Phi 40mm HRB600 niobium-vanadium composite steel bar and production method thereof

Abstract

The invention discloses a phi 40mm HRB600 niobium-vanadium composite steel bar and a production method thereof, and belongs to the technical field of steelmaking. The HRB600 niobium-vanadium composite steel bar is prepared from, by weight, 0.26%-0.28% of C, 1.47%-1.53% of Mn, 0.70%-0.80% of Si, 0.160%-0.168% of V, 0.016%-0.021% of Nb, smaller than or equal to 0.030% of S, smaller than or equal to 0.030% of P, 0.0240%-0.0320% of N and the balance Fe and inevitable impurities, the diameter of the steel bar is phi 40 mm, the yield strength is 625-680 MPa, the tensile strength is 800-850 MPa, the maximum total elongation is 9.0%-15.1%, the national standard is met, the surplus amount is high, and the HRB600 niobium-vanadium composite steel bar has very good application prospects.

Description

Technical Field

[0001] The invention belongs to the technical field of steelmaking, and particularly relates to a φ40mm HRB600 niobium-vanadium composite steel bar and a production method thereof. Background Art

[0002] Rebar is a fundamental material in modern construction and is widely used in the construction of projects such as dams, powerhouses, roads, and bridges. Under the same operating conditions, increasing the yield strength of rebar can reduce the diameter of the rebar, saving steel usage and lowering project costs. Currently, my country's infrastructure sector primarily utilizes 400MPa and 500MPa rebar grades. Therefore, promoting the use of 600MPa rebar and promoting its upgrading are of great significance for achieving reduced steel usage, improving project quality, and saving construction costs. Currently, there are many manufacturers capable of mass-producing 600MPa rebar grades below φ32mm, but mass production of grades up to φ40mm remains difficult. Summary of the Invention

[0003] In view of this, the purpose of the present invention is to provide a φ40mm HRB600 niobium-vanadium composite steel bar and a production method. The yield strength of the batch-produced φ40mm HRB600 niobium-vanadium composite steel bar is at least 625MPa, meeting the national standard and having a high performance margin.

[0004] In order to achieve the above object, the present invention provides the following technical solutions:

[0005] In a first aspect, the present invention provides a φ40mm HRB600 niobium-vanadium composite steel bar, whose chemical composition and weight percentage are: C: 0.26-0.28%, Mn: 1.47-1.53%, Si: 0.70-0.80%, V: 0.160-0.168%, Nb: 0.016-0.021%, S≤0.030%, P≤0.030%, N: 0.0240-0.0320%, and the balance is Fe and unavoidable impurities.

[0006] The main functions of the components in the niobium-vanadium composite steel bar of the present invention are as follows:

[0007] C: It is the most economical and effective element to improve strength. Its content should be controlled at 0.26-0.28% while meeting welding and plasticity requirements.

[0008] Mn: Improves the solid solution strengthening effect, refines the steel structure, and improves the strength and toughness; increases the solid solution accumulation of vanadium in austenite, enhancing its precipitation strengthening effect, but increases the carbon equivalent, which is not conducive to welding. Considering all factors, it is controlled at 1.47-1.53%;

[0009] Si: It is almost completely dissolved in ferrite in steel grades, which can significantly increase the yield and tensile strength, reduce the elongation and welding performance, and is controlled at 0.70-0.80% based on comprehensive considerations;

[0010] V, N: By making full use of the cheap nitrogen element, the precipitation effect of vanadium is improved, the fine grain strengthening and precipitation strengthening effects are better exerted, and the strength and toughness combination of steel is improved. The designed vanadium content is 0.160-0.168% and the nitrogen content is 0.0240-0.0320%;

[0011] Nb: Adding an appropriate amount of niobium refines the grains, improving both strength and toughness. However, excessive niobium in solid solution enhances hardenability and easily produces bainite structure, resulting in a less obvious yield platform. Therefore, considering all factors, the content is controlled at 0.016-0.021%.

