165 square billet HRB500E high-strength steel direct rolling process

Abstract

The invention relates to the technical field of high-strength steel processing, in particular to a 165 square billet HRB500E high-strength steel direct rolling process which comprises the following direct rolling steps: S1, preparing the following raw materials: carbon steel, vanadium and niobium, and doping the vanadium and the niobium into the carbon steel to prepare a steel billet to be processed; s2, the steel billet is heated, the heating temperature is accurately controlled, waste heat in flue gas is recycled to preheat flame-retardant air through a heat storage type combustion technology, and the steel billet is heated; and S3, the heated steel billet is fed into a roughing mill to be subjected to preliminary rolling, rough rolling and finish rolling. Vanadium and niobium are doped into carbon steel to improve the strength of the prepared reinforcing steel bar, a heat storage type combustion technology is adopted for temperature control, a steel billet is heated, the temperature is controlled, the heating efficiency is improved, energy consumption is reduced, furnace gas circulation in a heating furnace is enhanced through the heat storage type combustion technology, and the energy consumption is reduced. And the inconvenience of heating temperature control is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of high-strength steel processing, and specifically relates to a 165 square billet HRB500E high-strength steel direct rolling process. Background Art

[0002] 165 square billet, that is, a square billet with a cross-section of 165mm×165mm, is widely used in the steel industry. It is mainly used to roll various specifications of steel and wire, such as threaded steel, angle steel, channel steel, etc. These steel products have important applications in construction, machinery, automobiles, ships and other fields. HRB500E is a high-strength steel bar with high strength, high toughness, good weldability and seismic resistance. It is widely used in concrete of various important structures. In the prior art, the direct rolling process of HRB500E high-strength steel has strict requirements on the heating temperature of the steel billet. It is necessary to accurately control the temperature of the preheating section, heating section and soaking section to ensure that the steel billet reaches the appropriate deformation temperature and mechanical properties during the rolling process. However, due to factors such as uneven temperature distribution in the heating furnace and gas pressure fluctuations, it is difficult to control the heating temperature, and the strength of the processed steel bar is difficult to meet the standard. In this regard, we propose a 165 square billet HRB500E high-strength steel direct rolling process. Summary of the invention

[0003] In view of the deficiencies in the prior art, the present invention provides a 165 square billet HRB500E high-strength steel direct rolling process to solve the above technical problems.

[0004] To achieve the above object, the present invention provides the following technical solution: a 165 square billet HRB500E high-strength steel direct rolling process, the direct rolling steps are: S1. Prepare the following raw materials: carbon steel, vanadium and niobium, and add vanadium and niobium into the carbon steel to make a steel billet to be processed; S2. Heat the steel billet and precisely control the heating temperature. Regenerative combustion technology is used to recover the waste heat in the flue gas to preheat the flame-retardant air and heat the steel billet. S3, sending the heated steel billet to the rough rolling mill for preliminary rolling, and performing rough rolling and finishing rolling. On the steel dividing roller between the rough rolling and finishing rolling, the temperature and the head-tail temperature difference of the steel billet are controlled by controlling the opening and closing time of the heat preservation cover and the residence time of the steel billet on the roller, and rolling is performed to form a semi-finished product after rolling; S4. After rolling is completed, wait for natural cooling to control the structure and performance; S5, straightening the cooled steel bars, and cutting the steel bars after straightening; S6. Carry out quality inspection on the steel bars. If they meet the standards, they will be packaged.

[0005] Preferably, the step of adding vanadium and niobium to carbon steel in step S1 is performed by placing a carbon steel substrate, vanadium and niobium together in a smelting furnace, preheating and smelting, stirring during the smelting process to allow the vanadium and niobium elements to be evenly distributed in the molten steel to achieve alloying, austenitizing the smelted molten steel to transform the structure in the steel into austenite, rapidly cooling the austenitized steel to cause a phase change, and combining the vanadium and niobium elements with the carbon element in the steel to form vanadium carbide and niobium carbide compounds to improve the hardness, wear resistance and corrosion resistance of the steel, and finally tempering the cooled steel.

[0006] Preferably, the regenerative combustion technology in step S2 utilizes a heat storage body to recover heat from the flue gas, and uses this heat to preheat the air and coal gas entering the combustion chamber, so that the air and coal gas are preheated at high temperature to achieve the efficiency of waste heat recovery and heat the steel billet to increase the temperature.

[0007] Preferably, the preliminary rolling in step S3 is performed by cutting the heated billet to obtain billets of suitable size, and the billets are cut by flame cutting.

