Method for smelting HRB600 steel by using ferrotitanium instead of ferrocolumbium

Abstract

The invention belongs to the technical field of ferrous metallurgy, and particularly discloses a method for smelting HRB600 steel by using ferrotitanium instead of ferrocolumbium, which comprises the following steps of: pouring molten iron into a converter for smelting, sequentially adding silicon manganese alloy, ferrosilicon and vanadium nitrogen for alloying, and then smelting by blowing argon from the bottom, the method comprises the following steps: adding a silicon-manganese alloy, silicon iron and vanadium nitrogen according to argon station components, carrying out alloy fine adjustment until the alloy is in an internal control component range, putting a steel ladle into a refining furnace for smelting after argon blowing is completed, adding a titanium-iron alloy according to an end point sample Ti component, carrying out wire feeding soft blowing after smelting in the refining furnace is completed, enabling the soft blowing time to be greater than or equal to 5.5 minutes, standing after soft blowing is completed, and casting the steel ladle. The problems that in the HRB600 steel production process, the adding amount of vanadium-nitrogen alloy and niobium-iron alloy is large, and cost is high are solved. According to the method, through converter smelting, refining furnace adjustment, ferrotitanium adding, continuous casting and key parameter control, ferrotitanium is replaced with low-cost ferrotitanium, and the production cost is reduced on the premise that the mechanical property of the steel is guaranteed.

Description

Technical Field

[0001] This invention relates to the field of iron and steel metallurgy technology, specifically to a smelting method for HRB600 steel using ferrotitanium instead of ferroniobium. Background Technology

[0002] HRB600 high-strength threaded steel bars, a type of high-performance steel bar using a smelting method that replaces ferro-titanium alloy with ferro-niobium alloy, are widely used in construction projects in industrial and civil sectors, railways, bridges, and roads due to their excellent physical properties and chemical composition. In the production process of HRB600 high-strength threaded steel bars, in addition to adding a certain amount of silicon-manganese alloy and ferrosilicon alloy to the molten steel, some vanadium (V) and niobium (Nb) alloys are also added for microalloying to ensure the product performance meets national standards. Currently, most steel companies widely use low-cost vanadium-nitrogen and ferro-niobium alloys as microalloying alloys in the production of HRB600 high-strength threaded steel bars. With rising steel prices, the prices of vanadium-nitrogen and ferro-niobium alloys used in high-strength threaded steel bars have continued to rise. Given the increasingly low profit margins in steel production, steel companies are seeking ways to reduce alloy costs. Developing alternative additives for HRB600 high-strength threaded steel bars that can both meet national standards and reduce production costs is a crucial issue facing major steel companies.

[0003] Currently, adding vanadium-nitrogen alloys and niobium-iron alloys to the ladle for microalloying during the production of HRB600 high-strength rebar is the preferred process for steel companies. This process mainly involves adding vanadium-nitrogen alloys and niobium-iron alloys to the molten steel. The vanadium-nitrogen alloy's vanadium content refines the steel grains and increases toughness. Furthermore, vanadium and iron can form a continuous solid solution, significantly reducing the austenite phase region and thus improving the steel's physical and chemical properties. Niobium forms niobium carbonitride precipitates in the steel, inhibiting austenite grain growth and achieving grain refinement. The precipitated niobium carbonitride particles hinder dislocation movement, increasing steel strength and promoting the transformation of ferrite to pearlite, thus improving the internal microstructure. However, due to the large amount of vanadium-nitrogen alloys and niobium-iron alloys added during the production of HRB600 high-strength rebar, and their high price, the smelting cost for microalloying using these alloys in the production of HRB600 high-strength rebar is relatively high. Summary of the Invention

[0004] The purpose of this invention is to provide a smelting method for HRB600 steel using ferrotitanium instead of ferroniobium, in order to solve the problem that the production process of HRB600 high-strength rebar involves a large amount of vanadium-nitrogen alloy and ferroniobium alloy, which are expensive and thus result in high production costs.

