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    • 专利摘要:
    abstract “ht550 steel plate and method for manufacturing ht550 steel plate” a ht550 steel plate with very high hardness and excellent weldability and method for manufacturing it are disclosed. based on a component system with very low c, high mn, micro alloy nb, ultramicro ti treatment, mn / c is controlled in the range of 15 to approximately 30, (% of si) × (% of ceq) is less than or equal to 0.050 , (% of c) × (% of si) is less than or equal to 0.010, (% of mo) × [% of c) +0.13 (% of si)] is in the range of 0.003 to approximately 0.020, a ti / n ratio is in the range of 2.0 to approximately 4.0, the steel plate is connected with (cu + ni + mo), ni / cu is greater than or equal to 1.0, ca treatment is performed, and ca / s is in the range of 0.80 to approximately 3.00; by optimizing the tmcp process, the steel sheet has fine ferrite microstructures plus self-tempered bainite with an average grain size of less than or equal to 15 µm, deformation resistance being 460 mpa or more, the tensile strength being 550 at approximately 700 mpa, deformation ratio being 0.85 or less, and charpy impact energy at -60ºc (single value) being 60 j or more; therefore, the steel sheet is able to tolerate welding with great thermal intensity while obtaining uniform and excellent resistance, hardness and a strong plasticity correspondence, and is especially suitable for structures of oceanic bridges, structures of oceanic wind towers, structures of ocean platforms and hydroelectric structures.
    公开号:BR112015027406B1
    申请号:R112015027406-4
    申请日:2014-03-26
    公开日:2020-03-17
    发明作者:Zicheng Liu；Xianju Li
    申请人:Baoshan Iron & Steel Co., Ltd.；
    IPC主号:
    专利说明:

    “HT550 STEEL SHEET AND METHOD FOR MANUFACTURING AN HT550 STEEL SHEET” Field of the Invention [0001] The present invention relates to an HT550 steel sheet with very high toughness and excellent weldability and a method for making it. Through the TMCP process, a steel plate is obtained with a deformation resistance of 460 MPa or more, a tensile strength of 550 MPa at approximately 700 MPa, a deformation ratio of 0.85 or less, Charpy impact energy at -60 ° C (a single value) of 60 J or more and excellent weldability, which has fine ferrite microstructures plus self-tempered bainite with an average grain size of 15 pm or less.
    Background of the Invention [0002] As it is known, low-alloy and low-carbon (high strength) steel is one of the most important materials of engineering structures and is widely applied in oil and gas lines, offshore platforms, shipbuilding, bridge structures, boiler vessels, architectural structures, automobile industries, rail transport and mechanical production.
    [0003] The properties of low alloy and low carbon (high strength) steel depend on its chemical components and the process system in the manufacturing process, where strength, plasticity, toughness and weldability are the most important of the same, which finally they depend on the microstructures of finished steel products. As science and technology develop, higher requirements are proposed with regard to the high toughness and high plasticity of high strength steel. That is, the mechanical properties and operational performance can be significantly improved, while maintaining a low manufacturing cost, in order to reduce the amount of steel materials used, save on cost, and reduce the weight of the steel structure itself, and more importantly, to further improve safety, stability, durability and cold / hot machinability, to favor different construction environments and satisfy different requirements in processes.
    [0004] Currently, there is a climax in research and development for a new generation of high-performance steel and iron materials in Japan, Korea and the European Union. Efforts have been made to optimize alloy combinations and innovate manufacturing processes in order to achieve a better match between structures, so that high-strength steel can gain a better match between high toughness and high plasticity.
