Method for improving production efficiency of normalized rolled Q420NE wind power steel

Abstract

The application discloses a method for improving the production efficiency of normalized rolling Q420NE wind power steel, and the chemical components of the Q420NE wind power steel are as follows in percentage by weight: C: 0.16-0.18%; Si: 0.20-0.30%; Mn: 1.45-1.65%; Nb: 0.035-0.045%; V: 0.035-0.045%; Ti: 0.010-0.020%; P: less than or equal to 0.015%; S: less than or equal to 0.005%; Ca: 0.0008-0.0020%; Als: 0.015-0.030%; O: less than or equal to 0.0035%; N: less than or equal to 0.0052%; and the rest is iron and inevitable impurities; and a specific preparation process and control parameters are disclosed. The prepared steel plate has good strength, plasticity and toughness, and the structure is fine ferrite+pearlite+behenite.

Description

Technical Field

[0001] This invention belongs to the field of hot rolling technology, and in particular relates to a method for improving the production efficiency of normalized rolled Q420NE wind power steel. Background Technology

[0002] With the rapid development of my country's power grid construction and the continuous increase in the single-unit capacity of onshore wind turbines, higher load-bearing capacity is required for the towers. To ensure the safe operation of wind power equipment, the strength of wind power steel has been upgraded from Q355 to Q420 and Q500 levels. High-strength steel plates can reduce tower weight by 8% to 10%, making lightweight and high-efficiency wind power steel products a trend in the industry. Q420 steel differs from ordinary low-alloy steel. It is a new generation of low-alloy high-strength steel produced based on the smelting process of ordinary low-alloy steel. Through the application of strong carbide-forming elements such as Nb, V, and Ti, it establishes a steel strengthening and toughening mechanism mainly based on grain refinement and precipitation strengthening. Q420 steel is a micro-alloyed steel characterized by low carbon and high purity. It possesses excellent mechanical properties, maintaining good toughness while maintaining high strength. When used in power grid tower structures, it can greatly improve the stability of the towers.

[0003] New high-strength structural steel, represented by Q420 steel, is widely used in the production and construction of power grid towers. While ensuring the plate shape, surface quality, and mechanical properties of the steel plates, effectively increasing the output of Q420 grade wind power steel per unit time is a major challenge faced by steel companies.

[0004] Patent CN 119020666 A, entitled "A Low-Cost Method for Producing Q420ME Wind Power Steel," provides a low-cost method for producing Q420ME wind power steel. This method uses a 250mm thick cast billet, thermomechanical rolling, and hot charging / hot conveying processes. The surface quenching and cooling time of the slab is designed to be controlled between 180s and 250s, with a slow cooling time ≤ 250min. This patent uses either a 250mm or 300mm thick cast billet, a normalizing rolling process, and hot charging / hot conveying processes. It specifies in detail the water flow requirements of the upper and lower spray beams of the quenching machine, the upper and lower water flow ratio, the water column height of the lower spray beam, the continuous casting billet conveying speed within the quenching machine, and the quenching time of the cast billet, among other key process parameters. Furthermore, the quenching time of the cast billet is shortened to 130s-140s.

[0005] Patent CN 118422058 A, entitled "A Smelting Method for High-Toughness Q420MPa Wind Power Steel Plate," provides a smelting method for high-toughness Q420MPa wind power steel plate. This method primarily emphasizes the control of the steelmaking process for Q420MPa wind power steel plate. This patent mainly employs a direct furnace charging process for cast billets, focusing on the quenching process before direct furnace charging of Q420MPa wind power steel plate cast billets. Furthermore, the two patents differ in their component designs.

