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CN116334476B - Anti-fatigue coating steel plate and production method thereof - Google Patents

Anti-fatigue coating steel plate and production method thereof Download PDF

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Publication number
CN116334476B
CN116334476B CN202211610417.0A CN202211610417A CN116334476B CN 116334476 B CN116334476 B CN 116334476B CN 202211610417 A CN202211610417 A CN 202211610417A CN 116334476 B CN116334476 B CN 116334476B
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steel
controlled
steel plate
fatigue
temperature
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CN116334476A (en
Inventor
赵坦
王�华
陈妍
柴铁洋
于浩男
金耀辉
李文斌
朱隆浩
王长顺
李家安
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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
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • 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 by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
    • 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 by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221—Modifying the physical properties 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
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
    • 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
    • C22C38/005—Ferrous alloys, e.g. steel alloys containing rare earths, i.e. Sc, Y, Lanthanides
    • 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
    • C22C38/008—Ferrous alloys, e.g. steel alloys containing tin
    • 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
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
    • 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
    • C22C38/46—Ferrous alloys, e.g. steel alloys containing chromium with nickel with vanadium
    • 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
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/002—Bainite
    • 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
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/004—Dispersions; Precipitations
    • 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
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/005—Ferrite

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

Abstract

The invention discloses an anti-fatigue coating steel plate and a production method thereof, wherein the steel comprises the following components in percentage by weight: 0.3-0.45 wt%, mn 0.4-0.6 wt%, mg: 0.005-0.01 wt%, ca: 0.008-0.015 wt%, V: 0.04-0.06 wt%, N: 0.008-0.012 wt%, cu: 0.2-0.4 wt%, ni: 1-2 wt%, mo: 0.05-0.1 wt%, re: 0.03-0.04 wt%, cr: 1-1.5 wt%, REM: 0.03-0.05 wt%, sn: 0.25-0.35 wt%, P: 0.01-0.015 wt%, S: less than or equal to 0.005wt percent of Ti: less than or equal to 0.005. The production method comprises smelting, continuous casting, billet heating, controlled rolling and off-line treatment, wherein the temperature of cold charging of the billet is controlled to be 50-100 ℃, and multistage heating is adopted; 950-1000 ℃, the finishing temperature is controlled above 900 ℃, the rolling reduction is 20-30%, and the cooling speed after rolling is 3-7 ℃/s; and after the steel plate is taken off line, the regulation and control of the phase precipitation and the internal stress in the second stage are carried out by adopting a stacking and heat preservation treatment mode, and the low-temperature regulation and control are adopted at 320-390 ℃. The invention solves the fatigue-corrosion coupling problem faced by the anti-fatigue coated steel under the severe marine atmospheric environment corrosion condition.

Description

Anti-fatigue coating steel plate and production method thereof
Technical Field
The invention belongs to the technical field of metal material preparation, and particularly relates to a coating steel plate for fatigue resistance and a production method thereof.
Background
The tropical and subtropical sea areas have unique high temperature (the ocean surface temperature is 25-28 ℃ and reaches 30 ℃ at the highest), high salt (the Cl - deposition rate is more than 1.12mg/100cm 2. D), strong storm (the maximum wave height is nearly 30 m) and other strong corrosiveness and fatigue damage environmental factors, the natural environment is harsh, and the material corrosion problem is quite remarkable. According to the ISO9223 classification standard, the corrosion grade of the material in the area can reach the highest grade C5, and the water surface ship, the offshore floating platform, the island reef building and the equipment which are in service under the environment at present can be corroded seriously in a premature manner when compared with other areas even if corrosion protection measures are taken. The failure rate of equipment in the service of tropical and subtropical sea areas is 3 times that of other sea areas, and the equipment causes economic loss of nearly trillion yuan to the country every year. The tropical and subtropical sea areas comprise island reef construction, resource exploitation platforms, offshore living auxiliary equipment, offshore clean energy development equipment and the like, mainly take steel structures as main materials, and the steel consumption is expected to reach 100 ten thousand tons/year in the future 5-10 years in the tropical and subtropical sea areas.