    [0005] Traditionally thick steel plate with a tensile strength of more than 590 MPa is manufactured by more quenching heating and rapid cooling (RQ + T) which is also called 'off-line hardening', which requires central part of the steel sheet to have sufficiently high hardening capacity, that is, the hardening index DI is greater than or equal to 1.0 multiplied by the thickness of the steel sheet, where DI = 0.311C1 / 2 (1 + 0.64 Si) x (1 + 4.10 Mn) x (1 + 0.27 Cu) x (1 + 0.52 Ni) x (1 + 2.33 Cr) x (1 + 3.14 Mo ) x25.4 (mm), in order to ensure that the steel plate has sufficiently high strength, excellent toughness at very low temperature and uniform microstructures and properties along the direction of its thickness. Consequently, a number of alloying elements such as Cr, Mo, Ni, Cu are inevitably added to the steel (JPS59-129724, JPH1-219121). Ni can not only improve the strength and hardening capacity of the steel plate, but also reduce the temperature of the transition phase and fine tune the grain sizes of the bainite / martensite blade; most importantly, Ni is the only element to improve the toughness at low intrinsic temperature of the bainite / martensite sheets, increasing the orientation angle between the bainite / martensite sheets, and improving the crack expansion resistance in the bainite / martensite eutectic. As, the alloy content of the steel plate is high, which results not only in high production cost, but also in high carbon equivalent Ceq, and cold crack sensitivity index in high welding Pcm. This poses great difficulties for field welding, so pre-heating is necessary before welding, and heat treatment after welding is required, whereby the welding cost becomes higher, the welding efficiency is reduced, and the welding environment becomes worse. A large number of previous patent documents (for example, JPS63 - 93845, JPS63 - 79921, JPS60 -258410, JPH4 - 285119A, JPH4 - 308035A, JPH3 - 264614, JPH2 - 250917, JPH4 - 143246,, US patent 4855106, patent US 5183198, US patent 4137104) describe only how to obtain the low temperature toughness and toughness of the base steel plate, but not how to improve the welding performance of the steel plate and obtain excellent low temperature toughness of the heat-affected zone Welding HAZ, nor how to guarantee the hardening of the central part of the hardened plate, to guarantee the strength, toughness of the steel plate and the uniformity of resistance, toughness along the direction of the thickness of the same.
    [0006] Currently, in terms of improving the low temperature toughness of the zone affected by the heat from welding (HAZ) of steel plate welded with high heat intensity, only Japan's Nippon Steel Co. employs metallurgical oxide technology ( US patent 4629505, WO 01/59167 A1), that is, during the welding process with high heat intensity, TiN particles close to the casting lines, dissolve under the strong effect of high temperature, and fail. Ti2O3 is more stable than TiN, and does not dissolve even at a temperature above the melting point of steel. Ti2O3 particles can become the nucleation sites of austenite transgranular acicular ferrite-AF in order to promote nucleation, effectively divide austenite grains, smooth the HAZ structure, and form high strength acicular ferrite structures and high tenacity. In addition to Sumitomo Metal Co. of Japan employing the technical means of adding B, and controlling the B / N ratio greater than or equal to 0.5, low silicon level, ultra low aluminum, moderate N content, in order to solve the problem with the high heat intensity welding performance of 60 kg flat steel sheets, which has good effects and has been applied successfully to engineering practices (Iron And Steel, 1978, Vol. 64, page 2205).
    Brief Description of the Invention [0007] The purpose of the present invention is to provide an HT550 steel sheet with very high toughness and excellent weldability and a method for making it. Through the TMCP process, the final steel sheet product has fine ferrite plus bainite microstructures with an average grain size of 15 pm or less, deformation resistance of 460 MPa or greater, tensile strength of 550MPa to approximately 700MPa, strain rate of 0.85 or less, Charpy impact energy -60 ° C (a single value) of 60J or greater. By obtaining the uniform and excellent combination of high toughness and high plasticity, the steel sheet can tolerate welding processes with high heat intensity, and especially be applied to ocean bridge structures, ocean wind tower structures, offshore platform structures and hydroelectric structures, and can achieve stable, low-cost, batch industrial production.
    [0008] To achieve the aforementioned objective, the technical solution of the present invention is as follows: the present invention employs the technical means of metallurgy: based on a component system with very low C, high Mn, Nb micro alloy, ultramicro Ti treatment, Mn / C is controlled in the range of 15 to approximately 30, (% Si) χ (% Ceq) is less than or equal to 0.050, (% C) x (% Si) is less than or equal to 0.010, ( % Mo) x [% C) + 0.13 (% Si)] is in the range of 0.003 to approximately 0.020, Ti / N is in the range of 2.0 to approximately 4.0, the steel sheet is linked with (Cu + Ni + Mo), Ni / Cu is greater than or equal to 1.0, Ca treatment and Ca / S is in the range of 0.80 to approximately 3.00.
