KR20010056275A - Heat treatment method of ferrite stainless - Google Patents

Heat treatment method of ferrite stainless Download PDF

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KR20010056275A
KR20010056275A KR1019990057664A KR19990057664A KR20010056275A KR 20010056275 A KR20010056275 A KR 20010056275A KR 1019990057664 A KR1019990057664 A KR 1019990057664A KR 19990057664 A KR19990057664 A KR 19990057664A KR 20010056275 A KR20010056275 A KR 20010056275A
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heat treatment
stainless steel
ferritic stainless
scale
treatment method
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KR1019990057664A
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Korean (ko)
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KR100641758B1 (en
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류승기
하헌재
한상남
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이구택
포항종합제철 주식회사
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    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • 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
    • C21D8/0273—Final recrystallisation annealing
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/26—Methods of annealing
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/002—Heat treatment of ferrous alloys containing Cr
    • 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
    • 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

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Heat Treatment Of Sheet Steel (AREA)
  • Cleaning And De-Greasing Of Metallic Materials By Chemical Methods (AREA)

Abstract

PURPOSE: A method for heat treating ferritic stainless steel having superior descaling property is provided to increase the pickling speed and shorten the time required in removing scale completely by highly maintaining a ratio of Cr/Fe in scale during the annealing heat treatment, thereby relatively lowering a Cr content in a Cr depleted layer. CONSTITUTION: In a method for heat treating ferritic stainless steel, the method for heat treating ferritic stainless steel having superior descaling property comprises the processes of heat treating the ferritic stainless steel at an annealing temperature of 970 to 990 deg.C, thereby controlling a composition ratio of Cr/Fe in scale to 6.5 to 9.3 so that the descaling property is improved; and shortening the pickling time for improving productivity and decreasing the acid consumption.

Description

탈스케일성이 우수한 페라이트계 스테인레스강의 열처리 방법{Heat treatment method of ferrite stainless}Heat treatment method of ferrite stainless steel with excellent descaling property

본 발명은 페라이트계 스테인레스강의 열처리 방법에 관한 것이며, 특히, 탈스케일성이 우수하여 산 소모량을 줄이고 생산성을 향상시킬 수 있는 탈스케일성이 우수한 페라이트계 스테인레스강의 열처리 방법에 관한 것이다.The present invention relates to a method for heat treatment of ferritic stainless steel, and more particularly, to a method for heat treatment of ferritic stainless steel having excellent descalability, which can reduce acid consumption and improve productivity due to excellent descalability.

종래의 스테인레스 냉연강대의 소둔열처리방법은 강종에 따라 900 ∼ 1100℃사이에서 열처리를 실시한다. 이렇게 스테인레스강을 수둔열처리하는 목적은 압연 중 강내에 발생한 응력을 제거할 뿐만 아니라, 크롬고갈층을 형성시켜 산과의 반응을 촉진시켜 스케일을 가능한 한 빨리 제거하기 위해서다.In the conventional annealing heat treatment method of the stainless steel cold rolled steel strip is subjected to heat treatment between 900 ~ 1100 ℃ depending on the steel grade. The purpose of the heat treatment of stainless steel is not only to remove stress generated in the steel during rolling, but also to form a chromium depleted layer to promote the reaction with acid to remove the scale as soon as possible.

그리고, 스테인레스강의 스케일구조와 두께는 열처리 온도에 따라 크게 변하기 때문에, 열처리 온도범위가 크면 클수록 산세작업시 스케일을 완전히 제거하는 데 소요되는 시간이 달라 미산세 또는 과산세의 문제가 발생한다.In addition, since the scale structure and thickness of the stainless steel largely change according to the heat treatment temperature, the larger the heat treatment temperature range is, the longer the time required to completely remove the scale during pickling operation causes a problem of fine pickling or over pickling.

도면에서, 도 1은 소둔열처리된 스테인레스강의 형상을 도시한 도면이고, 도 2는 도 1에 도시된 스테인레스강의 위치에 따른 Cr함량을 도시한 그래프이며, 도 3은 도 1에 도시된 스테인레스강을 용융염에서 침지한 후의 상태를 도시한 도면이다.1 is a view showing the shape of the annealing heat treated stainless steel, Figure 2 is a graph showing the Cr content according to the position of the stainless steel shown in Figure 1, Figure 3 is a stainless steel shown in Figure 1 It is a figure which shows the state after immersion in molten salt.

