Super-thick steel plate and method for manufacturing the same

Abstract

The application relates to the technical field of plate production and manufacturing, in particular to a super-thick plate and a preparation method thereof. The method comprises the following steps: a first-stage heating-rolling-cooling treatment: a first heating is performed on a casting blank with a set chemical composition under the condition of a first set temperature; the first heating is performed on the casting blank, and process parameters of the first rolling are controlled, and then first-stage cooling is performed, so that a first steel plate is obtained; a second-stage heating-rolling-cooling treatment: the first steel plate is second heated under the condition of a second set temperature, and then intermediate cooling is performed; the first steel plate after the intermediate cooling is second rolled, and the finish rolling temperature of the second rolling is controlled, and then second-stage cooling is performed, so that a super-thick plate is obtained. The application solves the technical problem that the existing super-thick plate is difficult to simultaneously consider the uniformity of the performance and the structure in the full-thickness direction.

Description

Technical Field

[0001] This application relates to the field of medium and heavy plate manufacturing technology, and in particular to an extra-thick plate and its preparation method. Background Technology

[0002] With the rapid development of China's manufacturing industry, the demand for extra-thick plates is constantly increasing in applications such as container ships, offshore wind power, and bridges. Simultaneously, extra-thick plates are required to possess superior low-temperature impact toughness, high strength, good resistance to lamellar tearing, and weldability. However, due to limitations in raw material size, extra-thick plates have a low compression ratio. Furthermore, rolling deformation is difficult to penetrate to the core of the steel plate, and there are significant differences in cooling intensity across the thickness section, resulting in poor impact toughness, low strength, and poor resistance to lamellar tearing in the core of the extra-thick plate.

[0003] Currently, to improve the core properties of extra-thick plates, steel ingots are typically used to produce them, and large amounts of the precious metal Ni are added. This results in high costs and makes it difficult to solve the problems of uniform properties and poor resistance to lamellar tearing in extra-thick plates. Therefore, improving the properties and microstructure uniformity of extra-thick plates throughout their thickness direction is of great practical significance. Summary of the Invention

[0004] This application provides an extra-thick plate and its preparation method to solve the technical problem that existing extra-thick plates are difficult to simultaneously achieve both performance and microstructure uniformity throughout the thickness direction.

[0005] In a first aspect, this application provides a method for preparing an extra-thick plate, the method comprising:

[0006] A staged heating-rolling-cooling process is performed on a cast billet with a predetermined chemical composition to obtain an extra-thick plate; wherein the staged heating-rolling-cooling process includes:

[0007] The first stage of heating-rolling-cooling treatment: Under the condition of a first set temperature, the billet with a set chemical composition is first heated;

[0008] The first heated billet is subjected to a first rolling process, and the process parameters of the first rolling process are controlled. Then, a first stage cooling process is performed to obtain a first steel plate.

[0009] The second stage of heating-rolling-cooling treatment: Under the condition of a second set temperature, the first steel plate is heated a second time, followed by intermediate cooling;

[0010] The first steel plate, after intermediate cooling, is subjected to a second rolling process, and the final rolling temperature of the second rolling process is controlled. Then, a second stage of cooling is performed to obtain an extra-thick plate.

[0011] Optionally, the specified chemical composition includes: C, Si, Mn, Alt, Nb, Ti, Cr, P, S, and Fe; wherein,

[0012] The C content is 0.035-0.05 wt%, the Si content is 0.30-0.40 wt%, the Mn content is 1.90-2.00 wt%, the Alt content is 0.02-0.06 wt%, the Nb content is 0.015-0.025 wt%, the Ti content is 0.01-0.03 wt%, the Cr content is 0.20-0.30 wt%, the P content is <0.008 wt%, and the S content is <0.003 wt%.

[0013] Optionally, the first set temperature is 1180-1200℃.

[0014] Optionally, the process parameters for the first rolling process include: the initial rolling temperature of the first rolling process is 1160-1190℃, and the final rolling temperature of the first rolling process is 1120-1150℃.

