Production method of high-aluminum cold forging steel for medium-strength and high-strength standard parts

Abstract

The invention belongs to the technical field of cold forging steel manufacturing, and particularly discloses a production method of high-aluminum cold forging steel for medium-strength and high-strength standard parts, which comprises the following steps: controlling the slag alkalinity, the contents of C, S and P in molten steel, the tapping temperature, the thickness of a steel ladle slag layer and the tapping time during converter smelting; a deoxidizing agent, lime, low-carbon ferromanganese, silicon-manganese alloy, aluminum-iron alloy and a carburant are added, argon is blown into molten steel when calcium-iron wires are fed in an argon blowing station, components of a refining slag modifier are controlled to be added during LF refining, calcium carbide and the aluminum-iron alloy are added according to the oxygen content and the aluminum content in the molten steel, a tundish for continuous casting is protected by argon, and the molten steel is continuously cast. The thickness of a powder slag layer and the thickness of a liquid slag layer are controlled, a covering agent is added into the tundish, the purity of molten steel is increased by adjusting the whole process section, and therefore follow-up tundish nozzle nodulation is reduced, and the problem that in the prior art, due to the fact that the purity of molten steel is low, a high-aluminum cold heading steel casting continuous casting tundish nozzle is prone to nodulation is solved.

Description

Technical Field

[0001] The invention relates to the technical field of cold heading steel manufacturing, and in particular to a production method of high-aluminum cold heading steel for medium- and high-strength standard parts. Background Art

[0002] Cold heading steel is a carbon-free steel or carbide steel, which is processed by cold heading and has the characteristics of high hardness. Cold heading steel has good cold forming performance. The mechanical processing industry uses cold drawing instead of hot rolled steel. The advantage of this process is that it can save a lot of man-hours while reducing metal consumption by 10-30%. The product has high dimensional accuracy, good surface finish and high productivity. It is a more advanced machining process that has emerged in recent years. The use of cold heading process to manufacture fasteners is not only efficient and of good quality, but also saves materials and has low cost. The steel also has the characteristics of stable composition, low harmful elements, high steel purity, few surface defects, good drawing performance, and low cold heading cracking rate. Cold heading steel includes high-quality carbon steel, alloy structural steel, duplex steel, bearing steel and stainless steel. The production process is: molten iron, converter, refining furnace, continuous casting (mold casting), ingot inspection, initial rolling, continuous rolling, ingot grinding, high-speed hot-rolled wire rod, finished product inspection and warehousing. The key to smelting cold heading steel is to improve the purity of molten steel and reduce the pollution of non-metallic inclusions in molten steel. During the casting process of cold heading steel, stopper rod nodules and nozzle blockage are prone to occur. This is because the aluminum in the molten steel reacts with oxygen to form Al2O3, and improper calcium treatment generates high-melting-point, viscous substances such as calcium aluminate. These substances adhere to the stopper rod head or the inner wall of the nozzle, causing nodules. Nodules can cause blockage of the stopper rod, nozzle, etc., and thus affect the normal operation of the production line, which will not only reduce production efficiency, but may also cause equipment failure. Summary of the invention

[0003] The purpose of the present invention is to provide a method for producing high-aluminum cold heading steel for medium and high-strength standard parts, so as to solve the problem in the prior art that the purity of molten steel is low, resulting in easy nodule formation at the water inlet of the high-aluminum cold heading steel continuous casting ladle.

[0004] To achieve the above object, the basic scheme provided by the present invention is: a method for producing high-aluminum cold heading steel for medium and high-strength standard parts, comprising the following steps: S1. Converter smelting: control the S content in the molten iron, control the slag basicity and the C, S and P content in the molten steel during smelting, control the tapping temperature, the thickness of the ladle slag layer and the tapping time; S2. Deoxidation and alloying: When the molten steel enters the ladle, add deoxidizer and lime. When the molten steel fills the ladle to 1 / 3, start to add low-carbon ferromanganese, silicon-manganese alloy, aluminum-iron alloy, and carburizer in sequence. When the molten steel fills the ladle to 3 / 4, the addition is completed. At this time, the aluminum content is controlled to 0.03-0.035%; S3. Argon blowing treatment: The molten steel is sent to the argon blowing station, connected to the argon blowing port on the ladle, and argon is blown into the molten steel when the calcium iron wire is fed. The argon is weakly stirred and the oxygen content and aluminum content in the molten steel are measured; S4.LF refining: After argon blowing, the molten steel is sealed and enters the LF refining furnace. The refining slag regulator is added in a controlled manner. Calcium carbide is added according to the oxygen content in S3, and aluminum-iron alloy is added according to the aluminum content in S3. The fluidity of the white slag is maintained for no less than 15 minutes. The refining end temperature is 1600-1630℃ and the refining time is ≥30 minutes. S5. Continuous casting: The refined molten steel enters the tundish. The diameter of the tundish upper water inlet is 32mm, and the diameter of the immersion water inlet is 30mm. The tundish is protected by argon gas. The argon blowing time is ≥8min. The slag layer thickness of the tundish is 50-70mm. The thickness of the powder slag layer and the liquid slag layer is controlled. The slag is discharged from the tundish during the casting process. After the molten steel in the tundish reaches the liquid level, the immersion water inlet of the tundish is opened, and the molten steel flows into the crystallizer, where it is cooled and solidified to form a cast billet.

