A method for producing low rolling ratio high carbon alloy round steel by continuous casting of small section square billet

Abstract

The present invention belongs to the technical field of iron and steel metallurgy and steel rolling, and specifically relates to a method for producing low rolling ratio high carbon alloy round steel by continuous casting square billet with small section. The method comprises: calculating the liquid core length of continuous casting square billet, determining electromagnetic stirring process parameters, hot delivery or pit cooling of continuous casting square billet, high temperature heating and diffusion of continuous casting square billet, rolling force core penetration during rolling process, shearing, stacking and inspection of round steel; the present invention makes the steel liquid composition and solute in the continuous casting square billet evenly distributed by electromagnetic stirring; high temperature heating and diffusion are used to reduce segregation and improve the core quality; rolling force penetration technology is used to reduce the rolling speed, increase the unit rolling force, improve the viscosity coefficient of the rolling process, effectively improve the core quality of rolling, press fit looseness, shrinkage and other low-multiple defects, and improve the density; through high temperature rapid collection and stack cooling, the round steel bending is reduced, the residual thermal stress is reduced, cracking is avoided, and the surface quality is improved; the comprehensive performance of the material is improved, and significant technical effects are achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of iron and steel metallurgy and steel rolling, and specifically relates to a method for producing low rolling ratio high carbon alloy round steel by continuously casting small-section square billets. Background Art

[0002] Low rolling ratio high carbon alloy round steel mainly refers to hot rolled round steel with a carbon content of about 1.0%, an alloy content of less than 5%, and a rolling compression ratio of about 10, such as high carbon chromium bearing steel, grinding ball steel, high carbon tool steel, etc. The design characteristics of this type of special purpose steel are: high carbon content, and containing alloy elements such as silicon, manganese, and chromium. Therefore, the performance is manifested as: high hardness, good wear resistance, excellent hardenability, and certain toughness, corrosion resistance, and high fatigue performance characteristics. However, due to the high carbon content and the presence of certain alloy elements such as silicon, manganese, and chromium, and the continuous casting machine does not have a terminal light pressure reduction device, it is very easy to form metallurgical defects such as segregation, looseness, shrinkage, and cracks during the continuous casting process. In order to obtain and improve the quality of round steel, a method for producing low rolling ratio high carbon alloy round steel by continuous casting of small-section square billets is proposed. Summary of the invention

[0003] The purpose of the present invention is to provide a method for producing low rolling ratio high carbon alloy round steel by continuous casting square billets of small section, so as to solve the quality defects of high carbon alloy round steel in existing production technology, such as segregation, low multiple quality difference, and non-conforming rolling, improve the density and yield rate of low rolling ratio round steel, and reduce production costs.

[0004] In order to achieve the above purpose, the present invention provides a method for producing low rolling ratio high carbon alloy round steel by continuous casting of small section square billet, the production method comprising: calculating the liquid core length of the continuous casting square billet; determining the electromagnetic stirring process parameters; hot delivery or pit cooling of the continuous casting square billet; high temperature heating and diffusion of the continuous casting square billet; penetration of the rolling force center during the rolling process; shearing, stacking and inspection of the round steel. The specific operation steps and parameter settings are as follows.

[0005] (1) Calculating the liquid core length of the continuous casting billet: Based on the chemical composition of the high-carbon alloy round steel, the cross-sectional dimensions of the continuous casting billet, the superheat of the molten steel, the drawing speed, and the cooling conditions, the liquid metal ratio inside the continuous casting billet reaches a predetermined value of 25-40%. The liquid core length at this time is the liquid core length of the continuous casting billet to be calculated;

[0006] (2) Confirmation of electromagnetic stirring process parameters: Based on the liquid core length of the continuous casting billet in step (1), according to the liquid core length of the molten steel in the continuous casting billet and the position information of the electromagnetic stirring, the electromagnetic stirring process parameters are set for processing; the electromagnetic stirring includes mold electromagnetic stirring (M-EMS) and end electromagnetic stirring (F-EMS); the mold electromagnetic stirring parameter setting: the current is 250-400A, the frequency is 1-4Hz; the end electromagnetic stirring parameter setting: the current is 350-500A, the frequency is 8-12Hz;

