A fiber-layered steel plate and its preparation method and application

Abstract

The present invention discloses a fiber-layered steel plate and its preparation method and application, which belong to the technical field of steel materials. The preparation method comprises the following steps: subjecting a continuous casting steel billet or a die-cast steel ingot to blanking and forging, low-temperature multi-directional forging, and medium-low temperature rolling; wherein, the initial forging temperature of the low-temperature multi-directional forging is 600-640°C, and the final forging temperature is 500-540°C; the initial rolling temperature of the medium-low temperature rolling is between Ac1-100°C and Ac3, and the final rolling temperature is 600-660°C. The preparation method is simple and easy to operate, is not restricted by alloy elements, does not require subsequent heat treatment processes, and greatly reduces energy consumption. The steel plate prepared by this method can have good impact toughness at 84°C, and has better yield strength and elongation, which can meet the demand of marine engineering equipment such as offshore platforms, wind power generation, and marine ships for high-strength and low-temperature impact-resistant medium and thick steel plates.

Description

Technical Field

[0001] The present invention relates to the technical field of steel materials, and in particular to a fiber-layered steel plate and a preparation method and application thereof. Background Art

[0002] High-end marine engineering equipment urgently needs special steels with ultra-high strength and low-temperature toughness, which are generally low-carbon steel containing high nickel, austenitic stainless steel and Invar alloy. The high cost, low yield strength and low-temperature phase transformation limit their widespread application.

[0003] Traditional ferritic steel has a high yield strength, but its inherent ductile-brittle transition characteristics limit its low-temperature service life. At temperatures below -40°C, brittle fracture is very likely to occur. Therefore, improving the yield strength while ensuring good low-temperature toughness has become an important issue for marine engineering steel manufacturers and R&D personnel.

[0004] In view of this, the present invention is proposed. Summary of the Invention

[0005] The object of the present invention is to provide a fiber-layered steel plate and a preparation method and application thereof, so as to solve or improve the above-mentioned technical problems.

[0006] This application can be implemented as follows:

[0007] In a first aspect, the present application provides a method for preparing a fiber-layered steel plate, comprising the following steps: subjecting a continuous casting steel billet or a die-cast steel ingot to billet forging, low-temperature multi-directional forging, and medium-low temperature rolling;

[0008] Among them, the initial forging temperature of low-temperature multi-directional forging is 600-640℃, and the final forging temperature is 500-540℃;

[0009] The initial rolling temperature of medium and low temperature rolling is between Ac1-100℃ and Ac3, and the final rolling temperature is 600~660℃.

[0010] In an optional embodiment, the billet forging includes: keeping the continuous casting billet or the die casting ingot at 1100-1300° C. for 4-8 hours to obtain a billet; forging the billet into a square billet of a preset size, and then water-quenching it to room temperature to obtain a first intermediate square billet.

[0011] In an optional embodiment, the blanking and forging conditions include at least one of the following features:

[0012] Feature 1: The initial forging temperature of the reforming process is 1120-1180°C, and the final forging temperature is 830-870°C;

[0013] Feature 2: The preset width of the billet is 340-360mm, and the preset length is 440-460mm;

[0014] Feature 3: The material of the continuous casting billet or die casting ingot is low carbon alloy steel or medium carbon alloy steel.

[0015] In an optional embodiment, the low-temperature multi-directional forging method includes low-temperature sequential forging or low-temperature rotary forging.

[0016] In an optional embodiment, the low-temperature sequential forging includes: keeping the first intermediate billet at 640-660°C for 4-8 hours to obtain a second intermediate billet; forging the second intermediate billet along the length direction of the billet cross section, and after the total reduction reaches 90-100 mm, rotating the billet 90° and forging along the width direction of the billet cross section, and after the total reduction reaches 45-50 mm, rotating the billet 90° and forging again, repeating the above process until the thickness of the second intermediate billet is reduced to 40-45 mm or the total deformation in the thickness direction is 80-90%, and then air cooling to room temperature to obtain a third intermediate billet.

