Nickel-containing steel and preparation method thereof

Abstract

The invention discloses nickel-containing steel and a preparation method thereof. The technical problem that in the prior art, the mechanical property is guaranteed by increasing the nickel content, and the cost is high is solved. The preparation method of the nickel-containing steel comprises the following steps: heating a steel ingot or a steel billet to obtain a heated billet; sequentially carrying out first-pass rolling on the heating blank to obtain an intermediate blank; the intermediate billet is subjected to second-pass rolling and then directly cooled, and a steel plate is obtained; the steel plate is subjected to heat treatment, and nickel-containing steel is obtained; wherein the rolling deformation rate of the first-pass rolling and the rolling deformation rate of the second-pass rolling are both not lower than 45%, and the cooling rate of the cooling process is not lower than 25 DEG C / s. According to the preparation method of the nickel-containing steel, under the condition that the nickel content does not need to be increased, the mechanical property is further improved, and the production cost is reduced.

Description

Technical Field

[0001] This application belongs to the technical field of nickel steel materials, specifically relating to a nickel-containing steel and its preparation method. Background Technology

[0002] Nickel-containing steel typically has a nickel content higher than 1.5%, making it suitable for cryogenic pressure vessels such as LNG storage tanks, liquid oxygen tanks, or liquid nitrogen tanks. Since LNG storage tanks operate at temperatures below -162°C, the materials used to construct them must possess not only sufficient strength but also excellent cryogenic toughness.

[0003] In related technologies, although nickel-containing steel can meet the performance requirements of LNG storage tanks, its high Ni content results in very high costs. Therefore, there is an urgent need for a lower-cost method for preparing nickel-containing steel for cryogenic containers. Summary of the Invention

[0004] To address the high cost of achieving mechanical properties through high nickel content, this application provides a nickel-containing steel and its preparation method.

[0005] In a first aspect of this application, a method for preparing nickel-containing steel is provided, comprising: Heating steel ingots or billets yields heated billets; The heated billet is subjected to a first rolling pass to obtain an intermediate billet; The intermediate billet is subjected to a second rolling pass and then directly cooled to obtain a steel plate; The steel plate is heat-treated to obtain nickel-containing steel; The rolling deformation rate of the first and second rolling passes is not less than 45%, and the cooling rate of the cooling process is not less than 25°C / s.

[0006] In some embodiments, the deformation rate of the first rolling pass is 45% to 60%, and the deformation rate of the second rolling pass is 55% to 70%.

[0007] In some implementations, the deformation rate of the first rolling pass is less than that of the second rolling pass.

[0008] In some embodiments, the cooling rate of the cooling process is 25°C / s to 35°C / s.

[0009] In some embodiments, the cooling end temperature is 150°C to 250°C.

[0010] In some embodiments, the temperature of the first rolling pass is 950°C to 1000°C; and the temperature of the second rolling pass is 730°C to 850°C.

[0011] In some embodiments, the thickness of the heated billet is 100mm to 200mm, the thickness of the intermediate billet is 30mm to 100mm, and the thickness of the steel plate is 10mm to 40mm.

[0012] In some embodiments, the heat treatment temperature is 550℃~600℃, and the holding time during the heat treatment is 80min~120min.

[0013] In some embodiments, the mass fraction of Ni in the heated blank is 5.30% to 6.25%. In a second aspect of this application, a nickel-containing steel is provided, which is prepared using the method for preparing nickel-containing steel in the first aspect.

[0014] The method for preparing nickel-containing steel provided in this application employs a two-pass high-reduction rolling process to flatten and refine the austenite, introducing high-density dislocations, deformation bands, and substructure interfaces, thereby increasing the effective nucleation sites for quenching phase transformation. The residual heat from the second rolling pass is then used for direct high-rate cooling quenching, ensuring that the high-density dislocations, deformation bands, and substructure interfaces along the thickness direction, along with the refined austenite, are retained without reheating / recrystallization. This results in a fine and uniform lath martensite structure throughout the thickness of the steel plate, improving yield strength and tensile strength while ensuring uniformity of yield strength and tensile strength along the thickness. Because the lath martensite is abundant and fine, it possesses higher dislocation and interface conditions, promoting the formation of more and more stable reverse-transformed austenite, thus ensuring the low-temperature impact toughness of the nickel-containing steel.

