A smelting method for reducing the consumption of converter steel material

Abstract

The present invention belongs to the technical field of converter steelmaking, and specifically relates to a smelting method for reducing the consumption of converter steel materials. The converter scrap ratio is controlled at 15-25%, and the oxygen supply flow rate is controlled at 5.0-6.0 Nm 3 / (min•t), adding calcium ferrite dephosphorization agent and calcium ferrite slag-forming agent containing CaO·SiO2 in the smelting process can quickly form slag and improve the slag-forming effect. At the same time, combined with appropriate feeding system and oxygen supply system, it can improve the dephosphorization effect while reducing the amount of converter steelmaking slag and the total iron content of the slag.

Description

Technical Field

[0001] The invention belongs to the technical field of converter steelmaking, and in particular relates to a smelting method for reducing the consumption of converter steel material. Background Art

[0002] Low-cost converter smelting has always been the goal pursued by various steel mills. The consumption of converter steel generally accounts for more than 75% of the steelmaking cost. Reducing the consumption of steel can significantly reduce the cost of steelmaking. The iron loss in the converter steelmaking blowing process is mainly in the slag and flue gas, of which the iron loss caused by the slag accounts for more than 90%. From this analysis, it can be seen that reducing the total iron content in the slag and the amount of slag can greatly reduce iron loss and reduce steelmaking costs.

[0003] The purpose of converter steelmaking slag making is to remove harmful element phosphorus from molten steel. The dephosphorization reaction is: 2[P]+5(FeO)+3(CaO)=(3CaO·P2O5)+5[Fe]. Through the above reaction, phosphorus in molten steel can be removed into slag. In order to improve the dephosphorization effect, the slag is required to be liquid, which is usually referred to as improving the slag-forming effect. The slag-forming materials actually added to the converter are generally lime and light-burned dolomite, both of which are high-melting-point materials. In order to improve the slag-forming effect, the conventional method is to increase the gun position in the smelting process and add iron ore to increase the iron oxide in the slag. The iron oxide then combines with CaO to form a low-melting-point calcium ferrite phase to promote slag-forming; this method easily leads to a high total iron content in the slag, a slow slag-forming speed, and severe splashing.

[0004] Patent CN105177217A controls the phosphorus and sulfur content in sintered ore, lump ore, pellet ore, and coke by controlling the blast furnace smelting process, controlling the silicon content in molten iron to 0.25%-0.35%, the phosphorus content to be less than or equal to 0.10%, and the sulfur content to be less than or equal to 0.030%, and then adopts a 100t top and bottom double-blown converter for smelting, with slag splashing to protect the furnace, and the liquid slag in the furnace solidifying; after the blowing and dephosphorization stage, the intermediate slag pouring, and the slag basicity control; and then adding lime and light-burned dolomite to reduce the amount of converter slag slag. This smelting method has high requirements for molten iron and raw materials, and the need for intermediate slag pouring leads to a relatively long smelting cycle.

[0005] Patent CN114737011A discloses a slag-making agent composed of CaCO3 as the central material and CaO as the outer layer material, which is wrapped around the outer layer material of the central material, and replaces traditional lime for slag-making to reduce lime consumption. The lime consumption is 26-30kg / t steel, and the converter end point P is 0.0085%-0.0100%. In conjunction with the embodiment, the phosphorus content of molten iron is basically 0.09%, and the dephosphorization rate is 88.9-90.5% calculated based on the phosphorus content of steel tapping of 0.085-0.01%. The slag-making agent of this patent needs special process preparation, and the dephosphorization effect still needs further improvement. In addition, this patent does not disclose the silicon content of molten iron and the basicity of slag (the silicon content of molten iron has the greatest impact on the slag amount, and the higher the silicon content of molten iron, the larger the slag amount), so it is impossible to judge the slag amount under the corresponding silicon content of molten iron. Summary of the invention

[0006] The object of the present invention is to provide a smelting method for reducing the consumption of converter steel material. The present invention first designs the composition of a slag-forming agent and a dephosphorizing agent, designs a calcium ferrite slag-forming agent and a calcium ferrite dephosphorizing agent, and further optimizes the timing of adding the slag-forming agent and the dephosphorizing agent and the smelting process. The converter smelting method of the present invention can quickly slag and improve the slag-forming effect, while improving the dephosphorization effect, reducing the amount of converter steelmaking slag and the total iron content of the slag, thereby achieving the purpose of reducing the consumption of steel material.

