65Mn hot-rolled pickled steel plate for band saw and manufacturing method thereof

Abstract

The invention discloses a 65Mn hot-rolled pickled steel plate for a band saw and a manufacturing method of the 65Mn hot-rolled pickled steel plate. The technical problems that an existing band saw prepared from the 65Mn hot-rolled pickled steel plate is poor in abrasion resistance and short in service life are mainly solved. According to the technical scheme, the 65Mn hot-rolled pickled steel plate for the band saw comprises the following chemical components in percentage by weight: 0.65%-0.70% of C, 0.20%-0.30% of Si, 0.80%-1.10% of Mn, less than or equal to 0.020% of P, less than or equal to 0.005% of S, 0.01%-0.05% of Al, 0.10%-0.20% of Cr, 0.03%-0.05% of Nb, 0.0020%-0.0060% of N and the balance of Fe and inevitable impurity elements. The metallographic structure of the hot-rolled pickled steel plate comprises more than 95% of pearlite and ferrite by area fraction, and the pearlite block mass size is 15-30 microns.

Description

Technical Field

[0001] The present invention relates to a steel for band saws, and particularly to a 65Mn hot-rolled pickled steel plate for band saws and its manufacturing method. Specifically, it relates to a 65Mn hot-rolled pickled steel plate with a thickness of 2.7 - 5.0 mm for band saws and its manufacturing method, belonging to the technical field of iron-based alloys. Background Art

[0002] Carbon manganese steels generally have the characteristics of high hardness, easy cutting, and low price, and are widely used in saw blades and saw disks. In actual production, in order to further improve the hardness of products, most tool steels need to be quenched. Therefore, the hardenability of steel plates is also an important technical index for tool steel processing.

[0003] The hot-rolled pickled steel plate is processed into a finished band saw (saw blade) after cold rolling, annealing, quenching, and tempering. The performance of the finished band saw (saw blade) is directly related to the morphology, size, and precipitates of martensite after quenching and tempering.

[0004] 65Mn is one of the most widely used steels for band saws. In order to improve the hardenability, the prior art is to add about 0.2% of Cr element to the steel. On the one hand, the hardenability of the steel plate is significantly improved, and on the other hand, the hardness after quenching is also increased compared with the original product.

[0005] The service life of a band saw is an important factor in measuring the quality and economy of the band saw. For a band saw for cutting wood, its service life is generally between several hundred and several thousand hours. Except for external use conditions, the wear resistance of the band saw itself, that is, the volume wear rate per unit time, is an important factor in evaluating its service life. According to the standard test of GB / T 12444-2006 "Test Method for Wear of Metallic Materials - Ring-Block Sliding Wear Test", the volume wear rate of the existing 65Mn band saw is 1.4% - 1.6%. Although the hardness of the 65Mn steel added with Cr element after quenching has increased; the volume wear rate has dropped to 1.6% - 1.8%, and the wear resistance of the band saw has decreased instead, and the service life of the product has not been significantly improved. Therefore, the existing 65Mn and 65Mn added with trace amounts of Cr can only improve the hardness and hardenability of the band saw after heat treatment to a certain extent, and there is no improvement in the service life of the band saw.

[0006] The Chinese patent application with the application publication number CN114058951A discloses a 65Mn saw blade steel and its preparation method. By the compound addition of Sb, Ni, and Si, Sb blocks the movement path of oxygen ions and carbon ions, Ni increases the solubility of Sb element in the steel grade and raises the melting point of the eutectic product, and Si reduces the surface hot brittleness sensitivity and reduces the crack growth rate, thereby solving the problems of decarburization and edge cracking. However, the addition of Ni easily forms a network structure in the base layer of the scale, resulting in a significant decrease in the interface flatness, thus greatly increasing the pickling difficulty.

[0007] The Chinese patent application with the publication number CN103614628A discloses a 65MnTiB steel and a manufacturing method thereof for hot-rolled steel plates. Aiming at the problem that it is difficult to harden through for steel plates with a thickness of 8 - 14 mm, B is added to improve hardenability, but this increases the risk of corner cracking of the slab, and the small amount of network ferrite formed will affect the plasticity of the steel plate.

