High carbon steel 65mn hot-rolled steel plate and manufacturing method thereof

Abstract

The application discloses a high-carbon steel 65Mn hot-rolled steel plate and a manufacturing method thereof, and mainly solves the technical problem of deep decarburization and uneven structure and performance of the existing high-carbon steel 65Mn hot-rolled steel plate. The technical scheme is as follows: a high-carbon steel 65Mn hot-rolled steel plate, the chemical components of the high-carbon steel 65Mn hot-rolled steel plate are as follows: C: 0.64% to 0.70%, Si: 0.20% to 0.30%, Mn: 0.9% to 1.1%, P: less than or equal to 0.018%, S: less than or equal to 0.005%, Cr: 0.02% to 0.08%, N: less than or equal to 0.006%, Al: 0.010% to 0.050%, Ca: 0.0005% to 0.0040%, and the rest is iron and inevitable inclusions; the yield strength of the 2.3 to 8.0 mm thick hot-rolled steel plate is 460 to 680 MPa, and the single-side decarburization layer depth of the hot-rolled steel plate is less than or equal to 1.0% of the thickness of the steel plate; and the hot-rolled steel plate is mainly used in the field of tool steel such as saw blade steel.

Description

Technical Field

[0001] This invention relates to a hot-rolled high-carbon steel plate, and more particularly to a hot-rolled high-carbon steel 65Mn plate and its manufacturing method, belonging to the field of iron-based alloy technology. Background Technology

[0002] 65Mn is a steel grade in the Chinese standard GB / T 1222-2007, belonging to carbon-manganese steel for quenching and tempering. This grade of steel is characterized by high carbon content and high strength, while also requiring good toughness and plasticity. After appropriate heat treatment, it can achieve high hardness and good wear resistance, and is widely used in industries such as saw blades, hardware, household appliance parts, spring sheets, as well as in the automotive, railway, and electronics industries.

[0003] In the early stages, 65Mn steel was mostly produced using medium and small electric arc furnaces for smelting, followed by casting and then using an old-fashioned horizontal rolling mill. Currently, the advanced technology of converter smelting, ladle refining, continuous casting, and high-rigidity continuous rolling mills is widely adopted. With the rapid development of oxygen converter steelmaking technology, the proportion used for smelting alloy steel has gradually increased in recent years. However, in the process of producing high-carbon products using traditional hot rolling mills, there are problems such as deep decarburization (reaching 2.0% × steel plate thickness), uneven microstructure and properties leading to difficulties in uncoiling during subsequent annealing and cracking of the steel strip.

[0004] Chinese patent document CN101773930A discloses a method for producing 65Mn hot-rolled steel plates. The composition uses Ni, a precious alloying element, with a Ni content of ≤0.25%. The composition design is too broad, and the method is based on the production process of thin slab continuous casting and rolling.

[0005] Chinese patent document CN106702276A discloses a method for manufacturing 65Mn steel plate, which uses a common high-carbon manganese composition design without adding Cr and Ca elements, and does not disclose the technical indicators related to the control of hot rolling production process.

[0006] Chinese patent document CN111088458A discloses a hot-rolled pickled plate of medium and high carbon steel 65Mn and its production method. The composition is designed with low silicon and vanadium elements, with silicon and vanadium contents of 0.1-0.15% and 0.02-0.05%, respectively. Furthermore, the hot rolling process, such as coiling temperature control, uses a high coiling temperature design.

[0007] Chinese patent document CN103614628A discloses a method for manufacturing 65MnTiB steel and its hot-rolled steel plate. This patent mainly uses a composition design that adds Ti and B elements to the thickness of the steel plate above 8.0mm to improve the quenching hardness. The Ti and B contents are 0.005~0.025% and 0.0005~0.0050%, respectively, which increases the product manufacturing cost. In addition, the hot rolling process control, such as the coiling temperature, is designed to use a high coiling temperature.

[0008] Chinese patent document CN112430771A discloses a cold-rolled steel plate for precision stamping high-speed cutting chainsaw blades and its manufacturing method. The steel plate adopts a high carbon and low manganese design and uses precious alloying elements such as Ni and Mo. Its Ni and Mo contents are 0.2-0.4% and 0.05-0.25%, respectively, resulting in high manufacturing costs. Summary of the Invention

[0009] The purpose of this invention is to provide a hot-rolled high-carbon steel 65Mn steel plate and its manufacturing method, mainly solving the technical problems of deep decarburization and uneven microstructure and properties in existing hot-rolled high-carbon steel 65Mn steel plates. The hot-rolled steel plate of this invention is mainly used in the field of tool steels such as saw blades.

