In designing the brazing joint, the strength of the joint should be considered first, and then how to ensure the dimensional accuracy of the assembly, the assembly and positioning of the parts, the placement of the filler metal, the clearance of the brazing joint and other technological problems should be considered.

Then how to improve the bearing capacity of brazing joint?In brazing joint, one of the ways to increase the bearing capacity of joint is to use lap joint in joint design. Lap joint can have higher bearing capacity by increasing lap joint area.Another way to increase joint carrying capacity is to increase lap length, but excessive lap length does not increase joint carrying capacity proportionately.Practice shows that the lap length of the joint should be 3~4 times of the plate thickness.

Why is that?Butt joint has a uniform state of force, and save material, reduce the weight of the structure, so called the basic form of fusion welding joint.In brazing connection, because most of the strength of the solder is lower than the parent metal, and the strength of the weld is often lower than the parent metal, this makes the ordinary butt joint is difficult to give full play to the carrying capacity of the parent metal, and butt joint to ensure fitting to and strictly control the size of the gap is more difficult, especially when the workpiece thickness is small, will make its difficulty is increased significantly.So butt joint is seldom used in brazing structure.T-joints and Angle joints are similar to butt joints and are relatively rarely used.

In addition, by increasing the lap joint area, the joint can have the same or even higher bearing capacity as the base metal when the strength of the joint is lower than the base metal, and the assembly requirements of the lap joint are relatively simple. Therefore, the lap joint becomes the most basic form of brazing connection.

Although the lap joint has become the most basic form of brazing, it has some disadvantages.The section of the joint changes suddenly and thus causes stress concentration.Therefore, in the joint design, if the use of overlapped joints can meet the requirements of the product, it should not use overlapped joints as much as possible.When the lap joint is used as the load-bearing connection, certain measures should be taken to mitigate the effect of stress concentration, such as making the section of the joint smooth transition, as shown in the figure below.