CN110184528B - Q345R steel plate with excellent performance under high-temperature simulated postweld heat treatment condition and manufacturing method thereof - Google Patents

Q345R steel plate with excellent performance under high-temperature simulated postweld heat treatment condition and manufacturing method thereof Download PDF

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CN110184528B
CN110184528B CN201810592142.XA CN201810592142A CN110184528B CN 110184528 B CN110184528 B CN 110184528B CN 201810592142 A CN201810592142 A CN 201810592142A CN 110184528 B CN110184528 B CN 110184528B
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steel plate
temperature
heat treatment
steel
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CN110184528A (en
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刘海宽
钱刚
李经涛
苗丕峰
高助忠
张建
徐伟
恽鹏程
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Jiangyin Xingcheng Special Steel Works Co Ltd
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    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21DMODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0205Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21DMODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0226Hot rolling
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21DMODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0247Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C33/00Making ferrous alloys
    • C22C33/04Making ferrous alloys by melting
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/02Ferrous alloys, e.g. steel alloys containing silicon
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/04Ferrous alloys, e.g. steel alloys containing manganese
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/06Ferrous alloys, e.g. steel alloys containing aluminium
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/08Ferrous alloys, e.g. steel alloys containing nickel
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/12Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/14Ferrous alloys, e.g. steel alloys containing titanium or zirconium
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/16Ferrous alloys, e.g. steel alloys containing copper

Abstract

The invention relates to a Q345R steel plate with excellent performance under high-temperature simulated postweld heat treatment conditions, which comprises the following chemical components: 0.16-0.20%, Si: 0.25 to 0.45%, Mn: 1.40-1.60%, P: less than or equal to 0.008 percent, S: less than or equal to 0.002%, Al: 0.02-0.05%, Nb: 0.02-0.05%, Ti: 0.01-0.05%, Ni: 0.10-0.30%, Cu: 0.10 to 0.30 percent, the balance being Fe and inevitable impurity elements, and the carbon equivalent Ceq is less than or equal to 0.45 percent. The design of large compression ratio is adopted, and the main procedures comprise smelting, two-stage rolling and normalizing heat treatment. The steel plate is in a normalized delivery state, the Brinell hardness of the surface of the steel plate in the delivery state is less than or equal to 170HB, the transverse impact energy at the 1/2-30 ℃ position of the steel plate after high-temperature simulated postweld heat treatment is more than or equal to 100J, the yield strength is more than or equal to 325MPa, the tensile strength is more than or equal to 500MPa, the elongation A after fracture is more than or equal to 25.0 percent, and the flaw detection of the steel plate can meet the I-level qualification of NB.

Description

Q345R steel plate with excellent performance under high-temperature simulated postweld heat treatment condition and manufacturing method thereof
Technical Field
The invention belongs to the field of steel plate manufacturing, and particularly relates to a Q345R steel plate for boilers and pressure vessels, which has the thickness of 20-100mm and excellent performance under the condition of high-temperature simulated postweld heat treatment, and a manufacturing method thereof.
Background
The Q345R is a boiler and pressure vessel steel plate with the largest usage and the most extensive use in China, along with the rapid development of economic construction and petrochemical industry manufacturing industry, the demand of the Q345R steel plate in the market is larger and larger, the requirement of the steel plate on the simulated postweld heat treatment performance is higher and higher in design, and the simulated postweld heat treatment heat preservation temperature is increased to 650 ℃ from 580-635 ℃. In recent years, because the same container equipment is designed to simultaneously adopt two materials of Q345R and the hydrogen chromium molybdenum steel, and the whole body needs to be subjected to post-welding stress relief treatment after the equipment is manufactured, the Q345R and the hydrogen chromium molybdenum steel are required to adopt the same simulated post-welding heat treatment system: the simulated postweld heat treatment heat preservation temperature is 690 ℃ or 705 ℃, the heat preservation time is 12 hours, meanwhile, the tensile property and the impact property at 1/2 of the thickness of the steel plate after the simulated postweld heat treatment meet the standard requirements, the Brinell hardness of the delivered surface is less than or equal to 200HB, and the production technology difficulty is very large. At present, under the condition of limiting carbon equivalent in domestic steel plate production plants, the method for ensuring the performance of the high-temperature simulated post-weld heat treatment steel plate generally changes delivery state, changes normalizing delivery into normalizing accelerated cooling, or directly adopts quenching and tempering treatment, even directly adopts hot rolled steel plates for reducing cost, and has the defects of uneven steel plate structure, higher hardness, larger residual stress, and difficult subsequent processing and manufacturing, and for pressure vessel equipment which is contacted by corrosive media or used in extreme environment, the steel plate produced by adopting the method has certain quality hidden danger and risk. In the normalized delivery state, the technical difficulty of the production of the steel plate is to ensure that the delivery-state surface hardness and the simulated post-weld heat treatment strength and the impact toughness of the steel plate simultaneously meet the standard and the use requirement, and obtain the optimal matching.
