Methods for reducing the smelting cost of austenitic stainless steel
By performing high-carbon steel output in the AOD furnace and canceling the reduction and desulfurization periods, the slag-containing molten steel is transferred to the VOD furnace for further treatment, which solves the problem of chromium oxidation and entry into the slag in the molten steel, and achieves the effect of reducing smelting costs and energy consumption.
Patent Information
- Application Number
- CN202411986556.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-31
- Publication Date
- 2025-04-04
AI Technical Summary
In the existing AOD furnace smelting conventional austenitic stainless steel process, the chromium in the molten steel is easily oxidized into the slag, which increases production costs and a long smelting cycle, resulting in an increase in energy consumption.
By performing high-carbon steel discharge in the AOD furnace, the oxidation of chromium in the molten steel is reduced, and the reduction and desulfurization periods are abolished, the molten steel with slag is directly transferred to the VOD furnace for further treatment. In VOD furnaces, decarbonize, reduce chromium and desulfurize with low oxygen consumption, low ferrosilicon consumption and low lime consumption.
It effectively reduces the oxygen consumption and smelting cycle of the AOD furnace link, saves the use of ferrosilicon and lime, reduces the consumption of inert gas, improves the chromium yield, and significantly reduces production costs and energy consumption.
Smart Images
Figure CN119753488A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of stainless steel smelting, and relates to a method for reducing the smelting cost of austenitic stainless steel. Background Art
[0002] In the field of stainless steel smelting, the AOD furnace (argon oxygen refining furnace) is a key equipment for smelting conventional austenitic stainless steel, and its smelting process has a decisive influence on the quality and cost of the product. At present, the process flow of smelting conventional austenitic stainless steel in the AOD furnace usually includes a decarburization period and a subsequent reduction desulfurization period. During the decarburization period, the carbon content in the molten steel is reduced to the target value by blowing oxygen. However, during the decarburization process, the chromium in the molten steel is also easily oxidized into the slag, increasing the production cost.
[0003] To address this problem, the existing process sets a reduction desulfurization period after the AOD furnace decarburization is completed. During the reduction desulfurization period, reducing agents such as ferrosilicon are added to reduce the chromium in the slag, and slag desulfurization is carried out by adding lime and fluorite to further purify the molten steel. However, this process has many shortcomings. First, the carbon content of the steel tapped by the AOD furnace has reached the target carbon of the steel grade. The decarburization time of the AOD furnace is long, and the oxidized chromium in the molten steel is relatively large. In order to reduce the chromium in the slag into the molten steel as much as possible, the amount of reduced ferrosilicon consumed in the reduction period is large. Secondly, the processing cycle of the AOD furnace is long, which increases production costs and energy consumption. In addition, after the AOD furnace taps steel, it is necessary to determine whether to perform slag removal operations based on the amount of slag, which undoubtedly increases the complexity and labor intensity of the process.
[0004] In view of the above problems, it is particularly important to develop a more stable and lower-cost AOD furnace process for smelting conventional austenitic stainless steel. Summary of the invention
[0005] In view of this, the purpose of the present invention is to provide a method for reducing the smelting cost of austenitic stainless steel, high-carbon steel tapping in the AOD furnace, reducing the oxidation of chromium in the molten steel, reducing the oxygen consumption in the AOD furnace link, and shortening the decarburization time of the AOD furnace; no reduction period and desulfurization period are set in the AOD furnace, further reducing the smelting cycle of the AOD furnace, saving the consumption of ferrosilicon and lime in the AOD furnace link, and saving the consumption of inert gas; the AOD furnace taps steel with slag, and all the chromium oxidized into the slag in the AOD furnace link enters the VOD furnace link with the slag; the vacuum environment of the VOD furnace can further decarburize the molten steel, reduce the chromium in the slag, and desulfurize the molten steel with lower oxygen consumption, ferrosilicon consumption, and lime consumption compared to the AOD furnace. This method saves oxygen consumption in the entire process, reduces the ferrosilicon consumption in the reduction period, and simultaneously improves the chromium recovery rate of the entire process.
