Production method of oil casing resistant to hydrogen sulfide corrosion and oil casing resistant to hydrogen sulfide corrosion

Abstract

The present invention discloses a production method of an oil casing resistant to hydrogen sulfide corrosion and an oil casing resistant to hydrogen sulfide corrosion. The production method comprises the following steps: S1: Continuously casting the steel after steelmaking into a billet; S2: Sawing the billet, and then successively subjecting the billet to heating, piercing, hot rolling by a continuous rolling mill and sizing by a reducing mill to form a semi-finished oil casing; the billet is heated to 1170 °C - 1225 °C, and the heat preservation time is 2 - 3 h; the temperature before piercing is 1145 °C - 1200 °C, the temperature before hot rolling is 960 °C - 1150 °C, and the temperature before tension reducing is 820 °C - 950 °C; S3: Performing quenching and tempering heat treatment on the semi-finished oil casing. The quenching and tempering heat treatment successively includes quenching and two-stage tempering; the quenching temperature is 920 °C - 950 °C, and the heat preservation time is 30 - 50 min; during the two-stage tempering process, the first-stage tempering: the temperature is 700 °C - 710 °C; the second-stage tempering: the temperature is 680 °C - 685 °C; S4: Performing hot straightening after the quenching and tempering heat treatment, and then performing stacking cooling to obtain the finished oil casing. By this method, not only the mechanical properties of the oil casing are ensured, but also its hydrogen sulfide stress corrosion resistance is improved.

Description

Technical Field

[0001] The present invention relates to a production method of oil casing resistant to hydrogen sulfide corrosion and an oil casing resistant to hydrogen sulfide corrosion. Background Art

[0002] At present, oil casing is used in oilfield exploitation and is a steel pipe for supporting the wellbore of oil and gas wells to ensure the progress of the drilling process and the normal operation of the entire oil well after completion. Chinese Patent with the application publication number CN110303066A discloses a steel for oil casing with high transverse impact work and a preparation method thereof. In this method, molten steel is smelted and continuously cast into slab billets, and then the slab billets are heated, rough rolled, finish rolled and laminar cooled in sequence to obtain finished products. Heat treatment is not used in the method. Through the corresponding rolling process, although the transverse impact work of the steel is improved, the hydrogen sulfide corrosion resistance of the oil casing is not solved. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to overcome the defects of the prior art and provide a production method of oil casing resistant to hydrogen sulfide corrosion. Through this method, not only the mechanical properties of the oil casing are ensured, but also its hydrogen sulfide stress corrosion resistance is improved.

[0004] To solve the above technical problem, the technical solution of the present invention is: A production method of oil casing resistant to hydrogen sulfide corrosion, the production method comprising the following steps:

[0005] S1: After steelmaking, continuously cast into a tube blank;

[0006] S2: Saw cut the tube blank, and then sequentially pass through tube blank heating, piercing, hot rolling by a continuous rolling mill and sizing by a reducing mill to make a semi-finished oil casing; wherein, the tube blank is heated to 1170°C - 1225°C, and the holding time is 2 - 3h; the temperature before piercing is 1145°C - 1200°C, the temperature before hot rolling is 960°C - 1150°C, and the temperature before tension reducing is 820°C - 950°C;

[0007] S3: Perform quenching and tempering heat treatment on the semi-finished oil casing. The quenching and tempering heat treatment sequentially includes quenching and two-stage tempering; wherein, the quenching temperature is 920°C - 950°C, and the holding time is 30 - 50min; during the two-stage tempering process, the first-stage tempering: the temperature is 700°C - 710°C, and the holding time is 20 - 25min; the second-stage tempering: the temperature is 680°C - 685°C, and the holding time is 100 - 120min;

[0008] S4: After quenching and tempering heat treatment, perform hot straightening, and then perform stacking cooling to obtain the finished oil casing; wherein, the hot straightening temperature is above 550°C, and the cooling rate of stacking cooling ≤ 3°C / min.

[0009] Furthermore, steelmaking successively includes: hot metal pretreatment, converter smelting, secondary refining, vacuum degassing, and calcium treatment.

[0010] Furthermore, for hot metal pretreatment: desulfurization pretreatment is carried out on hot metal, and the sulfur content of the hot metal after desulfurization pretreatment is not higher than 0.005%.

[0011] Converter smelting: The pretreated hot metal is added to the converter for smelting, and auxiliary materials are added for smelting at the same time. The tapping temperature is controlled at 1625 - 1675 °C, and the mass percentage content of P at tapping is ≤0.01%. When 1 / 3 of the steel is tapped, ferrochrome and ferromolybdenum are added to the ladle for alloying.

[0012] Secondary refining: After tapping is completed, the ladle is subjected to secondary refining. The basicity of the refining slag is controlled at 2.5 - 3.5, and the white slag time is 25 - 30 min. During the refining process, ferrovanadium and ferroniobium are added for alloying. Samples are taken from the refined molten steel to measure the composition, and the mass percentages of the chemical components are adjusted according to the test results.

