Production method for reducing rotten steel of deformed steel bar and deformed steel bar

Abstract

The invention provides a production method for reducing rotten steel of deformed steel bars and the deformed steel bars. The method comprises the steps of molten steel refining, continuous casting and steel rolling. In the molten steel refining process, the nitrogen content is controlled to be 230 ppm or below, and the oxide inclusion size is controlled to be 10 microns or below; in the continuous casting process, the shearing temperature of a casting blank is controlled to be 850 DEG C or above; in the steel rolling process, the opening angle of a roll gap is adjusted to be 5-8 degrees, and the rolling reduction error is controlled to be within + / -0.15 mm. According to the invention, by accurately controlling the components of the molten steel, the refining process, the continuous casting parameters and the rolling conditions and adopting advanced rollers and guide and guard materials, the rotten steel rate is reduced to below 0.011% from 0.05% at present, and the product quality is improved.

Description

Technical Field

[0001] The present application relates to the technical field of steel refining, and in particular to a production method for reducing rotten steel of threaded steel and threaded steel. Background Art

[0002] Rebar is a widely used steel product in industries such as construction, highways, and nuclear power, and its quality is directly related to the safety of building structures. However, during rebar production, improper control of the steelmaking, continuous casting, and rolling processes can easily lead to problems such as rotten steel, including cracks, inclusions, and pores. This leads to a decrease in product qualification and yield rate. Existing technologies addressing rebar rotten steel have mostly focused on improving a single process, lacking systematic optimization and failing to fundamentally address the problem.

[0003] The reasons why rotten steel problems are prone to occur in existing processes are:

[0004] 1) Large fluctuations in molten steel composition or temperature lead to large fluctuations in rolled material properties, low-temperature dead flow in continuous casting, and cracks in the center (middle) of the high-temperature steel billet;

[0005] 2) Rolling cracks caused by high nitrogen and hydrogen content in molten steel;

[0006] 3) Inclusion of rotten steel caused by mold slag / steel slag being involved in the billet;

[0007] 4) Uneven cooling of the crystallizer, unreasonable distribution of cooling water in the secondary cooling section, nozzle blockage, etc., causing the billet to de-square / crack;

[0008] 5) The hydraulic shearing temperature is too low and the shear blade gap is too large, resulting in cracks on the shear end face of the steel billet;

[0009] 6) The unreasonable design of the roll pass leads to uneven metal flow, which is prone to folding or cracking;

[0010] 7) The guide device has poor centering, and the rolled piece collides with the roll after running off the track, resulting in roll misalignment or scratches;

[0011] 8) The rolling temperature control is not accurate, the austenite grains are coarse or the phase transformation is abnormal, which affects the plasticity of the material. Summary of the Invention

[0012] The present application is made in view of the above problems, and its purpose is to provide a production method and rebar that reduces rotten steel, and to improve the yield rate of rebar by controlling the rotten steel of rebar.

[0013] Specifically, a first aspect of the present application provides a method for reducing rotten steel in threaded steel, comprising the following steps:

[0014] steel refining, continuous casting and rolling;

[0015] During the molten steel refining process, the nitrogen content is controlled below 230ppm and the size of oxide inclusions is controlled below 10μm;

[0016] During the continuous casting process, the shear temperature of the cast billet is controlled to be above 850°C;

[0017] During the steel rolling process, the roll gap opening angle is adjusted to 5° to 8°, and the reduction error is controlled to within ±0.15mm.

[0018] Preferably, during the molten steel refining process, the temperature of the molten steel out of the LF furnace is controlled at 1545°C to 1575°C.

[0019] Preferably, the main components of the molten steel leaving the LF furnace are C 0.23-0.25%, Si 0.35-0.55%, Mn 1.25-1.40%, P≤0.045%, S≤0.045%, V 0.018-0.050%, Nb 0-0.015%, and N≤0.012%.

[0020] Preferably, the adjustment of the secondary cooling water content during the continuous casting process further comprises controlling the water content to be 1.15 to 1.25 L / kg when the casting speed is ≤ 2.6 m / min;

[0021] When the pulling speed is ≥2.6m / min and ≤3.8m / min, the specific water volume is 1.45~1.55L / kg;

[0022] When the pulling speed is greater than 3.8m / min, the specific water content is 1.58-1.62kg / kg.

[0023] Preferably, during the continuous casting process, the hydraulic shearing pressure is ≥12.5 MPa, and the hydraulic shearing blade gap is ≤0.8 mm.

[0024] Preferably, the intelligent temperature control rolling system is used to adjust the temperature gradient of the steel billet before rolling to ≤20°C / m, and maintain the temperature difference between the head and tail of the rolled piece to <30°C.

[0025] Preferably, the guide device is provided with a hydraulic cylinder and a displacement sensor, the hydraulic cylinder is used to adjust the displacement of the guide clamping center, and the displacement sensor is used to detect the position deviation of the guide clamping center, so that the centering accuracy of the guide clamping center and the rolled piece center is ≤±0.2mm.

[0026] Preferably, the guide device is lined with graphite blocks to lubricate the guide plates and reduce the surface friction coefficient of the rolled piece.

