A 1150MPa grade high-strength tool steel wire rod and its manufacturing method

Abstract

The present invention relates to a 1150MPa grade high-strength tool steel wire rod and a manufacturing method thereof. The wire rod is designed with a high Cr and medium carbon component. After the steel billet is rolled and spun into a wire rod, it undergoes an online molten salt low-temperature quenching isothermal treatment. The wire rod is controlled to first undergo a front-end molten salt treatment so that the wire rod enters a lower bainite phase region from a high-temperature austenite state at a cooling rate of ≥35°C / s, forming a structure mainly composed of quenched bainite. The wire rod then undergoes a rear-end molten salt heating isothermal tempering and toughening stress relief treatment, and finally undergoes a roller open cover slow cooling to form a wire rod with a microstructure including tempered bainite and ferrite. The invention can inhibit the initiation of abnormal brittle structure, effectively control the wire rod structure state, and improve the strength and toughness matching of the wire rod, achieving a tensile strength of 1050-1100MPa and a cross-sectional reduction rate of 59%-64%, so that the wire rod can be directly processed into parts after cold forming.

Description

Technical Field

[0001] The present invention belongs to the technical field related to hot-rolled wire rods, and specifically relates to a 1150MPa grade high-strength tool steel wire rod and a manufacturing method thereof. Background Art

[0002] Alloy tool steel is widely used in products such as cutting tools, measuring tools, and screwdrivers. As indispensable basic equipment in the fields of machinery, automobiles, construction, electronics, electrical appliances, and energy, its performance directly affects the production efficiency and development speed of related fields. Improving the grade of tool steel is conducive to reducing material consumption through weight-reduction design, improving tool service performance and fatigue limit, etc. In order to improve the performance of tools, existing high-strength tool steel wire rods, as tool steel base materials, need to be cold-formed and then combined with tempering heat treatment to improve product performance. However, this also increases the energy consumption and cost of tool production, affecting production efficiency. Therefore, it is necessary to develop an 1150MPa grade high-strength tool steel wire rod and its manufacturing method, so that the wire rod can be directly processed into parts after cold working to meet the manufacturing and market needs of the steel industry.

[0003] In the prior art, high-strength tool steel wire rods are often manufactured by adding appropriate amounts of alloying elements such as C, Mn, and Cr to improve hardenability, combined with low-temperature rolling and subsequent Stelmor air-cooling lines. However, the following technical problems exist:

[0004] (1) Although the improvement of alloying elements can improve the performance of tool products, the requirements for production control are also improved. For example, patent CN115976407B discloses a low-alloy hand tool steel coil with a tensile strength of 1000 MPa and a uniform structure, and its production method. It adopts a medium carbon composition design of C-Si-Mn-Cr-V-Al, combined with the Stelmor air-cooled line insulation cooling to produce pearlite + ferrite structure, so that the tensile strength of the wire rod is 1020~1100 MPa, but the Mn and Cr content is relatively high. On the one hand, excessive Mn and Cr content will aggravate the composition segregation, making the internal composition unevenness of the material increase. Even if the hood cooling control is adopted, the wire rod is in contact with the air for heat exchange. At the edge and center of the wire rod, Due to differences in heat dissipation conditions, the temperature drop rate is different. The high content of hardenability elements makes the effect of this temperature difference on the organizational transformation amplified, and the difficulty of air cooling increases, which easily leads to the initiation of low-temperature brittle organizations such as martensite. In subsequent cold processing, such as cold heading and drawing, when subjected to external forces, stress concentration is easily generated in the brittle organization, which leads to cold working cracking failure. On the other hand, components such as Mn significantly improve the stability of austenite, shift the C curve to the right, and extend the incubation period of austenite to pearlite transformation. Due to the limited length of the air cooling line, the wire rod continues to cool down, making it more difficult to improve the plasticity of the wire rod in subsequent processing. After the cold processing process, the wire rod needs to undergo tempering heat treatment to adjust the organizational properties, which affects the production energy consumption, efficiency and cost of the tool.

[0005] (2) In order to improve the problem that the martensitic wire rods with high hardness in the air-cooled line are prone to brittle fracture during packaging, transportation and user processing, although air-cooled / water-cooled lines are used to control the bainite phase transformation, for example, patent CN118621099A discloses an online bainite isothermal quenching process for alloy tool steel wire rods, which uses C-Si-Mn-Cr-Ni-Mo-V composition and combines the Stelmor air-cooled line to quickly cool to the bainite phase region and then maintain the temperature and cool. However, on the one hand, the maximum cooling capacity of the air-cooled line is limited, and the upper bainite phase will be entered under strong air cooling. The temperature difference between the windward and windward sides of the wire rod, the edge to the core, and the overlap and non-overlap positions will be increased, increasing the risk of precipitation of abnormal structures and causing uneven phase transformation of the structure, which will have a negative impact on the toughness and process stability of the wire rod. At the same time, due to insufficient cooling rate and the high transformation temperature of the upper bainite, the ferrite laths are wider and the cementite distribution is discontinuous. The upper bainite has lower strength and hardness than the lower bainite, but poorer plasticity and toughness, which affects the strong and tough mechanical properties of the tool steel and is prone to stress concentration when subjected to stress, thereby promoting crack propagation. On the other hand, the high Si content and the solid solution strengthening effect will cause serious distortion of the ferrite lattice. Even if a thermal insulation cover is used for treatment, the minimum cooling capacity is limited. At the same time, the wire rod is in a low temperature state after passing through the upper bainite phase transformation temperature range, and the structure state cannot be controlled. The structure has large residual stress, which increases the resistance to dislocation movement and reduces the plasticity and toughness of the steel. Cracks are easily generated during cold deformation, and it cannot be directly processed into parts after cold forming. Summary of the Invention

[0006] The present invention aims to solve at least one of the above-mentioned technical problems to a certain extent. The present invention provides an 1150MPa grade high-strength tool steel wire rod and a manufacturing method thereof, which can inhibit the initiation of abnormal brittle structure, effectively control the wire rod structure state, and improve the strength and toughness matching of the wire rod so that it can be directly processed into parts after cold forming.

