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

Abstract

The present invention provides a corrosion-resistant high-carbon steel plate having the following chemical composition by weight: C: 0.73% to 0.75%, Mn: 0.80% to 0.90%, Cr: 0.70% to 0.80%, Ni: 0.25% to 0.40%, Cu: 0.20% to 0.40%, Ca: 0.0010% to 0.0025%, Si: 0.30% to 0.40%, P: ≤0.012%, S: ≤0.003%, Al: 0.020% to 0.040%, H: ≤1.5 ppm, with the balance being Fe and unavoidable impurities. The present invention also provides a method for preparing the corrosion-resistant high-carbon steel plate. The present invention achieves a balance between high strength and high corrosion resistance through component-process-organization collaborative design, replacing expensive metal components such as Mo with ternary alloying of Cr-Ni-Cu. At the same time, it solves the problems of high-carbon steel processing and crack control by controlling Ni / Cu ≥ 1 and extremely low impurities, thus achieving significant cost advantages and technological breakthroughs.

Description

Technical Field

[0001] The present invention relates to the technical field of metal smelting, and in particular 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. It has the characteristics of high strength and high hardness. It is widely used in the manufacture of cutting tools, saw blades, etc. Among them, 75Cr1 is one of the most common high carbon steel products used for saw blades.

[0003] When saw blades are used for cutting stone, they generate a large amount of dust, which damages the environment. Dust suppression measures, such as spraying dust removal water, are often used to suppress this dust. However, saw blades made of 75Cr1 high-carbon steel are highly susceptible to rust and corrosion under alternating wet and dry conditions. During high-speed rotation, the rust layer easily breaks off, significantly shortening the blade's service life. Therefore, it is necessary to develop a high-carbon steel for saw blades with excellent corrosion resistance to meet the demands for long-life and economical saw blades. Patent CN103882310B discloses a corrosion-resistant high-carbon steel alloy material and its preparation method. Its chemical composition and mass percentages are as follows: 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, with the balance being iron. This patent utilizes a direct heat treatment process after casting, making it unsuitable for thin-gauge plate and strip production. Furthermore, the precious alloy Ni content is as high as 6.0-6.5%, along with precious metal elements such as Mo and Co, resulting in high manufacturing costs. Patent CN117512442A discloses an ultra-high-hardness steel for saw blades and a method for manufacturing the same. The steel contains, by mass percentage, the following chemical elements: 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%, with the remainder being Fe and unavoidable impurities. This patented steel contains the precious alloy Mo and a high Ni content, resulting in high manufacturing costs. In summary, in order to achieve excellent corrosion resistance, the existing technology often adds precious metals such as Mo and a high content of Ni, resulting in high costs. Summary of the Invention

[0004] The purpose of the present invention is to address the defects of the prior art and provide a corrosion-resistant high-carbon steel plate, the chemical composition of which is as follows by weight: 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.

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

[0006] Furthermore, calculated according to the weight percentage of the chemical composition, 1≤Ni / Cu≤2.

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

[0008] Furthermore, the temperature of the converter smelting is 1650°C~1670°C.

[0009] Furthermore, the refining adopts LF+RH double refining treatment, the weak stirring time of LF slagging and desulfurization is ≥15min, and the outlet temperature is 1570~1600℃; the degassing time of RH vacuum treatment is ≥10min, and the outlet temperature is 1530~1550℃.

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

[0011] Furthermore, during the hot rolling, after the slab is cut, it is quickly put into the heating furnace, the slab entry temperature is ≥700°C, the slab heating time is 120~150min, a weak reducing atmosphere is used in the heating furnace, the air excess coefficient is 0.9~1.0, and the temperature out of the heating furnace is controlled at 1170~1200°C.

[0012] Furthermore, during the hot rolling, the roughing temperature is ≥1060°C, the cumulative reduction rate of roughing is ≥80%, the cumulative reduction rate of finishing rolling is ≥80%, the starting temperature of finishing rolling is ≥1030°C, the finishing temperature of finishing rolling is 880°C~920°C, and after finishing rolling, the hot rolled coil 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.

[0013] Furthermore, during the heat treatment, the steel plate is subjected to quenching and tempering treatment at a quenching heating temperature of 820-860° C., a holding time of 10-20 minutes, and a tempering temperature of 430-480° C., a holding time of 7-10 hours, and then air-cooled to room temperature.

