High-carbon die steel and manufacturing method thereof

Abstract

The high-carbon die steel comprises the following chemical components in percentage by weight: 0.43 to 0.55 percent of C, 0.7 to 1.30 percent of Si, 0.30 to 0.50 percent of Mn, 4.5 to 5.30 percent of Cr, 1.20 to 1.50 percent of Mo, 0.85 to 1.30 percent of V, less than or equal to 0.015 percent of P, less than or equal to 0.005 percent of S and the balance of Fe and inevitable impurities. Comprising the following steps of electric arc smelting, LF refining, VD refining, pouring, forging, spheroidizing annealing and thermal refining. According to the high-carbon die steel, the matrix hardness is larger than or equal to 55 HRC, the hardening layer depth is larger than or equal to 20 mm, the hardness is larger than or equal to 60 HRC, and the impact toughness is larger than or equal to 15 J / cm The P content is less than or equal to 0.015%, and the S content is less than or O < = 15 ppm, and N < = 60 ppm; the inclusions in the steel are controlled below A0.5, B0.5, C0.5 and D0.5, and the steel has excellent mechanical properties and meets the use requirements of the hob cutter ring of the shield tunneling machine.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical metallurgy, and in particular relates to a high-carbon die steel and a manufacturing method thereof. Background Art

[0002] High-carbon tool steel is primarily used in shield machine cutter rings. The working environment of shield machine cutter rings is relatively harsh, so high-carbon tool steel has high requirements for strength and toughness. The sulfur compounds present in high-carbon tool steel have a low melting point, which can cause the steel to fracture during hot working. When the phosphorus content in high-carbon tool steel is high, phosphorus compounds precipitate along grain boundaries, causing the material to become cold and brittle. Therefore, both phosphorus and sulfur can degrade the steel's performance. When the gaseous elements N and O are too high in high-carbon tool steel, large-sized nitrides and oxides precipitate, reducing the material's impact and tensile properties. When the hydrogen content in high-carbon tool steel is too high, it accumulates during forging, causing stress concentration and crack initiation. To address this issue, the following improved technical solution is proposed to achieve the production of high-carbon tool steel for shield machine cutter rings with low phosphorus, low sulfur, low gas content, low inclusion content, and excellent mechanical properties. Summary of the Invention

[0003] The technical problem solved by the present invention is to provide a high-carbon die steel and a manufacturing method thereof, so as to realize the production of high-carbon die steel for shield machine hob cutter rings with low P, low S, low gas content, low inclusions and good mechanical properties.

[0004] The technical solution adopted by the present invention is as follows: a high-carbon die steel, whose chemical composition, calculated by weight percentage, is C: 0.43-0.55%, Si: 0.7-1.30%, Mn: 0.30-0.50%, Cr: 4.5-5.30%, Mo: 1.20-1.50%, V: 0.85-1.30%, P≤0.015%, S≤0.005%, and the balance is Fe and unavoidable impurities.

[0005] A method for manufacturing high-carbon die steel, comprising the following steps: Step 1: Electric arc furnace smelting: Select high-quality scrap steel and main alloy materials with S content not higher than 0.02%, P content not higher than 0.02% and low impurity content.

[0006] Before oxidation in the electric arc furnace, a CaO-SiO2-Al2O3 ternary slag system is produced. When the molten steel temperature is ≥1580℃, oxygen decarburization oxidation is carried out at an oxygen pressure of 0.7Mpa for 30 to 40 minutes. The P content is ≤0.015%. After the oxidation is completed, ≥80% of the oxidized slag is removed, and reducing slag is produced before reduction after slag flow.

[0007] The reduction is carried out in the electric arc furnace for 30 to 40 minutes, and lime and fluorite are added to make reducing slag. The reducing slag is a quaternary slag system of CaO-SiO2-Al2O3-MgO, and the slag amount is 25 to 30 kg / t steel; before tapping, 60 to 70% of the reducing slag is used to re-make the reducing slag. The reducing slag is a quaternary slag system of CaO-SiO2-Al2O3-MgO, and the S content after tapping is less than 0.01%. Silicon calcium barium composite deoxidation is added to the bottom of the ladle before tapping, and the amount of silicon calcium barium added is 3 to 4 kg / t steel.

[0008] Step 2, LF refining: Before LF refining, argon is blown through the furnace door to fill the ladle with argon atmosphere to heat the electrochemical slag. Low voltage and low power are used for slagging in the first 5 minutes; high voltage and high power are used for slagging after the slagging is completed and the temperature is raised to 1680-1700℃.

[0009] Aluminum ash deoxidizer is added to the molten steel at a rate of 0.5 kg / t to reduce the O content in the molten steel to below 20 ppm; during the LF refining process, the slag basicity is around 3.5, the refining time is not less than 30 minutes and the reducing atmosphere is maintained to ensure that the S content is ≤ 0.005%; while blowing argon and stirring, aluminum wire is fed after the refining is completed to strengthen deoxidation.

[0010] Step 3, VD refining: VD refining time is greater than 25 minutes, and low vacuum holding time is greater than 15 minutes; the argon flow rate is 10 L / min before the VD refining vacuum reaches 67 Pa, and the argon flow rate is 30 L / min when the vacuum reaches below 67 Pa; calcium is fed after VD refining; argon is blown for 3 to 5 minutes after calcium feeding, and the argon flow rate is 10 to 20 L / min.

[0011] Step 4, pouring: the pouring temperature is 1560-1570℃, the pouring steel ingot is preheated for ≥5h, the insulation temperature is 200-300℃, and argon gas is used for sealing and pouring.

[0012] Step 5, forging: heating temperature 1150 ~ 1180 ℃, initial forging temperature 1150 ℃, final forging temperature 950 ℃. If the temperature is lower than 950 ℃ during forging, it needs to be reheated to 1150 ℃ before forging.

[0013] Step 6, spheroidizing annealing: heat the forging billet to 850-900℃, keep it warm for 10-15h, cool it to 650-700℃, keep it warm for 10-15h, slowly cool it to 350-400℃, take it out of the furnace and air cool it to room temperature.

[0014] Step 7, quenching and tempering treatment: The rough-machined mold steel blank is subjected to vacuum conditioning treatment, kept at 1050-1170℃ for 2h, oil quenched, and then subjected to three high-temperature tempering at 500-570℃.

[0015] In the above technical solution, preferably: in the CaO-SiO2-Al2O3 ternary slag system in step 1, CaO accounts for 50-60%, SiO2 accounts for 10-20%, and Al2O3 accounts for 15-20%; in the CaO-SiO2-Al2O3-MgO quaternary slag system, CaO accounts for 40-50%, SiO2 accounts for 10-15%, Al2O3 accounts for 15-20%, and MgO accounts for 5-10%.

