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

Abstract

The present invention relates to a 1150MPa grade high-strength carbon tool steel wire rod and a manufacturing method thereof. The chemical composition and mass percentage of the wire rod include: C: 0.57%-0.62%, Si: 0.38%-0.47%, Mn: 0.53%-0.63%, P≤0.015%, S≤0.015%, and the remainder is Fe and inevitable impurities. After being rolled and spun into wire rod, the wire rod is subjected to an online molten salt isothermal toughening treatment to control the wire rod from a high-temperature austenite state to enter a sorbite phase region to form a structure dominated by sorbite with fine lamellar spacing. The wire rod is isothermal tempered and finally slowly cooled on a roller to form a wire rod with a microstructure including tempered sorbite, ferrite and fused sorbite. The wire rod can achieve a tensile strength of 1050-1100MPa and a cross-sectional reduction rate of 45%-50%. The wire rod is used in the manufacture of carbon tool steel and other application fields, so that it can be directly processed into tool 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 carbon tool steel wire rod and a manufacturing method thereof. Background Art

[0002] Carbon tool steel, due to its low raw material cost and relatively simple smelting process, is widely used in the manufacture of cutting tools, molds, and measuring tools after cold forming and heat treatment. Low cost and excellent durability, key competitive advantages of carbon tool steel, significantly impact companies' orders. However, continued improvements in the durability of carbon tool steel lead to increased production costs and a decline in companies' market competitiveness. Therefore, it is necessary to develop a heat-treatment-free, high-strength carbon tool steel wire rod and its manufacturing method, so that it can be directly processed into tool parts after cold forming, thereby rapidly improving companies' competitiveness.

[0003] Existing tool steel wire rods contain alloying elements such as Cr, V, and Nb and are produced using a Stelmor air-cooled line. For example, patent CN119640155A discloses a low-cost, high-plasticity sorbite tool alloy steel wire rod and its manufacturing method. This wire rod utilizes a medium-carbon, high-silicon composition of C-Si-Mn-Cr, combined with low-temperature rolling followed by air cooling and heat preservation cooling to produce a sorbite structure wire rod with a tensile strength of 1045-1075 MPa. While it lacks precious microalloying elements such as V and Mo, it does contain high Si, Mn, and Cr contents. Further reducing the alloying content and eliminating alloying elements in the manufacture of carbon tool steel wire rods presents the following technical challenges:

[0004] First, due to the absence of grain-refining elements such as V and Nb, in order to suppress grain coarsening during rolling and obtain sorbite structure on the air-cooling line, low-temperature controlled rolling and spinning are required to refine grains and retain some rolling distortion. However, this also leads to an increase in the deformation resistance of the rolled piece and the load demand of the rolling line, which will aggravate the wear of the rolling line, resulting in a decrease in rolling speed and efficiency, affecting production efficiency.

[0005] 2. In alloy steel wire rods, high silicon content is used for solid solution strengthening of ferrite, and Mn and Cr elements are used to improve the hardenability of the wire rods to promote the transformation of supercooled austenite to sorbite under air cooling. However, after reducing the alloy content and omitting the hardenability alloying elements, the stability of supercooled austenite decreases. Limited by the maximum cooling capacity of the Stelmor air-cooling line, coarse lamellar pearlite or a mixed structure of pearlite and ferrite is easily formed in the wire rod. The sorbite content is reduced, resulting in a significant decrease in the strength and toughness of the wire rod, affecting the durability of the tool steel. Cold processing has to use heat treatment to adjust the product performance, which also brings about problems of energy consumption, increased cost and decreased efficiency in the production of tool steel products. Therefore, conventional carbon steel wire rods generally compensate for strength by increasing the carbon content, but high carbon content will lead to network carbon problems and a sharp drop in plasticity, making it easy to crack during cold processing.

[0006] 3. After low alloying, the cooling rate sensitivity of wire rod increases. After the air cooling intensity is improved, the temperature difference between the windward side and the windward side, the overlap and the non-overlap will be further increased due to the instability of the fan air volume and air temperature. Due to the coarse grains and local rapid cooling, brittle phases such as widmanstatten and martensite are easily formed, resulting in higher tissue stress and deterioration of the plastic and toughness properties of the wire rod. At the same time, long-term heat preservation treatment at a higher hood temperature will affect the offline speed and production efficiency. The temperature gradient from the surface to the core will be further increased, making it easier for the core to form a soft phase pearlite structure at a slower cooling rate, which not only leads to a decrease in matrix strength and tissue uniformity, The fluctuation of mechanical properties will further increase, and will aggravate the accumulation of thermal stress before phase transformation, so that the surface will be constrained by the core to produce tensile stress, and the superposition will produce tissue stress. Limited by the length and minimum cooling capacity of the Stelmor air-cooling line, the wire rod requires a longer phase transformation incubation time during the continuous cooling process. The coarse and uneven distribution of cementite lamellae will increase the difficulty of stress release. The wire rod is in a low-temperature state after phase transformation incubation, so that there is a large amount of residual stress in the organization. In the subsequent cold processing, the residual stress is superimposed on the external load, and it is easy to reach the fracture strength in the stress concentration area, resulting in wire breakage or cracks in use, affecting the process qualification rate and durability of the tool steel. Summary of the Invention

[0007] 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 carbon tool steel wire rod and a manufacturing method thereof, which can reduce material costs and improve the overall strength and plasticity of the wire rod so that it can be directly processed into tool parts after cold forming, thereby reducing the production energy consumption and cost of tool steel products and improving production efficiency.

