Marine atmospheric corrosion resistant hot-rolled h-beam and method for manufacturing the same

Abstract

The application provides a hot-rolled H-shaped steel resistant to marine atmospheric corrosion and a manufacturing method thereof, and belongs to the technical field of H-shaped steel production. The chemical composition and mass fraction of the hot-rolled H-shaped steel are as follows: C: 0.07-0.12%, Si+Mn: 0.80-1.2%, Ni+Cu: 0.30-0.60%, 0.8 The chemical composition is smelted and cast into a steel billet, the steel billet is subjected to heating, hot rolling and post-rolling cooling, the yield strength of the H-shaped steel is 360-420 MPa, the tensile strength is 490-570 MPa, the elongation is greater than 30%, and the impact energy KV2 at-20 DEG C is greater than 120 J; the corrosion rate of the steel in a marine atmospheric environment is equivalent to 35% or less of that of Q355B, and the electrode potential of the corroded steel is-0.40-0.53 V.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of H-shaped steel production, and particularly relates to a hot-rolled H-shaped steel resistant to marine atmospheric corrosion and a manufacturing method thereof. BACKGROUND

[0002] The development and application of high-strength steel are indispensable to the development and utilization of the ocean, and the demand for marine engineering steel will continue to expand, and the research and development of marine engineering steel have become a focus of widespread attention. However, due to the complexity of the marine environment, marine engineering steel will be affected by marine environmental factors during service, resulting in problems such as corrosion cracking and mechanical property degradation of the steel due to electrochemical corrosion, which will shorten the service life of marine equipment.

[0003] With the development of the environment of marine engineering steel to high-cold polar regions and humid and harsh sea areas, there is a higher demand for the strength, toughness and marine environment corrosion resistance of marine engineering H-shaped steel. Therefore, it has become an inevitable trend to produce a marine atmospheric corrosion-resistant H-shaped steel.

[0004] After searching, Chinese patent CN 113528970 A discloses a low-compression-ratio yield strength 355MPa-grade thick heavy hot-rolled H-shaped steel and its production method and application. The hot-rolled H-shaped steel includes the following chemical components by weight percentage: C: 0.13~0.20%, Si: 0.15~0.40%, Mn: 1.10~1.50%, P: ≤0.035%, S: ≤0.035%, V: 0.030~0.060%, B: 0.0008% ~0.0015%, Nb: 0.02~0.05%, N: 0.015~0.020%, 3.5≤(Nb+V) / N≤5.5, Als: ≤0.005%, and the rest is Fe and unavoidable impurities. The obtained hot-rolled H-shaped steel has good mechanical properties, with a yield strength ≥355MPa, a tensile strength ≥570MPa, an elongation ≥20%, and a 0℃ longitudinal V-type impact energy KV2≥85J. The hot-rolled H-shaped steel provided by the prior art has a high carbon content and adds B element, and has poor welding performance and low-temperature impact toughness. Due to the addition of a large amount of Mn element, the degree of segregation in the steel plate is increased, and the low-temperature toughness and corrosion resistance of the steel plate are reduced. The corrosion resistance is not described.

[0005] Chinese patent CN 101760704 A discloses a vanadium-nitrogen-containing economic high-strength high-weathering hot-rolled H-shaped steel and its rolling method. The H-shaped steel includes the following weight percentages of chemical components: C: 0.07-0.12%, Si: 0.30-0.55%, Mn: 1.30-1.55%, P≤0.045%, S:≤0.010%, Cr: 0.20-0.30%, Ni: 0.15-0.30%, Cu: 0.25-0.35%, V: 0.010~0.015%, N: 0.10~0.015%, Alt: 0.006-0.03%, and the rest is Fe and unavoidable impurities. This prior art is similar to the present application, both of which obtain economic weathering steel by adding an appropriate amount of vanadium-nitrogen alloy. However, due to the high content of added Mn, the resistance to marine atmospheric corrosion performance deteriorates sharply, with a corrosion rate of 2.49~2.53g / m 2 h, which is 55% of the corrosion rate of Q345B steel, and poor corrosion performance.

