Smelting method of high-aluminum steel

Abstract

The invention relates to the technical field of steel and iron smelting, in particular to a high-aluminum steel smelting method which comprises the following steps: 1) blowing molten iron through a top-bottom combined blown converter to control the quality parameters of the produced molten steel, and tapping; 2) hoisting the molten steel produced in the step 1) to a refining process, and refining in an LF refining furnace and an RH refining furnace in sequence; (3) the molten steel refined in the step (2) is hoisted to a continuous casting procedure to be subjected to whole-course protective casting; according to the smelting method, the content of aluminum elements in molten steel and the content of gas hydrogen can be accurately controlled, the cleanliness of the molten steel is improved, the castability of the molten steel is guaranteed through continuous casting protection casting, the high-quality high-aluminum nitriding steel is successfully smelted, and the defect that due to the fact that the content of the aluminum elements in the high-aluminum steel is extremely high, the quality of the high-aluminum nitriding steel is poor is overcome. The secondary oxidation of the molten steel is easy to cause deterioration of the cleanliness of the steel and cause blockage of a water gap, so that the pouring is interrupted.

Description

Technical Field

[0001] The invention relates to the technical field of steel smelting, and in particular to a smelting method of high-aluminum steel. Background Art

[0002] High aluminum steel 38CrMoAl is mostly used to produce parts with low impact load and high wear resistance, such as lathe spindles, precision screws, high-pressure valves, valve stems, rollers, compressor piston rods, rotating sleeves, fixed sleeves, etc.) and nitrided parts with high strength and high dimensional accuracy after treatment (molds, cylinder liners, boring rods, worms, precision gears, speed regulators on steam turbines, etc.). However, the aluminum content in high aluminum steel is extremely high, and the secondary oxidation of molten steel can easily lead to the deterioration of steel cleanliness, causing nozzle blockage and interruption of casting. In addition, the aluminum element in steel easily reacts with SiO2 in the slag, resulting in changes in the performance of molten steel silicon increase and continuous casting protection slag, affecting the smoothness of the continuous casting process and the surface quality of the ingot.

[0003] The mass fraction of aluminum in high-aluminum steel 38CrMoAl is as high as 0.7% to 1.1%, far beyond the range of conventional deoxidation and grain refinement. The viscosity of the molten steel is large and the fluidity is poor. In addition, the chemical properties of aluminum are active and it is easy to react with oxygen and nitrogen in the air. There are several difficulties: 1. It is easy to undergo oxidation reaction, generating Al2O3 inclusions and aluminum-nitrogen inclusions, which leads to blockage of the nozzle during continuous casting; 2. Due to the high content of aluminum, it is easy to denature the mold protection slag, affecting the surface and internal quality of the continuous casting billet; 3. Aluminum has a low melting point, a small specific gravity, is easy to oxidize, and is not easy to add, resulting in unstable yield and difficulty in controlling the composition. If the method of adjusting the aluminum content in molten steel is improper, not only will the aluminum loss be large and the production cost will increase, but it will also cause the reaction products to deposit at the nozzle, causing floccules in the continuous casting process and even interruption of the casting. Under such conditions, how to ensure the cleanliness of molten steel has become a prominent problem faced in the production process of high-aluminum steel 38CrMoAl. Summary of the invention

[0004] The purpose of the present invention is to overcome the problem that due to the extremely high aluminum content in high-aluminum steel, the secondary oxidation of molten steel easily leads to the deterioration of steel cleanliness, causing nozzle blockage and thus interrupting pouring, and to provide a high-aluminum steel smelting method. The smelting method can accurately control the aluminum content and gas hydrogen content in the molten steel, improve the cleanliness of the molten steel, and adopt continuous casting protection casting to ensure the castability of the molten steel, and successfully smelt high-aluminum nitriding steel. At the same time, the smelting method is safe and reliable to implement, easy to operate, and suitable for industrial mass production.

