Method for smelting low-phosphorus low-cobalt stainless steel by using high-slag-content ferronickel in electric furnace
Through the electric furnace high-slag nickel-iron double-slag deep dephosphorization process, the problem of dephosphorization in high-slag nickel-iron electric furnace is solved, and the cheap smelting of low-phosphorus and low-cobalt stainless steel is achieved, and production costs are reduced.
Patent Information
- Application Number
- CN202411272915.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-12
- Publication Date
- 2025-02-11
AI Technical Summary
In the existing low-phosphorus and low-cobalt stainless steel smelting methods, high slag-containing nickel-iron electric furnaces have difficulty dephosphorizing, resulting in waste of resources and high production costs.
The electric furnace high-slag nickel-iron double-slag deep dephosphorization process is adopted. Through step-by-step slag production and deep oxidation dephosphorization, carbon scrap steel bottoming and high-slag nickel-iron iron as the main raw materials, the smelting of low-phosphorus and low-cobalt stainless steel is achieved.
The electric furnace has been able to use cheap, high slag-containing nickel and iron resources to smel low-phosphorus and low-cobalt stainless steel, which has reduced production costs and solved the problem of dephosphorization of electric furnaces.
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Abstract
Description
Technical Field
[0001] The invention relates to a stainless steel smelting method in the field of metallurgy, and in particular to a method for smelting low-phosphorus and low-cobalt stainless steel by using a high-slag ferronickel furnace. Background Art
[0002] At present, the production process of low-phosphorus and low-cobalt stainless steel generally uses converter dephosphorized molten iron + alloy melting furnace pre-melt production. The steelmaking raw materials of this process mainly use molten iron and pure nickel, resulting in high costs. The use of converters to smelt dephosphorized molten iron does not meet the requirements of low-carbon emission reduction. Another method of smelting low-phosphorus and low-cobalt stainless steel is to use electric furnaces to melt slag-free nickel iron, scrap steel, nickel pig iron and other materials. This method must use slag-free materials and low-cobalt nickel pig iron, which are limited in resources and expensive. When using high-slag materials, the electric furnace has serious slag sticking in the furnace and cannot be smelted, let alone dephosphorized.
[0004] High-slag-content nickel-ferro has the advantages of low price and low cobalt content, while electric furnace, as the core equipment for smelting stainless steel, has the advantages of low cost, low carbon, environmental protection and stable quality. If the advantages of the two can be combined, the problem of difficulty in dephosphorization in electric furnace caused by high-slag-content nickel-ferro slag (>26%) can be solved, and a high-slag-content nickel-ferro double-slag deep dephosphorization process in electric furnace can be developed to produce low-phosphorus and low-cobalt stainless steel, which can solve the problem of high cost and resource limitation of low-phosphorus and low-cobalt stainless steel.
[0005] The purpose of the present invention is to provide a method for deep dephosphorization of high-slag nickel-iron double slag in an electric furnace, so as to realize the use of cheap high-slag nickel-iron resources to produce low-phosphorus and low-cobalt stainless steel in the electric furnace smelting process, thereby reducing the production cost of stainless steel. Summary of the invention
[0006] The purpose of the present invention is to solve the above problems and provide a method for smelting low-phosphorus and low-cobalt stainless steel using high-slag ferronickel in an electric furnace.
