JP2010242163A - Method for manufacturing martensitic stainless steel seamless steel tube for oil well pipe - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a martensitic stainless steel tube for oil well pipe excellent in SSC resistant property. <P>SOLUTION: To a stainless seamless steel tube having the composition composed by mass% of &le;0.015% C, &le;1.0% Si, &le;2.0% Mn, &le;0.020% P, &le;0.010% S, 0.01-0.10% Al, 10-14% Cr, 3-8% Ni, 0.03-0.15% Ti, &le;0.015% N and further one or two elements selected among 1-4% Cu, 1-4% Mo, 1-4% W, 1-4% Co and the balance Fe with inevitable impurities, a quenching-treatment for quenching after heating to the temperature in the range of 750-840&deg;C and successively, a tempering-treatment at the temperature of &le;650&deg;C are applied. By this method, the martensitic stainless seamless steel tube for oil well pipe, providing high yield strength of 95 ksi-class and low hardness such as &lt;27 HRC and excellent in SSC resistant property, is obtained. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a martensitic stainless steel seamless pipe for oil well pipes, and more particularly to a method for producing a seamless steel pipe for oil well pipes having a yield strength YS of 95 ksi class (655 to 758 MPa) and excellent SSC resistance.

  In recent years, from the viewpoint of soaring crude oil prices and the depletion of oil resources expected in the near future, oil fields with deeper depths that were not previously excluded, and oil fields with severe corrosive environments including carbon dioxide, chloride ions, etc. The development of oil fields and other harsh drilling environments such as cold regions and the seabed has become active. The oil well steel pipe used in such an environment is required to have a material having high strength, excellent corrosion resistance, and excellent toughness.

Conventionally, carbon dioxide CO _2, chloride ion Cl ^- oilfield environment and the like, in the gas field, the 13% Cr martensitic stainless steel pipes are widely used as oil country tubular goods for use in mining. More recently, development of oil fields and the like in which the corrosive environment containing hydrogen sulfide H ₂ S in addition to carbon dioxide CO ₂ and chlorine ions Cl ⁻ is extremely severe has been carried out on a global scale. As an oil well pipe used for mining such oil and gas fields, a steel pipe having high strength even at high temperatures and having both corrosion resistance and stress corrosion cracking resistance is required.

In response to such a request, for example, in Patent Document 1, C: 0.05 mass% or less, Si: 0.50 mass% or less, Mn: 0.30 to 1.50 mass%, P: 0.03 mass% or less, S: 0.005 mass% or less , Cr: 11.0-17.0 mass%, Ni: 3.0-7.0 mass%, Mo: 0.5-5.0 mass%, Al: 0.05 mass% or less, N: 0.01-0.15 mass%, O: 0.005 mass% or less, and Contains at least one selected from Nb: 0.20 mass% or less, V: 0.20 mass% or less, with the balance being essentially Fe, and the following three relationships
0.8 (Nb%) + (V%): 0.02 to 0.20,
(Cr%) + 3.2 (Mo%) + 16 (N%) + 0.5 (Ni%) − 5 (C%): 17 or more,
1.1 {(Cr%) + 1.5 (Si%) + (Mo%)} − (Ni%) − 0.5 (Mn%) − 30 {(C%) + (N%)}: 6 or less,
A high-strength martensitic stainless steel for oil well pipes that satisfies the above requirements and has excellent stress corrosion cracking resistance and high-temperature tensile properties has been proposed.

