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

Abstract

The invention relates to a 1100MPa-grade high-strength tool steel wire rod and a manufacturing method thereof, the wire rod adopts a middle-carbon Nb-V-containing chemical component design, after a steel billet is rolled and spun into the wire rod according to the spinning temperature of more than or equal to 860 DEG C, online molten salt semi-quenching isothermal treatment is performed, the wire rod is controlled to be subjected to front-section molten salt treatment, and then the steel wire rod is subjected to hot rolling and hot rolling to obtain the 1100MPa-grade high-strength tool steel wire rod. According to the method, the steel wire rod enters a bainite phase region from a high-temperature austenite state at the cooling speed of more than or equal to 30 DEG C / s to form a structure taking quenched bainite as a main component, and then is subjected to rear-section molten salt heating isothermal tempering and toughening destressing treatment, and finally is subjected to roller way slow cooling to prepare the steel wire rod with a microscopic structure comprising tempered bainite and ferrite, so that the material cost can be reduced, and the production efficiency is improved. The method has the advantages that martensite brittle structures are effectively avoided, the structure state of the hot-rolled wire rod is controlled, the plasticity and cold working performance of the wire rod are improved, the tensile strength of the product can reach 980-1030 MPa, the percentage reduction of area is 61%-66%, and the product can be directly machined into tool parts after cold forming.

Description

Technical Field

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

[0002] As an indispensable basic industrial equipment in the industrial production process, tools determine the operation efficiency of mechanical equipment, the production efficiency, production cost and quality of industrial products. Tool steel is produced by machining and surface treatment of cold forming machines such as cutting and grinding with hot-rolled wire rods as the base material. The hot-rolled wire rods of high-strength tools also need to undergo heat treatment before cold forming to reduce the hardness of the material, improve plasticity and toughness, stabilize dimensions and properties, make the wire rods more likely to undergo plastic deformation during cold forming, reduce the generation of defects such as cracking, and ensure machining accuracy. However, the heat treatment process will also rapidly increase the production cost of tool products. Therefore, controlling the tissue state of hot-rolled wire rods and improving the plastic and tough properties of wire rods are of great significance for reducing the cost of 1100MPa grade high-strength tool steel, improving production efficiency and product quality.

[0003] Existing high-strength tools often add appropriate amounts of hardenability elements such as Cr and Mn to hot-rolled wire rods for tools and produce wire rods through a Stelmor air-cooling line. The reasons why they cannot meet the requirements of directly machining into parts after cold forming include: (1) In hot-rolled wire rods for tools, although the addition of hardenability elements such as Cr and Mn can improve the hardenability and comprehensive mechanical properties of the material, since the air-cooling line is air-cooled, even combined with a slow-cooling process, the minimum cooling capacity is limited, the instability and control difficulty are relatively large. Often, due to the uncontrollable cooling rate during the cooling phase transformation, the strengthening effect is weakened. At the same time, when the cooling rate is relatively fast, because the cooling rate exceeds the critical value, the probability of forming brittle tissues such as martensite and Widmanstatten in the wire rods on the air-cooling line will be significantly increased. At the same time, the martensite transformation is a non-diffusive shear process, which will generate large tissue stress and thermal stress, deteriorating the plasticity and toughness of the wire rods, and then leading to problems such as wire breakage and cracking during the cold processing process. At the same time, it is necessary to adjust the use performance of tool products through a combination of cold processing and heat treatment.

[0004] (2) To meet the tool performance requirements and prevent the precipitation of martensite during the rolling cooling process, although in the prior art, wire rods for tool steel use alloy element solid solution strengthening, precipitation strengthening, fine grain strengthening, etc., and combine low-temperature controlled rolling to produce wire rods with bainite structure. For example, a production process for alloy tool steel wire rods with all-bainite structure disclosed in Patent CN111690801B adopts a composition design of C-Si-Mn-Cr-Ni-Al-Mo-V-Nb, and combines low-temperature rolling and spinning, air cooling and cover cooling to produce all-bainite structure. However, on the one hand, low-temperature rolling exacerbates the wear and load on the rolling line, affecting production efficiency. The Si content in the steel is relatively high. Although it makes austenite more likely to supercool to the bainite range during cooling, it will also reduce its elongation and impact toughness. With the influence of the instability of air cooling and the limited length of the air cooling line, the temperature of the wire rod after cover cooling phase transformation is already in a low-temperature state. The obtained bainite has higher hardness and strength, and greater tissue stress, affecting machining performance, and heat treatment regulation is still required before cold processing; on the other hand, in the precipitation temperature range of carbides, affected by the instability of air cooling and the maximum cooling capacity limit, it affects the precipitation driving force of carbides. The coarsening and precipitation of carbides not only affect the tissue uniformity but also have an adverse effect on toughness. The addition of multi-components and high alloy content increases the material cost, which is not conducive to reducing the cost of tool steel. Summary of the Invention

[0005] The present invention aims to solve at least one of the above technical problems to some extent. The present invention provides a 1100MPa grade high-strength tool steel wire rod and its manufacturing method, which can reduce the material cost, effectively avoid martensite brittle structure, control the tissue state of the hot-rolled wire rod, improve the plasticity and cold processing performance of the wire rod, so that it can be directly processed into tool parts after cold forming.

