WO2024093354A1 - 一种1.2～2.0mm薄规格700MPa级热轧大梁钢及其制备方法 - Google Patents

一种1.2～2.0mm薄规格700MPa级热轧大梁钢及其制备方法 Download PDF

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WO2024093354A1
WO2024093354A1 PCT/CN2023/106970 CN2023106970W WO2024093354A1 WO 2024093354 A1 WO2024093354 A1 WO 2024093354A1 CN 2023106970 W CN2023106970 W CN 2023106970W WO 2024093354 A1 WO2024093354 A1 WO 2024093354A1
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steel
rolling
slag
temperature
rolled
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French (fr)
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周晏锋
刘志璞
苗隽
张城铭
马思远
许学利
于健
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本钢板材股份有限公司
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B1/00—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
    • B21B1/22—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling plates, strips, bands or sheets of indefinite length
    • B21B1/24—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling plates, strips, bands or sheets of indefinite length in a continuous or semi-continuous process
    • B21B1/26—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling plates, strips, bands or sheets of indefinite length in a continuous or semi-continuous process by hot-rolling, e.g. Steckel hot mill
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B37/00—Control devices or methods specially adapted for metal-rolling mills or the work produced thereby
    • B21B37/16—Control of thickness, width, diameter or other transverse dimensions
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B37/00—Control devices or methods specially adapted for metal-rolling mills or the work produced thereby
    • B21B37/74—Temperature control, e.g. by cooling or heating the rolls or the product
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
    • 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
    • C22C33/06—Making ferrous alloys by melting using master alloys
    • 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
    • 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
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • 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
    • C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/20—Recycling

Definitions

  • the invention belongs to the technical field of steel materials, and specifically relates to a hot-rolled high-strength steel with an extremely thin specification of 1.2-2.0 mm thickness and a tensile strength of 700 MPa, especially used as automobile side beams, longitudinal beams, etc.
  • the 600-700MPa grade beam steel used in the industry is generally a Nb+Ti composite component system, which is costly.
  • the next level is the Q355B strength level, which has low strength and unobvious weight reduction effect, and is accompanied by safety and quality issues. Due to the high strength of 700MPa-level high-strength beam steel, thin-gauge beam steel with a thickness of 1.2 to 2.0 mm is difficult to produce, and the chemical composition design and hot rolling process must have a high degree of matching. At the same time, the hot rolling process must meet the rolling capacity of the rolling mill, so there are fewer manufacturers that can supply the market.
  • the purpose of the present invention is to provide a 1.2-2.0mm thin gauge 700MPa grade hot-rolled beam steel and a preparation method thereof.
  • the 1.2-2.0mm thin gauge 700MPa grade hot-rolled beam steel of the present invention can very well achieve vehicle weight reduction effect, product upgrading, low cost, and improved safety of use.
  • the object of the present invention is to achieve the following:
  • the invention provides a 700MPa grade hot-rolled beam steel with a thin gauge of 1.2-2.0 mm.
  • the chemical composition and weight percentage of the steel are as follows: C: 0.05-0.10%, Si: 0.10-0.25%, Mn: 1.10-1.35%, Al: 0.020-0.050%, Ti: 0.105-0.130%, P ⁇ 0.020%, S ⁇ 0.005%, N: 0.0020-0.0050%, O: 0.0010-0.0030%, rare earth Re ⁇ 0.01%, and the balance is Fe and inevitable inclusions, wherein the rare earth Re is composed of Ce: 48%, La: 32%, Pr: 5%, Nd: 5%, Pm+Sm+Eu+Gd: 8%, and the rest is Fe and other inevitable impurities; the lower yield strength is ⁇ 610MPa, the tensile strength is ⁇ 680MPa, and the elongation after fracture A is ⁇ 15%.
  • the chemical composition and weight percentage of the 1.2-2.0 mm thin gauge 700 MPa grade hot-rolled beam steel are: C: 0.07-0.10%, Si: 0.10-0.20%, Mn: 1.15-1.30%, Al: 0.020-0.050%, Ti: 0.105-0.125%, P ⁇ 0.015%, S ⁇ 0.003%, N: 0.0020-0.0050%, O: 0.0010-0.0030%, rare earth Re: 0.001-0.005%, and the balance is Fe and unavoidable inclusions, wherein the rare earth Re consists of Ce: 48%, La: 32%, Pr: 5%, Nd: 5%, Pm+Sm+Eu+Gd: 8%, and the rest is Fe and other unavoidable impurities.
  • the main elements have the following functions:
  • C 0.07-0.10wt%
  • carbon is used to form sufficient carbide strengthening phase.
  • Steel with low carbon content has better toughness.
