E-grade weathering steel that can withstand 100kJ / cm high heat input welding and has a yield strength of no less than 370MPa

Abstract

The invention discloses an E-grade weathering steel which can withstand 100 kJ / cm high heat input welding and has a yield strength of not less than 370 MPa. The chemical composition is as follows by mass percentage: C 0.038-0.058, Si 0.20-0.35, Mn 1.00-1.10, P≤0.0015, S≤0.0005, Cu 0.25-0.45, Cr 0.30-0.50, Ni 0.25-0.40, Mo≤0.03, Nb≤0.014, V 0.010-0.025, Ti 0.005-0.012, B 0.0004-0.0008, Alt 0.015-0.034, Zr 0.010-0.025, Ce 0.004-0.009, La 0.004-0.006, N 0.0040-0.0080, O 0.0020-0.0030, and the rest are iron and unavoidable impurities. The E-grade weathering steel of the present invention has a welding heat-affected zone with a Charpy impact energy of not less than 47 J at 40°C when the welding heat input is 100 kJ / cm; the steel plate weathering index I is ≥6.5, and can be used for the production and manufacture of large steel structures such as ships, bridges, and buildings.

Description

Technical Field

[0001] The invention belongs to the technical field of weathering steel, and in particular relates to an E-grade weathering steel which can withstand 100 kJ / cm high heat input welding and has a yield strength of not less than 370 MPa. Background Art

[0002] With the continuous progress of my country's economic construction, the coordinated development between the eastern and western regions has become an important feature of the times. In order to strengthen communication and coordination between the two regions, the most urgent task at present is to gradually accelerate the construction of infrastructure between the two, including railways, bridges, etc. Due to the harsh environment in most western regions, higher requirements are placed on the performance of large steel structures. At present, using weathering steel as the main body of large-span bridges has become the mainstream design scheme, but because of the complex component system of weathering steel, its performance advantages are not reflected during high heat input welding, and the low-temperature impact performance of the welded joints does not meet the standards. Therefore, the E-grade weathering steel plate designed for high heat input welding, which takes into account both production and use performance, has become a technical problem that needs to be solved urgently.

[0003] In order to reduce the cost of manual maintenance and alleviate the environmental impact of high cold, hypoxia and strong ultraviolet rays in the western plateau area of ​​my country, researchers have conducted extensive exploration on the composition and performance of weathering steel. The relevant patent results are as follows:

[0004] Patent publication number "CN109097686A" discloses a weathering steel Q345qDNH steel strip for bridges and its production method. The advantage of this method is that on the basis of ordinary weathering steel, an appropriate amount of Cu, P, Cr, and Ni alloy elements that can improve corrosion resistance are added to the steel, so that a protective layer with a thickness of 10-13μm is formed on the surface of the weathering steel to inhibit the further development of corrosion behavior. However, this weathering steel belongs to D-grade steel, and it is impossible to determine whether the finished steel meets the E-grade steel standard. In addition, the patent lacks a description of welding performance, and further exploration is needed on the relationship between the two basic properties of weathering steel weather resistance and weldability.

[0005] Authorization announcement number "CN103451561B" discloses a weathering steel that can be welded with large heat input and its production method. The advantage of this method is that the heat input of the weathering steel plate produced can be increased from the current 50kJ / cm to 200-600kJ / cm, and the welding task of 40mm thick steel plate can be achieved by single pass of gas-electric vertical welding or single pass of multi-wire submerged arc welding, and the welding efficiency is increased by more than 5 times. However, the steel plate only tested the -20℃ impact performance of the welded joint, and did not list the -40℃ impact work of the steel plate welded joint, so the -40℃ low-temperature impact toughness needs to be tested.

[0006] Authorization announcement number "CN103451537B" discloses a low-temperature weathering steel plate with high welding performance and its production method. The advantage of this method is that by strictly controlling the content of the two main weathering elements Cu and P, and adding a large amount of Ni and trace amounts of Mo, W, and Sn to the steel, the weathering steel plate has excellent corrosion resistance while obtaining good weldability; using Ti-Zr composite deoxidation, more small and dense non-metallic inclusions appear in the steel, which inhibits the abnormal growth of grains in the welding heat affected zone, promotes the nucleation of intragranular ferrite, and improves the impact toughness of the welded joint. However, the Re element is not added to the steel plate, and more experiments are needed to study the effect of Re on the weathering performance of weathering steel.

