KR20120130269A - Heat treatment method for long material, manufacturing method for long material, and heat treatment furnace used in above methods - Google Patents

Abstract

As a method of heat-treating a long heat-treatment material using a cylindrical batch heat treatment furnace whose both ends are blocked and the inside is divided into a plurality of heating zones in the longitudinal direction,
In the heat treatment furnace, the heating zone of the shortest part is divided into a plurality of heating zones shorter than the length of the heating zones other than the shortest part, and a heat source is provided in each heating zone,
The heat treatment method,
(Step 1) Predetermining the heating output pattern of each heat source in each heating zone of the said shortest part based on the substance temperature measurement result at the edge part of a to-be-processed material at the time of heating,
(Step 2) In the heat treatment operation of the heat-treatment material, the heat output pattern of each heat source determined in step 1, and also based on the furnace temperature measurement results of the heating zones and other heating zones of the shortest part, Each step in the series of controlling the heating output. By this heat treatment method, even in a heat treatment furnace having no heat source on both end walls, the heat treated material can be uniformly heated with high accuracy over the entire length.

Description

Heat treatment method for long materials, manufacturing method for long materials, and heat treatment furnaces used in these methods

The present invention relates to a heat treatment method of a long material which enables heat treatment of a material longer than before, a method for producing a long material using this heat treatment method, and a heat treatment furnace used when performing these heat treatment methods and production methods.

Unless otherwise stated, the definitions of terms in the present specification are as follows.

"Long-length material": It refers to steel bar and other long materials including small diameter long metal pipe.

"Effective furnace length": The heat treatment furnace WHEREIN: The furnace length corresponded to the maximum length of the to-be-processed material which can be heat-processed at uniform temperature.

"Inclination heating": When heating a to-be-processed material using the long cylindrical batch heat processing furnace which closed the both ends, the heat processing furnace is divided into several heating zone in the longitudinal direction, and the heating zone of the shortest part of them is Moreover, it divides into a some heating zone, and a heat source is each provided in each heating zone, and it means heating by giving a high difference to the output of each heat source provided in the heating zone of the shortest part.

Usually, a batch type heat treatment furnace is used for heat treatment of a long material, such as a metal pipe and steel bars.

FIG. 1: is a figure which shows schematic structural example of the conventional long heat processing furnace for long materials, This figure (a) is a cross-sectional view, This figure (b) is a longitudinal cross-sectional view. As shown in the figure, the heat treatment furnace is a cylindrical container in which both ends are closed, and the furnace is divided into a plurality of heating zones in the longitudinal direction. The circumferential wall of the furnace has a double structure consisting of a water cooling wall 2 and a heat shielding wall 3, and both end walls of the furnace also have a double structure consisting of a water cooling wall 7 and a heat shielding wall 8, and on the inner peripheral surface of the circumferential wall of the furnace, The electric heater 1 is provided as a heat source for every heating zone. However, the heater 1 is not provided in the both end walls of a furnace.

Heat treatment of a long material is performed by charging the heat-treatment material 5 mounted on the trolley | bogie 4 in the space enclosed by the electric heater 1 in this heat processing furnace, ie, a heating zone, and heating it with the heater 1 . Control of the heat treatment temperature is performed by individually controlling the output of each heater 1 based on the in-temperature measurement result by the thermometer installed in the furnace.

As shown in Fig. 1, in a conventional heat treatment furnace, a plurality of heat sources (electric heaters) are provided on the circumferential wall of the furnace, but since the heat sources are not provided on both end walls of the furnace, the long material has an end portion that generates heat. ), And the temperature at the end is greatly reduced compared to the central portion. By this temperature decrease, the length of the long material which can be heat-treated is restrict | limited by the conventional heat processing furnace, and an effective furnace length becomes short.

Therefore, it is designed so that the length of the space in a furnace, ie, the total length of the part in which a heater is installed, is sufficiently long than the length of a to-be-processed material, and the effective furnace length is more than the length of a to-be-processed material.

However, when heat-treating a material longer than the prior art, if length of a heat processing furnace is lengthened in order to lengthen an effective furnace length, the facility renovation cost will increase by that much. In addition, when the furnace length is not lengthened, the length of the heat-treatment material must be shortened, and it is not possible to flexibly respond to the demand of the consumer. The conventional heat treatment furnace has such a problem.

As the temperature control method of the material to be treated, a method described below has been proposed.

For example, Patent Document 1 discloses that in a batch type heat treatment furnace in which a plurality of burners are burned to heat the heated object accommodated in the furnace, feedback control is performed so that the temperature of the combustion zone of each burner is constant. When the furnace temperature reaches the preset constant temperature range before it becomes a target temperature, the method of controlling the furnace temperature to a constant temperature by restricting the target temperature of a combustion zone to a predetermined constant value is disclosed.

Patent Literature 2 discloses a temperature control in which a heat generating amount of a lower heater and a calorific value of front and rear zones and an intermediate zone of an upper heater can be controlled independently of each other in a vacuum furnace having openings for entering and exiting a processed product on the front and rear surfaces thereof. A method is disclosed. In a vacuum furnace, since a processed product is heated up solely by radiant heating from a heater and there is almost no convection heating, it is difficult to uniformly heat the processed product, and because of this uneven heating, there is a possibility of causing a poor quality. To cope with the problem.