[0016] In the above technical solution, preferably: in step 2, the argon pressure of the argon blowing at the furnace door before LF refining is 0.05-0.1 MPa; the Al content of the aluminum ash deoxidizer is ≥30%; the argon pressure of the argon blowing and stirring is 0.2-0.3 MPa; the diameter of the aluminum wire for aluminum wire feeding enhanced deoxidation is 10 mm, the aluminum wire feeding amount is 0.3 kg / t steel, and the wire feeding speed is 1.0-2.0 m / s.

[0017] In the above technical solution, preferably: the vacuum degree of the low vacuum in step 3 is ≤30 Pa; the feeding amount of calcium is 0.1 kg / t steel, and the feeding line speed is 1.5-2 m / s.

[0018] In the above technical solution, preferably, in step 4, the argon gas pressure used for sealing and pouring is 0.2-0.3 MPa.

[0019] The present invention also seeks to protect an application of high-carbon die steel, wherein the high-carbon die steel is used for the production of a hob cutter ring of a shield machine.

[0020] The advantages of the present invention compared with the prior art are: 1. The high carbon die steel matrix produced by the present invention has a hardness of ≥55HRC, a hardened layer depth of ≥20mm, a hardness of ≥60HRC, and an impact toughness of ≥15J / cm 2 ; Low P and S content, P content ≤ 0.015%, S content ≤ 0.005%; low gas content, through electric arc furnace reduction, LF refining reduction, VD vacuum refining, O ≤ 15ppm, N ≤ 60ppm; inclusions in the steel are controlled below A0.5, B0.5, C0.5, D0.5, with excellent mechanical properties, meeting the use requirements of shield machine cutter rings.

[0021] 2. The carbon content of the mold steel of the present invention is between 0.43% and 0.55%, which belongs to the category of high carbon steel, making the steel have a relatively high hardness; high hardness is the basis for the mold steel to resist wear and deformation, and helps to extend the service life of the mold; the addition of alloying elements such as silicon (Si), manganese (Mn), chromium (Cr), molybdenum (Mo) and vanadium (V) enhances the hardness and wear resistance of the steel, and these elements improve the mechanical properties of the steel through solid solution strengthening, dispersion strengthening and other methods; chromium helps to improve the hardenability and corrosion resistance of the steel, while molybdenum enhances the thermal stability and fatigue resistance of the steel; vanadium can refine the grain size of the steel, improve the strength and toughness of the steel, and thus enhance its fatigue resistance; the content of phosphorus (P) and sulfur (S) elements is strictly controlled, which helps to reduce non-metallic inclusions in the steel and improve the purity and mechanical properties of the steel.

[0022] 3. The CaO-SiO2-Al2O3 ternary slag system with a specific ratio of the present invention helps to form a stable and fluid slag during the smelting process, which is beneficial to dephosphorization, desulfurization and removal of inclusions; the optimized slag system ratio can accelerate the chemical reaction in the smelting process, improve smelting efficiency and shorten the smelting time; at a specific molten steel temperature, oxygen decarburization and oxidation are blown at a specific pressure and for a specific time, rapidly reducing the carbon content of the molten steel, removing gas and inclusions, meeting the low phosphorus content requirements of high-carbon die steel, and improving purity and quality; removing 80% of the oxidized slag, further improving the quality of the molten steel; making reducing slag after slagging and before reduction helps to adjust the chemical composition and temperature of the molten steel, providing a good foundation for subsequent heat treatment and processing; through reasonable slag making operations, the microstructure and properties of the steel can be optimized, and its hardness, wear resistance, thermal stability and fatigue resistance can be improved.

[0023] 4. The reducing slag of the present invention is a specific ratio of the CaO-SiO2-Al2O3-MgO quaternary slag system, which helps to form high-basicity slag, which is beneficial to the desulfurization (S) and deoxidation (O) reactions; it effectively regulates viscosity, improves fluidity and protects the furnace lining; the addition of Al2O3 can also improve the stability of the slag, reduce fluctuations in the smelting process, and improve the efficiency of desulfurization, deoxidation and inclusion removal; the addition of lime and fluorite to form the reducing slag ensures a sufficient amount of slag for sufficient metallurgical reactions while avoiding the energy consumption and cost problems caused by excessive slag; 60% of the reducing slag is discharged before tapping to re-form the reducing slag, which helps to maintain the continuity and stability of the slag; a silicon-calcium-barium composite deoxidizer is added to the bottom of the ladle before tapping. The silicon-calcium-barium composite deoxidizer has a good deoxidation effect, can further reduce the oxygen content in the steel, and has a good desulfurization effect. The overall smelting process is stable and controllable, meeting the expected technical indicators.

[0024] 5. In the present invention, argon is blown through the furnace door before LF refining to ensure refining stability and safety; the control of relatively low argon pressure helps to reduce energy consumption and cost, avoid slag surface damage and exposure of molten steel; low voltage and low power are used for slagging operation, which helps to reduce energy consumption and gradually soften and evenly distribute the slag, laying a good foundation for subsequent high-power heating and refining processes; after slagging is completed, high voltage and high power are used for heating, which helps to accelerate chemical reactions in the molten steel, improve the efficiency of desulfurization, deoxidation and inclusion removal, and at the same time, facilitate the homogenization of the molten steel and the adjustment of its composition, providing good conditions for subsequent heat treatment and processing; the synergistic effect of argon blowing through the furnace door and electrochemical slag heating can significantly improve the refining efficiency.

[0025] 6. The addition of aluminum ash deoxidizer of the present invention meets the production requirements of high-quality steel; aluminum ash deoxidizer is processed from residual waste aluminum ash produced by aluminum processing plants, which can reduce steelmaking costs, help reduce dust pollutant emissions, and comply with the development trend of green steelmaking; during the LF refining process, the slag basicity is controlled at about 3.5, which meets the desulfurization requirements of high-quality steel; the refining time is not less than 30 minutes, which helps the chemical reaction in the molten steel to proceed fully and improve the refining effect. At the same time, maintaining a reducing atmosphere can avoid the oxygen content in the molten steel from rising, which is conducive to the continuous desulfurization and deoxidation reactions; argon blowing and stirring can cause the molten steel to generate a circular motion, which helps to accelerate the floating and removal of inclusions, especially the floating effect of solid inclusions (such as alumina) is more significant; argon blowing and stirring can also accelerate The temperature and composition of the molten steel are uniform, which is conducive to the rapid and precise adjustment of complex chemical composition. After refining, feeding aluminum wire can further enhance the deoxidation effect. The aluminum in the aluminum wire reacts with the residual oxygen in the molten steel to form aluminum oxide, further reducing the oxygen content in the molten steel. Feeding aluminum wire can also refine the steel grains and improve the toughness and plasticity of the steel. At the same time, the addition of aluminum wire also helps to improve the fluidity of the molten steel and ensure the filling and uniformity of the molten steel. The comprehensive application of a series of technical measures such as aluminum ash deoxidizer, LF refining, argon blowing and stirring, and aluminum wire feeding to enhance deoxidation can significantly improve the quality of steel, significantly reduce the content of harmful elements such as oxygen and sulfur in the molten steel, and improve the purity and uniformity of the molten steel. The implementation of these technical measures can also optimize the steelmaking production process and improve production efficiency.

