A production method of HRB400E straight-thread ribbed steel bars

Abstract

The present invention provides a production method for HRB400E straight ribbed steel bars, with C: 0.20 - 0.25% Wt, Si: 0.50 - 0.70 Wt, Mn: 1.15 - 1.40% Wt, and the Nb content being 0.020 - 0.035% Wt; no controlled cooling equipment is installed or used before the steel bars are fed onto the cooling bed after finish rolling, so that the steel bars are in a natural cooling state. The present invention can increase the thickness of the scale on the surface of the steel bars (radial thickness) to 13 μm or more.

Description

[0001] This application is a divisional application. The parent application number is 2021102081588, the application date is February 24, 2021, and the invention title is: Method for increasing the thickness of scale on the surface of high-speed bar and production method of HRB400E straight ribbed steel bar. Technical Field

[0002] The present invention relates to the metallurgical field, specifically to the rolling of high-speed bars, and particularly to a production method of HRB400E straight ribbed steel bars. Background Art

[0003] Currently, the scale on the surface of steel bars produced by high-speed bar production lines is relatively thin (usually the radial thickness is less than 8 μm). When the scale thickness is relatively thin, the rust prevention ability of the steel bars is weakened, affecting the product appearance and sales.

[0004] In summary, the following problems exist in the prior art: The scale on the surface of high-speed bars is relatively thin, affecting the product appearance and sales. Summary of the Invention

[0005] The present invention provides a method for increasing the thickness of scale on the surface of high-speed bars and a production method of HRB400E straight ribbed steel bars to solve the problem of relatively thin scale on the surface of high-speed bars.

[0006] To this end, the present invention proposes a method for increasing the thickness of scale on the surface of high-speed bars. The method for increasing the thickness of scale on the surface (circumferential surface) of high-speed bars includes: setting the finishing rolling speed of the high-speed bar production line at 30 - 45 m / s, and adopting the following steps:

[0007] Step A: Adopting Nb microalloying to increase the high-temperature strength and improve the mechanical properties of the steel bars at normal temperature;

[0008] Step B: Increasing the number of braking rollers to increase the contact area between the braking rollers and the bars, and improving the braking friction to increase the temperature of the steel bars when entering the cooling bed.

[0009] Further, the method for increasing the thickness of scale on the surface of high-speed bars further includes: Step C: Installing a heat preservation cover on the cooling bed to slow down heat dissipation and increase the residence time of the bars on the cooling bed in the high-temperature area.

[0010] Further, the method for increasing the thickness of scale on the surface of high-speed bars further includes: Step D: Changing the storage method of the bars on the cooling bed from storing one bar per tooth of the cooling bed rack to storing multiple bars per tooth.

[0011] Further, Step B specifically is: Increasing the number of braking rollers of each line of the high-speed bar production line to 2 groups or more.

[0012] Furthermore, the method for increasing the thickness of the scale on the surface of high-speed bar also includes: Step E: Improving the surface temperature by electromagnetic induction heating: Electromagnetic induction heating devices are respectively added before rough rolling, medium rolling, pre-finishing rolling, finishing rolling, and after finishing rolling, and the skin effect of electromagnetic induction heating is used to increase the surface temperature of the billet.

[0013] Furthermore, the method for increasing the thickness of the scale on the surface of high-speed bar also includes: Step F: Optimizing the roll cooling method and avoiding surface cooling: During the whole rolling process, controlled cooling equipment shall not be used between rolling mills to reduce the surface temperature of the rolled piece, and the surface cooling method of the roll of the rolling mill is also changed from full water cooling to air mist cooling.

[0014] Furthermore, Step F is specifically: The surface temperature of the rolled piece is maintained at 980 - 1040 °C by the electromagnetic induction heating device, while the internal temperature of the rolled piece is maintained at 920 - 970 °C.

[0015] Furthermore, in Step C: The top view projection of the heat preservation cover is rectangular, and the heat preservation cover is suspended above the cooling bed. The rectangle includes the long side and the short side of the heat preservation cover. A steel wire rope is connected to each short side of each heat preservation cover, and each steel wire rope is connected to a motor. And the steel wire rope is connected to the motor through a fixed pulley.

