Method for deep dephosphorization of chromium-nickel pig iron melt smelted in electric furnace

Abstract

The present invention discloses a method for deep dephosphorization of a chromium-nickel pig iron melt in an electric furnace, comprising: charging the chromium-nickel pig iron into an electric furnace and melting it into a chromium-nickel pig iron pre-melt; after the electric furnace is smelted clean, desiliconizing and dechromizing, adding a solid dephosphorizing agent, supplying oxygen through a furnace door oxygen lance, and adding lime to form slag; after stopping desiliconization and dechromization, skimming the slag and conducting electric furnace deep dephosphorization, adding a solid dephosphorizing agent, continuing to supply oxygen through the furnace door oxygen lance, spraying a powdered dephosphorizing agent through the electric furnace carbon powder lance, and adding lime to form slag; after completing the electric furnace deep dephosphorization, switching the furnace door oxygen lance to nitrogen for strong stirring. The present invention solves the technical problem of high cost caused by the difficulty of electric furnace dephosphorization of the chromium-nickel pig iron melt, which results in the need to use dephosphorized molten iron + pure nickel in stainless steel smelting. The present invention achieves the purpose of using cheap chromium-nickel pig iron as a raw material to prepare a low-phosphorus, high-nickel stainless steel mother liquor through electric furnace deep dephosphorization, and then producing a low-phosphorus special stainless steel variety by adding high-carbon ferrochrome to the low-phosphorus, high-nickel stainless steel mother liquor, thereby simplifying the production process and reducing smelting costs.

Description

Technical Field

[0001] The invention belongs to the technical field of stainless steel production, and in particular relates to a method for deep dephosphorization of chromium-nickel pig iron melt produced by electric furnace smelting. Background Art

[0002] Phosphorus is generally considered a harmful element in stainless steel. It has adverse effects on the steel's surface quality, cracking, ductility, tensile strength, pitting corrosion resistance, stress corrosion resistance, and weldability. It is particularly harmful due to cold brittleness at low temperatures. Therefore, further reducing the phosphorus content in stainless steel, smelting low-phosphorus and ultra-low-phosphorus stainless steels, and improving steel properties remain one of the development trends in stainless steel production.

[0003] As a corrosion-resistant, beautiful and recyclable green steel, stainless steel is increasingly used in special fields such as photovoltaics, nuclear power, fine strips, welding wires, etc., which puts higher requirements on the variety and quality of stainless steel. Some steel grades require the P content in the steel to be ≤ 0.015%. Therefore, in the production process, it is necessary to use pre-treated deep dephosphorized molten iron or ultra-low phosphorus scrap steel and add high-purity pure nickel (nickel plate, nickel bean) alloy. As a result, the smelting process of these stainless steel varieties is complicated and the manufacturing cost is high.

[0004] With the widespread adoption of the RKEF (Rotary Klin Electric Furnace) process for producing chromium-nickel pig iron from laterite nickel ore, the relatively low-priced nickel pig iron has become a primary raw material for stainless steel and is widely used in the production of standard stainless steel, reducing stainless steel smelting costs. However, nickel pig iron contains high levels of residual elements such as phosphorus, sulfur, and silicon, and because it lacks the ability to dephosphorize during stainless steel smelting, this inexpensive chromium-nickel pig iron cannot be used in large quantities in the production of low-phosphorus specialty stainless steel varieties. The production of low-phosphorus specialty stainless steel varieties still relies on blast furnace dephosphorized hot metal combined with pure nickel / high-nickel iron as the primary raw materials, resulting in complex processes and high smelting costs. Summary of the Invention

[0005] In order to solve the above-mentioned technical problems existing in the prior art, the present invention has developed a method for deep dephosphorization of chromium-nickel pig iron melt smelted in an electric furnace. Using cheap chromium-nickel pig iron as raw material, deep dephosphorization in the electric furnace is carried out to produce a stainless steel mother liquor with low phosphorus and high nickel content of P≤0.004%, thereby achieving the purpose of using chromium-nickel pig iron raw materials in batches to produce low-phosphorus special stainless steel varieties with P≤0.015% at low cost.

