JP2001116462A - Furnace operation method of mesh belt conveyor non- oxidation atmosphere heat treatment furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To extend the service line of a mesh belt by improving the furnace operation method of a mesh belt conveyor non-oxidation atmosphere heat treatment furnace. SOLUTION: A heat treatment furnace is provided with a furnace body where a heating camber 10 in that an entrance tunnel 11 and a heating part 12 are provided continuously is arranged in contact with the rear end of a mount stand 20, a heating source 25 in a heating part, and a high-temperature mesh belt 40 for configuring limitless orbit continuously traveling on a horizontal furnace floor surface 14a that penetrates through the entrance tunnel and the beating part from an area on a roller conveyor 21 being provided near the upper surface of the mount stand 20. In a first process, workpiece W being placed on the carrying stand by moving a mesh belt is fed into the heating chamber rapidly through the entrance tunnel before stopping. In a second process, the temperature of the workpiece in the heating chamber is increased based on a specific program by a heating source during the stop. In a third process, the mesh belt is moved again and the workpiece in the heating camber is taken out of the opening at the bottom of the furnace by moving the mesh belt again.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of operating a heat treatment furnace for a mesh belt conveyor in a non-oxidizing atmosphere, and more particularly to a method of operating a heat treatment furnace for a non-oxidizing atmosphere in a mesh belt conveyor capable of extending the service life of a high-temperature mesh belt. .

[0002]

2. Description of the Related Art FIG. 3 shows an example of the structure of a conventional heat treatment furnace for a continuous atmosphere of a mesh belt conveyor. A heating unit 1 b of the heating chamber 1 includes a heating source 7 such as an electric heating nichrome heater.
Is heated so as to have a predetermined temperature distribution, and the high-temperature mesh belt 5 having the endless track configuration enters the heating unit 1b from the loading table 4 through the entrance tunnel 1a of the heating chamber 1, and
After passing over the hearth 2, it is wound around the outer half circumference of the furnace bottom roller 6 b provided at the furnace bottom 1 c and turned around, and is constituted by a middle roller 6 c and a plurality of small rollers 6 d adjacent to each other as shown in FIG. After passing through the conveyor roller conveyor on the return side of the mesh belt 5, the middle roller 6c provided below the entrance of the heating unit 1b
The belt is turned upward so as to advance at a gentle angle.
Of the traction drive device 6 and returns to the main drive roller 6 a of the traction drive device 6.
The high-temperature mesh belt 5 returned to the main drive roller 6a is
The main drive roller 6 is wound around the outer half circumference of the roller and near the contact point with the pinch roller 6f combined therewith.
a, and pulls the return high-temperature mesh belt 5 by the rotational force of the roller. All the rollers in the heating chamber 1 such as the furnace bottom roller 6b, the middle roller 6c, and the small roller 6d mentioned above have the peripheral speed of the main driving roller 6a with respect to the moving direction of the mesh belt 5 for high temperature contact with each other. Is driven so as to substantially coincide with the peripheral speed value. The transfer speed is normally continuously variable, and the passage time of the heating chamber 1 is set to 1
It is often about 5 to 90 minutes. The processed product W placed on the high-temperature mesh belt 5 by the loading table 4 is fed into the heating section 1b of the heating chamber 1 through the entrance tunnel 1a at a constant speed, and heated and heated on a predetermined schedule while moving. After being maintained at a predetermined temperature (approximately 900 ° C. or less in a steel quenching furnace) for a predetermined time, the chute 3 is moved from the rear end of the high-temperature mesh belt 5 which is inverted by the furnace end roller 6b.
, Falls into oil (or water) of a quenching tank (not shown) and is rapidly cooled. The residence time of the processed product W in the furnace is 30
保持 60 minutes, and the holding time at the predetermined temperature is 10
About 20%.

In this type of mesh belt conveyor continuous atmosphere heat treatment furnace, a large amount of the heated treated product W is dropped from the high-temperature mesh belt 5 at the furnace bottom 1c and rapidly cooled in oil (water). The fumes occur continuously. On the other hand, the heating chamber 1 contains an atmosphere gas (for example, N ₂ ).
Is supplied continuously, but the high-temperature mesh belt 5
The height of the entrance opening tends to be larger in accordance with the loading height of the above processed products W, and the consumption of N ₂ increases. N supplied
₂ is heated to generate airflow from the furnace bottom 1c and the heating unit 1b toward the entrance tunnel 1a. Fume is furnace bottom 1
Heated by the heat from the heater c, etc., the chute 3 and the furnace butt opening rise up while flowing into the furnace butt 1c while increasing in volume, and move to the heating unit 1b. In order to prevent such a phenomenon and reduce its adverse effects, a fume discharge pipe having an inlet is provided below the chute 3 or the ceiling of the furnace butt 1c to generate a flow of exhaust gas in the furnace butt 1c, and the heating section 1b And furnace bottom 1c
Capturing a portion of N ₂ supplied to the fumes prevents from flowing into the heating portion 1b. However, even in this case, when the processing condition is such that the holding time after the processed product W reaches the predetermined temperature is 1 hour or more, the surface of the processed product W is affected for a long time. The consumption of N ₂ and the heating energy cost increase. Further, the lower surface of the high-temperature mesh belt 5 is worn due to friction generated between all the supporting structures in the forward path, in addition to the transport-side portion, which is particularly heavy. However, since the hardness of the heat-resistant steel wire constituting the high-temperature mesh belt 5 also decreases as the temperature increases, the maximum wear amount occurs when the workpiece W is loaded and moved on the high-temperature hearth 2. When the wire diameter of the wire constituting the lower surface of the high-temperature mesh belt 5 decreases due to abrasion, the proof balance of the upper and lower surfaces is lost, causing mesh deformation.

