A kind of steel for deep sea acid-resistant pipeline and its production method

Abstract

The invention discloses a deep-sea acid-resistant pipeline steel and a production method thereof, which relate to the technical field of steel production. The steel has the following chemical composition and mass percentage: C: 0.010%-0.040%, Si: 0.10%-0.30%, Mn: 1.00%-1.40%, P≤0.013%, S≤0.0010%, Nb: 0.030%-0.070%, V: 0.30%-0.70%, Ti: 0.008%-0.030%, Cr: 0.10%-0.30%, Ni: 0.10%-0.30%, Mo≤0.50%, Cu: 0.10%-0.30%, B≤0.0005%, Mg: 0.0008%-0.0015%, Al: 0.015%-0.030%, and the balance is Fe and unavoidable impurities. Top and bottom combined blowing, converter smelting and vacuum degassing are adopted to obtain high-cleanliness molten steel. Continuous casting with large reduction technology and controlled rolling process are used to obtain a microstructure type dominated by blocky ferrite, which meets the requirements of deep-sea acid-resistant pipeline steel for service.

Description

Technical Field

[0001] The invention relates to the technical field of steel production, and in particular to steel for deep-sea acid-resistant pipelines and a production method thereof. Background Art

[0002] With the rapid development of the steel industry, users have increasingly stringent requirements for steel performance. Therefore, improving steel quality is an urgent problem that major steel companies need to solve. More and more oil transportation uses low-cost and high-safety pipeline transportation. Since crude oil contains acidic gases, it corrodes steel quickly and easily produces hydrogen-induced cracks in the core of the steel plate, causing the steel plate to crack. At the same time, acid corrosion-resistant pipeline steel is mainly used to manufacture pipelines for transporting sour natural gas. Sour natural gas has extremely strong corrosiveness and impact friction. Therefore, the steel plate needs to have acid and corrosion resistance, as well as low-temperature crack resistance. In order to avoid cracking caused by stress in the pipe making process, it is necessary to ensure that the hardness of the product in the thickness direction is stable and meets the requirements of the specifications. Therefore, deep-sea acid-resistant pipeline steel is the most difficult type of oil and gas steel to produce. Summary of the invention

[0003] The present invention aims at the above technical problems, overcomes the shortcomings of the prior art, and provides a deep-sea acid-resistant pipeline steel, whose chemical composition and mass percentage are as follows: C: 0.010%-0.040%, Si: 0.10%-0.30%, Mn: 1.00%-1.40%, P≤0.013%, S≤0.0010%, Nb: 0.030%-0.070%, V: 0.30%-0.70%, Ti: 0.008%-0.030%, Cr: 0.10%-0.30%, Ni: 0.10%-0.30%, Mo≤0.50%, Cu: 0.10%-0.30%, B≤0.0005%, Mg: 0.0008%-0.0015%, Al: 0.015%-0.030%, and the balance is Fe and unavoidable impurities.

[0004] The technical solution further defined in the present invention is:

[0005] The chemical composition and mass percentage of the deep-sea acid-resistant pipeline steel mentioned above are as follows: C: 0.020%~0.035%, Si: 0.20%~0.23%, Mn: 1.10%~1.20%, P≤0.012%, S≤0.0010%, Nb: 0.040%~0.060%, V: 0.40%~0.50%, Ti: 0.010%~0.022%, Cr: 0.20%~0.25%, Ni: 0.15%~0.20%, Mo≤0.50%, Cu: 0.20%~0.25%, B≤0.0005%, Mg: 0.0010%~0.0013%, Al: 0.015%~0.030%, and the balance is Fe and unavoidable impurities.

[0006] Another object of the present invention is to provide a method for producing steel for deep-sea acid-resistant pipelines, comprising:

[0007] S1. Top and bottom combined blowing converter is used for smelting. The converter tapping temperature is 1680-1720 degrees. The oxygen content of the tapped steel is 600-1000ppm. Low carbon ferromanganese and aluminum blocks are added for deoxidation. The oxygen content of the molten steel is controlled at 50ppm-200ppm after tapping.

