WO2022131503A1 - Ferritic stainless steel having excellent heat resistance and method for manufacturing same - Google Patents

Ferritic stainless steel having excellent heat resistance and method for manufacturing same Download PDF

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Publication number
WO2022131503A1
WO2022131503A1 PCT/KR2021/014156 KR2021014156W WO2022131503A1 WO 2022131503 A1 WO2022131503 A1 WO 2022131503A1 KR 2021014156 W KR2021014156 W KR 2021014156W WO 2022131503 A1 WO2022131503 A1 WO 2022131503A1
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heat resistance
stainless steel
ferritic stainless
excellent heat
tensile strength
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PCT/KR2021/014156
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French (fr)
Korean (ko)
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박지언
백종수
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주식회사 포스코
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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
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/26—Ferrous alloys, e.g. steel alloys containing chromium with niobium or tantalum
    • 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
    • C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
    • 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
    • C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
    • 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
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/22—Ferrous alloys, e.g. steel alloys containing chromium with molybdenum or tungsten
    • 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

Definitions

  • the present invention relates to a ferritic stainless steel having excellent heat resistance and a method for manufacturing the same, and more particularly, to a ferritic stainless steel capable of improving the heat resistance of a material by controlling a solid solution alloy component in a final matrix through component system control, and manufacturing the same it's about how
  • Ferritic stainless steel is a steel material with high price competitiveness compared to austenitic stainless steel because it has excellent corrosion resistance while adding a small amount of expensive alloying elements.
  • Such ferritic stainless steel is used for exhaust manifold, which is an exhaust system component. Since the exhaust system exhaust manifold is directly exposed to high temperature exhaust gas of 700°C or higher, very high safety is required in a long-term operation environment.
  • Embodiments of the present invention by optimizing the steel composition and manufacturing process to control the solid solution alloy composition in the final matrix to improve the heat resistance of the material.
  • Ferritic stainless steel having excellent heat resistance according to an embodiment of the present invention, by weight, C: 0.0005 to 0.02%, N: 0.005 to 0.02%, Si: 0.01 to 1.0%, Mn: 0.01 to 1.2%, P : 0.001 to 0.05%, Cr: 10.0 to 25.0%, Mo: 1.5 to 3.0%, Nb: 0.3 to 0.7%, W: 0.5 to 2.0%, the remainder including Fe and unavoidable impurities, the weight ratio of dissolved Mo in the matrix 85% or more, the weight ratio of solid solution W is included as 85% or more, and the following formulas (1) and (2) are satisfied.
  • the ferritic stainless steel having excellent heat resistance may have a tensile strength of 47 MPa or more at 900°C.
  • the tensile strength reduction rate may be 10% or less.
  • the method for producing a ferritic stainless steel having excellent heat resistance is, by weight, C: 0.0005 to 0.02%, N: 0.005 to 0.02%, Si: 0.01 to 1.0%, Mn: 0.01 to 1.2%, P: 0.001 to 0.05%, Cr: 10.0 to 25.0%, Mo: 1.5 to 3.0%, Nb: 0.3 to 0.7%, W: 0.5 to 2.0%, including the remainder of Fe and unavoidable impurities, the following formula (1) and (2) by reheating the slab satisfying the condition, rough rolling, and finishing rolling to prepare a hot-rolled steel sheet; hot-rolling annealing at 1,020 to 1,100°C; and cold rolling, followed by cold rolling annealing at 1,050 to 1,100° C., wherein the holding time (seconds) before the start of the finish rolling satisfies the following Equation (3).
  • the ferritic stainless steel according to an embodiment of the present invention may provide a ferritic stainless steel having excellent heat resistance by increasing the amount of a solid solution alloy in a matrix.
  • the weight ratio of Mo and W dissolved in the matrix is 85% or more, and the tensile strength reduction rate is 10% or less, so high stability is secured even when used for a long time can do.
  • 1 is a graph showing the tensile strength of 900 °C according to the solid solution Mo and the solid solution W.
  • FIG. 2 is a graph showing the change in tensile strength at 900°C before/after heat treatment at 900°C for 100 hours.
  • Ferritic stainless steel having excellent heat resistance according to an embodiment of the present invention, by weight, C: 0.0005 to 0.02%, N: 0.005 to 0.02%, Si: 0.01 to 1.0%, Mn: 0.01 to 1.2%, P : 0.001 to 0.05%, Cr: 10.0 to 25.0%, Mo: 1.5 to 3.0%, Nb: 0.3 to 0.7%, W: 0.5 to 2.0%, the remainder including Fe and unavoidable impurities, the weight ratio of dissolved Mo in the matrix 85% or more, the weight ratio of solid solution W is included as 85% or more, and the following formulas (1) and (2) are satisfied.
  • Ferritic stainless steel having excellent heat resistance according to an embodiment of the present invention, by weight, C: 0.0005 to 0.02%, N: 0.005 to 0.02%, Si: 0.01 to 1.0%, Mn: 0.01 to 1.2%, P : 0.001 to 0.05%, Cr: 10.0 to 25.0%, Mo: 1.5 to 3.0%, Nb: 0.3 to 0.7%, W: 0.5 to 2.0%, remaining Fe and unavoidable impurities.
  • the unit is % by weight.
  • the content of C (carbon) is 0.0005 to 0.02%.
  • C is an element that greatly affects strength. If its content is less than 0.0005%, the refining price to reduce strength and make high-purity products is high. If it exceeds 0.02%, impurities in the material increase, resulting in elongation and work hardening index (n value) is decreased, and DBTT is increased to deteriorate the impact properties.
  • the content of N (nitrogen) is 0.005 to 0.02%.
  • N is an element that promotes recrystallization by precipitating austenite during hot rolling. If the content is less than 0.005%, TiN crystallization decreases and the equiaxed crystal rate of the slab decreases. On the other hand, when it exceeds 0.02%, impurities in the material increase, resulting in lower elongation, and higher DBTT, thereby lowering impact properties.
  • the content of Si is 0.01 to 1.0%.
  • Si is an element added for deoxidation of molten steel and stabilization of ferrite during steelmaking. If the content is less than 0.01%, the refining price increases, and if it exceeds 1.0%, impurities in the material increase, resulting in elongation and work hardening index ( n value) decreases, and Si-based inclusions increase, resulting in poor workability.
  • the content of Mn (manganese) is 0.01 to 1.2%.
  • Mn is an effective element for improving corrosion resistance, and when its content is less than 0.01%, there is a problem in that the refining price increases, and when it exceeds 1.2%, impurities in the material increase and elongation is lowered.
  • the content of P (phosphorus) is 0.001 to 0.05%.
  • P is an impurity contained inevitably in steel.
  • the content is controlled to less than 0.001%, the refining price increases, and when it exceeds 0.05%, the elongation and work hardening index are lowered due to the increase of impurities.
  • the content of Cr (chromium) is 10.0 to 25.0%.
  • Cr is an element effective for improving corrosion resistance and oxidation resistance of steel, and is added in an amount of 10.0% or more in the present invention. However, if the content is excessive, elongation is lowered and hot-rolled sticking defects occur, so it is limited to 25.0% or less.
  • the content of Mo (molybdenum) is 1.5 to 3.0%.
  • Mo serves to increase the corrosion resistance of ferritic stainless steel and at the same time improve the high-temperature strength. If the Mo content is less than 1.5%, the amount of solid solution in the material is small, so high-temperature strength and thermal fatigue properties deteriorate, and the probability of abnormal oxidation increases. In addition, if it exceeds 3.0%, the impact properties are deteriorated, the risk of fracture during processing increases, and there is a problem of increased cost.
  • Nb niobium
  • the Nb content is less than 0.3%, there is a problem that the high-temperature strength is lowered because the amount of solid solution in the material is small, and if it exceeds 0.7%, the Nb-based precipitates and the high-solute capacity are excessively increased, and the elongation and impact properties are lowered.
  • the content of W (tungsten) is 0.5 to 2.0%.