[0027] Preferably, a cooling water channel is designed inside the graphite block lubrication guide plate to reduce the working temperature.

[0028] A second aspect of the present application provides a threaded steel bar produced by the production method for reducing threaded steel rot.

[0029] The present invention has the following beneficial effects:

[0030] (1) The present application effectively limits the size of oxide inclusions by precisely controlling the nitrogen replenishment amount and composition during the molten steel refining process, thereby reducing cracks caused by inclusions during the rolling process. At the same time, by using a grooved crystallizer copper tube for cooling and dynamically adjusting the secondary cooling water ratio, uniform cooling and a suitable shear temperature of the ingot are ensured, avoiding cracking problems caused by uneven cooling or low shear temperature. In addition, during the steel rolling process, the coordinated work of the tungsten carbide alloy rollers and the guide device achieves precise control of the reduction error, further reducing rolling defects. Moreover, the present application also improves the precise control of the rolling temperature and the centering of the guide device through technical means such as the intelligent temperature control rolling system and the hydraulic cylinder fine-tuning guide clamping center, thereby significantly improving the product quality of the rebar. The process control method of the present application can significantly reduce the problem of rotten steel in the production process of rebar and improve the product qualification rate and yield rate.

[0031] (2) The present invention reduces the rotten steel rate from 0.05% before the process control to below 0.011% through process control. The reason is that the molten steel composition is controlled more accurately, which reduces cracks caused by composition segregation; the nitrogen and hydrogen contents are effectively controlled, avoiding the generation of rolling cracks; by optimizing refining, continuous casting and rolling, the occurrence of mixed rotten steel is reduced; the optimization of the crystallizer cooling technology and the cooling water distribution in the secondary cooling zone significantly reduces the surface and internal cracks of the steel billet; the precise control of the hydraulic shearing parameters reduces the shear end face cracks; the roll hole design and the adaptive adjustment of the guide device suppress the generation of folding defects. The production quality of threaded steel is improved through the above process control. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the embodiments of the present drawings or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present drawings. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0033] Figure 1 This is the structural diagram of the tungsten carbide roller ring;

[0034] Figure 2 This is a diagram of subcutaneous bubble defects in steel billets in the prior art;

[0035] Figure 3 This is a diagram showing the existence of end cracks in the steel billet in the prior art;

[0036] Figure 4 This is a schematic diagram of rotten rebar;

[0037] Figure 5 It is a schematic diagram of the steel billet structure of the present invention;

[0038] Figure 6 Schematic diagram of threaded steel of the present invention.

[0039] The purpose, features and advantages of this drawing will be further described with reference to the accompanying drawings in conjunction with the embodiments. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical solutions and advantages of this application more clearly understood, the present application is described and illustrated below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are merely used to explain this application and are not intended to limit this application. Based on the embodiments provided in this application, all other embodiments obtained by those of ordinary skill in the art without making any creative work are within the scope of protection of this application.

[0041] Obviously, the following descriptions are merely some examples or embodiments of the present application. Those skilled in the art can apply the present application to other similar scenarios without inventive effort. Furthermore, it is also understood that, although the effort involved in such a development process may be complex and lengthy, for those skilled in the art related to the content disclosed in the present application, changes in design, manufacturing, or production based on the technical content disclosed in the present application are merely conventional technical means and should not be construed as an insufficiency of the content disclosed in the present application.

[0042] Unless otherwise specified, the terms "include" and "comprising" used in this application may be open-ended or closed-ended. For example, "include" and "comprising" may mean that other components not listed may also be included or that only the listed components are included.

[0043] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, the condition "A or B" is satisfied if any of the following conditions are met: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0044] The first aspect of the present application provides a production method for reducing rotten steel of threaded steel, comprising the following contents:

[0045] steel refining, continuous casting and rolling;

[0046] 1) Control the amount of nitrogen blowing during molten steel refining. The nitrogen content of molten steel strengthened with microalloys (vanadium, niobium) is controlled to ≤230ppm, and the nitrogen content of molten steel strengthened without microalloys (vanadium, niobium) is controlled to ≤180ppm. Silicon-calcium composite deoxidizer is used to limit the size of oxide inclusions to ≤10μm.

[0047] 2) During the continuous casting process, grooved mold copper tube cooling is used. The secondary cooling water volume is dynamically adjusted based on the steel flow rate. When the steel flow rate is greater than 600 kg / min, the water volume is 1.5 to 1.6 L tons. When the steel flow rate is ≤ 600 kg / min (165 mm × 165 mm cross-section billet at a casting speed of 2.8 m / min), the water volume is 1.2 to 1.3 L tons. Ensure that the shear temperature of the billet is ≥ 850 ° C.

[0048] 3) During the steel rolling process, tungsten carbide alloy rollers and guide devices work together, see Figure 1 , Figure 1 This is the structural diagram of the carbide roller ring. The roller gap opening angle is adjusted from 5° to 8° to suppress the lateral flow resistance of the metal. The multi-objective optimization model is used to adjust the control reduction error in real time to within ±0.15mm.