[0007] (3) Hot delivery or pit cooling of the continuous casting billet: The continuous casting billet after the electromagnetic stirring treatment in step (2) is hot delivered to a heating furnace or placed in a slow cooling pit for slow cooling to obtain a treated continuous casting billet; the continuous casting billet is hot delivered to the heating furnace by a heat preservation vehicle, and the temperature of the hot delivery heating furnace is greater than 550°C; the slow cooling in the slow cooling pit is specifically: the continuous casting billet is cooled in the slow cooling pit for a time of ≥36h and a cooling temperature of ≤200°C;

[0008] (4) High-temperature heating and diffusion of the continuous casting billet: Based on the continuous casting billet treated in step (3), the continuous casting billet is placed in a heating furnace for heating, with the preheating section temperature ≤ 860°C, the heating section temperature 900-1100°C, the heating section temperature 1160-1230°C, the soaking section temperature 1160-1250°C, and the total heating time ≥ 240 min to obtain a heat-treated continuous casting billet;

[0009] (5) Penetration of the rolling force into the core of the rolling process: The continuous casting square billet after heat treatment in step (4) is dephosphorized by high-pressure water and then rolled, and the surface of the rolled piece is cooled by water after rough rolling and rough rolling to make the internal temperature of the rolled piece higher than the surface temperature, so that the rolling force penetrates into the core of the rolled piece to obtain the rolled round steel;

[0010] (6) Cutting, stacking and testing of round steel: Based on the round steel after rolling in step (5), the round steel is cut, and after cutting, the round steel is quickly collected and packaged at high temperature, and then stacked in a windproof place for cooling and testing.

[0011] Furthermore, the high carbon alloy round steel in step (1) includes GCr15SiMn bearing steel, GCr15 bearing steel and B350A grinding ball steel.

[0012] Furthermore, the cross-sectional size of the continuously cast square billet in step (1) is 220*220 mm.

[0013] Furthermore, the superheat control requirement of the molten steel in step (1) is 15-30°C; the specific measurement method is: before the molten steel is placed on the continuous casting rotating table, the temperature of the molten steel is measured and confirmed; the molten steel that meets the requirements is hoisted to the continuous casting rotating table, and a long water nozzle is installed and argon protection is turned on to protect the casting throughout the entire process; according to the continuous casting process, each stream is poured and accelerated one by one; after pouring, starting from the 10th minute, the temperature is collected every 5 minutes, and each continuous casting furnace number is measured 6 times; the temperature measuring gun head must be perpendicular to the molten steel liquid surface, the insertion depth of the molten steel is between 200 and 300 mm, the residence time is 5 to 7 seconds, and the actual measured temperature of the molten steel is recorded.

[0014] Furthermore, in step (1), the casting speed of the continuous casting billet varies in the range of 0.80 to 0.95 m / min, and the casting speed is constant throughout the entire process.

[0015] Furthermore, in step (1), the cooling adopts a weak cooling method, and the specific conditions are: water cooling in zone 1, air-water cooling in zones 2 and 3, wherein the water flow rates in zones 1, 2 and 3 are 34-38 L / min, 38-42 L / min, and 18-21 L / min, respectively.

[0016] Furthermore, in step (2), the electromagnetic stirring current of the crystallizer is 400A and the frequency is 2 Hz; the terminal electromagnetic stirring current is 500A and the frequency is 10 Hz.

[0017] Furthermore, the temperature of the hot delivery heating furnace in step (3) is 600°C; the slow cooling time of the slow cooling pit is 36 to 38 hours, and the cooling temperature is 100°C.

[0018] Furthermore, in step (4), the continuous casting billet is heated and diffused at high temperature. The continuous casting billet is loaded into a heating furnace for heating. The preheating temperature is 680-750°C, the heating temperature is 980-1050°C, the heating temperature is 1190-1200°C, the soaking temperature is 1200-1210°C, and the total heating time is 280-300min. This ensures that the billet is evenly burned through. When the temperature of the core of the billet is high, it is beneficial to improve defects such as looseness and shrinkage during rolling.

[0019] Furthermore, in step (4), the continuous casting billet is heated and diffused at high temperature, wherein the temperature reaches 1180-1210°C, which is considered to be in the high temperature range, and the holding time in the high temperature range is ≥150 minutes to promote diffusion; the holding time in the high temperature range is preferably 160-175 minutes.