[0006] Chinese patent CN 106947913 A discloses a high-strength high-toughness hot-rolled weathering steel plate and its preparation method. The hot-rolled weathering steel plate includes the following weight percentages of chemical components: C: 0.05%~0.10%, Si: 0.10%~0.50%, Mn: 1.00%~1.30%, P:≤0.015%, S:≤0.010%, Cr: 0.30%~0.70%, Ni: 0.10%~0.40%, Cu: 0.25%~0.50%, Al: 0.020% ~0.050%, Nb: 0.01%~0.04%, Ti: 0.010%~0.030%, and the rest is Fe and unavoidable impurities. This prior art is based on a traditional hot continuous rolling production line, and develops a high-strength high-toughness hot-rolled weathering steel plate suitable for thick specifications, with a yield strength of 450-500MPa, a tensile strength≥550MPa, an elongation of 25.0%-30.0%, and a longitudinal impact force at -60°C >300J. However, this product is a steel plate produced from a continuous casting billet, which has a large difference in process from the H-shaped steel produced from an abnormal billet. Moreover, due to the high content of added Mn, the resistance to marine atmospheric corrosion performance deteriorates sharply, with an average corrosion rate of 2.22~2.48g / m 2 h in marine environment, which is only 55% of the corrosion rate of Q345B steel.

[0007] Chinese patent CN112795844 A discloses a low-carbon Cr-Ni series high-strength corrosion-resistant steel and its preparation method. The corrosion-resistant steel comprises the following chemical composition by weight percentage: C: 0.01-0.03%, Si: 0.1-0.5%, Mn: 0.5-1.0%, Ni: 1.0-2.0%, Cr: 3.0-10.0%, Cu: 0.2-0.5%, N: 0.02-0.06%, P: 0.04-0.1%, S: ≤0.005%, with the remainder being Fe and unavoidable impurities. The corrosion rate of this material in a marine environment is 2.19-3.08 g / m³. 2 •h. The steel in this prior art contains a large amount of expensive alloying elements such as Cu, Ni, and Cr, with 4.2%≤Cu+Ni+Cr≤12.5%, resulting in high alloy costs; the steel also has a high P content, which will deteriorate the weldability and toughness of the steel, especially reducing the low-temperature impact toughness, but the low-temperature toughness is not mentioned.

[0008] Chinese Patent CN 105886961 A discloses a high-performance hot-rolled H-beam resistant to marine atmospheric corrosion and its preparation method. The H-beam comprises the following chemical composition by weight percentage: C: 0.015~0.075%, Si: 0.20~0.65%, Mn: 0.40~1.60%, P: ≤0.025%, S: ≤0.010%, Mo: 0.20~0.70%, Cu: 0.30~1.20%, Ni: 0.90~3.50%, Sb: 0.035~0.10%, Nb: 0.015~0.100%, Ti: 0.010~0.050%, Al: 0.015~0.100%, with the remainder being Fe and unavoidable impurities. The H-beam provided by this prior art exhibits good toughness and plasticity, excellent resistance to marine atmospheric corrosion, and excellent weldability. However, it contains a large amount of expensive alloying elements such as Cu, Ni, and Mo, with a content of 1.43%≤Cu+Ni+Mo+Sb+Nb+Ti≤5.65%, resulting in high alloy costs.

[0009] Chinese Patent CN 108396228 A discloses a high weather-resistant hot-rolled H-beam with a yield strength of 450 MPa and its heat treatment process. The high weather-resistant hot-rolled H-beam comprises the following chemical composition by weight percentage: C: 0.06-0.10%, Si: 0.20-0.40%, Mn: 0.40-0.70%, P≤0.035%, S:≤0.010%, Cr: 2.00-3.50%, Ni: 0.30-0.50%, Cu: 0.30-0.50%, V: 0.015~0.035%, Alt: 0.02-0.04%, with the remainder being Fe and unavoidable impurities. The high weather-resistant hot-rolled H-beam obtained by this prior art using a heat treatment process has a yield strength ≥480 MPa, tensile strength ≥600 MPa, elongation after fracture ≥20%, and KV2 type impact toughness ≥65 J at -40℃. However, the Cr content in H-beams reaches 2.00-3.50%, and 2.61%≤Cu+Ni+Cr+V≤4.53%, which increases the alloy cost and makes the hot rolling pressure greater. At the same time, the use of heat treatment processes increases production costs.