[0010] The technical concept of this invention is to reduce production costs, improve steel purity, and improve inclusion morphology by combining low-cost composition design with low carbon and manganese content, low sulfur, and calcium treatment, along with appropriate steelmaking process design. By matching the hot rolling heating process, hot rolling temperature, and slow cooling process, the decarburization degree of the hot-rolled steel plate surface is improved, resulting in uniform microstructure, good strength and toughness, and excellent comprehensive mechanical properties.

[0011] The technical solution adopted in this invention is a high-carbon steel 65Mn hot-rolled steel plate, the chemical composition by weight percentage of which is: C: 0.64%~0.70%, Si: 0.20%~0.30%, Mn: 0.9%~1.1%, P≤0.018%, S≤0.005%, Cr: 0.02%~0.08%, N≤0.006%, Al: 0.010%~0.050%, Ca: 0.0005%~0.0040%, with the remainder being iron and unavoidable inclusions.

[0012] The metallographic structure of the hot-rolled steel sheet of this invention is ferrite + pearlite, and the yield strength R of the 2.3-8.0 mm thick hot-rolled steel sheet is... eL The tensile strength is 460–680 MPa, and the tensile strength R is... m 800–1020 MPa; Elongation after fracture The content of inclusions in hot-rolled steel plates is 12% to 30%; the depth of the decarburized layer on one side of the hot-rolled steel plate is ≤1.0% × the thickness of the steel plate; according to the American Society for Testing and Materials (ASTM) E45-13 Standard Test Method for Determination of Inclusion Content in Steel, Method A is used to test the inclusions in hot-rolled steel plates, where inclusions of type A, B, and C are below grade 1.5, and inclusions of type D are below grade 0.5.

[0013] The reasons for limiting the chemical composition of the 65Mn hot-rolled steel sheet of the present invention to the above-mentioned range are as follows:

[0014] Carbon: Carbon is an element that affects the hardness of materials after annealing and quenching. If the carbon content is too low, the required hardness of the part will not be obtained after quenching; if the carbon content is too high, the material hardness will be too high, which is not conducive to subsequent stamping. The carbon content used in this invention is in the range of 0.64% to 0.70%.

[0015] Manganese: Manganese is a good deoxidizer and desulfurizer. A certain amount of manganese in steel can eliminate or reduce the hot brittleness caused by sulfur, thereby improving the hot working properties of the steel and increasing its hardenability. When the manganese content is high, the solid solution strengthening effect is significant, the strength is high, but the blanking performance decreases sharply, making it unsuitable for subsequent processing; this invention limits the Mn content to 0.9%–1.1%.

[0016] Silicon: Silicon is used as a deoxidizer in smelting and has certain deoxidation and desulfurization effects. However, excessive amounts can harden the ferrite phase, reduce processing performance, and cause rust-red iron oxide scale defects on the surface of steel coils during hot rolling, affecting the subsequent pickling surface. Therefore, it is advisable to control the SI content to the range of 0.20% to 0.30%.

[0017] Sulfur: Sulfur forms sulfide inclusions in steel, which reduces its ductility and toughness, and is detrimental to subsequent processing and forming. Therefore, this invention limits S to ≤ 0.005%.

[0018] Phosphorus: As an impurity element, phosphorus segregates at grain boundaries, which reduces processing performance. It is desirable to reduce its content as much as possible to improve molding performance. However, considering the controllability of process equipment and the cost of dephosphorization, this invention limits P to ≤ 0.018%.

[0019] Chromium: Chromium can increase the hardenability of steel and is a major alloying element for corrosion resistance and oxidation resistance; considering the cost of Cr, the Cr content is controlled at 0.02% to 0.08%;

[0020] Calcium: Calcium treatment can effectively improve the morphology of inclusions in steel, thereby effectively improving the processing and forming properties of steel plates. This invention limits the Ca content to 0.0005% to 0.0040%.