[0007] The technical solution adopted by the present invention to solve its technical problem is:

[0008] A method for manufacturing 1150MPa grade high-strength tool steel wire rod, the manufacturing method comprising:

[0009] The steel billet is rolled and spun into wire rod at a spinning temperature of ≥905℃, and then undergoes online molten salt low-temperature quenching isothermal treatment. The wire rod is controlled to undergo the front-end molten salt treatment first, so that the wire rod enters the lower bainite phase region from the high-temperature austenite state at a cooling rate of ≥35℃ / s, forming a structure mainly composed of quenched bainite, and then undergoes the back-end molten salt heating isothermal tempering, toughening and stress relief treatment, and finally undergoes roller open cover slow cooling to form a microstructure including tempered bainite and iron. The wire rod comprises a ferrite body, wherein the chemical composition and mass percentage of the wire rod include: C: 0.41% to 0.46%, Si: 0.10% to 0.18%, Mn: 0.45% to 0.60%, Cr: 0.52% to 0.60%, Nb: 0.015% to 0.025%, V: 0.025% to 0.035%, P≤0.015%, S≤0.015%, and the remainder is Fe and unavoidable impurities.

[0010] The chemical composition and mass percentage of the above-mentioned wire rod are designed based on the following:

[0011] (1) Carbon: As a carbide strengthening element and austenite forming element, C is relatively cheaper. With the increase of carbon content, it can improve the stability of supercooled austenite, delay the transformation of pearlite, and promote the formation of quenched bainite during the online molten salt low-temperature quenching isothermal treatment. It can promote the ferrite needles in the quenched bainite to be thinner, so that the needle-shaped ferrite intersects with each other to hinder the expansion of cracks, and the carbides are dispersed to reduce stress concentration, meeting the wear resistance and toughness requirements of hand tools. However, excessive carbon content will cause the bainite needle structure to coarsen, increase internal stress, and reduce the difficulty of improving the plasticity and cold formability of the wire rod. Therefore, in order to meet the wear resistance requirements of hand tool steel, control material costs, and facilitate the control of the microstructure of hot-rolled wire rods and improve the strength-toughness matching, a medium carbon content is used, and the mass percentage of C is controlled to be 0.41%~0.46%.

[0012] (2) Silicon: The Si element can inhibit the grain coarsening during the isothermal quenching of the molten salt online, improve the stability of the supercooled austenite, make the bainite transformation proceed at a lower temperature, compress the pearlite formation range, slightly strengthen the solid solution, and do not significantly affect the tempering softening. However, if the silicon content is too high, the solid solution strengthening effect of silicon will be too strong, which will hinder the complete transformation of bainite, aggravate the lattice distortion, reduce the toughness of the steel, affect the plasticity control, and lead to a decrease in plasticity during cold working. Therefore, the Si content is reduced, and the mass percentage of Si is controlled to be 0.10%~0.18%.

[0013] (3) Manganese: As an austenite-forming element, Mn can expand the austenite zone, increase the hardenability of the wire rod, reduce the tendency to form pearlite and ferrite, strongly delay the pearlite transformation, expand the bainite transformation temperature range, and make the bainite transformation proceed at a lower temperature. At the same time, it slows down the growth rate of the ferrite layer, so that the front molten salt can pass through the quenching, control the wire rod to form a structure dominated by quenched bainite, and form a bainite structure in the core of the wire rod cross section, thereby improving the matrix strength and meeting the wear resistance requirements of the tool. However, when the Mn content is too high, it will aggravate the segregation of alloy elements, increase the risk of precipitation of abnormal martensite structure, promote the coarsening of austenite grains, inhibit the recrystallization of ferrite and the aggregation of carbides during tempering, require higher energy for stress release, and reduce the toughness and plasticity of steel. Therefore, in order to take into account the wear resistance of hand tools and facilitate the bainite phase transformation and isothermal toughening stress relief control of the wire rod, the mass percentage of Mn is controlled to be 0.45%~0.60%.

[0014] (4) Chromium: As a strong carbide-forming element, Cr can form high-hardness alloy carbides, improve the hardenability of steel, reduce the diffusion coefficient of carbon in austenite, shift the pearlite transformation kinetic curve to the right, delay the precipitation of ferrite and pearlite, and make the quenched bainite become the main transformation product during the previous molten salt treatment. Chromium is dissolved in bainite ferrite, improving the resistance to tempering softening and avoiding the rapid decrease in strength during tempering, which is beneficial to improving the wear resistance and corrosion resistance of steel. However, too high Cr content will increase The drastic component segregation increases the difficulty of controlling the uniformity of the organization, delays the nucleation and growth of bainitic ferrite, takes longer to form quenched bainite, and increases the difficulty of improving plasticity. At the same time, the carbide distribution is uneven, forming coarse particles or a network structure, which will reduce the plasticity and cold workability. Therefore, in order to take into account the wear resistance and plasticity and toughness of hand tools, and to facilitate the regulation of the microstructure and organizational state of the wire rod mainly based on tempered bainite, the Cr content is appropriately increased, and the mass percentage of Cr is controlled at 0.52%~0.60%.

[0015] (5) Niobium: Nb microalloying element can precipitate in the initial rolling stage, pin the grain boundaries, inhibit the growth of austenite grains, and improve the strength and toughness through precipitation strengthening and grain refinement. It is beneficial to increase the nucleation sites of quenched bainite, make the quenched bainite structure finer and more dispersed, and retain more substructure strengthening effects. However, the price of Nb is relatively high, and coarse precipitated phases will increase the risk of cracking during cold working of wire rod. Therefore, based on the role of Nb element, cost and preparation control considerations, the mass percentage of Nb is controlled to be 0.015% to 0.025%.

[0016] (6) Vanadium: As an alloying element, V can pin the austenite grain boundaries during the controlled rolling stage, refine the original austenite grains, and promote the formation of high-density dislocations and twins in the bainitic ferrite. It can be dispersed and precipitated during the isothermal process of the subsequent molten salt treatment, which can make up for the strength loss of the quenched bainite softened by tempering, improve the strength without sacrificing toughness, and reduce the crack tendency during cold forming of hand tools. However, the cost of V is relatively high, and excessive addition is not conducive to controlling the cost of wire rods. Excessive V will also cause element enrichment and rapid coarsening of carbides, resulting in loss of strength and toughness. Therefore, based on the role of V, cost and preparation control, the mass percentage of V is controlled to be 0.025%~0.035%.

[0017] (7) Phosphorus and sulfur: P and S are impurity elements. The lower the better. Therefore, P is controlled to be ≤ 0.015% and S is controlled to be ≤ 0.015%.

