SA738GRB steel plate for nuclear power plant containment and manufacturing method

Abstract

Disclosed is a SA738GrB steel plate for nuclear power plant containment, relating to the technical field of steel smelting. The SA738GrB steel plate has a thickness specification of 101 mm and a width

Description

SA738GrB steel plate for nuclear power plant containment and manufacturing method TECHNICAL FIELD

[0001] The present application relates to the technical field of steel smelting, in particular to a SA738GrB steel plate for a nuclear power plant containment and a manufacturing method. BACKGROUND

[0002] At present, nuclear energy is recognized as a clean, efficient and safe energy. According to the prediction of international authoritative agencies, by 2038, 90 to 300 1600-megawatt reactors will be built worldwide, and the development of nuclear power will enter a rapid growth period. China's nuclear power construction started in the mid-1980s of last century, and developed rapidly. By 2017, there were 37 nuclear power units in operation in mainland China, and 19 nuclear power units under construction, with the largest number of nuclear power units under construction in the world. By 2020, China's nuclear power operation and under-construction installed capacity will reach 88 million kilowatts, and the nuclear power installed capacity will account for more than 5% of the total domestic power installed capacity.

[0003] The containment, as a protective device for nuclear island equipment, is an important part of the pressurized water reactor nuclear power plant and the last safety barrier to prevent radioactive material leakage. At present, the main nuclear power type in China is the AP1000 nuclear power type designed by Westinghouse Company, and the main material for the steel containment is SA738 Gr.B steel plate. The steel grade has a high thickness specification, and the technical index requirements are strict, and the performance control is difficult. With the increasing requirements for the safety of nuclear power plants, the performance requirements for the steel containment steel plate are also getting higher and higher. From the perspective of nuclear safety containment safety, the weld length of the assembly should be minimized, therefore, one of the development directions of the nuclear reactor containment is integration and integration, which improves the thickness and width while ensuring the performance, which is very difficult.

[0004] The ultra-wide and ultra-thick steel plate has both large thickness and large width, and has higher utilization rate than other size steel plates when making nuclear power plant containment, which not only saves welding work, but also improves the safety of the containment. At present, the invention patents of this steel grade cannot simultaneously reach 101mm thick and 4650mm wide, such as:

[0005] CN201811165254.3 discloses a kind of extra-wide extra-thick nuclear power plant conventional island equipment steel and its manufacturing method, steel contains C:0.10%~0.18%, Si:0.15%~0.40%, Mn:0.90%~1.50%, P≤0.02%, S≤0.005%, Ni:0.10%~0.30%, Cr:0.15%~0.30%, V:0.01%~0.05%, Nb:0.01%~0.05%, Als:0.015%~0.04%, the balance is iron and inevitable impurities.Heat temperature of continuous casting billet 1200~1250℃, furnace time 4~6h;First stage opening rolling temperature ≥1100℃, total reduction rate ≥60%;Second stage opening rolling temperature 900~950℃, finish rolling temperature 800~850℃;Normalizing temperature 880~920℃, holding time 1~3min / mm, after discharging natural cooling.Finished steel plate thickness 60~100mm, width 4000~5100mm, meet the use conditions of nuclear power plant conventional island equipment steel.The invention patent reaches the highest value in width aspect at present industry, but its 100mm thick steel plate width can only be made to 4200mm at most, and the strength is lower after normalizing.

[0006] CN201510302071.1 discloses a kind of large thickness SA738GrA steel plate and its production method, which is composed of the following weight percentage of components: C:0.14%~0.16%, Si:0.25%~0.45%, Mn:1.35%~1.45%, P≤0.020%, S≤0.010%, Cr:0.15%~0.20%, Mo≤0.06%, Ti≤0.02%, Ni:0.20%~0.30%, Cu≤0.05%, Al:0.020%~0.050%, V≤0.07%, Nb≤0.04%, Nb+V≤0.07%, the balance is Fe and inevitable impurities.The steel plate optimizes each element component and proportion in steel plate, so that the thickness of SA738GrA steel plate reaches 112mm, and the obtained steel plate meets the requirements of B level in ASME SA578 / SA578M flaw detection standard, but the width of the steel plate is unknown, the yield strength is only about 310MPa, and the low temperature toughness is poor, the impact energy at-46℃ is about 27 joules.

