Method for preparing high-strength building steel from niobium-phosphorus alloy at low cost

Abstract

The invention provides a low-cost method for preparing high-strength building steel from a niobium-phosphorus alloy, and belongs to the technical field of steel preparation. The method comprises the steps that waste steel is smelted in an electric furnace, the P content of molten steel at the end point of the electric furnace is controlled to be smaller than or equal to 0.012%, the C content of the molten steel is controlled to be 0.06%-0.1%, vanadium slag and silicon-manganese alloy are added along with steel flow in the tapping process, and then argon blowing stirring is conducted; molten steel is conveyed to an LF refining furnace, a first batch of ferrosilicon alloy, carbon powder and lime are added, the molten steel is electrified and heated to 1520-1540 DEG C, the P content in the molten steel is controlled to be smaller than or equal to 0.012%, the C content is controlled to be 0.14-0.16%, the silicon content is controlled to be 0.13-0.15%, and the phosphorus content is controlled to be smaller than or equal to 0.012%, the molten steel continues to be electrified and heated to make white slag, the lime and the remaining ferrosilicon alloy are supplemented, and when the molten steel meets the refining requirement, niobium-phosphorus alloy is added into the LF refining furnace; and controlling the temperature of the molten steel at the end of refining to obtain the high-strength building steel. According to the method, the absolute limitation on the phosphorus content of the raw materials in the steelmaking process is broken through, and the high-phosphorus alloy can be safely applied in the steelmaking process through the phosphorus content balance control strategy that the phosphorus content is low in the front and high in the rear.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of steel production, in particular to a method for low-cost preparation of high-strength building steel by using niobium-phosphorus alloy. BACKGROUND

[0002] The steel industry, as a typical basic manufacturing industry, is currently facing multiple challenges such as weak recovery of traditional market demand, intensified stage-by-stage mismatch between supply and demand, and sustained pressure on profitability. In particular, under the background of "double carbon", electric furnace short process steelmaking has become an important direction for industry transformation due to its significant environmental advantages, but cost control has always been a key factor restricting the competitiveness of enterprises. From the analysis of steelmaking cost structure, alloy cost accounts for about 20% of the total cost of electric furnace smelting. In the production of high-strength building steel, the traditional micro-alloying process mainly relies on vanadium-nitrogen alloy (V-N) to improve the strength and toughness of steel, but the high price of vanadium directly pushes up the total production cost, further compressing the profit space of enterprises. At the same time, there is a kind of niobium-phosphorus alloy with high phosphorus content in the industry at present (usually Nb content is about 40%, P content is as high as about 5%). Since phosphorus (P) is considered as a harmful impurity in most steel grades, it not only causes the "cold brittleness" phenomenon of steel, but also significantly worsens its welding performance and plasticity, so this high-phosphorus niobium-iron alloy has always been regarded as "waste" or low-value raw material in traditional steelmaking process, and it is difficult to achieve large-scale industrial application.

[0003] In the prior art, there is a lack of a process method that can safely and stably utilize this high-phosphorus niobium-iron alloy. If the quality risk brought by high phosphorus can be solved through process optimization, and the expensive vanadium-nitrogen alloy is replaced by cheap niobium-phosphorus alloy, it will bring huge economic benefits to steel enterprises in terms of cost reduction and efficiency improvement. SUMMARY

[0004] The present application provides a method for low-cost preparation of high-strength building steel by using niobium-phosphorus alloy, aiming at the problem in the prior art that the production of high-strength building steel relies on expensive vanadium-nitrogen alloy, resulting in high cost and high phosphorus content of niobium-phosphorus alloy which is difficult to be scaled up due to the harmfulness of phosphorus.

