CN115369215A - Method for reducing inclusion cracking defect in large-thinning-amount deep drawing forming IF steel - Google Patents
Method for reducing inclusion cracking defect in large-thinning-amount deep drawing forming IF steel Download PDFInfo
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- 229910052760 oxygen Inorganic materials 0.000 claims abstract description 107
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims abstract description 100
- 239000002893 slag Substances 0.000 claims abstract description 67
- 238000009749 continuous casting Methods 0.000 claims abstract description 48
- 238000005261 decarburization Methods 0.000 claims abstract description 36
- 238000007670 refining Methods 0.000 claims abstract description 33
- 238000007664 blowing Methods 0.000 claims abstract description 30
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 26
- 229910052782 aluminium Inorganic materials 0.000 claims abstract description 25
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims abstract description 25
- 238000003723 Smelting Methods 0.000 claims abstract description 21
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 17
- CSJDCSCTVDEHRN-UHFFFAOYSA-N methane;molecular oxygen Chemical compound C.O=O CSJDCSCTVDEHRN-UHFFFAOYSA-N 0.000 claims abstract description 11
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- 238000002844 melting Methods 0.000 description 2
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/10—Handling in a vacuum
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/16—Controlling or regulating processes or operations
- B22D11/18—Controlling or regulating processes or operations for pouring
- B22D11/181—Controlling or regulating processes or operations for pouring responsive to molten metal level or slag level
- B22D11/183—Controlling or regulating processes or operations for pouring responsive to molten metal level or slag level by measuring molten metal weight
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
- C21C5/28—Manufacture of steel in the converter
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/04—Removing impurities by adding a treating agent
- C21C7/06—Deoxidising, e.g. killing
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/04—Removing impurities by adding a treating agent
- C21C7/068—Decarburising
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Abstract
The invention discloses a method for reducing inclusion cracking defects in large-reduction-amount deep-drawing formed IF steel, which comprises the processes of converter smelting, RH refining and continuous casting pouring; the converter smelting process comprises the following steps: controlling the carbon-oxygen product of molten steel in a steel ladle after converter tapping to be 0.0018-0.0026, controlling the carbon content to be 0.030-0.07 wt% and controlling the oxygen content to be 300-700 ppm; the RH refining process comprises the following steps: the content of TFe in RH inbound ladle slag is less than or equal to 3.5wt%, and the content of TFe in outbound ladle slag is less than or equal to 6.5wt%; the decarburization rate is 0.27 to 0.35min ‑1 The oxygen blowing amount is not more than 100Nm at the temperature rise 3 (ii) a The continuous casting process: the tonnage of the tundish is ensured to be 35-70 tons according to the steel passing amount in the continuous casting pouring process; when the pulling speed stably rises to a target value, a plug rod sinusoidal vibration mode is started; after the pouring of the steel ladle is finished, slag is forbidden to be discharged, and the amount of the residual steel is required to be 8-15 tons; the difference between the aluminum in the continuous casting component and the aluminum in the refining outlet component is less than or equal to 100ppm. The method effectively reduces the surface defects of the product, improves the surface quality of the product, and reduces the occurrence frequency of the inclusion cracking sand hole defects from 849ppm to within 200 ppm.
Description
Technical Field
The invention relates to a steel-making smelting method of a deep drawing formed steel plate, in particular to a method for reducing the defect of inclusion cracking in large-reduction-amount deep drawing formed IF steel.
Background
In recent years, with the progress of society, the automobile industry in China is developed vigorously like bamboo shoots in the spring after rain, and the requirements of light weight and great thinning quantity of automobile bodies on the formability of materials are higher, so that the requirements of customers on the quality of automobile substrates are higher and higher, particularly the requirements of high-end customers on the surfaces of high-quality automobile substrates are more strict, and the formability of deep-drawing complex materials are particularly required to be zero tolerance and zero defect.
The inclusion cracking appearance of the large thinning amount deep drawing complex forming is similar to a sand hole state, the size is 0.2-2.0 mm, and the inclusion cracking appearance is irregularly distributed in the substrate. The control difficulty of the inclusion cracking defect is that steel making can not be directly detected, a cold rolled product surface detector can not realize judgment, and the metal flow blockage of inclusions in a base plate exists when the material reduction rate of an inner plate of a deep drawing complex door in a region near an R angle is more than 20%, so that the occurrence frequency of similar sand hole defects on the surface of the base plate is high and even reaches 1000ppm, and the surface quality of the base plate of an automobile plate is seriously influenced.
The defect of inclusion cracking sand hole of large thinning amount deep drawing complex forming is mainly caused by the inclusion in steel, which is Al gathered on the inner wall of SEN nozzle in the continuous casting pouring process 2 O 3 The inclusions fall into the crystallizer and enter the casting blank, generally resulting in fine inclusions formed under the casting blank. The reason is mainly because the high-quality automobile door inner panel is interstitial-free steel, the content of C, N in the steel is extremely low, and a certain amount of Ti content is often added in the smelting process to solidify C, N atoms in the steel, so that carbides and nitrides are formed, and therefore interstitial atoms do not exist in the steel. However, because the carbon content in steel is very low, the oxygen content in molten steel is relatively high according to the carbon-oxygen product balance principle of converter smelting, and in addition, the oxygen in the molten steel is easy to react with aluminum to generate Al 2 O 3 Impurities are continuously accumulated and grown in the continuous casting process, so that a water gap is blocked to cause drift, the impurities fall into a casting blank, and the impurities are rolled and deeply punched in the post process to cause the defect of inclusion cracking of the similar sand hole on the surface of the door panel of the automobile.
