A kind of normalized rolling H-beam with vanadium-nitrogen microalloying and its production method

Abstract

The present invention discloses a normalized rolling H-beam with vanadium-nitrogen microalloying. The mass percentage of its chemical composition includes: C 0.10% - 0.16%, Si 0.35% - 0.45%, Mn 1.30% - 1.40%, P ≤ 0.015%, S ≤ 0.015%, Ni 0.10 - 0.15%, V 0.010% - 0.012%, N 0.008 - 0.012%, and the rest is Fe and impurities, with the total mass fraction being 100%. The production method thereof is also disclosed. The purpose of the present invention is to provide a normalized rolling H-beam with vanadium-nitrogen microalloying and its production method to meet the requirements of steel for offshore engineering.

Description

Technical Field

[0001] The present invention relates to the technical field of smelting, and particularly to a normalized rolling H-beam with vanadium-nitrogen microalloying and a production method thereof. Background Art

[0002] With the wide application of H-beams, there are diverse personalized demands for domestic H-beams. Normalized H-beams have stable strength and toughness. In recent years, the demand for normalized rolling H-beams in China has gradually increased, especially for steel used in offshore engineering. Most domestic H-beams are delivered in the hot-rolled state. Due to its special delivery state, the finishing rolling temperature of normalized rolling H-beams is controlled more precisely than that in the hot-rolled state, and the process window is smaller. The production of high-strength and low-temperature-resistant normalized rolling H-beams is difficult. Summary of the Invention

[0003] The purpose of the present invention is to provide a normalized rolling H-beam with vanadium-nitrogen microalloying and a production method thereof to meet the demand for steel used in offshore engineering.

[0004] To solve the above technical problems, the present invention adopts the following technical solutions:

[0005] For a normalized rolling H-beam with vanadium-nitrogen microalloying of the present invention, the mass percentage content of its chemical components includes: C 0.10% - 0.16%, Si 0.35% - 0.45%, Mn 1.30% - 1.40%, P ≤ 0.015%, S ≤ 0.015%, Ni 0.10 - 0.15%, V 0.010% - 0.012%, N 0.008 - 0.012%, and the rest are Fe and impurities, with the total mass fraction being 100%.

[0006] Further, the mass percentage content of its chemical components includes: C 0.13%, Si 0.38%, Mn 1.40%, P 0.015%, S 0.006%, Ni 0.13%, V 0.011%, N 0.0095%, and the rest are Fe and impurities, with the total mass fraction being 100%.

[0007] Further, the mass percentage content of its chemical components includes: C 0.16%, Si 0.35%, Mn 1.31%, P 0.013%, S 0.003%, Ni 0.15%, V 0.010%, N 0.0118%, and the rest are Fe and impurities, with the total mass fraction being 100%.

[0008] Further, the mass percentage content of its chemical components includes: C 0.10%, Si 0.43%, Mn 1.30%, P 0.010%, S 0.008%, Ni 0.10%, V 0.012%, N 0.0083%, and the rest are Fe and impurities, with the total mass fraction being 100%.

[0009] Furthermore, the mass percentage of its chemical components includes: C 0.15%, Si 0.45%, Mn 1.38%, P 0.012%, S 0.015%, Ni 0.12%, V 0.011%, N 0.0102%, and the rest is Fe and impurities, with the total mass fraction being 100%.

[0010] A production method of a vanadium-nitrogen microalloyed normalized rolled H-beam, comprising:

[0011] Compound blowing converter smelting, the converter adopts high-pull supplementary blowing operation. When spot blowing, it is required to have a deep lance and a large flow rate. It is required that the carbon composition before tapping meets the tapping requirements after one spot blowing. The end-point control targets are: C: 0.04 - 0.06%, T ≥ 1610 °C. 200 - 300 kg of dolomite is added before tapping to thicken the slag, and slag blocking is carried out during tapping. The target P ≤ 0.015%. Argon blowing operation is carried out according to regulations; large argon stirring is carried out in the early stage of tapping. When the tapping amount is greater than 2 / 3, the argon flow rate is adjusted to be small for slag blocking operation;

[0012] When the refining is in place and heating, 30 kg of ferrosilicon aluminum is added, or 10 - 20 kg of aluminum pellets are spread on the liquid surface of the ladle. During the heating process, 0.5 kg / t - 1.5 kg / t of bauxite and 4 kg / t - 6 kg / t of quicklime are added as slag melting materials, and 80 - 150 meters of calcium wire is fed. The argon flow rate is appropriate when feeding the wire. The wire is fed at a speed of 1.5 m - 2 m / s without the calcium wire coiling. The soft blowing time for each furnace of steel during refining must be guaranteed for 15 minutes. During soft blowing, the molten steel cannot be exposed, and the steel slag has creep. The appropriate tapping temperature is controlled during refining, and the superheat is required to be controlled at ≤ 30 °C;

