TMCP type F-grade large-thickness bridge steel plate and production method thereof

Abstract

The invention relates to the technical field of ferrous metallurgy, in particular to a TMCP type F-grade large-thickness bridge steel plate and a production method thereof.The steel plate comprises, by mass, 0.03%-0.08% of C, 0.10%-0.40% of Si, 1.00%-1.35% of Mn, smaller than or equal to 0.006% of P, smaller than or equal to 0.005% of S, 0.010%-0.020% of Nb, 0.020%-0.040% of Al and the balance Fe and other inevitable impurities. The production method sequentially comprises the procedures of steelmaking, continuous casting and rolling. The obtained TMCP type F-grade large-thickness bridge steel plate is uniform and compact in internal structure, the structure is ferrite and pearlite, the strength and toughness of the produced steel plate are well matched, the yield strength is larger than or equal to 370 MPa, the tensile strength is 510-630 MPa, the V-shaped longitudinal-60-DEG C single-value impact energy at the position 1 / 2 of the plate thickness is larger than or equal to 120 J, and the yield ratio is smaller than or equal to 0.85.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of steel metallurgy, in particular to a TMCP type F-grade large-thickness bridge steel plate and a production method thereof. BACKGROUND

[0002] The F-grade large-thickness bridge steel plate refers to a bridge component with a thickness exceeding 50 mm or even more than 100 mm, which is a high-strength steel material used for bridge construction, and is mainly used for key positions subjected to heavy load and complex stress as a bridge joint and connecting part. The steel plate is used in extremely cold regions, such as the Sichuan-Tibet line with complex terrain. In the early stage, normalizing production is generally used more, but the normalizing steel plate has poor weldability due to high C and Mn content and heavy segregation, which is not conducive to on-site construction and connection. In order to improve the weldability of the large-thickness bridge plate, especially the high impact toughness performance after welding and the prevention of welding fracture, the present application provides a TMCP type F-grade large-thickness bridge steel plate and a production method thereof. SUMMARY

[0003] The present application overcomes the shortcomings of the prior art and provides a TMCP type F-grade large-thickness bridge steel plate and a production method thereof. Through reasonable chemical composition design and control of key production processes such as steelmaking, continuous casting and rolling, a bridge steel plate with uniform internal organization, good strength and toughness matching, stable performance and low production cost is obtained. Since no normalizing heat treatment process is required and no Ni and Cu noble alloy components are used, the production cost is greatly reduced and the competitiveness of the product is improved.

[0004] In a first aspect, the present application provides a TMCP type F-grade large-thickness bridge steel plate, which has the following chemical composition and mass percentage: C: 0.03-0.08%, Si: 0.10-0.40%, Mn: 1.00-1.35%, P≤0.006%, S≤0.005%, Nb: 0.010-0.020%, Al: 0.020-0.040%, and the rest is Fe and other unavoidable impurities.

[0005] Further, the microstructure of the steel plate is acicular ferrite and pearlite.

[0006] Further, the yield strength of the steel plate is ≥370 MPa, the tensile strength is 510-630 MPa, the V-type longitudinal -60℃ single value impact energy at 1 / 2 of the plate thickness is ≥120 J, and the yield strength ratio is ≤0.85.

[0007] Further, the thickness of the steel plate is 100-120 mm.

[0008] In the second aspect, the application further provides a production method of the TMCP type F-grade large-thickness bridge steel plate according to any one of the first aspect, which comprises, in sequence, a steelmaking process, a continuous casting process and a rolling process, in the steelmaking process, the molten steel after converter smelting is sent to a LF refining furnace for refining, argon blowing is good in the whole LF refining process, the total refining time is greater than or equal to 35 min, the white slag maintaining time is greater than or equal to 25 min, and the slag basicity at the end of refining is greater than or equal to 3.5.

[0009] Further, in the steelmaking process, after the LF furnace refining is completed, the molten steel is sent to a VD vacuum furnace for vacuum degassing treatment, the vacuum degree is less than or equal to 66.7 Pa, the vacuum maintaining time is greater than or equal to 18 min, and after the vacuum is destroyed, soft blowing is performed for 10-12 min, and 0.8-1.0 kg / t of steel calcium wire is fed for calcium treatment.

[0010] Further, in the continuous casting process, electromagnetic stirring and light pressing down technology are adopted during casting, and the crystallizer liquid level fluctuation range is ±3 mm, and the superheat degree is controlled to be 15-35 ℃.