In the service process, the tropical and subtropical ocean engineering structure is not only subjected to the severe and complex ocean environment with high salt and high temperature, but also is frequently subjected to the repeated action of environmental loads such as ocean wind, ocean wave, ocean current and the like and operation dynamic loads, for example, an ocean platform with the design life of 20-25 years can achieve hundreds of millions of times of alternating stress circulation times caused by wave action in the service period. In addition, the marine environment is used for constructing engineering structures, particularly ocean platforms, which often support various devices with a total mass of hundreds of tons, so that the devices bear extremely large working stress, the devices are large in size and thickness, joint defects such as microcracks, air holes, slag inclusion and unfused are extremely easy to become crack sources of corrosion and fatigue, and the fatigue toughness of the devices is reduced, so that the problems of fatigue must be considered in the use of the marine engineering structures and the service process of the marine engineering structures. At present, the research and development of special materials in the severe environment with four high and one high temperatures in tropical and subtropical sea areas in China is not systematic, and related researches are mainly carried out on the corrosion resistance of materials, the patent of the domestic application number 201710075154.0 is a high corrosion resistance low alloy steel suitable for the high-temperature coastal environment, the corrosion resistance is superior to that of Q235 carbon steel and other weather resistant steels, a high Ni system is adopted and is matched with elements such as Cu and Mo for alloying, the problems are that the cost is high, the problems are caused due to the fact that the alloying and the carbon equivalent are high, the welding performance is high, in addition, the yield strength of the system steel is often 600-800MPa, the fatigue problem of the steel is prominent, the potential safety hazard is generated, in addition, the corrosion resistance is huge for local failure and corrosion caused by the damage and aging of a coating in some coastal building environments with extremely severe environments, and application occasions with coating requirements, the long-term service performance of a combined use system of the steel and the coating is extremely important, the corrosion resistance of the steel is good, and the steel-coating interface is also required to have high corrosion resistance. At present, no report exists on the fatigue-resistant coated steel of materials under the conditions of strong corrosion, strong storm and high wave load in the tropical and subtropical sea areas.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide an anti-fatigue coating steel plate and a production method thereof, which have higher safety service performance and solve the fatigue-corrosion coupling problem faced by marine structures with strong storm and high wave load conditions.
In order to solve the problems, the technical scheme adopted by the invention is that the anti-fatigue coating steel plate comprises C:≤0.02wt％,Si：0.3-0.45wt％,Mn:0.4-0.6wt％,Mg：0.005-0.01wt％,Ca：0.008-0.015wt％,V：0.04-0.06wt％,N：0.008-0.012wt％,Cu：0.2-0.4wt％,Ni：1-2wt％,Mo：0.05-0.1wt％,Re：0.03-0.04wt％,Cr：1-1.5wt％,REM：0.03-0.05wt％,Sn：0.25-0.35wt％,P：0.01-0.015wt％,S：≤0.005wt％,Ti：0.001-0.005wt％, weight percent of Fe and unavoidable impurities as the balance.
Further, the steel sheet contains 55-70% bainite+25-35% ferrite (containing 7-12% acicular ferrite) structure in terms of area percentage, contains V (C, N) and Mo 2 C nano-phases dispersed and precipitated with an average size of 15-25nm, the average spacing of these phases is 1.2-1.5 μm, contains Cu nano-phases with an average size of 25-45nm, and the average spacing of the phases is 1.1-1.6 μm.
Further, the steel plate matrix contains V (C, N) and Mo 2 C which are dispersed and separated out, the size is 10-40nm, and the size of the Cu nano phase is 25-60nm.
Further, the average grain size of the steel plate surface layer-1/8 thickness is 10-20 μm.
Further, the steel plate has the yield strength of 420-460 mpa, the yield ratio of less than or equal to 0.75, the impact energy at minus 40 ℃ of not less than 190J, the elongation of not less than 20% and the area reduction of not less than 68%.
Further, when the loading stress ratio of the steel plate is 0.1, the frequency is 90HZ, the highest stress is 0.75Rp 0.2, and the cycle number reaches 10 7, the test sample is not broken, and the-20 DEG CCTOD delta m is more than 0.8mm.