[0006] In order to achieve the above object, the present invention provides the following technical solutions:
[0007] A method for reducing the smelting cost of austenitic stainless steel comprises the following steps:
[0008] Add stainless steel mother liquor: Add stainless steel mother liquor into AOD furnace;
[0009] AOD furnace desiliconization blowing: If the silicon content of the stainless steel mother liquor is greater than 0.5%, oxygen is blown from the top side for desiliconization blowing. Lime is added to make slag during the blowing process. After the desiliconization is completed, the gun is lifted and the desiliconized slag is poured out. If the silicon content of the stainless steel mother liquor is less than 0.5%, desiliconization blowing is not required;
[0010] AOD furnace decarburization: oxygen is blown from the top and side for decarburization, lime is added to make slag during the blowing process, alloy is added to adjust the composition, nitrogen is blown from the side for stirring during this process, and the carbon content of the steel out of the AOD furnace is controlled to be 0.2% to 0.3%;
[0011] AOD furnace tapping with slag: The molten steel and slag are mixed from the AOD furnace and poured into the molten steel tank, which is then hoisted into the VOD furnace;
[0012] Decarburization treatment in VOD furnace: During the vacuum treatment of VOD furnace, the top gun is used to force oxygen blowing and decarburization of the molten steel in the molten steel tank. After the forced decarburization is completed, natural decarburization is carried out through vacuum treatment.
[0013] Alloying, reduction and desulfurization in VOD furnace: After decarburization, ferrosilicon is added to reduce the chromium in the slag of the molten steel tank. In this process, lime is added to make slag and desulfurize, alloy is added to adjust the composition, and inert gas is blown at the bottom for stirring;
[0014] VOD furnace normal pressure treatment: After the VOD furnace breaks the vacuum, the temperature is measured and sampled, and wire feeding and soft blowing are carried out.
[0015] Furthermore, the stainless steel mother liquid has the following components: C<3.5%, Si<1.5%, Mn<0.1%, P≤0.035%, S≤0.15%, Ni=8~15%, Cr<7.0%, the remainder is iron, and the temperature is 1600℃.
[0016] Furthermore, the amount of stainless steel mother liquor added to the AOD furnace is 620-750 kg / t molten steel.
[0017] Furthermore, the oxygen supply intensity of the top gun and the side blowing tuyere during the desiliconization blowing stage in the AOD furnace is 1.8-2.2 Nm 3 / min.t, the end of desiliconization in the AOD furnace refers to the silicon content in the molten pool being 0.5% or less.
[0018] Furthermore, during the decarburization blowing stage of the AOD furnace, the oxygen supply intensity of the top gun and the side blowing tuyere is dynamically adjusted to a value of 1.2 to 2.2 Nm 3 / min.t.
[0019] Furthermore, the activity of lime used in the AOD furnace is not less than 320, the CaO content in the lime is not less than 90%, and the slag basicity of the AOD furnace is 1.0-1.7.
[0020] Furthermore, the oxygen supply intensity in the forced decarburization stage in the VOD furnace is 0.15-0.2 Nm 3 / min.t, and the VOD furnace has a forced oxygen blowing decarburization time of 8 to 15 minutes.
[0021] Furthermore, the natural decarburization time in the VOD furnace is 15 to 25 minutes.
[0022] Furthermore, the reduction desulfurization time of the VOD furnace is 15 to 25 minutes.
[0023] Furthermore, the soft blowing time of the VOD furnace after breaking air is 10 to 20 minutes.
[0024] The beneficial effects of the present invention are:
[0025] The present invention provides a method for reducing the smelting cost of austenitic stainless steel, the core of which is to combine the smelting process of the AOD furnace with that of the VOD furnace; by high-carbon steelmaking in the AOD furnace, the oxidation of chromium in the molten steel is effectively reduced, while the oxygen consumption in the AOD furnace link is reduced, and the decarburization time of the AOD furnace is shortened. This method eliminates the traditional reduction period and desulfurization period in the AOD furnace, further significantly shortens the smelting cycle, thereby saving the amount of ferrosilicon and lime, as well as the reduction in inert gas consumption due to the reduction in smelting time. This innovative process not only simplifies the operating steps of the AOD furnace, but also significantly reduces production costs and energy consumption.
[0026] In specific implementation, the present invention achieves efficient desiliconization and decarburization by precisely controlling the blowing parameters and slag-making conditions of the AOD furnace, while ensuring the stability of the molten steel composition. The strategy of tapping the steel with slag from the AOD furnace enables all the chromium oxidized into the slag during the AOD furnace to enter the VOD furnace with the slag, providing favorable conditions for subsequent chromium reduction. The vacuum treatment environment of the VOD furnace further enhances the effects of decarburization, reduction and desulfurization. Its unique combination of forced oxygen blowing and natural decarburization ensures high-quality treatment of molten steel while reducing oxygen consumption and ferrosilicon consumption.
[0027] The invention has significant beneficial effects, not only saving oxygen consumption and ferrosilicon consumption in the whole process, but also improving the chromium recovery rate in the whole process, especially in the VOD furnace link, the chromium recovery rate can reach 99%. This innovative method not only improves the economy and environmental protection of stainless steel smelting, but also provides a new technical path and reference for the stainless steel smelting industry, and has broad promotion value and application prospects.
