A 1100MPa grade high-strength tool steel wire rod and its manufacturing method

Abstract

The present invention relates to a 1100MPa grade high-strength tool steel wire rod and a manufacturing method thereof. The wire rod is designed with a chemical composition of medium carbon and Nb-V. The steel billet is rolled and spun into wire rod at a spinning temperature of 860°C or higher. The wire rod is then subjected to an online molten salt semi-quenching isothermal treatment. The wire rod is controlled to first undergo a front-end molten salt treatment so that the wire rod enters a bainite phase region from a high-temperature austenite state at a cooling rate of 30°C / s or higher, forming a structure mainly composed of quenched bainite. The wire rod is then subjected to a rear-end molten salt heating isothermal tempering and toughening stress relief treatment. Finally, the wire rod is slowly cooled on a roller to form a wire rod with a microstructure including tempered bainite and ferrite. The method can reduce material cost, effectively avoid martensitic brittle structure, control the microstructure of the hot-rolled wire rod, improve the plasticity and cold working performance of the wire rod, and achieve a product tensile strength of 980-1030MPa and a cross-sectional reduction rate of 61%-66%, so that the product can be directly processed into tool parts after cold forming.

Description

Technical Field

[0001] The present invention belongs to the technical field of hot-rolled wire rods, and in particular relates to a 1100MPa grade high-strength tool steel wire rod and a manufacturing method thereof. Background Art

[0002] Tools are indispensable basic industrial equipment in the industrial production process. They determine the operating efficiency of mechanical equipment and the production efficiency, production cost and quality of industrial products. Tool steel is produced by cold forming machine processing and surface treatment such as cutting and grinding with hot-rolled wire rod as the base material. Hot-rolled wire rod of high-strength tools must also undergo heat treatment before cold forming to reduce the hardness of the material, improve plasticity and toughness, stabilize size and performance, make the wire rod more prone to plastic deformation during the cold forming process, reduce the occurrence of defects such as cracking, and ensure processing accuracy. However, the heat treatment process will also quickly increase the production cost of tool products. Therefore, controlling the microstructure of hot-rolled wire rod and improving the plastic and toughness properties of wire rod are of great significance to reducing the cost of 1100MPa grade high-strength tool steel, improving production efficiency and product quality.

[0003] Existing high-strength tools are often produced by adding appropriate amounts of hardenability elements such as Cr and Mn to hot-rolled wire rods for tools. The wire rods are then air-cooled on a Stelmor line. However, the wire rods cannot be directly processed into parts after cold forming due to the following reasons:

[0004] (1) In hot-rolled wire rods for tools, the addition of hardenability elements such as Cr and Mn can improve the hardenability and comprehensive mechanical properties of the material. However, since the air-cooled line is air-cooled, even if it is produced in combination with a slow cooling process, the minimum cooling capacity is limited, the instability and control difficulty are relatively large. The strengthening effect is often weakened due to the uncontrollable cooling rate during the cooling phase transformation process. At the same time, when the cooling rate is relatively fast, the cooling rate exceeds the critical value, which significantly increases the probability of the wire rod forming brittle structures such as martensite and widmanstattenite on the air-cooled line. At the same time, the transformation of martensite into a non-diffusion shear process will generate large tissue stress and thermal stress, which will deteriorate the plastic toughness of the wire rod, and then lead to problems such as wire breakage and cracking during cold working. At the same time, it is necessary to adjust the performance of the tool product by combining cold working with heat treatment.

[0005] (2) In order to meet the tool performance requirements and prevent the precipitation of martensite structure during rolling and cooling, although the existing technology uses alloy element solid solution strengthening, precipitation strengthening, fine grain strengthening, etc. for tool steel wire rods, combined with low temperature controlled rolling to produce wire rods with bainite structure, for example: Patent CN111690801B discloses a production process for alloy tool steel wire rods with full bainite structure, which adopts C-Si-Mn-Cr-Ni-Al-Mo-V-Nb composition design, combines low temperature rolling and spinning, air cooling and hood cooling to produce full bainite structure, but on the one hand, low temperature rolling aggravates the wear and load on the rolling line, affects production efficiency, and the Si content in the steel is relatively high. High, although it makes it easier for austenite to be supercooled to the bainite range during cooling, it will also reduce its elongation and impact toughness. With the influence of air cooling instability and the limited length of the air cooling line, the wire rod temperature is already at a low temperature after the hood cooling phase transformation, and the resulting bainite has higher hardness and strength, and the tissue stress is larger, which affects the machining performance. Heat treatment regulation is still required before cold working; on the other hand, in the precipitation temperature range of carbides, it is limited by the instability of air cooling and the maximum cooling capacity, which affects the precipitation power of carbides. The coarsening precipitation of carbides not only affects the uniformity of the tissue but also is detrimental to the toughness. The addition of multiple components and high alloy content increases the material cost, which is not conducive to reducing the cost of tool steel. 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 1100MPa grade high-strength tool steel wire rod and a manufacturing method thereof, which can reduce material costs, effectively avoid martensitic brittle structure, control the microstructure state of hot-rolled wire rod, and improve the plasticity and cold working performance of wire rod so that it can be directly processed into tool parts after cold forming.