At present, domestic and foreign researches mainly focus on optimization and control of surface inclusion defects, and research on the surface sand hole defects of high-quality automobile substrates is not related.
For example, the chinese patent application No. 202010095551.6 discloses a method for producing IF steel for an automobile outer panel without inclusion defects, which optimizes key parameters such as IF steel for an automobile outer panel, converter end point oxygen content control, converter slag quantity, RH process oxygen supplementation, standing time, low-tonnage pouring, less aluminum loss, but does not relate to optimization of parameters such as immersion nozzle insertion depth, continuous casting ladle change rapid ladle change, and heat transfer billet.
The Chinese patent application with the application number of 201310388375.5 discloses a method for reducing the inclusion defect rate of a cold-rolled automobile plate, which adopts a slag dart to block slag during converter tapping, carries out slag modification after tapping, adopts measures such as RH natural decarburization and continuous casting argon blowing protective pouring and the like to reduce the inclusion defect of the cold-rolled automobile plate, and does not relate to technical measures such as converter high-tensile carbon, RH forced decarburization and the like.
The Chinese patent application with the application number of 202011291698.9 discloses an open type heating and heat-insulating hopper for reducing oxide inclusions and a pouring method.
The Chinese patent application with the application number of 201811324962.7 discloses a pouring method for improving the nozzle blockage of stopper rod flow control Al deoxidized steel, which makes detailed description on the nozzle nodulation blockage reduction probability by stopper rod shaking, but does not make research on other key control parameters of high-grade automobile plate converters, refining and continuous casting.
In the thesis of influence of the top slag modification process on inclusions in IF steel (journal of engineering science, pp. 174-179 in S1 of 2018), a modifier is added to different time nodes such as an argon station at which a converter is out of service, after RH deoxidation alloying and after RH refining is finished to modify the slag, so that the optimal top slag modification process is found out, but key parameters such as converter end-point oxygen control, a continuous casting process and the like are not researched.
The ' point ' inclusion defect analysis and control ' in the stamping process (the twenty-second national steel-making academic conference collection in 2020) is controlled by reducing the converter terminal oxygen content, modifying top slag, protecting and pouring in continuous casting, but does not relate to the technologies of RH strong oxygen blowing quick decarburization, heating oxygen blowing, continuous casting submerged nozzle insertion depth, stopper rod vibration and the like.
The prior art only analyzes the inclusion defect, but does not research the defect of the sand hole of complex punching large-thinning inclusion cracking.
Disclosure of Invention
The invention aims to solve the technical problem of providing a method for reducing the defect of inclusion cracking in deep drawing formed IF steel with large reduction amount so as to effectively improve the surface quality of the deep drawing formed steel plate.
In order to solve the technical problems, the technical scheme adopted by the invention is as follows: the method comprises the processes of converter smelting, RH refining and continuous casting pouring;
the converter smelting process comprises the following steps: controlling the carbon-oxygen product of molten steel in a steel ladle after converter tapping to be 0.0018-0.0026, controlling the carbon content to be 0.03-0.07 wt% and controlling the oxygen content to be 300-700 ppm;
the RH refining process comprises the following steps: the content of TFe in RH inbound ladle slag is less than or equal to 3.5wt%, and the content of TFe in outbound ladle slag is less than or equal to 6.5wt%; the decarburization rate is 0.27 to 0.35min -1 The oxygen blowing amount is not more than 100Nm at the temperature rise 3 ；
The continuous casting pouring process comprises the following steps: the tonnage of the tundish is ensured to be 35-70 tons according to the steel passing amount in the continuous casting pouring process; when the pulling speed stably rises to a target value, a plug rod sinusoidal vibration mode is started; after the pouring of the steel ladle is finished, slag is forbidden to be discharged, and the amount of the residual steel is required to be 8-15 tons; the difference between the aluminum in the continuous casting component and the aluminum in the refined component is less than or equal to 100ppm.
In the RH refining process, the decarburization rate is 0.27-0.35 min -1 。
In the RH refining process, caO/Al in slag is controlled after RH decarburization is finished and aluminum deoxidation is added 2 O 3 Is 1.0 to 1.4.
The stopper rod has a sinusoidal vibration mode with a vibration period of 1-2 s and a vibration amplitude of 0.5-1.0 mm.
In the continuous casting process, the submerged nozzle is replaced in advance when the furnace 4 is cast.
In the continuous casting process, the time of a slag adjusting line of the submerged nozzle is 100 min/time.
The technical principle analysis of the invention is as follows:
the invention controls the carbon content in the steel ladle molten steel after the steel is discharged from the converter to be 0.03-0.07 wt% and the oxygen content in the steel ladle molten steel to be 300-700 ppm by a converter high-carbon low-oxygen control technology. Aims at reducing the oxygen content in the molten steel from the root and reducing Al in the molten steel 2 O 3 The generation probability of inclusions is increased, and the cleanliness of molten steel is improved.