  • Si 0.10-0.20wt%
  • Si has a strong affinity with O and is a strong deoxidizing element. It exists in steel in the form of solid solution. Si can improve the strength, fatigue limit, corrosion resistance and wear resistance of steel. However, if the Si content is too high, oxides are easily generated during hot rolling, which reduces the surface quality of the steel.
  • Mn 1.15-1.30wt%
  • Mn exists in the steel in the form of solid solution and is a solid solution strengthening element. It mainly exists in the steel in the form of MnS.
  • Manganese is usually added as a desulfurizer and deoxidizer during the steel smelting process. Manganese and sulfur can prevent hot brittleness.
  • Ti 0.105 ⁇ 0.125wt%
  • Ti has the effects of grain refinement and precipitation strengthening. At high temperature, it can be dissolved into austenite to block the ( ⁇ ) phase transformation.
  • the TiN and TiC precipitated in the steel can prevent the grain growth in the austenite and hinder the recrystallization of the deformed austenite, thereby refining the grains.
  • the precipitated "effective Ti" TiC has a strong strengthening effect.
  • my country has abundant Ti content and low price.
  • N 0.0020-0.0050wt%
  • P not more than 0.015wt%.
  • phosphorus is a harmful element in steel, which increases the cold brittleness of steel, deteriorates welding performance, reduces plasticity, and deteriorates cold bending performance.
  • rare earth Re has the effects of fine grain strengthening, inclusion modification, improving toughness and plasticity, and improving fatigue performance in high-strength steel.
  • the segregation of rare earth at the grain boundary affects the metallographic structure and grain size of the steel.
  • Cerium has a significant effect of inhibiting grain growth, and with the increase of cerium content, this inhibitory effect is enhanced.
  • Rare earth treatment has solved the problem of grain coarsening caused by not adding expensive alloy niobium Nb. At the same time, rare earth treatment has a great effect on high-strength steel.
  • the performance optimization effect is better than calcium treatment.
  • the present invention also provides a preparation method of the above-mentioned 1.2-2.0 mm thin gauge 700 MPa grade hot-rolled beam steel, which mainly includes steelmaking, hot rolling, coiling and storage processes, wherein the steelmaking process includes a pretreatment process, a converter smelting process, a refining process and a continuous casting process; the hot rolling process includes a heating furnace heating process, a rough rolling process and a finishing rolling process; the coiling adopts a two-stage cooling method, and the coiling temperature is set at 630°C to 670°C; the storage is to slowly cool the rolled plate coil in a surrounding cooling method.
  • the pretreatment process using refined scrap steel; pretreatment into the furnace S ⁇ 0.0030%, and removing slag.
  • the converter smelting process the converter carbon pulling is hit once, the ladle is purged with argon before tapping, the early slag blocking: a slag blocking mud plug is used, and a suitable slag blocking mud plug is selected according to the size of the tapping port after the previous furnace tapping; slag blocking is carried out in the later stage of tapping to ensure that the slag thickness of the ladle is less than 120mm; the tapping time is guaranteed to be 4-7min, the shape of the tapping port is controlled, and the tapping flow is avoided; deoxidation and alloying are started when 1/5 of the steel is tapped, and the alloy is added when 4/5 is tapped, and deoxidation is carried out by ferrosilicon and ferroaluminum. Ferrosilicon is added first, and then high manganese is added. It must be more than 1min before ferroaluminum is added, and the ladle N is required to be ⁇ 25ppm.
  • the refining process refining adopts a single-path LF furnace, LF uses active lime and fluorite to make a reducing slag with good fluidity, strictly controls the argon blowing intensity to avoid exposure of molten steel; uses rare earth treatment containing cerium lanthanum iron to fully spheroidize inclusions and improve product performance, soft argon blowing is ⁇ 10min before the end of the treatment, and the LF leaving the station temperature of a normal furnace is controlled at 1563-1573°C.
  • the continuous casting process protective pouring is carried out throughout the whole process, argon is used to purge the middle ladle before pouring, no molten steel is exposed during the pouring process, the long nozzle is required to be cleaned after the pouring of each furnace, and the long nozzle is required to remain vertical during the pouring process; the immersion depth of the long nozzle of the large ladle is ensured to be 200-250mm, and the large ladle adopts slag detection to control the slag amount to avoid slag in the large ladle; the second cooling section adopts weak cooling mode, adopts light pressure mode, invests 3-5mm, and keeps the pulling speed constant. The pulling speed is controlled at 1.0-1.5m/min, and the continuous casting overheat control target is ⁇ 25°C.
  • the heating process of the heating furnace the outlet temperature of the heating furnace is 1220 ⁇ 1260°C; the atmosphere in the heating furnace is controlled to reduce the formation of oxide scale of the ingot, ensure uniform heating temperature, the time in the furnace is ⁇ 160min and the soaking period time is ⁇ 50min.
  • the heating process of the heating furnace is 1220-1260°C; the time in the furnace is 180-200 minutes and the soaking period time is 50-70 minutes.
