Production method of normalizing-free line pipe

Abstract

The invention discloses a production method of a normalizing-free pipeline pipe which comprises the following chemical components in percentage by mass: 0.08-0.12% of C, 0.15-0.40% of Si, 1.05-1.25% of Mn, 0.01-0.05% of Al, less than or equal to 0.015% of P, less than or equal to 0.003% of S and the balance of Fe and trace impurities, and the total mass fraction is 100%. Key process parameter control is also disclosed. By means of the method, as-rolled normalizing-free delivery is achieved, and the pipeline pipe has excellent hydrogen sulfide corrosion resistance and low-temperature obdurability under the condition that precious elements Mo, Nb, Cu and Ni are not added. Wherein the yield strength ranges from 245 MPa to 450 MPa, the tensile strength ranges from 415 MPa to 655 MPa, the transverse impact toughness AKV at the temperature of-20 DEG C is larger than or equal to 55 J, the Vickers hardness is smaller than or equal to 200 HV10, and the acid service requirement in the NACE MR0175 / ISO 15156 standard is met.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of material metallurgy, and particularly relates to a production method of a normalized-free line pipe. BACKGROUND

[0002] A certain oil field in China is an important oil and gas production base, and it faces significant hydrogen sulfide corrosion problems in the process of exploitation and transportation. At the same time, the minimum temperature in the winter in the area where the oil field is located can reach-20℃, which puts double strict requirements on the corrosion resistance and low-temperature toughness of the line pipe. At present, the line pipe used in the oil field adopts normalizing treatment process to ensure the performance, but the normalizing treatment not only increases the production process and prolongs the production cycle, but also leads to the increase of energy consumption and production cost, which is not conducive to large-scale supply.

[0003] In the prior art, the hydrogen sulfide-resistant line pipe relies on the addition of precious alloy elements or complex heat treatment process to improve performance, and there are problems of high cost or low production efficiency. For example, some line pipes need to add Mo elements to enhance corrosion resistance, or adopt normalizing + tempering process to refine the organization, which is different from the demand of the oil field for economic and efficient line pipe. In addition, the cleanliness requirement of the oil field working condition for the line pipe is very high, and the type and level of non-metallic inclusions directly affect the corrosion resistance and toughness, and the existing process still has optimization space in the control of inclusions.

[0004] In view of the above problems, a production method of a normalized-free, low-cost, high-cleanliness line pipe suitable for the special working conditions of a certain oil field in China is developed, which is the key to improve the safety of oil field transportation and reduce operation and maintenance cost. SUMMARY

[0005] In order to solve the problems of high energy consumption of normalizing process, high cost of precious alloy, and insufficient matching of hydrogen sulfide resistance and low-temperature toughness in the production of existing oil field line pipe, the purpose of the present application is to provide a production method of a normalized-free line pipe, which realizes the delivery of rolled state and meets the double working condition requirements of hydrogen sulfide-containing medium and low-temperature service in the oil field.

[0006] To solve the above technical problems, the present application adopts the following technical scheme:

[0007] The production method of the normalized-free line pipe of the present application comprises:

[0008] (1) Component system design: adopt "low-carbon medium-manganese + rare earth micro-alloying" system, use low-carbon to ensure toughness basis, and medium-manganese to realize solid solution strengthening; the specific chemical composition mass percentage is: C 0.08-0.12%, Si 0.15-0.40%, Mn 1.05-1.25%, Al 0.01-0.05%, P≤0.015%, S≤0.003%; the rest is Fe and trace impurities, and the mass fraction is 100% in total;

[0009] (2) Key process parameter control:

[0010] Hot metal pretreatment: Desulfurization with magnesium powder to make the S content of hot metal ≤0.010%, laying a foundation for subsequent low sulfur control;

[0011] Converter smelting: Adding 8% to 10% of high-quality scrap steel, smelting with single slag process, controlling the final slag basicity at 3.0 to 3.5, blocking slag operation at tapping, success rate of blocking slag ≥95%, adding silicon-manganese and ferromanganese deoxidizing alloy during tapping process, and using aluminum deoxidization for final deoxidization;

[0012] Refining treatment: LF furnace white slag refining, Ar blowing and stirring throughout the process, controlling the temperature rising speed from low to high gradient; VD vacuum treatment vacuum degree ≤67 Pa, holding time ≥15 min, removing gas and inclusions in the steel;

