CN113699441B - Flange super-thick hot-rolled H-shaped steel with good low-temperature impact toughness and production method thereof - Google Patents
Flange super-thick hot-rolled H-shaped steel with good low-temperature impact toughness and production method thereof Download PDFInfo
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- 238000000034 method Methods 0.000 claims abstract description 24
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims abstract description 16
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims abstract description 10
- 238000007670 refining Methods 0.000 claims abstract description 9
- 238000010438 heat treatment Methods 0.000 claims abstract description 8
- 239000012535 impurity Substances 0.000 claims abstract description 7
- 229910052757 nitrogen Inorganic materials 0.000 claims abstract description 7
- 238000005266 casting Methods 0.000 claims abstract description 6
- 229910052742 iron Inorganic materials 0.000 claims abstract description 6
- 229910052698 phosphorus Inorganic materials 0.000 claims abstract description 6
- 238000003723 Smelting Methods 0.000 claims abstract description 5
- 229910052786 argon Inorganic materials 0.000 claims abstract description 5
- 238000007664 blowing Methods 0.000 claims abstract description 5
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 12
- 229910001563 bainite Inorganic materials 0.000 claims description 10
- 239000000463 material Substances 0.000 claims description 3
- 238000004321 preservation Methods 0.000 claims description 2
- 230000008569 process Effects 0.000 abstract description 22
- 230000000694 effects Effects 0.000 abstract description 13
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- 229910001566 austenite Inorganic materials 0.000 description 22
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- 238000001953 recrystallisation Methods 0.000 description 6
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- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 2
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B1/00—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
- B21B1/08—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling structural sections, i.e. work of special cross-section, e.g. angle steel
- B21B1/088—H- or I-sections
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/005—Modifying the physical properties by deformation combined with, or followed by, heat treatment of ferrous alloys
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C33/00—Making ferrous alloys
- C22C33/04—Making ferrous alloys by melting
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/001—Ferrous alloys, e.g. steel alloys containing N
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/46—Ferrous alloys, e.g. steel alloys containing chromium with nickel with vanadium
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum
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Abstract
The invention discloses flange super-thick hot-rolled H-shaped steel with good low-temperature impact toughness and a production method thereof, belonging to the technical field of steel rolling production. The hot-rolled H-shaped steel comprises the following elements in percentage by mass: c:0.08 to 0.12%, si:0.35 to 0.55%, mn: 1.35-1.45%, P: less than or equal to 0.020%, S: less than or equal to 0.015 percent, V:0.050 to 0.070%, cr:0.40 to 0.60%, nb:0.020 to 0.040%, ni:0.10 to 0.30%, N: 0.0100-0.0120% and the balance of Fe and inevitable impurities. The production process comprises the following steps: molten iron pretreatment → converter smelting → argon blowing refining → LF refining → beam blank full-protection casting → blank heating → rolling → controlled cooling after rolling. According to the invention, through reasonable component proportion and rolling process, particularly through reduction distribution, temperature-controlled rolling and post-rolling cooling-controlled process, the hot-rolled H-shaped steel with excellent comprehensive mechanical property, flange thickness of 70-140 mm and excellent low-temperature impact toughness is obtained, so that the use effect of the hot-rolled H-shaped steel in a low-temperature environment can be effectively met.
Description
Technical Field
The invention belongs to the technical field of steel rolling production, and particularly relates to flange ultra-thick hot-rolled H-shaped steel with good low-temperature impact toughness and a production method thereof.
Background
In recent years, the number of super high-rise buildings in China is increasing, the super high-rise buildings have a great effect of reducing the occupied area of the buildings in China, and especially for the countries with more population in China, the development of the super high-rise buildings is undoubtedly an important measure for solving the problems that the occupied area of the buildings in China is increased and the per capita land is reduced. Super high-rise buildings in China are mainly used as office buildings, hotels or large-span commercial real estate and the like. The projected building area of the high-rise steel structure in the standard layer design application is usually small, so that the steel structure is easily influenced by small process field, more constructions, long process, complex coordination and the like in the installation process, and the stacking position of steel members on the site is limited to a certain extent.
