CN116815074A - High-strength and high-toughness Q690F super-thick weather-resistant steel plate with excellent thickness uniformity and preparation method thereof - Google Patents

Abstract

The invention provides a high-strength and tough Q690F extra-thick weather-resistant steel plate with excellent thickness uniformity and a preparation method, and relates to the technical field of high-strength alloy steel manufacturing. The thickness of the high-strength and tough Q690F extra-thick weathering steel plate with excellent thickness uniformity is 100-140mm, and the surface microstructure is quasi-polygonal ferrite + tempered martensite + carbide + M/A island, 1/4 and The microstructural changes of the 1/2 position are mainly reflected in further M/A island decomposition, carbide precipitation and coarsening and merger of martensite/bainite laths, and the uniformity of the structure along the thickness direction is high. The preparation method adopts the process of differential rolling + sub-temperature quenching + tempering. Compared with other traditional methods, the method of the present invention not only reduces the quenching temperature by sub-temperature quenching, but also after combined with the tempering process, the quasi-polygonal ferrite and nanoscale carbides obtained in the extra-thick steel plate can simultaneously improve the plasticity and properties of the plate. Low temperature impact toughness, thickness uniformity and atmospheric corrosion resistance are beneficial to industrial mass production.

Description

A high-strength and tough Q690F extra-thick weathering steel plate with excellent thickness uniformity and its preparation method

Technical field

The present invention relates to the technical field of manufacturing high-strength alloy steel, and in particular to a high-strength and tough Q690F extra-thick weather-resistant steel plate with excellent thickness uniformity and a preparation method.

Background technique

As one of the basic materials for national economic development, steel is an important pillar of industrial production. In accordance with the development concepts of innovation, coordination and green, the development themes of steel for large ships, steel for marine engineering, steel for long-span construction projects, steel for hydropower and steel for heavy machinery are moving towards large-scale, high-strength, green and Energy saving.

As a high-end plate product in the steel industry, extra-thick steel plates are difficult to produce, have high technical content, and have high added value.

In order to ensure the safety of actual service, higher requirements have been put forward for the mechanical properties and corrosion resistance of extra-thick steel plates, which must simultaneously meet high strength, excellent low-temperature toughness, good welding performance and corrosion resistance. In order to produce extra-thick weather-resistant steel plates with qualified performance, the research and development of relevant production new technologies has become the focus of close attention by major steel companies in the world.

Domestic Q690 steel plates have gradually begun to be used in many engineering applications such as building structures and bridge structures. However, domestic Q690 steel plates currently have technical defects such as poor uniformity of structure in the thickness direction, low low-temperature impact toughness, low strong plastic product, high preparation cost, and low efficiency.

For example: Chinese patent CN114107805A discloses a large thickness quenched and tempered Q690E/F high-strength steel and its manufacturing method. The preparation method is complex, the control of the steel plate structure and properties during the rolling process is poor, the quenching temperature is high, and the resulting The material has high hardness, low plasticity, low -60°C transverse impact energy, low atmospheric corrosion resistance, and poor welding performance.

Chinese patent CN109402508A discloses a low-carbon microalloyed Q690 grade high-strength weathering steel and its preparation method. It does not consider the impact of the heat treatment process on the plasticity and low-temperature impact properties, so the plasticity and low-temperature impact properties of the prepared material are poor; And the thickness of the steel plate is thin, and its resistance to lamellar tearing in the thickness direction is low.

Chinese patent CN110468349A discloses an earthquake-resistant high-strength weather-resistant bridge steel plate Q690qENHZ35 and its production method. Although it can prepare a special thick plate exceeding 100mm through hot rolling, sub-temperature quenching treatment and tempering treatment, the hot rolling, sub-temperature quenching process Pre-quenching is also provided between treatments, which increases process costs and weakens the effect of differential temperature rolling. The low-temperature impact toughness is only E-level and the impact energy is low.

Chinese patent CN103556076A discloses a production method of quenched and tempered high-strength Q690F extra-thick steel plate. The process steps are: molten iron pretreatment → converter steelmaking → refining outside the furnace → continuous casting (dynamic light pressing + electromagnetic stirring) → heating → Rolling → Pre-straightening → Online quenching → Off-line quenching → Tempering → Finishing → Performance inspection → Ultrasonic flaw detection; obviously the process steps are complex, the operation is difficult, and the plasticity and low-temperature impact properties are low.

Chinese patent CN104264064A discloses an extra-thick Q690 high-strength structural steel plate and its manufacturing method. The thickness of the steel plate is 160-180mm. The manufacturing process of the steel plate includes billet smelting - billet heating - high-pressure water descaling - rolling - straightening. Direct-DQ+ACC online quenching-slow cooling-tempering. The quenching used in the preparation process results in high structural hardness, and the prepared material has low impact toughness and poor plasticity.

Therefore, the Q690 extra-thick weather-resistant steel plates in the above-mentioned prior art all add corrosion-resistant elements and strengthening elements such as Cr, Ni, Cu, and Nb. Although the strength levels meet the technical index requirements and the yield strength is above 700MPa, the steel plate The elongation is generally low and difficult to reach 25% and above, and the low-temperature impact toughness of E/F grade is unstable and difficult to reach above 200J, failing to take into account excellent strength, toughness and corrosion resistance.

Contents of the invention

The technical problem to be solved by this invention is that in the current preparation process of Q690 extra-thick weather-resistant steel plates, most require heat treatment of quenching + tempering after hot rolling to improve the strength and plasticity of the plates. However, the low-temperature impact toughness and plasticity of the steel plates obtained in this way are The lamellar tear resistance is low, and the elongation is also low. Although it can be prepared by hot rolling, sub-temperature quenching and tempering, pre-quenching further reduces the low-temperature impact toughness of the prepared steel plate. Comprehensive The performance is poor and is not conducive to industrial production.

In order to solve the above-mentioned objects of the invention, the technical solutions provided by the present invention are as follows:

A high-strength and tough Q690F extra-thick weather-resistant steel plate with excellent thickness uniformity. The chemical composition and mass percentage of the high-strength and tough Q690F extra-thick weather-resistant steel plate are as follows: C: 0.06-0.15%, Mn: 1.1-1.65%, Si: 0.1- 0.3%, Cr: 0.25-0.5%, Ni: 0.6-1.4%, Al: 0.02-0.05%, Nb: 0.02-0.045%, Cu: 0.2-0.5%, Mo: 0.35-0.5%, V: 0.02-0.04 %, Ti: 0.005-0.02%, B: 0.001-0.0015%, P≤0.01%, S≤0.002%, the rest are Fe and inevitable impurity elements.

