420mpa grade heavy industrial atmosphere corrosion resistant bridge steel plate and production method thereof

Abstract

The application provides a 420MPa-grade heavy industrial atmosphere corrosion resistant bridge steel plate and a production method thereof. The steel plate comprises the following components in percentage by weight: C: 0.02% to 0.06%, Si: 0.05% to 0.13%, Mn: 0.80% to 1.20%, P: ≤0.010%, S: ≤0.003%, Nb: 0.03% to 0.05%, Ni: 0.10% to 0.40%, Cu: 0.20% to 0.50%, Mo: 0.10% to 0.40%, Cr: 1.80% to 2.80%, Ti: 0.015% to 0.035%, Sb: 0.08 to 0.18%, Al: 0.015% to 0.040%, Cr / Mo: 5 to 10, and the balance of iron and inevitable impurities. The production method comprises smelting, continuous casting, slab heating, rolling, cooling, straightening and stacking. The yield strength of the steel plate is greater than or equal to 420MPa, the tensile strength is greater than or equal to 570MPa, the elongation after fracture is greater than or equal to 25%, the yield strength ratio is less than or equal to 0.80, the thickness direction section shrinkage is greater than or equal to 70%, the low temperature impact energy at-40℃ is greater than or equal to 280J, the annual corrosion rate in a heavy industrial atmosphere environment is less than or equal to 0.04mm / a, and the corrosion performance is 5 to 8 times higher than that of ordinary Q420qE.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of metal materials, and particularly relates to a 420 MPa-grade heavy industrial atmosphere corrosion-resistant bridge steel plate and a production method thereof. BACKGROUND

[0002] With the vigorous development of the transportation industry, the requirements for the load capacity, seismic performance and corrosion resistance of bridge structures are continuously improved. Therefore, the bridge structure not only needs to consider the basic mechanical properties of the material, but also needs to consider the welding and corrosion resistance, especially in the heavy industrial atmosphere environment, to ensure the safety of the bridge life cycle.

[0003] At present, the existing bridge steel can meet most of the needs of the bridge market, but the corrosion problem of weathering bridge steel, especially in the heavy industrial complex atmosphere environment, needs to be studied. After searching, some patents and documents were found, but the contents recorded in the patents and documents are obviously different from the components, production methods, performances and product categories of the technical solutions of the present application.

[0004] Chinese patent application No. CN 109797342 A discloses a high-strength, high-toughness and atmospheric corrosion-resistant steel plate for steel structure manufacturing and a manufacturing method thereof. The element composition wt % is as follows: C: 0.03-0.10%, Si: 0.30-0.50%, Mn: 1.10-1.50%, P<0.010%, S<0.003%, Cr: 0.45-0.70%, Cu: 0.25-0.40%, Ni: 0.30-0.40%, Alt:≥0.030%, Ti: 0.006-0.030%, V: 0.040-0.080%, Mo: 0.02-0.08%, Ca: 0.0010-0.0030%, N: 0.0020-0.0080%, B: 0.0002-0.0030%, Ce: 0.001-0.010%, atmospheric corrosion resistance index I>6.5, CEV<0.54, Pcm<0.27, and the balance is Fe and unavoidable impurities. The present application adopts a specific chemical composition design and a steel plate modulation process to obtain a high-performance steel plate with a bainite structure, which can be used for steel structure manufacturing of bridges, high-rise buildings and the like. However, the present application has the following disadvantages: the steel plate does not have a low yield ratio, the safety performance is not good, and rare elements such as Ca, B and Ce are added, which makes smelting difficult and increases the production cost; the carbon equivalent is too high, the welding performance is poor, and the steel plate needs to be quenched and tempered, which is a complex process.

[0005] Chinese patent application No. CN 10738538 A discloses a TMCP type yield 420 MPa bridge steel plate and its production method. The chemical composition and mass percentage of the steel plate are as follows: C: 0.07-0.09%, Si: 0.25-0.50%, Mn: 1.40-1.60%, P≤0.015%, S≤0.005%, Ni: 0.15-0.25%, Cr: 0.10-0.20%, Nb: 0.020-0.030%, Al: 0.030-0.050%, V: 0.030-0.040%, and the balance is Fe and inevitable impurities. The production method includes smelting, continuous casting, heating, rolling, and cooling processes. The chemical composition of the steel plate is designed with low C, Nb, and V micro-alloying, supplemented with alloy elements such as Ni and Cr to ensure the strength and toughness matching of the steel plate, to obtain a composite structure of bainite and ferrite, and the maximum thickness of the steel plate can reach 70 mm. However, the patent application has the disadvantage of not having the ability to resist industrial atmospheric corrosion.