[0014] The beneficial effects of the present invention are:

[0015] 1. This invention uses a ternary Cr-Ni-Cu alloy to replace expensive metal components such as Mo and Ni through a coordinated design of composition, process, and structure. This achieves a balance between high strength (yield ≥ 1450 MPa) and high corrosion resistance (corrosion rate ≤ 70% relative to 75Cr1 high-carbon steel). At the same time, by using the ratio 1 ≤ Ni / Cu ≤ 2, it solves the crack control problem of corrosion-resistant high-carbon steel, achieving significant cost advantages and technological breakthroughs.

[0016] 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 an elongation of 16.0-20.0%. The high elongation facilitates heat treatment after subsequent product processing of the steel plate.

[0017] 3. Because the addition of Cr, Ni, and Cu improves the hardenability of high-carbon steel, its heat treatment process differs from that of ordinary high-carbon steel. The present invention further proposes a heat treatment process suitable for 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 the HRC is ≥47, demonstrating ultra-high strength and high hardness.

[0018] 4. The high-carbon steel plate of the present invention has excellent corrosion resistance. After 72 hours of accelerated corrosion test, a dense protective rust layer with good adhesion to the substrate is formed on the surface of the steel substrate, which improves the protection ability of the steel substrate. The corrosion rate relative to 75Cr1 high-carbon steel is ≤70%. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The microstructure morphology of Example 3 of the present invention in the hot-rolled state and after heat treatment under an optical microscope.

[0020] Figure 2 The macroscopic morphology of the surface rust layer of Example 3 of the present invention and Comparative Example 1 after 72 hours of immersion corrosion test. DETAILED DESCRIPTION

[0021] The method of the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments:

[0022] A corrosion-resistant high-carbon steel plate has the following chemical components in weight percentage: 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.

[0023] As a preferred embodiment, calculated based on the weight percentage of the chemical composition, 1 ≤ Ni / Cu ≤ 2. The high-carbon steel described herein has a carbon content of 0.73% to 0.75%, resulting in high crack sensitivity and prone to edge cracking during hot rolling. Cu, as a low-melting alloying 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-point binary alloy with Cu, and the melting point of the binary alloy increases with increasing Ni / Cu ratio. When Ni / Cu ≥ 1, the melting point of the binary alloy exceeds 1200°C, thus preventing the formation of liquid Cu during heating and reducing the impact of the low-melting-point alloying element Cu on cracking. When Ni / Cu ≥ 2, the high Ni content significantly increases the manufacturing cost of the material. Therefore, the present invention controls the Ni / Cu ratio to 1-2, taking into account the corrosion resistance, surface quality, and economic efficiency of the corrosion-resistant high-carbon steel plate.

[0024] The design principle of chemical composition weight percentage is as follows:

[0025] Carbon (C): Carbon is the most economical element for increasing steel strength. It exhibits significant interstitial solid solution strengthening, simultaneously improving both the hardenability and hardenability of steel, thereby increasing the hardness of the steel plate after heat treatment. However, excessive carbon content can deteriorate the steel's plasticity, while too little can result in insufficient strength. Furthermore, excessive fluctuations in carbon content can lead to significant fluctuations in the material's strength and hardness after heat treatment, hindering processing and use in downstream industries. Therefore, the present invention controls the carbon content to 0.73-0.75%.

[0026] Silicon (Si): Si helps refine corrosion products and promotes the formation of a dense protective rust layer on the steel surface, thereby improving corrosion resistance. However, excessive Si content can increase temper brittleness, while too little Si content is insufficient to form a dense protective rust layer on the steel surface. Therefore, the Si content in this invention is designed to be 0.30-0.40%.

[0027] Mn (Manganese): Mn is a key solid solution strengthening element in steel and a crucial deoxidizing element during the steelmaking process. Mn also improves the stability of supercooled austenite and reduces the critical cooling rate. However, excessive Mn content not only increases manufacturing costs but also increases temper brittleness. Therefore, its content is designed to be between 0.80% and 0.90%.

