Refining method for improving component hit rate of boron-containing steel

Abstract

The invention discloses a refining method for improving the hit rate of boron-containing steel components, which comprises the following steps: LF (ladle furnace) rapid deoxidation and slagging, whole-course micro-positive-pressure nitrogen control, out-station slag condition adjustment, RH (Ruhrstahl Heraeus) station entering and carbonized rice husk adding, steel ladle bottom blowing argon gas opening in advance at the RH vacuum final stage, RH vacuum breaking argon gas flow setting, bulk ferroboron weighing and bagging. Setting calcium treatment speed and argon bottom blowing; adding carbonized rice husks to cover an argon port after calcium treatment; and sampling to confirm the boron content. The method has the advantages that the boron content hit rate of the boron-containing steel is increased and stabilized in the RH furnace refining process, the alloying effect is obviously improved, the boron component control difficulty and the recovery rate fluctuation are reduced, and the ferroboron yield is increased.

Description

Technical Field

[0001] The invention belongs to the technical field of iron and steel metallurgy, and in particular relates to a refining method for improving the hit rate of boron-containing steel components. Background Art

[0002] As users' requirements for steel quality and performance are increasing, some steel grades are required to have good hardenability. Boron is an element that improves the hardenability of steel. Adding a proper amount of boron can improve the low-temperature impact resistance of steel and reduce the yield strength. Therefore, boron is widely used in steelmaking production. However, due to the very active chemical properties of boron and its easy oxidation, if the process and method are improper, it is easy to cause the boron recovery rate to be unstable, or the boron content of the same boron-containing steel batches to have a large difference.

[0003] At present, the recovery of boron and its requirements in steel have the following characteristics: (1) The O and N contents in steel directly affect the recovery rate of boron. O causes oxidation of boron, and N easily generates boron nitride, which reduces the use effect of boron. (2) If the O and N contents in the steel are high, the boron recovery rate will be low, and the boron reaction products will be detrimental to the performance of the steel. (3) The O and N contents in the steel are unstable, which directly leads to unstable boron recovery; (4) Boron in steel can only play an effective role when it exists in the form of acid-soluble boron; (5) It is difficult for boron to be evenly distributed in steel in a short period of time.

[0004] In addition, due to the narrow content range of wear-resistant high-strength boron, the steel slag making system requires a large amount of slag, the refining slag has poor fluidity, and the RH slag is viscous. When ferroboron is added, it is easy to enter the slag but not the molten steel, making it difficult to control the boron composition. At present, the alloying of boron has the following main defects: (1) Boron alloying of steel from converter. This method is affected by the converter endpoint control and the large fluctuation of oxygen content in steel. Therefore, the boron recovery rate is generally low and the recovery rate fluctuates greatly, generally around 10.65%; (2) LF refining boron alloying. This method has significantly improved the boron alloying effect compared with converter steelmaking, but it is closely related to the operation and control methods, and the fluctuation is also large, generally between 23.5% and 71.5%. Summary of the invention

[0005] The purpose of the present invention is to solve the problems of poor alloying effect, great control difficulty and low recovery rate of existing boron-containing steel, and provide a refining method for improving the hit rate of boron-containing steel components, which can improve and stabilize the hit rate of boron content in boron-containing steel during RH furnace refining, significantly improve the alloying effect, reduce the difficulty of boron component control and the fluctuation of recovery rate, and improve the recovery rate of ferroboron.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions: A refining method for improving the hit rate of boron-containing steel components, the steps of which are as follows: S1: LF rapid deoxidation and slagging, micro-positive pressure nitrogen control throughout the process, and adjustment of slag conditions at the exit; S2: RH station with carbonized rice husk added; S3: Open the bottom of the ladle to blow argon in advance at the end of RH vacuum; S4: RH air-breaking argon gas flow setting; S5: weigh the bulk ferroboron into bags and add at fixed points; S6: calcium treatment speed and bottom blowing argon setting; S7: after calcium treatment, carbonized rice husk was added to cover the argon port; S8: Take samples to confirm the boron content.

