JPH0718377A - Electric resistance welded tube excellent in sulfide stress corrosion cracking resistance - Google Patents

Abstract

PURPOSE:To produce an electric resistance welded tube excellent in sulfide stress corrosion cracking resistance. CONSTITUTION:In an electric resistance welded tube produced by steel having a basal compsn. of 0.05 to 0.35% C, 0.50 to 2.50% Si, 0.30 to 2.00%Mn, 0.0005 to 0.0080% Ca and 0.005 to 0.100% Al and contg., at need, one or <=two kindsamong Mo, Nb, V, Ti, B, Cu, Ni and Cr, among oxide inclusions contained within 100mum on both sides around the electric resistance welded abutting face, as the shape of the inclusions viewed in the cross section, the ratio of the length in the thick plate direction to the length in the circumferential direction is regulated to <=2, furthermore, the number of inclusions having >=10mum major axis to cut the cross section per mm<2> is regulated to <=5, moreover, around the electric resistance welded abutting face, the measured value of the hardness within 30mm on both sides is regulated to <=250 by Vickers hardness, and the hardness of the softest phase in the same area is regulated to >=100 by Vicker hardness.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric resistance welded steel pipe having high resistance to sulfide stress corrosion cracking (hereinafter referred to as SSC) caused by an environment containing moist hydrogen sulfide, and particularly to oil wells and gas wells. The present invention relates to the above-mentioned electric resistance welded steel pipe suitable as a structural member used in, for example, an oil well pipe or a line pipe.

[0002]

2. Description of the Related Art In recent years, in the development of oil and gas fields, due to the rapidly increasing demand and the progress of technology to meet the demand, it has been buried deep in the ground, which was either left unattended or difficult to develop. Moreover, development is gradually being focused on oils and gases that are so contaminated with sulfides such as hydrogen sulfide and that are in so-called sour environments.
Therefore, in the field of oil and natural gas production, it withstands external pressure (pressure in the formation) and internal pressure (pressure of oil and gas), or the tensile load due to the weight of the steel material, and can be used even in sour environments. There is a further demand for the development of a steel capable of exhibiting desired performance and having high strength and excellent sulfide stress corrosion cracking resistance (hereinafter referred to as SSC resistance).

Various means have been studied since 1950 for improving the SSC resistance of steel, and at present, the strength of steel is kept below the upper limit of hardness (strength) shown in NACE Standard MR-01-75, for example. It is said that the suppression is most effective for improving the SSC resistance, and in order to meet the user's request, L-80 based on this is added to the API standard.

However, it is naturally understood that the SSC resistance cannot be improved only by the upper limit of the hardness, and there are some other factors. As one of the factors that improve the SSC resistance, it is considered that the sour property is improved.
The improvement of the sour property is to reduce hydrogen blistering cracks in an environment containing hydrogen sulfide, and this fracture can be recognized even without an external load stress. When stress is applied in a sour environment, hydrogen blistering cracks occur in parallel with the stress axis, and these may connect to cause destruction. By preventing the hydrogen blistering cracks from occurring, SSC resistance can be improved. The idea is to improve the characteristics.

By the way, hydrogen blistering is a phenomenon in which hydrogen that has penetrated from the environment exists in the base metal and is elongated in the rolling direction.
It is generated by the gas pressure by accumulating at the boundary between A-type sulfide-based inclusions such as nS and the base metal, and is generated by the gas pressure. Parallel cracks on the plate surface using A-type sulfide-based inclusions such as MnS as the nucleus of the crack. And the parallel cracks in the plate surface are connected in the plate thickness direction. A-type sulfide inclusions such as MnS tend to become nuclei for cracks because the shape elongated in the rolling direction forms sharp notches, and is said to be the most harmful to this type of fracture.

[0006] Various studies have heretofore been made on steels having high resistance to hydrogen blistering, and various steels have been proposed. They utilize, for example, cracking prevention by adding Ca and Co, reduction of MnS by extremely low S, fixation of S by addition of Ca or rare earth elements, etc. Steel has been developed that can withstand the environment. Further, it is possible to improve the SSC resistance by using various means for improving the sour property.