[0028] Al (aluminum): Al is the primary deoxidizing element added during the steelmaking process. However, excessive Al content can increase the content of brittle Al₂O₃ inclusions in the steel, disrupting the continuity of the steel matrix, becoming a source of crack initiation, and reducing the material's plasticity and toughness. Therefore, the Al content is designed to be between 0.020% and 0.040%.

[0029] Cr (chromium): Cr is a key alloying element that improves the corrosion resistance of steel. It promotes the formation of a dense, protective rust layer (α-FeOOH) with good adhesion to the substrate, forming a dense Cr2O3 passivation film on the steel surface, significantly enhancing passivation performance. When the chromium content exceeds 0.65%, the corrosion rate of steel in alternating dry-wet environments can be reduced by over 40%. Cr also improves the material's hardenability and tempering stability. However, excessive Cr content increases manufacturing costs. Therefore, the present invention increases the Cr content to 0.70%-0.80%, exceeding the upper limit of 0.60% for conventional 75Cr1.

[0030] Cu (Copper): Cu promotes the formation of dense compounds such as alkaline copper hydroxide sulfate in corrosion products, acting as a corrosion barrier and inhibiting damage to the substrate by the corrosive medium. The combined action of Cu and Cr promotes the rapid formation of a dense and stable protective rust layer, significantly improving the material's corrosion resistance. During heat treatment, Cu-containing dual-phase particles precipitate, enhancing the material's strength. However, Cu has a melting point of only 1083°C, and excessive levels can further increase the crack sensitivity of high-carbon steel, making it more difficult to manufacture. Therefore, the Cu content is designed to be between 0.20% and 0.40%.

[0031] Nickel (Ni): Ni increases the self-corrosion potential of steel, inhibits the material's electrochemical corrosion tendency, and reduces the corrosion rate. It also reacts with Cu to form a high-melting-point Cu-Ni binary alloy phase, reducing the adverse effects of Cu on steel cracking. Adding Ni (0.25%-0.40%) and Cu (0.20%-0.40%) creates a complementary mechanism. Studies have shown that the combined addition of Ni and Cu can reduce pitting density by 60%-70% under alternating dry-wet conditions. However, Ni is a precious metal element, and excessive levels significantly increase steel manufacturing costs. Therefore, the Ni content is controlled between 0.25% and 0.40%.

[0032] Ca (Calcium): Ca promotes the spheroidization of non-metallic inclusions in steel. Calcium and sulfur have strong binding forces, forming spherical CaS that replaces elongated MnS. Ca treatment also transforms brittle Al2O3 inclusions in molten steel into low-melting calcium aluminates, which float to the slag layer, thereby reducing the number of brittle Al2O3 inclusions in the steel and improving the material's plasticity, toughness, and fatigue life. However, excessive Ca content reacts with refractory materials to form high-melting calcium aluminosilicates, which deposit on the inner wall of the continuous casting nozzle, blocking it and increasing the risk of flow accumulation. Therefore, the present invention controls the content of Ca within a range of 0.0010% to 0.0025%.

[0033] Phosphorus (P) and sulfur (S): P and S are harmful residual elements in steel. P tends to segregate at grain boundaries, while S easily reacts with manganese to form MnS non-metallic inclusions, reducing the material's plasticity. However, controlling P and S content to low levels significantly increases smelting costs. Therefore, the present invention controls the P content to ≤0.012% and the S content to ≤0.003%.

[0034] Hydrogen: Hydrogen is a harmful gas element in steel, especially for ultra-high-strength steel, where it significantly increases the risk of delayed fracture. Therefore, the present invention controls the hydrogen content to ≤1.5ppm.

[0035] As a preferred option, the metallographic structure of the corrosion-resistant high-carbon steel plate is tempered bainite, which is composed of a ferrite matrix and dispersed fine spherical carbides. The carbides are small and evenly distributed, reducing microscopic electrochemical heterogeneity and 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 uniform structure can also reduce surface microcracks generated during rolling or heat treatment, reducing the risk of corrosion initiation, and low residual stress can reduce stress corrosion sensitivity.

[0036] A method for processing corrosion-resistant high-carbon steel plates includes the following steps in sequence: molten iron pretreatment, converter smelting, refining, continuous casting, hot rolling, and heat treatment.

