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Diamond tool vacuum brazing

With the rapid development of automobiles, motorcycles, aerospace, computer, nuclear engineering, IT, medical equipment, precision instruments and other industries, the widespread use of CNC machine tools and machining center machine tools, the cutting accuracy, dimensional consistency, cutting Reliability, productivity and tool life are increasingly demanding. Because diamond integrates many excellent properties such as mechanics, optical heat, acoustics, etc., it has extremely high hardness and wear resistance, small friction coefficient, high thermal conductivity, low thermal expansion coefficient and chemical inertia, so it is the most suitable tool for manufacturing modern high-speed cutting tools. ideal material. Therefore, it is widely used in the precision and ultra-precision machining of non-ferrous metals and non-metallic materials in the modern manufacturing field.

The key technology of single crystal diamond tool manufacturing

Due to the anisotropy of single crystal diamond, the properties vary greatly in different crystal planes and in different directions. Correct material selection and orientation

It can not only simplify the processing technology and reduce the manufacturing cost, but also improve the quality and service life of the cutting edge of the tool, and give full play to the excellent performance of the diamond tool.

1.Material selection of single crystal diamond

According to the impurities contained in the diamond crystal, it can be divided into four types: Ia type, lb type, lla type and IIb type. Generally, the particle size (weight), shape, completeness, transparency, cracks, number of inclusions, color and uniformity of diamond crystals are used as the basis for evaluating the quality of diamonds. The quality requirements of diamond for cutting tools are: complete crystal, shape is dodecahedron, arc octahedron or transition crystal, crystal diameter is generally not less than 4mm, color is colorless, light green, yellow-brown, etc., no cracks are allowed , The crystal surface can be allowed to have inclusions and pits not greater than 0.5mm, and the weight is 0.7 ~ 3 carats. For ultra-precision machining tools such as ophthalmology, brain surgery scalpels, and laser mirrors that require extremely high precision, the materials should be selected from the I-grade or even gem-grade rough stones of the drawing die, and finally selected with a polarizing microscope or a more precise instrument with a small internal stress. of diamonds as tool blanks.

Synthetic single crystal diamond belongs to type Ib, because nitrogen atoms in its lattice uniformly replace carbon atoms, reducing the possibility of nitrogen atoms gathering at the cutting edge to form tiny chipping, and due to uniform lattice distortion, the hardness is slightly higher than that of natural ones. Single crystal diamond. In addition, due to the addition of an optimized process for removing internal stress, the cutting performance is more stable, reliable, and the discreteness is smaller. The direction of the crystal axis has been accurately determined when leaving the factory, so it is more suitable for the production of cutting tools. The disadvantage is that the brittleness of the Ib-type artificial single crystal is large.

It is more difficult to work than natural single crystal, and requires fine sharpening methods to obtain high-quality cutting edges.

2.Orientation of single crystal diamond

The purpose of orienting natural single crystal diamond is not only to maximize tool life, but also to minimize the friction between the flank and the machined surface and the stress on the cleavage surface near the cutting edge. The orientation of a single crystal diamond tool should include two aspects: the crystal plane where the front and flank faces are placed and the crystal axis direction of the crystal growth. Studies have shown that the orientation scheme of the tool is related to its wear mechanism during cutting. The wear of diamond tools is a very complex physical and chemical reaction process, different processing conditions and different processing

The workpiece material, its wear form and its proportion will also be different, and the wear rate depends on the dissolution rate of diamond in different materials. The wear forms include mechanical wear, thermochemical wear and micro chipping. Generally, the front and flank faces are set on the (110, 100) or (100, 100) crystal plane, and any direction of the (111) crystal plane is not easy to grind and should be avoided.

Methods of crystal orientation can be divided into instrumental (eg X-ray diffraction analyzer) orientation and artificial visual orientation. The instrument has high orientation accuracy, but it is expensive. Artificial visual orientation is based on the number and relative positions of atomic crystal planes to determine the crystal axis position and direction of the crystal. For example, in an octahedral crystal, three mutually perpendicular straight lines connected by three pairs of symmetrical vertices are the X, Y, and Z axes of the crystal. The crystal face of the octahedron is the (111) face, and the eight squares obtained by grinding its vertices perpendicular to the axis are the (100) face. Get (110) face.

3.Vacuum brazing of single crystal diamond

Due to the extremely high interfacial energy of diamond, the welding performance is extremely poor. Fixing diamond by mechanical clamping or insert brazing has been the traditional machining method. Because of the poor firmness of holding the diamond in this method, the blade is very easy to produce indiscernible tiny displacement and vibration during cutting, so it is impossible to meet the needs of ultra-precision mirror cutting. Therefore, in the 1970s, the specific conditions for brazing diamond (high vacuum environment) and the brazing alloy (silver-based alloy with titanium as the active element) were not found, which is one of the most important breakthroughs in diamond tool manufacturing technology. The brazing technology under inert gas protection (Brazing Unit DLA2500 from Kesel, Germany) and the diamond surface metallization brazing technology developed in recent years are another sign of the progress of this key technology.

4.Design of single crystal diamond tool

In the design of single crystal diamond tools, the geometric parameters of the tool are comprehensively designed according to the precision requirements of the processed parts, the actual processing conditions and the characteristics of the diamond material. The following principles should be followed in the design: ①Due to the high hardness of single crystal diamond and the difficulty in machining, the tool geometry should be as simple as possible. ②According to the characteristics of large brittleness and poor impact resistance of single crystal diamond, the geometric parameters should be optimized as far as possible in combination with the processing conditions to improve the impact resistance of the cutter head. ③ Design a reasonable length of the wiper edge according to the precision requirements of the parts to be cut, and consider the thinning ability of the cutting edge of the tool.

Vacuum brazing equipment selection: The RHVB series vacuum brazing furnace produced by SIMUWU is a high-quality product for vacuum heat treatment of tooling and moulds. Good temperature control accuracy and temperature control uniformity ensure the effective progress of the vacuum brazing process. SIMUWU specializes in the manufacture of vacuum furnaces, has more than ten years of relevant experience, and has a good reputation in the field of vacuum furnace manufacturing. The product line includes vacuum air quenching furnace, vacuum oil quenching furnace, vacuum annealing furnace, etc., which are widely sold in developed and developing countries.