Marine steel and its production method

Abstract

The present invention provides a marine steel and its production method. Its chemical composition and mass percentage are as follows: 0.06 wt% ≤ C ≤ 0.08 wt%, 0.10 wt% ≤ Si ≤ 0.20 wt%, 0.9 wt% ≤ Mn ≤ 1.1 wt%, P ≤ 0.015 wt%, S ≤ 0.005 wt%, 0.018 wt% ≤ Als ≤ 0.045 wt%, 0.02 wt% ≤ Nb ≤ 0.03 wt%, Ti ≤ 0.02 wt%, 0.0075 wt% ≤ N ≤ 0.011 wt%, 0.03 wt% ≤ V ≤ 0.04 wt%, Mg ≥ 0.0020 wt%, and the rest is iron and other inevitable impurities. The center segregation and center porosity of the slab of this marine steel are ≤ C1.0 level, and the average size of the inclusions in the marine steel is < 1 μm. Its Z-direction performance is excellent, and there will be no tensile delamination or suspected delamination phenomenon, so it has broad application prospects.

Description

Technical Field

[0001] The present invention relates to the field of metal casting, and particularly to a marine steel and a production method thereof. Background Art

[0002] For marine steel products used in ship structural parts, the steel plate material needs to be welded and processed with high surface aesthetics. At the same time, after the ship is built, the hull is subject to impacts during transportation and use, so the steel plate material is required to have good quality.

[0003] However, during the use of marine steel plates and in mechanical testing, delamination of the steel plates occurs, seriously affecting the safety of the ship during operation. Nowadays, the shipbuilding industry is developing rapidly, and the demand for steel products is gradually increasing. However, in the actual production process, the problem of delamination at the tensile fracture of marine steel plates often occurs, seriously affecting the first-pass production rate and internal quality of the products. Summary of the Invention

[0004] The main object of the present invention is to provide a marine steel and a production method thereof, aiming to solve the problems such as delamination at the tensile fracture of marine steel plates in the prior art.

[0005] To achieve the above object, the present invention provides a marine steel, and the chemical composition and mass percentage of the marine steel are 0.06 wt% ≤ C ≤ 0.08 wt%, 0.10 wt% ≤ Si ≤ 0.20 wt%, 0.9 wt% ≤ Mn ≤ 1.1 wt%, P ≤ 0.015 wt%, S ≤ 0.005 wt%, 0.018 wt% ≤ Als ≤ 0.045 wt%, 0.02 wt% ≤ Nb ≤ 0.03 wt%, Ti ≤ 0.02 wt%, 0.0075 wt% ≤ N ≤ 0.011 wt%, 0.03 wt% ≤ V ≤ 0.04 wt%, Mg ≥ 0.0020 wt%, and the rest is iron and other inevitable impurities; among the other inevitable impurities, As + Sn + Cu + Sb + Ni + Cr ≤ 0.03 wt%.

[0006] Further, the center segregation and center porosity of the slab of the marine steel are ≤ C1.0 level; the average size of the inclusions in the marine steel is < 1 μm.

[0007] Further, the Z-direction performance detection of the marine steel Z35 ≥ 45.

[0008] The present invention also provides a production method of the marine steel as described in any one of the above, including the steps:

[0009] Perform LF refining treatment on the molten iron to obtain refined molten iron; wherein, the R2 basicity of the refining slag is 5 - 6.

[0010] Nb, V microalloys and Mg are added to the refined molten iron for continuous casting treatment to obtain a continuous casting billet; wherein, the chemical composition and mass percentage of the tundish molten steel in the continuous casting treatment are 0.06 wt% ≤ C ≤ 0.08 wt%, 0.10 wt% ≤ Si ≤ 0.20 wt%, 0.9 wt% ≤ Mn ≤ 1.1 wt%, P ≤ 0.015 wt%, S ≤ 0.005 wt%, 0.018 wt% ≤ Als ≤ 0.045 wt%, 0.02 wt% ≤ Nb ≤ 0.03 wt%, Ti ≤ 0.02 wt%, 0.0075 wt% ≤ N ≤ 0.011 wt%, 0.03 wt% ≤ V ≤ 0.04 wt%, Mg ≥ 0.0020 wt%, and the rest is iron and other inevitable impurities.

