Seawater corrosion resistant H-shaped steel and preparation method thereof

Abstract

The invention provides seawater corrosion resistant H-shaped steel and a preparation method, and relates to the technical field of corrosion resistant low alloy steel. The seawater corrosion resistant H-shaped steel comprises the following chemical components in percentage by mass: 0.05%-0.1% of C, 0.50%-0.90% of Mn, 0.15%-0.35% of Si, 0.15%-0.25% of Ni, 0.6%-1.0% of Cr, 0.2%-0.3% of Cu, 1.0%-1.2% of Cu: Ni, 0.06%-0.15% of Mo, 0.04%-0.09% of Sb, less than 0.10% of Al, 0.41%-0.6% of Ni + Cu + Mo, 0.02%-0.06% of V + Nb + Ti, less than 0.04% of impurity elements P + S + O and the balance of Fe and inevitable elements. The preparation method is high in resource utilization rate, low in production cost, short in process, easy to operate, high in efficiency and beneficial to industrial large-scale production and popularization.

Description

Technical Field

[0001] The invention relates to the technical field of corrosion-resistant low-alloy steel, in particular to seawater corrosion-resistant H-shaped steel and a preparation method thereof. Background Art

[0002] Low alloy high strength seawater corrosion resistant H-beam is of great significance to the development of marine resources and is widely used in marine engineering, marine equipment, shipbuilding, offshore platforms and other places that are exposed to high concentrations of salt, oxygen, humid environments and various corrosive substances in seawater environments for a long time. Equipment, structures and components exposed to seawater environments for a long time are susceptible to corrosion, which limits the life and safety performance of marine engineering equipment and structures.

[0003] In order to solve the problem of steel corrosion in seawater environment, the research and development of seawater corrosion-resistant steel has become the focus of attention. On the basis of ensuring high strength and low cost, it is of great practical significance to develop steel with strong seawater corrosion resistance.

[0004] Currently, there is a lot of research on seawater corrosion-resistant steel, but steel with high strength, good corrosion resistance and low cost still needs further development.

[0005] For example, Chinese patent CN116043131A discloses a seawater corrosion-resistant steel for steel sheet piles and a manufacturing method thereof, wherein the seawater corrosion-resistant steel adopts the Al-Cr-Cu-Si element system, and the smelting process of the process flow requires two refining treatments of LF and RH, and the basicity of the mold protection slag and the cooling water flow of the wide and narrow sides of the crystallizer need to be adjusted. The thickness of the rolled plate is 3mm, and the yield strength and tensile strength of the finished product are both high, but the yield strength ratio is lower than 0.766, and the present invention adds a high content of precious metals such as Al, Cr, etc., which is costly and has no good economic benefits. Chinese patent CN108642386A also adds a lot of precious metals such as Cu, Ni, etc., which is costly, and the P content of the present invention is high, which will affect the welding performance of the finished steel; when the thickness of the finished steel is 15.6mm, the yield strength ratio cannot reach above 0.8, the strength-plasticity product is lower than 15GPa·%, and the strength-plasticity is poor. Chinese patent CN101319293A discloses a seawater corrosion-resistant steel and its production method. The Ni element is not added to the molten steel. Although the cost is reduced to a certain extent, the high Al content (0.45-0.6%) will bring a series of problems. The molten steel is difficult to smelt, which can easily make the internal quality of the steel plate unqualified. The prepared steel plate has a thickness of 16mm, a strength of less than 400MPa, and a relatively low yield strength ratio and strength-plasticity product. Chinese patent CN103741057A discloses a low-density, high marine environment corrosion-resistant steel plate and its production process. The steel plate adds a very small amount of about 0.04% of Cu element, but adds Mo element to improve the corrosion resistance, which also leads to an increase in material cost; the steel plate thickness is 16mm, 20mm and 24mm, and its strength is high, but the strength-plasticity product is low. The prepared steel plate cannot obtain high corrosion resistance and low-temperature impact performance on the basis of high strength, high yield strength ratio and high strength plasticity. Chinese patent CN101029372A discloses a seawater corrosion resistant steel and its production method. The addition of more precious alloy elements to the composition also increases the cost. However, although adding a trace amount of Ca can improve the corrosion resistance of steel, it is very difficult to add Ca in smelting, and the content is difficult to control and difficult to achieve. In particular, the annual corrosion rate in the ocean splash zone is equivalent to 3-10 times that of the ocean full immersion zone, and the performance data in Table 3 do not conform to this objective law. Chinese patent CN117867376A discloses a high-aluminum seawater corrosion resistant steel and its electric furnace smelting method. Its chemical composition adds a high content of precious metal elements, which greatly increases the production cost. The thickness of the prepared steel plate is 12-14.5mm, the strength-plasticity product is less than 17GPa·%, and the low-temperature impact energy performance is poor.Chinese patent CN101880835B discloses a seawater corrosion-resistant ultra-low carbon bainitic steel and its preparation method. The steel contains more precious metal elements such as Cu, Nb, Mo, and B, which greatly increases the cost. In addition, the rolling process is not simple enough, which also increases the production cost. The thickness of the prepared steel plate is 12-14.5mm, the strength is high, and the impact energy is low at -20°C. Chinese patent CN101787485A discloses a low-cost seawater corrosion-resistant steel. The steel contains simple elements, low corrosion resistance, low strength-plasticity product, and low low-temperature impact. Chinese patent CN113913687A discloses a low-carbon, high-strength seawater corrosion-resistant steel and its manufacturing method. The steel contains more precious metal elements such as Cu, Ni, Re, Zr, and Ti, and adopts the TMCP process + normalizing treatment method. Therefore, its manufacturing method is cumbersome, the process is long, and the efficiency is low. Finally, it is heat treated to improve the performance of the hot-rolled plate, which is costly. Chinese patent CN102534378A discloses a seawater corrosion-resistant structural steel with uniform metallographic structure and a production method thereof. The manganese content in the steel is relatively high and it needs to undergo three-stage hot rolling, which has a long preparation process. Although the prepared steel plate has a good combination of strength and toughness, no other alloy elements are added to improve the corrosion resistance, and the high corrosion resistance of the structural parts in the seawater environment cannot be guaranteed.

