CN112941412A - Production method of extra-thick 550 MPa-grade anti-seismic and weather-resistant steel - Google Patents

Abstract

The invention particularly relates to a production method of extra-thick 550 MPa-level anti-seismic and weather-resistant steel. The invention successfully develops the anti-seismic and weather-resistant steel with the thickness of 180-230mm by reasonable chemical component design and LF + VD process, and effectively implements the processes of water-cooling mold pouring, heating, rolling, primary quenching, sub-temperature quenching, tempering heat treatment and the like, wherein the basic structure of the anti-seismic and weather-resistant steel is tempered bainite, the weather resistance coefficient is 7.0-7.5, the yield strength is controlled at 573-614 MPa, the tensile strength is controlled at 721-777 MPa, the elongation is controlled at 20-24 percent, the V-shaped impact absorption energy at-20 ℃ is controlled at 118-236J, and the yield ratio is 0.78-0.80. The corrosion resistance is excellent through a periodic infiltration corrosion test. The super-thick 550 MPa-level anti-seismic weathering steel can be used for the large-scale hydropower industry, super high-rise steel structures, ocean environment platforms and the like.

Description

Production method of extra-thick 550 MPa-grade anti-seismic and weather-resistant steel

Technical Field

The invention belongs to the technical field of medium steel plate production, and particularly relates to a production method of extra-thick 550 MPa-level anti-seismic and weather-resistant steel.

Background

The weathering steel has stronger atmospheric corrosion resistance than plain carbon steel, can be directly used in atmospheric environment without painting, and has better corrosion resistance along with the increase of atmospheric exposure age. With the improvement of the economic construction level of China and the development of large-scale industrial infrastructure, especially in the aspect of use of large-scale hydropower industry, higher requirements are put forward on the weight, thickness, high strength, high anti-seismic performance, weather resistance and the like of materials, and the development of large-thickness anti-seismic weathering steel is urgently needed to meet the requirements of industrial design and use.

Disclosure of Invention

Aiming at the problems, the invention provides a production method of extra-thick 550 MPa-level anti-seismic and weather-resistant steel, which comprises the following specific scheme:

a production method of extra-thick 550 MPa-grade anti-seismic and weather-resistant steel comprises the following chemical components in percentage by mass: c: 0.11 to 0.14%, Si: 0.05 to 0.25%, Mn: 0.8-1.0%, P: less than or equal to 0.015%, S: less than or equal to 0.005 percent, Nb: 0.025-0.035%, V: 0.015 to 0.025%, 0.50 to 0.60% of Mo, Ni: 0.70-0.90%, Cu: 0.25 to 0.35%, 0.50 to 0.60% of Cr, 0.04 to 0.08% of Sb, 0.04 to 0.08% of Sn, Als: 0.030-0.050%, and the balance of Fe and residual elements; the steel ingot of the steel plate is poured by adopting a water-cooling mold, the ingot type is an ingot mold with the thickness of 800-1000 mm, the thickness of a finished steel plate is 180-230mm, the matrix structure is tempered bainite, the weather resistance coefficient is 7.0-7.5, the yield strength of the steel plate is controlled to 573-614 MPa, the tensile strength is controlled to 721-777 MPa, the elongation is controlled to 20-24%, the V-type impact absorption energy at minus 20 ℃ is controlled to 118-236J, and the yield ratio is 0.78-0.80.

