CN111748744B - Hot-rolled H-shaped steel and production method thereof - Google Patents

Hot-rolled H-shaped steel and production method thereof Download PDF

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CN111748744B
CN111748744B CN202010649420.8A CN202010649420A CN111748744B CN 111748744 B CN111748744 B CN 111748744B CN 202010649420 A CN202010649420 A CN 202010649420A CN 111748744 B CN111748744 B CN 111748744B
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flange
web
rolled
hot
yield strength
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CN111748744A (en
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夏勐
邢军
汪杰
陈辉
黄琦
丁朝晖
彭林
何军委
沈千成
彦井成
吴保桥
吴湄庄
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Maanshan Iron and Steel Co Ltd
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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
    • 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
    • C21D11/00—Process control or regulation for heat treatments
    • 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
    • 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
    • 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
    • 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
    • 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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  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Heat Treatment Of Steel (AREA)
  • Metal Rolling (AREA)

Abstract

The invention discloses hot-rolled H-shaped steel and a production method thereof, belonging to the field of metal material production. The invention relates to hot-rolled H-shaped steel, which comprises the following chemical components in percentage by mass: 0.09-0.19, Si: 0.15 to 0.40, Mn: 1.20-1.60, V: 0.040-0.120, N: 0.0060-0.0200, P: 0.025 or less, S: less than or equal to 0.015, and the balance of Fe and trace residual elements, wherein the CEV is less than or equal to 0.46 calculated according to the CEV which is C + Mn/6+ (Cr + Mo + V)/5+ (Ni + Cu)/15. The invention overcomes the problems that the yield strength difference of flanges and webs of H-shaped steel is large and the use safety is influenced in the prior art, and provides hot-rolled H-shaped steel and a production method thereof.

Description

Hot-rolled H-shaped steel and production method thereof
Technical Field
The invention relates to the technical field of metal material production, in particular to hot-rolled H-shaped steel and a production method thereof.
Background
In order to meet the pass rolling requirement of hot-rolled H-shaped steel, the deformation temperature and the reduction distribution of the flange and the web are different in the hot rolling stage, so that the mechanical properties of the flange and the web are different. Practice shows that for hot-rolled H-shaped steel with yield strength of 355-460 MPa, the flange is generally 13-36 MPa lower than the web in terms of yield strength, and the difference is more obvious when the strength level is higher and the thickness of the flange is larger. However, as an important support for structures such as buildings, machines, towers, etc., from the viewpoint of safety and applicability, the yield strength difference between the flanges and the webs of the hot-rolled H-section steel should be as small as possible, and it is desirable to control the yield strength to be not higher than 10 MPa.
According to the search, in patent document CN103056175B, a nozzle is additionally arranged on a rolling centering device, water is sprayed to a flange high-temperature area for cooling in the rolling process, the temperature difference between the surface of the flange and the thickness direction is reduced, the strength index is improved by refining the structure, and the yield strength difference in the thickness direction of the flange is reduced. By adopting the method, although the difference of the yield strength between the flange and the web can be reduced to a certain extent by improving the strength of the flange, the investment is large and the maintenance is difficult because water spray cooling equipment needs to be added on the movable part, the water spray process parameters need to be monitored in the biting stage, and the control is complex. In addition, the flange cooling also reduces the temperature of the web, and the yield strength difference between the two is maintained to be more than 15 MPa.
According to patent documents CN109576570A, CN109338040A and CN108642381B, the purpose of controlling the fluctuation of the yield strength is achieved by adopting component proportion optimization and controlled rolling and controlled cooling processes. However, the methods do not adopt a measure for reducing the yield strength difference between the flange and the web, the yield strength difference between the flange and the web is still large, and the difference between the flange and the web is even further enlarged by partial processes.
At present, a mode for effectively controlling the yield strength difference between the flange and the web of the hot-rolled H-shaped steel is lacked in the industry.
Disclosure of Invention
1. Technical problem to be solved by the invention
The invention aims to solve the problems that the yield strength difference between flanges and webs of hot-rolled H-shaped steel is large and the use safety is influenced in the prior art, and provides the hot-rolled H-shaped steel and the production method thereof.
2. Technical scheme
In order to achieve the purpose, the technical scheme provided by the invention is as follows:
the invention relates to hot-rolled H-shaped steel, which comprises the following chemical components in percentage by mass: 0.09-0.19, Si: 0.15 to 0.40, Mn: 1.20-1.60, V: 0.040-0.120, N: 0.0060-0.0200, P: 0.025 or less, S: less than or equal to 0.015, and the balance of Fe and trace residual elements, wherein the CEV is less than or equal to 0.46 calculated according to the CEV which is C + Mn/6+ (Cr + Mo + V)/5+ (Ni + Cu)/15.
Researches show that the structure strengthening, the solid solution strengthening, the precipitation strengthening and the fine grain strengthening all contribute to improving the yield strength. For each reinforcement mode, the yield strength is increased by Δ O, Δ S, Δ P, and Δ F, and subscripts "F" or "W" are added to the right side of the reference symbols to distinguish the flanges from the webs, that is, the yield strength of the flanges is Δ OF+△SF+△PF+△FFYield strength of web ═ Δ OW+△SW+△PW+△FWHereinafter, the same contents are represented by the symbols.