[0012] S, P: Sulfur seriously affects the strength of steel, and phosphorus is an element that easily segregates and affects welding performance. It is controlled at ≤0.030%.

[0013] Based on the above technical solution, further, the diameter of the HRB600 niobium-vanadium composite steel bar is φ40 mm, the yield strength is 625-680 MPa, the tensile strength is 800-850 MPa, and the maximum total elongation is 9.0-15.1%.

[0014] In a second aspect, the present invention provides a method for producing the above-mentioned φ40mm HRB600 niobium-vanadium composite steel bar, comprising converter smelting, LF refining, continuous casting, heating, and rolling;

[0015] In the converter smelting process, the final carbon content is controlled at 0.08-0.15%, the final phosphorus content is controlled at ≤0.030%, and the tapping temperature is controlled at 1620-1680°C; after the converter tapping is completed, the vanadium content is controlled at 0.150-0.165%, and the niobium content is controlled at 0.013-0.018%;

[0016] LF refining process, during which nitrogen alloy cored wire is fed, the nitrogen content in the molten steel is controlled at 240-320ppm;

[0017] In the continuous casting process, the specifications of the drawn steel billet are 160mm×160mm×11m, the casting speed is controlled at 1.9-2.3m / min, the superheat is controlled at 15-35℃, and nitrogen is blown through the ladle nozzle to protect the casting process.

[0018] Heating process: preheating section temperature control range 950 ~ 1050 ℃, heating section temperature control range 1190 ~ 1240 ℃, soaking section temperature control range 1190 ~ 1230 ℃, total heating time 120 ~ 160 min;

[0019] In the rolling process, the starting rolling temperature is controlled at 1140-1170°C, and the steel is rolled through rough rolling, intermediate rolling and finishing rolling mills, with the final rolling temperature at 1100-1130°C.

[0020] Based on the above technical solution, further, the converter smelting adopts a top and bottom double-blown converter for smelting.

[0021] Based on the above technical solution, further, silicon calcium barium, ferrosilicon, silicon manganese alloy, ferrovanadium nitride and ferroniobium alloy are added for deoxidation alloying after 1 / 4 of the steel is tapped, and the addition is completed when 3 / 4 of the steel is tapped;

[0022] Based on the above technical solution, further, the addition amount of silicon calcium barium is controlled at 0.80-1.20 kg / t, the addition amount of ferrosilicon is controlled at 6.0-7.0 kg / t, the addition amount of silicon manganese alloy is controlled at 22.0-23.0 kg / t, the addition amount of ferrovanadium nitride is controlled at 3.2-3.6 kg / t, and the addition amount of ferroniobium is controlled at 0.27-0.32 kg / t.

[0023] Based on the above technical solution, argon is further passed throughout the entire process from steel tapping to ladle hanging.

[0024] Based on the above technical solution, further, the feeding amount of the complex nitrogen alloy cored wire is 1.70-1.90 kg / t, and the feeding speed is 3-5 m / s.

[0025] Based on the above technical solution, further, heating adopts a 30.0m walking beam regenerative heating furnace.

[0026] Based on the above technical solution, further, a descaling operation is performed before the steel billet is rolled.

[0027] Based on the above technical solution, further, the negative difference of steel bars is controlled to be ≤5kg / t.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] The present invention rationally adjusts the main elements of carbon, silicon and manganese in steel, adopts niobium-vanadium composite microalloying technology and increases a certain nitrogen content in the steel, fully utilizing the precipitation strengthening of vanadium and the fine grain effect of niobium to improve the strength and toughness of the steel bar. Combined with reasonable heating and rolling processes, the negative difference increment is controlled. As a result, during the mass production of φ40mm HRB600 steel, the yield strength is as low as 625MPa, the tensile strength is ≥800MPa, and the maximum total elongation is ≥9.0%, meeting national standards with a high margin, and having very good application prospects. DETAILED DESCRIPTION

[0030] The present invention is described in detail below with reference to the embodiments, but the embodiments of the present invention are not limited thereto. Obviously, the embodiments described below are only some embodiments of the present invention. For those skilled in the art, other similar embodiments obtained without creative work all fall within the scope of protection of the present invention.