[0004] In a conventional furnace using the high-temperature mesh belt 5, the conveyor is constantly operating, so high-temperature wear causes a tension applied to the high-temperature mesh belt 5 and shortens the service life.

As the high-temperature mesh belt 5 for transporting the processed product W, 25Cr-20Ni-based, 35Ni-15C
Heat-resistant steels such as r-based and 80Ni-20Cr-based are used. Further, nitrogen gas or a mixed gas of nitrogen, hydrogen, carbon monoxide and carbon dioxide is supplied into the furnace to prevent oxidation and decarburization of the processed product W.

[0006]

In a mesh belt conveyor continuous atmosphere heat treatment furnace of this type, a mesh belt 5 for high temperature on which a processed product W is placed on each support portion of a loading table 4, an entrance tunnel 1a, and a hearth 2 is provided. Is pulled by the main drive roller 6a of the traction drive device 6 through the furnace end roller 6b, and the maximum value of the tension acting on the high-temperature mesh belt 5 on the transport side, which becomes high in temperature, is the maximum value of the portion immediately before being applied to the furnace end roller 6b. The value is the sum of the sum of the weight of the high-temperature mesh belt 5 itself and the processed product W applied to each support portion and the product of the coefficient of friction between each support portion and the high-temperature mesh belt 5. In addition, the temperature immediately before the furnace bottom roller 6b is the highest or a temperature equivalent thereto, so that it is exposed to the most severe conditions.

The high-temperature mesh belt is knitted with a heat-resistant steel wire. The creep strength indicating the durability of the heat-resistant steel at a high temperature is such that the steady-state creep rate in the second stage where the strain rate is almost constant is 1%. It is indicated by a stress that becomes / 10,000 hours. 25Cr-20Ni heat-resistant steel that is most often used as a mesh belt for high temperature (SCH2
The creep strength of 2) is, for example, 871 ° C. 4.22 kg / mm ² 982 ° C. 1.76 １０９ 1093 ° C. 0.46 １１ 1177 ° C. 0.1 、.
1%, 2% at 1177 ° C., especially 1100
Above ℃, the decrease in creep strength is remarkable.

[0008] The service life indicating the period up to the replacement of the mesh belt in this kind of mesh belt conveyor continuous atmosphere heat treatment furnace is about 36 months at 871 ° C, but if the service life is proportional to the creep strength, it is 1090. The temperature is about 4 months at 1 ° C. and about 0.7 months at 1170 ° C., and there is a problem that the mesh belt needs to be frequently replaced in a continuous atmosphere heat treatment furnace for a mesh belt conveyor used at a high temperature.

As a means for reducing the maximum value of the tensile stress generated in a portion of the high-temperature mesh belt immediately before it is applied to the furnace bottom roller, the width of the high-temperature mesh belt is increased to advance the portion on which the processed product is placed. It is conceivable to reduce the length in the direction. However, in order to obtain this effect, the width of the high-temperature mesh belt must be considerably large, and therefore, the traveling speed of the high-temperature mesh belt must be considerably slow in order to maintain the residence time in the furnace. However, in such a case, the high-temperature mesh belt is said to cause a "tightening" phenomenon in which the belt is repeatedly started and stopped. As a result, the high-temperature mesh belt is repeatedly subjected to a large tension at the time of starting, so that the time for receiving the large tension is greatly increased. The mesh belt for high temperature is preferably cooled rapidly between 900 ° C. and 500 ° C. due to its material. However, if the advancing speed is reduced, there is a problem that the mesh belt cannot be so cooled.

[0010] The present invention solves the above-mentioned problems in a mesh belt conveyor continuous atmosphere heat treatment furnace used at a high temperature by using common sense in a conventional mesh belt conveyor furnace, that is, during the heat treatment of a processed product, the conveyor in the furnace is continuously operated. The design concept of transporting processed products inside the furnace is reversed, and the characteristics of a batch furnace that the processed products remain stationary in the heating chamber during the heating and holding period, and the high temperature that the high-temperature processed products are transported little by little continuously. It is an object of the present invention to solve the problem by an apparatus that combines the transfer characteristics of a mesh belt furnace and a method of operating the furnace.

