Types of Braze Joints

Brazing is one of the many other metal joining methods. However whenever the debate about brazing versus other metal joining processes takes place, it heavily seems to favor brazing to get solid and clean joints. Different types of braze joints can be created by joining two similar or dissimilar metals. However, before knowing about types of braze joints, it is good to get basics of braze joints.

Braze Joints- The Basics
For getting a high-quality braze joint, the parts should always be closely fitted. The base metals should also be clean and free of oxides. For best capillary action and braze joint strength, generally, joint clearances of 0.03 to 0.08 mm (0.0012 to 0.0031 in) are recommended. However, it is not very uncommon to have joint clearances around 0.6 mm (0.024 in). The brazing surfaces have to be essentially clean because any contamination can lead to poor wetting. Professionals mostly make use of two methods for cleaning parts before heading towards a quality braze joint. These two cleaning methods are the chemical cleaning and abrasive (mechanical) cleaning. When abrasive or mechanical cleaning is done, proper surface roughness has to be maintained because wetting on a rough surface can show much easily than on a smooth surface having similar geometry.

Types of Braze Joints
Irrespective of the fact that there can be a variety of joints depending upon the style of joining, functions and assembly geometry, most of them are variety of two basic joints types that are Butt Joint and Lap Joint.

Butt Joint
When two metals are positioned in a head-to-head arrangement for brazing, it will result in a Butt joint. It provides the benefits of a single and consistent thickness at the joint. The preparation of this type of joint is very simple, while the proper result of butt joint are extra strong and possess sufficient tensile strength to serve different application.

A properly bonded butt joint is strong enough and have sufficient tensile strength to meet different application needs. The preparation of this type of joint is simple. The only drawback with butt joint is that the bonding area cannot be larger than the cross-section of the thinner member.

Lap Joints
Lap joint is the type of joint that have a larger surface area because it is formed by overlapping of two metals. This type of joint is preferred to those applications which require comparatively stronger bonds. It offers double thickness at the joining area. Due to overlapping, it helps in the maintenance of a uniform joint clearance mainly in tubular joints.

Usually the lap joint is self-supporting during the brazing process. As one flat member resides on the other, it helps to maintain a uniform joint clearance particularly in tubular joints, where nesting one tube inside the other holds them in proper alignment for brazing.

Butt-Lap Joint
It is a combination of both butt and lap type of joint and offers the advantages of both. Butt-lap joint give the profitable features of single thickness as well as of maximum strength. Self supporting in nature, butt-lap joint requires more work to assemble.

   
Advantages of a Brazed Joint

Tags:- Braze Joints, Butt-Lap Joint

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