JPH05212439A - Electrically resisting welded oil well tube excellent in crushing resistance and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide an electrically resisting welded oil well tube excellent in crushing resistance and manufacturing thereof. CONSTITUTION:In the electrically resisting welded steel tube which is manufactured from a low carbon steel hot coil as the blank, when I/I0>2.0 is used for intensity rate in an azimuth {211} <110> in the X-ray diffraction, the electrically resisting welded steel tube excellent in crush resistances can be obtained by raising a Young' modulus in the circumferential direction of the steel tube. When the low carbon hot coil is manufactured, the total draft is regulated to >=50% in the finish rolling in a temperature range of Ar1-Ar3+150 deg.C of the steel. The resistance welded steel tube manufactured by this method is tempered in a temperature range of 200-600 deg.C, if necessary.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a generally known value of Young's modulus in the circumferential direction of an electric resistance welded steel pipe of 21000 (kgf / kgf /
The present invention relates to an electric resistance welded well tube having a higher crushing property than that of mm ² ) and a manufacturing method thereof.

[0002]

2. Description of the Related Art In recent years, oil wells have become deeper and deeper, and along with this, there is an increasing demand for steel pipes for oil wells having excellent crushing characteristics. In addition, due to the high crush resistance,
Since it is possible to reduce the thickness of the oil well pipe, which can reduce the weight of the oil well, that is, reduce the steel material, from this point as well, there is a growing demand from customers for oil well steel pipes with excellent crushing characteristics. ..

As a prior art document relating to an electric resistance welded well tube having excellent crushing characteristics, there is JP-A-59-260442. This is a low temperature heat treatment after the production of ERW steel pipe,
By effectively utilizing the strain aging, the yield strength of the inner and outer surface portions of the pipe is increased, and thereby an electric resistance welded well tube having excellent crushing properties is obtained. In general, yield strength, residual stress,
Roundness, uneven thickness, etc. are mentioned. The Poisson's ratio and Young's modulus of steel are also considered to be factors that control the crushing property. Including the above-mentioned prior art, many attempts have been made to improve the crushing property by improving the yield strength, residual stress, roundness, uneven thickness, etc. of the steel pipe, but improving the Poisson's ratio and Young's modulus of the steel. No attempt has been made to improve the crushing property of the steel pipe. This is because these values were generally regarded as invariant values.

Generally, the Young's modulus of steel is 21,000 (kg
f / mm ² ). Metallurgically, the Young's modulus of ferrite in the <111> direction is 29000 (kgf
/ Mm ²⁾ is known to be, but because technology to align the <111> direction of the ferrite in one direction like never before, the Young's modulus 21000 (kgf / mm ²⁾
It was considered impossible to improve above.

[0005]

DISCLOSURE OF THE INVENTION According to the present invention, the crush characteristic is positively increased by positively increasing the Young's modulus (which affects the crush characteristic in the circumferential direction of the steel pipe), which has been a constant value. It is an object of the present invention to provide an electric resistance welded well tube and a manufacturing method thereof.

[0006]

The present inventors have considered that it is possible to increase the Young's modulus by aligning the crystal direction with the <111> direction. That is, by matching the crystal orientation in the circumferential direction of the steel pipe, which is the direction orthogonal to the coil, with the <111> direction, the Young's modulus in this direction is 210
It has been found that the crushing property of the electric resistance welded steel pipe can be improved by making it larger than 00 (kgf / mm ² ).

Therefore, the inventors of the present invention have conducted numerous experiments and detailed studies in order to improve the Young's modulus, which has been conventionally set to a constant value, and as a result, the conditions of finish rolling in hot rolling are significant. I found that there is. That is, it has been found that the so-called low-temperature finish rolling in which the finish rolling temperature in hot rolling is Ar ₃ + 150 ° C. or lower promotes the formation of the texture of steel and improves the Young's modulus. It was also found that when the finish rolling temperature was further lowered to a so-called two-phase region, the formation of texture was further promoted.

