JPH03193816A - Heat treatment furnace - Google Patents

Abstract

PURPOSE:To enable efficient high temp. and low temp. heat treatments by heating a material to be treated set in a heat treatment chamber surrounded with heat insulating wall and providing a cooler to the high temp. with a heater and soaking-stirring gas at the time of heating to the low temp. CONSTITUTION:The heat treatment chamber 3 surrounded with the heat insulating wall 2 is arranged in the furnace 1, and the cooler 11 and the gas stirring device 21 are set at the outer part thereof. In the above heat treatment furnace, in the case of executing the high temp. heat treatment of quenching, etc., the material 7 to be treated set on the setting place 5 in the heat treatment chamber 3 is heated to the high temp. with radiation heat transfer of the heater 8. After that, cold blast generated with the cooler 11 and a fan for cooling 13 is fed through a duct 10 and nozzle 9, etc., to rapidly cool the material to be treated. On the other hand, in the case of the comparatively low temp. treatment of tempering, etc., the material to be treated is suitably heated with the heater 8 and also the fan 22 for soaking in the gas stirring device 21 is carried in from an opening part 2a and atmospheric gas in the heat treatment chamber 3 is circulatively stirred to execute the soaking treatment. By this method, the high temp. and the low temp. heat treatments can efficiently be executed to the material 7 to be treated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to a heat treatment furnace used for subjecting various metal workpieces to heat treatments such as quenching and tempering.

[Technology from Bt] This type of furnace has the following structure. Inside the furnace body, there is a storage area for the material to be treated, which is surrounded by a heat insulating wall. A heater for heating the material to be treated is provided inside the chamber surrounded by the heat insulating wall. Inside the furnace body, outside the heat insulating wall, there are provided a cooler for cooling the gas inside the furnace body and a cooling fan for sending the gas cooled by the cooler to the storage location.

[Problem M to be solved by the invention] In this conventional heat treatment furnace, when heating the workpiece to a high temperature in order to perform high-temperature heat treatment such as quenching on the workpiece, it is necessary to use radiation heat transfer from the heater. The material to be treated can be efficiently heated by blowing. However, using the heater used for the above-mentioned high-temperature heat treatment,
For example, when the material to be treated is heated to a lower temperature than in the above case for low-temperature heat treatment such as tempering, sufficient radiation heat transfer cannot be obtained. The material to be treated is heated by heat. However, natural convection has the problem that the cold gas flowing in from outside the heat insulating wall remains in one place and tends to cause temperature unevenness in the gas, resulting in temperature unevenness in the material to be treated.

The present invention has been made in order to solve the above-mentioned problems of the prior art (technical problem 1II), and it is possible to stir the gas in the place where the material to be treated is kept by a soaking fan, and the heater used for high-temperature heat treatment. It is an object of the present invention to provide a heat treatment furnace that can heat a material to be treated to a -like temperature distribution even when the material to be treated is heated to a relatively tg temperature using a heat treatment furnace.

[! ! Means for Solving the Problems] In order to achieve the above object, the present invention takes the measures as described in the claims above, and its effects are as follows.

[Operation] When a material to be treated is subjected to high-temperature heat treatment, the material to be treated is efficiently heated to a high temperature by radiation heat transfer from the heater, and then cooled by gas cooled by a cooler. On the other hand, when the material to be treated is subjected to low-temperature heat treatment, the gas at the location where the material to be treated is located is heated by the heater.

The gas is stirred by a soaking fan. Due to convective heat transfer by the stirred gas, the material to be treated is heated with a -like temperature distribution. After heating, it is cooled by gas cooled by a cooler in the same way as in the above case.

[Example] The drawings showing the embodiments of the present application will be described below.

FIG. 1 shows a vacuum furnace as an example of a heat treatment furnace. In the vacuum furnace, members designated by reference numerals 1-14 are similar to those in the well-known vacuum furnace. That is, 1 indicates the furnace body. 2 is a heat insulating wall, and the space inside thereof serves as a heat treatment chamber 3.