In Patent Document 2, C: 0.003 to 0.050%, Si: 0.05 to 1.00%, Mn: 0.10 to 1.50%, Cr: 10.5 to 14.0%, Ni: 1.5 to 7.0%, V: 0.02 to 0.20%, N: 0.003 to 0.070%, and Ti: 0.300% or less, the balance being substantially made of Fe, P as an impurity is 0.035% or less, S is 0.010% or less, and {[Ti] -3.4 [ N]} / [C]> After heating and quenching a steel material having a composition satisfying 4.5 to 850 to 950 ° C., the tempering temperature T is within the range of Ac1 point ± 35 ° C. of the steel material, and the softening characteristic value LMP1 There is described a method for producing martensitic stainless steel characterized by tempering under the condition that the variation ΔLMP1 of (= T (20 + 1.7log (t)) × 10 ⁻³ ) is 0.5 or less. According to the technique described in Patent Document 2, by adjusting the chemical composition and quenching at an appropriate temperature, it is possible to prevent the temper softening curve from becoming a steep slope, and more rigorous tempering. By controlling the conditions, it is said that variations in the proof stress of martensitic stainless steel can be kept small.

Japanese Patent Laid-Open No. 10-130787 Japanese Patent Laid-Open No. 2004-2999

Recently, in the oil fields to be developed, oil fields with corrosive environments containing hydrogen sulfide H ₂ S in addition to carbon dioxide CO ₂ and chlorine ions Cl ⁻ have increased, and the concentration of hydrogen sulfide H ₂ S contained due to secular change has increased. There is concern about the increase. For this reason, improvement in SSC resistance has been emphasized with respect to the oil well pipe material to be used, and a reduction in hardness has been strictly demanded for the oil well pipe material. For example, a steel pipe of YS95ksi class (655 to 758 MPa) is required to satisfy the hardness upper limit of less than 27 in HRC.

  However, in response to such a request, the technique described in Patent Document 1 has a large change in yield strength during tempering, and the optimum tempering temperature range is narrow, so that the desired yield strength can be secured stably. In addition, there is a problem that it is difficult to combine desired low hardness. Further, according to the technique described in Patent Document 2, it is possible to manufacture a martensitic stainless steel pipe with a small variation in yield strength, but further strength stabilization has been required.

  The present invention solves such problems of the prior art, has a high yield strength of YS95ksi class, and has a low hardness of less than 27 in HRC, and has excellent SSC resistance and is excellent in martensite for oil well pipes. An object of the present invention is to provide a method for stably producing a stainless steel pipe.

  13Cr martensitic stainless steel pipe of conventional composition (composition containing 0.03% C-0.20% Si-0.65% Mn-13% Cr-5.5% Ni-2% Mo-0.01% V-0.05% N) FIG. 1 shows the change in strength when the steel was tempered by heating to 950 ° C. and then tempered at each temperature of 550 to 680 ° C. From FIG. 1, it is necessary to adjust the tempering temperature to a narrow temperature range in the conventional component composition in order to make the YS range of YS: 95 ksi class, and it is difficult to make the hardness less than HRC27. I understand that.

  Therefore, in order to achieve the above-mentioned object, the present inventors diligently studied the influence of the component composition and quenching conditions on the tempering characteristics of 13Cr martensitic stainless steel pipe. As a result, in order to achieve the desired low hardness first, the amount of C is as low as 0.015% by mass or less, and further, as a component system containing 0.03% by mass or more of Ti, further reduction of the amount of solid solution C is achieved. I realized that it was necessary to plan. Furthermore, the present inventors have newly found that the yield stress change with respect to the tempering temperature becomes small by reducing the quenching heating temperature to 750 to 840 ° C. after making it an extremely low C-Ti system. The present inventors considered the reason as follows.

By lowering the quenching heating temperature as described above, the formed austenite becomes very fine. The martensite obtained by quenching very fine austenite also becomes very fine. Such a very fine martensite structure has a large number of transformation start sites, and transformation to austenite starts at an early stage during reheating. That is, the _Ac1 transformation point is substantially lowered. This reduces the change in the amount of precipitated austenite with respect to the change in tempering temperature during tempering, and thus reduces the change in yield strength after tempering. By reducing the change in the yield stress with respect to the tempering temperature, a steel pipe having a desired range of yield strength can be manufactured stably.

