CN109852893B - Low-temperature high-toughness refractory steel and preparation method thereof - Google Patents
Low-temperature high-toughness refractory steel and preparation method thereof Download PDFInfo
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 112
- 239000010959 steel Substances 0.000 title claims abstract description 112
- 238000002360 preparation method Methods 0.000 title claims description 12
- 229910052804 chromium Inorganic materials 0.000 claims abstract description 13
- 229910052782 aluminium Inorganic materials 0.000 claims abstract description 11
- 229910052698 phosphorus Inorganic materials 0.000 claims abstract description 11
- 229910052802 copper Inorganic materials 0.000 claims abstract description 10
- 229910052750 molybdenum Inorganic materials 0.000 claims abstract description 10
- 229910052759 nickel Inorganic materials 0.000 claims abstract description 10
- 229910052758 niobium Inorganic materials 0.000 claims abstract description 9
- 239000012535 impurity Substances 0.000 claims abstract description 8
- 229910052748 manganese Inorganic materials 0.000 claims abstract description 8
- 239000000126 substance Substances 0.000 claims abstract description 8
- 229910052717 sulfur Inorganic materials 0.000 claims abstract description 8
- 239000000203 mixture Substances 0.000 claims abstract description 7
- 238000000034 method Methods 0.000 claims description 28
- 230000008569 process Effects 0.000 claims description 21
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 18
- 238000005266 casting Methods 0.000 claims description 17
- 238000005096 rolling process Methods 0.000 claims description 15
- 238000009628 steelmaking Methods 0.000 claims description 15
- 239000011651 chromium Substances 0.000 claims description 13
- 238000001816 cooling Methods 0.000 claims description 13
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 13
- 239000002893 slag Substances 0.000 claims description 12
- 238000007664 blowing Methods 0.000 claims description 11
- 238000010438 heat treatment Methods 0.000 claims description 11
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 10
- 229910052786 argon Inorganic materials 0.000 claims description 9
- 238000003723 Smelting Methods 0.000 claims description 8
- 229910045601 alloy Inorganic materials 0.000 claims description 8
- 239000000956 alloy Substances 0.000 claims description 8
- 238000005507 spraying Methods 0.000 claims description 8
- 238000009749 continuous casting Methods 0.000 claims description 6
- 239000002994 raw material Substances 0.000 claims description 6
- 229910052799 carbon Inorganic materials 0.000 claims description 5
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 4
- 229910052760 oxygen Inorganic materials 0.000 claims description 4
- 239000001301 oxygen Substances 0.000 claims description 4
- 230000001681 protective effect Effects 0.000 claims description 4
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 claims description 3
- 235000008733 Citrus aurantifolia Nutrition 0.000 claims description 3
- 229910000616 Ferromanganese Inorganic materials 0.000 claims description 3
- 229910001309 Ferromolybdenum Inorganic materials 0.000 claims description 3
- 229910000519 Ferrosilicon Inorganic materials 0.000 claims description 3
- 235000011941 Tilia x europaea Nutrition 0.000 claims description 3
- 238000005275 alloying Methods 0.000 claims description 3
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 3
- 239000011575 calcium Substances 0.000 claims description 3
- 229910052791 calcium Inorganic materials 0.000 claims description 3
- WUKWITHWXAAZEY-UHFFFAOYSA-L calcium difluoride Chemical compound [F-].[F-].[Ca+2] WUKWITHWXAAZEY-UHFFFAOYSA-L 0.000 claims description 3
- 238000005261 decarburization Methods 0.000 claims description 3
- 238000007599 discharging Methods 0.000 claims description 3
- 239000010436 fluorite Substances 0.000 claims description 3
- 229910052742 iron Inorganic materials 0.000 claims description 3
- DALUDRGQOYMVLD-UHFFFAOYSA-N iron manganese Chemical compound [Mn].[Fe] DALUDRGQOYMVLD-UHFFFAOYSA-N 0.000 claims description 3
- 239000004571 lime Substances 0.000 claims description 3
- 239000011574 phosphorus Substances 0.000 claims description 3
- 238000010926 purge Methods 0.000 claims description 3
- 230000009467 reduction Effects 0.000 claims description 3
- 238000007670 refining Methods 0.000 claims description 3
- 238000010079 rubber tapping Methods 0.000 claims description 3
- 238000010583 slow cooling Methods 0.000 claims description 3
