RH vacuum furnace treatment temperature control method

Abstract

The invention relates to an RH vacuum furnace treatment temperature control method which comprises the steps of molten iron pretreatment, converter blowing, RH treatment and continuous casting, in the converter blowing process, the sulfur mass content of end point molten steel is smaller than or equal to the upper limit of the sulfur mass content of a steel grade finished product, the temperature of the end point molten steel of a converter is 1630-1650 DEG C, and the mass content of free oxygen in the end point molten steel of the converter is 0.04-0.06%; and after tapping is finished, an aluminum-based modifier and lime are added into the molten steel, and slag materials in the molten steel are kept not to be accumulated. According to the method, the problems that in the RH single-link steelmaking process, the temperature required for converter tapping is high, and the oxidability of slag and the number of inclusions are increased due to oxygen blowing and temperature rising are solved.

Description

Technical Field

[0001] The invention relates to a RH vacuum furnace treatment temperature control method, in particular to a RH vacuum treatment molten steel temperature control method, belonging to the technical field of steelmaking. Background Art

[0002] The patent application with publication number CN117701827A discloses a low-cost oxygen blowing heating method, which adds slag-making materials after aluminum deoxidation, and the generated new slag layer can isolate silicon oxides from aluminum-containing molten steel, thereby reducing silicon addition and RH heating costs, and is suitable for low-silicon aluminum killed steel. It mainly solves the problem of silicon addition in low-silicon aluminum killed steel, but does not mention solving its impact on slag oxidizability and cleanliness.

[0003] The patent application with publication number CN116497179A discloses a method for controlling the RH refining temperature of non-oriented silicon steel, which controls the tapping temperature of non-oriented silicon steel within ±5°C of the design temperature value by accurately controlling the temperature of each process and coordinating RH oxygen blowing and heating, etc. It mainly solves the problem of accurate control of RH tapping temperature, but does not mention solving its influence on oxidizability and cleanliness of slag.

[0004] The patent application with publication number CN111910040B discloses a method for stabilizing the oxidizability of ultra-low carbon steel top slag, which effectively controls the oxidizability of the top slag by considering the oxygen mass content in the top slag and the total oxygen mass content in the steel and jointly modifying the oxygen mass content in the top slag and steel. The invention application mentions that during the RH oxygen blowing and heating process, oxygen blowing and aluminum addition are carried out simultaneously, and the appropriate oxygen blowing flow rate is controlled to suppress the impact of the rapid increase of oxygen in the steel on the top slag, but does not mention solving its impact on the oxidizability and cleanliness of the slag.

[0005] In summary, in the existing disclosed technologies, RH oxygen blowing and heating are mainly used to accurately control the process temperature and reduce the return of silicon in the smelting process. In the existing technologies, the following problems exist: 1) Oxygen blowing and heating increase the oxidizability of the slag; 2) Oxygen blowing and heating increase the number of inclusions; 3) The converter terminal temperature is high, the refractory erosion is serious, and the converter final slag has strong oxidizability. Summary of the invention

[0006] In order to solve the above problems, the present invention discloses a RH vacuum furnace treatment temperature control method to solve the problems of high converter tapping temperature, increased slag oxidation due to oxygen blowing and increased number of inclusions in the RH single-link steelmaking process. The specific technical solution is as follows: A RH vacuum furnace treatment temperature control method, comprising molten iron pretreatment → converter blowing → RH treatment → continuous casting, specifically: Step 1: Hot metal pretreatment: Determine the upper limit of sulfur content in the finished steel product to be produced. After hot metal pretreatment, the sulfur content in hot metal should be ≤ the upper limit of sulfur content in the finished steel product - 0.002%; Step 2: Converter blowing: The sulfur content of the converter end molten steel is ≤ the upper limit of the sulfur content of the finished steel product, the converter end molten steel temperature is 1630-1650°C, and the free oxygen content in the converter end molten steel is 0.04-0.06%; after the steel is tapped, aluminum-based modifier and lime are added to the molten steel, and slag is kept from accumulating in the molten steel; Step 3: RH treatment: After the molten steel arrives at the station, the temperature is measured and sampled. The T.Fe of the slag at the RH station is 3-6%. The vacuum pump is turned on to quickly reduce the pressure of the vacuum chamber to below 500Pa to carry out decarburization reaction. When the carbon content of the molten steel is ≤0.01%, the temperature of the molten steel is measured and oxygen is determined, and aluminum is added to blow oxygen to increase the temperature. After the RH decarburization is completed, alloying is carried out according to the target composition, and the net cycle is performed. The steel is broken and the steel is tapped. After breaking the air, carbonized rice husks are added, and the thickness of the rice husks is 5-15cm; Step 4: Continuous casting: The superheat of the tundish is 15-25℃.