By the way, the electric resistance welded steel pipe is for forming a steel plate such as a hot coil and performing electric resistance welding, and needless to say is a definite difference from the steel plate in that a welded portion and a weld heat affected zone are present. However, heretofore, almost no examples have been found in which the SSC resistance characteristics of the peripheral portion of the electric resistance welded portion, and also the C direction, were examined. This is because in the ordinary manufacturing process, a large amount of A-based sulfide inclusions such as MnS are present in the reverse segregation part and the V segregation part in the large steel ingot, and in the central segregation part in the continuous cast piece. The edge part is very small, and the microsegregation of Mn and P that promote parallel cracks on the plate surface is severe. It is the same as the part where many A-type sulfide inclusions such as MnS exist It has been understood that the so-called single width material manufactured by electric resistance welding of the edge portions of the steel sheet has good SSC resistance around the electric resistance welded portion because it is almost absent in the portion. Is. Further, in a so-called multi-strand electric resistance welded steel pipe manufactured by dividing one hot coil into two or more in the width direction, one or both of the electric resistance welded portions are susceptible to SSC such as an inverse V segregation portion or a center segregation portion. Is high, so S
There was recognition for SC. However, also in this case, the same measure as that of the base metal has been taken mainly as a measure, such as reduction of A-based sulfide-based inclusions such as MnS.

On the other hand, as a result of detailed investigation of the SSC resistance in the C direction of the electric resistance welded portion of the electric resistance welded steel pipe, the inventors of the present invention have found that the electric resistance resistance welded portion has no sulfide inclusions such as MnS. It was found that the SSC resistance of No. 1 may deteriorate. However, in the case of the electric resistance welded part, it is different from the base metal part in that the hydrogen swelling crack of the vertical type on the plate surface is the starting point of SSC.
There is concern that C may occur easily. Further, it has been found that SSC originating from this kind of hydrogen blistering crack is generated even in the case of a single-width material having essentially less microsegregation at the steel plate edge portion. The SSC of the electric resistance welded portion starting from the hydrogen blistering perpendicular to the plate surface has not been known so far, and is a more serious problem than the SSC originating from the hydrogen blistering crack parallel to the plate surface of the base metal. Is. But this crack
It has been found that conventional countermeasures against hydrogen blistering also occur in electric resistance welded steel pipes using steel and cannot be prevented by conventional techniques.

As a steel pipe having a high resistance to SSC originating from such completely new type plate vertical hydrogen blistering crack, there is a steel pipe described in JP-A-4-218799. This limits the number of stretched inclusions among the oxide inclusions contained in the electric resistance welded surface, and also determines the maximum and maximum and minimum values of hardness measured on the electric resistance welded surface. It is characterized by defining the difference between.

[0010]

However, the above-mentioned Japanese Unexamined Patent Application Publication No.
In the invention of Japanese Patent No. 218799, aside from the definition of the maximum value of hardness on the electric resistance abutting surface, reducing the difference between the maximum value and the minimum value involves considerable difficulty in actual operation. Further, since the hardness measurement region represented by Vickers hardness includes the softening phase and the hardening phase, it cannot be said that the hardness is defined in consideration of the structure in a precise sense. The present invention seeks to solve these problems.

[0011]

As a result of continuing the research to solve these problems, the present inventors found that the maximum hardness measurement value within 30 mm on both sides of the electric resistance joint surface was Vickers. It was found that the hardness is 250 or less, and the hardness of the softest phase in that region is 100 or more in Vickers hardness. Although the regulation of the maximum value of hardness is a conventional finding, regarding the necessity of the lower limit regulation of the hardness of the softest phase,
It is considered that the occurrence of cracks due to stress concentration in the softest phase deteriorates the SSC resistance. As a result of various studies on the method for defining the lower limit of the hardness of the softest phase, the present inventors have found that hardening of the ferrite phase by solid solution of Si is effective.