- 238000005452 bending Methods 0.000 abstract description 2
- 238000003466 welding Methods 0.000 abstract description 2
- PXHVJJICTQNCMI-UHFFFAOYSA-N nickel Substances [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 10
- 239000010955 niobium Substances 0.000 description 9
- 239000010949 copper Substances 0.000 description 8
- 229910000746 Structural steel Inorganic materials 0.000 description 7
- 230000009970 fire resistant effect Effects 0.000 description 6
- 238000010276 construction Methods 0.000 description 5
- 239000013078 crystal Substances 0.000 description 4
- 239000000463 material Substances 0.000 description 4
- 238000012360 testing method Methods 0.000 description 4
- 238000000576 coating method Methods 0.000 description 3
- 238000005260 corrosion Methods 0.000 description 3
- 230000007797 corrosion Effects 0.000 description 3
- 238000013461 design Methods 0.000 description 3
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 3
- 239000011159 matrix material Substances 0.000 description 3
- 230000009471 action Effects 0.000 description 2
- 229910001563 bainite Inorganic materials 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 239000011248 coating agent Substances 0.000 description 2
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium atom Chemical compound [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 description 2
- 230000007704 transition Effects 0.000 description 2
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 1
- 241001391944 Commicarpus scandens Species 0.000 description 1
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- 229910000599 Cr alloy Inorganic materials 0.000 description 1
- 229910000881 Cu alloy Inorganic materials 0.000 description 1
- 229910001182 Mo alloy Inorganic materials 0.000 description 1
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 description 1
- 229910000990 Ni alloy Inorganic materials 0.000 description 1
- 229910001566 austenite Inorganic materials 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- 239000011449 brick Substances 0.000 description 1
- 229910001567 cementite Inorganic materials 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
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- 239000012467 final product Substances 0.000 description 1
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- 238000009863 impact test Methods 0.000 description 1
- 238000009413 insulation Methods 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 150000001247 metal acetylides Chemical class 0.000 description 1
- 230000005012 migration Effects 0.000 description 1
- 238000013508 migration Methods 0.000 description 1
- 239000011733 molybdenum Substances 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 229910001562 pearlite Inorganic materials 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 230000002035 prolonged effect Effects 0.000 description 1
- 229910052596 spinel Inorganic materials 0.000 description 1
- 239000011029 spinel Substances 0.000 description 1
- 239000011573 trace mineral Substances 0.000 description 1
- 235000013619 trace mineral Nutrition 0.000 description 1
- 230000009466 transformation Effects 0.000 description 1
- 229910000859 α-Fe Inorganic materials 0.000 description 1
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- 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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Abstract
本发明的一种低温高韧性耐火钢，化学组成及其重量百分比为C：0.01～0.12％，Mn：0.30～1.60％，Si：0.10‑0.50％，Al：0.010‑0.050％，Cu：0.02‑0.05％，Cr：0.10‑0.90％，Mo：0.10‑0.80％，Ti：0.005‑0.060％，Nb：0.005‑0.080％，Ni：0.05‑0.30％，B≤0.0040％，P≤0.025％，S≤0.0020％，余量为Fe及不可避免的杂质。本发明通过添加一种或几种微合金元素，在一定的配比下，使其获得良好的耐火性能和低温韧性。钢在600℃时的屈服强度大于其室温标准要求屈服强度的2/3，‑40℃冲击功≥120J，并具有优良的成形性能、冷弯性能、焊接性能等。The low-temperature high-toughness refractory steel of the present invention has chemical composition and weight percentages of C: 0.01-0.12%, Mn: 0.30-1.60%, Si: 0.10-0.50%, Al: 0.010-0.050%, Cu: 0.02- 0.05%, Cr: 0.10‑0.90%, Mo: 0.10‑0.80%, Ti: 0.005‑0.060%, Nb: 0.005‑0.080%, Ni: 0.05‑0.30%, B≤0.0040%, P≤0.025%, S≤ 0.0020%, the balance is Fe and inevitable impurities. The present invention obtains good fire resistance and low temperature toughness by adding one or several microalloy elements under a certain ratio. The yield strength of steel at 600℃ is greater than 2/3 of the yield strength required by the room temperature standard, the impact energy at ‑40℃ is ≥120J, and it has excellent formability, cold bending performance, welding performance, etc.