[0013] Vacuum degassing: When the chemical components and mass percentages meet the target requirements, the ladle is subjected to vacuum degassing. The degassing time is ≥15 min, and hydrogen determination is carried out after degassing is completed. The hydrogen content should be ≤2 ppm.

[0014] Furthermore, in order to control the wall thickness deviation within a smaller range during the preparation process, make the pipeline deformation small during the subsequent heat treatment process, and the internal stress small after straightening, which is beneficial to improving the anti-hydrogen sulfide corrosion performance of the material. In step S2, during the piercing, hot rolling by the continuous rolling mill, and reducing by the reducing mill, the wall thickness deviation is controlled ≤10%.

[0015] Furthermore, in order to reasonably control the wall thickness deviation during the preparation process, in step S2, during piercing, the rolling center line is kept consistent with the piercing machine center line, so that the billet is under balanced stress during piercing, and the wall thickness accuracy is not affected by the single-sided stress during billet rolling.

[0016] Furthermore, in order to reasonably control the wall thickness deviation during the preparation process, in step S2, during piercing, the deviation between the center line of the three-roll centering for billet centering and the piercing machine center line is ≤1 mm.

[0017] Furthermore, in order to reasonably control the wall thickness deviation during the preparation process, in step S2, during hot rolling by the continuous rolling mill, the center lines of the continuous rolling mill and the mill housing should be kept consistent, and the deviation is ≤0.5 mm.

[0018] Furthermore, the performance parameters of the finished oil casing are as follows: yield strength: 770 - 810 MPa, tensile strength: 850 - 900 MPa, elongation ≥20%, impact toughness: longitudinal at 0 °C, ≥150 J, transverse at 0 °C, ≥120 J.

[0019] Further, in order to better ensure its mechanical properties and better improve its resistance to hydrogen sulfide stress corrosion, in step S1, steelmaking is carried out according to the chemical composition of the oil casing and its mass percentage; among them, the chemical composition of the oil casing and its mass percentage are as follows: C: 0.25 - 0.30%, Si: 0.2 - 0.6%, Mn: 0.3 - 0.7%, Cr: 0.3 - 0.6%, Mo: 0.7 - 1.0%, V: 0.05 - 0.15%, Nb: 0.03 - 0.1%, P ≤ 0.015%, S ≤ 0.0015%, and the rest are Fe and inevitable impurities, totaling 100%; among them, 1.2% ≤ Cr + Mo ≤ 1.4%.

[0020] The present invention also provides an oil casing resistant to hydrogen sulfide corrosion prepared by the above production method, and the chemical composition of the oil casing and its mass percentage are as follows:

[0021] C: 0.25 - 0.30%, Si: 0.2 - 0.6%, Mn: 0.3 - 0.7%, Cr: 0.3 - 0.6%, Mo: 0.7 - 1.0%, V: 0.05 - 0.15%, Nb: 0.03 - 0.1%, P ≤ 0.015%, S ≤ 0.0015%, and the rest are Fe and inevitable impurities, totaling 100%; among them, 1.2% ≤ Cr + Mo ≤ 1.4%.

[0022] After adopting the above technical solutions, the present invention has the following beneficial effects:

[0023] 1. The present invention adopts quenching + two-stage tempering for quenching and tempering heat treatment; among them, the heat treatment quenching temperature is 920°C - 950°C, which can not only ensure that the steel grade of the oil casing of the present invention is completely austenitized, but also avoid the increase of grain size caused by too high temperature. In the quenching and tempering heat treatment stage of the present invention, two-stage tempering is used to control the morphology of the precipitated phases, forming fine precipitated phases with a dispersed distribution, and avoiding the local growth of the precipitated phases. The first-stage tempering temperature is 700°C - 710°C, and the holding time is 20 - 25 min; the main function is to quickly eliminate the quenching stress and increase the nucleation driving force of the precipitated phases; the second-stage tempering temperature is 680°C - 685°C, and the holding time is 100 - 120 min. Adopting a longer tempering time can reduce the temperature difference between the core and the surface of the material, the performance difference between the core and the surface is smaller, and the performance fluctuation is small. The straightening temperature of the oil casing after tempering is above 550°C. After straightening, it is stacked and slowly cooled to reduce the residual stress. By the above measures, the metallographic structure is controlled, thereby finally improving the hydrogen sulfide corrosion resistance of the material;

[0024] 2. During the quenching process, the cooling rate is extremely fast, which will generate significant thermal stress. At the same time, martensitic transformation also occurs, generating transformation stress. If the wall thickness difference is relatively large, the steel pipe is very likely to deform and bend. During the subsequent straightening process, large plastic deformation will occur. As a result, large internal stress and high dislocation density will be generated in the pipeline, which will significantly reduce the anti-hydrogen sulfide corrosion performance of the material. The present invention improves the wall thickness control accuracy through a series of means, minimizes the deformation during the quenching process, and at the same time reduces the residual stress and dislocation density in the material through a relatively high straightening temperature and slow cooling measures, thereby improving the anti-hydrogen sulfide corrosion performance of the material.