  • the rough rolling pass selects the 3+5 mode, that is, R1 is rolled back and forth 3 times, and R2 is rolled back and forth 5 times, the purpose is to make the finished steel coil thinner and reduce the load of the finishing rolling unit.
  • the R1 rolling temperature is controlled to be ⁇ 1130°C, and water spraying descaling at high temperature can better remove the iron oxide scale on the surface of the steel; the thickness of the intermediate billet is 30-45mm, and the cumulative reduction rate in the rough rolling stage is greater than 75%.
  • R1 starting rolling temperature is 1140-1160°C
  • the intermediate billet thickness is 35-40mm
  • the cumulative reduction rate in the rough rolling stage is 80-85%.
  • the finishing rolling process the finishing rolling start temperature is 1030-1100°C, the F1 reduction rate is ⁇ 45%, the F2 reduction rate is ⁇ 25%, and thin-gauge high-strength steel, due to its greater deformation resistance, adopts high-temperature final rolling, and the final rolling temperature is ⁇ 890°C.
  • finishing rolling process F1 reduction rate 45-55%, F2 reduction rate 28-32%, final rolling temperature 890-920°C.
  • the 1.2-2.0 mm thin-gauge 700 MPa-grade hot-rolled beam steel prepared by the present invention achieves the production of extremely thin gauges under low-cost component design by well matching the hot rolling process with the rolling capacity of the rolling mill, taking into full consideration that my country's titanium and rare earth resources are very abundant, thereby adding high value-added products of this type of steel and filling the gap of thin gauges under this strength.
  • the cost per ton of steel is reduced by more than 50 yuan, thus achieving product upgrading and replacement, solving the problems of vehicle weight reduction, energy saving and consumption reduction, and rational use of resources such as titanium alloys, and at the same time being able to well ensure personal safety.
  • FIG. 1 is a process flow chart of an embodiment.
  • FIG2 is a continuous cooling transformation curve, wherein F is the ferrite transformation start temperature, Ps is the pearlite transformation start temperature, Bs is the bainite transformation start temperature, Pf is the pearlite transformation end temperature, and Bf is the bainite transformation end temperature.
  • FIG3 is the metallographic structure of the beam steel of Example 3.
  • This embodiment provides a method for preparing a 1.5 mm thick 700 MPa grade hot-rolled beam steel.
  • the components and weight percentages of the beam steel are shown in Table 1;
  • the main steps include:
  • Pretreatment process Use refined scrap steel; pre-treatment S ⁇ 0.0030% before entering the furnace, and remove slag;
  • Converter smelting process Carbon pulling in converter is done once to avoid spot blowing; argon gas purge of ladle before tapping; slag blocking in the early stage: slag blocking mud plug is used, and the appropriate slag blocking mud plug is selected according to the size of the tapping port after the last batch of tapping; slag blocking is carried out in the later stage of tapping to ensure that the slag thickness of the ladle is less than 120mm; the tapping time is guaranteed to be 5min, and the shape of the tapping port is controlled to avoid scattered flow of tapping; deoxidation and alloying are started when 1/5 of the steel is tapped, and the alloy is added when 4/5 is tapped.
  • Deoxidation is carried out by adding ferrosilicon and ferroaluminum, and a certain amount of ferrosilicon is added first, and then high manganese is added. It must be more than 1min before adding ferroaluminum, and the ladle N is required to be 23ppm;
  • Refining process Refining adopts single-path LF furnace, and LF uses active lime and fluorite to make reducing slag with good fluidity.
  • the argon blowing intensity is strictly controlled to avoid exposure of molten steel; rare earth treatment containing cerium lanthanum iron is adopted (rare earth Re is composed of Ce: 48%, La: 32%, Pr: 5%, Nd: 5%, Pm+Sm+Eu+Gd: 8%, and the rest is Fe and other inevitable impurities) to make inclusions fully spheroidized and improve product performance.
  • Soft argon blowing is carried out for 12 minutes before the end of the treatment.
  • the normal furnace LF leaving the station temperature is controlled at 1568°C;
  • Continuous casting process Protective pouring is carried out throughout the whole process. Argon gas is used to purge the middle ladle before pouring. No molten steel is exposed during the pouring process.
  • the long nozzle is required to be cleaned after each furnace pouring. The long nozzle is required to be kept vertical during the pouring process; the immersion depth of the long nozzle of the large ladle is ensured to be 230mm.
  • the large ladle adopts slag detection to control the slag amount to avoid slag in the large ladle; the second cooling section adopts weak cooling mode, adopts light pressure mode, and the input is 3mm.
  • the constant pulling speed is controlled at 1.1m/min, and the continuous casting superheat control target is 20°C;
  • Heating process of heating furnace the temperature of the heating furnace is 1250°C; the atmosphere of the heating furnace is controlled to reduce the formation of iron oxide scale of the ingot and ensure uniform heating temperature.
