Refining furnace smelting process of HRB600 high-strength steel

Abstract

The invention discloses a refining furnace smelting process of HRB600 high-strength steel. Vanadium in HRB600 must be fully strengthened by means of reasonable nitrogen content, so that the performance of steel is improved. In combination with the current situation that 150 * 150 small square billets are cast through a 50T top-blown converter and a 60-ton LF refining furnace in the existing steelmaking process, HRB600 chemical components are designed, and related process parameters in the LF refining process are controlled. Three processes of vanadium-nitrogen alloy nitrogen increasing, micro-nitrogen alloy nitrogen increasing and bottom blowing nitrogen increasing are synchronously carried out, the nitrogen flow and nitrogen blowing time are stably controlled through a flowmeter, then the bottom blowing nitrogen amount is controlled, stable control over the nitrogen content in molten steel is achieved, chemical component support is provided for high-strength steel production, the vanadium and nitrogen coincidence strengthening effect is fully exerted, and the production cost is reduced. The strength performance of the HRB600 steel can be guaranteed, and meanwhile the defect of casting blank bubbles caused by too high nitrogen content control is eradicated.

Description

Technical Field

[0001] This invention belongs to the field of high-strength steel smelting technology, specifically a refining furnace smelting process for HRB600 high-strength steel. Background Technology

[0002] HRB600 belongs to the high-strength steel series. For 600MPa grade products, simply increasing the content of silicon, manganese, and vanadium cannot guarantee its performance. A reasonable nitrogen content is necessary to fully utilize the strengthening effect of vanadium, improve the steel's strength, and solve the problem of bubble defects in the cast billet. Currently, nitrogen content is controlled through several methods: 1. Adding vanadium-nitrogen alloys, but using only vanadium-nitrogen alloys results in an increase of only about 0.01%; 2. Adding micro-nitrogen alloys or nitrogen lines, resulting in an increase of only about 0.0010%; 3. Using bottom-blown nitrogen, resulting in an increase of about 0.01%-0.015%. Compared to the first two methods, this method has a better nitrogen-increasing effect. However, achieving stable control of the nitrogen-increasing effect is a crucial factor affecting large-scale industrial production and urgently needs to be addressed. Summary of the Invention

[0003] Based on the above, the purpose of this invention is to provide a refining furnace smelting process for HRB600 high-strength steel, so as to achieve stable control of the nitrogen enhancement effect of HRB600 high-strength steel and solve the problems of insufficient strength and bubble defects in HRB600.

[0004] To achieve its purpose, the present invention adopts the following technical solution: Based on the existing steelmaking process of "50T top-blown converter → 60-ton LF refining furnace → casting 150×150 small square billets", the chemical composition of HRB600 is designed, and the relevant process parameters of the LF refining process are controlled. The specific operation is as follows: A refining furnace smelting process for HRB600 high-strength steel includes the following steps: Step 1: Converter smelting, with the final control of the carbon content in the molten steel at 0.07-0.15 wt%. Step 2: During the converter tapping process, add 20-25 kg / t of silicon-manganese alloy, 20-25 kg / t of silicon-iron alloy, and 1-1.5 kg / t of silicon-carbon alloy to the molten steel. Step 3: Blow argon gas through the bottom of the argon blowing station to fully melt the alloy; Step 4: The molten steel is fed into the refining furnace. The bottom blowing argon gas is turned on to blow up the surface of the molten steel. Lime and fluorite slag-forming materials are added and the slag is spread out. 2-2.5 kg / t of vanadium-nitrogen alloy and 0.4-0.6 kg / t of micro-nitrogen alloy are added to the molten steel. Step 5: Turn off the bottom-blowing argon gas and turn on the bottom-blowing nitrogen gas, controlling the nitrogen flow rate to 25m³ / h. 3 / h, nitrogen pressure 1.8MPa, heating for 8min, heating to 1550-1570℃; Step Six: During the heating process, add ferrosilicon and ferromanganese alloy according to the target composition of the molten steel; turn off the bottom-blowing nitrogen gas and turn on the bottom-blowing argon gas, controlling the argon gas flow rate to 15-20 m³ / h. 3 / h, argon pressure 0.8-1MPa, heating for 5-7min to 1570-1590℃; Step 7: Raise the electrode to measure temperature and take samples, controlling the argon gas flow rate to 10-15 m³ / h. 3 / h, argon pressure 0.5-0.8MPa, heating for 3-5 minutes to 1590-1610℃; fine-tune the chemical composition of molten steel according to sample test results; Step 8: After the composition adjustment is qualified, feed 0.6-1m / t of molten steel into the silicon-calcium wire, control the calcium content in the molten steel to be 0.0015-0.0025wt%, blow argon gas for 3min, and the molten steel exits the station. The composition of the molten steel, by mass percentage, is: C: 0.23-0.28%, Si: 0.65-0.80%, Mn: 1.45-1.60%, P: ≤0.025%, S: ≤0.015%, V: 0.185-0.205%, N: 0.020-0.025%. After the molten steel exits the station, cast billets are produced to obtain HRB600 high-strength steel.