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

[0008] A method for manufacturing 1100MPa 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 ≥860℃, and then undergoes online molten salt semi-quenching isothermal treatment. The wire rod is controlled to undergo the front-end molten salt treatment first, so that the wire rod enters the bainite phase region from the high-temperature austenite state at a cooling rate of ≥30℃ / 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 passes through the roller slow cooling to form a microstructure including tempered bainite and ferrite. The wire rod has the following chemical compositions and mass percentages: C: 0.40% to 0.45%, Si: 0.10% to 0.18%, Mn: 0.25% to 0.40%, Cr: 0.35% to 0.50%, 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: The C element improves the matrix strength by solid solution strengthening and forming carbides, and its price is relatively low. As the carbon content increases, 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 semi-quenching isothermal treatment. After a short period of molten salt treatment, a structure dominated by quenched bainite is quickly formed, which meets the hardness and wear resistance requirements of hand tools. However, excessive carbon content will increase the tendency of carbon segregation during the solidification of the steel billet, reduce the plasticity and cold formability of the wire rod, and affect the control of carbide precipitation. Therefore, in order to meet the high hardness and wear resistance requirements of hand tool steel, control material costs, and facilitate the control of the microstructure of hot-rolled wire rods and improve material plasticity, a medium carbon content is used, and the mass percentage of C is controlled to be 0.40%~0.45%.

[0012] (2) Silicon: The Si element can inhibit the grain coarsening during the online molten salt semi-quenching isothermal process, improve the stability of supercooled austenite, delay the precipitation of carbides, make the bainite transformation proceed at a lower temperature, expand the bainite transformation region, and compress the pearlite formation range. However, if the silicon content is too high, the solid solution strengthening effect of silicon will be too strong, the lattice distortion will be aggravated, the toughness of the steel will be reduced, the plasticity control will be affected, and the plasticity will decrease 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, significantly improve the stability of supercooled austenite, increase the hardenability of wire rod, reduce the tendency of pearlite and ferrite to form, strongly delay the pearlite transformation, and make the bainite transformation occur within a wider cooling rate range. Online molten salt semi-quenching isothermal can quickly form a structure dominated by quenched bainite in the wire rod through short-time quenching, improve the matrix strength, and be suitable for tools subjected to impact loads. However, when the Mn content is too high, it will aggravate the segregation of alloy elements, promote the growth of austenite grains, increase the difficulty of isothermal toughening, and reduce the toughness and plasticity of steel. Therefore, in order to take into account the impact fracture resistance of hand tools and facilitate the bainite phase transformation and isothermal toughening stress relief control of wire rod, the mass percentage of Mn is controlled to be 0.25%~0.40%.

[0014] (4) Chromium: Cr is a strong carbide-forming element that can form fine 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, which is beneficial to improving the wear resistance and corrosion resistance of steel. However, too high Cr content will aggravate component segregation, increase the difficulty of controlling the uniformity of the organization and the improvement of plasticity, and cause uneven distribution of carbides, forming coarse particles or network structures, which reduce plasticity and cold working properties. Therefore, in order to take into account the wear resistance and life of hand tools and facilitate the control of the microstructure and organizational state of the tempered bainite-based wire rod, the mass percentage of Cr is controlled to be 0.35%~0.50%.

[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. The refined austenite grains are conducive to increasing the nucleation sites of quenched bainite, making the quenched bainite structure finer and more dispersed. However, the price of Nb is relatively high. Therefore, based on the role, cost and preparation control of Nb element, the mass percentage of Nb is controlled to be 0.015%~0.025%.

[0016] (6) Vanadium: As an alloying element, V can pin the austenite grain boundaries during the controlled rolling stage, refining the original austenite grains. It can be dispersed and precipitated during the isothermal process of the subsequent molten salt treatment, which plays a role in rapidly improving the matrix strength, improving the toughness and cold working properties, and reducing 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. Too much V will also cause element enrichment and rapid coarsening of carbides. Coarsened carbides affect the strength and toughness properties, and are prone to cracking along the particle interface during cold forming. 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 chemical composition design with medium carbon and Nb-V. By adopting a relatively low content of Si / Mn / Cr composition, the C, Si, Mn, and Cr ratios are optimized to expand the bainite transformation range and reduce the probability of pearlite formation. In combination with Nb and V, grain refinement is achieved. This provides favorable conditions for the rapid formation of a structure dominated by quenched bainite through short quenching during the online molten salt semi-quenching isothermal process, reducing the difficulty of isothermal tempering stress relief, and promoting the dispersion and precipitation of microalloy carbides. On this basis, the wire rod after spinning does not pass through the air cooling line but adopts the online molten salt semi-quenching isothermal treatment:

[0019] 1. Compared with the air cooling line, which has limited maximum cooling capacity and unstable temperature control, causing pearlite transformation, and it is difficult to control brittle structures such as martensite and widmanstattenite, the wire rod is treated with molten salt in the front stage. On the one hand, the high heat exchange capacity of the molten salt can be used to significantly increase the cooling rate of the wire rod, control the wire rod to quickly cross the pearlite phase transformation sensitive range from the high temperature austenite state, reduce the atomic diffusion rate, inhibit the probability of pearlite formation, and inhibit grain coarsening. The wire rod is supercooled to the bainite phase transformation temperature range and maintains sufficient supercooling, providing a greater driving force for phase transformation. The refined grains increase the bainite nucleation point, promote the quenched bainite transformation, and form a structure dominated by quenched bainite after a short treatment to compensate for the reduction of C / Si / Mn / Cr causes strength loss, and there is no need to use high Si, Mn and other contents to promote bainite phase transformation. On the other hand, when the wire rod passes through the molten salt, it can pass through the front section of molten salt, so that the molten salt covers the surface of the wire rod for rapid and uniform heat exchange. Compared with air cooling, it can avoid the problem of wire rod temperature difference caused by limited air volume and cooling capacity between the windward side and the windward side. Compared with water cooling, it can avoid the generation of a large amount of gas attached to the surface of the wire rod and cause large cooling fluctuations. The front section of molten salt can control the cooling rate of the wire rod within the bainite transformation window, accurately control the cooling path, and uniformly cool the cross-section temperature gradient of the wire rod, so that the austenite is transformed as fully as possible in the bainite phase transformation range, reduce the amount of untransformed austenite, and avoid the formation of pearlite or martensite structure in local areas due to cooling lag.

[0020] 2. Compared with the air cooling line, the minimum cooling capacity is limited and the temperature control is unstable, which makes it difficult to control the state of the organization. The brittle stress of the obtained bainite is large, and it is difficult to control the dispersion, precipitation and strengthening and toughening effect of the microalloy carbides. In the online molten salt semi-quenching isothermal treatment, after the wire rod passes through the front section of molten salt and forms a structure mainly composed of quenched bainite, the quenched bainite is densely distributed with high-density dislocations. The wire rod can be controlled to enter the high-temperature isothermal zone by heating the molten salt in the back section. On the one hand, the wire rod temperature can be made consistent with the molten salt temperature, which is higher than the temperature of the bainite phase zone. The isothermal treatment time of the wire rod in the high-temperature zone can be extended instead of continuous cooling, which provides more thermal power for the organization state control and controls the wire rod to perform high-temperature quenching on the quenched structure in the high-temperature isothermal zone. Isothermal tempering and toughening stress relief treatment change the microstructure and precipitates in the quenched bainite structure, obtain a significantly toughened tempered bainite structure, and improve the strength-plasticity matching of the wire rod; on the other hand, it can prolong the time that the wire rod is in the temperature range of microalloy carbide dispersion and precipitation, uniformly cool the wire rod cross section to reduce the temperature gradient, control the microalloying elements to fully disperse and precipitate in the isothermal stage, inhibit the precipitation and coarsening of carbides, and play a role in quickly improving the strength and toughness of the matrix. Finally, the wire rod is slowly cooled by a roller to prevent the stress of the wire rod from increasing during the cooling process, promote further toughening of the wire rod structure, improve the softening effect of the wire rod, and effectively control the organizational state of the hot-rolled wire rod to produce a wire rod structure dominated by tempered bainite and containing a small amount of ferrite.

[0021] Before the rolling, in order to make the steel billet reach rollable plasticity, promote the homogenization of the internal composition of the steel billet, and avoid the risk of coarse grains and overburning caused by overheating, in the preferred technical solution, before the rolling, the heating furnace soaking temperature is controlled to be 1090~1140℃, and the time in the furnace is 80~135min.

[0022] Since the wire rod adopts online molten salt semi-quenching isothermal treatment to cool rapidly, the restriction on rolling can be reduced, and there is no need to use an excessively low rolling temperature. An appropriate initial rolling temperature can be selected to promote rapid rolling and reduce wear on the rolling line, so that the Nb microalloying element can precipitate in the initial rolling stage, pin the grain boundaries, control the intermediate rolling temperature and the final rolling reduction, promote dynamic recrystallization and refine the grains during the final rolling process, and retain deformation energy storage. In the preferred technical solution, during the rolling, the initial rolling temperature is controlled to be 1070~1100℃, the final rolling temperature is 880~910℃, and the final rolling reduction is 23%~29%.

[0023] When spinning, a higher spinning temperature is selected, which is beneficial to further allow the wire rod to undergo online molten salt treatment at a higher quenching temperature, thereby improving the strength and plasticity matching of the material. In the preferred technical solution, when spinning, the spinning temperature is controlled to be 860~900℃.

[0024] The molten salt temperature of the front-stage molten salt is in the bainite phase region. The lower the molten salt temperature and the longer the treatment time, the higher the supercooling degree can be, which provides more driving force for the bainite phase transformation and promotes the formation of a structure dominated by quenched bainite in the wire rod, with significant strengthening effect. However, if the molten salt temperature is too low and the treatment time is too long, it is not conducive to avoiding the formation of martensite structure, and the mechanical properties fluctuation increases, the internal stress increases, the difficulty of stress relief increases, and the treatment energy consumption increases; on the contrary, if the molten salt temperature is higher and the treatment time is shorter, the quenched bainite phase transformation decreases, and the matrix strength, stress relief difficulty and production energy consumption decrease. However, the molten salt temperature is too high, the treatment time is too short, and the supercooling is insufficient, which is not conducive to inhibiting the pearlite transformation and promoting the bainite phase transformation, affecting the matrix strength and strong-plastic properties. Therefore, the front-stage molten salt treatment can select appropriate molten salt temperature and treatment time to promote the wire rod from the high-temperature austenite state to enter the bainite phase region, forming a structure dominated by quenched bainite, avoiding the formation of abnormal martensite structure, and making organizational preparations for the toughening and stress relief of the rear-stage molten salt treatment. In the preferred technical solution, the molten salt temperature of the front-stage molten salt is 250~295℃, and the treatment time is 15~25s.