[0006] Patent CN 114807768 A, entitled "A Q420 Low-Alloy High-Strength Structural Steel and Its Production Method," provides a method for producing Q420 low-alloy high-strength structural steel. This method primarily addresses the challenges of nitrogen element instability, large temperature drops during the LF wire feeding process, and defects in the internal and surface quality of rectangular billets, thereby reducing production costs. This patent mainly employs a direct furnace charging process for cast billets, eliminating the slow cooling process and shortening the production cycle. Furthermore, the temperature of the directly charged billets is significantly higher than that of the cold-charged billets, reducing furnace heating energy consumption and thus improving production efficiency and lowering production costs. Summary of the Invention

[0007] The purpose of this invention is to provide a method for improving the production efficiency of normalized rolled Q420NE wind power steel. This method specifies in detail the key process parameters such as the water flow rate requirements of the upper and lower spray beams of the billet quenching machine, the upper and lower water flow rate ratio, the water column height of the lower spray beam, the continuous casting billet transfer speed within the quenching machine, and the billet quenching time. This method eliminates hot-charging cracks on the surface of the rolled steel plate, ensuring the uniformity of the finished steel plate's performance. The steel plate exhibits good strength, plasticity, and toughness, with a microstructure consisting of fine ferrite, pearlite, and bainite. The yield strength of the steel plate is between 455 and 523 MPa, the tensile strength is between 542 and 644 MPa, the elongation is between 21 and 26.5%, and the impact energy at -40℃ is between 149 and 237.

[0008] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0009] This invention discloses a method for improving the production efficiency of normalized rolled Q420NE wind power steel. The chemical composition of the Q420NE wind power steel, by weight percentage, is as follows: C: 0.16-0.18%; Si: 0.20-0.30%; Mn: 1.45-1.65%; Nb: 0.035-0.045%; V: 0.035-0.045%; Ti: 0.010-0.020%; P≤0.015%; S≤0.005%; Ca: 0.0008-0.0020%; Als: 0.015-0.030%; O: ≤0.0035%; N: ≤0.0052%; the remainder being iron and unavoidable impurities. The specific preparation method is as follows:

[0010] Molten steel is treated in an RH furnace for at least 17 minutes under a vacuum of no more than 112 Pa.

[0011] The thickness of the continuously cast billet is 250mm or 300mm. The superheat during steel pouring is controlled at 15–28℃, and the casting speed is 0.9–1.1m / min. Electromagnetic stirring and light reduction are used during continuous casting. The light reduction is applied in the third or fourth stage before the solidification end, with a total reduction of 8.0mm. Electromagnetic stirring is used in stages 4 and 5, with a stirring frequency of 5Hz and a current of 380A. The water flow rate on the wide side of the crystallizer is 4500L / min, and the water flow rate on the narrow side is 370L / min. The crystallizer inlet water temperature is controlled at 36±2℃. The temperature of the crystallizer inlet water should be controlled at 38±1℃, and the temperature of the secondary cooling water should be controlled at 22~25℃. The water quality indicators should meet the process requirements. Protective casting should be adopted. The argon pressure of the long nozzle sealing should be controlled at ≥0.3MPa, and the flow rate should be controlled at 130~160L / min. The argon pressure of the tundish immersion nozzle sealing should be 0.2Mpa, and the flow rate should be 15~20L / min. The billet straightening temperature should be controlled at 950~1000℃, and the temperature difference of the billet along the width direction should not exceed 50℃. Protective casting should be carried out to prevent secondary oxidation of molten steel and nitrogen absorption.

[0012] Slab quenching process: 250mm or 300mm thick continuously cast slabs are used for production. The slabs are charged directly into the heating furnace without being removed from the production line and undergoing slow cooling. To eliminate hot-charging cracks on the surface of the rolled steel plate and ensure the uniformity of the finished steel plate's properties, the continuously cast slabs must undergo a quenching process. To avoid large temperature differences between the upper and lower parts of the continuously cast slab, the quenching process requires an upper spray beam flow rate ≥ 75m³ / h. 3 / h, the flow rate of the lower spray beam is ≥150m³ / h. 3 / h, water flow ratio between upper and lower water is 2:1, water column height of lower spray beam is greater than 315mm; continuous casting billet transfer speed in quenching machine is 0.1m / s, quenching time for 250mm thick billet is 130s, quenching time for 300mm thick billet is 140s.