Description
Technical Field
The invention belongs to the technical field of steel rolling, and relates to low-temperature high-toughness refractory steel and a preparation method thereof.
Background
The yield strength of ordinary structural steel for construction at 600 c will drop below 1/2 of the room temperature yield strength, thereby losing the load-bearing capacity. Existing building standards specify that steel structures be protected with fire-resistant thermal insulation coatings. However, the work of spraying the fireproof heat-insulating coating is harmful to the health of workers, the construction period is prolonged, and the construction cost of the steel structure is increased. In addition, the spatter from the operation of spraying the refractory heat-insulating coating also causes environmental pollution.
The temperature in winter in northern China can reach-20 ℃ at the lowest, and can reach-40 ℃ in partial areas, the impact toughness of a steel structure for construction can be rapidly reduced in severe cold weather, and particularly, the steel structure is easy to break suddenly under the action of certain impact load under the extremely cold weather condition, so that major safety accidents are caused. In order to adapt to northern cold weather conditions and enhance the safety of high-rise buildings, a low-temperature high-toughness refractory steel which has higher strength at high temperature and good impact toughness at low temperature is urgently needed.
Disclosure of Invention
In order to solve the technical problems, the invention aims to provide low-temperature high-toughness refractory steel and a preparation method thereof, and the low-temperature high-toughness refractory steel has better refractory performance and low-temperature toughness.
The invention provides low-temperature high-toughness refractory steel which comprises the following chemical components in percentage by weight: 0.01 to 0.12%, Mn: 0.30-1.60%, Si: 0.10-0.50%, Al: 0.010-0.050%, Cu: 0.02-0.05%, Cr: 0.10-0.90%, Mo: 0.10-0.80%, Ti: 0.005-0.060%, Nb: 0.005-0.080%, Ni: 0.05-0.30 percent of the total weight of the alloy, less than or equal to 0.0040 percent of B, less than or equal to 0.025 percent of P, less than or equal to 0.0020 percent of S, and the balance of Fe and inevitable impurities.
The preparation method of the low-temperature high-toughness refractory steel comprises the following steps of:
a steel making process: smelting and casting into a slab according to the following chemical composition and weight percentage:
wherein C: 0.01 to 0.12%, Mn: 0.30-1.60%, Si: 0.10-0.50%, Al: 0.010-0.050%, Cu: 0.02-0.05%, Cr: 0.10-0.90%, Mo: 0.10-0.80%, Ti: 0.005-0.060%, Nb: 0.005-0.080%, Ni: 0.05-0.30 percent of the total weight of the alloy, less than or equal to 0.0040 percent of B, less than or equal to 0.025 percent of P, less than or equal to 0.0020 percent of S, and the balance of Fe and inevitable impurities;
a heating procedure: controlling the furnace chamber atmosphere of the heating furnace, reducing the generation of casting blank iron scale, ensuring the uniform heating temperature, and controlling the discharging temperature of the plate blank to be 1160-1200 ℃;
a rolling procedure: the rough rolling pass is controlled by selecting a 3+3 mode, and the final rolling temperature is greater than or equal to 800 ℃;
a cooling process: adopting an intermittent cooling mode, starting spraying water to carry out laminar cooling when the steel plate is discharged from a finishing mill, and reducing the water spraying amount by half;
a coiling step: the coiling temperature is greater than or equal to 400 ℃.