[0007] Patent publication number "CN110923572A" discloses a rare earth weathering steel rich in alloyed rare earth elements and its manufacturing method. The advantage of this method is that it reduces the content of Cu, Cr, and Ni elements on the basis of the national standard GB / T4171-2008, and adds trace rare earth elements La, Ce, Y, etc., which improves the mechanical properties without reducing the corrosion resistance of the steel plate. However, the content of P element in this patent is relatively high. Although it improves the corrosion resistance of the steel plate, it may have a certain negative impact on the welding performance of weathering steel. In order to clarify the influence of P / Re elements on weathering steel, it is necessary to separately study the contribution of P and Re elements in weathering steel to weather resistance and weldability.

[0008] For the current weathering steel plates for high heat input welding, the most important thing is the design of the alloy composition system, especially taking into account the influence of complex environmental factors in the western region. The production of weathering steel must take into account all aspects, and its mechanical properties, corrosion resistance and welding performance must meet certain requirements. Summary of the invention

[0009] The problem to be solved by the present invention is to provide an E-grade steel plate which can withstand 100kJ / cm high heat input welding and has a yield strength of not less than 370MPa, and the tensile strength of the base material of the steel plate is ≥510Mpa. When the welding heat input is 100kJ / cm, the -40℃ Charpy impact energy of the welding heat affected zone is not less than 47J; the steel plate weathering index I is ≥6.5. The high-heat input welding steel can be used for the production and manufacture of large steel structures such as ships, bridges, and buildings.

[0010] In order to solve the above technical problems, the technical solution adopted by the present invention is: an E-grade weathering steel that can withstand 100kJ / cm high heat input welding and has a yield strength of not less than 370MPa, and the chemical composition of the E-grade weathering steel is as follows by mass percentage: C 0.038~0.058, Si 0.20~0.35, Mn 1.00~1.10, P≤0.0015, S≤0.0005, Cu 0.25~0.45, Cr0.30~0.50, Ni 0.25~0.40, Mo≤0.03, Nb ≤0.014, V 0.010~0.025, Ti 0.005~0.012, B 0.0004~0.0008, Alt 0.015~0.034, Zr0.010~0.025, Ce 0.004~0.009, La 0.004~0.006, N 0.0040~0.0080, O 0.0020~0.0030, the rest are iron and inevitable impurities, the chemical compositions of Ti, V, B, C and N satisfy 0.057≤5.48Ti+2.64V+0.03B+0.08C+0.06N≤0.137.

[0011] Furthermore, among the particles with a size of 20-80 nm in the welding heat affected zone of the E-grade weathering steel that can inhibit the growth of austenite grains, the number of (V, Ti, B)(C, N) composite precipitated particles accounts for 45-55%.

[0012] Furthermore, among the particles with a size of 0.5-1.5 μm that have heterogeneous nucleation in the welding heat affected zone of the E-grade weathering steel, the number of composite precipitated particles of (V, Ti, B)(C, N) accounts for 43-56%.

[0013] Furthermore, the tensile properties of the E-grade weathering steel are ReL≥370MPa, Rm≥510MPa, and the steel plate weathering index I≥6.5.

[0014] Furthermore, the -40°C KV2 low-temperature impact energy of the welding heat-affected zone of the E-grade weathering steel is not less than 47J.

[0015] Furthermore, the E-grade weathering steel is produced by a controlled rolling and controlled cooling process, and the specific process parameters are as follows: the heating temperature is 1160-1280°C, the rolling temperature in the recrystallization zone is between 1050-1150°C, the rolling temperature in the non-recrystallization zone is between 760-820°C, and the steel is cooled to between 480-620°C at a cooling rate of 10-15°C / s, then discharged from water and air-cooled to room temperature.

[0016] The role of each element in the steel and the corresponding composition design are as follows:

[0017] C: C is a necessary alloying element in steel. Too high a content will increase the sensitivity of welding cracks, cause carbides to appear in the steel, and reduce the corrosion resistance of the steel. This element contributes significantly to strength, but the strength requirement in this patent is not high, so the C content is controlled at 0.038~0.058%.

[0018] Si: Si is a deoxidizing element and also a strengthening element. When Si < 0.05%, the deoxidizing effect is poor, and the steel plate surface is prone to pitting and red rust; but when Si > 0.35%, the structure becomes coarser, the MA component increases, and the sensitivity of welding cold and hot cracks increases. In the present invention, Si is controlled at 0.20-0.35%.