[0049] During the aforementioned steel refining process, nitrogen injection is controlled to a nitrogen content of ≤230ppm for microalloyed steel and ≤180ppm for non-microalloyed steel. This reduces nitrogen content in the steel and, in turn, reduces rolling cracking caused by high nitrogen content. The use of a silicon-calcium composite deoxidizer effectively controls the size of oxide inclusions, which are often the starting point of cracks. By limiting their size to less than 10μm, the risk of cracking caused by inclusions during rolling can be significantly reduced.

[0050] Furthermore, the continuous casting process is a complex and critical step, and its cooling effect directly affects the internal and surface quality of the ingot. Using grooved copper tubes for cooling in the mold can more effectively control the solidification process of the molten steel and reduce internal defects caused by uneven cooling. At the same time, dynamically adjusting the secondary cooling water ratio based on the amount of steel flowing through the mold ensures that the ingot receives the appropriate cooling rate and temperature distribution during cooling, avoiding cracking caused by excessively fast or slow cooling. In particular, when the amount of steel flowing through the mold is large, increasing the water ratio ensures sufficient cooling of the ingot, preventing low-temperature dead flow and center cracking caused by excessive temperatures. When the amount of steel flowing through the mold is small, appropriately reducing the water ratio can avoid surface cracking caused by excessively fast cooling.

[0051] The use of tungsten carbide alloy rollers and guide devices working together can significantly improve the wear resistance and thermal cracking resistance of the rollers, extend the service life of the rollers, and reduce rolling defects caused by roller wear or thermal cracking during the rolling process. Adjusting the roll gap opening angle from 5° to 8° helps to optimize the metal flow state and reduce the lateral flow resistance of the metal during the rolling process, thereby improving rolling efficiency and product quality. The implementation and adjustment of the multi-objective optimization model specifically include: 1. Converting quality, rolling speed, energy consumption, negative deviation, etc. into mathematical goals; 2. Using algorithms to generate the optimal solution set and select the best solution; 3. Fine-tuning the reduction amount based on real-time data feedback, controlling the reduction amount error to within ±0.15mm, and avoiding rolling defects such as folding and cracking caused by excessive or insufficient reduction.

[0052] The present application effectively limits the size of oxide inclusions by precisely controlling the nitrogen replenishment amount and composition during the molten steel refining process, thereby reducing cracks caused by inclusions during the rolling process. At the same time, by adopting grooved crystallizer copper tube cooling and dynamically adjusting the secondary cooling water ratio, uniform cooling and appropriate shear temperature of the ingot are ensured, avoiding cracking problems caused by uneven cooling or low shear temperature. In addition, during the steel rolling process, the coordinated work of the tungsten carbide alloy rollers and the guide device, as well as the real-time adjustment of the multi-objective optimization model, achieves precise control of the reduction error, further reducing rolling defects. Moreover, the present application also improves the precise control of the rolling temperature and the centering of the guide device through technical means such as the intelligent temperature control rolling system and the hydraulic cylinder fine-tuning guide clamping center, thereby significantly improving the product quality of the rebar. Through the process control method of the present application, it is possible to significantly reduce the problem of rotten steel in the production process of rebar and improve the product qualification rate and yield rate.

[0053] In an embodiment of the present invention, during the molten steel refining process, the temperature of the molten steel at the outlet of the LF furnace is controlled within a range of 1545°C to 1575°C to avoid large fluctuations in superheat and ensure the purity of the molten steel. The temperature of the molten steel at the outlet of the LF furnace can be any value or any combination range before 1545°C, 1550°C, 1555°C, 1560°C, 1565°C, 1570°C, and 1575°C. Too low a temperature may result in poor fluidity of the molten steel, increasing the difficulty of rolling and the risk of cracks; while too high a temperature may cause alloy elements in the molten steel to burn out, affecting the performance of the steel. Therefore, controlling the temperature of the molten steel at the outlet of the LF furnace within the range of 1545°C to 1575°C can ensure that the molten steel has good fluidity and stability, providing high-quality raw materials for the subsequent rolling process.

[0054] In the embodiment of the present invention, the main components of the molten steel leaving the LF furnace are C 0.23-0.25%, Si 0.35-0.55%, Mn 1.25-1.40%, P≤0.045%, S≤0.045%, V 0.018-0.050%, Nb0-0.015%, and N≤0.012%. The molten steel is strictly controlled (narrow composition control) by adopting off-furnace refining technology to ensure that the contents of elements such as carbon, silicon, manganese, phosphorus, and sulfur are within a reasonable range to avoid composition segregation.

[0055] In addition, during the refining process, the rhythm of continuous molten steel connection is controlled to avoid rushing to connect slag and mold slag / steel slag being drawn into the billet, ensuring the uniformity and stability of the molten steel composition and reducing the fluctuations in rolled material performance and cracking caused by composition fluctuations. At the same time, for molten steel strengthened with microalloys (such as vanadium and niobium), by precisely controlling the nitrogen content, rolling cracks caused by excessive nitrogen content can be effectively avoided, thereby improving the strength and toughness of the steel.

[0056] In the embodiment of the present invention, low superheat casting technology is also adopted to control the superheat of molten steel in the tundish to 15° C. to 25° C., thereby reducing internal cracks and component segregation in the steel billet.