[0011] The continuous casting billet is subjected to hot rolling treatment at 1200 - 1250 °C to obtain marine steel.

[0012] Furthermore, the holding time of the white slag in the LF refining treatment > 8 min.

[0013] Furthermore, in the continuous casting treatment, the superheat △T of the tundish molten steel is 20 - 25 °C.

[0014] Furthermore, in the continuous casting treatment, the H content of the tundish molten steel < 6.5 ppm.

[0015] Furthermore, the dynamic soft reduction amount in the continuous casting treatment is 3.0 - 4.5 mm.

[0016] Furthermore, the duration of the hot rolling treatment is 40 - 50 min.

[0017] Furthermore, the reduction ratio of the hot rolling treatment > 45%.

[0018] The beneficial effects achieved by the present invention:

[0019] The central segregation and central porosity of the slab of the marine steel provided by the present invention ≤ C1.0 level, and the average size of the inclusions in the marine steel < 1 μm, the Z-direction performance is excellent, Z35 is not less than 45, and there will be no tensile delamination or suspected delamination phenomenon, and the application prospect is broad.

[0020] The production method of the marine steel provided by the present invention, by adding Nb, V microalloys and Mg to the refined molten iron for continuous casting treatment and combining with various conventional elements, can ensure that the prepared marine steel has central segregation and central porosity of ≤ C1.0 level, ultra-small size inclusions, excellent anti-tensile performance, and the preparation process is simple and the applicability is strong. Description of the Drawings

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the accompanying drawings required in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can be obtained based on the structures shown in these drawings.

[0022] Figure 1 It is the microscopic analysis diagram of the marine steel in Embodiment 1 of the present invention; wherein, (a) is the SEM (scanning electron microscope) diagram of the marine steel; (b) is the statistical chart of the number of inclusions of different sizes in (a); (c) is the microscopic structure diagram of the marine steel;

[0023] Figure 2 It is the microscopic analysis diagram of the marine steel in Embodiment 2 of the present invention; wherein, (a) is the SEM (scanning electron microscope) diagram of the marine steel; (b) is the statistical chart of the number of inclusions of different sizes in (a); (c) is the microscopic structure diagram of the marine steel;

[0024] Figure 3 It is the microscopic analysis diagram of the marine steel in Embodiment 3 of the present invention; wherein, (a) is the SEM (scanning electron microscope) diagram of the marine steel; (b) is the statistical chart of the number of inclusions of different sizes in (a); (c) is the microscopic structure diagram of the marine steel;

[0025] Figure 4 It is the microscopic analysis diagram of the steel product in Comparative Example 1 of the present invention; wherein, (a) is the SEM (scanning electron microscope) diagram of the steel product; (b) is the statistical chart of the number of inclusions of different sizes in (a); (c) is the microscopic structure diagram of the steel product;

[0026] Figure 5 It is the microscopic analysis diagram of the steel product in Comparative Example 2 of the present invention; wherein, (a) is the SEM (scanning electron microscope) diagram of the steel product; (b) is the statistical chart of the number of inclusions of different sizes in (a); (c) is the microscopic structure diagram of the steel product.

[0027] The realization, functional features and advantages of the object of the present invention will be further described in conjunction with the embodiments with reference to the accompanying drawings. Specific Embodiments

[0028] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0029] It should be noted that, without conflict, the following embodiments and the features in the embodiments may be combined with each other. It should also be understood that the terms used in the embodiments of the present invention are for describing specific embodiments and are not intended to limit the protection scope of the present invention.

