Low-cost ultralow-temperature steel for pressure vessel and production method of low-cost ultralow-temperature steel

Abstract

The invention discloses steel for a low-cost ultralow-temperature pressure vessel and a production method of the steel. The steel plate comprises the following chemical components in percentage by mass: 0.03 to 0.05 percent of C, 1.91 to 1.98 percent of Mn, 0.11 to 0.19 percent of Si, less than or equal to 0.002 percent of S, less than or equal to 0.005 percent of P, 1.52 to 1.78 percent of Cr, 0.0015 to 0.0035 percent of B, 0.035 to 0.045 percent of Nb and the balance of Fe and inevitable impurities. The production method comprises the working procedures of converter smelting, refining, continuous casting, heating, rolling, cooling, quenching and tempering. According to the steel plate, precious alloy elements such as Ni are not added, the alloy cost is low, meanwhile, the steel plate has good plasticity and toughness and high strength, the yield strength of the steel plate is larger than or equal to 590 MPa, the tensile strength is larger than or equal to 700 MPa, the percentage elongation after fracture is larger than or equal to 19%, and the impact energy at the temperature of minus 196 DEG C is larger than or equal to 120 J.

Description

Technical Field

[0001] The present invention belongs to the technical field of steels for cryogenic pressure vessels, and particularly relates to a low-cost steel for cryogenic pressure vessels and a production method thereof. Background Art

[0002] With the development of petrochemical, energy, aerospace industries, new processes, new technologies and new equipment have emerged continuously. The development of new technologies and new equipment has promoted the development of steels for cryogenic pressure vessels. At the same time, with the continuous progress of domestic smelting, rolling and heat treatment technologies, the variety series and physical level of steels for cryogenic pressure vessels have been greatly improved. The energy industries such as petroleum and chemical industries need a large amount of cryogenic steels to manufacture various production and storage equipment for liquefied petroleum gas, liquid ammonia, liquid oxygen and liquid nitrogen. At present, the materials used under the conditions of -70~-196℃ in the energy industry are mostly Ni-based cryogenic steels, and the Ni content is between 0.5% and 9%. The Ni element content in the steel is relatively high, and the alloy cost is relatively high. Summary of the Invention

[0003] The purpose of the present invention is to provide a low-cost steel for cryogenic pressure vessels and a production method thereof, without adding expensive elements such as Ni, with low alloy cost. At the same time, the steel plate has good plasticity and toughness and relatively high strength, and fully meets the use requirements of Ni-based cryogenic pressure vessel steels.

[0004] To achieve the above purpose, the technical solution adopted by the present invention is: A low-cost steel for cryogenic pressure vessels, the chemical composition and its mass percentage content are: C: 0.03~0.05%, Mn: 1.91~1.98%, Si: 0.11~0.19%, S≤0.002%, P≤0.005%, Cr: 1.52~1.78%, B: 0.0015~0.0035%, Nb: 0.035~0.045%, and the balance is Fe and inevitable impurities.

[0005] The production method of the low-cost steel for cryogenic pressure vessels of the present invention includes converter smelting, refining, continuous casting, heating, rolling, cooling, quenching and tempering processes.

[0006] In the cooling process of the present invention, the return red temperature is controlled at 600 - 660℃ to refine the original hot-rolled structure and reduce segregation.

[0007] In the quenching process of the present invention, the quenching heating temperature is 870~890℃, the quenching heating coefficient is 1.8~2.5 min / mm, and the final cooling temperature is ≤40℃.

[0008] In the tempering process of the present invention, the tempering temperature is 510~540℃, and the tempering heating coefficient is 3.0~4.0 min / mm.

[0009] The thickness of the steel for low-cost ultra-low temperature pressure vessels described in the present invention is 8 - 80 mm.

[0010] For the steel for low-cost ultra-low temperature pressure vessels described in the present invention, the upper yield strength ≥ 590 MPa, the tensile strength ≥ 700 MPa, the elongation after fracture ≥ 19%, the impact energy at -196 °C ≥ 120 J, and the lateral expansion value ≥ 1.05 mm.

[0011] The inventive principle of the technical solution of the present invention lies in: By adopting narrow composition control, reducing the content of harmful elements such as P and S, ultra-low carbon control, reasonable proportioning of strengthening elements, increasing strengthening elements such as Mn, Cr, and Nb, and a reasonable controlled rolling and controlled cooling process to ensure that the original structure is dense and uniform; adopting a quenching + tempering process to further adjust the structure, so that the steel plate has good plasticity and toughness, high strength, and excellent low-temperature impact toughness.

