CN118653109A - A method for avoiding delayed cracking of low alloy high strength steel plate after cutting - Google Patents

A method for avoiding delayed cracking of low alloy high strength steel plate after cutting Download PDF

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Publication number
CN118653109A
CN118653109A CN202411118541.4A CN202411118541A CN118653109A CN 118653109 A CN118653109 A CN 118653109A CN 202411118541 A CN202411118541 A CN 202411118541A CN 118653109 A CN118653109 A CN 118653109A
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temperature
steel plate
cutting
section
rolling
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CN118653109B (en
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徐海健
韩楚菲
纪汶伯
王小强
杨雨泽
田洪鑫
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Angang Steel Co Ltd
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Angang Steel Co Ltd
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/54—Ferrous alloys, e.g. steel alloys containing chromium with nickel with boron
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/10—Supplying or treating molten metal
    • B22D11/11—Treating the molten metal
    • B22D11/114—Treating the molten metal by using agitating or vibrating means
    • B22D11/115—Treating the molten metal by using agitating or vibrating means by using magnetic fields
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/16—Controlling or regulating processes or operations
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/16—Controlling or regulating processes or operations
    • B22D11/22—Controlling or regulating processes or operations for cooling cast stock or mould
    • B22D11/225—Controlling or regulating processes or operations for cooling cast stock or mould for secondary cooling
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/0056—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00 using cored wires
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/04—Removing impurities by adding a treating agent
    • C21C7/06—Deoxidising, e.g. killing
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/04—Removing impurities by adding a treating agent
    • C21C7/064—Dephosphorising; Desulfurising
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING 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
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/18—Hardening; Quenching with or without subsequent tempering
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING 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
    • C21D8/00—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING 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
    • C21D8/00—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0226—Hot rolling
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING 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
    • C21D8/00—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0247—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C33/00—Making ferrous alloys
    • C22C33/04—Making ferrous alloys by melting
    • C22C33/06—Making ferrous alloys by melting using master alloys
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/50—Ferrous alloys, e.g. steel alloys containing chromium with nickel with titanium or zirconium
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING 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
    • C21D2261/00—Machining or cutting being involved
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/20—Recycling

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  • Chemical & Material Sciences (AREA)
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  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Heat Treatment Of Steel (AREA)

Abstract

本发明涉及一种避免低合金高强钢板切割后产生延迟裂纹的方法，钢板化学成分为：C 0.14%～0.19%，Si 0.15%～0.35%，Mn 1.05%～1.45%，P≤0.02%，S≤0.005%，Nb 0.010%～0.040%，Ti 0.010%～0.025%，Mo 0.5%～0.8%，Als 0.02%～0.05%，Ca 0.005%～0.010%，B 0.0008%～0.0018%，Cr 0.3%～0.5%，Ni 0.3%～0.5%，余量为Fe和杂质。钢板的生产工艺过程包括：钢水冶炼、炉外精炼+RH真空脱气、微Ti处理、B合金化、连铸、铸坯进坑加热缓冷、铸坯再加热、控制控冷、热矫直、钢板堆垛缓冷、淬火、回火及切割。本发明有效解决了钢切割后产生延迟裂纹的问题。The invention relates to a method for preventing delayed cracks from being generated after cutting a low alloy high strength steel plate. The chemical composition of the steel plate is as follows: C 0.14%-0.19%, Si 0.15%-0.35%, Mn 1.05%-1.45%, P≤0.02%, S≤0.005%, Nb 0.010%-0.040%, Ti 0.010%-0.025%, Mo 0.5%-0.8%, Als 0.02%-0.05%, Ca 0.005%-0.010%, B 0.0008%-0.0018%, Cr 0.3%-0.5%, Ni 0.3%-0.5%, and the balance is Fe and impurities. The production process of steel plate includes: molten steel smelting, refining outside the furnace + RH vacuum degassing, micro-Ti treatment, B alloying, continuous casting, heating and slow cooling of the ingot, reheating of the ingot, controlled cooling, hot straightening, slow cooling of steel plate stacking, quenching, tempering and cutting. The present invention effectively solves the problem of delayed cracking after steel cutting.

Description

Method for avoiding delayed cracking after cutting of low-alloy high-strength steel plate
Technical Field
The invention relates to the technical field of steel plate surface quality control, in particular to a method for preventing delayed cracking after cutting of a low-alloy high-strength steel plate for 1000 MPa-level engineering machinery with a thickness specification of 40-80 mm.
Background
In recent years, with the rapid development of industries such as hydropower, engineering machinery, wind power construction and the like, the demand for large-thickness steel plates is increasing. Low alloy high strength steel for engineering machinery is widely used because of low alloy element content (low cost), high strength and high toughness (good comprehensive performance); the later processing process of the steel plate can adopt methods such as laser cutting, plasma cutting, flame cutting and the like for cutting, wherein the thickness of the steel plate corresponding to the laser cutting and the plasma cutting is generally below 40mm, so that certain use limitations exist; flame cutting is widely used because of its low cost, easy operation, high cutting efficiency, and a wide range of thickness of the steel sheet that can be cut. The steel plate for the large-thickness high-strength engineering machinery is often cut by flame, but a flame section is easy to form delayed cracks after flame cutting, no obvious sign exists before the delayed cracks are generated, sudden brittle fracture can be caused after the delayed cracks are expanded, loss is caused for a user, and meanwhile, disastrous results can be caused. The fire section delayed cracking is caused by the fact that the cutting surface of the steel plate is affected by cutting thermal circulation to generate tissue transformation (such as segregation bands and large-size sharp-angle inclusions exist in tissues), hydrogen atoms are easy to capture, and therefore hydrogen embrittlement is initiated and delayed cracking is formed. The development of engineering machinery and other fields is severely restricted by the existence of the problems, and how to solve the problems becomes a matter which needs to be considered urgently by steel manufacturing enterprises.
The Chinese patent of invention with the application number of CN201510453518.5 discloses a control method for avoiding the cutting delay cracks of high-carbon steel with large thickness in winter, which adopts a high-carbon steel plate designed by high C, mn components to perform slow cooling after normalizing treatment and flame cutting, and enters a slow cooling pit for stress relief treatment after flame cutting, thereby reducing the generation of martensitic structure, reducing the stress concentration of the structure and avoiding the occurrence of stress delay cracks after flame cutting; however, the high-carbon steel plate after being cut by fire is put into a slow cooling pit or a single furnace with the temperature of 300-350 ℃, and is cooled to below 100 ℃ along with the furnace after being preserved for 1.5-2.5 hours, which tends to increase the production cost of users.