[0006] The technical solution adopted by the present invention to solve its technical problems is: A manufacturing method of a 1100MPa grade high-strength tool steel wire rod, the manufacturing method includes: After the steel billet is rolled and spun into a wire rod at a spinning temperature of ≥860°C, it undergoes online molten salt semi-quenching and isothermal treatment. The wire rod is controlled to first undergo front-section 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, forming a structure mainly composed of quenched bainite, and then undergoes post-section molten salt heating and isothermal tempering, toughening and stress relief treatment, and finally undergoes slow cooling through the roller table to produce 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.

[0007] The chemical composition and mass percentage design basis of the above wire rods include: (1) Carbon: Element C improves the matrix strength through solid solution strengthening and carbide formation, and has a relatively lower price. With the increase of carbon content, the stability of supercooled austenite can be improved, the pearlite transformation can be delayed, and the formation of quenched bainite during the online molten salt semi-quenching isothermal treatment can be promoted. Through short-term front-section molten salt treatment, a structure mainly composed of quenched bainite can be quickly formed to meet the requirements of hand tools for hardness and wear resistance. However, if the carbon content is too high, it will increase the carbon segregation tendency 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 requirements of high hardness and wear resistance of hand tool steel, control the material cost, and at the same time facilitate the control of the microstructure state of the hot-rolled wire rod and improve the material plasticity, a medium carbon content is adopted, and the mass percentage of C is controlled at 0.40% - 0.45%.

[0008] (2) Silicon: Element Si can inhibit the grain coarsening during the online molten salt semi-quenching isothermal treatment, improve the stability of supercooled austenite, delay the precipitation of carbides, make the bainite transformation occur at a lower temperature, expand the bainite transformation region, and compress the pearlite formation interval. 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, and the plasticity regulation will be affected, resulting in a decrease in plasticity during cold processing. Therefore, the Si content is reduced, and the mass percentage of Si is controlled at 0.10% - 0.18%.

[0009] (3) Manganese: As an austenite-forming element, Mn can expand the austenite region, significantly improve the stability of supercooled austenite, increase the hardenability of the wire rod, reduce the formation tendency of pearlite and ferrite, strongly delay the pearlite transformation, and make the bainite transformation occur within a wider cooling rate range. The online molten salt semi-quenching isothermal treatment can control the wire rod to quickly form a structure mainly composed of quenched bainite through short-term quenching, improving the matrix strength, which is suitable for tools subjected to impact loads. However, when the Mn content is too high, it will aggravate the segregation of alloying elements, promote the growth of austenite grains, increase the difficulty of isothermal toughening, and reduce the toughness and plasticity of the steel. Therefore, in order to balance the impact fracture resistance performance of hand tools and facilitate the bainite phase transformation and isothermal toughening stress relief regulation of the wire rod, the mass percentage of Mn is controlled at 0.25% - 0.40%.

[0010] (4) Chromium: As a strong carbide-forming element, the Cr element can form fine carbides, improve the hardenability of steel, reduce the diffusion coefficient of carbon in austenite, shift the pearlite transformation kinetics curve to the right, delay the precipitation of ferrite and pearlite, and make quenched bainite 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 exacerbate composition segregation, increase the control difficulty of tissue uniformity and plasticity improvement, the carbide distribution is uneven, forming coarse particles or network structures, reducing plasticity and cold workability. Therefore, in order to balance the wear resistance and life of hand tools and facilitate the regulation of the microstructure and tissue state mainly composed of tempered bainite in wire rods, the mass percentage of Cr is controlled at 0.35% - 0.50%.

[0011] (5) Niobium: The Nb microalloying element can precipitate in the primary rolling stage, pin the grain boundaries, inhibit the growth of austenite grains, and improve strength and toughness through precipitation strengthening and grain refinement strengthening. The refined austenite grains are beneficial to increasing the nucleation sites of quenched bainite and 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 the Nb element, the mass percentage of Nb is controlled at 0.015% - 0.025%.

[0012] (6) Vanadium: As an alloying element, the V element can pin the austenite grain boundaries during the controlled rolling stage, refine the original austenite grains, and can precipitate dispersedly during the isothermal process of the subsequent molten salt treatment, playing a role in quickly increasing the matrix strength, being beneficial to improving toughness and cold workability, and reducing the crack tendency during the cold forming of hand tools. However, the cost of the V element is relatively high, excessive addition is not conducive to controlling the cost of wire rods, too high V will also cause element enrichment and rapid coarsening of carbides, and the coarsened carbides affect the strength and toughness properties, and are prone to cracking along the grain boundaries during cold forming. Therefore, based on the role, cost and preparation control of the V element, the mass percentage of V is controlled at 0.025% - 0.035%.

[0013] (7) Phosphorus and sulfur: The P element and S element belong to impurity elements, and the lower the better. Therefore, P ≤ 0.015% and S ≤ 0.015% are controlled.

