Ultra-thin frame saw blade with 75cr1 cold-rolled steel strip and its production method

Abstract

This application provides a 75Cr1 cold-rolled steel strip for ultra-thin frame saw blades and its production method. The production method includes the following steps: pickling a hot-rolled steel coil, spheroidizing annealing, at least two sets of cold rolling-recrystallization annealing, and leveling treatment to obtain the 75Cr1 cold-rolled steel strip for ultra-thin frame saw blades; wherein the hot-rolled steel coil comprises the following components by mass percentage: C: 0.72–0.80%, Si: 0.20–0.45%, Mn: 0.60–0.90%, Cr: 0.30–0.60%, P: ≤0.015%, S: ≤0.005%; the remainder being Fe and unavoidable impurities; optionally, the hot-rolled steel coil has a size of 3.5–4.5 mm × 1000–1450 mm, and the metallographic structure of the hot-rolled steel coil comprises 100% pearlite by volume percentage. This application describes a method for producing 75Cr1 cold-rolled steel strips for ultra-thin frame saw blades by adjusting parameters. The 75Cr1 cold-rolled steel coils produced using this method can be used to manufacture 1.0-1.5mm ultra-thin marble frame saw blades. The steel strips have very fine and uniform grain and carbide particle sizes, high dimensional accuracy, and narrow-range fluctuations in mechanical properties.

Description

Technical Field

[0001] This application relates to the field of alloy tool steel manufacturing technology, specifically to 75Cr1 cold-rolled steel strip for ultra-thin frame saw blades and its production method. Background Technology

[0002] Frame saw blades are essential tools for producing marble slabs for large buildings such as train stations, airports, plazas, and libraries. 75Cr1 cold-rolled steel strip is one of the main raw materials used in producing marble frame saw blades. Currently, the main thicknesses of this raw material demanded domestically and internationally are 2.5mm, 2.0mm, and 1.8mm, used to produce frame saw blades of these thicknesses. To reduce stone waste during the sawing of large stone blocks and improve the yield and economic efficiency, thinner frame saw blades, such as 1.5mm, 1.2mm, and 1.0mm, can be used.

[0003] However, the quality requirements for cold-rolled raw materials for ultra-thin saw blades are significantly higher than those for the original 2.5mm, 2.0mm, and 1.8mm materials. The original process for producing thick 75Cr1 cold-rolled steel strips can no longer meet the requirements for ultra-thin steel strips. Products produced by the original process have problems such as large spheroidized grains and carbide particles, insufficient dimensional accuracy, large fluctuation range of mechanical properties, and insufficient stiffness and toughness of saw blades after heat treatment. Summary of the Invention

[0004] This application provides a method for producing 75Cr1 cold-rolled steel strip for ultra-thin frame saw blades, aiming to improve rigidity and toughness.

[0005] In a first aspect, embodiments of this application provide a method for producing 75Cr1 cold-rolled steel strip for ultra-thin frame saw blades, comprising the following steps:

[0006] Hot-rolled steel coils are pickled, spheroidized annealed, subjected to at least two sets of cold rolling-recrystallization annealing, and leveled to obtain 75Cr1 cold-rolled steel strip for ultra-thin frame saw blades.

[0007] The hot-rolled steel coil comprises the following components by mass percentage: C: 0.72–0.80%, Si: 0.20–0.45%, Mn: 0.60–0.90%, Cr: 0.30–0.60%, P: ≤0.015%, S: ≤0.005%; the remainder being Fe and unavoidable impurities; optionally, the hot-rolled steel coil has a size of 3.5–4.5 mm × 1000–1450 mm, and the metallographic structure of the hot-rolled steel coil comprises 100% pearlite by volume percentage;

[0008] The spheroidizing annealing process includes: freely heating the pickled hot-rolled steel coil from room temperature to 200℃; annealing using two holding platforms during the heating process, heating the hot-rolled steel coil to 450℃ and holding for 2 hours; then heating to 650℃ and holding for 2 hours; then heating to 720-740℃ and holding for 15-18 hours; after holding, slowly cooling to 600℃; then air cooling to 400℃; and finally water cooling to 100℃ before unloading from the furnace.

[0009] The cold rolling-recrystallization annealing process includes: cold rolling at least two passes per rolling cycle to obtain cold-rolled steel strip, with a total reduction of 40-60% per rolling cycle; freely heating the cold-rolled steel strip from room temperature to 200°C; annealing using two holding platforms during the heating process to ensure uniform temperature of the steel coil; heating the cold-rolled steel strip to 450°C and holding for 2 hours; reheating to 600°C and holding for 2 hours; then heating to 680-700°C and holding for 10-14 hours; slowly cooling to 600°C after holding; switching to air cooling to 400°C; and finally water cooling to 100°C before unloading from the furnace.

