CN111187990B - Hot-rolled H-shaped steel with yield strength of 500MPa and production method thereof - Google Patents
Hot-rolled H-shaped steel with yield strength of 500MPa and production method thereof Download PDFInfo
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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
- C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
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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
- C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
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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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- 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
- 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
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/005—Ferrite
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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
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/009—Pearlite
Abstract
The invention provides hot-rolled H-shaped steel with 500 MPa-grade yield strength and a production method thereof, and the hot-rolled H-shaped steel comprises the following components: c: 0.15 to 0.20%, Si: 0.25 to 0.40%, Mn: 1.25-1.50%, P: less than or equal to 0.025 percent, S: less than or equal to 0.015 percent, V: 0.06-0.08%, Nb: 0.020 to 0.030% of Fe and the balance of inevitable impurity elements. Reasonable component proportion and rolling process are adopted, particularly reasonable selection of blank compression ratio and distribution of rolling reduction are adopted, and then temperature control rolling process is matched; the complex phase structure of ferrite and pearlite is obtained by utilizing the mechanisms of fine crystal strengthening, precipitation strengthening and phase change strengthening, the yield strength of the product is more than 500MPa, the tensile strength is more than 600MPa, the elongation is more than 20 percent, and the vertical V-shaped impact energy KV at the temperature of minus 20 ℃ is KV2The average value is more than 100J.
Description
Technical Field
The invention relates to vehicle steel and a production method thereof, in particular to hot-rolled H-shaped steel for a special vehicle frame longitudinal beam with the yield strength of 500MPa and a production method thereof.
Background
In recent years, with the rapid increase of industrial modernization progress, the demand of special vehicles in the fields of road traffic, energy chemical engineering and the like keeps high-level growth for a long time. Due to the fact that the service condition of the special vehicle frame longitudinal beam is poor, the hot-rolled H steel for the longitudinal beam has to have excellent comprehensive mechanical property, welding property, dimensional precision and surface quality. With the continuous promotion and implementation of national environmental protection and policy for overtaking control and the continuous increase of strength, various large-scale vehicle production enterprises urgently need light-weight, high-strength and high-quality hot-rolled H-shaped steel to achieve the aim of vehicle body light weight.
At present, most H-shaped steel production enterprises in China successfully develop light high-strength high-precision hot-rolled H-shaped steel with yield strengths of 345MPa, 390MPa and 420 MPa. In order to ensure that the indexes of the steel such as strength and the like meet the standard requirements, the steel is produced by adopting a conventional hot rolling method with higher content of alloy elements such as Nb, V and Mn. The hot-rolled H-shaped steel with the yield strength exceeding 420MPa is obtained by adding high-content alloy elements (the V content is 0.10-0.15 wt%, the Mn content is as high as 1.30-1.70 wt%, and expensive metals such as Nb and Mo are added) and matching with a controlled rolling and cooling process to obtain the required mechanical properties. Because the content of the alloy elements is high, and a water-through cooling control technology after rolling needs to be utilized, the production cost is improved, meanwhile, the welding performance of the steel is further deteriorated due to the high content of the alloy elements, and the fatigue resistance of the steel is further deteriorated due to the uneven structure of the steel caused by the water-through cooling.
The invention discloses a production method of 500 MPa-grade forklift portal frame section steel, which is disclosed as CN103938076A, 7/23/2014 and named as a production method of 500 MPa-grade forklift portal frame section steel, and the production method sequentially comprises the steps of molten iron pre-desulfurization, converter smelting, LF refining, full-protection continuous casting and rolling, wherein the 500 MPa-grade forklift portal frame section steel consists of the following chemical components in percentage by weight: c: 0.24-0.30%, Si: 0.15-0.30%, Mn: 1.05-1.30%, P: less than or equal to 0.025%, S: less than or equal to 0.015 percent, V: 0.05-0.08%, and the balance of iron and inevitable impurities. According to the invention, the carbon content is increased, the sulfur and phosphorus content is reduced, the microalloying is only vanadium, no other element is added, cooling control is not required after rolling, and heat treatment is not required, so that the obtained steel has good mechanical properties, the average yield strength is 531MPa, the average tensile strength is 685MPa, the average elongation is 23.5%, the Brinell hardness is more than 210, and the average impact work at 20 ℃ is 59J, but the impact work at-20 ℃ is not mentioned.