[0015] In addition, this application uses the residual heat after the second pass for direct quenching, which reduces the risk of oxidation caused by offline reheating, reduces the number of process steps, and improves production efficiency.

[0016] This application improves the strength and low-temperature impact toughness of nickel-containing steel by using a two-stage high-pressure quenching method with a high cooling rate, thereby reducing the requirement for the amount of Ni alloy added and thus reducing costs. Attached Figure Description

[0017] Figure 1 The diagram shows the stress curve of the nickel-containing steel during the tensile process of Embodiment 1 of this application.

[0018] Figure 2 The microstructure of the edge in the thickness direction of the nickel-containing steel of Example 1 before heat treatment is shown.

[0019] Figure 3 The microstructure of the nickel-containing steel in Example 1 at the center in the thickness direction before heat treatment is shown.

[0020] Figure 4 The microstructure of the edge of the nickel-containing steel in the thickness direction of Example 1 is shown.

[0021] Figure 5 The microstructure of the nickel-containing steel in the thickness direction of Example 1 is shown. Detailed Implementation

[0022] To enable those skilled in the art to more clearly understand this application, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0023] According to the first aspect of this application, a method for preparing nickel-containing steel is provided. The prepared nickel-containing steel has high strength, good low-temperature solvent toughness, and more uniform mechanical properties in the thickness direction.

[0024] The method for preparing nickel-containing steel provided in this application includes steps 101, 102, 103, and 104: Step 101: Heat the steel ingot or billet to obtain a heated billet; Step 102: Perform the first rolling pass on the heated billet to obtain an intermediate billet; Step 103: After the intermediate billet is rolled in a second pass, it is directly cooled to obtain a steel plate; Step 104: Heat treat the steel plate to obtain nickel-containing steel.

[0025] For step 101, the raw material for nickel-containing steel can be steel ingots or steel billets. If steel billets are selected, they can be either slabs or square billets, and this application does not impose any restrictions.

[0026] In some embodiments, the chemical composition of steel ingots or billets may, by mass percentage, include: C: 0.04%–0.07%, Si: 0.05%–0.20%, Mn: 0.60%–1.00%, Ni: 5.30%–6.25%, Mo: 0.15%–0.30%, Alt: 0.02%–0.035%, P ≤ 0.006%, S ≤ 0.003%, with the balance being Fe and unavoidable impurities.

[0027] In other embodiments, the chemical composition of the steel ingot or billet may be further enhanced by adding Cr and Nb elements. That is, the chemical composition of the steel ingot or billet, by mass percentage, may include: C: 0.04%–0.07%, Si: 0.05%–0.20%, Mn: 0.60%–1.00%, Ni: 5.30%–6.25%, Mo: 0.15%–0.30%, Alt: 0.02%–0.035%, P≤0.006%, S≤0.003%, Cr≤0.08%, Nb: 0.01%–0.03%, with the balance being Fe and unavoidable impurities.

[0028] In some other embodiments, the chemical composition of the steel ingot or billet may also be the chemical composition of 9Ni steel in national standard GB / T 24510-2017, or the chemical composition of 7Ni steel in national standard GB / T 713.4.

[0029] The thickness of steel ingots or billets can be 100mm to 200mm, such as 110mm, 120mm, 130mm, 140mm, 150mm, 160mm, 170mm, 180mm or 190mm, etc.

[0030] The steel ingot or billet is heated to a temperature ranging from 1100℃ to 1200℃, such as 1110℃, 1115℃, 1120℃, 1125℃, 1130℃, 1135℃, 1140℃, 1145℃, or 1150℃. The heating time can range from 100 min to 250 min, such as 110 min, 120 min, 130 min, 140 min, 150 min, 160 min, 170 min, 180 min, 190 min, 200 min, 210 min, 220 min, 230 min, or 240 min.

