Control method for reducing smelting consumption of stainless steel and nickel-based alloy

Abstract

The invention relates to a control method for reducing smelting consumption of stainless steel and nickel-based alloy, and belongs to a metallurgical process. The control method sequentially comprises the following process steps: proportioning raw materials; smelting in a Consteel electric furnace and melting the alloy in an intermediate frequency furnace; refining in an AOD furnace; refining in a VOD furnace; lF argon blowing refining is carried out; and casting a continuous casting slab. According to the method, after raw material crude smelting of the molten steel is completed in the electric furnace, through rapid decarburization of the high-carbon molten iron in the AOD furnace and efficient decarburization of the low-carbon molten steel in the VOD furnace, the defects that in the decarburization process, after the carbon content is lower than the carbon critical point of decarburization and chromium protection in the original full AOD refining process, chromium oxidation is serious, the gas content in the molten steel is high, the smelting time is long, and consumption of reducing agents, auxiliary materials and gas media is large are overcome.

Description

Technical Field

[0001] The present invention relates to a control method, in particular to a control method for reducing the smelting consumption of stainless steel and nickel-based alloys, which belongs to the metallurgical process. Background Art

[0002] Due to their excellent corrosion resistance and good comprehensive properties, stainless steel and nickel-based alloys are increasingly widely used in various industrial and civil fields. The production of stainless steel and nickel-based alloys in China started late. In 2000, the long-term output hovering around 3 million tons ended, showing a rapid development trend of leapfrog and jump. In 2023, the global crude steel output of stainless steel and nickel-based alloys was about 58.44 million tons, and the output of stainless steel and nickel-based alloys in China reached 36.67 million tons, accounting for 62.8% of the global output. With the improvement of production capacity, it is urgent to optimize the process flow and reduce raw material costs to enhance the market competitiveness of enterprises.

[0003] At present, the mainstream smelting process of stainless steel and nickel-based alloys in the world is the two-step process, and its process route is (1) primary melting furnace (EAF, RKEF, IF) (2) AOD. Among them, the production capacity of the EAF to AOD process accounts for about 70% of the world's stainless steel production capacity. The EAF furnace is mainly used to melt scrap steel and alloy raw materials to produce molten metal pre-melt, and the molten metal pre-melt then enters the AOD furnace for smelting into qualified molten steel. Its advantages include: the electric furnace has low requirements for raw materials, a slightly shorter process, good flexibility, and can produce 95% of the varieties except for ultra-low carbon and nitrogen stainless steel.

[0004] The AOD argon-oxygen refining furnace is an indispensable equipment for smelting. Its working principle is to continuously adjust the ratio of oxygen to inert gas (N2, Ar) to reduce the partial pressure of carbon monoxide, so as to reduce the oxidation of precious metal chromium elements during the decarburization process. The disadvantages of the traditional AOD process include: first, the consumption of media such as argon and nitrogen is large; second, the consumption of ferrosilicon is high, and the slag volume per ton of steel is large; third, when producing ultra-low carbon and nitrogen stainless steel, the gas content in the steel is high and the quality is unstable; fourth, the AOD smelting time is long, the AOD furnace life is low and it becomes a limiting link.

[0005] Through the research on the traditional AOD smelting process, it is found that more than 70% of the consumption of the traditional AOD process occurs in the interval where the carbon content of the molten steel is low (carbon ≤ 0.5%), and the lower the carbon content of the molten steel, the greater the consumption. Summary of the Invention

[0006] The purpose of the present invention is to overcome the above-mentioned deficiencies existing in the prior art, and provide a control method for reducing the smelting consumption of stainless steel and nickel-based alloys with reasonable structural design, safety and reliability, stable quality, environmental protection and energy saving.

