Production process and application of cold-rolled tool steel strip for saw blade

Abstract

The invention provides a production process and application of a cold-rolled tool steel strip for a saw blade. Comprising the following steps that A1, a tool steel plate blank is heated and then continuously rolled, the coiling temperature is controlled to be 560-600 DEG C, and a hot-rolled wide plate coil is obtained; the method comprises the following steps: A1, carrying out hot rolling on a wide-width plate coil, A2, annealing the hot-rolled wide-width plate coil in a protective atmosphere, A3, carrying out acid pickling, rinsing and drying on the annealed steel coil, and then carrying out cold continuous rolling by adopting a multi-rack continuous rolling mill, A4, annealing the cold-rolled steel coil again in the protective atmosphere, and A5, cooling the annealed steel coil. The invention mainly aims to provide a production process and application of a 75Cr1 cold-rolled tool steel strip for a saw blade, and aims to solve the problems that in the prior art, in the whole-process production process of hot rolling, annealing and cold rolling, the size of cementite particles is difficult to effectively control, so that the structure of the steel strip is thick and large, and the service life of the steel strip is prolonged. And therefore, the technical problems of insufficient dissolution of carbides and low fatigue life during subsequent quenching heat treatment are solved.

Description

Technical Field

[0001] This invention relates to the field of steel production technology, and in particular to a production process and application of cold-rolled tool steel strip for saw blades. Background Technology

[0002] 75Cr1 is a high-carbon, low-alloy tool steel with a high carbon content (approximately 0.75%) and added chromium (approximately 1%). Due to its combination of high hardness, high strength, good elasticity, and excellent wear resistance, it is widely used in the manufacture of band saw blades, machine tools, automotive elastic components, and various small hardware tools. After appropriate heat treatment, its strength, hardness, hardenability, and fatigue performance are superior to commonly used 65Mn spring steel. Under conditions of complete hardening and uniform surface condition, its fatigue limit is comparable to some alloy structural steels. Furthermore, 75Cr1 maintains high hardness and structural stability at high temperatures and possesses a certain degree of corrosion resistance. It also exhibits good machinability, cold heading, and welding properties, making it a cost-effective engineering material with continuously growing market demand.

[0003] However, in actual production, the final performance of 75Cr1 cold-rolled steel strip is highly dependent on the microstructure of its precursors—hot-rolled and cold-rolled steel strips—especially the morphology, size, and distribution of cementite (Fe3C). Traditional 75Cr1 steel strip is mostly produced using single-stand reversible cold rolling or narrow strip slitting processes, coupled with conventional annealing, which easily leads to coarse cementite with a network or banded segregation distribution. This type of microstructure is difficult to fully dissolve during subsequent quenching heat treatment, resulting in uneven austenite composition, which in turn causes problems such as martensite coarsening and residual stress concentration, significantly reducing the fatigue life and edge wear resistance of saw blades and other products.

[0004] Furthermore, existing processes generally organize production in the form of narrow coils (typically <800 mm wide), requiring wide hot-rolled coils to be slit before pickling, annealing, and cold rolling. This not only increases the number of processes and reduces the yield (edge ​​loss reaches 3%–5%), but also leads to poor cold-rolled sheet shape and excessive thickness tolerances due to frequent end welding and large fluctuations in tension control. This makes it difficult to meet the requirements of high-end band saw blades for high flatness and high dimensional accuracy of the substrate (e.g., transverse thickness difference ≤15 μm). At the same time, the traditional annealing process has a fast heating rate and insufficient holding time, which cannot effectively promote the spheroidization and homogenization of cementite, further restricting the improvement of the material's heat treatment response performance.