[0007] CN201610058164.9 discloses a kind of nuclear island equipment with large thickness SA738GrB steel plate and production method, the weight percentage of steel plate component is as follows: C:0.05%~0.20%, Si:0.15%~0.55%, Mn:0.90%~1.60%, P≤0.009%, S≤0.006%, Cr≤0.30%, Mo≤0.30%, Cu≤0.35%, Ni≤0.60%, V≤0.07%, Nb≤0.04%, Ti≤0.03%, the balance is Fe and unavoidable impurities.The improved steel plate adopts quenching and tempering heat treatment process, through micro-alloying element forms composite strengthening, good strength and toughness matching is obtained.The thickest steel plate can reach 130mm, but there is no data for width.

[0008] SUMMARY

[0009] To solve the above technical problems, the present application provides a kind of SA738GrB steel plate for nuclear power plant containment, thickness specification is 101mm, width specification is 4650mm, its chemical composition and mass percentage are as follows: C≤0.2%, Si:0.13%~0.6%, Mn:0.9%~1.6%, Ni≤0.6%, Cr≤0.3%, Nb≤0.05%, Mo≤0.35%, V≤0.08%, Ti≤0.03%, the balance is Fe and unavoidable impurities.

[0010] Technical effects: the steel plate product designed in the present application has thickness of 101mm and width of 4650mm, has good strength and toughness, weldability and other advantages, meets the use requirements of nuclear power plant containment.

[0011] The further defined technical solutions of the present application are:

[0012] The SA738GrB steel plate for nuclear power plant containment described above has the following chemical composition and mass percentage: C:0.15%, Mn:1.53%, P:0.009%, S:0.001%, Si:0.25%, Ni:0.54%, Cr:0.022%, Nb:0.03%, Mo:0.17%, V:0.044%, Ti:0.016%, Alt:0.04%, the balance is Fe and unavoidable impurities.

[0013] The SA738GrB steel plate for nuclear power plant containment described above has the following chemical composition and mass percentage: C:0.14%, Mn:1.55%, P:0.008%, S:0.001%, Si:0.25%, Ni:0.55%, Cr:0.25%, Nb:0.03%, Mo:0.28%, V:0.044%, Ti:0.017%, Alt:0.02%, the balance is Fe and unavoidable impurities.

[0014] A SA738GrB steel plate for a nuclear power plant containment previously described, the chemical composition and mass percentage are as follows: C: 0.13%, Mn: 1.55%, P: 0.009%, S: 0.001%, Si: 0.25%, Ni: 0.56%, Cr: 0.23%, Nb: 0.03%, Mo: 0.27%, V: 0.045%, Ti: 0.016%, Alt: 0.05%, the balance is Fe and inevitable impurities.

[0015] Another purpose of the present application is to provide a manufacturing method of a SA738GrB steel plate for a nuclear power plant containment, comprising the following processes: molten steel pretreatment, converter smelting, refining, continuous casting, heating, rolling and heat treatment, characterized in that:

[0016] Molten iron desulfurization pretreatment: starting temperature 1330-1370℃, ending temperature 1320-1350℃, spray magnesium powder 0.3-1.0kg / ton, spray lime powder 2.5-4.0kg / ton, ending S≤0.005%;

[0017] After smelting and refining, the molten steel is continuously cast, the superheat degree of the molten steel is 5-25℃, the withdrawal speed is 0.55-0.75m / min, the continuous casting secondary cooling electromagnetic stirring is carried out by using current 200-450A and frequency 5-7Hz, the light reduction is carried out by using reduction interval 50-95% and reduction amount 4-8mm, and the continuous casting billet thickness is 320mm;

