Corrosion-resistant high-carbon steel plate and preparation method thereof

Abstract

The invention provides a corrosion-resistant high-carbon steel plate which comprises the following chemical components in percentage by weight: 0.73%-0.75% of C, 0.80%-0.90% of Mn, 0.70%-0.80% of Cr, 0.25%-0.40% of Ni, 0.20%-0.40% of Cu, 0.0010%-0.0025% of Ca, 0.30%-0.40% of Si, less than or equal to 0.012% of P, less than or equal to 0.003% of S, 0.020%-0.040% of Al, less than or equal to 1.5 ppm of H and the balance of Fe and inevitable impurities. The invention further provides a preparation method of the corrosion-resistant high-carbon steel plate. Through component-process-structure collaborative design, Cr-Ni-Cu ternary alloying replaces Mo and other expensive metal components, balance of high strength and high corrosion resistance is achieved, meanwhile, the high-carbon steel machining problem and the crack control problem are solved through Ni / Cu > = 1 and extremely low impurity control, and the high-carbon steel has the remarkable cost advantage and technical breakthrough.

Description

Technical Field

[0001] The present invention relates to the technical field of metal smelting, and particularly relates to a corrosion-resistant high-carbon steel plate and a preparation method thereof. Background Art

[0002] High-carbon steel is often used after heat treatment, and has characteristics such as high strength and high hardness. It is widely used in the manufacturing of tools, saw blades, etc. Among them, 75Cr1 is one of the most common high-carbon steel products specifically used for saw blades.

[0003] When the saw blade is used for stone cutting, a large amount of dust will be generated, which will damage the environment. Measures such as spraying dust removal water are often used to inhibit the dust from flying. However, when used under the alternating action of dry and wet, the saw blade made of 75Cr1 high-carbon steel material is extremely easy to rust and corrode. During the high-speed rotation of the saw blade, the rust layer is easy to fall off, significantly affecting the service life of the saw blade. Therefore, it is necessary to develop a high-carbon steel for saw blades with excellent corrosion resistance to meet the long-life requirements and economic requirements of saw blades. Patent CN103882310B discloses a corrosion-resistant high-carbon steel alloy material and a preparation method thereof. Its chemical element components and their mass percentages are: C: 0.7-1.0%, Si: 0.7-0.9%, Cu: 0.2-0.4%, Al: 0.05-0.08%, Mn: 2.5-3.5%, Ni: 6.0-6.5%, Ti: 0.05-0.09, B: 0.3-0.5, Mo: 0.1-0.3, Nb: 0.002-0.005, Ta: 0.001-0.003%, Co: 0.03-0.05, P≤0.030, S≤0.030, and the balance is iron. This patent is manufactured by a process of direct heat treatment after casting, which is not suitable for the production of thin-gauge strip steel. Moreover, the content of the precious alloy Ni is as high as 6.0-6.5%, and it contains precious metal elements such as Mo and Co, resulting in a high manufacturing cost. Patent CN117512442A discloses an ultra-high-hardness steel for saw blades and a manufacturing method thereof, which includes chemical elements in mass percentages: C: 0.76-0.90%, Si: 0.10-0.60%, Mn: 0.20-0.80%, Cr: 0.20-1.00%, V: 0.05-0.50%, Al: 0.010-0.050%, Ti: 0.005-0.080%, Ca: 0.0010-0.0040%, and one or more selected from Mo: 0.10-0.50%, Ni: 0.50-1.50%, Cu: 0.20-0.60%, and RE: 0.01-0.08%, and the balance is Fe and inevitable impurities. This patent contains the precious alloy Mo and has a relatively high Ni content, resulting in a high manufacturing cost. In summary, in order to achieve excellent corrosion resistance in the prior art, precious metals such as Mo and a relatively high content of Ni are often added, resulting in a high cost. Summary of the Invention

[0004] The object of the present invention is to provide a corrosion-resistant high-carbon steel plate in view of the defects of the prior art. The chemical composition of the steel plate by weight percentage is as follows: C: 0.73% - 0.75%, Mn: 0.80% - 0.90%, Cr: 0.70% - 0.80%, Ni: 0.25% - 0.40%, Cu: 0.20% - 0.40%, Ca: 0.0010% - 0.0025%, Si: 0.30% - 0.40%, P: ≤0.012%, S: ≤0.003%, Al: 0.020% - 0.040%, H: ≤1.5 ppm, and the balance is Fe and unavoidable impurities.

