A method for controlling multiple atomic nanoclusters in ultra-low carbon bainitic steel and a bainitic steel

Abstract

This invention discloses a method for controlling multiple atomic nanoclusters in ultra-low carbon bainitic steel and a bainitic steel, comprising the following steps: (1) melting, smelting and electroslag remelting the original ultra-low carbon bainitic steel under vacuum to obtain an ingot, with the vacuum degree controlled within 25 Pa; (2) hot rolling the ingot three times at a temperature of 1150-1300℃ to obtain a plate-shaped sample with a thickness of 25 mm; (3) solution treating the plate-shaped sample and water cooling to obtain a solution-treated block sample; (4) cold rolling the solution-treated block sample at room temperature on a rolling mill; (5) aging the cold-rolled sample in a vacuum tube furnace with nitrogen gas introduced, and then air cooling. This invention, by controlling multiple atomic nanoclusters in ultra-low carbon bainitic steel, can obtain bainitic steel with excellent strength, which has the advantages of low cost, easy implementation and high efficiency compared with traditional heat treatment modification.

Description

Technical Field

[0001] This invention belongs to the field of materials processing and control technology, specifically relating to a method for regulating multiple atomic nanoclusters in ultra-low carbon bainitic steel and a bainitic steel. Background Technology

[0002] Ultra-low carbon bainitic steel is widely used in transportation, infrastructure, and defense industries due to its excellent mechanical properties. EH960 possesses good comprehensive mechanical properties, weldability, and processing performance. It is used in the manufacture of structural components for ships in various navigation environments, including hull structures, docks, oil platforms, offshore pipelines, coastal power plants, and dock facilities. This steel plate is typically produced using a quenching and tempering process, with a yield strength ≥960 MPa and a tensile strength of 980-1150 MPa. With economic development and increasing demands in the energy transportation sector, how to manufacture higher-strength ultra-low carbon bainitic steel using more efficient and energy-saving technologies has become an urgent research and development need.

[0003] Ultra-low carbon bainitic steel can be strengthened through various methods. Among them, precipitation strengthening with nano-sized precipitates is a particularly effective approach, achieving both high tensile strength and maximizing elongation. The strengthening effect of nanoprecipitates largely depends on the microstructure characteristics and the morphology, size, quantity density, and structure of the precipitates. Regulating the precipitation characteristics of nanophases provides an effective method for optimizing performance. How to obtain an inexpensive, readily available, and highly efficient ultra-low carbon bainitic steel with excellent comprehensive mechanical properties using a low-cost, easy-to-implement, and efficient method has become a problem that needs to be solved in various fields such as transportation, infrastructure, and defense industries, including oil pipelines, shipbuilding, bridge construction, and aviation facilities. Summary of the Invention

[0004] To address the aforementioned technical problems, the present invention aims to provide a method for controlling multiple atomic nanoclusters in ultra-low carbon bainitic steel and a bainitic steel. The method measures the overall control effect by controlling the grain size, number density, and equivalent radius of the nano-atomic clusters in the ultra-low carbon bainitic steel, thereby obtaining the optimal control process. The ultra-low carbon bainitic steel prepared by the method of the present invention has excellent mechanical properties.

[0005] In one aspect, this invention provides a method for controlling multiple atomic nanoclusters in ultra-low carbon bainitic steel, comprising the following steps: (1) The original ultra-low carbon bainitic steel is melted, smelted and electroslag remelted under vacuum to obtain ingots, with the vacuum degree controlled within 25 Pa; (2) The ingot is hot rolled three times at a temperature of 1150-1300℃ to obtain a plate sample with a thickness of 25 mm; (3) The plate-shaped sample is subjected to solid solution treatment and then cooled with water to obtain a solid solution block sample; (4) The solid solution block sample is subjected to room temperature cold rolling on a rolling mill; (5) The cold-rolled sample is aged in a vacuum tube furnace with nitrogen gas, and then air-cooled.

