A low-cost smelting method for hard wire steel

Abstract

The present invention belongs to the field of metallurgical technology. The present invention has developed a low-cost smelting method for hard wire steel. By controlling the feeding system and oxygen supply system during the converter smelting process, efficient dephosphorization and desulfurization are carried out in the early and middle stages of converter smelting, and the lance is lifted to pour slag. In the later stage of blowing, a high-alkalinity and low-oxidizing slag is formed, and at the same time, a relatively high molten pool temperature is controlled to further desulfurize, ultimately meeting the goals of efficient dephosphorization and desulfurization in the converter. During the refining process, there is no need for desulfurization treatment. By recycling the hot surplus steel and surplus slag after continuous casting of the same steel grade, the purpose of reducing production costs is achieved. This method is simple to operate and convenient for popularization and application, and the cost per ton of steel can be reduced by more than 20 yuan.

Description

Technical Field

[0001] The present invention belongs to the technical field of metallurgy, and particularly relates to a method for low-cost smelting of hard wire steel. Background Art

[0002] 45 # 、60 # 、70 # Hard wire steels such as 45, 60, 70, etc. have high strength, good elongation performance and drawing performance, and are widely used in high-strength steel wires such as wire ropes, prestressed steel wires, steel strands, and bead wires, and have broad market prospects. Sulfur mainly exists in the form of sulfide (Mn, Fe)S in hard wire steel, which will significantly reduce the hot working performance, welding performance and drawing performance of the steel. Production practice shows that when the mass fraction of sulfur in hard wire steel is higher than 0.015%, cracks are likely to appear in the continuous casting billet, and phenomena such as breakage occur during subsequent processing. Therefore, the sulfur content in hard wire steel is generally required to be ≤0.015%. There are generally two methods for controlling the sulfur content in molten steel: Method 1, desulfurized hot metal + clean scrap steel, and no desulfurization in refining; Method 2, ordinary hot metal + ordinary scrap steel, and desulfurization in refining. Due to the insufficient production capacity of the desulfurization equipment and the shortage of clean scrap steel resources in our company, Method 2 is generally used to control sulfur. In the actual production process, due to the need for desulfurization treatment in refining, the remaining steel and slag of hard wire steel cannot be directly recycled by heat, resulting in waste of resources and environmental pollution. At present, there are also methods for desulfurization in converter smelting. For example, CN201510135407.X, a method for smelting low-phosphorus and low-sulfur molten steel in a converter, reduces the input of sulfur by controlling the sulfur content of raw materials and auxiliary materials. The sulfur content in the hot metal used as raw material is ≤0.0015%, and at the same time, the sulfur content of the scrap steel is ≤0.0060%, and the sulfur content of the slag-making materials is synchronously controlled; the double slag method is used for efficient dephosphorization in the early stage of smelting; at the end of smelting, high alkalinity, high temperature and low oxidability are controlled to improve the desulfurization effect; finally, the smelting of ultra-low phosphorus and ultra-low sulfur molten steel is realized. By controlling the high temperature at the end of the converter, the high-alkalinity slag at the end of the converter and the low-oxidability molten steel, the desulfurization ability of the slag at the end of the converter is improved, and the sulfur distribution ratio (LS = w(S) / w[S]) at the end of the converter is 3-7. The method realizes w[S] ≤ 0.0040% in the chemical composition of the molten steel tapped from the converter smelting. The desulfurization efficiency of this converter smelting is not high, and the sulfur distribution ratio is low, and it is difficult to be applicable to the desulfurization of raw materials with a relatively high sulfur content.

[0003] The smelting method for efficient desulfurization at the end of the converter with the application number CN202210330382.9 provides a converter desulfurization method, which adopts the following steps: (1) Adopt the double slag method for smelting. Pour out 20 - 35% of the high-silicon slag after blowing for 240 - 270 s, and 50 - 60% of the slag volume at the end point. (2) After pouring the slag at the end point of the converter, control the temperature above 1640 °C, and the oxygen content in the molten steel ≤ 500 ppm. (3) Add deoxidizer and desulfurizer, and carry out compound blowing and stirring for 4 - 7 min, and then tap the steel after desulfurization is completed. First of all, it needs to extend the converter smelting time, and it needs to pour slag twice, and it also needs to carry out additional secondary blowing for 4 - 7 min after smelting. It also needs to add deoxidizer additionally. All these operations lead to an increase in cost. And it pours out 50 - 60% of the slag at the end point of smelting, and adds deoxidizer. The slag pouring volume is insufficient and deoxidizer is added, which easily causes the phosphorus in the slag to be reduced into the molten steel, resulting in the phosphorus content in the molten steel exceeding the standard.