[0005] Further, the metallographic structure of the corrosion-resistant high-carbon steel plate is tempered sorbite.

[0006] Further, calculated by weight percentage of chemical composition, 1 ≤ Ni / Cu ≤ 2.

[0007] A processing method of a corrosion-resistant high-carbon steel plate successively includes the following steps: hot metal pretreatment, converter smelting, refining, continuous casting, hot tandem rolling, and heat treatment. Among them: the temperature of the converter smelting is 1600°C - 1700°C; the refining adopts double-refining treatment of LF (ladle furnace) slag-making desulfurization and RH (vacuum degassing) vacuum treatment; the continuous casting uses high-carbon steel protective slag for protective casting, the tundish molten steel temperature is controlled at 1450 - 1550°C, and the continuous casting billet drawing speed is controlled at 0.9 - 1.4 m / min; during the hot tandem rolling, after the billet is cut and put into a heating furnace for heating and then taken out, the rolling is carried out in two stages of rough rolling and finish rolling in sequence. After the finish rolling, it is water-cooled and coiled to obtain a hot-rolled coil. The hot-rolled coil is cooled to room temperature, and the cumulative reduction rate of the hot tandem rolling is ≥95%; during the heat treatment, the steel plate is subjected to quenching and tempering treatment. The quenching heating temperature is 800 - 900°C, the tempering temperature is 400 - 500°C, and after tempering, it is air-cooled to room temperature.

[0008] Further, the temperature of the converter smelting is 1650°C - 1670°C.

[0009] Further, the refining adopts LF+RH double-refining treatment. The weak stirring time for LF slag-making desulfurization is ≥15 min, and the tapping temperature is 1570 - 1600°C; the degassing time for RH vacuum treatment is ≥10 min, and the tapping temperature is 1530 - 1550°C.

[0010] Further, during the continuous casting, the tundish molten steel temperature is controlled at 1480 - 1500°C, and the continuous casting billet drawing speed is controlled at 1.0 - 1.3 m / min.

[0011] Furthermore, during hot continuous rolling, after the slab cutting is completed, the slab is quickly fed into the heating furnace. The slab inlet temperature is ≥700°C, the slab heating time is 120 - 150 min, a weak reducing atmosphere is adopted in the heating furnace, the air excess coefficient is 0.9 - 1.0, and the outlet temperature of the heating furnace is controlled at 1170 - 1200°C.

[0012] Furthermore, during hot continuous rolling, the rough rolling temperature is ≥1060°C, the cumulative reduction ratio of rough rolling is ≥80%, the cumulative reduction ratio of finish rolling is ≥80%, the start rolling temperature of finish rolling is ≥1030°C, the finish rolling temperature is 880 - 920°C, after finish rolling, it is water-cooled to 700 - 750°C for coiling, the cooling rate is controlled at 10 - 15°C / s, and the hot rolled coil is placed in a slow cooling pit to be cooled to below 200°C and then taken out for air cooling to room temperature.

[0013] Furthermore, during heat treatment, the quenching heating temperature for quenching and tempering treatment of the steel plate is 820 - 860°C, the holding time is 10 - 20 min, the tempering temperature is 430 - 480°C, and after holding for 7 - 10 h, it is air-cooled to room temperature.

[0014] The beneficial effects of the present invention are as follows: 1. Through the collaborative design of composition - process - microstructure, the present invention replaces expensive metals such as Mo and Ni with the collaborative design of Cr - Ni - Cu ternary alloy, achieving the balance between high strength (yield ≥1450 MPa) and high corrosion resistance (corrosion rate relative to 75Cr1 high carbon steel ≤70%). At the same time, by 1 ≤ Ni / Cu ≤ 2, the problem of crack control of corrosion-resistant high carbon steel is solved, having significant cost advantages and technological breakthroughs.

[0015] 2. The corrosion-resistant high carbon steel plate of the present invention has excellent strength - plasticity matching after hot rolling, with a yield strength of 550 - 650 MPa, Rm of 800 - 950 MPa, and elongation of 16.0 - 20.0%, and a high elongation, which is convenient for heat treatment after subsequent processing of steel plate products.