[0012] The beneficial effects produced by adopting the above technical solution are as follows: (1) The steel plate of the present invention does not add expensive elements such as Ni, has a low alloy cost, and high market competitiveness. (2) The production process is simple, and the steel for ultra-low temperature pressure vessels produced by using the composition and process of the present invention has good plasticity and toughness and high strength, fully meeting the use requirements of Ni-based low-temperature pressure vessel steels. Specific embodiments

[0013] The present invention will be further described in detail below with reference to specific embodiments. Example 1

[0014] The thickness of the steel for low-cost ultra-low temperature pressure vessels in this example is 8 mm, and the chemical composition and mass percentage content are shown in Table 1; its production method includes converter smelting, refining, continuous casting, heating, rolling, cooling, quenching, and tempering processes, and the specific process steps are as follows: (1) Cooling process: The return red temperature is 600 °C; (2) Quenching process: The quenching heating temperature is 890 °C, the quenching heating coefficient is 2.5 min / mm, and the final cooling temperature ≤ 31 °C; (3) Tempering process: The tempering temperature is 540 °C, and the tempering heating coefficient is 3.0 min / mm.

[0015] After heat treatment, the upper yield strength of the steel for low-cost ultra-low temperature pressure vessels is 628 MPa, the tensile strength is 796 MPa, the elongation after fracture is 30%, the impact energy at -196 °C is 187 J, and the lateral expansion value is 1.24 mm. Example 2

[0016] The thickness of the steel for low-cost ultra-low temperature pressure vessels in this embodiment is 30 mm, and the chemical composition and mass percentage are shown in Table 1. Its production method includes converter smelting, refining, continuous casting, heating, rolling, cooling, quenching and tempering processes. The specific process steps are as follows: (1) Cooling process: The red-return temperature is 617 °C; (2) Quenching process: The quenching heating temperature is 890 °C, the quenching heating coefficient is 2.0 min / mm, and the final cooling temperature is ≤26 °C; (3) Tempering process: The tempering temperature is 530 °C, and the tempering heating coefficient is 3.5 min / mm.

[0017] After heat treatment, the upper yield strength of the steel for low-cost ultra-low temperature pressure vessels is 614 MPa, the tensile strength is 779 MPa, the elongation after fracture is 26%, the impact energy at -196 °C is 189 J, and the lateral expansion value is 1.26 mm. Example 3

[0018] The thickness of the steel for low-cost ultra-low temperature pressure vessels in this embodiment is 50 mm, and the chemical composition and mass percentage are shown in Table 1. Its production method includes converter smelting, refining, continuous casting, heating, rolling, cooling, quenching and tempering processes. The specific process steps are as follows: (1) Cooling process: The red-return temperature is 637 °C; (2) Quenching process: The quenching heating temperature is 880 °C, the quenching heating coefficient is 2.0 min / mm, and the final cooling temperature is ≤38 °C; (3) Tempering process: The tempering temperature is 530 °C, and the tempering heating coefficient is 3.6 min / mm.

[0019] After heat treatment, the upper yield strength of the steel for low-cost ultra-low temperature pressure vessels is 610 MPa, the tensile strength is 751 MPa, the elongation after fracture is 22%, the impact energy at -196 °C is 143 J, and the lateral expansion value is 1.18 mm. Example 4

[0020] The thickness of the steel for low-cost ultra-low temperature pressure vessels in this embodiment is 70 mm, and the chemical composition and mass percentage are shown in Table 1. Its production method includes converter smelting, refining, continuous casting, heating, rolling, cooling, quenching and tempering processes. The specific process steps are as follows: (1) Cooling process: The red-return temperature is 652 °C; (2) Quenching process: The quenching heating temperature is 870 °C, the quenching heating coefficient is 1.9 min / mm, and the final cooling temperature is ≤33 °C; (3) Tempering process: The tempering temperature is 520 °C, and the tempering heating coefficient is 3.7 min / mm.