[0005] In order to achieve the above object, the present invention provides a smelting method of high aluminum steel, the smelting method comprising:

[0006] 1) The molten iron is blown through a top and bottom double-blown converter to control the quality parameters of the molten steel produced and to produce steel;

[0007] 2) the molten steel produced in step 1) is hoisted to the refining process, and refined in the LF refining furnace and the RH refining furnace in sequence;

[0008] 3) hoisting the molten steel refined in step 2) to the continuous casting process for full-process protected casting;

[0009] Wherein, the model of the high aluminum steel is 38CrMoAl.

[0010] Preferably, in step 1), the blowing is performed by a high-draw supplementary blowing method.

[0011] Preferably, in step 1), the quality parameters of the molten steel produced are controlled to include: controlling the carbon content in the molten steel to ≥0.08wt%, the phosphorus content to <0.015wt%, and the tapping temperature to 1650-1680°C.

[0012] Preferably, in step 1), the conditions for tapping the steel include: when the tapping amount is 1 / 4, firstly adding the alloy into the ladle, and then adding the slag.

[0013] Preferably, the conditions for adding the alloys include: the amount of silicon manganese alloy is 4 kg / t, the amount of ferromolybdenum alloy is 3.2 kg / t and the amount of high carbon ferrochrome alloy is 23 kg / t.

[0014] More preferably, the conditions for adding slag include: the amount of lime is 5 kg / t and the amount of fluorite is 1 kg / t.

[0015] Further preferably, after the steel tapping is completed, aluminum wire is fed on an argon blowing platform behind the furnace.

[0016] More preferably, the amount of the aluminum wire is 200-300 m / furnace.

[0017] More preferably, slag is strictly prohibited during the steel tapping process, and steel should be retained if necessary.

[0018] Preferably, the smelting method further comprises: in step 1), argon is blown from the bottom of the ladle throughout the entire process, and after steel tapping is completed, the flow rate of the bottom-blown argon is adjusted to a bright surface of 300-500 mm.

[0019] Preferably, in step 2), the control requirements of the components in the refined molten steel include: the content of carbon element is 0.35-0.42wt%, the content of silicon element is 0.20-0.45wt%, the content of phosphorus element is ≤0.035wt%, the content of manganese element is 0.30-0.60wt%, the content of chromium element is 1.35-1.65wt%, the content of sulfur element is ≤0.035wt%, and the content of molybdenum element is 0.17-0.25wt%.

[0020] Preferably, in step 2), the refining conditions in the LF refining furnace include: adding reducing slag after the molten steel enters the station; adding reducing agent to the molten steel for diffusion deoxidation during the power-on and temperature-raising process; and performing composition adjustment operation after the slag is refined.

[0021] Preferably, the reducing slag material comprises: lime in an amount of 2.5-3.5 kg / t and calcium carbide in an amount of 0.35-0.40 kg / t.

[0022] More preferably, the reducing agent is aluminum particles and / or carbon powder.

[0023] Further preferably, the composition adjustment operation includes: feeding aluminum wire to control the aluminum content in the molten steel to be 0.870-0.930wt%.

[0024] Preferably, in step 2), the refining conditions in the RH refining furnace include: RH vacuum refining degassing, and determining hydrogen and oxygen.

[0025] Preferably, the hydrogen and oxygen are determined using a Heraeus hydrogen determiner.

[0026] More preferably, the hydrogen content in the molten steel after refining in the RH refining furnace is ≤2ppm.

[0027] Preferably, in step 2), the refining conditions in the RH refining furnace further include: feeding aluminum wire after the RH vacuum refining and degassing are completed.

[0028] Preferably, the content of aluminum in the molten steel after refining in the RH refining furnace is 0.88-0.92wt%.

[0029] More preferably, the soft blowing time of the refining satisfies that the first pouring furnace is ≥15min and the continuous pouring furnace is ≥10min.

