A-grade marine steel plate and production method thereof

Abstract

The invention discloses an A-grade marine steel plate which comprises the following chemical components in percentage by mass: 0.12-0.18% of C, 0.1-0.3% of Si, 0.4-0.7% of Mn, less than or equal to 0.030% of P, less than or equal to 0.020% of S, less than or equal to 0.20% of Ni, less than or equal to 0.20% of Cu, less than or equal to 0.04% of Nb, less than or equal to 0.08% of Mo, less than or equal to 0.02% of Ti, 0.01-0.05% of Al and the balance of Fe and inevitable impurities. The method has the advantages that the segregation degree of the casting blank is obviously reduced, the mechanical property of the product is improved, the structure uniformity in the thickness direction of the casting blank and the welding performance of the product are improved, and the product quality is more stable.

Description

Technical Field

[0001] The present invention belongs to the technical field of iron and steel metallurgy, and in particular relates to a grade A shipbuilding steel plate and a production method thereof. Background Art

[0002] With the rapid development of the shipping industry, specialized ship types have received significant attention. More and more shipyards are transitioning from conventional bulk carriers and container ships to high-value-added ship types such as ro-ro passenger ships, ro-ro ships, luxury cruise ships, and polar vessels. These special ship types place significant demands on steel plate materials. Due to the unique hull structure of cruise ships, the center of gravity is relatively high, and the weight of the steel structure accounts for over 25% of the ship's total design weight. To accommodate more rooms, passengers, and amusement facilities for the same displacement, strict weight control requirements are imposed while ensuring operational safety. High-efficiency welding is employed in ship plates, requiring stringent control over cutting and welding distortion, plate shape, and internal stresses. Consequently, ship plate steel quality requirements are becoming increasingly stringent. Grade A marine steel plate has a wide range of applications, but currently, its quality is inconsistent, with high levels of ingot segregation and poor through-thickness microstructure uniformity, significantly compromising the product's mechanical properties. Summary of the Invention

[0003] The purpose of the present invention is to solve the problems of unstable quality, high degree of segregation of ingots, poor structural uniformity and limited mechanical properties of existing Class A marine steel plates, and to provide a Class A marine steel plate that can significantly reduce the degree of segregation of ingots, improve the mechanical properties of the product, enhance the structural uniformity of the ingot thickness direction and the welding performance of the product, and make the product quality more stable.

[0004] In order to achieve the above object, the present invention adopts the following technical solutions: A grade A shipbuilding steel plate, whose chemical composition and mass percentage include: C: 0.12-0.18%, Si: 0.1-0.3%, Mn: 0.4-0.7%, P≤0.030%, S≤0.020%, Ni≤0.20%, Cu≤0.20%, Nb≤0.04%, Mo≤0.08%, Ti≤0.02%, Al: 0.01-0.05%, and the balance is Fe and unavoidable impurities.

[0005] Furthermore, the chemical composition and mass percentage of the Grade A marine steel plate include: C: 0.12-0.16%, Si: 0.1-0.2%, Mn: 0.4-0.6%, P≤0.020%, S≤0.010%, Ni≤0.20%, Cu≤0.20%, Nb≤0.04%, Mo≤0.08%, Ti≤0.02%, Al: 0.01-0.04%, and the balance is Fe and unavoidable impurities.

[0006] Furthermore, the chemical composition and mass percentage of the Grade A marine steel plate include: C: 0.14-0.18%, Si: 0.2-0.3%, Mn: 0.5-0.7%, P≤0.018%, S≤0.010%, Ni≤0.20%, Cu≤0.20%, Nb≤0.04%, Mo≤0.08%, Ti≤0.02%, Al: 0.02-0.05%, and the balance is Fe and unavoidable impurities.

[0007] In order to further achieve the purpose of the present invention, a production method of Grade A marine steel plate is also provided, and the specific steps are as follows: (1) Smelting: The molten iron is transported through torpedo tanks, desulfurized, and sent to the converter for smelting after slag removal. The tapping temperature of the converter is 1660~1720℃. After the composition temperature meets the requirements, the aluminum block is used for deoxidation treatment, and the LF refining is followed by continuous casting. (2) Casting: Use a 150-460 mm cross section for casting, a casting speed of 0.50-0.70 m / min, a superheat of 10-20 °C, and an alternating electromagnetic stirring technique with an electromagnetic stirring current of 380 A and a frequency of 6.0; (3) Rolling: A two-stage rolling process is used, with the second opening temperature ≤ 990°C, the final rolling temperature 770-830°C, the cooling roller speed setting 0.5-1.5 m / s, and the acceleration 0.001-0.010 m / s 2 After cooling, the temperature is set to 650-750℃, and the steel plate is directly put into the cooling pit for cooling, and the cooling time is 20-30h.

