Production method of high-forming low-carbon low-silicon hot-rolled wire rod

Abstract

The invention relates to a production method of a high-forming low-carbon low-silicon hot-rolled wire rod. The wire rod comprises the following chemical components: less than or equal to 0.07% of C, less than or equal to 0.07% of Si, 0.15-0.30% of Mn, less than or equal to 0.025% of P, less than or equal to 0.025% of S, less than or equal to 0.20% of Cr, less than or equal to 0.20% of Ni, less than or equal to 0.20% of Cu and the balance of Fe and impurities. The production technology of converter smelting, argon blowing, square billet continuous casting, steel billet heating and controlled rolling and controlled cooling is adopted, a conventional LF furnace refining production mode is not adopted, the produced wire rod can meet the requirements of high forming and easy drawing, and compared with other similar products, the production and manufacturing cost is low.

Description

Technical Field

[0001] The invention relates to the technical field of wire rod production, and in particular to a production method of a high-forming low-carbon and low-silicon hot-rolled wire rod. Background Art

[0002] With the rapid development of industrial production, low-carbon and low-silicon wire rods have become the main raw materials for metal products. After further processing, they are made into a large number of galvanized steel wires, mesh wires, grids, nails, etc., and the market demand is relatively large. HFD380, developed by Bengang according to user needs, is a special high-forming wire rod steel with "low carbon and low silicon" composition characteristics. This steel is used for general cold heading purposes. At the same time, downstream users require "high forming and easy drawing" processing performance compared to ordinary Q235, Q195 and other steel grades, which puts higher requirements on chemical composition, organizational uniformity, and performance control.

[0003] The Chinese patent application with application publication number CN 114250419 A discloses "a 400MPa grade low carbon bead wire drawing steel BT400BK and its preparation method", wherein the chemical components and mass percentage contents of the low carbon bead wire drawing steel BT400BK are as follows: C: 0.09% to 0.12%, Si: 0.12% to 0.20%, Mn: 0.45% to 0.55%, P≤0.015%, S≤0.012%, Cr≤0.08%, Ni≤0.10%, Cu≤0.08%, Alt≤0.010%, As≤0.030%, Sn≤0.010%, Cu+Cr+Ni≤0.15%, N≤0.0070%, and the balance is Fe. The preparation method includes the steps of converter smelting, ladle alloying, static argon blowing, LF furnace refining, continuous casting, heating process and rolling process. The prepared finished steel has good tensile strength and good wire-pass property, excellent surface quality of the wire rod, and excellent plasticity and ductility. Compared with the wire rod, the wire rod of the present invention has different control ranges of C content, Si content, and Mn content, and a different production process. The molten steel in the present invention does not need to be refined in an LF furnace, so the outstanding advantage is low production cost; in addition, the 400MPa-grade low-carbon tire bead wire drawing steel BT400BK can only meet the drawing process requirements, while the wire rod produced by the present invention can not only meet the drawing performance, but also meet the requirements of cold forging test qualification, that is, it simultaneously meets the requirements of high forming and easy drawing.

[0004] A Chinese patent application with application publication number CN 110079736 A discloses a "low-carbon, low-silicon welding steel with uniform organizational properties and a preparation method thereof", which is prepared by sequentially casting, billet heating, rolling and Stelmor air cooling of molten steel, wherein: the chemical composition of the molten steel is calculated by weight percentage as follows: C≤0.06%, Si≤0.03%, Mn: 0.40-0.70%, P≤0.020%, S≤0.020%, Cr≤0.20%, Ni≤0.30%, Cu≤0.20%, As≤0.020%, and the remainder is Fe and unavoidable impurities; it can be seen from its embodiments that after argon blowing and refining, the molten steel is sent to the LF furnace for ladle refining. The tensile strength of the welding steel is 320-350MPa, the elongation A can reach 45.0-52.0%, and the cross-sectional shrinkage can reach 80.0-85.0%, meeting the use requirements of directly drawing a welding core wire with a diameter of 2.0-5.0mm. Compared with the present invention, the Mn content control range and the production process are different; the steel of the present invention does not need to be refined by LF furnace, has the advantage of low production cost, and also meets the requirements of high forming and easy drawing. Summary of the invention