[0017] In an optional embodiment, the low-temperature rotary forging includes: keeping the first intermediate billet at 640-660°C for 4-8 hours to obtain a second intermediate billet; forging the second intermediate billet along the length direction of the billet cross section, and after the total reduction reaches 30-50 mm, rotating the second intermediate billet 90° and forging along the width direction of the billet cross section, and after the total reduction reaches 15-25 mm, rotating the billet 90° again and forging, repeating the above process until the thickness of the second intermediate billet is reduced to 40-45 mm or the total deformation in the thickness direction is 80-90%, and air cooling to room temperature to obtain a third intermediate billet.

[0018] In an optional embodiment, the medium-low temperature rolling includes: keeping the third intermediate billet at Ac1-50°C to Ac3 conditions for 2 to 4 hours to obtain a fourth intermediate billet; rolling the fourth intermediate billet along the length direction of the billet with a reduction of 3 to 5 mm per pass until the billet thickness is reduced to a preset thickness, and water cooling to room temperature.

[0019] In a second aspect, the present application provides a fiber-layered steel plate prepared by the preparation method of any one of the aforementioned embodiments.

[0020] In an optional embodiment, the fiber-layered steel plate has at least one of the following features:

[0021] Feature 1: Fiber-layered steel plate has a fiberized structure and a layered structure, and the fiberized structure is mainly arranged in a directional manner;

[0022] Feature 2: The thickness of the fiber-layered steel plate is not less than 15 mm, preferably 15 to 25 mm;

[0023] Feature 3: The width of the fiber-layered steel plate is not less than 500mm;

[0024] Feature 4: The impact energy of fiber-layered steel plate at -84°C is not less than 250J;

[0025] Feature 5: The yield strength of fiber-layered steel plate is not less than 570MPa;

[0026] Feature 6: The elongation of the fiber-layered steel plate is not less than 26%.

[0027] In a third aspect, the present application provides an application of a fiber-layered steel plate according to the aforementioned embodiment, for example, for preparing marine engineering equipment.

[0028] In an optional embodiment, the offshore engineering equipment includes an offshore platform, a wind power generation unit or a marine vessel.

[0029] The beneficial effects of this application include:

[0030] This application creatively proposes a method for effectively producing fiber-layered steel plates with good impact toughness at -84°C, as well as excellent yield strength and elongation, by subjecting continuous-cast steel billets or die-cast ingots to cogging, low-temperature multi-directional forging, and medium-low-temperature rolling. This method is simple and easy to operate, is not restricted by alloying elements, and eliminates the need for subsequent heat treatment, significantly reducing energy consumption. The resulting steel plates can meet the demand for high-strength, low-temperature impact-resistant medium-thick steel plates for offshore platforms, wind power generation, marine vessels, and other marine equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0032] Figure 1 A schematic diagram of the preparation method provided in this application;

[0033] Figure 2 This is a schematic diagram of the low-temperature sequential forging process in this application;

[0034] Figure 3 Schematic diagram of the low-temperature rotary forging process in this application;

[0035] Figure 4 This is a microstructure diagram of the edge and core of the fiber-layered steel plate provided in this application. DETAILED DESCRIPTION

[0036] To make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer are used. Where the manufacturer of the reagents or instruments is not specified, all are conventional products that can be purchased commercially.

[0037] The fiber-layered steel plate provided in this application, its preparation method and application are described in detail below.

[0038] This application proposes a method for preparing a fiber-layered steel plate, such as Figure 1 As shown, it includes the following steps: subjecting the continuous casting steel billet or the die casting steel ingot to blanking and forging, low temperature multi-directional forging and medium and low temperature rolling.

[0039] Among them, the initial forging temperature of low-temperature multi-directional forging is 600-640℃, and the final forging temperature is 500-540℃;

[0040] The initial rolling temperature of medium and low temperature rolling is between Ac1-100℃ and Ac3, and the final rolling temperature is 600~660℃.

[0041] This preparation method is simple and easy to operate, is not restricted by alloying elements, and does not require conventional heat treatment, significantly reducing energy consumption. The steel plates produced using this method exhibit good impact toughness at -84°C, as well as excellent yield strength and elongation.