The invention patent with publication number CN106591723A relates to 'SA 516Gr70 steel plate and a production method thereof under high die welding conditions', and provides a method for producing the SA516Gr70 steel plate by adopting a II-type controlled rolling and normalizing accelerated cooling process, wherein the tensile and impact properties at the position of 1/2 part of the steel plate after die welding meet the standard requirements, the delivered-state surface Brinell hardness meets the requirements of users, the maximum thickness of the steel plate in the embodiment is 100mm, the impact temperature is higher than-5 ℃, the surface Brinell hardness is higher than 189-191HB, and the post-welding heat treatment process system is not specifically simulated.
The invention patent with publication number CN103361550A relates to 'Q370R steel with excellent simulated postweld heat treatment performance and a production method', and provides a Q370R steel plate with the thickness of 60-100mm and produced by adopting a 'two-stage rolling and normalizing' process and a production method thereof, wherein the simulated postweld heat treatment has good low-temperature impact toughness, high-temperature tensile property and Z-direction tensile property, but the simulated postweld heat treatment can only be suitable for lower simulated postweld heat treatment temperature, 600 +/-10 ℃.
The invention patent with publication number CN107619999A relates to a hydrogen sulfide corrosion resistant thin steel plate with long-time die welding heat treatment and a production method thereof, and provides a steel plate with the thickness of 8-20mm produced by adopting a two-stage rolling plus (quenching plus tempering) process and a production method thereof, wherein the steel plate after simulated postweld heat treatment can meet the requirements that the yield strength is more than or equal to 345MPa, the tensile strength is 510-640MPa, the transverse impact energy at minus 30 ℃ is more than or equal to 80J, the hardness is 130-180HB, a high-temperature simulated postweld heat treatment system is not involved, and the production thickness range of the steel plate is smaller.
None of the above patents relate to a steel plate product that can meet the requirements of high-temperature simulated postweld heat treatment at 690 ℃ or 705 ℃, and have the disadvantages of small thickness, poor performance matching and the like of the steel plate, and the requirements of development of the petrochemical industry cannot be completely met.
Disclosure of Invention
Based on the prior art, the inventor of the application provides a Q345R steel plate and a manufacturing method thereof, and the steel plate still has excellent mechanical properties under the simulated postweld heat treatment condition at the high temperature of 700 +/-10 ℃.
Specifically, the technical problem to be solved by the present invention is to provide a Q345R steel plate with excellent performance under the high-temperature simulated postweld heat treatment condition, which can be applied to the manufacturing of important structural components in the petrochemical industry, has good internal quality, still has excellent mechanical properties under the high-temperature simulated postweld heat treatment condition of 700 ± 10 ℃, and has good matching between the delivered surface brinell hardness of the steel plate and the simulated postweld heat treatment state tensile property and impact toughness, thereby completely meeting the development requirements of the petrochemical industry.
The specific technical scheme of the invention is as follows: a Q345R steel plate with excellent performance under high-temperature simulated postweld heat treatment conditions comprises the following chemical components in percentage by weight: 0.16-0.20%, Si: 0.25 to 0.45%, Mn: 1.40-1.60%, P: less than or equal to 0.008 percent, S: less than or equal to 0.002%, Al: 0.02-0.05%, Nb: 0.02-0.05%, Ti: 0.01-0.05%, Ni: 0.10-0.30%, Cu: 0.10-0.30%, the balance of Fe and inevitable impurity elements, the carbon equivalent Ceq is less than or equal to 0.45%, and the calculation formula of the carbon equivalent is as follows: ceq ═ C + Mn/6+ (Cr + Mo + V)/5+ (Ni + Cu)/15.
