CN117025892A - Production method of ultralow-nitrogen steel - Google Patents
Production method of ultralow-nitrogen steel Download PDFInfo
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- CN117025892A CN117025892A CN202311232056.5A CN202311232056A CN117025892A CN 117025892 A CN117025892 A CN 117025892A CN 202311232056 A CN202311232056 A CN 202311232056A CN 117025892 A CN117025892 A CN 117025892A
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 80
- 239000010959 steel Substances 0.000 title claims abstract description 80
- IJGRMHOSHXDMSA-UHFFFAOYSA-N nitrogen Substances N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 title claims abstract description 60
- 229910052757 nitrogen Inorganic materials 0.000 title claims abstract description 35
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 18
- 238000000034 method Methods 0.000 claims abstract description 47
- 238000009749 continuous casting Methods 0.000 claims abstract description 18
- 238000003723 Smelting Methods 0.000 claims abstract description 16
- 238000006477 desulfuration reaction Methods 0.000 claims abstract description 5
- 230000023556 desulfurization Effects 0.000 claims abstract description 5
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 38
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 38
- 239000002893 slag Substances 0.000 claims description 21
- 238000007664 blowing Methods 0.000 claims description 20
- 235000008733 Citrus aurantifolia Nutrition 0.000 claims description 19
- 235000011941 Tilia x europaea Nutrition 0.000 claims description 19
- 229910052786 argon Inorganic materials 0.000 claims description 19
- 239000004571 lime Substances 0.000 claims description 19
- 229910052742 iron Inorganic materials 0.000 claims description 17
- 238000005266 casting Methods 0.000 claims description 8
- 239000007789 gas Substances 0.000 claims description 8
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 claims description 7
- 229910045601 alloy Inorganic materials 0.000 claims description 7
- 239000000956 alloy Substances 0.000 claims description 7
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 7
- 229910052749 magnesium Inorganic materials 0.000 claims description 7
- 239000011777 magnesium Substances 0.000 claims description 7
- 239000000463 material Substances 0.000 claims description 7
- 239000001301 oxygen Substances 0.000 claims description 7
- 229910052760 oxygen Inorganic materials 0.000 claims description 7
- 238000010079 rubber tapping Methods 0.000 claims description 7
- 229910052782 aluminium Inorganic materials 0.000 claims description 5
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 5
- 239000007788 liquid Substances 0.000 claims description 5
- 238000007670 refining Methods 0.000 claims description 5
- 230000001276 controlling effect Effects 0.000 claims description 4
- 230000001681 protective effect Effects 0.000 claims description 4
- 239000003795 chemical substances by application Substances 0.000 claims description 3
- 238000001816 cooling Methods 0.000 claims description 3
- 125000004122 cyclic group Chemical group 0.000 claims description 3
- 230000001105 regulatory effect Effects 0.000 claims description 3
- 238000007789 sealing Methods 0.000 claims description 3
- 238000009489 vacuum treatment Methods 0.000 claims description 3
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 claims description 2
- 238000005262 decarbonization Methods 0.000 claims description 2
- 238000000465 moulding Methods 0.000 claims description 2
- 238000002161 passivation Methods 0.000 claims description 2
- 229910052717 sulfur Inorganic materials 0.000 claims description 2
- 239000011593 sulfur Substances 0.000 claims description 2
- 238000002347 injection Methods 0.000 claims 2
- 239000007924 injection Substances 0.000 claims 2
- 238000005457 optimization Methods 0.000 abstract description 3
- 238000005272 metallurgy Methods 0.000 abstract description 2
- 238000002360 preparation method Methods 0.000 abstract description 2
- 230000000052 comparative effect Effects 0.000 description 8
- 229910052799 carbon Inorganic materials 0.000 description 7
- 239000010459 dolomite Substances 0.000 description 7
- 229910000514 dolomite Inorganic materials 0.000 description 7
- 239000002994 raw material Substances 0.000 description 5
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 4
- 229910000519 Ferrosilicon Inorganic materials 0.000 description 4
- 239000011572 manganese Substances 0.000 description 4
- 235000019738 Limestone Nutrition 0.000 description 3
- 229910052581 Si3N4 Inorganic materials 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 239000006028 limestone Substances 0.000 description 3