[0021] After heat treatment, the low-cost ultra-low temperature pressure vessel steel has an upper yield strength of 596 MPa, a tensile strength of 744 MPa, an elongation after fracture of 21%, an impact energy of 140 J at -196 °C, and a lateral expansion value of 1.11 mm. Example 5

[0022] The thickness of the low-cost ultra-low temperature pressure vessel steel in this example is 80 mm, and its chemical composition and mass percentage are shown in Table 1. Its production method includes converter smelting, refining, continuous casting, heating, rolling, cooling, quenching, and tempering processes. The specific process steps are as follows: (1) Cooling process: The return red temperature is 660 °C; (2) Quenching process: The quenching heating temperature is 870 °C, the quenching heating coefficient is 1.8 min / mm, and the final cooling temperature is ≤ 40 °C; (3) Tempering process: The tempering temperature is 510 °C, and the tempering heating coefficient is 4.0 min / mm.

[0023] After heat treatment, the low-cost ultra-low temperature pressure vessel steel has an upper yield strength of 590 MPa, a tensile strength of 700 MPa, an elongation after fracture of 19%, an impact energy of 120 J at -196 °C, and a lateral expansion value of 1.05 mm. Example 6

[0024] The thickness of the low-cost ultra-low temperature pressure vessel steel in this example is 20 mm, and its chemical composition and mass percentage are shown in Table 1. Its production method includes converter smelting, refining, continuous casting, heating, rolling, cooling, quenching, and tempering processes. The specific process steps are as follows: (1) Cooling process: The return red temperature is 611 °C; (2) Quenching process: The quenching heating temperature is 880 °C, the quenching heating coefficient is 2.0 min / mm, and the final cooling temperature is ≤ 40 °C; (3) Tempering process: The tempering temperature is 520 °C, and the tempering heating coefficient is 3.5 min / mm.

[0025] After heat treatment, the low-cost ultra-low temperature pressure vessel steel has an upper yield strength of 621 MPa, a tensile strength of 785 MPa, an elongation after fracture of 25%, an impact energy of 194 J at -196 °C, and a lateral expansion value of 1.25 mm.

[0026] Table 1 Chemical composition of ultra-low temperature pressure vessel steel for each example (%)

[0027] The balance of the components in Table 1 is Fe and unavoidable impurities.

[0028] The above embodiments are only used to illustrate rather than limit the technical solutions of the present invention. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: modifications or equivalent replacements can still be made to the present invention, and any modification or partial replacement without departing from the spirit and scope of the present invention shall be covered by the scope of the claims of the present invention.

Claims

1. A steel for low-cost ultra-low temperature pressure vessels, characterized in that, The chemical composition and its mass percentage content of the low-cost ultra-low temperature pressure vessel steel are as follows: C: 0.03 - 0.05%, Mn: 1.91 - 1.98%, Si: 0.11 - 0.19%, S ≤ 0.002%, P ≤ 0.005%, Cr: 1.52 - 1.78%, B: 0.0015 - 0.0035%, Nb: 0.035 - 0.045%, and the balance is Fe and unavoidable impurities.

2. The steel for a low-cost ultra-low temperature pressure vessel according to claim 1, wherein The thickness of the low-cost ultra-low temperature pressure vessel steel is 8 - 80 mm.

3. The steel for a low-cost ultra-low temperature pressure vessel according to claim 1, characterized in that, For the low-cost ultra-low temperature pressure vessel steel, the upper yield strength ≥ 590 MPa, the tensile strength ≥ 700 MPa, the elongation after fracture ≥ 19%, the impact energy at -196 °C ≥ 120 J, and the lateral expansion value ≥ 1.05 mm.

4. The production method of the low-cost ultra-low temperature pressure vessel steel according to any one of claims 1-3, characterized in that, It includes the processes of converter smelting, refining, continuous casting, heating, rolling, cooling, quenching, and tempering.

5. The production method of a steel for low-cost ultra-low temperature pressure vessels according to claim 4, characterized in that, For the cooling process: control the red-return temperature at 600 - 660 °C.

6. The production method of a low-cost steel for ultra-low temperature pressure vessels according to claim 4, characterized in that, For the quenching process: the quenching heating temperature is 870 - 890 °C, the quenching heating coefficient is 1.8 - 2.5 min / mm, and the final cooling temperature ≤ 40 °C.

7. The production method of a steel for low-cost ultra-low temperature pressure vessels according to claim 4, characterized in that, For the tempering process: the tempering temperature is 510 - 540 °C, and the tempering heating coefficient is 3.0 - 4.0 min / mm.

Images