  • W increases the corrosion resistance of the ferritic stainless steel and at the same time improves the high temperature strength. Therefore, it is preferable to add 0.5% or more, and if it is less than 0.5%, there is a problem in that the amount of solid solution in the material is small and the high temperature strength is lowered. On the other hand, if it exceeds 2.0%, there is a problem in that excessive precipitates are generated and cracks occur frequently during processing.
  • the remainder of the stainless steel except for the above-mentioned alloying elements consists of Fe and other unavoidable impurities.
  • Equation (1) a range of components for improving heat resistance was derived using Equation (1).
  • Equation (1) has a value less than 3, the 900° C. tensile strength value is less than 47 Mpa, and the reduction rate of the tensile strength after heat treatment exceeds 10%, making it difficult to secure the target heat resistance.
  • the weight ratio of dissolved Mo means a ratio to the weight% of Mo dissolved in the matrix among weight% of the total Mo, and the same applies to W.
  • Equation (2) was derived in order to secure the target heat resistance.
  • the value of formula (2) is more than 8, the dissolved Mo is less than 85%, the dissolved W is less than 85%, so that the tensile strength at 900°C is less than 47Mpa, and the decrease in tensile strength after heat treatment exceeds 10% . Therefore, in order to ensure the target heat resistance, the value of Formula (2) is controlled to 8 or less.
  • the ferritic stainless steel having excellent heat resistance of the present invention requires not only component control but also control of the hot rolling process so that Mo, W and Nb do not precipitate in the laves phase in order to secure target heat resistance.
  • the method for producing a ferritic stainless steel having excellent heat resistance is, by weight, C: 0.0005 to 0.02%, N: 0.005 to 0.02%, Si: 0.01 to 1.0%, Mn: 0.01 to 1.2%, P: 0.001 to 0.05%, Cr: 10.0 to 25.0%, Mo: 1.5 to 3.0%, Nb: 0.3 to 0.7%, W: 0.5 to 2.0%, reheating the slab containing the remaining Fe and unavoidable impurities and rough rolling , the rough-rolled bar may be finish-rolled, the finish-rolled hot-rolled steel sheet may be wound, and the wound hot-rolled coil may be subjected to annealing heat treatment.
  • the hot-rolled reheating temperature of the slab must be controlled to 1,100° C. or higher. At this time, if the reheating temperature is too high, crystal grains may become coarse, so it is limited to 1,300° C. or less.
  • the total reduction ratio of the last two passes of rough rolling may be set to 50% or more in order to impart strain energy.
  • Rough rolling is typically composed of three to four rolling mills, the last two passes in the present invention may mean the last rolling mill and the second to last rolling mill.
  • the time (seconds) for which the rough-rolled rough-rolled bar is maintained before the start of finish rolling may satisfy Equation (3) below.
  • RHT means reheating temperature (°C).
  • the time maintained until finish rolling is 8,000/(reheating temperature (°C) - 1,000) seconds or more to give sufficient recrystallization time, and limiting it to 120 seconds or less to prevent coarsening of grains. This is to further impart a deformed structure during finish rolling to prevent coarsening of the precipitates and to be employed in the subsequent annealing process.
  • the winding temperature of the finish-rolled hot-rolled steel sheet may be 450 to 700 °C.
  • the coiling temperature should be controlled to 700° C. or less to prevent coarsening of the precipitates precipitated during hot rolling and to prevent precipitation in the form of labes, and it is preferable to control it to 450° C. or higher for shape and surface quality.
  • the hot-rolled material manufactured in this way must be subjected to hot-rolling annealing at 1020°C or higher, and cold-rolled annealing at 1050°C or higher after cold rolling.
  • the final product undergoes an annealing process, and the weight ratio of Mo and W dissolved in the matrix is 85% or more, and the tensile strength reduction rate is 10% or less, thereby securing the target heat resistance.
  • the coiling temperature and the annealing temperature are different from the manufacturing method according to an embodiment of the present invention, that is, the coiling temperature exceeds 700 °C, and the hot rolling/cold rolling annealing temperature is less than 1000 °C, even if the target component is secured, dissolved Mo and W are less than 85%, so the desired heat resistance cannot be secured.
  • High-temperature tensile strength of the final product was evaluated by performing a test at 900°C according to the JIS G 0567 method, and after maintaining at 900°C for 100 hours, high-temperature tensile strength was again measured at 900°C. Then, the amount of each alloying element was measured by extracting the precipitate residue from the material, and the difference was obtained from the amount of the added alloying element to measure the ratio of dissolved alloying elements. Each result is shown in Table 2.
  • the tensile strength at 900°C high temperature should be 47MPa or more, and the tensile strength reduction rate should be less than 10% even after long-time heat treatment.
  • the steel grades of Examples 1 to 3 satisfy that the value of Formula (1) is 3 or more and the value of Formula (2) is 8 or less, and the weight ratio of dissolved Mo and W is 85% or more , and it was confirmed that the tensile strength at 900°C was 49Mpa or more.
  • the 900°C tensile strength was 47Mpa or higher, confirming that the 900°C tensile strength reduction rate was 10% or less.
  • Comparative Example 4 the content of Mo, W, and Nb is included in the component range of the present invention, and the value of Formula (1) is 3 or more, but the value of Formula (2) is more than 8, resulting in a tensile strength of 900°C It was less than 47Mpa, and the rate of decrease in tensile strength at 900°C exceeded 10%.
  • the content of Mo, W, and Nb was included in the component range of the present invention, the value of Formula (1) was 3 or more, and the value of Formula (2) was 8 or less, It was confirmed that the coiling temperature was higher than 700 °C, the annealing temperature was lower than 1,000 °C, and the dissolved Mo and W were less than 85%, so that the desired heat resistance could not be obtained.
  • 1 is a graph showing the tensile strength of 900 °C according to the solid solution Mo and the solid solution W.
  • the dissolved Mo or W was less than 85%, it was confirmed that the 900°C tensile strength was less than 47Mpa, and when the dissolved Mo and W were 85% or more, the 900°C tensile strength was 47Mpa or more.
  • FIG. 2 is a graph showing the change in tensile strength at 900°C before/after heat treatment at 900°C for 100 hours.
  • Comparative Examples 1 to 6 in which dissolved Mo or W was less than 85%, it was confirmed that the tensile strength reduction rate after heat treatment at 900 ° C was more than 10%, and in Examples 1 to 3 in which dissolved Mo or W was 85% or more, tensile strength after heat treatment at 900 ° C. It was confirmed that the strength reduction rate was 10% or less.
  • the ferritic stainless steel having excellent heat resistance according to an example of the present invention improves heat resistance by increasing the amount of solid solution alloy in the matrix, and the weight ratio of Mo and W dissolved in the matrix after heat treatment at 900° C. for 100 hours is 85% or more, Because the tensile strength reduction rate is less than 10%, high stability can be secured even when used for a long time.

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Abstract

Disclosed is ferritic stainless steel having excellent heat resistance through the control of a component system. The ferritic stainless steel having excellent heat resistance according to an embodiment of the present invention comprises, by weight%, 0.0005-0.02% of C 0.005-0.02% of N, 0.01-1.0% of Si, 0.01-1.2% of Mn, 0.001-0.05% of P, 10.0-25.0% of Cr, 1.5-3.0% of Mo, 0.3-0.7% of Nb, 0.5-2.0% of W, and the remainder of Fe and inevitable impurities, wherein in a matrix, a weight proportion of solid solution Mo of 85% or more and a weight proportion of solid solution W of 85% or more are included, and expressions (1) and (2) below are satisfied. (1) Mo ＋ W ＋ Nb ≥ 3 (2) (Mo ＋ W)/Nb ≤ 8

Description

내열성이 우수한 페라이트계 스테인리스강 및 그 제조방법Ferritic stainless steel with excellent heat resistance and manufacturing method therefor
본 발명은 내열성이 우수한 페라이트계 스테인리스강 및 그 제조방법에 대한 것으로, 보다 상세하게는 성분계 제어를 통해 최종 기지 내의 고용 합금 성분을 제어함으로써 소재의 내열성을 개선할 수 있는 페라이트계 스테인리스강 및 그 제조방법에 관한 것이다.The present invention relates to a ferritic stainless steel having excellent heat resistance and a method for manufacturing the same, and more particularly, to a ferritic stainless steel capable of improving the heat resistance of a material by controlling a solid solution alloy component in a final matrix through component system control, and manufacturing the same it's about how
페라이트계 스테인리스강은 고가의 합금원소가 적게 첨가되면서도 내식성이 뛰어나 오스테나이트계 스테인리스강에 비하여 가격 경쟁력이 높은 강재이다.Ferritic stainless steel is a steel material with high price competitiveness compared to austenitic stainless steel because it has excellent corrosion resistance while adding a small amount of expensive alloying elements.