[0004] In view of the above situation, the present invention has developed a low-cost smelting method for hard wire steel. By controlling the feeding system and oxygen supply system in the converter smelting process, efficient dephosphorization and desulfurization are carried out in the early and middle stages of the converter smelting, and then the lance is lifted to pour the slag. Finally, the goals of efficient dephosphorization and desulfurization of the converter are simultaneously achieved. The desulfurization effect is remarkable, and a smelting process that does not require desulfurization during refining, recovers the hot surplus steel and surplus slag after continuous casting and directly utilizes them is realized. The cost per ton of steel can be reduced by more than 20 yuan. Summary of the Invention

[0005] The present invention provides a low-cost smelting method for hard wire steel. The specific method steps and controlled method parameters are as follows:

[0006] The process flow is: converter smelting → tapping → LF refining → continuous casting, which specifically includes the following steps:

[0007] Step 1: Converter smelting. The raw materials for converter steelmaking are scrap steel and hot metal. The scrap steel accounts for 10% - 20% of the total mass of the steelmaking raw materials, and the hot metal accounts for 80% - 90% of the total mass of the steelmaking raw materials. Control appropriate oxygen supply system and slag-making system during the smelting process. When blowing oxygen reaches 80% - 90%, lift the lance for the first time and pour the slag, and then blow oxygen again to make slag until the blowing ends. The tapping carbon content is 0.08% - 0.15%, the oxygen content in the molten steel is 0.01 - 0.03%, the tapping phosphorus content ≤ 0.015%, the tapping sulfur content ≤ 0.012%, and the tapping temperature: 1650 - 1700 °C.

[0008] Among them, the sulfur content in the scrap steel is 0.020% - 0.045%, and the phosphorus content in the scrap steel is 0.010 - 0.035%; the sulfur content in the hot metal is 0.020% - 0.035%, and the phosphorus content in the hot metal is 0.09 - 0.15%.

[0009] Step 2: Tapping. The ladle used for tapping in the continuous casting ladle furnace is the ladle returned after continuous casting, without slag pouring operation, recycling hot molten steel and slag. After 1 / 3 of the tapping, add 1.0 - 2.0 kg / t of silicon carbide, 5.0 - 6.0 kg / t of ferrosilicon manganese and 4.0 - 5.0 kg / t of carburizer in sequence; the bottom blowing flow rate is controlled at 2 - 4 L / min / t.

[0010] Step 3: LF furnace smelting. When refining arrives at the station, measure the temperature, take samples, and determine the oxygen content. Add 0.75 - 1.5 kg / t of calcium carbide, and make fine adjustments to the composition according to the composition of the molten steel arriving at the station. After the composition is qualified, leave the station.

[0011] Step 4: Continuous casting. Use the conventional process for casting, and the ladle with remaining molten steel and slag after casting is returned for use in the next furnace.

[0012] Furthermore, as an optimization, in Step 1, the oxygen supply system is as follows: from the start of blowing to 30% of oxygen supply, the lance position is controlled at 1.5 - 1.6 m; from 30% to 60% of oxygen blowing, the lance position is controlled at 1.6 - 1.8 m; from 60% of oxygen blowing to the first lance lifting, the lance position is controlled at 1.8 - 2.0 m; from the first lance lifting to the end of blowing, the lance position is controlled at 1.0 - 1.2 m. From the start of blowing to 60% of oxygen blowing, the oxygen supply intensity is controlled at 4.0 - 4.2 Nm 3 / t / min; from 60% of oxygen blowing to the first lance lifting, the oxygen supply intensity is controlled at 3.2 - 3.5 Nm 3 / t / min; from the first lance lifting to the end point of blowing, the oxygen supply intensity is controlled at 4.2 - 4.5 Nm 3 / t / min.

[0013] Furthermore, as an optimization, in Step 1, the feeding system is to calculate the amount of lime and ore based on the target slag basicity and temperature at the first lance lifting. When blowing oxygen from 0 to 30%, add 50% of the lime amount and 60% of the ore amount (the main component is Fe2O3). From 30% of oxygen blowing to the first lance lifting, add the remaining amount according to the principle of small quantity and multiple batches. From the first lance lifting to the end of blowing, add 5 - 15 kg / t of lime and 2 - 3 kg / t of slag melting agent. The composition of the slag melting agent is: Na3AlF6: 80% - 90%, CaO: 5% - 10%, Al2O3: 5% - 10%, and the rest are impurities.

