JPH06158164A - Manufacture of butt welded tube - Google Patents

Abstract

PURPOSE:To provide a manufacturing method of a butt welded tube where the bending of the tube can be effectively prevented by controlling the tube temperature when the carrying condition of the tube stock is changed outside the prescribed temperature range. CONSTITUTION:A butt welded tube stock 11' is obtained by butt welding a strip 11 by using a butt welding machine 14 or the like, and hot-cut by a hot saw 16. Then, a butt welded tube is manufactured by executing the finishing treatment using a cooling equipment 18 or the like. When the tube stock 11' is carried to the position to execute the finishing treatment after the tube stock 11' is cut, the tube temperature when the carrying condition of the tube stock 11' is changed is controlled to be outside the temperature range of the A3 transformation point of the material + or -25 deg.C by using thermometers 19, 20, an arithmetic unit 23, and a control unit 24. Temperature control of the tube treated is executed by cooling the tube stock 11'. This constitution allows the butt welded tube to be manufactured without increasing the power consumption due to the increase of the rolling load.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a forged tube.

[0002]

2. Description of the Related Art In a conventional forged pipe manufacturing line, as shown in FIG. 3, a strip steel 1 is heated in a heating furnace 2 and a strip steel edge to be a forged portion at a heating furnace outlet is heated to a required temperature by an edge heater 3. After locally heating, the pipe is made by the forging machine 4 and finished by the stretch reducer 5 to have a predetermined outer wall thickness.

The raw pipe finished to a predetermined size is cut into a fixed length by a hot saw 6 and conveyed in the longitudinal direction of the pipe, and then kicked out to a cooling stand 7 to change the conveying direction to a vertical direction. While being rotated in the top of the conveyor chain on 7 to correct the bend, it is conveyed to the subsequent process, where it is finished into a forged tube product.

In Japanese Patent Laid-Open Publication No. 54-112726, on the premise of such a method for manufacturing a forged tube, sizing (including a stretch reducer) is performed by straightening and cooling to a lower limit temperature that allows sizing after forging. A method of preventing bending is disclosed.

[0005]

However, in the conventional forged tube manufacturing line, after the tube is cut with the hot saw 6, extreme bending of the tube may occur when kicked out to the cooling table.

Further, in the technique disclosed in Japanese Patent Laid-Open No. 54-112726, such extreme bending does not occur, but there are disadvantages such as an increase in rolling load and an increase in power consumption. I will end up.

The present invention has been made in view of the above circumstances, and provides a method for manufacturing a forged tube capable of preventing the bending of the tube without causing an increase in power consumption due to an increase in rolling load. The purpose is to do.

[0008]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides a forged welded tube by forging a band steel, hot cutting the element tube, and then performing a finishing treatment. A method for manufacturing a forged tube, which is a method for manufacturing a forged tube, wherein the tube temperature when the tube transporting state changes when the tube is transported to a position where a finishing process is performed after cutting the tube. The method for producing a forged welded tube is characterized by controlling the temperature outside the range of the A ₃ transformation point of ± 25 ° C. In this case, the tube temperature can be controlled by cooling the raw tube.

As a result of examining the cause of the above-mentioned extreme bending of the pipe, the inventors of the present application have found that while the raw pipe is cut out to the cooling table after being cut, that is, when the transport state changes. It has been found that the cause is that a non-uniform temperature distribution occurs on the circumference of the tube, which causes the tube temperature to extend above and below the A ₃ transformation point. That is, the temperature of the forged part is highly controlled by automatic control of the heating device, etc., but the temperature of the pipe when cutting out the raw pipe with the hot saw to the cooling stand is not controlled. As a result, such non-uniformity of the temperature distribution occurs and the above-mentioned extreme bending occurs.

The present invention having the above-mentioned structure is based on the findings of the inventors of the present application, and in order to suppress the extreme bending, after the hot cutting of the raw pipe, the transport state of the raw pipe is The tube temperature when changing is controlled to be outside the range of the A ₃ transformation point ± 25 ° C. of the material.

[0011]

In the present invention, when the raw pipe is conveyed to the position where the finishing process is performed after cutting the raw pipe, the pipe temperature when the conveying state of the raw pipe changes is determined by the A ₃ transformation point ± of the material. Control outside the 25 ° C range. As a result, it is possible to substantially prevent the pipe temperature from crossing above and below the A ₃ transformation point, and it is possible to prevent extreme bending due to the presence of the transformed portion and the non-transformed portion.

Further, the tube temperature may be outside the range of the A ₃ transformation point ± 25 ° C., and it is not necessary to cool the tube extremely. Therefore, it is possible to avoid an increase in power consumption due to an increase in rolling load. You can

[0013]

Embodiments of the present invention will be described below.

