Preparation method of 3D printed metal powder
Release time:
2023-01-04
The quality of metal 3D printed parts largely depends on the performance of metal raw materials. There are mainly two types of raw materials for metal additive manufacturing: powder and wire. Among them, powder materials are widely used, such as laser metal deposition and selective laser melting, which are commonly used as raw materials in rapid prototyping manufacturing processes. The commonly used metal powder particle size range in additive manufacturing is 15-53 μ M (fine powder), 53-150 μ M (coarse powder).
The quality of metal 3D printed parts largely depends on the performance of metal raw materials. There are mainly two types of raw materials for metal additive manufacturing: powder and wire. Among them, powder materials are widely used, such as laser metal deposition and selective laser melting, which are commonly used as raw materials in rapid prototyping manufacturing processes. The commonly used metal powder particle size range in additive manufacturing is 15-53 μ M (fine powder), 53-150 μ M (coarse powder).
The selection of metal powder for additive manufacturing is generally based on three factors: energy source, powder supply method, product size, and precision requirements.
At present, the preparation methods of metal powder for 3D printing (additive manufacturing) mainly include atomization (mainly atomization, including vacuum atomization (VIGA) and electrode induction atomization (EIGA)) and plasma method (plasma rotating electrode atomization (PREP), plasma fusion atomization (WPA), and plasma spheroidization technology (PA), etc.)
① Aerosolization:
Gas atomization is the most commonly used method for producing high-quality metal 3D printing powders. The schematic diagram is as follows. This method uses a high-speed airflow (high-speed air, nitrogen, helium, or argon) to break the liquid metal stream into small droplets, which are then quickly condensed to form the formed powder. The main difference from water atomization is the change of atomization medium. Currently, the powder produced by atomization accounts for about 30% to 50% of the world's total powder production; The particle size of the metal powder prepared by this method is<
one hundred and fifty μ m. The advantages of good sphericity, high purity, low oxygen content, fast forming speed, and low environmental pollution make this type of technology suitable for the production of the vast majority of metal and alloy powders.
The traditional gas atomization method refers to the vacuum gas atomization powder making technology (VIGA), which works by using a crucible to heat and melt metal raw materials. The molten metal is subjected to gravity to form a liquid flow at the nozzle at the bottom of the crucible, which is then crushed into small droplets by a high-speed inert gas flow (mainly argon) under vacuum, and then condensed to form. The droplets self solidify into spherical or nearly spherical particles under surface tension during flight.
In order to prevent impurities from being introduced during the melting process due to the contact between the crucible and the metal raw material, the German company Leibao has invented a method called electrode induction melting atomization (EIGA). The principle of this technology is to use formed rods as electrodes to continuously melt in the high-frequency induction coil. Under the action of gravity, the metal liquid flows through the center hole of the atomizer, and after high-speed airflow impact atomization, the metal powder is obtained. By changing the method to free the powder from contamination by utensils, high-purity metal powder can be obtained.
② Rotating electrode method
The rotating electrode method is a powder making method that uses metal or alloy as a consumable electrode, whose end face is heated by an arc and melted into a liquid. Under the centrifugal force of high-speed rotation of the electrode, the liquid is thrown out and crushed into small droplets, which are then condensed into powder.
Preparation method of 3D printed metal powder
It completely avoids slag formation and contact with refractory materials during the melting and atomization process of metal, eliminates non-metallic inclusion pollution sources, and can produce high cleanliness powder. A typical rotating electrode pulverizing equipment is composed of a box with a diameter of over 2m. The rotating consumable electrode is loaded into it through a dynamic sealed bearing, and the long axis of the electrode is horizontally located at the center line of the box. The electrode rotation speed can reach up to 15000~25000 r/min. To avoid tungsten pollution, a plasma torch can be used at the tungsten electrode, known as the plasma rotating electrode atomization powder production method (PREP).
This technology can regulate the particle size of powder by adjusting the size of plasma arc current and the speed of consumable electrodes, improve the yield of specific particle size powder, and is beneficial for preparing spherical powder with high sphericity, high density, low porosity, low oxygen content, and smooth surface. There are basically no hollow powder or satellite powder, effectively reducing the spheroidization, agglomeration, and the introduction of impurities in the production process of additive manufacturing technology, resulting in pores Cracking phenomenon.
③ Plasma fuse atomization
The plasma melt atomization chemical art uses metal wire of specified size as raw materials, and is fed into the atomization furnace at a specific rate through a wire feeding system. After being heated by a circular plasma torch at the outlet, it is melted and atomized under the action of a focused plasma arc, ultimately obtaining metal powder.
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