[0015] Optionally, the first heating of the billet is followed by a first rolling process, with controlled process parameters, and then a first stage of cooling to obtain a first steel plate, comprising:

[0016] The first heated billet is subjected to a first rolling process, with controlled process parameters, followed by a first water cooling and a first heat treatment to obtain a first steel plate; wherein,

[0017] The cooling rate of the first water cooler is 5-10℃ / s, and the final temperature of the first water cooler is 630-690℃.

[0018] Optionally, the second set temperature is 880-895℃.

[0019] Optionally, the final temperature of the intermediate cooling is 800-820°C.

[0020] Optionally, the final rolling temperature of the second rolling process is 760-800℃.

[0021] Optionally, the first steel plate after intermediate cooling is subjected to a second rolling process, and the final rolling temperature of the second rolling process is controlled, followed by a second stage of cooling to obtain an extra-thick plate, comprising:

[0022] The first steel plate, after intermediate cooling, undergoes a second rolling process, with the final rolling temperature controlled. Following this, it undergoes a second water cooling and a second heat treatment to obtain an extra-thick plate.

[0023] The cooling rate of the second water cooler is 10-20℃ / s, and the final temperature of the second water cooler is 300-360℃.

[0024] Secondly, this application provides an extra-thick plate, which is prepared by the method described in any embodiment of the first aspect.

[0025] The technical solutions provided in this application have the following advantages compared with the prior art:

[0026] The method for preparing the extra-thick plate provided in this application embodiment controls the low carbon content to ensure the steel plate has good low-temperature toughness and weldability, and reduces cementite content and core microstructure segregation; it adopts a high Mn and high Cr composition design, and improves strength through solid solution strengthening; it reduces Nb content to control austenite grain growth, while weakening the inhibitory effect of Nb on recrystallization, thereby improving the grain refinement and homogenization effect of recrystallized grains; it does not add Ni element, avoiding the significant increase in cost caused by the addition of a large amount of Ni alloy in traditional thick plates; it adopts two heating processes, the first high-temperature heating to ensure sufficient solid solution of alloying elements and eliminate compositional and microstructure segregation in the core of the billet; the second low-temperature heating... Warm heating re-austenitizes the steel plate, avoiding grain coarsening caused by high-temperature heating. The large cumulative deformation in the non-recrystallized zone, combined with pre-rolling cooling, ensures sufficient flattening of the core structure, providing ample nucleation sites for subsequent phase transformations, resulting in a refined and homogenized microstructure across the entire thickness of the steel plate. Adding one heating and one cooling process increases the number of phase transformation processes, significantly refining the microstructure. Two rolling processes avoid the prolonged temperature control and waiting time required in a single rolling cycle, which affects rolling efficiency. It also prevents high core temperatures in the intermediate billet, which could lead to core growth and uneven microstructure and properties across the thickness. In summary, the process conditions designed in this application embodiment achieve low-cost production of extra-thick plates while maintaining uniform properties and microstructure across the entire thickness, and satisfying the requirements for high strength, good low-temperature toughness, and resistance to lamellar tearing. Attached Figure Description

[0027] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0028] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 A schematic flowchart illustrating a method for preparing an extra-thick plate according to an embodiment of this application;

[0030] Figure 2 This refers to the first rolling process in a method for preparing an extra-thick plate provided in Embodiment 1 of this application;

[0031] Figure 3 The surface microstructure of an extra-thick plate provided in Embodiment 1 of this application;

[0032] Figure 4 The surface microstructure of an extra-thick plate with a thickness of 1 / 4 is provided in Embodiment 1 of this application;

[0033] Figure 5 The surface microstructure of an extra-thick plate with a thickness of 1 / 2 is provided in Embodiment 1 of this application;

[0034] Figure 6 This is the first rolling process in a method for preparing an extra-thick plate provided in Embodiment 2 of this application;

[0035] Figure 7 This application provides a surface microstructure of an extra-thick plate according to Embodiment 2.

[0036] Figure 8 This application provides a surface microstructure of an extra-thick plate with a thickness of 1 / 4 as described in Embodiment 2.

[0037] Figure 9 The surface microstructure of an extra-thick plate with a thickness of 1 / 2 is provided in Embodiment 2 of this application. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0039] Various embodiments of this application may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limitation on the scope of this application; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Furthermore, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the referred range.

