JP2023162459A - Heating apparatus - Google Patents

Abstract

To provide a heating apparatus capable of suppressing a generation of an oxide compound on a surface of a metal material.SOLUTION: In a heating apparatus 100, a heating part 5 performs an alloying treatment for advancing an alloying of zinc in a plating layer 43. Here, a boiling point of an alloy layer for which alloying is sufficiently advanced by the alloying treatment is higher than that of zinc. Therefore, the heating part 5 heats a metal pipe material 40 after zinc alloying such that the metal pipe material is heated to a temperature higher than a zinc boiling point. Consequently, even if a temperature of the metal pipe material 40 becomes higher than a boiling point of zinc, a firing of zinc can be prevented because an alloying state of zinc has been sufficiently advanced to have a higher boiling point. Accordingly, a generation of an oxide compound formed on a surface of the metal pipe material 40 can be prevented.SELECTED DRAWING: Figure 1

Description

The present invention relates to a heating device.

Conventionally, forming apparatuses for forming metal materials are known. For example, Patent Document 1 below includes a molding die having a lower mold and an upper mold that pair with each other, and a fluid supply section that supplies fluid into a metal pipe material held between the molding molds. A molding apparatus is disclosed. In such a molding apparatus, a heating device is used to heat the metal material to be molded.

Japanese Patent Application Publication No. 2009-220141

The heating device as in the above-mentioned prior art heats the metal material to be formed by electrical heating. Here, since the heating device heats the metal material to a high temperature, oxide scale may be generated on the surface of the metal material due to oxidation of the metal material. Therefore, by forming a plating layer on the surface of the metal material, the generation of oxide scale may be suppressed. However, if the heating device heats up rapidly, the zinc contained in the plating layer may vaporize and ignite, resulting in the generation of zinc oxide. Therefore, it has been desired to suppress the generation of oxidized compounds such as oxide scale and zinc oxide.

The present invention has been made to solve such problems, and an object of the present invention is to provide a heating device that can suppress the generation of oxidized compounds on the surface of a metal material.

A heating device according to one aspect of the present invention is a heating device that heats a metal material to be formed, and includes a heating section that heats the metal material by electrical heating, and the metal material has a plating layer containing zinc. is formed, and the heating section performs an alloying process to promote alloying of the zinc in the plating layer, and after the alloying process and after the zinc is alloyed, the heating part is heated so that the temperature becomes higher than the boiling point of zinc. Heating the metal material to.

In the heating device according to one aspect of the present invention, the heating section performs an alloying process to promote alloying of zinc in the plating layer. Here, the boiling point of the alloy layer that has been sufficiently alloyed by the alloying treatment is higher than the boiling point of zinc. Therefore, after the alloying treatment, the heating section heats the metal material to a temperature higher than the boiling point of zinc. Therefore, even if the temperature of the metal material becomes higher than the boiling point of zinc, the zinc is sufficiently alloyed to have a high boiling point, so ignition of the zinc can be suppressed. As described above, by suppressing the generation of oxide scale and also suppressing the generation of zinc oxide by the plating layer, it is possible to suppress the generation of oxide compounds on the surface of the metal material.

The heating section may heat the metal material so that the temperature of the metal material draws a temperature profile in multiple stages. In this case, the heating section can heat the metal material to an appropriate temperature profile depending on the degree of progress of zinc alloying.

The heating section may heat to describe a temperature profile of a primary heating stage, a holding stage for maintaining the temperature, and a secondary heating stage. In this case, the heating section quickly raises the temperature to the target temperature for alloying treatment in the primary heating stage, and maintains it at the target temperature in the holding stage to proceed with alloying of zinc. After the alloying process, the heating section can raise the temperature of the metal material to the final target temperature in the secondary heating stage.

The heating unit may set the target temperature in the primary heating stage to 700°C or more and 800°C or less. In this case, it is possible to prevent the zinc from igniting while alloying the zinc while avoiding the need for excessive heating time.