[0008] The martensite structure obtained after quenching the existing 65Mn hot-rolled pickled steel plate is coarse, with a lath size of 15 - 30 μm. Although the steel plate with this composition and hot-rolled structure can meet the basic requirements during the production and use of ordinary band saws, the wear resistance of the band saw is poor, the service life is low, and the use cost of the band saw is high. Summary of the Invention

[0009] The purpose of the present invention is to provide a 65Mn hot-rolled pickled steel plate for band saws and a manufacturing method thereof, mainly solving the technical problems of poor wear resistance and low service life of the band saw prepared from the existing 65Mn hot-rolled pickled steel plate.

[0010] The technical idea of the present invention is that through appropriate addition of Nb in 65Mn steel and control of the hot-rolling process, the metallographic structure of the obtained hot-rolled pickled steel plate includes pearlite + ferrite with an area fraction of more than 95%, and the pearlite colony size is 15 - 30 μm; when the steel plate with this structure is subjected to high-temperature quenching, small acicular martensite lath structures with a size of 8 - 15 μm and high-hardness NbC and NbCN precipitates can be formed, so as to achieve the purpose of reducing the volume wear rate of the 65Mn band saw, improving wear resistance, and extending the service life of the product.

[0011] The technical solution adopted by the present invention is a 65Mn hot-rolled pickled steel plate for band saws, and its chemical composition by weight percentage is: C: 0.65% - 0.70%, Si: 0.20% - 0.30%, Mn: 0.80% - 1.10%, P ≤ 0.020%, S ≤ 0.005%, Al: 0.01% - 0.05%, Cr: 0.10% - 0.20%, Nb: 0.03% - 0.05%, N: 0.0020% - 0.0060%, and the balance is Fe and unavoidable impurity elements.

[0012] The metallographic structure of the hot-rolled pickled steel plate of the present invention includes pearlite + ferrite with an area fraction of more than 95%, and the pearlite colony size is 15 - 30 μm; for the hot-rolled pickled steel plate with a thickness of 2.7 - 5.0 mm, the yield strength R p0.2 is 570 - 700 MPa, and the tensile strength R m is 900 - 1100 MPa, and the elongation after fracture is 13% - 20%.

[0013] The hot-rolled pickled steel sheet of the present invention is annealed, cold-rolled to the thickness of the finished band saw, quenched, tempered, and cut to obtain the finished band saw; the quenching temperature is 880 - 900 °C, the quenching holding time is 20 - 30 min, the metallographic structure of the cold-rolled steel sheet after quenching is acicular martensite, the martensite lath size is 8 - 15 μm, and the Vickers hardness of the cold-rolled steel sheet after quenching is 780 - 820 HV1; the tempering temperature is 400 - 450 °C, the tempering holding time is 20 - 30 min, the metallographic structure of the cold-rolled steel sheet after tempering is tempered sorbite, and the Vickers hardness of the cold-rolled steel sheet after tempering is 390 - 410 HV1.

[0014] The wear experiment of the finished band saw prepared from the hot-rolled pickled steel sheet of the present invention is carried out according to GB-T12444-2006 "Test Ring-Block Sliding Wear Test for Metal Materials Wear Test Method", and the volume wear rate of the finished band saw is 1.2% - 1.3%.

[0015] The reasons for limiting the chemical composition of the 65Mn hot-rolled pickled steel sheet for the band saw of the present invention within the above range are as follows:

[0016] C: Carbon is the main element affecting the strength and hardness of the steel sheet after quenching. When the carbon content is low, the hardenability of the steel sheet is poor, and the hardness after heat treatment is low. However, when the C content is too high, the surface decarburization tendency increases, and the surface hardenability will be affected to a certain extent. The present invention sets C to 0.65% - 0.70%.