[0008] S2. After the molten steel reaches RH, it is vacuum decarburized to ensure that the decarburization is ≤0.010%. After the decarburization is completed, it is sent to LF for deoxidation and alloying. After the composition meets the requirements, magnesium treatment is carried out using magnesium-aluminum wire. After magnesium treatment, the molten steel is stirred for 15 to 30 minutes;

[0009] S3, the refined molten steel is sent to continuous casting for casting. The casting process is heated to 20-30 degrees, and horizontal dynamic light pressure is adopted, with a pressure reduction of 13-15mm;

[0010] S4, after the ingot is cut, it is sent to the hydrogen expansion furnace for hydrogen expansion operation, the hydrogen expansion temperature is 630-650 degrees, and the holding time is 20-30 hours;

[0011] S5. After the ingot is hydrogenated, it is cooled for 48 hours. After the ingot is inspected and qualified, it is put into the heating furnace for heating. The heating temperature is 1120-1220 degrees and the heating time is 9.0-13min / cm.

[0012] S6, adopt controlled rolling process, the second rolling temperature is 800-950 degrees, the final rolling temperature is 780-880 degrees, the cooling temperature is 770-830 degrees, and the red-returning temperature is 400-600 degrees;

[0013] S7. Steel plates are sheared, marked and inspected before being put into storage for shipment.

[0014] In the above-mentioned method for producing steel for deep-sea acid-resistant pipelines, step S1, 500 kg of low-carbon ferromanganese and 30-80 kg of aluminum blocks are added to the steel for deoxidation.

[0015] In the above-mentioned method for producing steel for deep-sea acid-resistant pipelines, in step S2, the amount of magnesium wire used is 280 to 320 meters.

[0016] The above-mentioned method for producing steel for deep-sea acid-resistant pipelines has a finished steel wall thickness of 6 to 50 cm and a steel grade of BMOS to X70MOS.

[0017] The above-mentioned method for producing steel for deep-sea acid-resistant pipelines,

[0018] The beneficial effects of the present invention are:

[0019] (1) The present invention adopts a low-carbon, ultra-low phosphorus and sulfur design, which reduces the aggregation of segregated elements in the core of the ingot and reduces the amount of manganese used. At the same time, the amount of Cr, Ni and Cu used is increased, which can effectively refine the grain size of the structure and increase the hardenability of the ingot, thus meeting the performance requirements of the product.

[0020] (2) The present invention adopts high superheat and large pressure reduction technology, which can effectively increase the density of the core of the ingot and reduce the harm of the banded structure. The high superheat is conducive to the floating of inclusions during the smelting process, effectively improving the purity of the molten steel;

[0021] (3) The present invention adopts RH decarburization treatment first, which ensures the stability of the carbon content of the product, avoids the production of hard phase structure due to high carbon content, avoids the penetration of corrosive gas, stabilizes the HIC performance of acid-resistant pipelines, and ensures the stability of ferrite content;

[0022] (4) The present invention adopts hydrogen expansion technology, which effectively reduces the accumulation of gas content in the blank, reduces the instability of the core and 1 / 4 negative segregation zone structure, solves the instability of the core and 1 / 4 structure gap, and improves the stability of acid resistance;

[0023] (5) The application of magnesium metallurgical technology in the present invention can improve the spheroidization of sulfur inclusions, produce fine inclusions not larger than 10 μm, and form nucleation points of original austenite grains, which can effectively refine the microstructure grain size of the rolled plate, improve the toughness and strength of the steel plate, and thus improve the stability of the HIC\CTOD performance of the acid-resistant pipeline. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 2 is the metallographic structure diagram of the steel plate of the present invention. Implementation Example

[0025] The present embodiment provides a deep-sea acid-resistant pipeline steel, steel grade X65MOS, with the following chemical composition and mass percentage: C: 0.013%, Si: 0.15%, Mn: 1.13%, P: 0.008%, S: 0.0008%, Nb: 0.039%, V: 0.36%, Ti: 0.017%, Cr: 0.19%, Ni: 0.150%, Mo: 0.003%, Cu: 0.16%, B: 0.0002%, Mg: 0.0009%, Al: 0.027%, and the balance is Fe and unavoidable impurities.

