JPH0112554B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for classifying iron powder after finish reduction. More specifically, the oversized iron powder classification system is equipped with a system that returns the iron powder to the classification system via the crusher and a system that discharges it outside the system, and a switching device that switches between the two systems is used to load the crusher. This invention relates to a classification device that switches according to the current value and has a high product yield.

Figures 1 and 2 show the conventional classification flow of iron powder. The crude reduced iron powder, which has been prepared in advance to a certain apparent density, is decarburized, deoxidized, and denitrified in a finishing reduction furnace 1 in an ammonia decomposition gas atmosphere at 800 to 1000°C. At the same time, iron powder is processed in finishing reduction furnace 1.
Due to the weak sintering effect, the particles bond together and are continuously discharged in the form of a cake. After this cake-like iron powder is crushed into pieces of about 1 mm or less in a crusher 9, it is supplied in fixed amounts into the air classification pipe 2 of the iron powder classification apparatus via a storage/cutting device 10.

The classification device consists of an air classification device consisting of a blower 8, an air classification pipe 2, a centrifugal air classifier 3, a cyclone 7, etc., and a sieving device consisting of a primary sieve 4, a secondary sieve 5, etc.

The iron powder supplied from the storage/cutting device 10 into the air classification pipe 2 is pneumatically transported to the centrifugal air classifier 3, where most of the relatively large particles are collected. The small particles enter the sieving devices 4 and 5, and then travel with the airflow to the cyclone 7, where they are collected and stored in the hopper 6E. The clean air leaving the cyclone 7 is recirculated to the blower 8.

The iron powder collected by the centrifugal air classifier 3 is passed through the primary sieve 4, for example, +90 mesh, 90 to 100 mesh.
mesh, separated into −100 meshes, and then −
100 mesh iron powder is sieved by a secondary sieve 5 and stored in hoppers 6A, 6B, 6C, and 6D according to particle size.

On the other hand, the oversized iron powder (+90 mesh) of the primary sieve is stored in the container 12. Thereafter, the required amount of iron powder is cut out from the hoppers 6A to 6E according to the required specifications of the product, and is shipped as a product through mixing, weighing, and packaging steps.

Most of the +90 mesh oversized iron powder stored in the container 12 is pseudo-particles, and if it is crushed again, it will become a product, so if it continues as it is, the yield will decrease. Another problem was that re-crushing at a later date required a lot of manpower.

Therefore, a crusher 11 as shown in FIG. 2 is installed,
Oversized iron powder from the primary sieve was supplied to the crusher 11 and the crushed material was returned to the air classification pipe 2. In this way, the crusher 1
1, a closed circuit (11 → 2 → 3 → 4 → 11) is created in which oversized iron powder circulates, and (1) eventually a large amount of iron powder flows through this closed circuit, causing the disintegration of the crusher 11. (2) Repeated crushing causes the physical properties of iron powder to change,
For example, problems such as apparent density, Rattler value, green density, etc. may deteriorate.

The object of the present invention is to provide an iron powder classification device that solves these problems.

FIG. 3 is a system diagram showing an embodiment of the present invention, and reference numerals 1 to 10 are the same as in FIGS. 1 and 2.

The present invention provides an apparatus for classifying iron powder cake after finishing reduction in iron powder production, including a system for returning oversized iron powder from the classification process to the classification process via a crusher 11, and a system outside the system. This iron powder classification apparatus is characterized in that it branches into a system for discharging iron powder and a system for discharging iron powder, and is provided with a flow path switching device 12 at the branch point that can be switched freely according to the load current value of the crusher.

The oversized iron powder from the primary sieve 4 enters the crusher 11 via the flow path switching device 12 and is further sent to the air classification piping 2 where it is circulated and then discharged to the outside of the system through the flow path switching device 12. , and a system stored in a container 13.

The flow path switching device 12 may be, for example, a system in which a switching damper provided at the branch point is switched using a cylinder or the like, or a switching chute 15 provided at the tip of the discharge pipe 14 as shown in FIG. The switching may be performed using the cylinder 16.

To switch the flow path switching device, a set current value is given to the ammeter 18 that detects the load current of the drive motor 17 of the crusher 11, and when the set current value is reached, an alarm is output or displayed. This is done using this set load current value. In other words, if the current is below the set current value, the flow switching device is switched to the crushing and classification system side to improve the yield of iron powder, and when the current is higher than the set current value, the flow switching device is switched to the discharge system side and stored. The supply from the device 10 is stopped to prevent deterioration of the physical properties (apparent density, etc.) of the iron powder.

This switching operation may be performed by manually operating the switching operation panel in response to the above-mentioned alarm, or by incorporating a comparator into the current measurement system to compare the set load current and the detected load current, and using its output to control the flow path switching device. It is also possible to input the information into the device and automatically control the flow path switching.

By the above switching control, the iron powder in the closed circuit will eventually reach the bottom of the primary sieve 4 and the secondary sieve 5, and the hopper 6A~
The amount of iron powder that is stored in the iron powder 6D or discharged outside the system by the flow path switching device 12 and stored in the container 13, and passes through the crusher 11 becomes zero. The no-load current of the crusher 11 at this time is captured and the storage/cutting device 10 is activated again, and the flow path switching device 12 is connected to the crusher 11 side.

At the time of discharge outside the system, the iron powder of the new feed that enters the air classification pipe 2 through the finishing reduction furnace 1 and the crusher 9 is stored in the storage/cutting device 10, and only the iron powder in the closed circuit is discharged outside the system. That will happen. Therefore, it is possible to improve the yield without changing the physical properties of the iron powder.

Although the present invention has been described using an air classification system, it can be similarly implemented using a system in which the air is supplied from the storage/cutting device 10 to a classification device via a bucket conveyor or the like.

Since the present invention is configured as described above, it is possible to classify iron powder with extremely high product yield.

[Brief explanation of drawings]

1 and 2 are system diagrams showing the flow of a conventional iron powder classifier, FIG. 3 is a system diagram of an embodiment of the present invention, and FIG. 4 is a schematic side view of a flow path switching device. 1... Finish reduction furnace, 2... Air classification piping, 3...
...Centrifugal air classifier, 4...Primary sieve, 5...Secondary sieve, 6 (6A, 6B, 6C, 6D, 6E)...Hotsupa, 7...Cyclone, 8...Blower, 9...
Crushing machine, 10...Storage and cutting device, 11...Crushing machine, 12...Flow path switching device, 13...Container,
14... Discharge channel, 15... Rotating chute, 16
...Cylinder, 17...Crusher motor, 18...
Ammeter.

Claims (1)

[Claims] 1. In an apparatus for classifying iron powder cake after finishing reduction in iron powder production, the discharge flow path for oversized iron powder from the classification process is divided into a system for returning it to the classification process via a crusher and a system for discharging it outside the system. 1. An apparatus for classifying iron powder, characterized in that the flow path is branched, and a flow path switching device that can be switched according to the load current value of the crusher is provided at the branch point.