[0005] The principle and beneficial effect of the present invention are as follows: the purity of molten steel is increased by adjusting the entire process section, the S content in the molten iron entering the converter stage is controlled respectively, the basicity, the tapping temperature, the thickness of the ladle slag layer and the C, S and P contents are controlled during smelting, the impurities in the molten steel are reduced from the initial stage, the addition amount of low-carbon ferromanganese, silicon-manganese alloy, aluminum-iron alloy and carburizer is controlled in the deoxidation and alloying stage to reduce the generation of non-metallic inclusions in the molten steel, the argon flow rate and the argon blowing time are controlled in the argon blowing treatment stage, the oxygen in the molten steel is reduced through the argon blowing station treatment, thereby reducing the generation of Al2O3, the composition of the refined slag and the final addition amount of each furnace slag material are controlled in the LF refining stage, especially in the continuous casting stage, the thickness of the powder slag layer and the liquid slag layer and the amount of the covering agent are strictly controlled to increase the purity of the molten steel during the continuous casting process, thereby reducing the occurrence of nodules at the water inlet of the tundish.

[0006] Scheme 2 is the preferred basic scheme. In step S1, the S content in the molten iron entering the furnace is ≤0.01%, the slag basicity R=2.9-3.3, the C content in the steel tapping end point is 0.12-0.16%, the S content is ≤0.02%, and the P content is 0.015%. The first furnace tapping temperature is 1630-1650°C, the subsequent tapping temperature is 1620-1650°C, the ladle slag layer thickness is 50-100mm, and the tapping time is ≥3min. The molten iron entering the furnace is controlled to reduce impurities in the molten steel from the beginning, and the element content at the steel tapping end point is controlled, thereby reducing the formation of non-metallic inclusions during the steelmaking process.

[0007] Scheme 3 is the preferred basic scheme. In step S2, the amount of deoxidizer added is 0.5-1.5 kg / t, the amount of lime added is 1.3 kg / t, the amount of low-carbon ferromanganese added is 1.7-3 kg / t, the amount of silicon-manganese alloy added is 3.3 kg / t, of which silicon accounts for 17.59% and manganese accounts for 65.78%, the amount of aluminum-iron alloy added is 2.4-2.9 kg / t, and the amount of carburizer added is 0.3-1.2 kg / t; by controlling the material and addition time of the deoxidizing alloy, the purity of the molten steel can be improved, the content of non-metallic inclusions in the molten steel can be reduced, and the cold heading steel can be ensured to have good cold forging performance and tensile strength.

[0008] Scheme 4 is the preferred basic scheme. In step S3, the feeding amount of calcium iron wire is 1.9-2.5m / t, the argon gas flow rate of the ladle bottom is 15-25m³ / h, and the argon blowing station treats the molten steel for ≥4min. After treatment at the argon blowing station, the oxygen content in the molten steel can be reduced, the generation of Al2O3 can be reduced, and the subsequent nodule formation at the water mouth of the tundish can be reduced.