[0006] In summary, the existing seawater corrosion resistant steel has a series of problems in production cost, manufacturing process, comprehensive performance, etc. The addition of precious elements increases the cost, the manufacturing method is cumbersome, and the steel performance may be low, which is not suitable for large-scale production. Therefore, in view of the problems existing in the existing seawater corrosion resistant steel, it is necessary to provide a seawater corrosion resistant steel with lower cost and better comprehensive performance. Summary of the invention

[0007] In order to solve the technical problems in the prior art of the preparation method of seawater corrosion resistant steel, such as high cost caused by adding precious elements, high preparation cost, complicated preparation method, and the inability to synergistically improve the mechanical properties and seawater corrosion resistance of the prepared steel, etc., the embodiment of the present invention provides a seawater corrosion resistant H-shaped steel and preparation method with low cost, high efficiency, and the ability to synergistically improve the comprehensive performance of steel. The technical solution is as follows:

[0008] A seawater corrosion resistant H-shaped steel, the chemical composition of which is calculated by mass percentage: C 0.05-0.1%, Mn 0.50-0.90%, Si 0.15-0.35%, Ni 0.15-0.25%, Cr 0.6-1.0%, Cu 0.2-0.3%, Cu:Ni=1.0-1.2%, Mo 0.06-0.15%, Sb 0.04-0.09%, Al<0.10%, Ni+Cu+Mo 0.41-0.6%, V+Nb+Ti 0.02-0.06%, impurity elements P+S+O<0.04%, and the rest are Fe and unavoidable elements.

[0009] Optionally, rare earth RE≤0.02% may be added to the seawater corrosion resistant H-beam.

[0010] Optionally, the metallographic composition of the seawater corrosion resistant H-beam is 81.81-100% ferrite structure + 0-18.19% pearlite.

[0011] Optionally, the seawater corrosion-resistant H-shaped steel has a tensile strength of 486-537MPa, a yield strength of 375-463MPa, a yield strength ratio of 0.785-0.882, an elongation of not less than 35%, a welding cold crack sensitivity coefficient of 0.179-0.225, an impact energy of not less than 240J at -20°C, and a corrosion rate of 0.675-0.973g / m² after simulating seawater environment corrosion. h, which is less than 40% of Q345B.

[0012] Optionally, when rare earth RE is added to the seawater corrosion resistant H-shaped steel, the tensile strength is 487-556MPa, the yield strength is 386-482MPa, the yield strength ratio is 0.764-0.873, the elongation is not less than 40%, the welding cold crack sensitivity coefficient is 0.153-0.217, the impact energy is not less than 260J at -20°C, and the corrosion rate after simulating seawater environment corrosion is 0.625-0.826g / m² h, which is less than 35% of Q345B.

[0013] A method for preparing the seawater corrosion resistant H-beam based on the above-mentioned method comprises the following steps:

[0014] S1. Raw material weighing: using molten iron and / or scrap steel and master alloy as raw materials, accurately weighing and proportioning the ingredients according to the chemical composition ratio to obtain the raw materials;

[0015] S2, continuous casting: S1 raw materials are melted and continuously cast to obtain ingots for H-beams resistant to seawater corrosion;

[0016] S3, hot rolling: heating and keeping the S2 seawater corrosion resistant H-shaped steel slab warm, and starting hot rolling to obtain a hot-rolled H-shaped steel plate;

[0017] S4, cooling: cooling the hot-rolled H-shaped steel plate in S3 to obtain a finished H-shaped steel product resistant to seawater corrosion.

[0018] Optionally, the hot rolling in S3 is conventional hot rolling or controlled hot rolling.

[0019] Optionally, the cooling treatment in S4 includes forced cooling to 590-700° C. after rolling and then air cooling to room temperature, or air cooling to 590-700° C. and then continuing to air cool to room temperature.

[0020] Technical principle of the present invention:

[0021] The properties of each element in the present invention are as follows:

[0022] Carbon element C: is an important strengthening element. It exists in the form of carbides in steel and plays a role in precipitation strengthening and fine grain strengthening with carbide-forming elements. It forms nano-scale second phase precipitation particles with microalloying elements such as Nb and V. However, when the carbon content is too high, it is not conducive to weldability. Therefore, the mass percentage of C element is designed to be 0.05%<C<0.1% in the present invention.

[0023] Manganese element Mn: Mn has a strong affinity with C and is an effective element for refining grains, ensuring comprehensive performance and improving hardenability. However, Mn is also an element that is easily segregated. When the Mn and C contents in the segregation zone reach a certain ratio, a martensite phase will be generated during steel production and welding. This phase will exhibit high hardness and have a great influence on the welding performance of the equipment. Therefore, considering the requirements for strength, the present invention designs the mass percentage of Mn element to be 0.50%<Mn<0.90%

[0024] Silicon element Si: It improves the strength of steel through solid solution strengthening. The addition of Si can also improve the steel's resistance to seawater corrosion, making its inner rust layer dense and preventing Cl - However, too high Si content will reduce the low temperature toughness and welding performance, so the mass percentage of Si element designed in the present invention is 0.15%<Si<0.35%.

[0025] Nickel element Ni: Ni is an important element for improving the corrosion resistance of steel. It can promote the stability of the rust layer, and Ni and Cr have a superimposed promoting effect on improving the compactness of corrosion products. However, adding too much Ni is not conducive to saving manufacturing costs, and too high a content of Ni will increase the adhesion of the oxide scale, and pressing it into the steel will form hot rolling defects on the surface. Therefore, the present invention designs the mass percentage of the Ni element to be 0.15%<Ni<0.25%.

[0026] Chromium element Cr: Adding Cr element can form stable and hard carbides in steel, which can significantly improve strength and hardness, and can greatly improve the hardenability of steel. At the same time, Cr element is an important element to improve the corrosion resistance of steel. It can form a passivation film rich in Cr oxide / hydroxide on the surface of steel. However, the Cr element content in steel should not be too high. When the Cr element content in steel is too high, it will reduce the toughness of the steel and affect the welding performance of high-strength steel. Therefore, the mass percentage of Cr element is designed to be 0.6%<Cr<1% in the present invention.