Preferably, the thickness of the high-strength Q690F extra-thick weathering steel plate with excellent thickness uniformity is 100-140mm, and the surface microstructure is quasi-polygonal ferrite + tempered martensite + carbide + M/A island, 1 The microstructural changes at /4 and 1/2 are mainly reflected in further M/A island decomposition, carbide precipitation and coarsening and merger of martensite/bainite laths, with high microstructure uniformity along the thickness direction. .

Preferably, the high-strength and tough Q690F extra-thick weather-resistant steel plate with excellent thickness uniformity has a yield strength of ≥780MPa at all positions along the thickness direction, a tensile strength of ≥820MPa, a yield-to-strength ratio of ≥0.92, an elongation after fracture of ≥20%, and a strong plastic product. ≥19.3GPa%, -60℃ low temperature impact energy ≥210J, the measured corrosion rate after 768h is 1.1-1.4mm/a, and the corrosion resistance is 1.8-2.5 times that of Q345E.

Preferably, the yield strength of the surface layer along the thickness direction of the high-strength and tough Q690F extra-thick weather-resistant steel plate with excellent thickness uniformity is ≥798MPa, the tensile strength is ≥854MPa, the elongation after fracture is ≥20.6%, and the -60°C low-temperature impact energy is ≥206J;

The high-strength and tough Q690F extra-thick weather-resistant steel plate with excellent thickness uniformity has a yield strength of 1/4 along the thickness direction ≥ 776MPa, a tensile strength ≥ 837MPa, an elongation after fracture ≥ 22.3%, and a low-temperature impact energy of -60°C ≥ 221J;

The high-strength and tough Q690F extra-thick weathering steel plate with excellent thickness uniformity has a yield strength of 1/2 along the thickness direction ≥ 769MPa, a tensile strength ≥ 828MPa, an elongation after fracture ≥ 23.2%, and a low-temperature impact energy of -60°C ≥ 213J.

A method for preparing a high-strength and tough Q690F extra-thick weather-resistant steel plate based on the excellent thickness uniformity. The preparation method of the high-strength and tough Q690F extra-thick weather-resistant steel plate with excellent thickness uniformity includes the following steps:

S1: Weigh the raw materials according to the composition of the high-strength and tough Q690F extra-thick weathering steel plate with excellent thickness uniformity, and then smelt it to obtain molten iron. Pre-treat the molten iron, converter smelting, LF furnace and RH furnace smelting, and then It is continuously cast into steel billet through continuous casting machine;

S2: The steel billet of S1 is subjected to high-temperature insulation treatment, and then multi-pass differential rolling is performed. After the rolling is completed, it is water-cooled, and then air-cooled to room temperature to obtain a differentially rolled steel plate;

S3: The steel plate after differential rolling in S2 is subjected to sub-temperature quenching + tempering heat treatment, and then air-cooled to room temperature to obtain the finished steel plate;

S4: Cut metallographic samples, tensile samples and impact samples from the surface layer, 1/4 and 1/2 of the finished steel plate in step S3 respectively, and conduct microstructure observation and mechanical property analysis;

S5: The finished steel plate in step S3 is subjected to a dry-wet cycle corrosion experiment in a simulated atmospheric corrosion environment. Using Q345E as the comparison object, three groups of parallel samples are selected for each steel type, and the average corrosion rate is calculated by calculating the corrosion weight loss rate per unit area. .

Preferably, the thickness of the steel billet of S1 is 340-380mm, the thickness of the intermediate billet of S2 is 160-200mm, and the thickness of the steel plate after differential temperature rolling is 100-140mm.

Preferably, the temperature of the high-temperature heat preservation treatment of S2 is 1150-1250°C and the time is 1-3h; the opening temperature of the multi-pass differential rolling is 1050-1150°C, the single-pass reduction rate is ≥20%, and the final rolling temperature is 1050-1150°C. The rolling temperature is finally stabilized at 840-870°C. The 2nd, 4th and 6th passes of the multi-pass differential rolling are cooled 2-4 times using differential cooling devices; the ACC water cooling system is used for water cooling. Cool to 640-660℃, cooling rate is 10-20℃/s.

Preferably, the sub-temperature quenching of S3 is performed in the two-phase region, and the quenching temperature is between A _c3 and A _c1 . The measured temperature of steel plate A _c3 is 830-870°C, and the temperature of A _c1 is 680-720°C; The subtemperature quenching temperature is 780-830℃, and the holding time is 50-80min; the tempering temperature range is 550-650℃, and the holding time is 100-130min.

Technical principle of the invention:

For a high-strength and tough Q690F extra-thick weathering steel plate with excellent thickness uniformity, the design idea of the composition system is mainly to add trace amounts of Mo, Cr, B and other alloying elements to improve the hardenability of the steel plate. At the same time, the Mo element can also interact with Ni and Cu elements form aggregates through synergistic action, increasing the stability and protection of corrosion products. Cr element is beneficial to promote the formation of a dense passivation film or protective rust layer; Ni element can also improve the hardenability and protection of steel plates. Corrosion resistance, and can promote bainite and martensite phase transformation, significantly improve low-temperature toughness, and reduce the ductile-brittle transition temperature; adding Nb, V, Ti can have a beneficial synergy with B, Al and other elements, which is beneficial to steel plates The improvement of strength and toughness and the addition of Cu, Cr and other elements that are beneficial to the formation of carbides can improve the strength and tempering stability of the steel plate.

The preparation method of differential temperature rolling + sub-temperature quenching + tempering (GTR+IT) used for a high-strength and tough Q690F extra-thick weathering steel plate with excellent thickness uniformity: rolling while rapidly cooling during differential temperature rolling , the cooling does not have time to penetrate deep into the core of the slab, forming a low temperature on the surface in the thickness direction of the slab, while the core still maintains a high temperature gradient. During rolling, the surface layer is not prone to deformation due to its high deformation resistance, while the core is prone to deformation due to its high temperature. It is beneficial to promote deformation deep into the core of the slab, eliminate core defects, and improve core quality and structural uniformity; the purpose of sub-temperature quenching is to introduce a certain volume fraction of quasi-polygonal ferrite, refine the grains, and have low hardness and Well-shaped quasi-polygonal ferrite can reduce stress concentration and hinder crack expansion, so it can improve the plasticity and low-temperature toughness of the material; during the final tempering process, due to the decomposition of bainite/martensite and the formation of carbides The precipitation and aggregation growth, the reduction of dislocation density and the recovery of α phase, the residual stress is basically eliminated, which can effectively improve the comprehensive mechanical properties of the material.

