WO2022174530A1 - 易切削非调质钢及其制备方法 - Google Patents

易切削非调质钢及其制备方法 Download PDF

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WO2022174530A1
WO2022174530A1 PCT/CN2021/096014 CN2021096014W WO2022174530A1 WO 2022174530 A1 WO2022174530 A1 WO 2022174530A1 CN 2021096014 W CN2021096014 W CN 2021096014W WO 2022174530 A1 WO2022174530 A1 WO 2022174530A1
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rolling
rolled material
quenched
free
tempered steel
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PCT/CN2021/096014
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English (en)
French (fr)
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周蕾
刘磊
付建勋
刘文学
邓伟
田钱仁
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南京钢铁股份有限公司
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Priority to EP21926247.4A priority Critical patent/EP4283008A1/en
Publication of WO2022174530A1 publication Critical patent/WO2022174530A1/zh

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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
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/0075—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for rods of limited length
    • 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
    • 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
    • B21B1/16—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 wire rods, bars, merchant bars, rounds wire or material of like small cross-section
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B3/00—Rolling materials of special alloys so far as the composition of the alloy requires or permits special rolling methods or sequences ; Rolling of aluminium, copper, zinc or other non-ferrous metals
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21C—MANUFACTURE OF METAL SHEETS, WIRE, RODS, TUBES OR PROFILES, OTHERWISE THAN BY ROLLING; AUXILIARY OPERATIONS USED IN CONNECTION WITH METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL
    • B21C37/00—Manufacture of metal sheets, bars, wire, tubes or like semi-manufactured products, not otherwise provided for; Manufacture of tubes of special shape
    • 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
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/02—Hardening articles or materials formed by forging or rolling, with no further heating beyond that required for the formation
    • 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
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/56—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering characterised by the quenching agents
    • C21D1/60—Aqueous agents
    • 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
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/005—Heat treatment of ferrous alloys containing Mn
    • 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
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/008—Heat treatment of ferrous alloys containing Si
    • 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
    • C21D7/00—Modifying the physical properties of iron or steel by deformation
    • C21D7/13—Modifying the physical properties of iron or steel by deformation by hot working
    • 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
    • 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
    • C21D8/06—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires
    • C21D8/065—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires of ferrous 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
    • C22C38/04—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
    • 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
    • C22C38/60—Ferrous alloys, e.g. steel alloys containing lead, selenium, tellurium, or antimony, or more than 0.04% by weight of sulfur
    • 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
    • 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
    • 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 relates to a steel and a preparation method thereof, in particular to a free-cutting non-quenched and tempered steel and a preparation method thereof.
  • Non-quenched and tempered steel is the most representative type of steel. It does not need to be quenched and tempered with energy consumption and polluting and high-temperature tempering, but has the same excellent properties as quenched and tempered steel. Therefore, non-tempered steel is vigorously developed. Quality steel technology has become the current mainstream trend.
  • Free-cutting non-quenched and tempered steel is based on non-quenched and tempered steel with a large amount of sulfur (S: 0.06 to 0.30%) added.
  • the sulfide formed by it has the functions of cutting off the continuity of the metal and lubricating the tool, so that the steel has good properties. It has excellent cutting performance and is widely used in precision machine tool processing and automobile parts manufacturing. However, because these sulfides have good deformability, they will deform into long strips along the rolling direction during the rolling process, which not only easily causes internal cracking and surface defects of the rolled material, but also causes deterioration of mechanical properties. Therefore, on the premise of ensuring the good cutting performance of the steel, how to formulate a reasonable heating system and rolling process to improve the product yield and overall quality has always been a difficult problem for researchers.
  • the invention patent whose publication number is CN 110681698A discloses a 38MnS6L non-quenched and tempered round steel rolling process, which reduces the heating temperature of the heating furnace and increases the tapping speed, and adopts a secondary phosphorus removal method to achieve as much as possible.
  • the patent only controls the surface quality of the rolled material, but the problem of internal cracking of the rolled material still exists, and the yield of the product is still not guaranteed. And because the high-pressure water is used to remove phosphorus again after the hot rolling, the production cost and energy loss are greatly increased.