The publication number is CN101899616A, the publication number is 12 months and 1 day 2010, and the patent document is named as 'a steel for 600MPa grade high-strength engineering machinery and a production method thereof', and the chemical components of the steel are as follows by weight percent: 0.06-0.09%, Si: 0.15-0.25%, Mn: 1.4-1.6%, P: less than or equal to 0.020%, S: less than or equal to 0.010 percent, Alt: 0.020 to 0.060%, Nb: 0.040-0.060%, Ti: 0.09-0.12 percent, and the balance of Fe and inevitable impurities. The steel does not need to add expensive elements such as Mo, V and the like, and produces the low-cost hot rolled coil with yield strength of more than 600MPa, V-shaped Charpy impact work at-20 ℃ of more than or equal to 40J and excellent strength and toughness. But a laminar cooling controlled cooling process is adopted after rolling, the cooling speed is controlled to be 5-10 ℃/s, the energy consumption is increased, and the thickness specification is limited to be 5-16 mm.
The patent document with the publication number of CN102644034A and the publication number of 2012, 8 and 22 is 'a cooling method after rolling of high-weather-resistance hot-rolled H-shaped steel with 500MPa of yield strength', and the steel comprises the following components in percentage by mass: c: 0.06-0.12, Si: 0.30-0.60, Mn: 0.80-1.20, P: 0.010-0.030, S: 0.001-0.015, Cu: 0.20 to 0.35, Cr: 0.20 to 0.40, Ni: 0.15 to 0.30, Nb: 0.040 to 0.060, Als: 0.003-0.030 percent, and the balance of iron and residual trace impurities. After rolling, the required mechanical performance is obtained by two-stage rapid cooling (the first stage cooling speed is 75-150 ℃/s, and the second stage cooling speed is 20-45 ℃/s), the production energy consumption is increased, and the requirement on cooling equipment is extremely high. Compared with the invention, the H-shaped steel product related by the invention can achieve the required mechanical property without adopting a controlled cooling process after rolling, and the production cost is lower.
The patent document with the publication number of CN103695772A and the publication date of 2014, 4, and 2, and the name of 'the fire-resistant weather-resistant earthquake-resistant construction steel with the yield strength of 550MPa grade and the production method thereof' comprises the following components in percentage by weight: c: 0.041-0.125%, Si: 0.31 to 0.62%, Mn: 1.81-2.40%, P: less than or equal to 0.008 percent, S: less than or equal to 0.002%, Nb: 0.041-0.065%, Ti: 0.007-0.020%, Mo: 0.41-0.63%, W: 0.07-0.10%, Mg: 0.0071-0.0098%, O: less than or equal to 0.0012 percent. The invention has higher Mn content, higher content of noble metals Nb and Mo, higher production cost, and increased production energy consumption because the mechanical property requirement is realized by a controlled cooling process after rolling. Compared with the invention, the invention relates to an H-shaped steel product, does not show the fire-resistant, weather-resistant and earthquake-resistant performance, does not need a controlled cooling process after rolling, has lower production cost and does not add noble metal elements such as Mo and the like.
The patent document with the publication number of CN102676919A and the publication number of 2012, 9 and 19 and the name of 'a method for cooling a low-alloy hot-rolled H-shaped steel with the yield strength of 550MPa after rolling', wherein the steel comprises the following components in percentage by mass: c: 0.13 to 0.18, Si: 0.30 to 0.50, Mn: 1.40-1.60, P: 0.025 or less, S: 0.025 or less, V: 0.10 to 0.12, N: 0.010-0.014, Als: 0.003-0.030 percent, and the balance of iron and residual trace impurities. After rolling, the required mechanical properties are obtained by two-stage rapid cooling (the first stage cooling speed is 75-150 ℃/s, and the second stage cooling speed is 20-45 ℃/s), the production energy consumption is increased, and the requirement on cooling equipment is extremely high.
