WO2023093802A1 - 一种油缸钢管及其制造方法 - Google Patents

一种油缸钢管及其制造方法 Download PDF

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WO2023093802A1
WO2023093802A1 PCT/CN2022/134015 CN2022134015W WO2023093802A1 WO 2023093802 A1 WO2023093802 A1 WO 2023093802A1 CN 2022134015 W CN2022134015 W CN 2022134015W WO 2023093802 A1 WO2023093802 A1 WO 2023093802A1
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Prior art keywords
steel pipe
oil cylinder
wall
cylinder steel
cooling
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PCT/CN2022/134015
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English (en)
French (fr)
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孙文
高展
马燕楠
左宏志
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宝山钢铁股份有限公司
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Publication of WO2023093802A1 publication Critical patent/WO2023093802A1/zh

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23P—METAL-WORKING NOT OTHERWISE PROVIDED FOR; COMBINED OPERATIONS; UNIVERSAL MACHINE TOOLS
    • B23P15/00—Making specific metal objects by operations not covered by a single other subclass or a group in this subclass
    • 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
    • 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
    • C21D11/00—Process control or regulation for heat treatments
    • 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
    • C21D11/00—Process control or regulation for heat treatments
    • C21D11/005—Process control or regulation for heat treatments for cooling
    • 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
    • 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
    • C21D6/005—Heat treatment of ferrous alloys containing Mn
    • 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
    • C21D6/008—Heat treatment of ferrous alloys containing Si
    • 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
    • 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
    • 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
    • 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
    • C21D9/085—Cooling or quenching
    • 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
    • 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
    • C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
    • 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
    • C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
    • 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
    • C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
    • 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
    • C21D2211/005—Ferrite
    • 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
    • C21D2211/009—Pearlite
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/20—Recycling

Definitions

  • the invention relates to the field of materials, in particular to an oil cylinder steel pipe and a manufacturing method thereof.
  • Oil cylinder steel pipes are widely used in construction machinery oil cylinders or cylinder barrels. During use, they are subjected to loads such as pulse fatigue and friction. Residual stress is an important factor affecting the fatigue life, collapse resistance, internal pressure resistance and machining deformation of seamless pipes. , Reducing or eliminating the residual stress of the cylinder steel pipe can greatly improve the service life of the cylinder steel pipe, which is one of the important directions for the subsequent production control of the cylinder steel pipe.
  • Chinese patent CN201810365440.5 discloses "the elimination method of the residual stress of quenched and tempered seamless steel pipe and the two-way chain cooling bed used", and the residual stress is eliminated by controlling the straightness of the steel pipe before quenching and tempering after rolling and the two-way chain of the cooling bed after quenching and tempering , eliminating the quenching and tempering stress relief annealing process to achieve the purpose of reducing costs.
  • Chinese patent CN201420805596.8 discloses "asymmetric steel pipe straightening roller", and a special straightening roller is designed to eliminate the residual stress and scale of the steel pipe by controlling the force on the steel pipe during the straightening process.
  • Chinese patent CN200910210718.2 discloses "a method for controlling the residual stress level of conveying steel pipes".
  • a formula is derived, and the residual stress level of steel pipes is obtained by measuring the springback of steel pipes and comparing with the formula, which is a A method of measuring and characterizing residual stress levels.
  • the object of the present invention is to provide an oil cylinder steel pipe and its manufacturing method. Compared with traditional oil cylinder steel pipe products, while having higher strength, the invention can significantly reduce the residual stress of the oil cylinder steel pipe and avoid cracking of the inner wall.
  • the yield strength of the oil cylinder steel pipe of the invention is ⁇ 600MPa, the tensile strength is ⁇ 730MPa, and the residual stress is ⁇ 50MPa.
  • the present invention provides an oil cylinder steel pipe, which, in addition to more than 90wt% of Fe and unavoidable impurities, also contains the following chemical elements in wt%: C: 0.16-0.3%, Si: 0.15- 0.5%, Mn: 1.2-1.8%, Nb: 0.02-0.04%, Mo: 0.1-0.2%, and optionally Ti: 0.015-0.03% and B: 0.0015-0.0035%.
  • the oil cylinder steel pipe contains the following chemical elements in wt %: C: 0.16-0.3%, Si: 0.15-0.5%, Mn: 1.2-1.8%, Nb: 0.02-0.04%, Mo: 0.1-0.2% %, optional Ti: 0.015-0.03% and B: 0.0015-0.0035%, the rest is Fe and unavoidable impurities.
  • P Preferably, among unavoidable impurities, P ⁇ 0.01%, S ⁇ 0.001%.
  • the wall thickness of the oil cylinder steel pipe is ⁇ 20mm, and the oil cylinder steel pipe contains Ti: 0.015-0.03% and B: 0.0015-0.0035%. In some embodiments, the wall thickness of the oil cylinder steel pipe is ⁇ 20 mm, and the oil cylinder steel pipe may or may not contain Ti: 0.015-0.03% and B: 0.0015-0.0035%.
  • the wall thickness of the oil cylinder steel pipe is ⁇ 9mm.
  • the microstructure from the outer wall to the position t/2 is tempered sorbite; the microstructure from the position t/2 to the inner wall is tempered sorbite+ferrite body, and the ferrite is distributed in a gradient, the closer to the inner wall, the higher the ferrite content; the ferrite content in the microstructure at the t/2 position is ⁇ 3%, and the ferrite in the microstructure of the inner wall (that is, at the surface of the inner wall) Body content ⁇ 5%.
  • t represents the wall thickness of the cylinder steel pipe (in mm).