[0005] The technical method of the present application is as follows: A method for low-cost preparation of high-strength building steel by using niobium-phosphorus alloy, comprising the following steps: Step S1, electric furnace smelting and tapping: smelting scrap steel in an electric furnace, controlling the P content of the electric furnace endpoint molten steel ≤0.012%, the C content 0.06~0.1%, adding vanadium slag and silicon-manganese alloy into the steel stream during the tapping process, and then performing argon blowing stirring; Step S2, LF Refining: The molten steel is transported to the LF refining furnace, and the first batch of ferrosilicon alloy, carbon powder, and lime are added. The furnace is then heated to 1520℃~1540℃, and the P content in the molten steel is controlled to be ≤0.012%, C content to be 0.14~0.16%, silicon content to be 0.13~0.15%, and phosphorus content to be ≤0.012%. The furnace continues to be heated to produce white slag, and lime and the remaining ferrosilicon alloy are added. When the molten steel meets the refining requirements, niobium-phosphorus alloy is added to the LF refining furnace. The entire LF refining process is bottom-blown argon. Step S3, Endpoint Control: Control the temperature of the molten steel at the end of refining to obtain high-strength construction steel.

[0006] Optionally, in step S1, the silicon-manganese alloy added during the steel tapping process has a Si content of 15%~25% and a Mn content of 65%~75%.

[0007] Optionally, between steps S1 and S2, the ladle containing molten steel is in a preheating state, and the temperature inside the ladle is maintained at 900℃~1100℃; and no scrap steel is added to the ladle during the tapping process and the subsequent LF refining process.

[0008] Optionally, the chemical composition of the niobium-phosphorus alloy, by mass percentage, includes: Nb content of 38%~43%, P content of 4.5%~5.5%, S≤0.1%, C≤0.3%, and the balance being Fe.

[0009] Optionally, the Si content in the first batch of ferrosilicon alloy and the remaining ferrosilicon alloy is 70-80%, with the balance being TFe; the carbon content in the carbon powder is >90%.

[0010] Optionally, the ratio of the first batch of ferrosilicon alloy, carbon powder, and lime is 0.35~0.45:0.2~0.4:5.5~6.5. The ratio of lime to the remaining ferrosilicon alloy is 1~2:0.1~0.2.

[0011] Optionally, in step S1, the argon flow rate is 100~150m³. 3 / hour; in step S2, the argon flow rate is 50~150m³ / h. 3 / Hour.

[0012] Optionally, the vanadium slag has a particle size of 20-50 mm. The vanadium slag includes ≥40 wt% niobium, ≥42 wt% iron, ≤5.5 wt% phosphorus, ≤0.3 wt% carbon, and ≤0.1 wt% sulfur.

[0013] Optionally, the temperature of the molten steel at the end of the refining process is 1590-1600℃.

[0014] The beneficial effects of this invention are: I. This invention realizes the resource utilization of high phosphorus resources: it breaks the absolute limitation on the phosphorus content of raw materials in the steelmaking process, and through the phosphorus content balance control strategy of "low at the beginning and high at the end" (that is, the phosphorus is first removed to below 0.012% in the electric furnace stage to accommodate the phosphorus brought in by niobium-phosphorus alloy), high phosphorus alloys can be safely used in the steelmaking process.

[0015] II. Stable product quality of the present invention: Although high-phosphorus raw materials such as high-phosphorus alloys are used, through the whole process control of the present invention, the P content of the final molten steel can be stably controlled below 0.040%, and the S content is controlled below 0.03%, which fully meets the national standard requirements for the composition and performance of high-strength building steel.

[0016] Third, this invention significantly reduces production costs and has outstanding cost advantages: by using inexpensive niobium-phosphorus alloys to replace expensive vanadium-nitrogen alloys, the raw material procurement cost of high-strength construction steel is greatly reduced. Attached Figure Description

[0017] Figure 1 A schematic diagram of a low-cost method for preparing high-strength building steel using niobium-phosphorus alloys is shown. Detailed Implementation

[0018] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] This invention provides a low-cost method for preparing high-strength construction steel using niobium-phosphorus alloys, such as... Figure 1 As shown, it includes the following steps: Step S1, Electric Furnace Smelting and Tapping: The scrap steel is smelted in an electric furnace. The P content of the molten steel at the end of the electric furnace is controlled to be ≤0.012%, and the C content is 0.06~0.1%. Vanadium slag and silicon-manganese alloy are added with the steel stream during tapping, and then argon blowing and stirring are performed.