[0005] The present invention provides a method for producing high-formability low-carbon and low-silicon hot-rolled wire rod, which adopts the production process of "converter smelting + argon blowing + square billet continuous casting + billet heating + controlled rolling and controlled cooling", and does not follow the conventional "LF furnace refining" production mode. The produced wire rod can meet the requirements of high formability and easy drawing, and has the advantage of low production cost compared with other similar products.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A high-formability low-carbon and low-silicon hot-rolled wire rod, the chemical composition of which is C≤0.07%, Si≤0.07%, Mn: 0.15%-0.30%, P≤0.025%, S≤0.025%, Cr≤0.20%, Ni≤0.20%, Cu≤0.20%, and the rest is Fe and unavoidable impurities.

[0008] The tensile strength of the finished wire rod is 324-376MPa, the elongation after fracture is 40%-47%, the cold bending test is qualified, and the 1 / 2 cold forging test is qualified.

[0009] A method for producing a high-forming low-carbon and low-silicon hot-rolled wire rod comprises the following steps:

[0010] 1) Converter smelting: During smelting, scrap steel accounts for 10% to 12% by weight, and molten iron accounts for 88% to 90% by weight. Top and bottom combined blowing converter is used for smelting, the tapping temperature is 1640 to 1705°C, the tapping end point [C] ≤ 0.05%, P ≤ 0.012%, slag is strictly prohibited: avoid spot blowing; the one-time pouring hit rate of the blowing process is controlled to be ≥ 95%;

[0011] 2) Ladle alloying: argon blowing time ≥ 5min; target amount of alloy added per ton of steel: silicon manganese 1.8-2.0kg / t steel, ferrosilicon 0.40-0.42kg / t steel; deoxidizer is aluminum iron, the addition amount is 1.5-1.6kg / t steel;

[0012] 3) Static argon blowing: argon blowing time ≥ 10min; first feed 25-35m of aluminum wire to precipitate and deoxidize the molten steel, then add aluminum particles to deoxidize the slag surface; during the process of adding aluminum particles, the argon blowing is soft blowing, and after adding aluminum particles, the oxygen blowing is adjusted to medium blowing; after static argon blowing treatment, the molten steel temperature is 1550℃~1605℃; when leaving the argon station, the oxygen content in the molten steel is controlled to be 30-50ppm;

[0013] 4) Continuous casting: adopt the whole process protection casting process, and use low-carbon protection slag for the crystallizer protection slag; the platform ladle temperature is 1635-1645℃, the middle ladle temperature is 1590℃-1612℃, the superheat is maintained at 20℃-30℃, the pulling speed is 2.4-2.6m / min, and the pulling speed is constant;

[0014] 5) Heating: adopt regenerative heating furnace for heating, the preheating section temperature is 930~970℃, the heating section temperature is 1080~1120℃, the soaking section temperature is 1130~1170℃, and the total heating time is 1.5~2.5h;

[0015] 6) Controlled rolling: Rough rolling temperature is 1000-1040°C, finishing rolling inlet temperature is 900-940°C, and wire laying temperature is 900-940°C;

[0016] 7) Control cooling: The air-cooled roller speed control includes setting the head roller speed to 0.18-0.22 m / s and the roller speed increase to 2%-5%; opening the first two and last two insulation covers; opening the 1# fan to 100% and other fans to all be closed.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] The production process of "converter smelting + argon blowing + billet continuous casting + billet heating + controlled rolling and controlled cooling" is adopted instead of the conventional "LF furnace refining" production mode. The wire rod produced can meet the requirements of high forming and easy drawing, and has the advantage of low production cost compared with other similar products. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a metallographic structure photograph of the high-formability low-carbon low-silicon hot-rolled wire rod described in the present invention (the metallographic structure is F+P). DETAILED DESCRIPTION

[0020] The invention discloses a high-formability low-carbon low-silicon hot-rolled wire rod, wherein the chemical composition of the wire rod is C≤0.07%, Si≤0.07%, Mn: 0.15%-0.30%, P≤0.025%, S≤0.025%, Cr≤0.20%, Ni≤0.20%, Cu≤0.20%, and the rest is Fe and unavoidable impurities.