[0026] Production methods include:

[0027] S1. Top and bottom combined blowing converter is used for smelting. The converter tapping temperature is 1693 degrees, the oxygen content of the tapping steel is 850ppm, 500kg low carbon ferromanganese and 60kg aluminum blocks are added for deoxidation, and the oxygen content of the molten steel is controlled at 80ppm after tapping;

[0028] S2. After the molten steel reaches RH, it is vacuum decarburized to ensure that the decarburization is ≤0.010%. After decarburization, it is sent to LF for deoxidation and alloying. After the composition meets the requirements, magnesium-aluminum wire is used for magnesium treatment. The amount of magnesium wire used is 300 meters. After magnesium treatment, the molten steel is stirred for 19 minutes;

[0029] S3, the refined molten steel is sent to continuous casting for casting. The casting process is hot at 26 degrees, horizontal dynamic light pressure is adopted, and the pressure reduction is 13mm;

[0030] S4, the ingot is cut and sent to the hydrogen expansion furnace for hydrogen expansion operation, the hydrogen expansion temperature is 645 degrees, and the holding time is 26 hours;

[0031] S5. After the hydrogen expansion of the ingot is completed, it is cooled for 48 hours. After the surface inspection is passed, it is put into the heating furnace for heating at a temperature of 1150 degrees and a heating time of 11 min / cm;

[0032] S6, adopts controlled rolling process, the second rolling temperature is 850 degrees, the final rolling temperature is 810 degrees, the cooling temperature is 798 degrees, and the red-returning temperature is 510 degrees;

[0033] S7. Steel plates are sheared, marked and inspected before being put into storage for shipment. Example

[0034] The present embodiment provides a deep-sea acid-resistant pipeline steel, steel grade X60MOS, with the following chemical composition and mass percentage: C: 0.033%, Si: 0.26%, Mn: 1.29%, P: 0.011%, S: ≤0.0007%, Nb: 0.063%, V: 0.59%, Ti: 0.017%, Cr: 0.24%, Ni: 0.27%, Mo: 0.0020%, Cu: 0.27%, B: 0.0002%, Mg: 0.0013%, Al: 0.027%, and the balance is Fe and unavoidable impurities.

[0035] Production methods include:

[0036] S1. Top and bottom combined blowing converter is used for smelting. The converter tapping temperature is 1710 degrees, the oxygen content of the tapping steel is 760ppm, 500kg low carbon ferromanganese and 50kg aluminum blocks are added for deoxidation, and the oxygen content of the molten steel is controlled at 70ppm after tapping;

[0037] S2. After the molten steel reaches RH, it is vacuum decarburized to ensure that the decarburization is ≤0.010%. After the decarburization is completed, it is sent to LF for deoxidation and alloying. After the composition meets the requirements, magnesium-aluminum wire is used for magnesium treatment. The amount of magnesium wire used is 290 meters. After magnesium treatment, the molten steel is stirred for 17 minutes;

[0038] S3, after refining, the molten steel is sent to continuous casting for casting. The casting process is heated to 22 degrees, and horizontal dynamic light pressure is adopted, with a pressure reduction of 13mm;

[0039] S4, after the ingot is cut, it is sent to the hydrogen expansion furnace for hydrogen expansion operation, the hydrogen expansion temperature is 650 degrees, and the holding time is 21 hours;

[0040] S5. After the ingot is hydrogenated, it is cooled for 48 hours. After the ingot is inspected and passed, it is put into the heating furnace for heating at a temperature of 1160 degrees and a heating time of 9.7 min / cm.

[0041] S6, adopts controlled rolling process, the second rolling temperature is 910 degrees, the final rolling temperature is 870 degrees, the cooling temperature is 820 degrees, and the red-returning temperature is 560 degrees;

[0042] S7. Steel plates are sheared, marked and inspected before being put into storage for shipment. Example

[0043] The present embodiment provides a deep-sea acid-resistant pipeline steel, steel grade X65MOS, with the following chemical composition and mass percentage: C: 0.033%, Si: 0.17%, Mn: 1.19%, P: 0.010%, S: ≤0.0007%, Nb: 0.051%, V: 0.53%, Ti: 0.013%, Cr: 0.17%, Ni: 0.19%, Mo: 0.0030%, Cu: 0.19%, B: 0.0001%, Mg: 0.0014%, Al: 0.023%, and the balance is Fe and unavoidable impurities.