[0030] Preferably, in step 3), the protective casting adopts a method of argon blowing protection of a large ladle casing and integral nozzle casting.

[0031] Preferably, the protective casting conditions also include: the superheat of the tundish of the first casting furnace is 35-45°C, the superheat of the tundish of the continuous casting furnace is 20-30°C, and the stirring method of crystallizer electromagnetic stirring plus end electromagnetic stirring is adopted during the casting process.

[0032] Through the above technical scheme, the smelting method of high aluminum steel of the present invention optimizes the operating process of the converter and the refining furnace and the white slag operation during the smelting process, and at the same time controls the adjustment method and addition timing of the aluminum element, thereby achieving precise control of the aluminum element in the molten steel, thereby controlling the number and shape of inclusions in the molten steel, and finally obtaining high aluminum steel by continuous casting.

[0033] Furthermore, the smelting method of the present invention uses a converter, off-furnace refining, and continuous casting steelmaking process to control the main chemical elements C, Si, Mn, Cr, Mo, and Al in high-aluminum steel, and uses RH off-furnace refining vacuum degassing to control the gas hydrogen content in the high-aluminum steel to ≤2ppm, and adjusts the aluminum content in the steel to 0.870-0.930wt% after the white slag is adjusted. At the same time, in the continuous casting process, a large ladle sleeve argon blowing protection and integral water nozzle casting are used to perform protective casting, and high-quality high-aluminum nitriding steel is successfully smelted. At the same time, the smelting method is safe and reliable to implement, easy to operate, and suitable for industrial mass production.

[0034] Other features and advantages of the present invention will be described in detail in the following detailed description. DETAILED DESCRIPTION

[0035] The specific embodiments of the present invention are described in detail below. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0036] The present invention provides a smelting method for high-aluminum steel, the smelting method comprising:

[0037] 1) The molten iron is blown through a top and bottom double-blown converter to control the quality parameters of the molten steel produced and to produce steel;

[0038] 2) the molten steel produced in step 1) is hoisted to the refining process, and refined in the LF refining furnace and the RH refining furnace in sequence;

[0039] 3) hoisting the molten steel refined in step 2) to the continuous casting process for full-process protected casting;

[0040] Wherein, the model of the high aluminum steel is 38CrMoAl.

[0041] The high-aluminum steel smelting method of the present invention achieves precise control of the aluminum element in molten steel by optimizing the operating processes of the converter and the refining furnace and the white slag operation during the smelting process, while controlling the adjustment method and addition timing of the aluminum element, thereby controlling the number and shape of inclusions in the molten steel, and finally obtaining high-aluminum steel by continuous casting.

[0042] Furthermore, the smelting method of the present invention uses a converter, off-furnace refining, and continuous casting steelmaking process to control the main chemical elements C, Si, Mn, Cr, Mo, and Al in high-aluminum steel, and uses RH off-furnace refining vacuum degassing to control the gas hydrogen content in the high-aluminum steel to ≤2ppm, and adjusts the aluminum content in the steel to 0.870-0.930wt% after the white slag is adjusted. At the same time, in the continuous casting process, a large ladle sleeve argon blowing protection and integral water nozzle casting are used to perform protective casting, and high-quality high-aluminum nitriding steel is successfully smelted. At the same time, the smelting method is safe and reliable to implement, easy to operate, and suitable for industrial mass production.

[0043] In a preferred embodiment of the present invention, in order to smelt high-quality high-aluminum nitriding steel, in step 1), the blowing is performed by a high-drawing supplementary blowing method.

[0044] In a preferred embodiment of the present invention, in order to smelt high-quality high-aluminum nitriding steel, in step 1), the quality parameters for controlling the output molten steel include: controlling the carbon content in the output molten steel to ≥0.08wt%, the phosphorus content to <0.015wt%, and the tapping temperature to 1650-1680°C.

