Narrow yield strength DH36 thin gauge medium plate and production method thereof

Abstract

The invention discloses a DH36 thin gauge medium plate with narrow yield strength. The medium plate is characterized by comprising the following chemical components in percentage by mass: less than or equal to 0.18% of C, 0.9-1.6% of Mn, less than or equal to 0.03% of P, less than or equal to 0.03% of S, less than or equal to 0.50% of Si, less than or equal to 0.05% of Nb, less than or equal to 0.4% of Ni, less than or equal to 0.2% of Cr, less than or equal to 0.35% of Cu, less than or equal to 0.08% of Mo, less than or equal to 0.1% of V, less than or equal to 0.02% of Ti and the balance of Fe and inevitable impurities. The yield strength of the medium-thickness plate is controlled to be 355-400 MPa, the subsequent machining performance of the steel plate is improved, the production efficiency of a shipyard is improved, the quality of a ship body is improved, and the labor cost of shipbuilding is reduced.

Description

Technical Field

[0001] The invention relates to a narrow yield strength DH36 thin-gauge medium and thick plate and a production method thereof. Background Art

[0002] DH36 grade medium and thick plates are commonly used in shipbuilding. During the construction of the hull, the main processing technologies used for medium and thick plates are bending deformation and welding. Because classification societies do not require the upper limit of the yield strength of DH36 grade ship plates, if the yield strengths of different batches of steel plates vary greatly, when the same bending process is used, the deformation degree of each steel plate will be different, requiring secondary correction, which reduces production efficiency. Even when processing thick and large parts, the bending capacity of the bending machine is insufficient due to the high yield strength, which in turn causes the scrapping of raw materials and affects the progress of the shipbuilding period. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a narrow yield strength DH36 thin-gauge medium and thick plate and a production method thereof in view of the shortcomings of the above-mentioned prior art. The yield strength of the medium and thick plate is controlled at 355-400MPa, the subsequent processing performance of the steel plate is improved, the production efficiency of the shipyard is improved, the hull quality is improved, and the labor cost of shipbuilding is reduced.

[0004] The technical solution of the present invention to solve the above technical problems is: a narrow yield strength DH36 thin-gauge medium and thick plate, the chemical composition and mass percentage of the medium and thick plate are as follows: C≤0.18%, Mn: 0.9%~1.6%, P≤0.03%, S≤0.03%, Si≤0.50%, Nb≤0.05%, Ni≤0.4%, Cr≤0.2%, Cu≤0.35%, Mo≤0.08%, V≤0.1%, Ti≤0.02%, and the rest are Fe and unavoidable impurities.

[0005] Furthermore, the chemical composition and mass percentage of the medium and thick plates are as follows: C: 0.14%~0.18%, Mn: 1.0%~1.6%, P≤0.02%, S≤0.01%, Si: 0.10%~0.30%, Nb≤0.05%, Ni≤0.1%, Cr≤0.1%, Cu≤0.1%, Mo≤0.08%, V≤0.1%, Ti≤0.02%, and the rest are Fe and unavoidable impurities.

[0006] Furthermore, the thickness of the medium and thick plate is: 4-40mm; the width is ≤5000mm; the length is ≤30m.

[0007] Furthermore, the yield strength of the medium and thick plate is 355-400 MPa, the tensile strength is 490-620 MPa, the tensile elongation is ≥21%, and the longitudinal impact value at -40°C is ≥34J.

[0008] A method for producing a narrow yield strength DH36 thin-gauge medium and thick plate, specifically comprising: S1 continuous casting billet rolling: the molten steel is sequentially subjected to KR pre-desulfurization → BOF converter smelting → LF refining → RH vacuum degassing → continuous casting → pile slow cooling to prepare continuous casting billets, the thickness of the continuous casting billets is 150-460mm; the width is ≤3250mm; the length is ≤18000mm; S2 billet heating: furnace entry temperature 40-80℃, furnace exit temperature 1100℃~1220℃, total furnace time ≥90min, soaking time ≥21min, temperature uniformity ≤15℃; S3 rolling: After the billet is discharged from the furnace, it is transferred through the roller table and first enters the descaling box to perform rough descaling on the upper and lower surfaces. After the rough descaling is completed, it is quickly transferred to the rolling mill area through the roller table and enters the rolling stage. The rolled piece is reciprocated by the four-roll reversible furnace coil mill. The rolling process is rough rolling and the first two rolling processes of finishing rolling are descaling. The second stage rolling temperature is 980±10℃, the final rolling temperature is 820±10℃, and after rolling, it enters the water cooling system for cooling between 30-60 seconds, and the red return temperature is 690±20℃.

[0009] Furthermore, before the S3 rolling, a descaling box is used to perform high-pressure water double-pump descaling, and the descaling pressure is ≥20MPa.