  • the yield strength of the oil cylinder steel pipe is ⁇ 600MPa
  • the tensile strength is ⁇ 730MPa
  • the residual stress is ⁇ 50MPa.
  • the residual stress of the oil cylinder steel pipe is ⁇ 40MPa.
  • the yield ratio (ie, the ratio of yield strength to tensile strength) of the oil cylinder steel pipe is ⁇ 0.92.
  • the ferrite content in the microstructure at the t/2 position of the oil cylinder steel pipe in the present invention is 0.5t to 1.0t%.
  • the ferrite content in the microstructure of the inner wall of the oil cylinder steel pipe in the present invention is 1.5t to 2.0t%.
  • the ferrite content refers to the proportion of ferrite in the microstructure in area %, which is determined according to the metallographic method.
  • C is an interstitial solid solution strengthening element and has a great influence on hardenability.
  • the C content is lower than 0.16%, the strength is too low; when the C content is higher than 0.3%, the inner wall will crack after graded cooling. Therefore, the C content is controlled within the range of 0.16 to 0.3% in the present invention.
  • Si Deoxidizer commonly used is also a strong ferrite precipitation element, which improves hardenability to a certain extent.
  • the Si content is less than 0.15%, the above effects cannot be fully exhibited; when the Si content is more than 0.5%, Si causes surface quality problems. Therefore, the Si content is controlled in the range of 0.15 to 0.5% in the present invention.
  • Mn is a solid-solution strengthening element and is also an element that strongly improves hardenability.
  • the Mn content is less than 1.2%, the hardenability is insufficient and the strength is low; when the Mn content is greater than 1.8%, the hardenability is too high, resulting in less precipitation of ferrite content from the t/2 position to the inner wall after staged cooling , the phase transition and thermal stress of the inner wall are large tensile stresses, resulting in cracking of the inner wall. Therefore, the Mn content is controlled in the range of 1.2 to 1.8% in the present invention.
  • Nb Carbide precipitation strengthening element, refines austenite grains, and at the same time acts as a nucleation point to promote the precipitation of ferrite during graded cooling.
  • element Mo can strongly improve hardenability, and can also improve strength-toughness matching and tempering stability.
  • Mo content is in the range of 0.1% to 0.2%, not only the influence of Mo on the hardenability can be used to control the gradient distribution of ferrite from t/2 to the inner wall, but also the strength can be guaranteed while avoiding the occurrence of staged cooling The inner wall is cracked.
  • Ti and B The combined addition of Ti and B can strongly improve the hardenability.
  • the oil cylinder steel pipe needs to have improved hardenability to avoid a large increase in the ferrite content of the inner wall from t/2 to the inner wall, resulting in low strength; at the same time, Ti is precipitated as carbonitride, which can be used as a step in the staged cooling process.
  • the nucleation point of ferrite can effectively control the proportion of ferrite precipitation.
  • the Ti content is controlled in the range of 0.015 to 0.03%
  • the B content is controlled in the range of 0.0015 to 0.0035%.
  • unavoidable impurities include P and S, both of which are harmful elements in steel. If the mass percentage of P is too high, the grain boundaries will be segregated, embrittled, and the toughness will be severely deteriorated. If the mass percentage of S is too high, the content of inclusions in the steel will increase, which is detrimental to the low temperature toughness. Therefore, the P and S content in steel should be reduced as much as possible.
  • the invention controls the ferrite distribution in the oil cylinder steel pipe by controlling the contents of Nb, Mo, Ti and other elements.
  • the microstructure from the outer wall to the t/2 position is tempered sorbite; the microstructure from the t/2 position to the inner wall is tempered sorbite+ferrite, and
  • the ferrite is distributed in a gradient, and the closer to the inner wall, the higher the ferrite content; the ferrite content in the microstructure at the position t/2 is ⁇ 3%, and the ferrite content in the microstructure of the inner wall is ⁇ 5%; among them, t is the wall thickness of the oil cylinder steel pipe, in mm.
  • the microstructure from the outer wall to the t/2 position is tempered sorbite.
  • the tempered sorbite has a good level of strength and toughness, which can ensure that the outer layer of the oil cylinder steel pipe has sufficient rigidity.
  • the microstructure from the t/2 position to the inner wall is sorbite + ferrite, which can ensure good toughness and low yield ratio of the cylinder steel pipe.
  • the precipitation of ferrite is distributed in a gradient distribution.
  • the ferrite content in the microstructure of the inner wall is 1.5t to 2.0t%. If the ferrite content is too low, the yield ratio will be too high, the residual stress will be too large, and the safety of use will be reduced. In addition, there will be a greater risk of cracking on the inner wall during water quenching.
  • the strength of the cylinder steel pipe will be too low to meet the requirements of use; if the wall thickness increases, if not enough ferrite is precipitated, the residual stress of the cylinder steel pipe will increase, and the inner wall will tend to crack. big.
  • the present invention provides a method for manufacturing the above oil cylinder steel pipe, comprising the following steps:
  • the opening and cooling temperature of the steel pipe is controlled to be ⁇ Ar 3 , B f ⁇
  • the final cooling temperature of the steel pipe is ⁇ B s- 100°C, and the cooling rate is 25 to 35°C/s;
  • Heating the straightened steel pipe to Ac 3 +30 to Ac 3 +60°C i.e. Ac 3 +30 ⁇ quenching temperature ⁇ Ac 3 +60°C
  • water-cooling method for graded cooling during which the steel pipe is rotated , when cooling, first use outer spray water for cooling, when Ar 3- 70 °C ⁇ inner wall temperature ⁇ less than Ar 3- 30 °C, start to inject water into the steel pipe from one end of the steel pipe until the cooling water fills the inner hole of the steel pipe, until the steel pipe is cooled to room temperature ;
  • the heating temperature is 1250 to 1280° C.