    [0009] Specifically, the HT550 steel sheet with very high toughness and excellent weldability of the present invention has the following components in weight percentage: C: 0.04% to approximately 0.09%; Si: less than or equal to 0.15%; Mn: 1.25% to approximately 1.55%; P: less than or equal to 0.013%; S: less than or equal to 0.003%; Cu: 0.10% to approximately 0.30%; Ni: 0.20% to approximately 0.60%; Mo: 0.05% to approximately 0.25%; Als: 0.030% to approximately 0.060%; Ti: 0.006% to approximately 0.014%; Nb: 0.015% to approximately 0.030%; N: less than or equal to 0.0050%; Ca: 0.001% to approximately 0.004%; the rest being Fe and unavoidable impurities; and, at the same time, the content of the elements described above must meet the following relationships: in terms of the relationship between C and Mn, the Mn / C ratio is greater than or equal to 15 and less than or equal to 30, in order to ensure that the steel sheet assumes in the ductile fracture region under the condition of -60 ° C of temperature, that is, the slit shear area of Charpy impact sample is greater than or equal to 50%, in order to guarantee that the sheet steel has excellent toughness at very low temperature, and -60 ° C of impact energy Charpy (single value) of 60J or more.
    [0010] (% Si) x (% Ceq) is less than or equal to 0.050, where Ceq = C + Mn / 6 + (Cu + Ni) / 15 + (Cr + Mo + V) / 5, which ensures that the steel plate has excellent weldability, inhibits MA island formations in the HAZ welding with high heat intensity, improves the very low temperature toughness of the HAZ welding with high heat intensity, eliminates the fragile local areas welding joints and improve the safety and reliability of the steel structure.
    [0011] (% Si) x (% C) is less than or equal to 0.010, which can increase the critical cooling speed of the bainite phase transition, reduce the average temperature of the phase transition region, improve the formation of proeutetoid ferrite, increase the temperability of austenite without transition phase to promote the formation of bainite, ensure that the microstructures of the steel sheet submitted to TMCP are more self-tempered bainite ferrite, and guarantee impact toughness at the very low temperature of the steel; and furthermore, inhibit the precipitation of the M-A island in the HAZ welding with high heat intensity, and improve the weldability and toughness at the very low temperature of the HAZ welding.
    [0012] The two points above guarantee the excellent welding performance of the steel plate.
    [0013] Through the TMCP process, a steel plate is obtained with a resistance to deformation of 460 MPa or more, tensile strength of 550 MPa to approximately 700 MPa, deformation ratio of 0.85 or less, impact energy Charpy a -60 ° C (a single value) of 60 J or more and excellent weldability, which has fine ferrite microstructures plus self-tempered bainite with an average grain size of 15 pm or less.
    [0014] (% Mo) x [(% C) + 0.13 (% Si)] is in the range of 0.003 to approximately 0.020, which ensures that the resistance caused by the reduction of C and Si is neutralized through addition of the Mo element, and that through the corresponding design between the elements of C, Si and Mo, properties such as strength, plasticity, weldability and toughness at very low temperatures, are balanced, so that the steel sheet can have excellent toughness at very low temperatures and weldability, while the strength and plasticity of the steel sheet meets the development objective, and the subsequent process window is large enough to carry out field practice easily.
    [0015] The Ti / N ratio is in the range of 2.0 to approximately 4.0, which ensures that the TiN particles formed are uniform and fine, the resistance to Ostwald Ripening is high, and the austenite grains during the The heating and lamination processes of the plate are uniform and fine, the growth of grains in the welding HAZ is inhibited, and the low temperature toughness of the HAZ welding with high heat intensity is improved.
    [0016] In terms of the relationship between Cu and Ni, the Ni / Cu ratio is greater than or equal to 1.0, which reduces the temperatures of Ar3, Ar1 of TMCP steel sheets, and fine-tunes the microstructures of the same, and prevents the copper fragility plates while ensuring the excellent low temperature toughness of the base steel plate.
    [0017] The relationship between Ca and S: the Ca / S ratio is in the range of 0.80 to approximately 3.0, which guarantees nodularization of sulfides in steel, and improves the weldability with high heat intensity of the steel plate, while avoiding the generation of hot cracks during the welding process with high heat intensity.
    [0018] In the component design of the present invention: [0019] C significantly affects the strength, low temperature toughness, elongation, and weldability of TMCP steel sheet. From the point of view of improving the low temperature toughness and weldability of the steel plate, it is expected that the C content should be controlled at a low level; whereas from the point of view of the hardness of the steel, high toughness and high plasticity in the steel sheet, the toughness at very low temperature, the control of the microstructures in the manufacturing process and the manufacturing cost, it is undesirable that the content of C is very low, due to this very low C content tends to result in a very high crystal limit migration rate, coarse grains in the base steel plate and welding HAZ, thereby seriously degrading its low temperature toughness; thus, the reasonable range of C content is 0.04% to approximately 0.09%.