[0010] In existing technologies, weather-resistant hot-rolled H-beams have a high Mn content, which easily increases the degree of segregation within the steel plate, reducing its low-temperature toughness and resistance to marine atmospheric corrosion. Due to the micro-cell effect between cementite and ferrite in pearlite, the corrosion rate is high. Adding more precious alloys increases the production cost of the steel. Furthermore, some alloying elements (Mo, Nb) lead to the formation of bainite or MA structures, requiring further heat treatment after hot rolling, which further increases the production cost of hot-rolled H-beams. Therefore, it is necessary to develop a cost-effective and high-performance weather-resistant hot-rolled H-beam, specifically one resistant to marine atmospheric corrosion. Summary of the Invention

[0011] This invention provides a hot-rolled H-beam resistant to marine atmospheric corrosion and its manufacturing method. Through reasonable chemical composition design, vanadium-nitrogen alloy and appropriate amounts of Cu, Ni and Cr elements are added, while trace amounts of Ce element are selectively added as needed, which greatly improves the corrosion resistance of hot-rolled H-beams in marine atmospheric environments.

[0012] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0013] The hot-rolled H-beams of this invention have the following chemical composition by mass ratio: C: 0.07-0.12%, Si+Mn: 0.80-1.2%, Ni+Cu: 0.30-0.60%, 0.8 < Ni / Cu < 1.25, Cr: 0.40-0.70%, V: 0.03-0.045%, 2.5 ≤ V / N ≤ 3.5, Ca: 0.001-0.002%, P ≤ 0.020%, S ≤ 0.005%, O ≤ 40 ppm, with the remainder being Fe and unavoidable impurity elements. The carbon equivalent (CEQ) of the steel is 0.39-0.45%.

[0014] Preferably, its chemical composition further includes Al<0.03%, Ce≤0.03%, and 0.6≤Ce / (S+O)≤4.5.

[0015] This invention also provides a method for preparing the aforementioned hot-rolled H-beams, comprising the following steps: melting and casting a steel billet with the above-mentioned chemical composition, heating it to 1180-1230℃ and then hot-rolling it to a final rolling temperature of 850-1000℃, cooling it to 600-750℃ at a rate of 2.5-30℃ / s after rolling, and then air-cooling it to room temperature. Because hot-rolled H-beams are suitable for high-temperature final rolling and temperature-controlled rolling, air cooling can meet performance control requirements. If temperature-controlled rolling and post-rolling controlled cooling are used, the steel's strength and toughness will be even higher.

[0016] Preferably, the hot-rolled H-beam has a yield strength of 360-420 MPa, a tensile strength of 490-570 MPa, an elongation of >30%, and an impact energy of >120 J at -20℃; in a marine atmospheric environment, the corrosion rate of the H-beam is ≤35% × the corrosion rate of Q355B steel, and the electrode potential of the steel after corrosion is -0.40~-0.53V.

[0017] Preferably, the room temperature microstructure of the hot-rolled H-beam is ferrite and a small amount of pearlite.

[0018] The hot-rolled H-beams, having undergone long-term service in marine atmospheric environments, form a corrosion and rust layer with a low elastic modulus and good adhesion. They can be used in coastal building structures, coastal bridges, offshore oil drilling platforms, and other structures subjected to dynamic loads, and are also suitable for cold regions below -20℃.

[0019] The roles of each element in this invention are analyzed as follows:

[0020] Carbon (C): Carbon is a fundamental element in steel and plays a crucial role in improving its strength. However, excessive carbon content can negatively impact the steel's resistance to atmospheric corrosion. Furthermore, carbon affects the steel's weldability, cold brittleness, and stamping properties. Therefore, in this invention, the carbon mass percentage is controlled between 0.08% and 0.12%.

[0021] Silicon (Si): Si acts as a solid solution strengthening agent in steel and serves as a reducing agent and deoxidizer during smelting. Si also improves the corrosion resistance of steel against marine atmospheres. When Si is used in combination with Cu, P, and Cr, it can effectively enhance the corrosion resistance of steel. However, excessively high Si content can reduce the low-temperature toughness and weldability of the steel.