[0007] The object of the present invention is achieved in this way: a method for smelting low-phosphorus and low-cobalt stainless steel using high-slag nickel-iron in an electric furnace, comprising the following steps: step one: charging: loading carbon scrap steel with a size of less than 1.2 meters, high-slag nickel-iron, and dust ash balls into the electric furnace in two baskets, and the basket loading requirements are: loading 10-20t of carbon scrap steel into the first basket for bottom laying, loading 40%-60% of high-slag nickel-iron, loading 10-20t of carbon scrap steel into the second basket, and loading all the remaining high-slag nickel-iron, loading 10-15t of dust ash balls, lifting the loaded baskets with a crane and adding them to the electric furnace, and rotating and covering the electric furnace cover after the charging is completed; step two: smelting: after power is supplied to the material to melt, use the furnace door oxygen gun to blow oxygen to assist melting, and start slag discharge from the slag door: adopt the electric furnace double slag dephosphorization process, that is, step-by-step slag making, the first step of the electric furnace Arcing is started at gear 1-4, voltage is 800-850V, current is 60-70KA, after stabilization, voltage increases to 900-950V, current is 70-80KA, no lime is added during the heating process, ferrosilicon is added according to the target silicon content of 1.0-1.2%, 20-30kg / t of red mud balls are added to slag, and 20-30kg / t of coke is added. After all the materials are loaded, the temperature continues to rise and slag is molten. The slag in the furnace is ensured to be clear. The power consumption per ton of steel is 250-350kwh / t to start slag discharge, and the target is to discharge 60-80% of the slag; after slag discharge, the electric furnace conducts secondary slag making: the second step of the electric furnace secondary slag making, add 20-25kg / t of lime, 5-8kg / t of coke, 8-12kg / t of red mud balls, after the slag is electrified, the furnace door manipulator blows oxygen for dephosphorization, and the oxygen supply intensity is 40-60Nm 3 / min, slag basicity is controlled at 1.2-1.6%, FeO in slag is controlled at 10-20%, phosphorus content of melt in electric furnace is ≤0.005%; the third step is steel is discharged from tapping port, slag is mixed out, and AOD is added after slag is removed at slag removal station.
[0008] High-slag-content nickel-iron is a high-slag-content nickel-iron with a slag content of 20%-40%. The carbon scrap steel at the bottom of the electric furnace is used, and the high-slag-content nickel-iron is used according to 80%-90% of the total material.
[0009] The beneficial effects of the present invention are as follows: the present invention makes full use of the electric furnace double slag deep dephosphorization process to achieve the purpose of reducing the smelting cost of low-phosphorus and low-cobalt stainless steel by using a large amount of cheap high-slag nickel-iron resources in the electric furnace. DETAILED DESCRIPTION
[0010] Traditional low-phosphorus stainless steel adopts the smelting process of "converter dephosphorized hot metal + alloy melting furnace-AOD". The steelmaking raw materials of this process mainly use hot metal and pure nickel, which leads to its high cost. The use of converter to smelt dephosphorized hot metal also has the problem of high carbon emissions. The existing electric furnace smelting low-phosphorus stainless steel process uses raw materials such as slag-free ferronickel, nickel pig iron, scrap steel, etc., which has the problems of high raw material prices and high cobalt content, and the process cannot solve the problems of serious slag sticking and difficult dephosphorization of high-slag ferronickel. The present invention is aimed at high-slag ferronickel resources with low price and low cobalt content (slag content>26%, cobalt content<0.30%), and develops an electric furnace high-slag ferronickel double slag deep dephosphorization process to produce low-phosphorus and low-cobalt stainless steel. A small amount of carbon scrap steel is used as the bottom of the electric furnace, and high-slag nickel-ferro is used as the main raw material (the usage accounts for more than 85% of the charging amount). Through the electric furnace double slag dephosphorization process, that is, step-by-step slag making, the early optimization of the power supply curve and the slag making system are used to standardize the slag dumping, and the later dephosphorization slag system is oxidized and deeply dephosphorized through carbon steel red mud balls and furnace door oxygen supply, so as to stably achieve the phosphorus content of the melt in the electric furnace ≤ 0.005%, and the cobalt content < 0.30%, so as to achieve the purpose of smelting low-phosphorus and low-cobalt stainless steel with low-cost and high-slag nickel-ferro.