According to the present invention, it is possible to provide a heating device that can suppress the generation of oxide compounds on the surface of a metal material.

1 is a schematic diagram of a molding apparatus that employs a heating device according to an embodiment of the present invention. FIG. 3 is a cross-sectional view showing the state when the nozzle seals the metal pipe material. FIG. 3 is an enlarged cross-sectional view of a plating layer. It is a graph showing the temperature profile of metal pipe material. It is a table showing the values of various parameters set in heating the heating section and the generation status of zinc oxide when those values are set. It is a table showing the values of various parameters when heating the heating part with a one-stage temperature profile, and the generation status of zinc oxide when those values are set. It is a figure showing the composition of the heating part of the heating device concerning a modification.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In addition, in each figure, the same parts or corresponding parts are given the same reference numerals, and overlapping explanations will be omitted.

FIG. 1 is a schematic diagram of a molding apparatus 1 that employs a heating device 100 according to this embodiment. As shown in FIG. 1, a forming apparatus 1 is an apparatus for forming a hollow metal pipe by blow molding. In this embodiment, the molding device 1 is installed on a horizontal surface. The molding device 1 includes a molding die 2, a drive mechanism 3, a holding section 4, a heating section 5, a fluid supply section 6, a cooling section 7, and a control section 8. Note that in this specification, the metal pipe refers to a hollow article after completion of molding in the molding device 1, and the metal pipe material 40 refers to a hollow article before completion of molding in the molding device 1. The metal pipe material 40 is a hardenable steel pipe material. Moreover, among the horizontal directions, the direction in which the metal pipe material 40 extends during molding may be referred to as the "longitudinal direction", and the direction orthogonal to the longitudinal direction may be referred to as the "width direction".

The molding mold 2 is a mold for molding the metal pipe material 40 into a metal pipe, and includes a lower mold 11 and an upper mold 12 that face each other in the vertical direction (first direction). The lower mold 11 and the upper mold 12 are constructed of steel blocks. The lower mold 11 is fixed to a base 13 via a die holder or the like. The upper mold 12 is fixed to the slide of the drive mechanism 3 via a die holder or the like.

The drive mechanism 3 is a mechanism that moves at least one of the lower mold 11 and the upper mold 12. In FIG. 1, the drive mechanism 3 has a configuration that moves only the upper mold 12. The drive mechanism 3 includes a slide 21 that moves the upper mold 12 so that the lower mold 11 and the upper mold 12 are brought together, and a pull-back cylinder as an actuator that generates a force to pull the slide 21 upward. 22, a main cylinder 23 as a drive source that pressurizes the slide 21 downward, and a drive source 24 that applies a drive force to the main cylinder 23.

The holding part 4 is a mechanism that holds the metal pipe material 40 placed between the lower mold 11 and the upper mold 12. The holding part 4 includes a lower electrode 26 and an upper electrode 27 that hold the metal pipe material 40 at one end in the longitudinal direction of the molding die 2, and a lower electrode 26 and an upper electrode 27 that hold the metal pipe material 40 at the other end in the longitudinal direction of the molding die 2. 40, a lower electrode 26 and an upper electrode 27 are provided. The lower electrode 26 and the upper electrode 27 on both sides in the longitudinal direction hold the metal pipe material 40 by sandwiching the vicinity of the end of the metal pipe material 40 from above and below. Note that grooves having a shape corresponding to the outer peripheral surface of the metal pipe material 40 are formed on the upper surface of the lower electrode 26 and the lower surface of the upper electrode 27. The lower electrode 26 and the upper electrode 27 are provided with a drive mechanism (not shown), and can each independently move in the vertical direction.

The heating unit 5 heats the metal pipe material 40. The heating unit 5 is a mechanism that heats the metal pipe material 40 by applying electricity to the metal pipe material 40. The heating section 5 heats the metal pipe material 40 between the lower mold 11 and the upper mold 12 in a state where the metal pipe material 40 is separated from the lower mold 11 and the upper mold 12. Heat 40. The heating unit 5 includes a lower electrode 26 and an upper electrode 27 on both sides in the longitudinal direction, and a power source 28 that supplies current to the metal pipe material via these electrodes 26 and 27. Note that the heating unit 5 may be arranged in a pre-process of the molding apparatus 1 and may be heated externally.