[0005] Therefore, there is an urgent need to develop an efficient and stable production process for wide-width 75Cr1 cold-rolled tool steel strip. By optimizing the hot rolling coiling process, designing segmented temperature-controlled annealing curves, and adopting key technologies such as high-precision multi-stand continuous rolling and roll shape control, the size of cementite particles can be effectively controlled to obtain a fine, dispersed, and uniformly distributed spheroidized structure. This will improve the heat treatment performance and fatigue life of the material while meeting the industrial production requirements of high efficiency, low cost, and high yield. Summary of the Invention

[0006] The main objective of this invention is to provide a production process and application of 75Cr1 cold-rolled tool steel strip for saw blades. This aims to solve the technical problem in the existing technology where the size of cementite particles is difficult to control effectively during the entire production process of hot rolling, annealing, and cold rolling, resulting in coarse and uneven steel strip structure. This, in turn, leads to insufficient carbide dissolution and low fatigue life during subsequent quenching heat treatment. Simultaneously, it overcomes the shortcomings of traditional narrow strip slitting production methods, such as cumbersome processes, high edge damage, poor shape and thickness accuracy, low production efficiency, and high cost. This invention achieves efficient, stable, and low-cost manufacturing of wide-width 75Cr1 cold-rolled steel strips with high dimensional accuracy and high structural uniformity, significantly improving the service performance and high-grade yield of end products such as saw blades.

[0007] To achieve the above objectives, the present invention provides a manufacturing process for cold-rolled tool steel strip for saw blades, comprising the following steps: A1. After heating the tool steel slab, it is continuously rolled, and the coiling temperature is controlled at 560-600℃ to obtain hot-rolled wide coils. A2. The hot-rolled wide coil is annealed under a protective atmosphere. The annealing process includes a heating stage, a slow cooling stage and a cooling stage. A3. The steel coils obtained after annealing are pickled, rinsed and dried, and then cold rolled in a multi-stand continuous rolling mill, using a roll shifting mode during the rolling process; A4. Anneal the cold-rolled steel coil again under a protective atmosphere, and keep the holding temperature above the recrystallization temperature. A5. Cool the annealed steel coil to below 45°C and perform a leveling process to obtain the final cold-rolled steel strip.

[0008] This invention utilizes low-temperature coiling control (560–600°C) in step A1 to precipitate carbides in a dispersed and fine form during hot rolling, forming a thin, lamellar pearlite matrix. This provides ideal initial conditions for carbide spheroidization during subsequent annealing. In step A2, nitrogen-protected stepped annealing, precise temperature rise, holding, and slow cooling control promotes full spheroidization of cementite and inhibits microstructure oxidation, resulting in a fine, uniform spheroidized pearlite microstructure. This not only improves the material's plasticity for cold rolling but also lays the foundation for the uniformity of the final product. Step A4, secondary protective atmosphere annealing, involves holding above the recrystallization temperature to allow the distorted grains generated during cold rolling to fully recrystallize, further refining the carbides and achieving microstructure homogenization. This significantly improves the toughness of the steel strip and its subsequent quenching responsiveness, making the carbides easier to dissolve and ultimately obtaining a fine, uniform quenched microstructure, greatly improving fatigue life. Secondly, regarding dimensional accuracy and production efficiency: Step A3 employs a multi-stand continuous rolling mill with a shifting roll pattern, achieving uniform distribution of deformation and stress under high compression ratios. Combined with pickling, rinsing, and drying processes to effectively remove the surface oxide layer, this ensures sheet shape accuracy and thickness consistency, significantly reducing edge cutting damage. Step A5's low-temperature leveling treatment further eliminates the yield plateau after annealing, optimizing surface quality and dimensional stability, resulting in finished products with both excellent processing performance and service reliability.

[0009] This invention not only achieves effective control over cementite particle size and a significant improvement in microstructure uniformity, but also overcomes the shortcomings of traditional narrow strip slitting processes, such as cumbersome procedures, low yield, and poor precision, through a wide-width, high-efficiency, and continuous production mode. It achieves efficient, stable, and low-cost manufacturing of 75Cr1 cold-rolled wide steel strips with high dimensional accuracy and high microstructure uniformity, providing high-performance and consistent quality key materials for downstream products such as saw blades, thereby comprehensively improving the service performance and high-grade yield of end products.

[0010] According to some embodiments of the present invention, the chemical composition of the tool steel slab, by mass percentage, includes: C 0.70-0.80%, Si ≤0.35%, Mn 0.60-0.90%, Cr 0.80-1.10%, P ≤0.020%, and S ≤0.015%.