[0027] Copper element Cu: Adding an appropriate amount of Cu element can improve the protection ability of the rust layer on the macro cathode area matrix, promote the formation of a dense rust layer on the steel surface, and significantly improve the seawater corrosion resistance of the steel. Cu can form Cu under acidic conditions in the occluded area and under certain potential conditions. 2+ It can combine with certain anions to form insoluble salts, thereby repairing and filling cracks and holes, reducing the hydrogen-induced crack sensitivity of steel. However, adding too high a content of Cu is prone to copper brittleness and deteriorating the surface properties of steel. Cu is a relatively expensive alloying element, and the amount of Cu added to steel should be controlled. Therefore, the present invention designs the mass percentage of Cu element to be 0.2%<Cu<0.3%.

[0028] Molybdenum element Mo: Mo is an element that forms ferrite. Mo has a solid solution strengthening effect on ferrite, and can also improve the stability of carbides, thereby improving the strength of steel. Mo can increase the passivation effect of steel and improve corrosion resistance, especially preventing the tendency of pitting corrosion. Mo can purify the steel surface in reducing acids and strong oxidizing salt solutions (especially those containing chloride ions), but when the Mo content exceeds 3%, the oxidation resistance of steel will be reduced. Mo can also increase the stability of austenite, promote the formation of bainite during the phase transformation of supercooled austenite, and obtain bainite structure at room temperature. The bainite content cannot be too high, which is unfavorable to the impact performance of steel. In addition, Mo is an expensive alloying element, and the amount of Mo added to steel should be controlled. While improving corrosion resistance, the alloy content and alloy cost should be controlled. Therefore, the mass percentage of Mo element designed in the present invention is 0.06%<Mo<0.15%.

[0029] Niobium, vanadium, titanium: V is a strong carbide-forming element, which can significantly improve the strength of steel in the form of dispersed precipitation. V can form stable carbides with C, inhibit the occurrence of carbon precipitation and intergranular corrosion at the grain boundary, and improve the corrosion resistance of the alloy. However, if the content is too high, large nitride particles are likely to appear, affecting the toughness of the steel. Titanium element Ti: Ti is a microalloying element. Adding a small amount of Ti to steel can improve the strength of the steel, improve the cold forming performance and welding performance of the steel, and can also produce strong precipitation strengthening and moderate grain refinement. Ti has strong chemical activity and is easy to form compounds with C, N, O, and S in steel. TiN can effectively prevent the growth of austenite grains during heating, play a role in refining austenite grains, and improve the toughness of the heat affected zone of welding, but excessive addition is prone to continuous casting defects. The Nb element not only refines the austenite grains, but also forms precipitates with C and N to have precipitation strengthening. The unprecipitated Nb has solid solution strengthening and phase transformation strengthening effects in steel. In summary, the present invention designs the mass percentage of the micro-alloying elements Nb+V+Ti to be 0.02-0.06%.

[0030] Aluminum element Al: Al is a ferrite-forming element, which is added to steel as a deoxidizer during the steelmaking process. A trace amount of Al forms fine AlN precipitation during steelmaking, which has the effect of refining austenite grains in the subsequent cooling process, improving the strength and toughness of steel. Al has good oxidation resistance, and can form a corrosion-resistant oxide layer on the surface when exposed to air, which can improve its corrosion resistance. However, when the Al element content is too high, delta ferrite will be formed during the solidification of the molten steel, and the cracking tendency of the ingot is serious. At the same time, bainite formation is increased during the low-temperature transformation of austenite, which leads to a decrease in steel toughness. Therefore, the mass percentage of Al element is designed in the present invention to be Al<0.1%.

[0031] Antimony element Sb: The addition of trace Sb can not only increase the polarization resistance, reduce the cathode current density, and slow down the oxygen reduction process, but more importantly, Sb can inhibit the local acidification at the bottom of the pit, thereby slowing down the local corrosion process of the rust / matrix interface and promoting the rust layer phase γ-FeOOH to Fe 3 O 4 The conversion of α-FeOOH improves the protective performance of the rust layer. Considering the cost problem, the mass percentage of Sb element is designed to be 0.04%<Sb<0.09%.

[0032] Rare earth element RE: Adding a small amount of rare earth element RE to steel can improve the shape, distribution and size of inclusions in the matrix, and react with inclusions to change the type of inclusions, replace harmful inclusions in steel, improve the mechanical properties of the steel matrix and effectively improve the seawater corrosion resistance of steel. The solid solubility of RE in steel is very low, and a trace amount of solid solubility is beneficial to improving the mechanical properties and stability of the rust layer. Therefore, the mass percentage of rare earth elements designed in the present invention is 0.007%≤RE<0.02%.

[0033] The key points of the present invention are:

[0034] 1. Compared with the prior art CN116043131A, the present invention is different in that although the content of alloy elements added is similar, the H-beam of the present invention obtains higher mechanical properties under a simpler hot working process, does not require subsequent heat treatment, reduces processing steps, and reduces production costs. In addition, the present invention has lower corrosion resistance in a seawater environment, and the corrosion rate is reduced by about 50% compared with the prior art.

[0035] 2. Compared with the prior art CN108642386A, the present invention is different in that the content of P element is better controlled, the welding performance and toughness of steel are further improved, and the yield strength, elongation and low-temperature toughness are better than that of the prior art; the corrosion rate of the present invention in a seawater-resistant environment is lower and the corrosion resistance is better.

[0036] 3. Compared with the prior art CN101319293A, the present invention is different in that the content of Mo+Cr in the present invention is much lower than that in the prior art, and has better economy in terms of the content of precious alloy elements; secondly, the Al content in the present invention is much lower than that in the prior art: 0.450%-0.600%, which greatly reduces the difficulty of smelting and continuous casting, improves the quality of the ingot, and reduces the heat treatment required to eliminate bainite; the H-beam of the present invention has higher strength and toughness, and the hot rolling process of the present invention is simpler than that of the prior art, thereby reducing the production cost.

