A steel plate with excellent low-temperature wear resistance and its preparation method

Abstract

This invention belongs to the field of iron and steel metallurgy technology, and particularly relates to a steel plate with excellent low-temperature wear resistance and its preparation method. The main chemical composition and proportions, calculated by mass percentage, are as follows: C: 0.05%–0.08%, Si: 0.6%–0.8%, Mn: 0.50%–0.8%, P: ≤0.015%, S: ≤0.005%, Nb: 0.01%–0.016%, V: ≤0.005%, Ti: ≤0.005%, Ni: 0.5%–0.8%, Cr: 0.5%–0.8%, Cu: 0.4%–0.6%, Als: 0.04%–0.05%, with the balance being Fe and unavoidable impurity elements. The steel plate has a dual-phase microstructure of ferrite and bainite. The preparation method includes smelting, continuous casting, slow cooling of the billet, reheating of the billet, controlled rolling and cooling, rolling, laminar flow cooling, and slow stacking cooling. Compared with the prior art, the beneficial effects of the present invention are: the deformation of each phase in the material under stress is more uniform and consistent, reducing the occurrence of large-scale spalling, thereby improving the overall low-temperature wear resistance of the material and reducing the low-temperature wear rate of the material.

Description

Technical Field

[0001] This invention belongs to the field of iron and steel metallurgy technology, and particularly relates to a steel plate with excellent low-temperature wear resistance and its preparation method. Background Technology

[0002] In recent years, the development of polar oil and gas resources has received increasing attention, leading to a significant increase in the demand for steel used in polar ships and buildings. The polar climate is frigid, with temperatures consistently below 0°C, and winter temperatures reaching -40°C or even lower. Moreover, unlike steel materials used in general low-temperature environments, the steel materials used in ships and buildings operating in polar environments not only need to withstand the low temperatures but also the friction and abrasion from media such as sea ice and reefs. This places higher demands on the low-temperature wear resistance of these materials.

[0003] Low temperatures directly impact the properties of steel. Generally, the strength of steel increases with decreasing temperature, while its plasticity and fracture resistance decrease. Specifically, at low temperatures, the wear mechanism of steel shifts from surface fatigue wear to surface adhesion and abrasive failure. This is due to the increased strength and hardness of the surface microstructure at low temperatures. If the difference in hardness between different phases (such as ferrite and bainite) in a dual-phase steel increases at low temperatures, the deformation of each phase under stress during low-temperature wear will be inconsistent. The lower-hardness phase will deform more, while the higher-hardness phase will deform less. Macroscopically, this manifests as numerous particles or micro-protrusions on the material surface. These particles and protrusions fracture and fail during further friction, leading to large-scale spalling and detachment of the material surface. This increases the material's low-temperature abrasion weight loss and reduces its resistance to low-temperature wear. Previously, people often only focused on the wear resistance of materials at room temperature and high temperatures, rarely paying attention to the wear performance of steel in polar low-temperature environments. However, with the increasing number of polar ships and structures, it is necessary to pay attention to the wear performance of steel materials in the low-temperature polar environment and to develop steel materials with better low-temperature wear performance. Currently, polar ships and structures mainly use the national standard for marine and offshore steel grade E. The qualification standard for grade E steel materials is to meet the impact test at -40℃, and the impact value must be greater than the value specified in the standard, but there are no requirements for the wear resistance of the material at low temperatures.

[0004] Chinese invention patent application number 20181083903.6 discloses a wear-resistant steel plate with excellent -60℃ ultra-low temperature impact toughness and its production method. The steel plate has a tensile strength ≥1300MPa, elongation ≥12%, and Charpy V-notch longitudinal impact energy ≥30J at -60℃; the surface and core Brinell hardness both meet 370~450HB; the plate shape is good, and the flatness of the steel plate is ≤5mm / m. This patent uses a quenching process, and the internal structure is martensitic, with high hardness and low impact toughness. The microstructure of this invention is completely different from that of this patent, and the patent does not provide the specific wear rate of the material under low temperature conditions. Summary of the Invention