[0016] 3. Due to the addition of Cr, Ni, and Cu elements, the hardenability of high carbon steel is improved, and its heat treatment process is different from that of ordinary high carbon steel. The present invention further proposes a heat treatment process applicable to the corrosion-resistant high carbon steel plate. After heat treatment, the yield strength is ≥1450 MPa, the tensile strength is ≥1550 MPa, the elongation is ≥7%, and HRC ≥ 47, having ultra-high strength and high hardness.

[0017] 4. The high carbon steel plate of the present invention has excellent corrosion resistance. After 72 h of accelerated corrosion test, a dense protective rust layer with good adhesion to the substrate is formed on the surface of the steel substrate, improving the protection ability of the steel substrate, and the corrosion rate relative to 75Cr1 high carbon steel ≤70%. Description of the Drawings

[0018] Figure 1 It is the microstructure morphology of the hot-rolled state and after heat treatment of Example 3 of the present invention under an optical microscope.

[0019] Figure 2 It is the macroscopic morphology of the surface rust layer after the 72h cyclic immersion corrosion test of Example 3 of the present invention and Comparative Example 1. Specific embodiments

[0020] The method of the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments: A corrosion-resistant high-carbon steel plate, the chemical composition by weight percentage is: C: 0.73% - 0.75%, Mn: 0.80% - 0.90%, Cr: 0.70% - 0.80%, Ni: 0.25% - 0.40%, Cu: 0.20% - 0.40%, Ca: 0.0010% - 0.0025%, Si: 0.30% - 0.40%, P: ≤0.012%, S: ≤0.003%, Al: 0.020% - 0.040%, H: ≤1.5ppm, and the balance is Fe and unavoidable impurities.

[0021] As a preferred solution, calculated by weight percentage of chemical composition, 1 ≤ Ni / Cu ≤ 2. The C content of the high-carbon steel of the present invention is 0.73% - 0.75%, and the material has strong crack sensitivity and is prone to edge cracks during hot rolling. Cu, as a low-melting alloy element (melting point 1083°C), further exacerbates the crack sensitivity of high-carbon steel. Therefore, the present invention adds Ni to form a high-melting binary alloy with Cu, and the melting point of the binary alloy increases with the increase of Ni / Cu; when Ni / Cu ≥ 1, the melting point of the binary alloy > 1200°C, thus avoiding the formation of liquid-phase Cu during heating and being able to weaken the influence of the low-melting alloy element Cu on cracks. When Ni / Cu ≥ 2, the Ni content is high, significantly increasing the manufacturing cost of the material. Therefore, considering the corrosion resistance, surface quality and economy of the corrosion-resistant high-carbon steel plate, the present invention controls Ni / Cu: 1 - 2.

[0022] The design principle of the chemical composition by weight percentage is as follows: C (carbon): C is the most economical element to improve the strength of steel, has a significant interstitial solid solution strengthening effect, can improve the hardenability and hardenability of steel at the same time, and then improve the hardness of the steel plate after heat treatment. However, too high a C content will deteriorate the plasticity of the steel, and too little C content will result in insufficient strength of the steel. In addition, too large a fluctuation in C content will cause large fluctuations in the strength and hardness of the material after heat treatment, which is not conducive to processing and use in the downstream industry. Therefore, the present invention controls the C content to 0.73 - 0.75%.

[0023] Si (silicon): Si is beneficial to refine corrosion products and promote the formation of a dense protective rust layer on the surface of steel, thereby improving corrosion resistance. However, too high a Si content will increase temper brittleness, and too little Si content will not be enough to form a dense protective rust layer on the surface of steel. Therefore, the present invention designs the Si content to be 0.30-0.40%.

[0024] Mn (Manganese): Mn is one of the important solid solution strengthening elements in steel and an important deoxidizing element in the steelmaking process. Mn can also improve the stability of supercooled austenite and reduce the critical cooling rate. However, too high a Mn content will not only increase the manufacturing cost, but also increase temper brittleness. Therefore, its content is designed to be 0.80~0.90%.

[0025] Als (aluminum): Al is the main deoxidizing element added during the molten steel smelting process. However, too high Al content will increase the content of brittle Al2O3 inclusions in the steel, destroy the continuity of the steel matrix, become a crack initiation source, and reduce the plasticity and toughness of the material. Therefore, its content is designed to be 0.020~0.040%.