However, these temperature control methods use individual heat sources (burners or heaters) based on the detected furnace temperature in order to maintain the temperature in the furnace at an appropriate temperature or to prevent temperature imbalance in the furnace by following the temperature change. ) Is independently controlled, and the method of controlling the temperature of the entire furnace is not sufficient, without considering the type of material to be treated or the interference between the heat sources. Therefore, the following method is proposed in consideration of them.

Patent Literature 3 discloses a heating furnace in which a heater disposed in a plurality of divided heating zones is independently temperature-controlled, to a deviation value between a measured temperature of each heater and a set temperature applied to each heater. Disclosed is a temperature control method of a heating furnace that multiplies a correction value giving a furnace-specific heater output distribution only as a time or as a function of time and temperature, and gives it as a heater output control value.

In addition, Patent Document 4 includes a plurality of heaters for heating a target material, and separately installs a calorific value regulator in a power supply path of each heater, and between the calorific value regulator and a temperature detector provided in the furnace. Disclosed is a control method using a vacuum furnace provided with individual deviation setters so as to cause variation in the amount of heat generated. And in the control method disclosed by patent document 4, in heating, one changes by changing the setting value of each deviation setter calculated | required previously according to the kind (size, shape, etc.) of the to-be-processed material, the pressure, and the temperature of atmospheric gas. In the detection value from the temperature detector, the calorific values of the plurality of heaters are controlled to be in a state in which they deviate from each other. For this reason, it is said that it can heat in the state to which the temperature of the whole to-be-processed material becomes uniform similarly to the case where the some heater was controlled individually.

In addition to the conventional temperature control for controlling individual burners and heaters independently, these methods attempt to equalize the in-temperature distribution of the entire heat treatment material by setting deviation values for each heating zone. However, as shown in FIG. 1, in the heat treatment furnace in which the heat source is provided in the circumferential wall corresponding to each heating zone, and the heat source is not provided in the both end walls, there is a significant temperature drop compared with the center portion at the end of the long material. Since it is generated, it is insufficient as a method of uniformizing the processing temperature of a long heat treated material such as a long material.

Patent Document 1: Japanese Patent Application Laid-Open No. 62-4828 Patent Document 2: Japanese Patent Application Laid-Open No. 5-271751 Patent Document 3: Japanese Patent Application Laid-Open No. 62-112726 Patent Document 4: Japanese Patent Application Laid-Open No. 4-52215

In the present invention, in a cylindrical batch heat treatment furnace in which both ends are closed and heat sources are provided on the peripheral wall, and heat sources are not provided on both end walls, the entire length of the material to be treated is maintained at a uniform temperature (for example, With respect to the target temperature, an effective furnace length that can be heated to ± 10 ° C. or less) is secured longer, and the heat treatment method of the long material which can heat-treat the heat treated material longer than conventionally even if the space length in the furnace is the same, and this It is an object to provide a method for producing a long material using a heat treatment method. Moreover, an object of this invention is to provide the heat processing furnace used when implementing those heat processing methods and a manufacturing method.

MEANS TO SOLVE THE PROBLEM In order to solve the said subject, the present inventors first use the conventional heat processing furnace in which the heat source is not provided in the both end walls, and the temperature distribution in especially the both ends of the to-be-processed material (long-length material) in this case is used. Investigated.

2 is a view showing an example of a temperature distribution in the longitudinal direction of a heat-treated material in a conventional heat treatment furnace of a long material. This is the result measured using the conventional heat treatment furnace shown in FIG. 1, and has shown the measurement result in the heating zone next to the heating zone of the shortest part of this furnace, and the heating zone of this shortest part. In FIG. 2, the material temperature of the vertical axis | shaft is represented by the temperature difference with respect to the target temperature.

As shown in FIG. 2, the material temperature located in the heating zone next to this shortest part from the center part vicinity of the heating zone of the shortest part was target temperature or temperature near it. However, the material temperature in the part near the end wall of a furnace from the center part of the heating zone of the shortest end did not reach target temperature, and was lowered about 80 degreeC in the vicinity of the end wall of a furnace. Although not shown in FIG. 2, the same tendency was recognized also in the heating zone of the shortest part on the opposite side to a heat processing furnace. That is, in the conventional heat treatment furnace shown in FIG. 1, uniform heating over the entire length of the material to be treated cannot be performed.

In actual operation, as shown in FIG. 2, the position of the edge part of a to-be-processed material (long-length material) is located in the vicinity of the center part of the heating zone of the shortest part of a furnace (in this example, the position of 1.4m from the end wall of a heat processing furnace). It is considered to fall within the range of effective furnace length.

In order to eliminate the temperature fall in the edge part of this to-be-processed material, the whole heating zone of the shortest part of a heat processing furnace is heated up rather than the center heating zone (heating zones other than the heating zone of the shortest part), and the material in this case The temperature was measured.

FIG. 3 is a view similarly showing the temperature distribution in the longitudinal direction of the heat-treatment material in the conventional heat treatment furnace of a long elongate material, wherein the heating zone at the shortest end is heated between the heating zones at the center (here, heating zones at both ends). Indicates a zone). In FIG. 3, the measurement result in the heating zone of the shortest part of a furnace and the heating zone following this heating zone of the shortest part is shown.

At the time of a test, the temperature of the heat-treatment material of the center heating zone was set to target temperature, and the temperature of the heat-treatment material of the heating zone of the shortest part was set to 20 degreeC or 40 degreeC higher than the temperature of the heat-treatment material of the next heating zone of the shortest part. . For comparison, the case where the heating zone of the shortest part was set to the same target temperature as the central heating zone was also performed.