The thickness of the steel plate is 20-100mm, the steel plate is in a normalized delivery state, the Brinell hardness of the surface of the steel plate in the delivery state is less than or equal to 170HB, after high-temperature simulated postweld heat treatment at 700 +/-10 ℃, the transverse impact energy at the 1/2-30 ℃ position of the steel plate can meet the requirement that the single value is more than or equal to 100J, the yield strength is more than or equal to 325MPa, the tensile strength is more than or equal to 500MPa, the elongation A after fracture is more than or equal to 25.0 percent, and the flaw detection of the steel plate can meet the I.
The design idea of the chemical components of the invention is to improve the content of solid solution strengthening and fine grain strengthening elements as much as possible within an allowable range to ensure that the steel plate has higher tensile property on the basis of ensuring that the steel plate has enough weldability and low-temperature impact toughness, and simultaneously ensure that the strength and the toughness of the steel plate are not obviously reduced after high-temperature simulated postweld heat treatment through reasonable combination and collocation of the chemical elements. The effect of the chemical elements in the steel is as follows:
c: carbon can significantly improve the strength of the steel sheet, but if the content is too high, the impact toughness of the steel sheet deteriorates, and if the content exceeds 0.23%, the weldability of the steel deteriorates, so that low alloy steels for welding generally contain no more than 0.20% carbon. The carbon content of the carbon-containing carbon is controlled to be 0.16-0.20%.
Mn: manganese has a strong solid solution strengthening effect and can improve the normal temperature strength and the hardness, but the welding stress is increased due to the excessively high content of manganese, the strength of steel is improved by strengthening ferrite and pearlite by using manganese in low alloy steel, the content of manganese is generally 1% -2%, and the content of manganese in the steel is controlled to be 1.40-1.60%.
Si: silicon is a good reducing agent and a good deoxidizing agent in the steelmaking process, has a strong solid solution strengthening effect, can improve the normal temperature strength and the hardness, but can reduce the impact toughness and the surface quality of a steel plate when the content is too high, and the content of the silicon in the steel plate is controlled to be 0.25-0.45%.
P is a harmful element, increases the cold brittleness of steel, deteriorates the plasticity and the welding performance, and is reduced as much as possible, and the phosphorus content is controlled below 0.008 percent.
S: sulfur is a harmful element, increases the hot brittleness of steel, reduces the toughness and the ductility, is unfavorable for welding performance, and should be reduced as much as possible, and the sulfur content of the steel is controlled below 0.002 percent.
Cu: copper has certain precipitation strengthening effect, but too high content can weaken the grain boundary, leads to the steel sheet surface to appear star crackle, and this patent copper content control is at 0.10 ~ 0.30%.
Ni can refine ferrite grains, obviously improve low-temperature impact toughness under the condition of the same strength, and can eliminate the adverse effect of Cu on steel, and meanwhile, the combination and matching of Ni and Cu can prevent the strength of the steel plate from being greatly reduced after the simulated postweld heat treatment. As Ni is a scarce resource, the production cost is increased by adding Ni element into steel, the use is controlled, and the content of nickel in the steel is controlled to be 0.10-0.30%.
Nb, Ti: niobium microalloy element and C, N element form carbonitride, which has the functions of delaying austenite recrystallization and refining ferrite grains, and can simultaneously improve the strength and toughness of the steel plate, wherein the Nb content is controlled to be 0.02-0.05%, and the Ti content is controlled to be 0.01-0.05%.
AL: the aluminum is mainly used for deoxidation and grain refinement, and the content of Al in the aluminum alloy is controlled to be 0.02-0.05%.
Another object of the present invention is to provide a method for manufacturing a Q345R steel sheet having excellent performance under high temperature simulated post-weld heat treatment conditions, which comprises the following steps:
in order to improve the rolling reduction ratio, a continuous casting slab with a section of 370mm/450mm is used as a blank, preferably a billet with the thickness of 450mm, the main production process comprises a smelting process, a rolling process and a heat treatment process, wherein the rolling process adopts two-stage rolling, the heat treatment process adopts normalizing process treatment, and the main process comprises the following specific operations:
1) smelting process
Smelting raw materials are sequentially subjected to KR molten iron pretreatment, converter smelting, LF refining, RH vacuum degassing treatment and slab continuous casting procedures, slag skimming treatment is carried out after converter smelting, calcium treatment is carried out after LF refining is finished, the RH vacuum treatment ultimate vacuum degree is less than or equal to 65Pa, the vacuum pressure maintaining time is more than or equal to 20min, the soft argon blowing time at the bottom of a steel ladle is more than or equal to 15min, molten steel is killed before pouring, the calming time is more than or equal to 25min, the nonmetal inclusions are ensured to be fully denatured and float into slag, and the purity of the molten steel is improved; the continuous casting process adopts low superheat degree and argon protection pouring in the whole process, and the continuous casting process adopts a dynamic soft reduction technology to reduce the defects of casting blank segregation and looseness. And stacking and slowly cooling the plate blank for more than 48 hours after the plate blank is off-line, and ensuring that hydrogen in the steel is fully diffused.