이러한 페라이트계 스테인리스강은 배기계 부품인 이그조스트 매니폴드(exhaust-manifold)에 사용된다. 배기계 이그조스트 매니폴드는 700℃ 이상의 고온의 배기가스에 직접 노출되기 때문에 장시간의 가동환경에서 매우 높은 안전성이 요구된다.Such ferritic stainless steel is used for exhaust manifold, which is an exhaust system component. Since the exhaust system exhaust manifold is directly exposed to high temperature exhaust gas of 700℃ or higher, very high safety is required in a long-term operation environment.
따라서, 고온 특성을 개선하기 위한 합금 성분 및 제조 방법에 대한 많은 연구들이 행해져 왔으나, 고온 특성을 향상시키는 원소인 Mo, Nb 등의 합금의 영향에 대한 연구 위주로 진행되었을 뿐, 실질적으로 고온에서 고용 원소와 고온 물성에 미치는 영향에 대한 파악은 미진한 상태이다.Therefore, many studies on alloy components and manufacturing methods for improving high-temperature characteristics have been conducted, but only studies on the effects of alloys such as Mo and Nb, which are elements that improve high-temperature characteristics, have been mainly conducted, and are substantially dissolved elements at high temperatures. and the effect of high-temperature properties on the properties are still incomplete.
이러한 고용 원소들에 대한 합금성분 및 제조방법의 최적화가 이뤄져야 점차 고성능화되어 가는 자동차 배기계 이그조스트 매니폴드용 소재로 적용이 가능할 것이다.It will be possible to apply it as a material for exhaust manifolds of automobiles, which are gradually increasing in performance, only when the alloy composition and manufacturing method for these dissolved elements are optimized.
본 발명의 실시예들은, 강 조성과 제조공정을 최적화하여 최종 기지 내의 고용 합금 성분을 제어함으로써 소재의 내열성을 개선하는 것을 목적으로 한다.Embodiments of the present invention, by optimizing the steel composition and manufacturing process to control the solid solution alloy composition in the final matrix to improve the heat resistance of the material.
본 발명의 일 실시예에 따른 내열성이 우수한 페라이트계 스테인리스강은, 중량%로, C: 0.0005 내지 0.02%, N: 0.005 내지 0.02%, Si: 0.01 내지 1.0%, Mn: 0.01 내지 1.2%, P: 0.001 내지 0.05%, Cr: 10.0 내지 25.0%, Mo: 1.5 내지 3.0%, Nb: 0.3 내지 0.7%, W: 0.5 내지 2.0%, 나머지 Fe 및 불가피한 불순물을 포함하고, 기지 내에 고용 Mo의 중량비는 85% 이상, 고용 W의 중량비는 85% 이상으로 포함되며, 하기 식 (1) 및 (2)를 만족한다.Ferritic stainless steel having excellent heat resistance according to an embodiment of the present invention, by weight, C: 0.0005 to 0.02%, N: 0.005 to 0.02%, Si: 0.01 to 1.0%, Mn: 0.01 to 1.2%, P : 0.001 to 0.05%, Cr: 10.0 to 25.0%, Mo: 1.5 to 3.0%, Nb: 0.3 to 0.7%, W: 0.5 to 2.0%, the remainder including Fe and unavoidable impurities, the weight ratio of dissolved Mo in the matrix 85% or more, the weight ratio of solid solution W is included as 85% or more, and the following formulas (1) and (2) are satisfied.
(1) Mo ＋ W ＋ Nb ≥ 3(1) Mo + W + Nb ≥ 3
(2) (Mo ＋ W)/Nb ≤ 8(2) (Mo + W)/Nb ≤ 8
(여기서, Mo, W, Nb는 각 원소의 함량(중량%)을 의미한다.)(Here, Mo, W, and Nb mean the content (wt%) of each element.)
또한, 내열성이 우수한 페라이트계 스테인리스강은 900℃ 인장강도가 47MPa 이상일 수 있다.In addition, the ferritic stainless steel having excellent heat resistance may have a tensile strength of 47 MPa or more at 900°C.
또한, 900℃에서 100시간 열처리 후 인장강도 감소율이 10% 이하일 수 있다.In addition, after heat treatment at 900° C. for 100 hours, the tensile strength reduction rate may be 10% or less.
본 발명의 일 실시예에 따른 내열성이 우수한 페라이트계 스테인리스강의 제조방법은 중량%로, C: 0.0005 내지 0.02%, N: 0.005 내지 0.02%, Si: 0.01 내지 1.0%, Mn: 0.01 내지 1.2%, P: 0.001 내지 0.05%, Cr: 10.0 내지 25.0%, Mo: 1.5 내지 3.0%, Nb: 0.3 내지 0.7%, W: 0.5 내지 2.0%, 나머지 Fe 및 불가피한 불순물을 포함하며, 하기 식 (1) 및 (2)를 만족하는 슬라브를 재가열하여 조압연한 다음, 마무리압연하여 열연 강판을 마련하는 단계; 1,020 내지 1,100℃로 열연 소둔하는 단계; 및 냉간 압연한 다음, 1,050 내지 1,100℃로 냉연 소둔하는 단계;를 포함하고, 상기 마무리압연 개시 전의 유지 시간(초)이 하기 식 (3)을 만족한다.The method for producing a ferritic stainless steel having excellent heat resistance according to an embodiment of the present invention is, by weight, C: 0.0005 to 0.02%, N: 0.005 to 0.02%, Si: 0.01 to 1.0%, Mn: 0.01 to 1.2%, P: 0.001 to 0.05%, Cr: 10.0 to 25.0%, Mo: 1.5 to 3.0%, Nb: 0.3 to 0.7%, W: 0.5 to 2.0%, including the remainder of Fe and unavoidable impurities, the following formula (1) and (2) by reheating the slab satisfying the condition, rough rolling, and finishing rolling to prepare a hot-rolled steel sheet; hot-rolling annealing at 1,020 to 1,100°C; and cold rolling, followed by cold rolling annealing at 1,050 to 1,100° C., wherein the holding time (seconds) before the start of the finish rolling satisfies the following Equation (3).
(1) Mo ＋ W ＋ Nb ≥ 3(1) Mo + W + Nb ≥ 3
(2) (Mo ＋ W)/Nb ≤ 8(2) (Mo + W)/Nb ≤ 8
(3) 8,000/(RHT - 1,000) ≤ 유지 시간 ≤ 120(3) 8,000/(RHT - 1,000) ≤ holding time ≤ 120
(여기서, Mo, W, Nb는 각 원소의 함량(중량%)을 의미하며, RHT는 재가열 온도(℃)를 의미한다)(Here, Mo, W, Nb means the content (wt%) of each element, and RHT means the reheating temperature (℃))
본 발명의 실시예에 따른 페라이트계 스테인리스강은 기지 내에 고용 합금 양을 증대시켜 내열성이 우수한 페라이트계 스테인리스강을 제공할 수 있다.The ferritic stainless steel according to an embodiment of the present invention may provide a ferritic stainless steel having excellent heat resistance by increasing the amount of a solid solution alloy in a matrix.
본 발명의 실시예에 따른 페라이트계 스테인리스강은 900℃에서 100시간 열처리 후 기지 내에 고용된 Mo 및 W의 중량비가 85% 이상이며, 인장강도 감소율이 10% 이하이기 때문에 장시간 사용시에도 높은 안정성을 확보할 수 있다.In the ferritic stainless steel according to an embodiment of the present invention, after heat treatment at 900° C. for 100 hours, the weight ratio of Mo and W dissolved in the matrix is 85% or more, and the tensile strength reduction rate is 10% or less, so high stability is secured even when used for a long time can do.