[0018] The continuous casting billet is heated at temperature 1180-1250℃, and the furnace time is 4.8-7.0h; after the billet is discharged and descaled, the billet is first transversely rolled to the finished product width and then longitudinally rolled, and the rolling is carried out in two stages: the first stage rolling temperature is 1000-1150℃, and the cumulative reduction is 50-70%; the second stage rolling thickness is 184mm, and the cumulative reduction is 40-60%; and the rolled steel plate is cooled in air;

[0019] Quenching: the steel plate is heated in a quenching furnace, the holding temperature of heating is 890-930℃, and the total holding time is 2.1min / mm; after the steel plate is held, the steel plate is subjected to laminar flow cooling in a roller quenching machine, the laminar flow cooling process includes a high pressure section and a low pressure section, the laminar flow pressure of the high pressure section is 0.8MPa, the upper and lower water ratio is 0.85, the laminar flow pressure of the low pressure section is 0.5MPa, the upper and lower water ratio is 0.88, and the roller gap of the quenching machine is set to 101mm; after cooling in the high pressure section, the steel plate is subjected to swinging for more than 18min in the low pressure section, so that the overall temperature of the steel plate after cooling is below 100℃;

[0020] Tempering: the steel plate is heated in a tempering furnace, heated to a tempering temperature of 660-680℃ for holding, the total holding time is more than 2.5min / mm, and the steel plate is discharged and air cooled after holding.

[0021] The beneficial effects of the present application are:

[0022] (1) The steel plate of the present application has a thickness specification of 101 mm and a width specification of 4650 mm, which can effectively reduce the length of the weld of the assembly from the perspective of the safety of the nuclear containment vessel, further realizing the integration and integrity of the containment vessel, and the steel plate utilization rate is high and the safety is good.

[0023] (2) The present application solves the problem of low low-temperature impact toughness of the ultra-wide and thick plate of the nuclear power steel by adopting high-clean smelting and low-segregation continuous casting, two-stage controlled rolling, and offline roll-type high-strength and high-uniformity quenching and tempering heat treatment, and the steel plate has good strength and toughness matching. The mechanical properties of the steel plate obtained by the method of the present application in the as-delivered state at the 1 / 4 thickness are: R P0.2 ≥ 635 MPa, R m ≥ 710 MPa, A 5d ≥ 20%, -25℃ K v8 (average value) ≥ 84 J, -35℃ K v8 (average value) ≥ 52 J; the performance after simulating post-weld heat treatment: R p0.2 ≥ 615 MPa, R m ≥ 710 MPa, A 5d ≥ 21%, -35℃ transverse K V8 impact energy average value ≥ 75 J;

[0024] (3) Compared with ordinary controlled rolling and heat treatment steel plate, the present application improves the comprehensive performance of the steel plate with the same chemical composition design, and the obtained steel plate has good strength and toughness, especially the low-temperature impact toughness is greatly improved, and the production resource consumption of the steel plate is reduced. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 is an SEM image of the steel plate obtained in Example 1 of the present application. DETAILED DESCRIPTION

[0026] A SA738GrB steel plate for a nuclear power plant containment vessel has a thickness specification of 101 mm and a width specification of 4650 mm, and the chemical composition and mass percentage are as follows: C ≤ 0.2%, Si: 0.13% ~ 0.6%, Mn: 0.9% ~ 1.6%, Ni ≤ 0.6%, Cr ≤ 0.3%, Nb ≤ 0.05%, Mo ≤ 0.35%, V ≤ 0.08%, Ti ≤ 0.03%, and the balance is Fe and unavoidable impurities.

[0027] The manufacturing method of the above-mentioned steel plate comprises the following steps: molten steel pretreatment, converter smelting, refining, continuous casting, heating, rolling, and heat treatment,

[0028] Molten iron desulphurization pretreatment: starting temperature 1330-1370℃, ending temperature 1320-1350℃, spraying magnesium powder 0.3-1.0kg / t, spraying lime powder 2.5-4.0kg / t, ending S≤0.005%;

[0029] After the molten steel is smelted and refined, the molten steel is continuously cast, the molten steel overheat degree is 5-25℃, the blank drawing speed is 0.55-0.75m / min, the continuous casting secondary electromagnetic stirring is carried out by using current 200-450A and frequency 5-7Hz, the light press-down is carried out by using press-down interval 50-95% and press-down amount 4-8mm, and the continuous casting blank thickness is 320mm.

