Preparation method of thin-gauge weather-proof bridge steel capable of improving low-temperature impact performance

Abstract

According to the preparation method of the thin-gauge weather-proof bridge steel capable of improving the low-temperature impact performance, through combined regulation and control of rolling and water cooling processes of the thin-gauge weather-proof bridge steel, the situation that granular bainite or lath bainite containing large-size MA components is easily formed in a steel plate due to addition of elements such as Cr, Ni and Cu of the weather-proof steel is avoided; and the steel plate is controlled to form a structure type of uniform and fine ferrite, poor pearlite and a small amount of granular bainite. The 10-16mm thin-gauge Q420-Q460-grade weather-resistant bridge steel produced by adopting the scheme can not be subjected to tempering heat treatment, the impact energy at-40 DEG C is more than or equal to 200J, the impact energy at-60 DEG C is more than or equal to 120J on the premise of ensuring that the strength of a steel plate meets the standard requirement, and the rolling-state low-temperature impact performance of the thin-gauge weather-resistant bridge steel is remarkably improved.

Description

Technical Field

[0001] The present invention belongs to the field of metal material production, and specifically relates to a method for preparing thin-gauge weather-resistant bridge steel with improved low-temperature impact performance. Background Art

[0002] With the rapid development of infrastructure construction such as roads and railways in my country, the technology of large-scale bridge construction has also been rapidly improved, and the production capacity of bridge steel plates used for bridge construction has also achieved a qualitative leap. Among them, weather-resistant bridge steel is used in more and more bridge structures due to its excellent properties such as high strength, high toughness and atmospheric corrosion resistance. However, due to the weather resistance requirements of weather-resistant bridge steel, special matching restrictions are required for Cr, Ni, Cu, Mo and other chemical components, resulting in the mechanical properties of high-strength weather-resistant bridge steel being more difficult to control compared with traditional low-alloy bridge steel, especially thin specifications often have unstable low-temperature impact properties, resulting in the need for steel plates to be delivered in a heat-treated state such as tempering, resulting in problems such as increased delivery time and increased costs.In view of this situation, the industry has also conducted a lot of research, such as publication number CN115961131A, a method for improving the impact energy of 10-14mm thick Q345qENH, which uses TMCP+650℃ offline high temperature tempering to improve the impact performance of thin weathering steel plates; publication number CN109112392A, TMCP type high strength and high fatigue weathering bridge steel plate and preparation method, which uses TMCP process to produce yield strength ≥500MPa, tensile strength ≥660MPa, -60℃ impact energy ≥220 J, -60℃ CTOD index ≥ 0.3mm high-toughness high-fatigue performance high-strength steel plate, but this scheme is mainly for 30-50mm thick weather-resistant bridge steel plate, the TMCP process used cannot be applied to thin steel plates ≤ 16mm; Publication No. CN111893402A, a kind of ultra-low temperature weather-resistant bridge steel and its production method, the scheme adopts TMCP rolling process to produce yield strength > 420MPa, -100℃ impact energy ≥ 120J weather-resistant bridge steel plate, the specific scheme involves relaxation process, the process is suitable for > 16 For the relatively thick specifications of mm or more, the relaxation process is very likely to form a large amount of proeutectoid ferrite before water cooling for thin-gauge steel plates, and the untransformed high-stability austenite is easy to form coarse granular structure in the subsequent cooling process, which is easy to cause the impact performance of the thin-gauge steel plate to be greatly reduced; Publication No. CN113699449A, a thin-gauge atmospheric corrosion-resistant bridge single-rolled easy-to-weld steel plate and its manufacturing method, on the one hand, the scheme adopts a low-carbon, low-manganese, high-Ni\Cr alloy design, which is significantly different from the current common weathering steel component system and is not comparable, on the other hand On the one hand, this scheme does not coordinate the finishing rolling temperature and the water entry temperature, and the finishing rolling temperature is 750-800 degrees Celsius, which is very likely to cause problems similar to those of scheme CN111893402A; Publication No. CN116005076A, a Nb-V-Ti composite micro-alloyed TMCP type bridge weathering steel and a manufacturing method thereof, the scheme adopts a rolling process combining austenite recrystallization zone rolling + austenite non-recrystallization zone rolling + (austenite + ferrite) dual-phase zone high temperature multi-pass small deformation rolling, and cooperates with a cooling process of cooling to Ms +30-50℃ range at 15-25℃ / s after rolling to obtain a fine-grained polygonal ferrite + lower bainite structure. This scheme can obtain higher tensile strength and lower yield strength ratio, but the rolling process is complicated and difficult to control, and the acquisition of lower bainite is easy to cause thin-gauge steel plate shape problems and reduced impact energy problems.

