Production process of steel for drilling tool

Abstract

The invention relates to the technical field of drilling tool steel, and discloses a drilling tool steel production process which comprises the following steps: S1, molten iron pretreatment; s2, converter smelting; s3, CAS refining is carried out; s4, secondary refining in an LF furnace; s5, vacuum decarburization in a VD furnace; s6, continuous casting processing; s7, casting blank inspection; s8, rolling is conducted; s9, heat preservation and slow cooling; s10, inspecting a finished product; s11, checking and coping are conducted; and S12, packaging and warehousing. According to the production process of the steel for the drilling tool, impurities in the molten steel are removed by using a dipping cover through CAS refining, the impurities and other harmful elements in the molten steel can be effectively removed in cooperation with secondary refining of an LF furnace, and in the process, ferromanganese and ferrosilicon are used for conducting Si and Mn alloying on the molten steel, so that the quality of the steel is improved. The self-strength and practicability of the steel for the drilling tool are further improved, the quality of finished steel is guaranteed, meanwhile, casting is conducted in a cast-on and continuous casting mode, argon blowing treatment is conducted in the whole casting process, and it is guaranteed that a casting blank is not interfered by air in the external environment in the forming process.

Description

Technical Field

[0001] The present invention relates to the technical field of steel for brazing tools, and specifically to a production process of steel for brazing tools. Background Art

[0002] A brazing tool can connect two or more parts together, increasing the strength and stability of the connection points, preventing the parts from loosening or breaking in high-pressure, high-temperature or harsh working environments, thereby improving the reliability and operating stability of mechanical equipment. Therefore, the service life and strength of the brazing tool are restricted and limited by the steel used to manufacture the brazing tool.

[0003] In the production process of existing brazing tools, it usually needs to go through blanking - drilling - adding a casing - adding a mandrel - heating - blooming into a 55-square billet - heating - rolling into a finished product - making a brazing tool - integral normalizing - hardening and tempering of the brazing tail - finished product inspection - finished product packaging to obtain the brazing tool. However, the steel material of the brazing tool produced by the above preparation process is very likely to crack or break during the rolling process, affecting the self-strength of the brazing tool and also the production and processing effect of the steel for brazing tools. In view of this, we have proposed a production process of steel for brazing tools. Summary of the Invention

[0004] The purpose of the present invention is to provide a production process of steel for brazing tools to solve the problems raised in the above background art.

[0005] To achieve the above purpose, the present invention provides the following technical solution: A production process of steel for brazing tools, including the following steps:

[0006] S1. Molten iron pretreatment: Heat the molten iron and then perform desulfurization, dephosphorization, decarburization, and degassing treatments, and use the precipitation method for impurity removal to obtain pure molten iron;

[0007] S2. Converter smelting: Pour the pure molten iron obtained in S1 into a converter, and add alloy materials during the steelmaking process in the converter, and finally pour out the molten steel;

[0008] S3. CAS refining: Pour the molten steel produced in S2 into a ladle, insert an oxygen-blowing pipe into the molten steel using an immersion hood to promote the removal of impurities and the deoxidation of the molten steel to obtain pure molten steel;

[0009] S4. Secondary refining in an LF furnace: Perform secondary refining on the pure molten steel obtained in S3 to remove impurities in the molten steel, and perform deoxidation, desulfurization, alloying, and heating on the molten steel to obtain purified molten steel;

[0010] S5. Vacuum decarburization in a VD furnace: Pour the purified molten steel obtained in S4 into a VD furnace, and evacuate the VD furnace to remove gases and impurities in the purified molten steel to obtain refined molten steel;

[0011] S6. Continuous casting process: The refined molten steel obtained in S5 is introduced into a continuous caster. The refined molten steel enters the mold in the continuous caster through a tundish via a nozzle, and solidifies to form a slab.

[0012] S7. Slab inspection: The slabs obtained in S6 are inspected for dimensions, weight, and appearance. Defective products are removed, and qualified slabs are retained.

[0013] S8. Rolling: The qualified slabs obtained in S7 are heated, and then rolled to obtain continuous rolling steel.