[0019] Mn: The atomic radius of Mn is similar to that of Fe, and substitution solid solution is easily formed between the two. It is a common element for improving the strength of steel plates. When the Mn content is too high, the MA content in the steel increases, and the toughness of the welding heat affected zone deteriorates. Therefore, in the present invention, Mn is controlled to be 1.00-1.10%.

[0020] P: P is often considered as an impurity element, which will increase the low-temperature brittleness of steel plates, especially during welding, and will increase the sensitivity of welding cold cracks. However, steel containing P has excellent corrosion resistance, so P often appears in weathering steel. However, in this patent, weather resistance is mainly provided by Cu and Re elements, so the P addition amount is ≤0.0015%.

[0021] S: S is an impurity element, which is easy to form sulfide inclusions with low melting point in steel, which is the main reason for hot brittleness and seriously affects the low-temperature toughness of steel. The appearance of irregular inclusions also destroys the continuity of the organization and is not conducive to weather resistance. Therefore, the S content shall not exceed 0.0005%.

[0022] Cu: Cu is a common alloying element in weathering steel and contributes greatly to corrosion resistance. Electrochemical experiments show that the rust layer formed by Cu-containing weathering steel is denser and can effectively slow down the electrochemical corrosion process. At the same time, an appropriate amount of Cu will promote the nucleation of acicular ferrite, but when the Cu content is too high, hot cracks will occur during rolling, which is not conducive to welding performance. Therefore, the Cu content is controlled at 0.25~0.45%.

[0023] Cr: Cr contributes to the corrosion resistance of the steel plate to a certain extent, but it should not be too much, otherwise it will affect the low-temperature toughness of the welding heat affected zone. Therefore, in the present invention, the Cr content is controlled to be 0.30-0.50%.

[0024] Ni: Ni has a significant effect on improving toughness; when added in combination with Cu and Cr, it significantly enhances corrosion resistance. However, Ni is a precious metal and should not be added in excess. Therefore, the Ni content in the present invention is controlled to be 0.25-0.40%.

[0025] Mo: A proper amount of Mo can form a dense rust layer on the surface of the steel plate, reducing the corrosion rate; at the same time, it can refine the grains in the heat-affected zone of welding and improve the toughness of the welded joint. However, if Mo is added too much, it will seriously reduce the toughness of the welded joint and increase the production cost, so Mo in steel is ≤0.03%.

[0026] Nb: Nb has a very significant grain refinement and precipitation strengthening effect on controlled rolling and controlled cooling steel, thereby improving the toughness of the base material. However, too much Nb will increase the production cost and is not conducive to the control of weldability. Therefore, the Nb content in the present invention is ≤0.014%.

[0027] V: V has a strong precipitation strengthening effect and has a significant effect on improving strength. It is easy to combine with C and N in steel to form V (C, N). This particle can serve as a nucleation core to promote the formation of intracrystalline ferrite, thereby improving the structure and improving low-temperature impact toughness. Therefore, the V content in the present invention is controlled to be 0.010-0.025%.

[0028] Ti: Ti is the main alloying element in steel for high heat input welding. Ti combines with N to form TiN, which prevents the growth of austenite grains and can effectively improve the toughness of the heat-affected zone. The addition of Ti can also reduce the solid solubility of N and improve the aging properties of steel. When Ti<0.008%, the number of beneficial nitrides formed is small, and the effect of inhibiting grain growth is weak; when Ti>0.025%, the amount of solid-dissolved Ti in the steel is too much, and the remaining Ti exists in the crystal in the form of solid solution, which increases the MA component and reduces the mechanical properties of the heat-affected zone. In the present invention, the Ti content is controlled at 0.005~0.012%.

[0029] Zr: The oxide formed by Zr during welding can serve as the nucleation core of intracrystalline acicular ferrite, forming a large number of acicular structures at the weld joint, thereby improving the low-temperature toughness of the weld joint. At the same time, an appropriate amount of Zr can also improve the corrosion resistance of the steel plate, but too high a content will increase the cold brittleness of the weld joint and reduce the welding performance. Therefore, in the present invention, Zr is controlled to 0.010~0.025%.

