CN116949247A - Method for controlling RH residual cold steel to stabilize molten steel cleanliness - Google Patents
Method for controlling RH residual cold steel to stabilize molten steel cleanliness Download PDFInfo
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- CN116949247A CN116949247A CN202310996383.1A CN202310996383A CN116949247A CN 116949247 A CN116949247 A CN 116949247A CN 202310996383 A CN202310996383 A CN 202310996383A CN 116949247 A CN116949247 A CN 116949247A
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 294
- 239000010959 steel Substances 0.000 title claims abstract description 294
- 238000000034 method Methods 0.000 title claims abstract description 54
- 230000003749 cleanliness Effects 0.000 title claims abstract description 18
- 229910052760 oxygen Inorganic materials 0.000 claims abstract description 58
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims abstract description 56
- 239000001301 oxygen Substances 0.000 claims abstract description 56
- 238000002844 melting Methods 0.000 claims abstract description 18
- 230000008018 melting Effects 0.000 claims abstract description 18
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 claims abstract description 17
- 239000003546 flue gas Substances 0.000 claims abstract description 17
- 238000009489 vacuum treatment Methods 0.000 claims abstract description 7
- 238000007664 blowing Methods 0.000 claims description 38
- 238000007598 dipping method Methods 0.000 claims description 8
- 238000010926 purge Methods 0.000 claims description 4
- 239000000161 steel melt Substances 0.000 claims 1
- 238000005086 pumping Methods 0.000 abstract description 12
- 230000000694 effects Effects 0.000 abstract description 9
- 238000005516 engineering process Methods 0.000 abstract description 4
- 230000002159 abnormal effect Effects 0.000 abstract description 3
- 238000009628 steelmaking Methods 0.000 abstract description 2
- 230000000087 stabilizing effect Effects 0.000 abstract 1
- 230000000052 comparative effect Effects 0.000 description 18
- 238000001816 cooling Methods 0.000 description 10
- 238000004519 manufacturing process Methods 0.000 description 7
- 238000007670 refining Methods 0.000 description 7
- 239000002893 slag Substances 0.000 description 7
- 238000003723 Smelting Methods 0.000 description 6
- 229910052799 carbon Inorganic materials 0.000 description 6
- 238000006243 chemical reaction Methods 0.000 description 5
- 239000007789 gas Substances 0.000 description 5
- 229910000658 steel phase Inorganic materials 0.000 description 5
- 229910052782 aluminium Inorganic materials 0.000 description 4
- 238000005261 decarburization Methods 0.000 description 4
- 230000007423 decrease Effects 0.000 description 4
- 239000010936 titanium Substances 0.000 description 4
- 229910052719 titanium Inorganic materials 0.000 description 4
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 3
- 238000009835 boiling Methods 0.000 description 3
- 238000007872 degassing Methods 0.000 description 3
- 239000002436 steel type Substances 0.000 description 3
- 229910000604 Ferrochrome Inorganic materials 0.000 description 2
- 229910000616 Ferromanganese Inorganic materials 0.000 description 2
- 229910000519 Ferrosilicon Inorganic materials 0.000 description 2
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N Iron oxide Chemical compound [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 description 2
- 238000005275 alloying Methods 0.000 description 2
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 2
- 238000009833 condensation Methods 0.000 description 2
- 230000005494 condensation Effects 0.000 description 2
- 238000009749 continuous casting Methods 0.000 description 2
- 230000002349 favourable effect Effects 0.000 description 2
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- 238000010438 heat treatment Methods 0.000 description 2
- 238000003780 insertion Methods 0.000 description 2
- 230000037431 insertion Effects 0.000 description 2
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- DALUDRGQOYMVLD-UHFFFAOYSA-N iron manganese Chemical compound [Mn].[Fe] DALUDRGQOYMVLD-UHFFFAOYSA-N 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- 238000010309 melting process Methods 0.000 description 2
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 2
- CSJDCSCTVDEHRN-UHFFFAOYSA-N methane;molecular oxygen Chemical compound C.O=O CSJDCSCTVDEHRN-UHFFFAOYSA-N 0.000 description 2
- 229910052757 nitrogen Inorganic materials 0.000 description 2
- 238000012545 processing Methods 0.000 description 2
- 239000011819 refractory material Substances 0.000 description 2
- 230000007306 turnover Effects 0.000 description 2
- 235000008733 Citrus aurantifolia Nutrition 0.000 description 1
- 235000011941 Tilia x europaea Nutrition 0.000 description 1
- 230000005856 abnormality Effects 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000009529 body temperature measurement Methods 0.000 description 1
- 238000005266 casting Methods 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 238000002485 combustion reaction Methods 0.000 description 1
- 230000003009 desulfurizing effect Effects 0.000 description 1
- 238000007654 immersion Methods 0.000 description 1
- 238000002347 injection Methods 0.000 description 1
- 239000007924 injection Substances 0.000 description 1
- 230000001788 irregular Effects 0.000 description 1
- 239000004571 lime Substances 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 239000003345 natural gas Substances 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- 230000002035 prolonged effect Effects 0.000 description 1