[0011] The invention discloses a method for deep dephosphorization of double slag of nickel and iron in an electric furnace with high slag content. The electric furnace smelting process comprises: charging of electric furnace - heating of electric furnace - slag making of electric furnace - slag discharge of electric furnace - secondary slag making of electric furnace - oxygen blowing dephosphorization of electric furnace - mixing of slag and steel in electric furnace - slag removal at slag removal station - pre-melt mixing in alloy melting furnace - AOD steel mixing. The electric furnace smelting process uses a large amount of cheap high slag content nickel and iron resources. Through the double slag dephosphorization process of the electric furnace, i.e., slag making in steps, optimization of power supply curve and slag making system and slag removal in early stage, 80% of slag is poured into the slag pot, lime and ferrosilicon are added again in the later stage to make a dephosphorization slag system, and deep oxidative dephosphorization is carried out through oxygen supply of carbon steel red mud balls and furnace door, so as to stably achieve that the phosphorus content of the melt in the electric furnace is ≤0.005%.
[0012] The technical scheme of the present invention is as follows: the process method for deep dephosphorization of double slag of nickel and iron in high slag content in an electric furnace of the present invention comprises the following steps: charging the electric furnace - heating the electric furnace - slagging the electric furnace - slagging the electric furnace - secondary slagging the electric furnace - oxygen blowing and dephosphorization of the electric furnace - mixing the slag and steel in the electric furnace - slagging at a slagging station - mixing the pre-melted liquid in an alloy melting furnace - mixing AOD with steel; lifting the basket loaded with scrap steel and nickel and iron with a crane and then adding it to the electric furnace; after the charging is completed, the electric furnace cover is rotated and covered, the electrode is lowered for heating, and fluorite, coke and silicon are added at the same time. Iron slag making, after power is supplied to the material to melt, oxygen is blown through the furnace door oxygen lance to assist melting, and slag is discharged from the slag door. Due to the large amount of slag in nickel iron, 60%-80% of the slag in the furnace should be discharged for the purpose of slag removal. After slag discharge, lime and fluorite are added to the electric furnace for secondary slag making. After slag making, oxygen dephosphorization is started. After sampling to confirm that the P component is appropriate, the electric furnace slag and steel are mixed into the ladle, and the ladle is hoisted to the slag removal station to remove the oxidized slag. After slag removal, the ladle is hoisted to the AOD and mixed with the pre-melted liquid of the alloy melting furnace into the AOD for smelting.
[0013] The process parameters of power supply, oxygen blowing, material addition and slag making for the electric furnace smelting process are as follows: (a) Carbon scrap steel, high slag content nickel iron, dust ash briquette and other raw materials that meet the furnace loading requirements are divided into two baskets and loaded into the electric furnace. All carbon scrap steel is used as the bottom and 60% of the high slag content nickel iron is loaded into the first basket.
[0014] (II) Smelting process: The first step is to start the arc at gear 4 of the electric furnace, with a voltage of 848V and a current of 66KA. After stabilization, the voltage is increased to 946V and the current is 73KA. No lime is added during the heating process. Ferrosilicon is added according to the target silicon content of 1.0-1.2%. 25kg / t of red mud balls are added during the slag-forming process, and 25kg / t of coke is added. After all the materials are loaded, the temperature is continued to form slag. During the process, priority is given to ensuring that the slag in the furnace is melted clean to avoid severe slag sticking that cannot be smelted. The power consumption per ton of steel is 300kwh / t, and slag is discharged starting from the time of slag discharge, with the goal of releasing 80% of the slag.
[0015] The second step is secondary slag making in the electric furnace, adding 20kg / t of lime, 5kg / t of coke, and 8kg / t of red mud balls. After the slag is electrified, the furnace door manipulator blows oxygen for dephosphorization. The optimal oxygen supply intensity is 40-60Nm3 / min, the slag basicity is controlled at 1.2-1.6%, and the FeO in the slag is controlled in the range of 10-20%.
[0016] In the third step, steel is discharged from the tapping port, slag is mixed out, and the slag is removed at the slag removal station before adding into AOD.