[0030] B: B is a characteristic element of the present invention, which allows solid solution B and BN to exist simultaneously in both the base material and the high-heat input welding HAZ, and embodies the effects of segregation and nucleation. BN precipitated in austenite acts as a phase transformation nucleus, improving the toughness by refining the structure of the HAZ, reducing the hardness, and reducing the MA content. On the other hand, if the amount of B contained exceeds 0.002%, coarse B precipitates will be produced, and the toughness of the HAZ will deteriorate. In order to improve the toughness of the HAZ, the B content is controlled to 0.0004~0.0008% in the present invention.

[0031] Al: Al is a major deoxidizer and has a significant deoxidizing effect during the steelmaking process; however, too much Al will take away N in the steel and affect the formation of precipitates, so the Al content in the present invention is controlled at 0.015-0.034%.

[0032] Ce / La: The role of Ce / La in steel is mainly to assist the formation of precipitated particles and promote the solid solution of microalloying elements in steel. It refines the size of precipitated particles and makes their distribution more uniform and dispersed, improving the heterogeneous nucleation ability of precipitated particles. At the same time, rare earth elements can also provide certain corrosion resistance, but too much Ce / La will form a large number of inclusions in the steel, deteriorating the low-temperature impact performance, so the Ce content is controlled at 0.004~0.009%, and the La content is controlled at 0.004~0.006%.

[0033] N: N is another important element in the present invention. N exists in two ways, one is solid solution, which is not good for the performance of the base material, and the other is to form dispersed fine-particle nitrides, which improves the toughness of the heat-affected zone of welding. Too high N content will lead to an increase in solid solution N, deterioration of the toughness and aging properties of the base material, and easy cracking of the continuous casting billet. In the present invention, the N content is 0.0040~0.0080%.

[0034] O: O is a common alloying element in steel. It will not have a significant adverse effect on the performance of steel plates. However, excessive O is easy to combine with Al to form Al2O3 inclusions whose shape and size are difficult to control. These inclusions are common crack sources and are detrimental to the low-temperature toughness of welded joints. Therefore, the O content is controlled at 0.0020~0.0030%.

[0035] The E-grade weathering steel of the present invention has particles with a size of 20-80 nm that can inhibit the growth of austenite grains in the welding heat affected zone, and another type of particles with a size of 0.5-1.5 μm that can heterogeneously nucleate. When the chemical composition of the weathering steel satisfies the relationship of 0.057≤5.48Ti+2.64V+0.03B+0.08C+0.06N≤0.137 and the particles with a size of 20-80 nm that can inhibit the growth of austenite grains in the welding heat affected zone and the particles with a size of 0.5-1.5 μm that can promote heterogeneous nucleation of AF meet the corresponding ratio, the growth of austenite grains can be effectively inhibited during high heat input welding, and a large amount of heterogeneously nucleated acicular ferrite is generated inside the grains, the organization is refined, the toughness is improved, and a certain strength is maintained. In the welding heat affected zone of the weathering steel of the present invention, among the particles with a size of 20-80 nm that can inhibit the growth of austenite grains, the number of (V, Ti, B)(C, N) composite precipitated particles accounts for 45-55%; among the particles with a size of 0.5-1.5 μm with heterogeneous nucleation in the welding heat affected zone, the number of (V, Ti, B)(C, N) composite precipitated particles accounts for 43-56%.

[0036] According to the calculation formula of steel plate weathering index I, it is required to calculate the five main weathering alloy elements of Cu, Ni, Cr, Si and P according to "I=26.01(%Cu)+3.88(%Ni)+1.20(%Cr)+1.49(%Si)+17.28(%P)-7.29(%Cu)(%Ni)-9.10(%Ni)(%P)-33.39(%Cu) 2 The lower limit of the weathering resistance index is controlled within the range of I≥6.5 to ensure that the corrosion thinning of the steel of the present invention does not exceed 1 mm in a hundred-year life cycle under typical atmospheric conditions of mild climate. Too low I value leads to insufficient weathering resistance, while too high I value impairs the comprehensive performance and increases the cost.