[0005] The purpose of this invention is to provide a steel plate with excellent low-temperature wear resistance and its preparation method, overcoming the shortcomings of existing technologies. It utilizes a high Si content composition design to enhance the strength and hardness of the ferrite structure, resulting in a more uniform hardness distribution across the material phases and better wear resistance at low temperatures. The TMCP production process is economical and convenient, suitable for mass production. This invention develops a high-strength, easily weldable steel material with good low-temperature wear resistance, suitable for service in polar cryogenic environments. It provides high-quality steel materials for the construction of polar ships, buildings, and other steel structures, meeting the requirements of Class E steel materials while offering excellent low-temperature wear resistance.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] One technical solution: A steel plate with excellent low-temperature wear resistance, characterized in that, calculated by mass percentage, its main chemical composition and proportions are as follows: C: 0.05%–0.08%, Si: 0.6%–0.8%, Mn: 0.50%–0.8%, P: ≤0.015%, S: ≤0.005%, Nb: 0.01%–0.016%, V: ≤0.005%, Ti: ≤0.005%, Ni: 0.5%–0.8%, Cr: 0.5%–0.8%, Cu: 0.4%–0.6%, Als: 0.04%–0.05%, with the balance being Fe and unavoidable impurity elements. The microstructure of the steel plate is a dual-phase structure of ferrite + bainite.

[0008] The mechanisms of action of each alloy component in the steel of this invention are as follows:

[0009] C: Carbon is the main alloying element in steel and plays a key role in strengthening the steel. However, as the carbon content increases, the plasticity, low-temperature toughness, and resistance to weld cracking of steel will decrease. Considering both product performance and economy, the present invention preferably controls the C content to be between 0.05% and 0.08%.

[0010] Silicon (Si): Silicon is a major deoxidizing component in steelmaking, acting as both a deoxidizer and a reducing agent. The Si content in many carbon steels is actually introduced during the steelmaking process as a reducing and deoxidizer, rather than being intentionally added in the composition design. Adding Si can improve the elastic limit, yield strength, and yield ratio of steel. However, higher Si levels may reduce the low-temperature toughness and deteriorate the surface quality. Therefore, many steel plates used in low-temperature environments generally employ a low-silicon, high-manganese composition. However, Si has strong solid solution properties, dissolving in ferrite and austenite to improve the hardness and strength of steel. Its effect is second only to phosphorus, and stronger than elements such as manganese, nickel, chromium, tungsten, molybdenum, and vanadium. In this invention, the main phases of the steel are ferrite and bainite. Increasing the Si content can enhance the strength and hardness of ferrite and improve its wear resistance. However, since bainite has a high carbon content, increasing the Si content has little effect on enhancing the strength and hardness of bainite. Thus, a suitable Si content reduces the difference in strength and hardness between ferrite and bainite in the dual-phase microstructure of the steel plate. During low-temperature wear, the deformation of each phase in the material is more uniform, making it less prone to the formation of microparticles or microprotrusions due to uneven plastic deformation, thereby reducing the occurrence of large-scale spalling and improving the overall low-temperature wear resistance of the material, thus reducing the low-temperature wear rate. In summary, the preferred Si content in this invention is 0.6% to 0.8%.

[0011] Manganese (Mn): Manganese can be infinitely dissolved in iron, which can improve the strength of steel plates while ensuring sufficient plasticity and toughness. Therefore, Mn is a widely used strengthening element in steel. Mn can react with sulfur (S) in steel to form MnS, thereby reducing the harmful effects of S. However, excessive Mn content will exacerbate segregation in continuously cast billets, leading to poor uniformity of the steel plate structure, which is detrimental to the steel plate's resistance to lamellar tearing, plasticity, and weldability. This invention has already incorporated a relatively high amount of silicon (Si). To ensure that the material has reduced sensitivity to weld cracking, the absolute content of Mn must be reduced. Therefore, the preferred Mn content range in this invention is 0.50% to 0.8%.

[0012] P: Phosphorus is a harmful element in steel, negatively impacting the material's plasticity and toughness. This invention aims for comprehensive performance at low temperatures; therefore, the P content is strictly controlled to ≤0.015%.

[0013] Sulfur (S) is a harmful element in steel, negatively impacting the material's plasticity and toughness. High S content easily leads to the formation of large amounts of long, thin inclusions such as MnS. Therefore, the S content must be strictly controlled to ≤0.005%.