[0021] The tensile strength of the finished wire rod is 324-376MPa, the elongation after fracture is 40%-47%, the cold bending test is qualified, and the 1 / 2 cold forging test is qualified.

[0022] The method for producing a high-forming low-carbon and low-silicon hot-rolled wire rod according to the present invention comprises the following steps:

[0023] 1) Converter smelting: During smelting, scrap steel accounts for 10% to 12% by weight, and molten iron accounts for 88% to 90% by weight. Top and bottom double-blown converters are used for smelting, the tapping temperature is 1640 to 1705°C, the tapping end point [C] ≤ 0.05%, P ≤ 0.012%, and slag is strictly prohibited: avoid spot blowing; the one-time pouring hit rate of the blowing process is controlled to be ≥ 99%;

[0024] 2) Ladle alloying: argon blowing time ≥ 5min; target amount of alloy added per ton of steel: silicon manganese 1.8-2.0kg / t steel, ferrosilicon 0.40-0.42kg / t steel; deoxidizer is aluminum iron, the addition amount is 1.5-1.6kg / t steel;

[0025] 3) Static argon blowing: argon blowing time ≥ 10min; first feed 25-35m of aluminum wire to precipitate and deoxidize the molten steel, then add aluminum particles to deoxidize the slag surface; during the process of adding aluminum particles, argon blowing is soft blowing, the purpose is to prevent the slag surface from being deoxidized due to excessive burning. After adding aluminum particles, the oxygen blowing is adjusted to medium blowing to avoid poor castability of the molten steel; the temperature of the molten steel after static argon blowing treatment is 1550℃~1605℃; the oxygen content in the molten steel is controlled to be 30~50ppm when leaving the argon station;

[0026] 4) Continuous casting: adopt the whole process protection casting process, and use low-carbon protection slag for the crystallizer protection slag; the platform ladle temperature is 1635-1645℃, the middle ladle temperature is 1590℃-1612℃, the superheat is maintained at 20℃-30℃, the pulling speed is 2.4-2.6m / min, and the pulling speed is constant to reduce liquid level fluctuations.

[0027] 5) Heating: adopt regenerative heating furnace for heating, the preheating section temperature is 930~970℃, the heating section temperature is 1080~1120℃, the soaking section temperature is 1130~1170℃, and the total heating time is 1.5~2.5h;

[0028] 6) Controlled rolling: Rough rolling temperature is 1000-1040°C, finishing rolling inlet temperature is 900-940°C, and wire laying temperature is 900-940°C;

[0029] 7) Control cooling: The air-cooled roller speed control includes setting the head roller speed to 0.18-0.22 m / s and the roller speed increase to 2%-5%; opening the first two and last two insulation covers; opening the 1# fan to 100% and other fans to all be closed.

[0030] The metallographic structure photo of the high-forming low-carbon low-silicon hot-rolled wire rod of the present invention is as follows: Figure 1 As shown, the metallographic structure is F (ferrite) + P (pearlite).

[0031] The following embodiments are implemented on the premise of the technical solution of the present invention, and provide detailed implementation methods and specific operation processes, but the protection scope of the present invention is not limited to the following embodiments.

