A method of smelting a steel for supercritical co2 pipeline transportation

Abstract

The application discloses a smelting method of supercritical CO2 pipeline conveying steel, which comprises the following steps: S1, desulfurization by using a KR method; S2, top and bottom combined blowing smelting is adopted in a converter, the bottom stirring flow is limited, slagging material and aluminum blocks are used for deoxidization, and carbon and manganese alloy are added for deoxidization and alloying; S3, LF+RH process is adopted for refining treatment, calcium treatment is carried out after RH vacuum treatment to modify and purify molten steel; S4, after the refining treatment of the molten steel, the molten steel is sent to continuous casting pouring, strong cooling mode is adopted for cooling, and the crystallizer adopts positive dazzle mode vibration; S5, during the pouring process, multi-point pressing down is adopted for pressing down, and large pressing down operation is carried out in the horizontal section; S6, after the blank cutting, slow cooling is carried out after waiting for temperature, and surface inspection is carried out after the heat preservation is finished. The application has the advantages that the grains of the narrow surface, upper and lower surfaces and core of the cast blank are refined, the hardenability of the product is improved, the homogenization in the longitudinal direction of the product is realized, the product quality is ensured, and the performance requirements of the supercritical CO2 pipeline conveying steel are met.

Description

Technical Field

[0001] This invention belongs to the field of metallurgical technology, and in particular relates to a smelting method for steel used in supercritical CO2 pipeline transportation. Background Technology

[0002] CO2 is mainly transported via pipelines, ships, tankers, and trains. Pipeline transport is the most cost-effective way to transport CO2 over long distances. However, the physical properties of CO2 differ significantly from those of crude oil and natural gas, and existing pipeline operation technologies cannot be directly applied. The ultra-high pressure and ultra-low temperature problems caused by the abrupt change in CO2 phase pose challenges to pipeline operation and material design. The steel used for pipeline transport needs to have good resistance to low-temperature brittle fracture, fracture toughness, and corrosion resistance. However, existing steels cannot adequately match good low-temperature toughness and strength, posing safety hazards to CO2 transport. Summary of the Invention

[0003] The purpose of this invention is to solve the problem of poor overall performance of existing CO2 pipeline steel. It provides a smelting method for supercritical CO2 pipeline steel, which makes the grains on the narrow face and upper and lower surfaces of the billet more refined, improves the hardenability of the product, and significantly refines the core grain structure, achieving longitudinal homogenization of the product, ensuring stable product quality, and meeting the performance requirements of supercritical CO2 pipeline steel.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: A method for smelting steel for supercritical CO2 pipeline transportation, wherein the chemical composition and mass percentage of the steel pipe include: C: 0.04%–0.08%, Si: 0.08%–0.38%, Mn: 1.30%–1.60%, P≤0.015%, S≤0.0020%, Nb: 0.060–0.080%, V≤0.010%, Ti: 0.008–0.030%, Cr≤0.05%, Ni≤0.05%, Mo: 0.20–0.30%, Cu: 0.20–0.30%, Al: 0.010%–0.050%, B≤0.00050%, Ca: 0.001–0.003%, N≤0.0060%, H≤0.0002%, with the balance being Fe and unavoidable impurities; the above steel pipe is smelted according to the following steps: S1: Molten iron is transported to the transfer station via a torpedo ladle and desulfurized using the KR method. The amount of desulfurizing agent used is 1500±50kg, and the temperature of the molten iron after desulfurization is 1250±50℃. S2: Hot metal charging rate 160-180t, converter adopts top and bottom blowing smelting, bottom stirring flow rate 0.20-0.30Nm 3 / (t·min), deoxidation is carried out using slag-forming materials and aluminum blocks, and carbon and manganese alloys are added for deoxidation and alloying. S3: Refining is carried out using the LF+RH process. After RH vacuum treatment, the molten steel is modified and purified by calcium treatment. After calcium treatment, the steel is stirred for 15-20 minutes. S4: After refining, the molten steel is sent to continuous casting for pouring. The superheat is 20-30℃, the casting speed is 0.6-0.9m / min, and strong cooling is used. The flow rate of the wide face of the crystallizer is 5500-6000L / min, and the flow rate of the narrow face is 900-1200L / min. The crystallizer is vibrated in a positive direction with an amplitude of 5-15mm and a vibration frequency of 200-300 times / min. S5: During the pouring process, multiple points are pressed down to reduce the pressure, and a large pressing operation is carried out when entering the horizontal section, with a pressing amount of 8-12mm. S6: After the billet is cut, it is allowed to cool slowly. The slow cooling pit is kept at 300-350℃ for 30-36 hours. After the insulation is completed, the surface is inspected.