[0014] Furthermore, as an optimization, in Step 1, at the first lance lifting and slag pouring, it is required that the slag pouring time ≥ 3 min and the slag pouring amount ≥ 80%; and the molten pool temperature at the first lance lifting is 1550 - 1600 °C, the carbon content of the molten steel is controlled at 0.3% - 0.5%, the slag basicity is controlled at 2.5 - 3.0, and the FeO content of the slag is controlled at 5% - 15%.

[0015] Further, as an optimization, in step one, the basicity of the slag at the end of smelting is controlled at 3.5 - 4.5, the FeO content in the slag is controlled at 5% - 10%, and the sulfur content in the slag is 0.25 - 0.35%.

[0016] Finally, the desulfurization rate of the present invention can be stably controlled at 60.0 - 80%, and the sulfur distribution ratio of the slag (sulfur content in the slag / sulfur content in the molten steel) is above 20. The sulfur distribution ratio of the slag is comprehensively determined by factors such as the molten bath temperature and the slag composition. The higher the sulfur distribution ratio of the slag, the better the desulfurization ability, and the desulfurization effect of the converter is excellent.

[0017] The beneficial effects of the present invention are as follows:

[0018] 1. The converter steelmaking process is optimized, enabling the converter to have the conditions for desulfurization and dephosphorization. The converter smelting can be carried out without using desulfurized hot metal and clean scrap steel, and there is no need for desulfurization and dephosphorization in the refining process.

[0019] 2. The converter makes the first lance lift and slag pouring at 80 - 90% of the oxygen blowing, controls appropriate molten bath temperature and slag conditions, and has the conditions for both dephosphorization and desulfurization. It not only solves the dephosphorization problem without worrying about dephosphorization subsequently, but also preliminarily carries out desulfurization, laying a foundation for subsequent desulfurization by making a low-oxidation slag.

[0020] 3. For the smelting of hard wire steel, the surplus steel and slag of the same steel type can be recycled, without re-making the slag, reducing the steelmaking cost and the solid waste discharge at the same time. Specific Embodiments

[0021] Example 1:

[0022] 1. Converter smelting, adding 22t of scrap steel + 120t of hot metal. The silicon content in the hot metal is 0.35%, the phosphorus content in the hot metal is 0.102%, the sulfur content in the hot metal is 0.026%, the sulfur content in the scrap steel is 0.03%, and the phosphorus content in the scrap steel is 0.025%.

[0023] Control key points: (1) Oxygen supply intensity control method during smelting process: From the start of blowing to 60% of oxygen blowing, the oxygen supply intensity is controlled at 33000 Nm 3 / h (the tapping volume is 135t); from 60% of oxygen blowing to the first lance lift, the oxygen supply intensity is controlled at 28000 Nm 3 / h; from the first lance lift to the end of blowing, the oxygen supply intensity is controlled at 36000 Nm 3 / h. (2) Lance position control method: From the start of blowing to 30% oxygen supply, the lance position is controlled at 1.55 m; from 30% to 60% oxygen blowing, the lance position is controlled at 1.8 m; from 60% oxygen blowing to the first lance lift, the lance position is controlled at 2.0 m; from the first lance lift to the end of blowing, the lance position is controlled at 1.0 m. (3) Charging system: From 0% to 30% oxygen blowing, 1500 kg of lime and 1500 kg of ore are added. From 30% oxygen blowing to the first lance lift, 1500 kg of lime and 1000 kg of ore are added in the principle of small quantity and multiple batches. From the first lance lift to the end of blowing, 1200 kg of lime and 350 kg of slag-making agent are added. When oxygen blowing reaches 83%, the first lance lift and slag pouring are carried out, and the slag pouring amount is 85%. At this time, the molten pool temperature is 1585 °C, and the molten steel composition is C: 0.45%, P: 0.012%, S: 0.020%. The slag basicity is 2.8, and the slag FeO is 13%; at the end point of converter smelting, the molten pool temperature is 1670 °C, and the molten steel composition is C: 0.12%, P: 0.012%, S: 0.010%, O: 0.0167%. The slag basicity is 4.2, the slag FeO is 6%, and the slag sulfur content is 0.32%. The desulfurization rate [(hot metal sulfur * hot metal quantity + scrap sulfur * scrap quantity - tapping steel sulfur * tapping steel quantity) / (hot metal sulfur * hot metal quantity + scrap sulfur * scrap quantity) * 100%] is 65.0%, and the sulfur distribution ratio is 32. The dephosphorization rate [(hot metal phosphorus * hot metal quantity + scrap phosphorus * scrap quantity - tapping steel phosphorus * tapping steel quantity) / (hot metal phosphorus * hot metal quantity + scrap phosphorus * scrap quantity) * 100%] is 87.3%.