In the preparation method of the low-temperature high-toughness refractory steel, the raw material adopts the fine scrap steel in the steelmaking process, and S is less than or equal to 0.005 percent when the raw material is pretreated and enters a furnace.
In the preparation method of the low-temperature high-toughness refractory steel, oxygen is blown only once when the converter decarburization treatment is carried out during the converter smelting in the steelmaking process; the steel tapping adopts low-carbon low-phosphorus ferromanganese, ferrosilicon, ferromolybdenum and high-chromium alloying; blowing by using argon when the converter pours the molten steel into the steel ladle, wherein the aluminum content of the steel ladle is 0.005-0.015%; the N of the steel ladle is required to be less than or equal to 25ppm, slag is blocked and steel is tapped, and the amount of slag entering the steel ladle is strictly controlled.
In the preparation method of the low-temperature high-toughness refractory steel, when external refining is carried out in the steelmaking process, the LF treatment process is required to keep micro-positive pressure, the increase of N in LF is strictly controlled, and the increase of N is required to be less than or equal to 10 ppm; the LF adopts active lime and fluorite to produce reducing slag with good fluidity, controls the argon blowing strength and avoids the exposure of molten steel; and performing calcium treatment after RH treatment, increasing soft blowing time and controlling inclusions in molten steel.
In the preparation method of the low-temperature high-toughness refractory steel, protective pouring is carried out in the whole process of continuous casting in the steelmaking process, an argon purging tundish is adopted before casting, no molten steel is exposed in the pouring process, the water mouth suction N is strictly controlled, and the increase of the N is controlled to be less than or equal to 5 ppm; high-alkalinity tundish slag is adopted to facilitate the removal of inclusions in steel; the pouring process of the molten steel adopts a soft reduction function, so that the internal quality of a casting blank is guaranteed; the constant drawing speed is kept in the steel casting process; controlling the temperature of the tundish according to the superheat degree of less than or equal to 30 ℃; after the continuous casting billet is poured, stacking and slow cooling are carried out to ensure that the casting billet is slowly cooled, and rolling is carried out after 72 hours.
The low-temperature high-toughness refractory steel and the preparation method thereof have the beneficial effects that:
(1) compared with the refractory steel of the same grade, the composition design adopts the design of low C and no V, and the proper amount of Cr, Mo, Ni and Cu alloy elements, so that various indexes on the mechanical property meet the requirements, and particularly, the impact toughness is particularly excellent. The high-performance refractory brick still has good refractory performance on the premise of not adding V element, has high product competitiveness and has good economic benefit.
(2) The yield strength of the low-temperature high-toughness fire-resistant steel at 600 ℃ is greater than 2/3 of the yield strength required by the room temperature standard, and the index requirement of fire resistance safety of modern building structural steel is met.
(3) Compared with common structural steel of the same grade, the low-temperature high-toughness fire-resistant steel produced by the process meets all index requirements except the normal-temperature mechanical property, all mechanical properties meet the requirements, the yield strength of the low-temperature high-toughness fire-resistant steel at 600 ℃ is greater than 2/3 of the yield strength required by the room-temperature standard, the index requirements of fire resistance safety of modern building structural steel are met, particularly, the impact toughness is particularly excellent, and the physical impact energy can reach more than or equal to 200J at-40 ℃.
Detailed Description
Ordinary structural steel for construction has good strength at room temperature, but as the temperature increases, the yield strength of the steel material decreases to below 1/2 of the room temperature yield strength, thereby losing the load-bearing capacity. The fire resistance of steel is judged internationally by the japanese standards: if the yield strength of the steel at 600 ℃ is greater than 2/3, which is the room temperature yield strength, the steel has fire resistance properties. The refractory steel of the invention has better refractory performance by adding Mo, Cr, Cu, Ni and other alloy elements into the steel.