The RH refining process dynamically adjusts the height of the oxygen lance and the oxygen flow according to the carbon content and the oxygen content of the station as the oxygen lance height and the oxygen flow are adjustedThe height of the oxygen lance and the flow of oxygen supply gas have important influence on the decarburization reaction, and if the height of the oxygen lance is too high and the flow of the oxygen supply gas is too small, the decarburization reaction rate is reduced; the oxygen lance is too low in height and too large in oxygen flow, so that oxygen is still rich after the oxygen meets the requirements of decarburization reaction, the oxygen content in molten steel is increased, and Al in the molten steel is increased 2 O 3 Probability of generation of inclusions. Therefore, when [ O ]]/[C]When the temperature is less than 1, the carbon content and the oxygen content in the RH inbound ladle are higher, the oxygen supply flow needs to be increased, and the height H of the oxygen lance is reduced (H is the distance from the oxygen lance to the surface of the molten steel); when [ O ]]/[C]When the oxygen content is more than or equal to 1, the RH station-entering ladle is indicated to have higher oxygen content and lower carbon content, and at the moment, the oxygen flow needs to be reduced, and the height H of the oxygen lance (H is the distance from the oxygen lance to the surface of molten steel) needs to be increased; finally realizing the rapid and high-efficiency decarburization rate by RH strong oxygen blowing.
The tonnage of the tundish is ensured to be 35-70 tons according to the steel passing amount in the continuous casting pouring process, and the residual steel amount is required to be 8-15 tons after the ladle pouring is finished, so that the aim of preventing the polluted molten steel in the ladle from entering the crystallizer to cause casting blank inclusion and influence the surface quality of a product is fulfilled. Meanwhile, when the pulling speed stably rises to a target value during continuous casting pouring, the plug rod is opened in a sinusoidal vibration mode, so that molten steel flowing through the head of the plug rod to the submerged nozzle forms fluctuation through the vibration function of the plug rod, and the phenomenon caused by Al is reduced 2 O 3 The probability of water gap adhesion and blockage caused by similar impurities effectively prevents the water gap from deflecting and falling blocks to cause the fluctuation of the liquid level of the crystallizer and influence the quality of casting blanks.
Adopt the produced beneficial effect of above-mentioned technical scheme to lie in: the invention realizes RH rapid deoxidation mainly through converter high-carbon low-oxygen control and RH refining strong oxygen blowing decarburization process, and the RH temperature rise oxygen blowing amount is controlled to be 100m 3 The cleanliness of molten steel is effectively improved; meanwhile, measures such as large-ladle residual steel, stopper rod vibration and the like are adopted in continuous casting, the casting performance of the continuous casting is obviously improved, and the surface quality of a product is obviously improved; the invention is suitable for deep drawing forming IF steel with large thinning amount, and is particularly suitable for producing the inner plate of the automobile door by deep drawing forming with large thinning amount, and the occurrence frequency of the surface blowhole defects of the obtained inner plate of the automobile door is reduced to be within 200ppm from 849 ppm.
Drawings
The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.
FIG. 1 is a schematic view of the surface of a deep drawn steel sheet obtained according to the present invention;
FIG. 2 is a schematic surface view of a deep drawn steel sheet obtained by a conventional method.
Detailed Description
The method for reducing the cracking defect of inclusions in the deeply-drawn IF steel with large reduction amount is suitable for producing the IF steel of the inner plate of the automobile door by adopting the following processes in the processes of converter smelting, RH refining and continuous casting pouring:
(1) The converter smelting process comprises the following steps: adopting a new process for controlling high carbon and low oxygen of the converter, controlling the carbon-oxygen product of the molten steel in a steel ladle after tapping of the converter to be 0.0018-0.0026, controlling the carbon content of the molten steel in the steel ladle to be 0.03-0.07 wt%, and controlling the oxygen content of the molten steel in the corresponding steel ladle to be 300-700 ppm; the carbon content in the steel ladle molten steel is improved, the oxygen content in the steel ladle molten steel is reduced, and the purpose is to improve the cleanliness of the molten steel. In the converter tapping process, the adding amount of the ladle top slag modifier is adjusted according to the terminal oxygen content of the converter, specifically, see table 1, lime is added in the tapping process, and aluminum slag is added after tapping is finished, so that the ladle top is ensured to be uniformly spread and not completely penetrated like a semi-molten state, and slag with high melting point and poor fluidity is formed to control the fluidity of the modified slag and reduce the risk of oxygen transfer to molten steel in the slag; preventing the oxygen content in the slag from being high and transferring oxygen into the molten steel, and reducing the TFe content in the RH station-entering slag to be less than or equal to 3.5wt percent.