[0026] 7. During the VD refining process, the present invention achieves a specific refining effect by controlling the vacuum level, which helps to quickly remove a large amount of gas from the molten steel in the early stages of refining. The total VD refining time ensures sufficient refining while avoiding increased energy consumption and excessive decrease in molten steel temperature caused by excessive refining time. Calcium feeding helps to change the composition of inclusions in the steel, converting sulfides into CaS or CaS-MnS, thereby avoiding the presence of pure MnS inclusions and improving steel performance. The wire feeding speed improves the refining effect. After the wire feeding is completed, argon blowing is performed to further stir the molten steel, promote the floating and discharge of inclusions, and improve the purity of the molten steel.

[0027] 8. The sealed pouring in the pouring step of the present invention can prevent the molten steel from absorbing air and improve the pouring stability; the appropriate pouring ladle temperature can ensure that the molten steel has sufficient fluidity during the pouring process, which is beneficial to the filling and uniform distribution of the molten steel; at the same time, other problems caused by the molten steel being too high in temperature, such as oxidation and air absorption, can also be avoided; preheating of the steel ingot can effectively reduce the thermal stress during the pouring process and avoid defects such as cracks in the casting due to excessive thermal stress; at the same time, preheating can also improve the filling and uniformity of the steel ingot, which is beneficial to obtaining high-quality castings; appropriate argon pressure can ensure that argon can effectively isolate the air during the pouring process and promote the discharge of gas and inclusions in the molten steel; at the same time, it can also avoid the adverse effects of too high or too low argon pressure on the pouring process.

[0028] 9. The heating temperature and initial forging temperature setting in the forging step of the present invention are conducive to the rearrangement and growth of the grains inside the metal, thereby significantly improving the plasticity of the material; high plasticity makes the metal more susceptible to plastic deformation during the forging process, reducing the difficulty of forging, and at the same time, helps to reduce the residual stress inside the metal and avoid cracks caused by stress concentration during the forging process; the final forging temperature setting ensures that the metal can deform evenly during the forging process, reducing the risk of plasticity degradation and cracks caused by too low a temperature; reheating and reforging ensure that the metal always maintains a high plasticity during the forging process, which is conducive to obtaining high-quality forgings; although reheating adds a process step, this step is crucial to ensuring forging quality and avoiding scrap. In the long run, by ensuring forging quality, the scrap rate and rework rate are reduced, and the overall production efficiency is improved; high-temperature forging helps to shorten the forging time, improve production efficiency, and can adapt to the forging needs of various materials.

[0029] 10. The spheroidizing annealing step of the present invention is conducive to the precipitation and spheroidization of carbides, resulting in lower hardness and higher plasticity and toughness, which is beneficial to subsequent cutting and quenching treatments; the long-term heat preservation process allows carbides to have enough time to be evenly distributed in the steel, avoiding the segregation and local hardening of carbides, thereby improving the overall performance of the material; the heating and heat preservation steps in the spheroidizing annealing process are conducive to grain refinement and improving the strength and toughness of the material; grain refinement can reduce defects and stress concentration on the grain boundaries, thereby improving the fatigue resistance and corrosion resistance of the material; the slow cooling process to room temperature helps to eliminate residual Stress, reducing the risk of cracks or deformation caused by stress concentration; heating and holding, this time setting not only ensures the full precipitation and spheroidization of carbides, but also avoids increased energy consumption and grain growth caused by too long heating; slow cooling in the furnace and then air cooling to room temperature after taking out of the furnace, this process helps to avoid structural stress and thermal stress caused by rapid cooling, ensuring the stability and reliability of the material; after spheroidizing annealing, the hardness of the material is reduced and the cutting performance is significantly improved, which is beneficial to subsequent machining operations; the uniform distribution of spheroidal carbides and refined grains provide favorable conditions for quenching treatment, making the quenched material have higher hardness and wear resistance.

[0030] 11. The vacuum conditioning treatment step of the present invention effectively prevents the mold steel blank from reacting with oxygen in the air during heating and cooling, thus avoiding oxidation and decarburization; maintains the purity of the mold steel and the stability of its chemical composition, and improves its performance and service life; the vacuum environment can reduce the pollution and impurities on the surface of the workpiece, making the surface of the mold steel blank after treatment smoother and flatter, which is beneficial to subsequent processing and polishing operations, and improves the mold manufacturing accuracy and appearance quality; compared with traditional heat treatment, vacuum conditioning treatment can reduce the distortion of the mold steel blank during heating and cooling; high-temperature heat preservation treatment can refine the grains in the mold steel; rapid oil quenching after high-temperature heat preservation can make the mold steel quickly Cooling and martensitic transformation occur, which helps to improve the hardenability of mold steel and make its internal structure more uniform and dense; high-temperature tempering can eliminate the residual stress generated by mold steel during the quenching process, avoid cracks and deformation caused by stress concentration, and help improve the fatigue resistance and stability of mold steel; through three high-temperature tempering, the martensite in the mold steel can be gradually transformed into tempered troostite, thereby improving its toughness and plasticity, helping the mold steel to perform when subjected to complex stresses and reducing the risk of brittle fracture; high-temperature tempering can also make the structure of mold steel more stable, avoid performance degradation due to long-term use or high-temperature environment, and help extend the service life of the mold and maintain its stable performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1This is the forging heating curve diagram of step 5 of the present invention; Figure 2 This is the spheroidizing annealing curve diagram of step 6 of the present invention; Figure 3 Flow chart of the manufacturing method of the present invention. DETAILED DESCRIPTION

[0032] The following is a combination of the embodiments of the present invention Figure 1-3 The technical solutions in the embodiments of the present invention are clearly and completely described. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0033] A high-carbon die steel has the following chemical compositions by weight: C: 0.43-0.55%, Si: 0.7-1.30%, Mn: 0.30-0.50%, Cr: 4.5-5.30%, Mo: 1.20-1.50%, V: 0.85-1.30%, P≤0.015%, S≤0.005%, and the balance being Fe and unavoidable impurities.

[0034] It should be noted that the carbon content of this mold steel is between 0.43% and 0.55%, placing it in the high-carbon steel category, resulting in high hardness. High hardness is essential for mold steel's resistance to wear and deformation, helping to extend the life of the mold. The addition of alloying elements such as silicon (Si), manganese (Mn), chromium (Cr), molybdenum (Mo), and vanadium (V) further enhances the steel's hardness and wear resistance. These elements improve the steel's mechanical properties through solid solution strengthening and dispersion strengthening. Chromium contributes to improved hardenability and corrosion resistance, while molybdenum enhances thermal stability and fatigue resistance. Vanadium refines the steel's grain size, increasing its strength and toughness, thereby enhancing its fatigue resistance. Strictly controlled phosphorus (P) and sulfur (S) content helps reduce non-metallic inclusions in the steel, improving its purity and mechanical properties.