[0008] The technical solution adopted by the present invention to solve its technical problem is:

[0009] A method for manufacturing 1150MPa grade high-strength carbon tool steel wire rod, the manufacturing method comprising:

[0010] The steel billet is rolled and spun into a wire rod at a spinning temperature of ≥850°C, and then subjected to an online molten salt isothermal toughening treatment. The wire rod is controlled to enter the sorbite phase region from the high-temperature austenite state at a cooling rate of ≥35°C / s to form a structure mainly composed of sorbite. The wire rod is controlled to be isothermal tempered in the isothermal range to promote the melting of the sorbite lamellae and toughening and stress relief treatment. Finally, it is slowly cooled by a roller to form a wire rod with a microstructure including tempered sorbite, ferrite and fused sorbite. The chemical composition and mass percentage of the wire rod include: C: 0.57%~0.62%, Si: 0.38%~0.47%, Mn: 0.53%~0.63%, P≤0.015%, S≤0.015%, and the rest are Fe and unavoidable impurities.

[0011] The chemical composition and mass percentage of the above-mentioned wire rod are designed based on the following:

[0012] (1) Carbon: C is an effective carbide strengthening element and austenite forming element. It is relatively cheap and can improve the hardness of wire rod and the wear resistance of tool steel through solid solution strengthening. As the carbon content increases, it can increase the carbon solubility of austenite, reduce the critical temperature of austenite to sorbite transformation, shift the temperature range of sorbite transformation to low temperature, inhibit the formation of ferrite, and slow the atomic diffusion rate at low temperature, which increases the nucleation rate of sorbite and reduces the interlamellar spacing during molten salt treatment. The hardness before tempering is higher and the tempering resistance is better. The softening ability is enhanced to provide a strong and tough foundation, but too high a carbon content will increase the decarburization sensitivity, the risk of carbon segregation and proeutectoid carbide precipitation during solidification and rolling, increase the difficulty of controlling the uniformity of the organization, prolong the incubation period of the sorbite phase transformation, increase the difficulty of eliminating the residual stress during tempering, and reduce the toughness and plasticity of the steel. Therefore, in order to meet the strength and durability requirements of tool steel, control material costs, and avoid excessive tempering softening and excessive decrease in strength and hardness, the mass percentage of C is controlled to 0.57%~0.62%.

[0013] (2) Silicon: Si is a deoxidizing element that can improve the purity of steel, increase the hardness of austenite through solid solution strengthening, and reduce the critical cooling rate of austenite to pearlite transformation, inhibit grain coarsening and cementite precipitation during online molten salt isothermal toughening treatment, help inhibit the formation of coarse pearlite lamellae, complete the phase transformation at a lower temperature, slow down the atomic diffusion rate, and easily form finer sorbite lamellae. During isothermal tempering, silicon can hinder the diffusion and migration of carbon atoms, improve the tempering stability, delay the hardness decline, and keep the hardness and wear resistance stable after cold working. However, too high silicon content will lead to an increase in inclusions, slow down the phase transformation inoculation transformation rate, reduce the plasticity and impact toughness of the wire rod, and affect the cold working performance. Therefore, in order to improve the matrix strength and adapt to the regulation of the organization by online molten salt, the mass percentage of Si is controlled to 0.38%~0.47%.

[0014] (3) Manganese: Mn is a hardenability element and a strong austenite stabilizing element. It can expand the austenite zone, significantly reduce the critical temperature of troostite transformation, inhibit the formation of ferrite and the coarsening of pearlite lamellae, and make the cementite lamellae of troostite thinner and smaller in spacing with molten salt treatment, thereby refining the structure. Because the lamellae are finer and the grain boundary area is larger, dislocation movement and slip are more likely to release residual stress through grain boundaries during tempering. However, when the Mn content is too high, it tends to promote the growth of steel grains. High temperature heating can easily lead to grain coarsening, increase the risk of segregation during the solidification process of the steel billet, and thus affect the local phase transformation rate, increase the phase transformation stress and the risk of precipitation of abnormal structure, and affect the impact toughness and fatigue performance of the wire rod. Therefore, in order to take into account the durability of tool steel wire rod, facilitate the regulation of microstructure phase transformation by molten salt treatment, and reduce the difficulty of controlling plasticity and microstructure uniformity, the mass percentage of Mn is controlled to be 0.53%~0.63%.

[0015] (4) 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%.

[0016] The above-mentioned wire rod adopts the carbon composition design of C-Si-Mn, does not contain alloying elements such as Cr and V, and has a lower Si content, which can reduce material costs. At the same time, it regulates the hardenability and temper softening resistance of the wire rod, and provides favorable conditions for the sorbite phase transformation to be carried out at a lower temperature to refine the interlamellar spacing, reduce the difficulty of organizational uniformity and plasticity control, and avoid excessive reduction in strength and hardness. On this basis, a higher spinning temperature is selected to keep the wire rod in a high-temperature austenite state, avoiding insufficient diffusion of carbon or alloying elements due to too low spinning temperature. The uniform austenite state provides a consistent matrix for the subsequent sorbite phase transformation, and makes organizational preparations for increasing supercooling, accelerating phase transformation dynamics, and suppressing coarse pearlite. After spinning, the wire rod is not air-cooled, but directly subjected to online molten salt isothermal toughening treatment in molten salt:

[0017] 1. Compared with the Stelmor air cooling line, which is difficult to suppress coarse pearlite or brittle abnormal structure due to limited maximum cooling capacity and unstable temperature control, on the one hand, molten salt can promote rapid cooling of wire rod, skip the pre-eutectoid precipitation stage of austenite to ferrite or cementite, avoid the interference of pre-eutectoid phase, cool down to the sorbite phase region, suppress the formation of coarse pearlite, use greater undercooling to increase the phase transformation driving force, promote the improvement of sorbite nucleation rate, generate sorbite structure with finer interlamellar spacing, make up for the omission of alloying elements such as V and Nb and Cr, Mo, etc. The adverse effect of hardenability elements on the sorbite phase transformation can promote the full transformation of austenite structure to sorbite as the processing time increases, forming a structure dominated by sorbite with fine lamellar spacing, reducing the proportion of ferrite, and providing a higher matrix strength and hardness foundation; on the other hand, when the wire rod passes through the molten salt, the molten salt covers the surface of the wire rod for uniform heat exchange, and there is no temperature difference problem between the winded side and the winded side, and between the overlap and non-overlap parts compared to air cooling, which can avoid local overcooling and the production of brittle structures such as martensite, improve the uniformity of the structure, and reduce the fluctuation of mechanical properties.