[0008] Compared with the prior art, the advantages of the technical solution of the present invention are: (1) The present invention reduces the segregation degree of the ingot through reasonable composition design, and the carbon content improves the mechanical properties of the product; (2) The present invention adopts high-temperature steelmaking technology and strong deoxidation technology, which increases the smelting rate, reduces production costs, and improves the competitiveness of the product; (3) The present invention adopts low-temperature casting and component design, which improves the uniformity of the structure in the thickness direction of the ingot and effectively improves the welding performance stability of the product; (4) The stack cooling process of the present invention plays a role in self-tempering, reduces the internal stress of the same plate, and improves the stability of the plate shape and the performance stability of the same plate. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 This is the metallographic structure diagram of the Class A marine steel plate of the present invention. DETAILED DESCRIPTION Example 1

[0010] To make the present invention more clear, a Class A marine steel plate and a production method thereof are further described below with reference to the accompanying drawings. The specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0011] In this embodiment, a grade A marine steel plate has the following chemical composition and its mass percentages: C: 0.15%, Si: 0.17%, Mn: 0.6%, P: 0.013%, S: 0.02%, Ni: 0.02%, Cu: 0.03%, Nb: 0.004%, Mo: 0.006%, Ti: 0.019%, Al: 0.028%, and the balance is Fe and unavoidable impurities.

[0012] The production method of the above-mentioned Grade A marine steel plate has the following steps, which are characterized by: (1) Smelting: The molten iron is transported through torpedo tanks, desulfurized, and sent to the converter for smelting after slag removal. The tapping temperature of the converter is 1699℃. After the composition temperature meets the requirements, the aluminum block is used for deoxidation treatment, and the LF refining is followed by continuous casting. (2) Casting: 370 mm cross section, pouring speed 0.60 m / min, superheat 18 °C, alternating electromagnetic stirring technology, electromagnetic stirring current 380 A, frequency 6.0; (3) Rolling: A two-stage rolling process is used, with the second rolling temperature at 930°C, the final rolling temperature at 810°C, the cooling roller speed at 0.7m / s, and the acceleration at 0.007m / s. 2 After cooling, the temperature is set to 689℃, and the steel plate is directly put into the cooling pit for cooling, and the cooling time is 26h. Example 2

[0013] In this embodiment, a grade A marine steel plate has the following chemical composition and its mass percentages: C: 0.15%, Si: 0.2%, Mn: 0.55%, P: 0.010%, S: 0.003%, Ni: 0.03%, Cu: 0.02%, Nb: 0.004%, Mo: 0.005%, Ti: 0.011%, Al: 0.03%, and the balance is Fe and unavoidable impurities.

[0014] The production method of the above-mentioned Grade A marine steel plate has the following steps, which are characterized by: (1) Smelting: The molten iron is transported through a torpedo tank, desulfurized, and then sent to a converter for smelting. The tapping temperature of the converter is 1677°C. After the composition temperature meets the requirements, the aluminum block is used for deoxidation. After LF refining, the molten iron is sent to continuous casting. (2) Casting: 220 mm cross section, pouring speed 0.70 m / min, superheat 17 °C, alternating electromagnetic stirring technology, electromagnetic stirring current 380 A, frequency 6.0; (3) Rolling: A two-stage rolling process is used, with the second rolling temperature at 980°C, the final rolling temperature at 820°C, the cooling roll speed at 1.3 m / s, and the acceleration at 0.009 m / s. 2 After cooling, the temperature is set to 730℃ and the steel plate is directly put into the cooling pit for cooling for 29h.

[0015] The metallographic structure diagram of the Class A marine steel plate produced by the production method of the present invention is as follows: Figure 1 As shown in the figure, by optimizing the composition design, improving the smelting technology level, applying high-temperature heating and rolling technology, and applying the rapid cooling process after rolling, a uniform fine-grained structure is obtained, the mechanical properties of Grade A ship plates are improved, and the customer's usage needs are met.

[0016] In addition to the above embodiments, the present invention may also have other implementations. Any technical solution formed by equivalent replacement or equivalent transformation falls within the scope of protection required by the present invention.

Claims

1. A grade A marine steel plate, characterized by: The chemical composition of the steel plate and its mass percentage include: C: 0.12-0.18%, Si: 0.1-0.3%, Mn: 0.4-0.7%, P≤0.030%, S≤0.020%, Ni≤0.20%, Cu≤0.20%, Nb≤0.04%, Mo≤0.08%, Ti≤0.02%, Al: 0.01-0.05%, and the balance is Fe and unavoidable impurities.