The present invention has been completed based on such findings and further studies. That is, the gist of the present invention is as follows.
(1) By mass%, C: 0.015% or less, Si: 1.0% or less, Mn: 2.0% or less, P: 0.020% or less, S: 0.010% or less, Al: 0.01-0.10%, Cr: 10-14% Ni: 3 to 8% or less, Ti: 0.03 to 0.15%, N: 0.015% or less, Cu: 1 to 4%, Mo: 1 to 4%, W: 1 to 4%, Co: 1 It hardens after heating to the temperature of the range of 750-840 degreeC to the stainless steel seamless steel pipe which contains the 1 type (s) or 2 types or more chosen from -4%, and has the composition which consists of remainder Fe and an unavoidable impurity. A stainless steel with excellent SSC resistance, with quenching treatment and tempering treatment tempering at a temperature of 650 ° C or less, combined with high yield strength of YS95ksi class and low hardness of Rockwell C hardness less than HRC27. The manufacturing method of the martensitic stainless steel seamless pipe for oil country tubular goods characterized by using a steel pipe.
(2) In (1), in addition to the above composition, in addition to mass, Nb: 0.10% or less, Zr: 0.10% or less, Hf: 0.10% or less, Ta: 0.10% or less Or the manufacturing method of the martensitic stainless steel seamless pipe for oil country tubular goods characterized by setting it as the composition containing 2 or more types.
(3) In (1) or (2), in addition to the above-mentioned composition, in mass%, Ca: 0.010% or less, REM: 0.010% or less, Mg: 0.010% or less, B: 0.010% or less The manufacturing method of the martensitic stainless steel seamless pipe for oil country pipes characterized by setting it as the composition containing 1 type, or 2 or more types.

  According to the present invention, the change in yield strength at the time of tempering is reduced, and a high strength of a yield strength of 95 ksi can be secured stably even in a narrow appropriate tempering temperature range, and a low hardness of less than HRC27 is also achieved. The martensitic stainless steel seamless pipe for oil well pipes with excellent SSC resistance that can be used in combination can be manufactured stably, and has a remarkable industrial effect.

It is a graph which shows the relationship between the intensity | strength after quenching and tempering treatment of the 13Cr martensitic stainless steel pipe of a conventional composition, and tempering temperature.

First, the reason for limiting the composition of a stainless steel seamless steel pipe as a starting material in the present invention will be described. Hereinafter, unless otherwise specified, mass% is simply referred to as%.
In the present invention, C: 0.015% or less, Si: 1.0% or less, Mn: 2.0% or less, P: 0.020% or less, S: 0.010% or less, Al: 0.01-0.10%, Cr: 10-14%, Ni: 3-8%, Ti: 0.03-0.15%, N: 0.015% or less, further Cu: 1-4%, Mo: 1-4%, W: 1-4%, Co: 1-4% A stainless steel seamless steel pipe having a composition comprising one or more selected from among them and the balance of Fe and inevitable impurities is used as a starting material.

C: 0.015% or less C is an important element related to the strength of martensitic stainless steel. To ensure the desired high strength, 0.003% or more is desirable, but more than 0.015% The desired low hardness cannot be realized, and the toughness and further the corrosion resistance are liable to be lowered. For this reason, in the present invention, C is limited to 0.015% or less. In addition, Preferably it is 0.010% or less.

Si: 1.0% or less
Si is an element that acts as a deoxidizing agent in the normal steelmaking process. In the present invention, it is desirable to contain 0.05% or more, but if it exceeds 1.0%, the toughness is lowered, and cold workability is further reduced. Also decreases. For this reason, Si was limited to 1.0% or less. In addition, Preferably, it is 0.10 to 0.30% from a viewpoint of ensuring stable strength.

