A super-thick long-time die-welding high-toughness pressure vessel steel plate and a production method thereof

Abstract

The application discloses a kind of extra-thick long-time mode welding high-toughness pressure vessel steel plate and its production method, the chemical composition of the steel plate is composed and mass content is as follows: C:0.15~0.18%, Si:0.15~0.35%, Mn:1.30~1.50%, P≤0.010%, S≤0.002%, V:0.20~0.30%, Nb:0.015~0.020%, Alt:0.020~0.050%, the balance is Fe and inevitable impurities;Carbon equivalent CE:0.42~0.44;Its production method includes heating, rolling, stack slow cooling and heat treatment process.The 140-160mm extra-thick steel plate produced by the application is stable in impact toughness at 1 / 4 place-20 DEG C and 1 / 2 place 0 DEG C after long-time mode welding, with moderate strength and hardness, and the comprehensive performance of the steel plate is stable, suitable for mass production.

Description

Technical Field

[0001] This invention belongs to the field of steel rolling and heat treatment, and specifically relates to a method for welding an extra-thick, long-term high-toughness steel plate for pressure vessels. Background Technology

[0002] With the significant advancements in petrochemical refining technology and the continuous growth in product demand, petrochemical production facilities are increasingly large-scale, with the processing capacity of individual units constantly expanding. Examples include common PTA crystallizer units, vacuum distillation units, catalytic cracking units, ethylene units, and nickel-cobalt hydrometallurgical units. This large-scale development leads to increased storage of hazardous materials within the system, increasing risks. Furthermore, the petrochemical production process is highly continuous, with interconnected units and close material supply; localized problems can affect the overall system. Therefore, container design institutes have extremely stringent requirements for the selection of materials and the technical quality of steel plates for large containers. Since 2020, the selection of Q345R and SA516Gr70 steel for large containers has generally involved greater thickness, heavier single-unit weight, and wider dimensions. Technical requirements, to ensure excellent processing performance and safety, generally include low CEV, low hardness, long-term simulated welding, and high impact energy at the 1 / 2 mark. Moreover, the demand for special requirements contracts is increasing year by year. Summary of the Invention

[0003] The purpose of this invention is to provide an extra-thick, long-duration die-welded high-toughness steel plate for pressure vessels and its production method. Through controlled rolling and cooling processes and heat treatment processes, the produced extra-thick steel plate exhibits stable impact toughness at -20℃ at 1 / 4 and 0℃ at 1 / 2 after long-duration die welding, with moderate strength and hardness. The overall performance of the steel plate is stable and suitable for mass production.

[0004] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0005] A type of extra-thick, long-duration die-welded high-toughness steel plate for pressure vessels has the following chemical composition and mass percentage: C: 0.15–0.18%, Si: 0.15–0.35%, Mn: 1.30–1.50%, P≤0.010%, S≤0.002%, V: 0.20–0.30%, Nb: 0.015–0.020%, Alt: 0.020–0.050%, with the balance being Fe and unavoidable impurities; carbon equivalent CE: 0.42–0.44.

[0006] Furthermore, the steel plate of the present invention has a thickness of 140-160mm.

[0007] Furthermore, the tensile strength Rm of the steel plate in the delivery state and the mold-welded state of the present invention is 500~620MPa, the impact energy at 1 / 4 point at -20℃ is ≥80J, the impact energy at 1 / 2 point at 0℃ is ≥60J, and the hardness is ≤190HB; the mold-welding process of the steel plate is 550-570℃, and the heat preservation time is 20-25h.

[0008] The production method of the extra-thick, long-duration die-welded high-toughness pressure vessel steel plate of the present invention includes heating, rolling, stacking and slow cooling and heat treatment processes.

[0009] The heating process described in this invention is as follows: steel ingots are loaded into a soaking furnace at a preheated temperature of 100-200℃. After loading, the steel ingots are steamed for 4-6 hours, then the temperature is increased to 700-750℃ at a rate of 60-80℃ / h and held for 4-6 hours. Then, the temperature is increased to 900-930℃ at a rate of 80-100℃ / h and held for 2-3 hours. Then, the temperature is increased to 1230-1250℃ at a rate of 100-120℃ / h and held for 8-10 hours. Finally, the temperature is increased to 1260-1270℃ and held for 5-7 hours. The target temperature for the steel ingots is 1250-1270℃.