[0011]

According to the present invention, there is provided a method for operating a heat treatment furnace of a mesh belt conveyor in a non-oxidizing atmosphere heat treatment furnace, wherein an entrance tunnel, a heating section, and a furnace bottom are continuous along a transport direction of a processed product. A heating chamber having a furnace bottom opening below the furnace is in contact with the rear end of the loading table, a furnace body arranged in-line, a heating unit and a heating source provided at the furnace bottom, and a vicinity of the upper surface of the loading table. After continuously moving on a horizontal furnace floor surface passing through an entrance tunnel of a heating chamber and a heating section from a roller conveyor having a conveyance level horizontal to a conveyance direction of a processed product provided in a furnace bottom, It is configured to continuously circulate in a path that reverses immediately below the opening and returns to the loading table through the lower side of the heating chamber, and conveys the processing products loaded on the loading table into the heating chamber and opens the furnace bottom opening. High temperature mesh with an endless orbit Mesh belt and the portion of the high-temperature mesh belt that has returned to the lower portion of the loading table, and pulls the return side of the high-temperature mesh belt, and drives the subsequent transport-side portion in the transport direction of the processed product. In a mesh belt conveyor non-oxidizing atmosphere heat treatment furnace comprising a driving device, a traction driving device is operated to quickly feed the processed product placed on the high-temperature mesh belt on the loading table into the heating unit through the entrance tunnel and stop. One step, a second step of raising the temperature of the processed product sent into the heating unit during the stop by a heating source based on a predetermined program and maintaining the temperature for a predetermined time, and after the completion of the second step It is characterized by comprising a third step of operating the traction drive device again to take out the processed product in the heating section from the furnace bottom opening to the outside of the heating chamber. In the first and third steps in which the high-temperature mesh belt is driven by the traction drive, a large tension is applied to the vicinity of the furnace end roller of the high-temperature mesh belt at the furnace end, but the second step occupies most of the heat treatment work time.
Since the high-temperature mesh belt is not driven in the process, no tension is applied to the high-temperature mesh belt. In the first step in which a large tension is applied, the temperature of the high-temperature mesh belt is low.

In the above invention, it is preferable to supply an inert gas into the heating section. By doing so, an atmosphere is formed in the heating chamber to prevent oxidation and decarburization of the processed product.

In the invention of the preceding two aspects, it is preferable that an entrance door is provided in the entrance tunnel, and the heating and holding of the processed product in the second step are performed with the entrance door closed. By doing so, the amount of heat in the heating chamber is less likely to leak to the outside, so that the heat loss is reduced, the accuracy of the temperature distribution inside the processed product is improved, and when an inert atmosphere gas is used, the outflow thereof is also reduced. Decrease.

In the invention described in the preceding paragraph, it is preferable that a swirl-type inlet baffle is provided in the inlet tunnel, and the heating and holding of the processed product in the second step are performed with the inlet baffle closed. In this way, since the entrance baffle blocks most of the opening area of the entrance tunnel, the heat radiation from the heating section and the outflow of the atmospheric gas described in the preceding section are further reduced.

[0015] In the invention of the preceding paragraph 4, the heating chamber is provided with a furnace butt portion which is located on the rear side of the heating section and has a furnace butt opening provided below, and the high-temperature mesh belt is provided inside the furnace butt opening. It is preferable that the workpiece is turned downward by the furnace bottom roller provided above and is guided to the traction driving device, and the processed product is dropped from the position past the furnace bottom roller through the furnace bottom opening to the quenching section in the third step.

In the above invention, it is preferable that an intermediate baffle is provided between the heating section and the furnace butt, and that the processed product is heated and held in the second step with the intermediate baffle closed.
By doing so, the amount of heat in the heating section is less likely to leak to the furnace bottom, so that the accuracy of the temperature distribution inside the treated product is improved, and the penetration of fume from the quenching section into the heating section is reduced.

In the invention of the preceding two aspects, it is preferable that an outlet baffle is provided at the furnace bottom opening, and that the processed product is heated and held with the outlet baffle closed. By doing so, the penetration of the fume from the quenching part into the furnace bottom is reduced.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method for operating a heat treatment furnace for a mesh belt conveyor in a non-oxidizing atmosphere according to the present invention will be described below. 1 and 2 show a configuration of an example of a heat treatment furnace in a non-oxidizing atmosphere atmosphere of a mesh belt conveyor to which the present invention is applied. That is, the loading table 20 and the heating chamber 10 having the entrance door 15 and the entrance tunnel 11 are arranged in-line on the floor surface G, and the loading table 2
0 and the furnace floor surface 14a of the heating chamber 10 are horizontally and at the same level. The heating chamber 10 is provided with an inner lining made of a combination of a fire-resistant heat-insulating brick and a heat-insulating board on the inner surface of a furnace shell having an all-round airtight welded structure of SS steel material. A furnace floor surface 14a in which a high-temperature mesh belt 40 for transport advances horizontally in the heating chamber 10.
Is used as the hearth refractory material 14 formed of a ceramic refractory such as SiC. The heating chamber 10 is constituted by a heating section 12 having an entrance tunnel 11 integrated in the front thereof, and a furnace butt section 13 continuous via an intermediate baffle 17. A heater 25 is provided on the ceiling of the heating unit 12 to heat the processed product W on the high-temperature mesh belt 40. If necessary, a radiator tube (RT) type heater 26 can be attached to the lower side of the hearth refractory material 14. Furnace bottom refractory 14
Of the furnace belt, and a large radiating pipe (R) on the ceiling, which is in contact with the end of the
A T) type heater 27 is provided. These heaters 25, 26, 27 use electricity or gas as a heat source.