The fluid supply unit 6 is a mechanism for supplying high-pressure fluid into the metal pipe material 40 held between the lower mold 11 and the upper mold 12. The fluid supply unit 6 supplies high-pressure fluid to the metal pipe material 40 which has been heated to a high temperature by the heating unit 5, thereby expanding the metal pipe material 40. The fluid supply section 6 is provided at both ends of the molding die 2 in the longitudinal direction. The fluid supply unit 6 includes a nozzle 31 that supplies fluid from an opening at the end of the metal pipe material 40 into the inside of the metal pipe material 40, and a drive that moves the nozzle 31 forward and backward with respect to the opening of the metal pipe material 40. A mechanism 32 and a source 33 for supplying high pressure fluid through the nozzle 31 into the metal pipe material 40 are provided. The drive mechanism 32 brings the nozzle 31 into close contact with the end of the metal pipe material 40 while ensuring sealing performance during fluid supply and exhaust (see FIG. 2), and brings the nozzle 31 into close contact with the end of the metal pipe material 40 at other times. Separate from. Note that the fluid supply unit 6 may supply gas such as high-pressure air or inert gas as the fluid. Furthermore, the fluid supply section 6 may be the same device as the holding section 4 having a mechanism for vertically moving the metal pipe material 40, including the heating section 5.

FIG. 2 is a cross-sectional view showing how the nozzle 31 seals the metal pipe material 40. As shown in FIG. 2, the nozzle 31 is a cylindrical member into which the end of the metal pipe material 40 can be inserted. The nozzle 31 is supported by the drive mechanism 32 so that the center line of the nozzle 31 coincides with the reference line SL1. The inner diameter of the supply port 31a at the end of the nozzle 31 on the metal pipe material 40 side substantially matches the outer diameter of the metal pipe material 40 after expansion molding. In this state, the nozzle 31 supplies high-pressure fluid to the metal pipe material 40 from the internal channel 36 . Note that an example of the high-pressure fluid is gas or the like.

Returning to FIG. 1, the cooling unit 7 is a mechanism that cools the molding die 2. By cooling the molding die 2, the cooling unit 7 can rapidly cool the expanded metal pipe material 40 when it comes into contact with the molding surface of the molding die 2. The cooling unit 7 includes a flow path 36 formed inside the lower mold 11 and the upper mold 12, and a water circulation mechanism 37 that supplies and circulates cooling water to the flow path 36.

The control unit 8 is a device that controls the entire molding apparatus 1. The control unit 8 controls the drive mechanism 3 , the holding unit 4 , the heating unit 5 , the fluid supply unit 6 , and the cooling unit 7 . The control unit 8 repeatedly performs the operation of molding the metal pipe material 40 with the molding die 2 .

Specifically, the control unit 8 controls the timing of transport from a transport device such as a robot arm, and places the metal pipe material 40 between the lower mold 11 and the upper mold 12 in the open state. Deploy. Alternatively, the control unit 8 may wait for the operator to manually place the metal pipe material 40 between the lower mold 11 and the upper mold 12. Further, the control unit 8 controls the actuator, etc. of the holding unit 4 so that the metal pipe material 40 is supported by the lower electrodes 26 on both sides in the longitudinal direction, and then the upper electrode 27 is lowered to sandwich the metal pipe material 40. Control. Further, the control unit 8 controls the heating unit 5 to heat the metal pipe material 40 by applying electricity. As a result, an axial current flows through the metal pipe material 40, and due to the electric resistance of the metal pipe material 40 itself, the metal pipe material 40 itself generates heat due to Joule heat.