[0017] Si: It has a strong solid solution strengthening effect. At the same time, since it significantly reduces the critical cooling rate of the steel, it can improve the hardenability of the steel. However, Si is easy to form iron silicate scale on the surface of the steel sheet during hot rolling, increasing the difficulty of pickling. Considering the product performance requirements and production manufacturing process capabilities, the present invention sets Si to 0.20% - 0.30%.

[0018] Mn: Manganese is one of the most effective elements to improve hardenability, and it is also a solid solution strengthening element. At the same time, with an appropriate ratio with silicon, it can reduce the decarburization phenomenon caused by silicon. However, too high a manganese content is likely to cause slab segregation, affecting the tissue uniformity of the hot-rolled sheet. The present invention sets Mn to 0.80% - 1.10%.

[0019] S, P: They are impurity elements in the steel, and the content should be as low as possible. At the same time, S is easy to form MnS in the steel, affecting the fatigue performance. Considering economy and feasibility, the present invention sets S ≤ 0.005%; P ≤ 0.020%.

[0020] Al: An element that forms strong oxidants, which can effectively reduce oxide inclusions in steel and purify the steel quality. However, at the same time, the formed Al2O3 particles are relatively large and not plastic, and it is difficult to deform during processing and use, resulting in stress concentration, which will have a certain impact on the fatigue strength of the band saw. Considering the production feasibility and product usage requirements, the present invention sets the content of Al to be 0.01% - 0.05%.

[0021] N: Significantly delays the austenite crystallization during quenching, controls the martensite size after quenching, and at the same time forms fine nitrides and carbonitrides with Nb in the steel, significantly improving the wear resistance of the band saw. However, the content of N cannot be too high to prevent possible secondary precipitation during the tempering process, which may lead to a decrease in the toughness of the steel. Therefore, the present invention limits the content of N to be 0.0020% - 0.0060%.

[0022] Cr: An element that can significantly improve the hardenability. At the same time, it is a strong carbide-forming element, which can strongly prevent the diffusion of carbon in austenite, thus reducing the carbon diffusion coefficient and the decarburization tendency. However, too high a content of Cr will increase the difficulty of hot rolling. Considering the product feasibility, the present invention limits the content of Cr to be 0.10% - 0.20%.

[0023] Nb: A strong carbide-forming element, and it can form Nb-containing carbonitrides with N to form fine precipitates. On the one hand, it delays the austenite crystallization and controls the lath size of martensite after quenching. On the other hand, the high-hardness precipitates are dispersed in the martensite matrix, greatly improving the wear resistance of the band saw blade, thus significantly extending its service life. However, the content of Nb cannot be too high, otherwise the strong grain refinement strengthening of the steel plate will make the strength of the steel plate too high, increase the hot rolling load, and increase the production difficulty of thin-gauge products. Considering the above factors, the present invention limits the content of Nb to be 0.03% - 0.05%.

[0024] A production method of a 65Mn hot-rolled pickled steel plate for band saws, comprising the following steps:

[0025] The molten steel is continuously cast to obtain a continuously cast slab, and the weight percentages of the chemical components of the molten steel are: C: 0.65% - 0.70%, Si: 0.20% - 0.30%, Mn: 0.80% - 1.10%, P ≤ 0.020%, S ≤ 0.005%, Al: 0.01% - 0.05%, Cr: 0.10% - 0.20%, Nb: 0.03% - 0.05%, N: 0.0020% - 0.0060%, and the balance is Fe and inevitable impurity elements;

[0026] The continuous casting slab is hot-rolled after being heated in a heating furnace. The continuous casting slab enters the heating furnace by means of hot charging and hot delivery. The temperature of the continuous casting slab entering the heating furnace is ≥400°C. The air excess coefficient in the heating furnace is 0.95 - 1.00. The heating temperature of the continuous casting slab is 1200 - 1240°C, and the heating time is 180 - 240 min. The hot rolling is a two-stage rolling process. The rough rolling is 6-pass continuous rolling, which is carried out above the austenite recrystallization temperature. The finishing temperature of the rough rolling is 1000 - 1050°C. After rough rolling, the thickness of the intermediate slab is 36 - 38 mm. The finish rolling is 7-pass continuous rolling, and the finish rolling temperature is 880 - 920°C. After finish rolling, the thickness of the steel plate is 2.7 - 5.0 mm. The laminar flow cooling adopts front-section cooling. The hot-rolled steel coil is coiled when the coiling temperature is 620 - 660°C.