[0020] Furthermore, the dephosphorization pressure in step (5) is 20-22 MPa; the rolling is performed at a low speed, and the low speed rolling refers to a rolling speed of 75-85% of the rolling speed of medium carbon low alloy steel of the same specification, that is, the rolling speed of GCr15SiMn bearing steel is 1.0-1.1 m / s, the rolling speed of GCr15 bearing steel is 0.8-1.0 m / s, and the rolling speed of B350A grinding ball steel is 0.8-1.0 m / s.

[0021] Furthermore, in step (6), the round steel is sheared, stacked and inspected. The starting shearing temperature of the round steel is greater than 500°C. The round steel is quickly collected at a high temperature above 350°C and slowly cooled in a cooling pit to prevent cracking at the end of the round steel. Samples are then taken for inspection.

[0022] The advantages and technical effects of the present invention are:

[0023] The above technical method has the following advantages: First, through the electromagnetic stirring effect, the electromagnetic stirring is a "crystallizer + end" combined electromagnetic stirring. Under the excitation of the three-phase power supply, a rotating magnetic field is generated at the center of the coil. When the molten steel passes through, the molten steel rotates under the action of the electromagnetic force, which has the effect of stirring; so that the liquid steel composition and solute in the continuous casting billet are evenly distributed. Second, the use of high-temperature heating and diffusion further reduces segregation and improves the quality of the core. Third, the use of rolling force penetration technology reduces the rolling speed and increases the unit rolling force to increase the viscosity coefficient of the rolling process. During the rolling process, the plastic deformation effectively penetrates into the core, promotes the effect of rolling force penetration into the core, and then effectively improves the quality of the core of the rolling, presses loose, shrinkage and other low-magnification defects, and improves the density. Fourth, through high-temperature rapid collection and stack cooling, the bending of round steel is reduced, the residual thermal stress is reduced, stress cracking is avoided, and the surface quality is improved. Fifth, the small-section continuous casting billet has obvious cost advantages under the premise of quality assurance. DETAILED DESCRIPTION

[0024] The present invention is described in detail below with reference to examples, but the present invention is not limited to these embodiments.

[0025] Embodiment 1:

[0026] Ф70mm GCr15SiMn bearing steel round steel production:

[0027] Chemical composition (mass percentage): C: 0.99%, Mn: 1.05%, Si: 0.58%, Cr: 1.47%, P: 0.014%, S: 0.002%, Ni: 0.022%, Cu: 0.06%, Mo: 0.008%, Al: 0.011%, Ti: 0.020%, Sn: 0.003%, Sb: 0.0001%, As: 0.006%, Pb: 0.0001, Ca: 0.0001, [O]: 0.0007%; the balance is Fe and unavoidable impurities.

[0028] The steps include: calculating the liquid core length of the continuous casting billet; determining the electromagnetic stirring process parameters; inspecting, hot-transporting or pit cooling the continuous casting billet; high-temperature heating and diffusion of the continuous casting billet; penetration of the rolling force center during the rolling process; and stacking and inspecting round steel.

[0029] (1) Calculation of the liquid core length of the continuous casting billet: Based on the chemical composition of GCr15SiMn bearing steel (see the above chemical composition), the cross-section of the continuous casting billet is 220*220mm, the superheat is 27°C, the pulling speed and continuous casting (see Table 1), and the cooling adopts a weak cooling method; specifically: water cooling in zone 1, air-water cooling in zones 2 and 3, where the water flow rates in zones 1, 2 and 3 are 34L / min, 38L / min and 18L / min respectively; the proportion of molten steel in the billet is obtained, and the liquid core length of the continuous casting billet (the length of the billet from the molten steel surface in the crystallizer to the time when the molten steel is completely solidified) is calculated.

[0030] Table 1

[0031]

[0032] (2) Determination of electromagnetic stirring process parameters: The continuous casting process is protected, the liquidus temperature of GCr15SiMn bearing steel is 1453°C, the molten steel inlet temperature is 1478°C, and the superheat range is 25-28°C; the crystallizer vibration, cooling, electric stirring, and secondary cooling are turned on, and the electromagnetic stirring position is gradually reached; the continuous casting billet pulling speed is 0.85m / min, and the crystallizer electromagnetic stirring is turned on at 6m, and the setting parameters are: 400A / 2Hz, and the end electromagnetic stirring is turned on at 8.6m, and the setting parameters are: 500A / 10Hz; at this time, the proportion of molten steel inside the continuous casting billet is 29.9%, and the length of the liquid core of the continuous casting billet flowing through the end electromagnetic stirring position is 9.9m;

[0033] (3) Hot delivery or pit cooling of continuous casting billets: The continuous casting billets are sampled and inspected. After passing the inspection, the continuous casting billets are placed in a slow cooling pit for slow cooling. The slow cooling time is 38 hours, and the cooling temperature after uncovering is 100°C.