[0006] Chinese patent application No. CN 106011658 A discloses a marine climate corrosion-resistant steel and its production method. The chemical composition (by weight percentage) is as follows: C: ≤0.06%, Si: ≤0.50%, Mn≤1.50%, P≤0.010%, S≤0.005%, Ni: 3.0%-4.5%, Cu: 0.8%-2.0%, Al: 0.5%-1.0%, and the balance is Fe and inevitable impurities. The manufacturing method includes: conventional converter smelting, etc., and continuous casting into billets, heating the continuous casting billets, hot rolling, coiling, and cooling to room temperature using a front-stage cooling mode. The corrosion resistance of the steel plate in high-temperature, high-humidity, and high-salinity marine climates is improved. The patent document invention is limited to the production of thin-gauge steel plates using hot continuous rolling, and the steel plates produced by hot continuous rolling have high internal stress, which is not suitable for further manufacturing into bridge components with complex shapes, etc. In addition, the steel grade does not have low-temperature toughness and is not suitable for use as a highway bridge.

[0007] CN 107177803 B A kind of industrial atmosphere corrosion resistant high-strength bolt steel for coating-free bridge structure and manufacturing method, belong to bridge structure high-strength bolt steel technical field.The weight percentage of its component is as follows: C 0.16~0.45%, Si 0.01~2.2%, Mn 0.3~2.2%, P 0.001~0.024%, S 0.002~0.025%, B 0.0005~0.0100%, Ti 0.04~0.50%, V 0.01~0.20%, Al 0.001~0.10%, Cr 0.001~0.34%, Cu 0.2~0.5%, Ni 0.2~1.5%, the balance is Fe and trace impurities.Suitable for producing bolt specification range is M16-30mm, bolt processing factory is made into bolt, and the quenching and tempering heat treatment process system is 840-920 ℃ oil quenching + 380-625 ℃ tempering, obtains the best strength and toughness match.The advantage lies in, for coating-free bridge structure plate, profile matching connection, has excellent industrial atmosphere corrosion resistance and low temperature resistance.The patent document invention is limited to producing bridge bolt, and there are more alloy elements such as C, Ni and B, and the process is complex, does not have low yield ratio and excellent plasticity and toughness, and is not suitable for bridge steel.

[0008] In summary, the prior art on heavy industrial atmosphere bridge steel plate still has deficiencies, and the current bridge steel plate mainly has the following problems:

[0009] 1. The steel plate does not have the ability to resist heavy industrial atmosphere corrosion, and the safety performance is poor.

[0010] 2. The rare element addition of weathering steel is more, smelting is difficult, and the cost is high.

[0011] 3. The strength of the steel plate is low, and the toughness is poor, which cannot meet the bridge engineering in cold regions.

[0012] 4. The yield ratio of the steel plate is high, which has certain influence on the seismic safety of the bridge.

[0013] 5. More alloy elements are added, and the welding performance is poor.

[0014] 6. There are few medium plate products, mainly hot-rolled coil and bolts, which cannot meet the demand of large-span bridge engineering. SUMMARY

[0015] In view of the deficiencies of the prior art, the application provides a 420MPa-grade heavy industrial atmosphere corrosion resistant bridge steel plate and a production method thereof.The product produced according to the chemical composition and production process requirements of the steel of the application has high toughness, low yield strength ratio, high plasticity and excellent heavy industrial atmosphere corrosion resistance, the whole plate performance is uniform, TMCP rolling can be used, subsequent heat treatment is not needed, the production efficiency can be further improved, the construction efficiency and overall safety of the bridge structure engineering are improved, the weathering steel does not need to be coated or needs to be coated less, resources are saved, the environment is protected, and the weathering steel is a low-carbon product.

