Production method of hot-rolled steel plate for bridge

Abstract

The present invention discloses a production method for hot-rolled steel plates for bridges. The chemical composition of the steel plates, in terms of mass percentage, includes: C: 0.10-0.13%, Si: 0.11-0.18%, Mn: 1.34-1.42%, Nb: 0.014-0.022%, Ti: 0.009-0.017%, Al: 0.026-0.046%, and the remainder is iron and impurities. The production method includes adopting a heating, controlled rolling, and controlled cooling process to prepare a finished steel plate with a thickness of 6-64 mm. During the heating process, the temperature of the heating section is above T1+10°C and below T2, and T1 is T NbC 、T NbN and T TiC The maximum value of T2 is T1+50℃, T TiN The larger value is 150℃, and the temperature in the soaking section is 20~40℃ lower than that in the heating section.

Description

Technical Field

[0001] The invention belongs to the technical field of steel alloy materials and relates to a production method of hot-rolled steel plates for bridges. Background Art

[0002] The rapid development of highways and high-speed railways has fueled the rapid growth of the steel bridge manufacturing industry. While maintaining their functional capabilities, steel bridges are evolving towards multi-functionality, multi-lane construction, heavy-load capabilities, and long spans. Structural steel for bridges is primarily used in key projects such as railways, highways, and cross-sea and river bridges. Due to the unique operating environments, these bridges have stringent requirements for comprehensive performance, such as a low yield strength ratio, excellent weldability, and high toughness. Summary of the Invention

[0003] The object of the present invention is to provide a production method of hot-rolled steel plates for bridges.

[0004] To achieve the above-mentioned object, one embodiment of the present invention provides a method for producing a hot-rolled steel plate for bridges. The chemical composition of the steel plate, in percentage by mass, comprises: C: 0.10-0.13%, Si: 0.11-0.18%, Mn: 1.34-1.42%, Nb: 0.014-0.022%, Ti: 0.009-0.017%, Al: 0.026-0.046%, P ≤ 0.0151%, S ≤ 0.0080%, N ≤ 0.0045%, and the remainder being iron and unavoidable impurities;

[0005] The production method includes adopting the process of heating, controlled rolling and controlled cooling to prepare the finished steel plate with a thickness of 6 to 64 mm;

[0006] In the heating process, the steel billet is heated in a heating furnace. The heating process includes a heating section and a soaking section. The temperature of the heating section is above T1+10°C and below T2. T1 is T NbC 、T NbN and T TiC The maximum value of T2 is T1+50℃, T TiN -150℃, the larger value, T NbC 、T NbN 、T TiC and T TiN They are the complete solution temperatures of NbC, NbN, TiC and TiN respectively. The temperature of the soaking section is 20-40°C lower than that of the heating section.

[0007] Preferably, in the controlled rolling process, the steel billet is first rolled at a rolling temperature of not less than T3 and not more than T3+40°C to a thickness of 4 to 6.8 times that of the finished product to obtain a first intermediate plate; then rolled at a rolling temperature of not less than T4-50°C and not more than T4+20°C to a thickness of 1.8 to 3.2 times that of the finished product to obtain a second intermediate plate; and finally rolled at a rolling temperature of not less than T5-55°C and not more than T5-15°C to the thickness of the finished product;

[0008] T3≥T4≥T5, T5=910-310[C]-80[Mn]-15[Cr],

[0009] More preferably, when rolling to obtain the first intermediate plate, the reduction in each pass is ≥20 mm; when rolling to obtain the second intermediate plate, the reduction in each pass is ≥12 mm; when rolling the second intermediate plate to the finished product thickness, the reduction in each pass is ≥4 mm.

[0010] More preferably, in the controlled cooling process, the steel plate is air-cooled at a cooling rate of 1 to 10°C / s to a temperature between T6-30°C and T6-10°C, then water-cooled at a cooling rate of 8 to 30°C / s to a temperature between T7+50°C and T7+90°C, and then naturally cooled to room temperature to obtain a finished steel plate; T5 ≥ T6 ≥ T7,

[0011] T7=539-423[C]-17.7[Ni]-12.1[Cr]-11[Si]-30.4[Mn],

[0012] T6=830-270[C]-90[Mn]-37[Ni]-70[Cr].