[0057] The use of grooved mold copper tube cooling technology allows for more effective control of the molten steel's solidification process and improves the quality of the cast ingot. The grooved mold copper tube design increases the contact area between the cooling water and the tube, improving heat transfer efficiency and enabling more uniform and rapid cooling of the molten steel during solidification. This cooling method helps reduce thermal stress within the ingot, thereby lowering the risk of internal cracks. Furthermore, uniform cooling helps minimize compositional segregation within the ingot, improving the overall performance of the steel. This cooling technology ensures uniform mold cooling, minimizing surface cracking and de-squareness.

[0058] Optimize the cooling water distribution in the secondary cooling zone to avoid excessive temperature gradient on the surface of the ingot and prevent the occurrence of cracks in the middle.

[0059] The secondary cooling water distribution table is as follows:

[0060] Pulling speed (m / min) 2.6 2.7 2.8 2.9 3 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 Specific water content (L / kg) 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 Hourly output (t / h) 31.5 32.7 33.9 35.1 36.3 37.5 38.7 39.9 41.1 42.4 43.6 44.8 46 <![CDATA[Total water volume (m 3 / h)]]> 47.2 49 50.8 52.6 54.5 56.3 58.1 59.9 61.7 63.5 65.3 67.2 69 <![CDATA[Area 1 (m 3 / h)]]> 16.5 17.2 17.8 18.4 19.1 19.7 20.3 21 21.6 22.2 22.9 23.5 24.1 <![CDATA[Second zone (m 3 / h)]]> 20.3 21.1 21.9 22.6 23.4 24.2 25 25.8 26.5 27.3 28.1 28.9 29.7 <![CDATA[Three zones (m 3 / h)]]> 4.72 4.9 5.08 5.26 5.45 5.63 5.81 5.99 6.17 6.35 9.15 9.4 9.66 <![CDATA[Four regions (m 3 / h)]]> 2 2 2 2 2 2 2 2 2 2 5.23 5.37 5.52

[0061] When the pulling speed is ≤2.6m / min, the water volume is controlled at 1.2L / kg and distributed to zones 1, 2, and 3 at a ratio of 35%:43%:10% to ensure that the temperature of the hydraulically sheared steel billet is not lower than 850℃;

[0062] When the pulling speed is ≥2.6m / min and ≤3.8m / min, the specific water volume is 1.5L / kg, and is distributed to zones 1, 2, and 3 at a ratio of 35%:43%:10%;

[0063] When the pulling speed is greater than 3.8m / min, the specific water content is 1.6kg / kg, which is distributed to zones 1, 2, 3 and 4 at the ratio of 35%:43%:14%:8%.

[0064] The second, third and fourth zones have a minimum water volume, zone two: 3m 3 / h; Zone 3: 3m 3 / h; Zone 4: 2m 3 / h.

[0065] In the embodiments of the present invention, when hydraulically shearing a billet, the gap between the hydraulic shear blades does not exceed 0.8 mm, and the hydraulic shearing pressure on a 165 mm x 165 mm billet cross-section is no less than 12.5 MPa. This ensures good cross-sectional quality and dimensional accuracy during the shearing process, while avoiding cracks and dimensional deviations caused by excessive shearing pressure or blade gap. Furthermore, the appropriate shearing pressure and blade gap reduce energy consumption and blade wear during the shearing process, improving production efficiency and economic benefits.

[0066] In an embodiment of the present invention, an intelligent temperature-controlled rolling system is used during steel rolling: through the regulation of the segmented heating furnace, an infrared thermometer is used to monitor the temperature of each section of the steel billet in real time, and the gas flow of the heating furnace is dynamically adjusted by the PID algorithm to ensure that the temperature gradient of the steel billet before rolling is ≤20°C / m. Temperature drop compensation is used in the rolling process, specifically, an induction heating device is added in front of the finishing rolling unit to maintain the temperature difference between the head and tail of the rolled piece <30°C. The above-mentioned technical means are used to ensure that the steel billet has a uniform temperature distribution during the rolling process, avoiding rolling defects such as cracks and folding caused by excessive temperature gradients. At the same time, the intelligent temperature-controlled rolling system can also improve the precise control of the rolling temperature to ensure that the performance and dimensional accuracy of the steel meet the requirements.

