High-strength crack arrest toughness steel suitable for high heat input welding and manufacturing method thereof

Abstract

The present invention provides a high-strength crack arrest toughness steel suitable for high heat input welding and a manufacturing method thereof. The steel has the following components by weight: C: 0.03%-0.05%, Si: 0.10%-0.25%, Mn: 0.80%-1.20%, P≤0.01%, S≤0.005%, Al: 0.005%-0.025%, Ti: 0.005%-0.015%, Ni: 0.35%-0.60%, Cu: 0.15%-0.30%, Ca: 0.020%-0.050%, Zr: 0.005%-0.02%, Cr: 0.15%-0.35%, V: 0.030%-0.060%, N: 0.0010%-0.0040%, Re: 0.01%-0.03%, and the balance is Fe and unavoidable impurities. The manufacturing method includes smelting, continuous casting, heating, controlled rolling and controlled cooling; the steel plate produced by the present invention has brittle fracture arrest toughness and high heat input welding characteristics, which meets the requirements of ultra-large container ships for efficient construction steel.

Description

Technical Field

[0001] The present invention belongs to the field of metal materials, and in particular relates to a high-strength crack arrest toughness steel suitable for high heat input welding and a manufacturing method thereof. Background Art

[0002] With the trend toward larger and more efficient shipbuilding, welding is the primary method of connecting steel structures during shipbuilding. 80% of shipbuilding workloads are welded, making high-heat-input welding key to achieving efficient shipbuilding and reducing manufacturing costs. Consequently, shipbuilders are increasingly demanding that shipbuilding steel meet high-heat-input requirements. Currently, large shipyards are widely adopting high-heat-input welding equipment such as multi-wire submerged arc welding, FCB welding, and electrogas vertical welding to achieve efficient shipbuilding.

[0003] However, during the welding process, the heat-affected zone (HAZ) of steel plates undergoes changes in structure and performance due to the effects of the welding heat cycle, and in particular, its low-temperature toughness is greatly reduced. To ensure the quality of steel structure weld joints, traditional structural steels generally require strict limits on welding line energy, weld bead layout, and interlayer temperature control, and sometimes preheating before welding is required. Although strict standardized operations can effectively guarantee the reliability of welded structural parts, they also significantly limit the efficiency of welding operations, thereby limiting the manufacturing efficiency of steel structures. Faced with the increasing amount of welding work on thick steel plates, material developers and welding process engineers have proposed the idea of ​​developing steel for high-line energy welding and have proposed their own different research and technical solutions.

[0004] Container ships, one of the three main ship types, are seeing an annual increase in orders. In particular, critical components such as hatch coamings on container ships utilize thicker steel plates. Improving welding efficiency can significantly reduce shipbuilding cycles, generating significant revenue for shipyards. Currently, there is some research on high-heat input welded steel both domestically and internationally. A search of patents and literature has uncovered some promising technologies, but their descriptions clearly fall short of the present invention's proposed technical solution in terms of composition, production methods, high-heat input weldability, and crack arrestability.

[0005] CN 112921150A discloses a "method for manufacturing aluminum-free low-alloy steel plates suitable for high-energy welding." Based on controlling the initial total oxygen content, the method adopts a composite addition of Mg and Ca to form beneficial inclusions in a complex phase, inhibiting grain growth. A two-stage controlled rolling process is used to obtain a 60mm thick, 36kg high-strength steel with high heat input characteristics. However, this product lacks crack arrestability and has low strength, making it unsuitable for use in the construction of container ships.

[0006] CN 109321847A discloses "A high-heat-input weldable EH420-grade thick steel plate for marine engineering and its preparation method." The method utilizes post-converter weak deoxidation to control the free oxygen content and form composite inclusions such as Al-Mg-Ti. Because inclusions are formed during the LF refining stage and subsequently undergo RH treatment, they coarsen and float, resulting in uncertain quality of the resulting molten steel and low reliability for high-heat-input welding.