도 1에 도시된 바와 같이, 소둔열처리과정에서 형성된 스케일(1)은 용융염에서 약 5 ∼ 10초간 침지하는 데, 그러면, 도 3에 도시된 바와 같이 스케일(1)에 틈이 생겨 산이 잘 침투하게 된다. 이런 산은 도 2에 도시된 바와 같이 소지메탈(3)보다 상대적으로 Cr함량이 낮은 크롬고갈층(2)에서 반응속도가 빠르기 때문에, 가능한 한 크롬고갈층(2)내의 Cr함량을 낮게 만드는 것이 산세속도에 유리하다.As shown in FIG. 1, the scale 1 formed during the annealing heat treatment is immersed in molten salt for about 5 to 10 seconds. Then, as shown in FIG. 3, a gap is formed in the scale 1, and the acid penetrates well. Done. This acid has a faster reaction rate in the chromium depleted layer 2 having a lower Cr content than the base metal 3 as shown in FIG. 2, so that the Cr content in the chromium depleted layer 2 as low as possible is pickled. Favorable for speed

따라서, 본 발명은 이러한 생각에 바탕을 두어 소둔열처리시 스케일내의 Cr/Fe의 비율을 높게 유지하여 크롬고갈층의 Cr함량을 상대적으로 낮추어 산세속도를 높이고 스케일을 완전히 제거하는 데 소요되는 시간을 단축할 수 있는 탈스케일성이 우수한 페라이트계 스테인레스강의 열처리 방법을 제공하는 데 그 목적이다.Therefore, based on this idea, the present invention maintains a high Cr / Fe ratio in the scale during annealing heat treatment to relatively lower the Cr content of the chromium depleted layer to increase the pickling rate and shorten the time required to completely remove the scale. An object of the present invention is to provide a heat treatment method of ferritic stainless steel having excellent descaleability.

도 1은 소둔열처리된 스테인레스강의 형상을 도시한 도면이고,1 is a view showing the shape of annealing heat treated stainless steel,

도 2는 도 1에 도시된 스테인레스강의 위치에 따른 Cr함량을 도시한 그래프이며,Figure 2 is a graph showing the Cr content according to the position of the stainless steel shown in Figure 1,

도 3은 도 1에 도시된 스테인레스강을 용융염에서 침지한 후의 상태를 도시한 도면.3 is a view showing a state after immersion in the molten salt of the stainless steel shown in FIG.

♠ 도면의 주요부분에 대한 부호의 설명 ♠♠ Explanation of symbols on the main parts of the drawing ♠

1 : 스케일 2 : 크롬고갈층1: scale 2: chromium depleted layer

3 : 소지금속3: base metal

위와 같은 목적을 달성하기 위한 본 발명에 따르면, 페라이트계 스테인레스강의 열처리 방법에 있어서, 소둔온도 970 ∼ 990℃에서 열처리하여 스케일 중 Cr/Fe의 조성비를 6.5 ∼ 9.3으로 조절하여 탈스케일성을 좋게하고 산세시간을 단축함으로써 생산성 향상 및 산 소모량을 줄이는 탈스케일성이 우수한 페라이트계 스테인레스강의 열처리 방법이 제공된다.According to the present invention for achieving the above object, in the heat treatment method of ferritic stainless steel, heat treatment at the annealing temperature of 970 ~ 990 ℃ to adjust the composition ratio of Cr / Fe in the scale to 6.5 to 9.3 to improve the descalability By shortening the pickling time, there is provided a heat treatment method of ferritic stainless steel excellent in descaling property which improves productivity and reduces acid consumption.

아래에서, 본 발명에 따른 탈스케일성이 우수한 페라이트계 스테인레스강의 열처리 방법의 양호한 실시예를 상세히 설명하겠다.In the following, a preferred embodiment of the heat treatment method of the ferritic stainless steel having excellent descaleability according to the present invention will be described in detail.