[0067] In an embodiment of the present invention, high-strength and wear-resistant tungsten carbide composite rollers (roller rings) are used in the steel rolling process, and the outer layer of the rollers (roller rings) is made of tungsten carbide alloy steel (hardness ≥ HRC65) to extend the service life. By optimizing the hole profile, the roller gap opening angle is increased by 5° to 8°, the lateral flow resistance of the metal is reduced, and folding defects are suppressed. An adaptive guide device (hydraulic servo guide) is used, and a displacement sensor is installed to detect the position of the rolled piece in real time. The guide clamping center is fine-tuned by the hydraulic cylinder, and the centering accuracy is ≤±0.2mm. Graphite lubricated guide plate: The guide lining is made of a composite material inlaid with graphite blocks to reduce the surface friction coefficient of the rolled piece (μ≤0.1). The guide device is welded with high-strength alloy steel, with high overall rigidity and strong deformation resistance. Two hydraulic cylinders (four in total) are located on either side of the guide assembly, each with a stroke of ±10 mm and a thrust of ≥10 kN. These cylinders are used by the control system to calculate the hydraulic cylinder adjustment based on deviation signals, actuating the cylinders to fine-tune the guide clamping center. Displacement sensors are installed at the guide entrance and exit to monitor the workpiece's positional deviation in real time, with an accuracy of ≤±0.05 mm. This ensures alignment between the guide clamping center and the workpiece center within an accuracy of ≤±0.2 mm. A servo control system receives the displacement sensor signals and controls the hydraulic cylinders using a PID algorithm, enabling dynamic adjustment of the guide clamping center. The operating principle of the guide assembly is as follows: When the workpiece enters the guide assembly, the displacement sensors detect its center position deviation. The servo control system calculates the hydraulic cylinder adjustment based on the deviation signals and actuates the hydraulic cylinders to fine-tune the guide clamping center. After adjustment, the guide clamping center maintains an alignment accuracy of ≤±0.2 mm, ensuring stable passage of the workpiece.

[0068] The steel passing capacity of a single groove of the high-speed steel roller K2 commonly used in the prior art is 300 tons, which can be increased to more than 2,000 tons by adopting the solution of the present invention. The steel passing capacity of a single groove of the K4 in the prior art is 1,750 tons, which can be increased to more than 10,000 tons by adopting the solution of the present invention. The frequency of roller replacement is reduced because the outer layer of the roller (roller ring) is made of tungsten carbide alloy steel, which has high strength and wear resistance, thereby greatly improving the service life of the roller (roller ring).

[0069] Through fine-tuning of the hydraulic cylinder, the present invention ensures accurate alignment between the guide clamping center and the center of the workpiece, avoiding rolling defects such as cracks and folds caused by poor alignment. Furthermore, the use of graphite lubricated guides reduces the friction coefficient on the workpiece surface, reducing energy consumption and roll wear during the rolling process, further improving production efficiency and economic benefits.

[0070] In an embodiment of the present invention, the graphite block lubrication guide is designed with cooling water channels to reduce operating temperatures. This effectively extends the service life of the graphite blocks and prevents the degradation of lubrication performance and increased wear caused by high temperatures. The design of the cooling water channels ensures that the graphite blocks maintain an appropriate temperature during operation, maintaining their excellent lubrication properties, thereby ensuring a smooth rolling process and stable product quality. This also further improves production efficiency and economic benefits, reducing downtime caused by graphite block replacement and maintenance.

[0071] Specifically, the graphite block-lubricated guide plate structure comprises a guide plate base, graphite inlay blocks, and cooling channels. The guide plate base is made of high-chromium cast iron (hardness ≥ HRC60), which has excellent wear resistance and long service life. The graphite inlay blocks (size: 10mm × 10mm × 5mm) are evenly inlaid on the guide working surface with 20mm spacing. The cooling channels are located inside the guide plate and are water-cooled to reduce operating temperatures. The working principle of the graphite lubricated guide plate is as follows: when the workpiece passes through the guide plate, the graphite blocks contact the workpiece surface, releasing graphite powder to form a lubricating film. The lubricating film reduces the surface friction coefficient of the workpiece (μ≤0.1), reducing scratches and surface defects. The cooling water channels are cooled by water to prevent the guide plate from softening or deforming due to high temperatures.

[0072] In addition, the present invention establishes a multi-objective optimization model of rolling speed, reduction, and roll gap value, specifically based on the production line rolling rebar variety specifications, steel tapping temperature, equipment status, etc., as well as the quality goals to be achieved (including surface quality, dimensional accuracy, negative deviation, etc. in compliance with standards), rolling speed (output) targets, and energy consumption targets, etc., using historical data and real-time data feedback to continuously optimize and correct the rolling speed, reduction, and roll gap value, and output the optimal parameter combination through historical data training. Specifically, taking the finishing rolling of Φ20mm rebar as an example, the rolling speed is 12m / s, the final finishing reduction is 6.5mm, and the roll gap value is 12.2mm. The core of the multi-objective optimization model is to balance the relationship between rolling speed, reduction, and roll gap value to achieve the optimal rolling effect. Among them, rolling speed is the key factor affecting production efficiency, reduction is directly related to the dimensional accuracy and internal structure of the rolled piece, and roll gap value determines the shape and surface quality of the rolled piece. By comprehensively considering these three parameters, the present invention can output the parameter combination that best suits the current production conditions, thereby minimizing the occurrence of threaded steel rot.

[0073] The present invention also adjusts the reduction amount of the last stand rolling mill in real time based on feedback from the online thickness gauge to ensure that the dimensional tolerance of the finished product meets the GB1499.2-2024 standard.

[0074] See also Figure 2-Figure 6 , Figure 2-Figure 4 It is a defect map of steel billets and rebars in the prior art; Figure 5 It is a schematic diagram of the steel billet structure of the present invention; Figure 6 The figure is a schematic diagram of the threaded steel of the present invention. It can be seen from the figure that the present invention significantly improves the product quality of the threaded steel through the improvement of the above technical solution. Figure 5 and Figure 6 As shown, the steel billet and threaded steel of the present invention exhibit excellent performance in both structure and appearance, and reduce the occurrence of defects.