[0018] 2. Compared with the Stelmor air-cooled line, which has limited minimum cooling capacity and continuous cooling, resulting in large fluctuations in the mechanical properties of the wire rod, insufficient uniformity and plasticity of the organization, and slow offline speed, on the one hand, the molten salt is in full contact with the surface of the wire rod and has a higher heat exchange efficiency, which can effectively reduce the cooling rate difference from the surface to the core of the wire rod, so that the entire cross-section of the wire rod enters the sorbite phase transformation zone synchronously, avoiding the differential distribution of fine sorbite on the surface and coarse pearlite in the core caused by the fast cooling rate on the surface and slow cooling rate in the core of the air-cooled line. As the treatment time of the wire rod at the peak precipitation temperature of sorbite is extended, the uniform and sufficient phase transformation of sorbite can be promoted, the uniformity of the organization can be improved, the fluctuation of mechanical properties can be further reduced, and the superposition of thermal stress and phase transformation stress can be reduced; on the other hand, after the phase transformation is incubated, the molten salt can control the temperature difference between the wire rod and the molten salt. Isothermal treatment is carried out at the same temperature rather than continuous cooling, which can extend the time that the wire rod is in the high-temperature isothermal temperature range, provide more thermal power to actively regulate the structure after the phase transformation, promote local melting of continuous sorbite lamellae through atomic diffusion, toughen and relieve stress treatment. Since the sorbite phase transformation is carried out at a lower temperature, with appropriate silicon to optimize the tempering softening resistance, it not only retains the interface strengthening effect of the fine lamellae, but also improves the plasticity and toughness through the melting structure, reduces stress concentration, and then slowly cools the wire rod through the roller to prevent the stress increase caused by the rapid cooling rate during the cooling process, promotes further toughening of the wire rod structure, improves the softening effect of the wire rod, and thus improves the overall strength and plasticity of the wire rod. There is no need to use excessively high hood entry temperature or long-term heat preservation treatment, so that it can be quickly offline to ensure production rhythm and efficiency.

[0019] Before the rolling, controlling the appropriate soaking temperature and time in the heating furnace can promote the full diffusion of carbon and alloy elements, reduce the influence of component segregation, promote the homogenization of austenite grains, improve rolling plasticity and avoid grain coarsening caused by excessive soaking temperature or excessive time in the furnace. In the preferred technical solution, before the rolling, the soaking temperature of the heating furnace is controlled to be 1070~1120℃, and the time in the furnace is 90~200min.

[0020] During the rolling, controlling the appropriate initial rolling temperature can make the rolling deformation resistance of the steel billet moderate, increase the rolling speed, avoid coarsening of austenite grains, avoid excessive wear or overload of the rolling line caused by too low an initial rolling temperature, control the appropriate final rolling temperature and final rolling reduction, refine the austenite grains through dynamic recrystallization, increase the grain boundary area, provide more locations for sorbite nucleation, avoid local stress concentration caused by too low a final rolling temperature and final rolling reduction or affect the spinning temperature. In the preferred technical solution, during the rolling, the initial rolling temperature is controlled to be 1015~1060℃, the final rolling temperature is controlled to be 860~910℃, and the final rolling reduction is controlled to be 15%~20%.

[0021] During the spinning, the spinning temperature can be further controlled to avoid the growth of austenite grains, which is beneficial to further reduce the thermal stress in the subsequent phase transformation process. In the preferred technical solution, during the spinning, the spinning temperature is controlled to be 850-895°C.

[0022] In the preferred technical solution, the online molten salt isothermal toughening treatment is divided into a front-stage molten salt treatment and a rear-stage molten salt treatment. The molten salt circulation volume of the front-stage molten salt treatment is greater than that of the rear-stage molten salt treatment. The use of a larger molten salt circulation volume in the front-stage molten salt treatment can control the molten salt temperature rise, promote rapid cooling of the wire rod, inhibit coarse lamellar pearlite and proeutectoid ferrite, and promote the formation of a structure dominated by fine lamellar troostite. The use of a smaller molten salt circulation volume in the rear-stage molten salt treatment can reduce production energy consumption and control the isothermal toughening treatment.

[0023] The molten salt temperature of the front-stage molten salt treatment is in the sorbite phase region. The lower the molten salt temperature, the greater the phase transformation driving force, the coarse lamellar pearlite is suppressed, and the nucleation rate of fine lamellar sorbite is increased. As the treatment time is prolonged, a structure dominated by sorbite with fine lamellar spacing can be formed, providing a higher strength and hardness basis. However, if the molten salt temperature is too low, the diffusion rate of carbon will be reduced, and the phase transformation incubation time will be increased. As the treatment time is too long, the production energy consumption will increase. Due to excessive segregation and supercooling, the risk of martensite brittle phase will increase. On the contrary, the higher the molten salt temperature, the more conducive it is to reducing the temperature gradient from the surface of the wire rod to the core, reducing thermal stress and phase transformation stress, and reducing The difficulty of softening is reduced as the processing time decreases, which is beneficial to reducing production energy consumption. However, if the molten salt temperature is too high and the processing time is too short, the phase change driving force will be lost, causing the interlamellar spacing to increase, the matrix strength to be lost, the mechanical property fluctuations to increase and the difficulty of melting. Therefore, the front-stage molten salt treatment can control the molten salt temperature and processing time, control the wire rod to quickly enter the sorbite phase region from the high-temperature austenite state, form a structure dominated by sorbite with fine interlamellar spacing, improve the uniformity of the structure, and make organizational preparations for the back-stage molten salt treatment. In the preferred technical solution, the molten salt temperature of the front-stage molten salt treatment is 450~495℃, and the processing time is 150~250s.