[0021] Aluminum: Aluminum acts as a deoxidizer and binds free nitrogen; as a strong deoxidizer, it reacts with oxygen in steel to form Al2O3, which is removed during steelmaking; in addition to combining with oxygen, aluminum also combines with nitrogen in steel to form compound AlN, preventing the coarsening of austenite grains. If the aluminum content is too high, excessive Al2O3 inclusions will form, which can easily clog the pouring nozzle during continuous casting; this invention limits the Al content to 0.010% to 0.050%.

[0022] Nitrogen: Excessive nitrogen content will severely deteriorate the plasticity and toughness of the material. This invention limits N to ≤ 0.0060%.

[0023] A method for manufacturing a hot-rolled high-carbon steel 65Mn sheet, the method comprising:

[0024] After refining in a ladle furnace and undergoing vacuum degassing, molten steel is continuously cast to obtain continuously cast slabs. The chemical composition of the molten steel by weight percentage is as follows: C: 0.64%–0.70%, Si: 0.20%–0.30%, Mn: 0.9%–1.1%, P≤0.018%, S≤0.005%, Cr: 0.02%–0.08%, N≤0.006%, Al: 0.010%–0.050%, Ca: 0.0005%–0.0040%, with the remainder being iron and unavoidable inclusions. The inclusion grade in the continuously cast slabs is controlled according to the American Society for Testing and Materials (ASTM) standard test method E45-13, "Standard Test Method for Determination of Inclusion Content in Steel," using Method A. Inclusions of grades A, B, and C are below grade 1.5, and inclusions of grade D are below grade 0.5.

[0025] The continuously cast slab is heated in a reducing atmosphere in a heating furnace with an excess air coefficient of 0.90–0.95. The slab is heated at 1180–1230℃ for 180–250 minutes before hot rolling. The hot rolling process is a two-stage rolling process: rough rolling consists of six passes, rolled above the austenite recrystallization temperature, with a finishing temperature of 1000–1050℃, and the intermediate slab thickness controlled at 36–42 mm; finish rolling consists of seven consecutive passes, rolled in the austenite single-phase region, with a finishing temperature of 880–920℃; after finish rolling, the steel plate thickness is controlled at 2.3–8.0 mm, and the steel plate crown is ≤35 μm; laminar cooling is achieved through front-stage cooling, and the hot-rolled steel coil is obtained at a coiling temperature of 590–640℃.

[0026] The hot-rolled steel coil is cooled slowly after being coiled, with a cooling rate of 3 to 6 °C / h to 200 °C.

[0027] Furthermore, the continuous casting slab drawing speed is 1.0 to 1.2 m / min, which yields excellent results.

[0028] The key technologies of this invention are mainly achieved through the rational control and matching of composition design, steelmaking, and hot rolling processes. Through simulation calculations and experimental verification, the Ar3 phase transformation temperature of the steel composition system of this invention is 733.5℃, and the Ar1 phase transformation temperature is 723.4℃. The hot rolling processes adopted in this invention are all based on the composition system of the steel of this invention and the phase transformation points calculated through simulation experiments.

[0029] The rationale for the production process adopted in this invention is as follows:

[0030] 1. Steel refining and continuous casting process settings,

[0031] The steel refining process employs a dual refining process: LF ladle furnace refining + RH vacuum furnace vacuum degassing. The continuous casting speed is controlled to regulate the inclusion grade in the continuously cast slab. The inclusion grade in the continuously cast slab is tested according to Method A of ASTM E45-13, the standard test method for determining inclusion content in steel. In this invention, the non-metallic inclusions in the continuously cast slab are ≤1.5 for categories A, B, and C, and ≤0.5 for category D. The continuous casting slab casting speed is set to 1.0–1.2 m / min.

[0032] 2. Setting the heating temperature, heating time, and heating atmosphere for continuously cast slabs.

[0033] The setting of heating temperature and time for continuously cast slabs not only ensures the full diffusion and solid solution of alloying elements such as C, Si, and Mn in the slab, the dissolution of coarse carbide particles, and the uniform distribution in the steel, but also controls the degree of oxidation and decarburization of the slab and the stability of subsequent production, especially thin-gauge rolling. Too low a temperature or too short a heating time will not meet these requirements. If the temperature is too high or the heating time is too long, the high carbon content in the steel will lead to severe oxidation and decarburization on the slab surface, which is detrimental to the final properties and surface quality of the strip steel, and also consumes energy. The setting of the heating atmosphere mainly controls the degree of oxidation and decarburization of the slab. Therefore, this invention sets the heating temperature of the continuously cast slab at 1180–1230℃, the heating time at 180–250 min, and uses a reducing atmosphere for heating, with an excess air coefficient controlled at 0.90–0.95.

