There are two types of chemical methods. The mechanical method is to use various mixers such as ball mill, V-shaped, conical and spiral mixers to mechanically mix each component powder evenly without chemical reaction. Mechanical mixing is divided  into dry mixing and wet mixing. The former is dry mixing in gaseous medium. The latter is wet mixing in liquid medium. The requirements for wet mixed media are that they do not react with the mixture, have low boiling point, are volatile, non-toxic, have wide sources, and have low cost. Commonly used wet mixed media include alcohol, gasoline, acetone, water, etc. The addition amount of wet mixed medium should be appropriate. If it is too much, the slurry volume will increase, the powder amount between balls will decrease, and the mixing efficiency will decrease. Too little will increase the viscosity of the slurry, make the ball difficult to move and reduce the mixing efficiency. When mixing with a ball mill, the mixing and grinding processes can be combined.

At this time, relatively strong mixing is adopted to further crush the particles at the same time. This has been widely used in the production of hard alloy and structural materials. Chemical mixing is to uniformly mix metal or compound powder with salt solution added with metal; Or all the components are mixed in the form of a certain salt solution, and then treated by precipitation, drying, reduction and the like to obtain a uniform mixture. Its uniformity is better than that of mechanical method, which is more conducive to alloying and homogenization during sintering. The obtained product has ideal microstructure and excellent properties. (4) granulation. The process of making small particle powder into large particle powder or bronze bushing Manufacturers pellet. It is commonly used to improve the fluidity of powder and stabilize the loose density of powder to facilitate automatic pressing. There are many methods of granulation. Take cemented carbide powder as an example, there are compact method, rolling method and spray drying method.

Granulation method. The agglomeration method is to press the powder material into agglomerates under low pressure, mash and sieve the agglomerates to obtain pellets. This method is complicated, with low productivity, hard particles, poor sphericity, poor fluidity and difficult process control. The rolling method is to send the mixture added with appropriate amount of alcohol or acetone into an inclined circular container rotating at a low speed, and obtain the granular mixture after rolling for a certain period of time. The spherical ratio of the obtained aggregates is higher than that of the pressure agglomeration method, the particle size is more uniform, and the process is simpler. Spray drying is an advanced process for granulation while drying slurry. The method comprises the following steps of: adding paraffin-alcohol solution or paraffin-acetone solution into powder and stirring to form a uniform slurry containing 75% ~ 80% powder. The slurry is transported to an atomizing tower with nitrogen for spraying. The slurry is atomized into spherical slurry droplets under the surface tension of alcohol or acetone. They meet with hot nitrogen and dry into fine spherical or pear-shaped pellets, which are collected at the bottom of the tower. Spray drying granulation has the following advantages: soft particles, uniform particle size, high sphericity and good fluidity; The particle size, loose density and dry and wet degree of the particles are easy to control. The drying and granulation time is short and the dirtiness is less. Continuous production is easy to realize automation. Therefore, although the equipment cost of this method is relatively high, the total cost is low and it is an economical granulation method. Major cemented carbide manufacturers in various countries have adopted spray drying granulation to produce cemented carbide mixtures. Powder granulation is also applied to the preparation of forming materials for ceramics, Mn-Zn ferrite and other powders. Preparation of powder: It mainly depends on the performance of the material and the cost of the preparation method. Powders are formed by transferring energy to the material,