[0018] The above-mentioned wire rod adopts a medium carbon composition design of C-Si-Mn-Cr-Nb-V, with low C and Si content, high Cr content, and trace addition of Nb and V, which can appropriately control material costs and take into account the wear resistance requirements of tools. It provides favorable conditions for delaying the precipitation of ferrite and pearlite, reducing the temperature of the lower bainite phase region, and promoting the rapid formation of a quenched bainite-based structure in the front-end molten salt treatment of online molten salt low-temperature quenching, and the rapid toughening and stress relief in the rear-end molten salt treatment to avoid excessive strength loss. On this basis, a higher spinning temperature can be selected to reduce the temperature limit of the rolling process, and a higher quenching temperature is used to promote the refinement of bainite phase transformation and improve the strength and toughness matching of the material, so as to avoid the low-temperature quenching affecting the diffusion coefficient of carbon and causing the incubation period to be extended. The wire rod after spinning is directly subjected to online molten salt low-temperature quenching isothermal treatment without air cooling:

[0019] 1. Compared with the Stelmor air-cooled line, the maximum cooling capacity is limited and the temperature control is unstable, which makes it difficult to suppress the formation of brittle structures such as martensite, the structure contains pearlite soft phase, and it is difficult to directly enter the lower bainite phase area. When the wire rod passes through the front molten salt treatment, on the one hand, the thermal conductivity of the molten salt is much higher than that of the air, which can promote the rapid cooling of the wire rod compared to air cooling, so that the wire rod can quickly cross the pearlite and upper bainite formation interval. Combined with the composition design, it avoids the formation of layered pearlite structure due to too slow cooling speed, which affects the strength performance, and avoids the preferential precipitation of ferrite laths in the upper bainite formation interval, and the diffusion of carbon between the laths to form discontinuous cementite, which produces upper bainite that is not conducive to strength, toughness and wear resistance. , the wire rod quickly enters the lower bainite phase region from the high-temperature austenite state, restricting the long-range diffusion of carbon, so that the austenite in this region is fully transformed into quenched bainite with better toughness; on the other hand, when the wire rod passes through the front molten salt, the molten salt covers the surface of the wire rod, which can reduce the temperature difference problem between the windward side and the winded side of the wire rod compared to air cooling, and can avoid a large number of bubbles generated by quenching and adhering to the surface of the wire rod to affect the heat transfer stability. It can reduce the temperature difference from the surface to the core of the wire rod, avoid directly entering the martensite region to form hard and brittle martensite, and promote the formation of a structure dominated by quenched bainite in the wire rod, avoid the residual austenite and form low-temperature abnormal structure in the subsequent cooling process, and have better organizational consistency.

[0020] 2. Compared with the limited minimum cooling capacity and continuous temperature reduction control of the Stelmore air-cooled wire hood cooling, which leads to large organizational stress and insufficient toughness, the wire rod can be subjected to isothermal treatment by heating after passing through the molten salt in the latter stage. On the one hand, compared with the slow cooling of the hood cooling in the pearlite / upper bainite phase region, the molten salt can maintain the wire rod at the molten salt temperature for isothermal treatment, prolonging the time of the wire rod in the high temperature range, providing more thermal power for organizational toughening, promoting the organization of quenched bainite as the main body, improving the high internal stress generated by the shear mechanism during the formation of quenched bainite, and the dislocations in the ferrite move by slipping, climbing, etc., reducing the brittleness of the organization, and further optimizing Matching strength and toughness reduces the tendency to crack; on the other hand, molten salt can heat the wire rod to the dispersion precipitation temperature range of microalloy carbides, increase the precipitation kinetics, and make the supersaturated solid solution microalloy elements begin to dissolve, forming dispersed nano-scale carbides, which are evenly distributed at the grain boundaries, producing a significant dispersion strengthening effect, while avoiding the precipitation and coarsening of carbides such as Cr, maximizing the strengthening effect of carbon elements, and improving the overall strength and plasticity of the wire rod. Finally, the wire rod is slowly cooled after the cover is opened, and the residual heat of the wire rod itself can be used to slowly cool down, continuing the toughening and stress relief effect of the molten salt in the later stage, avoiding stress increase, and at the same time increasing the line speed and promoting rapid production.

[0021] The use of high-temperature soaking and appropriate time in the furnace before rolling can fully dissolve carbon and alloy elements in austenite, improve the plasticity of austenite, lay the foundation for grain refinement control in the subsequent rolling process, and avoid uneven structure caused by component segregation during the rolling process. In the preferred technical solution, before rolling, the soaking temperature of the heating furnace is controlled to be 1100~1150℃, and the time in the furnace is 100~150min.

[0022] Since the spinning temperature is relatively high, it can offset the limitation of rolling temperature. Selecting higher initial rolling temperature and final rolling temperature can increase the rolling speed and reduce the wear effect on the rolling line. The micro-alloying elements can inhibit the growth of austenite grains through solid solution drag. The appropriate deformation amount is used to promote dynamic recrystallization in the final rolling process, refine the grains, provide more nucleation sites for subsequent phase transformation, and refine the structure. In the preferred technical solution, during the rolling, the initial rolling temperature is controlled to be 1020~1060℃, the final rolling temperature is 915~950℃, and the final rolling reduction is 25%~30%.

[0023] During the spinning, the spinning temperature can be further controlled to avoid the risk of austenite grain growth caused by excessive temperature. In a preferred technical solution, during the spinning, the spinning temperature is controlled to be 905-940°C.

[0024] The molten salt temperature of the front section molten salt is in the lower bainite phase region. The lower the molten salt temperature and the longer the treatment time, the faster the wire rod can be cooled, the higher the degree of supercooling can be achieved, and the longer the time is for sufficient atomic diffusion. Carbon is enriched in the untransformed austenite through sufficient diffusion, which inhibits the transformation of pearlite and promotes the transformation of a sufficient amount of high-temperature austenite to single quenched bainite, thus avoiding grain coarsening and improving the strength of the matrix. However, if the molten salt temperature is too low and the treatment time is too long, there is a risk of cooling to the martensite phase region to produce low-temperature abnormal tissue, affect tissue uniformity, increase production energy consumption and insufficient internal stress elimination. On the contrary, if the molten salt temperature is higher and the treatment time is shorter, production energy consumption and the difficulty of subsequent toughening and stress relief can be reduced, but If the molten salt temperature is too high and the treatment time is too short, the proportion of quenched bainite in the structure is small, and there is a risk of forming a soft phase structure during the subsequent heating and isothermal process, which will affect the strength and structure control of the wire rod. Therefore, the appropriate front-stage molten salt temperature and treatment time are selected to control the wire rod from the high-temperature austenite state to the lower bainite phase region, forming a structure mainly composed of quenched bainite, improving the matrix strength, activating the atomic diffusion ability, avoiding excessive residual austenite or the formation of pearlite / martensite mixed structure due to insufficient cooling rate, and making organizational preparations for the subsequent rear-stage molten salt treatment. In the preferred technical solution, the molten salt temperature of the front-stage molten salt is 270~320℃, and the treatment time is 40~65s.