Table 1: calculation of lime and aluminium slag addition under different terminal oxygen conditions
(2) RH refining process: and the traditional natural decarburization mode is abandoned, and the RH strong oxygen blowing fast and efficient decarburization mode is adopted, so that the RH refining decarburization rate is improved. The concrete conditions are as follows: (1) carrying out strong oxygen blowing fast decarburization control under the condition that the RH vacuum degree is 150-300 mbar; (2) the height H of the oxygen lance (the distance between the oxygen lance and the surface of the molten steel) is set within the range of 350-500 mm; (3) oxygen gasThe flow rate Q is 1200 Nm/h-3500 Nm/h for carrying out the dry top-up and bottom-up cultivation; (4) according to the carbon-oxygen product balance principle, based on RH inbound O/C, the accurate RH oxygen blowing amount control: when [ O ]]/[C]When the flow rate of the oxygen is more than or equal to 1, reducing the flow rate of the oxygen to 1200Nm 3 /h～2500Nm 3 Increasing the height H of the oxygen lance to 420-500 mm; when [ O ]]/[C]When the oxygen flow is less than 1, the oxygen flow is adjusted to 2500Nm 3 /h～3500Nm 3 Reducing the height H of the oxygen lance to 350-420 mm; obtaining the optimal oxygen blowing amount to achieve the rapid and high-efficiency decarburization rate of RH strong oxygen blowing; the decarburization rate was 0.23min from the previous natural decarburization mode -1 ～0.26min -1 Raising the temperature to 0.27-0.35 min -1 The RH vacuum treatment time is reduced from 32-39 min to 18-30 min, the temperature drop in the RH process is reduced, and the heating oxygen blowing amount is ensured not to exceed 100Nm 3 。
The TFe content of the RH station-entering ladle slag is less than or equal to 3.5wt percent, and CaO/Al in the slag is controlled after aluminum addition and deoxidation are carried out after RH decarburization is finished 2 O 3 At 1.0-1.4, the top slag is in a low melting point region, and has good fluidity, low surface tension and good impurity adsorption capacity; thereby controlling the TFe content in the outbound ladle slag to be less than or equal to 6.5wt percent.
(3) And (3) continuous casting pouring process: continuously and rapidly transferring the ladle during ladle changing in the continuous casting pouring process, and ensuring the tonnage of the tundish to be 35-70 tons according to the steel passing amount during pouring; the tonnage of the tundish is less than 35 tons, and the whole furnace casting blank is not used for producing the deep-drawing formed steel. In order to avoid the influence of drift on steady-state pouring caused by the accumulation of inclusions in the submerged nozzle, the submerged nozzle is replaced in advance when the furnace 4 is cast, and the risks of nozzle blockage and blockage falling are prevented.
The stopper rod is opened in a vibration mode to reduce the probability of bonding and blocking a water gap; the stopper rod vibration adjusting method comprises the following steps: the vibration mode of the stopper rod is not started temporarily when the continuous casting is started; when the pulling speed stably rises to a target value, the stopper rod vibration mode is started, the vibration period is 1-2 s, and the vibration amplitude is 0.5-1.0 mm. Further, after the pulling speed stably rises to a target value, starting a stopper rod vibration mode, wherein the vibration period is 1.4-2 s, and the vibration amplitude is 0.5-0.7 mm; in the later stage of pouring, generally until the furnace 4 is poured, the cleanliness of the molten steel in the tundish is deteriorated and the water gap is easy to block, and after the submerged water gap is replaced in the furnace 4, the vibration period of the stopper rod is adjusted to 1-1.3 s, and the vibration amplitude is increased to 0.8-1.0 mm; the later heat of the pouring keeps the vibration period of 1 to 1.3s and the vibration amplitude of 0.8 to 1.0mm. The target values of the pulling speed are as follows: the section of the casting blank is 900-1200 mm, and the target pulling speed is 1.5m/min; the section is 1250-1450 mm, and the target pulling speed is 1.4m/min; the section is 1500-1700 mm, and the target pulling speed is 1.2m/min; the section is 1750-1850 mm, and the target pulling speed is 1.1m/min; the section is 1900-2150 mm, and the target pulling speed is 1.0m/min.
In order to ensure the stable flow field in the crystallizer in the continuous casting pouring process, the slag line adjusting time of the submerged nozzle is optimized from one time of adjusting every 85min to one time of adjusting every 100min, namely 100 min/time, so that the steady state pouring in the same slag line state for a long time is ensured as much as possible, and the casting blank corresponding to the slag line adjusting time is not used for producing the deep-drawn formed steel. In order to ensure the cleanliness of molten steel, slag is forbidden to be discharged after the pouring of the steel ladle is finished, and the residual steel quantity is required to be 8-15 tons. The submerged pouring with long nozzle and the sealing between the long nozzle and the tundish cover are increased, and the difference between the continuous casting component and the aluminum in the refined outlet component (aluminum loss) is reduced to less than or equal to 100ppm. In order to reduce unstable risk of the transfer billet casting process and reduce the degradation amount of the transfer billet, the size of the transfer billet in a furnace is optimized, namely 2 normal transfer billets are optimized into 1 transfer billet, and the transfer billet is not used for the deep-drawing formed steel. In order to ensure the surface quality of the deep drawing formed steel, the first furnace is poured for the next time and is not used as the deep drawing formed steel.
Example 1: the method for reducing the inclusion cracking defect in the deep drawing forming IF steel with large thinning amount adopts the following specific process.
(1) Converter smelting and RH refining processes: smelting three furnaces to produce IF steel of the automobile door inner plate, wherein the casting blank section is 1350mm, the casting blank thickness is 240mm, and the casting is performed in the No. 2, no. 3 and No. 4 furnaces of the same casting time. The converter adopts a new high-carbon low-oxygen end point control process, the carbon content of molten steel in a steel ladle is controlled to be 0.041%, 0.033% and 0.055%, the oxygen content is controlled to be 512ppm, 551ppm and 391ppm, and the carbon oxygen product is 0.0021, 0.0018 and 0.0022.
Adjusting the addition of the ladle top slag modifier according to the terminal oxygen content of the converter, wherein the specific addition of the modifier and the CaO/Al discharged from RH are 2 O 3 The ratio and the content of TFe in the slag are shown in Table 2.