[0006] In step (1) of this invention, the entire melting and smelting process is carried out in a vacuum induction furnace with a vacuum degree controlled within 25 Pa. Then, the resistance heat generated by the current passing through the slag is used as the smelting heat source to perform electroslag remelting to obtain the melt, which can further improve the purity.

[0007] As a further embodiment of the present invention: in step (1), the melting is repeated 3 times, followed by electroslag remelting, and the ingot is cast.

[0008] In this invention, repeated melting three times results in a more uniform composition. The melt is then poured into a mold to obtain an ingot.

[0009] As a further aspect of the present invention: In step (1), the chemical composition of the original ultra-low carbon bainitic steel, by weight percentage, is C: 0.007%-0.012%, Si: 0.07%-0.10%, Mn: 0.049%-0.630%, Ni: 8.60%-8.99%, Cr: 0.61%-0.67%, Mo: 0.54%-0.61%, V: 0.098%-0.124%, Cu: 1.47%-1.71%, Ti: 0.009%-0.012%, with the balance being Fe.

[0010] As a further aspect of the present invention: in step (2), the deformation amount of the first hot rolling is ≤10%; And / or, the deformation amount during the second hot rolling is ≤30%; And / or, the deformation amount during the third hot rolling is ≤50%; And / or, the hot rolling temperature is 1200℃.

[0011] Specifically, the first hot rolling is rough rolling, and the third hot rolling is finish rolling.

[0012] As a further embodiment of the present invention: in step (3), the solution temperature is 800-1100℃; And / or, the heat preservation time is 30 min-120 min.

[0013] As a further aspect of the present invention: in step (3), the solution temperature is 900°C; The heat preservation time is 60 minutes.

[0014] As a further aspect of the present invention: in step (4), the room temperature cold rolling is a multi-pass rolling process, and the reduction rate of each pass is between 5% and 15%. And / or, the cumulative deformation is 25%-55%.

[0015] As a further aspect of the present invention: in step (5), the aging temperature is 360-560℃; And / or, the heat preservation time is 60 min-480 min.

[0016] As a further aspect of the present invention: in step (5), the aging temperature is 460°C; And / or, the heat preservation time is 240 min.

[0017] In another aspect, the present invention also provides a bainitic steel, which is prepared by the above-described method for controlling multiple atomic nanoclusters in ultra-low carbon bainitic steel.

[0018] After controlling various atomic nanoclusters in ultra-low carbon bainitic steel using the method of this invention, the bainitic steel structure becomes a body-centered cubic (BCC) structure, with Cu-rich phases and carbide-formed atomic nanoclusters in the matrix.

[0019] The beneficial effects of this invention are as follows: 1. The method of the present invention achieves the purpose of controlling multiple atomic nanoclusters in ultra-low carbon bainitic steel by cold rolling the sample with different deformation amounts, thereby bringing about changes in grain size and dislocations through rolling. This results in bainitic steel with excellent strength. Compared with the traditional method of modification by simple heat treatment, it has the advantages of low cost, easy implementation and high efficiency.

[0020] 2. Through the method of the present invention, the overall effect can be further measured by controlling the number density and equivalent radius of Cu-rich phase and carbide-forming atomic clusters in the ultra-low carbon bainitic steel matrix, so as to obtain the optimal control process.

[0021] 3. The method of this invention can refine the equivalent radius of Cu-rich phase-forming atomic clusters and increase their number density. Simultaneously, this method can coarsen the size of carbide-forming atomic clusters and reduce their number density. By optimizing various nano-atomic clusters, the precipitation strengthening effect can be optimized, resulting in steel with higher strength and hardness. Attached Figure Description

