WO2011118201A1

WO2011118201A1 - Heat treatment method for long material, manufacturing method for long material, and heat treatment furnace used in above methods

Info

Publication number: WO2011118201A1
Application number: PCT/JP2011/001684
Authority: WO
Inventors: 和人久保田; 岡田　誠司; 幹雄辰岡
Original assignee: 住友金属工業株式会社
Priority date: 2010-03-25
Filing date: 2011-03-23
Publication date: 2011-09-29
Also published as: CN102822358B; EP2551361B1; KR20120130269A; EP2551361A4; JPWO2011118201A1; CN102822358A; JP4868091B2; EP2551361A1; CA2790579A1; KR101380456B1; CA2790579C

Abstract

Disclosed is a method which is for carrying out heat treatment on long material to be heat treated, and which uses a batch-type heat treatment furnace which is cylindrical in shape, and the inside of which has been divided into a plurality of heating zones along the length-wise direction thereof, and both ends of which have been blocked. The end-most sections of the heat treatment furnace are divided into a plurality of heating zones which are shorter in length than the heating zones which are not in the end most sections, and a heat source is disposed in every heating zone. The heat treatment method comprises a series of steps: in advance, determine the heating output pattern of each heat source in each heating zone in the end-most sections, on the basis of the results of actual measured temperatures during the heating of the end sections of the material to be heat treated (step one); individually control the heating output of the heat sources during the heat treatment of the material to be heat treated, on the basis of the heating output pattern of each heat source, as determined in step one, and the results of measuring the inside-furnace temperature of each heating zone in the end-most sections and the other heating zones (step two). This heat treatment method enables material to be heat treated to be accurately and evenly heated along the entire length thereof, even in heat treatment furnaces which do not have heat sources in both end walls.

Description

Heat treatment method for long material, method for producing long material, and heat treatment furnace used in those methods

INDUSTRIAL APPLICABILITY The present invention is used when performing a heat treatment method for a long material capable of heat-treating a material longer than conventional materials, a method for producing a long material using this heat treatment method, and a heat treatment method and a production method thereof. It relates to a heat treatment furnace.

Unless otherwise stated, the definitions of terms in this specification are as follows.
“Long material”: A long diameter metal tube, steel bar, and other long materials.
“Effective furnace length”: A furnace length corresponding to the maximum length of a heat-treated material that can be heat-treated at a uniform temperature in a heat treatment furnace.
“Inclined heating”: When a material to be heat-treated is heated using a long cylindrical batch-type heat treatment furnace closed at both ends, the heat treatment furnace is divided into a plurality of heating zones in the longitudinal direction, and the end of them. The heating zone is further divided into a plurality of heating zones, and each heating zone is provided with a heat source, and heating is performed with a difference in the output of each heat source provided in the heating zone at the end. To do.

Usually, a batch heat treatment furnace is used for heat treatment of a long material such as a metal tube or a steel bar.
FIG. 1 is a diagram schematically showing a schematic configuration example of a conventional long material heat treatment furnace, in which FIG. 1 (a) is a transverse sectional view and FIG. 1 (b) is a longitudinal sectional view. As shown in the figure, the heat treatment furnace is a cylindrical container closed at both ends, and the inside of the furnace is divided into a plurality of heating zones in the longitudinal direction. The peripheral wall of the furnace has a double structure made up of the water-cooled wall 2 and the heat shield wall 3, and both end walls of the furnace also have a double structure made up of the water-cooled wall 7 and the heat shield wall 8. On the inner peripheral surface of the peripheral wall of the furnace, an electric heater 1 is disposed as a heat source for each heating zone. However, the heater 1 is not provided in the both end walls of the furnace.

In the heat treatment of the long material, the material to be heat-treated 5 placed on the carriage 4 is inserted into the space surrounded by the electric heater 1 in the heat treatment furnace, that is, the heating zone, and heated by the heater 1. Done. The heat treatment temperature is controlled by individually controlling the output of each heater 1 based on the temperature measurement result in the furnace by a thermometer provided 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 peripheral wall of the furnace, but since no heat sources are provided on both end walls of the furnace, The heat is removed from the part, and the temperature of the end part is greatly reduced as compared with the central part. Since this temperature drop occurs, the length of the long material that can be heat-treated is restricted in the conventional heat treatment furnace, and the effective furnace length is shortened.

Therefore, the space length in the furnace, that is, the total length of the portion where the heater is disposed is secured sufficiently longer than the length of the material to be heat treated, and the effective furnace length is designed to be equal to or longer than the length of the material to be heat treated. ing.

However, when heat-treating longer materials than before, if the length of the heat treatment furnace is increased in order to increase the effective furnace length, the cost of equipment modification increases accordingly. In addition, when the furnace length is not lengthened, the length of the material to be heat-treated has to be shortened, and the demand of the customer cannot be flexibly handled. Conventional heat treatment furnaces have these problems.

As a temperature control method for the material to be heat-treated, the following method has been proposed.
For example, in Patent Document 1, in a batch-type heat treatment furnace in which a plurality of burners are burned to heat-treat an object to be heated contained in the furnace, feedback control is performed so that the temperature in the combustion zone of each burner becomes constant. On the other hand, by limiting the target temperature in the combustion zone to a predetermined constant value when the temperature in the furnace reaches a predetermined temperature range before the target temperature is reached, the temperature in the furnace is reduced. A method of controlling to a constant temperature is disclosed.