[0005] As a further preferred embodiment of the technical solution of the present invention, in step (1), the tapping temperature of the converter is controlled at 1620-1660℃.

[0006] Furthermore, in step (3), the bottom blowing argon time is 3-5 min.

[0007] Furthermore, in step (4), the amount of lime added is 8.5-9.5 kg / t of molten steel, and the amount of fluorite added is 3-4 kg / t of molten steel.

[0008] Furthermore, in step (4), the thickness of the slag material is 20-30 mm.

[0009] Further, in step (4), the vanadium-nitrogen alloy contains 76-77 wt% V and 14-16 wt% N, and the micro-nitrogen alloy contains 13-16 wt% N.

[0010] By adopting the above technical solution, the beneficial effects of the present invention are as follows: This invention simultaneously implements three processes: vanadium-nitrogen alloy nitrogen enrichment, micro-nitrogen alloy nitrogen enrichment, and bottom-blowing nitrogen enrichment. By using a flow meter to stably control the nitrogen flow rate and blowing time, the amount of bottom-blowing nitrogen is controlled, thereby achieving stable control of the nitrogen content in molten steel. This can ensure the strength performance of HRB600 steel while eliminating billet bubble defects caused by excessive nitrogen content. Attached Figure Description

[0011] Figure 1This is a finished product image of the cast billet in Embodiment 1 of the present invention; Figure 2 This is a finished product image of the cast billet in Embodiment 2 of the present invention; Figure 3 This is a finished product image of the cast billet in Embodiment 3 of the present invention. Detailed Implementation

[0012] The smelting process of the present invention will be described in detail below through specific embodiments.

[0013] Example 1 1. HRB600 finished product ingredients The specific production process control instructions are as follows: 1.1 Converter endpoint control C: 0.10%, tapping temperature 1647℃.

[0014] 1.2 During the tapping process, 23 kg / t of silicon-manganese alloy, 24 kg / t of silicon-iron alloy, and 1 kg / t of silicon-carbon alloy are added to the molten steel.

[0015] 1.3 Blow argon gas at the bottom of the argon blowing station for 4 minutes to promote full melting of the alloy.

[0016] 1.4 When molten steel is fed into the LF furnace, the bottom blowing argon gas is turned on to blow up the surface of the molten steel. 8.5 kg / t of lime and 3.2 kg / t of fluorite are added as slag-forming material, and the slag is spread evenly with a top slag thickness of 22 mm. 2.5 kg / t of vanadium-nitrogen alloy and 0.4 kg / t of micro-nitrogen alloy are added to the molten steel.

[0017] 1.5 Turn off the bottom-blowing argon gas and turn on the bottom-blowing nitrogen gas, using a flow meter to control the nitrogen flow rate to 25m³ / h. 3 / h, nitrogen pressure 1.8MPa, start heating.

[0018] 1.6 Bottom-blown nitrogen gas is used to heat the gas to 1562℃ for 8 minutes, during which ferrosilicon and ferromanganese alloy are added according to the target composition. The bottom-blown nitrogen gas is then turned off, and the bottom-blown argon gas is turned on, with the argon flow rate controlled at 17 m³ / min. 3 / h, argon pressure 0.8MPa, heating for 7min to 1590℃.

[0019] 1.7 Raise the electrode for temperature measurement and sampling, and control the argon flow rate to 15m³. 3 At a constant temperature of 0.8 MPa, the temperature was increased to 1605 °C over 5 minutes. The chemical composition was then fine-tuned based on the sample test results.