For the same hot rolled H-shaped steel product, the flange or the web is not separately cooled at a speed of 10 ℃/s or more, and the content difference of each component in the room-temperature microstructures of the two rolled products is smallThe contribution of the structure strengthening is consistent, and it can be considered that Δ OF＝△OW. When the C, Mn element is controlled to a certain range, the elements such as Cr, Cu, and Ti are not added, and the quenching treatment is not performed on the flange or the web separately, the contribution of the solid solution strengthening of the both is the same, and Δ S can be considered to beF＝△SW. The yield strength difference between the flanges and the web is therefore mainly due to the difference between Δ P and Δ F. Generally, Δ PF+△FFBelow Δ PW+△FWI.e. the flanges have a lower yield strength than the webs.
The general idea of the invention is as follows: based on the fact that the flange of the hot-rolled H-shaped steel has no deformation in the thickness direction in the cogging rolling stage and the total reduction of the web in the thickness direction is large, the delta O and the delta S of the flange of the hot-rolled H-shaped steel are ensured to be the same through component proportion optimization, reduction distribution adjustment, rolling temperature limitation and the like; the flange adopts the measure of inducing secondary phase precipitation in an austenite non-recrystallization region under high pressure, the precipitation strengthening effect is highlighted, and high delta P is formedF+ Low Δ FFThe state of (1); the method adopts the measures of austenite complete recrystallization area under high pressure and inhibiting secondary phase precipitation to the web plate, so as to highlight the fine grain strengthening effect and form low delta PW+ high Δ FWThe state of (1); the yield strength difference between the flange and the web is reduced by adjusting the contribution of the flange and the web to the yield strength improvement in the aspects of precipitation strengthening and fine grain strengthening.
Specifically, the functions and the component proportions (by mass percent) of each element in the invention are as follows:
carbon (C): the effect is to improve the strength, and the lower limit of the content is controlled to be 0.09 to obtain the effect. The research of the invention finds that if the content exceeds 0.19, the precipitated phase is coarsened, the precipitation strengthening effect is reduced, the function of delta P in contribution and adjustment is limited, the sensitivity of solid solubility to the process is enhanced, the large difference of solid solution strengthening functions of flanges and webs is caused, and delta S is causedFAnd Δ SWIn contrast, the base of the strength contribution formulation is damaged, and the toughness is damaged, so the upper limit of the content is controlled to be 0.19 in the invention.
Silicon (Si): the strength is improved, the steel-making deoxidizing element is also used, the molten steel fluidity during continuous casting is improved, and the lower limit of the content is controlled to be 0.15 to obtain the effect. According to the research of the invention, if the content exceeds 0.40, the effect of improving the strength is saturated, and impurities distributed along the intermediate layer of the furnace-growing iron oxide scale are easily formed with Fe element in the heating stage, so that the water spraying descaling effect is reduced, and the surface quality after rolling is damaged, therefore, the upper limit of the content is controlled to be 0.40.
Manganese (Mn): the strength is improved, the toughness is improved, the structure is refined to a certain degree, and in order to obtain the effect, the lower limit of the content is controlled to be 1.20. The research of the invention finds that if the content exceeds 1.60, excessive pearlite or bainite is formed, the sensitivity of the component content to the process is enhanced, the pearlite or bainite content of the flange is obviously less than that of the web, and the result is delta OFAnd Delta OWThe large difference is generated, the base of strength contribution and blending is damaged, macro composition segregation is easy to form, the continuity of the matrix is damaged, and the toughness is damaged, so the upper limit of the control content in the invention is 1.60.
Vanadium (V): the strength is improved, the strength is a core element contributing to the strengthening effect of the adjustment flange and the web, the precipitation strengthening effect of the flange needs to reach a critical value, and in order to obtain the effect, the lower limit of the content is controlled to be 0.040. According to the research of the invention, if the content exceeds 0.120, the precipitation strengthening effect is saturated, the precipitation is also coarsened seriously, the effect of delta P in the strength contribution and adjustment is limited, cracks are easy to generate at the junction of large particles and a matrix, cracks on the surface of an end part or an inner fillet are easy to generate in the blank straightening and pulling process, the plasticity and the toughness are damaged, and the surface quality after rolling is influenced, so that the upper limit of the content is controlled to be 0.120 in the invention.
Nitrogen (N): the synergistic element for promoting the separation of the V element is a core element contributing to the blending strength, the separation degree of the V element is increased along with the increase of the content of the N element, and the lower limit of the content is controlled to be 0.0060 in order to fully promote the separation of the flange. The research of the invention finds that if the content exceeds 0.020, the precipitation promoting effect is saturated, the precipitation amount of a web plate is increased, and the low delta P is damagedW+ high Δ FWThe state (2) is not beneficial to the strength contribution and the adjustment, island martensite is easily formed, and the plasticity and the toughness are damaged, so the content is controlled in the inventionThe upper limit is 0.020.
Phosphorus (P): impurity elements are easy to solidify, segregate and enrich, damage plasticity and toughness and have adverse effects on weldability, so the upper limit of the control content is 0.025 in the invention.
Sulfur (S): the impurity elements are rolled to form long-strip-shaped inclusions, the atomic arrangement of a contact surface is disordered, the energy is high, cracks are easy to generate, and the plasticity and the toughness are damaged, so the upper limit of the control content is 0.015.
Carbon Equivalent (CEV): carbon equivalent is a reference index for evaluating the weldability of a product. With the increase of carbon equivalent, the preparation work before welding is complicated, and the cold cracking sensitivity after welding is increased. According to the regulation of the standard GB/T1591, the applicability of the product application is fully considered in the component design, so the upper control limit in the invention is 0.46.