    [0020] Si can promote deoxidation of molten steel and improve the strength of the steel sheet, but for molten steel that is deoxidized by Al, the deoxidative effect of Si is not significant. Although Si can improve the strength of the steel sheet, the Si also seriously impairs the toughness at very low temperature, elongation and weldability of the steel sheet, especially in the case of welding with high heat intensity, the Si can not only promote the formation of islands of MA, but also produces the size of the coarse islands of MA, more, and irregularly distributed, which seriously impairs the toughness of the welding affected by the heat (HAZ) of welding. Thus, the Si content should be as low as possible. Taking into account the economy and functionality during the steelmaking process, the Si content must be controlled below 0.15%.
    [0021] Mn, as the most important element, has, in addition to improving the strength of the steel plate, also has effects of widening the austenite phase region, reducing the temperatures of Ar1 and Ar3, fine tuning the microstructures of the steel plate TMCP in order to improve the toughness at low temperature, and promote the formation of the phase transition structure at low temperature in order to improve the strength of the steel plate; but the Mn tends to separate during the solidification of the molten steel, and especially, when the Mn content is high, it can not only result in difficulties in the smelting operation, but also the segregation combined with C, P, S, etc. ., especially when the C content in steel is high, it can produce segregation and detachment from the central parts of the melt and the accumulation of the most severe oxygen sulfide inclusions. Severe segregation of the central parts of the castings can tend to form abnormal structures in subsequent rolling and welding processes, which can result in lower toughness at low temperature and cracks in the welding joints of the steel sheets. Consequently, depending on the C content range, the selection for a suitable Mn range is very important for TMCP steel sheet. According to the component system and C content of the present invention, the appropriate Mn content is in the range of 1.25% to approximately 1.55%, and when the C content is high, the Mn content can be appropriately reduced; conversely, when the C content is low, the Mn content can be appropriately increased.
    [0022] P, like the harmful impurity in steel, has tremendously harmful effects on the mechanical properties, especially in the toughness to impact at very low temperature, elongation and weldability (especially weldability with high heat intensity) and the performance of the gasket. welding, and thus, theoretically, the lower the content, the better. However, considering the operability and cost of steel production, the P content must be controlled below or equal to 0.013% for steel plate TMCP that requires welding with high heat intensity, toughness at -60 ° C and excellent compatibility between high toughness and high plasticity.
    [0023] S, like the harmful impurity in steel, has a very harmful effect on the toughness to impact at very low temperature of the steel and, more importantly, S combines with Mn to form MnS impurity, which can extend along of the rolling direction due to its plasticity during the hot rolling process, and forming MnS impurity band along the rolling direction, seriously damaging the low temperature impact toughness, elongation, Z-orientation properties, weldability and properties of the welding joint. At the same time, S is also the main element to generate hot brittleness during the hot rolling process and, theoretically, the lower the content of the same, the better. However, considering the operability, cost of steel production, the principle of smooth logistics, the S content must be controlled below or equal to 0.003% for TMCP steel sheets that require welding with high heat intensity, toughness at -60 ° C and excellent compatibility between high toughness and high plasticity.
    [0024] Cu is also an element for stabilizing austenite. The addition of Cu can also reduce the temperatures of Ari and Ar3, improve the resistance to the hardness and weathering of the steel plate, fine tune the microstructures of the TMCP steel plate, and improve the toughness at its very low temperature. However, too much Cu, for example, more than 0.30%, can cause brittleness to the copper, cracking surface of the casting blacking, internal cracks and especially the degradation of the properties of the steel sheet welding joints thick; very little Cu, for example, less than 0.10%, can have some effects. Thus, the Cu content must be controlled in the range of 0.10% to approximately 0.30%. In addition to reducing the copper brittleness of the steel containing Cu and smoothing the intercrystalline cracking during the hot rolling process, even more important, due to the fact that Cu and Ni are elements for stabilizing austenite, the addition of both Cu and Ni can significantly reduce Ari and Ar3 temperatures and improve the driving force for the transition from austenite to ferrite, to cause austenite to change phases under low temperatures, significantly fine tune the microstructure of the TMCP steel plate, increase the angle of orientation between the bainite lathe, improve the resistance to expand the cracks in the eutectic bainite, thereby improving the toughness at very low temperature of the TMCP steel sheet.