[0031] For step 102, the heated billet is rolled in the first pass, during which the austenite is extended to form dislocations and deformation bands / shear bands, thereby inducing dynamic recrystallization and forming recrystallized austenite grains; these recrystallized austenite grains provide the initial austenite structure for the second stage of rolling.

[0032] In the first rolling pass, the rolling deformation rate is not less than 45%. The large rolling deformation rate allows the austenite to have sufficient extension and the density of dislocations and deformation bands / shear bands is high, which makes the dynamic recrystallization more complete and the recrystallized austenite grains finer. These finer recrystallized austenite grains provide a fine initial austenite structure for the second stage rolling.

[0033] In some embodiments, the rolling deformation rate of the first pass can be 45% to 60%, such as 47%, 49%, 50%, 52%, 54%, 55%, 57%, 58%, or 59%, which ensures the formation of fine recrystallized austenite. In other embodiments, the rolling deformation rate of the first pass can also be 30% to 40%, which also forms recrystallized austenite, while the mill rolling force is small and the plate shape is good.

[0034] In some embodiments, the temperature of the first rolling pass can be 950℃ to 1000℃, such as 955℃, 958℃, 960℃, 962℃, 965℃, 968℃, 970℃, 974℃, 978℃, 980℃, 982℃, 985℃, 987℃, 990℃, 992℃, 994℃, 996℃, or 998℃. Within the temperature range of 950℃ to 1000℃, austenitization can be achieved, promoting dynamic recrystallization and facilitating the refinement of austenite grains during deformation, resulting in a more uniform composition and microstructure. If the temperature of the first rolling pass is too high, it may, to some extent, cause coarsening of austenite grains and growth of recrystallized grains, leading to a coarse internal structure and reduced strength in nickel-containing steel. If the temperature of the first rolling pass is too low, it may result in insufficient austenitization of the material and suppression of dynamic recrystallization; it may also increase deformation resistance, increase rolling load, and increase the risk of cracks / edge cracks.

[0035] The thickness of the intermediate billet formed after the first rolling pass can be 30mm to 100mm, such as 40mm, 45mm, 50mm, 55mm, 60mm, 65mm, 70mm, 75mm, 80mm, 85mm or 90mm, etc.

[0036] For step 103, a second rolling pass is performed on the intermediate section. The deformation rate of the second rolling pass can be 55%–70%, such as 57%, 58%, 60%, 62%, 65%, 67%, or 69%. The deformation amount of the second rolling pass is very large, which further improves the deformation energy storage and deformation band density. This allows the austenite to be more fully flattened based on the fine initial austenite structure in the first stage, thereby introducing more high-angle interfaces / substructure boundaries. This provides fine and uniform austenite for subsequent direct cooling and quenching, ensuring the formation of fine martensite and improving the strength of nickel-containing steel.

[0037] In some embodiments, the deformation rate of the second rolling pass is greater than that of the first rolling pass. Since the first rolling pass has already formed a fine initial austenite structure, a larger deformation rate in the second rolling pass is necessary to achieve sufficient flattening of the austenite, resulting in ultrafine martensite after subsequent direct cooling and quenching, thus ensuring the strength of the nickel-containing steel. In other embodiments, the deformation rate of the second rolling pass can also be the same as that of the first rolling pass, which can also achieve sufficient flattening of the austenite to a certain extent, resulting in fine martensite after quenching.