[0024] 2. Tapping: The ladle used is the ladle returned after continuous casting pouring without slag pouring operation, and the hot residual steel and slag are recovered. After 1 / 3 of tapping, 200 kg of silicon carbide, 700 kg of silicomanganese and 600 kg of carburizer are added in sequence; the bottom blowing flow rate is controlled at 450 L / min.

[0025] 3. LF furnace smelting: When refining arrives at the station, the temperature is measured, samples are taken, and oxygen is determined. 150 kg of calcium carbide is added, and the composition is slightly adjusted according to the molten steel composition when arriving at the station. After the composition is qualified, it leaves the station.

[0026] 4. After continuous casting pouring, the ladle with residual steel and slag returns to be used in the next furnace.

[0027] Example 2:

[0028] 1. Converter smelting: 20 t of scrap steel + 122 t of hot metal are added. The silicon content of hot metal is 0.55%, the phosphorus content of hot metal is 0.11%, the sulfur content of hot metal is 0.028%, the sulfur content of scrap steel is 0.025%, and the phosphorus content of scrap steel is 0.025%. Control points: (1) Oxygen supply intensity control method during smelting process: From the start of blowing to 60% oxygen blowing, the oxygen supply intensity is controlled at 33000 Nm 3 / h; from 60% oxygen blowing to the first lance lift, the oxygen supply intensity is controlled at 28000 Nm3 / h; From the first lance lifting to the end of blowing, the oxygen supply intensity is controlled at 36000 Nm 3 / h. (2) Lance position control method: From the start of blowing to 30% oxygen supply, the lance position of the oxygen lance is controlled at 1.5 - 1.6 m; from 30% to 60% oxygen blowing, the lance position of the oxygen lance is controlled at 1.8 - 2.0 m; from 60% oxygen blowing to the first lance lifting, the lance position of the oxygen lance is controlled at 2.0 - 2.2 m; from the first lance lifting to the end of blowing, the lance position of the oxygen lance is controlled at 1.0 - 1.2 m. (3) Charging system: When blowing 0 - 30% oxygen, 2000 kg of lime and 1800 kg of ore are added. From 30% oxygen blowing to the first lance lifting, 1800 kg of lime and 1200 kg of ore are added in accordance with the principle of small amounts and multiple batches. From the first lance lifting to the end of blowing, 1300 kg of lime and 350 kg of slag-making agent are added. When blowing 85% oxygen, the first lance lifting is carried out for slag tapping, and the slag tapping amount is 88%. At this time, the molten bath temperature is 1590 °C, and the molten steel composition is C: 0.39%, P: 0.013%, S: 0.018%. The slag basicity is 3.0, and the slag FeO is 12.0%; at the end point of converter smelting, the molten bath temperature is 1665 °C, and the molten steel composition is C: 0.13%, P: 0.011%, S: 0.008%, O: 0.0152%. The slag basicity is 4.5, the slag FeO is 7%, the slag sulfur content is 0.31%, the desulfurization rate is 73.0%, the sulfur distribution ratio is 38.7, and the dephosphorization rate is 89.3%.

[0029] 2. Tapping: The ladle used is the ladle returned after continuous casting pouring without slag tapping operation, and the hot molten steel and molten slag are recycled. After 1 / 3 of the tapping, 200 kg of silicon carbide, 700 kg of silicomanganese, and 600 kg of carburizer are added in sequence; the bottom blowing flow rate is controlled at 450 L / min.

[0030] 3. LF furnace smelting: When refining arrives at the station, the temperature is measured, samples are taken, and the oxygen is determined. 150 kg of calcium carbide is added, and the composition is slightly adjusted according to the molten steel composition when arriving at the station. After the composition is qualified, it leaves the station.

[0031] 4. After continuous casting pouring, the ladle with remaining molten steel and molten slag returns to be used in the next furnace.

