JPH04254521A - Method for manufacturing ERW oil country tubular goods with high Young's modulus in the circumferential direction of steel pipes and excellent crushing properties - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention provides an electric resistance welded steel pipe having a circumferential Young's modulus of 2.10×104 (
The present invention relates to a method for producing an ERW oil country tubular product having a higher crushing property (kgf/mm2) and excellent crushing properties.

0002

BACKGROUND OF THE INVENTION In recent years, the drilling depth of oil wells has tended to become deeper and deeper, and as a result, there has been an increasing demand for steel pipes for oil wells with excellent crushing characteristics. In addition, by increasing the collapse resistance, it becomes possible to reduce the thickness of oil country tubular goods, which makes it possible to reduce the weight of oil wells and reduce the amount of steel used. Requirements for steel pipes for industrial use are becoming extremely strict.

[0003] As a prior art related to electric resistance welded oil country tubular goods having excellent crushability, there is one described in Japanese Patent Application Laid-Open No. 59-260442 [High crush type oil country tubular goods with high yield strength on inner and outer surfaces of pipe]. This technology uses low-temperature heat treatment after manufacturing ERW steel pipes and effectively utilizes strain aging to increase the yield strength of the pipe's inner and outer surfaces, thereby producing ERW oil country tubular goods with excellent crushing properties. That is.

0004

[Problem to be Solved by the Invention] Generally, the factors governing the crushing characteristics of steel pipes for oil wells are yield strength, residual stress,
Examples include the roundness of the steel pipe and the unevenness of wall thickness. In addition, the Poisson's ratio and Young's modulus of steel are also considered to be factors that control the crushing properties, but these values were generally considered to be unchangeable values.

[0005] The present invention improves the Young's modulus, which has conventionally been assumed to be a constant value (the Young's modulus in the circumferential direction of the steel pipe that affects the crushing characteristics is 2.10×104 (kgf/mm2)). The object of the present invention is to provide a manufacturing technology for ERW oil country tubular goods that improves the crushing characteristics by actively increasing the crushing characteristics.

[0006]

[Means for Solving the Problems] The gist of the present invention is as follows. (1) C: 0.05-0.50%, Si: 0.05
~0.30%, Mn: 0.5~2.0% as a basic component, and the balance is Fe and unavoidable impurity elements.
℃] An ERW oil country pipe having a high circumferential Young's modulus and excellent crushing properties, characterized in that the cumulative rolling reduction in the temperature range up to Ar1 point is 3% or more and 10% or less of the initial slab thickness. manufacturing method.

(2) C: 0.05-0.50%, S
i; 0.05 to 0.30%, Mn; 0.5 to 2.0 as basic components, Nb; 0.005 to 0.060%, V;
0.005-0.060%, Mo; 0.10-1.00
%, Ti; 0.005 to 0.030%, and the balance is Fe and unavoidable impurity elements.
An electric resistance welded steel pipe having a high Young's modulus in the circumferential direction and excellent crushing properties, characterized in that the cumulative rolling rate in the temperature range up to point +50℃] or below Ar1 is 3% or more and 10% or less of the initial slab thickness. Method of manufacturing oil country tubular goods.

Generally, the Young's modulus of steel is 2.10×104
(kgf/mm2). On the other hand, it is known that when steel is subjected to strong warm or cold working, a texture is formed and the Young's modulus changes accordingly. Metallurgically, it is known that the Young's modulus of an α-iron single crystal in the [111] direction is at most 2.90×10 4 (kgf/mm 2 ). Also, the Young's modulus in the [110] direction is 2.1
It is said to be 6×104 (kgf/mm2). That is, it is possible to increase the Young's modulus by aligning the crystal orientation in the [111] direction. By aligning the crystal orientation in the direction perpendicular to the rolling of the coil, that is, in the circumferential direction of the steel pipe, to the [111] direction, the Young's modulus in this direction is 2.
10×10 4 (kgf/mm 2 ), thereby making it possible to improve the crushing characteristics of the ERW steel pipe.