[0020] 1.8 After the composition adjustment is qualified, 0.8 m / t of molten steel with a calcium content of 0.0020% is fed into the silicon-calcium wire line. Argon gas is then gently blown in for 3 minutes, and the molten steel exits the station. The resulting billet is then cast. The finished billet drawing is shown below. Figure 1As shown, the cast billet has no air bubble defects. After rolling, the yield strength of the 22mm specification billet is 645MPa, which meets the national standard requirements.

[0021] Example 2 1. HRB600 finished product composition The specific production process control instructions are as follows: 1.1 Converter endpoint control: C: 0.09%, tapping temperature 1650℃.

[0022] 1.2 During the steelmaking process, 24 kg / t of silicon-manganese alloy, 23 kg / t of silicon-iron alloy, and 1 kg / t of silicon-carbon alloy are added.

[0023] 1.3 Blow argon gas at the bottom of the argon blowing station for 5 minutes to promote full melting of the alloy.

[0024] 1.4 Molten steel is fed into the LF furnace. Bottom-blowing argon gas is turned on to blow up the surface of the molten steel. 9 kg / t of lime and 3.6 kg / t of fluorite are added as slag-forming material. The slag material is spread evenly, with a top slag thickness of 24 mm. 2.5 kg / t of vanadium-nitrogen alloy and 0.5 kg / t of micro-nitrogen alloy are added.

[0025] 1.5 Turn off the bottom-blowing argon gas and turn on the bottom-blowing nitrogen gas, using a flow meter to control the nitrogen flow rate to 25m³ / h. 3 / h, nitrogen pressure 1.8MPa, start heating.

[0026] 1.6 Bottom-blown nitrogen gas is used to heat the gas to 1570℃ for 8 minutes, during which ferrosilicon and ferromanganese alloy are added according to the target composition. The bottom-blown nitrogen gas is then turned off, and the bottom-blown argon gas is turned on, with the argon gas flow rate controlled at 15 m³ / min. 3 / h, argon pressure 0.8MPa, heating for 6min to 1592℃.

[0027] 1.7 Raise the electrode for temperature measurement and sampling, and control the argon flow rate to 13m³. 3 At a constant temperature of 0.6 MPa, the temperature was increased to 1608 °C over 4 minutes. The chemical composition was then fine-tuned based on the sample test results.

[0028] 1.8 After the composition is properly adjusted, feed in a 0.9m / t silicon-calcium wire with a calcium content of 0.0022%, and gently blow argon gas for 4 minutes. The molten steel then exits the station. The resulting billet is shown in the image below. Figure 2 As shown, the cast billet has no air bubble defects. After rolling, the 22mm diameter billet has a yield strength of 650MPa, meeting the national standard requirements.

[0029] Example 3 1. HRB600 finished product ingredients The specific production process control instructions are as follows: 1.1 Converter endpoint control C: 0.013%, tapping temperature 1647℃.

[0030] 1.2 During the steelmaking process, 21 kg / t of silicon-manganese alloy, 25 kg / t of silicon-iron alloy, and 1 kg / t of silicon-carbon alloy are added.

[0031] 1.3 Blow argon gas at the bottom of the argon blowing station for 3 minutes to promote full melting of the alloy.

[0032] 1.4 Molten steel is fed into the LF furnace. Bottom-blowing argon gas is turned on to blow up the surface of the molten steel. 9.5 kg / t of lime and 4 kg / t of fluorite are added as slag-forming material. The slag material is spread evenly, with a top slag thickness of 28 mm. 2.5 kg / t of vanadium-nitrogen alloy and 0.5 kg / t of micro-nitrogen alloy are added.

[0033] 1.5 Turn off the bottom-blowing argon gas and turn on the bottom-blowing nitrogen gas, using a flow meter to control the nitrogen flow rate to 25m³ / h. 3 / h, nitrogen pressure 1.8MPa, start heating.

[0034] 1.6 Bottom-blown nitrogen gas is used to heat the gas to 1567℃ for 8 minutes, during which ferrosilicon and ferromanganese alloy are added according to the target composition. The bottom-blown nitrogen gas is then turned off, and the bottom-blown argon gas is turned on, with the argon gas flow rate controlled at 15 m³ / min. 3 / h, argon pressure 0.8MPa, heating for 6min to 1587℃.