[0006] The method for deep dephosphorization of chromium-nickel pig iron melt smelted in an electric furnace of the present invention comprises the following steps:

[0007] Step 1: Load chromium-nickel pig iron into an electric furnace and melt the chromium-nickel pig iron to form a chromium-nickel pig iron pre-melt;

[0008] Step 2: After the electric furnace is melted, desiliconization and dechromization operations are carried out. In this process, solid dephosphorization agent is added in batches from the high-level silo of the electric furnace. The total amount of solid dephosphorization agent added per ton of steel is controlled to be 20-25 kg. Oxygen is supplied by the furnace door oxygen lance, and the oxygen flow rate per ton of steel is controlled to be 0.24-0.32 Nm 3 / min; lime is added in batches during the process, and the total amount of lime added is controlled to 15-20kg per ton of steel, to produce desiliconized slag with a basicity of 1.8-2.5. During the smelting process, the electric furnace continuously supplies electrified slag, and the temperature of the molten steel in the electric furnace is controlled at 1420-1480℃;

[0009] Step 3: When Si≤0.02% and Cr≤0.80% in the molten steel, stop desiliconization and dechromization, and perform the electric furnace slag removal operation to remove ≥70% of the desiliconization slag;

[0010] Step 4: After the slagging is completed, the deep dephosphorization operation of the electric furnace is carried out. Solid dephosphorization agent is added in batches from the high-level silo of the electric furnace for multiple times. The total amount of solid dephosphorization agent added per ton of steel is controlled to be 15-18 kg; the oxygen lance at the furnace door continues to supply oxygen, and the oxygen flow rate per ton of steel is controlled to be 0.30-0.38 Nm 3 / min, and simultaneously spray powdered dephosphorization agent into the electric furnace with a carbon powder gun. The carrier gas for the powdered dephosphorization agent is nitrogen, and the nitrogen pressure is controlled at 1.0MPa. During the dephosphorization process, lime is added in batches from a high position, and the total amount of lime added is controlled to be 15-18kg per ton of steel. Dephosphorization slag with a basicity of 5-8 is prepared for deep dephosphorization. During the dephosphorization process, the electric furnace continuously supplies electrified slag, and the molten steel temperature is controlled at 1500-1550℃.

[0011] Step 5: When P in the molten steel is less than or equal to 0.004%, dephosphorization is completed, oxygen lances at the furnace door stop blowing oxygen, and nitrogen is blown for strong stirring. The nitrogen supply flow rate per ton of steel is controlled at 0.35-0.45 Nm 3 / min, stir for 3 to 5 minutes, continue to supply power to the electric furnace to raise the temperature to above 1630℃, remove ≥80% of the dephosphorization slag, and produce low-phosphorus high-nickel stainless steel mother liquor.

[0012] Furthermore, in the above-mentioned method for deep dephosphorization of chromium-nickel pig iron melt smelted in an electric furnace, the solid dephosphorization agent is prepared from converter dust ash, sintered ore and light-burned magnesium powder in a ratio of 70:20:10 by weight, and the composition of the solid dephosphorization agent is controlled as follows: FeOx: 56-70%, CaO: 10-18%, MgO: 3-8%, and SiO2: 1.5-3%.

[0013] Furthermore, in the above-mentioned method for deep dephosphorization of chromium-nickel pig iron melt smelted in an electric furnace, the powdery dephosphorization agent is prepared by lime powder with CaO ≥ 90.0%, fluorite powder with CaF2 ≥ 88.0%, and iron oxide scale powder with FeOx ≥ 95.0% in a ratio of 60:10:30 by weight, and the particle size of the powdery dephosphorization agent is controlled to be 3 to 5 mm.

[0014] Furthermore, in the above-mentioned method for deep dephosphorization of chromium-nickel pig iron melt smelted in an electric furnace, the composition of the desiliconized slag is controlled to be: TFe: 10-15%, CaO: 45-50%, SiO2: 18-20%, MgO: 5-7%, Cr2O3: 8-15%.