2) Heating step
Adopting a sectional heating mode: the temperature of the second heating section is controlled to be 1210-1250 ℃, the temperature of the soaking section is controlled to be 1190-1250 ℃, the total heating time of the continuous casting slab with the 370mm section is not less than 8h, the total heating time of the second heating section and the soaking section is not less than 120min, the total heating time of the continuous casting slab with the 450mm section is not less than 10h, and the total heating time of the second heating section and the soaking section is not less than 200min, so that the core of the casting slab is heated to the target temperature and uniformly and thoroughly burnt.
3) Rolling process
Rolling the heated billet by two stages, wherein the first stage is a rough rolling stage and adopts a high-temperature high-reduction process, and the reduction of at least two times of single pass is more than or equal to 50 mm; and the second stage is a finish rolling stage, the thickness of the dried steel is more than or equal to 2.5 times of the thickness of the finished steel plate, the accumulated reduction rate is more than or equal to 50%, the final rolling temperature is controlled to be 780-820 ℃, ACC is adopted for rapid cooling after rolling, the final cold red return temperature is 630-670 ℃, the steel plate is rapidly off-line stacked and slowly cooled for more than or equal to 48 hours, and hydrogen is fully diffused.
4) Thermal treatment
Adopting a normalizing process, wherein the normalizing temperature is 870 ℃ and 910 ℃, and the heat preservation time is as follows: 1.8min/mm, cooling the steel plate on a cooling bed after the steel plate is discharged from the furnace, wherein the minimum distance between the steel plates is 2 meters for ensuring the cooling effect, and the surface temperature of the steel plate is less than or equal to 200 ℃ on line.
Compared with the prior art, the invention has the following characteristics:
the invention relates to a Q345R steel plate with excellent performance under the high-temperature simulated postweld heat treatment condition, which can be applied to the manufacturing of important structural components in the petrochemical industry, has good internal quality, still has excellent mechanical property under the high-temperature simulated postweld heat treatment condition of 700 +/-10 ℃, is delivered in a normalized state, has low surface Brinell hardness and good matching of simulated postweld heat treatment state strength and impact toughness, and can completely meet the development requirement of the petrochemical industry.
In order to achieve the purpose, the invention adopts 370mm/450mm large-thickness high-quality continuous casting plate blank to produce, under the same condition, the 450mm section continuous casting plate blank is preferentially selected, the internal quality and the mechanical property of the steel plate are improved by reasonable component design, the steel rolling compression ratio and the molten steel purity are improved, and the subsequent heat treatment cooling condition is controlled, and each process needs to strictly control the production process.
In the aspect of steel plate component design, on the basis of fully considering the welding performance of the steel plate, the strength of the steel plate is improved by improving the content of solid solution strengthening elements such as C, Mn and Si and the content of fine crystal strengthening elements Nb and Ti, the toughness of the steel plate is improved by adding Ni elements, and meanwhile, the Ni and Cu elements are added in a combined manner, so that the adverse effect of the Cu elements on the surface quality of the steel plate can be eliminated, and the strength and the toughness of the steel plate after high-temperature simulated postweld heat treatment can not be greatly reduced.
In the steelmaking process, calcium treatment is arranged before an RH process, and after the RH process is broken, enough calming time is ensured on the basis of ensuring certain soft argon blowing time at the bottom of a ladle, so that secondary oxidation of molten steel can be prevented, nonmetallic inclusions are fully denatured and float upwards, and the purity of the molten steel is effectively improved.