[0022] Manganese (Mn): Manganese is a solid solution strengthening element in steel. Adding an appropriate amount of Mn to steel is beneficial for improving the strength and hardenability of the steel plate. However, a high Mn content increases the degree of segregation within the steel plate, reduces the uniformity of its mechanical properties and low-temperature toughness, and also adversely affects its formability. Furthermore, a high Mn content drastically deteriorates the steel plate's resistance to marine atmospheric corrosion. Therefore, in this invention, the mass percentage of Mn+Si is controlled between 0.80% and 1.20%.

[0023] Nickel (Ni): Nickel is a relatively stable element. Adding Ni oxide to steel can improve cation selectivity and prevent Cl from forming in the rust layer. - Ion diffusion can significantly improve the corrosion resistance of steel in marine atmospheric environments, while also effectively enhancing its strength and toughness. Therefore, theoretically, the higher the Ni content in steel within a certain range, the better. However, Ni is a very expensive alloying element, and from the perspective of low-cost mass production, the Ni content should be controlled.

[0024] Copper (Cu): Copper is the most important alloying element for improving atmospheric corrosion resistance. To enhance atmospheric corrosion resistance and reduce the hot working sensitivity of Cu-containing steel, it needs to be used in combination with Ni to improve hot cracking. However, adding too high a content of Cu can easily lead to copper embrittlement, deteriorating the surface properties of the steel. Therefore, in this invention, the mass percentage of Cu+Ni is controlled at 0.30-0.60%, and the Ni / Cu ratio is 0.8-1.25.

[0025] Chromium (Cr): Chromium can form a dense oxide film on the surface of steel, improving its passivation ability, slowing down rust growth, and enhancing its resistance to marine atmospheric corrosion. Simultaneously, chromium is a solid solution strengthening element, enhancing the hardenability of steel and delaying the austenite-ferrite transformation. Chromium is a carbide-forming element; high Cr content leads to Cr reacting with C to form M... 23 C7 type carbides reduce the corrosion resistance of Cr and may also reduce the toughness and weldability of steel. Therefore, in this invention, the Cr mass percentage is controlled at 0.40-0.70%.

[0026] Vanadium (V) and nitrogen (N): The addition of nitrogen promotes the precipitation rate of V in the alloy system, significantly increasing the volume fraction of V(C,N) particles and enhancing the precipitation strengthening effect of vanadium. Vanadium, a strong carbide-forming element, has a strong binding ability with C and N, allowing fine and dispersed VN or V(C,N) particles to precipitate in the γ phase, thus achieving a fine-grain strengthening effect and greatly improving the strength and toughness of the steel. Simultaneously, as a corrosion-resistant alloying element, V increases the self-corrosion potential of steel, which is beneficial to its resistance to marine atmospheric corrosion. However, vanadium alloys have a high unit price, and excessive addition will increase production costs. The introduction of N into the molten steel by vanadium-nitrogen alloys may lead to further nitrogen absorption or loss during the smelting process. To better achieve the precipitation strengthening and fine-grain strengthening effects of vanadium, the vanadium-nitrogen ratio should be controlled. Therefore, in this invention, the mass percentage of V is controlled between 0.030-0.045%, and 2.5 ≤ V / N ≤ 3.5. This ensures that the vanadium-nitrogen ratio is within a certain range, maximizing the strengthening effect of vanadium and nitrogen in steel.

[0027] Aluminum (Al): Aluminum is a strong deoxidizing element and can be used to remove oxygen from molten steel. However, unremoved Al₂O₃ inclusions in molten steel can cause localized corrosion of the matrix surrounding the inclusions, and large Al₂O₃ inclusions can also reduce the toughness of the steel. Aluminum can also inhibit nitrogen solidification in ferrite, forming AlN to suppress grain coarsening. However, AlN tends to aggregate and grow in molten steel, increasing crack susceptibility and making the surface prone to cracking. Furthermore, excessive Al in the steel can preempt nitrogen, reducing the amount of second-phase particles such as V (C,N) precipitated and weakening the effect of V. Therefore, in this invention, the mass percentage of Al is controlled at 0.02-0.04%.