[0008] Preferably, in step S3, a heat preservation cover is installed on the rollers on the roughing mill and the finishing mill to maintain the temperature of the intermediate billet.

[0009] Preferably, the cooling time after rolling in step S4 is 1 hour, and the rolled steel is cooled under the blowing of natural wind.

[0010] Preferably, in step S5, the steel bar straightening pre-checks the steel bars to be straightened, determines the degree of bending and the material, and selects manual straightening or mechanical straightening for straightening, wherein manual straightening is suitable for steel bars with a small degree of bending, and mechanical straightening is suitable for steel bars with a large degree of bending. The manual straightening method is performed by placing the bent part of the steel bar between the wrenches, straightening the bent part of the steel bar with a flat-headed horizontal wrench, and then placing the preliminarily straightened steel bar on a workbench, and flattening it with a straightening hammer until the steel bar rolls on the workbench to be qualified.

[0011] Preferably, mechanical straightening adjusts the parameters of the straightening machine according to the material and bending degree of the steel bars, the parameters include the position, spacing and angle of the straightening blocks, the steel bars to be straightened are placed into the entrance of the straightening machine, ensuring that the steel bars are in good contact with the straightening blocks, the straightening machine is started, and the steel bars are gradually straightened under the action of the straightening blocks. After the steel bars are completely straightened, the straightening machine is closed and the steel bars are taken out from the outlet to check whether the steel bars are straightened.

[0012] Preferably, the quality inspection in step S6 includes appearance inspection and mechanical property inspection of the steel bars. The appearance inspection standard is that the ends of the steel bars should be straight, the cross-section should be flat, and the surface should be free of cracks. The surface of the steel bars should be directly observed with the naked eye to check for defects, and the dimensions of the steel bars should be accurately measured using measuring tools to verify whether they meet the standard requirements.

[0013] Preferably, the mechanical property test of the steel bar includes the tensile test of the steel bar, the bending test of the steel bar, and the impact test. The strength test of the steel bar is performed by using a testing machine to test the strength of the steel bar and recording the test data.

[0014] Compared with the prior art, the present invention has the following beneficial effects: The present application improves the strength of the prepared steel bars by adding vanadium and niobium to carbon steel, and adopts regenerative combustion technology to control the temperature, so as to heat the steel billet, control the temperature, improve the heating efficiency and reduce the energy consumption. The regenerative combustion technology strengthens the furnace gas circulation in the heating furnace, makes the temperature field in the furnace more uniform, improves the heating quality and reduces the inconvenience of heating temperature control. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a flowchart of the direct rolling steps of the present invention. DETAILED DESCRIPTION

[0016] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0017] The present invention provides a technical solution: a 165 square billet HRB500E high-strength steel direct rolling process, the direct rolling steps are: S1. Prepare the following raw materials: carbon steel, vanadium and niobium, and add vanadium and niobium into the carbon steel to make a steel billet to be processed; S2. Heat the steel billet and precisely control the heating temperature. Regenerative combustion technology is used to recover the waste heat in the flue gas to preheat the flame-retardant air and heat the steel billet. S3, sending the heated steel billet to the rough rolling mill for preliminary rolling, and performing rough rolling and finishing rolling. On the steel dividing roller between the rough rolling and finishing rolling, the temperature and the head-tail temperature difference of the steel billet are controlled by controlling the opening and closing time of the heat preservation cover and the residence time of the steel billet on the roller, and rolling is performed to form a semi-finished product after rolling; S4. After rolling is completed, wait for natural cooling to control the structure and performance; S5, straightening the cooled steel bars, and cutting the steel bars after straightening; S6. Carry out quality inspection on the steel bars. If they meet the standards, they will be packaged.

[0018] Furthermore, in step S1, the step of adding vanadium and niobium to carbon steel is performed by placing the carbon steel substrate, vanadium and niobium into a smelting furnace together for preheating and smelting. Preheating helps to reduce thermal stress during the smelting process, and smelting allows the raw materials to be fully melted and mixed evenly. During the smelting process, stirring is performed to allow the vanadium and niobium elements to be evenly distributed in the molten steel to achieve alloying. The smelted molten steel is austenitized, and the heating temperature and holding time need to be controlled to ensure that the vanadium and niobium elements can be fully dissolved in the austenite, and the structure in the steel is transformed into austenite. The austenitized steel is quickly cooled to cause a phase change, and the vanadium and niobium elements are combined with the carbon element in the steel to form vanadium carbide and niobium carbide compounds to improve the hardness, wear resistance and corrosion resistance of the steel. Finally, the cooled steel is tempered.