[0003] Therefore, from the above public information, in addition to the common TMCP+tempering process, the TMCP process has the problem that the final cooling temperature is low, the thin plate shape is difficult to control, and the impact energy is unstable due to bainite. At the same time, from the author's actual on-site batch production experience, the production of thin high-strength weather-resistant bridge steel plates using conventional TMCP or hot rolling processes does have many of the above problems, resulting in the need for offline tempering heat treatment to save the steel plates, resulting in increased delivery time and cost. Therefore, this scheme proposes a method for preparing thin weather-resistant bridge steel with improved low-temperature impact performance. Summary of the invention

[0004] The purpose of the present invention is to provide a method for preparing thin-gauge weather-resistant bridge steel with improved low-temperature impact performance, so as to solve the problems in the prior art.

[0005] The present invention is achieved through the following technical solutions: A method for preparing thin-gauge weather-resistant bridge steel with improved low-temperature impact performance, characterized in that the chemical composition of the thin-gauge weather-resistant bridge steel plate (Q420-Q460 grade) should be within the following range: C: 0.05-0.07%; Si: 0.20-0.30%; Mn: 1.25-1.40%; P≤0.020%; S≤0.004%; Als≥0.015%; Cr: 0.40-0.50%; Ni: 0.30-0.40%; Cu: 0.25-0.35%; Mo≤0.05%; Nb: 0.025-0.040; Ti: 0.008-0.018%, V≤0.04%, and Nb+V+Ti≤0.08%; the rest is Fe and unavoidable impurity elements.

[0006] The chemical composition of high-strength weather-resistant bridge steel produced by this rolling method is required to meet the above range mainly based on the following considerations: C: Carbon is the main strengthening element in steel. The GB / T 714 standard stipulates that the C content of weather-resistant bridge steel is ≤0.11%. In fact, for thin-gauge weather-resistant steel ≤16mm, a high carbon content is not conducive to low-temperature toughness, while a too low carbon content easily leads to insufficient yield strength. Therefore, the C content range applicable to this method is: 0.05-0.07%.

[0007] Si: Silicon has a weak deoxidation effect and a solid solution strengthening effect, but does not have the effect of improving low-temperature toughness and weather resistance. Therefore, it should not be added too much. The present invention limits Si to 0.20-0.30%.

[0008] Mn: Mn has the effect of stabilizing austenite and refining the structure after phase transformation in steel, and has a significant effect on improving low-temperature toughness. However, Mn is easy to segregate. Excessive addition can easily lead to an increase in banded structure, while a low addition will reduce the stability of austenite and easily form pre-precipitated ferrite during rolling, affecting the low-temperature toughness of weathering steel. Therefore, the present invention limits Mn to 1.25-1.40%.

[0009] P, S: Phosphorus and sulfur are harmful elements in steel. When production conditions permit, they should be removed from steel as much as possible. The appropriate content range is: P≤0.020%; S≤0.004%.

[0010] Cr, Ni, Cu, Mo: These elements are necessary alloying elements for weathering steel to achieve weathering resistance. Various standards have their lower limit requirements. In addition to meeting the weathering resistance requirements, these elements also have the effect of stabilizing austenite and improving low-temperature toughness. However, under the production conditions of thin-gauge steel plates described in this method, it is almost inevitable that ferrite will be first precipitated due to low carbon, low manganese and other conditions. Excessive addition of elements such as Cr, Ni, Cu, and Mo will easily increase the stability of untransformed austenite, and then form hard phase structures such as bainite in the subsequent phase transformation process, resulting in a decrease in the impact toughness of thin-gauge steel plates. Therefore, the excessive addition of these elements should be limited to a certain extent. Therefore, the suitable content range of the present invention is Cr: 0.40-0.50%; Ni: 0.30-0.40%; Cu: 0.25-0.35%; Mo≤0.05%.