Mn: 2.0% or less
Mn is an element that increases the strength. In the present invention, Mn is desirably contained in an amount of 0.1% or more in order to ensure the strength required as a steel pipe for oil country tubular goods. However, the content exceeding 2.0% adversely affects toughness. For this reason, Mn was limited to 2.0% or less. In addition, Preferably it is 0.3 to 0.8%.
P: 0.020% or less P is an element that deteriorates corrosion resistance such as carbon dioxide corrosion resistance. In this invention, it is desirable to reduce it as much as possible, but extreme reduction leads to an increase in manufacturing cost. P is limited to 0.020% or less as a range that can be industrially implemented at a relatively low cost and does not deteriorate the corrosion resistance such as carbon dioxide corrosion resistance. In addition, Preferably it is 0.015% or less.

S: 0.010% or less S is an element that significantly deteriorates hot workability in the pipe manufacturing process, and it is desirable that it be as small as possible, but if it is reduced to 0.010% or less, pipes can be manufactured in the normal process. Therefore, S is limited to 0.010% or less. In addition, Preferably it is 0.002% or less.
Al: 0.01-0.10%
Al is an element having a strong deoxidizing action, and in order to obtain such an effect, the content of 0.01% or more is required, but the content exceeding 0.10% adversely affects toughness. For this reason, Al was limited to 0.01 to 0.10%. In addition, Preferably it is 0.04% or less.

Cr: 10-14%
Cr is an element that improves the corrosion resistance by forming a protective film, and is an element that contributes effectively to the improvement of carbon dioxide gas corrosion resistance, carbon dioxide stress corrosion cracking resistance, SSC resistance, and the like. If Cr is contained in an amount of 10% or more, the corrosion resistance necessary for oil well pipes can be ensured. Therefore, in the present invention, 10% is set as the lower limit of the Cr content. On the other hand, a large content exceeding 14% facilitates the formation of ferrite, and requires the addition of a large amount of expensive austenite-generating elements to ensure the stability of the martensite phase or prevent the hot workability from decreasing. Disadvantageous. For this reason, Cr was limited to the range of 10 to 14%. Preferably, it is 11.5 to 13.5% from the viewpoint of desired corrosion resistance, strength stabilization after tempering and ensuring hot workability.

Ni: 3-8%
Ni is an element that has an effect of strengthening the protective coating, and improves corrosion resistance such as carbon dioxide corrosion resistance and also improves toughness. In order to obtain such an effect, the content of 3% or more is required. However, the content exceeding 8% stabilizes the austenite phase, makes it difficult to form a martensite phase, and prevents stable structure formation. At the same time, the manufacturing cost increases. For this reason, Ni was limited to the range of 3 to 8% or less. In addition, Preferably it is 5 to 7%.

Ti: 0.03-0.15%
Ti is an important element in the present invention, and combines with C to form Ti carbide, thereby reducing solid solution C, achieving an extremely low C and realizing a desired low hardness. In order to obtain such an effect, a content of 0.03% or more is required. On the other hand, the content exceeding 0.15% lowers toughness. For this reason, Ti was limited to the range of 0.03-0.15%. In addition, Preferably it is 0.06-0.10%.

N: 0.015% or less N is an element that has the effect of improving the pitting corrosion resistance and also has the effect of increasing the strength in the same manner as C by being dissolved in steel. Further, N combines with Ti to form Ti nitride, and reduces the effective Ti amount that effectively acts to reduce the hardness. For this reason, in the present invention, it is desirable to reduce N as much as possible. If the content exceeds 0.015%, the desired low hardness cannot be achieved. Therefore, in the present invention, N is limited to 0.015% or less. In addition, Preferably it is 0.010% or less.

One or more selected from Cu: 1-4%, Mo: 1-4%, W: 1-4%, Co: 1-4%
Cu, Mo, W, and Co are all elements that have an action of improving corrosion resistance, and are selected and contained as necessary.
Cu is an element that has a function of strengthening the protective film and improving the pitting corrosion resistance, and effectively acts to improve the corrosion resistance. In order to obtain such an effect, it is desirable to contain 1% or more. On the other hand, if the content exceeds 4%, a part of it is precipitated and the toughness is lowered. For this reason, when it contained, Cu was limited to 1-4%. In addition, Preferably it is 1-2%.