[0007] In the steps of LF rapid deoxidation and slagging, whole-process micro-positive pressure nitrogen control, and outgoing slag condition adjustment, the specific operations are as follows: (S11) Before production, timely understand the situation of converter slag and deoxidizer addition, observe the color and melting of slag on the surface of molten steel, and preliminarily judge the oxidizability and consistency of slag; (S12) After the molten steel enters the station, use 10~6-level lower electrodes and a bottom blowing flow rate of 150~200NL / min; adjust the dust removal flap to a slightly positive pressure state; after the submerged arc is stable, increase the heating level and bottom blowing flow rate to quickly slag; adjust the slag fluidity in time according to the slag condition at the station; add ≤50kg of fluorite per batch, and ≤200kg of lime per batch; (S13) After the slag is melted, aluminum wire is fed in. The aluminum content of the sample after the converter is referred to. The feeding amount of aluminum wire is controlled by reducing the aluminum upper limit of the steel grade by 0.010~0.020%. When feeding aluminum wire, it is necessary to observe the bottom blowing and slag melting in front of the furnace to adjust the slag fluidity in time. The aluminum content of the process is controlled to be 0.030~0.040%; (S14) After the aluminum wire is fed, the electrode is lowered and the bottom blowing is controlled at 200~400NL / min, which is conducive to the formation of foam slag; at the same time, aluminum wire is added to the slag surface, and the amount of aluminum wire added is 20~50kg per batch; when taking the first sample, slag samples must be taken to observe the slag condition and judge the slag deoxidation; adjust the slag fluidity in time and continue to diffuse and deoxidize the slag; when the slag is slightly thick, use aluminum wire to adjust the slag fluidity; when taking the second sample, take slag samples at the same time, observe the slag condition and judge the slag deoxidation; when the slag sample color is not good, reduce the argon gas to 150~200NL / min, and increase the amount of aluminum wire added to diffuse and deoxidize the slag; (S15) When the amount of aluminum wire used is greater than 4 batches, observe the slag condition before leaving the station. When the slag fluidity is poor, add a small amount of fluorite ≤50kg to adjust the final slag. Ensure that the LF slag has good fluidity when leaving the station, and leave the station in white slag with an iron oxide content of ≤0.5% and an aluminum oxide content of 0.25~0.30%.

[0008] Furthermore, in step S2, when the RH molten steel arrives at the station, 10-25 kg of carbonized rice husk is added according to the slag conditions to spread the slag surface so that the steel slag does not form a crust.

[0009] Furthermore, in step S3, the wear-resistant and high-strength vacuum time is long. To ensure that the air-permeable bricks are not blocked when the vacuum ends, the argon flow rate at the bottom of the ladle is adjusted to 30NL / min 3 minutes before the vacuum ends. After breaking the air, 10-25kg of carbonized rice husks are added to flatten the slag surface, and the softened slag shell is covered again.

[0010] Furthermore, in step S4, the bottom blowing of argon is set to 200 / 200 NL / min after breaking the air to ensure that the bottom blowing of argon is good, and ferroboron can be added only after the slag shell is broken.

[0011] Furthermore, in step S5, the on-site ferroboron is bulk ferroboron, and the required amount of ferroboron to be added is calculated, accurately weighed, and then put into a woven bag; and argon gas is added at a fixed point.

[0012] Furthermore, in step S6, the calcium treatment speed is set at 100-120 m / min, and after the calcium line ensures that the molten steel is fed, the bottom blowing of the ladle is set at 100 / 100 NL / min; after the calcium treatment is completed, the static stirring flow rate is set at 30-80 NL / min; and the bottom blowing of argon is turned off before the ladle is hung.

[0013] Furthermore, in step S7, after the calcium treatment, 10-15 kg of carbonized rice husk is added to the argon inlet for covering to prevent secondary oxidation of the molten steel.

[0014] Furthermore, in step S8, after static stirring for 3 minutes, sampling is performed to confirm the boron content; when the B component deviation is large, additional boron is added at the argon port until it is qualified.