Compared with the existing technology, the above technical solution has at least the following beneficial effects:

Based on the above solution, the present invention proposes a high-strength and tough Q690F extra-thick weather-resistant steel plate with excellent thickness uniformity. It uses multi-pass differential temperature rolling + sub-temperature quenching + tempering to prepare the plate with the required performance, and retains the deformation structure after rolling. In order to increase the phase deformation nuclei and refine the grains, it also improves the structural uniformity of the steel plate along the thickness direction. The subsequent sub-temperature quenching + tempering introduces some quasi-polygonal ferrite and promotes the formation of nanoscale carbides in the tempered structure. The precipitation improves the strength and toughness matching of the steel plate and has excellent corrosion resistance.

The invention describes a high-strength and tough Q690F extra-thick weather-resistant steel plate with excellent thickness uniformity. In order to improve the strength, toughness and corrosion resistance, it adopts a reasonable low-carbon micro-alloying component design and gives full play to the advantages of differential temperature rolling. By adjusting the process parameters of differential rolling and sub-temperature quenching + tempering, the yield strength of the produced steel plate is ≥780MPa, the tensile strength is ≥820MPa, and the elongation after fracture is ≥ 20%, -60℃ low temperature impact energy ≥210J, corrosion rate after 768h is 1.1-1.4mm/a, corrosion resistance is 1.8-2.5 times that of Q345E, with excellent strength, toughness and corrosion resistance.

The invention is based on actual industrial production conditions. The differential temperature rolling process is highly controllable and easy to implement. It eliminates the need for complete austenitizing quenching after rolling and improves production efficiency. It is widely used in heavy machinery manufacturing, marine engineering construction, pressure vessel manufacturing, etc. The field has broad application prospects.

The thickness of the high-strength Q690F extra-thick weathering steel plate with excellent thickness uniformity described in the present invention is 100-140mm, and the surface microstructure is quasi-polygonal ferrite + tempered martensite + carbide + M/A island, 1 The microstructural changes at /4 and 1/2 are mainly reflected in further M/A island decomposition, carbide precipitation and coarsening and merger of martensite/bainite laths, with high microstructure uniformity along the thickness direction. .

In short, compared with other traditional methods, the method of the present invention not only reduces the quenching temperature by sub-temperature quenching, but also after combined with the tempering process, the quasi-polygonal ferrite and nanoscale carbides obtained in the extra-thick steel plate can simultaneously improve the strength of the plate. Plasticity, low temperature impact toughness, thickness uniformity and atmospheric corrosion resistance are beneficial to industrial mass production.

Description of the drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings without exerting creative efforts.

Figure 1 is a schematic diagram of the preparation method of a high-strength Q690F extra-thick weather-resistant steel plate with excellent thickness uniformity according to the present invention;

Figure 2 is an SEM structure diagram at different thickness positions of a high-strength Q690F extra-thick weathering steel plate with excellent thickness uniformity in Embodiment 1 of the present invention;

Figure 3 is a TEM structure diagram at different thickness positions of a high-strength and tough Q690F extra-thick weathering steel plate with excellent thickness uniformity in Embodiment 1 of the present invention.

Detailed ways

In order to make the purpose, technical solutions and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings of the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Based on the described embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

Example 1

A high-strength and tough Q690F extra-thick weather-resistant steel plate with excellent thickness uniformity. The chemical composition and mass percentage of the high-strength and tough Q690F extra-thick weather-resistant steel plate are as follows: C: 0.08%, Mn: 1.43%, Si: 0.21%, Cr: 0.36 %, Ni: 1.2%, Al: 0.023%, Nb: 0.04%, Cu: 0.24%, Mo: 0.44%, V: 0.024%, Ti: 0.013%, B: 0.0012%, P: 0.008%, S: 0.0013 %, the rest is Fe and inevitable impurity elements.

The preparation method of the high-strength Q690F extra-thick weathering steel plate with excellent thickness uniformity is shown in Figure 1, which includes the following steps:

S1: Weigh the raw materials according to the composition of the high-strength and tough Q690F extra-thick weathering steel plate with excellent thickness uniformity, and then smelt it to obtain molten iron. Pre-treat the molten iron, converter smelting, LF furnace and RH furnace smelting, and then It is continuously cast into a 350mm thick steel billet through a continuous casting machine;

S2: The 350mm thick steel billet of S1 is subjected to high-temperature insulation treatment. The temperature of the high-temperature insulation treatment is 1160°C and the time is 2.5h; then multi-pass differential temperature rolling is performed, the opening rolling temperature is 1110°C, and the rolling is performed in a single pass. The rate is ≥20%, the thickness of the intermediate billet is 175mm, the final rolling temperature is finally stabilized at 850°C, and the second, fourth and sixth passes of the multi-pass differential rolling are carried out using a differential cooling device 3 Secondary cooling; after the rolling is completed, water cooling is performed, using the ACC water cooling system to cool to 645°C, with a cooling rate of 16°C/s and then air cooling to room temperature to obtain a 120mm thick steel plate after differential temperature rolling;

S3: The 120mm thick steel plate after differential rolling of S2 is subjected to sub-temperature quenching + tempering heat treatment, in which: sub-temperature quenching is performed in the two-phase area. The measured A _c3 temperature of the steel plate is 845°C and the A _c1 temperature is 694 ℃, the sub-temperature quenching temperature is 810°C, the holding time is 60min, the tempering temperature range is 570°C, the holding time is 105min; then air-cooled to room temperature to obtain the finished steel plate;

S4: Cut metallographic samples, tensile samples and impact samples from the surface layer, 1/4 and 1/2 of the finished steel plate in step S3 respectively, and conduct microstructure observation and mechanical property analysis;

S5: The finished steel plate in step S3 is subjected to a 768-hour alternating wet and dry cycle corrosion experiment in a simulated atmospheric corrosion environment. Using Q345E as the comparison object, three groups of parallel samples are selected for each steel type, and the average corrosion weight loss rate per unit area is calculated. Corrosion rate.

The thickness of the finished steel plate in this example is 120mm. The surface microstructure is quasi-polygonal ferrite + tempered martensite + carbide + M/A island. The microstructural changes of the structure at 1/4 and 1/2 It is mainly reflected in the further decomposition of M/A islands, precipitation of carbides and coarsening and merging of martensite/bainite laths. The uniformity of the structure along the thickness direction is relatively high. The specific structure is shown in Figures 2 and 3.