[0007] 3) CN 109321815A discloses a "method for manufacturing high-strength thick steel plates resistant to high-heat input welding." The strength grade is 36 kg, which is only suitable for ordinary ship structures. In addition, in the implementation of high-heat input welding, Ti alloying is used. However, due to the preferential oxidation of C, Si, Mn, Al, etc. caused by oxygen blowing in RH, resulting in component loss, the particle size of the secondary oxidation products formed by this method is uncontrollable, and the obtained inclusion particle size and distribution are unreliable. Therefore, it is not a perfect technical method.

[0008] 4) CN 109321846A discloses a "Method for Manufacturing Steel with a Yield Strength of 355 MPa for High-Input Heat Welding." Similar to the aforementioned patent, its strength does not meet the crack arrest toughness requirements for critical container ship construction. Furthermore, due to the high free oxygen concentration of over 700 ppm after converter smelting and the intense turbulence of the molten steel during tapping, Ti oxides in the steel are difficult to form a uniform and stable distribution, and most of them float out. During subsequent refining, oxides of Al, Ca, and other materials continue to aggregate with the original oxides and float out into the slag. Consequently, the oxide particle size and bulk density in the resulting steel are uncertain, making it difficult to ensure reliable high-input heat welding performance.

[0009] 5) CN 109321816A discloses a "Method for Manufacturing Steel with a Yield Strength of 460 MPa for High-Input Heat Welding." This method still uses weak deoxidizers such as Si and Mn in the first half of the converter tapping process, followed by the addition of Ti iron in the second half to achieve a free oxygen content of 100 ppm. At this free oxygen content, the Ti in the steel primarily exists as large oxide particles, which are difficult to retain in the steel during subsequent refining. Consequently, high-input heat welding is unstable. Furthermore, the steel lacks crack arrest toughness, making it unsuitable for use in critical container ship structures.

[0010] In summary, although these manufacturing methods can obtain steel plates suitable for large-line energy welding, the above-mentioned preparation methods of the prior art are difficult to stably obtain effective inclusions that are conducive to large-line energy welding, and the prepared steel plates do not meet the technical index requirements of crack-arresting steel for container ships. Summary of the Invention

[0011] The object of the present invention is to overcome the above-mentioned problems and deficiencies and to provide a steel plate having high strength, high crack arrest toughness, and a suitable heat input of more than 400 kJ / cm, and a production method thereof, which solves the difficult problem of matching technical indicators such as high strength, excellent low-temperature toughness, brittle fracture resistance, and high heat input welding. It can meet the material requirements for the efficient construction of ultra-large container ships and provide high-strength crack arrest toughness steel suitable for high heat input welding and a manufacturing method thereof.

[0012] The object of the invention is achieved like this:

[0013] A high-strength, crack-arresting toughness steel suitable for high heat input welding. The steel has the following components by weight: C: 0.03%-0.05%, Si: 0.10%-0.25%, Mn: 0.80%-1.20%, P≤0.01%, S≤0.005%, Al: 0.005%-0.025%, Ti: 0.005%-0.015%, Ni: 0.35%-0.60%, Cu: 0.15%-0.30%, Ca: 0.020%-0.050%, Zr: 0.005%-0.02%, Cr: 0.15%-0.35%, V: 0.030%-0.060%, N: 0.0010%-0.0040%, Re: 0.01%-0.03%, and the balance consisting of Fe and unavoidable impurities.

[0014] The Ca / S ratio in the steel is ≥6.0.

[0015] The microstructure of the steel is a multiphase structure including fine lath bainite + acicular ferrite + a small amount of polygonal ferrite, wherein the lath bainite accounts for 30% to 40%, the acicular ferrite accounts for 40% to 60%, and the polygonal ferrite accounts for 10% to 20%. The average grain size of the steel plate microstructure is less than 10 μm.

[0016] The microstructure also includes oxynitrides formed by Zr, Ti, Ca, V elements and O, N. The oxynitrides have a compound size of 20 to 100 nm, which fully exerts its fine grain and precipitation strengthening effects, thereby improving the strength and toughness of the steel plate.