[0017] The low-phosphorus and low-cobalt nickel steel has been changed from the original electric furnace melting slag-free nickel iron and nickel pig iron dephosphorization process to the use of high-slag nickel iron with a slag content of >26%, and the electric furnace high-slag nickel iron double slag deep dephosphorization process technology has been developed. The electric furnace uses a large amount of high-slag nickel iron with carbon scrap steel as the bottom, and adopts the electric furnace double slag dephosphorization process, that is, step-by-step slag making, optimizing the power supply curve and slag making system in the early stage, and pouring 80% of the slag into the slag pot. Later, lime and ferrosilicon are added to make a dephosphorization slag system, and deep oxidation dephosphorization is carried out through carbon steel red mud balls and furnace doors to supply oxygen, so as to stably achieve a phosphorus content of ≤0.005% in the melt in the electric furnace; measures are formulated to prevent slag sticking to the furnace wall and difficulty in slag melting caused by excessive slag in the electric furnace.
[0018] The method of the high-slag nickel-iron double slag deep dephosphorization process of the electric furnace described in the present invention requires thermodynamic theoretical research on the composition of high-slag nickel-iron slag and the influencing factors and influencing mechanisms of the electric furnace slag making and dephosphorization process in order to use cheap high-slag nickel-iron. The composition of high-slag nickel-iron slag is shown in the following table.
[0019] CaO <![CDATA[SiO 2 ]]> <![CDATA[Al 2 THE 3 ]]> TFe Alkalinity 30.2％ 13.0％ 9.1％ 23.6％ 2.3
[0020] The composition of high-slag ferronickel slag is close to that of converter slag, which is highly oxidized alkaline slag. According to this composition, the early slag making system of the electric furnace is adjusted, and some ferrosilicon is added to deoxidize and reduce the alkalinity. No lime is added to achieve the purpose of rapid slag formation, which is conducive to pouring out a large amount of slag. Because the slag content of ferrosilicon is >26%, the amount of slag in the early furnace is >40t, and poor slag removal will cause smelting failure, so slag removal is necessary. After testing, it was found that the amount of ferrosilicon added in the early stage was controlled according to the silicon content of 1.0%-1.2%, which can control the slag alkalinity to 1.0-1.2, the slag has good fluidity, and the slag pouring effect is good.
[0021] After slag pouring, re-slag dephosphorization is carried out. According to the lime dephosphorization reaction, carbon-oxygen reaction Gibbs free energy curve, etc., under the steelmaking temperature, only in the lower temperature range (1578-1684K) will P be preferentially oxidized to C. Therefore, in order to meet the preferential oxidation of P, excessively high temperature should be avoided to reduce the dephosphorization rate. However, if the temperature is too low, the fluidity of the mother liquor and slag will be poor, which is not conducive to dephosphorization. Through experiments on the main factors affecting the dephosphorization reaction, such as mother liquor temperature, carbon content, oxygen supply intensity, slag alkalinity and oxidizability, it was found that in order to meet the target of P content <0.010%, the carbon content should be greater than 1.0%, and the temperature should be controlled at 1440-1550℃. By studying the effects of oxygen potential and slag on the dephosphorization reaction, combined with a large number of production practices, it is clear that the optimal oxygen supply intensity for dephosphorization is 40-60Nm 3 / min range, slag basicity is controlled in the range of 1.2-1.6%, and FeO in the slag is controlled in the range of 10-20%, which can achieve efficient dephosphorization.
[0022] Based on the above research results, a high-slag nickel-iron double slag deep dephosphorization process technology for electric furnaces has been developed. The electric furnace uses a maximum of high-slag nickel-iron and carbon scrap steel as the bottom, and adopts an electric furnace double slag dephosphorization process, i.e., step-by-step slag making. The power supply curve and slag making system are optimized in the early stage to standardize slag pouring, and 80% of the slag is poured into the slag pot. In the later stage, lime and ferrosilicon are added again to make a dephosphorization slag system, and deep oxidative dephosphorization is carried out through carbon steel red mud balls and furnace door oxygen supply, so as to stably achieve a phosphorus content of ≤0.005% in the melt in the electric furnace.
[0023] Example
[0024] The specific implementation method of the method for deep dephosphorization of high-slag nickel-iron double slag in electric furnace is described in detail below with reference to the embodiments.