The yield strength of the finished steel plate in this embodiment at all positions along the thickness direction is 781MPa, the tensile strength is 840MPa, the yield-to-strength ratio is 0.93, the elongation after fracture is 23.3%, the strong plastic product is 19.6GPa%, and the -60°C low temperature impact energy is 215J, the corrosion rate measured after 768h is 1.25mm/a, and the corrosion resistance is 2.1 times that of Q345E.

The yield strength of the surface layer of the finished steel plate in this embodiment along the thickness direction is 798MPa, the tensile strength is 854MPa, the elongation after fracture is 21.5%, the yield-strength ratio is 0.93, the strong plastic product is 18.4GPa%, and the -60°C low-temperature impact energy is 206J;

The yield strength of the finished steel plate in this embodiment along 1/4 of the thickness direction is 776MPa, the tensile strength is 837MPa, the elongation after fracture is 23.3%, the yield-to-strength ratio is 0.93, the strong-plastic product is 19.5GPa%, and the temperature is -60°C. The impact energy is 221J;

The yield strength of the finished steel plate in this embodiment along 1/2 of the thickness direction is 769MPa, the tensile strength is 828MPa, the elongation after fracture is 25.2%, the yield-to-strength ratio is 0.93, the strong-plastic product is 20.9GPa%, and the temperature is -60°C. The impact energy is 218J.

Example 2

A high-strength and tough Q690F extra-thick weather-resistant steel plate with excellent thickness uniformity. The chemical composition and mass percentage of the high-strength and tough Q690F extra-thick weather-resistant steel plate are as follows: C: 0.10%, Mn: 1.25%, Si: 0.16%, Cr: 0.42 %, Ni: 1.4%, Al: 0.034%, Nb: 0.03%, Cu: 0.32%, Mo: 0.41%, V: 0.028%, Ti: 0.009%, B: 0.0015%, P: 0.006%, S: 0.0012 %, the rest is Fe and inevitable impurity elements.

The preparation method of the high-strength Q690F extra-thick weathering steel plate with excellent thickness uniformity is shown in Figure 1, which includes the following steps:

S1: Weigh the raw materials according to the composition of the high-strength and tough Q690F extra-thick weathering steel plate with excellent thickness uniformity, and then smelt it to obtain molten iron. Pre-treat the molten iron, converter smelting, LF furnace and RH furnace smelting, and then It is continuously cast into a 360mm thick steel billet through a continuous casting machine;

S2: The 360mm thick steel billet of S1 is subjected to high-temperature insulation treatment. The temperature of the high-temperature insulation treatment is 1180°C and the time is 1.8h; then multi-pass differential temperature rolling is performed, the opening rolling temperature is 1140°C, and the rolling is performed in a single pass. The rate is ≥20%, the thickness of the intermediate billet is 185mm, the final rolling temperature is finally stable at 865°C, and the second, fourth and sixth passes of the multi-pass differential rolling are carried out using a differential cooling device 3 Secondary cooling; after the rolling is completed, water cooling is performed, using the ACC water cooling system to cool to 658°C, with a cooling rate of 14°C/s and then air cooling to room temperature, to obtain a 130mm thick steel plate after differential temperature rolling;

S3: The 130mm thick steel plate after differential rolling of S2 is subjected to sub-temperature quenching + tempering heat treatment, in which: sub-temperature quenching is performed in the two-phase area. The measured steel plate A _c3 temperature is 860°C and A _c1 temperature is 705 ℃, the sub-temperature quenching temperature is 820°C, the holding time is 70min, the tempering temperature range is 620°C, the holding time is 120min; then air-cooled to room temperature to obtain the finished steel plate;

S4: Cut metallographic samples, tensile samples and impact samples from the surface layer, 1/4 and 1/2 of the finished steel plate in step S3 respectively, and conduct microstructure observation and mechanical property analysis;

S5: The finished steel plate in step S3 is subjected to a 768-hour alternating wet and dry cycle corrosion experiment in a simulated atmospheric corrosion environment. Using Q345E as the comparison object, three groups of parallel samples are selected for each steel type, and the average corrosion weight loss rate per unit area is calculated. Corrosion rate.

The thickness of the finished steel plate in this example is 130mm. The surface microstructure is quasi-polygonal ferrite + tempered martensite + carbide + M/A island. The microstructural changes of the structure at 1/4 and 1/2 It is mainly reflected in the further decomposition of M/A islands, precipitation of carbides and coarsening and merging of martensite/bainite laths, resulting in higher microstructure uniformity along the thickness direction.

The yield strength of the finished steel plate in this embodiment is 790MPa at all positions along the thickness direction, the tensile strength is 852MPa, the yield-to-strength ratio is 0.93, the elongation after fracture is 22.6%, the strong plastic product is 19.3GPa%, and the -60°C low temperature impact energy It is 218J, and the corrosion rate after 768h is measured to be 1.1mm/a, and the corrosion resistance is 1.8 times that of Q345E.

The yield strength of the surface layer of the finished steel plate in this embodiment along the thickness direction is 806MPa, the tensile strength is 862MPa, the elongation after fracture is 20.6%, the yield-strength ratio is 0.94, the strong plastic product is 17.8GPa%, and the -60°C low-temperature impact energy is 217J;

The finished steel plate in this embodiment has a yield strength of 1/4 along the thickness direction of 787MPa, a tensile strength of 851MPa, an elongation after fracture of 22.3%, a yield-to-strength ratio of 0.92, a strong-plastic product of 19.0GPa%, and a low temperature of -60°C. The impact power is 224J;

The yield strength of the finished steel plate in this embodiment along 1/2 of the thickness direction is 776MPa, the tensile strength is 843MPa, the elongation after fracture is 24.8%, the yield-to-strength ratio is 0.92, the strong-plastic product is 20.9GPa%, and the temperature is -60°C. The impact energy is 213J.

Example 3

A high-strength and tough Q690F extra-thick weather-resistant steel plate with excellent thickness uniformity. The chemical composition and mass percentage of the high-strength and tough Q690F extra-thick weather-resistant steel plate are as follows: C: 0.09%, Mn: 1.3%, Si: 0.14%, Cr: 0.29 %, Ni: 0.9%, Al: 0.027%, Nb: 0.02%, Cu: 0.26%, Mo: 0.37%, V: 0.032%, Ti: 0.014%, B: 0.0013%, P: 0.007%, S: 0.0009 %, the rest is Fe and inevitable impurity elements.