    [0025] The addition of Ni can improve the mobility of phase displacement of the ferrite, promote the displacement of slip with deviation (dislocation cross slip) and improve the intrinsic plasticity and toughness of the ferrite grain and blades of bainite (bainite lathes) ; in addition, Ni, as an element for stabilizing austenite, can significantly reduce the temperatures of Ar1 and Ar3 and improve the driving force for the transition from austenite to ferrite in order to induce austenite to change phases at lower temperatures, to significantly tune the microstructure of the TMCP steel sheet, increase the orientation angle between the bainite sheets, improve the crack expansion resistance in the eutectic bainite, thereby significantly improving the toughness at the very low temperature of the TMCP steel sheet. In this way, Ni has the function of simultaneously improving resistance to elongation, and low temperature toughness of TMCP steel sheet. The addition of Ni to the steel can also reduce the copper brittleness of the steel containing Cu, relieve intercrystalline cracking during the hot rolling process, and improve the hardness and weather resistance of the steel plate. Theoretically speaking, the higher the Ni content in the steel, the better. But too much Ni can harden the area affected by heat, and be harmful to the weldability of the steel plate and the SR properties of the welding joints; at the same time, Ni is an expensive element, and considering the cost efficiency, the Ni content must be controlled in the range of 0.20% to approximately 0.60%.
    [0026] The addition of Mo can significantly improve the hardening capacity of the steel plate, and promote the formation of bainite during rapid cooling. However, Mo, as an element for the formation of strong carbide, can also increase the size of the eutectic bainite and reduce the difference in orientation between the formed bainite lathes, in order to decrease the resistance of the cracks that pass through the eutectic bainites. . Therefore, Mo significantly improves the strength of the hardened steel sheet, while reducing the low temperature toughness and elongation of the TMCP steel sheet. In addition, too much Mo can not only seriously damage the elongation, weldability with high heat intensity and properties of the steel plate welding joints, but also increase the cost of manufacturing it. But it is highly efficient to add Mo and reduce the C content to balance the high toughness and high plasticity, improve the toughness at very low temperature and the weldability. Therefore, considering comprehensively the effects on the strengthening of the phase transition, the low temperature toughness of the base steel plate, the elongation and weldability of Mo and the cost factors, the content of Mo must be controlled in the range of 0 , 05% to 0.25%.
    [0027] Als in the steel can make the [N] free stable in it and reduce the free [N] in the zone affected by the welding heat (ZAC), thereby improving the low temperature toughness in the welding HAZ. Consequently, the lower limit of Als is controlled at 0.030%. However, excessive Als in steel can result not only in difficulties in casting, but also in a large number of dispersed acicular Al2O3 impurities, which are harmful to endoplasmic integrity, low temperature toughness and high intensity weldability, thus the ceiling limit of Als must be controlled at 0.060%.
    [0028] The Ti content is in the range of 0.006% to approximately 0.014%, which inhibits the excessive growth of austenite grains in the plate heating and hot rolling processes; and, most importantly, it inhibits the growth of HAZ grains during the welding process, and improves HAZ toughness. Second, because the affinity between Ti and N is much greater than the affinity between Al and N, when Ti is being added, it is preferable that N be combined with Ti to form dispersed TiN particles, which significantly reduce o [N] free in the zone affected by the welding heat (HAZ), thereby improving the low temperature toughness in the welding HAZ.
    [0029] The addition of a trace of Nb in the steel is to carry out the controlled rolling without recrystallization, in order to improve the strength and toughness of the steel sheet. When the Nb content is less than 0.015%, the effects on controlled rolling are not achieved and the ability to reinforce the TMCP steel sheet is insufficient. When the Nb content is greater than 0.030%, the formation of bainite (Bu) and the weakening of secondary precipitation of Nb (C, N) are induced under the condition of welding with high heat intensity, which can seriously damage the low temperature toughness of the zone affected by welding heat (HAZ) with high heat intensity. The content of Nb must be controlled in the range of 0.015% to 0.030%, in order to have the effects of controlled controlled rolling, to perceive the correspondence between the high tenacity and high plasticity of the TMCP steel sheet, at the same time not being harmful to the HAZ toughness of welding.
    [0030] The content of N in steel is difficult to control. In order to guarantee the existence of a solid solution [B] in the steel plate and prevent a lot of AlN precipitation along the limits of the original austenite grain (which is detrimental to the impact toughness of the steel plate), the N content steel plate is not greater than 0.005%.