[0025] The following table lists the key parameter examples of the present invention for smelting low-phosphorus stainless steel using a large amount of cheap chromium-nickel materials in a 160t electric furnace. However, the specific implementation of the method of the high-slag nickel-iron double slag deep dephosphorization process in the electric furnace is not limited to the following embodiments.
[0026] Example 1
[0027] Table 1 Material structure and P content of Z2CN18-10 steel in 160t electric furnace
[0028]
[0029] (1) Carbon scrap steel with a size of less than 1.2 meters, high-slag nickel iron, and dust ash briquette are loaded into the electric furnace in two baskets. The loading requirements of the baskets are: the first basket is loaded with 10.2 tons of carbon scrap steel and 78.0 tons of high-slag nickel iron, and the second basket is loaded with 12.0 tons of carbon scrap steel, 52.1 tons of high-slag nickel, and 10 tons of dust ash briquette;
[0030] (2) Smelting process: In the first step, the arc is started at the third gear of the electric furnace, the voltage is 810V, and the current is 65KA. After stabilization, the voltage is increased to 946V and the current is 73KA. No lime is added during the heating process. Ferrosilicon is added according to the target silicon content of 1.0%. During the process, 21kg / t of red mud balls are added to slag. Coke is added at 22kg / t. After all the materials are loaded, the temperature is continued to slag. During the process, the slag in the furnace is melted. The power consumption per ton of steel is 310kwh / t. Slag is discharged and 80% of the slag is discharged. In the second step, the electric furnace is secondary slag-making, 21kg / t of lime is added, 5kg / t of coke and 8kg / t of red mud balls are added. After the slag is electrified, the furnace door manipulator blows oxygen for dephosphorization. The oxygen supply intensity is 50Nm 3 / min, slag basicity is controlled at 1.2, and FeO in slag is controlled within 10%; in the third step, steel is discharged from the tapping port, steel slag is mixed out, and AOD is added after slagging.
[0031] Example 2
[0032] Table 2 Material structure and P content of Z2CN18-10 steel in 160t electric furnace
[0033]
[0034] (1) Carbon scrap steel with a size of less than 1.2 meters, high-slag nickel iron, and dust ash briquette are loaded into the electric furnace in two baskets. The loading requirements of the baskets are: the first basket is loaded with 10.0 tons of carbon scrap steel and 65.0 tons of high-slag nickel iron, and the second basket is loaded with 10.0 tons of carbon scrap steel, 64.7 tons of high-slag nickel, and 10 tons of dust ash briquette;
[0035] (2) Smelting process: In the first step, the arc is started at the 2nd gear of the electric furnace, the voltage is 800V, and the current is 62KA. After stabilization, the voltage is increased to 940V and the current is 70KA. No lime is added during the heating process. Ferrosilicon is added according to the target silicon content of 1.1%. During the process, 22kg / t of red mud balls are added to slag. Coke is added at 22kg / t. After all the materials are loaded, the temperature is continued to slag. During the process, the slag in the furnace is melted. The power consumption per ton of steel is 305kwh / t. Slag is discharged and 70% of the slag is discharged. In the second step, the electric furnace is secondary slag-making, 20kg / t of lime is added, 5kg / t of coke and 8kg / t of red mud balls are added. After the slag is electrified, the furnace door manipulator blows oxygen for dephosphorization. The oxygen supply intensity is 50Nm3 / min, slag basicity is controlled at 1.3, and FeO in slag is controlled at 11%; in the third step, steel is discharged from the tapping port, steel slag is mixed out, and AOD is added after slagging.