[0009] Scheme 5 is the preferred basic scheme. In step S4, the refining slag conditioning agent comprises SiO2≤5wt%, 30-50wt% Al2O3, 25-35wt% CaO, and MgO≤5wt%. If the oxygen content in the molten steel is ≥15ppm, 0.6kg / t of calcium carbide is added. If the oxygen content in the molten steel is <15ppm, no calcium carbide is added. If the aluminum content in the molten steel is ≤0.04%, 1kg / t of aluminum-iron alloy is continued to be added. If the aluminum content in the molten steel is >0.04%, no aluminum-iron alloy is added. Finally, the components added to each slag are controlled to be 2.6kg / tCaO, 1kg / t aluminum slag balls, 0.6kg / tCaF2, and 0.6kg / t deoxidizer. Controlling the amount of slag added can ensure that the refined slag is fully dispersed in the molten steel and fully contacts the molten steel, thereby more thoroughly removing inclusions and improving the purity of the molten steel.

[0010] Scheme 6, which is the preferred basic scheme, in step S5, the insertion depth of the ladle long nozzle is 250±50mm, the insertion depth of the immersion nozzle is 100±20mm, the flow rate of argon gas introduced into the stopper rod is 3L / min, the flow rate of argon gas introduced into the immersion nozzle is 6L / min, the thickness of the powder slag layer is controlled at: 20-30mm, and pre-melted hollow particle protective slag is used, the main components are 34.5wt% SiO2, 4.84wt% Al2O3, 27.16wt% CaO, 2.03wt% MgO, 14.75wt% C; the particle size is 0.1-1mm; The thickness of the liquid slag layer is controlled at 6-9mm. After the liquid level of the first furnace tundish reaches 100mm, a covering agent is added. The covering agent is alkaline pre-melted hollow particles, and the main components are 34.5wt% SiO2, 4.84wt% Al2O3, 27.16wt% CaO, 2.03wt% MgO, and 14.75wt% C; the particle size is 0.1-3mm, and 1.3kg / t of covering agent is added to the tundish of each furnace, and 0.26kg / t of covering agent is added to the impact zone; the appropriate slag layer thickness can provide sufficient slag to absorb inclusions in the steel, thereby increasing the purity of the molten steel.

[0011] Option 7 is the preferred option of Option 6. When the molten steel level in the tundish reaches 700mm, the submerged water inlet of the tundish is opened, and the molten steel enters the crystallizer. The tundish slag is discharged once every 5 heats of steel, and the temperature of the tundish is measured at 10min / time. A protective film can be formed to isolate the contact between air and molten steel, thereby reducing the oxidation of the molten steel, and helping to control the formation and stability of the slag layer, reducing the heat loss of the molten steel and the generation of inclusions. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 The present invention is a flow chart of a method for producing high-aluminum cold heading steel for medium and high-strength standard parts. DETAILED DESCRIPTION