[0034] Table 2 Sampling test data

[0035]

[0036] (4) High-temperature heating and diffusion of continuous casting billets: The continuous casting billets are loaded into the heating furnace for heating, with the preheating section temperature at 750°C, the heating section temperature at 1000°C, the heating section temperature at 1190°C, the soaking section temperature at 1205°C, the total heating time at 300 min, and the high-temperature section (heating section 2 and soaking section) time at 175 min, to ensure uniform burning through of the billet and high-temperature diffusion effect, so as to improve defects such as porosity, shrinkage, and segregation;

[0037] (5) The rolling force penetration in the core of the rolling process: After the continuous casting billet leaves the heating furnace, it is dephosphorized by high-pressure water before rolling (the dephosphorization pressure is 22 MPa). The low-speed rolling is adopted, and the finished product speed is reduced from the normal 1.4 m / s to 1.1 m / s to increase the unit rolling force. The rough rolling and water cooling after rough rolling are used to make the core temperature of the rolled material higher than the surface temperature, so as to facilitate the penetration of the rolling force into the core.

[0038] (6) Shearing, stacking and inspection of round steel: The starting shearing temperature of round steel is 520℃, and the stacking temperature is 380℃. After rapid collection at high temperature, the steel is slowly cooled in a cooling pit to prevent cracking at the end of the round steel, and samples are taken for inspection.

[0039] The bearing rings were inspected according to the delivery standards. The specific results are shown in Table 3. All the results are qualified.

[0040] Table 3

[0041] Inspection items Test results gas Oxygen content 7ppm Low magnification Central looseness 1.0, general looseness 0.5, central segregation 0.5, stereotyped segregation 0, other defects none Non-metallic inclusions A coarse 0 level, A fine ≤ 0.5 level, B ≤ 0.5 level, C 0 level, D ≤ 0.5 level, DS ≤ 0.5 level carbide Strip ≤2.0, liquid analysis ≤0.5, hot rolled mesh qualified Micropores qualified Total decarburized layer 0.15~0.25mm Ultrasonic flaw detection GB / T 4162-2008 B grade, 100% qualified

[0042] Embodiment 2:

[0043] Ф75mm GCr15 bearing steel round steel production:

[0044] Chemical composition (mass percentage): C: 1.01%, Mn: 0.35%, Si: 0.26%, Cr: 1.48%, P: 0.012%, S: 0.002%, Ni: 0.031%, Cu: 0.07%, Mo: 0.004%, Al: 0.012%, Ti: 0.0017%, Sn: 0.003%, Sb: 0.0001%, As: 0.008%, Pb: 0.0001, Ca: 0.0001, [O]: 0.0006%; the balance is Fe and unavoidable impurities.

[0045] The steps include: calculating the liquid core length of the continuous casting billet; determining the electromagnetic stirring process parameters; inspecting, hot-transporting or pit cooling the continuous casting billet; high-temperature heating and diffusion of the continuous casting billet; penetration of the rolling force center during the rolling process; and stacking and inspecting round steel.

[0046] (1) Calculation of the liquid core length of the continuous casting billet: Based on the chemical composition of GCr15 bearing steel (see the above chemical composition), the cross-section of the continuous casting billet is 220*220 mm, the superheat is 29°C, the pulling speed and continuous casting (see Table 4), and the cooling adopts a weak cooling method; specifically: water cooling in zone 1, air-water cooling in zones 2 and 3, where the water flow rates in zones 1, 2 and 3 are 38 L / min, 42 L / min and 21 L / min respectively; the proportion of molten steel in the billet is obtained, and the liquid core length of the continuous casting billet (the length of the billet from the molten steel surface in the crystallizer to the time when the molten steel is completely solidified) is calculated.