[0025] Since the temperature difference between the high-temperature austenite state and the bainite phase region is large, selecting a larger molten salt circulation rate can control the molten salt temperature rise and improve the processing accuracy. In the preferred technical solution, the molten salt circulation rate of the front-stage molten salt is 500~800t / h, and the molten salt temperature rise is ≤8℃.

[0026] The molten salt temperature of the latter section is in the high-temperature isothermal temperature range. The higher the molten salt temperature and the longer the treatment time, the more thermal power can be provided for the quenching and tempering of bainite, promote the toughening of the organization and release the stress, and significantly improve the plasticity of the wire rod. The carbide pinning effect of V and Nb is used to compensate for the strength drop caused by the quenching and tempering of bainite, and the excessive loss of strength is suppressed while improving the plasticity. However, if the molten salt temperature is too high and the treatment time is too long, the organization will soften too quickly, which is not conducive to the strength of the wire rod. At the same time, if the molten salt temperature is too high, the driving force for the precipitation of microalloy carbides will be reduced. As the treatment time is prolonged, there is a risk that the carbides will aggregate, grow and coarsen, and lose the strong and plastic properties. On the contrary, the lower the molten salt temperature and the shorter the treatment time, the isothermal tempering effect will decrease, and the plasticity of the wire rod will decrease. However, if the molten salt temperature is too low and the treatment time is too short, it will be difficult to provide thermal power for tempering, and the residual stress will be eliminated. In addition, the plasticity of the wire rod will be significantly lost. At the same time, the processing time is too short, which affects the sufficient dispersion and precipitation of microalloy carbides and will cause a loss of strength performance. Therefore, the molten salt in the latter stage can select appropriate molten salt temperature and processing time, and control the wire rod to perform high-temperature isothermal tempering and toughening and stress relief treatment on the quenched structure in the high-temperature isothermal range. The precipitation and phase change regulation of microalloy elements can be used to achieve the best balance between toughening and softening of the wire rod structure and improve the strength-plasticity matching of the wire rod. In the preferred technical solution, the molten salt temperature of the latter stage molten salt is 535~565℃, and the processing time is 200~450s.

[0027] Since there is a certain temperature difference between the molten salt in the front section and the molten salt in the rear section, in order to take into account the production energy consumption and further promote the stability of the high-temperature isothermal annealing and toughening stress relief effects, the stability of the temperature of the molten salt in the rear section is controlled, and the molten salt circulation rate of the molten salt in the rear section can be further controlled. In the preferred technical solution, the molten salt circulation rate of the molten salt in the rear section is 450~650t / h.

[0028] Since the wire rod is still at a relatively high temperature after passing through the rear molten salt, in the preferred technical solution, the roller slow cooling controls the wire rod to cool slowly at a cooling rate of 0.2~0.5℃ / s, which can prevent the wire rod from cooling too fast during the cooling process, avoid physical shrinkage leading to increased stress and fluctuations in mechanical properties, and continue the treatment effect of the rear molten salt, promote further toughening of the wire rod structure, and improve the softening effect of the wire rod.

[0029] In the preferred technical solution, the roller slow cooling can be achieved by inputting the hot air from the online molten salt semi-quenching isothermal treatment into the insulation cover, and the wire rods are transported by the conveying roller into the insulation cover for cooling control, which can further recover heat energy and reduce production energy consumption.

[0030] A 1100 MPa grade high-strength tool steel wire rod is manufactured by any one of the above-mentioned methods for manufacturing 1100 MPa grade high-strength tool steel wire rods.

[0031] The above-mentioned wire rod adopts the chemical composition design of C-Si-Mn-Cr-Nb-V, and the carbon and alloy component contents are relatively lower. Nb and V are added in trace amounts, and the material cost is lower. The low alloy component reduces the degree of dendrite segregation during solidification, and reduces the structural inhomogeneity caused by component segregation during the solidification of the steel billet, especially the segregation coefficient of elements such as Mn and Cr. Combined with the online molten salt semi-quenching isothermal technology, a microstructure mainly composed of isothermal treated tempered bainite and a small amount of ferrite is obtained. Compared with the tool steel wire rod with pearlite / bainite microstructure, it can effectively avoid the risk of brittle structures such as martensite and widmanstattenite produced by C and Cr elements, and the structural uniformity is better. The uniform structure will exhibit more stable mechanical properties during service. At the same time, there are high-density dislocations and fine substructures in the quenched bainite structure, and the lattice distortion is significant, which makes its strength It is higher than the soft phase structure such as pearlite. Compared with the tool steel wire rod with bainite structure, the structure mainly composed of quenched bainite is effectively controlled after isothermal tempering and toughening, the dislocation density is reduced, the lattice distortion is reduced, the carbides in the tempered bainite are more stable, and the internal stress of the organization is further reduced. Therefore, the toughness is significantly improved without much loss of strength, and the organization is transformed from hard and brittle to strong and tough, which can maximize the strengthening effect of carbon element, combine with micro-alloying elements to refine the grains, fully precipitate NbC and VC, and dispersed carbides pin dislocations, which synergistically compensate for the loss of strength and toughness caused by reducing the alloy component content, and improve the overall strength and plasticity of the wire rod, so that it can be directly processed into tool parts after cold forming.