[0011] Further, in the rolling process, the casting blank is heated in a continuous furnace, when the furnace temperature T is less than or equal to 600 ℃, the heating speed is less than or equal to 200 ℃ / h; when the furnace temperature is greater than 600 ℃ and less than or equal to 1200 ℃, the heating speed is less than or equal to 350 ℃ / h; the highest heating temperature is 1270 ℃, the soaking segment temperature is 1230-1250 ℃, and the total heating coefficient is greater than or equal to 10 min / cm.

[0012] Further, the rolling process adopts a two-stage controlled rolling process, the one-stage rough rolling temperature is 1010-1100 ℃, a large reduction rolling process is adopted, and the air cooling thickness is h+70 mm, the h is the thickness of the finished steel plate, the two-stage rough rolling temperature is 800-750 ℃, the finish rolling temperature is 770-730 ℃, and the steel plate red temperature is 540-600 ℃.

[0013] The application has the following beneficial effects: (1) The TMCP type F-grade large-thickness bridge steel plate provided by the application has reasonable chemical component design, the internal organization of the steel plate is uniform, no noble metal Ni and Cu is added, the cost is low, and the market competitiveness is strong; (2) The application adopts the LF, VD, calcium treatment and soft blowing process to reduce the endogenous inclusions generated by the molten steel, at the same time, the metal yield is improved by using the continuous casting blank, the production cost is greatly reduced, in addition, through the reasonable controlled rolling process, the steel plate has good comprehensive performance, and compared with the normalized large-thickness bridge steel plate, the production cost is greatly reduced; (3) The TMCP type F grade large thickness bridge steel plate produced by the application has uniform and dense internal structure, the structure is ferrite and pearlite, the strength and toughness of the produced steel plate are well matched, the yield strength is greater than or equal to 370 MPa, the tensile strength is 510-630 MPa, the V type longitudinal -60 DEG C single value impact energy at 1 / 2 of the plate thickness is greater than or equal to 120 J, and the yield strength ratio is less than or equal to 0.85; in addition, the produced steel plate is more pure, the impurity content is low, P is less than or equal to 0.006%, S is less than or equal to 0.005%, the thickness specification of the steel plate is 100-120 mm, and the performance of the large thickness bridge steel plate meets the requirements of users. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 The microstructure schematic diagram of the TMCP type F grade large thickness bridge steel plate obtained by the embodiment 1 of the application is shown in the figure. Figure 2 The microstructure schematic diagram of the TMCP type F grade large thickness bridge steel plate obtained by the embodiment 2 of the application is shown in the figure. Figure 3 The microstructure schematic diagram of the TMCP type F grade large thickness bridge steel plate obtained by the embodiment 3 of the application is shown in the figure. DETAILED DESCRIPTION

[0015] Embodiment 1: The embodiment provides a TMCP type F grade large thickness bridge steel plate, the chemical component composition and mass percentage content are as follows: C: 0.03%, Si: 0.10%, Mn: 1.35%, P: 0.001%, S: 0.004%, Nb: 0.018%, Al: 0.020%, and the rest is Fe and other inevitable impurities.

[0016] The production method of the TMCP type F grade large thickness bridge steel plate in the embodiment includes a steelmaking, continuous casting and rolling process, and the specific process steps are as follows: (1) Steelmaking process: the molten steel of the converter smelting is sent into the LF refining furnace for refining, argon blowing is good in the whole process, the total refining time is 45 min, the white slag maintaining time is 25 min, and the slag basicity is 3.6 at the end of the refining; after the refining is completed, the molten steel is sent into the VD furnace for vacuum degassing treatment, the vacuum degree is 60 Pa, the vacuum maintaining time is 19 min, soft blowing is performed for 10 min after the vacuum is destroyed, so that the inclusions can be fully floated, and 0.8 kg / t of calcium wire is fed for calcium treatment to accelerate the spheroidization and floating of the inclusions; (2) Continuous casting process: a large section continuous casting machine is used, the liquid level of the crystallizer is automatically controlled, the fluctuation range is ±3 mm, the superheat degree of the tundish is 16 DEG C, electromagnetic stirring, light pressing and solidification end strong cooling technology are used, and a large section high quality continuous casting billet is casted; (3) Rolling process: The continuous casting billet is heated in a continuous furnace with a furnace temperature of 550°C and a heating rate of 160°C / h; the maximum heating temperature is 1270°C, the soaking zone temperature is 1230°C, and the total heating coefficient is 11 min / cm; A two-stage controlled rolling process is adopted, with the first-stage starting rolling temperature at 1010°C, high reduction rolling, and a steel thickness of 170mm; the second-stage starting rolling temperature is 800°C, the final rolling temperature is 770°C, and the red-returning temperature is 600°C.