[0028] Other advantages, objectives and features of the present invention will be described in the following description to some extent, and to some extent, will be obvious to those skilled in the art based on the following examination and study, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS
[0029] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below in conjunction with the accompanying drawings, wherein:
[0030] Figure 1 It is a schematic diagram of the process of the present invention.
[0031] Figure numerals: 1-premelting tank; 2-AOD furnace; 3-molten steel tank; 4-VOD furnace. DETAILED DESCRIPTION
[0032] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner, and the following embodiments and features in the embodiments can be combined with each other without conflict.
[0033] Among them, the drawings are only used for illustrative explanations, and they only represent schematic diagrams rather than actual pictures, and should not be understood as limitations on the present invention. In order to better illustrate the embodiments of the present invention, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of actual products. For those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.
[0034] The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if the terms "upper", "lower", "left", "right", "front", "rear", etc. indicate the orientation or position relationship, they are based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, the terms describing the position relationship in the drawings are only used for illustrative purposes and cannot be understood as limiting the present invention. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.
[0035] See also Figure 1, is a method for reducing the smelting cost of austenitic stainless steel, comprising the following steps:
[0036] Add stainless steel mother liquor: Add the stainless steel mother liquor provided by the previous process into AOD furnace 2;
[0037] AOD furnace desiliconization blowing: oxygen is blown from the top side for desiliconization blowing. Lime is added to make slag during the blowing process. After desiliconization, the gun is lifted and the desiliconized slag is poured out. If the silicon content of the initial AOD furnace mother liquor is less than 0.5%, this step can be omitted and the AOD furnace decarburization link can be directly entered;
[0038] AOD furnace decarburization: top and side oxygen blowing decarburization, lime is added to make slag during blowing, ferrochrome and other alloys are added to adjust the composition, and nitrogen is blown sideways for stirring during the process;
[0039] AOD furnace tapping with slag: The molten steel and slag are mixed out of the AOD furnace, and all the slag is poured into the molten steel tank 3, and then the molten steel tank is hoisted into the VOD furnace;
[0040] Decarburization treatment in VOD furnace: During the vacuum treatment of VOD furnace, the top gun is used to force decarburization of molten steel. After the forced decarburization is completed, natural decarburization is carried out through vacuum treatment.
[0041] Alloying, reduction and desulfurization in VOD furnace: after decarburization, ferrosilicon is added to reduce the chromium in the slag of the molten steel tank, lime is added to make slag and desulfurize, alloy composition is added to adjust, and argon is blown at the bottom for strong stirring;
[0042] VOD furnace normal pressure treatment: after breaking the vacuum, temperature measurement and sampling, then wire feeding and soft blowing.
[0043] Furthermore, after the VOD furnace treatment is completed, it is determined whether to undergo LF furnace refining treatment based on the molten steel temperature and the requirements of the continuous casting process.
[0044] Furthermore, the preceding process provides stainless steel mother liquor for the AOD furnace 2, and the stainless steel mother liquor is added into the AOD furnace 2 through the pre-melting tank 1, and the composition of the stainless steel mother liquor is C<3.5%, Si<1.5%, Mn<0.1%, P≤0.035%, S≤0.15%, Ni=8~15%, Cr<7.0%, and the balance is iron, and the temperature of the stainless steel mother liquor is 1600℃; the amount of stainless steel mother liquor added into the AOD furnace is about 620~750kg / t molten steel.
[0045] Specifically, the AOD pre-furnace process can be set as a medium frequency furnace, an electric furnace, or an ore-arc furnace.
[0046] The oxygen supply intensity of the top gun and the side blowing port in the desiliconization blowing stage of the AOD furnace 2 is 1.8-2.2Nm 3 / min.t, the oxygen supply intensity of the top gun and the side blowing port is dynamically adjusted during the decarburization blowing stage of the AOD furnace, and the oxygen supply intensity is 1.2-2.2Nm 3 / min.t; the end of desiliconization in the AOD furnace means that the silicon content in the molten pool is 0.5% or less.
[0047] The activity of lime used in the AOD furnace is not less than 320, the CaO content in the lime is not less than 90%, and the slag basicity of the AOD furnace is 1.0-1.7; the AOD furnace is stirred by blowing inert gas throughout the process, and the stirring inert gas used is N2;
[0048] The tapping temperature of the AOD furnace is 1750-1780° C., and the carbon content of the tapping steel is 0.2%-0.3%.