[0037] 4. Compared with the prior art CN103741057A, the present invention is different in that the seawater corrosion rate of the present invention is lower than that of the prior art, the seawater corrosion resistance is better, and the comprehensive mechanical properties are better. From the perspective of the content of precious alloy elements, the total amount of precious alloy elements in the present invention is relatively lower, and the cost is lower; and the processing technology of the present invention is simpler.

[0038] 5. The present invention is different from the prior art CN101029372A in that the total amount of precious metal elements Cr+Cu+Mo and Nb++Ti added in the present invention is lower than that in the prior art, and has better economy; and the prior art adds the Ca element, and it is very difficult to add Ca in smelting, and the content is difficult to control and achieve.

[0039] 6. The present invention is different from the prior art CN117867376A in that the present invention has better comprehensive mechanical properties and the added content of precious metal elements Mo+Cr in the present invention is lower than that in the prior art, thereby reducing costs.

[0040] 7. The difference between the present invention and the prior art CN101880835B is that the present invention has higher strength and toughness. Although the technology has higher strength, it has lower low-temperature impact toughness and cannot guarantee the comprehensive mechanical properties of steel. In addition, the added content of precious metals Ni+Cu+Mo in the present invention is lower, which has better economy.

[0041] The relevant data of the present invention and the comparison information of the prior art are shown in Table 1 below:

[0042] Table 1

[0043]

[0044] It can be seen from the above table that the present application has a relatively lower corrosion rate in terms of corrosion resistance in H-shaped steel adapted to the seawater corrosion environment, and has a competitive advantage; in terms of mechanical properties, the strength and toughness are relatively high, and the strength-plasticity, yield strength ratio and low-temperature impact energy not shown are also relatively high, and has good comprehensive mechanical properties; in terms of precious alloy elements, as shown in Table 2 below, the total amount of Nb+V+Ti and Ni+Cu+Cr+Mo is relatively low, and the alloy cost control also has an advantage.

[0045] Table 2

[0046]

[0047] Compared with the prior art, the above technical solution has at least the following beneficial effects:

[0048] The above scheme, the present invention proposes a seawater corrosion resistant H-shaped steel and a preparation method, which can solve the technical problems existing in the preparation method of seawater corrosion resistant steel, such as high cost caused by adding precious elements, high preparation cost, complicated preparation method, and the inability to synergistically improve many properties of the prepared steel, such as mechanical properties and seawater corrosion resistance.

[0049] The present invention comprehensively considers multiple factors such as mechanical properties, corrosion properties, welding properties, and cost, and reduces the addition of precious elements in the composition through reasonable composition design and calculation, thereby reducing the total amount of Nb+V+Ti and Ni+Cu+Cr+Mo, and adding rare earth elements is selected according to the situation, so that hot-rolled H-shaped steel with high comprehensive performance and low cost can be obtained.

[0050] The present invention adopts a reasonable hot processing technology, i.e. conventional hot rolling or controlled hot rolling, and selects the corresponding hot processing technology and its process parameters according to multiple factors such as mechanical properties, corrosion properties, welding properties, cost, etc., to obtain the desired organizational structure and distribution of hot-rolled H-shaped steel, so that the comprehensive performance can be greatly improved.

[0051] The seawater corrosion-resistant H-shaped steel of the present invention has a tensile strength of 486-537MPa, a yield strength of 375-463MPa, a yield strength ratio of 0.785-0.882, an elongation of not less than 35%, a welding cold crack sensitivity coefficient of 0.179-0.225, an impact energy of not less than 240J at -20°C, and a corrosion rate of 0.675-0.973g / m² after simulating seawater corrosion. h, which is less than 40% of Q345B.

[0052] The seawater corrosion resistant H-shaped steel of the present invention has a tensile strength of 487-556MPa, a yield strength of 386-482MPa, a yield strength ratio of 0.764-0.873, an elongation of not less than 40%, a welding cold crack sensitivity coefficient of 0.153-0.217, an impact energy of not less than 260J at -20°C, and a corrosion rate of 0.625-0.826g / m² after simulating seawater environment corrosion. h, which is less than 35% of Q345B.

[0053] In summary, compared with other traditional methods, the method of the present invention comprehensively considers mechanical properties, corrosion properties, welding properties, cost and other factors, and simplifies and improves the component design and preparation method, so that the prepared H-shaped steel has high strength, high strength-to-plasticity, high yield ratio, high weldability and high corrosion resistance; and has high resource utilization, low production cost, short process, easy operation, high efficiency, and is conducive to large-scale industrial production and promotion. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0055] Figure 1 is an electrochemical polarization curve diagram of seawater corrosion resistant H-beam prepared by the preparation method of Example 1 of the present invention;

[0056] Figure 2 is an electrochemical polarization curve diagram of seawater corrosion resistant H-beam prepared by the preparation method of Example 2 of the present invention;

[0057] Figure 3 is an electrochemical polarization curve diagram of seawater corrosion resistant H-beam prepared by the preparation method of Example 3 of the present invention;

[0058] Figure 4 It is a comparison chart of the corrosion weight loss rate of the seawater corrosion resistant H-shaped steel prepared by the preparation methods of Examples 1, 2, 3 of the present invention and Comparative Examples 1, 2, 3, 4 respectively. DETAILED DESCRIPTION

[0059] The technical solution of the present invention is described below in conjunction with the accompanying drawings.

[0060] In the embodiments of the present invention, words such as "exemplarily" and "for example" are used to indicate examples, illustrations or explanations. Any embodiment or design described as "example" in the present invention should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of the word "example" is intended to present the concept in a specific way. In addition, in the embodiments of the present invention, the meaning expressed by "and / or" can be both, or it can be either of the two.

[0061] In the embodiments of the present invention, "image" and "picture" can sometimes be used interchangeably. It should be noted that when the difference between them is not emphasized, the meanings they want to express are the same. "of", "corresponding" and "corresponding" can sometimes be used interchangeably. It should be noted that when the difference between them is not emphasized, the meanings they want to express are the same.

[0062] In the embodiments of the present invention, sometimes the subscripts such as W 1 It may be written in non-subscript form such as W1. When the difference is not emphasized, the meaning is the same.