[0013] Compared with the prior art, the beneficial effect of one embodiment is that: by controlling the chemical composition and heating, a low-alloy component system is adopted, for example, the content of conventionally used alloying elements such as Ni, Mo, and Cr is reduced. At the same time, the toughness brought by these elements is not reduced due to the reduction of the content of these elements. Instead, through temperature control in the heating process, the steel plate is achieved to have excellent strength, toughness and yield strength ratio. In addition, the defect of poor welding performance caused by high alloy can be eliminated, so that the steel plate can be comprehensively improved in low yield strength ratio, easy welding, and high strength and toughness under the conditions of low alloy content, low production difficulty, and short production process. DETAILED DESCRIPTION

[0014] As mentioned in the background technology, existing bridge steel is required to have excellent mechanical properties and toughness. To this end, one embodiment of the present invention provides a production method for bridge hot-rolled steel plates, which, based on the setting of chemical composition and heating process, uses low alloy content to ensure comprehensive performance, especially improve toughness.

[0015] Specifically, the chemical composition of the steel plate includes, by mass percentage, C: 0.10-0.13%, Si: 0.11-0.18%, Mn: 1.34-1.42%, Nb: 0.014-0.022%, Ti: 0.009-0.017%, Al: 0.026-0.046%, P≤0.0151%, S≤0.0080%, N≤0.0045%, and the rest is iron and unavoidable impurities.

[0016] The role and control of each chemical component are described in detail below.

[0017] C: Carbon is the most economical strengthening element in steel. It has a significant solid solution strengthening effect and can effectively reduce the yield strength ratio. At the same time, it forms carbides with Nb, Ti, Cr, Mo, etc., which has a precipitation strengthening effect. When the carbon content is lower than 0.08%, the effect of increasing strength and reducing the yield strength ratio is not obvious. When the carbon content is higher than 0.11%, it will lead to deterioration of toughness and welding performance.

[0018] Si: Silicon has a solid solution strengthening effect in steel. When the Si content is lower than 0.11%, the solid solution strengthening effect is not obvious; when the Si content exceeds 0.18%, Fe2SiO4 is easily generated on the surface of the continuous casting billet, which is difficult to remove during descaling and is detrimental to the surface quality of the steel plate.

[0019] Mn: Manganese plays a role in solid solution strengthening in steel and is the most economical strengthening element besides carbon. When the Mn content is lower than 1.39%, the solid solution strengthening effect is not obvious; when the Mn content exceeds 1.47%, it is easy to form segregation in the center of the slab, reducing the low-temperature toughness of the steel plate and at the same time being detrimental to the welding performance.

[0020] Nb: Niobium is an important grain-refining element in steel. When the Nb content exceeds 0.021%, niobium carbonitride precipitates are formed during the rolling process, refining the recrystallized grains. During the cooling process, niobium can continue to precipitate in the form of carbonitrides, refining the microstructure after phase transformation and improving strength and toughness. However, when the Nb content is greater than 0.029%, the alloy cost will increase, and precipitation strengthening will be detrimental to the yield strength ratio.

[0021] Ti: Titanium is a nitrogen-fixing element in steel. It can form dispersed titanium nitride particles, which inhibit the coarsening of austenite grains during billet heating and rolling. However, when the Ti content is less than 0.009%, Ti cannot fully play its role. When the Ti content is greater than 0.017%, titanium carbonitride precipitation is easily formed in the core of the ingot, affecting the low-temperature toughness of the steel plate core.

[0022] Al: Aluminum is a deoxidizing element in steel. When the content is lower than 0.026%, Al cannot effectively achieve its deoxidation effect. When the content is higher than 0.046%, the Al2O3 inclusions in the steel increase, affecting the low-temperature toughness of the steel.

[0023] P, S, and N: impurity elements. However, S can also form MnS inclusions with Mn, reducing the low-temperature toughness of the steel. In this application, P ≤ 0.02%, S ≤ 0.0080%, and N ≤ 0.0045%. In some embodiments, the P content is preferably 0.0101-0.0151%, the N content is preferably 0.0025-0.0045%, and the S content is preferably 0.0020-0.0080%.

[0024] In this way, in terms of chemical composition, a low-alloy component system is adopted, for example, the content of conventionally used alloy elements such as Ni, Mo, and Cr is reduced, while also ensuring excellent mechanical properties and toughness.

[0025] Next, the production method includes adopting the processes of heating, controlled rolling and controlled cooling to prepare a finished steel plate with a thickness of 6 to 64 mm.