[0032] The higher the proportion of the tempered bainite in the microstructure, the higher the strength and toughness of the wire rod. In a preferred technical solution, the volume percentage of the tempered bainite is ≥93%.

[0033] In the preferred technical solution, the diameter of the wire rod is 5.5~8mm, the tensile strength is 980~1030MPa, and the cross-sectional shrinkage rate is 61%~66%. Small-sized wire rods can be used for cold forming processes such as drills, cutters, etc. The plasticity is significantly better than that of traditional pearlite / bainite-containing tool steel wire rods. The toughened structure can be directly used as cold forming raw material, reducing subsequent processing steps and costs.

[0034] Uniform structure is beneficial to reducing the fluctuation of the mechanical properties of the wire rod, and high plasticity is beneficial to reducing the deformation resistance of the wire rod during direct cold processing, effectively reducing cracks or fractures. In the preferred technical solution, the mechanical property difference of the wire rod is ≤30MPa.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] (1) Aiming at the current situation that the addition of hardenability elements such as Cr and Mn to the existing high-strength tool steel wire rod increases the probability of brittle structure on the air-cooling line / water-cooling line, and the uniformity, state and strength and plasticity of the structure are difficult to control, the manufacturing method of the present invention adopts Nb-V chemical composition design combined with online molten salt semi-quenching isothermal technology to control the wire rod to quickly enter the bainite phase region from the high-temperature austenite state, forming a structure mainly composed of quenched bainite, which can effectively avoid the risk of brittle structures such as martensite and widmanstattenite produced by C and Cr elements. The quenched structure is subjected to high-temperature isothermal tempering in the high-temperature isothermal range, toughening and stress relief treatment, promoting the dispersion and precipitation of NbC and VC in the isothermal stage, improving the strength and plasticity matching of the wire rod, and slowly cooling through the roller to avoid stress increase, promote further toughening of the wire rod structure, improve the softening effect of the wire rod, effectively control the structure state of the hot-rolled wire rod, and has good industrial adaptability.

[0037] (2) In view of the fact that the existing high-strength tool steel wire rods have high alloy content and material costs, are accompanied by brittle structure, insufficient structural uniformity and plasticity, which lead to wire breakage and cracking during cold working. At the same time, the heat treatment process before cold working will also rapidly increase the production cost of tool products, the wire rod of the present invention has relatively lower carbon and alloy component contents, and Nb and V are added in trace amounts, which has lower material costs. The microstructure type includes a mixed structure composed mainly of tempered bainite and a small amount of ferrite. The product tensile strength can reach 980~1030MPa and the cross-sectional shrinkage rate is 61%~66%. It is used in the manufacture of high-strength tool steel and other application fields. After cold forming, it can be directly processed into tool parts, which is beneficial to reduce the risk of wire breakage and cracking during cold working and has good market application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] 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:

[0039] Figure 1 is a metallographic structure diagram of Example 1 of the present invention;

[0040] Figure 2 This is the metallographic structure diagram of Example 2 of the present invention. DETAILED DESCRIPTION

[0041] 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:

[0042] A preferred embodiment of the method for manufacturing 1100MPa grade high-strength tool steel wire rod of the present invention comprises the following chemical compositions and mass percentages: C: 0.4%, Si: 0.15%, Mn: 0.38%, Cr: 0.47%, Nb: 0.015%, 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 semi-quenching isothermal → roller slow cooling → coiling, specifically:

[0043] 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. 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 promote dynamic recrystallization in the final rolling process and refine the grains. Specifically, the soaking temperature of the heating furnace is controlled to be 1090°C, the time in the furnace is 135min, the initial rolling temperature is 1070°C, the final rolling temperature is 880°C, and the final rolling reduction is 27.5%; the wire-spinning process is used to convert the wire exiting the rolling line into a wire rod through a wire-spinning mechanism. 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 the strength-plasticity matching of the material is improved with a higher quenching temperature; specifically, the wire-spinning temperature is controlled to be 860°C.

[0044] The online molten salt semi-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 the front-stage molten salt treatment, so that the wire rod is cooled at a cooling rate of 38°C / s, and quickly enters the bainite phase region from the high-temperature austenite state to form a structure mainly composed of quenched bainite. After that, the wire rod is conveyed by a roller through the second salt bath tank for the 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 range, toughening and stress relief treatment, promote the dispersion and precipitation of microalloy carbides, inhibit the growth of carbide strengthening phases, and improve the strength and plasticity matching of the wire rod. Specifically: the molten salt temperature of the front-stage molten salt is 264°C, the processing time is 19s, the molten salt circulation volume is 605t / h, and the molten salt temperature rise is ≤8°C; the molten salt temperature of the rear-stage molten salt is 542°C, the processing time is 275s, and the molten salt circulation volume is 480t / h.