[0007] Furthermore, if the finished steel product is low carbon steel with a carbon mass content of >0.01%: If the oxygen mass content is greater than 0.03%, add aluminum blocks or aluminum particles to make the aluminum mass content per ton of molten steel equal to (outgoing station temperature - arrival temperature + 20) × 0.025kg, that is, the amount of aluminum blocks or aluminum particles added is: (outgoing station temperature - arrival temperature + 20) × 0.025kg / t molten steel. After the addition of aluminum begins and the molten steel circulates once, control the oxygen lance position to start blowing oxygen, so that the volume content of oxygen per ton of molten steel is (amount of aluminum added × 0.78-0.175) m 3 , that is, the oxygen blowing amount is: (amount of aluminum added × 0.78-0.175) m 3 / t molten steel; If the oxygen mass content is ≤0.03%, add aluminum blocks or aluminum particles to make the aluminum mass content in each ton of molten steel equal to (outgoing station temperature - arrival temperature + 24) × 0.025kg, that is, the amount of aluminum blocks or aluminum particles added is: (outgoing station temperature - arrival temperature + 24) × 0.025kg / t molten steel. After the addition of aluminum begins and the molten steel circulates once, control the oxygen lance position to start blowing oxygen, so that the volume content of oxygen in each ton of molten steel is (amount of aluminum added × 0.78) m 3 , that is, the oxygen blowing amount is: (amount of aluminum added × 0.78) m 3 / t molten steel.

[0008] Furthermore, after RH decarburization, the free oxygen mass content of the molten steel is less than 0.01%; the T.Fe of the slag before RH alloying is 3-5%.

[0009] Furthermore, if the finished steel product is ultra-low carbon steel with a carbon mass content of ≤0.01%: If the oxygen mass content is greater than 0.03%, add aluminum blocks or aluminum particles to make the aluminum mass content per ton of molten steel equal to (outgoing station temperature - arrival temperature + 28) × 0.025kg, that is, the amount of aluminum blocks or aluminum particles added is: (outgoing station temperature - arrival temperature + 28) × 0.025kg / t molten steel. After the addition of aluminum begins and the molten steel circulates once, control the oxygen lance to blow oxygen, so that the volume content of oxygen per ton of molten steel is (amount of aluminum added × 0.78-0.0875)m 3 , that is, the oxygen blowing amount is: (amount of aluminum added × 0.78-0.0875) m 3 / t molten steel; If the oxygen mass content is ≤0.03%, add aluminum blocks or aluminum particles to make the aluminum mass content in each ton of molten steel equal to (outgoing station temperature - arrival temperature + 32) × 0.025kg, that is, the amount of aluminum blocks or aluminum particles added is: (outgoing station temperature - arrival temperature + 32) × 0.025kg / t molten steel. After the addition of aluminum begins and the molten steel circulates once, control the oxygen lance to blow oxygen to make the volume content of oxygen in each ton of molten steel equal to (amount of aluminum added × 0.78) m 3 , that is, the oxygen blowing amount is (amount of aluminum added × 0.78) m 3 / t molten steel.

[0010] Furthermore, after RH decarburization, the free oxygen mass content of the molten steel is less than 0.03%; the T.Fe of the slag before RH alloying is 3-6%.

[0011] Furthermore, when blowing oxygen to increase temperature, the oxygen lance position is 4-6m, and the oxygen flow rate is 3000-4000m 3 / h, oxygen pressure is 13-15bar.

