Saw blade welding process

To ensure smooth welding, silver brazing flux must be applied to the mating surfaces of the components. This promotes the reduction , facilitates the melting of the silver brazing sheet, and improves the fluidity of the brazing sheet. The selected brazing sheet must meet the following requirements: its melting temperature must be lower than that of the serrations, generally by 100-200°C. If the temperature difference is too small, the low-melting-point components in the serrations may melt during welding, affecting  the weld quality .

01 Saw blade welding (brazing)

Saw blade brazing is generally a process that bonds the base material and the alloy together through heating. During brazing, it is essential to ensure that the surfaces of both the base material and the alloy are free of dust and oil. Oil can be cleaned with alcohol or gasoline, and dust on the base material can be removed with an air gun.

During brazing, the brazing temperature and heating rate affect the welding quality. Excessively high welding temperature or excessively fast heating rate will generate large internal stresses in the cemented carbide, which will easily lead to cracks and chipping after welding.

Saw blade brazing  process: heating -- heat preservation -- cooling -- tempering -- completion.

02 Welding wire/sheet

The scientific name is brazing filler metal, which is the filler material added to the gap between two materials when they are joined together. Welding wire is divided into: silver-free welding wire and silver-containing welding wire.

The main metallic components of welding wire are silver, copper, nickel, and zinc. Silver primarily ensures its low-temperature performance, nickel and zinc enhance wetting and flowability, and copper strengthens the weld.

Soldering electrodes are categorized into: sandwich electrodes (commonly 49% and 30% silver content) and mixed electrodes (below 30%). The melting point of solder wire/electrode is determined by its silver content; silver content is inversely proportional to melting point (higher silver content results in a lower melting point). Sandwich electrodes consist of two layers of molten metal (silver and other fluxing metals) with copper in the middle. The copper layer in the middle allows for plastic deformation, reducing internal stress generated during heating, thus making sandwich electrodes less prone to chipping. The silver content Umicore and melting point vary depending on the solder wire/electrode manufacturer's formulation; please refer to the table below.

When using welding wire or welding sheet of the above specifications, in order to improve welding flow and lubrication, the melting point should be increased by about ten degrees to ensure welding strength.

03 solder paste

The scientific name for brazing flux is a fluxing agent that helps melt the welding wire and welding sheet during welding (currently, domestic customers use Belgian Umicore H285 flux for high-frequency automatic welding).

04 Welding thermal stress

Internal stress is generated during welding heating  HYPERLINK . High internal stress can cause chipping and cracks in cemented carbide.

05 Welding Temperature and Settings

Welding temperature refers to the temperature set during welding (the welding temperature depends on the silver content of the brazing filler metal). The correct welding temperature is determined by the silver content of the brazing filler metal (wire or solder sheet) . For example, if a 30%  silver solder sheet is provided , its melting point is between 750-780°C. Ignoring external factors, we should weld within ten degrees of this melting point range (to increase weld strength).

06 Saw Blade Cooling and Tempering