[0025] Since the temperature difference between the spinning temperature of the wire rod and the molten salt temperature of the front section is large, a larger molten salt circulation rate is used to control the molten salt temperature rise, which is beneficial to further control the tissue consistency within the entire length of the wire rod. In the preferred technical solution, the molten salt circulation rate of the front section molten salt is 460~760t / h, and the molten salt temperature rise is ≤8°C.

[0026] The molten salt temperature of the latter section molten salt is in the range of high temperature and microalloy dispersion precipitation temperature. Both Mn and Cr improve the tempering stability of the wire rod. Stress release requires higher energy. The higher the molten salt temperature and the longer the treatment time, the more thermal power can be provided, so that the wire rod can be isothermally tempered in the high-temperature isothermal range for the quenched structure after the front section molten salt treatment, which promotes the reduction of dislocation density, helps to fully release the internal stress of the wire rod, improves the plasticity of the wire rod, and promotes the full dispersion and precipitation of microalloy carbides. However, if the molten salt temperature is too high and the treatment time is too long, it will soften too quickly, and there is a risk of excessive softening leading to a decrease in the bearing capacity of the wire rod and the aggregation and coarsening of alloy carbides, thereby losing strength and plasticity. On the contrary, the lower the molten salt temperature, the The dispersion and precipitation of alloy carbides provide more driving force. As the processing time is shortened, the production energy consumption and softening effect can be reduced. However, if the molten salt temperature is too low and the processing time is too short, the residual stress of the organization will be high, the alloy carbides will not have time to be fully precipitated, and the stability of the precipitated phase will be poor, which will lead to a hard and brittle core and affect the strength and plasticity of the wire rod. Therefore, appropriate molten salt temperature and processing time can be selected for toughening and stress relief treatment to regulate the organizational state and carbide precipitation and improve the strength and plasticity matching of the wire rod. In the preferred technical solution, the molten salt temperature of the latter section is 570~595℃, and the processing time is 120~280s.

[0027] Since the temperature difference between the front-end molten salt and the rear-end molten salt is large, the rear-end molten salt avoids too low a molten salt circulation rate, which helps to maintain the molten salt temperature of the rear-end molten salt stable and reduce production energy consumption by appropriately reducing the molten salt circulation rate. In the preferred technical solution, the molten salt circulation rate of the rear-end molten salt is 350~440t / h.

[0028] In the preferred technical solution, the roller open cover slow cooling controls the wire rod to slowly cool to below 300°C at a cooling rate of 0.7~1.2°C / s, which can prevent the wire rod from cooling too fast during the cooling process, resulting in increased stress, and promote further toughening of the wire rod structure, thereby improving the softening effect of the wire rod. At the same time, it can avoid the cooling rate being too slow, resulting in a slow production rhythm and reduced production efficiency.

[0029] A 1150MPa grade high-strength tool steel wire rod is manufactured by any of the above-mentioned methods for manufacturing 1150MPa grade high-strength tool steel wire rods.

[0030] The above-mentioned wire rod adopts high Cr chemical composition design combined with online molten salt low-temperature quenching isothermal technology. The resulting wire rod structure is mainly tempered bainite with a small amount of ferrite. Compared with the pearlite wire rod structure formed on the air-cooling line, the tempered bainite can retain the strength characteristics of the quenched bainite, make up for the strength loss caused by reducing the alloy content, and avoid abnormal brittle structures such as martensite. Compared with the upper bainite structure formed on the air-cooling line, the ferrite laths are wide and the cementite is discontinuous. Although the plasticity is slightly better than pearlite, the strength is insufficient, and the uneven distribution of cementite can easily become a crack initiation point. The quenching structure formed by the molten salt in the front section The needles of fire bainite are thin and interlaced with each other, and small, dispersed carbides are distributed on the matrix. The performance is between pearlite and martensite, with a balance of high strength and good toughness. It is suitable for tool steels that require impact resistance and wear resistance. After molten salt quenching, it is combined with high-temperature isothermal tempering and toughening and stress relief treatment to transform it into strong and tough tempered bainite. The tempered bainite provides a strong and tough base, and the dispersed carbides further strengthen the matrix, avoiding the decrease in toughness caused by relying solely on solid solution strengthening. It can be further combined with carbide precipitation to optimize the strength and toughness match so that it can be directly processed into parts after cold forming.

[0031] The higher the proportion of tempered bainite in the wire rod microstructure, the better the strength and wear resistance, while maintaining a certain toughness, making the wire rod less likely to suffer brittle fracture. In the preferred technical solution, the volume percentage of the tempered bainite is ≥96%.

[0032] In the preferred technical solution, the diameter of the wire rod is 5.5~10mm, the tensile strength is 1050~1100MPa, the cross-sectional shrinkage rate is 59%~64%, the mechanical property same-circle difference is ≤33MPa, and the wire rod diameter is suitable for processing small and medium-sized hand tools such as wrenches, hammers, and screwdriver rods. The wire rod has good strength, which can prevent the tool from breaking when overloaded. The cross-sectional shrinkage rate reflects the plastic deformation ability of the material, has good toughness reserve and cold formability, can absorb impact energy, and reduce the risk of direct cold processing or sudden fracture during use. The mechanical property same-circle difference reflects the performance uniformity of the wire rod, which is conducive to mass production, and can be directly processed into parts after cold forming, thereby improving the yield rate, tool life, and reducing production costs.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] (1) Aiming at the current situation that it is difficult to control the microstructure and performance of the post-rolling air-cooling line in order to improve the performance of the tool and increase the content of hardenability alloy elements, the present invention combines the online molten salt low-temperature quenching isothermal technology with the design of high Cr chemical composition. With a higher quenching temperature combined with the front-stage molten salt, the wire rod is controlled to quickly pass through the pearlite and upper bainite formation interval and enter the lower bainite phase region to form a structure dominated by quenched bainite. Then, the wire rod is controlled by the rear-stage molten salt to perform high-temperature isothermal tempering on the quenched structure in the high-temperature isothermal interval, toughening and stress relief treatment, control the dispersion and precipitation of carbides, and improve the strength and plasticity matching of the wire rod. Finally, the wire rod structure is further toughened by slow cooling through the roller cover. The wire rod can be quickly offline to improve production efficiency, effectively inhibit the initiation of abnormal brittle structure, control the tempering state of the wire rod structure, improve the strength and toughness matching of the wire rod, reduce the fluctuation of mechanical properties, and has good industrial adaptability.