As shown in FIG. 3, the temperature of the heat-treatment material is overheated beyond the target temperature near the center of the heating zone of the shortest part, while the temperature drop still remains at the end of the heat-treatment material close to the end wall of the furnace, and the whole of the heat-treatment material There is no uniform heating over the length.

Subsequently, a heat shielding plate is provided on the outer side of the end face of the heat-treatment material to suppress heat generation from the end of the material, and in addition to the heating zone at the end of the furnace and the next heating zone adjacent to the end of the furnace, the heat is inclined. Reviewed. This is because it is possible to prevent significant overheating of the material to be treated in the vicinity of the center of the heating zone of the shortest part and to suppress the temperature drop of the material to be treated.

4: is a figure which shows schematic structure of the heat processing furnace which installed the heat shielding plate, This figure (a) is a cross-sectional view, This figure (b) is a longitudinal cross-sectional view. In the heat treatment furnace shown in the same figure, twelve heat shielding plates 9 made of SUS 304 are provided on the outer side of the end face of the heat-treated material placed on the trolley 4. Using this heat treatment furnace, the material temperature when the heating amount of the heating zone of the shortest part was slightly raised with respect to that of the heating zone next to the shortest part was measured.

FIG. 5: is a figure which shows the result of having measured the temperature distribution of the to-be-processed material (long-length material) in the heating zone of the shortest part and the heating zone next to the shortest part using the heat processing furnace provided with this heat shielding plate. For comparison, the case where the heating amount of the heating zone of the shortest part and the next heating zone of the shortest part is made equal is also written together.

From the result shown in FIG. 5, when the permissible range of the temperature distribution over the entire length of the heat-treatment material is set to ± 10 ° C or less with respect to the target temperature, the heat input amount of the heating zone at the shortest part is slightly lower than that of the heating zone next to the shortest part. By increasing it, it is possible to suppress the overheat of the heat-treatment material at or below the upper limit of the allowable range near the center of the heating zone of the shortest part, and to avoid the temperature drop at the end of the heat-treatment material and to heat the heat-treatment material uniformly. Able to know.

However, in this heat treatment furnace, although the cooling gas is introduced from the end wall of the furnace after the treatment to cool the heat-treatment material, since the gas is blocked by the heat shield plate 9, the cooling rate is lowered, and the time required for cooling is conventionally. There was a problem that is about 2-3 times longer. In addition, it is necessary to examine the number of sheets and the mounting location of the heat shield plate depending on the number and dimensions of materials to be loaded on the trolley, and this is not a realistic method.

Therefore, the present inventors divide the heating zone of the shortest part of a furnace shorter than the length of the center heating zone, provide a heat source in each divided heating zone, and heating only the heating zone of the shortest part diagonally (inclined heating). The temperature of the heat-treatment material located in the heating zone of the shortest part was attempted to become the same throughout the heating zone of the shortest part. That is, the application of the method of controlling the temperature of the edge part of a to-be-processed material (henceforth a "divided gradient heating control method") was examined by changing the heating output provided to a heat source between divided heating zones.

Since the number of heating zones does not affect the solution of the subject by this invention, below, for convenience of description, the heating zone of the shortest part of one side is also called "m zone", and the heating zone of the opposite side is also called "n zone". Display.

FIG. 6 is a diagram illustrating a measurement result of the temperature distribution of the heat-treated material in the m zone and the next heating zone after the m zone when the divided gradient heating control method is applied. In this example, the m zone of the shortest part is divided into three heating zones of the m-1 zone, the m-2 zone, and the m-3 zone in order from the end, and the heating amount (only in the m-1 zone) Gradient heating to increase the amount of heat input) was performed.

In FIG. 6, "after remodeling" is a case where oblique heating is performed using a heat treatment furnace in which m zones are divided into three, and "before remodeling" uses the same three-part heat treatment furnace. This is the case of the conventional heating system in which the heating amounts of the m-2 zones and the m-3 zones are uniform and no gradient heating is performed. In addition, the increase rate of the heating amount with respect to the m-1 zone in the case of remodeling was set to +35% with reference to the examination result by the electrothermal simulation shown in FIG. 7 mentioned later.

As is apparent from the results shown in Fig. 6, by applying the divided gradient heating control method in the heating zone of the shortest part of the furnace, the overheating of the end portion of the heat-treatment material is suppressed within an allowable range, and the temperature decrease at the end portion is avoided to perform the heat treatment. It turns out that the whole ash can be heated uniformly.

FIG. 7: is a result of examination by electrothermal simulation, and is a figure which shows the relationship between the amount of heat input increase in a m <-1> zone, and a cleavage when the division | segmentation gradient heating control method is applied. "Polarization" is a difference between the highest value and the lowest value in the temperature distribution of the heat-treatment material in the heating zone next to the m zone and the m zone. As shown in Fig. 7, in the case where the heat input increase amount for the m-1 zone is 0 (i.e., a conventional heating method not to perform oblique heating), the polarization is about 80 deg. C, whereas the deterioration is reduced by performing oblique heating. , The minimum value of 10 ° C is shown when the heat input increase amount is + 35%.

As mentioned above, although the case where the m zone was divided | segmented into 3 and diagonally heated was demonstrated, generally, the heating zone (m zone and n zone) of the shortest part of a furnace is divided | segmented shorter than the length of the center heating zone, and this divided individual heating By controlling the heating output of the zone, it has been found that the entire length of the material to be treated, including the end portion, can be heated to a uniform temperature. For this reason, even if the space length in a furnace is the same, it becomes possible to significantly increase the effective furnace length.