4 is a door that can be opened and closed and forms a part of the heat insulation N2. Reference numeral 6 indicates a location determined approximately at the center of the heat treatment chamber 3 where the material to be treated is placed. Reference numeral 6 denotes a support device for the material to be processed, which supports the material to be processed 7 at the storage location 5. The materials 7 to be treated include various mechanical parts made of steel.

8 is a heater, for example an electric heater is used. 9
．． 9 is a nozzle shown as a cooling gas feeding means, to which a gas supply duct 10 is connected. Next, 11 is a cooler for gas cooling, and 12 is a ventilation chamber configured by partitioning a part of the space inside the furnace body 1, to which the duct 10 is connected, and a cooling fan 13 is placed sideways. .

14 is a motor for driving the fan 13.

Next, 15 shows the jump wJ device installed in the duct 10. To explain this, 16 is the frontage of the duct 100, 1
Reference numeral 7 denotes a lid for freely opening and closing the opening 16, and is moved forward and backward toward the frontage 16 by a cylinder 18 attached to the furnace body 1.

Next, a structure provided for stirring the gas in the heat treatment chamber a will be explained. A shield 20 constitutes a part of the heat insulating wall 2, and can be opened and closed by moving in a direction perpendicular to the plane of the drawing. Reference numeral 21 indicates a gas stirring device, which will be explained below. The device 21 includes a heat soaking fan 22, a motor 23 for driving the fan 22, a moving mechanism 24 for moving the fan 22 in and out of the heat treatment chamber 3, and the
0 and a lid 25 made of a heat insulating material for closing the opening 2a of the heat insulating wall 2. As the fan 22, an axial fan is used as an example, but other types may be used as long as the fan can stir the gas in the heat treatment chamber 3.

The moving mechanism 24 is composed of a rail 26 attached to the furnace body 1 and a moving table 27 that is movable along the rail 26, and the motor 23 is mounted on the moving table 27.

Next, a second example of heat treatment of a material to be treated using the above-mentioned vacuum furnace will be described.
This will be explained based on the diagram. Figure 2 shows the temperature change of the treated material and the furnace body l when the treated material is subjected to quenching as an example of high-temperature heat treatment and high-temperature tempering as an example of low-temperature heat treatment.
This shows the change in pressure inside. First, in the state shown by the solid line in FIG. 1, in step A, the material to be treated 7 is placed in the storage location 5 under atmospheric pressure, and then in step B, the inside of the furnace body 1 is evacuated to a vacuum. Next, a hardening process is performed. This step is carried out by introducing nitrogen gas, for example, at one atmospheric pressure, into the heat treatment chamber 3 as an atmospheric gas.

First, the heater 8 generates heat and the material 7 to be treated is heated. This heating is performed, for example, by changing the temperature stepwise as shown in the figure. In the case of this heating, since the temperature is high, heat transfer from the heater 8 to the treated material 7 is mainly performed by radiation heat transfer. When the material 7 to be treated reaches a predetermined high temperature and a predetermined period of time has elapsed, the material 7 to be treated is cooled as follows. Heat generation of the heater 8 is stopped. On the other hand, the cooler 11 and the cooling fan 13 are operated while the fan 14 is turned off.

Further, nitrogen gas is fed into the furnace 1 to a pressure of, for example, 6 bar. As a result, the above-mentioned high pressure gas is cooled by the cooler 11 and cooled by the cooling fan 13.
The gas is sent from the blowing chamber 12 to the duct IO, blown out as a cooling gas from the many nozzles 9 into the heat treatment chamber 3, and circulated along the route from the heat treatment chamber 3 to the cooler 11 again. As a result of this high pressure cooling gas circulation,
The material 7 to be treated is rapidly cooled. With this, the hardening process is completed.

Note that the time for this quenching step is, for example, 3.5 hours.