[0038] In some embodiments, the temperature of the second rolling pass can be 730°C to 850°C, for example, 740°C, 745°C, 750°C, 752°C, 756°C, 760°C, 762°C, 764°C, 768°C, 770°C, 775°C, 778°C, 781°C, 784°C, 785°C, 789°C, 790°C, 795°C, 800°C, 810°C, 820°C, 830°C, 835°C, 840°C, or 845°C. Controlling the temperature of the second rolling pass to 730°C to 850°C ensures that the austenite is in the non-recrystallization region or close to the austenite. r3 Within a specific temperature range, the effective nucleation sites for martensite, such as austenite grain boundaries, deformation bands, and substructure interfaces, can be significantly increased. This refines the subsequent quenching phase transformation microstructure, specifically refining lath martensite and briquettes, thereby improving the strength and low-temperature impact toughness of nickel-containing steel. However, if the second rolling pass temperature is too high, austenite recrystallization may be more complete, leading to grain growth, weakening deformation bands and energy storage, reducing the effective nucleation sites for martensite, and ultimately resulting in a coarse microstructure and low low-temperature impact toughness.

[0039] After the second rolling pass, the thickness of the steel plate can be 10mm to 40mm, such as 12mm, 13mm, 14mm, 15mm, 16mm, 17mm, 20mm, 22mm, 24mm, 26mm, 28mm, 30mm, 32mm, 34mm, 36mm or 38mm, etc.

[0040] Because the temperature of the second rolling pass is lower than that of the first rolling pass, the intermediate billet needs to be air-dried before the second rolling. This means that the intermediate billet is directly cooled after the second rolling, including air-drying, the second rolling, and direct cooling. Air-drying the intermediate billet, besides requiring matching the required second rolling temperature, creates a temperature gradient between the upper and lower surfaces and the core in the thickness direction. The surface cools faster than the core. During the second rolling process, this forces deformation to shift towards the core in the thickness direction, significantly refining the microstructure of the middle portion in the thickness direction, resulting in fine and uniform austenite throughout the thickness direction after the second rolling.

[0041] In some embodiments, the rolling speed of the first pass can be 0.6 m / s to 1 m / s, such as 0.7 m / s, 0.8 m / s, or 0.9 m / s, and the cooling time is 25 s to 60 s, such as 27 s, 30 s, 31 s, 32 s, 33 s, 34 s, 40 s, 45 s, 50 s, or 55 s. Since the deformation of the upper and lower surfaces is greater than that of the center in the thickness direction during the first pass rolling, the rolling speed of the first pass is relatively fast, which can provide sufficient time for the steel to cool and form a surface "hard shell" on the intermediate billet. This allows for significant refinement of the microstructure in the middle part during the second pass rolling, thereby improving the uniformity of the strength and low-temperature impact toughness of the nickel-containing steel in the thickness direction.

[0042] Direct cooling in step 103 refers to cooling without reheating after the second rolling pass. During direct cooling quenching, the fine, uniform austenite formed after the second rolling stage undergoes a phase transformation, forming refined and uniform lath martensite, thus increasing the strip's strength. Because the cooling rate is no less than 25℃ / s, this high rate allows for the formation of a large amount of lath martensite in the center of the strip's thickness direction, improving both the strip's strength and ensuring uniformity in thickness direction strength and low-temperature impact toughness. During heat treatment, the high dislocation density within the lath martensite and the interfacial conditions promote the nucleation and stabilization of reverse-transformed austenite, thereby improving the low-temperature impact toughness of nickel-containing steel and ensuring its uniformity. Furthermore, direct cooling can reduce process steps and improve production efficiency.

[0043] In some embodiments, the cooling rate of the cooling process can be 25℃ / s to 35℃ / s, such as 27℃ / s, 28℃ / s, 29℃ / s, 30℃ / s, 31℃ / s, 32℃ / s, 33℃ / s, or 34℃ / s. A fast cooling rate ensures that the core of the strip in the thickness direction also has a faster cooling rate, allowing fine lath martensite to form in the center of the strip in the thickness direction, reducing performance fluctuations between the strip surface and the core. If the cooling rate is too high, the superposition of thermal stress and phase transformation stress may result in high residual stress after heat treatment; if the cooling rate is too low, it may lead to low core strength in the thickness direction, uneven strength in the thickness direction, and reduced low-temperature impact toughness.