[0040] In this application, unless otherwise stated, directional terms such as "upper" and "lower" specifically refer to the drawing directions in the accompanying drawings. Furthermore, in the description of this application, terms such as "comprising" and "including" mean "including but not limited to." In this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. In this document, "and / or" describes the relationship between related objects, indicating that three relationships can exist; for example, A and / or B can represent: A alone, A and B simultaneously, or B alone. A and B can be singular or plural. In this document, "at least one" means one or more, and "more than one" means two or more. "At least one," "at least one of the following," or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, "at least one of a, b, or c" or "at least one of a, b, and c" can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be a single or multiple.

[0041] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0042] Firstly, this application provides a method for preparing an extra-thick plate; please refer to [link to relevant documentation]. Figure 1 The method includes:

[0043] S0. A billet with a set chemical composition is subjected to a staged heating-rolling-cooling process to obtain an extra-thick plate; wherein, the staged heating-rolling-cooling process includes:

[0044] S1. First stage heating-rolling-cooling treatment: Under the condition of a first set temperature, the billet with a set chemical composition is first heated;

[0045] The first heated billet is subjected to a first rolling process, and the process parameters of the first rolling process are controlled. Then, a first stage cooling process is performed to obtain a first steel plate.

[0046] In some embodiments, the specified chemical composition includes:

[0047] C, Si, Mn, Alt, Nb, Ti, Cr, P, S, and Fe; among which,

[0048] The C content is 0.035-0.05 wt%, the Si content is 0.30-0.40 wt%, the Mn content is 1.90-2.00 wt%, the Alt content is 0.02-0.06 wt%, the Nb content is 0.015-0.025 wt%, the Ti content is 0.01-0.03 wt%, the Cr content is 0.20-0.30 wt%, the P content is <0.008 wt%, and the S content is <0.003 wt%.

[0049] In the embodiments of this application, the chemical composition design controls the low carbon content to ensure that the steel plate has good low-temperature toughness and weldability, and reduces cementite content and core segregation; a high Mn and high Cr composition design is adopted to improve strength through solid solution strengthening; the Nb content is reduced to control austenite grain growth, while weakening the Nb's inhibitory effect on recrystallization and improving the grain refinement and homogenization effect of recrystallization; and no Ni element is added to avoid the significant increase in cost caused by adding a large amount of Ni alloy in traditional thick plates.

[0050] The positive effects of controlling the carbon content to 0.035-0.05% by weight are: low carbon content ensures good low-temperature toughness and weldability of the steel plate, and reduces cementite content and core segregation. If the carbon content is too high, it will affect impact toughness and weldability to some extent; if the carbon content is too low, it will result in insufficient strength of the steel plate to some extent. Specifically, the carbon content can be 0.035% by weight, 0.04% by weight, 0.045% by weight, 0.05% by weight, etc.

[0051] The positive effects of controlling the Si content to 0.30-0.40 wt% include improved strength through solid solution strengthening. If the Si content is too high, it will affect the weldability of the steel plate to some extent; if the Si content is too low, it will reduce the strength of the steel plate to some extent. Specifically, the Si content can be 0.30 wt%, 0.35 wt%, 0.40 wt%, etc.

[0052] The positive effects of controlling the Mn content to 1.90-2.00 wt% include improved strength through solid solution strengthening. However, excessively high Mn content can negatively impact the weldability of the steel plate; conversely, excessively low Mn content can reduce strength and impact toughness. Specifically, the Mn content can be 1.90 wt%, 1.95 wt%, 2.00 wt%, etc.

[0053] The positive effects of controlling the Nb content to 0.015-0.025 wt% include: refining the microstructure and improving strength and toughness. If the Nb content is too high, it can lead to excessive inhibition of recrystallization, affecting the recrystallization effect and causing unstable impact toughness in the steel plate; if the Nb content is too low, it can result in insufficient strength in the steel plate. Specifically, the Nb content can be 0.015 wt%, 0.020 wt%, 0.025 wt%, etc.

[0054] The positive effects of controlling the Ti content to 0.01-0.03 wt% include: inhibiting austenite growth during heating, refining the microstructure, and improving strength and toughness. If the Ti content is too high, it can lead to a significant increase in precipitates, affecting impact toughness; conversely, if the Ti content is too low, it can result in insufficient inhibition of austenite growth during heating, also affecting impact toughness. Specifically, the Ti content can be 0.01 wt%, 0.02 wt%, 0.03 wt%, etc.