[0017] The mechanical properties of the crack arrest steel plate are yield strength 540-620MPa, tensile strength 650-720MPa, elongation after fracture ≥23.5%; at -10°C, Kca ≥6800N / mm 3 / 2 At -60°C, the impact energy of the steel plate is ≥280J. After welding with a heat input of more than 400KJ / cm, the impact energy of the heat-affected zone of the steel plate is ≥140J, both exceeding the requirements of international classification society standards. After 5% deformation and strain aging at 250°C for 1 hour, the aging impact energy of the steel plate at -60°C is ≥140J.

[0018] The reasons for the composition design of the present invention are as follows:

[0019] C is an essential element for maintaining steel strength, especially for TMCP steel plates. Its content should be above 0.02%. However, exceeding a certain level significantly deteriorates the material's low-temperature toughness, crack arrest toughness, and weldability. Furthermore, increasing C content increases the tendency for retained austenite to form during cooling, so the upper limit is 0.07%. The preferred C content is 0.03% to 0.05%.

[0020] Si: A major deoxidizing component in the steelmaking process, Si must contain at least 0.10% to achieve a sufficient deoxidizing effect. However, exceeding this limit reduces the toughness of the base metal and welds. Si in solid solution increases strength while also raising the ductile-brittle transition temperature. Therefore, the Si content is limited to 0.10% to 0.25%.

[0021] Mn: An essential element for ensuring the strength and toughness of steel. Mn combines with sulfur to form MnS, which prevents the formation of low-melting-point FeS at grain boundaries and causes hot cracking, thereby greatly reducing the harmful effects of S. Mn is also a good deoxidizer. Manganese is a low-cost strengthening and toughening element. Too low a content of manganese cannot guarantee the material's strength. However, when the Mn content exceeds 1.50%, it will aggravate the segregation of the ingot and deteriorate the low-temperature toughness of the coarse-grained heat-affected zone (CGHAZ). Therefore, the preferred Mn content is 0.80-1.20%.

[0022] P: is an unavoidable impurity element in steel that deteriorates the toughness and weldability of the steel. Studies have shown that when the P content exceeds 0.012%, its embrittlement performance increases significantly, so the upper limit is preferably 0.010%.

[0023] If the S content exceeds 0.01%, a large number of MnS inclusions will form in the steel. The formation of MnS inclusions and the resulting anisotropy will seriously reduce the toughness, ductility, and weldability of the steel plate. Furthermore, an increase in S content increases the tendency of hot-rolled steel plates to undergo hot cracking. Therefore, measures are taken during the smelting process to minimize the S content in the steel. In the present invention, the upper limit of the S content is determined to be 0.005%.

[0024] Al: As a deoxidizing and grain-refining element, it's generally added at levels above 0.005%. However, exceeding 0.05% can easily cause hot cracking in cast slabs. Furthermore, the solid-state transformation products of Al-deoxidized steel are a small amount of PF and a large amount of BU. This results in unrestricted growth of ferrite laths, which grow very easily and eventually intersect at the center of the original austenite grains. This results in very long lath bundles, essentially half the width of the grain. High-carbon MA components and carbides form between the lath bundles, increasing brittleness and reducing the toughness of the welded steel plate. Therefore, the upper limit of Al content is 0.025%, with a preferred range of 0.005% to 0.025%.

[0025] Ni: As an austenite-stabilizing element, its addition enhances solid solution strengthening. It also lowers the ferrite transformation temperature and refines the ferrite grain size, contributing to grain refinement. Furthermore, nickel promotes the formation of acicular ferrite, which, while also enhancing transformation strengthening, increases grain boundary area, improving the steel plate's fracture toughness and crack arrestability. Therefore, the preferred Ni content is between 0.35% and 0.60%.

[0026] Cu: It can significantly improve the hardenability and corrosion resistance of the steel plate. It is also an austenite stabilizing element in steel. The appropriate addition can refine the microstructure of the TMCP steel plate and improve the low-temperature toughness. However, excessive addition will cause "copper brittleness" tendency, easily causing cracks on the surface and inside of the ingot, reducing the mechanical properties of the rolled steel plate, and reducing toughness, causing embrittlement of the steel plate. Therefore, the Cu content of the present invention is controlled at 0.15% to 0.30%.