FIG. 1 is a schematic configuration diagram showing manufacturing equipment for carrying out the method for manufacturing a forged tube according to the present invention. Strip steel 11
After being heated at about 1200 ° C. in the heating furnace 12, only the edge portion is locally heated to about 1400 ° C. by the edge heater 13. Reference numeral 21 is a thermometer provided immediately after the edge heater 13, and the temperature of the strip steel 11 is controlled by this.

Strip steel 11 after exiting the edge heater 13
Is then pipe-formed by the forging machine 14. Thereafter, the raw tube 11 ′ thus formed by the tube forming is finished by the stretch reducer 15 to have a predetermined outer wall thickness. The raw pipe 11 ′ is cut into a fixed length by the hot saw 16, conveyed in the longitudinal direction of the pipe, and kicked out to the cooling table 17. In the cooling table 17, the transport direction of the raw pipe 11 'is changed from the longitudinal direction to the vertical direction.

On the other hand, in the production line from the stretch reducer 15 to the cooling stand 17, a thermometer 19 is provided upstream of the hot saw 16 and a thermometer 20 is provided downstream. Further, a cooling device 18 is provided adjacent to the stretch reducer 15.

As shown in FIG. 2, the cooling device 18 includes a housing 18a and four cooling water nozzle heads 22 for cooling the raw pipe 11 'by injecting cooling water into the raw pipe 11' from four directions. Have

The temperature detection signals of the thermometers 19 and 20 are output to the arithmetic unit 23. In the arithmetic unit 23, information on the A ₃ transformation point of the raw tube material is input in advance, and calculation is performed between the actual temperature data and the input value. And the arithmetic unit 2
The calculation result of 3 is output to the control device 24, and the control device 24
A control signal is output from the cooling device 18 to the cooling device 18. That is,
The temperature is controlled by the cooling device 18 so that the values of the thermometers 19 and 20 do not reach the A ₃ transformation point ± 25 ° C. of the material of the raw tube 11 ′.

[0019] Thus, the temperature of the mother pipe 11 'strides over and below the A ₃ transformation point is substantially avoided to prevent excessive bending due to the portion not transformed with the transformed portion is present You can Further, since it is possible to control the temperature close to the A ₃ transformation point −25 ° C. and it is not necessary to perform extreme cooling, it is possible to avoid an increase in power consumption due to an increase in rolling load. It is also possible to avoid troubles such as operation interruption of the production line or reduction in yield due to inability to convey due to bending and tube entanglement. In this way, the temperature of the raw pipe 11 'is controlled, the transport direction is changed by the cooling stand 17, and the raw pipe 11' is transported to a predetermined device for finishing treatment to be finished into a forged welded pipe.

The present invention is not limited to the above embodiment, but can be variously modified. For example, although the cooling device that ejects the cooling water from the water cooling nozzle head has been shown, it may be cooled by gas depending on the material.
Further, the temperature control means is not limited to that described in this embodiment.

[0021]

According to the present invention, since the tube temperature when the transport state of the raw tube changes is controlled to be outside the region of the A ₃ transformation point ± 25 ° C. of the material, the rolling load increases. Provided is a method for manufacturing a forged tube which can effectively prevent the bending of the tube without increasing the power consumption.

[Brief description of drawings]

FIG. 1 is a schematic view showing equipment for carrying out a method for manufacturing a forged tube according to an embodiment of the present invention.

FIG. 2 is a schematic diagram of a cooling device used in the equipment of FIG.

FIG. 3 is a schematic diagram showing conventional manufacturing equipment for a forged tube.

[Explanation of symbols]

11; strip steel, 11 '; blank tube,
12; heating furnace, 13; edge heater, 14;
Forging machine, 15; Stretch reducer, 16; Hot saw, 17; Cooling stand, 18; Cooling device,
18a; Housing 19, 20, 21; Thermometer 22; Cooling water nozzle head 23; Arithmetic device 24; Control device

Claims (2)

[Claims] 1. A method for producing a forged tube, comprising forging a strip steel to obtain a forged tube, hot cutting the tube, and then performing a finishing treatment to produce the forged tube. In transporting the raw pipe to the position where the finishing process is performed after cutting the steel, it is necessary to control the pipe temperature when the transport state of the raw pipe changes outside the region of the A ₃ transformation point ± 25 ° C of the material. A method for manufacturing a forged tube characterized by the above. 2. The method for producing a forged tube according to claim 1, wherein the control of the tube temperature is performed by cooling the raw tube.