[0035] (2) In order to improve the performance of tools, appropriate amounts of alloy elements such as C, Mn, and Cr are often added to improve hardenability, and after cold forming, tempering heat treatment is combined to improve product performance, which leads to the initiation of brittle structure, cold working cracking failure, and high energy consumption and cost of tempering heat treatment. The present invention has low C and Si content, high Cr content, and trace additions of Nb and V, which can appropriately control material costs and take into account the wear resistance requirements of tools. At the same time, the microstructure is mainly tempered bainite with a small amount of ferrite structure. Compared with the pearlite wire rod structure formed on the air-cooled line, it can make up for the strength loss caused by reducing the alloy content. Compared with the upper bainite structure formed on the air-cooled line, the tempered bainite is both strong and tough, which can maximize the strengthening effect of carbon elements. Combined with carbide precipitation to optimize the strength and toughness matching, it can achieve a tensile strength of 1050~1100MPa and a cross-sectional shrinkage rate of 59%~64%. After cold forming, it can be directly processed into hand tool parts, which has good market application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments with reference to the accompanying drawings, in which:

[0037] Figure 1 is a metallographic structure diagram of Example 1 of the present invention;

[0038] Figure 2 This is the metallographic structure diagram of Example 2 of the present invention. DETAILED DESCRIPTION

[0039] The embodiments described below with reference to the accompanying drawings are exemplary and are only for illustration and do not limit the description of the features and characteristics of the present invention. They are intended to propose the best way to implement the present invention, are intended to explain the present invention, and are sufficient to enable those skilled in the art to practice the present invention, but should not be understood as limiting the scope of the present invention, which is defined solely by the appended claims. The wire rods obtained in the following embodiments and comparative examples are subjected to microstructure and performance testing, including: tensile testing using "GB-T 228.1-2021 Metallic Materials Tensile Testing Part 1: Room Temperature Test Method" to obtain tensile strength and cross-sectional reduction rate; microstructure testing is performed in accordance with the metal microstructure testing method of GB / T13298 standard; mechanical property same-turn difference test method: 2 turns of wire rod are taken 5m away from the end of the coil, and each turn of wire rod is divided into 8 equal sections with the overlap area as the base point. 1 tensile specimen is taken from each section, and the extreme difference in strength of the tensile specimens after the tensile test is the mechanical property same-turn difference. Example 1:

[0040] A preferred embodiment of the method for manufacturing 1150MPa grade high-strength tool steel wire rod of the present invention comprises the following chemical compositions and mass percentages: C: 0.46%, Si: 0.17%, Mn: 0.60%, Cr: 0.59%, Nb: 0.025%, V: 0.029%, P: 0.013%, S: 0.012%, and the remainder being Fe and unavoidable impurities; the manufacturing method is manufactured according to the process flow of rolling → spinning → online molten salt low-temperature quenching isothermal → roller open cover slow cooling → coiling, specifically:

[0041] The rolling process is used to heat a steel billet with a specification of 220mm×220mm through a heating furnace to achieve a high-temperature steel billet with rollable plasticity, reduce the influence of segregation, and control the heating furnace according to a three-stage temperature rise program of a preheating section, a heating section, and a soaking section. The high-temperature steel billet is rolled into a wire rod with a diameter of 10mm through a rolling line. Appropriate rolling temperature and reduction are selected to increase the rolling speed, promote dynamic recrystallization during the final rolling process, and refine the grains. Specifically, the soaking temperature of the heating furnace is controlled to be 1150°C, the furnace time is 100min, the initial rolling temperature is 1060°C, the final rolling temperature is 950°C, and the final rolling reduction is 25%; the wire-spinning process is used to convert the wire rod exiting the rolling line into a wire rod through a wire-spinning mechanism, and the wire rod is spread on a roller and transported along the roller, so that the wire rod is in a high-temperature austenite state and is prepared for tissue quenching with a higher quenching temperature; specifically, the wire-spinning temperature is controlled to be 940°C.

[0042] The online molten salt low-temperature quenching isothermal process adopts a two-stage salt bath tank with molten salt inside. The wire rod after spinning is conveyed by a roller through the first salt bath tank for front-stage molten salt treatment, so that the wire rod is cooled at a cooling rate of 41°C / s, and quickly passes through the pearlite and upper bainite formation interval from the high-temperature austenite state to enter the lower bainite phase region, forming a structure mainly composed of quenched bainite. After that, the wire rod is conveyed by a roller through the second salt bath tank for rear-stage molten salt treatment, and the wire rod is controlled to perform high-temperature isothermal tempering of the quenched structure in the high-temperature isothermal interval, toughening and stress relief treatment, promote the dispersion and precipitation of microalloy carbides, inhibit carbide coarsening, and improve the strength and plasticity matching of the wire rod. Specifically: the molten salt temperature of the front-stage molten salt is 270°C, the treatment time is 65s, the molten salt circulation volume is 760t / h, and the molten salt temperature rise is ≤8°C; the molten salt temperature of the rear-stage molten salt is 594°C, the treatment time is 280s, and the molten salt circulation volume is 440t / h.

[0043] The roller open cover slow cooling process adopts the method of adjusting the opening of the insulation cover, and the wire rod conveyed by the conveyor roller through the second section of the salt bath tank is slowly cooled through the insulation cover to prevent the wire rod from cooling too fast during the cooling process, thereby increasing the stress, promoting further toughening of the wire rod structure, and improving the softening effect of the wire rod until it is coiled. Specifically: the wire rod is controlled to slowly cool to 291°C at a cooling rate of 1.2°C / s; the coiling process is used to coil the wire rod into a coil through a coiling drum, and the finished wire rod is obtained after packaging and storage. Its metallographic structure diagram is as follows Figure 1 shown.

[0044] Comparative Example 1:

[0045] A method for manufacturing wire rod, which differs from that of Example 1 in that: the manufacturing method is manufactured according to the process flow of rolling → spinning → Stelmor air cooling line → coiling, specifically: in the rolling process, the heating furnace soaking temperature is controlled to 1050°C, the furnace time is 175 minutes, the initial rolling temperature is 1005°C, the final rolling temperature is 840°C, and the spinning temperature is controlled to be 815°C. The Stelmor air cooling line adopts the front 1~6# insulation covers to be opened, and the fan is turned on to control the wire rod to be cooled to 675°C at a rate of 4.5°C / s. Thereafter, the insulation cover is closed, the wire rod enters the insulation cover and is cooled to 290°C at a rate of 2.6°C / s, and is collected by the coiling drum to obtain a finished wire rod.

