Important steps in the production of diamond powder – grinding and shaping
At present, the most common diamond powder is produced by grinding, purifying, classifying and other processes of artificial diamond.
Among them, the diamond crushing and shaping process plays an important role in the production of micro powder, and directly affects the shape of the micro powder particles and the content of the target particle size. Different crushing methods will produce different crushing effects. The scientific and reasonable crushing and shaping process can not only quickly crush coarse-grained diamond raw materials (conventional particle size 100-500 microns) into diamond powder particles with a particle size range of approximately (0-80 microns), but also optimize the particle shape. , making the particles of micro powder products more round and regular, reducing or even completely eliminating long strips, flakes, pins and rods and other particles that affect the final quality of micro powder. Maximize the proportion of marketable target particle size output.
In the production of micro powder, the crushing method can be divided into dry method and wet method. Different crushing and shaping methods are used, and their working principles and process parameters are also different.
Process control points of dry grinding method of ball mill
Taking the horizontal ball mill dry grinding method as an example, the main process control points are ball mill speed, ball-to-material ratio, filling coefficient, steel ball ratio, etc. In actual production, they can be flexibly controlled according to different raw materials and the purpose of crushing and shaping.
1. Ball mill speed
The reasonable rotation speed of the ball mill is an important condition for exerting its production capacity. When the diameter of the ball mill barrel is the same. The higher the rotational speed, the greater the centrifugal force generated, and the higher the distance the steel ball is driven to rise along the cylinder wall.
It is generally believed that the suitable working speed of the ball mill is 75%-88% of the theoretical critical speed.
2. Filling coefficient, ball-to-material ratio
In the crushing and shaping process, the appropriate ball-to-material ratio and filling coefficient are crucial. If the ball-to-material ratio and filling coefficient are too high or too low, they will affect the production efficiency and product quality of the ball mill. If the ball-to-material ratio is too high or the filling coefficient is too low, the feeding capacity of a single machine will be restricted.
Practice has proved that for the crushing of diamond raw materials, the loading coefficient is generally 0.45. The ratio of ball to material is 4:1.
3. Steel ball diameter and ratio
In order to crush diamond more effectively, when the ball mill filling coefficient and ball loading amount are determined, steel balls of different diameters should be selected and assembled in proportion to obtain better particle shape and faster crushing and shaping efficiency.
Segmented grinding
In the production process of micro powder, wet crushing is more effective than dry crushing. Because when dry crushing reaches a certain fineness, wall sticking is easy to occur, reducing the crushing effect; with wet crushing, the raw materials always exist in the form of slurry, and it is easy to increase the proportion of fine particle size.
In order to control the particle size ratio, when more fine-grained micro powder needs to be produced, segmented crushing should be used, especially wet segmented crushing is better. This can not only avoid excessive crushing of materials, but also achieve segmentation according to strength during the crushing process.
Jet milling
Another crushing method is the airflow pulverizer crushing method. The airflow pulverizer uses compressed air as the working medium. The compressed air is sprayed into the crushing chamber at high speed through a special supersonic nozzle. The airflow carries the material in high-speed movement, causing the material to move between them. Produce strong collision, friction and shear to achieve the purpose of crushing. Fragmentation occurs when the force acting on the particle is greater than its failure stress. High-speed impact collision causes volumetric fragmentation of particles, while shearing and grinding effects cause surface fragmentation of particles. This crushing method is very beneficial to the production of diamond powder because it can produce ideal particle shapes. The biggest advantage of the airflow pulverizer is that it is not limited by the mechanical linear speed and can produce very high airflow speeds. In particular, the supersonic airflow pulverizer can produce a flow rate several times the speed of sound, so it can generate huge kinetic energy and it is easier to obtain micron-level particles. and submicron ultrafine powders.