[0010] According to an embodiment of the first aspect of this application, at least two sets of cold rolling-recrystallization annealing processes include: a first cold rolling pass—a first recrystallization annealing—a second cold rolling pass—a second recrystallization annealing; wherein, the first cold rolling pass process includes: using three passes of cold rolling, with a total reduction rate of 40-60%, wherein the proportions of the three passes are 10-15%, 20-30%, and 10-15%, respectively; the second cold rolling pass process includes: using two passes of cold rolling, with a total reduction rate of 40-60%, wherein the proportions of the two passes are 20-30% and 20-30%, respectively; the second recrystallization annealing process is the same as the first recrystallization annealing process.

[0011] According to the embodiment of the first aspect of this application, both the first and second cold rolling passes adopt single-stand cold rolling. The intermediate roll profile parameters of the single stand are as follows: the length of the flat roll section of the intermediate roll body is 1 / 2 of the middle part, and the length of the roll body of each side is arc-shaped, which is 1 / 4 of the length of the roll body.

[0012] According to an embodiment of the first aspect of this application, the pickling process includes: pickling with hydrochloric acid using a push-pull process followed by rinsing with water; and drying the rinsed strip with hot air; wherein the concentration of the hydrochloric acid pickling solution is 15% to 20%, and the acid solution temperature is 80 to 85°C; and the rinsing temperature of the water rinsing solution is 70 to 85°C.

[0013] According to an embodiment of the first aspect of this application, the pickling rate of the pickling process is 50-80 m / min.

[0014] According to an embodiment of the first aspect of this application, the leveling process includes: leveling using a constant rolling force of 300–600 tons, with an uncoiling section tension of 0.03–0.06 KN / mm. 2 The tension of the winding section is 0.04~0.08KN / mm.2 .

[0015] According to an embodiment of the first aspect of this application, the specifications of the 75Cr1 steel strip for the ultra-thin frame saw blade are 1.0~1.5mm×1000~1450mm.

[0016] Secondly, embodiments of this application provide a 75Cr1 cold-rolled steel strip for ultra-thin frame saw blades, produced by the aforementioned production method, comprising the following components by mass percentage: C: 0.72–0.80%, Si: 0.20–0.45%, Mn: 0.60–0.90%, Cr: 0.30–0.60%, P: ≤0.015%, S: ≤0.005%; the remainder being Fe and unavoidable impurities; by volume percentage, the metallographic structure of the 75Cr1 cold-rolled steel strip for ultra-thin frame saw blades comprises 100% spheroidized pearlite structure.

[0017] According to an embodiment of the second aspect of this application, the grain size of the 75Cr1 cold-rolled steel strip used for ultra-thin frame saw blades does not exceed 5μm, and the carbide size does not exceed 0.5μm.

[0018] According to an embodiment of the second aspect of this application, the yield strength of the 75Cr1 steel strip used for the ultra-thin frame saw blade is 400MPa to 450MPa, the tensile strength is 580MPa to 620MPa, and the elongation is 22% to 25%.

[0019] Compared with the prior art, the present invention has at least the following beneficial effects:

[0020] This application describes a method for producing 75Cr1 cold-rolled steel strips for ultra-thin frame saw blades by adjusting parameters. The 75Cr1 cold-rolled steel coils produced using this method can be used to manufacture 1.0-1.5mm ultra-thin marble frame saw blades. The steel strips have very fine and uniform grain and carbide particle sizes, high dimensional accuracy, and narrow-range fluctuations in mechanical properties. Attached Figure Description

[0021] The features, advantages, and technical effects of exemplary embodiments of this application will now be described with reference to the accompanying drawings.

[0022] Figure 1 This is the roll profile curve of the intermediate roll in the single-stand configuration of this application;

[0023] Figure 2 This is a microstructure diagram of the 75Cr1 cold-rolled steel strip used for the ultra-thin frame saw blade of Embodiment 1 of this application;

[0024] Figure 3 This is a microstructure diagram of the 75Cr1 cold-rolled steel strip used for the ultra-thin frame saw blade of Embodiment 2 of this application;

[0025] Figure 4This is a microstructure diagram of the 75Cr1 cold-rolled steel strip used for the ultra-thin frame saw blade of Embodiment 3 of this application. Detailed Implementation

[0026] The embodiments of this application will be described in further detail below with reference to the accompanying drawings and examples. The detailed description of the following embodiments and the accompanying drawings are used to illustrate the principles of this application by way of example, but should not be used to limit the scope of this application, that is, this application is not limited to the described embodiments.

[0027] In the description of this application, it should be noted that, unless otherwise stated, "a plurality of" means two or more; the terms "upper," "lower," "left," "right," "inner," and "outer," etc., indicating orientation or positional relationships, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this application. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance. "Vertical" does not require strict verticality, but may include permissible errors. "Parallel" does not require strict parallelism, but may include permissible errors.