[0025] 3. In addition, by adding Cr and Mo to improve the strength, promote the precipitation of fine precipitates in the steel, and at the same time avoid the precipitation of large-sized M23C6 at the grain boundaries. Both Cr and Mo are strong carbide-forming elements. The fine carbides precipitated during the tempering process can not only improve the yield strength of the material but also are good hydrogen traps, which can improve the anti-hydrogen sulfide corrosion performance of the material. However, when the content of Cr element is too high, large-sized carbides M23C6 will be generated at the grain boundaries, reducing the grain boundary strength and affecting the anti-hydrogen sulfide corrosion performance of the material. And if only Mo is added for strengthening, it will lead to a significant increase in the material cost. Therefore, the present invention not only specifies the composition ranges of Cr and Mo, Cr: 0.3 - 0.6%, Mo: 0.7 - 1.0%, but also limits the total addition amount of the two, 1.2 ≤ Cr + Mo ≤ 1.4. This can not only ensure the yield strength of the material but also avoid the formation of large-sized M23C6 at the grain boundaries.

[0026] 4. The present invention also improves the anti-hydrogen sulfide corrosion performance of the material by controlling the purity of the oil casing steel, that is, controlling the contents of P and S, improving the purity, and avoiding grain boundary embrittlement and large-sized manganese sulfide inclusions. Specific embodiments

[0027] The present invention provides a production method of an anti-hydrogen sulfide corrosion oil casing and an anti-hydrogen sulfide corrosion oil casing. Those skilled in the art can draw on the content of this article and appropriately modify the process parameters to achieve it. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art, and they all fall within the protection scope of the present invention. The method and application of the present invention have been described through preferred embodiments. Relevant personnel can obviously make changes or appropriate alterations and combinations to the methods and applications in this article without departing from the content, spirit, and scope of the present invention to implement and apply the technology of the present invention.

[0028] A production method of an anti-hydrogen sulfide corrosion oil casing, the production method comprising the following steps:

[0029] S1: After steelmaking, continuously cast the billet into a tube blank. After cutting the tube blank into a fixed-length, place it in a slow-cooling pit for slow cooling, and the slow-cooling time is ≥ 48 h. Among them, during the casting process, the tundish is induction-heated to ensure that the superheat is stably maintained at 20 - 30 °C;

[0030] S2: Saw-cut the tube blank according to requirements. The cutting slope of the tube blank cross-section is ≤ 3 mm, and then successively pass through tube blank heating, piercing, hot rolling by a continuous rolling mill, and reducing the diameter by a reducing mill to make a semi-finished oil casing. Among them, the tube blank is heated to 1170 °C - 1225 °C, and the holding time is 2 - 3 h. If the holding time is too short, the temperature uniformity of the tube blank is poor, and the wall thickness is uneven easily during the piercing process. If the time is too long, the oxidation and burning loss are serious. Therefore, the holding time is limited to 2 - 3 h; the temperature before piercing is 1145 °C - 1200 °C, the temperature before hot rolling is 960 °C - 1150 °C, and the temperature before tension reducing is 820 °C - 950 °C;

[0031] S3: Perform quenching and tempering heat treatment on the semi-finished oil casing. The quenching and tempering heat treatment successively includes quenching and two-stage tempering. Among them, the quenching temperature is 920 °C - 950 °C, and the holding time is 30 - 50 min; during the two-stage tempering process, the first-stage tempering: the temperature is 700 °C - 710 °C, and the holding time is 20 - 25 min; the second-stage tempering: the temperature is 680 °C - 685 °C, and the holding time is 100 - 120 min;

[0032] S4: After quenching and tempering heat treatment, perform hot straightening, and then perform stacking and cooling to obtain the finished oil casing. Among them, the hot straightening temperature is above 550 °C, and the cooling rate during stacking and cooling is ≤ 3 °C / min.

[0033] In the present invention, quenching + two-stage tempering is adopted for quenching and tempering heat treatment; among them, the quenching temperature during heat treatment is 920 °C - 950 °C, which can not only ensure that the oil casing steel type of the present invention is completely austenitized, but also avoid the grain size from becoming larger due to too high temperature. In the quenching and tempering heat treatment stage of the present invention, the morphology of the precipitated phase is controlled by two-stage tempering to form finely dispersed precipitated phases, avoiding the local growth of the precipitated phase. The first-stage tempering temperature is 700 °C - 710 °C, and the holding time is 20 - 25 min; the main function is to quickly eliminate the quenching stress and increase the nucleation driving force of the precipitated phase; the second-stage tempering temperature is 680 °C - 685 °C, and the holding time is 100 - 120 min. Adopting a longer tempering time can reduce the temperature difference between the center and the surface of the material, the performance difference between the center and the surface is smaller, and the performance fluctuation is small. The straightening temperature of the oil casing after tempering is above 550 °C. After straightening, stack and slow cool to reduce the residual stress. By the above measures, the metallographic structure is controlled, so as to finally improve the anti-hydrogen sulfide corrosion performance of the material;

[0034] Specifically, steelmaking successively includes: hot metal pretreatment, converter smelting, secondary refining, vacuum degassing, and calcium treatment.