[0044] Production methods include:

[0045] S1. Top and bottom combined blowing converter smelting is adopted. The converter tapping temperature is 1681 degrees, the tapping oxygen content is 900ppm, 500kg low carbon ferromanganese and 80kg aluminum blocks are added for deoxidation, and the oxygen content of molten steel is controlled at 150ppm after tapping;

[0046] S2. After the molten steel reaches RH, it is vacuum decarburized to ensure that the decarburization is ≤0.010%. After the decarburization is completed, it is sent to LF for deoxidation and alloying. After the composition meets the requirements, magnesium treatment is performed using magnesium-aluminum wire. The amount of magnesium wire used is 320 meters. After magnesium treatment, the molten steel is stirred for 26 minutes;

[0047] S3, the refined molten steel is sent to continuous casting for casting. The casting process is heated to 21 degrees, and horizontal dynamic light pressure is used with a pressure reduction of 15mm;

[0048] S4, after the ingot is cut, it is sent to the hydrogen expansion furnace for hydrogen expansion operation, the hydrogen expansion temperature is 650 degrees, and the holding time is 30 hours;

[0049] S5. After the ingot is hydrogenated, it is cooled for 48 hours. After the ingot is inspected and passed, it is put into the heating furnace for heating at a temperature of 1210 degrees and a heating time of 11 min / cm.

[0050] S6, adopts controlled rolling process, the second rolling temperature is 850 degrees, the final rolling temperature is 810 degrees, the cooling temperature is 798 degrees, and the red-returning temperature is 468 degrees;

[0051] S7. Steel plates are sheared, marked and inspected before being put into storage for shipment.

[0052] The mechanical properties of the steel plates of Examples 1, 2 and 3 are shown in Table 1, and the HIC / CTOD tests are shown in Table 2:

[0053] Table 1

[0054]

[0055] Table 2

[0056]

[0057] By adopting the present invention, acid-resistant steel for deep-sea pipelines in the Middle East has been successfully developed and supplied. At the same time, the solution is more suitable for acid-resistant steel for land pipelines and pipeline steel plates with low-temperature toughness requirements.

[0058] In addition to the above embodiments, the present invention may also have other implementation modes. Any technical solution formed by equivalent replacement or equivalent transformation falls within the protection scope required by the present invention.

Claims

1. A method for producing steel for deep-sea acid-resistant pipelines, characterized in that: Its chemical composition and mass percentage are as follows: C: 0.020%-0.035%, Si: 0.20%-0.23%, Mn: 1.10%-1.20%, P≤0.012%, S≤0.0010%, Nb: 0.040%-0.060%, V: 0.40%-0.50%, Ti: 0.010%-0.022%, Cr: 0.20%-0.25%, Ni: 0.15%-0.20%, Mo≤0.50%, Cu: 0.20%-0.25%, B≤0.0005%, Mg: 0.0010%-0.0013%, Al: 0.015%-0.030%, the balance is Fe and unavoidable impurities; S1. Top and bottom combined blowing converter is used for smelting. The converter tapping temperature is 1680-1720 degrees. The oxygen content of the tapped steel is 600-1000ppm. Low carbon ferromanganese and aluminum blocks are added for deoxidation. The oxygen content of the molten steel is controlled at 50ppm-200ppm after tapping. S2. After the molten steel reaches RH, it is vacuum decarburized to ensure that the decarburization is ≤0.010%. After the decarburization is completed, it is sent to LF for deoxidation and alloying. After the composition meets the requirements, magnesium treatment is carried out using magnesium-aluminum wire. After magnesium treatment, the molten steel is stirred for 15 to 30 minutes; S3, the refined molten steel is sent to continuous casting for casting. The casting process is heated to 20-30 degrees, and horizontal dynamic light pressure is adopted, with a pressure reduction of 13-15mm; S4, after the ingot is cut, it is sent to the hydrogen expansion furnace for hydrogen expansion operation, the hydrogen expansion temperature is 630-650 degrees, and the holding time is 20-30 hours; S5. After the ingot is hydrogenated, it is cooled for 48 hours. After the ingot is inspected and qualified, it is put into the heating furnace for heating. The heating temperature is 1120-1220 degrees and the heating time is 9.0-13min / cm. S6, adopt controlled rolling process, the second rolling temperature is 800-950 degrees, the final rolling temperature is 780-880 degrees, the cooling temperature is 770-830 degrees, and the red-returning temperature is 400-600 degrees; S7. Steel plates are sheared, marked and inspected before being put into storage for shipment.

2. The method for producing deep-sea acid-resistant pipeline steel according to claim 1, characterized in that: In step S1, 500 kg of low carbon ferromanganese and 30-80 kg of aluminum blocks are added to the steel for deoxidation.

3. The method for producing deep-sea acid-resistant pipeline steel according to claim 1, characterized in that: In the step S2, the amount of magnesium aluminum wire used is 280 to 320 meters.

4. The method for producing deep-sea acid-resistant pipeline steel according to claim 1, characterized in that: The finished steel wall thickness is 6 to 50 cm.

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