[0014] S9. Heat preservation and slow cooling: The continuous rolling steel obtained by rolling in S8 is cooled, and slowly cooled to room temperature in the form of slow cooling in a pit.

[0015] S10. Final product inspection: A batch of continuous rolling steel is sampled and tested according to inspection items, sampling quantity, sampling part, and test method, and defective products are removed. Qualified products enter the subsequent process.

[0016] S11. Inspection and grinding: The defects such as lugs, scratches, cracks, burrs, and flash on the surface of the qualified products in S10 are ground. After grinding, there are no cracks or folds visible to the naked eye on the surface, the cleared area is smooth without sharp corners, and the cleared width is more than five times the cleared depth.

[0017] S12. Packaging and warehousing: The qualified products after grinding are packed, recorded, and warehoused.

[0018] Preferably, the phosphorus content in the purified molten iron after treatment in S1 is less than 0.01%, the tin content is less than 0.008%, the temperature of the molten iron is greater than 1280 °C, and the raw materials in the molten iron pretreatment also include the defective slabs removed in S7 and S10 and the defective continuous rolling steel. Before adding scrap steel, the front and rear ends of the slabs and continuous rolling steel are cut off, so that steel materials refined multiple times are used in the production of steel for rock drills, and they are mixed with the newly added molten iron during the process of remelting. This can not only reduce waste of waste materials, but also further improve the purity of the molten iron and ensure the purity of the molten steel in the subsequent molten steel refining process.

[0019] Preferably, the alloy materials added in S2 include SiMn, SiFe, MoFe, and SiCaBa. The alloy materials are kept dry. Before converter smelting, the converter is slag-turned to ensure the cleanliness inside the converter. Meanwhile, the number of top-blown supplementary blows during the converter smelting process does not exceed 2 times. When tapping the molten steel from the converter, slag-stopping tapping is adopted. Meanwhile, a feeding component is arranged at the discharge port of the converter. The alloy materials are arranged inside the feeding component. The feeding component starts to feed materials after one-fourth of the molten steel in the converter is discharged. Ferromanganese and ferrosilicon are used to alloy the molten steel with Si and Mn. During the tapping process, molybdenum iron, ferrosilicon, and ferromanganese alloys are added first. After tapping is completed, a deoxidizer is added to obtain alloyed molten steel. In S3, CAS refining is carried out for deoxidation by blowing argon throughout the process, and the argon-blowing time is not less than 10 min. After CAS refining is completed, the pure molten steel is sampled and tested to ensure that the C content is between 0.45% and 0.50%, the Si content is between 1.10% and 1.20%, and the Mn content is between 0.65% and 0.75%. Meanwhile, the argon pressure during the argon-blowing process is set at 0.2 - 2.0 MPa.

[0020] Preferably, during the secondary refining in LF furnace in S4, the energization time of the molten steel is not less than 25 min, and the argon-blowing time in the LF furnace is not less than 40 min to quickly form a white slag for deoxidation and desulfurization. Before the secondary refining in the LF furnace, aluminum pellets are added to assist in deoxidation and refine the grains. Meanwhile, it can improve the oxidation resistance of the alloy. Before the end of the secondary refining in the LF furnace, Ga wire is added to the LF furnace for calcification treatment. The calcium wire reacts with the aluminum oxide in the molten steel to form large particles of calcium aluminate that float in the molten steel and are easily removed, reducing the number of inclusions in the steel and improving the quality of the steel. The feeding amount of the Ga wire is 200 - 300 m.

[0021] Preferably, during the secondary refining in S4, lime is added to the furnace. The addition amount of lime is set at 700 - 800 Kg, pre-melted slag 100 - 200 Kg, and aluminum powder 20 - 100 Kg. When tapping the molten steel from the LF furnace, the tapping time is 18 - 20 min earlier than the casting plan of the previous furnace to ensure that the molten steel arrives at the VD furnace 10 min earlier. Before the molten steel is tapped from the LF furnace, the molten steel in the LF furnace is sampled for component detection, and the target components in the molten steel are fine-tuned according to the alloy bulk materials to ensure that Als in the purified molten steel discharged from the LF furnace is controlled within the range of 0.035% - 0.045%, and the C content is within the range of 0.535% - 0.545%.