In Patent Document 2, in a vacuum furnace having openings for allowing processed products to enter and exit from the front and rear surfaces, the heat generation amount of the lower heater and the heat generation amounts of the front and rear zones and the intermediate zone of the upper heater can be controlled independently of each other. A temperature control method is disclosed. In a vacuum furnace, the treated product is heated by radiation heating from the heater, and there is almost no convection heating, so it is difficult to heat the treated product uniformly, and this non-uniform heating may cause poor quality. This is to deal with this problem.

However, these temperature control methods are based on the detected furnace temperature in order to maintain the furnace temperature at an appropriate temperature or to prevent temperature fluctuations in the furnace by following the temperature change. The heat source (burner and heater) is controlled independently, and it does not take into account the type of material to be heat-treated and the interference between heat sources, and is not sufficient as a method for controlling the temperature inside the furnace. It was. Therefore, the following methods that take them into consideration have been proposed.

In Patent Document 3, in the heating furnace in which the heaters respectively arranged in the heating zones divided into a plurality are controlled in temperature independently, the deviation value between the measured temperature of each heater and the set temperature given to each heater is A heating furnace temperature control method is disclosed in which a correction value that gives a heater output distribution peculiar to a furnace in a soaking zone is multiplied by time alone or as a function of time and temperature, and this is given as a heater output control value.

Further, Patent Document 4 includes a plurality of heaters for heating a material to be processed, and a heating value adjuster is individually provided in the power supply path of each heater, and the temperature detection provided in the heating value adjuster and the furnace. A control method using a vacuum furnace in which individual deviation setting devices are provided so as to allow deviations in the calorific values of a plurality of heaters is disclosed. In the control method disclosed in Patent Document 4, the set values of the deviation setting devices obtained in advance according to the type (size, shape, etc.) of the material to be processed, the pressure of the atmospheric gas, and the temperature during heating. By changing the above, the heating values of a plurality of heaters are controlled with deviations from each other by the detection value from one temperature detector. As a result, as in the case where a plurality of heaters are individually controlled, heating can be performed in a state where the temperature of the entire material to be processed is uniform.

In these methods, in addition to the conventional temperature control in which individual burners and heaters are controlled independently, by setting a deviation value for each heating zone, the temperature distribution in the furnace throughout the material to be heat treated should be made uniform. It is what. However, as shown in FIG. 1, in a heat treatment furnace in which a heat source is provided on the peripheral wall corresponding to each heating zone, but no heat source is provided on both end walls, the end of the long material is at the center. As a result, a significant temperature drop occurs, which is insufficient as a method for uniformizing the processing temperature of a long heat-treated material such as a long material.

Japanese Patent Laid-Open No. 62-4828 Japanese Patent Application Laid-Open No. 5-271751 JP-A-62-112726 JP-A-4-52215

In the cylindrical batch type heat treatment furnace in which both ends are closed and a heat source is disposed on the peripheral wall, but no heat source is provided on both end walls, the entire length of the material to be heat treated is a uniform temperature (for example, a target temperature). On the other hand, a longer effective furnace length that can be heated to ± 10 ° C. or less is ensured, and even if the space length in the furnace is the same, a long heat treatment material can be heat-treated compared to the conventional one. It is an object of the present invention to provide a heat treatment method for a scale material and a method for producing a long material using this heat treatment method. Moreover, an object of this invention is to provide the heat processing furnace used when implementing those heat processing methods and manufacturing methods.

In order to solve the above-mentioned problems, the present inventors first used a conventional heat treatment furnace in which heat sources are not provided on both end walls, and in this case, the temperature of the material to be heat treated (long material), particularly at both ends. The distribution was investigated.

FIG. 2 is a diagram showing an example of a temperature distribution in the longitudinal direction of a material to be heat-treated in a conventional long material heat treatment furnace. This is a result of measurement using the conventional heat treatment furnace shown in FIG. 1, and shows measurement results in the heating zone at the extreme end of the furnace and the heating zone next to the heating zone at the extreme end. . In FIG. 2, the material temperature on the vertical axis is displayed as a temperature difference with respect to the target temperature.

As shown in FIG. 2, the material temperature located in the heating zone next to the extreme end from the vicinity of the center of the extreme heating zone was the target temperature or a temperature close thereto. However, the temperature of the material in the portion near the end wall of the furnace from the center of the heating zone at the extreme end did not reach the target temperature and was lower by about 80 ° C. near the end wall of the furnace. Although not shown in FIG. 2, the same tendency was observed in the heating zone at the extreme end on the opposite side of the heat treatment furnace. That is, the conventional heat treatment furnace shown in FIG. 1 cannot perform uniform heating over the entire length of the material to be heat treated.

In actual operation, as shown in FIG. 2, the position of the end of the material to be heat treated (long material) is near the center of the heating zone at the end of the furnace (in this example, the end of the heat treating furnace). It is 1.4m from the wall) and is considered to fall within the range of the effective furnace length.

In order to eliminate the temperature drop at the end of the heat-treated material, the entire heating zone at the end of the heat treatment furnace is heated higher than the central heating zone (heating zone other than the heating zone at the end) The material temperature was measured.