The second technical scheme of the invention is a production method of the anti-fatigue coating steel plate, which comprises smelting, continuous casting, billet heating, controlled rolling and off-line treatment, and comprises the following specific contents:
Heating the steel billet, namely controlling the temperature of cold charging of the steel billet into a furnace to be 50-100 ℃, adopting multi-stage heating, controlling the total time of 500-900 ℃ to be 0.1-0.2min/mm, controlling the total time of 1150-1180 ℃ to be within 0.1min/mm, and controlling the total time of a soaking section 1120-1150 ℃ to be 0.2-0.4min/mm;
Rolling is controlled, namely rolling is started when the temperature of the billet is 950-1000 ℃ after the billet is discharged from the furnace, the final rolling temperature is controlled to be more than 900 ℃, the pass reduction is controlled to be 20-30% at the stage, and the cooling speed after rolling is controlled to be 3-7 ℃ per second;
And (3) performing off-line treatment, namely performing regulation and control of phase precipitation and internal stress in a second stage by adopting a heat preservation treatment mode after the steel plate is off-line, wherein the heat preservation regulation and control temperature is 320-390 ℃.
Further, the billet is prepared by converter smelting and continuous casting, the billet is pretreated in a quick cooling mode during the billet ejection, the temperature of the cold surface is controlled at 815-890 ℃, the cooling speed is controlled at 2-8 ℃ per second, and then the billet is subjected to low-temperature heating treatment, wherein the treatment temperature is 220-370 ℃.
Further, the steel grade is smelted by adopting a converter, the Ti element in molten iron is controlled below 0.005%, and Si and Mn are used for deoxidization.
The anti-fatigue coated steel produced according to the scheme has the following beneficial effects:
1. The corrosion resistance of the steel plate is greatly improved through the addition and the synergistic effect of the composite microelements. The coating system corrosion resistance of the steel plate is improved by 90-150% compared with 3.5Ni system steel by adopting a simulated tropical and subtropical sea area sea water splash zone peri-immersion test.
2. The alloy has good comprehensive mechanical property, structural safety and weldability, the yield strength is 420-460 mpa, the yield ratio is less than or equal to 0.75, the impact energy at minus 40 ℃ is not less than 190J, the elongation is more than or equal to 20%, and the area shrinkage is more than or equal to 68%.
3. The loading stress ratio is 0.1, the frequency is 90HZ, when the highest stress is 0.75Rp 0.2, and the cycle number reaches 10 7, the sample is not broken, -20 DEG CCTOD delta m >0.8mm
Detailed Description
The following description of the technical solutions in the embodiments of the present invention will be clear and complete, and it is obvious that the described embodiments are only some embodiments of the present invention, but not all embodiments. All other examples of modifications and alterations will be apparent to those skilled in the art based on the examples herein, and are intended to be within the scope of the invention. It should be understood that the embodiments of the present invention are only used for illustrating the technical effects of the present invention, and are not used for limiting the scope of the present invention.
Aiming at the more complex environment of high temperature, unstable oxygen, low pH value and high Cl - of the steel material under a coating system, the pH value of an anode region is reduced by micro-alloying compounding action of Sn, re, REM, N, V, cr, W, ca, mg, sb and other elements, so that the potential of the system is increased, the local pH value is reduced, the coupling passivation capability of the steel-coating system is improved, and the developed steel plate has good comprehensive performance of mechanical-corrosion resistance matching, coating coupling corrosion resistance and higher fatigue resistance. The corrosion resistance of a coating system of the steel plate is improved by 90-150% compared with that of 3.5Ni system steel by adopting a circumferential immersion test of simulating the sea water splash zone of the tropical and subtropical sea areas, so that the fatigue failure problem of deep-open sea coating equipment in the marine environment is effectively solved.
The steel composition of the present invention will be described in detail below, and unless otherwise specified, it is shown that the% content of each element is based on weight.
The invention relates to a coating steel plate for fatigue resistance, which comprises the following components in percentage by weight C:≤0.02wt％,Si：0.3-0.45wt％,Mn:0.4-0.6wt％,Mg：0.005-0.01wt％,Ca：0.008-0.015wt％,V：0.04-0.06wt％,N：0.008-0.012wt％,Cu：0.2-0.4wt％,Ni：1-2wt％,Mo：0.05-0.1wt％,Re：0.03-0.04wt％,Cr：1-1.5wt％,REM：0.03-0.05wt％,Sn：0.25-0.35wt％,P：0.01-0.015wt％,S：≤0.005wt％,Ti：0.001-0.005wt％,, and the balance of Fe and unavoidable impurities.