[0037] 1) Hot metal pretreatment and converter smelting: Steelmaking is performed according to the aforementioned chemical composition. Before entering the converter, desulfurization (e.g., by injecting a magnesium-based desulfurizer), dephosphorization, and desiliconization are performed to reduce the content of harmful elements such as sulfur (S) and phosphorus (P). The converter smelting endpoint temperature is controlled between 1650°C and 1670°C. Decarburization is the primary focus, reducing the carbon content in the hot metal from approximately 4% to 0.02%-0.8% through oxidation reactions. Simultaneously, some silicon, manganese, and phosphorus are removed, and the steel composition is adjusted to the target range. A converter endpoint temperature exceeding 1670°C can lead to overoxidation of the steel, coarsening of inclusions, and erosion of the furnace lining. A converter endpoint temperature below 1650°C can result in insufficient decarburization, alloy segregation, and blockages in the continuous casting process.

[0038] 2) Refining: Dual refining processes, LF (ladle furnace) and RH (vacuum degassing), are employed. LF slag desulfurization, with a weak stirring time of ≥15 minutes and an outlet temperature of 1570-1600°C, promotes the floating of non-metallic inclusions and improves molten steel cleanliness. RH vacuum degassing, with a degassing time of ≥10 minutes and an outlet temperature of 1530-1550°C, controls the H gas content. This dual LF and RH refining process efficiently removes all-size inclusions and offers exceptional degassing capabilities.

[0039] 3) Continuous Casting: Use high-carbon steel mold slag for protective casting. The tundish molten steel temperature is controlled between 1480°C and 1500°C. This temperature range balances fluidity and solidification quality, avoids surface and internal defects, optimizes the lubrication and insulation properties of the mold slag, and maintains process stability. Exceeding this range will directly damage the quality of the ingot (cracks, segregation, inclusions) and continuous casting efficiency (nozzle blockage, steel leakage). The continuous casting ingot casting speed is controlled between 1.0 and 1.3 m / min. Excessive casting speeds can easily cause cracks in the ingot, while too low casting speeds can reduce production efficiency.

[0040] 4) Hot Rolling: After the slab is cut, it is quickly placed in the heating furnace. The slab entry temperature is ≥700°C to prevent cracking caused by the slab being too cold and effectively shorten the heating time in the heating furnace. The slab enters the heating furnace for heating, and the exit temperature is controlled between 1170°C and 1210°C. The furnace stay time is 120-150 minutes. A weak reducing atmosphere is used in the heating furnace, with an excess air coefficient of 0.9-1.0. By synergistically controlling the heating temperature, furnace stay time, and furnace atmosphere, the depth of the decarburization layer on the surface of the steel coil is reduced. After the slab exits the heating furnace, ultra-high pressure water is used to descale the surface iron oxide scale. The descaling water pressure is 190-210 bar. Rolling is carried out in two stages: roughing and finishing. The roughing stage utilizes two four-high reversing mills for reciprocating rolling. The roughing temperature is controlled above 1060°C, and the cumulative roughing reduction is ≥80%. Multiple high-temperature, high-deformation passes promote recovery and recrystallization of deformed austenite grains, refining the austenite grain size. The finishing stage utilizes seven four-high mills. The start temperature for finishing is ≥1030°C, and the final temperature for finishing is 880-920°C. The cumulative finishing reduction is ≥80%. Due to the high alloy content of high-carbon steel, excessively low finishing temperatures can result in excessive deformation resistance and make rolling difficult. After finishing, the steel is water-cooled to 700-750°C for coiling, with a cooling rate of 10-15°C / s. The cumulative hot rolling reduction is ≥95%. If the coiling temperature is too low, martensite will form, resulting in excessive strength and a significant decrease in elongation, making the hot-rolled coil prone to brittle fracture during uncoiling. If the coiling temperature is too high, the material's deformation resistance will be insufficient, making the coil prone to flattening. Hot-rolled coils should be slowly cooled in a slow cooling pit to below 200°C, then removed and air-cooled to room temperature to avoid rapid cooling and the formation of martensite. During this process, the steel transforms from austenite to pearlite.

