Marine organism corrosion resistant high-strength ship plate and manufacturing method thereof

Abstract

The invention belongs to the field of metal material production, and particularly relates to a marine organism corrosion-resistant high-strength ship deck and a manufacturing method thereof, and the marine organism corrosion-resistant high-strength ship deck comprises the following components in percentage by weight: 0.030 to 0.120 percent of C, 0.050 to 0.250 percent of Si, 0.80 to 1.30 percent of Mn, 0.006 to 0.020 percent of P, less than or equal to 0.005 percent of S, 0.040 to 0.080 percent of Nb, 0.050 to 0.150 percent of V, 0.0220 to 0.0280 percent of N, 1.00 to 2.00 percent of Cu, 1.00 to 2.00 percent of Ni, 0.50 to 1.00 percent of Cr, 0.006 to 0.030 percent of Ti, 0.020 to 0.050 percent of Als, 0.20 to 0.70 percent of Sb, 0.20 to 0.70 percent of Sn and the balance of Fe. The material has the advantage of excellent marine organism corrosion resistance.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of metal material production, and particularly relates to a high-strength ship plate resistant to marine biological corrosion and a manufacturing method. BACKGROUND

[0002] Ship serves in the marine environment, and has to withstand the action of wind and wave, rain and snow, low temperature and other harsh environments for a long time, so the ship steel is required to have good strength and toughness. In addition, the corrosion effect of the marine environment also has a great influence on the service life of the ship, especially the corrosion of marine organisms to the steel plate, which has attracted more and more attention in recent years. The biological corrosion is mainly local corrosion, and the occurrence and development of corrosion are unpredictable in time and space, so the safety problem caused thereby is more and more prominent. For the ship, the attachment of marine organisms on the outer surface of the ship body will also significantly increase the surface friction resistance, so as to increase the fuel consumption of the ship and reduce the speed. In order to solve the adverse effects of marine organisms, the development of ship steel resistant to marine biological fouling is the best technical scheme.

[0003] Currently, the ship steel with marine bio-corrosion resistance is mostly added with specific element combination to improve its marine bio-corrosion resistance. Patent application No. CN202011054693.4 discloses a kind of corrosion and bio-attachment resistant EH690 steel plate and its manufacturing method, its chemical composition is: C: 0.09%-0.12%, Si: 0.15%-0.35%, Mn: 1.0%-1.5%, P: 0.02%-0.03%, S≤0.01%, Als: 0.01%-0.03%, Ni: 1.5%-3.0%, Cr: 0.3-0.6%, Mo: 0.3-0.5%, Cu: 0.5-1.5%, V: 0.03%-0.06%, Ti: 0.005%-0.02%, B: 0.0005%-0.001%, Sb: 0.005%-0.3%, Sn: 0.005-0.3%, the balance is iron and inevitable impurities, the production process is: one-stage open rolling temperature 1000-1050℃, two-stage open rolling temperature 900-1000℃, finish rolling temperature 900-950℃, quenching temperature 830-870℃, holding time 1.0-2.0min / mm, tempering temperature 600-630℃, holding time 2-3min / mm, tempering cooling rate 5-15℃ / s. The steel plate has excellent marine environment corrosion resistance, but its process adopts quenching and tempering process, the process is complex, and the production cost is increased. Patent application No. CN202210685312.5 discloses a kind of 960MPa grade ultra-high strength steel plate with marine bio-attachment resistance and its manufacturing method, its chemical composition is: C: 0.03%-0.12%, Si: 0.05%-0.20%, Mn: 0.50-2.00%, P≤0.015%, S≤0.005%, Cu: 1.60-3.00%, Cr: 0.10%-1.00%, Ni: 2.0%-6.0%, Mo: 0.10%-1.00%, Nb≤0.10%, V≤0.10%, Ti≤0.02%, Al≤0.04%, the balance is Fe and inevitable impurity elements. The patent adopts TMCP process for preparation, the steel plate has good mechanical properties and marine bio-attachment resistance without secondary heating after rolling, but its chemical composition contains high Ni, Mo and other precious metal elements, which will inevitably increase its production cost.The patent with the application number CN202210139047.0 discloses a copper-containing low-alloy steel resistant to marine biological corrosion and a preparation method thereof. The chemical composition of the steel is as follows: Cu: 0.9%-1.1%, Mo: 0.20-0.40, V: 0.06-0.12, Ti: 0.04-0.08, Cr: 0.7-1.2, Ni: 0.8-1.2, C: 0.03-0.08, Mn: 0.35-0.65, Si: 0.25-0.35, S≤0.010, P≤0.02, N≤0.0020, and the rest is Fe. The KV2(-40℃) impact energy of the steel is greater than or equal to 100 J, and the elongation is greater than or equal to 25%. The steel has the ability to resist marine microbial corrosion, but the impact toughness is low, and the ability to resist marine biological corrosion is insufficient, which cannot meet the use requirements of high-tech ships.

