JPS5814842B2 - Sintering furnace for powder metallurgy - Google Patents

Description

[Detailed Description of the Invention] There are various types of continuous sintering furnaces for powder metallurgy, but pusher type furnaces and mesh belt type furnaces are the most popular in terms of the feeding method for the compact to be sintered. Separated.

The former usually has a higher furnace throughput, but the latter is more suitable for automatic insertion of molded bodies.

Next, in the sintering furnace, the lubricant contained in the compact is dewaxed at the front of the furnace, and then sintering is performed at the center of the furnace.

However, with this method, it is difficult to perform complete dewaxing and completely prevent the removed lubricant from entering the sintered part, and the incompleteness often causes defects.

In order to eliminate this drawback, it is appropriate to separate the dewaxing section and the sintering section into separate furnaces.

In addition, in a general sintering furnace, the entire furnace including its entrance and exit is horizontally constructed, and a flame curtain formed by combustion of combustible gas is provided at the entrance and exit to prevent air from entering the furnace.

However, the feeding speed of the molded body is usually 2 to 20 cm/min.
This method has problems such as discoloration of the molded product while it passes through the flame, and if the molded product contains low melting point components, its composition is obscured, so if possible, there is no flame curtain. This is desirable.

One way to achieve this is to tilt the entrance and exit of the furnace downward so that the opening is below the level of the hearth, and to use the difference in specific gravity between the atmospheric gas inside the furnace and the air outside the furnace to eliminate the frame curtain. It is being

Now, the three desirable conditions mentioned above are: - Separate the dewaxing furnace and sintering furnace - Connect these two furnaces with a single belt - Make the entrance and exit of each furnace downwardly inclined. If you draw a diagram of a furnace equipped with everything, it will look like Figure 1.

In the figure, 10 is a dewaxing furnace, 20 is a sintering furnace, and the ports 11, 21 and outlets 12, 22 of each furnace are inclined downward.

An endless belt 30 driven by a pulley 40 communicates these two furnaces.

Note that this drawing omits everything that is not directly related to the explanation of the invention, such as the furnace mount.

However, as you can see from a glance at this diagram, this concept cannot be implemented as it stands.

This is because, as the belt 30 moves under tension due to the rotation of the pulley 40, the belt between the furnaces must also be tensioned as shown in the figure, but the downwardly sloping structure of the furnace entrances and exits 12 and 21 does not allow this. That's because there isn't.

This invention is based on the concept shown in FIG. 1, with improvements made to make it practicable.

That is, as a device for driving the belt 30, in addition to the existing feeding device (for example, the pulley 40), an auxiliary feeding device is provided in the dewaxing furnace 10 or near the outlet 12 thereof, so that the belt 30 can be moved between the dewaxing furnace 10 and the dewaxing furnace 10. It is characterized by having a slack in the part between it and the sintering furnace 20 so that it can be bent according to the inclination of the entrances and exits 12 and 21 of the furnace.

As the above-mentioned auxiliary feeding device, feeding holes are provided at regular intervals in the lug portion of the belt 30, and the dewaxing furnace 1
There is also a method of feeding by a sprocket provided on the exit side of the zero.

However, in this case, the belt 30 is custom-made and is therefore more expensive.

FIG. 2 shows an example of the most preferred embodiment of the present invention in which a belt 50 driven by a pulley 60 is interposed between the hearth of the dewaxing furnace 10 and the belt 30 to serve as an auxiliary feeding device. According to this method, a commercially available belt 30 can be used as is.

That is, in this case, the belt 30 is moved by the belt 5 due to frictional resistance.
Therefore, when starting the operation of this furnace, the pulley 60 is first driven, and after slack is generated in the belt 30 between the outlet of the dewaxing furnace and the inlet of the sintering furnace, the pulley 4 is sent together with the dewaxing furnace.
It is sufficient to drive 0.

The specifications of each part in this embodiment are shown below.

Horizontal length of furnace: 420cIIL...Dewaxing furnace: 4
5 0C7rL - Sintering furnace Furnace width (inner diameter): 30C:rrL... Common to both furnaces Furnace height (〃): 6crrL... Common to both furnaces Entrance/exit length: 60cIrL... 4 locations Common slope angle: 8
°...Common belt feed speed for 4 locations: 5crrt/min...Belt 3
0 Distance between the outlet of the dewaxing furnace and the inlet of the sintering furnace: 65 cm In FIG. 3, the main feed device and the auxiliary feed device (in this example, the pulley 4 This figure shows an example of a control system for synchronized operation of the belt 30 and the pulley 60, in which the amount of slack in the belt 30 is detected by a position sensor, and a control signal corresponding to the detected signal is used to control the operation of the auxiliary feed device, for example, the pulley 60. It is designed to control the

However, this control system is not absolutely essential.

A lead bronze-based powder compact (bearing material) to which graphite was added was sintered using the above-mentioned furnace.

The atmosphere in the furnace is ammonia decomposition gas, the dewaxing temperature is 500°C, and the sintering temperature is 760°C.

When this material is sintered in a normal flame curtain type furnace, defects such as discoloration and rough skin occur, so conventionally separate furnaces were used for dewaxing and sintering, and the molded body was sintered from the dewaxing furnace. Previously, the process of transferring to a furnace was required, but this invention has made it possible to perform an integrated process of dewaxing and sintering.

Since the sintering furnace according to the present invention has the above configuration, there is no need to worry about the inside of the sintering furnace being contaminated with lubricant, and since there is no need for a frame curtain, the amount of atmospheric gas consumed is small. It has the advantage that it has no adverse effect on the compact, and furthermore, it facilitates automation from the powder compacting machine to the sintering furnace.

[Brief explanation of the drawing]

FIG. 1 is a diagram illustrating a problem to be solved by the present invention, FIG. 2 is a diagram illustrating an embodiment of the present invention, and FIG. 3 is an explanatory diagram of a control system of an auxiliary feeding device. 10... Dewaxing furnace, 20... (main) sintering furnace, 11, 21... Furnace inlet, 12, 22...
...Furnace outlet, 30,50...Belt, 4
0,60...Hooley.

Claims (1)

[Claims] 1 The dewaxing section and the sintering section are separated into a dewaxing furnace 10 and a sintering furnace 20, respectively, and the inlet 11, 21 and outlet 12, 22 of each furnace are of a downwardly inclined type, and these two furnaces are In a sintering furnace in which a belt 30 driven by a feeding device 40 is connected, an auxiliary feeding device for feeding the belt 30 is provided in the dewaxing furnace 10 or near the outlet thereof, and a portion of the belt 30 between the furnaces is provided. A sintering furnace for powder metallurgy, characterized in that it has a slack that can be bent according to the inclination of an inlet/outlet 12.21.