[0022] Preferably, during step S5, argon blowing is started throughout the process when the pure molten steel enters the VD furnace, and the argon blowing time in the VD furnace is not less than 40 minutes, so that the pure molten steel can be isolated from air in the VD furnace, avoiding reactions of the pure molten steel affected by oxygen and other gases in the air, which may affect the quality of the pure molten steel. When the VD furnace is evacuated, the pressure is reduced to below 67 Pa, and the vacuum holding time is not less than 15 minutes. After breaking the vacuum, the soft blowing time is not less than 15 minutes. At the same time, 50 - 60 Kg of carbonized rice husk is added into the VD furnace before the refined molten steel is discharged from the station to keep the refined molten steel warm after discharging. Carbonized rice husk is light in weight and low in thermal conductivity, and can adsorb inclusions on the surface layer of the refined molten steel, thus improving the purity of the refined molten steel after subsequent treatment.

[0023] Preferably, during continuous casting in step S6, the continuous caster includes a starting furnace and a continuous casting furnace. Before the refined molten steel is discharged from the VD furnace in step S5, the starting furnace and the continuous casting furnace are preheated. The temperature in the starting furnace is maintained at 1540 - 1545 °C, and the temperature in the continuous casting furnace is maintained at 1525 - 1535 °C. During the process of molten steel entering and leaving the starting furnace, hydrogen detection is carried out to ensure that the hydrogen content in the molten steel is controlled within a certain range to avoid adverse effects on the quality of the billet. In subsequent heats, hydrogen and oxygen detection is carried out for at least 1 heat, and the target value of H is not more than 2.0 ppm, and the target value of O is not more than 5.0 ppm. The superheat temperature of the tundish molten steel in the starting furnace and the continuous casting furnace does not exceed 35 °C and 30 °C respectively, thus avoiding damage to the tundish caused by overheated molten steel.

[0024] Preferably, during continuous casting in step S6, the long nozzle of the continuous caster is treated with argon blowing throughout the process to protect the molten steel, thus avoiding exposure of the molten steel in the tundish and the mold. During continuous casting, the tundish liquid level is controlled to be greater than 400 mm during starting pouring and greater than 600 mm during normal pouring. The continuous casting speed is 0.80 - 0.90 m / min, and the typical casting speed is 0.80 m / min. After continuous casting, the billets are stacked and cooled intensively with close arrangement, ensuring that the two ends of the billets are aligned, and the suspended length at both ends does not exceed 300 mm. The stacking and cooling time is not less than 24 hours. Stacking and cooling can significantly utilize the hydrogen removal peak effect during phase change to effectively remove hydrogen from the continuous casting billets. During the stacking and cooling process, the two ends of the billets will warp and deform at the initial stage of cooling, but after covering with a heat preservation cover, the billets can return to straightness at the later stage of cooling without reverse bending, and the residual stress in the billets will also become smaller. By controlling the stacking and cooling process, the billets are cooled to achieve uniform temperature or symmetry up and down, which can eliminate or reduce the adverse effects caused by temperature differences on the billets. At the same time, the mold of the continuous caster is protected by high-carbon steel protective slag, and the high-carbon steel protective slag is dried before use.

[0025] Preferably, when preheating the qualified billets before rolling S8, it includes a preheating section, a heating section, and a soaking section. The temperature of the preheating section is set at 800 - 850 °C, and the heating time of the qualified billets in the preheating section is not less than 70 min. The temperature of the heating section is set at 1170 - 1200 °C, and the heating time of the qualified billets in the heating section is not less than 70 min. The temperature of the soaking section is set at 1180 - 1210 °C, and the heating time of the qualified billets in the soaking section is not less than 70 min. This enables the qualified billets to gradually heat up to the state required for rolling operations, and the gradual heating can avoid affecting the strength of the qualified billets and prevent them from cracking or developing surface cracks.

[0026] Preferably, during the rolling process of S8, high-pressure water descaling is used throughout the process. The descaling working pressure is set to not less than 16 Mpa. By impacting the surface of the steel billet with high-pressure water flow, the scale is peeled off from the surface of the steel billet, thus achieving the purpose of removing the scale and ensuring the surface quality of the steel.