[0055] The positive effects of controlling the Cr content to 0.20-0.30 wt% include improved hardenability and increased strength. However, excessively high Cr content can negatively impact the weldability of the steel plate, while excessively low Cr content can reduce its strength. Specifically, the Cr content can be 0.20 wt%, 0.25 wt%, 0.30 wt%, etc.

[0056] The positive effects of controlling the phosphorus (P) content to <0.008 wt% include reducing the content of harmful elements and improving impact toughness. However, excessively high P content can reduce the impact toughness of the steel plate to some extent. Specifically, the P content can be 0.0075 wt%, 0.007 wt%, etc.

[0057] The positive effects of controlling the sulfur (S) content to <0.003% by weight include reducing the content of harmful elements and improving resistance to lamellar tearing. However, excessively high S content can negatively impact the steel plate's resistance to lamellar tearing. Specifically, the S content can be 0.0025% by weight, 0.002% by weight, etc.

[0058] In the manufacturing process, two heating processes are employed. The first, high-temperature heating ensures full solid solution of alloying elements and eliminates segregation in the cast billet. The second, low-temperature heating avoids microstructure coarsening. Through two rolling processes and two water cooling processes, the microstructure is fully homogenized and refined, improving the uniformity of properties in the thickness direction. This allows the steel plate to simultaneously meet the requirements of high strength, good weldability, low-temperature toughness, and excellent resistance to lamellar tearing.

[0059] Before step S0, the process includes the following steps: Smelting: KR desaturation and converter smelting are used, followed by top and bottom combined blowing; vacuum treatment is performed using LF furnace and VD furnace to reduce the content of harmful gases such as O and H, as well as P and S. Continuous casting: The continuous casting billet shape is designed with a thickness of 400 mm and a width of 1800-2400 mm; the center segregation of the billet is controlled to be lower than Class C 1.0.

[0060] In some implementations, the first set temperature is 1180-1200°C.

[0061] In this embodiment, "first set temperature" refers to the temperature of the first heating. The positive effects of controlling the first heating temperature to 1180-1200℃ are: high-temperature heating ensures sufficient solid solution of alloying elements and eliminates compositional and microstructural segregation in the core of the cast billet. If the temperature is too high, it can lead to abnormal austenite growth and grain coarsening, affecting the final performance; if the temperature is too low, it can lead to insufficient solid solution of Nb, resulting in poor resistance to lamellar tearing, reduced strength, and severe compositional and microstructural segregation, affecting core performance. Specifically, the first heating temperature can be 1180℃, 1190℃, 1200℃, etc. The duration of the first heating is 400-600 minutes.

[0062] In some embodiments, the process parameters of the first rolling process include: the initial rolling temperature of the first rolling process is 1160-1190°C, and the final rolling temperature of the first rolling process is 1120-1150°C.

[0063] The positive effects of controlling the process parameters of the first rolling process are as follows: The first rolling is performed in the fully recrystallized zone, and the thickness at the end of the first rolling is 2.5 times the finished product thickness, ensuring sufficient recrystallization. Simultaneously, it reserves sufficient deformation for the second rolling in the non-recrystallized zone, allowing the austenite to be fully flattened, providing numerous nucleation sites for subsequent phase transformations, and resulting in a sufficiently refined microstructure. Specifically, the initial rolling temperature of this first rolling can be 1160℃, 1170℃, 1180℃, or 1190℃, and the final rolling temperature can be 1120℃, 1130℃, 1140℃, or 1150℃, etc. At least two passes in the first rolling process must have a reduction rate ≥18%, as detailed in [reference needed]. Figure 2 and Figure 6 .

[0064] In some embodiments, the first heating of the billet followed by a first rolling process, controlling the process parameters of the first rolling, and then performing a first staged cooling to obtain a first steel plate, includes:

[0065] The first heated billet is subjected to a first rolling process, with controlled process parameters, followed by a first water cooling and a first heat treatment to obtain a first steel plate; wherein,

[0066] The cooling rate of the first water cooler is 5-10℃ / s, and the final temperature of the first water cooler is 630-690℃.