[0013] Protective casting is adopted throughout the process, with a superheat of 20 °C - 30 °C. Medium cooling system is adopted for secondary cooling, and constant casting speed operation is adopted. The casting speed of the BB1 section is controlled at 1.1 ± 0.1 m / min; the casting speed of BB2 is controlled at 0.8 ± 0.1 m / min;

[0014] The temperature of the preheating section ≤ 900 °C, the temperature of the heating section I is 1120 °C - 1220 °C, the temperature of the heating section II is 1200 °C - 1330 °C, the soaking section temperature is 1180 °C - 1300 °C, the tapping temperature ≥ 1180 °C, and the residence time in the furnace is 150 min - 210 min;

[0015] BD1 blooming, the blooming temperature ≥ 1150 °C. The rolling passes are formulated according to the final product specifications, and the total reduction ratio ≥ 50%;

[0016] CCS universal rolling, the temperature of the last pass of finishing rolling is controlled at 900 °C - 930 °C;

[0017] The cooling bed is naturally cooled, and straightening is carried out below 100 °C.

[0018] Furthermore, it is applicable to the cross-sections of special-shaped blooms of 350×290×100 mm (BB1) and 555×440×105 mm (BB2); it is applicable to finished H-beams with flange thickness ≤ 16 mm.

[0019] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0020] The yield strength of the H-beam is ≥ 420 MPa, the tensile strength is ≥ 530 MPa, and the impact toughness at -40°C is ≥ 50 J.

[0021] This patent adopts the vanadium-nitrogen microalloying strengthening mechanism. While enhancing the strength of the steel, it ensures the low-temperature impact toughness. Compared with the existing normalized rolling H-beams, it has higher strength and a more reasonable strength-ductility matching. Usually, a good strength-ductility matching relationship can be obtained under controlled rolling and controlled cooling or low-temperature finishing rolling conditions. However, it is not easy to still maintain high strength and good strength-ductility matching under normalized rolling conditions or normalizing conditions. Specific embodiments

[0022] The following further elaborates on the present invention in detail.

[0023] A production method of a vanadium-nitrogen microalloyed normalized rolling H-beam, the mass percentage content of its chemical composition includes: C 0.10% - 0.16%, Si 0.35% - 0.45%, Mn 1.30% - 1.40%, P ≤ 0.015%, S ≤ 0.015%, Ni 0.10 - 0.15, V 0.10% - 0.12%, N 0.008 - 0.012%, and the rest are Fe and impurities, and the total mass fraction is 100%.

[0024] A production method of a vanadium-nitrogen microalloyed normalized rolling H-beam, comprising:

[0025] Smelting process: converter smelting, LF refining, and continuous casting of special-shaped blooms.

[0026] Compound blowing converter smelting, the converter adopts the operation of high-pull and supplementary blowing. When spot blowing, it is required to have a deep lance and a large flow rate. It is required that the carbon content of the molten steel meets the tapping requirements after one spot blowing. End-point control target: C: 0.04 - 0.06%, T ≥ 1610°C. 200 - 300 kg of dolomite is added before tapping to thicken the slag, and slagging tapping is carried out, with the target P ≤ 0.015%. Argon blowing operation is carried out according to regulations; large argon stirring is carried out in the early stage of tapping, and the argon flow rate is reduced for slagging operation when the tapping amount is greater than 2 / 3.

[0027] When refining and positioning for heating, add 30 kg of ferrosilicon aluminum, or spread 10 - 20 kg of aluminum pellets on the surface of the ladle. During the heating process, add 0.5 kg / t - 1.5 kg / t of bauxite and 4 kg / t - 6 kg / t of quicklime as slag - melting materials. Feed 80 - 150 meters of calcium wire. When feeding the wire, the argon flow rate should be appropriate. Feed the wire at a speed of 1.5 m - 2 m / s without the calcium wire coiling. The soft - blowing time for each heat of refining must be maintained for 15 minutes. During soft - blowing, the molten steel should not be exposed, and the slag should be in a creeping state. Control the appropriate tapping temperature for refining, and require the superheat to be controlled at ≤30°C.

[0028] The chemical composition of the molten steel for continuous casting is C 0.10% - 0.16%, Si 0.35% - 0.45%, Mn 1.30% - 1.40%, P ≤ 0.015%, S ≤ 0.015%, Ni 0.10 - 0.15, V 0.10% - 0.12%, N 0.008 - 0.012%, and the rest is Fe and impurities, with the total mass fraction being 100%.

[0029] Adopt protective casting throughout the process, with a superheat of 20°C - 30°C. For secondary cooling, adopt medium - cooling regime and constant casting speed operation. The casting speed for the BB1 section is controlled at 1.1 ± 0.1 m / min; the casting speed for BB2 is controlled at 0.8 ± 0.1 m / min.