Further, the chemical components are calculated according to mass percent, C: 0.09-0.13, Si: 0.15 to 0.35, Mn: 1.20 to 1.50, V: 0.040 to 0.100, N: 0.0060-0.0120, P: 0.025 or less, S: less than or equal to 0.015, and the balance of Fe and trace residual elements, wherein the CEV is less than or equal to 0.38 calculated according to the CEV which is C + Mn/6+ (Cr + Mo + V)/5+ (Ni + Cu)/15.
Further, the chemical components are calculated according to mass percent, C: 0.13 to 0.19, Si: 0.20 to 0.40, Mn: 1.30-1.60, V: 0.060 to 0.120, N: 0.0080-0.0200, P: 0.025 or less, S: less than or equal to 0.015, and the balance of Fe and trace residual elements, wherein the CEV is less than or equal to 0.46 calculated according to the CEV which is C + Mn/6+ (Cr + Mo + V)/5+ (Ni + Cu)/15.
Further, the flanges and webs in the same cross section are longitudinally sampled with the width from the end 1/6 and the height from the end 1/4 as axes, respectively, as shown in fig. 1, the room temperature microstructure includes 60% to 90% ferrite by area percentage, and the remaining structure is pearlite or/and bainite, i.e., pearlite and bainite exist simultaneously or separately; the grain size grades of ferrite of the flange and the web are 7.0-11.0 and 8.5-13.0 respectively, and the grain size grade of the web is 1.5-3.0 higher than that of the flange; the secondary phase precipitation density of the flange is not less than 600/mm2The secondary phase precipitation density of the web plate is not higher than 80/mm2。
In particular toIn addition, the hot-rolled H-shaped steel of the invention relates to a product with yield strength of 355 MPa-460 MPa, wherein the ferrite content of the product with yield strength of 355 MPa-460 MPa is 60% -90%, the higher the strength grade is, the lower the ferrite content is, and the pearlite or bainite content is increased. The research of the invention finds that if the ferrite content is lower than 60%, excessive pearlite or bainite is formed, the sensitivity of the component content to the process is enhanced, so that the pearlite or bainite content of the flange is obviously less than that of the web, and delta O is causedFAnd Delta OWLarge gaps occur, and the strength contribution allocation foundation is damaged. Therefore, the invention finally controls the lower limit of the ferrite content in the product to be 60% by adjusting the processing technology and the component content. If the ferrite content is higher than 90%, the fine-grain strengthening contribution of the web is obviously strong and the precipitation strengthening of the flange is caused, so that the delta P is causedW+△FWWell above Δ PF+△FFThe difference between the yield strengths of the two is increased. Therefore, the upper limit of the content of the final control product is 90 percent.
The research of the invention finds that if the grain size grade of flange ferrite is lower than 7.0, the indexes of strength, plasticity and toughness are poorer, and the product loses the use value. Therefore, the lower limit of the grain size grade of the flange ferrite in the final control product is 7.0. Because the flange basically has no deformation in the thickness direction in the cogging stage, the deformation refinement grain degree is limited in the universal rolling stage, and the ferrite grain size grade cannot exceed 11.0. Therefore, the upper limit of the grain size grade of the flange ferrite in the final control product is 11.0.
According to the research of the invention, if the ferrite grain size grade of the web is lower than 8.5, the delta F cannot be causedWAnd Δ FFForming effective gap, reducing the effect of fine grain strengthening in the strength contribution preparation, and being not beneficial to the strength contribution preparation. Therefore, the lower limit of the ferrite grain size grade of the web plate in the final control product is 8.5. If the grain size grade exceeds 13.0, Δ FWWell above Δ FFThe difference between the yield strengths of the two is increased. Therefore, the upper limit of the ferrite grain size grade of the web plate in the final control product is 13.0.
The research of the invention finds that the iron of the web plateThe grain size grade of the element body is higher than that of the flange by less than 1.5 or more than 3.0, the fine grain strengthening effect of the flange is insufficient, or the strengthening effect is ultrahigh, the contribution degree to the yield strength improvement does not fall in a reasonable interval, and the delta P is causedW+△FWAnd Δ PF+△FFThe difference in (a) increases. The difference between the ferrite grain size grade of the web plate in the final control product and the flange grade is 1.5 at the lower limit and 3.0 at the upper limit.
The research of the invention finds that the secondary phase precipitation density of the flange is lower than 600/mm2If the precipitation quantity is insufficient, the dispersion distribution is insufficient, the precipitation strengthening effect is reduced, and the high Delta P cannot be formedF+ Low Δ FFStatus. The lower limit of the secondary phase precipitation density of the flange in the final control product is 600/mm2. Because of the restriction of the content of V, N, C elements and the like, the precipitation density of the secondary phase is not higher than 2000/mm2Even if a special case exceeding this limit occurs, adjacent precipitates are attracted to each other by too close distance, and the density is lowered.