The control unit 8 controls the drive mechanism 3 to lower the upper mold 12 and bring it close to the lower mold 11, thereby closing the molding mold 2. On the other hand, the control section 8 controls the fluid supply section 6 to seal the openings at both ends of the metal pipe material 40 with the nozzle 31 and supply fluid. As a result, the metal pipe material 40 softened by heating expands and comes into contact with the molding surface of the molding die 2 . Then, the metal pipe material 40 is molded so as to follow the shape of the molding surface of the molding die 2. When the metal pipe material 40 comes into contact with the molding surface, the metal pipe material 40 is quenched by the molding die 2 cooled by the cooling unit 7, thereby quenching the metal pipe material 40.

Among the components of the above-described molding device 1, the heating device 100 includes a heating section 5 and a control section 8 (heating control section). The heating device 100 is a device that heats a metal pipe material (metal material) to be formed. Further, as described above, the heating section 5 heats the metal pipe material 40 by electrical heating. The control section 8 controls the heating section 5 .

As shown in FIG. 3(a), a plating layer 43 is formed on the surface (outer peripheral surface and inner peripheral surface) of the metal pipe material 40 according to this embodiment. This plating layer 43 contains at least zinc as a component. The plating layer 43 can suppress the generation of oxide scale due to oxidation of iron, which is the base material of the metal pipe material 40, during heating.

Here, in the plating layer 43, a region whose boiling point has become sufficiently high due to sufficient alloying is referred to as "region E2", and a region in a state before sufficient alloying is "region E1". ”. In FIG. 3, a gray scale is attached to the region E2. In a state before heating is started, the entire area of the plating layer 43 becomes a region E1, as shown in FIG. 3(a). Region E1 contains pure zinc before being alloyed. Furthermore, in the plating process for forming the plating layer 43, since the temperature of the plating layer is 440 to 460° C., iron may diffuse into the zinc to some extent. Therefore, the region E1 may include a zinc-iron alloy layer with a low iron content. Examples of alloys included in region E1 include ζ layer alloys with an iron content of about 6%, δ1 layer alloys with an iron content of about 7 to 11%, and Γ layer alloys with an iron content of 11% or more. The iron content in region E1 is less than 30%. Region E2 is a region in which a FeZn solid solution phase with a high iron concentration is generated by heating. The iron content of the alloy in region E2 is 30% or more. In this specification, expanding the region E2 by proceeding with the alloying of zinc in the region E1 is referred to as "alloying treatment."

When the alloying process is started by heating the metal pipe material 40, the zinc contained in the region E1 of the plating layer 43 is alloyed by an alloying reaction with iron, which is the base material of the metal pipe material 40. It becomes an alloy of iron and zinc. Alternatively, the alloy layer with a low iron content in the region E1 of the plating layer 43 has a high iron content as alloying of zinc is further promoted. As a result, in the middle of the alloying process, the plating layer 43 has regions E1 and E2 mixed together, as shown in FIG. 3(b). When the alloying process of the plating layer 43 is completed, the entire area of the plating layer 43 becomes a region E2, as shown in FIG. 3(c).

Here, in order to sufficiently harden the metal pipe after forming, the heating unit 5 heats the metal pipe material 40 to a temperature of Ac3 or higher in order to transform it into austenite during heating. There is a need to. That is, the target temperature of the heating section 5 (the temperature that the metal pipe material 40 reaches) is about 900° C. to 1000° C., which is the Ac3 point or higher. On the other hand, unalloyed zinc has a boiling point of 907°C. That is, the final target temperature of the heating section 5 is higher than the boiling point of zinc. On the other hand, the boiling point of the fully alloyed zinc (alloy of iron and zinc) in the region E2 after the alloying treatment is higher than the boiling point of zinc. That is, the boiling point of the alloyed zinc after the alloying treatment is higher than the final target temperature of the heating section 5. Therefore, if the entire region of the plating layer 43 is in the region E2 (the state shown in FIG. 3(c)), even if the heating unit 5 heats the metal pipe material 40 to the target temperature, the components of the plating layer 43 It can suppress vaporization and ignition.