[0030] It is applicable to special - shaped billet cross - sections of 350×290×100 mm (BB1) and 555×440×105 mm (BB2); it is applicable to finished H - shaped steel with flange thickness ≤ 16 mm.

[0031] Rolling process: walking - beam reheating furnace, BD blooming, CCS universal rolling, walking - beam cooling bed for cooling.

[0032] The temperature of the pre - heating section ≤ 900°C, the temperature of heating section I is 1120°C - 1220°C, the temperature of heating section II is 1200°C - 1330°C, the temperature of the soaking section is 1180°C - 1300°C, and the tapping temperature ≥ 1180°C. The residence time in the furnace is 150 min - 210 min.

[0033] BD1 blooming, the starting rolling temperature ≥ 1150°C. Determine the rolling passes according to the final product specifications, and the total reduction ratio ≥ 50%.

[0034] CCS universal rolling, the temperature of the last pass of finishing rolling is controlled at 900°C - 930°C.

[0035] The cooling bed cools naturally, and straightening is carried out below 100°C.

[0036] Table 1 Chemical Compositions of Each Example

[0037] Example C Si Mn P S V Ni N CEV Example 1 0.13 0.38 1.40 0.015 0.006 0.011 0.13 0.0095 0.37 Example 2 0.16 0.35 1.31 0.013 0.003 0.010 0.15 0.0118 0.39 Example 3 0.10 0.43 1.30 0.010 0.008 0.012 0.10 0.0083 0.33 Example 4 0.15 0.45 1.38 0.012 0.015 0.011 0.12 0.0102 0.39

[0038] Table 2 Casting Speed and Superheat Control Corresponding to the Cross-section of Each Example

[0039]

[0040] Table 3 Rolling Start and Finish Temperature Control of Each Example

[0041] Example Start rolling temperature (°C) Final rolling temperature (°C) Example 1 1175 930 Example 2 1182 902 Example 3 1150 917 Example 4 1168 926

[0042] Table 4 Mechanical Properties of Each Example

[0043]

[0044]

[0045] The embodiments described above are only descriptions of the preferred embodiments of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A normalized rolling H-beam with vanadium-nitrogen microalloying, characterized in that: The mass percentage content of its chemical components includes C 0.15%, Si 0.45%, Mn 1.38%, P 0.012%, S 0.015%, Ni 0.12%, V 0.011%, N 0.0102%, and the rest is Fe and impurities, with the total mass fraction being 100%; Its production method includes: Compound blowing converter smelting. The converter adopts the operation of high pulling and supplementary blowing. When spot blowing, it is required to have a deep lance and a large flow rate. It is required that the carbon content of the molten steel meets the tapping requirement after one spot blowing. The end-point control targets are: C: 0.04 - 0.06%, T≥1610°C. 200 - 300 kg of dolomite is added before tapping to thicken the slag, and slag blocking tapping is carried out. The target P≤0.015%. Argon blowing operation is carried out according to regulations; During the early stage of tapping, large argon stirring is carried out. When the tapping amount is greater than 2 / 3, the argon flow rate is adjusted to a smaller value for slag blocking operation; When the refining unit is in place for heating, 30 kg of ferrosilicon aluminum is added, or 10 - 20 kg of aluminum pellets are spread on the liquid surface of the ladle. During the heating process, 0.5 kg / t - 1.5 kg / t of bauxite and 4 kg / t - 6 kg / t of quicklime are added as slag melting materials, and 80 - 150 meters of calcium wire is fed. The argon flow rate is appropriate during wire feeding. The wire is fed at a speed of 1.5 m - 2 m / s without the calcium wire coiling. The soft blowing time for each heat of refining must be guaranteed for 15 minutes. During soft blowing, the molten steel cannot be exposed, and the molten slag has creep. The appropriate tapping temperature is controlled during refining, and the superheat is required to be controlled at ≤30°C; Protecting casting is adopted throughout the process, with a superheat of 28°C. Medium cooling regime is adopted for secondary cooling, and constant casting speed operation is adopted. The casting speed of the BB1 section is controlled at 1.15 m / min, and the size of the BB1 section is 350×290×100 mm; The temperature of the preheating section ≤900°C, the temperature of heating section I is 1120°C - 1220°C, the temperature of heating section II is 1200°C - 1330°C, the temperature of the soaking section is 1180°C - 1300°C, the tapping temperature ≥1180°C, and the residence time in the furnace is 150 min - 210 min; BD1 blooming, the starting rolling temperature is 1168°C. The rolling passes are formulated according to the final product specifications, and the total reduction ratio ≥50%; CCS universal rolling, the temperature of the last finishing pass is controlled at 926°C; The cooling bed is cooled naturally, and straightening is carried out below 100°C.

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