    [0031] The Ca in the steel can, on the one hand, still purify the molten steel, and on the other hand, perform the denaturation treatment on the sulfides in the steel to change them to thin, stable and non-deformable sulfide spheres, inhibit the fragility of S to heat, improve the toughness at low temperature, the elongation and Z orientation properties and improve the anisotropy of the toughness of the steel sheet. The amount of Ca added to the steel depends on the content of S. The excessively low Ca content has little effect; excessively high Ca can form Ca (O, S) with excessively large size and greater fragility, which can become starting points for cracks, reduce the low temperature toughness and elongation of the steel plate and contaminate the molten steel through this decreasing the purity of the steel. In general, the Ca content should be controlled according to the equation: ESSP = (%, by weight, of Ca) [1-1.24 (%, by weight, of S)] / 1.25 (%, by weight, of S), where ESSP is the control index of the form of sulfide impurities, which is better in the range of 0.5 to approximately 5. Thus, the appropriate range of Ca content is 0.0010 % to approximately 0.0040%.
    [0032] The method for making the HT550 steel sheet with very high toughness and excellent weldability of the present invention, comprises the following steps: 1) casting and molding; wherein a plate is manufactured by casting and molding according to the components described above; 2) heating; wherein the heating temperature of the plate is controlled in the range of 1050 ° C to approximately 1150 ° C. 3) controlled rolling with the total compression ratio, that is, the thickness of the plate / final thickness of the steel plate greater than or equal to 4.0; where the first stage is the crude lamination stage, in which a continuous lamination is performed by the maximum capacity of the cylinder with the passage reduction greater than or equal to 8%, total reduction of 50% and final lamination temperature greater than or equal to 1000 ° C; after rough lamination, the intermediate plate is rapidly cooled by forced water cooling, in order to ensure that the intermediate plate reduces the initial lamination temperature required by controlled lamination by non-recrystallization in a time less than or equal to 10 min, to avoid that the intermediate plate does not form crystals, and ensure that the microstructures of the steel plate are thin and uniform, in order to obtain toughness at very low temperatures of -60 ° C; in the second stage, the controlled lamination operation without recrystallization is carried out with an initial lamination temperature of 780 ° C to approximately 840 ° C, a reduction in lamination in each pass greater than or equal to 7%, total reduction greater than or equal to 50 % and the final lamination temperature from 760 ° C to approximately 800 ° C. 4) controlled cooling; immediately after controlled rolling, the steel sheet is taken to an accelerated cooling device to be cooled, with a cooling temperature of 690 ° C to approximately 730 ° C, a cooling temperature greater than or equal to 6 ° C / s , a final cooling temperature of 350 ° C to approximately 600 ° C, and then the surface temperature of the steel sheet is maintained greater than 300 ° C for at least 24 hours.
    [0033] In the manufacturing method, according to the C, Mn, Nb, N and Ti content range mentioned above, the temperature for heating the plate is controlled in the range of 1050 ° C to approximately 1150 ° C, so to ensure that the austenite grains on the plate do not grow abnormally, while all the Nb in the steel is soluble in the solid in the austenite during the heating of the plate;
    [0034] The total compression ratio of the steel plate (the thickness of the plate / thickness of the final steel plate) greater than or equal to 4.0 ensures that the rolling deformation occurs even in the core of the steel plate, in order to improve the microstructure and performance of the central part of it.
    [0035] The first stage is the crude lamination stage, in which a continuous lamination is performed by the maximum capacity of the cylinder with the passage reduction greater than or equal to 8%, total reduction of 50% and final lamination temperature greater than or equal at 1000 ° C, in order to ensure that the deformed metals are subjected to dynamic / static recrystallization and the austenite grains of the intermediate plate are honed;
    [0036] After crude lamination, the intermediate plate is quickly cooled by forced cooling water, in order to ensure that the intermediate plate reduces to the initial lamination temperature required by the controlled lamination without recrystallization in a time less than or equal to 10 min.
    [0037] The second stage is the controlled lamination stage without recrystallization with an initial lamination of 780 ° C to approximately 840 ° C, a reduction in lamination in each pass greater than or equal to 7%, total reduction greater than or equal to 50% and a final lamination temperature of 760 ° C to approximately 800 ° C, according to the above Nb content range in the steel, and to ensure the effect of controlled lamination without recrystallization.
    [0038] After controlled rolling, the steel sheet is cooled to a cooling temperature by immersion in a rolling table, with the initial cooling temperature of 690 ° C to approximately 730 ° C, a cooling temperature of 350 ° C to approximately 600 ° C, and then the surface temperature of the steel sheet is kept higher than 300 ° C for at least 24 hours, to ensure that the steel sheet is cooled in the ferrite phase regions and austenite and the final microstructures are fine ferrite plus self-tempered bainite, in order to reach the deformation ratio less than or equal to 0.85.