[0045] The roller slow cooling process adopts the method of closing the insulation cover, inputting the hot air of the online molten salt semi-quenching isothermal treatment into the insulation cover, and conveying the wire rod through the second section of the salt bath tank by the conveyor roller into 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 286°C at a cooling rate of 0.32°C / s; the coiling process is used to coil the wire rod into a coil through a coiling drum, and obtain the finished wire rod after packaging and storage. Its metallographic structure diagram is as follows Figure 1 shown.

[0046] Comparative Example 1:

[0047] 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 → Stelmore air cooling line → coiling, specifically: in the rolling process, the heating furnace soaking temperature is controlled to 1055°C, the furnace time is 150 minutes, the initial rolling temperature is 1025°C, the final rolling temperature is controlled to 845°C, the spinning temperature is controlled to 825°C, the Stelmore air cooling line is closed with an insulation cover, and the wire rod after spinning is transported along the Stelmore air cooling line by a roller, the cooling rate of the wire rod in the insulation cover is controlled to 3.2°C / s, the temperature is reduced to 290°C and collected by a coiling drum to obtain a finished wire rod.

[0048] Comparative Example 2:

[0049] A method for manufacturing a wire rod, which differs from Example 1 in that: the soaking temperature of the heating furnace is controlled to 1055°C, the time in the furnace is 150 minutes, the initial rolling temperature is 1025°C, the final rolling temperature is 845°C, the spinning temperature is controlled to be 825°C, the wire rod is treated with molten salt in the front section and cooled at a cooling rate of 29°C / s to obtain a finished wire rod. Example 2:

[0050] A preferred embodiment of the method for manufacturing 1100MPa grade high-strength tool steel wire rod of the present invention comprises the following chemical compositions and mass percentages: C: 0.42%, Si: 0.15%, Mn: 0.40%, Cr: 0.35%, Nb: 0.018%, V: 0.030%, P: 0.012%, 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 semi-quenching isothermal → roller slow cooling → coiling, specifically:

[0051] 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 plastic. 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 6.5mm through a rolling line. Appropriate rolling temperature and reduction are selected to promote dynamic recrystallization in the final rolling process and refine the grains. Specifically, the soaking temperature of the heating furnace is controlled to be 1105°C, the time in the furnace is 115min, the initial rolling temperature is 1080°C, the final rolling temperature is 895°C, and the final rolling reduction is 26%; the wire-spinning process is used to convert the wire exiting the rolling line into a wire rod through a wire-spinning mechanism. 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 the strength-plasticity matching of the material is improved with a higher quenching temperature; specifically, the wire-spinning temperature is controlled to be 875°C.

[0052] The online molten salt semi-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 the front-stage molten salt treatment, so that the wire rod is cooled at a cooling rate of 37°C / s, and quickly enters the bainite phase region from the high-temperature austenite state to form a structure mainly composed of quenched bainite. After that, the wire rod is conveyed by a roller through the second salt bath tank for the 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 range, toughening and stress relief treatment, promote the dispersion and precipitation of microalloy carbides, inhibit the growth of carbide strengthening phases, and improve the strength and plasticity matching of the wire rod. Specifically: the molten salt temperature of the front-stage molten salt is 295°C, the processing time is 25s, the molten salt circulation volume is 500t / h, and the molten salt temperature rise is ≤8°C; the molten salt temperature of the rear-stage molten salt is 565°C, the processing time is 450s, and the molten salt circulation volume is 450t / h.

[0053] The roller slow cooling process adopts the method of closing the insulation cover, inputting the hot air of the online molten salt semi-quenching isothermal treatment into the insulation cover, and conveying the wire rod through the second salt bath tank by the conveyor roller into 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 275°C at a cooling rate of 0.5°C / s; the coiling process is used to coil the wire rod into a coil through a coiling drum, and obtain the finished wire rod after packaging and storage. Its metallographic structure diagram is as follows Figure 2 shown.

[0054] Comparative Example 3:

[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 33°C / s, the molten salt temperature of the front-stage molten salt is 325°C, and the treatment time is 12s to obtain a finished wire rod.

[0056] Comparative Example 4:

[0057] 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 42°C / s, the molten salt temperature of the front-stage molten salt is 245°C, and the treatment time is 35s to obtain a finished wire rod. Example 3:

[0058] A preferred embodiment of the method for manufacturing 1100MPa grade high-strength tool steel wire rod of the present invention comprises the following chemical compositions and mass percentages: C: 0.42%, Si: 0.18%, Mn: 0.36%, Cr: 0.5%, Nb: 0.025%, 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 semi-quenching isothermal → roller slow cooling → coiling, specifically:

[0059] 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 plastic. 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 8mm through a rolling line. Appropriate rolling temperature and reduction are selected to promote dynamic recrystallization in the final rolling process and refine the grains. Specifically, the soaking temperature of the heating furnace is controlled to be 1140°C, the time in the furnace is 80min, the initial rolling temperature is 1100°C, the final rolling temperature is 910°C, and the final rolling reduction is 23%; the wire-spinning process is used to convert the wire exiting the rolling line into a wire rod through a wire-spinning mechanism. 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 the strength-plasticity matching of the material is improved with a higher quenching temperature; specifically, the wire-spinning temperature is controlled to be 900°C.