[0046] Comparative Example 2:

[0047] A method for manufacturing a wire rod, which differs from Example 1 in that: the soaking temperature of the heating furnace is controlled to 1065°C, the time in the furnace is 165 minutes, the initial rolling temperature is 1010°C, the final rolling temperature is 875°C, the spinning temperature is controlled to be 855°C, the wire rod is treated with molten salt in the front section and cooled at a cooling rate of 34°C / s to obtain a finished wire rod. Example 2:

[0048] A preferred embodiment of the method for manufacturing 1150MPa grade high-strength tool steel wire rod of the present invention comprises the following chemical compositions and mass percentages: C: 0.42%, Si: 0.10%, Mn: 0.49%, Cr: 0.52%, Nb: 0.015%, V: 0.025%, P: 0.015%, S: 0.015%, and the remainder being Fe and unavoidable impurities; the manufacturing method is manufactured according to the process flow of rolling → spinning → online molten salt low-temperature quenching isothermal → roller open cover slow cooling → coiling, specifically:

[0049] The rolling process is used to heat a steel billet with a specification of 180mm×180mm through a heating furnace to achieve a high-temperature steel billet with rollable plasticity, reduce the influence of segregation, and control the heating furnace according to a three-stage temperature rise program of a preheating section, a heating section, and a soaking section. The high-temperature steel billet is rolled into a wire rod with a diameter of 5.5mm through a rolling line. Appropriate rolling temperature and reduction are selected to increase the rolling speed, promote dynamic recrystallization during the final rolling process, and refine the grains. Specifically, the soaking temperature of the heating furnace is controlled to be 1100°C, the furnace time is 150min, the initial rolling temperature is 1020°C, the final rolling temperature is 915°C, and the final rolling reduction is 30%; the wire-spinning process is used to convert the wire rod exiting the rolling line into a wire rod through a wire-spinning mechanism, and the wire rod is spread on a roller and transported along the roller, so that the wire rod is in a high-temperature austenite state and is prepared for tissue quenching with a higher quenching temperature; specifically, the wire-spinning temperature is controlled to be 905°C.

[0050] The online molten salt low-temperature quenching isothermal process adopts a two-stage salt bath tank with molten salt inside. The wire rod after spinning is conveyed by a roller through the first salt bath tank for front-stage molten salt treatment, so that the wire rod is cooled at a cooling rate of 35°C / s, and quickly passes through the pearlite and upper bainite formation interval from the high-temperature austenite state to enter the lower bainite phase region, forming a structure mainly composed of quenched bainite. After that, the wire rod is conveyed by a roller through the second salt bath tank for rear-stage molten salt treatment, and the wire rod is controlled to perform high-temperature isothermal tempering of the quenched structure in the high-temperature isothermal interval, toughening and stress relief treatment, promote the dispersion and precipitation of microalloy carbides, inhibit carbide coarsening, and improve the strength and plasticity matching of the wire rod. Specifically: the molten salt temperature of the front-stage molten salt is 320°C, the treatment time is 40s, the molten salt circulation volume is 460t / h, and the molten salt temperature rise is ≤8°C; the molten salt temperature of the rear-stage molten salt is 570°C, the treatment time is 120s, and the molten salt circulation volume is 350t / h.

[0051] The roller open cover slow cooling process adopts the method of adjusting the opening of the insulation cover, and the wire rod conveyed by the conveyor roller through the second section of the salt bath tank is slowly cooled through the insulation cover to prevent the wire rod from cooling too fast during the cooling process, thereby increasing the stress, promoting further toughening of the wire rod structure, and improving the softening effect of the wire rod until it is coiled. Specifically: the wire rod is controlled to slowly cool to 298°C at a cooling rate of 0.7°C / s; the coiling process is used to coil the wire rod into a coil through a coiling drum, and the finished wire rod is obtained after packaging and storage. Its metallographic structure diagram is as follows Figure 2 shown.

[0052] Comparative Example 3:

[0053] A method for manufacturing wire rod, which differs from Example 2 in that: the wire rod is treated with a front-stage molten salt and cooled at a cooling rate of 32°C / s, the molten salt temperature of the front-stage molten salt is 335°C, and the treatment time is 25s to obtain a finished wire rod.

[0054] Comparative Example 4:

[0055] A method for manufacturing wire rod, which differs from Example 2 in that: the wire rod is treated with a front-stage molten salt and cooled at a cooling rate of 29°C / s, the molten salt temperature of the front-stage molten salt is 265°C, and the treatment time is 68s to obtain a finished wire rod. Example 3:

[0056] A preferred embodiment of the method for manufacturing 1150MPa grade high-strength tool steel wire rod of the present invention comprises the following chemical compositions and mass percentages: C: 0.41%, Si: 0.18%, Mn: 0.55%, Cr: 0.60%, Nb: 0.02%, V: 0.035%, P: 0.012%, S: 0.012%, and the remainder being Fe and unavoidable impurities; the manufacturing method is manufactured according to the process flow of rolling → spinning → online molten salt low-temperature quenching isothermal → roller open cover slow cooling → coiling, specifically:

[0057] The rolling process is used to heat a steel billet with a specification of 180mm×180mm through a heating furnace to achieve a high-temperature steel billet with rollable plasticity, reduce the influence of segregation, and control the heating furnace according to a three-stage temperature rise program of a preheating section, a heating section, and a soaking section. The high-temperature steel billet is rolled into a wire rod with a diameter of 9mm through a rolling line. Appropriate rolling temperature and reduction are selected to increase the rolling speed, promote dynamic recrystallization during the final rolling process, and refine the grains. Specifically, the soaking temperature of the heating furnace is controlled to be 1135°C, the furnace time is 120min, the initial rolling temperature is 1050°C, the final rolling temperature is 945°C, and the final rolling reduction is 26%; the wire-spinning process is used to convert the wire rod exiting the rolling line into a wire rod through a wire-spinning mechanism, and the wire rod is spread on a roller and transported along the roller, so that the wire rod is in a high-temperature austenite state and is prepared for tissue quenching with a higher quenching temperature; specifically, the wire-spinning temperature is controlled to be 928°C.