[0028] Rare earth element Ce: Rare earth elements are extremely reactive and act as strong deoxidizers and desulfurizers, primarily purifying steel by forming inclusions such as CeO2, Ce2O2S, or CeAlO3. Simultaneously, the fine oxides formed by Ce promote the precipitation of Nb and V, refining the grain size and altering the state of inclusions in the steel. The corrosion products formed by rare earth inclusions (CeO2, Ce2O2S, or CeAlO3) during corrosion are alkaline and preferentially corrode the matrix, reducing corrosion initiation points and thus improving the steel's atmospheric corrosion resistance. Secondly, the corrosion of rare earth elements dissolved in steel alters the mechanical properties of the rust layer, reducing its elastic modulus, stabilizing its structure, improving its adhesion, and enhancing its corrosion resistance. Thirdly, Ce can reduce aluminum oxides in molten steel, preventing the influence of alumina inclusions on plasticity and toughness. Furthermore, rare earth elements can modify inclusions, causing carbides, sulfides, etc., to spheroidize, refine, and uniformly distribute, thereby improving the ductility and toughness of steel. Therefore, in this invention, the mass percentage of rare earth element Ce is controlled at ≤0.03%, and the Ce / (S+O) mass ratio is controlled within the range of 0.6≤Ce / (S+O)≤4.5, based on the content of S and O impurities in the steel.

[0029] Phosphorus and sulfur (P and S) are impurity elements that negatively impact the plasticity, toughness, and weldability of steel. While the combined addition of P and Cu to steel exhibits a better synergistic effect, excessive P content deteriorates weldability and toughness, particularly drastically reducing low-temperature impact toughness. It also facilitates localized segregation, forming banded structures. S readily forms MnS during segregation, causing weld cracks, reduced toughness, and resistance to lamellar tearing. Therefore, in this invention, the mass percentages of P and S are controlled at P ≤ 0.020% and S ≤ 0.005%.

[0030] The key technical point of this invention is:

[0031] 1. The difference between this invention and the prior art CN 108396228 A is that the content of precious alloying elements is much lower than that of the prior art, which greatly reduces the cost of the alloy; and this invention has lower corrosion resistance and better corrosion resistance in marine atmospheric environments; in addition, this invention does not require further heat treatment after rolling, which reduces production steps and lowers production costs.

[0032] 2. The difference between this invention and the prior art CN 105886961 A is that the corrosion rate of this invention is lower in marine atmospheric environment and the corrosion resistance is better; and the use of vanadium-nitrogen alloy instead of vanadium-iron alloy for vanadium alloying reduces the addition of expensive alloying elements and lowers the alloy cost.

[0033] 3. Compared with the prior art CN 106947913 A, the present invention differs in that although the content of the added precious alloying elements is similar, the present invention has better low-temperature toughness and formability; lower corrosion rate in marine atmospheric environment and better corrosion resistance; and the present invention can better control the content of Mn element, effectively improving the mechanical properties and corrosion resistance of steel.

[0034] 4. Compared with the prior art CN 112795844 A, the present invention has higher strength, better weldability and cold crack sensitivity; lower corrosion rate and better corrosion performance in marine atmospheric environment; in terms of precious alloy element content, the content of the present invention is much lower than that of the prior art, which has better economic efficiency; and the present invention better controls the content of P element, which further improves the weldability and toughness of steel.

[0035] Table 1 shows the relevant data of this invention and the comparison information of the prior art.

[0036] Table 1

[0037]

[0038] As can be seen from the table above, the total content of precious alloying elements Nb+V+Ti+Ni+Cu+Cr in the weathering steel adapted to marine atmospheric corrosion environment is low, which gives it an advantage in alloy cost; in terms of corrosion resistance, the corrosion rate is relatively low, which gives it a competitive advantage.

[0039] Compared with the prior art, the outstanding advantages of the present invention are as follows:

[0040] (1) This invention incorporates appropriate amounts of Cu, Ni and Cr elements through a reasonable chemical composition design, and uses vanadium-nitrogen alloy to replace vanadium-iron alloy for vanadium alloying, which significantly improves the strength of steel and enhances its comprehensive performance. The addition of trace rare earth element Ce can be selected to further improve the toughness and corrosion resistance of the material while ensuring high strength.