[0011] According to some embodiments of the present invention, the chemical composition of the tool steel slab is: C 0.70-0.80%, Si≤0.35%, Mn 0.60-0.90%, Cr 0.80-1.10%, P≤0.020% and S≤0.015%, with the remainder being Fe and unavoidable impurities.

[0012] According to some embodiments of the present invention, in step A1, the heating temperature is 1150~1120°C.

[0013] According to some embodiments of the present invention, in step A1, the continuous rolling process involves repeating 8 to 12% of the reduction per pass until a steel coil with a thickness of 2.0-5.0 mm is obtained, wherein the width of the steel coil is 1100-1300 mm.

[0014] This compositional design provides a crucial material foundation for subsequent processes: the moderate carbon and chromium content work synergistically to form fine, dispersed alloy cementite, creating favorable conditions for the uniform spheroidization and refinement of carbides during subsequent annealing. The low silicon, phosphorus, and sulfur content ensures material purity, contributing to a uniform microstructure. The appropriate manganese content improves the material's hot working properties, making it more suitable for subsequent hot rolling and cold continuous rolling processes.

[0015] This composition system works in synergy with the entire process to ensure that the material has ideal alloying potential from the source. This enables subsequent precise controlled rolling and cooling, annealing and leveling processes to more effectively achieve fine control of cementite size, significant improvement of microstructure uniformity and optimization of dimensional accuracy. Ultimately, this achieves efficient and stable manufacturing of high-performance 75Cr1 cold-rolled wide steel strip, providing a high-quality and reliable material basis for saw blades and other tool products.

[0016] According to some embodiments of the present invention, the width of the hot-rolled wide coil is 1100-1300 mm and the thickness is 2.0-5.0 mm.

[0017] According to some embodiments of the present invention, the continuous rolling in step A1 is carried out using a hot continuous rolling mill, and the final rolling temperature is controlled at 850-900°C.

[0018] Under the above conditions, on the one hand, it ensures that the material remains in a fully austenitic state during final rolling, possessing excellent plastic deformation capacity, which is conducive to achieving a stable and uniform continuous rolling process and laying the foundation for obtaining good plate shape and thickness accuracy; on the other hand, this temperature range can effectively suppress the premature precipitation and coarsening of carbides during rolling, allowing the austenite grains to be sufficiently refined after deformation, creating favorable grain structure conditions for the dispersion and fine precipitation of carbides during subsequent coiling.

[0019] According to some embodiments of the present invention, the temperature of the heat preservation stage in step A2 is 680-720°C, and the heat preservation time is 10-20 hours.

[0020] Under the above conditions, the initial rapid heating to 180–220℃ helps to quickly cross the low-temperature range where the temperature difference between the surface and core of the steel coil is large, reducing thermal stress caused by uneven heating. Subsequently, heating at a medium rate of 50–70℃ / h to 380–420℃ and holding at this temperature for 3–5h not only makes the overall temperature of the steel coil sufficiently uniform, but more importantly, the material undergoes a recovery process within this temperature range, dislocations begin to reorganize, and internal stress is partially eliminated, providing structural preparation for the subsequent phase transformation process at higher temperatures. Finally, heating at the same rate to the spheroidization temperature (680–720℃) and holding at this temperature for a long time (10–20h) ensures that the pearlite lamellar cementite is fully dissolved, carbon atoms diffuse, and spherical carbides are uniformly precipitated. The above conditions effectively prevent structural stress and deformation caused by excessively rapid heating; promote the elimination of internal stress and homogenization of the structure through medium-temperature heat preservation; and provide a stable and uniform temperature field and sufficient thermodynamic conditions for the final spheroidization stage, thereby ensuring the acquisition of fine, uniform and stable spherical carbide distribution.

[0021] According to some embodiments of the present invention, the annealing heating process in step A2 includes: first heating to 180-220°C within 20-30 minutes, then heating to 380-420°C at a rate of 50-70°C / h and holding at that temperature for 3-5 hours, and then continuing to heat to 680-720°C at a rate of 50-70°C / h and holding at that temperature for 10-20 hours.