As mentioned above, the control of the heating output of each heating zone divided | segmented in the heating zone of the shortest part of a furnace is based on the actual temperature measurement result at the edge part of a to-be-processed material at the time of heating, and the temperature of the end of a to-be-processed material is the shortest part of a furnace. It can be performed by obtaining in advance the ratio (hereinafter referred to as a "heating output pattern") of the output of each heat source in each of the divided heating zones so as to be the same throughout the heating zone.

This invention is made | formed based on such knowledge, The summary is the heat processing of (3) used for the heat processing method of the long material of following (1), the manufacturing method of the long material of (2), and those heat processing methods and manufacturing methods Is on the road.

(1) A heat treatment method of a long material, in which both ends are closed and the inside is divided into a plurality of heating zones in a longitudinal direction, and a long heat treatment material is charged into the inside of the heat treatment furnace to perform heat treatment. As

In the said heat processing furnace, the heating zone of the shortest part among the said heating zones is divided into several heating zones shorter than the length of heating zones other than the shortest part, and a heat source is provided in each heating zone,

The heat treatment method,

(Step 1) Predetermining the heating output pattern of each heat source in each heating zone of the said shortest part based on the substance temperature measurement result at the edge part of a to-be-processed material at the time of heating,

(Step 2) At the time of heat treatment of the heat-treatment material, based on the heating output pattern of each heat source determined in Step 1 and the in-temperature measurements of the furnaces of the heating zones other than the shortest portions and the heating zones of the shortest portions, And a series of steps for controlling the heating output of the heat source.

In the heat treatment method of the long material of the present invention, in step 2, the heating output of each heat source in each heating zone of the shortest part is adjusted based on the actual temperature measurement result at the end of the heat-treatment material during the heat treatment operation. Therefore, the temperature control of the heat-treatment material with higher precision becomes possible.

In the heat treatment method of the long material of the present invention, in the steps 1 and 2, if the electric heater is used as the heat source, it is easy to adjust the heating output pattern, and if the heating of the material to be treated is radiant heating, accurate temperature control is performed. easy to do.

(2) A method for producing a long material, characterized in that heat treatment is performed using the heat treatment method of the long material described in (1) above.

(3) A batch heat treatment furnace of a long material in which both ends are occluded and the inside is divided into a plurality of heating zones in the longitudinal direction, and a long heat treatment material is charged to perform heat treatment.

The heat treatment furnace,

The heating zone of the shortest part among the said heating zones is divided into several heating zones shorter than the length of heating zones other than the shortest part, and a heat source is provided in each of the heating zones,

Means for determining a heating output pattern of each heat source in each heating zone of at least the shortest portion;

Means for measuring the furnace temperature of each heating zone of the shortest part and a heating zone other than the shortest part;

And a means for controlling the heating output of each heat source for each of said heating zones.

As for the heat treatment of the long material of the present invention, if it has a means for measuring the actual temperature of the end portion of the heat treatment material, temperature control of the heat treatment material with higher accuracy becomes possible.

In the heat treatment furnace of the elongate material of this invention, if a heat source is an electric heater, adjustment of a heating output pattern is easy, and if heating of a to-be-processed material is by radiant heating, it will be easy to perform temperature control with high precision.

According to the heat treatment method of the long material of the present invention, when the heat treatment is performed using a cylindrical batch heat treatment furnace in which both ends are closed and heat sources are provided on the peripheral wall, and heat sources are not provided on both end walls, Even if the length is the same, the effective furnace length can be secured longer, and the long heat treated material can be heated to a uniform temperature with high accuracy over the entire length. For this reason, the facility remodeling cost of a furnace can be reduced significantly.

Moreover, the manufacturing method of the elongate material of this invention is a manufacturing method using this heat processing method, and the elongate material without an imbalance in quality characteristic is possible.

When the heat treatment furnace of the long material of this invention is used, the heat processing method of this invention and the manufacturing method of a long material can be performed easily.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows typically a schematic structural example of the conventional heat processing furnace for long materials, FIG. 1 (a) is a cross-sectional view, and FIG. 1 (b) is a longitudinal cross-sectional view.
2 is a view showing an example of a temperature distribution in the longitudinal direction of a heat-treated material in a conventional heat treatment furnace of a long material.
3 is a view showing an example of the temperature distribution in the longitudinal direction of the heat-treatment material in this case by raising the heating zone of the shortest part than the heating zone in the center by using a conventional long heat treatment furnace.
4: is a figure which shows schematic structure of the heat processing furnace provided with the heat shield plate, FIG. 4 (a) is a cross-sectional view and FIG. 4 (b) is a longitudinal cross-sectional view.
FIG. 5: is a figure which shows the result of having measured the temperature distribution of the to-be-processed material in the heating zone of the shortest part and the heating zone next to the shortest part using the heat processing furnace provided with the heat shielding plate.
FIG. 6 is a diagram illustrating a measurement result of the temperature distribution of the heat-treated material in the m zone and the next heating zone after the m zone when the divided gradient heating control method is applied.
FIG. 7: is a result of examination by electrothermal simulation, and is a figure which shows the relationship between the amount of heat increase and a cleavage with respect to the m-1 zone when the division | segmentation gradient heating control method is applied.
FIG. 8: is a figure which shows schematic structure of the heat processing furnace used for the heat processing method of the elongate material of this invention, FIG. 8 (a) is a cross-sectional view, FIG. 8 (b) is a longitudinal cross-sectional view.
FIG. 9 is a diagram showing an installation position of a thermocouple on a heat treatment material charged into a heat treatment furnace in the embodiment.
It is a result obtained in the Example and is a figure which shows an example of the temperature measurement result of the edge part of a to-be-processed material at the time of a heating.