[0020] In this embodiment, the scrap steel includes: 85%~95% iron, 0.1%~1.0% carbon, 0.1%~0.4% silicon, 0.2%~0.8% manganese, 0.02%~0.05% phosphorus, 0.02%~0.05% sulfur, 0.1%~0.4% copper, 0.1%~0.3% nickel, 0.1%~0.3% chromium, and ≤0.05% molybdenum, tin, and lead.

[0021] In this embodiment, silicon-manganese can be deoxidized and alloyed.

[0022] In this embodiment, the silicon-manganese alloy added during the steelmaking process has a Si content of 15%~25% and a Mn content of 65%~75%.

[0023] In this embodiment, the particle size of the niobium-phosphorus alloy is 20~50mm. The vanadium slag includes ≥40wt% niobium, ≥42wt% iron, ≤5.5wt% phosphorus, ≤0.3wt% carbon, and ≤0.1wt% sulfur.

[0024] In this embodiment, the melting temperature is 1600~1640℃.

[0025] In this embodiment, the argon flow rate is 100~150m³. 3 / Hour.

[0026] Between steps S1 and S2, the ladle containing molten steel is in a preheating state, and the temperature inside the ladle is maintained at 900℃~1100℃; and no scrap steel is added to the ladle during the tapping process and the subsequent LF refining process to prevent phosphorus from re-entering.

[0027] Step S2, LF Refining: The molten steel is transported to the LF refining furnace, and the first batch of ferrosilicon alloy, carbon powder and lime are added. The furnace is heated to 1520℃~1540℃, and the P content in the molten steel is controlled to be ≤0.012%, C content to be 0.14~0.16%, silicon content to be 0.13~0.15%, and phosphorus content to be ≤0.012%. The furnace continues to be heated to produce white slag, and lime and the remaining ferrosilicon alloy are added. When the molten steel meets the refining requirements, niobium-phosphorus alloy is added to the LF refining furnace.

[0028] In this embodiment, the addition of the first batch of ferrosilicon alloy, carbon powder and lime can deoxidize and produce reducing slag. The addition of lime and the remaining ferrosilicon alloy can increase the alkalinity to produce white slag and improve alloying.

[0029] In this embodiment, the ratio of the first batch of ferrosilicon alloy, carbon powder, and lime is 0.35~0.45:0.2~0.4:5.5~6.5.

[0030] In this embodiment, the LF refining process involves bottom blowing argon throughout. The argon flow rate is 50~150m³. 3 / Hour.

[0031] In this embodiment, the Si content in the first batch of ferrosilicon alloy and the remaining ferrosilicon alloy is 70-80%, and the balance is TFe.

[0032] In this embodiment, the carbon content in the toner is >90%.

[0033] In this embodiment, the ratio of lime to the remaining ferrosilicon alloy is 1~2:0.1~0.2.

[0034] In this embodiment, the chemical composition of the niobium-phosphorus alloy, by mass percentage, includes: Nb content of 38%~43%, P content of 4.5%~5.5%, S≤0.1%, C≤0.3%, and the balance being Fe.

[0035] In this embodiment, the conditions for molten steel to meet refining requirements are as follows: Carbon (C): lower limit 0.21, upper limit 0.23, target value 0.22; Silicon (Si): lower limit 0.45, upper limit 0.55, target value 0.50; Manganese (Mn): lower limit 1.40, upper limit 1.50, target value 1.45; Niobium (Nb): lower limit 0.015, upper limit 0.02, target value 0.018; Nitrogen (N): lower limit 0.008, upper limit 0.012, target value 0.01; other components: controlled according to the original process requirements.

[0036] Step S3, Endpoint Control: Control the temperature of the molten steel at the end of refining to obtain high-strength construction steel.

[0037] In this embodiment, the temperature of the molten steel at the end of refining is 1590-1600℃.

[0038] Using this method, taking an electric arc furnace plant with an annual output of 3 million tons as an example, the price of the conventionally used 70 vanadium-nitrogen alloy is 140,000 yuan / ton, and the price of the niobium-phosphorus alloy is 68,000 yuan / ton.