The present invention relates to a manufacturing technique for an electric resistance welded steel pipe that improves crushing characteristics by actively increasing the Young's modulus in the circumferential direction of the electric resistance welded steel pipe. To control the crystal orientation of steel, it is generally considered that a method of generating texture by changing hot rolling conditions is considered, but the present invention is capable of controlling the cumulative rolling amount during hot rolling to improve the orientation in the circumferential direction of the steel pipe. Young's modulus was set to the conventional value (2.10×104 (kgf/mm2
)) by about 8%, thereby providing an ERW oil country pipe with superior crushing properties compared to conventional ones.

The means for increasing Young's modulus will be specifically explained below. Continuous casting slab of that steel Ac3
After heating the steel to a temperature higher than the point, hot rolling is performed, but there are no particular restrictions on the initial rolling.
It is necessary to carry out finish rolling between Ar1 points and to make the cumulative rolling amount 3% or more of the initial slab thickness. Although there is no particular restriction on the upper limit of the cumulative rolling amount, 10% or less is appropriate in view of the capacity of the rolling mill.

[0011] Finish rolling is carried out in a low temperature range below [Ar3 point + 50°C], and the formation of the texture of the steel is promoted by applying strong reduction such that the reduction amount is 3% or more of the initial slab thickness. be done. This creates anisotropy between the Young's modulus in the rolling direction and the Young's modulus in the direction perpendicular to the rolling direction. This is because at temperatures below [Ar3 point +50°C], the steel remains in its processed structure. That is, recrystallization of austenite is difficult to occur in such a low temperature range, and therefore a texture is formed.

Further, when the final rolling is carried out in the so-called two-phase region between the Ar3 point and the Ar1 point, where ferrite transformation begins, the formation of texture is further promoted. In this way, the final rolling of hot rolling is carried out at [Ar3 point +50℃] or below.
By performing this between one point, a texture is formed, and thereby L and C anisotropy can be generated in the Young's modulus of the coil. In this case, the Young's modulus of the coil in the rolling direction is approximately 2
．． 10×10 4 (kgf/mm 2 ), the Young's modulus in the direction perpendicular to rolling increases by about 7 to 8% with the formation of texture (anisotropy of Young's modulus).

By manufacturing a steel plate under the above hot rolling conditions, the generally used Young's modulus (2.
10×104 kgf/mm2), the Young's modulus in the circumferential direction of the steel pipe can be improved by about 8% at most. In such a high-pressure collapse type ERW oil country pipe, there are no particular restrictions on its components, and the component system may be selected as necessary, but it is preferable to manufacture the product using a component system that is as inexpensive as possible.

[0014] The ingredients recommended by the present inventors will be briefly introduced below. C is important in order to obtain the necessary strength, but if it is less than 0.05%, it is very difficult to secure the yield strength of 35 kgf/mm2 or more, which is the aim of the present invention, so C is contained in an amount of 0.05% or more. It is preferable to do so. Also, if it exceeds 0.50%, the strength will become too high,
Since low-temperature toughness and corrosion characteristics are significantly deteriorated, an appropriate upper limit is 0.50%.

[0015]Si is also important in order to obtain the necessary strength, but from the viewpoint of electric resistance weldability, it is preferably 0.05% to 0.30%. Mn is also important to obtain the necessary strength, but if it is less than 0.5%, the yield strength targeted by the present invention is 35%.
Since it is very difficult to ensure a content of kgf/mm2 or more, it is preferable to contain 0.5% or more. Also, 2
．． The upper limit is 2.0%, considering that if it exceeds 0%, the low temperature toughness will significantly deteriorate and the alloy cost will increase.
% is desirable.

[0016] Although C, Si, and Mn are used as the basic components above,
If necessary, one or more of Nb, V, Ti, and Mo may be added. First, Nb has the effect of greatly suppressing recrystallization of austenite during hot rolling, and is therefore effective in forming texture. However, 0
．． If it is less than 0.005%, the effect cannot be expected;
Even if it is added in excess of 60%, the effect will not change, so 0.
0.005% to 0.060% is appropriate.

There is also a report that V has a slight effect of retarding the recrystallization of austenite during hot rolling, similar to Nb, but this is not clear. Since V is effective in improving low-temperature toughness and strength, it is effective to add it as necessary. However, if it is less than 0.005%, the effect cannot be expected, and if it is added in excess of 0.060%, the effect will not change, so 0.005% to 0.060% is preferable.