[0049] The oxygen supply intensity of the VOD furnace 4 during the forced decarburization stage is 0.15-0.2 Nm 3 / min.t, the forced oxygen decarburization time of the VOD furnace is 8 to 15 minutes; the natural decarburization time of the VOD furnace is 15 to 25 minutes; the reduction desulfurization time of the VOD furnace is 15 to 25 minutes; the inert gas blowing intensity at the bottom of the VOD furnace is 6 to 7L / min.t; the soft blowing time of the VOD furnace after breaking the air is 10 to 20 minutes.
[0050] According to experiments, the chromium recovery rate in the VOD furnace link can reach 99% by adopting the method for reducing the smelting cost of austenitic stainless steel provided by the present invention.
[0051] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution, which should be included in the scope of the claims of the present invention.
Claims
1. A method for reducing the smelting cost of austenitic stainless steel, characterized in that: The following steps are involved: Add stainless steel mother liquor: Add stainless steel mother liquor into AOD furnace; AOD furnace desiliconization blowing: If the silicon content of the stainless steel mother liquor is greater than 0.5%, oxygen is blown from the top side for desiliconization blowing. Lime is added to make slag during the blowing process. After the desiliconization is completed, the gun is lifted and the desiliconized slag is poured out. If the silicon content of the stainless steel mother liquor is less than 0.5%, desiliconization blowing is not required; AOD furnace decarburization: oxygen is blown from the top and side for decarburization, lime is added to make slag during the blowing process, alloy is added to adjust the composition, nitrogen is blown from the side for stirring during this process, and the carbon content of the steel out of the AOD furnace is controlled to be 0.2% to 0.3%; AOD furnace tapping with slag: The molten steel and slag are mixed from the AOD furnace and poured into the molten steel tank, which is then hoisted into the VOD furnace; Decarburization treatment in VOD furnace: During the vacuum treatment of VOD furnace, the top gun is used to force oxygen blowing and decarburization of the molten steel in the molten steel tank. After the forced decarburization is completed, natural decarburization is carried out through vacuum treatment. Alloying, reduction and desulfurization in VOD furnace: After decarburization, ferrosilicon is added to reduce the chromium in the slag of the molten steel tank. In this process, lime is added to make slag and desulfurize, alloy is added to adjust the composition, and inert gas is blown at the bottom for stirring; VOD furnace normal pressure treatment: After the VOD furnace breaks the vacuum, the temperature is measured and sampled, and wire feeding and soft blowing are carried out.
2. The method for reducing the smelting cost of austenitic stainless steel according to claim 1, characterized in that: The stainless steel mother liquid has the following components: C<3.5%, Si<1.5%, Mn<0.1%, P≤0.035%, S≤0.15%, Ni=8~15%, Cr<7.0%, the remainder is iron, and the temperature is 1600℃.
3. The method for reducing the smelting cost of austenitic stainless steel according to claim 1, characterized in that: The amount of stainless steel mother liquor added to the AOD furnace is 620-750 kg / t molten steel.
4. The method for reducing the smelting cost of austenitic stainless steel according to claim 1, characterized in that: The oxygen supply intensity of the top gun and the side blowing port during the desiliconization blowing stage in the AOD furnace is 1.8-2.2Nm 3 / min.t, the end of desiliconization in the AOD furnace refers to the silicon content in the molten pool being 0.5% or less.
5. The method for reducing the smelting cost of austenitic stainless steel according to claim 1, characterized in that: The AOD furnace dynamically adjusts the oxygen supply intensity of the top gun and the side blowing port during the decarburization blowing stage, and the oxygen supply intensity is 1.2-2.2Nm 3 / min.t.
6. The method for reducing the smelting cost of austenitic stainless steel according to claim 1, characterized in that: The activity of lime used in the AOD furnace is not less than 320, the CaO content in the lime is not less than 90%, and the slag basicity of the AOD furnace is 1.0-1.
7.
7. The method for reducing the smelting cost of austenitic stainless steel according to claim 1, characterized in that: The oxygen supply intensity in the forced decarburization stage of the VOD furnace is 0.15-0.2 Nm 3 / min.t, and the VOD furnace has a forced oxygen blowing decarburization time of 8 to 15 minutes.
8. The method for reducing the smelting cost of austenitic stainless steel according to claim 1, characterized in that: The natural decarburization time in the VOD furnace is 15 to 25 minutes.
9. The method for reducing the smelting cost of austenitic stainless steel according to claim 1, characterized in that: The reduction desulfurization time of the VOD furnace is 15 to 25 minutes.
10. The method for reducing the smelting cost of austenitic stainless steel according to claim 1, characterized in that: The soft blowing time of the VOD furnace after breaking air is 10 to 20 minutes.