Based on the above points, the details of the control of the heating section 5 by the control section 8 will be explained. The control unit 8 controls the heating unit 5 to perform an alloying process to promote alloying of zinc in the plating layer 43, and after the alloying process, heats the metal pipe so that the temperature is higher than the boiling point of zinc. Heat the material 40. At the time when the control unit 8 starts heating the metal pipe material 40, the plating layer 43 is in the state shown in FIG. When the amount of zinc alloyed increases and the alloying process is completed, the state shown in FIG. 3(c) is reached. The control unit 8 controls the heating unit 5 so that the temperature of the metal pipe material 40 is equal to or lower than the boiling point of zinc before the alloying process of the plating layer 43 is completed. Preferably, the control unit 8 sets the zinc alloying process to a completed state (the state shown in FIG. 3(c)) before the temperature of the metal pipe material 40 reaches the boiling point of zinc.

The control unit 8 controls the heating unit 5 so that the temperature of the metal pipe material 40 draws a temperature profile with multiple stages. Note that the temperature profile refers to a graph formed by plotting the relationship between the time from the start of heating and the temperature of the metal pipe material 40.

A specific example of the temperature profile drawn under the control of the control unit 8 will be described with reference to FIG. 4(a). FIG. 4(a) is a graph showing an example of a temperature profile. The horizontal axis indicates the elapsed time from the start of heating of the heating section 5. The vertical axis indicates the temperature of the metal pipe material 40. As shown in FIG. 4(a), the control unit 8 controls the heating unit 5 so as to draw a temperature profile of a primary heating stage, a holding stage for maintaining the temperature, and a secondary heating stage. As shown in FIG. 4(a), the primary heating stage is performed during a time period t1 from the start of heating (0 seconds), and is a stage in which the temperature of the metal pipe material 40 is increased at a predetermined temperature increase rate. The control unit 8 controls the heating unit 5 so that the metal pipe material 40 reaches a predetermined target temperature T1 when the primary heating stage is completed. The holding step is performed between time t1 and time t2, and the temperature of the metal pipe material 40 is held constant for a predetermined holding time. Next, the secondary heating step is performed between time t2 and time t3, and is a step in which the temperature of the metal pipe material 40 is increased at a predetermined temperature increase rate. The control unit 8 controls the heating unit 5 so that the temperature of the metal pipe material 40 increases at a predetermined temperature increase rate and reaches the final target temperature T2. Note that when the final target temperature T2 is reached, the temperature of the metal pipe material 40 rapidly decreases because forming is performed.

Parameters set for the control of the control unit 8 include the temperature increase rate in the primary heating stage, the target temperature in the primary heating stage, the holding time in the holding stage, the rate of increase in the secondary heating stage, and the target in the secondary heating stage. temperature (final target temperature). The specific values of these parameters can be adjusted as appropriate in consideration of heating conditions and total heating time. For example, the control unit 8 may set the temperature increase rate in the primary heating stage to 50 to 150° C./sec. By setting within this range, the target temperature can be reached quickly. The temperature increase rate in the primary heating stage may be set to a higher value than the temperature increase rate in the secondary heating stage. The control unit 8 may set the target temperature of the primary heating stage to 700°C or more and 800°C or less. By setting the temperature within this range, it is possible to prevent the zinc from igniting while proceeding with the alloying of the zinc while avoiding the need for an excessive heating time. The control unit 8 may set the holding time of the holding stage to a range of 10 to 30 seconds. The control unit 8 may set the temperature increase rate in the secondary heating stage to 5 to 150° C./sec. The control unit 8 may set the target temperature of the secondary heating stage to about 900° C. to 1000° C., which is the temperature of the Ac3 point or higher, as described above.

Next, the functions and effects of the heating device 100 according to this embodiment will be explained.