[0005] Further, the chemical composition and its mass percentage of the steel pipe include: C: 0.04%~0.06%, Si: 0.08%~0.18%, Mn: 1.30%~1.50%, P≤0.015%, S≤0.0020%, Nb: 0.060~0.070%, V≤0.010%, Ti: 0.008~0.020%, Cr≤0.05%, Ni≤0.05%, Mo: 0.25~0.30%, Cu: 0.25~0.30%, Al: 0.020%~0.050%, B≤0.00050%, Ca: 0.002~0.003%, N≤0.0060%, H≤0.0002%, with the balance being Fe and unavoidable impurities.

[0006] Further, the chemical composition and its mass percentage of the steel pipe include: C: 0.06%~0.08%, Si: 0.18%~0.38%, Mn: 1.40%~1.60%, P≤0.015%, S≤0.0020%, Nb: 0.070~0.080%, V≤0.010%, Ti: 0.018~0.030%, Cr≤0.05%, Ni≤0.05%, Mo: 0.20~0.25%, Cu: 0.20~0.25%, Al: 0.010%~0.040%, B≤0.00050%, Ca: 0.001~0.002%, N≤0.0060%, H≤0.0002%, with the balance being Fe and unavoidable impurities.

[0007] Compared with the prior art, the advantages of the technical solution of the present invention are as follows: (1) The steel grade of the product of the present invention is X52M to X65M, and its performance meets the requirements of API standards. Through desulfurizing agent and converter bottom stirring mode, the sulfur content of molten steel after converter tapping is effectively reduced, the pressure of refining treatment is reduced, the number of inclusions generated is reduced, and the cleanliness of molten steel is improved. (2) This invention improves the composition and temperature uniformity of molten steel through vacuum treatment and calcium modification, which is more conducive to the smooth casting of continuous casting, and provides a guarantee for strong cooling and low temperature casting of continuous casting, thereby realizing the refinement of grains and improvement of internal quality in continuous casting. (3) This invention uses a high-flow-rate cooling method in the casting crystallizer to strongly cool the billet, resulting in a chilled layer with a thickness of more than 50 mm. The grains on the narrow face and upper and lower surfaces of the billet are finer. At the same time, combined with the advantages of composition design, the hardenability of the product is improved, and the core grain structure is also significantly refined. This provides the core accumulation of harmful oxygen, nitrogen and hydrogen gases to achieve the low-temperature toughness of ultra-low carbon dioxide products, realizes the homogenization of the product in the longitudinal direction, ensures the stability of product quality, and meets the performance requirements of steel for supercritical CO2 pipeline transportation. Attached Figure Description

[0008] Figure 1 This is a low-magnification tissue photograph from an embodiment of the present invention. Detailed Implementation Example 1

[0009] To make the present invention clearer, the following description, in conjunction with the accompanying drawings, further illustrates a smelting method for steel used in supercritical CO2 pipeline transportation. The specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the invention.