1.Heat treatment method of long material

The heat treatment method of the long material of the present invention is a heat treatment method using a cylindrical batch heat treatment furnace in which both ends are closed and the inside is divided into a plurality of heating zones in the longitudinal direction. It is divided into several heating zones shorter than the length of heating zones other than the shortest part, The heat source is provided in each heating zone, respectively, and is characterized by including the following steps 1 and 2.

(Step 1) Predetermining the heating output pattern of each heat source in each heating zone of the said shortest part based on the substance temperature measurement result at the edge part of a to-be-processed material at the time of heating,

(Step 2) On the basis of the heating output pattern of each heat source determined in Step 1 and the in-temperature measurement results of the heating zones other than the shortest portion and the heating zones other than the shortest portion in the heat treatment operation of the heat treated material, Controlling the heating output of a heat source.

FIG. 8: is a figure which shows schematic structure of the heat processing furnace used for the heat processing method of the elongate material of this invention, This figure (a) is a cross-sectional view, This figure (b) is a longitudinal cross-sectional view. In this heat treatment furnace, among the plurality of heating zones shown in FIG. 1, one of the shortest heating zones, that is, the m zone, is divided into three heating zones: an m-1 zone, an m-2 zone, and an m-3 zone. The heat processing furnace which divided | segmented the heating zone of the shortest part of the opposite side, ie, the n zone into three heating zones of n-1 zone, n-2 zone, and n-3 zone.

And as shown in FIG. 8, this heat processing furnace is a cylindrical container with the both ends closed | blocked, The circumferential wall of a furnace becomes the double structure which consists of a water-cooled wall 2 and a heat shielding wall 3, and the both end walls of a furnace are also numbered It has a double structure composed of a cooling wall 7 and a heat shielding wall 8. On the inner circumferential surface of the circumferential wall of the furnace, an electric heater 6 is provided as a heat source for each heating zone. However, the heater 6 is not provided in the both end walls of the furnace.

In the heat treatment furnace used in the heat treatment method of the present invention, a plurality of heating zones (m-1 zone, m-2 zone and m-) whose shortest heating zones (m zone and n zone) are shorter than the length of the central heating zone. 3 zones, n-1 zones, n-2 zones, and n-3 zones), for example, as shown in FIG. 3, heats up the entire heating zone of the shortest part during the heat treatment of the long material. This is because the temperature of the heat-treatment material is overheated near the center of the heating zone of the shortest part, and at the end of the heat-treatment material close to the end wall of the furnace, the temperature decreases and uniform heating cannot be performed.

That is, in the heat treatment furnace of the present invention, the heating zone of the shortest part is divided into a plurality of heating zones in order to subdivide the heating zone of the shortest part so that the output ratio of each heat source in each divided heating zone can be adjusted. to be. Although the division number of the heating zone of the shortest part of a furnace is 3 in either the m zone and the n zone in the heat processing furnace illustrated in FIG. 8, the situation of the temperature fall in the heating zone of the shortest part is grasped | ascertained previously based on it. You may decide appropriately.

In advance, the heating output pattern of each heat source in each heating zone of the shortest part is determined based on the actual temperature measurement result at the end of the heat-treatment material at the time of heating in order to uniformly heat both ends of the long material.

Substantial temperature measurement of said heat-treatment material is corresponded to temperature measurement in the individual heating zone which comprises the heating zone of the shortest part of a furnace, and can measure temperature by attaching a thermocouple to the predetermined part of the edge part of a heat-treatment material. By the actual temperature measurement, the temperature measurement results at the ends (parts receiving mainly heat from each heat source of each heating zone) of the heat-treatment material are obtained in advance in correspondence with the heating zones of the shortest portion divided shortly, The heating output pattern (output ratio of each heat source) of each heat source in each divided heating zone is determined.

As a preferable example of a heating output pattern, as shown to said FIG. 6, FIG. 7, the pattern which divides the m zone of the shortest part of a furnace into three, and heat-increasing amount in the m-1 zone among them is +35% is mentioned. For this reason, it can be expected to suppress the uneven heat of the to-be-processed material in m zone and the next heating zone of m zone to about 10 degrees C or less.

On the basis of the heating output pattern of each heat source determined as described above at the time of the heat treatment of the elongate material, and also the furnace temperature measurement results of the respective heating zones of the shortest part of the furnace and the central heating zone (heating zones other than the heating zone of the shortest part), The heating output of each heat source is controlled to heat the entire length of the material to be treated to a uniform temperature with high accuracy.

That is, in addition to heating each heating zone of the shortest part of a furnace with the heating output pattern previously determined and set as mentioned above, In addition, the inside temperature of a furnace in heating zones other than each heating zone of the shortest part of a furnace and the heating zone of the shortest part of a furnace is heated. In consideration of the results, the heating output of the individual heat sources is controlled. For this reason, the fluctuation | variation of the low temperature resulting from the number of the to-be-processed material, the fluctuation | variation in arrangement | positioning, etc. in this furnace can be suppressed, and the precision of the uniform heating of the whole length of the to-be-processed material including the edge part can be improved.