  • the invention patent with publication number CN108246801A discloses a large-scale non-quenched and tempered steel rolling equipment and its rolling production method, which stably controls the final rolling temperature of the non-quenched and tempered steel bar.
  • the cooling rate is used to refine the grains and stabilize the structure, thereby improving the mechanical properties and surface quality of the rolled material.
  • the patent also only improves the surface quality of the product, and does not control any cracks that may occur inside.
  • the S content of the implementation object in this patent is only 0.02-0.07%, and the sulfur content in the free-cutting non-quenched and tempered steel is generally 0.06-0.30%, the probability of cracking of the rolled material will inevitably increase with the increase of the sulfur content. , the cracking of the rolled material cannot be avoided only by refining the grains, so the patent has a large composition limitation.
  • the invention patent with publication number CN 105234170 A discloses a large-scale free-cutting steel rolling method, which adjusts the form of sulfide by controlling the temperature in the rolling process, so that the rolled material can obtain better cutting performance and surface quality.
  • the heating temperature of the slab and the rolling temperature are set too low.
  • the lower heating temperature will lead to the failure of the microalloying elements to completely dissolve into the steel matrix, resulting in the loss of the mechanical properties of the rolled product.
  • a lower starting rolling temperature will not only affect and reduce the crack resistance of the material, but also lower the lower limit of the finishing rolling temperature, while an excessively low finishing rolling temperature will lead to an increase in the deformation force of the steel, which is easy to cause difficulty in rolling.
  • the invention patent with publication number CN 109207840 A discloses a free-cutting steel and its manufacturing method.
  • the steel manufacturing method includes: smelting and refining, casting, rolling, forging, and two-stage cooling (the cooling rate of the first stage is 20 ⁇ 30°C/min cooling to 650°C ⁇ 700°C, air cooling to room temperature in the second stage).
  • the length direction of the sulfide is adjusted to be consistent with the rolling direction of the steel plate by rolling, but in the actual production process, too low rolling temperature will cause the steel grade to be prone to "splitting" during the rolling process.
  • the present invention provides a free-cutting non-quenched and tempered steel with high yield and overall quality.
  • Another object of the present invention is to provide a preparation method of the above-mentioned free-cutting non-quenched and tempered steel, which can improve the crack resistance and mechanical properties of the rolled material without increasing the production cost, thereby alleviating the sulfide-induced Cracking of rolled products and deterioration of mechanical properties.
  • the free cutting non-quenched and tempered steel according to the present invention the composition is calculated by mass percentage, including C: 0.15-0.34%, Si: 0.10-0.81%, Mn: 0.45-1.60%, P: 0.02-0.09 , S: 0.08-0.38%, V: 0.05-0.20%, Nb: 0.05-0.15%, the balance of iron and inevitable impurities.
  • the structure of the free-cutting non-quenched and tempered steel is ferrite + pearlite, wherein the proportion of ferrite is 20% to 52%, and the balance is pearlite.
  • the finished product size of steel is ⁇ 20 ⁇ 150mm.
  • the technical solution adopted by the preparation method provided by the present invention includes the following steps:
  • the slab In the heating furnace, the slab is heated to 800-900°C at a heating rate of 15-20°C/min. The faster heating rate in the early stage can make the deformation force inside the slab get faster. It is beneficial to improve the internal defects of the casting billet; it is then heated to 900 to 1000 °C at a heating rate of 6 to 10 °C/min to ensure that the microalloying elements are dissolved into the steel matrix as much as possible, thereby improving the product's various properties. Finally, the billet is heated to 1150-1200°C at a heating rate of 4-8°C/min, and kept for 70-90min; the inside of the billet is heated evenly, which greatly improves its crack resistance;
  • Hot tandem rolling and finishing rolling The rolling material is sent to the hot tandem rolling and finishing rolling unit for rolling.
  • the control of the finishing rolling temperature is extremely important in the whole rolling process. Rolling at a lower finishing rolling temperature is extremely important. The material has high tensile strength, and its crack resistance will also be significantly improved.