[0014] The above wire rods adopt a chemical composition design of medium carbon containing Nb-V. By using relatively low contents of Si / Mn / Cr components, optimizing the ratios of C, Si, Mn, and Cr to expand the bainite transformation range and reduce the probability of pearlite formation, and cooperating with Nb and V to refine grains, it provides favorable conditions for quickly forming a structure mainly composed of quenched bainite through short-time quenching during the on-line molten salt semi-quenching isothermal process, reducing the difficulty of isothermal tempering to remove stress, and promoting the dispersed precipitation of microalloy carbides. On this basis, the wire rods after spinning do not pass through the air-cooling line but adopt on-line molten salt semi-quenching isothermal treatment: 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.

[0015] 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.

[0016] Before rolling, in order to make the billet reach the rollable plasticity, promote the homogenization of the internal composition of the billet, and avoid the risks of overheating leading to coarse grains and burning, in the preferred technical solution, before rolling, the soaking temperature of the heating furnace is controlled at 1090 - 1140 °C, and the residence time in the furnace is 80 - 135 min.

[0017] Since the wire rod can be rapidly cooled by online molten salt semi-quenching and isothermal treatment, the limitation on rolling can be reduced. There is no need to adopt too low rolling temperature. An appropriate initial rolling temperature can be selected to promote rapid rolling and reduce the wear on the rolling line, enabling the Nb microalloying element to precipitate in the initial rolling stage, pin the grain boundaries, control the temperature in the intermediate rolling stage and the reduction ratio in the finish rolling stage, promote the dynamic recrystallization and grain refinement in the finish rolling process, and retain the deformation energy. In the preferred technical solution, during rolling, the initial rolling temperature is controlled at 1070 - 1100 °C, the finish rolling temperature is controlled at 880 - 910 °C, and the reduction ratio in the finish rolling is 23% - 29%.

[0018] When coiling, selecting a relatively high coiling temperature is beneficial to further subject the wire rod to online molten salt treatment at a relatively high quenching temperature, improving the strength-plasticity matching of the material. In the preferred technical solution, when coiling, the coiling temperature is controlled at 860 - 900 °C.

[0019] 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 greater the supercooling degree can be increased, providing more driving force for bainite transformation, promoting the formation of a structure mainly composed of quenched bainite in the wire rod, and the strengthening effect is significant. 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 fluctuate more, the internal stress increases, which will increase the difficulty of stress relief, and at the same time the treatment energy consumption increases; on the contrary, the higher the molten salt temperature and the shorter the treatment time, the less the quenched bainite transformation, the matrix strength, the stress relief difficulty and the production energy consumption decrease. However, if the molten salt temperature is too high and the treatment time is too short, the supercooling degree is insufficient, which is not conducive to suppressing pearlite transformation and promoting bainite transformation, affecting the matrix strength and strength-plasticity performance. Therefore, an appropriate molten salt temperature and treatment time can be selected for the front-stage molten salt treatment to promote the wire rod to enter the bainite phase region from the high-temperature austenite state, form a structure mainly composed of quenched bainite, and avoid the formation of abnormal martensite structure, making organizational preparations for toughening and stress relief in the subsequent-stage molten salt treatment. In the preferred technical solution, the molten salt temperature of the front-stage molten salt is 250 - 295 °C, and the treatment time is 15 - 25 s.

[0020] Due to the large temperature difference between the high-temperature austenite state and the bainite phase region, selecting a relatively large molten salt circulation rate can control the molten salt temperature rise and improve the treatment accuracy. In the preferred technical solution, the molten salt circulation rate of the front-stage molten salt is 500 - 800 t / h, and the molten salt temperature rise ≤ 8 °C.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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, resulting in lower material costs. The low alloy components reduce the degree of dendritic segregation during solidification, and reduce the tissue inhomogeneity caused by compositional segregation during the solidification of steel billets. Especially for the segregation coefficients of elements such as Mn and Cr, combined with the online molten salt semi-quenching isothermal technology, a microstructure mainly composed of tempered bainite after isothermal treatment and containing a small amount of ferrite is obtained. Compared with the tool steel wire rod with a pearlite / bainite-containing microstructure, it can effectively avoid the risk of brittle tissues such as martensite and Widmanstatten structure generated by C and Cr elements, and has better tissue uniformity. The uniform tissue will exhibit more stable mechanical properties during service. At the same time, there are high-density dislocations and fine substructures in the quenched bainite tissue, and the lattice distortion is significant, making its strength higher than that of soft phase tissues such as pearlite. Compared with the tool steel wire rod with a bainite structure, the tissue mainly composed of quenched bainite is toughened by isothermal tempering, effectively controlling the tissue state of the wire rod, reducing the dislocation density, alleviating the lattice distortion, making the carbides in the tempered bainite more stable, and further reducing the internal stress in the tissue. Therefore, without much loss of strength, the toughness is significantly improved, making the tissue change from hard and brittle to strong and tough, which can maximize the strengthening effect of carbon elements. Combining with the grain refinement of microalloying elements, NbC and VC are fully precipitated, and the dispersed carbides pin the dislocations, synergistically compensating for the loss of strength and toughness caused by reducing the alloy component content, and improving the overall strength and plasticity of the wire rod, so that it can be directly processed into tool parts after cold forming.

[0027] The higher the proportion of the tempered bainite in the microstructure, the higher the strength and toughness of the wire rod. In the preferred technical solution, the volume percentage of the tempered bainite ≥ 93%.