[0027] The hot-rolled steel coil after coiling is slowly cooled. The cooling rate of the hot-rolled steel coil when it is cooled to 200°C is 4 - 8°C / h.

[0028] After the hot-rolled steel coil is uncoiled again, it is pickled, rinsed, dried, and oiled, and then coiled to obtain the finished hot-rolled pickled steel plate.

[0029] The reasons for the production process adopted in the present invention are as follows:

[0030] 1. Setting of the temperature of the continuous casting slab entering the heating furnace, the heating temperature of the continuous casting slab, and the heating time

[0031] Due to the high carbon and alloy content of the steel in the present invention, rapid heating from the cold state will generate certain thermal stress, causing deformation or cracking of the continuous casting slab. Therefore, it is generally required that the continuous casting slab enters the furnace in a hot state after cutting. The continuous casting slab enters the heating furnace by means of hot charging and hot delivery, and the temperature of the continuous casting slab entering the heating furnace is ≥400°C.

[0032] After the continuous casting slab enters the heating furnace, it gradually austenitizes as the temperature rises, which can significantly improve various composition and structure segregations brought about during the solidification process of the slab. Generally speaking, the higher the heating temperature and the longer the holding time, the better the composition and structure uniformity. However, due to the high carbon content, the decarburization tendency will increase during the heating process, and the depth of the decarburized layer will increase accordingly, which is not conducive to the surface quality. Therefore, considering the cost and operability comprehensively, the heating temperature of the continuous casting slab in this application is set at 1200 - 1240°C, and the heating time is 180 - 240 min. In addition, the atmosphere in the heating furnace also has a certain influence on decarburization. The air excess coefficient in this application is set at 0.95 - 1.00.

[0033] 2. Setting of the finish rolling temperature, laminar flow cooling method, laminar flow cooling rate, laminar flow cooling end temperature, and coiling temperature

[0034] The finish rolling temperature is generally set to ensure that the entire slab is fully rolled in the austenite region and avoid mixed crystals caused by rolling in the two-phase region at the end of rolling. The finish rolling temperature in this application is set at 880 - 900°C.

[0035] The setting of the laminar cooling rate after rolling and the coiling temperature mainly considers the requirements for the final microstructure of the steel plate. At the same time, it also has a certain influence on the thickness and structure of the scale on the hot-rolled steel plate. For this application, the final metallographic structure of the steel plate is pearlite. A relatively low coiling temperature can obtain relatively fine pearlite, which is beneficial for the spheroidizing annealing before rolling by the user. At the same time, the scale is thinner and is not prone to eutectoid reaction during the subsequent slow cooling stage, which is beneficial for pickling. However, the coiling temperature cannot be too low, otherwise the strength of the steel plate is too high, which is not conducive to subsequent processing and production. In this application, the laminar cooling is set to use front-section cooling; the hot-rolled steel coil is coiled when the coiling temperature is 620 - 660 °C.

[0036] 3. Setting of the cooling rate of the hot-rolled steel coil

[0037] The formulation of the cooling process for high-carbon steel mainly considers the phase transformation and microstructure uniformity during the subsequent gradual cooling process after the steel plate is coiled. Research shows that when the cooling rate ≤ 7 °C / s, the proportion of ferrite increases, which may affect the hardenability. If the cooling rate is too fast, the pearlite lamellar spacing is refined, the strength increases, and the plasticity decreases. At the same time, too fast a cooling rate will also cause non-uniformity of the internal structure of the steel coil to varying degrees. Therefore, the cooling process setting of this application requires that the steel coil enter the slow-cooling wall or slow-cooling hood for cooling as soon as possible after coiling, and the cooling rate of the hot-rolled steel coil cooled to 200 °C is 4 - 8 °C / h.