[0022] Figure 1 The static tensile stress-strain diagram of an ultra-low carbon bainitic steel sample prepared by 30% rolling in Example 1 of this invention. Figure 2TEM image of an ultra-low carbon bainitic steel sample prepared by 30% rolling in Example 1 of this invention; Figure 3 The three-dimensional spatial distribution of each element is presented in the APT data of an ultra-low carbon bainitic steel sample prepared by 30% rolling in Example 1 of the present invention. Figure 4 The static tensile stress-strain diagram of an ultra-low carbon bainitic steel sample prepared by 50% rolling in Example 2 of this invention. Figure 5 TEM image of an ultra-low carbon bainitic steel sample prepared by 50% rolling in Example 2 of this invention; Figure 6 The three-dimensional spatial distribution of each element is presented in the APT data of an ultra-low carbon bainitic steel sample prepared by 50% rolling in Example 2 of this invention. Figure 7 The static tensile stress-strain diagram of an unrolled ultra-low carbon bainitic steel sample prepared in Comparative Example 1 of this invention is shown. Figure 8 This is a TEM image of an unrolled ultra-low carbon bainitic steel sample prepared in Comparative Example 1 of this invention. Figure 9 The three-dimensional spatial distribution of each element is presented in the APT data of an unrolled ultra-low carbon bainitic steel sample prepared in Comparative Example 1 of this invention. Figure 10 The ultra-low carbon bainitic steels provided in Examples 1-2 and Comparative Example 1 of this invention have equal concentrations of 4% Cu and 0.3% C. Detailed Implementation

[0023] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0024] In the embodiments, the chemical composition of the original ultra-low carbon bainitic steel, calculated by weight percentage, is: C: 0.007%-0.012%, Si: 0.07%-0.10%, Mn: 0.049%-0.630%, Ni: 8.60%-8.99%, Cr: 0.61%-0.67%, Mo: 0.54%-0.61%, V: 0.098%-0.124%, Cu: 1.47%-1.71%, Ti: 0.009%-0.012%, with the balance being Fe.

[0025] The original ultra-low carbon bainitic steel was obtained as ingots through vacuum smelting followed by electroslag remelting. The smelting process was carried out in a vacuum induction furnace, with the vacuum level controlled below 25 Pa throughout the process. To ensure uniform composition, the melting was repeated three times. To further improve purity, the resistance heat generated by current passing through the molten slag was used as the heat source for electroslag remelting, and the ingots were then cast using molds.

[0026] The ingot is hot-rolled three times at a temperature of 1150-1300℃ to form a steel plate with a thickness of 25 mm. The deformation amount of the first rough rolling is ≤10%, the deformation amount of the second rolling is ≤30%, and the deformation amount of the third finishing rolling is ≤50%.

[0027] The hot-rolled steel plate was cut into rectangular specimens, and the specimens were solution treated at 800-1100℃ for 30-120 min and then water-cooled.

[0028] The quenched samples were machined to the required dimensions using wire cutting, and then subjected to multi-pass room temperature cold rolling on a rolling mill, with the reduction rate controlled between 5% and 15% per pass, and the cumulative deformation amount between 25% and 55%. The rolled samples were then aged at 360-560℃ in a vacuum tube furnace for 60-480 min.

[0029] Example 1: (1) Ultra-low carbon bainitic steel with the following chemical composition by weight percentage: C: 0.010%, Si: 0.095%, Mn: 0.055%, Ni: 8.80%, Cr: 0.65%, Mo: 0.60%, V: 0.10%, Cu: 1.57%, Ti: 0.011%, with the balance being Fe, was smelted in a vacuum induction furnace. The vacuum degree was controlled within 25 Pa throughout the process. To ensure uniform composition, the steel was melted three times. To further improve purity, the resistance heat generated by the current passing through the slag was used as the smelting heat source for electroslag remelting, and the resulting ingot was cast using a mold.

[0030] (2) The ingot is hot rolled three times on a rolling mill at a temperature of 1200℃ to form a steel plate with a thickness of 25 mm. The deformation amount of the first rough rolling is 10%, the deformation amount of the second rolling is 20%, and the deformation amount of the third finishing rolling is 50%.

[0031] (3) Cut the steel plate into rectangular blocks with a length of 150 mm, a width of 100 mm, and a thickness of 25 mm.

