High strength ultralow temperature wire rod and method of use

Abstract

The application discloses a kind of high-strength ultra-low temperature wire rod, and the wire rod includes the following weight percentage of each component: C is 0.48%~0.62%, Si is 0.01%~0.03%, Mn is 9.8%~28.5%, Cr is 3.15%~5.23%, Ni is 8.5%~16.3%, Mo is 0.2%~1.8%, Cu≤0.15%, Ti≤0.012%, V≤0.02%, P≤0.002%, S≤0.002%, the balance is Fe and inevitable impurities.The application is lower in cost relative to Ni-based alloy, and the strength can reach 600MPa while meeting the toughness of-165℃ low temperature.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of steel, in particular to a high-strength ultra-low-temperature wire rod and a use method thereof. BACKGROUND

[0002] The energy industry is the foundation of industry, and the transportation of energy is an important part. In order to efficiently and safely transport energy such as oil and natural gas, chemical raw materials, etc., it is often necessary to liquefy these materials and fill them into storage tanks, and the liquefaction temperature point of these energy materials is very low, so pressure-resistant and low-temperature-resistant steel plates and welding materials must be used to make the storage tanks.

[0003] High-strength low-temperature-resistant steel plates can greatly reduce the self-weight of the storage tank and improve the storage and transportation efficiency compared to ordinary low-temperature-resistant steel plates, but at the same time, high-strength low-temperature-resistant welding materials are needed. Most welding materials are made by drawing and subsequent processing of wire rods, so the development of high-strength ultra-low-temperature wire rods is the focus of the industry, and the key is the innovation of the composition. "CN95103056.6" designs a high-strength and high-toughness composition that can be used to make welding material wire rods for high-pressure storage tanks. By adding about 3% Ni and about 0.5% Mo, the strength of the material is improved and the toughness is ensured, and the strength can reach 800 MPa, but it can only be used in service environments of-40℃ and above; "CN202010157399.X" proposes a composition of 12% Ni, 18% Cr, and ultra-low C content to promote the formation of austenite to meet the requirements of-165℃ low-temperature toughness service, but the material strength is insufficient and can only be matched with storage tanks with a strength of about 500 MPa; "CN201710432013.X" discloses an ultra-low-temperature composition that mainly promotes the formation of austenite through high Mn design, and the material strength can reach 650 MPa and the service temperature can reach-196℃, but the molten pool flowability is poor during welding due to the high Mn content, making it difficult to achieve good forming effect. Many inventors use Ni-based alloys for composition design, but such compositions are expensive and greatly increase production costs.

[0004] Therefore, it is necessary to develop high-strength ultra-low-temperature wire rods and their use methods that are low-temperature-resistant and high-strength to save costs. SUMMARY

[0005] The present application provides a high-strength ultra-low-temperature wire rod and a use method thereof, which is lower in cost than Ni-based alloys, meets-165℃ low-temperature toughness, and has a strength of 600 MPa.

[0006] Technical solution: The high-strength ultra-low temperature wire rod of the application is characterized in that the wire rod comprises the following components in percentage by weight: C is 0.48% to 0.62%, Si is 0.01% to 0.03%, Mn is 9.8% to 28.5%, Cr is 3.15% to 5.23%, Ni is 8.5% to 16.3%, Mo is 0.2% to 1.8%, Cu is less than or equal to 0.15%, Ti is less than or equal to 0.012%, V is less than or equal to 0.02%, P is less than or equal to 0.002%, S is less than or equal to 0.002%, and the balance is Fe and inevitable impurities.

[0007] In the preparation, the raw materials are smelted into molten steel, and then the square billets of 180mm are prepared through continuous casting; the square billets are placed in a heating furnace for 4h at 600℃, and then are sent to a wire rod rolling unit to be rolled into wire rods of Φ6.5mm at a temperature of 810℃ to 830℃, and then are air-cooled after rolling.

