Brazing is an economical method for making robust permanent metal joints.

 

There are many options for joining metal parts, including adhesives, nuts and bolts, as well as many other types of mechanical fasteners. But for sturdy permanent metal joints,

Welding or brazing is usually chosen.

 

Welding combines metals by melting and melting, usually with filler material added. Fusion needs to be concentrated directly at the joint, and the temperature must exceed the melting point of the metal and filler. Welded joints are usually stronger or stronger than the base material.

 

Brazing differs from soldering in that the temperature is much lower and does not melt the base metal. Instead, the heat source melts the filler metal and draws it into the joint by capillary action. It creates a metallurgical bond between the filler metal and the surface of the part.

 

Like welding, the joint strength usually exceeds the strength of a single part. For example, stainless steel joints can have tensile strengths in excess of 130,000 psi. However, since the brazing temperature is low, usually 1,150 to 1,600 °F, most of the physical properties are not affected. The deformation and warpage are minimal and the stress in the joint region is minimized. Lower temperatures also require less energy, which can save a lot of money.

 

Welding and brazing

Both methods produce a strong permanent joint, so the obvious question is which method is best for the particular application. Let's look at a few key considerations:

 

Assembly size. Welding is usually more suitable for joining large assemblies. Brazing applies heat to a wide area, usually the entire assembly. Larger components can dissipate heat and may make it difficult to reach the flow point of the filler metal. The strong local heat of the weld overcomes this shortcoming and can track the joint.

 

thickness. Both methods are applicable if both metal parts are relatively thick (eg 0.5 inch or larger). However, the thin portion will tilt the scales to facilitate brazing. For example, for a 0.005 inch T-joint, brazing is a better choice. Sheet metal is combined to 0.5 inches. stock. The intense heat of the weld is likely to burn through or at least warp the thin section. Brazing has a wider heating and a lower temperature to allow the parts to be seamlessly joined.

 

Joint configuration. Soldering and brazing are all prone to spot welding. The heat of welding is usually local, which has certain advantages. For example, if two metal strips are joined at one point, resistance welding provides a fast, economical way to make thousands of solid, permanent joints.

 

However, linear joints are usually easier to braze than welding. Welding requires heating one end of the interface to the melting temperature, then slowly traveling along the bond line and depositing the filler metal in synchronization with the heat. Brazing does not require manual tracking, and the filler metal can be pulled equally well into a straight, curved or irregular joint configuration.

 

material type. Brazing has significant advantages when connecting dissimilar metals. As long as the filler material is metallurgically compatible with the two base metals and has a melting point lower than either, they can form a strong joint with minimal change in the properties of the base metal.

 

Since welding causes the base metal to melt, for example, attempts to combine copper (melting point 1,981 °F) with steel (melting point of 2,500 °F) will require complex and expensive welding techniques. And it is very likely that copper will even melt before the steel reaches the soldering temperature.

 

The ability to braze combined with dissimilar metals allows the user to select the metal that best suits the functional requirements of the application, regardless of the difference in melting temperature.

 

Production. Jobs that require only a few assemblies are likely to be done manually. The choice between welding and brazing depends on size, thickness, construction and material considerations.

 

However, when the number of parts reaches hundreds of thousands, production technology and cost become critical. Both methods can be automated, but differ in flexibility. Welding is often an all-or-nothing claim. Either manually solder once or install expensive precision equipment to handle a large number of identical components. There is very little practical relationship between the two.

 

Brazing allows it to be automated. For example, for moderate production runs, simple automation techniques (such as pre-welded components and predetermined lengths of filler metal) can speed up production. For larger runs, the assembly is conveyed through a heated torch bundle and the robot then uses a predetermined amount of filler metal.

 

appear. Brazing usually produces small, neat fillets compared to irregular welds in welded joints. This is especially important for consumer goods where appearance is critical. Brass welds can be used almost directly without additional finishing operations.