2. The Grade A marine steel plate according to claim 1, characterized in that: The chemical composition and mass percentage of the Grade A marine steel plate include: C: 0.12-0.16%, Si: 0.1-0.2%, Mn: 0.4-0.6%, P≤0.020%, S≤0.010%, Ni≤0.20%, Cu≤0.20%, Nb≤0.04%, Mo≤0.08%, Ti≤0.02%, Al: 0.01-0.04%, and the balance is Fe and unavoidable impurities.

3. The Grade A marine steel plate according to claim 1, characterized in that: The chemical composition and mass percentage of the Grade A marine steel plate include: C: 0.14-0.18%, Si: 0.2-0.3%, Mn: 0.5-0.7%, P≤0.018%, S≤0.010%, Ni≤0.20%, Cu≤0.20%, Nb≤0.04%, Mo≤0.08%, Ti≤0.02%, Al: 0.02-0.05%, and the balance is Fe and unavoidable impurities.

4. A method for producing the Grade A marine steel plate according to any one of claims 1 to 3, characterized in that: (1) Smelting: The molten iron is transported through torpedo tanks, desulfurized, and sent to the converter for smelting after slag removal. The tapping temperature of the converter is 1660~1720℃. After the composition temperature meets the requirements, the aluminum block is used for deoxidation treatment, and the LF refining is followed by continuous casting. (2) Casting: Use a 150-460 mm cross section for casting, a casting speed of 0.50-0.70 m / min, a superheat of 10-20 °C, and an alternating electromagnetic stirring technique with an electromagnetic stirring current of 380 A and a frequency of 6.0; (3) Rolling: A two-stage rolling process is used, with the second opening temperature ≤ 990°C, the final rolling temperature 770-830°C, the cooling roller speed setting 0.5-1.5 m / s, and the acceleration 0.001-0.010 m / s 2 After cooling, the temperature is set to 650-750℃, and the steel plate is directly put into the cooling pit for cooling, and the cooling time is 20-30h.

5. The method for producing Grade A marine steel plate according to claim 4, characterized in that: The chemical composition of the steel plate and its mass percentages include: C: 0.15%, Si: 0.17%, Mn: 0.6%, P: 0.013%, S: 0.02%, Ni: 0.02%, Cu: 0.03%, Nb: 0.004%, Mo: 0.006%, Ti: 0.019%, Al: 0.028%, and the balance is Fe and unavoidable impurities. The production method thereof is as follows: (1) Smelting: The molten iron is transported through torpedo tanks, desulfurized, and sent to the converter for smelting after slag removal. The tapping temperature of the converter is 1699℃. After the composition temperature meets the requirements, the aluminum block is used for deoxidation treatment, and the LF refining is followed by continuous casting. (2) Casting: 370 mm cross section, pouring speed 0.60 m / min, superheat 18 °C, alternating electromagnetic stirring technology, electromagnetic stirring current 380 A, frequency 6.0; (3) Rolling: A two-stage rolling process is used, with the second rolling temperature at 930°C, the final rolling temperature at 810°C, the cooling roller speed at 0.7m / s, and the acceleration at 0.007m / s. 2 After cooling, the temperature is set to 689℃, and the steel plate is directly put into the cooling pit for cooling, and the cooling time is 26h.

6. The method for producing Grade A marine steel plate according to claim 4, wherein: The chemical composition of the steel plate and its mass percentages include: C: 0.15%, Si: 0.2%, Mn: 0.55%, P: 0.010%, S: 0.003%, Ni: 0.03%, Cu: 0.02%, Nb: 0.004%, Mo: 0.005%, Ti: 0.011%, Al: 0.03%, and the balance is Fe and unavoidable impurities. The production method thereof is as follows: (1) Smelting: The molten iron is transported through a torpedo tank, desulfurized, and then sent to a converter for smelting. The tapping temperature of the converter is 1677°C. After the composition temperature meets the requirements, the aluminum block is used for deoxidation. After LF refining, the molten iron is sent to continuous casting. (2) Casting: 220 mm cross section, pouring speed 0.70 m / min, superheat 17 °C, alternating electromagnetic stirring technology, electromagnetic stirring current 380 A, frequency 6.0; (3) Rolling: A two-stage rolling process is used, with the second rolling temperature at 980°C, the final rolling temperature at 820°C, the cooling roll speed at 1.3 m / s, and the acceleration at 0.009 m / s. 2 After cooling, the temperature is set to 730℃ and the steel plate is directly put into the cooling pit for cooling for 29h.

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