Further, regarding the rolling reduction at this time, it is not effective unless it is a certain amount of strong rolling, and it was also clarified that a rolling reduction of 50% or more in finish rolling in that temperature range is required. Further, as a result of detailed investigation of the mechanism of Young's modulus improvement due to the formation of these textures, when finish rolling is performed in this temperature range, a stable orientation of {211} <110> ferrite rolling is formed, which results in the width of hot rolling. It was found that the <111> orientation was aligned with the direction.

Furthermore, the present inventors have found that {211} <1
It was also found that when the 10> ferrite rolling stability orientation is I / I ₀ > 2.0 in terms of the X-ray diffraction intensity ratio, the Young's modulus is significantly improved. Here, I ₀ represents the X-ray diffraction intensity of the stable orientation of {211} <110> ferrite rolling with respect to the material having a completely random orientation, and I is the {211} of the material having a texture by the above manufacturing method. <11
0> shows the X-ray diffraction intensity in the stable orientation of ferrite rolling.

In addition, the reason why the {211} <110> ferrite rolling stable orientation is formed by the above manufacturing method can be explained by the rolling texture of austenite phase and the lattice relationship of austenite / ferrite transformation. did. Based on such knowledge, the present invention enables production of an electric resistance welded oil country tubular good with a high Young's modulus in the circumferential direction of the steel tube and excellent crushing characteristics, and the gist thereof is as follows. .. (1) In an electric resistance welded steel pipe manufactured by using a low carbon steel hot coil as a raw material, a crushing characterized by an intensity ratio of {211} <110> directions in X-ray diffraction of I / I ₀ > 2.0 ERW oil well tube with excellent characteristics. (2) When producing a hot coil as a material for ERW steel pipe, the crushing property is characterized in that the cumulative rolling rate in finish rolling in the temperature range of Ar _{1 to} Ar ₃ + 150 ° C. of the steel is 50% or more. Excellent ERW oil well pipe manufacturing method. (3) A method for producing an electric resistance welded well tube having excellent crushing characteristics, characterized by tempering an electric resistance welded steel pipe formed using the hot coil manufactured under the conditions of the preceding paragraph 2 in a temperature range of 200 to 600 ° C. ..

[0011]

In the present invention, the texture is developed in the material for electric resistance welded steel pipe, and {211} <110> by X-ray diffraction is developed.
By setting the azimuth intensity ratio to I / I ₀ > 2.0, the Young's modulus in the circumferential direction of the steel pipe is increased, and as a result, the crushing property of the electric resistance welded steel pipe is successfully improved. {211}
The X-ray diffraction intensity ratio in the <110> direction is defined as I / I ₀ > 2.0 because the texture is defined when the X-ray diffraction intensity ratio in the {211} <110> direction is I / I ₀ ≦ 2.0. Is not fully developed,
As a result, the Young's modulus and the crushing property cannot be improved.

Next, the hot rolling conditions and the production conditions of the electric resistance welded steel pipe of the present invention will be described. When hot finish rolling the steel having the above components, the heating conditions are Ac ₃ temperature or higher,
The temperature is preferably 1000 to 1300 ° C., but at the time of performing hot finish rolling, it is necessary to secure at least 50% of the cumulative rolling reduction at Ar ₃ + 150 ° C. to Ar ₁ . Its This is the gist of the present invention, is essential conditions since it is in the development of ferritic rolling texture, to complete the hot rolling finish rolling at Ar ₃ + 0.99 ° C. greater than even finished with Ar ₃ + 0.99 ° C. or less Cumulative rolling ratio in finish rolling in the temperature range is 5
When it is less than 0%, the ferrite rolling stable orientation is {2.
11} <110> does not develop sufficiently and the crushing property is insufficient. Further, the lower limit of the hot rolling finish rolling temperature is the Ar ₁ temperature. Below this temperature, a recrystallized structure is likely to be formed by low temperature rolling, which results in a ferrite rolling stable orientation {2
11} <110> structure disappears, and the effect of the present invention cannot be obtained.