[0067] The positive effects of controlling the cooling rate of the first water cooling to 5-10℃ / s and the final temperature of the first water cooling to 630-690℃ are as follows: After the first rolling, the steel plate quickly enters laminar flow cooling for water cooling, which further refines the recrystallized structure. If water cooling is not performed or the final temperature of the first water cooling is too high, it can lead to coarse grains, affecting the final properties; if the final temperature of the water cooling is too low, it can lead to poor plate shape, which is detrimental to subsequent rolling. The final cooling temperature of the first water cooling can be 630℃, 650℃, 670℃, 690℃, etc.

[0068] S2, Second stage heating-rolling-cooling treatment: Under the condition of the second set temperature, the first steel plate is heated a second time, and then intermediate cooling is performed;

[0069] The first steel plate, after intermediate cooling, is subjected to a second rolling process, and the final rolling temperature of the second rolling process is controlled. Then, a second stage of cooling is performed to obtain an extra-thick plate.

[0070] In some embodiments, the second set temperature is 880-895°C.

[0071] In this embodiment, "second set temperature" refers to the temperature of the second heating. Controlling the second heating temperature to 880-895℃ has the positive effect of ensuring complete austenitization of the steel plate. If the temperature is too high, it can lead to grain coarsening to some extent; if the temperature is too low, it can lead to incomplete austenitization of the microstructure and excessive resistance to rolling deformation. Specifically, the second heating temperature can be 880℃, 890℃, 895℃, etc. The duration of the second heating is 1.6-1.8 times the thickness of the finished product.

[0072] In some embodiments, the endpoint temperature of the intermediate cooling is 800-820°C.

[0073] The positive effects of controlling the final temperature of intermediate cooling to 800-820℃: The second rolling is done in the non-recrystallization zone. After the steel plate exits the furnace, it is cooled with water to 800-820℃ before rolling. The purpose is to create a significant temperature difference in the thickness direction of the steel plate, which is conducive to the penetration of rolling force into the core and refines the microstructure of the steel plate's core. If this final temperature is too high, it will affect the microstructure refinement to some extent, resulting in decreased strength and impact toughness; if this final temperature is too low, it will lead to increased deformation resistance to some extent, making rolling difficult. Specifically, the final temperature of this intermediate cooling can be 800℃, 810℃, 820℃, etc.

[0074] In some embodiments, the final rolling temperature of the second rolling is 760-800°C.

[0075] The positive effects of controlling the final rolling temperature of the second rolling process to 760-800℃ include: sufficient microstructure refinement and improved performance through low-temperature rolling. If the final rolling temperature is too high, it can lead to insufficient microstructure refinement, resulting in poor strength and low-temperature toughness; if the final rolling temperature is too low, it can lead to the formation of proeutectoid ferrite during the rolling process. Specifically, the final rolling temperature of the second rolling process can be 760℃, 780℃, 800℃, etc.

[0076] In some embodiments, the second rolling of the first steel plate after intermediate cooling, controlling the final rolling temperature of the second rolling, followed by a second stage of cooling to obtain an extra-thick plate, includes:

[0077] The first steel plate, after intermediate cooling, undergoes a second rolling process, with the final rolling temperature controlled. Following this, it undergoes a second water cooling and a second heat treatment to obtain an extra-thick plate.

[0078] The cooling rate of the second water cooler is 10-20℃ / s, and the final temperature of the second water cooler is 300-360℃.

[0079] The positive effects of controlling the cooling rate of the second water cooling to 10-20℃ / s and the final temperature of the second water cooling to 300-360℃ are as follows: After the second rolling, the steel plate quickly enters laminar flow cooling for water cooling, which further refines the microstructure after deformation. If the final temperature of the water cooling is too high, the microstructure may not be sufficiently refined, resulting in poor strength and low-temperature toughness. If the final temperature of the water cooling is too low, martensitic microstructure may be formed, leading to poor steel plate performance. If the water cooling rate is too high, the difference in microstructure across the entire thickness of the steel plate may increase, affecting performance uniformity. If the water cooling rate is too low, the microstructure may become too coarse, resulting in poor strength and low-temperature toughness of the steel plate. Specifically, the cooling rate of the second water cooling can be 10℃ / s, 15℃ / s, 20℃ / s, etc., and the final temperature of the second water cooling can be 300℃, 320℃, 340℃, 360℃, etc.