[0045] In a preferred embodiment of the present invention, in order to accurately control the content of aluminum in the molten steel, in step 1), the conditions for tapping include: when the tapping amount is 1 / 4, first adding alloy to the ladle and then adding slag.

[0046] In a preferred embodiment of the present invention, in order to smelt high-quality high-aluminum nitriding steel, the conditions for adding alloys include: the amount of silicon-manganese alloy is 4 kg / t, the amount of molybdenum-iron alloy is 3.2 Kg / t and the amount of high-carbon ferrochromium alloy is 23 Kg / t.

[0047] In a preferred embodiment of the present invention, in order to smelt high-quality high-aluminum nitriding steel, the conditions for adding slag include: the amount of lime is 5 kg / t and the amount of fluorite is 1 kg / t.

[0048] In a preferred embodiment of the present invention, after the steel is tapped, aluminum wire is fed to the argon blowing platform behind the furnace. After the steel is tapped, a portion of aluminum alloying will be performed on the argon blowing platform behind the furnace. The purpose is to deoxidize and increase Al in advance, ensure sufficient time for inclusions to float up and be removed, and improve the cleanliness of the molten steel.

[0049] In a preferred embodiment of the present invention, in order to accurately control the content of aluminum in the molten steel, the amount of the aluminum wire is 200-300 m / furnace.

[0050] In a preferred embodiment of the present invention, in order to smelt high-quality high-aluminum nitriding steel, slag is strictly prohibited during the steel tapping process, and steel should be retained when necessary.

[0051] In a preferred embodiment of the present invention, in order to smelt high-quality high-aluminum nitriding steel, the smelting method also includes: in step 1), argon is blown from the bottom of the ladle throughout the entire process, and after the steel is tapped, the bottom blowing argon flow rate is adjusted to 300-500mm on the bright surface.

[0052] In a preferred embodiment of the present invention, in order to control the contents of the main chemical elements C, Si, Mn, Cr, Mo, and Al in high aluminum steel, in step 2), the control requirements of the components in the refined molten steel include: the content of carbon element is 0.35-0.42wt%, the content of silicon element is 0.20-0.45wt%, the content of phosphorus element is ≤0.035wt%, the content of manganese element is 0.30-0.60wt%, the content of chromium element is 1.35-1.65wt%, the content of sulfur element is ≤0.035wt%, and the content of molybdenum element is 0.17-0.25wt%.

[0053] In a preferred embodiment of the present invention, in order to control the content of the main chemical elements C, Si, Mn, Cr, Mo, and Al in high aluminum steel, in step 2), the refining conditions in the LF refining furnace include: adding reducing slag after the molten steel enters the station; adding a reducing agent to the molten steel for diffusion deoxidation during the power-on and temperature-raising process; and performing a composition adjustment operation after the slag is refined.

[0054] In a preferred embodiment of the present invention, the reducing slag material comprises: lime in an amount of 2.5-3.5 kg / t and calcium carbide in an amount of 0.35-0.40 kg / t.

[0055] In a preferred embodiment of the present invention, in order to accurately control the content of aluminum in the molten steel, the reducing agent is aluminum particles and / or carbon powder.

[0056] In a preferred embodiment of the present invention, in order to accurately control the content of aluminum in the molten steel, the composition adjustment operation includes: feeding aluminum wire to control the aluminum content in the molten steel to be 0.870-0.930wt%.

[0057] In a preferred embodiment of the present invention, in order to control the content of gaseous hydrogen in the molten steel, in step 2), the refining conditions in the RH refining furnace include: RH vacuum refining degassing, and hydrogen and oxygen determination.

[0058] In a preferred embodiment of the present invention, in order to accurately control the content of gaseous hydrogen in the molten steel, the hydrogen and oxygen are determined using a Heraeus hydrogen meter.

[0059] In a preferred embodiment of the present invention, in order to control the amount and form of inclusions in the molten steel, the hydrogen content in the molten steel after refining in the RH refining furnace is ≤2ppm.