It should be noted that, in terms of chemical composition, reasonable carbon content is beneficial to improving the strength and hardenability of the steel plate; nb, V and Al can all play a role in refining grains and improving the toughness of steel, particularly, Nb has an obvious effect on refining grains, and Al has the worst effect on refining grains of steel compared with Nb and V, but because die casting production is adopted, casting blank cracks caused by high Als can not be caused, so that more Al can be properly added to achieve the effect of refining grains, and for tempered steel, the yield strength is obviously improved by precipitation strengthening of V, but the content of V is not easy to control too high in consideration of earthquake resistance; sb and Sn are generally harmful elements in steel, but a compact oxide film can be formed by the composite addition of Sb, Sn and Cr, so that the corrosion resistance of the steel is obviously improved, but the content of Sb and Sn is not suitable to be too high; ni is the most effective element for improving the low-temperature toughness of steel and reducing the brittle transition temperature, the higher the Ni content is, the better the impact toughness of the steel at the extremely low temperature is, and meanwhile, the three elements of Ni, Cr and Cu are added, so that a compact protective film with strong adhesiveness can be formed on the surface of the steel, corrosion diffusion and development are hindered, a substrate below a rust layer is protected, the corrosion speed of the substrate is reduced, but the corrosion resistance is not good after the Cu content is higher than 0.4%. Thereby obtaining the steel plate with excellent quality and meeting the requirement of design performance index.

The production method adopted by the invention comprises the following steps: converter smelting, LF refining, VD vacuum degassing, die casting ingot casting, steel ingot heating, rolling, slow cooling and heat treatment;

a. smelting in a converter: the tapping temperature of the converter is 1600-1650 ℃, and the tapping carbon is as follows: c is more than or equal to 0.07 percent and less than or equal to 0.10 percent, P is less than or equal to 0.008 percent during tapping, no deoxidizing agent and alloy are added into molten steel during tapping, a slag blocking cone is adopted to block slag after the tapping of the converter is finished, and the slag discharging thickness of the converter is controlled to be less than 20mm so as to avoid slag discharging and P returning;

and b, LF refining: after the first refining and heating, the slag turns white or yellowish white, the white slag is kept for 30-35 min, the final slag after the refining is foamed white slag with good fluidity and proper viscosity, and a deoxidizer in the refining process mainly comprises aluminum particles; the ferrochrome alloy uses low-carbon low-silicon ferrochrome, the manganese alloy uses low-carbon ferromanganese according to the content of C, when all alloys are subjected to fine adjustment, any alloy containing Si is not adopted, and the fine adjustment frequency of the Als component in the LF refining process is controlled within 2 times;

and (c) VD vacuum degassing: in the vacuum refining process, the pressure maintaining time is controlled according to 20-25 min under the pressure less than or equal to 67Pa, and rice hulls are added in time to perform soft blowing for 5-8 min after vacuum breaking;

d. pouring a cast ingot: adopting a water-cooled mold of a copper plate crystallizer for pouring, selecting an ingot mold with the thickness of 800-1000 mm, ensuring that the compression ratio of a finished steel plate is more than or equal to 4.0, controlling the casting and pouring temperature according to 1555-1565 ℃, executing a soft argon blowing process after molten steel arrives at a station, controlling the argon blowing time to be 5-7 min, and starting pouring after the argon blowing is finished and the sedation is required to be 5 min;

e. heating a steel ingot: beginning to charge steel when the furnace temperature is 400-600 ℃, annealing the steel for 3 hours, heating to 800-850 ℃ at a heating rate of 60-80 ℃/h after annealing is finished, preserving heat for 8-10 hours in the temperature interval, then heating to 1000 ℃ at a heating rate of 80-100 ℃/h, heating to 1270-1280 ℃ at a heating rate of 100-140 ℃/h above 1000 ℃, and preserving heat for 18-20 hours;

f. rolling: two-stage rolling is adopted, the rolling temperature of one stage is 1050-1150 ℃, the pass reduction is 50-60 mm, the rotating speed is controlled to be less than or equal to 20rad/min, and the steel airing thickness is 300-350 mm; the initial rolling temperature of the second stage is 820-860 ℃, and the final rolling temperature is 780-820 ℃; cooling the rolled steel plate by ACC laminar flow, wherein the temperature of red return is 660-680 ℃;

g. slow cooling: putting the steel plate into a slow cooling pit at the temperature of 550-650 ℃, and slowly cooling for 48 hours;

h. and (3) heat treatment: adopting a primary quenching, sub-temperature quenching and tempering process, wherein the primary quenching is carried out at the heat preservation temperature of 900-920 ℃ for 2.0-2.2 mim/mm, and quenching to normal temperature; carrying out sub-temperature quenching at the heat preservation temperature of 820-840 ℃, and quenching to normal temperature; the tempering heat preservation temperature is 580-600 ℃, the heat preservation time is 3.8-4.2 min/mm, and the steel plate is air-cooled to the normal temperature after being taken out of the furnace.