[0026] In the heating process, the steel billet is heated in a heating furnace. The heating process includes a heating section and a soaking section. The temperature of the heating section is above T1+10°C and below T2. T1 is T NbC 、T NbN and T TiC The maximum value of T2 is T1+50℃, T TiN -150℃, the larger value, T NbC 、T NbN 、T TiC and T TiN They are the complete solution temperatures of NbC, NbN, TiC and TiN respectively. The temperature of the soaking section is 20-40°C lower than that of the heating section.

[0027] In this way, combined with the previous chemical composition, and by controlling the heating temperature and the soaking section temperature in the heating process, on the one hand, by controlling the temperature in the heating furnace to be above T1+10°C and below T2, it can be ensured that the Nb precipitates in the steel are completely dissolved, the Ti carbides are completely dissolved, and the Ti nitrides are retained, thereby preventing the abnormal growth of austenite grains and ultimately ensuring the comprehensive performance of the finished steel plate; on the other hand, by controlling the soaking section temperature to be 20 to 40°C lower than the heating section temperature, it was unexpectedly discovered that the toughness of the finished steel plate can be further improved.

[0028] In summary, by controlling the chemical composition and heating, a low-alloy composition system is adopted. For example, the content of conventional alloying elements such as Ni, Mo, and Cr is reduced. At the same time, the toughness brought by these elements is not reduced due to the reduction of the content of these elements. Instead, through temperature control in the heating process, the steel plate is made to have excellent strength, toughness and yield ratio. In addition, the defects of poor welding performance caused by high alloy content can be eliminated. As a result, the steel plate can achieve comprehensive improvements in low yield ratio, easy welding, and high strength and toughness under the conditions of low alloy content, low production difficulty, and short production process.

[0029] Furthermore, the yield strength of the steel plate is ≥390MPa, the tensile strength is ≥530MPa, the elongation is ≥28%, the yield strength ratio is ≤0.75, the impact energy KV2 at 0°C is ≥280J, the impact energy KV2 at -20°C is ≥260J, and the impact energy KV2 at -40°C is ≥250J.

[0030] The above properties can be tested for mechanical properties, including yield strength, tensile strength, and elongation, in accordance with GB / T 228.1-2021 "Tensile tests on metallic materials - Part 1: Test methods at room temperature"; and can be tested for low-temperature toughness in accordance with GB / T 229-2007 "Charpy pendulum impact test method for metallic materials", that is, the test of impact energy at various temperatures.

[0031] Preferably, the carbon equivalent CEV of the chemical composition of the steel plate satisfies 0.328 to 0.371.

[0032] Among them, carbon equivalent CEV = [C] + [Mn] / 6 + ([Cr] + [Mo] + [V]) / 5 + ([Cu] + [Ni]) / 15, where [C], [Mn], [Cr], [Mo], [V], [Cu], and [Ni] represent the mass percentages of elements such as C, Mn, Cr, Mo, V, Cu, and Ni in the steel. For example, when the mass percentage of C in the steel is 0.09%, the mass percentage of C is 0.09, and this value is substituted into the CEV formula.

[0033] In this way, the steel plate has excellent welding performance, which greatly improves the safety factor and service life of the steel plate in bridge engineering.

[0034] Preferably, in the heating process of the production method, the steel billet used can be a continuous casting billet prepared by KR desulfurization, converter smelting, RH refining, LF refining and continuous casting. It can be understood that the chemical composition of the continuous casting billet is the same as the chemical composition of the final steel plate product.

[0035] In an optional embodiment, the method can be implemented by lg([Nb]×[N])=3.70-10800 / (T NbN+273.15), lg([Nb]×[C])=2.26-6770 / (T NbC +273.15), lg([Ti]×[C])=5.33-10475 / (T TiC +273.15), lg([Ti]×[N])=0.32-8000 / (T TiN +273.15) and calculate T NbC 、T NbN 、T TiC and T TiN , [Nb], [N]), [C], and [Ti] are the mass percentages of Nb, N, C, and Ti in the steel billet, respectively.

[0036] Of course, in a variant embodiment, T NbC 、T NbN 、T TiC and T TiN It can also be obtained using methods known in the art, such as industry experience values.

[0037] Preferably, in one embodiment, the steel billet adopts a five-stage process in the heating furnace, including a heat recovery section, a preheating section, a heating section, a heating section and a soaking section, the temperature of the heat recovery section is ≤900°C, the temperature of the preheating section is ≤1000°C, and the temperature of the heating section is 1120±15°C.