[0032] (4) First, heat the muffle furnace to 900°C at a heating rate of 5°C / min. After the temperature reaches 900°C, put the sample in and keep it at that temperature for 60 min. Then immediately cool it with water.

[0033] (5) Cut the water-cooled sample into pieces with dimensions of 150 × 50 × 1.42 mm. 3 The sample is in block form. The block sample is subjected to multi-pass room temperature cold rolling on a rolling mill, with the reduction rate of each pass controlled between 5% and 15%, and the cumulative deformation during rolling preferably being 30%.

[0034] (6) Turn on the vacuum tube furnace and heat it at a heating rate of 5℃ / min. Place the alumina ceramic crucible into the tube furnace and heat it along with the furnace. After the furnace temperature reaches 460℃ and stabilizes, place the sample obtained in step (5) into the alumina ceramic crucible and push it to the middle of the tube furnace. When the pressure is below 5×10 -1 The aging treatment was carried out under a nitrogen atmosphere of Pa. After holding at this temperature for 240 min, the sample was removed and cooled to room temperature.

[0035] Example 2: (1) Ultra-low carbon bainitic steel with the following chemical composition by weight percentage: C: 0.010%, Si: 0.095%, Mn: 0.055%, Ni: 8.80%, Cr: 0.65%, Mo: 0.60%, V: 0.10%, Cu: 1.57%, Ti: 0.011%, with the balance being Fe, was smelted in a vacuum induction furnace. The vacuum degree was controlled within 25 Pa throughout the process. To ensure uniform composition, the steel was melted three times. To further improve purity, the resistance heat generated by the current passing through the slag was used as the smelting heat source for electroslag remelting, and the resulting ingot was cast using a mold.

[0036] (2) The ingot is hot rolled three times on a rolling mill at a temperature of 1200℃ to form a steel plate with a thickness of 25 mm. The deformation amount of the first rough rolling is 10%, the deformation amount of the second rolling is 30%, and the deformation amount of the third finishing rolling is 50%.

[0037] (3) Cut the steel plate into rectangular blocks with a length of 150 mm, a width of 100 mm, and a thickness of 25 mm.

[0038] (4) First, heat the muffle furnace to 900°C at a heating rate of 5°C / min. After the temperature reaches 900°C, put the sample in and keep it at that temperature for 60 min. Then immediately cool it with water.

[0039] (5) Cut the water-cooled sample into pieces with dimensions of 150 × 50 × 2 mm. 3 The sample is in block form. The block sample is subjected to multi-pass room temperature cold rolling on a rolling mill, with the reduction rate of each pass controlled between 5% and 15%, and the cumulative deformation during rolling preferably being 50%.

[0040] (6) Turn on the vacuum tube furnace and heat it at a heating rate of 5℃ / min. Place the alumina ceramic crucible into the tube furnace and heat it along with the furnace. After the furnace temperature reaches 460℃ and stabilizes, place the sample obtained in step (5) into the alumina ceramic crucible and push it to the middle of the tube furnace. When the pressure is below 5×10 -1 The aging treatment was carried out under a nitrogen atmosphere of Pa. After holding at this temperature for 240 min, the sample was removed and cooled to room temperature.

[0041] Comparative Example 1 (1) Ultra-low carbon bainitic steel with the following chemical composition by weight percentage: C: 0.010%, Si: 0.095%, Mn: 0.055%, Ni: 8.80%, Cr: 0.65%, Mo: 0.60%, V: 0.10%, Cu: 1.57%, Ti: 0.011%, with the balance being Fe, was smelted in a vacuum induction furnace. The vacuum degree was controlled within 25 Pa throughout the process. To ensure uniform composition, the steel was melted three times. To further improve purity, the resistance heat generated by the current passing through the slag was used as the smelting heat source for electroslag remelting, and the resulting ingot was cast using a mold.