[0060] The online molten salt semi-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 the front-stage molten salt treatment, so that the wire rod is cooled at a cooling rate of 41°C / s, and quickly enters the bainite phase region from the high-temperature austenite state to form a structure mainly composed of quenched bainite. After that, the wire rod is conveyed by a roller through the second salt bath tank for the 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 range, toughening and stress relief treatment, promote the dispersion and precipitation of microalloy carbides, inhibit the growth of carbide strengthening phases, and improve the strength and plasticity matching of the wire rod. Specifically: the molten salt temperature of the front-stage molten salt is 252°C, the treatment time is 15s, the molten salt circulation volume is 800t / h, and the molten salt temperature rise is ≤8°C; the molten salt temperature of the rear-stage molten salt is 535°C, the treatment time is 200s, and the molten salt circulation volume is 650t / h.

[0061] The roller slow cooling process adopts the method of closing the insulation cover, inputting the hot air of the online molten salt semi-quenching isothermal treatment into the insulation cover, and conveying the wire rod through the second salt bath tank by the conveyor roller into the insulation cover, so as to prevent the wire rod from cooling too fast during the cooling process, thereby causing stress increase, and promoting further toughening of the wire rod structure, improving the softening effect of the wire rod, until coiling. Specifically: the wire rod is controlled to slowly cool to 291°C at a cooling rate of 0.23°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.

[0062] Comparative Example 5:

[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 585° C., the processing time is 460 s, and the finished wire rod is obtained.

[0064] Comparative Example 6:

[0065] 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 525° C., the processing time is 150 s, and the finished wire rod is obtained. Example 4:

[0066] A preferred embodiment of the method for manufacturing 1100MPa grade high-strength tool steel wire rod of the present invention comprises the following chemical compositions and mass percentages: C: 0.45%, Si: 0.10%, Mn: 0.25%, Cr: 0.41%, Nb: 0.022%, V: 0.035%, 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 semi-quenching isothermal → roller slow cooling → coiling, specifically:

[0067] 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 plastic. 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 5.5mm through a rolling line. Appropriate rolling temperature and reduction are selected to promote dynamic recrystallization in the final rolling process and refine the grains. Specifically, the soaking temperature of the heating furnace is controlled to be 1125°C, the time in the furnace is 105min, the initial rolling temperature is 1095°C, the final rolling temperature is 900°C, and the final rolling reduction is 29%; the wire-spinning process is used to convert the wire exiting the rolling line into a wire rod through a wire-spinning mechanism. 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 the strength-plasticity matching of the material is improved with a higher quenching temperature; specifically, the wire-spinning temperature is controlled to be 885°C.

[0068] The online molten salt semi-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 the front-stage molten salt treatment, so that the wire rod is cooled at a cooling rate of 39°C / s, and quickly enters the bainite phase region from the high-temperature austenite state to form a structure mainly composed of quenched bainite. After that, the wire rod is conveyed by a roller through the second salt bath tank for the 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 range, toughening and stress relief treatment, promote the dispersion and precipitation of microalloy carbides, inhibit the growth of carbide strengthening phases, and improve the strength-plasticity matching of the wire rod. Specifically: the molten salt temperature of the front-stage molten salt is 281°C, the processing time is 23s, the molten salt circulation volume is 710t / h, and the molten salt temperature rise is ≤8°C; the molten salt temperature of the rear-stage molten salt is 557°C, the processing time is 395s, and the molten salt circulation volume is 530t / h.

[0069] The roller slow cooling process adopts the method of closing the insulation cover, inputting the hot air of the online molten salt semi-quenching isothermal treatment into the insulation cover, and conveying the wire rod through the second salt bath tank by the conveyor roller into the insulation cover, so as to prevent the wire rod from cooling too fast during the cooling process, thereby causing stress increase, and promoting further toughening of the wire rod structure, improving the softening effect of the wire rod, until coiling. Specifically: the wire rod is controlled to slowly cool to 282°C at a cooling rate of 0.4°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.

[0070] Comparative Example 7:

[0071] 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 semi-quenching isothermal → air cooling → coiling. Specifically: the air cooling process is to open the insulation cover and transport the wire rod through the second salt bath tank by a conveyor roller. The wire rod is cooled to 279°C at a cooling rate of 1.6°C / s to obtain the wire rod.

[0072] 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:

[0073] Table 1. Comparison of microstructure and properties of different wire rod compositions and manufacturing methods

[0074]

[0075] The comparison results of Example 1 and Comparative Example 1 show that C and Cr, as relatively low-priced and effective carbide strengthening elements and austenite forming elements, often weaken the strengthening effect due to the uncontrollable cooling rate during the air-cooled line cooling phase transformation, and lead to the generation of abnormal structures such as martensite. Although Comparative Example 1 adopts lower C, Si, Cr, and Mn contents, combined with low-temperature rolling and spinning + insulation cooling control, the obtained wire rod with sorbite + ferrite structure has insufficient strength and plasticity, and the mechanical properties fluctuate greatly. However, the present application combines the Nb-V chemical composition design with the online molten salt semi-quenching isothermal technology to control the wire rod fast cooling. The hot rolled wire rod is quickly converted from a high-temperature austenite state into a bainite phase region to form a structure dominated by quenched bainite. The high-temperature isothermal tempering of the wire rod is then controlled, toughening and stress relief treatment is performed, and the structure state of the hot rolled wire rod is effectively controlled to obtain a mixed structure dominated by tempered bainite and containing a small amount of ferrite. As can be seen from the results of Examples 1 to 4, the product tensile strength can reach 980 to 1030 MPa and the cross-sectional reduction rate can reach 61% to 66%. It is used in application fields such as the manufacture of high-strength tool steel, which is beneficial to eliminating the heat treatment process before cold working. After cold forming, it can be directly processed into tool parts, and the risk of wire breakage and cracking during cold working is reduced.