In addition, in each heating zone of the shortest part of a furnace, although a heating output pattern is set previously, since a heating output is changed by the heating output control based on the furnace temperature measurement result at the time of actual heat processing, a heating output pattern is previously made. It may shift from the set pattern.

By the way, since the temperature uniformity method of the to-be-processed material described in the said patent document 4 changes temperature according to the kind of to-be-processed material at the time of a heating, after changing the setting value of each deviation setter previously calculated | required, the heat processing method of this invention There may be similarities with.

However, the method described in Patent Document 4 focuses on controlling the temperature control of the plurality of heating zones by the detection value of one thermometer by using a deviation setter provided in each zone. On the other hand, in the heat treatment method of the present invention, in order to prevent the temperature drop at the end of the long material, only the heating zone at the shortest part is divided and the heating output pattern is set in advance, and each of the heating zones is considered in consideration of the furnace temperature measurement results. Since it is a method of controlling the heating output of the heat source in a heating zone, it differs clearly from the method of patent document 4.

Moreover, in the method of patent document 4, although it controls to a fixed setting value during heat processing, in this invention, it may shift | deviate gradually from the heating output pattern set previously, and this also differs in this point.

In the heat treatment method of the long material of the present invention, there is also taken an embodiment in which the heating output of each heat source in each heating zone of the shortest part of the furnace is adjusted based on the actual temperature measurement result at the end of the heat-treatment material during the heat treatment operation. Can be. Substantial temperature measurement of the end portion of the heat-treatment material is measured by attaching a thermocouple to the end of the heat-treatment material during actual heat treatment.

In the actual heat treatment, the number of the heat-treatment material and the arrangement in the furnace are different. Therefore, after the heat treatment is started with a predetermined heating output pattern, the heating zones other than the heating zones of each heating zone and the shortest heating zone of the furnace The heating output of the individual heat sources is controlled based on the furnace temperature measurement results.

However, in the heat treatment method of the long material of this invention, the form which adjusts the heating output of the heat source of each heating zone can also be employ | adopted based on the actual temperature measurement result of the edge part of a to-be-processed material. This adjustment can take various forms depending on the result of temperature measurement, such as adjusting all the heating zones of the shortest part divided | segmentally shortened, and adjusting only one of them.

By adopting this embodiment, the temperature imbalance at the end of the heat-treatment material is further reduced, and the temperature control of the heat-treatment material with higher accuracy becomes possible.

In the heat treatment method of the long material of this invention, it is preferable to use an electric heater as a heat source for heating a to-be-processed material. As a heat source, a burner, a radiant tube, etc. can also be applied, but the heating by an electric heater is easy to adjust a heating output pattern, and it is suitable.

Moreover, in the heat processing method of the elongate material of this invention, when the heating of a to-be-processed material is a radiation heating, it is easy to perform temperature control with high precision. However, as in the heat treatment method of the present invention, when only the end portion of the heat-treatment material is controlled by a predetermined heating output pattern, if convection occurs in the furnace, even if the heating output pattern is determined, the heating is not performed as it is and the control is accurate. Becomes difficult.

Therefore, it is preferable to apply the heat processing method of this invention to control in a vacuum heat processing furnace, and control in the heat processing furnace by the radiation heating in gas atmosphere with a small heat capacity like hydrogen gas. Among them, hydrogen gas is also difficult to manage the gas, it can be said that it is more preferable to apply to the control in the vacuum heat treatment furnace.

According to the heat treatment method of the long material of the present invention described above, in the case of using a cylindrical batch heat treatment furnace in which both ends are closed and heat sources are provided on the peripheral wall, and heat sources are not provided on both end walls, the space length in the furnace is used. Even if it is the same, the effective furnace length can be ensured longer, and the longer to-be-processed material than before can be heated to uniform temperature with high precision over the whole length.

In the heat treatment method of the elongate material of this invention, division of the heating zone of the shortest part of a furnace may consist of either shortest part, and the above-mentioned effect can be acquired from the divided side.

2. Manufacturing method of long material

The manufacturing method of the elongate material of this invention is a manufacturing method characterized by heat-processing using the heat processing method of the elongate material of this invention mentioned above.

That is, in manufacture of the elongate material normally performed, only a heat processing process is performed using the heat processing method of this invention, and other processes are performed according to the conventional method.

According to the method for producing a long material of the present invention, in the heat treatment step, the entire length can be heated to a uniform temperature for a heat treated material longer than conventional ones, so that an unbalance in quality characteristics such as mechanical properties and corrosion resistance It is possible to manufacture a long long material.

3. Heat treatment furnace of long material

The heat treatment furnace of the long material of the present invention has a cylindrical shape in which both ends are closed and the inside is divided into a plurality of heating zones in the longitudinal direction, and a long heat treatment material is charged and the heat treatment material is a batch heat treatment furnace for performing heat treatment. Characterized in that made. That is, in the heat processing furnace of this invention, the heating zone of the shortest part is divided into several heating zones shorter than the length of heating zones other than the shortest part among the said heating zones, and a heat source is provided in each heating zone. In the heat treatment furnace of the present invention, at least the means for determining a heating output pattern of each heat source in each heating zone of the shortest portion, the heating zones of the heating zones other than the heating zones of the shortest portion and the shortest portion, It has a means for measuring and a means for controlling the heating output of each heat source for every said heating zone.

The heat treatment furnace of the long material of this invention is illustrated by the schematic structure shown in said FIG. In addition, in the structure illustrated by this figure, although the heating zone (m zone and n zone) of both ends of a furnace is divided | segmented short, the heat processing furnace which divided the heating zone of either shortest part may be sufficient.