[0005] To achieve the above objectives, the basic solution provided by this invention is: a smelting method for HRB600 steel using ferrotitanium instead of ferroniobium, comprising the following steps: S1. Pour molten iron into a converter for smelting, control the converter endpoint [C] to be 0.07%~0.16%, the endpoint [P] ≤0.025%, and the tapping temperature to be 1640℃~1680℃. During the tapping process, silicon manganese alloy, ferrosilicon and vanadium nitrogen are added in sequence for alloying. All alloys are added starting when 1 / 3 of the steel is tapped and all alloys are added when 3 / 4 of the steel is tapped. S2. After the molten steel arrives at the station, the ladle car is driven to the smelting station for electric smelting. Lime, slag-forming agent and composite deoxidizer are added to form slag. According to the composition of the argon station, silicon manganese alloy, ferrosilicon and vanadium nitrogen are added to fine-tune the alloy to the internal control composition range. S3. After argon blowing is completed, the molten steel ladle is hoisted to the refining furnace for smelting, and the final sample of the refining furnace is taken. According to the Ti composition of the final sample, titanium-iron alloy is added to supplement the Ti composition to 0.014% to 0.020%. S4. After the refining furnace is smelted, wire feeding and soft blowing are carried out. The soft blowing time is ≥5.5 minutes. After the soft blowing is completed, the molten steel ladle is hoisted to the continuous casting ladle turret after standing for 2-3 minutes. S5. The continuous casting ladle turret is rotated to the tundish casting position, the ladle slide is pulled open, and the molten steel is poured into the tundish for casting.

[0006] The beneficial effects of this invention are as follows: by converter smelting, refining furnace adjustment, addition of ferrotitanium, continuous casting, and control of key parameters, it is possible to replace high-cost ferroniobium with low-cost ferrotitanium in the production of HRB600 rebar, and to achieve precipitation strengthening and fine grain strengthening through Ti microalloying, thereby significantly reducing alloy costs while ensuring that the mechanical properties of the steel meet the standards.

[0007] Option 2, which is the preferred option of the basic option, involves adding a composite deoxidizer during tapping based on the endpoint control conditions. The amount added per batch is controlled at 13 kg, with an interval of >5 seconds. The composite deoxidizer is controlled at 1.0-1.5 kg / t of steel. This avoids over-oxidation of molten steel, improves alloy yield, reduces deoxidizer waste, helps control the oxygen content in the steel, and improves the purity and performance stability of the steel.

[0008] Option 3, which is the preferred option of the basic option, in S5, the protective slag used in the continuous casting process is dry low-carbon hollow pre-dissolved granular slag. The protective slag must be baked before use. The casting cross section is 150mm×150mm, and the billet length is 8500~12000mm. This improves the surface quality and internal structure of the billet, reduces cracks and inclusions, and increases the yield of the continuous casting billet.

[0009] Option 4, the preferred option of the basic option, in S5, has a liquidus temperature of 1498℃, a tundish baking temperature of 1100~1250℃, a target temperature of molten steel in the ladle of the start-up furnace of 1610~1640℃, a target temperature of molten steel in the tundish of >1560℃, a target temperature of molten steel in the ladle of the continuous casting furnace of 1610~1640℃, and a target temperature of molten steel in the tundish of 1520~1530℃. This ensures good fluidity and solidification characteristics of the molten steel, reduces temperature loss and solidification defects during the casting process, and is beneficial to the uniformity of the billet structure and the consistency of mechanical properties.

[0010] Option 5, which is the preferred option of the basic option, is as follows: the continuous casting water distribution method is as follows: the flow rate of the crystallizer is 2000-2100 L / min, the secondary cooling gas pressure in each section is 0.23-0.30 MPa, and when the casting speed is lower than 2.0 m / min, the secondary cooling gas pressure is 0.15-0.20 MPa; the cooling intensity and uniformity are optimized to prevent internal cracks or surface defects caused by uneven cooling inside and outside the billet, thereby improving the quality of the billet.