[0024] The front-stage molten salt treatment can further control the molten salt circulation rate, utilize a higher molten salt circulation rate to enhance the heat exchange between the molten salt and the wire rod surface, quickly take away the heat, reduce the temperature gradient from the surface of the wire rod cross section to the core, and inhibit the phase change difference caused by carbon or manganese segregation. In the preferred technical solution, the molten salt circulation rate of the front-stage molten salt treatment is 480~680t / h, and the molten salt temperature rise is ≤8°C.

[0025] The molten salt temperature of the latter molten salt treatment is in the high-temperature isothermal range. The higher the molten salt temperature and the longer the treatment time, the more thermal power is provided, the more thermal power is provided, the more thermal stress and tissue stress are released, the more plastic and toughness of the wire rod are improved, the difference in tissue between the surface and the core of the wire rod is reduced, and the processing performance is improved. However, if the molten salt temperature is too high, the diffusion rate of carbon and the melting rate of the sorbite lamella are accelerated. As the treatment time is prolonged, the cementite of the sorbite is rapidly coarsened and over-softened, which will cause excessive loss of matrix strength. On the contrary, the lower the molten salt temperature and the shorter the treatment time, the faster the atomic diffusion rate. The strength loss and production energy consumption can be reduced, but the molten salt temperature is too low and the treatment time is too short, the sorbite lamellae are not easy to break, the stress release is insufficient, and the improvement of the plasticity and toughness is limited. Therefore, the molten salt temperature and treatment time can be controlled in the latter stage of the molten salt treatment, and the wire rod can be controlled to perform high-temperature isothermal tempering and toughening and stress relief treatment on the structure in the high-temperature isothermal range to promote the melting of the sorbite lamellae without excessive loss of strength, and improve the strength-plasticity matching of the wire rod. In the preferred technical solution, the molten salt temperature of the latter stage of the molten salt treatment is 475~500℃, and the treatment time is 200~300s.

[0026] Since the temperature difference between the wire rod temperature after the front-stage molten salt treatment and the molten salt temperature after the rear-stage molten salt treatment is small, selecting a smaller molten salt circulation volume can reduce production energy consumption, while controlling the molten salt temperature rise and promoting uniform toughening and stress relief. In the preferred technical solution, the molten salt circulation volume of the rear-stage molten salt treatment is 200~400t / h, and the molten salt temperature rise is ≤3°C.

[0027] The temperature of the wire rod after the latter molten salt treatment is relatively high and the structure has undergone sufficient phase change. The roller slow cooling uses a lower cooling rate to avoid the increase of stress in the wire rod due to too fast cooling rate. At the same time, the high temperature state of the wire rod is used to continue the effect of the latter molten salt treatment, promote the toughening of the wire rod, and avoid the cooling rate being too low to affect the offline efficiency. In the preferred technical solution, the roller slow cooling controls the wire rod to slowly cool to below 300°C at a cooling rate of 0.2~0.65°C / s.

[0028] A 1150MPa grade high-strength carbon tool steel wire rod is manufactured by any one of the above-mentioned methods for manufacturing 1150MPa grade high-strength carbon tool steel wire rods.

[0029] The above-mentioned wire rod adopts the carbon steel component system of C, Si, and Mn. Compared with the alloy tool steel wire rod, the composition is simpler and Si is less. Compared with the carbon tool steel wire rod, the carbon and alloy content is less, which can effectively reduce the material cost. At the same time, the microstructure includes a mixed structure mainly composed of tempered troostite and fused troostite, and a small amount of ferrite. Compared with the pearlite / troostite + ferrite structure tool steel wire rod of the air-cooled line, it can avoid the formation of abnormal structure due to abnormal local cooling and the formation of coarsened pearlite due to slow cooling of the core. The interlamellar spacing of troostite is finer than that of pearlite, and the strength and toughness are better. It can reduce the proportion of ferrite in the structure, improve the strengthening effect of carbon element, and the matrix. Strength and organizational uniformity, reduce mechanical property fluctuations, compensate for the adverse effects of reducing alloy content and eliminating alloy elements on wire rod strength and toughness, meet the performance consistency requirements of high-strength tool steel, and at the same time release organizational stress to promote the melting of troostite lamellae and transform them into intermediate transition state tempered troostite and fused troostite that transform to spheroidized organization. When subjected to stress, it can not only maintain a high load-bearing capacity, but also improve the matching of plasticity and strength through the slip coordination effect after the lamellae are melted, reduce the risk of cracking in cold working, avoid cracks caused by stress concentration, and then can be directly processed into tool parts after cold forming, thereby improving the durability of tool steel.

[0030] In the microstructure, the greater the volume proportion of tempered bainite and the finer the interlamellar spacing, the higher the matrix strength; the greater the volume proportion of fused bainite, the better the matrix plasticity and toughness. In the preferred technical solution, the volume percentage of tempered bainite is 64%~79%, the interlamellar spacing is 90~120nm, the volume percentage of fused bainite is 18%~28%; the volume percentage of ferrite is 3%~8%.