[0026] Cr (chromium): Cr is an important alloying element for improving the corrosion resistance of steel. It promotes the formation of a dense protective rust layer α-FeOOH with good adhesion to the substrate, forms a dense Cr2O3 passivation film on the surface of the steel, and significantly improves the passivation ability. When the chromium content exceeds 0.65%, the corrosion rate of steel in a dry-wet alternating environment can be reduced by more than 40%. Cr can also improve the hardenability of the material and improve the tempering stability of steel. However, too high a Cr content will increase the manufacturing cost. Therefore, the present invention increases the Cr content to 0.70%-0.80%, exceeding the upper limit of traditional 75Cr1 (0.60%).

[0027] Cu (copper): Cu promotes the formation of dense compounds such as alkaline copper hydroxide sulfate in corrosion products, acts as a corrosion barrier, and inhibits the damage of the corrosive medium to the matrix. When Cu and Cr are combined, they promote the rapid formation of a dense and stable protective rust layer, which significantly improves the corrosion resistance of the material. During the heat treatment process, Cu-containing two-phase particles are precipitated to improve the strength of the material. However, the melting point of Cu is only 1083°C. Too high a content will further increase the crack sensitivity of high-carbon steel materials and increase the difficulty of steel manufacturing. Therefore, the Cu content is designed to be 0.20~0.40%.

[0028] Ni (Nickel): Ni can increase the self - corrosion potential of steel, inhibit the tendency of electrochemical corrosion of materials, and reduce the corrosion rate of steel; it can also react with Cu to form a high - melting - point Cu - Ni binary alloy phase, reducing the adverse effect of Cu on steel cracks. Adding Ni (0.25% - 0.40%) and Cu (0.20% - 0.40%) forms a complementary mechanism. Research has confirmed that the combined addition of Ni - Cu can reduce the pitting density by 60% - 70% in the wet - dry alternating environment. However, Ni is a precious metal element, and too high a content will significantly increase the manufacturing cost of steel. Therefore, the Ni content is controlled within 0.25 - 0.40%.

[0029] Ca (Calcium): Ca can promote the spheroidization of non - metallic inclusions in steel. Calcium has a strong binding force with sulfur, forming spherical CaS and replacing long - strip MnS. At the same time, Ca treatment can transform the brittle Al2O3 inclusions in the molten steel into low - melting - point calcium aluminates, which float to the slag layer, thus reducing the number of brittle Al2O3 inclusions in the steel and improving the plasticity, toughness and fatigue life of the material. However, too high a Ca content reacts with refractory materials to form high - melting - point calcium aluminosilicates, which deposit on the inner wall of the continuous casting nozzle and block the nozzle, increasing the risk of continuous casting stopper flow. Therefore, in this invention, its content is controlled within 0.0010% - 0.0025%.

[0030] P (Phosphorus), S (Sulfur): P and S are harmful residual elements in steel. P is easy to segregate at the grain boundaries, and S is easy to react with Mn to form MnS non - metallic inclusions, reducing the plasticity of the material. However, controlling P and S at low contents will significantly increase the smelting cost. Therefore, in this invention, the P content is controlled within ≤0.012%, and the S content is controlled within ≤0.003%.

[0031] H (Hydrogen): H is a harmful gas element in steel. Especially for ultra - high - strength steel, the risk of hydrogen - induced delayed fracture is greatly increased. Therefore, in this invention, the H content is controlled within ≤1.5 ppm.

[0032] As a preferred solution, the metallographic structure of the corrosion - resistant high - carbon steel plate is tempered sorbite. Tempered sorbite is composed of a ferrite matrix and finely dispersed spherical carbides. The carbides are fine and evenly distributed, reducing micro - electrochemical non - uniformity, having the characteristics of low residual stress and uniform structure. The uniform distribution of carbides reduces the potential difference between ferrite and carbides, weakening the driving force of local electrochemical corrosion (such as microporous corrosion). The characteristic of uniform structure can also reduce the surface micro - cracks generated during rolling or heat treatment, reducing the risk of corrosion initiation, and the low residual stress can reduce the stress corrosion sensitivity.