- 238000010791 quenching Methods 0.000 description 1
- 230000000171 quenching effect Effects 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 230000033764 rhythmic process Effects 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
- 238000010079 rubber tapping Methods 0.000 description 1
- 238000005070 sampling Methods 0.000 description 1
- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 description 1
- 229910010271 silicon carbide Inorganic materials 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
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Classifications
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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
-
- 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
- C21C7/0075—Treating in a ladle furnace, e.g. up-/reheating of molten steel within the ladle
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Treatment Of Steel In Its Molten State (AREA)
Abstract
The invention belongs to the technical field of steelmaking technology, and relates to a method for controlling RH residual cold steel to stabilize molten steel cleanliness. According to the method, the melting state of the RH furnace cold steel is judged by utilizing the CO concentration change trend in the flue gas of the RH furnace, RH is broken and emptied to be restored to the atmospheric pressure during initial melting of the cold steel, the cold steel is pre-melted under the heat effect brought by the circulation of RH molten steel, the cold steel is quickly purged by an oxygen lance to drop into a cold steel collecting tank, then the vacuum pumping is quickly restored to the preset vacuum degree, RH vacuum treatment is continued, and the time (namely the cold steel treatment time) for starting breaking and emptying to be re-pumped to the target vacuum degree is less than or equal to 120 seconds. The method can ensure that the O content of molten steel in the RH process is stably reduced to the ideal level of the O content in the RH treatment period, thereby stabilizing the cleanliness of the molten steel and avoiding the problem of sudden abnormal rise of the O content caused by the pollution of the molten steel by cold steel.
Description
Technical Field
The invention belongs to the technical field of steelmaking technology, and particularly relates to a method for controlling RH residual cold steel to stabilize molten steel cleanliness.
Background
The purity has great influence on the fatigue life of the steel, wherein the control of the O content is particularly important, and the smaller the size of inclusions in the steel is, the more easily the bearing steel and gear steel with high life are obtained. In general, a production process of BOF/EAF- & gt LF- & gtRH- & gtCCM is often adopted in high-end clean steel type smelting, when molten steel passes through an RH process, cold steel in the former furnaces remained in the RH furnaces pollutes the molten steel, so that the problem of sudden abnormal rise of O content of the molten steel in the heat is caused, the rise of the abnormal O content is difficult to reduce to an ideal level in the subsequent RH treatment process, the cleanliness of the molten steel is deteriorated, and therefore, the problem of realizing effective removal of cold steel in the RH furnaces and ensuring continuous operation of the RH furnaces to obtain stable ultra-high clean steel smelting becomes a key problem in smelting industry.
Through searching, many people at home and abroad research on the aspect of RH furnace cold steel control.
The patent CN109423537A relates to a method for rapidly removing cold steel in an RH vacuum chamber, which changes an energy medium for off-line baking of the RH vacuum chamber into oxygen, and starts to bake off-line within 30 minutes after the last furnace molten steel treatment in the working period of the RH vacuum chamber; carrying out immersion reset operation on a slag-containing molten steel tank for receiving molten slag in a vacuum chamber according to a jacking mode during molten steel treatment, setting the total oxygen blowing amount of an RH top lance, igniting the oxygen blowing flow and the oxygen blowing lance position; starting oxygen blowing operation, and adjusting oxygen blowing flow when the oxygen lance reaches a set position and the flow reaches a set value; after the liquid slag flows out of the insertion tube, the position of the RH oxygen lance is adjusted, the oxygen blowing period is adjusted for 2 to 5 times, and the oxygen blowing time is 5 to 20 minutes each time; after the slag melting operation is completed, the RH top lance nitrogen protection gas is started to purge the vacuum chamber, so that the oxygen concentration in the vacuum chamber is reduced. Realizing quick baking and melting of cold steel. So that the RH top lance has the function of oxygen baking during non-treatment of molten steel. The baking time is shortened by 1.5 hours by changing the vacuum chamber off-line baking process. The other patent emphasizes that the conventional cold steel operation after RH use cannot solve the behavior of the cold steel in the continuous use process, and meanwhile, the cold steel is melted by using natural gas and the like again due to the lower temperature of the cold steel in a colder RH furnace, so that the period of the integrated cold steel is longer.