Mo is an element that has an effect of increasing resistance to pitting corrosion caused by Cl ⁻ and effectively acts to improve corrosion resistance. In order to obtain such an effect, Mo is preferably contained in an amount of 1% or more. . On the other hand, when it contains exceeding 4%, toughness will fall and material cost will be raised. For this reason, when it contained, Mo was limited to 1-4%. In addition, Preferably it is 1-3%.

W is an element that increases resistance to pitting corrosion and effectively acts to improve corrosion resistance. In order to obtain such an effect, W is desirably contained in an amount of 1% or more. On the other hand, when it contains exceeding 4%, toughness will fall and material cost will be raised. For this reason, when it contained, W was limited to 1-4%. In addition, Preferably it is 1-2%.
Co is an element that strengthens the protective film and effectively acts to improve pitting corrosion resistance. In order to obtain such an effect, it is desirable to contain 1% or more. On the other hand, when it contains exceeding 4%, toughness will fall and material cost will be raised. For this reason, when it contained, Co was limited to 1-4%. In addition, Preferably it is 1-2%.

The above-mentioned components are basic components. In addition to these basic compositions, Nb: 0.10% or less, Zr: 0.10% or less, Hf: 0.10% or less, Ta: 0.10% or less as a selective element One or more selected, and / or Ca: not more than 0.010%, REM: not more than 0.010%, Mg: not more than 0.010%, B: not more than 0.010%, Can be contained.
One or more selected from Nb: 0.10% or less, Zr: 0.10% or less, Hf: 0.10% or less, Ta: 0.10% or less
Nb, Zr, Hf, and Ta are all elements that have the effect of forming carbides and increasing the strength of steel, and can be selected as necessary to contain one or more.

  In order to obtain such effects, it is desirable to contain Nb: 0.01% or more, Zr: 0.01% or more, Hf: 0.01% or more, Ta: 0.01% or more. On the other hand, when Nb: 0.10%, Zr: 0.10%, Hf: 0.10% and Ta: 0.10% are contained, the toughness decreases. For this reason, when it contains, it is preferable to limit to Nb: 0.10% or less, Zr: 0.10% or less, Hf: 0.10% or less, Ta: 0.10% or less, respectively.

One or more selected from Ca: 0.010% or less, REM: 0.010% or less, Mg: 0.010% or less, B: 0.010% or less
Ca, REM, Mg, and B are all elements that have the effect of improving the corrosion resistance, particularly SSC resistance, through the shape control of inclusions, and one or more elements can be selected and contained as necessary. . In order to obtain such an effect, it is desirable to contain Ca: 0.0005% or more, REM: 0.0005% or more, Mg: 0.0005% or more, B: 0.0005% or more, but Ca: 0.010%, REM: 0.010%, Inclusions exceeding Mg: 0.010% and B: 0.010% lower toughness and carbon dioxide corrosion resistance. For this reason, when it contains, it is preferable to limit to Ca: 0.010% or less, REM: 0.010% or less, Mg: 0.010% or less, B: 0.010% or less, respectively.

  The balance other than the components described above consists of Fe and inevitable impurities. As unavoidable impurities, it is desirable to adjust to V: 0.03% or less and O: 0.010% or less. If V as an impurity is contained in a large amount exceeding 0.03%, the strength is remarkably increased, and a desired high yield strength and a desired low hardness cannot be secured stably. For this reason, it is desirable that V be 0.03% or less. In addition, More preferably, it is 0.01% or less.