[0027] Zr: Zr has a strong affinity with O and N and is a typical nitrogen oxide-forming element. Dispersed nitrogen oxides can become nucleation cores that induce ferrite phase transformation. During high heat input welding, it can effectively inhibit grain coarsening and improve the post-weld low-temperature toughness of the material. The preferred content range is 0.005% to 0.02%.

[0028] Ti: Trace amounts of titanium combine with carbon and nitrogen in the steel to form small, stable carbon and nitrogen compound particles. This effectively prevents austenite grain coarsening during slab heating and suppresses the effects of welding heat on grain coarsening during welding, improving the low-temperature toughness of the matrix and weld heat-affected zone. The Ti content in this invention is controlled to 0.005%-0.015%.

[0029] V: V is a precipitation strengthening element, and particularly at relatively low controlled rolling temperatures, can achieve excellent precipitation strengthening effects. Furthermore, the combination of V and N is also an important means of inhibiting grain boundary growth and migration during the welding thermal cycle. In the present invention, medium-low temperatures are used for TMCP finishing and final cooling. While V exerts its strengthening effect, its VN particles also promote high-heat input welding. The preferred V content in the present invention is 0.03%-0.06%.

[0030] Ca: Calcium treatment modifies inclusions. CaO combines with Al2O3 inclusions to form calcium aluminate, which floats into the slag. Ca also combines with S to form CaS, which coats the alumina and forms spherical particles, reducing the proportion of MnS formed and thereby improving the transverse properties of the steel plate. In the present invention, the formation of CaS and finely sized CaO creates intragranular mass transfer-induced phase deformation nuclei within the austenite, contributing to grain refinement and improved toughness. Therefore, Ca is set to 0.020% to 0.050%, with a Ca / S ratio of ≥6. The ratio of residual Ca to S after compounding should be greater than 1.5.

[0031] Cr: Chromium is a weak carbide-forming element. Adding a certain amount of Cr can improve the hardenability of the steel plate and promote the formation of strengthening structures represented by bainite. It can replace part of the strengthening elements such as C and Mn, reducing the toughness deterioration caused by the former due to the increase in strength. However, the addition of higher Cr will also lead to the deterioration of welding performance. Therefore, under the TMCP process, the preferred Cr content range is between 0.15% and 0.35%.

[0032] N: It can form fine precipitates with elements such as Al, Ti, V, and Zr. The precipitates are dispersed in the steel, which can effectively inhibit the growth of grains, give full play to the effects of fine grains and precipitation strengthening, and improve strength and toughness. However, if the content is too high, free N will easily form in the steel, which will increase the aging sensitivity of the steel, reduce its low-temperature toughness, and deteriorate its welding performance. In summary, it is appropriate to control its content within the range of 0.0010% to 0.0040%.

[0033] Re: Rare earth elements (RE) significantly reduce the deterioration caused by the segregation of low-melting-point elements at grain boundaries in steel, improving strength and toughness by purifying the grain boundaries. They also alter the distribution and morphology of sulfides in steel. In particular, MnS inclusions in steel tend to form thin strips during hot rolling, resulting in significant anisotropy in the steel's properties and severely deteriorating transverse properties. Furthermore, a certain amount of RE can improve the weldability and corrosion resistance of steel, with a preferred content of 0.01% to 0.03%.

[0034] The second technical solution of the present invention is to provide a method for manufacturing high-strength crack arrest toughness steel suitable for high heat input welding, including smelting, continuous casting, heating, controlled rolling and controlled cooling;

[0035] Smelting:

[0036] (1) Using low carbon / low aluminum clean steel as raw material, FeOx cored wire is fed into the molten steel tank during vacuum treatment to increase oxygen, and the oxygen content in the molten steel is controlled to be 5-15ppm. Argon is blown in and stirred for 3-6 minutes;

[0037] (2) The smelting process adopts high carbon single-point blowing method. The main elements of the steel are adjusted to the range of the present invention in the converter, and other alloy components are added as required for smelting.