[0016] The low-yield-strength heavy industrial atmosphere corrosion resistant bridge steel plate and the production method thereof have the following advantages: the component design improves the welding performance and toughness of the material by low C and low Mn, Nb and Ti elements are used to inhibit the austenite grain growth and promote the nucleation in the austenite transformation process to refine the grains, the thickness center structure of the steel plate is controlled, and the uniformity of the structure is improved; the strength of the steel plate is improved by the precipitation strengthening of Nb and Ti in the process of rapid cooling after rolling; the rolling temperature is improved by using the recrystallization inhibition effect of Nb, the grains are refined, and the corrosion performance is improved; meanwhile, the atmospheric corrosion resistance of the steel plate is improved by using Cr, Ni, Cu and Sb elements, and the hardenability of the steel plate is also increased by the combined addition of Cr and Mo, the cooling rate is improved in the cooling process, the grains are refined, the strength is improved, and the uniformity of the structure in the thickness direction is achieved.

[0017] The application is achieved as follows:

[0018] The low-yield-strength heavy industrial atmosphere corrosion resistant bridge steel plate comprises the following components in percentage by weight: C: 0.02%-0.06%, Si: 0.05%-0.13%, Mn: 0.80%-1.20%, P≤0.010%, S≤0.003%, Nb: 0.03%-0.05%, Ni: 0.10%-0.40%, Cu: 0.20%-0.50%, Mo: 0.10%-0.40%, Cr: 1.80%-2.80%, Ti: 0.015%-0.035%, Sb: 0.08-0.18%, Al: 0.015%-0.040%, and the balance is iron and inevitable impurities.

[0019] Further, the component Cr / Mo of the steel plate is 5-10 。

[0020] Further, the component of the steel plate satisfies the atmospheric corrosion resistance index I value≥6.80

[0021]

[0022] Further, the steel plate has a yield strength ≥ 420 MPa, a tensile strength ≥ 570 MPa, an elongation after fracture ≥ 25%, a yield ratio ≤ 0.80, a thickness direction section shrinkage rate ≥ 70%, and a low temperature impact energy at -40 ℃ ≥ 280 J.

[0023] Further, the steel plate has a microstructure of ferrite + pearlite + bainite, wherein the volume percentage of ferrite is 50% to 70%.

[0024] Further, the steel plate has a thickness of 6 to 100 mm.

[0025] The component design reasons of the present application are as follows:

[0026] C: 0.02% to 0.06%

[0027] C has a great influence on the strength, toughness and welding performance of the steel, and also has an influence on the corrosion resistance of the steel; when C is low, the toughness, welding performance and corrosion resistance are improved; however, when C is lower than 0.020%, the strength is low and the smelting and welding are difficult; when C is higher than 0.06%, more pearlite is generated, which is not conducive to the performance of the bridge steel resistant to atmospheric corrosion, and the strength, elongation and toughness are reduced; therefore, the content of C is limited to 0.02% to 0.06% in the present application.

[0028] Si: 0.05% to 0.13%

[0029] Si is a necessary element for deoxidization of steelmaking, and can also play a solid solution strengthening role to improve the strength of the steel; Si can also improve the corrosion resistance of the steel; however, too high Si content will reduce the toughness of the steel and is not conducive to the welding performance; therefore, the content of Si is limited to 0.05% to 0.13% in the present application.

[0030] Mn: 0.80% to 1.20%

[0031] Mn can form a replacement solid solution in the steel to play a strong solid solution strengthening role to linearly increase the yield strength and tensile strength; within a certain range, the content of the element increases the strength of the steel while hardly reducing the plasticity and toughness of the steel; however, too high Mn content can increase the carbon equivalent of the steel and reduce the heavy industrial atmospheric corrosion resistance of the steel; therefore, the appropriate range of Mn is added according to the strength requirement in the steel of the present application, which is 0.80% to 1.20%.

[0032] P ≤ 0.010%

[0033] P is one of the most effective alloying elements for improving the corrosion resistance of the steel plate. When P and Cu are jointly added to the steel, a barrier layer with Cu and P as the main components can be formed between the base and the rust layer, showing a better composite effect. However, P deteriorates the welding performance of the steel, deteriorates the plasticity and toughness of the steel, and especially severely reduces the low-temperature impact toughness. It is also prone to local segregation and form banded structure. Therefore, in the present application, the content of P is controlled to be P≤0.010%.