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 description 3
- 229910001200 Ferrotitanium Inorganic materials 0.000 description 2
- 229910001209 Low-carbon steel Inorganic materials 0.000 description 2
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 2
- 238000005260 corrosion Methods 0.000 description 2
- 230000007797 corrosion Effects 0.000 description 2
- 239000012535 impurity Substances 0.000 description 2
- 229910052748 manganese Inorganic materials 0.000 description 2
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 1
- 229910000851 Alloy steel Inorganic materials 0.000 description 1
- 229910000616 Ferromanganese Inorganic materials 0.000 description 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- 229910000914 Mn alloy Inorganic materials 0.000 description 1
- 229910000746 Structural steel Inorganic materials 0.000 description 1
- OLBVUFHMDRJKTK-UHFFFAOYSA-N [N].[O] Chemical compound [N].[O] OLBVUFHMDRJKTK-UHFFFAOYSA-N 0.000 description 1
- 238000005275 alloying Methods 0.000 description 1
- 238000005452 bending Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 238000007872 degassing Methods 0.000 description 1
- 230000001627 detrimental effect Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000004868 gas analysis Methods 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- DALUDRGQOYMVLD-UHFFFAOYSA-N iron manganese Chemical compound [Mn].[Fe] DALUDRGQOYMVLD-UHFFFAOYSA-N 0.000 description 1
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 1
- WPBNNNQJVZRUHP-UHFFFAOYSA-L manganese(2+);methyl n-[[2-(methoxycarbonylcarbamothioylamino)phenyl]carbamothioyl]carbamate;n-[2-(sulfidocarbothioylamino)ethyl]carbamodithioate Chemical compound [Mn+2].[S-]C(=S)NCCNC([S-])=S.COC(=O)NC(=S)NC1=CC=CC=C1NC(=S)NC(=O)OC WPBNNNQJVZRUHP-UHFFFAOYSA-L 0.000 description 1
- 229910000734 martensite Inorganic materials 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 150000004767 nitrides Chemical class 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
- 238000005070 sampling Methods 0.000 description 1
- 238000005507 spraying Methods 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 229910000859 α-Fe Inorganic materials 0.000 description 1
Classifications
-
- 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
- C21C7/064—Dephosphorising; Desulfurising
-
- 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
- B22D11/10—Supplying or treating molten metal
- B22D11/11—Treating the molten metal
- B22D11/111—Treating the molten metal by using protecting powders
-
- 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
- B22D11/182—Controlling or regulating processes or operations for pouring responsive to molten metal level or slag level by measuring temperature
-
- 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
- B22D11/20—Controlling or regulating processes or operations for removing cast stock
-
- 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
- C21C5/30—Regulating or controlling the blowing
- C21C5/35—Blowing from above and through the bath
-
- 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
- C21C7/0006—Adding metallic additives
-
- 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
-
- 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
-
- 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
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Mechanical Engineering (AREA)
- Manufacturing & Machinery (AREA)
- Treatment Of Steel In Its Molten State (AREA)
Abstract
The invention provides a production method of ultralow-nitrogen steel, and relates to the technical field of metallurgy. The production method provided by the invention comprises the processes of pretreatment desulfurization, converter smelting, RH treatment, continuous casting and forming and the like, and the preparation of high-quality ultralow-nitrogen (less than 10 ppm) steel is realized through the improvement and optimization of the process.
Description
Technical Field
The invention relates to the technical field of metallurgy, in particular to a production method of ultralow-nitrogen steel.
Background
The nitrogen content in the steel can affect the structure, performance and corrosion resistance of the steel. In general, as the nitrogen content increases, the plasticity and toughness of the steel are significantly reduced, weldability and cold-bending properties are also deteriorated, and cold-shortness and hot-shortness are also exacerbated. Too high a nitrogen content can also lead to detrimental intermetallic phases in the steel, such as martensite, ferrite, nitrides, etc., which reduce the corrosion resistance and stability of the steel.