Table 2: the addition amount of the modifier and the content of TFe in RH station
In Table 2, the CaO/Al 2 O 3 CaO/Al in RH out-station ladle slag 2 O 3 That is, after the RH decarburization is finished and the Al deoxidation is carried out, caO/Al in the slag is 2 O 3 The ratio of (a) to (b).
Adopting RH strong oxygen blowing fast and high-efficient decarbonization mode, carrying out strong oxygen blowing fast decarbonization under the conditions of RH vacuum degree of 200mbar, 240mbar and 180mbar, and leading RH into station [ O ]]/[C]The ratio of 1.5, 1.2, 0.8, and the oxygen flow rate was adjusted to 1500Nm 3 /h、2000Nm 3 /h、3200Nm 3 The corresponding oxygen lance heights H are 500mm, 450mm and 400mm, and the RH refining decarburization rates are 0.31min respectively -1 、0.33min -1 、0.34min -1 RH vacuum treatment time 24min, 27min, 26min, heating oxygen blowing amount 50Nm 3 、60Nm 3 、80Nm 3 。
(2) And (3) continuous casting pouring process: continuously and rapidly transferring the ladle during continuous casting pouring ladle changing, wherein the tonnage of the tundish is respectively 55 tons, 40 tons and 52 tons; the casting process is stably controlled to 59-62 tons. Pouring and replacing the submerged nozzle in the 4 th furnace in the pouring time; the inner wall of the lower water opening is blocked by 3-5 mm, the discharge Kong Sibian is almost clearly visible, and the inner wall of the lower water opening and the discharge hole are slightly blocked.
Starting a stopper rod vibration mode temporarily when casting is started, and starting the stopper rod vibration mode when the pulling speed stably rises to 1.4m/min, wherein the vibration period is 1.4s, and the vibration amplitude is 0.7mm; after the submerged nozzle is replaced when the pouring is finished in the furnace 4, the vibration period of the stopper rod is adjusted to 1.0s, and the vibration amplitude is increased to 1.0mm until the pouring of the whole pouring time is finished.
The three furnaces are casting-time 2, 3 and 4 furnaces, a slag line is adjusted after casting is started for 100min, and a casting blank corresponding to the slag line is not used for producing the automobile door inner plate.
And in order to ensure the cleanliness of molten steel, carrying out ladle residual steel operation, wherein the residual steel amount is respectively 8 tons, 11 tons and 10 tons. The differences in aluminum (aluminum loss) between the continuously cast components and the refining off-site components were 35ppm, 61ppm and 58ppm, respectively. Optimizing the normal 2 handover blanks per stream to 1 handover blank, and the handover blanks are not used for producing the automobile door inner panel.
(3) Surface blowhole defect: FIG. 1 is a schematic surface view of an IF steel coil obtained in the first furnace of the present embodiment; FIG. 2 is a schematic view of the surface of an IF steel coil obtained by a conventional method, wherein a surface sand hole defect exists in a circle shown in FIG. 2; therefore, the embodiment eliminates the surface sand hole defect of the IF steel coil obtained by the conventional method. The steel coil that three stoves of this embodiment correspond is used through user's punching press and is not found the base plate surface sand hole defect, and user's feedback quality is good.
Example 2: the method for reducing the inclusion cracking defect in the deep drawing forming IF steel with large thinning amount adopts the following specific process.
(1) Converter smelting and RH refining processes: smelting two furnaces to produce IF steel of the automobile door inner plate, wherein the section of a casting blank is 1550mm, the thickness of the casting blank is 240mm, and the two furnaces are 3 rd and 4 th furnaces of the same casting time. The converter adopts a new high-carbon low-oxygen end point control process, the carbon content of the molten steel in the steel ladle is controlled to be 0.048 percent and 0.060 percent, the oxygen content is controlled to be 432ppm and 381ppm, and the carbon oxygen product is 0.0021 and 0.0023.
Adjusting the addition of the ladle top slag modifier according to the terminal oxygen content of the converter, wherein the specific addition of the modifier and the CaO/Al discharged from RH are 2 O 3 The ratio and the content of TFe in the slag are shown in Table 3.
Table 3: the addition amount of the modifier and the content of TFe in RH station
In Table 2, the CaO/Al 2 O 3 CaO/Al in RH outbound ladle slag 2 O 3 That is, after the RH decarburization is finished and the Al deoxidation is carried out, caO/Al in the slag is 2 O 3 The ratio of (a) to (b).
Adopting RH strong oxygen blowing fast and high-efficient decarbonization mode, carrying out strong oxygen blowing fast decarbonization under the conditions that RH vacuum degree is 300mbar and 280mbar, and RH station entering [ O ]]/[C]The ratio was 0.9 to 0.7, and the oxygen flow rate was adjusted to 3000Nm 3 /h、3200Nm 3 H is 400mm and 350mm corresponding to the height H of the oxygen lance, and the decarburization rate of RH refining is 0.32min -1 、0.27min -1 RH vacuum treatment time of 26min and 29min, heating oxygen blowing amount of 100Nm 3 、61Nm 3 。
(2) And (3) continuous casting pouring process: continuously and rapidly transferring the ladle during continuous casting pouring ladle changing, wherein the tonnage of the tundish is 43 tons and 47 tons respectively; the casting process is stably controlled to be 62 to 70 tons. And (4) starting the casting furnace in the casting time 4 to replace the submerged nozzle, wherein the inner wall of the replaced nozzle and the discharge hole are slightly blocked, the inner wall is blocked by 4-6 mm, and the lower part of the discharge hole is slightly blocked.