[0007] The present invention provides a smelting method for reducing the consumption of converter steel material, and the specific method steps are as follows:

[0008] The scrap ratio of the converter is controlled at 15-25%, and the molten iron ratio is controlled at 75-85% for blowing;

[0009] Oxygen supply system: The oxygen supply intensity of the entire blowing process is controlled at 5.0~6.0Nm 3 / (min·t);

[0010] Feeding system: oxygen supply 8-15%, add lime 10-25kg / t, light-burned dolomite 10-20kg / t, calcium ferrite dephosphorization agent 5-15kg / t, calcium ferrite slag-forming agent 3-15kg / t; oxygen supply 35%-70%, due to the violent carbon-oxygen reaction, a large amount of iron oxides in the slag are consumed, which is easy to cause dry-out. At this time, according to the slag-forming situation, calcium ferrite slag-forming agent should be added in small batches to supplement iron oxides and prevent dry-out; oxygen supply exceeds 70% to the end of blowing, and no slag-forming material is added; among them, calcium ferrite The composition of the dephosphorization agent is: Fe2O3: 10-20%, CaO·2Fe2O3: 5-15%, CaO·Fe2O3: 5-15%, 2CaO·Fe2O3: 50-60%, 2CaO·SiO2: 10-20%, basicity 3.0-4.5, and some inevitable impurities; the composition of the ferrite calcium slag-forming agent is: Fe2O3: 30-40%, CaO·2Fe2O3: 50-60%, CaO·Fe2O3: 10-20%, and some inevitable impurities.

[0011] The basicity of the converter final slag is controlled at 2.2-2.8, the MgO content of the slag is controlled at 8-10%, and the total iron content of the slag is controlled at 8-15%.

[0012] The present invention further improves the position control of the oxygen lance. Preferably, the oxygen lance position is controlled at 1.6-1.8m from the start of blowing to 80% oxygen supply; and the oxygen lance position is controlled at 1.4-1.6m from the oxygen supply exceeding 80% to the end of blowing.

[0013] Furthermore, the method of using the calcium ferrite dephosphorization agent and the calcium ferrite slag-forming agent during the period of oxygen blowing of 8-15% is: when the silicon content of molten iron is ≤0.4%, the amount of lime: the amount of calcium ferrite dephosphorization: the amount of calcium ferrite slag-forming agent = 4: (1-2): (0.5-1.0); when the silicon content of molten iron is greater than 0.4%, the amount of lime: the amount of calcium ferrite dephosphorization: the amount of calcium ferrite slag-forming agent = 4: (1-2): (0-0.5).

[0014] Compared with the prior art, the present invention provides a calcium ferrite slag forming agent and a calcium ferrite dephosphorization agent, wherein the melting point of the calcium ferrite slag forming agent is 1250-1350°C, and the melting point of the calcium ferrite dephosphorization agent is 1150-1250°C. In the early stage of converter smelting, the calcium ferrite dephosphorization agent can be quickly melted into slag, and the CaO·Fe2O3 and 2CaO·Fe2O3 therein can directly react with the phosphorus in the molten steel to form 3CaO·P2O5, and the generated 3CaO·P2O5 can combine with 2CaO·SiO2 in the calcium ferrite dephosphorization agent to form a solid solution phase of 3CaO·P2O5 and 2CaO·SiO2, which plays the role of dephosphorization and phosphorus fixation, and dephosphorization is efficient; the CaO·2Fe2O3 and Fe2O3 phases in the calcium ferrite slag-forming agent can combine with the CaO in the lime to form low-melting-point CaO·Fe2O3 and 2CaO·Fe2O3 phases, achieving the purpose of efficient slag-forming, and then participating in the dephosphorization reaction, which can effectively control the slag-forming, splashing and dephosphorization of the smelting process, and realize converter slag-less slag smelting. In addition, the present invention uses a calcium ferrite dephosphorizing agent and a calcium ferrite slag-forming agent, and adopts low-gun position smelting throughout the whole process, which can significantly reduce the total iron content of the slag and reduce the consumption of steel materials. DETAILED DESCRIPTION

[0015] In a specific implementation manner of the present invention, a 130t converter is used for oxygen top-blown converter smelting.

[0016] Example 1

[0017] 130t converter, raw materials: molten iron 115t, molten iron temperature 1360℃, molten iron silicon 0.25%, molten iron phosphorus: 0.13%, scrap steel 25t. Blowing time: 8.65min.

