Q420DR steel plate for mobile tank car and production method of Q420DR steel plate

Abstract

The invention discloses a Q420DR steel plate for a movable tank car and a production method of the Q420DR steel plate, and belongs to the technical field of metallurgy. The steel plate comprises the following chemical components in percentage by mass: 0.12 to 0.15 percent of C, 0.15 to 0.45 percent of Si, 1.40 to 1.60 percent of Mn, less than or equal to 0.010 percent of P, less than or equal to 0.002 percent of S, 0.30 to 0.40 percent of Ni, 0.020 to 0.040 percent of Nb, 0.050 to 0.060 percent of V, 0.020 to 0.050 percent of Alt and the balance of Fe and inevitable impurities. The production method comprises the steps of steelmaking, heating rolling and heat treatment. The delivery-state yield and tensile strength Rel of the steel plate is larger than or equal to 450 MPa, Rm is larger than or equal to 610 MPa, A is larger than or equal to 20%, the-40 DEG C low-temperature impact value is larger than or equal to 100 J, the low-temperature impact toughness is good, the strength is moderate, the comprehensive performance is stable, and the steel plate is suitable for batch production.

Description

Technical Field

[0001] The present invention belongs to the field of metallurgical technology, and particularly relates to a Q420DR steel plate for mobile tank trucks and a production method thereof. Background Art

[0002] The Q420DR steel plate is a low-temperature steel in the new national standard GB / T 713.3 - 2023. This standard clearly stipulates the chemical composition, mechanical properties, delivery state, etc. of the steel plate, providing a unified technical basis for the production, inspection, and use of the Q420DR steel plate.

[0003] With the rapid development of modern industry, the demand for pressure vessels in the fields of petroleum, chemical industry, energy, etc. is continuously increasing, and the performance requirements for them are also getting higher and higher. Pressure vessels need to withstand complex conditions such as high pressure, high temperature, or low temperature in different working environments. Therefore, high-strength, high-toughness steels with good welding performance are required to ensure their safety and reliability. In some special industrial scenarios, such as the storage and transportation of liquefied gases, low-temperature chemical processes, etc., pressure vessels need to work stably in low-temperature environments. Ordinary steels are prone to problems such as reduced toughness and increased brittleness at low temperatures, leading to safety accidents such as container rupture. To meet the needs of these low-temperature application scenarios, it has become an inevitable trend to develop a steel plate that can maintain good mechanical properties at low temperatures. Summary of the Invention

[0004] The purpose of the present invention is to provide a Q420DR steel plate for mobile tank trucks and a production method thereof. Through process control in the steelmaking process, optimization of the controlled rolling and controlled cooling and heat treatment processes in rolling, the provided steel plate has good low-temperature impact toughness, moderate strength, and stable comprehensive performance.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is: A Q420DR steel plate for mobile tank trucks, the chemical composition and mass percentage content of the steel plate are: C: 0.12 - 0.15%, Si: 0.15 - 0.45%, Mn: 1.40 - 1.60%, P≤0.010%, S≤0.002%, Ni: 0.30 - 0.40%, Nb: 0.020 - 0.040%, V: 0.050 - 0.060%, Alt: 0.020 - 0.050%, and the balance is Fe and unavoidable impurities.

[0006] The thickness of the steel plate of the present invention is 10 - 20 mm.

[0007] The microstructure of the steel plate of the present invention is bainite + ferrite.

[0008] For the steel plate delivered in the as - received condition of the present invention, the yield strength Rel≥450MPa, the tensile strength Rm≥610MPa, the elongation A≥20%, the low - temperature impact value at - 40°C≥100J, the low - temperature impact toughness is good, the strength is moderate, and the comprehensive performance is stable.

[0009] The production method of Q420DR steel plate for mobile tank cars of the present invention includes steelmaking, hot rolling and heat treatment processes.

[0010] In the steelmaking process of the present invention: in the LF furnace refining process, when the temperature of the molten steel rises to the range of 1570 - 1600°C, low - carbon ferromanganese alloy and ferrosilicon alloy are added in sequence according to the process order; then wire feeding operation of aluminum wire is carried out at a standard amount of 1.3 - 1.5kg / t of steel; before vacuum, calcium - based conditioning treatment is performed, and the feeding amount of calcium wire is controlled at 0.3 - 0.5kg / t of steel.

[0011] In the steelmaking process of the present invention: during continuous casting, the superheat range of the tundish≤30°C, the casting speed of the continuous casting billet is 0.8 - 0.95m / min, and the casting billets are stacked offline for 24 - 30h.