  • the time in the furnace is 189min; the soaking time is 60min;
  • the rough rolling pass selects the 3+5 mode, that is, R1 is rolled back and forth 3 times, and R2 is rolled back and forth 5 times.
  • the purpose is to make the finished steel coil thinner and reduce the load of the finishing mill.
  • the R1 rolling temperature is controlled at 1156°C, and water spraying is performed at high temperature to remove the iron oxide scale on the surface of the steel.
  • the thickness of the intermediate billet is 37.2mm, and the cumulative reduction rate in the rough rolling stage is 83.8%;
  • finishing rolling process The finishing rolling start temperature is 1077°C, the F1 reduction rate is 50.3%, and the F2 reduction rate is 29.8%. Since thin-gauge high-strength steel has a large deformation resistance, high-temperature final rolling is adopted, and the final rolling temperature is 905°C;
  • the two-stage cooling method is more convenient for large-scale production.
  • High-titanium steel is more sensitive to temperature. Setting the coiling temperature to 650°C is conducive to the full precipitation of "effective Ti" TiC, which plays a good precipitation strengthening role. If the coiling temperature is too low, it is not conducive to plate shape control and is not easy to control during rolling. If the coiling temperature is too high, the amount of TiC precipitation is insufficient, the cooling rate is insufficient, the precipitation strengthening and fine grain strengthening effects are not obvious, and the strength is not appropriate.
  • the rolled coil is slowly cooled ( ⁇ 32 hours) in an enclosure cooling method, that is, it is placed inside other high-temperature coils, away from the warehouse door, and cooled fully and slowly to ensure the plate shape and the release of internal stress.
  • This embodiment provides a method for preparing 1.8 mm thick 700 MPa grade hot-rolled beam steel, the steps are the same as those in Example 1, and the only difference is the following aspects:
  • the temperature out of the heating furnace is 1255°C, the time in the furnace is 192 min; the soaking period time is 58 min, the R1 rolling temperature is 1150°C, the intermediate billet thickness is 38.1 mm, and the cumulative reduction rate in the rough rolling stage is 83.4%; the finishing rolling start temperature is 1068°C, the F1 reduction rate is 49.9%, the F2 reduction rate is 30.6%, the final rolling temperature is 896°C, and the coiling temperature is 645°C.
  • This embodiment provides a method for preparing 2.0 mm thick 700 MPa grade hot-rolled beam steel, the steps are the same as those in Example 1, and the only difference is the following aspects:
  • the temperature out of the heating furnace is 1246°C, the time in the furnace is 183 min; the soaking period time is 55 min, the R1 rolling temperature is 1142°C, the intermediate billet thickness is 38.5 mm, and the cumulative reduction rate in the rough rolling stage is 83.3%; the finishing rolling start temperature is 1050°C, the F1 reduction rate is 50.6%, the F2 reduction rate is 30.1%, the final rolling temperature is 901°C, and the coiling temperature is 658°C.

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  • Engineering & Computer Science (AREA)
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  • Organic Chemistry (AREA)
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Abstract

本发明公开了一种1.2～2.0mm薄规格700MPa级热轧大梁钢及其制备方法，属于钢铁材料技术领域。本发明的热轧大梁钢的化学成分及重量百分比为：C：0.05-0.10％，Si：0.10-0.25％，Mn：1.10-1.35％，Al：0.020-0.050％，Ti：0.105～0.130％，P≤0.020％，S≤0.005％，N：0.0020-0.0050％，O：0.0010-0.0030％，稀土Re≤0.01％，余量为Fe及不可避免夹杂物，其中，稀土Re中Ce≥40％、La≥30％。本发明通过热轧工艺与轧机轧制能力的良好匹配，实现了在低成本的成分设计下极限薄规格的生产，增添了该钢种高附加值产品，填补了该强度下薄规格的空白，同时与同级别相比吨钢成本降低50元以上，实现产品升级换代，解决了车辆减重、节能降耗、钛合金等资源合理使用问题，同时能够很好的保证了人身安全。

Description

一种1.2～2.0mm薄规格700MPa级热轧大梁钢及其制备方法 技术领域
本发明属于钢铁材料技术领域，具体涉及一种极薄规格1.2～2.0mm厚、抗拉强度700MPa级的热轧高强钢，尤其是用作汽车边梁、纵梁等方面。
背景技术
随着汽车工业的快速发展，汽车的保有量不断增加，世界对环保、资源和能源越来越重视，这就要求汽车工业向轻量化、安全、环保以及节能方向发展。随着新修订的GB1589-2016《汽车、挂车及汽车列车外廓尺寸、载荷及质量限值》标准的颁布，车辆的超载超限现象将严格把控，高强度边梁钢可以减轻汽车重量，既提高了汽车的安全性能，又节省了燃油，同时减少了尾气排放，推动绿色发展，共建自然生态和谐发展型社会。我国是一个资源大国，其中钛合金、稀土含量蕴藏十分丰富，但是铌合金十分短缺，故导致钛合金价格低廉，铌合金价格昂贵。目前业内使用的600-700MPa级大梁钢普遍为Nb+Ti复合的成分体系，成本高。而下一等级的为Q355B强度级别，强度低，减重效果又不明显，同时伴随着安全问题和质量问题，而700MPa级别高强大梁钢由于强度高，薄规格1.2～2.0mm厚度下的大梁钢生产起来难度较大，化学成分设计与热轧工艺匹配度要求较高，同时热轧工艺必须满足轧机轧制能力，故市场能供货的厂家较少。
发明内容
为解决背景技术中存在的技术问题，本发明的目的是提供了一种1.2～2.0mm薄规格700MPa级热轧大梁钢及其制备方法，本发明的1.2～2.0mm薄规格700MPa级热轧大梁钢可以非常好的实现车辆减重效果、产品升级换代、成本低廉、提高了使用安全性。
