Thick-specification D-grade ship deck and preparation method thereof

Abstract

The invention relates to the technical field of steel and iron material processing, and provides a thick-specification D-grade ship deck and a preparation method thereof. A thick-specification D-grade ship deck is composed of, by weight, 0.11%-0.13% of C, 0.15%-0.24% of Si, 0.80%-0.90% of Mn, smaller than or equal to 0.015% of P, smaller than or equal to 0.005% of S, 0.020%-0.040% of Alt, 0.005%-0.015% of Ti and the balance Fe and inevitable impurities, C + Mn / 6 is smaller than or equal to 0.40, and the ratio of (C + Si) / Ti is (24-52): 1. By means of the technical scheme, the problem that in the prior art, the toughness of the thick-specification D-level ship plate is insufficient is solved.

Description

Technical Field

[0001] This invention relates to the field of steel material processing technology, specifically to a thick grade D ship plate and its preparation method. Background Technology

[0002] In the shipbuilding industry, ship plate steel, as a core material of the hull structure, directly determines the safety of ship navigation through its performance stability and compliance. The certification of steel mills' ship plate steel production qualifications by classification societies is a crucial threshold for ensuring material quality. In recent years, with the increasing demand for larger and safer ships, the certification standards for ship plate steel production qualifications by major global classification societies have become significantly stricter, especially for thicker ship plate steel, where certification requirements are even more stringent.

[0003] Traditional Grade D ship plate steel generally suffers from insufficient performance stability in the production of thick-gauge products. In low-temperature environmental adaptability testing, the value of the impact energy at -40℃ fluctuates greatly and has limited margin. It is common for some indicators of a single batch of products to be close to the qualified threshold, which greatly increases the risk of failure for steel mills in the certification of ship plate steel production qualifications and seriously restricts the process of steel mills entering the high-end ship steel market.

[0004] To improve the low-temperature impact performance of thick-gauge ship plate steel, existing technologies, such as the solution disclosed in patent CN119956209A, can achieve good low-temperature impact performance, but require the addition of a large amount of precious metal alloys, leading to a significant increase in material production costs and hindering subsequent large-scale, low-cost mass production. Furthermore, some technical solutions rely on micro-alloying with precious metal elements such as Nb and V, which not only further increases costs but also makes it difficult to balance performance stability and cost-effectiveness due to the high difficulty in controlling the uniformity of precious metal elements in thick-gauge plates.

[0005] Therefore, it is necessary to develop a thick-gauge Class D ship plate with better toughness. Summary of the Invention

[0006] This invention proposes a thick-gauge D-grade ship plate and its preparation method, which solves the problem of insufficient toughness of thick-gauge D-grade ship plates in related technologies.

[0007] The technical solution of the present invention is as follows: The present invention proposes a thick grade D ship plate, which, by weight percentage, is composed of the following components: C 0.11%~0.13%, Si 0.15%~0.24%, Mn 0.80%~0.90%, P≤0.015%, S≤0.005%, Alt 0.020%~0.040%, Ti 0.005%~0.015%, with the balance being Fe and unavoidable impurities, wherein C+Mn / 6≤0.40, and (C+Si) / Ti=24~52:1.

[0008] In the thick D-grade ship plate of the present invention, the Si content is 0.15%~0.24%, which can balance the strength and toughness of the thick D-grade ship plate, act as a strong deoxidizer, ensure the purity of molten steel, and improve the low-temperature impact toughness of the thick D-grade ship plate.

[0009] In the thick-gauge D-grade ship plate of the present invention, the Mn content is 0.80%~0.90%, which can refine the grains, maintain the strength of the ship plate, fix harmful sulfur (MnS), and improve the toughness of the thick-gauge D-grade ship plate.

[0010] In the thick-gauge D-grade ship plates of this invention, P≤0.015% and S≤0.005% are strictly controlled to prevent cracking, embrittlement and other phenomena.

[0011] In the thick-gauge D-grade ship plate of the present invention, the content of Alt is 0.020%~0.040%, which can deeply deoxidize, pin the austenite grain boundaries, and eliminate aging embrittlement.

[0012] This invention also proposes a method for preparing a thick-gauge Class D ship plate, which includes the following steps: S1. The mixture is prepared according to the stated ingredients, and then smelted and refined to obtain a melt; S2. The melt is poured and continuously cast to obtain a billet; S3. The billet is heated to 1100~1200℃, held at that temperature, and then subjected to rough rolling, fine rolling, and cooling to obtain a thick D-grade ship plate.

[0013] As a further technical solution, during the refining process, the superheat of the molten steel is 15~25℃, the length of the calcium wire fed is 200~300 meters / furnace, the feeding speed is 240~300m / min, and the calcium wire is fed vertically.

[0014] As a further technical solution, in step S1, the refining time is 35~45 minutes.