[0011] Nb, V, Ti: Microalloying elements mainly improve the effect of controlled rolling and controlled cooling through precipitation strengthening. In particular, Nb can significantly increase the non-recrystallization temperature of steel, which makes it possible to roll at a relatively high temperature during the finishing rolling stage of this scheme; V has the effect of improving the strength of steel plates, and can be appropriately added according to the different strength requirements of steel plates, but excessive addition is easy to damage the yield strength ratio and low-temperature toughness. At the same time, the total amount of Nb+V+Ti is controlled, mainly considering that the steel plate specifications are thin and the temperature drops quickly. Even if a large amount is added, the precipitation strengthening effect will not increase year-on-year. On the contrary, more solid solution exists in the steel, which is not conducive to toughness and economic efficiency. Therefore, the suitable content range of this scheme is Nb: 0.025-0.040; Ti: 0.008-0.018%, V≤0.04%, but Nb+V+Ti≤0.08%.

[0012] The thin-gauge weather-resistant bridge steel plate with improved low-temperature impact performance is produced by processes including converter, LF+RH refining, continuous casting, heating, rolling, ACC, straightening, etc. The steel plate thickness is 10-16 mm, and the state is hot-rolled or TMCP. The preparation method of the thin-gauge weather-resistant bridge steel with improved low-temperature impact performance includes: 1) Use 250mm thick continuous casting billet, heating temperature of walking beam heating furnace is 1220℃~1240℃, furnace time is 285-375min. This part of the requirement is to ensure a sufficiently large total compression ratio, considering the high content of alloy elements such as Cr, Ni, Cu in steel, and adopt relatively low heating temperature and long heating time to avoid excessive growth of original austenite on the basis of fully homogenizing alloy elements in steel, in order to obtain a good low-temperature human nature typical foundation; after rough rolling and widening, the longitudinal rolling stage requires at least 3 passes with a single pass reduction rate of ≥18%, the intermediate billet thickness is 65-75mm, and the rough rolling final rolling temperature is ≥980℃. This part of the requirement is to repeatedly recrystallize and refine the austenite in the steel through repeated large reduction rolling in the high temperature stage. Low rough rolling temperature or insufficient pass reduction will weaken this effect, which is easy to cause fluctuations in low-temperature impact energy. At the same time, sufficient thickness is left after rough rolling to allow the cumulative reduction in the second stage to reach more than 4.5 times the thickness of the finished product, which strengthens the effect of the second stage cumulative strain of the steel and lays the foundation for obtaining a refined ferrite structure after phase transformation. 2) The second stage finishing rolling start temperature is ≤920℃, the finishing rolling passes are 6 or 8 passes, and the finishing rolling final temperature is controlled according to T+(70-100)℃. After rolling, the steel plate is quickly thrown into water, and the target water entry temperature is T±15℃, where T=935-330*(C+(Mn+Mo) / 3.5+Cu / 15+Cr / 23+Ni / 6)+0.85*t, t is the finished product thickness, and the value is substituted in mm. This part is one of the core features of the present invention. The temperature at which the steel plate starts the ferrite phase transformation is calculated by the empirical formula T. This empirical formula takes into account the influence of the main alloying elements on the phase transformation temperature and the influence of different steel plate thicknesses on the temperature drop. By controlling the water entry temperature of the steel plate within the range of T±15℃, the steel plate will not precipitate or precipitate a small amount of proeutectoid ferrite in the high temperature stage before entering the water. This can avoid the precipitation of a large amount of proeutectoid ferrite before the thin gauge steel plate enters the water, and the remaining untransformed austenite will be directly transformed into a large block of MA structure or lath bainite during the subsequent phase transformation due to the enrichment of alloy elements, which will greatly reduce the low temperature impact toughness of the steel plate. The final rolling temperature of the steel plate is set to T+(70-100)℃ according to the target water entry temperature and the temperature loss of the steel plate after finishing rolling to before entering the water. The start rolling temperature of finishing rolling is ≤930℃, and the finishing rolling is completed in 6 or 8 passes. In fact, in order to ensure the water entry temperature of the steel plate, the overall finishing rolling process temperature has been greatly improved compared with the conventional TMCP process. This improvement is theoretically unfavorable to the toughness of the steel plate, but by controlling the steel plate starting rolling temperature ≤ 930 ° C, finishing rolling is completed in 6 or 8 passes, and the finishing cumulative compression ratio is ≥ 4.5 times the finished product thickness, so that a large cumulative strain is completed in the high temperature range of the non-recrystallization zone, which can also lay the foundation for the subsequent uniform and fine ferrite nucleation. Of course, within the temperature range of this scheme, the lower the finishing rolling temperature is controlled, the more favorable it is to toughness; 3) The ACC mode is adopted in the controlled cooling stage, and the water group adopts the front-end continuous opening mode. According to the thickness of the steel plate, 4-8 groups are opened respectively, and the average cooling rate is controlled to be 12-18℃ / s, and the average red-return temperature of the steel plate is 650~680℃. Water cooling is another control core of this scheme. The water group adopts the front-end continuous opening mode with the water inlet temperature of T±15℃, which can avoid the continuous nucleation of pro-eutectoid ferrite during the cooling process, and ensure that the steel plate still maintains the original austenite or the original austenite + a small amount of pro-eutectoid ferrite in the water cooling process. The average cooling rate is controlled at 12-18℃ / s. If the cooling rate is too small, the steel plate is not undercooled enough, the size of the subsequent phase deformation nucleus ferrite will increase, and the pearlite content will increase, which is not conducive to the improvement of toughness; if the cooling rate is too large, the shape of the steel plate is difficult to control and it is easy to increase the bainite content and the yield strength ratio of the steel plate. By opening 4-8 water groups for steel plates of different thicknesses, the average red-return temperature of the steel plates is controlled at 650~680℃, so that the steel plates can obtain a uniform and fine ferrite + poor pearlite + a small amount of granular bainite structure type, wherein the MA component in the small amount of granular bainite is different from the aforementioned large block of MA structure, which is finer and more evenly distributed, has less damage to toughness and can improve the tensile strength of the steel plate to a certain extent. If the red-return temperature is higher, the steel plate structure will be mainly coarser ferrite + pearlite, and the strength and toughness of the steel plate will be reduced. If the red-return temperature is lower, the proportion of bainite will increase, resulting in an increase in the yield strength ratio and a decrease in low-temperature toughness.