    [0039] The benefits of the present invention are, through the simple design of combination of components together with the TMCP manufacturing process, the present invention can not only manufacture TMCP steel sheet with excellent complete performance at a low cost, but also reduce the manufacturing time significantly, in order to create great value for companies and produce the most environmentally friendly manufacturing process. The high performance and high added value of the steel plate are incorporated with an excellent combination of high toughness and high plasticity, excellent weldability (especially weldability with high heat intensity) and toughness at very low temperature, in the elimination of the local fragile region welding joints, and also in solving the problem with non-uniform performance along the thickness direction of the TMCP steel plate, so that the safety, stability and anti-fatigue of the large and heavy steel structure are greatly improved. For users, excellent weldability can save cost and reduce the time to manufacture steel members, thereby creating great value for users. In addition to the high additional value and effects that respect the environment, these steel sheets form one of the main manufacturing techniques and, thus, promote the image and competitiveness of BAOSHAN IRON & STEEL CO., LTD.
    Brief Description of the Figures [0040] Figure 1 shows the microstructures of steel 3 (1/4 of the thickness) according to an embodiment of the present invention.
    Detailed Description of the Invention [0041] From this point on, a further description of the present invention will be given in conjunction with the embodiments and figures.
    [0042] Table 1 shows the steel components in the embodiments of the present invention, Tables 2 and 3 show the process parameters for making steel for the embodiments, and Table 4 shows the properties of the steel in the embodiments of the present invention. .
    [0043] As shown in Figure 1, the final microstructures of the steel plate in the present invention are fine ferrite plus self-tempered bainite with an average grain size of 15 pm or less.
    [0044] Through the simple design of the combination of components together with the TMCP manufacturing process, the present invention can not only manufacture TMCP steel sheet with excellent complete performance at a low cost, but also significantly reduce the manufacturing time, creating great value for companies and producing the most environmentally friendly manufacturing process. The high performance and high added value of the steel plate are incorporated with an excellent combination of high toughness and high plasticity, excellent weldability (especially weldability with high heat intensity) and toughness at very low temperature, in the elimination of the local fragile region welding joints, and also in solving the problem with non-uniform performance along the thickness direction of the TMCP steel plate, so that the safety, stability and anti-fatigue of the large and heavy steel structure are greatly improved. For users, excellent weldability can save cost and reduce the time to manufacture steel members, thereby creating great value for users.
    [0045] The steel sheets of the present invention are the main materials used, mainly used for marine bridge structure, oceanic wind tower structure, offshore platform structure and hydroelectric power. Steel sheets produced by most steel mills in China (except BAOSHAN IRON & STEEL CO., LTD.) Do not meet all requirements for very low temperature toughness, especially for very low temperature toughness of -50 ° C from central parts of steel sheets with a thickness of more than 80 mm, and they have a large area of the local fragile region of the welding joints, which has high requirements in the field welding process and construction management. In addition, the steel structure fabrication work period cannot meet requirements on varied design schedules, which forces users to order a certain number of steel sheets in advance to perform a complete set of process evaluations. welding and adaptability testing of the deposited welding process, whereby the manufacturing time for steel structures is prolonged and the production cost remains high.
    [0046] With the development of the economy in China, the construction of a harmonious and conservation-oriented society, the construction of infrastructure projects and the development of clean energy were placed on the agenda. Currently, the construction of infrastructure projects and the development of clean energy are still in progress, therefore, the main materials of the same - HTCP50 steel sheets with very high tenacity and excellent weldability, have broad prospects for commercialization.
    Table 1 Unit: Weight Percentage Table 2 Table 3 Table 4 Claims
    权利要求:
    Claims (2)
    [1]
    1. HT550 STEEL SHEET, with high toughness and excellent weldability, having the following components in percentage of weight: C: 0.04% to 0.09%; Si: <0.15%; Mn: 1.25% to 1.55%; P: <0.013%; S: <0.003%; Cu: 0.10% to 0.30%; Ni: 0.20% to 0.60%; Mo: 0.05% to 0.25%; Als: 0.030% to 0.060%; Ti: 0.006% to 0.014%; Nb: 0.015% to 0.030%; N: <0.0050%; Ca: 0.001% to 0.004%; the remainder being Fe and unavoidable impurities; characterized by, simultaneously, the contents of the elements described above satisfy the following relationships: the relationship between C and Mn: the Mn / C ratio is greater than or equal to 15 and less than or equal to 30; (% Si) x (% Ceq) is less than or equal to 0.050, where Ceq = C + Mn / 6 + (Cu + Ni) / 15 + (Cr + Mo + V) / 5; (% Si) x (% C) is less than or equal to 0.010; (% Mo) x [(% C) + 0.13 (% Si)] is in the range of 0.003 to 0.020; the Ti / N ratio is in the range of 2.0 to 4.0; the ratio between Cu and Ni: Ni / Cu is greater than or equal to 1.0; the relationship between Ca and S: the Ca / S ratio is in the range of 0.80 to 3.0; steel sheet which has a deformation resistance of 460 MPa or more, a tensile strength of 550 MPa to 700 MPa, a deformation ratio of 0.85 or less, Charpy impact energy at -60 ° C of 60 J or more, and the microstructures of the same being fine ferrites plus self-tempered bainite with an average grain size less than or equal to 15 pm.