[0028] The 75Cr1 cold-rolled steel strip produced by the existing process has problems such as large grain and carbide particle size, insufficient dimensional accuracy, large fluctuation range of mechanical properties, and insufficient stiffness and toughness of the saw blade after heat treatment.

[0029] In view of this, the inventors of this application, through extensive experimental research, provide a production method for 75Cr1 cold-rolled steel strip for ultra-thin frame saw blades and 75Cr1 cold-rolled steel strip for ultra-thin frame saw blades, aiming to improve rigidity and toughness.

[0030] Production method of 75Cr1 cold-rolled steel strip for ultra-thin frame saw blades

[0031] In a first aspect, embodiments of this application provide a method for producing 75Cr1 cold-rolled steel strip for ultra-thin frame saw blades, characterized by comprising the following steps:

[0032] Hot-rolled steel coils are pickled, spheroidized annealed, subjected to at least two sets of cold rolling-recrystallization annealing, and leveled to obtain 75Cr1 cold-rolled steel strip for ultra-thin frame saw blades.

[0033] The hot-rolled steel coil comprises the following components by mass percentage: C: 0.72–0.80%, Si: 0.20–0.45%, Mn: 0.60–0.90%, Cr: 0.30–0.60%, P: ≤0.015%, S: ≤0.005%; the remainder being Fe and unavoidable impurities; optionally, the hot-rolled steel coil has a size of 3.5–4.5 mm × 1000–1450 mm, and the metallographic structure of the hot-rolled steel coil comprises 100% pearlite by volume percentage;

[0034] The spheroidizing annealing process includes: freely heating the pickled hot-rolled steel coil from room temperature to 200℃; annealing using two holding platforms during the heating process, heating the hot-rolled steel coil to 450℃ and holding for 2 hours; then heating to 650℃ and holding for 2 hours; then heating to 720-740℃ and holding for 15-18 hours; after holding, slowly cooling to 600℃; then air cooling to 400℃; and finally water cooling to 100℃ before unloading from the furnace.

[0035] For example, the heating rate during the spheroidizing annealing process can be between 40℃ / h and 60℃ / h, such as 40℃ / h, 42℃ / h, 44℃ / h, 46℃ / h, 48℃ / h, 50℃ / h, 52℃ / h, 54℃ / h, 56℃ / h, 58℃ / h, 60℃ / h, or any range of two of the above values. The heating rates in each heating step can be the same or different. By controlling the heating rate within the above range, grain growth can be adjusted, and production progress can be effectively guaranteed.

[0036] The cold rolling-recrystallization annealing process includes: cold rolling at least two passes per rolling cycle to obtain cold-rolled steel strip, with a total reduction of 40-60% per rolling cycle; freely heating the cold-rolled steel strip from room temperature to 200°C; using two holding platforms for annealing during the heating process to better ensure the uniformity of the steel coil temperature; heating the cold-rolled steel strip to 450°C and holding for 2 hours; reheating to 600°C and holding for 2 hours; then heating to 680-700°C and holding for 10-14 hours; after holding, slowly cooling to 600°C; switching to air cooling to 400°C; and switching to water cooling to 100°C before unloading from the furnace.

[0037] For example, the heating rate in the cold rolling-recrystallization annealing process can be between 40℃ / h and 60℃ / h, such as 40℃ / h, 42℃ / h, 44℃ / h, 46℃ / h, 48℃ / h, 50℃ / h, 52℃ / h, 54℃ / h, 56℃ / h, 58℃ / h, 60℃ / h, or any range of two of the above values. The heating rates in each heating step can be the same or different. By controlling the heating rate within the above range, grain growth can be adjusted, and production progress can be effectively guaranteed.

[0038] In this embodiment, fine-grained 100% pearlitic 75Cr1 hot-rolled steel strip is used. Cold rolling is performed in two passes, with the reduction rate of each pass maintained between 40% and 60%. By setting optimal spheroidizing annealing and recrystallization annealing processes, the size of cementite and the grain size of the ferrite matrix after annealing are controlled. Compared with conventional or thick-gauge frame saw blades made of 75Cr1 steel strip, the finished steel strip has very fine and uniform grain and carbide particle sizes, with the ferrite matrix grain size below 5 μm and the carbide size below 0.5 μm.

[0039] For example, the reduction rate for each rolling pass can be 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, or a range of any two of the above values.

[0040] The annealing heating process uses a double-insulation platform to uniformly heat the inside and outside of the steel coil, reducing the temperature difference between hot and cold spots. The finishing process uses a constant rolling force mode for leveling. Compared with 75Cr1 steel strip used for conventional or thick-gauge frame saw blades, the fluctuation of mechanical properties is significantly reduced, the fluctuation of tensile strength can be controlled within 50MPa, and the fluctuation of hardness can be controlled within 3HRB.

