JPS6151609B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for efficiently and uniformly heat treating metal strips having different wall thicknesses, particularly large ones with large thickness differences.

Recently, metal structures used for offshore development are large in size, and the natural environment in which they are installed is harsh, so they are easily destroyed by wind and waves. be.

Conventionally, from the viewpoint that it is necessary to increase the strength of the above structures in order to prevent such destruction, high tensile and thick steel materials have been used as structural materials. It is believed that accidents such as objects being submerged in the sea occur because of problems with the low-temperature toughness, weldability, etc. of the above-mentioned structural materials.

Therefore, in order to construct a structure with sufficient strength and excellent toughness, it is necessary to improve the toughness of the structural material by tempering the structural material after the structure or shape has been adjusted to a certain extent. It is also desirable to use threaded joints to connect the strength joints, avoiding welding, which is likely to cause defects. Considering this point when steel pipes are used as structural materials, it is necessary to form thick-walled parts at the ends of the steel pipes for threaded joints, and to increase the toughness of steel pipes with different wall thicknesses, it is necessary to This means that uniform heat treatment must be applied to the entire surface.

However, since the above-mentioned steel pipes are used as structural materials, their overall wall thickness is large, and the pipe ends formed into threaded joints are formed to be, for example, three times as thick as other parts. There is a large difference in thickness, and the overall shape ranges from about 50 cm in diameter to several meters, is at least 12 m long, and weighs at least 7 or 8 tons, so Depending on the heat treatment method and equipment, it is virtually impossible to efficiently and uniformly heat treat the steel pipe as described above.

As mentioned above, the present invention is effective for metal strips such as steel pipes, which are large in size and have a large overall wall thickness, and the thick wall portions formed at the ends are thicker with a larger difference in wall thickness. This method was developed with the aim of providing a method that can perform heat treatment well and uniformly, and its structure consists of vertically or is placed in a horizontal direction, and annular inductors are placed on the starting end sides of parts with different wall thicknesses, and the inductors are moved in the longitudinal direction of the strip to continuously move the strip. In the heat treatment in which cooling water is continuously supplied to the heated part while heating, one thick part of the strip is placed in a predetermined state with the entire thick part surrounded by an inductor for the thick part. Heating the inductor until it reaches a certain temperature, and then supplying power to the inductor to compensate for the radiation convection loss in the heated part, so that the rear end of the inductor reaches the boundary with the stationary part or its vicinity. The thick part is heat-treated by continuously supplying cooling water to the heated part in synchronization with this movement, and following this treatment, the steady part following the thick part is heated. Power is supplied to the inductor for the stationary section placed on the starting end side to start heating the stationary section, and the inductor is moved toward the other end of the stationary section and heated by the inductor in synchronization with the movement. The stationary section is continuously heat-treated by continuously supplying cooling water to the stationary section. Power is supplied to the inductor for the thick wall so that the time required to heat the entire other thick wall part to a predetermined temperature by the inductor for the thick wall matches. When the inductor for the stationary section reaches the end of the stationary section or the vicinity thereof, the power supply to the inductor for the stationary section is stopped and the other inductor for the thick section is heated. The inductor is moved from the boundary side of the stationary part to the other end side while supplying enough power to compensate for the radiation convection loss of the heated part, and the inductor is heated in synchronization with this movement. The feature is that cooling water is continuously supplied to the parts.

Next, embodiments of the present invention will be described with reference to the drawings.

Reference numeral 1 denotes a steel pipe as a structural member in which thick-walled portions 1a and 1b are formed in order to form threaded joints at both ends, and 1c is a stationary portion between the two thick-walled portions.

Therefore, the steel pipe 1 has a nominal diameter of 500 mm, for example.
mm, the total length is 12 m, the wall thickness of the steady part 1c is 25 mm, the wall thickness of the thick wall parts 1a and 1b at both ends is 75 mm, and the length of the thick wall part is 700 mm, but the present invention Of course, the metal strips to which this can be applied are not limited to the above-mentioned steel pipes. Incidentally, the structure shown in FIG. 1 differs in the form of the thick portions 1a and 1b.

2 is an inductor for the thick-walled portion 1a of the steel pipe 1, 3 is an inductor for the steady-state portion 1c, and 4 is an inductor for the thick-walled portion 1b. Although different inductors are prepared for each thick-walled portion, if the thick-walled portions 1a and 1b have the same form, one thick-walled inductor is sufficient. FIG. 2 shows an example of this case.