[0080] The specific steps of the first and second batch cooling are as follows: the steel plate is placed in a slow cooling pit and cooled to room temperature with the environment. The upper and lower surfaces are covered with steel plates at a temperature of 400-500°C. The purpose is to release the stress in the steel plate, achieve the self-tempering effect, and improve the internal quality of the steel plate.

[0081] Secondly, this application provides an extra-thick plate, which is prepared by the method described in any embodiment of the first aspect. The extra-thick plate exhibits good uniformity of its microstructure throughout its thickness. (See also...) Figure 3-5 and Figure 7-9 .

[0082] This extra-thick plate is realized based on the above-described method for preparing extra-thick plates. The specific steps of the preparation method can be referred to in the above embodiments. Since this extra-thick plate adopts some or all of the technical solutions of the above embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be elaborated here.

[0083] The present application is further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the application. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to national standards. If there is no corresponding national standard, then general international standards, conventional conditions, or conditions recommended by the manufacturer are followed.

[0084] Example 1

[0085] An extra-thick plate has the following chemical composition by mass percentage (wt%): C: 0.041, Si: 0.36, Mn: 1.92, Alt: 0.036, Nb: 0.018, Ti: 0.015, Cr: 0.26, P: 0.005, S: 0.002, with the remainder being Fe and residual elements. The billet dimensions are 400*2000*3700 (mm), the center segregation of the billet is C-class 0.5, and the plate dimensions are 90*2200*13500 (mm). The first heating temperature was 1195℃, the furnace time was 436 min, the first rolling start temperature was 1175℃, the final rolling temperature was 1136℃, the thickness at the end of the first rolling was 225 mm, the first final cooling temperature was 657℃, and the cooling rate was 7℃ / s. The second heating temperature was 890℃, the furnace time was 375 min, the intermediate cooling endpoint temperature was 815℃, the second rolling start temperature was 806℃, the final rolling temperature was 789℃, the second final cooling temperature was 331℃, and the cooling rate was 18℃ / s. Mechanical properties are shown in Table 1, and the first rolling procedure is as follows: Figure 2 Metallographic structure Figure 3 , Figure 4 and Figure 5 .

[0086] Table 1 Performance of an extra-thick plate with a thickness of 90mm

[0087]

[0088] Example 2

[0089] An extra-thick plate has the following chemical composition by mass percentage (wt%): C: 0.043, Si: 0.32, Mn: 1.97, Alt: 0.042, Nb: 0.020, Ti: 0.022, Cr: 0.27, P: 0.005, S: 0.001, with the remainder being Fe and residual elements. The billet dimensions are 400*2200*3300 (mm), the center segregation of the billet is C-class 0.5, and the plate dimensions are 100*2300*10500 (mm). The first heating temperature was 1190℃, furnace time was 452 min, first rolling temperature was 1170℃, final rolling temperature was 1145℃, first rolling thickness was 250 mm, first final cooling temperature was 682℃, and cooling rate was 6℃ / s. The second heating temperature was 886℃, furnace time was 420 min, intermediate cooling endpoint temperature was 807℃, second rolling temperature was 809℃, final rolling temperature was 796℃, second final cooling temperature was 353℃, and cooling rate was 15℃ / s. Mechanical properties are shown in Table 2, and the first rolling procedure is as follows: Figure 6 Metallographic structure Figure 7 , Figure 8 and Figure 9 .