[0038] The metallographic structure of the hot-rolled pickled steel plate produced by the method of the present invention includes pearlite + ferrite with an area fraction of more than 95%, and the pearlite colony size is 15 - 30 μm; the yield strength R p0.2 of the hot-rolled pickled steel plate with a thickness of 2.7 - 5.0 mm is 570 - 700 MPa, and the tensile strength R m is 900 - 1100 MPa, and the elongation after fracture is 13% - 20%.

[0039] The hot-rolled pickled steel plate produced by the method of the present invention is annealed, cold-rolled to the thickness of the finished band saw, quenched, tempered, and cut to obtain the finished band saw; the quenching temperature is 880 - 900 °C, the quenching holding time is 20 - 30 min, the metallographic structure of the cold-rolled steel plate after quenching is acicular martensite, the martensite lath size is 8 - 15 μm, and the Vickers hardness of the cold-rolled steel plate after quenching is 780 - 820 HV1; the tempering temperature is 400 - 450 °C, the tempering holding time is 20 - 30 min, the metallographic structure of the cold-rolled steel plate after tempering is tempered sorbite, and the Vickers hardness of the cold-rolled steel plate after tempering is 390 - 410 HV1.

[0040] The finished band saw prepared from the hot-rolled pickled steel sheet produced by the method of the present invention was subjected to a wear test in accordance with GB-T12444-2006 "Test Ring-Block Sliding Wear Test for Metal Materials Wear Test Methods", and the volumetric wear rate of the finished band saw was 1.2% - 1.3%.

[0041] The present invention has the following positive effects compared with the prior art: 1. By adding an appropriate amount of Nb to 65Mn steel, the present invention not only meets the hardness requirements for the processing and use of 65Mn for band saws, but also significantly improves the wear resistance of the band saw. The volumetric wear rate of the band saw is reduced from the existing 1.4% - 1.6% to 1.2% - 1.3%, and the service life of the band saw is increased by more than 10%. 2. Through the composite composition design of appropriately reducing Cr and adding a small amount of Nb, the present invention effectively solves the problem that although the addition of a single Cr can improve hardenability, the wear resistance of the product is significantly reduced. The volumetric wear rate of the single Cr addition is reduced from the existing 1.6% - 1.8% to 1.2% - 1.3%, achieving a dual improvement in hardenability and wear resistance. Brief Description of the Drawings

[0042] Figure 1 It is a metallographic structure photograph of the hot-rolled pickled steel sheet of Example 1 of the present invention.

[0043] Figure 2 It is a metallographic structure photograph of the cold-rolled steel sheet obtained by annealing, cold-rolling the hot-rolled pickled steel sheet of Example 1 of the present invention to the thickness of the finished saw blade, and quenching. The quenching temperature is 890 °C, and the quenching holding time is 25 min.

[0044] Figure 3 It is a metallographic structure photograph of the cold-rolled steel sheet obtained by annealing, cold-rolling the hot-rolled pickled steel sheet of Example 1 of the present invention to the thickness of the finished saw blade, quenching, and tempering. The quenching temperature is 890 °C, the quenching holding time is 25 min, the tempering temperature is 430 °C, and the tempering holding time is 25 min. Detailed Embodiments

[0045] The present invention will be further described below in conjunction with Examples 1 - 5, as shown in Tables 1 - 8.

[0046] Table 1 shows the chemical composition (by weight percentage) of the examples of the present invention, and the balance is Fe and unavoidable impurities.

[0047] Table 1 shows the chemical composition of the steel in the examples of the present invention, unit: weight percentage.

[0048]

[0049] The molten steel meeting the requirements of chemical composition is obtained through converter smelting. The molten steel is treated by blowing Ar during the refining process in the LF ladle furnace, and vacuum circulating degassing treatment and composition fine-tuning are carried out in the RH furnace. The molten steel is continuously cast into a continuous casting slab under the protection of blowing Ar throughout the process; the thickness of the continuous casting slab is 210 - 230 mm, the width is 800 - 1300 mm, and the length is 5000 - 10000 mm.