[0012] In the hot rolling process of the present invention: the continuous casting billets are heated in a continuous furnace at 1230 - 1250°C, the total heating time is 9 - 11min / cm, the reduction per pass in rough rolling is 25 - 30mm, rolled to an intermediate thickness of 40 - 50mm and then finish - rolled by a finishing mill, the finishing rolling temperature is 820 - 840°C, and the recrystallization temperature is 680 - 700°C.

[0013] In the heat treatment process: quenching in a quenching furnace, the quenching temperature is 800 - 840°C, the total heating time is PLC + 20 - 30min, the high - pressure section of quenching is 4200 - 4300m 3 / h, the roll speed V = 8 - 10m / min, cooled to room temperature, and tempered at 600 - 630°C with a holding time of 100 - 120min.

[0014] The invention principle of the present invention is as follows: By optimizing the entire process of steelmaking, rolling, and heat treatment, the comprehensive properties of Q420DR steel plates have been significantly improved. In the steelmaking process, the step-by-step alloying of "low-carbon ferromanganese - ferrosilicon" and the precise aluminum-calcium composite deoxidation technology are adopted, combined with the continuous casting with low superheat and slow cooling and stacking processes, which greatly reduce the inclusion content and inhibit segregation; in the rolling process, through high-temperature short-time heating, large reduction in rough rolling (25 - 30 mm per pass), and two-phase zone controlled rolling (finishing rolling at 820 - 840 °C), the synergistic refinement of grains by austenite dynamic recrystallization and deformation-induced ferrite transformation is achieved; the heat treatment adopts a combined process of subcritical quenching (800 - 840 °C) and high-temperature tempering (600 - 630 °C), forming high-density dislocation martensite and dispersed carbides to strengthen the matrix. Finally, a low-temperature high-strength and tough steel plate with a yield strength ≥ 540 MPa and an impact energy at -40 °C ≥ 100 J is obtained, meeting the safety service requirements of mobile tank cars under extreme working conditions.

[0015] The beneficial effects of adopting the above technical solutions are as follows: Through the process control in the steelmaking process, strictly implementing the controlled rolling and controlled cooling process in rolling, and optimizing the heat treatment process, the yield and tensile strengths Rel ≥ 450 MPa, Rm ≥ 610 MPa, A ≥ 20%, and the low-temperature impact value at -40 °C ≥ 100 J of the produced steel plates are obtained. The impact toughness is good, the strength is moderate, and the comprehensive properties of the steel plates are stable, suitable for mass production. Brief Description of the Drawings

[0016] Figure 1 It is the microstructural diagram of the Q420DR steel plate for mobile tank cars in Example 1. Detailed Description of the Embodiments

[0017] The present invention will be further described in detail below with reference to the drawings and specific embodiments. Example 1

[0018] The thickness of the Q420DR steel plate for mobile tank cars in this example is 10 mm, and its chemical composition and mass percentage content are as follows: C: 0.12%, Si: 0.15%, Mn: 1.40%, P 0.010%, S 0.002%, Ni: 0.30%, Nb: 0.020%, V: 0.050%, Alt: 0.020%, and the balance is Fe and unavoidable impurities.

[0019] The production method of the Q420DR steel plate for mobile tank cars in this example includes steelmaking, hot rolling, and heat treatment processes: (1)Steelmaking process: In the LF furnace refining process, when the molten steel temperature rises to 1570 °C, low-carbon ferromanganese alloy and ferrosilicon alloy are added in sequence according to the process order; then wire feeding of aluminum wire is carried out at a standard amount of 1.3 kg / t of steel. Before vacuum, calcium-based conditioning treatment is carried out, and the feeding amount of calcium wire is controlled at 0.3 kg / t of steel. During continuous casting, the superheat range of the tundish is 30 °C, the drawing speed of the continuous casting billet is 0.8 m / min, and the billets are stacked offline for 24 h.

[0020] (2)Heating and rolling process: The continuous casting billets are heated in a continuous furnace at 1230 °C, with a total heating time of 9 min / cm. The reduction per pass in rough rolling is 25 mm, and it is rolled to an intermediate thickness of 40 mm and then finish-rolled by a finishing mill. The final rolling temperature is 820 °C, and the recrystallization temperature is 680 °C.

[0021] (3)Heat treatment process: Quenching in a quenching furnace, the quenching temperature is 800 °C, the total heating time is PLC + 20 min, the high-pressure section of quenching is 4200 m 3 / h, the roll speed V = 8 m / min, cooled to room temperature, tempered at 600 °C, and the holding time is 100 min.

