Low-cost 200 series stainless steel smelting process

Abstract

The invention belongs to the technical field of stainless steel smelting, and relates to a low-cost 200 series stainless steel smelting process, comprising the following steps: adding nickel iron water from a small blast furnace into a pretreatment furnace; performing desiliconization blowing in the pretreatment furnace, adding lime to make slag during the blowing process, adding high-carbon ferrochrome to the pretreatment furnace for temperature adjustment, and stopping the desiliconization blowing after the desiliconization is completed; adding ferrochrome into an alloy melting furnace and melting it, and adding the ferrochrome water into a premelting tank; hoisting the premelting tank connected with the ferrochrome water to the pretreatment furnace, and pouring the ferrochrome water into the premelting tank with slag; hoisting the premelting tank to a slag removal station, performing strong stirring treatment by top blowing inert gas, reducing the chromium in the premelting tank by using silicon in the ferrochrome water, and removing the slag in the premelting tank after the reduction is completed; and adding the stainless steel mother liquor after the slag removal treatment into an AOD furnace for stainless steel refining treatment. The present invention combines the smelting processes of a pretreatment furnace, an alloy melting furnace and a slag removal station, reduces the silicon content of stainless steel mother liquor entering the AOD furnace, saves oxygen consumption in desiliconization in the AOD furnace link, improves the chromium recovery rate of the entire process, and reduces the production cost of 200 series stainless steel smelting.

Description

Technical Field

[0001] The invention belongs to the technical field of stainless steel smelting, and relates to a low-cost 200 series stainless steel smelting process. Background Art

[0002] The production process of 200 series stainless steel using nickel iron water from a small blast furnace as raw material makes full use of the physical heat of nickel iron water from a small blast furnace to avoid energy loss; at the same time, since the nickel content of nickel iron water from a small blast furnace is close to that of 200 series stainless steel, and the molten iron contains some chromium, the use of nickel iron water from a small blast furnace to smelt 200 series stainless steel can save the amount of nickel and chromium alloys used in subsequent smelting, which has cost advantages. However, due to the high Si content in nickel iron water from a small blast furnace, the operation difficulty of AOD is increased. In order to ensure the stability of subsequent AOD furnace smelting, it is considered to configure a pretreatment furnace in the process, first desiliconize the nickel iron water from a small blast furnace, and then add it to the AOD furnace for smelting. However, during the desiliconization pretreatment process of the pretreatment furnace, the chromium in the nickel iron water from the small blast furnace will be oxidized and enter the slag at the same time. In order to increase the recovery rate of chromium in the molten iron, a reduction period is usually set after the desiliconization of the pretreatment furnace is completed to reduce the chromium in the slag and increase the recovery rate of chromium in the pretreatment link. In the existing process scheme, ferrosilicon is often used as a reducing agent in the reduction period of the pretreatment furnace. Although this process reduces the chromium in the molten iron that is oxidized during the desiliconization process of the low-nickel molten iron in the small blast furnace, it increases the consumption of ferrosilicon during the reduction period. At the same time, the silicon in the molten chromium iron added in the alloy melting furnace in the subsequent AOD furnace stage also needs to be desiliconized by blowing oxygen in the AOD furnace.

[0003] In the prior art, the patent application number CN201911182249.8 discloses a pretreatment process and application of chromium-containing low-nickel iron water for 200 series stainless steel production. This method adds chromium-containing low-nickel iron water into the top and bottom double-blowing primary refining furnace, adds solid high-carbon ferrochrome and molten high-carbon ferrochrome water into the primary refining furnace after oxygen desiliconization in the primary refining furnace, and then blows nitrogen or inert gas into the molten pool through the bottom gun of the primary refining furnace for stirring, and uses the silicon in the ferrochrome water to reduce the chromium in the primary refining furnace slag, thereby saving the consumption of ferrosilicon in the reduction period and reducing production costs. This invention also utilizes the chromium in the silicon reduction slag in the molten chromium, but the molten chromium in the alloy melting furnace needs to be added to the primary smelting furnace. The process of adding iron will extend the smelting cycle of the primary smelting furnace. In addition, there is a temperature loss of 30 to 50°C during the process of adding iron in the alloy melting furnace. At the same time, the molten iron in the alloy melting furnace is added from the alloy melting furnace into the pre-melting tank, and then from the pre-melting tank into the primary smelting furnace. After the primary smelting furnace is processed, it is transferred back to the pre-melting tank from the primary smelting furnace. The three tank additions increase metal loss.

