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Dip Brazing

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Last updated Jul 11, 2024 | Published on Jul 11, 2024

Aluminum Dip Brazing: Strong, Efficient, and Cost-Effective Joining

Dip brazing offers numerous benefits. Each project requires little to no equipment, keeping tooling costs low and allowing for easy configuration changes with common fixtures. The process creates sturdy, leak-proof, EMI-shielded joints, improving overall strength. This method also ensures higher quality at a lower cost by brazing many smaller parts simultaneously. Aluminum dip brazing produces joints with better conductivity than adhesive or mechanical attachments. It brazes all joints of a component simultaneously, producing durable components quickly and evenly.

What is Dip Brazing?

Dip brazing is a metal fabrication process that joins metal surfaces by immersing a pre-assembled component containing braze alloy into a molten bath of the flux. This process uses capillary action to draw the molten braze alloy between the tightly fitted parts, forming a strong and permanent thermal and mechanical bond when it cools.

Why Use Dip Brazing?

Dip brazing efficiently joins metal surfaces across multiple planes in a single 60-second operation, simplifying assembly compared to the multi-step process of welding, which requires careful structural planning and additional time.

In contrast, vacuum brazing effectively joins components in the same plane, such as liquid cold plates and tube-and-fin heat exchangers but lacks dip brazing’s versatility across different planes. Welding, which handles complex structural requirements and provides higher joint strength, uses a fluxless process. Dip brazing efficiently handles multiple component planes in one operation, providing a balanced alternative to welding and vacuum brazing in liquid cooling systems.

When Not to Use Dip Brazing?

Liquid cooling applications or sensitive applications that demand meticulous cleaning are better suited to vacuum brazing or welding. Dip brazing can leave flux reside in smaller cavities that may be difficult to flush out in complex assemblies, which pose risks for sensitive electronics.

What Products and Applications Use Dip Brazing?

Dip brazing is a critical manufacturing process for a variety of products and applications that need high durability and reliability. Dip brazing creates robust and reliable joints essential to maximize performance and longevity across industries such as aerospace, defense, automotive, and electronics. Its versatility and reliability make it indispensable to fabricate intricate metal assemblies and components quickly with high reliability.

Chassis and Enclosures:

In the aerospace sector, dip brazing provides the structural integrity needed for aircraft frames and components. Dip brazing makes these assemblies better able to endure rigorous environmental conditions while ensuring optimal performance and safety.

In electronics applications, manufacturers use dip brazing to produce equipment enclosures. Devices such as communication systems, radar equipment, and power electronics rely on dip brazed enclosures for EMI shielding and structural stability.

The automotive industry uses dip brazing to fabricate chassis components and enclosures. This process ensures the durability and performance of vehicle frames, heat exchangers, and battery enclosures under demanding conditions.

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Machined Components:

Dip brazing enhances the efficiency and durability of heat exchangers in HVAC systems, automotive cooling systems, and industrial machinery by creating robust joints for optimal heat transfer. Manufacturers utilize dip brazing for precision instruments that require exact alignment and structural integrity, such as optical mounts, sensor housings, and medical equipment parts. Power transmission equipment, including gearboxes, couplings, and shaft assemblies, rely on dip brazing for durable and reliable joints, ensuring smooth operation and longevity in critical systems.

Common Dip Brazing Materials

While Boyd only uses aluminum-based alloys, dip brazing relies on a selection of common materials tailored to ensure strong, reliable joints across various metal compositions. Among the critical components of the dip brazing process are base metals and brazing alloys.

Base Metals:

Aluminum Alloys: Ideal for aluminum and its alloys due to compatibility and low melting temperatures.

Boyd only specializes in aluminum alloy dip brazing.

Copper Alloys: Suitable for brazing copper, brass, and bronze components. Steel: Used for a variety of applications requiring robust, durable joints.

Stainless Steel: Offers corrosion resistance and strength, commonly brazed for critical applications.

Nickel Alloys: Suitable for high-temperature materials such as stainless steel and nickel alloys.

Titanium Alloys: Used in aerospace and other industries where lightweight, high-strength joints are required.

Magnesium Alloys: Commonly brazed for applications requiring lightweight components.

Brazing Alloys:

Aluminum-Based Alloys: Specifically designed for brazing aluminum and its alloys, featuring low melting temperatures and excellent compatibility.

Since Boyd only does aluminum dip brazing, we only use aluminum dip brazing alloys.

Silver-Based Alloys: Versatile and widely used for joining steel, stainless steel, copper, and brass components.

Copper-Based Alloys: Often chosen for brazing copper, brass, and bronze components, offering good strength and conductivity.

Nickel-Based Alloys: Suitable for joining high-temperature materials such as stainless steel and nickel alloys, providing strong and durable joints.

Fluxes:

Boyd’s large-scale dip brazing installation maintains only a single flux chloride-based flux. Other dip brazing installations can use different fluxes, based upon the parent and braze alloys.

Borax-Based Fluxes: Commonly used for aluminum and aluminum alloys, facilitating the removal of oxides and ensuring good wetting of the brazing alloy.