The preparation method of the high-strength Q690F extra-thick weathering steel plate with excellent thickness uniformity is shown in Figure 1, which includes the following steps:

S1: Weigh the raw materials according to the composition of the high-strength and tough Q690F extra-thick weathering steel plate with excellent thickness uniformity, and then smelt it to obtain molten iron. Pre-treat the molten iron, converter smelting, LF furnace and RH furnace smelting, and then It is continuously cast into a 345mm thick steel billet through a continuous casting machine;

S2: The 345mm thick steel billet of S1 is subjected to high-temperature insulation treatment. The temperature of the high-temperature insulation treatment is 1200°C and the time is 1 hour; then multi-pass differential temperature rolling is performed, the opening rolling temperature is 1150°C, and the single-pass reduction rate is ≥20%, the thickness of the intermediate billet is 165mm, the final rolling temperature is finally stabilized at 870°C, and the second, fourth and sixth passes of the multi-pass differential rolling are carried out three times using a differential cooling device Cooling: After the rolling is completed, water cooling is performed, using the ACC water cooling system to cool to 644°C, with a cooling rate of 17°C/s and then air cooling to room temperature to obtain a 105mm thick steel plate after differential temperature rolling;

S3: The 105mm thick steel plate after differential rolling of S2 is subjected to sub-temperature quenching + tempering heat treatment, in which: sub-temperature quenching is performed in the two-phase area. The measured steel plate A _c3 temperature is 850°C and A _c1 temperature is 715 ℃, the sub-temperature quenching temperature is 830°C, the holding time is 55min, the tempering temperature range is 630°C, the holding time is 110min; then air-cooled to room temperature to obtain the finished steel plate;

S4: Cut metallographic samples, tensile samples and impact samples from the surface layer, 1/4 and 1/2 of the finished steel plate in step S3 respectively, and conduct microstructure observation and mechanical property analysis;

S5: The finished steel plate in step S3 is subjected to a 768-hour alternating wet and dry cycle corrosion experiment in a simulated atmospheric corrosion environment. Using Q345E as the comparison object, three groups of parallel samples are selected for each steel type, and the average corrosion weight loss rate per unit area is calculated. Corrosion rate.

The thickness of the finished steel plate in this example is 105mm. The surface microstructure is quasi-polygonal ferrite + tempered martensite + carbide + M/A island. The microstructural changes of the structure at 1/4 and 1/2 It is mainly reflected in the further decomposition of M/A islands, precipitation of carbides and coarsening and merging of martensite/bainite laths, resulting in higher microstructure uniformity along the thickness direction.

The yield strength of the finished steel plate in this embodiment at all positions along the thickness direction is 797MPa, the tensile strength is 867MPa, the yield-to-strength ratio is 0.92, the elongation after fracture is 23.4%, the strong plastic product is 20.3GPa%, and -60°C low temperature impact The work is 229J, the corrosion rate measured after 768h is 1.34mm/a, and the corrosion resistance is 2.3 times that of Q345E.

The yield strength of the surface layer of the finished steel plate in this embodiment along the thickness direction is 813MPa, the tensile strength is 883MPa, the elongation after fracture is 22.4%, the yield-strength ratio is 0.92, the strong plastic product is 19.8GPa%, and the -60°C low-temperature impact energy is 213J;

The finished steel plate in this embodiment has a yield strength of 1/4 along the thickness direction of 797MPa, a tensile strength of 866MPa, an elongation after fracture of 23.2%, a yield-to-strength ratio of 0.92, a strong-plastic product of 20.1GPa%, and a low temperature of -60°C. The impact energy is 241J;

The yield strength of the finished steel plate in this embodiment along 1/2 of the thickness direction is 782MPa, the tensile strength is 851MPa, the elongation after fracture is 24.6%, the yield-to-strength ratio is 0.92, the strong-plastic product is 20.9GPa%, and the temperature is -60°C. The impact energy is 232J.

Example 4

A high-strength and tough Q690F extra-thick weather-resistant steel plate with excellent thickness uniformity. The chemical composition and mass percentage of the high-strength and tough Q690F extra-thick weather-resistant steel plate are as follows: C: 0.12%, Mn: 1.15%, Si: 0.17%, Cr: 0.44 %, Ni: 1.1%, Al: 0.038%, Nb: 0.04%, Cu: 0.37%, Mo: 0.38%, V: 0.031%, Ti: 0.008%, B: 0.0014%, P: 0.009%, S: 0.0015 %, the rest is Fe and inevitable impurity elements.

The preparation method of the high-strength Q690F extra-thick weathering steel plate with excellent thickness uniformity is shown in Figure 1, which includes the following steps:

S1: Weigh the raw materials according to the composition of the high-strength and tough Q690F extra-thick weathering steel plate with excellent thickness uniformity, and then smelt it to obtain molten iron. Pre-treat the molten iron, converter smelting, LF furnace and RH furnace smelting, and then It is continuously cast into a 380mm thick steel billet through a continuous casting machine;

S2: The 380mm thick steel billet of S1 is subjected to high-temperature insulation treatment. The temperature of the high-temperature insulation treatment is 1150°C and the time is 3 hours; then multi-pass differential temperature rolling is performed, the opening rolling temperature is 1060°C, and the single-pass reduction rate ≥20%, the thickness of the intermediate billet is 196mm, the final rolling temperature is finally stabilized at 845°C, and the second, fourth and sixth passes of the multi-pass differential rolling are carried out three times using a differential cooling device Cooling: After the rolling is completed, water cooling is performed, and the ACC water cooling system is used to cool to 648°C with a cooling rate of 18°C/s and then air cooling to room temperature to obtain a 135mm thick steel plate after differential temperature rolling;

S3: The 135mm thick steel plate after differential rolling of S2 is subjected to sub-temperature quenching + tempering heat treatment, in which: sub-temperature quenching is performed in the two-phase area. The measured A _c3 temperature of the steel plate is 835°C and the A _c1 temperature is 688 ℃, the sub-temperature quenching temperature is 805℃, the holding time is 80min, the tempering temperature range is 610℃, the holding time is 130min; then air-cooled to room temperature to obtain the finished steel plate;

S4: Cut metallographic samples, tensile samples and impact samples from the surface layer, 1/4 and 1/2 of the finished steel plate in step S3 respectively, and conduct microstructure observation and mechanical property analysis;

S5: The finished steel plate in step S3 is subjected to a 768-hour alternating wet and dry cycle corrosion experiment in a simulated atmospheric corrosion environment. Using Q345E as the comparison object, three groups of parallel samples are selected for each steel type, and the average corrosion weight loss rate per unit area is calculated. Corrosion rate.