도 1은 고용 Mo와 고용 W에 따른 900℃ 인장강도를 도시한 그래프이다.1 is a graph showing the tensile strength of 900 ℃ according to the solid solution Mo and the solid solution W.
도 2는 900℃ 100시간 열처리 전/후의 900℃ 인장강도 변화를 도시한 그래프이다.2 is a graph showing the change in tensile strength at 900°C before/after heat treatment at 900°C for 100 hours.
본 발명의 일 실시예에 따른 내열성이 우수한 페라이트계 스테인리스강은, 중량%로, C: 0.0005 내지 0.02%, N: 0.005 내지 0.02%, Si: 0.01 내지 1.0%, Mn: 0.01 내지 1.2%, P: 0.001 내지 0.05%, Cr: 10.0 내지 25.0%, Mo: 1.5 내지 3.0%, Nb: 0.3 내지 0.7%, W: 0.5 내지 2.0%, 나머지 Fe 및 불가피한 불순물을 포함하고, 기지 내에 고용 Mo의 중량비는 85% 이상, 고용 W의 중량비는 85% 이상으로 포함되며, 하기 식 (1) 및 (2)를 만족한다.Ferritic stainless steel having excellent heat resistance according to an embodiment of the present invention, by weight, C: 0.0005 to 0.02%, N: 0.005 to 0.02%, Si: 0.01 to 1.0%, Mn: 0.01 to 1.2%, P : 0.001 to 0.05%, Cr: 10.0 to 25.0%, Mo: 1.5 to 3.0%, Nb: 0.3 to 0.7%, W: 0.5 to 2.0%, the remainder including Fe and unavoidable impurities, the weight ratio of dissolved Mo in the matrix 85% or more, the weight ratio of solid solution W is included as 85% or more, and the following formulas (1) and (2) are satisfied.
(1) Mo ＋ W ＋ Nb ≥ 3(1) Mo + W + Nb ≥ 3
(2) (Mo ＋ W)/Nb ≤ 8(2) (Mo + W)/Nb ≤ 8
(여기서, Mo, W, Nb는 각 원소의 함량(중량%)을 의미한다.)(Here, Mo, W, and Nb mean the content (wt%) of each element.)
이하에서는 본 발명의 실시예를 첨부 도면을 참조하여 상세히 설명한다. 이하의 실시예는 본 발명이 속하는 기술분야에서 통상의 지식을 가진 자에게 본 발명의 사상을 충분히 전달하기 위해 제시하는 것이다. 본 발명은 여기서 제시한 실시예만으로 한정되지 않고 다른 형태로 구체화될 수도 있다. 도면은 본 발명을 명확히 하기 위해 설명과 관계없는 부분의 도시를 생략하고, 이해를 돕기 위해 구성요소의 크기를 다소 과장하여 표현할 수 있다.Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The following examples are presented in order to sufficiently convey the spirit of the present invention to those of ordinary skill in the art to which the present invention pertains. The present invention is not limited to the embodiments presented herein, and may be embodied in other forms. The drawings may omit illustration of parts irrelevant to the description in order to clarify the present invention, and slightly exaggerate the size of the components to help understanding.
또한 어떤 부분이 어떤 구성요소를 "포함"한다고 할 때, 이는 특별히 반대되는 기재가 없는 한 다른 구성요소를 제외하는 것이 아니라 다른 구성요소를 더 포함할 수 있는 것을 의미한다.Also, when a part "includes" a component, it means that other components may be further included, rather than excluding other components, unless otherwise stated.
단수의 표현은 문맥상 명백하게 예외가 있지 않는 한, 복수의 표현을 포함한다.The singular expression includes the plural expression unless the context clearly dictates otherwise.
본 발명의 일 실시예에 따른 내열성이 우수한 페라이트계 스테인리스강은, 중량%로, C: 0.0005 내지 0.02%, N: 0.005 내지 0.02%, Si: 0.01 내지 1.0%, Mn: 0.01 내지 1.2%, P: 0.001 내지 0.05%, Cr: 10.0 내지 25.0%, Mo: 1.5 내지 3.0%, Nb: 0.3 내지 0.7%, W: 0.5 내지 2.0%, 나머지 Fe 및 불가피한 불순물을 포함한다.Ferritic stainless steel having excellent heat resistance according to an embodiment of the present invention, by weight, C: 0.0005 to 0.02%, N: 0.005 to 0.02%, Si: 0.01 to 1.0%, Mn: 0.01 to 1.2%, P : 0.001 to 0.05%, Cr: 10.0 to 25.0%, Mo: 1.5 to 3.0%, Nb: 0.3 to 0.7%, W: 0.5 to 2.0%, remaining Fe and unavoidable impurities.
이하, 본 발명의 실시예에서의 합금성분 원소 함량의 수치한정 이유에 대하여 설명한다. 이하에서는 특별한 언급이 없는 한 단위는 중량%이다.Hereinafter, the reason for numerical limitation of the alloying element content in the embodiment of the present invention will be described. Hereinafter, unless otherwise specified, the unit is % by weight.
C(탄소)의 함량은 0.0005 내지 0.02%이다.The content of C (carbon) is 0.0005 to 0.02%.
C는 강도에 크게 영향을 미치는 원소로써, 그 함량이 0.0005% 미만이면 강도 저하 및 고순도 제품을 만들기 위한 정련 가격이 비싸지고, 0.02%를 초과하면 소재의 불순물이 증가하여 연신율과 가공경화지수(n값)가 낮아지며, DBTT가 높아져 충격 특성이 저하된다.C is an element that greatly affects strength. If its content is less than 0.0005%, the refining price to reduce strength and make high-purity products is high. If it exceeds 0.02%, impurities in the material increase, resulting in elongation and work hardening index (n value) is decreased, and DBTT is increased to deteriorate the impact properties.
N(질소)의 함량은 0.005 내지 0.02%이다.The content of N (nitrogen) is 0.005 to 0.02%.
N은 열간압연 시 오스테나이트를 석출시켜 재결정을 촉진시키는 역할을 하는 원소로, 그 함량이 0.005% 미만이면 TiN 정출이 적어져 슬라브의 등축정율이 낮아진다. 반면, 0.02%를 초과하면 소재의 불순물이 증가하여 연신율이 낮아지고, DBTT가 높아져 충격 특성이 저하된다.N is an element that promotes recrystallization by precipitating austenite during hot rolling. If the content is less than 0.005%, TiN crystallization decreases and the equiaxed crystal rate of the slab decreases. On the other hand, when it exceeds 0.02%, impurities in the material increase, resulting in lower elongation, and higher DBTT, thereby lowering impact properties.
Si의 함량은 0.01 내지 1.0%이다.The content of Si is 0.01 to 1.0%.
Si는 제강 시 용강의 탈산과 페라이트 안정화를 위해 첨가되는 원소로, 그 함량이 0.01% 미만이면 정련 가격이 증가하는 문제가 있고, 1.0%를 초과하면 소재의 불순물이 증가하여 연신율과 가공경화지수(n값)가 낮아지며, Si계 개재물이 증가하여 가공성이 나빠진다.Si is an element added for deoxidation of molten steel and stabilization of ferrite during steelmaking. If the content is less than 0.01%, the refining price increases, and if it exceeds 1.0%, impurities in the material increase, resulting in elongation and work hardening index ( n value) decreases, and Si-based inclusions increase, resulting in poor workability.
Mn(망간)의 함량은 0.01 내지 1.2%이다.The content of Mn (manganese) is 0.01 to 1.2%.
Mn은 내식성 개선에 유효한 원소로, 그 함량이 0.01% 미만이면 정련 가격이 증가하는 문제가 있고, 1.2%를 초과하면 소재의 불순물이 증가하여 연신율이 낮아진다.Mn is an effective element for improving corrosion resistance, and when its content is less than 0.01%, there is a problem in that the refining price increases, and when it exceeds 1.2%, impurities in the material increase and elongation is lowered.
P(인)의 함량은 0.001 내지 0.05%이다.The content of P (phosphorus) is 0.001 to 0.05%.