[0015] Furthermore, in the above-mentioned method for deep dephosphorization of chromium-nickel pig iron melt smelted in an electric furnace, the composition of the dephosphorization slag is controlled to be: TFe: 18-25%, CaO: 35-45%, SiO2: 5-8%, MgO: 6-9%, and CaF2: 8-10%.

[0016] Furthermore, in the above-mentioned method for deep dephosphorization of chromium-nickel pig iron melt smelted in an electric furnace, in the desiliconization and dechromization operation of step 2, the oxygen pressure is controlled to be 1.0 MPa, and the angle between the furnace door oxygen lance and the molten steel surface is controlled to be 25-30°.

[0017] Furthermore, in the above-mentioned method for deep dephosphorization of chromium-nickel pig iron melt in electric furnace, in the deep dephosphorization operation in step 4, the oxygen pressure is controlled to be 1.0 MPa, and the angle between the furnace door oxygen lance and the molten steel surface is controlled to be 30-40°.

[0018] Furthermore, in the above-mentioned method for deep dephosphorization of chromium-nickel pig iron melt smelted in an electric furnace, the composition of the chromium-nickel pig iron is: C≤3.0%, Si≤2.5%, P≤0.050%, Cr≤4.0%, Ni: 7~15%, and the rest is iron and residual elements.

[0019] The method for deep dephosphorization of chromium-nickel pig iron melt smelted in an electric furnace of the present invention has the following advantages and beneficial effects: the method solves the technical problem of high cost caused by the need to use dephosphorized molten iron + pure nickel in stainless steel smelting due to the difficulty in electric furnace dephosphorization of chromium-nickel pig iron melt, and achieves the purpose of using cheap chromium-nickel pig iron as a raw material to prepare low-phosphorus high-nickel stainless steel mother liquor through deep dephosphorization in an electric furnace, and adding high-carbon ferrochrome to the low-phosphorus high-nickel stainless steel mother liquor to produce a low-phosphorus special stainless steel variety. The smelting of low-phosphorus stainless steel no longer uses blast furnace dephosphorized molten iron, and the blast furnace molten iron production process is eliminated, thereby simplifying the production process and reducing carbon emissions. In addition, since expensive pure nickel is no longer needed, the smelting cost of low-phosphorus stainless steel is reduced, and the method has good promotion value and economic benefits. DETAILED DESCRIPTION

[0020] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0021] The present invention aims to solve the technical problem of high cost caused by the need to use dephosphorized molten iron + pure nickel in stainless steel smelting due to the difficulty in dephosphorizing chromium-nickel pig iron melt in an electric furnace. A method for deep dephosphorization of chromium-nickel pig iron melt in an electric furnace has been developed. The electric furnace uses chromium-nickel pig iron as a raw material to produce a low-phosphorus, high-nickel stainless steel mother liquor with a phosphorus content of 0.004%. The basic process is as follows: the electric furnace uses chromium-nickel pig iron as a raw material to melt to form a chromium-nickel pig iron pre-melt, first desiliconizes and dechromizes, and after desiliconization and dechromization are completed, the desiliconized slag is poured out from the furnace door, and then deep dephosphorization is started to produce the low-phosphorus, high-nickel stainless steel mother liquor.

[0022] Specifically, the method for deep dephosphorization of chromium-nickel pig iron melt from electric furnace smelting of the present invention comprises the following steps:

[0023] (1) An electric furnace is charged with chromium-nickel pig iron, and the chromium-nickel pig iron is melted to form a chromium-nickel pig iron pre-melt, wherein the composition of the chromium-nickel pig iron is: C ≤ 3.0%, Si ≤ 2.5%, P ≤ 0.050%, Cr ≤ 4.0%, Ni: 7-15%, and the rest is iron and residual elements.