[0032] Example 3:

[0033] 1. Converter smelting: 21 t of scrap steel + 121 t of hot metal are added. The silicon content of the hot metal is 0.62%, the phosphorus content of the hot metal is 0.12%, the sulfur content of the hot metal is 0.028%, the sulfur content of the scrap steel is 0.026%, and the phosphorus content of the scrap steel is 0.03%. Control points: (1) Oxygen supply intensity control method during smelting process: From the start of blowing to 60% oxygen blowing, the oxygen supply intensity is controlled at 33000 Nm 3 / h; From 60% oxygen blowing to the first lance lifting, the oxygen supply intensity is controlled at 28000 Nm 3 / h; From the first lance lift to the end of blowing, the oxygen supply intensity is controlled at 36000 Nm 3 / h. (2) Lance position control method: From the start of blowing to 30% oxygen supply, the lance position of the oxygen lance is controlled at 1.5 - 1.6 m; from 30% to 60% oxygen blowing, the lance position of the oxygen lance is controlled at 1.8 - 2.0 m; from 60% oxygen blowing to the first lance lift, the lance position of the oxygen lance is controlled at 2.0 - 2.2 m; from the first lance lift to the end of blowing, the lance position of the oxygen lance is controlled at 1.0 - 1.2 m. (3) Charging system: When blowing 0 - 30% oxygen, 2500 kg of lime and 2200 kg of ore are added; from 30% oxygen blowing to the first lance lift, 2000 kg of lime and 1500 kg of ore are added in the principle of small amount and multiple batches. From the first lance lift to the end of blowing, 1300 kg of lime and 350 kg of slag melting agent are added. When blowing 87% oxygen, the first lance lift is carried out for slag pouring, and the slag pouring amount is 88%. At this time, the molten pool temperature is 1592 °C, and the molten steel composition is C: 0.42%, P: 0.012%, S: 0.017%, the slag basicity is 2.9, and the slag FeO is 11.2%; at the end of converter smelting, the molten pool temperature is 1672 °C, and the molten steel composition is C: 0.11%, P: 0.011%, S: 0.007%, O: 0.0163%, the slag basicity is 4.6, the slag FeO is 6%, the sulfur content in the slag is 0.30%, the desulfurization rate is 76.5%, the sulfur distribution ratio is 42.9, and the dephosphorization rate is 90.2%.

[0034] 2. Tapping: The ladle used is the ladle returned after continuous casting pouring without slag pouring operation, and the hot residual steel and slag are recycled. After 1 / 3 of the tapping, 210 kg of silicon carbide, 710 kg of silicomanganese and 610 kg of carburizer are added in sequence; the bottom blowing flow rate is controlled at 450 L / min.

[0035] 3. LF furnace smelting: When refining arrives at the station, the temperature is measured, samples are taken, and oxygen is determined. 150 kg of calcium carbide is added, and the composition is fine-tuned according to the molten steel composition at the arrival station. After the composition is qualified, it leaves the station.

[0036] 4. After continuous casting pouring, the ladle with residual steel and slag returns to be used in the next furnace.

[0037] Comparative Example 1:

[0038] 1. Converter smelting: 22 t of scrap steel + 120 t of hot metal are added. The silicon content of the hot metal is 0.35%, the phosphorus content of the hot metal is 0.105%, and the sulfur content of the hot metal is 0.024%. The converter uses the single slag method for smelting. Oxygen supply system: The constant pressure and variable lance position operation is adopted, and the oxygen supply flow rate is 33000 Nm 3 / h, oxygen supply is 0 - 20%, lance position is 1.5 m, oxygen supply is 20 - 95%, lance position is 1.5 - 1.8 m, oxygen supply is 95% - raising the lance, lance position is 1.3 m. Charging system: during the oxygen supply of 0 - 36%, 3200 kg of lime and 2000 kg of lightly burned dolomite are added; during the oxygen supply of 36 - 85%, 500 kg and 500 kg of lime are added respectively at 40% and 50% of oxygen supply, and 500 kg, 500 kg and 600 kg of ore are added at 50%, 60% and 70% of oxygen supply. The chemical composition of the molten steel at the end of smelting is C: 0.06%, P: 0.014%, S: 0.022%, the basicity of the slag is 3.2, and the FeO in the slag is 18%. After the converter smelting is completed, the slag is poured out and the steel is tapped.