The thickness of the finished steel plate in this example is 135mm. The surface microstructure is quasi-polygonal ferrite + tempered martensite + carbide + M/A island. The microstructural changes of the structure at 1/4 and 1/2 It is mainly reflected in the further decomposition of M/A islands, precipitation of carbides and coarsening and merging of martensite/bainite laths, resulting in higher microstructure uniformity along the thickness direction.

The yield strength of the finished steel plate in this embodiment at all positions along the thickness direction is 816MPa, the tensile strength is 862MPa, the yield-to-strength ratio is 0.95, the elongation after fracture is 22.4%, the strong plastic product is 19.3GPa%, and the -60°C low temperature impact energy is 238J, the corrosion rate after 768h is measured to be 1.38mm/a, and the corrosion resistance is 2.4 times that of Q345E.

The yield strength of the surface layer of the finished steel plate in this embodiment along the thickness direction is 839MPa, the tensile strength is 878MPa, the elongation after fracture is 21.7%, the yield-strength ratio is 0.96, the strong plastic product is 19.1GPa%, and the -60°C low-temperature impact energy is 227J;

The finished steel plate in this embodiment has a yield strength of 1/4 along the thickness direction of 813MPa, a tensile strength of 864MPa, an elongation after fracture of 22.4%, a yield-to-strength ratio of 0.94, a strong-plastic product of 19.4GPa%, and a low temperature of -60°C. The impact energy is 251J;

The yield strength of the finished steel plate in this embodiment along 1/2 of the thickness direction is 795MPa, the tensile strength is 845MPa, the elongation after fracture is 23.2%, the yield-to-strength ratio is 0.94, the strong-plastic product is 19.6GPa%, and the temperature is -60°C. The impact energy is 236J.

Example 5

A high-strength and tough Q690F extra-thick weather-resistant steel plate with excellent thickness uniformity. The chemical composition and mass percentage of the high-strength and tough Q690F extra-thick weather-resistant steel plate are as follows: C: 0.07%, Mn: 1.45%, Si: 0.18%, Cr: 0.45 %, Ni: 1.0%, Al: 0.028%, Nb: 0.035%, Cu: 0.35%, Mo: 0.39%, V: 0.025%, Ti: 0.009%, B: 0.0014%, P≤0.01%, S: 0.0012 %, the rest is Fe and inevitable impurity elements.

The preparation method of the high-strength Q690F extra-thick weathering steel plate with excellent thickness uniformity is shown in Figure 1, which includes the following steps:

S1: Weigh the raw materials according to the composition of the high-strength and tough Q690F extra-thick weathering steel plate with excellent thickness uniformity, and then smelt it to obtain molten iron. Pre-treat the molten iron, converter smelting, LF furnace and RH furnace smelting, and then It is continuously cast into a 370mm thick steel billet by a continuous casting machine;

S2: The 370mm thick steel billet of S1 is subjected to high-temperature insulation treatment. The temperature of the high-temperature insulation treatment is 1180°C and the time is 1.8h; then multi-pass differential temperature rolling is performed, the opening rolling temperature is 1090°C, and the rolling is performed in a single pass. The rate is ≥20%, the thickness of the intermediate billet is 170mm, the final rolling temperature is finally stabilized at 850°C, and the second, fourth and sixth passes of the multi-pass differential rolling are carried out using a differential cooling device 3 Secondary cooling; after the rolling is completed, water cooling is performed, using the ACC water cooling system to cool to 650°C, with a cooling rate of 15°C/s and then air cooling to room temperature to obtain a 120mm thick steel plate after differential temperature rolling;

S3: The 120mm thick steel plate after differential rolling of S2 is subjected to sub-temperature quenching + tempering heat treatment, in which: sub-temperature quenching is performed in the two-phase area, the quenching temperature is between A _c3 and A _c1 , the measured steel plate A The temperature of _c3 is 840℃, the temperature of A _c1 is 690℃; the subtemperature quenching temperature is 790℃, the holding time is 70min, the tempering temperature range is 600℃, the holding time is 110min; then air-cooled to room temperature to obtain the finished steel plate;

S4: Cut metallographic samples, tensile samples and impact samples from the surface layer, 1/4 and 1/2 of the finished steel plate in step S3 respectively, and conduct microstructure observation and mechanical property analysis;

S5: The finished steel plate in step S3 is subjected to a 768-hour alternating wet and dry cycle corrosion experiment in a simulated atmospheric corrosion environment. Using Q345E as the comparison object, three groups of parallel samples are selected for each steel type, and the average corrosion weight loss rate per unit area is calculated. Corrosion rate.

The thickness of the finished steel plate in this example is 120mm. The surface microstructure is quasi-polygonal ferrite + tempered martensite + carbide + M/A island. The microstructural changes of the structure at 1/4 and 1/2 It is mainly reflected in the further decomposition of M/A islands, precipitation of carbides and coarsening and merging of martensite/bainite laths, resulting in higher microstructure uniformity along the thickness direction.

The yield strength of the finished steel plate in this embodiment at all positions along the thickness direction is 786MPa, the tensile strength is 849MPa, the yield-strength ratio is 0.93, the elongation after fracture is 22.7%, the strong plastic product is 19.3GPa, and the -60°C low-temperature impact energy is 217J, the measured corrosion rate after 768h is 1.2mm/a, and the corrosion resistance is 2.2 times that of Q345E.

The yield strength of the surface layer of the finished steel plate in this embodiment along the thickness direction is 802MPa, the tensile strength is 853MPa, the yield-strength ratio is 0.94, the elongation after fracture is 21.5%, the strong plastic product is 18.3GPa, and the -60°C low-temperature impact energy is 215J. ;

The yield strength of the finished steel plate in this embodiment along 1/4 of the thickness direction is 785MPa, the tensile strength is 848MPa, the yield-to-strength ratio is 0.93, the elongation after fracture is 22.0%, the strong plastic product is 18.7GPa, and the -60°C low temperature impact The work is 219J;

The yield strength of the finished steel plate in this embodiment along 1/2 of the thickness direction is 772MPa, the tensile strength is 845MPa, the yield-to-strength ratio is 0.91, the elongation after fracture is 24.6%, the strong plastic product is 20.8GPa, and the -60°C low temperature impact The work is 216J.

Example 6

A high-strength and tough Q690F extra-thick weather-resistant steel plate with excellent thickness uniformity. The chemical composition and mass percentage of the high-strength and tough Q690F extra-thick weather-resistant steel plate are as follows: C: 0.11%, Mn: 1.38%, Si: 0.8%, Cr: 0.41 %, Ni: 0.8%, Al: 0.029%, Nb: 0.035%, Cu: 0.28%, Mo: 0.39%, V: 0.035%, Ti: 0.012%, B: 0.0012%, P: 0.0075%, S: 0.0014 %, the rest is Fe and inevitable impurity elements.