[0010] The rolling process described in this invention is as follows: In the roughing stage, the single-pass reduction in longitudinal rolling is 35-40 mm; in the widening stage, the single-pass reduction is 20-25 mm; after widening, the reduction is 15-20 mm; after rolling to an intermediate thickness of 190-210 mm, the rolling proceeds to finish rolling. The temperature after roughing is 910-940℃, with immediate cooling in between, and a pressure of 1.3-2.0 MPa. In the second-stage rolling, the starting temperature is 840-860℃, with a single-pass reduction of 10-20 mm; the starting cooling temperature is 840-860℃; the roll speed is 0.4-0.6 m / s; and the total flow rate is 1250-1290 m³ / s. 3 / h, water pressure 0.2-0.3MPa, red glow temperature 500-600℃.

[0011] The stacking and slow cooling process described in this invention has a stacking temperature ≥350℃ and a stacking time of 31-40h.

[0012] The heat treatment process described in this invention is as follows: normalizing in a thick plate quenching furnace at a temperature of 880-910℃, holding time of 2-2.5 min / mm, and air cooling.

[0013] The beneficial effects of adopting the above technical solution are as follows:

[0014] This invention controls the rolling and cooling process and the heat treatment process to produce 140-160mm extra-thick steel plates. After long-term die welding, the impact toughness at 1 / 4 of the plate at -20℃ and 1 / 2 of the plate at 0℃ is stable, the strength and hardness are moderate, and the overall performance of the steel plate is stable.

[0015] The steel plates for pressure vessels provided by this invention, in both the delivery state and the mold-welded state, have the following characteristics: tensile strength Rm: 500~620MPa, impact energy at -20℃ at 1 / 4 position ≥80J, impact energy at 0℃ at 1 / 2 position ≥60J, and hardness ≤190HB.

[0016] The product standard for low alloy steel plates for pressure vessels in this invention is based on ASME SA-516 / SA-516M:2021, and the test method is based on SA370. Attached Figure Description

[0017] Figure 1 This is a microstructure diagram of the extra-thick, long-duration mold-welded high-toughness pressure vessel steel plate obtained in Example 1. Implementation

[0018] The present invention will be further described in detail below with reference to the embodiments. Example 1

[0019] In this embodiment, the steel plate for the extra-thick, long-duration die-welded high-toughness pressure vessel has a thickness of 140mm. Its chemical composition and mass percentage are as follows: C: 0.15%, Si: 0.15%, Mn: 1.30%, P: 0.010%, S: 0.002%, V: 0.20%, Nb: 0.015%, Alt: 0.020%, with the balance being Fe and unavoidable impurities; carbon equivalent CE: 0.42. Its production method includes heating, rolling, slow cooling in stacks, and heat treatment processes, as detailed below:

[0020] (1) Heating process: The steel ingot is loaded into the soaking furnace with the temperature at 100℃. After the steel ingot is loaded into the furnace, it is simmered for 4 hours. Then, the temperature is increased to 700℃ at a rate of 60℃ / h and held for 4 hours. Then, the temperature is increased to 900℃ at a rate of 80℃ / h and held for 2 hours. Then, the temperature is increased to 1230℃ at a rate of 100℃ / h and then held for 8 hours. Then, the temperature is slowly increased to 1260℃ and held for 5 hours. The target temperature of the steel ingot is 1250℃.

[0021] (2) Rolling process: In the roughing stage, the single-pass reduction in longitudinal rolling is 35mm; in the widening stage, the single-pass reduction is 20mm; after widening, the reduction is 15mm; after rolling to an intermediate thickness of 190mm, it is transferred to finish rolling. The temperature after roughing is 910℃, and instant cooling is used in the middle. The pressure is 1.3MPa. The starting temperature of the second stage rolling is 840℃, the reduction per pass is 10mm, the starting cooling temperature is 840℃, the roll speed is 0.4m / s, and the total flow rate is 1250m³. 3 / h, water pressure 0.2MPa, red glow temperature 500℃.

[0022] (3) Stacking and slow cooling process, stacking temperature 350℃, stacking time 31h.

[0023] (4) Heat treatment process: Thick plate quenching furnace normalizing, normalizing temperature 880℃, holding time 2min / mm, cooling method: air cooling.