  • the final rolling temperature should not be too low. Too low final rolling temperature will cause the deformation force of the rolled material to decrease and form hot forging cracks. Therefore, the final rolling temperature should be controlled at 950-990 °C;
  • Controlled cooling of the rolled material After finishing rolling, part of the welding ring is removed, and the rolled material is cooled by water spray, and the rolled material is cooled to 580-620 °C, which is conducive to the formation of ferrite + pearlescent with higher toughness
  • the body structure can improve the overall mechanical properties of the steel; it is then transported to the cooling bed for air cooling, so that the hydrogen in the rolled material is released, thereby reducing the phenomenon of hydrogen embrittlement and effectively reducing the probability of cracking during the use of the product.
  • the step of finishing the rolled material is also included: after the air cooling, the rolled material is straightened, and the surface is polished to eliminate local defects and further improve the surface quality of the rolled material.
  • the free-cutting non-quenched and tempered steel can alleviate the cracking and mechanical properties of the rolled material caused by sulfide by formulating a reasonable heating system and rolling process without increasing the production cost and energy consumption. Performance degradation phenomenon.
  • the three-stage heating method and measures such as increasing the opening rolling temperature and reducing the final rolling temperature not only effectively improve the crack resistance of the rolled material, but also make various micro-alloying elements as solid solution into the steel matrix as much as possible to improve
  • the mechanical properties of the product are improved; and by taking measures such as high-pressure water spray, head welding ring, cooling bed air cooling and rolling surface grinding, the probability of cracks during the rolling process is further reduced and the surface quality of the product is improved.
  • Example 1 Free-cutting non-quenched and tempered steel
  • the section of the slab is 200mm ⁇ 200mm, and the components are C: 0.28%, Si: 0.52%, Mn: 1.21%, P: 0.05%, S: 0.21%, V by mass percentage : 0.10%, Nb: 0.08%, and the balance is Fe and impurities.
  • the composition meets the requirements of the free-cutting non-quenched and tempered steel grade, and the heating and rolling methods in this embodiment are as follows:
  • the first stage firstly heat the slab to 880°C at a heating rate of 18°C/min, the second stage: then gently heat it to 960°C at a heating rate of 7°C/min, the third stage: finally heat it to 6°C /min heating speed to slowly heat it to 1170 °C, and keep it for 75min;
  • the rolled material is cooled by water spray, and after the temperature of the rolled material is reduced to 600 °C, it is transported to a cooling bed for air cooling;
  • the free-cutting non-quenched and tempered steel product rolled by the above process has a diameter of 30mm, a Brinell hardness of 158, a tensile strength of 720MPa, and a microstructure of 36% ferrite + 64% pearlite.
  • the overall mechanical properties of the product are good.
  • the cracking phenomenon of the obtained free-cutting non-quenched and tempered steel rolling material basically disappears, and the finished product rate is increased from the original 60% to 90%.