[0038] (3) The molten steel removed from the converter is subjected to secondary refining to further reduce the content of harmful impurities such as O, S, and non-metallic inclusions;

[0039] (4) Add Zr and Ca to the steel in a wire feeding manner, controlling the amount of Zr in the molten steel to be 5-15 ppm and the amount of Ca to be 10-25 ppm; then blow argon into the molten steel through the argon holes at the bottom of the tank to stir it, with the diameter of the exposed surface of the molten steel ≤80 mm, and the stirring time to be 4-9 min; after stirring, put it on the machine for pouring within 15 min.

[0040] Continuous Casting:

[0041] The superheat of the tundish steel liquid is controlled at 15-25°C. Soft reduction and electromagnetic stirring at the end of the crystallizer are used during the continuous casting process. Preferably, the soft reduction is 5.0-10.0 mm. The secondary cooling adopts segmented cooling. Preferably, the cooling rate of the vertical section strong cooling is 10.0-20.0°C / s, and the cooling rate of the bending section weak cooling is 3.0-5.0°C / s. The continuous casting billet drawing speed is 0.8-1.2 m / min, and the casting slab thickness is 250-300 mm.

[0042] heating:

[0043] The continuous casting billet heating temperature is 1100℃~1150℃;

[0044] The steel slab is heated to a temperature not lower than 1100°C but not higher than 1150°C. This is because temperatures below 1100°C are insufficient for the alloying elements to fully dissolve into the austenite, preventing the required finishing temperature for hot rolling. Temperatures above 1150°C significantly coarsen the original austenite grains, reducing the low-temperature toughness of the steel.

[0045] Controlled rolling and controlled cooling: rolling in the austenite recrystallization zone and rolling in the non-recrystallization zone;

[0046] Austenite recrystallization zone rolling: starting rolling temperature 900℃~1050℃, cumulative reduction rate not less than 45%, single pass reduction rate ≥10%;

[0047] Rolling in the non-recrystallization zone: the starting rolling temperature is 750-800℃, the finishing rolling temperature is about 730-780℃, the cumulative reduction rate is not less than 45%, and the single-pass reduction rate is ≥10%;

[0048] Laminar cooling is used for post-rolling cooling, and the cooling rate is controlled at 2.0-5.0°C / s to cool the steel plate to 530-580°C; the final structure of the steel is fine lath B+acicular ferrite+a small amount of polygonal ferrite.

[0049] After the steel plates come off the production line, they should be stacked and slowly cooled. The starting temperature of slow cooling should be between 350 and 450°C, and the stacking time should be no less than 48 hours.

[0050] The beneficial effects of the present invention are:

[0051] 1) Based on the chemical composition system of the traditional 40kg steel grade specified by classification societies, the steel of the present invention produces a crack arrest steel plate with brittle fracture arrest toughness and high heat input welding properties, meeting the requirements for efficient steel construction for ultra-large container ships.

[0052] 2) The composition of the present invention is controlled by low C and low Mn, that is, low carbon equivalent composition, to ensure the weldability and low-temperature toughness of the material, and the low-temperature toughness is improved by using Ni. Elements such as Zr, Ti and Ca are combined with O and N to form fine nitrogen oxides with a compound size of 20-100nm, which inhibit the growth and coarsening of austenite grains at high temperatures and promote the nucleation of acicular ferrite during the austenite transformation process to refine the grains, solving the problem of strength and toughness matching in high-input welding.

[0053] 3) Add appropriate amounts of strengthening elements such as Ni, Cu, and Cr to the steel plate to compensate for the insufficient strength caused by low carbon and avoid the deterioration of low-temperature toughness, crack arrest performance, and weldability;

[0054] 4) By adding appropriate amounts of strengthening elements and combining them with precisely controlled smelting and TMCP processes, the combined effects of grain refinement, precipitation, and phase transformation strengthening are achieved.

[0055] 5) The crack-arrest steel obtained using the composition design and production method of the present invention has a multiphase structure consisting of fine lath B, acicular ferrite, and a small amount of polygonal ferrite, with an average grain size of the base material less than 10 μm. The original austenite grain size is controlled by low-temperature heating. A cumulative reduction rate of no less than 45% is applied in both the recrystallization zone and the unrecrystallization zone, with a single-pass reduction rate of no less than 10%, to break up coarse as-cast grains and obtain cumulative deformation energy to enhance the driving force for recrystallization and phase transformation. Ultimately, effective control of grain size is achieved, ensuring the acquisition of strength and toughness. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 This is a metallographic diagram of the microstructure of Example 1 of the present invention.

