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US-12617007-B2 - Anti-collapse oil casing with high strength and manufacturing method therefor

US12617007B2US 12617007 B2US12617007 B2US 12617007B2US-12617007-B2

Abstract

An anti-collapse oil casing with high strength and a manufacturing method therefor, comprising the following chemical elements in percentage by mass: C: 0.08%-0.18%; Si: 0.1%-0.4%; Mn: 0.1%-0.28%; Cr: 0.2%-0.8%; Mo: 0.2%-0.6%; Nb: 0.02%-0.08% b; V: 0.01%-0.15%; Ti: 0.02%-0.05%; B: 0.0015%-0.005%; and Al: 0.01%-0.05%. The manufacturing method for the anti-collapse oil casing with high strength comprises the steps of: (1) smelting and continuous casting; (2) perforating, rolling, and sizing; (3) controlled cooling: the initial cooling temperature being Ar3+50° C. and the final cooling temperature being ≤80° C.; the cooling step being performed only to the outer surface of the casing without performing to the inner wall of the casing; and the rate of the controlled cooling being 30-70° C./s; (4) tempering; and (5) thermal straightening. The anti-collapse oil casing with high strength according to the present invention has reasonable chemical composition and process design, which not only has excellent economic efficiency, but also has high strength, high toughness and high anti-collapse performance.

Inventors

  • Xiaoming Dong
  • Zhonghua Zhang
  • Weiguo Yang
  • Jiaming LIU

Assignees

  • BAOSHAN IRON & STEEL CO., LTD.

Dates

Publication Date
20260505
Application Date
20210506
Priority Date
20200511

Claims (12)