[0042] For reference, the process of converting a billet into a forging process can be as follows: a continuously cast billet or a die-cast ingot is held at 1100°C to 1300°C (e.g., 1100°C, 1150°C, 1200°C, 1250°C, or 1300°C) for 4 to 8 hours (e.g., 4 hours, 5 hours, 6 hours, 7 hours, or 8 hours) to produce a billet. The billet is then forged into a billet of a predetermined size, which is then water-quenched to room temperature to produce a first intermediate billet.

[0043] The initial forging temperature of the above-mentioned reforming forging process may be 1120-1180°C, such as 1120°C, 1130°C, 1140°C, 1150°C, 1160°C, 1170°C or 1180°C, etc. The final forging temperature may be 830-870°C, such as 830°C, 840°C, 850°C, 860°C or 870°C, etc.

[0044] For example, the preset width of the billet may be 340-360 mm, such as 340 mm, 345 mm, 350 mm, 355 mm or 360 mm, etc. The preset length may be 440-460 mm, such as 440 mm, 445 mm, 450 mm, 455 mm or 460 mm, etc.

[0045] The material of the continuous casting billet or die casting ingot can be low carbon alloy steel or medium carbon alloy steel, wherein the carbon content of low carbon alloy steel is less than 0.25%, and the carbon content of medium carbon alloy steel is approximately between 0.25% (inclusive) and 0.6% (inclusive).

[0046] In the present application, the initial forging temperature of low-temperature multi-directional forging can be 600°C, 605°C, 610°C, 615°C, 620°C, 625°C, 630°C, 635°C or 640°C, or any other value within the range of 600-640°C.

[0047] The final forging temperature of low-temperature multi-directional forging can be 500°C, 505°C, 510°C, 515°C, 520°C, 525°C, 530°C, 535°C or 540°C, or any other value within the range of 500-540°C.

[0048] It should be noted that if the initial forging temperature of low-temperature multi-directional forging is lower than 600°C, it is not conducive to sheet forming; if the initial forging temperature is higher than 640°C, it is not conducive to the formation of an ideal microstructure. If the final forging temperature of low-temperature multi-directional forging is lower than 500°C, it is not conducive to sheet forming.

[0049] For reference, low-temperature multi-directional forging can adopt low-temperature sequential forging method or low-temperature rotary forging method.

[0050] The low temperature sequential forging may include: keeping the first intermediate billet at 640-660°C (such as 640°C, 645°C, 650°C, 655°C or 660°C) for 4-8 hours (such as 4 hours, 4.5 hours, 5 hours, 5.5 hours, 6 hours, 6.5 hours, 7 hours, 7.5 hours or 8 hours) to obtain a second intermediate billet; forging the second intermediate billet along the length direction of the billet cross section until the total reduction reaches 90-100 mm (such as 90 mm, 92 mm, 95 mm, 98 mm or 100 mm), rotating the billet 90 degrees along the billet cross section. Forging is performed in the width direction of the cross section. After the total reduction reaches 45 to 50 mm (such as 45 mm, 46 mm, 47 mm, 48 mm, 49 mm or 50 mm, etc.), the billet is rotated 90° for forging again, and the above process is repeated until the thickness of the second intermediate billet is reduced to 40 to 45 mm (such as 40 mm, 41 mm, 42 mm, 43 mm, 44 mm or 45 mm, etc.) or the total deformation in the thickness direction is 80 to 90% (such as 80%, 82%, 85%, 88% or 90%, etc.), and then air-cooled to room temperature to obtain a third intermediate billet.