[0039] 2. Tapping: The ladle is the ladle that has been returned after continuous casting and slag has been poured out, without remaining steel and slag. After 1 / 3 of the steel is tapped, 250 kg of silicon carbide, 720 kg of silicomanganese, 630 kg of carburizer, 500 kg of lime and 200 kg of fluorite are added in sequence; the bottom blowing flow rate is controlled at 450 L / min.

[0040] 3. LF furnace smelting: When refining arrives at the station, the temperature is measured, samples are taken, and the oxygen is determined. 200 kg of calcium carbide is added, and the chemical composition is fine-tuned according to the chemical composition of the molten steel at the arrival station. When further desulfurization treatment is required, 200 kg of lime and 100 kg of fluorite are added as supplements. After the chemical composition and temperature are qualified, the steel is sent out of the station and sent to the continuous casting.

[0041] In the comparative example, the desulfurization task was not completed at the end of the converter smelting in Example 1, and desulfurization needed to be continued during the refining process, and the recycling of remaining steel and slag could not be achieved.

[0042] Comparative Example 2:

[0043] 1. Converter smelting: 22 t of scrap steel + 120 t of hot metal are added. The silicon content of the hot metal is 0.35%, the phosphorus content of the hot metal is 0.102%, the sulfur content of the hot metal is 0.026%, and the sulfur content of the scrap steel is 0.03%.

[0044] Control key points: (1) Oxygen supply intensity control method during smelting process: From the start of blowing to 60% of oxygen blowing, the oxygen supply intensity is controlled at 33000 Nm 3 / h; from 60% of oxygen blowing to the first lance raising, the oxygen supply intensity is controlled at 28000 Nm 3 / h; from the first lance raising to the end of blowing, the oxygen supply intensity is controlled at 36000 Nm 3 / h. (2) Lance position control method: From the start of blowing to 30% oxygen supply, the lance position is controlled at 1.55 m; from 30% to 60% oxygen blowing, the lance position is controlled at 1.8 m; from 60% oxygen blowing to the first lance lift, the lance position is controlled at 2.0 m; from the first lance lift to the end of blowing, the lance position is controlled at 1.0 m. (3) Charging system: From 0% to 30% oxygen blowing, 1500 kg of lime and 1500 kg of ore are added. From 30% oxygen blowing to the first lance lift, 1500 kg of lime and 1000 kg of ore are added in the principle of small quantity and multiple batches. From the first lance lift to the end of blowing, 1200 kg of lime and 350 kg of slag-making agent are added. When the oxygen blowing reaches 70%, the first lance lift for slag pouring is carried out, and the slag pouring amount is 85%. At this time, the molten pool temperature is 1525 °C, and the molten steel composition is C: 1.05%, P: 0.045%, S: 0.026%. The slag basicity is 2.8, and the slag FeO is 7.0%; at the end of converter smelting, the molten pool temperature is 1670 °C, and the molten steel composition is C: 0.12%, P: 0.026%, S: 0.016%, O: 0.0167%. The slag basicity is 4.2, the slag FeO is 6%, the sulfur content in the slag is 0.21%, the desulfurization rate is 44.0%, and the sulfur distribution ratio is 13.1.

[0045] Comparing Comparative Example 2 with Example 1, the timing of the first lance lift is 70% of the oxygen blowing amount. The carbon content of the molten steel is too high, the oxidability of the slag is low, and the molten steel temperature is low. The dephosphorization and desulfurization capabilities become poor. Eventually, the dephosphorization requirement cannot be met at the end of converter smelting, and additional blowing is needed to complete dephosphorization, and the sulfur content cannot be met. The desulfurization task is not completed at the end of converter smelting, and desulfurization needs to be continued during the refining process, and the recycling of surplus steel and slag cannot be achieved.

[0046] Since both the phosphorus content and the sulfur content fail to meet the requirements, additional blowing is carried out subsequently. After additional blowing, the phosphorus content of the molten steel is 0.013%, and the sulfur content of the molten steel is 0.018%. The sulfur content fails to meet the requirements, and refining desulfurization is needed, and the recycling of surplus steel and slag cannot be achieved.

[0047] Comparative Example 3:

[0048] 1. Converter smelting, adding 22 t of scrap steel + 120 t of hot metal. The silicon content of the hot metal is 0.35%, the phosphorus content of the hot metal is 0.102%, the sulfur content of the hot metal is 0.026%, and the sulfur content of the scrap steel is 0.03%.