Hot rolled H-section steel is currently widely used in various fields. On the one hand, in the high-rise building, the characteristics of more building structure layers and large span are considered, and the H-shaped steel is required to be large in size and thickness; on the other hand, heavy hot-rolled H-section steel is increasingly favored because it is required to have high strength, good toughness, and excellent welding performance in view of safety, economy of construction, and convenience of material selection. Generally, H-shaped steel with the thickness of more than 40mm has a large interface which is equivalent to a box-shaped upright post formed by welding steel plates, and in comparison, hot rolling H-shaped steel needs fewer welding joints, so that the H-shaped steel is an ideal upright post material for high-rise buildings, and has the advantages of high safety, less occupied space and short manufacturing period.
However, when the existing hot-rolled H-shaped steel with thicker thickness is produced, because the reduction rate of the hot-rolled H-shaped steel with super-thick flange thickness in the flange thickness direction in the rolling process is smaller, the deformation and penetration are more difficult, and the product with better performance is difficult to obtain by adopting the traditional process, the performance of each aspect of the hot-rolled H-shaped steel can not meet the actual use requirement, especially under the condition of meeting the flange thickness of 70-140 mm, the hot-rolled H-shaped steel has the performance that the yield strength is more than or equal to 450MPa, the tensile strength is more than or equal to 550MPa, the KV2 mean value of the longitudinal V-shaped impact power at minus 40 ℃ is more than or equal to 100J, and the use requirement under the low-temperature environment can not be met easily.
Through search, the Chinese patent publication number is CN101824581B, the publication date is 2012, 5 and 30, and the name of the invention creation is as follows: a high-strength weather-resistant steel plate with the yield strength of 450MPa and a production method thereof. The steel disclosed in the patent comprises the following chemical components in percentage by weight: c:0.040% -0.080%, si: 0.15-0.35%, mn: 1.20-1.40%, P: less than or equal to 0.025 percent, S: less than or equal to 0.008 percent, nb:0.01 5% -0.035%, cu:0.25% -0.40%, ni:0.1 2-0.35%, cr:0.45% -0.75%, als: 0.020-0.045 percent, and the balance of Fe and inevitable impurity elements. The produced steel has yield strength of 485MPa or more, tensile strength of 590MPa or more, elongation of 28% or more and-40 ℃ V-shaped notch Charpy impact energy of 105J or more. The steel plate produced in the patent has excellent yield strength, tensile strength and low-temperature impact toughness, but the thickness of the steel plate is less than 8mm, and the production of ultra-thick flange products is difficult to realize.
For another example, the patent document with publication number CN102925798B, publication date 7/2/2014, entitled "a steel with 450 MPa-level yield strength for parts of railway freight car and production method" includes the following components: c:0.01 to 0.07%, si: less than or equal to 0.045%, mn:0.45 to 1.15%, P: less than or equal to 0.025%, S: less than or equal to 0.010 percent, nb:0.01 to 0.08%, V:0.02 to 0.10%, N:0.0030 to 0.010 percent. The invention uses C-Mn as a base and is matched with a matched process to refine grains and strengthen precipitation, and produces the steel with yield strength more than or equal to 450MPa, tensile strength more than or equal to 550MPa, elongation more than or equal to 20 percent, V-shaped notch Charpy impact energy at minus 40 ℃ more than or equal to 70J, good welding performance and low cost. However, this steel needs to be subjected to laminar cooling after rolling, and the cooling rate is controlled to 25 to 45 ℃/s, which requires high cooling equipment and is high in production cost, and the thickness of the steel is limited to 14mm or less, and it is also difficult to produce a steel sheet with an ultra-thick flange.