[0058] The online molten salt low-temperature quenching isothermal process adopts a two-stage salt bath tank with molten salt inside. The wire rod after spinning is conveyed by a roller through the first salt bath tank for front-stage molten salt treatment, so that the wire rod is cooled at a cooling rate of 39°C / s, and quickly passes through the pearlite and upper bainite formation interval from the high-temperature austenite state to enter the lower bainite phase region, forming a structure mainly composed of quenched bainite. After that, the wire rod is conveyed by a roller through the second salt bath tank for rear-stage molten salt treatment, and the wire rod is controlled to perform high-temperature isothermal tempering of the quenched structure in the high-temperature isothermal interval, toughening and stress relief treatment, promote the dispersion and precipitation of microalloy carbides, inhibit carbide coarsening, and improve the strength and plasticity matching of the wire rod. Specifically: the molten salt temperature of the front-stage molten salt is 279°C, the processing time is 58s, the molten salt circulation volume is 675t / h, and the molten salt temperature rise is ≤8°C; the molten salt temperature of the rear-stage molten salt is 583°C, the processing time is 245s, and the molten salt circulation volume is 415t / h.

[0059] The roller open cover slow cooling process adopts the method of adjusting the opening of the insulation cover, and the wire rod transported by the conveyor roller through the second salt bath tank is slowly cooled through the insulation cover to prevent the wire rod from cooling too fast during the cooling process, which leads to increased stress, and promotes further toughening of the wire rod structure, thereby improving the softening effect of the wire rod until it is coiled. Specifically: the wire rod is controlled to slowly cool to 295°C at a cooling rate of 1.1°C / s; the coiling process is used to coil the wire rod into a coil through a coiling drum, and the finished wire rod is obtained after packaging and storage.

[0060] Comparative Example 5:

[0061] A method for manufacturing a wire rod, which differs from the manufacturing method of Example 3 in that the molten salt temperature of the rear stage molten salt is 600° C., the processing time is 360 s, and the finished wire rod is obtained.

[0062] Comparative Example 6:

[0063] A method for manufacturing a wire rod, which differs from Example 3 in that the molten salt temperature of the rear-stage molten salt is 560° C., the processing time is 100 s, and the finished wire rod is obtained. Example 4:

[0064] A preferred embodiment of the method for manufacturing 1150MPa grade high-strength tool steel wire rod of the present invention comprises the following chemical compositions and mass percentages: C: 0.43%, Si: 0.12%, Mn: 0.45%, Cr: 0.54%, Nb: 0.022%, V: 0.03%, P: 0.014%, S: 0.013%, and the remainder being Fe and unavoidable impurities; the manufacturing method is manufactured according to the process flow of rolling → spinning → online molten salt low-temperature quenching isothermal → roller open cover slow cooling → coiling, specifically:

[0065] The rolling process is used to heat a steel billet with a specification of 180mm×180mm through a heating furnace to achieve a high-temperature steel billet with rollable plasticity, reduce the influence of segregation, and the heating furnace is controlled according to a three-stage temperature rise program of a preheating section, a heating section and a soaking section. The high-temperature steel billet is rolled into a wire with a diameter of 7mm through a rolling line. Appropriate rolling temperature and reduction are selected to increase the rolling speed, promote dynamic recrystallization during the final rolling process, and refine the grains. Specifically, the soaking temperature of the heating furnace is controlled to be 1115°C, the time in the furnace is 135min, the initial rolling temperature is 1035°C, the final rolling temperature is 925°C, and the final rolling reduction is 28%; the wire-spinning process is used to convert the wire exiting the rolling line into a wire rod through a wire-spinning mechanism, and the wire rod is spread on a roller and transported along the roller, so that the wire rod is in a high-temperature austenite state and is prepared for tissue quenching with a higher quenching temperature; specifically, the wire-spinning temperature is controlled to be 915°C.

[0066] The online molten salt low-temperature quenching isothermal process adopts a two-stage salt bath tank with molten salt inside. The wire rod after spinning is conveyed by a roller through the first salt bath tank for front-stage molten salt treatment, so that the wire rod is cooled at a cooling rate of 37°C / s, and quickly passes through the pearlite and upper bainite formation interval from the high-temperature austenite state to enter the lower bainite phase region, forming a structure mainly composed of quenched bainite. After that, the wire rod is conveyed by a roller through the second salt bath tank for rear-stage molten salt treatment, and the wire rod is controlled to perform high-temperature isothermal tempering of the quenched structure in the high-temperature isothermal interval, toughening and stress relief treatment, promote the dispersion and precipitation of microalloy carbides, inhibit carbide coarsening, and improve the strength and plasticity matching of the wire rod. Specifically: the molten salt temperature of the front-stage molten salt is 298°C, the processing time is 46s, the molten salt circulation volume is 565t / h, and the molten salt temperature rise is ≤8°C; the molten salt temperature of the rear-stage molten salt is 576°C, the processing time is 183s, and the molten salt circulation volume is 380t / h.

[0067] The roller open cover slow cooling process adopts the method of adjusting the opening of the insulation cover, and the wire rod transported by the conveyor roller through the second salt bath tank is slowly cooled through the insulation cover to prevent the wire rod from cooling too fast during the cooling process, thereby increasing the stress, promoting further toughening of the wire rod structure, and improving the softening effect of the wire rod until it is coiled. Specifically: the wire rod is controlled to slowly cool to 297°C at a cooling rate of 0.85°C / s; the coiling process is used to coil the wire rod into a coil through a coiling drum, and the finished wire rod is obtained after packaging and storage.

[0068] Comparative Example 7:

[0069] A method for manufacturing a wire rod, which differs from Example 4 in that: the manufacturing method follows a process flow of rolling → spinning → online molten salt low-temperature quenching isothermal → air cooling → coiling. Specifically: the air cooling process uses a wire rod transported by a conveyor roller through a second salt bath tank to naturally cool in the air. The wire rod is cooled to 290°C at a cooling rate of 2.2°C / s to obtain the wire rod.

[0070] The structure and performance of the wire rods obtained in Examples 1 to 4 and Comparative Examples 1 to 7 were tested, and the comparative results are shown in Table 1 below:

[0071] Table 1. Comparison of microstructure and properties of different wire rod compositions and manufacturing methods

[0072]

[0073] From the comparison results of Example 1 and Comparative Example 1, it can be seen that compared with the air-cooled line, the strengthening effect is often weakened due to the uncontrollable cooling rate during the cooling phase transformation process, and abnormal structures such as martensite are generated. The present invention can effectively avoid the risk of C and Cr elements generating brittle structures such as martensite and widmanstattenite through online molten salt isothermal toughening technology, and can maximize the strengthening effect of carbon elements, thereby improving the overall strength and plasticity of the wire rod; from the results of Examples 1 to 4, it can be seen that the present invention adopts a high Cr chemical composition design combined with online molten salt low-temperature quenching isothermal technology, and the obtained wire rod structure is mainly tempered bainite with a small amount of ferrite, which effectively controls the wire rod structure state and improves the strength and toughness matching of the wire rod, reaching a tensile strength of 1050~1100MPa and a cross-sectional shrinkage rate of 59%~64%, so that it can be directly processed into parts after cold forming, eliminating the tempering heat treatment after cold working, improving production efficiency and reducing production costs.