[0075] A second aspect of the present application provides a rebar produced by the aforementioned method for reducing rebar rot. The rebar not only has excellent mechanical properties, such as high strength, good toughness, and fatigue resistance, but also has high dimensional accuracy and good surface quality, and can meet the requirements of use in various complex environments.

[0076] Example 1

[0077] This embodiment produces Φ20mm HRB400(E) hot-rolled ribbed steel bars, including the following:

[0078] The composition of the molten steel leaving the LF furnace is: C 0.24%, Si 0.45%, Mn 1.35%, P 0.04%, S 0.04%, V 0.035%, Nb 0.01%, N 0.01%. The nitrogen blowing rate during the molten steel refining process is controlled at 200ppm. The pouring temperature of the molten steel leaving the LF furnace is 1580℃, and the continuous pouring temperature is 1565℃.

[0079] The continuous casting process uses an arc-shaped continuous casting machine with an arc radius of 8 meters, a grooved crystallizer for cooling, a billet cross-section of 165×165mm, and a casting speed of 2.8m / min.

[0080] Continuous casting cooling water control is as follows:

[0081]

[0082] The hydraulic shear blade gap of continuous casting billet is 0.7mm, and the hydraulic shear pressure of 165mm×165mm cross-section billet is 14.5Mpa;

[0083] During rolling, the heating section temperature is 1150°C, the tapping temperature is 950°C, the finishing inlet temperature is 970°C, and the upper cooling bed temperature is 820°C. The roll diameter is Φ380mm, the roll length is 650mm, and the roll gap is preset to 1.7mm. A segmented heating furnace is used for control, and infrared thermometers are used to monitor the temperature of each section of the billet in real time. The heating furnace gas flow is dynamically adjusted using a PID algorithm to ensure a billet temperature gradient of ≤20°C / m before rolling. An induction heating device is added before the finishing mill to maintain a temperature difference of less than 30°C between the head and tail of the rolled piece. High-strength and wear-resistant tungsten carbide composite rolls with a roll gap opening angle of 6° are used. Displacement sensors are installed to detect the position of the rolled piece in real time. The guide clamping center is fine-tuned by a hydraulic cylinder, with an alignment accuracy of ≤±0.2mm. The guide lining is made of a composite material inlaid with graphite blocks to reduce the surface friction coefficient of the rolled piece (μ≤0.1). According to the feedback from the online thickness gauge, the reduction of the last stand rolling mill is adjusted in real time to ensure that the dimensional tolerance of the finished product meets the GB1499.2-2024 standard.

[0084] Example 2

[0085] This embodiment produces Φ20mm HRB400(E) hot-rolled ribbed steel bars, including the following:

[0086] The composition of the molten steel leaving the LF furnace is: C 0.25%, Si 0.40%, Mn 1.25%, P 0.035%, S 0.035%, V 0.050%, Nb 0.015%, N 0.009%. The nitrogen blowing rate during the molten steel refining process is controlled at 200ppm. The pouring temperature of the molten steel leaving the LF furnace is 1600℃, and the continuous pouring temperature is 1555℃.

[0087] The continuous casting process uses an arc-shaped continuous casting machine with an arc radius of 8 meters, a grooved crystallizer for cooling, a billet cross-section of 165×165mm, and a casting speed of 2.8m / min.

[0088] Continuous casting cooling water control is as follows:

[0089]

[0090] The hydraulic shearing blade clearance of continuous casting billet is ≤0.7mm, and the hydraulic shearing pressure of 165mm×165mm cross-section billet is 13Mpa;

[0091] During rolling, the heating section temperature is 1145°C, the tapping temperature is 960°C, the finishing inlet temperature is 980°C, and the upper cooling bed temperature is 830°C. The roll diameter is Φ380mm, the roll length is 650mm, and the roll gap is preset to 1.5mm. A segmented heating furnace is used for control, and infrared thermometers are used to monitor the temperature of each section of the billet in real time. The heating furnace gas flow is dynamically adjusted using a PID algorithm to ensure a billet temperature gradient of ≤20°C / m before rolling. An induction heating device is added before the finishing mill to maintain a temperature difference of less than 30°C between the head and tail of the rolled piece. High-strength and wear-resistant tungsten carbide composite rolls with an 8° roll gap opening angle are used. Displacement sensors are installed to detect the position of the rolled piece in real time. The guide clamping center is fine-tuned by a hydraulic cylinder, with an alignment accuracy of ≤±0.2mm. The guide lining is made of a composite material inlaid with graphite blocks to reduce the surface friction coefficient of the rolled piece (μ≤0.1). According to the feedback from the online thickness gauge, the reduction of the last stand rolling mill is adjusted in real time to ensure that the dimensional tolerance of the finished product complies with the GB1499.2-2024 standard.