After passing through the above steps, it is air-cooled or forcedly cooled and wound into a coil, but the winding temperature is not particularly specified. However, if it is wound up at an excessively high temperature, the texture may disappear, so the winding temperature is preferably 720 ° C. or lower. There is no limitation on the cooling rate from finish rolling to winding, and it is allowable as long as it is within the range of the cooling rate used in ordinary hot finish rolling.

Although an electric resistance welded steel pipe is manufactured by molding from a hot coil, the manufacturing method is not particularly limited. By the way, among the electric resistance welded steel pipes manufactured by the above method, some of them have poor toughness depending on the type of steel, and there is a case where tempering treatment is necessary after the electric resistance welded steel pipe molding to improve the toughness. At that time, as the tempering temperature, the upper limit is 600 ° C. because the texture disappears if tempered at an excessively high temperature.
And However, when the tempering temperature is low and is lower than 200 ° C., the tempering effect is almost lost and the toughness may not be improved. Therefore, the lower limit is set to 200 ° C.

Further, the normal treatment or QT treatment which is reheated to a temperature higher than 600 ° C. causes the texture to disappear, so that the above characteristics cannot be obtained. The present invention can be applied to low carbon steel with good results. As a preferable component composition, C: 0.03 to 0.30% Si: 0.02 to 0.50% Mn: 0.50 to 2.00% Al: 0.001 to 0.100% N: 0.0. Depending on the required characteristics of low carbon steel having 0005 to 0.0100% as a basic component, or strength steel in addition to the above basic components, Cu: 2.0% or less Ni: 9.5% or less Cr: 5.5% or less Mo: 2.0% or less Nb: 0.15% or less V: 0.3% or less Ti: 0.15% or less B: 0.0003 to 0.0030% Ca: 0.0080% or less One or two. You may add 1 or more types.

C has the effect of increasing the strength of the steel material, and
Although it is added in an amount of 03% or more, if it is added in an amount of more than 0.30%, the toughness is significantly deteriorated.
Was set to 0.30%. Si has the effect of strengthening the solid solution and the effect of improving the strength and ductility of the steel material.
Although it is added as described above, if added in excess of 0.50%, the toughness of the steel material deteriorates, so its content is 0.02 to 0.
It was set to 50%.

Like C, Mn also has the effect of increasing the strength of the steel material and is added in an amount of 0.50% or more. However, if its content exceeds 2.00%, not only is it economical because of the difficulty in steelmaking work. Since the weldability is impaired, its content is set to 0.50 to 2.00%. Al is necessary for deoxidation in the steelmaking stage, and its lower limit was made 0.001%. Further, if added over 0.100%, the amount of inclusions increases and the cleanliness of the steel is lost, and it interferes with the steelmaking work. Therefore, the range is set to 0.001.
˜0.100%.

N is generally contained in steel as an unavoidable impurity, but if the amount of N is too low, the cost for steelmaking increases remarkably, so the lower limit was made 0.0005%. Further, if the amount of N increases, the weldability of the steel material deteriorates, and it also promotes the generation of surface flaws in the continuous cast slab.
The upper limit was 0.0100%. Cu is added because it is useful for increasing the strength and improving the corrosion resistance, but even if it is added over 2.0%, there is almost no increase in strength, so the upper limit of the content is made 2.0%.

Ni is useful for improving the low temperature toughness and is added. However, since it is an expensive element, the upper limit of its content is 9.5%. Cr is useful for increasing the strength and improving the corrosion resistance, but if it increases, it impairs the low temperature toughness and weldability, so the upper limit of the content is 5.5%. Mo is useful for increasing strength, but if it increases, it impairs weldability, so the content is 2.
The upper limit is 0%.