[0011] Option 6, an optimal choice from the basic option, involves the following temperature and casting speed control methods in S5: Casting speed ≤ 1.8 m / min when temperature ≥ 1550℃; 1.8–2.4 m / min when temperature is 1540–1550℃; 2.4–2.8 m / min when temperature is 1530–1540℃; 2.8–3.3 m / min when temperature is 1520–1530℃; and ≥ 3.3 m / min when temperature < 1520℃. This achieves matched control of temperature and casting speed, ensuring the billet is formed under optimal solidification conditions and avoiding quality fluctuations caused by excessively fast or slow casting speeds.

[0012] Option 7, which is the preferred option of Option 6, adjusts the casting speed to 0-0.4 m / min when production is abnormal; when the S in the molten steel is ≥0.035%, the casting speed is reduced by 0.2-0.4 m / min; under abnormal conditions, fine-tuning the casting speed can help avoid defects in the billet. Detailed Implementation

[0013] The present invention will be further described in detail below through specific embodiments: A smelting method for HRB600 steel using ferrotitanium instead of ferroniobium includes the following steps: S1. Pour molten iron into a converter for smelting, controlling the converter endpoint [C] to be 0.07%~0.16%, the endpoint [P] to be ≤0.025%, and the tapping temperature to be 1640℃~1680℃. When tapping, add composite deoxidizer according to the endpoint control, with each batch adding 13kg, with an interval of >5 seconds. The composite deoxidizer is controlled at 1.0~1.5kg / t per ton of steel. During the tapping process, add silicon manganese alloy, ferrosilicon, and vanadium nitrogen in sequence for alloying. All alloys are added starting when 1 / 3 of the steel is tapped and all alloys are added when 3 / 4 of the steel is tapped. If the molten steel is over-oxidized, composite deoxidizer can be added again, with a dosage of 0.2~0.3kg / t. S2. After the molten steel arrives at the station, the ladle car is driven to the smelting station for electric smelting. Lime, slag-forming agent and composite deoxidizer are added to form slag. According to the composition of the argon station, silicon manganese alloy, ferrosilicon and vanadium nitrogen are added to fine-tune the alloy to the internal control composition range (Table 1). Silicon manganese alloy 22kg / t, ferrosilicon 7kg / t, vanadium nitrogen 23kg / t. Table 1. Argon Station Composition Control Table S3. After argon blowing is completed, the molten steel ladle is hoisted to the refining furnace for smelting, and the final sample of the refining furnace is taken. According to the Ti composition of the final sample, titanium-iron alloy is added to supplement the Ti composition to 0.014% to 0.020%. Table 2. Refining Furnace End-Point Component Control Requirements S4. After the refining furnace is smelted, wire feeding and soft blowing are carried out. The soft blowing time is ≥5.5 minutes. After the soft blowing is completed, the molten steel ladle is hoisted to the continuous casting ladle turret after standing for 2-3 minutes. S5. The continuous casting ladle turret is rotated to the tundish casting position. The ladle slide is opened, and molten steel is poured into the tundish for casting. During the continuous casting process, dry low-carbon hollow pre-dissolved granular slag is used as the protective slag. The protective slag must be baked before use. The casting cross section is 150mm×150mm, the billet length is 8500~12000mm, the liquidus temperature is 1498℃, the tundish baking temperature is 1100~1250℃, the target temperature of molten steel in the ladle of the start-up furnace is 1610~1640℃, the target temperature of molten steel in the tundish is >1560℃, the target temperature of molten steel in the ladle of the continuous casting furnace is 1610~1640℃, and the target temperature of molten steel in the tundish is 1520~1530℃. Continuous casting water distribution method: The flow rate of the crystallizer is 2000~2100L / min, and the secondary cooling gas pressure in each section is 0.23~0.30MPa. When the casting speed is lower than 2.0m / min, the secondary cooling gas pressure is 0.15~0.20MPa. The foot roll section uses a water-cooled nozzle of model 165-01-s with high efficiency; the first section of the secondary cooling uses aerosol nozzle of model 165-02 with high efficiency; the second section of the secondary cooling uses aerosol nozzle of model 165-03 with high efficiency; and the third section of the secondary cooling uses aerosol nozzle of model 165-04 with high efficiency. Temperature and casting speed control: When the temperature is ≥1550℃, the casting speed is ≤1.8m / min; when the temperature is 1540~1550℃, the casting speed is 1.8~2.4m / min; when the temperature is 1530~1540℃, the casting speed is 2.4~2.8m / min; when the temperature is 1520~1530℃, the casting speed is 2.8~3.3m / min; when the temperature is <1520℃, the casting speed is ≥3.3m / min. In case of production abnormalities, the casting speed is adjusted to 0~0.4m / min. When the sulfur content in the molten steel is ≥0.035%, the casting speed is reduced by 0.2~0.4m / min. For HRB600 steel, the cast billet is not hot-sent; after casting, the billet is placed for 3-5 days before being sent to the rolling mill.

