Production method of thick X65M pipeline steel

Abstract

The invention discloses a production method of thick X65M pipeline steel. The thick X65M pipeline steel comprises the following chemical components in percentage by weight: 0.06%-0.08% of C, 0.10%-0.30% of S i, 1.45%-1.60% of Mn, less than or equal to 0.015% of P, less than or equal to 0.003% of S, 0.040%-0.060% of Nb, 0.020%-0.040% of V, 0.015%-0.030% of T i, 0.20%-0.40% of Cr, 0.020%-0.050% of Al and the balance of Fe and inevitable impurities. The invention further discloses a main preparation process and parameters. The thick X65M pipeline steel with good strength and low-temperature toughness is produced by adopting low-C, high-Mn and Nb-V-T i-Cr alloy components and combining a TMCP rolling process.

Description

Technical Field

[0001] This invention belongs to the field of iron and steel metallurgy technology, and in particular relates to a method for producing thick X65M pipeline steel. Background Technology

[0002] Oil and natural gas are important strategic and reserve materials for the national economy. Pipeline transportation offers advantages such as large capacity, low cost, high safety, convenience, and efficiency, making it the most economical mode of transportation for long-distance oil and natural gas transport. With the continuous increase in demand for oil and natural gas, the transport pressure and pipe diameter of pipelines are also constantly increasing. To ensure the safety and stability of oil and gas pipeline transportation, higher requirements are placed on the thickness and toughness of materials. How to ensure the strength and toughness of thick-gauge, high-grade pipeline steel has become a key research focus.

[0003] Patent publication number CN 119177402 A discloses a hot-rolled high-strength, thick-gauge pipeline steel and its preparation method. The composition and weight percentages are: C: 0.05–0.08%, Si: 0.16–0.24%, Mn: 1.50–1.59%, Cr: 0.12–0.20%, Nb: 0.057–0.067%, Mo: 0.04–0.08%, Ti: 0.012–0.020%, Alt: 0.02–0.05%, P≤0.018%, S≤0.005%, Ni≤0.15%, Cu≤0.1%, V≤0.03%, B≤0.005%, with the remainder being iron and unavoidable impurities. The pipeline steel produced by the alloying process meets the requirements for various properties. However, this invention uses C-Mn-Nb-Mo alloying, which results in high alloy costs and only provides impact energy at 0°C, without mentioning low-temperature toughness.

[0004] Patent publication number CN 117947349 B discloses a hot-rolled coil of L450 grade pipeline steel for surface gathering and transportation and its production method. The chemical composition of the steel is: C: 0.061%~0.070%, Si: 0.15%~0.25%, Mn: 0.39%~0.48%, P≤0.012%, S: 0.0028%~0.003%, Als: 0.030%~0.045%, Nb: 0.032%~0.038%, Ti: 0.020%~0.023%, Cu: 0.34%~0.42%, Cr: 0.32%~0.39%, N≤0.004%, with the remainder being iron and impurities. The resulting hot-rolled pipeline steel coil meets the performance requirements and has good corrosion resistance, but the addition of alloys Cu and Cr is high, and the strength margin is relatively small. Summary of the Invention

[0005] The purpose of this invention is to provide a method for producing thick-gauge X65M pipeline steel. The steel coil thickness is 17-22mm, and it adopts a low C, high Mn and Nb-V-Ti-Cr alloy composition, combined with TMCP rolling process, to produce thick-gauge X65M pipeline steel with good strength and low-temperature toughness.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0007] This invention discloses a method for producing thick-gauge X65M pipeline steel. The chemical composition of the thick-gauge X65M pipeline steel, by weight percentage, is: C: 0.06-0.08%, Si: 0.10-0.30%, Mn: 1.45-1.60%, P: ≤0.015%, S: ≤0.003%, Nb: 0.040-0.060%, V: 0.020-0.040%, Ti: 0.015-0.030%, Cr: 0.20-0.40%, Al: 0.020-0.050%, with the balance being Fe and unavoidable impurities. The main process and parameters are as follows:

[0008] 1) Smelting and casting

[0009] The smelting process uses the KR method to desulfurize the molten iron, and the S content after desulfurization is ≤0.003%.

