Tool Vacuum Welding Process Application
What is brazing?
Brazing is one of the welding processes widely used in many industries. The process of brazing is often used in the welding process of the tool making process.
The definition of brazing is: adding solder (brazing material) between two or more workpieces to be welded, heating to melt the solder, and forming a connection between the same or dissimilar materials through the molten solder.
Commonly used brazing methods are: flame brazing, high frequency (induction) brazing, vacuum brazing, resistance brazing, etc. The welding workpieces can be of the same material or different materials, metal to metal, metal to nonmetal, and even nonmetal and nonmetal materials can be brazed. Since the brazing process can well realize the connection (welding) of dissimilar materials, it is widely used in the production of cutting tools.
Application and Development of Vacuum Welding Technology in Cutting Tool Production
Requirements and process of tool welding
In the production of cutting tools, brazing is mostly used to weld hard cutting heads (including: high-speed steel, alloy, ceramics, CBN, PCD, single crystal diamond and other materials) to relatively soft cutting bodies (such as: steel parts, alloy matrix), the cutter body acts as a carrier, and the cutter head acts as a cutting edge.
The basic requirements of cutting tools for welding are: no cracks in welding, no false welding, and the welding strength meets the requirements of use.
Therefore, different tool materials have different requirements for welding processes. For example, materials such as PCD, single crystal, and high-speed steel require lower welding temperatures to avoid the impact of high welding temperatures on their performance; materials such as alloys and ceramics It is necessary to control the stress after welding to prevent cracks; CBN and other materials require higher welding temperature and welding strength to ensure that the high temperature of the tool tip will not lead to tooth loss during machining instead of grinding. At present, the most common methods in cutting tool production are high-frequency (induction) brazing and vacuum welding.
Vacuum welding process status
For tool products, the vacuum welding process can be described as two parts outside the furnace and inside the furnace:
outside the furnace:For tool products that require vacuum welding, select the appropriate vacuum solder (usually solder paste) and apply it to the blade groove correctly, then place the blade to the required position, and wait for the solder paste to solidify after fixing;
inside the furnace:Put the processed tool products into the vacuum furnace, seal and continuously evacuate, heat the products according to the procedure in the vacuum state, melt the solder to complete the welding action, cool down, and come out of the furnace. The purpose of vacuum welding is also to allow the molten solder to be evenly distributed to all parts of the weld under the action of the capillary to achieve the ideal welding effect. Cutting tool products using vacuum welding should be placed in the furnace and heated after vacuuming, and the entire furnace will reach the welding temperature. Therefore: vacuum welding is especially suitable for welding processing of small and medium-sized cutting tool products, and can weld multiple points at a time, especially small-sized cutting tool products, but the cutting tool material must withstand the temperature change during the welding process.
Heating method for welding:Traditional resistance wire heating and new lamp heating
Chamber structure:The current welding furnace still has two structures, vertical and horizontal, in terms of structure. The two structures have their own advantages: the vertical furnace has a larger charging capacity and is easy to operate; although the horizontal furnace has a slightly less charging capacity, the temperature is higher. Uniform, and the interaction between the tools is smaller and more efficient. The welding furnaces of the two structures can meet the welding needs of most products at present.
Development of Vacuum Solder:
The development of solder used in vacuum soldering In addition to the advancement of equipment, the types of vacuum solder have also derived a variety of specifications according to different applications. From the very beginning, there were only a few options to choose from, and now there are many Available options: inactive, active; high temperature, low temperature, ultra-low temperature; good ductility and anti-crack and other solder (paste) to meet the welding needs of various tools, not only can meet the welding of conventional blades, It can also well meet the needs of various occasions such as milling tools, alloy tools, high-temperature welding of CBN, low-temperature welding of single crystal, and butt welding. At the same time, the application of flow blocking agent to prevent molten solder from flowing everywhere also makes the soldering application of small-sized precision tool products more controllable.
The silicon carbide substrate preparation process mainly includes raw material synthesis, silicon carbide crystal growth, ingot processing, ingot cutting, cutting piece grinding, grinding piece polishing, polishing piece cleaning, etc.Among them, the key and difficult points of preparation are mainly the crystal growth, cutting, grinding and polishing links, which are the key points and difficulties in the entire substrate production process, and become the bottleneck that limits the yield rate and production capacity of silicon carbide.
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