[0027] Compared with the prior art, the present invention provides a production process for steel for rock drills, with the following beneficial effects:

[0028] 1. In this production process for steel for rock drills, impurities in the molten steel are removed by using an immersion hood during CAS refining, and in combination with the secondary refining in the LF furnace, impurities and other harmful elements in the molten steel can be effectively removed. During the above process, ferromanganese and ferrosilicon are used to alloy the molten steel with Si and Mn, further enhancing the self-strength and practicality of the steel for rock drills, ensuring the quality of the finished steel. At the same time, casting is carried out by means of starting casting and continuous casting, and argon blowing treatment is carried out throughout the casting process to ensure that the billets are not interfered by air in the external environment during the forming process, ensuring the forming quality of the billets and thus the product quality of the steel for rock drills.

[0029] 2. In this production process for steel for rock drills, by adding carbonized rice husk to the molten steel before the VD furnace discharges the molten steel, the remaining inclusions in the refined molten steel can be effectively adsorbed. And because carbonized rice husk is light in weight and low in thermal conductivity, excessive heat loss does not occur during the transportation of the refined molten steel to the continuous caster, avoiding affecting the effect of the molten steel during the billet forming process.

[0030] 3. The production process of the steel for drill tools. In order to avoid centralized cooling of the formed continuous casting billets by adopting the method of intensive stacking and cooling, and to utilize the hydrogen removal peak effect during phase transformation to effectively remove hydrogen from the continuous casting billets. During the stacking and cooling process, the two ends of the continuous casting billets will warp and deform in the initial stage of cooling. However, after covering with a heat preservation cover, the continuous casting billets can return to straightness in the later stage of cooling without reverse bending, and the residual stress in the continuous casting billets will also become smaller. Moreover, by controlling the stacking and cooling process, the temperature of the continuous casting billets can be made uniform or symmetric up and down, and the adverse effects caused by temperature differences on the continuous casting billets can be eliminated or alleviated. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a schematic diagram of the production process steps of the present invention;

[0032] Figure 2 It is a schematic diagram of the rolling and inspection process of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0033] As Figure 1 - Figure 2 shown, the present invention provides a technical solution: a production process of steel for drill tools, including the following steps:

[0034] S1. Molten iron pretreatment: After heating the molten iron, desulfurization, dephosphorization, decarburization, and degassing treatments are carried out, and impurity removal is carried out by the precipitation method to obtain pure molten iron;

[0035] S2. Converter smelting: The pure molten iron obtained in S1 is introduced into a converter, and alloy materials are added during the process of steelmaking in the converter, and finally molten steel is discharged;

[0036] S3. CAS refining: The molten steel produced in S2 is introduced into a ladle, and an oxygen blowing pipe is inserted into the molten steel using an immersion hood to promote the removal of impurities and the deoxidation of the molten steel to obtain pure molten steel;

[0037] S4. Secondary refining in LF furnace: The pure molten steel obtained in S3 is subjected to secondary refining to remove impurities in the molten steel, and the molten steel is deoxidized, desulfurized, alloyed, and heated to obtain purified molten steel;

[0038] S5. Vacuum decarburization in VD furnace: The purified molten steel obtained in S4 is introduced into a VD furnace, and the VD furnace is evacuated to remove gases and impurities in the purified molten steel to obtain refined molten steel;

[0039] S6. Continuous casting processing: The refined molten steel obtained in S5 is introduced into a continuous caster, and the refined molten steel enters the mold in the continuous caster through a tundish via a nozzle and solidifies to form a continuous casting billet;

[0040] S7. Inspection of continuous casting billets: The continuous casting billets obtained in S6 are inspected for dimensions, weight, and appearance, defective products are removed, and qualified continuous casting billets are retained;

[0041] S8. Rolling: Heat the qualified cast billets obtained in S7, and then roll the cast billets to obtain continuous rolling steel.

[0042] S9. Heat preservation and slow cooling: Cool the continuous rolling steel obtained by rolling in S8, and slowly cool it to room temperature in the form of slow cooling in a pit.