The Chinese patent application with the application number of CN202210040898.X discloses a method for preventing cutting delay cracks of large-thickness low-alloy martensitic steel, which adopts reasonable content proportion of Ti, nb, mo, al and B elements to control the hardenability and inclusion size of the large-thickness steel plate; in addition, the secondary quenching and low-temperature tempering heat treatment process is adopted, so that the formation and the expansion of delayed cracks are avoided; the steel plate is cut by flame, the steel plate is preheated before flame cutting, and after wind-shielding cutting, refractory heat-insulating cotton is covered or moved into a heat-insulating pit for slow cooling, so that delayed cracks caused by stress after cutting are effectively avoided, but the thickness of the limited steel plate is 70mm at maximum, the requirement on the Ti/N ratio is strict, and in addition, the secondary quenching process is adopted, so that the heat treatment production cost is increased.
Disclosure of Invention
The invention provides a method for avoiding delayed cracking after cutting of a low-alloy high-strength steel plate, which aims at the high-strength steel plate for engineering machinery with the thickness specification of more than 1000MPa grade of 40-80 mm, and adopts the method for optimizing continuous casting, heating, rolling, heat treatment and cutting processes, so that the problem of delayed cracking after cutting of the steel is effectively solved, and the cut steel plate does not have delayed cracking after being placed for more than 60 days.
In order to achieve the above purpose, the invention is realized by adopting the following technical scheme:
A method for avoiding delayed cracking after cutting low-alloy high-strength steel plate comprises controlling chemical components of the steel plate and controlling the production process of the steel plate; the steel plate comprises the following chemical components in percentage by weight, wherein the balance of ：C 0.14%～0.19%,Si 0.15%～0.35%,Mn 1.05%～1.45%,P≤0.02%,S≤0.005%,Nb 0.010%～0.040%,Ti 0.010%～0.025%,Mo 0.5%～0.8%,Als 0.02%～0.05%,Ca 0.005%～0.010%,B 0.0008%～0.0018%,Cr 0.3%～0.5%,Ni 0.3%～0.5%, is Fe and unavoidable impurities, and the total amount of impurity elements is less than 0.05%; the production process of the steel plate comprises the following steps: molten steel smelting, external refining +RH vacuum degassing, micro Ti treatment, B alloying, continuous casting, casting blank pit heating and slow cooling, casting blank reheating, control cooling, hot straightening, steel plate stacking and slow cooling, quenching, tempering and cutting.
Further, the production process of the steel plate comprises the following steps:
1) Smelting molten steel until casting blank enters a pit, heating and slowly cooling:
Controlling the S content to be lower than 0.015% during molten iron pretreatment, controlling the P content to be less than or equal to 0.02% during converter smelting, and controlling the C content at the end point of converter smelting to be 0.14% -0.19%; argon is blown for 25-35 min when tapping in the converter; in the LF refining process, si-Ca wires are fed for external refining treatment; maintaining RH vacuum degassing for more than 25min, adding Al according to Als content requirement after degassing treatment, adding Ti-Fe for micro Ti treatment, and adding B-Fe alloy for B alloying; the superheat degree is controlled to be 15-25 ℃ during continuous casting, and the continuous casting blank drawing speed is 0.8-1.3 m/min; the electromagnetic stirring current intensity of the secondary cooling zone in the continuous casting stage is 100-150A, and the secondary cooling specific water quantity is 1.3-2.0L/kg; casting blank rolling reduction is 30-45 mm after heavy rolling is put into the horizontal sector section, namely the solidification tail end; slowly cooling the casting blank after the casting blank is taken off line, wherein the temperature of pit entering is not lower than 600 ℃, the slow cooling temperature is 600-650 ℃, the slow cooling time is 48-72 h, and discharging the casting blank after the temperature in the pit is reduced to be lower than 150 ℃;
2) Reheating the casting blank: the temperature of the preheating section is 900-1050 ℃, the temperature of the soaking section and the temperature of the heating section are 1225-1250 ℃, the total heating time of the soaking section and the heating section is 4-5.5 h, and the total furnace time is 6-8 h;
3) Rolling and cooling control and hot straightening: rolling is carried out in two stages: the initial rolling temperature of rough rolling is not less than 1120 ℃, and the final rolling temperature of rough rolling is 980-1025 ℃; rough rolling is not more than 6 times, and the reduction rate of at least the first 2 times is more than 15%; spraying at least 2 times of descaling water in the intermediate blank temperature waiting process, wherein the descaling time of each time is 1-2 min, and the descaling water pressure is 15-20 MPa; the finish rolling temperature is 860-920 ℃, and the finish rolling temperature is 820-850 ℃; finish rolling is not more than 6 times, and the reduction rate of at least the first 2 times is more than 20%; the finish rolling stage adopts slow rolling with the rolling speed of 1-2 m/s; the straightening temperature of hot straightening is 750-800 ℃, the straightening force is 3000-4500 kN, the roll bending amount is 1.2-1.8 mm, and the tilting value is 3.5-5.5 mm;
4) Stacking and slow cooling of steel plates: immediately stacking and slowly cooling after the hot straightening is finished, wherein the stacking temperature is not lower than 400 ℃, and the slowly cooling time is not less than 48 hours;
5) Quenching; the quenching heating comprises a low-temperature section, a high-temperature section and a cooling section; the temperature of the low temperature section is 620-680 ℃, and the time of the low temperature section in the furnace is 2.0-3.5 min/mm; the temperature of the high temperature section is 880-920 ℃, and the time of the high temperature section in the furnace is 1.5-1.8 min/mm; the temperature of the cooling section is 760-810 ℃, and the time of the cooling section in the furnace is 0.5-0.9 min/mm; the quenching average cooling speed is 20-45 ℃/s; the quenching finishing temperature is 180-250 ℃;
6) Tempering; the tempering heating temperature is 150-180 ℃, and the tempering heat preservation time is 2.0-3.5 min/mm;
7) Cutting; the preheating temperature of the steel plate is 100-200 ℃, the cutting is carried out at normal temperature, the energy of a welding line is controlled below 20kJ/cm during the cutting, the cutting edge and a heat affected zone are covered by an asbestos cloth heat-insulating blanket after the cutting, and the steel plate is slowly cooled to room temperature.