[0012] Furthermore, the ladle empty time is ≤45min, and the RH vacuum tank waiting time is ≤30min.

[0013] The beneficial effects of the present invention are: The converter tapping temperature is high. On the one hand, the T.Fe content of the converter final slag is high, which in turn leads to a high T.Fe content in the ladle slag. On the other hand, the converter refractory erosion rate is fast, which seriously affects the service life of the converter refractory. Improper RH vacuum oxygen blowing and aluminum heating will cause the slag to be secondary oxidized by highly oxidizing molten steel, increasing the T.Fe content. In the subsequent treatment process, the molten steel is secondary oxidized to produce non-metallic inclusions. At the same time, it also leads to a high free oxygen content in the molten steel at the end of decarburization, which in turn leads to an increase in non-metallic inclusions produced by deoxidation.

[0014] The present invention solves the problems of increased slag oxidation due to the oxygen blowing and heating process, increased number of inclusions due to the oxygen blowing and heating operation, and reduces the converter terminal temperature, increases the life of refractory materials, and reduces converter terminal overoxidation through the selection of the timing of oxygen blowing and aluminum addition, the design of oxygen lance parameters, and special process design under different molten steel conditions. DETAILED DESCRIPTION

[0015] The present invention will be further described below in conjunction with specific embodiments. It should be understood that the following specific embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0016] The RH vacuum furnace treatment temperature control method includes molten iron pretreatment → converter blowing → RH treatment → continuous casting, specifically: Step 1: Hot metal pretreatment: Determine the upper limit of sulfur content in the finished steel product to be produced. After hot metal pretreatment, the sulfur content in hot metal should be ≤ the upper limit of sulfur content in the finished steel product - 0.002%; Step 2: Converter blowing: The sulfur content of the converter end molten steel is ≤ the upper limit of the sulfur content of the finished steel product, the converter end molten steel temperature is 1630-1650℃, and the free oxygen content in the converter end molten steel is 0.04-0.06%; after the steelmaking is completed, add aluminum-based modifier and lime to the molten steel, and keep the slag in the molten steel from accumulating.

[0017] If the finished steel is low carbon steel with carbon content > 0.01%: During the converter blowing process, when the carbon content of the molten steel is less than 0.01%, the temperature is measured and the oxygen is determined, and aluminum is added to blow oxygen to increase the temperature. If the oxygen content is greater than 0.03%, add aluminum blocks or aluminum particles to make the aluminum content per ton of molten steel equal to (outgoing temperature - arrival temperature + 20) × 0.025kg, that is, the amount of aluminum blocks or aluminum particles added is: (outgoing temperature - arrival temperature + 20) × 0.025kg / t molten steel. After the addition of aluminum begins and the molten steel circulates once, lower the oxygen lance to 4-6m and the oxygen flow rate to 3000-4000m 3 / h, oxygen pressure is 13-15bar, oxygen blowing volume is (amount of aluminum added × 0.78-0.175) m 3 / t molten steel; when adding aluminum and blowing oxygen to heat up, the free oxygen content of the molten steel is less than 0.01%; the T.Fe of the slag before RH alloying is 3-5%; If the oxygen content is ≤0.03%, add aluminum blocks or aluminum particles to make the aluminum content per ton of molten steel equal to (outgoing station temperature - arrival temperature + 24) × 0.025kg, that is, the amount of aluminum blocks or aluminum particles added is: (outgoing station temperature - arrival temperature + 24) × 0.025kg / t molten steel. After the addition of aluminum begins and the molten steel circulates once, lower the oxygen lance to 4-6m and the oxygen flow rate to 3000-4000m 3 / h, oxygen pressure is 13-15bar, oxygen blowing volume is (amount of aluminum added × 0.78) m 3 / t of molten steel, when adding aluminum and blowing oxygen to heat up, the free oxygen mass content of the molten steel is less than 0.01%, and the T.Fe of the slag before RH alloying is 3-5%.

