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Vacuum Brazing Process of Core Drill
Core drill bits are also called hollow drill bits, which are mainly used to drill holes in steel plates and other products. The hollow drill bit is matched with a special core bit machine, which has the characteristics of high efficiency and low cost. The cutting edge of the core drill bit is made of carbide and reinforced with a layer of diamond. It is widely used in various coring operations, including engineering industry, geological industry, etc.
There are currently two processes used in the manufacture of synthetic diamond polycrystalline core drills. One is to use the powder metallurgy process to manufacture the impregnated matrix core drill bit, and the other is to use the brazing process to manufacture the surface-mounted core drill bit. The manufacturing application of welding process is very common, but the traditional welding manufacturing has the following disadvantages:
(1) The welding process is complex and there are many processes. The polycrystal needs to be subjected to high temperature twice, and the wear ratio has a downward trend.
(2) Manual welding is labor-intensive and has high-frequency microwave radiation, which is harmful to the human body.
(3) It is difficult to control the temperature of each polycrystal in high-frequency induction brazing, which affects the brazing quality.
(4) The outer layer of artificial diamond-impregnated inserts is mechanically bonded, and the polycrystals may fall off during use.
(5) Steel body coring bit, the bit body is not wear-resistant and not resistant to erosion during coring.
To solve the above problems, the vacuum brazing process can be adopted. Vacuum brazing means that the workpiece is heated in a vacuum chamber, and it is mainly used for welding of high-quality products and easily oxidized materials. Vacuum brazing technology has become a very promising welding technology since the 1940s. Widely used in the welding of various tool materials and hard alloys. The vacuum brazed joint has high strength, no oxidation, the brazing gap is filled evenly, and the brazing quality is high. The RHVB high-temperature vacuum brazing furnace produced by SIMUWU can complete the brazing polycrystalline and surface hardening of the drill body at one time. Fully automatic control, no pollution, no heavy work, mass production, effectively reducing production costs and improving production efficiency.
Process flow: Surface cleaning——Assembly——Preheating (120°C)——Plasma spraying——Vacuumizing the furnace——Filling with Ar protective gas——Heating up and brazing——Stopping the furnace to cool down——Out of the furnace
The core bit is vacuum brazed with nickel-based solder.
The specific process is as follows:
1.Evacuate and fill with argon: evacuate to 2.7Pa under normal pressure to reduce the partial pressure of oxygen in the furnace, and then start to heat up and fill with argon to 26.7kPa. Filling with argon can prevent the evaporation of alloying elements, prevent surface contamination, and improve the quality of vacuum brazing.
Heat at a rate of 450°C/h to 500°C and keep warm for 5-10 minutes; heat at a rate of 850°C/h to 900°C and keep warm for 10-15 minutes; heat at a rate of 500°C/h to 1050°C and start keeping warm. The heating process is determined according to the brazing matrix and solder.
Incubate at 1050°C±5°C for 20±2min. The specific heat preservation process is related to the amount of brazing furnace, brazing material, and brazing workpiece, which can be selected freely.
4.Out of the oven
The furnace temperature is selected according to the actual situation. Due to mainly relying on radiation cooling in vacuum, the cooling in the low temperature stage is slow. Therefore, a higher furnace temperature can be selected to save cooling time. The RHVB vacuum furnace produced by SIMUWU is equipped with a cooling circulation system and a heat exchanger, which can quickly cool the workpiece and provide assistance for production.
Through long-term production practice comparison, the advantages of vacuum brazing have been further verified. By adopting vacuum brazing, the weldability of the drill bit is solved and the process is simplified. The quality of the brazing seam and hardened layer is improved, and at the same time, it replaces the silver-based solder used in traditional welding, reducing the cost of brazing. Increase the amount of teeth on the crown of the drill bit to ensure consistent cutting edge, which is beneficial to improve the core footage and pure drilling time, and improve the service life of the drill bit.
The vacuum brazing process can precisely control the brazing temperature, and the overall heating of the workpiece can achieve one-time brazing of more than 500 workpieces. It is easy to realize mass production, the quality is guaranteed by the process equipment, and it can ensure safe production and prevent harm to the human body. Vacuum brazing will not have defects such as pores and slag inclusions, and will not produce oxide films. Effectively increase the quality of finished products, improve the yield rate and production efficiency, and serve multiple purposes.
Excellent technology must be matched with excellent equipment to play a role, and the brazing furnace selected in vacuum brazing is very important. The RHVB vacuum high-temperature brazing furnace produced by SIMUWU is an excellent product for handling such processes. With its excellent temperature control accuracy and temperature uniformity, it can realize the brazing of workpieces evenly, so as to achieve high-level brazing standards, reduce scrap rate, increase production efficiency and reduce costs.
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