[0028] In the preferred technical solution, the diameter of the wire rod is 5.5 - 8 mm, the tensile strength is 980 - 1030 MPa, and the reduction of area is 61% - 66%. The small-sized wire rod can be used for cold forming processing such as drill bits and cutters. Its plasticity is significantly better than that of the traditional tool steel wire rod with a pearlite / bainite-containing microstructure. The toughened tissue can be directly used as the cold forming raw material, reducing subsequent processing procedures and costs.

[0029] The uniform tissue is beneficial to reducing the mechanical property fluctuation of the wire rod, and the high plasticity is beneficial to reducing the deformation resistance during the direct cold processing of the wire rod, effectively reducing cracks or fractures. In the preferred technical solution, the difference in mechanical properties within the same coil of the wire rod ≤ 30 MPa.

[0030] Compared with the prior art, the beneficial effects of the present invention are at least as follows: (1)In view of the current situation that the addition of hardenability elements such as Cr and Mn in the wire rods for existing high-strength tool steels increases the probability of brittle structures on the air-cooling line / water-cooling line, and it is difficult to control the tissue uniformity, state, strength, and plastic properties, the manufacturing method of the present invention adopts the Nb-V chemical composition design combined with the 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 Widmanstatten structures caused by C and Cr elements. High-temperature isothermal tempering is carried out on the quenched structure in the high-temperature isothermal range for toughening and stress relief treatment, promoting the dispersion precipitation of NbC and VC in the isothermal stage, improving the strength-plasticity matching of the wire rod, and slow cooling through the roller table to avoid stress increase and promote further toughening of the wire rod structure, improving the softening effect of the wire rod, effectively controlling the tissue state of the hot-rolled wire rod, and having good industrial adaptability.

[0031] (2)In view of the current situation that the alloy content and material cost of the existing wire rods for high-strength tool steels are relatively high, accompanied by brittle structures, insufficient tissue uniformity and plasticity, resulting in cold working wire breakage and cracking, and at the same time, the heat treatment process before cold working will also rapidly increase the production cost of tool products, the carbon and alloy component contents of the wire rods of the present invention are relatively lower, with trace addition of Nb and V, the material cost is lower, and the microscopic tissue type includes a mixed tissue mainly composed of tempered bainite and containing a small amount of ferrite. The tensile strength of the product can reach 980-1030 MPa, and the reduction of area is 61%-66%. It is used in application fields such as manufacturing high-strength tool steels. After cold forming, it can be directly processed into tool parts, which is beneficial to reducing the risk of cold working wire breakage and cracking and has good market application prospects. Brief Description of the Drawings

[0032] The above and / or additional aspects and advantages of the present invention will become obvious and easy to understand from the description of the embodiments in conjunction with the following drawings, where: Figure 1 is the metallographic structure diagram of Embodiment 1 of the present invention; Figure 2 is the metallographic structure diagram of Embodiment 2 of the present invention. Detailed Description of the Embodiments

[0033] The embodiments described below with reference to the accompanying drawings are exemplary, solely for the purpose of illustration and do not limit the description of the features and characteristics of the present invention. To present the best mode of implementing the present invention, it is intended to explain the present invention and is sufficient for those skilled in the art to be able to implement the present invention. It should not be construed as any limitation on the scope of the present invention, which is only defined by the appended claims; the wire rods obtained from the following examples and comparative examples were subjected to microstructure and property tests, including: the tensile test was carried out in accordance with "GB-T 228.1-2021 Metallic materials-Tensile testing-Part 1: Method of test at room temperature" to obtain the tensile strength and reduction of area; the microstructure was detected by the metallic microstructure detection method in accordance with the GB / T13298 standard; the method for testing the difference in mechanical properties within the same coil: take 2 coils of wire rods at 5 m from the end of the coil, with the lap area as the base point, evenly divide each coil of wire rod into 8 segments on average, take 1 tensile specimen on each segment, and the strength range of the tensile specimens after the tensile test is the difference in mechanical properties within the same coil. Example 1:

[0034] A preferred embodiment of the manufacturing method of the 1100 MPa grade high-strength tool steel wire rod of the present invention, the chemical composition and mass percentage of the wire rod include 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 rest is Fe and unavoidable impurities; its manufacturing method is manufactured according to the process flow of rolling → wire laying → online molten salt semi-quenching isothermal → slow cooling on the roller table → coiling, specifically: The rolling process is used to heat the steel billet with a specification of 180 mm × 180 mm into a high-temperature steel billet that reaches the plastic state for rolling through a heating furnace. The heating furnace is controlled according to the three-stage temperature rising program of the preheating section, heating section, and soaking section. The high-temperature steel billet is rolled into a wire rod with a diameter specification of 7 mm through the rolling line. Appropriate rolling temperature and reduction ratio are selected to promote dynamic recrystallization during the finishing rolling process and refine the grains. Specifically: control the soaking temperature of the heating furnace to be 1090 °C, the residence time in the furnace to be 135 min, the initial rolling temperature to be 1070 °C, the finishing rolling temperature to be 880 °C, and the finishing rolling reduction ratio to be 27.5%; the wire laying process is used to make the wire rod exiting the rolling line into a wire rod through a wire laying machine. The wire rod is scattered on the roller table and conveyed along the roller table, 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: control the wire laying temperature to be 860 °C.