[0033] The processing method of the corrosion - resistant high - carbon steel plate described in one item includes the following steps in sequence: hot metal pretreatment, converter smelting, refining, continuous casting, hot continuous rolling, and heat treatment. Among them: 1) Hot metal pretreatment and converter smelting: The molten steel is smelted according to the above chemical composition. Before the hot metal enters the converter, through processes such as desulfurization (e.g., injecting magnesium-based desulfurizer), dephosphorization, and de-siliconization, the contents of harmful elements such as sulfur (S) and phosphorus (P) in the hot metal are reduced. The end-point temperature of converter smelting is controlled at 1650°C - 1670°C. With decarburization as the main process, the carbon content in the hot metal is reduced from about 4% to 0.02% - 0.8% through oxidation reaction. At the same time, some elements such as silicon, manganese, and phosphorus are removed, and the composition of the molten steel is adjusted to the target range. If the end-point temperature of converter smelting is greater than 1670°C, it will cause over-oxidation of the steel, coarsening of inclusions, and erosion of the furnace lining. If the end-point temperature of converter smelting is less than 1650°C, it will result in insufficient decarburization, alloy segregation, and continuous casting blockage.

[0034] 2) Refining: Double refining treatment of LF (ladle furnace) and RH (vacuum degassing) is adopted. LF makes slag for desulfurization, and the weak stirring time is ≥15 min. The tapping temperature is 1570 - 1600°C, which promotes the floating of non-metallic inclusions and improves the cleanliness of the molten steel; the degassing time of RH vacuum treatment is ≥10 min, and the tapping temperature is 1530 - 1550°C, which controls the content of H gas element. The double refining treatment of LF and RH can efficiently remove inclusions of all sizes and has extremely strong degassing ability.

[0035] 3) Continuous casting: High-carbon steel protective slag is used for protective casting. The molten steel temperature in the tundish is controlled at 1480°C - 1500°C. Within this temperature range, the fluidity and solidification quality can be balanced, surface and internal defects can be avoided, the lubrication and heat insulation functions of the protective slag can be optimized, and the process stability can be maintained. Beyond this range, the quality of the continuous casting billet (cracks, segregation, inclusions) and the continuous casting efficiency (nozzle blockage, steel leakage) will be directly damaged. The casting speed of the continuous casting billet is controlled at 1.0 - 1.3 m / min. If the casting speed is too high, cracks are likely to occur in the casting billet; if the casting speed is too low, the production efficiency is low.

[0036] 4) Hot continuous rolling: After the slab cutting is completed, the slab is quickly fed into the heating furnace. The slab inlet temperature ≥ 700 °C to avoid cracks caused by too low slab temperature and effectively shorten the heating time of the slab in the heating furnace. The slab enters the heating furnace for heating, and the outlet temperature is controlled at 1170 - 1210 °C, and the residence time in the furnace is 120 - 150 min. A weak reducing atmosphere is adopted in the heating furnace, and the air excess coefficient is 0.9 - 1.0. By jointly controlling the heating temperature, residence time in the furnace and heating furnace atmosphere, the depth of the decarburized layer on the steel coil surface is reduced. After the slab leaves the heating furnace, ultra-high pressure water is used for descaling to remove the surface scale. The descaling water pressure is 190 - 210 Bar. The rolling is carried out in two stages: rough rolling and finish rolling. In the rough rolling stage, 2 four-high reversible rolling mills are used for reciprocating rolling. The rough rolling temperature is controlled above 1060 °C, and the cumulative reduction ratio of rough rolling ≥ 80%. Multiple large deformations are carried out at high temperature to promote the recovery and recrystallization of deformed austenite grains and refine the austenite grain size. In the finish rolling stage, 7 four-high rolling mills are used for tandem rolling. The finish rolling starting temperature ≥ 1030 °C, the finish rolling ending temperature is 880 - 920 °C, and the cumulative reduction ratio of finish rolling ≥ 80%. Due to the high alloy content of high-carbon steel, too low finish rolling temperature will lead to too large deformation resistance of the material and difficult rolling. After finish rolling, it is water-cooled to 700 - 750 °C for coiling, and the cooling rate is controlled at 10 - 15 °C / s. The cumulative reduction ratio in the hot continuous rolling process ≥ 95%. Too low coiling temperature is likely to form martensite structure, resulting in too high material strength and significant decrease in elongation, and brittle fracture is likely to occur during the uncoiling process of the hot rolled coil; too high coiling temperature, the deformation resistance of the material is insufficient, and it is easy to form flat coils. The hot rolled coil is placed in a slow cooling pit and slowly cooled to below 200 °C and then taken out and air-cooled to room temperature to avoid the formation of martensite structure due to too fast cooling of the hot rolled coil. At the same time, during this process, the steel changes from austenite to pearlite.