[0039] (1) Calculation of vanadium addition cost for 70% vanadium-nitrogen alloy The amount of vanadium metal required per ton of steel = 1000 × 0.02% = 0.2 kg The amount of vanadium-nitrogen alloy required per ton of steel = 0.2 ÷ 70% = 0.286 kg The cost of adding vanadium using 70 vanadium-nitrogen alloy = 0.286 ÷ 1000 × 140000 = 40.04 yuan / ton of steel (2) Calculation of niobium-phosphorus alloy niobium addition cost The amount of niobium metal required per ton of steel = 1000 × 0.02% = 0.2 kg The amount of niobium-phosphorus alloy required per ton of steel = 0.2 ÷ 40% = 0.5 kg The cost of using 40% niobium-phosphorus alloy = 0.5 ÷ 1000 × 68000 = 34 yuan / ton of steel Profit per ton of steel = 40.04 - 34 = 6.04 yuan Based on the results of this invention, it is estimated that the benefits generated will be over 6 yuan per ton of steel.

[0040] In this invention, unless otherwise specified, all raw materials used in the preparation are commercially available products well known to those skilled in the art.

[0041] The present invention will be described in detail below through embodiments and experimental examples. However, these are merely examples and do not limit the present invention in any way.

[0042] Example 1 This embodiment provides a method for preparing high-strength construction steel from niobium-phosphorus alloys at low cost, including the following steps: Step 1: After being blown through an electric furnace to the final composition, the steel output is 140 tons. The final steel composition is: C content 0.08%, Si content 0.003%, Mn content 0.03%, P content 0.010%.

[0043] Step 2: The ladle that holds the molten steel from the electric furnace is kept in a preheated state before being transported to the tapping position, and the temperature of the scrap steel inside the ladle is 1000℃.

[0044] Step 3: When tapping the steel, add 13 kg of silicon-manganese alloy per ton of steel. After the silicon-manganese alloy is added, stir with argon gas for 5 minutes at a flow rate of 120 m³ / ton. 3 At a pressure of 1.0 MPa per hour, the molten steel ladle is immediately transported to the LF refining process, where argon is blown from the bottom throughout. Upon arrival at the LF station, 0.4 kg of ferrosilicon (70-80% Si content, balance TFe) and 150 kg of carbon powder (carbon content >90%) are added, along with 1000 kg of lime. The ladle is heated for 5 minutes to 1530℃. Analysis of the molten steel composition reveals a carbon content of 0.15%, a silicon content of 0.14%, and a vanadium content of 0.013%. Heating continues, and 900 kg of lime (5-7 kg per ton of steel) is added to create "white slag." The remaining ferrosilicon and other alloys required for the specific steel grade are then added. The qualified niobium-phosphorus alloy was transported to the LF alloy material silo in 10 kg bags. 70 kg of niobium-phosphorus alloy (i.e., 0.5 kg / ton of steel) was added manually. The niobium-phosphorus composition was: Nb 40%, P 4.9%, S 0.08%, C 0.26%, and the remainder was Fe. The particle size of the vanadium slag was 20~50 mm.

[0045] At the end of refining, the molten steel temperature is 1590℃. At this point, the main components of the molten steel are as follows: C content 0.23%, Si content 0.31%, Mn content 1.0%, P content <0.040%, and S content <0.03%. After the above process steps are completed, the target Nb-containing molten steel is obtained, which is then used for continuous casting.

[0046] Example 2 This embodiment provides a method for preparing high-strength construction steel from niobium-phosphorus alloys at low cost, including the following steps: Step 1: After being blown through an electric furnace to the final composition, the steel output was 141 tons. The final steel composition was: C content 0.07%, Si content 0.004%, Mn content 0.04%, P content 0.009%.

[0047] Step 2: The ladle containing the molten steel from the electric furnace is kept in a preheated state before being transported to the tapping position, and the temperature of the scrap steel inside the ladle is 950℃.