The preparation method of the high-strength Q690F extra-thick weathering steel plate with excellent thickness uniformity is shown in Figure 1, which includes the following steps:

S1: Weigh the raw materials according to the composition of the high-strength and tough Q690F extra-thick weathering steel plate with excellent thickness uniformity, and then smelt it to obtain molten iron. Pre-treat the molten iron, converter smelting, LF furnace and RH furnace smelting, and then It is continuously cast into a 350mm thick steel billet through a continuous casting machine;

S2: The 350mm thick steel billet of S1 is subjected to high-temperature insulation treatment. The temperature of the high-temperature insulation treatment is 1220°C and the time is 1.5h; then multi-pass differential temperature rolling is performed, the opening rolling temperature is 1150°C, and the rolling is performed in a single pass. The rate is ≥20%, the thickness of the intermediate billet is 180mm, the final rolling temperature is finally stabilized at 860°C, and the second, fourth and sixth passes of the multi-pass differential rolling are carried out using a differential cooling device 3 Secondary cooling; after the rolling is completed, water cooling is performed, using the ACC water cooling system to cool to 650°C, with a cooling rate of 17°C/s and then air cooling to room temperature to obtain a 120mm thick steel plate after differential temperature rolling;

S3: The 120mm thick steel plate after differential rolling of S2 is subjected to sub-temperature quenching + tempering heat treatment, where: sub-temperature quenching is performed in the two-phase area, the quenching temperature is between A _c3 and A _c1 , the measured steel plate A The temperature of _c3 is 860℃, the temperature of A _c1 is 698℃; the subtemperature quenching temperature is 790℃, the holding time is 66min, the tempering temperature range is 580℃, the holding time is 120min; then air-cooled to room temperature to obtain the finished steel plate;

S4: Cut metallographic samples, tensile samples and impact samples from the surface layer, 1/4 and 1/2 of the finished steel plate in step S3 respectively, and conduct microstructure observation and mechanical property analysis;

S5: The finished steel plate in step S3 is subjected to a 786-hour alternating wet and dry cycle corrosion experiment in a simulated atmospheric corrosion environment. Using Q345E as the comparison object, three groups of parallel samples are selected for each steel type, and the average corrosion weight loss rate per unit area is calculated. Corrosion rate.

The thickness of the finished steel plate in this example is 120mm. The surface microstructure is quasi-polygonal ferrite + tempered martensite + carbide + M/A island. The microstructural changes of the structure at 1/4 and 1/2 It is mainly reflected in the further decomposition of M/A islands, precipitation of carbides and coarsening and merging of martensite/bainite laths, resulting in higher microstructure uniformity along the thickness direction.

The yield strength of the finished steel plate in this embodiment at all positions along the thickness direction is 810MPa, the tensile strength is 859MPa, the yield-to-strength ratio is 0.94, the elongation after fracture is 22.6%, the strong plastic product is 19.4GPa%, and the -60°C low temperature impact energy The corrosion rate is 236J, and the corrosion rate after 768h is measured to be 1.1mm/a, and the corrosion resistance is 2.3 times that of Q345E.

The yield strength of the surface layer of the finished steel plate in this embodiment along the thickness direction is 828MPa, the tensile strength is 863MPa, the yield strength ratio is 0.96, the elongation after fracture is 22.0%, and the -60°C low temperature impact energy is 220J;

The yield strength of the finished steel plate in this embodiment along 1/4 of the thickness direction is 805MPa, the tensile strength is 861MPa, the yield strength ratio is 0.93, the elongation after fracture is 22.6%, and the -60°C low temperature impact energy is 247J;

The yield strength of the finished steel plate in this embodiment at 1/2 of the thickness direction is 798MPa, the tensile strength is 853MPa, the yield-strength ratio is 0.94, the elongation after fracture is 23.3%, and the -60°C low-temperature impact energy is 240J.

Based on the above solution, the present invention proposes a high-strength and tough Q690F extra-thick weather-resistant steel plate with excellent thickness uniformity. It uses multi-pass differential temperature rolling + sub-temperature quenching + tempering to prepare the plate with the required performance, and retains the deformation structure after rolling. In order to increase the phase deformation nuclei and refine the grains, it also improves the structural uniformity of the steel plate along the thickness direction. The subsequent sub-temperature quenching + tempering introduces some quasi-polygonal ferrite and promotes the formation of nanoscale carbides in the tempered structure. The precipitation improves the strength and toughness matching of the steel plate and has excellent corrosion resistance.

The invention describes a high-strength and tough Q690F extra-thick weather-resistant steel plate with excellent thickness uniformity. In order to improve the strength, toughness and corrosion resistance, it adopts a reasonable low-carbon micro-alloying component design and gives full play to the advantages of differential temperature rolling. By adjusting the process parameters of differential rolling and sub-temperature quenching + tempering, the yield strength of the produced steel plate is ≥780MPa, the tensile strength is ≥820MPa, and the elongation after fracture is ≥ 20%, -60℃ low temperature impact energy ≥210J, corrosion rate after 768h is 1.1-1.4mm/a, corrosion resistance is 1.8-2.5 times that of Q345E, with excellent strength, toughness and corrosion resistance.

The invention is based on actual industrial production conditions. The differential temperature rolling process is highly controllable and easy to implement. It eliminates the need for complete austenitizing quenching after rolling and improves production efficiency. It is widely used in heavy machinery manufacturing, marine engineering construction, pressure vessel manufacturing, etc. The field has broad application prospects.

The thickness of the high-strength Q690F extra-thick weathering steel plate with excellent thickness uniformity described in the present invention is 100-140mm, and the surface microstructure is quasi-polygonal ferrite + tempered martensite + carbide + M/A island, 1 The microstructural changes at /4 and 1/2 are mainly reflected in further M/A island decomposition, carbide precipitation and coarsening and merger of martensite/bainite laths, with high microstructure uniformity along the thickness direction. .

In short, compared with other traditional methods, the method of the present invention not only reduces the quenching temperature by sub-temperature quenching, but also after combined with the tempering process, the quasi-polygonal ferrite and nanoscale carbides obtained in the extra-thick steel plate can simultaneously improve the strength of the plate. Plasticity, low temperature impact toughness, thickness uniformity and atmospheric corrosion resistance are beneficial to industrial mass production.