[0022] Under these conditions, rapidly heating to 180–220°C within 20–30 minutes can quickly cross the low-temperature range where the surface temperature difference of the steel coil is significant, effectively reducing the accumulation of internal stress caused by thermal shock. Heating to 380–420°C at a rate of 50–70°C / h and holding for 3–5 hours not only promotes the homogenization of the overall temperature field of the steel coil, but more importantly, the material undergoes sufficient recovery within this mid-temperature range, the dislocation structure rearranges, and the internal stress is further eliminated, providing a stable microstructure for the subsequent phase transformation process at high temperatures. Continuing to heat to 680–720°C at the same rate and holding for 10–20 hours ensures the stable progress of the spheroidizing annealing core process, allowing the cementite lamellars to fully dissolve, carbon atoms to fully diffuse, and carbon atoms to precipitate uniformly as spherical carbides.

[0023] According to some embodiments of the present invention, in step A2, the slow cooling step includes: air cooling to 380~400°C.

[0024] According to some embodiments of the present invention, in step A2, the cooling step includes: water cooling to 90~110°C and then removing from the furnace.

[0025] According to some embodiments of the present invention, in step A3, the multi-stand continuous rolling mill is a five-stand cold continuous rolling mill with a total reduction rate of 40% to 60%.

[0026] Under the above conditions, selecting a five-stand cold rolling mill means having multi-pass, continuous deformation capabilities. This allows for the rational distribution of the total reduction (40%–60%) of the deformation across each stand, enabling precise control over the material deformation process. This provides sufficient driving force for the subsequent A4 step of recrystallization annealing, which is beneficial for obtaining a fine and uniform recrystallized structure. Furthermore, this reduction rate is within the reasonable window for cold rolling, achieving significant work hardening and microstructure refinement while avoiding problems such as shape deterioration, edge cracking, or excessive rolling load caused by excessive deformation.

[0027] According to some embodiments of the present invention, in step A3, the acid concentration of the pickling solution is 14% to 20%, the acid temperature is 80 to 90°C, and the pickling speed is 200 to 260 m / min.

[0028] According to some embodiments of the present invention, in step A3, the rinsing temperature is 60~80°C.

[0029] According to some embodiments of the present invention, in step A3, the drying step includes drying at 110-120°C under hot air conditions.

[0030] According to some embodiments of the present invention, in step A3, the cold rolling step includes: production on a five-stand continuous rolling mill, cold rolling work rolls are rolled using 2.0-3.5μm rough rolls; cold rolling reduction of 40-60%; rolling using a roll shifting mode, with the negative shifting value set to 30-10mm.

[0031] According to some embodiments of the present invention, in step A4, the annealing step includes: A4.1 First, raise the temperature to 190-210℃ in 25-35 minutes, then raise it to 390-410℃ at a heating rate of 55-65℃ / h, and hold it at this temperature for 3.5-4.5 hours. Continue heating at a heating rate of 55-65℃ / h to 660-700℃ and hold it for 10-20 hours. After holding, cool it to 640-660℃ at a cooling rate of ≤30℃ / h. Then, under air cooling conditions, cool it to 390-410℃ and switch to water cooling. After cooling to 90-100℃, remove it from the furnace.

[0032] First, during the heating and holding stages, the steel coils with high dislocation density and distorted microstructure after cold rolling were ensured to smoothly and uniformly enter the recrystallization process. The holding stage, with a temperature of 660–700℃, is above the material's recrystallization temperature. This promotes complete recrystallization of distorted grains, significantly improving the material's plasticity and toughness. Furthermore, at this temperature, the further dissolution, precipitation, and maturation of spherical carbides are effectively controlled, preventing abnormal grain growth and resulting in finer, more dispersed carbide particles. Second, during the cooling stage, a multi-stage cooling method was adopted, first slow cooling (≤30℃ / h) to 640–660℃, followed by air cooling and water cooling. This allowed the material to cool slowly within the critical temperature range, promoting stable carbide precipitation and microstructure stabilization, and reducing internal stress and microstructure inhomogeneity caused by excessively rapid cooling. This controlled cooling design ensures the full formation and stability of the spheroidized microstructure while avoiding the risk of deformation and cracking caused by rapid cooling, thus contributing to improved dimensional stability and surface quality of the steel strip.