[0031] In the preferred technical solution, the diameter of the wire rod is 6~10mm, the tensile strength is 1050~1100MPa, the cross-sectional shrinkage rate is 45%~50%, the mechanical property difference in the circle is ≤28MPa, the wire rod diameter is small and medium-sized, which can reduce the number of cold working passes and material loss. The wire rod has high tensile strength and is used in application fields such as manufacturing carbon tool steel. It can save additional heat treatment after cold working so that the target strength can be achieved directly after cold working, thereby enhancing the load and durability of the tool steel. The wire rod has a high cross-sectional shrinkage rate and a small mechanical property difference in the circle, which can reduce the risk of wire breakage or cracks during cold working, improve the production yield and process stability of tool steel, and increase the fatigue performance of tool steel.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] (1) In view of the current situation that it is difficult to develop heat-treatment-free high-strength carbon tool steel wire rods due to the limitations of the Stelmor air-cooling line production process, the present invention adopts carbon chemical composition design combined with online molten salt strong isothermal toughening technology, without the need for low-temperature controlled rolling. The wire rod after spinning can quickly enter the sorbite phase region from the high-temperature austenite state, inhibit pearlite and brittle abnormal structures, and form a structure dominated by sorbite with fine lamellar spacing, thereby improving the uniformity of the structure. The wire rod is then controlled to perform high-temperature isothermal tempering on the quenched structure in the high-temperature isothermal range, toughening and stress relief treatment, promoting the melting of the sorbite lamellar layer, and improving the matching of strength and plasticity. Finally, the slow cooling of the roller promotes further toughening of the wire rod structure, which can improve the overall strength and plasticity of the wire rod and has good industrial adaptability.

[0034] (2) In view of the current situation that the cost of existing alloy tool steel wire rods is high, the strength and plasticity of carbon tool steel wire rods are insufficient, the mechanical properties fluctuate greatly, and additional heat treatment is required after cold working, the present invention adopts a carbon steel component system of C, Si, and Mn, which has a simple composition and less alloy content, can effectively reduce material costs, and the microstructure includes tempered bainite, ferrite and fused bainite, which can make up for the adverse effects of reducing alloy content and eliminating alloy elements on the strength and toughness of wire rods, improve the matching of strength and plasticity, and achieve a product tensile strength of 1050~1100MPa and a cross-sectional shrinkage rate of 45%~50%. It is used in the manufacture of carbon tool steel and other application fields, and can be directly processed into tool parts after cold forming, reducing the production energy consumption and cost of tool steel products and improving production efficiency, and has good market application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] 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:

[0036] Figure 1 is a metallographic structure diagram of Example 1 of the present invention;

[0037] Figure 2 is a metallographic structure diagram of Example 2 of the present invention;

[0038] Figure 3 This is the metallographic structure diagram of Example 3 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 to propose the best way to implement the present invention, are intended to be used 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 limited only by the appended claims; the wire rods obtained in the following embodiments and comparative examples are subjected to organizational and performance testing, including: tensile testing using "GB-T228.1-2021 Metallic Materials Tensile Testing Part 1: Room Temperature Test Method" to obtain tensile strength and cross-sectional shrinkage; organizational testing is performed in accordance with the metal microstructure detection method of GB / T13298 standard; mechanical property same-circle difference test method: take 2 circles of wire rod 5m away from the end of the coil, and divide each circle of wire rod into 8 sections with the overlap area position as the base point, and take 1 tensile specimen on each section. The extreme difference in strength of the tensile specimens after tensile testing is the mechanical property same-circle difference. Example 1:

[0040] A preferred embodiment of the method for manufacturing 1150MPa grade high-strength carbon tool steel wire rod of the present invention comprises the following chemical compositions and mass percentages: C: 0.57%, Si: 0.44%, Mn: 0.57%, P: 0.013%, S: 0.014%, with the remainder being Fe and unavoidable impurities; the manufacturing method follows the process flow of rolling → spinning → online molten salt isothermal toughening treatment → roller slow cooling → coiling, specifically:

[0041] 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 that can be rolled into plasticity, promote the full diffusion of carbon and alloy elements, control the heating furnace according to a three-stage temperature increase program of a preheating section, a heating section and a soaking section, and roll the high-temperature steel billet into a wire with a diameter of 7.5mm through a rolling line. The appropriate rolling temperature and reduction amount are selected to improve the rolling efficiency and avoid grain coarsening, promote dynamic recrystallization during the final rolling process, refine the grains, and have The heating furnace soaking temperature is controlled at 1080°C, the furnace time is 180 minutes, the initial rolling temperature is 1035°C, the final rolling temperature is 880°C, and the final rolling reduction is 19%. The spinning process is used to make the wire rods leaving the rolling line into wire rods through a spinning mechanism. The wire rods are spread on the roller and transported along the roller, so that the wire rods are in a high-temperature austenite state, in order to increase the degree of supercooling, accelerate the phase transformation dynamics, and suppress the coarse pearlite. Specifically, the spinning temperature is controlled at 865°C.

[0042] The online molten salt isothermal toughening process adopts a two-stage salt bath tank with molten salt inside. The wire rod after spinning is conveyed by rollers through the first salt bath tank for the front molten salt treatment, so that the wire rod is cooled at a cooling rate of 37°C / s, quickly entering the sorbite phase region from the high-temperature austenite state, suppressing coarse pearlite and forming a structure dominated by sorbite with fine lamellar spacing. After that, the wire rod is conveyed by rollers through the second salt bath tank for the rear molten salt treatment, reducing the molten salt circulation amount and controlling the wire rod. The wire rod is isothermally tempered in the high-temperature isothermal range to promote the melting of the sorbite lamellar layer, toughening and stress relief treatment, avoid excessive softening, and improve the strength and plasticity matching of the wire rod. Specifically: the molten salt temperature of the front molten salt treatment is 466°C, the treatment time is 185s, the molten salt circulation volume is 520t / h, and the molten salt temperature rise is ≤8°C; the molten salt temperature of the rear molten salt treatment is 495°C, the treatment time is 250s, the molten salt circulation volume is 255t / h, and the molten salt temperature rise is ≤3°C.