[0035] Example 1: A high carbon die steel, whose chemical composition, by weight percentage, is C: 0.43%, Si: 0.7%, Mn: 0.30%, Cr: 4.5%, Mo: 1.20%, V: 0.85%, P: 0.01%, S: 0.002%, and the balance is Fe and unavoidable impurities.

[0036] Example 2: A high carbon die steel, whose chemical composition, by weight percentage, is C: 0.45%, Si: 1%, Mn: 0.40%, Cr: 5.0%, Mo: 1.30%, V: 1.0%, P: 0.012%, S: 0.003%, and the balance is Fe and unavoidable impurities.

[0037] Example 3: A high carbon die steel, whose chemical composition, by weight percentage, is C: 0.5%, Si: 0.9%, Mn: 0.30%, Cr: 4.8%, Mo: 1.40%, V: 1.2%, P: 0.013%, S: 0.004%, and the balance is Fe and unavoidable impurities.

[0038] Example 4: A high carbon die steel, whose chemical composition, by weight percentage, is C: 0.55%, Si: 1.30%, Mn: 0.50%, Cr: 5.30%, Mo: 1.50%, V: 1.30%, P: 0.015%, S: 0.005%, and the balance is Fe and unavoidable impurities.

[0039] A method for manufacturing high-carbon die steel, comprising the following steps: Example 1: Step 1: Electric arc furnace smelting: Select high-quality scrap steel and main alloy materials with S content not higher than 0.02%, P content not higher than 0.02% and low impurity content.

[0040] Before oxidation in the electric arc furnace, a CaO-SiO2-Al2O3 ternary slag system is produced. In the above embodiment, preferably, the CaO-SiO2-Al2O3 ternary slag system in step 1 comprises 50% CaO, 10% SiO2, and 15% Al2O3. Oxygen decarburization oxidation is performed at a molten steel temperature of 1580°C and an oxygen pressure of 0.7 MPa for 30 minutes, with a phosphorus content of 0.015%. After oxidation, 80% of the oxidized slag is removed, and reducing slag is produced after slag flow and before reduction.

[0041] It should be noted that the specific CaO-SiO2-Al2O3 ternary slag system helps form a stable and fluid slag during the smelting process, facilitating dephosphorization, desulfurization, and inclusion removal. This optimized slag system accelerates chemical reactions during the smelting process, improving smelting efficiency and shortening smelting time. When the molten steel temperature reaches 1580°C, oxygen decarburization and oxidation are carried out at an oxygen pressure of 0.7 MPa for 30 minutes. This step rapidly reduces the carbon content in the molten steel while removing gases and inclusions. Through oxygen decarburization and oxidation, the phosphorus content in the molten steel is precisely controlled to below 0.015%, meeting the low phosphorus requirement for high-carbon mold steel. The oxygen decarburization and oxidation process effectively removes non-metallic inclusions and gases from the molten steel, improving its purity and quality. After oxidation, 80% of the slag is removed, helping to reduce impurities and inclusions in the molten steel and further improving its quality. Creating reducing slag after slagging and before reduction helps adjust the chemical composition and temperature of the molten steel, providing a good foundation for subsequent heat treatment and processing. Proper slagging operations can optimize the microstructure and properties of steel, improving its hardness, wear resistance, thermal stability, and fatigue resistance.

[0042] Reduction is carried out in an electric arc furnace for 30 minutes, and lime and fluorite are added to produce a reducing slag. The reducing slag is a CaO-SiO2-Al2O3-MgO quaternary slag system, in which CaO accounts for 40%, SiO2 accounts for 10%, Al2O3 accounts for 15%, and MgO accounts for 5%. The slag volume is 25 kg / t of steel. Before tapping, 60% of the reducing slag is discharged to produce a new reducing slag. The reducing slag is a CaO-SiO2-Al2O3-MgO quaternary slag system. The sulfur content after tapping is 0.01%. Before tapping, a silicon-calcium-barium composite deoxidation is added to the bottom of the ladle at a rate of 3 kg / t of steel. The quaternary slag system of the present invention not only ensures good basicity for desulfurization, deoxygenation, and inclusion removal, but also ensures good fluidity of the slag system.

[0043] It should be noted that the reducing slag is a quaternary slag system consisting of CaO-SiO2-Al2O3-MgO. CaO accounts for up to 40% of the slag system, contributing to the formation of a high-basicity slag. High-basicity slag is beneficial for desulfurization (S) and deoxidation (O) reactions, as high basicity drives these reactions in the forward direction. SiO2 accounts for 10%, Al2O3 for 15%, and MgO for 5%. These components in the slag regulate viscosity, improve fluidity, and protect the furnace lining. The addition of Al2O3 also enhances slag stability and reduces fluctuations during the smelting process. This quaternary slag system exhibits excellent fluidity, which facilitates sufficient contact and reaction between the slag and the molten steel, thereby improving the efficiency of desulfurization, deoxidation, and inclusion removal. After 30 minutes of reduction in an electric arc furnace, lime and fluorite are added to produce the reducing slag. Lime primarily provides CaO, while fluorite improves slag fluidity. The slag volume is 25kg / t steel, which is a relatively reasonable slag volume range. It not only ensures sufficient slag for sufficient metallurgical reaction, but also avoids the energy consumption and cost problems caused by excessive slag. Before tapping, 60% of the reducing slag is re-made into reducing slag, which helps to maintain the continuity and stability of the slag. Before tapping, a silicon-calcium-barium composite deoxidizer is added to the bottom of the ladle at an amount of 3kg / t steel. The silicon-calcium-barium composite deoxidizer has a good deoxidation effect and can further reduce the oxygen content in the steel. After tapping, the sulfur content in the steel dropped to 0.01%, which shows that the steelmaking process has a good desulfurization effect. The overall smelting process is stable and controllable, meeting the expected technical indicators.

[0044] Step 2, LF Refining: Before LF refining, argon is blown through the furnace door to fill the ladle with an argon atmosphere, heating the electrochemical slag. In the above embodiment, the preferred argon pressure in Step 2 is 0.05 MPa, with the slag surface experiencing slight creep without breaking. Low voltage and low power are used for the first 5 minutes of slag removal. After slag removal, high voltage and high power are used, and the temperature is raised to 1680°C.