[0031] Examples 1-10

[0032] This embodiment provides a method for producing φ40mm HRB600 niobium-vanadium composite steel bars. The chemical composition and mass percentage of the steel bars are shown in Table 1.

[0033] Table 1 Chemical composition and mass percentage (wt, %) of niobium-vanadium composite steel bars of Examples 1-10

[0034] Example C Mn Si V Nb S P N 1 0.27 1.50 0.78 0.163 0.019 0.018 0.023 0.0303 2 0.26 1.52 0.75 0.163 0.017 0.020 0.024 0.0286 3 0.27 1.49 0.75 0.162 0.017 0.029 0.028 0.0260 4 0.28 1.51 0.75 0.163 0.018 0.028 0.018 0.0265 5 0.28 1.49 0.74 0.164 0.018 0.020 0.025 0.0295 6 0.28 1.51 0.76 0.166 0.019 0.016 0.025 0.0297 7 0.27 1.50 0.75 0.166 0.018 0.021 0.022 0.0281 8 0.28 1.51 0.78 0.167 0.018 0.024 0.010 0.0291 9 0.28 1.50 0.74 0.164 0.018 0.027 0.019 0.0287 10 0.28 1.50 0.77 0.164 0.019 0.017 0.027 0.0281

[0035] The steps include:

[0036] (1) Steelmaking adopts 120-ton top-bottom combined-blowing converter, with the final carbon controlled at 0.09-0.012%, the final phosphorus controlled at 0.025-0.030%, and the tapping temperature at 1620-1680°C;

[0037] (2) After 1 / 4 of the steel is tapped, silicon calcium barium (dosage 0.80-1.2 kg / t), ferrosilicon (dosage 6.0-7.0 kg / t), silicon manganese alloy (dosage 22.0-23.0 kg / t), ferrovanadium nitride (dosage 3.2-3.6 kg / t), ferroniobium (dosage 0.27-0.32 kg / t) and other alloys are added in sequence. The addition is completed when 3 / 4 of the steel is tapped. It is not allowed to add alloys and slag to the bottom of the ladle before tapping. The double-permeable bricks of the ladle are in good condition, and argon is passed throughout the process from tapping to hanging the ladle.

[0038] (3) After the converter tapping is completed, the vanadium content is controlled at 0.155-0.165% and the niobium content is controlled at 0.014-0.018%;

[0039] (4) During the LF refining process, the complex nitrogen alloy cored wire is fed at a rate of 1.70-1.90 kg / t and a speed of 4 m / s. The vanadium content out of the station is controlled at 0.162-0.168%, the niobium content at 0.016-0.020%, and the nitrogen content at 240-290 ppm.

[0040] (5) The specifications of the continuous casting billet are 160mm×160mm×11m, the working speed is 1.9~2.3m / min, the superheat is controlled at 15~35℃, and nitrogen is blown through the ladle nozzle to protect the casting process;

[0041] (6) Heating adopts 30.0m walking beam regenerative heating furnace, the temperature control range of preheating section is 950~1050℃, the temperature control range of heating section is 1190~1240℃, the temperature control range of soaking section is 1190~1230℃, and the total heating time is 120~160min;

[0042] (7) After the steel billet is descaled, the starting rolling temperature is 1140-1160°C, and it is rolled through rough rolling, intermediate rolling, and finishing rolling mills, with the final rolling temperature being 1100-1130°C;

[0043] (8) Negative difference control of steel bars: -2.3~4.9Kg / T.

