Application of Vacuum Brazing CBN tools

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1、Introduction
The CBN tool was first synthesized by the United States General Electric (GE) company in the 1950s using artificial methods under high temperature and high pressure conditions with CBN fine powder and a small amount of binder. Its hardness is second only to diamond and much higher than other materials. It and diamond are collectively called superhard materials.
In the 1970s, the former Soviet Union, China, the United States, the United Kingdom and other countries have successfully developed CBN sintered body-Cubic Boron Nitride (CBN) as cutting tools. Since then, CBN (cubic boron nitride) has been applied to the cutting of high-hardness materials and difficult-to-machine materials with its superior cutting performance, such as hardened steel, high-alloy wear-resistant cast iron, high-temperature alloys, high-speed steel, surface spray welding materials, Cutting of difficult materials such as sintered metal materials.

The following is a comparison chart of the hardness and toughness of CBN tools and other tool materials.

2. Performance advantages of CBN tools
(1) High hardness and wear resistance
The microhardness of CBN single crystal is HV8000-9000, which is the second highest hardness material known at present. The hardness of CBN composite sheet is generally HV3000-5000.

(2) Has high thermal stability and high temperature hardness
The heat resistance of CBN can reach 1400 ～ 1500 ℃, and the hardness at 800 ℃ is the normal temperature hardness of Al2O3 / TiC ceramics.

(3) High chemical stability
CBN has high anti-oxidation ability, and does not produce oxidation at 1000 ℃, nor does it react with iron-based materials at 1200 ～ 1300 ℃.

Has good thermal conductivity and low coefficient of friction.

3. Advantages of CBN tools compared to other materials
(1) Compared with cemented carbide tools: CBN tools have high hardness and excellent wear resistance, and their wear resistance is 30-50 times that of ordinary cemented carbide tools.

(2) Compared with ceramic tools: CBN tools have excellent wear resistance, strong impact toughness and fracture resistance, and high metal cutting rate. Especially when intermittently processing workpieces above HRC60, they do not collapse.

(3)Compared with imported CBN tools: the cutting performance is stable and the cost performance is higher, especially in the field of high-speed cutting hardened steel and gray cast iron.

4. Structure of CBN tool
The structure of CBN tools is divided into welding CBN tools and integral CBN tools. Among them, welding CBN tools are divided into mosaic CBN tools and compound CBN tools.

Mosaic CBN tool: to achieve high-speed cutting, multi-edge cutting is more economical, flexible blade clamping method, excellent wear resistance, mainly used in semi-finishing and finishing processes.

Compound CBN tool: Realizes high-speed cutting, balanced wear resistance and chipping resistance, excellent tip strength, excellent performance in intermittent machining, mainly used in semi-finishing and finishing processes.

Integral polycrystalline CBN tool: all the cutter blocks are made of CBN material, which combines high hardness, high wear resistance, heat resistance, and chipping resistance. It can realize heavy-load cutting, hard cutting, turning instead of grinding , Both roughing and finishing.

At the same time, it can also provide positioning groove, chip breaking groove, smoothing edge, coating and other products.

5. Advantages of vacuum brazing CBN tool
1. Vacuum brazing not only saves a lot of expensive metal flux, but also does not require complex flux cleaning procedures, reducing production costs.

2.Vacuum brazing, because no flux is used, significantly improves the corrosion resistance of the product, avoids all kinds of pollution, pollution-free processing equipment costs, and has good safe production conditions.

3.The vacuum brazing filler metal has good wettability and fluidity, and can weld more complicated and narrow channel devices. Vacuum brazing improves the yield of the product and obtains a sturdy and clean working surface.

4.Vacuum brazing CBN tools do not require post-weld processing. After the workpiece is vacuum brazed, the production process is completed and the process steps are reduced.

6. Vacuum brazing CBN tool process
1. The CBN tool needs to be treated with oil on the surface before vacuum brazing, and it should be cleaned with an ultrasonic cleaner or wiped with alcohol;

2.After the cleaning is completed, the solder paste is applied, and the amount of solder paste is determined according to the size of the CBN workpiece;

3.The CBN pretreatment tool after coating needs to be baked in the oven at 200C for 30-40 minutes, pre-fixing the position of the cutter head and the mother body, to prevent the movement of the cutter head during personnel operation and subsequent vacuum brazing;

4.Vacuum brazing, put the pre-processed CBN tool into the heating chamber of the vacuum furnace, set the heating process, maximum 680C, brazing;

5.Welding completed.

SIMUWU company specializes in the development of a vacuum brazing furnace for diamond tools. It can be used for the vacuum brazing of rod and sheet diamond tools to process polycrystalline diamond tools in batches.

Copyright: SIMUWU Vacuum Furnace

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