[0036] Example 3
[0037] Table 3 Material structure and P content of Z2CN18-10 steel in 160t electric furnace
[0038]
[0039] (1) Carbon scrap steel with a size of less than 1.2 meters, high-slag nickel iron, and dust ash briquette are loaded into the electric furnace in two baskets. The loading requirements of the baskets are: the first basket is loaded with 10.3 tons of carbon scrap steel and 65.0 tons of high-slag nickel iron, and the second basket is loaded with 10.5 tons of carbon scrap steel, 64.1 tons of high-slag nickel, and 10 tons of dust ash briquette;
[0040] (2) Smelting process: In the first step, the arc is started at the third gear of the electric furnace, the voltage is 811V, the current is 66KA, and after stabilization, the voltage is increased to 947V and the current is 75KA. No lime is added during the heating process, and ferrosilicon is added according to the target silicon content of 1.2%. During the process, 22kg / t of red mud balls are added to slag, and 21kg / t of coke is added. After all the materials are loaded, the temperature is continued to slag. During the process, the slag in the furnace is melted and the power consumption per ton of steel is 315kwh / t. Slag is discharged and 80% of the slag is discharged; in the second step, the electric furnace is secondary slag-making, 20kg / t of lime is added, 6kg / t of coke and 8kg / t of red mud balls are added. After the slag is electrified, the furnace door manipulator blows oxygen for dephosphorization, and the oxygen supply intensity is 50Nm 3 / min, slag basicity is controlled at 1.3, and FeO in slag is controlled within 10%; in the third step, steel is discharged from the tapping port, steel slag is mixed out, and AOD is added after slagging.
[0041] Comparative Example
[0042] Table 4 Material structure and P content of Z2CN18-10 steel in 160t electric furnace
[0043]
[0044] The above description is only a specific embodiment of the present invention, but the structural features of the protection scope of the present invention are not limited thereto. Any changes or modifications made by any technician in the field of the present invention are all covered by the patent scope of the present invention.
Claims
1. A method for smelting low-phosphorus and low-cobalt stainless steel using high-slag ferronickel in an electric furnace, characterized in that: The following steps are involved: Step 1: Loading: Load carbon scrap steel with a size of less than 1.2 meters, high-slag nickel-iron, and dust ash briquette into the electric furnace in two baskets. The requirements for loading the baskets are as follows: Load 10-20t of carbon scrap steel in the first basket for bottom laying, 40%-60% of high-slag nickel-iron, 10-20t of carbon scrap steel in the second basket, and all the remaining high-slag nickel-iron, 10-15t of dust ash briquette, lift the loaded baskets with an overhead crane and add them to the electric furnace. After the loading is completed, rotate and cover the electric furnace cover; Step 2: Smelting: After the power is supplied to the material to melt, oxygen is blown to assist melting using the furnace door oxygen lance, and slag is discharged from the slag door: the electric furnace double slag dephosphorization process is adopted, that is, step-by-step slag making, the first step is arc starting at the electric furnace gear 1-4, the voltage is 800-850V, the current is 60-70KA, and after stabilization, the voltage is increased to 900-950V, the current is 70-80KA, no lime is added during the heating process, and ferrosilicon is added according to the target silicon content of 1.0-1.2%, and red mud balls are added in the process. 20-30kg / t of slag, coke Carbon is added at 20-30kg / t. After all materials are loaded, the temperature continues to rise and slag is melted. The process ensures that the slag in the furnace is melted clean. The power consumption per ton of steel is 250-350kwh / t to start slag discharge, and the goal is to release 60-80% of the slag. After slag discharge, the electric furnace conducts secondary slag making: In the second step, the electric furnace conducts secondary slag making, adding 20-25kg / t of lime, 5-8kg / t of coke, and 8-12kg / t of red mud balls. After the slag is electrified, the furnace door manipulator blows oxygen for dephosphorization, and the oxygen supply intensity is 40-60Nm 3 / min, slag basicity is controlled at 1.2-1.6%, FeO in slag is controlled at 10-20%, and phosphorus content of melt in electric furnace is ≤0.005%; in the third step, steel is discharged from tapping port, slag is mixed out, and AOD is added after slag removal at slag removal station.
2. The method of the electric furnace high slag nickel-iron double slag deep dephosphorization process according to claim 1, characterized in that: High-slag-content nickel-iron is a high-slag-content nickel-iron with a slag content of 20%-40%. The carbon scrap steel at the bottom of the electric furnace is used, and high-slag-content nickel-iron is used at 80%-90% of the total material.