[0034] 3. Setting the roughing rolling end temperature and intermediate billet thickness

[0035] The roughing rolling process needs to be controlled above the austenite recrystallization temperature. If the roughing rolling end temperature is too high, excessive secondary iron oxide scale will easily form, which is difficult to remove during the finishing rolling process, affecting the surface of the steel plate and its use by the user; if the roughing rolling end temperature is too low, it will affect the stability of subsequent finishing rolling of thin specifications. The roughing rolling end temperature of this invention is set at 1000℃~1050℃.

[0036] The thickness of the intermediate slab affects the final rolling temperature and finishing rolling load of the steel plate. If the intermediate slab thickness is too low, the strip temperature drop will be too large, resulting in an excessive reduction in the subsequent final rolling temperature and a low reduction ratio, which will affect the microstructure and properties of the strip. If the intermediate slab thickness is too high, it will increase the finishing rolling load and rolling stability. This invention sets the intermediate slab thickness to 36mm to 42mm.

[0037] 4. Setting the finishing temperature

[0038] The finishing rolling temperature setting of this invention has two functions. On the one hand, by rolling the material in the non-recrystallized austenite region, flat austenite grains with internal deformation bands are obtained, which are then transformed into fine ferrite grains during the subsequent laminar cooling process, thus reducing the effect of banded segregation. On the other hand, considering the high strength of this product and taking into account the impact of rolling load on the rolls, plate stability, and plate shape control, this invention sets the finishing rolling end temperature to 880-920℃.

[0039] 5. Setting the crown of hot-rolled steel plates

[0040] To ensure smooth subsequent uncoiling processing for users and to improve coil shape control, this invention sets the crown of the hot-rolled steel plate to ≤35μm;

[0041] 6. Setting the laminar flow cooling method after finishing rolling

[0042] This invention primarily considers that laminar cooling after finishing rolling can promote the rapid transformation of austenite into ferrite in the microstructure of the material after finishing rolling, resulting in refined grains, a uniform microstructure, and reduced banded segregation. Therefore, this invention adopts a front-stage cooling process for laminar cooling after finishing rolling.

[0043] 7. Setting the hot rolling coiling temperature

[0044] For high-carbon steel products, the setting of the coiling temperature mainly affects the microstructure and properties of the material. If the coiling temperature is too high, although it is beneficial to control the coil shape through phase transformation, it has a very negative impact on the decarburization and intergranular oxidation of the steel plate surface and the uniformity of the microstructure. If the coiling temperature is too low, the high strength after rolling will result in large residual stress, poor plate shape, and difficulty for users to perform subsequent cold working. Therefore, in order to ensure that the strength is not too high and the microstructure is uniform, and in order to further reduce the degree of surface oxidation and decarburization, this invention sets the hot rolling coiling temperature to 590-640℃.

[0045] 8. Setting the cooling rate of hot-rolled steel coils

[0046] The hot-rolled steel coil is transferred to the slow cooling wall to ensure slow cooling time, which can not only effectively improve the uniformity of microstructure and properties, but also reduce the steel plate and residual stress, improve the plate shape, and facilitate subsequent cold working by the user. The present invention sets the cooling rate of the hot-rolled steel coil to 200°C to be 3-6°C / h.

[0047] The metallographic structure of the hot-rolled steel sheet produced by the method of this invention is ferrite + pearlite. The yield strength R of the 2.3-8.0 mm thick hot-rolled steel sheet is... eL The tensile strength is 460–680 MPa, and the tensile strength R is... m 800–1020 MPa; Elongation after fracture The content of inclusions in hot-rolled steel plates is 12% to 30%; the depth of the decarburized layer on one side of the hot-rolled steel plate is ≤1.0% × the thickness of the steel plate; according to the American Society for Testing and Materials (ASTM) E45-13 Standard Test Method for Determination of Inclusion Content in Steel, Method A is used to test the inclusions in hot-rolled steel plates, where inclusions of type A, B, and C are below grade 1.5, and inclusions of type D are below grade 0.5.