[0032] [Example]

[0033] In this embodiment, the chemical composition of the high-forming low-carbon and low-silicon hot-rolled wire rod is shown in Table 1, the converter smelting process parameters are shown in Table 2, the ladle alloying process parameters are shown in Table 3, the static argon blowing process parameters are shown in Table 4, the continuous casting process parameters are shown in Table 5, the heating process parameters are shown in Table 6, the rolling process parameters are shown in Table 7, the cooling process parameters are shown in Table 8, the ingot low-magnification structure defect inspection results are shown in Table 9, the finished product mechanical properties are shown in Table 10, and the finished product microstructure and non-metallic inclusion inspection results are shown in Table 11.

[0034] Table 1 Chemical composition of wire rod (mass percentage, %)

[0035] Example C Si Mn P S Cr Ni Cu 1 0.055 0.052 0.17 0.016 0.019 0.18 0.08 0.20 2 0.059 0.059 0.22 0.022 0.019 0.09 0.10 0.14 3 0.036 0.051 0.20 0.020 0.020 0.11 0.16 0.15 4 0.061 0.031 0.39 0.021 0.024 0.16 0.12 0.06 5 0.068 0.046 0.32 0.009 0.025 0.13 0.17 0.14 6 0.065 0.035 0.28 0.024 0.022 0.14 0.07 0.10

[0036] Table 2 Converter smelting process parameters

[0037]

[0038] Table 3 Ladle alloying process parameters

[0039] Example Argon blowing time, min Silicon manganese addition amount, kg / t steel Ferrosilicon addition amount, kg / t steel Aluminum and iron addition amount, kg / t steel 1 5.1 1.85 0.40 1.51 2 5.5 1.81 0.41 1.58 3 5.3 1.99 0.41 1.60 4 5.8 1.93 0.40 1.55 5 5.4 1.90 0.42 1.56 6 6.0 1.88 0.40 1.53

[0040] Table 4 Static argon blowing process parameters

[0041] Example Argon blowing time, min Feeding aluminum wire length, m Molten steel temperature after treatment, ℃ Oxygen content of molten steel outgoing, ppm 1 11.5 32 1552 32 2 12 30 1584 41 3 10.2 31 1573 42 4 10.5 30 1603 38 5 11 35 1591 47 6 10.6 28 1568 45

[0042] Table 5 Continuous casting process parameters

[0043] Example Platform ladle temperature, ℃ Middle package temperature, ℃ Superheat, ℃ Pulling speed, m / min 1 1642 1605 26 2.41 2 1644 1593 30 2.52 3 1637 1598 24 2.56 4 1640 1610 28 2.44 5 1641 1607 25 2.48 6 1638 1590 22 2.50

[0044] Table 6 Heating process parameters

[0045] Example Preheating temperature, °C Heating section temperature, °C Soaking section temperature, ℃ Total heating time, h 1 968 1081 1136 1.5 2 955 1103 1152 2.0 3 934 1114 1168 2.2 4 960 1095 1159 1.7 5 961 1100 1144 2.3 6 946 1117 1161 2.4

[0046] Table 7 Rolling process parameters

[0047] Example Rough rolling temperature, ℃ Finishing rolling inlet temperature, ℃ Spinning temperature, ℃ 1 1028 935 930 2 1033 932 926 3 1005 908 905 4 1022 911 908 5 1016 922 920 6 1037 915 910

[0048] Table 8 Cooling process parameters

[0049] Example Head roller speed, m / s Roller speed, % Number of insulation covers opened, pcs Number of fans turned on, 1 0.19 4.2％ Front 2 + rear 2 1# fan, 100% opening 2 0.20 3.8％ Front 2 + rear 2 1# fan, 100% opening 3 0.21 4.5％ Front 2 + rear 2 1# fan, 100% opening 4 0.22 3.4％ Front 2 + rear 2 1# fan, 100% opening 5 0.18 2.1％ Front 2 + rear 2 1# fan, 100% opening 6 0.20 2.3％ Front 2 + rear 2 1# fan, 100% opening