[0022] The microstructure of the Q420DR steel plate for mobile tank cars in this example is shown in Figure 1 , from Figure 1 it can be seen that its structure is bainite + ferrite. The results of its property inspection: the yield and tensile strength in the as-delivered state are Rel 480 MPa, Rm 630 MPa, A 22%, and the low-temperature impact value at -40 °C is 120 / 146 / 157 J. Example 2

[0023] The thickness of the Q420DR steel plate for mobile tank cars in this example is 20 mm, and its chemical composition and mass percentage are as follows: C: 0.15%, Si: 0.45%, Mn: 1.60%, P 0.009%, S 0.0017%, Ni: 0.40%, Nb: 0.040%, V: 0.060%, Alt: 0.050%, and the balance is Fe and unavoidable impurities.

[0024] The production method of the Q420DR steel plate for mobile tank cars in this example includes steelmaking, heating and rolling, and heat treatment processes: (1)Steelmaking process: In the LF furnace refining process, when the molten steel temperature rises to 1600 °C, low-carbon ferromanganese alloy and ferrosilicon alloy are added in sequence according to the process order; then wire feeding of aluminum wire is carried out at a standard amount of 1.5 kg / t of steel. Before vacuum, calcium-based conditioning treatment is carried out, and the feeding amount of calcium wire is controlled at 0.5 kg / t of steel. During continuous casting, the superheat range of the tundish is 29 °C, the drawing speed of the continuous casting billet is 0.95 m / min, and the billets are stacked offline for 30 h.

[0025] (2) Hot rolling process: The continuous casting billet is heated in a continuous furnace at 1250 °C for a total heating time of 11 min / cm. The reduction per pass in rough rolling is 30 mm, and it is rolled to an intermediate thickness of 50 mm and then finish-rolled by a finishing mill. The finish rolling temperature is 840 °C, and the recrystallization temperature is 700 °C.

[0026] (3) Heat treatment process: Quenching in a quenching furnace at a quenching temperature of 840 °C for a total heating time of PLC + 30 min. The high-pressure section of quenching is 4300 m 3 / h, the roll speed V = 10 m / min, cooled to room temperature, tempered at 630 °C for a holding time of 120 min.

[0027] The performance test results of the Q420DR steel plate for mobile tank cars in this example: The yield and tensile strength in the as-delivered state are Rel 465 MPa, Rm 634 MPa, A 21%, and the low-temperature impact value at -40 °C is 147 / 178 / 163 J. Example 3

[0028] The thickness of the Q420DR steel plate for mobile tank cars in this example is 12 mm, and its chemical composition and mass percentage are as follows: C: 0.13%, Si: 0.20%, Mn: 1.45%, P 0.008%, S 0.0018%, Ni: 0.35%, Nb: 0.025%, V: 0.055%, Alt: 0.025%, and the balance is Fe and unavoidable impurities.

[0029] The production method of the Q420DR steel plate for mobile tank cars in this example includes steelmaking, hot rolling and heat treatment processes: (1) Steelmaking process: In the LF furnace refining process, when the molten steel temperature rises to 1580 °C, low-carbon ferromanganese alloy and ferrosilicon alloy are added in sequence according to the process. Subsequently, wire feeding of aluminum wire is carried out at a standard amount of 1.35 kg / t of steel. Before vacuum, calcium-based conditioning treatment is performed, and the feeding amount of calcium wire is controlled at 0.35 kg / t of steel. During continuous casting, the tundish superheat range is 28 °C, the continuous casting billet casting speed is 0.85 m / min, and the cast billet is stacked offline for 27 h.

[0030] (2) Hot rolling process: The continuous casting billet is heated in a continuous furnace at 1235 °C for a total heating time of 10 min / cm. The reduction per pass in rough rolling is 28 mm, and it is rolled to an intermediate thickness of 45 mm and then finish-rolled by a finishing mill. The finish rolling temperature is 830 °C, and the recrystallization temperature is 690 °C.

[0031] (3) Heat treatment process: Quenching in a quenching furnace at a quenching temperature of 820 °C for a total heating time of PLC + 25 min. The high-pressure section of quenching is 4250 m 3 / h, the roll speed V = 9 m / min, cooled to room temperature, tempered at 620 °C for a holding time of 110 min.

[0032] Performance inspection results of Q420DR steel plate for mobile tank trucks in this embodiment: Yield and tensile strength in the as-delivered state are Rel 470 MPa, Rm 640 MPa, A 22%, and the low-temperature impact value at -40 °C is 148 / 170 / 154 J. Example 4

[0033] The thickness of the Q420DR steel plate for mobile tank trucks in this embodiment is 15 mm, and its chemical composition and mass percentage are as follows: C: 0.14%, Si: 0.22%, Mn: 1.46%, P 0.009%, S 0.002%, Ni: 0.36%, Nb: 0.030%, V: 0.057%, Alt: 0.030%, and the balance is Fe and unavoidable impurities.