[0010] In this embodiment, a steel for supercritical CO2 pipeline transportation is provided, the chemical composition and mass percentage of which are as follows: C: 0.05%, Si: 0.13%, Mn: 1.40%, P: 0.011%, S: 0.0011%, Nb: 0.063%, V: 0.003%, Ti: 0.013%, Cr: 0.02%, Ni: 0.02%, Mo: 0.26%, Cu: 0.28%, Al: 0.031%, B: 0.00020%, Ca: 0.0023%, N: 0.00310%, H: 0.0001%, with the balance being Fe and unavoidable impurities.

[0011] The smelting method for the steel used in supercritical CO2 pipeline transportation described above is carried out according to the following steps: (1) The molten iron is transported to the transfer station by torpedo ladle and desulfurized using the KR method. The amount of desulfurizing agent used is 1490 kg, and the temperature of the molten iron after desulfurization is 1269℃. (2) The amount of molten iron charged is 165t. The converter adopts top and bottom blowing smelting, the bottom stirring flow rate is 0.26Nm³ / (t·min), slag-forming materials and aluminum blocks are used for deoxidation, and carbon and manganese alloys are added for deoxidation and alloying. (3) Refining is carried out using the LF+RH process. After RH vacuum treatment, calcium treatment is carried out to modify and purify the molten steel. After calcium treatment, the steel is stirred for 16 minutes. (4) After the steel is refined, it is sent to the continuous casting for casting. The superheat is 27°C, the casting speed is 0.8m / min, and strong cooling is used. The flow rate of the wide face of the crystallizer is 5700L / min, the flow rate of the narrow face is 1100L / min, and the crystallizer is vibrated in the positive direction with an amplitude of 8mm and a vibration frequency of 260 times / min. (5) During the pouring process, multiple points are pressed down, and a large pressing operation is carried out when entering the horizontal section, with a pressing amount of 11mm; (6) After the billet is cut, it is allowed to cool slowly. The slow cooling pit is kept at 330°C for 35 hours. After the insulation is completed, the surface is inspected. Example 2

[0012] In this embodiment, a steel for supercritical CO2 pipeline transportation is provided, the chemical composition and mass percentage of which are as follows: C: 0.07%, Si: 0.26%, Mn: 1.53%, P: 0.010%, S: 0.0013%, Nb: 0.074%, V: 0.003%, Ti: 0.023%, Cr: 0.02%, Ni: 0.02%, Mo: 0.22%, Cu: 0.23%, Al: 0.035%, B: 0.00030%, Ca: 0.0016%, N: 0.0030%, H: 0.0001%, with the balance being Fe and unavoidable impurities.

[0013] The smelting method for the steel used in supercritical CO2 pipeline transportation described above is carried out according to the following steps: (1) The molten iron is transported to the transfer station by torpedo ladle and desulfurized using the KR method. The amount of desulfurizing agent used is 1540 kg, and the temperature of the molten iron after desulfurization is 1270℃. (2) The amount of molten iron charged is 163t. The converter adopts top and bottom blowing smelting, the bottom stirring flow rate is 0.26Nm³ / (t·min), slag-forming materials and aluminum blocks are used for deoxidation, and carbon and manganese alloys are added for deoxidation and alloying. (3) Refining is carried out using the LF+RH process. After RH vacuum treatment, calcium treatment is carried out to modify and purify the molten steel. After calcium treatment, the steel is stirred for 19 minutes. (4) After the steel is refined, it is sent to the continuous casting for casting. The superheat is 29°C, the casting speed is 0.8m / min, and the cooling is carried out by strong cooling. The flow rate of the wide face of the crystallizer is 5700L / min, the flow rate of the narrow face is 1000L / min, and the crystallizer is vibrated in the positive direction with an amplitude of 13mm and a vibration frequency of 290 times / min. (5) During the pouring process, multiple points are pressed down, and a large pressing operation is carried out when entering the horizontal section, with a pressing amount of 8mm; (6) After the billet is cut, it is allowed to cool slowly. The slow cooling pit is kept at 310℃ for 35 hours. After the insulation is completed, the surface is inspected.