In a molding apparatus 1 as shown in FIG. 1, a high-strength molded product is molded by performing hardening at the same time as molding. Here, in order to perform sufficient quenching, it is necessary to heat to a temperature of Ac3 or higher in order to cause austenite transformation during heating. However, when the metal pipe material 40 is heated to a high temperature, the base material of the metal pipe material 40 is oxidized, and oxide scale may be generated on the surface. In order to suppress the generation of such oxide scale, a plating layer 43 is formed on the surface of the metal pipe material 40. However, the boiling point of zinc contained in the plating layer 43 is relatively low at 907° C., and if it vaporizes during heating, it will easily catch fire. When zinc vaporizes and ignites in this way, zinc oxide is generated. In particular, in the space on the inner circumferential side of the metal pipe material 40, the concentration of vaporized zinc is higher than that on the outside, so ignition tends to occur more easily at lower temperatures, and the amount of zinc oxide generated also tends to increase. There is. If the zinc oxide generated in this way adheres to the molded product, it will interfere with post-processes such as painting, so a process to remove the zinc oxide will be required, resulting in an increase in cost. Further, if zinc oxide is dispersed into the surrounding atmosphere in powder form, problems will occur in the working environment, and a removal device on the equipment side will be required, which will also increase costs.

When the final target temperature T2 is set and the temperature increase rate is set to a constant value, a temperature profile as shown in FIG. 4(b) is obtained, for example. Then, conditions as shown in FIG. 6 are set as the temperature increase rate and target temperature. Further, FIG. 6 also shows the results as to whether or not zinc oxide was generated. As shown in FIG. 6, it is confirmed that zinc oxide was generated when the temperature increase rate was set high.

On the other hand, in the heating device 100 according to the present embodiment, the control unit 8 performs an alloying process to advance alloying of the plating layer 43 by controlling the heating unit 5. Thereby, the heating unit 5 performs an alloying process to advance alloying of the plating layer 43. Here, the boiling point of the alloy layer that has been sufficiently alloyed by the alloying treatment is higher than the boiling point of zinc. Therefore, after the alloying treatment, the heating unit 5 heats the metal pipe material 40 to a temperature higher than the boiling point of zinc. Therefore, even if the temperature of the metal pipe material 40 becomes higher than the boiling point of zinc, the zinc is sufficiently alloyed to have a high boiling point, so that ignition of the zinc can be suppressed. As described above, by suppressing the generation of oxide scale and also suppressing the generation of zinc oxide by the plating layer, it is possible to suppress the generation of oxide compounds on the surface of the metal pipe material 40.

Here, as shown in FIG. 6, it is confirmed that the generation of zinc oxide can be avoided if the target temperature is set low and the temperature increase rate is set low. In other words, if the heating rate is kept low, alloying will progress while the temperature is rising, and by the time the temperature is raised to the boiling point of zinc, the alloying of zinc will be completed and ignition of zinc will be prevented. Prevented. However, if the temperature increase rate is kept low, the heating time of electrical heating (the "total heating time" shown in FIG. 4) becomes long. Moreover, the upper limit of the final target temperature is also limited, and the control range of the allowable heating temperature becomes narrow.

On the other hand, the control unit 8 controls the heating unit 5 so that the temperature of the metal pipe material 40 draws a temperature profile in multiple stages. Thereby, the heating unit 5 heats the metal pipe material 40 so that the temperature of the metal pipe material 40 draws a temperature profile in multiple stages. In this case, the heating unit 5 can heat the metal pipe material 40 to obtain an appropriate temperature profile depending on the degree of progress of zinc alloying. This makes it possible to raise the temperature to the final target temperature after completing alloying of zinc while keeping the total heating time short.

The control unit 8 controls the heating unit 5 so as to draw the temperature profiles of the primary heating stage, the holding stage for maintaining the temperature, and the secondary heating stage. Thereby, the heating unit 5 heats so as to draw a temperature profile of a primary heating stage, a holding stage for maintaining the temperature, and a secondary heating stage. In this case, the heating unit 5 quickly raises the temperature to the target temperature for alloying treatment in the primary heating stage, and maintains it at the target temperature in the holding stage to proceed with alloying of zinc. After the alloying process, the heating unit 5 can raise the temperature of the metal pipe material 40 to the final target temperature in the secondary heating stage. Thereby, the total heating time can be kept short and the reliability of suppressing the generation of zinc oxide can be improved.