[0035] Specifically, for hot metal pretreatment: desulfurization pretreatment is carried out on hot metal, and the sulfur content of the hot metal after desulfurization pretreatment is not higher than 0.005%;

[0036] Converter smelting: The pretreated hot metal is added to the converter for smelting, and at the same time, auxiliary materials such as scrap steel and lime are added for smelting. The tapping temperature is controlled at 1625 - 1675 °C, and the mass percentage content of P at tapping is ≤0.01%. When 1 / 3 of the steel is tapped, ferrochrome and ferromolybdenum are added to the ladle for alloying; the used ferrochrome and ferromolybdenum are low-S and low-P alloys to avoid introducing excessive impurity elements;

[0037] Secondary refining: After tapping is completed, the ladle undergoes secondary refining. The basicity of the refining slag is controlled at 2.5 - 3.5, and the white slag time is 25 - 30 min. During the refining process, ferroniobium and ferrovanadium are added for alloying. Samples are taken from the refined molten steel to measure the composition, and the mass percentages of the chemical components are adjusted according to the test results;

[0038] Vacuum degassing: When the chemical components and mass percentages meet the target requirements, the ladle undergoes vacuum degassing. The degassing treatment should be carried out under a high vacuum degree (≤0.26 kPa) to achieve the purpose of dehydrogenation and removing deoxidation inclusions in the steel. The degassing time is ≥15 min, and hydrogen determination is carried out after degassing is completed, and the hydrogen content should be ≤2 ppm.

[0039] Specifically, in step S2, during the piercing, hot rolling by the continuous rolling mill, and reducing by the reducing mill, the wall thickness deviation is controlled to be ≤10%. Controlling the wall thickness deviation within a small range results in less deformation of the pipe during the subsequent heat treatment process, less internal stress after straightening, which is beneficial to improving the anti-hydrogen sulfide corrosion performance of the material.

[0040] During the quenching process, the cooling rate is very fast, which will generate large thermal stress. At the same time, martensitic transformation also occurs, generating transformation stress. If the wall thickness difference is large, the steel pipe is prone to deformation and bending, and during the subsequent straightening process, large plastic deformation will occur. Thus, large internal stress and high dislocation density are generated in the oil casing pipe, which will significantly reduce the anti-hydrogen sulfide corrosion performance of the material. The present invention improves the wall thickness control accuracy through a series of means, minimizes the deformation during the quenching process, and at the same time reduces the residual stress and dislocation density in the material through a higher straightening temperature and slow cooling measures to improve the anti-hydrogen sulfide corrosion performance of the material.

[0041] Specifically, in step S2, during piercing, the rolling center line is aligned with the piercing mill center line to ensure balanced stress on the billet during piercing, avoiding uneven stress on one side during billet rolling and affecting the wall thickness accuracy. During piercing, the deviation between the center line of the three-roll centering for billet centering and the piercing mill center line is ≤1 mm. During hot rolling of the continuous rolling mill, the center lines of the continuous rolling mill and the rolling mill housing should be aligned, with a deviation ≤0.5 mm. The above measures are all to reasonably control the wall thickness deviation during the preparation process, thereby reducing the deformation during subsequent heat treatment and the internal stress after straightening, which is beneficial to improving the hydrogen sulfide corrosion resistance of the material.

[0042] Specifically, the performance parameters of the finished oil casing are as follows: yield strength: 770 - 810 MPa, tensile strength: 850 - 900 MPa, elongation ≥20%, impact toughness: longitudinal at 0°C, ≥150 J, transverse at 0°C, ≥120 J.

[0043] Specifically, in step S1, steelmaking is carried out according to the chemical composition and its mass percentage of the oil casing. Among them, the chemical composition and its mass percentage of the oil casing are as follows: C: 0.25 - 0.30%, Si: 0.2 - 0.6%, Mn: 0.3 - 0.7%, Cr: 0.3 - 0.6%, Mo: 0.7 - 1.0%, V: 0.05 - 0.15%, Nb: 0.03 - 0.1%, P ≤ 0.015%, S ≤ 0.0015%, and the rest are Fe and unavoidable impurities, totaling 100%; among them, 1.2% ≤ Cr + Mo ≤ 1.4%.

[0044] C is an important element to ensure strength. When the C content is less than 0.25%, the strength is difficult to guarantee. When the C content is greater than 0.3%, the stress during quenching is large, not only prone to cracks during the quenching process, but also resulting in reduced toughness of the material and increased stress corrosion sensitivity. Therefore, the present invention controls the C content within the range of 0.25 - 0.3%.

[0045] Si is an important deoxidizing element. When the Si content is too low, the deoxidation effect is poor and the number of inclusions is large. But when it is too much, it will increase the cold brittleness tendency of the steel. The present invention limits the Si content to 0.2 - 0.6%.

