JPS60221130A - Device for regulating residual stress of pipe - Google Patents

Abstract

PURPOSE:To give a residual tensile stress on the inner peripheral face of a pipe and to elevate the collapse strength by giving compression work continuously on four places of the outer periphery of a steel pipe. CONSTITUTION:There are two upper rollers 1 and two lower rollers 2 which mutually sandwich a steel pipe 3 at respectively two places from up and down. The shafts of rollers are respectively at right angles to the normal line of the steel pipe 3 and in a skew arrangement inclined at a certain angle towards the pipe shaft. The steel pipe 3 is driven with a motor 4 installed on a movable stand 10 with its rotation in peripheral direction under compression load loading condition via rollers 1, 1, 2, 2 by an actuator 12, and is propelled to axial direction and continuous compression work is given.

Description

[Detailed Description of the Invention] (Field of Industrial Application) The present invention is directed to a device that applies compression processing continuously to four locations on the outer periphery of a W4 pipe to apply residual tensile stress to the inner circumferential surface of the pipe. Prior Art) For steel pipes for oil wells, there has been an increasing demand for steel pipes with excellent Coffus Ig (strength against crushing due to external pressure).

In recent years, there has been a marked trend toward deeper oil and natural gas wells, which has placed higher demands on the strength and corrosion resistance of the coffers.One way to increase the strength of 1717 is to raise the yield point. An increase in yield point is usually accompanied by an increase in tensile strength, and an increase in tensile strength is directly linked to a deterioration in corrosion resistance.

That is, it is essentially difficult to achieve both corrosion resistance and collapse strength, and simple means such as adjusting the composition of pipe materials cannot meet the increasingly sophisticated performance requirements that accompany recent increasingly severe usage conditions.

In order to meet these increasingly sophisticated requirements, a means is needed to improve collapse strength independently of corrosion resistance.

As a means for this purpose, it is known that residual stress is applied to the inner circumference of the tube without affecting the collapse strength of the tube.

For conventional steel pipes, straighteners are used to perform cold rotary bending by sandwiching the steel pipe between several opposing slanted rolls for the purpose of straightening the pipe after hot processing and improving roundness. Processing has been carried out using machines. However, in this machining, two points on the tube cross section are loaded at the same time, and after machining, circumferential compressive residual stress is generated on the inner surface of the tube, resulting in crushing strength (
(Corapunu strength) was decreased.

Although it is possible to remove the residual stress by heating at a high temperature, the residual stress cannot be removed unless the steel pipe is heated to nearly 500° C., which increases the consumption of energy such as fuel and electricity.

The inventor of the present invention confirmed that by bringing the residual stress on the inner surface of the tube to the tensile side during cold working, a significant improvement in the strength of the tube can be expected.
We have proposed a manufacturing method 1 for high-coffin strength steel pipes.

This means that when a compressive load P is applied to four points on the cross section of the pipe (3) shown in Figure 1 from both sides, the bending moment at point A is MA B, and the bending moment at Hirote is MB, the point of force application is If the central angle 2α is within the range of 40 to 90°, then the MB value (compressing the inner surface) > the MA value (pulling the inner surface), the stress at point A, σA%, the stress at point B, generated on the inner surface Then, 17B (compression)>σA (tension). When a pipe rotates while being subjected to compressive loads at four locations, for example when point A rotates to point B, the stress under compression will go around the stress under tension once.
When the compressive load is removed, the compressive stress on the inner surface of the tube is removed, so that the tensile stress remains. In this way, we have found a method for producing a tube with high strength by generating residual tensile stress δ on the inner surface of the tube.

OBJECTS OF THE INVENTION The present invention relates to an apparatus directly used for carrying out this manufacturing method. That is, the object of the present invention is to provide a device that adjusts the inner circumferential surface of a pipe to have residual tensile stress.

(Structure of the Invention) Two sets of two adjacent rotating bodies are provided, and the two sets are arranged such that the adjacent rotating bodies and the rear face each other, and a steel pipe is placed in the center of the arrangement of the rotating bodies. and a processing device that applies a compressive load to four locations on the outer surface of the tube so as to sandwich it from both sides; It is characterized in that compression processing can be performed continuously by moving the holding steel pipe in a loaded state while rotating it in the circumferential direction and propelling it in the axial direction.

(Sudden example) Next, we will discuss examples of heroes and their effects.