Nb is added because it is useful for refining austenite grains and increasing strength, but if it increases, it impairs weldability, so the upper limit of the content is 0.15%. V is useful for precipitation strengthening, but if it increases, the weldability is impaired, so the content is made 0.3% as the upper limit. Ti is useful for making austenite grains finer and is added, but if it increases, the weldability is impaired. Therefore, the upper limit of the content is 0.15%.

B has an effect of remarkably enhancing the hardenability of steel by adding a trace amount. In order to effectively obtain this effect, it is necessary to add at least 0.0003%. However, if added excessively, a B compound is produced and the toughness is deteriorated, so the upper limit is made 0.0030%. C
a is useful for controlling the morphology of sulfide inclusions and is added,
If it increases, it forms inclusions in the steel and deteriorates the properties of the steel, so the upper limit of the content is 0.0080%.

The electric resistance welded steel pipe thus obtained has a Young's modulus of 21,000 (kgf / mm ² ) in general,
The Young's modulus in the circumferential direction of the steel pipe can be improved by up to about 10%.

[0023]

EXAMPLES Table 1 shows the chemical composition of the test material, and Table 2 shows the hot rolling conditions of the steel pipe, the Young's modulus in the circumferential direction and the crushing pressure of the obtained steel pipe. At this time, the size of the steel pipe is 33 OD
The thickness is unified to 9.7 mm and the wall thickness is 9.6 mm.

Regarding the measurement of Young's modulus, two methods of resonance method and steel sound velocity measuring method were adopted, and it was confirmed that the measured values of both were almost the same. Also {211} <110>
The X-ray diffraction method was used to measure the azimuth intensity ratio. Steel pipe No. shown in Table 2 A1, B1, C1, D1, E1, F
1, G1, H1, I1, J1, K1, L1, M1, N
1, O1, P1, Q1, R1, S1, T1, U1, V1
Are steels according to the present invention, and are {211} <110>.
By setting the strength ratio of the azimuth to I / I ₀ > 2.0, the improvement of the Young's modulus in the circumferential direction of the steel pipe (about 10%) and the improvement of the crushing pressure due to this are achieved.

On the other hand, A2, B2, C2, D2, E
2, F2 has a cumulative rolling reduction of less than 50% in finish rolling of Ar ₃ + 150 ° C. to Ar ₁ and thus does not develop a texture ({2
11} <110> orientation X-ray diffraction intensity ratio is I / I ₀ ≦
2.0), Young's modulus is low, and crushing pressure is not high.

[0026]

[Table 1]

[0027]

[Table 2]

[0028]

As described above in detail, according to the present invention, the Young's modulus in the circumferential direction of the electric resistance welded steel pipe is 21000, which has been conventionally known.
(EN) Provided is an electric resistance welded well tube having a crushing property which is about 10% higher than (kgf / mm ² ), and a method for producing the same. In the present invention, in order to improve the crushing property by increasing the Young's modulus in the circumferential direction of the electric resistance welded steel pipe, in comparison with the steel pipe in the elastic region size, which has hitherto been influenced only by the dimensions (outer diameter, wall thickness) of the steel pipe. However, it is very effective.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location C21D 8/10 D 7412-4K 9/08 FE21B 17/00 9229-2D

Claims (3)

[Claims] 1. An electric resistance welded steel pipe manufactured using a low carbon steel hot coil as a raw material, wherein {211} <11 by X-ray diffraction.
The electric resistance welded oil country tubular good having excellent crushing characteristics, characterized in that the strength ratio of 0> direction is I / I ₀ > 2.0. 2. When producing a hot coil as a raw material for an electric resistance welded steel pipe, the crushing is characterized in that the cumulative rolling ratio in finish rolling of the steel in the temperature range of Ar _{1 to} Ar ₃ + 150 ° C. is 50% or more. A method of manufacturing an electric resistance welded well tube having excellent characteristics. 3. An electric resistance welded well tube excellent in crushing characteristics, characterized in that an electric resistance welded steel pipe molded using a hot coil manufactured under the conditions of claim 2 is tempered in a temperature range of 200 to 600 ° C. Manufacturing method.