[0045] It should be noted that argon is blown through the furnace door before LF refining, filling the ladle with an argon atmosphere and effectively isolating the air to prevent secondary oxidation of the molten steel. As an inert gas, argon does not chemically react with the molten steel, ensuring a stable and safe refining process. The argon pressure is controlled at a relatively low 0.05 MPa, which helps reduce energy consumption and costs. The optimal state is when the slag surface gently creeps without breaking it. This ensures effective argon stirring while avoiding slag damage and exposure to the molten steel. During the first five minutes of refining, slagging is performed using low voltage and low power, which helps reduce energy consumption while gradually softening and evenly distributing the slag, laying a good foundation for subsequent high-power heating and refining. After slagging is completed, high voltage and high power heating are used to rapidly raise the molten steel temperature to 1680°C. This high temperature accelerates chemical reactions in the molten steel, improving the efficiency of desulfurization, deoxidation, and inclusion removal. It also facilitates homogenization and composition adjustment of the molten steel, providing excellent conditions for subsequent heat treatment and processing. The synergistic effect of argon blowing through the furnace door and electrochemical slag heating can significantly improve refining efficiency. The stirring effect of argon accelerates the chemical reaction between the molten steel and the slag, while electrochemical slag heating provides the necessary energy support. During the refining process, the protection and stirring effect of argon and the chemical reaction at high temperature help remove harmful gases and inclusions from the molten steel. At the same time, the homogenization process at high temperature also helps to improve the purity and quality of the molten steel. Through reasonable voltage and power control strategies and optimized argon blowing pressure selection, energy consumption and costs can be reduced while ensuring the refining effect, which helps to achieve green, environmentally friendly and sustainable steelmaking production.

[0046] Aluminum ash deoxidizer, with an Al content of 30%, is added to the molten steel at a rate of 0.5 kg / t, reducing the oxygen content to below 20 ppm. During LF refining, the slag basicity is maintained at approximately 3.5, and the refining time is maintained for at least 30 minutes in a reducing atmosphere to ensure a sulfur content of 0.005%. Argon is blown and stirred, and aluminum wire is fed after refining to enhance deoxidation. The argon pressure during the argon blowing and stirring is 0.2 MPa, creating a circular motion in the molten steel and promoting the removal of inclusions. The aluminum wire used for enhanced deoxidation is 10 mm in diameter, fed at a rate of 0.3 kg / t of steel, and fed at a speed of 1.0 m / s.

[0047] It should be noted that aluminum ash deoxidizer is added to the molten steel at a rate of 0.5 kg / t. Since the aluminum ash deoxidizer has an Al content of 30%, it provides sufficient aluminum to react with oxygen in the molten steel to form alumina, thereby reducing the oxygen content in the steel. By precisely controlling the amount of aluminum ash deoxidizer added, the oxygen content in the steel can be reduced to below 20 ppm, meeting the production requirements for high-quality steel. Aluminum ash deoxidizer is made from aluminum ash, a residual waste product from aluminum processing plants. The rational use of this waste can reduce steelmaking costs and also help reduce dust emissions, aligning with the development of green steelmaking. During the LF refining process, the slag basicity is controlled at around 3.5, which promotes the formation of high-basicity reducing refining slag. High-basicity slag significantly improves desulfurization capacity, ensuring that the sulfur content in the molten steel is reduced to below 0.005%, meeting the desulfurization requirements for high-quality steel. Refining time should be no less than 30 minutes. This helps ensure sufficient chemical reactions in the molten steel, improving refining efficiency. Maintaining a reducing atmosphere prevents a rebound in oxygen levels, facilitating the continued progress of desulfurization and deoxidation reactions. Argon agitation creates a circulation in the molten steel, which accelerates the flotation and removal of inclusions, particularly solid inclusions such as alumina. Argon agitation also accelerates temperature and composition homogenization in the molten steel, facilitating rapid and precise adjustment of complex chemical compositions. Feeding aluminum wire after refining further enhances deoxidation. The aluminum in the wire reacts with residual oxygen in the molten steel to form alumina, further reducing the oxygen content. Feeding aluminum wire also refines the steel's grain size, improving its toughness and ductility. Furthermore, the addition of aluminum wire improves the fluidity of the molten steel, ensuring filling and uniformity. The comprehensive application of a series of technical measures, including aluminum ash deoxidizers, LF refining, argon blowing and stirring, and aluminum wire feeding for enhanced deoxidation, can significantly improve steel quality, significantly reducing the content of harmful elements such as oxygen and sulfur in the molten steel while improving its purity and uniformity. The implementation of these technical measures can also optimize the steelmaking process and improve production efficiency.

[0048] Step 3, VD refining: The VD refining time is 25 minutes, and the low vacuum is maintained for 15 minutes. In the above embodiment, preferably, the low vacuum degree in step 3 is 30 Pa. The argon flow rate is 10 L / min before the VD refining vacuum degree reaches 67 Pa, and the argon flow rate is 30 L / min when the vacuum degree drops below 67 Pa. After the VD refining is completed, calcium is fed at a rate of 0.1 kg / t of steel, and the wire feeding speed is 1.5 m / s. After the wire feeding is completed, argon is blown for 3 minutes at a flow rate of 10 L / min.

[0049] It should be noted that during the VD refining process, the vacuum level is controlled to achieve a specific refining effect. The low vacuum level is set at 30 Pa, which helps to quickly remove large amounts of gas from the molten steel in the early stages of refining. When the vacuum level drops below 67 Pa, the argon flow rate is further adjusted to ensure continuous and stable gas discharge from the molten steel. Before the vacuum level reaches 67 Pa, the argon flow rate is 10 L / min, which helps maintain agitation and temperature uniformity in the molten steel during the initial refining period. When the vacuum level drops below 67 Pa, the argon flow rate is increased to 30 L / min to enhance agitation and promote the removal of gas and inclusions. The total VD refining time is 25 minutes, of which the low vacuum holding time is 15 minutes. This time setting ensures sufficient refining while avoiding increased energy consumption and excessive drop in molten steel temperature caused by excessive refining time. The calcium feed rate is 0.1 kg / t steel, which helps change the composition of steel inclusions, converting sulfides into CaS or CaS-MnS, thereby avoiding the presence of pure MnS inclusions and improving steel properties. A wire feed speed of 1.5 m / s ensures uniform calcium wire feeding and enhances refining results. After wire feeding, an argon flushing treatment is performed for 3 minutes at a flow rate of 10 L / min. This further agitates the molten steel, promotes the floating and removal of inclusions, and improves steel purity.

[0050] Step 4, pouring: the pouring temperature is 1560℃, the pouring steel ingot is preheated for 5 hours, the holding temperature is 200℃, and argon gas is used for sealing pouring. In the above embodiment, preferably, the argon pressure of argon gas for sealing pouring in step 4 is 0.2Mpa.