Further, the finished steel plate is more than 1000MPa grade steel plate.
Further, the thickness of the finished steel plate is 40-80 mm; the thickness of the casting blank is 250-300 mm; the thickness of the intermediate blank is 2.5-3.5 times of the thickness of the finished steel plate.
Further, in the step 7), the steel plate is preheated by a flame gun, an electronic heating pad or a heating furnace.
Compared with the prior art, the invention has the beneficial effects that:
1) Argon blowing and sedation are adopted before continuous casting and during converter tapping, so that the removal of inclusions in molten steel is promoted, and the uniformity of molten steel components is improved; in the external refining process, si-Ca wires are fed for external refining treatment, so that the oxygen and sulfur content in molten steel can be effectively reduced, sulfide and oxide inclusions are changed into calcium-containing spherical inclusions, and the number of inclusions is reduced, thereby achieving the purposes of purifying molten steel, improving the quality of steel and reducing the local internal stress of the steel plate during rolling. Quality defects of the core part and the corner part of the casting blank can be effectively reduced by controlling the continuous casting superheat degree and the blank drawing rate; the average index of carbon segregation can be reduced by optimizing the current intensity of electromagnetic stirring in the secondary cooling area and the secondary cooling specific water quantity, so that segregation is inhibited; by limiting the secondary cooling strength, the tendency of the crack in the center of the cast slab to deteriorate is suppressed. The steel billet segregation can be reduced by being put under heavy pressure, austenite grains are refined, and internal structure defects are reduced; the casting blank enters the pit and is slowly cooled, so that the center segregation of the casting blank is reduced, and the H content in the casting blank is effectively reduced.
2) When the casting blank is heated, the carbide of Ti and Nb is ensured to be quickly and fully dissolved in the matrix by controlling the temperature of the preheating section, and fully diffused; the high heating temperature is adopted, the in-furnace time and the total in-furnace time of the soaking section and the heating section are ensured, elements such as C, mn, mo, H are effectively promoted to be fully diffused, and the tissue uniformity of the rolled steel plate is ensured.
3) Adopting a two-stage control rolling process, and ensuring that the intermediate billet temperature waiting process is in an austenite recrystallization temperature range by controlling the final rolling temperature in the rough rolling stage, ensuring the tissue uniformity, limiting the rolling reduction rate of two-stage rolling and the thickness of the intermediate billet, and ensuring the tissue uniformity of the rolled steel plate in the thickness direction; the scale water is sprayed in the process of waiting for the temperature of the intermediate blank, so that the growth of austenite grains can be restrained, meanwhile, the temperature gradient is generated on the inner surface and the outer surface of the steel blank, the penetration of rolling deformation to the thickness center is promoted, the grains at the 1/2 thickness position are thinned, the improvement of the core structure of the thick steel plate is facilitated, and the structure stress generated by the uneven structure is reduced; the deformation penetration quantity of the core part of the steel plate is improved by adopting slow rolling, so that the tissue uniformity is further improved; meanwhile, the straightening process parameters are optimized, and the internal stress is promoted to be fully released.
4) The hot straightened steel plate adopts stacking slow cooling, and simultaneously limits the slow cooling time and temperature so as to accelerate the diffusion of C, mn and H elements in the core part of the steel plate, inhibit the segregation of the C, mn and H elements and slow down the poor structural stress of the core part of the steel plate and the occurrence of hydrogen induced cracks of the steel plate.
5) The quenching and heating of the steel plate comprises a low-temperature section, a high-temperature section and a cooling section. The temperature of the low-temperature section and the furnace time are controlled, and the purpose of the method is to continuously promote outward diffusion of H element in the steel plate and reduce the H content of the steel plate on one hand, and promote massive precipitation of Nb and Ti composite carbides through long-time heat preservation on the other hand, and the carbides provide massive hydrogen traps for the interior of the steel plate. The high temperature section temperature and the furnace time are limited, and the purpose of the method is to rapidly heat the steel plate to the austenitizing temperature, provide tissue guarantee for obtaining martensite for subsequent quenching of the steel plate, and simultaneously prevent coarsening of crystal grains and coarsening of Nb and Ti composite carbides caused by overhigh temperature, so that the number of hydrogen traps in the steel plate is greatly reduced, and the risk of cracks is increased. The temperature of the cooling section and the furnace time are limited, and the purpose of the cooling section is to enable austenite to be reduced to be above Ar3 temperature in the cooling section, namely, the full austenitizing state of the steel plate is ensured, the quenched steel plate is fully hardened, meanwhile, the lower the temperature of the steel plate for quenching is, the lower the stress level of the steel plate is in the quenching process, and the cracking condition of the steel plate caused by the quenching process can be avoided. Meanwhile, in order to avoid the occurrence of quenching cracks caused by overlarge steel plate stress due to overlarge cooling speed in the quenching process, the average quenching cooling speed is designed to be 20-45 ℃/s, and the quenching finishing temperature is limited, so that the stress in the steel plate quenching process is reduced, the occurrence of quenching cracks is avoided, and meanwhile, the austenite in the steel plate is ensured to fully complete martensitic transformation.
6) Preheating and cutting the steel plate, limiting the energy of a welding line, and preventing coarsening of a heat affected zone structure caused by overlarge input energy from causing cracks caused by overlarge internal stress after the steel plate is cooled; after cutting, the cutting edge and the heat affected zone are covered by an asbestos cloth heat insulation blanket, the temperature is slowly cooled to the room temperature, the moisture environment is avoided in the slow cooling process, liquids such as water and the like are strictly forbidden, and the aim of preventing the crack caused by tissue stress due to rapid cooling of the cut steel plate is achieved.
7) After the process is adopted, the cut steel plate is placed for more than 60 days, and no delayed crack defect occurs.
Detailed Description
The invention relates to a method for avoiding delayed cracking after cutting a low-alloy high-strength steel plate, which comprises the following chemical components in percentage by weight, wherein the balance of ：C 0.14%～0.19%,Si 0.15%～0.35%,Mn 1.05%～1.45%,P≤0.02%,S≤0.005%,Nb 0.010%～0.040%,Ti 0.010%～0.025%,Mo 0.5%～0.8%,Als 0.02%～0.05%,Ca 0.005%～0.010%,B 0.0008%～0.0018%,Cr 0.3%～0.5%,Ni 0.3%～0.5%, is Fe and unavoidable impurities, and the total content of impurity elements is lower than 0.05%.