[0035] The online molten salt semi-quenching isothermal process uses a two-stage salt bath tank with molten salt inside. The wire rod after wire laying is transported through the first-stage salt bath tank by a roller table for the front-stage molten salt treatment, so that the wire rod cools down at a cooling rate of 38 °C / s, quickly enters the bainite phase region from the high-temperature austenite state, and forms a structure mainly composed of quenched bainite. Then the wire rod is transported through the second-stage salt bath tank by a roller table for the back-stage molten salt treatment, controlling the wire rod to perform high-temperature isothermal tempering on the quenched structure in the high-temperature isothermal range, toughening and stress-relieving treatment, promoting the dispersion precipitation of micro-alloy carbides, inhibiting the growth of carbide strengthening phases, and improving the strength-plasticity matching of the wire rod. Specifically: the molten salt temperature of the front-stage molten salt is 264 °C, the treatment time is 19 s, the molten salt circulation rate is 605 t / h, and the molten salt temperature rise ≤ 8 °C; the molten salt temperature of the back-stage molten salt is 542 °C, the treatment time is 275 s, and the molten salt circulation rate is 480 t / h.

[0036] The roller table slow cooling process uses a closed heat preservation cover. The hot air from the online molten salt semi-quenching isothermal treatment is input into the heat preservation cover. The wire rod transported by the conveying roller table after passing through the second-stage salt bath tank enters the heat preservation cover, preventing the wire rod from increasing stress due to too fast cooling rate during the cooling process, and promoting the further toughening of the wire rod structure, improving the softening effect of the wire rod until coiling. Specifically: control the wire rod 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 by a coiling drum, and after packaging and warehousing, the finished wire rod is obtained, and its metallographic structure diagram is as Figure 1 shown.

[0037] Comparative Example 1: A manufacturing method of a wire rod, the difference between its manufacturing method and that of Example 1 is that: its manufacturing method is carried out according to the technological process of rolling → wire laying → Stelmor air cooling line → coiling. Specifically: in the rolling process, control the soaking temperature of the heating furnace to be 1055 °C, the time in the furnace to be 150 min, the initial rolling temperature to be 1025 °C, the final rolling temperature to be 845 °C, control the wire laying temperature to be 825 °C, the Stelmor air cooling line uses a closed heat preservation cover, the wire rod after wire laying is transported along the Stelmor air cooling line by a roller table, control the cooling rate of the wire rod in the heat preservation cover to be 3.2 °C / s, cool down to 290 °C and collect it by a coiling drum to obtain the finished wire rod.

[0038] Comparative Example 2: A manufacturing method of a wire rod, the difference between its manufacturing method and that of Example 1 is that: control the soaking temperature of the heating furnace to be 1055 °C, the time in the furnace to be 150 min, the initial rolling temperature to be 1025 °C, the final rolling temperature to be 845 °C, control the wire laying temperature to be 825 °C, the wire rod undergoes the front-stage molten salt treatment and cools down at a cooling rate of 29 °C / s to obtain the finished wire rod. Example 2:

[0039] A preferred embodiment of the manufacturing method of the 1100MPa grade high-strength tool steel wire rod. The chemical composition and mass percentage of the wire rod include 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 rest are Fe and inevitable impurities. Its manufacturing method is carried out according to the technological process of rolling → wire laying → on-line molten salt semi-quenching isothermal → slow cooling on the roller table → coiling. Specifically: The rolling process is used to heat a steel billet with a specification of 180mm×180mm into a high-temperature steel billet that reaches the plastic state for rolling through a heating furnace. The heating furnace is controlled according to the three-stage temperature rising program of the preheating section, heating section, and soaking section. The high-temperature steel billet is rolled into a wire rod with a diameter specification of 6.5mm through the rolling line. Appropriate rolling temperature and reduction are selected to promote dynamic recrystallization during the finishing rolling process, refine the grains. Specifically: control the soaking temperature of the heating furnace to be 1105°C, the residence time in the furnace to be 115min, the initial rolling temperature to be 1080°C, the finishing rolling temperature to be 895°C, and the finishing rolling reduction to be 26%; The wire laying process is used to make the wire rod coming out of the rolling line into a wire rod through a wire laying machine. The wire rod is scattered on the roller table and transported along the roller table, so that the wire rod is in the high-temperature austenite state, and the strength and plasticity matching of the material are improved with a higher quenching temperature. Specifically: control the wire laying temperature to be 875°C.

[0040] The on-line molten salt semi-quenching isothermal process uses a two-stage salt bath tank with molten salt inside. The wire rod after wire laying is transported through the roller table and passes through the first-stage salt bath tank for the front-stage molten salt treatment, so that the wire rod cools down at a cooling rate of 37°C / s, quickly enters the bainite phase region from the high-temperature austenite state, and forms a structure mainly composed of quenched bainite. Then the wire rod is transported through the roller table and passes through the second-stage salt bath tank for the back-stage molten salt treatment, controlling the wire rod to perform high-temperature isothermal tempering on the quenched structure in the high-temperature isothermal interval, toughening and stress relieving treatment, promoting the dispersion precipitation of microalloy carbides, inhibiting the growth of carbide strengthening phases, and improving the strength and plasticity matching of the wire rod. Specifically: the molten salt temperature of the front-stage molten salt is 295°C, the treatment time is 25s, the molten salt circulation volume is 500t / h, and the molten salt temperature rise ≤ 8°C; the molten salt temperature of the back-stage molten salt is 565°C, the treatment time is 450s, and the molten salt circulation volume is 450t / h.