Starting a stopper rod vibration mode temporarily when casting is started, and starting the stopper rod vibration mode after the pulling speed is stably increased to 1.2m/min, wherein the vibration period is 1.8s, and the vibration amplitude is 0.6mm; after the pouring into the 4 th furnace is finished and the submerged nozzle is replaced, the vibration period of the stopper rod is adjusted to 1.2s, and the vibration amplitude is increased to 0.9mm until the pouring of the whole pouring time is finished.
The two furnaces are the 3 rd furnace and the 4 th furnace, a slag line is adjusted after the casting is started for 100min, and casting blanks corresponding to the slag line are not used for producing high-quality automobile door inner plates.
In order to ensure the cleanliness of molten steel, the steel ladle is subjected to residual steel operation, and the residual steel amount is 10 tons and 15 tons respectively. The difference in aluminum (aluminum loss) between the continuous casting composition and the refining composition was 51ppm and 100ppm, respectively. And optimizing the normal 2 joint blanks of each stream into 1 joint blank, wherein the joint blanks are not used for producing high-quality automobile door inner plates. And (4) performing machine cleaning treatment on the casting blank, wherein the four sides of the casting blank are completely cleaned in a machine cleaning mode, and the cleaning depth is 3.5mm.
(3) Surface blowhole defect: the steel coils corresponding to the two furnaces are punched by a user and are used without finding the sand hole defect on the surface of the substrate, and the user feedback quality is good.
Example 3: the method for reducing the inclusion cracking defect in the deep drawing forming IF steel with large thinning amount adopts the following specific process.
(1) Converter smelting and RH refining processes: smelting four furnaces to produce IF steel of the automobile door inner plate, wherein the casting blank section is 1750mm, the casting blank thickness is 240mm, and the four furnaces are 2 nd, 3 rd, 4 th and 5 th furnaces of the same casting time. The converter adopts a new high-carbon low-oxygen end point control process, the carbon content of the molten steel in the steel ladle is controlled to be 0.037%, 0.042%, 0.061% and 0.045%, the oxygen content is controlled to be 700ppm, 592ppm, 300ppm and 431ppm, and the carbon oxygen product is 0.0026, 0.0025, 0.0018 and 0.0019.
Adjusting the addition of the ladle top slag modifier according to the terminal oxygen content of the converter, wherein the specific addition of the modifier and the CaO/Al discharged from RH are 2 O 3 The ratio and the content of TFe in the slag are shown in Table 4.
Table 4: the addition amount of the modifier and the content of TFe in RH station
In Table 4, the CaO/Al 2 O 3 CaO/Al in RH outbound ladle slag 2 O 3 That is, after the RH decarburization is finished and the Al deoxidation is carried out, caO/Al in the slag is 2 O 3 The ratio of (a) to (b).
Adopting RH strong oxygen blowing fast and high-efficient decarbonization mode, carrying out strong oxygen blowing fast decarbonization under the conditions of RH vacuum degree of 200mbar, 150mbar, 220mbar and 250mbar, and leading RH to station [ O ]]/[C]The ratio was 1.6, 1.3, 0.6, 0.9, and the oxygen flow rate was adjusted to 1200Nm 3 /h、1800Nm 3 /h、3500Nm 3 /h、3000Nm 3 The corresponding oxygen lance height H is 500mm, 450mm, 350mm and 400mm, the RH refining decarburization rate is 0.33min -1 、0.30min -1 、0.28min -1 、0.35min -1 RH vacuum treatment time of 26min, 18min, 30min and 25min, and heating oxygen blowing amount of 61Nm 3 、38Nm 3 、58Nm 3 、40Nm 3 。
(2) And (3) continuous casting pouring process: continuously and rapidly transferring the ladle during continuous casting pouring ladle changing, wherein the tonnage of the tundish is respectively 35 tons, 47 tons, 49 tons and 46 tons; the casting process is stably controlled to be 60 to 64 tons. And (4) casting and replacing the submerged nozzle in the 4 th furnace in the casting time, wherein the inner wall of the lower nozzle and the discharge hole are slightly blocked, the inner wall is blocked for 3-6 mm, and the lower part of the discharge hole is slightly blocked.
Starting a stopper rod vibration mode temporarily when casting is started, and starting the stopper rod vibration mode when the pulling speed is stably increased to 1.1m/min, wherein the vibration period is 2s, and the vibration amplitude is 0.5mm; after the submerged nozzle is replaced when the pouring is finished in the furnace 4, the vibration period of the stopper rod is adjusted to 1.3s, and the vibration amplitude is increased to 0.8mm until the pouring of the whole pouring time is finished.
The four furnaces are casting-time 2, 3, 4 and 5 furnaces, a slag line is adjusted after casting is started for 100min, and casting blanks corresponding to the slag line are not used for high-quality automobile door inner plates.
And in order to ensure the cleanliness of molten steel, carrying out ladle residual steel operation, wherein the residual steel amount is respectively 9 tons, 12 tons, 11 tons and 12 tons. The differences in aluminum (aluminum loss) between the continuous casting components and the refining outlet components were 38ppm, 59ppm, 48ppm and 63ppm, respectively. And optimizing the normal 2 joint blanks of each stream into 1 joint blank, wherein the joint blanks are not used for producing high-quality automobile door inner plates.