[0046] Mn has the effect of increasing hardenability. Adding an appropriate amount of Mn can ensure that the material is completely transformed into martensite after quenching. But Mn is also an important element that promotes the formation of banded structure. Adding too much will aggravate segregation, increase the performance difference between different tissues, reduce the material uniformity, and affect the hydrogen sulfide corrosion resistance. Therefore, the content of Mn is set to 0.3 - 0.7%.

[0047] Both Cr and Mo are strong carbide - forming elements. The fine carbides precipitated during tempering can not only improve the yield strength of the material, but also serve as good hydrogen traps, enhancing the material's resistance to hydrogen sulfide corrosion. However, when the Cr element content is too high, large - sized carbides M23C6 will form at the grain boundaries, reducing the grain boundary strength and affecting the material's resistance to hydrogen sulfide corrosion. If only Mo is added for strengthening, it will lead to a significant increase in material cost. Therefore, this patent not only stipulates the composition ranges of Cr and Mo, Cr: 0.3 - 0.6%, Mo: 0.7 - 1.0%, but also restricts the total addition amount of the two, 1.2 ≤ Cr + Mo ≤ 1.4. This can not only ensure the yield strength of the material but also avoid the formation of large - sized M23C6 at the grain boundaries.

[0048] V and Nb are important grain - refining elements. At the same time, they can also produce fine precipitation phases, improving the yield strength and hydrogen sulfide corrosion resistance of the material. However, when the added amount is too much, coarse carbides will form. Especially when too much Nb is added, serious liquid segregation will occur, reducing the mechanical properties of the material. Therefore, this invention sets V: 0.05 - 0.15% and Nb: 0.03 - 0.1%.

[0049] P and S are harmful elements. P is prone to form abnormal tissue segregation and increase the cold brittleness of steel. S is easy to form sulfide inclusions, seriously affecting the sulfur - resistance performance. Therefore, the contents of P and S should be reduced as much as possible and controlled at P ≤ 0.015% and S ≤ 0.0015%.

[0050] An oil - casing pipe resistant to hydrogen sulfide corrosion prepared by the above - mentioned production method, the chemical composition of the oil - casing pipe and its mass percentages are as follows:

[0051] C: 0.25 - 0.30%, Si: 0.2 - 0.6%, Mn: 0.3 - 0.7%, Cr: 0.3 - 0.6%, Mo: 0.7 - 1.0%, V: 0.05 - 0.15%, Nb: 0.03 - 0.1%, P ≤ 0.015%, S ≤ 0.0015%, and the rest are Fe and unavoidable impurities, totaling 100%; among them, 1.2% ≤ Cr + Mo ≤ 1.4%.

[0052] To make the content of this invention easier to be clearly understood, the following further detailed description of the invention is provided according to specific embodiments.

[0053] Example 1: A production method of an oil - casing pipe resistant to hydrogen sulfide corrosion, the production method includes the following steps:

[0054] S1: Steelmaking is carried out according to the chemical composition and mass percentage of the oil casing pipe. After steelmaking, it is continuously cast into a billet. After the billet is cut into a fixed length, it is placed in a slow cooling pit for slow cooling, and the slow cooling time is ≥ 48 h. Among them, during the casting process, the tundish is induction heated to ensure that the superheat is stable at 20 - 30 °C. The steelmaking process successively includes: hot metal pretreatment, converter smelting, secondary refining, vacuum degassing, and calcium treatment. The chemical composition and mass percentage of the oil casing pipe are as follows: C: 0.25%, Si: 0.3%, Mn: 0.3%, Cr: 0.4%, Mo: 1.0%, V: 0.05%, Nb: 0.03%, P: 0.009%, S: 0.0011%, and the rest are Fe and unavoidable impurities, totaling 100%. Among them, Cr + Mo = 1.4%.

[0055] S2: The billet is sawed according to requirements. The chamfer of the billet cross-section is ≤ 3 mm, and then it is successively heated, pierced, hot rolled by a continuous rolling mill, and reduced in diameter by a reducing mill to form a semi-finished oil casing pipe. Among them, the billet is heated to 1170 °C and the holding time is 2 h. The temperature before piercing is 1145 °C, the temperature before hot rolling is 960 °C, and the temperature before tension reducing is 820 °C. During the processes of piercing, hot rolling by a continuous rolling mill, and reducing in diameter by a reducing mill, the wall thickness deviation is controlled to be ≤ 10%. The rolling center line is kept consistent with the piercing machine center line to make the billet keep balanced stress during piercing and avoid uneven stress on one side during billet rolling, which affects the wall thickness accuracy. During piercing, the deviation between the center line of the three-roll centering for billet centering and the piercing machine center line is ≤ 1 mm. During hot rolling by a continuous rolling mill, the center lines of the continuous rolling mill and the rolling mill housing should be kept consistent, and the deviation is ≤ 0.5 mm.