The patent CN102851456A relates to a method for online removing RH vacuum chamber cold steel, which is characterized in that a top lance oxygen blowing method is adopted to online remove cold steel during RH treatment of molten steel, and the operation steps are as follows: 1) Before molten steel is processed in the vacuum chamber, the temperature of the inner wall of the vacuum chamber is required to be more than or equal to 1350 ℃; 2) During the treatment of boiling steel, the gun position and the oxygen flow are controlled, and the secondary combustion effect of CO generated by molten steel decarburization is utilized to heat the vacuum inner wall, so that the splashing adhesion of molten steel is reduced. And the method can also be used for online removal of cold steel by adopting a top lance oxygen injection method immediately after the RH treatment of molten steel is finished. Compared with the prior art, the beneficial effects are that: 1) The rapid removal of cold steel in the vacuum chamber is realized, the cold steel can be removed within 30min at the highest speed, and the blockage of molten steel slag in the inner cavity of the insertion tube is effectively avoided. 2) The vacuum chamber refractory material is not damaged in the process of removing the cold steel. 3) The production cost is reduced, the labor intensity is lightened, and the labor safety guarantee is improved. The other patent is to conduct cold steel melting operation in the RH treatment process, because the other steel is boiling steel with high oxygen content, all the melted cold steel enters molten steel, although the O content of the molten steel can be increased, the steel is boiling steel and cannot be negatively influenced, but the steel is high-end clean steel, and the cold steel is not allowed to drop into the molten steel. Meanwhile, the treatment period reaches 30min, and for high-end clean steel, the RH treatment period is less than 30 min.
The patent CN107828938A discloses a method for preventing bonding of vacuum tank cold steel in an RH vacuum circulation degassing process, and provides a method for preventing bonding of vacuum tank cold steel in an RH vacuum circulation degassing process. The method comprises the following steps: (1) The ladle adopts a normal turnover ladle, and the turnover time is less than 60 minutes; (2) Molten steel feeding RH furnace strippingControlling the temperature of the molten steel to be higher than 1620 ℃ and controlling the temperature of the molten steel which is not deoxidized to be higher than 1600 ℃; (3) The vacuum degree in the groove is 5-15kpa when the temperature of the RH refining furnace OB is raised or the OB is subjected to forced decarburization, and the circulating gas flow is 1400NL/min; (4) The circulation flow gas flow rate is controlled to 1600NL/min 5min before decarburization of the RH refining furnace, and the circulation flow gas flow rate is controlled to 2000NL/min from 5min to the end of decarburization; (5) Adding aluminum into molten steel for deoxidizing for 3min, and then adding other alloys; (6) adding 200kg of desulfurizing agent after alloying the molten steel; (7) Raising the temperature of the upper tank and the hot bent pipe by using top lance heating, wherein the top lance position is 8.5m, and the gas flow is 200Nm 3 /h, oxygen flow 220Nm 3 /h; (8) The pure degassing circulation time of the molten steel is longer than 8min, and the treatment is finished. Can effectively prevent cold steel in the vacuum tank from bonding and improve the operation rate of the RH furnace. The other patent puts forward a plurality of strict parameter requirements on the RH furnace, has higher requirements on the overall manufacturing cost of RH, such as the requirement of top lance heating, the requirement of larger ring flow facilities of the RH furnace, the requirement of vacuum alloying facilities and the like, and is not suitable for common RH furnace equipment. In addition, in the actual process, no cold steel can remain in the RH furnace.
Therefore, aiming at the RH furnace cooling steel problem faced by adopting an RH process to produce clean steel, the invention provides a method for controlling the cleanliness of the RH residual cooling steel to stabilize molten steel, and aiming at the independent cooling steel operation after the traditional RH furnace is taken off line, the continuous and monitorable rapid cooling steel process of the conventional RH furnace is realized, and the aim of smelting high-purity steel of the RH process is fulfilled.
Disclosure of Invention
The invention aims to develop a method for controlling the cleanliness of RH residual cold steel to stabilize molten steel, which can replace the traditional method of cooling steel after RH is off-line or adding expensive RH equipment, so that the RH cold steel can be easily removed, and stable high-cleanliness steel types can be obtained.
The steel grade belongs to the steel grade with the requirement of ultra-high cleanliness, such as ultra-high cleanliness bearing steel, gear steel, hub steel and other products.
A method for controlling the cleanliness of RH residual cold steel stable molten steel, comprising the following steps:
(1) Judging whether cold steel melting occurs in the RH furnace according to the CO concentration change trend in the flue gas of the RH furnace. If the concentration of CO naturally drops after reaching the peak value, the problem of residual cold steel in the RH furnace is solved, and the conventional RH vacuum treatment is continued; if the CO concentration starts to decrease after reaching the peak value, but increases again, the timing at which the increase starts again indicates that the cold steel remaining in the RH furnace starts to melt under the heat from the RH molten steel circulation during the RH treatment.
(2) The RH is broken to be at atmospheric pressure at the moment when the cold steel starts to melt (i.e. at the moment when the CO concentration starts to fall and rise again after reaching the peak value), and the ladle is rotated or moved to enable the cold steel collecting tank to be located right below the RH furnace so as to facilitate cold steel collection.