[0090] Table 2 Performance of an extra-thick plate with a thickness of 100 mm

[0091]

[0092]

[0093] Example 3

[0094] An extra-thick plate has the following chemical composition by mass percentage (wt%): C: 0.035, Si: 0.30, Mn: 1.90, Alt: 0.02, Nb: 0.015, Ti: 0.010, Cr: 0.2, P: 0.005, S: 0.002, with the remainder being Fe and residual elements. The slab dimensions are 400*2200*3300 (mm), the center segregation of the slab is C-class 0.5, and the plate dimensions are 100*2300*10500 (mm). The first heating temperature was 1180℃, the furnace time was 400 min, the first rolling temperature was 1160℃, the final rolling temperature was 1120℃, the thickness at the end of the first rolling was 250 mm, the first final cooling temperature was 630℃, and the cooling rate was 5℃ / s. The second heating temperature was 880℃, the furnace time was 420 min, the intermediate cooling endpoint temperature was 805℃, the second rolling temperature was 809℃, the final rolling temperature was 760℃, the second final cooling temperature was 300℃, and the cooling rate was 10℃ / s. The mechanical properties are shown in Table 3.

[0095] Table 3 Performance of an extra-thick plate with a thickness of 100mm

[0096]

[0097] Example 4

[0098] An extra-thick plate has the following chemical composition by mass percentage (wt%): C: 0.05, Si: 0.40, Mn: 2.0, Alt: 0.06, Nb: 0.025, Ti: 0.03, Cr: 0.3, P: 0.005, S: 0.001, with the remainder being Fe and residual elements. The slab dimensions are 400*2200*3300 (mm), the center segregation of the slab is C-class 0.5, and the plate dimensions are 100*2300*10500 (mm). The first heating temperature was 1200℃, the furnace time was 600 min, the first rolling temperature was 1190℃, the final rolling temperature was 1150℃, the thickness at the end of the first rolling was 250 mm, the first final cooling temperature was 690℃, and the cooling rate was 10℃ / s. The second heating temperature was 895℃, the furnace time was 420 min, the intermediate cooling endpoint temperature was 810℃, the second rolling temperature was 806℃, the final rolling temperature was 800℃, the second final cooling temperature was 360℃, and the cooling rate was 20℃ / s. The mechanical properties are shown in Table 4.

[0099] Table 4 Performance of an extra-thick plate with a thickness of 100 mm

[0100]

[0101]

[0102] Comparative Example 1

[0103] An extra-thick plate has the following chemical composition by mass percentage (wt%): C: 0.035, Si: 0.30, Mn: 1.90, Alt: 0.02, Nb: 0.015, Ti: 0.010, Ni: 0.55, Cr: 0.2, P: 0.005, S: 0.002, with the remainder being Fe and residual elements. The slab dimensions are 400*2200*3300 (mm), the center segregation of the cast slab is C-class 0.5, and the plate dimensions are 100*2300*10500 (mm). A one-stage heating-rolling-water-cooling process is employed: heating temperature 1160℃, furnace time 460 min, initial rolling temperature 1135℃, controlled thickness 250 mm, final rolling temperature 760℃, final cooling temperature 315℃, and cooling rate 12℃ / s. Mechanical properties are shown in Table 5.

[0104] Table 5 Performance of an extra-thick plate with a thickness of 100mm

[0105]

[0106] Comparative Example 2

[0107] An extra-thick plate has the following chemical composition by mass percentage (wt%): C: 0.065, Si: 0.30, Mn: 1.55, Alt: 0.02, Nb: 0.015, Ti: 0.010, Cr: 0.2, P: 0.005, S: 0.002, with the remainder being Fe and residual elements. The slab dimensions are 400*2200*3300 (mm), the center segregation of the slab is C-class 0.5, and the plate dimensions are 100*2300*10500 (mm). The first heating temperature was 1191℃, the furnace time was 400 min, the first rolling temperature was 1171℃, the final rolling temperature was 1126℃, the thickness at the end of the first rolling was 250 mm, the first final cooling temperature was 656℃, and the cooling rate was 7℃ / s. The second heating temperature was 883℃, the furnace time was 451 min, the intermediate cooling endpoint temperature was 815℃, the second rolling temperature was 810℃, the final rolling temperature was 771℃, the second final cooling temperature was 323℃, and the cooling rate was 12℃ / s. Mechanical properties are shown in Table 6.