[0014] Als: Aluminum acts as a deoxidizing and grain-refining element, but excessive amounts can easily cause hot cracks in the cast billet and reduce the toughness of the steel. Therefore, the preferred Al content range in this invention is 0.04% to 0.05%.

[0015] Niobium (Nb) can effectively refine the grain size of steel, improving its strength and toughness. The effect is not significant when the addition amount is less than 0.01%; excessive amounts may reduce the toughness and weldability of the steel. Therefore, this invention preferably controls the Nb content to be between 0.01% and 0.016%.

[0016] Cr: Chromium is an important element for improving the hardenability of steel. An appropriate amount of chromium can improve the corrosion resistance of steel plates. Therefore, the preferred Cr content in this invention is controlled at 0.5% to 0.8%.

[0017] Cu (Cu): Copper can improve the corrosion resistance and strength of steel, as well as its weldability and formability. However, Cu tends to cause hot brittleness in steel and needs to be used in combination with Ni (Ni). Therefore, the preferred Cu content range in this invention is 0.4% to 0.6%.

[0018] Ni: Nickel has a solid solution strengthening effect, which can promote the formation of a stable austenitic structure in alloy steel and improve the toughness of steel. It also has a beneficial effect on improving the strength and corrosion resistance of steel. In addition, the addition of Ni can reduce the tendency of hot cracking when the Cu content is high. Therefore, the Ni content in this invention is controlled at 0.5% to 0.8%.

[0019] Ti: Titanium can improve the strength of steel and plays a role mainly in the form of TiN. This invention does not rely on Ti as the main strengthening component, so the vanadium content is controlled at 0% to 0.005%.

[0020] Vanadium (V) has a significant precipitation strengthening effect on steel. Fine, dispersed vanadium particles can precipitate from the martensitic or ferrite matrix, thus significantly strengthening the steel. This invention does not rely on vanadium as the main strengthening component; therefore, the vanadium content is controlled at 0%–0.005%.

[0021] O and H: Harmful gaseous elements. Oxygen easily forms inclusions, and hydrogen easily produces white spots, greatly reducing the plasticity and toughness of steel plates and leading to delayed cracking and other hazards. Therefore, this invention strictly controls the content of both: O content ≤ 0.0018%; H content ≤ 0.0002%.

[0022] Technical Solution Two: A method for preparing steel plates with excellent low-temperature wear resistance, comprising smelting, continuous casting, billet reheating, controlled rolling and cooling, rolling, laminar flow cooling and slow stacking cooling, the specific steps of which are as follows:

[0023] Smelting: Smelting is carried out in a converter according to the chemical composition, avoiding exceeding the upper limit of carbon equivalent, and ladle refining is performed. The refined molten steel is then subjected to RH treatment for 20-40 minutes. After RH treatment, to prevent an increase in gas content, continuous casting should be carried out immediately to ensure that [H] ≤ 2.0 ppm and [O] ≤ 18 ppm in the steel.

[0024] Continuous casting: The molten steel obtained from smelting is continuously cast to obtain the required billet, and the superheat of the tundish is controlled to be ≤30℃;

[0025] Billet reheating: The cooled continuous casting billet is heated to 1080-1150℃, and the temperature of the soaking zone is maintained between 1050-1080℃. The heating time in the furnace is 5.5h, of which the holding time in the soaking zone is 30-60min.

[0026] Rolling: The entire process uses TMCP rolling technology, employing a two-stage controlled rolling technique in the austenite recrystallization zone and the austenite non-recrystallization zone. The initial rolling temperature is 980-1030℃, ensuring a single-pass deformation rate of ≥15%. The second stage is the finishing rolling stage, ensuring a single-pass deformation rate of ≥13% and a cumulative deformation of greater than 60%. The thickness of the intermediate billet is 3-3.5 times that of the finished steel plate. The finishing rolling temperature is between 780-850℃, and the final rolling temperature is between 680-720℃. The larger rolling deformation can refine the original austenite structure, obtaining uniform fine grains in the full-thickness section, thereby improving the strength and toughness of the steel plate and increasing its wear resistance.