[0019] Furthermore, in step S2, the regenerative combustion technology utilizes the regenerative body to recover the heat in the flue gas, and uses this part of the heat to preheat the air and coal gas entering the combustion chamber, so that the air and coal gas are preheated at high temperature to achieve the efficiency of waste heat recovery and heat the steel billet to increase the temperature; Regenerative combustion technology can significantly improve the energy utilization rate of heating furnaces, especially the rational use of low calorific value fuels. By recovering the heat in the flue gas, it reduces energy waste and reduces energy consumption. Regenerative combustion technology strengthens the gas circulation in the heating furnace, makes the temperature field in the furnace more uniform, and improves the heating quality.

[0020] Furthermore, in step S3, the preliminary rolling is performed by cutting the heated billet to obtain billets of suitable size, and the billets are cut by flame cutting; Flame cutting uses a high-temperature flame formed by the combustion of oxygen to quickly heat the steel bars to a molten state, and blows away the molten metal through the oxygen flow, thereby achieving rapid cutting. This efficient operation method can significantly improve construction efficiency. The precision incision of flame cutting is relatively smooth, which can meet the cutting quality requirements of general projects.

[0021] Furthermore, in step S3, a heat preservation cover is installed on the rollers on the roughing mill and the finishing mill to maintain the temperature of the intermediate billet. In step S4, the cooling time after rolling is 1 hour, and the rolled steel is cooled under the blowing of natural wind.

[0022] Furthermore, in step S5, the steel bar straightening pre-checks the steel bars to be straightened, determines the degree of bending and the material, and selects manual straightening or mechanical straightening for straightening, wherein manual straightening is suitable for steel bars with a small degree of bending, and mechanical straightening is suitable for steel bars with a large degree of bending. The manual straightening method is to place the bent part of the steel bar between the wrenches, straighten the bent part of the steel bar with a flat-headed horizontal wrench, and then place the preliminarily straightened steel bar on a workbench, and flatten it with a straightening hammer until the steel bar rolls on the workbench to be qualified.

[0023] Furthermore, mechanical straightening adjusts the parameters of the straightening machine according to the material and bending degree of the steel bars, including the position, spacing and angle of the straightening blocks. The steel bars to be straightened are placed into the entrance of the straightening machine to ensure good contact between the steel bars and the straightening blocks. The straightening machine is started to allow the steel bars to gradually become straightened under the action of the straightening blocks. After the steel bars are completely straightened, the straightening machine is turned off and the steel bars are taken out from the outlet to check whether they are straightened.

[0024] Example 1 A 165 square billet HRB500E high-strength steel direct rolling process, the direct rolling steps are: S1. Prepare the following raw materials: carbon steel, vanadium and niobium, and add vanadium and niobium into the carbon steel to make a steel billet to be processed; S2. Heat the steel billet and precisely control the heating temperature. Regenerative combustion technology is used to recover the waste heat in the flue gas to preheat the flame-retardant air and heat the steel billet. S3, sending the heated steel billet to the rough rolling mill for preliminary rolling, and performing rough rolling and finishing rolling. On the steel dividing roller between the rough rolling and finishing rolling, the temperature and the head-tail temperature difference of the steel billet are controlled by controlling the opening and closing time of the heat preservation cover and the residence time of the steel billet on the roller, and rolling is performed to form a semi-finished product after rolling; S4. After rolling is completed, wait for natural cooling to control the structure and performance; S5, straightening the cooled steel bars, and cutting the steel bars after straightening; S6. Carry out quality inspection on the steel bars. If they meet the standards, they will be packaged.

[0025] Comparative Example 1 The production steps of steel bars are: A1. Select steel billets that meet production requirements, ensure that their chemical composition and physical properties meet the standards of HRB500E high-strength steel, classify and stack the steel billets according to different specifications and batches, and mark them to prevent confusion; A2. Heat the steel billet according to the heating system to ensure that the steel billet reaches the appropriate temperature range during the rolling process; the temperature of the preheating section is controlled at 700±50℃, the temperature of the heating section is controlled at 950℃--1100℃, and the temperature of the soaking section is controlled at 1150±50℃; A3. The heated steel billet is fed into a rough rolling mill for preliminary rolling, and the steel billet is rolled into a semi-finished product with a certain shape and size through multiple rolling passes; A4. Send the semi-finished products after rough rolling to the finishing mill for further rolling. By accurately controlling the rolling force and rolling speed, the steel bar can reach the required diameter and mechanical properties; A5. Use natural cooling to cool the rolled steel bars to control their structure and properties; A6. Straighten the cooled steel bars to eliminate the defects such as bending and twisting generated during the rolling process, and cut the straightened steel bars into required lengths to obtain finished steel bars that meet the requirements; A7. Conduct quality inspection on finished steel bars, including appearance quality, dimensional accuracy, mechanical properties, etc. to ensure that they meet the standard requirements. Finished steel bars that pass the inspection will be packaged and stored in warehouses in accordance with relevant regulations.