[0008] In the preparation, the raw materials are smelted into molten steel, and then the square billets of 180mm are prepared through continuous casting; the square billets are placed in a heating furnace for 4h at 600℃, and then are sent to a wire rod rolling unit to be rolled into wire rods of Φ6.5mm at a temperature of 810℃ to 830℃, and then are air-cooled after rolling.

[0009] In the preparation, the raw materials are smelted into molten steel, and then the square billets of 180mm are prepared through continuous casting; the square billets are placed in a heating furnace for 4h at 600℃, and then are sent to a wire rod rolling unit to be rolled into wire rods of Φ6.5mm at a temperature of 810℃ to 830℃, and then are air-cooled after rolling.

[0010] In the preparation, the raw materials are smelted into molten steel, and then the square billets of 180mm are prepared through continuous casting; the square billets are placed in a heating furnace for 4h at 600℃, and then are sent to a wire rod rolling unit to be rolled into wire rods of Φ6.5mm at a temperature of 810℃ to 830℃, and then are air-cooled after rolling.

[0011] Advantages: Compared with the prior art, the application has the following advantages: the application adopts high-carbon design, meets the requirement of 600MPa strength, reduces the addition of other alloys, and reduces the cost. The application adds Cr and Mo alloy elements, which can refine the grain of the weld and improve the strength, but too much Mo element will lead to insufficient toughness and poor plasticity. The application places the square billets in a heating furnace for 4h at 600℃, and then sends them to a wire rod rolling unit, which can ensure the temperature homogenization of the square billets, and avoid the rolling defects caused by too large temperature difference at different positions in the subsequent heating and rolling process. The application rolls the square billets into wire rods of Φ6.5mm at a temperature of 810℃ to 830℃, which is the best temperature range for the plasticity of the composition, and air-cools after rolling, which effectively inhibits the precipitation of carbides. Specific implementation

[0012] The technical solution of the application is further described below in combination with the specific implementation.

[0013] Example 1

[0014] The high-strength super-low-temperature wire rod of the embodiment has the following chemical components: C is 0.48 wt%, Si is 0.02 wt%, Mn is 9.8 wt%, Cr is 4.25 wt%, Ni is 16.3 wt%, Mo is 1.8 wt%, Cu≤0.15 wt%, Ti≤0.012 wt%, V≤0.02 wt%, P≤0.002 wt%, S≤0.002 wt%, and the balance is Fe and inevitable impurities.

[0015] The molten steel with the above chemical components is smelted, and a 180 mm square billet is formed by continuous casting. The square billet is placed in a heating furnace at 600 ℃ for 4 h, and then is sent to a wire rod rolling unit to be rolled into a Φ6.5 mm wire rod at a temperature of 810 ℃ to 830 ℃, and is air-cooled after rolling.

[0016] The wire rod is uncoiled and mechanically drawn to remove the surface oxide skin. Then, the wire rod is reduced in diameter from Φ6.5 mm to Φ3.5 mm through three drawing processes, and then is annealed. After annealing, the wire rod is again reduced in diameter from Φ3.5 mm to Φ1.5 mm through three drawing processes, and finally is fine-drawn to Φ1.2 mm to form the gas shielded welding wire.

[0017] The above gas shielded welding wire is subjected to deposited metal detection.

[0018] The welding wire is welded under the protection of 80% Ar+20% CO2 by volume, with a welding current of 140 A to 180 A and a voltage of 22 V to 28 V. The obtained weld metal has a low-temperature impact of 88, 78, 78 J at -165 ℃, and a strength of 617 MPa.

[0019] Embodiment 2:

[0020] The high-strength super-low-temperature wire rod of the embodiment has the following chemical components: C is 0.62 wt%, Si is 0.01 wt%, Mn is 28.5 wt%, Cr is 3.15 wt%, Ni is 8.5 wt%, Mo is 0.2 wt%, Cu≤0.15 wt%, Ti≤0.012 wt%, V≤0.02 wt%, P≤0.002 wt%, S≤0.002 wt%, and the balance is Fe and inevitable impurities.