[0004] In summary, the production of high-strength ship plates resistant to marine biological corrosion has the following problems.

[0005] 1) The production process of the steel plate is complex, the production cycle is long, and the production cost is high;

[0006] 2) The chemical composition of the steel plate contains valuable alloy elements, resulting in high production cost;

[0007] 3) The mechanical properties and resistance to marine biological corrosion of the steel plate are insufficient, which cannot meet the use requirements of high-tech ships. SUMMARY

[0008] To overcome the shortcomings of the prior art, the purpose of the present application is to provide a high-strength ship plate resistant to marine biological corrosion with reasonable composition design and simple process, and a manufacturing method. The low-temperature toughness of the steel is improved by chemical composition design, and the resistance to marine environment and marine biological corrosion is improved. The mechanical properties and resistance to marine biological corrosion of the steel plate are improved by optimizing the continuous casting and rolling processes.

[0009] To achieve the above-mentioned purpose, the present application realizes the following technical solutions:

[0010] A high-strength ship plate resistant to marine biological corrosion, the composition of the ship plate is as follows in terms of weight percentage:

[0011] C: 0.030%~0.120%, Si: 0.050%~0.250%, Mn: 0.80%~1.30%, P: 0.006%~0.020%, S≤0.005%, Nb: 0.040%~0.080%, V: 0.050%~0.150%, N: 0.0220%~0.0280%, Cu: 1.00%~2.00%, Ni: 1.00%~2.00%, Cr: 0.50%~1.00%, Ti: 0.006%~0.030%, Als: 0.020%~0.050%, Sb: 0.20%~0.70%, Sn: 0.20%~0.70%, the balance is Fe and unavoidable impurities.

[0012] The metallographic structure of the ship plate is ferrite + bainite structure, and the proportion of ferrite in terms of area ratio is ≤10%.

[0013] The functions of the chemical components in the present invention are described in detail below.

[0014] C: A crucial strengthening element in steel. In the technical solution of this invention, it controls the microstructure of the steel plate, optimizes the precipitation of microalloying elements, and ensures the strength and hardness of the steel plate after rolling. Low C content reduces carbide formation, affecting grain refinement during rolling. High C content increases the cementite content in the steel, adversely affecting the steel plate's low-temperature toughness, corrosion resistance, and weldability. Therefore, considering cost and performance factors, the C content is controlled within a range of 0.030% to 0.120%.

[0015] Si: It improves the strength and hardness of steel and acts as a deoxidizer during the steelmaking process. However, excessive Si content can increase the ductile-brittle transition temperature, reduce the low-temperature toughness of the steel plate, and affect the surface quality. Taking into account factors such as cost and performance, the Si content is controlled within a range of 0.050% to 0.250%.