[0051] Low temperature rotary forging may include: keeping the first intermediate billet at 640-660°C (such as 640°C, 645°C, 650°C, 655°C or 660°C) for 4-8 hours (such as 4 hours, 4.5 hours, 5 hours, 5.5 hours, 6 hours, 6.5 hours, 7 hours, 7.5 hours or 8 hours) to obtain a second intermediate billet; forging the second intermediate billet along the length direction of the billet cross section until the total reduction reaches 30-50 mm (such as 30 mm, 35 mm, 40 mm, 45 mm or 50 mm), and then rotating the second intermediate billet 90 degrees. Forging is performed along the width direction of the billet cross section. After the total reduction reaches 15 to 25 mm (such as 15 mm, 18 mm, 20 mm, 22 mm or 25 mm, etc.), the billet is rotated 90° for forging again, and the above process is repeated until the thickness of the second intermediate billet is reduced to 40 to 45 mm (such as 40 mm, 41 mm, 42 mm, 43 mm, 44 mm or 45 mm, etc.) or the total deformation in the thickness direction is 80 to 90% (such as 80%, 85% or 90%, etc.), and then air-cooled to room temperature to obtain a third intermediate billet.

[0052] For example, the second intermediate billet has four side faces, namely, side A, side B, side C (not shown) and side D (not shown), which are connected end to end. Side A and side C are arranged opposite to each other, and side B and side D are arranged opposite to each other. Figure 2 Low-temperature sequential forging can be understood as: first forging the A and C surfaces (in the length direction of the billet cross section) of the second intermediate billet until the preset total reduction of the surface is reached; then forging the B and D surfaces (in the width direction of the billet cross section) of the second intermediate billet until the preset size of the third intermediate billet is reached.

[0053] Reference Figure 3 Low-temperature rotary forging can be understood as follows: first, forging the A and C surfaces (in the length direction of the billet cross section) of the second intermediate billet so that both surfaces have the first intermediate depression; then forging the B and D surfaces so that both surfaces have the first intermediate depression; then forging the A and C surfaces again so that the first intermediate depression of surfaces A and C becomes the second intermediate depression; then forging the B and D surfaces again so that the first intermediate depression of surfaces B and D becomes the second intermediate depression. This process continues until all surfaces have reached the preset dimensions of the third intermediate billet.

[0054] In the present application, the initial rolling temperature of the medium-low temperature rolling may be between Ac1-100°C and Ac3, wherein Ac1 refers to the austenite transformation start temperature and Ac3 refers to the complete austenitization temperature.

[0055] If the initial rolling temperature of medium and low temperature rolling is lower than Ac1-50℃, it is not conducive to sheet forming; if the initial rolling temperature of medium and low temperature rolling is higher than Ac3, it is not conducive to forming an ideal microstructure.

[0056] For reference, the medium and low temperature rolling may include: keeping the third intermediate billet at Ac1-50℃ to Ac3 for 2 to 4 hours (such as 2 hours, 2.5 hours, 3 hours, 3.5 hours or 4 hours, etc.) to obtain a fourth intermediate billet; rolling the fourth intermediate billet along the length direction of the billet with a reduction of 3 to 5 mm (such as 3 mm, 3.5 mm, 4 mm, 4.5 mm or 5 mm, etc.) per pass until the billet thickness is reduced to a preset thickness, and then water-cooling to room temperature.

[0057] It should be emphasized that in the prior art, high temperature rolling is usually used for rolling, such as rolling temperature of 1100℃ and above. Under such high temperature rolling conditions, the obtained steel plate structure is equiaxed crystal and the ductile-brittle transition temperature is high. However, the present application adopts medium and low temperature rolling under specific conditions, combined with the early low temperature multi-directional forging process, to make the steel plate have a specific fibrous structure and layered structure (such as Figure 4 ), the steel plate with this kind of structure can not only obtain an excellent match between strength and low-temperature impact toughness, as well as good plasticity; it also has a lower ductile-brittle transition temperature, and can obtain higher toughness at low temperatures; in addition, the steel plate with this kind of structure is not restricted by alloy elements, especially the impurity elements such as S and P in the steel have little effect on the performance of the steel plate, and no subsequent heat treatment process is required, which reduces energy consumption.

[0058] Accordingly, the present application provides a fiber-layered steel plate, which is prepared by the above-mentioned preparation method.