Next, as an example of the tempering process, high temperature tempering is performed as follows. The prisoner 20 is removed, and the heat soaking fan n is moved forward and placed in the heat treatment chamber 3. At this time, the lid 25
Reduce a. Further, the cap 4 is closed, and the operation of the cooler 11 and the cooling fan 13 is stopped. Further, in the opening/closing device 15, a frontage portion 16 is closed by a lid 17. In this state, the heater 8 generates heat, and the heat equalizing fan 22
is operated to stir the gas in the heat treatment chamber 3. As a result, the gas in the heat treatment chamber 3 is heated to a -like temperature distribution,
The material 7 to be treated is heated to a temperature distribution of - by convection heat transfer from the gas having a temperature distribution of -. In this case, even if a large number of materials 7 are piled up, the materials 7
Since the high-temperature gas stirred by the fan 22 is sufficiently distributed in the space between them, the material to be processed 7 in the center of the stack is quickly heated as well as the materials in the periphery. . When the material 7 to be treated reaches a predetermined high temperature by the above-mentioned heating and this state continues for a predetermined time, the material to be treated is then cooled in the same manner as in the case of quenching, and the tempering process is performed. is completed. The time for this tempering process is, for example, 2.
It is 8 hours. Note that the tempering step may be performed by returning the gas pressure in the furnace body 1 to atmospheric pressure.

The tempering step as described above is performed, for example, twice.

Thereafter, the inside of the furnace body 1 is returned to a high voltage, the material to be treated 7 is taken out of the furnace from the storage location 5, and a series of heat treatments on the material to be treated 7 are completed.

In this specification, high-temperature heat treatment refers to a temperature at which heat is efficiently transferred from the heater 8 to the material to be treated 7 mainly by radiation heat transfer (this temperature is referred to as the first high temperature in this specification). Low-temperature heat treatment refers to a temperature that is lower than the above temperature and at which the efficiency of radiation heat transfer from the heater 8 to the treated material 7 is relatively low (this temperature is referred to as the second high temperature in this specification). This refers to heating and heat treatment.

[Effects of the Invention] As described above, in the present invention, when it is desired to perform high-temperature heat treatment on the material 7 to be treated, the material 7 placed in the storage area can be efficiently treated by radiation heat transfer from the heater 8. The material to be treated can be cooled by heating the material to a high temperature of There are benefits that can be provided.

Moreover, after the above heat treatment, when the workpiece is heated to a second high temperature lower than the first high temperature in order to perform another low-temperature heat treatment on the workpiece, the heating temperature used in the high-temperature heat treatment is Since the heater 8 is used for heating, even if sufficient radiant heat transfer cannot be obtained as in the case described above, the gas in the storage location 5 can be stirred by the heat equalizing fan 22.
The above storage location 5 is
It has the advantage that the material 7 to be treated can be heated to a -like temperature distribution. This is useful, for example, in the case of high-temperature tempering where slight unevenness in heating temperature tends to cause large hardness unevenness, the material to be treated can be heat-treated to have a -like hardness.

Furthermore, it is also possible to use the soaking fan 22 to accelerate the temperature increase in the temperature increase step for performing high-temperature heat treatment.

[Brief explanation of drawings]

The drawings show an embodiment of the present application, and FIG. 1 is a longitudinal cross-sectional view of a vacuum furnace, and FIG. 2 is a diagram showing an example of changes in the pressure inside the furnace and the temperature of the material to be treated during heat treatment. l...Furnace body, 2...Insulating wall, 5...Storage location, 7
... material to be treated, 8... heater, 11... cooler,
13... Cooling fan, 22... Uniqueizing fan. Figure 1 Figure 2

Claims (1)

[Claims] The furnace body has a place for storing the material to be treated surrounded by a heat insulating wall, and inside the furnace body surrounded by the heat insulating wall,
A heater is provided for heating the material to be treated at the storage location to the first high temperature by radiation heat transfer, while a heater is provided outside the heat insulating wall in the furnace body for cooling the gas inside the furnace body. In the heat treatment furnace, the heat treatment furnace is equipped with a cooler and a cooling fan for sending the gas cooled by the cooler to the storage location. A heat treatment furnace characterized in that it is equipped with a soaking fan for stirring the gas within the heat insulating wall when heating to a second high temperature lower than the above temperature.