[0013] The present invention is further described in detail below through specific embodiments: Example like Figure 1 As shown: A production method of high aluminum cold heading steel for medium and high strength standard parts, comprising the following steps: S1. Converter smelting: Control the S content in the molten iron entering the furnace, control the slag basicity and the C, S and P contents in the molten steel during smelting, control the tapping temperature, the thickness of the ladle slag layer and the tapping time. The S content in the molten iron entering the furnace is ≤0.01%, the slag basicity R=2.9-3.3, the C content at the end of tapping is 0.12-0.16%, the S content is ≤0.02%, and the P content is 0.015%. The tapping temperature of the first furnace after startup is 1630-1650℃, the subsequent tapping temperature is 1620-1650℃, the ladle slag layer thickness is 50-100mm, the tapping time is ≥3min, and the slag is blocked by slag cone, slag plug or slide plate; S2. Deoxidation and alloying: When the molten steel enters the ladle, deoxidizer and lime are added. When the molten steel fills the ladle to 1 / 3, low-carbon ferromanganese, silicon-manganese alloy, aluminum-iron alloy and carburizer are added in sequence. The amount of deoxidizer added is 0.5-1.5kg / t, the amount of lime added is 1.3kg / t, the amount of low-carbon ferromanganese added is 1.7-3kg / t, the amount of silicon-manganese alloy added is 3.3kg / t, of which silicon accounts for 17.59%, manganese accounts for 65.78%, the amount of aluminum-iron alloy added is 2.4-2.9kg / t, and the amount of carburizer added is 0.3-1.2kg / t. When the molten steel fills the ladle to 3 / 4, the addition is completed. At this time, the aluminum content is controlled to be 0.03-0.035%; S3. Argon blowing treatment: The ladle delivers the molten steel to the argon blowing station, and then connects the argon blowing port on the ladle. When the calcium iron wire is fed, argon is blown into the molten steel. The argon is weakly stirred, and the oxygen content and aluminum content in the molten steel are measured. The calcium iron wire feeding amount is 1.9-2.5m / t, the argon flow rate of the ladle bottom is 15-25m³ / h, and the argon blowing station treats the molten steel for ≥4min; S4.LF refining: After argon blowing treatment, the molten steel is sealed and enters the LF refining furnace. The refining slag-adjusting agent is added in a controlled manner. The refining slag-adjusting agent has the following components: SiO2≤5wt%, 30-50wt% Al2O3, 25-35wt% CaO, MgO≤5wt%. Calcium carbide is added appropriately according to the oxygen content in S3. If the oxygen content in the molten steel is ≥15ppm, 0.6kg / t of calcium carbide is added. If the oxygen content in the molten steel is <15ppm, no calcium carbide is added. According to the aluminum content in S3, Add aluminum-iron alloy in appropriate amount. If the aluminum content of molten steel is ≤0.04%, continue to add aluminum-iron alloy 1kg / t. If the aluminum content of molten steel is >0.04%, then no aluminum-iron alloy is needed. Finally, the components added to each slag material are controlled to be 2.6kg / tCaO, 1kg / t aluminum slag balls, 0.6kg / tCaF2, and 0.6kg / t deoxidizer. The fluidity of white slag is maintained for not less than 15min, the refining end temperature is 1600-1630℃, and the refining time is ≥30min. S5. Continuous casting: The refined molten steel enters the tundish, the tundish upper water inlet aperture is 32mm, the immersion water inlet aperture is 30mm, the ladle long water inlet insertion depth is 250±50mm, the immersion water inlet insertion depth is 100±20mm, the tundish is protected by argon, the flow rate of argon gas entering the stopper rod is 3L / min, the flow rate of argon gas entering the immersion water inlet is 6L / min, the argon blowing time is ≥8min, the tundish slag layer thickness is 50-70mm, the thickness of the powder slag layer is controlled at: 20-30mm, using pre-melted hollow particle protective slag, the main components are 34.5wt% SiO2, 4.84wt% Al2O3, 27.16wt% CaO, 2.03wt% MgO, 14.75wt% C; the particle size is 0.1-1mm; the thickness of the liquid slag layer is controlled at 6-9mm. After the liquid level of the first furnace tundish reaches 100mm, a covering agent is added. The covering agent is alkaline pre-melted hollow particles, and the main components are 34.5wt% SiO2, 4.84wt% Al2O3, 27.16wt% CaO, 2.03wt% MgO, 14.75wt% C, and the particle size is 0.1-3mm. The covering agent added to the tundish is 1.3kg / t, and the covering agent added to the impact zone is 0.26kg / t. When the molten steel level in the tundish reaches 700mm, the immersed water inlet of the tundish is opened, and the molten steel flows into the crystallizer, where it is cooled and solidified to form a cast billet. The tundish slag removal operation is performed once every 5 furnaces of steel, and the temperature of the tundish is measured at 10min / time.

[0014] The implementation method of this embodiment is: molten iron with an S content of ≤0.01% is introduced into a converter for smelting, and the slag basicity R is controlled to be 2.9-3.3 during smelting, the C content at the end of steel tapping is 0.12-0.16%, the S content is ≤0.02%, and the P content is 0.015%, the first steel tapping temperature is 1630-1650°C, and the subsequent steel tapping temperature is 1620-1650°C, the ladle slag layer thickness is 50-100mm, the steel tapping time is ≥3min, and slag is blocked by slag blocking cones, slag blocking plugs or slide plates.

[0015] When the molten steel enters the ladle from the converter, deoxidizer and lime are added. The amount of deoxidizer added is 0.5-1.5kg / t, and the amount of lime added is 1.3kg / t. When the molten steel fills the ladle to 1 / 3, low-carbon ferromanganese, silicon-manganese alloy, aluminum-iron alloy, and carburizer are added in sequence. The amount of low-carbon ferromanganese added is 1.7-3kg / t, the amount of silicon-manganese alloy added is 3.3kg / t, of which silicon accounts for 17.59%, manganese accounts for 65.78%, and aluminum-iron alloy adds 1. The amount of carbon increaser added is 2.4-2.9kg / t, the amount of carburizer added is 0.3-1.2kg / t, and it is added when the molten steel fills the ladle to 3 / 4. At this time, the aluminum content is controlled to be 0.03-0.035%. During argon blowing treatment, the argon blowing port on the ladle is connected, and argon is blown into the molten steel when the calcium iron wire is fed. The amount of calcium iron wire fed is 1.9-2.5m / t, the argon flow rate of the ladle bottom is 15-25m³ / h, and the argon blowing time is ≥4min.