[0038] The residence time of the billet in the heating section is 0.07-0.13 min / mm, and the total time in the heating furnace is 1.15-1.35 min / mm. Here, the unit min / mm refers to the unit thickness of the billet per minute, and the unit thickness is calculated in mm.

[0039] Of course, in an optional variation, the steel billet may also be heated in a heating furnace using a three-stage process comprising a preheating stage, a heating stage and a soaking stage, wherein the temperature of the preheating stage is ≤1000°C.

[0040] Furthermore, in a preferred embodiment, in the controlled cooling process, the steel plate is air-cooled to above T6-30°C and below T6-10°C at a cooling rate of 1-10°C / s, then water-cooled to above T7+50°C and below T7+90°C at a cooling rate of 8-30°C / s, and then naturally cooled to room temperature to obtain a finished steel plate.

[0041] Among them, T6≥T7, T7=539-423[C]-17.7[Ni]-12.1[Cr]-11[Si]-30.4[Mn], T6=830-270[C]-90[Mn]-37[Ni]-70[Cr], where [C], [Si], [Ni], [Mn], and [Cr] are the mass percentages of C, Si, Ni, Mn, and Cr in the steel billet, respectively.

[0042] In this way, the cooling of hot-rolled steel plates is divided into three stages with different cooling rates and cooling methods. In the first cooling stage, ferrite phase transformation occurs, and the presence of ferrite ensures the low yield strength of the steel plate. Moreover, in the second stage, the carbon-rich supercooled austenite phase in the steel plate is rapidly cooled to transform it into acicular ferrite / bainite structure, and the acicular ferrite / bainite phase transformation is completed by controlling the final cooling temperature. In addition, the control of the cooling rate effectively avoids the formation of martensite phase or pearlite phase. Furthermore, the above temperature control can also improve the plate shape of the finished steel plate.

[0043] For example, through the above-mentioned controlled cooling process, the obtained steel plate has an excellent plate shape with an unevenness of ≤1 mm / m, where the unit mm / m refers to mm per unit length of the steel plate, and the unit length is calculated in m.

[0044] Specifically, in the controlled cooling process, cooling can be carried out in an ultra-fast cooling system. For example, the cooling water manifolds in the front section of the system can be closed and the roller speed can be 0.5 to 2.2 m / s to cool at a low cooling rate; while in the rear section of the system, 5 to 24 groups of cooling water manifolds can be opened and the roller speed can be 0.6 to 2.3 m / s to achieve rapid cooling.

[0045] In addition, in the controlled rolling process: the steel billet is first rolled at a rolling temperature of not less than T3 and not more than T3+40°C to a thickness of 4 to 6.8 times that of the finished product to obtain a first intermediate plate; then, the steel billet is rolled at a rolling temperature of not less than T4-50°C and not more than T4+20°C to a thickness of 1.8 to 3.2 times that of the finished product to obtain a second intermediate plate; and finally, the steel billet is rolled at a rolling temperature of not less than T5-55°C and not more than T5-15°C to the thickness of the finished product.

[0046] Among them, T3≥T4≥T5≥T6, T5=910-310[C]-80[Mn]-15[Cr], [C], [Nb], [Ti], [Al], [Si], and [Ni] are the mass percentages of C, Nb, Ti, Al, Si, and Ni in the steel billet, respectively.

[0047] In this way, by controlling the temperature of the steel billet during rolling to 4 to 6.8 times the thickness of the finished product, the temperature during rolling from 4 to 6.8 times the thickness of the finished product to 1.8 to 3.2 times the thickness of the finished product, and the temperature during rolling from 1.8 to 3.2 times the thickness of the finished product to the completion of rolling, on the one hand, sufficient recrystallization and refinement of the recrystallized grains can be ensured first, on the other hand, the recrystallized equiaxed grains can be deformed and flattened, and on the other hand, rolling deformation can be used to induce ferrite phase transformation, and ferrite phase transformation occurs on the deformation band or in the grain boundary to obtain fine ferrite grains, thereby further improving the yield strength and good toughness of the steel plate.

[0048] More specifically, during rolling the steel slab into the first intermediate plate, the start rolling temperature is greater than or equal to T3+20°C and less than or equal to T3+40°C, and the finish rolling temperature is greater than or equal to T3 and less than or equal to T3+20°C.

[0049] Furthermore, preferably, during rolling the first intermediate plate into the second intermediate plate, the start rolling temperature is greater than T4 and less than T4+20°C, and the finish rolling temperature is greater than T4-50°C and less than T4-30°C.