[0041] (2) This invention proposes a method for manufacturing hot-rolled H-beams resistant to marine atmospheric corrosion. After smelting, continuous casting, heating, high-temperature final rolling (950-1000℃) or controlled final rolling (850-950℃), hot-rolled H-beams with the required properties can be obtained without heat treatment process, which effectively improves industrial production efficiency and reduces production costs.

[0042] (3) The hot-rolled H-beam described in this invention not only has high strength and toughness, but also excellent corrosion resistance. Its yield strength is 360-420MPa, tensile strength is 490-570MPa, elongation is >30%, and impact energy at -20℃ is >200J. In marine atmospheric environment, the corrosion rate is equivalent to less than 35% of Q355B, and the electrode potential of the steel after corrosion is -0.40~-0.53V. Attached Figure Description

[0043] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0044] Figure 1 The metallographic structure of the steel in Example 1 of this invention;

[0045] Figure 2 The graph shows the corrosion rate of six types of steel subjected to a 168-hour salt spray corrosion test in the embodiments and comparative examples of this invention. Detailed Implementation

[0046] To make the technical problems, technical solutions and advantages of the present invention clearer, a detailed description will be given below in conjunction with the accompanying drawings and specific embodiments.

[0047] This invention provides a hot-rolled H-beam resistant to marine atmospheric corrosion. The hot-rolled H-beam has the following alloy element mass percentages and chemical composition: C: 0.07-0.12%, Si+Mn: 0.80-1.2%, Ni+Cu: 0.30-0.60%, 0.8 < Ni / Cu < 1.25, Cr: 0.40-0.70%, V: 0.03-0.045%, 2.5 ≤ V / N ≤ 3.5, Ca: 0.001-0.002%, P ≤ 0.020%, S ≤ 0.005%, O ≤ 40 ppm, with the remainder being Fe and unavoidable impurities, and a carbon equivalent (CEQ) of 0.39-0.45%. Preferably, its chemical composition includes Al < 0.03%, Ce ≤ 0.03%, and 0.6 ≤ Ce / (S+O) ≤ 4.5. The yield strength of hot-rolled H-beams is 360-420 MPa, the tensile strength is 490-570 MPa, the elongation is >30%, and the impact energy at -20℃ is >120 J. The room temperature microstructure of H-beams consists of ferrite and a small amount of pearlite.

[0048] The following description, in conjunction with specific embodiments, illustrates this point.

[0049] Example 1

[0050] A type of hot-rolled H-beam resistant to marine atmospheric corrosion, the alloy element content, by mass percentage, is as follows:

[0051] Carbon composition: C: 0.12%, Si: 0.15%, Mn: 0.75%, Cr: 0.56%, Cu: 0.276%, Ni: 0.274%, V: 0.038%, N: 0.014%, Ca: 0.0015%, P: 0.0017%, S: 0.0032%, O: 0.0039%, with the remainder being Fe. Carbon equivalent (CEQ): 0.40%.

[0052] The steel billet, after being smelted and cast, was heated to 1230℃ and then hot-rolled. The final rolling temperature was 960℃. After rolling, it was cooled to 600℃ at a rate of 12℃ / s and then air-cooled to room temperature to obtain the final sample. Its yield strength was 378MPa, tensile strength was 537MPa, elongation was 35%, impact energy at -20℃ was 206J, and the corrosion rate of the steel after 168h corrosion in a marine atmospheric environment was 1.150g / m²∙h.

[0053] Example 2

[0054] A type of hot-rolled H-beam resistant to marine atmospheric corrosion, the alloy element content, by mass percentage, is:

[0055] C: 0.11%, Si: 0.20%, Mn: 0.80%, Cr: 0.67%, Cu: 0.28%, Ni: 0.28%, V: 0.036%, N: 0.010%, Ca: 0.0018%, P: 0.0015%, S: 0.0048%, O: 0.0036%, with the remainder being Fe. Carbon equivalent (CEQ): 0.42%.