P는 강 중 불가피하게 함유되는 불순물로써, 그 함량을 0.001% 미만으로 제어하는 경우 정련 가격이 증가하며, 0.05%를 초과하면 불순물 증가로 인해 연신율 및 가공경화지수가 낮아진다.P is an impurity contained inevitably in steel. When the content is controlled to less than 0.001%, the refining price increases, and when it exceeds 0.05%, the elongation and work hardening index are lowered due to the increase of impurities.
Cr(크롬)의 함량은 10.0 내지 25.0%이다.The content of Cr (chromium) is 10.0 to 25.0%.
Cr은 강의 내식성 및 내산화성 향상에 효과적인 원소로, 본 발명에서는 10.0% 이상 첨가한다. 다만, 그 함량이 과다할 경우 연신율이 낮아지고 열연 스티킹(sticking) 결함이 발생하는 문제가 있어 25.0% 이하로 제한한다.Cr is an element effective for improving corrosion resistance and oxidation resistance of steel, and is added in an amount of 10.0% or more in the present invention. However, if the content is excessive, elongation is lowered and hot-rolled sticking defects occur, so it is limited to 25.0% or less.
Mo(몰리브덴)의 함량은 1.5 내지 3.0%이다.The content of Mo (molybdenum) is 1.5 to 3.0%.
Mo는 페라이트계 스테인리스강의 내식성을 증가시킴과 동시에 고온강도를 향상시키는 역할을 한다. Mo 함량이 1.5% 미만이면 소재 내 고용되는 양이 적어 고온강도 및 열피로 특성 열화가 발생되며, 이상 산화 발생 확률이 높아진다. 또한, 3.0%를 초과하면 충격 특성이 떨어져 가공 시 파단 발생 위험이 커지고 비용 증가의 문제가 있다.Mo serves to increase the corrosion resistance of ferritic stainless steel and at the same time improve the high-temperature strength. If the Mo content is less than 1.5%, the amount of solid solution in the material is small, so high-temperature strength and thermal fatigue properties deteriorate, and the probability of abnormal oxidation increases. In addition, if it exceeds 3.0%, the impact properties are deteriorated, the risk of fracture during processing increases, and there is a problem of increased cost.
Nb(나이오븀)의 함량은 0.3 내지 0.7%이다.The content of Nb (niobium) is 0.3 to 0.7%.
Nb 함량이 0.3% 미만이면 소재 내 고용되는 양이 적어 고온강도가 저하되는 문제가 있고, 0.7%를 초과하면 Nb계 석출물과 고용량이 과도하게 늘어나 연신율과 충격 특성이 낮아진다.If the Nb content is less than 0.3%, there is a problem that the high-temperature strength is lowered because the amount of solid solution in the material is small, and if it exceeds 0.7%, the Nb-based precipitates and the high-solute capacity are excessively increased, and the elongation and impact properties are lowered.
W(텅스텐)의 함량은 0.5 내지 2.0%이다.The content of W (tungsten) is 0.5 to 2.0%.
W는 페라이트계 스테인리스강의 내식성을 증대함과 동시에 고온 강도를 향상시킨다. 따라서, 0.5% 이상 첨가하는 것이 바람직하며, 0.5% 미만이면 소재 내 고용되는 양이 적어 고온강도가 저하되는 문제가 있다. 반면, 2.0%를 초과하면 과도한 석출물이 생성되어 가공 시 크랙이 다발하는 문제가 있다.W increases the corrosion resistance of the ferritic stainless steel and at the same time improves the high temperature strength. Therefore, it is preferable to add 0.5% or more, and if it is less than 0.5%, there is a problem in that the amount of solid solution in the material is small and the high temperature strength is lowered. On the other hand, if it exceeds 2.0%, there is a problem in that excessive precipitates are generated and cracks occur frequently during processing.
상술한 합금원소들을 제외한 스테인리스강의 나머지는 Fe 및 기타 불가피한 불순물로 이루어진다.The remainder of the stainless steel except for the above-mentioned alloying elements consists of Fe and other unavoidable impurities.
스테인리스강의 고온 강도를 향상시키기 위해서는 내열성을 향상시키는 원소인 Mo, W, Nb의 함량을 제어하여야 한다.In order to improve the high-temperature strength of stainless steel, it is necessary to control the content of Mo, W, and Nb, which are elements that improve heat resistance.
본 발명에서는 식 (1)을 사용하여 내열성을 향상시키는 성분 범위를 도출하였다.In the present invention, a range of components for improving heat resistance was derived using Equation (1).
(1) Mo ＋ W ＋ Nb ≥ 3(1) Mo + W + Nb ≥ 3
(여기서, Mo, W, Nb는 각 원소의 함량(중량%)을 의미한다.)(Here, Mo, W, and Nb mean the content (wt%) of each element.)
식 (1)이 3 미만의 값을 가지는 경우, 900℃ 인장강도 값이 47Mpa 미만이고, 열처리 후 인장강도의 감소율이 10%를 초과하게 되어 목표하는 내열성을 확보하기 어렵다.When Equation (1) has a value less than 3, the 900° C. tensile strength value is less than 47 Mpa, and the reduction rate of the tensile strength after heat treatment exceeds 10%, making it difficult to secure the target heat resistance.
또한, 식 (1)을 만족시키는 범위에서 Mo, W 및 Nb의 비를 제어할 필요가 있다. Moreover, it is necessary to control the ratio of Mo, W, and Nb in the range which satisfy|fills Formula (1).
Mo와 W가 Nb 대비 과도하게 많으면, 고용 Mo 및 W의 중량비가 85% 미만이 되어 목표하는 내열성을 확보하기 어렵다. 고용 Mo의 중량비는 전체 Mo의 중량% 중 기지 내 고용된 Mo의 중량%에 대한 비를 의미하며, 이는 W도 동일하게 적용된다.When Mo and W are excessively large compared to Nb, the weight ratio of dissolved Mo and W becomes less than 85%, so that it is difficult to secure the target heat resistance. The weight ratio of dissolved Mo means a ratio to the weight% of Mo dissolved in the matrix among weight% of the total Mo, and the same applies to W.
본 발명에서는 목표하는 내열성을 확보하기 위해 식(2)를 도출하였다.In the present invention, Equation (2) was derived in order to secure the target heat resistance.
(2) (Mo ＋ W)/Nb ≤ 8(2) (Mo + W)/Nb ≤ 8
(여기서, Mo, W, Nb는 각 원소의 함량(중량%)을 의미한다.)(Here, Mo, W, and Nb mean the content (wt%) of each element.)
식 (2)의 값이 8 초과인 경우, 고용 Mo가 85% 미만이고, 고용 W가 85% 미만이 되어 900℃ 인장강도가 47Mpa 미만이며, 열처리 후 인장강도의 감소율이 10%를 초과하게 된다. 따라서, 목표하는 내열성을 확보하기 위해 식 (2)의 값을 8 이하로 제어한다.When the value of formula (2) is more than 8, the dissolved Mo is less than 85%, the dissolved W is less than 85%, so that the tensile strength at 900°C is less than 47Mpa, and the decrease in tensile strength after heat treatment exceeds 10% . Therefore, in order to ensure the target heat resistance, the value of Formula (2) is controlled to 8 or less.
다음으로, 본 발명의 일 실시예에 따른 내열성이 우수한 페라이트계 스테인리스강의 제조방법에 대하여 설명한다.Next, a method for manufacturing a ferritic stainless steel having excellent heat resistance according to an embodiment of the present invention will be described.
본 발명의 내열성이 우수한 페라이트계 스테인리스강은 목표로 하는 내열성을 확보하기 위해 Mo, W 및 Nb가 라베스(Laves)상으로 석출되지 않도록 성분 제어뿐만 아니라 열연 공정의 제어도 요구된다.The ferritic stainless steel having excellent heat resistance of the present invention requires not only component control but also control of the hot rolling process so that Mo, W and Nb do not precipitate in the laves phase in order to secure target heat resistance.