[0033] In step A4, the heat preservation process also includes cooling, which includes cooling to 640~660℃, air cooling to 380~400℃, and then water cooling to 100℃.

[0034] In step A5, the leveling process includes cooling the steel coil to below 45°C and then leveling it using a 6-roll mill with a leveling reduction of 50-100 μm.

[0035] This application significantly improves production efficiency and reduces manufacturing costs by employing wide-width coil pickling and subsequent bell-type annealing. The cold rolling process utilizes a multi-stand continuous cold rolling mill with high equipment precision and work roll shifting capabilities, enabling efficient and stable rolling of cold-rolled wide coils with uniform thickness and excellent shape. During bell-type annealing, precise control of annealing temperature and holding time effectively regulates the precipitation behavior and particle size of carbides in 75Cr1 steel, providing an ideal microstructure for downstream quenching and tempering heat treatment processes. In summary, the process route proposed in this application is particularly suitable for the large-scale production of 75Cr1 spring steel cold-rolled wide coils, ensuring consistent product performance.

[0036] The present invention also proposes an application of the aforementioned production process in the manufacture of band saw blades, machine tools, automotive elastic elements, or hardware tools. Detailed Implementation

[0037] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0039] To further illustrate the present invention, the following examples are provided: Example 1 A1. The selected steel grade is 75Cr1 alloy steel. After cold rolling, the finished product size is 1.3×1250mm. The following process steps are adopted: Using 75Cr1 slabs as raw materials, the chemical composition is: 0.75%C, 0.32%Si, 0.75%Mn, 0.017%P, 0.002%S, 0.32%Cr, with the remainder being Fe and unavoidable impurities. The slabs are heated to 1180℃, and the spring steel is continuously rolled with a 10% reduction per pass until the thickness of the steel coil is 2.4mm, and the width of the steel coil is 1250mm. After rolling, the coils are cooled and leveled, and the temperature of the steel coils is reduced by spray cooling. After cooling to the target coiling temperature of 590℃, the coils are coiled into a roll shape using a coiler to obtain wide-width coils. A2. The temperature setting process is as follows: the steel coil is heated freely from room temperature (about 30 minutes) to 200℃; then heated to 400℃ at a heating rate of 60℃ / h and held for 4 hours; then heated to 690℃ at a heating rate of 60℃ / h and held for 15 hours; after the holding period, it is slowly cooled to about 650℃; then air-cooled to 400℃; and finally water-cooled to 100℃ before being removed from the furnace. A3. The elongation of the cold rolling mill leveler is set to 2.5%. Hydrochloric acid pickling is performed at a concentration of 16% and a temperature of 80℃. The pickling rate is 240 m / min. The strip is then rinsed with demineralized water at a temperature of 70℃. After rinsing, the strip is dried with hot air at a temperature of 110℃. Cold rolling is carried out using a five-stand continuous rolling mill. The cold rolling work rolls are made with 2.0μm rough rolls. The cold rolling reduction is 45%. Rolling is performed using a roll shifting mode, with the roll shifting values ​​for F1 to F5 set to 30mm, 20mm, 20mm, 10mm, and 0mm, respectively. A4. The steel coil is heated freely from room temperature to 200℃ (about 30 minutes); then heated to 400℃ at a heating rate of 60℃ / h and held for 4 hours; then heated to 670℃ at a heating rate of 60℃ / h and held for 12 hours; after holding, it is slowly cooled to 640℃; then air-cooled to 400℃; finally water-cooled to 100℃ and removed from the furnace. A5. After the steel coil is cooled to below 45℃, it is leveled using a 6-roll mill with a leveling reduction of 50μm. After annealing, a 1.3×1250mm 75Cr1 cold-rolled finished coil is produced, with a thickness accuracy of ±10μm and a crown C40 within 6μm. The steel coil surface is free of oxide residue, the microstructure is grade 5 spheroidized pearlite, the carbide particle grade is 2.1, and the hardness is 167HV.