  • the heating time is 3 to 4 hours.
  • the piercing temperature is 1100 to 1230°C.
  • the finish rolling temperature is 900 to 1000°C.
  • the steel pipe is air-cooled to below Ar 3-50 °C, and then reheated to 950 to 980°C.
  • the contraction temperature is 850 to 900°C.
  • the straightened steel pipe is naturally cooled to room temperature.
  • tempering temperature (550-2 ⁇ t)°C.
  • the straightening temperature is ⁇ 400°C.
  • the invention designs the components of the oil cylinder steel pipe and controls the cooling process in the water quenching process, and can reduce the residual stress of the oil cylinder steel pipe and improve the service performance of the oil cylinder steel pipe without adding additional production processes.
  • the steel pipe is stretched and reduced at 850 to 900° C . After the stretch is reduced , only the outer wall of the steel pipe is water - cooled.
  • the temperature at the end of the bainite transformation, B s is the temperature at the beginning of the bainite transformation during the cooling process, and the cooling rate is controlled within the range of 25 to 35 °C/s during the cooling process.
  • the main purpose of this process is to quickly cool and harden the steel pipe through uniform cooling, to ensure that the straightness of the steel pipe is ⁇ 2mm/m, preferably ⁇ 1.5mm/m, and to refine the rolled structure at the same time, so as to obtain a good performance match for subsequent quenching and tempering lay the foundation.
  • cooling through this cooling method reduces the residual stress level in the rolling state.
  • straightening is carried out immediately. Straightening with temperature is beneficial to ensure straightness, and at the same time reduces the residual stress level in the rolled state.
  • the straightness of the steel pipe after straightening is ⁇ 2mm/m, preferably ⁇ 1.5mm/ m, and then naturally cooled to room temperature on a cooling bed.
  • the steel pipe of the present invention adopts water-cooling method to carry out graded cooling.
  • the steel pipe is rotated.
  • the outer wall of the steel pipe is cooled by spraying water first.
  • Turn on the inner spray water to inject water into the steel pipe to cool the inner wall of the steel pipe, and the cooling water fills the inner hole of the steel pipe until the steel pipe cools to room temperature.
  • the present invention adopts the principle of cooling the oil cylinder steel pipe by the staged cooling process:
  • the residual stress of the steel pipe is closely related to the phase transformation and thermal stress during the cooling process.
  • the distribution of phase transformation and thermal stress on the entire wall thickness of the steel pipe can be effectively controlled by staged cooling, and the interaction between martensitic transformation stress and thermal stress can be realized. Elimination can effectively reduce the residual stress level of the steel pipe.
  • the staged cooling method of spraying outside first and then spraying inside the phase transition stress on the outer wall of the steel pipe is tensile stress, while the thermal stress is compressive stress, the phase transition stress at the center of the steel pipe is compressive stress, and the thermal stress is tensile stress. The two cancel each other out.
  • phase transformation stress and thermal stress of the inner wall are both tensile stresses, but the inner wall is On the cold side, after the external shower cooling, the cooling starts when Ar 3- 70 °C ⁇ inner wall temperature ⁇ Ar 3- 30 °C.
  • the inner wall has precipitated ferrite structure, which reduces the transformation ratio of martensite structure and reduces the The phase change stress at the position of the inner wall is reduced, thereby effectively reducing the residual stress level of the inner wall and avoiding cracking of the inner wall.
  • the post-stretch cooling process of the present invention adopts rapid cooling to increase the hardness and uniformity of the oil cylinder steel pipe and reduce the residual stress level of the rolled oil cylinder steel pipe. Further, through the staged cooling after quenching, a cooling rate gradient is formed in the wall thickness direction. During the cooling process, the outer wall is cooled first, and the center and inner wall are cooled later. The cooling rate of the inner wall of the center is slower than that of the outer wall, and the ferrite structure occurs first. Transformation, and then martensitic transformation occurs, the closer to the inner wall, the cooling rate gradually slows down, and the precipitated ferrite content increases. And as the wall thickness of the oil cylinder steel pipe increases, the cooling rate of the center and inner wall further decreases, which promotes the precipitation of ferrite, and the precipitation content of ferrite will increase accordingly.
  • the invention controls the precipitation of ferrite in the microstructure of the steel pipe of the oil cylinder through a graded cooling process, and the closer to the inner wall, the higher the ferrite content. Since ferrite has good plasticity and toughness, it can ensure that the inner wall of the oil cylinder steel pipe has good residual stress control during the cooling process, and prevents cracking of the inner wall during water quenching.
  • the hardenability of the oil cylinder steel pipe is improved by controlling the content of C, Si, and Mn elements, and the inner wall of the oil cylinder steel pipe is prevented from cracking during the subsequent graded cooling process.
  • the content of Nb and Mo elements the distribution of ferrite in the oil cylinder steel pipe is controlled, and the cracking of the inner wall during the staged cooling process is further avoided.
  • adding Ti and B to improve hardenability can avoid t/2 to a large increase in inner wall ferrite content and cause low strength.
  • the present invention adopts different graded cooling processes after the steel pipe is stretched and quenched.