[0015] Compared with the prior art, the advantages of the technical solution of the present invention are: (1) The LF of the present invention adopts full-process bottom blowing of argon and deep deoxidation white slag submerged arc operation, and full-process micro-positive pressure operation. By adjusting the slag fluidity and controlling the micro-positive pressure, the oxygen content and nitrogen content in the steel are reduced, and the combination of nitrogen and boron is reduced; (2) A small amount of carbonized rice husk is added after the RH is fed into the station, broken through the air, and fed into the wire, so as to soften the slag shell and effectively prevent the situation where the ferroboron cannot penetrate the slag layer and enter the molten steel when added; (3) The present invention uses bulk ferroboron, which is packed into a woven bag and argon is added at a fixed point, thereby reducing the contact between ferroboron and slag and improving the yield of ferroboron. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The main chemical composition (%) of NM450-1 in the embodiment of the present invention is shown in the table; Figure 2 This is a table of converter end point composition (%) in the embodiments of the present invention; Figure 3 This is a table of main components (%) of molten steel at the end point of LF furnace in the embodiment of the present invention; Figure 4 This is a table of main components (%) of molten steel at the end point of the RH furnace in the embodiments of the present invention. DETAILED DESCRIPTION Example

[0017] To make the present invention more clear, a refining method for improving the hit rate of boron-containing steel components of the present invention is further described below in conjunction with the accompanying drawings. The specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0018] A refining method for improving the hit rate of boron-containing steel components, the specific steps are as follows, characterized in that: S1: LF rapid deoxidation and slagging, micro-positive pressure nitrogen control throughout the process, and adjustment of slag conditions at the exit.

[0019] (S11) Before production, timely understand the situation of converter slag and deoxidizer addition, observe the color and melting of slag on the surface of molten steel, and preliminarily judge the oxidizability and consistency of slag; (S12) After the molten steel enters the station, use 10~6-level lower electrodes and a bottom blowing flow rate of 150~200NL / min; adjust the dust removal flap to a slightly positive pressure state; after the submerged arc is stable, increase the heating level and bottom blowing flow rate to quickly slag; adjust the slag fluidity in time according to the slag condition at the station; add ≤50kg of fluorite per batch, and ≤200kg of lime per batch; (S13) After the slag is melted, aluminum wire is fed in. The aluminum content of the sample after the converter is referred to. The feeding amount of aluminum wire is controlled by reducing the aluminum upper limit of the steel grade by 0.010~0.020%. When feeding aluminum wire, it is necessary to observe the bottom blowing and slag melting in front of the furnace to adjust the slag fluidity in time. The aluminum content of the process is controlled to be 0.030~0.040%; (S14) After the aluminum wire is fed, the electrode is lowered and the bottom blowing is controlled at 200~400NL / min, which is conducive to the formation of foam slag; at the same time, aluminum wire is added to the slag surface, and the amount of aluminum wire added is 20~50kg per batch; when taking the first sample, slag samples must be taken to observe the slag condition and judge the slag deoxidation; adjust the slag fluidity in time and continue to diffuse and deoxidize the slag; when the slag is slightly thick, use aluminum wire to adjust the slag fluidity; when taking the second sample, take slag samples at the same time, observe the slag condition and judge the slag deoxidation; when the slag sample color is not good, reduce the argon gas to 150~200NL / min, and increase the amount of aluminum wire added to diffuse and deoxidize the slag; (S15) When the amount of aluminum wire used is greater than 4 batches, observe the slag condition before leaving the station. When the slag fluidity is poor, add a small amount of fluorite ≤50kg to adjust the final slag. Ensure that the LF slag has good fluidity when leaving the station, and leave the station in white slag with an iron oxide content of ≤0.5% and an aluminum oxide content of 0.25~0.30%.

[0020] S2, adding carbonized rice husk into RH station: When RH molten steel arrives at the station, add 10~25kg carbonized rice husk according to the slag conditions to spread the slag surface flat so that the steel slag does not crust.