[0049] Control key points: (1) Oxygen supply intensity control method during smelting process: From the start of blowing to 60% oxygen blowing, the oxygen supply intensity is controlled at 33000 Nm 3 / h; from 60% oxygen blowing to the first lance lift, the oxygen supply intensity is controlled at 28000 Nm 3 / h; from the first lance lift to the end of blowing, the oxygen supply intensity is controlled at 36000 Nm 3 / h. (2) Lance position control method: From the start of blowing to 30% oxygen supply, the lance position is controlled at 1.55 m; from 30% to 60% oxygen blowing, the lance position is controlled at 1.8 m; from 60% oxygen blowing to the first lance lift, the lance position is controlled at 2.0 m; from the first lance lift to the end of blowing, the lance position is controlled at 1.0 m. (3) Charging system: From 0% to 30% oxygen blowing, 1500 kg of lime and 1500 kg of ore are added; from 30% oxygen blowing to the first lance lift, 1500 kg of lime and 1000 kg of ore are added in accordance with the principle of small amounts in multiple batches. From the first lance lift to the end of blowing, 1200 kg of lime and 350 kg of slag-making agent are added. When the oxygen blowing reaches 95%, the first lance lift and slag tapping are carried out, and the slag tapping amount is 85%. At this time, the molten bath temperature is 1585 °C, and the molten steel composition is C: 0.17%, P: 0.012%, S: 0.025%. The slag basicity is 2.8, and the slag FeO is 17.0%; at the end point of converter smelting, the molten bath temperature is 1670 °C, and the molten steel composition is C: 0.05%, P: 0.012%, S: 0.020%, O: 0.052%. The slag basicity is 4.2, the slag FeO is 12%, the slag sulfur content is 0.18%, the desulfurization rate is 30.0%, and the sulfur distribution ratio is 9.

[0050] Compared with Example 1, the timing of the first lance lift is 95% of the oxygen blowing amount. The carbon content of the molten steel is too low, the oxidability of the slag is high, and subsequent overblowing occurs to ensure the molten bath temperature and desulfurization time. Neither the oxidability of the slag nor the carbon content of the molten steel can meet the requirements. The primary desulfurization cannot meet the requirements, and the sulfur content at the final smelting end point also fails to meet the requirements. Desulfurization needs to be continued during the refining process, and the recycling of surplus steel and slag cannot be achieved.

[0051] Comparative Example 4:

[0052] 1. In converter smelting, 22 t of scrap steel + 120 t of hot metal are added. The silicon content of the hot metal is 0.35%, the phosphorus content of the hot metal is 0.102%, the sulfur content of the hot metal is 0.026%, and the sulfur content of the scrap steel is 0.03%. Control points: (1) Oxygen supply intensity control method during smelting process: From the start of blowing to 60% oxygen blowing, the oxygen supply intensity is controlled at 33000 Nm 3 / h; from 60% oxygen blowing to the first lance lift, the oxygen supply intensity is controlled at 28000 Nm 3 / h; from the first lance lift to the end of blowing, the oxygen supply intensity is controlled at 36000 Nm 3 / h. (2) Lance position control method: From the start of blowing to 30% oxygen supply, the lance position is controlled at 1.55 m; from 30% to 60% oxygen blowing, the lance position is controlled at 1.8 m; from 60% oxygen blowing to the first lance lifting, the lance position is controlled at 2.0 m; from the first lance lifting to the end of blowing, the lance position is controlled at 1.0 m. (3) Charging system: When blowing 0 - 30% oxygen, 1500 kg of lime and 1500 kg of ore are added. From 30% oxygen blowing to the first lance lifting, 1500 kg of lime and 1000 kg of ore are added in the principle of small quantity and multiple batches. From the first lance lifting to the end of blowing, 1200 kg of lime and 350 kg of slag-making agent are added. When blowing 83% oxygen, the first lance lifting and slag pouring are carried out, and the slag pouring amount is 85%. At this time, the molten bath temperature is 1585 °C, and the molten steel composition is C: 0.45%, P: 0.012%, S: 0.020%, the slag basicity is 2.8, and the slag FeO is 13%; at the end point of converter smelting, the molten bath temperature is 1670 °C, the molten steel composition is C: 0.04%, P: 0.010%, S: 0.019%, O: 0.062%, the slag basicity is 4.2, the slag FeO is 16.5%, the slag sulfur content is 0.18%, the desulfurization rate is 33.0%, and the sulfur distribution ratio is 9.5.