[0059] like Figure 4 As shown, the steel plate provided by the present application has a fiberized structure (also known as fiber crystals) and a layered structure, and the fiberized structure is mainly arranged in a direction. It can be understood that the above-mentioned steel plate has a layered structure as a whole, and the fiberized structure is distributed in roughly the same direction, rather than being randomly distributed.

[0060] In some embodiments, the thickness of the fiber-layered steel plate may be, for example, but not limited to, no less than 15 mm, such as 15 to 25 mm. The width of the fiber-layered steel plate may be, for example, but not limited to, no less than 500 mm.

[0061] In some embodiments, the fiber-layered steel plate has an impact energy of not less than 250 J at -84°C, a yield strength of not less than 570 MPa, and an elongation of not less than 26%.

[0062] In addition, the present application also provides an application of the fiber-layered steel plate according to the aforementioned embodiment, which can be used, for example, to prepare marine engineering equipment.

[0063] For reference, offshore equipment may include offshore platforms, wind power generation or marine vessels, etc.

[0064] The features and performance of the present invention are further described in detail below with reference to the embodiments.

[0065] Example 1

[0066] This embodiment provides a medium-thick fiber-layered steel plate, the preparation method of which includes the following steps:

[0067] S1: Start from blanking to forging.

[0068] The continuously cast steel billet is heated in a heating furnace to 1200°C and held at this temperature for 6 hours to produce a billet. The billet is removed from the heating furnace and placed on a forging press, where it begins reforging at 1120°C and ends when the temperature drops to 870°C. The billet is then water-quenched to room temperature to produce the first intermediate billet. The cross-sectional area of ​​the reforged first intermediate billet is 350 mm x 450 mm.

[0069] The chemical composition of the continuous casting steel billet is, in percentage by weight, C 0.41%, Si 0.27%, Mn 0.65%, P < 0.035%, S < 0.035%, Cr 1.05%, Mo 0.2%, Ni < 0.3%, and the remainder is Fe and trace elements inevitable in the manufacturing process.

[0070] S2: Low temperature multi-directional forging.

[0071] The reforged first intermediate billet is reheated in a heating furnace to 650°C and held for 6 hours to obtain a second intermediate billet. The second intermediate billet is removed from the heating furnace and placed on a forging press to begin low-temperature sequential forging at 630°C. The forging is terminated when the temperature drops to 500°C and air-cooled to room temperature to obtain a third intermediate billet.

[0072] The forging order of low-temperature sequential forging is to forge along the length direction of the billet section first. After the total reduction reaches 100mm, the billet is rotated 90° and forged along the width direction of the billet section. After the total reduction reaches 50mm, the billet is rotated 90° again for forging. The above process is repeated until the billet thickness is reduced to 44mm.

[0073] S3: Medium and low temperature rolling.

[0074] The third intermediate billet is reheated in the heating furnace to 770°C and held for 3 hours to produce the fourth intermediate billet. The fourth intermediate billet is removed from the heating furnace and placed on the rolling mill roller table. Rolling begins at 750°C and ends when the temperature drops to 650°C. The billet is then water-cooled to room temperature. Rolling is carried out along the billet's length, with a reduction of 4 mm per pass, until the billet thickness is reduced to 20 mm.

[0075] Example 2

[0076] The difference between this embodiment and embodiment 1 is that the low-temperature multidirectional forging is carried out by low-temperature rotary forging, the initial forging temperature of the low-temperature rotary forging is 620°C, and the final forging temperature is 510°C; the total reduction along the length direction of the square billet cross section in each pass is 50 mm, and the total reduction along the width direction of the square billet cross section in each pass is 20 mm.

[0077] Example 3

[0078] This embodiment provides a medium-thick fiber-layered steel plate, the preparation method of which includes the following steps:

[0079] S1: Start from blanking to forging.

[0080] The continuously cast steel billet is heated in a heating furnace to 1200°C and held at this temperature for 6 hours to produce a billet. The billet is removed from the heating furnace and placed on a forging press, where it begins reforging at 1150°C and ends when the temperature drops to 850°C. The billet is then water-quenched to room temperature to produce the first intermediate billet. The cross-sectional area of ​​the reforged first intermediate billet is 340 mm x 460 mm.