[0016] Furthermore, in Step C: Upper limit and lower limit are set for the heat preservation cover to prevent equipment damage in case of control failure; The lowest lower limit of the heat preservation cover is 10 cm away from the cooling bed plane.

[0017] Furthermore, the bar is a plain bar or a deformed steel bar, and the Nb content is 0.020 - 0.035% Wt.

[0018] The present invention also provides a production method of HRB400E straight deformed steel bar, adopting the method for increasing the thickness of the scale on the surface of high-speed bar described above. The bar is HRB400E straight deformed steel bar, C: 0.20 - 0.25% Wt, Si: 0.50 - 0.70 Wt, Mn: 1.15 - 1.40% Wt, and the Nb content is 0.020 - 0.035% Wt.

[0019] The applicant found in the research that: the finishing rolling speed of ordinary bars is within 18 m / s, and conventional production usually controls it within 16 m / s. When producing small and medium-sized products (straight bars with a diameter of 10 - 20 mm), the method to improve production efficiency is to use the split rolling process. For single-line and two-line high-speed bars, braking rollers must be used to brake before they enter the cooling bed after finishing rolling. When the temperature of the bars entering the cooling bed is too high, if the clamping force of the braking rollers is too large, the bars are likely to be deformed by pressing and their external dimensions exceed the national standard; if the clamping force is too small, the braking effect is insufficient. Therefore, domestic high-speed bar production lines often use the controlled rolling and controlled cooling process, and the bars enter the cooling bed at a lower temperature (780 - 840 °C) to increase the strength of the bars to resist the braking pressure and achieve the braking effect, while reducing the alloy consumption and production cost. However, the lower temperature at which the bars enter the cooling bed makes the scale on the surface of the high-speed bars produced by the production line relatively thin (usually less than 8 μm).

[0020] Based on the above analysis, the applicant sets the finishing rolling speed of the high-speed bar production line at 30 - 45 m / s, which can reduce heat dissipation. The applicant designs the Nb microalloying composition to increase the high-temperature strength. Multiple groups of braking rollers are used to increase the friction of the braking device. Through the above measures, the thickness of the scale on the surface of the bars (radial thickness) can be increased to 13 μm or more. Description of the Drawings

[0021] Figure 1 It is a schematic structural diagram of a heat preservation cover adopted by the present invention;

[0022] Figure 2 It is a schematic structural diagram of another heat preservation cover adopted by the present invention.

[0023] Explanation of the reference numerals in the drawings: 1. Heat preservation cover; 2. Steel wire rope; 3. Fixed pulley; 4. Motor. Detailed Embodiments

[0024] In order to have a clearer understanding of the technical features, objectives, and effects of the present invention, the present invention will now be described.

[0025] 1. Let the high-speed bars enter the cooling bed at a high temperature:

[0026] Nb microalloying is used to increase the high-temperature strength of the bars and improve their mechanical properties at normal temperature; the number of braking rollers is increased to increase the contact area with the bars, and the braking friction is increased to raise the temperature at which the bars enter the cooling bed; a heat preservation cover is installed on the cooling bed, and the storage method of the bars on the cooling bed is changed from one bar per tooth to multiple bars per tooth, slowing down heat dissipation and increasing the residence time of the bars in the high-temperature zone on the cooling bed. The specific technical measures include:

[0027] The production process of single-line high-speed bar steel is as follows: blast furnace hot metal smelting → hot metal desulfurization pretreatment → converter steelmaking → bloom continuous casting → reheating furnace heating → rough rolling (6 stands) → intermediate rolling (6 stands) → pre-finishing rolling (6 stands) → single line → controlled cooling and recovery section → finishing rolling (6 stands) → post-rolling controlled cooling and recovery section → pinch roll → flying shear → braking device → rotary device → cooling bed cooling → sizing shearing, inspection, packaging and warehousing