[0041] The above rolling process can be used to develop 75Cr1 cold-rolled steel strips for ultra-thin frame saw blades with thicknesses of 1.5mm, 1.2mm, and 1.0mm, achieving sawing performance and service life comparable to saw blades with thicknesses of 1.8mm, 2.0mm, and 2.5mm.

[0042] In some embodiments, at least two sets of cold rolling-recrystallization annealing processes include: a first cold rolling pass—a first recrystallization annealing—a second cold rolling pass—a second recrystallization annealing; wherein, the first cold rolling pass includes: three-pass cold rolling with a total reduction of 40-60%, wherein the proportions of the three passes are 10-15%, 20-30%, and 10-15%, respectively; the second cold rolling pass includes: two-pass cold rolling with a total reduction of 40-60%, wherein the proportions of the two passes are 20-30% and 20-30%, respectively; the second recrystallization annealing process is the same as the first recrystallization annealing process.

[0043] In some embodiments, both the first and second cold rolling passes are cold rolling using a single stand. The intermediate roll profile parameters of the single stand are as follows: the length of the flat section of the intermediate roll body is 1 / 2 of the length of the middle section, and the length of the roll body on each side is arc-shaped, which is 1 / 4 of the length of the roll body on each side.

[0044] The cold-rolling single-stand mill produces high-precision cold-rolled 75Cr1 steel strip by using a special roll profile curve for the intermediate roll. The longitudinal tolerance of the 1.0-1.5mm steel strip is ±8μm, and the transverse three-point difference (at the 40mm edge position) is within 10μm.

[0045] In some embodiments, the pickling process includes: pickling with hydrochloric acid using a push-pull process followed by rinsing with water; and drying the rinsed strip with hot air; wherein the concentration of the hydrochloric acid pickling solution is 15% to 20%, and the acid solution temperature is 80 to 85°C; and the rinsing temperature of the water is 70 to 85°C.

[0046] In some embodiments, the pickling rate is 50–80 m / min. Exemplarily, the pickling rate can be 50 m / min, 55 m / min, 60 m / min, 65 m / min, 70 m / min, 75 m / min, 80 m / min, or a range of any two of these values. A pickling rate within this range ensures both pickling effectiveness and production efficiency.

[0047] In some embodiments, the leveling process includes: leveling using a constant rolling force of 300–600 tons, with an uncoiling section tension of 0.03–0.06 KN / mm. 2 The tension of the winding section is 0.04~0.08KN / mm. 2 For example, the leveling process using a constant rolling force mode can be 300 tons, 350 tons, 400 tons, 450 tons, 500 tons, 550 tons, 600 tons, or any combination of two of the above values; the tension in the uncoiling section can be 0.03 kN / mm. 2 0.04KN / mm 2 0.05KN / mm 2 0.06KN / mm 2 The tension of the winding section can be 0.04 kN / mm. 2 0.05KN / mm 2 0.06KN / mm 2 0.07KN / mm 2 0.08KN / mm 2 The above-mentioned leveling treatment can improve the surface uniformity of the cold-rolled steel strip of this application, and improve the three-point difference.

[0048] In some embodiments, the specifications of the 75Cr1 cold-rolled steel strip used for ultra-thin frame saw blades are 1.0~1.5mm×1000~1450mm.

[0049] Secondly, embodiments of this application provide a 75Cr1 cold-rolled steel strip for ultra-thin frame saw blades, produced by the aforementioned production method, comprising the following components by mass percentage: C: 0.72–0.80%, Si: 0.20–0.45%, Mn: 0.60–0.90%, Cr: 0.30–0.60%, P: ≤0.015%, S: ≤0.005%; the remainder being Fe and unavoidable impurities; the metallographic structure of the 75Cr1 cold-rolled steel strip for ultra-thin frame saw blades, by volume percentage, comprises 100% spheroidized pearlite. This 100% spheroidized pearlite structure allows the 75Cr1 cold-rolled steel strip for ultra-thin frame saw blades of this application to possess lower hardness and better ductility and toughness.

[0050] In some embodiments, the grain size of the 75Cr1 cold-rolled steel strip used for ultra-thin frame saw blades does not exceed 5 μm, and the carbide size does not exceed 0.5 μm.

[0051] For example, the grain size of the 75Cr1 cold-rolled steel strip for ultra-thin frame saw blades can be 1μm, 1.5μm, 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 4.5μm, 5μm or any combination of two of the above values.

[0052] In some embodiments, the yield strength of 75Cr1 cold-rolled steel strip for ultra-thin frame saw blades is 400MPa to 450MPa, the tensile strength is 580MPa to 620MPa, and the elongation is 22% to 25%.