Disclosure of Invention
1. Problems to be solved
The invention aims to solve the problems that the performance stability is difficult to control and the existing hot-rolled H-shaped steel is difficult to produce and obtain the H-shaped steel which simultaneously has an ultra-thick flange and is excellent in low-temperature impact toughness during production, and provides the flange ultra-thick hot-rolled H-shaped steel with good low-temperature impact toughness and the production method thereof. By adopting the technical scheme of the invention, the problems can be effectively solved, and the super-thick hot-rolled H-shaped steel with excellent low-temperature impact toughness is produced, so that the super-thick hot-rolled H-shaped steel can be effectively used in a low-temperature environment, and the manufacturing cost is relatively low.
2. Technical scheme
In order to solve the problems, the technical scheme adopted by the invention is as follows:
the flange ultra-thick hot-rolled H-shaped steel with good low-temperature impact toughness comprises the following elements in percentage by mass: c:0.08 to 0.12%, si:0.35 to 0.55%, mn:1.35 to 1.45%, P: less than or equal to 0.020%, S: less than or equal to 0.015 percent, V: 0.050-0.070%, cr:0.40 to 0.60%, nb:0.020 to 0.040%, ni:0.10 to 0.30%, N: 0.0100-0.0120% and the balance of Fe and inevitable impurities.
Further, the content ratio of V to N satisfies (4-6): 1.
Furthermore, the bainite structure morphology reaches 1/4 of the thickness of the whole flange, and the bainite content reaches 20-30%.
Furthermore, the thickness of the flange is 70-140 mm, the yield strength is more than or equal to 450MPa, the tensile strength is more than or equal to 550MPa, the elongation is more than or equal to 20 percent, the KV2 average value of the longitudinal V-shaped impact energy at minus 40 ℃ is more than or equal to 100J, and the Z-direction performance is more than or equal to 20 percent.
The invention relates to a production method of flange super-thick hot-rolled H-shaped steel with good low-temperature impact toughness, which comprises the following process steps: molten iron pretreatment → converter smelting → argon blowing refining → LF refining → shaped blank full-protection casting → blank heating → rolling → controlled cooling after rolling.
Further, the rolling stage includes a rough rolling stage and a finish rolling stage, wherein: the initial rolling temperature in the rough rolling stage is controlled to be 1150-1180 ℃, and the final rolling temperature is controlled to be more than 1000 ℃; the finish rolling adopts two-stage controlled rolling, the first stage controls the rolling start temperature to be 980-1000 ℃, and the finish rolling temperature to be above 960 ℃; the second stage controls the initial rolling temperature of the rolling to be 930-950 ℃ and the final rolling temperature to be 830-850 ℃.
Furthermore, during rough rolling, the pass reduction rate is controlled to be 15-20% in the temperature range of 1100-1150 ℃; in the temperature range of 1050-1100 ℃, the pass reduction rate is controlled to be 20-25 percent; in the temperature range of 1000-1050 ℃, the pass reduction rate is controlled to be 25-30%, and the total reduction rate of the blank is controlled to be 40-50%.
Furthermore, in the finish rolling, the pass reduction rate is controlled to be 5% -10% in the first stage of controlled rolling, and the pass reduction rate is reduced along with the reduction of the rolling temperature; and when the rolling is controlled in the second stage, the pass reduction rate is controlled to be 5-30%, and when the rolling is controlled in the second stage, the flange selective cooling is started for each pass of rolling, the water pressure is controlled to be 0.5-0.7 MPa, and the water flow is controlled to be 1500-2000m < 3 >/h.
Furthermore, when controlled cooling is carried out after rolling, the water pressure is controlled to be 1.0-1.2 MPa, the water flow is controlled to be 3500-4000m < 3 >/h, and the cooling time is controlled to be 20-40 s.
Furthermore, when the blank is heated, the heating temperature is controlled to be 1200-1250 ℃, and the heat preservation time is 150-180 min.
3. Advantageous effects
Compared with the prior art, the invention has the beneficial effects that:
(1) According to the flange ultra-thick hot-rolled H-shaped steel with good low-temperature impact toughness, the components and the mass percentage ranges of the components are optimally designed, so that the comprehensive mechanical property of the obtained hot-rolled H-shaped steel can be ensured, particularly, the obtained product has higher strength and low-temperature impact toughness under the condition of ultra-thick flange thickness, the using effect of the product in a low-temperature environment is effectively met, and the economic benefit is higher.