In the heat treatment furnace of the present invention, the shortest heating zone is divided shorter than the length of the central heating zone, as described in the heat treatment method of the present invention. This is to adjust the output ratio of each heat source installed in each zone.

In the heat treatment furnace of the present invention, the means for determining the heating output pattern of each heat source in each heating zone of at least the shortest end is for uniformly heating both ends of the long material. In addition, "at least" means that you may have a means for determining the heating output pattern which also included heating zones other than the shortly divided heating zone.

In determining the above heating output pattern, first, in order to correspond to each heating zone constituting the heating zone of the shortest part of the furnace, it is necessary to obtain the temperature measurement result at the end of the heat-treatment material in advance. Can be obtained in advance by attaching a thermocouple to the end portion of the heat-treated material and measuring the temperature. Next, the heating output pattern (output ratio of each heat source) of each heat source in each heating zone of the shortest part of the furnace is determined based on the actual temperature measurement result, but this is set by the operator based on the actual temperature measurement result. It is possible to.

In addition, for example, an output pattern setter is attached to the heat treatment furnace, and the relationship between the actual temperature measurement result and the heating output pattern to be set in advance is input thereto, and the output pattern setter receives the signal of the temperature measurement result and individually It is also possible to select a suitable heating output pattern based on the temperature measurement result of and to give an output instruction to each heat source of each heating zone.

Accordingly, the means for determining the heating output pattern may be a method of artificially determining the thermocouple attached to the material to be treated and the actual temperature measurement result, or a method of automatically determining the result by an output pattern setter. have.

In the heat treatment furnace of the present invention, each of the heating zones of the shortest part and the heating zones other than the shortest part has a means for measuring the heating output of each heat source for each heating zone. By controlling the heating output of the heat source of the heating zone, the fluctuation of the low temperature during the heat treatment is suppressed and the precision of uniform heating over the entire length of the heat-treated material including the end portion is improved.

As a low temperature measuring means for every heating zone, the temperature detector conventionally used for the measurement of the furnace temperature is good. For example, a thermocouple can be mentioned.

As a heating output control means, the output controller etc. which input the target value of the furnace temperature in advance, and compare a signal from a temperature detector with this target temperature, and output a control signal to a heat source, performing PID control can be used.

As for the heat treatment of the long material of the present invention, if it has a means for measuring the actual temperature of the end portion of the heat treated material, temperature control of the heat treated material with higher accuracy becomes possible.

As said temperature measuring means, the thermocouple which can adhere and measure to the edge part of a to-be-processed material at the time of actual heat processing is mentioned.

When the heat treatment furnace of the long material of this invention demonstrated above is used, the heat processing method of this invention and the manufacturing method of a long material can be performed easily.

Moreover, the form of the practical heat processing operation by the heat processing method of this invention is as follows. As the heat treatment furnace, a vacuum heat treatment furnace employing an electric heater as a heat source is adopted:

(1) At the time of heat processing, first, the furnace temperature of the center heating zone except the heating zone of the shortest part of a furnace is collectively controlled to initial target temperature (temperature lower than the material temperature required for a to-be-processed material);

(2) after reaching the initial target temperature, all heating zones are switched to individual control, and the furnace temperature of each heating zone is individually controlled to the target temperature (final temperature required for the material to be treated);

Regarding the heating zone of the shortest part to (3), inclination heating is controlled by the heating output pattern predetermined and set by the dividing gradient heating control method previously;

(4) The temperature in the furnace of each heating zone is finely adjusted so that the temperature of the material to be treated becomes a control value.

Example

By using the heat treatment furnace of the present invention having the structure shown in FIG. 8 above, a metal tube is charged into the furnace as a long heat treatment material (long material), and applied to the end portion of the heat treatment material when heated by applying the heat treatment method of the present invention. The temperature distribution in was investigated. For comparison, the same investigation was conducted for the case where the conventional heat treatment method was applied.

In the used heat treatment furnace, the inside is divided into a plurality of heating zones from the m zone to the n zone, and the length of each heating zone is 3 m. Here, the m zone, which is one of the shortest parts, is divided into three zones in the order of m-1, m-2, and m-3 zones from the end, and the n zone, which is the shortest part on the opposite side, is n-1, in order, from the end. It is divided into three zones by zone, n-2 zone and n-3 zone. The length after the division | segmentation of each heating zone which comprises the m zone and n zone of the shortest part is all 1 m.

In this heat treatment furnace, the heat treatment material is disposed so that the pipe end of the heat treatment material is placed in the m-1 zone that is the shortest part of the m zone, and the total of four places at 200 mm pitch including the 600 mm position from the end wall of the furnace and 1500 mm from the same end wall. Thermocouples were attached to 5 locations in total.

9 is a diagram illustrating a mounting position of a thermocouple. Also in n zone, the thermocouple was attached to five places of the to-be-processed material similarly to the situation in m zone. Numerals 1-5 and 6-10 of the original character in this figure show the installation position of a thermocouple.

The output of each heat source of each heating zone (m-1, m-2 and m-3 zones) divided into three zones of m zones is equal to the output of the central heating zone, that is, the angle of the central heating zone. The heating was started with 100% of the output ratio to the heat source, and on the way, heating was performed by changing the output ratio of the m-1 zone to 142% and the output ratio of the m-2 zone to 85% (the output ratio of the m-3 zone was not changed). Without, 100%).

