Because the physical functions of carbide and carbon steel are quite different, brazing and dispersion welding are still feasible and useful welding methods. In addition, some new welding methods such as tungsten inert gas maintenance arc welding (TIG), electron beam welding (EB-W), laser welding (LBW), etc. are also being actively discussed and explored. In the future, they may be used in cemented carbide welding. Get used.
(1) Brazing
Brazing is a traditional and widely used cemented carbide welding method. Among the brazing methods of cemented carbide and steel, depending on the heating method, there are gas flame brazing, furnace brazing, vacuum brazing, induction brazing, resistance brazing, and laser brazing. No matter which method is used, the melting point of the solder is lower than the liquidus of the base metal, and flows into the joint by means of capillary attraction. The connected commodities include oil well drill bits, hot and cold stamping dies, powder metallurgy dies, rolls, cutting tools and measuring tools, rock drilling tools, woodworking tools, etc.
The brazing material is the filling material used during brazing, and it plays an important role in the function of the brazed joint. Solder function is one of the important factors that determine the quality of brazing.
The gas flame brazing equipment is simple, according to the shape of the workpiece, multiple flames can be heated and welded together. The brazing filler metal is mostly copper-based or silver-based filler metal in wire or sheet form, which is suitable for single-piece and small batch production. However, there are many uncertain factors such as the selection of gas torch and post-brazing heat treatment, and the brazing quality is reliable. For large cemented carbide products, because the temperature and speed of flame heating are difficult to control, a large temperature gradient will occur during heating, which will simply cause cracks, so this method is usually not used.
The production rate of carbide tools for induction brazing, resistance brazing and furnace brazing is high, and the quality is relatively stable, but the equipment and skills are messy. Others have higher requirements for the size and shape of the workpiece, and vacuum brazing can reach Very high brazing quality, but the equipment is expensive and the skills are difficult.
As a new type of welding heat source, laser has the characteristics of fast heating speed, narrow heat-affected zone, post-weld deformation and small residual stress. Especially in weakening the embrittlement of the joint fusion zone, it has common advantages, which makes it also used For the welding of cemented carbide. Therefore, when selecting the welding method, the suitable method should be the main priority. Usually, the brazing in the furnace can satisfy the request of the tool brazing.
(2) Disperse welding
Vacuum dispersion welding and hot isostatic pressure dispersion welding can be applied to the welding of cemented carbide. In vacuum dispersion welding, there are many factors that affect the quality of the joint, such as the composition of the material, the quality of the welded surface, the degree of vacuum, the material of the center sandwich, and the heating and cooling speed, but the most important factors are temperature, pressure and time. The increase of welding pressure is particularly important to shorten the welding time and improve the yield; the shear strength of the weld usually increases with the increase of the welding time, because the extension of the welding time can cause most of the micro bumps on the welded surface to disappear, obviously adding In the touch area, the dispersion of atoms is abundant, and the welding rate can be significantly improved.
(3) Tungsten inert gas maintenance arc welding
TIG welding, as a new method of joining cemented carbide and steel, is still in the experimental period.
(4) Electron beam welding
Electron beam welding has the advantages of high heating power density, small post-weld deformation, large aspect ratio of the weld, and wide adjustment scale of standard parameters, and because the welding heat process is extremely short, the dispersion of control elements to a certain extent may become a kind of welding. A new approach to cemented carbide.