(2) According to the flange ultra-thick hot-rolled H-shaped steel with good low-temperature impact toughness, the design idea of C + V + Nb + Cr + Ni components is adopted, fine grain strengthening, solid solution strengthening and precipitation strengthening are realized, and the requirement on the comprehensive mechanical property of the product is met. Particularly, the content ratio of V to N is controlled to be (4-6): 1 in composition, so that on one hand, the obtained product can be effectively ensured to have higher surface quality, and a large amount of linear defects on the surface of the product are avoided; on the other hand, the production cost can be further reduced by reasonably controlling the content of the sodium chloride.
(3) According to the flange ultra-thick hot-rolled H-shaped steel with good low-temperature impact toughness, the effect of the composite action of Ni and Cr is fully exerted by compositely adding Ni and Cr, the austenite area of the steel is expanded by using Ni, ferrite grains are refined, the low-temperature toughness is improved, and the purpose that the KV2 mean value of longitudinal V-shaped impact power at the temperature of-40 ℃ is more than or equal to 100J can be achieved. Meanwhile, the hardenability of the structure is improved by matching with Cr, and the structure transformation of steel is promoted, so that the strength and the toughness of the steel are simultaneously improved, the better welding performance is kept, and the comprehensive mechanical property of the obtained product is effectively optimized.
(4) According to the production method of the flange ultra-thick hot-rolled H-shaped steel with good low-temperature impact toughness, the component proportion and the production process are optimally designed to play a role together, particularly, the rolling and cooling process parameters are designed, the distribution of the reduction is strictly controlled, and then the temperature-controlled rolling process and the controlled cooling after rolling are matched, so that the hot-rolled H-shaped steel with thicker flange thickness can be obtained, the flange thickness can reach 70-140 mm, the yield strength is more than or equal to 450MPa, the tensile strength is more than or equal to 550MPa, the elongation A is more than or equal to 20%, the longitudinal V-shaped impact power KV2 at minus 40 ℃ is more than or equal to 100J, Z is more than or equal to 20%, the hot-rolled H-shaped steel has higher strength, good plasticity, particularly excellent low-temperature toughness, and the use requirement of the hot-rolled H-shaped steel in a low-temperature environment can be effectively met.
(5) According to the production method of the flange super-thick hot-rolled H-shaped steel with good low-temperature impact toughness, during rough rolling, strict temperature control rolling is adopted, pass reduction rate of rolling is optimized in combination with a temperature range, austenite recrystallization percentage of each pass is guaranteed to reach more than 50%, austenite crystals are continuously refined, meanwhile, solute dragging effect of solid solution Nb and pinning effect of Nb (C, N) compounds are combined to further refine austenite grains, ferrite grain size of a final product reaches more than 10 levels, and final comprehensive mechanical property requirements of the product are met.
(6) According to the production method of the flange ultra-thick hot-rolled H-shaped steel with good low-temperature impact toughness, the finish rolling adopts two-stage controlled rolling, the rolling temperature and the rolling pass reduction rate are strictly controlled, and the rolling in the first stage avoids larger deformation as much as possible, so that the unevenness of austenite grains of the structure is avoided, and the performance stability of the product is ensured; and in the second stage of rolling, on the basis of the first stage of rolling, ferrite phase transformation nucleation is further promoted, ferrite tissues are refined, SFC (flange selective cooling) is started during each rolling, the deformation and permeation effect of each pass in the second stage can be maximally ensured to reach 1/4 position of the flange thickness and above, austenite grains are further refined, and the low-temperature impact toughness and strength of the obtained product can be further improved under the condition of ultra-thick flange thickness, so that the comprehensive mechanical property of the product can be conveniently controlled and stabilized.