[0030] Unless otherwise defined, all technical and scientific terms used in the present invention, based on the understanding of those skilled in the art of the present technology field and the description of the present invention, any methods, devices, and materials similar or equivalent to those described in the embodiments of the present invention in the prior art can also be used to implement the present invention.

[0031] When an embodiment gives a numerical range, it should be understood that, unless otherwise specified in the present invention, both endpoints of each numerical range and any value between the two endpoints can be selected. For the test methods without specific conditions noted in the following embodiments, they are usually carried out under conventional conditions or according to the conditions recommended by each manufacturer. The materials or reagents required in the following embodiments are commercially available unless otherwise specified.

[0032] To solve the problems such as delamination at the tensile fracture of marine steel plates in the prior art, the present invention provides a marine steel. The chemical composition and mass percentage of the marine steel are 0.06 wt% ≤ C ≤ 0.08 wt%, 0.10 wt% ≤ Si ≤ 0.20 wt%, 0.9 wt% ≤ Mn ≤ 1.1 wt%, P ≤ 0.015 wt%, S ≤ 0.005 wt%, 0.018 wt% ≤ Als ≤ 0.045 wt%, 0.02 wt% ≤ Nb ≤ 0.03 wt%, Ti ≤ 0.02 wt%, 0.0075 wt% ≤ N ≤ 0.011 wt%, 0.03 wt% ≤ V ≤ 0.04 wt%, Mg ≥ 0.0020 wt%, and the rest is iron and other inevitable impurities; among other inevitable impurities, As + Sn + Cu + Sb + Ni + Cr ≤ 0.03 wt%. Specifically, by mainly controlling P ≤ 0.015 wt%, S ≤ 0.005 wt%, 0.06 wt% ≤ C ≤ 0.08 wt%, and 0.9 wt% ≤ Mn ≤ 1.1 wt%, the inclusions, banded structure, and center segregation of the finished material of the marine steel can be controlled, and the strip-shaped MnS inclusions and the segregation of elements such as C and Mn can be effectively avoided.

[0033] In addition, by controlling Mg ≥ 0.0020 wt%, preferably the content of Mg is 0.0020 - 0.0025 wt%, the average size of the inclusions can be controlled to be < 1 μm.

[0034] The center segregation and center porosity of the slab of the marine steel provided by the present invention are ≤ C1.0 level, and the average size of the inclusions of the marine steel is < 1 μm. The Z-direction performance is excellent, Z35 is not less than 45, and there will be no tensile delamination or suspected delamination phenomenon, and it has broad application prospects.

[0035] Furthermore, the center segregation and center porosity of the slab of the marine steel are ≤ C1.0 level; the average size of the inclusions in the marine steel is < 1 μm. Specifically, the marine steel with center segregation and center porosity of the slab ≤ C1.0 level and an average inclusion size < 1 μm has excellent Z-direction performance and will not have problems such as delamination of the tensile fracture surface.

[0036] Furthermore, the Z-direction performance detection of the marine steel shows that Z35 ≥ 45. It can be seen that the Z35 performance of this marine steel is excellent and there will be no problems such as delamination of the tensile fracture surface.

[0037] The present invention also provides a production method of the marine steel as described in any one of the above, including the steps:

[0038] Perform LF refining treatment on the molten iron to obtain refined molten iron; wherein, the R2 basicity of the refining slag is 5 - 6.