[0035] 1.7 Raise the electrode for temperature measurement and sampling, and control the argon flow rate to 11 m³ / s. 3 At a constant temperature of 0.6 MPa, the temperature was increased to 1601 °C over 5 minutes. The chemical composition was then fine-tuned based on the sample test results.

[0036] 1.8 After the composition is properly adjusted, feed in a 0.9m / t silicon-calcium wire with a calcium content of 0.0020%, and gently blow argon gas for 3 minutes. The molten steel then exits the station. The resulting billet is shown in the image below. Figure 3 As shown, the cast billet has no air bubble defects. After rolling, the yield strength of the 22mm specification billet is 644MPa, which meets the national standard requirements.

Claims

1. A refining furnace smelting process for HRB600 high-strength steel, characterized in that, Includes the following steps: Step 1: Converter smelting, with the final control of the carbon content in the molten steel at 0.07-0.15 wt%. Step 2: During the converter tapping process, add 20-25 kg / t of silicon-manganese alloy, 20-25 kg / t of silicon-iron alloy, and 1-1.5 kg / t of silicon-carbon alloy to the molten steel. Step 3: Blow argon gas through the bottom of the argon blowing station to fully melt the alloy; Step 4: The molten steel is fed into the refining furnace. The bottom blowing argon gas is turned on to blow up the surface of the molten steel. Lime and fluorite slag-forming materials are added and the slag is spread out. 2-2.5 kg / t of vanadium-nitrogen alloy and 0.4-0.6 kg / t of micro-nitrogen alloy are added to the molten steel. Step 5: Turn off the bottom-blowing argon gas and turn on the bottom-blowing nitrogen gas, controlling the nitrogen flow rate to 25m³ / h. 3 / h, nitrogen pressure 1.8MPa, heating for 8min, heating to 1550-1570℃; Step Six: During the heating process, add ferrosilicon and ferromanganese alloy according to the target composition of the molten steel; turn off the bottom-blowing nitrogen gas and turn on the bottom-blowing argon gas, controlling the argon gas flow rate to 15-20 m³ / h. 3 / h, argon pressure 0.8-1MPa, heating for 5-7min to 1570-1590℃; Step 7: Raise the electrode to measure temperature and take samples, controlling the argon gas flow rate to 10-15 m³ / h. 3 / h, argon pressure 0.5-0.8MPa, heating for 3-5 minutes to 1590-1610℃; fine-tune the chemical composition of molten steel according to sample test results; Step 8: After the composition adjustment is qualified, feed 0.6-1m / t of molten steel into the silicon-calcium wire, control the calcium content in the molten steel to be 0.0015-0.0025wt%, and gently blow argon gas for 3-4 minutes. The molten steel exits the station, and the composition of the molten steel, by mass percentage, is C: 0.23-0.28%, Si: 0.65-0.80%, Mn: 1.45-1.60%, P: ≤0.025%, S: ≤0.015%, V: 0.185-0.205%, N: 0.020-0.025%. After the molten steel exits the station, cast billets are produced to obtain HRB600 high-strength steel.

2. The refining furnace smelting process for HRB600 high-strength steel as described in claim 1, characterized in that, In step (1), the tapping temperature of the converter is controlled at 1620-1660℃.

3. The refining furnace smelting process for HRB600 high-strength steel as described in claim 1, characterized in that, In step (3), the bottom blowing time of argon gas is 3-5 minutes.

4. The refining furnace smelting process for HRB600 high-strength steel as described in claim 1, characterized in that, In step (4), the amount of lime added is 8.5-9.5 kg / t of molten steel, and the amount of fluorite added is 3-4 kg / t of molten steel.

5. The refining furnace smelting process for HRB600 high-strength steel as described in claim 1, characterized in that, In step (4), the thickness of the slag is 20-30 mm.

6. The refining furnace smelting process for HRB600 high-strength steel as described in any one of claims 1-5, characterized in that, In step (4), the vanadium-nitrogen alloy contains 76-77 wt% V and 14-16 wt% N, and the micro-nitrogen alloy contains 13-16 wt% N.

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