[0014] During the smelting process, by controlling the effective Ti content and combining it with a low-carbon equivalent design, titanium-iron alloy is added to the molten steel. Ti forms a very strong TiC in the steel, which can be stabilized up to 1300℃. This stabilizes the highly dispersed TiC particles, making the internal structure of the steel denser, refining grain strength, and improving the steel's strength. Furthermore, compared to existing niobium-iron microalloying technology, titanium-iron alloy has a stable price and a significant cost advantage.

[0015] The specific production process was first theoretically analyzed, revealing that titanium (Ti) forms titanium carbonitride (TiN) and other precipitates in steel, preventing austenite grain growth and refining the grain size. Simultaneously, the precipitated nano-sized TiN particles hinder dislocation movement, enhancing precipitation strengthening. The higher the [N] concentration in the steel, the more V (C, N) precipitates during rolling. Using composite vanadium-nitrogen alloys can effectively promote the strengthening effect in steel, improving its strength. V-Ti microalloyed high-strength threaded steel bars were trial-produced under optimized cooling rates (1.0-1.5℃ / s), achieving a yield strength ≥635 MPa, tensile strength ≥820 MPa, elongation after fracture ≥20%, and a strength-to-yield ratio ≥1.25, meeting the requirements for finished product trial production.

[0016] In the smelting process of HRB600 high-strength threaded steel bars, ferrotitanium alloy is added to the ladle to replace the existing ferroniobium alloy. In the molten steel, this further enhances the steel's strength through precipitation strengthening and grain refinement. Furthermore, using ferrotitanium alloy instead of the existing ferroniobium alloy optimizes the Nb content control range in the production of HRB600 threaded steel bars, reduces alloy consumption costs, and achieves the goal of cost reduction and efficiency improvement.

[0017] Table 3. Composition of the finished test steel Table 4. Mechanical properties of the test steel Table 5. Cost Calculation of Titanium-Iron Alloy as a Substitute for Niobium-Iron Alloy Through experiments, using ferrotitanium tinplate instead of ferroniobium alloy in the production of HRB600 high-strength threaded steel bars, with rolled specifications of Φ12, Φ14, Φ22, Φ18, and Φ25, all mechanical properties met national standards, with an average yield strength of 695 MPa. Compared to using ferroniobium alloy, the alloy cost was reduced by 16.471 yuan / ton of steel. Based on this cost saving of 16.471 yuan per ton of steel, a steel mill producing 300,000 tons of HRB600 high-strength threaded steel bars annually would see an annual benefit of 300,000 × 16.471 = 4,941,300 yuan after applying this process. This not only ensures the stability of the steel's strength properties but also reduces alloy costs, achieving the goal of cost reduction and efficiency improvement.