[0048] Step 3: Add 14 kg / ton of ferrosilicon manganese alloy during tapping. After adding vanadium slag and ferrosilicon manganese alloy, stir with argon gas for 5 minutes at a flow rate of 110 m³ / ton. 3 At a pressure of 1.1 MPa per hour, molten steel ladles are randomly transported to the LF refining process, which involves bottom-blowing argon throughout. Upon arrival at the LF station, 0.39 kg of ferrosilicon (70-80% Si content, balance TFe) and 160 kg of carbon powder (carbon content >90%) are added, along with 900 kg of lime. The mixture is heated for 5 minutes to 1540℃. Analysis of the molten steel composition reveals a carbon content of 0.14%, a silicon content of 0.15%, and a vanadium content of 0.02%. Heating continues, and 900 kg of lime (5-7 kg per ton of steel) is added to create "white slag." The remaining ferrosilicon and other alloys required for the specific steel grade are then added. The qualified niobium-phosphorus alloy was transported to the LF alloy material silo in 10 kg bags. 70 kg of niobium-phosphorus alloy (i.e., 0.5 kg / ton of steel) was added manually. The niobium-phosphorus composition was: Nb 42%, P 5.1%, S 0.09%, C 0.29%, and the remainder was Fe. The particle size of the vanadium slag was 20~50 mm.

[0049] Various embodiments of the present invention may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limitation on the scope of the invention; therefore, it should be considered that the range description has specifically disclosed all possible subranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed subranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Furthermore, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the range referred to.

[0050] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for low-cost preparation of high-strength construction steel using niobium-phosphorus alloy, characterized in that, Includes the following steps: Step S1, Electric Furnace Smelting and Tapping: The scrap steel is smelted in an electric furnace. The P content of the molten steel at the end of the electric furnace is controlled to be ≤0.012%, and the C content is 0.06~0.1%. Vanadium slag and silicon-manganese alloy are added with the steel stream during the tapping process, and then argon blowing and stirring are carried out. Step S2, LF Refining: The molten steel is transported to the LF refining furnace, and the first batch of ferrosilicon alloy, carbon powder, and lime are added. The furnace is then heated to 1520℃~1540℃, and the P content in the molten steel is controlled to be ≤0.012%, C content to be 0.14~0.16%, silicon content to be 0.13~0.15%, and phosphorus content to be ≤0.012%. The furnace continues to be heated to produce white slag, and lime and the remaining ferrosilicon alloy are added. When the molten steel meets the refining requirements, niobium-phosphorus alloy is added to the LF refining furnace. The entire LF refining process is bottom-blown argon. Step S3, Endpoint Control: Control the temperature of the molten steel at the end of refining to obtain high-strength construction steel.

2. The method according to claim 1, characterized in that, The chemical composition of the niobium-phosphorus alloy, by mass percentage, includes: Nb content of 38%~43%, P content of 4.5%~5.5%, S≤0.1%, C≤0.3%, and the balance being Fe.

3. The method according to claim 1, characterized in that, In step S1, the silicon-manganese alloy added during the steel tapping process has a Si content of 15%~25% and a Mn content of 65%~75%.

4. The method according to claim 1, characterized in that, Between steps S1 and S2, the ladle containing molten steel is in a preheating state, and the temperature inside the ladle is maintained at 900℃~1100℃; and no scrap steel is added to the ladle during the tapping process and the subsequent LF refining process.

5. The method according to claim 1, characterized in that, The first batch of ferrosilicon alloy and the remaining ferrosilicon alloy contain 70-80% Si, with the balance being TFe. The carbon content in the toner is >90%.

6. The method according to claim 1, characterized in that, The ratio of the first batch of ferrosilicon alloy, carbon powder, and lime is 0.35~0.45:0.2~0.4:5.5~6.

5.

7. The method according to claim 1, characterized in that, The ratio of lime to residual ferrosilicon alloy is 1~2:0.1~0.

2.

8. The method according to claim 1, characterized in that, In step S1, the argon flow rate is 100~150m³. 3 / Hour; In step S2, the argon flow rate is 50~150m³. 3 / Hour.

9. The method according to claim 1, characterized in that, The particle size of the vanadium slag is 20~50mm.

10. The method according to claim 1, characterized in that, The temperature of the molten steel at the end of the refining process is 1590-1600℃.

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