The casting blank is heated in a sectional heating mode, the total time of the second heating section and the soaking section is prolonged, the core part of the casting blank can be completely burnt, the internal temperature and the external temperature are uniform, and favorable conditions are created for the implementation of a high-temperature high-pressure rolling process in the rough rolling stage.
The rolling procedure adopts two-stage rolling, the rough rolling stage adopts a high-reduction rolling process, and rolling passes are reasonably distributed, so that the main purpose is to press loose defects in steel and ensure the internal quality of a steel plate; in the finish rolling stage, the crystal grains are refined by controlling the finish rolling temperature, the accumulated reduction rate, cooling after rolling and other measures, so that organization preparation is made for normalizing treatment.
The heat treatment process of the steel plate adopts a normalizing process, the cooling condition after the steel plate is discharged is crucial to the performance of the steel plate, the steel plate is cooled on a cooling bed after the steel plate is discharged, the minimum distance between the steel plates is controlled to be 2 meters, and the steel plate is cooled at the surface temperature of less than or equal to 200 ℃ so as to effectively prevent the crystal grains of the steel plate from being coarsened and ensure the normalized steel plate to have higher strength and impact toughness.
Detailed Description
The present invention will be described in further detail with reference to examples.
Example 1
The thickness of the steel plate in the embodiment is 20mm, and the steel plate comprises the following chemical components in percentage by weight: the chemical components of the material by weight percentage are as follows: c: 0.165%, Si: 0.41%, Mn: 1.42%, P: 0.006%, S: 0.001%, Al: 0.032%, Nb: 0.030%, Ti: 0.015%, Ni: 0.22%, Cu: 0.20 percent, the balance being Fe and inevitable impurity elements, 0.435 percent of carbon equivalent Ceq, and the calculation formula of the carbon equivalent is as follows: ceq ═ C + Mn/6+ (Cr + Mo + V)/5+ (Ni + Cu)/15.
The manufacturing process of the steel plate comprises the following steps:
a continuous casting slab with a section of 370mm is used as a blank, and the main process comprises the following specific operations:
1) smelting process
Smelting raw materials are sequentially subjected to KR molten iron pretreatment, converter smelting, LF refining, RH vacuum degassing treatment and slab continuous casting. Slagging-off treatment is carried out after smelting in a converter, calcium treatment is carried out after LF refining is finished, the ultimate vacuum degree of RH vacuum treatment is 62Pa, the vacuum pressure maintaining time is 22min, the soft argon blowing time at the bottom of a steel ladle is 18min, and the calming time before pouring is 28min, so that the nonmetal inclusions are ensured to be fully denatured and float into slag, and the purity of molten steel is improved; in the continuous casting process, low superheat degree is adopted for whole-process argon protection pouring, and the segregation and loosening defects of the casting blank are reduced by a dynamic soft reduction technology. And stacking and slowly cooling the plate blank for more than 48 hours after the plate blank is off-line, and ensuring that hydrogen in the steel is fully diffused.
2) Heating step
Adopting a sectional heating mode: the temperature of the second heating section is 1242 ℃, the temperature of the soaking section is 1235 ℃, the total heating time of the continuous casting slab is 8.5h, and the total heating time of the second heating section and the soaking section is 142min, so that the core of the casting slab is heated to the target temperature and is uniformly and thoroughly burnt.
3) Rolling process
Two-stage rolling is adopted, the first stage is a rough rolling stage, a high-temperature large-reduction process is adopted, 4 single-pass reduction amounts of longitudinal rolling passes are more than or equal to 50mm, and are respectively 55mm, 52mm, 55mm and 56 mm; the second stage is a finish rolling stage, the airing thickness is 3.5 times of the thickness of a finished steel plate, the accumulated reduction rate is 62%, the finish rolling temperature is 815 ℃, ACC is rapidly cooled after rolling, the finish cooling temperature is 652 ℃, the steel plate is rapidly off-line, stacked and slowly cooled for more than or equal to 48 hours, and hydrogen is fully diffused.
4) Heat treatment Process
Adopting a normalizing process, wherein the normalizing temperature is 890 ℃, and the heat preservation time coefficient is as follows: 1.8min/mm, cooling the steel plates on a cooling bed after the steel plates are discharged from the furnace, wherein the minimum distance between the steel plates is 2 meters in order to ensure the cooling effect, and the surface temperature of the steel plates is less than or equal to 200 ℃ on the lower line.