[0057] Figure 2 This is a metallographic diagram of the HAZ microstructure of the steel plate after welding at 500 kJ / cm in Example 1 of the present invention. DETAILED DESCRIPTION

[0058] The present invention will be further described below by way of examples.

[0059] The embodiment of the present invention performs smelting, continuous casting, heating, controlled rolling and controlled cooling, and stacking and slow cooling according to the component ratio of the technical solution.

[0060] Heating: The continuous casting billet heating temperature is 1100℃~1150℃;

[0061] Controlled rolling and controlled cooling: rolling in the austenite recrystallization zone and rolling in the non-recrystallization zone;

[0062] Austenite recrystallization zone rolling: rolling temperature 900℃~1050℃, cumulative reduction rate not less than 45%;

[0063] Rolling in the non-recrystallization zone: the starting rolling temperature is 750-800℃, the finishing rolling temperature is about 730-780℃, and the cumulative reduction rate is not less than 45%; laminar cooling is adopted for post-rolling cooling, and the cooling rate is controlled at 2-5℃ / s to cool the steel plate to 530-580℃;

[0064] Stacking and slow cooling: The steel plates should be stacked and slow cooled after they come off the line. The slow cooling starting temperature should be between 350 and 450°C, and the stacking time should be no less than 48 hours.

[0065] Further; during the smelting process,

[0066] (1) Using low carbon / low aluminum clean steel as raw material, FeOx cored wire is fed into the molten steel tank during vacuum treatment to increase oxygen, and the oxygen content in the molten steel is controlled to be 5-15ppm. Argon is blown in and stirred for 3-6 minutes;

[0067] (2) The smelting process adopts high carbon single-point blowing method. The main elements of the steel are adjusted to the range of the present invention in the converter, and other alloy components are added as required for smelting.

[0068] (3) The molten steel removed from the converter is subjected to secondary refining to further reduce the content of harmful impurities such as O, S, and non-metallic inclusions;

[0069] (4) Add Zr and Ca to the steel in a wire feeding manner, controlling the amount of Zr in the molten steel to be 5-15 ppm and the amount of Ca to be 10-25 ppm; then blow argon into the molten steel through the argon holes at the bottom of the tank to stir it, with the diameter of the exposed surface of the molten steel ≤80 mm, and the stirring time to be 4-9 min; after stirring, put it on the machine for pouring within 15 min.

[0070] Furthermore, during the continuous casting process, the superheat of the tundish steel liquid is 15-25°C, soft pressure and electromagnetic stirring are used at the end of the crystallizer during the continuous casting process, segmented cooling is used for secondary cooling, the continuous casting billet drawing speed is 0.8-1.2m / min, and the casting slab thickness is 250-300mm.

[0071] Further; the segmented cooling is a vertical segment strong cooling and a curved segment weak cooling; the cooling rate of the vertical segment strong cooling is 10.0 to 20.0 ° C / s, and the cooling rate of the curved segment weak cooling is 3.0 to 5.0 ° C / s,

[0072] Further, the light pressing amount is 5.0-10.0mm.

[0073] The composition of the steel of the present invention is shown in Table 1. The smelting and continuous casting processes of the steel of the present invention are shown in Table 2. The main rolling process parameters of the steel of the present invention are shown in Table 3. The welding process of the steel of the present invention is shown in Table 4. The properties of the steel of the present invention are shown in Table 5. The microstructure of the steel of the present invention is shown in Table 6.