Example 4: the method for reducing the inclusion cracking defect in the deep drawing forming IF steel with large thinning amount adopts the following specific process.
(1) Converter smelting and RH refining processes: smelting IF steel of the automobile door inner plate by two furnaces, wherein the section of a casting blank is 1200mm, the thickness of the casting blank is 240mm, and the casting is performed in the 3 rd furnace and the 4 th furnace in the same casting time. The converter adopts a new high-carbon low-oxygen end point control process, the carbon content of molten steel in a steel ladle is controlled to be 0.036 percent and 0.030 percent, the oxygen content is controlled to be 639ppm and 667ppm, and the carbon-oxygen product is 0.0023 and 0.0020.
Adjusting the addition of the ladle top slag modifier according to the terminal oxygen content of the converter, wherein the specific addition of the modifier and the CaO/Al discharged from RH are 2 O 3 The ratio and the content of TFe in the slag are shown in Table 5.
Table 5: the addition amount of the modifier and the content of TFe in RH station
In Table 5, the CaO/Al 2 O 3 CaO/Al in RH outbound ladle slag 2 O 3 That is, after the RH decarburization is finished and the Al deoxidation is carried out, caO/Al in the slag is 2 O 3 The ratio of (a) to (b).
Adopts an RH strong oxygen blowing fast and high-efficiency decarburization mode, and is carried out under the conditions that the RH vacuum degree is 160mbar and 200mbarStrong oxygen blowing for quick decarbonization, RH station entering [ O ]]/[C]The ratio was 1.0 to 0.8, and the oxygen flow rate was adjusted to 2500Nm 3 /h、2800Nm 3 H, corresponding to the height H of the oxygen lance is 420mm and 380mm, and the RH refining decarburization rate is 0.29min respectively -1 、0.33min -1 RH vacuum treatment time of 20min and 21min, and heating oxygen blowing amount of 42Nm 3 、53Nm 3 。
(2) And (3) continuous casting pouring process: continuously and rapidly transferring the ladle during continuous casting pouring ladle changing, wherein the tonnage of the tundish is respectively 50 tons and 60 tons; the casting process is stably controlled to be 62 to 70 tons. And (4) starting the casting furnace in the casting time 4 to replace the submerged nozzle, wherein the inner wall of the replaced nozzle and the discharge hole are slightly blocked, the inner wall is blocked by 4-6 mm, and the lower part of the discharge hole is slightly blocked.
Starting a stopper rod vibration mode temporarily when casting is started, and starting the stopper rod vibration mode when the pulling speed stably rises to 1.5m/min, wherein the vibration period is 1.5s, and the vibration amplitude is 0.6mm; after the submerged nozzle is replaced when the pouring is finished in the furnace 4, the vibration period of the stopper rod is adjusted to 1.1s, and the vibration amplitude is increased to 1.0mm until the pouring of the whole pouring time is finished.
The two furnaces are the 3 rd furnace and the 4 th furnace, a slag line is adjusted after the casting is started for 100min, and casting blanks corresponding to the slag line are not used for producing high-quality automobile door inner plates.
And in order to ensure the cleanliness of molten steel, carrying out ladle residual steel operation, wherein the residual steel amount is 14 tons and 13 tons respectively. The difference in aluminum (aluminum loss) between the continuous casting composition and the refining composition was 67ppm and 81ppm, respectively. And optimizing the normal 2 joint blanks of each stream into 1 joint blank, wherein the joint blanks are not used for producing high-quality automobile door inner plates. And (3) performing machine cleaning on the casting blank, and completely cleaning four sides in a machine cleaning mode, wherein the cleaning depth is 3.5mm.
(3) Surface blowhole defect: the steel coils corresponding to the two furnaces are punched by a user and are used without finding the sand hole defect on the surface of the substrate, and the user feedback quality is good.
Example 5: the method for reducing the inclusion cracking defect in the deep drawing forming IF steel with large thinning amount adopts the following specific process.
(1) Converter smelting and RH refining processes: smelting two furnaces to produce IF steel of the automobile door inner plate, wherein the cross section of a casting blank is 1900mm, the thickness of the casting blank is 240mm, and the two furnaces are 3 rd and 4 th furnaces of the same casting time. The converter adopts a new high-carbon low-oxygen end point control process, the carbon content of molten steel in a steel ladle is controlled to be 0.070 percent and 0.067 percent, the oxygen content is controlled to be 315ppm and 358ppm, and the carbon oxygen product is controlled to be 0.0022 and 0.0024.
Adjusting the addition of the ladle top slag modifier according to the terminal oxygen content of the converter, wherein the specific addition of the modifier and the CaO/Al discharged from RH are 2 O 3 The ratio and the content of TFe in the slag are shown in Table 6.
Table 6: addition amount of modifier and TFe content of RH station
In Table 6, the CaO/Al 2 O 3 CaO/Al in RH outbound ladle slag 2 O 3 That is, after the RH decarburization is finished and the Al deoxidation is carried out, caO/Al in the slag is 2 O 3 The ratio of (a) to (b).