[0053] For example, the yield strength of 75Cr1 cold-rolled steel strip for ultra-thin frame saw blades can be 400 MPa, 410 MPa, 420 MPa, 430 MPa, 440 MPa, 450 MPa or any combination of two of the above values.

[0054] For example, the tensile strength of 75Cr1 cold-rolled steel strip for ultra-thin frame saw blades can be 580 MPa, 590 MPa, 600 MPa, 610 MPa, 620 MPa or any combination of two of the above values.

[0055] For example, the elongation of the 75Cr1 cold-rolled steel strip used for ultra-thin frame saw blades can be 22%, 23%, 24%, 25%, or a range of any two of the above values.

[0056] Example

[0057] The following embodiments describe the disclosure of this application in more detail. These embodiments are merely illustrative, as various modifications and variations will be apparent to those skilled in the art within the scope of the disclosure of this application. Unless otherwise stated, all parts, percentages, and ratios reported in the following embodiments are based on weight, and all reagents used in the embodiments are commercially available or synthesized by conventional methods and can be used directly without further processing, and the instruments used in the embodiments are commercially available.

[0058] Example 1:

[0059] Using 75Cr1 hot-rolled steel coils with high dimensional accuracy as raw material, the chemical composition of the coils by mass percentage is: C: 0.76%, Si: 0.28%, Mn: 0.71%, Cr: 0.32%, P: 0.011%, S: 0.002%; the remainder is Fe and unavoidable impurities. The microstructure is uniform and fine, consisting entirely of pearlite. The hot-rolled steel coil specifications are 3.5mm × 1200mm.

[0060] The pickling process is as follows: push-pull hydrochloric acid pickling, acid concentration 18%, acid temperature 80℃. Water rinsing, rinsing temperature 78℃. The rinsed strip is then dried with hot air at approximately 120℃. The pickling rate is 60 m / min.

[0061] The spheroidizing annealing process is as follows: the steel coil is freely heated from room temperature to 200℃; during the heating process, two holding platforms are used for annealing to better ensure the uniformity of the steel coil temperature. It is heated to 450℃ at a heating rate of 50℃ / h and held for 2 hours; then heated to 650℃ at a rate of 50℃ / h and held for 2 hours; then heated to 720℃ at a rate of 50℃ / h and held for 16 hours; after the holding period, it is slowly cooled to 600℃; then air-cooled to 400℃; and finally water-cooled to 100℃ before being unloaded from the furnace.

[0062] The first cold rolling process: three passes are used for cold rolling, with a total reduction rate of 45.7%. The proportions of the three passes are 10%, 25%, and 10.7% respectively, and the steel strip is cold rolled into a 1.9mm semi-finished 75Cr1 steel strip.

[0063] First recrystallization annealing process: The steel coil is freely heated from room temperature to 200℃; during the heating process, two holding platforms are used for annealing to better ensure the uniformity of the steel coil temperature. It is heated to 450℃ at a heating rate of 50℃ / h and held for 2 hours; then heated to 600℃ at a rate of 50℃ / h and held for 2 hours; then heated to 680℃ at a rate of 50℃ / h and held for 12 hours; after the holding period, it is slowly cooled to 600℃; then air-cooled to 400℃; and finally water-cooled to 100℃ before being unloaded from the furnace.

[0064] The second cold rolling process: adopts two-pass cold rolling with a total reduction rate of 46%, of which the two passes account for 25% and 21% respectively.

[0065] The second recrystallization annealing process is the same as the first.

[0066] The roll profile parameters for the intermediate rolls of the first and second passes of cold rolling mills on a single stand are as follows: the length of the flat section of the intermediate roll body is 1 / 2 of the middle section, and the length of the roll body on each side is arc-shaped. The specific roll profile curve is shown in the figure below. Figure 1 .

[0067] Leveling parameters: Leveling is performed using a constant rolling force of 400 tons, with an uncoiling section tension of 0.03 KN / mm² and a coiling section tension of 0.04 KN / mm². The finished cold-rolled steel strip is leveled to a size of 1.0 mm × 1200 mm.

[0068] Example 2:

[0069] Using 75Cr1 hot-rolled steel coils with high dimensional accuracy as raw material, the chemical composition of the coils by mass percentage is: C: 0.77%, Si: 0.31%, Mn: 0.65%, Cr: 0.34%, P: 0.009%, S: 0.002%; the remainder is Fe and unavoidable impurities. The microstructure is uniform and fine, consisting entirely of pearlite. The hot-rolled steel coil specifications are 4.0mm × 1200mm.

[0070] The pickling process is as follows: push-pull hydrochloric acid pickling, acid concentration 15%, acid temperature 83℃. Water rinsing, rinsing temperature 79℃. The rinsed strip is then dried with hot air at approximately 120℃. The pickling rate is 50 m / min.