The impact energy of the common structural steel for the building is required to be more than or equal to 27J, the ductile-brittle transition temperature is-20 ℃, and the material is easy to generate brittle fracture under the action of impact load in the environment with the temperature lower than-20 ℃. According to the low-temperature high-toughness refractory steel, the Nb microalloying element is added into the steel, and the cooling speed is controlled in the processing process, so that the grain structure is refined, and the impact energy of a final product object at-40 ℃ is more than or equal to 200J, so that the low-temperature high-toughness refractory steel has good low-temperature toughness.
In order to obtain good fire resistance and low-temperature toughness, the low-temperature high-toughness refractory steel must have good purity and low C content of molten steel, and special alloy addition is designed.
The invention relates to low-temperature high-toughness refractory steel, which comprises the following chemical components in percentage by weight: 0.01 to 0.12%, Mn: 0.30-1.60%, Si: 0.10-0.50%, Al: 0.010-0.050%, Cu: 0.02-0.05%, Cr: 0.10-0.90%, Mo: 0.10-0.80%, Ti: 0.005-0.060%, Nb: 0.005-0.080%, Ni: 0.05-0.30 percent of the total weight of the alloy, less than or equal to 0.0040 percent of B, less than or equal to 0.025 percent of P, less than or equal to 0.0020 percent of S, and the balance of Fe and inevitable impurities.
According to the low-temperature high-toughness refractory steel, a plurality of microalloy elements are added, so that the low-temperature high-toughness refractory steel has good refractory performance and low-temperature toughness in a certain proportion. The yield strength of the refractory steel at 600 ℃ is greater than 2/3 of the yield strength required by the room temperature standard, the impact energy at-40 ℃ is more than or equal to 120J, and the refractory steel has excellent forming performance, cold bending performance, welding performance and the like.
The fire-resistant mechanism of steel: the Mo element added into the refractory steel can remarkably increase the stability of the undercooled austenite in a pearlite transformation region, thereby being beneficial to the formation of bainite or MA structures. Therefore, at a lower cooling speed, the refractory steel has a mixed structure of ferrite, bainite and MA, and the phase boundary of the mixed structure can effectively block dislocation movement, so that the high-temperature strength of the steel is improved.
Molybdenum and niobium are both strong carbide forming elements. Mo favors the formation of more fine stable carbides (Mo)2C) The carbide is Fe3C is more stable and is difficult to decompose and grow up at high temperature. Niobium forms a fine second phase of NbC in the steel and has a high structural stability. The fine dispersed Nb (C, N) can hinder the migration of crystal boundary, improve the growth temperature of crystal grains, achieve the fine crystal effect, and the refined crystal grains can effectively prevent the expansion of cracks, thereby improving the low-temperature toughness of the refractory steel.
After the steel is added with trace elements such as copper, chromium, nickel and the like, a compact protective film with strong adhesiveness is formed on the surface of the steel, so that the corrosion is prevented from diffusing and developing inwards, and a matrix below the rust layer is protected to slow down the corrosion speed. An amorphous spinel type oxide compact layer with the thickness of about 50-100 mu m is formed between the rust layer and the matrix, and the compact oxide film prevents oxygen and water in the air of the external environment from permeating into the steel matrix, slows down the deep development of rust to steel materials and improves the corrosion resistance of the steel materials.
The preparation method of the low-temperature high-toughness refractory steel comprises the following steps of:
a steel making process: smelting and pouring into a plate blank according to the following chemical compositions in percentage by weight:
wherein C: 0.01 to 0.12%, Mn: 0.30-1.60%, Si: 0.10-0.50%, Al: 0.010-0.050%, Cu: 0.02-0.05%, Cr: 0.10-0.90%, Mo: 0.10-0.80%, Ti: 0.005-0.060%, Nb: 0.005-0.080%, Ni: 0.05-0.30 percent of the total weight of the alloy, less than or equal to 0.0040 percent of B, less than or equal to 0.025 percent of P, less than or equal to 0.0020 percent of S, and the balance of Fe and inevitable impurities;
a heating procedure: controlling the furnace chamber atmosphere of the heating furnace, reducing the generation of casting blank iron scale, ensuring the uniform heating temperature, and controlling the discharging temperature of the plate blank to be 1160-1200 ℃;
a rolling procedure: the rough rolling pass is controlled by selecting a 3+3 mode, and the final rolling temperature is greater than or equal to 800 ℃;
a cooling process: adopting an intermittent cooling mode, starting spraying water to carry out laminar cooling when the steel plate is discharged from a finishing mill, and reducing the water spraying amount by half;
a coiling step: the coiling temperature is greater than or equal to 400 ℃.