The invention discloses a patent document with publication number CN103243272A and publication number 2013, 8, 14 and named as 'a rolling process of vanadium-containing weather-resistant hot-rolled H-shaped steel with 500 MPa-grade yield strength', and discloses a rolling process of vanadium-containing weather-resistant hot-rolled H-shaped steel with 500 MPa-grade yield strength, wherein the vanadium-containing weather-resistant hot-rolled H-shaped steel comprises the following components in percentage by mass: c: 0.09-0.12, Si: 0.43 to 0.55, Mn: 1.39-1.49, P: 0.013-0.017, S: 0.011-0.016, Cu: 0.27 to 0.36, Cr: 0.32 to 0.38, Ni: 0.25 to 0.32, V: 0.098-0.110, A1S: 0.014-0.023, and the balance of iron and residual trace impurities. After rolling, the required mechanical properties are obtained through two-stage rapid cooling (the first stage cooling speed is 97-128 ℃/s, and the second stage cooling speed is 36-45 ℃/s), the production energy consumption is increased, and the requirement on cooling equipment is extremely high.
The patent document with the publication number of CN104962807A, 10.2015 and 7.2015 entitled "a high-strength hot rolled steel and a preparation method and application thereof" comprises the following chemical components in percentage by weight: 0.05 to 0.10 percent of C, 1.30 to 1.60 percent of Mn, 0.06 to 0.09 percent of V, less than or equal to 0.30 percent of Si, less than or equal to 0.020 percent of P, less than or equal to 0.010 percent of S, and the balance of Fe and inevitable impurities. The method adopts a manganese and vanadium microalloying mode, and controls cooling after rolling (the rolled plate blank is cooled to 720 ℃ at a cooling speed of 5-30 ℃/s, air-cooled for 8-10 s, then cooled to 350-450 ℃ at a cooling speed of 5-30 ℃/s, and curled to obtain a ferrite and bainite steel structure), wherein the yield strength of the plate blank reaches over 600MPa, the tensile strength reaches over 650MPa, the elongation reaches over 15 percent, and the impact power performance is not mentioned.
The invention provides a structural steel with 500MPa grade yield strength and a preparation method thereof, which is a patent document with the publication number of CN107964624A and the publication number of 2018, 4 and 27, and the patent document is named as 'the structural steel with 500MPa grade yield strength and the preparation method thereof', and the structural steel with 500MPa grade yield strength comprises the following chemical components in percentage by weight: c: 0.07-0.09%, Si: 0-0.1%, Mn: 1.5-1.7%, S is less than or equal to 0.005%, P is less than or equal to 0.015%, Nb: 0.03 to 0.05%, Ti: 0.03-0.05%, Mg: 0.0005 to 0.0030%, Al: 0.01-0.04%, N is less than or equal to 0.006%, the balance is Fe and inevitable impurities, the upper yield strength of the hot rolled steel plate is more than or equal to 500Mpa, the elongation after fracture is more than or equal to 19%, the impact energy performance is not mentioned, and the thickness specification is limited to 2-6 mm.