[0007] The technical solution adopted by the present invention to solve the above problems is as follows: The control method for reducing the smelting consumption of stainless steel and nickel-based alloys is characterized by including the following technological steps:

[0008] (S1) Raw material batching;

[0009] (S2) Melting in a Consteel electric furnace and melting alloys in an intermediate frequency furnace;

[0010] (S3) Refining in an AOD furnace;

[0011] (S4) Refining in a VOD furnace;

[0012] (S5) LF argon blowing refining;

[0013] (S6) Continuous casting slab casting;

[0014] Among them, the refining section process (the smelting of stainless steel is divided into rough smelting and refining, the electric furnace and the intermediate frequency furnace belong to the rough smelting section process, and the AOD furnace refining, VOD furnace refining, and LF argon blowing refining all belong to the refining section process) includes the following steps:

[0015] (1) Steel charging: Composition of the AOD mother liquid: carbon 1 - 3%, silicon 0 - 2%, chromium 0 - 16%, nickel 10 - 15%;

[0016] (2) Adding alloys and auxiliary materials: Adding high-carbon ferrochrome to the AOD to make up chromium to the target value, controlling the silicon content in the molten steel at 0.1 - 0.3% with large-flow oxygen supply, adding lime at the same time, with the binary basicity of the slag being 1.3 - 1.5, and removing the slag completely;

[0017] (3) Slag flowing;

[0018] (4) Oxidative decarburization: Continuing large-flow oxygen supply with the top lance and side lance of the AOD, fine-tuning the chromium, nickel, and molybdenum components at the same time, controlling the binary basicity of the slag at 1.2 - 1.5, and controlling the carbon content in the molten steel at 0.2 - 0.4%;

[0019] (5) Mixing out of oxidized slag and molten steel: Mixing out all the steel and slag into the ladle, and not adding a reducing agent for reduction in the AOD;

[0020] (6) VOD vacuum oxygen blowing decarburization: Hoisting the molten steel to the VOD, starting the vacuum system, waiting for the vacuum degree to drop to 150 - 250 mbar, starting the VOD oxygen blowing decarburization stage, with the oxygen blowing height of 1500 - 1800 mm, the oxygen supply intensity of 20 - 30 Nm 3 / min.t, the oxygen blowing volume of 2 - 4 Nm 3 / t, and ending the oxygen blowing;

[0021] (7) VCD deep vacuum free decarburization: Pumping the vacuum degree below 1 mbar to reduce the gas content in the molten steel;

[0022] (8) Vacuum reduction degassing and inclusion removal: Raise the vacuum degree to about 100 mbar, add auxiliary materials and reducing agents, reduce metal oxides in the reducing slag while degassing the molten steel, and the reduction time is 15 - 20 min.

[0023] Preferably, in the step (S2) of the present invention, in the Consteel electric furnace and the intermediate frequency furnace, the raw materials of Ni% and Mo% required in the steel are added in place, and only a small amount of fine-tuning is carried out in the subsequent processes, and the molten iron P is controlled within the target range.

[0024] Preferably, in the step (S3) of the present invention, during the entire smelting process of AOD, there is no need to use expensive argon gas as the dilution and protection gas.

[0025] Preferably, in the step (S3) of the present invention, the AOD treatment time is 40 - 50 min.

[0026] Preferably, in the step (S4) of the present invention, the reducing agents during the reduction period of the VOD refining furnace are ferrosilicon, aluminum, or low-carbon silicomanganese.

[0027] Preferably, in the step (S4) of the present invention, the VOD vacuum treatment time is 40 - 50 min.

[0028] Preferably, in the present invention, the high-carbon molten iron maintains a high oxygen supply intensity and a high decarburization efficiency throughout the AOD furnace.

[0029] Preferably, in the present invention, AOD decarburizes the carbon to near the "decarburization to protect chromium" carbon critical point without reduction, and the slag rich in chromium oxide and the molten steel enter the VOD smelting.

[0030] Preferably, in the present invention, in VOD, by adjusting the vacuum degree, the carbon content of the molten steel is always above the "decarburization to protect chromium" carbon critical point, ensuring a high decarburization efficiency and the vacuum degree is pumped to 0.67 mbar - 1.5 mbar before the reduction ends after VOD decarburization, reducing the gas content in the molten steel before reduction.

[0031] Preferably, in the reduction period of the present invention's VOD, according to the Mn% content requirement of the steel grade, the corresponding low-carbon silicomanganese alloy is added. The addition of ferrosilicon alloy or aluminum alloy is calculated by subtracting the oxygen amount (NM 3 ) required for decarburization and oxidation of silicon in the molten steel from the total oxygen amount (NM 3 ) of oxygen blown into the AOD and VOD furnaces to calculate the total weight of the reduced ferrosilicon alloy or aluminum alloy, and then subtracting the weight of the reducing agent silicon contained in the low-carbon silicomanganese to obtain the weight of the ferrosilicon alloy or aluminum alloy to be added during the reduction stage.