[0043] The roller slow cooling process adopts the method of closing the heat preservation cover, and the wire rod conveyed by the conveyor roller through the second salt bath tank is slowly cooled through the heat preservation cover to prevent the wire rod from cooling too fast during the cooling process, which leads to an increase in 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 0.35°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 a wire rod, which differs from 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 be 1040°C, the furnace time is 215min, the initial rolling temperature is 975°C, the final rolling temperature is 820°C, the spinning temperature is controlled to be 800°C, the Stelmor air cooling line uses 75% of the air volume of 1~4# fans to control the wire rod to cool to 682°C at a speed of 7.2°C / s, 5~14# fans are opened at 25%, the wire rod is controlled to cool to 290°C at a speed of 2.5°C / s, and the total air volume of the fan is 200,000 m 3 / h, collected by a collecting drum to obtain a finished wire rod, the volume percentage of pearlite in the wire rod microstructure is 75%, the interlamellar spacing is 198nm, the volume percentage of ferrite is 25%, the tensile strength is 727MPa, the cross-sectional shrinkage rate is 35%, and the mechanical property difference in the same circle is 73MPa.

[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 1050°C, the time in the furnace is 200 minutes, the initial rolling temperature is 985°C, the final rolling temperature is 835°C, the spinning temperature is controlled to be 815°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 carbon tool steel wire rod of the present invention comprises the following chemical compositions and mass percentages: C: 0.62%, Si: 0.47%, Mn: 0.53%, P: 0.015%, S: 0.015%, with the remainder being Fe and unavoidable impurities; the manufacturing method follows the process flow of rolling → spinning → online molten salt isothermal toughening treatment → roller 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 that can be rolled into plasticity, promote the full diffusion of carbon and alloy elements, and control the heating furnace according to a three-stage temperature increase 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 9mm through a rolling line. Appropriate rolling temperature and reduction are selected to improve rolling efficiency and avoid grain coarsening, promote dynamic recrystallization during the final rolling process, and refine grains. : The soaking temperature of the heating furnace is controlled to be 1100°C, the time in the furnace is 150 minutes, the initial rolling temperature is 1050°C, the final rolling temperature is 895°C, and the final rolling reduction is 17.5%; the wire-spinning process is used to make the wire rods leaving the rolling line into wire rods through a wire-spinning mechanism, and the wire rods are spread on the roller and transported along the roller, so that the wire rods are in a high-temperature austenite state, in order to increase the degree of supercooling, accelerate the phase transformation dynamics, and suppress the coarse pearlite. Specifically: the wire-spinning temperature is controlled to be 875°C.

[0050] The online molten salt isothermal toughening process adopts a two-stage salt bath tank with molten salt inside. The wire rod after spinning is conveyed by rollers through the first salt bath tank for the front molten salt treatment, so that the wire rod is cooled at a cooling rate of 37°C / s, quickly entering the sorbite phase region from the high-temperature austenite state, suppressing coarse pearlite and forming a structure dominated by sorbite with fine lamellar spacing. After that, the wire rod is conveyed by rollers through the second salt bath tank for the rear molten salt treatment, reducing the molten salt circulation amount and controlling the wire rod. The wire rod is isothermally tempered in the high-temperature isothermal range to promote the melting of the sorbite lamellar layer, toughening and stress relief treatment, avoid excessive softening, and improve the strength and plasticity matching of the wire rod. Specifically: the molten salt temperature of the front molten salt treatment is 479°C, the treatment time is 205s, the molten salt circulation volume is 605t / h, and the molten salt temperature rise is ≤8°C; the molten salt temperature of the rear molten salt treatment is 488°C, the treatment time is 280s, the molten salt circulation volume is 360t / h, and the molten salt temperature rise is ≤3°C.

[0051] The roller slow cooling process adopts the method of closing the heat preservation cover, and the wire rod conveyed by the conveyor roller through the second salt bath tank is slowly cooled through the heat preservation cover to prevent the wire rod from cooling too fast during the cooling process, which leads to an increase in 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 292°C at a cooling rate of 0.55°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 subjected to a front-stage molten salt treatment and cooled at a cooling rate of 36°C / s, the molten salt temperature of the front-stage molten salt treatment is 505°C, and the treatment time is 110s 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 subjected to a front-stage molten salt treatment and cooled at a cooling rate of 43°C / s, the molten salt temperature of the front-stage molten salt treatment is 420°C, and the treatment time is 270s to obtain a finished wire rod. Example 3:

[0056] A preferred embodiment of the method for manufacturing 1150MPa grade high-strength carbon tool steel wire rod of the present invention comprises the following chemical compositions and mass percentages: C: 0.58%, Si: 0.38%, Mn: 0.60%, P: 0.015%, S: 0.015%, with the remainder being Fe and unavoidable impurities; the manufacturing method follows the process flow of rolling → spinning → online molten salt isothermal toughening treatment → roller 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 that can be rolled into plasticity, promote the full diffusion of carbon and alloy elements, and control the heating furnace according to a three-stage temperature increase 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 6mm through a rolling line. Appropriate rolling temperature and reduction are selected to improve rolling efficiency and avoid grain coarsening, promote dynamic recrystallization during the final rolling process, and refine grains. The soaking temperature of the heating furnace is controlled to be 1070°C, the time in the furnace is 200 minutes, the initial rolling temperature is 1015°C, the final rolling temperature is 860°C, and the final rolling reduction is 20%; the wire-laying process is used to make the wire rods exiting the rolling line into wire rods through a wire-laying mechanism, and the wire rods are spread on the roller and transported along the roller, so that the wire rods are in a high-temperature austenite state, in order to increase the degree of supercooling, accelerate the phase transformation dynamics, and suppress the coarse pearlite. Specifically, the wire-laying temperature is controlled to be 850°C.