  • the distribution of phase transformation and thermal stress on the entire wall thickness of the cylinder steel pipe the mutual elimination of martensitic transformation stress and thermal stress can be achieved, which can effectively reduce the residual stress level of the steel pipe;
  • the distribution of ferrite in the microstructure of the cylinder steel pipe the phase transition stress at the position of the inner wall is reduced, thereby effectively reducing the residual stress level of the inner wall, avoiding cracking of the inner wall, and obtaining an oil cylinder with higher strength and low residual stress
  • the yield strength is ⁇ 600MPa
  • the tensile strength is ⁇ 730MPa
  • 0 ⁇ residual stress ⁇ 50MPa the yield strength is ⁇ 600MPa
  • Fig. 1 is a picture of measuring the residual stress of the oil cylinder steel pipe prepared in Comparative Example 1 of the present invention by the slotting method.
  • Fig. 2 is a picture of measuring the residual stress of the oil cylinder steel pipe in Example 1 of the present invention by the slotting method.
  • Fig. 3 is a photograph of the metallographic structure of the outer wall surface of the oil cylinder steel pipe in Example 1 of the present invention.
  • Fig. 4 is a photograph of the metallographic structure at the 1/2 wall thickness of the oil cylinder steel pipe in Example 1 of the present invention.
  • Fig. 5 is a photograph of the metallographic structure of the inner wall surface of the oil cylinder steel pipe in Example 1 of the present invention.
  • the oil cylinder steel pipes of Examples 1-8 of the present invention were manufactured according to the method described above.
  • the oil cylinder steel pipes of Comparative Examples 1-8 are manufactured in substantially the same manner as in Examples 1-8, but one or more of the elemental composition and/or manufacturing process parameters of Comparative Examples 1-8 do not fall within the requirements of the present invention In the range.
  • step 1) the molten steel is smelted and cast according to the element composition shown in Table 1 to obtain a billet; in step 7), the steel pipe after the treatment in step 6) is straightened, and the straightened The steel pipe is naturally cooled to room temperature.
  • yield strength and tensile strength are measured according to GB/T 228, and residual stress is measured according to ISO/TR10400 standard.
  • Fig. 1 and Fig. 2 are the picture that measures the residual stress of the oil cylinder steel pipe prepared in comparative example 1 and embodiment 1 of the present invention respectively by slotting method, as can be seen from the figure, the residual stress of oil cylinder steel pipe of the present invention will obviously be less than