[0041] The slow cooling process on the roller table uses a closed heat preservation cover. The hot air from the on-line molten salt semi-quenching isothermal treatment is input into the heat preservation cover. The wire rod passing through the second-stage salt bath tank is transported into the heat preservation cover by the conveying roller table, preventing the wire rod from cooling too fast during the cooling process, resulting in an increase in stress, and promoting further toughening of the wire rod structure, improving the softening effect of the wire rod until coiling. Specifically: control the wire rod to cool slowly at a cooling rate of 0.5°C / s to 275°C; The coiling process is used to coil the wire rod into a coil through a coiling drum. After packaging and storing in the warehouse, the finished wire rod is obtained, and its metallographic structure diagram is asFigure 2 as shown

[0042] Comparative Example 3: A method for manufacturing a wire rod, which is different from that of Example 2 in that: the wire rod is subjected to molten salt treatment in the front stage 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 12 s to obtain a finished wire rod product.

[0043] Comparative Example 4: A method for manufacturing a wire rod, which is different from that of Example 2 in that: the wire rod is subjected to molten salt treatment in the front stage 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 35 s to obtain a finished wire rod product. Example 3:

[0044] A preferred embodiment of the method for manufacturing the 1100 MPa grade high-strength tool steel wire rod according to the present invention. The chemical composition and mass percentage of the wire rod include 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 rest are Fe and inevitable impurities. Its manufacturing method is carried out according to the technological process of rolling → wire laying → on-line molten salt semi-quenching isothermal → slow cooling on the roller table → coiling. Specifically: The rolling process is used to heat a steel billet with a specification of 180 mm × 180 mm into a high-temperature steel billet that reaches the plastic state for rolling through a heating furnace. The heating furnace is controlled according to the three-stage heating program of the preheating section, the heating section, and the soaking section. The high-temperature steel billet is rolled into a wire rod with a diameter specification of 8 mm through the rolling line. Appropriate rolling temperature and reduction are selected to promote dynamic recrystallization during the finishing rolling process and refine the grains. Specifically: control the soaking temperature of the heating furnace to be 1140 °C, the residence time in the furnace to be 80 min, the initial rolling temperature to be 1100 °C, the finishing rolling temperature to be 910 °C, and the finishing rolling reduction to be 23%; the wire laying process is used to make the wire rod coming out of the rolling line into a wire rod through a wire laying machine. The wire rod is scattered on the roller table and conveyed along the roller table, 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: control the wire laying temperature to be 900 °C.

[0045] The online molten salt semi-quenching and isothermal process uses a two-stage salt bath tank with molten salt inside. The wire rod after wire laying is transported through the first-stage salt bath tank by a roller table for the front-stage molten salt treatment, so that the wire rod cools down at a cooling rate of 41 °C / s, quickly enters the bainite phase region from the high-temperature austenite state, and forms a structure mainly composed of quenched bainite. Then the wire rod is transported through the second-stage salt bath tank by a roller table for the rear-stage molten salt treatment, controlling the wire rod to perform high-temperature isothermal tempering on the quenched structure in the high-temperature isothermal interval, toughening and stress relieving treatment, promoting the dispersion precipitation of micro-alloy carbides, inhibiting the growth of carbide strengthening phases, and improving the strength-ductility matching of the wire rod. Specifically: the molten salt temperature of the front-stage molten salt is 252 °C, the treatment time is 15 s, the molten salt circulation rate is 800 t / h, and the molten salt temperature rise ≤ 8 °C; the molten salt temperature of the rear-stage molten salt is 535 °C, the treatment time is 200 s, and the molten salt circulation rate is 650 t / h.

[0046] The roller table slow cooling process adopts closing the heat preservation cover, inputting the hot air of the online molten salt semi-quenching and isothermal treatment into the heat preservation cover, and the wire rod transported by the conveying roller table through the second-stage salt bath tank enters the heat preservation cover, preventing the wire rod from increasing stress due to too fast cooling rate during the cooling process, and promoting the further toughening of the wire rod structure, improving the softening effect of the wire rod until coiling. Specifically: controlling the wire rod 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 warehousing.

[0047] Comparative Example 5: A manufacturing method of a wire rod, the difference between its manufacturing method and that of Example 3 is that: the molten salt temperature of the rear-stage molten salt is 585 °C, the treatment time is 460 s, and the finished wire rod is obtained.