[0013] Heating process: The surface temperature of the slab entering the furnace shall not exceed 650℃. A walking beam furnace shall be used for heating the slab. The temperature of the continuously cast slab exiting the furnace shall be 1150~1250℃, and the heating time shall be 220~260 minutes. The heating time of the slab in the soaking zone shall not be less than 30 minutes. When the slab is heated in the furnace, the moving speed of the movable beam supporting the slab shall be 1.10m / min.

[0014] Steel plate rolling forming process: After the slab is heated, controlled rolling is carried out. The initial rolling thickness in the first stage is the same as the slab thickness, the initial rolling temperature in the first stage is 1130~1220℃, the final rolling temperature in the first stage is ≥1050℃, the single-pass reduction rate in the first stage high-temperature extension rolling is ≥12%, the rolling speed in the first stage is 1.7~3.1m / s, and the torque set in the first stage rolling is 2150kN·m. In the second stage, the initial rolling thickness of the steel plate is 3 times the thickness of the finished steel plate, the initial rolling temperature in the second stage is 870~910℃, the final rolling temperature in the second stage is 810~850℃, the rolling speed in the second stage is 3.5~4.5m / s, the torque set in the second stage rolling is 2280kN·m, and the final reduction rate in the second stage is ≥5.5%.

[0015] Furthermore, the chemical composition of the Q420NE wind power steel, by weight percentage, is as follows: C 0.16%, Si 0.24%, Mn 1.51%, P 0.011%, S 0.005%, Als 0.027%, Nb 0.038%, V 0.041%, Ti 0.014%, Ca 0.0005%, H 0.6 ppm; O: 0.0032%; N 0.0040%; the balance being Fe and unavoidable impurities.

[0016] Furthermore, the chemical composition of the Q420NE wind power steel, by weight percentage, is as follows: C 0.17%, Si 0.22%, Mn 1.5%, P 0.014%, S 0.005%, Als 0.027%, Nb 0.037%, V 0.041%, Ti 0.020%, Ca 0.0003%, H 0.5 ppm; O: 0.0027%; N: 0.0035%; the balance being Fe and unavoidable impurities.

[0017] Furthermore, the chemical composition of the Q420NE wind power steel, by weight percentage, is as follows: C 0.17%, Si 0.26%, Mn 1.53%, P 0.010%, S 0.002%, Als 0.022%, Nb 0.040%, V 0.041%, Ti 0.015%, Ca 0.0004%, H 0.4 ppm; O: 0.0028%; N: 0.0031%; the balance being Fe and unavoidable impurities.

[0018] Furthermore, the billet thickness is 250mm, and the flow rate of the spray beam on the quenching machine is 77m³ / h. 3 / h, flow rate of the lower spray beam is 150m³ / h. 3 The quenching time is 130 seconds. After quenching, the billet is placed in a heating furnace and heated for 180 minutes, followed by a soaking time of 35 minutes.

[0019] Furthermore, the billet thickness is 300mm, and the flow rate of the spray beam on the quenching machine is 78m³ / h. 3 / h, the flow rate of the lower spray beam is 152m³ / h. 3 The quenching time is 140s, and after quenching, the billet is placed in the heating furnace for 208 minutes, with a high-temperature time of 134 minutes.

[0020] Furthermore, the billet thickness is 300mm, and the flow rate of the spray beam on the quenching machine is 77m³ / h. 3 / h, the flow rate of the lower spray beam is 154m³ / h. 3 The quenching time is 140 seconds. After quenching, the billet is placed in a heating furnace and heated for 210 minutes, with a high-temperature time of 135 minutes.