Abstract

本发明公开了一种易切削非调质钢及其制备方法，在不提高生产成本及能源损耗的前提下，通过制定合理的加热制度以及轧制工艺，缓解了因硫化物引发的轧材开裂及力学性能恶化现象。采取三段式加热方法以及提高开轧温度、降低终轧温度等措施，不仅有效提高了轧材的抗裂纹能力，并且使各种微合金元素都尽可能地固溶进了钢基体中从而提高了产品力学性能；而通过采取高压喷水、头部焊环、冷床空冷以及轧材表面打磨等措施，则更进一步的降低了轧制过程中裂纹产生的几率，提高了产品的表面质量。采用本发明所提供的轧制方法生产出的易切削非调质钢产品具有较高的成材率以及更为优良的性能。

Description

易切削非调质钢及其制备方法 技术领域
本发明涉及一种钢及其制备方法，具体涉及一种易切削非调质钢及其制备方法。
背景技术
随着钢铁工业的迅速发展，各种不可再生资源的储量正在不断下降，各国钢铁企业都在大力研发低能耗、低成本的产品以应对资源消耗危机。非调质钢就是其中最具代表的钢种，其不需要采用能耗、污染极大的淬火和高温回火的调质处理，却与调质钢拥有相同的优良性能，因此大力发展非调质钢技术已经成为了目前的主流趋势。
易切削非调质钢是在非调质钢的基础上添加了大量的硫元素(S：0.06～0.30％)，其形成的硫化物具有隔断金属连续性及润滑刀具的作用，使钢材拥有良好的切削加工性能，被广泛应用于精密机床加工以及汽车零件制造。但由于这些硫化物具有良好的变形能力，在轧制过程中会延轧制方向变形成长条状，不仅极易造成轧材内部开裂以及表面缺陷，还会造成力学性能恶化。因此在保证钢材具有良好切削性能的前提下，如何制定合理的加热制度以及轧制工艺来提高产品成材率以及整体质量一直都是困扰科研人员的难题。
公开号为CN 110681698A的发明专利公开了一种38MnS6L非调质圆钢轧制工艺，降低了加热炉的加热温度的同时提高了出钢速度，并采用了二次除磷手段，以达到尽可能减少钢材表面氧化铁皮的目的，从而提高了轧材的表面质量。该专利只是对轧材的表面质量进行了控制，但轧材内部开裂的问题依然存在，产品的成材率依然得不到保障。并且由于在热轧结束后再次使用高压水除磷极大提高了生产成本以及能源损耗。
公开号为CN108246801A的发明专利公开了一种大规格非调质钢轧制设备及其轧制生产方法，稳定控制了非调质钢棒材的终轧温度，通过调整轧制结束后棒材的冷却速度以达到细化晶粒，稳定组织的作用，从而提高了轧材的力学性能和表面质量。该专利同样只是提高了产品的表面质量，并未对内部可能产生的裂纹进行任何控制。并且由于该专利中实施对象的S含量仅为0.02～0.07％，而易切削非调质钢中的硫含量一般在0.06～0.30％，随着硫含量的提高轧材的开裂的几率必然会提高，仅仅依靠细化晶粒还是无法避免轧材的开裂，因此该专利存在 着较大的成分局限性。
公开号为CN 105234170 A的发明专利公开了一种大规模易切削钢轧制方法，通过控制轧制过程中的温度来调整硫化物的形态，使轧材获得更好的切削性能以及表面质量。该专利为了实现对硫化物的调控，将铸坯的加热温度以及开轧温度设置的过低。较低的加热温度会导致微合金元素无法完全固溶进钢基体中造成轧材力学性能的损失。较低的开轧温度不仅会影响降低材料的抗裂纹能力，还降低了终轧温度的下限，而过低的终轧温度则会导致钢材的变形力提高，易造成轧制困难。
公开号为CN 109207840 A的发明专利公开了一种易切削钢及其制造方法，该钢种制造方法包括：冶炼和精炼、浇铸、轧制、锻造、两段式冷却(第一阶段冷却速度20～30℃/min冷却至650℃～700℃，第二阶段空冷到室温)。该专利通过轧制调整硫化物长度方向与钢板的轧制方向一致，但在实际生产过程中，过低的轧制温度会导致该钢种在轧制过程容易出现“劈头”现象。
发明内容
发明目的：为了克服现有技术的缺陷，本发明提供一种易切削非调质钢，该钢具有较高的成材率和整体质量。
本发明的另一目的是提供一种上述易切削非调质钢的制备方法，该方法能够在不增加生产成本的前提下，提高轧材的抗裂纹能力以及力学性能，从而缓解硫化物引发的轧材开裂及力学性能恶化现象。