本发明目的是通过以下方式实现：
本发明提供一种1.2～2.0mm薄规格700MPa级热轧大梁钢，其化学成分及重量百分比为：C：0.05-0.10％，Si：0.10-0.25％，Mn：1.10-1.35％，Al：0.020-0.050％，Ti：0.105～0.130％，P≤0.020％，S≤0.005％，N：0.0020-0.0050％，O：0.0010-0.0030％，稀土Re≤0.01％，余量为Fe及不可避免夹杂物，其中，稀土Re由Ce：48％，La：32％，Pr：5％，Nd：5％，Pm+Sm+Eu+Gd：8％，其余为Fe和其他不可避免杂质组成；下屈服强度≥610MPa，抗拉强度≥680MPa，断后伸长率A≥15％。
基于上述技术方案，进一步地，所述的1.2～2.0mm薄规格700MPa级热轧大梁钢的化学成分及重量百分比为：C：0.07-0.10％，Si：0.10-0.20％，Mn：1.15-1.30％，Al：0.020-0.050％，Ti：0.105～0.125％，P≤0.015％，S≤0.003％，N：0.0020-0.0050％，O：0.0010-0.0030％，稀土Re：0.001-0.005％，余量为Fe及不可避免夹杂物，其中，稀土Re由Ce：48％，La：32％，Pr：5％，Nd：5％，Pm+Sm+Eu+Gd：8％，其余为Fe和其他不可避免杂质组成。
主要元素作用如下：
C：0.07-0.10wt％，碳用于形成足够碳化物强化相，碳含量越高，脆性和硬度越大，含碳低的钢韧性较好。
Si：0.10-0.20wt％，Si和O的亲和力较强，属于强脱氧元素，并以固溶形式存在于钢中，Si可以提高钢的强度、疲劳极限、耐腐蚀性和耐磨性，但Si含量过高，热轧时易产生氧化物，降低钢材表面质量。
Mn：1.15-1.30wt％，Mn在钢中以固溶态存在，属固溶强化元素，在钢中主要以MnS状态存在，锰在冶炼钢铁过程中通常作为脱硫剂和脱氧剂而特意加入，锰和硫作用可防止热脆。
Ti：0.105～0.125wt％，Ti具有细晶强化和析出强化作用，在高温时，可以溶入奥氏体，阻滞(γ→α)相变发生，钢中析出的TiN、TiC在奥氏体中可以阻止晶粒长大，阻碍变形奥氏体发生再结晶，从而起到细化晶粒的作用，同时析出的“有效Ti”TiC具有很强的强化作用，并且我国Ti含量丰富，价格低廉。
N：0.0020-0.0050wt％，N含量过高会影响有效Ti的形成，影响强度。
O:0.0010-0.0030wt％，低O控制，减少夹杂物，减少缺陷产生，提高韧塑性。
P：不大于0.015wt％，一般来说，磷是钢中有害元素，增加钢的冷脆性，焊接性能恶化，降低塑性，使冷弯性能变坏。
S：不大于0.003wt％，作为有害元素，其使钢产生热脆性，降低钢的延展性和韧性，在轧制过程中易产生裂纹，同时对焊接性能也不利。
Re：0.001-0.005wt％，稀土Re在高强钢具有细晶强化、夹杂物变质、改善韧塑性、提高疲劳性能等的作用，稀土在晶界的偏聚影响了钢的金相组织和晶粒度，随着钢中稀土含量的增加，珠光体相变开始线右移，即产生珠光体相变的孕育期增大，铈具有明显抑制晶粒长大的作用，且随着铈含量的增加，这种抑制作用增强，稀土处理很好的解决了未添加昂贵合金铌Nb而带来的晶粒粗化的问题，同时，稀土处理对高强钢 性能优化作用优于钙处理。
本发明还提供上述的1.2～2.0mm薄规格700MPa级热轧大梁钢的制备方法，主要包括炼钢、热轧、卷取和存放工艺，其中，所述的炼钢工艺包括预处理工序、转炉冶炼工序、精炼工序和连铸工序；所述的热轧工艺包括加热炉加热工序、粗轧工序和精轧工序；所述的卷取采用两段冷却方式，卷取温度设定在630℃～670℃；所述的存放为将轧后板卷以围冷方式进行缓冷。
基于上述技术方案，进一步地，预处理工序：采用精料废钢；预处理入炉S≤0.0030％，扒净渣。
基于上述技术方案，进一步地，转炉冶炼工序：转炉拉碳一次命中，出钢前钢包氩气吹扫，前期挡渣：采用挡渣泥塞，根据上1炉次出钢后，出钢口大小，选择合适挡渣泥塞；出钢后期挡渣，以保证钢包渣厚小于120mm；出钢时间保证4～7min，控制出钢口形状、避免出钢散流；出钢1/5时开始进行脱氧合金化，出至4/5时加完合金，采用硅铁加铝铁方式脱氧，先加入硅铁，再加入高锰，必须大于1min后再加入铝铁，要求钢包N≤25ppm。
基于上述技术方案，进一步地，精炼工序：精炼采用单路径LF炉，LF采用活性石灰、萤石造流动性好的还原渣，严格控制吹氩强度，避免钢液裸露；采用含铈镧铁的稀土处理，使夹杂物充分的球化，改善产品性能，处理结束前软吹氩≥10min，正常炉次LF离站温度按1563～1573℃控制。
基于上述技术方案，进一步地，连铸工序：全程进行保护浇注，开浇前采用氩气吹扫中包，浇注过程做到无钢液裸露，要求每炉浇注结束后长水口要清理干净，浇注过程中要求长水口保持垂直状态；保证大包长水口的浸入深度200～250mm，大包采用下渣检测控制下渣量，避免大包下渣；二冷段采用弱冷模式，采用轻压下模式，投入3-5mm，恒拉速，拉速控制在1.0-1.5m/min，连铸过热度控制目标≤25℃。
基于上述技术方案，进一步地，加热炉加热工序：加热炉出炉温度1220～1260℃；控制加热炉炉膛气氛，减少铸坯氧化铁皮的生成，保证加热温度均匀，在炉时间≥160min且均热段时间≥50min。