The research of the invention shows that the secondary phase precipitation density of the web plate is higher than 80/mm2Then reduce Δ PFAnd Δ PWThe difference of (A) is not favorable for contribution of blending, even high-delta P is formedW+ high Δ FWThe condition, in turn, increases the yield strength difference between the flanges and the web. The upper limit of the secondary phase precipitation density of the web plate in the final control product is 80/mm2。
Furthermore, the flanges and the webs in the same cross section are respectively sampled along the longitudinal direction by taking the width from the end 1/6 and the height from the end 1/4 as axes, the room-temperature microstructure comprises 80 to 90 percent of ferrite in percentage by area, and the rest structure is pearlite; the grain size grades of ferrite of the flange and the web are 7.0-10.0 and 8.5-12.0 respectively, and the grain size grade of the web is 1.5-2.0 higher than that of the flange; the secondary phase precipitation density of the flange is 800/mm21100/mm2The secondary phase precipitation density of the web is 10/mm240 pieces/mm2。
Further, the flanges and webs in the same cross-sectionThe plate is longitudinally sampled by taking the width from the end 1/6 and the height from the end 1/4 as axes respectively, the room-temperature microstructure comprises 60-70 percent of ferrite by area percentage, and the rest structure is pearlite or/and bainite; wherein the grain size grades of ferrite of the flange and the web are respectively 8.5-11.0 and 10.0-13.0, and the grain size grade of the web is 2.0-2.5 higher than that of the flange; the secondary phase precipitation density of the flange is 1100/mm21800 pieces/mm2The secondary phase precipitation density of the web is 40/mm270 pieces/mm2。
Furthermore, the hot-rolled H-section steel of the invention relates to a product with yield strength of 355 MPa-460 MPa, according to the standard GB/T2975, the flange is sampled longitudinally with the width from the end 1/6 as an axis, and the web is sampled longitudinally with the height from the end 1/4 as an axis; carrying out a room temperature tensile test according to the specification of a standard GB/T228.1, and carrying out a low temperature impact test according to the specification of a standard GB/T229; wherein for a product with yield strength of 355MPa, the flange yield strength is not lower than 355MPa, the tensile strength is not lower than 470MPa, the yield ratio is not higher than 0.80, the elongation after fracture is not lower than 25.0 percent, and the impact power value at-20 ℃ is not lower than 80J; for a product with the yield strength of 460MPa, the flange yield strength is not lower than 460MPa, the tensile strength is not lower than 540MPa, the yield ratio is not higher than 0.80, the elongation after fracture is not lower than 20.0 percent, and the impact power value at-20 ℃ is not lower than 80J; for the products with yield strength of 355 MPa-460 MPa, the actual yield strength difference between the flange and the web plate is not more than 10 MPa.
The invention relates to a production method of hot-rolled H-shaped steel, which comprises the working procedures of molten iron pretreatment → converter smelting → argon blowing refining → external refining → beam blank continuous casting → blank heating → cogging rolling → universal rolling, wherein the working procedures of molten iron pretreatment, converter smelting, argon blowing refining, external refining and beam blank continuous casting in a steel area can be produced according to the conventional method known in the industry at present, so that qualified beam blanks meeting the chemical composition requirements of the invention can be ensured, and the invention needs to be noted that the invention adopts beam blank rolling, the heating temperature is 1150-1300 ℃ in the blank heating stage, and the heating time is not less than 120 min. Further optionally, the heating temperature is 1150-1250 ℃, and the heating time is 144-173 min; further optionally, the heating temperature is 1250-1300 ℃, and the heating time is 124-148 min.
The blank is heated mainly to ensure that alloy elements are fully dissolved and homogenized and reduce the rolling deformation resistance. If the temperature is lower than 1150 ℃, the solid solution and homogenization of alloy elements are insufficient, the tissue homogenization degree is also insufficient, and the comprehensive mechanical property of the rolled product is influenced. Therefore, the lower limit of the control temperature in the present invention is 1100 ℃. If the temperature exceeds 1300 ℃, the original crystal grain size is excessively increased, which is disadvantageous to the later-stage dispersion distribution of precipitates and is liable to cause surface cracks by overburning. Therefore, the upper limit of the temperature is 1300 ℃ in the present invention.
Similarly, if the heating time is less than 120min, the core of the ingot cannot be burned through, and the alloying elements in this region cannot be dissolved and homogenized sufficiently. Therefore, the lower limit of the control time in the present invention is 120 min. In view of reducing oxidation burning loss and reducing heating energy consumption, it is not suitable to exceed 180 min.
Furthermore, in the cogging rolling stage, the accumulated reduction rate of the web in the thickness direction is not lower than 50%, and the final rolling temperature of the web is not lower than 980 ℃; preferably, in the cogging rolling stage, the accumulated reduction rate of the web in the thickness direction is controlled to be 50-65%, and the final rolling temperature of the web is controlled to be 985-1010 ℃; more preferably, in the cogging rolling stage, the accumulated reduction rate of the web in the thickness direction is controlled to be 55-65%, and the final rolling temperature of the web is controlled to be 990-1000 ℃.
Cogging and rolling, which is mainly to shape a special-shaped blank so as to obtain a blank shape suitable for universal rolling deformation. The step is two-roller special-shaped hole rolling, the deformation amount in the thickness direction of the flange is small and can be ignored, and the compression deformation is only carried out in the thickness direction of the web. The invention controls and limits the reduction rate and the finish rolling temperature of the web plate, and aims to implement large deformation above the austenite complete recrystallization critical temperature, fully refine austenite grains and be beneficial to finally forming a composite strengthening action combination mainly based on fine grain strengthening.
The research of the invention finds that if the accumulated reduction rate of the web in the thickness direction is lower than 50 percent, the deformation energy storage for promoting the complete dynamic recrystallization of austenite is insufficient, and the dynamic state is realizedInsufficient crystallization leads to insufficient refinement of austenite grains or abnormal growth of austenite grains, and the Delta F cannot be causedWAnd Δ FFForming effective gap, reducing the function of fine crystal strengthening in the strength contribution and preparation, and damaging the plasticity and the toughness. Therefore, the lower limit of the accumulated reduction rate of the web in the thickness direction is controlled to 50% in the present invention. Considering the requirement of coordinated deformation of the subsequent flanges and the web in the universal rolling stage, the accumulated reduction rate in the stage is not higher than 65%.