[0034] The production method of the Q420DR steel plate for mobile tank trucks in this embodiment includes steelmaking, hot rolling, and heat treatment processes: (1) Steelmaking process: In the LF furnace refining process, when the molten steel temperature rises to 1590 °C, low-carbon ferromanganese alloy and ferrosilicon alloy are added in sequence according to the process order; subsequently, wire feeding operation of aluminum wire is carried out at a standard amount of 1.4 kg / t of steel. Calcareous conditioning treatment is performed before vacuum, and the feeding amount of calcium wire is controlled at 0.4 kg / t of steel. During continuous casting, the superheat range of the tundish is 30 °C, the casting speed of the continuous casting billet is 0.90 m / min, and the casting billet is stacked offline for 28 h.

[0035] (2) Hot rolling process: The continuous casting billet is heated in a continuous furnace at 1240 °C, the total heating time is 11 min / cm, the single-pass reduction of rough rolling is 29 mm, it is rolled to an intermediate thickness of 48 mm and then finished rolling on a finishing mill, the finish rolling temperature is 835 °C, and the recrystallization temperature is 695 °C.

[0036] (3) Heat treatment process: Quenching in a quenching furnace, the quenching temperature is 835 °C, the total heating time is PLC + 25 min, the high-pressure section of quenching is 4270 m 3 / h, the roll speed V = 9 m / min, cooled to room temperature, tempered at 625 °C, and the holding time is 115 min.

[0037] Performance inspection results of Q420DR steel plate for mobile tank trucks in this embodiment: Yield and tensile strength in the as-delivered state are Rel 478 MPa, Rm 645 MPa, A 21%, and the low-temperature impact value at -40 °C is 142 / 178 / 165 J.

[0038] 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: The present invention can still be modified or equivalently replaced, 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 Q420DR steel plate for mobile tank trucks, characterized in that, The chemical composition and mass percentage of the steel plate are as follows: C: 0.12 - 0.15%, Si: 0.15 - 0.45%, Mn: 1.40 - 1.60%, P ≤ 0.010%, S ≤ 0.002%, Ni: 0.30 - 0.40%, Nb: 0.020 - 0.040%, V: 0.050 - 0.060%, Alt: 0.020 - 0.050%, and the balance is Fe and inevitable impurities.

2. The Q420DR steel plate for mobile tank trucks according to claim 1, wherein The thickness of the steel plate is 10 - 20 mm.

3. A Q420DR steel plate for mobile tank trucks according to claim 1, characterized in that, The microstructure of the steel plate is bainite + ferrite.

4. A Q420DR steel plate for mobile tank trucks according to claim 1, characterized in that, For the steel plate in the delivered state, the yield strength Rel ≥ 450 MPa, the tensile strength Rm ≥ 610 MPa, the elongation A ≥ 20%, and the low-temperature impact value at -40 °C ≥ 100 J.

5. A production method of Q420DR steel plate for mobile tank trucks according to any one of claims 1-4, characterized in that, The production method includes steelmaking, hot rolling and heat treatment processes; the heat treatment process: quenching in a quenching furnace, the quenching temperature is 800 - 840 °C, the total heating time is PLC + 20 - 30 min, the high-pressure section of quenching is 4200 - 4300 m 3 / h, the roll speed V = 8 - 10 m / min, cooling to room temperature, tempering at 600 - 630 °C, and the holding time is 100 - 120 min.

6. The production method of Q420DR steel plate for mobile tank trucks according to claim 5, characterized in that, The steelmaking process: In the LF furnace refining process, when the molten steel temperature rises to the range of 1570 - 1600 °C, low-carbon ferromanganese alloy and ferrosilicon alloy are added in sequence according to the process order; then wire feeding of aluminum wire is carried out at a standard amount of 1.3 - 1.5 kg / t of steel; calcium-based conditioning treatment is performed before vacuum, and the feeding amount of calcium wire is controlled at 0.3 - 0.5 kg / t of steel.

7. The production method of Q420DR steel plate for mobile tank trucks according to claim 5, characterized in that, The steelmaking process: During continuous casting, the superheat range of the tundish ≤ 30 °C, the casting speed of the continuous casting billet is 0.8 - 0.95 m / min, and the casting billets are stacked offline for 24 - 30 h.

8. The production method of Q420DR steel plate for mobile tank trucks according to claim 5, characterized in that, The heating and rolling process: The continuous casting billets are heated in a continuous furnace at 1230 - 1250 °C, the total heating time is 9 - 11 min / cm, the reduction per pass in rough rolling is 25 - 30 mm, rolled to an intermediate thickness of 40 - 50 mm and then finish-rolled by a finishing mill, the finish rolling temperature is 820 - 840 °C, and the recrystallization temperature is 680 - 700 °C.

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