[0048] Compared with existing technologies, this invention has the following positive effects: 1. By employing a composition design with carbon, manganese, and trace amounts of chromium, and through a coupled design of steelmaking and hot rolling processes, the inherent quality and microstructure of the product obtained by this invention meet the processing requirements of tool steels such as saw blade steel. 2. This invention, mainly through a low-cost composition design combining carbon and manganese content, low sulfur, and calcium treatment, along with a suitable steelmaking process design, not only reduces production costs but also improves steel purity and inclusion morphology, meeting the inherent requirements of users for high-quality products. 3. Through a process design that matches the hot rolling heating process, hot rolling temperature, and slow cooling process, this invention not only improves the degree of decarburization on the strip surface, meeting users' high-quality product requirements, but also produces uniform microstructure and properties, exhibiting uniform fine grain characteristics, good toughness, and excellent comprehensive mechanical properties, meeting the requirements of users for subsequent cold working. Attached Figure Description

[0049] Figure 1 This is a metallographic photograph of the hot-rolled steel plate of Embodiment 1 of the present invention.

[0050] Figure 2 This is a photograph of the decarburized layer of the hot-rolled steel plate in Embodiment 1 of the present invention. Detailed Implementation

[0051] The present invention will be further described below with reference to Examples 1 to 5, as shown in Tables 1 to 3.

[0052] Table 1 shows the chemical composition (by weight percentage) of the steel in the embodiments of the present invention, with the balance being Fe and unavoidable impurities.

[0053] Table 1 Chemical composition of steel in the embodiments of the present invention, unit: weight percentage.

[0054]

[0055]

[0056] Molten steel meeting basic chemical composition requirements is obtained through converter smelting. The steel is then refined in an LF ladle furnace and degassed under vacuum circulation in an RH vacuum furnace. Continuous casting yields slabs. The casting speed is 1.0–1.2 m / min. Inclusion grades in the slabs are controlled according to ASTM E45-13, a standard test method for determining inclusion content in steel, using Method A. Inclusions of grades A, B, and C are below grade 1.5, and inclusions of grade D are below grade 0.5. The slab thickness is 210–230 mm, width is 800–1630 mm, and length is 8500–11000 mm.

[0057] The slabs produced in steelmaking are sent to a heating furnace for heating, and after descaling, they are sent to a hot continuous rolling mill for rolling. The rolling is controlled by the roughing and finishing continuous rolling mills, and after laminar flow cooling, they are coiled. The laminar flow cooling adopts front-end cooling to produce qualified hot-rolled steel coils; the thickness of the hot-rolled steel plate is 2.3 to 8.0 mm; the hot rolling process control parameters are shown in Table 2.

[0058] Table 2 Hot rolling process control parameters of the present invention embodiments

[0059]

[0060] For hot-rolled steel sheets obtained using the above method, see [link to relevant documentation]. Figure 1 , Figure 2 The microstructure of hot-rolled steel sheet is ferrite + pearlite. The yield strength R of hot-rolled steel sheet with a thickness of 2.3–8.0 mm is... eL The tensile strength is 460–680 MPa, and the tensile strength R is... m 800–1020 MPa; Elongation after fracture The decarburization layer depth on one side of hot-rolled steel plate is ≤1.0% × plate thickness, ranging from 12% to 30%.

[0061] The hot-rolled steel plate obtained by this invention was sampled, and transverse specimens were taken for tensile and bending tests, and longitudinal specimens were taken for impact tests. Tensile tests were carried out in accordance with GB / T228.1-2010 Metallic Materials - Tensile Testing - Part 1: Test Method at Room Temperature; its mechanical properties are shown in Table 3.

[0062] Table 3 Performance indicators of hot-rolled steel plates in embodiments of the present invention

[0063]

[0064]

[0065] As shown in Table 3, the hot-rolled steel sheet obtained by the present invention has uniform microstructure, good toughness and excellent comprehensive mechanical properties, which meet the requirements of users for subsequent cold working.

[0066] In addition to the embodiments described above, the present invention may have other implementations. All technical solutions formed by equivalent substitution or equivalent transformation fall within the protection scope claimed by the present invention.

