JP2921415B2 - Pipe end processing method for oil country tubular goods - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to the production of the oil well pipe,
The present invention relates to a method of reducing the outer diameter of an oil country tubular good by squeezing the end of the oil country tubular good prior to performing pipe end threading.

[0002]

2. Description of the Related Art Oil-well pipes are subjected to swaging in which the pipe end is cut into a narrowed shape in order to stabilize thread quality by reducing the diameter of the pipe end and correcting the pipe end before performing pipe end thread cutting. As a method of performing this swaging, a method in which a die adapted to the processing shape is pushed in the pipe axis direction, a die adapted to the processing shape is divided in the pipe axis direction, and concentric with the pipe axis at a predetermined position at the pipe end. Method (Japanese Unexamined Patent Publication No.
No. 0-141333) and a method in which a processing roller adapted to a processing shape is gradually pressed against a rotating pipe end to continuously perform processing (Japanese Patent Laid-Open No. 63-309333).

FIGS. 4 (a) and 4 (b) show during and after processing.
The state of the oil country tubular goods is shown. Assuming that the pressure extension of the oil country tubular goods 1 to be processed is s and the roll diameter of the processing roller 2 is R, for example, when the processing rate e is 5%, the ratio R between the pressure extension and the roll diameter is 5%.
If / s is greater than 5, springback occurs in the reduced diameter portion due to the elasticity of the material itself, and the oil well tube 1
Has a tapered shape. The processing rate e
Is represented by the following equation 1.

[0004]

[Number 1] _{e = (D 0 -D) /} D 0 D 0: the outside diameter D of the oil well pipe prior to processing: the outer diameter of the oil well pipe after processing

[0005]

However, all of the above-mentioned methods are based on cold working, and a residual stress is generated in the oil well tube due to the working, and the material properties are changed by the residual stress. I do. For example, as shown in FIG. 5, the hardness changes with an increase in the working ratio. In order to remove the above residual stress, the oil country tubular goods must be subjected to a heat treatment before the pipe end threading process, and the productivity is not good.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a method of performing swaging on the end of an oil country tubular good without generating residual stress even in processing with a high processing rate. The purpose is.

[0007]

Means for Solving the Problems In order to achieve the above object, the present inventor has conducted extensive experiments focusing on the fact that hot working is effective for working with a large working rate, and as a result, the temperature As shown in FIG. 3, when the oil country tubular goods are processed in a state where the drop is within 90 ° C. from the tempering temperature, it is found that the hardness does not increase so much even when the working ratio increases, and no residual stress is generated. Of the present invention. That is, the present invention
In diameter reduction <br/> be that way the tube end of the oil well pipe by grooved rollers paired, is carried out of the tempering furnace, a tube of OCTG state temperature drop is within 90 ° C. from the tempering temperature Only the end portion is inserted into the roller, and the diameter is reduced.

[0008]

According to the present invention, only the pipe end of the oil country tubular good is transported from the tempering furnace and whose temperature drop is within 90 ° C. from the tempering temperature, and the diameter is reduced. The pipe end of the oil country tubular good can be reduced in diameter without generating stress.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a diagram showing an outline of equipment for carrying out the method of the present invention, in which (a) shows the arrangement of a tempering furnace and a roll stand, and (b) shows holes provided in the roll stand. view of the mold roller from the conveying direction of the diameter OCTG, (c) is a diagram showing a state in which grooved rollers are processed OCTG end, FIG. 2 is processed step by equipment shown in FIG. 1 FIG.

In FIG. 1, reference numeral 11 denotes a roll stand for processing the end of the oil country tubular good 1 in which, for example, a pair of two-hole rollers 12 and 13 are disposed. At the front and rear of the roll stand 11, sensors 15 and 16 for measuring the temperatures at the front end and the rear end of the oil country tubular good 1 are arranged. Further, the grooved rollers 12, 13 are configured so that the roll stand 11 in the conveying direction and perpendicular to the direction of oil well pipe 1 may contact and separation movement, diameter reduction of the front end of the oil well pipe 1 is completed Thereafter, the hole rollers 12 and 13 are separated from each other, and once pass through the oil well tube 1. Thereafter, the hole rollers 12 and 13 are approached to convey the oil well tube 1 in the opposite direction again and the rear end portion is moved. Reduce diameter. The diameter reduction lengths of these hole rollers 12 and 13 are detected by sensors 17 and 18, respectively.