  • the gap of the seamless pipe obtained by the method of the present invention of the traditional oil cylinder steel pipe is smaller than that of the seamless pipe prepared by the traditional process.
  • the residual stress of the seamless pipe obtained by the present invention (such as Example 1) is obviously smaller than that of the traditional process (such as Comparative Example 1).
  • Fig. 3 to Fig. 5 are photographs of the metallographic structure of different parts of the oil cylinder steel pipe of the present invention. It can be seen from the picture that the metallographic structure from the outer wall to the t/2 position is tempered sorbite, the t% ratio ferrite structure is precipitated at the t/2 position, and the ferrite from the t/2 position to the inner wall is gradient Distribution, the closer to the inner wall, the higher the ferrite content, and the ferrite content in the metallographic structure of the inner wall reaches 2t%.
  • the residual stress of the oil cylinder steel pipes obtained in Comparative Examples 1-8 is relatively high, and cracks may also appear on the inner wall ;
  • the present invention obtains an oil cylinder steel pipe with excellent comprehensive performance by designing the chemical element composition of the oil cylinder steel pipe and cooperating with a specific manufacturing process.

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Abstract

一种油缸钢管及其制造方法，其除90wt％以上的Fe和不可避免的杂质之外，还包含以wt％计的如下化学元素：C：0.16-0.3％，Si：0.15-0.5％，Mn：1.2-1.8％，Nb：0.02-0.04％，Mo：0.1-0.2％；以及可选的Ti：0.015-0.03％和B：0.0015-0.0035％。本发明在钢管张减和淬火后，分别采用不同的分级冷却工艺，通过增加钢管的刚度和直度水平，控制油缸钢管整个壁厚上相变和热应力的分布，控制油缸钢管微观组织中铁素体分布，有效降低油缸钢管的残余应力，避免了内壁发生开裂，从而获得强度较高、残余应力低的油缸钢管，油缸钢管屈服强度≥600MPa，抗拉强度≥730MPa，残余应力≤50MPa。

Description

一种油缸钢管及其制造方法 技术领域
本发明涉及材料领域，特别是涉及一种油缸钢管及其制造方法。
背景技术
油缸钢管广泛应用于工程机械油缸或气缸缸筒，其在使用过程中承受脉冲疲劳、摩擦等载荷，残余应力是影响无缝管疲劳寿命、抗挤毁、抗内压以及机加工变形的重要因素，降低或消除油缸钢管的残余应力可以大幅提升油缸钢管的使用寿命，是后续油缸钢管生产控制的重要方向之一。
目前降低或消除残余应力常规手段包括高温去应力退火及机械物理方法，但此类工艺方法成本高，且增加了生产流程。
中国专利CN201810365440.5公开了“调质无缝钢管残余应力的消除方法及采用的双向链式冷床”，通过控制轧后调质前钢管直度以及调质后冷床双向链来消除残余应力，省去调质去应力退火工序，实现降低成本目的。
中国专利CN201420805596.8公开了“非对称的钢管矫直辊”，设计了一种特殊的矫直辊，通过控制矫直过程中钢管受力，用于消除钢管的残余应力和氧化皮。
中国专利CN200910210718.2公开了“一种输送钢管残余应力水平的控制方法”，该专利中推导出了一个公式，通过测量钢管的弹复量和公式比较，从而得到钢管的残余应力水平，是一种测量表征残余应力水平的方法。
发明内容
本发明的目的在于提供一种油缸钢管及其制造方法。与传统油缸钢管产品相比，在具有较高强度的同时，本发明能够明显降低油缸钢管的残余应力，避免了内壁发生开裂。本发明油缸钢管的屈服强度≥600MPa，抗拉强度≥730MPa，残余应力≤50MPa。
在一方面，本发明提供了一种油缸钢管，其除90wt％以上的Fe和不可避免的杂质之外，还包含以wt％计的如下化学元素：C：0.16-0.3％，Si：0.15-0.5％，Mn：1.2-1.8％，Nb：0.02-0.04％，Mo：0.1-0.2％，以及可选的Ti：0.015-0.03％和B：0.0015-0.0035％。
优选地，所述油缸钢管包含以wt％计的如下化学元素：C：0.16-0.3％，Si：0.15-0.5％，Mn：1.2-1.8％，Nb：0.02-0.04％，Mo：0.1-0.2％，可选的Ti：0.015-0.03％和B：0.0015-0.0035％，其余为Fe和不可避免的杂质。