[0039] Add Nb, V microalloy and Mg to the refined molten iron for continuous casting treatment to obtain a continuous casting billet; wherein, the chemical composition and mass percentage of the molten steel in the tundish during continuous casting treatment are 0.06 wt% ≤ C ≤ 0.08 wt%, 0.10 wt% ≤ Si ≤ 0.20 wt%, 0.9 wt% ≤ Mn ≤ 1.1 wt%, P ≤ 0.015 wt%, S ≤ 0.005 wt%, 0.018 wt% ≤ Als ≤ 0.045 wt%, 0.02 wt% ≤ Nb ≤ 0.03 wt%, Ti ≤ 0.02 wt%, 0.0075 wt% ≤ N ≤ 0.011 wt%, 0.03 wt% ≤ V ≤ 0.04 wt%, Mg ≥ 0.0020 wt%, and the rest is iron and other inevitable impurities. Specifically, the converter charging system can be used for control. In an optional embodiment, the single consumption of the refined molten iron for the charging amount is not less than 750 Kg, the slag material consumption is 45 Kg, and the waste steel structure is controlled to control the intake of residual elements such as As, Sn, Cu, Sb, Ni, and ensure that As + Sn + Cu + Sb + Ni + Cr ≤ 0.03 wt%. During the converter smelting process, the P content is controlled ≤ 0.015 wt%, and the slag amount during converter tapping is controlled not to exceed 4 Kg / t.

[0040] Perform hot rolling treatment on the continuous casting billet at 1200 - 1250 °C to obtain the marine steel. Specifically, the continuous casting billet is heated in a heating furnace, and the soaking temperature of the heating furnace is not less than 1200 °C to reduce the banded structure of the steel and the segregation of Nb, V, and Ti compounds, thereby reducing the delamination of the tensile fracture surface of the steel plate.

[0041] The production method of marine steel provided by the present invention involves adding Nb, V microalloys, and Mg to the molten iron after refining and then performing continuous casting. In combination with various conventional elements, it can ensure that the prepared marine steel has a slab center segregation and center porosity of ≤C1.0 level, ultra-small-sized inclusions, excellent tensile resistance, and a simple preparation process with strong applicability.

[0042] Further, the holding time of the white slag during LF refining treatment > 8 min. Preferably, the holding time of the white slag during LF refining treatment is above 10 min. The refined white slag indicates that the molten steel is well-deoxidized. The white slag has good desulfurization, deoxidation ability, and the ability to adsorb inclusions. A white slag time of more than 10 min gives the molten steel high cleanliness.

[0043] Further, during continuous casting, the superheat △T of the tundish molten steel is 20 - 25°C. By controlling the superheat of the molten steel during casting, the equiaxed crystal ratio of the billet can be increased, and good internal quality such as center segregation of the billet can be controlled. Specifically, low-temperature casting is adopted. When rolling cast steel with a thickness specification of 20 mm or more, the superheat of the casting molten steel does not exceed 30°C. Measures such as slow cooling for more than 8 hours can also be adopted to optimize the low-magnification structure such as center segregation of the slab.

[0044] Further, during continuous casting, the H content of the tundish molten steel < 6.5 ppm.

[0045] Further, the dynamic soft reduction amount during continuous casting is 3.0 - 4.5 mm.

[0046] Further, the duration of hot rolling treatment is 40 - 50 min. Hot rolling treatment for 40 - 50 min can heat the core of the slab well, ensuring uniform core temperature and consistent with the surface temperature.

[0047] Further, the reduction ratio of hot rolling treatment > 45%.

[0048] For a further understanding of the present invention, examples are given below for illustration:

[0049] Example 1:

[0050] 1. The molten iron charge is 780 Kg / t. The converter tapping operation retains slag, and the slag volume is 3 Kg / t. The LF refining time is 66 min, the R2 of the refining slag is 5.8, the white slag retention time is more than 12 min, and the Nb, V microalloy, and rare earth Mg treatment process is adopted; the superheat △T of the tundish molten steel during continuous casting is 22°C, the dynamic soft reduction amount is 3.5 mm, and the H content of the tundish is 6.2 ppm.

[0051] 2. Chemical composition of molten steel in tundish: C: 0.07%, Si: 0.165%, Mn: 0.95%, P: 0.0156%, S: 0.003%, Als: 0.0287%, Nb: 0.0246%, Ti: 0.0157%, N: 0.0082%, V: 0.033%, Mg: 0.0021%.