(3) And (3) rapidly blowing and melting cold steel by using an oxygen lance, wherein the oxygen blowing time is less than or equal to 60s, and dripping the cold steel into a cold steel collecting tank.
(4) And after the cold steel blowing and dripping is finished, rotating or moving the ladle to enable the cold steel collecting tank to be positioned at the lower part of the dipping pipe, rapidly vacuumizing to a preset vacuum degree, and continuing RH vacuum treatment.
Further, when the RH furnace is broken to the atmospheric pressure in the step (2), the temperature of the RH furnace is more than or equal to (T0+30) DEG C, T0 is the corresponding liquidus temperature of molten steel (namely the temperature when the molten steel is completely melted into liquid), and the measurement point is the temperature of the inner wall of the RH lower port refractory.
Further, the oxygen lance oxygen blowing flow in the step (3) is 1600-2000 Nm 3 /h。
Further, the predetermined vacuum degree in the step (4) is less than or equal to 67Pa.
Further, the time taken from the start of breaking the air to the re-pumping to the preset vacuum is less than or equal to 120s.
Judging whether cold steel melting occurs in the RH furnace or not according to the CO concentration change trend in the flue gas of the RH furnace: if the concentration of CO naturally drops after reaching the peak value, the problem of residual cold steel in the RH furnace is solved, and the conventional RH vacuum treatment is continued; if the CO concentration starts to decrease after reaching the peak value, but increases again, the timing at which the increase is started again indicates a request for starting melting of cold steel remaining in the RH furnace by heat generated by the RH molten steel circulation during the RH treatment.
Because the conventional RH furnace has a flue gas analysis function and is used for judging the progress of the carbon-oxygen reaction of molten steel, wherein the conventional analysis components comprise CO, the change of the concentration of CO can represent the reaction of C and O occurring in the molten steel, and the vacuum pumping is usually started and the target vacuum is reached to generate [ C ]]+[O]The reaction of { CO } can be known to reach an equilibrium state at a certain moment according to thermodynamics, the C and O in molten steel do not react any more, and the concentration of CO in flue gas is increased, approaches to equilibrium and then decreases according to the principle. If there are other reasons for abnormality in the process, such as the presence of cold steel, the state that has reached equilibrium is broken, and, for example, the CO concentration starts to decrease after reaching equilibrium, the phenomenon of rising again occurs. Since the main component of cold steel is metallic Fe and its oxide (Fe x O y ) After entering molten steel, iron oxide in cold steel can transfer O content to molten steel, so that the O content of molten steel is raised again, and the carbon-oxygen reaction ([ C ] is promoted]+[O]-CO) continues to occur, which in turn results in a situation where the CO concentration in the flue gas increases again. Therefore, the behavior of whether cold steel is melted into molten steel can be characterized by the corresponding irregular change of the concentration of CO in the flue gas. If the residual cold steel in the RH furnace is not removed and participates in the molten steel circulation reaction, the O content of the molten steel is abnormally increased, and the residual cold steel is difficult to be reduced to a reasonable level in the RH circulation treatment period in the subsequent RH circulation treatment process.
The requirement for restoring RH void to atmospheric pressure at the point when the cold steel begins to melt (i.e., begins to fall and rise again after the CO concentration reaches a peak value) is met by rotating or moving the ladle so that the cold steel collection tank is located directly below the RH furnace to facilitate cold steel collection.
Since the CO concentration characterizes the behavior of residual cold steel entering molten steel in the RH furnace, the residual cold steel must be removed from the RH furnace to ensure that it does not enter molten steel, and since it is impossible for RH to linearize cold steel to ensure that molten cold steel does not drip into the ladle, it is necessary to perform a process of breaking the RH, i.e., restoring to atmospheric pressure, while rotating the ladle or rotating the RH furnace to ensure that subsequent molten cold steel drips into a dedicated cold steel collection device.
Aiming at the condition that when the RH furnace breaks the air to the atmospheric pressure, the temperature of the RH furnace meets the requirements of not less than (T0+30) DEG C, T0 is the liquidus temperature of the corresponding molten steel, and the measuring point is the temperature of the inner wall of the RH lower port refractory.
And after RH is broken, cooling steel is performed, and the higher the temperature of the cooling steel is, the more favorable for rapid melting and dripping during cooling steel. Since the temperature measurement of cold steel is very difficult, the temperature of the RH furnace is used to characterize the temperature of the cold steel in the furnace, and if the RH temperature is higher, the temperature of the cold steel in the furnace can be characterized as higher. On the other hand, the higher the self temperature of the RH furnace is, the more favorable is for cold steel to smoothly enter the cold steel collecting tank in the process of dripping along the furnace wall, and the secondary condensation of the cold steel on the inner wall of the RH furnace caused by the excessively low furnace temperature in the process of dripping is avoided, so that the removal of the cold steel is not influenced. Production practice proves that the removal of the molten cold steel can be ensured when the temperature of the RH furnace is more than or equal to (T0+30) DEG C.
