METAL JOINING: BRAZING VS WELDING

There are several methods available for joining metals, including welding, brazing and soldering. What is the difference between welding and brazing? What is the difference between brazing and soldering? Let’s explore the distinctions plus comparative advantages as well as common applications. This discussion will deepen your understanding of metal joining and help you identify the optimal approach for your application.

Brazing:

A joint created through brazing follows a distinct process compared to a welded joint. The primary distinction lies in temperature – brazing does not involve melting the base metals, resulting in lower brazing temperatures that are consistently below the melting points of the base metals. Additionally, brazing temperatures are notably lower than welding temperatures for the same base metals, resulting in reduced energy consumption.

Since brazing doesn’t merge the base metals, it achieves bonding by creating a metallurgical connection between the filler metal and the surfaces of the metals being joined. This is facilitated through capillary action, where the filler metal is drawn through the joint. During brazing, heat is applied to the base metals, causing the filler metal to melt upon contact and flow through the joint via capillary action, resulting in a secure brazed joint.

Brazing finds wide-ranging applications in industries such as electronics/electrical, aerospace, automotive, HVAC/R, construction, and beyond. Its versatility is evident in various examples, from automotive air conditioning systems to delicate jet turbine blades, satellite components, and even exquisite jewelry. One of brazing’s notable advantages lies in its ability to join dissimilar base metals like copper and steel, as well as non-metals such as tungsten carbide, alumina, graphite, and diamond, making it indispensable in diverse manufacturing and fabrication settings.

When comparing advantages, a brazed joint offers notable strengths. A well-executed brazed joint can often match or exceed the strength of the base metals, akin to a welded joint. Additionally, brazing occurs at comparatively low temperatures, typically ranging from 1150°F to 1600°F (620°C to 870°C), further highlighting its versatility and utility in various applications.

One of the most notable advantages of brazing is that it doesn’t involve melting the base metals. This preservation of the base metals’ physical properties is a hallmark of brazed joints, whether they’re thin- or thick-section joints. Additionally, the lower heat involved in brazing reduces the risk of metal distortion or warping, contributing to the overall integrity of the joint. Furthermore, the lower temperatures required for brazing translate to reduced energy consumption, making it a cost-effective option.

Brazing offers a significant advantage in joining dissimilar metals effortlessly using flux or flux-cored/coated alloys. Unlike welding, where melting the base metals is necessary for fusion, brazing allows for seamless bonding regardless of the metals’ divergent melting points. This means that whether it’s steel to copper or steel to steel, brazing provides a straightforward solution without the need for complex and costly welding techniques. This versatility enables engineers to select the most suitable metals for a given assembly’s function, confident that brazing will seamlessly join them, regardless of their melting temperature discrepancies.

Furthermore, brazed joints exhibit a sleek and appealing appearance compared to the bulkier, uneven appearance of welded joints. This aesthetic difference is crucial in consumer products, where appearance plays a significant role. Brazed joints often require minimal finishing, if any, saving on costs and ensuring a polished final product.

Brazing presents a notable advantage over welding as operators often learn brazing skills faster than welding skills. This distinction stems from the inherent differences in the two processes. Welding demands precise synchronization of heat application and filler metal deposition along a linear joint, whereas brazing, facilitated by capillary action, tends to flow more naturally. In fact, a significant portion of brazing skill lies in joint design and engineering, making training for skilled operators comparatively faster and cost-effective.

Moreover, brazing lends itself well to automation. Its broad heat applications and straightforward filler metal positioning reduce the likelihood of complications. With various automated heating methods, filler metal forms, and deposition techniques available, brazing operations can be easily automated for different production levels.

WELDING

Welding is a metal joining process that involves melting and fusing metals together, often with the addition of a welding filler metal. The resulting joints are typically very strong, sometimes even stronger than the base metals themselves. To achieve fusion, a concentrated heat is applied directly to the joint area, reaching high temperatures necessary for melting both the base metals and the filler metals.

Welding is commonly used for joining large assemblies where the metal sections are thick and joined at a single point. However, the irregular appearance of welded joints makes them less suitable for products requiring cosmetic joints. Industries like transportation, construction, manufacturing, and repair shops extensively use welding for applications such as robotic assemblies, pressure vessels, bridges, aircraft, pipelines, and more.

One advantage of welding is its localized and pinpointed heat application, making it practical for joining small strips of metal at a single point, as seen in electrical resistance welding. This approach is fast, economical, and produces strong, permanent joints in bulk quantities.

However, welding becomes challenging when dealing with linear joints. The localized heat can lead to issues like distortion, warping, or stresses around the weld area, especially with thin metal sections. Moreover, the high temperatures required in welding contribute to production costs, as heat equals energy consumption, which translates to expenses.

Automating welding for mass production introduces complexities, especially for linear joints that require tracing. While automation is feasible for large-scale, identical parts production, it involves sophisticated setups and specialized equipment, often with substantial costs.

Despite advancements in welding techniques like electron beam welding or friction welding, which offer precise and efficient joining, they require expensive equipment and setups, making them more practical for long production runs or specific industrial needs rather than everyday metal joining tasks.

Choose Right Metal Joining Process

If durability and strength are paramount in your joint requirements, your choices for metal joining will likely boil down to welding versus brazing. Both welding and brazing involve the use of heat and filler metals and can be scaled for production purposes. However, beyond these similarities, they diverge significantly in their approaches. Consider the following factors when weighing brazing versus welding:

Size of the assembly: Welding is typically preferred for larger assemblies, while brazing can be more versatile for smaller or intricate components.

Thickness of the base metal sections: Welding is suitable for thicker base metal sections, whereas brazing can handle thinner materials effectively.
Spot or line joint requirements: Welding is commonly used for linear joints, while brazing is versatile for both spot and linear joints.
Metals being joined: Welding is more suitable for joining similar metals, while brazing excels in joining dissimilar metals.

Final assembly quantity needed: For large-scale production runs, welding may offer efficiency, while brazing can be cost-effective for smaller quantities.
Alternative options: Mechanically fastened joints, such as threaded, staked, or riveted joints, may not match brazed joints in terms of strength, shock resistance, vibration resistance, or leak-tightness. Adhesive bonding and soldering can provide permanent bonds but may not match the strength or temperature resistance of brazed joints.

When seeking permanent and robust metal-to-metal joints capable of withstanding various conditions, brazing emerges as a compelling choice due to its strength, versatility in joining dissimilar metals, and ability to withstand high temperatures.