Generally, the nitrogen content of common steel grades such as low carbon steel, low alloy steel, carbon structural steel and the like needs to be reduced so as to ensure the plasticity, toughness and weldability of the steel. Therefore, reducing the nitrogen content in steel is one of the important ways to improve the quality of steel. For example: the patent with the application number of CN103667581B provides a smelting method of low-nitrogen SWRH82B steel, which can reduce the nitrogen content in SWRH82B coil steel to below 40 ppm. Patent application number CN202110373701.X provides a smelting method of low nitrogen steel, and the nitrogen content of the low nitrogen steel obtained by the method is 20-60ppm. The patent with application number of CN201210164848.9 provides a method for controlling the nitrogen content of ultra-low carbon steel, and finally, the steel billet with the nitrogen content not higher than 35ppm is obtained.
As can be seen, most of the current processes can control the nitrogen content in steel at a lower level, but generally only reach the level of about 20-60ppm, and the control of steel with lower nitrogen content is difficult to realize. However, the nitrogen content of about 20-60ppm cannot meet the control requirement of certain special fields on the nitrogen content in the steel. Therefore, how to further reduce the nitrogen content in the steel is one of the technical problems that needs to be overcome at present.
Disclosure of Invention
In order to solve the problems, the invention provides a production method of ultralow nitrogen steel, and the nitrogen content in the steel is successfully controlled within 10ppm through adjustment and optimization of the process.
The production method of the ultra-low nitrogen steel comprises the following steps:
s1, pretreatment desulfurization: blowing passivation magnesium and lime to desulphurize by taking compressed air as a carrier until the sulfur content is less than 0.001%, wherein the bright surface of the molten iron is more than 95%;
s2, converter smelting: transferring to a combined blown converter, adding clean scrap steel at the same time, performing oxygen supply operation, adding slag forming materials into the converter, adopting a combined blown process in the smelting process of the converter, and tapping after smelting is completed;
s3, RH treatment: adding extra lime to cover the liquid level of molten steel in the ladle, directly conveying the ladle to an RH furnace without deoxidizing the molten steel, and circularly refining;
s4, continuous casting molding: adding aluminum into the molten steel after cyclic refining for deoxidization, adding alloy elements, finally adding a ladle covering agent, hanging the ladle onto a continuous casting ladle frame, adding covering slag into the tundish, protecting and casting in the whole process, casting a steel billet continuously, controlling the temperature of the tundish and the pulling speed of the steel slab, and cooling to obtain the steel ladle.
Further, the blowing amount of the passivated magnesium is 1.2-2.5 kg/ton iron, the blowing amount of the lime is 1.5-3.5 kg/ton iron, the pressure of the compressed air is 0.3-0.65 MPa, and the instantaneous flow rate is 2350Nm 3 And/h, intermittently jetting for three times, wherein each time is 5-7 min, and slag skimming is performed at intervals for three times.
Furthermore, the clean scrap steel adopts a low-carbon cold-rolled intermediate billet flying shear head, so that the clean scrap steel is ensured to be clean and free of impurity pollution, and the addition amount of the clean scrap steel is less than or equal to 15 t/furnace.
Further, the slag forming material is one or more of lime, dolomite, limestone and sinter.
Further, the lime is superfine lime, the activity degree is more than 320ml, the effective CaO content is more than 90%, the S content is less than 0.020%, and the addition amount is 35-45 kg/ton steel; the dolomite is light burned dolomite, the S content is less than 0.020%, and the addition amount is 25-35 kg/ton steel; the addition amount of the limestone is 0-15 kg/ton of steel; the addition amount of the sinter is 0-25 kg/ton steel.
Further, the converter smelting further comprises a slag adjusting step, specifically slag adjustment is carried out by adopting iron scales, and the addition amount of the iron scales is less than or equal to 25 kg/ton of steel.