본 발명의 일 실시예에 따른 내열성이 우수한 페라이트계 스테인리스강의 제조방법은 중량%로, C: 0.0005 내지 0.02%, N: 0.005 내지 0.02%, Si: 0.01 내지 1.0%, Mn: 0.01 내지 1.2%, P: 0.001 내지 0.05%, Cr: 10.0 내지 25.0%, Mo: 1.5 내지 3.0%, Nb: 0.3 내지 0.7%, W: 0.5 내지 2.0%, 나머지 Fe 및 불가피한 불순물을 포함하는 슬라브를 재가열하여 조압연하고, 조압연 바(bar)를 마무리압연하고, 마무리압연된 열연 강판을 권취하고, 권취된 열연 코일을 소둔 열처리할 수 있다.The method for producing a ferritic stainless steel having excellent heat resistance according to an embodiment of the present invention is, by weight, C: 0.0005 to 0.02%, N: 0.005 to 0.02%, Si: 0.01 to 1.0%, Mn: 0.01 to 1.2%, P: 0.001 to 0.05%, Cr: 10.0 to 25.0%, Mo: 1.5 to 3.0%, Nb: 0.3 to 0.7%, W: 0.5 to 2.0%, reheating the slab containing the remaining Fe and unavoidable impurities and rough rolling , the rough-rolled bar may be finish-rolled, the finish-rolled hot-rolled steel sheet may be wound, and the wound hot-rolled coil may be subjected to annealing heat treatment.
먼저, 슬라브 주조 중에 생성된 조대한 석출물들을 재분해하기 위해 슬라브의 열연 재가열 온도를 1,100℃ 이상으로 제어하여야 한다. 이때 재가열 온도가 너무 높은 경우 결정립이 조대화될 수 있어 1,300℃ 이하로 제한한다.First, in order to re-decompose the coarse precipitates generated during slab casting, the hot-rolled reheating temperature of the slab must be controlled to 1,100° C. or higher. At this time, if the reheating temperature is too high, crystal grains may become coarse, so it is limited to 1,300° C. or less.
이어서, 조압연 공정에서는 변형에너지를 부여하기 위해 조압연 마지막 2패스의 총 압하율을 50% 이상으로 할 수 있다. 조압연은 통상적으로 3개 내지 4개의 압연밀로 구성되는데, 본 발명에서의 마지막 2패스는 마지막 압연밀 및 마지막에서 두 번째 압연밀을 의미할 수 있다. 마지막 2패스의 압하율 합을 50% 이상으로 강압하함으로써 전위 생성을 원활하게 할 수 있다.Subsequently, in the rough rolling process, the total reduction ratio of the last two passes of rough rolling may be set to 50% or more in order to impart strain energy. Rough rolling is typically composed of three to four rolling mills, the last two passes in the present invention may mean the last rolling mill and the second to last rolling mill. By reducing the sum of the reduction ratios of the last two passes to 50% or more, it is possible to smoothly generate dislocations.
조압연된 조압연 바(bar)가 마무리압연 개시 전까지 유지되는 시간(초)은 아래 식 (3)을 만족할 수 있다.The time (seconds) for which the rough-rolled rough-rolled bar is maintained before the start of finish rolling may satisfy Equation (3) below.
(3) 8,000/(RHT - 1,000) ≤ 유지 시간 ≤ 120(3) 8,000/(RHT - 1,000) ≤ holding time ≤ 120
(여기서, RHT는 재가열 온도(℃)를 의미한다.)(Here, RHT means reheating temperature (℃).)
조압연 후 마무리압연까지 유지되는 시간을 8,000/(재가열 온도(℃) - 1,000) 초 이상으로 하여 충분한 재결정 시간을 부여하고, 120초 이하로 제한하여 결정립의 조대화를 방지한다. 이는 마무리압연 시 변형 조직을 더욱 부여하여 석출물들의 조대화를 방지하고 이후 소둔 공정에서 고용될 수 있도록 하는 것이다.After rough rolling, the time maintained until finish rolling is 8,000/(reheating temperature (℃) - 1,000) seconds or more to give sufficient recrystallization time, and limiting it to 120 seconds or less to prevent coarsening of grains. This is to further impart a deformed structure during finish rolling to prevent coarsening of the precipitates and to be employed in the subsequent annealing process.
또한, 마무리압연된 열연 강판의 권취 온도는 450 내지 700℃일 수 있다. 열간 압연 중에 석출된 석출물들의 조대화를 방지하고 라베스상으로 석출되지 않도록 권취 온도를 700℃ 이하로 제어하여야 하며, 형상 및 표면품질을 위해 450℃ 이상으로 제어하는 것이 바람직하다.In addition, the winding temperature of the finish-rolled hot-rolled steel sheet may be 450 to 700 ℃. The coiling temperature should be controlled to 700° C. or less to prevent coarsening of the precipitates precipitated during hot rolling and to prevent precipitation in the form of labes, and it is preferable to control it to 450° C. or higher for shape and surface quality.
이와 같은 방법으로 제조된 열간압연재는 1020℃ 이상에서 열연소둔이 이루어져야 하며, 냉간압연을 거친 후 1050℃ 이상에서 냉연소둔이 이루어져야 한다. The hot-rolled material manufactured in this way must be subjected to hot-rolling annealing at 1020°C or higher, and cold-rolled annealing at 1050°C or higher after cold rolling.
소둔 공정을 거친 최종 제품은 900℃에서 100시간 열처리 후 기지 내에 고용된 Mo 및 W의 중량비가 85% 이상이며, 인장강도 감소율이 10% 이하를 만족하여 목표로 하는 내열성을 확보할 수 있다.After heat treatment at 900°C for 100 hours, the final product undergoes an annealing process, and the weight ratio of Mo and W dissolved in the matrix is 85% or more, and the tensile strength reduction rate is 10% or less, thereby securing the target heat resistance.
한편, 권취 온도 및 소둔 온도가 본 발명의 일 실시예에 의한 제조방법과 다른 경우, 즉 권취온도가 700℃를 초과하고, 열연/냉연소둔 온도가 1000℃ 미만인 경우에는 목표 성분을 확보하더라도 고용 Mo와 W가 85% 미만이 되어 원하는 내열성을 확보할 수 없다.On the other hand, when the coiling temperature and the annealing temperature are different from the manufacturing method according to an embodiment of the present invention, that is, the coiling temperature exceeds 700 ℃, and the hot rolling/cold rolling annealing temperature is less than 1000 ℃, even if the target component is secured, dissolved Mo and W are less than 85%, so the desired heat resistance cannot be secured.
이하 본 발명의 바람직한 실시예를 통해 보다 상세히 설명하기로 한다.Hereinafter, it will be described in more detail through preferred embodiments of the present invention.
실시예Example
스테인리스강 lab scale 용해 및 Ingot 생산 설비를 활용하여 아래 표 1에 기재된 합금 성분계로 20mm 바 샘플을 제조하였다. 이후 열간압연을 진행한 뒤 표 2에 기재된 권취 온도, 열연소둔 온도 및 냉연소둔 온도로 처리하여 최종 제품을 생산하였다.Using the stainless steel lab scale melting and ingot production equipment, 20 mm bar samples were prepared using the alloy composition system shown in Table 1 below. Thereafter, after hot rolling was performed, the final product was produced by treatment with the coiling temperature, hot rolling annealing temperature and cold rolling annealing temperature shown in Table 2.