[0050] The continuous casting slab is directly sent to the heating furnace for heating, and the hot charging and hot sending method is adopted when the continuous casting slab enters the heating furnace; after being heated by the heating furnace, the continuous casting slab is hot-rolled. The said hot rolling is a two-stage rolling process, controlled by the rough rolling and finish rolling continuous rolling mills, and coiled after laminar cooling. The laminar cooling adopts front-section cooling to produce qualified hot-rolled steel coils. The thickness of the hot-rolled steel plate is 2.7 - 5.0 mm; the process control parameters of the heating furnace are shown in Table 2; the process control parameters of the hot rolling are shown in Table 3.

[0051] Table 2 Process control parameters of the heating furnace in the embodiment of the present invention

[0052]

[0053] Table 3 Process control parameters of the hot rolling in the embodiment of the present invention

[0054]

[0055] The coiled hot-rolled steel coil is transferred to a slow cooling hood for slow cooling. The process control parameters of the slow cooling of the hot-rolled steel coil are shown in Table 4.

[0056] Table 4 Process control parameters of the slow cooling of the hot-rolled steel coil in the embodiment of the present invention

[0057] Slow cooling parameters Temperature entering the slow cooling hood / °C Temperature leaving the slow cooling hood / °C Cooling rate / °C / h The present invention 550-600 100-200 4-8 Example 1 555 180 7.9 Example 2 585 175 6.8 Example 3 565 145 7.9 Example 4 575 155 4.4 Example 5 595 140 5.6

[0058] For the hot-rolled pickled steel plate obtained by the above method, see Figure 1 , the metallographic structure of the hot-rolled pickled steel plate includes pearlite + ferrite with an area fraction of more than 95%, and the pearlite colony size is 15 - 30 μm; the yield strength R p0.2 of the hot-rolled pickled steel plate with a thickness of 2.7 - 5.0 mm is 570 - 700 MPa, the tensile strength R m is 900 - 1100 MPa, and the elongation after fracture is 13% - 20%.

[0059] The hot-rolled pickled steel plate obtained by the present invention is subjected to a tensile test in accordance with "GB / T228.1-2010 Metallic materials - Tensile testing - Part 1: Method of test at room temperature", and its mechanical property parameters are shown in Table 5.

[0060] Table 5 Mechanical properties of the hot-rolled pickled steel plate in the embodiment of the present invention

[0061]

[0062] The hot-rolled pickled steel plate of the present invention is annealed, cold-rolled to the thickness of the finished band saw, quenched, tempered, and cut to obtain a finished band saw; Figure 2 The metallographic structure of the cold-rolled steel plate after quenching is acicular martensite. The Vickers hardness of the cold-rolled steel plate after quenching is shown in Table 6; Figure 3 The metallographic structure of the cold-rolled steel plate after tempering is tempered bainite. The Vickers hardness of the cold-rolled steel plate after tempering is shown in Table 7.

[0063] Table 6 Hardness parameters of cold-rolled steel sheets obtained by annealing, cold rolling and quenching the steel sheets according to the embodiment of the present invention

[0064] Performance indicators Quenching temperature / °C Holding time / min Vickers hardness of the cold-rolled steel sheet after quenching / HV1 The present invention 880-900 20-30 780-820 Example 1 890 25 798 Example 2 890 25 815 Example 3 890 25 808 Example 4 890 25 803 Example 5 890 25 785

[0065] Table 7 Hardness parameters of cold-rolled steel sheets obtained by annealing, cold rolling, quenching and tempering of the steel sheets according to the embodiment of the present invention

[0066]

[0067] The finished band saw made of the hot-rolled pickled steel plate of the present invention was subjected to a wear test according to GB-T12444-2006 "Metallic material wear test method test ring-test block sliding wear test". The volume wear rate of the finished band saw is shown in Table 8.

[0068] Table 8 Volume wear rate parameters of finished band saws made of steel plates according to the present invention

[0069]

[0070]

[0071] As shown in Table 8, the volume wear rate of the finished band saw made of the hot-rolled pickled steel plate of the present invention is 1.2% to 1.3%, which is 1.4% to 1.6% of the existing band saw, and the service life of the band saw is increased by more than 10%.