[0032] Compared with the prior art, the present invention has the following advantages and effects: (1) The overall structure is reasonably designed, safe and reliable, reducing the total output of slag per ton of steel by about 30%; (2) The consumption of argon and nitrogen is reduced by about 70%; (3) Solve the problems that when producing ultra-low carbon and nitrogen stainless steel and nickel-based alloys, the gas content in the steel is high, the quality is unstable, and it cannot meet the high-end application requirements; (4) Shorten the AOD smelting time, increase the AOD furnace life, and meet the usage requirements. Detailed implementation manners

[0033] The present invention will be further described in detail below in conjunction with and by way of embodiments. The following embodiments are explanations of the present invention and the present invention is not limited to the following embodiments.

[0034] Embodiment

[0035] The control method for reducing the smelting consumption of stainless steel and nickel-based alloys in this embodiment successively includes the following technological steps: (S1) Raw material batching; (S2) Melting alloys in a Consteel electric furnace and an intermediate frequency furnace; (S3) Refining in an AOD furnace; (S4) Refining in a VOD furnace; (S5) LF argon blowing refining; (S6) Continuous casting slab casting; wherein the refining includes the following steps: (1) Charging molten steel; (2) Adding alloys and auxiliary materials; (3) Flowing slag; (4) Oxidative decarburization; (5) Mixing out the oxidative slag and molten steel; (6) VOD vacuum oxygen blowing decarburization; (7) VCD deep vacuum free decarburization; (8) Vacuum reduction degassing to remove inclusions.

[0036] In the Consteel electric furnace and the intermediate frequency furnace, the required Ni% and Mo% raw materials in the steel are added in place, and only a small amount of fine-tuning is carried out in the subsequent processes, and the iron water P is controlled within the target range.

[0037] In this embodiment, the high-carbon hot metal maintains a high oxygen supply intensity and a high decarburization efficiency throughout the AOD furnace.

[0038] In this embodiment, the AOD decarburizes carbon to near the "decarburization to protect chromium" carbon critical point, without reduction, and the chromium-rich oxidative slag and molten steel enter the VOD smelting.

[0039] In this embodiment, by adjusting the vacuum degree in the VOD, the carbon content of the molten steel is always above the "decarburization to protect chromium" carbon critical point, ensuring a high decarburization efficiency and the vacuum degree is pumped to 0.67 mbar - 1.5 mbar before the reduction in the VOD decarburization ends, reducing the gas content in the molten steel before reduction.

[0040] In this embodiment, the reducing agent in the reduction period of the VOD refining furnace is ferrosilicon (aluminum) or low-carbon silicomanganese.

[0041] In this embodiment, during the reduction period of the VOD, the corresponding low-carbon silicomanganese alloy is added according to the Mn% content requirement of the steel grade, and the addition of the ferrosilicon (aluminum) alloy is through blowing the total amount of oxygen in the AOD + VOD furnaces (NM3 ) Subtract the amount of oxygen required for decarburization and silicon oxidation in the molten steel (NM 3 ), calculate the total weight of reduced ferrosilicon (aluminum), and then subtract the weight of reducing agent silicon contained in low-carbon silicomanganese to obtain the weight of ferrosilicon (aluminum) to be added during the reduction stage.

[0042] This embodiment adopts the production process route of consteel electric furnace + AOD + VOD. The AOD and subsequent specific implementation methods are as follows (taking 316L as an example):

[0043] (1) Composition of the AOD mother liquor: carbon 1-3%, silicon 0-2%, chromium 0-16%, nickel 10-15%.

[0044] (2) Add high-carbon ferrochrome to the AOD to replenish chromium to the target value. Supply oxygen at a large flow rate to control the silicon content in the molten steel at 0.1-0.3%. At the same time, add lime, and the binary basicity of the slag is 1.3-1.5. Remove the slag completely.