[0051] It should be noted that argon, as an inert gas, effectively isolates the atmosphere during the pouring process, preventing the molten steel from reacting with oxygen in the air and thus avoiding secondary oxidation. This helps maintain the purity of the molten steel, reduces the formation of oxide inclusions, and improves the quality of the steel. Argon blanketing also reduces the content of non-metallic inclusions in the molten steel. These inclusions can affect the mechanical properties and corrosion resistance of the steel. Argon blanketing can minimize these inclusions, thereby improving the overall performance of the steel. During the pouring process, argon blanketing prevents the formation of an oxide layer on the casting surface, which can affect the appearance and performance of the casting. Argon blanketing ensures a smooth, defect-free surface and improves the overall quality of the casting. Sealed pouring prevents air absorption in the molten steel and improves pouring stability. An appropriate pouring ladle temperature ensures sufficient fluidity of the molten steel during pouring, facilitating filling and uniform distribution of the molten steel. It also avoids other problems caused by excessively high molten steel temperatures, such as oxidation and air absorption. Preheating the steel ingot effectively reduces thermal stress during the pouring process, preventing defects such as cracks in the casting caused by excessive thermal stress. Preheating also improves the filling and uniformity of the steel ingot, contributing to high-quality castings. Proper argon pressure ensures that the gas effectively isolates the air during the pouring process and facilitates the removal of gases and inclusions from the molten steel. It also prevents the adverse effects of excessive or insufficient argon pressure on the pouring process.

[0052] Step 5, forging: heating temperature 1150℃, initial forging temperature 1150℃, final forging temperature 950℃. If the temperature is lower than 950℃ during forging, it needs to be reheated to 1150℃ before forging.

[0053] It should be noted that the heating and initial forging temperatures are set at 1150°C, which is generally above the recrystallization temperature of most metals. This promotes the rearrangement and growth of the metal's internal grains, significantly improving the material's plasticity. This high plasticity makes the metal more susceptible to plastic deformation during the forging process, reducing the difficulty of forging. Furthermore, the high temperature of 1150°C also helps reduce residual stress within the metal, preventing cracks caused by stress concentration during forging. The final forging temperature is set at 950°C, which remains within the metal's high plasticity range. This ensures uniform deformation during the forging process and reduces the risk of plasticity loss and cracking caused by excessively low temperatures. If the forging temperature drops below 950°C, the metal is reheated to 1150°C before forging. This process ensures that the metal maintains high plasticity throughout the forging process, resulting in high-quality forgings. Although reheating adds a processing step, it is crucial for ensuring forging quality and avoiding scrap. By ensuring forging quality, this reduces scrap and rework rates, thereby improving overall production efficiency. In addition, high-temperature forging helps shorten forging times because it's easier for metals to achieve the desired degree of deformation at higher temperatures, thereby improving production efficiency. This forging technique is adaptable to a variety of metal materials. Although the recrystallization temperature and plastic deformation temperature range may vary between materials, heating and forging at higher initial temperatures can accommodate the forging needs of a wide range of materials. At the same time, the reheating step also provides flexibility for processing forgings of varying shapes and sizes.

[0054] Step 6: Spheroidizing annealing: heat the forging billet to 850°C, keep it warm for 10 hours, cool it to 650°C, keep it warm for 10 hours, slowly cool it to 350°C in the furnace, and air-cool it to room temperature.

[0055] It should be noted that: by heating the forging blank to 850℃ and keeping it warm for a period of time, and then cooling it to 650℃ and keeping it warm again, this process is conducive to the precipitation and spheroidization of carbides. Spheroidal carbides have lower hardness and higher plasticity and toughness than lamellar or network carbides, which is conducive to subsequent cutting and quenching. The long-term holding process allows the carbides to have enough time to be evenly distributed in the steel, avoiding the segregation and local hardening of carbides, thereby improving the overall performance of the material. The heating and holding steps in the spheroidizing annealing process help to refine the grains and improve the strength and toughness of the material. Refining the grains can reduce defects and stress concentration on the grain boundaries, thereby improving the fatigue resistance and corrosion resistance of the material. The process of slowly cooling to room temperature helps to eliminate the residual stress generated by processing processes such as forging, and reduce the risk of cracks or deformation caused by stress concentration. Heating to 850°C and holding for 10 hours, and cooling to 650°C and holding for another 10 hours, this time setting not only ensures the full precipitation and spheroidization of carbides, but also avoids increased energy consumption and grain growth caused by excessive heating. Slowly cooling to 350°C in the furnace and then air-cooling to room temperature helps avoid structural stress and thermal stress caused by rapid cooling, ensuring the stability and reliability of the material. After spheroidizing annealing, the hardness of the material is reduced and the cutting performance is significantly improved, which is beneficial for subsequent machining operations. The uniform distribution of spheroidal carbides and refined grains provide favorable conditions for quenching treatment, making the quenched material have higher hardness and wear resistance.

[0056] Step 7, quenching and tempering treatment: The rough-machined mold steel blank is subjected to vacuum conditioning treatment, kept at 1050℃ for 2h, oil quenched, and then subjected to three high-temperature tempering at 500℃.

[0057] It should be noted that quenching and tempering in a vacuum environment effectively prevents the mold steel blank from reacting with oxygen in the air during heating and cooling, avoiding oxidation and decarburization. This helps maintain the purity and chemical stability of the mold steel, thereby improving its performance and service life. The vacuum environment reduces contamination and impurities on the workpiece surface, resulting in a smoother and flatter surface. This facilitates subsequent machining and polishing, improving mold manufacturing precision and appearance quality. Compared to traditional heat treatment, vacuum tempering reduces distortion of the mold steel blank during heating and cooling. This is because the vacuum environment reduces thermal and structural stresses, making the workpiece more stable during heat treatment. Holding at 1050°C refines the grain size of the mold steel. This grain refinement helps improve the strength and toughness of the mold steel while reducing defects and stress concentrations at grain boundaries. Rapid oil quenching after high-temperature holding allows the mold steel to cool rapidly and undergo martensitic transformation. This helps improve the hardenability of the mold steel and makes its internal structure more uniform and dense. High-temperature tempering eliminates residual stresses generated during the quenching process, preventing cracks and deformation caused by stress concentration. This helps improve the fatigue resistance and stability of the mold steel. Three high-temperature tempering cycles gradually transform the martensite in the mold steel into tempered troostite, thereby increasing its toughness and plasticity. This improves the mold steel's performance under complex stresses and reduces the risk of brittle fracture. High-temperature tempering also stabilizes the mold steel's microstructure, preventing performance degradation caused by prolonged use or high-temperature environments. This helps extend the mold's service life and maintain its stable performance.

[0058] Example 2: Step 1: Electric arc furnace smelting: Select high-quality scrap steel and main alloy materials with S content not higher than 0.02%, P content not higher than 0.02% and low impurity content.

[0059] Before oxidation in the electric arc furnace, a CaO-SiO2-Al2O3 ternary slag system is produced. In the above embodiment, preferably, the CaO-SiO2-Al2O3 ternary slag system in step 1 comprises 55% CaO, 15% SiO2, and 18% Al2O3. Oxygen decarburization and oxidation are performed at a molten steel temperature of 1590°C and an oxygen pressure of 0.7 MPa for 35 minutes, resulting in a phosphorus content of 0.013%. After oxidation, 85% of the oxidized slag is removed, and reducing slag is produced after slag flow and before reduction.