At the entrance side of the entrance tunnel 11, as shown in the figure, a closed position where the lower end edge is close to the high-temperature mesh belt 40 moving on the bottom surface (part of the hearth surface 14 a), An entrance door 15 that slides between the moved open position is provided. In the middle of the entrance tunnel 11, a revolving entrance baffle 16 is attached to reduce the cross-sectional area. In addition, a direct-acting intermediate baffle 17 that similarly operates between the closed position and the open position is provided between the heating unit 12 and the furnace bottom 13. A chute 19 extending toward a quenching section (not shown) such as a water cooling tank provided below is connected to the lower side of the furnace butt opening 13a, and the upper portion inside the chute 19 heats and holds the processed product W. During the second step, a revolving outlet baffle 18 is provided to keep the opening area of the furnace bottom opening 13a to a minimum. Furnace butt roller 32 is provided in furnace butt portion 13 to turn high-temperature mesh belt 40 passing through heating section 12 downward.

A plurality of rows of suction holes are provided on the horizontal upper surface of a rectangular suction duct 28 attached to the lower surface of the entrance door 15 provided at the entrance of the entrance tunnel 12. The lower surface of the high-temperature mesh belt 40 is in contact with the upper surface of the suction duct 28, and orthogonally advances to the entrance tunnel 11. The entrance door 15 is lowered, and the lower surface of the high-temperature mesh belt 40 has an upper surface of several mm. When it stops close to the position, the suction of the atmospheric exhaust gas flowing back through the heating unit 12 and the entrance tunnel 11 in the traveling direction of the mesh belt 40 for high temperature becomes good, and the entrance tunnel 11
Prevent air from entering the air. Further, a frame curtain burner 29 is provided in parallel with the suction duct 28, and the entrance tunnel 1 is provided.
1 is generated, and while the entrance door 15 is opened and the high-temperature mesh belt 40 conveys and passes over the processed product W, it is attached to the processed product W and the high-temperature mesh belt 40. Purging air (O _{2 in} ).

The entrance baffle 16 provided in the entrance tunnel 11 can be fixed at an arbitrary angle during an operation angle of about 90 °. In this way, the opening area of the entrance tunnel 11 can be minimized when the conveyor is stopped and when the conveyor is operated without loading the processed product W, and the high-temperature mesh belt 40 transports the processed product W and moves the entrance tunnel 11 through the entrance tunnel 11. At the time of passing, the degree of shielding of the entrance baffle 16 is changed according to the pile height of the processed products W, and the opening area of the entrance tunnel 11 can be minimized.

A roller conveyor 21 provided near the upper surface of the loading table 20 located at the forefront of the furnace main body and having a horizontal transfer level in the transfer direction A of the processing product W is provided in the heating chamber 10.
Are arranged in-line at the same transfer level as the horizontal hearth surface 14a. Slightly away from the front end of the roller conveyor 21, a medium-sized free roller 33 having an axis parallel to the conveyor roller and attached to the same conveyance level to turn the slack-side high-temperature mesh belt 40.
Is provided. The high-temperature mesh belt 40 constituting the endless track passes from the roller conveyor 21 above the loading table 20 on the hearth surface 14a in the heating chamber 10 and then has an outer peripheral upper end at the same level as the hearth surface 14a, Further, after winding around the outer periphery of the furnace end roller 32 provided in the furnace end portion 13 so that the axis is perpendicular to the transport direction A and turning downward by about 90 °, the free roller 34 near the upper end of the chute 19 is turned. Again, and passes through the sealing mechanism 38 (air intrusion prevention mechanism) connected to the chute 19, reaches the main drive roller 31 of the traction drive device 30 via the return belt guide 37 and the free roller 35. At a position wrapped around the outer half circumference, the pinch roller 36 is pressed. The main shaft of the main drive roller 31 is driven by an electric variable speed reduction mechanism (all not shown) composed of a continuously variable transmission with a motor, a speed reducer, and various other transmission components, and rotates in the direction of the arrow to return to the return side. The mesh belt for high temperature 40 is pulled, and the mesh belt for high temperature 40 on the transport side is pulled through the furnace end roller 32. The furnace bottom roller 32 is driven in synchronization with the peripheral speed of the main drive roller 31.
Further, the roller conveyor 21 of the loading table 20 is either a free roller conveyor or an electric roller conveyor.

Further, similarly to the conventional furnace, a fume discharge pipe having an inlet is provided at the ceiling of the furnace bottom 13 and below the chute 19 to generate an exhaust flow near the furnace bottom 13, but a small amount of heating is always performed. In the furnace of the present invention, in which a large amount of heated processed product W is quenched in a short time, compared with the conventional furnace in which the processed product W is quenched continuously, the time when the intermediate baffle 17 and the outlet baffle 18 are opened Are provided with a more powerful fume discharger that operates for a short time.