[0024] (2) After the electric furnace is melted, desiliconization and dechromization are first carried out. The desiliconization and dechromization are carried out by solid-gas oxidation desiliconization and dephosphorization method. In which, solid dephosphorization agent is added in batches from the high-level material bin of the electric furnace for multiple times. The total amount of solid dephosphorization agent added per ton of steel is controlled to be 20-25 kg. The solid dephosphorization agent is prepared from converter dust, sintered ore and light-burned magnesium powder in a weight percentage ratio of 70:20:10. The composition of the solid dephosphorization agent is: FeOx: 56-70%, CaO: 10-18%, MgO: 3-8%, SiO2: 1.5-3%; oxygen is supplied by the furnace door oxygen gun, the oxygen pressure is controlled to be 1.0 MPa, and the oxygen supply flow rate per ton of steel is controlled to be 0.24-0.32 Nm 3 / min, the angle between the oxygen lance of the furnace door and the liquid surface of the molten steel is controlled at 25-30°; lime is added in batches during the process, and the total amount of lime added is controlled at 15-20 kg per ton of steel, and desiliconized slag with a basicity of 1.8-2.5 is produced. The composition of the desiliconized slag is controlled as follows: TFe: 10-15%, CaO: 45-50%, SiO2: 18-20%, MgO: 5-7%, Cr2O3: 8-15%. During the smelting process, the electric furnace continuously supplies electrified slag to control the temperature of the molten steel in the electric furnace at 1420-1480℃.

[0025] (3) When Si≤0.02% and Cr≤0.80% in the molten steel, stop desiliconization and dechromization, and carry out the electric furnace slag removal operation to remove most of the desiliconization slag, and the proportion of the slag removed to the total slag volume is ≥70%.

[0026] (4) After the slagging is completed, the deep dephosphorization operation of the electric furnace is carried out. Solid dephosphorization agent is added in batches from the high-level silo of the electric furnace for multiple times. The total amount of solid dephosphorization agent added per ton of steel is controlled to be 15-18 kg; the oxygen lance at the furnace door continues to supply oxygen, the oxygen pressure is controlled to be 1.0 MPa, and the oxygen flow rate per ton of steel is controlled to be 0.30-0.38 Nm 3 / min, the angle between the furnace door oxygen gun and the molten steel surface is controlled at 30-40 degrees to enhance the stirring effect of the electric furnace. At the same time, the electric furnace carbon powder gun sprays a powdered dephosphorization agent, which is prepared by lime powder with CaO ≥ 90.0%, fluorite powder with CaF2 ≥ 88.0%, and iron oxide powder with FeOx ≥ 95.0% in a weight percentage ratio of 60:10:30. The particle size of the powdered dephosphorization agent is controlled at 3-5 mm, and the carrier gas for spraying the powdered dephosphorization agent is nitrogen. The pressure is controlled at 1.0 MPa. During the dephosphorization process, lime is added in batches from a high position. The total amount of lime added is controlled to 15-18 kg per ton of steel. Dephosphorization slag with a basicity of 5-8 is used for deep dephosphorization. The composition of the dephosphorization slag is controlled to be: TFe: 18-25%, CaO: 35-45%, SiO2: 5-8%, MgO: 6-9%, CaF2: 8-10%. During the dephosphorization process, the electric furnace continuously supplies electrified slag to control the molten steel temperature at 1500-1550°C.

[0027] (5) When P in molten steel is less than or equal to 0.004%, dephosphorization is terminated, oxygen lance at furnace door stops blowing oxygen, and nitrogen is blown for strong stirring. The nitrogen supply flow rate per ton of steel is controlled at 0.35-0.45 Nm 3 / min, stir for 3 to 5 minutes to promote uniform temperature and composition of the molten steel, continue to power the electric furnace to raise the temperature to above 1630℃, remove the dephosphorization slag, and the slag removal amount accounts for ≥80% of the total slag amount to produce low-phosphorus high-nickel stainless steel mother liquor, which can be subsequently sent to the AOD furnace for refining of low-phosphorus special stainless steel with P≤0.015%.