FIG. 3 is a view showing the temperature distribution in the longitudinal direction of the material to be heat-treated in a conventional long material heat treatment furnace, and the heating zone at the end is the central heating zone (here, the heating zones at both ends). The temperature is higher than that of the heating zone between the two. FIG. 3 shows the measurement results in the heating zone at the extreme end of the furnace and the heating zone next to the heating zone at the extreme end.

During the test, the temperature of the heat-treated material in the central heating zone is set to the target temperature, and the temperature of the heat-treated material in the outermost heating zone is set to the temperature of the heat-treated material in the next heating zone at the outermost portion. Was also set 20 ° C. or 40 ° C. higher. For comparison, the heating zone at the extreme end was also set to the same target temperature as the central heating zone.

As shown in FIG. 3, the temperature of the material to be heat-treated exceeds the target temperature in the vicinity of the center of the heating zone at the extreme end, while the temperature decreases at the end of the material to be heat-treated near the end wall of the furnace. It still remains, and uniform heating over the entire length of the material to be heat treated has not been made.

Subsequently, a heat shield plate is installed outside the end face of the material to be heat treated to suppress heat removal from the end of the material, and the heating zone at the extreme end of the furnace and the next heating at the extreme end adjacent thereto A method of applying heat to the zone in an inclined manner was studied. This is because significant overheating of the heat-treated material can be prevented in the vicinity of the center of the heating zone at the extreme end, and the temperature decrease of the heat-treated material can be expected.

FIG. 4 is a diagram showing a schematic configuration of a heat treatment furnace provided with a heat shield, wherein FIG. 4 (a) is a transverse sectional view and FIG. 4 (b) is a longitudinal sectional view. In the heat treatment furnace shown in the figure, twelve heat shield plates 9 made of SUS304 are placed on the outside of the end face of the heat treated material placed on the carriage 4. Using this heat treatment furnace, the material temperature was measured when the heating amount in the heating zone at the extreme end was slightly increased relative to that in the heating zone next to the extreme end.

FIG. 5 shows the results of measuring the temperature distribution of the material to be heat treated (long material) in the heating zone at the extreme end and the heating zone next to the extreme end using a heat treatment furnace provided with this heat shield. FIG. For comparison, the case where the heating amount of the heating zone at the endmost portion and the heating zone next to the endmost portion are the same is also shown.

From the results shown in FIG. 5, when the allowable range of the temperature distribution over the entire length of the material to be heat treated is set to ± 10 ° C. or less with respect to the target temperature, the heat input of the heating zone at the extreme end is set to the heating zone next to the extreme end By slightly increasing it, the overheat of the heat-treated material is suppressed below the upper limit of the allowable range in the vicinity of the center of the heating zone at the end, and the temperature drop at the end of the heat-treated material is avoided. It can be seen that the heat-treated material can be heated uniformly.

However, in this heat treatment furnace, a cooling gas is introduced from the end wall of the furnace after the treatment to cool the material to be heat treated. However, the gas is blocked by the heat shield plate 9, the cooling rate is reduced, and the time required for the cooling is conventional. There was a problem that it was about 2 to 3 times longer. Moreover, it is necessary to consider the number of installed heat shield plates and the installation location depending on the number and size of materials loaded on the cart, and this is not a realistic method.

Therefore, the present inventors divided the heating zone at the extreme end of the furnace shorter than the length of the central heating zone, arranged a heat source in each of the divided heating zones, and heated the heating at the extreme end. By heating only the zone in an inclined manner (inclined heating), an attempt was made to make the temperature of the heat-treated material located in the heating zone at the endmost portion equal throughout the heating zone at the endmost portion. That is, the application of a method for controlling the temperature of the end portion of the material to be heat-treated (hereinafter referred to as “divided gradient heating control method”) by changing the heating output to be applied to the heat source between the individual heating zones divided.

Since the number of heating zones does not affect the solution of the problem according to the present invention, hereinafter, for convenience of explanation, the heating zone at one end is referred to as “m zone” and the heating zone at the opposite end as “n”. “Zone” is also displayed.

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

In FIG. 6, “after remodeling” is a case where gradient heating is performed using a heat treatment furnace in which the m zone is divided into three parts, and “before remodeling” is using the same three-part heat treatment furnace. However, this is the case of the conventional heating method in which the heating amounts in the m-1 zone, the m-2 zone, and the m-3 zone are made uniform and no gradient heating is performed. It should be noted that the rate of increase in the heating amount with respect to the m-1 zone after remodeling was set to + 35% with reference to the result of examination by heat transfer simulation shown in FIG. 7 described later.

As apparent from the results shown in FIG. 6, by applying the divided gradient heating control method in the heating zone at the extreme end of the furnace, the overheating of the end of the heat-treated material is suppressed within an allowable range, and the end It can be seen that the whole material to be heat treated can be heated uniformly while avoiding the temperature drop at.

FIG. 7 is a result of examination by a heat transfer simulation, and is a diagram showing a relationship between an increase in heat input to the m-1 zone and an uneven heat when the divided gradient heating control method is applied. Here, “biased heat” is the difference between the highest value and the lowest value in the temperature distribution of the heat-treated material in the m zone and the heating zone next to the m zone. As shown in FIG. 7, when the amount of heat input to the m-1 zone is 0 (that is, the conventional heating method in which gradient heating is not performed), the partial heat is about 80 ° C., whereas gradient heating is performed. When this is done, the partial heat is reduced, and when the heat input increase is + 35%, a minimum value of 10 ° C. is shown.