[0013] Continuous casting process: Using low speed constant speed control, casting speed 0.8 to 1.0 m / min, electromagnetic stirring intensity 100 to 120 A, full-protective pouring, and superheat degree of molten steel ΔT ≤25℃; flame cutting after casting blank straightening, and slow cooling for 48 h or more for eliminating internal stress;

[0014] Rolling and cooling: The temperature of each section of the ring heating furnace is controlled at preheating I section 980 to 1080℃, preheating II section 1100 to 1200℃, heating I section 1200 to 1270℃, heating II section 1250 to 1290℃, soaking I section 1250 to 1290℃, and soaking II section 1240 to 1280℃; after the tube blank is perforated, it is continuously rolled by the PQF pipe rolling unit, and is micro-tension sizing; after rolling, it is cooled online at a cooling speed of 2 to 5℃ / s, and is cooled to 300 to 400℃ before entering the cooling bed for air cooling.

[0015] Further, the specific chemical composition mass percentage is: C 0.09%, Si 0.22%, Mn 1.15%, Al 0.03%, P 0.012%, S 0.003%; the rest is Fe and trace impurities, and the mass fraction is 100%.

[0016] Further, the specific chemical composition mass percentage is: C 0.10%, Si 0.25%, Mn 1.12%, Al 0.02%, P 0.011%, S 0.002%; the rest is Fe and trace impurities, and the mass fraction is 100%.

[0017] Further, the raw material ratio is: 90 tons of hot metal from blast furnace + 10 tons of high-quality scrap steel, P ≤0.010%, S ≤0.005%;

[0018] Hot metal pretreatment: Desulfurization with magnesium powder, and the S content of hot metal after treatment is 0.008%;

[0019] Converter smelting: adding pretreated hot metal and scrap steel, single slag process smelting, final slag basicity 3.2, adding silicon manganese 200 kg, ferromanganese 150 kg for deoxidization and alloying at tapping, adding aluminum wire 30 kg for final deoxidization, blocking slag and tapping, adding lime block 180 kg after alloying is completed;

[0020] Refining treatment: white slag refining in LF furnace, stirring by blowing Ar, heating to 1550℃, entering VD vacuum treatment after composition adjustment, vacuum degree 50 Pa, pressure maintaining 18 min;

[0021] Continuous casting: casting speed 0.9 m / min, electromagnetic stirring intensity 110 A, superheat of molten steel 22℃, protective casting, casting blank specification Stacking and slow cooling for 50 h.

[0022] Further, rolling and cooling: the temperature of each section of the ring heating furnace is controlled according to preheating I section 1050℃, preheating II section 1150℃, heating I section 1250℃, heating II section 1270℃, soaking I section 1270℃, and soaking II section 1260℃; after the pipe blank is perforated, it is rolled by PQF pipe rolling mill, sizing is Specification, rolling cooling speed 3℃ / s, cooling to 350℃ into the cooling bed.

[0023] Further, raw material ratio: 90 tons of blast furnace hot metal + 10 tons of high-quality scrap steel;

[0024] Hot metal pretreatment: desulfurization by magnesium powder, S content of treated hot metal 0.007%;

[0025] Converter smelting: final slag basicity 3.0, adding silicon manganese 190 kg and ferromanganese 140 kg at tapping, adding aluminum wire 28 kg for final deoxidization, adding lime block 190 kg after blocking slag and tapping;

[0026] Refining treatment: white slag refining in LF furnace, VD vacuum treatment vacuum degree 45 Pa, pressure maintaining 20 min;

[0027] Continuous casting: casting speed 0.8 m / min, electromagnetic stirring intensity 100 A, superheat of molten steel 20℃, casting blank specification Stacking and slow cooling for 52 h.

[0028] Further, rolling and cooling: the temperature of each section of the ring heating furnace is controlled according to preheating I section 1030℃, preheating II section 1130℃, heating I section 1230℃, heating II section 1260℃, soaking I section 1260℃, and soaking II section 1250℃; the pipe blank is rolled into Specification, rolling cooling speed 4℃ / s, cooling to 320℃ into the cooling bed.