In the present invention, a stainless steel seamless steel pipe having the above-described composition is used as a starting material, and a quenching process and a tempering process are performed.
In the present invention, the production method of the starting material having the above composition is not particularly limited, but the molten steel having the above composition is melted by a generally known melting method such as a converter, an electric furnace, a vacuum melting furnace or the like. It is preferable to produce a steel pipe material such as billet by a usual method such as manufacturing, continuous casting method, ingot-making-slabbing method. Next, these steel pipe materials are heated and hot-worked and piped using a normal Mannesmann-plug mill method or Mannesmann-Mandrel mill manufacturing process to produce seamless steel pipes of the desired dimensions, and used as starting materials. Is preferred. In addition, you may manufacture a seamless steel pipe by the hot extrusion by a press system. Moreover, it is preferable that a seamless steel pipe is cooled to room temperature at a cooling rate equal to or higher than air cooling after pipe making.

The starting material (seamless steel pipe) is first quenched.
The quenching process in the present invention is a process of quenching after heating to a temperature in the range of 750 to 840 ° C. By heating to a temperature within this range and quenching, a fine martensite phase is formed, and during the tempering process, rapid γ formation is suppressed, and the amount of γ to be formed is adjusted within the appropriate range. Facilitates the precipitation of Ti carbide. For this reason, the change (decrease) in the yield strength accompanying the change in the tempering temperature is small, and it becomes possible to stably secure the desired yield strength and the desired low hardness. If the heating temperature for quenching is less than 750 ° C., complete austenite cannot be achieved, and a desired yield strength cannot be ensured after tempering. On the other hand, when the temperature exceeds 840 ° C., the austenite grains become coarse, and abrupt austenite formation occurs in the subsequent tempering treatment, making it difficult to adjust the amount of austenite. As a result, the yield strength varies, and the desired yield strength cannot be secured stably. The cooling at the time of quenching is preferably performed from the heating temperature to a temperature range of 100 ° C. or lower at a cooling rate of air cooling or higher. Since the starting material in the present invention has high hardenability, a sufficient quenched structure (martensitic structure) can be obtained by cooling to a temperature range of 100 ° C. or lower at a cooling rate of about air cooling. The holding time at the quenching temperature is preferably 10 min or more from the viewpoint of homogenizing the structure.

  The seamless steel pipe that has been subjected to the quenching process is subsequently subjected to a tempering process. The heating temperature (tempering temperature) in the tempering treatment is 650 ° C. or lower, preferably 550 ° C. or higher. In the present invention, it is important to select an appropriate tempering temperature according to the composition so that a desired yield strength can be secured. When the tempering temperature is higher than 650 ° C., the amount of γ formed increases, and the desired yield strength cannot be ensured. If the temperature is lower than 550 ° C., the tempering effect cannot be expected, and the desired yield strength cannot be ensured. In the present invention, it is important to select an appropriate tempering temperature in accordance with the composition within the above-described temperature range so that a desired yield strength can be ensured. The holding time at the tempering temperature is preferably 20 minutes or more from the viewpoint of preventing strength variation. In the tempering process, after holding for a predetermined time at the above-described tempering temperature, cooling is preferably performed at a cooling rate equal to or higher than air cooling.

The seamless steel pipe obtained by the manufacturing method described above has the above-described composition, and a structure containing mainly a tempered martensite phase and a residual γ phase in an area ratio of 5 to 25%, preferably 10 to 15%. It is a martensitic stainless steel seamless steel pipe for oil well pipes that has a yield strength of 95 ksi class (655 to 758 MPa) and a low hardness of less than 27 in HRC and excellent in SSC resistance.
Hereinafter, the present invention will be described based on examples.

The molten steel having the composition shown in Table 1 was degassed and cast into billets (size: 207 mmφ) by a continuous casting method to obtain a steel pipe material. These steel pipe materials were heated, hot-processed using the Mannesmann manufacturing process, piped, and then air-cooled to obtain seamless steel pipes (outer diameter 177.8 mmφ x wall thickness 12.7 mm).
A test material (steel pipe) was collected from the obtained seamless steel pipe, and the test material (steel pipe) was quenched and tempered under the conditions shown in Table 2.