[0063] In order to make the technical problems, technical solutions and advantages to be solved by the present invention more clear, a detailed description will be given below with reference to the accompanying drawings and specific embodiments.

[0064] A seawater corrosion resistant H-shaped steel, the chemical composition of which is calculated by mass percentage: C 0.05-0.1%, Mn 0.50-0.90%, Si 0.15-0.35%, Ni 0.15-0.25%, Cr 0.6-1.0%, Cu 0.2-0.3%, Cu:Ni=1.0-1.2%, Mo 0.06-0.15%, Sb 0.04-0.09%, Al<0.10%, Ni+Cu+Mo 0.41-0.6%, V+Nb+Ti 0.02-0.06%, impurity elements P+S+O<0.04%, and the rest are Fe and unavoidable elements.

[0065] In particular, rare earth RE≤0.02% may be added to the seawater corrosion resistant H-beam.

[0066] Particularly, the metallographic composition of the seawater corrosion resistant H-beam is 81.81-100% of ferrite structure + 0-18.19% of pearlite.

[0067] In particular, the seawater corrosion-resistant H-shaped steel has a tensile strength of 486-537MPa, a yield strength of 375-463MPa, a yield strength ratio of 0.785-0.882, an elongation of not less than 35%, a welding cold crack sensitivity coefficient of 0.179-0.225, an impact energy of not less than 240J at -20°C, and a corrosion rate of 0.675-0.973g / m² after simulating seawater environment corrosion. h, which is less than 40% of Q345B.

[0068] In particular, the tensile strength of the seawater corrosion-resistant H-shaped steel is 487-556MPa, the yield strength is 386-482MPa, the yield strength ratio is 0.764-0.873, the elongation is not less than 40%, the welding cold crack sensitivity coefficient is 0.153-0.217, the impact energy is not less than 260J at -20℃, and the corrosion rate after simulating seawater environment corrosion is 0.625-0.826g / m² h, which is less than 35% of Q345B.

[0069] A method for preparing the seawater corrosion resistant H-beam based on the above-mentioned method comprises the following steps:

[0070] S1. Raw material weighing: using molten iron and / or scrap steel and master alloy as raw materials, accurately weighing and proportioning the ingredients according to the chemical composition ratio to obtain the raw materials;

[0071] S2, continuous casting: S1 raw materials are melted and continuously cast to obtain ingots for H-beams resistant to seawater corrosion;

[0072] S3, hot rolling: heating and keeping the S2 seawater corrosion resistant H-shaped steel slab warm, and starting hot rolling to obtain a hot-rolled H-shaped steel plate;

[0073] S4, cooling: cooling the hot-rolled H-shaped steel plate in S3 to obtain a finished H-shaped steel product resistant to seawater corrosion.

[0074] In particular, the hot rolling in S3 is conventional hot rolling or controlled hot rolling.

[0075] In particular, the cooling treatment in S4 includes forced cooling to 590-700° C. after rolling and then air cooling to room temperature, or air cooling to 590-700° C. and then continuing air cooling to room temperature.

[0076] Example 1

[0077] A seawater corrosion-resistant H-shaped steel. The chemical composition of the seawater corrosion-resistant H-shaped steel in this embodiment is as follows by mass percentage: C=0.1%, Mn=0.66%, Si=0.31%, Ni=0.19%, Cr=0.95%, Cu=0.26%, V=0.044%, Al=0.024%, Sb=0.08%, P=0.0015%, S=0.0022%, Ce=0.007%, N=0.0076%, and the rest are Fe and unavoidable elements.

[0078] The preparation method of the seawater corrosion resistant H-beam comprises the following steps:

[0079] S1. Raw material weighing: using molten iron and / or scrap steel and master alloy as raw materials, accurately weighing and proportioning the ingredients according to the chemical composition ratio to obtain the raw materials;

[0080] S2, continuous casting: S1 raw materials are melted and continuously cast to obtain H-shaped steel slabs resistant to seawater corrosion;

[0081] S3, hot rolling: heating and keeping the S2 seawater corrosion resistant H-shaped steel slab warm, starting hot rolling, when the hot rolling is conventional hot rolling, the temperature of the heat preservation treatment is 1230°C, the starting rolling temperature is 1170-1220°C, the final rolling temperature is 960°C, and the hot rolled H-shaped steel plate is obtained;

[0082] S4, cooling: cooling the S3 hot-rolled H-shaped steel plate, i.e. air-cooling it to room temperature after rolling, to obtain a finished H-shaped steel product resistant to seawater corrosion.

[0083] The metallographic composition of the seawater corrosion resistant H-beam prepared in this embodiment is 81.81% ferrite structure + 18.19% pearlite structure.

[0084] The seawater corrosion resistant H-beam prepared in this embodiment has a tensile strength of 504MPa, a yield strength of 386MPa, a yield strength ratio of 0.766, an elongation of 34%, a strength-ductility product of 17.136GPa·%, a welding cold crack sensitivity coefficient of 0.162, and an impact energy of 240.7J at -20°C. Figure 1 As shown, the corrosion rate after simulating seawater corrosion is 0.821g / m² h, which is 34% of Q345B.

[0085] Example 2

[0086] A seawater corrosion-resistant H-shaped steel. The chemical composition of the seawater corrosion-resistant H-shaped steel in this embodiment is as follows by mass percentage: C=0.02%, Mn=0.65%, Si=0.3%, Ni=0.2%, Cr=0.6%, Cu=0.25%, Mo=0.1%, Ti=0.08%, P=0.0016%, S=0.006%, N=0.0025%, and the rest are Fe and unavoidable elements.

[0087] The preparation method of the seawater corrosion resistant H-beam comprises the following steps:

[0088] S1. Raw material weighing: using molten iron and / or scrap steel and master alloy as raw materials, accurately weighing and proportioning the ingredients according to the chemical composition ratio to obtain the raw materials;

[0089] S2, continuous casting: S1 raw materials are melted and continuously cast to obtain H-shaped steel slabs resistant to seawater corrosion;

[0090] S3, hot rolling: heating and keeping the S2 seawater corrosion resistant H-shaped steel slab warm, starting hot rolling, when hot rolling is controlled hot rolling, the temperature of the heat preservation treatment is 1230°C, the rolling start temperature is 1170-1220°C, the first stage final rolling temperature is 960°C, the second stage final rolling temperature is 850°C, and the hot rolled H-shaped steel plate is obtained;

[0091] S4, cooling: The S3 hot-rolled H-shaped steel plate is subjected to cooling treatment, that is, forced cooling to 590-700°C by water cooling, and then air cooling to room temperature to obtain a finished H-shaped steel product resistant to seawater corrosion.