[0044] In some embodiments, the cooling termination temperature can be between 150°C and 250°C, such as 160°C, 170°C, 180°C, 190°C, 200°C, 210°C, 220°C, 230°C, or 240°C. Controlling the cooling termination temperature to between 150°C and 250°C ensures sufficient martensite while allowing for subsequent slow cooling or self-heating treatments to release internal stress and improve plate shape.

[0045] For step 104, heat treatment, namely tempering, promotes the precipitation of dispersed carbides and causes moderate recovery of lath martensite, reducing the residual stress and brittleness of direct quenching; at the same time, under high dislocation and interface conditions, it promotes the nucleation and stabilization of reverse austenite, and improves the low-temperature impact toughness of nickel-containing steel.

[0046] In some embodiments, the heat treatment temperature can be 550℃~600℃, such as 560℃, 565℃, 570℃, 575℃, 580℃, 585℃, 590℃ or 595℃, etc., and the holding time in the heat treatment can be 80min~120min, such as 90min, 93min, 95min, 97min, 98min, 100min, 105min, 108min, 110min, 113min, 115min or 118min, etc.

[0047] Based on the same technical concept as the first aspect, the second aspect of this application provides a nickel-containing steel.

[0048] The nickel-containing steel provided in this application embodiment is prepared using the nickel-containing steel preparation method of any embodiment of the first aspect.

[0049] Example 1 Example 1 provides a method for preparing nickel-containing steel. In this example, a steel billet with a thickness of 100 mm is used. The chemical composition of the billet, calculated by mass percentage, includes: C 0.04%, Si 0.05%, Mn 0.61%, Ni 5.33%, Mo 0.15%, Nb 0.01%, Alt 0.02%, P 0.006%, S 0.003%, with the balance being Fe and unavoidable impurities. Using this billet, 5.5Ni steel with a thickness of 10 mm for cryogenic containers is prepared. The specific rolling method includes the following steps: S1. Heat the steel billet to 1150 ℃ for a total heating time of 150 min; roll the heated steel billet in the first pass, and then let the resulting steel plate air dry. S2. The steel plate is subjected to a second stage of rolling, with a rolling deformation temperature range of 840℃; S3. The rolled steel plate is cooled in water at a final cooling temperature of 150 ℃ and a cooling rate of 35 ℃ / s to prepare nickel-saving steel for cryogenic containers with a thickness of 10 mm.

[0050] S4. The steel plate obtained after rolling is subjected to heat treatment at a temperature of 580 ℃ for a time of 80 min.

[0051] Example 2 Example 2 provides a method for preparing nickel-containing steel. In this example, a steel billet with a thickness of 100 mm is used. The chemical composition of the billet, calculated by mass percentage, includes: C 0.06%, Si 0.17%, Mn 0.76%, Ni 5.58%, Mo 0.22%, Nb 0.02%, Alt 0.025%, P 0.004%, S 0.001%, with the balance being Fe and unavoidable impurities. A 20 mm thick nickel-saving steel for cryogenic containers is prepared using this billet. The specific rolling method includes the following steps: S1. Heat the steel billet to 1150 ℃ for a total heating time of 150 min; perform the first stage rolling on the heated steel billet, with a rolling deformation temperature range of 955 ℃. The thickness of the steel plate obtained from the first stage rolling is 50 mm, and the rolling deformation is 50%. Then, the obtained steel plate is left to air dry. S2. The steel plate is subjected to a second stage of rolling, with a rolling deformation temperature range of 775℃ and a rolling deformation amount of 60%. S3. The rolled steel plate is cooled in water at a final cooling temperature of 100 ℃ and a cooling rate of 35 ℃ / s to prepare nickel-saving steel for cryogenic containers with a thickness of 20 mm.

[0052] S4. The rolled steel plate is subjected to heat treatment at a temperature of 580 ℃ for 100 min.