[0014] In addition to the embodiments described above, the present invention may have other implementations. All technical solutions formed by equivalent substitution or equivalent transformation fall within the protection scope claimed by the present invention.

Claims

1. A method for smelting steel for supercritical CO2 pipeline transportation, characterized in that: The chemical composition and mass percentage of the steel pipe include: C: 0.04%–0.08%, Si: 0.08%–0.38%, Mn: 1.30%–1.60%, P≤0.015%, S≤0.0020%, Nb: 0.060–0.080%, V≤0.010%, Ti: 0.008–0.030%, Cr≤0.05%, Ni≤0.05%, Mo: 0.20–0.30%, Cu: 0.20–0.30%, Al: 0.010%–0.050%, B≤0.00050%, Ca: 0.001–0.003%, N≤0.0060%, H≤0.0002%, with the balance being Fe and unavoidable impurities; the above steel pipe is smelted according to the following steps: S1: Molten iron is transported to the transfer station via a torpedo ladle and desulfurized using the KR method. The amount of desulfurizing agent used is 1500±50kg, and the temperature of the molten iron after desulfurization is 1250±50℃. S2: Hot metal charging rate 160-180t, converter adopts top and bottom blowing smelting, bottom stirring flow rate 0.20-0.30Nm 3 / (t·min), deoxidation is carried out using slag-forming materials and aluminum blocks, and carbon and manganese alloys are added for deoxidation and alloying. S3: Refining is carried out using the LF+RH process. After RH vacuum treatment, the molten steel is modified and purified by calcium treatment. After calcium treatment, the steel is stirred for 15-20 minutes. S4: After refining, the molten steel is sent to continuous casting for pouring. The superheat is 20-30℃, the casting speed is 0.6-0.9m / min, and strong cooling is used. The flow rate of the wide face of the crystallizer is 5500-6000L / min, and the flow rate of the narrow face is 900-1200L / min. The crystallizer is vibrated in a positive direction with an amplitude of 5-15mm and a vibration frequency of 200-300 times / min. S5: During the pouring process, multiple points are pressed down to reduce the pressure, and a large pressing operation is carried out when entering the horizontal section, with a pressing amount of 8-12mm. S6: After the billet is cut, it is allowed to cool slowly. The slow cooling pit is kept at 300-350℃ for 30-36 hours. After the insulation is completed, the surface is inspected.

2. The smelting method for steel used in supercritical CO2 pipeline transportation according to claim 1, characterized in that: The chemical composition and its mass percentage of the steel pipe include: C: 0.04%~0.06%, Si: 0.08%~0.18%, Mn: 1.30%~1.50%, P≤0.015%, S≤0.0020%, Nb: 0.060~0.070%, V≤0.010%, Ti: 0.008~0.020%, Cr≤0.05%, Ni≤0.05%, Mo: 0.25~0.30%, Cu: 0.25~0.30%, Al: 0.020%~0.050%, B≤0.00050%, Ca: 0.002~0.003%, N≤0.0060%, H≤0.0002%, with the balance being Fe and unavoidable impurities.

3. The smelting method for steel used in supercritical CO2 pipeline transportation according to claim 1, characterized in that: The chemical composition and its mass percentage of the steel pipe include: C: 0.06%~0.08%, Si: 0.18%~0.38%, Mn: 1.40%~1.60%, P≤0.015%, S≤0.0020%, Nb: 0.070~0.080%, V≤0.010%, Ti: 0.018~0.030%, Cr≤0.05%, Ni≤0.05%, Mo: 0.20~0.25%, Cu: 0.20~0.25%, Al: 0.010%~0.040%, B≤0.00050%, Ca: 0.001~0.002%, N≤0.0060%, H≤0.0002%, with the balance being Fe and unavoidable impurities.