[0092] The metallographic composition of the seawater corrosion resistant H-beam prepared in this embodiment is almost entirely ferrite.

[0093] The seawater corrosion resistant H-beam prepared in this embodiment has a tensile strength of 525 MPa, a yield strength of 454 MPa, a yield strength ratio of 0.865, an elongation of 32.4%, a strength-ductility product of 17.01 GPa·%, a welding cold crack sensitivity coefficient of 0.186, and an impact energy of 230.9 J at -20°C when no rare earth elements are added. Figure 2 As shown, the corrosion rate after simulating seawater corrosion is 0.685g / m² h, which is 28% of Q345B.

[0094] Example 3

[0095] A seawater corrosion-resistant H-shaped steel. The chemical composition of the seawater corrosion-resistant H-shaped steel in this embodiment is as follows by mass percentage: C=0.1%, Mn=0.77%, Si=0.347%, Ni=0.2%, Cr=1%, Cu=0.22%, Mo=0.118%, V=0.054%, Al=0.022%, Ti=0.017%, Sb=0.144%, P=0.0062%, S=0.0036%, Ce=0.02%, N=0.0065%, and the rest are Fe and unavoidable elements.

[0096] The preparation method of the seawater corrosion resistant H-beam comprises the following steps:

[0097] S1. Raw material weighing: using molten iron and / or scrap steel and master alloy as raw materials, accurately weighing and proportioning the ingredients according to the chemical composition ratio to obtain the raw materials;

[0098] S2, continuous casting: S1 raw materials are melted and continuously cast to obtain H-shaped steel slabs resistant to seawater corrosion;

[0099] S3, hot rolling: heating and keeping the S2 seawater corrosion resistant H-shaped steel slab warm, starting hot rolling, when the hot rolling is conventional hot rolling, the temperature of the heat preservation treatment is 1230°C, the starting rolling temperature is 1170-1220°C, the final rolling temperature is 960°C, and the hot rolled H-shaped steel plate is obtained;

[0100] S4, cooling: cooling the S3 hot-rolled H-shaped steel plate, i.e. air-cooling it to room temperature after rolling, to obtain a finished H-shaped steel product resistant to seawater corrosion.

[0101] The metallographic composition of the seawater corrosion resistant H-beam prepared in this embodiment is 82.68% ferrite structure + 17.32% pearlite structure.

[0102] The seawater corrosion resistant H-beam prepared in this embodiment has a tensile strength of 487MPa, a yield strength of 383MPa, a yield strength ratio of 0.786, an elongation of 36%, a strength-ductility product of 17.532GPa·%, a welding cold crack sensitivity coefficient of 0.179, and an impact energy of 159.1J at -20°C. Figure 3 As shown, the corrosion rate after simulating seawater corrosion is 0.734g / m² h, which is 30% of Q345B.

[0103] Comparative Example 1

[0104] A seawater corrosion resistant H-shaped steel. The chemical composition of the seawater corrosion resistant H-shaped steel in this comparative example is as follows by mass percentage: C=0.107%, Mn=0.66%, Si=0.32%, Ni=0.19%, Cr=0.47%, Cu=0.27%, Mo=0.33%, Al=0.13%, V=0.045%, Ce=0.0086%, P=0.0014%, S=0.003%, N=0.007%, and the rest are Fe and unavoidable elements.

[0105] The preparation method of the seawater corrosion resistant H-beam comprises the following steps:

[0106] S1. Raw material weighing: using molten iron and / or scrap steel and master alloy as raw materials, accurately weighing and proportioning the ingredients according to the chemical composition ratio to obtain the raw materials;

[0107] S2, continuous casting: S1 raw materials are melted and continuously cast to obtain H-shaped steel slabs resistant to seawater corrosion;

[0108] S3, hot rolling: heating and keeping the S2 seawater corrosion resistant H-shaped steel slab warm, starting hot rolling, when the hot rolling is conventional hot rolling, the temperature of the heat preservation treatment is 1230°C, the starting rolling temperature is 1170-1220°C, the final rolling temperature is 960°C, and the hot rolled H-shaped steel plate is obtained;

[0109] S4, cooling: cooling the S3 hot-rolled H-shaped steel plate, i.e. air-cooling it to room temperature after rolling, to obtain a finished H-shaped steel product resistant to seawater corrosion.

[0110] The metallographic composition of the seawater corrosion resistant H-beam prepared in this comparative example is 81.37% of ferrite structure + 18.63% of pearlite structure.

[0111] The seawater corrosion-resistant H-shaped steel prepared in this comparative example has a tensile strength of 488MPa, a yield strength of 259MPa, a yield strength ratio of 0.531, an elongation of 35%, a strength-ductility product of 17.080GPa·%, a welding cold crack sensitivity coefficient of 0.195, an impact energy of 94J at -20°C, and a corrosion rate of 0.854g / m² after simulating seawater corrosion. h, which is 39% of Q345B.

[0112] Comparative Example 2

[0113] A seawater corrosion resistant H-shaped steel. The chemical composition of the seawater corrosion resistant H-shaped steel in this comparative example is as follows by mass percentage: C=0.1%, Mn=0.66%, Si=0.31%, Ni=0.22%, Cr=0.93%, Cu=0.24%, Mo=0.29%, Al=0.014%, V=0.045%, P=0.0014%, S=0.005%, N=0.007%, and the rest are Fe and unavoidable elements.

