Classifications

• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
  • C21D9/08—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for tubular bodies or pipes
  • C21D9/14—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for tubular bodies or pipes wear-resistant or pressure-resistant pipes
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
  • C21D1/18—Hardening; Quenching with or without subsequent tempering
  • C21D1/19—Hardening; Quenching with or without subsequent tempering by interrupted quenching
  • C21D1/22—Martempering
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D6/00—Heat treatment of ferrous alloys
  • C21D6/004—Heat treatment of ferrous alloys containing Cr and Ni
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
  • C21D9/08—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for tubular bodies or pipes
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/004—Very low carbon steels, i.e. having a carbon content of less than 0,01%
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
  • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
  • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
  • C22C38/58—Ferrous alloys, e.g. steel alloys containing chromium with nickel with more than 1.5% by weight of manganese
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D2211/00—Microstructure comprising significant phases
  • C21D2211/008—Martensite
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
  • C21D8/10—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of tubular bodies
  • C21D8/105—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of tubular bodies of ferrous alloys

Definitions

• the present invention relates to a martensitic stainless steel seamless pipe for oil well pipes, and in particular, a seamless steel pipe for oil well pipes having a high yield strength YS of llOksi (758MPa) or more and excellent low temperature toughness and its manufacture. Regarding the method. Background art
• Patent Document 1 includes C: 0.01 to 0.1%, Cr: 9 to 15%, N: 0.1% or less, even though it has a relatively high C content and high strength.
• a martensitic stainless steel that has high toughness and is suitable for oil well pipes has been proposed.
• the amount of carbide existing in the prior austenite grain boundaries is reduced to 0.5 volume% or less, and the maximum minor axis length of carbide is 10 to 200 nm.
• the technique described in Patent Document 1 uses the power of air cooling after hot working (cooling) and air cooling after solution treatment.
• Patent Document 1 Japanese Patent Laid-Open No. 2002-363708 Disclosure of Invention
• the desired yield strength is llOksi class in the case of air cooling (cooling) after hot rolling or air cooling (cooling) after solution forming.
• the object of the present invention is to solve the problems of the prior art, and to propose a seamless steel pipe for oil well pipes having a high yield strength of llOksi class and excellent low temperature toughness, and a stable manufacturing method thereof.
• excellent low temperature toughness refers to the case where the fracture surface transition temperature vTrs force S-60 ° C or less in the Charbee impact test.
• the present inventors diligently studied the influence of the component composition and heat treatment conditions on the change in toughness accompanying the increase in strength of a 13Cr martensitic stainless steel pipe.
• the C content is limited to less than 0.001%
• the Cr content is set to a relatively low content of about ll% Cr
• the Ni content is also set to a relatively low Ni content of 4.0% or less.
• the seamless steel pipe having a composition the balance Fe, after subjected to quenching treatment (810 ° CX 15min), heating to a temperature of 425 ⁇ 5 7 5 ° C Then, it was tempered to cool. In addition, correction treatment was performed during cooling of the tempering treatment.
• the obtained seamless steel pipe was subjected to tensile test and Charpy impact test, and tensile properties
• the composition further contains, in mass%, one or two selected from Cu: 2.0% or less, Mo: 2.0% or less A martensitic stainless steel seamless pipe for oil well pipes, characterized by (3)
• V 0.10% or less
• Nb 0.10% or less
• Ti 0.10% or less A martensitic stainless steel seamless steel pipe for oil country tubular goods characterized by having a composition containing at least seeds.
• the tempering treatment is performed by heating and cooling to a tempering temperature exceeding 450 ° C and 550 ° C or less, and yield strength characterized by applying llOksi-class high strength and excellent low-temperature toughness Of martensitic stainless steel seamless pipe for oil well pipes.
• the composition further contains one or two kinds selected from mass%, Cu: 2.0% or less, Mo: 2.0% or less.
• a seamless steel pipe for oil well pipes that has both high yield strength llOksi class strength and excellent low temperature toughness of fracture surface transition temperature vTrs force S-60 ° C or less can be easily and stably produced. It can be manufactured and has a remarkable industrial effect.
• Figure 1 is a graph showing the relationship between yield strength YS, tensile strength TS, fracture surface transition temperature vTrs, and tempering temperature.
• the manufacturing method of the seamless steel pipe for oil country tubular goods of this invention is demonstrated.
• the starting material is mass%, C: less than 0.001%, Si: 1.0% or less, Mn: 0.1 to 2.0%, P: 0.020% or less, S: 0 010% or less, A1: 0. 10% or less, Cr: 10-14%, Ni: 0.1-0%, N: 0.05% or less, the remainder consisting of Fe and inevitable impurities
• ma SS % is simply expressed as%.