[0034] S≤0.003%

[0035] S is the most harmful element to the corrosion resistance of the steel grade. Reducing the sulfur content has a good effect on the corrosion resistance of the steel grade to industrial atmosphere, H2S corrosion resistance, etc. At the same time, high sulfur also has an adverse effect on the toughness and plasticity of the steel. The steel grade of the present application controls S≤0.003%.

[0036] Nb: 0.030% to 0.050%

[0037] Nb is an important additive element in the present application. Nb generates Nb2O5 in a salt solution, which is a very stable oxide that adheres to the steel base, preventing contact between the corrosion medium and oxygen and the steel base, and inhibiting corrosion. It can effectively delay the recrystallization of deformed austenite, prevent austenite grain growth, increase the austenite recrystallization temperature, refine the grains, and improve the strength and toughness of the steel. Moreover, Nb is a strong carbon and nitride forming element that can combine with carbon and nitrogen to form stable and fine carbon and nitride precipitates during rapid water cooling, and the dispersed precipitates can make the corrosion uniform. Therefore, in the present application, the content of Nb is limited to 0.030% to 0.050%.

[0038] Ti: 0.015% to 0.035%

[0039] The addition of Ti can refine the austenite grains of the steel billet during reheating and in the welding heat affected zone, improving the plasticity and toughness of the steel plate. Moreover, Ti can form fine carbides or nitrides with C and N, preventing grain growth during heating, rolling, and welding, and improving the toughness of the base material and the welding heat affected zone. Therefore, in the present application, the content of Ti is limited to 0.015% to 0.035% in combination with the content of N in the steel.

[0040] Cr: 1.8% to 2.8%

[0041] Cr is used to improve the corrosion resistance of the steel in heavy industrial atmosphere. The enrichment of Cr in the rust layer can accelerate the transformation of unstable γ-FeOOH into more stable α-FeOOH, making the rust layer grain finer. The enriched Cr can fill the cracks and holes in the rust layer, improving the density and stability of the rust layer. The addition of Cr changes the structure of the rust layer and forms a dense oxide layer with Cu, preventing the entry of oxygen. Cu and Cr are simultaneously solid-solved in the matrix and precipitate with oxygen at the defects (cracks, holes) in the rust layer as corrosion proceeds, thereby preventing the entry of corrosive media into the matrix and slowing down the corrosion of the metal. Cu and Sb elements cooperate with each other and synergize to form a dense rust film layer of α-FeOOH and δ-FeOOH on the surface of the steel plate, protecting the steel from further corrosion. When the Cr content is less than 1.8%, the corrosion resistance in heavy industrial atmosphere is poor. When the Cr content is higher than 2.8%, the steelmaking difficulty is large, the hot workability of the steel plate is deteriorated, and the cost is too high. Therefore, the Cr content is limited to 1.8% to 2.8%.

[0042] Cu: 0.20% to 0.50%

[0043] Cu can effectively improve the corrosion resistance of steel in heavy industrial atmosphere. Cu can promote the anodic passivation of the steel matrix and inhibit the rust crystallization, retard the growth of rust crystals, and refine the inner rust layer grain, thereby forming a more protective rust layer. The enrichment of Cu can hinder the crystallization of the rust layer, inhibit the entry of O, reduce the conductivity of the rust layer, and hinder the deposition of corrosion on the surface. However, high Cu content can deteriorate the surface properties of the steel plate. In addition, at a certain Cu content, it is beneficial to the strength and hot workability of the steel plate, effectively reduces the hot rolling edge crack tendency of the steel plate, and significantly improves the surface quality of the steel plate. Cu also has the effect of reducing work hardening, improving the plasticity of the steel plate, and greatly improving the low temperature toughness. Therefore, the Cu content in the steel of the present application is limited to 0.20% to 0.50%.