[0010] During converter smelting, self-produced low-sulfur scrap steel is used, and the tapping temperature is ≥1620℃;

[0011] After LF refining, S ≤ 0.003%. During the LF refining process, ferromanganese, ferrosilicon, ferroniobium and ferrochrome alloys are added to finely adjust the composition of the molten steel to the target range.

[0012] During the RH vacuum treatment process, titanium iron is added. After vacuum treatment, calcium wire is fed in for calcium treatment. After calcium treatment, the soft blowing time is greater than 10 minutes to fully denature and float the inclusions.

[0013] During slab continuous casting, the entire process is protected during pouring, the superheat is controlled at 15-30℃, the casting speed is 1.0-1.2m / min, and the center segregation of the slab is no greater than grade C 3.0.

[0014] 2) Heating and rolling

[0015] The slab heating temperature is 1180-1220℃, and the heating time is ≥180min to ensure uniform billet temperature. The manufacturing process consists of two stages: roughing and finishing. The initial rolling temperature of roughing is 1140-1170℃, the first pass reduction rate is >10%, and the final pass reduction rate is ≥25%, in order to fully refine the original austenite grains. The initial rolling temperature of finishing is ≤1000℃, the final rolling temperature is 820~850℃, and the finishing compression ratio is ≥3.

[0016] 3) Cooling

[0017] After controlled rolling, the coil enters a dense laminar flow cooling zone and is cooled to 480-520℃ at a cooling rate of 10-30℃ / s. Then it is coiled and cooled to room temperature.

[0018] Furthermore, the chemical composition of the thick-gauge X65M pipeline steel, by weight percentage, is C: 0.06%, Si: 0.12%, Mn: 1.50%, P: 0.013%, S: 0.003%, Nb: 0.045%, V: 0.025%, Ti: 0.015%, Cr: 0.25%, Al: 0.028%, with the balance being Fe and unavoidable impurities.

[0019] Furthermore, the chemical composition of the thick-gauge X65M pipeline steel, by weight percentage, is C: 0.07%, Si: 0.20%, Mn: 1.55%, P: 0.011%, S: 0.003%, Nb: 0.052%, V: 0.033%, Ti: 0.022%, Cr: 0.35%, Al: 0.035%, with the balance being Fe and unavoidable impurities.

[0020] Furthermore, the chemical composition of the thick-gauge X65M pipeline steel, by weight percentage, is C: 0.08%, Si: 0.28%, Mn: 1.58%, P: 0.012%, S: 0.002%, Nb: 0.060%, V: 0.038%, Ti: 0.030%, Cr: 0.30%, Al: 0.040%, with the balance being Fe and unavoidable impurities.

[0021] Furthermore, the smelting process employs the KR method to desulfurize the molten iron, resulting in a sulfur content of 0.003%. During converter smelting, self-produced low-sulfur scrap steel is used, with a tapping temperature of 1625℃. After LF refining, the sulfur content is 0.003%. During the LF refining process, ferromanganese, ferrosilicon, ferroniobium, and ferrochrome alloys are added to finely adjust the steel composition to the target range. During RH vacuum treatment, ferrotitanium is added, and after vacuum treatment, calcium wire is fed in for calcium treatment. The soft blowing time after calcium treatment is 12 minutes to fully deform and float inclusions. During slab continuous casting, the entire process is protected during pouring, with superheat controlled at 18℃ and a casting speed of 1.0 m / min. The center segregation of the slab is grade C 3.0.

[0022] The slab heating temperature is 1180℃, and the heating time is 180min; the roughing rolling temperature is 1140℃, the first pass reduction rate is 11%, and the last pass reduction rate is 26%; the finishing rolling temperature is 980℃, the finishing rolling temperature is 820℃, the thickness is 17mm, the intermediate slab thickness is 55mm, and the finishing rolling compression ratio is 3.2.