C:≤0.02wt%
The element C is a main phase change control element which takes 55-70% of bainite and 25-35% of ferrite (containing 7-12% of acicular ferrite) as a matrix corrosion resistant structure, is an important element for ensuring the strength of steel, and is suitable for promoting the generation of a micro cathode phase V (C, N) important in the invention and controlling the precipitation of massive carbide of Cr, and the phases are beneficial to improving the corrosion resistance of steel;
Si:0.3-0.45wt%
The Si element plays a certain role in strengthening, is one of the important deoxidizers, can promote the surface enrichment of Sn, and forms surface oxides with Cu and Sn, so that the corrosion resistance is effectively improved, and proper Si is helpful for improving the potential of a coating system and controlling the local PH value, so that the content of Si is controlled to be 0.3-0.45wt%;
Mn:0.4-0.6wt%
Mn element plays a certain role in the combination control of strengthening and fatigue performance, is one of the important deoxidizers, and can reduce the corrosion resistance of steel and influence the solid solution effect of the corrosion resistant element in the steel, so that the Mn content is controlled to be 0.4-0.6wt%;
Mg:0.005-0.01wt%;Ca:0.008-0.015wt%
In addition, trace Ca and Mg can be dissolved in Fe to make corrosion resistant elements such as Ni, cu, cr, sn and the like enriched relatively at the initial stage of corrosion after the surface Fe is dissolved, thus improving corrosion resistance, reducing the problem of toughness reduction caused by adding elements such as high Sn and the like, and the elements can also form coupling effect with Zn in the primer in a weak acid environment to improve the corrosion resistance of a steel-coating system. Based on the design, the content of Ca element and Mg element is controlled to be 0.008-0.015wt% and 0.005-0.01wt% respectively;
V:0.04-0.06wt%
The V element mainly plays an important role in the toughness and corrosion resistance of steel in a precipitation strengthening mode, the V element mainly forms V (C, N) with C and N in proper proportion, and as the steel material is a multiphase structure formed by multi-element alloying, the control of the proportion of a cathode and an anode in a micro-area is very important, and the control of the corrosion resistance of a refined, dispersed, uniform and distributed cathode design relative to a complex structural system of the steel material is very important. In the present invention, under the control of cathode phase and the element configuration of V, C, N, cr, etc., V (C, N) with the average interval of 1.2-1.5 microns and with the average interval of 10-40nm is produced in the steel matrix, so as to prevent fatigue and other crack growth. Based on the design, the content of V is 0.04-0.06wt%;
N:0.008-0.012wt%;
The N element is mainly used for promoting the compound precipitation of V (C, N) and Fe 3 C of fine particles, and in addition, the solid solution N is beneficial to improving the corrosion resistance of the steel;
Cu:0.2-0.4wt%;
Cu is an important corrosion-resistant and toughening element, on one hand, in early stage of corrosion, after the surface is subjected to preliminary corrosion, an enrichment layer and an oxidation layer are formed, no obvious segregation behavior is improved, in addition, a nano phase with an average size of 25-45nm is formed in the steel plate, the average distance of the phases is 1.1-1.6 mu m, after the rust layer on the surface layer is damaged, a large number of fine cathode phases are further formed, a special cathode size and distribution control system is formed by the V (C, N) and the Fe 3 C, the corrosion speed is controlled, the improvement and control of the weldability are facilitated, and excessive Cu is not beneficial to the further exertion of the corrosion resistance, and the unnecessary cost is increased, so that the Cu is controlled to be 0.2-0.4wt%;
Ni:1-2wt%;
The invention adopts low Mn component design, so that Ni can more effectively promote the generation of Fe 3O4 oxide, and Ni 2+ in a rust layer can more effectively occupy the gap position of Fe 3O4 to form stable and compact intermetallic compound of Fe and Ni, thereby preventing Cl - from diffusing to a matrix, reducing acidification and improving the PH value of electrolyte in the rust layer, and further fully achieving the corrosion resistance by only adopting 1-2wt% of Ni.