[0017] like Figure 1 As shown in the figure, the microstructure of the steel plate obtained after cooling is ferrite and pearlite, the yield strength of the steel plate is 420MPa, the tensile strength is 550MPa, the yield strength ratio is 0.75, the minimum single value of the V-shaped longitudinal -60℃ impact energy at 1 / 2 of the plate thickness is 156J, and the thickness is 100mm. The produced F-grade bridge steel has excellent comprehensive performance, high strength, good impact toughness and stable performance.

[0018] Example 2: This example provides a TMCP type F-grade thick bridge steel plate, the chemical composition and mass percentage of which are: C: 0.05%, Si: 0.25%, Mn: 1.25%, P: 0.003%, S: 0.002%, Nb: 0.012%, Al: 0.030%, and the rest are Fe and other unavoidable impurities.

[0019] The production method of the TMCP type F-grade thick bridge steel plate in this embodiment includes steelmaking, continuous casting, and rolling processes. The specific process steps are as follows: (1) Steelmaking process: The molten steel smelted in the primary refining furnace is sent to the LF refining furnace for refining. During the LF refining process, argon blowing is good throughout the whole process. The total refining time is 40 minutes, the white slag holding time is 30 minutes, and the slag basicity is 3.5 after the refining is completed. After the refining is completed, the molten steel is sent to the VD furnace for vacuum degassing treatment. The vacuum degree is 66.7Pa, the vacuum holding time is 18 minutes, and the vacuum is broken and soft blowing is performed for 12 minutes to allow the inclusions to fully float. At the same time, 0.9kg / t of calcium wire is fed into the molten steel for calcium treatment to promote the spheroidization and floating of the inclusions. (2) Continuous casting process: Using a large-section continuous casting machine, the mold liquid level is automatically controlled with a fluctuation range of ±3mm, the tundish superheat is 35°C, and electromagnetic stirring, soft pressure reduction and strong cooling at the end of solidification are used to cast large-section high-quality continuous casting billets; (3) Rolling process: The continuous casting billet is heated in a continuous furnace with a furnace temperature of 600°C and a heating rate of 200°C / h; the maximum heating temperature is 1270°C, the soaking zone temperature is 1240°C, and the total heating coefficient is 10 min / cm; The second-order controlled rolling process is adopted, the first-stage rough rolling temperature is 1090℃, large reduction is adopted, and the air-cooled thickness is 180mm; the second-stage rough rolling temperature is 770℃, the finish rolling temperature is 740℃, and the re-drying temperature is 550℃.

[0020] As shown in Figure 2 the steel plate obtained after cooling has a ferrite and pearlite structure, the yield strength of the steel plate is 410MPa, the tensile strength is 577MPa, the yield strength ratio is 0.71, the V-shaped longitudinal impact energy at 1 / 2 of the plate thickness is 207J at -60℃, the thickness is 110mm, and the F-grade bridge steel produced has excellent comprehensive performance, high strength, good impact toughness, and stable performance.

[0021] In this embodiment, the TMCP type F-grade large-thickness bridge steel plate has a chemical composition and mass percentage of C: 0.07%, Si: 0.38%, Mn: 1.00%, P: 0.003%, S: 0.001%, Nb: 0.020%, Al: 0.040%, and the rest is Fe and other unavoidable impurities.

[0022] The production method of the TMCP type F-grade large-thickness bridge steel plate in this embodiment includes a steelmaking, continuous casting, and rolling process, and the specific process steps are as follows: (1) Steelmaking process: the molten steel smelted by the converter is sent to the LF refining furnace for refining, argon is blown well during the whole LF refining process, the total refining time is 50min, the white slag maintaining time is 35min, and the slag basicity at the end of refining is 4.0; after the refining is completed, the molten steel is sent to the VD furnace for vacuum degassing treatment, the vacuum degree is 50Pa, the vacuum maintaining time is 20min, and after the vacuum is destroyed, soft blowing is performed for 11min to make the inclusions fully float up, and 1.0kg / t of calcium wire is fed for calcium treatment to accelerate the sphericalization and floating of the inclusions; (2) Continuous casting process: a large-section continuous casting machine is used, the liquid level of the crystallizer is automatically controlled, the fluctuation range is ±3mm, the superheating degree of the tundish is 30℃, electromagnetic stirring, light reduction, and solidification end strong cooling technology are adopted, and a large-section high-quality continuous casting billet is cast; (3) Rolling process: the continuous casting billet is heated in the continuous furnace, the furnace temperature is 1200℃, the heating speed is 300℃ / h, the maximum heating temperature is 1270℃, the soaking segment temperature is 1240℃, and the total heating coefficient is 12min / cm; The second-order controlled rolling process is adopted, the first-stage rough rolling temperature is 1090℃, large reduction is adopted, and the air-cooled thickness is 180mm; the second-stage rough rolling temperature is 770℃, the finish rolling temperature is 740℃, and the re-drying temperature is 550℃.