The present invention has been made based on these findings, and the gist thereof is as follows. (1) C: 0.05 to 0.35%, Si: 0.50
Ca in addition to 2.50%, Mn: 0.30 to 2.00%
0.0005-0.0080% and Al 0.005-
In an electric resistance welded steel pipe made of a steel containing 0.100% of balance Fe and inevitable impurities, an oxide inclusion included within 100 μm on both sides of the electric resistance joint surface as seen from the cross section. As the shape of the object, the ratio of the length in the plate thickness direction to the length in the circumferential direction is 2 or more, and the number of inclusions having a major axis of 10 μm or more that cuts the cross section per 1 mm ² is 5 or less, and the electric resistance welding The maximum value of hardness measured within 30 mm on both sides of the plane is Vickers hardness of 250 or less, and the hardness of the softest phase in that region is Vickers hardness of 100 or more. ERW steel pipe with excellent resistance to sulfide stress corrosion cracking.

(2) C: 0.05 to 0.35%, Si:
0.50 to 2.50%, Mn: 0.30 to 2.00%, 0.0005 to 0.0080% of Ca and 0.005 to 0.100% of Al, and Mo: 0. .1
~ 2.0%, Nb: 0.01 to 0.15%, V: 0.0
1 to 0.30%, Ti: 0.001 to 0.050%,
B: 1 or 2 out of 0.0003 to 0.0040%
In an electric resistance welded steel pipe made of a steel containing at least one of the above and consisting of the balance Fe and unavoidable impurities, among oxide inclusions contained within 100 μm on both sides of the electric resistance contact surface, inclusions seen in cross section are included. As a shape, the ratio of the length in the plate thickness direction to the length in the circumferential direction is 2 or more, and the number of inclusions having a major axis of 10 μm or more cuts the cross section per 1 mm ² is 5 or less, and The maximum value of hardness measured within 30 mm on both sides of the center is 250 or less in Vickers hardness, and the hardness of the softest phase in that region is 100 or more in Vickers hardness. ERW steel pipe with excellent sulfide stress corrosion cracking resistance.

(3) C: 0.05 to 0.35%, Si:
0.50 to 2.50%, Mn: 0.30 to 2.00%, 0.0005 to 0.0080% of Ca and 0.005 to 0.100% of Al, and Cu: 0. .1
~ 2.0%, Ni: 0.1-9.5%, Cr: 0.1
In an electric resistance welded steel pipe made of a steel containing one or more of 3.0% and the balance being Fe and unavoidable impurities, an oxide-based inclusion included within 100 μm on both sides of the electric resistance welding surface as a center. As for the shape of inclusions in the cross section, the ratio of the length in the plate thickness direction to the length in the circumferential direction is 2 or more, and the number of inclusions having a major axis of 10 μm or more cuts the cross section per 1 mm ² is 5 or less. In addition, the maximum value of hardness measured within 30 mm on both sides of the electric resistance contact surface is Vickers hardness of 250 or less, and the hardness of the softest phase in that region is Vickers hardness. ERW steel pipe excellent in sulfide stress corrosion cracking resistance, which is 100 or more.

(4) C: 0.05 to 0.35%, Si:
0.50 to 2.50%, Mn: 0.30 to 2.00%, 0.0005 to 0.0080% of Ca and 0.005 to 0.100% of Al, and Mo: 0. .1
~ 2.0%, Nb: 0.01 to 0.15%, V: 0.0
1 to 0.30%, Ti: 0.001 to 0.050%,
B: 1 or 2 out of 0.0003 to 0.0040%
Seed or higher and Cu: 0.1 to 2.0%, Ni: 0.1
9.5%, Cr: 0.1 to 3.0%, one or two
In an electric resistance welded steel pipe made of a steel containing at least one of the above and consisting of the balance Fe and unavoidable impurities, among oxide inclusions contained within 100 μm on both sides of the electric resistance contact surface, inclusions seen in cross section are included. As a shape, the ratio of the length in the plate thickness direction to the length in the circumferential direction is 2 or more, and the number of inclusions having a major axis of 10 μm or more cuts the cross section per 1 mm ² is 5 or less, and The maximum value of hardness measured within 30 mm on both sides of the center is 250 or less in Vickers hardness, and the hardness of the softest phase in that region is 100 or more in Vickers hardness. ERW steel pipe with excellent sulfide stress corrosion cracking resistance.