Mo:0.05-0.1wt%;
The Mo element can densify the rust layer and is combined with Si and Cu simultaneously, so that the formed oxide film is effective for initial corrosion, and the Mo 4 2- is eluted with the anodic reaction of the steel material, and the Mo 4 2- is distributed on the rust layer, thereby generating ion selection and resisting the invasion of Cl - of the corrosion promoting factor. In addition, the addition of Mo is beneficial to improving the low-temperature and high-temperature stability of the dispersed phase of V and Cu, and simultaneously separating out 10-40nmMo 2 C, so that the pitting corrosion resistance and the fatigue resistance of the alloy are improved. Too high Mo will deteriorate toughness, too low is detrimental to fatigue resistance, too high is detrimental to coupling of the coating and steel, and thus is controlled to be 0.05-0.1wt%;
Re:0.03-0.04wt%;
Re element is uniformly distributed between dendrite stems and dendrite in the solidification process, is an important solid solution strengthening element, has the corrosion potential of about 0.3V, can enable the corrosion potential to positively shift, effectively improves the corrosion potential of a matrix, reduces the corrosion current of a system and improves the corrosion resistance of steel. In addition, the proper amount of Re and Ni and Cu can effectively promote the anode passivation and improve the cathode efficiency, and the anode current in the passivation area is several orders of magnitude smaller than the current of activation dissolution, so that the corrosion resistance of the alloy is effectively improved by utilizing the cathode element. In addition, the compound addition of Re and V, ni can effectively control the toughness control problem caused by the addition of elements such as Sn and the like, and improve the combination of steel and a coating. Thus controlling the weight of the catalyst to be 0.03-0.04wt%;
Cr:1-1.5wt%;
In addition, in the component design of the multi-element system, solid solution elements such as Cr and the like are fully dissolved in a matrix, the solid solution capacity of V is reduced, the precipitation behavior of the V is improved, the effect of controlling thermodynamic and kinetic changes of V (C, N) is indirectly achieved, and after the stable rust layer is formed by the compounding effect of the elements such as Cr, V and the like, the inductive reactance effect tends to completely disappear, so that the fatigue resistance and the pitting resistance of the material are optimally matched. However, too much Cr is detrimental to the control of pH under the coating, so that Cr of the present invention is controlled to be 1 to 1.5wt%.
REM:0.03-0.05wt%;
On the one hand, REM rare earth elements can change the size of cathode phases such as V (C, N), improve the dispersity, improve the potential and reduce the cathode effect, and as the content reaches 0.03-0.05wt%, the REM rare earth elements are fully dissolved in a matrix to play a role in improving the potential of the matrix and directly generate corrosion resistance, while RE absorbed by the mismatch positions of grain boundaries, subgrain boundaries and educts plays a role in balancing the segregation of elements such as Cr, cu, and the like, thereby reducing inter-crystal and inter-phase corrosion caused by the segregation.
Sn:0.25-0.35wt%;
On one hand, sn element reduces the energy level of steel in a simple substance solid solution mode, weakens the electrochemical activity of the steel, is beneficial to forming oxides such as SnO and the like to be deposited on the corrosion front edge, promotes the generation of alpha-FeOOH, and compacts an oxide layer together with the alpha-FeOOH, when the Sn element is dissolved together with Fe, the ionic Sn element can be combined with Cl -, the local PH value is improved, the corrosion process acceleration is controlled, the local PH value is improved, particularly for PH under a coating, the effect of controlling the corrosion process acceleration is achieved, and the Sn element is controlled to be 0.25-0.35wt%.
P:0.01-0.015wt%;
The element P is mainly used for reducing the anodic polarization degree, promoting the uniform dissolution of steel and the oxidation rate of iron, promoting the formation of a non-static protective film, and being matched with Re, cu and the like to resist the invasion of Cl -, and considering that excessive P reduces the weldability of the coated steel to a certain extent, the P is controlled to be 0.01-0.015wt%;
S:≤0.005wt%;
s, sulfide formed by elements accelerates corrosion and weakens toughness, so that the sulfide needs to be strictly controlled to be less than or equal to 0.005wt%;
Ti:0.001-0.005wt%
ti element contributes to control of the initial grain size, but too much N element is consumed to affect the strength and corrosion resistance of the steel, for which the Ti of the present invention is controlled to be 0.001-0.005wt%.
The balance of Fe and unavoidable impurities in the present invention may be Fe and unavoidable impurities in addition to the above-mentioned steel components. Unavoidable impurities cannot be completely removed as impurities which are not artificially mixed in a general steel manufacturing process, and the meaning thereof can be easily understood by those skilled in the art of general steel manufacturing. Moreover, the present invention does not completely exclude the addition of other components in addition to the steel components described above.