Further, the oxygen supply intensity of the top lance in the combined blowing process is 2.8-4.5 Nm 3 The gun position control adopts a high-low-high-low four-stage method per ton steel.min,argon is blown in the whole smelting process, and the intensity of the corresponding bottom blowing argon is 0.5-1.50 Nm 3 And the bottom blowing mode is a high-low-high-strong four-stage method per ton of steel.min.
Further, in the four-stage method, the top-blowing instantaneous flow rate is high (28000-34000 Nm 3 /h and not 28000Nm 3 /h) -low (instantaneous flow 25000-28000 Nm 3 High (instantaneous flow 32000-36000 Nm) 3 /h and not 32000Nm 3 /h) -low (instantaneous flow 30000-32000 Nm 3 /h)。
Further, in the four-stage method, the bottom blowing instantaneous flow rate is high (800 to 900 Nm) 3 /h) -low (550-650 Nm) 3 High (900-1000 Nm) 3 High (1200-1500 Nm) 3 /h)。
Further, the carbon content in the molten iron at the smelting end point is 0.035-0.12 wt% and the oxygen content is 400-850 ppm.
Further, the tapping temperature is 1620-1680 ℃.
Further, the addition amount of the extra lime in the ladle is 1.35-3.5 kg/t steel.
Further, the RH treatment adopts a new vacuum tank with the tank age less than 55 furnaces, and before the vacuum treatment, all nitrogen pipelines are confirmed to be thoroughly cut off.
Further, the RH treatment vacuum degree is 67-100 Pa, and the riser argon instantaneous flow is 550-1200 Nm 3 Vacuum decarbonization time is 6-15 min, the circulation gas flow is regulated to 40m in the stage of pre-vacuumizing 3 /h。
Preferably, the argon instantaneous flow of the riser is 650-1100 Nm 3 /h
Further, the alloy element is one or more of ferrosilicon, electrolytic manganese, ferrotitanium and silicon nitride.
Further, the addition amount of ferrosilicon is 0-35 kg/ton steel, the addition amount of electrolytic manganese is 0-4.5 kg/ton steel, the addition amount of ferrotitanium is 0-15 kg/ton steel, and the addition amount of silicon nitride is 0-1.5 kg/ton steel.
Further, the addition amount of aluminum in the aluminum-added deoxidization is 2.5-4.5 kg/ton steel.
Further, the covering slag is ultralow-carbon and low-nitrogen covering slag, and the addition amount is 0.35-0.5 kg/ton of steel.
Further, the covering slag is composed of the following raw materials in percentage by weight: siO (SiO) 2 36.85wt％、CaO 2 9.93wt％、MgO 2.41wt％、Fe 2 O 3 0.72wt％、Al 2 O 3 2.13wt％、N＜80PPm、C＜2.0wt％、H 2 O is less than 0.35wt percent, and the balance is ash.
Furthermore, in the continuous casting process, a new ladle is used for casting a protection sleeve for each furnace, and the protection sleeve adopts a double-ring sealing seam.
Further, the argon pressure in the continuous casting process is 0.15MPa, and the flow is 0.4Nm 3 /h; the tundish is fully sealed, and the flow is 0.2Nm 3 /h; argon protection is carried out on the stopper rod, the argon pressure is 0.15MPa, and the flow is 0.2Nm 3 /h; the argon seal of the slide plate surface has the pressure of 0.15MPa and the flow of 0.4Nm 3 And/h, the fluctuation of the liquid level of the crystallizer is < + -3 mm.
Further, the temperature of the tundish is 1525-1555 ℃, and the pulling speed of the slab is 0.95-1.35 m/min.
The invention adopts a gas sampler for sampling in each working procedure (link), processes the gas into a gas analysis standard shape, adopts a American leco oxygen nitrogen hydrogen gas analyzer for analyzing the gas content in each link, and finally the nitrogen content in the finished steel product is less than or equal to 10ppm.