[0037] 5) Heat treatment: The steel plate is subjected to quenching and tempering treatment (quenching + tempering). The quenching heating temperature is 820 - 860 °C to re-transform pearlite into austenite, and the holding time is 10 - 20 min to promote complete austenitization and form fine and uniform austenite grains; then it is oil-cooled to room temperature to avoid deformation or cracking caused by too fast cooling rate. During the oil-cooling process, austenite directly transforms into martensite during cooling, skipping the pearlite transformation zone. If the quenching heating temperature is too low and incomplete austenitization occurs, the hardness of the material after quenching will be reduced; if the quenching heating temperature is too high, the austenite grains will coarsen, reducing the hardness of the material after quenching. The tempering temperature is 430 - 480 °C, and after holding for 7 - 10 h, it is air-cooled to room temperature. During tempering, martensite decomposes into tempered sorbite structure. If the tempering temperature is too low, carbide precipitation is insufficient, and a large amount of carbon atoms are still dissolved in the ferrite matrix, and the material still maintains high strength and poor plasticity; if the tempering temperature is too high, the carbon atoms dissolved in the ferrite matrix are completely precipitated, and the ferrite grains coarsen, reducing the hardness of the material.

[0038] According to the chemical composition and preparation method of the corrosion-resistant high-carbon steel plate of the present invention, Examples 1, 2, 3, and 4 were obtained, and Comparative Examples 1, 2, 3, and 4 were additionally prepared. The specific components are shown in Table 1.

[0039] Table 1 Chemical Compositions of Examples and Comparative Examples of the Present Invention

[0040] The main process parameters of the steelmaking and hot rolling processes of each example and comparative example of the present invention are shown in Table 2.

[0041] Table 2 Main Process Parameters of Steelmaking and Hot Rolling Processes of Each Example of the Present Invention Sample Number Weak Stirring Time in LF Furnace / min Casting Speed of Slab m / min Furnace Charging Temperature / °C Heating Temperature / °C Heating Time / min Final Rolling Temperature / °C Cooling Rate / °C / s Coiling Temperature / °C Cooling Method of Hot Rolled Coil Surface Condition Example 1 16 1.2 717 1208 148 883 14 728 Slow Cooling in Slow Cooling Pit No Crack Example 2 19 1.3 723 1201 137 916 11 746 Slow Cooling in Slow Cooling Pit No Crack Example 3 18 1.1 756 1189 122 898 13 733 Slow Cooling in Slow Cooling Pit No Crack Example 4 15 1.0 741 1173 141 885 12 712 Slow Cooling in Slow Cooling Pit No Crack Comparative Example 1 18 1.2 756 1193 133 897 10 725 Slow Cooling in Slow Cooling Pit Crack in Casting Slab Comparative Example 2 17 1.3 722 1205 125 905 14 739 Slow Cooling in Slow Cooling Pit Crack in Casting Slab Comparative Example 3 16 1.1 709 1189 135 912 45 425℃ Natural Cooling Crack in Hot Rolled Coil Comparative Example 4 19 1.2 718 1176 142 886 13 741 Slow Cooling in Slow Cooling Pit No Crack The heat treatment process parameters of each example and comparative example of the present invention are shown in Table 3.

[0042] Table 3 Heat Treatment Process Parameters of Each Example and Comparative Example of the Present Invention

[0043] The mechanical properties of the hot-rolled and heat-treated states of each example and comparative example of the present invention are shown in Table 4. The tensile property test was carried out in accordance with GB / T 228.1-2010 "Metallic materials - Tensile testing - Part 1: Method of test at room temperature"; the Rockwell hardness test was carried out in accordance with GB / T 230.1 "Metallic materials - Rockwell hardness test - Part 1: Test method".

[0044] Table 4 Mechanical Properties of Each Example of the Present Invention after Hot Rolling and Heat Treatment

[0045] A 72-hour cyclic immersion corrosion test was carried out. The corrosion solution was: 0.0 mol / L NaHSO3. Using the commonly used 75Cr1 saw blade steel as a comparison, the corrosion weight loss rates of each example and comparative example of the present invention are shown in Table 5.