[0021] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0022] 1) This invention adopts a low-composition design, using only inexpensive alloys such as Si, Mn, Nb, V, and Ti. Through appropriate smelting, continuous casting, heating, controlled rolling, and controlled cooling processes, it produces wind power steel with a yield strength of 420MPa and excellent comprehensive performance. Through precise control of the online quenching process of the slab, the process parameters such as the water volume and water ratio of the upper and lower spray beams of the online quenching equipment, the continuous casting slab transfer speed, and the quenching time are specified in detail. This effectively eliminates hot-fix cracks on the surface of the rolled steel plate, ensures the uniformity of the performance of the finished steel plate, improves rolling efficiency, reduces slab heating time, and reduces slab heating energy consumption.

[0023] 2) The steel plate has good strength, plasticity, and toughness, and its microstructure consists of fine ferrite, pearlite, and bainite. The yield strength of the steel plate is between 455 and 523 MPa, the tensile strength is between 542 and 644 MPa, the elongation is between 21 and 26.5%, and the impact energy at -40℃ is between 149 and 237. Attached Figure Description

[0024] The present invention will be further described below with reference to the accompanying drawings.

[0025] Figure 1 Image of the microstructure of a 300mm Q420NE billet after cooling for 140s, at a position 52mm from the top surface (microstructure is M+B+minor P).

[0026] Figure 2 Image of the microstructure (B+F+P) of a 300mm Q420NE billet at a position 63mm from the top surface after 140s of cooling;

[0027] Figure 3 Image of the surface microstructure of a 300mm Q420NE billet after cooling for 140s, at a position 23mm from the lower surface (microstructure is M+B+minor P).

[0028] Figure 4 The microstructure of a 300mm Q420NE billet is B+F+P, located 30mm from the lower surface after 140s of cooling.

[0029] Image of surface tissue. Detailed Implementation

[0030] The present invention will be further described below with reference to embodiments.

[0031] Example 1

[0032] The slabs to be rolled after smelting and continuous casting enter a quenching machine. The slab thickness is 250 mm. The flow rate of the upper spray beam in the quenching machine is 77 m³ / h, and the flow rate of the lower spray beam is 150 m³ / h. The quenching time is 130 s. After quenching, the slab is placed in a heating furnace for 180 minutes of heating and 35 minutes of soaking. The chemical composition of the slab is as follows (mass percentage): C 0.16%, Si 0.24%, Mn 1.51%, P 0.011%, S 0.005%, Als 0.027%, Nb 0.038%, V 0.041%, Ti 0.014%, Ca 0.0005%, H 0.6 ppm; O 0.0032%; N 0.0040%; balance Fe and unavoidable impurities. The slab is rolled into a 20 mm thick steel plate. Detailed rolling process is shown in Table 1, and its mechanical properties are shown in Table 2.

[0033] Example 2

[0034] The slabs to be rolled after smelting and continuous casting are fed into a quenching machine. The slab thickness is 300 mm. The flow rate of the upper spray beam in the quenching machine is 78 m³ / h, and the flow rate of the lower spray beam is 152 m³ / h. The quenching time is 140 s. After quenching, the slab is placed in a heating furnace and heated for 208 minutes, with a high-temperature time of 134 minutes. The chemical composition of the slab is as follows (mass percentage): C 0.17%, Si 0.22%, Mn 1.5%, P 0.014%, S 0.005%, Als 0.027%, Nb 0.037%, V 0.041%, Ti 0.020%, Ca 0.0003%, H 0.5 ppm; O: 0.0027%; N: 0.0035%; the balance is Fe and unavoidable impurities. The slab is rolled into a 40 mm thick steel plate. Detailed rolling process is shown in Table 1, and its mechanical properties are shown in Table 2.