The invention successfully develops the anti-seismic and weather-resistant steel with the thickness of 180 mm-230 mm by reasonable chemical component design and LF + VD process, and effectively implements the processes of heating, rolling, primary quenching, sub-temperature quenching, tempering heat treatment and the like, wherein the basic structure of the anti-seismic and weather-resistant steel is tempered bainite, the weather resistance coefficient is 7.0-7.5, the yield strength is 573-614 MPa, the tensile strength is 721-777 MPa, the elongation is 20-24 percent, the V-shaped impact absorption energy at-20 ℃ is 118-236J, and the yield ratio is 0.78-0.80. And a periodic infiltration corrosion test is adopted, so that the corrosion resistance is excellent. The super-thick 550 MPa-level anti-seismic weathering steel can be used for the large-scale hydropower industry, super high-rise steel structures, ocean environment platforms and the like.

Drawings

FIG. 1 is a metallographic structure diagram of the thickness M100 times of the aseismic weatherproof steel plate 1/4 according to the present invention.

Detailed Description

The 550 MPa-level earthquake-resistant and weather-resistant steel with the thickness of 180 mm-230 mm comprises the following chemical components in percentage by mass: c: 0.11 to 0.14%, Si: 0.05 to 0.25%, Mn: 0.8-1.0%, P: less than or equal to 0.015%, S: less than or equal to 0.005 percent, Nb: 0.025-0.035%, V: 0.015 to 0.025%, 0.50 to 0.60% of Mo, Ni: 0.70-0.90%, Cu: 0.25 to 0.35%, 0.50 to 0.60% of Cr, 0.04 to 0.08% of Sb, 0.04 to 0.08% of Sn, Als: 0.030-0.050%, and the balance of Fe and residual elements.

The production method adopted by the invention comprises the following steps: converter smelting, LF refining, VD vacuum degassing, die casting ingot casting, steel ingot heating, rolling, slow cooling and heat treatment;

smelting in a converter: the tapping temperature of the converter is 1600-1650 ℃, and the tapping carbon is as follows: c is more than or equal to 0.07 percent and less than or equal to 0.10 percent, P is less than or equal to 0.008 percent during tapping, no deoxidizing agent and alloy are added into molten steel during tapping, a slag blocking cone is adopted to block slag after the tapping of the converter is finished, and the slag discharging thickness of the converter is controlled to be less than 20mm so as to avoid slag discharging and P returning;

LF refining: after the first refining and heating, the slag turns white or yellowish white, the white slag is kept for 30-35 min, the final slag after the refining is foamed white slag with good fluidity and proper viscosity, and a deoxidizer in the refining process mainly comprises aluminum particles; the ferrochrome alloy uses low-carbon low-silicon ferrochrome, the manganese alloy uses low-carbon ferromanganese according to the content of C, when all alloys are subjected to fine adjustment, any alloy containing Si is not adopted, and the fine adjustment frequency of the Als component in the LF refining process is controlled within 2 times;

VD vacuum degassing: in the vacuum refining process, the pressure maintaining time is controlled according to 20-25 min under the pressure less than or equal to 67Pa, and rice hulls are added in time to perform soft blowing for 5-8 min after vacuum breaking;

pouring a cast ingot: adopting a water-cooled mold of a copper plate crystallizer for pouring, selecting an ingot mold with the thickness of 800-1000 mm, ensuring that the compression ratio of a finished steel plate is more than or equal to 4.0, controlling the casting and pouring temperature according to 1555-1565 ℃, executing a soft argon blowing process after molten steel arrives at a station, controlling the argon blowing time to be 5-7 min, and starting pouring after the argon blowing is finished and the sedation is required to be 5 min;