[0016]

The present invention will be described in detail below along with its operation.
First, the present invention is intended for all electric resistance welded steel pipes excellent in SSC resistance, and the reasons for defining the above components are as follows. C has the effect of increasing the strength of the steel material,
If added in excess of 0.35%, the toughness will be significantly deteriorated.
It was set to 05 to 0.35%.

Si has a solid solution strengthening action, and has an action of improving the strength and ductility of the steel material. In particular, in order to improve the hardness of ferrite, it is necessary to add 0.50% or more, but if added in excess of 2.50%, the toughness of the steel material deteriorates, so its content should be 0.50%. ˜2.50%. Like C, Mn also has the effect of increasing the strength of the steel material and is added in an amount of 0.30% or more, but its content is 2.0.
If it exceeds 0%, not only is the steelmaking operation difficult and uneconomical, but also the weldability is impaired, so the content was made 0.30 to 2.00%.

Ca is controlled by the morphology of sulfide inclusions.
It is effective in preventing hydrogen blistering cracks, which is the starting point of SSC, and is added in an amount of 0.0005% or more. However, if it increases, it forms inclusions in the steel and deteriorates the properties of the steel. It was set to 0.0080%. Al is necessary for deoxidation in the steelmaking stage, and its lower limit was made 0.005%. If added in excess of 0.100%, the amount of inclusions will increase and the cleanliness of the steel will be lost, and the steelmaking operation will be impaired.
˜0.100%.

Mo is useful for increasing the strength and is added in an amount of 0.10% or more in order to improve the hardness of ferrite. However, if it increases, it deteriorates the weldability.
It was set to 2.0%. Nb is useful for refining the austenite grains and increasing the strength, and is added in an amount of 0.01% or more, but if it increases, it deteriorates the weldability, so the range is 0.01-0.1.
It was set to 5%.

V is useful for precipitation strengthening and is added in an amount of 0.01% or more, but if it increases, it deteriorates the weldability, so the range was made 0.01 to 0.30%. Ti is useful for making austenite grains finer and is added in an amount of 0.001% or more.
If it increases, the weldability is impaired.
It was set to 1 to 0.050%.

B has the effect of remarkably enhancing the hardenability of steel by the addition of a trace amount. To obtain this effect effectively, at least 0.0003% of B is necessary, but if added in excess, it forms a B compound and deteriorates the toughness of the steel, so the range is 0.0003 to 0.0040. %. Cu is effective in increasing the strength and improving the corrosion resistance and is added in an amount of 0.1% or more. However, even if added in an amount of more than 2.0%, there is almost no increase in strength.
%.

Ni is effective for improving the low temperature toughness and is added in an amount of 0.1% or more. However, since it is an expensive element, the range is set to 0.1 to 9.5%. Cr is effective in increasing strength and improving corrosion resistance and is added in an amount of 0.1% or more. However, if it increases, it impairs low temperature toughness and weldability, so the range is 0.1 to 3.0.
%. P is an element that facilitates the propagation of hydrogen blistering cracks in the base material, and should be 0.03% or less.

Further, S is combined with Mn to form MnS which is a starting point of hydrogen blistering crack in the base metal portion, so 0.005%
Should be kept below. Next, as described above, among the oxide-based inclusions contained within 100 μm on both sides of the electric resistance abutting surface as a center, the shape of the inclusions as seen in the cross section is defined by the length in the plate thickness direction and the length in the circumferential direction. Ratio is 2 or more and major axis is 10
It is necessary that the number of inclusions having a size of μm or more that cuts the cross section per 1 mm ² be 5 or less, which is based on the following.

First, the reason that the range defining the inclusions is set within 100 μm on both sides of the electric resistance abutting portion is that many SSC resistance tests and detailed observations are performed on the test piece including the electric resistance abutting surface. As a result, hydrogen blistering cracks, which are the starting point of SSC generation, are generated at 100 μm on both sides from the center of the electric resistance joint.
And the number of plate-like oxide inclusions as the starting point is 1
This is because most of them are aggregated within 00 μm.
This is because it rarely exists in the range of more than 0 μm, and even if cracks nucleate, they do not connect, and therefore they cannot grow into macroscopic cracks.