구분division 강종steel grade CC NN SiSi MnMn PP CrCr MoMo NbNb WW 식
(1)ceremony
(One) 		식
(2)ceremony
(2)
비교예 1Comparative Example 1 AA 0.00880.0088 0.01140.0114 0.30.3 0.40.4 0.020.02 18.018.0 1.11.1 0.520.52 1.21.2 2.82.8 4.44.4
비교예 2Comparative Example 2 BB 0.01040.0104 0.00830.0083 0.20.2 0.50.5 0.030.03 17.817.8 2.02.0 0.540.54 0.30.3 2.82.8 4.34.3
비교예 3Comparative Example 3 CC 0.00890.0089 0.00910.0091 0.30.3 0.40.4 0.020.02 18.418.4 1.91.9 0.210.21 0.40.4 2.52.5 11.011.0
비교예 4Comparative Example 4 DD 0.01230.0123 0.01020.0102 0.40.4 0.30.3 0.030.03 18.618.6 2.52.5 0.350.35 0.90.9 3.83.8 9.79.7
실시예 1Example 1 EE 0.00920.0092 0.00900.0090 0.20.2 0.40.4 0.020.02 22.422.4 1.71.7 0.530.53 1.71.7 3.93.9 6.46.4
실시예 2Example 2 FF 0.00960.0096 0.01100.0110 0.30.3 0.40.4 0.020.02 18.218.2 2.12.1 0.560.56 1.11.1 3.83.8 5.75.7
실시예 3Example 3 GG 0.01340.0134 0.00970.0097 0.30.3 0.50.5 0.020.02 16.416.4 2.32.3 0.550.55 0.70.7 3.63.6 5.55.5
최종 제품에 대하여 고온 인장 강도는 JIS G 0567 방법에 의거하여 900℃에서 테스트를 진행하여 평가하였고, 900℃에서 100시간 유지 후에 다시 900℃에서 고온 인장을 하여 인장강도를 측정하였다. 그리고 소재로부터 석출물 잔사 추출을 하여 각 합금원소들의 양을 측정한 뒤 첨가된 함금원소의 양에서 차를 구하여 고용되어 있는 합금원소의 비율을 측정하였다. 각각의 결과에 대해서는 표 2에 기재하였다.High-temperature tensile strength of the final product was evaluated by performing a test at 900°C according to the JIS G 0567 method, and after maintaining at 900°C for 100 hours, high-temperature tensile strength was again measured at 900°C. Then, the amount of each alloying element was measured by extracting the precipitate residue from the material, and the difference was obtained from the amount of the added alloying element to measure the ratio of dissolved alloying elements. Each result is shown in Table 2.
구분division 강종steel grade 고용Mo
(%)EmploymentMo
(%) 		고용W
(%)employment W
(%) 		900℃
인장강도
(MPa)900℃
The tensile strength
(MPa) 		열처리후
900℃
인장강도
(MPa)after heat treatment
900℃
The tensile strength
(MPa) 		900℃
인장강도
감소율(%)900℃
The tensile strength
Decrease rate (%)
비교예 1Comparative Example 1 AA 7575 8888 4343 3838 11.611.6
비교예 2Comparative Example 2 B B 9494 6161 4444 3737 15.915.9
비교예 3Comparative Example 3 C C 8383 7272 3939 3333 15.415.4
비교예 4Comparative Example 4 DD 8282 7373 4646 4040 13.013.0
비교예 5Comparative Example 5 FF 6969 7777 4545 3838 15.615.6
비교예 6Comparative Example 6 GG 7474 7272 4545 3737 17.817.8
실시예 1Example 1 EE 8989 9696 5252 5050 3.83.8
실시예 2Example 2 F F 9191 9292 5050 4949 2.02.0
실시예 3Example 3 G G 9393 8686 4949 4747 4.14.1
자동차 배기계 Hot Part 부품에 쓰이기 위한 소재는 900℃ 고온 인장강도가 47MPa 이상이고, 장시간 열처리 후에도 인장강도 감소율이 10% 미만이어야 한다.For materials used for automobile exhaust system hot parts, the tensile strength at 900℃ high temperature should be 47MPa or more, and the tensile strength reduction rate should be less than 10% even after long-time heat treatment.
표 1 및 표 2를 함께 살펴보면, 실시예 1 내지 3 강종은 식 (1)의 값이 3 이상이고, 식 (2)의 값이 8 이하임을 만족하였으며, 고용 Mo 및 W의 중량비가 85% 이상으로 나타나 900℃ 인장강도가 49Mpa 이상임을 확인하였다.Looking at Tables 1 and 2 together, the steel grades of Examples 1 to 3 satisfy that the value of Formula (1) is 3 or more and the value of Formula (2) is 8 or less, and the weight ratio of dissolved Mo and W is 85% or more , and it was confirmed that the tensile strength at 900°C was 49Mpa or more.
또한, 열처리 후 900℃ 인장강도가 47Mpa 이상으로 나타나 900℃ 인장강도 감소율이 10% 이하임을 확인하였다.In addition, after heat treatment, the 900°C tensile strength was 47Mpa or higher, confirming that the 900°C tensile strength reduction rate was 10% or less.
반면, 비교예 1은 Mo의 함량이, 비교예 2는 W의 함량이, 비교예 3은 Nb 및 W의 함량이 본 발명의 성분 범위에 포함되지 않고, 식 (1)의 값이 3 미만으로 나타나 소재 내에 고용되는 Mo 및 W가 적어 900℃ 인장강도가 47Mpa에 못 미치는 것으로 나타났다.On the other hand, the content of Mo in Comparative Example 1, the content of W in Comparative Example 2, and the content of Nb and W in Comparative Example 3 were not included in the component range of the present invention, and the value of Formula (1) was less than 3. As a result, the Mo and W dissolved in the material were small, indicating that the tensile strength at 900°C was less than 47Mpa.
또한, 비교예 4는 Mo, W, Nb의 함량이 본 발명의 성분 범위에 포함되며, 식 (1)의 값이 3 이상이나, 식 (2)의 값이 8 초과로 나타나 900℃ 인장강도가 47Mpa에 못 미치며, 900℃ 인장강도 감소율이 10%를 초과하는 것으로 나타났다.In addition, in Comparative Example 4, the content of Mo, W, and Nb is included in the component range of the present invention, and the value of Formula (1) is 3 or more, but the value of Formula (2) is more than 8, resulting in a tensile strength of 900°C It was less than 47Mpa, and the rate of decrease in tensile strength at 900℃ exceeded 10%.
한편, 비교에 5 및 6은 Mo, W, Nb의 함량이 본 발명의 성분 범위에 포함되고, 식 (1)의 값이 3 이상이며, 식 (2)의 값이 8 이하로 나타났으나, 권취 온도가 700℃를 초과하고, 소둔 온도가 1,000℃ 미만으로 이루어져 고용 Mo와 W가 85% 미만이 되어 원하는 내열성을 얻을 수 없음을 확인하였다.On the other hand, in 5 and 6 in comparison, the content of Mo, W, and Nb was included in the component range of the present invention, the value of Formula (1) was 3 or more, and the value of Formula (2) was 8 or less, It was confirmed that the coiling temperature was higher than 700 °C, the annealing temperature was lower than 1,000 °C, and the dissolved Mo and W were less than 85%, so that the desired heat resistance could not be obtained.
도 1은 고용 Mo와 고용 W에 따른 900℃ 인장강도를 도시한 그래프이다. 고용 Mo 또는 W가 85% 미만인 경우 900℃ 인장강도가 47Mpa에 못 미치며, 고용 Mo 및 W가 85% 이상인 경우 900℃ 인장강도가 47Mpa 이상임을 확인하였다.1 is a graph showing the tensile strength of 900 ℃ according to the solid solution Mo and the solid solution W. When the dissolved Mo or W was less than 85%, it was confirmed that the 900℃ tensile strength was less than 47Mpa, and when the dissolved Mo and W were 85% or more, the 900℃ tensile strength was 47Mpa or more.
도 2는 900℃ 100시간 열처리 전/후의 900℃ 인장강도 변화를 도시한 그래프이다. 고용 Mo 또는 W가 85% 미만인 비교예 1 내지 6의 경우 900℃ 열처리 후 인장강도 감소율이 10% 초과임을 확인하였으며, 고용 Mo 또는 W가 85% 이상인 실시예 1 내지 3의 경우 900℃ 열처리 후 인장강도 감소율이 10% 이하임을 확인하였다.2 is a graph showing the change in tensile strength at 900°C before/after heat treatment at 900°C for 100 hours. In Comparative Examples 1 to 6 in which dissolved Mo or W was less than 85%, it was confirmed that the tensile strength reduction rate after heat treatment at 900 ° C was more than 10%, and in Examples 1 to 3 in which dissolved Mo or W was 85% or more, tensile strength after heat treatment at 900 ° C. It was confirmed that the strength reduction rate was 10% or less.