heating a steel ingot: beginning to charge steel when the furnace temperature is 400-600 ℃, annealing the steel for 3 hours, heating to 800-850 ℃ at a heating rate of 60-80 ℃/h after annealing is finished, preserving heat for 8-10 hours in the temperature interval, then heating to 1000 ℃ at a heating rate of 80-100 ℃/h, heating to 1270-1280 ℃ at a heating rate of 100-140 ℃/h above 1000 ℃, and preserving heat for 18-20 hours;

rolling: two-stage rolling is adopted, the rolling temperature of one stage is 1050-1150 ℃, the pass reduction is 50-60 mm, the rotating speed is controlled to be less than or equal to 20rad/min, and the steel airing thickness is 300-350 mm; the initial rolling temperature of the second stage is 820-860 ℃, and the final rolling temperature is 780-820 ℃; cooling the rolled steel plate by ACC laminar flow, wherein the temperature of red return is 660-680 ℃;

slow cooling: putting the steel plate into a slow cooling pit at the temperature of 550-650 ℃, and slowly cooling for 48 hours;

and (3) heat treatment: adopting a primary quenching, sub-temperature quenching and tempering process, wherein the primary quenching is carried out at the heat preservation temperature of 900-920 ℃ for 2.0-2.2 mim/mm, and quenching to normal temperature; carrying out sub-temperature quenching at the heat preservation temperature of 820-840 ℃, and quenching to normal temperature; the tempering heat preservation temperature is 580-600 ℃, the heat preservation time is 3.8-4.2 min/mm, and the steel plate is air-cooled to the normal temperature after being taken out of the furnace.

Example detection

The 550 MPa-grade anti-seismic and weather-resistant steel with the thickness of 180 mm-230 mm, which is designed according to the composition of the invention, is obtained by the processes of converter smelting, LF refining, VD vacuum degassing, die casting, steel ingot heating, rolling, slow cooling, heat treatment and the like, and the process parameters and mechanical properties of the steel are shown in the following tables 1, 2 and 3:

chemical components of 550 MPa-grade earthquake-resistant and weather-resistant steel with extra thickness of 1180-230 mm (Wt%)

Mechanical property of 550 MPa-level earthquake-resistant and weather-resistant steel with meter 2180 mm-230 mm extra thickness

550 MPa-level earthquake-resistant weather-resistant corrosion-resistant property with surface 3180 mm-230 mm extra thickness

The corrosion resistance test conditions of the panels were as follows: periodic immersion corrosion is adopted, and each cycle of the test period: 60 +/-3 min, infiltration time: 12 plus or minus 1.5 min;

sample size: 4 x 40 x 60 mm;

solution: 0.01mol/L NaHSO3 solution, wherein the initial pH value is 4.4-4.8;

temperature: 45 +/-2 ℃;

relative humidity: 70 + -5% RH;

maximum temperature of sample surface after baking: 45 +/-10 ℃;

the M100 times metallographic structure of the 230mm thick aseismic weatherproof steel plate 1/4 is shown in figure 1.

The test results show that the 180 mm-230 mm extra-thick 550 MPa-grade anti-seismic weathering steel has excellent performance indexes and can completely meet the use requirements of large-scale hydropower industry, super high-rise steel structures, ocean environment platforms and the like.

Claims (2)

1. The production method of the extra-thick 550 MPa-grade anti-seismic and weather-resistant steel is characterized in that the steel plate comprises the following chemical components in percentage by mass: c: 0.11 to 0.14%, Si: 0.05 to 0.25%, Mn: 0.8-1.0%, P: less than or equal to 0.015%, S: less than or equal to 0.005 percent, Nb: 0.025-0.035%, V: 0.015 to 0.025%, 0.50 to 0.60% of Mo, Ni: 0.70-0.90%, Cu: 0.25 to 0.35%, 0.50 to 0.60% of Cr, 0.04 to 0.08% of Sb, 0.04 to 0.08% of Sn, Als: 0.030-0.050%, and the balance of Fe and residual elements; the steel ingot of the steel plate is poured by adopting a water-cooling mold, the ingot type is an ingot mold with the thickness of 800-1000 mm, the thickness of a finished steel plate is 180-230mm, the matrix structure is tempered bainite, the weather resistance coefficient is 7.0-7.5, the yield strength of the steel plate is controlled to 573-614 MPa, the tensile strength is controlled to 721-777 MPa, the elongation is controlled to 20-24%, the V-type impact absorption energy at minus 20 ℃ is controlled to 118-236J, and the yield ratio is 0.78-0.80.