[0029] Further, the pipeline produced has the following performance indexes: yield strength 245-450 MPa, tensile strength 415-655 MPa, yield strength ratio ≤0.9, transverse impact toughness AKV at-20℃ ≥55 J, Vickers hardness ≤200 HV10, grain size ≥ASTM E112 standard 8 levels; the total level of coarse and fine A, B, C and D non-metallic inclusions is ≤2.0 level, and the banded structure is ≤2.0 level.

[0030] Further, the pipeline produced meets the requirements of NACE MR0175 / ISO 15156 standard; the HIC test (NACE TM0284-2016) CLR ≤5%, CTR ≤1.5%, and CSR ≤0.5%; and the SSC test (NACE TM0177-2016) has no visible cracks under 10 times low-power microscope.

[0031] Compared with the prior art, the present application has the following beneficial technical effects:

[0032] 1. Energy-saving and efficient without normalizing: the traditional normalizing process is replaced by on-line controlled cooling after rolling, the production cycle is shortened by more than 15%, the energy consumption per ton of steel is reduced by 80-100 kg of standard coal, and the production cost is reduced by 10%-12%;

[0033] 2. Excellent corrosion resistance: through low P, S control and rare earth inclusion spheroidizing treatment, the total level of coarse and fine A, B, C and D non-metallic inclusions in the steel is ≤2.0 level, the banded structure is ≤2.0 level, the HIC test (NACE TM0284-2016 standard) CLR ≤5%, CTR ≤1.5%, and CSR ≤0.5%, the SSC test (NACE TM0177-2016 standard) has no visible cracks under 10 times low-power microscope, and meets the service requirements in oil fields containing hydrogen sulfide medium;

[0034] 3. Low-temperature strength and toughness matching: transverse impact toughness AKV at-20℃ ≥55 J, shear area ratio ≥85%, yield strength 245-450 MPa, tensile strength 415-655 MPa, yield strength ratio ≤0.9, and grain size reaching ASTM E112 standard 8 levels and finer, which can adapt to the low-temperature working conditions in oil fields in winter;

[0035] 4. Outstanding economy: no addition of Mo, Nb and other valuable alloys, using 90% blast furnace molten iron + 10% high-quality scrap steel raw materials, industrialization yield ≥85%, qualified rate ≥90%, and having large-scale supply capacity. DETAILED DESCRIPTION

[0036] The present application will be described in detail below through specific examples, and the process parameters not mentioned in the examples are executed according to the foregoing technical solutions.

[0037] Example 1

[0038] 1. Raw material ratio: 90 tons of blast furnace molten iron + 10 tons of high-quality scrap steel (P≤0.010%, S≤0.005%);

[0039] 2. Molten iron pretreatment: magnesium powder is used for desulfurization, and the S content of the treated molten iron is 0.008%;

[0040] 3. Converter smelting: the pretreated molten iron and scrap steel are added, single slag process smelting is performed, the final slag basicity is 3.2, 200 kg of silicon manganese and 150 kg of ferromanganese are added for deoxidization and alloying at the time of tapping, 30 kg of aluminum wire is added for final deoxidization, slag blocking is performed at the time of tapping, and 180 kg of lime block is added after the completion of alloying;

[0041] 4. Refining treatment: white slag refining is performed in an LF furnace, Ar is blown for stirring, the temperature is raised to 1550°C, and after composition adjustment, VD vacuum treatment is performed at a vacuum degree of 50 Pa and a pressure maintaining time of 18 min;

[0042] 5. Continuous casting: the casting speed is 0.9 m / min, the electromagnetic stirring intensity is 110 A, the molten steel superheat is 22°C, and protective casting is performed, and the casting blank specification is stacking and slow cooling for 50 h;

[0043] 6. Rolling and cooling: the temperature of each section of the ring heating furnace is controlled according to preheating I section 1050°C, preheating II section 1150°C, heating I section 1250°C, heating II section 1270°C, soaking I section 1270°C, and soaking II section 1260°C; after the pipe blank is perforated, it is continuously rolled by a PQF pipe rolling unit, the sizing is the specification, the cooling speed after rolling is 3°C / s, and the pipe blank is cooled to 350°C and then enters the cooling bed;

[0044] 7. Product detection: the chemical composition of the pipe blank and the performance detection results of the finished product are shown in Tables 1 and 2, respectively.