[0045] (3) The top lance and side lance of the AOD continue to supply oxygen at a large flow rate. At the same time, finely adjust the components of chromium, nickel, and molybdenum and control the binary basicity of the slag at 1.2-1.5. To balance the production rhythm between each process, control the carbon content in the molten steel at 0.2-0.4%. Mix the steel and slag and discharge all of them into the ladle. Do not add reducing agents such as ferrosilicon for reduction in the AOD.

[0046] (4) No expensive argon gas is required as a dilution and protection gas during the entire smelting process of the AOD.

[0047] (5) The above AOD treatment time is 40-50 minutes, which is 30-40 minutes shorter than the traditional AOD process time.

[0048] (6) Lift the molten steel to the VOD, turn on the vacuum system. When the vacuum degree drops to 150-250 mbar, start the VOD oxygen blowing decarburization stage. The oxygen blowing height is 1500-1800 mm, the oxygen supply intensity is 20-30 Nm 3 / min.t, and the oxygen blowing amount is 2-4 Nm 3 / t. After the oxygen blowing ends, enter the VCD deep decarburization stage, and pump the vacuum degree below 1 mbar to reduce the gas content in the molten steel.

[0049] (7) Raise the vacuum degree to about 100 mbar, add auxiliary materials and reducing agents such as lime, ferrosilicon, and fluorite. Reduce the metal oxides in the reducing slag and degasify the molten steel at the same time. The reduction time is 15-20 minutes.

[0050] (8) The above VOD vacuum treatment time is 40-50 minutes, which is 15-20 minutes shorter than the traditional AOD reduction and slag removal and then VOD vacuum refining.

[0051] To produce green, environmentally friendly, and resource-saving stainless steel and high-temperature resistant nickel-based alloys, this embodiment selects a new stainless steel production process route: the Consteel electric furnace + AOD + VOD production process route. The advantage of the melting section is that the Consteel electric furnace preheats the raw materials with the waste gas generated during smelting, reducing the melting power consumption by about 30% compared to traditional electric furnaces. The refining section adopts the double-link method of AOD and VOD.

[0052] In this embodiment, after the raw materials are roughly refined in the electric furnace, the molten steel undergoes rapid decarburization in the AOD furnace with high-carbon hot metal and high-efficiency decarburization in the VOD furnace for low-carbon molten steel, reducing the disadvantages of severe chromium oxidation during decarburization, high gas content in the molten steel, long smelting time, and large consumption of reducing agents, auxiliary materials, and gas media after the carbon content in the original full-AOD refining process is lower than the carbon critical point of "decarburization to protect chromium".

[0053] Through the above description, those skilled in the art can already implement it.

[0054] In addition, it should be noted that for the specific embodiments described in this specification, the shapes, names of parts and components, etc. can be different. The above content described in this specification is only an example of the structure of the present invention. Any equivalent changes or simple changes made according to the structure, features, and principles of the present invention's patent concept are included in the protection scope of the present invention's patent. Those skilled in the technical field to which the present invention belongs can make various modifications, supplements, or use similar methods to replace the specific embodiments described, as long as they do not deviate from the structure of the present invention or exceed the scope defined by this claim book, they should fall within the protection scope of the present invention.