[0081] The chemical composition of the continuous casting steel billet is, in percentage by weight, C 0.2%, Si 0.27%, Mn 1.05%, P < 0.035%, S < 0.035%, Cr 1.15%, Mo 0.2%, and the remainder is Fe and trace elements inevitable in the manufacturing process.

[0082] S2: Low temperature multi-directional forging.

[0083] The reforged first intermediate billet is reheated in a heating furnace to 650°C and held for 6 hours to obtain a second intermediate billet. The second intermediate billet is removed from the heating furnace and placed on a forging press to begin low-temperature sequential forging at 620°C. The forging is terminated when the temperature drops to 520°C and air-cooled to room temperature to obtain a third intermediate billet.

[0084] The forging order of low-temperature sequential forging is to first forge along the length direction of the billet section. After the total reduction reaches 100mm, the billet is rotated 90° and forged along the width direction of the billet section. After the total reduction reaches 50mm, the billet is rotated 90° again for forging. The above process is repeated until the billet thickness is reduced to 40mm.

[0085] S3: Medium and low temperature rolling.

[0086] The third intermediate billet is reheated in the heating furnace to 780°C and held for 3 hours to produce the fourth intermediate billet. The fourth intermediate billet is removed from the heating furnace and placed on the rolling mill roller table. Rolling begins at 760°C and ends when the temperature drops to 610°C. The billet is then water-cooled to room temperature. Rolling is carried out along the billet's length, with a reduction of 3mm per pass, until the billet thickness is reduced to 22mm.

[0087] Example 4

[0088] The difference between this embodiment and embodiment 3 is that the low-temperature multi-directional forging is carried out by low-temperature rotary forging, the initial forging temperature of the low-temperature rotary forging is 640°C, and the final forging temperature is 530°C; the total reduction along the length direction of the square billet cross section in each pass is 45 mm, and the total reduction along the width direction of the square billet cross section in each pass is 23 mm.

[0089] Example 5

[0090] This embodiment provides a medium-thick fiber-layered steel plate, the preparation method of which includes the following steps:

[0091] S1: Start from blanking to forging.

[0092] The continuously cast steel billet is heated in a heating furnace to 1200°C and held at that temperature for 6 hours to produce a billet. The billet is removed from the heating furnace and placed on a forging press, where it begins reforging at 1170°C and ends when the temperature drops to 840°C. The billet is then water-quenched to room temperature to produce the first intermediate billet. The cross-sectional area of ​​the reforged first intermediate billet is 340 mm x 440 mm.

[0093] The chemical composition of the continuous casting steel billet is, in weight percentage, C 0.055%, Si 0.2%, Mn 0.9%, P < 0.015%, S < 0.015%, Nb 0.015%, V 0.035%, Ti 0.011%, and the balance is Fe and trace elements inevitable in the manufacturing process.

[0094] S2: Low temperature multi-directional forging.

[0095] The reforged first intermediate billet is reheated in a heating furnace to 650°C and held for 6 hours to obtain a second intermediate billet. The second intermediate billet is removed from the heating furnace and placed on a forging press to begin low-temperature sequential forging at 610°C. The forging is terminated when the temperature drops to 530°C and air-cooled to room temperature to obtain a third intermediate billet.

[0096] The forging order of low-temperature sequential forging is to first forge along the length direction of the billet section. After the total reduction reaches 90mm, the billet is rotated 90° and forged along the width direction of the billet section. After the total reduction reaches 45mm, the billet is rotated 90° again for forging. The above process is repeated until the billet thickness is reduced to 42mm.

[0097] S3: Medium and low temperature rolling.

[0098] The third intermediate billet is reheated in the heating furnace to 800°C and held for 3 hours to produce the fourth intermediate billet. The fourth intermediate billet is removed from the heating furnace and placed on the rolling mill roller table. Rolling begins at 750°C and ends when the temperature drops to 630°C. The billet is then water-cooled to room temperature. Rolling is carried out along the billet's length, with a reduction of 4 mm per pass, until the billet's thickness is reduced to 18 mm.

