Method for producing high-phosphorus steel by using low-calorific-value molten iron

Abstract

The invention relates to the technical field of converter steelmaking, in particular to a method for producing high-phosphorus steel by using low-calorific-value molten iron, which comprises the following steps: after slag splashing furnace protection is finished, all slag is poured out; waste steel and molten iron are loaded, and the proportion of the waste steel and the molten iron is controlled; in the blowing process, dolomite and limestone are used for slagging, the lance position of an oxygen lance is reduced along with the increase of the blowing duration, the carbon content at the blowing end point is controlled to be 0.04-0.07%, and the temperature of molten iron is 1630-1650 DEG C; the low-calorific-value molten iron with low silicon content is selected, the addition amount of iron ore and limestone in the process is reduced, and the FeO content and alkalinity in the slag in the smelting process are reduced. By controlling molten iron parameters and adjusting an oxygen supply system and a slagging system, low alkalinity and low FeO content of slag in the smelting process are achieved, the purposes of removing carbon and keeping phosphorus are achieved, furnace lining erosion caused by high-temperature tapping is avoided, and furnace body maintenance is utilized; meanwhile, the consumption of ferrophosphorus is reduced, and the production cost is saved.

Description

Technical Field

[0001] The invention relates to the technical field of converter steelmaking, in particular to a method for producing high-phosphorus steel by utilizing low calorific value molten iron. Background Art

[0002] For most steel grades, phosphorus is one of the harmful elements, and the lower the phosphorus content, the better. However, for some special steel grades, such as weathering steel and container steel, phosphorus is a beneficial element. The phosphorus content of some steel products is required to be controlled above 0.070%, which can improve the weather resistance and hardness of the steel, improve impact resistance, reduce iron loss, etc. This type of steel is usually called high-phosphorus steel. At present, some domestic steel companies use traditional smelting processes to produce high-phosphorus steel. The phosphorus content at the end of smelting is low, and a large amount of ferrophosphorus needs to be added for phosphorus matching.

[0003] Although the prior art discloses some methods for producing high-phosphorus steel, they all have certain defects. For example, Chinese patent document CN102776313A (application number 201210296289.7) discloses a method for smelting high-phosphorus steel in a converter using low-temperature low-silicon molten iron, requiring the final temperature of the converter molten steel to be controlled at 1670-1690°C, and Chinese patent document CN104294000A (application number 201410570349.9) discloses a method for producing high-phosphorus steel in a 180t ore furnace, requiring the final temperature to be 1660-1690°C, but the above two technical solutions both have high requirements for the converter end point, causing serious erosion of the lining refractory material, which is not conducive to furnace body maintenance; another example is Chinese patent document CN114292983A (application number 202210017613.0) discloses a method for producing high-phosphorus steel, which uses only raw dolomite for slag making without adding any other slag making agent for production, which is easy to cause high viscosity of the final slag and blockage of the tapping port during the steel tapping process. Summary of the invention

[0004] The purpose of the present invention is to overcome the deficiencies of the above-mentioned prior art and provide a method for producing high-phosphorus steel using low calorific value molten iron. By using limestone instead of lime for slag making, the consumption of auxiliary materials and ferrophosphorus can be effectively reduced, and the production cost can be effectively reduced. At the same time, by controlling the gun position during the smelting process, the basicity of the smelting process and the FeO content in the slag can be significantly reduced, thereby achieving the effect of decarbonization and phosphorus preservation.

[0005] In order to achieve the above technical effects, the present invention adopts the following technical solutions:

[0006] A method for producing high-phosphorus steel using low calorific value molten iron comprises the following steps:

[0007] S1. After the slag splashing and furnace protection is completed, pour out all the slag;

[0008] S2. Loading scrap steel and molten iron, and controlling the ratio of scrap steel to molten iron;

[0009] S3. During the blowing process, dolomite and limestone are used for slag making, and the position of the oxygen lance decreases with the increase of the blowing time, the carbon content is controlled at 0.04% to 0.07% at the end of the blowing, and the molten iron temperature is 1630 ℃ to 1650 ℃;

[0010] In step S2, the silicon content in the molten iron is below 0.30%, and the molten iron temperature is ≤1300°C, and the mass ratio of scrap steel to molten iron is (7-13):100.

[0011] The present invention uses low silicon content and low calorific value molten iron in order to reduce the amount of iron ore and limestone added in the process, thereby reducing the FeO content and basicity in the slag during the smelting process.

[0012] Preferably, in step S2, the addition ratio of scrap steel to molten iron is controlled according to the temperature of molten iron. Specifically,

[0013] When the molten iron temperature is less than 1250°C, the mass ratio of scrap steel to molten iron is (7-8.5):100;

[0014] When the molten iron temperature is 1250℃≤≤1300℃, the mass ratio of scrap steel to molten iron is (8.5~13):100.