The invention discloses a patent document with publication number CN108411191A, publication number 2018, 8, 17 and name "a normalized rolling yield strength 500 MPa-grade H-shaped steel and a preparation method thereof", and discloses normalized rolling yield strength 500 MPa-grade H-shaped steel and a preparation method thereof, wherein the H-shaped steel comprises the following chemical components in percentage by weight: c: 0.07 to 0.10; si: less than or equal to 0.3; mn: 1.3 to 1.5; nb: 0.025-0.035; v: 0.05 to 0.09; ti: 0.015 to 0.025; ni: 0.35 to 0.7; p is less than or equal to 0.015; s is less than or equal to 0.01; n is less than or equal to 0.015; mo: 0.25 to 0.35; o is less than or equal to 0.004; n is less than or equal to 0.01, and the balance of Fe and inevitable impurities; the yield strength of the H-shaped steel is more than or equal to 530MPa, the tensile strength is more than or equal to 680MPa, the elongation is more than or equal to 18 percent, and the impact energy at minus 40 ℃ is more than or equal to 110J. According to the invention, the precious metal Mo with high content is added, the alloy cost is improved, and the alloy needs to enter a heat-insulating cover for heat insulation after finish rolling, so that the production energy consumption is increased, and the production efficiency is influenced.
Patent document CN105088068A, published on 2015, 11 and 25 and entitled "a 500MPa grade plated steel for automobile beam and its ultra-fast cooling production method", the chemical composition and wt% of the steel are: c: 0.06-0.09%, Si is less than or equal to 0.025%, Mn: 1.10-1.29%, P is less than or equal to 0.015%, S is less than or equal to 0.006%, Als: 0.020 to 0.060%, Nb: 0.025 to 0.034%. The invention adopts a design with lower alloy components, needs ultra-fast cooling and sectional cooling processes to meet the mechanical property after rolling, increases the production energy consumption, has high requirement on cooling control equipment, and does not mention the impact power property.
The steel is disclosed as CN105063509A, 11.18.2015, and is named as 'structural steel for bridges with 500MPa yield strength and a production method thereof', and the steel comprises the following chemical components in percentage by weight: c: 0.01 to 0.09%, Si: 0.10 to 0.40%, Mn: 0.80-2.10%, P is less than or equal to 0.018%, S is less than or equal to 0.005%, Cu is less than or equal to 0.40%, B is less than or equal to 0.0003%, and Ni: 0.10-0.55%, Mo: 0.10-0.30%, Cr: 0.15-0.60%, V: 0.040-0.080%, Nb: 0.010-0.035%, Ti: 0.005-0.035%, less than or equal to 0.060% of Als, and the balance of Fe and inevitable impurities. According to the invention, the high-content precious metal Mo is added, the alloy cost is improved, and after finish rolling, grading cooling control and tempering treatment are required, so that the production energy consumption is increased, and the production efficiency is influenced.
Disclosure of Invention
The invention aims to provide hot-rolled H-shaped steel with yield strength of 500MPa, yield strength of more than 500MPa, tensile strength of more than 600MPa, elongation of more than 20 percent and longitudinal V-shaped impact energy KV of-20 DEG C2The average value is more than 100J.
The invention also aims to provide a production method of the hot-rolled H-shaped steel with the yield strength of 500MPa, and the hot-rolled H-shaped steel with the excellent comprehensive mechanical property for the special vehicle frame longitudinal beam with the flange thickness of 10-30 mm and the yield strength of 500MPa is obtained through reasonable component proportion and rolling process, particularly through blank selection, reduction distribution and temperature-controlled rolling, and by utilizing a fine-grain strengthening mechanism, a precipitation strengthening mechanism, a phase-change strengthening mechanism and an air cooling process after rolling.
The specific technical scheme of the invention is as follows:
a hot-rolled H-shaped steel with 500 MPa-grade yield strength comprises the following elements in percentage by mass: c: 0.15 to 0.20%, Si: 0.25 to 0.40%, Mn: 1.25-1.50%, P: less than or equal to 0.025 percent, S: less than or equal to 0.015 percent, V: 0.06-0.08%, Nb: 0.020 to 0.030% of Fe and the balance of inevitable impurity elements.
The chemical components of the invention adopt the design idea of Nb + V, and combine with appropriate amount of elements such as C, Si, Mn and the like, considering the production cost, the total amount of Nb + V is strictly controlled to be less than or equal to 0.10%, and the content of each component is controlled as follows:
c: 0.15 to 0.20%, C is an essential element in steel and plays an important role in improving the strength of steel, and in order to obtain higher strength and reduce the difficulty of steel-making and decarburization, the lower limit is set to 0.15%, and when the content of C is too high, the plasticity, toughness and weldability of steel are seriously deteriorated, and the upper limit is set to 0.20%.