[0060] In a preferred embodiment of the present invention, in order to accurately control the content of aluminum in the molten steel, in step 2), the refining conditions in the RH refining furnace further include: feeding aluminum wire after the RH vacuum refining and degassing is completed.

[0061] In a preferred embodiment of the present invention, in order to control the amount and shape of inclusions in the molten steel, the content of aluminum in the molten steel after refining in the RH refining furnace is 0.88-0.92wt%.

[0062] In a preferred embodiment of the present invention, the soft blowing time of the refining satisfies that the first pouring furnace is ≥15min and the continuous pouring furnace is ≥10min.

[0063] In a preferred embodiment of the present invention, in step 3), the protective casting adopts a method of argon blowing protection of a large ladle casing and integral nozzle casting.

[0064] In a preferred embodiment of the present invention, the protective casting conditions also include: the superheat of the tundish in the first casting furnace is 35-45°C, the superheat of the tundish in the continuous casting furnace is 20-30°C, and the stirring method of crystallizer electromagnetic stirring plus end electromagnetic stirring is adopted during the casting process.

[0065] The present invention will be described in detail below through examples. In the following examples, the drugs and pharmaceutical agents are all conventional commercial products.

[0066] Example

[0067] The production process of the smelting method of the high aluminum steel of the present invention is: hot metal desulfurization → converter smelting → LF refining → RH vacuum degassing → continuous casting → heating → blanking machine → hydraulic shear → continuous rolling → metal saw → cooling bed → obtaining high aluminum steel, wherein

[0068] (1) Continuous casting and rolling process: Control the superheat of the continuous casting protection casting and the tundish molten steel to 30-40℃, maintain a constant pulling speed of 0.28m / min; adopt the hot charging process, the heating temperature is 1110-1150℃, the holding time is 420-480min, and high-pressure water is used for dephosphorization after the heating furnace. The descaling water pressure is ≥10MPa, and the rolling temperature is 1120±20℃.

[0069] (2) The composition control of each embodiment is shown in Table 1, and the conditions of the continuous casting and rolling process are shown in Table 2.

[0070] Table 1 Composition control (wt%)

[0071] C Si Mn P S Cr Mo Al Example 1 0.38 0.27 0.42 0.015 0.001 1.44 0.19 0.849 Example 2 0.38 0.29 0.42 0.013 0.001 1.43 0.19 0.852 Example 3 0.38 0.25 0.43 0.016 0.002 1.42 0.19 0.873

[0072] Table 2 Continuous casting and rolling process conditions

[0073]

[0074] Test Example 1

[0075] The mechanical properties of the high aluminum steels prepared in the above embodiments were tested, and the results are shown in Table 3.

[0076] Table 3 Mechanical properties of high aluminum steel obtained in Examples 1-3

[0077]

[0078] It can be seen from the results in Table 3 that the high aluminum steels produced according to the high aluminum steel smelting method of the present invention can meet the national standards and customer performance requirements.

[0079] In summary, the smelting method of high aluminum steel of the present invention realizes precise control of the aluminum element in molten steel by optimizing the operating processes of the converter and the refining furnace and the white slag operation during the smelting process, while controlling the adjustment method and addition timing of the aluminum element, thereby controlling the number and shape of inclusions in the molten steel, and finally continuously casting to produce high aluminum steel that meets national standards and customer performance requirements.

[0080] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0081] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0082] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A method for smelting high-aluminum steel, characterized in that: The smelting method comprises: 1) The molten iron is blown through a top and bottom double-blown converter to control the quality parameters of the molten steel produced and to produce steel; 2) the molten steel produced in step 1) is hoisted to the refining process, and refined in the LF refining furnace and the RH refining furnace in sequence; 3) hoisting the molten steel refined in step 2) to the continuous casting process for full-process protected casting; Wherein, the model of the high aluminum steel is 38CrMoAl.