Aiming at the requirement that oxygen lance is utilized to rapidly purge and melt cold steel, the oxygen blowing time is less than or equal to 60s, and the cold steel is melted and dripped into a cold steel collecting tank.
Because the RH breaks the sky and then the cold steel will lose the heat source, the cold steel will begin to condense at this moment, so need to blow oxygen fast under the cold steel condition that has begun to melt and continue to melt the cold steel in order to promote its drip, the shorter the time of blowing oxygen and melting the cold steel, the more can guarantee its temperature, just can guarantee the quick removal of cold steel yet. Production practice proves that the oxygen blowing time is less than or equal to 60 seconds, and the rapid melting and dripping of the molten cold steel can be ensured.
Aiming at the time required for breaking the air and re-pumping to the preset vacuum after the cold steel is blown and dripped, namely the removal time of the cold steel is less than or equal to 120s.
The reason is that the RH process is in the middle process of linking the LF and the CCM, the time of the whole cold steel melting process needs to be ensured to be as short as possible so as not to influence the temperature or the subsequent CCM process, and on the other hand, the RH treatment process bears the tasks of removing inclusions and reducing the O content, and the time of the cold steel melting process needs to be ensured to be very short so as to meet the normal RH treatment time, thereby ensuring that the O content of molten steel meets the requirement.
The method for controlling the cleanliness of the RH residual cold steel to stabilize the molten steel can replace the traditional method for melting the cold steel after RH is off-line or adding expensive RH equipment, so that the RH cold steel can be easily removed, and meanwhile, stable high-cleanliness steel types can be obtained. Through production practice test, the method can ensure that the O content of molten steel is stably controlled to an ideal level after RH treatment.
The invention has the following advantages:
judging whether cold steel participates in molten steel circulation or not according to a trend result of CO flue gas analysis of the RH furnace, namely judging whether the problem that the O content of the molten steel is influenced by the cold steel or not; if the influence is judged to occur, when the CO concentration change signal is obtained, RH is restored to the atmospheric pressure, the cold steel at the moment is premelted under the heat effect brought by RH molten steel circulation, the premelted cold steel is continuously melted through oxygen blowing operation to drop the premelted cold steel into a cold steel collecting tank, then the normal RH processing pressure requirement is quickly restored, and RH processing is continuously executed. The continuous and monitorable rapid cooling steel process of the conventional RH furnace is realized, and the O content of the RH ending molten steel is stably controlled to an ideal level.
Description of the drawings:
FIG. 1 is a graph showing the CO concentration change in the RH furnace of example 1; FIG. 2 is a graph showing the change in O content of molten steel in example 1;
FIG. 3 is a graph showing the CO concentration change in the RH furnace of example 2; FIG. 4 is a graph showing the change in O content of molten steel in example 2;
FIG. 5 is a graph showing the CO concentration change in the RH furnace of comparative example 1; FIG. 6 is a graph showing the change in O content of molten steel in comparative example 1;
FIG. 7 is a graph showing the CO concentration change in the comparative example 2RH furnace; FIG. 8 is a graph showing the change in O content of molten steel in comparative example 2;
FIG. 9 is a graph showing the CO concentration change in the RH furnace of comparative example 3; FIG. 10 is a graph showing the change in O content of molten steel in comparative example 3;
FIG. 11 is a graph showing the CO concentration change in the RH furnace of comparative example 4; FIG. 12 is a graph showing the change in O content of molten steel in comparative example 4;
FIG. 13 is a graph showing the CO concentration change in the comparative example 5RH furnace; FIG. 14 is a graph showing the change in O content of molten steel in comparative example 5;
FIG. 15 is a graph showing the CO concentration change in the RH furnace of comparative example 6; FIG. 16 is a graph showing the change in O content of molten steel in comparative example 6.
Detailed Description
The steel smelting adopts the production process of BOF/EAF- & gt LF- & gt RH- & gt CCM, and adopts a 120-ton top-bottom combined blown converter- & gt 120-ton LF refining furnace- & gt 120-ton RH refining furnace- & gt 300 x 325 section continuous casting machine to produce the bearing steel.
Wherein, the BOF/EAF technology uses a 120 ton top-bottom combined blown converter and adopts a conventional converting method. The end point temperature of the converter is controlled to be about 1625 ℃, the end point C is controlled to be about 0.15%, 200kg of aluminum cake, 280kg of low-aluminum low-titanium ferrosilicon, 300kg of high-carbon ferromanganese, 2200kg of low-titanium high-carbon ferrochrome and 900kg of carburant are firstly added during tapping of the converter, and then 400kg of lime and 1000kg of slag are added during refining of the converter.