The invention puts the pretreated molten iron into the top-bottom combined blown converter, and simultaneously adds clean scrap steel with proper proportion to carry out oxygen supply operation, and adds proper amount of slag forming materials in the blowing process to ensure stable reaction and good slag formation in the converter. Meanwhile, the top-bottom combined blowing strength is enhanced, and good degassing in the converter is ensured. And the carbon and steel are pulled once at the end point of the converter, so that the supplementary blowing is stopped. Molten steel with qualified blowing temperature and components is tapped from the converter into a ladle, and deoxidation and alloying operations are not performed in the tapping process. And adding a proper amount of lime in the tapping process, covering the molten steel surface, isolating air and preventing the molten steel from increasing N. In the RH processing link, a new vacuum tank is adopted to prevent air leakage and increase N. And all nitrogen valves are thoroughly closed, so that the possibility of nitrogen permeation is avoided. In the pre-vacuumizing stage, the circulation gas flow is regulated to be small, and in the vacuum stage, the circulation flow control is enhanced so as to limit the possibility of increasing N of the molten steel rising and exposing contact air. In the continuous casting production process, the whole protection casting is enhanced. And (3) carrying out system optimization on the large ladle sleeve, the argon seal, the tundish seal and the slide plate surface seal, so that the continuous casting N increase is controlled within 0-2 ppm.
Compared with the prior art, the invention has the beneficial technical effects that:
the invention realizes the preparation of high-quality ultra-low nitrogen (< 10 ppm) top-quality steel by improving and optimizing the converter raw and auxiliary materials adding process, converter bottom blowing process, process in tapping and argon station treatment process, RH treatment process and continuous casting production process.
Detailed Description
The technical scheme provided by the invention is further described below by combining with the embodiment.
The production method of the ultra-low nitrogen steel comprises the following steps:
adding passivated magnesium and lime into a desulfurization station of the blast furnace, taking compressed air as a carrier, adding the passivated magnesium and the lime, taking the compressed air as the carrier, intermittently spraying and blowing for three times, 5min each time, and carrying out slag skimming for three times at intervals, wherein the desulfurization is carried out until the content of the passivated magnesium and the lime is less than 0.001%, and the bright surface of the molten iron is more than 95%. Transferring to a combined blown converter, wherein all the scrap steel adopts low-carbon cold-rolled intermediate billet flying shears, and is clean and free from impurity pollution. Adding slag materials of lime, dolomite, limestone and sinter into a converter, wherein the slag materials of the lime, the dolomite and the sinter adopt superfine lime, the activity is more than 320mL, the effective CaO content is more than 90 percent, and the S content is less than 0.020 percent; the S content of the light burned dolomite is less than 0.020%, and iron scale is adopted for slag adjustment in the production process of some products. The converter smelting process adopts a combined blowing process. Argon is blown in the whole smelting process, and the bottom blowing mode is high (the instantaneous flow rate is 650 Nm) 3 /h) -low (instantaneous flow 550 Nm) 3 High (instantaneous flow 850 Nm) 3 High (instantaneous flow 1000 Nm) 3 High (post-stirring instantaneous flow 1500 Nm) 3 /h). And (3) carrying out primary carbon pulling at the end point of the converter, wherein tapping is not deoxidized or alloyed, and adding extra lime to cover the liquid level of molten steel in the ladle. The ladle is directly sent to an RH furnace without deoxidization of molten steel, and cyclic refining is carried out. Subsequent implementationThe original technology comprises the following steps: RH vacuum treatment, aluminum deoxidation, subsequent ferrosilicon, manganese and other alloy adding, and final ladle covering agent adding. And (3) hanging the steel ladle on a continuous casting steel ladle frame, adding covering slag into the middle ladle, protecting and casting in the whole process, controlling the temperature of the middle ladle and the pulling speed of a plate blank, and cooling to obtain the steel ladle. In the continuous casting production process, a new ladle is used for each furnace to cast a protective sleeve, and the protective sleeve must adopt a double-ring sealing seam.
