Production method of high-strength steel for wind power fasteners

Abstract

The invention discloses a production method of steel for a high-strength wind power fastener. The production method comprises the steps of converter smelting, LF refining, VD vacuum degassing, continuous casting, casting blank heating furnace heating, round steel rolling and heat treatment. The high-strength steel for the wind power fasteners comprises the following chemical components in percentage by mass: 0.38%-0.42% of C, 0.23%-0.27% of Si, 0.50%-0.55% of Mn, less than or equal to 0.007% of P, less than or equal to 0.005% of S, 1.00%-1.10% of Cr, 0.53%-0.57% of Mo, 0.70%-0.80% of Ni, 0.11%-0.12% of V, 0.02%-0.03% of Nb, 0.02%-0.03% of Al and the balance of iron and impurities. According to the method, the alloy steel with high tensile strength, high yield strength, excellent low-temperature impact toughness and hydrogen-induced delayed fracture resistance can be produced, and meanwhile, the production cost is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of special steel materials and processing thereof, and in particular relates to a production method of high-strength steel for wind power fasteners. Background Art

[0002] As the global warming problem intensifies, countries are increasingly demanding renewable energy. Wind power generation has become one of the key directions of energy transformation due to its clean and renewable characteristics. In recent years, with the rapid increase in the capacity and power of wind turbines, the specifications and performance requirements of wind power fasteners, as an important part of wind power equipment, have also increased significantly. Wind power fasteners are mainly used for connection and fixing, including ground anchor bolts, tower bolts, blade bolts and nacelle bolts, etc., which need to withstand complex stresses and harsh working environments.

[0003] At present, 42CrMo steel is widely used in the manufacture of wind power fasteners after quenching and tempering due to its good comprehensive mechanical properties. However, the critical hardening diameter of 42CrMo steel is about 40mm, which is difficult to meet the performance requirements of high strength and toughness of large-size wind power fasteners such as M64-M72. Although 40CrNiMo steel has better mechanical properties, its production cost is high, which is not conducive to large-scale promotion and application.

[0004] In order to meet the requirements of large-scale wind power fasteners for high strength, excellent low-temperature toughness and resistance to hydrogen-induced delayed fracture, while reducing production costs, it is urgent to develop an alloy steel with high strength, low-temperature toughness and economy and its production method. The present invention is aimed at the above technical difficulties and proposes a new production method for high-strength steel for wind power fasteners to achieve the best balance between performance and cost. Summary of the invention

[0005] The purpose of the present invention is to provide a production method for high-strength steel for wind power fasteners, which can produce alloy steel with high tensile strength, high yield strength, excellent low-temperature impact toughness and resistance to hydrogen-induced delayed fracture, while reducing production costs and meeting the performance requirements of M64-M72 large-size wind power fasteners in harsh working environments. The present invention achieves a significant improvement in the comprehensive performance of the material by optimizing the chemical composition design, smelting process, continuous casting process, controlled rolling and controlled cooling and heat treatment process, overcomes the problem of insufficient performance or high cost of traditional materials, and has broad industrial application prospects.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0007] The present invention discloses a production method of high-strength steel for wind power fasteners, comprising converter smelting, LF refining, VD vacuum degassing, continuous casting, heating in a casting furnace, round steel rolling, and heat treatment; wherein:

[0008] Combined blowing converter smelting, using 120t top and bottom combined blowing converter steelmaking, controlling the molten iron ratio ≥80%, the tapping temperature is 1600-1680℃; the final slag basicity is controlled at 3.0, the end point control target C ≥0.10%, SiMn, MnFe and CrFe are used for deoxidation and alloying, and Al deoxidation is used for final deoxidation;

[0009] During the white slag refining operation, Ar is blown throughout the process to promote the aggregation and floating of inclusions and improve the purity of molten steel.