[0044] Sb: 0.08% to 0.18%

[0045] The addition of Sb can promote the formation of a uniform and dense oxide film (rich in Sb, Cu, Cr, etc.) on the surface of the steel plate matrix. The Cu2 + Sb can promote the increase of δ-FeOOH, which can effectively prevent the entry of moisture, oxygen, sulfides, etc. in heavy industrial atmosphere into the matrix to form a corrosive internal environment. Sb can also produce a synergistic effect with α-FeOOH and δ-FeOOH to improve the corrosion resistance of the body. Low Sb content can cause uneven distribution of the passivation film, which cannot achieve the overall corrosion resistance effect. When the Sb content exceeds the upper limit, the corrosion prevention effect is achieved, but the hot workability is significantly reduced. Therefore, the Sb content is limited to 0.08% to 0.18%.

[0046] Mo: 0.10% to 0.40%

[0047] Mo element plays a more prominent role in improving the heavy industrial atmosphere corrosion resistance of weathering steel, Mo element in the rust layer is easy to convert into molybdate, with corrosion, molybdate reacts with iron ions to generate FeMoO4, and deposits in the anode active site, thereby inhibiting anode dissolution and significantly slowing down the corrosion. Especially in the industrial atmosphere environment containing sulfide, the ability to resist pitting and crevice corrosion can be significantly improved, and Mo helps to refine the austenite grains during rolling, but when the addition exceeds 0.5%, the weldability decreases; in addition, Mo is a precious element, which leads to a substantial increase in the cost of steel. Therefore, the Mo content in the present steel is limited to 0.10% to 0.40%.

[0048] Ni: 0.10% to 0.40%

[0049] The addition of Ni can make the self-corrosion potential of the metal positive shift, and can refine the inner rust layer grains, increase the density of the inner rust layer, and achieve the purpose of slowing down the corrosion. Ni can effectively improve the low temperature toughness of the steel, and can also improve the hot brittleness caused by copper in the steel. Ni element has no adverse effect on the hardening and toughness of the steel in the heat affected zone of welding; but Ni is a precious element, and the content should not be too high. Therefore, the Ni content in the present steel is limited to 0.10% to 0.40%.

[0050] Al: 0.015% to 0.040%

[0051] Al is a common deoxidizer in steel, and a small amount of Al added to the steel can refine the grains and improve the impact toughness. Al also has oxidation resistance and corrosion resistance. Al combined with Cr and Si can significantly improve the high temperature non-scaling performance of the steel and improve the surface quality of the steel plate. Al is easy to form oxide inclusions when it is too high. Therefore, the Al content in the present invention is limited to 0.015% to 0.040%.

[0052] The second technical scheme of the present invention provides a manufacturing method of a 420MPa grade heavy industrial atmosphere corrosion resistant bridge steel plate, which comprises smelting, continuous casting, slab heating, rolling, cooling, straightening and stacking.

[0053] The overheat pouring temperature of the continuous casting blank is 10 to 22℃, and the thickness of the continuous casting blank / the thickness of the finished steel plate is 3 to 30; the control of the overheat pouring temperature and the casting speed of the continuous casting blank can effectively reduce the quality defects of the casting blank; and increasing the compression ratio of the continuous casting blank to the finished steel plate can effectively control the grain size.

[0054] The temperature of the heating section of the continuous casting billet is 1220-1250℃, the temperature of the soaking section is 1200-1230℃, and the soaking section time is not less than 95 min; the heating temperature can satisfy the solid solution of the alloy, especially the Nb, Cr and Ni elements, and meanwhile, the overgrowth of austenite grains is prevented; and the heating time can ensure the uniformity of the billet temperature.

[0055] The rough rolling starting temperature is 1080-1110℃, the rough rolling finishing temperature is 1030-1060℃, the rolling temperature and deformation process in the rough rolling stage recrystallize the austenite grains and inhibit the grain growth, the rough rolling stage ensures that the deformation rate of at least the last two passes is greater than 13% and the pass interval is not more than 15s, and the cumulative reduction is greater than or equal to 50%; the large reduction and short interval process at the end of the rough rolling can reduce the equipment load of the construction steel, utilize the deformation superposition effect of the multi-pass large reduction rate, promote the recrystallization of the austenite, and achieve the grain refinement goal, which is suitable for the production of the bridge steel plate resistant to the atmospheric corrosion of heavy industry.