[0060] Reduction is carried out in an electric arc furnace for 35 minutes, and lime and fluorite are added to produce a reducing slag. The reducing slag is a quaternary slag system of CaO-SiO2-Al2O3-MgO, in which CaO accounts for 45%, SiO2 accounts for 12%, Al2O3 accounts for 17%, and MgO accounts for 8%. The slag volume is 28kg / t of steel. Before tapping, 65% of the reducing slag is discharged to produce a new reducing slag system of CaO-SiO2-Al2O3-MgO. The sulfur content after tapping is 0.005%. Before tapping, a silicon-calcium-barium composite deoxidation is added to the bottom of the ladle at a rate of 3.5kg / t of steel. The quaternary slag system of the present invention not only ensures good basicity for desulfurization, deoxygenation, and inclusion removal, but also ensures good fluidity of the slag system.

[0061] Step 2, LF Refining: Before LF refining, argon is blown through the furnace door to fill the ladle with an argon atmosphere, heating the electrochemical slag. In the above embodiment, the preferred argon pressure in Step 2 is 0.055 MPa, with the slag surface experiencing slight creep without breaking. Low voltage and low power are used for the first 5 minutes of slagging; at the end of slagging, high voltage and high power are used, raising the temperature to 1690°C.

[0062] Aluminum ash deoxidizer, with an Al content of 35%, is added to the molten steel at a rate of 0.5 kg / t, reducing the O content to below 20 ppm. During LF refining, the slag basicity is maintained at approximately 3.5, and the refining time is maintained for at least 30 minutes in a reducing atmosphere to ensure a S content of 0.003%. Argon is blown and stirred, and aluminum wire is fed after refining to enhance deoxidation. The argon pressure during the argon blowing and stirring is 0.25 MPa, creating a circular motion in the molten steel and promoting the removal of inclusions. The aluminum wire used for enhanced deoxidation is 10 mm in diameter, fed at a rate of 0.3 kg / t of steel, and fed at a speed of 1.5 m / s.

[0063] Step 3, VD refining: the VD refining time is 28 minutes, and the low vacuum holding time is 20 minutes; in the above embodiment, preferably: the vacuum degree of the low vacuum in step 3 is 25 Pa.

[0064] Before the VD refining vacuum reaches 67Pa, the argon flow rate is 10L / min, and when the vacuum reaches below 67Pa, the argon flow rate is 30L / min; after the VD refining is completed, calcium is fed, the calcium feeding amount is 0.1kg / t steel, and the feeding line speed is 1.8m / s; after the feeding line is completed, argon is blown for 4 minutes, and the argon flow rate is 15L / min.

[0065] Step 4, pouring: the pouring temperature is 1565℃, the pouring steel ingot is preheated for 6 hours, the holding temperature is 250℃, and argon gas is used for sealing pouring. In the above embodiment, preferably: the argon pressure of argon gas for sealing pouring in step 4 is 0.25Mpa.

[0066] Step 5, forging: heating temperature 1160℃, initial forging temperature 1150℃, final forging temperature 950℃. If the temperature is lower than 950℃ during forging, it needs to be reheated to 1150℃ before forging.

[0067] Step 6, spheroidizing annealing: heat the forging billet to 870℃, keep it warm for 12 hours, cool it to 680℃, keep it warm for 12 hours, slowly cool it to 380℃ in the furnace, and air-cool it to room temperature.

[0068] Step 7, quenching and tempering treatment: The rough-machined mold steel blank is subjected to vacuum conditioning treatment, kept at 1120℃ for 2h, oil quenched, and then subjected to three high-temperature tempering at 550℃.

[0069] Example 3: Step 1: Electric arc furnace smelting: Select high-quality scrap steel and main alloy materials with S content not higher than 0.02%, P content not higher than 0.02% and low impurity content.

[0070] Before oxidation in the electric arc furnace, a CaO-SiO2-Al2O3 ternary slag system is produced. In the above embodiment, preferably, the CaO-SiO2-Al2O3 ternary slag system in step 1 comprises 60% CaO, 20% SiO2, and 20% Al2O3. Oxygen decarburization and oxidation are performed at a molten steel temperature of 1600°C and an oxygen pressure of 0.7 MPa for 40 minutes, with a phosphorus content of 0.012%. After oxidation, 90% of the oxidized slag is removed, and reducing slag is produced after slag flow and before reduction.

[0071] Reduction is carried out in an electric arc furnace for 40 minutes, followed by the addition of lime and fluorite to create a quaternary slag system of CaO-SiO2-Al2O3-MgO, comprising 50% CaO, 15% SiO2, 20% Al2O3, and 10% MgO. The slag yield is 30 kg / t of steel. Before tapping, 70% of the reduced slag is used to create a new quaternary slag system of CaO-SiO2-Al2O3-MgO. The post-tapping sulfur content is 0.003%. A silicon-calcium-barium composite deoxidation slag is added to the ladle bottom before tapping, at a rate of 4 kg / t of steel.

[0072] The quaternary slag system of the present invention can ensure good basicity to facilitate the removal of sulfur, oxygen and inclusions, and can also ensure that the slag system has good fluidity.

[0073] Step 2, LF Refining: Before LF refining, argon is blown through the furnace door to fill the ladle with an argon atmosphere, heating the electrochemical slag. In the above embodiment, the preferred argon pressure in Step 2 is 0.1 MPa, with the slag surface experiencing slight creep without breaking. Low voltage and low power are used for the first 5 minutes of slagging; at the end of slagging, high voltage and high power are used, raising the temperature to 1700°C.

[0074] Aluminum ash deoxidizer, with an Al content of 50%, is added to the molten steel at a rate of 0.5 kg / t, reducing the oxygen content to below 20 ppm. During LF refining, the slag basicity is maintained at approximately 3.5, and the refining time is maintained for at least 30 minutes in a reducing atmosphere to ensure a sulfur content of 0.002%. Argon is blown and stirred, and aluminum wire is fed after refining to enhance deoxidation. The argon pressure during the argon blowing and stirring is 0.3 MPa, creating a circular motion in the molten steel and promoting the removal of inclusions. The aluminum wire used for enhanced deoxidation is 10 mm in diameter, fed at a rate of 0.3 kg / t of steel, and fed at a speed of 2.0 m / s.

[0075] Step 3, VD refining: The VD refining time is 35 minutes, and the low vacuum holding time is 25 minutes. In the above embodiment, preferably, the low vacuum degree in step 3 is 20 Pa. The argon flow rate is 10 L / min before the VD refining vacuum degree reaches 67 Pa, and the argon flow rate is 30 L / min when the vacuum degree drops below 67 Pa. After the VD refining is completed, calcium is fed at a rate of 0.1 kg / t of steel, and the wire feeding speed is 2 m / s. After the wire feeding is completed, argon is blown for 5 minutes at a flow rate of 20 L / min.

[0076] Step 4, pouring: the pouring temperature is 1570℃, the pouring steel ingot is preheated for 7 hours, the holding temperature is 300℃, and argon gas is used for sealing pouring. In the above embodiment, preferably, the argon pressure of argon gas for sealing pouring in step 4 is 0.3Mpa.

