JPS6270501A - Sealing device for outlet side of belt furnace for heat treatment of metallic powder - Google Patents

Abstract

PURPOSE:To continuously extract powder with less fluctuations by providing a gas sealing hopper to the outlet of a belt furnace and discharging the ground metallic powder while maintaining the specified powder level in the hopper by a level measuring instrument. CONSTITUTION:The 1st sealing damper 30 for ground cake and a sealing chamber 29 sealed with sealing rolls 32 are provided to the outlet of the belt furnace and a grinding mill 34 is provided below the 1st sealing damper 30. The gas sealing hopper 38 is provided via a flexible joint 36 below the mill 34 and a load cell converter 41 is provided to the level measuring instrument 40 of the ground metallic powder of the hopper38. A discharger 42 which discharges the ground metallic powder in the hopper 38 at a specified level in accordance with the signal of the instrument 40 is provided. The discharger is so constituted as to be turned on and off according to the level of the ground powder. The 2nd sealing damper 44 and the flexible joint 36 are provided below the hopper 38. The metallic powder subjected to a heat treatment in the belt furnace is thus ground without the deterioration in the quality thereof.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an exit side sealing device for a belt furnace for metal powder heat treatment, and is suitable for heat treatment of iron-based, copper-based, etc. metal powders used as raw materials for powder metallurgy. used in the field.

[Conventional technology]

Generally, metal powder used in sintered parts etc. is heat treated in a belt furnace through deoxidation, decarburization, denitrification, etc., but the conventional belt furnace outlet side sealing device is explained in Figures 2 and 3. do. The raw metal powder is passed through the steel belt 2 from the inlet side.
After being heated to 500°C or higher in a reducing atmosphere gas such as ammonia decomposition gas to undergo reactions such as deoxidation, decarburization, and denitrification, it is reoxidized using a cooling device such as a water cooling jacket. The cake 4, on which the metal powder has adhered, is crushed by the crusher 6, and the steel belt 2 is passed through the outlet pulley 8 and snap roll 10. It travels all the way outside the furnace and returns to the inlet side.

On the exit side, a luer t seals the furnace atmosphere from the atmosphere.
Place the cake 4 on the A6 steel belt 2 and press it with the upper and lower pressure rolls 12 while keeping it intact.
An inert gas such as N or gas is introduced into the furnace through an inert gas pipe 14. As shown in Fig. 3, the pressure roll 12 needs to evenly seal the part of the steel belt z on which the cake 4 is placed and the parts of only the steel belt 2 on both sides thereof, so it is necessary to use an elastic material such as sponge. It is used. In such a sealing method, the pressure roll 12 itself has air permeability, and the pressure roll 12 itself has air permeability.
Cake 4 loses its elasticity over time and undergoes plastic deformation.
When only the steel belt 2 passes through both ends of the steel belt 2 or after the charging is stopped, the shape of the pressure roll 12 cannot follow the shape and the seal becomes incomplete, and the pressure roll 12 is also severely worn and a large amount of inert gas is required to maintain operation. Not only is it expensive, but sometimes it's impossible to install! Gas may flow into the deoxidizing chamber and adversely affect product properties.

The present inventors have proposed a method for improving sealing performance and preventing wear and tear on sponge rolls in Utility Model Application No. 59-30978. In other words, as shown in FIG. In this method, the steel belt 2 is placed in a different position from the cake 4 and sealed using a second son method. However, in this device, it is necessary to frequently open and close the automatic opening/closing dampers 18A, 18B, and 18C alternately and intermittently, resulting in the following problems.

For example, when damper 18B is open, damper 18At-closed seals the gas when 18C is open, and the cake is dammed up on damper 18A, causing the cake to be discharged from the furnace intermittently. It is necessary to increase the capacity of subsequent crushers, sieves, etc. Also, sometimes the cake hangs on the shelf and cannot be discharged properly. Friends who solve this problem dampers 18A, 18B, 18
Shortening the opening/closing interval of C increases the frequency of opening/closing operations, increasing wear and tear on mechanical and electrical devices.