[0056] The intermediate warm-kept billet thickness is 1.5t-4.5t, wherein t is the thickness of the finished steel plate, the finish rolling starting temperature is 830-860℃, the finish rolling finishing temperature is 780-820℃, and the single-pass deformation rate is not less than 10%; the suitable intermediate warm-kept billet thickness can satisfy the austenite deformation and deformation energy accumulation in the unrecrystallized zone, and can also ensure that sufficient deformation rate is obtained in the rough rolling stage under the condition that the original casting billet thickness is certain, so that the grain refinement goal is achieved; the low finish rolling temperature promotes the accumulation of the austenite deformation energy and the induced precipitation of the Nb and Ti fine precipitates, and increases the nucleation sites; sufficient deformation at the finish rolling end near the phase transition point temperature is beneficial to the generation of fine ferrite, can reduce the effective grain size, and significantly improves the low-temperature toughness.

[0057] The rolled steel plate is subjected to accelerated water cooling, the steel plate is kept warm after rolling, the starting water cooling temperature is 680-720℃, the re-red temperature is 500-650℃, and the cooling speed is 8-22℃ / s; then, hot straightening and stacking slow cooling are carried out, and the stacking temperature is 300-400℃. Controlling the starting water cooling temperature of the steel plate can improve the excessive stress of the steel plate during cooling, ensures the shape of the steel plate, controlling the open cooling temperature can make a part of the steel plate produce proeutectoid ferrite, the grain size is more uniform, and the yield strength ratio of the steel plate is further reduced; the final cooling temperature can promote the refinement of the core structure of the steel plate, ensure the formation of a part of the bainite structure, increase the tensile strength, and reduce the yield strength ratio; in the stacking self-tempering process, the strength of the steel can be adjusted, the toughness and plasticity of the steel are improved, and the performance homogenization goal is achieved.

[0058] The final microstructure of the steel plate is fine ferrite+pearlite+bainite, wherein the volume percentage of the ferrite is 50%-70%, the steel plate has low yield strength ratio, high elongation and good low-temperature toughness, and meets the requirements of bridge engineering use under the atmospheric conditions of heavy industry.

[0059] The present application has the advantages of:

[0060] The present application is based on low C and low Si, and focuses on using Nb and Ti elements to inhibit austenite grain growth and precipitate phase formed in the rapid cooling process to refine the grain and increase the strength, through the matching of Cr, Mo, Cu, Ni, Sb and other heavy industrial atmosphere corrosion resistant alloy elements, and through the corresponding unique production process, a kind of comprehensive performance excellent heavy industrial atmosphere corrosion resistant bridge steel is produced. The product organization is ferrite + pearlite + granular bainite complex phase organization, the yield strength is greater than or equal to 420 MPa, the tensile strength is greater than or equal to 570 MPa, the elongation after fracture is greater than or equal to 25%, the yield strength ratio is less than or equal to 0.80, the thickness direction section shrinkage is greater than or equal to 70%, and the low temperature impact energy at-40 DEG C is greater than or equal to 280 J.

[0061] The annual corrosion rate of the steel in the heavy industrial atmosphere environment is less than or equal to 0.04 mm / a, which is 5-8 times higher than that of ordinary Q420qE, and can be widely used in bridge, pipe gallery and other engineering structures in heavy industrial atmosphere environment, and can also replace galvanized or coated repeated coating, which is beneficial to environmental protection and belongs to green manufacturing, filling the blank in the field. BRIEF DESCRIPTION OF DRAWINGS

[0062] Figure 1 The microstructure metallographic chart (ferrite + pearlite + granular bainite) of the embodiment 1 of the present application. DETAILED DESCRIPTION

[0063] The present application will be further described below by examples.

[0064] According to the component matching of the technical scheme, the embodiment of the present application is smelted, continuously casted, slab heated, rolled, cooled, straightened and stacked.