The main elements in the steel plate have the following functions:
C: carbon is an important element for ensuring the hardenability of the steel plate, is also an important factor for determining the carbon equivalent, and has great influence on the strength, toughness, plasticity and weldability of the steel. The welding performance of the steel plate is affected by the excessive carbon content. The carbon content is too low, which affects the overall strength of the steel sheet. The invention controls the carbon content to be 0.14-0.19% on the premise of ensuring the strength required by the steel plate.
Si: the deoxidizing essential element has certain solid solution strengthening effect, and the excessive content can affect the toughness, the uniformity of the ultra-thick plate performance and the weldability of the steel, and the silicon content is controlled to be 0.15-0.35 percent in the invention.
Mn: the important solid solution strengthening elements in the steel can reduce the transformation temperature, refine the microstructure, improve the toughness and improve the hardenability while strengthening the steel plate. Too high a manganese content can cause segregation and is detrimental to welding and toughness. The invention controls the manganese content to be 1.05-1.45%.
Ni: can improve the low-temperature toughness and the plasticity of the steel. For extra thick plates, the low-temperature impact performance at 1/4 and 1/2 of the thickness direction can be improved, and the low-temperature impact strength is an indispensable alloy element; ni can also delay pearlite transformation, promote formation of medium-temperature transformation structure, and reduce the limit of cooling speed of thick-specification steel plates. However, the price of nickel is high, and the production cost is comprehensively considered, and the Ni content is controlled to be 0.3-0.5 percent.
Cr: can increase the hardenability of steel, refine the structure and reduce the ductile-brittle transition temperature; chromium and manganese are used together, so that the hardenability of the steel can be improved, and the mechanical properties of the steel can be improved; chromium has smaller segregation tendency than manganese, and partial manganese is replaced by chromium, so that the segregation of the core part of the steel plate can be reduced, the internal quality of the steel plate can be improved, and the uniformity of mechanical properties can be improved; the invention controls the chromium content to be 0.3-0.5%.
Mo: can obviously increase the hardenability and hardenability of steel, refine the microstructure of the quenched steel and improve the toughness. However, molybdenum is a noble alloy, and in order to reduce the production cost and ensure the performance, less molybdenum or no molybdenum can be selected according to the thickness of the steel plate, so that the content of the molybdenum is controlled to be 0.50-0.80%.
Nb: is one of common elements in modern microalloyed steel, has good fine grain strengthening and precipitation strengthening effects, and can delay austenite recrystallization, but excessive Nb can increase production cost and control difficulty of continuous casting process. The invention selects Nb content range of 0.01% -0.04%, and simultaneously, by matching with a reasonable TMCP process, a uniform composite phase mainly based on acicular ferrite structure can be obtained, so that the finished steel plate has good toughness.
Ti: is a strong solid N element, and exists in the form of TiN in the continuous casting billet. The fine TiN particles can effectively inhibit the growth of austenite grains when the continuous casting billet is reheated, and are beneficial to improving the solid solubility of Nb in austenite and improving the impact toughness of a welding heat affected zone. However, when the Ti addition exceeds a certain value, tiN particles coarsen, thereby improving the stress concentration level of the particle interface and the matrix. Therefore, the Ti content is controlled to be in the range of 0.01-0.025%.
B: is an effective element for obviously improving the hardenability of steel, is extremely easy to segregate in grain boundaries, can prevent carbon from being precipitated, and can play an obvious role by a trace amount of boron. When the boron content is too high, boron carbonitride is easy to form, toughness is reduced, thermal embrittlement is caused, and the content range of the boron carbonitride is controlled to be 0.0008-0.0018%.
Ca: the trace amount of calcium can be used as a deoxidizing and desulfurizing purifying agent in steel to improve the morphology of nonmetallic inclusions, and is widely used for calcium treatment of clean steel. By adding trace amounts of calcium elements to the steel, dispersed, thermally stable calcium-containing oxide particles of the second phase can be formed in the steel. The research results show that the dispersed calcium-containing oxide particles pin the austenite grain boundary migration of the CGHAZ in the welding thermal cycle process, limit the growth of austenite grains, obtain finer welding CGHAZ grain size and further improve the toughness of the welding CGHAZ of the micro-calcium steel. However, too high Ca can be biased at grain boundaries to adversely affect the hardenability and impact toughness of steel, and the content of Ca is controlled to be 0.005-0.0010%.
Als: it is usually used as a deoxidizer in steel and has the effect of refining the structure if AlN is formed. When the Al content exceeds 0.05%, excessive aluminum oxide inclusions may reduce the cleanliness of the steel. If the Al content is too low, the deoxidization will be insufficient, and oxides will be formed from easily oxidized elements such as Ti, and the lower limit of the Al content is set to 0.02%.
P, S: an excessively high P, S is an unavoidable impurity element in steel, and affects toughness and welding performance of the steel sheet, so that the lower the amount is, the better. But cannot be unlimited low for smelting process considerations. Therefore, the upper limit of P, S content is set to 0.02% and 0.005% respectively.
The method is suitable for the low-alloy high-strength steel plate for engineering machinery with the thickness specification of 40-80 mm and the strength level of more than 1000MPa, and the whole process flow from molten steel smelting to cutting of the steel plate comprises molten steel smelting, external refining +RH vacuum degassing, micro Ti treatment, B alloying, continuous casting, casting blank pit heating and slow cooling, casting blank reheating, controlled rolling and controlled cooling, hot straightening, steel plate stacking slow cooling, quenching, tempering and steel plate cutting.
The invention mainly controls the following technical processes:
1) Smelting molten steel until casting blank enters a pit, heating and slowly cooling:
pretreating raw materials by KR molten iron, controlling the content of S to be lower than 0.015%, and feeding the raw materials into a converter after slag skimming; the double slag method is adopted for P removal in converter smelting, the P content is controlled to be less than or equal to 0.02 percent, the C content is controlled to be 0.14 to 0.19 percent at the end point of converter smelting, and argon is blown for 25 to 35 minutes when the converter is tapped; the inclusion removal in the molten steel can be promoted by blowing argon and calming before continuous casting, and the uniformity of the molten steel components is improved.