[0048] Comparative Example 6: A manufacturing method of a wire rod, the difference between its manufacturing method and that of Example 3 is that: the molten salt temperature of the rear-stage molten salt is 525 °C, the treatment time is 150 s, and the finished wire rod is obtained. Example 4:

[0049] A preferred implementation of the manufacturing method of the 1100 MPa grade high-strength tool steel wire rod described in the present invention, the chemical composition and mass percentage of the wire rod include 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 rest are Fe and inevitable impurities; its manufacturing method is manufactured according to the process flow of rolling → wire laying → online molten salt semi-quenching and isothermal → roller table slow cooling → coiling. Specifically: The rolling process is used to heat a billet with a specification of 180mm×180mm into a hot billet with rollable plasticity through a heating furnace. The heating furnace is controlled according to a three-stage temperature rising program of a preheating section, a heating section, and a soaking section. The hot billet is rolled into wire rods with a diameter specification of 5.5mm through a rolling line. Appropriate rolling temperature and reduction are selected to promote dynamic recrystallization during the finishing rolling process, refine the grains. Specifically: control the soaking temperature of the heating furnace to be 1125°C, the residence time in the furnace to be 105min, the initial rolling temperature to be 1095°C, the finishing rolling temperature to be 900°C, and the finishing rolling reduction to be 29%; The wire laying process is used to make the wire rods exiting the rolling line into coil bars through a wire laying machine. The coil bars are scattered on the roller table and transported along the roller table, keeping the coil bars in a high-temperature austenite state to improve the strength-plasticity matching of the material with a relatively high quenching temperature. Specifically: control the wire laying temperature to be 885°C.

[0050] The online molten salt semi-quenching and isothermal process uses a two-stage salt bath tank with molten salt inside. The coil bars after wire laying are transported through the first-stage salt bath tank by the roller table for the front-stage molten salt treatment, cooling the coil bars at a cooling rate of 39°C / s, quickly entering the bainite phase region from the high-temperature austenite state to form a structure mainly composed of quenched bainite. Then the coil bars are transported through the second-stage salt bath tank by the roller table for the rear-stage molten salt treatment, controlling the coil bars to perform high-temperature isothermal tempering on the quenched structure in the high-temperature isothermal interval, toughening and stress relieving treatment, promoting the dispersion precipitation of microalloy carbides, inhibiting the growth of carbide strengthening phases, and improving the strength-plasticity matching of the coil bars. Specifically: the molten salt temperature of the front-stage molten salt is 281°C, the treatment time is 23s, the molten salt circulation volume is 710t / h, and the molten salt temperature rise ≤ 8°C; the molten salt temperature of the rear-stage molten salt is 557°C, the treatment time is 395s, and the molten salt circulation volume is 530t / h.

[0051] The slow cooling process of the roller table uses a closed heat preservation cover. The hot air from the online molten salt semi-quenching and isothermal treatment is input into the heat preservation cover. The coil bars transported by the conveying roller table passing through the second-stage salt bath tank enter the heat preservation cover to prevent the coil bars from having too fast a cooling rate during the cooling process, resulting in increased stress, and promoting further toughening of the coil bar structure, improving the softening effect of the coil bars until coiling. Specifically: control the coil bars to slowly cool to 282°C at a cooling rate of 0.4°C / s; The coiling process is used to coil the coil bars into coils through a coiling drum, and the coil bar finished products are obtained after packaging and warehousing.

[0052] Comparative Example 7: A manufacturing method of coil bars, the difference between its manufacturing method and that of Example 4 is that: its manufacturing method is carried out according to the technological process of rolling → wire laying → online molten salt semi-quenching and isothermal → air cooling → coiling. Specifically: the air cooling process uses an open heat preservation cover, and the coil bars transported by the conveying roller table passing through the second-stage salt bath tank are cooled at a cooling rate of 1.6°C / s to 279°C to obtain coil bars.

[0053] The wire rods obtained from the above Examples 1-4 and Comparative Examples 1-7 were subjected to microstructure and property tests, and the comparison results obtained are shown in Table 1 below: Table 1. Comparison results of microstructure and properties of different wire rod compositions and manufacturing methods

[0054] From the comparison results between Example 1 and Comparative Example 1, C and Cr, as relatively low-cost and effective carbide strengthening elements and austenite-forming elements, often weaken the strengthening effect due to the uncontrollable cooling rate during the cooling phase transformation in the air-cooling line, and lead to the appearance of abnormal structures such as martensite. Although Comparative Example 1 uses lower contents of C, Si, Cr, and Mn, combined with low-temperature rolling and coiling + heat preservation cooling control, the wire rods with sorbite + ferrite structure obtained have insufficient strength and plasticity, and the mechanical properties fluctuate greatly. However, through the Nb-V chemical composition design combined with the online molten salt semi-quenching and isothermal technology in this application, the wire rods can be controlled to quickly enter the bainite phase region from the high-temperature austenite state, forming a structure mainly composed of quenched bainite. Then, by controlling the high-temperature isothermal tempering of the wire rods and toughening and stress-relieving treatment, the microstructure state of the hot-rolled wire rods can be effectively controlled, and a mixed structure mainly composed of tempered bainite and containing a small amount of ferrite is obtained. From the results of Examples 1-4, it can be seen that the tensile strength of the product can reach 980-1030 MPa, and the reduction of area is 61%-66%. It is used in application fields such as manufacturing high-strength tool steels, 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 can be reduced.

