Brazing and welding are two of the most popular metal joining processes commercially available, for a number of reasons:
Brazing is a metal fabrication process that uses a filler metal to join two solid pieces of metal. Unlike welding, brazing only melts the filler metal and uses it as a sort of adhesive that holds the base metals in a solid grip when solidified. That’s the simple explanation for it.
The more scientifically accurate explanation is that brazing uses a process known as the capillary action to bond two metals together. Thanks to the capillary action, the molten filler metal finds its way into the microscopic gaps, crevices, and, imperfections of the base metals. As it cools down, the filler metal creates a solid piece of metal that is now a part of both base metals – creating a very solid and durable bond.
Different filler metals can be used in brazing as long as one rule is followed – the melting point of the filler metal is lower than that of the base metals. This means that the filler metal can be melted without the heat affecting the structural integrity of the base metals.
For instance, a common filler metal is silver. It is a versatile filler metal that is used to join both ferrous and non-ferrous base metals and has a melting point of 1,763°F (steel has a melting point of 2500°F). There are many other filler metals available for brazing as well. They are classified into eight categories:
Braze filler metals come in different shapes and sizes like rods, sheets, powder, wire in coils, and pre-made forms that are specifically designed for a particular joint.
The two basic types of braze joints are butt joints and lap joints. The former refers to a design where the two base metals are connected end-to-end or butted against each other. The lap joint is an even simpler design where the two base metals are laid upon each other and the braze filler metal is used to join the overlapping areas.
There are quite a few brazing processes to choose from. The decision is usually made on the basis of the base metals, brazing environment, application, joint design, and required outcome. Following are the most popular brazing processes:
Brazing is a cheap alternative to welding that produces permanent joints and can be easily automated. For these reasons, brazing can be found in various industries with varying levels of complexities. The smooth finish you get from brazing makes it ideal for consumer goods and workpieces where the form is just as important as function, if not more. Here are some of the commercial applications of brazing:
Cutting, drilling, excavation tools.
Domestic and industrial cooling and heat exchanges like radiators.
Welding is the most popular process for joining metals. Unlike brazing, welding uses the fusion process instead of capillary action to bond two base metals together. The fusion process uses extremely high temperatures to melt both base metals together to form a liquid weld pool that solidifies to form a permanent joint. Welding can also be done without any filler metal but some types of welding (and some joint types) require a filler metal.
When we say welding, we’re usually thinking of arc welding, which creates a high-temperature electric arc. The welding arc is very precise and temperatures can be extremely high, which makes the process perfect for thick workpieces that need to be joined at a single point. However, the liquid weld pool created in welding means that welding is more affected by the environment (especially wind) and its finish is not as clean. In most cases, the welded joint requires grinding for a cleaner finish.
There are some other limitations to welding as well but when pitted against the brazing the most glaring disadvantage of welding is its limited ability to weld dissimilar metals. Though it’s not impossible, in comparison to brazing, welding dissimilar metals is quite costly, complex, and time-consuming.
The key differentiating factor in the different brazing processes is the types of filler metal and application. Choosing welding process, on the other hand, depends on the benefits of each, characteristics of the workpiece and workplace, and the skill level of the operator. That said, here are the five main types of welding processes in the United States.
Welding is usually the preferred method of metal fabrication in industries where a lot of thick metalwork is involved or where precise welds are required. Here are some of the major applications of welding:
Sparks can easily burn your skin and clothes and while you’re definitely required to be covered from head to toe, your everyday clothes just won’t cut it as they can still catch fire. We recommend investing in a high-quality leather apron to wear over your clothes to protect yourself from sparks. Do not use a synthetic apron as it can catch fire just as easily as your normal cotton/woolen clothes (if not faster).
Welding can get very hot that will naturally lead to sweating but you definitely don’t want to work with voltage equipment in clothes that are wet with sweat. Leather boots are also important and ensure they’re complete as well, just like the rest of your clothing.
The biggest concern people have when choosing brazing over welding is the strength of the brazed joint, mostly because the capillary action is microscopic, whereas we can see the base metals fusing together with our own eyes in welding. But brazed joints are extremely durable and permanent, just like welded a joint. In fact, brazing is so durable and strong that it plays a critical role in manufacturing tough aerospace components resistant to corrosion and high temperatures.
A perfectly welded joint will likely be stronger, that’s true, but it’s not very easy to make perfect welds.