[0030] The continuous casting blank heating temperature is 1180-1250℃, the furnace time is 4.8-7.0h, after the steel blank is discharged and descaled, the steel blank is first transversely rolled to the finished product width and then longitudinally rolled, and the rolling is carried out in two stages: the first stage rolling temperature is 1000-1150℃, and the cumulative press-down amount is 50-70%; the second stage rolling thickness is 184mm, and the cumulative press-down amount is 40-60%, and the rolled steel plate is cooled in air.

[0031] Quenching: the steel plate is heated in a quenching furnace, the heating holding temperature is 890-930℃, and the total holding time is 2.1min / mm; after the steel plate is held, the steel plate is subjected to laminar flow cooling in a roller quenching machine, the laminar flow cooling process includes a high pressure section and a low pressure section, the laminar flow pressure of the high pressure section is 0.8MPa, the upper and lower water ratio is 0.85, the laminar flow pressure of the low pressure section is 0.5MPa, the upper and lower water ratio is 0.88, and the quenching machine roller gap is set to 101mm; after the high pressure section cooling, the steel plate is subjected to low pressure section swinging for more than 18min, so that the overall temperature of the cooled steel plate is below 100℃;

[0032] Tempering: the steel plate is heated in a tempering furnace, heated to a tempering temperature of 660-680℃ for holding, the total holding time is more than 2.5min / mm, and the steel plate is discharged and air cooled after holding.

[0033] The technical solutions of the present application are further described below in combination with examples 1-3.

[0034] Table 1: Steel smelting chemical components of each example (wt, %)

[0035]

[0036] Heating and rolling process: the continuous casting blank heating temperature is 1180-1250℃, the furnace time is 4.8-7.0h, after the steel blank is discharged and descaled, the steel blank is first transversely rolled to the finished product width and then longitudinally rolled. The rolling is carried out in two stages: the first stage rolling temperature is 1050℃, and the cumulative press-down amount is 55%; the second stage rolling thickness is 184mm, and the cumulative press-down amount is 45%. The rolled steel plate is cooled in air.

[0037] Table 2 Heat treatment process of each example steel

[0038]

[0039] Table 3 Mechanical properties of each example steel in tempered state

[0040]

[0041] The steel plates of the examples were sampled to perform a simulated post-weld heat treatment experiment, with the process being: holding temperature 620±10℃, holding time 10h, and discharge furnace temperature ≤425℃, with a temperature rising and falling rate of 56℃ / h above 425℃.

[0042] Table 4 Mechanical properties of each example steel in simulated post-weld heat treatment

[0043]

[0044] As shown in FIG. 1, a uniform tempered bainite structure is obtained at the 1 / 4 thickness of the steel plate. The steel plate designed in the present application has a thickness specification of up to 101mm and a width specification of up to 4650mm, which can effectively reduce the weld length of the assembly from the perspective of nuclear safety containment safety, further realizing the integration and integrity of the containment, and the steel plate utilization rate is high, and the safety is good. Compared with ordinary controlled rolling and heat treated steel plates, the same chemical composition design improves the comprehensive performance of the steel plate, and the obtained steel plate has good strength and toughness, especially the low temperature impact toughness is greatly improved, and the production resource consumption of the steel plate is reduced.

[0045] In addition to the above examples, the present application can have other implementation manners. Any technical solution formed by equivalent replacement or equivalent transformation falls within the protection scope required by the present application.

Claims

1. An SA738GrB steel plate for nuclear power plant containment, characterized in that: The thickness specification is 101 mm, and the width specification is 4650 mm. Its chemical composition and mass percentage are as follows: C ≤ 0.2%, Si: 0.13% - 0.6%, Mn: 0.9% - 1.6%, Ni ≤ 0.6%, Cr ≤ 0.3%, Nb ≤ 0.05%, Mo ≤ 0.35%, V ≤ 0.08%, Ti ≤ 0.03%, and the balance is Fe and unavoidable impurities.