[0043] S10. Final product inspection: Sample and test a batch of continuous rolling steel according to inspection items, sampling quantity, sampling part and test method, and reject defective products, while qualified products enter the subsequent process.

[0044] S11. Inspection and grinding: Grind the defects such as fins, scratches, cracks, burrs and flash on the surface of the qualified products in S10. After grinding, there are no cracks or folds visible to the naked eye on the surface, the cleared part is smooth without sharp corners, and the cleared width is more than five times the cleared depth.

[0045] S12. Packaging and warehousing: Pack, record and warehousing the qualified products after grinding.

[0046] In an embodiment of the present invention, the phosphorus content in the pure molten iron after being treated in S1 is less than 0.01%, the tin content is less than 0.008%, the temperature of the molten iron is greater than 1280 °C, and the raw materials in the molten iron pretreatment further include the defective cast billets and defective continuous rolling steel rejected in S7 and S10. Before adding scrap steel, the front and rear ends of the cast billets and continuous rolling steel are cut off, so that the production of steel for drill tools uses steel materials refined many times, and it is mixed with the newly added molten iron during the process of remelting, which can not only reduce the waste of waste materials, but also further improve the purity of the molten iron and ensure the purity of the molten steel in the subsequent molten steel refining process.

[0047] Further, the alloy materials added in S2 include SiMn, SiFe, MoFe, and SiCaBa. The alloy materials are kept dry. Before converter smelting, the converter is slag-turned to ensure the cleanliness inside the converter. At the same time, the number of top-up blows during converter smelting does not exceed 2 times. When tapping the molten steel from the converter, slag-stopping tapping is adopted. Meanwhile, a feeding component is arranged at the discharge port of the converter. The alloy materials are arranged inside the feeding component. The feeding component starts feeding after one-fourth of the molten steel in the converter is discharged. Ferromanganese and ferrosilicon are used to alloy the molten steel with Si and Mn. During tapping, ferromolybdenum, ferrosilicon, and ferromanganese alloys are added first. After tapping is completed, a deoxidizer is added to obtain alloyed molten steel. In S3, CAS refining is carried out for deoxidation by blowing argon throughout the process, and the argon-blowing time is not less than 10 min. After CAS refining is completed, a sample of the pure molten steel is taken for testing to ensure that the C content is 0.45% - 0.50%, the Si content is 1.10% - 1.20%, and the Mn content is 0.65% - 0.75%. At the same time, the argon pressure during the argon-blowing process is set at 0.2 - 2.0 MPa.

[0048] In addition, when carrying out secondary refining in the LF furnace in S4, the energization time of the molten steel is not less than 25 min, and the argon-blowing time in the LF furnace is not less than 40 min to quickly form a white slag for deoxidation and desulfurization. Aluminum pellets are added before secondary refining in the LF furnace to assist in deoxidation and refine the grains. At the same time, it can improve the oxidation resistance of the alloy. Before the end of secondary refining in the LF furnace, a Ga wire is added to the LF furnace for calcification treatment. The Ga wire reacts with the aluminum oxide in the molten steel to generate large particles of calcium aluminate that float in the molten steel and are easily removed, reducing the number of inclusions in the steel and improving the quality of the steel. The feeding amount of the Ga wire is 200 - 300 m. Specifically, during the process of secondary refining in S4, lime is added to the furnace. The addition amount of lime is set at 700 - 800 Kg, the pre-melted slag is 100 - 200 Kg, and the aluminum powder is 20 - 100 Kg. When tapping the molten steel from the LF furnace, the tapping time is 18 - 20 min earlier than the continuous casting plan of the previous furnace to ensure that the molten steel arrives at the VD furnace 10 min earlier. Before the molten steel is tapped, a sample of the molten steel in the LF furnace is taken for component testing, and the target components in the molten steel are fine-tuned according to the alloy bulk materials to ensure that the Als in the purified molten steel discharged from the LF furnace is controlled within 0.035% - 0.045% and the C content is within the range of 0.535% - 0.545%.