[0015] Preferably, in step S3, the oxygen lance position adjustment method is as follows:

[0016] Oxygen supply time 0~4min, oxygen lance position 1600mm~1650mm;

[0017] Oxygen supply time 4min~11min, oxygen lance position 1450mm~1500mm;

[0018] Oxygen supply time 11min~13min, oxygen lance position 1400mm~1450mm;

[0019] Oxygen supply time is 13 minutes to stop blowing, and the position of oxygen gun is 1200mm~1250mm.

[0020] By gradually lowering the position of the oxygen lance, the FeO content in the slag during the smelting process can be reduced.

[0021] Further preferably, in step S3,

[0022] Oxygen supply time 0~4min, oxygen supply flow rate (400~450)Nm 3 / min;

[0023] Oxygen supply time 4min~stop blowing, oxygen supply flow rate is (450~500)Nm 3 / min.

[0024] When the gun position of the oxygen gun is lowered, the oxygen pressure and oxygen supply flow rate are adjusted accordingly.

[0025] Further preferably, in step S3,

[0026] Oxygen supply (400~600)Nm 3 During this period, dolomite (12-15) kg / t was added and oxygen supply (1000-1200) Nm 3 During this period, add limestone (5-10) kg / t;

[0027] Oxygen supply (3000~4500)Nm 3 During this period, limestone and iron ore are added in batches, and the weight of each batch of limestone and iron ore is controlled at (1.50-2.70) kg / t. Each batch of limestone and iron ore is added at the same time, and the limestone and iron ore are added in equal mass ratio.

[0028] Further preferably, in step S3, the interval between feeding adjacent batches of limestone and iron ore is 40s to 60s.

[0029] By controlling the feeding interval of limestone and iron ore, the frequent addition of iron ore can be prevented from causing a surge in the FeO content in the slag, thereby ensuring the effect of carbon removal and phosphorus retention.

[0030] The beneficial effects of the present invention are as follows:

[0031] The present invention controls molten iron parameters and adjusts the oxygen supply system and slag making system to achieve low basicity and low FeO content in the slag during the smelting process, thereby achieving the purpose of removing carbon and retaining phosphorus, avoiding corrosion of the furnace lining during high-temperature steel tapping, and utilizing furnace body maintenance; at the same time, it reduces phosphorus and iron consumption and saves production costs. DETAILED DESCRIPTION

[0032] The present invention will be described in detail below with reference to the embodiments, but is not limited thereto.

[0033] The raw materials used in each example are all conventional commercially available materials in the art, and the specific sources of the raw materials are not described here in detail.

[0034] Examples 1 to 6

[0035] According to the method for producing high-phosphorus steel using low calorific value molten iron provided by the present invention, six heats of steel are smelted in a converter, and the specific steps and conditions are controlled as follows:

[0036] 1. After the slag splashing and furnace protection is completed, pour out all the slag and load the pre-treated molten iron and scrap steel into the furnace. The silicon content of the molten iron is required to be controlled below 0.30% and the temperature of the molten iron is less than 1300℃.

[0037] 2. Determine the scrap ratio according to the molten iron conditions. When the molten iron temperature is less than 1250°C, the scrap ratio is controlled between 7% and 8.5%. When the molten iron temperature is between 1250 and 1300°C, the scrap ratio is controlled between 8.5 and 13%. The molten iron composition, molten iron temperature, and the amount of molten iron and scrap added in Examples 1 to 6 are shown in Table 1.

[0038] Table 1 Statistics of molten iron composition, molten iron temperature, molten iron and scrap steel addition amount in Examples 1 to 6

[0039]

[0040] 3. Process blowing process:

[0041] Early stage of smelting: oxygen supply time 0~4min, that is, oxygen supply volume 0~1600Nm 3 , gun position 1600~1650mm, oxygen flow rate: 400~450Nm 3 / min; oxygen supply during this period is 400~600Nm 3 After that, add 12-15kg / t of dolomite and 1000-1200Nm 3 Add limestone 5-10kg / t;

[0042] Mid-smelting period: oxygen supply time 4min~11min, i.e. oxygen supply volume 1600Nm 3 ~4800Nm 3 , gun position 1500~1450mm, oxygen flow rate: 450~500Nm 3 / min; oxygen supply 3000~4500Nm 3 During this period, limestone and iron ore are added in batches according to the temperature. Each batch of limestone and iron ore is controlled at 1.50-2.70 kg / t. Each batch of limestone and iron ore is added at the same time, and the addition ratio is controlled at 1:1.

[0043] In the middle and late stages of smelting: oxygen supply time is 11min to 13min, i.e. oxygen supply volume is 4800 to 5200Nm 3 , gun position 1450~1400mm, oxygen flow rate: 450~500Nm 3 / min; no material is added during this period;

[0044] End gun position: oxygen supply time 13min to stop blowing, that is, oxygen supply 5200Nm 3 ~Stop blowing, use gun position 1250~1200mm, oxygen flow rate: 450~500Nm 3 / min.

