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Carbide wood knife tools vacuum brazing
This paper takes the vacuum brazing process of cutting tool carbide as the research object. By studying its process and mastering its working principle, the blanks of rotary cutting tool carbide vacuum brazing can be qualified for batch production.
Vacuum brazing of carbide tools is a very important process. Because the chemical composition and physical and mechanical properties of cemented carbide and steel are completely different, cracks are often generated during welding and the cemented carbide is scrapped. Improving and improving welding quality is of great significance for reducing tool waste, improving the quality of carbide tools, and prolonging the service life of tools.
1.Tool body 2. Inner hole 3. Support surface 4. Chip groove 5. Carbide cutting edge 6. Rake angle 7. Tool tip angle 8. Relief angle 9. Edge inclination angle 10. Side relief angle d: Tool diameter D : Tool edge diameter H: Cutting width
The main problems existing in the welding process of cemented carbide woodworking tools
(1) Due to the different linear expansion coefficient and thermal conductivity of cemented carbide blade and steel (the linear expansion coefficient of cemented carbide is 5~7×10-6/℃, while that of steel is 11~14×10-6/°C). C), when the blade is cooled under the high temperature of welding, internal stress often occurs, resulting in cracks in the blade.
(2) Due to the poor wettability of ordinary solder to cemented carbide, the blade is often not welded firmly, and desoldering will occur under the impact of cutting force. Therefore, in order to prevent welding cracks and desoldering phenomena, it is necessary to study the welding stress, solder wettability, flux and welding process specifications during welding of cemented carbide tools.
The characteristics of vacuum brazing of carbide tools
Whether it is thermal conductivity, thermal expansion coefficient, or heat capacity, cemented carbide and tool shank materials are quite different. Therefore, if the welding heating or cooling speed is too fast, the temperature difference between the blade and the shank, the blade surface and the core will increase, resulting in excessive expansion or contraction stress and cracks in the blade. The larger the blade size, the more serious this phenomenon is.
Weld cracks on cemented carbide are caused by excessive welding stress. After sufficient heating, the tool begins to cool and the solder solidifies. Since the thermal expansion coefficient of steel is 2~3 times larger than that of cemented carbide, different shrinkage occurs on steel and cemented carbide. After reaching room temperature, the shrinkage of steel is that of cemented carbide. twice. As a result of the gradual shrinkage, tensile stress is generated on the cemented carbide, resulting in weld cracking. In addition, the cemented carbide will be violently oxidized at 950 ° C ~ 1100 ° C, and the formed oxide film has many voids, which makes the cemented carbide brittle, thereby reducing the mechanical properties of the alloy. Therefore, when welding, oxidation of the welding area must be avoided.
The steps of cemented carbide welding
1.Thoroughly clean the shank and blade
(1) cemented carbide should be sandblasted
(2) the arbor, blade and solder should be degreased
(3) grind off the oxide layer on the welding surface and make it smooth.
2.After the blade is preheated, borax should be boiled so that the surface is covered with a layer of flux.
(1) the correct choice of flux
(2) flux can be used to clean rust, grease, etc., to prevent the oxidation of the blade and the blade.
(1) first heat the bottom of the tool holder during welding
(2) uniform heat, prevent thermal cracking
(3) do not overheat
(4) after reaching the welding temperature, according to the size of the alloy sheet, it should be kept for 10-30 seconds to make the temperature on the welding surface uniform.
4.Clean the alloy sheet and the adhesive at the welding part, and carefully check whether the blade and the insert groove are wetted by the solder.
6.Sandblasting after welding
Selection of vacuum brazing equipment: The RHVB series vacuum brazing furnace produced by SIMUWU is a high-quality product for handling such processes. Good temperature control accuracy and temperature control uniformity ensure the effective progress of the vacuum brazing process. With more than ten years of sales and manufacturing experience, it is exported to developed regions in Europe, America and Asia. It is a widely acclaimed vacuum furnace product.
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