Metal Jointing Basics: Brazing & Soldering Vs. Welding

When it comes to joining metals, several options are possible, including welding, brazing and soldering. What is the difference between these processes? Let’s take a look.

Brazing And Soldering

• In brazed and soldered joints, the base metals are not fused. Instead, brazing and soldering create a bond between a filler metal and the surfaces of the two metals being joined.
• During a brazing/soldering session, heat is applied to the base metals at a temperature well below their melting point; a filler metal is then brought into contact with the heated parts. The heated base metal instantly melts the filler metal, which is drawn by capillary action completely through the joint.
• Overall, brazing and soldering temperatures are always significantly lower than the melting points of the base metals used, which means that brazing and soldering use less energy than welding. The American Welding Society (AWS) defines brazing as such a process that involves a filler metal that has a melting point above 450°C (842°F), while soldering involves filler metals with a melting point of 450°C or below.
• Brazing and soldering applications include electronics/electrical, aerospace, automotive, HVAC/R, construction and more. Examples range from air conditioning systems for automobiles to highly sensitive jet turbine blades to satellite components to fine jewelry.
• Brazing offers a significant advantage in applications that require the joining of dissimilar base metals, including copper and steel as well as non-metals such as tungsten carbide, alumina, graphite, and diamond.
• A properly made brazed joint will in many cases be as strong or stronger than the metals being joined. Since the base metals are not melted, they retain most of their integrity and physical properties during the bonding process, with minimal distortion or warping.
• Brazing also makes it easy to join dissimilar metals using flux or flux-cored/coated alloys. Since the base metals don’t have to melt, you avoid working with materials that have vastly different melting points (for example: copper at 1,981°F to steel at 2,500°F). That gives you the flexibility to select metals that are best suited to the function of the assembly.
• Brazed joints have a neat and attractive appearance – a big contrast with the irregular bead of a welded joint. This is important for products where appearance is critical.
• Brazing skills are typically easier to acquire than welding skills; most of the skill involved in brazing is rooted in the design and engineering of the joint. Brazing is also relatively easy to automate.

Welding

• Welding joins metals by melting and fusing them together – usually with the addition of a welding filler metal.
• To fuse the metals, a welder applies high heat directly to the joint area. The temperature of this heat might be high enough to melt both the metals to be joined, along with any filler metals.
• The joints produced by welding are strong – usually as strong as the metals joined, or even stronger.
• Welding is generally used for large projects where both metal sections are relatively thick (0.5”+) and joined at a single point.
• Since the bead of a welded joint is irregular, it is not typically used in products that require fine cosmetic presentation. Applications include transportation, construction, manufacturing and repair shops. Examples are robotic assemblies plus fabrication of pressure vessels, bridges, building structures, aircraft, railway coaches and tracks, pipelines and more.
• Welding works with an intense, pinpoint heat source. This provides advantages and disadvantages. On one hand, the production of hundreds or even thousands of strong, permanent joints can be made using conventional welding. On the other, high temperatures can distort or warp base metals, creating stress around the weld area. These dangers are minimal when the metals are thick, but increase as metals thin.
• Welding presents problems in automation. A joint made at a single point is relatively easy to automate. However, once the point becomes a line, it requires a complex and exacting setup warranted only when you have large production runs of identical parts.

Choosing The Right Process

If you need strong, permanent joints, you will likely narrow your choices to welding and brazing. Both use heat and filler metals, and both be used on a production line.

Mostly, the choice comes down to:

• the size of the assembly;
• the thickness of the base metal sections;
• whether joints are made in one spot or on a line;
• which metals being joined; and
• the quality of assemblies needed.

Starting up a new welding project? James Oxygen has the welding supplies, welding machines, and welding safety equipment you need to get the ball rolling. Contact us today to learn more about welding supplies in western North Carolina!