During the gas atomization powder production process, the powder particle size is mainly controlled by the following factors:
Atomization medium pressure: The higher the pressure, the stronger the impact of the atomization medium on the metal liquid flow, the better the crushing effect, and the finer the powder.
Metal flow column diameter: The smaller the diameter, the easier the metal liquid flow is to be crushed, and the finer the powder particle size.
Metal melt temperature: The higher the temperature, the lower the viscosity of the metal melt, the better the fluidity, and the easier it is to be crushed into fine liquid droplets.
Angle between the two streams: The larger the angle, the stronger the impact of the atomization medium on the metal liquid flow, the better the crushing effect, and the finer the powder.
Atomization medium type: When using a liquid atomization medium, its mass is greater than that of gas, and it carries more energy, resulting in better crushing effect and finer powder.
In addition, the surface tension and viscosity of the metal melt, the structural parameters of the atomization device (such as nozzle type, injection parameters), and the powder collection device parameters will also have an impact on the powder particle size.
The specific adjustment range of the process parameters for gas atomization powder production is as follows:
Atomizing gas pressure: 10 - 40 atmospheres (approximately 1 - 4 MPa)
Metal flow column diameter: Needs to be adjusted according to specific equipment and materials. The smaller the diameter, the finer the powder.
Metal melt temperature: Needs to be adjusted according to the melting point of the alloy. It is usually 50 - 100°C higher than the melting point.
Two-stream angle: 40° - 75°
Gas atomization chamber pressure: Needs to maintain a vacuum state. Usually within the range of 1 - 10 torr (approximately 0.13 - 1.33 kPa)
These parameters need to be precisely controlled according to the specific alloy composition and powder performance requirements.
The temperature of the metal melt directly affects the particle size of the powder by altering the viscosity and surface tension of the melt. Specifically:
1. As the temperature increases, the viscosity decreases. When the temperature rises from 150°C to 300°C, the average particle size of Pd-Ag-Cu powder decreases from 101 μm to 33 μm. High temperatures make the metal liquid more prone to breaking into fine droplets, but exceeding the critical value (such as 300°C) will cause the droplets to stick together, thereby increasing the particle size.
2. Changes in surface tension
High temperatures reduce surface tension, making the droplets more dispersible. The experiment shows that for stainless steel powder, the average particle size decreases by approximately 5 μm for every 50 K increase in superheat. However, excessively high temperatures will prolong the solidification time and increase the risk of satellite powder formation.
3. Optimal temperature window
Stainless steel: The yield of fine powder is highest when the superheat is 245 K.
High-entropy alloy: When heated at 1200°C, Dv(50) of titanium alloy reaches 57.3 μm, which is 1.1 μm higher than that at 1100°C. Titanium: To stabilize atomization, the temperature needs to be maintained at 1300-1400°C.
4. Synergy with other parameters
It needs to be adjusted in conjunction with atomization pressure (4.0 MPa), gas type (helium is the finest), etc. For example, when atomizing with argon, for every 100°C increase in temperature, the powder particle size can be reduced by 15-20%.