[0004] In summary, in order to solve the shortcomings of the existing technology in the process of producing 200 series stainless steel using low-nickel iron water from a small blast furnace as the main raw material, it is urgently necessary to propose a new smelting process to further reduce the production cost of 200 series stainless steel smelting. Summary of the invention

[0005] In view of this, the object of the present invention is to provide a low-cost 200 series stainless steel smelting process, which utilizes silicon in ferrochrome melted by an alloy melting furnace as a reducing agent, thereby eliminating the consumption of ferrosilicon in the reduction period of the pre-treatment furnace. At the same time, the ferrochrome melted by the alloy melting furnace is only added with iron once before entering the AOD furnace (i.e., added from the alloy melting furnace into the pre-melting tank), thereby reducing the temperature loss caused by multiple iron additions and improving the metal recovery rate. In addition, after the silicon in the ferrochrome is consumed as a reducing agent, the stability of the AOD smelting is guaranteed, the oxygen consumption of the desiliconization in the AOD furnace link is reduced, the chromium recovery rate of the whole process is improved, and the production cost of 200 series stainless steel smelting is further reduced.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] A low-cost 200 series stainless steel smelting process comprises the following steps:

[0008] Adding small blast furnace nickel iron water: Add the small blast furnace nickel iron water into the pretreatment furnace;

[0009] Desiliconization and blowing in the pretreatment furnace: Desiliconization and blowing are carried out in the pretreatment furnace. Lime is added to make slag during the blowing process, and high carbon ferrochrome is added to the pretreatment furnace to adjust the temperature. After desiliconization is completed, desiliconization and blowing are stopped;

[0010] Alloy melting furnace melts ferrochrome: add ferrochrome into the alloy melting furnace and melt it, and add the molten ferrochrome into the pre-melting tank;

[0011] Pretreatment furnace iron tapping: The premelting tank with chromium iron water is hoisted to the pretreatment furnace, and the pretreatment furnace iron tapping with slag is poured into the premelting tank and mixed with chromium iron water to form one tank;

[0012] Reduction and slag removal at the slag removal station: The premelt tank is hoisted to the slag removal station and subjected to strong stirring treatment by top blowing of inert gas. The silicon in the molten chromium is used to reduce the chromium in the premelt tank. After the reduction is completed, the slag in the premelt tank is removed;

[0013] AOD furnace stainless steel refining treatment: the stainless steel mother liquor after slagging treatment is added into the AOD furnace for stainless steel refining treatment.

[0014] Furthermore, the composition of the small high-nickel molten iron is C=4.0-5.0%, Si=0.8-1.0%, Mn=0.9-1.0%, P≤0.035%, S≤0.02%, Ni=1.3-1.6%, Cr=4.0-5.0%, the remainder is iron, and the temperature is 1350°C.

[0015] Furthermore, the composition of the molten chromium iron is C=6.0-8.0%, Si=4.0-5.0%, P≤0.03%, S≤0.03%, Cr=49.0-50.0%, the remainder is iron, and the temperature is 1570°C.

[0016] Furthermore, in the step of adding the small blast furnace nickel iron water, the amount of the pretreatment furnace high nickel iron water added is about 680-705 kg / t molten steel.