The Q345R steel plate with the thickness of 20mm prepared by the manufacturing process can meet the I-grade qualification of NB/T47013.3 standard, has excellent mechanical properties in a delivery state and under the high-temperature simulated postweld heat treatment condition, and is detailed in tables 1 and 2.
Example 2
The thickness of the steel plate in the embodiment is 50mm, and the steel plate comprises the following chemical components in percentage by weight: c: 0.16%, Si: 0.42%, Mn: 1.42%, P: 0.005%, S: 0.0008%, Al: 0.034%, Nb: 0.032%, Ti: 0.016%, Ni: 0.25%, Cu: 0.21 percent, the balance being Fe and inevitable impurity elements, 0.44 percent of carbon equivalent Ceq, and the calculation formula of the carbon equivalent is as follows: ceq ═ C + Mn/6+ (Cr + Mo + V)/5+ (Ni + Cu)/15.
The manufacturing process of the steel plate comprises the following steps:
a continuous casting slab with a section of 450mm is used as a blank, and the main procedures are as follows:
1) smelting process
Smelting raw materials are sequentially subjected to KR molten iron pretreatment, converter smelting, LF refining, RH vacuum degassing treatment and slab continuous casting. Slagging-off treatment is carried out after smelting in a converter, calcium treatment is carried out after LF refining is finished, the ultimate vacuum degree of RH vacuum treatment is 60Pa, the vacuum pressure maintaining time is 25min, the soft argon blowing time at the bottom of a steel ladle is 16min, and the calming time before pouring is 30min, so that the nonmetal inclusions are ensured to be fully denatured and float into furnace slag, and the purity of molten steel is improved; in the continuous casting process, low superheat degree is adopted for whole-process argon protection pouring, and the segregation and loosening defects of the casting blank are reduced by a dynamic soft reduction technology. And stacking and slowly cooling the plate blank for more than 48 hours after the plate blank is off-line, and ensuring that hydrogen in the steel is fully diffused.
2) Heating step
Adopting a sectional heating mode: the temperature of the second heating section is 1245 ℃, the temperature of the soaking section is 1238 ℃, the total heating time of the continuous casting slab is 11h, and the total heating time of the second heating section and the soaking section is 215min, so that the core of the casting slab is heated to the target temperature and uniformly and thoroughly burnt.
3) Rolling process
Two-stage rolling is adopted, the first stage is a rough rolling stage, a high-temperature large-reduction process is adopted, 4 single-pass reduction amounts of longitudinal rolling passes are more than or equal to 50mm and are respectively 52mm, 55mm and 55 mm; the second stage is a finish rolling stage, the airing thickness is 3.0 times of the thickness of a finished steel plate, the accumulated reduction rate is 65%, the finish rolling temperature is 810 ℃, the ACC is rapidly cooled after rolling, the finish cooling temperature is 645 ℃, the steel plate is rapidly off-line, stacked and slowly cooled for more than or equal to 48 hours, and hydrogen is fully diffused.
4) Heat treatment Process
Adopting a normalizing process, wherein the normalizing temperature is 890 ℃, and the heat preservation time coefficient is as follows: 1.8min/mm, cooling the steel plates on a cooling bed after the steel plates are discharged from the furnace, wherein the minimum distance between the steel plates is 2 meters in order to ensure the cooling effect, and the surface temperature of the steel plates is less than or equal to 200 ℃ on the lower line.
The Q345R steel plate with the thickness of 50mm prepared by the manufacturing process can meet the I-grade qualification of NB/T47013.3 standard, has excellent mechanical properties in a delivery state and under the high-temperature simulated postweld heat treatment condition, and is detailed in tables 1 and 2.
Example 3
The thickness of the steel plate in the embodiment is 100mm, and the steel plate comprises the following chemical components in percentage by weight: c: 0.17%, Si: 0.45%, Mn: 1.45%, P: 0.005%, S: 0.0005%, Al: 0.035%, Nb: 0.035%, Ti: 0.014%, Ni: 0.23%, Cu: 0.22 percent, the balance of Fe and inevitable impurity elements, 0.445 percent of carbon equivalent Ceq, and the calculation formula of the carbon equivalent is as follows: ceq ═ C + Mn/6+ (Cr + Mo + V)/5+ (Ni + Cu)/15.