[0028] The production process of double-line high-speed bar steel is as follows: blast furnace hot metal smelting → hot metal desulfurization pretreatment → converter steelmaking → bloom continuous casting → reheating furnace heating → rough rolling (6 stands) → intermediate rolling (6 stands) → pre-finishing rolling (6 stands) and splitting into double lines → controlled cooling and recovery section × 2 → finishing rolling (6 stands) × 2 → post-rolling controlled cooling and recovery section × 2 → pinch roll × 2 → flying shear × 2 → braking device × 2 → rotary device × 2 → cooling bed cooling → sizing shearing, inspection, packaging and warehousing

[0029] Among them, the technological characteristics of each stage are as follows:

[0030] Converter steelmaking: The hot metal charged into the furnace is required to have S ≤ 0.040Wt%; the whole process uses bottom blowing argon gas, and the gas flow rate is increased in the later stage of blowing to strengthen the molten pool stirring; the converter end-point control is C ≤ 0.15Wt%, P ≤ 0.037Wt%;

[0031] Bloom continuous casting: Ladle slag detection control is adopted, the tundish pouring temperature is 1520 - 1540°C, ordinary covering agent is used in the tundish, ordinary bloom protective slag is used, and the single-strand casting speed of the billet is 3.0 - 4.0m / min.

[0032] High-speed bar rolling: The heating temperature of the billet is controlled at 1050 - 1170°C, the heating time of the steel billet is 80 - 120 minutes, the starting rolling temperature is 1000 - 1040°C, 24 stands of high-speed non-twist rolling are adopted (6 stands for rough rolling, intermediate rolling, pre-finishing rolling, and finishing rolling respectively), the finishing rolling is double-line and controlled cooling equipment is used in the pre-finishing rolling, and the temperature entering the finishing rolling is controlled at 900 ± 20°C. No controlled cooling equipment is installed or used before the steel bar reaches the cooling bed after finishing rolling, so that the steel bar is in a natural cooling state, and the steel bar surface obtains a relatively high temperature when entering the cooling bed.

[0033] (1) Nb microalloying improves the temperature strength: At the same temperature during rolling, the high-temperature strength of the Nb microalloyed steel billet is slightly higher. Applying Nb microalloying can improve the ability of the steel bar to resist pressure deformation during braking, increase the temperature of the steel bar when entering the cooling bed, and increase the thickness of the scale. At the same time, the addition of microalloying elements can improve the mechanical properties of the steel bar and make up for the loss of mechanical properties caused by rolling at a relatively high temperature. The composition design is as shown in the following table (Table 5).

[0034] Table 5: Composition table of HRB400E

[0035] C Si Mn P S Nb HRB400E 0.20～0.25 0.50～0.70 1.15～1.40 ≤0.040 ≤0.035 0.020～0.035

[0036] (2) Increase the friction of the braking device: According to the requirements of the temperature on the cooling bed, the number of braking rollers on each line of the high-speed bar production line can be increased to 2 groups or more. Increasing the number of braking rollers can increase the contact area with the steel bars, and increasing the braking friction can effectively increase the temperature of the steel bars on the cooling bed and increase the thickness of the scale.

[0037] (3) Slow down the heat dissipation of the cooling bed: Use a heat preservation device on the cooling bed, and change the storage method of the steel bars on the cooling bed from one tooth per bar to multiple bars per tooth, which can slow down the heat dissipation and increase the residence time of the steel bars in the high-temperature area on the cooling bed.

[0038] 2. Liftable Cooling Bed Heat Preservation Cover

[0039] At present, during the production of straight-thread steel bars, there is no heat preservation device on the cooling bed and it is in a natural cooling state. Especially in the high-speed bar production line, the storage method of the steel bars on the cooling bed is one tooth per bar, and the steel bars dissipate heat quickly on the cooling bed and the high-temperature area time is short.

[0040] The cooling bed is rectangular as a whole, as Figure 1 and Figure 2 shown. A plurality of horizontally arranged rectangular heat preservation covers 1 are arranged in the length direction of the cooling bed. The specific technical measures include:

[0041] (1) The heat preservation cover 1 is rectangular and horizontally arranged in the length direction of the cooling bed. The heat preservation cover is a rectangular flat plate.