If the finishing temperature of the web is lower than 980 ℃, the thermal activation energy for promoting complete dynamic recrystallization of austenite is insufficient, the dynamic crystallization is insufficient, and the influence is particularly obvious when the cumulative reduction rate is only 50-65%. Therefore, the lower limit of the finishing temperature of the control web plate is 980 ℃. In order to avoid excessive growth of austenite grains at the flange part in a high-temperature deformation-free stage and damage the dispersion precipitation effect of a final secondary phase, the final rolling temperature of the web is not more than 1010 ℃ by combining the actual condition that the temperature of the flange is higher than that of the web by more than 100 ℃ in the cogging rolling stage.
Furthermore, in the universal rolling stage, the accumulated reduction rate of the flange in the thickness direction is not lower than 50%, and the final rolling temperature of the flange is controlled to be 800-850 ℃. Preferably, in the universal rolling stage, the accumulated reduction rate in the thickness direction of the flange is controlled to be 55-75%, and the final rolling temperature of the flange is controlled to be 810-840 ℃. More preferably, in the universal rolling stage, the accumulated reduction rate in the thickness direction of the flange is controlled to be 60-70%, and the final rolling temperature of the flange is controlled to be 815-830 ℃.
And (4) universal rolling, which is mainly used for simultaneously performing compression deformation on the flange and the web in the thickness direction to obtain the final shape and size of a finished product. The method controls and limits the reduction rate and the finish rolling temperature of the flange, and aims to implement large deformation below the austenite non-recrystallization critical temperature, obtain enough strain accumulation, fully induce secondary phase to be precipitated in a universal stage, control the air cooling initial temperature within a certain range, improve the precipitation dispersion distribution effect and be beneficial to finally forming a composite strengthening action combination based on precipitation strengthening. Meanwhile, the condition that the temperature of the web is lower than that of the flange is utilized, the element diffusion driving force of the web is reduced, secondary phase precipitation is planned, and the increase of the difference of the mechanical properties of the web and the flange is avoided.
The research of the invention finds that if the accumulated reduction rate in the thickness direction of the flange is lower than 50 percent, the strain accumulation of the austenite non-recrystallization zone is insufficient, the quantity of the secondary phases induced to be precipitated is insufficient, the distribution is concentrated, and the delta P cannot be causedFAnd Δ PWForming effective gap, reducing the function of precipitation strengthening in the strength contribution and allocation. Therefore, the lower limit of the accumulated reduction rate in the thickness direction of the flange is controlled to be 50 percent. The cumulative reduction at this stage does not exceed 80% considering the limit of the original size of the billet.
The research of the invention finds that if the flange finish rolling temperature is lower than 800 ℃, the atomic diffusion required by secondary phase precipitation at the flange is insufficient, the precipitation quantity is insufficient, and the precipitation strengthening effect is reduced. Therefore, the lower limit of the final rolling temperature of the flange is controlled to be 800 ℃. If the finishing rolling temperature is higher than 850 ℃, the secondary terms are easy to gather and coarsen after being separated out, cannot form dispersion distribution, and also reduces the precipitation strengthening effect. In addition, the practical situation that the temperature of the flange is higher than that of the web by more than 80 ℃ in the universal rolling stage is considered, when the temperature of the flange is higher than 850 ℃, the temperature of the web is higher than 770 ℃, a certain amount of secondary phases are induced to be precipitated by a small amount of deformation, so that the web obtains stronger fine-grain strengthening and precipitation strengthening effects at the same time, and the flange only has stronger precipitation strengthening effect, so that delta P is causedW+△FWWell above Δ PF+△FFThe difference between the yield strengths of the two is enlarged. Therefore, the upper limit of the final rolling temperature of the flange is controlled to be 850 ℃.
Furthermore, after the universal rolling stage, rapid cooling is not carried out; or only water mist with the cooling speed lower than 6 ℃/s is adopted for auxiliary cooling.
It should be noted that, the present inventors found that, if the flange or web is rapidly cooled at a speed of 10 ℃/s or more after the universal rolling stage, excessive bainite or martensite is formed, the sensitivity of the component content and solid solution content to the process is greatly enhanced, and Δ O is causedFAnd Delta OWAnd Δ SFAnd Δ SWThe difference is obviously increased, and the strength contribution allocation base is damaged. In addition, because the flanges and the web are taken as a whole, the rapid cooling process is adopted,it is not possible to obtain a uniform cooling rate over the entire cross-section, further exacerbating the mechanical property gap between the different zones. However, a water mist auxiliary cooling measure with a cooling speed lower than 6 ℃/s is adopted to further plan the coarsening of the flange secondary phase or the precipitation of the web secondary phase, and is a conceivable option. Therefore, after universal finish rolling, the invention does not adopt any other rapid cooling process except water mist auxiliary cooling.