The LF technology uses a 120 ton LF refining furnace, molten steel is sampled after the temperature is raised to 1550 ℃, the sampled components are fed back to a main control room, then 140kg of silicon carbide is added for slag surface deoxidation, and low-titanium high-carbon ferrochrome, high-carbon ferromanganese, low-aluminum low-titanium ferrosilicon, low-nitrogen carburant and the like are added for component adjustment.
Wherein, the RH process uses a 120 ton RH refining furnace, the vacuum treatment is carried out for 35min, and the soft blowing is carried out for 20min after the RH is finished.
The CCM process uses a 300 x 325 section continuous casting machine, and adopts whole-process protection casting to produce bearing steel.
Example 1: (RH furnace is a pure new furnace body)
The RH furnace is a pure new furnace body, the vacuum pumping operation is carried out after the RH enters the station, the vacuum pressure target value is less than or equal to 67Pa, the CO concentration change of the flue gas is tracked, and the RH total treatment time is 34min as shown in figure 1. Samples were taken at 2 minute intervals from the start of RH start-up to examine the trend of the molten steel O content, and the results are shown in FIG. 2. Because the pure new RH furnace is adopted for smelting, the problem of residual cold steel of the RH furnace does not exist, and the O content of the molten steel after RH treatment can be stably controlled to be less than or equal to 4.5ppm.
Example 2: (implemented according to the scheme of this patent)
The RH furnace is a non-pure new furnace body, the vacuum pumping operation is performed after the RH enters the station, the vacuum pressure target value is less than or equal to 67Pa, the CO concentration change of the flue gas is tracked, and the operation of breaking the air to the atmospheric pressure is performed immediately when the CO concentration starts to rise secondarily as shown in the figure 3. Moving the ladle car to lead the RH furnace to be aligned with the cold steel collecting tank, and measuring the temperature of the inner wall of the RH dip pipe to be 1518 ℃ (the temperature of the bearing molten steel phase line to be 1453 ℃ and the temperature of the molten steel to be 1542 ℃ when the ladle car breaks the air). The oxygen lance is utilized to quickly cool the steel, so that the steel is cooledDripping into a cold steel collecting tank, and blowing oxygen for 52s at 1800Nm 3 And (h) after the blowing and dripping are finished, rotating or moving the ladle to enable the cold steel collecting tank to be positioned at the lower part of the dipping pipe, starting breaking the air until the re-vacuumizing is less than or equal to 67Pa, and taking 110 seconds and 35 minutes of RH total treatment time. Samples were taken at 2 minute intervals from the start of RH start-up to examine the trend of the molten steel O content, and the results are shown in FIG. 4. According to the scheme, the O content of the molten steel after RH treatment can be stably controlled to be less than or equal to 4.5ppm.
Comparative example 1: (RH-not performed Cold Steel)
The RH furnace is a non-pure new furnace body, the vacuum pumping operation is performed after the RH enters the station, the vacuum pressure target value is less than or equal to 67Pa, the CO concentration change of the flue gas is tracked, and as shown in figure 5, the operation from the air break to the atmospheric pressure is not performed when the CO concentration starts to rise for the second time, and the RH conventional treatment is continued. RH total treatment time was 35min. Samples were taken at 2 minute intervals from the start of RH start-up to examine the trend of the molten steel O content, and the results are shown in FIG. 6. As the RH cold steel completely enters the molten steel, the oxygen content is higher, and the O content of the molten steel after RH treatment is 6.7ppm finally.
Comparative example 2: (quenching of Cold Steel before the second increase in CO concentration)
The RH furnace is a non-pure new furnace body, the vacuum pumping operation is carried out after the RH enters a station, the vacuum pressure target value is less than or equal to 67Pa, the CO concentration change of the flue gas is tracked, as shown in figure 7, the operation of breaking the air to the atmospheric pressure is carried out when the CO concentration reaches the highest point for the first time, the ladle car is moved to enable the RH furnace to be aligned to a cold steel collecting tank, and the temperature of the inner wall of the RH dip pipe is measured to 1523 ℃ (the temperature of the bearing molten steel phase line 1453 ℃), and the molten steel temperature during breaking the air is measured to 1548 ℃). The oxygen lance is utilized to quickly cool the steel, so that the cold steel is dripped into the cold steel collecting tank, the total oxygen blowing time is 60 seconds, and the oxygen blowing flow is 1800Nm 3 And (3) after the blowing and dripping are completed, rotating or moving the ladle to enable the cold steel collecting tank to be positioned at the lower part of the dipping pipe, starting breaking the air until the re-vacuumizing is less than or equal to 67Pa, and taking 120 seconds and 36 minutes of RH total treatment time. Samples were taken at 2 minute intervals from the start of RH start-up to examine the trend of the molten steel O content, and the results are shown in FIG. 8. As the concentration of CO is not increased secondarily, the cold steel in the RH furnace is not melted, the temperature of the cold steel is low, and the effect of using an oxygen lance to perform cold steel melting is poor, so that the molten steel O after RH treatment containsThe amount was 6.8ppm.