[0092] Example 3

[0093] This embodiment produces Φ20mm HRB400(E) hot-rolled ribbed steel bars, including the following:

[0094] The composition of the molten steel leaving the LF furnace is: C 0.24%, Si 0.35%, Mn 1.25%, P 0.015%, S 0.015%, V 0.028%, Nb 0.012%, N 0.012%. The nitrogen blowing rate during the molten steel refining process is controlled at 210ppm. The pouring temperature of the molten steel leaving the LF furnace is 1590℃, and the continuous pouring temperature is 1545℃.

[0095] The continuous casting process uses an arc-shaped continuous casting machine with an arc radius of 8 meters, a grooved crystallizer for cooling, a billet cross-section of 165×165mm, and a casting speed of 2.8m / min.

[0096] Continuous casting cooling water control is as follows:

[0097]

[0098] The hydraulic shearing blade gap of continuous casting billet is 0.8mm, and the hydraulic shearing pressure of 165mm×165mm cross-section billet is 14Mpa;

[0099] During rolling, the heating section temperature is 1140°C, the tapping temperature is 950°C, the finishing inlet temperature is 970°C, and the upper cooling bed temperature is 820°C. The roll diameter is Φ380mm, the roll length is 650mm, and the roll gap is preset to 2.0mm. A segmented heating furnace is used for control, and infrared thermometers are used to monitor the temperature of each section of the billet in real time. The heating furnace gas flow is dynamically adjusted using a PID algorithm to ensure a billet temperature gradient of ≤20°C / m before rolling. An induction heating device is added before the finishing mill to maintain a temperature difference of less than 30°C between the head and tail of the rolled piece. High-strength and wear-resistant tungsten carbide composite rolls with a roll gap opening angle of 6° are used. Displacement sensors are installed to detect the position of the rolled piece in real time. The guide clamping center is fine-tuned by a hydraulic cylinder, with an alignment accuracy of ≤±0.2mm. The guide lining is made of a composite material inlaid with graphite blocks to reduce the surface friction coefficient of the rolled piece (μ≤0.1). According to the feedback from the online thickness gauge, the reduction of the last stand rolling mill is adjusted in real time to ensure that the dimensional tolerance of the finished product meets the GB1499.2-2024 standard.

[0100] Example 4

[0101] This embodiment produces Φ20mm HRB400(E) hot-rolled ribbed steel bars, including the following:

[0102] The composition of the molten steel leaving the LF furnace is: C 0.23%, Si 0.55%, Mn 1.38%, P 0.045%, S 0.045%, V 0.018%, Nb 0.005%, N 0.011%. The nitrogen blowing rate during the molten steel refining process is controlled at 200ppm. The pouring temperature of the molten steel leaving the LF furnace is 1575℃, and the continuous pouring temperature is also 1575℃.

[0103] The continuous casting process uses an arc-shaped continuous casting machine with an arc radius of 8 meters, a grooved crystallizer for cooling, a billet cross-section of 165×165mm, and a casting speed of 2.8m / min.

[0104] Continuous casting cooling water control is as follows:

[0105]

[0106] The hydraulic shear blade gap of continuous casting billet is 0.7mm, and the hydraulic shear pressure of 165mm×165mm cross-section billet is 13.5Mpa;

[0107] During rolling, the heating section temperature is 1160°C, the tapping temperature is 940°C, the finishing inlet temperature is 960°C, and the upper cooling bed temperature is 810°C. The roll diameter is Φ380mm, the roll length is 650mm, and the roll gap is preset to 1.8mm. A segmented heating furnace is used for control, and infrared thermometers are used to monitor the temperature of each section of the billet in real time. The heating furnace gas flow is dynamically adjusted using a PID algorithm to ensure a billet temperature gradient of ≤20°C / m before rolling. An induction heating device is added before the finishing mill to maintain a temperature difference of less than 30°C between the head and tail of the rolled piece. High-strength and wear-resistant tungsten carbide composite rolls with a roll gap opening angle of 5° are used. Displacement sensors are installed to detect the position of the rolled piece in real time. The guide clamping center is fine-tuned by a hydraulic cylinder, with an alignment accuracy of ≤±0.2mm. The guide lining is made of a composite material inlaid with graphite blocks to reduce the surface friction coefficient of the rolled piece (μ≤0.1). According to the feedback from the online thickness gauge, the reduction of the last stand rolling mill is adjusted in real time to ensure that the dimensional tolerance of the finished product meets the GB1499.2-2024 standard.

[0108] Comparative Example 1

[0109] This comparative example is basically the same as Example 1, except that the amount of nitrogen supplementary blowing during the molten steel refining process is controlled to be 240 ppm.

[0110] Comparative Example 2

[0111] This comparative example is basically the same as Example 1, except that the specific water volume in the secondary cooling zone is 1.4 L / ton.

[0112] Comparative Example 3

[0113] This comparative example is substantially the same as Example 1, except that the shearing temperature is set at 800°C.

[0114] Comparative Example 4

[0115] This comparative example is basically the same as Example 1, except that the steel rolling process uses traditional high chromium cast iron rolls + steel-based guides.

[0116] Comparative Example 5

[0117] This comparative example is basically the same as Example 1, except that the temperature difference between the head and tail of the rolled piece is greater than 50°C.