Fluoride-Based Fluxes: Effective for brazing stainless steel and other high-temperature alloys, aiding in the removal of surface contaminants and promoting proper alloy flow.

Chloride-Based Fluxes: Suitable for brazing copper and brass components, assisting in the removal of oxides and ensuring strong, clean joints.

These materials are carefully selected based on factors such as base metal compatibility, operating conditions, and specific application requirements, ensuring optimal performance and reliability in dip brazing processes.

Dip Brazing Process

The dip brazing process consists of a series of meticulous steps aimed at achieving strong, reliable bonds between metal components. Each step contributes to ensuring the quality and integrity of the final assembly. From surface preparation to cleaning, we carefully orchestrate every stage to facilitate the flow of molten brazing alloy and create robust joints.

  1. Prepare the Assembly: Remove grease, oil, oxides, and scale from the component surfaces to ensure proper wetting of the alloy.
  2. Select and Position Brazing Filler Metal: Choose the appropriate brazing filler metal, ensuring it contacts all the metals being joined.
  3. Fixture the Assembly: Use fixtures to hold the assembled parts in place during brazing, using rods, hooks, or baskets.
  4. Preheat the Assembly: Heat up the assembled components to just below the melting point of the filler metal to minimize furnace time and ensure uniform heating.
  5. Perform Brazing: Move assembly from preheat and immerse it in the dip brazing furnace for a specific duration, allowing the brazing alloy to flow through the joint by capillary action.
  6. Quench the Assembly: After brazing, rapidly cool the parts to a lower temperature to anneal the assembly and set the material’s mechanical properties. Boyd can use air, mist, or immersion to quench dip brazed assemblies.
  7. Clean the Assembly: Remove flux residue from the components using chemical cleaning methods to ensure a clean finished assembly.
  8. Age the Assembly: The part is artificially aged in an oven to lock in the mechanical properties set during the quench operation.

Key Considerations for Dip Brazing

For successful dip brazing, several key considerations must be addressed to ensure strong, reliable joints. This process involves immersing metals in a molten flux bath and requires meticulous planning. Attention to material compatibility, surface preparation, joint design, fixture design, brazing alloy selection, temperature control, flux selection, cooling and quenching, and quality control is crucial.

Material Compatibility: Ensure the materials being joined are compatible with both the brazing process and the brazing alloy. Consider the melting points, thermal expansion coefficients, and chemical compositions of the base metals and the brazing filler.

Surface Preparation: Proper cleaning and surface preparation are crucial for successful brazing. Remove any contaminants, such as oils, oxides, or coatings, from the surfaces to be joined to promote good wetting and adhesion of the brazing alloy.

Joint Design: Design the joint to facilitate capillary action and ensure the proper flow of the brazing alloy. Tight fits, appropriate gap sizes, and joint geometry promote capillary flow for stronger and more reliable joints.

Fixture Design: Use fixtures to hold the parts in the correct position during brazing and prevent distortion or misalignment. Design fixtures to withstand the thermal stresses of the brazing process and provide adequate support for the parts.

Brazing Alloy Selection: Choose the right brazing alloy to achieve the desired properties in the joint. Consider factors such as melting temperature, fluidity, strength, corrosion resistance, and compatibility with the base metals.

Temperature Control: Maintaining precise control over the brazing temperature ensures proper wetting and bonding of the brazing alloy without overheating the base metals. Ensure temperature uniformity throughout the assembly to prevent localized overheating or underheating.

Flux Selection: Select the appropriate flux for the application based on materials and brazing alloys. Ensure the flix bath is uniformly heated to the required temperature based on the materials being brazed.

Cooling and Quenching: Control cooling and quenching after brazing solidifies the brazing alloy, preventing the formation of undesirable metallurgical phases. Use controlled cooling rates to minimize residual stresses in the joint and reduce the risk of distortion.

Quality Control and Inspection: Regular inspection of the brazed joints for defects such as incomplete penetration, voids, cracks, or excess filler metal is crucial to ensure the quality and integrity of the assembly. Employing non-destructive testing methods such as visual inspection, leak testing, dye penetrant testing, or X-ray inspection as part of the quality control process.

Each of these factors plays a vital role in achieving the desired results and maintaining the structural integrity of the assembled components.

Why Use Boyd for Dip Brazing

Boyd’s total process control and breadth of experience enables us to meet demanding customer drawings and tolerances. Our expertise allows us to design dip braze assemblies, knowing how the material will react to each step of the manufacturing process. We can mitigate process-induced warping and distortion at each point through our deep skill and knowledge of the dip braze process to meet final dimensional requirements. And anything that we can’t adjust in the brazing process, we can machine in secondary operations on-site.

Boyd has been dip brazing complex assemblies for decades, making us an ideal partner when designing and fabricating your next project. We strive for excellence in each step of the dip brazing process and meticulously examine each detail of your application to ensure we produce a product that meets your requirements. Learn more about our chassis and enclosures or contact us today about your latest project.

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