[0047] Table 4

[0048]

[0049] (2) Determination of electromagnetic stirring process parameters: The continuous casting is protected throughout the casting process, the liquidus temperature of GCr15 bearing steel is 1451℃, the molten steel inlet temperature is 1480℃, and the superheat range is 29-30℃; turn on the crystallizer vibration, cooling, electric stirring, and secondary cooling, and gradually reach the electromagnetic stirring position. The continuous casting billet pulling speed is 0.9m / min, and the crystallizer electromagnetic stirring is turned on at 6m, and the setting parameters are: 400A / 2Hz. The end electromagnetic stirring is turned on at 8.6m, and the setting parameters are: 500A / 10Hz; at this time, the proportion of molten steel inside the continuous casting billet is 35.6%, and the length of the liquid core of the continuous casting billet flowing through the end electromagnetic stirring point is 10.2m;

[0050] (3) Hot delivery or pit cooling of continuous casting billets: Sampling and testing of continuous casting billets are carried out. After passing the test, the continuous casting billets are directly hot delivered to the heating furnace, and the charging temperature is 600°C;

[0051] Table 5 Sampling test data

[0052]

[0053] (4) High-temperature heating and diffusion of continuous casting billets: The continuous casting billets are loaded into the heating furnace for heating, with the preheating section temperature at 680°C, the heating section temperature at 980°C, the heating section temperature at 1190°C, the soaking section temperature at 1200°C, the total heating time at 280 min, and the high-temperature section (heating section 2 and soaking section) time at 160 min, to ensure uniform burning through of the billet and high-temperature diffusion effect, so as to improve defects such as porosity, shrinkage, and segregation;

[0054] (5) The rolling force penetration in the core of the rolling process: After the continuous casting billet leaves the heating furnace, it is dephosphorized by high-pressure water before rolling (the dephosphorization pressure is 21 MPa). The low-speed rolling is adopted, and the finished product speed is reduced from the normal 1.2 m / s to 1.0 m / s to increase the unit rolling force. The rough rolling and water cooling after rough rolling are used to make the core temperature of the rolled material higher than the surface temperature, so as to facilitate the penetration of the rolling force into the core.

[0055] (6) Shearing, stacking and inspection of round steel: The starting shearing temperature of round steel is 505℃, and the stacking temperature is 372℃. After rapid collection at high temperature, the steel is slowly cooled in a cooling pit to prevent cracking at the end of the round steel, and samples are taken for inspection.

[0056] The bearing rings were inspected according to the delivery standards. The specific results are shown in Table 6. All the results are qualified.

[0057] Table 6

[0058]

[0059] Embodiment 3:

[0060] Ф76mm B350A grinding ball steel round steel production:

[0061] Chemical composition (mass percentage): C: 1.02%, Mn: 1.01%, Si: 0.27%, Cr: 0.70%, P: 0.015%, S: 0.003%, Ni: 0.023%, Cu: 0.014%, Mo: 0.012%, Al: 0.020%, Ti: 0.020%, V: 0.02%, Sn: 0.004%, [O]: 0.0009%, [N]: 0.0085%, [H]: 0.00013%; the balance is Fe and unavoidable impurities.

[0062] The steps include: calculating the liquid core length of the continuous casting billet; determining the electromagnetic stirring process parameters; inspecting, hot-transporting or pit cooling the continuous casting billet; high-temperature heating and diffusion of the continuous casting billet; penetration of the rolling force center during the rolling process; and stacking and inspecting round steel.

[0063] (1) Calculation of the liquid core length of the continuous casting billet: Based on the chemical composition of B350A grinding ball steel (see the above chemical composition), the cross-section of the continuous casting billet is 220*220 mm, the superheat is 25°C, the pulling speed and continuous casting (see Table 7), and the cooling adopts a weak cooling method; specifically: water cooling in zone 1, air-water cooling in zones 2 and 3, where the water flow rates in zones 1, 2 and 3 are 35 L / min, 40 L / min and 20 L / min respectively; the proportion of molten steel in the billet is obtained, and the liquid core length of the continuous casting billet (the length of the billet from the molten steel surface in the crystallizer to the time when the molten steel is completely solidified) is calculated.

[0064] Table 7

[0065]

[0066] (2) Determination of electromagnetic stirring process parameters: Continuous casting is protected throughout the casting process, the liquidus temperature of B350A grinding ball steel is 1448°C, the molten steel inlet temperature is 1472°C, and the superheat range is 24-26°C. Turn on the crystallizer vibration, cooling, electric stirring, and secondary cooling, and gradually reach the electromagnetic stirring position. The pulling speed of the continuous casting billet is 0.95m / min. The crystallizer electromagnetic stirring is turned on at 6m, and the setting parameters are: 400A / 2Hz. The end electromagnetic stirring is turned on at 8.6m, and the setting parameters are: 500A / 10Hz. At this time, the proportion of molten steel inside the continuous casting billet is 39.2%, and the length of the liquid core of the continuous casting billet flowing through the end electromagnetic stirring point is 11m.