[0027] Laminar flow cooling: ACC fully automatic laminar flow accelerated cooling is used, with a cooling start temperature of 640-680℃, a cooling rate controlled at 10℃ / s~20℃ / s, and a red-hot temperature controlled between 420-480℃;

[0028] Stacking and slow cooling: After cooling, the steel plates are stacked and slow cooled for ≥24 hours. During the slow cooling period, the steel plates are not allowed to be moved.

[0029] Compared with the prior art, the beneficial effects of the present invention are:

[0030] 1) The present invention preferably uses the alloy composition of steel to make full use of the solid solution strengthening effect of Si element on ferrite structure, reducing the hardness difference between ferrite phase and bainite phase. During low temperature wear, the deformation of each phase in the material under stress is more uniform and consistent, and it is not easy to generate microparticles or microprotrusions due to uneven plastic deformation, reducing the occurrence of large-scale spalling, thereby improving the overall low temperature wear resistance of the material and reducing the low temperature wear rate of the material.

[0031] 2) This invention uses TMCP technology, which eliminates the need for complex conditioning processes, resulting in low production costs and high efficiency;

[0032] 3) This invention is applicable to ships, buildings and other engineering projects in polar cold regions, and is especially suitable for steel used in ships and engineering projects that are resistant to low-temperature wear. Attached Figure Description

[0033] Figure 1 These are 3D morphological comparison images of wear tracks at room temperature for embodiments and comparative samples of the present invention;

[0034] Figure 2 These are 3D morphological comparison images of the wear at -40℃ in the embodiments and comparative samples of the present invention. Detailed Implementation

[0035] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0036] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0037] The components of the embodiments of the invention described and shown in the accompanying drawings can typically be arranged and designed in numerous different configurations. Therefore, the following detailed description of the embodiments of the invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention.

[0038] The present invention relates to a steel plate with excellent low-temperature wear resistance. Its composition, by mass percentage, is as follows: C: 0.05%–0.08%, Si: 0.6%–0.8%, Mn: 0.50%–0.8%, P: ≤0.015%, S: ≤0.005%, Nb: 0.01%–0.016%, V: ≤0.005%, Ti: ≤0.005%, Ni: 0.5%–0.8%, Cr: 0.5%–0.8%, Cu: 0.4%–0.6%, Al: 0.03%–0.05%, with the balance being Fe and unavoidable impurity elements.

[0039] Table 1 shows the chemical composition of Examples 1-6 and Comparative Samples 1-2 of the present invention; Table 2 shows the comparison of rolling method parameters of the Examples and Comparative Samples of the present invention; Table 3 shows the basic performance data of Examples 1-6 and Comparative Samples 1-2 of the present invention; Table 4 shows the low-temperature wear rate data of Examples 1-6 and Comparative Samples 1-2 of the present invention; Table 5 shows the comparison of wear rate data of Examples 1-6 and Comparative Samples 1-2 of the present invention under normal temperature and low temperature environments.

[0040] Table 1 shows the chemical composition of Examples 1-6 and Comparative Samples 1-2 of the present invention.

[0041]

[0042] Table 2 Rolling methods of embodiments and comparative samples of the present invention

[0043]

[0044] Table 3 Basic performance of embodiments and comparative samples of the present invention

[0045]

[0046] Table 4 Low-temperature wear rate of the embodiments of the present invention and the comparative samples

[0047]

[0048] Note: Wear rate is calculated using the following formula:

[0049]

[0050] In the formula: w represents the wear rate, in mm. 3 / (N·m); Δm represents the weight loss due to wear; N represents the frictional load in N; D represents the wear distance; ρ represents the density of the material.

[0051] Table 5 Comparison of wear rates of the embodiments of the present invention and comparative samples under normal temperature and low temperature environments.