[0042] (2) The ingot is hot rolled three times on a rolling mill at a temperature of 1200℃ to form a steel plate with a thickness of 25 mm. The deformation amount of the first rough rolling is 10%, the deformation amount of the second rolling is 30%, and the deformation amount of the third finishing rolling is 50%.

[0043] (3) Cut the steel plate into rectangular blocks with a length of 150 mm, a width of 100 mm, and a thickness of 25 mm.

[0044] (4) First, heat the muffle furnace to 900°C at a heating rate of 5°C / min. After the temperature reaches 900°C, put the sample in and keep it at that temperature for 60 min. Then immediately cool it with water.

[0045] (5) Cut the water-cooled sample into pieces with dimensions of 150 × 50 × 1 mm. 3 Blocky.

[0046] (6) Turn on the vacuum tube furnace and heat it at a heating rate of 5℃ / min. Place the alumina ceramic crucible into the tube furnace and heat it along with the furnace. After the furnace temperature reaches 460℃ and stabilizes, place the sample obtained in step (5) into the alumina ceramic crucible and push it to the middle of the tube furnace. When the pressure is below 5×10 -1 The aging treatment was carried out under a nitrogen atmosphere of Pa. After holding at this temperature for 240 min, the sample was removed and cooled to room temperature.

[0047] Example of effect: The products prepared in Examples 1-2 and Comparative Example 1 were subjected to application performance tests, and the test standards or methods are as follows: I. Tensile Strength: Tensile tests were conducted using a universal testing machine equipped with a video extensometer, model LE5105. The tensile rate was 0.05 mm / min.

[0048] II. Matrix structure: The matrix structure was observed using a JEM-F200 cold field emission transmission electron microscope at an operating voltage of 30 kV and a temperature of -30℃.

[0049] III. Elemental Distribution: Elemental analysis was performed using a Leap 4000 XR atomic probe chromatography (APT) instrument. Data analysis was conducted using IVAS 3.8.8 software.

[0050] Experimental test analysis: The size and density of Cu-rich phases and carbide-formed atomic nanoclusters in the ultra-low carbon bainitic steel prepared in Example 1 were statistically analyzed, based on... Figure 1 It can be seen that the tensile strength of the ultra-low carbon bainitic steel prepared in Example 1 reaches 1236 MPa; from Figure 2 Transmission electron microscopy images and diffraction patterns show that the microstructure of the regulated ultra-low carbon bainitic steel remains primarily BCC (Brown-Crusted Carbon) structure. Figure 3 The spatial distribution of elements in the three-dimensional atomic probe shows that Cu atoms exhibit significant segregation, Ni, Mn, and C also show significant segregation, while Ti, V, Mo, and Cr elements also show slight segregation.

[0051] The method for preparing ultra-low carbon bainitic steel in Example 2, involving multiple atomic nanoclusters, was experimentally verified. Figure 4 It can be seen that the tensile strength of the ultra-low carbon bainitic steel prepared in Example 2 reaches 1718 MPa; from Figure 5 Transmission electron microscopy images and diffraction patterns show that the microstructure of the regulated ultra-low carbon bainitic steel remains primarily BCC (Brown-Crusted Carbon) structure. Figure 6 The spatial distribution of elements in the three-dimensional atomic probe shows that the elemental agglomeration is intensified at this time. Cu, Ni and Mn elements agglomerate at the same position, suggesting that the Cu-rich phase-related elements at this position form atomic clusters. C, Ti, V, Mo and Cr elements agglomerate at the same position, suggesting that the carbide elements at this position form atomic clusters.

[0052] The method for preparing ultra-low carbon bainitic steel in Comparative Example 1, which involves multiple atomic nanoclusters, was experimentally verified. Figure 7 It can be seen that the tensile strength of the ultra-low carbon bainitic steel prepared in Comparative Example 1 is 1048 MPa; from Figure 8Transmission electron microscopy images and diffraction patterns reveal that the microstructure of the regulated ultra-low carbon bainitic steel matrix is ​​a BCC structure. Figure 9 The spatial distribution of elements in the three-dimensional atomic probe shows that Cu elements segregate, Ni, Mn, and C elements segregate slightly, and no segregation of other elements is observed.