优选地，在不可避免的杂质中，P≤0.01％，S≤0.001％。
在一些实施方式中，所述油缸钢管的壁厚≥20mm，并且所述油缸钢管包含Ti：0.015-0.03％和B：0.0015-0.0035％。在一些实施方式中，所述油缸钢管的壁厚<20mm，所述油缸钢管可以包含或不包含Ti：0.015-0.03％和B：0.0015-0.0035％。
优选地，所述油缸钢管的壁厚≥9mm。
优选地，在所述油缸钢管的壁厚方向上，外壁至t/2位置处的微观组织为回火索氏体；t/2位置处至内壁的微观组织为回火索氏体+铁素体，且铁素体呈梯度分布，距离内壁越近，铁素体含量越高；t/2位置处的微观组织中铁素体含量≥3％，内壁(即内壁表面处)的微观组织中铁素体含量≥5％。
在本文中，除非另有明确说明，否则t表示油缸钢管的壁厚(单位mm)。
优选地，所述油缸钢管的屈服强度≥600MPa，抗拉强度≥730MPa，残余应力≤50MPa。
优选地，所述油缸钢管的残余应力≤40MPa。
优选地，所述油缸钢管的屈强比(即屈服强度与抗拉强度的比值)≤0.92。
优选地，本发明所述油缸钢管t/2位置处的微观组织中铁素体含量为0.5t至1.0t％。
优选地，本发明所述油缸钢管内壁的微观组织中铁素体含量为1.5t至2.0t％。
在本文中，铁素体含量是指微观组织中以面积％计的铁素体占比，根据金相法进行测定。
在本发明所述油缸钢管中，各元素的设计原理如下：
C：C是间隙固溶强化元素，且对淬透性影响较大。当C含量低于0.16％时，强度太低；当C含量高于0.3％时，分级冷却后内壁会发生开裂。因此，本发明中C含量被控制在0.16至0.3％范围内。
Si：常规使用的脱氧剂，也是强铁素析出元素，一定程度上改善淬透性。当Si含量低于0.15％时，不能充分发挥上述效果；当Si含量高于0.5％时，Si会导致表面质量问题。因此，本发明中Si含量被控制在0.15至0.5％范围内。
Mn：Mn为固溶强化元素，也是强烈提升淬透性元素。当Mn含量小于1.2％时，淬透性不足，强度偏低；当Mn含量大于1.8％时，淬透性太高，导致分级冷却后t/2位置处至内壁的铁素体含量析出较少，内壁相变及热应力均为较大的拉应力，致使内壁发生开裂。因此，本发明中Mn含量被控制在1.2至1.8％的范围内。
Nb：碳化物析出强化元素，细化奥氏体晶粒，同时作为形核点作为促进分级冷却过程中铁素体的析出。
Mo：元素Mo可以强烈提升淬透性，也可以提升强韧性匹配和回火稳定性。当Mo含量在0.1％至0.2％范围内时，不仅可以通过Mo对淬透性的影响来控制t/2至内壁的铁素体呈梯度分布，还可以在保证强度同时避免分级冷却过程中发生内壁开裂。
Ti和B：复合添加的Ti和B可以强烈提升淬透性。对于壁厚20mm以上管材，需要油缸钢管具有提升的淬透性，避免t/2至内壁铁素体含量大幅提升，导致强度偏低；同时Ti作为碳氮化物析出，可作为分级冷却过程中的铁素体的形核点，可有效控制铁素体析出的比例。当Ti含量低于0.015％或B含量低于0.0015％时，不能充分实现上述效果；当Ti含量高于0.03％或B含量高于0.0035％时，对于提高淬透性无明显提升作用。因此，本发明中Ti含量被控制在0.015至0.03％范围内，B含量被控制在0.0015至0.0035％范围内。
需要说明的是，不可避免的杂质包括P和S，二者为钢中的有害元素。P的质量百分比过高会偏聚晶界，脆化晶界，严重恶化韧性。S的质量百分比过高会导致钢中夹杂物含量增多，对低温韧性不利。因此，应尽量降低钢中的P、S含量。
本发明通过控制Nb、Mo、Ti等元素含量，控制油缸钢管中铁素体分布。在所述油缸钢管的壁厚方向上，外壁至t/2位置处的微观组织为回火索氏体；t/2位置处至内壁的微观组织为回火索氏体+铁素体，且铁素体呈梯度分布，距离内壁越近，铁素体含量越高；t/2位置处的微观组织中铁素体含量≥3％，内壁的微观组织中铁素体含量≥5％；其中，t为油缸钢管的壁厚，单位mm。外壁至t/2位置处的微观组织为回火索氏体，回火索氏体具有良好的强度和韧性水平，可保证油缸钢管外层具有足够的刚性。t/2位置处至内壁的微观组织为索氏体+铁素体，可保证油缸钢管良好的韧性，低的屈强比。
另外，铁素体组织的析出呈梯度分布，距离内壁越近，铁素体含量越高，由于铁素体具有良好的塑韧性，其可保证油缸钢管内壁在冷却过程中有良好的残余应力控制，防止内壁水淬过程中的开裂，而且在保证油缸钢管具有较高强度的同时，能够明显降低油缸钢管的残余应力。
本发明人通过广泛研究发现，油缸钢管中铁素体的析出量与油缸钢管的壁厚直接存在特定关系，壁厚的t/2位置处的铁素体含量为0.5t至1.0t％；油缸钢管内壁的微观组织中铁素体含量为1.5t至2.0t％。如果铁素体含量过低，导致屈强比过高，残余应力过大，使用安全性降低，另外会导致水淬过程中内壁存在较大的开裂风险。如果铁素体含量过高，会导致油缸钢管的强度过低，不能满足使用要求；壁厚增加，如不析出足够多的铁素体，会导致油缸钢管的残余应力增大，内壁开裂倾向很大。
在另一方面，本发明提供制造上述油缸钢管的方法，包括以下步骤：
1)冶炼和铸造：
按照上述元素组成对钢水进行冶炼和铸造，得到铸坯；
2)对铸坯进行加热；
3)对加热后的铸坯进行穿孔；
4)连轧，得到钢管；
5)对钢管进行风冷和再加热；
6)对再加热后的钢管进行张减和冷却：
对再加热后的钢管进行张减(即张力减径)，张减后只对钢管外壁进行水冷(即在此步骤中不对钢管内壁进行水冷)，控制钢管开冷温度≥Ar 3，B f≤钢管终冷温度≤B s-100℃，冷却速度为25至35℃/s；
7)对冷却后的钢管进行矫直；
8)对矫直后的钢管进行淬火：
将矫直后的钢管加热至Ac 3+30至Ac 3+60℃(即Ac 3+30≤淬火温度≤Ac 3+60℃)，之后采用水冷方式进行分级冷却，冷却过程中对钢管进行旋转，冷却时先采用外淋水进行冷却，Ar 3-70℃≤内壁温度≤小于Ar 3-30℃时，开始从钢管一端向钢管内注水，至冷却水充满钢管内孔，直至钢管冷却至室温；
9)对淬火后的钢管进行回火；
10)出炉后对钢管进行矫直，得到所述油缸钢管。
优选地，步骤2)中，加热温度为1250至1280℃，加热时间为3至4h。
优选地，步骤3)中，穿孔温度为1100至1230℃。
优选地，步骤4)中，终轧温度为900至1000℃。
优选地，步骤5)中，钢管被风冷至Ar 3-50℃以下，之后被再加热至950至980℃。