[0046] Table 5 Corrosion Resistance of Each Example and Comparative Example of the Present Invention Sample Number Thickness / mm <![CDATA[Corrosion weight loss rate g / (m 2 ·h)]]> Relative Corrosion Rate / % Example 1 3 1.53 63.5 Example 2 4 1.57 65.1 Example 3 6 1.62 67.2 Example 4 8 1.68 69.7 Comparative Example 1 6 2.33 97.1 Comparative Example 2 6 1.96 81.3 Comparative Example 3 6 1.65 68.5 Comparative Example 4 6 1.60 66.4 75Cr1 6 2.41 100 Figure 1 This is the microstructural morphology of Example 3 of the present invention in the hot-rolled state and after heat treatment under an optical microscope. The hot-rolled microstructure is a pearlite structure, and the structure after heat treatment is a tempered sorbite structure.

[0047] Figure 2 This is the macroscopic morphology of the surface rust layer of Example 3 and Comparative Example 1 of the present invention after a 72-hour cyclic immersion corrosion test. Among them, the rust layer of Example 3 is tightly bonded to the substrate, while the rust layer of Comparative Example 1 has peeled off.

[0048] Based on the analysis of the above experimental results, in terms of the chemical composition of the steel, the present invention adopts ternary coordination of Cr-Ni-Cu (Cr forms a dense rust layer, Ni inhibits the corrosion tendency, and Cu improves the corrosion resistance), replacing the traditional Mo alloying to reduce costs; Ni / Cu≥1 inhibits the crack sensitivity of Cu and solves the processing problems of high-carbon steel; the extremely low P, S, and H contents (P≤0.012%, S≤0.003%, H≤1.5ppm) improve the material purity. In the preparation process, high-efficiency removal of inclusions of all sizes is achieved through LF+RH double refining (weak stirring ≥15min, degassing ≥10min); controlled rolling and slow cooling (final rolling temperature 880~920°C, coiling temperature 700~750°C) refine austenite grains; quenching and tempering treatment (quenching at 820~860°C + tempering at 430~480°C) forms uniform tempered sorbite and reduces the driving force of electrochemical corrosion. Finally, a yield strength ≥1450MPa, tensile strength ≥1550MPa, elongation ≥7%, HRC≥47, and relative corrosion rate of the high-carbon steel 75Cr1 ≤70% are achieved.

[0049] In addition, compared with the Mo alloying of the prior art, the present invention still achieves high corrosion resistance without Mo. The mechanism analysis is as follows: Cr-Ni-Cu is coordinated to replace Mo: Cr (0.70%~0.80%) generates a dense Cr2O3 oxide film on the steel surface to block the penetration of corrosive media; Ni (0.25%~0.40%) increases the self-corrosion potential and inhibits anodic dissolution; Cu (0.25%~0.40%) combines with Cr to promote the rapid formation of a protective rust layer, and at the same time precipitates as a Cu-Ni binary high-temperature alloy phase to offset the negative impact of the low-melting-point Cu on increasing crack sensitivity. Tempered sorbite (ferrite + dispersed carbides) reduces the potential difference between ferrite and carbide and weakens the driving force of microporous corrosion. Low residual stress (quenching and tempering treatment) reduces the stress corrosion sensitivity. Ultra-low S (≤0.003%) reduces MnS inclusions and inhibits the origin of pitting corrosion. Ultra-low H (≤1.5ppm) avoids hydrogen embrittlement and delayed fracture. LF+RH double refining reduces oxide inclusions, improves surface densification, protects casting (high-carbon steel protective slag) to prevent secondary oxidation, and reduces surface defects.

[0050] In summary, through the collaborative design of composition - process - microstructure, the Cr content of the present invention is increased to 0.75% and the addition of Ni / Cu promotes the formation of a dense rust layer with good adhesion to the substrate on the surface of the steel, avoiding the shedding of the rust layer, and doubling the life of the cyclic corrosion test (simulating wet - dry alternation). The collaborative design of a small amount of Cr - Ni - Cu ternary alloy replaces expensive metal components such as Mo and high Ni content, achieving a balance between high strength (yield ≥ 1450 MPa) and high corrosion resistance (corrosion rate relative to 75Cr1 high - carbon steel ≤ 70%). At the same time, the problem of crack control in corrosion - resistant high - carbon steel is solved by 1 ≤ Ni / Cu ≤ 2. On the premise of maintaining the core performance of 75Cr1, the present invention improves the corrosion resistance through economic alloying elements (Ni / Cu replaces precious metal Mo), solving the "hardness - corrosion resistance - cost" triangular contradiction. It has significant cost advantages and technological breakthroughs.

[0051] The above - mentioned embodiments are only used to illustrate the technical solutions of the present application, not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application, and should all be included in the protection scope of the present application.