[0018] The composition of calcium ferrite dephosphorization agent is: Fe2O3: 10%, CaO·2Fe2O3: 8%, CaO·Fe2O3: 10%, 2CaO·Fe2O3: 56%, 2CaO·SiO2: 13%, basicity 3.5, and some inevitable impurities; the composition of calcium ferrite slag-forming agent is Fe2O3: 35%, CaO·2Fe2O3: 52%, CaO·Fe2O3: 10%, and some inevitable impurities.

[0019] Oxygen supply system: (1) Oxygen blowing flow rate, the top blowing flow rate of the whole process is set to 43000Nm 3 / h; (2) Gun position, oxygen supply 0-80%, oxygen gun position 1.65m, oxygen supply 80-100%, gun position 1.5m.

[0020] Feeding system: oxygen supply 12%, add 2000kg lime, add 1800kg light-burned dolomite, add 1000kg calcium ferrite dephosphorization agent, add 500kg calcium ferrite slag-forming agent; oxygen supply 35-70%, add calcium ferrite slag-forming agent in small batches according to the slag-forming situation, each time adding 200kg; no slag is added afterwards. The total amount of lime is 2000kg, the amount of light-burned dolomite is 1800kg, the amount of calcium ferrite dephosphorization agent is 1000kg, and the amount of calcium ferrite slag-forming agent is 1100kg.

[0021] Smelting by the above method, the final converter temperature is: 1612℃, final carbon: 0.08%, final phosphorus: 0.010%, dephosphorization rate: 92.3%, final slag basicity: 2.69, final slag total iron: 13.5%, and slag amount: 65kg / t.

[0022] Example 2

[0023] 130t converter, raw materials: molten iron 115t, molten iron temperature 1330℃, molten iron silicon 0.35%, molten iron phosphorus: 0.131%, scrap steel 25t. Blowing time 8.82min.

[0024] The composition of calcium ferrite dephosphorization agent is: Fe2O3: 12%, CaO·2Fe2O3: 8%, CaO·Fe2O3: 10%, 2CaO·Fe2O3: 56%, 2CaO·SiO2: 12%, basicity 3.7, and some inevitable impurities; the composition of calcium ferrite slag-forming agent is Fe2O3: 32%, CaO·2Fe2O3: 53%, CaO·Fe2O3: 13%, and some inevitable impurities.

[0025] Oxygen supply system: (1) Oxygen blowing flow rate, the top blowing flow rate of the whole process is set to 43000Nm 3 / h; (2) Gun position, oxygen supply 0-80%, oxygen gun position 1.70m, oxygen supply 80-100%, gun position 1.5m.

[0026] Feeding system: oxygen supply 10%, add 2800kg lime, add 1900kg light-burned dolomite, add 1200kg calcium ferrite dephosphorization agent, add 700kg calcium ferrite slag-forming agent; oxygen supply 35-70%, add calcium ferrite slag-forming agent in small batches according to the slag-forming situation, each time adding 200kg; after that, no slag is added. The total amount of lime is 2800kg, the amount of light-burned is 1900kg, the amount of calcium ferrite dephosphorization agent is 1200kg, and the amount of calcium ferrite slag-forming agent is 1300kg.

[0027] Smelting by the above method, the final converter temperature is: 1609℃, the final carbon: 0.082%, the final phosphorus: 0.008%, the dephosphorization rate: 93.9%, the final slag basicity is 2.75, the final slag total iron: 12.7%, and the slag amount is 75kg / t.

[0028] Example 3

[0029] 130t converter, raw materials: molten iron 110t, molten iron temperature 1380℃, molten iron silicon 0.41%, molten iron phosphorus: 0.152%, scrap steel 30t. Blowing time 8.88min.

[0030] The composition of calcium ferrite dephosphorization agent is: Fe2O3: 10%, CaO·2Fe2O3: 10%, CaO·Fe2O3: 10%, 2CaO·Fe2O3: 52%, 2CaO·SiO2: 16%, basicity 3.3, and some inevitable impurities; the composition of calcium ferrite slag-forming agent is Fe2O3: 35%, CaO·2Fe2O3: 52%, CaO·Fe2O3: 12%, and some inevitable impurities.