[0049] In an embodiment of the present invention, during S5, argon blowing is started throughout the process when pure molten steel enters the VD furnace, and the argon blowing time in the VD furnace is not less than 40 min, so that the pure molten steel can be isolated from air in the VD furnace, avoiding the reaction of the pure molten steel with oxygen and other gases in the air, which may affect the quality of the pure molten steel. When the VD furnace is evacuated, the pressure is reduced to below 67 Pa, and the vacuum holding time is not less than 15 min. After breaking the vacuum, the soft blowing time is not less than 15 min. At the same time, 50 - 60 Kg of carbonized rice husk is added into the VD furnace before the refined molten steel is discharged from the station to keep the refined molten steel warm after it is discharged. The carbonized rice husk is light in weight and low in thermal conductivity, and can adsorb inclusions on the surface layer of the refined molten steel, thus improving the purity of the refined molten steel after subsequent treatment. In addition, during continuous casting in S6, the continuous casting machine includes a starting furnace and a continuous casting furnace. Before the refined molten steel is discharged from the VD furnace in S5, the starting furnace and the continuous casting furnace are preheated. The temperature in the starting furnace is maintained at 1540 - 1545 °C, and the temperature in the continuous casting furnace is maintained at 1525 - 1535 °C. During the process of molten steel entering and leaving the starting furnace, hydrogen determination detection is carried out to ensure that the hydrogen content in the molten steel is controlled within a certain range to avoid adverse effects on the quality of the billet. In subsequent heats, hydrogen and oxygen determination detection is carried out for not less than 1 heat, and the target value of H is not more than 2.0 ppm, and the target value of O is not more than 5.0 ppm. The superheat temperatures of the tundish molten steel in the starting furnace and the continuous casting furnace do not exceed 35 °C and 30 °C respectively, thus avoiding damage to the tundish caused by overheated molten steel.

[0050] In the present invention, during continuous casting in S6, the long nozzle of the continuous casting machine is treated with argon blowing throughout the process to protect the molten steel, thus avoiding the exposure of the molten steel in the tundish and the mold. During continuous casting, the liquid level in the tundish is controlled to be greater than 400 mm during starting casting and greater than 600 mm during normal casting. The continuous casting speed is 0.80 - 0.90 m / min, and the typical casting speed is 0.80 m / min. After continuous casting, the billets are stacked and cooled intensively in a dense arrangement, ensuring that the two ends of the billets are aligned, and the suspended length at both ends does not exceed 300 mm. The stacking and cooling time is not less than 24 hours. Stacking and cooling can significantly utilize the dehydrogenation peak effect during phase transformation to effectively remove hydrogen from the continuous casting billets. During the stacking and cooling process, the two ends of the billets will warp and deform at the initial stage of cooling, but after covering with a heat preservation cover, the billets can return to straightness at the later stage of cooling without reverse bending, and the residual stress in the billets will also become smaller. By controlling the stacking and cooling process, the billets are cooled to achieve uniform temperature or symmetry up and down, which can eliminate or reduce the adverse effects caused by temperature differences on the billets. At the same time, the mold of the continuous casting machine is protected by high-carbon steel protective slag, and the high-carbon steel protective slag is dried before use.

[0051] It should be noted that when preheating qualified billets before rolling in S8, it includes a preheating section, a heating section, and a soaking section. The temperature of the preheating section is set at 800 - 850 °C, and the heating time of the qualified billets in the preheating section is not less than 70 min. The temperature of the heating section is set at 1170 - 1200 °C, and at the same time, the heating time of the qualified billets in the heating section is not less than 70 min. The temperature of the soaking section is set at 1180 - 1210 °C, and the heating time of the qualified billets in the soaking section is not less than 70 min. Thus, the qualified billets are gradually heated to the state required for rolling operations, and the gradual heating can avoid affecting the strength of the qualified billets and prevent them from cracking or developing surface cracks. Further, during the rolling process in S8, high-pressure water descaling is used throughout. The descaling working pressure is set to not less than 16 Mpa. By impacting the surface of the steel billet with high-pressure water flow, the scale is peeled off from the surface of the steel billet, thereby achieving the purpose of removing the scale and ensuring the surface quality of the steel.