Thus, the whole process is strictly controlled, and the N content in the steel is ensured to be controlled within 10ppm.
TABLE 1
The N content (ppm) of each stage of the products of examples 1-5 was measured and the results are shown in Table 2:
TABLE 2
| Sequence number | Furnace number | Steel grade | Converter endpoint | RH inbound station | RH outbound | Continuous casting tundish | Continuous casting crystallizer | Finished product |
| Example 1 | 2310204683 | PYDC04 | 6 | 6 | 6 | 7 | 8 | 8 |
| Example 2 | 2310204684 | PYDC04 | 7 | 7 | 7 | 8 | 9 | 9 |
| Example 3 | 2312204792 | PYCGO01 | 5 | 6 | 6 | 6 | 8 | 8 |
| Example 4 | 2312206603 | PYW270 | 6 | 7 | 7 | 8 | 9 | 8 |
| Example 5 | 2312206604 | PYW270 | 8 | 8 | 8 | 9 | 9 | 10 |
Comparative example
The molten iron adopted in the comparative example and the embodiment of the invention comprises less than or equal to 0.12wt% of P, less than or equal to 0.001wt% of S, less than or equal to 0.45wt% of Si, less than or equal to 0.020wt% of S in scrap steel, more than or equal to 99.5wt% of O2 and less than or equal to 0.001wt% of N2 in oxygen, more than or equal to 53wt% of Fe in sinter, more than or equal to 92wt% of CaO in lime, more than or equal to 35wt% of CaO in light burned dolomite, more than or equal to 28wt% of MgO, more than or equal to 65% of Fe2O3 in iron scale, more than or equal to 99.9% of Ar in argon, the balance trace amount, more than or equal to 99.5wt% of Al in aluminum particles, and ferromanganese alloy is composed of the following raw materials: 65wt% of Mn, less than or equal to 6.5wt% of C, less than or equal to 0.30wt% of S, less than or equal to 0.15wt% of P, less than or equal to 0.15wt% of Al, and the balance of Fe; the metal manganese alloy is composed of the following raw materials: 99.5wt% of Mn, less than or equal to 0.02wt% of C, less than or equal to 0.020wt% of S, less than or equal to 0.010wt% of P, less than or equal to 0.02wt% of Al, and the balance of Fe; the silicon nitride alloy consists of the following raw materials: 25wt% of Si, less than or equal to 28wt% of N, less than or equal to 0.05wt% of C, less than or equal to 0.020wt% of S, less than or equal to 0.15wt% of P, less than or equal to 0.15wt% of Al, and the balance of Fe; the ferrosilicon alloy is composed of the following raw materials: 72wt% of Si, less than or equal to 0.02wt% of C, less than or equal to 0.020wt% of S, less than or equal to 0.15wt% of P, less than or equal to 0.02wt% of Al, and the balance of Fe.
TABLE 3 Table 3
The N content (ppm) of each stage of the products of comparative examples 1 to 5 was measured, and the results are shown in Table 4:
TABLE 4 Table 4
Comparative example 6
The difference from example 1 is that: the bottom-blowing gas was replaced with Ar.
Comparative example 7
The difference from example 1 is that: the service life of the vacuum tank in production is 85 times.
Comparative example 8
The difference from example 1 is that: in the pre-vacuumizing stage, the circulation gas flow rate is 50m 3 /h。
Comparative example 9
The difference from example 1 is that: the large ladle sleeve is not changed into every two ladle of new sleeve, and every ladle of large ladle drain is changed into every ladle of new process.