[0021] S3, open the bottom of the ladle to blow argon in advance at the end of RH vacuum: wear-resistant, high-strength vacuum time is long. To ensure that the air-permeable bricks are not blocked at the end of vacuum, 3 minutes before the end of vacuum, the argon flow rate of the bottom of the ladle is adjusted to 30NL / min. After breaking the air, add 10~25kg of carbonized rice husk to flatten the slag surface, and cover the softened slag shell again.

[0022] S4, RH breaking argon flow setting: after breaking, the bottom blowing argon is set to 200 / 200 NL / min to ensure that the bottom blowing argon is good. Ferroboron can be added only after the slag shell is broken.

[0023] S5, weigh bulk ferroboron into bags and add at fixed points: the ferroboron on site is bulk ferroboron, calculate the amount of ferroboron required, weigh it accurately, and put it into a woven bag; add argon at a fixed point.

[0024] S6, calcium treatment speed and bottom blowing argon setting: the calcium treatment speed is set at 100~120m / min, and after the calcium line ensures the feeding of molten steel, the bottom blowing argon of the ladle is set at 100 / 100 NL / min; after the calcium treatment is completed, the static stirring flow rate is set at 30~80NL / min; the bottom blowing argon is turned off before hanging the ladle.

[0025] S7, adding carbonized rice husk to cover the argon port after calcium treatment: After calcium treatment, add 10-15 kg of carbonized rice husk to cover the argon port to prevent secondary oxidation of the molten steel.

[0026] S8, take samples to confirm the boron content.

[0027] In this embodiment, NM450-1 steel is selected and smelted in a 150-ton converter, a 150-ton LF furnace, and a 150-ton RH furnace. The main chemical components of NM450-1 steel are as follows: Figure 1 shown.

[0028] The whole smelting process is controlled as follows: (1) Converter blowing. The blowing end composition and temperature control are as follows: Figure 2 shown.

[0029] (2) LF refining furnace: slag melting → slag forming submerged arc → heating alloying → continuous slag deoxidation → desulfurization → adjustment of outlet slag condition, outlet composition control such as Figure 3 shown.

[0030] (3) RH degassing: vacuum degree 0.3 mbar, holding time 20 min, static stirring time after calcium treatment 15 min, outgoing composition control as follows Figure 4 shown.

[0031] In the present invention, LF is used for rapid deoxidation and slag making, nitrogen is controlled by micro-positive pressure throughout the process, and the slag condition at the exit is adjusted → carbonized rice husk is added to the RH station → the bottom of the ladle is opened in advance to blow argon at the end of the RH vacuum → the argon flow rate of the RH air-breaking is set → bulk ferroboron is weighed into the bag and added at a fixed point → the calcium treatment speed and the bottom blowing argon are set → carbonized rice husk is added to cover the argon port after calcium treatment → sampling is performed to confirm the boron content. The process can be used to control the composition of molten steel to: N content ≤ 0.0040%, H content ≤ 0.0002%, and B accurately hits the target composition, thereby reducing harmful elements in molten steel and improving the hit rate of molten steel boron composition, and can meet the requirements of large-scale production on site.

[0032] In addition to the above embodiments, the present invention may also have other implementation modes. Any technical solution formed by equivalent replacement or equivalent transformation falls within the protection scope required by the present invention.