[0114] The preparation method of the seawater corrosion resistant H-beam comprises the following steps:

[0115] S1. Raw material weighing: using molten iron and / or scrap steel and master alloy as raw materials, accurately weighing and proportioning the ingredients according to the chemical composition ratio to obtain the raw materials;

[0116] S2, continuous casting: S1 raw materials are melted and continuously cast to obtain H-shaped steel slabs resistant to seawater corrosion;

[0117] S3, hot rolling: heating and keeping the S2 seawater corrosion resistant H-shaped steel slab warm, starting hot rolling, when the hot rolling is conventional hot rolling, the temperature of the heat preservation treatment is 1230°C, the starting rolling temperature is 1170-1220°C, the final rolling temperature is 1000°C, and the hot-rolled H-shaped steel plate is obtained;

[0118] S4, cooling: cooling the S3 hot-rolled H-shaped steel plate, i.e. air-cooling it to room temperature after rolling, to obtain a finished H-shaped steel product resistant to seawater corrosion.

[0119] The metallographic composition of the seawater corrosion resistant H-beam prepared in this comparative example is 79.18% ferrite structure + 20.82% pearlite structure.

[0120] The seawater corrosion-resistant H-shaped steel prepared in this comparative example has a tensile strength of 521MPa, a yield strength of 319MPa, a yield strength ratio of 0.612, an elongation of 27%, a strength-ductility product of 14.067GPa·%, a welding cold crack sensitivity coefficient of 0.184, an impact energy of 55.6J at -20°C, and a corrosion rate of 1.08g / m² after simulating seawater corrosion. h, which is 44% of Q345B.

[0121] Comparative Example 3

[0122] A seawater corrosion resistant H-shaped steel. The chemical composition of the seawater corrosion resistant H-shaped steel in this comparative example is as follows by mass percentage: C=0.05%, Mn=0.5%, Si=0.15%, Cr=0.9%, Cu=0.2%, Ti=0.04%, Al=0.55%, P=0.01%, S=0.0009%, N=0.0038%, and the rest are Fe and unavoidable elements.

[0123] The preparation method of the seawater corrosion resistant H-beam comprises the following steps:

[0124] S1. Raw material weighing: using molten iron and / or scrap steel and master alloy as raw materials, accurately weighing and proportioning the ingredients according to the chemical composition ratio to obtain the raw materials;

[0125] S2, continuous casting: S1 raw materials are melted and continuously cast to obtain H-shaped steel slabs resistant to seawater corrosion;

[0126] S3, hot rolling: heating and keeping the S2 seawater corrosion resistant H-shaped steel slab warm, starting hot rolling, when the hot rolling is conventional hot rolling, the temperature of the heat preservation treatment is 1220°C, the starting rolling temperature is 1170-1220°C, the final rolling temperature is 858°C, and the hot rolled H-shaped steel plate is obtained;

[0127] S4, curling: The S3 hot-rolled H-shaped steel plate is curled at a curling temperature of 570°C to obtain a finished H-shaped steel product resistant to seawater corrosion.

[0128] The metallographic composition of the seawater corrosion resistant H-beam prepared in this comparative example is 75.62% of ferrite structure + 24.38% of pearlite structure.

[0129] The seawater corrosion-resistant H-shaped steel prepared in this comparative example has a tensile strength of 503MPa, a yield strength of 372MPa, a yield strength ratio of 0.740, an elongation of 28%, a strength-ductility product of 14.084GPa·%, a welding cold crack sensitivity coefficient of 0.207, an impact energy of 61J at -20°C, and a corrosion rate of 1.10g / m² after simulating seawater corrosion. h, which is 45% of Q345B.

[0130] Comparative Example 4

[0131] A seawater corrosion resistant H-shaped steel. The chemical composition of the seawater corrosion resistant H-shaped steel in this comparative example is as follows by mass percentage: C=0.09%, Mn=0.72%, Si=0.28%, Ni=0.23%, Cr=0.93%, Cu=0.26%, Mo=0.17%, Al=0.18%, V=0.033%, Nb=0.015, P=0.0013%, S=0.0053%, N=0.0066%, and the rest are Fe and unavoidable elements.

[0132] The preparation method of the seawater corrosion resistant H-beam comprises the following steps:

[0133] S1. Raw material weighing: using molten iron and / or scrap steel and master alloy as raw materials, accurately weighing and proportioning the ingredients according to the chemical composition ratio to obtain the raw materials;

[0134] S2, continuous casting: S1 raw materials are melted and continuously cast to obtain H-shaped steel slabs resistant to seawater corrosion;

[0135] S3, hot rolling: heating and keeping the S2 seawater corrosion resistant H-shaped steel slab warm, starting hot rolling, when the hot rolling is conventional hot rolling, the temperature of the heat preservation treatment is 1230°C, the starting rolling temperature is 1170-1220°C, the final rolling temperature is 960°C, and the hot rolled H-shaped steel plate is obtained;

[0136] S4, cooling: cooling the S3 hot-rolled H-shaped steel plate, i.e. air-cooling it to room temperature after rolling, to obtain a finished H-shaped steel product resistant to seawater corrosion.

[0137] The metallographic composition of the seawater corrosion resistant H-beam prepared in this comparative example is 66.58% of ferrite structure + 33.42% of pearlite structure.

[0138] The seawater corrosion-resistant H-shaped steel prepared in this comparative example has a tensile strength of 593MPa, a yield strength of 356MPa, a yield strength ratio of 0.600, an elongation of 28%, a strength-ductility product of 16.604GPa·%, a welding cold crack sensitivity coefficient of 0.216, an impact energy of 117.6J at -20°C, and a corrosion rate of 1.14g / m² after simulating seawater corrosion. h, which is 47% of Q345B.

[0139] In summary, the corrosion weight loss rate of the seawater corrosion resistant H-beam prepared by the preparation methods of Examples 1, 2, 3 and Comparative Examples 1, 2, 3, 4 is compared. Figure 4 As shown, by comparison, it can be found that the corrosion rates of Examples 1, 2, and 3 in the marine atmosphere environment are lower than those of the comparative example, and the corrosion rate provided by the examples is much lower than that of Q345B steel, which is equivalent to less than 40% of the corrosion rate of Q345B steel.