[0108] Table 6 Performance of an extra-thick plate with a thickness of 100mm

[0109]

[0110]

[0111] Comparative Example 3

[0112] An extra-thick plate has the following chemical composition by mass percentage (wt%): C: 0.035, Si: 0.30, Mn: 1.90, Alt: 0.02, Nb: 0.035, Ti: 0.010, Cr: 0.45, P: 0.005, S: 0.002, with the remainder being Fe and residual elements. The slab dimensions are 400*2200*3300 (mm), the center segregation of the slab is C-class 0.5, and the plate dimensions are 100*2300*10500 (mm). The first heating temperature was 1186℃, the furnace time was 436 min, the first rolling temperature was 1165℃, the final rolling temperature was 1129℃, the thickness at the end of the first rolling was 250 mm, the first final cooling temperature was 663℃, and the cooling rate was 8℃ / s. The second heating temperature was 883℃, the furnace time was 462 min, the intermediate cooling endpoint temperature was 811℃, the second rolling temperature was 811℃, the final rolling temperature was 768℃, the second final cooling temperature was 351℃, and the cooling rate was 13℃ / s. Mechanical properties are shown in Table 7.

[0113] Table 7 Performance of an extra-thick plate with a thickness of 100mm

[0114]

[0115] In Examples 1-4, low-cost production of extra-thick plates was achieved, with uniform properties in the thickness direction, and the steel plates simultaneously met the requirements of high strength, good low-temperature toughness, and resistance to lamellar tearing. In Comparative Example 1, the Ni content was changed, and a one-stage heating-rolling-water-cooling process was used; in Comparative Example 2, the C and Mn contents were changed; and in Comparative Example 3, the Nb content was changed. All of these are outside the embodiments of this application, and the mechanical properties of the extra-thick plates prepared are worse than those of the examples.

[0116] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for preparing an extra-thick plate, characterized in that, The method includes: A staged heating-rolling-cooling process is performed on a cast billet with a predetermined chemical composition to obtain an extra-thick plate; wherein the staged heating-rolling-cooling process includes: The first stage of heating-rolling-cooling treatment: Under the condition of a first set temperature, the billet with a set chemical composition is first heated; The first heated billet is subjected to a first rolling process, and the process parameters of the first rolling process are controlled. Then, a first stage of cooling is performed to obtain a first steel plate. The second stage of heating-rolling-cooling treatment: Under the condition of a second set temperature, the first steel plate is heated a second time, followed by intermediate cooling; The first steel plate after intermediate cooling is subjected to a second rolling process, and the final rolling temperature of the second rolling process is controlled. Then, a second stage cooling process is performed to obtain an extra-thick plate. The specified chemical components include: C, Si, Mn, Alt, Nb, Ti, Cr, P, S, and the balance being Fe; among which, The C content is 0.035-0.05 wt%, the Si content is 0.30-0.40 wt%, the Mn content is 1.90-2.00 wt%, the Alt content is 0.02-0.06 wt%, the Nb content is 0.015-0.025 wt%, the Ti content is 0.01-0.03 wt%, the Cr content is 0.20-0.30 wt%, the P content is <0.008 wt%, and the S content is <0.003 wt%. The first set temperature is 1180-1200℃; The process parameters for the first rolling process include: The initial rolling temperature of the first rolling process is 1160-1190℃, and the final rolling temperature of the first rolling process is 1120-1150℃. The process involves first rolling the heated billet, controlling the process parameters of the first rolling, followed by first-stage cooling to obtain a first steel plate, comprising: The first heated billet is subjected to a first rolling process, with controlled process parameters, followed by a first water cooling and a first heat treatment to obtain a first steel plate; wherein, The cooling rate of the first water cooler is 5-10℃ / s, and the final temperature of the first water cooler is 630-690℃. The second set temperature is 880-895℃; The final temperature of the intermediate cooling is 800-820℃; The final rolling temperature of the second rolling process is 760-800℃; The process involves performing a second rolling process on the first steel plate after intermediate cooling, controlling the final rolling temperature of the second rolling process, followed by a second stage of cooling to obtain an extra-thick plate, comprising: The first steel plate, after intermediate cooling, undergoes a second rolling process, with the final rolling temperature controlled. Following this, it undergoes a second water cooling and a second heat treatment to obtain an extra-thick plate. The cooling rate of the second water cooler is 10-20℃ / s, and the final temperature of the second water cooler is 300-360℃.

2. An extra-thick plate, characterized in that, The extra-thick plate is prepared by the method described in claim 1.

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