[0028] The method for deep dephosphorization of chromium-nickel pig iron melt from electric furnace smelting of the present invention is described in detail below in conjunction with specific embodiments of the present invention.

[0029] Example 1

[0030] Example 1 of the present invention is used to melt chromium-nickel pig iron in a 160-ton electric furnace and perform deep dephosphorization in the electric furnace to produce a low-phosphorus, high-nickel stainless steel mother liquor for AOD production of low-phosphorus stainless steel varieties. The specific implementation process is as follows:

[0031] (1) 165 tons of chromium-nickel pig iron is loaded into the electric furnace. The composition of the chromium-nickel pig iron is: C: 2.5%, Si: 1.5%, P: 0.050%, Ni: 15%, Cr: 2.5%, and the rest are iron and residual elements. The electric furnace is powered to melt the chromium-nickel pig iron into a chromium-nickel pig iron pre-melt. After melting, desiliconization and dechromization are first performed. The desiliconization and dechromization operation is performed by solid-gas oxidation desiliconization and dephosphorization method. Among them, solid dephosphorization agent is added in batches from the high-level silo of the electric furnace. The total amount of solid dephosphorization agent added is 3.3 tons. The solid dephosphorization agent is prepared from converter dust, sintered ore and light-burned magnesium powder in a weight percentage ratio of 70:20:10. The composition of the solid dephosphorization agent is: FeOx: 70%, CaO: 18%, MgO: 5%, SiO2: 2%; oxygen is supplied by a furnace door oxygen gun. The oxygen pressure is 1.0 MPa and the oxygen flow rate is 45 Nm 3 / min, the angle between the furnace door oxygen lance and the molten steel surface is 25°; lime is added in batches during the process, and the total amount of lime added is controlled to 3 tons to produce desiliconized slag with a basicity of 1.8-2.5. The desiliconized slag composition is: TFe: 12%, CaO: 48%, SiO2: 19%, MgO: 6%, Cr2O3: 13%. During the smelting process, the electric furnace continuously supplies electrified slag to control the molten steel temperature in the electric furnace at 1420-1450℃.

[0032] (2) When Si≤0.02% and Cr≤0.80% in the molten steel, stop desiliconization and dechromization, and carry out the electric furnace slag removal operation to remove more than 70% of the desiliconization slag.

[0033] (3) After the slagging is completed, the deep dephosphorization operation of the electric furnace is carried out. Solid dephosphorization agent is added in batches from the high-level silo of the electric furnace for multiple times. The total amount of solid dephosphorization agent added is controlled to be 2.9 tons; the oxygen gun at the furnace door continues to supply oxygen, the oxygen pressure is 1.0 MPa, and the oxygen flow rate is 60 Nm 3 The furnace was heated at a rate of 150 mph (300 mph) per minute. The angle between the furnace door oxygen lance and the molten steel surface was 35° to enhance the stirring effect of the electric furnace. Simultaneously, a powdered dephosphorization agent was sprayed into the furnace through a carbon powder gun. The powdered dephosphorization agent consisted of lime powder with CaO ≥ 90.0%, fluorite powder with CaF2 ≥ 88.0%, and iron oxide scale powder with FeOx ≥ 95.0% in a weight ratio of 60:10:30. The particle size of the powdered dephosphorization agent was controlled to be 3-5 mm. Nitrogen was used as the carrier gas for the injection of the powdered dephosphorization agent at a nitrogen pressure of 1.0 MPa. During the dephosphorization process, lime was added in batches from a high position. A total of 2.9 tons of lime was added. Deep dephosphorization was performed using dephosphorization slag with an alkalinity of 6.7. The dephosphorization slag had the following composition: TFe: 20%, CaO: 40%, SiO2: 6%, MgO: 8%, and CaF2: 9%. During the dephosphorization process, the furnace was continuously fed with electrified slag to control the molten steel temperature at 1530°C.