[0042] (2) The heat preservation cover is suspended above the cooling bed. As Figure 2 shown, the 4 corners of the top surface (upper surface) facing away from the cooling bed are connected by steel wires 2. The two short sides of the rectangular heat preservation cover are respectively driven by pulleys and 1 motor 4, and the direction is adjusted through fixed pulleys 3. The entire heat preservation cover is driven by two motors to move, realizing the coverage of different heights in the full range of the cooling bed to adjust the temperature drop of the cooling bed. When the cooling bed is under maintenance, the heat preservation cover can be in a high position, which is convenient for maintenance. When this structure is hoisted, all four corners are stressed and the stress is relatively balanced. Another structure of the heat preservation cover 1 is to directly connect the steel wires 2 to the midpoints of the short sides of the heat preservation cover. In this way, the balance of gravity can also be achieved.

[0043] (3) The heat preservation cover is composed of two parts. The surface facing the cooling bed is the lower surface, and the surface facing away from the cooling bed is the upper surface. The upper surface is a structural layer composed of a side frame, a middle X-shaped reinforcing rib, and a flat plate, and the material is aluminum alloy; the lower surface is a refractory fiber cotton heat preservation layer with a thickness of 10 cm, which is fixed on the upper surface by steel strips. The lower surface can not only play a heat preservation role but also avoid the deformation of the outer layer caused by high-temperature baking, and at the same time, it also reduces the weight of the heat preservation cover.

[0044] (4) When the heat preservation cover moves, the upper limit and the lower limit are set by setting the length of the steel wire rope to prevent equipment damage in case of control failure; the lower limit is at least 10 cm away from the cooling bed plane, which can achieve the heat preservation effect and avoid the steel bars on the cooling bed touching the heat preservation cover during movement.

[0045] The above measures can effectively control the temperature drop of the steel bars on the cooling bed.

[0046] 3. Method for increasing the temperature of high-speed bar steel on the cooling bed by electromagnetic induction heating:

[0047] Specific technical measures include:

[0048] The production process of single-line high-speed bar steel is: blast furnace hot metal smelting → hot metal desulfurization pretreatment → converter steelmaking → billet continuous casting → reheating furnace heating → rough rolling (6 stands) → medium rolling (6 stands) → pre-finishing rolling (6 stands) → single line → controlled cooling and recovery section → finishing rolling (6 stands) → post-rolling controlled cooling and recovery section → pinch roll → flying shear → braking device → rotary table device → cooling bed cooling → sizing shearing and inspection packaging and warehousing

[0049] The production process of double-line high-speed bar steel is: blast furnace hot metal smelting → hot metal desulfurization pretreatment → converter steelmaking → billet continuous casting → reheating furnace heating → rough rolling (6 stands) → medium rolling (6 stands) → pre-finishing rolling (6 stands) and splitting into double lines → controlled cooling and recovery section × 2 → finishing rolling (6 stands) × 2 → post-rolling controlled cooling and recovery section × 2 → pinch roll × 2 → flying shear × 2 → braking device × 2 → rotary table device × 2 → cooling bed cooling → sizing shearing and inspection packaging and warehousing

[0050] Among them, the technological characteristics of each stage are:

[0051] Converter steelmaking: The hot metal charged into the furnace requires S ≤ 0.040 Wt%; the whole process of bottom blowing argon is adopted during smelting, and the gas flow rate is increased in the later stage of blowing to strengthen the molten pool stirring; the converter end-point control is C ≤ 0.15 Wt%, P ≤ 0.037 Wt%;

[0052] Billet continuous casting: Ladle slag detection control is adopted, the tundish pouring temperature is 1520 - 1540 °C, ordinary covering agent is used in the tundish, ordinary billet mold powder is used, and the single-strand casting speed of the billet is 3.0 - 4.0 m / min.