[0010] The beneficial effects of the present invention are as follows: the present invention controls the yield strength range of DH36 marine medium and thick plates with a thickness of ≤40 mm to between 355 and 400 MPa through a series of measures such as component design, heating, rolling process, and descaling distribution optimization, thereby meeting the shipyard's requirements for easy deformation processing of steel plates, improving the shipyard's production efficiency, improving the stability of hull performance, and reducing labor costs. DETAILED DESCRIPTION Example

[0011] The present embodiment provides a narrow yield strength DH36 thin-gauge medium and thick plate, and the chemical composition and mass percentage of the medium and thick plate are as follows: C: 0.17%, Mn: 1.12%, P: 0.012%, S: 0.01%, Si: 0.19%, Nb: 0.002%, Ni: 0.01%, Cr: 0.02%, Cu: 0.01%, Mo: 0.008%, V: 0.001%, Ti: 0.014%, and the rest are Fe and unavoidable impurities; The production method of the above-mentioned narrow yield strength DH36 thin-gauge medium and thick plate specifically comprises: S1 continuous casting billet rolling: the raw materials allocated by group are smelted into molten steel, and the molten steel is sequentially subjected to KR pre-desulfurization → BOF converter smelting → LF refining → RH vacuum degassing → continuous casting → pile slow cooling to prepare continuous casting billets, with a continuous casting billet size of 150mm×2550mm×8500mm; S2 billet heating: furnace entry temperature 65°C, furnace exit temperature 1168°C, total furnace time 158min, soaking time 25min, temperature uniformity 12°C; S3 rolling: After the billet is discharged from the furnace, it is transferred through the roller table and first enters the descaling box to perform rough descaling on the upper and lower surfaces. The descaling pressure is ≥20MPa. After the rough descaling is completed, it is quickly transferred to the rolling mill area through the roller table and enters the rolling stage. The rolled piece is reciprocated by the four-roll reversible furnace coil mill. The rolling process is descaling in the first two rolling processes of rough rolling and finishing rolling. The second-stage rolling temperature is 980℃, the final rolling temperature is 825℃, and the water cooling system is cooled within 45 seconds after rolling. The red return temperature is 682℃, and the steel plate size is 15mm×2500mm×12000mm.

[0012] In addition to the above embodiments, the present invention may also have other implementation modes. Any technical solution formed by equivalent replacement or equivalent transformation falls within the protection scope required by the present invention.

Claims

1. A narrow yield strength DH36 thin gauge medium and thick plate, characterized by: The chemical composition and mass percentage of medium and thick plates are as follows: C≤0.18%, Mn: 0.9%~1.6%, P≤0.03%, S≤0.03%, Si≤0.50%, Nb≤0.05%, Ni≤0.4%, Cr≤0.2%, Cu≤0.35%, Mo≤0.08%, V≤0.1%, Ti≤0.02%, and the rest are Fe and unavoidable impurities.

2. The narrow yield strength DH36 thin gauge medium plate according to claim 1, characterized in that: The chemical composition and mass percentage of the medium and thick plates are as follows: C: 0.14%-0.18%, Mn: 1.0%-1.6%, P≤0.02%, S≤0.01%, Si: 0.10%-0.30%, Nb≤0.05%, Ni≤0.1%, Cr≤0.1%, Cu≤0.1%, Mo≤0.08%, V≤0.1%, Ti≤0.02%, and the rest are Fe and unavoidable impurities.

3. The narrow yield strength DH36 thin gauge medium plate according to claim 1, characterized in that: The thickness of the medium and thick plate is 4-40 mm; the width is ≤5000 mm; and the length is ≤30 m.

4. The narrow yield strength DH36 thin gauge medium plate according to claim 1, characterized in that: The medium and thick plate has a yield strength of 355-400 MPa, a tensile strength of 490-620 MPa, a tensile section elongation of ≥21%, and a -40°C longitudinal impact value of ≥34 J.

5. A method for producing a narrow yield strength DH36 thin-gauge medium and thick plate according to any one of claims 1-2, characterized in that: Specifically include: S1 continuous casting billet rolling: the molten steel is sequentially subjected to KR pre-desulfurization → BOF converter smelting → LF refining → RH vacuum degassing → continuous casting → pile slow cooling to prepare continuous casting billets, the thickness of the continuous casting billets is 150-460mm; the width is ≤3250mm; the length is ≤18000mm; S2 billet heating: furnace entry temperature 40-80℃, furnace exit temperature 1100℃~1220℃, total furnace time ≥90min, soaking time ≥21min, temperature uniformity ≤15℃; S3 rolling: After the billet is discharged from the furnace, it is transferred through the roller table and first enters the descaling box to perform rough descaling on the upper and lower surfaces. After the rough descaling is completed, it is quickly transferred to the rolling mill area through the roller table and enters the rolling stage. The rolled piece is reciprocated by the four-roll reversible furnace coil mill. The rolling process is rough rolling and the first two rolling processes of finishing rolling are descaling. The second stage rolling temperature is 980±10℃, the final rolling temperature is 820±10℃, and after rolling, it enters the water cooling system for cooling between 30-60 seconds, and the red return temperature is 690±20℃.

6. The method for producing a narrow yield strength DH36 thin-gauge medium and thick plate according to claim 1, characterized in that: Before the S3 rolling, a descaling box is used to perform high-pressure water double pump descaling, and the descaling pressure is ≥20MPa.