In the above, the case where the m zone is divided into three and heated by the gradient has been described. In general, the heating zone (m zone and n zone) at the extreme end of the furnace is divided shorter than the length of the central heating zone, and this division is performed. It has been found that by controlling the heating output of each individual heating zone, the entire length of the heat-treated material including the ends can be heated to a uniform temperature. Thereby, even if the space length in the furnace is the same, the effective furnace length can be greatly expanded.

As described above, the control of the heating power of each heating zone divided by the heating zone at the extreme end of the furnace is based on the actual temperature measurement result at the end of the heat-treated material during heating. The ratio of the output of each heat source in each heating zone at the endmost part of the furnace (hereinafter referred to as “heating output pattern”) is determined in advance so that the temperature of the furnace becomes equal throughout the heating zone at the endmost part of the furnace. Can be done.

The present invention has been made on the basis of such knowledge, and the gist thereof is the following (1) the heat treatment method for the long material, (2) the method for producing the long material, and the heat treatment method and It exists in the heat processing furnace of (3) used for a manufacturing method.

(1) Using a cylindrical batch heat treatment furnace whose both ends are closed and the inside is divided into a plurality of heating zones in the longitudinal direction, heat treatment is performed by inserting a long heat-treated material into the heat treatment furnace. A heat treatment method for a long material,
In the heat treatment furnace, the heating zone at the endmost portion of the heating zones is divided into a plurality of heating zones shorter than the length of the heating zone other than the endmost portion, and a heat source is provided in each heating zone. And
The heat treatment method is as follows:
(Step 1) Predetermining the heating output pattern of each heat source in each heating zone at the endmost part based on the actual temperature measurement result at the end of the material to be heat-treated at the time of heating,
(Step 2) During the heat treatment operation of the material to be heat-treated, the heating output pattern of each heat source determined in Step 1 and further the temperature measurement result in the furnace of each heating zone at the extreme end and the heating zone other than the extreme end To control the heating output of individual heat sources,
Including a series of steps,
The heat processing method of the elongate material characterized by these.

In the heat treatment method for a long material according to the present invention, in step 2, the heating output of each heat source in each heating zone at the extreme end is adjusted based on the actual temperature measurement result at the end of the heat treatment material during the heat treatment operation. By doing so, it becomes possible to control the temperature of the heat-treated material with higher accuracy.

In the long material heat treatment method of the present invention, if an electric heater is used as a heat source in

steps

1 and 2, the heating output pattern can be easily adjusted, and if the heat treatment material is radiantly heated. Easy to perform accurate temperature control.

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

(3) A batch-type heat treatment furnace for a long material 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-treated material is inserted and heat-treated. ,
The heat treatment furnace
Of the heating zones, the heating zone at the endmost part is divided into a plurality of heating zones that are shorter than the length of the heating zone other than the endmost part, and a heat source is provided in each heating zone,
Means for determining a heating output pattern of each heat source in each heating zone at least at the extreme end;
Means for measuring the temperature in the furnace of each heating zone at the extreme end and the heating zone other than the extreme end;
Means for controlling the heating output of each heat source for each heating zone,
A heat treatment furnace for long materials.

If the long material heat treatment furnace of the present invention further has means for measuring the actual temperature of the end of the material to be heat treated, temperature control of the material to be heat treated can be performed with higher accuracy.

In the heat treatment furnace for the long material of the present invention, if the heat source is an electric heater, the heating output pattern can be easily adjusted, and if the heat treatment of the heat-treated material is by radiant heating, accurate temperature control is performed. Easy to do.

According to the heat treatment method for a long material of the present invention, heat treatment is performed using a cylindrical batch heat treatment furnace in which both ends are closed and a heat source is provided on the peripheral wall, but no heat source is provided on both end walls. When performing, even if the space length in the furnace is the same, a longer effective furnace length can be ensured, and a long heat-treated material can be accurately heated to a uniform temperature over the entire length. Thereby, the equipment modification cost of a furnace body 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 can manufacture the elongate material without a quality characteristic variation.
If the long material heat treatment furnace of the present invention is used, the heat treatment method and the long material manufacturing method of the present invention can be easily carried out.

FIG. 1 is a diagram schematically showing a schematic configuration example of a conventional long material heat treatment furnace, in which FIG. 1 (a) is a transverse sectional view and FIG. 1 (b) is a longitudinal sectional view. FIG. 2 is a diagram illustrating an example of a temperature distribution in a longitudinal direction of a heat-treated material in a conventional long-length heat treatment furnace. FIG. 3 is a diagram showing an example of the temperature distribution in the longitudinal direction of the heat-treated material in this case where the heat treatment furnace of the longest material is used to raise the heating zone at the endmost part from the central heating zone. is there. 4A and 4B are diagrams showing a schematic configuration of a heat treatment furnace provided with a heat shield plate. FIG. 4A is a transverse sectional view, and FIG. 4B is a longitudinal sectional view. FIG. 5 is a diagram showing the results of measuring the temperature distribution of the heat-treated material in the heating zone at the extreme end and the heating zone next to the extreme end using a heat treatment furnace provided with a heat shield. FIG. 6 is a diagram illustrating measurement results of the temperature distribution of the heat-treated material in the m zone and the heating zone next to the m zone when the divided gradient heating control method is applied. FIG. 7 is a result of examination by a heat transfer simulation, and is a diagram showing a relationship between an increase in heat input to the m−1 zone and an uneven heat when the divided gradient heating control method is applied. FIGS. 8A and 8B are diagrams illustrating a schematic configuration of a heat treatment furnace used in the heat treatment method for a long material according to the present invention. FIG. 8A is a transverse sectional view, and FIG. 8B is a longitudinal sectional view. FIG. 9 is a diagram showing the attachment position of the thermocouple to the heat-treated material charged in the heat treatment furnace in the example. FIG. 10 is a diagram illustrating an example of a temperature measurement result of the end portion of the heat-treated material during heating, which is the result obtained in the example.