    [2]
    2. METHOD FOR MANUFACTURING THE HT550 STEEL SHEET, with high toughness and excellent weldability, as defined in claim 1, characterized by comprising the following steps: 1) casting and molding; wherein a plate is formed by casting and molding according to the components described above; 2) heating; wherein the heating temperature of the plate is controlled in the range of 1050 ° C to 1150 ° C; 3) controlled rolling with the total compression ratio, that is, the thickness of the plate to the final thickness of the steel plate greater than or equal to 4.0; where a first stage is a crude lamination stage, that is, a recrystallization lamination stage, in which a continuous lamination is performed by the maximum capacity of the laminator with the passage reduction greater than or equal to 8%, total reduction of 50 % and final lamination temperature greater than or equal to 1000 ° C; after crude lamination, the intermediate plate is quickly cooled by forced cooling water, in order to ensure that the intermediate plate reduces to the beginning of the lamination temperature required by the controlled lamination without recrystallization in a time less than or equal to 10 min; in the second stage, the controlled lamination operation without recrystallization is carried out with an initial lamination temperature of 780 ° C to 840 ° C, a reduction of lamination in each pass greater than or equal to 7%, total reduction greater than or equal to 50% and the final lamination temperature of 760 ° C to 800 ° C; 4) controlled cooling; after controlled rolling, the steel sheet is cooled to an initial cooling temperature by rotating on a roller table, with the initial cooling temperature from 690 ° C to 730 ° C, to ensure that the steel sheet is cooled in the regions of ferrite and austenite phases, and the final microstructures are fine ferrite plus self-tempered bainite, and with a cooling temperature greater than or equal to 6 ° C / s, a stop cooling temperature of 350 ° C to 600 ° C and then the surface temperature of the steel sheet is maintained at more than 300 ° C for at least 24 hours; and the final steel sheet having a deformation resistance of 460 MPa or more, a tensile strength of 550 Mpa to 700 MPa, a deformation ratio of 0.85 or less, Charpy impact energy at -60 ° C of 60J or more , and the microstructures of the same being fine ferrites plus self-tempered bainite with an average grain size less than or equal to 15 pm.
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    同族专利:
    公开号 | 公开日
    CN103320692A|2013-09-25|
    JP2016524653A|2016-08-18|
    CA2914441A1|2014-12-24|
    ES2790421T3|2020-10-27|
    WO2014201887A1|2014-12-24|
    US10208362B2|2019-02-19|
    JP6198937B2|2017-09-20|
    EP3012340A4|2017-03-08|
    EP3012340B1|2020-05-06|
    US20160122844A1|2016-05-05|
    KR20150143838A|2015-12-23|
    CA2914441C|2019-03-05|
    EP3012340A1|2016-04-27|
    CN103320692B|2016-07-06|
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    法律状态:
    2018-11-13| B06F| Objections, documents and/or translations needed after an examination request according art. 34 industrial property law|
    2019-06-04| B07A| Technical examination (opinion): publication of technical examination (opinion)|
    2020-02-11| B09A| Decision: intention to grant|
    2020-03-17| B16A| Patent or certificate of addition of invention granted|Free format text: PRAZO DE VALIDADE: 20 (VINTE) ANOS CONTADOS A PARTIR DE 26/03/2014, OBSERVADAS AS CONDICOES LEGAIS. |
    优先权:
    申请号 | 申请日 | 专利标题
    CN201310244712.3|2013-06-19|
    CN201310244712.3A|CN103320692B|2013-06-19|2013-06-19|Superhigh tenacity, superior weldability HT550 steel plate and manufacture method thereof|
    PCT/CN2014/074084|WO2014201887A1|2013-06-19|2014-03-26|Ht550 steel plate with ultrahigh toughness and excellent weldability and manufacturing method therefor|
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