[0053] Comparing Example 4 with Example 1, the oxygen content of the molten steel at the end point of the converter is too high, and the oxidability of the slag is too strong. Finally, the desulfurization target cannot be achieved. The sulfur content fails to meet the requirements, and refining desulfurization is needed, and the recycling of surplus steel and slag cannot be realized.

[0054] As mentioned above, it is only the preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and its concept of the present invention, makes equivalent substitution or change, and all should be covered within the protection scope of the present invention.

Claims

1. A low-cost smelting method for hard wire steel, characterized in that: The process flow is converter smelting → LF refining → continuous casting. The specific operation steps are as follows: Step 1, Converter smelting: The raw materials for converter steelmaking are scrap steel and hot metal. The scrap steel accounts for 10% - 20% of the total mass of the steelmaking raw materials, and the hot metal accounts for 80% - 90% of the total mass of the steelmaking raw materials. During the smelting process, the oxygen supply system and slag-making system are controlled. When the oxygen blowing reaches 80% - 90%, the lance is lifted for the first time and the slag is poured out. Then, oxygen blowing and slag-making are restarted until the blowing ends. The carbon content of the molten steel at tapping is 0.08% - 0.15%, the oxygen content of the molten steel is 0.01 - 0.03%, the phosphorus content of the molten steel at tapping is ≤0.015%, the sulfur content of the molten steel at tapping is ≤0.012%, and the tapping temperature is 1650 - 1700°C. In Step 1, the sulfur content in the scrap steel is 0.020% - 0.045%, and the phosphorus content in the scrap steel is 0.010 - 0.035%; the sulfur content in the hot metal is 0.020% - 0.035%, and the phosphorus content in the hot metal is 0.09 - 0.15%. The oxygen supply system is specifically as follows: from the start of blowing to 30% oxygen supply, the lance position is controlled at 1.5 - 1.6 m; from 30% to 60% oxygen blowing, the lance position is controlled at 1.6 - 1.8 m; from 60% oxygen blowing to the first lance lift, the lance position is controlled at 1.8 - 2.0 m; from the first lance lift to the end of blowing, the lance position is controlled at 1.0 - 1.2 m; from the start of blowing to 60% oxygen blowing, the oxygen supply intensity is controlled at 4.0 - 4.2 Nm 3 / t / min; from 60% oxygen blowing to the first lance lift, the oxygen supply intensity is controlled at 3.2 - 3.5 Nm 3 / t / min; from the first lance lift to the end point of blowing, the oxygen supply intensity is controlled at 4.2 - 4.5 Nm 3 / t / min; Slag-making system: Calculate the amount of lime and ore based on the target slag basicity and temperature at the first lance lift. When the oxygen blowing is 0 - 30%, add 50% of the lime amount and 60% of the ore amount. From 30% of oxygen blowing to the first lance lift, add the remaining amount according to the principle of small quantity and multiple batches; from the first lance lift to the end of blowing, add 5 - 15 kg / t of lime and 2 - 3 kg / t of slag melting agent. The composition of the slag melting agent is: Na3AlF6: 80% - 90%, CaO: 5% - 10%, Al2O3: 5% - 10%, and the rest are impurities. Step 2, Tapping: The ladle used for continuous casting tapping is the ladle returned after continuous casting, without slag pouring operation. Recover the hot waste steel and slag. After 1 / 3 of the tapping, add silicon carbide, ferrosilicon manganese, and carburizer in sequence; the bottom blowing flow rate is controlled at 2 - 4 L / min / t. Step 3, LF furnace refining: When refining arrives at the station, measure the temperature, take samples, and determine the oxygen content, add calcium carbide, and make fine adjustments to the composition according to the composition of the molten steel at the station. After the composition is qualified, leave the station. Step 4, Continuous casting: The ladle with remaining steel and slag after casting is returned for use in the next furnace.

2. The low-cost smelting method of hard wire steel according to claim 1, characterized in that: In Step 1, when the lance is lifted for the first time and the slag is poured out, it is required that the slag pouring time ≥3.0 min and the slag pouring amount ≥80%; and the molten pool temperature at the first lance lift is 1550 - 1600°C, and the carbon content of the molten steel is controlled at 0.3% - 0.5%.

3. The low-cost smelting method of hard wire steel according to claim 1, characterized in that: In Step 1, the basicity of the smelting end slag is controlled at 3.5 - 4.5, the FeO content of the slag is controlled at 5% - 10%, and the sulfur content of the slag is 0.25 - 0.35%.