[0050] When the second intermediate plate is rolled to the finished thickness, the starting rolling temperature is higher than T5-30°C and lower than T5-15°C, and the finishing rolling temperature is higher than T5-55°C and lower than T5-40°C.

[0051] By such control, combined with heating, rolling and cooling, the metallographic structure of the final steel plate product is a complex phase structure of deformation-induced ferrite + polygonal ferrite + acicular ferrite + bainite.

[0052] Here, the metallographic structure of the steel can be obtained by conducting tissue testing using the standard GB / T 15125-2009 “Specimens and test methods for metallographic examination of metallic materials”.

[0053] Among them, the area of ​​deformation-induced ferrite in the metallographic sampling surface accounts for approximately 35% to 45%, the area of ​​polygonal ferrite in the metallographic sampling surface accounts for approximately 10% to 30%, the area of ​​acicular ferrite in the metallographic sampling surface accounts for approximately 15% to 25%, and the area of ​​bainite in the metallographic sampling surface accounts for approximately 10% to 30%.

[0054] In addition, in the controlled rolling process, during the rolling of the steel billet into the first intermediate plate, the reduction in each pass is ≥20mm; during the rolling of the first intermediate plate into the second intermediate plate, the reduction in each pass is ≥12mm; during the rolling of the second intermediate plate into the finished thickness, the reduction in each pass is ≥4mm.

[0055] In summary, the beneficial effects of the present invention are:

[0056] By controlling the chemical composition and heating, a low-alloy composition system is adopted. For example, the content of commonly used alloying elements such as Ni, Mo, and Cr is reduced. At the same time, the toughness brought by these elements is not reduced due to the reduction of the content of these elements. Instead, through the temperature control in the heating process, the steel plate has excellent strength, toughness and yield strength ratio. In addition, the defects of poor welding performance caused by high alloy can be eliminated. Therefore, the comprehensive improvement of the steel plate in low yield strength ratio, easy welding and high strength and toughness can be achieved with low alloy content, low production difficulty and short production process.

[0057] Some specific embodiments are described below. In these embodiments, the chemical composition of the steel is shown in Table 1.

[0058] [Table 1]

[0059]

[0060] The thickness and properties of the steel of each embodiment are shown in Table 2. In addition, the steel plate roughness of each embodiment is ≤1 mm / m and the welding performance is excellent.

[0061] [Table 2]

[0062]

[0063] The preparation process of the above-mentioned embodiment 1 is as follows: a continuous casting billet is prepared by steelmaking and continuous casting; a five-stage process is adopted, the temperature of the heat recovery section is ≤900°C, the temperature of the preheating section is ≤1000°C, the temperature of the first adding section is 1120°C, the temperature of the heating section is 1188°C, and the temperature of the soaking section is 1158°C; after leaving the heating furnace, the billet is first rolled to 160mm at a starting rolling temperature of 972±10°C and a finishing rolling temperature of 952±10°C; then rolled to 84mm at a starting rolling temperature of 859±10°C and a finishing rolling temperature of 809±10°C; finally rolled to 28mm at a starting rolling temperature of 733~748°C and a finishing rolling temperature of 708~723°C to obtain a hot-rolled steel plate; the hot-rolled steel plate is air-cooled to 656±10°C at a cooling rate of 1~10°C / s, then water-cooled to 519±10°C at a cooling rate of 5~30°C / s, and then naturally cooled to room temperature to obtain a finished steel plate.

[0064] The preparation process of the above-mentioned embodiment 2 is as follows: a continuous casting billet is prepared by steelmaking and continuous casting; a three-stage process is adopted, the temperature of the preheating section is ≤1000°C, the temperature of the heating section is 1209°C, and the temperature of the soaking section is 1179°C; after leaving the heating furnace, the billet is first rolled to 200mm at a starting rolling temperature of 959±5°C and a finishing rolling temperature of 939±5°C; then rolled to 100mm at a starting rolling temperature of 854±5°C and a finishing rolling temperature of 804±5°C; finally, rolled to 50mm at a starting rolling temperature of 738±5°C and a finishing rolling temperature of 708±5°C to obtain a hot-rolled steel plate; the hot-rolled steel plate is air-cooled to 653±10°C at a cooling rate of 1~10°C / s, then water-cooled to 510±10°C at a cooling rate of 5~30°C / s, and then naturally cooled to room temperature to obtain a finished steel plate.