(7) According to the production method of the flange ultra-thick hot-rolled H-shaped steel with good low-temperature impact toughness, the cooling mode after rolling is optimized, particularly the cooling time is controlled, preferably 20-40 s, the temperature drop time can be shortened, the supercooling degree of phase change is expanded, the distortion caused by internal rolling deformation is kept to the maximum extent, the microstructure transformation of austenite after rolling is controlled by matching with the action of microalloy elements, and the phase change structure is refined.
Drawings
FIG. 1 is a table showing values (wt%) of chemical components of each example and each comparative example in the present invention, and the balance being Fe and unavoidable impurities;
FIG. 2 is a table 1 of the main process parameters for various embodiments of the present invention and comparative examples;
FIG. 3 is a table 2 of the main process parameters for each embodiment and comparative example of the present invention;
FIG. 4 shows the performance test results of the products obtained in the examples and comparative examples of the present invention.
Detailed Description
The flange ultra-thick hot-rolled H-shaped steel with good low-temperature impact toughness comprises the following elements in percentage by mass: c:0.08 to 0.12%, si:0.35 to 0.55%, mn:1.35 to 1.45%, P: less than or equal to 0.020%, S: less than or equal to 0.015 percent, V:0.050 to 0.070%, cr:0.40 to 0.60%, nb:0.020 to 0.040%, ni:0.10 to 0.30%, N:0.0100 to 0.0120 percent of Fe and the balance of inevitable impurities. By optimally designing the components and the mass percentage ranges of the components, the comprehensive mechanical property of the obtained hot-rolled H-shaped steel can be ensured, particularly, the design idea of C + V + Nb + Cr + Ni components is adopted for the chemical components, the production cost is considered, the fine grain strengthening, the solid solution strengthening and the precipitation strengthening are realized, and the comprehensive property requirement of the product can be effectively met.
It should be noted that it is difficult to produce the super-thick flange hot-rolled H-section steel with excellent comprehensive mechanical properties (especially, high strength and excellent low-temperature impact toughness), the control requirements on the components are strict, and the product performance is greatly affected by the fluctuation of the components. On one hand, the coupling effect between the V and the N elements can be fully exerted by controlling the content ratio of the V to the N to be (4-6) 1,V to the N, the subsequent rolling process is matched, a large amount of second phase particles such as VN or V (CN) can be optimally dispersed and finely precipitated in the steel, and the finished product is ensured to have higher surface quality. The applicant finds out in tests that when the element content ratio of V to N is controlled within the range, the linear defects on the surface of the obtained product can be reduced to the maximum extent, and meanwhile, when the element content ratio of V to N is controlled within the range, the element V can be dissolved in steel as much as possible and cannot be separated out, so that the waste of the element V can be effectively avoided, the utilization efficiency of the element is obviously improved, the manufacturing cost is greatly reduced to a certain extent, and the economic benefit is better.
On the other hand, the composite effect of Ni and Cr can be fully exerted by the composite addition of Ni and Cr and the synergistic effect of other component elements. Specifically, ni can be continuously dissolved in steel in a solid manner, so that the dislocation movement resistance is effectively reduced, the plasticity and toughness of the steel can be obviously improved, and meanwhile, the compactness and stability of a rust layer on the surface of the steel can be improved, so that the surface quality of a product is effectively improved. And the addition content range of the Ni element is controlled within the range (0.10 to 0.30%) determined in the present invention to be able to function at the maximum, and its upper limit value can be appropriately lowered in consideration of the cost. The addition of Cr can obviously improve the hardenability of steel, increase the undercooling capability of austenite and delay bainite phase transformation, thereby being beneficial to obtaining a metastable austenite region between a ferrite transformation region and a bainite transformation region and forming a microstructure mainly comprising bainite. The invention controls the content within the range of 0.40-0.60%, and can effectively ensure the strength and hardenability of the product under the condition of adding other alloy elements, because when the content is too high, the plasticity, toughness and weldability of the steel are not influenced under the condition of adopting the component design of the invention. During rolling, ni and Cr are added in a combined manner, ni can be used for expanding an austenite region of steel, ferrite grains are refined, low-temperature impact toughness is remarkably improved, the KV2 mean value of longitudinal V-shaped impact power at-40 ℃ is not less than 100J, and the hardenability of a structure can be further increased by matching with Cr, so that the structure transformation of steel is promoted, the strength and the toughness of a product are improved at the same time, and the product has better welding performance.