[0052] 3. Control rolling according to the hot rolling process. The soaking time in the heating furnace is 48 min, and the soaking temperature is 1210 °C. The reduction ratio exceeds 45% to obtain shipbuilding steel.

[0053] Example 2

[0054] 1. The charged amount of hot metal is 750 Kg / t. The slag remaining operation is carried out during tapping from the converter, and the amount of slag falling is 3 Kg / t. The refining time in LF is 58 min, the R2 of the refining slag is 5.5, and the retention time of white slag is more than 13 min. The Nb, V microalloying and rare earth Mg treatment process is adopted; the superheat ΔT of molten steel in the tundish for continuous casting is 18 °C, the dynamic soft reduction amount is 4.0 mm, and the H content in the tundish is 5.2 ppm.

[0055] 2. Chemical composition of molten steel in tundish: C: 0.065%, Si: 0.185%, Mn: 0.957%, P: 0.0116%, S: 0.002%, Als: 0.0307%, Nb: 0.0256%, Ti: 0.0137%, N: 0.0078%, V: 0.032%, Mg: 0.0025%.

[0056] 3. Control rolling according to the hot rolling process. The soaking time in the heating furnace is 44 min, and the soaking temperature is 1220 °C. The reduction ratio exceeds 45% to obtain shipbuilding steel.

[0057] Example 3

[0058] 1. The charged amount of hot metal is 800 Kg / t. The slag remaining operation is carried out during tapping from the converter, and the amount of slag falling is 2.5 Kg / t. The refining time in LF is 52 min, the R2 of the refining slag is 5.4, and the retention time of white slag is more than 15 min. The Nb, V microalloying and rare earth Mg treatment process is adopted; the superheat ΔT of molten steel in the tundish for continuous casting is 20 °C, the dynamic soft reduction amount is 4.0 mm, and the H content in the tundish is 5.5 ppm.

[0059] 2. Chemical composition of molten steel in tundish: C: 0.075%, Si: 0.215%, Mn: 0.96%, P: 0.0106%, S: 0.002%, Als: 0.0327%, Nb: 0.0246%, Ti: 0.0147%, N: 0.0087%, V: 0.034%, Mg: 0.0023%.

[0060] 3. Control rolling according to the hot rolling process. The soaking time of the heating furnace is 50 min, and the soaking temperature is 1200 °C. The reduction ratio exceeds 45%, and marine steel is obtained.

[0061] Comparative Example 1

[0062] 1. The hot metal charge is 750 Kg / t. The slag remaining operation is carried out during tapping from the converter, and the slag entrainment amount is 3 Kg / t. The LF refining time is 66 min, the R2 of the refining slag is 6.1, the white slag retention time is 6.5 min, and Nb microalloy is used; the superheat of molten steel in the continuous casting tundish △T is 25 °C, the dynamic soft reduction amount is 3.5 mm, and the H content in the tundish is 6.8 ppm.

[0063] 2. The chemical composition of molten steel in the tundish: C: 0.08%, Si: 0.18%, Mn: 1.25%, P: 0.022%, S: 0.0055%, Als: 0032%, Nb: 0.028%, Ti: 0.0156%, N: 0.0066%.

[0064] 3. The slab stacking cooling time is 12 hours before entering the heating furnace. Control rolling according to the hot rolling process. The soaking time of the heating furnace is 48 min, and the soaking temperature is 1210 °C. Steel products are obtained.

[0065] Comparative Example 2

[0066] 1. The hot metal charge is 720 Kg / t. The slag remaining operation is carried out during tapping from the converter, and the slag entrainment amount is 3 Kg / t. The LF refining time is 128 min, the R2 of the refining slag is 8.7, and Nb microalloy is used; the superheat of molten steel in the continuous casting tundish △T is 38 °C, the dynamic soft reduction amount is 3.8 mm, and the H content in the tundish is 8.4 ppm.

