Difference Between Welding, Brazing, and Soldering

Welding, Brazing, and Soldering: Understanding the Difference 

Welding, brazing, and soldering techniques are used to join two or more pieces of material, especially metals, by the application of heat. The techniques are also used to fill gaps between the metal parts. The main differences between welding, brazing, and soldering relate to two key factors – temperature used and the impact of temperature on the state of the base material. Each process is used for different applications. So which technique is best? This depends on the type of material being used, desired strength, and application.  Let’s review each of the processes, and their distinctions, advantages, disadvantages, and applications.  

How Welding Works 

In welding, two or more metals are joined by melting and fusing, usually with the addition of welding filler metals and shielding gases. The resulting joint is as strong as, or stronger than, the metals. A concentrated heat is applied directly to the area to be joined. The applied heat should be at a high enough temperature to melt the base metals (metals that are joined) and filler metals. Therefore, you need to start the welding temperature at the melting point of the base metals.  

Welding is suitable for joining large assemblies. The welding process does produce irregular beads, however, making the method unsuitable for applications requiring cosmetic joints.  

The various types of welding include: 

Gas Metal Arc Welding (GMAW) 

Shielded Metal Arc Welding (SMAW) 

Flux-Cored Arc Welding (FCAW) 

Gas Tungsten Arc Welding (GTAW) 

Advantages of Welding 

• Welding produces stronger joints than brazing and soldering 
• Welded joints are suitable for high-temperature applications 
• Welding can join both thin and thick sections of materials 

Disadvantages of Welding 

• High processing temperature causes greater thermal distortion and residual stress in the joints compared to brazing and soldering  
• Post-processing treatment is necessary to relieve joint residual stress 
• The welding method is unsuitable to join dissimilar metals 
• The welded joint has irregular beads, making the method unsuitable where cosmetic appearance is critical 

Welding Applications  

Welding is used in manufacturing, construction, transportation, and repair shops. Some examples of welding applications include robotic assemblies, building structures, bridges, fabrication of pressure vessels, aircraft, pipelines, railway tracks, and coaches.  

How Brazing Works 

In brazing, two or more materials are joined by melting a filler metal into the joints of the base materials to create strong bonds. Brazing doesn’t melt the base metals to fuse together. Thus, the brazing temperature needs to be lower than the melting points of the base metals being used. The brazing technique works by creating a metallurgical bond between the surface of the metals being joined and the filler metal. The process requires a small joint spacing to draw the melted filler metal into the joint through capillary action when the metals reach a temperature above 840°F (450°C). 

During brazing, heat is applied to the base metals that will be joined. The filler metal is then brought into contact with the heated base metals to instantly melt it. The melted filler metal gets completely drawn into the small joint spacing by capillary action to form a brazed joint. Various types of brazing include torch, furnace, induction, and resistance. 

Advantages of Brazing 

• Requires low power input and processing temperature (ranging between 1150°F to 1600°F or 620°C to 870°C) compared to welding, thus saving cost on power 
• Capable of joining dissimilar metals using flux or flux-coated alloys 
• Produces stronger joint than soldering. Brazing when done properly can produce joints stronger than the base metal 
• Unlike welding, brazing produces smooth joints with regular beads making the method suitable where cosmetic appearance is critical 
• Produces joints with minimal residual stress and thermal distortion compared to welding due to low processing temperature  
• Doesn’t require any post-processing heat treatment, resulting in cost savings 
• Base metals don’t melt, but instead regain most of their physical properties 
• Brazing is easier to learn than welding 

Disadvantages of Brazing 

• Brazed joints have lower strength than welded joints  
• Unlike welded joints, brazed joints are not suitable for high-temperature applications  
• Fluxes may contain toxic components 

Brazing Applications 

The brazing method is used to make joints in radiators, automotive, glasses, electromechanical systems, tanks, axles, lighting and light fixtures, solar panels, calibration instruments, tubular solutions, jewelry and silverware, hard metal, and diamond.  

How Soldering Works 

In soldering, metals are joined by melting a filler metal into the joints of the base materials to create strong bonds. The process is carried out at a temperature below 840°F, which is much lower than the welding and brazing temperature. The soldering method may or may not require capillary action to form the joint. The method can be used to join different metals including gold, brass, and copper. Soldering is classified in two types – hard soldering and soft soldering. Like brazing, soldering also uses flux to improve and strengthen the mechanical properties of the metal.  

Soldering may seem similar to welding, but it is used in different applications. Solder is soft and is available in tubes and reels. Solders are often used in electronic devices, as they allow the parts to connect electronically. When compared to welding and brazing, the soldered joint is weaker but allows the joined pieces to conduct electricity. 

The American Welding Society (AWS) classifies soldering as a liquid-solid phase bonding process. Liquid implies the filler metal is melted, and solid implies that the base materials are not melted.  

Advantages of Soldering 

• The method is capable of joining dissimilar metals of varying thickness 
• As soldering doesn’t involve high heat, there is a smaller chance of damaging the base materials 
• Realignment is easy in soldering 

Disadvantages of Soldering 

• Produces low-strength joints in comparison to welding and brazing, making the method unsuitable for load-bearing applications 
• Soldered joints are unsuitable for high-temperature applications 
• The method cannot be used to join large sections 
• Fluxes may contain toxic components 

Soldering Applications 

The soldering method is used to bond metal workpieces in heating, electronics, air conditioning, fire sprinklers, radiators, stained glass work, jewelry, automobiles, and plumbing. 

Conclusion 

Welding, brazing, and soldering methods work differently and are used for different applications. The differences between the methods relate to two key factors – temperature used and the impact of temperature on the state of the material. Depending on the application, you can choose any of these methods to join materials. When choosing a joining technique, some of the factors that you need to consider include the size of the assembly, type, and thickness of base materials, desired strength, and spot or joint requirements. You can master each of the techniques with practice.