The invention relates to flange super-thick hot-rolled H-shaped steel with good low-temperature impact toughness, which comprises the following production process steps: molten iron pretreatment → converter smelting → argon blowing refining → LF refining → beam blank full-protection casting → blank heating → rolling → controlled cooling after rolling.
The production method specifically comprises the following steps:
(1) The molten iron is pretreated and then smelted in a converter;
(2) Blowing inert gas argon in the smelting process, removing dissolved gas and suspended non-metallic inclusions of steel, and purifying molten steel;
(3) Refining in an LF furnace, controlling impurity precipitation, further controlling the content of each alloy element, and then continuously casting into a blank;
(4) The casting blank enters a heating furnace, is heated to 1200-1250 ℃ by the heating furnace, and is kept warm for 150-180 min, so that the alloy elements are fully dissolved in solution, and overburning and excessive austenite grain coarsening are avoided;
(5) Rolling and controlled cooling after rolling.
It is worth explaining that the invention can obtain the hot-rolled H-shaped steel with thicker flange thickness by optimally designing the component proportion and the production process, cooperating each element to play a role together, especially designing the rolling and cooling process parameters, strictly controlling the distribution of the reduction, cooperating the temperature-controlled rolling process and the controlled cooling after rolling, the flange thickness of the hot-rolled H-shaped steel can reach 70-140 mm, the yield strength is more than or equal to 450MPa, the tensile strength is more than or equal to 550MPa, the elongation A is more than or equal to 20%, the longitudinal V-shaped impact power KV2 at minus 40 ℃ is more than or equal to 100J, Z is more than or equal to 20%, the hot-rolled H-shaped steel has higher strength, good plasticity, especially excellent low-temperature toughness, thereby effectively meeting the use requirements under the low-temperature environment.
Specifically, the initial rolling temperature in the rough rolling stage is controlled to be 1150-1180 ℃, and the final rolling temperature is controlled to be more than 1000 ℃. Furthermore, the pass reduction rate is controlled to be 15-20% in the temperature range of 1100-1150 ℃; in the temperature range of 1050-1100 ℃, the pass reduction rate is controlled to be 20-25 percent; in the temperature range of 1000-1050 ℃, the pass reduction rate is controlled to be 25-30%, and the total reduction rate of the blank is controlled to be 40-50%. The stage is in the austenite recrystallization temperature range, and the pass reduction rate control in different temperature ranges is to ensure that the austenite recrystallization percentage of each pass reaches more than 50 percent, and austenite grains are continuously refined through large rolling deformation and repeated recrystallization of austenite. Meanwhile, as Nb alloy elements are added, the solute dragging effect of solid solution Nb and the pinning effect of Nb (C, N) compounds further refine austenite grains, so that the ferrite grain size of a final product reaches more than 10 grades, and the final comprehensive mechanical property requirement of the product is met.
After the rough rolling is finished, the process enters a finish rolling stage, the finish rolling adopts two-stage controlled rolling, the initial rolling temperature of the first stage controlled rolling is controlled to be 980-1000 ℃, the final rolling temperature is controlled to be above 960 ℃, and the pass reduction rate of the first stage is controlled to be 5-10%. The stage is in the austenite partial recrystallization temperature range, large deformation is avoided as much as possible, austenite grains are not uniform, the performance of the final product is reduced, and the performance of the product can be well stabilized by controlling the reduction rate.