Test example 1
The N content (ppm) of each stage of the products of comparative examples 6 to 9 was measured, and the results are shown in Table 5:
TABLE 5
| Sequence number | Furnace number | Steel grade | Converter endpoint | RH inbound station | RH outbound | Continuous casting tundish | Continuous casting crystallizer | Finished product |
| Example 6 | 2310203557 | Q355qD | 25 | 27 | 27 | 30 | 32 | 32 |
| Example 7 | 2312203895 | SPHC | 35 | 35 | 34 | 36 | 37 | 38 |
| Example 8 | 2312205885 | Q195L | 27 | 28 | 27 | 30 | 33 | 35 |
| Example 9 | 2310226321 | Q390qD | 31 | 35 | 33 | 35 | 37 | 36 |
The principles and embodiments of the present invention have been described herein with reference to specific examples, the description of which is intended only to assist in understanding the methods of the present invention and the core ideas thereof; also, it is within the scope of the present invention to be modified by those of ordinary skill in the art in light of the present teachings. In view of the foregoing, this description should not be construed as limiting the invention.
Claims (8)
1. The production method of the ultralow-nitrogen steel is characterized by comprising the following steps of:
s1, pretreatment desulfurization: blowing passivation magnesium and lime to desulphurize by taking compressed air as a carrier until the sulfur content is less than 0.001%, wherein the bright surface of the molten iron is more than 95%;
s2, converter smelting: transferring to a combined blown converter, adding clean scrap steel at the same time, performing oxygen supply operation, adding slag forming materials into the converter, adopting a combined blown process in the smelting process of the converter, and tapping after smelting is completed;
s3, RH treatment: adding extra lime to cover the liquid level of molten steel in the ladle, directly conveying the ladle to an RH furnace without deoxidizing the molten steel, and circularly refining;
s4, continuous casting molding: adding aluminum into the molten steel after cyclic refining for deoxidization, adding alloy elements, finally adding a ladle covering agent, hanging the ladle onto a continuous casting ladle frame, adding covering slag into the tundish, protecting and casting in the whole process, casting a steel billet continuously, controlling the temperature of the tundish and the pulling speed of the steel slab, and cooling to obtain the steel ladle.
2. The production method according to claim 1, wherein the injection amount of the passivated magnesium is 1.2-2.5 kg/ton iron, the injection amount of the lime is 1.5-3.5 kg/ton iron, the compressed air pressure is 0.3-0.65 MPa, and the instantaneous flow rate is 2350Nm 3 And/h, intermittently jetting for three times, wherein each time is 5-7 min, and slag skimming is performed at intervals for three times.
3. The production method according to claim 1, wherein the converter smelting further comprises a slag adjusting step, specifically adopting iron scales for slag adjustment, and the adding amount of the iron scales is 0-25 kg/ton of steel.
4. The production method according to claim 1, wherein the oxygen supply intensity of the top lance in the combined blowing process is 2.8-4.5 Nm 3 The gun position control adopts a high-low-high-low four-stage method per ton of steel.min, argon is blown in the whole smelting process, and the intensity of the corresponding bottom-blown argon is 0.5-1.50 Nm 3 And the bottom blowing mode is a high-low-high-strong four-stage method per ton of steel.min.
5. The method of claim 1, wherein the RH treatment is performed using a new vacuum tank having a tank life of < 55 furnace, and wherein all nitrogen lines are confirmed to be completely shut off before the vacuum treatment.
6. The method according to claim 1The production method is characterized in that the RH treatment vacuum degree is 67-1000 Pa, and the riser argon instantaneous flow is 550-1200 Nm 3 Vacuum decarbonization time is 6-15 min, the circulation gas flow is regulated to 40m in the stage of pre-vacuumizing 3 /h。
7. The method according to claim 1, wherein a new ladle is used for casting a protective sleeve for each furnace during the continuous casting, and the protective sleeve adopts a double-ring sealing seam.
8. The method according to claim 1, wherein the argon pressure during the continuous casting is 0.15MPa and the flow is 0.4Nm 3 /h; the tundish is fully sealed, and the flow is 0.2Nm 3 /h; argon protection is carried out on the stopper rod, the argon pressure is 0.15MPa, and the flow is 0.2Nm 3 /h; the argon seal of the slide plate surface has the pressure of 0.15MPa and the flow of 0.4Nm 3 And/h, the fluctuation of the liquid level of the crystallizer is < + -3 mm.
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