4. The smelting method for steel used in supercritical CO2 pipeline transportation according to claim 1, characterized in that: The chemical composition and mass percentage of the steel pipe are as follows: C: 0.05%, Si: 0.13%, Mn: 1.40%, P: 0.011%, S: 0.0011%, Nb: 0.063%, V: 0.003%, Ti: 0.013%, Cr: 0.02%, Ni: 0.02%, Mo: 0.26%, Cu: 0.28%, Al: 0.031%, B: 0.00020%, Ca: 0.0023%, N: 0.00310%, H: 0.0001%, balance Fe and unavoidable impurities; The smelting steps are as follows: (1) The molten iron is transported to the transfer station by torpedo ladle and desulfurized using the KR method. The amount of desulfurizing agent used is 1490 kg, and the temperature of the molten iron after desulfurization is 1269℃. (2) The amount of molten iron charged is 165t. The converter adopts top and bottom blowing smelting, the bottom stirring flow rate is 0.26Nm³ / (t·min), slag-forming materials and aluminum blocks are used for deoxidation, and carbon and manganese alloys are added for deoxidation and alloying. (3) Refining is carried out using the LF+RH process. After RH vacuum treatment, calcium treatment is carried out to modify and purify the molten steel. After calcium treatment, the steel is stirred for 16 minutes. (4) After the steel is refined, it is sent to the continuous casting for casting. The superheat is 27°C, the casting speed is 0.8m / min, and strong cooling is used. The flow rate of the wide face of the crystallizer is 5700L / min, the flow rate of the narrow face is 1100L / min, and the crystallizer is vibrated in the positive direction with an amplitude of 8mm and a vibration frequency of 260 times / min. (5) During the pouring process, multiple points are pressed down, and a large pressing operation is carried out when entering the horizontal section, with a pressing amount of 11mm; (6) After the billet is cut, it is allowed to cool slowly. The slow cooling pit is kept at 330°C for 35 hours. After the insulation is completed, the surface is inspected.

5. The smelting method for steel used in supercritical CO2 pipeline transportation according to claim 1, characterized in that: The chemical composition and mass percentage of the steel pipe are as follows: C: 0.07%, Si: 0.26%, Mn: 1.53%, P: 0.010%, S: 0.0013%, Nb: 0.074%, V: 0.003%, Ti: 0.023%, Cr: 0.02%, Ni: 0.02%, Mo: 0.22%, Cu: 0.23%, Al: 0.035%, B: 0.00030%, Ca: 0.0016%, N: 0.0030%, H: 0.0001%, with the balance being Fe and unavoidable impurities; The smelting steps are as follows: (1) The molten iron is transported to the transfer station by torpedo ladle and desulfurized using the KR method. The amount of desulfurizing agent used is 1540 kg, and the temperature of the molten iron after desulfurization is 1270℃. (2) The amount of molten iron charged is 163t. The converter adopts top and bottom blowing smelting, the bottom stirring flow rate is 0.26Nm³ / (t·min), slag-forming materials and aluminum blocks are used for deoxidation, and carbon and manganese alloys are added for deoxidation and alloying. (3) Refining is carried out using the LF+RH process. After RH vacuum treatment, calcium treatment is carried out to modify and purify the molten steel. After calcium treatment, the steel is stirred for 19 minutes. (4) After the steel is refined, it is sent to the continuous casting for casting. The superheat is 29°C, the casting speed is 0.8m / min, and the cooling is carried out by strong cooling. The flow rate of the wide face of the crystallizer is 5700L / min, the flow rate of the narrow face is 1000L / min, and the crystallizer is vibrated in the positive direction with an amplitude of 13mm and a vibration frequency of 290 times / min. (5) During the pouring process, multiple points are pressed down, and a large pressing operation is carried out when entering the horizontal section, with a pressing amount of 8mm; (6) After the billet is cut, it is allowed to cool slowly. The slow cooling pit is kept at 310℃ for 35 hours. After the insulation is completed, the surface is inspected.

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