본 발명의 발명자는 가장 양호한 탈스케일성이 우수한 페라이트계 스테인레스강의 열처리 조건을 구하기 위하여, 스테인레스 436LT 냉연강판을 930 ∼ 1000℃에서 소둔열처리한 다음, 약 500℃의 용융염에서 5 ∼ 10초간 전처리한 다음 표 1에서와 같은 산세조건에서 산세성을 각각 실험하였고, 그 실험 결과를 표 2에 나타냈다.The inventors of the present invention, in order to obtain the heat treatment conditions of the ferritic stainless steel having the best descalability, the annealing heat treatment of stainless 436LT cold-rolled steel sheet at 930 ~ 1000 ℃, and then pretreated for 5 to 10 seconds in a molten salt of about 500 ℃ The pickling properties were tested under the same pickling conditions as in Table 1, and the test results are shown in Table 2.

구분division 황산조Sulfuric acid tank 혼산조Mixed acid tank 농도(%)density(%) 온도(℃)Temperature (℃) 시간(초)Time in seconds 질산(%)nitric acid(%) 붕산(%)Boric acid (%) 온도(℃)Temperature (℃) 시간(초)Time in seconds 66 5050 1010 88 1One 5050 12 ∼ 3012-30

구분division 열처리온도(℃)Heat treatment temperature (℃) 스케일중 Cr/Fe비율(at. % 기준)Cr / Fe ratio in scale (at.% Basis) 탈스케일시간(초)Descale Time (sec) 비고Remarks 종래예Conventional example 950 ∼ 980950-980 4.9 ∼ 7.54.9 to 7.5 16 ∼ 2516-25 온도별 스케일 두께 편차 심함Severe scale thickness deviation by temperature 실험예1Experimental Example 1 930930 3.23.2 3030 실험예2Experimental Example 2 950950 4.94.9 2323 실험예3Experimental Example 3 960960 5.25.2 2121 실험예4Experimental Example 4 970970 6.56.5 1717 실험예5Experimental Example 5 980980 7.57.5 1515 실험예6Experimental Example 6 990990 9.39.3 1212 실험예7Experimental Example 7 10001000 9.59.5 1212 결정립 조대Grain coarseness

표 2에서 알 수 있듯이, 종래예에서는 소둔온도범위가 넓어 거기에 따른 온도별 스케일 두께 편차가 심해 스케일을 완전히 제거하는 시간이 많이 다르고, 따라서 산세시간도 모든 소둔조건에서 산세가 가능한 약 25초의 산세시간을 적용하기 때문에, 소둔온도가 높은 조건에서 열처리한 시편은 필요 이상으로 산세를 함으로써 산 소모 증가의 원인이 되었다.As can be seen from Table 2, in the conventional example, the annealing temperature range is wide, and the scale thickness variation according to the temperature is so great that the time to completely remove the scale is different. Therefore, the pickling time is also about 25 seconds of pickling that can be pickled under all annealing conditions. Because of the time applied, the specimens heat-treated under conditions with high annealing temperature were pickled more than necessary, resulting in increased acid consumption.

그러나, 표 2에서와 같이 930 ∼ 1000℃ 범위에서 열처리하여 온도별 Cr/Fe 분율과 완전한 탈스케일에 걸리는 시간을 측정한 결과, 실험예1과 같이 930℃에서 열처리할 경우에는 완전한 재결정이 되지 않는 미소둔 조직이 나왔으며, 실험예2와 실험예3의 경우에는 소둔조직은 완전한 재결정이 일어나지만 다소 산세시간이 많이 걸리는 단점이 있었다.However, as shown in Table 2, as a result of measuring the Cr / Fe fraction and the time taken for complete descaling for each temperature by heat treatment in the range of 930 ~ 1000 ℃, when the heat treatment at 930 ℃ as in Experimental Example 1 is not completely recrystallized The microstructure was obtained, and in the case of Experimental Example 2 and Experimental Example 3, the annealing tissue was completely recrystallized, but it had a disadvantage that it took some pickling time.