[0052]

[0053] As can be seen from the embodiments, this invention, by rationally controlling the content of Si element and combining it with a reasonable proportion of alloying elements such as Ni, Cr, and Cu, fully utilizes the solid solution strengthening ability of silicon to improve the material strength while ensuring that the material still has good plasticity and low-temperature toughness. Compared with the comparative sample, this invention has higher strength and slightly lower low-temperature impact toughness, but the wear rate at low temperature (-40℃) is much lower than that of the comparative sample, indicating good low-temperature wear resistance. Combining the 3D morphology of low-temperature wear, it can be seen that the mechanism of low-temperature wear resistance of this invention is that the low-temperature hardness among the components of the material is more uniform, and the deformation of each phase under stress tends to be consistent. Macroscopically, this manifests as fewer particles or micro-protrusions on the material surface, thereby reducing the possibility of large-area spalling and reducing the amount of low-temperature wear.

[0054] In summary, the steel plate of this invention exhibits excellent low-temperature wear resistance, with a yield strength ≥420MPa, tensile strength ≥600MPa, elongation ≥17%, and an impact test result of ≥60J at -40℃. The wear rate at -40℃ is ≤1.5E-04mm³ / (N·m), demonstrating good overall low-temperature wear resistance, making it suitable for service in wear-resistant environments, especially in polar and extremely cold regions.

[0055] The embodiments of the present invention have been described above with reference to data. However, the present invention is not limited to the above embodiments. Various changes can be made according to the purpose of the invention. Any changes, modifications, substitutions, combinations or simplifications made in accordance with the spirit and principle of the technical solution of the present invention shall be equivalent substitutions. As long as they meet the purpose of the invention and do not deviate from the technical principle and inventive concept of the present invention, they shall fall within the protection scope of the present invention.

Claims

1. A steel plate with excellent low-temperature wear resistance, characterized in that, The main chemical components and their important proportions, calculated by mass percentage, are as follows: C: 0.05%~0.08%, Si: 0.74%~0.8%, Mn: 0.50%~0.8%, P: ≤0.015%, S: ≤0.005%, Nb: 0.01%~0.016%, V: ≤0.005%, Ti: ≤0.005%, Ni: 0.5%~0.8%, Cr: 0.5%~0.8%, Cu: 0.4%~0.6%, Al: 0.04~0.05%, with the balance being Fe and unavoidable impurities; The steel plate has a dual-phase structure of ferrite and bainite, a yield strength ≥420MPa, a tensile strength ≥600MPa, an elongation ≥17%, an impact test result of 60J at -40℃, and a thickness of 20~40mm. The steel plate was tested for low-temperature wear performance using a friction and wear testing machine at a test temperature of -40℃. Under these conditions, a wear rate of ≤15E-05mm was obtained. 3 / (N·m).

2. The method for manufacturing a steel plate with excellent low-temperature wear resistance according to claim 1, characterized in that, The process includes smelting, continuous casting, billet reheating, rolling, laminar flow cooling, and slow stacking cooling. The specific steps are as follows: 1) Smelting: The steel is smelted in a converter according to the chemical composition ratio and then refined outside the ladle. The refined steel is then treated with RH to ensure that [H] ≤ 2.0 ppm and [O] ≤ 18 ppm. 2) Continuous casting: The molten steel obtained in step 1) is continuously cast to obtain the required billet, and the superheat of the tundish is controlled to be ≤30℃. 3) Reheating the billet: The temperature of the continuously cast billet is heated to 1080-1150℃, and the temperature of the soaking zone is maintained between 1050-1080℃. The heating time in the furnace is 5.5 hours, of which the holding time in the soaking zone is 30-60 minutes. 4) Rolling: The entire process uses the TMCP rolling process, employing a two-stage controlled rolling technology in the austenite recrystallization zone and the austenite non-recrystallization zone. The initial rolling temperature is 980-1030℃, ensuring a single-pass deformation rate of ≥15%. The second stage is the finishing rolling stage, ensuring a single-pass deformation rate of ≥13% and a cumulative deformation of greater than 60%. The thickness of the intermediate billet steel plate before heating is 3-3.5 times the thickness of the finished steel plate. The finishing rolling temperature is between 780-850℃, and the final rolling temperature is between 680-720℃. 5) Laminar flow cooling: ACC fully automatic laminar flow accelerated cooling is used. The cooling start temperature is 640-680℃, the cooling rate is controlled at 10℃ / s~20℃ / s, and the red temperature is controlled between 420-480℃. 6) Stacking and slow cooling: After cooling, the steel plates are stacked and slow cooled to room temperature for ≥24 hours.

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