[0024] Mesh belt conveyors are used in a wide range of industrial fields such as the food and chemical industries, and there are many types of wire conveyor belts of this type made of metal wire depending on the application. The high-temperature mesh belt 40 used in the present invention is one of the areas. With the rapid development of mass production technology in the machine industry from around 1940, it is used as a conveyor for automatic conveyance heat treatment at a high temperature exceeding 1100 ° C. It became so. At present, there are many high temperature mesh belt manufacturers in Japan,
There is no extreme difference in product, 25Cr in terms of heat resistance
A -20Ni wire belt is frequently used. 35Ni-20Cr-based, 80N, depending on the type of atmosphere gas in the furnace
The i-20Cr system is used as recommended by the belt manufacturer. A typical mesh used as a high-temperature belt is as shown in FIG.

A first example of a furnace operation method in the case where the above-described heat treatment furnace of a mesh belt conveyor in a non-oxidizing atmosphere is used for solution heat treatment of austenitic heat-resistant steel parts will be described below. The heating part 12 and the furnace butt part 13 are heated for several hours and heated to a predetermined temperature (for example, 1150 ° C. in the heating part 12).
Heating room 1 including the entrance tunnel 11
The space in 0 is purged with air by an inert gas (for example, N ₂ ) from a plurality of atmospheric gas supply ports (not shown) provided at appropriate positions. During this period, the entrance door 15 and each of the baffles 16, 17, 18 are in the closed position. The operation starts with loading of the processed product W. First, in the first step, after the traction drive device 30 is stopped and the high-temperature mesh belt 40 is stopped, the processed product W is placed thereon, and then the flame curtain burner 29 is ignited to generate a frame curtain. The door 15 is opened, the traction drive device 30 is activated, and the high-temperature mesh belt 40 is advanced in the transport direction A, and the processed product W is sent into the heating unit 12 within several minutes.

When this is completed, the traction drive 3
0 is stopped to stop the high-temperature mesh belt 40, the entrance door 15 is closed, and the frame curtain burner 29 is stopped. A suction duct 28 directly below the entrance door 15 is connected to a blower through a pipe, and exhausts air in accordance with the supply amount of the atmospheric gas. In the first step, the frame curtain generated on the front side of the entrance tunnel 12 and the inert gas supplied into the heating unit 12 make it difficult for air to enter the heating unit 12, and also prevent processing air W and high temperature. The air taken in between the mesh belts 40 is also purged when passing through the entrance tunnel 11, and is greatly reduced.

In the second step performed while the high-temperature mesh belt 40 is stopped, the heaters 25 and 26 are operated based on a predetermined program to control the temperature of the heating unit 12, and After completion of the 1150 ° C. temperature rise, the temperature is maintained for a predetermined time (for example, 60 minutes). After the holding is completed, the heaters 25 and 26 are automatically turned off, the temperature of the heating unit 12 starts to decrease, and decreases to a predetermined temperature (for example, 1050 ° C.). Furnace butt 13 is heated and maintained by heater 27 at a temperature lower than the temperature of heating unit 12 (for example, 1050 ° C.). In the second step, the entrance door 15, the baffle 16,
Since the heaters 17 and 18 are closed, the heat loss from the heater 12 is reduced and the temperature distribution in the heater 12 is improved.
Further, the contamination of the atmosphere in the heating section 12 by air or fumes from the quenching tank is small, so that the heat treatment quality of the processed product W is also improved. Further, while the high-temperature mesh belt 40 is stopped in the second step, the loading table 2 is prepared for the next heat treatment operation.
The processed product W is placed on the high-temperature mesh belt 40 on the top.

The temperature of the processed product W decreases (for example, 1050
C)), the flame curtain burner 29 is ignited to generate a flame curtain, the entrance door 15 and each of the baffles 16, 17, 18 are opened, and the traction drive device 30 is activated to activate the traction drive device 30 for high temperature. The mesh belt 40 is advanced. As a result, the processed product W heated and held at a predetermined temperature in the heating unit 12 is sequentially turned to the quenching unit through the chute 19 from the furnace butt opening 13a when the high-temperature mesh belt 40 is turned downward by the furnace butt roller 32. Fall and quench. The time required for this third step is several minutes, and in parallel with this, the processed product W placed on the high-temperature mesh belt 40 on the loading table 20 in the second step of the first heat treatment is moved to the entrance tunnel. It is fed into the heating section 12 through 11 and this is the first step of the second heat treatment operation.
Hereinafter, the heat treatment operation of each time is repeatedly performed in the same manner.

Next, a description will be given of a second example of the furnace operation method in the case where the same heat treatment as that of the first example is performed. Also in this method, the furnace operation method from the start of heating the empty furnace in the heating chamber 10 to the end of the second step is exactly the same as the first example except for the following point. The difference is that the processed product W is not placed on the loading table 20 in preparation for the next heat treatment operation during the progress of the second step.