그리고, 실험예4 내지 실험예6까지의 소둔온도 970 ∼ 990℃에서 열처리할 경우에는 스케일 중 Cr/Fe비율이 6.5 ∼ 9.3으로 높아져 산세시간이 단축되는 특징이 있었다. 그러나, 실험예7에서와 같이 소둔온도가 1000℃를 넘을 경우에는 결정립 조대화가 일어나 가공시 품질특성이 나빠지는 단점이 있었다.In the case of heat treatment at annealing temperatures of 970 to 990 ° C. from Experimental Examples 4 to 6, the Cr / Fe ratio in the scale was increased to 6.5 to 9.3, and the pickling time was shortened. However, when the annealing temperature exceeds 1000 ℃ as in Experimental Example 7, there was a disadvantage in that the grain coarsening caused the quality characteristics during processing worse.

위와 같은 실험에서 알 수 있듯이, 소둔온도 970 ∼ 990℃에서 열처리할 경우에는 종래의 소둔온도 950 ∼ 980℃에서 열처리할 때의 스케일 중 Cr/Fe비율 4.5 ∼ 7.5를 6.5 ∼ 9.3으로 높여 산세시간을 종래의 약 25초에서 12 ∼ 17초로 단축할 수 있었다.As can be seen from the above experiment, when the heat treatment at the annealing temperature of 970 ~ 990 ℃ to increase the pickling time by raising the Cr / Fe ratio 4.5 to 7.5 of 6.5 when the heat treatment at the conventional annealing temperature of 950 ~ 980 ℃ to 6.5 to 9.3 It was shortened from 12 to 17 seconds in about 25 seconds.

앞서 상세히 설명한 바와 같이 본 발명의 탈스케일성이 우수한 페라이트계 스테인레스강의 열처리 방법은 소둔온도 970 ∼ 990℃에서 열처리하여 스케일 중 Cr/Fe비율을 6.5 ∼ 9.3으로 높이고 산세시간을 12 ∼ 17초로 단축함으로, 생산성 향상 및 산 소모량을 현저하게 줄일 수 있다.As described in detail above, the heat treatment method of the ferritic stainless steel having excellent descalability is heat treated at annealing temperature of 970 to 990 ° C. to increase the Cr / Fe ratio to 6.5 to 9.3 and shorten pickling time to 12 to 17 seconds. In addition, productivity and acid consumption can be significantly reduced.

이상에서 본 발명의 탈스케일성이 우수한 페라이트계 스테인레스강의 열처리 방법에 대한 기술사상을 첨부도면과 함께 서술하였지만 이는 본 발명의 가장 양호한 실시예를 예시적으로 설명한 것이지 본 발명을 한정하는 것은 아니다.Although the technical idea of the heat treatment method of the ferritic stainless steel excellent in descalability of the present invention has been described with the accompanying drawings, this is by way of example and not by way of limitation.

또한, 이 기술분야의 통상의 지식을 가진 자이면 누구나 본 발명의 기술사상의 범주를 이탈하지 않는 범위내에서 다양한 변형 및 모방이 가능함은 명백한 사실이다.In addition, it is obvious that any person skilled in the art can make various modifications and imitations without departing from the scope of the technical idea of the present invention.

Claims (1)

페라이트계 스테인레스강의 열처리 방법에 있어서,In the heat treatment method of ferritic stainless steel, 소둔온도 970 ∼ 990℃에서 열처리하여 스케일 중 Cr/Fe의 조성비를 6.5 ∼ 9.3으로 조절하여 탈스케일성을 좋게하고 산세시간을 단축함으로써 생산성 향상 및 산 소모량을 줄이는 것을 특징으로 하는 탈스케일성이 우수한 페라이트계 스테인레스강의 열처리 방법.Heat treatment at annealing temperature of 970 ℃ -990 ℃ adjusts the composition ratio of Cr / Fe to 6.5-9.3 to improve descaling and shorten pickling time to improve productivity and reduce acid consumption. Heat treatment method of ferritic stainless steel.
KR1019990057664A 1999-12-14 1999-12-14 Heat treatment method of ferrite stainless KR100641758B1 (en)

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EP1498508A1 (en) * 2003-07-17 2005-01-19 Sumitomo Metal Industries, Ltd. Stainless steel and stainless steel pipe having resistance to carburization and coking

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JPH1053810A (en) * 1996-08-06 1998-02-24 Nkk Corp Stainless steel sheet excellent in descaling treatability, and its solution heat treatment

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1498508A1 (en) * 2003-07-17 2005-01-19 Sumitomo Metal Industries, Ltd. Stainless steel and stainless steel pipe having resistance to carburization and coking

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