The microstructure of the present invention is described in further detail below.
The invention relates to a coating steel plate for fatigue resistance, which comprises V (C, N) and Mo 2 C which are dispersed and precipitated in a matrix with the size of 10-40nm (average size of 15-25 nm), wherein the average distance between the V and Mo 2 C is 1.2-1.5 mu m, and the average distance between the Cu nano phases with the size of 25-60nm (average size of 25-45 nm) is 1.1-1.6 mu m. After the steel plate is rolled, a corrosion-resistant structure which takes 55-70% of bainite and 25-35% of ferrite (containing 7-12% of acicular ferrite) as a matrix is formed, wherein the percentage is the area percentage, and the average grain size of the steel plate surface layer-1/8 thickness is 10-20 mu m.
The production process of the present invention is described in further detail below.
The production method of the anti-fatigue coating steel plate comprises smelting, continuous casting, billet heating, controlled rolling and off-line treatment, and comprises the following specific contents:
Smelting, namely smelting the steel grade by adopting a converter, deoxidizing by adopting Si and Mn, and strictly controlling the use of Al, wherein the addition of Al consumes N element and has harmful effect on the surface quality of a steel billet, and the similar adopted molten iron is strictly controlled to introduce Ti and Nb elements (controlled below 0.005 percent) to influence the precipitation effect of V and Cu, so that the formation of carbonitrides such as Ti, al and Nb is avoided, and the corrosion resistance is unfavorable.
In order to control the initial surface grain size of the continuous casting blank and the solid distribution of corrosion resistant elements, the continuous casting blank is pretreated in a quick cooling mode during the ejection, the surface temperature for opening and cooling is controlled at 815-890 ℃, the cooling speed is controlled at 2-8 ℃ per second, the continuous casting blank is not suitable for hot charging, low-temperature heating treatment is needed, the treatment temperature is 220-370 ℃, and the surface quality and the thermal stress distribution of the steel blank are controlled.
And heating the steel billet, namely controlling the temperature of cold charging of the steel billet into a furnace to be 50-100 ℃, adopting multi-stage heating, controlling the total time of 500-900 ℃ to be 0.1-0.2min/mm, controlling the total time of 1150-1180 ℃ to be within 0.1min/mm, and controlling the total time of a soaking section 1120-1150 ℃ to be 0.2-0.4min/mm. The aim is to control the initial distribution of alloying elements and trace elements before hot working. Due to the distribution and composition of grains, particularly grain boundaries, there is a great influence on corrosion, and therefore, it is necessary to reasonably control the initial grain size.
Rolling is controlled by adopting high temperature control and high pressure rolling, a specific billet is rolled after being discharged from a furnace and is heated to 950-1000 ℃, the rolling temperature is controlled to be more than 900 ℃, the pass rolling reduction in the stage is controlled to be 20-30%, the rolled billet rapidly passes through an austenite phase transformation zone in a rapid cooling mode, and the cooling speed is controlled to be 3-7 ℃ per second, so that the aim of balancing phase transformation and grain size is achieved. The grain size of the surface is controlled, the average grain size of the surface layer-1/8 thickness of the steel plate is controlled to be 10-20 mu m, the distribution state of surface corrosion-resistant elements is controlled, the precipitation of elements such as V, cu, mo and the like is inhibited, the supercooling of components in steel is improved, the balance of mechanical property and corrosion resistance can be ensured by controlling the grain size of the surface, and 55-70% bainite and 25-35% ferrite (containing 7-12% acicular ferrite) are formed as a matrix corrosion-resistant structure in the process.
And the offline treatment, namely the second-stage precipitated phase and internal stress regulation and control are carried out by adopting a heat preservation treatment mode after the steel plate is offline, the cooling improves the precipitation power of the micro phase, and the low-temperature regulation and control can be adopted for 320-390 ℃, so that on one hand, the hardness of the surface layer can be regulated and controlled, the mechanical property of the surface of the steel plate is improved, on the other hand, finer precipitates are formed, and the overall corrosion resistance of the steel plate is improved. V (C, N) and Mo 2 C which are dispersed and separated out with the size of 10-40nm (average size of 15-25 nm) are generated in the regulated steel matrix, the average distance between the phases is 1.2-1.5 mu m, meanwhile, a Cu nano phase with the size of 25-60nm (average size of 25-45 nm) is also present in the matrix, and the average distance between the phases is 1.1-1.6 mu m.