[0015] As a further technical solution, in step S2, during continuous casting, the total slag layer thickness of the continuous casting protective slag is 30-50 mm, the liquid slag layer thickness is 10-15 mm, the insertion depth of the submerged entry nozzle is 100-140 mm, and the flow rate of argon blowing between plates is 0.1-0.4 m³ / s. 3 The tapping temperature is 1600~1610℃, and the tapping speed is 1m / min.

[0016] As a further technical solution, in step S3, the heat preservation time is 400~420 minutes.

[0017] In the preparation process of the thick D-grade ship plate of the present invention, the holding time set after heating the billet in step S3 can ensure that the microalloying elements are fully dissolved.

[0018] As a further technical solution, in step S3, the initial rolling temperature of the roughing mill is 1040~1060℃, and the final rolling temperature of the roughing mill is 950~970℃.

[0019] As a further technical solution, in step S3, the initial rolling temperature of the finishing mill is 830~850℃, and the final rolling temperature of the finishing mill is 770~790℃.

[0020] As a further technical solution, in step S3, the cooling includes the following steps: the slab after precision rolling is first water-cooled to 600~640℃, and then air-cooled to room temperature.

[0021] As a further technical solution, the water cooling is a two-stage water cooling system, with different cooling rates for the first and second stages.

[0022] As a further technical solution, the water cooling includes the following steps: the slab after precision rolling is first subjected to a first stage of water cooling to 680~700℃, and then subjected to a second stage of water cooling to 600~640℃.

[0023] As a further technical solution, the cooling rate of the first stage water cooling is 10~12℃ / s, preferably 10℃ / s, and the cooling rate of the second stage water cooling is 5~8℃ / s, preferably 6℃ / s.

[0024] In the preparation process of the thick-gauge Class D ship plate of this invention, water cooling is divided into two stages with different cooling rates. The first stage of high-speed water cooling can significantly shorten the high-temperature residence time of the ship plate, refine the ferrite grains, and the rapid cooling can inhibit the recrystallization and growth of austenite grains before phase transformation, providing a fine-grained matrix for subsequent pearlite transformation. The second stage of low-speed water cooling ensures that carbon atoms have enough time to diffuse orderly at the austenite grain boundaries and ferrite interface, forming fine pearlite with uniform lamellar spacing. The two-stage water cooling process solves the problems of grain coarsening, uneven structure, and internal stress cracking that are prone to occur in thick-plate water cooling, effectively improving the strength of thick-gauge Class D ship plates.

[0025] As a further technical solution, the cooling rate of the air cooler is 0.5~0.8℃ / s, preferably 0.6℃ / s.

[0026] The working principle and beneficial effects of this invention are as follows: In the composition of the thick-gauge D-grade ship plate of the present invention, the C+Mn / 6 ≤ 0.40 is strictly controlled. By limiting the synergistic content of C and Mn, the good plasticity and low-temperature toughness of the material are maintained. The use of precious metals such as Nb and V is eliminated. By adding a small amount of Ti, the relationship between C, Si and Ti is made to satisfy the formula (C+Si) / Ti = 24~52:1. This ratio limitation not only effectively avoids the formation of coarse TiN particles caused by excessive Ti, but also avoids the lack of grain refinement effect caused by insufficient Ti, thereby effectively improving the low-temperature toughness of the thick-gauge D-grade ship plate. Detailed Implementation

[0027] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0028] In the following examples and comparative examples: Example 1 Thick-gauge Grade D ship plates, by weight percentage, consist of the following components: C 0.11%, Si 0.15%, Mn 0.80%, P 0.014%, S 0.002%, Alt 0.020%, Ti 0.005%, with the balance being Fe and unavoidable impurities. A method for preparing a thick-gauge Class D ship plate includes the following steps: S1. According to the ingredients, smelt and refine for 35 minutes to obtain the melt; S2. The melt is poured and continuously cast to obtain a billet; During continuous casting, argon blowing is used in the ladle during the initial pouring and production process. Full-process protective pouring is required, and open pouring and exposed molten steel surfaces are strictly prohibited. The total slag layer thickness for continuous casting is 30mm, the liquid slag layer thickness is 10mm, the insertion depth of the submerged entry nozzle is 100mm, and the argon blowing flow rate between plates is 0.1m³. 3 / h, the tapping temperature is 1600℃, and the tapping speed is 1m / min; S3. The billet is heated to 1100℃ and held for 420 minutes. After rough rolling, fine rolling and cooling, thick D-grade ship plates are obtained. The initial rolling temperature of the roughing mill is 1040℃, the final rolling temperature of the roughing mill is 950℃, the initial rolling temperature of the finishing mill is 830℃, and the final rolling temperature of the finishing mill is 770℃. The cooling process includes the following steps: the finished slab is first water-cooled to 600°C at a rate of 10°C / s, and then air-cooled to room temperature at a rate of 0.6°C / s.

