JPH078824A - Method for adjusting pressure of atmosphere gas in attrition mill - Google Patents

Abstract

PURPOSE:To prevent the air from entering a vessel and also to decrease the use quantity of gas in the case a raw material powder is pulverized in the vessel of an attrition mill into which atmosphere gas is introduced, by feeding the gas when the pressure of the gas is decreased to a prescribed level. CONSTITUTION:An attrition mill vessel 10 is packed with raw material powder consisting of metal and steel balls 12, and they are made to collide with each other by an agitating bar 14, thus to subject the raw material powder to grinding and/or mechanical alloying treatment. At this time, in order to prevent the oxidation or nitridation of the raw material powder in the ambient atmosphere, for example, gaseous Ar is fed into an outlet conduit 20 from an inlet conduit 16. And, for example, a free end 26 of the outlet conduit 20 is immersed in water in a water tank 28. That is, it is immersed in at least to the depth at which the length of a water column corresponding to the 1st pressure value is obtained. And the gaseous Ar is stopped from being fed when its pressure rises to the 1st pressure value, while the gaseous Ar is fed when its pressure drops to the 2nd pressure value lower than the 1st.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for adjusting the gas pressure of an atmospheric gas introduced into a mill when carrying out mechanical alloying treatment using an attrition mill.

[0002]

2. Description of the Related Art As shown in FIG. 4, a raw metal powder and a steel ball (12) are filled in an attrition mill container (10),
A method is known in which a raw metal powder is pulverized and / or mechanically alloyed by rotating a stirring rod (14) to collide the raw powder with a steel ball.

During operation of the attrition mill, the raw material powder is
The impact from the steel balls causes the compression, crushing and adhesion to be repeated. When the raw material powder is crushed, a new surface is exposed, but since the new surface is active, in an air atmosphere,
There is the inconvenience of causing oxidation and nitriding. For this reason,
These treatments are performed in an Ar gas atmosphere.

In FIG. 4, Ar gas is introduced into the inlet conduit (16).
From the outlet conduit (20). But,
Since Ar gas is expensive, it is not economical to keep supplying gas during the operation of the attrition mill. Therefore, when the atmosphere in the mill (12) is replaced with Ar gas by introducing Ar gas, the valve (18) on the gas inlet side and the valve (22) on the gas outlet side are closed, and the mill container (10 The operation of the attrition mill was performed with the Ar gas being filled in ().

However, it is difficult to completely seal the bearing portion (24) of the stirring rod (14). For this reason, use a stirring rod of about 200-300
When rotating at rpm, the internal pressure of the atmospheric gas locally increases, the Ar gas in the container leaks to the outside little by little through the bearing portion (24), and the pressure of the Ar gas in the container decreases. When the pressure difference between the inside and the outside of the container becomes small, the outside air may enter the container (10) through the bearing (24), which may cause the powder being processed to be oxidized or nitrided. It was

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for easily detecting a pressure drop of atmospheric gas in a container and supplying the atmospheric gas only when the pressure drops to a predetermined pressure value. To do.

[0007]

[Means for Solving the Problems] When the outlet pressure of atmospheric gas rises to a first pressure value (h1), gas supply is stopped, and when it falls to a second pressure value (h2), gas supply is performed. In the preferred embodiment, the outlet conduit (2
The free end portion (26) of (0) is made to enter the water in the water tank (28) to a depth at which a water column length corresponding to at least the first pressure value (h1) is obtained.

[0008]

Before the atmospheric gas is introduced, the water level in the outlet conduit and the water level in the water tank are at the same level. When the valves (18) and (22) of the inlet conduit and the outlet conduit are opened and the atmospheric gas is continuously introduced, the pressure in the mill container increases and the water level in the outlet conduit lowers accordingly. When the water surface level corresponding to the first pressure value (h1) is reached, the valves (18) and (22) are closed and the supply of atmospheric gas is stopped. The operation of the attrition mill is continued in this state. When the gas pressure gradually decreases and the water level in the outlet conduit rises to a level corresponding to the second pressure value (h2), the valves (18) and (22) are opened and the supply of atmospheric gas is restarted.