[0044] Table 2 Converter smelting process parameters of Examples 1-10

[0045]

[0046] Table 3 LF refining process parameters of Examples 1-10

[0047]

[0048] Table 4 Continuous casting process parameters of Examples 1-10

[0049]

[0050]

[0051] Table 5 Heating process parameters of the heating furnace of Examples 1-10

[0052]

[0053] Table 6 Rolling process parameters of Examples 1-10

[0054] Example Rolling temperature (℃) Finish rolling temperature (℃) Negative difference control (kg / t) 1 1148 1105 2.402 2 1150 1107 1.850 3 1147 1112 4.813 4 1141 1103 3.833 5 1142 1114 4.542 6 1150 1116 3.466 7 1152 1118 2.791 8 1159 1126 2.814 9 1160 1128 -1.537 10 1153 1126 3.179

[0055] Table 7 Mechanical properties of niobium-vanadium composite steel bars of Examples 1-10

[0056]

[0057]

[0058] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A φ40mm HRB600 niobium-vanadium composite steel bar, characterized in that: Its chemical composition and weight percentage are: C: 0.26-0.28%, Mn: 1.47-1.53%, Si: 0.70-0.80%, V: 0.160-0.168%, Nb: 0.016-0.021%, S≤0.030%, P≤0.030%, N: 0.0240-0.0320%, and the balance is Fe and unavoidable impurities.

2. The φ40mm HRB600 niobium-vanadium composite steel bar according to claim 1, characterized in that: The HRB600 niobium-vanadium composite steel bar has a diameter of φ40 mm, a yield strength of 625-680 MPa, a tensile strength of 800-850 MPa, and a maximum total elongation of 9.0-15.1%.

3. The production method of φ40mm HRB600 niobium-vanadium composite steel bar according to claim 1 or 2, characterized in that: Including converter smelting, LF refining, continuous casting, heating and rolling; In the converter smelting process, the final carbon content is controlled at 0.08-0.15%, the final phosphorus content is controlled at ≤0.030%, and the tapping temperature is controlled at 1620-1680°C; after the converter tapping is completed, the vanadium content is controlled at 0.150-0.165%, and the niobium content is controlled at 0.013-0.018%; LF refining process, during which nitrogen alloy cored wire is fed, the nitrogen content in the molten steel is controlled at 240-320ppm; In the continuous casting process, the specifications of the drawn steel billet are 160mm×160mm×11m, the casting speed is controlled at 1.9-2.3m / min, the superheat is controlled at 15-35℃, and nitrogen is blown through the ladle nozzle to protect the casting process. Heating process: preheating section temperature control range 950 ~ 1050 ℃, heating section temperature control range 1190 ~ 1240 ℃, soaking section temperature control range 1190 ~ 1230 ℃, total heating time 120 ~ 160 min; In the rolling process, the starting rolling temperature is controlled at 1140-1170°C, and the steel is rolled through rough rolling, intermediate rolling and finishing rolling mills, with the final rolling temperature at 1100-1130°C.

4. The production method according to claim 3, characterized in that After 1 / 4 of the steel is tapped, silicon calcium barium, ferrosilicon, silicon manganese alloy, vanadium nitride iron and niobium iron alloy are added for deoxidation and alloying, and the addition is completed when 3 / 4 of the steel is tapped.

5. The production method according to claim 4, characterized in that The addition amount of silicon calcium barium is controlled at 0.80-1.20 kg / t, the addition amount of ferrosilicon is controlled at 6.0-7.0 kg / t, the addition amount of silicon manganese alloy is controlled at 22.0-23.0 kg / t, the addition amount of ferrovanadium nitride is controlled at 3.2-3.6 kg / t, and the addition amount of ferroniobium is controlled at 0.27-0.32 kg / t.

6. The production method according to claim 3, characterized in that Argon is used throughout the entire process from steel tapping to ladle hanging.

7. The production method according to claim 3, characterized in that The feeding amount of complex nitrogen alloy cored wire is 1.70~1.90kg / t, and the feeding speed is 3~5m / s.

8. The production method according to claim 3, characterized in that The steel billet is descaled before rolling.

9. The production method according to claim 3, characterized in that The negative difference of steel bars is controlled at ≤5kg / t.

Images