[0018] The above descriptions are merely embodiments of the present invention, and common knowledge regarding specific structures and characteristics is not elaborated upon here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the structure of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A smelting method for HRB600 steel using ferrotitanium instead of ferroniobium, characterized in that, Includes the following steps: S1. Pour molten iron into a converter for smelting, control the converter endpoint [C] to be 0.07%~0.16%, the endpoint [P] ≤0.025%, and the tapping temperature to be 1640℃~1680℃. During the tapping process, silicon manganese alloy, ferrosilicon and vanadium nitrogen are added in sequence for alloying. All alloys are added starting when 1 / 3 of the steel is tapped and all alloys are added when 3 / 4 of the steel is tapped. S2. After the molten steel arrives at the station, the ladle car is driven to the smelting station for electric smelting. Lime, slag-forming agent and composite deoxidizer are added to form slag. According to the composition of the argon station, silicon manganese alloy, ferrosilicon and vanadium nitrogen are added to fine-tune the alloy to the internal control composition range. S3. After argon blowing is completed, the molten steel ladle is hoisted to the refining furnace for smelting, and the final sample of the refining furnace is taken. According to the Ti composition of the final sample, titanium-iron alloy is added to supplement the Ti composition to 0.014% to 0.020%. S4. After the refining furnace is smelted, wire feeding and soft blowing are carried out. The soft blowing time is ≥5.5 minutes. After the soft blowing is completed, the molten steel ladle is hoisted to the continuous casting ladle rotary table after standing for 2-3 minutes. S5. The continuous casting ladle turret is rotated to the tundish casting position, the ladle slide is pulled open, and the molten steel is poured into the tundish for casting.

2. The smelting method for HRB600 steel using ferrotitanium instead of ferroniobium according to claim 1, characterized in that, In S1, a composite deoxidizer is added during tapping according to the endpoint control situation. The amount added per batch is controlled at 13kg, with an interval of >5 seconds. The composite deoxidizer is controlled at 1.0~1.5kg / t per ton of steel.

3. The smelting method for HRB600 steel using ferrotitanium instead of ferroniobium according to claim 1, characterized in that, In S5, the protective slag used in the continuous casting process is dry, low-carbon, hollow, pre-dissolved granular slag. The protective slag must be baked before use. The casting cross-section is 150mm×150mm, and the billet length is 8500~12000mm.

4. The smelting method for HRB600 steel using ferrotitanium instead of ferroniobium according to claim 1, characterized in that, In S5, the liquidus temperature is 1498℃, the tundish baking temperature is 1100~1250℃, the target temperature of molten steel in the ladle of the start-up furnace is 1610~1640℃, the target temperature of molten steel in the tundish is >1560℃, the target temperature of molten steel in the ladle of the continuous casting furnace is 1610~1640℃, and the target temperature of molten steel in the tundish is 1520~1530℃.

5. The smelting method for HRB600 steel using ferrotitanium instead of ferroniobium according to claim 1, characterized in that, In S5, the continuous casting water distribution method is as follows: the flow rate of the crystallizer is 2000~2100L / min, the secondary cooling gas pressure in each section is 0.23~0.30MPa, and when the casting speed is lower than 2.0m / min, the secondary cooling gas pressure is 0.15~0.20MPa.

6. The smelting method for HRB600 steel using ferrotitanium instead of ferroniobium according to claim 1, characterized in that, In S5, the temperature and pulling speed are controlled as follows: when the temperature is ≥1550℃, the pulling speed is ≤1.8m / min; when the temperature is 1540~1550℃, the pulling speed is 1.8~2.4m / min; when the temperature is 1530~1540℃, the pulling speed is 2.4~2.8m / min; when the temperature is 1520~1530℃, the pulling speed is 2.8~3.3m / min; and when the temperature is <1520℃, the pulling speed is ≥3.3m / min.

7. A smelting method for HRB600 steel using ferrotitanium instead of ferroniobium according to claim 6, characterized in that, In case of production abnormalities, adjust the drawing speed to 0-0.4 m / min; when the S content in the molten steel is ≥0.035%, reduce the drawing speed by 0.2-0.4 m / min.

Images