[0024] This embodiment describes the die welding process for extra-thick, long-duration die-welded high-toughness pressure vessel steel plates: 550℃, heat treatment for 20 hours. Steel plate performance test results: Tensile strength Rm in both the delivered state and die-welded state: 540MPa; Impact energy at -20℃ (1 / 4 section): 100J; Impact energy at 0℃ (1 / 2 section): 80J; Hardness: 178HB; Microstructure of the steel plate is shown in [details omitted]. Figure 1 ,Depend on Figure 1 It is known that its microstructure consists of ferrite and pearlite. The microstructure of the steel plates in other embodiments is similar and will not be shown one by one. Example 2

[0025] In this embodiment, the steel plate for the extra-thick, long-duration die-welded high-toughness pressure vessel is 150mm thick. Its chemical composition and mass percentage are as follows: C: 0.18%, Si: 0.35%, Mn: 1.50%, P: 0.009%, S: 0.001%, V: 0.30%, Nb: 0.020%, Alt: 0.050%, with the balance being Fe and unavoidable impurities; carbon equivalent CE: 0.44. The production method includes heating, rolling, slow cooling in stacks, and heat treatment processes, as detailed below:

[0026] (1) Heating process: The steel ingot is loaded into the soaking furnace with the temperature at 200℃. After the steel ingot is loaded into the furnace, it is simmered for 6 hours. Then, the temperature is increased to 750℃ at a rate of 80℃ / h and held for 6 hours. Then, the temperature is increased to 930℃ at a rate of 100℃ / h and held for 3 hours. Then, the temperature is increased to 1250℃ at a rate of 120℃ / h and then held for 10 hours. Then, the temperature is slowly increased to 1270℃ and held for 7 hours. The target temperature of the steel ingot is 1270℃.

[0027] (2) Rolling process: In the roughing stage, the single-pass reduction in longitudinal rolling is 40mm; in the widening stage, the single-pass reduction is 25mm; after widening, the reduction is 20mm; after rolling to an intermediate thickness of 210mm, it is transferred to finish rolling. The temperature after roughing is 940℃, and instant cooling is used in the middle. The pressure is 2.0MPa. The starting temperature of the second stage rolling is 860℃, the reduction per pass is 20mm, the starting cooling temperature is 860℃, the roll speed is 0.6m / s, and the total flow rate is 1290m³. 3 / h, water pressure 0.3MPa, red glow temperature 600℃.

[0028] (3) Stacking and slow cooling process, stacking temperature 370℃, stacking time 40h.

[0029] (4) Heat treatment process: Thick plate quenching furnace normalizing, normalizing temperature 910℃, holding time 2.5min / mm, cooling method: air cooling.

[0030] The welding process for the extra-thick, long-duration mold-welded high-toughness pressure vessel steel plate in this embodiment is as follows: 570℃, heat preservation for 25 hours. Steel plate performance test results: Tensile strength Rm in both the delivered state and the mold-welded state: 610MPa; Impact energy at -20℃ at 1 / 4 section: 120J; Impact energy at 0℃ at 1 / 2 section: 90J; Hardness: 185HB. Example 3

[0031] In this embodiment, the steel plate for the extra-thick, long-duration die-welded high-toughness pressure vessel is 160mm thick. Its chemical composition and mass percentage are as follows: C: 0.17%, Si: 0.20%, Mn: 1.40%, P: 0.010%, S: 0.002%, V: 0.25%, Nb: 0.017%, Alt: 0.030%, with the balance being Fe and unavoidable impurities; carbon equivalent (CE): 0.43. The production method includes heating, rolling, slow cooling in stacks, and heat treatment processes, as detailed below.

[0032] (1) Heating process: The steel ingot is loaded into the soaking furnace with the temperature at 150℃. After the steel ingot is loaded into the furnace, it is simmered for 5 hours. Then, the temperature is increased to 740℃ at a rate of 70℃ / h and held for 5 hours. Then, the temperature is increased to 920℃ at a rate of 90℃ / h and held for 2.5 hours. Then, the temperature is increased to 1240℃ at a rate of 110℃ / h and then held for 9 hours. The target temperature of the steel ingot is 1260℃.