Next, attention was paid to oxide-based inclusions as the target inclusions. As described above, the oxide-based inclusions are deformed by the thermal effect of welding and the pressure applied by the squeeze roll, and hydrogen blistering cracks occur. This will cause here,
The oxide-based inclusions in the present invention refer to inclusions composed of oxides and composites containing oxides as a main component and a small amount of sulfides. In addition, if added for reference, the present invention is not limited to the present invention, and the steel whose amount of sulfide inclusions is remarkably reduced in order to secure the sour resistance of the base metal is the main object. It focuses on.

As a shape of the inclusion, the ratio of the length in the plate thickness direction to the length in the circumferential direction is set to 2 or more. As a result of a detailed observation, the inclusion deformed into such a plate shape generates a nucleus of a crack. This is because the results of the experiments revealed that inclusions having a ratio of the length in the plate thickness direction to the length in the circumferential direction of less than 2 are not harmful to cracking. In the present invention, the direction of deformation of the oxide-based inclusions is defined in the plate thickness direction and the circumferential direction. However, since the deformation of the inclusions is caused by heating during welding heating, the oxide-based inclusions Objects do not always extend correctly in the plate thickness direction, and there are some that are slightly slanted, but of course, even if they are slightly slanted, there is no change in the origin of cracking. In the present invention, it is considered that such inclusions have a ratio of the length in the longest diagonal direction and the length in the direction perpendicular thereto to 2 or more.
The inclusion having a major axis of 10 μm or more is based on the finding by experiments that even if the length ratio is 2 or more, a fine inclusion having a major axis of less than 10 μm does not become a starting point of cracking. .

Further, in the present invention, the number of these inclusions cutting the cross section per 1 mm ² is set to 5 or less, because the inclusions having the above-mentioned shape and size cross over 5 per 1 mm ^2. This is based on the finding by experiments that nucleated hydrogen swelling cracks are interconnected when a plane is cut. In order to satisfy the above requirements, it is possible to achieve them by applying the following techniques, for example. First, deoxidation of molten steel,
It is effective to thoroughly remove oxide-based inclusions remaining after treatment such as desulfurization or Ca addition, which promotes the floating of molten steel inclusions by, for example, blowing an inert gas from the bottom of the molten steel container. It can be realized by
In addition, by adding a large amount of elements that form high-melting-point oxides such as Al and Ti, the oxide inclusions in the steel are changed to single-component and high-melting-point compounds, making it difficult to deform during welding. It is also effective to do.

Alternatively, it is extremely effective to reduce the pressure applied by the squeeze roll during electric resistance welding to prevent or reduce the change of oxide inclusions. However, in this case, needless to say, it is necessary to control welding conditions and applied pressure so as not to cause electric resistance welding defects. Various other techniques can be applied, but in short, oxide inclusions that cause plate-like inclusions in the base metal should be reduced, or inclusions that have a composition that is difficult to deform during welding should be positively applied. It is possible to satisfy the requirements of the present invention by, for example, forming it in the form of a wire, or by welding with less deformation during electric resistance welding.

As the manufacturing process of the steel of the present invention, hot rolling may be performed as it is, or a process of normalizing, tempering or quenching and tempering a rolled material may be applied. After electric resistance welding, a step of normalizing, tempering, or quenching and tempering only the vicinity of the electric resistance welded portion or the entire steel pipe may be applied. At this time, as described above, in order to prevent cracking due to stress concentration at the part where the hardness distribution is different, the maximum value of the hardness measured within 30 mm on both sides of the electric resistance joint surface is the Vickers hardness. It is necessary that the hardness is 250 or less, and the hardness of the softest phase in that region is 100 or more in Vickers hardness. Usually, the softest phase of the seam heat-treated electric resistance welded portion is ferrite, but it may be tempered martensite depending on the heat treatment of the pipe. At that time, as a method of measuring the hardness of the softest phase, it is desirable to set the load to 1.0 gf or less in order to accurately measure the hardness in the grain.
Whether or not the steel or the steel pipe is subjected to the heat treatment may be determined according to the need to secure other mechanical properties such as strength and toughness, in addition to the above-mentioned requirement for hardness.

The effects of the present invention will be described in more detail below with reference to examples.