[0037] The beneficial effects of the present invention are:

[0038] (1) By optimizing the alloying element ratio, the particles with a size of 20-80 nm that can inhibit the growth of austenite grains are dissolved during the welding thermal cycle, but the overall number is still sufficient to inhibit the growth of austenite grains and control the austenite grain size in the heat-affected zone;

[0039] (2) By optimizing the alloying element ratio, a large number of particles with a size of 0.5-1.5 μm that can promote the heterogeneous nucleation of AF are present. Such particles can promote the nucleation of intragranular acicular ferrite and optimize the microstructure and toughness of the heat affected zone of welding;

[0040] (3) By optimizing the ratio of alloying elements, the two types of second phase particles are made to form a bimodal size distribution state, giving full play to the characteristics of the two types of particles in the solid phase reaction to regulate the high heat input welding performance of the steel, avoiding the complicated liquid phase reaction control, and enabling stable mass production;

[0041] (4) The E-grade steel plate described in the present invention can withstand 100 kJ / cm high heat input welding and has a yield strength of not less than 370 MPa, wherein the yield strength ReL ≥ 370 MPa, the tensile strength Rm ≥ 510 MPa, the steel plate weathering index I ≥ 6.5, and when welding with 100 kJ / cm high heat input, the low-temperature impact energy of the welding heat affected zone at -40°C KV2 is not less than 47 J.

[0042] The present invention is described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 This is a microstructure diagram of the parent material of steel embodiment 1 of the present invention;

[0044] Figure 2 This is a microstructure diagram of the parent material of steel Example 4 of the present invention;

[0045] Figure 3The microstructure of the heat affected zone of the steel example 1 of the present invention at a welding heat input of 100 KJ / cm;

[0046] Figure 4 This is the microstructure of the heat affected zone of steel Example 4 of the present invention at a welding heat input of 100 KJ / cm. DETAILED DESCRIPTION

[0047] The invention provides an E-grade weathering steel which can withstand 100 kJ / cm high heat input welding and has a yield strength of not less than 370 MPa. The chemical composition of E grade weathering steel is calculated by mass percentage: C 0.038~0.058, Si 0.20~0.35, Mn1.00~1.10, P≤0.0015, S≤0.0005, Cu 0.25~0.45, Cr0.30~0.50, Ni 0.25~0.40, Mo≤0.03, Nb ≤0.014, V 0.010~0.025, Ti 0.005~0.012, B 0.0004~0.0008, Alt 0.015~0.034, Zr0.010~0.025, Ce 0.004~0.009, La 0.004~0.006, N 0.0040~0.0080, O 0.0020~0.0030, the rest is iron and inevitable impurities. Among them, the chemical composition of Ti, V, B, C and N satisfies 0.057≤5.48Ti+2.64V+0.03B+0.08C+0.06N≤0.137.

[0048] The chemical compositions, elemental relationships, and the proportions of the two types of precipitated particles of Examples 1 to 5 and Comparative Examples 1, 2, and 3 are shown in Table 1.

[0049] Table 1 Chemical composition of weathering steel ingot (wt%)

[0050] .

[0051] In order to ensure the corrosion resistance of the steel plate, the steel plate produced according to the present invention needs to detect the contents of the five main weathering alloy elements of Cu, Ni, Cr, Si and P (in mass percentage by wt%), and then according to the formula I*= 26.01Cu +3.88Ni+1.20Cr +1.49Si +17.28P -7.29Cu·Ni -9.10Ni·P -33.39Cu 2 The weathering index I is calculated and its value shall not be less than 6.5 to ensure that the corrosion thinning of the steel plate produced according to the present invention does not exceed 1 mm during the 100-year life cycle under typical atmospheric conditions of mild climate.

[0052] The E-grade weathering steel plate of the present invention has main alloy components including Ti, V, B, C, N, etc. The relationship Eq=5.48Ti+2.64V+0.03B+0.08C+0.06N determined by these main alloy elements must have a value within the range of 0.057~0.137.

[0053] The actual process parameters of Examples 1 to 5 and Comparative Examples 1, 2, and 3 during the rolling process are shown in Table 2.

[0054] Table 2 Process parameters of weathering steel plate rolling process

[0055] .

[0056] The tensile property test results and -40°C Charpy impact test results of the steel plate base materials of Examples 1 to 5 and Comparative Examples 1, 2, and 3 are shown in Table 3.

[0057] Table 3 Mechanical properties of steel plate base material

[0058] .

[0059] The results of the -40°C Charpy impact tests on the heat affected zones of the steel plates of Examples 1 to 5 and Comparative Examples 1, 2, and 3 are shown in Table 4.

[0060] Table 4 Mechanical properties of heat affected zone of steel plate welding

[0061] .