[0053] High-speed bar rolling: Control the heating temperature of the continuous casting billet at 980 - 1100 °C, the heating time of the billet at 80 - 120 minutes, and the billet discharging temperature at 920 - 970 °C. Adopt 24 stands of high-speed non-twist single-line rolling (6 stands for rough rolling, 6 stands for medium rolling, 6 stands for pre-finishing rolling, and 6 stands for finishing rolling), and add electromagnetic induction heating equipment before rough rolling, medium rolling, pre-finishing rolling, before finishing rolling, and after finishing rolling respectively. Utilize the "skin effect" of electromagnetic induction heating to increase the surface temperature of the rolled piece, while the internal temperature of the rolled piece is relatively low at this time. Control the rolling start temperature, the temperature entering medium rolling, the temperature entering pre-finishing rolling, and the temperature entering finishing rolling of the rolled piece surface at 980 - 1040 °C, while the internal temperature of the rolled piece is maintained at 920 - 970 °C, and the finished steel bar also maintains this state when exiting the finishing rolling. The surface temperature of the finished steel bar is high and the internal temperature is low, which can provide sufficient deformation resistance when the braking device presses down for braking, and can also maintain a high temperature on the surface of the steel bar to form a relatively thick scale. During the entire rolling process, do not use controlled cooling equipment to reduce the surface temperature of the rolled piece, and change the surface cooling method of the rolling mill rolls from full water cooling to aerosol cooling, which ensures the cooling effect of the rolls and can avoid excessive water flowing onto the rolled piece to reduce the surface temperature of the rolled piece. The above measures can increase the scale thickness (radial thickness) of the steel bar surface to 16 μm and above when the final rolling speed of the high-speed bar production line is 30 - 45 m / s, and the mechanical properties are qualified.

[0054] 4. A method for high-speed bar to enter the cooling bed at high temperature:

[0055] (1) The process for producing Φ10 - 20 mm straight ribbed steel bars by double-line high-speed bar is: blast furnace hot metal smelting → hot metal desulfurization pretreatment → converter steelmaking → billet continuous casting → heating furnace heating → rough rolling (6 stands) → medium rolling (6 stands) → pre-finishing rolling (6 stands) and split into double lines → controlled cooling and recovery section × 2 → finishing rolling (6 stands) × 2 → post-rolling controlled cooling and recovery section × 2 → pinch rolls × 2 → flying shear × 2 → braking device × 2 → rotary device × 2 → cooling bed cooling → length cutting, shearing and inspection, packaging and warehousing

[0056] (2) Control the heating temperature of the continuous casting billet at 1050 - 1170 °C, the heating time of the billet at 80 - 120 minutes, the rolling start temperature at 1000 - 1040 °C, adopt 24 stands of high-speed non-twist rolling (6 stands for rough rolling, 6 stands for medium rolling, 6 stands for pre-finishing rolling, and 6 stands for finishing rolling), the finishing rolling is double-line and use controlled cooling equipment in pre-finishing rolling, and control the temperature entering finishing rolling at 900 ± 20 °C.

[0057] (3) Do not install or use controlled cooling equipment from after finishing rolling to before entering the cooling bed, so that the steel bars are in a natural cooling state, and the steel bars obtain a relatively high temperature when entering the cooling bed.

[0058] (4) The number of braking rolls for each line is 2 groups, and use heat preservation devices on the cooling bed, and the storage method of the steel bars on the cooling bed is 2 bars per tooth.

[0059] (5) Adopt the following component ratios and specific processes. Among them, Table 1 shows the components of the steel in each embodiment (by weight percentage). Table 2 shows the production specifications, process parameters, mechanical properties, and scale thickness corresponding to the steel in the embodiments described in Table 1.

[0060] Table 1: Chemical composition of the product (wt%)

[0061] Example C Si Mn P S Nb Example 1 0.21 0.55 1.28 0.030 0.021 0.026 Example 2 0.22 0.58 1.31 0.026 0.022 0.027 Example 3 0.25 0.59 1.32 0.032 0.030 0.031 Example 4 0.23 0.54 1.30 0.027 0.033 0.024 Example 5 0.24 0.60 1.29 0.028 0.025 0.026

[0062] Table 2: Specific process parameters and mechanical properties of each embodiment

[0063]

[0064] 2. Lifting cold bed thermal insulation cover

[0065] The cold bed of the 24-stand high-speed bar hot continuous rolling production line is rectangular, 120 m long and 11.5 m wide. Horizontally arranged along the length direction of the cold bed are 12 thermal insulation covers, each 10 m wide and 11.5 m long.