0 N compared to the devices shown in Figures 2 and 3.

Although the amount of inert gas used such as gas is small, automatic supply valve 26
N supplied by more! Since the gas flows into the furnace when the damper 18A is opened, the total concentration of N in the atmospheric gas, such as ammonia decomposition gas, increases, and the partial pressure of N1 in the furnace increases, which adversely affects the denitrification reaction.

[Problem that the invention seeks to solve]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art and to provide an outlet sealing device for a belt furnace for metal powder heat treatment, which has excellent sealing effects and is capable of continuous discharge.

[Ninth way to solve the problem]

The gist of the present invention is as follows.

That is, in the outlet side sealing device of a belt furnace for metal powder heat treatment in which metal powder is heat treated on a steel belt in a reducing atmosphere, a second pipe is connected to the reducing atmosphere to crush the cake that has been heat treated and fixed, and to discharge the crushed cake. 1
Seal damper and seal roll of said steel belt'
To! a pulverizer provided below the first seal damper; a gas seal hopper provided below the pulverizer; and a level measuring device for the next pulverized metal powder accommodated in the gas seal hopper. a discharge control device that discharges the crushed metal powder in the gas seal hopper so as to keep the level constant based on a signal from the level measuring device; and a second seal damper provided below the gas seal hopper. N1 gas piping for purging, automatic valve for N gas supply, exhaust gas piping, exhaust valve and oxygen concentration meter,
An exit side sealing device for a metal powder heat treatment belt furnace, characterized by comprising:

The details of the invention will be explained with reference to the embodiment shown in FIG.

The sealing chamber 28, which communicates with the reducing atmosphere, is sealed by a first sealing damper 30 and a sealing roll 32. A crusher 34 is provided below the first seal damper 30. A gas seal hopper 38 is provided below the crusher 34 via a flexible joint 36. Further, a load cell converter 41 is provided as a level measuring device 40 for the crushed metal powder in the gas seal hopper 38. A discharge device 42 is provided for discharging the pulverized metal powder Th from the gas seal hopper 38 at a constant level based on a signal from a level measuring device 40. The discharge device 42 is turned on and off depending on the level of crushed powder in the gas seal hopper 38.

Further, a second seal damper 44 and a flexible joint 36 are provided below the gas seal hopper 38.

Furthermore, the gas seal hopper 38 is equipped with N, gas piping 45, and N.
An exhaust gas pipe 48, an exhaust valve 50, and an oxygen concentration meter 52 are provided below the automatic gas supply valve 46 and the first seal damper 30. In addition, gas seal hopper 3
8 is an upper limit level meter 54 and a lower limit level meter 5 for crushed metal powder.
6 is provided.

[Effect]

Next, the operation of the outlet sealing device of the present invention will be explained.

During normal heat treatment, the first and second seal dampers 30, 4
The solidified cake 4 is crushed by a crusher 6, passes through a first seal damper 30, is crushed by a crusher 34, passes through a flexible joint 36, and is crushed into a gas seal hopper 38. The gas seal hopper 38 is supported by a load cell and is activated by a signal from a load cell converter 41. A device 42 discharges the ground metal powder while maintaining a constant level to maintain a seal. Here, by integrating the weight increase per unit time by using load detection by a load cell as a means of controlling the powder level, the powder level can be kept constant and the throughput of the belt furnace can be accurately grasped. be able to.

As a means of keeping the powder level t constant in the gas seal hopper 38, it is also possible to control using the output signal of a continuous level meter, such as a weight type or ultrasonic type, which is different from the above-mentioned load cell type, but in this case. is gas seal hopper 3
8 The upper and lower flexible joints 36 are not necessary, but
Irregularities in the surface shape of the powder inside the gas seal hopper 38 cause disturbances, making it impossible to accurately grasp the throughput of the belt furnace.

However, the upper limit level meter 54 and lower limit level meter 56 installed in the gas seal hopper 38 are level measuring bag #40.
This bank-up device is for emergency use, and when the upper limit level meter 54 is activated, it slows down or stops the line speed of the belt furnace, and when the lower limit level meter 56 is activated, it operates the discharge device 42 to reduce the amount of discharge. The discharge is stopped and the gas seal hopper 38 is restored to its normal level.