[0065] Slab heating

[0066] The heating section temperature of the continuously casted slab is 1220-1250 DEG C, the soaking section temperature is 1200-1230 DEG C, and the soaking section time is not less than 95 min;

[0067] Rolling

[0068] The rough rolling opening rolling temperature is 1080-1110 DEG C, the rough rolling final rolling temperature is 1030-1060 DEG C, the rough rolling stage ensures that the deformation rate of at least the last two passes is greater than 13% and the pass interval is not more than 15 s, and the cumulative reduction is greater than or equal to 50%;

[0069] The intermediate waiting slab thickness is 1.5t-4.5t, wherein t is the thickness of the finished steel plate, the finish rolling opening rolling temperature is 830-860 DEG C, the finish rolling final rolling temperature is 780-820 DEG C, and the single pass deformation rate is not less than 10%;

[0070] cooling

[0071] The rolled steel plate is accelerated water cooled, and the steel plate is kept warm after rolling, the water cooling temperature is 680-720℃, the red temperature is 500-650℃, and the cooling speed is 8-22℃ / s;

[0072] Further, the continuous casting process has a continuous casting billet pouring superheat of 10-22℃.

[0073] Further, the stacking temperature is 300-400℃.

[0074] The chemical composition of the embodiment of the present application is shown in Table 1; the smelting, continuous casting and slab heating process of the corresponding embodiment is shown in Table 2; the rough rolling process of the corresponding embodiment is shown in Table 3; the finish rolling process of the corresponding embodiment is shown in Table 4; the cooling process of the corresponding embodiment is shown in Table 5; the performance and microstructure proportion of the corresponding embodiment are shown in Table 6; the main components and content of the heavy industrial atmosphere corrosion solution are shown in Table 7; and the dry-wet alternating corrosion rate of the embodiment in the heavy industrial atmosphere is shown in Table 8.

[0075] Table 1 Chemical composition of the embodiment of the present application wt%

[0076]

[0077] Table 2 Continuous casting and casting billet heating process of the embodiment of the present application

[0078]

[0079] Table 3 Rough rolling process of the embodiment of the present application

[0080]

[0081] Table 4 Finish rolling process of the embodiment of the present application

[0082]

[0083] Table 5 Cooling and stacking process of the embodiment of the present application

[0084]

[0085] Table 6 Performance and microstructure proportion of the embodiment of the present application

[0086]

[0087] The heavy industrial atmosphere corrosion resistant steel of the above embodiment and the comparative example Q420qE steel are processed into corrosion test samples, and the dry-wet alternating accelerated corrosion test in the heavy industrial atmosphere environment is carried out by using the immersion method, and the physicochemical properties of the corrosion solution are shown in Table 6. The test material is taken out after being corroded in the medium for 360 hours for data processing, and the corrosion test results are shown in Table 7.

[0088]

[0089] Table 8 Example in heavy industry atmosphere of wet and dry alternate corrosion rate (360h)

[0090]

[0091] From the above, the steel plate of the application is based on low C and low Si, focuses on using Nb and Ti elements to inhibit austenite grain growth and precipitated phase formed in the process of rapid cooling to refine the grain and increase the strength, through the matching of Cr, Mo, Cu, Ni, Sb and other heavy industry atmosphere corrosion resistant alloy elements, through the corresponding unique production process, a kind of comprehensive performance excellent heavy industry atmosphere corrosion resistant bridge steel is produced. The product organization is ferrite + pearlite + granular bainite complex phase organization, yield strength ≥420MPa, tensile strength ≥570MPa, elongation ≥25%, yield ratio ≤0.80, thickness direction section shrinkage rate ≥70%,-40℃ low temperature impact energy ≥280J. The annual corrosion rate of the steel in heavy industry atmosphere environment is ≤0.04mm / a, which is 5-8 times higher than that of ordinary Q420qE, and can be widely used in bridge, pipe gallery and other engineering structures under heavy industry atmosphere environment, and can also replace galvanized or repeated coating of coating.

[0092] In order to describe the application, the above embodiment is appropriately and sufficiently described in the above embodiment, the above embodiment is only used to illustrate the application, and is not limited to the application, and ordinary skilled in the art can make various changes and modifications without departing from the spirit and scope of the application, any modification, equivalent replacement, improvement, etc. made should be included in the protection scope of the application, and the patent protection scope of the application should be limited by the claims.