[0074] Table 1 Composition of steel according to the present invention (wt%)

[0075] Example 1 2 3 4 5 6 7 8 9 10 C 0.035 0.05 0.03 0.04 0.045 0.032 0.038 0.043 0.046 0.049 Si 0.22 0.1 0.18 0.16 0.25 0.13 0.24 0.14 0.11 0.19 Mn 1.10 1.20 1.14 0.85 0.95 0.84 0.97 1.16 0.88 0.93 P 0.005 0.009 0.005 0.01 0.008 0.007 0.006 0.008 0.009 0.007 S 0.002 0.001 0.004 0.002 0.005 0.003 0.002 0.001 0.003 0.002 Al 0.012 0.017 0.02 0.005 0.025 0.008 0.021 0.014 0.019 0.023 Ti 0.005 0.011 0.01 0.012 0.006 0.013 0.009 0.014 0.007 0.008 Ni 0.46 0.59 0.42 0.36 0.53 0.39 0.54 0.48 0.56 0.57 Cu 0.3 0.25 0.27 0.25 0.15 0.17 0.23 0.29 0.26 0.19 Ca 0.02 0.031 0.025 0.04 0.05 0.023 0.037 0.042 0.047 0.046 Zr 0.006 0.015 0.02 0.008 0.011 0.018 0.014 0.017 0.016 0.019 Cr 0.25 0.3 0.27 0.15 0.35 0.17 0.24 0.31 0.34 0.19 Re 0.011 0.021 0.024 0.030 0.028 0.016 0.018 0.014 0.026 0.019 V 0.035 0.06 0.03 0.04 0.05 0.032 0.036 0.043 0.052 0.047 N 0.0024 0.0017 0.0021 0.0035 0.0028 0.0019 0.0037 0.0013 0.0029 0.0023 Ceq 0.32 0.38 0.33 0.26 0.33 0.25 0.31 0.36 0.33 0.31 Ca / S 10.00 31.00 6.25 20.00 10.00 7.67 18.50 42.00 15.67 23.00

[0076] Table 2 Main process parameters of smelting and continuous casting of steel according to the present invention

[0077]

[0078] Table 3 Main rolling process parameters of the steel according to the embodiment of the present invention

[0079]

[0080] Table 4 Main process parameters for welding steel in the embodiment of the present invention

[0081]

[0082] Table 5 Properties of Steels in Examples of the Invention

[0083]

[0084] Table 6 Microstructure of steel according to the present invention

[0085]

[0086] As can be seen from the above, the mechanical properties of the crack arrest steel plate produced by the present invention are yield strength 540-620MPa, tensile strength 650-720MPa, elongation after fracture ≥ 23.5%; at -10℃, Kca ≥ 6800N / mm 3 / 2 At -60℃, the impact energy of the steel plate is ≥280J. After welding with a heat input of more than 400KJ / cm, the impact energy of the heat-affected zone of the steel plate is ≥140J. After 5% deformation and strain aging at 250℃ for 1 hour, the aging impact energy of the steel plate at -60℃ is ≥140J.

[0087] In order to describe the present invention, the present invention has been appropriately and fully illustrated through the examples above. The above embodiments are only used to illustrate the present invention, and are not intended to limit the present invention. Ordinary technicians in the relevant technical field can make various changes and modifications without departing from the spirit and scope of the present invention. Any modifications, equivalent substitutions, improvements, etc. made should be included in the scope of protection of the present invention, and the patent protection scope of the present invention should be defined by the claims.

Claims

1. A high-strength crack arrest toughness steel suitable for high heat input welding, characterized in that: The composition of the steel is as follows by weight percentage: C: 0.03%~0.05%, Si: 0.10%~0.25%, Mn: 0.80%~1.20%, P≤0.01%, S≤0.005%, Al: 0.005%~0.025%, Ti: 0.005%~0.015%, Ni: 0.35%~0.60%, Cu: 0.15%~0.30%, Ca: 0.020%~0.050%, Zr: 0.005%~0.02%, Cr: 0.15%~0.35%, V: 0.030%~0.060%, N: 0.0010%~0.0040%, RE: 0.01%~0.03%, and the balance is Fe and unavoidable impurities; The microstructure of the high-strength crack arrest toughness steel suitable for high heat input welding is a multiphase structure of fine lath bainite + acicular ferrite + a small amount of polygonal ferrite, wherein the lath bainite accounts for 30% to 40%, the acicular ferrite accounts for 40% to 60%, and the polygonal ferrite accounts for 10% to 20%, and the average grain size of the steel plate microstructure is less than 10 μm; The method for manufacturing high-strength crack arrest toughness steel suitable for high heat input welding comprises smelting, continuous casting, heating, controlled rolling and controlled cooling, and stacking and slow cooling; Heating: The continuous casting billet heating temperature is 1100℃~1150℃; Controlled rolling and controlled cooling: rolling in the austenite recrystallization zone and rolling in the non-recrystallization zone; Austenite recrystallization zone rolling: rolling temperature 900℃~1050℃, cumulative reduction rate not less than 45%; Rolling in the non-recrystallization zone: the starting rolling temperature is 750~800℃, the finishing rolling temperature is 730~780℃, and the cumulative reduction rate is not less than 45%; laminar cooling is adopted for post-rolling cooling, and the cooling rate is controlled at 2~5℃ / s to cool the steel plate to 530~580℃; Stacking and slow cooling: The steel plates should be stacked and slow cooled after they come off the line. The slow cooling starting temperature should be between 350 and 450°C, and the stacking time should be no less than 48 hours.