[0041] 5) Heat Treatment: The steel plate undergoes a quenching and tempering treatment (quenching + tempering). The quenching temperature is 820-860°C to transform pearlite back into austenite. The holding time is 10-20 minutes to promote complete austenitization and form fine, uniform austenite grains. The plate is then oil-cooled to room temperature to avoid deformation or cracking caused by excessive cooling. During the oil cooling process, the austenite skips the pearlite transformation zone and directly transforms to martensite. If the quenching temperature is too low, complete austenitization is not achieved, reducing the hardness of the quenched material. If the quenching temperature is too high, the austenite grains coarsen, reducing the hardness of the quenched material. The tempering temperature is 430-480°C, the holding time is 7-10 hours, and then air-cooled to room temperature. During the tempering process, the martensite decomposes into tempered bainite. If the tempering temperature is too low, the carbide precipitation is insufficient, and a large amount of carbon atoms are still dissolved in the ferrite matrix. The material still maintains a high strength but poor plasticity. If the tempering temperature is too high, the carbon atoms dissolved in the ferrite matrix are completely precipitated, the ferrite grains are coarsened, and the hardness of the material decreases.

[0042] 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 also prepared. The specific compositions are shown in Table 1.

[0043] Table 1 Chemical compositions of various embodiments and comparative examples of the present invention

[0044]

[0045] The main process parameters of the steelmaking and hot rolling processes of the embodiments of the present invention and the comparative examples are shown in Table 2.

[0046] Table 2 Main process parameters of steelmaking and hot rolling process of various embodiments of the present invention

[0047] Sample number LF furnace weak stirring time / min Billet casting speed m / min Furnace temperature / ℃ Heating temperature / ℃ Heating time / min Finish rolling temperature / ℃ Cooling rate / ℃ / s Coiling temperature / ℃ Hot rolled coil cooling method Surface state Example 1 16 1.2 717 1208 148 883 14 728 Slow cooling pit slow cooling No cracks Example 2 19 1.3 723 1201 137 916 11 746 Slow cooling pit slow cooling No cracks Example 3 18 1.1 756 1189 122 898 13 733 Slow cooling pit slow cooling No cracks Example 4 15 1.0 741 1173 141 885 12 712 Slow cooling pit slow cooling No cracks Comparative Example 1 18 1.2 756 1193 133 897 10 725 Slow cooling pit slow cooling Ingot cracks Comparative Example 2 17 1.3 722 1205 125 905 14 739 Slow cooling pit slow cooling Ingot cracks Comparative Example 3 16 1.1 709 1189 135 912 45 425℃ Natural cooling Hot rolled coil cracks Comparative Example 4 19 1.2 718 1176 142 886 13 741 Slow cooling pit slow cooling No cracks

[0048] The heat treatment process parameters of the embodiments of the present invention and the comparative examples are shown in Table 3.

[0049] Table 3 Heat treatment process parameters of various embodiments of the present invention and comparative examples

[0050]

[0051] The mechanical properties of the hot-rolled and heat-treated steel sheets of the embodiments and comparative examples of the present invention are shown in Table 4. Tensile testing was conducted in accordance with GB / T 228.1-2010, "Metallic Materials - Tensile Tests - Part 1: Room Temperature Test Methods." Rockwell hardness testing was conducted in accordance with GB / T 230.1, "Metallic Materials - Rockwell Hardness Tests - Part 1: Test Methods."

[0052] Table 4 Mechanical properties of various embodiments of the present invention after hot rolling and heat treatment

[0053]

[0054] A 72-hour immersion corrosion test was conducted using 0.0 mol / L NaHSO 3 as the corrosive solution. The corrosion weight loss rates of the embodiments of the present invention and the comparative example were compared with the commonly used 75Cr1 saw blade steel. Table 5 shows the corrosion weight loss rates of the embodiments of the present invention and the comparative example.

[0055] Table 5 Corrosion resistance of various embodiments of the present invention and comparative examples

[0056] 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

[0057] Figure 1 The microstructure morphology of Example 3 of the present invention in the hot-rolled state and after heat treatment under an optical microscope is shown. The hot-rolled microstructure is pearlite, and the microstructure after heat treatment is tempered bainite.

[0058] Figure 2The macroscopic morphology of the surface rust layer of Example 3 and Comparative Example 1 after 72 hours of immersion corrosion test is shown. The rust layer of Example 3 is tightly bonded to the substrate, while the rust layer of Comparative Example 1 has fallen off.