The initial rolling temperature of the second stage of finish rolling is controlled to be 930-950 ℃, the final rolling temperature is controlled to be 830-850 ℃, the rest deformation of the blank is finished in the stage, the pass reduction rate is controlled to be 5-30%, and the pass reduction rate is reduced along with the reduction of the temperature in the stage. The phase is in the austenite non-recrystallization temperature range, and austenite grains in a rolled piece structure can be effectively promoted to be distorted by controlling the rolling temperature and the rolling reduction rate, so that a large number of deformation zones, twin crystals and dislocations are conveniently formed, the position of a nucleation point is increased, a large number of distortion energy can be obtained, a large number of second phase grains such as VN or V (CN) are promoted to be separated out, ferrite phase transformation nucleation is promoted, a ferrite structure is refined, and the distortion energy caused by large deformation can also provide enough kinetic energy for bainite phase transformation. More optimally, in the process of controlling rolling at the second stage, the SFC (flange selective cooling) is started in each rolling pass, the water pressure is controlled to be 0.5-0.7 MPa, and the water flow is controlled to be 1500-2000m 3 And h, the surface temperature of the product can be reduced, so that the hardening effect is achieved, and the deformation and penetration effect of each pass at the stage can be maximally ensured to reach 1/4 position of the thickness of the flange and above by matching with rolling, so that austenite grains can be further refined, and the comprehensive performance of the obtained product is stabilized and improved.
After rolling, the H-shaped steel enters a controlled cooling device after rolling, the water pressure is controlled to be 1.0-1.2 MPa, and the water flow is controlled to be 3500-4000m 3 The cooling time is controlled to be 20-40 s.It needs to be further explained that the cooling time is too short, the thickness of the bainite layer can not reach 1/4 of the thickness of the flange, and the bainite content is less than 20% -30%; if the cooling time is too long, the structure of the steel sheet becomes martensite, and the structure is unfavorable for the toughness of the product. In the stage, an ultra-fast cooling technology is utilized, the temperature reduction time is shortened, the supercooling degree of phase change is enlarged, the distortion caused by internal rolling deformation is retained to the maximum extent, the structural transformation of austenite after rolling is further controlled by matching the comprehensive action of micro-alloy elements, and the phase change structure is refined.
The invention is further described with reference to specific examples.
Examples 1 to 5
The weight percentage ranges of the components of the flange super-thick hot-rolled H-shaped steel with good low-temperature impact toughness of the embodiment are listed in the chemical component value list in FIG. 1.
The processing steps adopt the process flow of the invention, wherein, the main process parameters are shown in the process parameter lists in fig. 2 and fig. 3.
The properties of the obtained product were measured and the results are shown in the table in fig. 4.
Comparative examples 1 to 2
The hot-rolled H-shaped steel of the comparative example had the weight percentage ranges of the components as listed in the chemical composition value list in FIG. 1.
The components of the steel are adopted according to the component proportion and the values are taken within the limited range, the process adopts the prior art, and the main process parameters are shown in process parameter lists in figures 2 and 3.
The properties of the obtained product were measured and the results are shown in the table in fig. 4.
Comparative example 3
The hot-rolled H-shaped steel of the comparative example had the weight percentage ranges of the components as listed in the chemical composition value list in FIG. 1.
The components of the conventional steel are adopted in the component ratio, the process adopts the process disclosed by the invention, and the main process parameters are shown in process parameter lists in figures 2 and 3.
The properties of the obtained product were measured and the results are shown in the table in fig. 4.
As can be seen by combining the figures 1-4, the flange thickness of the hot-rolled H-shaped steel obtained in the examples 1-5 is 70-140 mm, the yield strength is more than or equal to 450MPa, the tensile strength is more than or equal to 550MPa, the elongation is more than or equal to 20%, the KV2 mean value of the longitudinal V-shaped impact energy at minus 40 ℃ is more than or equal to 100J, the Z-direction performance is more than or equal to 20%, compared with the performance of the product obtained in the comparative examples 1-3, the mechanical performance is more excellent, and the product obtained in the comparative examples has poorer comprehensive mechanical performance calibration when the flange thickness is within 70-140 mm, particularly, the difference between the low-temperature impact toughness and the examples is larger, the use requirement at low temperature is difficult to meet, and simultaneously, the yield strength and the tensile strength are also lower than the data of the examples.