[0023] After controlled rolling, the coil enters a dense laminar flow cooling zone and is cooled to 520°C at a cooling rate of 15°C / s. Then it is coiled and cooled to room temperature.

[0024] Furthermore, the smelting process employs the KR method to desulfurize the molten iron, resulting in a sulfur content of 0.003% after desulfurization. During converter smelting, self-produced low-sulfur scrap steel is used, with a tapping temperature of 1632℃. After LF refining, the sulfur content is 0.003%. During the LF refining process, ferromanganese, ferrosilicon, ferroniobium, and ferrochrome alloys are added to finely adjust the composition of the molten steel to the target range. During the RH vacuum treatment, ferrotitanium is added, and after vacuum treatment, calcium wire is fed in for calcium treatment. The soft blowing time after calcium treatment is 11 minutes to fully deform and float the inclusions. During slab continuous casting, the entire process is protected during pouring, with the superheat controlled at 25℃ and the casting speed at 1.1 m / min. The center segregation of the slab is grade C 2.0.

[0025] The slab heating temperature is 1200℃ and the heating time is 190min; the roughing rolling temperature is 1150℃, the first pass reduction rate is 12%, and the last pass reduction rate is 27%; the finishing rolling temperature is 990℃, the finishing rolling temperature is 840℃, the thickness is 20mm, the intermediate slab thickness is 62mm, and the finishing rolling compression ratio is 3.1.

[0026] After controlled rolling, the coil enters a dense laminar flow cooling zone and is cooled to 500°C at a cooling rate of 22°C / s. Then it is coiled and cooled to room temperature.

[0027] Furthermore, the smelting process employs the KR method to desulfurize the molten iron, resulting in a sulfur content of 0.002% after desulfurization. During converter smelting, self-produced low-sulfur scrap steel is used, with a tapping temperature of 1636℃. After LF refining, the sulfur content is 0.002%. During the LF refining process, ferromanganese, ferrosilicon, ferroniobium, and ferrochrome alloys are added to finely adjust the composition of the molten steel to the target range. During RH vacuum treatment, ferrotitanium is added, and after vacuum treatment, calcium wire is fed in for calcium treatment. The soft blowing time after calcium treatment is 15 minutes to fully deform and float the inclusions. During slab continuous casting, the entire process is protected during pouring, with the superheat controlled at 30℃ and the casting speed at 1.1 m / min. The center segregation of the slab is grade C1.0.

[0028] The slab heating temperature is 1220℃, and the heating time is 200min; the roughing rolling temperature is 1170℃, the first pass reduction rate is 12%, and the last pass reduction rate is 26%; the finishing rolling temperature is 970℃, the finishing rolling temperature is 850℃, the thickness is 22mm, the intermediate slab thickness is 66mm, and the finishing rolling compression ratio is 3.0.

[0029] After controlled rolling, the coil enters a dense laminar flow cooling zone and is cooled to 480°C at a cooling rate of 30°C / s. Then it is coiled and cooled to room temperature.

[0030] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0031] X65M pipeline steel with a thickness of 17-22mm is designed with low C, high Mn and Nb-V-Ti-Cr composition, combined with controlled rolling and controlled cooling process. The resulting X65M pipeline steel has high strength, good low temperature toughness and drop hammer tear resistance, low production cost and excellent comprehensive performance. Attached Figure Description

[0032] The present invention will be further described below with reference to the accompanying drawings.

[0033] Figure 1 The metallographic structure is shown in Example 1 of this invention. Detailed Implementation

[0034] The present invention will be further described in detail below with reference to specific embodiments. These embodiments are merely descriptions of the best mode of implementation of the present invention and do not limit the scope of the present invention in any way.

[0035] Examples 1-3 illustrate the chemical composition and process steps used in the production method of thick-gauge X65M pipeline steel according to the present invention. The chemical composition of each example is shown in Table 1, and the mechanical properties are shown in Table 2.