[0045] Example 2

[0046] 1. Raw material ratio: 90 tons of blast furnace molten iron + 10 tons of high-quality scrap steel;

[0047] 2. Molten iron pretreatment: magnesium powder is used for desulfurization, and the S content of the treated molten iron is 0.007%;

[0048] 3. Converter smelting: the final slag basicity is 3.0, 190 kg of silicon manganese and 140 kg of ferromanganese are added at the time of tapping, 28 kg of aluminum wire is added for final deoxidization, and 190 kg of lime block is added after the tapping of the slag;

[0049] 4. Refining treatment: white slag refining is performed in an LF furnace, and VD vacuum treatment is performed at a vacuum degree of 45 Pa and a pressure maintaining time of 20 min;

[0050] 5. Continuous casting: the casting speed is 0.8 m / min, the electromagnetic stirring intensity is 100 A, the molten steel superheat is 20°C, and the casting blank specification​ Stack slow cooling 52h;

[0051] 6. Rolling and cooling: The temperature of each section of the circular heating furnace is controlled as follows: preheating I section 1030℃, preheating II section 1130℃, heating I section 1230℃, heating II section 1260℃, soaking I section 1260℃, and soaking II section 1250℃. The pipe blank is rolled into a specified size, and after rolling, the cooling speed is 4℃ / s, and the pipe blank is cooled to 320℃ and then put into a cooling bed;

[0052] 7. Product detection: The chemical composition of the pipe blank and the performance detection results of the finished product are shown in Table 1 and Table 2, respectively.

[0053] Table 1

[0054] Element C Si Mn Al P S Example 1 0.09 0.22 1.15 0.03 0.012 0.003 Example 2 0.10 0.25 1.12 0.02 0.011 0.002

[0055] Table 2

[0056]

[0057]

[0058] The above-described embodiments are only used to describe the preferred modes of the present application, and do not limit the scope of the present application. Without departing from the design spirit of the present application, various modifications and improvements to the technical solutions of the present application made by those skilled in the art shall fall within the protection scope determined by the claims of the present application.

Claims

1. A method for producing a normalizing-free pipeline pipe, characterized in that, include: (1) Composition system design: The "low carbon medium manganese + rare earth microalloying" system is adopted. Low carbon ensures the toughness foundation, and medium manganese achieves solid solution strengthening. The specific chemical composition by mass percentage is: C 0.08~0.12%, Si 0.15~0.40%, Mn 1.05~1.25%, Al 0.01~0.05%, P≤0.015%, S≤0.003%; the remainder is Fe and trace impurities, with a total mass fraction of 100%. (2) Control of key process parameters: Hot metal pretreatment: Desulfurization is carried out using metallic magnesium powder to ensure that the sulfur content of the hot metal is ≤0.010%, laying the foundation for subsequent low sulfur control; Converter smelting: Add 8% to 10% high-quality scrap steel, smelt using single slag process, control the final slag basicity at 3.0 to 3.5, perform slag blocking operation during tapping, with a slag blocking success rate of ≥95%, add silicon manganese and ferromanganese for deoxidation and alloying during tapping, and use aluminum deoxidation for final deoxidation; Refining process: White slag refining in LF furnace, Ar blowing and stirring throughout the process, with the heating rate controlled from low to high gradient; VD vacuum treatment with a vacuum degree ≤67Pa and a holding time ≥15min to remove gas and inclusions from the steel; Continuous casting process: Low-speed constant speed control is adopted, with a casting speed of 0.8 to 1.0 m / min, electromagnetic stirring intensity of 100 to 120 A, full-process protective pouring, and steel superheat ΔT ≤ 25℃; after billet straightening, flame cutting is performed, and the billets are stacked and slowly cooled for more than 48 hours to eliminate internal stress; Rolling and cooling: The temperature of each section of the annular heating furnace is controlled as follows: preheating section I 980-1080℃, preheating section II 1100-1200℃, heating section I 1200-1270℃, heating section II 1250-1290℃, soaking section I 1250-1290℃, and soaking section II 1240-1280℃. After the billet is pierced, it is continuously rolled by the PQF tube rolling mill and sized with micro-tension. After rolling, it is cooled online with a cooling rate of 2-5℃ / s. After cooling to 300-400℃, it is air-cooled in a cooling bed.