优选地，步骤6)中，张减温度为850至900℃。
优选地，步骤7)中，将矫直后的钢管自然冷却至室温。
优选地，步骤9)中，回火温度＝(550-2×t)℃。
优选地，步骤10)中，矫直温度≥400℃。
本发明对油缸钢管的成分进行设计并结合控制水淬过程中的冷却工艺，在不增加额外的生产工序的情况下，可以降低油缸钢管的残余应力，提升油缸钢管使用性能。
在850至900℃下对钢管进行张减，张减后只对钢管外壁进行水冷，控制开冷温度≥Ar 3，B f≤终冷温度≤B s-100℃，B f为冷却过程中贝氏体相变结束时的温度，B s为冷 却过程中贝氏体相变开始时的温度，冷却过程中冷速控制在25至35℃/s范围内。此工序主要目的为通过均匀化冷却，快速使钢管冷却硬化，保证了钢管的直度≤2mm/m、优选<1.5mm/m，同时细化轧态组织，为后续调质后获得良好性能匹配打下基础。另外，通过此种冷却方式冷却，减少了轧态的残余应力水平。
钢管快速冷却至终冷温度后，立马进行矫直，带温矫直利于保证直度，同时减小轧态的残余应力水平，矫直后钢管的直度≤2mm/m、优选<1.5mm/m，然后上冷床自然冷却至室温。
本发明钢管在淬火之后采用水冷方式进行分级冷却，冷却过程中对钢管进行旋转，冷却时先对钢管外壁采用外淋水进行冷却，Ar 3-70℃≤内壁温度≤小于Ar 3-30℃时，开启内喷水向钢管内注水，对钢管内壁进行冷却，冷却水充满钢管内孔，直至钢管冷却至室温。
本发明采用分级冷却工艺对油缸钢管进行冷却的原理：
1)由于外淋水为整个钢管长度同时冷却，冷却均匀性较好，而对钢管内壁进行冷却时，钢管一端先冷，一端后冷，可以增加钢管刚度，其较好的冷却均匀性保证了钢管较好的直度水平，避免了后续由于管子弯曲，矫直变形带来的较大残余应力。
2)钢管的残余应力与冷却过程中的相变和热应力密切相关，通过分级冷却可有效控制钢管整个壁厚上相变和热应力的分布，实现马氏体相变应力和热应力的相互消掉，可有效降低钢管的残余应力水平。在本发明所述技术方案中先外淋后内喷的分级冷却方式，钢管外壁相变应力为拉应力，而热应力为压应力，钢管中心相变应力为压应力，热应力为拉应力，两者相互抵消。
3)内壁冷却转变组织析出部分铁素体组织，而非完全马氏体组织，可以有效降低内壁残余应力，在本发明技术方案中，内壁相变应力和热应力均为拉应力，但内壁为晚受冷面，待外淋冷却后，Ar 3-70℃≤内壁温度≤Ar 3-30℃时才开始冷却，此时内壁已经析出铁素体组织，减少了马氏体组织转变比例，降低了内壁位置的相变应力，从而有效降低了内壁的残余应力水平，避免了内壁发生开裂。
本发明张减后冷却工艺，采用快速冷却，增加油缸钢管硬度及均匀性，减少轧态油缸钢管的残余应力水平。进一步，通过淬火后的分级冷却，在壁厚方向形成冷速梯度，在冷却过程中外壁先冷，中心及内壁后冷，且中心内壁冷速相比外壁较慢，其先发生铁素体组织转变，而后发生马氏体转变，越靠近内壁，冷速逐渐减慢，析出的铁素体含量增加。且随油缸钢管的壁厚增加，中心及内壁冷速进一步降低，促进了铁素体的析出，铁素体析出含量会相应增加。
Ar 3-70℃≤内壁温度≤Ar 3-30℃时，才开始向内壁通水冷却，此时内壁已经析出铁素体组织，减少了马氏体组织转变比例，使得有效降低了距离内壁1mm范围内的残余应力水平。
本发明通过分级冷却工艺，控制油缸钢管微观组织中铁素体的析出，距离内壁越近，铁素体含量越高。由于铁素体具有良好的塑韧性，其可保证油缸钢管内壁在冷却过程中有良好的残余应力控制，防止内壁水淬过程中的开裂。
本发明的有益效果：
本发明油缸钢管在成分设计上，通过控制C、Si、Mn元素的含量，提高油缸钢管的淬透性，避免在在后续分级冷却过程中油缸钢管内壁发生开裂。同时，通过控制Nb、Mo元素含量，控制油缸钢管中铁素体分布，进一步避免分级冷却过程中内壁的开裂。
另外，根据油缸钢管的壁厚，当油缸钢管的壁厚在20mm以上时，添加Ti和B提升淬透性，可以避免t/2至内壁铁素体含量大幅提升而导致强度偏低。
本发明在成分设计的基础上，在钢管张减和淬火后，分别采用不同的分级冷却工艺，一方面，通过增加钢管的刚度和直度水平，避免了后续由于管子弯曲，矫直变形带来的较大残余应力；另一方面，通过控制油缸钢管整个壁厚上相变和热应力的分布，实现马氏体相变应力和热应力的相互消掉，可有效降低钢管的残余应力水平；最后，通过控制油缸钢管微观组织中铁素体分布，降低了内壁位置的相变应力，从而有效降低了内壁的残余应力水平，避免了内壁发生开裂，从而获得具有较高强度和低残余应力的油缸钢管，其屈服强度≥600MPa，抗拉强度≥730MPa，0≤残余应力≤50MPa。
附图说明
图1是通过割缝法测量本发明比较例1制备的油缸钢管的残余应力的图片。
图2是通过割缝法测量本发明实施例1的油缸钢管的残余应力的图片。
图3是本发明实施例1油缸钢管的外壁表面的金相组织照片。
图4是本发明实施例1油缸钢管的1/2壁厚处的金相组织照片。
图5是本发明实施例1油缸钢管的内壁表面的金相组织照片。
具体实施方式
下面通过实施例对本发明做进一步说明。
按照上文所述方法来制造本发明实施例1-8的油缸钢管。比较例1-8的油缸钢管采用与实施例1-8大致相同的方法进行制造，但是比较例1-8的元素组成和/或制造工 艺参数中的一个或多个没有落入本发明要求保护的范围内。
本发明的实施例1-8和比较例1-8的化学成分参见表1。
本发明的实施例1-8和比较例1-8的具体制造工艺参数参见表2。其中，步骤1)中，根据表1中所示的元素组成对钢水进行冶炼和铸造，得到铸坯；步骤7)中，对经步骤6)处理后的钢管进行矫直，将矫直后的钢管自然冷却至室温。
本发明的实施例1-8和比较例1-8中获得的油缸钢管的性能参数参见表3。
在本申请中，屈服强度和抗拉强度根据GB/T 228进行测量，残余应力根据ISO/TR10400标准进行测量。
图1和图2分别为通过割缝法测量本发明的比较例1和实施例1中制备的油缸钢管的残余应力的图片，由图上可以看出，本发明油缸钢管的残余应力要明显小于传统油缸钢管本发明方法所获得无缝管的缝隙小于传统工艺制备的无缝管，显然本发明(例如实施例1)所获得无缝管的残余应力要明显小于传统工艺(例如比较例1)制备的无缝管。
图3至图5为本发明油缸钢管不同部位金相组织照片。由图片可以看出，外壁至t/2位置处的金相组织为回火索氏体，t/2位置处析出t％比例铁素体组织，t/2位置处至内壁铁素体呈梯度分布，距离内壁越近，铁素体含量越高，内壁位置金相组织中铁素体含量达到2t％。