In the specific implementation, in the steelmaking process, the raw materials adopt refined scrap steel, and when the raw materials are pretreated and fed into a furnace, S is less than or equal to 0.005 percent.
In the specific implementation, only one time of oxygen blowing is carried out when the decarburization treatment of the converter is carried out during the smelting of the converter in the steelmaking process; the steel tapping adopts low-carbon low-phosphorus ferromanganese, ferrosilicon, ferromolybdenum and high-chromium alloying; blowing by using argon when the converter pours the molten steel into the steel ladle, wherein the aluminum content of the steel ladle is 0.005-0.015%; the N of the steel ladle is required to be less than or equal to 25ppm, slag is blocked and steel is tapped, and the amount of slag entering the steel ladle is strictly controlled.
In the specific implementation, when the external refining is carried out in the steelmaking process, the LF treatment process is required to keep micro-positive pressure, the increase of N in LF is strictly controlled, and the increase of N is required to be less than or equal to 10 ppm; the LF adopts active lime and fluorite to produce reducing slag with good fluidity, controls the argon blowing strength and avoids the exposure of molten steel; and performing calcium treatment after RH treatment, increasing soft blowing time and controlling inclusions in molten steel.
During specific implementation, protective pouring is carried out in the whole process of continuous casting in the steelmaking process, an argon purging tundish is adopted before casting, no molten steel is exposed in the pouring process, N is strictly controlled to be absorbed at a water port, and the increase of N is controlled to be less than or equal to 5 ppm; high-alkalinity tundish slag is adopted to facilitate the removal of inclusions in steel; the pouring process of the molten steel adopts a soft reduction function, so that the internal quality of a casting blank is guaranteed; the constant drawing speed is kept in the steel casting process; controlling the temperature of the tundish according to the superheat degree of less than or equal to 30 ℃; after the continuous casting billet is poured, stacking and slow cooling are carried out to ensure that the casting billet is slowly cooled, and rolling is carried out after 72 hours.
Example 1
Smelting and pouring into slab blanks according to the following chemical compositions and weight percentages thereof
C: 0.06%, Mn: 0.8%, Si: 0.12%, Al: 0.030%, Cu: 0.31%, Cr: 0.32%, Mo: 0.4%, Ti: 0.008%, Nb: 0.03%, Ni: 0.13%, B: 0.0002%, P: 0.01%, S: 0.001%, and the balance of Fe and inevitable impurities;
and then the plate blank is sequentially subjected to a heating process, a rolling process, a cooling process and a coiling process to obtain the low-temperature high-toughness refractory steel.
Example 2
Smelting and pouring into slab blanks according to the following chemical compositions and weight percentages thereof
C: 0.1%, Mn: 1.4%, Si: 0.28%, Al: 0.025%, Cu: 0.40%, Cr: 0.55%, Mo: 0.35%, Ti: 0.030%, Nb: 0.01%, Ni: 0.18%, B: 0.0001%, P: 0.012%, S: 0.002%, and the balance of Fe and inevitable impurities;
and then the plate blank is sequentially subjected to a heating process, a rolling process, a cooling process and a coiling process to obtain the low-temperature high-toughness refractory steel.