[0018] If the finished steel product is ultra-low carbon steel with a carbon mass content of ≤0.01%: During the converter blowing process, when the carbon content of the molten steel is less than 0.01%, aluminum is added and oxygen is blown to increase the temperature. If the oxygen content is greater than 0.03%, add aluminum blocks or aluminum particles to make the aluminum content per ton of molten steel equal to (outgoing temperature - arrival temperature + 28) × 0.025kg, that is, the amount of aluminum blocks or aluminum particles added is: (outgoing temperature - arrival temperature + 28) × 0.025kg / t molten steel. After the addition of aluminum begins and the molten steel circulates once, lower the oxygen lance to 4-6m at an oxygen flow rate of 3000-4000m 3 / h, oxygen pressure is 13-15bar, oxygen blowing volume is (amount of aluminum added × 0.78-0.0875) m 3 / t molten steel; when adding aluminum and blowing oxygen to heat up, the free oxygen mass content of the molten steel is less than 0.03%; the T.Fe of the slag before RH alloying is 3-6%; If the oxygen content is ≤0.03%, add aluminum blocks or aluminum particles to make the aluminum content per ton of molten steel equal to (outgoing station temperature - arrival temperature + 32) × 0.025kg, that is, the amount of aluminum blocks or aluminum particles added is: (outgoing station temperature - arrival temperature + 32) × 0.025kg / t molten steel. After the addition of aluminum begins and the molten steel circulates once, lower the oxygen lance to 4-6m and the oxygen flow rate to 3000-4000m 3 / h, oxygen pressure is 13-15bar, oxygen blowing volume is (amount of aluminum added × 0.78) m 3 / t of molten steel, when aluminum is added and oxygen is blown to heat up, the free oxygen mass content of the molten steel is less than 0.03%, and the T.Fe of the slag before RH alloying is 3-6%.

[0019] Step 3: RH treatment: After the molten steel arrives at the station, the temperature is measured and sampled. The RH of the slag at the station is 3-6% T.Fe. The vacuum pump is turned on to quickly reduce the pressure of the vacuum chamber to below 500Pa for decarburization reaction. According to the target composition, alloying is carried out, and the steel is produced after the air is broken. Carbonized rice husks are added after the air is broken. The thickness of the rice husks is 5-15cm. Step 4: Continuous casting: Tundish superheat 15-25℃.

[0020] Two specific embodiments are given below to verify the specific use effect of the present invention: Example 1

[0021] For low-carbon tinplate whose smelting process is hot metal pretreatment → converter blowing → RH treatment → continuous casting, its carbon content is 0.05-0.07% and sulfur content is ≤0.008%. The ladle capacity is 180t. The RH breaking temperature is required to be 1585℃.

[0022] Hot metal pretreatment: After pretreatment, the sulfur content of hot metal is 0.0033%.

[0023] Converter blowing: The converter final sulfur content is 0.0043%, the converter final temperature is 1643℃, and the converter final free oxygen is 0.0543%; after the steelmaking is completed, aluminum-based modifiers and lime are added, and the slag is not accumulated.

[0024] RH treatment: After the molten steel arrives at the station, the temperature is measured and sampled. The RH arrival temperature is 1591℃, and the RH arrival slag T.Fe is 5.4%. Turn on the vacuum pump and quickly reduce the vacuum chamber pressure to below 500Pa to carry out the decarburization reaction.

[0025] After RH vacuum treatment for 5 minutes, the carbon content of the molten steel is 0.0057%, and the free oxygen content of the molten steel is 0.0477%. Aluminum blocks or aluminum particles are added at a rate of 0.35 kg / t steel. After aluminum addition begins and the molten steel circulates once, the oxygen lance is lowered to a position of 5.6 m and an oxygen flow rate of 3666 m 3 / h, oxygen pressure is 14.2bar, oxygen blowing volume is 0.098m 3 / t. After adding aluminum and blowing oxygen to raise the temperature, the free oxygen content of the molten steel is 0.0088%. The T.Fe of the slag before RH alloying is 4.2%.

[0026] According to the target composition, alloying, clean circulation, breaking the air to produce steel. After breaking the air, add carbonized rice husks, the thickness of the rice husk is 12.5cm.

[0027] Continuous casting: Tundish superheat 21°C.

[0028] Others: Ladle emptying time is 41 minutes, and RH vacuum tank waiting time is 19 minutes.