2. The smelting method according to claim 1, characterized in that: In step 1), the blowing is performed by a high-draw supplementary blowing method.

3. The smelting method according to claim 1 or 2, characterized in that: In step 1), the quality parameters of the molten steel produced are controlled by controlling the carbon content in the molten steel to be ≥0.08wt%, the phosphorus content to be <0.015wt%, and the tapping temperature to be controlled to be 1650-1680°C.

4. The smelting method according to any one of claims 1 to 3, characterized in that: In step 1), the conditions for tapping include: when the tapping amount is 1 / 4, first adding alloy into the ladle, and then adding slag; Preferably, the conditions for adding the alloys include: the amount of silicon manganese alloy is 4 kg / t, the amount of ferromolybdenum alloy is 3.2 kg / t and the amount of high carbon ferrochrome alloy is 23 kg / t; More preferably, the conditions for adding slag materials include: the amount of lime is 5 kg / t and the amount of fluorite is 1 kg / t; Further preferably, after the steel tapping is completed, aluminum wire is fed on an argon blowing platform behind the furnace; More preferably, the amount of the aluminum wire is 200-300 m / furnace; More preferably, slag is strictly prohibited during the steel tapping process, and steel should be retained if necessary.

5. The smelting method according to any one of claims 1 to 4, characterized in that: The smelting method further comprises: in step 1), argon is blown from the bottom of the ladle throughout the whole process, and after the steel is tapped, the flow rate of the bottom-blown argon is adjusted to 300-500 mm above the bright surface.

6. The smelting method according to any one of claims 1 to 5, characterized in that: In step 2), the control requirements of the components in the refined molten steel include: the content of carbon element is 0.35-0.42wt%, the content of silicon element is 0.20-0.45wt%, the content of phosphorus element is ≤0.035wt%, the content of manganese element is 0.30-0.60wt%, the content of chromium element is 1.35-1.65wt%, the content of sulfur element is ≤0.035wt%, and the content of molybdenum element is 0.17-0.25wt%.

7. The smelting method according to any one of claims 1 to 6, characterized in that: In step 2), the refining conditions in the LF refining furnace include: adding reducing slag after the molten steel enters the station; adding reducing agent to the molten steel for diffusion deoxidation during the power-on and temperature-raising process; and performing composition adjustment operation after the slag is refined; Preferably, the reducing slag material comprises: lime in an amount of 2.5-3.5 kg / t and calcium carbide in an amount of 0.35-0.40 kg / t; More preferably, the reducing agent is aluminum particles and / or carbon powder; Further preferably, the composition adjustment operation includes: feeding aluminum wire to control the aluminum content in the molten steel to be 0.870-0.930wt%.

8. The smelting method according to any one of claims 1 to 7, characterized in that: In step 2), the refining conditions in the RH refining furnace include: RH vacuum refining degassing, fixing hydrogen and oxygen; Preferably, the hydrogen and oxygen are determined using a Heraeus hydrogen determination instrument; More preferably, the hydrogen content in the molten steel after refining in the RH refining furnace is ≤2ppm.

9. The smelting method according to any one of claims 1 to 8, characterized in that: In step 2), the refining conditions in the RH refining furnace further include: feeding aluminum wire after the RH vacuum refining degassing is completed; Preferably, the aluminum content in the molten steel after refining in the RH refining furnace is 0.88-0.92wt%; More preferably, the soft blowing time of the refining satisfies that the first pouring furnace is ≥15min and the continuous pouring furnace is ≥10min.

10. The smelting method according to any one of claims 1 to 9, characterized in that: In step 3), the protective casting adopts a method of argon blowing protection of a large sleeve and integral nozzle casting; Preferably, the protective casting conditions also include: the superheat of the tundish of the first casting furnace is 35-45°C, the superheat of the tundish of the continuous casting furnace is 20-30°C, and the stirring method of crystallizer electromagnetic stirring plus end electromagnetic stirring is adopted during the casting process.

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