[0031]

EXAMPLE Steels having the compositions shown in Table 1 were hot-rolled into a steel plate having a thickness of 13 mm, and then made into an electric resistance welded steel pipe in a usual process. Especially AC
Are those that sufficiently performed to remove the inclusions in the molten steel by blowing an inert gas, D to F in the almost completely inclusions in steel by adding a large amount of Al Al ₂ O ₃
It is what

Next, from the direction of the electric resistance welded portion C of these electric resistance welded steel pipes, SSC test pieces of the constant load method were sampled as shown in FIG. At that time, the electric resistance welded portion was made to cross the central portion of the sample. As a test for evaluating the SSC resistance,
Tested according to the NACE TM-01-77 standard test method,
The absolute value of the critical stress (σth) and the ratio of the critical stress (σth) to the yield strength (σy) in the C direction of the electric resistance welded portion were evaluated, and σth ≧ 358N / mm ² and σth / σy ≧ 0.7.
If both 5 are satisfied, it is considered to be good. σth ≧ 35
8 N / mm ² was calculated from 80% of the lower limit of standard yield strength of API5LX65.

Table 2 shows the test results. A1, B
1, C1 and D1 are the steels of the present invention, and among inclusions 1 (the number of inclusions that cut the cross-section per 1 mm ² within 100 μm from the electric resistance abutting portion (pieces), the major axis / minor axis ratio is 2 or more and Major axis 1
The number of inclusions of 0 μm or more) is 5 or less, the maximum value of Hv is 250 or less, and the hardness of the softest softening phase is 100 or more. Therefore, good SSC resistance (σth / σy ≧ 0.7)
5) is shown. On the other hand, A2, B2, C2, D
2 is inclusion 1 is 5 or less, and the hardness of the softest phase is 1
However, since the maximum value of Hv exceeds 250, σth / σy <0.75. Also E1,
In F1, the hardness of ferrite, which is the softest phase, is less than 100 because the Si content in steel is less than 0.50%,
σth <358 N / mm ² . Also G1, H
1, I1, J1 and K1 have maximum Hv values of 250 or less and hardness of the softest phase of 100 or more, but inclusion 1
Since there are more than five, σth / σy <0.75.

[0034]

[Table 1]

[0035]

[Table 2]

Note 1): Of the number of inclusions (pieces) cutting the cross section per 1 mm ² within 100 μm from the electric resistance abutting portion,
The number of inclusions with a major axis / minor axis ratio of 2 or more and a major axis of 10 μm or more. Note 2): Of the number of inclusions (pieces) within 1 μm ² within 100 μm from the electric resistance abutting portion, the number of inclusions having a major axis / minor axis ratio of 2 or more and a major axis of less than 10 μm. Note 3): Among the number of inclusions (pieces) that cut the cross section within 1 mm ² within 100 μm from the electric resistance abutting portion, the number of inclusions with a major axis / minor axis ratio of less than 2. Note 4) Within 30mm on both sides of the electric resistance contact surface.
Maximum Vickers hardness with a load of 500g. Note 5): Vickers hardness of the softest phase measured with a load of 0.5 g. Note 6): The unit is N / mm ² . Note 7): In the table, Q indicates that only the electric resistance welded portion after the electric resistance welding is quenched. QT has been hardened and tempered only at the electric resistance welded part. N is the electric resistance welded part that has been subjected to normal processing. The FBN is a tube body that has been subjected to normal processing after electric resistance welding.

[0037]

As can be seen from the above test results, the present invention makes it possible to provide an electric resistance welded steel pipe which does not deteriorate the SSC resistance even in a low pH and severe environment. There is an extremely great contribution to.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an abutting portion of an electric resistance welded steel pipe and regions on both sides thereof where the amount of oxide inclusions is limited.

FIG. 2 is a diagram showing a procedure for collecting test pieces in Examples.