[0067] (3) Hot delivery or pit cooling of continuous casting billets: The continuous casting billets are sampled and tested. After passing the test, the continuous casting billets are placed in a slow cooling pit for slow cooling. The slow cooling time is 37 hours and the cooling temperature after uncovering is 100°C.

[0068] Table 8 Sampling inspection data

[0069]

[0070]

[0071] (4) High-temperature heating and diffusion of continuous casting billets: The continuous casting billets are loaded into the heating furnace for heating, with the preheating section temperature at 720°C, the heating section temperature at 1050°C, the heating section temperature at 1195°C, the soaking section temperature at 1200°C, the total heating time at 290 min, and the high-temperature section (heating section 2 and soaking section) time at 170 min, to ensure uniform burning through of the billet and high-temperature diffusion effect, so as to improve defects such as porosity, shrinkage, and segregation;

[0072] (5) The core penetration of rolling force during the rolling process: After the continuous casting billet leaves the heating furnace, it is dephosphorized by high-pressure water before rolling (dephosphorization pressure 20 MPa). Low-speed rolling is adopted, and the finished product speed is reduced from the normal 1.2 m / s to 1.0 m / s to increase the unit rolling force. Rough rolling and water cooling after rough rolling are used to make the core temperature of the rolled material higher than the surface temperature, so as to facilitate the penetration of the rolling force into the core.

[0073] (6) Shearing, stacking and inspection of round steel: The starting shearing temperature of round steel is 510℃, and the stacking temperature is 375℃. After rapid collection at high temperature, the steel is slowly cooled in a cooling pit to prevent cracking at the end of the round steel, and samples are taken for inspection.

[0074] The inspection was carried out according to the delivery standard of grinding ball steel. The specific results are shown in Table 9. All the results are qualified.

[0075] Table 9

[0076] Inspection items Test results gas Oxygen content 9ppm; Nitrogen content 85ppm Carbon segregation index 1.0 Non-metallic inclusions Class A, B, C, D≤1.0 Austenite grain size 7.5 flaw detection GB / T 4162-2008 B grade, 100% qualified Low magnification Central porosity 1.0, general porosity 0.5, central segregation 1.0, ingot segregation 0, other defects none Total decarburized layer 0.2~0.3mm

[0077] Note: The above embodiments are only used to illustrate the present invention and are not intended to limit the technical solutions described in the present invention; therefore, although this specification has described the present invention in detail with reference to the above embodiments, a person skilled in the art should understand that the present invention can still be modified or replaced by equivalents; and all technical solutions and improvements thereof that do not depart from the spirit and scope of the present invention should be included in the scope of the claims of the present invention.

Claims

1. A method for producing low rolling ratio high carbon alloy round steel by continuous casting of small section square billets, characterized in that: The following steps are involved: According to the chemical composition of the high-carbon alloy round steel, the cross-sectional dimensions of the continuous casting billet, the superheat of the molten steel, the drawing speed, and the cooling conditions, the liquid metal ratio inside the continuous casting billet reaches a predetermined value of 25-40%, and the liquid core length at this time is the liquid core length of the continuous casting billet to be calculated; Based on the liquid core length of the continuous casting billet in step (1), according to the liquid core length of the molten steel in the continuous casting billet and the position information of the electromagnetic stirring, the electromagnetic stirring process parameters are set for processing; the electromagnetic stirring includes the crystallizer electromagnetic stirring and the end electromagnetic stirring; the crystallizer electromagnetic stirring parameter setting: the current is 250-400A, the frequency is 1-4Hz; the end electromagnetic stirring parameter setting: the current is 350-500A, the frequency is 8-12Hz; The continuous casting billet after the electromagnetic stirring treatment in step (2) is hot-sent to a heating furnace or placed in a slow cooling pit for slow cooling to obtain a treated continuous casting billet; the continuous casting billet is hot-sent to the heating furnace by a heat preservation vehicle, and the temperature of the hot-sent heating furnace is greater than 550°C; the slow cooling in the slow cooling pit is specifically as follows: the continuous casting billet is cooled in the slow cooling pit for a time of ≥36h, and the cooling temperature is ≤200°C; The continuously cast square billet treated in step (3) is placed in a heating furnace for heating, wherein the preheating temperature is ≤860°C, the first heating temperature is 900-1100°C, the second heating temperature is 1160-1230°C, the soaking temperature is 1160-1250°C, and the total heating time is ≥240 min, thereby obtaining a continuously cast square billet after heat treatment; The continuous casting billet after heat treatment in step (4) is dephosphorized by high-pressure water and then rolled, and the surface of the rolled piece is cooled by water after rough rolling and rough rolling to make the internal temperature of the rolled piece higher than the surface temperature, so that the rolling force penetrates into the core of the rolled piece, thereby obtaining a rolled round steel; Based on step (5), the rolled round steel is sheared, and after shearing, the round steel is quickly collected and packaged at high temperature, and then piled in a windproof place for cooling and inspection.