Thus, the inductors 2 and 4 for thick-walled parts are each in the form of a wide band that completely covers the thick-walled parts 1a and 1b, and each has a cooling water jacket having nozzles 2b and 4b for spouting cooling water at its lower end. In addition, the inductor 3 for the stationary section is provided with the inductors 2 and 4a.
As shown in FIG. 3, the cooling water jackets 3a and 31a have two types of cooling water jetting nozzles 3b and 31b.

When carrying out the method of the present invention, the inductors 2 to 4 are placed at the first
The steel pipe 1 is set in the state shown in the figure, and the steel pipe 1 is continuously subjected to heat treatment through the steps shown in FIGS. 5 to 10.

First, as shown in Figure 5, while the inductor 3 is kept stationary, power is supplied to it to begin heating the thick portion 1a until the thick portion 1a reaches a predetermined temperature, for example, 900°C. At this time, other inductors 3 and 4
is not activated. In the figure, H is a heated portion.

When the thick portion 1a is heated to a predetermined temperature, the power supplied to the inductor 2 is reduced to a level that compensates for the heat radiation convection loss of the heated portion H, and at the same time the inductor 2 is moved upward. The cooling water C2 starts to move toward the
(See Figure 6).

As a result of the above, the thick wall portion 1a is sequentially and continuously heat treated from the bottom to the top, and the temperature above the thick wall portion 1a, which is later cooled due to the heat retention heating action of the inductor 2, does not drop. Therefore, uniform heat treatment of the thick portion 1a can be realized. In addition, C in the figure
is the part that has been cooled after heating.

When the inductor 2 continues to move upward and the entire area of the part H heated by the inductor 2 is heat-treated, the supply of power to the inductor 2 and the spouting of cooling water are stopped, and at the same time, the stationary part 1c is stopped. Electric power is supplied to the inductor 3 for the stationary section set at the lower end, and it begins to move upward, and the inductor 3 begins heat treatment of the stationary section 1c (see FIG. 7). Incidentally, when the upper thick wall portion 1b has the same shape as the thick wall portion 1a that has already been heat treated, the inductor 2 for the thick wall portion is further moved upward and set at the upper thick wall portion 1b. I will do it.

The heat treatment of the stationary part 1c is carried out by heating the inductor 3 and moving the cooling water C3 through the nozzle 3 of the jacket 3a.
When the inductor 3 reaches a predetermined position in the stationary part 1c, the inductor 4 set in the upper thick part 1b heats the part 1b. (See Figure 8).

That is, the predetermined position is the inductor 3 for heating the stationary part 1c.
When the time required for the thick portion 1b to reach the terminal end of the stationary portion 1c from an appropriate position during movement coincides with the time required for heating the thick portion 1b to a predetermined temperature, for example, 900° C. by the inductor 4. Determined, S=
Vt (S: remaining moving distance of steady section inductor 3 mm,
V: moving speed of the inductor 3 mm/sec, t: time required to heat the thick portion 1b to a predetermined temperature
sec).

The upper thick part 1b begins to be heated by the stationary heating of the inductor 4 and reaches a predetermined temperature, for example, 900°C.
℃, the inductor 3 for the stationary portion 1c reaches approximately the upper end of the portion 1c. Here, steady part 1
c is cooled by the cooling water C3 jetted from the nozzle 3b of the cooling water jacket 3a disposed below the inductor 3, so when the inductor 3 reaches a position where it cannot move any further, its guidance The area directly below the child can be cooled. Therefore, the inductor 3
Water is passed through a jacket 31a provided in the upper half, and cooling water C31 is spouted from a nozzle 31b of the jacket 31a, thereby cooling the upper end of the stationary portion 1c (see FIG. 9).

On the other hand, when the heat treatment for the entire area of the stationary part 1c is completed as described above, the inductor 4 that was subsequently heating the upper thick part 1b is driven with a heating output that is sufficient to compensate for the radiation convection loss of heat. At the same time, the cooling water C4 begins to move upward, and the cooling water C4 starts to move upward from the nozzle 4b of the cooling water jacket 4a.
is ejected, and the thick portion 1b is continuously heat-treated (see FIG. 10).

In this way, metal strips such as steel pipes having different wall thicknesses can be heat-treated continuously, but the method of the present invention is suitable for treating large objects with large differences in wall thickness. The feature that conventional methods do not have is that heat treatment can be performed efficiently and with uniform quality.