The control unit 8 sets the target temperature of the primary heating stage to 700°C or more and 800°C or less. Thereby, the heating unit 5 sets the target temperature of the primary heating stage to 700°C or more and 800°C or less. In this case, it is possible to prevent the zinc from igniting while alloying the zinc while avoiding the need for excessive heating time.

For example, various parameters were set to values as shown in FIG. 5, and the generation status of zinc oxide was confirmed. As shown in FIG. 5, when the target temperature in the primary heating stage is 500° C. or lower, the generation of zinc oxide is suppressed, but the total heating time tends to be longer. On the other hand, when the target temperature in the primary heating stage is 600° C. or higher and 700° C. or lower, zinc oxide is generated by vaporizing and burning zinc before alloying progresses. Therefore, in these temperature ranges, it is necessary to lengthen the total heating time by, for example, keeping the temperature increase rate low. On the other hand, if the target temperature is set and maintained at a temperature above the range and lower than the boiling point of zinc, alloying of zinc will proceed due to the high temperature, and zinc will not vaporize during subsequent heating. This has prevented the generation of zinc oxide. This makes it possible to shorten the total heating time.

The invention is not limited to the embodiments described above.

For example, there are no particular limitations on how the control section 8 controls the heating section 5 so as to draw a temperature profile. For example, the control unit 8 may omit the holding step. For example, when the target temperature of the primary heating stage is reached, the secondary heating stage may be immediately started. Further, the control unit 8 may control the heating unit 5 so as to draw a further multistage temperature profile. For example, in the holding stage, the temperature does not have to be kept completely constant, but may be gradually increased. As a result, the temperature profile may have three heating stages.

Further, if the metal pipe material 40 is heated to a temperature higher than the boiling point of zinc after zinc is alloyed, the control unit 8 may be configured to heat the metal pipe material 40 to a temperature higher than the boiling point of zinc. The heating unit 5 may be controlled so as to draw a stepwise temperature profile.

In addition, in the above-mentioned embodiment, the metal mold|die adopted in the molding apparatus for STAF was made into an example, and was demonstrated. However, the type of molding apparatus in which the mold according to the present invention is employed is not particularly limited, and may be any type of molding apparatus that molds a heated metal material. Further, the shape of the metal material is not limited to a pipe, and may be a plate-shaped metal material.

In the embodiment described above, the heating unit 5 heated the metal pipe material 40 inside the mold. Instead of this, a heating section 5 that performs heating outside the mold may be employed. For example, as shown in FIG. 7, the holding unit 4 may include a robot arm 130 that moves the metal pipe material 40 from the outside of the molding die 2 to between the lower mold 11 and the upper mold 12. Further, the robot arm 130 may include a heating unit 5 that heats the metal pipe material 40 while holding the metal pipe material 40. The robot arm 130 is equipped with an upper electrode 131 and a lower electrode 132 at its tip. The robot arm 130 can hold the metal pipe material 40 between electrodes 131 and 132 and heat the metal pipe material 40 by applying electric power from the power supply cable 133.

5... Heating section, 8... Control section (heating control section), 40... Metal pipe material, 43... Plating layer, 100... Heating device.

Claims (4)

A heating device that heats a metal material to be formed,
a heating section that heats the metal material by electrical heating;
A plating layer containing zinc is formed on the metal material,
The heating unit is a heating device that performs an alloying process to promote alloying of zinc in the plating layer, and after the alloying process, heats the metal material to a temperature higher than the boiling point of zinc. The heating device according to claim 1, wherein the heating unit heats the metal material so that the temperature of the metal material draws a temperature profile in multiple stages. The heating device according to claim 2, wherein the heating is performed so as to draw a temperature profile of a primary heating stage, a holding stage for maintaining the temperature, and a secondary heating stage. The heating device according to claim 3, wherein the heating unit sets a target temperature of the primary heating stage to 700°C or more and 800°C or less.

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