[0072] In addition to the above embodiments, the present invention may also have other implementations. Any technical solution formed by equivalent replacement or equivalent transformation falls within the scope of protection required by the present invention.

Claims

1. A 65Mn hot-rolled pickled steel sheet for band saws, with the following chemical composition by weight percentage: C: 0.65% - 0.70%, Si: 0.20% - 0.30%, Mn: 0.80% - 1.10%, P ≤ 0.020%, S ≤ 0.005%, Al: 0.01% - 0.05%, Cr: 0.10% - 0.20%, Nb: 0.03% - 0.05%, N: 0.0020% - 0.0060%, and the balance being Fe and inevitable impurity elements; the metallographic structure of the hot-rolled pickled steel sheet includes pearlite + ferrite with an area fraction of more than 95%, and the pearlite colony size is 15 - 30 μm; the yield strength R p0.2 of the hot-rolled pickled steel sheet with a thickness of 2.7 - 5.0 mm is 570 - 700 MPa, and the tensile strength R m is 900 - 1100 MPa, and the elongation after fracture is 13% - 20%.

2. The 65Mn hot-rolled pickled steel sheet for band saw as described in claim 1 is characterized in that, The hot-rolled pickled steel sheet is annealed, cold-rolled to the thickness of the finished band saw, quenched, tempered, and cut to obtain the finished band saw; the quenching temperature is 880 - 900 °C, the quenching holding time is 20 - 30 min, the metallographic structure of the cold-rolled steel sheet after quenching is acicular martensite, the martensite lath size is 8 - 15 μm, and the Vickers hardness of the cold-rolled steel sheet after quenching is 780 - 820 HV1; the tempering temperature is 400 - 450 °C, the tempering holding time is 20 - 30 min, the metallographic structure of the cold-rolled steel sheet after tempering is tempered sorbite, and the Vickers hardness of the cold-rolled steel sheet after tempering is 390 - 410 HV1; the volumetric wear rate of the finished band saw is 1.2% - 1.3%.

3. The manufacturing method of the 65Mn hot-rolled pickled steel sheet for band saws as described in claim 1, characterized in that, It includes the following steps: The molten steel is continuously cast to obtain a continuous casting slab. The weight percentages of the chemical components of the molten steel are: C: 0.65% - 0.70%, Si: 0.20% - 0.30%, Mn: 0.80% - 1.10%, P ≤ 0.020%, S ≤ 0.005%, Al: 0.01% - 0.05%, Cr: 0.10% - 0.20%, Nb: 0.03% - 0.05%, N: 0.0020% - 0.0060%, and the balance is Fe and inevitable impurity elements. The continuous casting slab is hot-rolled after being heated in a heating furnace. The continuous casting slab is fed into the heating furnace in a hot charging and hot sending manner. The temperature of the continuous casting slab entering the heating furnace is ≥ 400 °C, the air excess coefficient in the heating furnace is 0.95 - 1.00, the heating temperature of the continuous casting slab is 1200 - 1240 °C, and the heating time is 180 - 240 min; the hot rolling is a two-stage rolling process. The rough rolling is 6-pass continuous rolling, rolled above the austenite recrystallization temperature, and the rough rolling end temperature is 1000 - 1050 °C; the thickness of the intermediate slab after rough rolling is 36 - 38 mm; the finish rolling is 7-pass continuous rolling, and the finish rolling end temperature is 880 - 920 °C; after finish rolling, the thickness of the steel sheet is 2.7 - 5.0 mm; laminar cooling adopts front-stage cooling; the hot-rolled steel coil is coiled when the coiling temperature is 620 - 660 °C. The coiled hot-rolled steel coil is slowly cooled, and the cooling rate of the hot-rolled steel coil cooled to 200 °C is 4 - 8 °C / h. After the hot-rolled steel coil is uncoiled again, it is pickled, rinsed, dried, and oiled, and then coiled to obtain the finished hot-rolled pickled steel sheet.

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