[0018] Ti suppresses austenite grain coarsening during slab heating, and as a result, ferrite grains become finer, so it is effective in improving low-temperature toughness. However, if it is less than 0.005%, the effect cannot be expected;
．． Even if it is added in excess of 0.30%, the effect will not change, so
0.005% to 0.030% is preferred. Mo is a very effective element for improving strength. however,
If it is less than 0.10%, the effect cannot be expected;
Even if it is added in excess of 0%, the effect will not change, so 0.1
0% to 1.00% is preferred.

[0019] Other P and S that are unavoidably obtained during refining
It is preferable that the number of cases is as small as possible. The components shown above are just examples; other components include Ni, Cu, and C.
r, Zr, etc. may be added as necessary. Next, a method for measuring Young's modulus will be briefly explained.

There are methods for measuring Young's modulus, such as a method of measuring resonance frequency using magnetic vibration, but in the present invention, Young's modulus was calculated by measuring the sound velocity of steel. The method is to take a small test piece 1 as shown in Figure 1 from a steel pipe, polish each surface, and then emit ultrasonic waves in the tube axis direction 2 and tube circumferential direction 3, and calculate Young's modulus from the velocity at that time. did. The calculation formula used for the calculation is theoretically determined from the wave equation, and the details are omitted, but only the calculation formula obtained as a result is shown below.

[0021]

[Math 1]

[0022]

[Examples] Examples of the present invention are shown in Tables 1 and 2 (continued from Table 1). Nos. 1 to 12 show examples of the present invention, and Nos. 13 to 17 show conventional comparative materials. Furthermore, Table 1
All of the examples shown in Table 2 (continued from Table 1) are electrical resistance welded oil country tubular goods having an outer diameter of 339.7 mm and a wall thickness of 9.6 mm.

[0023] In Examples 1 to 12 of the present invention, the Young's modulus in the C direction of the steel pipe was increased by setting the cumulative rolling amount between [Ar3 +50°C and Ar1] to 3 to 10% as the rolling conditions for hot rolling. The conventional general value is 2.10×104 (
kgf/mm2) by about 8%, which improves the crushing properties compared to conventional materials. In the examples shown in Tables 1 and 2 (continued from Table 1), the crushing value is improved by about 15% compared to the conventional material.

[0024]

[Table 1]

[0025]

[Table 2]

[0026]

Effects of the Invention The present invention provides an electric resistance welded steel pipe with a circumferential Young's modulus of 2.10×104, which is a commonly known value.
The present invention provides a method for manufacturing ERW oil country tubular goods having an excellent crushing property and approximately 8% higher than kgf/mm2. In the present invention, in order to improve the crushing characteristics by increasing the Young's modulus in the circumferential direction of the ERW steel pipe, we have developed It is also very effective.

[Brief explanation of the drawing]

[Fig. 1] Fig. 1 shows the Young's modulus (L,
FIG.

Claims (2)

[Claims] Claim 1: C: 0.05-0.50%, Si: 0
．． 05 to 0.30%, Mn: 0.5 to 2.0% as a basic component, and the balance is Fe and unavoidable impurity elements. A method for producing an ERW oil country pipe having a high circumferential Young's modulus and excellent crushing properties, characterized in that the cumulative rolling reduction in the temperature range up to the Ar1 point is 3% or more and 10% or less of the initial slab thickness. . Claim 2: C: 0.05-0.50%, Si: 0
．． 05-0.30%, Mn; 0.5-2.0 as the basic component, Nb; 0.005-0.060%, V; 0.0
05-0.060%, Mo; 0.10-1.00%, T
When hot rolling a cast slab containing one or more of 0.005 to 0.030% and the balance consisting of Fe and unavoidable impurity elements, the [Ar3 point +5
An ERW oil well having a steel pipe with a high circumferential Young's modulus and excellent crushing properties, characterized in that the cumulative rolling reduction in the temperature range up to Ar1 point (0℃) or below is 3% or more and 10% or less of the initial slab thickness. Method of manufacturing tubes.