由表3可知，本发明获得的油缸钢管内壁无开裂情况，且残余应力均低于50MPa，甚至可以实现残余应力为0。
由于元素组成和/或制造工艺参数中的一个或多个没有落入本发明要求保护的范围内，比较例1-8中获得的油缸钢管的残余应力较高，且内壁还会出现开裂的情况；在壁厚超过20mm时，比较例4和5由于没有添加Ti、B元素，虽然油缸钢管具有较低的残余应力，但强度也不能达到本发明的要求。
综上，与现有技术相比，本发明通过对油缸钢管的化学元素组成进行设计，并配合特定制造工艺，获得了综合性能优异的油缸钢管。
Figure PCTCN2022134015-appb-000001
Figure PCTCN2022134015-appb-000002
Figure PCTCN2022134015-appb-000003

Claims (10)

  1. 一种油缸钢管，其除90wt％以上的Fe和不可避免的杂质之外，还包含以wt％计的如下化学元素：C：0.16-0.3％，Si：0.15-0.5％，Mn：1.2-1.8％，Nb：0.02-0.04％，Mo：0.1-0.2％，以及可选的Ti：0.015-0.03％和B：0.0015-0.0035％。
  2. 根据权利要求1所述的油缸钢管，其中，所述油缸钢管包含以wt％计的如下化学元素：C：0.16-0.3％，Si：0.15-0.5％，Mn：1.2-1.8％，Nb：0.02-0.04％，Mo：0.1-0.2％，可选的Ti：0.015-0.03％和B：0.0015-0.0035％，其余为Fe和不可避免的杂质。
  3. 根据权利要求1或2所述的油缸钢管，其中，所述油缸钢管的壁厚≥20mm，并且所述油缸钢管包含Ti：0.015-0.03％和B：0.0015-0.0035％。
  4. 根据权利要求1-3中任一项所述的油缸钢管，其中，在所述油缸钢管的壁厚方向上，外壁至t/2位置处的微观组织为回火索氏体；t/2位置处至内壁的微观组织为回火索氏体+铁素体，且铁素体呈梯度分布，距离内壁越近，铁素体含量越高；t/2位置处的微观组织中铁素体含量≥3％，内壁的微观组织中铁素体含量≥5％；其中，t为油缸钢管的壁厚，单位mm。
  5. 根据权利要求1-4中任一项所述的油缸钢管，其中，所述油缸钢管的屈服强度≥600MPa，抗拉强度≥730MPa，残余应力≤50MPa、优选≤40MPa；优选地，所述油缸钢管的屈强比≤0.92。
  6. 根据权利要求1-5中任一项所述的油缸钢管，其中，所述油缸钢管t/2位置处的微观组织中铁素体含量为0.5t至1.0t％。
  7. 根据权利要求1-6中任一项所述的油缸钢管，其中，所述油缸钢管内壁的微观组织中铁素体含量为1.5t至2.0t％。
  8. 根据权利要求1-7中任一项所述的油缸钢管，其中，所述油缸钢管的壁厚≥9mm。
  9. 制造权利要求1-8中任一项所述的油缸钢管的方法，包括以下步骤：
    1)冶炼和铸造：
    按照权利要求1中的元素组成对钢水进行冶炼和铸造，得到铸坯；
    2)对铸坯进行加热；
    3)对加热后的铸坯进行穿孔；
    4)连轧，得到钢管；
    5)对钢管进行风冷和再加热；
    6)对再加热后的钢管进行张减和冷却：
    对再加热后的钢管进行张减，张减后对钢管外壁进行水冷，控制钢管开冷温度 ≥Ar 3，B f≤钢管终冷温度≤B s-100℃，冷却速度为25至35℃/s；
    7)对冷却后的钢管进行矫直；
    8)对矫直后的钢管进行淬火：
    Ac 3+30≤淬火温度≤Ac 3+60℃，之后采用水冷方式进行分级冷却，冷却过程中对钢管进行旋转，冷却时先采用外淋水进行冷却，Ar 3-70℃≤内壁温度≤小于Ar 3-30℃时，开始从钢管一端向钢管内注水，至冷却水充满钢管内孔，直至钢管冷却至室温；
    9)对淬火后的钢管进行回火；
    10)出炉后对钢管进行矫直，得到所述油缸钢管。
  10. 根据权利要求9所述的方法，其中，所述方法满足如下中的一个以上：
    步骤2)中，加热温度为1250至1280℃，加热时间为3至4h；
    步骤3)中，穿孔温度为1100至1230℃；
    步骤4)中，终轧温度为900至1000℃；
    步骤5)中，钢管被风冷至Ar 3-50℃以下，之后被再加热至950至980℃；
    步骤6)中，张减温度为850至900℃；
    步骤7)中，将矫直后的钢管自然冷却至室温；
    步骤9)中，回火温度＝(550-2×t)℃；以及
    步骤10)中，矫直温度≥400℃。
PCT/CN2022/134015 2021-11-25 2022-11-24 一种油缸钢管及其制造方法 WO2023093802A1 (zh)

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JPH07233416A (ja) * 1994-02-23 1995-09-05 Nippon Steel Corp 冷間成形による建築用低降伏比ＴＳ（引張強度）５９０Ｎ／ｍｍ２ 級鋼管の製造法
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US20140299235A1 (en) * 2013-04-08 2014-10-09 Dalmine S.P.A. Heavy wall quenched and tempered seamless steel pipes and related method for manufacturing said steel pipes
CN105925883A (zh) * 2016-05-27 2016-09-07 宝鸡石油钢管有限责任公司 一种高强高韧n80q石油套管及其制造方法

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH07233416A (ja) * 1994-02-23 1995-09-05 Nippon Steel Corp 冷間成形による建築用低降伏比ＴＳ（引張強度）５９０Ｎ／ｍｍ２ 級鋼管の製造法
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