[0010] Vacuum degree ≤67Pa, deep vacuum time ≥20min, further remove impurities in molten steel; feed 150m of silicon calcium wire after breaking vacuum;

[0011] Electromagnetic stirring and soft pressure reduction technology are used to optimize the center segregation and looseness of the ingot; the cooling water volume is controlled to 0.15-0.18L / kg, and the ingot is slowly cooled at above 600℃ to avoid cracks;

[0012] The billet heating temperature is 1200℃, the total heating time is controlled to be 3h, the rolling temperature is 1090~1130℃, overheating, overburning and decarburization are prevented, the temperature is slowly increased to ensure uniform billet heating temperature and reduce temperature difference; the final rolling temperature is 840℃; the insulation cover is used for slow cooling to improve the uniformity and microstructure performance after rolling;

[0013] The quenching temperature is 880℃ and the tempering temperature is 630℃;

[0014] The mass percentage of the chemical composition of the high-strength steel for wind power fasteners includes: C 0.38%-0.42%, Si 0.23%-0.27%, Mn 0.50%-0.55%, P≤0.007%, S≤0.005%, Cr 1.00-1.10%, Mo 0.53-0.57%, Ni 0.70%-0.80%, V 0.11%-0.12%, Nb 0.02-0.03%, Al 0.02-0.03%, and the rest are Fe and unavoidable impurities, with a total mass fraction of 100%.

[0015] Furthermore, the mass percentage of the chemical composition of the high-strength steel for wind power fasteners includes: C 0.40%, Si 0.25%, Mn 0.53%, P 0.005%, S 0.003%, Cr 1.05%, Mo 0.55%, Ni 0.75%, V 0.115%, Nb 0.025%, Al 0.023%, and the rest is Fe and inevitable trace impurities, with a total mass fraction of 100%.

[0016] Furthermore, the specification of the continuous casting billet is 410mm×530mm.

[0017] Furthermore, the tensile strength of the high-strength steel for wind power fasteners produced reaches 1282MPa, the yield strength reaches 1230MPa, and the impact energy at -40℃ reaches 62J.

[0018] Furthermore, the high-strength steel for wind power fasteners produced can meet the performance requirements of 12.9 grade wind power fasteners.

[0019] Furthermore, the high-strength steel for wind power fasteners produced is suitable for use in M64-M72 large-size fasteners.

[0020] Furthermore, the high-strength steel for wind power fasteners produced solves the problem of insufficient performance of traditional 42CrMo steel in large-size fastener applications, while improving the material's resistance to hydrogen-induced delayed fracture to meet the requirements of harsh operating environments.

[0021] The present invention optimizes the performance of steel by using the composite alloying principle of the following elements:

[0022] Composite alloying of manganese (Mn), chromium (Cr), and molybdenum (Mo): Mn, Cr, and Mo work synergistically in steel to significantly improve the hardenability of steel, ensuring that large-size wind power fasteners obtain uniform structure and performance after quenching and tempering. Cr and Mo can also improve the high strength and high temperature resistance of the material by refining the structure and suppressing overheating sensitivity.

[0023] Nickel (Ni) alloying: The addition of Ni improves the hardenability of steel and improves low-temperature impact toughness, ensuring that the steel has excellent ductility and impact toughness in low-temperature environments. Ni can also improve the corrosion resistance of steel, making it adaptable to the harsh conditions in wind power environments.

[0024] Microalloying of vanadium (V) and niobium (Nb): The addition of V and Nb improves the strength and toughness of steel by refining grains and precipitation strengthening, especially the ability to resist hydrogen-induced delayed fracture. These two elements can also inhibit grain boundary segregation and improve the uniformity and purity of the material.

[0025] Deoxidation effect of aluminum (Al): As a strong deoxidizer, the addition of Al effectively reduces the content of non-metallic inclusions in steel and improves the purity and mechanical properties of steel.

[0026] Strict control of phosphorus (P) and sulfur (S): The P and S contents are strictly controlled at low levels, which further improves the toughness and welding performance of the steel and reduces the crack sensitivity of the material during service.