[0017] Furthermore, desiliconization is carried out through the oxygen lance of the pretreatment furnace, and the oxygen supply intensity is 2.0-2.5Nm 3 / min.t;

[0018] The activity of lime used for slag making is not less than 320, the CaO content in lime is not less than 90%, and the slag making basicity is 2.0-2.5;

[0019] The Cr content in the high carbon ferrochrome used for temperature control is 49% to 50%.

[0020] Furthermore, the desiliconization completion refers to the silicon content of the molten pool in the pretreatment furnace being 0.2% or less.

[0021] Furthermore, the amount of ferrochrome water provided by the alloy melting furnace is 40-50% of the total amount of ferrochrome added required for the production target of 200 stainless steel.

[0022] Furthermore, the stirring intensity of the inert gas in the slag removal station is not less than 0.15Nm 3 / min.t, stirring time shall not be less than 6min.

[0023] Furthermore, in the reduction and slagging steps of the slag removal station, the end of reduction means that the Cr2O3 content in the slag is not higher than 0.3%.

[0024] Furthermore, after the stainless steel refining process is completed, the stainless steel mother liquor is poured into a molten steel tank to complete the smelting.

[0025] The beneficial effects of the present invention are:

[0026] The present invention uses high-nickel molten iron from a small blast furnace as raw material, and mixes it into a pretreatment furnace for desiliconization treatment first. Lime is added during the blowing process to make slag. During the process, part of high-carbon ferrochrome is added through a high-level silo to adjust the temperature. After the desiliconization is completed, the gun is lifted, and no reduction period is set in the pretreatment furnace. During the process, the alloy melting furnace melts the high-carbon molten chromium, and the premelting tank first connects the molten chromium from the alloy melting furnace and then connects to the desiliconized molten iron from the pretreatment furnace. The pretreatment furnace produces steel with slag; the premelting tank is hoisted to the slag removal station, and the top gun is lowered to blow nitrogen and stir, and then the slag in the premelting tank is removed; the stainless steel mother liquor after slag removal is mixed into the AOD furnace for stainless steel refining treatment; this process does not set a reduction period in the pretreatment furnace link, and the steel produced with slag is mixed with the molten chromium from the alloy melting furnace into one tank, a reduction period is set at the slag removal station, and a top gun is set to blow nitrogen to remove the slag. The stainless steel mother liquor is strongly stirred, and the silicon in the ferrochrome water is used to reduce the chromium in the pre-treated slag; the ferrochrome water melted in the alloy melting furnace is only added with iron once before entering the AOD furnace, that is, it is only added from the alloy melting furnace to the pre-dissolving tank, which reduces the temperature loss of iron addition and improves the metal recovery rate. In addition, after the silicon in the ferrochrome water is consumed as a reducing agent, the stability of AOD smelting is guaranteed, the oxygen consumption of desiliconization in the AOD furnace link is reduced, the chromium recovery rate of the whole process is improved, and the production cost of 200 series stainless steel smelting is further reduced.

[0027] 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

[0028] 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:

[0029] Figure 1 The present invention is a process flow chart of a low-cost 200 series stainless steel smelting process.

[0030] Figure numerals: 1-pretreatment furnace oxygen lance; 2-pretreatment furnace; 3-alloy melting furnace; 4-premelting tank; 5-slag removal station top blowing nitrogen lance; 6-slag removal machine; 7-AOD furnace; 8-molten steel tank. DETAILED DESCRIPTION

[0031] 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.

[0032] 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.

[0033] 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.

[0034] See also Figure 1 , is a low-cost 200 series stainless steel smelting process, comprising the following steps:

[0035] Adding small blast furnace nickel iron water: adding small blast furnace nickel iron water into the pretreatment furnace 2;

[0036] Desiliconization and blowing in the pretreatment furnace: Desiliconization and blowing are carried out through the oxygen lance 1 of the pretreatment furnace. Lime is added to make slag during the blowing process, and high-carbon ferrochrome is added to the pretreatment furnace 2 through the high-level silo to adjust the temperature. The lance is removed after desiliconization is completed;