[0033] (2) Rolling process: In the roughing stage, the single-pass reduction in longitudinal rolling is 37mm, and in the widening stage, the single-pass reduction is 23mm, and the reduction after widening is 17mm. After rolling to an intermediate thickness of 200mm, it is transferred to finish rolling. The temperature after roughing rolling is 920℃, and instant cooling is used in the middle. The pressure is 1.5MPa. In the second stage, the starting rolling temperature is 850℃, the reduction per pass is 15mm, the starting cooling temperature is 850℃, the roll speed is 0.5m / s, and the total flow rate is 1280m³. 3 / h, water pressure 0.25MPa, red glow temperature 550℃.

[0034] (3) Stacking and slow cooling process, stacking temperature 380℃, stacking time 35h.

[0035] (4) Heat treatment process: Thick plate quenching furnace normalizing, normalizing temperature 900℃, holding time 2.2min / mm, cooling method: air cooling.

[0036] The welding process for the extra-thick, long-duration mold-welded high-toughness pressure vessel steel plate in this embodiment is as follows: 560℃, heat preservation for 23 hours. Steel plate performance test results: Tensile strength Rm in both the delivered state and the mold-welded state: 600MPa; Impact energy at -20℃ at 1 / 4 section: 110J; Impact energy at 0℃ at 1 / 2 section: ≥75J; Hardness: 178HB. Example 4

[0037] In this embodiment, the steel plate for the extra-thick, long-duration die-welded high-toughness pressure vessel has a thickness of 145mm. Its chemical composition and mass percentage are as follows: C: 0.16%, Si: 0.18%, Mn: 1.45%, P: 0.008%, S: 0.002%, V: 0.23%, Nb: 0.018%, Alt: 0.35%, with the balance being Fe and unavoidable impurities; carbon equivalent CE: 0.425. The production method includes heating, rolling, slow cooling in stacks, and heat treatment processes, as detailed below:

[0038] (1) Heating process: The steel ingot is loaded into the soaking furnace with the temperature at 130℃. After loading the steel ingot into the furnace, it is simmered for 4.5h. Then, the temperature is increased to 730℃ at a rate of 65℃ / h and held for 5.5h. Then, the temperature is increased to 910℃ at a rate of 85℃ / h and held for 2.6h. Then, the temperature is increased to 1235℃ at a rate of 105℃ / h and then held for 8.5h. Then, the temperature is slowly increased to 1265℃ and held for 5.5h. The target temperature of the steel ingot is 1255℃.

[0039] (2) Rolling process: In the roughing stage, the single-pass reduction in longitudinal rolling is 36mm, the single-pass reduction in the widening stage is 22mm, and the reduction after widening is 17mm. Rolling to an intermediate thickness of 195mm, then turning to finish rolling. The temperature after roughing is 925℃, with instant cooling in between, and the pressure is 1.4MPa. In the second stage, the starting rolling temperature is 845℃, the reduction per pass is 13mm, the starting cooling temperature is 845℃, the roll speed is 0.45m / s, and the total flow rate is 1255m³ / s. 3 / h, water pressure 0.22MPa, red glow temperature 540℃.

[0040] (3) Stacking and slow cooling process, stacking temperature 390℃, stacking time 34h.

[0041] (4) Heat treatment process: Thick plate quenching furnace normalizing, normalizing temperature 885℃, holding time 2.4min / mm, cooling method: air cooling.

[0042] The welding process for the extra-thick, long-duration mold-welded high-toughness pressure vessel steel plate in this embodiment is as follows: 555℃, heat preservation for 22 hours. Steel plate performance test results: Tensile strength Rm in both the delivered state and mold-welded state: 570MPa; Impact energy at 1 / 4 section (-20℃): 125J; Impact energy at 1 / 2 section (0℃): 100J; Hardness: 188HB.

Claims

1. A steel plate for extra-thick, long-duration die-welded high-toughness pressure vessels, characterized in that, The chemical composition and mass percentage of the steel plate are as follows: C: 0.15–0.18%, Si: 0.15–0.35%, Mn: 1.30–1.50%, P≤0.010%, S≤0.002%, V: 0.20–0.30%, Nb: 0.015–0.020%, Alt: 0.020–0.050%, with the balance being Fe and unavoidable impurities; carbon equivalent CE: 0.42–0.