[0076] From the comparison results of Example 1 and Comparative Example 2, it can be seen that using a higher quenching temperature to supercool the wire rod to the bainite phase transformation temperature range and maintain sufficient supercooling is beneficial to providing a greater phase transformation driving force, promoting the quenched bainite transformation, and improving the material strength-plasticity matching after tempering treatment.

[0077] From the comparison results of Example 2 and Comparative Example 3, it can be seen that the higher the molten salt temperature of the front-stage molten salt and the shorter the treatment time, the less quenching bainite phase transformation, the matrix strength, stress relief difficulty and production energy consumption are reduced. However, if the molten salt temperature is too high, the treatment time is too short, and the supercooling is insufficient, it is not conducive to promoting the bainite phase transformation and affects the matrix strength and strong-plastic properties.

[0078] 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 higher the supercooling degree can be, and the wire rod can be promoted to form a structure mainly composed of quenched bainite, with a significant strengthening effect. However, if the molten salt temperature is too low and the treatment time is too long, it is not conducive to avoiding the formation of martensite structure, the mechanical properties fluctuation increases, the internal stress increases, the difficulty of stress relief will be increased, and the processing energy consumption will increase.

[0079] From the comparison results of Example 3 and Comparative Example 5, it can be seen that the higher the molten salt temperature of the latter molten salt and the longer the treatment time, the more thermal power can be provided for the tempering of quenched bainite, the toughening of the structure can be promoted to release stress, the plasticity of the wire rod can be significantly improved, and the plasticity can be improved while suppressing excessive loss of strength by utilizing the dispersion and precipitation of carbides. However, if the molten salt temperature is too high and the treatment time is too long, the structure will soften too quickly, which is not conducive to the strength of the wire rod. At the same time, if the molten salt temperature is too high, the driving force for the precipitation of microalloy carbides will be reduced. As the treatment time increases, there is a risk of carbide coarsening and loss of strong and plastic properties.

[0080] From the comparison results of Example 3 and Comparative Example 6, it can be seen that the lower the molten salt temperature of the rear-stage molten salt and the shorter the treatment time, the lower the isothermal tempering effect and the plasticity of the wire rod. However, if the molten salt temperature is too low and the treatment time is too short, it is difficult to provide thermal power for tempering, the residual stress is insufficiently eliminated, and the plasticity of the wire rod will be significantly lost.

[0081] From the comparison results of Example 4 and Comparative Example 7, it can be seen that the use of slow roller cooling can prevent the wire rod from cooling too fast during the cooling process, avoid physical shrinkage leading to increased stress and fluctuations in mechanical properties, and continue the treatment effect of the molten salt in the later stage, promote further toughening of the wire rod structure, and improve the softening effect of the wire rod.

[0082] 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 1100MPa 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 ≥860°C, and then undergoes an online molten salt semi-quenching isothermal treatment. The wire rod is controlled to first undergo a front-end molten salt treatment so that the wire rod enters the bainite phase region from the high-temperature austenite state at a cooling rate of ≥30°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 is slowly cooled by a roller 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: 0.40%~0.45 %, Si: 0.10%~0.18%, Mn: 0.25%~0.40%, Cr: 0.35%~0.50%, 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-stage molten salt is 250~295℃, and the processing time is 15~25s; the molten salt temperature of the rear-stage molten salt is 535~565℃, and the processing time is 200~450s.

2. The method for manufacturing 1100 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 1090-1140° C., and the soaking time in the furnace is 80-135 minutes.

3. The method for manufacturing 1100 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 1070-1100° C., the final rolling temperature is controlled to be 880-910° C., and the final rolling reduction is controlled to be 23%-29%.

4. The method for manufacturing 1100 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 860-900°C.

5. The method for manufacturing 1100 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 500-800 t / h, and the molten salt temperature rise is ≤8°C; the molten salt circulation rate of the rear-stage molten salt is 450-650 t / h.

6. The method for manufacturing 1100 MPa grade high strength tool steel wire rod according to claim 1, characterized in that: The roller slow cooling controls the wire rod to be slowly cooled at a cooling rate of 0.2-0.5°C / s.

7. A 1100MPa grade high strength tool steel wire rod, characterized in that: The wire rod is manufactured by the manufacturing method of 1100 MPa grade high strength tool steel wire rod according to any one of claims 1 to 6.

8. The 1100 MPa grade high strength tool steel wire rod according to claim 7, characterized in that: The volume percentage of the tempered bainite is ≥93%.

9. The 1100 MPa grade high strength tool steel wire rod according to claim 7, characterized in that: The diameter of the wire rod is 5.5-8 mm, the tensile strength is 980-1030 MPa, the cross-sectional shrinkage is 61%-66%, and the mechanical property difference within the same circle is ≤30 MPa.

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