The thickness range of the flange of the hot-rolled H-shaped steel finished product finally processed by the method is 10-50 mm. In this case, the web thickness ranges from 8mm to 35 mm. The research of the invention finds that if the thickness of the flange is less than 10mm, the total reduction of the flange and the web is very large, the strength contribution ratio of delta F is far greater than delta P, so that the adjustment effect of the latter is reduced, the yield strength difference between the flange and the web cannot be effectively reduced, and the flange thickness of 10mm is the minimum thickness required by a common steel structure. Therefore, the lower limit of the thickness of the flange is controlled to be 10mm in the invention. If the thickness of the flange is higher than 50mm, the deformation and penetration depth of the flange in the universal rolling stage is limited, so that the strain accumulation required by the core part to induce secondary phase precipitation is insufficient, the air cooling initial cooling temperature is far beyond 850 ℃, precipitates are easy to aggregate and coarsen, and the precipitation strengthening effect is greatly reduced. Therefore, the upper limit of the thickness of the flange is controlled to be 50mm in the invention.
According to the technical characteristics of the specification of the hot-rolled H-shaped steel, the thickness of the web is preferably controlled to be 8-35 mm when the thickness of the flange is 10-50 mm from the aspects of structural stability and production realizability.
3. Advantageous effects
Compared with the prior art, the technical scheme provided by the invention has the following beneficial effects:
(1) the production method of the hot-rolled H-shaped steel is based on the fact that deformation conditions of flanges and webs are different, and by optimizing component proportion, adjusting reduction distribution and limiting rolling temperature, the contribution of the components to yield strength improvement in the aspects of precipitation strengthening and fine grain strengthening is adjusted, the products with the flange thickness of 10-50 mm and the yield strength of 355-460 MPa are guaranteed, the difference value of the actual yield strength of the flanges and the webs does not exceed 10MPa, and ideal requirements of most steel structures on the safety and the applicability of supporting parts are met.
Drawings
FIG. 1 is a schematic view showing the cross-sectional marking and sampling positions of hot rolled H-section steel in the present invention, wherein B denotes the width of the H-section steel, H denotes the height of the H-section steel, t1 denotes the thickness of the web, and t2 denotes the thickness of the flange.
Detailed Description
For a further understanding of the invention, reference should be made to the following detailed description taken in conjunction with the accompanying drawings.
In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience of description and simplicity of description, but do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
The present invention will be further described with reference to the following examples.
Example 1
The chemical composition of a hot-rolled H-section steel of this example is shown in Table 1 as example 1 in terms of mass%.
The production method of the hot-rolled H-shaped steel of the embodiment includes the steps of molten iron pretreatment → converter smelting → argon blowing refining → external refining → beam blank continuous casting → blank heating → cogging rolling → universal rolling, wherein the steps of molten iron pretreatment → converter smelting → argon blowing refining → external refining → beam blank continuous casting are all processed by using the conventional technology in the industry, and it is to be noted that in the step of heating the blank, the heating temperature is 1256 ℃, and the heating time is 124 min. In the cogging rolling stage, the accumulated reduction rate of the web in the thickness direction is 50%, and the final rolling temperature of the web is 1010 ℃; in the universal rolling stage, the accumulated reduction rate of the flange in the thickness direction is 75%, and the final rolling temperature of the flange is controlled at 850 ℃. After the universal rolling stage, rapid cooling is not carried out; or only water mist with the cooling speed lower than 6 ℃/s is adopted for auxiliary cooling. Specific process parameters are specifically shown in example 1 in table 2.
The hot-rolled H-shaped steel with the flange thickness of 10 mm-50 mm produced by the method of the embodiment can meet the product requirement of 355 MPa-460 MPa yield strength. Specific microstructure conditions are shown in table 3.
As shown in FIG. 1, according to the standard GB/T2975, it is provided that the flange is sampled longitudinally, with the axis of width from end 1/6, and the web is sampled longitudinally, with the axis of height from end 1/4; carrying out a room temperature tensile test according to the specification of a standard GB/T228.1, and carrying out a low temperature impact test according to the specification of a standard GB/T229; for a product with yield strength of 355MPa, the flange yield strength is not lower than 355MPa, the tensile strength is not lower than 470MPa, the yield ratio is not higher than 0.80, the elongation after fracture is not lower than 25.0 percent, and the impact power value at-20 ℃ is not lower than 80J; for a product with the yield strength of 460MPa, the flange yield strength is not lower than 460MPa, the tensile strength is not lower than 540MPa, the yield ratio is not higher than 0.80, the elongation after fracture is not lower than 20.0 percent, and the impact power value at-20 ℃ is not lower than 80J; for products with yield strength of 355 MPa-460 MPa, the actual yield strength difference between the flange and the web plate is not more than 10MPa, and the ideal requirements of most steel structures on the safety and the applicability of the support are met. The specific mechanical properties are shown in Table 4.
Example 2
A hot rolled H-section steel of this example was substantially the same as example 1 except that the chemical composition of the hot rolled H-section steel was slightly different in this example as shown in Table 1.
The production method of the hot-rolled H-shaped steel of this example is basically the same as that of example 1, except that the specific process parameters in this example are slightly different, as shown in Table 2.
In the hot-rolled H-shaped steel processed by the embodiment, the flanges and the webs in the same cross section are respectively sampled along the longitudinal direction by taking the width from the end 1/6 and the height from the end 1/4 as axes, and the condition of the room-temperature microstructure is specifically shown in Table 3; the specific mechanical properties are shown in Table 4.
Example 3
A hot rolled H-section steel of this example was substantially the same as example 1 except that the chemical composition of the hot rolled H-section steel was slightly different in this example as shown in Table 1.
The production method of the hot-rolled H-shaped steel of this example is basically the same as that of example 1, except that the specific process parameters in this example are slightly different, as shown in Table 2.