[0031] Oxygen supply system: (1) Oxygen blowing flow rate, the top blowing flow rate of the whole process is set to 43000Nm 3 / h; (2) Gun position, oxygen supply 0-80%, oxygen gun position 1.75m, oxygen supply 80-100%, gun position 1.5m.

[0032] Feeding system: oxygen supply 9%, add 3200kg lime, add 2000kg light-burned dolomite, add 1500kg calcium ferrite dephosphorization agent, add 350kg calcium ferrite slag-forming agent; oxygen supply 35-70%, add calcium ferrite slag-forming agent in small batches according to the slag-forming situation, each time adding 200kg; no slag is added afterwards. The total amount of lime is 3000kg, the amount of light-burned dolomite is 2000kg, the amount of calcium ferrite dephosphorization agent is 1500kg, and the amount of calcium ferrite slag-forming agent is 950kg.

[0033] Smelting by the above method, the final converter temperature is: 1623℃, final carbon: 0.073%, final phosphorus: 0.010%, dephosphorization rate: 93.4%, final slag basicity: 2.67, final slag total iron: 13.2%, and slag amount: 78kg / t.

[0034] Comparative Example 1

[0035] Compared with Example 1, in this comparative example, only calcium ferrite dephosphorization agent is added during the smelting process, and no calcium ferrite slag forming agent is added. Other conditions are the same as in Example 1.

[0036] Feeding system: oxygen supply 12%, add 2000kg lime, add 1800kg light-burned dolomite, add 1500kg calcium ferrite dephosphorization agent; oxygen supply 35-70%, add calcium ferrite dephosphorization agent in small batches, each adding 200kg; no slag is added afterwards. The total amount of lime is 2000kg, the amount of light-burned dolomite is 1800kg, and the amount of calcium ferrite dephosphorization agent is 2100kg.

[0037] The above method is used for smelting, but the slag is not well smelted and the final phosphorus content is high. The final converter temperature is 1612℃, the final carbon is 0.08%, the final phosphorus is 0.020%, the dephosphorization rate is 84.6%, the final slag basicity is 2.71, the final slag total iron is 13.7%, and the slag volume is 65.5kg / t.

[0038] Comparative Example 2

[0039] Compared with Example 1, this comparative example does not add calcium ferrite dephosphorization agent during the smelting process, and is completely replaced by calcium ferrite slag-forming agent. Other conditions are the same as in Example 1.

[0040] Feeding system: when oxygen supply is 12%, 2300kg of lime, 1800kg of light-burned dolomite and 1500kg of calcium ferrite slag-forming agent are added; when oxygen supply is 35-70%, calcium ferrite slag-forming agent is added in small batches, with 200kg added each time; when oxygen blowing is 40%, splashing occurs, 500kg of lime and 500kg of light-burned dolomite are added for slag pressing, and the gun position is lowered by 10cm; when oxygen blowing exceeds 70%, no slag is added; the total amount of lime is 2800kg, the amount of light-burned dolomite is 2300kg, and the amount of calcium ferrite slag-forming agent is 2100kg.

[0041] When smelting by the above method, splashing occurs during the smelting process, and the final phosphorus content is high. The final converter temperature is 1612℃, the final carbon is 0.08%, the final phosphorus is 0.017%, the dephosphorization rate is 86.9%, the final slag basicity is 2.95, the final slag total iron is 13.5%, and the slag volume is 70kg / t.

[0042] Comparative Example 3

[0043] 130t converter, raw materials: molten iron 115t, molten iron temperature 1330℃, molten iron silicon 0.35%, molten iron phosphorus: 0.131%, scrap steel 25t. Blowing time 9.35min.

[0044] Oxygen supply system: (1) Oxygen blowing flow rate, the top blowing flow rate of the whole process is set to 43000Nm 3 / h; (2) Gun position: oxygen supply 0-20%, oxygen gun position 1.70m; oxygen supply 20-50%, oxygen gun position 1.80m; oxygen supply 50-70%, oxygen gun position 1.9m; ​​oxygen supply 70-95%, oxygen gun position 2.0m; oxygen supply 95-100%, oxygen gun position 1.5m.

[0045] Feeding system: supply oxygen 10%, add 3500kg of lime, add 1200kg of light-burned dolomite, and add 1500kg of ore; supply oxygen 35-100%, add slag and ore in small batches according to the slagging situation; the total amount of lime is 4300kg, the amount of light-burned dolomite is 2100kg, and the amount of ore is 2100kg; splashing occurs when blowing oxygen 42%.