[0071] The spheroidizing annealing process is as follows: the steel coil is freely heated from room temperature to 200℃; during the heating process, two holding platforms are used for annealing to better ensure the uniformity of the steel coil temperature. It is heated to 450℃ at a heating rate of 50℃ / h and held for 2 hours; then heated to 650℃ at a rate of 50℃ / h and held for 2 hours; then heated to 720℃ at a rate of 50℃ / h and held for 18 hours; after the holding period, it is slowly cooled to 600℃; then air-cooled to 400℃; and finally water-cooled to 100℃ before being unloaded from the furnace.

[0072] The first cold rolling process: three passes are used for cold rolling with a total reduction of 45%, of which the proportions of the three passes are 10%, 25% and 10% respectively, to produce a 2.2mm semi-finished 75Cr1 steel strip.

[0073] First recrystallization annealing process: The steel coil is freely heated from room temperature to 200℃; during the heating process, two holding platforms are used for annealing to better ensure the uniformity of the steel coil temperature. It is heated to 450℃ at a heating rate of 50℃ / h and held for 2 hours; then heated to 600℃ at a rate of 50℃ / h and held for 2 hours; then heated to 700℃ at a rate of 50℃ / h and held for 14 hours; after the holding period, it is slowly cooled to 600℃; then air-cooled to 400℃; and finally water-cooled to 100℃ before being unloaded from the furnace.

[0074] The second cold rolling process: adopts two-pass cold rolling with a total reduction rate of 44%, of which the two passes account for 24% and 20% respectively.

[0075] The second recrystallization annealing process is the same as the first.

[0076] The roll profile parameters for the intermediate rolls of the first and second passes of cold rolling mills on a single stand are as follows: the length of the flat section of the intermediate roll body is 1 / 2 of the middle section, and the length of the roll body on each side is arc-shaped. The specific roll profile curve is shown in the figure below. Figure 1 .

[0077] Leveling parameters: Leveling is performed using a constant rolling force of 500 tons, with a tension of 0.04 KN / mm² in the uncoiling section and 0.05 KN / mm² in the coiling section. The cold-rolled steel strip is leveled to a diameter of 1.2 mm × 1200 mm.

[0078] Example 3:

[0079] Using 75Cr1 hot-rolled steel coils with high dimensional accuracy as raw material, the chemical composition of the coils by mass percentage is: C: 0.74%, Si: 0.25%, Mn: 0.75%, Cr: 0.32%, P: 0.013%, S: 0.001%; ​​the remainder is Fe and unavoidable impurities. The microstructure is uniform and fine, consisting entirely of pearlite. The hot-rolled steel coil specifications are 4.5mm × 1200mm.

[0080] The pickling process is as follows: push-pull hydrochloric acid pickling, acid concentration 18%, acid temperature 85℃. Water rinsing, rinsing temperature 82℃. The rinsed strip is then dried with hot air at approximately 120℃. The pickling rate is 50 m / min.

[0081] The spheroidizing annealing process is as follows: the steel coil is freely heated from room temperature to 200℃; during the heating process, two holding platforms are used for annealing to better ensure the uniformity of the steel coil temperature. It is heated to 450℃ at a heating rate of 50℃ / h and held for 2 hours; then heated to 650℃ at a rate of 50℃ / h and held for 2 hours; then heated to 740℃ at a rate of 50℃ / h and held for 18 hours; after the holding period, it is slowly cooled to 600℃; then air-cooled to 400℃; and finally water-cooled to 100℃ before being unloaded from the furnace.

[0082] The first cold rolling process: three passes are used for cold rolling with a total reduction of 40%, of which the proportions of the three passes are 10%, 20% and 10% respectively, to produce a 2.7mm semi-finished 75Cr1 steel strip.

[0083] First recrystallization annealing process: The steel coil is freely heated from room temperature to 200℃; during the heating process, two holding platforms are used for annealing to better ensure the uniformity of the steel coil temperature. It is heated to 450℃ at a heating rate of 50℃ / h and held for 2 hours; then heated to 600℃ at a rate of 50℃ / h and held for 2 hours; then heated to 700℃ at a rate of 50℃ / h and held for 14 hours; after the holding period, it is slowly cooled to 600℃; then air-cooled to 400℃; and finally water-cooled to 100℃ before being unloaded from the furnace.

[0084] The second cold rolling process: adopts two-pass cold rolling with a total reduction rate of 43%, of which the two passes account for 23% and 20% respectively.

[0085] The second recrystallization annealing process is the same as the first.

[0086] The roll profile parameters for the intermediate rolls of the first and second passes of cold rolling mills on a single stand are as follows: the length of the flat section of the intermediate roll body is 1 / 2 of the middle section, and the length of the roll body on each side is arc-shaped. The specific roll profile curve is shown in the figure below. Figure 1 .