[0034] (4) When P in molten steel is less than or equal to 0.004%, dephosphorization is terminated, oxygen lance at furnace door stops blowing oxygen, and nitrogen is blown for strong stirring. The nitrogen supply flow rate is 65Nm 3 / min, stirring for 3 minutes to promote the uniformity of the temperature and composition of the molten steel, the electric furnace continues to supply power to raise the temperature to above 1650℃, and more than 80% of the dephosphorization slag is removed to produce low-phosphorus high-nickel stainless steel mother liquor.

[0035] Using Example 1, 160 tons of low-phosphorus, high-nickel stainless steel mother liquor was finally prepared, and the steel composition was: C: 1.0%, Si: 0.01%, P: 0.004%, Ni: 15%, Cr: 0.40%. The low-phosphorus, high-nickel stainless steel mother liquor can be subsequently sent to an AOD furnace for refining of a low-phosphorus special stainless steel with P ≤ 0.015%.

[0036] In summary, the method for deep dephosphorization of chromium-nickel pig iron melt from electric furnace smelting of the present invention uses chromium-nickel pig iron as raw material for electric furnace deep dephosphorization, adds a solid dephosphorizing agent into the electric furnace, sprays a powdered dephosphorizing agent, and blows oxygen into the oxygen lance for coordinated dephosphorization to produce a low-phosphorus, high-nickel stainless steel mother liquor. The electric furnace endpoint phosphorus content of the low-phosphorus, high-nickel stainless steel mother liquor reaches the target of P≤0.004%, and can be directly used as a stainless steel mother liquor for refining low-phosphorus special stainless steel with P≤0.015% in an AOD furnace.

[0037] Compared with the prior art, the method for deep dephosphorization of chromium-nickel pig iron melt smelted in an electric furnace of the present invention has the following advantages and beneficial effects: the present invention solves the technical problem of high cost caused by the need to use dephosphorized molten iron + pure nickel in stainless steel smelting due to the difficulty in dephosphorizing the chromium-nickel pig iron melt in an electric furnace, and achieves the purpose of using cheap chromium-nickel pig iron as a raw material to prepare a low-phosphorus, high-nickel stainless steel mother liquor through deep dephosphorization in an electric furnace, and adding high-carbon ferrochrome to the low-phosphorus, high-nickel stainless steel mother liquor to produce a low-phosphorus special stainless steel variety. The smelting of low-phosphorus stainless steel no longer uses blast furnace dephosphorized molten iron, and the blast furnace molten iron production process is eliminated, thereby simplifying the production process and reducing carbon emissions. In addition, since expensive pure nickel is no longer needed, the smelting cost of low-phosphorus stainless steel is reduced, and the method has good promotion value and economic benefits.

[0038] It should be noted that, in this article, the term "comprise" or any other variation thereof is intended to cover non-exclusive inclusion, so that an article or device that includes a series of elements includes not only those elements, but also includes other elements that are not explicitly listed, or also includes elements that are inherent to such article or device.

[0039] It should also be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the present invention.

Claims

1. A method for deep dephosphorization of chromium-nickel pig iron melt smelted in an electric furnace, characterized in that: The steps include: Step 1: Load chromium-nickel pig iron into an electric furnace and melt the chromium-nickel pig iron to form a chromium-nickel pig iron pre-melt; Step 2: After the electric furnace is melted, desiliconization and dechromization operations are carried out. In this process, solid dephosphorization agent is added in batches from the high-level silo of the electric furnace. The total amount of solid dephosphorization agent added per ton of steel is controlled to be 20-25 kg. Oxygen is supplied by the furnace door oxygen lance, and the oxygen flow rate per ton of steel is controlled to be 0.24-0.32 Nm 3 / min; lime is added in batches during the process, and the total amount of lime added is controlled to 15-20kg per ton of steel, to produce desiliconized slag with a basicity of 1.8-2.