[0009]

As the gas pressure of the atmospheric gas in the attrition mill drops to a predetermined level, the gas is supplied, so that the gas pressure in the mill container falls below a dangerous level at which there is a risk of atmospheric air intrusion. The atmosphere is prevented from entering the mill container. Further, when the gas pressure reaches a certain level or more, the supply of the atmospheric gas is stopped, so that it is economical without supplying unnecessary atmospheric gas.

[0010]

EXAMPLE As shown in FIG. 1, the free end (2
Let 6) enter the water in the water tank (28). The end portion (26) needs to be penetrated to a depth at which a water column length corresponding to at least the first pressure value (h1) (see FIG. 2) is obtained. In addition,
The outlet conduit (20) and the water tank are preferably made of a transparent material so that the water surface level can be observed from the outside.

The first pressure value is a value higher than the dangerous level at which the atmospheric gas pressure in the mill is likely to enter the atmosphere.
In the case of a general attrition mill, if the gas pressure in the mill container drops below 20 cmAq, there is a risk of air intrusion into the mill container. Set 10 cmAq higher to 30 cmAq. In this case, h1 is 30c
m. Since the second pressure value is set to eliminate the possibility of entering the atmosphere, as described above, for example,
It is 20 cmAq and h2 is 20 cm.

Needless to say, these pressure set values differ depending on the sealing property of the mill container. In the case of a general attrition mill, the first pressure value h1 of the atmospheric gas is 30c.
When mAq and the second pressure value h2 are set to 20 cmAq, it takes about 12 hours to decrease the pressure from 30 cmAq to 20 cmAq. Therefore, periodically check the water level in the outlet conduit and check the valve (18) (2
The opening and closing of 2) should be operated manually. If it is desired to increase the valve opening / closing interval time, the set pressure value of the first pressure value h1 may be set high.

In the above embodiment, the gas pressure in the attrition mill was detected by putting the free end of the outlet conduit into the water in the water tank and detecting the fluctuation of the water level in the conduit. Instead of the above configuration, a pressure gauge may be provided in the outlet conduit. Further, by electrically connecting the pressure gauge and the valves (18) and (22), it is possible to automatically open and close the valves (18) and (22) after reaching the set pressure by electrical control.
In this case, the difference between the first pressure value h1 and the second pressure value h2 can be set to be small (for example, h1-h2 = 2 to 3 cmAq), and fine gas pressure control can be performed.

Regardless of whether the atmospheric gas is adjusted manually or automatically, sufficient Ar gas is supplied to the inside of the attrition mill before the opening / closing operation of the valves (18) and (22) is started. It is desirable to replace all the contained air with Ar gas.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an apparatus configuration for implementing a method of the present invention.

FIG. 2 is an explanatory diagram showing a state when the gas pressure in the outlet conduit is at a first pressure value h1.

FIG. 3 is an explanatory view showing a state when the gas pressure in the outlet conduit is at a second pressure value h2.

FIG. 4 is an explanatory diagram of a device configuration for performing a conventional method.

[Explanation of symbols]

 (10) Attrition mill container (14) Stir bar (16) Inlet conduit (18) (22) Valve (20) Outlet conduit (28) Water tank

Claims (1)

[Claims] 1. A method in which an atmospheric gas is introduced into an attrition mill, and the raw material powder is pulverized in the mill to perform a pulverizing treatment or a mechanical alloying treatment of the raw material powder, wherein the atmospheric gas has a first pressure value. The method for controlling the atmospheric gas pressure in an attrition mill, characterized in that the gas supply is stopped when the temperature rises up to a second pressure value, and the gas supply is performed when the pressure falls down to a second pressure value.