2. The SA738GrB steel plate for nuclear power plant containment according to claim 1, characterized in that, Its chemical composition and mass percentage are as follows: C: 0.15%, Mn: 1.53%, P: 0.009%, S: 0.001%, Si: 0.25%, Ni: 0.54%, Cr: 0.022%, Nb: 0.03%, Mo: 0.17%, V: 0.044%, Ti: 0.016%, Alt: 0.04%, and the balance is Fe and unavoidable impurities.

3. The SA738GrB steel plate for nuclear power plant containment according to claim 1, characterized in that, Its chemical composition and mass percentage are as follows: C: 0.14%, Mn: 1.55%, P: 0.008%, S: 0.001%, Si: 0.25%, Ni: 0.55%, Cr: 0.25%, Nb: 0.03%, Mo: 0.28%, V: 0.044%, Ti: 0.017%, Alt: 0.02%, and the balance is Fe and unavoidable impurities.

4. The SA738GrB steel plate for nuclear power plant containment according to claim 1, characterized in that, Its chemical composition and mass percentage are as follows: C: 0.13%, Mn: 1.55%, P: 0.009%, S: 0.001%, Si: 0.25%, Ni: 0.56%, Cr: 0.23%, Nb: 0.03%, Mo: 0.27%, V: 0.045%, Ti: 0.016%, Alt: 0.05%, and the balance is Fe and unavoidable impurities.

5. A manufacturing method for the SA738GrB steel plate for nuclear power plant containment according to claim 1, including the following processes: molten steel pretreatment - converter smelting - refining - continuous casting - heating - rolling - heat treatment, characterized in that: Hot metal desulfurization pretreatment: starting temperature 1330 - 1370 °C, ending temperature 1320 - 1350 °C, injecting magnesium powder 0.3 - 1.0 kg / ton and lime powder 2.5 - 4.0 kg / ton, and the ending S ≤ 0.005%; After the molten steel is smelted and refined, continuous casting is carried out. The superheat of the molten steel is 5 - 25 °C, the casting speed is 0.55 - 0.75 m / min, continuous casting secondary cooling electromagnetic stirring: current 200 - 450 A, frequency 5 - 7 Hz, soft reduction: reduction range 50 - 95%, reduction amount 4 - 8 mm, and the thickness of the continuous casting billet is 320 mm; The heating temperature of the continuous casting billet is 1180 - 1250 °C, and the time in the furnace is 4.8 - 7.0 h. After the steel billet is descaled when it comes out of the furnace, it is first cross-rolled to the finished width and then longitudinally rolled. The rolling is carried out in two stages: the rolling temperature in the first stage is 1000 - 1150 °C, and the cumulative reduction amount is 50 - 70%; the starting thickness for rolling in the second stage is 184 mm, and the cumulative reduction amount is 40 - 60%. The rolled steel plate is cooled in the air; Quenching: The steel plate is heated in a quenching furnace. The holding temperature for heating is 890 - 930 °C, and the total holding time is 2.1 min / mm. After holding, the steel plate undergoes laminar flow cooling on a roller quenching machine. The laminar flow cooling process includes a high-pressure section and a low-pressure section. The laminar flow pressure in the high-pressure section is 0.8 MPa, and the upper and lower water ratio is 0.

85. The laminar flow pressure in the low-pressure section is 0.5 MPa, and the upper and lower water ratio is 0.

88. The roll gap of the quenching machine is set to 101 mm. After cooling in the high-pressure section, the steel plate undergoes a swing time of more than 18 min in the low-pressure section to ensure that the overall temperature of the steel plate after cooling is below 100 °C. Tempering: The steel plate is heated in a tempering furnace, held at a tempering temperature of 660 - 680 °C, with a total holding time of 2.5 min / mm or more, and then air-cooled after being taken out of the furnace after holding.

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