[0087] Leveling parameters: Leveling is performed using a constant rolling force of 600 tons, with a tension of 0.06 KN / mm² in the uncoiling section and 0.08 KN / mm² in the coiling section. The cold-rolled steel strip is leveled to a diameter of 1.5 mm × 1200 mm.

[0088] Comparative Example 1

[0089] Similar to the production process in Example 1, the difference lies in the spheroidizing annealing treatment, which includes: heating to 450°C at a heating rate of 50°C / h and holding for 2 hours; then heating to 720–740°C at a heating rate of 50°C / h and holding for 15–18 hours; after holding, slowly cooling to 600°C; then air cooling to 400°C; and finally water cooling to 100°C before unloading from the furnace. The produced cold-rolled steel strip has a specification of 1.2mm × 1200mm.

[0090] Comparative Example 2

[0091] Similar to the production process in Example 1, the difference lies in the use of a lower cold rolling reduction rate, including a total reduction rate of 30% in the first cold rolling pass and a total reduction rate of 30% in the second cold rolling pass. The produced cold-rolled steel strip has a specification of 1.2mm × 1200mm.

[0092] Comparative Example 3

[0093] Similar to the production process in Example 1, the difference lies in that the cold rolling-recrystallization annealing includes: freely heating the cold-rolled steel strip from room temperature to 200°C; the heating process uses two holding platforms for annealing, heating to 450°C at a heating rate of 50°C / h and holding for 2 hours; then heating to 680-700°C at 50°C / h and holding for 10-14 hours; after the holding period, slowly cooling to 600°C; switching to air cooling to 400°C; and switching to water cooling to 100°C before unloading from the furnace.

[0094] Comparative Example 4

[0095] Similar to the production process in Example 1, the difference lies in the leveling process, which includes: leveling using a constant rolling force of 250 tons and an uncoiling section tension of 0.028 KN / mm. 2 The tension of the winding section is 0.04 kN / mm. 2 The cold-rolled steel strip produced has a specification of 1.2mm × 1200mm.

[0096] Comparative Example 5

[0097] Similar to the production process in Example 1, the difference lies in that the intermediate roll of the single stand adopts a non-designed roll profile curve and is rolled with a commonly used tapered roll (100mm tapered length). The produced cold-rolled steel strip has a specification of 1.2mm × 1200mm.

[0098] The performance of the ultra-thin frame saw blades obtained in Examples 1-3 and Comparative Examples 1-5 was tested according to the test methods in GB / T228.1-2021 and GB / T 6394-2002 using 75Cr1 hot-rolled steel strip; the results are shown in Table 1.

[0099] Table 1. Performance test results of Examples 1-3 and Comparative Examples 1-5

[0100]

[0101]

[0102] Figure 2 This is a microstructure diagram of the 75Cr1 cold-rolled steel strip used for the ultra-thin frame saw blade of Embodiment 1 of this application; Figure 3 This is a microstructure diagram of the 75Cr1 cold-rolled steel strip used for the ultra-thin frame saw blade of Embodiment 2 of this application; Figure 4 This is a microstructure diagram of the 75Cr1 hot-rolled steel strip used for the ultra-thin frame saw blade of Embodiment 3 of this application.

[0103] Combination Figures 2 to 4As can be seen from Table 1, the 75Cr1 cold-rolled steel strips for ultra-thin frame saw blades in Examples 1-3 have very fine and uniform grain and carbide particle sizes, high dimensional accuracy and narrow range of fluctuating mechanical properties, which improves the stiffness and toughness of the obtained 75Cr1 cold-rolled steel strips for ultra-thin frame saw blades.

[0104] In Comparative Example 1, the spheroidizing annealing process was reduced to a 2-hour holding time at 650℃. Due to the larger temperature range, the strength was higher, but the elongation was lower, resulting in reduced mechanical properties and microstructure uniformity, leading to decreased rolling stability and increased three-point difference. In Comparative Example 2, a lower cold rolling reduction rate was used, resulting in coarser grain size and poorer mechanical properties and three-point difference. In Comparative Example 3, the cold rolling-recrystallization annealing process was reduced to a 2-hour holding time at 600℃. Due to the larger temperature range, the strength was higher, but the elongation was lower, resulting in reduced mechanical properties and microstructure uniformity, leading to decreased rolling stability and increased three-point difference. In Comparative Example 4, the leveling mode was changed to a constant rolling force mode of 250 tons, resulting in worse surface performance uniformity and three-point difference. In Comparative Example 5, the type of intermediate roll in the single stand was changed to a commonly used conical roll (100mm cone length), resulting in a significant worsening of the three-point difference.