Aiming at the complex environments of strong corrosion and high wave load faced by the marine building structures in tropical and subtropical sea areas, the invention provides a brand-new component system design and a corresponding production process, and the developed steel grade simultaneously gives consideration to toughness, weldability and yield ratio, and has good fatigue resistance and coating coupling service performance.
According to the chemical composition and the production process, the actual smelting composition of the invention is shown in table 1, the actual process parameters of the invention are shown in tables 2-5, and the physical properties are shown in tables 6-10.
Table 1 Components (wt%)
C Si Mn Mg Ca V N Cu Ni Mo Re Cr REM Sn P S Ti
1 0.02 0.35 0.56 0.008 0.012 0.056 0.011 0.37 1.62 0.05 0.03 1.47 0.04 0.25 0.013 0.003 0.003
2 0.01 0.31 0.46 0.007 0.013 0.042 0.008 0.38 1.33 0.07 0.036 1.32 0.04 0.35 0.011 0.002 0.001
3 0.02 0.3 0.55 0.008 0.01 0.052 0.009 0.4 1.25 0.07 0.032 1.45 0.03 0.25 0.012 0.002 0.004
4 0.02 0.4 0.59 0.006 0.012 0.043 0.008 0.29 1.32 0.1 0.038 1.18 0.04 0.25 0.015 0.002 0.003
5 0.02 0.35 0.54 0.009 0.008 0.044 0.011 0.24 1.88 0.08 0.04 1.15 0.05 0.34 0.014 0.003 0.003
6 0.02 0.34 0.43 0.01 0.01 0.058 0.008 0.33 1.65 0.06 0.035 1.27 0.05 0.33 0.011 0.003 0.005
7 0.01 0.33 0.58 0.008 0.015 0.054 0.009 0.26 1.87 0.07 0.038 1.3 0.03 0.32 0.013 0.003 0.003
8 0.02 0.41 0.41 0.008 0.015 0.045 0.01 0.32 2 0.06 0.037 1.25 0.03 0.27 0.012 0.003 0.004
9 0.02 0.32 0.51 0.01 0.01 0.059 0.009 0.29 1.81 0.06 0.03 1.34 0.04 0.32 0.014 0.005 0.002
10 0.01 0.33 0.57 0.01 0.013 0.05 0.008 0.34 1.68 0.1 0.033 1.11 0.05 0.31 0.013 0.002 0.002
TABLE 2 pretreatment of blanks
Table 3 heating process
TABLE 4 Rolling Process and tissue control results
TABLE 5 Steel plate off-line Process and tissue proportion level
Table 6 mechanical properties of examples
Table 7 fatigue properties of examples
Table 8 welding performance (line energy 35KJ, submerged arc welding) of examples
The test steel and the comparison steel adopt four layers of protection based on Zn-rich primer to prepare a coated steel accelerated corrosion hanging piece, and the steel-coated accelerated corrosion experiment is carried out, wherein the single test method comprises the following steps:
1. 42 ℃, relative humidity 90%, time 5h;
2. an accelerated corrosion experiment for simulating sea conditions of tropical and subtropical sea areas is adopted, wherein a 2% NaCl solution has a PH value of 6-6.9, and the soaking temperature is 42+/-2 ℃ for 1h;
3. The exposure temperature is 45+/-2 ℃, the exposure humidity is 60 percent, and the time is 10 hours;
the number of times of 10% coating deterioration (peeling of notched part, bubbling, etc.) after corrosion cycle is taken as the evaluation of corrosion resistance of the system, the number of corrosion cycle is 44-64, and the relative corrosion resistance is 194% -252%.
