JPS58107245A - Heating device for end of steel tube - Google Patents

Abstract

PURPOSE:To heat the end of a steel tube in a relatively short time and in a small space, by providing a heating furnace that heat the end of a steel tube uniformly in the outlet side of an induction heating device that heats the end of a steel tube rapidly. CONSTITUTION:Steel tubes 1 carried in by an inlet side skid rail 21 are carried onto flat rolls one by one and inserted into the heating area 11A of an induction heating device 11. The tube is then carried sidewise continuously by a chain conveyor 24 and dropped onto a V-roller 25. It is drawn out in the axial direction by the V-roller, and kicked out to a skid rail 27 by a kick-out device 26. The steel tube 1 is carried on the skid rail 27 and introduced into the heating area of a burner type heating furnace 12 and heated uniformly to target temperature while being carried continuously sidewise by a chain conveyor 28, and carried onto a skid rail 29.

Description

[Detailed description of the invention] The present invention relates to a heating device for an end of a steel pipe.

Conventionally, when upsetting the end of a steel pipe,
The end of the steel pipe is heated to a predetermined temperature using an induction heating device as shown in FIGS. 1 and 2, or a burner type heating furnace as shown in FIG.

The induction heating device shown in FIG. 1 inserts steel pipes 1 one by one into an induction coil 2 from the axial direction and extracts them after heating.The induction heating device shown in FIG. A coil 3 heats a plurality of steel pipes 1 while simultaneously moving them horizontally, and the heated steel pipes 1 are sequentially extracted. By the way, the induction heating device shown in FIGS. 1 and 2 above can change the heating rate to a desired state by adjusting the electrical input, and can be installed in a relatively small space. . However, in this induction heating device, due to the skin effect where the current concentrates on the surface of the steel pipe, heating occurs rapidly from the surface, and especially for thick-walled steel pipes where the wall thickness varies greatly, the thick wall part and the thin wall part A large temperature difference occurs between the parts, resulting in uneven heating conditions. Furthermore, it is not appropriate to prolong the heating time in order to uniformly heat the entire steel pipe, as this may cause overheating in the heating section or reduce productivity.

That is, in the above induction heating apparatus, for example, a steel pipe having a maximum outer diameter of 115 mm, an average inner diameter of 80 mm, and an average wall thickness of 17.5 mm is heated at a power frequency of 3 K.
Using a Hz induction heating device, the average temperature increase rate was 5℃/8e
When heated at 125,011° C., a temperature difference of about 100° C. occurs between the thin and thick portions. If an end portion of a steel pipe having such a temperature difference in its thick wall portion is upset-processed, it will not be possible to obtain a predetermined upset shape, and there is a risk that a large defect will occur in the upset portion. In addition, even if the power supply frequency of the induction heating device is set low in order to uniformly heat the entire steel pipe, it is not possible to eliminate uneven heating with the frequency ING (, for example, 05K) (if the frequency is lowered to z) This is not appropriate as the energy efficiency would be extremely low and the heating time would be significantly prolonged.

The burner type heating furnace 4 shown in FIG.
It is extracted sequentially from . In such a burner type heating furnace 4, by controlling the furnace temperature, it is possible to easily uniformly heat a steel pipe of any cross section without causing overheating. However, if the burner-type heating furnace 4 is to be installed with high productivity, the furnace will not only be very long, requiring a large amount of factory space, but also requiring the heated end of the steel pipe 1 to remain in the furnace for a long time. Due to the If the steel pipes being heated remain in the furnace due to trouble occurring downstream of the furnace, it is difficult to dispose of the retained steel pipes, and (g) V at the start of operation or adjustment operation.
C has problems such as a long period of time from the start of insertion of the steel pipe to the time of extraction, which significantly reduces its operating rate.

The present invention has been made in view of the above problems of the conventional art [8], and an object of the present invention is to provide a heating device for the end of a steel pipe that can uniformly heat the end of the steel pipe in a small space and in a relatively short time. purpose.

In order to achieve the above object, the present invention provides a steel pipe end heating device that is capable of heating the end portion of a steel pipe while conveying the same, and includes an induction heating device that is capable of rapidly heating the steel pipe end portion. A heating furnace is installed to uniformly heat the end of the steel pipe.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 4 is a perspective view showing a ninth embodiment in which the present invention is applied to an upset processing line. This upset processing line includes an induction heating device 1 that can rapidly heat the end of the steel pipe 1.
1 is installed, a burner-type heating furnace 12 that can uniformly heat the end of the steel pipe 1 is installed on the outlet side of the induction heating device 11, and an upsetter 13 is installed on the outlet side of the burner-type heating furnace 12. . The induction heating device 11, the burner type heating furnace 12, and the upsetter 13 are arranged close to each other in order to minimize the temperature drop that occurs in the steel pipe 1 transferred between these devices.

Here, the steel pipe 1 can be introduced into the flat row 223 via the entry side skid rail 21 and the kick-in device 22. The flat roller 23 allows the end of the steel pipe 1 to be inserted into the entrance side of the heating area 11A of the induction heating device 11. The steel pipe 1 inserted into the heating area 11AK of the induction heating device 11 is continuously fed laterally by the chain conveyor 24, and its end portion is heated to near the target temperature. Here, the conveyance speed of the chain conveyor 24 can be freely changed. The steel pipe 1 that has reached the exit side of the heating area 11A of the induction heating device 11 can be extracted in the axial direction by the V rollers 25. The steel pipe 1 extracted by the V rollers 25 can be transferred to a transfer skid rail 27 by a kickout device 26.