Therefore, the third step is started while the loading table 20 is empty, and the towing is performed with the intermediate baffle 17 and the outlet baffle 18 opened while the entrance door 15 and the entrance baffle 16 are closed. The driving device 30 is operated to move the high-temperature mesh belt 40 in the transport direction A of the processed product. As a result, the processed product W heated and held at a predetermined temperature in the heating unit 12 sequentially falls through the chute 19 from the furnace butt opening 13a when the high-temperature mesh belt 40 is turned downward by the furnace butt roller 32. And quenched. During this time, the frame curtain burner 29 remains stopped, and the time required for this third step is several minutes. After the fall of the processed product W is completed, the traction drive device 30 is stopped.

In the first step immediately after that, the processed product W of the next heat treatment is loaded on the loading table 20, but it is desirable to use a high-speed automatic loading device to shorten the loading time. After the loading is completed, the next processed product W is carried into the heating unit 12 after the intermediate baffle 17 and the outlet baffle 18 are closed, and then the entrance door 15 is closed.
And open the entrance baffle 16 and open the frame curtain burner 29
When the loading is completed, the mesh belt for high temperature 40 is stopped, the entrance door 15 and the entrance baffle 16 are closed, and the frame curtain burner 29 is stopped. Then, the start of the heating of the processed product W is the start of the second step.

According to the furnace operating method of the first example, the quenching of the heated and held processed product W and the transport of the next processed product W to the heating section 12 are performed almost simultaneously. Each of the baffles 16, 17, and 18 provided inside open,
Although the period of the first step is short, the inside of the heating chamber 10 is in the same state as the conventional furnace. According to the furnace operation method of the second example,
During the third step, since the entrance door 15 and the entrance baffle 16 are closed and only the high-temperature mesh belt 40 advances into the heating chamber 10, the flow resistance of the N ₂ gas from the heating unit 12 to the entrance door 15 is high, and the furnace The heat treatment quality of the processed product W becomes more stable in order to prevent diffusion of the fumes of the buttocks 13 and prevent an increase in heat loss from the heating unit 12.

However, according to this furnace operation method, in the third step, only the workpiece W heated and held in the heating section 12 is rapidly cooled, so that the operation time is shortened as compared with the case of the first example. However, in the furnace control method of the first example, the loading of the processed product W on the loading table 20 which can be performed with a margin during the second process is performed.
Since the next first step is started, the work time directly affects the heat treatment cycle, and rapid loading is desirable. On the other hand, at the start of the third step, the processed product W is placed on the loading table 20.
However, only the weight of the processed product W in the heating unit 12 becomes a load on the high-temperature mesh belt 40 heated to a high temperature. Therefore, particularly for the high-temperature mesh belt 40 of 25Cr-20Ni heat-resistant steel wire, For the heating temperature of 1150 ° C. or more, maintenance of the service life becomes easier as compared with the furnace operating method of the first example.

In the non-oxidizing atmosphere heat treatment furnace as described above, the roller conveyor 2 of the loading table 20 is used.
Since the mesh belt for high temperature 40 on which the processed product W is placed on each of the supporting portions of the furnace floor surface 14a of the heating chamber 1 and the heating chamber 10 is pulled by the traction drive device 30 through the furnace bottom roller 32, the high temperature (for example, 1150 ° C., Intermediate temperature of 1050 ° C)
The maximum value of the tension acting on the lower high-temperature mesh belt 40 is determined by the lower surface of the high-temperature mesh belt 40 and the furnace bottom roller 32.
It is a value near the tangent to the top. However, according to the furnace operation method described above, the high-temperature mesh belt 40 is not driven in the second step, which occupies most of each heat treatment operation time, so that no tension acts on the high-temperature mesh belt 40,
In the first step in which the above-mentioned tension acts, the temperature of the high-temperature mesh belt 40 is low, so that the above-mentioned tension acts on the high-temperature mesh belt 40 and is exposed to a high temperature only in the third step. Therefore, the high-temperature mesh belt 40 extends substantially only in the third step by creep. When the maximum value of the tension under the high temperature acting on the high-temperature mesh belt 40 at the time of the start is obtained, the following is obtained. A. The sum of the weight of the processed product W heated to a high temperature in the heating unit 12 and the weight of the high-temperature mesh belt 40 is generated between the furnace floor surface 14a of the heating unit 12 and the lower surface of the high-temperature mesh belt 40. The value of the friction force multiplied by the friction coefficient. B. The weight of each of the heated high-temperature mesh belts 40 in the entrance tunnel 11 and the furnace bottom portion 13 corresponds to the furnace floor surface 1.
4a and a value of a frictional force multiplied by a frictional coefficient generated between the lower surface of the high-temperature mesh belt 40 and the lower surface. C. Room temperature high-temperature mesh belt 4 on loading table 20
0 and the weight of the processed product W of the next charge are added to the roller conveyor 21 on the lower surface of the high-temperature mesh belt 40.
The value of friction force multiplied by the friction coefficient of. The maximum value of the tension acting on the high-temperature mesh belt 40 in the vicinity of the furnace end roller 32 at the start of the third step is the sum of A, B, and C, but A occupies the majority. That is, C is the same as A in that the processed product W and the high-temperature mesh belt 40 become loads on the supporting portion, but the frictional force at the time of startup is lower because the roller is on the roller conveyor 21 of the free roller or the electric roller. In the former case, it is greatly reduced, and in the latter case, it completely disappears and the start-up is accelerated.
As a result, the configuration of the frictional force that causes the maximum tension that acts on the high-temperature mesh belt 40 near the furnace end roller 32 on the high-temperature mesh belt 40 that has been heated and held at a high temperature together with the processed product W in the heating unit 12 is simplified. That figure also drops.