[0059] Analysis of the experimental results above shows that the present invention utilizes a ternary Cr-Ni-Cu synergistic steel composition (Cr forms a dense rust layer, Ni inhibits corrosion, and Cu improves corrosion resistance) to replace traditional Mo alloying, reducing costs. A Ni / Cu ratio of ≥1 suppresses Cu crack sensitivity, addressing high-carbon steel processing challenges. Extremely low P, S, and H contents (P ≤ 0.012%, S ≤ 0.003%, H ≤ 1.5 ppm) enhance material purity. Furthermore, the manufacturing process utilizes LF+RH dual refining (weak stirring ≥ 15 minutes, degassing ≥ 10 minutes) to efficiently remove full-size inclusions. Temperature-controlled rolling and slow cooling (finishing rolling temperature 880-920°C, coiling temperature 700-750°C) refine austenite grains. Tempering treatment (820-860°C quenching followed by 430-480°C tempering) forms uniformly tempered bainite, reducing the driving force of electrochemical corrosion. Finally, the yield strength ≥1450MPa, tensile strength ≥1550MPa, elongation ≥7%, HRC ≥47, and corrosion rate ≤70% relative to 75Cr1 high carbon steel were achieved.

[0060] Furthermore, compared to existing Mo alloying methods, this invention achieves high corrosion resistance without Mo. The mechanism is analyzed as follows: Cr-Ni-Cu synergistically replaces Mo: Cr (0.70%-0.80%) forms a dense Cr2O3 oxide film on the steel surface, blocking the penetration of corrosive media; Ni (0.25%-0.40%) increases the natural corrosion potential and inhibits anodic dissolution; Cu (0.25%-0.40%) combines with Cr to promote the rapid formation of a protective rust layer, while simultaneously precipitating a Cu-Ni binary high-temperature alloy phase, offsetting the negative impact of low-melting-point Cu on increased crack susceptibility. Tempered bainite (ferrite + dispersed carbides) reduces the potential difference between ferrite and carbides, weakening the driving force for microporous corrosion; low residual stress (due to quenching and tempering) reduces stress corrosion susceptibility. Ultra-low sulfur (≤0.003%) reduces MnS inclusions, inhibiting the initiation of pitting corrosion; and ultra-low hydrogen (≤1.5 ppm) prevents hydrogen embrittlement and delayed fracture. LF+RH double refining reduces oxide inclusions, improves surface density, protects casting (high carbon steel protective slag) to prevent secondary oxidation, and reduces surface defects.

[0061] In summary, this invention achieves a synergistic design of composition, process, and microstructure. Raising the Cr content to 0.75% and adding Ni / Cu promotes the formation of a dense, well-adherent rust layer on the steel surface, preventing rust shedding and doubling the lifespan in cyclic corrosion tests (simulating wet-dry cycles). By replacing expensive metal components such as Mo and high Ni content with a small amount of a ternary Cr-Ni-Cu alloy, this synergistic design achieves a balance between high strength (yield ≥ 1450 MPa) and high corrosion resistance (corrosion rate ≤ 70% relative to 75Cr1 high-carbon steel). Furthermore, by achieving a Ni / Cu ratio of 1 ≤ 2, this overcomes the challenge of crack control in corrosion-resistant high-carbon steel. While maintaining the core performance of 75Cr1, this invention enhances corrosion resistance through economical alloying elements (Ni / Cu replacing precious Mo), resolving the "hardness-corrosion resistance-cost" dilemma. This presents significant cost advantages and represents a technological breakthrough.

[0062] The above-described embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present application, and should all be included in the scope of protection of the present application.