[0021] The molten steel with the above chemical components is smelted, and a 180 mm square billet is formed by continuous casting. The square billet is placed in a heating furnace at 600 ℃ for 4 h, and then is sent to a wire rod rolling unit to be rolled into a Φ6.5 mm wire rod at a temperature of 810 ℃ to 830 ℃, and is air-cooled after rolling.

[0022] The wire rod is uncoiled and mechanically drawn to remove the surface oxide skin. Then, the wire rod is reduced in diameter from Φ6.5 mm to Φ3.5 mm through three drawing processes, and then is annealed. After annealing, the wire rod is again reduced in diameter from Φ3.5 mm to Φ1.5 mm through three drawing processes, and finally is fine-drawn to Φ1.2 mm to form the gas shielded welding wire.

[0023] The gas shielded welding wire is subjected to deposited metal detection.

[0024] The welding current is 140A-180A, the voltage is 22V-28V, and the obtained weld metal has a low temperature impact of 64, 58, 66J at -165℃ and a strength of 640MPa.

[0025] Example 3

[0026] The high-strength ultra-low-temperature wire rod of the example has the following chemical components: C is 0.55wt%, Si is 0.03wt%, Mn is 19.6wt%, Cr is 5.23wt%, Ni is 12.5wt%, Mo is 1.2wt%, Cu≤0.15wt%, Ti≤0.012wt%, V≤0.02wt%, P≤0.002wt%, S≤0.002wt%, and the balance is Fe and inevitable impurities.

[0027] The above chemical components are used to smelt the molten steel, and a 180mm square billet is prepared by continuous casting. The square billet is placed in a heating furnace at 600℃ for 4h and then sent to a wire rod rolling mill to be rolled into a Φ6.5mm wire rod at a temperature of 810℃-830℃, and air cooling is performed after rolling.

[0028] The wire rod is uncoiled and mechanically drawn to remove the surface oxide skin. Then, three drawing is performed to reduce the diameter from Φ6.5mm to Φ3.5mm, and then annealing is performed. After annealing, three drawing is performed again to reduce the diameter from Φ3.5mm to Φ1.5mm, and finally fine drawing is performed to Φ1.2mm to prepare a gas shielded welding wire.

[0029] The gas shielded welding wire is subjected to deposited metal detection.

[0030] The welding current is 140A-180A, the voltage is 22V-28V, and the obtained weld metal has a low temperature impact of 64, 58, 66J at -165℃ and a strength of 640MPa.

Claims

1. A high strength ultra low temperature wire rod characterized by: The wire rod comprises the following weight percentages of components: C 0.48%-0.62%, Si 0.01%-0.03%, Mn 9.8%-28.5%, Cr 3.15%-5.23%, Ni 8.5%-16.3%, Mo 0.2%-1.8%, Cu≤0.15%, Ti≤0.012%, V≤0.02%, P≤0.002%, S≤0.002%, the balance being Fe and inevitable impurities; in the preparation, the raw materials are subjected to molten steel smelting, and are formed into 180mm square billets through continuous casting; the square billets are placed in a heating furnace for 4h at 600°C, and are then sent into a wire rod rolling unit and rolled into Φ6.5mm wire rods at a temperature of 810°C-830°C, and are air-cooled after rolling.

2. The method of use of high strength super low temperature wire rod as claimed in claim 1, wherein: The wire rod is uncoiled and mechanically drawn to remove the surface oxide skin; then is reduced in diameter from Φ6.5mm to Φ3.5mm through three drawing processes, and then is annealed, and is again reduced in diameter from Φ3.5mm to Φ1.5mm through three drawing processes after annealing, and finally is fine-drawn to Φ1.2mm to form the gas shielded welding wire.

3. The method of use of high strength super low temperature wire rod as claimed in claim 2, wherein: The gas shielded welding wire is protected by 80% Ar+20% CO2 in volume percentage, the welding current is 140A-180A, and the voltage is 22V-28V.

4. The method of use of high strength super low temperature rod as claimed in claim 2, wherein: The weld formed by welding the gas shielded welding wire satisfies the low-temperature toughness of-165°C, and the strength reaches 600MPa.