技术方案：本发明所述的一种易切削非调质钢，成分以质量百分比计，包括C：0.15～0.34％、Si：0.10～0.81％、Mn：0.45～1.60％、P：0.02～0.09、S：0.08～0.38％、V：0.05～0.20％、Nb：0.05～0.15％，余量的铁及不可避免的杂质。
具体的，该易切削非调质钢的组织为铁素体+珠光体，其中铁素体的比例在20％～52％，余量为珠光体。
钢的成品尺寸为φ20～150mm。
对应于上述易切削非调质钢，本发明提供的制备方法所采用的技术方案，包括如下步骤：
(1)三段式加热：在加热炉中先以15～20℃/min的加热速度将铸坯加热至800～900℃，前期较快的加热速度可以使铸坯内部的变形力得到更快的释放，有利于改善铸坯的内部缺陷；再以6～10℃/min的加热速度加热至900～1000℃，以保证微合金元素尽可能地固溶进钢基体中，从而提高产品的各项力学性能；最后 以4～8℃/min的加热速度将铸坯加热至1150～1200℃，并保温70～90min；使铸坯内部受热均匀，极大提高了其抗裂纹能力；
(2)高压水去除氧化铁皮：由于加热后的铸坯表面产生了一层氧化铁皮，这些氧化铁皮会在后续的轧制过程中与钢基体发生挤压从而降低轧材的表面质量，因此在粗轧前需要采用高压水对表面的氧化铁皮进行喷除。水压过高会导致轧材表面温降过大，过低则会导致不能有效去除氧化铁皮，所以需将水压控制在18～22Mpa；
(3)对铸坯进行粗轧：开轧温度控制在1130～1180℃，在较高的开轧温度下材料具有更高的抗裂纹能力，其在轧制过程中受硫化物的影响也越小，轧材也越不易开裂；粗轧结束后喷冷却水对轧材进行降温，将轧材的表面温度控制在1000～1040℃；
(4)轧材劈头处理：经冷却水降温后，由于轧材劈头部分的温降较大，因此需要将原有劈头去除后再对头部进行焊环处理；可以有效解决热连轧过程中因轧材受热不均匀引发的劈头开裂问题；
(5)热连轧及精轧：将轧材送入热连轧和精轧机组进行轧制，终轧温度的控制在整个轧制过程中是极为重要的，较低的终轧温度下轧材具有较高的抗拉强度，其抗裂纹能力也会得到明显提高。但终轧温度也不宜过低，过低的终轧温度会导致轧材变形力下降，形成锻造热裂纹，因此终轧温度控制在950～990℃；
(6)轧材控冷：精轧结束后将焊环部分去除，并对轧材采取喷水冷却处理，将轧材冷却至580～620℃，有利于形成韧性较高的铁素体+珠光体组织，可以提高钢材的整体力学性能；随后将其运送至冷床上进行空冷，使轧材中的氢散发出来，从而降低氢脆现象，可有效降低产品使用过程中的开裂几率。
其中，还包括轧材精整的步骤：空冷结束后对轧材进行矫直处理，并对表面进行打磨，消除局部缺陷，进一步提高轧材的表面质量。
有益效果：与现有技术相比，该易切削非调质钢在不增加生产成本及能源消耗的前提下，通过制定合理的加热制度以及轧制工艺缓解了硫化物引发的轧材开裂及力学性能恶化现象。采取三段式加热方法以及提高开轧温度、降低终轧温度等措施，不仅有效提高了轧材的抗裂纹能力，并且使各种微合金元素都尽可能地固溶进了钢基体中从而提高了产品力学性能；而通过采取高压喷水、头部焊环、冷床空冷以及轧材表面打磨等措施，则更进一步的降低了轧制过程中裂纹产生的几率，提高了产品的表面质量。极大的提高了易切削非调质钢的产品成材率和整 体质量。
具体实施方式
实施例1：易切削非调质钢铸坯断面为200mm×200mm，成分以质量百分比计为C：0.28％、Si：0.52％、Mn：1.21％、P：0.05％、S：0.21％、V：0.10％、Nb：0.08％，余量为Fe和杂质。成分符合该易切削非调质钢钢种要求，本实施例中的加热及轧制方法如下：
(1)采用三段式加热方式。第一段：先以18℃/min的加热速度将铸坯加热至880℃，第二段：再以7℃/min的加热速度将其平缓加热至960℃，第三段：最后以6℃/min的加热速度将其缓慢加热到1170℃，并保温75min；