[0013] Furthermore, the present invention is applicable to steel plates with a thickness of 10-16 mm, a steel plate yield strength ≥ 460 MPa, a tensile strength ≥ 570 MPa, a yield strength ratio ≤ 0.85, an impact energy of ≥ 200 J at -40°C, and an impact energy of ≥ 120 J at -60°C. Compared with the prior art, firstly, the tempering process is eliminated for thin-gauge high-strength weather-resistant bridge steel plates, which reduces the production cycle and cost of the steel plates. At the same time, the TMCP process production solution does not have the problems of difficult control of thin-gauge plate shape due to low final cooling temperature, and unstable impact energy caused by bainite. It can meet the stable production needs of thin-gauge weather-resistant bridge steel.

[0014] The advantages of the present invention are: the thickness of the steel plate of the present invention is 10-16mm, the yield strength of the steel plate is ≥460MPa, the tensile strength is ≥570 MPa, the yield strength ratio is ≤0.85, the impact energy at -40℃ is ≥200J, and the impact energy at -60℃ is ≥120J. Compared with the prior art, firstly, the tempering process is eliminated for thin-gauge high-strength weather-resistant bridge steel plates, which reduces the production cycle and cost of the steel plates. At the same time, the TMCP process production scheme does not have the problems of the thin-gauge plate shape being difficult to control due to the low final cooling temperature, and the impact energy being unstable due to bainite. It can meet the stable production needs of thin-gauge weather-resistant bridge steel. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1This is the metallographic structure of the steel plate of Example 4 (1 / 4 thickness position).

[0016] Figure 2 This is the metallographic structure of the steel plate of Comparative Example 2 (1 / 4 thickness position).