Adopting RH strong oxygen blowing fast and high-efficiency decarburization mode, carrying out strong oxygen blowing fast decarburization under the conditions that RH vacuum degree is 180mbar and 210mbar, and RH station entry [ O ]]/[C]The ratio was 1.2 to 0.9, and the oxygen flow rate was adjusted to 2000Nm 3 /h、2500Nm 3 The corresponding oxygen lance height H is 450mm and 420mm, the RH refining decarburization rate is 0.34min respectively -1 、0.30min -1 RH vacuum treatment time of 26min and 29min, heating oxygen blowing amount of 77Nm 3 、83Nm 3 。
(2) And (3) continuous casting pouring process: continuously and rapidly transferring the ladle during continuous casting pouring ladle changing, wherein the tonnage of the tundish is 40 tons and 45 tons respectively; the pouring process is stably controlled to 35 to 60 tons. And (4) starting the casting furnace in the casting time 4 to replace the submerged nozzle, wherein the inner wall of the replaced nozzle and the discharge hole are slightly blocked, the inner wall is blocked by 4-6 mm, and the lower part of the discharge hole is slightly blocked.
Starting a stopper rod vibration mode temporarily when casting is started, and starting the stopper rod vibration mode when the pulling speed stably rises to 1.0m/min, wherein the vibration period is 1.6s, and the vibration amplitude is 0.5mm; after the pouring into the 4 th furnace is finished and the submerged nozzle is replaced, the vibration period of the stopper rod is adjusted to 1.2s, and the vibration amplitude is increased to 0.9mm until the pouring of the whole pouring time is finished.
The two furnaces are the 3 rd furnace and the 4 th furnace in the casting process, a slag line is adjusted after the casting process is started for 100min, and casting blanks corresponding to the slag line are not used for producing high-quality automobile door inner plates.
In order to ensure the cleanliness of molten steel, the steel ladle residual steel operation is carried out, and the residual steel amount is respectively 10 tons and 8 tons. The difference in aluminum (aluminum loss) between the continuous casting composition and the refining composition was 55ppm and 58ppm, respectively. And optimizing the normal 2 joint blanks of each stream into 1 joint blank, wherein the joint blanks are not used for producing high-quality automobile door inner plates. And (4) performing machine cleaning treatment on the casting blank, wherein the four sides of the casting blank are completely cleaned in a machine cleaning mode, and the cleaning depth is 3.5mm.
(3) Surface blowhole defect: the steel coils corresponding to the two furnaces are punched by a user and are used without finding the sand hole defect on the surface of the substrate, and the user feedback quality is good.
Claims (6)
1. A method for reducing inclusion cracking defects in large-thinning-amount deep drawing formed IF steel is characterized in that: the method comprises the processes of converter smelting, RH refining and continuous casting pouring;
the converter smelting process comprises the following steps: controlling the carbon-oxygen product of molten steel in a steel ladle after converter tapping to be 0.0018-0.0026, controlling the carbon content to be 0.03-0.07 wt% and controlling the oxygen content to be 300-700 ppm;
the RH refining process comprises the following steps: the content of TFe in RH inbound ladle slag is less than or equal to 3.5wt%, and the content of TFe in outbound ladle slag is less than or equal to 6.5wt%; the decarburization rate is 0.27 to 0.35min -1 The oxygen blowing amount is not more than 100Nm at the temperature rise 3 ；
The continuous casting pouring process comprises the following steps: the tonnage of the tundish is ensured to be 35-70 tons according to the steel passing amount in the continuous casting pouring process; when the pulling speed stably rises to a target value, a plug rod sinusoidal vibration mode is started; after the pouring of the steel ladle is finished, slag is forbidden to be discharged, and the amount of residual steel is required to be 8-15 tons; the difference between the aluminum in the continuous casting component and the aluminum in the refined component is less than or equal to 100ppm.
2. The method for reducing inclusion cracking defects in a high reduction depth draw formed IF steel in accordance with claim 1, wherein: in the RH refining process, the decarburization rate is 0.27-0.35 min -1 。
3. The method for reducing inclusion cracking defects in a large reduction amount deep drawing forming IF steel according to claim 1, wherein: in the RH refining process, after the RH decarburization is finished and the aluminum deoxidation is carried out, caO/Al in the slag is controlled 2 O 3 Is 1.0 to 1.4.
4. The method for reducing inclusion cracking defects in a high reduction depth draw formed IF steel in accordance with claim 1, wherein: the vibration period of the sinusoidal vibration mode of the stopper rod is 1-2 s, and the vibration amplitude is 0.5-1.0 mm.
5. The method for reducing inclusion cracking defects in a high reduction depth draw formed IF steel in accordance with claim 1, wherein: in the continuous casting process, the submerged nozzle is replaced in advance when the furnace 4 is cast.
6. The method for reducing inclusion cracking defects in a high reduction depth drawing formed IF steel in accordance with any one of claims 1 to 5, wherein: in the continuous casting process, the time of a submerged nozzle slag adjusting line is 100 min/time.
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| CN109332625A (en) * | 2018-11-08 | 2019-02-15 | 武汉钢铁有限公司 | A kind of casting method improving stopper rod flow control Al dexidized steel nozzle blocking |
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| CN109332625A (en) * | 2018-11-08 | 2019-02-15 | 武汉钢铁有限公司 | A kind of casting method improving stopper rod flow control Al dexidized steel nozzle blocking |
| CN112011670A (en) * | 2020-08-20 | 2020-12-01 | 邯郸钢铁集团有限责任公司 | Method for increasing RH refining decarburization rate of ultra-low carbon steel and side blowing device |
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