(2)采用高压水对铸坯加热后表面存在的氧化铁皮进行处理，水压控制在21MPa；
(3)采用双辊可逆式轧机对铸坯进行粗轧，开轧温度控制在1160℃，粗轧结束后喷冷却水对轧材进行降温，将轧材表面温度控制在1030℃；
(4)经冷却水降温后由于导热原因，轧材劈头部分的温度只有960℃，因此采用液压剪将劈头去除后再对头部进行焊环处理；
(5)将焊环处理后的轧材送入热连轧和精轧机组进行轧制，终轧温度控制在970℃，精轧结束后使用液压剪将焊环部分去除；
(6)精轧结束后对轧材采取喷水冷却处理，轧材温度降低至600℃后，运送至冷床上进行空冷；
(7)空冷结束后对轧材进行矫直处理，同时对表面进行打磨，消除局部缺陷。
按上述工艺轧制出的易切削非调质钢成品直径为30mm，布氏硬度为158，抗拉强度为720MPa，组织为36％铁素体+64％珠光体，产品整体力学性能良好。
其他实施例的制备过程与实施例1一致，各参数略有不同。各实施例的成分见表1所示，余量为Fe和杂质。
表1实施例2-6成分(wt.％)
Figure PCTCN2021096014-appb-000001
Figure PCTCN2021096014-appb-000002
实施例2-6的制备参数见表2所示：
表2各实施例工艺参数
Figure PCTCN2021096014-appb-000003
实施例2-6轧制出的易切削非调质钢成品的技术参数见表3所示：
表3各实施例钢技术参数
Figure PCTCN2021096014-appb-000004
采用本发明的成分设计和制备方法，得到的易切削非调质钢轧材开裂现象基本消失，成材率由原来的60％提高至90％。

Claims (8)

  1. 一种易切削非调质钢，其特征在于，成分以质量百分比计，包括C：0.15～0.34％、Si：0.10～0.81％、Mn：0.45～1.60％、P：0.02～0.09、S：0.08～0.38％、V：0.05～0.20％、Nb：0.05～0.15％，余量的铁及不可避免的杂质。
  2. 根据权利要求1所述的易切削非调质钢，其特征在于，组织为铁素体+珠光体，其中铁素体的比例在20％～52％，余量为珠光体。
  3. 根据权利要求1所述的易切削非调质钢，其特征在于，钢的成品尺寸为
    Figure PCTCN2021096014-appb-100001
  4. 一种根据权利要求1-3任一项所述的易切削非调质钢的制备方法，其特征在于，包括如下步骤：
    (1)三段式加热：先以15～20℃/min的加热速度将铸坯加热至800～900℃，再以6～10℃/min的加热速度加热至900～1000℃，最后以4～8℃/min的加热速度将铸坯加热至1150～1200℃，并保温70～90min；
    (2)高压水去除氧化铁皮：水压控制在18～22MPa；
    (3)对铸坯进行粗轧：开轧温度控制在1130～1180℃，粗轧结束后喷冷却水对轧材进行降温，将轧材的表面温度控制在1000～1040℃；
    (4)轧材劈头处理：将原有劈头去除后再对头部进行焊环处理；
    (5)热连轧及精轧：将轧材送入热连轧和精轧机组进行轧制，终轧温度控制在950～990℃；
    (6)轧材控冷：精轧结束后将焊环部分去除，并对轧材采取喷水冷却处理，将轧材冷却至580～620℃，随后将其运送至冷床上进行空冷。
  5. 根据权利要求4所述的制备方法，其特征在于，还包括轧材精整的步骤：空冷结束后对轧材进行矫直处理，并对表面进行打磨，消除局部缺陷。
  6. 根据权利要求3所述的制备方法，其特征在于，所述步骤(3)中，采用双辊可逆轧机对铸坯进行粗轧。
  7. 根据权利要求3所述的制备方法，其特征在于，所述步骤(4)中，采用液压剪将轧材劈头部分去除。
  8. 根据权利要求3所述的制备方法，其特征在于，所述步骤(6)中，精轧结束后使用液压剪将焊环部分去除。
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