[0067] 2. The chemical composition of molten steel in the tundish: C: 0.066%, Si: 0.22%, Mn: 1.32%, P: 0.24%, S: 0.0032%, Als: 0.0352%, Nb: 0.032%, Ti: 0.0146%, N: 0.0068%.

[0068] 3. The slab stacking cooling time is 12 hours before entering the heating furnace. Control rolling according to the hot rolling process. The soaking time of the heating furnace is 48 min, and the soaking temperature is 1210 °C. Steel products are obtained.

[0069] Analysis Example 1

[0070] 1. The product thickness, macrosegregation of the continuous casting billet, grain size test, banded structure test, and Z-direction performance test are respectively carried out on Examples 1 - 3 and Comparative Examples 1 - 2, and the test results are shown in Table 1.

[0071] Table 1 Comparison of Test Results of Examples 1 - 3 and Comparative Examples 1 - 2

[0072]

[0073] As can be seen from Table 1, the Z35 index of the marine steels in Examples 1 to 3 is significantly superior to the performance of the steel products in Comparative Examples 1 to 2, indicating that delamination of the materials in Examples 1 to 3 is less likely to occur.

[0074] 2. Grain structure detection was carried out on Examples 1 to 3 and Comparative Examples 1 to 2, and the detection results of each product are as Figures 1 to 5 shown. The inclusions of each product are compared as shown in Table 2.

[0075] Table 2 Comparison of inclusions in the products of Examples 1 to 3 and Comparative Examples 1 to 2

[0076]

[0077] As can be seen from Table 2, the inclusions in Examples 1 to 3 are small in size, the proportion of inclusions less than 1μm in each size of inclusions is high, the cleanliness of the molten steel is high, and delamination will not occur.

[0078] Figure 1 Microscopic analysis diagram of the marine steel of Example 1; among them, (a) is the SEM (scanning electron microscope) diagram (50μm) of the marine steel. (b) is the statistical chart of the number of inclusions of different sizes in (a); the inclusions are small in size, and no MnS banded inclusions are seen. (c) is the microscopic structure diagram (50μm) of the marine steel. According to its microscopic structure diagram, it can be known that its structure is ferrite, pearlite and a small amount of bainite, and the banded structure is controlled at level 1.0.

[0079] Figure 2 Microscopic analysis diagram of the marine steel in Example 2 of the present invention; among them, (a) is the SEM (scanning electron microscope) diagram (100μm) of the marine steel. (b) is the statistical chart of the number of inclusions of different sizes in (a); the inclusions are small in size, and no MnS banded inclusions are seen. (c) is the microscopic structure diagram (200μm) of the marine steel. According to its microscopic structure diagram, it can be known that its structure is ferrite, pearlite and a small amount of bainite, and the banded structure is controlled at level 1.0.

[0080] Figure 3 Microscopic analysis diagram of the marine steel in Example 3 of the present invention; among them, (a) is the SEM (scanning electron microscope) diagram (100μm) of the marine steel. (b) is the statistical chart of the number of inclusions of different sizes in (a); the inclusions are small in size, and no MnS banded inclusions are seen. (c) is the microscopic structure diagram (200μm) of the marine steel. According to its microscopic structure diagram, it can be known that its structure is ferrite, pearlite and a small amount of bainite, and the banded structure is controlled at level 1.0.

[0081] Figure 4Microscopic analysis diagram of the steel product in Comparative Example 1 of the present invention; among them, (a) is the SEM (scanning electron microscope) diagram (20 μm) of the steel product. (b) is the statistical chart of the number of inclusions of different sizes in (a); the inclusions are relatively large in size, and it can be seen that there are a large number of strip-shaped MnS inclusions and large particle calcium-aluminum inclusions. (c) is the microscopic structure diagram (100 μm) of the steel product. According to its microscopic structure diagram, it can be known that its structure is ferrite, pearlite and a small amount of bainite, and the banded structure is controlled at level 2.5.