Claims

1. A 420MPa grade heavy industrial atmospheric corrosion resistant bridge steel plate, characterized in that, By weight percentage, it comprises the following components: C: 0.02%–0.06%, Si: 0.05%–0.13%, Mn: 0.80%–1.20%, P≤0.010%, S≤0.003%, Nb: 0.03%–0.05%, Ni: 0.10%–0.40%, Cu: 0.20%–0.50%, Mo: 0.10%–0.40%, Cr: 1.80%–2.80%, Ti: 0.015%–0. The composition is 0.35% Cu, 0.08%–0.18% Sb, 0.015%–0.040% Al, with the remainder being Fe and unavoidable impurities; the composition satisfies an atmospheric corrosion resistance index (I) value ≥ 6.80, where 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 manufacturing method of a 420MPa grade heavy industrial atmospheric corrosion resistant bridge steel plate includes smelting, continuous casting, slab heating, rolling, cooling, straightening, and stacking. Slab heating The temperature of the heating section of the continuously cast billet is 1220~1250℃, the temperature of the soaking section is 1200~1230℃, and the soaking time is not less than 95min; Rolling The initial rolling temperature of roughing is 1080–1110℃, and the final rolling temperature of roughing is 1030–1060℃. During the roughing stage, the deformation rate of each pass in at least the last two passes must be greater than 13% and the interval between passes must not exceed 15s, with a cumulative reduction rate ≥50%. The thickness of the intermediate preheated billet is 1.5t to 4.5t, where t is the thickness of the finished steel plate. The initial rolling temperature of the finishing mill is 830 to 860℃, the final rolling temperature of the finishing mill is 780 to 820℃, and the deformation rate per pass is not less than 10%. cool down After rolling, the steel plate is subjected to accelerated water cooling. After rolling, the steel plate is allowed to heat up. The initial water cooling temperature is 680-720℃, the reheating temperature is 500-650℃, and the cooling rate is 8-22℃ / s.

2. The 420MPa grade heavy industrial atmospheric corrosion resistant bridge steel plate according to claim 1, characterized in that, The component Cr / Mo ratio is 5–10.

3. The 420MPa grade heavy industrial atmospheric corrosion resistant bridge steel plate according to claim 1, characterized in that, The steel plate has a yield strength ≥420MPa, tensile strength ≥570MPa, elongation after fracture ≥25%, yield strength ratio ≤0.80, reduction of area in the thickness direction ≥70%, and impact energy at -40℃ ≥280J.

4. The 420MPa grade heavy industrial atmospheric corrosion resistant bridge steel plate according to claim 1, characterized in that, The microstructure of the steel plate is ferrite + pearlite + bainite, wherein the volume percentage of ferrite is 50% to 70%.

5. A 420MPa grade heavy industrial atmospheric corrosion resistant bridge steel plate according to claim 1, characterized in that, The thickness of the steel plate is 6 to 100 mm.

6. A method for manufacturing a 420MPa grade heavy industrial atmospheric corrosion resistant bridge steel plate according to any one of claims 1 to 5, comprising smelting, continuous casting, slab heating, rolling, cooling, straightening, and stacking, characterized in that, Slab heating The temperature of the heating section of the continuously cast billet is 1220~1250℃, the temperature of the soaking section is 1200~1230℃, and the soaking time is not less than 95min; Rolling The initial rolling temperature of roughing is 1080–1110℃, and the final rolling temperature of roughing is 1030–1060℃. During the roughing stage, the deformation rate of each pass in at least the last two passes must be greater than 13% and the interval between passes must not exceed 15s, with a cumulative reduction rate ≥50%. The thickness of the intermediate preheated billet is 1.5t to 4.5t, where t is the thickness of the finished steel plate. The initial rolling temperature of the finishing mill is 830 to 860℃, the final rolling temperature of the finishing mill is 780 to 820℃, and the deformation rate per pass is not less than 10%. cool down After rolling, the steel plate is subjected to accelerated water cooling. After rolling, the steel plate is allowed to heat up. The initial water cooling temperature is 680-720℃, the reheating temperature is 500-650℃, and the cooling rate is 8-22℃ / s.

7. The method for manufacturing a 420MPa grade heavy industrial atmospheric corrosion resistant bridge steel plate according to claim 6, characterized in that, The continuous casting process involves casting billets with a superheat of 10–22°C.

8. The method for manufacturing a 420MPa grade heavy industrial atmospheric corrosion resistant bridge steel plate according to claim 6, characterized in that, The stacking temperature is 300~400℃.

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