Therefore, a large increase in the tension acting on the high-temperature mesh belt 40 is mitigated by the large static friction coefficient at the time of starting, the transition to the conveyance with the small dynamic friction coefficient becomes smooth, and the constant speed conveyance at a high speed (for example, 100mm /
Minutes). As a result, the "tightening" phenomenon, which is supposed to occur in the conventional furnace, in which the transfer speed in the furnace tends to be extremely slow, which is limited by the processing amount of the processed product W and the time required for heating and holding, is greatly reduced. And the high-temperature mesh belt 40 is stretched by creep.
The elongation in the third step can be further reduced, and in particular, in the second example, the service life of the high-temperature mesh belt obtained by implementing the furnace control method of the first example can be extended, resulting in a further extension. The invention contributes to reducing the running cost of the furnace.

The description of the maximum value of the high-temperature tension acting on the high-temperature mesh belt 40 in the furnace of the present invention has been made with reference to the first example of the above-mentioned furnace operating method. In the case of the second example of the method, both the next processed product W on the loading table 20 and the heated and held completed processed product W on the hearth surface 14a of the heating unit 12 are placed on the high-temperature mesh belt 40 on the transport side. Unlike the first example in which the transport conveyor is activated while being loaded, only one of the processed products W is loaded and activated, so that in any case, the maximum value of the first example is not exceeded.

[0037]

As described above, according to the present invention, since the mesh belt is not driven in the second step, which occupies most of the heat treatment time, no tension is applied to the high-temperature mesh belt. In the first step in which is added, the temperature of the high-temperature mesh belt is low, so that the above-described tension acts on the high-temperature mesh belt, and only the third step is exposed to high temperatures. Therefore, the mesh belt for high temperature is substantially extended only by the third step by creep, so that the service life of the mesh belt for high temperature is greatly extended, and the maintenance cost of the non-oxidizing atmosphere heat treatment furnace for the mesh belt conveyor is greatly reduced. I do.

According to the invention of the preceding paragraph, in which the inert gas is supplied into the heating chamber, the oxidation of the processed product into the heating chamber,
Since an atmosphere for preventing decarburization or the like is formed, the quality of the heat treatment of the processed product is improved in addition to the effects described in the above item.

According to the second aspect of the present invention, the processing and heating of the processed product are performed with the entrance door provided in the entrance tunnel closed, so that the heat loss is reduced and the temperature distribution inside the processed product is reduced. Is also improved, so that in addition to the effects described above, energy required for heating is saved, and the quality of heat treatment of the processed product is also improved. In addition, when an inert atmosphere gas is used, the outflow thereof is reduced, so that the consumption of the inert gas can be reduced. To further explain the reduction in consumption, the consumption of the atmospheric gas (for example, N ₂ ) is assumed to be proportional to the opening area of the inlet (for example, 50 liter / cm ² h). When stopping close to the upper surface of the high-temperature mesh belt traveling toward the entrance tunnel (the closed state), the opening height becomes extremely small. The opening height in conventional furnaces changes depending on the dimensions (height of the unit) and the loading height of the processed product.
Atmospheric gas increased. According to the present invention, the opening height can be kept to a minimum irrespective of the height of the processed product during the heating and holding period that requires the longest time in the heat treatment of the processed product. The gas consumption can be greatly reduced, and even if the width of the high-temperature mesh belt is increased, the increase in the atmospheric gas consumption is not so great as to be problematic. Therefore, in the case where the effective length is 4B with respect to the conventional belt width B for the same effective area of the heating section, the configuration of the heating chamber in which the effective length is 2B with respect to the belt width 2B becomes easy. Belt width B ・ 2
In both cases, the tension acting on the high-temperature mesh belt is equal in both cases, and in 2B, the stress generated in the mesh belt is reduced by half, so that a great effect can be expected to maintain the service life. Since the travel distance per charge of the mesh belt is reduced by half, this is an effective measure for preventing the deformation of the net due to abrasion.

According to the invention described in the preceding paragraph, in the heating and holding of the processed product in the second step with the entrance baffle provided in the entrance tunnel closed, the heat radiation from the heating section and the atmospheric gas Is further reduced, thereby further reducing the heat loss and improving the accuracy of the actual temperature distribution inside the processed product, so that the energy required for heating is further saved and the heat treatment quality of the processed product is further improved. .

In the invention of the preceding item 4, the furnace body is provided with a furnace bottom roller provided at the furnace bottom provided behind the heating section, and the processed product is the third product.
According to the method of dropping from the position past the furnace bottom roller to the quenching section through the furnace bottom opening in the process,
In addition to the effects of the item, the heat treatment operation for rapid cooling becomes easy.