Claims

1. A high carbon steel 65Mn hot-rolled steel plate, having a chemical composition in weight percent of: C: 0.64% to 0.70%, Si: 0.20% to 0.30%, Mn: 0.9% to 1.1%, P≤0.018%, S≤0.005%, Cr: 0.02% to 0.08%, N≤0.006%, Al: 0.010% to 0.050%, Ca: 0.0005% to 0.0040%, and the balance being iron and unavoidable impurities; the hot-rolled steel plate having a microstructure of ferrite + pearlite, a yield strength R eL of 460 to 680 MPa, a tensile strength R m of 800 to 1020 MPa, and an elongation A of 12% to 30%; the hot-rolled steel plate having a single-side decarburized layer depth of ≤1.0% x the thickness of the steel plate; and a method of manufacturing the hot-rolled steel plate, comprising the steps of: The molten steel is continuously cast into a continuous casting slab after being refined by a ladle furnace and vacuum degassing treatment, and the chemical composition of the molten steel by weight percentage is: C: 0.64% to 0.70%, Si: 0.20% to 0.30%, Mn: 0.9% to 1.1%, P≤0.018%, S≤0.005%, Cr: 0.02% to 0.08%, N≤0.006%, Al: 0.010% to 0.050%, Ca: 0.0005% to 0.0040%, and the rest is iron and unavoidable inclusions; the inclusion level in the continuous casting slab is controlled, and the test is performed according to the ASTM E45-13 Standard Test Method for Determining the Amount of Inclusions in Steel by Method A, wherein the A-type, B-type and C-type inclusions are below level 1.5, and the D-type inclusion is below level 0.5; The continuous casting slab is heated in a heating furnace in a reducing atmosphere environment, the excess air coefficient is 0.90 to 0.95, the continuous casting slab is heated at 1180 to 1230℃ for 180 to 250 minutes, and then hot-rolled, the hot-rolling is a two-stage rolling process, the rough rolling is 6 passes, the rough rolling is performed above the austenite recrystallization temperature, the rough rolling end temperature is 1000 to 1050℃, and the intermediate slab thickness after the rough rolling is controlled to be 36 to 42mm; the finish rolling is 7 passes, the finish rolling is performed in the austenite single-phase zone, and the finish rolling end temperature is 880 to 920℃; after the finish rolling, the steel plate thickness is controlled to be 2.3 to 8.0mm, and the steel plate crown is ≤35μm; the laminar cooling is performed by front-stage cooling, and the hot-rolled steel coil is coiled at a coiling temperature of 590 to 640℃; The hot-rolled steel coil after coiling is slowly cooled, and the cooling speed of the hot-rolled steel coil to 200℃ is 3 to 6℃ / h.

2. A method of manufacturing a high carbon steel 65Mn hot-rolled steel sheet, characterized by, The method comprises the following steps: The molten steel is continuously cast into a continuous casting slab after being refined by a ladle furnace and vacuum degassing treatment, and the chemical composition of the molten steel by weight percentage is: C: 0.64% to 0.70%, Si: 0.20% to 0.30%, Mn: 0.9% to 1.1%, P≤0.018%, S≤0.005%, Cr: 0.02% to 0.08%, N≤0.006%, Al: 0.010% to 0.050%, Ca: 0.0005% to 0.0040%, and the rest is iron and unavoidable inclusions; the inclusion level in the continuous casting slab is controlled, and the test is performed according to the ASTM E45-13 Standard Test Method for Determining the Amount of Inclusions in Steel by Method A, wherein the A-type, B-type and C-type inclusions are below level 1.5, and the D-type inclusion is below level 0.5; The heating furnace heats the continuous casting slab in a reducing atmosphere environment, the excess air ratio is 0.90-0.95, the continuous casting slab is heated at 1180-1230 DEG C for 180-250 min, then hot-rolled, the hot-rolling is a two-stage rolling process, the rough rolling is 6 passes, rolled above the austenite recrystallization temperature, the rough rolling end temperature is 1000-1050 DEG C, the intermediate slab thickness after the rough rolling is controlled to be 36-42 mm; the finish rolling is 7 passes, rolled in the austenite single-phase region, the finish rolling end temperature is 880-920 DEG C; after the finish rolling, the steel plate thickness is controlled to be 2.3-8.0 mm, the steel plate crown is ≤35 μm; the laminar cooling uses front-stage cooling, the hot-rolled steel coil is coiled at a coiling temperature of 590-640 DEG C; The hot-rolled steel coil after coiling is slowly cooled, the cooling speed of the hot-rolled steel coil to 200 DEG C is 3-6 DEG C / h.

3. The method of producing a high carbon steel 65Mn hot-rolled steel sheet according to claim 2, characterized by, The continuous casting slab drawing speed is 1.0-1.2 m / min.

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