44. The steel plate production method includes heating, rolling, stacking and slow cooling and heat treatment processes; The heating process is as follows: Steel ingots are loaded into a preheated soaking furnace at a preheated temperature of 100-200℃. After loading, the ingots are steamed for 4-6 hours. Then, the temperature is increased to 700-750℃ at a rate of 60-80℃ / h and held for 4-6 hours. Next, the temperature is increased to 900-930℃ at a rate of 80-100℃ / h and held for 2-3 hours. Then, the temperature is increased to 1230-1250℃ at a rate of 100-120℃ / h and held for 8-10 hours. Finally, the temperature is increased to 1260-1270℃ and held for 5-7 hours. The target temperature for the steel ingots is 1250-1270℃. The rolling process is as follows: In the roughing stage, the single-pass reduction is 35-40 mm; in the widening stage, the single-pass reduction is 20-25 mm; after widening, the reduction is 15-20 mm; rolling to an intermediate thickness of 190-210 mm, then transitioning to finish rolling. The temperature after roughing is 910-940℃, with immediate cooling during the process, and a pressure of 1.3-2.0 MPa. In the second stage, the initial rolling temperature is 840-860℃, the single-pass reduction is 10-20 mm, the initial cooling temperature is 840-860℃, the roll speed is 0.4-0.6 m / s, and the total flow rate is 1250-1290 m³ / s. 3 / h, water pressure 0.2-0.3MPa, red glow temperature 500-600℃; The heat treatment process is as follows: normalizing in a thick plate quenching furnace at a temperature of 880-910℃ and a holding time of 2-2.5 min / mm. The cooling method is air cooling.

2. The extra-thick, long-duration die-welded high-toughness steel plate for pressure vessels according to claim 1, characterized in that, The steel plate is 140-160 mm thick.

3. The extra-thick, long-duration die-welded high-toughness steel plate for pressure vessels according to claim 1 or 2, characterized in that, The tensile strength Rm of the steel plate in the delivery state and the mold-welded state is 500~620MPa, the impact energy at 1 / 4 point at -20℃ is ≥80J, the impact energy at 1 / 2 point at 0℃ is ≥60J, and the hardness is ≤190HB.

4. The steel plate for extra-thick, long-duration die-welded high-toughness pressure vessels according to claim 3, characterized in that, The steel plate mold welding process is as follows: 550-570℃, heat preservation for 20-25 hours.

5. The method for producing extra-thick, long-duration die-welded high-toughness steel plates for pressure vessels according to any one of claims 1-4, characterized in that, This includes heating, rolling, stacking and slow cooling, and heat treatment processes; The heating process is as follows: Steel ingots are loaded into a preheated soaking furnace at a preheated temperature of 100-200℃. After loading, the ingots are steamed for 4-6 hours. Then, the temperature is increased to 700-750℃ at a rate of 60-80℃ / h and held for 4-6 hours. Next, the temperature is increased to 900-930℃ at a rate of 80-100℃ / h and held for 2-3 hours. Then, the temperature is increased to 1230-1250℃ at a rate of 100-120℃ / h and held for 8-10 hours. Finally, the temperature is increased to 1260-1270℃ and held for 5-7 hours. The target temperature for the steel ingots is 1250-1270℃. The rolling process is as follows: In the roughing stage, the single-pass reduction is 35-40 mm; in the widening stage, the single-pass reduction is 20-25 mm; after widening, the reduction is 15-20 mm; rolling to an intermediate thickness of 190-210 mm, then transitioning to finish rolling. The temperature after roughing is 910-940℃, with immediate cooling during the process, and a pressure of 1.3-2.0 MPa. In the second stage, the initial rolling temperature is 840-860℃, the single-pass reduction is 10-20 mm, the initial cooling temperature is 840-860℃, the roll speed is 0.4-0.6 m / s, and the total flow rate is 1250-1290 m³ / s. 3 / h, water pressure 0.2-0.3MPa, red glow temperature 500-600℃; The heat treatment process is as follows: normalizing in a thick plate quenching furnace at a temperature of 880-910℃ and a holding time of 2-2.5 min / mm. The cooling method is air cooling.

6. The method for producing extra-thick, long-duration die-welded high-toughness steel plates for pressure vessels according to claim 5, characterized in that, The stacking and slow cooling process involves a stacking temperature ≥350℃ and a stacking time of 31-40 hours.

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