[0045] The specific gun positions and oxygen supply flow rates in the early, middle and late stages of smelting of Examples 1 to 6 are shown in Table 2, the feeding amounts in the early stages of smelting of Examples 1 to 6 are shown in Table 3, and the specific feeding conditions in the middle stages of smelting are shown in Table 4.

[0046] Table 2 Specific parameters of blowing gun position and oxygen supply flow rate in smelting process of Examples 1 to 6

[0047]

[0048] Table 3 Statistical table of the amount of limestone and dolomite added in the early stage of Examples 1 to 6

[0049]

[0050]

[0051] Table 4 Statistical table of specific material addition during the smelting process of Examples 1 to 6

[0052] Serial number Limestone addition amount / (kg / t) Iron ore addition amount (kg / t) Join Batch Example 1 3.08 3.08 2 Example 2 5.38 5.38 3 Example 3 4.23 4.23 3 Example 4 4.81 4.81 3 Example 5 3.46 3.46 3 Example 6 5.77 5.77 3

[0053] The input amount of limestone and iron ore is calculated comprehensively based on the chemical elements in the molten iron, the molten iron temperature, the amount of scrap steel and the converter endpoint control requirements. In the above embodiment, the calculation process is automatically calculated by the secondary program.

[0054] 4. Smelting endpoint control: carbon: 0.04% to 0.07%, temperature 1630 to 1650° C. The temperature measurement, carbon determination and phosphorus content of the TSO of the sub-lances of Examples 1 to 6 are shown in Table 5.

[0055] Table 5 Statistics of temperature measurement, carbon determination and sampling for phosphorus content of auxiliary gun TSO

[0056]

[0057]

[0058] From the data measured in Table 5, it can be seen that the method provided by the present invention ensures that the phosphorus content in the prepared molten iron is above 0.070%. At the same time, the molten iron temperature is between 1630°C and 1650°C, which avoids the corrosion of the furnace lining refractory. At the same time, by using limestone instead of lime for slag making, the addition of iron ore is reduced. By controlling the oxygen lance position, oxygen supply flow rate and ore (dolomite, limestone and iron ore) addition parameters during the blowing process, the FeO content is effectively controlled to ensure the effect of carbon removal and phosphorus preservation.

Claims

1. A method for producing high-phosphorus steel using low calorific value molten iron, comprising the following steps: S1. After the slag splashing and furnace protection is completed, pour out all the slag; S2. Loading scrap steel and molten iron, and controlling the ratio of scrap steel to molten iron; S3. During the blowing process, dolomite and limestone are used for slag making, and the position of the oxygen lance decreases with the increase of the blowing time, the carbon content is controlled at 0.04% to 0.07% at the end of the blowing, and the molten iron temperature is 1630 ℃ to 1650 ℃; In step S2, the silicon content in the molten iron is below 0.30%, and the molten iron temperature is ≤1300°C, and the mass ratio of scrap steel to molten iron is (7-13):

100.

2. The method according to claim 1, characterized in that In step S2, the addition ratio of scrap steel to molten iron is controlled according to the temperature of molten iron. Specifically, When the molten iron temperature is less than 1250°C, the mass ratio of scrap steel to molten iron is (7-8.5):100; When the molten iron temperature is 1250℃≤≤1300℃, the mass ratio of scrap steel to molten iron is (8.5~13):

100.

3. The method according to claim 1, characterized in that In step S3, the oxygen lance position adjustment method is as follows: Oxygen supply time 0~4min, oxygen lance position 1600mm~1650mm; Oxygen supply time 4min~11min, oxygen lance position 1450mm~1500mm; Oxygen supply time 11min~13min, oxygen lance position 1400mm~1450mm; Oxygen supply time is 13 minutes to stop blowing, and the position of oxygen gun is 1200mm~1250mm.

4. The method according to claim 3, characterized in that In step S3, Oxygen supply time 0~4min, oxygen supply flow rate (400~450)Nm 3 / min; Oxygen supply time 4min~stop blowing, oxygen supply flow rate is (450~500)Nm 3 / min.

5. The method according to claim 3, characterized in that In step S3, Oxygen supply (400~600)Nm 3 During this period, dolomite (12-15) kg / t was added and oxygen supply (1000-1200) Nm 3 During this period, add limestone (5-10) kg / t; Oxygen supply (3000~4500)Nm 3 During this period, limestone and iron ore are added in batches, and the weight of each batch of limestone and iron ore is controlled at (1.50-2.70) kg / t. Each batch of limestone and iron ore is added at the same time, and the limestone and iron ore are added in equal mass ratio.

6. The method according to claim 5, characterized in that In step S3, the feeding interval between adjacent batches of limestone and iron ore is 40s to 60s.

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