That is, in the test of an Example, the divided diagonal heating control method employ | adopted by the heat processing method of this invention was applied. The output ratio here was determined and set based on the actual temperature measurement result of the heat processing material calculated | required previously. Moreover, also in n zone, the output ratio was changed and it heated similarly in the middle of heating.

10 shows an example of the temperature measurement result at the end portion of the heat treatment material. 10 is a chart in which the temperature measurement results of the heat-treatment material are automatically recorded, and numerals 1 to 10 of the original characters shown in FIG. 10 indicate material temperatures measured by thermocouples at the respective installation positions shown in FIG. 9.

As shown in Fig. 10, the temperature of the heat treated material measured at a position near the end, among the temperatures measured at individual thermocouples, after the start of heating (heating) and before the change of output (starting of gradient heating) (number 1 in the original character). , 2 and 6, 7) deviated greatly from the target temperature ± 10 ° C, and the difference with the target temperature was about 50 ° C at the maximum.

During the heating, after changing the output applied to the heat sources in the m-1 zone and the m-2 zone as described above and starting the gradient heating, as shown in FIG. 10, the temperature of the heat treated material is It turns out that it is suppressed within +/- 10 degreeC with respect to target temperature in any temperature measurement location.

6 is a view obtained by gathering an example of the temperature measurement result at the end portion of the heat-treatment material thus performed. When the output ratio of each heating zone (each zone of m-1, m-2, and m-3) divided into three zones of m zones is 100% (white square display (□) in the drawing) ) Has a temperature difference of about 45 ° C from the next heating zone in the m zone at a position near the end of the heat-treated material (near the center of the m-1 zone). In contrast, in the case where the heat treatment method of the present invention is applied (indicated by the black circle (●) in the drawing, "after remodeling"), the temperature difference with the next heating zone of the m zone is greatly reduced within 7 ° C. It can be seen that.

10 and the results of FIG. 6, by applying the heat treatment method of the present invention, in the cylindrical batch heat treatment furnace in which heat sources are not provided at both end walls, the effective furnace length is secured longer, and Over the entire length including the end, it was confirmed that temperature management within ± 10 ° C could be sufficiently performed with respect to the target temperature.

(Industrial availability)

According to the heat treatment method of the elongate material of this invention, an effective furnace length can be ensured longer and a long length to-be-heat-treated material can be heated to uniform temperature precisely over the whole length.

According to the manufacturing method of the elongate material of this invention using this heat processing method, manufacture of the material which does not have an imbalance in quality characteristics, such as mechanical characteristics and corrosion resistance, is possible. Moreover, if the heat treatment furnace of the long material of this invention is used, the heat processing method and manufacturing method of this invention can be performed easily.

Therefore, the heat processing method of this invention, the manufacturing method of the long material of this invention to which this method is applied, and the heat processing furnace of this invention can be used effectively for the heat processing and manufacture of a long material.

1: Electric heater
2: water cooling wall
3: heat shield wall
4: Balance
5: heat treatment material
6: Electric heater
7: Water cooling wall
8: heat shield
9: heat shield

Claims (9)

A heat treatment method of a long material in which both ends are occluded and the inside is divided into a plurality of heating zones in a longitudinal direction, and a long heat treatment material is charged into the inside of the heat treatment furnace to perform heat treatment.
In the said heat processing furnace, the heating zone of the shortest part among the said heating zones is divided into several heating zones shorter than the length of heating zones other than the shortest part, and a heat source is provided in each heating zone,
The heat treatment method,
(Step 1) Predetermining the heating output pattern of each heat source in each heating zone of the said shortest part based on the substance temperature measurement result at the edge part of a to-be-processed material at the time of heating,
(Step 2) On the basis of the heating output pattern of each heat source determined in Step 1 and the in-temperature measurement results of the heating zones other than the shortest portion and the heating zones other than the shortest portion in the heat treatment operation of the heat treated material, And a series of steps for controlling the heating output of the heat source. The method according to claim 1,
In step 2,
And a heating output of each heat source in each heating zone of the shortest part is adjusted based on the actual temperature measurement result at the end of the heat-treated material in the heat treatment operation. The method according to claim 1 or 2,
In steps 1 and 2, an electric heater is used as a heat source. The method according to any one of claims 1 to 3,
A heat treatment method of a long material, characterized in that the heating of the material to be treated is radiation heating. Heat-treatment is performed using the heat-treatment method in any one of Claims 1-4, The manufacturing method of the elongate material characterized by the above-mentioned. A batch heat treatment furnace of a long material in which both ends are occluded and the inside is divided into a plurality of heating zones in the longitudinal direction, and a long heat treatment material is charged to perform heat treatment.
The heat treatment furnace,
The heating zone of the shortest part among the said heating zones is divided into several heating zones shorter than the length of heating zones other than the shortest part, and a heat source is provided in each heating zone, respectively,
Means for determining a heating output pattern of each heat source in each heating zone of at least the shortest portion;
Means for measuring the furnace temperature of each heating zone of the shortest part and a heating zone other than the shortest part;
And a means for controlling the heating output of each heat source for each of said heating zones. The method of claim 6,
A heat treatment furnace for a long material, further comprising means for measuring the actual temperature at the end of the material to be treated. The method according to claim 6 or 7,
Heat treatment furnace of the long material, characterized in that the heat source is an electric heater. The method according to any one of claims 6 to 8,
A heat treatment furnace for a long material, characterized in that the heating of the material to be treated is radiation heating.

Images