[0017] Figure 3 Tables 1 to 4. DETAILED DESCRIPTION

[0018] The invention discloses a method for preparing a thin-gauge weather-resistant bridge steel with improved low-temperature impact performance. The steel plate comprises the following components in percentage by mass: C: 0.05-0.07%; Si: 0.20-0.40%; Mn: 1.25-1.40%; P≤0.020%; S≤0.004%; Als≥0.015%; Cr: 0.40-0.50%; Ni: 0.30-0.40%; Cu: 0.25-0.35%; Mo≤0.05%; Nb: 0.025-0.040; Ti: 0.008-0.018%, V≤0.04%, and Nb+V+Ti≤0.08%; the rest are Fe and unavoidable impurity elements; The method for preparing the thin weather-resistant bridge steel plate comprises the steps of converter, LF+RH refining, continuous casting production, heating, rolling, ACC, straightening, etc., wherein: 1) Use 250mm thick continuous casting billet, heating temperature of walking beam heating furnace is 1220℃~1240℃, furnace time is 285-375min, and the longitudinal rolling stage after rough rolling and widening requires at least 3 passes with a single pass reduction rate of ≥18%, intermediate billet thickness is 65-75mm, and rough rolling final rolling temperature is ≥980℃; 2) The second stage finishing rolling start temperature is ≤930℃, the finishing rolling passes are 6 or 8, and the finishing rolling final rolling temperature is controlled according to T+(70-100)℃. After rolling, the steel plate is quickly thrown into water, and the target water entry temperature is T±15℃, where T=935-330*(C+(Mn+Mo) / 3.5+Cu / 15+Cr / 23+Ni / 6)+0.85*t, t is the finished product thickness in millimeters; 3) The ACC mode is adopted in the cooling control stage, and the water groups are opened in sequence in sequence at the front end, with 4-8 groups opened, the average cooling rate is controlled at 12-18℃ / s, and the average red-return temperature of the steel plate is 650~680℃.

[0019] Preferably, the finishing rolling temperature is controlled at T+(70-100)°C.

[0020] Preferably, the steel plate obtains a microstructure of uniform and fine ferrite + poor pearlite + a small amount of granular bainite.

[0021] Preferably: the thickness of the steel plate is 10-16 mm, the yield strength of the steel plate is ≥460 MPa, the tensile strength is ≥570 MPa, the yield strength ratio is ≤0.85, the impact energy at -40°C is ≥200 J, and the impact energy at -60°C is ≥120 J.

[0022] Preferably, the steel plate is in the hot-rolled or TMCP state.

[0023] The present invention is further described below by way of examples.

[0024] Examples 1-4: Four different specifications of Q420qENH and Q460qENH bridge steels were prepared according to the above method. The specific specifications, composition and comparative information are shown in Table 1. As can be seen from the table, the chemical composition of the steel plates in the examples is designed with low carbon and low manganese, and the addition of alloys such as Ni, Cr, Cu, and Mo meets the requirements for the addition of main weathering alloy elements in weathering steel. The main difference between Q420 and Q460 is the small addition of Mo and V elements. The comparative examples use chemical compositions similar to those in the examples.

[0025] The steel plate is rolled in a 5m wide and thick plate production line, and the specific rolling process information is shown in Appendix 2. As can be seen from the table, Examples 1-4 all adopt the rolling method of this scheme, wherein 250mm thick continuous casting billets are used, the actual heating temperature is 1228-1235℃, the steel plate is heated in the heating furnace for 305-365min, the rough rolling and final rolling temperature is as low as 998℃, the last three rough rolling reductions are as low as 18.8%, the finishing rolling start temperature is 921-899℃, and the finishing rolling finish temperature is 848-861℃. Comparative Examples 1-2 adopt the conventional TMCP process for rolling, and compared with the examples, there are significant differences in billet thickness, furnace time, finishing rolling start temperature, and finishing rolling finish temperature.

[0026] After the steel plates were rolled, a rapid water entry strategy was adopted, and the water cooling information of the steel plates is shown in Table 3. From the water cooling information, it can be seen that the average water entry temperature of Examples 1-4 is controlled between 752-781°C, and the final cooling temperature is 658-672°C, while the water entry temperature of Comparative Examples 1-2 is lower than 730°C, the final cooling temperature of Comparative Example 1 is basically the same as that of the embodiment, and the final cooling temperature of Comparative Example 2 is significantly lower than that of the embodiment.

[0027] The mechanical properties of the steel plate are shown in Table 4. As can be seen from the table, the actual yield strength of Examples 1-4 is 480-502MPa, the tensile strength is 594-607MPa, the elongation is ≥21.8%, and the yield strength ratio is ≤0.83. The strength level of the steel plate meets the requirements of the Q460 grade standard. In terms of low-temperature toughness, the actual value of the impact energy at -40°C is ≥200J, and the actual value of the impact energy at -60°C is ≥120J, which fully meets the mechanical property requirements of high-strength weather-resistant bridge steel; the actual yield strength of Comparative Examples 1-2 is significantly lower, while the tensile strength is higher, resulting in a lower yield strength than the Examples, but the low-temperature impact of the steel plate is significantly reduced, and the mechanical property requirements of the corresponding steel grade are no longer met.

