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The manufacturing methods of pre-alloyed iron powder are divided into atomization method, wet metallurgy method, and mechanical alloying method.
High pressure atomization
The pre-alloy powder high-pressure atomization method is based on the designed carcass ratio, sintering the various components of the metal into an alloy before sintering, and then atomizing and dusting to obtain the carcass powder with the required particle size. The atomization method may adopt water atomization or gas atomization. Gas atomization can use air, nitrogen or argon gas, fast cooling rate, fine powder grains, high powder yield and low cost. By adjusting the nozzle geometry and controlling the atomizing medium and other process parameters, a certain size and shape (spherical or irregular shape) of metal powder can be obtained.
The hydrometallurgy method is to dissolve metal ions in water. Metals of different elements in the alloy (such as cobalt, copper, and ferrous salt solutions) are mixed in the solution in the correct ratio to form metal salts, and then precipitated and reduced to obtain very fine metal alloy powders with a particle size of less than 10 μm and a shape of Spherical porous agglomerates have good fluidity, compactability and good sintering performance. The sintering temperature is low, the hardness is high, the toughness is good, the diamond has a good holding force, and the diamond tools made are very good.
The mechanical alloying method is to place two or more metal powders in a high-energy ball mill, and through the long-term fierce impact and collision between the powder particles and the grinding ball, the powder particles are repeatedly cold-welded and fractured. Atoms diffuse in the powder particles, thereby obtaining an alloyed powder.
Pre-alloyed powder Because each powder particle contains various metal elements that make up the alloy, the uniformity of the composition of the pre-alloyed powder is quite good. Because its eutectic point is much lower than the melting point of the single element in the alloy, during the sintering process, as long as the temperature reaches a point above the liquidus of the prealloy powder, the powder of the entire bonding metal component melts, so the prealloy powder has a low sintering degree. The use of pre-alloyed powder has the following significant advantages:
(1) The element distribution of pre-alloyed powder blades is more uniform than that of mechanically mixed powder blades, which fundamentally avoids component segregation;
(2) The pre-alloyed powder is fully alloyed and has a uniform structure, which greatly improves the compressive and flexural strength of the sintered product, and easily meets the performance requirements of the diamond product carcass;
(3) Because the pre-alloying greatly reduces the activation energy required for the diffusion of metal atoms during sintering, reduces the sintering temperature, shortens the sintering time, and avoids high temperature damage to the diamond;
(4) Low entanglement temperature. Reduce energy consumption and help reduce costs;
(5) Reduce the consumption of graphite mold, which is also conducive to reducing costs;
(6) Pre-alloy powder has strong oxidation resistance and good sintering performance;
(7) Pre-alloy powder matrix has high hardness and high impact strength;
(8) The pre-alloy powder can hold the diamond according to the high holding power, and the diamond is prominent, thereby improving the sharpness of the diamond tool and extending the service life of the tool;
(9) In the case of the same cutting performance, the use of pre-alloyed powder can reduce the diamond concentration by 15% to 20%, making the production cost lower.
Cobalt has many superior properties. For example, the diamond has better holding power, good sintering performance, high product density, and good compatibility with other metal powders. It has been widely used in diamond tool pre-alloyed powder, but due to its high cost, the supply channel Instability, and strategic resource status in the aerospace, defense industry, cemented carbide and battery industries. In recent years, the development and production of diamond tool pre-alloyed powders have mainly focused on cobalt-based pre-alloyed powders.
(1) The chemical composition of pre-alloyed powders is developed towards low-cobalt and cobalt-free tires to further reduce costs and improve cost performance.
(2) The performance of pre-alloyed powder is further improved and improved. For example, various methods are used to increase the density, impact strength and hardness of the pre-alloy powder, reduce its sintering temperature, reduce the generation of brittle phases, and improve the uniformity of its composition;
(3) The product develops towards full pre-alloying of the carcass. Different from the main production of basic pre-alloyed powders in the early stage of the development of pre-alloyed powders, the recently developed pre-alloyed powders are all specific pre-alloyed powder bodies that do not need to add other powders.