[0074] From the comparison results of Example 1 and Comparative Example 2, it can be seen that low-temperature quenching affects the diffusion coefficient of carbon and causes the incubation period to be extended. Under the same conditions of the previous molten salt treatment, it affects the quenched bainite phase change. A higher quenching temperature is beneficial to promote the refinement of the bainite phase transformation and improve the strength and toughness of the material.

[0075] From the comparison results of Example 2 and Comparative Example 3, it can be seen that the molten salt temperature of the front stage is too high and the treatment time is too short, which can reduce production energy consumption and the difficulty of subsequent toughening and stress relief. However, the molten salt temperature is too high and the treatment time is too short, and the proportion of quenched bainite in the structure is small, and there is a risk of forming a soft phase structure in the subsequent heating and isothermal process, which will affect the strength and structure control of the wire rod.

[0076] From the comparison results of Example 2 and Comparative Example 4, it can be seen that the lower the molten salt temperature of the front-stage molten salt and the longer the treatment time, the more it can promote the full transformation of the wire rod from high-temperature austenite to quenched bainite and improve the matrix strength. However, if the molten salt temperature is too low and the treatment time is too long, there is a risk of cooling to the martensite phase region to produce low-temperature abnormal structure, affect the uniformity of the structure, increase production energy consumption and insufficient elimination of internal stress.

[0077] From the comparison results of Example 3 and Comparative Example 5, it can be seen that the higher the molten salt temperature of the rear-stage molten salt and the longer the treatment time, the more thermal power can be provided, which is conducive to the full release of the internal stress of the wire rod, the improvement of the plasticity of the wire rod, and the promotion of the full dispersion and precipitation of microalloy carbides. However, if the molten salt temperature is too high and the treatment time is too long, there is a risk of excessive softening leading to a decrease in the bearing capacity of the wire rod and the aggregation and coarsening of alloy carbides, resulting in a loss of strength and plasticity.

[0078] From the comparison results of Example 3 and Comparative Example 6, it can be seen that the lower the molten salt temperature of the latter molten salt, the more conducive it is to the dispersion and precipitation of alloy carbides. However, if the molten salt temperature is too low and the processing time is too short, the residual stress of the organization will be high, the alloy carbides will not have time to fully precipitate, and the precipitated phase stability will be poor, which will make the core hard and brittle, affecting the plasticity and organizational uniformity of the wire rod.

[0079] From the comparison results of Example 4 and Comparative Example 7, it can be seen that slow cooling with the roller cover open can control the slow cooling of the wire rod compared to air cooling, promote further toughening of the wire rod structure, improve the softening effect of the wire rod, and avoid stress increase caused by excessive cooling. At the same time, closing the insulation cover more completely can promote the rapid offline of the wire rod, thereby improving production rhythm and efficiency.

[0080] The series of detailed descriptions listed above are only specific descriptions of feasible embodiments of the present invention. They are not intended to limit the scope of protection of the present invention. Any equivalent embodiments or changes that do not deviate from the technical spirit of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for manufacturing 1150MPa grade high strength tool steel wire rod, characterized in that: The manufacturing method includes: The steel billet is rolled and spun into a wire rod at a spinning temperature of ≥905°C, and then subjected to an online molten salt low-temperature quenching isothermal treatment. The wire rod is controlled to first undergo a front-end molten salt treatment so that the wire rod enters the lower bainite phase region from the high-temperature austenite state at a cooling rate of ≥35°C / s to form a structure mainly composed of quenched bainite. The steel billet is then subjected to a rear-end molten salt heating isothermal tempering and toughening stress relief treatment, and finally subjected to a roller open cover slow cooling to form a wire rod with a microstructure including tempered bainite and ferrite. The chemical composition and mass percentage of the wire rod include: C: 0.41%~0.46%, Si: 0.10%~0.18%, M:

0. n: 0.45%~0.60%, Cr: 0.52%~0.60%, Nb: 0.015%~0.025%, V: 0.025%~0.035%, P≤0.015%, S≤0.015%, and the rest are Fe and unavoidable impurities; the molten salt temperature of the front section molten salt is 270~320℃, and the processing time is 40~65s; the molten salt temperature of the rear section molten salt is 570~595℃, and the processing time is 120~280s, and the roller open cover slow cooling controls the wire rod to slowly cool to below 300℃ at a cooling rate of 0.7~1.2℃ / s.

2. The method for manufacturing 1150 MPa grade high strength tool steel wire rod according to claim 1, characterized in that: Before the rolling, the soaking temperature of the heating furnace is controlled to be 1100-1150° C., and the soaking time in the furnace is 100-150 minutes.

3. The method for manufacturing 1150 MPa grade high strength tool steel wire rod according to claim 1, characterized in that: During the rolling, the initial rolling temperature is controlled to be 1020-1060° C., the final rolling temperature is controlled to be 915-950° C., and the final rolling reduction is controlled to be 25%-30%.

4. The method for manufacturing 1150 MPa grade high strength tool steel wire rod according to claim 1, characterized in that: During the spinning process, the spinning temperature is controlled to be 905-940°C.

5. The method for manufacturing 1150 MPa grade high strength tool steel wire rod according to claim 1, characterized in that: The molten salt circulation rate of the front-stage molten salt is 460-760 t / h, and the molten salt temperature rise is ≤8°C; the molten salt circulation rate of the rear-stage molten salt is 350-440 t / h.

6. A 1150MPa grade high strength tool steel wire rod, characterized in that: The wire rod is manufactured by the manufacturing method of 1150MPa grade high strength tool steel wire rod according to any one of claims 1 to 5.

7. The 1150 MPa grade high strength tool steel wire rod according to claim 6, characterized in that: The volume percentage of the tempered bainite is ≥96%.

8. The 1150 MPa grade high strength tool steel wire rod according to claim 6, characterized in that: The wire rod has a diameter of 5.5-10 mm, a tensile strength of 1050-1100 MPa, a cross-sectional shrinkage rate of 59%-64%, and a mechanical property difference of ≤33 MPa.

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