[0016] Mn: An element that expands the austenite phase, forming a substitutional solid solution in steel. It can dissolve in large quantities in the Fe matrix, increasing the steel's strength through solid solution strengthening and positively impacting grain refinement. It can also delay the transformation of ferrite and pearlite in steel, significantly increasing its hardenability, lowering its ductile-brittle transition temperature, and modifying its impact toughness. It can also eliminate the effects of sulfur in steel and improve its hot working properties. However, excessive Mn content can easily lead to segregation in the steel, adversely affecting both its plasticity and toughness. Taking all factors into consideration, the Mn content should be controlled within a range of 0.80% to 1.30%.

[0017] P: improve the corrosion resistance of steel in marine environment, with Cu element can form a variety of complex salt, make the grain size of inner rust layer small, dense, can resist the destruction of Cl-, reduce the corrosion rate of steel, but the content is too high, the low temperature toughness and welding performance of steel is not beneficial. Therefore, the range of P is 0.006%~0.020%.

[0018] Nb: grain refinement element, the undissolved Nb carbon, nitride particles distributed on the austenite grain boundary when heating, can hinder the growth of austenite grain when heating; can effectively delay the recrystallization of deformed austenite during cooling, prevent the growth of austenite grain, refine the ferrite grain, improve the strength and toughness of steel. Therefore, the range of Nb is 0.040%~0.080%.

[0019] V: important strengthening and toughening element of the application, has strong affinity with nitrogen and carbon, is a strong carbide and nitride forming element, can form extremely stable carbonitride with nitrogen and carbon. The strength of steel is improved by fine grain strengthening, precipitation strengthening and solid solution strengthening. With the increase of V content, the ductile-brittle transition temperature of steel decreases. But when the content is too high, the ductile-brittle transition temperature increases. Vanadium carbonitride can precipitate at low temperature to hinder dislocation movement, play a role in strengthening and toughening, and has a significant effect on improving the comprehensive mechanical properties of steel plate. Considering comprehensively, the range of V is 0.050%~0.150%.

[0020] N: another important strengthening and toughening element of the application, the addition of N element is beneficial to promote the formation of V (CN) in steel, so as to refine the grain and improve the plasticity and toughness of steel. Nitrogen containing steel not only eliminates the cost increase caused by degassing and denitrification during steelmaking process, but also can fully play the role of micro alloying elements by increasing nitrogen in steel, thereby saving the amount of alloying elements, greatly reducing the production cost. The addition of N can partially replace the role of C, reduce the carbon equivalent of steel, and improve its welding performance. Considering the performance and cost, the range of N is 0.0220%~0.0280%.

[0021] Cu: can improve the stability of austenite in steel, increase the hardenability of steel, improve the strength, plasticity and low temperature toughness of steel when added appropriately, can produce ε-Cu precipitation during low temperature treatment, thereby improving the strength of steel. Cu can effectively improve the corrosion resistance of steel under reducing atmosphere, and can effectively inhibit the growth and adhesion of microorganisms, but when the content is too high, the hot shortness of steel deteriorates, and hot cracks are easy to produce. Therefore, the range of Cu is 1.00%~2.00%.

[0022] Ni: has no adverse effect on the hardenability and toughness of the heat-affected zone of the steel during welding, and can improve the plasticity and low-temperature toughness of the steel, in addition, the addition of Ni can also reduce the hot cracking tendency when the Cu content is high, and has a beneficial effect on the corrosion resistance of the steel plate in the marine environment. Considering the cost, performance and other factors, the range of Ni is controlled to be 1.00%~2.00%.

[0023] Cr: increases the hardenability of the steel and has a secondary hardening effect, which can improve the strength, hardness and wear resistance of the steel, and can form a dense oxide film on the surface of the steel, which has a positive effect on the corrosion resistance of the steel plate in seawater, but when the content is too high, it is not beneficial to the low-temperature toughness and welding performance of the steel plate, and the range of Cr is controlled to be 0.50%~1.00%.

[0024] Ti: can produce strong precipitation strengthening effect, improve the strength of the steel, and also can prevent austenite recrystallization; at the same time, can produce grain refinement effect, improve the yield strength of the steel. The carbon and nitride of Ti has high dissolution temperature, which can prevent the growth of austenite grains during heating, thereby refining the grain size of the steel plate and improving its strength and toughness, and promoting the comprehensive mechanical properties of the steel plate. Considering comprehensively, the range of Ti is controlled to be 0.006%~0.030%.