[0056] S3: The semi-finished oil casing pipe is subjected to quenching and tempering heat treatment. The quenching and tempering heat treatment successively includes quenching and two-stage tempering. Among them, the quenching temperature is 920 °C and the holding time is 30 min. During the two-stage tempering process, the first-stage tempering: the temperature is 700 °C and the holding time is 20 min; the second-stage tempering: the temperature is 680 °C and the holding time is 100 min.

[0057] S4: After quenching and tempering heat treatment, hot straightening is carried out, and then stacking cooling is carried out to obtain the finished oil casing pipe. Among them, the hot straightening temperature is 600 °C, and the cooling rate of stacking cooling is about 2.3 °C / min.

[0058] Example 2: The production method of the oil casing pipe resistant to hydrogen sulfide corrosion in this example is basically the same as that in Example 1, except that: the chemical composition and mass percentage of the oil casing pipe are as follows: C: 0.26%, Si: 0.4%, Mn: 0.45%, Cr: 0.45%, Mo: 0.9%, V: 0.07%, Nb: 0.04%, P: 0.008%, S: 0.001%, and the rest are Fe and inevitable impurities, totaling 100%; among them, Cr + Mo = 1.35%; in step S2, the tube blank is heated to 1225 °C and the holding time is 3 h; the temperature before piercing is 1200 °C, the temperature before hot rolling is 1150 °C, and the temperature before stretch reducing is 950 °C; in step S3, the semi-finished oil casing pipe is subjected to quenching and tempering heat treatment, and the quenching and tempering heat treatment successively includes quenching and two-stage tempering; among them, the quenching temperature is 950 °C and the holding time is 50 min; during the two-stage tempering process, the first-stage tempering: the temperature is 710 °C and the holding time is 25 min; the second-stage tempering: the temperature is 685 °C and the holding time is 120 min; in step S4, the hot straightening temperature is 550 °C, and the cooling rate of stacking cooling is about 2.9 °C / min.

[0059] Example 3: The production method of the oil casing pipe resistant to hydrogen sulfide corrosion in this example is basically the same as that in Example 1, except that: the chemical composition and mass percentage of the oil casing pipe are as follows: C: 0.30%, Si: 0.45%, Mn: 0.5%, Cr: 0.55%, Mo: 0.8%, V: 0.07%, Nb: 0.04%, P: 0.011%, S: 0.0009%, and the rest are Fe and inevitable impurities, totaling 100%; among them, Cr + Mo = 1.35%; in step S2, the tube blank is heated to 1200 °C and the holding time is 2.5 h; the temperature before piercing is 1160 °C, the temperature before hot rolling is 1050 °C, and the temperature before stretch reducing is 900 °C; in step S3, the semi-finished oil casing pipe is subjected to quenching and tempering heat treatment, and the quenching and tempering heat treatment successively includes quenching and two-stage tempering; among them, the quenching temperature is 935 °C and the holding time is 40 min; during the two-stage tempering process, the first-stage tempering: the temperature is 705 °C and the holding time is 22 min; the second-stage tempering: the temperature is 682 °C and the holding time is 110 min; in step S4, the hot straightening temperature is 650 °C, and the cooling rate of stacking cooling is about 2 °C / min.

[0060] Example 4: The production method of the oil casing pipe resistant to hydrogen sulfide corrosion in this example is basically the same as that in Example 1, except that: the chemical composition and mass percentage of the oil casing pipe are as follows: C: 0.26%, Si: 0.35%, Mn: 0.47%, Cr: 0.55%, Mo: 0.75%, V: 0.12%, Nb: 0.06%, P: 0.012%, S: 0.0012%, and the rest are Fe and inevitable impurities, totaling 100%; among them, Cr + Mo: 1.3%.

[0061] Example 5: The production method of the oil casing pipe resistant to hydrogen sulfide corrosion in this example is basically the same as that in Example 1, except that: the chemical composition and mass percentage of the oil casing pipe are as follows: C: 0.26%, Si: 0.4%, Mn: 0.46%, Cr: 0.6%, Mo: 0.7%, V: 0.15%, Nb: 0.03%, P≤0.01%, S≤0.0008%, and the rest are Fe and inevitable impurities, totaling 100%; among them, Cr + Mo = 1.3%.

[0062] Comparative Example 1

[0063] The production method of the oil casing pipe in this comparative example is basically the same as that in Example 1, except that: the chemical composition and mass percentage of the oil casing pipe are as follows: C: 0.26%, Si: 0.4%, Mn: 0.46%, Cr: 0.6%, Mo: 0.7%, V: 0.15%, Nb: 0.03%, P: 0.011%, S: 0.0012%, and the rest are Fe and inevitable impurities, totaling 100%; among them, Cr + Mo = 1.3%; in step S4, the hot straightening temperature is 300°C, and air cooling is adopted after hot straightening.

[0064] Comparative Example 2

[0065] The production method of the oil casing pipe in this comparative example is basically the same as that in Comparative Example 1, except that; in step S3, the semi-finished oil casing pipe is subjected to quenching and tempering heat treatment, and the quenching and tempering heat treatment includes quenching and one-stage tempering in sequence; among them, the quenching temperature is 935°C, and the holding time is 40 min; the first-stage tempering: the temperature is 705°C, and the holding time is 22 min.