Next, at the start of operation, the first and second seal dampers 30
．． 44 is closed, N gas is supplied from the gas pipe 45 and N gas supply automatic valve 46, and the exhaust gas pipe 48 and exhaust valve 50 are fully opened, so that the oxygen concentration in the oxygen concentration meter 52 becomes below a certain value. - until gas seal hopper 3
8 and the crusher 34, etc., are purged.

When the fourth crusher 34 or the flexible joint 36 breaks down, the first gas seal damper 30 is closed and repairs can be made while maintaining the reducing atmosphere in the belt furnace.

At the end of the operation, when the lower limit level meter 56 is activated, the first seal damper 30 is closed, and the automatic gas supply valve 46 is opened to open the gas seal hopper 38 and the crusher 52.
purge etc.

In the outlet sealing device of the present invention, sealing N2 gas is not required at all during continuous operation, and since the powder extraction from the belt furnace is constant, the load on subsequent devices can be made uniform.

〔Example〕

Produces reduced iron powder for powder metallurgy by reducing sponge iron as raw material. The conventional sealing devices shown in FIGS. 2 and 4 are used as manufacturing equipment, and the conventional sealing devices shown in FIGS.

Each operating condition and total carbon content of raw materials and products TC,
Metallic Fe amount (M, Fe) and total nitrogen amount T.

Analytical values such as N and product compressibility etc. are shown in Table 1.

As is clear from Table 1, in the example of the present invention, both the atmospheric gas (ammonia decomposition gas) and sealing N gas required to maintain the same furnace pressure were reduced compared to the conventional example, and the product chemical Analysis showed that the total nitrogen content of the inventive examples was significantly reduced, resulting in a significant improvement in compressibility.

〔Effect of the invention〕

As is clear from the above embodiments, the present invention includes a gas seal hopper installed at the outlet of a belt furnace, and continuously supplies crushed metal powder while maintaining a constant powder level in the gas seal hopper based on a signal from a level measuring device. By discharging the waste, you can achieve the following results.

(b) Powder extraction from the belt furnace is continuous and there is little variation, so the load on subsequent equipment becomes uniform.

(b) Atmosphere gas for reducing atmosphere and N for sealing.

Gas consumption could be reduced.

(c) Product quality could be improved.

[Brief explanation of drawings]

Fig. 1 is a sectional view showing the exit sealing device of the present invention, Fig. 2 is a sectional view showing the conventional exit sealing device, Fig. 3 is a sectional view taken along the line 1-111 in Fig. 2, and Fig. 2 is a sectional view showing the conventional exit sealing device. FIG. 3 is a sectional view showing another outlet sealing device of FIG. 2...Steel belt 4...Cake 6...
Crusher 28...Seal chamber 30-° first seal damper 32°゛° seal roll 34...
Crusher 36...Flexible joint 38°'' Gas seal hopper 40...Level measuring device 42...Discharge device 44...Second seal damper 45...N, gas piping 46...・N, automatic valve for gas supply 48°°°exhaust gas piping 50...exhaust valve 52・
・・Oxygen concentration meter agent Takeo Nakaji, patent attorney Figure 1 1 Akitomoki

Claims (1)

[Claims] (1) In the outlet side sealing device of a belt furnace for metal powder heat treatment in which metal powder is heat treated on a steel belt in a reducing atmosphere, the cake that has been heat treated and fixed in communication with the reducing atmosphere is crushed and the cake is discharged. a seal chamber having a first seal damper and a seal roll of the steel belt, a crusher provided below the first seal damper, a gas seal hopper provided below the crusher, and the gas seal a level measuring device for pulverized metal powder contained in a hopper; a discharge control device for discharging the pulverized metal powder in the gas seal hopper so that the level of the pulverized metal powder in the gas seal hopper is constant based on a signal from the level measuring device; a second seal damper provided below, an N_2 gas pipe for purging, an automatic valve for N_2 gas supply, an exhaust gas pipe, an exhaust valve, and an oxygen concentration meter;
An exit side sealing device for a metal powder heat treatment belt furnace, comprising: