WO2020111478A1 - Austenitic lightweight steel material having high toughness and preparation method therefor - Google Patents

Austenitic lightweight steel material having high toughness and preparation method therefor Download PDF

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Publication number
WO2020111478A1
WO2020111478A1 PCT/KR2019/012316 KR2019012316W WO2020111478A1 WO 2020111478 A1 WO2020111478 A1 WO 2020111478A1 KR 2019012316 W KR2019012316 W KR 2019012316W WO 2020111478 A1 WO2020111478 A1 WO 2020111478A1
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high toughness
weight
steel material
lightweight steel
steel
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PCT/KR2019/012316
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French (fr)
Korean (ko)
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박준영
박성준
강전연
김성대
문준오
이창훈
이태호
장재훈
하헌영
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한국기계연구원
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • 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
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • 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
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0226—Hot rolling
    • 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
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/04—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing
    • 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
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/04—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing
    • C21D8/0447—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing characterised by the heat treatment
    • C21D8/0463—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing characterised by the heat treatment following hot rolling
    • 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
    • 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
    • C21D9/0062—Heat-treating apparatus with a cooling or quenching zone
    • 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
    • C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
    • 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
    • C21D2211/001—Austenite

Definitions

  • the present invention relates to an austenitic lightweight steel material and a method for manufacturing the same, and more specifically, a minimum that can secure high toughness through a correlation between the Al content and the cooling rate in the Fe-C-Mn-Al alloy composition.
  • the present invention relates to an austenitic lightweight steel material having high toughness with a known cooling rate and a method for manufacturing the same.
  • Fuel consumption and environmental regulations are being strengthened due to rising energy resource prices due to exhaustion of fossil fuels and environmental pollution. Accordingly, in the field of structural materials for automobiles and transportation equipment, a weight reduction technology for a vehicle body for increasing energy efficiency is becoming important.
  • lightweight steel materials contain a large amount of aluminum (Al) having a low atomic weight, while having a low density, and can secure high strength and excellent ductility, and have attracted much attention as a material for weight reduction since the 2000s.
  • Al aluminum
  • the object of the present invention is a Fe-C-Mn-Al alloy composition in the austenite-based lightweight steel material with high toughness to find out the minimum cooling rate to ensure high toughness through the correlation between the content of Al and the cooling rate and It is to provide the manufacturing method.
  • Method for producing austenitic lightweight steel having high toughness is (a) manganese (Mn): 28 to 32% by weight, aluminum (Al): 7.5 to 10.5% by weight, Carbon (C): 0.9 to 1.1% by weight and the remaining iron (Fe) and hot rolling the steel containing inevitable impurities; (B) homogenizing heat treatment of the hot-rolled steel material; And (c) cooling the homogenized heat-treated steel material at a cooling rate of 20° C./min or more; and after the step (c), the steel material has an impact absorption energy of 50 J or more at 25° C. Is done.
  • molybdenum (Mo): 1.5 to 2.5% by weight may be further added to the steel.
  • the cooling is more preferably performed at a cooling rate of 20 ⁇ 21,000 °C / min.
  • the steel material has a density of 7 g/cm 3 or less.
  • the steel material has a Vickers hardness of 200 Hv or more.
  • Austenitic lightweight steel having high toughness is manganese (Mn): 28 to 32 wt%, aluminum (Al): 7.5 to 10.5 wt%, carbon (C): It contains 0.9 to 1.1% by weight and the rest of iron (Fe) and inevitable impurities, and is manufactured by cooling at a cooling rate of 20°C/min or higher after hot rolling and homogenizing heat treatment, and the shock absorption energy at 25°C is 50J or more. It is characterized by having.
  • the aluminum (Al) is more preferably added in an amount of 8.0 to 10.4% by weight.
  • the carbon (C) is more preferably added at 0.92 to 1.01% by weight.
  • Molybdenum (Mo): 1.5 to 2.5% by weight may be further added to the steel.
  • the steel material has a density of 7 g/cm 3 or less.
  • the steel material has a Vickers hardness of 200 Hv or more.
  • the austenitic lightweight steel having high toughness according to the present invention and its manufacturing method have a lower limit of the cooling rate that can secure high toughness through a correlation between the Al content and the cooling rate in the Fe-C-Mn-Al alloy composition. Found out.
  • the austenite-based lightweight steel material having high toughness according to the present invention and its manufacturing method have a Vickers hardness of 200 Hv or more and 7 g/cm 3 through a correlation between the Al content and the cooling rate in the Fe-C-Mn-Al alloy composition. While having the following density, the lower limit value of the cooling rate at which the shock absorption energy at 25°C was 50 J or more was found.
  • FIG. 1 is a process flow chart showing a method of manufacturing austenitic lightweight steel having high toughness according to the present invention.
  • Figure 2 is a TEM photograph of the specimen according to Example 4.
  • Figure 3 is a TEM photograph of the specimen according to Example 6.
  • the austenitic lightweight steel material having high toughness has a Vickers hardness of 200 Hv or more through a correlation between the Al content and the cooling rate in the Fe-C-Mn-Al alloy composition, and at 25°C. The lower limit of the cooling rate at which the shock absorption energy is 50 J or more was found.
  • austenitic lightweight steel having high toughness is manganese (Mn): 28 to 32 wt%, aluminum (Al): 7.5 to 10.5 wt%, carbon (C): 0.9 to 1.1 It contains weight percent and the remaining iron (Fe) and unavoidable impurities, and is produced by performing hot rolling and homogenizing heat treatment, and cooling at a cooling rate of 20° C./min or higher.
  • molybdenum (Mo): 1.5 to 2.5% by weight may be further added to the steel.
  • the steel material has a density of 7 g/cm 3 or less.
  • Manganese (Mn) is an austenite stabilizing element.
  • the austenitic lightweight steel according to the present invention has a large amount of ferrite stabilizing element Al compared to the conventional twin-inorganic plasticity (TWIP, TWin Induced Plasticity) steel, thereby austenite-based austenitic single-phase structure
  • TWIP twin-inorganic plasticity
  • the manganese (Mn) content must be increased to 28% by weight or more compared to TWIP steel.
  • the amount of manganese (Mn) is added in excess of 32% by weight, it acts as a factor that deteriorates ductility and toughness by accelerating the formation of vulnerable ⁇ -Mn phase.
  • manganese (Mn) is preferably added at a content ratio of 28 to 32% by weight of the total weight of the austenite-based lightweight steel according to the present invention, and a more preferred range may present 29 to 30% by weight.
  • Aluminum (Al) is an essential element for weight reduction, and is lighter than Fe atoms and has a large volume per mole, thereby reducing the density of steel.
  • the cooling rate slows down, resulting in a decrease in toughness. Accordingly, in the present invention, it has been found that while aluminum is added at a content ratio of 10.5 weight or less, the cooling rate must be controlled to 20°C/min or more, more preferably 20 to 21,000°C/min to ensure high toughness.
  • the aluminum (Al) is added at a content ratio of 7.5 to 10.5% by weight of the total weight of the austenite-based lightweight steel according to the present invention, and a more preferred range may be 8.0 to 10.4% by weight.
  • a more preferred range may be 8.0 to 10.4% by weight.
  • the addition amount of aluminum (Al) is less than 7.5% by weight, the addition amount is insufficient, and it may be difficult to properly exhibit a light weight effect.
  • the amount of aluminum (Al) added exceeds 10.5% by weight, the stability of the austenite phase is reduced, and impact toughness is generated by generating ferrite and a large amount of ⁇ -carbide precipitates of Fe 3 AlC type. It can decrease.
  • Carbon (C) is an austenite stabilizing element and is required for the production of austenitic lightweight steel. In addition, carbon (c) contributes to an increase in tensile strength due to the precipitation strengthening effect through carbide formation.
  • the carbon (C) is preferably added at a content ratio of 0.9 to 1.1% by weight of the total weight of the austenite-based lightweight steel according to the present invention, and a more preferable range may be 0.92 to 1.01% by weight.
  • a more preferable range may be 0.92 to 1.01% by weight.
  • the addition amount of carbon (C) is less than 0.9% by weight, the addition amount is insufficient, and thus it may be difficult to properly exhibit the strength improving effect.
  • the addition amount of carbon (C) exceeds 1.1% by weight, as a large amount of Fe 3 AlC type ⁇ -carbide precipitates are generated, impact toughness is reduced and it may act as a cause of cracking during rolling. You can.
  • Molybdenum (Mo) is an element that retards the precipitation of ⁇ -carbide in austenite and contributes to improving the toughness of lightweight steel.
  • the molybdenum (Mo) is preferably added at a content ratio of 1.5 to 2.5% by weight of the total weight of the austenite-based lightweight steel according to the present invention, and more preferably 1.8 to 2.0% by weight.
  • the amount of molybdenum (Mo) added is less than 1.5% by weight, it is difficult to properly exhibit the above effects.
  • the amount of molybdenum (Mo) exceeds 2.5% by weight, by forming Mo carbide (Mo-enriched carbide) it can increase the strength and cause a problem of dropping toughness.
  • FIG. 1 is a process flow chart showing a method for manufacturing austenitic lightweight steel having high toughness according to the present invention.
  • a method of manufacturing austenitic lightweight steel having high toughness includes a hot rolling step (S110), a homogenizing heat treatment step (S120) and a cooling step (S130).
  • manganese (Mn) 28 to 32 wt%
  • aluminum (Al) 7.5 to 10.5 wt%
  • carbon (C) 0.9 to 1.1 wt%
  • the remaining iron (Fe) and unavoidable impurities The steel material to be hot rolled.
  • molybdenum (Mo) 1.5 to 2.5% by weight may be further added to the steel.
  • hot rolling is preferably performed at a finishing rolling temperature of 900°C or higher, and more preferably 900 to 1,150°C can be suggested.
  • finish rolling temperature is less than 900°C, Fe 3 AlC type ⁇ -carbide is formed in a large amount at the grain boundary, thereby lowering the impact toughness, which may increase the possibility of breakage during the manufacturing process of the lightweight steel.
  • the hot-rolled steel material is subjected to a homogenization heat treatment at 1,000 to 1,100°C for 1 to 3 hours.
  • the homogenization treatment temperature is less than 1,000°C, Fe 3 AlC type ⁇ -carbide, which may occur during cooling after rolling, may not be dissolved.
  • the homogenization heat treatment temperature exceeds 1,100°C, strength and impact toughness may be deteriorated due to grain coarsening.
  • the homogenized heat-treated steel is cooled to room temperature at a cooling rate of 20°C/min or higher.
  • the room temperature may be 1 ⁇ 40 °C, but is not limited thereto.
  • the cooling is more preferably carried out at a cooling rate of 20 ⁇ 21,000 °C / min.
  • the content of aluminum (Al) exceeds 10.5% by weight, it was confirmed that the toughness is lowered when the cooling rate is slowed while being added in a large amount.
  • the cooling rate should be controlled to 20°C/min or more, more preferably 20 to 21,000°C/min to ensure high toughness. I figured it out.
  • the austenitic lightweight steel having high toughness manufactured by the above steps can secure high toughness through a correlation between the Al content and the cooling rate in the Fe-C-Mn-Al alloy composition. The lower limit of the cooling rate was found.
  • the austenite-based lightweight steel material having high toughness manufactured by the method according to the embodiment of the present invention has a Vickers hardness of 200 Hv or more through a correlation between the Al content and the cooling rate in the Fe-C-Mn-Al alloy composition, and While having a density of 7 g/cm 3 or less, the lower limit of the cooling rate at which the shock absorption energy at 25° C. is 50 J or more was found.
  • the ingot having the chemical components listed in Table 1 was prepared in a vacuum induction melting furnace, the ingot was reheated at 1,150°C for 2 hours, and hot rolled to a thickness of 12 mm under the condition of 1,000°C finish hot rolling. Subsequently, after performing a homogenization heat treatment at 1,050° C. for 2 hours, the specimens according to Examples 1 to 15 and Comparative Examples 1 to 15 were prepared by cooling to room temperature at the cooling rates shown in Table 2.
  • Table 2 shows the mechanical property evaluation results for the specimens according to Examples 1 to 15 and Comparative Examples 1 to 15.
  • the specimens according to Examples 1 to 15 satisfy both Vickers hardness of 200 Hv or more and density of 7 g/cm 3 or less corresponding to the target value. That is, the specimens according to Examples 1 to 15 can be confirmed to have a low specific gravity as measured by a density of 7 g/cm 3 or less by adding 9 to 10.41 wt% of Al as a result of density measurement.
  • FIG. 2 is a TEM photograph of the specimen according to Example 4
  • FIG. 3 is a TEM photograph of the specimen according to Example 6
  • FIG. 4 is a TEM photograph of the specimen according to Comparative Example 13.
  • the specimen according to Example 4 can be confirmed that the microstructure is composed of a single phase of austenite ( ⁇ ) by cooling at a rapid cooling rate of 20,000° C./min after homogenization heat treatment.
  • the specimen according to Example 6 is cooled at a slow cooling rate of 25° C./min after homogenization heat treatment, so that the microstructure is in the austenite ( ⁇ ) phase and austenite ( ⁇ ) phase in the mouth.
  • Fe 3 AlC type ⁇ -carbide ⁇ -carbide
  • ⁇ -carbide of Fe 3 AlC type is also developed at the grain boundary.
  • the microstructure has a composite structure of austenite and ferrite ( ⁇ + ⁇ ), as shown in Figure 4, after homogenization heat treatment, cooling using a rapid cooling rate of 20,000 °C / min.
  • Fe 3 AlC type ⁇ -carbide was developed in the austenite ( ⁇ ) granules and grain boundaries. Even though it was rapidly cooled by a relatively high Al content, compared to Example 6, a relatively large grain of Fe 3 AlC type ⁇ -carbide was formed at the grain boundary, and an excessive amount of Fe in the mouth. 3 It is thought that the impact toughness was deteriorated due to the development of ⁇ -carbide of AlC type.

Abstract

Disclosed are: austenitic lightweight steel material having high toughness, in which the minimum cooling rate capable of securing high toughness is determined through the correlation between Al content and cooling rate in an Fe-C-Mn-Al alloy composition; and a preparation method therefor.

Description

고인성을 갖는 오스테나이트계 경량 강재 및 그 제조 방법Austenitic lightweight steel with high toughness and its manufacturing method
본 발명은 오스테나이트계 경량 강재 및 그 제조 방법에 관한 것으로, 보다 상세하게는 Fe-C-Mn-Al 합금 조성에서 Al의 함량과 냉각속도 간의 상관 관계를 통하여 고인성을 확보할 수 있는 최소한의 냉각속도를 알아낸 고인성을 갖는 오스테나이트계 경량 강재 및 그 제조 방법에 관한 것이다.The present invention relates to an austenitic lightweight steel material and a method for manufacturing the same, and more specifically, a minimum that can secure high toughness through a correlation between the Al content and the cooling rate in the Fe-C-Mn-Al alloy composition. The present invention relates to an austenitic lightweight steel material having high toughness with a known cooling rate and a method for manufacturing the same.
화석연료 고갈에 따른 에너지 자원 가격 상승과 환경오염 문제로 인해 연비 및 환경 규제가 강화되고 있다. 이에 따라, 자동차 및 수송기기의 구조재료분야에서는 에너지 효율을 증가시키기 위한 차체 경량화 기술이 중요시되고 있다.Fuel consumption and environmental regulations are being strengthened due to rising energy resource prices due to exhaustion of fossil fuels and environmental pollution. Accordingly, in the field of structural materials for automobiles and transportation equipment, a weight reduction technology for a vehicle body for increasing energy efficiency is becoming important.
자동차용 철강소재 연구는 대부분 DP(dual phase) 강, TRIP(transformation-induced plasticity) 강, TWIP(twin-induced plasticity) 강과 같은 고강도강 개발을 통해 부품의 두께를 감소시키는 방향으로 진행되어 왔다.Most steel materials research for automobiles has been conducted in the direction of reducing the thickness of parts through the development of high-strength steels such as dual phase (DP) steel, transformation-induced plasticity (TRIP) steel, and twin-induced plasticity (TWIP) steel.
그러나, 부품 두께 감소는 강성 저하로 이어져, 진동과 소음 증가의 원인이 될 수 있다. 따라서, 고강도화를 통한 경량화 연구는 점차 한계에 이르고 있다.However, the decrease in part thickness leads to a decrease in stiffness, which may cause vibration and noise increase. Therefore, research on weight reduction through high strength is gradually reaching its limit.
한편, 경량 강재는 낮은 원자량을 갖는 알루미늄(Al)을 다량 함유하여 낮은 밀도를 가지면서, 높은 강도 및 우수한 연성을 확보할 수 있어, 2000년대 이후 경량화를 위한 소재로서 많은 관심을 받고 있다.On the other hand, lightweight steel materials contain a large amount of aluminum (Al) having a low atomic weight, while having a low density, and can secure high strength and excellent ductility, and have attracted much attention as a material for weight reduction since the 2000s.
본 발명의 목적은 Fe-C-Mn-Al 합금 조성에서 Al의 함량과 냉각속도 간의 상관 관계를 통하여 고인성을 확보할 수 있는 최소한의 냉각속도를 알아낸 고인성을 갖는 오스테나이트계 경량 강재 및 그 제조 방법을 제공하는 것이다.The object of the present invention is a Fe-C-Mn-Al alloy composition in the austenite-based lightweight steel material with high toughness to find out the minimum cooling rate to ensure high toughness through the correlation between the content of Al and the cooling rate and It is to provide the manufacturing method.
상기 목적을 달성하기 위한 본 발명의 실시예에 따른 고인성을 갖는 오스테나이트계 경량 강재 제조 방법은 (a) 망간(Mn) : 28 ~ 32 중량%, 알루미늄(Al) : 7.5 ~ 10.5 중량%, 탄소(C) : 0.9 ~ 1.1 중량% 및 나머지 철(Fe)과 불가피한 불순물을 포함하는 강재를 열간압연하는 단계; (b) 상기 열간압연된 강재를 균질화 열처리하는 단계; 및 (c) 상기 균질화 열처리된 강재를 20℃/min 이상의 냉각속도로 냉각하는 단계;를 포함하며, 상기 (c) 단계 이후, 상기 강재는 25℃에서의 충격흡수에너지가 50J 이상을 갖는 것을 특징으로 한다.Method for producing austenitic lightweight steel having high toughness according to an embodiment of the present invention for achieving the above object is (a) manganese (Mn): 28 to 32% by weight, aluminum (Al): 7.5 to 10.5% by weight, Carbon (C): 0.9 to 1.1% by weight and the remaining iron (Fe) and hot rolling the steel containing inevitable impurities; (B) homogenizing heat treatment of the hot-rolled steel material; And (c) cooling the homogenized heat-treated steel material at a cooling rate of 20° C./min or more; and after the step (c), the steel material has an impact absorption energy of 50 J or more at 25° C. Is done.
상기 (a) 단계에서, 상기 강재에는 몰리브덴(Mo) : 1.5 ~ 2.5 중량%가 더 첨가되어 있을 수 있다.In the step (a), molybdenum (Mo): 1.5 to 2.5% by weight may be further added to the steel.
상기 (c) 단계에서, 상기 냉각은 20 ~ 21,000℃/min의 냉각속도로 실시하는 것이 보다 바람직하다.In the step (c), the cooling is more preferably performed at a cooling rate of 20 ~ 21,000 ℃ / min.
또한, 상기 (c) 단계 이후, 상기 강재는 7g/㎤ 이하의 밀도를 갖는다.In addition, after step (c), the steel material has a density of 7 g/cm 3 or less.
이에 더불어, 상기 (c) 단계 이후, 상기 강재는 200Hv 이상의 비커스 경도를 갖는다.In addition, after the step (c), the steel material has a Vickers hardness of 200 Hv or more.
상기 목적을 달성하기 위한 본 발명의 실시예에 따른 고인성을 갖는 오스테나이트계 경량 강재는 망간(Mn) : 28 ~ 32 중량%, 알루미늄(Al) : 7.5 ~ 10.5 중량%, 탄소(C) : 0.9 ~ 1.1 중량% 및 나머지 철(Fe)과 불가피한 불순물을 포함하며, 열간압연 및 균질화 열처리를 실시한 후, 20℃/min 이상의 냉각속도로 냉각하여 제조되어, 25℃에서의 충격흡수에너지가 50J 이상을 갖는 것을 특징으로 한다.Austenitic lightweight steel having high toughness according to an embodiment of the present invention for achieving the above object is manganese (Mn): 28 to 32 wt%, aluminum (Al): 7.5 to 10.5 wt%, carbon (C): It contains 0.9 to 1.1% by weight and the rest of iron (Fe) and inevitable impurities, and is manufactured by cooling at a cooling rate of 20°C/min or higher after hot rolling and homogenizing heat treatment, and the shock absorption energy at 25°C is 50J or more. It is characterized by having.
상기 알루미늄(Al)은 8.0 ~ 10.4 중량%로 첨가된 것이 보다 바람직하다.The aluminum (Al) is more preferably added in an amount of 8.0 to 10.4% by weight.
상기 탄소(C)는 0.92 ~ 1.01 중량%로 첨가되는 것이 보다 바람직하다.The carbon (C) is more preferably added at 0.92 to 1.01% by weight.
상기 강재에는 몰리브덴(Mo) : 1.5 ~ 2.5 중량%가 더 첨가되어 있을 수 있다.Molybdenum (Mo): 1.5 to 2.5% by weight may be further added to the steel.
또한, 상기 강재는 7g/㎤ 이하의 밀도를 갖는다.Further, the steel material has a density of 7 g/cm 3 or less.
이에 더불어, 상기 강재는 200Hv 이상의 비커스 경도를 갖는다.In addition to this, the steel material has a Vickers hardness of 200 Hv or more.
본 발명에 따른 고인성을 갖는 오스테나이트계 경량 강재 및 그 제조 방법은 Fe-C-Mn-Al 합금 조성에서 Al의 함량과 냉각속도 간의 상관 관계를 통하여 고인성을 확보할 수 있는 냉각속도의 하한값을 알아내었다.The austenitic lightweight steel having high toughness according to the present invention and its manufacturing method have a lower limit of the cooling rate that can secure high toughness through a correlation between the Al content and the cooling rate in the Fe-C-Mn-Al alloy composition. Found out.
이 결과, 본 발명에 따른 고인성을 갖는 오스테나이트계 경량 강재 및 그 제조 방법은 Fe-C-Mn-Al 합금 조성에서 Al의 함량과 냉각속도 간의 상관 관계를 통하여 200Hv 이상의 비커스 경도 및 7g/㎤ 이하의 밀도를 가지면서, 25℃에서의 충격흡수에너지가 50J 이상을 나타내는 냉각속도의 하한값을 알아내었다.As a result, the austenite-based lightweight steel material having high toughness according to the present invention and its manufacturing method have a Vickers hardness of 200 Hv or more and 7 g/cm 3 through a correlation between the Al content and the cooling rate in the Fe-C-Mn-Al alloy composition. While having the following density, the lower limit value of the cooling rate at which the shock absorption energy at 25°C was 50 J or more was found.
도 1은 본 발명에 따른 고인성을 갖는 오스테나이트계 경량 강재 제조 방법을 나타낸 공정 순서도.1 is a process flow chart showing a method of manufacturing austenitic lightweight steel having high toughness according to the present invention.
도 2는 실시예 4에 따른 시편에 대한 TEM 사진.Figure 2 is a TEM photograph of the specimen according to Example 4.
도 3은 실시예 6 따른 시편에 대한 TEM 사진.Figure 3 is a TEM photograph of the specimen according to Example 6.
도 4는 비교예 13에 따른 시편에 대한 TEM 사진.4 is a TEM photograph of the specimen according to Comparative Example 13.
본 발명의 이점 및 특징, 그리고 그것들을 달성하는 방법은 첨부되는 도면과 함께 상세하게 후술되어 있는 실시예를 참조하면 명확해질 것이다. 그러나, 본 발명은 이하에서 개시되는 실시예에 한정되는 것이 아니라 서로 다른 다양한 형태로 구현될 것이며, 단지 본 실시예는 본 발명의 개시가 완전하도록 하며, 본 발명이 속하는 기술분야에서 통상의 지식을 가진 자에게 발명의 범주를 완전하게 알려주기 위해 제공되는 것이며, 본 발명은 청구항의 범주에 의해 정의될 뿐이다. 명세서 전체에 걸쳐 동일 참조 부호는 동일 구성요소를 지칭한다.Advantages and features of the present invention, and methods for achieving them will be clarified with reference to embodiments described below in detail together with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in various different forms, and only the present embodiments allow the disclosure of the present invention to be complete, and the ordinary knowledge in the technical field to which the present invention pertains. It is provided to fully inform the holder of the scope of the invention, and the invention is only defined by the scope of the claims. The same reference numerals refer to the same components throughout the specification.
이하 첨부된 도면을 참조하여 본 발명의 바람직한 실시예에 따른 고인성을 갖는 오스테나이트계 경량 강재 및 그 제조 방법에 관하여 상세히 설명하면 다음과 같다.Hereinafter, an austenitic lightweight steel material having high toughness and a method for manufacturing the same according to a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.
고인성을 갖는 오스테나이트계 경량 강재Austenitic lightweight steel with high toughness
본 발명의 실시예에 따른 고인성을 갖는 오스테나이트계 경량 강재는 Fe-C-Mn-Al 합금 조성에서 Al의 함량과 냉각속도 간의 상관 관계를 통하여 200Hv 이상의 비커스 경도를 가지면서, 25℃에서의 충격흡수에너지가 50J 이상을 나타내는 냉각속도의 하한값을 알아내었다.The austenitic lightweight steel material having high toughness according to the embodiment of the present invention has a Vickers hardness of 200 Hv or more through a correlation between the Al content and the cooling rate in the Fe-C-Mn-Al alloy composition, and at 25°C. The lower limit of the cooling rate at which the shock absorption energy is 50 J or more was found.
이를 위해, 본 발명의 실시예에 따른 고인성을 갖는 오스테나이트계 경량 강재는 망간(Mn) : 28 ~ 32 중량%, 알루미늄(Al) : 7.5 ~ 10.5 중량%, 탄소(C) : 0.9 ~ 1.1 중량% 및 나머지 철(Fe)과 불가피한 불순물을 포함하며, 열간압연 및 균질화 열처리를 실시한 후, 20℃/min 이상의 냉각속도로 냉각하여 제조된다.To this end, austenitic lightweight steel having high toughness according to an embodiment of the present invention is manganese (Mn): 28 to 32 wt%, aluminum (Al): 7.5 to 10.5 wt%, carbon (C): 0.9 to 1.1 It contains weight percent and the remaining iron (Fe) and unavoidable impurities, and is produced by performing hot rolling and homogenizing heat treatment, and cooling at a cooling rate of 20° C./min or higher.
또한, 상기 강재에는 몰리브덴(Mo) : 1.5 ~ 2.5 중량%가 더 첨가되어 있을 수 있다.In addition, molybdenum (Mo): 1.5 to 2.5% by weight may be further added to the steel.
또한, 상기 강재는 7g/㎤ 이하의 밀도를 갖는다.Further, the steel material has a density of 7 g/cm 3 or less.
이하, 본 발명에 따른 고인성을 갖는 오스테나이트계 경량 강재에 포함되는 각 성분의 역할 및 그 함량에 대하여 설명하면 다음과 같다.Hereinafter, the roles and contents of each component included in the austenitic lightweight steel having high toughness according to the present invention are as follows.
망간(Mn)Manganese (Mn)
망간(Mn)은 오스테나이트 안정화 원소이다. 이때, 본 발명에 따른 오스테나이트계 경량 강재는 종래의 쌍정유기소성(TWIP, TWin Induced Plasticity) 강에 비해 페라이트 안정화 원소인 Al이 다량 첨가되어 있으며, 이로 인해 오스테나이트계 단상 조직을 갖는 오스테나이트계 경량 강재를 제조하기 위해서는 TWIP 강에 비해서 망간(Mn) 함량을 28 중량% 이상으로 증가시켜야 한다. 다만, 망간(Mn)의 첨가량이 32 중량%를 초과하여 과도하게 첨가될 경우에는 취약한 β-Mn 상의 생성을 촉진시켜서 연성과 인성을 저하시키는 요인으로 작용한다.Manganese (Mn) is an austenite stabilizing element. At this time, the austenitic lightweight steel according to the present invention has a large amount of ferrite stabilizing element Al compared to the conventional twin-inorganic plasticity (TWIP, TWin Induced Plasticity) steel, thereby austenite-based austenitic single-phase structure In order to manufacture lightweight steel, the manganese (Mn) content must be increased to 28% by weight or more compared to TWIP steel. However, when the amount of manganese (Mn) is added in excess of 32% by weight, it acts as a factor that deteriorates ductility and toughness by accelerating the formation of vulnerable β-Mn phase.
따라서, 망간(Mn)은 본 발명에 따른 오스테나이트계 경량 강재 전체 중량의 28 ~ 32 중량%의 함량비로 첨가되는 것이 바람직하고, 보다 바람직한 범위로는 29 ~ 30 중량%를 제시할 수 있다.Therefore, manganese (Mn) is preferably added at a content ratio of 28 to 32% by weight of the total weight of the austenite-based lightweight steel according to the present invention, and a more preferred range may present 29 to 30% by weight.
알루미늄(Al)Aluminum (Al)
알루미늄(Al)은 경량화를 위해 필수적인 원소로서, Fe 원자에 비해서 가벼우면서 몰 당 부피가 커서 강의 밀도를 낮추는 효과가 있다. 다만, 알루미늄(Al)의 함량이 10.5 중량%를 초과하여 다량 첨가되면서 냉각 속도가 느려지면 인성(toughness)이 저하된다. 따라서, 본 발명에서는 알루미늄이 10.5 중량 이하의 함량비로 첨가되면서, 냉각 속도를 20℃/min 이상, 보다 바람직하게는 20 ~ 21,000℃/min로 제어해야 고인성을 확보할 수 있다는 것을 알아내었다.Aluminum (Al) is an essential element for weight reduction, and is lighter than Fe atoms and has a large volume per mole, thereby reducing the density of steel. However, when the content of aluminum (Al) exceeds 10.5% by weight and is added in a large amount, the cooling rate slows down, resulting in a decrease in toughness. Accordingly, in the present invention, it has been found that while aluminum is added at a content ratio of 10.5 weight or less, the cooling rate must be controlled to 20°C/min or more, more preferably 20 to 21,000°C/min to ensure high toughness.
보다 바람직하게, 상기 알루미늄(Al)은 본 발명에 따른 오스테나이트계 경량 강재 전체 중량의 7.5 ~ 10.5 중량%의 함량비로 첨가되고, 보다 더 바람직한 범위로는 8.0 ~ 10.4 중량%를 제시할 수 있다. 알루미늄(Al)의 첨가량이 7.5 중량% 미만일 경우에는 그 첨가량이 불충분하여 경량화 효과를 제대로 발휘하는데 어려움이 따를 수 있다. 반대로, 알루미늄(Al)의 첨가량이 10.5 중량%를 초과할 경우에는 오스테나이트 상의 안정성을 떨어뜨리고 페라이트 및 다량의 Fe3AlC 타입의 κ-카바이드(κ-carbide) 석출물을 생성시킴에 따라 충격인성을 저하시킬 수 있다.More preferably, the aluminum (Al) is added at a content ratio of 7.5 to 10.5% by weight of the total weight of the austenite-based lightweight steel according to the present invention, and a more preferred range may be 8.0 to 10.4% by weight. When the addition amount of aluminum (Al) is less than 7.5% by weight, the addition amount is insufficient, and it may be difficult to properly exhibit a light weight effect. Conversely, when the amount of aluminum (Al) added exceeds 10.5% by weight, the stability of the austenite phase is reduced, and impact toughness is generated by generating ferrite and a large amount of κ-carbide precipitates of Fe 3 AlC type. It can decrease.
탄소(C)Carbon (C)
탄소(C)는 오스테나이트 안정화 원소로서, 오스테나이트계 경량 강재의 제조를 위해 필요하다. 또한, 탄소(c)는 탄화물 형성을 통한 석출강화 효과로 인장강도 증가에 기여한다.Carbon (C) is an austenite stabilizing element and is required for the production of austenitic lightweight steel. In addition, carbon (c) contributes to an increase in tensile strength due to the precipitation strengthening effect through carbide formation.
상기 탄소(C)는 본 발명에 따른 오스테나이트계 경량 강재 전체 중량의 0.9 ~ 1.1 중량%의 함량비로 첨가되는 것이 바람직하고, 보다 바람직한 범위로는 0.92 ~ 1.01 중량%를 제시할 수 있다. 탄소(C)의 첨가량이 0.9 중량% 미만일 경우에는 그 첨가량이 불충분하여 강도 향상 효과를 제대로 발휘하는데 어려움이 따를 수 있다. 반대로, 탄소(C)의 첨가량이 1.1 중량%를 초과할 경우에는 다량의 Fe3AlC 타입의 κ-카바이드(κ-carbide) 석출물이 생성됨에 따라 충격인성을 떨어뜨리고 압연 시 균열발생의 원인으로 작용할 수 있다.The carbon (C) is preferably added at a content ratio of 0.9 to 1.1% by weight of the total weight of the austenite-based lightweight steel according to the present invention, and a more preferable range may be 0.92 to 1.01% by weight. When the addition amount of carbon (C) is less than 0.9% by weight, the addition amount is insufficient, and thus it may be difficult to properly exhibit the strength improving effect. Conversely, when the addition amount of carbon (C) exceeds 1.1% by weight, as a large amount of Fe 3 AlC type κ-carbide precipitates are generated, impact toughness is reduced and it may act as a cause of cracking during rolling. You can.
몰리브덴(Mo)Molybdenum (Mo)
몰리브덴(Mo)은 오스테나이트 내에서 κ-카바이드(k-carbide)의 석출을 지연시키는 원소로서 경량 강재의 인성을 향상시키는데 기여한다.Molybdenum (Mo) is an element that retards the precipitation of κ-carbide in austenite and contributes to improving the toughness of lightweight steel.
상기 몰리브덴(Mo)은 본 발명에 따른 오스테나이트계 경량 강재 전체 중량의 1.5 ~ 2.5 중량%의 함량비로 첨가되는 것이 바람직하고, 보다 바람직한 범위로는 1.8 ~ 2.0 중량%를 제시할 수 있다. 몰리브덴(Mo)의 첨가량이 1.5 중량% 미만일 경우에는 상기의 효과를 제대로 발휘하기 어렵다. 반대로, 몰리브덴(Mo)의 첨가량이 2.5 중량%를 초과할 경우에는 Mo 탄화물(Mo-enriched carbide)을 형성시킴으로써 강도를 급격하게 증가시키고 인성을 떨어뜨리는 문제를 유발할 수 있다.The molybdenum (Mo) is preferably added at a content ratio of 1.5 to 2.5% by weight of the total weight of the austenite-based lightweight steel according to the present invention, and more preferably 1.8 to 2.0% by weight. When the amount of molybdenum (Mo) added is less than 1.5% by weight, it is difficult to properly exhibit the above effects. Conversely, when the amount of molybdenum (Mo) exceeds 2.5% by weight, by forming Mo carbide (Mo-enriched carbide) it can increase the strength and cause a problem of dropping toughness.
고인성을 갖는 오스테나이트계 경량 강재 제조 방법Method for manufacturing austenitic lightweight steel with high toughness
도 1은 본 발명에 따른 고인성을 갖는 오스테나이트계 경량 강재 제조 방법을 나타낸 공정 순서도이다.1 is a process flow chart showing a method for manufacturing austenitic lightweight steel having high toughness according to the present invention.
도 1을 참조하면, 본 발명에 따른 고인성을 갖는 오스테나이트계 경량 강재 제조 방법은 열간압연 단계(S110), 균질화 열처리 단계(S120) 및 냉각 단계(S130)를 포함한다.Referring to Figure 1, a method of manufacturing austenitic lightweight steel having high toughness according to the present invention includes a hot rolling step (S110), a homogenizing heat treatment step (S120) and a cooling step (S130).
열간압연Hot rolled
열간압연 단계(S110)에서는 망간(Mn) : 28 ~ 32 중량%, 알루미늄(Al) : 7.5 ~ 10.5 중량%, 탄소(C) : 0.9 ~ 1.1 중량% 및 나머지 철(Fe)과 불가피한 불순물을 포함하는 강재를 열간압연한다. 이때, 강재에는 몰리브덴(Mo) : 1.5 ~ 2.5 중량%가 더 첨가되어 있을 수 있다.In the hot rolling step (S110), manganese (Mn): 28 to 32 wt%, aluminum (Al): 7.5 to 10.5 wt%, carbon (C): 0.9 to 1.1 wt%, and the remaining iron (Fe) and unavoidable impurities The steel material to be hot rolled. At this time, molybdenum (Mo): 1.5 to 2.5% by weight may be further added to the steel.
본 단계에서, 열간압연은 900℃ 이상의 마무리 압연온도 조건으로 실시하는 것이 바람직하며, 보다 바람직한 범위로는 900 ~ 1,150℃를 제시할 수 있다. 마무리 압연온도가 900℃ 미만일 경우에는 Fe3AlC 타입의 κ-카바이드(κ-carbide)가 입계에 다량 형성되어 충격인성을 저하시켜 경량 강재의 제조 과정 중 파손이 발생할 가능성이 높아질 수 있다.In this step, hot rolling is preferably performed at a finishing rolling temperature of 900°C or higher, and more preferably 900 to 1,150°C can be suggested. When the finish rolling temperature is less than 900°C, Fe 3 AlC type κ-carbide is formed in a large amount at the grain boundary, thereby lowering the impact toughness, which may increase the possibility of breakage during the manufacturing process of the lightweight steel.
균질화 열처리Homogenization heat treatment
균질화 열처리 단계(S120)에서는 열간압연된 강재를 1,000 ~ 1,100℃에서 1 ~ 3시간 동안 균질화 열처리한다. 이때, 균질화 처리 온도가 1,000℃ 미만일 경우에는 압연 후 냉각 중 발생할 수 있는 Fe3AlC 타입의 κ-카바이드(κ-carbide)가 용해되지 않을 수 있다. 반대로, 균질화 열처리 온도가 1,100℃를 초과할 경우에는 결정립 조대화로 인하여 강도 및 충격인성이 저하될 수 있다.In the homogenization heat treatment step (S120), the hot-rolled steel material is subjected to a homogenization heat treatment at 1,000 to 1,100°C for 1 to 3 hours. At this time, if the homogenization treatment temperature is less than 1,000°C, Fe 3 AlC type κ-carbide, which may occur during cooling after rolling, may not be dissolved. Conversely, when the homogenization heat treatment temperature exceeds 1,100°C, strength and impact toughness may be deteriorated due to grain coarsening.
냉각Cooling
냉각 단계(S130)에서는 균질화 열처리된 강재를 20℃/min 이상의 냉각 속도로 상온까지 냉각한다. 이때, 상온은 1 ~ 40℃일 수 있으나, 이에 제한되는 것은 아니다.In the cooling step (S130), the homogenized heat-treated steel is cooled to room temperature at a cooling rate of 20°C/min or higher. At this time, the room temperature may be 1 ~ 40 ℃, but is not limited thereto.
본 단계에서, 냉각은 20 ~ 21,000℃/min의 냉각속도로 실시하는 것이 보다 바람직하다. 이때, 본 발명에서, 알루미늄(Al)의 함량이 10.5 중량%를 초과하여 다량 첨가되면서 냉각속도가 느려지면 인성(toughness)이 저하되는 것을 확인하였다. 이에 따라, 본 발명에서는 알루미늄(Al)이 10.5 중량% 이하의 함량비로 첨가되면서, 냉각속도를 20℃/min 이상, 보다 바람직하게는 20 ~ 21,000℃/min로 제어해야 고인성을 확보할 수 있다는 것을 알아내었다.In this step, the cooling is more preferably carried out at a cooling rate of 20 ~ 21,000 ℃ / min. At this time, in the present invention, the content of aluminum (Al) exceeds 10.5% by weight, it was confirmed that the toughness is lowered when the cooling rate is slowed while being added in a large amount. Accordingly, in the present invention, while aluminum (Al) is added at a content ratio of 10.5% by weight or less, the cooling rate should be controlled to 20°C/min or more, more preferably 20 to 21,000°C/min to ensure high toughness. I figured it out.
본 단계에서, 냉각 속도가 20℃/min 미만일 경우에는 냉각시 다량의 조대한 탄화물이 생성되어 목표로 하는 충격인성을 확보하는데 어려움이 따를 수 있다. 반대로, 냉각속도가 21,000℃/min를 초과할 경우에는 강재의 중심부와 표면부의 냉각속도 차이에 의한 열응력으로 강재에 균열이 발생할 가능성이 있으므로, 강재 제조에 어려움이 따를 수 있다.In this step, when the cooling rate is less than 20°C/min, a large amount of coarse carbides are generated during cooling, and thus it may be difficult to secure a target impact toughness. Conversely, when the cooling rate exceeds 21,000°C/min, there is a possibility of cracking in the steel due to thermal stress due to a difference in the cooling speed between the center and the surface of the steel, so that the manufacturing of the steel may be difficult.
상기의 과정(S110 ~ S130)에 의해 제조되는 고인성을 갖는 오스테나이트계 경량 강재는 Fe-C-Mn-Al 합금 조성에서 Al의 함량과 냉각속도 간의 상관 관계를 통하여 고인성을 확보할 수 있는 냉각속도의 하한값을 알아내었다.The austenitic lightweight steel having high toughness manufactured by the above steps (S110 to S130) can secure high toughness through a correlation between the Al content and the cooling rate in the Fe-C-Mn-Al alloy composition. The lower limit of the cooling rate was found.
이 결과, 본 발명의 실시예에 따른 방법으로 제조되는 고인성을 갖는 오스테나이트계 경량 강재는 Fe-C-Mn-Al 합금 조성에서 Al의 함량과 냉각속도 간의 상관 관계를 통하여 200Hv 이상의 비커스 경도 및 7g/㎤ 이하의 밀도를 가지면서, 25℃에서의 충격흡수에너지가 50J 이상을 나타내는 냉각속도의 하한값을 알아내었다.As a result, the austenite-based lightweight steel material having high toughness manufactured by the method according to the embodiment of the present invention has a Vickers hardness of 200 Hv or more through a correlation between the Al content and the cooling rate in the Fe-C-Mn-Al alloy composition, and While having a density of 7 g/cm 3 or less, the lower limit of the cooling rate at which the shock absorption energy at 25° C. is 50 J or more was found.
실시예Example
이하, 본 발명의 바람직한 실시예를 통해 본 발명의 구성 및 작용을 더욱 상세히 설명하기로 한다. 다만, 이는 본 발명의 바람직한 예시로 제시된 것이며 어떠한 의미로도 이에 의해 본 발명이 제한되는 것으로 해석될 수는 없다.Hereinafter, the configuration and operation of the present invention will be described in more detail through preferred embodiments of the present invention. However, this is provided as a preferred example of the present invention and cannot be interpreted as limiting the present invention by any means.
여기에 기재되지 않은 내용은 이 기술 분야에서 숙련된 자이면 충분히 기술적으로 유추할 수 있는 것이므로 그 설명을 생략하기로 한다.The contents not described here will be sufficiently technically inferred by those skilled in the art, and thus the description thereof will be omitted.
1. 시편 제조1. Specimen preparation
표 1에 기재된 화학성분을 갖는 잉곳을 진공유도용해로에서 제조한 후, 잉곳을 1,150℃에서 2시간 동안 재가열하고, 1,000℃의 마무리 열간압연 조건으로 12mm의 두께가 되도록 열간압연을 실시하였다. 이후, 1,050℃에서 2시간 동안 균질화 열처리를 실시한 후, 표 2에 기재된 냉각속도로 상온까지 냉각하여 실시예 1 ~ 15 및 비교예 1 ~ 15에 따른 시편을 제조하였다.After the ingot having the chemical components listed in Table 1 was prepared in a vacuum induction melting furnace, the ingot was reheated at 1,150°C for 2 hours, and hot rolled to a thickness of 12 mm under the condition of 1,000°C finish hot rolling. Subsequently, after performing a homogenization heat treatment at 1,050° C. for 2 hours, the specimens according to Examples 1 to 15 and Comparative Examples 1 to 15 were prepared by cooling to room temperature at the cooling rates shown in Table 2.
[표 1] (단위 : 중량%)[Table 1] (unit: wt%)
Figure PCTKR2019012316-appb-I000001
Figure PCTKR2019012316-appb-I000001
2. 기계적 물성 평가2. Mechanical property evaluation
표 2는 실시예 1 ~ 15 및 비교예 1 ~ 15에 따른 시편에 대한 기계적 물성 평가 결과를 나타낸 것이다.Table 2 shows the mechanical property evaluation results for the specimens according to Examples 1 to 15 and Comparative Examples 1 to 15.
[표 2][Table 2]
Figure PCTKR2019012316-appb-I000002
Figure PCTKR2019012316-appb-I000002
표 1 및 표 2에 도시된 바와 같이, 실시예 1 ~ 15에 따른 시편은 목표값에 해당하는 25℃에서의 충격흡수에너지가 50J 이상을 모두 만족하는 것을 확인할 수 있다.As shown in Table 1 and Table 2, it can be seen that the specimens according to Examples 1 to 15 satisfy all of the shock absorption energy at 50° C. or higher corresponding to the target value.
또한, 실시예 1 ~ 15에 따른 시편은 목표값에 해당하는 200Hv 이상의 비커스 경도 및 7g/㎤ 이하의 밀도를 모두 만족하는 것을 확인할 수 있다. 즉, 실시예 1 ~ 15에 따른 시편은 밀도측정 결과, 9 ~ 10.41wt%의 Al 첨가에 의해 7g/㎤ 이하의 밀도로 측정되어 낮은 비중을 것을 확인할 수 있다.In addition, it can be seen that the specimens according to Examples 1 to 15 satisfy both Vickers hardness of 200 Hv or more and density of 7 g/cm 3 or less corresponding to the target value. That is, the specimens according to Examples 1 to 15 can be confirmed to have a low specific gravity as measured by a density of 7 g/cm 3 or less by adding 9 to 10.41 wt% of Al as a result of density measurement.
반면, 비교예 4 ~ 15에 따른 시편의 경우, 비커스 경도는 대부분 목표값을 만족하였으나, 25℃에서의 충격흡수에너지가 30J 이하로 측정되어 목표값에 확연히 미달하는 것을 확인할 수 있다.On the other hand, in the case of the specimens according to Comparative Examples 4 to 15, the Vickers hardness mostly satisfied the target value, but the impact absorption energy at 25°C was measured to be 30 J or less, so it can be confirmed that the target value was significantly lower.
또한, 비교예 1 ~ 3에 따른 시편은 경도 및 25℃에서의 충격흡수에너지가 목표값을 대부분 만족하였으나, Al 첨가량이 7.01wt%로 첨가되는데 기인하여 밀도가 목표값을 벗어난 것을 확인할 수 있다.In addition, in the specimens according to Comparative Examples 1 to 3, the hardness and the impact absorption energy at 25°C mostly satisfied the target value, but it can be confirmed that the density was out of the target value due to the addition of the Al addition amount to 7.01 wt%.
한편, 도 2는 실시예 4에 따른 시편에 대한 TEM 사진이고, 도 3은 실시예 6 따른 시편에 대한 TEM 사진이며, 도 4는 비교예 13에 따른 시편에 대한 TEM 사진이다.Meanwhile, FIG. 2 is a TEM photograph of the specimen according to Example 4, FIG. 3 is a TEM photograph of the specimen according to Example 6, and FIG. 4 is a TEM photograph of the specimen according to Comparative Example 13.
도 2에 도시된 바와 같이, 실시예 4에 따른 시편은 균질화 열처리 후 20,000℃/min의 빠른 냉각속도로 냉각되어 미세조직이 오스테나이트(γ) 단상으로 구성되어 있는 것을 확인할 수 있다.As shown in Figure 2, the specimen according to Example 4 can be confirmed that the microstructure is composed of a single phase of austenite (γ) by cooling at a rapid cooling rate of 20,000° C./min after homogenization heat treatment.
또한, 도 3에 도시된 바와 같이, 실시예 6에 따른 시편은 균질화 열처리 후 25℃/min의 느린 냉각속도로 냉각되어 미세조직이 오스테나이트(γ) 상과, 오스테나이트(γ) 상의 입내에 Fe3AlC 타입의 κ-카바이드(κ-carbide)가 발달해 있는 것을 확인할 수 있다. 또한, 입계에도 Fe3AlC 타입의 κ-카바이드(κ-carbide)가 발달되어 있는 것을 확인할 수 있다. 입계와 입내에 Fe3AlC 타입의 κ-카바이드(κ-carbide)가 발달되어 있으나, 그 양과 크기가 작아 충격인성이 50J 이하로 감소하지 않은 것으로 파악된다.In addition, as shown in FIG. 3, the specimen according to Example 6 is cooled at a slow cooling rate of 25° C./min after homogenization heat treatment, so that the microstructure is in the austenite (γ) phase and austenite (γ) phase in the mouth. It can be confirmed that Fe 3 AlC type κ-carbide (κ-carbide) was developed. In addition, it can be confirmed that κ-carbide of Fe 3 AlC type is also developed at the grain boundary. Although Fe 3 AlC type κ-carbide has been developed in the grain boundaries and in the mouth, it is understood that the impact toughness does not decrease below 50 J due to its small size and size.
한편, 비교예 13에 따른 시편은 미세조직이 오스테나이트 및 페라이트(γ + α)의 복합 조직을 가지며, 도 4에 도시된 바와 같이, 균질화 열처리 후 20,000℃/min의 빠른 냉각속도를 이용하여 냉각하였음에도, 도 2의 실시예 4와 달리 오스테나이트(γ) 입내 및 입계에 Fe3AlC 타입의 κ-카바이드(κ-carbide)가 발달해 있는 것을 확인할 수 있다. 상대적으로 높은 Al 함량에 의해 빠른 속도로 냉각되었음에도, 실시예 6과 비교할 때, 상대적으로 입계에는 조대한 Fe3AlC 타입의 κ-카바이드(κ-carbide)가 형성되고, 입내에는 과도한 양의 Fe3AlC 타입의 κ-카바이드(κ-carbide)가 발달해 충격인성이 저하된 것으로 판단된다.On the other hand, the specimen according to Comparative Example 13, the microstructure has a composite structure of austenite and ferrite (γ + α), as shown in Figure 4, after homogenization heat treatment, cooling using a rapid cooling rate of 20,000 ℃ / min Even though, it can be seen that unlike Example 4 of FIG. 2, Fe 3 AlC type κ-carbide was developed in the austenite (γ) granules and grain boundaries. Even though it was rapidly cooled by a relatively high Al content, compared to Example 6, a relatively large grain of Fe 3 AlC type κ-carbide was formed at the grain boundary, and an excessive amount of Fe in the mouth. 3 It is thought that the impact toughness was deteriorated due to the development of κ-carbide of AlC type.
실시예 4, 6 및 비교예 13에 따른 시편 결과에서 알 수 있듯이, 입계에 형성되는 조대한 κ-카바이드(κ-carbide)와 입내에 다량으로 형성되는 κ-카바이드(κ-carbide)는 충격 인성에 저하를 야기하는 것으로 판단된다. 또한, Al 함량이 10.5 중량%를 초과하여 다량 첨가되는 경량 강재의 경우, Al 증가에 따라 형성될 수 있는 κ-카바이드(κ-carbide) 이외의 다른 상들도 충격 인성 저하에 영향을 줄 수 있는 것으로 판단된다.As can be seen from the specimen results according to Examples 4, 6 and Comparative Example 13, coarse κ-carbide formed in the grain boundary and κ-carbide formed in a large amount in the mouth were impact toughness. It is believed to cause degradation. In addition, in the case of a lightweight steel material in which a large amount of Al is added in excess of 10.5% by weight, other phases other than κ-carbide, which may be formed by increasing Al, may also affect impact toughness deterioration. Is judged.
이상에서는 본 발명의 실시예를 중심으로 설명하였지만, 본 발명이 속하는 기술분야에서 통상의 지식을 가진 기술자의 수준에서 다양한 변경이나 변형을 가할 수 있다. 이러한 변경과 변형은 본 발명이 제공하는 기술 사상의 범위를 벗어나지 않는 한 본 발명에 속한다고 할 수 있다. 따라서 본 발명의 권리범위는 이하에 기재되는 청구범위에 의해 판단되어야 할 것이다.In the above, the embodiments of the present invention have been mainly described, but various changes or modifications can be made at the level of a person skilled in the art to which the present invention pertains. Such changes and modifications can be said to belong to the present invention without departing from the scope of the technical idea provided by the present invention. Therefore, the scope of the present invention should be judged by the claims set forth below.
[부호의 설명][Description of codes]
S110 : 열간압연 단계S110: hot rolling step
S120 : 균질화 열처리 단계S120: Homogenization heat treatment step
S130 : 냉각 단계S130: cooling step

Claims (11)

  1. (a) 망간(Mn) : 28 ~ 32 중량%, 알루미늄(Al) : 7.5~ 10.5 중량%, 탄소(C) : 0.9 ~ 1.1 중량% 및 나머지 철(Fe)과 불가피한 불순물을 포함하는 강재를 열간압연하는 단계; (a) Manganese (Mn): 28 to 32% by weight, aluminum (Al): 7.5 to 10.5% by weight, carbon (C): 0.9 to 1.1% by weight, and the remaining iron (Fe) and steel containing unavoidable impurities Rolling;
    (b) 상기 열간압연된 강재를 균질화 열처리하는 단계; 및 (B) homogenizing heat treatment of the hot-rolled steel material; And
    (c) 상기 균질화 열처리된 강재를 20℃/min 이상의 냉각속도로 냉각하는 단계;를 포함하며, (c) cooling the homogenized heat-treated steel at a cooling rate of 20°C/min or higher;
    상기 (c) 단계 이후, 상기 강재는 25℃에서의 충격흡수에너지가 50J 이상을 갖는 고인성을 갖는 오스테나이트계 경량 강재 제조 방법.After the step (c), the steel material is a method of manufacturing an austenitic lightweight steel material having high toughness having an impact absorption energy of 50 J or more at 25°C.
  2. 제1항에 있어서,According to claim 1,
    상기 (a) 단계에서,In step (a),
    상기 강재에는 The steel material
    몰리브덴(Mo) : 1.5 ~ 2.5 중량%가 더 첨가되어 있는 것을 특징으로 하는 고인성을 갖는 오스테나이트계 경량 강재 제조 방법.Molybdenum (Mo): A method of manufacturing austenitic lightweight steel having high toughness, characterized in that 1.5 to 2.5 wt% is further added.
  3. 제1항에 있어서,According to claim 1,
    상기 (c) 단계에서, In step (c),
    상기 냉각은 The cooling
    20 ~ 21,000℃/min의 냉각속도로 실시하는 것을 특징으로 하는 고인성을 갖는 오스테나이트계 경량 강재 제조 방법.A method of manufacturing an austenitic lightweight steel having high toughness, characterized in that it is performed at a cooling rate of 20 to 21,000°C/min.
  4. 제1항에 있어서,According to claim 1,
    상기 (c) 단계 이후, After step (c),
    상기 강재는 The steel material
    7g/㎤ 이하의 밀도를 갖는 것을 특징으로 하는 고인성을 갖는 오스테나이트계 경량 강재 제조 방법.A method of manufacturing an austenitic lightweight steel material having high toughness, which has a density of 7 g/cm 3 or less.
  5. 제1에 있어서,According to claim 1,
    상기 (c) 단계 이후, After step (c),
    상기 강재는 The steel material
    200Hv 이상의 비커스 경도를 갖는 것을 특징으로 하는 고강도 및 고인성을 갖는 오스테나이트계 경량 강재 제조 방법.A method of manufacturing an austenitic lightweight steel having high strength and high toughness, characterized by having a Vickers hardness of 200 Hv or more.
  6. 망간(Mn) : 28 ~ 32 중량%, 알루미늄(Al) : 7.5 ~ 10.5 중량%, 탄소(C) : 0.9 ~ 1.1 중량% 및 나머지 철(Fe)과 불가피한 불순물을 포함하며, Manganese (Mn): 28 to 32% by weight, aluminum (Al): 7.5 to 10.5% by weight, carbon (C): 0.9 to 1.1% by weight, and iron (Fe) and inevitable impurities,
    열간압연 및 균질화 열처리를 실시한 후, 20℃/min 이상의 냉각속도로 냉각하여 제조되어, 25℃에서의 충격흡수에너지가 50J 이상을 갖는 고인성을 갖는 오스테나이트계 경량 강재.An austenitic lightweight steel material having high toughness having a heat absorption and homogenization heat treatment and cooling at a cooling rate of 20° C./min or higher, and a shock absorption energy at 25° C. of 50 J or higher.
  7. 제6항에 있어서,The method of claim 6,
    상기 알루미늄(Al)은 The aluminum (Al) is
    8.0 ~ 10.4 중량%로 첨가된 것을 특징으로 하는 고인성을 갖는 오스테나이트계 경량 강재.Austenitic lightweight steel with high toughness characterized by being added at 8.0 to 10.4% by weight.
  8. 제6항에 있어서,The method of claim 6,
    상기 탄소(C)는 The carbon (C) is
    0.92 ~ 1.01 중량%로 첨가된 것을 특징으로 하는 고인성을 갖는 오스테나이트계 경량 강재.Austenitic lightweight steel with high toughness characterized by being added at 0.92 to 1.01% by weight.
  9. 제6항에 있어서,The method of claim 6,
    상기 강재에는 The steel material
    몰리브덴(Mo) : 1.5 ~ 2.5 중량%가 더 첨가되어 있는 것을 특징으로 하는 고인성을 갖는 오스테나이트계 경량 강재.Molybdenum (Mo): Austenitic lightweight steel with high toughness, characterized in that 1.5 to 2.5% by weight is further added.
  10. 제6항에 있어서,The method of claim 6,
    상기 강재는 The steel material
    7g/㎤ 이하의 밀도를 갖는 것을 특징으로 하는 고인성을 갖는 오스테나이트계 경량 강재.Austenitic lightweight steel with high toughness characterized by having a density of 7 g/cm 3 or less.
  11. 제6에 있어서,The method of claim 6,
    상기 강재는 The steel material
    200Hv 이상의 비커스 경도를 갖는 것을 특징으로 하는 고인성을 갖는 오스테나이트계 경량 강재.Austenitic lightweight steel with high toughness characterized by having a Vickers hardness of 200 Hv or more.
PCT/KR2019/012316 2018-11-26 2019-09-23 Austenitic lightweight steel material having high toughness and preparation method therefor WO2020111478A1 (en)

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2005015909A (en) * 2003-06-05 2005-01-20 Nippon Steel Corp High-strength low-specific-gravity steel sheet and method for manufacturing the same
JP2006118000A (en) * 2004-10-21 2006-05-11 Nippon Steel Corp Lightweight high strength steel having excellent ductility and its production method
JP2006176843A (en) * 2004-12-22 2006-07-06 Nippon Steel Corp High-strength and low-density steel sheet superior in ductility and manufacturing method therefor
KR101568552B1 (en) * 2013-12-26 2015-11-11 주식회사 포스코 High specific strength steel sheet and method for manufacturing the same
WO2017148892A1 (en) * 2016-03-01 2017-09-08 Tata Steel Nederland Technology B.V. Austenitic, low-density, high-strength steel strip or sheet having a high ductility, method for producing said steel and use thereof

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0699775B2 (en) * 1991-12-27 1994-12-07 東大精密鋳造股▲フン▼有限公司 Precision casting method for iron-manganese-aluminum alloy
JP4084733B2 (en) 2003-10-14 2008-04-30 新日本製鐵株式会社 High strength low specific gravity steel plate excellent in ductility and method for producing the same

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2005015909A (en) * 2003-06-05 2005-01-20 Nippon Steel Corp High-strength low-specific-gravity steel sheet and method for manufacturing the same
JP2006118000A (en) * 2004-10-21 2006-05-11 Nippon Steel Corp Lightweight high strength steel having excellent ductility and its production method
JP2006176843A (en) * 2004-12-22 2006-07-06 Nippon Steel Corp High-strength and low-density steel sheet superior in ductility and manufacturing method therefor
KR101568552B1 (en) * 2013-12-26 2015-11-11 주식회사 포스코 High specific strength steel sheet and method for manufacturing the same
WO2017148892A1 (en) * 2016-03-01 2017-09-08 Tata Steel Nederland Technology B.V. Austenitic, low-density, high-strength steel strip or sheet having a high ductility, method for producing said steel and use thereof

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