[0026] Table 1 shows the test results of the high-strength steel prepared in the examples and comparative examples.

[0027] Table 1 Appearance inspection: The inspection standard is that the ends of the steel bars should be straight, the cross section should be flat, and there should be no cracks on the surface; Use the naked eye to directly observe the surface of the steel bar to check for defects, and use measuring tools to accurately measure the size of the steel bar to verify whether it meets the standard requirements; During the testing process, each steel bar should be thoroughly inspected to avoid missing any possible defects. Problems found during the testing process should be recorded and reported in a timely manner.

[0028] Tensile test: Follow the "Metallic Material Tensile Test Part: Room Temperature Test Method" as the benchmark; Ensure that the test is carried out at a suitable ambient temperature, generally within the range of 10 to 35°C from room temperature. For tests requiring strict conditions, the temperature should be controlled at 23±5°C; Check and calibrate the universal material testing machine to ensure that the equipment is in good working condition; Estimate the maximum load according to the strength grade and diameter of the steel bar, select the appropriate range of the testing machine, and control it between 20% and 80% to ensure that the accuracy does not exceed ±1%; Fix the upper end of the specimen in the upper fixture of the testing machine, adjust the zero point of the testing machine, and then fix the lower end of the specimen with the lower fixture to ensure that the specimen does not slide during the stretching process and is subject to axial tension; Start the testing machine to stretch, and the stretching speed must meet the test conditions until the specimen breaks; Record the test data. After the sample is broken, connect the broken parts tightly together and try to make them lie on one axis. Use a vernier caliper to measure the gauge length L1 after breaking, accurate to 0.25mm; Calculate the elongation after fracture using the formula: δ = (L1-L0) / L0×100%, where L1 is the gauge length after fracture and L0 is the length of the specimen before stretching; Compare the test results with the standard requirements to assess whether the tensile properties of the steel bars are qualified.

[0029] Table 2 below is the data table of tensile test records

[0030] Table 2 Curvature detection: Prepare testing instruments, including steel bar cold bending test machine, angle ruler, thickness ruler, bending die, vernier caliper, steel ruler and prepared samples; Ensure that the temperature in the test room is appropriate and controlled between 10℃-35℃; Place the steel bar specimen in the bending die, ensuring that the center of the specimen is aligned with the center of the die; Select the appropriate bending angle and bending diameter according to the diameter of the steel bar and test requirements; Start the testing machine and perform a bending test on the steel bar. During the bending process, pay attention to the deformation of the steel bar. If there is any abnormality, stop the test in time. Use an angle ruler to measure the angle of the steel bar after bending and record the data. Check whether there are cracks, peeling and other defects in the bent part of the steel bar, and record the observation results. According to the test standards and observation results, determine whether the curvature of the steel bar meets the requirements.

[0031] Impact testing of steel bars: Impact testing is carried out using an impact testing machine, which can generate a predetermined impact energy and apply it to the steel sample. During the test, a steel sample of a certain shape is placed in the fixture of the testing machine, and then an impact load is applied to the sample through a mechanical device to make it break quickly. During the test, the impact energy (Ak) required to break the sample is recorded. This value reflects the impact toughness of the steel bar. The impact test of steel bars should comply with relevant national or international standards, GB / T 229-2007 "Charpy Pendulum Impact Test Method for Metallic Materials".

[0032] Example 1: By adding vanadium and niobium to carbon steel, the strength of the prepared steel bars is improved, and the heat storage combustion technology is used to control the temperature, so as to heat the steel billet, control the temperature, improve the heating efficiency and reduce energy consumption. The heat storage combustion technology strengthens the furnace gas circulation in the heating furnace, makes the temperature field in the furnace more uniform, improves the heating quality, and reduces the inconvenience of heating temperature control.