[0099] Example 6

[0100] The difference between this embodiment and embodiment 5 is that the low-temperature multi-directional forging is carried out by low-temperature rotary forging, the initial forging temperature of the low-temperature rotary forging is 610°C, the final forging temperature is 520°C, the total reduction along the length direction of the square billet cross section in each pass is 40 mm, and the total reduction along the width direction of the square billet cross section in each pass is 20 mm.

[0101] Comparative Example 1

[0102] This embodiment provides a medium-thick steel plate, the preparation method of which includes the following steps:

[0103] The continuous casting steel billet (same as Example 1) was heated to 1200°C in a heating furnace and kept warm for 6 hours. It was then taken out of the heating furnace and placed on a forging press for reforging. The initial forging temperature was 1150°C and the final forging temperature was 850°C. It was then air-cooled to room temperature. The cross-sectional area of ​​the billet after reforging was 300mm×500mm.

[0104] The reforged billet is then heated to 1200°C in a heating furnace and held there for 6 hours. It is then removed from the furnace and rolled on a rolling mill table. The initial rolling temperature is 1150°C, and the final rolling temperature is 990°C. The billet is then air-cooled to room temperature. Rolling is carried out along the billet's length, with a reduction of 46mm per pass, until the billet thickness is reduced to 24mm.

[0105] The rolled billet is heated to 880℃ in the heating furnace and kept at this temperature for 1 hour. Then it is taken out from the heating furnace and quenched in quenching oil to cool to room temperature. The quenched billet is heated to 660℃ in the tempering furnace and kept at this temperature for 1 hour. Then it is taken out from the heating furnace and air-cooled to complete the tempering treatment.

[0106] Comparative Example 2

[0107] This comparative example provides a medium and thick steel plate, the chemical composition of the continuous casting steel billet used is the same as that in Example 3, and the preparation method is different from that in Comparative Example 1 in that: the initial forging temperature of the modified forging is 1120°C, the final forging temperature is 860°C, and the cross-sectional area of ​​the billet after the modified forging is 310mm×490mm; the initial rolling temperature of the rolling is 1130°C, the final rolling temperature is 950°C, the reduction per pass is 48mm, and the billet thickness is reduced to 22mm; the quenching temperature is 850°C, and the tempering temperature is 200°C.

[0108] Comparative Example 3

[0109] This comparative example provides a medium and thick steel plate, the chemical composition of the continuous casting steel billet used is the same as that in Example 5, and the preparation method is different from that in Comparative Example 1 in that: the initial forging temperature of the modified forging is 1140°C, the final forging temperature is 820°C, and the cross-sectional area of ​​the billet after the modified forging is 310mm×500mm; the initial rolling temperature of the rolling is 1160°C, the final rolling temperature is 980°C, the reduction per pass is 49mm, and the billet thickness is reduced to 16mm; the quenching temperature is 890°C, and the tempering temperature is 550°C.

[0110] Test example

[0111] The performance tests of the medium-thick steel plates obtained in Examples 1-6 and Comparative Examples 1-3 were performed, and the results are shown in Table 1.

[0112] Among them, the yield strength and elongation are measured with reference to "GBT 228.1 Metallic materials tensile test Part 1: Room temperature test method", and the -84°C impact energy is measured with reference to "GBT 229 Metallic materials Charpy pendulum impact test method".

[0113] Table 1 Performance comparison results

[0114]

[0115]

[0116] As can be seen from Table 1, the embodiments provided in the present application can obtain medium and thick steel plates with significantly better low-temperature impact toughness than the comparative examples without performing a heat treatment process, and the corresponding steel plates also have good yield strength and elongation.

[0117] In summary, the method for preparing fiber-layered steel plates provided in this application is simple, easy to operate, unrestricted by alloying elements, and eliminates the need for subsequent heat treatment, significantly reducing energy consumption. The steel plates produced using this method exhibit excellent impact toughness at -84°C, along with excellent yield strength and elongation, meeting the demand for high-strength, low-temperature impact-resistant medium-thick steel plates for offshore platforms, wind turbines, marine vessels, and other marine equipment.