[0035] Example 3

[0036] The slabs to be rolled after smelting and continuous casting enter a quenching machine. The slab thickness is 300 mm. The flow rate of the upper spray beam in the quenching machine is 77 m³ / h, and the flow rate of the lower spray beam is 154 m³ / h. The quenching time is 140 s. After quenching, the slab is placed in a heating furnace and heated for 210 minutes, with a high-temperature time of 135 minutes. The chemical composition of the slab is as follows (mass percentage): C 0.17%, Si 0.26%, Mn 1.53%, P 0.010%, S 0.002%, Als 0.022%, Nb 0.040%, V 0.041%, Ti 0.015%, Ca 0.0004%, H 0.4 ppm; O: 0.0028%; N: 0.0031%; the balance is Fe and unavoidable impurities. The slab is rolled into a steel plate with a thickness of 80 mm. Detailed rolling process is shown in Table 1, and its mechanical properties are shown in Table 2.

[0037] Table 1. Process parameters for Examples 1-3

[0038]

[0039] Table 2 Mechanical properties of Examples 1-4

[0040]

[0041] 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 improving the production efficiency of normalized rolled Q420NE wind power steel, characterized in that, The chemical composition of the Q420NE wind power steel, by weight percentage, is as follows: C: 0.16–0.18%; Si: 0.20–0.30%; Mn: 1.45–1.65%; Nb: 0.035–0.045%. V：0.035～0.045%； Ti: 0.010~0.020%; P≤0.015%; S≤0.005%; Ca: 0.0008~0.0020%; Al: 0.015–0.030%; O: ≤0.0035%; N: ≤0.0052%; the remainder is iron and unavoidable impurities; the specific preparation method is as follows: Molten steel is treated in an RH furnace for at least 17 minutes under a vacuum of no more than 112 Pa. The thickness of the continuously cast billet is 250mm or 300mm. The superheat during steel pouring is controlled at 15–28℃, and the casting speed is 0.9–1.1m / min. Electromagnetic stirring and light reduction are used during continuous casting. The light reduction is applied in the third or fourth stage before the solidification end, with a total reduction of 8.0mm. Electromagnetic stirring is used in stages 4 and 5, with a stirring frequency of 5Hz and a current of 380A. The water flow rate on the wide side of the crystallizer is 4500L / min, and the water flow rate on the narrow side is 370L / min. The crystallizer inlet water temperature is controlled at 36±2℃. The temperature of the crystallizer inlet water should be controlled at 38±1℃, and the temperature of the secondary cooling water should be controlled at 22~25℃. The water quality indicators should meet the process requirements. Protective casting should be adopted. The argon pressure of the long nozzle sealing should be controlled at ≥0.3MPa, and the flow rate should be controlled at 130~160L / min. The argon pressure of the tundish immersion nozzle sealing should be 0.2Mpa, and the flow rate should be 15~20L / min. The billet straightening temperature should be controlled at 950~1000℃, and the temperature difference of the billet along the width direction should not exceed 50℃. Protective casting should be carried out to prevent secondary oxidation of molten steel and nitrogen absorption. Slab quenching process: 250mm or 300mm thick continuously cast slabs are used for production. The slabs are charged directly into the heating furnace without being removed from the production line and undergoing slow cooling. To eliminate hot-charging cracks on the surface of the rolled steel plate and ensure the uniformity of the finished steel plate's properties, the continuously cast slabs must undergo a quenching process. To avoid large temperature differences between the upper and lower parts of the continuously cast slab, the quenching process requires an upper spray beam flow rate ≥ 75m³ / h. 3 / h, the flow rate of the lower spray beam is ≥150m³ / h. 3 / h, water flow ratio between upper and lower water is 2:1, water column height of lower spray beam is greater than 315mm; continuous casting billet transfer speed in quenching machine is 0.1m / s, quenching time for 250mm thick billet is 130s, quenching time for 300mm thick billet is 140s. Heating process: The surface temperature of the slab entering the furnace shall not exceed 650℃. A walking beam furnace shall be used for heating the slab. The temperature of the continuously cast slab exiting the furnace shall be 1150~1250℃, and the heating time shall be 220~260 minutes. The heating time of the slab in the soaking zone shall not be less than 30 minutes. When the slab is heated in the furnace, the moving speed of the movable beam supporting the slab shall be 1.10m / min. Steel plate rolling forming process: After the slab is heated, controlled rolling is carried out. The initial rolling thickness in the first stage is the same as the slab thickness, the initial rolling temperature in the first stage is 1130~1220℃, the final rolling temperature in the first stage is ≥1050℃, the single-pass reduction rate in the first stage high-temperature extension rolling is ≥12%, the rolling speed in the first stage is 1.7~3.1m / s, and the torque set in the first stage rolling is 2150kN·m. In the second stage, the initial rolling thickness of the steel plate is 3 times the thickness of the finished steel plate, the initial rolling temperature in the second stage is 870~910℃, the final rolling temperature in the second stage is 810~850℃, the rolling speed in the second stage is 3.5~4.5m / s, the torque set in the second stage rolling is 2280kN·m, and the final reduction rate in the second stage is ≥5.5%.