[0062] Using a vacuum furnace, the test steels of various chemical compositions listed in Table 1 were melted in a laboratory manner, cast into 75kg steel ingots, and then hot-rolled into 60mm thick slabs. Then the slabs were loaded into a heating furnace, the heating temperature was controlled to be 1160-1280℃, the rolling temperature of the recrystallization zone was between 1050-1150℃, and the rolling temperature of the non-recrystallization zone was between 760-820℃. The slabs were cooled to between 480-620℃ at a cooling rate of 10-15℃ / s, then discharged from the water and air-cooled to room temperature. The final steel plate thickness was 24mm. Figure 1 and 2 The metallographic structures of the parent materials of Examples 1 and 4 of the present invention are all composed of granular bainite, acicular ferrite and blocky ferrite, which ensures that the weathering steel parent material has good comprehensive properties of strength, toughness and low yield ratio.

[0063] The steel plate produced by the present invention is subjected to 100 kJ / cm high heat input welding, and there are two types of precipitated particles in the welding heat affected zone: particles with a size of 20-80 nm that can inhibit the growth of austenite grains and particles with a size of 0.5-1.5 μm that can promote AF heterogeneous nucleation. When the two meet the corresponding ratio, the growth of austenite grains can be effectively inhibited during high heat input welding, and a large amount of heterogeneous nucleation needle-shaped ferrite can be generated inside the grains, which can refine the structure, improve toughness, and maintain a certain strength. Figure 3 and 4 , which are the microstructures of the coarse-grained heat-affected zone after 100 kJ / cm high heat input welding. They contain a large amount of heterogeneous nucleation ferrite, and under the high heat input welding conditions, the grain size is small, which provides the necessary conditions for the high heat input welding heat-affected zone to have excellent toughness.

[0064] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, ordinary technicians in the field should understand that the specific implementation methods of the present invention can still be modified or some technical features can be replaced by equivalents without departing from the spirit of the technical solution of the present invention, which should be included in the scope of the technical solution for protection of the present invention.

Claims

1. An E-grade weathering steel that can withstand 100 kJ / cm high heat input welding and has a yield strength of not less than 370 MPa, characterized in that: The chemical composition of the E-grade weathering steel is as follows in terms of mass percentage: C 0.038~0.058, Si 0.20~0.35, Mn 1.00~1.10, P≤0.0015, S≤0.0005, Cu 0.25~0.45, Cr 0.30~0.50, Ni 0.25~0.40, Mo≤0.03, Nb ≤0.014, V 0.010~0.025, Ti 0.005~0.012, B0.0004~0.0008, Alt 0.015~0.034, Zr 0.010~0.025, Ce 0.004~0.009, La 0.004~0.006, N0.0040~0.0080, O 0.0020~0.0030, the rest is iron and inevitable impurities, The chemical compositions of Ti, V, B, C and N satisfy 0.057≤5.48Ti+2.64V+0.03B+0.08C+0.06N≤0.

137.

2. The E-grade weathering steel according to claim 1, characterized in that: Among the particles with a size of 20-80 nm in the welding heat affected zone of the E-grade weathering steel that can inhibit the growth of austenite grains, the number of (V, Ti, B)(C, N) composite precipitated particles accounts for 45-55%.

3. The E-grade weathering steel according to claim 1, characterized in that: Among the particles with a size of 0.5-1.5 μm that have heterogeneous nucleation in the welding heat affected zone of the E-grade weathering steel, the number of composite precipitated particles of (V, Ti, B)(C, N) accounts for 43-56%.

4. The E-grade weathering steel according to claim 1, characterized in that: The tensile properties of the E-grade weathering steel are ReL≥370MPa, Rm≥510MPa, and the steel plate weathering index I≥6.

5.

5. The E-grade weathering steel according to claim 1, characterized in that: The -40°C KV2 low-temperature impact energy of the welding heat-affected zone of the E-grade weathering steel is not less than 47J.

6. The E-grade weathering steel according to any one of claims 1 to 5, characterized in that: The E-grade weathering steel is produced by a controlled rolling and controlled cooling process, with specific process parameters as follows: a heating temperature of 1160-1280°C, a rolling temperature in a recrystallization zone of 1050-1150°C, a rolling temperature in a non-recrystallization zone of 760-820°C, and cooling at a cooling rate of 10-15°C / s to between 480-620°C, then exiting the water and air cooling to room temperature.

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