2. The high-strength crack arrest toughness steel suitable for high heat input welding according to claim 1, characterized in that: The high-strength crack arrest toughness steel suitable for high heat input welding has a Ca / S ratio of ≥6.

0.

3. The high-strength crack arrest toughness steel suitable for high heat input welding according to claim 1, characterized in that: The microstructure also includes oxynitrides formed by Zr, Ti, Ca, V elements, O, and N, and the size of the oxynitrides is 20-100 nm.

4. The high-strength crack arrest toughness steel suitable for high heat input welding according to claim 1, characterized in that: The mechanical properties of the high-strength crack arrest toughness steel suitable for high heat input welding are yield strength of 540-620 MPa, tensile strength of 650-720 MPa, elongation after fracture ≥ 23.5%; at -10°C, Kca ≥ 6800 N / mm 3 / 2 At -60℃, the impact energy of the steel plate is ≥280J. After welding with a heat input of more than 400KJ / cm, the impact energy of the heat-affected zone of the steel plate is ≥140J. After 5% deformation and strain aging at 250℃ for 1 hour, the aging impact energy of the steel plate at -60℃ is ≥140J.

5. The high-strength crack arrest toughness steel suitable for high heat input welding according to claim 1, characterized in that: During the smelting process, (1) Using low carbon / low aluminum clean steel as raw material, feeding FeOx cored wire into the molten steel tank during vacuum treatment to increase oxygen, controlling the oxygen content in the molten steel to 5-15ppm, blowing in argon and stirring for 3-6 minutes; (2) The smelting process adopts high-draw carbon one-shot blowing method; the main elements of the steel are adjusted to the required range in the converter, and other alloy components are added as required for smelting; (3) The molten steel removed from the converter undergoes secondary refining; (4) Add Zr and Ca to the steel in a wire feeding manner, controlling the amount of Zr in the molten steel to be 5-15 ppm and the amount of Ca to be 10-25 ppm; then blow argon into the molten steel through the argon hole at the bottom of the tank to stir it, with the diameter of the exposed surface of the molten steel ≤80 mm, and the stirring time to be 4-9 min; after stirring, put it on the machine for pouring within 15 min.

6. The high-strength crack arrest toughness steel suitable for high heat input welding according to claim 1, characterized in that: During the continuous casting process, the superheat of the tundish steel liquid is between 15 and 25°C. Soft reduction and electromagnetic stirring at the end of the crystallizer are used during the continuous casting process. The secondary cooling adopts segmented cooling. The continuous casting billet drawing speed is 0.8 to 1.2 m / min, and the casting slab thickness is 250 to 300 mm.

7. The high-strength crack arrest toughness steel suitable for high heat input welding according to claim 6, characterized in that: The segmented cooling includes strong cooling in the vertical section and weak cooling in the curved section; the cooling rate of the strong cooling in the vertical section is 10.0-20.0°C / s, and the cooling rate of the weak cooling in the curved section is 3.0-5.0°C / s.

8. The high-strength crack arrest toughness steel suitable for high heat input welding according to claim 6, characterized in that: The light pressing amount is 5.0-10.0 mm.

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