The manufacturing process of the steel plate comprises the following steps:
a continuous casting slab with a section of 450mm is used as a blank, and the main procedures are as follows:
1) smelting process
Smelting raw materials are sequentially subjected to KR molten iron pretreatment, converter smelting, LF refining, RH vacuum degassing treatment and slab continuous casting. Slagging-off treatment is carried out after smelting in a converter, calcium treatment is carried out after LF refining is finished, the ultimate vacuum degree of RH vacuum treatment is 60Pa, the vacuum pressure maintaining time is 25min, the soft argon blowing time at the bottom of a steel ladle is 20min, and the calming time before pouring is 30min, so that the nonmetal inclusions are ensured to be fully denatured and float into furnace slag, and the purity of molten steel is improved; in the continuous casting process, low superheat degree is adopted for whole-process argon protection pouring, and the segregation and loosening defects of the casting blank are reduced by a dynamic soft reduction technology. And stacking and slowly cooling the plate blank for more than 48 hours after the plate blank is off-line, and ensuring that hydrogen in the steel is fully diffused.
2) Heating step
Adopting a sectional heating mode: the temperature of the second heating section is 1241 ℃, the temperature of the soaking section is 1238 ℃, the total heating time of the continuous casting slab is 11.5h, and the total heating time of the second heating section and the soaking section is 225min, so that the core of the casting slab is heated to the target temperature and uniformly and thoroughly burnt.
3) Rolling process
Two-stage rolling is adopted, the first stage is a rough rolling stage, a high-temperature high-pressure reduction process is adopted, and 2 single-pass reduction amounts of longitudinal rolling passes are more than or equal to 50mm, namely 55mm and 55mm respectively; the second stage is a finish rolling stage, the airing thickness is 2.5 times of the thickness of a finished steel plate, the accumulated reduction rate is 48%, the finish rolling temperature is 808 ℃, ACC is rapidly cooled after rolling, the finish cooling temperature is 642 ℃, the steel plate is rapidly off-line stacked and slowly cooled for more than or equal to 48 hours, and hydrogen is fully diffused.
4) Heat treatment Process
Adopting a normalizing process, wherein the normalizing temperature is 905 ℃, and the heat preservation time coefficient is as follows: 1.8min/mm, cooling the steel plates on a cooling bed after the steel plates are discharged from the furnace, wherein the minimum distance between the steel plates is 2 meters in order to ensure the cooling effect, and the surface temperature of the steel plates is less than or equal to 200 ℃ on the lower line.
The Q345R steel plate with the thickness of 100mm prepared by the manufacturing process can meet the I-grade qualification of NB/T47013.3 standard, has excellent mechanical properties in a delivery state and under the high-temperature simulated postweld heat treatment condition, and is detailed in tables 1 and 2.
TABLE 1 mechanical Properties of the steel sheets produced in the examples
Note: () The average value is shown in the specification, and the sample blank simulation postweld heat treatment system comprises: the temperature of the furnace is increased to 700 ℃ for 12h, the temperature of the furnace is increased or decreased to 400 ℃, and the temperature rising and decreasing speed is less than or equal to 50 ℃/h.
TABLE 2 Brinell hardness of the surface of the steel sheet produced in each example
Note: () The average value is shown in the specification, and the sample blank simulation postweld heat treatment system comprises: the temperature of the furnace is increased to 700 ℃ for 12h, the temperature of the furnace is increased or decreased to 400 ℃, and the temperature rising and decreasing speed is less than or equal to 50 ℃/h.
In addition to the above embodiments, the present invention also includes other embodiments, and any technical solutions formed by equivalent transformation or equivalent replacement should fall within the scope of the claims of the present invention.