Claims

1. A refining method for improving the hit rate of boron-containing steel components, comprising the following steps, characterized in that: S1, LF rapid deoxidation and slagging, whole process micro-positive pressure nitrogen control, exit slag condition adjustment: (S11) Before production, timely understand the situation of converter slag and deoxidizer addition, observe the color and melting of slag on the surface of molten steel, and preliminarily judge the oxidizability and consistency of slag; (S12) After the molten steel enters the station, use 10~6-level lower electrodes and a bottom blowing flow rate of 150~200NL / min; adjust the dust removal flap to a slightly positive pressure state; after the submerged arc is stable, increase the heating level and bottom blowing flow rate to quickly slag; adjust the slag fluidity in time according to the slag condition at the station; add ≤50kg of fluorite per batch, and ≤200kg of lime per batch; (S13) After the slag is melted, aluminum wire is fed in. The aluminum content of the sample after the converter is referred to. The feeding amount of aluminum wire is controlled by reducing the aluminum upper limit of the steel grade by 0.010~0.020%. When feeding aluminum wire, it is necessary to observe the bottom blowing and slag melting in front of the furnace to adjust the slag fluidity in time. The aluminum content of the process is controlled to be 0.030~0.040%; (S14) After the aluminum wire is fed, the electrode is lowered and the bottom blowing is controlled at 200~400NL / min, which is conducive to the formation of foam slag; at the same time, aluminum wire is added to the slag surface, and the amount of aluminum wire added is 20~50kg per batch; when taking the first sample, slag samples must be taken to observe the slag condition and judge the slag deoxidation; adjust the slag fluidity in time and continue to diffuse and deoxidize the slag; when the slag is slightly thick, use aluminum wire to adjust the slag fluidity; when taking the second sample, take slag samples at the same time, observe the slag condition and judge the slag deoxidation; when the slag sample color is not good, reduce the argon gas to 150~200NL / min, and increase the amount of aluminum wire added to diffuse and deoxidize the slag; (S15) When the amount of aluminum wire used is greater than 4 batches, observe the slag condition when leaving the station. When the slag fluidity is poor, add a small amount of fluorite ≤50kg to adjust the final slag; ensure that the LF slag fluidity is good when leaving the station, white slag leaves the station, and the iron oxide content in the slag is ≤0.5%, and the aluminum oxide content is 0.25~0.30%; S2: RH station with carbonized rice husk added; S3: Open the bottom of the ladle to blow argon in advance at the end of RH vacuum; S4: RH air-breaking argon gas flow setting; S5: weigh the bulk ferroboron into bags and add at fixed points; S6: calcium treatment speed and bottom blowing argon setting; S7: after calcium treatment, carbonized rice husk was added to cover the argon port; S8: Take samples to confirm the boron content.

2. The refining method for improving the hit rate of boron-containing steel components according to claim 1, characterized in that: In step S2, when the RH molten steel arrives at the station, 10-25 kg of carbonized rice husk is added according to the slag conditions to spread the slag surface so that the steel slag does not form a crust.

3. The refining method for improving the hit rate of boron-containing steel components according to claim 1 or 2, characterized in that: In the step S3, the wear-resistant and high-strength vacuum time is long. To ensure that the air-permeable bricks are not blocked at the end of the vacuum, the argon flow rate of the ladle bottom is adjusted to 30NL / min 3 minutes before the end of the vacuum. After breaking the air, 10-25kg of carbonized rice husk is added to flatten the slag surface, and the slag shell is covered and softened again.

4. The refining method for improving the hit rate of boron-containing steel components according to claim 1 or 2, characterized in that: In the step S4, the bottom blowing argon is set to 200 / 200 NL / min after breaking the air to ensure that the bottom blowing argon is good. Ferroboron can be added only after the slag shell is broken.

5. The refining method for improving the hit rate of boron-containing steel components according to claim 1 or 2, characterized in that: In step S5, the on-site ferroboron is bulk ferroboron, and the required amount of ferroboron is calculated, accurately weighed, and put into a woven bag; an argon inlet is added at a fixed point.

6. The refining method for improving the hit rate of boron-containing steel components according to claim 1 or 2, characterized in that: In step S6, the calcium treatment speed is set at 100-120 m / min, and after the calcium line is ensured to feed molten steel, the bottom blowing of argon gas in the ladle is set at 100 / 100 NL / min; after the calcium treatment is completed, the static stirring flow rate is set at 30-80 NL / min; and the bottom blowing of argon gas is turned off before hanging the ladle.

7. The refining method for improving the hit rate of boron-containing steel components according to claim 1 or 2, characterized in that: In step S7, after the calcium treatment, 10-15 kg of carbonized rice husk is added to the argon inlet for covering to prevent secondary oxidation of the molten steel.

8. The refining method for improving the hit rate of boron-containing steel components according to claim 1 or 2, characterized in that: In the step S8, after stirring for 3 minutes, samples are taken to confirm the boron content; when the B component deviation is large, additional argon is added at the argon port until it is qualified.

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