[0053] Example 3 Example 3 provides a method for preparing nickel-containing steel. In this example, a steel billet with a thickness of 200 mm is used. The chemical composition of the billet, calculated by mass percentage, includes: C 0.07%, Si 0.20%, Mn 0.98%, Ni 6.24%, Mo 0.29%, Nb 0.03%, Alt 0.035%, P 0.005%, S 0.002%, with the balance being Fe and unavoidable impurities. A 40 mm thick nickel-saving steel for cryogenic containers is prepared using this billet. The specific rolling method includes the following steps: S1. Heat the steel billet to 1110 ℃ for a total heating time of 240 min; perform the first stage rolling on the heated steel billet to obtain a steel plate with a thickness of 100 mm and a rolling deformation of 50%; then allow the obtained steel plate to air dry. S2. The steel plate is subjected to a second stage of rolling, with a rolling deformation temperature range of 735℃ and a rolling deformation amount of 60%; S3. The rolled steel plate was cooled in water at a final cooling temperature of 220 ℃ and a cooling rate of 25 ℃ / s to prepare nickel-saving steel for cryogenic containers with a thickness of 40 mm.

[0054] S4. The rolled steel plate is subjected to heat treatment at a temperature of 580 ℃ for 120 min.

[0055] Example 4 Example 4 provides a method for preparing nickel-containing steel. Example 4 is based on Example 1. The only difference between Example 4 and Example 1 is that the steel billet does not contain Nb and Alt elements, while the other components and processes are the same.

[0056] Comparative Example 1 Comparative Example 1 provides a method for preparing nickel-containing steel. Comparative Example 1 is based on Example 1. The only difference between Comparative Example 1 and Example 1 is that the mass fraction of nickel in the steel billet is 4.50%, while the other components and preparation process are exactly the same as in Example 1.

[0057] Comparative Example 2 Comparative Example 2 provides a method for preparing nickel-containing steel. Comparative Example 2 is based on Example 1. The only difference between Comparative Example 2 and Example 1 is that the rolling deformation temperature range in the second stage is 915°C. The other processes are exactly the same as in Example 1.

[0058] Comparative Example 3 Comparative Example 3 provides a method for preparing nickel-containing steel. Comparative Example 3 is based on Example 1. The only difference between Comparative Example 3 and Example 1 is that the heat treatment temperature is 350 °C, and the other processes are exactly the same as those in Example 1.

[0059] Table 1

[0060] Table 2

[0061] Table 3

[0062] Table 4

[0063] The nickel-containing steels provided in Examples 1 to 4 and Comparative Examples 1 to 3 were sampled and tested for mechanical properties and low-temperature impact energy. The results are shown in Table 4.

[0064] As shown in Table 4, the nickel-containing steels provided in Examples 1 to 4 have a yield strength of not less than 799 MPa, a tensile strength of not less than 834 MPa, an elongation of not less than 21.7%, good mechanical properties, a low-temperature impact energy of not less than 185 J at -196℃, and good low-temperature impact toughness.

[0065] Due to the size limitations of nickel-containing steel, it was not possible to take multiple samples along the thickness direction for mechanical property and low-temperature impact toughness testing. Therefore, samples were taken from the nickel-containing steel plates of Example 1 before and after heat treatment, and samples were taken at one-quarter and one-half of the thickness direction for observation. Figure 2 and Figure 3 The microstructures of the nickel-containing steel in Example 1 at one-quarter and one-half of its thickness before heat treatment are shown respectively. Figure 2 as well as Figure 3 Observations show that a large number of fine lath martensite particles are formed at the quarter and half of the thickness, and the size of the lath martensite particles is very similar at both locations. Therefore, the mechanical properties of nickel-containing steel are more uniform in the thickness direction.