Si: 0.25-0.40%, Si with proper content can play a strong solid solution strengthening role, Si is also an important reduction and deoxidation element in the steelmaking process, in order to obtain higher strength, the lower limit value is set to be 0.25%, but the Si content cannot be too high, researches show that the high Si content can accelerate high-temperature stripping, reduce toughness and lamellar tearing resistance, and red iron oxide scales are easily generated on the surface of steel to influence the surface quality of products, and the upper limit value is set to be 0.40%.
Mn: 1.25-1.50%, Mn is used as a strengthening element in the steel, the strength and the hardenability of the steel can be improved, in order to ensure the strength of the steel, the lower limit value is set to be 1.25%, but the Mn content cannot be too high, so that the feasibility of casting blank segregation is obviously increased, the forming performance of the steel is adversely affected, and the upper limit value is set to be 1.50%.
P, S as impurity elements, which can adversely affect the plasticity, toughness and weldability of steel, should be strictly controlled, and in consideration of the difficulty of steel making control, the ratio of P: less than or equal to 0.025 percent, S: less than or equal to 0.015 percent.
V: 0.060 to 0.080%, V is a strong carbide forming element, V (C, N) dispersoid formed with C, N element does not have great effect on controlling austenite grain size, mainly plays a role of precipitation strengthening through precipitation during and after austenite-to-ferrite phase transformation, and in order to improve strength, the lower limit is set to 0.060%, but the content of V is too high, and the corresponding effect cannot be played beyond a certain value, and research shows that when the content of V exceeds 0.12%, the precipitation strengthening effect tends to be saturated, and the upper limit is set to 0.080% in consideration of production cost factors.
Nb: 0.020-0.030%, Nb is a strong carbon and nitrogen compound forming element, the strength of the steel is improved mainly by refining grains at high temperature, the dissolved Nb plays a role in dragging solute to the growth of austenite grains and preventing the austenite grains from growing, meanwhile, the undissolved Nb and C, N elements form Nb (C, N) compounds which can be obviously pinned at the austenite grain boundary, refine the austenite grains and refine the final product structure, in order to improve the strength and the plasticity of the steel, the lower limit value is set to be 0.020%, but the Nb content is too high, so that cracks are easily generated on the surface of a casting blank, the surface quality of the final product is influenced, and researches show that when the Nb content exceeds 0.04%, the strength is saturated, the grain refining effect tends to be unchanged, meanwhile, the higher Nb content is not beneficial to cost control, and the upper limit value is set to be 0.030%.
A production method of hot-rolled H-shaped steel with 500 MPa-level yield strength comprises the following production process steps: molten iron pretreatment → converter smelting → argon blowing refining → LF refining → full protection casting of a special-shaped blank or a rectangular blank → blank heating → rolling → air cooling after rolling.
The rolling comprises a rough rolling stage and a finish rolling stage.
In the production process, the selection of the blank is as follows: the compression ratio between the blank and the final product is 8-15; and after the rough rolling stage is finished, the compression ratio of the flange thickness of the blank to the flange thickness of the final product is 5-7.
The compression ratio between the blank and the final product is the ratio of the sectional area of the blank to the sectional area of the finished product, and the finished product is the final product.