[0016] The molten steel after argon blowing treatment is sealed and enters the LF refining furnace. The refining slag regulating agent is controlled to be added. The components of the refining slag regulating agent are SiO2≤5wt%, 30-50wt% Al2O3, 25-35wt% CaO, MgO≤5wt%. Calcium carbide is added according to the oxygen content in the molten steel. If the oxygen content in the molten steel is ≥15ppm, 0.6kg / t of calcium carbide is added. If the oxygen content in the molten steel is <15ppm, no calcium carbide is added. Aluminum is added according to the aluminum content of the molten steel. Ferroalloy: if the aluminum content of molten steel is ≤0.04%, continue to add 1kg / t of aluminum-iron alloy; if the aluminum content of molten steel is >0.04%, no aluminum-iron alloy is needed. The final composition of each slag material is controlled to be 2.6kg / tCaO, 1kg / t aluminum slag balls, 0.6kg / tCaF2, and 0.6kg / t deoxidizer. The fluidity of white slag is maintained for not less than 15min, the final refining temperature is 1600-1630℃, and the refining time is ≥30min.

[0017] The refined molten steel enters the tundish, the aperture of the tundish upper water inlet is 32mm, the aperture of the immersion water inlet is 30mm, the insertion depth of the ladle long water inlet is 250±50mm, the insertion depth of the immersion water inlet is 100±20mm, the argon flow rate of the stopper rod is 3L / min, the argon flow rate of the immersion water inlet is 6L / min, the argon blowing time is ≥8min, the slag layer thickness of the tundish is 50-70mm, the thickness of the powder slag layer is controlled at: 20-30mm, and the pre-melted hollow particle protective slag is used, the main components are 34.5wt% SiO2, 4.84wt% Al2O3, 27.16wt% CaO, 2.03wt% MgO, 14.75wt% C; the particle size is 0.1-1mm; the liquid slag layer The thickness is controlled at 6-9mm. After the liquid level of the first tundish reaches 100mm, a covering agent is added. The covering agent is alkaline pre-melted hollow particles. The main components are 34.5wt% SiO2, 4.84wt% Al2O3, 27.16wt% CaO, 2.03wt% MgO, 14.75wt% C, and the particle size is 0.1-3mm. 1.3kg / t of covering agent is added to the tundish of each furnace, and 0.26kg / t of covering agent is added to the impact zone. When the molten steel level in the tundish reaches 700mm, the submerged water inlet of the tundish is opened, and the molten steel flows into the crystallizer, where it is cooled and solidified to form a cast billet. The tundish slag discharge operation is carried out every 5 furnaces of steel, and the temperature of the tundish is measured at 10min / time.

[0018] The above is only an embodiment of the present invention, and the common knowledge such as the known specific structure and characteristics in the scheme is not described in detail here. It should be pointed out that for those skilled in the art, several deformations and improvements can be made without departing from the structure of the present invention, which should also be regarded as the protection scope of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. A method for producing high-aluminum cold heading steel for medium and high-strength standard parts, characterized in that: The following steps are involved: S1. Converter smelting: control the S content in the molten iron entering the furnace, control the slag basicity, C, S and P content in the molten steel, tapping temperature, ladle slag layer thickness and tapping time during smelting; S2. Deoxidation and alloying: When the molten steel enters the ladle, add deoxidizer and lime. When the molten steel fills the ladle to 1 / 3, start to add low-carbon ferromanganese, silicon-manganese alloy, aluminum-iron alloy, and carburizer in sequence. When the molten steel fills the ladle to 3 / 4, the addition is completed. At this time, the aluminum content is controlled to 0.03-0.035%; S3. Argon blowing treatment: The molten steel is sent to the argon blowing station, connected to the argon blowing port on the ladle, and argon is blown into the molten steel when the calcium iron wire is fed, and the oxygen content and aluminum content in the molten steel are measured; S4.LF refining: After argon blowing, the molten steel is sealed and enters the LF refining furnace. The refining slag regulator is added in a controlled manner. Calcium carbide is added according to the oxygen content in S3, and aluminum-iron alloy is added according to the aluminum content in S3. The fluidity of the white slag is maintained for no less than 15 minutes. The refining end temperature is 1600-1630℃, and the refining time is ≥30 minutes. S5. Continuous casting: The refined molten steel enters the tundish. The diameter of the tundish upper water inlet is 32mm, and the diameter of the immersion water inlet is 30mm. The tundish is protected by argon gas. The argon blowing time is ≥8min. The slag layer thickness of the tundish is 50-70mm. The thickness of the powder slag layer and the liquid slag layer is controlled. The slag is discharged from the tundish during the casting process. After the molten steel in the tundish reaches the liquid level, the immersion water inlet of the tundish is opened, and the molten steel flows into the crystallizer, where it is cooled and solidified to form a cast billet.