[0040] Example 2 A1. 75Cr1 alloy steel is selected. The finished product after cold rolling has a size of 2.1×1250mm. The following process steps are adopted: 75Cr1 slab is used as raw material. The chemical composition is: 0.77%C, 0.32%Si, 0.75%Mn, 0.016%P, 0.002%S, 0.35%Cr, with the remainder being Fe and unavoidable impurities. The slab is heated to 1180℃, and the spring steel is continuously rolled with a 10% reduction per pass until the thickness of the steel coil is 3.8mm, and the width of the steel coil is 1250mm. After rolling, the coil is cooled and leveled. The temperature of the steel coil is reduced by spray cooling. After cooling to the target coiling temperature of 580℃, the coil is coiled into a roll shape using a coiler to obtain a wide-width plate coil. A2. The bell-type furnace uses a nitrogen atmosphere for protection. The temperature setting process is as follows: the steel coil is freely heated from room temperature (about 30 minutes) to 200℃; then heated to 400℃ at a heating rate of 60℃ / h and held for 4 hours; then heated to 700℃ at a heating rate of 60℃ / h and held for 15 hours; after the holding period, it is slowly cooled to about 650℃; then air-cooled to 400℃; and finally water-cooled to 100℃ before being unloaded from the furnace. A3. The elongation of the cold rolling mill leveler is set to 2.5%. Hydrochloric acid pickling is performed at a concentration of 16% and a temperature of 80℃. The pickling rate is 200 m / min. The strip is then rinsed with demineralized water at a temperature of 70℃. After rinsing, the strip is dried with hot air at a temperature of 110℃. Cold rolling is carried out using a five-stand continuous rolling mill. The cold rolling work rolls are made with 3.5μm rough rolls. The cold rolling reduction is 45%. Rolling is performed using a roll shifting mode, with the roll shifting values ​​for F1 to F5 set to 20mm, 20mm, 20mm, 10mm, and 0mm, respectively. A4. The steel coil is heated freely from room temperature to 200℃ (about 30 minutes); then heated to 400℃ at a heating rate of 60℃ / h and held for 4 hours; then heated to 680℃ at a heating rate of 60℃ / h and held for 14 hours; after holding, it is slowly cooled to 640℃; then air-cooled to 400℃; finally water-cooled to 100℃ and removed from the furnace. A5. After the steel coil is cooled to below 45℃, it is leveled using a 6-roll mill with a leveling reduction of 50μm. After annealing, a 2.1×1250mm 75Cr1 cold-rolled finished coil is produced, with a thickness accuracy of ±10μm and a crown C40 within 6μm. The steel coil surface is free of oxide residue, the microstructure is grade 5 spheroidized pearlite, the carbide particle grade is 2.1, and the hardness is 161HV.

[0041] Comparative Example 1 The difference between this comparative example and Example 1 is that the coiling temperature after hot rolling is 650°C, while the other conditions are the same.

[0042] In Comparative Example 1, the higher winding temperature of 650℃ led to an increase in the average size of the carbides, which locally exhibited a network or coarse lamellar morphology, losing the fine, dispersed structure required for efficient spheroidization precursors. Although subsequent staged temperature-controlled annealing (A2 and A4) was carried out according to the original scheme, the coarse initial microstructure limited spheroidization kinetics, and significant lamellar carbides remained after A4 annealing. The hardness of the final product fluctuated significantly, and the coarse carbides were prone to becoming fatigue cracks during service, resulting in a decrease in the fatigue life of the band saw blade substrate.

[0043] Comparative Example 2 The difference between this comparative example and Example 1 is that in step A2, the annealing method is continuous annealing (heating rate 30℃ / s, soaking zone 720℃×90s, rapid cooling to room temperature), and the bell-type annealing is not used, while the other conditions are the same.

[0044] Under the above conditions, it is difficult to achieve sufficient spheroidization, and lamellar pearlite or coarse carbides are easily left behind, which is not conducive to subsequent quenching and dissolution.