[0077] Step 5, forging: heating temperature 1180℃, initial forging temperature 1150℃, final forging temperature 950℃. If the temperature is lower than 950℃ during forging, it needs to be reheated to 1150℃ before forging.

[0078] Step 6: Spheroidizing annealing: heat the forging billet to 900°C, keep it warm for 15 hours, cool it to 700°C, keep it warm for 15 hours, slowly cool it to 400°C in the furnace, and air-cool it to room temperature.

[0079] Step 7, quenching and tempering treatment: The rough-machined mold steel blank is subjected to vacuum conditioning treatment, oil quenching at 1170℃ for 2h, and then high-temperature tempering at 570℃ for three times.

[0080] The present invention also seeks to protect an application of high-carbon die steel, wherein the high-carbon die steel is used for the production of a hob cutter ring of a shield machine.

[0081] From the above description, it can be found that the high carbon die steel matrix made by the present invention has a hardness of ≥55HRC, a hardened layer depth of ≥20mm, a hardness of ≥60HRC, and an impact toughness of ≥15J / cm 2; Low P and S content, P content ≤ 0.015%, S content ≤ 0.005%; low gas content, through electric arc furnace reduction, LF refining reduction, VD vacuum refining, O ≤ 15ppm, N ≤ 60ppm; inclusions in the steel are controlled below A0.5, B0.5, C0.5, D0.5, with excellent mechanical properties, meeting the use requirements of shield machine cutter rings.

[0082] It should be understood that those skilled in the art should regard the specification as a whole, and the technical solutions in this embodiment may also be properly arranged and combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A high carbon die steel, characterized in that: Calculated by weight percentage, its chemical composition is C: 0.43-0.55%, Si: 0.7-1.30%, Mn: 0.30-0.50%, Cr: 4.5-5.30%, Mo: 1.20-1.50%, V: 0.85-1.30%, P≤0.015%, S≤0.005%, and the balance is Fe and unavoidable impurities.

2. A method for manufacturing high carbon die steel, characterized in that: Manufacturing the high carbon die steel as claimed in claim 1 comprises the following steps: Step 1, electric arc furnace smelting: select high-quality scrap steel and main alloy materials with S content not higher than 0.02%, P content not higher than 0.02% and low impurity content; Before oxidation in the electric arc furnace, a CaO-SiO2-Al2O3 ternary slag system is produced. When the molten steel temperature is ≥1580℃, oxygen decarburization oxidation is carried out at an oxygen pressure of 0.7Mpa for 30-40 minutes. The P content is ≤0.015%. After the oxidation is completed, ≥80% of the oxidized slag is removed. After slag flow and before reduction, a reducing slag is produced. Reduction is carried out in an electric arc furnace for 30 to 40 minutes, and lime and fluorite are added to produce a reducing slag. The reducing slag is a quaternary slag system of CaO-SiO2-Al2O3-MgO, and the slag amount is 25 to 30 kg / t steel. Before tapping, 60 to 70% of the reducing slag is used to re-produce a reducing slag of a quaternary slag system of CaO-SiO2-Al2O3-MgO. The sulfur content after tapping is less than 0.01%. Silicon calcium barium composite deoxidation is added to the bottom of the ladle before tapping, and the amount of silicon calcium barium added is 3 to 4 kg / t steel. Step 2, LF refining: Before LF refining, argon is blown through the furnace door to fill the ladle with argon atmosphere to heat the electrochemical slag. Low voltage and low power are used for slagging in the first 5 minutes. After slagging is completed, high voltage and high power are used for slagging and the temperature is raised to 1680-1700℃. Aluminum ash deoxidizer is added to the molten steel at a rate of 0.5 kg / t to reduce the oxygen content in the molten steel to below 20 ppm. During the LF refining process, the slag basicity is around 3.5, the refining time is not less than 30 minutes, and a reducing atmosphere is maintained to ensure that the sulfur content is ≤ 0.005%. After the refining is completed, aluminum wire is fed to enhance deoxidation while blowing argon and stirring. Step 3, VD refining: VD refining time> 25min, low vacuum holding time> 15min; VD refining vacuum degree before reaching 67Pa, argon flow rate is 10L / min, when the vacuum degree reaches below 67Pa, argon flow rate is 30L / min; after VD refining is completed, calcium is fed, and argon is blown for 3-5min after calcium feeding, and the argon flow rate is 10-20L / min; Step 4, pouring: the pouring temperature is 1560-1570℃, the pouring steel ingot is preheated for ≥5h, the holding temperature is 200-300℃, and argon gas is used for sealing and pouring; Step 5, forging: heating temperature 1150 ~ 1180 ℃, initial forging temperature 1150 ℃, final forging temperature 950 ℃, if the temperature is lower than 950 ℃ during forging, it needs to be reheated to 1150 ℃ before forging; Step 6, spheroidizing annealing: heat the forging billet to 850-900℃, keep it warm for 10-15h, cool it to 650-700℃, keep it warm for 10-15h, slowly cool it to 350-400℃, take it out of the furnace and air cool it to room temperature; Step 7, quenching and tempering treatment: The rough-machined mold steel blank is subjected to vacuum conditioning treatment, kept at 1050-1170℃ for 2h, oil quenched, and then subjected to three high-temperature tempering at 500-570℃.

3. The manufacturing method according to claim 2, characterized in that: In the CaO-SiO2-Al2O3 ternary slag system described in step 1, CaO accounts for 50-60%, SiO2 accounts for 10-20%, and Al2O3 accounts for 15-20%; in the CaO-SiO2-Al2O3-MgO quaternary slag system, CaO accounts for 40-50%, SiO2 accounts for 10-15%, Al2O3 accounts for 15-20%, and MgO accounts for 5-10%.

4. The manufacturing method according to claim 2, characterized in that: In step 2, the argon pressure of the argon blowing at the furnace door before LF refining is 0.05-0.1 MPa; the Al content of the aluminum ash deoxidizer is ≥30%; the argon pressure of the argon blowing and stirring is 0.2-0.3 MPa; the diameter of the aluminum wire for aluminum wire feeding enhanced deoxidation is 10 mm, the aluminum wire feeding amount is 0.3 kg / t steel, and the wire feeding speed is 1.0-2.0 m / s.

5. The manufacturing method according to claim 2, characterized in that: The vacuum degree of the low vacuum in step 3 is ≤30 Pa; the feeding amount of calcium is 0.1 kg / t steel, and the feeding line speed is 1.5-2 m / s.

6. The manufacturing method according to claim 2, characterized in that: In step 4, argon gas is used for sealing and pouring, and the argon pressure is 0.2-0.3 MPa.

7. An application of the high carbon die steel according to claim 1 or the high carbon die steel manufactured by the manufacturing method according to any one of claims 2 to 6, characterized in that: The high carbon die steel is used for producing the cutter ring of a shield machine.

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