1. Heat Treatment Method for Long Material The heat treatment method for a long material according to the present invention uses 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 as described above. The heating zone at the extreme end of the heat treatment furnace is divided into a plurality of heating zones that are shorter than the length of the heating zone other than the extreme end, and each heating zone is provided with a heat source.

Steps

1 and 2 are included.
(Step 1) Predetermining the heating output pattern of each heat source in each heating zone at the endmost part based on the actual temperature measurement result at the end of the material to be heat-treated at the time of heating,
(Step 2) During the heat treatment operation of the material to be heat-treated, the heating output pattern of each heat source determined in Step 1 and further the temperature measurement result in the furnace of each heating zone at the extreme end and the heating zone other than the extreme end Based on the control of the heating output of individual heat sources.

FIG. 8 is a diagram illustrating a schematic configuration of a heat treatment furnace used in the heat treatment method for a long material of the present invention, where FIG. 8 (a) is a cross-sectional view and FIG. 8 (b) is a vertical cross-sectional view. is there. This heat treatment furnace has three heating zones, namely, m-1 zone, m-2 zone and m-3 zone, among the plurality of heating zones shown in FIG. The heat treatment furnace is divided into heating zones, and the heating zone at the extreme end on the opposite side, that is, the n zone, is divided into three heating zones, an n-1 zone, an n-2 zone, and an n-3 zone.

As shown in FIG. 8, this heat treatment furnace is a cylindrical container with both ends closed, and the peripheral wall of the furnace has a double structure comprising a water-cooled wall 2 and a heat shield wall 3, and both end walls of the furnace. Also, a double structure comprising the water cooling wall 7 and the heat shield wall 8 is adopted. On the inner peripheral surface of the peripheral wall of the furnace, an electric heater 6 is disposed 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 heating zones (m zone and n zone) at the extreme end are shorter than the length of the central heating zone. m-3 zone, and n-1 zone, n-2 zone, and n-3 zone), for example, as shown in FIG. When the entire heating zone is heated, the temperature of the heat-treated material is overheated near the center of the heating zone at the outermost end, and the temperature is lowered at the end of the heat-treated material near the end wall of the furnace. This is because uniform heating is not possible.

That is, in the heat treatment furnace of the present invention, the endmost heating zone is divided into a plurality of heating zones because the endmost heating zone is subdivided and the output ratio of each heat source in each divided heating zone This is so that the adjustment can be made. The number of divisions of the heating zone at the end of the furnace is 3 in both the m zone and the n zone in the heat treatment furnace illustrated in FIG. 8, but the state of temperature drop in the heating zone at the end is grasped in advance. In addition, it may be determined appropriately based on that.

The heating output pattern of each heat source in each heating zone at the extreme end is determined based on the actual temperature measurement results at the end of the heat-treated material during heating in advance. It is to do.

The above-described actual temperature measurement of the material to be heat treated corresponds to the temperature measurement in each heating zone constituting the heating zone at the end of the furnace, and is measured by attaching a thermocouple to a predetermined part at the end of the material to be heat treated. Can be warmed. By this actual temperature measurement, the temperature measurement result at the end of the material to be heat-treated (the portion that mainly receives heat from each heat source in each heating zone) is obtained in advance corresponding to each heating zone at the end most shortly divided. Then, based on this, the heating output pattern (output ratio of the individual heat sources) of each heat source in the divided individual heating zones is determined.

As a desirable example of the heating output pattern, as shown in FIGS. 6 and 7, the m zone at the extreme end of the furnace is divided into three, and the increase in heat input in the m-1 zone is + 35%. Pattern. Thereby, it can be expected that the uneven heat of the heat-treated material in the m zone and the heating zone next to the m zone is suppressed to about 10 ° C. or less.

During the heat treatment operation of the long material, the heating output pattern of each heat source determined as described above, and each heating zone at the extreme end of the furnace and the central heating zone (heating zones other than the heating zone at the extreme end) The reason why the heating output of each heat source is controlled based on the temperature measurement result in the furnace is to accurately heat the entire length of the heat-treated material to a uniform temperature.

That is, for each heating zone at the outermost end of the furnace, heating is performed with the heating output pattern determined and set in advance as described above, and further, other than each heating zone at the outermost end of the furnace and the heating zone at the outermost end. The heating output of each heat source is controlled in consideration of the temperature measurement result in the heating zone. Thereby, the fluctuation | variation of the furnace temperature resulting from the fluctuation | variation of the number of to-be-processed materials, the arrangement | positioning in a furnace, etc. can be suppressed, and the precision of the uniform heating of the to-be-processed material full length including an edge part can be improved.