Claims

1. A corrosion-resistant high-carbon steel plate, characterized by: The chemical composition weight percentage content 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, the balance is Fe and unavoidable impurities, wherein, calculated according to the chemical composition weight percentage, 1≤Ni / Cu≤2; The preparation method comprises the following steps in sequence: molten iron pretreatment, converter smelting, refining, continuous casting, hot rolling, and heat treatment; Wherein: the temperature of the converter smelting is 1600℃~1700℃; The refining adopts LF slagging desulfurization and RH vacuum treatment double refining process; The continuous casting adopts high carbon steel protective slag for protective casting, the temperature of molten steel in the tundish is controlled at 1450-1550°C, and the continuous casting billet drawing speed is controlled at 0.9-1.4m / min; During the hot rolling, after the ingot is cut, it is placed in a heating furnace for heating and then taken out. The rolling is carried out in two stages, namely rough rolling and finishing rolling. After finishing rolling, the hot rolled coil is water-cooled to 700°C to 750°C to obtain the hot rolled coil. The hot rolled coil is cooled to room temperature at a cooling rate of 10 to 15°C / s. The hot rolled coil is placed in a slow cooling pit for cooling. The cumulative reduction rate of the hot rolling is ≥95%; During the heat treatment, the steel plate is subjected to quenching and tempering treatment, which includes quenching and tempering. The quenching heating temperature is 800-900°C, the quenching holding time is 10-20 minutes, the tempering temperature is 400-500°C, the tempering holding time is 7-10 hours, and the steel plate is air-cooled to room temperature after tempering.

2. The corrosion-resistant high carbon steel plate according to claim 1, characterized in that: The metallographic structure of the corrosion-resistant high carbon steel plate is tempered troostite.

3. The method for processing a corrosion-resistant high-carbon steel plate according to any one of claims 1 to 2, characterized in that: The following steps are included in sequence: Hot metal pretreatment, converter smelting, refining, continuous casting, hot rolling, heat treatment, including: The temperature of the converter smelting is 1600°C to 1700°C; The refining adopts LF slagging desulfurization and RH vacuum treatment double refining process; The continuous casting adopts high carbon steel protective slag for protective casting, the temperature of molten steel in the tundish is controlled at 1450-1550°C, and the continuous casting billet drawing speed is controlled at 0.9-1.4m / min; During the hot rolling, after the slab is cut, it is placed in a heating furnace for heating and then taken out. The rolling is carried out in two stages, namely rough rolling and finishing rolling. After finishing rolling, the slab is water-cooled and rolled to obtain a hot-rolled coil. The hot-rolled coil is cooled to room temperature, and the cumulative reduction rate of the hot rolling is ≥95%; During the heat treatment, the steel plate is subjected to a quenching and tempering treatment, which includes quenching and tempering. The quenching heating temperature is 800-900° C., the tempering temperature is 400-500° C., and after tempering, the steel plate is air-cooled to room temperature.

4. The method for processing a corrosion-resistant high-carbon steel plate according to claim 3, wherein: The temperature of the converter smelting is 1650°C to 1670°C.

5. The method for processing a corrosion-resistant high-carbon steel plate according to claim 3, wherein: The refining adopts LF+RH double refining treatment, the weak stirring time of LF slagging and desulfurization is ≥15 minutes, and the outlet temperature is 1570~1600℃; the degassing time of RH vacuum treatment is ≥10 minutes, and the outlet temperature is 1530~1550℃.

6. The method for processing a corrosion-resistant high-carbon steel plate according to claim 3, wherein: The temperature of the molten steel in the tundish during continuous casting is controlled at 1480-1500° C., and the casting speed of the continuous casting billet is controlled at 1.0-1.3 m / min.

7. The method for processing a corrosion-resistant high-carbon steel plate according to claim 3, wherein: During the hot rolling, after the slab is cut, it is quickly put into the heating furnace, the slab entering the furnace temperature is ≥700°C, the slab stays in the heating furnace for 120-150 minutes, a weak reducing atmosphere is used in the heating furnace, the air excess coefficient is 0.9-1.0, and the temperature out of the heating furnace is controlled at 1170-1210°C.

8. The method for processing a corrosion-resistant high-carbon steel plate according to claim 3, wherein: During the hot rolling, the roughing temperature is ≥1060°C, the cumulative roughing reduction is ≥80%, the cumulative finishing reduction is ≥80%, the finishing start temperature is ≥1030°C, the finishing temperature is 880°C to 920°C, and after finishing rolling, the hot rolled coil is water cooled to 700°C to 750°C for coiling, with the cooling rate controlled at 10 to 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.

9. The method for processing a corrosion-resistant high-carbon steel plate according to claim 3, wherein: During the heat treatment, the steel plate is subjected to quenching and tempering treatment at a quenching heating temperature of 820-860° C. for a holding time of 10-20 minutes, and a tempering temperature of 430-480° C. for a holding time of 7-10 hours before air cooling to room temperature.

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