Claims

1. A control method for reducing the smelting consumption of stainless steel and nickel-based alloys, characterized in that: It includes the following technological steps: (S1) Raw material batching; (S2) Melting in a Consteel electric furnace and melting alloys in an intermediate frequency furnace; (S3) Refining in an AOD furnace; (S4) Refining in a VOD furnace; (S5) Refining by blowing argon in an LF furnace; (S6) Casting continuous casting slabs; Among them, (S3) refining in an AOD furnace, (S4) refining in a VOD furnace, and (S5) refining by blowing argon in an LF furnace all belong to the refining section processes. The refining section processes include the following steps: (1) Steel charging: The composition of the AOD mother liquid for charging: carbon 1-3%, silicon 0-2%, chromium 0-16%, nickel 10-15%; (2) Adding alloys and auxiliary materials: Adding high-carbon ferrochrome to the AOD to make up chromium to the target value, controlling the silicon in the molten steel at 0.1-0.3% by large-flow oxygen supply, adding lime at the same time, with the binary basicity of the slag being 1.3-1.5, and removing the slag completely; (3) Slag flowing; (4) Oxidative decarburization: Continuing large-flow oxygen supply with the top lance and side lance of the AOD, fine-tuning the components of chromium, nickel, and molybdenum at the same time and controlling the binary basicity of the slag at 1.2-1.5, and controlling the carbon in the molten steel at 0.2-0.4%; (5) Mixing out oxidative slag and molten steel: Mixing out all the steel and slag into the ladle, and not adding a reducing agent for reduction in the AOD; (6)VOD Vacuum Oxygen Decarburization: The molten steel is lifted to the VOD, and the vacuum system is started. When the vacuum degree is reduced to 150 - 250 mbar, the VOD oxygen blowing decarburization stage begins. The oxygen blowing height is 1500 - 1800 mm, the oxygen supply intensity is 20 - 30 Nm 3 / min.t, the oxygen blowing volume is 2 - 4 Nm 3 / t, and the oxygen blowing ends; (7) Deep vacuum free decarburization in VCD: Pumping the vacuum degree below 1 mbar to reduce the gas content in the molten steel; (8) Vacuum reduction degassing and inclusion removal: Raising the vacuum degree to about 100 mbar, adding auxiliary materials and a reducing agent, reducing metal oxides in the slag and degassing the molten steel at the same time, with a reduction time of 15-20 min.

2. The control method for reducing the smelting consumption of stainless steel and nickel-based alloys according to claim 1, characterized in that: In the step (S2), in the Consteel electric furnace and the intermediate frequency furnace, the raw materials of Ni% and Mo% required in the steel are added in place, only a small amount of fine-tuning is carried out in the subsequent processes, and the iron water P is controlled within the target range.

3. The control method for reducing the smelting consumption of stainless steel and nickel-based alloys according to claim 1, characterized in that: In the step (S3), no expensive argon gas is used as a dilution and protection gas during the whole smelting process of the AOD.

4. The control method for reducing the smelting consumption of stainless steel and nickel-based alloys according to claim 1, characterized in that: In the step (S3), the treatment time of the AOD is 40-50 min.

5. The control method for reducing the smelting consumption of stainless steel and nickel-based alloys according to claim 1, characterized in that: In the (S4), the reducing agents during the reduction period of the VOD refining furnace are ferrosilicon, aluminum, or low-carbon silicomanganese.

6. The control method for reducing the smelting consumption of stainless steel and nickel-based alloys according to claim 1, characterized in that: In the (S4), the vacuum treatment time of the VOD is 40-50 min.

7. The control method for reducing the smelting consumption of stainless steel and nickel-based alloys according to claim 1, characterized in that: High-carbon hot metal maintains a high oxygen supply intensity and a high decarburization efficiency throughout the AOD furnace.

8. The control method for reducing the smelting consumption of stainless steel and nickel-based alloys according to claim 1, characterized in that: The AOD decarburizes carbon to near the "decarburization to protect chromium" carbon critical point, without reduction, and the slag rich in chromium oxide and the molten steel enter the VOD for smelting.

9. The control method for reducing the smelting consumption of stainless steel and nickel-based alloys according to claim 1, characterized in that: The VOD adjusts the vacuum degree, and the carbon content in the molten steel is always above the "decarburization to protect chromium" carbon critical point, ensuring a high decarburization efficiency and pumping the vacuum degree to 0.67 mbar - 1.5 mbar before the reduction ends after the VOD decarburization, reducing the gas content in the molten steel before reduction.

10. The control method for reducing the smelting consumption of stainless steel and nickel-based alloys according to claim 1, characterized in that: During the VOD reduction period, the corresponding low-carbon ferrosilicon manganese alloy, ferrosilicon alloy or aluminum alloy is added according to the Mn% content requirement of the steel grade. The addition of ferrosilicon alloy or aluminum alloy is calculated by blowing the total amount of oxygen in the AOD and VOD furnaces (NM 3 ) minus the amount of oxygen required for decarburization and oxidation of silicon in the molten steel (NM 3 ) to calculate the total weight of the reduced ferrosilicon alloy or aluminum alloy, and then subtracting the weight of the reducing agent silicon contained in the low-carbon ferrosilicon manganese to obtain the weight of the ferrosilicon alloy or aluminum alloy to be added during the reduction stage.