The rolling process of the H-shaped steel comprises the following steps:
1) the casting blank enters a heating furnace, is heated to 1200-1250 ℃ by the heating furnace, and is kept warm for 20-30 min, so that the alloy elements are fully dissolved in solution, and overburning and excessive austenite grain coarsening are avoided;
2) the initial rolling temperature in the rough rolling stage is controlled to be 1150-1180 ℃, the final rolling temperature is controlled to be more than 1020 ℃, the compression ratio in the thickness direction of the flange in the rough rolling stage is controlled to be 5-10%, and the total compression ratio of the blank is controlled to be 40-50%. In the stage, within the austenite recrystallization temperature range, austenite grains are continuously refined through larger rolling deformation and repeated recrystallization of austenite, along with the addition of 0.020-0.030% of Nb alloy element, the solute dragging effect of solid solution Nb and the pinning effect of Nb (C, N) compounds further refine the austenite grains, and the excessive coarsening of austenite in a flange area under the micro-deformation condition is avoided, so that the ferrite grain size of a final product reaches over 9.0 grade.
3) The finish rolling adopts two-stage controlled rolling, the initial rolling temperature of the first stage is controlled at 980-1000 ℃, the finish rolling temperature is controlled at more than 960 ℃, the compression ratio of the flange in the thickness direction of the flange in the stage is 10-15%, and the total compression ratio of the blank is controlled at 45-55%. The stage is in the austenite partial recrystallization temperature range, and large deformation is avoided as much as possible, so that austenite grains are not uniform, and the performance of the final product is reduced. The initial rolling temperature of the second stage is controlled to be 920-940 ℃, the final rolling temperature is controlled to be 830-850 ℃, and the residual deformation in the thickness direction of the flange is in the current stageThe segment is complete. The phase is within the austenite non-recrystallization temperature range, the large deformation causes the austenite grains in the flange area to be elongated, a large amount of deformation zones, twin crystals and dislocation are formed, the nucleation point position is increased, meanwhile, enough kinetic energy is provided for pearlite phase transformation by strain storage energy caused by the large deformation, the addition of Nb and V alloy elements causes the C curve to move to the right, the nose tip temperature of pearlite transformation is moved upwards, the pearlite phase transformation temperature range is expanded, the pearlite transformation is further promoted, the pearlite proportion reaches 30% -40%, and the increase of the pearlite content is favorable for improving the strength. With the addition of 0.060-0.080 percent of V alloy element, the strength and toughness of the V (C, N) compound are further improved by the precipitation effect of the V alloy element, so that the yield strength of the final product is more than or equal to 500MPa, the tensile strength is more than or equal to 600MPa, and the elongation A is higher than50Not less than 20 percent and-20 ℃ longitudinal V-shaped impact energy KV2≥100J。
The hot-rolled H-shaped steel obtained by adopting the technical scheme has a structure of a ferrite and pearlite complex phase structure, the ferrite grain size grade is more than 9.0 grade, and the pearlite proportion reaches 30-40%; the yield strength is more than or equal to 500MPa, the tensile strength is more than or equal to 600MPa, and the elongation percentage A is50Not less than 20 percent and-20 ℃ longitudinal V-shaped impact energy KV2≥100J。
Compared with the prior art, the rolling process of the high-strength hot-rolled H-shaped steel with the yield strength of 500MPa adopts reasonable component proportion and rolling process under the condition of comprehensively considering the cost and the quality, particularly reasonable selection of blank compression ratio and distribution of rolling reduction, and is matched with a temperature-controlled rolling process; by utilizing mechanisms of fine grain strengthening, precipitation strengthening and phase change strengthening, a complex phase structure of ferrite and pearlite is obtained, the grain size grade of the ferrite is more than 9.0 grade, and the pearlite accounts for 30-40 percent; the H-shaped steel produced by the rolling process of the hot-rolled H-shaped steel with the yield strength of 500MPa is more than 500MPa, the tensile strength is more than 600MPa, the elongation is more than 20 percent, and the vertical V-shaped impact energy KV at the temperature of minus 20 ℃ is KV2The average value is more than 100J; the requirements of light, high-strength and high-quality hot-rolled H-shaped steel for the frame longitudinal beam of the special vehicle in the fields of road traffic, energy chemical engineering and the like are met. Moreover, the invention does not adopt the control of water penetration after rollingAnd cooling, so that the production process is simpler, the production energy consumption is low, and the production cost of each ton of steel can be reduced by about 10-20 yuan.