Claims

1. A corrosion-resistant high-carbon steel plate, characterized in that: The chemical composition by weight percentage is: C: 0.73% - 0.75%, Mn: 0.80% - 0.90%, Cr: 0.70% - 0.80%, Ni: 0.25% - 0.40%, Cu: 0.20% - 0.40%, Ca: 0.0010% - 0.0025%, Si: 0.30% - 0.40%, P: ≤0.012%, S: ≤0.003%, Al: 0.020% - 0.040%, H: ≤1.5 ppm, and the balance is Fe and unavoidable impurities.

2. The corrosion-resistant high-carbon steel plate according to claim 1, wherein: The metallographic structure of the corrosion-resistant high-carbon steel plate is tempered sorbite.

3. The corrosion-resistant high-carbon steel plate according to claim 1, wherein: Calculated by weight percentage of chemical composition, 1 ≤ Ni / Cu ≤ 2.

4. The processing method of the corrosion-resistant high-carbon steel plate according to any one of claims 1 to 3, characterized in that, It successively includes the following steps: Hot metal pretreatment, converter smelting, refining, continuous casting, hot continuous rolling, and heat treatment, where: The temperature of the converter smelting is 1600°C - 1700°C; The refining adopts a double-refining treatment of LF slag-making desulfurization and RH vacuum treatment; During continuous casting, high-carbon steel protective slag is used for protective casting, the tundish molten steel temperature is controlled at 1450 - 1550°C, and the continuous casting billet drawing speed is controlled at 0.9 - 1.4 m / min; During hot continuous rolling, after the casting billet is cut, it is put into a heating furnace for heating and then taken out. The rolling is carried out in two stages of rough rolling and finish rolling in sequence. After finish rolling, it is water-cooled and coiled to obtain a hot-rolled coil. The hot-rolled coil is cooled to room temperature, and the cumulative reduction rate of hot continuous rolling ≥ 95%; During heat treatment, the steel plate is subjected to quenching and tempering treatment. The quenching heating temperature is 800 - 900°C, the tempering temperature is 400 - 500°C, and it is air-cooled to room temperature after tempering.

5. The processing method of the corrosion-resistant high-carbon steel plate according to claim 4, characterized in that: The temperature of the converter smelting is 1650°C - 1670°C.

6. The processing method of the corrosion-resistant high-carbon steel plate according to claim 4, characterized in that: The refining adopts LF + RH double-refining treatment. The weak stirring time for LF slag-making desulfurization ≥ 15 min, and the tapping temperature is 1570 - 1600°C; the degassing time for RH vacuum treatment ≥ 10 min, and the tapping temperature is 1530 - 1550°C.

7. The processing method of the corrosion-resistant high-carbon steel plate according to claim 4, characterized in that: During continuous casting, the tundish molten steel temperature is controlled at 1480 - 1500°C, and the continuous casting billet drawing speed is controlled at 1.0 - 1.3 m / min.

8. The processing method of the corrosion-resistant high-carbon steel plate according to claim 4, characterized in that: During hot continuous rolling, when the casting billet is cut, it is quickly put into the heating furnace. The billet inlet furnace temperature ≥ 700°C, the billet residence time in the heating furnace is 120 - 150 min, a weak reducing atmosphere is adopted in the heating furnace, the air excess coefficient is 0.9 - 1.0, and the outlet furnace temperature is controlled at 1170 - 1210°C.

9. The processing method of the corrosion-resistant high-carbon steel plate according to claim 4, characterized in that: During hot continuous rolling, the rough rolling temperature ≥ 1060°C, the cumulative reduction rate of rough rolling ≥ 80%, the cumulative reduction rate of finish rolling ≥ 80%, the finish rolling start rolling temperature ≥ 1030°C, the finish rolling final rolling temperature is 880°C - 920°C. After finish rolling, it is water-cooled to 700°C - 750°C for coiling, and the cooling rate is controlled at 10 - 15°C / s. The hot-rolled coil is placed in a slow cooling pit and cooled to below 200°C and then taken out and air-cooled to room temperature.

10. The processing method of the corrosion-resistant high-carbon steel plate according to claim 4, characterized in that: During heat treatment, the quenching heating temperature for the quenching and tempering treatment of the steel plate is 820 - 860°C, the holding time is 10 - 20 min, the tempering temperature is 430 - 480°C, and it is air-cooled to room temperature after holding for 7 - 10 h.

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