In the method of the present invention, for example, the pipe end of the oil country tubular good 1 is processed by the process shown in FIG.
First, the oil well pipe 1 sent from the outlet of the tempering furnace 14 after moving the grooved rollers 12 and 13 close to each other at a predetermined interval.
The temperature of the front end of the oil well tube 1 is measured by a sensor 15 and only the front end of the oil well pipe 1 in a state where the temperature drop is within 90 ° C. from the tempering temperature is inserted into the roller-shaped rollers 12 and 13 to reduce the diameter by a predetermined length. Process. The processing length at this time is confirmed by the detection value of the sensor 17.

The oil well tube 1 is conveyed in the roll stand 11 by moving the hole type rollers 12 and 13 away from each other in the roll stand 11, and the rear end portion of the oil well tube 1 is detected by the sensor 16. Measure the temperature of. Again, the hole type roller 12,
13 is moved at a predetermined interval, the oil country tubular good 1 is sent in the direction opposite to the transport direction, and the temperature drop is 90 ° C. from the tempering temperature.
Only the rear end of the oil country tubular good 1
2 and 13 and are reduced in diameter by a predetermined length. After confirming the processing length at this time by the detection value of the sensor 18, the oil country tubular good 1 is conveyed to the next thread cutting.

As described above, if the roll stand 11 is constructed and installed so as to continuously process the end of the oil country tubular good 1 sent from the tempering furnace 14, swaging can be automated. Incidentally, instead of dispensed with diameter reduction by only 1 °, 90 ° oil well pipe 1 in the circumferential direction, is rotated 45 degrees, it is also possible to apply a reduced diameter processing for several times.

According to the above-described method of the present invention, a roll stand provided with two paired roller rollers having a roll hole diameter of 230 mm and an outer diameter of 244.5 mm and a wall thickness of 13.8 is provided.
At the end of a 4 mm oil country tubular good, the outer diameter is 230 mm and the pressure extension is 1
Swaging of 20 mm (processing rate 5%) was performed. The temperature of the oil country tubular goods during processing was 580 ° C and the tempering temperature was 6 ° C.
70 ° C. As a result, in the conventional cold working method, the reduced diameter portion hardens and the hardness exceeds the upper limit of the measured value, and the residual stress also remains, so heat treatment for removing the residual stress was necessary. According to this, since the hardness can be kept within the specified value, the heat treatment becomes unnecessary.

[0015]

As described above, according to the present invention, even in the case of diameter reduction processing with a high processing rate, processing can be performed without generating residual stress, so that heat treatment for removing residual stress is unnecessary, and Productivity can be improved. Further, labor saving can be achieved by automation.

[Brief description of the drawings]

FIG. 1 is a diagram showing an outline of equipment for carrying out the method of the present invention, in which (a) shows an arrangement of a tempering furnace and a roll stand, and (b) is arranged in a roll stand. view of the grooved roller from the conveying direction of the diameter OCTG is a diagram showing a (c) a state in which grooved rollers are processed OCTG end.

FIG. 2 is a flowchart showing a processing step by the equipment shown in FIG. 1;

FIG. 3 is a diagram showing a relationship between a working ratio and hardness according to the method of the present invention.

FIG. 4A is a diagram showing a state of an oil country tubular good to be processed;
(B) is the figure which showed the state of the oil country tubular goods after processing.

FIG. 5 is a diagram showing a relationship between a processing rate and hardness according to a conventional processing method.

[Explanation of symbols]

1 Oil Well Pipe 11 Roll Stand 12 Hole Roller 13 Hole Roller 14 Tempering Furnace

Claims (1)

(57) [Claims] 1. A pair of how you diametral reduction to the tube end portion of the oil well pipe by grooved rollers forming a, is carried out of the tempering furnace, the state temperature drop is within 90 ° C. from the tempering temperature
A method for processing a pipe end of an oil country tubular good , wherein only the pipe end of the oil country tubular good is loaded into the roller and the diameter of the pipe is reduced so that residual stress does not occur .