Claims (2)
1. The flange ultra-thick hot-rolled H-shaped steel with good low-temperature impact toughness is characterized in that: the material comprises the following elements in percentage by mass: c:0.08 to 0.12%, si:0.35 to 0.55%, mn: 1.35-1.45%, P: less than or equal to 0.020%, S: less than or equal to 0.015%, V: 0.050-0.070%, cr:0.40 to 0.60%, nb:0.020 to 0.040%, ni:0.10 to 0.30%, N: 0.0100-0.0120% and the balance of Fe and inevitable impurities; the element content ratio of V to N satisfies (4-6) 1;
the bainite structure morphology of the steel plate reaches 1/4 of the thickness of the whole flange, and the bainite content reaches 20% -30%;
the flange thickness is 70-140 mm, the yield strength is more than or equal to 450MPa, the tensile strength is more than or equal to 550MPa, the elongation is more than or equal to 20 percent, and the longitudinal V-shaped impact energy KV at minus 40 DEG C 2 The average value is more than or equal to 100J, and the Z-direction performance is more than or equal to 20 percent.
2. The production method of the flange ultra-thick hot-rolled H-shaped steel with good low-temperature impact toughness according to the claim 1, characterized by comprising the following process steps: molten iron pretreatment → converter smelting → argon blowing refining → LF refining → beam blank full-protection casting → blank heating → rolling → controlled cooling after rolling;
the rolling stage comprises a rough rolling stage and a finish rolling stage, wherein: the initial rolling temperature in the rough rolling stage is controlled to be 1150-1180 ℃, and the final rolling temperature is controlled to be more than 1000 ℃; the finish rolling adopts two-stage controlled rolling, the first stage controls the rolling start temperature to be 980-1000 ℃, and the finish rolling temperature to be above 960 ℃; in the second stage, the initial rolling temperature of rolling is controlled to be 930-950 ℃, and the final rolling temperature is controlled to be 830-850 ℃;
during rough rolling, the pass reduction rate is controlled to be 15-20% in the temperature range of 1100-1150 ℃; in the temperature range of 1050-1100 ℃, the pass reduction rate is controlled to be 20-25 percent; in the temperature range of 1000-1050 ℃, the pass reduction rate is controlled to be 25-30%, and the total reduction rate of the blank is controlled to be 40-50%;
during finish rolling, the pass reduction rate is controlled to be 5-10% during first-stage controlled rolling, and the pass reduction rate is reduced along with the reduction of the rolling temperature; the rolling reduction of each pass is controlled to be 5-30% in the second stage of rolling control, the flange selective cooling is started in each pass of rolling control, the water pressure is controlled to be 0.5-0.7 MPa, and the water flow is controlled to be 1500-2000m 3 /h；
When the controlled cooling is carried out after rolling, the water pressure is controlled to be 1.0-1.2 MPa, and the water flow is controlled to be 3500-4000m 3 The cooling time is controlled to be 20-40 s;
when the blank is heated, the heating temperature is controlled to be 1200-1250 ℃, and the heat preservation time is 150-180 min.
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| CN115433874B (en) * | 2022-08-31 | 2023-08-25 | 马鞍山钢铁股份有限公司 | Hot rolled angle steel with yield strength of 460MPa and minus 20 ℃ resistance and production method thereof |
| CN115369328B (en) * | 2022-09-22 | 2024-01-23 | 马鞍山钢铁股份有限公司 | Low-temperature-resistant rolled steel and production method thereof |
| CN115415311B (en) * | 2022-10-08 | 2024-12-24 | 包头钢铁（集团）有限责任公司 | A rolling method for hot-rolled H-shaped steel for marine engineering structures with ultra-high strength and good toughness |
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| JP3004155B2 (en) * | 1993-09-10 | 2000-01-31 | 新日本製鐵株式会社 | Manufacturing method of shaped steel with excellent toughness |
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| JP6344191B2 (en) * | 2014-10-15 | 2018-06-20 | 新日鐵住金株式会社 | High-strength ultra-thick H-shaped steel with excellent toughness and method for producing the same |
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