The above is the preferred embodiment of the present invention. It should be pointed out that for those of ordinary skill in the art, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications It should also be regarded as the protection scope of the present invention.

Claims (10)

1. A high-strength and tough Q690F extra-thick weather-resistant steel plate with excellent thickness uniformity, characterized in that the chemical composition and mass percentage of the high-strength and tough Q690F extra-thick weather-resistant steel plate are as follows: C: 0.06-0.12%, Mn: 1.10-1.65 %, Si: 0.1-0.3%, Cr: 0.25-0.50%, Ni: 0.6-1.4%, Al: 0.02-0.05%, Nb: 0.020-0.045%, Cu: 0.2-0.5%, Mo: 0.35-0.50% , V: 0.02-0.04%, Ti: 0.005-0.020%, B: 0.0010-0.0015%, P≤0.01%, S≤0.002%, the rest are Fe and inevitable impurity elements. 2. The high-strength and tough Q690F extra-thick weather-resistant steel plate with excellent thickness uniformity according to claim 1, characterized in that the thickness of the high-strength and tough Q690F extra-thick weather-resistant steel plate with excellent thickness uniformity is 100-140mm, and the surface layer is microscopic The structure is quasi-polygonal ferrite+tempered martensite+carbide+M/A islands. The microstructure changes at 1/4 and 1/2 are mainly reflected in further decomposition of M/A islands and precipitation of carbides. Combined with the coarsening of martensite/bainite laths, the microstructure uniformity along the thickness direction is high. 3. The high-strength and tough Q690F extra-thick weather-resistant steel plate with excellent thickness uniformity according to claim 1, characterized in that the yield strength of the high-strength and tough Q690F extra-thick weather-resistant steel plate with excellent thickness uniformity at all positions along the thickness direction is ≥780MPa. , tensile strength ≥820MPa, yield ratio ≥0.92, elongation after fracture ≥20%, strong plastic volume ≥19.3GPa%, -60℃ low temperature impact energy ≥210J, the measured corrosion rate after 768h is 1.1-1.4mm/ a. The corrosion resistance is 1.8-2.5 times that of Q345E. 4. The high-strength and tough Q690F extra-thick weather-resistant steel plate with excellent thickness uniformity according to claim 1, characterized in that the yield strength of the surface layer along the thickness direction of the high-strength and tough Q690F extra-thick weather-resistant steel plate with excellent thickness uniformity is ≥798MPa. , tensile strength ≥854MPa, elongation after break ≥20.6%, -60℃ low temperature impact energy ≥206J; The high-strength and tough Q690F extra-thick weather-resistant steel plate with excellent thickness uniformity has a yield strength of 1/4 along the thickness direction ≥ 776MPa, a tensile strength ≥ 837MPa, an elongation after fracture ≥ 22.3%, and a low-temperature impact energy of -60°C ≥ 221J; The high-strength and tough Q690F extra-thick weathering steel plate with excellent thickness uniformity has a yield strength of 1/2 along the thickness direction ≥ 769MPa, a tensile strength ≥ 828MPa, an elongation after fracture ≥ 23.2%, and a low-temperature impact energy of -60°C ≥ 213J. 5. A method for preparing the high-strength and tough Q690F extra-thick weather-resistant steel plate with excellent thickness uniformity according to claims 1-4, characterized in that the preparation method of the high-strength and tough Q690F extra-thick weather-resistant steel plate with excellent thickness uniformity includes Following steps: S1: Weigh the raw materials according to the composition of the high-strength and tough Q690F extra-thick weather-resistant steel plate with excellent thickness uniformity, and then smelt it to obtain molten iron. The molten iron is pretreated, smelted in a converter, LF furnace and RH furnace, and then It is continuously cast into steel billet through continuous casting machine; S2: The steel billet of S1 is subjected to high-temperature insulation treatment, and then multi-pass differential rolling is performed. After the rolling is completed, it is water-cooled, and then air-cooled to room temperature to obtain a differentially rolled steel plate; S3: The steel plate after differential rolling in S2 is subjected to sub-temperature quenching + tempering heat treatment, and then air-cooled to room temperature to obtain the finished steel plate; S4: Cut metallographic samples, tensile samples and impact samples from the surface layer, 1/4 and 1/2 of the finished steel plate in step S3 respectively, and conduct microstructure observation and mechanical property analysis; S5: The finished steel plate in step S3 is subjected to a dry-wet cycle corrosion experiment in a simulated atmospheric corrosion environment. Using Q345E as the comparison object, three groups of parallel samples are selected for each steel type, and the average corrosion rate is calculated by calculating the corrosion weight loss rate per unit area. . 6. The preparation method of the high-strength Q690F extra-thick weather-resistant steel plate with excellent thickness uniformity according to claim 5, characterized in that the thickness of the steel billet of S1 is 340-380mm, the thickness of the intermediate billet of S2 is 160-200mm, and the differential temperature rolling The thickness of the finished steel plate is 100-140mm. 7. The preparation method of the high-strength Q690F extra-thick weather-resistant steel plate with excellent thickness uniformity according to claim 5, characterized in that the temperature of the high-temperature insulation treatment of S2 is 1150-1250°C, and the time is 1-3h; multiple passes The opening temperature of differential rolling is 1050-1150°C, the single-pass reduction rate is ≥20%, the final rolling temperature is finally stabilized at 840-870°C, and the second and third passes of multi-pass differential rolling are The 4th pass and the 6th pass use a differential cooling device for 2-4 times of cooling; the water cooling uses an ACC water cooling system to cool to 640-660°C, with a cooling speed of 10-20°C/s. 8. The preparation method of the high-strength Q690F extra-thick weather-resistant steel plate with excellent thickness uniformity according to claim 5, characterized in that the sub-temperature quenching of S3 is performed in the two-phase region, and the quenching temperature is between A _c3 and A Between _c1 , the temperature of steel plate A _c3 measured is 830-870℃, the temperature of A _c1 is 680-720℃; the subtemperature quenching temperature is 780-830℃, the holding time is 50-80min; the tempering temperature range is 550-650 ℃, holding time is 100-130min. 9. The method for preparing a high-strength Q690F extra-thick weather-resistant steel plate with excellent thickness uniformity according to claim 5, characterized in that the tensile sample size of S4 is a gauge length of 50 mm and the shape is a round rod. 10. The method for preparing the high-strength Q690F extra-thick weather-resistant steel plate with excellent thickness uniformity according to claim 5, characterized in that the time of the S5 alternating wet and dry cycle corrosion test is 768-786 hours.