Comparative example 3: (delay of cold steel after the second increase in CO concentration)
The RH furnace is a non-pure new furnace body, the vacuum pumping operation is carried out after the RH enters a station, the vacuum pressure target value is less than or equal to 67Pa, the CO concentration change of the flue gas is tracked, as shown in figure 9, the operation of breaking the air to the atmospheric pressure is carried out after the CO concentration reaches the highest point for the second time, the ladle car is moved to enable the RH furnace to be aligned with a cold steel collecting tank, and the temperature 1510 ℃ of the inner wall of an RH dip pipe (the temperature of a bearing molten steel phase line is 1453 ℃) and the temperature of molten steel in breaking the air is 1521 ℃) are measured. The oxygen lance is utilized to quickly cool the steel, so that the cold steel is dripped into the cold steel collecting tank, the total oxygen blowing time is 29s, and the oxygen blowing flow is 1800Nm 3 And (h) after the blowing and dripping are completed, rotating or moving the ladle to enable the cold steel collecting tank to be positioned at the lower part of the dipping pipe, starting breaking the air until the re-vacuumizing is less than or equal to 67Pa, and taking 88 seconds for 34 minutes for RH total treatment time. Sampling is carried out at intervals of 2 minutes at the beginning of RH start-up to detect the trend of the O content of molten steel, and the result is shown in FIG. 10. The cold steel treatment is carried out after the concentration of CO is secondarily increased, at the moment, the oxide of the cold steel enters the molten steel, the oxygen content of the molten steel is increased, the cold steel treatment effect is poor, and the O content of the molten steel after the RH treatment is 6.7ppm.
Comparative example 4: (reducing the temperature of the furnace body when the RH furnace breaks the air)
The RH furnace is an impure new furnace body, and the molten steel temperature is reduced when RH enters a station to reduce the RH space-time breaking temperature. And after RH enters the station, vacuumizing operation is performed, the vacuum pressure target value is less than or equal to 67Pa, the CO concentration change of the flue gas is tracked, and as shown in FIG. 11, the operation of breaking the air to the atmospheric pressure is immediately performed when the CO concentration starts to rise secondarily. Moving the ladle car to lead the RH furnace to be aligned with the cold steel collecting tank, and measuring the temperature 1471 ℃ of the inner wall of the RH dip pipe (the temperature 1453 ℃ of the phase line of the bearing molten steel and the temperature 1491 ℃ of the molten steel during the breaking of the air). The oxygen lance is utilized to quickly cool the steel, so that the cooled steel is dripped into a cooled steel collecting tank, the total oxygen blowing time is 58 seconds, and the oxygen blowing flow is 1800Nm 3 And (h) rotating or moving the ladle to enable the cold steel collecting tank to be positioned at the lower part of the dipping pipe after the blowing and dripping are finished, wherein the time for starting breaking the air until the re-vacuumizing is less than or equal to 67Pa is 117s, and the RH total treatment time is 35min. Samples were taken at 2 minute intervals from the start of RH start-up to examine the trend of the change in the O content of molten steel, and the results are shown in FIG. 12. Due toThe premelting effect of the cold steel is poor after the temperature of the molten steel is reduced, so that the oxygen lance cold steel melting effect is poor, the temperature of the RH dip pipe is also low, condensation exists in the molten steel along the lower flow of the RH furnace, the cold steel melting effect is poor, and finally the O content of the molten steel after RH treatment is 6.5ppm.
Comparative example 5: (delay of oxygen blowing time)
The RH furnace is a non-pure new furnace body, the vacuum pumping operation is performed after the RH enters the station, the vacuum pressure target value is less than or equal to 67Pa, the CO concentration change of the flue gas is tracked, and the operation of breaking the air to the atmospheric pressure is performed immediately when the CO concentration starts to rise secondarily as shown in fig. 13. Moving the ladle car to lead the RH furnace to be aligned with the cold steel collecting tank, and measuring the temperature of the inner wall of the RH dip pipe to be 1516 ℃ (the temperature of the bearing molten steel phase line to be 1453 ℃ and the temperature of the molten steel to be 1541 ℃ when the ladle car breaks the air). The intermittent cold steel melting operation is carried out by using the oxygen lance to melt cold steel in a mode of firstly suspending for 5 seconds, then blowing oxygen for 10 seconds and suspending for 5 seconds so as to delay the oxygen blowing time and ensure that the oxygen blowing flow is 1800Nm 3 And (h) dripping cold steel into a cold steel collecting tank, wherein the total oxygen blowing time is 93s, and after the dripping is completed, rotating or moving the ladle to enable the cold steel collecting tank to be positioned at the lower part of the dipping pipe, starting to break the air until the re-vacuumizing is less than or equal to 67Pa, and taking 152s, wherein the total RH treatment time is 36min. Samples were taken at 2 minute intervals from the start of RH start-up to examine the trend of the change in the O content of molten steel, and the results are shown in FIG. 14. Because the rhythm of the oxygen blowing and oxidizing cold steel is slowed down, the temperature drop of the cold steel and the refractory material is possible, the effect of the cold steel is poor, and the O content of the molten steel after the RH treatment is 6.2ppm.