Figure 2 (a) (top view) ←) (front view) shows the upper and lower sets of two adjacent rotating bodies arranged diagonally. There are two upper loaves (1), and a lower loaf (2) (second
There are two steel pipes (indicated by broken lines in figure (a)) and
Pinch in two places each from the top and bottom. The upper and lower rotary bodies rotate the male side of the roll so that it makes linear contact with the outer surface of the tube. The shafts on both sides of the toe lower row may be supported by flat bearings, loaf bearings, or pole bearings, like pressure treatment rolls. A bearing outer ring can also be used for the rotating body. The axes of the rollers are each arranged perpendicular to the normal to the steel tube and inclined at an angle to the tube axis.

The vertical and horizontal compression loads αη are applied to the upper and lower loaves (1) (2J), and the steel pipe is clamped at four locations on the outer surface of the steel pipe.The steel pipe is rotated between the upper and lower loafs. If inserted in this condition, the steel pipe is rotated and propelled in the axial direction, undergoing continuous spiral compression processing.

Figure 3 shows the means for rotating the steel pipe, and Figure (A) shows the motor (4).
) through the universal joint (5) and the steel pipe (3) Ic bottle (
The structure for rotating the drive shaft (6) attached in 9) is shown.

(b) The figure shows a structure in which a hydraulic pressure band (8) is attached to a steel pipe in place of the bottle (9).

Figure 4 shows the hero embodiment of the present invention, in which a steel pipe (3) is rotated in the circumferential direction with a compressive load applied via rollers (1) (1 bar 2) (2) by an actuator (2). This figure shows continuous compression processing by propelling it in the axial direction while driving it with a motor (9) installed on a movable table aO.

Instead of rotating the pipe as in this example, the upper and lower loaves may be driven by a motor via a universal joint, and the steel pipe may be rotated and propelled by the loaf rotation.

(Effects of the invention) The effects of the invention are shown in FIG. cold straightener
By compressing the processed steel pipe using the apparatus of the present invention, the residual stress on the inner surface of the pipe is ashed on the tensile side. The test tube has an outer diameter of 177.8'W, a wall thickness of 9.2M, and a yield strength of 66.2.
kg sill - Chemical components are shown in Table 1.

Lobe bearings (
12019) was used.

In the figure, processing degree - (roller displacement) / (iiA pipe diameter)
The relationship between the residual stress on the inner surface of the tube after compression processing is shown, and the initial residual stress of the steel pipe is -80 to -40 kg (compression)6, but as the degree of compression processing increases, the compressive residual stress on the inner surface of the tube after processing decreases. When a compression process of 1.4% or more is applied, the residual stress on the inner surface of the tube changes to the tensile side (residual stress is greater than 0).

As is clear from the above description, the present invention makes it possible to adjust the residual tensile stress to the inner circumferential surface of the pipe, and is particularly applicable to the production of oil country tubular goods where corrosion resistance and high stiffness are required. It can be said that it is extremely effective industrially.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram of a situation in which compressive loads are applied at four locations from both sides of the pipe, and Figure 2 is an explanatory diagram showing how a steel pipe is processed into a spiral shape using two skew lobes each at the top and bottom (A).
(plane rotation) is a side view, Fig. 8 shows a device for rotating a steel pipe, (a) shows a drive shaft, and (b) shows a device using a hydraulic pressing pad. Fig. 4 is an explanation of the rush mode of the present invention. FIG. 5 is a diagram showing the relationship between the degree of compression work and the residual stress on the inner surface of the tube. 1: Upper loaf, 2: Lower loaf, 3: Pipe, 4: Motor,
5: Universal joint, 6: Drive shaft, 7: Pressing pad, 8: Hydraulic pressure, 9: Bin, 1o: Moving platform, 11: Compressive load. Fig. 1 Fig. 11 Fig. 3 Fig. 4 Fig. 5 →ffi # H construction (%)

Claims (1)

[Claims] (1) Two adjacent rotating bodies are used as one set, and these two sets are arranged so that the adjacent rotating bodies and the rear face each other.The steel pipe is placed in the center of the arrangement, and the rotating bodies It is equipped with a processing device that applies a compressive load to four locations on the outer surface of the tube so as to be sandwiched from both sides, and the rotary body has a skew arrangement in which its axes are aligned and are perpendicular to the normal line of the holding H4 tube and inclined with respect to the tube axis. A residual stress adjusting device for a pipe, characterized in that it is capable of continuous compression processing by propelling the holding steel pipe in the axial direction while rotating it in the local direction while it is in a loaded state.