Process characteristics of magnetic powder in the process of preparing ferrite magnet, still need to study powder raw material and forming with aggregate process features.
Powder technology features including powder, such as apparent density, liquidity and suppression performance.
Powder of apparent density and density of powder loading container, between particles have many pores, the pore volume is associated with acceptable.
When powder is apparent,
Don't vibration doesn't add any pressure)
State, the quality of the unit volume called the apparent density of the powder (
Its measurement method as shown in figure 2.
That apparent powder is apparent density = mass M/powder occupy the apparent density of powder size is more than a factor parameter, and powder particle size, particle size distribution, particle shape true density and porosity in the granules, powder and other factors.
Apparent density is the important basis of die design, at the same time also influence forming, sintering process and product quality.
Particle size distribution of apparent density of the influence of particle size distribution is very narrow powder, particle size uniform, apparent density is small.
Appropriate particle size distribution, fine particles fully filling pore between large particles, larger apparent density can be obtained.
The influence of particle shape on the apparent density particle shape the rules, the more apparent when easy filling, the greater the apparent density of powder.
Such as spherical particle powder apparent density than the apparent density of large irregular shape powder.
True density, powder on the influence of the apparent density of pore in the same situation in other conditions, true density, the greater the powder inside the pore (less
Powder particles density)
, the apparent density, the greater the ^ powder loading container, the container vibration, stacked closer between the powder particles.
At this time, the quality of the unit volume called powder rock density,
The same powder material density is greater than the apparent density.
The apparent density and density (
Its measurement method as shown in figure 2.
3, in figure 2.
Rely on the measurement of numerical method.
So in production, with uniform method of measurement, the result is available for comparison.
Powder powder body with packing container liquidity liquidity (
The test method as shown in figure 2.
Powder liquidity on behalf of its ability to filling a certain shape container.
Powder of liquidity and the liquidity of different liquid, powder with powder from inclined plane through the liquid velocity, said is available through the hole to the size of the ability to express.
Sometimes measured by particle phi is the Angle of r particle friction or particle degree of the size of the group of liquidity.
It refers to a loose accumulation windrow contained by conical slope and the horizontal plane Angle.
Powder liquidity is associated with multiple factors, of which mainly depends on the friction between the powder particles, which is influenced by particle size and particle shape.
The granularity of general rule is that the fine, the more complex the particle shape, powder more illiquid.
In addition, the powder liquidity also associated with powder humidity, the wet powder, liquidity is poor.
Zinc and iron oxide in ferrite materials, due to the grain size is fine, liquidity is poorer;
Liquidity and coarser granularity of manganese carbonate is good.
Ferrite molding with aggregate is a magnetic substance, liquidity is still affected by magnetic effect.
In addition, liquidity is associated with presintering temperature, for a ferrite, presintering temperature is high, will be better to liquidity;
Presintering temperature is low, liquidity is poorer.
Suppression characteristics of powder pressed powder features include powder compressibility and formability of powder.
Usually with a certain pressure (
Commonly used 4 000 kg/cm2)
The compact density (
Said powder compressibility.
Powder compressibility reflects to the difficulty of the powder is compacted.
Powder compressibility is associated with plastic powder particles.
Of plastic powder, the better, the more pressure molding under low pressure, namely under the same pressure, the higher the density and strength of ware.
In addition, the powder particle size and particle shape affects powder compressibility.
A percentage of coarse and fine powder mixed powder, can obtain better compressibility.
Formability reflection of the powder molding powder easily and pressure after the ability to maintain a certain shape.
The formability of the powder has no strict definition, observation of powder forming method is qualitatively the compact crack, surface quality, the gu.
Quantitatively compare the formability of the powder, can be compact compression test.
With the ultimate compressive strength (
Destroy the critical pressure ware)
And the formability of the ratio of thrust pressure said powder.
The ratio is larger, the better formability is powder.
Magnet, samarium cobalt, rubber magnetic, ferrite, alnico, permanent magnets