2. The method for improving the production efficiency of normalized rolled Q420NE wind power steel according to claim 1, characterized in that, The chemical composition of the Q420NE wind power steel, by weight percentage, is as follows: C 0.16%, Si 0.24%, Mn 1.51%, P 0.011%, S 0.005%, Als 0.027%, Nb 0.038%, V 0.041%, Ti 0.014%, Ca 0.0005%, H 0.6 ppm; O: 0.0032%; N 0.0040%; the balance being Fe and unavoidable impurities.

3. The method for improving the production efficiency of normalized rolled Q420NE wind power steel according to claim 1, characterized in that, The chemical composition of the Q420NE wind power steel, by weight percentage, is as follows: C 0.17%, Si 0.22%, Mn 1.5%, P 0.014%, S 0.005%, Als 0.027%, Nb 0.037%, V 0.041%, Ti 0.020%, Ca 0.0003%, H 0.5 ppm; O: 0.0027%; N: 0.0035%; the balance being Fe and unavoidable impurities.

4. The method for improving the production efficiency of normalized rolled Q420NE wind power steel according to claim 1, characterized in that, The chemical composition of the Q420NE wind power steel, by weight percentage, is as follows: C 0.17%, Si 0.26%, Mn 1.53%, P 0.010%, S 0.002%, Als 0.022%, Nb 0.040%, V 0.041%, Ti 0.015%, Ca 0.0004%, H 0.4 ppm; O: 0.0028%. N: 0.0031%; balance is Fe and unavoidable impurities.

5. The method for improving the production efficiency of normalized rolled Q420NE wind power steel according to claim 2, characterized in that, The billet thickness is 250mm, and the flow rate of the spray beam on the quenching machine is 77m³ / h. 3 / h, flow rate of the lower spray beam is 150m³ / h. 3 The quenching time is 130 seconds. After quenching, the billet is placed in a heating furnace and heated for 180 minutes, followed by a soaking time of 35 minutes.

6. The method for improving the production efficiency of normalized rolled Q420NE wind power steel according to claim 3, characterized in that, The billet thickness is 300mm, and the flow rate of the spray beam on the quenching machine is 78m³. 3 / h, the flow rate of the lower spray beam is 152m³ / h. 3 The quenching time is 140s, and after quenching, the billet is placed in the heating furnace for 208 minutes, with a high-temperature time of 134 minutes.

7. The method for improving the production efficiency of normalized rolled Q420NE wind power steel according to claim 4, characterized in that, The billet thickness is 300mm, and the flow rate of the spray beam on the quenching machine is 77m³ / h. 3 / h, the flow rate of the lower spray beam is 154m³ / h. 3 The quenching time is 140 seconds. After quenching, the billet is placed in a heating furnace and heated for 210 minutes, with a high-temperature time of 135 minutes.

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