In the process of external refining (LF refining), the Si-Ca wire is fed to conduct external refining treatment on molten steel, so that the content of oxygen and sulfur in the molten steel can be effectively reduced, sulfide and oxide inclusions are changed into calcium-containing spherical inclusions, the number of inclusions is reduced, the purposes of purifying the molten steel and improving the quality of steel are achieved, and the local internal stress of a steel plate during rolling is reduced. RH vacuum degassing is maintained for more than 25 min; after the degassing treatment is finished, adding Al according to the Als content requirement; then adding Ti-Fe to carry out micro-titanium treatment, and adding B-Fe alloy; when the alloy is added, the alloy is ensured to be added into molten steel, and is prevented from floating on a slag layer.
When the slab is continuously cast, the continuous casting superheat degree is controlled to be 15-25 ℃, the continuous casting blank drawing speed is controlled to be 0.8-1.3 m/min, and the quality defects of the central part and the corner part of the casting blank can be effectively reduced through the control of the continuous casting superheat degree and the continuous casting blank drawing speed. The electromagnetic stirring current intensity of the secondary cooling area in the continuous casting stage is controlled to be 100-150A, the secondary cooling specific water quantity is controlled to be 1.3-2.0L/kg, so that the average carbon segregation index is reduced, segregation is inhibited, and meanwhile, the trend of crack deterioration in the center of a casting blank is inhibited by controlling the secondary cooling intensity. Casting under heavy pressure at the solidification end of the horizontal sector section, wherein the rolling reduction of the continuous casting billet is 30-45 mm; the heavy pressure can help to reduce steel billet segregation, refine austenite grains and reduce internal structure defects.
Slowly cooling the casting blank after the casting blank is taken off line, wherein the temperature of the pit entering is not lower than 600 ℃, the slow cooling temperature is 600-650 ℃, the slow cooling time is 48-72 hours, and discharging the casting blank after the temperature in the pit is reduced to 150 ℃; the casting blank enters the pit and is slowly cooled, so that the center segregation of the casting blank is reduced, and the H content in the casting blank is effectively reduced.
2) Reheating the casting blank: feeding a casting blank (with the thickness of 250-300 mm) into a step heating furnace for heating, wherein the temperature interval of a preheating section is 900-1050 ℃, and the aim is to promote carbide of Ti and Nb to be quickly and fully dissolved in a matrix and fully diffused; the temperature of the soaking section and the heating section are 1225-1250 ℃, the total heating time of the soaking section and the heating section is 4-5.5 hours, and the total furnace time is 6-8 hours; the high heating temperature is adopted, meanwhile, the furnace time of the soaking section and the heating section is ensured, the total furnace time is improved, the aim is to effectively promote C, mn, mo, H and other elements to be fully diffused, and the uniformity of the rolled steel plate structure is ensured.
3) Rolling and cooling control and hot straightening:
Rolling in two stages; the first stage is recrystallization rolling (rough rolling), the initial rolling temperature of rough rolling is more than or equal to 1120 ℃, the final rolling temperature range of rough rolling is 980-1025 ℃, the rough rolling is not more than 6 times, and the reduction rate of the first 2 times of pass reduction system is preferably more than 15%. The thickness of the intermediate blank is 2.5-3.5 times of the thickness of the finished steel plate. In the intermediate blank waiting temperature process, 2-pass descaling water is sprayed, the descaling time is 1-2 min, and the pressure of a descaling machine is 15-20 MPa; the method aims to inhibit the growth of austenite grains, simultaneously generate temperature gradients on the inner surface and the outer surface of a steel billet, promote the penetration of rolling deformation to the thickness center, refine the grains at the 1/2 thickness position, improve the core structure of a thick steel plate and reduce the structure stress generated by uneven structure.
The second stage is non-recrystallization rolling (finish rolling), the finish rolling initial temperature range is 860-920 ℃, the finish rolling final temperature range is 820-850 ℃, the finish rolling is not more than 6 times, and the reduction ratio of the first 2 times is preferably more than 20%. The finish rolling stage adopts slow rolling with the rolling speed of 1-2 m/s.
The final rolling temperature in the rough rolling stage is controlled, so that the intermediate billet is always in an austenite recrystallization temperature range in the process of waiting for temperature, and the tissue uniformity is ensured; the rolling reduction rate of the two-stage rolling is limited, so that the tissue uniformity of the rolled steel plate in the thickness direction is ensured.
The straightening temperature during hot straightening is 750-800 ℃, the straightening force is 3000-4500 kN, the roll bending amount is set to be 1.2-1.8 mm, and the tilting value is set to be 3.5-5.5 mm; and by optimizing the straightening process parameters, the internal stress is promoted to be fully released.
4) Stacking and slow cooling of steel plates: immediately stacking and slowly cooling after hot straightening, wherein the stacking temperature is not lower than 400 ℃, and the slow cooling time is not less than 48 hours; the stacking slow cooling accelerates the diffusion of elements C, mn and H in the core of the steel plate, inhibits the segregation of the elements C, mn and H, and slows down the poor structural stress of the core of the steel plate and the occurrence of hydrogen induced cracks of the steel plate.
5) Quenching;
In the invention, the quenching and heating of the steel plate comprises a low-temperature section, a high-temperature section and a cooling section.
The low-temperature section temperature of the quenching heat treatment furnace is 620-680 ℃, and the low-temperature section is 2.0-3.5 min/mm in the furnace time, so that on one hand, H in the steel plate is continuously promoted to be outwards diffused, the H content of the steel plate is reduced, and on the other hand, a large amount of Nb and Ti composite carbides are promoted to be precipitated through long-time heat preservation, and the carbides provide a large amount of hydrogen traps for the inside of the steel plate. Considering that the Nb and Ti composite carbide coarsens due to the over-high temperature, and cracks appear due to stress aggregation in the subsequent forming process of the steel plate, the low temperature Duan Baowen is not more than 680 ℃.
The temperature of the high-temperature section is 880-920 ℃, and the time of the high-temperature section in the furnace is 1.5-1.8 min/mm, so that the steel plate is quickly heated to the austenitizing temperature, and the tissue guarantee is provided for the martensite obtained by the subsequent steel plate quenching; however, the too high temperature can cause coarsening of crystal grains and further coarsening of Nb and Ti composite carbides, so that the number of hydrogen traps in the steel plate is greatly reduced, and the risk of cracks is increased; therefore, the heat preservation time of the high temperature section is not more than 1.8min/mm.