2. The method for producing non-normalizing pipeline pipe according to claim 1, characterized in that, The specific chemical composition by mass percentage is as follows: C 0.09%, Si 0.22%, Mn 1.15%, Al 0.03%, P 0.012%, S 0.003%; the remainder is Fe and trace impurities, with a total mass fraction of 100%.

3. The method for producing non-normalizing pipeline pipe according to claim 1, characterized in that, The specific chemical composition by mass percentage is as follows: C 0.10%, Si 0.25%, Mn 1.12%, Al 0.02%, P 0.011%, S 0.002%; the remainder is Fe and trace impurities, with a total mass fraction of 100%.

4. The method for producing non-normalizing pipeline pipe according to claim 2, characterized in that, Raw material ratio: 90 tons of blast furnace molten iron + 10 tons of high-quality scrap steel, P≤0.010%, S≤0.005%; Hot metal pretreatment: Desulfurization is carried out using metallic magnesium powder, and the sulfur content of the hot metal after treatment is 0.008%; Converter smelting: Add pretreated molten iron and scrap steel, smelt using single slag process, final slag basicity 3.2, add 200kg silicon manganese and 150kg ferromanganese for deoxidation and alloying when tapping, add 30kg aluminum wire for final deoxidation, tap the steel with slag blocked, and add 180kg quicklime after alloying. Refining process: White slag is refined in LF furnace, stirred by Ar blowing, heated to 1550℃, and after composition adjustment, it enters VD vacuum treatment with a vacuum degree of 50Pa and a holding pressure of 18min. Continuous casting: casting speed 0.9 m / min, electromagnetic stirring intensity 110 A, molten steel superheat 22℃, protective casting, billet specifications. Stack and slow cool for 50 hours.

5. The method for producing non-normalizing pipeline pipe according to claim 3, characterized in that, Rolling and Cooling: The temperatures of each section of the annular heating furnace are controlled as follows: Preheating Section I 1050℃, Preheating Section II 1150℃, Heating Section I 1250℃, Heating Section II 1270℃, Soaking Section I 1270℃, and Soaking Section II 1260℃; after the billet is pierced... PQF tube rolling mill continuous rolling, sizing is Specifications: Cooling rate after rolling is 3℃ / s, and the product is cooled to 350℃ before being placed in the cooling bed.

6. The method for producing non-normalizing pipeline pipe according to claim 3, characterized in that, Raw material ratio: 90 tons of blast furnace molten iron + 10 tons of high-quality scrap steel; Hot metal pretreatment: Desulfurization with magnesium powder, the sulfur content of the hot metal after treatment is 0.007%; Converter smelting: final slag basicity 3.0, add 190kg silicon manganese and 140kg ferromanganese when tapping steel, add 28kg aluminum wire for final deoxidation, and add 190kg quicklime blocks after slag blocking and tapping steel. Refining process: White slag refining in LF furnace, VD vacuum treatment at a vacuum degree of 45 Pa and pressure holding for 20 min; Continuous casting: casting speed 0.8 m / min, electromagnetic stirring intensity 100 A, molten steel superheat 20℃, billet specifications Stack and cool slowly for 52 hours.

7. The method for producing non-normalizing pipeline pipe according to claim 6, characterized in that, Rolling and Cooling: The temperatures of each section of the annular heating furnace are controlled as follows: Preheating Section I 1030℃, Preheating Section II 1130℃, Heating Section I 1230℃, Heating Section II 1260℃, Soaking Section I 1260℃, and Soaking Section II 1250℃; Rolling is completed... Specifications: Cooling rate after rolling is 4℃ / s, and the product is cooled to 320℃ before being placed in the cooling bed.

8. The method for producing non-normalizing pipeline pipe according to claim 1, characterized in that, The performance indicators of the produced pipeline pipes are as follows: yield strength 245~450MPa, tensile strength 415~655MPa, yield ratio ≤0.9, transverse impact toughness AKV≥55J at -20℃, Vickers hardness ≤200HV10, grain size ≥ASTM E112 standard grade 8; the total grade of coarse and fine non-metallic inclusions of categories A, B, C, and D is ≤2.0, and the banded structure is ≤2.

0.

9. The production method according to claim 1, characterized in that, The manufactured pipeline pipes meet the requirements of NACE MR0175 / ISO15156 standards; HIC test results show CLR≤5%, CTR≤1.5%, and CSR≤0.5%; SSC test results show no visible cracks under a 10x low-power microscope.

Images