Difference Between Soldering, Brazing, and Welding

On the surface, joining metal seems like a straightforward process. However, anyone in the manufacturing industry knows there are a variety of techniques to get the job done. Three of the most common methods for joining two or more pieces of metal are welding, brazing, and soldering. While they might appear similar, understanding their key differences is essential for choosing the right process.

The main difference between these three methods is the temperature used to create the bond and whether the base metals are melted.

Soldering: The Low-Heat Connection

Soldering is a metallurgical joining method that differs from welding in that it operates at a lower temperature. Soldering is performed at a much lower temperature than brazing (below 450°C), and the filler metal, or solder, is typically made of a tin-based alloy.

A soldered joint is the weakest of the three and is not suitable for bearing a significant mechanical load. Its primary use is for creating reliable electrical connections in electronics and circuit boards, where the low temperature prevents damage to sensitive components.

Best use: Used for joining small, delicate components where electrical conductivity is key, like in electronics and circuit boards, as it has the lowest melting temperature.

Brazing: A Strong Bond Without Melting

Brazing is a metal-joining process where a filler metal is melted into a joint. Unlike welding, the base metals remain solid and are not melted during the process. Brazing is performed at a high temperature, but one that is still below the melting point of the base metals (above 450°C). The molten filler metal is drawn into the joint by capillary action, creating a strong, durable inter-atomic bond.

Brazing is used to join dissimilar metals—like steel and copper—because the process doesn't melt the parent materials. This makes it an ideal technique for plumbing and HVAC systems and for building strong joints in bicycle frames.

Best Use: Ideal for joining dissimilar metals or parts that require a strong, leak-proof bond, such as in plumbing and HVAC systems.

Welding: Fusion at High Heat

Welding is the process of melting two pieces of metal together so they become one solid piece. It's like using a very hot glue gun, but instead of glue, you're using extreme heat to fuse the metals themselves. The defining feature of welding is that it melts and fuses the base metals, often with the help of a filler material. This creates a powerful, monolithic joint that is generally stronger than the surrounding metal.

Because the base metals are melted, welding requires very high temperatures, typically above 3800°C. This process is used for structural applications where strength is paramount, such as in the construction of car frames, pipelines, and bridges.

A few common types of welding include:

• MIG (GMAW): Uses an electric arc and a continuously fed wire electrode.
• Stick (SMAW): Uses a consumable electrode coated in flux.
• TIG (GTAW): Uses a non-consumable tungsten electrode for highly precise welds.

Best Use: Best for creating permanent, high-strength bonds on large structures and thick materials, commonly used in construction, automotive, and shipbuilding.

Quick Comparison: Welding vs. Brazing vs. Soldering

Selecting the optimal method hinges on the specific application, the materials involved, and the required strength of the joint.

Conclusion

Examine the application before selecting a method, such as soldering, brazing, or welding. The kind of metal or nonmetal materials used, the purpose and design of the joint, and the size of the structure determine the process type. The quantity of heat used, which varies depending on the application, is the main distinction between the methods.