[0055] From the comparison results between Example 1 and Comparative Example 2, with a higher quenching temperature, the wire rods are supercooled to the bainite phase transformation temperature range and maintain a sufficient degree of supercooling, which is beneficial to providing a greater phase transformation driving force and promoting the quenched bainite transformation. After tempering treatment, the strength and plasticity matching of the material can be improved.

[0056] From the comparison results between Example 2 and Comparative Example 3, the higher the molten salt temperature and the shorter the treatment time of the front-stage molten salt, the less the quenched bainite phase transformation, and the matrix strength, stress-relieving difficulty, and production energy consumption decrease. However, if the molten salt temperature is too high and the treatment time is too short, the degree of supercooling is insufficient, which is not conducive to promoting the bainite phase transformation and affects the matrix strength and strength-plasticity performance.

[0057] From the comparison results between Example 2 and Comparative Example 4, the lower the molten salt temperature and the longer the treatment time of the front-stage molten salt, the supercooling degree can be increased, and the wire rods 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 fluctuate more, the internal stress increases, the stress-relieving difficulty will increase, and the treatment energy consumption also increases.

[0058] It can be seen from the comparison results between Example 3 and Comparative Example 5 that the higher the molten salt temperature and the longer the treatment time of the molten salt in the latter stage, the more thermal power can be provided for the tempering of quenched bainite, promoting the toughening of the structure and releasing stress, significantly improving the plasticity of the wire rod. While using the precipitation of carbides to improve plasticity, it can also inhibit excessive loss of strength. 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 beneficial 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, and with the extension of the treatment time, there is a risk of coarsening of carbides and loss of strength and plasticity performance.

[0059] It can be seen from the comparison results between Example 3 and Comparative Example 6 that the lower the molten salt temperature and the shorter the treatment time of the molten salt in the latter stage, the worse the isothermal tempering effect and the lower 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, and the residual stress cannot be eliminated sufficiently, resulting in an obvious loss of the plasticity of the wire rod.

[0060] It can be seen from the comparison results between Example 4 and Comparative Example 7 that adopting slow cooling on the roller table can prevent the wire rod from cooling too fast during the cooling process, avoid the increase of stress and the fluctuation of mechanical properties caused by physical contraction, and continue the treatment effect of the molten salt in the latter stage, promoting the further toughening of the wire rod structure and improving the softening effect of the wire rod.

[0061] The series of detailed descriptions listed above are only specific descriptions of the feasible embodiments of the present invention, and they are not intended to limit the protection scope of the present invention. Any equivalent embodiments or changes made without departing from the technical spirit of the present invention should be included within the protection scope of the present invention.

Claims

1. A manufacturing method of a 1100MPa grade high-strength tool steel wire rod, characterized in that, The manufacturing method includes: After the steel billet is rolled and spun into wire rods at a spinning temperature of ≥860°C, it undergoes on-line molten salt semi-quenching and isothermal treatment. The wire rods are first treated in the front-section molten salt, causing the wire rods to enter the bainite phase region from the high-temperature austenite state at a cooling rate of ≥30°C / s, forming a structure mainly composed of quenched bainite. Then, it undergoes post-section molten salt heating and isothermal tempering and toughening stress relief treatment. Finally, it is slowly cooled on the roller table to produce wire rods with a microstructure including tempered bainite and ferrite. The chemical composition and mass percentage of the wire rods are as follows: 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 is Fe and unavoidable impurities.

2. The manufacturing method of the 1100 MPa grade high-strength tool steel wire rod according to claim 1, characterized in that, Before rolling, the soaking temperature of the heating furnace is controlled at 1090 - 1140°C, and the residence time in the furnace is 80 - 135 min.

3. The manufacturing method of the 1100 MPa grade high-strength tool steel wire rod according to claim 1, characterized in that During rolling, the initial rolling temperature is controlled at 1070 - 1100°C, the final rolling temperature is 880 - 910°C, and the final rolling reduction is 23% - 29%.

4. The manufacturing method of the 1100 MPa grade high-strength tool steel wire rod according to claim 1, characterized in that, During spinning, the spinning temperature is controlled at 860 - 900°C.

5. The manufacturing method of the 1100 MPa grade high-strength tool steel wire rod according to claim 1, characterized in that, The molten salt temperature of the front-section molten salt is 250 - 295°C, and the treatment time is 15 - 25 s; the molten salt temperature of the post-section molten salt is 535 - 565°C, and the treatment time is 200 - 450 s.

6. The manufacturing method of the 1100 MPa grade high-strength tool steel wire rod according to claim 5, characterized in that, The molten salt circulation rate of the front-section molten salt is 500 - 800 t / h, and the molten salt temperature rise ≤ 8°C; the molten salt circulation rate of the post-section molten salt is 450 - 650 t / h.

7. The manufacturing method of the 1100 MPa grade high-strength tool steel wire rod according to claim 5, characterized in that, The slow cooling on the roller table controls the wire rods to cool slowly at a cooling rate of 0.2 - 0.5°C / s.

8. A 1100 MPa grade high-strength tool steel wire rod, characterized in that, The wire rods are manufactured by the manufacturing method of the 1100 MPa grade high-strength tool steel wire rods described in any one of claims 1 - 7.

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

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

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