[0056] The steel billet, after being smelted and cast, was heated to 1230℃ and then hot-rolled. The final rolling temperature was 880℃. After rolling, it was cooled to 600℃ at a rate of 10℃ / s and then air-cooled to room temperature to obtain the final sample. Its yield strength was 385MPa, tensile strength was 556MPa, elongation was 32%, impact energy at -20℃ was 232J, and the corrosion rate of the steel after 168h of corrosion in a marine atmospheric environment was 1.045g / m²∙h.

[0057] Example 3

[0058] A type of hot-rolled H-beam resistant to marine atmospheric corrosion, the alloy element content, by mass percentage, is:

[0059] Carbon composition: C: 0.10%, Si: 0.25%, Mn: 0.65%, Cr: 0.65%, Cu: 0.22%, Ni: 0.24%, V: 0.030%, N: 0.0092%, Ca: 0.0014%, P: 0.0017%, S: 0.0045%, O: 0.0037%, Ce: 0.008%, Al: 0.023%, with the remainder being Fe. Carbon equivalent (CEQ): 0.43%.

[0060] The steel billet, after being smelted and cast, was heated to 1230℃ and then hot-rolled. The final rolling temperature was 880℃. After rolling, it was cooled to 600℃ at a rate of 10℃ / s and then air-cooled to room temperature to obtain the final sample. Its yield strength was 396MPa, tensile strength was 568MPa, elongation was 36%, impact energy at -20℃ was 247J, and the corrosion rate of the steel after 168h of corrosion in a marine atmospheric environment was 0.976g / m²∙h.

[0061] Comparative Example 1

[0062] A type of hot-rolled H-beam resistant to marine atmospheric corrosion, the alloy element content, by mass percentage, is:

[0063] C: 0.11%, Si: 0.30%, Mn: 0.50%, Cr: 0.67%, Cu: 0.32%, Ni: 0.28%, V: 0.035%, N: 0.012%, Ca: 0.0015%, P: 0.004%, S: 0.004%, O: 0.0036%, with the remainder being Fe and unavoidable impurities.

[0064] The steel billet, after being smelted and cast, was heated to 1240℃ and then hot-rolled. The final rolling temperature was 940℃. After cooling to room temperature, it was reheated to 550℃ and held for 5 hours to obtain the final sample. The yield strength was 365MPa, the tensile strength was 512MPa, the elongation was 23%, and the impact energy at -20℃ was 89J.

[0065] Comparative Example 1 employed a post-rolling annealing process, while the Example did not require a heat treatment process, effectively improving industrial production efficiency and reducing production costs. The steel in the Example had better mechanical properties. Furthermore, the corrosion rate of Comparative Example 1 after 168 hours of corrosion in a marine atmospheric environment was 1.46 g / m²∙h, which was higher than the corrosion rate of the Example, indicating relatively poor corrosion resistance.

[0066] Comparative Example 2

[0067] A type of hot-rolled H-beam resistant to marine atmospheric corrosion, the alloy element content, by mass percentage, is:

[0068] C: 0.07%, Si: 0.30%, Mn: 1.00%, Cr: 0.43%, Cu: 0.25%, Ni: 0.30%, V: 0.032%, N: 0.011%, Ca: 0.0012%, P: 0.0012%, S: 0.003%, O: 0.0037%, with the remainder being Fe and unavoidable impurities.

[0069] The steel billet, after being smelted and cast, was heated to 1230℃ and then hot-rolled. The final rolling temperature was 880℃. After rolling, it was cooled to 600℃ at a rate of 10℃ / s and then air-cooled to room temperature to obtain the final sample. The yield strength was 369MPa, the tensile strength was 514MPa, the elongation was 25%, and the impact energy at -20℃ was 73J.

[0070] Compared with Examples 1-3, the Mn content in Comparative Example 2 was increased to 1.00%, and the mechanical properties of the steel in the example were better; moreover, the corrosion rate of Comparative Example 2 after 168 hours of corrosion in a marine atmospheric environment was 1.54 g / m²∙h, which was higher than the corrosion rate of the examples, and its corrosion resistance was relatively poor.