[0058] The online molten salt isothermal toughening process adopts a two-stage salt bath tank with molten salt inside. The wire rod after spinning is conveyed by rollers through the first salt bath tank for the front molten salt treatment, so that the wire rod is cooled at a cooling rate of 39°C / s, quickly entering the sorbite phase region from the high-temperature austenite state, suppressing coarse pearlite and forming a structure dominated by sorbite with fine lamellar spacing. After that, the wire rod is conveyed by rollers through the second salt bath tank for the rear molten salt treatment, reducing the molten salt circulation amount and controlling the wire rod. The wire rod is isothermally tempered in the high-temperature isothermal range to promote the melting of the sorbite lamellar layer, toughening and stress relief treatment, avoid excessive softening, and improve the strength-plasticity matching of the wire rod. Specifically: the molten salt temperature of the front molten salt treatment is 450°C, the treatment time is 150s, the molten salt circulation volume is 480t / h, and the molten salt temperature rise is ≤8°C; the molten salt temperature of the rear molten salt treatment is 500°C, the treatment time is 200s, the molten salt circulation volume is 200t / h, and the molten salt temperature rise is ≤3°C.

[0059] The roller slow cooling process adopts the method of closing the heat preservation cover, and the wire rod conveyed by the conveyor roller through the second salt bath tank is slowly cooled through the heat preservation cover to prevent the wire rod from cooling too fast during the cooling process, which leads to an increase in 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 298°C at a cooling rate of 0.2°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 3 shown.

[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 latter molten salt treatment is 515° C., the treatment time is 350 s, and the finished wire rod is obtained.

[0062] Comparative Example 6:

[0063] A method for manufacturing a wire rod, which differs from the manufacturing method of Example 3 in that the molten salt temperature of the latter molten salt treatment is 450° C., the treatment time is 150 s, and the finished wire rod is obtained. Example 4:

[0064] A preferred embodiment of the method for manufacturing 1150MPa grade high-strength carbon tool steel wire rod of the present invention comprises the following chemical compositions and mass percentages: C: 0.60%, Si: 0.40%, Mn: 0.63%, P: 0.015%, S: 0.015%, with the remainder being Fe and unavoidable impurities; the manufacturing method follows the process flow of rolling → spinning → online molten salt isothermal toughening treatment → roller 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 that can be rolled into plasticity, promote the full diffusion of carbon and alloy elements, control the heating furnace according to a three-stage temperature increase program of a preheating section, a heating section and a soaking section, and roll the high-temperature steel billet into a wire with a diameter of 10mm through a rolling line. The appropriate rolling temperature and reduction amount are selected to improve the rolling efficiency and avoid grain coarsening, promote dynamic recrystallization during the final rolling process, refine the grains, and have The heating furnace soaking temperature is controlled at 1120°C, the furnace time is 90 minutes, the initial rolling temperature is 1060°C, the final rolling temperature is 910°C, and the final rolling reduction is 15%. The spinning process is used to convert the wire rods leaving the rolling line into wire rods through a spinning mechanism. The wire rods are spread on a roller and transported along the roller, so that the wire rods are in a high-temperature austenite state, in order to increase the degree of supercooling, accelerate the phase transformation dynamics, and suppress the coarse pearlite. Specifically, the spinning temperature is controlled at 895°C.

[0066] The online molten salt isothermal toughening process adopts a two-stage salt bath tank with molten salt inside. The wire rod after spinning is conveyed by rollers through the first salt bath tank for the front molten salt treatment, so that the wire rod is cooled at a cooling rate of 39°C / s, quickly entering the sorbite phase region from the high-temperature austenite state, suppressing coarse pearlite and forming a structure dominated by sorbite with fine lamellar spacing. After that, the wire rod is conveyed by rollers through the second salt bath tank for the rear molten salt treatment, reducing the molten salt circulation amount and controlling the wire rod. The wire rod is isothermally tempered in the high-temperature isothermal range to promote the melting of the sorbite lamellar layer, toughening and stress relief treatment, avoid excessive softening, and improve the strength-plasticity matching of the wire rod. Specifically: the molten salt temperature of the front molten salt treatment is 495°C, the treatment time is 250s, the molten salt circulation volume is 680t / h, and the molten salt temperature rise is ≤8°C; the molten salt temperature of the rear molten salt treatment is 475°C, the treatment time is 300s, the molten salt circulation volume is 400t / h, and the molten salt temperature rise is ≤3°C.

[0067] The roller slow cooling process adopts the method of closing 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 290°C at a cooling rate of 0.65°C / s; the coiling process is used to coil the wire rod into a coil by 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 isothermal toughening treatment → 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 285°C at a cooling rate of 1.6°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 2 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 carbon tool steel wire rod with reduced alloy content and omitted alloy elements, which is produced by Stelmor air-cooled line, it is easy to form coarse lamellar pearlite or a mixed structure of pearlite and ferrite, resulting in a significant decrease in the strength and toughness of the wire rod, large fluctuations in mechanical properties, affecting the durability of tool steel, and cold processing has to use heat treatment to adjust product performance. The present invention adopts carbon chemical composition design combined with online molten salt strong isothermal toughening technology, without the need for low-temperature controlled rolling, and the wire rod after spinning can be quickly heated from high temperature to high temperature. The austenite state enters the sorbite phase region, suppressing pearlite and brittle abnormal tissues, forming a tissue mainly composed of sorbite with fine lamellar spacing, improving tissue uniformity, and then controlling the wire rod to perform high-temperature isothermal tempering on the quenched tissue in the high-temperature isothermal range, toughening and stress relief treatment, and improving the matching of strength and plasticity. It can be seen from the results of Examples 1 to 4 that the product tensile strength can reach 1050~1100MPa and the cross-sectional shrinkage rate is 45%~50%. It is used in application fields such as manufacturing carbon tool steel and can be directly processed into tool parts after cold forming.