基于上述技术方案，进一步地，加热炉加热工序：加热炉出炉温度1220～1260℃；在炉时间180～200min且均热段时间50～70min。
基于上述技术方案，进一步地，粗轧工序：粗轧道次选择3+5模式，即R1来回轧制3次，R2来回轧制5次，目的在于成品钢卷厚度较薄，减小精轧机组负荷，同 时控制R1开轧温度≥1130℃，高温下进行喷水除鳞能更好的去除钢种表面氧化铁皮；中间坯厚度30～45mm，粗轧阶段累积压下率大于75％。
基于上述技术方案，进一步地，粗轧工序：R1开轧温度1140～1160℃；中间坯厚度35～40mm，粗轧阶段累积压下率80～85％。
基于上述技术方案，进一步地，精轧工序：精轧开轧温度为1030～1100℃，F1压下率≥45％，F2压下率≥25％，薄规格高强钢，由于具有较大的变形抗力，故采用高温终轧，终轧温度≥890℃。
基于上述技术方案，进一步地，精轧工序：F1压下率45～55％，F2压下率28～32％，终轧温度890～920℃。
本发明相对于现有技术具有的有益效果如下：
本发明制备的1.2～2.0mm薄规格700MPa级热轧大梁钢，通过热轧工艺与轧机轧制能力的良好匹配，充分考虑到我国钛、稀土资源十分丰富，实现了在低成本的成分设计下极限薄规格的生产，增添了该钢种高附加值产品，填补了该强度下薄规格的空白，同时与同级别相比吨钢成本降低50元以上，实现产品升级换代，解决了车辆减重、节能降耗、钛合金等资源合理使用问题，同时能够很好的保证了人身安全。
附图说明
为了更清楚地说明本发明实施例，下面将对实施例涉及的附图进行简单地介绍。
图1为实施例的工艺流程图。
图2为连续冷却转变曲线图，其中，F：铁素体转变开始温度，Ps：珠光体转变开始温度，Bs：贝氏体转变开始温度，Pf：珠光体转变终止温度，Bf：贝氏体转变终止温度。
图3为实施例3的大梁钢金相组织。
图4为实施例3的大梁钢180°(d＝0a)弯曲试验，其中，(a)为俯视图，(b)为侧视图。
具体实施方式
下面结合实施例对本发明进行详细的说明，但本发明的实施方式不限于此，显而易见地，下面描述中的实施例仅是本发明的部分实施例，对于本领域技术人员来讲，在不付出创造性劳动性的前提下，获得其他的类似的实施例均落入本发明的保护范围。
实施例1
本实施例提供1.5mm厚700MPa级热轧大梁钢的制备方法，大梁钢的组分及重量百分比见表1；
表1.大梁钢的规格、组分及重量百分比/％
主要包括以下步骤：
一、炼钢
1、预处理工序：采用精料废钢；预处理入炉S≤0.0030％，扒净渣；
2、转炉冶炼工序：转炉拉碳一次命中、避免点吹；出钢前钢包氩气吹扫，前期挡渣：采用挡渣泥塞，根据上1炉次出钢后，出钢口大小，选择合适挡渣泥塞；出钢后期挡渣，以保证钢包渣厚小于120mm；出钢时间保证5min，控制出钢口形状、避免出钢散流；出钢1/5时开始进行脱氧合金化，出至4/5时加完合金，采用硅铁加铝铁方式脱氧，先加入定量硅铁，再加入高锰，必须大于1min后再加入铝铁，要求钢包N 23ppm；
3、精炼工序：精炼采用单路径LF炉，LF采用活性石灰、萤石造流动性好的还原渣，严格控制吹氩强度，避免钢液裸露；采用含铈镧铁的稀土处理(稀土Re由Ce：48％，La：32％，Pr：5％，Nd：5％，Pm+Sm+Eu+Gd：8％，其余为Fe和其他不可避免杂质组成)，使夹杂物充分球化，改善产品性能，处理结束前软吹氩12min，正常炉次LF离站温度按1568℃控制；
4、连铸工序：全程进行保护浇注，开浇前采用氩气吹扫中包，浇注过程做到无钢液裸露，要求每炉浇注结束后长水口要清理干净，浇注过程中要求长水口保持垂直状态；保证大包长水口的浸入深度230mm，大包采用下渣检测控制下渣量，避免大包下渣；二冷段采用弱冷模式，采用轻压下模式，投入3mm，恒拉速控制在1.1m/min，连铸过热度控制目标20℃；
二、热轧
1、加热炉加热工序：加热炉出炉温度1250℃；控制加热炉炉膛气氛，减少铸坯氧化铁皮的生成，保证加热温度均匀，在炉时间189min；均热段时间60min；
2、粗轧工序：粗轧道次选择3+5模式，即R1来回轧制3次，R2来回轧制5次，目的在于成品钢卷厚度较薄，减小精轧机组负荷，同时控制R1开轧温度1156℃，高温下进行喷水除鳞去除钢种表面氧化铁皮；中间坯厚度37.2mm，粗轧阶段累积压下率83.8％；
3、精轧工序：精轧开轧温度为1077℃，F1压下率为50.3％，F2压下率为29.8％，薄规格高强钢由于具有较大的变形抗力，故采用高温终轧，终轧温度905℃；
三、卷取
采用两段冷却方式，更易于大规模生产，高钛钢对温度较为敏感，将卷取温度设定为650℃，有利于“有效Ti”TiC的充分析出，起到良好的析出强化作用；若卷取温度偏低，不利于板形控制，且轧制过程中也不容易控制；若卷取温度偏高，TiC析出量不足，冷速不足，析出强化和细晶强化作用不明显，强度不合；
四、存放
轧后板卷以围冷方式进行缓冷(≥32小时)，即将其放在其他高温卷内部，远离库房门口方向，充分缓慢的冷却，保证板形以及内应力的释放。
本实施例制备的大梁钢的性能要求及检测结果如表2所示。
表2.大梁钢的性能要求及检测结果
实施例2
本实施例提供1.8mm厚700MPa级热轧大梁钢的制备方法，步骤同实施例1，区别仅在于以下方面：