[0066] Comparative Example 3

[0067] The production method of the oil casing pipe in this comparative example is basically the same as that in Example 1, except that: the chemical composition and mass percentage of the oil casing pipe are as follows: C: 0.23%, Si: 0.4%, Mn: 0.56%, Cr: 0.6%, Mo: 0.71%, V: 0.15%, Nb: 0.03%, P: 0.01%, S: 0.0012%, and the rest are Fe and inevitable impurities, totaling 100%; among them, Cr + Mo = 1.31%.

[0068] Comparative Example 4

[0069] The production method of the casing pipe in this comparative example is basically the same as that in Example 1, except that: the chemical composition and mass percentage of the casing pipe are as follows: C: 0.23%, Si: 0.4%, Mn: 0.56%, Cr: 0.6%, Mo: 0.71%, V: 0.15%, Nb: 0.03%, P: 0.012%, S: 0.0011%, and the rest are Fe and inevitable impurities, totaling 100%; among them, Cr + Mo = 1.31%. The second tempering: the temperature is 650 °C, and the heat preservation time is 120 min.

[0070] Comparative Example 5

[0071] The production method of the casing pipe in this comparative example is basically the same as that in Example 1, except that: the chemical composition and mass percentage of the casing pipe are as follows: C: 0.32%, Si: 0.37%, Mn: 0.45%, Cr: 0.6%, Mo: 0.67%, V: 0.15%, Nb: 0.03%, P: 0.01%, S: 0.0012%, and the rest are Fe and inevitable impurities, totaling 100%; among them, Cr + Mo = 1.31%.

[0072] Comparative Example 6

[0073] The production method of the casing pipe in this comparative example is basically the same as that in Example 1, except that: the chemical composition and mass percentage of the casing pipe are as follows: C: 0.27%, Si: 0.4%, Mn: 0.46%, Cr: 0.9%, Mo: 0.5%, V: 0.15%, Nb: 0.03%, P: 0.009%, S: 0.0014%, and the rest are Fe and inevitable impurities, totaling 100%; among them, Cr + Mo = 1.3%.

[0074] Comparative Example 7

[0075] The production method of the casing pipe in this comparative example is basically the same as that in Example 1, except that: the chemical composition and mass percentage of the casing pipe are as follows: C: 0.26%, Si: 0.45%, Mn: 0.56%, Cr: 0.2%, Mo: 0.75%, V: 0.15%, Nb: 0.03%, P: 0.011%, S: 0.001%, and the rest are Fe and inevitable impurities, totaling 100%; among them, Cr + Mo = 0.95%.

[0076] Comparative Example 8

[0077] The production method of the casing and tubing in this comparative example is basically the same as that in Example 1, except that: the chemical composition and mass percentage of the casing and tubing are as follows: C: 0.26%, Si: 0.4%, Mn: 0.46%, Cr: 0.6%, Mo: 0.9%, V: 0.15%, Nb: 0.03%, P: 0.012%, S: 0.0007%, and the rest are Fe and inevitable impurities, totaling 100%; among them, Cr + Mo = 1.5%.

[0078] Comparative Example 9

[0079] The production method of the casing and tubing in this comparative example is basically the same as that in Example 1, except that: in step S2, during the piercing, hot rolling by the continuous rolling mill, and reducing by the reducing mill, the wall thickness deviation is relatively large, being 12.4%.

[0080] The properties of the casing and tubing prepared by using the production methods of the above examples and comparative examples are as follows after testing:

[0081]

[0082] In the above examples and comparative examples, the hydrogen sulfide corrosion resistance test was carried out according to the A-NACE standard tensile test in ANSI / NACE TM0177-2016. 20 specimens were tested for each test case, and the passing rate was calculated based on the specimens that passed the test. The compositions of Examples 1-5 met the requirements, and quenching + two-stage tempering, a straightening temperature above 550°C, and stacking and slow cooling were adopted, and the mechanical properties such as yield strength met the requirements of the C110 steel grade, and the passing rate of the hydrogen sulfide corrosion resistance test was ≥95%. In Comparative Example 1, the straightening temperature was lower than 550°C, and it became air-cooled after straightening, and the passing rate of the hydrogen sulfide corrosion resistance test dropped to 70%. In Comparative Example 2, one-stage tempering was adopted, and the passing rate of the hydrogen sulfide corrosion resistance test also decreased significantly. In Comparative Example 3, the carbon content was lower than the lower limit, and the strength was significantly reduced, not meeting the requirements of the C110 steel grade. The compositions of Comparative Example 4 and Comparative Example 3 were generally the same, and the strength was increased to the C110 steel grade by adjusting the tempering temperature, but the passing rate of the hydrogen sulfide corrosion resistance test decreased significantly. In Comparative Example 5, the carbon content exceeded the upper limit, the strength was relatively high, and the passing rate of the hydrogen sulfide corrosion resistance test was only 50%. In Comparative Example 6, the Cr content exceeded the upper limit of this patent, and the passing rate of the hydrogen sulfide corrosion resistance test was only 30%. In Comparative Example 7, the Cr content was lower than the lower limit of this patent, and the strength did not meet the requirements. In Comparative Example 8, the Cr + Mo content exceeded the upper limit of this patent, and the passing rate of the hydrogen sulfide corrosion resistance test dropped to 50%; in Comparative Example 9, the wall thickness deviation was relatively large, the bending phenomenon was serious after quenching, the residual stress was relatively large after straightening, and the passing rate of the hydrogen sulfide corrosion resistance dropped to 70%.