[0036] Example 1: The smelting process uses the KR method to desulfurize the molten iron, resulting in a sulfur content of 0.003%. During converter smelting, self-produced low-sulfur scrap steel is used, and the tapping temperature is 1625℃. After LF refining, the sulfur content is 0.003%. During LF refining, ferromanganese, ferrosilicon, ferroniobium, and ferrochrome alloys are added to finely adjust the steel composition to the target range. During RH vacuum treatment, ferrotitanium is added. After vacuum treatment, calcium wire is fed in for calcium treatment, followed by a soft blowing time of 12 minutes to fully deform and float inclusions. During slab continuous casting, full-process protective pouring is used, with superheat controlled at 18℃ and a casting speed of 1.0 m / min. The center segregation of the slab is grade C 3.0.

[0037] The slab is heated to 1180℃ for 180 minutes. The roughing rolling temperature is 1140℃, with a first pass reduction of 11% and a final pass reduction of 26%. The finishing rolling temperature is 980℃, with a final rolling temperature of 820℃, a thickness of 17mm, an intermediate slab thickness of 55mm, and a finishing rolling compression ratio of 3.2.

[0038] After controlled rolling, the coil enters a dense laminar flow cooling zone and is cooled to 520°C at a cooling rate of 15°C / s. Then it is coiled and cooled to room temperature.

[0039] Example 2: The smelting process uses the KR method to desulfurize the molten iron, resulting in a sulfur content of 0.003%. During converter smelting, self-produced low-sulfur scrap steel is used, and the tapping temperature is 1632℃. After LF refining, the sulfur content is 0.003%. During LF refining, ferromanganese, ferrosilicon, ferroniobium, and ferrochrome alloys are added to finely adjust the steel composition to the target range. During RH vacuum treatment, ferrotitanium is added. After vacuum treatment, calcium wire is fed in for calcium treatment, followed by soft blowing for 11 minutes to fully deform and float inclusions. During slab continuous casting, full-process protective pouring is used, with superheat controlled at 25℃ and a casting speed of 1.1 m / min. The center segregation of the slab is grade C 2.0.

[0040] The slab is heated to 1200℃ for 190 minutes. The roughing rolling temperature is 1150℃, with a first pass reduction of 12% and a final pass reduction of 27%. The finishing rolling temperature is 990℃, with a final rolling temperature of 840℃, a thickness of 20mm, an intermediate slab thickness of 62mm, and a finishing rolling compression ratio of 3.1.

[0041] After controlled rolling, the coil enters a dense laminar flow cooling zone and is cooled to 500°C at a cooling rate of 22°C / s. Then it is coiled and cooled to room temperature.

[0042] Example 3: The smelting process uses the KR method to desulfurize the molten iron, resulting in a sulfur content of 0.002%. During converter smelting, self-produced low-sulfur scrap steel is used, and the tapping temperature is 1636℃. After LF refining, the sulfur content is 0.002%. During LF refining, ferromanganese, ferrosilicon, ferroniobium, and ferrochrome alloys are added to finely adjust the steel composition to the target range. During RH vacuum treatment, ferrotitanium is added. After vacuum treatment, calcium wire is fed in for calcium treatment, followed by a soft blowing time of 15 minutes to fully deform and float inclusions. During slab continuous casting, full-process protective pouring is performed, with superheat controlled at 30℃ and a casting speed of 1.1 m / min. The center segregation of the slab is grade C1.0.

[0043] The slab is heated to 1220℃ for 200 minutes. The roughing rolling temperature is 1170℃, with a first pass reduction of 12% and a final pass reduction of 26%. The finishing rolling temperature is 970℃, with a final rolling temperature of 850℃, a thickness of 22mm, an intermediate slab thickness of 66mm, and a finishing rolling compression ratio of 3.0.

[0044] After controlled rolling, the coil enters a dense laminar flow cooling zone and is cooled to 480°C at a cooling rate of 30°C / s. Then it is coiled and cooled to room temperature.