[0045] Comparative Example 3 This comparative example maintains all other process conditions (including 75Cr1 steel composition, hot rolling regime, A2 annealing parameters, pickling conditions, five-stand cold continuous rolling with roll shifting mode, total reduction rate of 40-60%, etc.) completely identical to those in Example 2, but omits the second annealing after cold rolling (A4) and only retains the first annealing after hot rolling (A2).

[0046] Under the above conditions, the final microstructure still contains a large amount of unspheroidized lamellar pearlite, with a spheroidization grade of only ≤2. This ultimately leads to a decrease in the fatigue life of the band saw blade.

[0047] The above technical solutions of the present invention are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. All equivalent structural transformations made using the specification and contents of the present invention under the technical concept of the present invention, or direct / indirect applications in other related technical fields, are included in the patent protection scope of the present invention.

Claims

1. A manufacturing process for cold-rolled tool steel strip for saw blades, characterized in that, Includes the following steps: A1. After heating the tool steel slab, it is continuously rolled, and the coiling temperature is controlled at 560-600℃ to obtain hot-rolled wide coils. A2. The hot-rolled wide coil is annealed under a protective atmosphere. The annealing process includes a heating stage, a slow cooling stage and a cooling stage. A3. The steel coils obtained after annealing are pickled, rinsed and dried, and then cold rolled in a multi-stand continuous rolling mill, using a roll shifting mode during the rolling process; A4. After annealing the cold-rolled steel coil again under a protective atmosphere, the holding temperature is controlled to be higher than the recrystallization temperature. A5. Cool the annealed steel coil to below 45°C and perform a leveling process to obtain the final cold-rolled steel strip.

2. The production process according to claim 1, characterized in that, The chemical composition of the tool steel slab, by mass percentage, includes: C 0.70-0.80%, Si ≤0.35%, Mn 0.60-0.90%, Cr 0.30-1.10%, P ≤0.020%, and S ≤0.015%.

3. The production process according to claim 2, characterized in that, The chemical composition of the tool steel slab, by mass percentage, includes: C 0.75-0.80%, Si 0.32-0.35%, Mn 0.70-0.80%, Cr 0.30-1.10%, P ≤0.020%, and S ≤0.015%.

4. The production process according to claim 1, characterized in that, The hot-rolled wide strip has a width of 1100–1300 mm and a thickness of 2.0–5.0 mm.

5. The production process according to claim 1, characterized in that, The continuous rolling process described in step A1 uses a hot continuous rolling mill, with the final rolling temperature controlled between 850 and 900°C.

6. The production process according to claim 1, characterized in that, The annealing heating process described in step A2 includes: first heating to 180-220°C within 20-30 minutes, then heating to 380-420°C at a rate of 50-70°C / h and holding for 3-5 hours, and then continuing to heat to 680-720°C at a rate of 50-70°C / h and holding for 10-20 hours.

7. The production process according to claim 1, characterized in that, The multi-stand continuous rolling mill mentioned in step A3 is a five-stand cold continuous rolling mill with a total reduction rate of 40% to 60%.

8. The production process according to claim 1, characterized in that, In step A3, the acid concentration for pickling is 14%–20%, the acid temperature is 80–90℃, and the pickling speed is 200–260 m / min.

9. The production process according to claim 1, characterized in that, In step A4, the annealing step includes: A4.1 First, raise the temperature to 190-210℃ in 25-35 minutes, then raise it to 390-410℃ at a heating rate of 55-65℃ / h, and hold it at this temperature for 3.5-4.5 hours. Continue heating at a heating rate of 55-65℃ / h to 660-700℃ and hold it for 10-20 hours. After holding, cool it to 640-660℃ at a cooling rate of ≤30℃ / h. Then, under air cooling conditions, cool it to 390-410℃ and switch to water cooling. After cooling to 90-100℃, remove it from the furnace.

10. The application of a manufacturing process as described in any one of claims 1 to 9 in the manufacture of band saw blades, machine tools, automotive elastic elements, or hardware tools.