[0027] Compared with the prior art, the beneficial technical effects of the present invention are:

[0028] (1) Through component design and process optimization, the steel produced by the present invention has excellent comprehensive mechanical properties, with a tensile strength of 1282MPa, a yield strength of 1230MPa, and an impact energy of 62J at -40°C, which can meet the performance requirements of 12.9-level wind power fasteners and is particularly suitable for use in M64-M72 large-size fasteners;

[0029] (2) Compared with the traditional 40CrNiMo steel, the composition design adopted by the present invention significantly reduces the amount of alloy elements used, optimizes the smelting and heat treatment processes, thereby effectively reducing production costs and enhancing the economy and promotion value of steel;

[0030] (3) The present invention ensures the high purity, uniform structure and stable performance of the steel by strictly controlling the process parameters of smelting, continuous casting, rolling and heat treatment, effectively solving the problem of insufficient performance of traditional 42CrMo steel in large-size fastener applications, while improving the material's resistance to hydrogen-induced delayed fracture and meeting the requirements of stringent use environments. DETAILED DESCRIPTION

[0031] The following is a further detailed description of a method for producing high-strength steel for wind power fasteners of the present invention.

[0032] Embodiment: This embodiment is a preferred embodiment among various implementation modes of the present invention.

[0033] The production method of high-strength steel for wind power fasteners in this embodiment has the following chemical components in percentage by weight: C 0.40%, Si 0.25%, Mn 0.53%, P 0.005%, S 0.003%, Cr 1.05%, Mo0.55%, Ni0.75%, V 0.115%, Nb 0.025%, Al 0.023%, and the rest are Fe and inevitable trace impurities, with a total mass fraction of 100%.

[0034] The production method of the high-strength steel for wind power fasteners in this embodiment is: converter smelting, LF refining, VD vacuum degassing, continuous casting, heating in a casting furnace, round steel rolling, and heat treatment.

[0035] Combined blowing converter smelting, using 120t top and bottom combined blowing converter steelmaking, controlling the molten iron ratio ≥80%, the tapping temperature is 1600-1680℃; the final slag basicity is controlled at 3.0, the end point control target C ≥0.10%, SiMn, MnFe and CrFe are used for deoxidation and alloying, and Al deoxidation is used for final deoxidation;

[0036] During the white slag refining operation, Ar is blown throughout the process to promote the aggregation and floating of inclusions and improve the purity of molten steel.

[0037] Vacuum degree ≤67Pa, deep vacuum time ≥20min, further remove impurities in molten steel; feed 150m of silicon calcium wire after breaking vacuum;

[0038] The specification of continuous casting billet is 410mm×530mm. Electromagnetic stirring and light pressure reduction technology are used to optimize the center segregation and looseness of the billet. The cooling water volume is controlled to be 0.15-0.18L / kg, and the billet is slowly cooled in the pit at above 600℃ to avoid cracks.

[0039] The billet heating temperature is 1200℃, the total heating time is controlled at 3h, the starting rolling temperature is 1090-1130℃, overheating, overburning and decarburization are prevented, the temperature is raised slowly to ensure uniform billet heating temperature and reduce temperature difference; the final rolling temperature is 840℃; use a heat preservation cover for slow cooling to improve uniformity and organizational properties after rolling.

[0040] The quenching temperature is 880℃ and the tempering temperature is 630℃.

[0041] The high-strength steel for wind power fasteners produced by the chemical composition and process flow of the present invention has a tensile strength of 1282MPa, a yield strength of 1230MPa, a cross-sectional shrinkage rate of 57%, and an impact energy of 62J at -40°C after tempering, which meets the performance requirements of 12.9-level wind power fasteners.

[0042] Comparative Example 1:

[0043] Comparative Example 1 is identical to the embodiment except that the steel type is 42CrMo steel (chemical composition mass fraction is C 0.40%, Si 0.30%, Mn 0.60%, P 0.020%, S 0.015%, Cr 0.90%, Mo 0.20%, without adding Ni, V and Nb) and the conventional heat treatment process (quenching 880℃+tempering 600℃) is adopted. The properties are as follows: tensile strength 1210MPa, yield strength 1120MPa, cross-sectional shrinkage 45%, -40℃ impact energy 45J.

[0044] Comparative Example 2:

[0045] Comparative Example 2 is completely the same as the Example except that the tempering temperature is 600°C (lower than that of the Example), and has the following properties: tensile strength 1400MPa, yield strength 1350MPa, cross-sectional shrinkage 45%, and -40°C impact energy 30J.

[0046] Comparative Example 3:

[0047] Comparative Example 3 is completely the same as the example except that the final rolling temperature is 950°C and there is no heat preservation cover for slow cooling. The properties are: tensile strength 1250MPa, yield strength 1180MPa, cross-sectional shrinkage 50%, -40°C impact energy 45J.