5. During the smelting process, the electric furnace continuously supplies electrified slag, and the temperature of the molten steel in the electric furnace is controlled at 1420-1480℃; Step 3: When Si≤0.02% and Cr≤0.80% in the molten steel, stop desiliconization and dechromization, and perform the electric furnace slag removal operation to remove ≥70% of the desiliconization slag; Step 4: After the slagging is completed, the deep dephosphorization operation of the electric furnace is carried out. Solid dephosphorization agent is added in batches from the high-level silo of the electric furnace for multiple times. The total amount of solid dephosphorization agent added per ton of steel is controlled to be 15-18 kg; the oxygen lance at the furnace door continues to supply oxygen, and the oxygen flow rate per ton of steel is controlled to be 0.30-0.38 Nm 3 / min, and simultaneously spray powdered dephosphorization agent into the electric furnace with a carbon powder gun. The carrier gas for the powdered dephosphorization agent is nitrogen, and the nitrogen pressure is controlled at 1.0MPa. During the dephosphorization process, lime is added in batches from a high position, and the total amount of lime added is controlled to be 15-18kg per ton of steel. Dephosphorization slag with a basicity of 5-8 is prepared for deep dephosphorization. During the dephosphorization process, the electric furnace continuously supplies electrified slag, and the molten steel temperature is controlled at 1500-1550℃. Step 5: When P in the molten steel is less than or equal to 0.004%, dephosphorization is completed, oxygen lances at the furnace door stop blowing oxygen, and nitrogen is blown for strong stirring. The nitrogen supply flow rate per ton of steel is controlled at 0.35-0.45 Nm 3 / min, stir for 3 to 5 minutes, continue to supply power to the electric furnace to raise the temperature to above 1630℃, remove ≥80% of the dephosphorization slag, and produce low-phosphorus high-nickel stainless steel mother liquor.

2. The method for deep dephosphorization of chromium-nickel pig iron melt from electric furnace smelting according to claim 1, characterized in that: The solid dephosphorization agent is prepared from converter dust, sintered ore and light-burned magnesium powder in a weight percentage ratio of 70:20:

10. The composition of the solid dephosphorization agent is controlled to be: FeOx: 56-70%, CaO: 10-18%, MgO: 3-8%, and SiO2: 1.5-3%.

3. The method for deep dephosphorization of chromium-nickel pig iron melt from electric furnace smelting according to claim 2, characterized in that: The powdery dephosphorization agent is prepared by mixing lime powder with CaO≥90.0%, fluorite powder with CaF2≥88.0%, and iron oxide powder with FeOx≥95.0% in a weight percentage ratio of 60:10:

30. The particle size of the powdery dephosphorization agent is controlled to be 3-5 mm.

4. The method for deep dephosphorization of chromium-nickel pig iron melt from electric furnace smelting according to claim 3, characterized in that: The composition of the desiliconized slag is controlled as follows: TFe: 10-15%, CaO: 45-50%, SiO2: 18-20%, MgO: 5-7%, Cr2O3: 8-15%.

5. The method for deep dephosphorization of chromium-nickel pig iron melt from electric furnace smelting according to claim 4, characterized in that: The composition of the dephosphorization slag is controlled as follows: TFe: 18-25%, CaO: 35-45%, SiO2: 5-8%, MgO: 6-9%, CaF2: 8-10%.

6. The method for deep dephosphorization of chromium-nickel pig iron melt from electric furnace smelting according to claim 1, characterized in that: In the desiliconization and dechromization operation of step 2, the oxygen pressure is controlled to be 1.0 MPa, and the angle between the furnace door oxygen lance and the molten steel surface is controlled to be 25-30 degrees.

7. The method for deep dephosphorization of chromium-nickel pig iron melt from electric furnace smelting according to claim 1, characterized in that: In the electric furnace deep dephosphorization operation in step 4, the oxygen pressure is controlled to be 1.0 MPa, and the angle between the furnace door oxygen lance and the molten steel surface is controlled to be 30-40°.

8. The method for deep dephosphorization of chromium-nickel pig iron melt produced by electric furnace smelting according to any one of claims 1 to 7, characterized in that: The composition of chromium-nickel pig iron is: C≤3.0%, Si≤2.5%, P≤0.050%, Cr≤4.0%, Ni: 7~15%, and the rest is iron and residual elements.