[0046] The above method is used for smelting, and the converter terminal temperature is 1609°C, the terminal carbon is 0.06%, the terminal phosphorus is 0.009%, the dephosphorization rate is 93.1%, the final slag basicity is 3.52, the final slag iron is 16.5%, and the slag amount is 92kg / t. Compared with Example 2, the smelting process does not add calcium ferrite dephosphorization agent and calcium ferrite slag agent, the slag consumption is high, the smelting process gun position is high, the slag amount is increased from 75kg / t to 92kg / t, and the slag iron is increased from 12.7% to 16.5%.

[0047] Comparative Example 4

[0048] 130t converter, raw materials: molten iron 115t, molten iron temperature 1330℃, molten iron silicon 0.35%, molten iron phosphorus: 0.131%, scrap steel 25t.

[0049] The calcium ferrite dephosphorization agent does not contain 2CaO·SiO2 phase, and its composition is: Fe2O3: 12%, CaO·2Fe2O3: 8%, CaO·Fe2O3: 10%, 2CaO·Fe2O3: 56%, CaO: 12%, and some inevitable impurities; the composition of the calcium ferrite slag-forming agent is Fe2O3: 32%, CaO·2Fe2O3: 53%, CaO·Fe2O3: 13%, and some inevitable impurities.

[0050] The oxygen supply system and the feeding system are the same as those in Example 2.

[0051] Smelting by the above method, the final converter temperature is: 1609℃, final carbon: 0.082%, final phosphorus: 0.011%, dephosphorization rate: 91.6%, final slag basicity: 2.82, final slag total iron: 13.1%, and slag amount: 76kg / t.

Claims

1. A smelting method for reducing the consumption of converter steel material, characterized in that: The smelting method comprises: The scrap ratio of the converter is controlled at 15-25%, and the molten iron ratio is controlled at 75-85% for blowing; Oxygen supply system: The oxygen supply intensity of the entire blowing process is controlled at 5.0~6.0Nm 3 / (min·t); Feeding system: oxygen supply 8-15%, add 10-30kg / t lime, 10-20kg / t light-burned dolomite, 5-15kg / t calcium ferrite dephosphorization agent, 3-15kg / t calcium ferrite slag-forming agent; oxygen supply 35-70%, add calcium ferrite slag-forming agent in batches according to the slag-forming situation; oxygen supply exceeds 70% until the end of blowing, and no slag-forming material is added; Among them, the components of calcium ferrite dephosphorization agent are: Fe2O3: 10-20%, CaO·2Fe2O3: 5-15%, CaO·Fe2O3: 5-15%, 2CaO·Fe2O3: 50-60%, 2CaO·SiO2: 10-20%, basicity 3.0-4.5, and inevitable impurities; the components of calcium ferrite slag-forming agent are: Fe2O3: 30-40%, CaO·2Fe2O3: 50-60%, CaO·Fe2O3: 10-20%, and inevitable impurities.

2. The smelting method for reducing the consumption of converter steel material according to claim 1, characterized in that: From the start of blowing to 80% oxygen supply, the oxygen lance position is controlled at 1.6-1.8m; from the oxygen supply exceeding 80% to the end of blowing, the oxygen lance position is controlled at 1.4-1.6m.

3. The smelting method for reducing the consumption of converter steel material according to claim 1, characterized in that: The oxygen supply is 8-15%, and the amount of calcium ferrite dephosphorization agent and calcium ferrite slag-forming agent added is calculated according to the silicon content of the molten iron; when the silicon content of the molten iron is ≤0.4%, the mass ratio of lime, calcium ferrite dephosphorization agent and calcium ferrite slag-forming agent is 4:1-2:0.5-1.

0.

4. The smelting method for reducing the consumption of converter steel material according to claim 1, characterized in that: The oxygen supply is 8-15%, and the amount of calcium ferrite dephosphorization agent and calcium ferrite slag-forming agent added is calculated according to the silicon content of the molten iron; when the silicon content of the molten iron is greater than 0.4%, the mass ratio of lime, calcium ferrite dephosphorization agent and calcium ferrite slag-forming agent is 4:1-2:0-0.

5.

5. The smelting method for reducing the consumption of converter steel material according to claim 1, characterized in that: The basicity of the converter final slag is controlled at 2.2-2.8, and the total iron content of the slag is controlled at 8-15%.