As we said, brazing is excellent at joining dissimilar metals with ease. You don’t need any special equipment or extra training for this, just standard brazing equipment that’s available commercially will do the job and deliver excellent, durable results.
This is one of the key advantages of brazing over welding because welding different metals require far more time, money, and energy and still the results might not be as expected. On top of this, metals don’t just have to be dissimilar in chemical nature, you can also readily join very thin metal to thick metal.
It’s also impossible to weld metals to ceramics but it’s easy to join metals to ceramics through brazing. In fact, joining metals and ceramics through furnace brazing is quite common.
Welding workpieces that have complex assemblies with varying levels of thickness and/or different metals can be very difficult, especially for beginners. Brazing not only offers an easy but also a cost-effective approach to this problem. For instance, through furnace brazing and pre-placed brazing filler metal, complex assemblies with various joints can be joined quickly, without much effort.
Though the same result can be achieved with welding, brazing gives a better finish, is faster, cheaper, and easier.
Welding uses a pin-point arc to weld joints. The arc can join large seems, gaps, and panels at its edges but the surface area of the joint is still limited. With brazing, you can work on joints that have a much greater surface area.
For instance, two metal plates with grooves for cooling can be brazed together with the use of filler metal in the form of foil, creating a perfect seal between the two plates.
Heat affects the physical properties of metal and severe heat can cause permanent change (distortion) or even damage to the structural integrity of the base metals. In brazing, the base metals aren’t heated at all and the induced heat of the filler metal is generally not enough to cause stress or damage to the base metal. Even in furnace brazing, the temperature of the furnace is only enough to melt the filler metal and there are no stress points or temperature differential on the workpiece as everything gets heated uniformly.
Welding, on the other hand, requires the base metals to be melted which affects the areas surrounding the weld. This is also known as heat-affected zones (HAZ) and it’s been a major problem in welding for a long time now. That said, newer welding technologies like laser welding have significantly reduced the presence of HAZ although these technologies are not as cheap as regular welding equipment.
The pin-point welding arc gives the operator unmatched precision and usability in fabrication work. This is especially useful when working on large workpieces that cannot be placed in a furnace or in small workpieces where a filler metal cannot be placed. In newer laser welding machines, the arc is even more precise.
The joints made with welding will be just as strong as the base metals and often even stronger than its base metals. On the other hand, in brazing, the joints are usually only as strong as the filler metal and while those joints aren’t weak by any means, the joints in welding are still stronger.
The brazed joint is also at a disadvantage in high-temperature environments because of softer filler metal.
Some welding processes can fuse two metals together without the need for filler metal. In these cases, the welded joint is lighter than the brazed joint. If your project requires saving every gram possible, then welding is the way to go.
A large workpiece is better at dispersing heat which means the braze filler metal might not stay in a liquid form as the operator is working on the assembly. This means the filler metal might have to be reheated multiple times. It’s possible to avoid this with furnace brazing but the furnace will not be able to accommodate very large workpieces.
Welding, on the other hand, offers extreme heat at a localized point which makes it better for working on large assemblies.
Apart from the advantages and disadvantages, there are a few other factors that influence your decision when choosing between brazing and welding.
When it comes to spot joints, both welding and brazing are equally cost-effective and easy but brazing is at an advantage for linear joints since a filler metal (wire) can be pre-placed along the gap or panel, irrespective of its shape. Manual welding though requires the operator to trace the linear joint by hand which requires greater skill and time.
Both welding and brazing can be automated for large production volumes. In fact, you often see automated welding machines in factories instead of brazing equipment because welding can be faster and more efficient at shorter production runs and for assembly configurations that do not change. Brazing, however, is much cheaper to automate and is a more versatile alternative for short-medium runs.
If the appearance of the joint is important, as in the case of consumer goods, then go with brazing. A brazed joint is much cleaner and requires minimal secondary finishing. On the other hand, welded joints can create beads of the solidified weld pool and unaesthetic textures that need a much greater finishing touch.
This article lists the advantages and disadvantages of brazing and welding but benefits alone should not dictate your decision. When it comes to metal fabrication and joining, there are quite a few options and no one option is simply the best for all. The right option depends on your requirements and what you want in the finished workpiece. And with that, this definitive guide comes to an end. If you have any questions or suggestions for us, please leave a comment down below.