In each heating zone at the extreme end of the furnace, a heating output pattern is set in advance, but the heating output is changed by the heating output control based on the temperature measurement result in the furnace during the actual heat treatment. The output pattern may deviate from a preset pattern.

By the way, in the temperature equalization method of the material to be processed described in the above-mentioned Patent Document 4, the temperature control is performed after changing the set value of each deviation setting device obtained in advance according to the type of the material to be processed at the time of heating. Therefore, it can be said that there is a similarity with the heat treatment method of the present invention.

However, the method described in Patent Document 4 is mainly intended to control the temperature control of a plurality of heating zones with the detection value of one thermometer by using a deviation setting device provided in each zone. It is. 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 extreme end is divided to set the heating output pattern in advance, This is a method of controlling the heating output of the heat source in each heating zone in consideration of the temperature measurement result, and is clearly different from the method described in Patent Document 4.

Further, in the method described in Patent Document 4, control is performed with a constant set value during the heat treatment, whereas in the present invention, there is a case where it gradually deviates from a preset heating output pattern. .

In the heat treatment method for a long material according to the present invention, the heating output of each heat source in each heating zone at the extreme end of the furnace is adjusted based on the actual temperature measurement result at the end of the heat treated material during the heat treatment operation. Can take form. The actual temperature measurement at the end of the material to be heat-treated is measured by attaching a thermocouple to the end of the material to be heat-treated at the time of actual heat treatment.

In actual heat treatment, the number of materials to be heat-treated and the arrangement in the furnace differ, so after starting heat treatment with a predetermined heating power pattern, each heating zone at the extreme end of the furnace and heating at the extreme end The heating output of each heat source is controlled based on the in-furnace temperature measurement result of the heating zone other than the zone.

However, in the heat treatment method for a long material of the present invention, it is possible to further adopt a mode in which the heating output of the heat source of each heating zone is adjusted based on the actual temperature measurement result at the end of the heat treated material. This adjustment may have various modes depending on the temperature measurement result, for example, when adjusting all of the heating zones at the extreme end divided shortly, or adjusting only one of them.

By adopting this embodiment, temperature variation at the end of the material to be heat-treated can be further reduced, and temperature control of the material to be heat-treated can be performed with higher accuracy.

In the long material heat treatment method of the present invention, an electric heater is preferably used as a heat source for heating the heat treated material. As the heat source, a burner, a radiant tube, or the like can be applied. However, heating with an electric heater is preferable because the heating output pattern can be easily adjusted.

Further, in the heat treatment method for a long material of the present invention, if the material to be heat treated is radiant heating, it is easy to perform accurate temperature control. However, as in the heat treatment method of the present invention, when only the end of the material to be heat treated is controlled with a predetermined heating output pattern, if convection occurs in the furnace, heating is performed even if the heating output pattern is determined. It is not performed as it is, and accurate control becomes difficult.

Therefore, the heat treatment method of the present invention is preferably applied to control in a vacuum heat treatment furnace or control in a heat treatment furnace by radiant heating in a gas atmosphere having a small heat capacity such as hydrogen gas. Among them, hydrogen gas is difficult to manage, so it can be said that it is more desirable to apply it to control in a vacuum heat treatment furnace.

According to the above-described heat treatment method for a long material of the present invention, when a cylindrical batch type heat treatment furnace in which both ends are closed and a heat source is provided on the peripheral wall but no heat source is provided on both end walls is used. In addition, even if the space length in the furnace is the same, it is possible to secure a longer effective furnace length, and heat the heat-treated material that is longer than the conventional one to a uniform temperature over the entire length. Can do.

In the long material heat treatment method of the present invention, the heating zone at the extreme end of the furnace may be divided at either extreme end, and the above-described effects can be obtained at the divided side.

2. Manufacturing method of long material The manufacturing method of the long material of this invention is a manufacturing method characterized by performing heat processing using the heat processing method of the long material of this invention mentioned above.

That is, in the production of a long material that is usually performed, only the heat treatment step is performed using the heat treatment method of the present invention, and the other steps are performed according to conventional methods.

According to the method for producing a long material of the present invention, the heat treatment step can heat the entire length of the material to be heat-treated to a uniform temperature for a longer heat treatment material than before, so that the mechanical properties and corrosion resistance can be increased. It is possible to produce long materials with no variation in quality characteristics such as.

3. Heat treatment furnace for long material The heat treatment furnace for 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. A long-type batch-type heat treatment furnace for heat treatment, which is characterized by the following configuration. That is, in the heat treatment furnace of the present invention, the heating zone at the end of the heating zone is divided into a plurality of heating zones shorter than the length of the heating zone other than the end, and a heat source is arranged in each heating zone. It is installed. The heat treatment furnace of the present invention includes at least means for determining a heating output pattern of each heat source in each heating zone at the endmost part, each heating zone at the endmost part, and a furnace in a heating zone other than the endmost part. Means for measuring the internal temperature, and means for controlling the heating output of each heat source for each heating zone.