[0033] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0034] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A 165 square billet HRB500E high-strength steel direct rolling process, characterized in that: The direct rolling steps are: S1. Prepare the following raw materials: carbon steel, vanadium and niobium, and add vanadium and niobium into the carbon steel to make a steel billet to be processed; S2. Heat the steel billet and precisely control the heating temperature. Regenerative combustion technology is used to recover the waste heat in the flue gas to preheat the flame-retardant air and heat the steel billet. S3, sending the heated steel billet to the rough rolling mill for preliminary rolling, and performing rough rolling and finishing rolling. On the steel dividing roller between the rough rolling and finishing rolling, the temperature and the head-tail temperature difference of the steel billet are controlled by controlling the opening and closing time of the heat preservation cover and the residence time of the steel billet on the roller, and rolling is performed to form a semi-finished product after rolling; S4. After rolling is completed, wait for natural cooling to control the structure and performance; S5, straightening the cooled steel bars, and cutting the steel bars after straightening; S6. Carry out quality inspection on the steel bars. If they meet the standards, they will be packaged.

2. The 165 square billet HRB500E high-strength steel direct rolling process according to claim 1 is characterized in that: In step S1, the step of adding vanadium and niobium to carbon steel is carried out by placing the carbon steel substrate, vanadium and niobium into a smelting furnace together, preheating and smelting, stirring during the smelting process to allow the vanadium and niobium elements to be evenly distributed in the molten steel to achieve alloying, austenitizing the smelted molten steel to transform the structure in the steel into austenite, and rapidly cooling the austenitized steel to cause a phase change, so that the vanadium and niobium elements combine with the carbon element in the steel to form vanadium carbide and niobium carbide compounds to improve the hardness, wear resistance and corrosion resistance of the steel, and finally tempering the cooled steel.

3. The 165 square billet HRB500E high-strength steel direct rolling process according to claim 1 is characterized in that: In step S2, the regenerative combustion technology utilizes the regenerative body to recover the heat in the flue gas, and uses this part of the heat to preheat the air and coal gas entering the combustion chamber, so that the air and coal gas are preheated at high temperature to achieve the waste heat recovery efficiency and heat the steel billet to increase the temperature.

4. The 165 square billet HRB500E high-strength steel direct rolling process according to claim 1 is characterized in that: In step S3, the initial rolling is performed by cutting the heated billet to obtain billets of suitable size, which are cut by flame cutting.

5. The 165 square billet HRB500E high strength steel direct rolling process according to claim 1, characterized in that: In step S3, the heat preservation cover is installed on the rollers of the roughing mill and the finishing mill to maintain the temperature of the intermediate billet.

6. The 165 square billet HRB500E high strength steel direct rolling process according to claim 1, characterized in that: In step S4, the cooling time after rolling is 1 hour, and the rolled steel is cooled under the blowing of natural wind.

7. The 165 square billet HRB500E high strength steel direct rolling process according to claim 1, characterized in that: In step S5, the steel bar straightening pre-checks the steel bars to be straightened, determines the degree of bending and material, and selects manual straightening or mechanical straightening for straightening. Manual straightening is suitable for steel bars with a small degree of bending, and mechanical straightening is suitable for steel bars with a large degree of bending. The manual straightening method is to place the bent part of the steel bar between the wrenches, straighten the bent part of the steel bar with a flat-headed horizontal wrench, and then place the preliminarily straightened steel bar on the workbench and flatten it with a straightening hammer until the steel bar rolls on the workbench to pass.

8. The 165 square billet HRB500E high strength steel direct rolling process according to claim 7, characterized in that: Mechanical straightening adjusts the parameters of the straightening machine according to the material and bending degree of the steel bars. The parameters include the position, spacing and angle of the straightening blocks. Place the steel bars to be straightened into the entrance of the straightening machine, ensure that the steel bars are in good contact with the straightening blocks, start the straightening machine, and allow the steel bars to gradually straighten under the action of the straightening blocks. After the steel bars are completely straightened, turn off the straightening machine and take out the steel bars from the outlet to check whether the steel bars are straightened.

9. The 165 square billet HRB500E high strength steel direct rolling process according to claim 1, characterized in that: The quality inspection in step S6 includes the appearance inspection and mechanical property inspection of the steel bars. The appearance inspection standard is that the ends of the steel bars should be straight, the cross-section should be flat, and there should be no cracks on the surface. The surface of the steel bars should be directly observed with the naked eye to check for defects. The size of the steel bars should be accurately measured using measuring tools to verify whether they meet the standard requirements.

10. The 165 square billet HRB500E high strength steel direct rolling process according to claim 9, characterized in that: The mechanical properties testing of steel bars includes steel bar tensile testing, steel bar bending testing, and impact test testing.

Images