[0029] Example 2 Thick-gauge Grade D ship plates, by weight percentage, consist of the following components: C 0.12%, Si 0.2%, Mn 0.85%, P 0.010%, S 0.003%, Alt 0.030%, Ti 0.01%, with the balance being Fe and unavoidable impurities. A method for preparing a thick-gauge Class D ship plate includes the following steps: S1. According to the ingredients, smelt and refine for 40 minutes to obtain the melt; S2. The melt is poured and continuously cast to obtain a billet; During continuous casting, argon blowing is used in the tundish during the initial pouring and production process. Full-process protective pouring is required, and open pouring and exposed molten steel surfaces are strictly prohibited. The total slag layer thickness for continuous casting is 40mm, the liquid slag layer thickness is 12mm, the submerged entry nozzle insertion depth is 120mm, and the argon blowing flow rate between plates is 0.2m³. 3 / h, the tapping temperature is 1605℃, and the tapping speed is 1m / min; S3. The billet is heated to 1150℃ and held for 410 minutes. After rough rolling, fine rolling and cooling, thick D-grade ship plates are obtained. The initial rolling temperature of the roughing mill is 1050℃, the final rolling temperature of the roughing mill is 960℃, the initial rolling temperature of the finishing mill is 840℃, and the final rolling temperature of the finishing mill is 780℃. The cooling process includes the following steps: the finished slab is first water-cooled to 620°C at a rate of 10°C / s, and then air-cooled to room temperature at a rate of 0.6°C / s.

[0030] Example 3 Thick-gauge Grade D ship plates, by weight percentage, consist of the following components: C 0.13%, Si 0.24%, Mn 0.90%, P 0.011%, S 0.004%, Alt 0.040%, Ti 0.015%, with the balance being Fe and unavoidable impurities. A method for preparing a thick-gauge Class D ship plate includes the following steps: S1. According to the ingredients, smelt and refine for 45 minutes to obtain the melt; S2. The melt is poured and continuously cast to obtain a billet; During continuous casting, argon blowing is used in the tundish during the initial pouring and production process. Full-process protective pouring is required, and open pouring and exposed molten steel surfaces are strictly prohibited. The total slag layer thickness for continuous casting is 50mm, the liquid slag layer thickness is 15mm, the insertion depth of the submerged entry nozzle is 140mm, and the argon blowing flow rate between plates is 0.4m³. 3 / h, the tapping temperature is 1610℃, and the tapping speed is 1m / min; S3. The billet is heated to 1200℃ and held for 400 minutes. After rough rolling, fine rolling and cooling, thick grade D ship plates are obtained. The initial rolling temperature of the roughing mill is 1060℃, the final rolling temperature of the roughing mill is 970℃, the initial rolling temperature of the finishing mill is 850℃, and the final rolling temperature of the finishing mill is 790℃. The cooling process includes the following steps: the finished slab is first water-cooled to 640°C at a rate of 10°C / s, and then air-cooled to room temperature at a rate of 0.6°C / s.

[0031] Example 4 Compared with Example 2, Example 4 differs in that the thick grade D ship plate, by weight percentage, consists of the following components: C 0.12%, Si 0.2%, Mn 0.85%, P 0.0115%, S 0.003%, Alt 0.035%, Ti 0.012%, with the balance being Fe and unavoidable impurities.

[0032] Example 5 Compared with Example 4, Example 5 differs in that the cooling process is different. The cooling in this example includes the following steps: the slab after finishing rolling is first subjected to a first stage of water cooling at a cooling rate of 10℃ / s to 690℃, then subjected to a second stage of water cooling at a cooling rate of 6℃ / s to 620℃, and finally air-cooled to room temperature at a rate of 0.6℃ / s.

[0033] Example 6 Compared with Example 4, Example 6 differs in that the cooling process is different. The cooling in this example includes the following steps: the slab after finishing rolling is first subjected to a first stage of water cooling at a cooling rate of 6℃ / s to 690℃, then subjected to a second stage of water cooling at a cooling rate of 10℃ / s to 620℃, and finally air-cooled to room temperature at a rate of 0.6℃ / s.

[0034] Example 7 Compared with Example 4, Example 7 differs in that the cooling process is different. The cooling in this example includes the following steps: the slab after finishing rolling is first subjected to a first stage of water cooling at a cooling rate of 14℃ / s to 690℃, then subjected to a second stage of water cooling at a cooling rate of 10℃ / s to 620℃, and finally air-cooled to room temperature at a rate of 0.6℃ / s.