The long material heat treatment furnace of the present invention is exemplified by the schematic configuration shown in FIG. In the configuration illustrated in the figure, any of the heating zones (m zone and n zone) at both ends of the furnace is divided shortly, but heat treatment in which one of the heating zones at the extreme end is divided. It may be a furnace.

In the heat treatment furnace of the present invention, the heating zone at the extreme end is divided shorter than the length of the central heating zone, as described in the heat treatment method of the invention, and the heating zone at the extreme end is divided short. In order to adjust the output ratio of each heat source disposed in each of the divided heating zones.

In the heat treatment furnace of the present invention, the reason for having a means for determining the heating output pattern of each heat source in at least each heating zone at the extreme end is to uniformly heat both ends of the long material. Note that “at least” means that there may be means for determining a heating output pattern including a heating zone other than the heating zones that are divided into short parts.

In determining the heating output pattern, first, as a procedure, first, a temperature measurement result at the end of the material to be heat-treated is obtained in advance corresponding to each heating zone constituting the heating zone at the outermost end of the furnace. However, the actual temperature measurement result is obtained in advance by attaching a thermocouple to the end of the heat-treated material and measuring the temperature. Next, based on the actual temperature measurement result, the heating output pattern (output ratio of each heat source) of each heat source in each heating zone at the extreme end of the furnace is determined by the operator. It is possible to set based on the actual temperature measurement result.

Also, for example, an output pattern setting device is attached to the heat treatment furnace, and the relationship between the actual temperature measurement result and the heating output pattern to be set is input in advance, and the output pattern setting device receives the signal of the temperature measurement result. It is also possible to select a proper heating output pattern based on the individual temperature measurement results and to give an output instruction to each heat source in each heating zone.

Therefore, as the means for determining the heating output pattern, a method of artificially determining the thermocouple attached to the heat-treated material and the actual temperature measurement result, or a method of automatically determining by the output pattern setting device, etc. Can be mentioned.

In the heat treatment furnace of the present invention, there are means for measuring the furnace temperature of each heating zone other than the endmost part and the heating zone other than the endmost part, and means for controlling the heating output of each heat source for each heating zone; The reason for this is to control the heating output of the heat source of each heating zone to suppress the fluctuation of the furnace temperature during the heat treatment and to improve the accuracy of uniform heating over the entire length of the heat-treated material including the end. .

As the furnace temperature measuring means for each heating zone, a temperature detector conventionally used for measuring the furnace temperature may be used. An example is a thermocouple.

As the heating output control means, an output controller that inputs a target value of the furnace temperature in advance and outputs a control signal to the heat source while performing PID control by comparing the signal from the temperature detector with the target temperature. Etc. can be used.

The temperature measuring means includes a thermocouple that can be attached to the end of the material to be heat-treated during actual heat treatment.

If the heat treatment furnace for a long material of the present invention described above is used, the heat treatment method and the method for producing a long material of the present invention can be easily carried out.

In addition, the aspect 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 using an electric heater as a heat source is adopted:
(1) During heat treatment, first, the furnace temperature in the central heating zone excluding the heating zone at the extreme end of the furnace is set to the initial target temperature (temperature lower than the material temperature finally required for the material to be heat treated). Control all at once;
(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 (the material temperature finally required for the material to be heat treated);
(3) With respect to the heating zone at the extreme end of the furnace, gradient heating is controlled with a heating output pattern determined and set in advance by a divided gradient heating control method;
(4) Finely adjust the furnace temperature in each heating zone so that the temperature of the material to be heat-treated becomes a control value.

Using the heat treatment furnace of the present invention having the configuration shown in FIG. 8, a metal tube was inserted into the furnace as a long heat-treated material (long material) and heated by applying the heat treatment method of the present invention. The temperature distribution at the end of the material to be heat treated was investigated. For comparison, the same investigation was performed when the conventional heat treatment method was applied.

The heat treatment furnace used 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 the one endmost part is divided into the m-1 zone, the m-2 zone and the m-3 zone in order from the end, and the n zone which is the opposite end part is the end zone. Are divided into n-1, n-2 and n-3 zones in order. Each of the heating zones constituting the m-zone and n-zone at the extreme end has a length after division of 1 m.

In this heat treatment furnace, the heat treatment material is arranged so that the tube end of the heat treatment material is located in the m-1 zone, which is the end of the m zone, and a pitch of 200 mm starting from a position of 600 mm from the end wall of the furnace. Then, thermocouples were attached to a total of four places, ie, a total of five places, 1500 mm from the end wall.

FIG. 9 is a diagram showing the attachment position of the thermocouple. Also in the n zone, thermocouples were attached to a total of five locations of the heat-treated material in the same manner as in the m zone. Circled numbers 1 to 5 and 6 to 10 in FIG.

The output of each heat source in each of the three heating zones (m-1, m-2, and m-3) divided into three zones is the same as the output in the central heating zone, that is, each of the central heating zones Heating was started at an output ratio of 100% with respect to the heat source, and in the middle, 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% (m-3 zone). The output ratio is not changed and remains 100%).

That is, in the test of the example, the divided gradient heating control method adopted in the heat treatment method of the present invention was applied. The output ratio here was determined and set based on the actual temperature measurement result of the heat-treated material obtained in advance. In addition, also in the n zone, the power ratio was changed in the same way during the heating, and the heating was performed.

