 abr 2024) https://www.arccaptain.com/es/blogs/article/what-is-fusion-welding?s
3. Codam: Soldadura en metales no ferrosos (Ago 16, 2024) https://codam.com.ar/2024/08/16/soldadura-en-metales-no-ferrosos/

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