[0118] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for preparing a fiber-layered steel plate, characterized in that: The following steps are involved: The continuous casting steel billet or die casting steel ingot is subjected to billet forging, low temperature multi-directional forging and medium and low temperature rolling; Among them, the initial forging temperature of low-temperature multi-directional forging is 600~640℃, and the final forging temperature is 500~540℃; The initial rolling temperature of medium and low temperature rolling is between Ac1-100℃ and Ac3, and the final rolling temperature is 600~660℃; The material of the continuous casting steel billet or die casting steel ingot is low carbon alloy steel or medium carbon alloy steel; The process of forging includes: keeping a continuous cast steel billet or a die cast steel ingot at 1100-1300°C for 4-8 hours to obtain a billet; forging the billet into a billet of a preset size, and then water-quenching it to room temperature to obtain a first intermediate billet; the low-temperature multi-directional forging method includes low-temperature sequential forging or low-temperature rotary forging; The low-temperature sequential forging includes: holding the first intermediate billet at 640-660°C for 4-8 hours to obtain a second intermediate billet; forging the second intermediate billet along the length direction of the billet cross section until the total reduction reaches 90-100 mm, rotating the second intermediate billet 90° and forging along the width direction of the billet cross section until the total reduction reaches 45-50 mm, then rotating the billet 90° and forging again, repeating the above process until the thickness of the second intermediate billet is reduced to 40-45 mm or the total deformation in the thickness direction reaches 80-90%, and then air cooling to room temperature to obtain a third intermediate billet; The low-temperature rotary forging includes: keeping the first intermediate billet at 640-660°C for 4-8 hours to obtain a second intermediate billet; forging the second intermediate billet along the length direction of the billet cross section until the total reduction reaches 30-50 mm, rotating the billet 90° and forging along the width direction of the billet cross section until the total reduction reaches 15-25 mm, and then rotating the billet 90° and forging again. The above process is repeated until the thickness of the second intermediate billet is reduced to 40-45 mm or the total deformation in the thickness direction is 80-90%, and then air-cooling to room temperature to obtain a third intermediate billet.

2. The preparation method according to claim 1, characterized in that The blanking and forging conditions include at least one of the following characteristics: Feature 1: The initial forging temperature of the reforming process is 1120~1180℃, and the final forging temperature is 830~870℃; Feature 2: The preset width of the billet is 340-360 mm, and the preset length is 440-460 mm.

3. The preparation method according to claim 1, characterized in that The medium-low temperature rolling includes: keeping the third intermediate billet at Ac1-50°C to Ac3 conditions for 2-4 hours to obtain a fourth intermediate billet; rolling the fourth intermediate billet along the length direction of the billet with a reduction of 3-5 mm per pass until the billet thickness is reduced to a preset thickness, and water cooling to room temperature.

4. A fiber-layered steel plate, characterized in that: The invention is prepared by the preparation method according to any one of claims 1 to 3.

5. The fiber-layered steel plate according to claim 4, characterized in that: The fiber-layered steel plate has at least one of the following characteristics: Feature 1: The fiber-layered steel plate has a fiberized structure and a layered structure, and the fiberized structure is mainly arranged in a direction; Feature 2: The thickness of the fiber-layered steel plate is not less than 15 mm; Feature 3: The width of the fiber-layered steel plate is not less than 500 mm; Feature 4: The impact energy of the fiber-layered steel plate at -84°C is not less than 250J; Feature 5: The yield strength of the fiber-layered steel plate is not less than 570 MPa; Feature 6: The elongation of the fiber-layered steel plate is not less than 26%.

6. The fiber-layered steel plate according to claim 5, characterized in that: The thickness of the fiber-layered steel plate is 15-25 mm.

7. Use of the fiber-layered steel plate according to any one of claims 4 to 6, characterized in that: The fiber-layered steel plate is used for preparing marine engineering equipment.

8. The use according to claim 7, characterized in that The marine engineering equipment includes offshore platforms, wind power generation or marine vessels.

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