[0045] Table 1 Chemical composition (wt%) of each example

[0046]

[0047] Table 2 Mechanical Properties

[0048]

[0049] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for producing thick-gauge X65M pipeline steel, characterized in that: The chemical composition of the thick-gauge X65M pipeline steel, by weight percentage, is: C: 0.06-0.08%, Si: 0.10-0.30%, Mn: 1.45-1.60%, P: ≤0.015%, S: ≤0.003%, Nb: 0.040-0.060%, V: 0.020-0.040%, Ti: 0.015-0.030%, Cr: 0.20-0.40%, Al: 0.020-0.050%, with the balance being Fe and unavoidable impurities. The main processes and parameters are as follows: 1) Smelting and casting The smelting process uses the KR method to desulfurize the molten iron, and the S content after desulfurization is ≤0.003%. During converter smelting, self-produced low-sulfur scrap steel is used, and the tapping temperature is ≥1620℃; After LF refining, S ≤ 0.003%. During the LF refining process, ferromanganese, ferrosilicon, ferroniobium and ferrochrome alloys are added to finely adjust the composition of the molten steel to the target range. During the RH vacuum treatment process, titanium iron is added. After vacuum treatment, calcium wire is fed in for calcium treatment. After calcium treatment, the soft blowing time is greater than 10 minutes to fully denature and float the inclusions. During slab continuous casting, the entire process is protected during pouring, the superheat is controlled at 15-30℃, the casting speed is 1.0-1.2m / min, and the center segregation of the slab is no greater than grade C 3.

0. 2) Heating and rolling The slab heating temperature is 1180-1220℃, and the heating time is ≥180min to ensure uniform billet temperature. The manufacturing process consists of two stages: roughing and finishing. The initial rolling temperature of roughing is 1140-1170℃, the first pass reduction rate is >10%, and the final pass reduction rate is ≥25%, in order to fully refine the original austenite grains. The initial rolling temperature of finishing is ≤1000℃, the final rolling temperature is 820~850℃, and the finishing compression ratio is ≥3. 3) Cooling After controlled rolling, the coil enters a dense laminar flow cooling zone and is cooled to 480-520℃ at a cooling rate of 10-30℃ / s. Then it is coiled and cooled to room temperature.

2. The method for producing thick-gauge X65M pipeline steel according to claim 1, characterized in that: The chemical composition of the thick-gauge X65M pipeline steel, by weight percentage, is C: 0.06%, Si: 0.12%, Mn: 1.50%, P: 0.013%, S: 0.003%, Nb: 0.045%, V: 0.025%, Ti: 0.015%, Cr: 0.25%, Al: 0.028%, with the balance being Fe and unavoidable impurities.

3. The method for producing thick-gauge X65M pipeline steel according to claim 1, characterized in that: The chemical composition of the thick-gauge X65M pipeline steel, by weight percentage, is C: 0.07%, Si: 0.20%, Mn: 1.55%, P: 0.011%, S: 0.003%, Nb: 0.052%, V: 0.033%, Ti: 0.022%, Cr: 0.35%, Al: 0.035%, with the balance being Fe and unavoidable impurities.

4. The method for producing thick-gauge X65M pipeline steel according to claim 1, characterized in that: The chemical composition of the thick-gauge X65M pipeline steel, by weight percentage, is C: 0.08%, Si: 0.28%, Mn: 1.58%, P: 0.012%, S: 0.002%, Nb: 0.060%, V: 0.038%, Ti: 0.030%, Cr: 0.30%, Al: 0.040%, with the balance being Fe and unavoidable impurities.