According to the invention of the preceding paragraph, in the heating and holding of the processed product in the second step with the intermediate baffle provided between the heating section and the furnace butt section closed, according to the invention, Since the amount of heat leaking to the bottom of the furnace is reduced, the accuracy of the actual temperature distribution inside the treated product is improved, and fumes from the quenching part are less likely to leak into the heating part.
In addition to the effects of the preceding paragraph, the heat treatment quality of the processed product is improved.

According to the second aspect of the invention, the heating and holding of the processed product is performed in a state where the outlet baffle provided at the furnace bottom opening is closed. Since it is difficult to penetrate and the amount thereof is reduced, the heat treatment quality of the processed product is further improved.

[Brief description of the drawings]

FIG. 1 is an overall side sectional view showing an example of a non-oxidizing atmosphere heat treatment furnace for a mesh belt conveyor used in the present invention.

FIG. 2 is a partially broken plan view of the non-oxidizing atmosphere heat treatment furnace of the mesh belt conveyor shown in FIG.

FIG. 3 is an overall cross-sectional view showing one example of a conventional heat treatment furnace for a mesh belt conveyor in a non-oxidizing atmosphere.

FIG. 4 is a partial plan view showing a plurality of typical meshes of a mesh belt used in a non-oxidizing atmosphere heat treatment furnace of this type of a mesh belt conveyor.

[Explanation of symbols]

10: heating chamber, 11: entrance tunnel, 12: heating unit, 1
2a: Exit tunnel, 13: Furnace bottom, 13a: Furnace bottom opening, 14a: Furnace floor, 15: Entrance door, 16: Entrance baffle, 17: Intermediate baffle, 18: Exit baffle, 20 ...
Loading table, 21: roller conveyor, 25, 26: heating source (heater), 30: traction drive, 32: furnace bottom roller,
40: mesh belt, 50: cooling unit, 53: middle door,
A: transport direction, W: processed product.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4K034 AA01 AA19 BA05 CA05 DB08 EA01 EA04 EA11 4K038 AA01 BA01 BA02 CA02 DA03 EA02 4K050 AA02 BA02 CA01 CA11 CC07 CD08 CF06 CF16 CG09 EA02

Claims (7)

[Claims] 1. An inlet tunnel, a heating chamber, and a furnace butt are continuous along a processing product transport direction, and a heating chamber having a furnace butt opening below the furnace butt contacts a rear end of the loading table. A furnace body disposed in-line, a heating source provided in the heating chamber and the furnace bottom, and a transfer level provided near the upper surface of the loading table and horizontal to the transfer direction of the processing product. After continuously moving on a horizontal hearth surface traversing the entrance tunnel of the heating chamber and the heating chamber from above the roller conveyor having the heating chamber, it is inverted just below the furnace butt opening to be below the heating chamber. Is configured to continuously circulate in a path that returns to the loading table through the processing table, and transports the processed product loaded on the loading table into the heating chamber, and removes the processed product from the furnace butt opening to the outside of the heating chamber. High-temperature mesh belt of track configuration and the loading platform A pulling drive device that engages with the portion of the high-temperature mesh belt that has returned to the lower portion, pulls the return side of the high-temperature mesh belt, and drives a transport-side portion that is continuous with the high-speed mesh belt in the transport direction of the processed product. In a mesh belt conveyor non-oxidizing atmosphere heat treatment furnace comprising:
A first step of operating the traction drive device to quickly feed and stop the processed product placed on the high-temperature mesh belt on the loading table through the entrance tunnel into the heating unit; and A second step of raising the temperature of the processed article sent into the unit by the heating source based on a predetermined program and maintaining the temperature for a predetermined time; and after the completion of the second step, the traction drive device is operated again. A third step of taking out the processed product in the heating section from the furnace bottom opening to the outside of the heating chamber by a third step. 2. The method according to claim 1, wherein an inert gas is supplied into the heating chamber. 3. The method according to claim 1, wherein an entrance door is provided in the entrance tunnel, and heating and holding of the processed product in the second step are performed with the entrance door closed. The furnace operating method of the mesh belt conveyor described in the non-oxidizing atmosphere heat treatment furnace. 4. The apparatus according to claim 3, wherein a swirling-type entrance baffle is provided in the entrance tunnel, and heating and holding of the processing product in the second step are performed with the entrance baffle closed. Method of operating a non-oxidizing atmosphere heat treatment furnace of a mesh belt conveyor. 5. The heating chamber is provided with the furnace butt portion which is located behind the heating section and has the furnace butt opening provided below, and the high-temperature mesh belt is provided in the furnace butt portion in the furnace butt portion. It is turned downward by the furnace tail roller provided above the tail opening and guided to the traction drive device, and the processed product passes through the furnace tail opening from the position past the furnace tail roller in the third step to the quenching section. The method according to any one of claims 1 to 4, wherein the furnace is dropped. 6. A process according to claim 5, wherein an intermediate baffle is provided between the heating section and the furnace bottom, and heating and holding of the processed product in the second step are performed with the intermediate baffle closed. The furnace operation method of the mesh belt conveyor non-oxidizing atmosphere heat treatment furnace according to 4. 7. An outlet baffle is provided at the furnace bottom opening,
The method according to claim 5 or 6, wherein the heating and holding of the processed product are performed with the outlet baffle closed.