2. The method for producing low rolling ratio high carbon alloy round steel by continuous casting of small section square billets according to claim 1, characterized in that: The high carbon alloy round steel described in step (1) includes GCr15SiMn bearing steel, GCr15 bearing steel and B350A grinding ball steel.

3. The method for producing low rolling ratio high carbon alloy round steel by continuous casting of small section square billets according to claim 1, characterized in that: The cross-sectional size of the continuous casting billet in step (1) is 220*220mm; the superheat control requirement of the molten steel is 15-30°C; the casting speed of the continuous casting billet varies in the range of 0.80-0.95m / min, and the casting speed is constant throughout the entire process; the cooling adopts a weak cooling method, and the specific conditions are: water cooling in zone 1, air-water cooling in zones 2 and 3, wherein the water flow rates in zones 1, 2 and 3 are 34-38L / min, 38-42L / min and 18-21L / min, respectively.

4. The method for producing low rolling ratio high carbon alloy round steel by continuous casting of small section square billets according to claim 1, characterized in that: In step (2), the crystallizer electromagnetic stirring current is 400A and the frequency is 2 Hz; the end electromagnetic stirring current is 500A and the frequency is 10 Hz.

5. The method for producing low rolling ratio high carbon alloy round steel by continuous casting of small section square billets according to claim 1, characterized in that: The temperature of the hot delivery heating furnace in step (3) is 600°C; the slow cooling time of the slow cooling pit is 36-38h, and the cooling temperature is 100°C.

6. The method for producing low rolling ratio high carbon alloy round steel by continuous casting of small section square billets according to claim 1, characterized in that: In step (4), the continuous casting billet is heated and diffused at high temperature. The continuous casting billet is loaded into a heating furnace for heating. The preheating temperature is 680-750°C, the heating temperature is 980-1050°C, the heating temperature is 1190-1200°C, the soaking temperature is 1200-1210°C, and the total heating time is 280-300 min. This ensures that the billet is evenly burned through. When the temperature of the core of the billet is high, it is beneficial to improve defects such as looseness and shrinkage during rolling.

7. The method for producing low rolling ratio high carbon alloy round steel by continuous casting of small section square billets according to claim 1, characterized in that: In step (4), the continuous casting billet is heated and diffused at high temperature, wherein the temperature reaches 1180-1210°C, which is considered to be in the high temperature range, and the insulation time in the high temperature range is ≥150 minutes.

8. The method for producing low rolling ratio high carbon alloy round steel by continuous casting of small section square billets according to claim 7, characterized in that: The insulation time in the high temperature range is 160~175min.

9. The method for producing low rolling ratio high carbon alloy round steel by continuous casting of small section square billets according to claim 1, characterized in that: The dephosphorization pressure in step (5) is 20-22 MPa; the rolling is performed at a low speed, which refers to 75-85% of the rolling speed of medium-carbon low-alloy steel of the same specification, that is, the rolling speed for GCr15SiMn bearing steel is 1.0-1.1 m / s, the rolling speed for GCr15 bearing steel is 0.8-1.0 m / s, and the rolling speed for B350A grinding ball steel is 0.8-1.0 m / s.

10. The method for producing low rolling ratio high carbon alloy round steel by continuous casting of small section square billets according to claim 1, characterized in that: In step (6), the starting shearing temperature of the round steel is greater than 500°C, and the high temperature above 350°C is quickly collected and slowly cooled in a cooling pit to prevent cracking of the end of the round steel, and samples are taken for inspection.

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