[0053] In summary, the method of the present invention, after introducing appropriate cold deformation before aging, through... Figure 10 As shown in the surface data for 4% Cu and 0.3% C concentrations, the number density and equivalent radius of Cu-rich atomic clusters increase and decrease respectively with increasing cold deformation, while the number density and equivalent radius of carbide atomic clusters decrease and increase respectively with increasing cold deformation. Statistical analysis was performed on the number density and equivalent radius of various atomic nanoclusters in the strengthened ultra-low carbon bainitic steels provided in Examples 1-2 and Comparative Example 1 of this invention. The results are shown in Table 1. It can be seen that the method of this invention can effectively control various atomic clusters in ultra-low carbon bainitic steel to achieve control over the comprehensive mechanical properties of the steel. Based on this, the strength of the ultra-low carbon bainitic steel is improved, compensating for the strength loss originally caused by the reduction in carbon content, ultimately yielding an ultra-low carbon bainitic steel with a strength of 1718 MPa.

[0054] Table 1

[0055] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A method for controlling multiple atomic nanoclusters in ultra-low carbon bainitic steel, characterized in that, Includes the following steps: (1) The original ultra-low carbon bainitic steel is melted, smelted and electroslag remelted under vacuum to obtain ingots, with the vacuum degree controlled within 25 Pa; (2) The ingot is hot rolled three times at a temperature of 1150-1300℃ to obtain a plate sample with a thickness of 25 mm; (3) The plate-shaped sample is subjected to solid solution treatment and then cooled with water to obtain a solid solution block sample; (4) The solid solution block sample is subjected to room temperature cold rolling with a cumulative deformation of 50% on a rolling mill; (5) The cold-rolled sample was aged at 460°C in a vacuum tube furnace with nitrogen gas introduced, held for 240 min, and then air-cooled. The original ultra-low carbon bainitic steel has the following chemical composition by weight percentage: C: 0.007%-0.012%, Si: 0.07%-0.10%, Mn: 0.049%-0.630%, Ni: 8.60%-8.99%, Cr: 0.61%-0.67%, Mo: 0.54%-0.61%, V: 0.098%-0.124%, Cu: 1.47%-1.71%, Ti: 0.009%-0.012%, with the balance being Fe.

2. The method for controlling multiple atomic nanoclusters in ultra-low carbon bainitic steel according to claim 1, characterized in that, In step (1), the melting is repeated 3 times, followed by electroslag remelting, and then the ingot is cast.

3. The method for controlling multiple atomic nanoclusters in ultra-low carbon bainitic steel according to claim 1, characterized in that, In step (2), the deformation amount during the first hot rolling is ≤10%; And / or, the deformation amount during the second hot rolling is ≤30%.

4. The method for controlling multiple atomic nanoclusters in ultra-low carbon bainitic steel according to claim 1, characterized in that, In step (2), the deformation amount of the third hot rolling is ≤50%; And / or, the hot rolling temperature is 1200℃.

5. The method for controlling multiple atomic nanoclusters in ultra-low carbon bainitic steel according to claim 1, characterized in that, In step (3), the solution treatment temperature is 800-1100℃; And / or, the heat preservation time is 30 min-120 min.

6. The method for controlling multiple atomic nanoclusters in ultra-low carbon bainitic steel according to claim 5, characterized in that, In step (3), the solution treatment temperature is 900℃; And / or, the heat preservation time is 60 minutes.

7. The method for controlling multiple atomic nanoclusters in ultra-low carbon bainitic steel according to claim 1, characterized in that, In step (4), the room temperature cold rolling is a multi-pass rolling process, with a reduction rate of 5% to 15% per pass.

8. A bainitic steel, characterized in that, The bainitic steel is prepared by controlling multiple atomic nanoclusters in ultra-low carbon bainitic steel according to any one of claims 1 to 7.

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