  1. 1 . An oil casing, comprising the following chemical elements in percentage by mass: C: 0.08-0.18%; Si: 0.1-0.4%; Mn: 0.1-0.28%; Cr: 0.2-0.8%; Mo: 0.2-0.6%; Nb: 0.02-0.08%; V: 0.01-0.15%; Ti: 0.02-0.05%; B: 0.0015-0.005%; and Al: 0.01-0.05%; wherein a microstructure of the oil casing is tempered sorbite, and wherein the oil casing has a yield strength of 810-965 MPa.
  2. 2 . The oil casing according to claim 1 , characterized in that the content of each chemical element in percentage by mass satisfies the following: C: 0.08-0.18%; Si: 0.1-0.4%; Mn: 0.1-0.28%; Cr: 0.2-0.8%; Mo: 0.2-0.6%; Nb: 0.02-0.08%; V: 0.01-0.15%; Ti: 0.02-0.05%; B: 0.0015-0.005%; Al: 0.01-0.05%; and the balance of Fe and other inevitable impurities.
  3. 3 . The oil casing according to claim 2 , characterized in that the inevitable impurities comprise S, P and N, wherein contents of S, P and N satisfy at least one of: P≤0.015%, 0<N≤0.008%, and S≤0.003%.
  4. 4 . The oil casing according to claim 2 , characterized in that the content of each chemical element in percentage by mass satisfies at least one of the following: C: 0.1-0.16%; Si: 0.15-0.35%; Mn: 0.15-0.25%; Cr: 0.4-0.7%; Mo: 0.25-0.5%; Nb: 0.02-0.06%; V: 0.05-0.12%; Ti: 0.02-0.04%; B: 0.0015-0.003%; and Al: 0.015-0.035%.
  5. 5 . The oil casing according to claim 2 , characterized in that the oil casing has properties satisfying at least one of: a tensile strength of ≥862 MPa, an elongation rate of ≥18%, a residual stress of ≤120 MPa, a 0° C. transverse charpy impact energy of ≥80 J, and an anti-collapse strength of 55 MPa or more at a specification of Φ244.48*11.99 mm, which exceeds the required value of the API standard by 40% or more.
  6. 6 . The oil casing according to claim 1 , characterized in that the content of each chemical element in percentage by mass satisfies at least one of the following: C: 0.1-0.16%; Si: 0.15-0.35%; Mn: 0.15-0.25%; Cr: 0.4-0.7%; Mo: 0.25-0.5%; Nb: 0.02-0.06%; V: 0.05-0.12%; Ti: 0.02-0.04%; B: 0.0015-0.003%; and Al: 0.015-0.035%.
  7. 7 . The oil casing according to claim 1 , characterized in that the oil casing has properties satisfying at least one of: a tensile strength of ≥862 MPa, an elongation rate of ≥18%, a residual stress of ≤120 MPa, a 0° C. transverse charpy impact energy of ≥80 J, and an anti-collapse strength of 55 MPa or more at a specification of Φ244.48*11.99 mm, which exceeds the required value of the API standard by 40% or more.
  8. 8 . A manufacturing method for the oil casing according to claim 1 , comprising the steps of: (1) smelting and continuous casting; (2) perforating, rolling, and sizing; (3) controlled cooling: an initial cooling temperature being Ar3+30° C. to Ar3+70° C., and a final cooling temperature being ≤80° C.; the cooling step being performed only to an outer surface of the casing without performing to an inner wall of the casing; and controlling a cooling rate to be 30-70° C./s; (4) tempering; and (5) thermal straightening.
  9. 9 . The manufacturing method according to claim 8 , characterized in that in the continuous casting of the step (1), controlling a superheat degree of molten steel to be less than 30° C., and a pulling rate of the continuous casting to be 1.6-2.0 m/min.
  10. 10 . The manufacturing method according to claim 8 , characterized in that in the step (2), a round billet is subjected to soaking in a furnace at 1260-1290° C.; a perforating temperature is controlled to be 1180-1260° C.; a final rolling temperature is controlled to be 900-980° C.; and a sizing temperature after final rolling is 850-920° C.
  11. 11 . The manufacturing method according to claim 8 , characterized in that in the step (4), a tempering temperature is 500-600° C., and a holding time is 50-80 min.
  12. 12 . The manufacturing method according to claim 8 , characterized in that in the step (4), a thermal straightening temperature is 400-500° C.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application is a U.S. national phase entry under 35 USC § 371 of Patent Cooperation Treaty Application No. PCT/CN2021/091903 filed May 6, 2021, which in turn claims priority from Chinese Patent Application 202010392682.0 filed May 11, 2020. Each of the above described applications is hereby incorporated herein by reference in their entireties. TECHNICAL FIELD The present invention relates to a metal material and a manufacturing method therefor, in particular to an oil casing and a manufacturing method therefor. BACKGROUND With the increasing depth and difficulty of oil & gas resource exploitation domestically or abroad at present, the fluid field, pressure field or the like of the stratum will undergo great changes, and the service conditions and stress conditions of casings for oil and water wells are also becoming more complex. About 20% of oil and water wells in China have encountered casing collapses, or even 50% or more in particular regions. A collapsed casing may affect the regular production of crude oil in mild cases, and in severe cases, the entire oil well will be scrapped, which causes huge economic loss. Therefore, in order to sufficiently exploit the existing resources, to improve the recovery efficiency and to reduce unnecessary loss, it is essential to effectively solve the problem of casing collapse. At present, a number of domestic or abroad research work have been completed on mechanisms, influencing factors, detection methods of casing collapse, as well as the research and development of casings having high anti-collapse performance, which provide a series of casing products for different steel grades and different specifications, which have been applied in oil field exploitation and production at present, but the industrial and mining conditions of the oil field in service are not only extremely complex, but are also greatly different between each oil fields. Therefore, it put forward more differentiated demands for anti-collapse casings. The Japanese patent having publication No. JPH11-131189A which published on May 18, 1999 and entitled as “Manufacturing Method of Steel Pipe” discloses a manufacturing method of a steel pipe. In the manufacturing method, heating is performed within a temperature range of 750-400° C., and rolling is performed within a range of deformation of 20% or 60%, so as to produce a steel pipe product having a yield strength of 950 Mpa or more and good toughness. However, due to the low heating temperature of this technique, the difficulties for rolling would be high. In addition, low rolling temperature would cause the formation of martensite structure which is not desired in oil casing products. The Japanese patent having publication No. JP04059941A which published on Feb. 26, 1992 and entitled as “Tough High-Strength TRIP Steel” recites that the tensile strength can reach 120-160 ksi by controlling the proportions of retained austenites (20%-45%) and upper bainites in the steel substrate through thermal treatment process. The composition design mentioned in this patent are characterized by high carbon and high silicon content. The two components can significantly increase the strength, however, it would also reduce the toughness. At the same time, the retained austenites may undergo structural transformation during the use of the oil pipe (the service temperature of the oil pipe for a deep well is 120° C. or more), which will improve the strength while reduce the toughness. SUMMARY OF THE INVENTION One of the objectives of the present invention is to provide an anti-collapse oil casing with high strength. In the chemical component design of the anti-collapse oil casing with high strength, Cr and B are added to replace Mn to increase the hardenability of steel, and Ti is used to suppress the embrittlement effect of N on grain boundaries, thereby reducing the cost for the alloying elements added into the oil casing and preventing quench cracking. The anti-collapse oil casing has high strength, high toughness and high anti-collapse performance, and specifically has a yield strength of 758-965 MPa, a tensile strength of ≥862 MPa, an elongation rate of ≥18% and a residual stress of ≤120 MPa, and has a 0° C. transverse charpy impact energy of ≥80 J. Moreover, the anti-collapse strength is 55 MPa or more at a typical specification of Φ244.48*11.99 mm, which exceeds the required value of the API standard by 40% or more, so that the high-strength anti-collapse oil casing can meet the demands required by deep wells and oil & gas fields with respect to strength and anti-collapse performance of the oil well casings. In order to achieve the above-mentioned objective, the present invention provides an anti-collapse oil casing with high strength, comprising the following chemical elements in percentage by mass: C: 0.08-0.18%;Si: 0.1-0.4%;Mn: 0.1-0.28%;Cr: 0.2-0.8%;Mo: 0.2-0.6%;Nb: 0.02-0.08%;V: 0.01-0.15%;Ti: 0.02-0.05%;B: 0.0015-0