[0023] As shown in Figure 3As shown, the microstructure of the obtained steel plate after cooling is ferrite and pearlite, the yield strength of the steel plate is 400 MPa, the tensile strength is 530 MPa, the yield strength ratio is 0.75, the minimum V-type longitudinal impact energy at the thickness of 1 / 2 is 190 J at-60 DEG C, the thickness is 120 mm, and the produced F-grade bridge steel has excellent comprehensive performance, high strength, good impact toughness and stable performance.

[0024] In addition to the above embodiments, the present application can also have other implementation manners. Any technical solutions formed by equivalent replacement or equivalent transformation fall within the protection scope of the present application.

Claims

1. A TMCP type F-grade thick bridge steel plate, characterized in that: Its chemical composition and mass percentage are as follows: C: 0.03 - 0.08%, Si: 0.10 - 0.40%, Mn: 1.00 - 1.35%, P ≤ 0.006%, S ≤ 0.005%, Nb: 0.010 - 0.020%, Al: 0.020 - 0.040%, and the rest are Fe and other inevitable impurities.

2. The TMCP type F-grade thick bridge steel plate according to claim 1, characterized in that: The microstructure of the steel plate is acicular ferrite and pearlite.

3. The TMCP type F-grade thick bridge steel plate according to claim 1, characterized in that: The yield strength of the steel plate is ≥370 MPa, the tensile strength is 510 - 630 MPa, the V-notch longitudinal -60°C single value impact energy at 1 / 2 of the plate thickness is ≥120 J, and the yield ratio is ≤0.

85.

4. The TMCP type F-grade thick bridge steel plate according to claim 1, characterized in that: The thickness of the steel plate is 100 - 120 mm.

5. The method for producing TMCP type F-grade thick bridge steel plate according to any one of claims 1 to 4, characterized in that: It successively includes steelmaking, continuous casting, and rolling processes. In the steelmaking process, the molten steel smelted in the converter is fed into the LF refining furnace for refining. During the LF refining process, the total refining time is ≥35 min, the white slag holding time is ≥25 min, and the slag basicity at the end of refining is ≥3.

5.

6. The production method according to claim 5, characterized in that In the steelmaking process, after the LF furnace refining is completed, the molten steel is fed into the VD vacuum furnace for vacuum degassing treatment. The vacuum degree is ≤66.7 Pa, the vacuum holding time is ≥18 min, soft blowing is carried out for 10 - 12 min after the vacuum is broken, and at the same time, a calcium wire of 0.8 - 1.0 kg / t of steel is fed for calcium treatment.

7. The production method according to claim 5, characterized in that In the continuous casting process, electromagnetic stirring and soft reduction technologies are adopted during casting, and the liquid level fluctuation range of the mold is ±3 mm, and the superheat is controlled at 15 - 35°C.

8. The production method according to claim 5, characterized in that In the rolling process, the slab is heated in a continuous furnace. When the furnace temperature T ≤ 600°C, the heating rate is ≤200°C / h; when the furnace temperature is 600°C < T ≤ 1200°C, the heating rate is ≤350°C / h; the maximum heating temperature is 1270°C, the soaking section temperature is 1230 - 1250°C, and the total heating coefficient is ≥10 min / cm.

9. The production method according to claim 5, characterized in that The rolling process adopts a two-stage controlled rolling process. The starting rolling temperature in the first stage is 1010 - 1100°C, and a large reduction rolling process is adopted. The air-cooled thickness is h + 70 mm, where h is the thickness of the finished steel plate. The starting rolling temperature in the second stage is 800 - 750°C, the finishing rolling temperature is 770 - 730°C, and the steel plate recrystallization temperature is 540 - 600°C.

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