5. The method for producing thick-gauge X65M pipeline steel according to claim 2, characterized in that: The smelting process uses the KR method to desulfurize the molten iron, resulting in a sulfur content of 0.003%. During converter smelting, self-produced low-sulfur scrap steel is used, and the tapping temperature is 1625℃. After LF refining, the sulfur content is 0.003%. During the LF refining process, ferromanganese, ferrosilicon, ferroniobium, and ferrochrome alloys are added to finely adjust the composition of the molten steel to the target range. During RH vacuum treatment, ferrotitanium is added, and after vacuum treatment, calcium wire is fed in for calcium treatment. The soft blowing time after calcium treatment is 12 minutes to fully deform and float the inclusions. During slab continuous casting, the entire process is protected during pouring, the superheat is controlled at 18℃, the casting speed is 1.0 m / min, and the center segregation of the slab is grade C 3.

0. The slab heating temperature is 1180℃, and the heating time is 180min; the roughing rolling temperature is 1140℃, the first pass reduction rate is 11%, and the last pass reduction rate is 26%; the finishing rolling temperature is 980℃, the finishing rolling temperature is 820℃, the thickness is 17mm, the intermediate slab thickness is 55mm, and the finishing rolling compression ratio is 3.

2. After controlled rolling, the coil enters a dense laminar flow cooling zone and is cooled to 520°C at a cooling rate of 15°C / s. Then it is coiled and cooled to room temperature.

6. The method for producing thick-gauge X65M pipeline steel according to claim 3, characterized in that: The smelting process uses the KR method to desulfurize the molten iron, resulting in a sulfur content of 0.003%. During converter smelting, self-produced low-sulfur scrap steel is used, and the tapping temperature is 1632℃. After LF refining, the sulfur content is 0.003%. During the LF refining process, ferromanganese, ferrosilicon, ferroniobium, and ferrochrome alloys are added to finely adjust the composition of the molten steel to the target range. During the RH vacuum treatment, ferrotitanium is added, and after vacuum treatment, calcium wire is fed in for calcium treatment. The soft blowing time after calcium treatment is 11 minutes to fully deform and float the inclusions. During slab continuous casting, the entire process is protected during pouring, the superheat is controlled at 25℃, the casting speed is 1.1m / min, and the center segregation of the slab is grade C 2.

0. The slab heating temperature is 1200℃ and the heating time is 190min; the roughing rolling temperature is 1150℃, the first pass reduction rate is 12%, and the last pass reduction rate is 27%; the finishing rolling temperature is 990℃, the finishing rolling temperature is 840℃, the thickness is 20mm, the intermediate slab thickness is 62mm, and the finishing rolling compression ratio is 3.

1. After controlled rolling, the coil enters a dense laminar flow cooling zone and is cooled to 500°C at a cooling rate of 22°C / s. Then it is coiled and cooled to room temperature.

7. The method for producing thick-gauge X65M pipeline steel according to claim 4, characterized in that: The smelting process uses the KR method to desulfurize the molten iron, resulting in a sulfur content of 0.002%. During converter smelting, self-produced low-sulfur scrap steel is used, and the tapping temperature is 1636℃. After LF refining, the sulfur content is 0.002%. During the LF refining process, ferromanganese, ferrosilicon, ferroniobium, and ferrochrome alloys are added to finely adjust the composition of the molten steel to the target range. During the RH vacuum treatment, ferrotitanium is added, and after vacuum treatment, calcium wire is fed in for calcium treatment. After calcium treatment, the soft blowing time is 15 minutes to fully deform and float the inclusions. During slab continuous casting, the entire process is protected during pouring, the superheat is controlled at 30℃, the casting speed is 1.1m / min, and the center segregation of the slab is grade C1.

0. The slab is heated to 1220℃ for 200 minutes. The roughing rolling temperature is 1170℃, the first pass reduction rate is 12%, and the last pass reduction rate is 26%; the finishing rolling temperature is 970℃, the finishing rolling temperature is 850℃, the thickness is 22mm, the intermediate billet thickness is 66mm, and the finishing rolling compression ratio is 3.

0. After controlled rolling, the coil enters a dense laminar flow cooling zone and is cooled to 480°C at a cooling rate of 30°C / s. Then it is coiled and cooled to room temperature.

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