[0052] The above has generally described the present invention in detail. However, based on the present invention, some modifications or improvements can be made, which are obvious to those of ordinary skill in the technical field. Therefore, modifications or improvements made without departing from the spirit and concept of the present invention are within the protection scope of the present invention.

Claims

1. A process for producing steel for drilling tools, characterized in that: The following steps are involved: S1. Hot metal pretreatment: After heating the hot metal, desulfurization, dephosphorization, decarbonization and degassing are performed, and impurities are removed by precipitation method to obtain pure hot metal; S2, converter smelting: the pure molten iron obtained in S1 is introduced into the converter, and alloy materials are added during the process of smelting steel in the converter, and finally the molten steel is output; S3, CAS refining: The molten steel produced in S2 is introduced into the ladle, and the oxygen blowing tube is inserted into the molten steel using an immersion hood to promote the removal of impurities and deoxidation of the molten steel to obtain pure molten steel; S4, LF furnace secondary refining: secondary refining of the pure molten steel obtained in S3 to remove impurities in the molten steel, and deoxidize, desulfurize, alloy and heat the molten steel to obtain purified molten steel; S5, VD furnace vacuum decarburization: the purified molten steel obtained in S4 is introduced into the VD furnace, and the VD furnace is evacuated to remove gas and impurities in the purified molten steel to obtain refined molten steel; S6, continuous casting: the refined molten steel obtained in S5 is introduced into a continuous casting machine, and the refined molten steel passes through a tundish and a water inlet into a crystallizer in the continuous casting machine, and forms a casting billet after solidification; S7, ingot inspection: inspect the size, weight and appearance of the ingot obtained in S6, remove defective ingots and retain qualified ingots; S8, rolling: heating the qualified ingot obtained in S7, and then rolling the ingot to obtain a continuously rolled steel product; S9, heat preservation and slow cooling: cooling the continuously rolled steel obtained in S8, and slowly cooling it to room temperature in the form of slow cooling in a pit; S10, Finished product inspection: Sampling and testing of a batch of continuous rolled steel products according to the inspection items, sampling quantity, sampling part and test method, and rejecting the waste products, while the qualified products enter the subsequent process; S11. Inspection and grinding: Grind the ears, scratches, cracks, burrs and flash defects on the surface of qualified products in S10. After grinding, there are no cracks or folds visible to the naked eye, the cleaned area is smooth without sharp corners, and the cleaned width is greater than five times the cleaned depth; S12. Packing and warehousing: Pack, record and store the qualified products after grinding.

2. A process for producing steel for drilling tools according to claim 1, characterized in that: The phosphorus content of the pure molten iron after treatment in S1 is less than 0.01%, and the tin content is less than 0.008%, and the temperature of the molten iron is greater than 1280°C. The raw materials in the molten iron pretreatment also include the defective ingots and waste continuous rolled steel products eliminated in S7 and S10, and the front and rear ends of the ingots and continuous rolled steel products are cut off before adding the scrap steel.

3. A process for producing steel for drilling tools according to claim 2, characterized in that: The alloy materials added in the S2 include SiMn, SiFe, MoFe, and SiCaBa, and the alloy materials are kept dry, and the slag in the converter is turned before the converter smelting to ensure the cleanliness of the inside of the converter. At the same time, the number of high-position supplementary blowing during the converter smelting process does not exceed 2 times, and the converter adopts slag blocking to discharge steel when discharging molten steel. At the same time, a feeding component is provided at the discharge port of the converter, and the alloy materials are arranged inside the feeding component, and the feeding component starts to discharge after a quarter of the molten steel in the converter is discharged. The CAS refining in the S3 adopts the method of blowing argon throughout the process for deoxidation, and the argon blowing time is not less than 10 minutes, and the pure molten steel is sampled and tested after the CAS refining is completed to ensure that the C content is 0.45% to 0.50%, the Si content is 1.10% to 1.20%, and the Mn content is 0.65% to 0.75%, and the argon pressure is set at 0.2 to 2.0 MPa during the argon blowing process.