[0035] Example 8 Compared with Example 4, Example 8 differs in that the cooling process is different. The cooling in this example includes the following steps: the slab after finishing rolling is first subjected to a first stage of water cooling at a cooling rate of 8°C / s to 690°C, then subjected to a second stage of water cooling at a cooling rate of 3°C / s to 620°C, and finally air-cooled to room temperature at a rate of 0.6°C / s.

[0036] Comparative Example 1 Compared with Example 2, Comparative Example 1 differs in that the thick grade D ship plate, by weight percentage, consists of the following components: C 0.12%, Si 0.2%, Mn 0.85%, P 0.010%, S 0.003%, Alt 0.030%, Ti 0.018%, with the balance being Fe and unavoidable impurities.

[0037] Comparative Example 2 Compared with Example 2, Comparative Example 2 differs in that the thick grade D ship plate, by weight percentage, consists of the following components: C 0.12%, Si 0.2%, Mn 0.85%, P 0.010%, S 0.003%, Alt 0.030%, Ti 0.004%, with the balance being Fe and unavoidable impurities.

[0038] Experimental Example 1 The D-grade thick ship plates prepared in Examples 1-4 and Comparative Examples 1-2 were tested according to the test method specified in GB / T 229-2020 "Metallic Materials Charpy Pendulum Impact Test Method" to test the impact energy of the samples. The V-type impact test was conducted, and the sample size was 10mm×10mm×55mm.

[0039] The test results are shown in Table 1: Table 1 Performance test results of thick grade D ship plates obtained in Examples 1-4 and Comparative Examples 1-2

[0040] As shown in Table 1, the toughness of thick D-grade ship plates can be improved when the composition of C+Mn / 6≤0.40 and (C+Si) / Ti=24~52:1.

[0041] Experiment Example 2 The tensile strength of the D-grade thick ship plates prepared in Examples 4-8 was tested according to the tensile strength test method specified in GB / T 228.1-2021 "Metallic materials, tensile testing - Part 1: Test method at room temperature".

[0042] The test results are shown in Table 2: Table 2 Performance test results of thick grade D ship plates obtained in Examples 4-8

[0043] As shown in Table 2, when the water cooling is a two-stage water cooling system, and the cooling rate of the first stage water cooling is 10~12℃ / s and the cooling rate of the second stage water cooling is 5~8℃ / s, the tensile strength of the thick D-grade ship plate can be further improved.

[0044] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A type of thick-gauge Class D ship plate, characterized in that, By weight percentage, it consists of the following components: C 0.11%~0.13%, Si 0.15%~0.24%, Mn 0.80%~0.90%, P≤0.015%, S≤0.005%, Alt 0.020%~0.040%, Ti 0.005%~0.015%, with the balance being Fe and unavoidable impurities, wherein C+Mn / 6≤0.40 and (C+Si) / Ti=24~52:

1.

2. A method for preparing a thick-gauge Class D ship plate, used to prepare the thick-gauge Class D ship plate as described in claim 1, characterized in that, Includes the following steps: S1. The mixture is prepared according to the stated ingredients, and then smelted and refined to obtain a melt; S2. The melt is poured and continuously cast to obtain a billet; S3. The billet is heated to 1100~1200℃, held at that temperature, and then subjected to rough rolling, fine rolling, and cooling to obtain a thick D-grade ship plate.

3. The method for preparing a thick-gauge D-grade ship plate according to claim 2, characterized in that, In step S1, the refining time is 35-45 minutes.

4. The method for preparing a thick-gauge D-grade ship plate according to claim 2, characterized in that, In step S3, the heat preservation time is 400~420 minutes.

5. The method for preparing a thick-gauge D-grade ship plate according to claim 2, characterized in that, In step S3, the initial rolling temperature of the roughing mill is 1040~1060℃, and the final rolling temperature of the roughing mill is 950~970℃.

6. The method for preparing a thick-gauge D-grade ship plate according to claim 2, characterized in that, In step S3, the initial rolling temperature of the finishing mill is 830~850℃, and the final rolling temperature of the finishing mill is 770~790℃.

7. The method for preparing a thick-gauge D-grade ship plate according to claim 2, characterized in that, In step S3, the cooling includes the following steps: the finished slab is first water-cooled to 600~640℃, and then air-cooled to room temperature.

8. The method for preparing a thick grade D ship plate according to claim 7, characterized in that, The water cooling system consists of two stages, with different cooling rates for the first and second stages.

9. The method for preparing a thick-gauge D-grade ship plate according to claim 8, characterized in that, The water cooling process includes the following steps: the finished slab is first subjected to a first stage of water cooling, which cools it to 680~700℃, and then a second stage of water cooling, which cools it to 600~640℃.

10. The method for preparing a thick-gauge D-grade ship plate according to claim 8, characterized in that, The cooling rate of the first stage of water cooling is 10~12℃ / s, and the cooling rate of the second stage of water cooling is 5~8℃ / s.

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