Claims (5)

1. A manufacturing method of a Q345R steel plate with excellent performance under high-temperature simulated postweld heat treatment conditions is characterized by comprising the following steps:
the method is characterized in that a continuous casting slab with a section of 370mm/450mm is used as a blank, and the main production procedures comprise a smelting procedure, a rolling procedure and a heat treatment procedure, wherein the rolling procedure adopts two-stage rolling, and the heat treatment procedure adopts a normalizing process for treatment; the main process comprises the following specific operations:
1) smelting process
Smelting raw materials are sequentially subjected to KR molten iron pretreatment, converter smelting, LF refining, RH vacuum degassing treatment and slab continuous casting procedures, slag removal treatment is carried out after converter smelting, calcium treatment is carried out after LF refining is finished, the RH vacuum treatment ultimate vacuum degree is less than or equal to 65Pa, the vacuum pressure maintaining time is more than or equal to 20min, the soft argon blowing time at the bottom of a steel ladle is more than or equal to 15min, molten steel is calmed before casting, the calmed time is more than or equal to 25min, the nonmetal inclusions are ensured to be fully denatured and float into slag, the purity of the molten steel is improved, and the chemical components of the obtained molten steel are calculated as: 0.16-0.20%, Si: 0.25 to 0.45%, Mn: 1.40-1.60%, P: less than or equal to 0.008 percent, S: less than or equal to 0.002%, Al: 0.02-0.05%, Nb: 0.02-0.05%, Ti: 0.01-0.05%, Ni: 0.10-0.30%, Cu: 0.10 to 0.30% by weight, and the balance of Fe and inevitable impurity elements; in the continuous casting process, low-superheat-degree argon protection pouring is adopted in the whole process, and the slabs are stacked and slowly cooled for more than 48 hours after being off-line, so that hydrogen in steel is fully diffused;
2) heating step
Adopting a sectional heating mode: controlling the temperature of the second heating section to be 1210-1250 ℃, the temperature of the soaking section to be 1190-1250 ℃, the total heating time of the continuous casting slab with the 370mm section to be more than or equal to 8h, the total heating time of the second heating section and the soaking section to be more than or equal to 120min, the total heating time of the continuous casting slab with the 450mm section to be more than or equal to 10h, and the total heating time of the second heating section and the soaking section to be more than or equal to 200min, so as to ensure that the core part of the casting slab is heated to the;
3) rolling process
Rolling the heated billet by two stages, wherein the first stage is a rough rolling stage and adopts a high-temperature high-reduction process, and the reduction of at least two times of single pass is more than or equal to 50 mm; the second stage is a finish rolling stage, the thickness of the dried steel is more than or equal to 2.5 times of the thickness of a finished steel plate, the accumulated reduction rate is more than or equal to 50%, the final rolling temperature is controlled to be 780-820 ℃, ACC is adopted for rapid cooling after rolling, the final cold red return temperature is 630-670 ℃, the steel plate is rapidly off-line stacked and slowly cooled for more than or equal to 48 hours, and hydrogen is fully diffused;
4) thermal treatment
Adopting a normalizing process, wherein the normalizing temperature is 870 ℃ and 910 ℃, and the heat preservation time is as follows: 1.8min/mm, cooling the steel plate on a cooling bed after the steel plate is discharged from the furnace, wherein the minimum distance between the steel plates is 2 meters for ensuring the cooling effect, and the surface temperature of the steel plate is less than or equal to 200 ℃ on line.
2. The method for manufacturing a Q345R steel sheet having excellent performance under high-temperature simulated post-weld heat treatment conditions according to claim 1, wherein: and (3) in the continuous casting process in the step (1), the defects of casting blank segregation and porosity are reduced by adopting a dynamic soft reduction technology.
3. The method for manufacturing a Q345R steel sheet having excellent performance under high-temperature simulated post-weld heat treatment conditions according to claim 1, wherein: the chemical components of the steel plate meet that the carbon equivalent Ceq is less than or equal to 0.45 percent, and the calculation formula of the carbon equivalent is as follows: ceq = C + Mn/6+ (Cr + Mo + V)/5+ (Ni + Cu)/15.
4. The method for manufacturing a Q345R steel sheet having excellent performance under high-temperature simulated post-weld heat treatment conditions according to claim 1, wherein: the thickness of the steel plate is 20-100mm, the steel plate is in a normalized delivery state, the Brinell hardness of the surface of the steel plate in the delivery state is less than or equal to 170HB, after high-temperature simulated postweld heat treatment, the transverse impact energy at the 1/2-30 ℃ position of the steel plate can meet the requirements that the single value is more than or equal to 100J, the yield strength is more than or equal to 325MPa, the tensile strength is more than or equal to 500MPa, the elongation A after fracture is more than or equal to 25.0 percent, and the flaw detection of the steel plate can meet the.
5. The method for manufacturing a Q345R steel sheet having excellent performance under high-temperature simulated post-weld heat treatment conditions according to claim 1, wherein: the temperature involved in the high-temperature simulated postweld heat treatment is 700 +/-10 ℃.
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