FIG. 10 shows an example of the temperature measurement result at the end of the heat-treated material. FIG. 10 is a chart in which the temperature measurement results of the heat-treated material are automatically recorded. The circled numbers 1 to 10 shown in FIG. 10 are measured by thermocouples at the respective attachment positions shown in FIG. Represents the material temperature.

As shown in FIG. 10, after the start of heating (temperature increase) and before the change of output (inclined heating start), among the temperatures measured by individual thermocouples, the measured temperature was measured particularly near the end. The temperature of the heat-treated material (circled

numbers

1, 2 and 6, 7) deviated greatly from the target temperature ± 10 ° C., and the difference from the target temperature was about 50 ° C. at the maximum.

During the heating, after changing the output given to the heat source of the m-1 zone and the m-2 zone as described above and starting the gradient heating, as indicated by the ellipse mark (broken line) in FIG. It can be seen that the temperature of the material to be heat-treated is suppressed to within ± 10 ° C. with respect to the target temperature at any temperature measurement location.

FIG. 6 is a diagram obtained by organizing an example of the temperature measurement result at the end of the heat-treated material thus performed. When the output ratio of each of the heating zones (m-1, m-2, and m-3) divided into 3 zones is 100% (remodeled with white squares (□) in the figure) “Previous” is a position near the end of the heat-treated material (near the center of the m-1 zone), and there was a temperature difference of about 45 ° C. from the heating zone next to the m zone. In contrast, when the heat treatment method of the present invention is applied (indicated by black circles (●) in the figure, “after remodeling”), the temperature difference between 7 ° C. and the next heating zone after the m zone. It can be seen that is greatly reduced.

From the results of FIG. 10 and FIG. 6, further, by applying the heat treatment method of the present invention, a longer effective furnace length is ensured in a cylindrical batch heat treatment furnace in which no heat source is provided on both end walls. It was confirmed that temperature control within ± 10 ° C. with respect to the target temperature can be sufficiently performed over the entire length including the end of the heat-treated material of the scale.

According to the heat treatment method for a long material of the present invention, it is possible to secure a longer effective furnace length and to heat a long heat-treated material to a uniform temperature with high accuracy over the entire length.
According to the method for producing a long material of the present invention using this heat treatment method, it is possible to produce a material having no variation in quality characteristics such as mechanical characteristics and corrosion resistance. Moreover, if the heat processing furnace of the long material of this invention is used, the heat processing method and manufacturing method of this invention can be implemented easily.
Therefore, the heat treatment method of the present invention, the production method of the long material of the present invention to which this method is applied, and the heat treatment furnace of the present invention can be effectively used for heat treatment and production of the long material.

1: Electric heater, 2: Water cooling wall, 3: Heat shield wall,
4: Cart, 5: Heat-treated material, 6: Electric heater,
7: Water cooling wall, 8: Heat shield wall, 9: Heat shield plate

Claims

Using a cylindrical batch heat treatment furnace whose ends are closed and the inside is divided into a plurality of heating zones in the longitudinal direction, a long material to be heat-treated by inserting a long heat-treated material into the heat treatment furnace A heat treatment method of
In the heat treatment furnace, the heating zone at the endmost portion of the heating zones is divided into a plurality of heating zones shorter than the length of the heating zone other than the endmost portion, and a heat source is provided in each heating zone. And
The heat treatment method is as follows:
(Step 1) Predetermining the heating output pattern of each heat source in each heating zone at the endmost part based on the actual temperature measurement result at the end of the material to be heat-treated at the time of heating,
(Step 2) During the heat treatment operation of the material to be heat-treated, the heating output pattern of each heat source determined in Step 1 and further the temperature measurement result in the furnace of each heating zone at the extreme end and the heating zone other than the extreme end To control the heating output of individual heat sources,
Including a series of steps,
The heat processing method of the elongate material characterized by these.
In step 2,
Adjusting the heating output of each heat source in each heating zone at the extreme end based on the actual temperature measurement result at the end of the material to be heat treated during the heat treatment operation,
The heat processing method of the elongate material of Claim 1 characterized by these.
In steps 1 and 2, using an electric heater as the heat source,
The heat treatment method for a long material according to claim 1 or 2.
The heating of the heat-treated material is radiant heating,
The method for heat-treating a long material according to any one of claims 1 to 3, wherein:
Performing a heat treatment using the heat treatment method according to any one of claims 1 to 4,
A method for producing a long material characterized by the above.
A batch-type heat treatment furnace of a long material 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-treated material is inserted to perform heat treatment,
The heat treatment furnace
Of the heating zones, the heating zone at the endmost part is divided into a plurality of heating zones shorter than the length of the heating zone other than the endmost part, and a heat source is provided in each heating zone,
Means for determining a heating output pattern of each heat source in each heating zone at least at the extreme end;
Means for measuring the temperature in the furnace of each heating zone at the extreme end and the heating zone other than the extreme end;
Means for controlling the heating output of each heat source for each heating zone,
A heat treatment furnace for long materials.
Furthermore, having means for measuring the actual temperature of the end of the material to be heat treated,
The long material heat treatment furnace according to claim 6.
The heat source is an electric heater,
The long material heat treatment furnace according to claim 6 or 7.
The heating of the heat-treated material is radiant heating,
The long material heat treatment furnace according to any one of claims 6 to 8.