[0025] Al: a strong deoxidizer in steel, a small amount of addition can generate highly fine and ultra-micro oxides, which has a beneficial effect on improving the purity of the steel. Therefore, the range of Als is controlled to be 0.020%~0.050%.

[0026] Sb: generally has an adverse effect on the mechanical properties of the steel, which reduces the strength of the steel and increases the brittleness, but if a certain amount of antimony is added to the steel, the corrosion resistance and wear resistance of the steel can be improved to varying degrees. When Sn and Sb are added together, Sn is enriched and Sb is uniformly distributed in the rust layer of the steel, and SnO2-Sb2O5 corrosion-resistant oxide film is formed on the surface of the steel, which can improve the ability to block the penetration of Cl-, thereby further improving the corrosion resistance of the steel. Therefore, the range of Sb is controlled to be 0.20%~0.70%.

[0027] Sn: similar to Sb, appropriate addition can improve the corrosion resistance of the steel, and can inhibit the attachment of marine organisms. When Sn and Sb are added together, the corrosion resistance of the steel can be further improved. Therefore, the range of Sn is controlled to be 0.20%~0.70%.

[0028] The yield strength of the ship plate is 570~620MPa, the tensile strength is 630~710MPa, the elongation after fracture is ≥24.0%, and the impact energy at-60℃ is ≥200J; the biological attachment rate of the steel plate is ≤8.0% after 12 months, and the biological attachment rate is ≤11.5% after 24 months.

[0029] A method for manufacturing a high-strength marine-bio-corrosion-resistant ship plate, comprising smelting, continuous casting, heating furnace heating, rolling, on-line accelerated cooling, and tempering heat treatment, and specifically as follows:

[0030] 1) Smelting:

[0031] a) Adjust the contents of C, Si, Mn, P, and S elements and add other alloying components during converter smelting;

[0032] b) Refine the molten steel and adjust the contents of other alloying elements;

[0033] c) Perform RH treatment on the refined molten steel, with an RH treatment time of 40-60 min, nitrogen blowing throughout the RH treatment, a pressure of 600-620 Pa, ensuring that the final N content is within the set range, and controlling [H] in the steel to be ≤1.5 ppm and [O] to be ≤10 ppm.

[0034] 2) Continuous casting:

[0035] Step 1) The molten steel obtained in step 1) is used to produce the required casting blank, and high superheat is used in the tundish during continuous casting, with the tundish superheat controlled at 40-60 ℃, the superheat protected throughout pouring, the casting speed controlled at 0.50-1.00 m / min, the secondary cooling water ratio controlled at 0.50-0.80 m 3 / t, electromagnetic stirring is used during continuous casting, with a stirring current of 450-550 A, and a light press-down process is used at the end of continuous casting, with a press-down amount of 10.0-15.0 mm;

[0036] To control the grain size of the continuous casting blank, the continuous casting blank is subjected to rapid cooling, with a cooling start temperature of 950-1050 ℃ and a final cooling temperature of 800-850 ℃, followed by stack slow cooling, with a stack start temperature of 750-780 ℃ and a slow cooling time of ≥36 h;

[0037] 3) Heating furnace heating:

[0038] The casting blank is heated to 1100-1250 ℃, with a holding time of 0.5-1.5 h and a total furnace time of 4.0-6.0 h;

[0039] 4) Rolling:

[0040] The casting blank is rolled into a hot-rolled steel plate in two stages:

[0041] To fully break up the columnar crystals of the continuous casting blank and prepare for subsequent grain refinement, the first stage is performed using high-temperature fast rolling + heavy press-down, with the casting blank heated to 950-1000 ℃ after descaling and then rolled, the roll speed controlled at 1.00-2.00 m / s, the first pass press-down amount controlled at 40-50 mm, the final rolling temperature controlled at 880-920 ℃, and the thickness of the temperature-controlled blank controlled at (1.5-2.5) t, t being the final product thickness;

