The Benefits of Brazing vs Welding to Join Materials

Brazing and welding are two of the most widely used metal joining techniques. Each method has its own specific strengths and advantages, and engineers must carefully evaluate which method best suits the requirements of each application. 

In many cases, particularly where precision joining, hermetic sealing, or large surface areas are involved, the benefits of brazing provide significant advantages over traditional welding.

The decision often comes down to a combination of factors. The required material properties for the finished product take precedence, followed by the most appropriate method for applying heat to form the joint. For the materials being joined, the geometry of the parts, and the required tolerances and performance requirements all play a major role in selecting the right process.

Though most clients that come to us for materials joining have already determined that welding is not the most suitable option for their needs, it helps to understand why the choice is made.

Through 50 years of experience, Vacuum Process Engineering (VPE) has become a premier provider of vacuum brazing services for demanding industrial applications.

Brazing vs. Welding: Understanding the Core Differences

Both brazing and welding are part of the same family of joining techniques. Each uses intense heat to join objects together, but the methods by which they accomplish this differ greatly. 

Let’s look at welding first. 

Welding

Welding joins two or more materials together by using extreme localized heat to physically melt the base materials. Temperatures used in welding often exceed 3,000°F, depending on the exact process and materials involved. This creates a molten pool along the joint line, which then solidifies and joins the materials together.

Welders may sometimes employ a filler material to strengthen the bond. When the filler material used is the same metal as the parent material, it is called a homogeneous weld. When a different material is used, it is called a heterogeneous weld.

Brazing

Brazing features a fundamental difference from welding: it does not require the parent materials to be melted to create a bond.

Instead, brazing melts a filler material known as a braze alloy. When the braze alloy melts, it flows into the joint line and solidifies, bonding the parent materials together. In many braze joints, capillary action draws the molten alloy into the joint area.

For the braze to be successful, the braze alloy must have a melting point that is lower than that of the parent materials. This ensures that the parent materials retain their integrity and shape, while the braze alloy melts. In addition, the surfaces to be bonded together must be clean and oxide-free to allow the braze alloy molecules to react with the surface to form a strong bond.

Because brazing occurs at temperatures above 840°F (450°C), filler materials such as aluminum, copper, nickel, and silver are commonly used as braze alloys. The specific alloys used will vary based on the materials being joined and the joint requirements.

At VPE, we specialize in vacuum brazing. Our furnaces are designed to give our engineers and technicians control over the temperature uniformity, heating all parts evenly and resulting in fewer thermal gradients compared to welding. 

Within the vacuum furnace chamber, there are tooling fixtures to keep the assemblies in place, while the vacuum removes atmospheric contaminants. The furnace provides a uniform temperature which keeps the parent materials from deforming, creating high strength brazed joints with tight

tolerances.

At VPE, we specialize in vacuum brazing. Our furnaces are designed to give our engineers and technicians control over the temperature uniformity, heating all parts evenly and resulting in fewer thermal gradients compared to welding. 

The Benefits of Brazing

When to use brazing vs welding depends on your overall project and goals, but the benefits of brazing warrant significant consideration in many projects. These benefits of brazing are among the most important for engineers when considering which type of joining to use.

1. Dimensional Stability

During welding, extreme localized heat guarantees that part of the material is going to be melted. If not done carefully, this can distort the part. 

Brazing offers greater control over part geometry because it heats the entire assembly uniformly without melting the base materials. Only the filler material melts in the joint area. 

This process avoids uneven thermal expansion and reduces any stress concentrations, which helps the assembly maintain its original geometry. 

2. Dissimilar Materials Joining

Not all materials can be welded. Ceramic to metal joining is one such combination where welding is ineffective. 

Brazing makes this possible, allowing medical devices and aerospace and defense components to combine the electrical insulation and heat resistance of ceramics with the strength of metals. 

Since the ceramic surfaces are composed of oxides, nitrides, or carbides that are unwanted in metal-to-metal brazing, special techniques are employed to ensure that the ceramic will form a high quality braze joint.

Other dissimilar material brazing includes dissimilar metal combinations like copper to steel (HVAC), aluminum to copper (automotive), and tungsten to copper (electrical).

3. Joining Large Surface Areas

Typically, welding can only penetrate a small distance between the adjoining parent materials, making it difficult to join large surface areas. Brazing solutions are ideal when a joint requires a bonded surface over a large area. 

Heat exchangers, including car radiators and cold plates, are a prime example where brazing is the primary joining method, although other joining methods may also be used. 

Heat exchanger cores require continuous solid joints between internal components for effective heat transfer, with many being fabricated by aluminum brazing. 

Due to difficulty in performing secondary brazing operations, heat exchanger manifolds are often welded or glued onto the cores in subsequent assembly operations.

4. Superior Hermetic Sealing

Welding is a capable method for creating airtight or leak-proof hermetic seals, but in mission-critical applications brazing may be the better choice. 

That is because the braze alloy can flow evenly into the extremely small gap between the parts (often between 0.001 — 0.005in) to create a continuous and fully sealed joint. 

Vacuum brazing goes one step further, removing contaminants that could cause oxidation to form, and ensuring there are no pores in the final joint. 

In applications where a leak-proof or airtight seal is non-negotiable, such as aerospace components, vacuum systems, and medical devices, brazing is the method that engineers trust. 

5. Production Efficiency

Some clients assume that because welding is more common, it is more efficient. But that isn’t always the case. A single welder can only weld a single piece at a time, while a vacuum brazing furnace can braze dozens, even hundreds of parts in a single batch. 

While vacuum brazing typically involves longer furnace cycles, it is often less labor intensive and is highly repeatable in batch production environments.  Other brazing methods, such as induction brazing or continuous protective atmosphere brazing, offer alternatives that provide other options for production volumes and brazing cycle rates.

When Welding Offers a Better Choice

While there are many benefits of brazing, whether you use brazing vs welding will often depend on the specific situation.

When very large parts need joining that cannot fit in a vacuum furnace, welding is often the most suitable joining method. Long and slender objects like tubes offer another use case where welding is preferred.

Additionally, when a material is thin and the use of a braze filler may negatively alter the parent material properties, welding may be the better option.

The wide availability of welders often makes it a more accessible choice for joining metals. Applications that do not require the precision of brazing services, or those where absolute hermetic seals are not needed, can use welding to solve their joining needs.

VPE: 50 Years of Vacuum Brazing Expertise

Both brazing and welding are proven reliable techniques for joining metals, but choosing the right method ultimately depends on the needs of the specific application.

When projects call for precise dimensional controls, high-strength joints, reliable hermetic sealing, or the ability to join large surface areas, brazing offers substantial benefits.

Selecting the right production partner is just as important as choosing the right joining technique. For organizations in need of high-performance precision brazing services, VPE offers decades of proven expertise.

For more than 50 years, VPE has been a leader in vacuum brazing and precision materials joining. With over 150,000 square feet of manufacturing, laboratory, and quality assurance facilities, VPE has the expertise and technical capabilities to support even the most demanding applications.

To learn more about VPE’s precision brazing services, contact our team to discuss how vacuum brazing can support your next manufacturing project.