From the test material (steel pipe) subjected to the quenching treatment and the tempering treatment, a structure observation specimen was collected. After polishing the tissue observation specimen, the amount of residual γ was measured using an X-ray diffraction method.
Also, API arc-shaped tensile test specimens are collected from the quenching and tempering test materials (steel pipes) so that the tensile direction is in the direction of the pipe axis, and a tensile test is performed in accordance with the provisions of API-5CT. Tensile properties (yield strength YS, tensile strength TS) were determined.

In addition, V-notched specimens (10 mm thick) were sampled from test materials that had been quenched and tempered in accordance with JIS Z 2242, conducted Charpy impact tests, and fracture surface transition temperature Trs50 And toughness was evaluated.
Moreover, a corrosion test piece having a thickness of 3 mm, a width of 30 mm, and a length of 40 mm was produced from the test material by machining, and a corrosion test was performed.

Corrosion test, the test solution retained in the autoclave: 20% NaCl aqueous solution (liquid temperature: 0.99 ° C., CO ₂ gas atmosphere at 30 atm) during the corrosion test piece was immersed for one week immersion period (168h) As implemented. The test piece after the corrosion test was weighed, and the corrosion rate was calculated from the weight loss before and after the corrosion test.
The SSC test was performed in accordance with NACE TM0177 Method-A. The test solution used was a 5% NaCl-0.5% CH ₃ COOH aqueous solution with CH ₃ COONa added to a pH of 3.5. The hydrogen sulfide partial pressure was 0.10 bar. The applied stress was 655 MPa.

  The obtained results are shown in Table 3.

  All of the examples of the present invention have sufficient corrosion resistance as an oil well pipe, further satisfy a high yield strength of YS of 95 ksi or more and a low hardness of less than 27 in HRC, and have excellent toughness and SSC resistance. Stainless steel seamless steel pipe. Moreover, the example of this invention is a steel pipe with a small change of yield strength with respect to the change of tempering temperature. On the other hand, the comparative examples that are out of the scope of the present invention are too hard to satisfy the desired low hardness, or the change in yield strength with respect to the change in tempering temperature is large, or the toughness is reduced. Furthermore, desired corrosion resistance, particularly excellent SSC resistance cannot be ensured.

Claims (3)

% By mass
C: 0.015% or less, N: 0.015% or less,
Si: 1.0% or less, Mn: 2.0% or less,
P: 0.020% or less, S: 0.010% or less,
Al: 0.01-0.10%, Cr: 10-14%,
Ni: 3 to 8% or less, Ti: 0.03 to 0.15%,
N: 0.015% or less, further Cu: 1-4%, Mo: 1-4%, W: 1-4%, Co: 1 to 4% selected from 1 to 4% Containing stainless steel seamless steel pipe having a composition consisting of the remainder Fe and inevitable impurities,
A quenching process in which the steel is heated to a temperature in the range of 750 to 840 ° C. and then quenched.
Tempering treatment tempering at a temperature of 650 ° C or lower,
Of martensitic stainless steel seamless pipe for oil well pipes, which has a high strength of YS95ksi class and low hardness of less than Rockwell C hardness HRC27 and is excellent in SSC resistance. Production method.   In addition to the above composition, the composition further contains, in mass%, one or more selected from Nb: 0.10% or less, Zr: 0.10% or less, Hf: 0.10% or less, Ta: 0.10% or less. The method for producing a martensitic stainless steel seamless pipe for oil country tubular goods according to claim 1.   In addition to the above composition, the composition further contains one or more kinds selected from Ca: 0.010% or less, REM: 0.010% or less, Mg: 0.010% or less, and B: 0.010% or less in terms of mass%. The method for producing a martensitic stainless steel seamless pipe for oil country tubular goods according to claim 1 or 2.

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