[0082] Figure 5 Microscopic analysis diagram of the steel product in Comparative Example 2 of the present invention; among them, (a) is the SEM (scanning electron microscope) diagram (20 μm) of the steel product. (b) is the statistical chart of the number of inclusions of different sizes in (a); the inclusions are relatively large in size, and it can be seen that there are a large number of strip-shaped MnS inclusions and large particle calcium-aluminum inclusions. (c) is the microscopic structure diagram (100 μm) of the steel product. According to its microscopic structure diagram, it can be known that its structure is ferrite, pearlite and a small amount of bainite, and the banded structure is controlled at level 3.0.

[0083] In summary, in the above technical solutions of the present invention, the above are only the preferred embodiments of the present invention, and do not limit the patent scope of the present invention accordingly. Any equivalent structural transformation made under the technical concept of the present invention by using the content of the specification and drawings of the present invention, or any direct / indirect application in other related technical fields is included in the patent protection scope of the present invention.

Claims

1. A marine steel, characterized in that, The chemical composition and mass percentage of the marine steel are as follows: 0.06wt% ≤ C ≤ 0.08wt%, 0.10wt% ≤ Si ≤ 0.20wt%, 0.9wt% ≤ Mn ≤ 1.1wt%, P ≤ 0.015wt%, S ≤ 0.005wt%, 0.018wt% ≤ Als ≤ 0.045wt%, 0.02wt% ≤ Nb ≤ 0.03wt%, Ti ≤ 0.02wt%, 0.0075wt% ≤ N ≤ 0.011wt%, 0.03wt% ≤ V ≤ 0.04wt%, 0.0020wt% ≤ Mg ≤ 0.0025wt%, and the rest is iron and other inevitable impurities; Among the other inevitable impurities, As + Sn + Cu + Sb + Ni + Cr ≤ 0.03wt%; The center segregation and center porosity of the slab of the marine steel ≤ grade C1.0; the average size of the inclusions in the marine steel < 1µm; The Z-direction performance test of the marine steel, Z35 ≥ 45.

2. A production method of the marine steel as described in claim 1, characterized in that, It includes the steps: Perform LF refining treatment on the hot metal to obtain refined hot metal; among them, the R2 basicity of the refining slag is 5 - 6; Add Nb, V microalloys and Mg to the refined hot metal for continuous casting treatment to obtain a continuous casting billet; among them, the chemical composition and mass percentage of the tundish molten steel in the continuous casting treatment are 0.06wt% ≤ C ≤ 0.08wt%, 0.10wt% ≤ Si ≤ 0.20wt%, 0.9wt% ≤ Mn ≤ 1.1wt%, P ≤ 0.015wt%, S ≤ 0.005wt%, 0.018wt% ≤ Als ≤ 0.045wt%, 0.02wt% ≤ Nb ≤ 0.03wt%, Ti ≤ 0.02wt%, 0.0075wt% ≤ N ≤ 0.011wt%, 0.03wt% ≤ V ≤ 0.04wt%, 0.0020wt% ≤ Mg ≤ 0.0025wt%, and the rest is iron and other inevitable impurities; Perform hot rolling treatment on the continuous casting billet at 1200 - 1250°C to obtain marine steel.

3. The production method according to claim 2, characterized in that, The white slag holding time of the LF refining treatment > 8min.

4. The production method according to claim 2, characterized in that, In the continuous casting treatment, the superheat △T of the tundish molten steel is 20 - 25°C.

5. The production method according to claim 2, characterized in that, In the continuous casting treatment, the H content of the tundish molten steel < 6.5ppm.

6. The production method according to claim 2, characterized in that, The dynamic soft reduction amount of the continuous casting treatment is 3.0 - 4.5mm.

7. The production method according to claim 2, characterized in that, The duration of the hot rolling treatment is 40 - 50min.

8. The production method according to claim 2, characterized in that, The reduction rate of the hot rolling treatment > 45%.

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