4. A process for producing steel for drilling tools according to claim 3, characterized in that: When the LF furnace secondary refining is carried out in S4, the molten steel is powered on for no less than 25 minutes, and the argon blowing time in the LF furnace is no less than 40 minutes, and aluminum particles are added before the LF furnace secondary refining, and the Ga wire added to the LF furnace is calcified before the end of the LF furnace secondary refining. The calcium wire reacts with the aluminum oxide in the molten steel to generate large particles of calcium aluminate that float in the molten steel. The Ga wire feeding amount is 200-300m3.

5. A process for producing steel for drilling tools according to claim 4, characterized in that: During the secondary refining process in S4, lime is added into the furnace, and the amount of lime added is set at 700-800 kg, pre-melted slag is 100-200 kg, and aluminum powder is 20-100 kg. When the molten steel is discharged from the LF furnace, it is discharged 18-20 minutes earlier than the planned start time of the previous continuous casting furnace. Before the molten steel is discharged, the molten steel in the LF furnace is sampled and tested for composition, and the target composition in the molten steel is fine-tuned according to the alloy bulk material to ensure that the Als content in the purified molten steel discharged from the LF furnace is controlled within the range of 0.035%-0.045%, and the C content is within the range of 0.535%-0.545%.

6. A process for producing steel for drilling tools according to claim 5, characterized in that: In S5, argon blowing starts when the pure molten steel enters the VD furnace, and the argon blowing time in the VD furnace is not less than 40 minutes. When the VD furnace is evacuated, the argon is evacuated to below 67 Pa, and the vacuum time is maintained for not less than 15 minutes. The soft blowing time after breaking the air is not less than 15 minutes. At the same time, 50 to 60 kg of carbonized rice husks are added into the VD furnace before the refined molten steel leaves the station to keep the refined molten steel warm after leaving the station.

7. A process for producing steel for drilling tools according to claim 6, characterized in that: When continuous casting is carried out in S6, the continuous casting machine includes a pouring furnace and a continuous casting furnace, and the pouring furnace and the continuous casting furnace are preheated before the refined molten steel is discharged from the VD furnace in S5 to ensure that the temperature in the pouring furnace is between 1540 and 1545°C, and the temperature in the continuous casting furnace is between 1525 and 1535°C, and hydrogen determination detection is performed during the process of molten steel entering and leaving the pouring furnace, and hydrogen and oxygen determination detection is performed for no less than one furnace in subsequent furnaces, and the target value of H is limited to no more than 2.0ppm, and the target value of O is limited to no more than 5.0ppm, and the overheating temperature of the molten steel in the pouring furnace and the continuous casting furnace does not exceed 35°C and 30°C, respectively.

8. A process for producing steel for drilling tools according to claim 7, characterized in that: The long water nozzle of the continuous casting machine in the S6 is treated with argon blowing throughout the continuous casting process, and the liquid level of the middle bag is controlled to be greater than 400mm when pouring starts, and greater than 600mm during normal casting. The continuous casting pulling speed is 0.80-0.90m / min, and the typical pulling speed is 0.80m / min. At the same time, after the continuous casting is completed, the ingots are concentrated and densely stacked for cooling to ensure that the two ends of the ingots are aligned. The stacking cooling time is not less than 24 hours. At the same time, the crystallizer of the continuous casting machine is protected by high-carbon steel protective slag, and the high-carbon steel protective slag is dried before use.

9. A process for producing steel for drilling tools according to claim 8, characterized in that: The S8 comprises a preheating section, a heating section and a soaking section for preheating the qualified ingot before rolling. The temperature of the preheating section is set at 800-850°C, and the heating time of the qualified ingot in the preheating section is not less than 70 minutes. The temperature of the heating section is set at 1170-1200°C, and the heating time of the qualified ingot in the heating section is not less than 70 minutes. The temperature of the soaking section is set at 1180-1210°C, and the heating time of the qualified ingot in the soaking section is not less than 70 minutes.

10. A process for producing steel for drilling tools according to claim 9, characterized in that: In S8, high-pressure water is used for descaling throughout the rolling process, and the descaling working pressure is set to be no less than 16 MPa.

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