Comparative example 6: (delay of re-evacuation time)
The RH furnace is a non-pure new furnace body, the vacuum pumping operation is performed after the RH enters the station, the vacuum pressure target value is less than or equal to 67Pa, the CO concentration change of the flue gas is tracked, and the operation of breaking the air to the atmospheric pressure is performed immediately when the CO concentration starts to rise secondarily as shown in fig. 15. Moving the ladle car to lead the RH furnace to be aligned with the cold steel collecting tank, and measuring the temperature of the inner wall of the RH dip pipe to be 1517 ℃ (the temperature of the bearing molten steel phase line to be 1453 ℃ and the temperature of the molten steel to be 1543 ℃ in the process of breaking the air). The oxygen lance is utilized to quickly cool the steel, so that the cooled steel is dripped into a cooled steel collecting tank, the total oxygen blowing time is 51s, and the oxygen blowing flow is 1800Nm 3 And (h) after the blowing and dripping are completed, rotating or moving the ladle to enable the cold steel collecting tank to be positioned at the lower part of the dipping pipe, and re-pumpingAnd when the vacuum is less than or equal to 67Pa, reducing the number of the vacuumizing pumps, prolonging the re-vacuumizing time, starting breaking the air until the re-vacuumizing time is less than or equal to 67Pa, and taking 336s, wherein the RH total treatment time is 34min. Samples were taken at 2 minute intervals from the start of RH start-up to examine the trend of the change in the O content of molten steel, and the results are shown in FIG. 16. As the RH re-pumping time is prolonged after cooling the steel, the overall RH treatment time is shortened, the overall cleanliness of the molten steel is deteriorated, and the O content of the molten steel after RH treatment is 5.5ppm.
The present invention is not limited to the above-mentioned embodiments, and any person skilled in the art, based on the technical solution of the present invention and the concept thereof, can be replaced or changed equally within the scope of the present invention.
Claims (5)
1. A method for controlling RH residual cold steel to stabilize molten steel cleanliness is characterized by comprising the following steps: the method comprises the following steps:
(1) Judging whether cold steel melting occurs in the RH furnace according to the CO concentration change trend in the flue gas of the RH furnace: if the concentration of CO naturally drops after reaching the peak value, the problem of residual cold steel in the RH furnace is solved, and the conventional RH vacuum treatment is continued; if the CO concentration starts to drop after reaching the peak value, but rises again, the moment of starting to rise again indicates that the residual cold steel in the RH furnace starts to melt under the action of heat brought by the circulation of RH molten steel in the RH treatment process;
(2) Breaking the RH furnace to restore to the atmospheric pressure at the moment when the cold steel begins to melt, and rotating or moving the ladle to enable the cold steel collecting tank to be positioned right below the RH furnace so as to facilitate cold steel collection;
(3) Utilizing an oxygen lance to quickly purge and melt cold steel, and dripping the cold steel melt into a cold steel collecting tank;
(4) And after the cold steel blowing and dripping is finished, rotating or moving the ladle to enable the cold steel collecting tank to be positioned at the lower part of the dipping pipe, rapidly vacuumizing to a preset vacuum degree, and continuing RH vacuum treatment.
2. The method for controlling the cleanliness of stable molten steel of RH residual cold steel according to claim 1, wherein: when the RH furnace is broken and the atmospheric pressure is recovered in the step (2), the temperature of the RH furnace is more than or equal to (T0+30), T0 is the liquidus temperature of the corresponding molten steel, and the measuring point is the temperature of the inner wall of the refractory at the lower opening of the RH furnace.
3. The method for controlling the cleanliness of stable molten steel of RH residual cold steel according to claim 1, wherein: the purging time in the step (3) is less than or equal to 60s, and the oxygen flow of the oxygen lance is 1600-2000 Nm 3 /h。
4. The method for controlling the cleanliness of stable molten steel of RH residual cold steel according to claim 1, wherein: the predetermined vacuum degree in the step (4) is 67Pa or less.
5. The method for controlling the cleanliness of stable molten steel of RH residual cold steel according to claim 1, wherein: the time taken for breaking the air and re-vacuumizing to the preset vacuum degree is less than or equal to 120s.
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