That is, in the present invention, a plurality of inductors are used depending on the wall thickness, and after heating including preheating is applied to the thick wall portion, the heating output of the inductor is converted to the radiation convection of the heat of the heated portion. Since the heated part is cooled and heat-treated continuously, there is no uneven heat treatment in the thick-walled part. The stationary part that follows is continuously subjected to effective heating and cooling using a dedicated inductor.
Furthermore, for other thick parts following this steady part,
Using a dedicated inductor, heating is started in the middle of the processing of the stationary part, and once the heat treatment of the stationary part is completed, the inductor is immediately moved and cooling is performed at the same time, so multiple inductors are used. However, it is possible to perform continuous heat treatment without uneven treatment on strips having different thicknesses.

Incidentally, although it is theoretically possible to heat strips with different wall thicknesses with a single inductor, if the entire strip is large and the difference in wall thickness is large, it may be extremely large. It requires a power supply device, which makes the equipment cost extremely high and is not only impractical, but also
The disadvantage is that heating efficiency is poor due to the large difference in wall thickness.

In the present invention, since the object to be treated is a steel pipe with a large wall thickness, if a sufficient heat treatment effect cannot be obtained only by external heating, a heat treatment device is installed inside the steel pipe 1 as shown in Fig. 3. cooling jacket 5
The inductor 5 equipped with a may be operated in synchronization with the heat treatment operation described in the previous embodiment.

In this case, the inductor 3 for the stationary part 1c reaches the upper end of the part 1c, and the cooling water jacket 3
When spouting cooling water C31 from 1a, the inductor 5 on the inner surface side jets the cooling water C5 from the nozzle 5b, and quickly moves only the portion corresponding to the inductor 3 to form a section for the thick portion 1b. To be able to synchronize with the movement of the inductor 4.

This is to prevent differences in cooling timing between the inner and outer surfaces of the steel pipe.

The present invention is as described above, and in particular, a metal strip such as a steel pipe which is large in size as a whole and has a large difference in wall thickness, is provided with a plurality of heating inductors and a cooling water supply means. Since heat treatment can be carried out continuously, efficiently and uniformly using this method, it is extremely useful as a heat treatment method for structural materials of marine structures, etc.

[Brief explanation of the drawing]

FIG. 1 is a partially sectional front view showing the implementation state of the method of the present invention, FIG. 2 is a front view of another example,
FIG. 3 is a front view of another example, FIG. 4 is a partially enlarged sectional view of an inductor for heating a stationary part, and FIGS. 5 to 10 are process diagrams of an example of the method of the present invention. 1... Steel pipe, 1a, 1b... Thick wall part, 1c...
Stationary part, 2-5... Inductor, 2a-5a, 31a
...Cooling water jacket, 2b to 5b, 31b...
Cooling water jet nozzle.

Claims (1)

[Claims] 1 Metal strips with different wall thicknesses with both ends thicker than the stationary part are placed vertically or horizontally, and annular inductors are placed on the starting end sides of the parts with different wall thicknesses. In the heat treatment, the strip is continuously heated by moving the inductor in the longitudinal direction of the strip, and cooling water is continuously supplied to the heated portion. One of the thick parts is heated until it reaches a predetermined temperature with the entire thick part surrounded by an inductor for the thick part, and then the radiation convection loss of the part heated by the inductor is compensated. By supplying power and moving the inductor until its rear end reaches the boundary with the stationary part or its vicinity, and in synchronization with this movement, continuously supplying cooling water to the heated part. The thick portion is subjected to heat treatment, and following this treatment, power is supplied to an inductor for the steady portion disposed on the starting end side of the steady portion following the thick portion to start heating the steady portion, and the inductor is heated. The stationary section is continuously heat-treated by moving the inductor toward the other end of the stationary section and continuously supplying cooling water to the part heated by the inductor in synchronization with the movement. The time required for the inductor, which is in the middle of the heat treatment of the steady part, to reach the end of the steady part from there, and the time required to heat the entire other thick part to a predetermined temperature by the inductor for the thick part. In order to match, power is supplied to the other thick-walled inductor to start heating the thick-walled part, and when the steady-state inductor reaches the end of the steady-state part or its vicinity, the heating of the thick-walled part starts. While stopping the power supply to the inductor for the stationary section and supplying sufficient power to the other inductor for the thick section to compensate for the radiation convection loss of the heated section, the inductor is connected to the inductor for the stationary section. A method for heat treatment of metal strips having different wall thicknesses, characterized by moving metal strips from a boundary side to the other end side and continuously supplying cooling water to a portion heated by the inductor in synchronization with this movement.