[0066] Figure 4 and Figure 5 The microstructures of the nickel-containing steel in Example 1 at one-quarter and one-half of its thickness are shown respectively. Figure 4 as well as Figure 5 Observations show that a large number of fine lath martensite particles are formed at the quarter and half of the thickness, and the size of the lath martensite particles at both locations is very close. The grain boundaries of the lath martensite form reverse-transformed austenite, which makes the low-temperature impact toughness of nickel-containing steel more uniform in the thickness direction.

[0067] This application employs a two-pass continuous high-reduction controlled rolling process, which ensures that the austenite in all parts of the strip in the thickness direction is fully flattened before quenching, introducing high-density dislocations, deformation bands, and substructure interfaces. This increases the effective nucleation sites for phase transformation and refines the microstructure before quenching. After the second pass, residual heat is used for direct high-rate quenching, allowing the aforementioned deformation defects and refined state to be preserved without reheating / recrystallization. Simultaneously, the cooling rate of the core in the thickness direction is maintained, resulting in a fine and uniform lath martensite microstructure throughout the thickness direction. This improves yield strength and tensile strength while ensuring strength uniformity in the thickness direction.

[0068] Subsequently, during the heat treatment, i.e., tempering, the dislocation enrichment regions in the thickness direction are nearly identical to the lath boundary conditions, promoting the nucleation and stabilization of reverse-transformed austenite in all thickness directions, thereby significantly improving the low-temperature impact toughness at -196℃ while ensuring the uniformity of the low-temperature impact toughness in the thickness direction. In this application, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "on top of," and "over" the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0069] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", and "counterclockwise" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0070] In this application, unless otherwise expressly specified and limited, the terms "connection," "fixed," etc., should be interpreted broadly. For example, "fixed" can mean a fixed connection, a detachable connection, or an integral part; it can mean a mechanical connection or an electrical connection; it can mean a direct connection or an indirect connection through an intermediate medium; it can mean the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0071] Furthermore, the use of terms such as "first" and "second" in this application is for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, features defined with "first" or "second" may explicitly or implicitly include one or more features. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0072] Although embodiments of this application have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the claims and their equivalents.

Claims

1. A method for preparing nickel-containing steel, characterized in that, include: Heating steel ingots or billets yields heated billets; The heated billet is subjected to a first rolling pass to obtain an intermediate billet; The intermediate billet is subjected to a second rolling pass and then directly cooled to obtain a steel plate; The steel plate is heat-treated to obtain nickel-containing steel; The rolling deformation rate of the first and second rolling passes is not less than 45%, and the cooling rate of the cooling process is not less than 25°C / s.

2. The method for preparing nickel-containing steel according to claim 1, characterized in that, The deformation rate of the first rolling pass is 45% to 60%, and the deformation rate of the second rolling pass is 55% to 70%.

3. The method for preparing nickel-containing steel according to claim 2, characterized in that, The deformation rate of the first rolling pass is less than that of the second rolling pass.

4. The method for preparing nickel-containing steel according to any one of claims 1-3, characterized in that, The cooling rate of the cooling process is 25℃ / s to 35℃ / s.

5. The method for preparing nickel-containing steel according to claim 4, characterized in that, The cooling end temperature is 150℃~250℃.

6. The method for preparing nickel-containing steel according to any one of claims 1-3, characterized in that, The rolling temperature for the first pass is 950℃~1000℃; the rolling temperature for the second pass is 730℃~850℃.

7. The method for preparing nickel-containing steel according to any one of claims 1-3, characterized in that, The thickness of the heated billet is 100mm~200mm, the thickness of the intermediate billet is 30mm~100mm, and the thickness of the steel plate is 10mm~40mm.

8. The method for preparing nickel-containing steel according to any one of claims 1-3, characterized in that, The heat treatment temperature is 550℃~600℃, and the holding time during the heat treatment is 80min~120min.

9. The method for preparing nickel-containing steel according to any one of claims 1-3, characterized in that, In the heated blank, the mass fraction of Ni is 5.30% to 6.25%.

10. A nickel-containing steel, characterized in that, The nickel-containing steel is prepared using any one of the preparation methods of claims 1-9.

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