[0118] The performance test results of the threaded steel prepared by the methods of Examples 1-4 and Comparative Examples 1-5 are as follows:

[0119] project Rotten steel rate (%) Example 1 0.011 Example 2 0.015 Example 3 0.017 Example 4 0.012 Comparative Example 1 0.065 Comparative Example 2 0.046 Comparative Example 3 0.052 Comparative Example 4 0.043 Comparative Example 5 0.058

[0120] From Examples 1-4 and Comparative Example 1, it can be seen that when the nitrogen supplementation amount during the molten steel refining process is controlled to 240ppm, the rotten steel rate of the rebar increases to 0.065%. This is because excessive nitrogen supplementation may cause the gas content in the molten steel to increase, thereby forming bubbles or inclusions during the rolling process, increasing the risk of rotten steel. At the same time, the results of Comparative Example 2 show that when the water content in the secondary cooling zone is reduced to 1.4L / ton, the rotten steel rate also increases to 0.046%. This may be because the appropriate amount of cooling water is crucial for controlling the temperature of the steel billet and avoiding internal defects. Reducing the amount of cooling water may cause the internal stress of the steel billet to increase, making it easy to crack and rotten steel. In addition, when the shear temperature in Comparative Example 3 is set to 800℃, the rotten steel rate is 0.052%. Compared with the temperature setting in the embodiment, the lower shear temperature may be detrimental to the stability of the internal structure of the steel billet, thereby increasing the possibility of rotten steel. Comparative Example 4 uses traditional high-chromium cast iron rolls + steel-based guides, and the steel rot rate is 0.043%. This is because the traditional roll and guide materials have poor wear resistance, which easily leads to severe wear of the rolls and guides, increasing friction and resistance during the rolling process, thereby exacerbating the occurrence of steel rot. In Comparative Example 5, the temperature difference between the head and tail of the rolled piece is greater than 50°C, and the steel rot rate is 0.058%. This is because excessive temperature difference may cause thermal stress in the rolled piece during rolling, which in turn causes cracks and steel rot. In summary, by precisely controlling the molten steel composition, refining process, continuous casting parameters, rolling conditions, and using advanced roll and guide materials, the present invention successfully reduces the steel rot rate of rebar and improves product quality.

[0121] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A production method for reducing rotten steel of threaded steel, characterized in that: The following steps are involved: steel refining, continuous casting and rolling; During the molten steel refining process, the nitrogen content is controlled below 230ppm and the size of oxide inclusions is controlled below 10μm; During the continuous casting process, the shear temperature of the cast billet is controlled to be above 850°C; During the steel rolling process, the roll gap opening angle is adjusted to 5° to 8°, and the reduction error is controlled to within ±0.15mm.

2. The method for reducing rotten steel of threaded steel according to claim 1, characterized in that: During the molten steel refining process, the temperature of the molten steel out of the LF furnace is controlled to be between 1545°C and 1575°C.

3. The method for reducing rotten steel of threaded steel according to claim 2, characterized in that: The main components of the molten steel leaving the LF furnace are C 0.23-0.25%, Si 0.35-0.55%, Mn 1.25-1.40%, P≤0.045%, S≤0.045%, V 0.018-0.050%, Nb 0-0.015%, and N≤0.012%.

4. The method for reducing rotten steel of threaded steel according to claim 1, characterized in that: The adjustment of the secondary cooling water content during the continuous casting process further includes controlling the water content to be 1.15 to 1.25 L / kg when the casting speed is ≤ 2.6 m / min; When the pulling speed is ≥2.6m / min and ≤3.8m / min, the specific water volume is 1.45~1.55L / kg; When the pulling speed is greater than 3.8m / min, the specific water content is 1.58-1.62kg / kg.

5. The method for reducing rotten steel of threaded steel according to claim 1, characterized in that: During the continuous casting process, the hydraulic shearing pressure is ≥12.5 MPa, and the hydraulic shearing blade gap is ≤0.8 mm.

6. The method for reducing rotten steel of threaded steel according to claim 1, characterized in that: The intelligent temperature control rolling system is used to adjust the temperature gradient of the steel billet before rolling to ≤20°C / m, and maintain the temperature difference between the head and tail of the rolled piece to <30°C.

7. The method for reducing rotten steel of threaded steel according to claim 1, characterized in that: The guide device is provided with a hydraulic cylinder and a displacement sensor. The hydraulic cylinder is used to adjust the displacement of the guide clamping center, and the displacement sensor is used to detect the position deviation of the guide clamping center, so that the centering accuracy of the guide clamping center and the rolled piece center is ≤±0.2mm.

8. The method for reducing threaded steel rot according to claim 1, characterized in that: The guide device is lined with graphite blocks and lubricated on the guide plate to reduce the surface friction coefficient of the rolled piece.

9. The method for reducing rotten steel of threaded steel according to claim 1, characterized in that: A cooling water channel is designed inside the graphite block lubrication guide plate to reduce the working temperature.

10. A threaded steel bar, characterized in that: The invention is prepared by the production method for reducing threaded steel rot according to any one of claims 1 to 9.

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