(1)大梁钢的组分及重量百分比见表3；
表3.大梁钢的规格、组分及重量百分比/％
(2)加热炉出炉温度1255℃，在炉时间192min；均热段时间58min，R1开轧温度1150℃，中间坯厚度38.1mm，粗轧阶段累积压下率83.4％；精轧开轧温度1068℃，F1压下率为49.9％，F2压下率为30.6％，终轧温度896℃，卷取温度645℃。
本实施例制备的大梁钢的性能要求及检测结果如表4所示。
表4.大梁钢的性能要求及检测结果
实施例3
本实施例提供2.0mm厚700MPa级热轧大梁钢的制备方法，步骤同实施例1，区别仅在于以下方面：
(1)大梁钢的组分及重量百分比见表5；
表5.大梁钢的规格、组分及重量百分比/％
(2)加热炉出炉温度1246℃，在炉时间183min；均热段时间55min，R1开轧温度1142℃，中间坯厚度38.5mm，粗轧阶段累积压下率83.3％；精轧开轧温度1050℃，F1压下率为50.6％，F2压下率为30.1％，终轧温度901℃，卷取温度658℃。
本实施例制备的大梁钢的性能要求及检测结果如表6所示。
表6.大梁钢的性能要求及检测结果
本实施例的2.0mm厚700MPa级热轧大梁钢的金相组织为多边形铁素体，晶粒度≥13.0级(图3)，180°弯曲试验d＝0a折弯完好(图4)。
最后应说明的是：以上各实施例仅用以说明本发明的技术方案，而非对其限制；尽管参照前述各实施例对本发明进行了详细的说明，本领域的普通技术人员应当理解：其依然可以对前述各实施例所记载的技术方案进行修改，或者对其中部分或者全部技术特征进行等同替换；而这些修改或者替换，并不使相应技术方案的本质脱离本发明各实施例技术方案的范围。

Claims (10)

  1. 一种1.2～2.0mm薄规格700MPa级热轧大梁钢，其特征在于，其化学成分及重量百分比为：C：0.05-0.10％，Si：0.10-0.25％，Mn：1.10-1.35％，Al：0.020-0.050％，Ti：0.105～0.130％，P≤0.020％，S≤0.005％，N：0.0020-0.0050％，O：0.0010-0.0030％，稀土Re≤0.01％，余量为Fe及不可避免夹杂物，其中，稀土Re中Ce≥40％、La≥30％；下屈服强度≥610MPa，抗拉强度≥680MPa，断后伸长率A≥15％。
  2. 根据权利要求1所述的1.2～2.0mm薄规格700MPa级热轧大梁钢，其特征在于，所述的1.2～2.0mm薄规格700MPa级热轧大梁钢的化学成分及重量百分比为：C：0.07-0.10％，Si：0.10-0.20％，Mn：1.15-1.30％，Al：0.020-0.050％，Ti：0.105～0.125％，P≤0.015％，S≤0.003％，N：0.0020-0.0050％，O：0.0010-0.0030％，稀土Re：0.001-0.005％，余量为Fe及不可避免夹杂物，其中，稀土Re中Ce≥40％、La≥30％。
  3. 权利要求1或2所述的1.2～2.0mm薄规格700MPa级热轧大梁钢的制备方法，其特征在于，主要包括炼钢、热轧、卷取和存放工艺，其中，所述的炼钢工艺包括预处理工序、转炉冶炼工序、精炼工序和连铸工序；所述的热轧工艺包括加热炉加热工序、粗轧工序和精轧工序；所述的卷取工艺采用两段冷却方式，卷取温度设定在630℃～670℃；所述的存放工艺为将轧后板卷以围冷方式进行缓冷。
  4. 根据权利要求3所述的制备方法，其特征在于，预处理工序：预处理入炉S≤0.0030％，扒净渣。
  5. 根据权利要求3所述的制备方法，其特征在于，转炉冶炼工序：转炉拉碳一次命中，前期挡渣，出钢后期挡渣，以保证钢包渣厚小于120mm；出钢时间保证4～7min；出钢1/5时开始进行脱氧合金化，出至4/5时加完合金，采用硅铁加铝铁方式脱氧，钢包N≤25ppm。
  6. 根据权利要求3所述的制备方法，其特征在于，精炼工序：精炼采用单路径LF炉，LF采用活性石灰、萤石造还原渣，避免钢液裸露；采用含铈镧铁的稀土处理，处理结束前软吹氩≥10min，LF离站温度控制在1563～1573℃。
  7. 根据权利要求3所述的制备方法，其特征在于，连铸工序：全程进行保护浇注，开浇前采用氩气吹扫中包，浇注过程保持无钢液裸露，浇注过程中长水口保持垂直状态；保证大包长水口的浸入深度200～250mm，大包采用下渣检测控制下渣量，避免大包下渣；二冷段采用弱冷模式，采用轻压下模式，恒拉速，拉速控制在1.0-1.5m/min，连铸过热度≤25℃。
  8. 根据权利要求3所述的制备方法，其特征在于，加热炉加热工序：加热炉出炉 温度1220～1260℃；在炉时间≥160min且均热段时间≥50min。
  9. 根据权利要求3所述的制备方法，其特征在于，粗轧工序：粗轧道次选择3+5模式，即R1来回轧制3次，R2来回轧制5次，同时控制R1开轧温度≥1130℃，高温下进行喷水除鳞；中间坯厚度30～45mm，粗轧阶段累积压下率大于75％。
  10. 根据权利要求3所述的制备方法，其特征在于，精轧工序：精轧开轧温度为1030～1100℃，F1压下率≥45％，F2压下率≥25％，终轧温度≥890℃。
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