[0050] Table 9 Results of macroscopic defects inspection of ingot

[0051] Example Loose center Center Segregation Shrinkage Corner cracks Edge cracks Middle crack Center Crack Subcutaneous bubbles 1 1.0 0.5 1.0 0.5 1.0 0.5 0.5 0.5 2 0.5 0.5 0.5 1.0 0.5 0.5 0.5 0.5 3 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 4 0.5 0.5 1.0 0.5 0.5 0.5 0.5 0.5 5 1.0 0.5 1.0 0.5 0.5 0.5 0.5 0.5 6 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5

[0052] Table 10 Mechanical properties of finished products

[0053] Example tensile strength Elongation after fracture Cold bending test 180°; d = 0 1 / 2 Cold Heading 1 346 41.5 qualified qualified 2 350 42 qualified qualified 3 344 41.5 qualified qualified 4 349 41.5 qualified qualified 5 337 42.5 qualified qualified 6 340 43 qualified qualified

[0054] Table 11 Finished product microstructure and non-metallic inclusion inspection results

[0055]

[0056] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A high-forming low-carbon low-silicon hot-rolled wire rod, characterized in that: The chemical composition of the wire rod is C≤0.07%, Si≤0.07%, Mn: 0.15%~0.30%, P≤0.025%, S≤0.025%, Cr≤0.20%, Ni≤0.20%, Cu≤0.20%, and the rest is Fe and unavoidable impurities.

2. The high-formability low-carbon low-silicon hot-rolled wire rod according to claim 1, characterized in that: The tensile strength of the finished wire rod is 324-376MPa, the elongation after fracture is 40%-47%, the cold bending test is qualified, and the 1 / 2 cold forging test is qualified.

3. A method for producing a high-forming low-carbon low-silicon hot-rolled wire rod as claimed in claim 1 or 2, characterized in that: The steps include: 1) Converter smelting: During smelting, scrap steel accounts for 10% to 12% by weight, and molten iron accounts for 88% to 90% by weight. Top and bottom combined blowing converter is used for smelting, the tapping temperature is 1640 to 1705°C, the tapping end point [C] ≤ 0.05%, P ≤ 0.012%, slag is strictly prohibited: avoid spot blowing; the one-time pouring hit rate of the blowing process is controlled to be ≥ 95%; 2) Ladle alloying: argon blowing time ≥ 5min; target amount of alloy added per ton of steel: silicon manganese 1.8-2.0kg / t steel, ferrosilicon 0.40-0.42kg / t steel; deoxidizer is aluminum iron, the addition amount is 1.5-1.6kg / t steel; 3) Static argon blowing: argon blowing time ≥ 10min; first feed 25-35m of aluminum wire to precipitate and deoxidize the molten steel, then add aluminum particles to deoxidize the slag surface; during the process of adding aluminum particles, the argon blowing is soft blowing, and after adding aluminum particles, the oxygen blowing is adjusted to medium blowing; after static argon blowing treatment, the molten steel temperature is 1550℃~1605℃; when leaving the argon station, the oxygen content in the molten steel is controlled to be 30-50ppm; 4) Continuous casting: adopt the whole process protection casting process, and use low-carbon protection slag for the crystallizer protection slag; the platform ladle temperature is 1635-1645℃, the middle ladle temperature is 1590℃-1612℃, the superheat is maintained at 20℃-30℃, the pulling speed is 2.4-2.6m / min, and the pulling speed is constant; 5) Heating: adopt regenerative heating furnace for heating, preheating section temperature is 930~970℃, heating section temperature is 1080~1120℃, soaking section temperature is 1130~1170℃, total heating time is 1.5~2.5h; 6) Controlled rolling: Rough rolling temperature is 1000-1040°C, finishing rolling inlet temperature is 900-940°C, and wire laying temperature is 900-940°C; 7) Control cooling: The air-cooled roller speed control includes setting the head roller speed to 0.18-0.22 m / s and the roller speed increase to 2%-5%; opening the first two and last two insulation covers; opening the 1# fan to 100% and other fans to all be closed.

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