• C is an important element related to the strength of martensitic stainless steel. To ensure the desired strength, C is preferably contained in an amount of 0.003% or more. , Toughness and corrosion resistance are likely to decrease. Therefore, in this effort, C is limited to less than 0.001%. Preferably, it is in the range of 0.003 to 0.008% from the viewpoint of ensuring the stability of strength and toughness.
• Si is an element that acts as a deoxidizing agent in the normal steelmaking process.
• it is desirable to contain 0.1% or more, but if it exceeds 1.0%, the toughness decreases, and further, Hot workability also decreases. For this reason, Si is limited to 1.0% or less.
• the content is preferably 0.1 to 0.3%.
• Mn is an element that increases the strength. In this invention, it is necessary to contain 0.1% or more in order to ensure the strength required for steel pipes for oil well pipes, but it must contain more than 2.0 ° / o. Adversely affects toughness. For this reason, Mn was limited to the range of 0.1 to 2.0%. Preferably, the content is 0.5 to 1.5%.
• P is an element that deteriorates corrosion resistance such as carbon dioxide gas 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 implemented industrially at a relatively low cost and does not deteriorate the corrosion resistance such as carbon dioxide corrosion resistance. The content is preferably 0.015% or less.
• S is an element that significantly degrades the hot workability in the pipe manufacturing process, and it is desirable that it be as small as possible. , S is limited to 0.010% or less. In addition, Preferably it is 0.003% or less.
• A1 is an element having a strong deoxidizing action, and in order to obtain such an effect, it is desirable to contain 0.001% or more. However, if it exceeds 0.10%, the toughness is adversely affected. . For this reason, A1 is limited to 0.10% or less. It is preferably 0.05% or less. '
• Cr is an element that improves the corrosion resistance by forming a protective film.
• Cr is an element that effectively contributes to the improvement of carbon dioxide corrosion resistance and carbon dioxide stress corrosion cracking resistance. If it contains 10% or more, the required corrosion resistance for oil well pipes can be secured, so in this effort 10% was made the lower limit.
• a large content exceeding 14% facilitates the formation of ferrite and requires the addition of a large amount of expensive austenite-generating elements in order to ensure the stability of the martensite phase or prevent the hot workability from being deteriorated. Economic disadvantage. For this reason, Cr was limited to the range of 10-14%. In addition, it is preferably 10.5-11. 5% from the viewpoint of securing a more stable structure and hot workability.
• Ni is an element that has a function of strengthening the protective film and enhances corrosion resistance such as carbon dioxide corrosion resistance. In order to obtain such an effect, a content of 0.1% or more is required. On the other hand, if it exceeds 4.0%, the improvement effect will be saturated and the production cost will only rise. For this reason, Ni was limited to the range of 0.1 to 4.0%. In addition, Preferably it is 1.5 to 3.0%.
• N is an element that remarkably improves the pitting corrosion resistance. Such an effect becomes remarkable when the content is 0.003% or more. -On the other hand, a content exceeding 0.05% reduces the toughness by forming various nitrides. Therefore, N is limited to 0.05% or less. In addition, Preferably it is 0.01 to 0.02%.
• the above components are basic components of the starting material.
• Cu is not more than 2.0% and Mo is not more than 2.0%.
• Z or V 0.10% or less
• Nb 0.10% or less
• Ti 0.10% or less selected from 1 or 2 or more types may be contained .
• Both Cu and Mo are elements that have the effect of improving corrosion resistance, and can be selected and contained as necessary.
• Cu is an element having an action of strengthening the protective film and improving the pitting corrosion resistance. In order to obtain such an effect, it is desirable to contain 0.2% or more. On the other hand, if the content exceeds 2.0%, a part of it precipitates and the toughness decreases. Therefore, if contained, Cu is preferably limited to 2.0% or less. More preferably, the content is 0.2 to 1.0%.
• Mo is an element having an action of increasing resistance to pitting corrosion caused by C1, and in order to obtain such an effect, it is desirable to contain 0.2% or more. On the other hand, if the content exceeds 2.0%, the strength decreases and the material cost increases. Make it. For this reason, Mo is preferably limited to 2.0% or less. More preferably, it is 0.2 to 1.0%. '
• V 0.1% or less
• b 0.1% or less
• Ti 0.1% or less selected from 10% or less
• V, Nb, and Ti are all elements that increase the strength, and can be selected according to need and contained in one or more kinds.
• V 0.02% or more
• Nb 0.01% or more
• Ti 0.02% or more
• the toughness decreases.
• V 0.1% or less if it is contained, it is preferable to limit to V 0.1% or less, Nb: 0.1% or less, and Ti: 0.1% or less. More preferably, V: 0.02 to 0.05%, Nb: 0.01 to 0.05%, Ti: 0.02 to 0.05%.
• the balance other than the above components is Fe and inevitable impurities. As an inevitable impurity, O: 0.000% or less is acceptable.
• the method for producing the starting material having the above-described composition is not particularly limited.
• the molten steel having the above-described composition can be produced by a generally known melting method such as a converter, an electric furnace, or a vacuum melting furnace.
• a steel pipe material such as a billet by a usual method such as melting, continuous forging method, ingot lump rolling method or the like.
• these steel pipe materials are heated and hot-processed and piped using the usual Mannesmann-one plug mill method or Mannesmann-Mandler Minore manufacturing process to produce seamless steel pipes of the desired dimensions, which are used as starting materials.