2. The method for producing the extra-thick 550MPa grade earthquake resistant and weathering steel of claim 1,

the production method of the steel plate comprises the following steps: converter smelting, LF refining, VD vacuum degassing, die casting ingot casting, steel ingot heating, rolling, slow cooling and heat treatment;

a. smelting in a converter: the tapping temperature of the converter is 1600-1650 ℃, and the tapping carbon is as follows: c is more than or equal to 0.07 percent and less than or equal to 0.10 percent, P is less than or equal to 0.008 percent during tapping, no deoxidizing agent and alloy are added into molten steel during tapping, a slag blocking cone is adopted to block slag after the tapping of the converter is finished, and the slag discharging thickness of the converter is controlled to be less than 20mm so as to avoid slag discharging and P returning;

and b, LF refining: after the first refining and heating, the slag turns white or yellowish white, the white slag is kept for 30-35 min, the final slag after the refining is foamed white slag with good fluidity and proper viscosity, and a deoxidizer in the refining process mainly comprises aluminum particles; the ferrochrome alloy uses low-carbon low-silicon ferrochrome, the manganese alloy uses low-carbon ferromanganese according to the content of C, when all alloys are subjected to fine adjustment, any alloy containing Si is not adopted, and the fine adjustment frequency of the Als component in the LF refining process is controlled within 2 times;

and (c) VD vacuum degassing: in the vacuum refining process, the pressure maintaining time is controlled according to 20-25 min under the pressure less than or equal to 67Pa, and rice hulls are added in time to perform soft blowing for 5-8 min after vacuum breaking;

d. pouring a cast ingot: adopting a water-cooled mold of a copper plate crystallizer for pouring, selecting an ingot mold with the thickness of 800-1000 mm, ensuring that the compression ratio of a finished steel plate is more than or equal to 4.0, controlling the casting and pouring temperature according to 1555-1565 ℃, executing a soft argon blowing process after molten steel arrives at a station, controlling the argon blowing time to be 5-7 min, and starting pouring after the argon blowing is finished and the sedation is required to be 5 min;

e. heating a steel ingot: beginning to charge steel when the furnace temperature is 400-600 ℃, annealing the steel for 3 hours, heating to 800-850 ℃ at a heating rate of 60-80 ℃/h after annealing is finished, preserving heat for 8-10 hours in the temperature interval, then heating to 1000 ℃ at a heating rate of 80-100 ℃/h, heating to 1270-1280 ℃ at a heating rate of 100-140 ℃/h above 1000 ℃, and preserving heat for 18-20 hours;

f. rolling: two-stage rolling is adopted, the rolling temperature of one stage is 1050-1150 ℃, the pass reduction is 50-60 mm, the rotating speed is controlled to be less than or equal to 20rad/min, and the steel airing thickness is 300-350 mm; the initial rolling temperature of the second stage is 820-860 ℃, and the final rolling temperature is 780-820 ℃; cooling the rolled steel plate by ACC laminar flow, wherein the temperature of red return is 660-680 ℃;

g. slow cooling: putting the steel plate into a slow cooling pit at the temperature of 550-650 ℃, and slowly cooling for 48 hours;

h. and (3) heat treatment: adopting a primary quenching, sub-temperature quenching and tempering process, wherein the primary quenching is carried out at the heat preservation temperature of 900-920 ℃ for 2.0-2.2 mim/mm, and quenching to normal temperature; carrying out sub-temperature quenching at the heat preservation temperature of 820-840 ℃, and quenching to normal temperature; the tempering heat preservation temperature is 580-600 ℃, the heat preservation time is 3.8-4.2 min/mm, and the steel plate is air-cooled to the normal temperature after being taken out of the furnace.

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