[Explanation of symbols]

 1 ERW steel pipe 2 Abutting part 3 Heat affected zone 4 Welding direction 5 Test piece

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location C22C 38/16

Claims (4)

[Claims] 1. C: 0.05 to 0.35%, Si: 0.
50 to 2.50%, Mn: 0.30 to 2.00%, 0.0005 to 0.0080% of Ca and 0.0 of Al.
In an electric resistance welded steel pipe made of a steel containing 0.05 to 0.100% of balance Fe and unavoidable impurities, a cross section of an oxide inclusion included within 100 μm on both sides of the electric resistance welding surface as a center. As the shape of inclusions seen, the ratio of the length in the plate thickness direction to the length in the circumferential direction is 2 or more and the major axis is 10 μ.
The number of inclusions of m or more per cross section of 1 mm ² is 5 or less, and both sides are 30 m centering on the electric resistance abutting surface.
The maximum value of hardness measured within m is 25 in Vickers hardness.
An electric resistance welded steel pipe excellent in sulfide stress corrosion cracking resistance, which is 0 or less and the hardness of the softest phase in that region is 100 or more in Vickers hardness. 2. C: 0.05 to 0.35%, Si: 0.
50 to 2.50%, Mn: 0.30 to 2.00%, 0.0005 to 0.0080% of Ca and 0.0 of Al.
05: 0.100%, and Mo: 0.1-2.
0%, Nb: 0.01 to 0.15%, V: 0.01 to
0.30%, Ti: 0.001 to 0.050%, B:
In an electric resistance welded steel pipe produced from a steel containing one or more of 0.0003 to 0.0040% and the balance Fe and unavoidable impurities, the electric resistance welded steel pipe is contained within 100 μm on both sides of the electric resistance welding surface. Among the oxide inclusions, the shape of the inclusions as viewed in cross section has a ratio of the length in the plate thickness direction to the length in the circumferential direction of 2 or more and the inclusion having a major axis of 10 μm or more cuts the cross section per 1 mm ^2. The number is 5 or less, and the maximum value of hardness measured within 30 mm on both sides of the electric resistance joint surface is Vickers hardness of 250 or less, and the hardness of the softest phase in that region is Vickers hardness of 10
ERW steel pipe with excellent resistance to sulfide stress corrosion cracking characterized by being 0 or more. 3. C: 0.05 to 0.35%, Si: 0.
50 to 2.50%, Mn: 0.30 to 2.00%, 0.0005 to 0.0080% of Ca and 0.0 of Al.
05: 0.100%, and further Cu: 0.1-2.
0%, Ni: 0.1 to 9.5%, Cr: 0.1 to 3.0
%, And an electric resistance welded steel pipe made of steel containing the balance Fe and unavoidable impurities, containing one or more of
Of the oxide inclusions contained within 100 μm on both sides of the electric resistance abutting surface, the shape of the inclusions as viewed in cross section has a ratio of the length in the plate thickness direction to the length in the circumferential direction of 2 or more and the major axis. The number of inclusions of 10 μm or more that cuts the cross section per 1 mm ² is 5 or less, and the maximum hardness measurement value within 30 mm on both sides of the electric resistance joint surface is Vickers hardness of 250 or less. An electric resistance welded steel pipe having excellent sulfide stress corrosion cracking resistance, characterized in that the hardness of the softest phase in that region is 100 or more in Vickers hardness. 4. C: 0.05 to 0.35%, Si: 0.
50 to 2.50%, Mn: 0.30 to 2.00%, 0.0005 to 0.0080% of Ca and 0.0 of Al.
05: 0.100%, and Mo: 0.1-2.
0%, Nb: 0.01 to 0.15%, V: 0.01 to
0.30%, Ti: 0.001 to 0.050%, B:
One or more of 0.0003 to 0.0040%, Cu: 0.1 to 2.0%, Ni: 0.1 to 9.
5%, Cr: 0.1 to 3.0% of one or more of 0.1 to 3.0%, and an electric resistance welded steel pipe manufactured from a steel composed of the balance Fe and unavoidable impurities. Of the oxide inclusions contained within 100 μm, the inclusions with a ratio of the length in the plate thickness direction to the length in the circumferential direction of 2 or more and the major axis of 10 μm or more per 1 mm ² as the shape of the inclusions as seen in the cross section Is less than 5 and the maximum hardness measured within 30 mm on both sides of the electric resistance abutting surface is Vickers hardness of 250 or less, and the softest in that region. The hardness of the phase is Vickers hardness of 10
ERW steel pipe with excellent resistance to sulfide stress corrosion cracking characterized by being 0 or more.