• a seamless steel pipe may be manufactured by hot extrusion using a press method.
• the seamless steel pipe is cooled to room temperature at a cooling rate higher than that of air cooling.
• the starting material (seamless steel pipe) is first quenched.
• the quenching treatment in the present invention is a treatment of reheating to a quenching temperature not lower than the Ac 3 transformation point and then cooling from the quenching temperature to a temperature range of 100 ° C. or lower at a cooling rate higher than air cooling. As a result, a fine martensite structure can be obtained. Quenching heating If the temperature is lower than the Ac 3 transformation point, the austenite single-phase region cannot be heated, and a sufficient martensite structure cannot be obtained by subsequent cooling, so that the desired strength cannot be ensured. For this reason, the heating temperature of the quenching treatment was limited to the Ac 3 transformation point or higher. In addition, Preferably it is 950 degrees C or less.
• Cooling from the quenching heating temperature is performed to a temperature range of 100 ° C or less at an air cooling rate 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. Also, the holding time at the quenching temperature is preferably lOmin or more from the viewpoint of soaking.
• Tempered seamless steel pipes will continue to be tempered.
• the tempering process is an important process for securing excellent low temperature toughness.
• the tempering treatment in the present invention is performed by heating to a tempering temperature in the range of 450 ° C. to 550 ° C., preferably after holding at 3 Omin or higher, preferably at a cooling rate of air cooling or higher, preferably to room temperature. Cooling is performed at This results in a seamless steel pipe with high strength over YSllOksi and excellent low temperature toughness with vTrs below -60 ° C.
• the tempering temperature is 450 ° C or lower, the tempering is insufficient and the toughness decreases, and it is impossible to combine high strength and high toughness.
• the tempering temperature is preferably 500 ° C or higher and 550 ° C or lower.
• the holding time at the tempering temperature is preferably 30 min or more from the viewpoint of ensuring the stability of the material. Cooling from the tempering temperature is preferably air cooling or higher.
• a correction treatment can be performed to correct defects in the steel pipe shape during cooling during the tempering treatment.
• the straightening treatment is preferably performed in a temperature range of 400 ° C or higher. If the temperature of the straightening treatment is less than 400 ° C, Processing strain is added locally, and variations in mechanical properties are likely to occur. For this reason, it was decided to perform the correction process in a temperature range of 400 ° C or higher.
• the seamless steel pipe manufactured by the above manufacturing method has the above composition, yield strength llOksi class high strength and fracture surface transition temperature of Charpy impact test vTrs -60 ° C or less excellent low temperature toughness And martensitic stainless steel seamless pipe.
• This martensitic stainless steel seamless pipe has a structure mainly composed of a tempered martensite phase. As a result, the steel pipe has a desired high strength and a desired high toughness and also has sufficient corrosion resistance as an oil well pipe.
• the slab was made into a slab by a continuous forging method, and the slab was re-heated and billet (size: 207 ⁇ ) obtained by billet rolling was used as the steel pipe material.
• billet size: 207 ⁇
• 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 mm ⁇ X wall thickness 12.7 mm).
• the obtained seamless steel pipe was subjected to quenching treatment, tempering treatment, or further straightening treatment under the conditions shown in Table 2.
• API arc-shaped tensile test specimens are collected from the quenched and tempered seamless steel pipes and subjected to tensile tests to determine the tensile properties (yield strength YS, tensile strength TS). It was.
• V-notch specimens (10 mm thick) were sampled from seamless steel pipes that had been quenched, tempered, or further straightened in accordance with JIS Z 2242 and subjected to Charpy impact testing. Conducted fracture surface transition temperature vTrs, and absorbed energy vE_6 at -60 ° C. And toughness was evaluated.
• specimens were collected from 12 locations around the circumference, and subjected to a Charpy impact test at -60 ° C. Absorbed energy V E- 6 . The variation was evaluated by the average value (ave) and the minimum value (rain).
• a corrosion test specimen with a thickness of 3 mm, a width of 25 mm, and a length of 50 mm was produced from the steel pipe by machining, and a corrosion test was conducted.
• Each of the inventive examples has sufficient corrosion resistance as an oil well pipe, and YS has a high strength of llOksi class and has excellent low temperature toughness with vTrs of -60 ° C or less. It has become.
• the comparative examples which are out of the scope of the present invention cannot secure the desired high strength and high toughness because the strength is insufficient or the low temperature toughness is lowered.

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• 2007
  • 2007-06-29 JP JP2007172560A patent/JP5145793B2/ja not_active Expired - Fee Related
  • 2007-10-10 WO PCT/JP2007/070209 patent/WO2009004741A1/ja active Application Filing
  • 2007-10-10 CN CN2007800007846A patent/CN101437973B/zh not_active Expired - Fee Related
  • 2007-10-10 EP EP07829943.5A patent/EP2172573B1/en not_active Not-in-force
  • 2007-10-10 US US12/665,097 patent/US20100193087A1/en not_active Abandoned
  • 2007-10-10 RU RU2010102917/02A patent/RU2431693C1/ru active

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