2. The method for producing high-aluminum cold heading steel for medium and high-strength standard parts according to claim 1, characterized in that In step S1, the S content in the molten iron is ≤0.01%, the slag basicity R=2.9-3.3, the C content in the steel tapping end is 0.12-0.16%, the S content is ≤0.02%, and the P content is 0.015%. The first steel tapping temperature is 1630-1650℃, the subsequent steel tapping temperature is 1620-1650℃, the ladle slag layer thickness is 50-100mm, and the steel tapping time is ≥3min.

3. The method for producing high-aluminum cold heading steel for medium and high-strength standard parts according to claim 1, characterized in that: In step S2, the amount of deoxidizer added is 0.5-1.5kg / t, the amount of lime added is 1.3kg / t, the amount of low carbon ferromanganese added is 1.7-3kg / t, the amount of silicon manganese alloy added is 3.3kg / t, of which silicon accounts for 17.59% and manganese accounts for 65.78%, the amount of aluminum-iron alloy added is 2.4-2.9kg / t, and the amount of recarburizer added is 0.3-1.2kg / t.

4. The method for producing high-aluminum cold heading steel for medium and high-strength standard parts according to claim 1, characterized in that: In step S3, the feeding amount of calcium iron wire is 1.9-2.5m / t, the argon gas flow rate of the ladle bottom is 15-25m³ / h, and the time for the argon blowing station to treat the molten steel is ≥4min.

5. The method for producing high-aluminum cold heading steel for medium and high-strength standard parts according to claim 1, characterized in that In step S4, the composition of the refining slag conditioning agent is: SiO2≤5wt%, 30-50wt% Al2O3, 25-35wt% CaO, MgO≤5wt%, if the oxygen content in the molten steel is ≥15ppm, add 0.6kg / t of calcium carbide, if the oxygen content in the molten steel is <15ppm, then no calcium carbide is added, if the aluminum content of the molten steel is ≤0.04%, continue to add 1kg / t of aluminum-iron alloy, if the aluminum content of the molten steel is >0.04%, then no aluminum-iron alloy is added, and finally the composition added to each slag material is controlled to be: 2.6kg / tCaO, 1kg / t aluminum slag ball, 0.6kg / tCaF2, 0.6kg / t deoxidizer.

6. The method for producing high-aluminum cold heading steel for medium and high-strength standard parts according to claim 1, characterized in that: In step S5, the ladle long nozzle is inserted to a depth of 250±50mm, the immersion nozzle is inserted to a depth of 100±20mm, the flow rate of argon gas introduced into the stopper rod is 3L / min, the flow rate of argon gas introduced into the immersion nozzle is 6L / min, the thickness of the powder slag layer is controlled at 20-30mm, and a pre-melted hollow particle protective slag is used, the main components of which are 34.5wt% SiO2, 4.84wt% Al2O3, 27.16wt% CaO, 2.03wt% MgO, and 14.75wt% C; The degree is 0.1-1mm; the thickness of the liquid slag layer is controlled at 6-9mm. After the liquid level of the first furnace tundish reaches 100mm, a covering agent is added. The covering agent is alkaline pre-melted hollow particles, and the main components are 29.7wt% SiO2, 10.14wt% Al2O3, 24.64wt% CaO, 4wt% MgO, and 9.78wt% C; the particle size is 0.1-3mm, and 1.3kg / t of covering agent is added to the tundish of each furnace, and 0.26kg / t of covering agent is added to the impact zone of the tundish.

7. The method for producing high-aluminum cold heading steel for medium and high-strength standard parts according to claim 6, characterized in that: When the molten steel level in the tundish reaches 700mm, the immersion water inlet of the tundish is opened and the molten steel enters the crystallizer. The slag removal operation of the tundish is carried out every 5 heats of steel, and the temperature of the tundish is measured every 10 minutes.

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