[0083] The specific embodiments described above further elaborate on the technical problems solved, technical solutions, and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for producing oil casing resistant to hydrogen sulfide corrosion, characterized in that: The production method comprises the following steps: S1: After steelmaking, the tubes are continuously cast into billets, which are cut into fixed lengths and then placed in a slow cooling pit for slow cooling. The slow cooling time is ≥ 48h. During the casting process, the tundish is heated by induction to ensure that the superheat is stable at 20-30℃. S2: sawing the tube billet, and then successively heating the tube billet, piercing, hot rolling by a continuous rolling mill, and reducing the diameter by a reducing mill to make a semi-finished oil casing pipe; wherein the tube billet is heated to 1170℃~1200℃, and the holding time is 2~3h; the temperature before piercing is 1145℃~1200℃, the temperature before hot rolling is 960℃~1150℃, and the temperature before tension reducing is 820℃~900℃; S3: The semi-finished oil casing is subjected to quenching and tempering heat treatment, which includes quenching and two-stage tempering in sequence; wherein, the quenching temperature is 920℃~935℃, and the holding time is 30-50min; in the two-stage tempering process, the first stage tempering: temperature 700℃-710℃, holding time 20-25min; the second stage tempering: temperature 680℃-685℃, holding time 100-120min; S4: After the quenching and tempering heat treatment, heat straightening is performed, followed by stack cooling to obtain a finished oil casing; wherein the heat straightening temperature is above 550°C, and the cooling rate of the stack cooling is ≤3°C / min; In step S1, steelmaking is performed according to the chemical composition and mass percentage of the oil casing; wherein the chemical composition and mass percentage of the oil casing are as follows: C: 0.26-0.30%, Si: 0.2-0.45%, Mn: 0.45-0.7%, Cr: 0.3-0.6%, Mo: 0.7-1.0%, V: 0.05-0.15%, Nb: 0.03-0.1%, P≤0.015%, S≤0.0015%, and the rest are Fe and unavoidable impurities, totaling 100%; wherein 1.2%≤Cr+Mo≤1.4%; Steelmaking includes: hot metal pretreatment, converter smelting, refining outside the furnace, vacuum degassing and calcium treatment; Hot metal pretreatment: The hot metal is subjected to desulfurization pretreatment. The sulfur content of the hot metal after desulfurization pretreatment is not higher than 0.005%; Converter smelting: add the pretreated molten iron into the converter for smelting, and add auxiliary materials for smelting at the same time. The tapping temperature is controlled at 1625~1675℃. The mass percentage of P during tapping is ≤0.01%. When 1 / 3 of the steel is tapped, add ferrochrome and ferromolybdenum into the ladle for alloying. Refining outside the furnace: After the steel is tapped, the ladle is refined outside the furnace, the basicity of the refined slag is controlled at 2.5-3.5, the white slag time is 25-30 minutes, ferrovanadium and ferroniobium are added during the refining process for alloying, samples are taken from the refined molten steel to determine the composition, and the mass percentage of the chemical composition is adjusted according to the test results; Vacuum degassing: When the chemical composition and mass percentage meet the target requirements, the ladle is vacuum degassed, the degassing time is ≥15min, and the hydrogen content is determined after the degassing is completed. The hydrogen content should be ≤2ppm; In step S2, during the perforation, hot rolling of the continuous rolling mill and the diameter reduction of the diameter reducing mill, the wall thickness deviation is controlled to be ≤10% to reduce the deformation of the pipeline in the subsequent heat treatment process and reduce the internal stress after straightening; In step S2, during punching, the rolling center line is kept consistent with the punching machine center line, so that the force on the tube billet is balanced during punching, and the wall thickness accuracy is not affected by the force on one side of the tube billet during rolling; In step S2, during punching, the deviation between the center line of the three rollers used to center the tube and the center line of the punching machine is ≤1 mm; In step S2, when the continuous rolling mill is hot rolling, the center line of the continuous rolling mill and the rolling mill arch should be kept consistent, with a deviation of ≤0.5mm.

2. The production method according to claim 1, characterized in that The performance parameters of finished oil casing are as follows: yield strength: 770~810MPa, tensile strength: 850~900MPa, elongation ≥20%, impact toughness: longitudinal 0℃, ≥150J, transverse 0℃, ≥120J.

3. A hydrogen sulfide corrosion resistant oil casing, characterized in that: It is prepared based on the production method according to any one of claims 1 to 2.

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