[0029] Through the implementation 1 of the present invention, the final temperature of converter smelting is reduced from more than 1680°C in the traditional technology to less than 1650°C, the RH broken slag T.Fe can be stably controlled below 5%, the pouring performance of molten steel is significantly improved, and the number of continuous casting furnaces can reach more than 15 furnaces. Example 2

[0030] For ultra-low carbon IF steel whose smelting process is hot metal pretreatment → converter blowing → RH treatment → continuous casting, its carbon content is ≤0.003% and sulfur content is ≤0.006%. Ladle capacity is 180t. RH air breaking temperature is required to be 1590℃.

[0031] Hot metal pretreatment: After pretreatment, the sulfur content of hot metal is 0.0019%.

[0032] Converter blowing: The converter final sulfur content is 0.0028%, the converter final temperature is 1654℃, and the converter final free oxygen is 0.0551%; after the steelmaking is completed, aluminum-based modifiers and lime are added, and the slag is not accumulated.

[0033] RH treatment: After the molten steel arrives at the station, the temperature is measured and sampled. The RH arrival temperature is 1597℃, and the RH arrival slag T.Fe is 4.2%. Turn on the vacuum pump and quickly reduce the vacuum chamber pressure to below 500Pa to carry out the decarburization reaction.

[0034] After RH treatment for 12 minutes, when the carbon content of the molten steel is 0.0032%, the free oxygen content of the molten steel is 0.0234%, aluminum blocks or aluminum particles are added, and the addition amount is 0.625kg / t steel. After aluminum addition begins, the molten steel circulates once, and the oxygen lance is lowered to 5.3m, and the oxygen blowing flow rate is 2999m 3 / h, oxygen pressure is 13.5bar, oxygen blowing volume is 0.488m 3 / t steel. After adding aluminum and blowing oxygen to heat up, the free oxygen content of the molten steel is 0.0258%. The T.Fe of the slag before RH alloying is 4.5%.

[0035] According to the target composition, alloying, clean circulation, breaking the air to produce steel. After breaking the air, add carbonized rice husks, the thickness of the rice husk is 11.2cm.

[0036] Continuous casting: Tundish superheat 19°C.

[0037] Others: Ladle emptying time is 37 minutes, RH vacuum tank waiting time is 17 minutes.

[0038] Through implementation 2 of the present invention, the final temperature of converter smelting is reduced from more than 1680°C in the traditional technology to less than 1650°C, the RH broken slag T.Fe can be stably controlled below 5%, the pouring performance of molten steel is significantly improved, and the number of continuous casting furnaces can reach more than 15 furnaces.

[0039] Based on the above ideal embodiments of the present invention, the relevant staff can make various changes and modifications without departing from the technical concept of the present invention through the above description. The technical scope of the present invention is not limited to the contents of the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. A RH vacuum furnace treatment temperature control method, characterized in that: Including molten iron pretreatment → converter blowing → RH treatment → continuous casting, specifically: Step 1: Hot metal pretreatment: Determine the upper limit of sulfur content in the finished steel product to be produced. After hot metal pretreatment, the sulfur content in hot metal should be ≤ the upper limit of sulfur content in the finished steel product - 0.002%; Step 2: Converter blowing: The sulfur content of the converter end molten steel is ≤ the upper limit of the sulfur content of the finished steel product, the converter end molten steel temperature is 1630-1650°C, and the free oxygen content in the converter end molten steel is 0.04-0.06%; after the steel is tapped, aluminum-based modifier and lime are added to the molten steel, and slag is kept from accumulating in the molten steel; Step 3: RH treatment: After the molten steel arrives at the station, the temperature is measured and sampled. The T.Fe of the slag at the RH station is 3-6%. The vacuum pump is turned on to quickly reduce the pressure of the vacuum chamber to below 500Pa to carry out decarburization reaction. When the carbon content of the molten steel is ≤0.01%, the temperature of the molten steel is measured and oxygen is determined, and aluminum is added to blow oxygen to increase the temperature. After the RH decarburization is completed, alloying is carried out according to the target composition, and the net cycle is performed. The steel is broken and the steel is tapped. After breaking the air, carbonized rice husks are added, and the thickness of the rice husks is 5-15cm; Step 4: Continuous casting: The superheat of the tundish is 15-25℃.