Claims

1. A method for producing hot-rolled steel plates for bridges, characterized in that: The chemical composition of the steel plate includes, by mass percentage, C: 0.10-0.13%, Si: 0.11-0.18%, Mn: 1.34-1.42%, Nb: 0.014-0.022%, Ti: 0.009-0.017%, Al: 0.026-0.046%, P≤0.0151%, S≤0.0080%, N≤0.0045%, and the remainder is iron and unavoidable impurities; The production method includes adopting a process of heating, controlled rolling, and controlled cooling to prepare a finished steel plate with a thickness of 6 to 64 mm; In the heating process, the steel billet is heated in a heating furnace. The heating process includes a heating section and a soaking section. The temperature of the heating section is above T1+10°C and below T2. T1 is T NbC 、T NbN and T TiC The maximum value of T2 is T1+50℃, T TiN -150℃, the larger value, T NbC 、T NbN 、T TiC and T TiN The complete solution temperatures of NbC, NbN, TiC and TiN are respectively. The temperature of the soaking section is 20~40℃ lower than that of the heating section. By lg([Nb]×[N])=3.70-10800 / (T NbN +273.15), lg([Nb]×[C])=2.26-6770 / (T NbC +273.15), lg([Ti]×[C])=5.33-10475 / (T TiC +273.15), lg([Ti]×[N])=0.32-8000 / (T TiN +273.15) and calculate T NbC 、T NbN 、T TiC and T TiN , [Nb], [N]), [C], and [Ti] are the mass percentages of Nb, N, C, and Ti in the steel billet, respectively; In the controlled rolling process, the steel billet is first rolled to 4 to 6.8 times the thickness of the finished product to obtain a first intermediate plate, wherein the starting rolling temperature is greater than T3+20°C and less than T3+40°C, and the final rolling temperature is greater than T3 and less than T3+20°C; then rolled to 1.8 to 3.2 times the thickness of the finished product to obtain a second intermediate plate, wherein the starting rolling temperature is greater than T4 and less than T4+20°C, and the final rolling temperature is greater than T4-50°C and less than T4-30°C; finally rolled to the thickness of the finished product, wherein the starting rolling temperature is greater than T5-30°C and less than T5-15°C, and the final rolling temperature is greater than T5-55°C and less than T5-40°C; T3≥T4≥T5, T3=887+464[C]+6445[Nb]-644 +890[Ti]+363[Al]-357[Si], T5=910-310[C]-80[Mn]-15[Cr], T4=910-203 -15.2[Ni]+44.7[Si]; In the controlled cooling process, the steel plate is air-cooled at a cooling rate of 1-10°C / s to a temperature between T6-30°C and T6-10°C, then water-cooled at a cooling rate of 8-30°C / s to a temperature between T7+50°C and T7+90°C, and then naturally cooled to room temperature to obtain a finished steel plate; T5 ≥ T6 ≥ T7, T7 = 539-423[C]-17.7[Ni]-12.1[Cr]-11[Si]-30.4[Mn], T6 = 830-270[C]-90[Mn]-37[Ni]-70[Cr].

2. The method for producing hot-rolled steel plates for bridges according to claim 1, characterized in that: The steel billet adopts a five-stage process in the heating furnace, including heat recovery section, preheating section, first heating section, heating section and soaking section. The temperature of the first heating section is 1120±15℃.

3. The method for producing hot-rolled steel plates for bridges according to claim 1, characterized in that: The residence time of the billet in the heating section is 0.07~0.13min / mm, and the total time in the heating furnace is 1.15~1.35min / mm.

4. The method for producing hot-rolled steel plates for bridges according to claim 1, characterized in that: When rolling to obtain the first intermediate plate, the reduction in each pass is ≥20mm; when rolling to obtain the second intermediate plate, the reduction in each pass is ≥12mm; when rolling the second intermediate plate to the finished product thickness, the reduction in each pass is ≥4mm.

5. The method for producing hot-rolled steel plates for bridges according to claim 1, characterized in that: The carbon equivalent CEV of the chemical composition of the steel plate satisfies 0.328-0.

371.

6. The method for producing hot-rolled steel plates for bridges according to claim 1, characterized in that: The yield strength of the steel plate is ≥390MPa, the tensile strength is ≥530MPa, the elongation is ≥28%, the yield strength ratio is ≤0.75, the impact energy KV2 at 0°C is ≥280J, the impact energy KV2 at -20°C is ≥260J, the impact energy KV2 at -40°C is ≥250J, and the steel plate unevenness is ≤1mm / m.

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