[0066] (1) The thermal insulation cover is suspended above the cold bed. The four corners of the upper surface (the side facing away from the cold bed) of the top are connected by steel wires. The two short sides of the rectangular thermal insulation cover are respectively driven by pulleys and one motor.

[0067] (2) When the thermal insulation cover moves, upper and lower limits are set. The upper limit is at most 3.5 m away from the cold bed plane, and the lower limit is at least 10 cm away from the cold bed plane.

[0068] (3) When the outside is winter and the temperature is 0 °C, the 12 thermal insulation covers are adjusted to the lowest position, reducing the temperature drop of the steel bars on the cold bed.

[0069] 3. A method for using electromagnetic induction heating to increase the temperature of high-speed bars on the cold bed:

[0070] (1) The single-line high-speed bar steel bar production process is: blast furnace hot metal smelting → hot metal desulfurization pretreatment → converter steelmaking → billet continuous casting → heating furnace heating → rough rolling (6 stands) → medium rolling (6 stands) → pre-finishing rolling (6 stands) → single line → controlled cooling and recovery section → finishing rolling (6 stands) → post-rolling controlled cooling and recovery section → pinch roll → disk multiple cutters → braking device → rotary hub device → cold bed cooling → fixed-length shearing and inspection packaging and warehousing

[0071] (2) Control the casting billet heating temperature to be 980 - 1100 °C, the steel billet heating time to be 80 - 120 minutes, and the casting billet furnace outlet temperature to be 920 - 970 °C. Adopt 24-stand high-speed non-twist single-line rolling (6 stands for rough rolling, medium rolling, pre-finishing rolling, and finishing rolling respectively). Add electromagnetic induction heating equipment before rough rolling, medium rolling, pre-finishing rolling, before and after finishing rolling, and use the "skin effect" of electromagnetic induction heating to increase the surface temperature of the rolled piece.

[0072] (3) During the entire rolling process, no controlled cooling equipment is used between rolling mills to reduce the surface temperature of the rolled piece. The surface cooling method of the rolling mill rolls is also changed from full water cooling to air mist cooling, which ensures the cooling effect of the rolls and can avoid excessive water flowing onto the rolled piece, reducing the surface temperature of the rolled piece.

[0073] (4) The number of braking rolls is 2 groups, and a heat preservation device is used on the cooling bed. The storage method of reinforcing bars on the cooling bed is 2 bars per tooth.

[0074] (5) The following component ratios and specific processes are adopted. Among them, Table 3 shows the composition of the steel in each embodiment (by weight percentage). Table 4 shows the production specifications (reinforcing bars), process parameters, mechanical properties, and scale thickness corresponding to the steel in the embodiments described in Table 3.

[0075] Table 3: Chemical composition of the product (wt%)

[0076]

[0077]

[0078] Table 4: Specific process parameters and mechanical properties of each embodiment

[0079]

[0080] The above is only the schematic specific implementation manner of the present invention and is not intended to limit the scope of the present invention. The components of the present invention can be combined with each other under the condition of no conflict. Any equivalent changes and modifications made by any person skilled in the art without departing from the concept and principle of the present invention shall fall within the scope of protection of the present invention.