The temperature of the cooling section is 760-810 ℃, the time of the cooling section in the furnace is 0.5-0.9 min/mm, and the purpose is to reduce austenite to above Ar3 temperature in the cooling section, namely to ensure the full austenitizing state of the steel plate and fully harden the quenched steel plate; meanwhile, the lower the initial quenching temperature of the steel plate is, the lower the stress level of the steel plate in the quenching process is, and the cracking condition of the steel plate caused by the quenching process can be avoided.
After the steel plate is out of the quenching heat treatment furnace, the steel plate enters a rolling quenching machine for quenching, so as to obtain sufficient martensitic transformation, and meanwhile, the excessive stress of the steel plate caused by excessive cooling speed is avoided, quenching cracks appear, and the average quenching speed is 20-45 ℃/s; the quenching finishing temperature is 180-250 ℃, so as to reduce the stress of the steel plate in the quenching process, avoid quenching cracks, and ensure that the austenite of the steel plate can fully complete martensitic transformation.
6) Tempering; tempering is a main technical means for reducing the residual stress of quenching, and fully releases the residual stress of the steel plate on the premise of ensuring the hardness of the steel plate, and the tempering heating temperature is controlled to be 150-180 ℃ and the tempering heat preservation time is controlled to be 2.0-3.5 min/mm.
7) Cutting; the preheating temperature of the steel plate is 100-200 ℃, and the steel plate can be heated by a flame gun or an electronic heating pad or a heating furnace; welding is carried out at normal temperature, the overheat of a welding area is controlled, the welding line energy is controlled below 20kJ/cm (the control input energy is too large, the structure of a heat affected zone is coarsened, the internal stress is too large after the steel plate is cooled, cracks are generated), the cutting edge and the heat affected zone are covered by an asbestos cloth heat insulation blanket after cutting, the temperature is slowly cooled to the room temperature, the slow cooling process avoids a humid environment, liquids such as water are strictly forbidden (the rapid cooling of the steel plate after cutting is avoided, and the structural stress is caused to generate cracks).
The invention finally solves the problem that the low alloy high strength steel for engineering machinery with the thickness specification of 40-80 mm and the strength level of more than 1000MPa generates delayed cracks after being cut by optimizing smelting, heating, rolling, heat treatment and cutting processes, and the cut steel plate does not generate delayed cracks after being placed for more than 60 days.
Embodiments of the present invention will be further described with reference to examples for more intuitively embodying the present invention. The following examples are only preferred embodiments of the present invention, but the scope of the present invention is not limited thereto, and any technical solutions that can be obviously obtained by those skilled in the art within the technical scope of the present invention, including simple changes or equivalent substitutions, are within the scope of the present invention.
Examples
Table 1 shows chemical components in each example steel, table 2 shows smelting, continuous casting and casting blank pit entry slow cooling process parameters of each example steel, table 3 shows heating process parameters of each example casting blank, table 4 shows rolling process parameters of each example steel plate, table 5 shows hot straightening and stacking slow cooling process parameters of each example steel plate, table 6 shows heat treatment process parameters of each example steel plate, and table 7 shows cutting process parameters and surface states of each example steel plate.
Table 1 chemical composition (wt.%)
Examples C Si Mn Mo Als B Ti Nb Ni Cr Ca
1 0.17 0.16 1.21 0.56 0.033 0.0013 0.018 0.025 0.42 0.39 0.007
2 0.14 0.32 1.19 0.65 0.045 0.0008 0.021 0.034 0.39 0.44 0.008
3 0.16 0.27 1.33 0.79 0.025 0.0017 0.023 0.015 0.36 0.43 0.006
4 0.18 0.33 1.09 0.74 0.037 0.0010 0.014 0.036 0.49 0.38 0.008
5 0.17 0.23 1.43 0.62 0.047 0.0013 0.019 0.032 0.38 0.47 0.010
6 0.19 0.29 1.26 0.55 0.036 0.0009 0.017 0.026 0.32 0.37 0.005
Note that: the impurity element P in the steel is less than or equal to 0.02 percent, and S is less than or equal to 0.005 percent.
Table 2 parameters of process for smelting, continuous casting and slow cooling of cast blank in pit
Examples Argon blowing time/min RH vacuum degassing time/min Degree of superheat/. Degree.C Pulling speed/(m.min -1) Electromagnetic stirring current intensity/A Continuous casting billet reduction/mm Secondary cooling specific water quantity/(L/kg) Pit entry temperature/°c Slow cooling temperature/°c Slow cooling time/h Pit outlet temperature/DEGC
1 28 28 17 0.9 120 36 1.6 620 630 50 130
2 25 25 23 1.3 140 33 2.0 615 640 70 150
3 26 27 25 1.2 135 39 1.4 620 635 48 145
4 32 30 21 1.0 150 45 1.8 605 645 65 110
5 30 32 24 1.1 140 35 1.9 640 650 72 120
6 33 28 20 0.8 125 38 1.7 630 640 50 130
TABLE 3 heating process parameters of casting blanks
Table 4 rolling process parameters of steel sheet
Examples Roughing start temperature/°c Rough rolling finishing temperature/°c Rough rolling pass First pass reduction/% Second pass reduction/% Finish rolling start temperature/DEGC Finish rolling finishing temperature/°c Finish rolling pass First pass reduction rate/% Second pass reduction rate/% 2-Pass descaling time/min Descaling water pressure/MPa Thickness/mm of intermediate blank Rolling speed/m/s
1 1130 1012 4 18 20 910 840 5 22 24 1.0、1.6 18、20 200 1.5
2 1125 1015 5 16 18 900 820 6 22 25 1.2、1.8 15、19 140 1.3
3 1120 1025 6 16 20 885 825 5 22 23 1.3、2.0 16、18 180 1.6
4 1120 1005 5 16 18 880 830 5 22 23 1.2、1.8 15、18 200 1.7
5 1135 996 4 17 19 900 840 6 22 25 1.7、1.9 16、20 150 1.2
6 1135 985 5 18 16 890 845 5 22 25 1.2、1.6 18、20 150 1.8
TABLE 5 thermal straightening and Stacking Cold Process parameters for Steel plates
Examples Temperature of thermal correction/. Degree.C Straightening force/kN Roll bending amount/mm Tilting value/mm Stacking temperature/°c Stacking time/h
1 750 3200 1.2 3.6 500 50
2 785 4200 1.6 5.5 520 52
3 770 4500 1.7 4.8 560 50
4 780 3500 1.5 4.5 530 49
5 775 3600 1.8 3.8 525 60
6 760 4300 1.3 5.3 570 48
TABLE 6 Steel plate heat treatment Process parameters
Examples Low temperature section temperature/°c The low temperature section is in furnace time/min/mm High temperature section temperature/DEGC The high temperature section is in furnace time/min/mm Temperature/DEGC of cooling section The temperature reduction section is at furnace time/min/mm Average cooling rate/. Degree.C/s Quenching end temperature/DEGC Tempering temperature/DEGC Tempering time/min/mm
1 660 2.8 880 1.7 780 0.6 25 200 160 2.5
2 680 3.2 905 1.5 800 0.8 30 230 180 3.0
3 630 3.3 910 1.5 770 0.9 35 185 170 3.3
4 650 2.1 920 1.8 790 0.7 28 190 160 3.1
5 670 2.6 885 1.6 810 0.8 40 220 150 2.2
6 665 2.8 890 1.7 805 0.7 36 230 165 2.6
TABLE 7 Steel plate cutting Process parameters and surface State after cutting
Examples Plate thickness/mm Preheating temperature/DEGC Weld line energy/kJ/cm Days of placement With or without cracks
1 60 150 18 65 Without any means for
2 40 180 15 80 Without any means for
3 70 200 19 60 Without any means for
4 80 180 16 70 Without any means for
5 45 178 18 100 Without any means for
6 50 190 17 120 Without any means for
The foregoing is only a preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art, who is within the scope of the present invention, should make equivalent substitutions or modifications according to the technical scheme of the present invention and the inventive concept thereof, and should be covered by the scope of the present invention.