[0071] Comparative Example 3

[0072] A type of hot-rolled H-beam resistant to marine atmospheric corrosion, the alloy element content, by mass percentage, is:

[0073] C: 0.09%, Si: 0.18%, Mn: 1.20%, Cr: 0.56%, Cu: 0.22%, Ni: 0.30%, V: 0.040%, N: 0.011%, Ca: 0.0010%, P: 0.015%, S: 0.004%, O: 0.0036%, with the remainder being Fe and unavoidable impurities.

[0074] The steel billet, after being smelted and cast, was heated to 1230℃ and then hot-rolled. The final rolling temperature was 880℃. After rolling, it was cooled to 600℃ at 10℃ / s and then air-cooled to room temperature to finally obtain the sample. The yield strength was 367MPa, the tensile strength was 509MPa, the elongation was 23%, and the impact energy at -20℃ was 68J.

[0075] Compared with Comparative Example 2, Comparative Example 3 has a further increased Mn content, resulting in better mechanical properties of the steel in the example. Furthermore, the corrosion rate of Comparative Example 3 after 168 hours of corrosion in a marine atmospheric environment is 1.73 g / m²∙h, which is higher than the corrosion rate of the example, indicating relatively poor corrosion resistance.

[0076] Figure 1 The metallographic structure of the steel in Example 1 of the present invention shows that it contains ferrite and a small amount of pearlite, wherein the bright polygonal grain structure is ferrite and the black area is pearlite. Figure 2The graph shows the corrosion rate of six steels tested for 168 hours in the salt spray corrosion test of the embodiments and comparative examples of the present invention. It can be seen that under the same corrosion time in the marine atmospheric environment, the corrosion rates of Examples 1, 2 and 3 are all lower than the corrosion rates of the comparative examples.

[0077] The mechanical properties and corrosion rates of the steels in the above embodiments and comparative examples are compared in Tables 2 and 3. It can be seen that the mechanical properties of Examples 1, 2, and 3 are all superior to those of the comparative examples. The corrosion rates of Examples 1, 2, and 3 under marine atmospheric corrosion conditions are all lower than those of the comparative examples. Furthermore, the corrosion rate of the H-beams provided by the embodiments is significantly lower than that of Q355B steel, equivalent to less than 35% of the corrosion rate of Q355B steel.

[0078] Table 2 Comparison of mechanical properties of different steels

[0079]

[0080] Table 3 Comparison of corrosion rates of different steels after 168 hours of corrosion.

[0081]

[0082] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A hot-rolled H-beam resistant to marine atmospheric corrosion, characterized in that, The hot-rolled H-beam has the following chemical composition by mass ratio: C: 0.07-0.12%, Si+Mn: 0.80-1.2%, Ni+Cu: 0.30-0.60%, 0.8 < Ni / Cu < 1.25, Cr: 0.40-0.70%, V: 0.03-0.045%, 2.5 ≤ V / N ≤ 3.5, Ca: 0.001-0.002%, P ≤ 0.020%, S ≤ 0.005%, O ≤ 40ppm, Al < 0.03%, Ce ≤ 0.03%, and 0.6 ≤ Ce / (S+O) ≤ 4.5, with the remainder being Fe and unavoidable impurity elements; The carbon equivalent (CEQ) of the hot-rolled H-beam is 0.39-0.45%.

2. The marine atmospheric corrosion resistant hot-rolled H-beam according to claim 1, characterized in that, The hot-rolled H-beam has a yield strength of 360-420MPa, a tensile strength of 490-570MPa, an elongation of >30%, and an impact energy of >120J at -20℃.

3. The marine atmospheric corrosion resistant hot-rolled H-beam according to claim 2, characterized in that, In a marine atmospheric environment, the corrosion rate of the H-beam is ≤35% × the corrosion rate of Q355B steel, and the electrode potential of the steel after corrosion is -0.40~-0.53V.

4. The method for manufacturing hot-rolled H-beams resistant to marine atmospheric corrosion according to claim 1, characterized in that, The steel billet, which is smelted and cast with the chemical composition, is heated to 1180-1230℃ and then hot-rolled. The final rolling temperature is 850-1000℃. After rolling, it is cooled to 600-750℃ at a rate of 2.5-30℃ / s and then air-cooled to room temperature.

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