Claims

1. A production method of HRB400E straight-thread ribbed steel bars, characterized in that, A method for increasing the thickness of scale on the surface of high-speed bars is adopted. The bars are straight threaded steel bars of HRB400E, with C: 0.20 - 0.25% Wt, Si: 0.50 - 0.70 Wt, Mn: 1.15 - 1.40% Wt, and the Nb content is 0.020 - 0.035% Wt. The production method includes: converter steelmaking, bloom continuous casting, and hot continuous rolling. Among them, Converter steelmaking: The molten iron charged into the furnace requires S ≤ 0.040 Wt%; the whole process of bottom blowing argon is adopted during smelting, the gas flow rate is increased in the later stage of blowing, and the stirring of the molten bath is strengthened; the converter end-point control is C ≤ 0.15 Wt%, P ≤ 0.037 Wt%; Bloom continuous casting: Ladle slag detection control is adopted, the tundish pouring temperature is 1520 - 1540 °C, and the single-strand casting speed of the billet is 3.0 - 4.0 m / min; Hot continuous rolling: Control the heating temperature of the billet to be 1050 - 1170 °C, the heating time of the steel billet is 80 - 120 minutes, the rolling start temperature is 1000 - 1040 °C, 24 stands of high-speed non-twist rolling are adopted, the temperature before entering the finishing mill is controlled to be 900 ± 20 °C, and no controlled cooling equipment is installed or used before the finishing mill and before the steel bar enters the cooling bed, so that the steel bar is in a natural cooling state; The method for increasing the thickness of scale on the surface of high-speed bars includes: setting the final rolling speed of the high-speed bar production line at 30 - 45 m / s, and adopting the following steps: Step A: Adopt Nb microalloying to increase the high-temperature strength and improve the mechanical properties of the steel bar at room temperature; the Nb content is 0.020 - 0.035% wt; Step B: Increase the number of braking rollers to increase the contact area between the braking rollers and the bars, improve the braking friction force, and thus increase the temperature of the steel bar entering the cooling bed; The specific content of Step B is: Increase the number of braking rollers on each line of the high-speed bar production line to 2 groups or more; The radial thickness of the scale on the surface of the steel bar is increased to 13 μm or more.

2. The production method of HRB400E straight ribbed steel bars according to claim 1, characterized in that, The HRB400E straight threaded steel bar is a threaded steel bar.

3. The production method of the HRB400E straight ribbed steel bar according to claim 1, characterized in that, The method for increasing the thickness of scale on the surface of high-speed bars further includes: Step D: The storage method of the bars on the cooling bed is changed from storing one bar per tooth of the cooling bed rack to storing multiple bars per tooth.

4. The production method of the HRB400E straight ribbed steel bar according to claim 1, characterized in that, The method for increasing the thickness of scale on the surface of high-speed bars further includes: Step C: Install a heat preservation cover on the cooling bed to slow down heat dissipation and increase the residence time of the bars on the cooling bed in the high-temperature area.

5. The production method of the straight threaded HRB400E steel bars according to claim 1, characterized in that, The method for increasing the thickness of scale on the surface of high-speed bars further includes: Step E: Electromagnetic induction heating to increase the surface temperature: Add electromagnetic induction heating devices before rough rolling, medium rolling, pre-finishing rolling, before finishing rolling, and after finishing rolling respectively, and use the skin effect of electromagnetic induction heating to increase the surface temperature of the billet.

6. The production method of HRB400E straight ribbed bars according to claim 1, characterized in that, The specific content of Step E is: Maintain the surface temperature of the rolled piece at 980 - 1040 °C through the electromagnetic induction heating device, while the internal temperature of the rolled piece is maintained at 920 - 970 °C.

7. The production method of HRB400E straight ribbed steel bars according to claim 1, characterized in that, In Step C: The projection of the heat preservation cover in the top view direction is a rectangle. The heat preservation cover is suspended above the cooling bed. The rectangle includes the long side and the short side of the heat preservation cover. A steel wire rope is connected to each short side of each heat preservation cover, and each steel wire rope is connected to a motor. And the steel wire rope is connected to the motor through a fixed pulley.

8. The production method of the HRB400E straight ribbed steel bar according to claim 1, characterized in that, The straight ribbed threaded steel bar of HRB400E, with a specification of Φ18mm.

9. The production method of the HRB400E straight-thread ribbed steel bar according to claim 1, characterized in that, The chemical composition of the straight ribbed threaded steel bar: C: 0.24% Wt, Si: 0.60 Wt, Mn: 1.29% Wt, and the Nb content is 0.026% Wt.

10. The production method of HRB400E straight ribbed bars according to claim 1, characterized in that, The chemical composition of the straight ribbed threaded steel bar: C: 0.21% Wt, Si: 0.48 Wt, Mn: 1.19% Wt, and the Nb content is 0.025% Wt.

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