Claims (5)

1.一种避免低合金高强钢板切割后产生延迟裂纹的方法，其特征在于，包括控制钢板化学成分及控制钢板生产工艺过程；钢板的化学成分按重量百分比计包括：C 0.14%～0.19%，Si 0.15%～0.35%，Mn 1.05%～1.45%，P≤0.02%，S≤0.005%，Nb 0.010%～0.040%，Ti0.010%～0.025%，Mo 0.5%～0.8%，Als 0.02%～0.05%，Ca 0.005%～0.010%，B 0.0008%～0.0018%，Cr 0.3%～0.5%，Ni 0.3%～0.5%，余量为Fe和不可避免的杂质，且杂质元素总量低于0.05%；钢板的生产工艺过程包括：钢水冶炼、炉外精炼+RH真空脱气、微Ti处理、B合金化、连铸、铸坯进坑加热缓冷、铸坯再加热、控轧控冷、热矫直、钢板堆垛缓冷、淬火、回火及切割。1. A method for preventing delayed cracking of a low alloy high strength steel plate after cutting, characterized in that it comprises controlling the chemical composition of the steel plate and controlling the production process of the steel plate; the chemical composition of the steel plate comprises, by weight percentage: C 0.14% to 0.19%, Si 0.15% to 0.35%, Mn 1.05% to 1.45%, P≤0.02%, S≤0.005%, Nb 0.010% to 0.040%, Ti0.010% to 0.025%, Mo 0.5% to 0.8%, Als 0.02% to 0.05%, Ca 0.005% to 0.010%, B 0.0008% to 0.0018%, Cr 0.3% to 0.5%, Ni 0.3%～0.5%, the balance is Fe and unavoidable impurities, and the total amount of impurity elements is less than 0.05%; the production process of steel plate includes: molten steel smelting, refining outside the furnace + RH vacuum degassing, micro-Ti treatment, B alloying, continuous casting, heating and slow cooling of ingots into the pit, reheating of ingots, controlled rolling and controlled cooling, hot straightening, slow cooling of steel plate stacking, quenching, tempering and cutting. 2.根据权利要求1所述的一种避免低合金高强钢板切割后产生延迟裂纹的方法，其特征在于，所述钢板的生产工艺过程具体如下：2. The method for preventing delayed cracking of a low alloy high strength steel plate after cutting according to claim 1 is characterized in that the production process of the steel plate is as follows: 1）钢水冶炼至铸坯进坑加热缓冷：1) Molten steel smelting to casting billet heating and slow cooling: 铁水预处理时控制S含量低于0.015%，转炉冶炼时控制P含量≤0.02%，转炉冶炼终点C含量控制在0.14%～0.19%；转炉出钢时吹氩气25～35min；LF精炼过程中，喂Si-Ca线进行炉外精炼处理；RH真空脱气保持25min以上，脱气处理结束后按照Als含量要求加入Al，并加入Ti-Fe进行微Ti处理，加入B-Fe合金进行B合金化；连铸时控制过热度为15～25℃，连铸拉坯速率为0.8～1.3m/min；连铸阶段二冷区电磁搅拌电流强度为100～150A，二次冷却比水量为1.3～2.0L/kg；在水平扇形段即凝固末端投入重压下，铸坯压下量为30～45mm；铸坯下线后进坑缓冷，进坑温度不低于600℃，缓冷温度为600～650℃，缓冷时间为48～72h，在坑内降温到150℃以下后出坑；During the pretreatment of molten iron, the S content is controlled to be less than 0.015%, during the converter smelting, the P content is controlled to be ≤0.02%, and the C content at the end of the converter smelting is controlled to be 0.14%-0.19%; argon is blown for 25-35 minutes when the converter is tapped; during the LF refining process, Si-Ca wire is fed for refining outside the furnace; RH vacuum degassing is maintained for more than 25 minutes, and Al is added according to the Als content requirements after the degassing treatment is completed, and Ti-Fe is added for micro-Ti treatment, and B-Fe alloy is added for B alloying; during continuous casting The superheat is controlled at 15-25℃, and the continuous casting billet drawing rate is 0.8-1.3m/min; the electromagnetic stirring current intensity in the secondary cooling zone during the continuous casting stage is 100-150A, and the secondary cooling water volume is 1.3-2.0L/kg; the billet is pressed down by 30-45mm under heavy pressure at the horizontal fan-shaped section, i.e., the end of solidification; the billet is put into the pit for slow cooling after it comes off the line, and the pit temperature is not less than 600℃, the slow cooling temperature is 600-650℃, and the slow cooling time is 48-72h. The billet is cooled down to below 150℃ in the pit before leaving the pit; 2）铸坯再加热：预热段温度为900～1050℃，均热段和加热段温度均为1225～1250℃，均热段和加热段的总加热时间为4～5.5h，总在炉时间为6～8h；2) Reheating of ingot: the temperature of preheating section is 900-1050℃, the temperature of soaking section and heating section are both 1225-1250℃, the total heating time of soaking section and heating section is 4-5.5h, and the total time in furnace is 6-8h; 3）控制轧制及冷却：分两阶段进行轧制：粗轧开轧温度≥1120℃，粗轧终轧温度为980～1025℃；粗轧不多于6道次，至少前2个道次的压下率在15%以上；中间坯待温过程中至少喷2道次除鳞水，每道次除鳞时间1～2min，除鳞水压力15～20MPa；精轧开轧温度为860～920℃，精轧终轧温度为820～850℃；精轧不多于6道次，至少前2个道次的压下率在20%以上；精轧阶段采用慢速轧制，轧制速度为1～2m/s；热矫直的矫直温度为750～800℃，矫直力为3000～4500kN，弯辊量为1.2～1.8mm，倾动值为3.5～5.5mm；3) Controlled rolling and cooling: Rolling is carried out in two stages: the starting temperature of rough rolling is ≥1120℃, and the final rolling temperature of rough rolling is 980～1025℃; the rough rolling is not more than 6 passes, and the reduction rate of at least the first 2 passes is more than 15%; during the intermediate billet