In the hot-rolled H-shaped steel processed by the embodiment, the flanges and the webs in the same cross section are respectively sampled along the longitudinal direction by taking the width from the end 1/6 and the height from the end 1/4 as axes, and the condition of the room-temperature microstructure is specifically shown in Table 3; the specific mechanical properties are shown in Table 4.
Example 4
A hot rolled H-section steel of this example was substantially the same as example 1 except that the chemical composition of the hot rolled H-section steel was slightly different in this example as shown in Table 1.
The production method of the hot-rolled H-shaped steel of this example is basically the same as that of example 1, except that the specific process parameters in this example are slightly different, as shown in Table 2.
In the hot-rolled H-shaped steel processed by the embodiment, the flanges and the webs in the same cross section are respectively sampled along the longitudinal direction by taking the width from the end 1/6 and the height from the end 1/4 as axes, and the condition of the room-temperature microstructure is specifically shown in Table 3; the specific mechanical properties are shown in Table 4.
Example 5
A hot rolled H-section steel of this example was substantially the same as example 1 except that the chemical composition of the hot rolled H-section steel was slightly different in this example as shown in Table 1.
The production method of the hot-rolled H-shaped steel of this example is basically the same as that of example 1, except that the specific process parameters in this example are slightly different, as shown in Table 2.
In the hot-rolled H-shaped steel processed by the embodiment, the flanges and the webs in the same cross section are respectively sampled along the longitudinal direction by taking the width from the end 1/6 and the height from the end 1/4 as axes, and the condition of the room-temperature microstructure is specifically shown in Table 3; the specific mechanical properties are shown in Table 4.
Example 6
A hot rolled H-section steel of this example was substantially the same as example 1 except that the chemical composition of the hot rolled H-section steel was slightly different in this example as shown in Table 1.
The production method of the hot-rolled H-shaped steel of this example is basically the same as that of example 1, except that the specific process parameters in this example are slightly different, as shown in Table 2.
In the hot-rolled H-shaped steel processed by the embodiment, the flanges and the webs in the same cross section are respectively sampled along the longitudinal direction by taking the width from the end 1/6 and the height from the end 1/4 as axes, and the condition of the room-temperature microstructure is specifically shown in Table 3; the specific mechanical properties are shown in Table 5.
Example 7
A hot rolled H-section steel of this example was substantially the same as example 1 except that the chemical composition of the hot rolled H-section steel was slightly different in this example as shown in Table 1.
The production method of the hot-rolled H-shaped steel of this example is basically the same as that of example 1, except that the specific process parameters in this example are slightly different, as shown in Table 2.
In the hot-rolled H-shaped steel processed by the embodiment, the flanges and the webs in the same cross section are respectively sampled along the longitudinal direction by taking the width from the end 1/6 and the height from the end 1/4 as axes, and the condition of the room-temperature microstructure is specifically shown in Table 3; the specific mechanical properties are shown in Table 5.
Example 8
A hot rolled H-section steel of this example was substantially the same as example 1 except that the chemical composition of the hot rolled H-section steel was slightly different in this example as shown in Table 1.
The production method of the hot-rolled H-shaped steel of this example is basically the same as that of example 1, except that the specific process parameters in this example are slightly different, as shown in Table 2.
In the hot-rolled H-shaped steel processed by the embodiment, the flanges and the webs in the same cross section are respectively sampled along the longitudinal direction by taking the width from the end 1/6 and the height from the end 1/4 as axes, and the condition of the room-temperature microstructure is specifically shown in Table 3; the specific mechanical properties are shown in Table 5.
Example 9
A hot rolled H-section steel of this example was substantially the same as example 1 except that the chemical composition of the hot rolled H-section steel was slightly different in this example as shown in Table 1.
The production method of the hot-rolled H-shaped steel of this example is basically the same as that of example 1, except that the specific process parameters in this example are slightly different, as shown in Table 2.
In the hot-rolled H-shaped steel processed by the embodiment, the flanges and the webs in the same cross section are respectively sampled along the longitudinal direction by taking the width from the end 1/6 and the height from the end 1/4 as axes, and the condition of the room-temperature microstructure is specifically shown in Table 3; the specific mechanical properties are shown in Table 5.
Example 10
A hot rolled H-section steel of this example was substantially the same as example 1 except that the chemical composition of the hot rolled H-section steel was slightly different in this example as shown in Table 1.
The production method of the hot-rolled H-shaped steel of this example is basically the same as that of example 1, except that the specific process parameters in this example are slightly different, as shown in Table 2.
In the hot-rolled H-shaped steel processed by the embodiment, the flanges and the webs in the same cross section are respectively sampled along the longitudinal direction by taking the width from the end 1/6 and the height from the end 1/4 as axes, and the condition of the room-temperature microstructure is specifically shown in Table 3; the specific mechanical properties are shown in Table 5.
TABLE 1 chemical composition (unit: wt%) of inventive examples 1 to 10
Figure BDA0002574343020000111
TABLE 2 Main Process parameters of examples 1 to 10 of the present invention
Figure BDA0002574343020000112
TABLE 3 microstructure conditions of inventive examples 1 to 10
Figure BDA0002574343020000121
TABLE 4 mechanical Properties of examples 1 to 5 of the present invention
Figure BDA0002574343020000122
TABLE 5 mechanical Properties of examples 6 to 10 of the present invention
Figure BDA0002574343020000131
The present invention and its embodiments have been described above schematically, without limitation, and what is shown in the drawings is only one of the embodiments of the present invention, and the actual structure is not limited thereto. Therefore, if the person skilled in the art receives the teaching, without departing from the spirit of the invention, the person skilled in the art shall not inventively design the similar structural modes and embodiments to the technical solution, but shall fall within the scope of the invention.