[0042] Second stage roughing temperature 770~820℃, finish rolling temperature 700~750℃;

[0043] 5) Online accelerated cooling:

[0044] In order to keep the fine grains after rolling and prevent the grains from growing, the steel plate is subjected to ultra-fast cooling (UFC cooling) after rolling, the cooling speed is 10.0~25.0℃ / s, and the re-red temperature is 350~450℃;

[0045] 6) Slow cooling:

[0046] In order to release the internal stress formed in the process of rolling and cooling of the steel plate and further form fine precipitated phases, the steel plate after cooling is subjected to slow cooling by stacking, the stacking temperature is 200~300℃, and the stacking time is ≥20h;

[0047] 7) Tempering heat treatment:

[0048] The steel plate after stacking is subjected to tempering treatment, the tempering temperature is 400~600℃, and the holding time is 2.5~5.0min / mm.

[0049] Compared with the prior art, the beneficial effects of the present application are:

[0050] The present application adopts a low-carbon chemical composition system to improve the low-temperature toughness of the steel, and adds Nb, V-N, Ti and other grain refining elements, at the same time promotes the formation of ferrite structure in the steel, uses Ni, Cr, Sb, Sn, P and other elements to improve the corrosion resistance in marine environment, uses the addition of Cu element to improve the resistance of the steel plate to marine biological adhesion, and further improves the marine biological corrosion resistance of the steel plate. In the continuous casting process, the center segregation of the casting blank is controlled by adopting high superheat + strong secondary cooling water + electromagnetic stirring + light pressing process, and fine initial austenite grains are obtained; the continuous casting blank is subjected to fast cooling + slow cooling by stacking process, the grain growth is controlled and the precipitated phase of the casting blank is adjusted. The rolling process adopts TMCP process based on two-stage controlled rolling + offline tempering process, and the final steel plate has excellent mechanical properties and marine biological corrosion resistance. The metallographic structure of the steel plate is ferrite + bainite structure, the ferrite content is ≤10%, the yield strength is 570-620MPa, the tensile strength is 630~710MPa, the elongation after fracture is ≥24.0%, the impact energy at -60℃ is ≥200J; the biological adhesion rate of the steel plate is ≤8.0% for 12 months, and the biological adhesion rate is ≤11.5% for 24 months. BRIEF DESCRIPTION OF DRAWINGS

[0051] Figure 1 is the metallographic structure diagram of the high-strength ship plate resistant to marine biological corrosion. DETAILED DESCRIPTION

[0052] The application will be described in more detail below by way of examples, which are merely illustrative of the best mode of the application and do not limit the scope of the application in any way.

[0053] The steel plate of the application is obtained by smelting according to the chemical composition range designed by the application, the metallographic structure of the steel plate is shown in Table 1. Figure 1 The molten steel is obtained by continuous casting, heating, rolling and cooling to obtain the steel plate of the application, the smelting process is shown in Table 2, the heating process is shown in Table 3, the rolling process is shown in Table 4, and the cooling process is shown in Table 5.

[0054] Table 1 Smelting process and chemical composition (wt%) of the example steel

[0055]

[0056] Table 2 Smelting process of the example steel

[0057]

[0058] Table 3 Cooling and reheating process of the cast blank

[0059]

[0060] Table 4 Rolling process of the example steel

[0061]

[0062] Table 5 Cooling and heat treatment process of the example steel

[0063]

[0064] The mechanical properties and marine organism corrosion resistance of the example steel of the application are tested, and the results are shown in Table 6.

[0065] Table 6 Mechanical properties and marine organism corrosion resistance of the example steel

[0066] .