2. The RH vacuum furnace treatment temperature control method according to claim 1, characterized in that: If the finished steel is low carbon steel with carbon content > 0.01%: If the oxygen mass content is greater than 0.03%, add aluminum blocks or aluminum particles to make the aluminum mass content per ton of molten steel equal to (outgoing station temperature - arrival temperature + 20) × 0.025kg, that is, the amount of aluminum blocks or aluminum particles added is: (outgoing station temperature - arrival temperature + 20) × 0.025kg / t molten steel. After the addition of aluminum begins and the molten steel circulates once, control the oxygen lance position to start blowing oxygen, so that the volume content of oxygen per ton of molten steel is (amount of aluminum added × 0.78-0.175) m 3 , that is, the oxygen blowing amount is: (amount of aluminum added × 0.78-0.175) m 3 / t molten steel; If the oxygen mass content is ≤0.03%, add aluminum blocks or aluminum particles to make the aluminum mass content in each ton of molten steel equal to (outgoing station temperature - arrival temperature + 24) × 0.025kg, that is, the amount of aluminum blocks or aluminum particles added is: (outgoing station temperature - arrival temperature + 24) × 0.025kg / t molten steel. After the addition of aluminum begins and the molten steel circulates once, control the oxygen lance position to start blowing oxygen, so that the volume content of oxygen in each ton of molten steel is (amount of aluminum added × 0.78) m 3 , that is, the oxygen blowing amount is: (amount of aluminum added × 0.78) m 3 / t molten steel.

3. The RH vacuum furnace treatment temperature control method according to claim 2, characterized in that: After RH decarburization, the free oxygen mass content of the molten steel is less than 0.01%; the T.Fe of the slag before RH alloying is 3-5%.

4. The RH vacuum furnace treatment temperature control method according to claim 1, characterized in that: If the finished steel product is ultra-low carbon steel with a carbon mass content of ≤0.01%: If the oxygen mass content is greater than 0.03%, add aluminum blocks or aluminum particles to make the aluminum mass content per ton of molten steel equal to (outgoing station temperature - arrival temperature + 28) × 0.025kg, that is, the amount of aluminum blocks or aluminum particles added is: (outgoing station temperature - arrival temperature + 28) × 0.025kg / t molten steel. After the addition of aluminum begins and the molten steel circulates once, control the oxygen lance to blow oxygen, so that the volume content of oxygen per ton of molten steel is (amount of aluminum added × 0.78-0.0875)m 3 , that is, the oxygen blowing amount is: (amount of aluminum added × 0.78-0.0875) m 3 / t molten steel; If the oxygen mass content is ≤0.03%, add aluminum blocks or aluminum particles to make the aluminum mass content in each ton of molten steel equal to (outgoing station temperature - arrival temperature + 32) × 0.025kg, that is, the amount of aluminum blocks or aluminum particles added is: (outgoing station temperature - arrival temperature + 32) × 0.025kg / t molten steel. After the addition of aluminum begins and the molten steel circulates once, control the oxygen lance to blow oxygen to make the volume content of oxygen in each ton of molten steel equal to (amount of aluminum added × 0.78) m 3 , that is, the oxygen blowing amount is (amount of aluminum added × 0.78) m 3 / t molten steel.

5. The RH vacuum furnace treatment temperature control method according to claim 4, characterized in that: After RH decarburization, the free oxygen mass content of the molten steel is less than 0.03%; the T.Fe of the slag before RH alloying is 3-6%.

6. The RH vacuum furnace treatment temperature control method according to claim 1, 2 or 4, characterized in that: When blowing oxygen to increase temperature, the oxygen lance position is 4-6m, and the oxygen flow rate is 3000-4000m 3 / h, oxygen pressure is 13-15bar.

7. The RH vacuum furnace treatment temperature control method according to claim 1, characterized in that: The ladle emptying time is ≤45min, and the RH vacuum tank waiting time is ≤30min.