[0140] The above scheme, the present invention proposes a seawater corrosion resistant H-shaped steel and a preparation method, which can solve the technical problems existing in the preparation method of seawater corrosion resistant steel, such as high cost caused by adding precious elements, high preparation cost, complicated preparation method, and the inability to synergistically improve many properties of the prepared steel, such as mechanical properties and seawater corrosion resistance.

[0141] The present invention comprehensively considers multiple factors such as mechanical properties, corrosion properties, welding properties, and cost, and reduces the addition of precious elements in the composition through reasonable composition design and calculation, thereby reducing the total amount of Nb+V+Ti and Ni+Cu+Cr+Mo, and adding rare earth elements is selected according to the situation, so that hot-rolled H-shaped steel with high comprehensive performance and low cost can be obtained.

[0142] The present invention adopts a reasonable hot processing technology, i.e. conventional hot rolling or controlled hot rolling, and selects the corresponding hot processing technology and its process parameters according to multiple factors such as mechanical properties, corrosion properties, welding properties, cost, etc., to obtain the desired organizational structure and distribution of hot-rolled H-shaped steel, so that the comprehensive performance can be greatly improved.

[0143] The seawater corrosion-resistant H-shaped steel of the present invention has a tensile strength of 486-537MPa, a yield strength of 375-463MPa, a yield strength ratio of 0.785-0.882, an elongation of not less than 35%, a welding cold crack sensitivity coefficient of 0.179-0.225, an impact energy of not less than 240J at -20°C, and a corrosion rate of 0.675-0.973g / m² after simulating seawater corrosion. h, which is less than 40% of Q345B.

[0144] The seawater corrosion resistant H-shaped steel of the present invention has a tensile strength of 487-556MPa, a yield strength of 386-482MPa, a yield strength ratio of 0.764-0.873, an elongation of not less than 40%, a welding cold crack sensitivity coefficient of 0.153-0.217, an impact energy of not less than 260J at -20°C, and a corrosion rate of 0.625-0.826g / m² after simulating seawater environment corrosion. h, which is less than 35% of Q345B.

[0145] In summary, compared with other traditional methods, the method of the present invention comprehensively considers mechanical properties, corrosion properties, welding properties, cost and other factors, and simplifies and improves the component design and preparation method, so that the prepared H-shaped steel has high strength, high strength-to-plasticity, high yield ratio, high weldability and high corrosion resistance; and has high resource utilization, low production cost, short process, easy operation, high efficiency, and is conducive to large-scale industrial production and promotion.

[0146] It should be understood that the term "and / or" in this article is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. A and B can be singular or plural. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship, but it may also indicate an "and / or" relationship. Please refer to the context for specific understanding.

[0147] In the present invention, "at least one" means one or more, and "plurality" means two or more. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single items or plural items. For example, at least one of a, b, or c can be represented by: a, b, c, ab, ac, bc, or abc, where a, b, and c can be single or multiple.

[0148] It should be understood that in various embodiments of the present invention, the size of the serial numbers of the above-mentioned processes does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0149] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A seawater corrosion resistant H-beam, characterized in that: The chemical composition of the seawater corrosion resistant H-beam is as follows by mass percentage: C 0.05-0.1%, Mn 0.50-0.90%, Si 0.15-0.35%, Ni 0.15-0.25%, Cr 0.6-1.0%, Cu0.2-0.3%, Cu:Ni=1.0-1.2%, Mo 0.06-0.15%, Sb 0.04-0.09%, Al<0.10%, Ni+Cu+Mo 0.41-0.6%, V+Nb+Ti 0.02-0.06%, impurity elements P+S+O<0.04%, and the rest are Fe and unavoidable elements.

2. The seawater corrosion resistant H-beam according to claim 1, characterized in that: Rare earth RE≤0.02% may be added to the seawater corrosion resistant H-shaped steel.

3. The seawater corrosion resistant H-beam according to claim 1, characterized in that: The metallographic composition of the seawater corrosion resistant H-shaped steel is 81.81-100% of ferrite structure + 0-18.19% of pearlite.

4. The seawater corrosion resistant H-beam according to claim 1, characterized in that: The seawater corrosion resistant H-shaped steel has a tensile strength of 486-537MPa, a yield strength of 375-463MPa, a yield strength ratio of 0.785-0.882, an elongation of not less than 35%, a welding cold crack sensitivity coefficient of 0.179-0.225, an impact energy of not less than 240J at -20°C, and a corrosion rate of 0.675-0.973g / m² after simulating seawater environment corrosion. h, which is less than 40% of Q345B.

5. The seawater corrosion resistant H-beam according to claim 2, characterized in that: When rare earth RE is added, the tensile strength of the H-shaped steel resistant to seawater corrosion is 487-556MPa, the yield strength is 386-482MPa, the yield strength ratio is 0.764-0.873, the elongation is not less than 40%, the welding cold crack sensitivity coefficient is 0.153-0.217, the impact energy is not less than 260J at -20°C, and the corrosion rate after simulating seawater environment corrosion is 0.625-0.826g / m² h, which is less than 35% of Q345B.

6. A method for preparing seawater corrosion resistant H-beam according to claim 1, characterized in that: The preparation method of the seawater corrosion resistant H-beam comprises the following steps: S1. Raw material weighing: using molten iron and / or scrap steel and master alloy as raw materials, accurately weighing and proportioning the ingredients according to the chemical composition ratio to obtain the raw materials; S2, continuous casting: S1 raw materials are melted and continuously cast to obtain ingots for H-beams resistant to seawater corrosion; S3, hot rolling: heating and keeping the S2 seawater corrosion resistant H-shaped steel slab warm, and starting hot rolling to obtain a hot-rolled H-shaped steel plate; S4, cooling: cooling the hot-rolled H-shaped steel plate in S3 to obtain a finished H-shaped steel product resistant to seawater corrosion.

7. The method for preparing seawater corrosion resistant H-beam according to claim 6, characterized in that: The hot rolling in S3 is conventional hot rolling or controlled hot rolling.

8. The method for preparing seawater corrosion resistant H-beam according to claim 6, characterized in that: The cooling treatment in S4 includes forced cooling to 590-700°C after rolling and then air cooling to room temperature, or air cooling to 590-700°C and then continuing air cooling to room temperature.

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