[0037] Alloy melting furnace melts ferrochrome: add ferrochrome into alloy melting furnace 3, and melt it by electricity, and add molten ferrochrome into pre-melting tank 4;

[0038] Pre-treatment furnace iron discharge: the pre-melting tank 4 which has been connected with the molten chromium iron from the alloy melting furnace is hoisted to the pre-treatment furnace 2, and the iron discharged from the pre-treatment furnace with slag is poured into the pre-melting tank 4 and mixed with the molten chromium iron from the alloy melting furnace to form one tank;

[0039] Reduction and slag removal at the slag removal station: the premelting tank 4 is hoisted to the slag removal station, and the slag in the premelting tank 4 is fully reduced by the silicon in the molten chromium using the top blowing nitrogen gun 5 of the slag removal station. After the reduction is completed, the slag in the premelting tank 4 is removed by the slag removal machine 6;

[0040] AOD furnace stainless steel refining treatment: the stainless steel mother liquor after slagging treatment is added into the AOD furnace 7 for stainless steel refining treatment, and after the stainless steel refining treatment is completed, it is poured into the molten steel tank 8.

[0041] Furthermore, small blast furnace nickel iron water is used as the main raw material, and the composition of the small high-nickel iron water is C=4.0-5.0%, Si=0.8-1.0%, Mn=0.9-1.0%, P≤0.035%, S≤0.02%, Ni=1.3-1.6%, Cr=4.0-5.0%, and the balance is iron, and the temperature is controlled to be 1350°C.

[0042] The composition of the molten chromium in the alloy melting furnace is C=6.0-8.0%, Si=4.0-5.0%, P≤0.03%, S≤0.03%, Cr=49.0-50.0%, and the remainder is iron. The temperature of melting the molten chromium in the alloy melting furnace is 1570°C.

[0043] In the step of adding small blast furnace nickel iron water, the amount of the pretreatment furnace high nickel iron water added is about 680-705 kg / t molten steel.

[0044] During the desiliconization blowing stage of the pretreatment furnace, the oxygen supply intensity of the oxygen lance is 2.0-2.5 Nm 3 / min.t; the activity of lime used in the pretreatment furnace is not less than 320, and the CaO content in the lime is not less than 90%; the slag basicity of the pretreatment furnace is 2.0-2.5.

[0045] Specifically, the desiliconization is completed when the silicon content in the molten pool is 0.2% or less; the pretreatment furnace is provided with bottom blowing and stirring, and the inert gas used is N2. The Cr content in the high carbon ferrochrome is 49% to 50%.

[0046] The amount of ferrochrome water provided by the alloy melting furnace is 40-50% of the total amount of ferrochrome added required for the production target of 200 stainless steel; the inert gas used for stirring in the slag removal station is N2.

[0047] The stirring intensity of the inert gas in the slag removal station is not less than 0.15Nm 3 / min.t, the stirring time is not less than 6min; the end of reduction at the slag removal station means that the Cr2O3 content in the slag is not higher than 0.3%.

[0048] Specifically, the oxygen supply intensity of the desiliconization oxygen gun of the pretreatment furnace is 2.0-2.5 Nm 3 / min.t, lime is added to slag during the desiliconization process, and the slag basicity is 2.0-2.5. In order to prevent the pretreatment furnace from heating up too quickly, high carbon ferrochrome is added to adjust the temperature during the desiliconization process. When the silicon content in the molten pool is lower than 0.2%, the gun is lifted, and the pretreatment furnace does not have a reduction period; during the process, the alloy melting furnace melts the high carbon chromium iron water, the premelting tank first connects the chromium iron water of the alloy melting furnace and then connects the desiliconized iron water of the pretreatment furnace, and the pretreatment furnace taps the steel with slag; the premelting tank is hoisted to the slag removal station, and the top gun is lowered to blow nitrogen for stirring, and the stirring intensity is not less than 0.15Nm 3 / min.t, the stirring time is not less than 6min, so as to fully reduce the chromium in the slag, and then remove the slag in the pre-melting tank; the stainless steel mother liquor after slag removal is added to the AOD furnace 7 for the next step of stainless steel refining treatment, and after the stainless steel refining treatment is completed, it is poured into the molten steel tank.