[0028] As can be seen from the attached figure, Figure 1 This is the metallographic structure of the steel plate (16 mm) of Example 4 (1 / 4 of the thickness). As can be seen from the figure, the structure is mainly composed of fine ferrite + poor pearlite + a small amount of granular bainite.

[0029] Figure 2 This is the metallographic structure of the steel plate (16 mm) of comparative example 2 (1 / 4 thickness position). As can be seen from the figure, the structure is proeutectoid ferrite (some ferrite grains are relatively coarse) + large-sized granular bainite + a small amount of lath bainite.

[0030] From the processing results of the embodiment, the thickness of the steel plate of the present invention is 10-16mm, the yield strength of the steel plate is ≥460MPa, the tensile strength is ≥570 MPa, the yield strength ratio is ≤0.85, the impact energy at -40℃ is ≥200J, and the impact energy at -60℃ is ≥120J. Compared with the prior art, firstly, the tempering process is cancelled for thin-gauge high-strength weather-resistant bridge steel plates, which reduces the production cycle and cost of the steel plates. At the same time, the TMCP process production scheme does not have the problems of difficult control of thin-gauge plate shape due to low final cooling temperature and unstable impact energy caused by bainite. It can meet the stable production needs of thin-gauge weather-resistant bridge steel.

Claims

1. A method for preparing thin-gauge weather-resistant bridge steel with improved low-temperature impact performance, characterized in that: The thin-gauge weather-resistant bridge steel comprises the following components in percentage by mass: C: 0.05-0.07%; Si: 0.20-0.40%; Mn: 1.25-1.40%; P≤0.020%; S≤0.004%; Als≥0.015%; Cr: 0.40-0.50%; Ni: 0.30-0.40%; Cu: 0.25-0.35%; Mo≤0.05%; Nb: 0.025-0.040; Ti: 0.008-0.018%, V≤0.04%, and Nb+V+Ti≤0.08%; the rest are Fe and unavoidable impurity elements; The method for preparing thin-gauge weather-resistant bridge steel with improved low-temperature impact performance comprises the steps of converter, LF+RH refining, continuous casting production, heating, rolling, ACC, and straightening, wherein: 1) Use 250mm thick continuous casting billet, heating temperature of walking beam heating furnace is 1220℃~1240℃, furnace time is 285-375min, and the longitudinal rolling stage after rough rolling and widening requires at least 3 passes with a single pass reduction rate of ≥18%, intermediate billet thickness is 65-75mm, and rough rolling final rolling temperature is ≥980℃; 2) The second stage finishing rolling start temperature is ≤930℃, the finishing rolling passes are 6 or 8, and the finishing rolling final temperature is controlled according to T+(70-100)℃. After rolling, the steel plate is quickly thrown into water, and the target water entry temperature is T±15℃, where T=935-330*(C+(Mn+Mo) / 3.5+Cu / 15+Cr / 23+Ni / 6)+0.85*t, t is the finished product thickness in millimeters; 3) The ACC mode is adopted in the cooling control stage, and the water groups are opened in sequence in sequence at the front end, with 4-8 groups opened, the average cooling rate is controlled at 12-18℃ / s, and the average red-return temperature of the steel plate is 650~680℃.

2. The method for preparing thin-gauge weather-resistant bridge steel with improved low-temperature impact performance according to claim 1, characterized in that: The final rolling temperature is T+(70-100)℃.

3. The method for preparing thin-gauge weather-resistant bridge steel with improved low-temperature impact performance according to claim 1, characterized in that: The steel plate obtains a uniform and fine ferrite + poor pearlite + a small amount of granular bainite structure.

4. The method for preparing thin-gauge weather-resistant bridge steel with improved low-temperature impact performance according to claim 1, characterized in that: The thickness of the steel plate is 10-16mm, the yield strength of the steel plate is ≥460MPa, the tensile strength is ≥570MPa, the yield strength ratio is ≤0.85, the impact energy at -40℃ is ≥200J, and the impact energy at -60℃ is ≥120J.

5. The method for preparing thin-gauge weather-resistant bridge steel with improved low-temperature impact performance according to claim 1, characterized in that: The steel plate state is hot rolled or TMCP.

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