waiting for temperature, at least 2 passes of descaling water are sprayed, and the descaling time of each pass is 1～2min, and the descaling water pressure is 15～20MPa; the starting temperature of finishing rolling is 860～920℃, and the final rolling temperature of finishing rolling is 820～850℃; the finishing rolling is not more than 6 passes, and the reduction rate of at least the first 2 passes is more than 20%; slow rolling is adopted in the finishing rolling stage, and the rolling speed is 1～2m/s; the straightening temperature of hot straightening is 750～800℃, the straightening force is 3000～4500kN, the bending roll amount is 1.2～1.8mm, and the tilting value is 3.5～5.5mm; 4）钢板堆垛缓冷：热矫直结束后立即堆垛缓冷，堆垛温度不低于400℃，缓冷时间不少于48h；4) Steel plates are stacked and slowly cooled: After hot straightening, they are immediately stacked and slowly cooled. The stacking temperature is not less than 400°C and the slow cooling time is not less than 48 hours. 5）淬火；淬火加热包括低温段、高温段和降温段；低温段温度为620～680℃，低温段在炉时间2.0～3.5min/mm；高温段温度为880～920℃，高温段在炉时间1.5～1.8min/mm；降温段温度为760～810℃，降温段在炉时间0.5～0.9min /mm；淬火平均冷却速度为20～45℃/s；淬火终了温度为180～250℃；5) Quenching; quenching heating includes low temperature section, high temperature section and cooling section; the temperature of low temperature section is 620～680℃, the time of low temperature section in furnace is 2.0～3.5min/mm; the temperature of high temperature section is 880～920℃, the time of high temperature section in furnace is 1.5～1.8min/mm; the temperature of cooling section is 760～810℃, the time of cooling section in furnace is 0.5～0.9min/mm; the average cooling rate of quenching is 20～45℃/s; the final temperature of quenching is 180～250℃; 6）回火；回火加热温度为150～180℃，回火保温时间为2.0～3.5min/mm；6) Tempering: The tempering heating temperature is 150-180°C, and the tempering holding time is 2.0-3.5min/mm; 7）切割；钢板预热温度为100℃～200℃，切割在常温下进行，切割时焊接线能量控制在20kJ/cm以下，切割后用石棉布隔热毯将切割边及热影响区覆盖，缓冷到室温。7) Cutting: The preheating temperature of the steel plate is 100℃~200℃, and the cutting is carried out at room temperature. The welding line energy is controlled below 20kJ/cm during cutting. After cutting, the cutting edge and heat-affected zone are covered with asbestos cloth insulation blanket and slowly cooled to room temperature. 3.根据权利要求1所述的一种避免低合金高强钢板切割后产生延迟裂纹的方法，其特征在于，成品钢板为1000MPa级以上钢板。3. A method for preventing delayed cracking of low alloy high strength steel plates after cutting according to claim 1, characterized in that the finished steel plates are steel plates of 1000 MPa or above. 4.根据权利要求1所述的一种避免低合金高强钢板切割后产生延迟裂纹的方法，其特征在于，成品钢板的厚度为40～80mm；铸坯厚度为250～300mm；中间坯厚度为成品钢板厚度的2.5～3.5倍。4. A method for avoiding delayed cracking of low alloy high strength steel plate after cutting according to claim 1, characterized in that the thickness of the finished steel plate is 40 to 80 mm; the thickness of the ingot is 250 to 300 mm; the thickness of the intermediate ingot is 2.5 to 3.5 times the thickness of the finished steel plate. 5.根据权利要求2所述的一种避免低合金高强钢板切割后产生延迟裂纹的方法，其特征在于，所述步骤7）中，钢板预热采用火焰烧枪、电子加热垫或加热炉进行加热。5. A method for preventing delayed cracking of low alloy high strength steel plate after cutting according to claim 2, characterized in that in said step 7), the steel plate is preheated by a flame torch, an electronic heating pad or a heating furnace.
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CN120738436A (en) * 2025-08-27 2025-10-03 马鞍山钢铁有限公司 Slow cooling and preparation method for improving uniformity
CN120843958A (en) * 2025-09-23 2025-10-28 鞍钢股份有限公司 A control method to avoid fracture of saw blade steel continuous casting billet

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JP2000144331A (en) * 1998-08-25 2000-05-26 Nsk Ltd Rolling bearing
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CN102747303A (en) * 2012-06-29 2012-10-24 宝山钢铁股份有限公司 High-strength steel sheet with yield strength of 1100MPa and manufacturing method thereof

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JP2000144331A (en) * 1998-08-25 2000-05-26 Nsk Ltd Rolling bearing
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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN120738436A (en) * 2025-08-27 2025-10-03 马鞍山钢铁有限公司 Slow cooling and preparation method for improving uniformity
CN120843958A (en) * 2025-09-23 2025-10-28 鞍钢股份有限公司 A control method to avoid fracture of saw blade steel continuous casting billet

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