The steel pipe 1 transferred to the skid rail 27 is introduced into the entrance side of the heating area 12A of the burner-type heating furnace 12, and is continuously conveyed horizontally by the chain conveyor 28Vc and uniformly heated to the target temperature K.

Here, the chain conveyor 28 is capable of freely changing its conveyance speed, and is also capable of passing through the steel pipe 1 at high speed when it is not necessary to uniformly heat the steel pipe 1 with a burner. The steel pipe 1 that has been uniformly heated to a predetermined target temperature by the heating area 12A of the burner type heating furnace 12 is delivered to the skid rail 29 from the exit side of the heating area 12A.

The steel pipe 1 delivered to the skid rail 29 is axially adjusted in position by the aligning V-row 230 and the aligning stopper 31 before upsetting, and then transferred to the carrier 32, and the upsetter 13 controls the end of the steel pipe 1. The desired upset process can be applied to the part.

Next, the operation of the above embodiment will be explained. The steel pipe 1 carried in by the entry side skid rail 21 is placed in the kick-in device i.
1t 22 K, one by one is transferred onto the flat roller 23, and the induction heating device 1 is transferred to the flat roller 23 by the flat roller 23.
It is inserted into the heating area 11A of No. 1. Induction heating device 11
The steel pipe 1 inserted into the heating area 11A is continuously fed horizontally by the chain conveyor 24, and when the end thereof is heated to near the target temperature, it is installed at the exit side of the heating area 11A. It rolls down onto the V roller 25, is quickly extracted in the axial direction by the V roller 25, and is kicked out onto the skid rail 27 by the kickout device 26. The steel pipe 1 kicked out onto the skid rail 27 is transferred onto the skid rail 27, and is transferred to the burner type heating furnace 1.
2 is introduced into the heating area 12A. The steel pipe 1 is connected to a heating area 12A't chain conveyor 28 of a bath type heating furnace 12.
After being heated uniformly to a target temperature while being continuously fed across the board, it is delivered to the skid rail 29.

The steel pipe 1 sent to the skid rail 29 is transferred to the V roller 3
0 and the stopper 31, and then transferred to the conveyance carriage 32 and subjected to upset processing by the upsetter 13.

Next, specific implementation results of the above embodiment will be explained with full reference to FIG. 5. The steel pipe 1 used in this implementation had an outer diameter of 8 & 9-,
The average wall thickness is 6.45-, and the average wall thickness is 6.451-
= - has a wall thickness change of 15% at most. In addition, the power frequency of the induction heating device ft11 is IKF
(zVc is set, and the furnace temperature of the burner type heating furnace 12 is 125
The temperature was set at 0°C. The curve shown by the solid line in FIG. 5 shows the temperature state of the thick part of the steel pipe 1, and the curve shown by the broken line shows the temperature state of the thin part. That is, according to FIG. 5, after insertion into the induction heating device 11,
While being heated by ICI near the Curie point Q, there is almost no temperature difference between the thin part and the thick part. However, 3.7 minutes after insertion into the induction heating device 11, when the temperature of the thin part is heated to 11250°C, the temperature of the thick part becomes 1150°C, and the difference between the thin part and the thick part is increased. During this time, a temperature difference of 100°C occurs, which makes upset processing difficult. Therefore, when the steel pipe 1 is inserted into the burner type heating furnace 12 and heated for 5.3 minutes after insertion, the entire steel pipe 1 becomes uniformly heated to a target temperature of approximately 1250°C.

According to the above embodiment, the steel pipe 1 is heated by the induction heating device 11.
After heating the end of the steel pipe to near the target temperature, it becomes possible to uniformly heat the end of the steel pipe to the target temperature using the continuous burner heating furnace 12. Therefore, the end of the steel pipe can be uniformly heated in a relatively short time in a small space. This makes it possible to perform high quality and highly productive upsetting on the ends of steel pipes. In addition, the amount of upset at the end of the steel pipe is large, and 2
When it is necessary to perform upsetting for three times or three times, a large change in wall thickness occurs in the axial direction of the end of the steel pipe after the first and second upsetting. It becomes possible to uniformly heat even the entire end of a steel pipe, and it becomes possible to perform upsetting processing with a large amount of upsetting well.

In addition, although the above-mentioned Example explained the case where this invention was applied to an upset processing line, this invention is widely applicable not only to an upset processing line but a general steel pipe processing line.

As described above, the present invention provides a heating device for a steel pipe end that can completely heat the end of a steel pipe while conveying the steel pipe. Since a heating furnace is installed to uniformly heat the end of the steel pipe, it is possible to uniformly heat the end of the steel pipe in a small space and in a relatively short time.

[Brief explanation of the drawing]

1 and 2 are perspective views showing an induction heating device according to a conventional example, FIG. 3 is a perspective view showing a burner type heating furnace according to a conventional example, and FIG. 4 is a perspective view showing an embodiment of the present invention. 5 are diagrams showing concrete implementation results of the present invention. 1... Steel pipe, 11... Induction heating device, 12...
・Burner type heating furnace. Agent Patent Attorney Osamu Shiokawa

Claims (1)

[Claims] (1) In a heating device for the end of a steel pipe that can heat the end of the steel pipe while conveying the pipe, the end of the steel pipe can be uniformly heated on the exit side of the induction heating device that can rapidly heat the end of the steel pipe. A heating device for the end of a steel pipe, characterized in that it is equipped with a heating furnace.