Drawings
FIG. 1 is a microstructure of H-shaped steel obtained in example 1, the microstructure is a ferrite + pearlite complex phase structure, the grain size grade is 10.5 grade, and the pearlite proportion reaches 33%;
FIG. 2 is a microstructure of the H-shaped steel obtained in example 2, the microstructure is a ferrite + pearlite complex phase structure, the grain size grade is 9.0 grade, and the pearlite proportion reaches 37%;
FIG. 3 is a microstructure of the H-shaped steel obtained in example 3, which is a complex phase structure of ferrite and pearlite, and has a grain size grade of 9.5 and a pearlite content of 31%.
Detailed Description
The following description of preferred embodiments and comparative examples will explain the present invention in further detail.
Example 1 to example 3
A hot-rolled H-shaped steel with 500 MPa-grade yield strength comprises the following elements in percentage by mass: see in particular table 1 below; the balance of Fe and inevitable impurity elements.
The production method of the hot-rolled H-shaped steel with the yield strength of 500MPa, which is disclosed by the embodiments 1 to 3, comprises the following process flows: molten iron pretreatment → converter smelting → argon blowing refining → LF refining → full protection casting of a special-shaped blank or a rectangular blank → blank heating → rolling → air cooling after rolling.
The rolling comprises a rough rolling stage and a finish rolling stage.
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) in the production process, the selection of the blank is as follows: the compression ratio (the ratio of the sectional area of the blank to the sectional area of the finished product) between the blank and the final product is 8-15; and after the rough rolling stage is finished, the compression ratio of the flange thickness of the blank to the flange thickness of the final product is 5-7.
5) The casting blank enters a heating furnace, is heated to 1200-1250 ℃ by the heating furnace, is kept warm for 20-30 min,
6) the initial rolling temperature in the rough rolling stage is controlled to be 1150-1180 ℃, the final rolling temperature is controlled to be more than 1020 ℃, the compression ratio in the thickness direction of the flange in the rough rolling stage is controlled to be 5-10%, and the total compression ratio of the blank is controlled to be 40-50%.
7) The finish rolling adopts two-stage controlled rolling, the initial rolling temperature of the first stage is controlled at 980-1000 ℃, the finish rolling temperature is controlled at more than 960 ℃, the compression ratio of the flange in the thickness direction of the flange in the stage is 10-15%, and the total compression ratio of the blank is controlled at 45-55%. The second stage is controlled to be at the initial rolling temperature of 920-940 ℃, the final rolling temperature of 830-850 ℃, and the rest deformation in the thickness direction of the flange is finished in the second stage.
8) And air cooling after rolling.
Examples 1-3 process parameters during the production of hot rolled H-section steel are controlled as in table 2 below.
Comparative examples 1 to 4
The hot-rolled H-shaped steel comprises the following elements in percentage by mass: see in particular table 1 below; the balance of Fe and inevitable impurity elements.
The production process steps of the hot-rolled H-shaped steel described in comparative examples 1 to 4 are the same as those of the examples of the present application, except that the parameters of each step are controlled, and the specific process parameters are as shown in the following Table 2.
Table 1 tabulation (wt%) of chemical compositions of inventive examples 1-3 and comparative examples 1-4,
the balance being Fe and unavoidable impurities
TABLE 2 List of the main process parameters of inventive examples 1-3 and comparative examples 1-4
The properties of the H-shaped steels produced in examples 1 to 3 and comparative examples 1 to 4 were measured as shown in Table 3.
TABLE 3 List of the performance test cases of inventive examples 1-3 and comparative examples 1-4
It should be noted that comparative examples 1 to 3 are the components of the steel of the present invention, and values are taken within the limited range, and the process adopts the prior art; comparative example 4 is a prior art composition and the process used the process of the present invention.