[0105] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this application, and these modifications or substitutions should all be covered within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for producing 75Cr1 cold-rolled steel strip for ultra-thin frame saw blades, characterized in that, Includes the following steps: Hot-rolled steel coils are pickled, spheroidized annealed, subjected to at least two sets of cold rolling-recrystallization annealing, and leveled to obtain 75Cr1 cold-rolled steel strip for ultra-thin frame saw blades. The hot-rolled steel coil comprises the following components by mass percentage: C: 0.72~0.80%, Si: 0.20~0.45%, Mn: 0.60~0.90%, Cr: 0.30~0.60%, P: ≤0.015%, S: ≤0.005%; the remainder being Fe and unavoidable impurities; the hot-rolled steel coil has a size of 3.5~4.5mm × 1000~1450mm, and by volume percentage, the metallographic structure of the hot-rolled steel coil comprises 100% pearlite; The spheroidizing annealing process includes: freely heating the pickled hot-rolled steel coil from room temperature to 200°C; the heating process uses a two-heating platform annealing method, heating the hot-rolled steel coil to 450°C and holding it for 2 hours; then heating it to 650°C and holding it for 2 hours; then heating it to 720-740°C and holding it for 15-18 hours; after the holding period, slowly cooling it to 600°C; then air cooling to 400°C; and finally water cooling to 100°C before unloading from the furnace. The cold rolling-recrystallization annealing process includes: a first cold rolling pass – a first recrystallization annealing – a second cold rolling pass – a second recrystallization annealing; each pass uses at least two cold rolling passes to obtain cold-rolled steel strip, with a total reduction rate of 40-60% per pass; the cold-rolled steel strip is freely heated from room temperature to 200°C; the heating process uses two holding platforms for annealing to ensure the uniformity of the coil temperature; the cold-rolled steel strip is heated to 450°C and held for 2 hours; then heated to 600°C and held for 2 hours; then heated to 680-700°C and held for 10-14 hours; after holding, it is slowly cooled to 600°C; then air-cooled to 400°C; finally water-cooled to 100°C before being removed from the furnace. Both the first and second cold rolling passes are single-stand cold rolling processes. The intermediate roll profile parameters of the single stand are as follows: the length of the flat roll section of the intermediate roll body is 1 / 2 of the length of the middle part, and the length of the roll body of each side is arc-shaped, which is 1 / 4 of the length of the roll body. The leveling process includes: leveling using a constant rolling force of 300–600 tons, with a tension of 0.03–0.06 KN / mm in the uncoiling section. 2 The tension of the winding section is 0.04~0.08KN / mm. 2 .

2. The production method according to claim 1, characterized in that, The first cold rolling process includes: three-pass cold rolling with a total reduction of 40-60%, wherein the proportions of the three passes are 10-15%, 20-30%, and 10-15%, respectively. The second cold rolling process includes: using two-pass cold rolling with a total reduction of 40-60%, wherein the proportions of the two passes are 20-30% and 20-30%, respectively; The second recrystallization annealing treatment is the same as the first recrystallization annealing treatment.

3. The production method according to claim 1, characterized in that, The pickling process includes: pickling with hydrochloric acid using a push-pull process followed by rinsing with water; and drying the rinsed strip with hot air. The concentration of the hydrochloric acid pickling solution is 15%~20%, and the acid temperature is 80~85℃; the rinsing temperature of the water rinsing solution is 70~85℃.

4. The production method according to claim 3, characterized in that, The pickling rate of the pickling process is 50 m / min to 80 m / min.

5. The production method according to claim 1, characterized in that, The specifications of the 75Cr1 cold-rolled steel strip used for the ultra-thin frame saw blade are 1.0mm~1.5mm×1000mm~1450mm.

6. A type of 75Cr1 cold-rolled steel strip for ultra-thin frame saw blades, produced by the production method described in any one of claims 1-5, characterized in that, It includes the following components by mass percentage: C: 0.72~0.80%, Si: 0.20~0.45%, Mn: 0.60~0.90%, Cr: 0.30~0.60%, P: ≤0.015%, S: ≤0.005%; the remainder is Fe and unavoidable impurities; The metallographic structure of the 75Cr1 cold-rolled steel strip used for the ultra-thin frame saw blade, by volume percentage, comprises 100% spheroidized pearlite.

7. The 75Cr1 cold-rolled steel strip for ultra-thin frame saw blades according to claim 6, characterized in that, The grain size of the 75Cr1 steel strip used for the ultra-thin frame saw blade does not exceed 5μm, and the carbide size does not exceed 0.5μm.

8. The 75Cr1 cold-rolled steel strip for ultra-thin frame saw blades according to claim 6, characterized in that, The yield strength of the 75Cr1 cold-rolled steel strip used for the ultra-thin frame saw blade is 400MPa~450MPa, the tensile strength is 580MPa~620MPa, and the elongation is 22%~25%.

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