Claims (8)

1. A hot-rolled H-shaped steel is characterized in that: the chemical components of the material comprise, by mass percent, C: 0.09-0.19, Si: 0.15 to 0.40, Mn: 1.20-1.60, V: 0.040-0.120, N: 0.0060-0.0200, P: 0.025 or less, S: not more than 0.015, and the balance of Fe and trace residual elements, wherein the CEV is not more than 0.46 according to the CEV which is C + Mn/6+ (Cr + Mo + V)/5+ (Ni + Cu)/15; the flanges and the webs in the same cross section are sampled along the longitudinal direction by taking the width from the end 1/6 and the height from the end 1/4 as axes respectively, the room temperature microstructure comprises 60 to 90 percent of ferrite by area percentage, and the rest structure is pearlite or bainite; the grain size grades of ferrite of the flange and the web are 7.0-11.0 and 8.5-13.0 respectively, and the grain size grade of the web is 1.5-3.0 higher than that of the flange; the secondary phase precipitation density of the flange is not less than 600/mm2The secondary phase precipitation density of the web plate is not higher than 80/mm2。
2. A hot-rolled H-section steel according to claim 1, characterized in that: the chemical components comprise the following components in percentage by mass: 0.09-0.13, Si: 0.15 to 0.35, Mn: 1.20 to 1.50, V: 0.040 to 0.100, N: 0.0060-0.0120, P: 0.025 or less, S: less than or equal to 0.015, and the balance of Fe and trace residual elements, wherein the CEV is less than or equal to 0.38 calculated according to the CEV which is C + Mn/6+ (Cr + Mo + V)/5+ (Ni + Cu)/15.
3. A hot-rolled H-section steel according to claim 1, characterized in that: the chemical components comprise the following components in percentage by mass: 0.13 to 0.19, Si: 0.20 to 0.40, Mn: 1.30-1.60, V: 0.060 to 0.120, N: 0.0080-0.0200, P: 0.025 or less, S: less than or equal to 0.015, and the balance of Fe and trace residual elements, wherein the CEV is less than or equal to 0.46 calculated according to the CEV which is C + Mn/6+ (Cr + Mo + V)/5+ (Ni + Cu)/15.
4. A hot-rolled H-section steel according to claim 1, characterized in that: the flanges and the webs in the same cross section are sampled along the longitudinal direction by taking the width from the end 1/6 and the height from the end 1/4 as axes respectively, the room temperature microstructure comprises 80-90% of ferrite by area percentage, and the rest structure is pearlite; the grain size grades of ferrite of the flange and the web are 7.0-10.0 and 8.5-12.0 respectively, and the grain size grade of the web is 1.5-2.0 higher than that of the flange; the secondary phase precipitation density of the flange is 800/mm21100/mm2The secondary phase precipitation density of the web is 10/mm240 pieces/mm2。
5. A hot-rolled H-section steel according to claim 1, characterized in that: the flanges and the webs in the same cross section are sampled along the longitudinal direction by taking the width from the end 1/6 and the height from the end 1/4 as axes respectively, the room temperature microstructure comprises 60 to 70 percent of ferrite by area percentage, and the rest structure is pearlite or bainite; wherein the grain size grades of ferrite of the flange and the web are respectively 8.5-11.0 and 10.0-13.0, and the grain size grade of the web is 2.0-2.5 higher than that of the flange; two of the flangeThe density of precipitated secondary phase is 1100/mm21800 pieces/mm2The secondary phase precipitation density of the web is 40/mm270 pieces/mm2。
6. A hot-rolled H-section steel according to claim 1, characterized in that: products with yield strength of 355 MPa-460 MPa are involved, wherein for the products with yield strength of 355MPa, the yield strength of the flange is not lower than 355MPa, the tensile strength is not lower than 470MPa, the yield ratio is not higher than 0.80, the elongation after fracture is not lower than 25.0%, and the impact power value at-20 ℃ is not lower than 80J; for a product with the yield strength of 460MPa, the flange yield strength is not lower than 460MPa, the tensile strength is not lower than 540MPa, the yield ratio is not higher than 0.80, the elongation after fracture is not lower than 20.0 percent, and the impact power value at-20 ℃ is not lower than 80J; for the products with yield strength of 355 MPa-460 MPa, the actual yield strength difference between the flange and the web plate is not more than 10 MPa.
7. The production method of a hot-rolled H-type steel according to any one of claims 1 to 6, comprising the steps of molten iron pretreatment → converter smelting → argon blowing refining → external refining → beam blank continuous casting → billet heating → cogging rolling → universal rolling, characterized in that: after the universal rolling stage, rapid cooling is not carried out; or only water mist with the cooling speed lower than 6 ℃/s is adopted for auxiliary cooling; a blank heating stage, wherein the heating temperature is 1150-1300 ℃, and the heating time is not less than 120 min; in the cogging rolling stage, the accumulated reduction rate of the web in the thickness direction is not lower than 50%, and the final rolling temperature of the web is not lower than 980 ℃; in the universal rolling stage, the accumulated reduction rate of the flange in the thickness direction is not lower than 50%, and the final rolling temperature of the flange is controlled at 800-850 ℃.
8. The production method of a hot-rolled H-section steel according to claim 7, characterized in that: the thickness range of the flange of the hot-rolled H-shaped steel is 10 mm-50 mm; the thickness of the web plate ranges from 8mm to 35 mm.
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