As can be seen from Table 3, the hot-rolled H-shaped steel obtained by the production process has a structure of a ferrite plus pearlite complex phase structure, the ferrite grain size grade is above 9.0 grade, and the pearlite proportion reaches 30-40%; the yield strength is more than or equal to 500MPa, the tensile strength is more than or equal to 600MPa, and the elongation percentage A is50Not less than 20 percent and-20 ℃ longitudinal V-shaped impact energy KV2≥100J。
Claims (6)
1. The hot-rolled H-shaped steel with the yield strength of 500MPa is characterized by comprising the following chemical components in percentage by mass: c: 0.15 to 0.20%, Si: 0.25 to 0.40%, Mn: 1.25-1.50%, P: less than or equal to 0.025 percent, S: less than or equal to 0.015 percent, V: 0.06-0.08%, Nb: 0.020 to 0.030 percent of Fe and inevitable impurity elements in balance;
the production method of the hot-rolled H-shaped steel with the yield strength of 500MPa comprises the following process steps: molten iron pretreatment → converter smelting → argon blowing refining → LF refining → special-shaped blank or rectangular blank full-protection casting → blank heating → rolling → air cooling after rolling;
the rolling comprises a rough rolling stage and a finish rolling stage;
the finish rolling adopts two-stage controlled rolling, the initial rolling temperature of the first stage of the finish rolling is controlled to be 980-1000 ℃, and the final rolling temperature is controlled to be above 960 ℃;
the compression ratio of the flange in the thickness direction of the first stage of finish rolling is 10-15%, the initial rolling temperature of the second stage of finish rolling is controlled to be 920-940 ℃, and the final rolling temperature is controlled to be 830-850 ℃;
the hot-rolled H-shaped steel with the yield strength of 500MPa is a complex phase structure of ferrite and pearlite, the ferrite grain size grade is more than 9.0 grade, the pearlite proportion reaches 30-40%, the hot-rolled H-shaped steel with the yield strength of 500MPa is not less than 500MPa, and the tensile strength is not less than 600 MPa.
2. The hot-rolled H-shaped steel with 500MPa grade yield strength according to claim 1, characterized in that the total amount of Nb + V is less than or equal to 0.10 percent.
3. The hot-rolled H-shaped steel with the yield strength of 500MPa according to claim 1, wherein in the production process, the shape selection of the blank is as follows: the compression ratio between the blank and the final product is 8-15; and after the rough rolling stage is finished, the compression ratio of the flange thickness of the blank to the flange thickness of the final product is 5-7.
4. The hot-rolled H-shaped steel with a yield strength of 500MPa according to claim 1 or 3, wherein the blank heating comprises: and (3) feeding the casting blank into a heating furnace, heating to 1200-1250 ℃ by the heating furnace, and preserving heat for 20-30 min.
5. The hot-rolled H-shaped steel with the yield strength of 500MPa according to claim 1 or 3, 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 1020 ℃.
6. The hot-rolled H-shaped steel with the yield strength of 500MPa according to claim 1 or 3, wherein the compression ratio of the flange in the thickness direction in the rough rolling stage is controlled to be 5-10%, and the total compression ratio of the blank is controlled to be 40-50%.
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| CN113528970B (en) * | 2021-07-20 | 2022-05-24 | 马鞍山钢铁股份有限公司 | Low-compression-ratio yield strength 355 MPa-grade heavy hot-rolled H-shaped steel and production method and application thereof |
| CN113604746B (en) * | 2021-08-12 | 2023-03-28 | 马鞍山钢铁股份有限公司 | High-temperature-resistant hot-rolled H-shaped steel and production method thereof |
| CN115679181B (en) * | 2022-08-31 | 2023-12-19 | 马鞍山钢铁股份有限公司 | Hot rolled angle steel with yield strength of 420MPa and minus 20 ℃ resistance and production method thereof |
| CN115821154B (en) * | 2022-09-07 | 2023-12-01 | 马鞍山钢铁股份有限公司 | Super-thick hot-rolled H-shaped steel with good Z-direction performance and production method thereof |
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