상술한 바에 있어서, 본 발명의 예시적인 실시예들을 설명하였지만, 본 발명은 이에 한정되지 않으며 해당 기술 분야에서 통상의 지식을 가진 자라면 다음에 기재하는 청구범위의 개념과 범위를 벗어나지 않는 범위 내에서 다양한 변경 및 변형이 가능함을 이해할 수 있을 것이다.In the above description, exemplary embodiments of the present invention have been described, but the present invention is not limited thereto, and those of ordinary skill in the art will not depart from the concept and scope of the following claims. It will be appreciated that various modifications and variations are possible.
본 발명의 일 예에 따른 내열성이 우수한 페라이트계 스테인리스강은 기지 내에 고용 합금 양을 증대시켜 내열성을 향상시키고, 900℃에서 100시간 열처리 후 기지 내에 고용된 Mo 및 W의 중량비가 85% 이상이며, 인장강도 감소율이 10% 이하이기 때문에 장시간 사용시에도 높은 안정성을 확보할 수 있다.The ferritic stainless steel having excellent heat resistance according to an example of the present invention improves heat resistance by increasing the amount of solid solution alloy in the matrix, and the weight ratio of Mo and W dissolved in the matrix after heat treatment at 900° C. for 100 hours is 85% or more, Because the tensile strength reduction rate is less than 10%, high stability can be secured even when used for a long time.

Claims (4)

  1. 중량%로, C: 0.0005 내지 0.02%, N: 0.005 내지 0.02%, Si: 0.01 내지 1.0%, Mn: 0.01 내지 1.2%, P: 0.001 내지 0.05%, Cr: 10.0 내지 25.0%, Mo: 1.5 내지 3.0%, Nb: 0.3 내지 0.7%, W: 0.5 내지 2.0%, 나머지 Fe 및 불가피한 불순물을 포함하고, By weight, C: 0.0005 to 0.02%, N: 0.005 to 0.02%, Si: 0.01 to 1.0%, Mn: 0.01 to 1.2%, P: 0.001 to 0.05%, Cr: 10.0 to 25.0%, Mo: 1.5 to 3.0%, Nb: 0.3 to 0.7%, W: 0.5 to 2.0%, including the remainder of Fe and unavoidable impurities,
    기지 내에 고용 Mo의 중량비는 85% 이상, 고용 W의 중량비는 85% 이상으로 포함되며, The weight ratio of dissolved Mo in the base is 85% or more, and the weight ratio of dissolved W is 85% or more,
    하기 식 (1) 및 (2)를 만족하는 내열성이 우수한 페라이트계 스테인리스강:Ferritic stainless steel having excellent heat resistance satisfying the following formulas (1) and (2):
    (1) Mo ＋ W ＋ Nb ≥ 3(1) Mo + W + Nb ≥ 3
    (2) (Mo ＋ W)/Nb ≤ 8(2) (Mo + W)/Nb ≤ 8
    (여기서, Mo, W, Nb는 각 원소의 함량(중량%)을 의미한다).(Here, Mo, W, and Nb mean the content (wt%) of each element).
  2. 제1항에 있어서,The method of claim 1,
    900℃ 인장강도가 47MPa 이상인 내열성이 우수한 페라이트계 스테인리스강.Ferritic stainless steel with excellent heat resistance with a tensile strength of 47 MPa or higher at 900°C.
  3. 제1항에 있어서,The method of claim 1,
    900℃에서 100시간 열처리 후 인장강도 감소율이 10% 이하인 내열성이 우수한 페라이트계 스테인리스강.Ferritic stainless steel with excellent heat resistance with a tensile strength reduction of 10% or less after heat treatment at 900°C for 100 hours.
  4. 중량%로, C: 0.0005 내지 0.02%, N: 0.005 내지 0.02%, Si: 0.01 내지 1.0%, Mn: 0.01 내지 1.2%, P: 0.001 내지 0.05%, Cr: 10.0 내지 25.0%, Mo: 1.5 내지 3.0%, Nb: 0.3 내지 0.7%, W: 0.5 내지 2.0%, 나머지 Fe 및 불가피한 불순물을 포함하며, 하기 식 (1) 및 (2)를 만족하는 슬라브를 재가열하여 조압연한 다음, 마무리압연하여 열연 강판을 마련하는 단계;By weight, C: 0.0005 to 0.02%, N: 0.005 to 0.02%, Si: 0.01 to 1.0%, Mn: 0.01 to 1.2%, P: 0.001 to 0.05%, Cr: 10.0 to 25.0%, Mo: 1.5 to 3.0%, Nb: 0.3 to 0.7%, W: 0.5 to 2.0%, containing the remaining Fe and unavoidable impurities, by reheating a slab that satisfies the following formulas (1) and (2) to rough rolling, and then finish rolling preparing a hot-rolled steel sheet;
    1,020 내지 1,100℃로 열연 소둔하는 단계; 및hot-rolling annealing at 1,020 to 1,100°C; and
    냉간 압연한 다음, 1,050 내지 1,100℃로 냉연 소둔하는 단계;를 포함하고,After cold rolling, cold rolling annealing at 1,050 to 1,100 ° C. includes;
    상기 마무리압연 개시 전의 유지 시간(초)이 하기 식 (3)을 만족하는 내열성이 우수한 페라이트계 스테인리스강의 제조방법:A method for producing a ferritic stainless steel having excellent heat resistance, in which the holding time (seconds) before the start of the finish rolling satisfies the following formula (3):
    (1) Mo ＋ W ＋ Nb ≥ 3(1) Mo + W + Nb ≥ 3
    (2) (Mo ＋ W)/Nb ≤ 8(2) (Mo + W)/Nb ≤ 8
    (3) 8,000/(RHT - 1,000) ≤ 유지 시간 ≤ 120(3) 8,000/(RHT - 1,000) ≤ holding time ≤ 120
    (여기서, Mo, W, Nb는 각 원소의 함량(중량%)을 의미하며, RHT는 재가열 온도(℃)를 의미한다).(Here, Mo, W, Nb means the content (wt%) of each element, RHT means the reheating temperature (℃)).
PCT/KR2021/014156 2020-12-18 2021-10-14 Ferritic stainless steel having excellent heat resistance and method for manufacturing same WO2022131503A1 (en)

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR20120108786A (en) * 2011-03-25 2012-10-05 주식회사 포스코 Fabrication method of ferritic stainless steel having excellent high temperatures strength
JP2013209726A (en) * 2012-03-30 2013-10-10 Nippon Steel & Sumikin Stainless Steel Corp Heat-resistant ferritic stainless cold rolled steel sheet excellent in workability, ferritic stainless hot rolled steel sheet for cold rolled raw material, and method for manufacturing them
CN105200330A (en) * 2015-09-24 2015-12-30 宝钢不锈钢有限公司 High-temperature-resistant ferritic stainless steel and manufacturing method thereof
KR20180109865A (en) * 2016-02-02 2018-10-08 닛신 세이코 가부시키가이샤 Nb-containing ferritic stainless steel hot-rolled steel sheet and manufacturing method thereof, Nb-containing ferritic stainless steel cold-rolled steel sheet and manufacturing method thereof
KR20200033055A (en) * 2018-09-19 2020-03-27 주식회사 포스코 Ferritic stainless steel excellent in workability and high temperature strength and manufacturing method thereof

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR20120108786A (en) * 2011-03-25 2012-10-05 주식회사 포스코 Fabrication method of ferritic stainless steel having excellent high temperatures strength
JP2013209726A (en) * 2012-03-30 2013-10-10 Nippon Steel & Sumikin Stainless Steel Corp Heat-resistant ferritic stainless cold rolled steel sheet excellent in workability, ferritic stainless hot rolled steel sheet for cold rolled raw material, and method for manufacturing them
CN105200330A (en) * 2015-09-24 2015-12-30 宝钢不锈钢有限公司 High-temperature-resistant ferritic stainless steel and manufacturing method thereof
KR20180109865A (en) * 2016-02-02 2018-10-08 닛신 세이코 가부시키가이샤 Nb-containing ferritic stainless steel hot-rolled steel sheet and manufacturing method thereof, Nb-containing ferritic stainless steel cold-rolled steel sheet and manufacturing method thereof
KR20200033055A (en) * 2018-09-19 2020-03-27 주식회사 포스코 Ferritic stainless steel excellent in workability and high temperature strength and manufacturing method thereof

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