[0048] It can be seen from the above embodiments and comparative examples that comparative example 1 lacks the composite alloying effect of Ni, V and Nb, resulting in a significant decrease in strength and low-temperature impact toughness; the tempering temperature of comparative example 2 is relatively low, resulting in increased strength but significantly reduced toughness, increased fracture risk, and is not suitable for the actual application requirements of wind power fasteners; the final rolling temperature of comparative example 3 is too high, resulting in uneven structure, decreased low-multiple structure performance and impact toughness, and the overall performance is not as good as the embodiments.

[0049] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for producing high-strength steel for wind power fasteners, characterized in that: Including converter smelting, LF refining, VD vacuum degassing, continuous casting, billet heating furnace heating and round steel rolling, heat treatment; Among them: Combined blowing converter smelting, using 120t top and bottom combined blowing converter steelmaking, controlling the molten iron ratio ≥80%, the tapping temperature is 1600-1680℃; the final slag basicity is controlled at 3.0, the end point control target C ≥0.10%, SiMn, MnFe and CrFe are used for deoxidation and alloying, and Al deoxidation is used for final deoxidation; During the white slag refining operation, Ar is blown throughout the process to promote the aggregation and floating of inclusions and improve the purity of molten steel. Vacuum degree ≤67Pa, deep vacuum time ≥20min, further remove impurities in molten steel; feed 150m of silicon calcium wire after breaking vacuum; Electromagnetic stirring and soft pressure reduction technology are used to optimize the center segregation and looseness of the ingot; the cooling water volume is controlled to 0.15-0.18L / kg, and the ingot is slowly cooled at above 600℃ to avoid cracks; The billet heating temperature is 1200℃, the total heating time is controlled to be 3h, the rolling temperature is 1090~1130℃, overheating, overburning and decarburization are prevented, the temperature is slowly increased to ensure uniform billet heating temperature and reduce temperature difference; the final rolling temperature is 840℃; the insulation cover is used for slow cooling to improve the uniformity and microstructure performance after rolling; The quenching temperature is 880℃ and the tempering temperature is 630℃; The mass percentage of the chemical composition of the high-strength steel for wind power fasteners includes: C 0.38%-0.42%, Si 0.23%-0.27%, Mn 0.50%-0.55%, P≤0.007%, S≤0.005%, Cr 1.00-1.10%, Mo 0.53-0.57%, Ni 0.70%-0.80%, V 0.11%-0.12%, Nb 0.02-0.03%, Al 0.02-0.03%, and the rest are Fe and unavoidable impurities, with a total mass fraction of 100%.

2. The method for producing high-strength steel for wind power fasteners according to claim 1, characterized in that: The chemical composition of the high-strength steel for wind power fasteners includes by weight percentage: C 0.40%, Si 0.25%, Mn 0.53%, P 0.005%, S 0.003%, Cr 1.05%, Mo 0.55%, Ni 0.75%, V 0.115%, Nb 0.025%, Al 0.023%, and the rest is Fe and unavoidable trace impurities, with a total weight fraction of 100%.

3. The method for producing high-strength steel for wind power fasteners according to claim 1, characterized in that: The specifications of continuous casting billet are 410mm×530mm.

4. The method for producing high-strength steel for wind power fasteners according to claim 1, characterized in that: The tensile strength of the high-strength steel for wind power fasteners produced reaches 1282MPa, the yield strength reaches 1230MPa, and the impact energy at -40℃ reaches 62J.

5. The method for producing high-strength steel for wind power fasteners according to claim 1, characterized in that: The high-strength steel for wind power fasteners produced can meet the performance requirements of 12.9 grade wind power fasteners.

6. The method for producing high-strength steel for wind power fasteners according to claim 1, characterized in that: The high-strength steel for wind power fasteners produced is suitable for use in M64-M72 large-size fasteners.

7. The method for producing high-strength steel for wind power fasteners according to claim 1, characterized in that: The high-strength steel for wind power fasteners produced solves the problem of insufficient performance of traditional 42CrMo steel in large-size fastener applications, while improving the material's resistance to hydrogen-induced delayed fracture to meet the requirements of harsh operating environments.