[0049] 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 low-cost 200 series stainless steel smelting process, characterized in that: The following steps are involved: Adding small blast furnace nickel iron water: Add the small blast furnace nickel iron water into the pretreatment furnace; Desiliconization and blowing in the pretreatment furnace: Desiliconization and blowing are carried out in the pretreatment furnace. Lime is added to make slag during the blowing process, and high carbon ferrochrome is added to the pretreatment furnace to adjust the temperature. After desiliconization is completed, desiliconization and blowing are stopped; Alloy melting furnace melts ferrochrome: add ferrochrome into the alloy melting furnace and melt it, and add the molten ferrochrome into the pre-melting tank; Pretreatment furnace iron tapping: The premelting tank with chromium iron water is hoisted to the pretreatment furnace, and the pretreatment furnace iron tapping with slag is poured into the premelting tank and mixed with chromium iron water to form one tank; Reduction and slag removal at the slag removal station: The premelt tank is hoisted to the slag removal station and subjected to strong stirring treatment by top blowing of inert gas. The silicon in the molten chromium is used to reduce the chromium in the premelt tank. After the reduction is completed, the slag in the premelt tank is removed; AOD furnace stainless steel refining treatment: the stainless steel mother liquor after slagging treatment is added into the AOD furnace for stainless steel refining treatment.

2. The low-cost 200 series stainless steel smelting process according to claim 1, characterized in that: The composition of the small high-nickel iron water is C=4.0-5.0%, Si=0.8-1.0%, Mn=0.9-1.0%, P≤0.035%, S≤0.02%, Ni=1.3-1.6%, Cr=4.0-5.0%, the remainder is iron, and the temperature is 1350°C.

3. The low-cost 200 series stainless steel smelting process according to claim 1, characterized in that: The molten chromium iron has the following components: C=6.0-8.0%, Si=4.0-5.0%, P≤0.03%, S≤0.03%, Cr=49.0-50.0%, the remainder being iron, and the temperature is 1570°C.

4. The low-cost 200 series stainless steel smelting process according to claim 1, characterized in that: In the step of adding small blast furnace nickel iron water, the amount of the pretreatment furnace high nickel iron water added is about 680-705 kg / t molten steel.

5. The low-cost 200 series stainless steel smelting process according to claim 1, characterized in that: Desiliconization blowing is carried out through the oxygen lance of the pretreatment furnace, and the oxygen supply intensity is 2.0~2.5Nm 3 / min.t; The activity of lime used for slag making is not less than 320, the CaO content in lime is not less than 90%, and the slag making basicity is 2.0-2.5; The Cr content in the high carbon ferrochrome used for temperature control is 49% to 50%.

6. The low-cost 200 series stainless steel smelting process according to claim 1, characterized in that: The desiliconization completion means that the silicon content in the molten pool of the pretreatment furnace is 0.2% or less.

7. The low-cost 200 series stainless steel smelting process according to claim 1, characterized in that: The amount of ferrochrome water provided by the alloy melting furnace is 40-50% of the total amount of ferrochrome added required for the production target of 200 stainless steel.

8. The low-cost 200 series stainless steel smelting process according to claim 1, characterized in that: The stirring intensity of the inert gas in the slag removal station is not less than 0.15Nm 3 / min.t, stirring time shall not be less than 6min.

9. The low-cost 200 series stainless steel smelting process according to claim 1, characterized in that: In the reduction and slagging steps of the slag removal station, the end of reduction means that the Cr2O3 content in the slag is not higher than 0.3%.

10. The low-cost 200 series stainless steel smelting process according to claim 1, characterized in that: After the stainless steel refining process is completed, the stainless steel mother liquor is poured into the molten steel tank to complete the smelting.

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