Claims

1. A high-strength ship plate resistant to marine biocorrosion, characterized in that: The composition of the ship plate is as follows by weight percentage: C: 0.030%~0.120%, Si: 0.050%~0.250%, Mn: 0.80%~1.30%, P: 0.006%~0.020%, S≤0.005%, Nb: 0.040%~0.080%, V: 0.050%~0.150%, N: 0.0220%~0.0280%, Cu: 1.00%~2.00%, Ni: 1.00%~2.00%, Cr: 0.50%~1.00%, Ti: 0.006%~0.030%, Als: 0.020%~0.050%, Sb: 0.20%~0.70%, Sn: 0.20%~0.70%, the balance is Fe and unavoidable impurities.

2. The high-strength ship plate resistant to marine biocorrosion according to claim 1, characterized in that: The metallographic structure of the ship plate is ferrite + bainite structure, and the proportion of ferrite in terms of area ratio is ≤10%.

3. The high-strength ship plate resistant to marine biocorrosion according to claim 1, characterized in that: The ship plate has a yield strength of 570-620 MPa, a tensile strength of 630-710 MPa, an elongation after fracture of ≥24.0%, and an impact absorption energy of ≥200 J at -60°C; a biological attachment rate of the steel plate of ≤8.0% in 12 months and ≤11.5% in 24 months.

4. A method for manufacturing a high-strength ship plate resistant to marine biocorrosion according to any one of claims 1 to 3, characterized in that: Including smelting, continuous casting, heating furnace heating, rolling, online accelerated cooling, tempering heat treatment, as follows: 1) Smelting: Obtain molten steel with chemical composition within the set range; 2) Continuous casting: Step 1) The obtained molten steel is continuously cast to obtain the required casting billet. During continuous casting, the superheat of the tundish is controlled at 40~60℃, and the superheat is protected during the casting process. The casting speed is controlled at 0.50~1.00m / min, and the water volume of the secondary cooling water is 0.50~0.80m 3 / t, electromagnetic stirring is used during continuous casting, with a stirring current of 450~550A, and a soft reduction process is used at the end of continuous casting, with a reduction of 10.0~15.0mm; The continuous casting billet is rapidly cooled, with the cooling start temperature at 950~1050℃ and the final cooling temperature at 800~850℃, followed by stacking and slow cooling, with the stacking start temperature at 750~780℃ and the slow cooling time ≥36h; 3) Heating furnace heating: The slab is heated to 1100~1250℃, the holding time is 0.5~1.5h, and the total furnace time is 4.0~6.0h; 4) Rolling: The ingot is rolled into hot rolled steel plate in two stages: The first stage adopts high-temperature rapid rolling + large reduction method. After the ingot is removed from the furnace and descaled, it is heated to 950-1000℃ before rolling. The roller speed is controlled at 1.00-2.00 m / s, the first pass reduction is 40-50 mm, the final rolling temperature is 880-920℃, and the thickness of the warm billet is (1.5-2.5)t, where t is the thickness of the final product. The second stage rolling temperature is 770~820℃, and the final rolling temperature is 700~750℃; 5) Online accelerated cooling: After rolling, the steel plate is cooled at ultra-fast speed, with a cooling rate of 10.0~25.0℃ / s and a red-hot temperature of 350~450℃; 6) Slow cooling: After cooling, the steel plates are stacked and slowly cooled, with a stacking temperature of 200-300°C and a stacking time of ≥20h; 7) Tempering heat treatment: The stacked steel plates are tempered at a temperature of 400-600°C and a holding time of 2.5-5.0 min / mm.

5. The method for manufacturing a high-strength ship plate resistant to marine biocorrosion according to claim 4, characterized in that: The specific process of smelting in step 1) is as follows: a) Adjust the content of C, Si, Mn, P, and S elements during converter smelting, and add other alloy components for smelting; b) Refining the molten steel and adjusting the content of other alloying elements; c) The refined molten steel is subjected to RH treatment for 40-60 min. Nitrogen is blown throughout the RH treatment at a pressure of 600-620 Pa to ensure that the final nitrogen content is within the set range, and to control [H] ≤ 1.5 ppm and [O] ≤ 10 ppm in the steel.

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