TABLE 1 comparison of mechanical Properties of refractory steels and common structural steels
TABLE 2 impact test of fire-resistant steel series
As can be seen from Table 1, the high temperature properties of the fire resistance test steels of example 1 and the fire resistance test steels of example 2 both satisfy the high temperature fire resistance requirement, and the design goal that the steels can resist fire is achieved. As the steel of the embodiment 1 is added with more alloy, the strength of the steel of the embodiment 1 is higher than that of the steel of the embodiment 2, and compared with Q345B common hot-rolled structural steel, the test steels of the embodiment 1 and the embodiment 2 have better impact toughness, and as can be seen from the table 2, the test steels of the embodiment 1 and the embodiment 2 still have good impact toughness at-60 ℃, which indicates that the refractory steel of the invention still does not reach the ductile-brittle transition temperature point at-60 ℃, and meets the service conditions of low-temperature service in northern areas.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the scope of the present invention, which is defined by the appended claims.
Claims (1)
1. The preparation method of the low-temperature high-toughness refractory steel is characterized by comprising the following steps of:
a steel making process: smelting and casting into a slab according to the following chemical composition and weight percentage:
wherein C: 0.01 to 0.12%, Mn: 0.30-1.60%, Si: 0.10-0.50%, Al: 0.010-0.050%, Cu: 0.02-0.05%, Cr: 0.10-0.90%, Mo: 0.10-0.80%, Ti: 0.005-0.060%, Nb: 0.005-0.080%, Ni: 0.05-0.30 percent of the total weight of the alloy, less than or equal to 0.0040 percent of B, less than or equal to 0.025 percent of P, less than or equal to 0.0020 percent of S, and the balance of Fe and inevitable impurities;
a heating procedure: controlling the furnace chamber atmosphere of the heating furnace, reducing the generation of casting blank iron scale, ensuring the uniform heating temperature, and controlling the discharging temperature of the plate blank to be 1160-1200 ℃;
a rolling procedure: the rough rolling pass is controlled by selecting a 3+3 mode, and the final rolling temperature is greater than or equal to 800 ℃;
a cooling process: adopting an intermittent cooling mode, starting spraying water to carry out laminar cooling when the steel plate is discharged from a finishing mill, and reducing the water spraying amount by half;
a coiling step: the coiling temperature is more than or equal to 400 ℃;
in the steelmaking process, the raw material adopts refined scrap steel, and when the raw material is pretreated and fed into a furnace, S is less than or equal to 0.005 percent;
in the steelmaking process, oxygen blowing is only carried out once when the decarburization treatment of the converter is carried out during the smelting of the converter; the steel tapping adopts low-carbon low-phosphorus ferromanganese, ferrosilicon, ferromolybdenum and high-chromium alloying; blowing by using argon when the converter pours the molten steel into the steel ladle, wherein the aluminum content of the steel ladle is 0.005-0.015%; the N of the steel ladle is required to be less than or equal to 25ppm, slag is blocked and steel is tapped, and the amount of slag entering the steel ladle is strictly controlled;
when the external refining is carried out in the steelmaking procedure, the LF treatment process is required to keep micro-positive pressure, the increase of N in LF is strictly controlled, and the increase of N is required to be less than or equal to 10 ppm; the LF adopts active lime and fluorite to produce reducing slag with good fluidity, controls the argon blowing strength and avoids the exposure of molten steel; performing calcium treatment after RH treatment, increasing soft blowing time and controlling inclusions in molten steel;
protective pouring is carried out in the whole process during continuous casting in the steelmaking process, argon is adopted to purge a tundish before casting, no molten steel is exposed in the pouring process, N is strictly controlled to be absorbed at a water port, and the increase of N is controlled to be less than or equal to 5 ppm; high-alkalinity tundish slag is adopted to facilitate the removal of inclusions in steel; the pouring process of the molten steel adopts a soft reduction function, so that the internal quality of a casting blank is guaranteed; the constant drawing speed is kept in the steel casting process; controlling the temperature of the tundish according to the superheat degree of less than or equal to 30 ℃; after the continuous casting billet is poured, stacking and slow cooling are carried out to ensure that the casting billet is slowly cooled, and rolling is carried out after 72 hours.
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