[0074] From the comparison results of Example 1 and Comparative Example 2, it can be seen that a higher spinning temperature is selected to keep the wire rod in a high-temperature austenite state, which can avoid insufficient diffusion of carbon or alloy elements caused by too low a spinning temperature, and make organizational preparations for increasing supercooling, accelerating phase transformation dynamics, and suppressing coarse pearlite. At the same time, it reduces the restriction on rolling temperature to improve rolling efficiency.

[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 molten salt treatment is in the sorbite phase region. The higher the molten salt temperature, the more conducive it is to reducing the temperature gradient from the surface of the wire rod to the core, reducing thermal stress and phase change stress, and reducing the difficulty of softening. As the treatment time is shortened, it is beneficial to reduce production energy consumption. However, if the molten salt temperature is too high and the treatment time is too short, the phase change driving force will be lost, resulting in an increase in the interlamellar spacing, a loss of matrix strength, an increase in mechanical property fluctuations and a difficulty in melting.

[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 treatment, the greater the phase transformation driving force, the inhibition of coarse lamellar pearlite, and the increase of the nucleation rate of fine lamellar sorbite. As the treatment time increases, a structure dominated by sorbite with fine lamellar spacing can be formed, providing a higher strength and hardness foundation. However, if the molten salt temperature is too low, the diffusion rate of carbon will be reduced, the phase transformation incubation time will be increased, and as the treatment time is too long, the production energy consumption will increase.

[0077] From the comparison results of Example 3 and Comparative Example 5, it can be seen that the molten salt temperature of the latter molten salt treatment is in the high-temperature isothermal range. The higher the molten salt temperature and the longer the treatment time, the more conducive it is to provide more thermal power, promote the melting of the sorbite lamellae, release thermal stress and tissue stress, improve the plasticity and toughness of the wire rod, reduce the tissue difference between the surface and the core of the wire rod, and improve the processing performance. However, if the molten salt temperature is too high, the diffusion rate of carbon and the melting rate of the sorbite lamellae will accelerate. As the treatment time increases, the cementite particles of the sorbite will coarsen rapidly and soften excessively, resulting in excessive loss of matrix strength.

[0078] From the comparison results of Example 3 and Comparative Example 6, it can be seen that the lower the molten salt temperature and the shorter the treatment time of the later molten salt treatment, the lower the atomic diffusion rate, which can reduce the strength loss and production energy consumption. However, if the molten salt temperature is too low and the treatment time is too short, the troostite lamellae are not easy to break, the stress release is insufficient, and the improvement of plasticity and toughness is limited.

[0079] From the comparison results of Example 4 and Comparative Example 7, it can be seen that the temperature of the wire rod after the latter molten salt treatment is relatively high and the structure is fully phase-changed. The use of slow roller cooling can avoid the increase of stress in the wire rod due to too fast cooling rate. At the same time, the high temperature state of the wire rod is used to continue the effect of the latter molten salt treatment, promote the toughening of the wire rod, and improve the softening effect.

[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 carbon 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 ≥850°C, and then subjected to an online molten salt isothermal toughening treatment. The wire rod is controlled to enter the sorbite phase region from the high-temperature austenite state at a cooling rate of ≥35°C / s to form a structure mainly composed of sorbite. The wire rod is controlled to be isothermal tempered in the isothermal region to promote the melting of the sorbite lamellae and toughening and stress relief treatment. Finally, it is slowly cooled by a roller to form a wire rod with a microstructure including tempered sorbite, ferrite and fused sorbite. The chemical composition and mass percentage of the wire rod include: C: 0.57%~0.62%, Si: 0.38%~ 0.47%, Mn: 0.53%~0.63%, P≤0.015%, S≤0.015%, and the rest are Fe and unavoidable impurities; the online molten salt isothermal toughening treatment is divided into a front-stage molten salt treatment and a rear-stage molten salt treatment, the molten salt temperature of the front-stage molten salt treatment is 450~495℃, and the treatment time is 150~250s; the molten salt temperature of the rear-stage molten salt treatment is 475~500℃, and the treatment time is 200~300s; the roller slow cooling controls the wire rod to slowly cool to below 300℃ at a cooling rate of 0.2~0.65℃ / s.

2. The method for manufacturing 1150 MPa grade high strength carbon 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 1070-1120° C., and the soaking time in the furnace is 90-200 minutes.

3. The method for manufacturing 1150 MPa grade high strength carbon tool steel wire rod according to claim 1, characterized in that: During the rolling, the initial rolling temperature is controlled to be 1015-1060° C., the final rolling temperature is controlled to be 860-910° C., and the final rolling reduction is controlled to be 15%-20%; during the wire drawing, the wire drawing temperature is controlled to be 850-895° C.

4. The method for manufacturing 1150 MPa grade high strength carbon tool steel wire rod according to claim 1, characterized in that: The molten salt circulation amount of the front-stage molten salt treatment is greater than the molten salt circulation amount of the back-stage molten salt treatment.

5. The method for manufacturing 1150 MPa grade high strength carbon tool steel wire rod according to claim 4, characterized in that: The molten salt circulation rate of the front-stage molten salt treatment is 480~680t / h, and the molten salt temperature rise is ≤8°C; the molten salt circulation rate of the back-stage molten salt treatment is 200~400t / h, and the molten salt temperature rise is ≤3°C.

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

7. The 1150 MPa grade high strength carbon tool steel wire rod according to claim 6, characterized in that: The volume percentage of the tempered bainite is 64% to 79%, the interlamellar spacing is 90 to 120 nm, the volume percentage of the fused bainite is 18% to 28%, and the volume percentage of the ferrite is 3% to 8%.

8. The 1150 MPa grade high strength carbon tool steel wire rod according to claim 6, characterized in that: The wire rod has a diameter of 6-10 mm, a tensile strength of 1050-1100 MPa, a cross-sectional shrinkage rate of 45%-50%, and a mechanical property difference of ≤28 MPa.

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