Table 9 corrosion resistance of examples
Number of corrosion cycles Relative corrosion resistance
Comparative example (3.5 Ni steel) 33 100%
Example 1 78 229%
Example 2 71 208%
Example 3 75 220%
Example 4 79 232%
Example 5 86 252%
Example 6 69 203%
Example 7 67 197%
Example 8 66 194%
Example 9 74 217%
Example 10 70 205%
It should be noted that the above embodiments are merely for illustrating the technical solution of the present invention and not for limiting the same, and although the present invention has been described in detail with reference to the above embodiments, it should be understood by those skilled in the art that the technical solution described in the above embodiments may be modified or some or all of the technical features may be equivalently replaced, and these modifications or substitutions do not make the essence of the corresponding technical solution deviate from the scope of the technical solution of the embodiments of the present invention.

Claims (6)

1. A coating steel plate for resisting fatigue is characterized in that the steel plate comprises C:≤0.02 wt%,Si：0.3-0.45wt%,Mn:0.4-0.6wt%,Mg：0.005-0.01 wt%,Ca：0.008-0.015wt%,V：0.04-0.06 wt%,N：0.008-0.012 wt%,Cu：0.2-0.4 wt%,Ni：1-2wt%, Mo：0.05-0.1 wt%,Re：0.03-0.04 wt%,Cr：1-1.5wt%,REM：0.03-0.05 wt%,Sn：0.25-0.35wt%,P：0.01-0.015 wt%,S：≤0.005 wt%,Ti：0.001-0.005wt%, weight percent of Fe and unavoidable impurities as the rest;
The steel plate contains 55-70% of bainite+25-35% of ferrite structure, 7-12% of acicular ferrite in 25-35% of ferrite, wherein the percentage is area percentage, V (C, N) and Mo 2 C nano phases which are dispersed and precipitated with the average size of 15-25nm are contained, the average interval of the phases is 1.2-1.5 mu m, cu nano phases with the average size of 25-45nm are contained, and the average interval of the Cu nano phases is 1.1-1.6 mu m;
the steel plate matrix contains V (C, N) and Mo 2 C which are dispersed and separated out, the size is 10-40nm, and the size of the Cu nano phase is 25-60nm;
the average grain size of the steel plate surface layer-1/8 thickness is 10-20 mu m.
2. The steel sheet for fatigue resistance coating according to claim 1, wherein the steel sheet has a yield strength of 420 to 460mpa, a yield ratio of 0.75 or less, an impact energy of-40 ℃ of 190J or more, an elongation of 20% or more, and a reduction of area of 68% or more.
3. The steel sheet for fatigue resistance coating according to claim 1, wherein the steel sheet is not broken when the number of cycles reaches 10 7 at a loading stress ratio of 0.1, a frequency of 90HZ, and a maximum stress of 0.75Rp 0.2, -20 ℃ CTOD δm >0.8mm.
4. A method for producing the anti-fatigue coating steel plate according to any one of claims 1 to 3, comprising the steps of smelting, continuous casting, billet heating, controlled rolling and off-line treatment, wherein the specific contents are as follows:
heating the steel billet, namely controlling the temperature of cold charging of the steel billet into a furnace to be 50-100 ℃, adopting multi-stage heating, controlling the total time of 500-900 ℃ to be 0.1-0.2min/mm, controlling the total time of 1150-1180 ℃ to be within 0.1min/mm, and controlling the total time of a soaking section 1120-1150 ℃ to be 0.2-0.4min/mm;
Rolling is controlled, namely rolling is started when the temperature of the billet is 950-1000 ℃ after the billet is discharged from the furnace, the final rolling temperature is controlled to be more than 900 ℃, the pass reduction is controlled to be 20-30% at the stage, and the cooling speed after rolling is controlled to be 3-7 ℃ per second;
And (3) performing off-line treatment, namely performing regulation and control of phase precipitation and internal stress in a second stage by adopting a heat preservation treatment mode after the steel plate is off-line, wherein the heat preservation regulation and control temperature is 320-390 ℃.
5. The method for producing a coated steel sheet for fatigue resistance according to claim 4, wherein the steel slab is produced by converter smelting and continuous casting, the steel slab is pretreated by rapid cooling during the tapping, the cooling surface temperature is controlled at 815-890 ℃, the cooling rate is controlled at 2-8 ℃ per second, and then the steel slab is subjected to low-temperature heating treatment at 220-370 ℃.
6. The method for producing a coated steel sheet for fatigue resistance according to claim 4, wherein the steel slab is smelted by a converter, and the molten iron is deoxidized with Si and Mn while controlling Ti element content to 0.005% or less.
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